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1

Measuring redshift-space distortions with future SKA surveys  

E-Print Network [OSTI]

The peculiar motion of galaxies can be a particularly sensitive probe of gravitational collapse. As such, it can be used to measure the dynamics of dark matter and dark energy as well the nature of the gravitational laws at play on cosmological scales. Peculiar motions manifest themselves as an overall anisotropy in the measured clustering signal as a function of the angle to the line-of-sight, known as redshift-space distortion (RSD). Limiting factors in this measurement include our ability to model non-linear galaxy motions on small scales and the complexities of galaxy bias. The anisotropy in the measured clustering pattern in redshift-space is also driven by the unknown distance factors at the redshift in question, the Alcock-Paczynski distortion. This weakens growth rate measurements, but permits an extra geometric probe of the Hubble expansion rate. In this chapter we will briefly describe the scientific background to the RSD technique, and forecast the potential of the SKA phase 1 and the SKA2 to measure the growth rate using both galaxy catalogues and intensity mapping, assessing their competitiveness with current and future optical galaxy surveys.

Alvise Raccanelli; Philip Bull; Stefano Camera; David Bacon; Chris Blake; Olivier Dore; Pedro Ferreira; Roy Maartens; Mario Santos; Matteo Viel; Gong-bo Zhao

2015-01-15T23:59:59.000Z

2

Measuring redshift-space distortions with future SKA surveys  

E-Print Network [OSTI]

The peculiar motion of galaxies can be a particularly sensitive probe of gravitational collapse. As such, it can be used to measure the dynamics of dark matter and dark energy as well the nature of the gravitational laws at play on cosmological scales. Peculiar motions manifest themselves as an overall anisotropy in the measured clustering signal as a function of the angle to the line-of-sight, known as redshift-space distortion (RSD). Limiting factors in this measurement include our ability to model non-linear galaxy motions on small scales and the complexities of galaxy bias. The anisotropy in the measured clustering pattern in redshift-space is also driven by the unknown distance factors at the redshift in question, the Alcock-Paczynski distortion. This weakens growth rate measurements, but permits an extra geometric probe of the Hubble expansion rate. In this chapter we will briefly describe the scientific background to the RSD technique, and forecast the potential of the SKA phase 1 and the SKA2 to measu...

Raccanelli, Alvise; Camera, Stefano; Bacon, David; Blake, Chris; Dore, Olivier; Ferreira, Pedro; Maartens, Roy; Santos, Mario; Viel, Matteo; Zhao, Gong-bo

2015-01-01T23:59:59.000Z

3

Testing cosmological structure formation using redshift-space distortions  

E-Print Network [OSTI]

Observations of redshift-space distortions in spectroscopic galaxy surveys offer an attractive method for observing the build-up of cosmological structure. In this paper we develop and test a new statistic based on anisotropies in the measured galaxy power spectrum, which is independent of galaxy bias and matches the matter power spectrum shape on large scales. The amplitude provides a constraint on the derivative of the linear growth rate through f.sigma_8. This demonstrates that spectroscopic galaxy surveys offer many of the same advantages as weak lensing surveys, in that they both use galaxies as test particles to probe all matter in the Universe. They are complementary as redshift-space distortions probe non-relativistic velocities and therefore the temporal metric perturbations, while weak lensing tests the sum of the temporal and spatial metric perturbations. The degree to which our estimator can be pushed into the non-linear regime is considered and we show that a simple Gaussian damping model, similar to that previously used to model the behaviour of the power spectrum on very small scales, can also model the quasi-linear behaviour of our estimator. This enhances the information that can be extracted from surveys for LCDM models.

Will J Percival; Martin White

2008-07-31T23:59:59.000Z

4

Redshift?space distortions in deep redshift surveys as a probe of the invisible Universe  

Science Journals Connector (OSTI)

Massive redshift surveys of galaxies beyond the local Universe (i.e.z>0.3) provide an exhaustive probe of the observed acceleration of cosmic expansion. While they have the ability to measure the expansion history H(z) through Baryonic Acoustic Oscillations in the galaxy power spectrum they can at the same time probe f(z) using the redshift?space distortions introduced in the observed clustering pattern by galaxy peculiar motions. Coupling these two measurements one can in principle distinguish whether cosmic acceleration is due to a new form of ‘dark energy’ in the cosmic budget or rather requires a modification of General Relativity. These two radically alternative scenarios are degenerate when considering H(z) alone as yielded e.g. by the Hubble diagram of Type Ia supernovae. We review our recent measurements of redshift distortions at z? 1 based on the VIMOS VLT Deep Survey “Wide” data and discuss the revived interest on this technique in the context of dark energy. Current results are consistent with the simplest cosmological?constant scenario but error bars are still too large to rule out alternative models. Forecasts based both on extensive simulations and Fisher?matrix computations show that next?generation deep surveys optimizing the combination of large volumes and good galaxy sampling will be able to use redshift distortions as a key tool to understand the physical origin of cosmic acceleration. Among these we introduce the newly started VIMOS Public Extragalactic Redshift Survey (VIPERS) at the ESO VLT which is building at ?0.8 a sample comparable to current local redshift surveys (10 5 redshifts in a volume 5×10 7 ? h ?1 ? Mpc 3 ). Finally we provide an example of the exquisite accuracy that could be reached on measurements of redshift?space distortions (among many others) with a massive 20 000? deg 2 near?infrared spectroscopic survey from space as foreseen by the EUCLID mission for the ESA ‘Cosmic Vision’ program.

Luigi Guzzo; Olivier Le Fèvre

2010-01-01T23:59:59.000Z

5

Assembly Bias & Redshift-Space Distortions: Impact on cluster dynamics tests of general relativity  

E-Print Network [OSTI]

The redshift-space distortion (RSD) of galaxies surrounding massive clusters is emerging as a promising testbed for theories of modified gravity. Conventional applications of this method rely upon the assumption that the velocity field in the cluster environment is uniquely determined by the cluster mass profile. Yet, real dark matter halos in N-body simulations are known to violate the assumption that virial mass determines the configuration space distribution, an effect known as assembly bias. In this Letter, I show that assembly bias in simulated dark matter halos also manifests in velocity space. In the 1-10 Mpc environment surrounding a cluster, high-concentration "tracer" halos exhibit a 10-20% larger pairwise-velocity dispersion profile relative to low-concentration tracer halos of the same mass. This difference is comparable to the size of the RSD signal predicted by f(R) models designed to account for the cosmic acceleration. I use the age matching technique to study how color-selection effects may i...

Hearin, Andrew P

2015-01-01T23:59:59.000Z

6

Redshift Distortions and Omega in IRAS Surveys  

E-Print Network [OSTI]

Redshift space distortions on large scales can be used to measure the linear growth rate parameter $\\ff \\approx \\Omega^{0.6}/b$. I report here measurements of such distortions in the IRAS 2 Jy, 1.2 Jy, and QDOT redshift surveys, finding $\\ff = 0.69^{+ .21}_{- .19}$ from a merged QDOT plus 1.2 Jy catalogue. Unfortunately, confidence in this result is undermined by a marked ($4\\sigma$) change in the pattern of clustering in QDOT beyond about $80 h^{-1} Mpc$. A similar effect may be present at a mild level in the 1.2 Jy survey. The effect may be caused by systematic variation in the effective flux limit of the IRAS PSC over the sky, with a dispersion of $\\sim 0.1$ Jy on scales $\\sim 7^{\\circ}$. If so, then the value of $\\ff$ inferred from redshift distortions in IRAS surveys may be systematically underestimated.

A. J. S. Hamilton

1995-07-06T23:59:59.000Z

7

Redshift-space distortions  

Science Journals Connector (OSTI)

...PhysRevD.82.063522 ) 10 Alcock, C. , and B. Paczynski1979An evolution...1086/148982 ) 18 Crittenden, R. C. , and N. Turok1996Looking for a cosmological...arxiv.org/abs/0902.1759 ) 20 Shapiro, C. , R. G. Crittenden, and W. J...

2011-01-01T23:59:59.000Z

8

Monte Carlo Study on Distortion of the Space-Dimension in COBE Monopole Data  

E-Print Network [OSTI]

A concise explanation of studies on distortion of space-time dimension is briefly introduced. Second we obtain the limits (i.e., bounded values) of the dimensionless chemical potential $\\mu$, the Sunyaev--Zeldovich (SZ) effect y and distortion of the space-dimension $\\varepsilon$ by Monte Carlo (MC) analysis of the parameter set (T, $d=3+\\varepsilon$, $\\mu$, and $y$) in cosmic microwave data assuming that the SZ effect is positive (y>0). In this analysis, the magnitude of the space-dimension d with distortion of the space-dimension $\\varepsilon$ is defined by $d=3+\\varepsilon$. The limits of $\\mu$ and $y$ are determined as $|\\mu| |y|$. The estimated limit of $|y| < 5\\times 10^{-6}$ appears to be related to re-ionization processes occurring at redshift $z_{ri}\\sim 10$. We also present data analysis assuming a relativistic SZ effect.

Minoru Biyajima; Takuya Mizoguchi

2013-05-31T23:59:59.000Z

9

Designing a space-based galaxy redshift survey to probe dark energy  

E-Print Network [OSTI]

A space-based galaxy redshift survey would have enormous power in constraining dark energy and testing general relativity, provided that its parameters are suitably optimized. We study viable space-based galaxy redshift surveys, exploring the dependence of the Dark Energy Task Force (DETF) figure-of-merit (FoM) on redshift accuracy, redshift range, survey area, target selection, and forecast method. Fitting formulae are provided for convenience. We also consider the dependence on the information used: the full galaxy power spectrum P(k, P(k) marginalized over its shape, or just the Baryon Acoustic Oscillations (BAO). We find that the inclusion of growth rate information (extracted using redshift space distortion and galaxy clustering amplitude measurements) leads to a factor of ~ 3 improvement in the FoM, assuming general relativity is not modified. This inclusion partially compensates for the loss of information when only the BAO are used to give geometrical constraints, rather than using the full P(k) as a standard ruler. We find that a space-based galaxy redshift survey covering ~20,000 deg^2 over 0.5surveys to enable robust modeling of systematic effects. We argue that these parameters are close to their optimal values given current instrumental and practical constraints.

Yun Wang; Will Percival; Andrea Cimatti; Pia Mukherjee; Luigi Guzzo; Carlton M. Baugh; Carmelita Carbone; Paolo Franzetti; Bianca Garilli; James E. Geach; Cedric G. Lacey; Elisabetta Majerotto; Alvaro Orsi; Piero Rosati; Lado Samushia; Giovanni Zamorani

2010-06-17T23:59:59.000Z

10

Probing reionization with LOFAR using 21-cm redshift space distortions  

Science Journals Connector (OSTI)

......3 m is a massively parallel hybrid (mpi-+-openmp) particle-particle-particle-mesh...at short distances and on a grid for long distances. For this...then make a u, v-coverage grid based on the positions of the...acknowledge the Swedish National Infrastructure for Computing (SNIC) resources......

Hannes Jensen; Kanan K. Datta; Garrelt Mellema; Emma Chapman; Filipe B. Abdalla; Ilian T. Iliev; Yi Mao; Mario G. Santos; Paul R. Shapiro; Saleem Zaroubi; G. Bernardi; M. A. Brentjens; A. G. de Bruyn; B. Ciardi; G. J. A. Harker; V. Jelic; S. Kazemi; L. V. E. Koopmans; P. Labropoulos; O. Martinez; A. R. Offringa; V. N. Pandey; J. Schaye; R. M. Thomas; V. Veligatla; H. Vedantham; S. Yatawatta

2013-01-01T23:59:59.000Z

11

A test of the nature of cosmic acceleration using galaxy redshift distortions  

E-Print Network [OSTI]

Observations of distant supernovae indicate that the Universe is now in a phase of accelerated expansion the physical cause of which is a mystery. Formally, this requires the inclusion of a term acting as a negative pressure in the equations of cosmic expansion, accounting for about 75 per cent of the total energy density in the Universe. The simplest option for this "dark energy" corresponds to a cosmological constant, perhaps related to the quantum vacuum energy. Physically viable alternatives invoke either the presence of a scalar field with an evolving equation of state, or extensions of general relativity involving higher-order curvature terms or extra dimensions. Although they produce similar expansion rates, different models predict measurable differences in the growth rate of large-scale structure with cosmic time. A fingerprint of this growth is provided by coherent galaxy motions, which introduce a radial anisotropy in the clustering pattern reconstructed by galaxy redshift surveys. Here we report a...

Guzzo, L; Meneux, B; Branchini, E; Le Fèvre, O; Marinoni, C; Garilli, B; Blaizot, J; De Lucia, G; Pollo, A; McCracken, H J; Bottini, D; Le Brun, V; MacCagni, D; Picat, J P; Scaramella, R; Scodeggio, M; Tresse, L; Vettolani, G; Zanichelli, A; Adami, C; Arnouts, S; Bardelli, S; Bolzonella, M; Bongiorno, A; Cappi, A; Charlot, S; Ciliegi, P; Contini, T; Cucciati, O; De la Torre, S; Dolag, K; Foucaud, S; Franzetti, P; Gavignaud, I; Ilbert, O; Iovino, A; Lamareille, F; Marano, B; Mazure, A; Memeo, P; Merighi, R; Moscardini, L; Paltani, S; Pellò, R; Pérez-Montero, E; Pozzetti, L; Radovich, M; Vergani, D; Zamorani, G; Zucca, E

2008-01-01T23:59:59.000Z

12

Environmental Effects on Real-Space and Redshift-Space Galaxy Clustering  

E-Print Network [OSTI]

Galaxy formation inside dark matter halos, as well as the halo formation itself, can be affected by large-scale environments. Evaluating the imprints of environmental effects on galaxy clustering is crucial for precise cosmological constraints with data from galaxy redshift surveys. We investigate such an environmental impact on both real-space and redshift-space galaxy clustering statistics using a semi-analytic model derived from the Millennium Simulation. We compare clustering statistics from original SAM galaxy samples and shuffled ones with environmental influence on galaxy properties eliminated. Among the luminosity-threshold samples examined, the one with the lowest threshold luminosity (~0.2L_*) is affected by environmental effects the most, which has a ~10% decrease in the real-space two-point correlation function (2PCF) after shuffling. By decomposing the 2PCF into five different components based on the source of pairs, we show that the change in the 2PCF can be explained by the age and richness dependence of halo clustering. The 2PCFs in redshift space are found to change in a similar manner after shuffling. If the environmental effects are neglected, halo occupation distribution modeling of the real-space and redshift-space clustering may have a less than 6.5% systematic uncertainty in constraining beta from the most affected SAM sample and have substantially smaller uncertainties from the other, more luminous samples. We argue that the effect could be even smaller in reality. In the Appendix, we present a method to decompose the 2PCF, which can be applied to measure the two-point auto-correlation functions of galaxy sub-samples in a volume-limited galaxy sample and their two-point cross-correlation functions in a single run utilizing only one random catalog.

Ying Zu; Zheng Zheng; G. T. Zhu; Y. P. Jing

2007-12-20T23:59:59.000Z

13

Testing dark energy using pairs of galaxies in redshift space  

Science Journals Connector (OSTI)

......galaxy redshift survey to constrain...signals for dark energy and modified...theory|dark energy|large-scale...future galaxy surveys is to determine...covered by future surveys, it is likely...accepted that the dark energy challenge should......

E. Jennings; C. M. Baugh; S. Pascoli

2012-02-21T23:59:59.000Z

14

Resumming Cosmological Perturbations via the Lagrangian Picture: One-loop Results in Real Space and in Redshift Space  

E-Print Network [OSTI]

We develop a new approach to study the nonlinear evolution in the large-scale structure of the Universe both in real space and in redshift space, extending the standard perturbation theory of gravitational instability. Infinite series of terms in standard Eulerian perturbation theory are resummed as a result of our starting from a Lagrangian description of perturbations. Delicate nonlinear effects on scales of the baryon acoustic oscillations are more accurately described by our method than the standard one. Our approach differs from other resummation techniques recently proposed, such as the renormalized perturbation theory, etc., in that we use simple techniques and thus resulting equations are undemanding to evaluate, and in that our approach is capable of quantifying the nonlinear effects in redshift space. The power spectrum and correlation function of our approach are in good agreement with numerical simulations in literature on scales of baryon acoustic oscillations. Especially, nonlinear effects on the baryon acoustic peak of the correlation function are accurately described both in real space and in redshift space. Our approach provides a unique opportunity to analytically investigate the nonlinear effects on baryon acoustic scales in observable redshift space, which is requisite in constraining the nature of dark energy, the curvature of the Universe, etc., by redshift surveys.

Takahiko Matsubara

2008-04-04T23:59:59.000Z

15

Designing a space-based galaxy redshift survey to probe dark energy  

Science Journals Connector (OSTI)

......space-based galaxy redshift survey to probe dark energy Yun Wang 1 * Will Percival...conventional FoM for comparing dark energy surveys proposed by the DETF (Albrecht...dramatic over ground-based surveys when dark energy density is allowed to be......

Yun Wang; Will Percival; Andrea Cimatti; Pia Mukherjee; Luigi Guzzo; Carlton M. Baugh; Carmelita Carbone; Paolo Franzetti; Bianca Garilli; James E. Geach; Cedric G. Lacey; Elisabetta Majerotto; Alvaro Orsi; Piero Rosati; Lado Samushia; Giovanni Zamorani

2010-12-01T23:59:59.000Z

16

What can we learn from higher multipole power spectra of galaxy distribution in redshift space?  

E-Print Network [OSTI]

We investigate a potential of the higher multipole power spectra of the galaxy distribution in redshift space as a cosmological probe on halo scales. Based on the fact that a halo model explains well the multipole power spectra of the luminous red galaxy (LRG) sample in the Sloan Digital Sky Survey (SDSS), we focus our investigation on the random motions of the satellite LRGs that determine the higher multipole spectra at large wavenumbers. We show that our theoretical model fits the higher multipole spectra at large wave numbers from N-body numerical simulations and we apply these results for testing the gravity theory and the velocity structure of galaxies on the halo scales. In this analysis, we use the multipole spectra P_4(k) and P_6(k) on the small scales of the range of wavenumber 0.3testing gravity by targeting the linear growth rate on very large scales. We demonstrate that our method could be useful for testing gravity on the ha...

Kanemaru, Tatsuro; Huetsi, Gert; Terukina, Ayumu; Yamamoto, Kazuhiro

2015-01-01T23:59:59.000Z

17

Improving the modelling of redshift-space distortions – I. A bivariate Gaussian description for the galaxy pairwise velocity distributions  

Science Journals Connector (OSTI)

......with its own mean and covariance matrix. Tests using numerical simulations explicitly...et-al. 2008). However, first accurate tests with simulations showed that the method...bivariate Gaussianity; in Section-3 we test the effectiveness of these assumptions......

Davide Bianchi; Matteo Chiesa; Luigi Guzzo

2015-01-01T23:59:59.000Z

18

WiggleZ Dark Energy Survey: Cosmological neutrino mass constraint from blue high-redshift galaxies  

Science Journals Connector (OSTI)

The absolute neutrino mass scale is currently unknown, but can be constrained by cosmology. The WiggleZ high redshift, star-forming, and blue galaxy sample offers a complementary data set to previous surveys for performing these measurements, with potentially different systematics from nonlinear structure formation, redshift-space distortions, and galaxy bias. We obtain a limit of ?m?<0.60??eV (95% confidence) for WiggleZ+Wilkinson?Microwave?Anisotropy?Probe. Combining with priors on the Hubble parameter and the baryon acoustic oscillation scale gives ?m?<0.29??eV, which is the strongest neutrino mass constraint derived from spectroscopic galaxy redshift surveys.

Signe Riemer–Sørensen et al.

2012-04-23T23:59:59.000Z

19

Studying large-scale structure with the 2dF Galaxy Redshift Survey  

E-Print Network [OSTI]

The 2dF Galaxy Redshift Survey is the first to observe more than 100,000 redshifts. This allows precise measurements of many of the key statistics of galaxy clustering, in particular redshift-space distortions and the large-scale power spectrum. This paper presents the current 2dFGRS results in these areas. Redshift-space distortions are detected with a high degree of significance, confirming the detailed Kaiser distortion from large-scale infall velocities, and measuring the distortion parameter beta equiv Omega_m^{0.6}/b = 0.43 +- 0.07. The power spectrum is measured to 0.02 h Mpc^{-1}, and is well fitted by a CDM model with Omega_m h = 0.20 +- 0.03 and a baryon fraction of 0.15 +- 0.07. A joint analysis with CMB data requires Omega_m = 0.29 +- 0.05, assuming scalar fluctuations, but no priors on other parameters. Two methods are used to determine the large-scale bias parameter: an internal bispectrum analysis yields b = 1.04 +- 0.11, in very good agreement with the b = 1.10 +- 0.08 obtained from a joint 2dFGRS+CMB analysis, again assuming scalar fluctuations. These figures refer to galaxies of approximate luminosity 2L^*; luminosity dependence of clustering is detected at high significance, and is well described by b/b^* = 0.85 + 0.15(L/L^*).

J. A. Peacock; M. Colless; I. Baldry; C. Baugh; J. Bland-Hawthorn; T. J. Bridges; R. Cannon; S. Cole; C. A. Collins; W. Couch; G. B. Dalton; R. De Propris; S. P. Driver; G. Efstathiou; R. S. Ellis; C. S. Frenk; K. Glazebrook; C. A. Jackson; O. Lahav; I. J. Lewis; S. Lumsden; S. J. Maddox; D. Madgwick; P. Norberg; W. Percival; B. A. Peterson; W. J. Sutherland; K. Taylor

2002-05-28T23:59:59.000Z

20

The WiggleZ Dark Energy Survey: Cosmological neutrino mass constraint from blue high-redshift galaxies  

E-Print Network [OSTI]

The absolute neutrino mass scale is currently unknown, but can be constrained from cosmology. The WiggleZ high redshift star-forming blue galaxy sample is less sensitive to systematics from non-linear structure formation, redshift-space distortions and galaxy bias than previous surveys. We obtain a upper limit on the sum of neutrino masses of 0.60eV (95% confidence) for WiggleZ+Wilkinson Microwave Anisotropy Probe. Combining with priors on the Hubble Parameter and the baryon acoustic oscillation scale gives an upper limit of 0.29eV, which is the strongest neutrino mass constraint derived from spectroscopic galaxy redshift surveys.

Signe Riemer-Sørensen; Chris Blake; David Parkinson; Tamara M. Davis; Sarah Brough; Matthew Colless; Carlos Contreras; Warrick Couch; Scott Croom; Darren Croton; Michael J. Drinkwater; Karl Forster; David Gilbank; Mike Gladders; Karl Glazebrook; Ben Jelliffe; Russell J. Jurek; I-hui Li; Barry Madore; D. Christopher Martin; Kevin Pimbblet; Gregory B. Poole; Michael Pracy; Rob Sharp; Emily Wisnioski; David Woods; Ted K. Wyder; H. K. C. Yee

2011-12-21T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

Phenomenology of dark energy: exploring the space of theories with future redshift surveys  

E-Print Network [OSTI]

We use the effective field theory of dark energy to explore the space of modified gravity models which are capable of driving the present cosmic acceleration. We identify five universal functions of cosmic time that are enough to describe a wide range of theories containing a single scalar degree of freedom in addition to the metric. The first function (the effective equation of state) uniquely controls the expansion history of the universe. The remaining four functions appear in the linear cosmological perturbation equations, but only three of them regulate the growth history of large scale structures. We propose a specific parameterization of such functions in terms of characteristic coefficients that serve as coordinates in the space of modified gravity theories and can be effectively constrained by the next generation of cosmological experiments. We address in full generality the problem of the soundness of the theory against ghost-like and gradient instabilities and show how the space of non-pathological models shrinks when a more negative equation of state parameter is considered. This analysis allows us to locate a large class of stable theories that violate the null energy condition (i.e. super-acceleration models) and to recover, as particular subsets, various models considered so far. Finally, under the assumption that the true underlying cosmological model is the $\\Lambda$ Cold Dark Matter ($\\Lambda$CDM) scenario, and relying on the figure of merit of EUCLID-like observations, we demonstrate that the theoretical requirement of stability significantly narrows the empirical likelihood, increasing the discriminatory power of data. We also find that the vast majority of these non-pathological theories generating the same expansion history as the $\\Lambda$CDM model predict a different, lower, growth rate of cosmic structures.

Federico Piazza; Heinrich Steigerwald; Christian Marinoni

2013-12-20T23:59:59.000Z

22

The Universe Adventure - Redshift  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Expansion of the Universe Expansion of the Universe Redshift Expansion of Space Redshifts Light The expansion of space redshifts light. As space expands, light waves get stretched and their wavelengths shift. The more that light is stretched, the longer its wavelengths become, and the color of each wave shifts toward the red end of the light spectrum. We say that this light is redshifted. The Doppler Effect in action. A moving fire truck's siren changes pitch as it moves past you. This is known as the Doppler Effect. To get a better idea of how this actually works, we'll look at a common phenomenon: the Doppler Effect. Imagine you hear a fire truck coming right toward you. As the truck approaches, the pitch of the siren gets higher and higher. As soon as the truck passes you however, the pitch drops lower as

23

The 2dF Galaxy Redshift Survey: galaxy clustering per spectral type  

E-Print Network [OSTI]

We have calculated the two-point correlation functions in redshift space, xi(sigma,pi), for galaxies of different spectral types in the 2dF Galaxy Redshift Survey. Using these correlation functions we are able to estimate values of the linear redshift-space distortion parameter, beta = Omega_m^0.6/b, the pairwise velocity dispersion, a, and the real-space correlation function, xi(r), for galaxies with both relatively low star-formation rates (for which the present rate of star formation is less than 10% of its past averaged value) and galaxies with higher current star-formation activity. At small separations, the real-space clustering of passive galaxies is very much stronger than that of the more actively star-forming galaxies; the correlation-function slopes are respectively 1.93 and 1.50, and the relative bias between the two classes is a declining function of radius. On scales larger than 10 h^-1 Mpc there is evidence that the relative bias tends to a constant, b(passive)/b(active) ~ 1. This result is consistent with the similar degrees of redshift-space distortions seen in the correlation functions of the two classes -- the contours of xi(sigma,pi) require beta(active)=0.49+/-0.13, and beta(passive)=0.48+/-0.14. The pairwise velocity dispersion is highly correlated with beta. However, despite this a significant difference is seen between the two classes. Over the range 8-20 h^-1 Mpc, the pairwise velocity dispersion has mean values 416+/-76 km/s and 612+/-92 km/s for the active and passive galaxy samples respectively. This is consistent with the expectation from morphological segregation, in which passively evolving galaxies preferentially inhabit the cores of high-mass virialised regions.

D. S. Madgwick; E. Hawkins; O. Lahav; S. Maddox; P. Norberg; J. Peacock; I. K. Baldry; C. M. Baugh; J. Bland-Hawthorn; T. Bridges; R. Cannon; S. Cole; M. Colless; C. Collins; W. Couch; G. Dalton; R. De Propris; S. P. Driver; G. Efstathiou; R. S. Ellis; C. S. Frenk; K. Glazebrook; C. Jackson; I. Lewis; S. Lumsden; B. A. Peterson; W. Sutherland; K. Taylor

2003-03-31T23:59:59.000Z

24

The 2dF Galaxy Redshift Survey: Spherical Harmonics analysis of fluctuations in the final catalogue  

E-Print Network [OSTI]

We present the result of a decomposition of the 2dFGRS galaxy overdensity field into an orthonormal basis of spherical harmonics and spherical Bessel functions. Galaxies are expected to directly follow the bulk motion of the density field on large scales, so the absolute amplitude of the observed large-scale redshift-space distortions caused by this motion is expected to be independent of galaxy properties. By splitting the overdensity field into radial and angular components, we linearly model the observed distortion and obtain the cosmological constraint Omega_m^{0.6} sigma_8=0.46+/-0.06. The amplitude of the linear redshift-space distortions relative to the galaxy overdensity field is dependent on galaxy properties and, for L_* galaxies at redshift z=0, we measure beta(L_*,0)=0.58+/-0.08, and the amplitude of the overdensity fluctuations b(L_*,0) sigma_8=0.79+/-0.03, marginalising over the power spectrum shape parameters. Assuming a fixed power spectrum shape consistent with the full Fourier analysis produces very similar parameter constraints.

Will J. Percival; Daniel Burkey; Alan Heavens; Andy Taylor; Shaun Cole; John A. Peacock; Carlton M. Baugh; Joss Bland-Hawthorn; Terry Bridges; Russell Cannon; Matthew Colless; Chris Collins; Warrick Couch; Gavin Dalton; Roberto De Propris; Simon P. Driver; George Efstathiou; Richard S. Ellis; Carlos S. Frenk; Karl Glazebrook; Carole Jackson; Ofer Lahav; Ian Lewis; Stuart Lumsden; Steve Maddox; Peder Norberg; Bruce A. Peterson; Will Sutherland; Keith Taylor

2004-06-23T23:59:59.000Z

25

Differentiating dark energy and modified gravity with galaxy redshift surveys  

Science Journals Connector (OSTI)

The observed cosmic acceleration today could be due to an unknown energy component (dark energy), or a modification to general relativity (modified gravity). If dark energy models and modified gravity models are required to predict the same cosmic expansion history H(z), they will predict different growth rates for cosmic large scale structure, fg(z). If gravity is not modified, the measured H(z) leads to a unique prediction for fg(z), fgH(z), if dark energy and dark matter are separate. Comparing fgH(z) with the measured fg(z) provides a transparent and straightforward test of gravity. We show that a simple ?2 test provides a general figure of merit for our ability to distinguish between dark energy and modified gravity given the measured H(z) and fg(z). We find that a magnitude-limited NIR galaxy redshift survey covering >10?000 (deg)2 and a redshift range of 0.5zH(z) to 1–2% accuracy via baryon acoustic oscillation measurements, and fg(z) to the accuracy of a few per cent via the measurement of redshift-space distortions and the bias factor which describes how light traces mass. We show that if the H(z) data are fitted by both a DGP gravity model and an equivalent dark energy model that predict the same H(z), a survey area of 11?931 (deg)2 is required to rule out the DGP gravity model at the 99.99% confidence level. It is feasible for such a galaxy redshift survey to be carried out by the next generation space missions from NASA and ESA, and it will revolutionize our understanding of the universe by differentiating between dark energy and modified gravity.

Yun Wang

2008-01-01T23:59:59.000Z

26

Optimal multihump filter for photometric redshifts  

E-Print Network [OSTI]

We propose a novel type filter for multicolor imaging to improve on the photometric redshift estimation of galaxies. An extra filter - specific to a certain photometric system - may be utilized with high efficiency. We present a case study of the Hubble Space Telescope's Advanced Camera for Surveys and show that one extra exposure could cut down the mean square error on photometric redshifts by 34% over the z<1.3 redshift range.

Tamas Budavari; Alexander S. Szalay; Istvan Csabai; Andrew J. Connolly; Zlatan Tsvetanov

2001-06-05T23:59:59.000Z

27

The 2dF Galaxy Redshift Survey: correlation functions, peculiar velocities and the matter density of the Universe  

E-Print Network [OSTI]

We present a detailed analysis of the two-point correlation function, from the 2dF Galaxy Redshift Survey (2dFGRS). We estimate the redshift-space correlation function, xi(s), from which we measure the redshift-space clustering length, s_0=6.82+/-0.28 Mpc/h. We also estimate the projected correlation function, Xi(sigma), and the real-space correlation function, xi(r), which can be fit by a power-law, with r_0=5.05+/-0.26Mpc/h, gamma_r=1.67+/-0.03. For r>20Mpc/h, xi drops below a power-law as is expected in the popular LCDM model. The ratio of amplitudes of the real and redshift-space correlation functions on scales of 8-30Mpc/h gives an estimate of the redshift-space distortion parameter beta. The quadrupole moment of xi on scales 30-40Mpc/h provides another estimate of beta. We also estimate the distribution function of pairwise peculiar velocities, f(v), including rigorously the effect of infall velocities, and find that it is well fit by an exponential. The accuracy of our xi measurement is sufficient to constrain a model, which simultaneously fits the shape and amplitude of xi(r) and the two redshift-space distortion effects parameterized by beta and velocity dispersion, a. We find beta=0.49+/-0.09 and a=506+/-52km/s, though the best fit values are strongly correlated. We measure the variation of the peculiar velocity dispersion with projected separation, a(sigma), and find that the shape is consistent with models and simulations. Using the constraints on bias from recent estimates, and taking account of redshift evolution, we conclude that beta(L=L*,z=0)=0.47+/-0.08, and that the present day matter density of the Universe is 0.3, consistent with other 2dFGRS estimates and independent analyses.

E. Hawkins; S. Maddox; S. Cole; O. Lahav; D. Madgwick; P. Norberg; J. Peacock; I. Baldry; C. Baugh; J. Bland-Hawthorn; T. Bridges; R. Cannon; M. Colless; C. Collins; W. Couch; G. Dalton; R. De Propris; S. Driver; G. Efstathiou; R. Ellis; C. Frenk; K. Glazebrook; C. Jackson; B. Jones; I. Lewis; S. Lumsden; W. Percival; B. Peterson; W. Sutherland; K. Taylor

2003-08-05T23:59:59.000Z

28

Galaxies at High Redshifts  

E-Print Network [OSTI]

Several conclusions have been reached over the last few years concerning high-redshift galaxies: (1) The excess of faint blue galaxies is due to dwarf galaxies. (2) Star formation peaks at redshifts z ~1-2. (3) It appears to occur piecemeal in any given galaxy and there is no evidence for starbursting throughout a large ~10 kpc galaxy. (4) There is significant and sharp diminution in the number of L* spiral galaxies at redshifts 1redshifts 2.5redshift galaxies in universes with larger volumes per unit redshift, i.e., open or lambda models, which have lower deceleration parameters.

A. Yahil; K. M. Lanzetta; A. Fernandez-Soto

1998-03-05T23:59:59.000Z

29

Self calibration of galaxy bias in spectroscopic redshift surveys of baryon acoustic oscillations  

E-Print Network [OSTI]

Baryon acoustic oscillation (BAO) is a powerful probe on the expansion of the universe, shedding light on elusive dark energy and gravity at cosmological scales. BAO measurements through biased tracers of the underlying matter density field, as most proposals do, can reach high statistical accuracy. However, possible scale dependence in bias may induce non-negligible systematical errors, especially for the most ambitious spectroscopic surveys proposed. We show that precision spectroscopic redshift information available in these surveys allows for {\\it self calibration} of the galaxy bias and its stochasticity, as function of scale and redshift. Through the effect of redshift distortion, one can simultaneously measure the real space power spectra of galaxies, galaxy-velocity and velocity, respectively. At relevant scales of BAO, galaxy velocity faithfully traces that of the underlying matter. This valuable feature enables a rather model independent way to measure the galaxy bias and its stochasticity by comparing the three power spectra. For the square kilometer array (SKA), this self calibration is statistically accurate to correct for 1% level shift in BAO peak positions induced by bias scale dependence. Furthermore, we find that SKA is able to detect BAO in the velocity power spectrum, opening a new window for BAO cosmology.

Pengjie Zhang

2008-02-18T23:59:59.000Z

30

ON COMPLEMENTED VERSIONS OF JAMES'S DISTORTION WILLIAM B. JOHNSON  

E-Print Network [OSTI]

ON COMPLEMENTED VERSIONS OF JAMES'S DISTORTION THEOREMS WILLIAM B. JOHNSON AND NARCISSE. 1 #12;2 JOHNSON AND RANDRIANANTOANINA Question 2. If a Banach space X contains a complemented

Johnson, William B.

31

Memory distortion: an adaptive perspective  

E-Print Network [OSTI]

concerning factors that can influence the occurrence of memory distortions, such as sleep and retrieval kinds of errors and distortions. Studies of memory distortion have a long history in both theoretical narrative that becomes our autobiography. In the process of reconstructing the past, we color and shape our

Schacter, Daniel

32

Clustering of High Redshift (z>2.9) Quasars from the Sloan Digital Sky Survey  

SciTech Connect (OSTI)

We study the two-point correlation function of a uniformly selected sample of 4,428 optically selected luminous quasars with redshift 2.9 {le} z {le} 5.4 selected over 4041 deg{sup 2} from the Fifth Data Release of the Sloan Digital Sky Survey. We fit a power-law to the projected correlation function w{sub p}(r{sub p}) to marginalize over redshift space distortions and redshift errors. For a real-space correlation function of the form {zeta}(r) = (r/r{sub 0}){sup -{gamma}}, the fitted parameters in comoving coordinates are r{sub 0} = 15.2 {+-} 2.7 h{sup -1} Mpc and {gamma} = 2.0 {+-} 0.3, over a scale range 4 {le} r{sub p} {le} 150 h{sup -1} Mpc. Thus high-redshift quasars are appreciably more strongly clustered than their z {approx} 1.5 counterparts, which have a comoving clustering length r{sub 0} {approx} 6.5 h{sup -1} Mpc. Dividing our sample into two redshift bins: 2.9 {le} z {le} 3.5 and z {ge} 3.5, and assuming a power-law index {gamma} = 2.0, we find a correlation length of r{sub 0} = 16.9 {+-} 1.7 h{sup -1} Mpc for the former, and r{sub 0} = 24.3 {+-} 2.4 h{sup -1} Mpc for the latter. Strong clustering at high redshift indicates that quasars are found in very massive, and therefore highly biased, halos. Following Martini & Weinberg, we relate the clustering strength and quasar number density to the quasar lifetimes and duty cycle. Using the Sheth & Tormen halo mass function, the quasar lifetime is estimated to lie in the range 4 {approx} 50 Myr for quasars with 2.9 {le} z {le} 3.5; and 30 {approx} 600 Myr for quasars with z {ge} 3.5. The corresponding duty cycles are 0.004 {approx} 0.05 for the lower redshift bin and 0.03 {approx} 0.6 for the higher redshift bin. The minimum mass of halos in which these quasars reside is 2-3 x 10{sup 12} h{sup -1} M{sub {circle_dot}} for quasars with 2.9 {le} z {le} 3.5 and 4-6 x 10{sup 12} h{sup -1} M{sub {circle_dot}} for quasars with z {ge} 3.5; the effective bias factor b{sub eff} increases with redshift, e.g., b{sub eff} {approx} 8 at z = 3.0 and b{sub eff} {approx} 16 at z = 4.5.

Shen, Yue; Strauss, Michael A.; Oguri, Masamune; Hennawi, Joseph F.; Fan, Xiaohui; Richards, Gordon T.; Hall, Patrick B.; Schneider, Donald P.; Szalay, Alexander S.; Thakar, Anirudda R.; Berk, Daniel E.Vanden; Anderson, Scott F.; Bahcall, Neta A.; /KIPAC, Menlo Park

2006-11-30T23:59:59.000Z

33

Distortion operator and Entanglement Information Rate Distortion of Quantum Gaussian Source  

E-Print Network [OSTI]

Quantum random variable, distortion operator are introduced based on canonical operators. As the lower bound of rate distortion, the entanglement information rate distortion is achieved by Gaussian map for Gaussian source. General Gaussian maps are further reduced to unitary transformations and additive noises from the physical meaning of distortion. The entanglement information rate distortion function then are calculated for one mode Gaussian source. The rate distortion is accessible at zero distortion point. For pure state, the rate distortion function is always zero. In contrast to the distortion defined via fidelity, our definition of the distortion makes it possible to calculate the entanglement information rate distortion function for Gaussian source.

Xiao-yu Chen

2005-11-30T23:59:59.000Z

34

On the gravitational redshift  

E-Print Network [OSTI]

The study of the gravitational redshift\\,---\\,a relative wavelength increase of $\\approx 2 \\times 10^{-6}$ was predicted for solar radiation by Einstein in 1908\\,---\\,is still an important subject in modern physics. In a dispute whether or not atom interferometry experiments can be employed for gravitational redshift measurements, two research teams have recently disagreed on the physical cause of the shift. Regardless of any discussion on the interferometer aspect\\,---\\,we find that both groups of authors miss the important point that the ratio of gravitational to the electrostatic forces is generally very small. For instance, the gravitational force acting on an electron in a hydrogen atom situated in the Sun's photosphere to the electrostatic force between the proton and the electron is approximately $3 \\times 10^{-21}$. A comparison of this ratio with the predicted and observed solar redshift indicates a discrepancy of many orders of magnitude. Here we show, with Einstein's early assumption of the frequency of spectral lines depending only on the generating ion itself as starting point, that a solution can be formulated based on a two-step process in analogy with Fermi's treatment of the Doppler effect. It provides a sequence of physical processes in line with the conservation of energy and momentum resulting in the observed shift and does not employ a geometric description. The gravitational field affects the release of the photon and not the atomic transition. The control parameter is the speed of light. The atomic emission is then contrasted with the gravitational redshift of matter-antimatter annihilation events.

Klaus Wilhelm; Bhola N. Dwivedi

2014-04-16T23:59:59.000Z

35

Space  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Energy Earth Materials Science Technology The Lab All Paul Johnson Unusual light in dark space revealed by Los Alamos, NASA By looking at the dark spaces between visible...

36

The 2dF Galaxy Redshift Survey: Luminosity dependence of galaxy clustering  

E-Print Network [OSTI]

We investigate the dependence of the strength of galaxy clustering on intrinsic luminosity using the Anglo-Australian two degree field galaxy redshift survey (2dFGRS). The 2dFGRS is over an order of magnitude larger than previous redshift surveys used to address this issue. We measure the projected two-point correlation function of galaxies in a series of volume-limited samples. The projected correlation function is free from any distortion of the clustering pattern induced by peculiar motions and is well described by a power-law in pair separation over the range 0.1 < r /h Mpc < 10. The clustering of L* galaxies in real space is well fit by a correlation length r0 = 4.9 +/- 0.3 /h Mpc and power-law slope gamma = 1.71 +/- 0.06. The clustering amplitude increases slowly with absolute magnitude for galaxies fainter than M*, but rises more strongly at higher luminosities. At low luminosities, our results agree with measurements from the SSRS2 by Benoist et al. However, we find a weaker dependence of clustering strength on luminosity at the highest luminosities. The correlation function amplitude increases by a factor of 4.0 between $M_{b_{J}} -5\\log_{10}h = -18$ and -22.5, and the most luminous galaxies are 3.0 times more strongly clustered than L* galaxies. The power-law slope of the correlation function shows remarkably little variation for samples spanning a factor of 20 in luminosity. Our measurements are in very good agreement with the predictions of the hierarchical galaxy formation models of Benson et al.

P. Norberg; C. M. Baugh; E. Hawkins; S. Maddox; J. A. Peacock; S. Cole; C. S. Frenk; J. Bland-Hawthorn; T. Bridges; R. Cannon; M. Colless; C. Collins; W. Couch; G. Dalton; S. P. Driver; G. Efstathiou; R. S. Ellis; K. Glazebrook; C. Jackson; O. Lahav; I. Lewis; S. Lumsden; B. A. Peterson; W. Sutherland; K. Taylor; the 2dFGRS Team

2001-10-19T23:59:59.000Z

37

PHOTOMETRIC REDSHIFTS OF SUBMILLIMETER GALAXIES  

SciTech Connect (OSTI)

We use the photometric redshift method of Chakrabarti and McKee to infer photometric redshifts of submillimeter galaxies with far-IR (FIR) Herschel data obtained as part of the PACS Evolutionary Probe program. For the sample with spectroscopic redshifts, we demonstrate the validity of this method over a large range of redshifts (4 {approx}> z {approx}> 0.3) and luminosities, finding an average accuracy in (1 + z{sub phot})/(1 + z{sub spec}) of 10%. Thus, this method is more accurate than other FIR photometric redshift methods. This method is different from typical FIR photometric methods in deriving redshifts from the light-to-gas mass (L/M) ratio of infrared-bright galaxies inferred from the FIR spectral energy distribution, rather than dust temperatures. To assess the dependence of our photometric redshift method on the data in this sample, we contrast the average accuracy of our method when we use PACS data, versus SPIRE data, versus both PACS and SPIRE data. We also discuss potential selection effects that may affect the Herschel sample. Once the redshift is derived, we can determine physical properties of infrared-bright galaxies, including the temperature variation within the dust envelope, luminosity, mass, and surface density. We use data from the GOODS-S field to calculate the star formation rate density (SFRD) of submillimeter bright sources detected by AzTEC and PACS. The AzTEC-PACS sources, which have a threshold 850 {mu}m flux {approx}> 5 mJy, contribute 15% of the SFRD from all ultraluminous infrared galaxies (L{sub IR} {approx}> 10{sup 12} L{sub Sun }), and 3% of the total SFRD at z {approx} 2.

Chakrabarti, Sukanya [School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623 (United States); Magnelli, Benjamin; Lutz, Dieter; Berta, Stefano; Popesso, Paola [Max-Planck-Institut fuer Extraterrestrische Physik, Postfach 1312, Giessenbachstrasse 1, D-85741 Garching (Germany); McKee, Christopher F. [Physics and Astronomy Departments, UC Berkeley, Berkeley, CA 94720 (United States); Pozzi, Francesca, E-mail: chakrabarti@astro.rit.edu [Dipartimento di Astronomia, Universita degli Studi di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)

2013-08-20T23:59:59.000Z

38

Probabilistic selection of high-redshift quasars  

Science Journals Connector (OSTI)

......5) decreases from at a redshift of 6.0 to at a redshift of= 6.5. At higher redshifts, however, the small increase inis much less important than the large increase in the HZQs expectedvalues. As a result the effective depth at a redshift of 7......

Daniel J. Mortlock; Mitesh Patel; Stephen J. Warren; Paul C. Hewett; Bram P. Venemans; Richard G. McMahon; Chris Simpson

2012-01-01T23:59:59.000Z

39

Exponential cosmological redshift in a linearly expanding universe  

E-Print Network [OSTI]

Analytical solution of the Maxwell equations in a flat expanding Friedmann-Robertson-Walker space-time is presented. The solution is valid for arbitrary sources and for expansion rates described by positive functions of time. The near-, intermediate-, and far-field terms are explicitly identified. It is shown that the cosmological redshift introduced by a linearly expanding space-time is an exponential function of the distance factor.

Budko, Neil V

2009-01-01T23:59:59.000Z

40

Centrifugal Distortion in Asymmetric Molecules. II. HDS  

Science Journals Connector (OSTI)

A perturbation method for relating the theory of centrifugal distortion in asymmetric top molecules to observed microwave Q branch, a or c type transitions, is presented. The formula for the distortion correction is expressed in terms of the total angular momentum, J, the symmetry axis momentum of the nearest symmetric top, K, and five distortion constants. The formula yields a satisfactory fit to the observed spectrum of HDS (??-0.5). The electric dipole moment is determined as 1.02±0.02 debye. The inertia defect and distortion constants are calculated. The effective structure for the HDS molecule so determined is in agreement with infrared determinations.

R. E. Hillger and M. W. P. Strandberg

1951-08-01T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

The 2dF Galaxy Redshift Survey: The dependence of galaxy clustering on luminosity and spectral type  

E-Print Network [OSTI]

We investigate the dependence of galaxy clustering on luminosity and spectral type using the 2dF Galaxy Redshift Survey (2dFGRS). Spectral types are assigned using the principal component analysis of Madgwick et al. We divide the sample into two broad spectral classes: galaxies with strong emission lines (`late-types'), and more quiescent galaxies (`early-types'). We measure the clustering in real space, free from any distortion of the clustering pattern due to peculiar velocities, for a series of volume-limited samples. The projected correlation functions of both spectral types are well described by a power law for transverse separations in the range 2 < (sigma/Mpc/h) < 15, with a marginally steeper slope for early-types than late-types. Both early and late types have approximately the same dependence of clustering strength on luminosity, with the clustering amplitude increasing by a factor of ~2.5 between L* and 4 L*. At all luminosities, however, the correlation function amplitude for the early-types is ~50% higher than that of the late-types. These results support the view that luminosity, and not type, is the dominant factor in determining how the clustering strength of the whole galaxy population varies with luminosity.

P. Norberg; C. M. Baugh; E. Hawkins; S. Maddox; D. Madgwick; O. Lahav; S. Cole; C. S. Frenk; I. Baldry; J. Bland-Hawthorn; T. Bridges; R. Cannon; M. Colless; C. Collins; W. Couch; G. Dalton; S. P. Driver; G. Efstathiou; R. S. Ellis; K. Glazebrook; C. Jackson; I. Lewis; S. Lumsden; J. A. Peacock; B. A. Peterson; W. Sutherland; K. Taylor; the 2dFGRS Team

2002-01-24T23:59:59.000Z

42

Lattice Distortions and Oxygen Vacancies Produced in Au+-Irradiated...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Lattice Distortions and Oxygen Vacancies Produced in Au+-Irradiated Nanocrystalline Cubic Zirconia. Lattice Distortions and Oxygen Vacancies Produced in Au+-Irradiated...

43

Exponential cosmological redshift in a linearly expanding universe  

E-Print Network [OSTI]

The first principles analysis of the radiation by an arbitrary source in a flat Friedmann-Robertson-Walker space-time is presented. The obtained analytical solution explicitly shows that the cosmological redshift is not of kinematic origin and that the source and the observer may be regarded as being at rest with respect to eachother at all times. At the same time the effect of the time-variation of the metric on the propagation of light appears to be underestimated in the standard cosmology. The cosmological redshift caused by the linear time-variation of the metric turns out to be an exponential rather than linear function of the well-defined spatial distance and the apparent brightness of the source contains an even stronger exponential decay factor.

Neil V. Budko

2009-07-03T23:59:59.000Z

44

Estimation problems in the space of distorted stochastic processes  

E-Print Network [OSTI]

weighted average of the response variables near the point t. More formally we will defined: T m(t) = T-'g WTi(t)Z(t) (3. 13) i=i where (WT, (t))T l denotes a sequence of weights which depends on the kind of smoother selected T m, (t) = T... weighted average of the response variables near the point t. More formally we will defined: T m(t) = T-'g WTi(t)Z(t) (3. 13) i=i where (WT, (t))T l denotes a sequence of weights which depends on the kind of smoother selected T m, (t) = T...

Moutran, Cyril

2012-06-07T23:59:59.000Z

45

Optical Approach to Gravitational Redshift  

E-Print Network [OSTI]

An optical approach begins by interpreting the gravitational redshift resulting to a change in the relative velocity of light due to the medium of propagation in the gravitational field. The discussion continues by pointing out an agreement in structure between the equation for rays in geometrical optics and the geodesic equation of general relativity. From their comparison we learn that the path of rays should be given by the relation $ds^2=n^2(r)dr^2+r^2d\\theta^2$, not by $ds^2=dr^2+r^2d\\theta^2$, in a medium with spherical symmetry of refractive index $n(r)$. The development of an optical analogy suggests introducing $n^2(r)$ in place of $g_{rr}$ as an optical version of the Schwarzschild metric. In form and content, $n^2(r)$ is different from $g_{rr}$. The optical point of view replaces the general-relativity explanations in terms of time and gravitation.

Y. G. Yi

2012-04-12T23:59:59.000Z

46

Estimating photometric redshifts with artificial neural networks  

E-Print Network [OSTI]

A new approach to estimating photometric redshifts - using Artificial Neural Networks (ANNs) - is investigated. Unlike the standard template-fitting photometric redshift technique, a large spectroscopically-identified training set is required but, where one is available, ANNs produce photometric redshift accuracies at least as good as and often better than the template-fitting method. The Bayesian priors on the underlying redshift distribution are automatically taken into account. Furthermore, inputs other than galaxy colours - such as morphology, angular size and surface brightness - may be easily incorporated, and their utility assessed. Different ANN architectures are tested on a semi-analytic model galaxy catalogue and the results are compared with the template-fitting method. Finally the method is tested on a sample of ~ 20000 galaxies from the Sloan Digital Sky Survey. The r.m.s. redshift error in the range z < 0.35 is ~ 0.021.

Andrew E. Firth; Ofer Lahav; Rachel S. Somerville

2002-03-15T23:59:59.000Z

47

Memory Distortion in People Reporting Abduction by Aliens Susan A. Clancy, Richard J. McNally,  

E-Print Network [OSTI]

Memory Distortion in People Reporting Abduction by Aliens Susan A. Clancy, Richard J. Mc memories of traumatic events that are unlikely to have occurred: abduction by space aliens. A variant to examine false recall and false recognition in 3 groups: people reporting recovered memories of alien

Schacter, Daniel

48

Zigzag laser with reduced optical distortion  

DOE Patents [OSTI]

The architecture of the present invention has been driven by the need to solve the beam quality problems inherent in Brewster's angle tipped slab lasers. The entrance and exit faces of a solid state slab laser are cut perpendicular with respect to the pump face, thus intrinsically eliminating distortion caused by the unpumped Brewster's angled faces. For a given zigzag angle, the residual distortions inherent in the remaining unpumped or lightly pumped ends may be reduced further by tailoring the pump intensity at these ends. 11 figures.

Albrecht, G.F.; Comaskey, B.; Sutton, S.B.

1994-04-19T23:59:59.000Z

49

Zigzag laser with reduced optical distortion  

DOE Patents [OSTI]

The architecture of the present invention has been driven by the need to solve the beam quality problems inherent in Brewster's angle tipped slab lasers. The entrance and exit faces of a solid state slab laser are cut perpendicular with respect to the pump face, thus intrinsically eliminating distortion caused by the unpumped Brewster's angled faces. For a given zigzag angle, the residual distortions inherent in the remaining unpumped or lightly pumped ends may be reduced further by tailoring the pump intensity at these ends.

Albrecht, Georg F. (Livermore, CA); Comaskey, Brian (Stockton, CA); Sutton, Steven B. (Manteca, CA)

1994-01-01T23:59:59.000Z

50

MEDIEVAL DISTORTIONS: THE PROJECTIONS OF ANCIENT MAPS  

E-Print Network [OSTI]

MEDIEVAL DISTORTIONS: THE PROJECTIONS OF ANCIENT MAPS W.R TOBLER University of Michigan, Ann Arbor ABSTRACT. Estimates of the map projection employed for an ancient map is a prerequisite for a variety for the Hereford map and illustrated the agreement of a portolan chart with an oblique Mercator projection

Tobler, Waldo

51

Redshift indicators for gamma-ray bursts  

E-Print Network [OSTI]

The measure of the distances and luminosities of gamma-ray bursts (GRBs) led to the discovery that many GRB properties are strongly correlated with their intrinsic luminosity, leading to the construction of reliable luminosity indicators. These GRB luminosity indicators have quickly found applications, like the construction of 'pseudo-redshifts', or the measure of luminosity distances, which can be computed independently of the measure of the redshift. In this contribution I discuss various issues connected with the construction of luminosity-redshift indicators for gamma-ray bursts.

J-L. Atteia

2005-05-04T23:59:59.000Z

52

The CNOC2 Field Galaxy Redshift Survey  

E-Print Network [OSTI]

This paper provides a brief description of the CNOC2 Redshift Survey being carried out at CFHT, giving the scope, technique, and current status of the survey, and some preliminary results.

H. K. C. Yee; M. J. Sawicki; R. G. Carlberg; H. Lin; ; S. L. Morris; ; D. R. Patton; G. D. Wirth; ; C. W. Shepherd; ; E. Ellingson; ; D. Schade; R. Marzke

1997-10-30T23:59:59.000Z

53

Observed Cosmological Redshifts Support Contracting Accelerating Universe  

E-Print Network [OSTI]

The main argument that Universe is currently expanding is observed redshift increase by distance. However, this conclusion may not be correct, because cosmological redshift depends only on the scaling factors, the change in the size of the universe during the time of light propagation and is not related to the speed of observer or speed of the object emitting the light. An observer in expanding universe will measure the same redshift as observer in contracting universe with the same scaling. This was not taken into account in analysing the SN Ia data related to the universe acceleration. Possibility that universe may contract, but that the observed light is cosmologically redshifted allows for completely different set of cosmological parameters $\\Omega_M, \\Omega_{\\Lambda}$, including the solution $\\Omega_M=1, \\Omega_{\\Lambda}=0$. The contracting and in the same time accelerating universe explains observed deceleration and acceleration in SN Ia data, but also gives significantly larger value for the age of the universe, $t_0 = 24$ Gyr. This allows to reconsider classical cosmological models with $\\Lambda =0$. The contracting stage also may explain the observed association of high redshifted quasars to low redshifted galaxies.

Branislav Vlahovic

2012-07-02T23:59:59.000Z

54

Radio Observations of High Redshift Radio Galaxies  

E-Print Network [OSTI]

We review some aspects of radio continuum polarimetric imaging of high redshift radio galaxies. The correlation between extreme values of Faraday rotation observed toward radio emitting structures in nearby radio galaxies, and X-ray emitting cluster atmospheres, is presented as a method for targeting objects at high redshift for deep X-ray searches. We present an X-ray detection of the extreme rotation measure radio galaxy PKS 1138-262 at z = 2.156, and we argue that the X-ray emission is from a cluster atmosphere with a luminosity of 1.7x10^{44} h^{-2} ergs sec^{-1}. We also present results on the correlation between size and redshift for a sample of ultra-luminous radio galaxies between 0 < z < 4.3. Source sizes decrease systematically with redshift, suggesting either denser environments, or younger sources, at high redshift. An alternative explanation is significant inverse Compton losses off the microwave background at high redshift.

C. L. Carilli; H. J. A. Rottgering; G. K. Miley L. Pentericci; D. E. Harris

1998-02-18T23:59:59.000Z

55

Galaxy Groups at Intermediate Redshift  

E-Print Network [OSTI]

Galaxy groups likely to be virialized are identified within the CNOC2 intermediate redshift galaxy survey using an iterative method. The number-velocity dispersion relation is in agreement with the low-mass extrapolation of the cluster normalized Press-Schechter function. The two-point group-group correlation function has r_0=6.8+/- 0.3 Mpc, which is larger than the correlations of individual galaxies at the level predicted from n-body calibrated halo clustering. The groups are stacked in velocity and position to create a sample large enough for measurement of a density and velocity dispersion profile. The stacked mean galaxy density profile falls nearly as a power law with r^{-2.5} and has no well-defined core. The projected velocity dispersion is examined for a variety of samples with different methods and found to be either flat or slowly rising outwards. The combination of a steeper-than-isothermal density profile and the outward rising velocity dispersion implies that the mass-to-light ratio of groups rises with radius. The M/L can be kept nearly constant if the galaxy orbits are nearly circular, although such strong tangential anisotropy is not supported by other evidence. The segregation of mass and light is not dependent on galaxy luminosity but is far more prominent in the red galaxies than the blue. The M/L gradient could arise from orbital ``sloshing'' of the galaxies in the group halos, dynamical friction acting on the galaxies in a background of ``classical'' collisionless dark matter, or, more speculatively, the dark matter may have a true core.

R. G. Carlberg; H. K. C. Yee; S. L. Morris; H. Lin; P. B. Hall; D. R. Patton; M. Sawicki; C. W. Shepherd

2000-08-14T23:59:59.000Z

56

Explicit deconvolution of wellbore storage distorted well test data  

E-Print Network [OSTI]

The analysis/interpretation of wellbore storage distorted pressure transient test data remains one of the most significant challenges in well test analysis. Deconvolution (i.e., the "conversion" of a variable-rate distorted pressure profile...

Bahabanian, Olivier

2007-04-25T23:59:59.000Z

57

Thermally induced wave-front distortions in laser windows  

SciTech Connect (OSTI)

A simple analytical expression is given for wave-front distortions and birefringence due to heating in laser windows. (AIP)

Greninger, C.E.

1986-08-01T23:59:59.000Z

58

Is the Time a Dimension of an Alien Universe? (this hypothesis gives an additional redshift)  

E-Print Network [OSTI]

On the base of the hypothesis about a nature of the time as a dimension of alien Universe relation between alteration of time with coordinates $\\frac{\\partial t}{\\partial x}$ and time {t} offered: $ \\frac{\\partial t} {\\partial x} = H_{t} t$ . This relation is an analogy of the Habble law in the time space. The consequence of it is additional redshift $Z_{DT}$ depending on differences $\\tau$ of times existence of the objects with redshift that are compared ($t_{0}$ is the time existence of more old object): $Z_{DT}=\\frac{1+\\frac{\\tau}{t_{0}}}{\\sqrt{1-(\\frac{\\tau}{t_{0}}})^{2}}-1$. The redshift of Arp galaxies may be explained if this relation is used and this explanation doe's not contradict Arp hypothesis about supernova explosions. Discussion a possibilities of experimental verification of the hypothesis is considered.

L. Ya. Kobelev

2000-05-25T23:59:59.000Z

59

Differentiating dark energy and modified gravity with galaxy redshift surveys  

E-Print Network [OSTI]

The observed cosmic acceleration today could be due to an unknown energy component (dark energy), or a modification to general relativity (modified gravity). If dark energy models and modified gravity models are required to predict the same cosmic expansion history H(z), they will predict different growth rate for cosmic large scale structure, f_g(z)=d\\ln \\delta/d\\ln a (\\delta=(\\rho_m-\\bar{\\rho_m})/\\bar{\\rho_m}), a is the cosmic scale factor). If gravity is not modified, the measured H(z) leads to a unique prediction for f_g(z), f_g^H(z). Comparing f_g^H(z) with the measured f_g(z) provides a transparent and straightforward test of gravity. We show that a simple \\chi^2 test provides a general figure-of-merit for our ability to distinguish between dark energy and modified gravity given the measured H(z) and f_g(z). We study a magnitude-limited NIR galaxy redshift survey covering >10,000 (deg)^2 and the redshift range of 0.5dark energy model that predict the same expansion history, a survey area of 11,931 (deg)^2 is required to rule out the DGP gravity model at the 99.99% confidence level. It is feasible for such a galaxy redshift survey to be carried out by the next generation space missions from NASA and ESA, and it will revolutionize our understanding of the universe by differentiating between dark energy and modified gravity.

Yun Wang

2007-10-21T23:59:59.000Z

60

The Properties of Field Elliptical Galaxies at Intermediate Redshift. I: Empirical Scaling Laws  

E-Print Network [OSTI]

We present measurements of the Fundamental Plane (FP) parameters (the effective radius, the mean effective surface brightness, and the central velocity dispersion) of six field elliptical galaxies at intermediate redshift. The imaging is taken from the Medium Deep Survey of the Hubble Space Telescope, while the kinematical data are obtained from long-slit spectroscopy using the 3.6-m ESO telescope. The Fundamental Plane appears well defined in the field even at redshift $\\approx$ 0.3. The data show a shift in the FP zero point with respect to the local relation, possibly indicating modest evolution, consistent with the result found for intermediate redshift cluster samples. The FP slopes derived for our field data, plus other cluster ellipticals at intermediate redshift taken from the literature, differ from the local ones, but are still consistent with the interpretation of the FP as a result of homology, of the virial theorem and of the existence of a relation between luminosity and mass, $L \\propto M^{\\eta}$. We also derive the surface brightness vs. effective radius relation for nine galaxies with redshift up to $z \\approx0.6$, and data from the literature; the evolution that can be inferred is consistent with what is found using the FP.

T. Treu; M. Stiavelli; S. Casertano; P. Møller; G. Bertin

1999-04-23T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

The CNOC2 field galaxy redshift survey  

Science Journals Connector (OSTI)

...0.2 and possibly somewhat lower. 6. Ultra-large-scale power The power spectrum...Measurement of the power spectrum on this ultra-large scale requires a survey that covers...of galaxies around galaxies, with the Mk,e R LCRS and CNOC2 sample at low redshift...

1999-01-01T23:59:59.000Z

62

The 2dF Galaxy Redshift Survey: Spectra and redshifts  

E-Print Network [OSTI]

The 2dF Galaxy Redshift Survey (2dFGRS) is designed to measure redshifts for approximately 250000 galaxies. This paper describes the survey design, the spectroscopic observations, the redshift measurements and the survey database. The 2dFGRS uses the 2dF multi-fibre spectrograph on the Anglo-Australian Telescope, which is capable of observing 400 objects simultaneously over a 2-degree diameter field. The source catalogue for the survey is a revised and extended version of the APM galaxy catalogue, and the targets are galaxies with extinction-corrected magnitudes brighter than b_J=19.45. The main survey regions are two declination strips, one in the southern Galactic hemisphere spanning 80deg x 15deg around the SGP, and the other in the northern Galactic hemisphere spanning 75deg x 10deg along the celestial equator; in addition, there are 99 fields spread over the southern Galactic cap. The survey covers 2000 sq.deg and has a median depth of z=0.11. Adaptive tiling is used to give a highly uniform sampling rate of 93% over the whole survey region. Redshifts are measured from spectra covering 3600A-8000A at a two-pixel resolution of 9.0A and a median S/N of 13 per pixel. All redshift identifications are visually checked and assigned a quality parameter Q in the range 1-5; Q>=3 redshifts are 98.4% reliable and have an rms uncertainty of 85 km/s. The overall redshift completeness for Q>=3 redshifts is 91.8%, but this varies with magnitude from 99% for the brightest galaxies to 90% for objects at the survey limit. The 2dFGRS database is available on the WWW at http://www.mso.anu.edu.au/2dFGRS

Matthew Colless; G. B. Dalton; S. J. Maddox; W. J. Sutherland; P. Norberg; S. Cole; J. Bland-Hawthorn; T. J. Bridges; R. D. Cannon; C. A. Collins; W. J Couch; N. G. J. Cross; K. Deeley; R. DePropris; S. P. Driver; G. Efstathiou; R. S. Ellis; C. S. Frenk; K. Glazebrook; C. A. Jackson; O. Lahav; I. J. Lewis; S. L. Lumsden; D. S. Madgwick; J. A. Peacock; B. A. Peterson; I. A. Price; M. Seaborne; K. Taylor

2001-12-10T23:59:59.000Z

63

Importance of diminished local structural distortions and magnetism...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

from Atoms to Systems Importance of diminished local structural distortions and magnetism in causing iron-based superconductivity September 29, 2014 Figure 1:...

64

REDSHIFT CATALOG FOR SWIFT LONG GAMMA-RAY BURSTS  

SciTech Connect (OSTI)

We present a catalog of the redshifts for most long-duration gamma-ray bursts (GRBs) by Swift from 2004 December 20 to 2008 July 23 (258 bursts in total). All available information is collected, including spectroscopic redshifts, photometric redshift limits, and redshifts calculated from various luminosity relations. Error bars for the redshifts derived from the luminosity relations are asymmetric, with tails extended to the high-redshift end, and this effect is evaluated by looking at the 30% of Swift bursts with spectroscopic redshifts. A simulation is performed to eliminate this asymmetric effect, and the resultant redshift distribution is deconvolved. We test and confirm this simulation on the sample of bursts with known spectroscopic redshifts and then apply it to the 70% of Swift bursts that do not have spectroscopic measures. A final intrinsic redshift distribution is then made for almost all Swift bursts, and the efficiency of the spectroscopic detections is evaluated. The efficiency of spectroscopic redshifts varies from near unity at low redshift to 0.5 at z = 1, to near 0.3 at z = 4, and to 0.1 at z = 6. We also find that the fraction of GRBs with z>5 is {approx}10%, and this fraction is compared with simulations from a cosmological model.

Xiao Limin; Schaefer, Bradley E., E-mail: lxiao1@lsu.edu [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States)

2011-04-20T23:59:59.000Z

65

Redshifts of the Long Gamma-Ray Bursts  

E-Print Network [OSTI]

The low energy spectra of some gamma-ray bursts' show excess components beside the power-law dependence. The consequences of such a feature allows to estimate the gamma photometric redshift of the long gamma-ray bursts in the BATSE Catalog. There is good correlation between the measured optical and the estimated gamma photometric redshifts. The estimated redshift values for the long bright gamma-ray bursts are up to z=4, while for the the faint long bursts - which should be up to z=20 - the redshifts cannot be determined unambiguously with this method. The redshift distribution of all the gamma-ray bursts with known optical redshift agrees quite well with the BATSE based gamma photometric redshift distribution.

Z. Bagoly; I. Csabai; A. Meszaros; P. Meszaros; I. Horvath; L. G. Balazs; R. Vavrek

2007-04-06T23:59:59.000Z

66

TWO NEW TIDALLY DISTORTED WHITE DWARFS  

SciTech Connect (OSTI)

We identify two new tidally distorted white dwarfs (WDs), SDSS J174140.49+652638.7 and J211921.96-001825.8 (hereafter J1741 and J2119). Both stars are extremely low mass (ELM, {<=} 0.2 M{sub Sun }) WDs in short-period, detached binary systems. High-speed photometric observations obtained at the McDonald Observatory reveal ellipsoidal variations and Doppler beaming in both systems; J1741, with a minimum companion mass of 1.1 M{sub Sun }, has one of the strongest Doppler beaming signals ever observed in a binary system (0.59% {+-} 0.06% amplitude). We use the observed ellipsoidal variations to constrain the radius of each WD. For J1741, the star's radius must exceed 0.074 R{sub Sun }. For J2119, the radius exceeds 0.10 R{sub Sun }. These indirect radius measurements are comparable to the radius measurements for the bloated WD companions to A-stars found by the Kepler spacecraft, and they constitute some of the largest radii inferred for any WD. Surprisingly, J1741 also appears to show a 0.23% {+-} 0.06% reflection effect, and we discuss possible sources for this excess heating. Both J1741 and J2119 are strong gravitational wave sources, and the time-of-minimum of the ellipsoidal variations can be used to detect the orbital period decay. This may be possible on a timescale of a decade or less.

Hermes, J. J.; Montgomery, M. H.; Winget, D. E. [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Kilic, Mukremin [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks St., Norman, OK 73019 (United States); Brown, Warren R., E-mail: jjhermes@astro.as.utexas.edu [Smithsonian Astrophysical Observatory, 60 Garden St, Cambridge, MA 02138 (United States)

2012-04-10T23:59:59.000Z

67

The Galaxy Correlation Function in the CNOC2 Redshift Survey: Dependence on Color, Luminosity and Redshift  

E-Print Network [OSTI]

We examine how the spatial correlation function of galaxies from the CNOC2 Field Galaxy Redshift Survey depends on galaxy color, luminosity and redshift. The projected correlation function w_p is determined for volume-limited samples of objects with 0.12 < z < 0.51 and evolution-compensated Rc absolute magnitudes M < -20, over the comoving projected separation range 0.04 Mpc/h < r_p < 10 Mpc/h. Our sample consists of 2937 galaxies which are classified as being either early- or late-type objects according to their spectral energy distribution (SED), determined from UBVRcIc photometry. For simplicity, galaxy SEDs are classified independently of redshift: our classification scheme therefore does not take into account the colour evolution of galaxies.

C. W. Shepherd; R. G. Carlberg; H. K. C. Yee; S. L. Morris; H. Lin; M. Sawicki; P. B. Hall; D. R. Patton

2001-06-14T23:59:59.000Z

68

Variance, Skewness & Kurtosis: results from the APM Cluster Redshift Survey and model predictions  

E-Print Network [OSTI]

We estimate the variance $\\xibar_2$, the skewness $\\xibar_3$ and the kurtosis $\\xibar_4$ in the distribution of density fluctuations in a complete sample from the APM Cluster Redshift Survey with 339 clusters and a mean depth $ \\sim 250\\Mpc$. We are able to measure the statistics of fluctuations in spheres of radius $R \\simeq 5-80 \\Mpc$, with reasonable errorbars. The statistics in the cluster distribution follow the hierarchical pattern $\\xibar_J=S_J~\\xibar_2^{J-1}$ with $S_J$ roughly constant, $S_3 \\simeq 2$ and $S_4 \\sim 8$. We analyse the distribution of clusters taken from N-body simulations of different dark matter models. The results are compared with an alternative method of simulating clusters which uses the truncated Zel'dovich approximation. We argue that this alternative method is not reliable enough for making quantitative predictions of $\\xibar$. The N-body simulation results follow similar hierarchical relations to the observations, with $S_J$ almost unaffected by redshift distortions from peculiar motions. The standard $\\Omega=1$ Cold Dark Matter (CDM) model is inconsistent with either the second, third or fourth order statistics at all scales. However both a hybrid Mixed Dark Matter model and a low density CDM variant agree with the $\\xibar_J$ observations.

Enrique Gaztañaga; Rupert Croft; Gavin Dalton

1995-01-31T23:59:59.000Z

69

A CRITICAL ASSESSMENT OF PHOTOMETRIC REDSHIFT METHODS: A CANDELS INVESTIGATION  

SciTech Connect (OSTI)

We present results from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) photometric redshift methods investigation. In this investigation, the results from 11 participants, each using a different combination of photometric redshift code, template spectral energy distributions (SEDs), and priors, are used to examine the properties of photometric redshifts applied to deep fields with broadband multi-wavelength coverage. The photometry used includes U-band through mid-infrared filters and was derived using the TFIT method. Comparing the results, we find that there is no particular code or set of template SEDs that results in significantly better photometric redshifts compared to others. However, we find that codes producing the lowest scatter and outlier fraction utilize a training sample to optimize photometric redshifts by adding zero-point offsets, template adjusting, or adding extra smoothing errors. These results therefore stress the importance of the training procedure. We find a strong dependence of the photometric redshift accuracy on the signal-to-noise ratio of the photometry. On the other hand, we find a weak dependence of the photometric redshift scatter with redshift and galaxy color. We find that most photometric redshift codes quote redshift errors (e.g., 68% confidence intervals) that are too small compared to that expected from the spectroscopic control sample. We find that all codes show a statistically significant bias in the photometric redshifts. However, the bias is in all cases smaller than the scatter; the latter therefore dominates the errors. Finally, we find that combining results from multiple codes significantly decreases the photometric redshift scatter and outlier fraction. We discuss different ways of combining data to produce accurate photometric redshifts and error estimates.

Dahlen, Tomas; Ferguson, Henry C. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Mobasher, Bahram [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Faber, Sandra M.; Barro, Guillermo; Guo, Yicheng [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Finkelstein, Steven L. [Department of Astronomy, The University of Texas at Austin, Austin, TX 78712 (United States); Finlator, Kristian [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen (Denmark); Fontana, Adriano [INAF-Osservatorio Astronomico di Roma, Via Frascati 33, I-00040, Monteporzio (Italy); Gruetzbauch, Ruth [Center for Astronomy and Astrophysics, Observatorio Astronomico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa (Portugal); Johnson, Seth [Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States); Pforr, Janine; Dickinson, Mark E. [NOAO, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Salvato, Mara; Wuyts, Stijn [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching bei München (Germany); Wiklind, Tommy [Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago (Chile); Acquaviva, Viviana [Physics Department, CUNY NYC College of Technology, 300 Jay Street, Brooklyn, NY 11201 (United States); Huang, Jiasheng [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Huang, Kuang-Han [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Newman, Jeffrey A., E-mail: dahlen@stsci.edu [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States); and others

2013-10-01T23:59:59.000Z

70

ANNz: estimating photometric redshifts using artificial neural networks  

E-Print Network [OSTI]

We introduce ANNz, a freely available software package for photometric redshift estimation using Artificial Neural Networks. ANNz learns the relation between photometry and redshift from an appropriate training set of galaxies for which the redshift is already known. Where a large and representative training set is available ANNz is a highly competitive tool when compared with traditional template-fitting methods. The ANNz package is demonstrated on the Sloan Digital Sky Survey Data Release 1, and for this particular data set the r.m.s. redshift error in the range 0 < z < 0.7 is 0.023. Non-ideal conditions (spectroscopic sets which are small, or which are brighter than the photometric set for which redshifts are required) are simulated and the impact on the photometric redshift accuracy assessed.

Adrian A. Collister; Ofer Lahav

2003-11-03T23:59:59.000Z

71

The CNOC2 Field Galaxy Redshift Survey  

E-Print Network [OSTI]

The CNOC2 field galaxy redshift survey is designed to provide measurements of the evolution of galaxies and their clustering over the redshift range 0 to 0.7. The sample is spread over four sky patches with a total area of about 1.5 square degrees. Here we report preliminary results based on two of the sky patches, and the redshift range of 0.15 to 0.55. We find that galaxy evolution can be statistically described as nearly pure luminosity evolution of early and intermediate SED types, and nearly pure density evolution of the late SED types. The correlation of blue galaxies relative to red galaxies is similar on large scales but drops by a factor of three on scales less than about 0.3/h mpc, approximately the mean scale of virialization. There is a clear, but small, 60%, change in clustering with 1.4 mag of luminosity. To minimize these population effects in our measurement of clustering evolution, we choose galaxies with M_r^{k,e}<= -20 mag as a population whose members are most likely to be conserved with redshift. Remarkably, the evolution of the clustered density in proper co-ordinates at r < 10/h Mpc, proportional to r_0^gamma (1+z)^3, is best described as a ``de-clustering'', (1+z)^{0.6+/-0.4}. Or equivalently, there is a weak growth of clustering in co-moving co-ordinates, x_0~ (1+z)^{-0.3 +/- 0.2}. This conclusion is supported by the pairwise peculiar velocities which rise slightly, but not significantly, into the past. The Cosmic Virial Theorem applied to the CNOC2 data gives Q Omega_M/b=0.11 +/- 0.04$, where Q is the three point correlation parameter and b the bias. Similarly, galaxy groups have a virial mass-to-light ratio (evolution corrected) of M_{virial}/L_R^{k,e} = 215h Lsun/Msun, or Omega_M=0.15 +/- 0.05.

R. G. Carlberg; H. K. C. Yee; S. L Morris; H. Lin; M. Sawicki; G. Wirth; D. Patton; C. W. Shepherd; E. Ellingson; D. Schade; C. J. Pritchet; F. D. A. Hartwick

1998-05-11T23:59:59.000Z

72

The DEEP2 Galaxy Redshift Survey: The Voronoi-Delaunay Method Catalog of Galaxy Groups  

SciTech Connect (OSTI)

We use the first 25% of the DEEP2 Galaxy Redshift Survey spectroscopic data to identify groups and clusters of galaxies in redshift space. The data set contains 8370 galaxies with confirmed redshifts in the range 0.7 {<=} z {<=} 1.4, over one square degree on the sky. Groups are identified using an algorithm (the Voronoi-Delaunay Method) that has been shown to accurately reproduce the statistics of groups in simulated DEEP2-like samples. We optimize this algorithm for the DEEP2 survey by applying it to realistic mock galaxy catalogs and assessing the results using a stringent set of criteria for measuring group-finding success, which we develop and describe in detail here. We find in particular that the group-finder can successfully identify {approx}78% of real groups and that {approx}79% of the galaxies that are true members of groups can be identified as such. Conversely, we estimate that {approx}55% of the groups we find can be definitively identified with real groups and that {approx}46% of the galaxies we place into groups are interloper field galaxies. Most importantly, we find that it is possible to measure the distribution of groups in redshift and velocity dispersion, n({sigma}, z), to an accuracy limited by cosmic variance, for dispersions greater than 350 km s{sup -1}. We anticipate that such measurements will allow strong constraints to be placed on the equation of state of the dark energy in the future. Finally, we present the first DEEP2 group catalog, which assigns 32% of the galaxies to 899 distinct groups with two or more members, 153 of which have velocity dispersions above 350 km s{sup -1}. We provide locations, redshifts and properties for this high-dispersion subsample. This catalog represents the largest sample to date of spectroscopically detected groups at z {approx} 1.

Gerke, Brian F.; /UC, Berkeley; Newman, Jeffrey A.; /LBNL, NSD; Davis, Marc; /UC, Berkeley /UC, Berkeley, Astron.Dept.; Marinoni, Christian; /Brera Observ.; Yan, Renbin; Coil, Alison L.; Conroy, Charlie; Cooper, Michael C.; /UC, Berkeley, Astron.Dept.; Faber, S.M.; /Lick Observ.; Finkbeiner, Douglas P.; /Princeton U. Observ.; Guhathakurta, Puragra; /Lick Observ.; Kaiser, Nick; /Hawaii U.; Koo, David C.; Phillips, Andrew C.; /Lick Observ.; Weiner, Benjamin J.; /Maryland U.

2012-02-14T23:59:59.000Z

73

Is there a maximum observable redshift in an open universe?  

E-Print Network [OSTI]

An estimate of the maximum observable redshift is obtained using only t_{0} approximately equal to (14+- 3)10^{9}years, H_{0} approximately equal to 65 +- 10Km\\sec^{-1}Mpc^{-1}(t_{0}H_{0} approximately equal to 0.91 +- 0.08/0.18) assuming \\Lambda approximately equal to 0. The resulting maximum redshift z_{+} approximately equal to 10 appears to give a reasonable upper limit to the highest actually observed redshifts. Some implications are discussed.

J. A. Gonzalo

2000-10-10T23:59:59.000Z

74

The 2dF Galaxy Redshift Survey: A targeted study of catalogued clusters of galaxies  

E-Print Network [OSTI]

We have carried out a study of known clusters within the 2dF Galaxy Redshift Survey (2dFGRS) observed areas and have identified 431 Abell, 173 APM and 343 EDCC clusters. Precise redshifts, velocity dispersions and new centroids have been measured for the majority of these objects, and this information has been used to study the completeness of these catalogues, the level of contamination from foreground and background structures along the cluster's line of sight, the space density of the clusters as a function of redshift, and their velocity dispersion distributions. We find that the Abell and EDCC catalogues are contaminated at the level of about 10%, whereas the APM catalogue suffers only 5% contamination. If we use the original catalog centroids, the level of contamination rises to approximately 15% for the Abell and EDCC catalogues, showing that the presence of foreground and background groups may alter the richness of clusters in these catalogues. There is a deficiency of clusters at $z \\sim 0.05$ that may correspond to a large underdensity in the Southern hemisphere. From the cumulative distribution of velocity dispersions for these clusters, we derive an upper limit to the space density of $\\sigma > 1000 \\kms$ clusters of $3.6 \\times 10^{-6} \\hdens$. This result is used to constrain models for structure formation; our data favour low-density cosmologies, subject to the usual assumptions concerning the shape and normalization of the power spectrum.

Roberto De Propris; Warrick Couch; Matthew Colless; Gavin Dalton; Chris Collins; Carlton Baugh; Joss-Bland-Hawthorn; Terry Bridges; Russell Cannon; Shaun Cole; Nicholas Cross; Kathryn Deeley; Simon Driver; George Efstathiou; Richard Ellis; Carlos Frenk; Kark Glazebrook; Carole Jackson; ofer Lahav; Ian Lewis; Stuart Lumsden; Steve Maddox; Darren Madgwick; Stephen Moody; Peder Norberg; John Peacock; Will Percival; Bruce Peterson; Will Sutherland; Keith Taylor

2002-02-06T23:59:59.000Z

75

The 2dF Galaxy Redshift Survey: The bias of galaxies and the density of the Universe  

E-Print Network [OSTI]

We compute the bispectrum of the 2dF Galaxy Redshift Survey (2dFGRS) and use it to measure the bias parameter of the galaxies. This parameter quantifies the strength of clustering of the galaxies relative to the mass in the Universe. By analysing 80 million triangle configurations in the wavenumber range 0.1 < k < 0.5 h/Mpc (i.e. on scales roughly between 5 and 30 Mpc/h) we find that the linear bias parameter is consistent with unity: b_1=1.04 pm 0.11, and the quadratic (nonlinear) bias is consistent with zero: b_2=-0.054 pm 0.08. Thus, at least on large scales, optically-selected galaxies do indeed trace the underlying mass distribution. The bias parameter can be combined with the 2dFGRS measurement of the redshift distortion parameter beta = Omega_m^{0.6}/b_1, to yield Omega_m = 0.27 pm 0.06 for the matter density of the Universe, a result which is determined entirely from this survey, independently of other datasets. Our measurement of the matter density of the Universe should be interpreted as Omega_m at the effective redshift of the survey (z=0.17).

Licia Verde; Alan F. Heavens; Will J. Percival; Sabino Matarrese; C. M. Baugh; J. Bland-Hawthorn; T. Bridges; R. Cannon; S. Cole; M. Colless; C. Collins; W. Couch; G. Dalton; R. De Propris; S. P. Driver; G. Efstathiou; R. S. Ellis; C. S. Frenk; K. Glazebrook; C. Jackson; O. Lahav; I. Lewis; S. Lumsden; S. Maddox; D. S. Madgwick; P. Norberg; J. A. Peacock; B. A. Peterson; W. Sutherland; K. Taylor

2002-05-01T23:59:59.000Z

76

Equivalent Circuit Analysis of Harmonic Distortions in Photodiode  

E-Print Network [OSTI]

and C. Boisrobert, “Photodiode for coherent detection:Harmonic Distortions in Photodiode H. Jiang and P. K. L. Yu,coef?cient S 11 of the photodiode under dc illumination.

Yu, Paul K.L.

1998-01-01T23:59:59.000Z

77

Power factor and harmonic distortion characteristics of energy efficient lamps  

SciTech Connect (OSTI)

This paper evaluates the performance of a new class of lamps which are generally classified as the energy-saving lamps. It is shown that, when compared with the incandescent lamps, these lamps indeed consume less real power and have higher relative illumination. However, the energy-saving lamps operate at a low power factor and produce current distortion which are much higher than the distortion produced by the traditional incandescent lamps.

Etezadi-Amoli, M.; Florence, T.

1989-07-01T23:59:59.000Z

78

Redshift drift exploration for interacting dark energy  

E-Print Network [OSTI]

By detecting redshift drift in the spectra of Lyman-$\\alpha$ forest of distant quasars, Sandage-Loeb (SL) test directly measures the expansion of the universe, covering the "redshift desert" of $2 \\lesssim z \\lesssim5$. Thus this method is definitely an important supplement to the other geometric measurements and will play a crucial role in cosmological constraints. In this paper, we quantify the ability of SL test signal by a CODEX-like spectrograph for constraining interacting dark energy. Four typical interacting dark energy models are considered: (\\romannumeral1) $Q=\\gamma H\\rho_c$, (\\romannumeral2) $Q=\\gamma H\\rho_{de}$, (\\romannumeral3) $Q=\\gamma H_0\\rho_c$, and (\\romannumeral4) $Q=\\gamma H_0\\rho_{de}$. The results show that for all the considered interacting dark energy models, relative to the current joint SN+BAO+CMB+$H_0$ observations, the constraints on $\\Omega_m$ and $H_0$ would be improved by about 60\\% and 30--40\\%, while the constraints on $w$ and $\\gamma$ would be slightly improved, with a 30-y...

Geng, Jia-Jia; Zhang, Jing-Fei; Zhang, Xin

2015-01-01T23:59:59.000Z

79

DISCOVERY OF A QUADRUPLE LENS IN CANDELS WITH A RECORD LENS REDSHIFT z = 1.53  

SciTech Connect (OSTI)

Using spectroscopy from the Large Binocular Telescope and imaging from the Hubble Space Telescope we discovered the first strong galaxy lens at z {sub lens} > 1. The lens has a secure photometric redshift of z = 1.53 ± 0.09 and the source is spectroscopically confirmed at z = 3.417. The Einstein radius (0.''35; 3.0 kpc) encloses 7.6 × 10{sup 10} M {sub ?}, with an upper limit on the dark matter fraction of 60%. The highly magnified (40×) source galaxy has a very small stellar mass (?10{sup 8} M {sub ?}) and shows an extremely strong [O III]{sub 5007Å} emission line (EW{sub 0} ? 1000 Å) bolstering the evidence that intense starbursts among very low-mass galaxies are common at high redshift.

Van der Wel, A.; Van de Ven, G.; Maseda, M.; Rix, H. W.; Rudnick, G. H. [Max-Planck Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany)] [Max-Planck Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Grazian, A. [INAF - Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio (Italy)] [INAF - Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio (Italy); Finkelstein, S. L. [George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States)] [George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States); Koo, D. C.; Faber, S. M. [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)] [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Ferguson, H. C.; Koekemoer, A. M.; Grogin, N. A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)] [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Kocevski, D. D., E-mail: vdwel@mpia.de [Department of Physics and Astronomy, University of Kentucky, 505 Rose Street, Lexington, KY 40506 (United States)

2013-11-01T23:59:59.000Z

80

Calibrating Redshift Distributions Beyond Spectroscopic Limits with Cross-Correlations  

E-Print Network [OSTI]

We describe a new method for measuring the true redshift distribution of any set of objects studied only photometrically. The angular cross-correlation between objects in a photometric sample with objects in some spectroscopic sample as a function of the spectroscopic z, in combination with standard correlation measurements, provides sufficient information to reconstruct the true redshift distribution of the photometric sample. This technique enables the robust calibration of photometric redshifts even beyond spectroscopic limits. The spectroscopic sample need not resemble the photometric one in galaxy properties, but must overlap in sky coverage and redshift range. We test this new technique with Monte Carlo simulations using realistic error estimates. RMS errors in recovering both the mean and sigma of the true, Gaussian redshift distribution of a single photometric redshift bin are 1.4x10^(-3) (sigma_z/0.1) (Sigma_p/10)^(-0.3) (dN_s/dz / 25,000)^(-0.5), where sigma_z is the true sigma of the redshift distribution, Sigma_p is the surface density of the photometric sample in galaxies/arcmin^2, and dN_s/dz is the number of galaxies with a spectroscopic redshift per unit z. We test the impact of redshift outliers and of a variety of sources of systematic error; none dominate measurement uncertainties in reasonable scenarios. With this method, the true redshift distributions of even arbitrarily faint photometric redshift samples may be determined to the precision required by proposed dark energy experiments (errors in mean and sigma below 3x10^(-3) at z~1) using expected extensions of current spectroscopic samples.

Jeffrey A. Newman

2008-05-09T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

The Two-Point Correlation Function at Redshift 1/3  

E-Print Network [OSTI]

We present the results of a study of the two-point correlation function for a sample of field galaxies taken from the CNOCI cluster survey. The sample consists of 144 galaxies within a contiguous region of space subtending 225 square arcminutes. The objects have r-band magnitudes 17.0 < r < 21.7 and redshifts 0.21 < z < 0.53. The median redshift of the sample is 0.36. The real space correlation function is found to be consistent with a power law \\xi(r) = (r/r_0)^-1.7 with r_0 = 2.1 +0.6/-0.3 (\\Omega_0=1), or r_0 = 2.5 +0.7/-0.4 (\\Omega_0=0.2). Uncertainties are estimated using the bias-corrected bootstrap resampling method, with 300 resamplings. This low correlation length implies strong evolution since z~0.36 has occurred in either the correlation function or the luminosity function; if the observed correlation function is modeled as \\xi(r,z) = \\xi(r,0) * (1+z)^-(3+\\epsilon) with \\xi(r,0) = (r/5.1 h^-1Mpc)^-1.7, then \\epsilon = 0.8 +1.0/-1.3. Comparison of the redshift space and real space correlation function indicates that the one-dimensional pairwise peculiar velocity dispersion \\sigma at z~0.36 is weakly inconsistent with 770 km s^-1, the value predicted by the Cosmic Virial Theorem if \\Omega_0=1. The observed correlation function is, however, consistent with \\sigma=400 km s^-1, the value expected if \\Omega_0=0.2.

C. W. Shepherd; R. G. Carlberg; H. K. C. Yee; E. Ellingson

1996-01-04T23:59:59.000Z

82

The AAO 2dF QSO Redshift Survey  

E-Print Network [OSTI]

We describe the aims, strategy and status of the AAO 2dF QSO redshift survey. This goal of the survey is to obtain redshifts for 30000 QSOs in a homogeneous magnitude limited (B<21) survey. The survey began in early 1997 and should be complete by the end of 1999.

Boyle; R. J. Smith; T. Shanks; S. M. Croom; L. Miller

1997-10-20T23:59:59.000Z

83

On the Nature and Redshift Evolution of DLA Galaxies  

E-Print Network [OSTI]

We extend our spiral galaxy models that successfully describe nearby template spectra as well as the redshift evolution of CFRS and HDF spirals to include - in a chemically consistent way - the redshift evolution of a series of individual elements. Comparison with observed DLA abundances shows that DLAs might well be the progenitors of present-day spiral types Sa through Sd. Our models bridge the gap between high redshift DLA and nearby spiral HII region abundances. The slow redshift evolution of DLA abundances is a natural consequence of the long SF timescales for disks, the scatter at any redshift reflects the range of SF timescales from early to late spiral types. We claim that while at high redshift all spiral progenitor types seem to give rise to DLA absorption, towards low redshifts, the early type spirals seem to drop out of DLA samples due to low gas and/or high metal and dust content. Model implications for the spectrophotometric properties of the DLA galaxy population are discussed in the context of campaigns for the optical identifications of DLA galaxies both at low and high redshift.

U. Fritze-v. Alvensleben; U. Lindner; C. S. Möller; K. J. Fricke

1999-04-16T23:59:59.000Z

84

Photometric Redshift Determination with the BATC Multicolor System  

E-Print Network [OSTI]

In this paper, we present the methodology of photometric redshift determination with the BATC 15-color system by using hyperz program. Both simulated galaxies and real galaxies with known redshifts were used to estimate the accuracy of redshifts inferred from the multicolor photometry. From the test with simulated galaxies, the uncertainty in the inferred redshifts is about $0.02\\sim0.03$ for a given range of photometric uncertainty of $0.05 \\sim 0.10$. The results with the 27 real galaxies are in good agreement with the simulated ones. The advantage of using BATC intermediate-band system to derive redshift is clear through the comparison with the UBVRI broad-band system. The accuracy in redshift determination with BATC system is mainly affected by the selection of filters and the photometric uncertainties in the observation. When we take the limiting magnitudes of the 15 filters into account, we find that redshift can be determined with good accuracy for galaxies with redshifts less than 0.5, using only filt...

Xia, L; Ma, J; Wu, H; Sun, W H; Jiang, Z; Xue, S; Chen, J; Chen, W; Xia, Lifang; Zhou, Xu; Ma, Jun; Wu, Hong; Sun, Wei-Hsin; Jiang, Zhaoji; Xue, Suijian; Chen, Jiansheng; Chen, Wenping

2002-01-01T23:59:59.000Z

85

Effects of cosmological model assumptions on galaxy redshift survey measurements  

Science Journals Connector (OSTI)

......observations|dark energy|distance scale...Galaxy redshift surveys will become an...redshifts over which dark energy dominates, according...precision that these surveys will achieve...mission to study dark energy through an imaging survey of galaxy shapes......

Lado Samushia; Will J. Percival; Luigi Guzzo; Yun Wang; Andrea Cimatti; Carlton Baugh; James E. Geach; Cedric Lacey; Elisabetta Majerotto; Pia Mukherjee; Alvaro Orsi

2011-01-21T23:59:59.000Z

86

The environment of low-redshift quasar pairs  

Science Journals Connector (OSTI)

......2014 research-article Article The environment of low-redshift quasar pairs A. Sandrinelli...investigate the properties of the galaxy environment of a sample of 14 low-redshift (z...separation does not require any extraordinary environment. galaxies: clusters: general|quasars......

A. Sandrinelli; R. Falomo; A. Treves; E. P. Farina; M. Uslenghi

2014-01-01T23:59:59.000Z

87

Angular Size-Redshift: Experiment and Calculation  

E-Print Network [OSTI]

In this paper the next attempt is made to clarify the nature of the Euclidean behavior of the boundary in the angular size-redshift cosmological test. It is shown experimentally that this can be explained by the selection determined by anisotropic morphology and anisotropic radiation of extended radio sources. A catalogue of extended radio sources with minimal flux densities of about 0.01 Jy at 1.4 GHz was compiled for conducting the test. Without the assumption of their size evolution, the agreement between the experiment and calculation was obtained both in the Lambda CDM model (Omega_m=0.27 , Omega_v=0.73.) and the Friedman model (Omega = 0.1 ).

Amirkhanyan, V R

2015-01-01T23:59:59.000Z

88

Atomic and Molecular Absorption at High Redshift  

E-Print Network [OSTI]

Strong constraints on possible variations in fundamental constants can be derived from HI 21-cm and molecular rotational absorption lines observed towards quasars. With the aim of forming a statistical sample of constraints we have begun a program of systematic searches for such absorption systems. Here we describe molecular rotational searches in 25 damped Lyman-alpha systems where, in many cases, we set optical depth limits an order of magnitude better than that required to detect the 4 known redshifted millimeter-wave absorbers. We also discuss the contributory factors in the detectability of HI 21-cm absorption, focusing on possible biases (e.g.low covering factors) in the currently known sample of absorbers and non-detections.

S. J. Curran; J. K. Webb; M. T. Murphy; Y. M. Pihlström

2004-05-14T23:59:59.000Z

89

The Redshift Distribution of Flat-Spectrum Radio Sources  

E-Print Network [OSTI]

The redshift distribution of flat-spectrum radio sources with 5 GHz flux densities S>5 mJy is a key component in using current radio lens surveys to probe the cosmological model. We have constructed the first flat-spectrum radio sample in the flux density range 3-20 mJy. Our new sample has 33 sources; we have determined the redshifts of 14 of these (42% complete). The low mean redshift, ~0.75, of our faintest sample needs to be confirmed by further observations to improve the sample completeness. We also increased the redshift completeness of several surveys of brighter flat-spectrum sources. While the mean redshift, ~1.1 of flat-spectrum samples fainter than 1 Jy is nearly constant, the fraction of the sources identifiable as quasars steadily drops from ~80% to ~10% as the flux density of the sources decreases.

J. A. Munoz; E. E. Falco; C. S. Kochanek; J. Lehar; E. Mediavilla

2003-05-20T23:59:59.000Z

90

Doping evolution of antiferromagnetic order and structural distortion in LaFeAsO{sub 1-x}F{sub x}  

SciTech Connect (OSTI)

We use neutron scattering to study the structural distortion and antiferromagnetic (AFM) order in LaFeAsO{sub 1-x}F{sub x} as the system is doped with fluorine (F) to induce superconductivity. In the undoped state, LaFeAsO exhibits a structural distortion, changing the symmetry from tetragonal (space group P4/nmm) to orthorhombic (space group Cmma) at 155 K, and then followed by an AFM order at 137 K. Doping the system with F gradually decreases the structural distortion temperature, but suppresses the long range AFM order before the emergence of superconductivity. Therefore, while superconductivity in these Fe oxypnictides can survive in either the tetragonal or the orthorhombic crystal structure, it competes directly with static AFM order.

Huang, Q.; Lynn, J. W. [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102 (United States); Zhao Jun [Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996-1200 (United States); Chen, G. F.; Luo, J. L.; Wang, N. L. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100080 (China); Dai Pengcheng [Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996-1200 (United States); Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393 (United States)

2008-08-01T23:59:59.000Z

91

THE DISCOVERY OF THE MOST DISTANT KNOWN TYPE Ia SUPERNOVA AT REDSHIFT 1.914  

SciTech Connect (OSTI)

We present the discovery of a Type Ia supernova (SN) at redshift z = 1.914 from the CANDELS multi-cycle treasury program on the Hubble Space Telescope (HST). This SN was discovered in the infrared using the Wide-Field Camera 3, and it is the highest-redshift Type Ia SN yet observed. We classify this object as a SN Ia by comparing its light curve and spectrum with those of a large sample of Type Ia and core-collapse SNe. Its apparent magnitude is consistent with that expected from the {Lambda}CDM concordance cosmology. We discuss the use of spectral evidence for classification of z > 1.5 SNe Ia using HST grism simulations, finding that spectral data alone can frequently rule out SNe II, but distinguishing between SNe Ia and SNe Ib/c can require prohibitively long exposures. In such cases, a quantitative analysis of the light curve may be necessary for classification. Our photometric and spectroscopic classification methods can aid the determination of SN rates and cosmological parameters from the full high-redshift CANDELS SN sample.

Jones, David O.; Rodney, Steven A.; Riess, Adam G. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Mobasher, Bahram [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Dahlen, Tomas; Casertano, Stefano; Koekemoer, Anton [Space Telescope Science Institute, Baltimore, MD 21218 (United States); McCully, Curtis; Keeton, Charles R.; Patel, Brandon [Department of Physics and Astronomy, Rutgers, State University of New Jersey, Piscataway, NJ 08854 (United States); Frederiksen, Teddy F.; Hjorth, Jens [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Strolger, Louis-Gregory [Department of Physics, Western Kentucky University, Bowling Green, KY 42101 (United States); Wiklind, Tommy G. [Joint ALMA Observatory, ESO, Santiago (Chile); Challis, Peter [Harvard/Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Graur, Or [School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978 (Israel); Hayden, Brian; Garnavich, Peter [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Weiner, Benjamin J. [Department of Astronomy, University of Arizona, Tucson, AZ 85721 (United States); Filippenko, Alexei V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); and others

2013-05-10T23:59:59.000Z

92

Photometric redshift analysis in the Dark Energy Survey Science Verification data  

E-Print Network [OSTI]

We present results from a study of the photometric redshift performance of the Dark Energy Survey (DES), using the early data from a Science Verification (SV) period of observations in late 2012 and early 2013 that provided science-quality images for almost 200 sq.~deg.~at the nominal depth of the survey. We assess the photometric redshift performance using about 15000 galaxies with spectroscopic redshifts available from other surveys. These galaxies are used, in different configurations, as a calibration sample, and photo-$z$'s are obtained and studied using most of the existing photo-$z$ codes. A weighting method in a multi-dimensional color-magnitude space is applied to the spectroscopic sample in order to evaluate the photo-$z$ performance with sets that mimic the full DES photometric sample, which is on average significantly deeper than the calibration sample due to the limited depth of spectroscopic surveys. Empirical photo-$z$ methods using, for instance, Artificial Neural Networks or Random Forests, y...

Sánchez, C; Lin, H; Miquel, R; Abdalla, F B; Amara, A; Banerji, M; Bonnett, C; Brunner, R; Capozzi, D; Carnero, A; Castander, F J; da Costa, L A N; Cunha, C; Fausti, A; Gerdes, D; Greisel, N; Gschwend, J; Hartley, W; Jouvel, S; Lahav, O; Lima, M; Maia, M A G; Martí, P; Ogando, R L C; Ostrovski, F; Pellegrini, P; Rau, M M; Sadeh, I; Seitz, S; Sevilla-Noarbe, I; Sypniewski, A; de Vicente, J; Abbot, T; Allam, S S; Atlee, D; Bernstein, G; Bernstein, J P; Buckley-Geer, E; Burke, D; Childress, M J; Davis, T; DePoy, D L; Dey, A; Desai, S; Diehl, H T; Doel, P; Estrada, J; Evrard, A; Fernández, E; Finley, D; Flaugher, B; Gaztanaga, E; Glazebrook, K; Honscheid, K; Kim, A; Kuehn, K; Kuropatkin, N; Lidman, C; Makler, M; Marshall, J L; Nichol, R C; Roodman, A; Sánchez, E; Santiago, B X; Sako, M; Scalzo, R; Smith, R C; Swanson, M E C; Tarle, G; Thomas, D; Tucker, D L; Uddin, S A; Valdés, F; Walker, A; Yuan, F; Zuntz, J

2014-01-01T23:59:59.000Z

93

ALMA REDSHIFTS OF MILLIMETER-SELECTED GALAXIES FROM THE SPT SURVEY: THE REDSHIFT DISTRIBUTION OF DUSTY STAR-FORMING GALAXIES  

SciTech Connect (OSTI)

Using the Atacama Large Millimeter/submillimeter Array, we have conducted a blind redshift survey in the 3 mm atmospheric transmission window for 26 strongly lensed dusty star-forming galaxies (DSFGs) selected with the South Pole Telescope. The sources were selected to have S{sub 1.4{sub mm}} > 20 mJy and a dust-like spectrum and, to remove low-z sources, not have bright radio (S{sub 843{sub MHz}} < 6 mJy) or far-infrared counterparts (S{sub 100{sub {mu}m}} < 1 Jy, S{sub 60{sub {mu}m}} < 200 mJy). We robustly detect 44 line features in our survey, which we identify as redshifted emission lines of {sup 12}CO, {sup 13}CO, C I, H{sub 2}O, and H{sub 2}O{sup +}. We find one or more spectral features in 23 sources yielding a {approx}90% detection rate for this survey; in 12 of these sources we detect multiple lines, while in 11 sources we detect only a single line. For the sources with only one detected line, we break the redshift degeneracy with additional spectroscopic observations if available, or infer the most likely line identification based on photometric data. This yields secure redshifts for {approx}70% of the sample. The three sources with no lines detected are tentatively placed in the redshift desert between 1.7 < z < 2.0. The resulting mean redshift of our sample is z-bar = 3.5. This finding is in contrast to the redshift distribution of radio-identified DSFGs, which have a significantly lower mean redshift of z-bar = 2.3 and for which only 10%-15% of the population is expected to be at z > 3. We discuss the effect of gravitational lensing on the redshift distribution and compare our measured redshift distribution to that of models in the literature.

Weiss, A. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany)] [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); De Breuck, C.; Aravena, M.; Biggs, A. D. [European Southern Observatory, Karl-Schwarzschild Strasse, D-85748 Garching bei Muenchen (Germany)] [European Southern Observatory, Karl-Schwarzschild Strasse, D-85748 Garching bei Muenchen (Germany); Marrone, D. P.; Bothwell, M. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)] [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Vieira, J. D.; Bock, J. J. [California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States)] [California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Aguirre, J. E. [University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States)] [University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Aird, K. A. [University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)] [University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Ashby, M. L. N.; Bayliss, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)] [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L. [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)] [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Bethermin, M. [Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu - CNRS - Universite Paris Diderot, CEA-Saclay, Orme des Merisiers, F-91191 Gif-sur-Yvette (France)] [Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu - CNRS - Universite Paris Diderot, CEA-Saclay, Orme des Merisiers, F-91191 Gif-sur-Yvette (France); Bradford, C. M. [Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)] [Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Brodwin, M. [Department of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States)] [Department of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States); Chapman, S. C. [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 3J5 Canada (Canada)] [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 3J5 Canada (Canada); and others

2013-04-10T23:59:59.000Z

94

The Distortion of the Hexagonal Close Packing of Oxygen Atoms in Co(OH)2 Compared to Isotypic Brucite-Type Structures  

Science Journals Connector (OSTI)

?A refinement of the crystal structure of Co(OH)2 (structure type brucite; a=3.186(1), c=4.653(1) Å; space group P;m1) is the basis for crystal chemical considerations about distortions of the MeO6 octahedra and ...

Franz Pertlik

1999-09-01T23:59:59.000Z

95

Earth-to-deep-space optical communications system with adaptive tilt and scintillation correction by use of near-Earth relay mirrors  

Science Journals Connector (OSTI)

Performance of an Earth-to-deep-space optical telecommunications system is degraded by distortion of the beam as it propagates through the turbulent atmosphere. Conventional approaches...

Armstrong, J W; Yeh, C; Wilson, K E

1998-01-01T23:59:59.000Z

96

Investigation of distortional buckling of cold-formed steel sections  

E-Print Network [OSTI]

Investigation of distortional buckling of cold-formed steel sections Researcher: Chong Ren Supervisors: Dr Long-yuan Li Dr Jian Yang Aims and Objectives Thin-walled, cold-formed steel sections considered to be the most popular products and account for a substantial proportion of cold-formed steel

Birmingham, University of

97

Spectral distortions from the dissipation of tensor perturbations  

E-Print Network [OSTI]

Spectral distortions of the cosmic microwave background (CMB) may become a powerful probe of primordial perturbations at small scales. Existing studies of spectral distortions focus almost exclusively on primordial scalar metric perturbations. Similarly, vector and tensor perturbations should source CMB spectral distortions. In this paper, we give general expressions for the effective heating rate caused by these types of perturbations, including previously neglected contributions from polarization states and higher multipoles. We then focus our discussion on the dissipation of tensors, showing that for nearly scale invariant tensor power spectra, the overall distortion is some six orders of magnitudes smaller than from the damping of adiabatic scalar modes. We find simple analytic expressions describing the effective heating rate from tensors using a quasi-tight coupling approximation. In contrast to adiabatic modes, tensors cause heating without additional photon diffusion and thus over a wider range of scales, as recently pointed out by Ota et. al 2014. Our results are in broad agreement with their conclusions, but we find that small-scale modes beyond kpower spectra. At small scales, also the effect of neutrino damping on the tensor amplitude needs to be included.

Jens Chluba; Liang Dai; Daniel Grin; Mustafa A. Amin; Marc Kamionkowski

2014-11-13T23:59:59.000Z

98

Distortion risk measures, ambiguity aversion and optimal effort  

E-Print Network [OSTI]

as the amount of money that should be added as a buffer to a risk so that it becomes acceptable to an internalDistortion risk measures, ambiguity aversion and optimal effort Christian Y. ROBERT & Pierre E distribution that is used to evaluate risk measures. Almost all models used in the theory of risk measures

Maume-Deschamps, Véronique

99

Harmonic Distortion Analysis via Perturbation K. Odame, P. E. Hasler  

E-Print Network [OSTI]

Harmonic Distortion Analysis via Perturbation Methods K. Odame, P. E. Hasler School of Electrical series analysis. This paper describes some elementary results that come from applying perturbation, is modeled by h(x). In practice, h(x) is typically some non-ideality such as finite output resistance

Odam, Kofi

100

Compact Groups of Galaxies in the Las Campanas Redshift Survey  

E-Print Network [OSTI]

We have recently extracted a catalog of compact groups of galaxies (CGs) from the Las Campanas Redshift Survey. This catalog of Las Campanas Compact Groups (LCCGs) contains 76 CGs with a median redshift of z_med = 0.08. The physical properties of these CGs are similar to those from the Hickson (1982) and the Barton et al. (1996) catalogs. Here, we present an atlas of our catalog and briefly describe its general properties.

S. S. Allam; D. L. Tucker

2000-06-12T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

Sheath-induced distortions in particle distributions near enhanced polar outflow probe particle sensors  

SciTech Connect (OSTI)

We discuss sheath and kinetic effects on ion and electron distribution functions at the aperture of enhanced Polar Outflow Probe particle sensors. For this purpose, the interaction between the CASSIOPE spacecraft and space environment is simulated fully kinetically using the electrostatic Particle In Cell code PTetra. The simulations account for the geometry of the main features of the spacecraft body, the booms, and the sensors. In addition to the background plasma, the model also accounts for Earth magnetic field. The plasma parameters assumed in the simulations are obtained from the latest version of the International Reference Ionosphere (IRI) model and the value of magnetic field is obtained from the International Geophysical Reference Field model. Our analysis shows significant distortions in the ion distribution function in the plane of the sensor aperture, as well as in the direction along the boom holding the sensor. We argue that significant distortions and asymmetries should also occur at the aperture of the suprathermal electron imager when suprathermal electrons are detected, with energies of 5?eV or more.

Hussain, S. [Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2E1 (Canada); Theoretical Physics Division, PINSTECH, Nilore, Islamabad (Pakistan); Department of Physics and Applied Mathematics, PIEAS, Nilore, Islamabad (Pakistan); Marchand, R. [Department of Physics, University of Alberta, Edmonton, T6G 2E1 Alberta (Canada)

2014-07-15T23:59:59.000Z

102

 

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

model of redshift space distortions worthy of BOSS data model of redshift space distortions worthy of BOSS data Beth Reid (LBNL) Abstract: Interest in using redshift space distortions (RSD) as a precise test of General Relativity on large scales has exploded in the last few years, but our theoretical models must be improved to match the statistical precision of current data. In this talk I will review of physics of redshift space distortions in configuration space and present projections for RSD constraints from the BOSS survey. While many recent studies focus on understanding dark matter clustering in redshift space, galaxies occupy special places in the universe: dark matter halos. Our model reproduces the complex dependence of redshift space clustering on halo bias seen in N-body simulations and is sufficiently precise to model the final BOSS data set on

103

Bond Distortions in Armchair Type Single Wall Carbon Nanotubes  

E-Print Network [OSTI]

The energy band gap structure and stability of (3,3) and (10,10) nanotubes have been comparatively investigated in the frameworks of the traditional form of the Su-Schrieffer-Heeger (SSH) model and a toy model including the contributions of bonds of different types to the SSH Hamiltonian differently. Both models give the same energy band gap structure but bond length distortions in different characters for the nanotubes.

N. Sunel; E. Rizaoglu; K. Harigaya; O. Ozsoy

2005-03-03T23:59:59.000Z

104

Spectroscopic Needs for Calibration of LSST Photometric Redshifts  

E-Print Network [OSTI]

This white paper summarizes the conclusions of the Snowmass White Paper "Spectroscopic Needs for Imaging Dark Energy Experiments" (arXiv:1309.5384) which are relevant to the calibration of LSST photometric redshifts; i.e., the accurate characterization of biases and uncertainties in photo-z's. Any significant miscalibration will lead to systematic errors in photo-z's, impacting nearly all extragalactic science with LSST. As existing deep redshift samples have failed to yield highly-secure redshifts for a systematic 20%-60% of their targets, it is a strong possibility that future deep spectroscopic samples will not solve the calibration problem on their own. The best options in this scenario are provided by cross-correlation methods that utilize clustering with objects from spectroscopic surveys (which need not be fully representative) to trace the redshift distribution of the full sample. For spectroscopy, the eBOSS survey would enable a basic calibration of LSST photometric redshifts, while the expected LSST...

Schmidt, Samuel J; Abate, Alexandra

2014-01-01T23:59:59.000Z

105

RedShift Systems Corporation | Open Energy Information  

Open Energy Info (EERE)

RedShift Systems Corporation RedShift Systems Corporation Jump to: navigation, search Name RedShift Systems Corporation Address 41 Second Avenue Place Burlington, Massachusetts Zip 01803 Sector Efficiency Product Thermal imaging systems for building efficiency tools, smart grid monitoring Website http://redshiftsystems.com/sit Coordinates 42.483819°, -71.222836° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":42.483819,"lon":-71.222836,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

106

Radio-loud high-redshift protogalaxy candidates in Bootes  

E-Print Network [OSTI]

We used the Near Infrared Camera on Keck I to obtain Ks-band images of four candidate high-redshift radio galaxies selected using optical and radio data in the NOAO Deep Wide-Field Survey in Bootes. Our targets have 1.4 GHz radio flux densities greater than 1 mJy, but are undetected in the optical to fainter than 24 Vega mag. Spectral energy distribution fitting suggests that three of these objects are at z > 3, with radio luminosities near the FR-I / FR-II break. The other has photometric redshift 1.2, but may in fact be at higher redshift. Two of the four objects exhibit diffuse morphologies in Ks -band, suggesting that they are still in the process of forming.

Steve Croft; Wil van Breugel; Michael J. I. Brown; Wim de Vries; Arjun Dey; Peter Eisenhardt; Buell Jannuzi; Huub Röttgering; S. A. Stanford; Daniel Stern; S. P. Willner

2008-03-04T23:59:59.000Z

107

Could Dark Energy be Measured from Redshift Surveys ?  

E-Print Network [OSTI]

We review the ability of redshift surveys to provide constraints on the Dark Energy content of the Universe. The matter power spectrum and dynamics at the present epoch are nearly `blind' to Dark Energy, but combined with the CMB they can provide a constraint on the Equation of State parameter w. A representative result from the 2dF galaxy redshift survey combined with the CMB is w = -1), consistent with Einstein's Cosmological Constant model (w=-1). More complicated forms of Quintessence (e.g. epoch-dependent w or w<-1) are not yet ruled out. At higher redshifts, the abundance of galaxies and clusters of galaxies, variants of the Alcock-Paczynski curvature test and cross correlation of the CMB with radio sources look potentially promising, but they suffer from degeneracy with other parameters such as the matter density and galaxy biasing.

Ofer Lahav

2002-12-16T23:59:59.000Z

108

Gravitation as a Plastic Distortion of the Lorentz Vacuum  

E-Print Network [OSTI]

In this paper we present a theory of the gravitational field where this field (a kind of square root of g) is represented by a (1,1)-extensor field h describing a plastic distortion of the Lorentz vacuum (a real substance that lives in a Minkowski spacetime) due to the presence of matter. The field h distorts the Minkowski metric extensor in an appropriate way (see below) generating what may be interpreted as an effective Lorentzian metric extensor g and also it permits the introduction of different kinds of parallelism rules on the world manifold, which may be interpreted as distortions of the parallelism structure of Minkowski spacetime and which may have non null curvature and/or torsion and/or nonmetricity tensors. We thus have different possible effective geometries which may be associated to the gravitational field and thus its description by a Lorentzian geometry is only a possibility, not an imposition from Nature. Moreover, we developed with enough details the theory of multiform functions and multiform functionals that permitted us to successfully write a Lagrangian for h and to obtain its equations of motion, that results equivalent to Einstein field equations of General Relativity (for all those solutions where the manifold M is diffeomorphic to R^4. However, in our theory, differently from the case of General Relativity, trustful energy-momentum and angular momentum conservation laws exist. We express also the results of our theory in terms of the gravitational potential 1-form fields (living in Minkowski spacetime) in order to have results which may be easily expressed with the theory of differential forms. The Hamiltonian formalism for our theory (formulated in terms of the potentials) is also discussed. The paper contains also several important Appendices that complete the material in the main text.

Virginia V. Fernandez; Waldyr A. Rodrigues Jr

2014-08-14T23:59:59.000Z

109

MID-INFRARED SPECTROSCOPY OF HIGH-REDSHIFT 3CRR SOURCES  

SciTech Connect (OSTI)

Using the Spitzer Space Telescope, we have obtained rest-frame 9-16 {mu}m spectra of 11 quasars and 9 radio galaxies from the 3CRR catalog at redshifts 1.0 < z < 1.4. This complete flux-limited 178 MHz selected sample is unbiased with respect to orientation and therefore suited to studying orientation-dependent effects in the most powerful active galactic nuclei (AGNs). The mean radio-galaxy spectrum shows a clear silicate absorption feature ({tau}{sub 9.7{mu}m} = 1.1) whereas the mean quasar spectrum shows silicates in emission. The mean radio-galaxy spectrum matches a dust-absorbed mean quasar spectrum in both shape and overall flux level. The data for individual objects conform to these results. The trend of the silicate depth to increase with decreasing core fraction of the radio source further supports that for this sample orientation is the main driver for the difference between radio galaxies and quasars, as predicted by AGN unification. However, comparing our high-z sample with lower redshift 3CRR objects reveals that the absorption of the high-z radio galaxy MIR continuum is lower than expected from a scaled-up version of lower luminosity sources, and we discuss some effects that may explain these trends.

Leipski, C.; Antonucci, R. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Haas, M.; Chini, R.; Heymann, F. [Astronomisches Institut, Ruhr-Universitaet Bochum, Universitaetsstrasse 150, 44801 Bochum (Germany); Willner, S. P.; Ashby, M. L. N.; Wilkes, B. J.; Fazio, G. G. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Barthel, P. [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen (Netherlands); Siebenmorgen, R. [European Southern Observatory, Karl-Schwarzschildstrasse 2, 85748 Garching (Germany); Ogle, P., E-mail: leipski@physics.ucsb.ed [Spitzer Science Center, California Institute of Technology, Mail Code 220-6, Pasadena, CA 91125 (United States)

2010-07-10T23:59:59.000Z

110

The 2dF Galaxy Redshift Survey: Hierarchical galaxy clustering  

E-Print Network [OSTI]

We use the two-degree field Galaxy Redshift Survey (2dFGRS) to test the hierarchical scaling hypothesis: namely, that the $p$-point galaxy correlation functions can be written in terms of the two point correlation function or variance. This scaling is expected if an initially Gaussian distribution of density fluctuations evolves under the action of gravitational instability. We measure the volume averaged $p$-point correlation functions using a counts in cells technique applied to a volume limited sample of 44,931 $L_*$ galaxies. We demonstrate that $L_{*}$ galaxies display hierarchical clustering up to order $p=6$ in redshift space. The variance measured for $L_{*}$ galaxies is in excellent agreement with the predictions from a $\\Lambda$-cold dark matter N-body simulation. This applies to all cell radii considered, $0.3<(R/h^{-1}{\\rm Mpc})<30$. However, the higher order correlation functions of $L_*$ galaxies have a significantly smaller amplitude than is predicted for the dark matter for $R<10h^{-1}$Mpc. This disagreement implies that a non-linear bias exists between the dark matter and $L_*$ galaxies on these scales. We also show that the presence of two rare, massive superclusters in the 2dFGRS has an impact on the higher-order clustering moments measured on large scales.

C. M. Baugh; D. J. Croton; E. Gaztanaga; P. Norberg; M. Colless; I. K. Baldry; J. Bland-Hawthorn; T. Bridges; R. Cannon; S. Cole; C. Collins; W. Couch; G. Dalton; R. De Propris; S. P. Driver; G. Efstathiou; R. S. Ellis; C. S. Frenk; K. Glazebrook; C. Jackson; O. Lahav; I. Lewis; S. Lumsden; S. Maddox; D. Madgwick; J. A. Peacock; B. A. Peterson; W. Sutherland; K. Taylor

2004-06-20T23:59:59.000Z

111

MEASURING BARYON ACOUSTIC OSCILLATIONS ON 21 cm INTENSITY FLUCTUATIONS AT MODERATE REDSHIFTS  

SciTech Connect (OSTI)

After reionization, emission in the 21 cm hyperfine transition provides a direct probe of neutral hydrogen distributed in galaxies. Different from galaxy redshift surveys, observation of baryon acoustic oscillations in the cumulative 21 cm emission may offer an attractive method for constraining dark energy properties at moderate redshifts. Keys to this program are techniques to extract the faint cosmological signal from various contaminants, such as detector noise and continuum foregrounds. In this paper, we investigate the possible systematic and statistical errors in the acoustic scale estimates using ground-based radio interferometers. Based on the simulated 21 cm interferometric measurements, we analyze the performance of a Fourier-space, light-of-sight algorithm in subtracting foregrounds, and further study the observing strategy as a function of instrumental configurations. Measurement uncertainties are presented from a suite of simulations with a variety of parameters, in order to have an estimate of what behaviors will be accessible in the future generation of hydrogen surveys. We find that 10 separate interferometers, each of which contains {approx}300 dishes, observing an independent patch of the sky and producing an instantaneous field of view (FOV) of {approx}100 deg{sup 2}, can be used to make a significant detection of acoustic features over a period of a few years. Compared to optical surveys, the broad bandwidth, wide FOV, and multi-beam observation are all unprecedented capabilities of low-frequency radio experiments.

Mao Xiaochun, E-mail: xcmao@bao.ac.cn [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2012-06-20T23:59:59.000Z

112

Optical distortions in electron/positron storage rings  

SciTech Connect (OSTI)

We have studied the optical distortions in the PEP electron/positron storage ring for various optical configurations using the computer programs DIMAT, HARMON, PATRICIA, and TURTLE. The results are shown graphically by tracing several thousand trajectories from one interaction region to the next using TURTLE and by tracing a few selected rays several hundred turns using the programs DIMAT and PATRICIA. The results show an interesting correlation between the calculated optical cleanliness of a particular lattice configuration and the observed operating characteristics of the machine.

Brown, K.L.; Donald, M.; Servranckx, R.

1983-01-01T23:59:59.000Z

113

Are high-redshift DLA galxies Lyman-break galaxies?  

E-Print Network [OSTI]

We use deep HST STIS and NICMOS images of three spectroscopically confirmed galaxy counterparts of high-redshift damped Ly-alpha (DLA) absorbers (one of which is a new discovery) to test the hypothesis that high-redshift DLA galaxies are Lyman-break galaxies. If this hypothesis is correct the emission properties of DLA galaxies must lie within the range of emission properties measured for Lyman-break galaxies of similar absolute magnitude. This will be true regardless of selection biases in the sample of detected DLA galaxies. We test this prediction using several emission properties: half-light radius, radial profile (Sersic n parameter), optical-to-near-infrared colour, morphology, Ly alpha emission equivalent width, and Ly alpha emission velocity structure. In all cases the measured values for the DLA galaxies lie within the range measured for the population of Lyman-break galaxies. None of the measurements is in conflict with the prediction. We conclude that the measured emission properties of the three DLA galaxies studied here are consistent with the conjecture that high-redshift DLA galaxies are Lyman-break galaxies. We show that this result does not conflict with the observation that the few high-redshift DLA galaxies discovered are mostly fainter than spectroscopically confirmed L* Lyman-break galaxies.

P. Møller; S. J. Warren; S. M. Fall; J. U. Fynbo; P. Jakobsen

2002-03-21T23:59:59.000Z

114

Detection of a redshift 3.04 filament  

E-Print Network [OSTI]

The filamentary structure of the early universe has until now only been seen in numerical simulations. Despite this lack of direct observational evidence, the prediction of early filamentary structure formation in a Cold Dark Matter dominated universe has become a paradigm for our understanding of galaxy assembly at high redshifts. Clearly observational confirmation is required. Lyman Break galaxies are too rare to be used as tracers of filaments and we argue that to map out filaments in the high z universe, one will need to identify classes of objects fainter than those currently accessible via the Lyman Break technique. Objects selected via their Ly-alpha emission, and/or as DLA absorbers, populate the faintest accessible part of the high redshift galaxy luminosity function, and as such make up good candidates for objects which will map out high redshift filaments. Here we present the first direct detection of a filament (at z=3.04) mapped by those classes of objects. The observations are the deepest yet to have been done in Ly-alpha imaging at high redshift, and they reveal a single string of proto-galaxies spanning about 5 Mpc (20 Mpc comoving). Expanding the cosmological test proposed by Alcock & Paczynski (1979), we outline how observations of this type can be used to determine Omega_Lambda at z=3.

P. Moller; J. U. Fynbo

2001-05-07T23:59:59.000Z

115

Galaxy Clustering in the CNOC2 Redshift Survey  

E-Print Network [OSTI]

The correlation evolution of a high luminosity subsample of the CNOC2 redshift survey is examined. The sample is restricted to galaxies for which the k corrected and evolution corrected R luminosity is M_R <=-20 mag, where M_* ~= -20.3 mag. This subsample contains about 2300 galaxies. In consort with 13000 galaxies in a similarly defined low redshift sample from the Las Campanas Redshift survey we find that the comoving correlation can be described as xi(r|z) = (r_00/r)^gamma (1+z)^{-(3+e)} with r_00=5.08 +/- 0.08/h Mpc, e=0.02 +/- 0.23 and gamma=1.81 +/- 0.03 over the z=0.03 to 0.65 redshift range in a cosmology with Omega_M=0.2, Lambda=0. The measured clustering amplitude, and its evolution, are dependent on the adopted cosmology. The evolution rates for Omega_M=1 and flat low density models are e=0.9 +/- 0.3 and e=-0.5 +/- 0.2, respectively, with r_00 ~= 5/h Mpc in all cases.

R. G. Carlberg; H. K. C. Yee; S. L. Morris; H. Lin; P. Hall; D. Patton; M. Sawicki; C. W. Shepherd

1999-10-06T23:59:59.000Z

116

Multi-parameter estimating photometric redshifts with artificial neural networks  

E-Print Network [OSTI]

We calculate photometric redshifts from the Sloan Digital Sky Survey Data Release 2 Galaxy Sample using artificial neural networks (ANNs). Different input patterns based on various parameters (e.g. magnitude, color index, flux information) are explored and their performances for redshift prediction are compared. For ANN technique, any parameter may be easily incorporated as input, but our results indicate that using dereddening magnitude produces photometric redshift accuracies often better than the Petrosian magnitude or model magnitude. Similarly, the model magnitude is also superior to Petrosian magnitude. In addition, ANNs also show better performance when the more effective parameters increase in the training set. Finally, the method is tested on a sample of 79, 346 galaxies from the SDSS DR2. When using 19 parameters based on the dereddening magnitude, the rms error in redshift estimation is sigma(z)=0.020184. The ANN is highly competitive tool when compared with traditional template-fitting methods where a large and representative training set is available.

Lili Li; Yanxia Zhang; Yongheng Zhao; Dawei Yang

2006-12-28T23:59:59.000Z

117

The Star Formation Rate-Density Relationship at Redshift Three  

E-Print Network [OSTI]

We study the star formation rate (SFR) as a function of environment for UV selected Lyman break galaxies (LBGs) at redshift three. From deep UBVI KPNO 4-m/MOSAIC images, covering a total of 0.90 deg^2, we select 334 LBGs in slices 100 Mpc (co-moving) deep spanning the redshift range 2.9projected density to the 5th nearest neighbor. These mock catalogs have a redshift depth of 100 Mpc, similar to our slice width. The large area of the MOSAIC images, 40x40 Mpc (co-moving) per field, allows us to measure the SFR from the dust-corrected UV continuum as a function of $\\Sigma_5$. In contrast to low-redshift galaxies, we find that the SFR (or UV luminosity) of LBGs at z=3 shows no detectable dependence on environment over 2 orders of magnitude in density. To test the significance of our result, we use Monte Carlo simulations (from the mock catalogs) and the same projected density estimators we applied to our data. We find that we can reject the steep z=0 SFR-density at the 5-$\\sigma$ level. We conclude that the SFR-density at z=3 must be at least 3.6 times flatter than it is locally, i.e. the SFR of LBGs is significantly less dependent on environment than the SFR of local star-forming galaxies. We find that the rest-frame UV colors are also independent of environment.

Nicolas Bouche; James D. Lowenthal

2005-03-04T23:59:59.000Z

118

QSO Metal Absorption Systems at High Redshift Toru Misawa1  

E-Print Network [OSTI]

QSO Metal Absorption Systems at High Redshift Toru Misawa1 , Nobunari Kashikawa2 , Youichi Ohyama2 Abstract. Quasar absorption systems give us useful information about very faint objects that we cannot detect directly. For example, metal absorption systems are generally provided by star formation

Iye, Masanori

119

The Age-Redshift Relation for Standard Cosmology  

E-Print Network [OSTI]

We present compact, analytic expressions for the age-redshift relation $\\tau(z)$ for standard Friedmann-Lema\\^ \\itre-Robertson-Walker (FLRW) cosmology. The new expressions are given in terms of incomplete Legendre elliptic integrals and evaluate much faster than by direct numerical integration.

R. C. Thomas; R. Kantowski

2000-08-10T23:59:59.000Z

120

THE EVOLUTION OF LYMAN LIMIT ABSORPTION SYSTEMS TO REDSHIFT SIX  

SciTech Connect (OSTI)

We have measured the redshift evolution of the density of Lyman limit systems (LLSs) in the intergalactic medium over the redshift range 0 < z < 6. We have used two new quasar samples to (1) improve coverage at z {approx} 1, with GALEX grism spectrograph observations of 50 quasars with 0.8 < z{sub em} < 1.3, and (2) extend coverage to z {approx} 6, with Keck ESI spectra of 25 quasars with 4.17 < z{sub em} < 5.99. Using these samples together with published data, we find that the number density of LLS per unit redshift, n(z), can be well fit by a simple evolution of the form n(z) = n{sub 3.5}[(1 + z)/4.5]{sup {gamma}} with n{sub 3.5} = 2.80 {+-} 0.33 and {gamma} = 1.94{sup +0.36}{sub -0.32} for the entire range 0 < z < 6. We have also reanalyzed the evolution of damped Ly{alpha} systems (DLAs) in the redshift range 4 < z < 5 using our high-redshift quasar sample. We find a total of 17 DLAs and sub-DLAs, which we have analyzed in combination with published data. The DLAs with log H{sub I} column density > 20.3 show the same redshift evolution as the LLS. When combined with previous results, our DLA sample is also consistent with a constant {Omega}{sub DLA} = 9 x 10{sup -4} from z = 2 to z = 5. We have used the LLS number density evolution to compute the evolution in the mean free path (mfp) of ionizing photons. We find a smooth evolution to z {approx} 6, very similar in shape to that of Madau et al. but about a factor of two higher. Recent theoretical models roughly match to the z < 6 data but diverge from the measured power law at z>6 in different ways, cautioning against extrapolating the fit to the mfp outside the measured redshift range.

Songaila, Antoinette; Cowie, Lennox L. [W. M. Keck Observatory, which is jointly operated by the California Institute of Technology, University of California, and National Aeronautics and Space Administration. (United States)

2010-10-01T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
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121

EVOLUTION OF GALAXY LUMINOSITY FUNCTION USING PHOTOMETRIC REDSHIFTS  

SciTech Connect (OSTI)

We examine the impact of using photometric redshifts for studying the evolution of both the global galaxy luminosity function (LF) and that for different galaxy types. To this end, we compare the LFs obtained using photometric redshifts from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) D1 field with those from the spectroscopic survey VIMOS VLT Deep Survey (VVDS) comprising {approx}4800 galaxies. We find that for z {<=} 2.0, in the interval of magnitudes considered by this survey, the LFs obtained using photometric and spectroscopic redshifts show a remarkable agreement. This good agreement led us to use all four Deep fields of the CFHTLS comprising {approx}386,000 galaxies to compute the LF of the combined fields and directly estimate the error in the parameters based on the field-to-field variation. We find that the characteristic absolute magnitude M* of Schechter fits fades by {approx}0.7 mag from z {approx} 1.8 to z {approx} 0.3, while the characteristic density {phi}* increases by a factor of {approx}4 in the same redshift interval. We use the galaxy classification provided by the template fitting program used to compute photometric redshifts and split the sample into galaxy types. We find that these Schechter parameters evolve differently for each galaxy type, an indication that their evolution is a combination of several effects: galaxy merging, star formation quenching, and mass assembly. All these results are compatible with those obtained by different spectroscopic surveys such as VVDS, DEEP2, and zCosmos, which reinforces the fact that photometric redshifts can be used to study galaxy evolution, at least for the redshift bins adopted so far. This is of great interest since future very large imaging surveys containing hundreds of millions of galaxies will allow us to obtain important precise measurements to constrain the evolution of the LF and to explore the dependence of this evolution on morphology and/or color helping constrain the mechanisms of galaxy evolution.

Ramos, B. H. F.; Pellegrini, P. S.; Da Costa, L. N.; Maia, M. A. G.; Ogando, R. L. C.; De Simoni, F. [Observatorio Nacional, Rua Gal. Jose Cristino 77, Rio de Janeiro, RJ 20921-400 (Brazil); Benoist, C.; Makler, M. [Laboratorio Interinstitucional de e-Astronomia-LIneA, Rua Gal. Jose Cristino 77, Rio de Janeiro, RJ 20921-400 (Brazil); Mesquita, A. A., E-mail: ramos@linea.gov.br, E-mail: pssp@linea.gov.br, E-mail: ldacosta@linea.gov.br, E-mail: maia@linea.gov.br, E-mail: ogando@linea.gov.br, E-mail: fsimoni@linea.gov.br, E-mail: benoist@oca.eu, E-mail: martin@cbpf.br, E-mail: albertoalves@on.br [Universidade Federal do Rio de Janeiro, Observatorio do Valongo, Ladeira do Pedro Antonio, 43 Rio de Janeiro, RJ 20080-090 (Brazil)

2011-08-15T23:59:59.000Z

122

Photometric redshift analysis in the Dark Energy Survey Science Verification data  

Science Journals Connector (OSTI)

......Photometric redshift analysis in the Dark Energy Survey Science Verification data C...redshift performance of the Dark Energy Survey (DES), using the early data...the photometric survey. The Dark Energy Survey (DES; Flaugher 2005) is one......

C. Sánchez; M. Carrasco Kind; H. Lin; R. Miquel; F. B. Abdalla; A. Amara; M. Banerji; C. Bonnett; R. Brunner; D. Capozzi; A. Carnero; F. J. Castander; L. A. N. da Costa; C. Cunha; A. Fausti; D. Gerdes; N. Greisel; J. Gschwend; W. Hartley; S. Jouvel; O. Lahav; M. Lima; M. A. G. Maia; P. Martí; R. L. C. Ogando; F. Ostrovski; P. Pellegrini; M. M. Rau; I. Sadeh; S. Seitz; I. Sevilla-Noarbe; A. Sypniewski; J. de Vicente; T. Abbot; S. S. Allam; D. Atlee; G. Bernstein; J. P. Bernstein; E. Buckley-Geer; D. Burke; M. J. Childress; T. Davis; D. L. DePoy; A. Dey; S. Desai; H. T. Diehl; P. Doel; J. Estrada; A. Evrard; E. Fernández; D. Finley; B. Flaugher; J. Frieman; E. Gaztanaga; K. Glazebrook; K. Honscheid; A. Kim; K. Kuehn; N. Kuropatkin; C. Lidman; M. Makler; J. L. Marshall; R. C. Nichol; A. Roodman; E. Sánchez; B. X. Santiago; M. Sako; R. Scalzo; R. C. Smith; M. E. C. Swanson; G. Tarle; D. Thomas; D. L. Tucker; S. A. Uddin; F. Valdés; A. Walker; F. Yuan; J. Zuntz

2014-01-01T23:59:59.000Z

123

Can a galaxy redshift survey measure dark energy clustering?  

E-Print Network [OSTI]

(abridged) A wide-field galaxy redshift survey allows one to probe galaxy clustering at largest spatial scales, which carries an invaluable information on horizon-scale physics complementarily to the cosmic microwave background (CMB). Assuming the planned survey consisting of z~1 and z~3 surveys with areas of 2000 and 300 square degrees, respectively, we study the prospects for probing dark energy clustering from the measured galaxy power spectrum, assuming the dynamical properties of dark energy are specified in terms of the equation of state and the effective sound speed c_e in the context of an adiabatic cold dark matter dominated model. The dark energy clustering adds a power to the galaxy power spectrum amplitude at spatial scales greater than the sound horizon, and the enhancement is sensitive to redshift evolution of the net dark energy density, i.e. the equation of state. We find that the galaxy survey, when combined with Planck, can distinguish dark energy clustering from a smooth dark energy model such as the quintessence model (c_e=1), when c_esurvey of z~1 galaxies allows the detection when c_edark energy clustering and the non-relativistic neutrinos implied from the neutrino oscillation experiments, because the two effects both induce a scale-dependent modification in the galaxy power spectrum shape at largest spatial scales accessible from the galaxy survey. It is shown that a wider redshift coverage can efficiently separate the two effects by utilizing the different redshift dependences, where dark energy clustering is apparent only at low redshifts z<1.

Masahiro Takada

2006-06-21T23:59:59.000Z

124

The Premature Formation of High Redshift Galaxies  

E-Print Network [OSTI]

Observations with WFC3/IR on the Hubble Space Telescope and the use of gravitational lensing techniques have facilitated the discovery of galaxies as far back as z ~ 10-12, a truly remarkable achievement. However, this rapid emergence of high-z galaxies, barely ~ 200 Myr after the transition from Population III star formation to Population II, appears to be in conflict with the standard view of how the early Universe evolved. This problem has much in common with the better known (and probably related) premature appearance of supermassive black holes at z ~ 6. It is difficult to understand how ~ 10^9 solar-mass black holes could have appeared so quickly after the big bang without invoking non-standard accretion physics and the formation of massive seeds, neither of which is seen in the local Universe. In earlier work, we showed that the appearance of high-z quasars could instead be understood more reasonably in the context of the R_h=ct Universe, which does not suffer from the same time compression issues as L...

Melia, Fulvio

2014-01-01T23:59:59.000Z

125

FIREBALL: The Faint Intergalactic medium Redshifted Emission Balloon --Overview and 1st Science Flight Results  

E-Print Network [OSTI]

Ly (1216Ã?), OVI (1033Ã?) and CIV (1549Ã?) are redshifted into the 1950-2250Ã? stratospheric balloon

Martin, Chris

126

The Premature Formation of High Redshift Galaxies  

E-Print Network [OSTI]

Observations with WFC3/IR on the Hubble Space Telescope and the use of gravitational lensing techniques have facilitated the discovery of galaxies as far back as z ~ 10-12, a truly remarkable achievement. However, this rapid emergence of high-z galaxies, barely ~ 200 Myr after the transition from Population III star formation to Population II, appears to be in conflict with the standard view of how the early Universe evolved. This problem has much in common with the better known (and probably related) premature appearance of supermassive black holes at z ~ 6. It is difficult to understand how ~ 10^9 solar-mass black holes could have appeared so quickly after the big bang without invoking non-standard accretion physics and the formation of massive seeds, neither of which is seen in the local Universe. In earlier work, we showed that the appearance of high-z quasars could instead be understood more reasonably in the context of the R_h=ct Universe, which does not suffer from the same time compression issues as LCDM does at early epochs. Here, we build on that work by demonstrating that the evolutionary growth of primordial galaxies was consistent with the current view of how the first stars formed, but only with the timeline afforded by the R_h=ct cosmology. We also show that the growth of high-z quasars was mutually consistent with that of the earliest galaxies, though it is not yet clear whether the former grew from 5-20 solar-mass seeds created in Population III or Population II supernova explosions.

Fulvio Melia

2014-03-03T23:59:59.000Z

127

HIGH-REDSHIFT METALS. II. PROBING REIONIZATION GALAXIES WITH LOW-IONIZATION ABSORPTION LINES AT REDSHIFT SIX  

SciTech Connect (OSTI)

We present a survey for low-ionization metal absorption line systems toward 17 QSOs at redshifts z{sub em} = 5.8-6.4. Nine of our objects were observed at high resolution with either Keck/HIRES or Magellan/MIKE, and the remainder at moderate resolution with Keck/ESI. The survey spans 5.3 < z{sub abs} < 6.4 and has a path length interval {Delta}X = 39.5 or {Delta}z = 8.0. In total we detect ten systems, five of which are new discoveries. The line-of-sight number density, l(X) = 0.25{sup +0.21}{sub -0.13} (95% confidence), is consistent with the combined number density at z {approx} 3 of damped Ly{alpha} systems (DLAs) and sub-DLAs, which comprise the main population of low-ionization systems at lower redshifts. This apparent lack of evolution may occur because low-ionization systems are hosted by lower-mass halos at higher redshifts, or because the mean cross section of low-ionization gas at a given halo mass increases with redshift due to the higher densities and lower ionizing background. The roughly constant number density notably contrasts with the sharp decline at z > 5.3 in the number density of highly ionized systems traced by C IV. The low-ionization systems at z {approx} 6 span a similar range of velocity widths as lower-redshift sub-DLAs but have significantly weaker lines at a given width. This may imply that the mass-metallicity relation of the host galaxies evolves toward lower metallicities at higher redshifts. These systems lack strong Si IV and C IV, which are common among lower-redshift DLAs and sub-DLAs. This is consistent, however, with a similar decrease in the metallicity of the low- and high-ionization phases, and does not necessarily indicate a lack of nearby, highly ionized gas. The high number density of low-ionization systems at z {approx} 6 suggests that we may be detecting galaxies below the current limits of i-dropout and Ly{alpha} emission galaxy surveys. These systems may therefore be the first direct probes of the 'typical' galaxies responsible for hydrogen reionization.

Becker, George D.; Calverley, Alexander P. [Kavli Institute for Cosmology and Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA (United Kingdom); Sargent, Wallace L. W. [Palomar Observatory, California Institute of Technology, Pasadena, CA 91125 (United States); Rauch, Michael, E-mail: gdb@ast.cam.ac.uk, E-mail: acalver@ast.cam.ac.uk, E-mail: wws@astro.caltech.edu, E-mail: mr@obs.carnegiescience.edu [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

2011-07-10T23:59:59.000Z

128

X-RAY ABSORPTION OF HIGH-REDSHIFT QUASARS  

SciTech Connect (OSTI)

The soft X-ray photoelectric absorption of high-z quasars has been known for two decades, but has no unambiguous astrophysical context. We construct the largest sample to date of 58 high-redshift quasars (z > 0.45) selected from the XMM-Newton archive based on a high photon count criterion (>1800). We measure the optical depth {tau} at 0.5 keV and find that 43% of the quasars show significant absorption. We aim to find which physical parameters of the quasars, e.g., redshift, radio luminosity, radio loudness, or X-ray luminosity, drive their observed absorption. We compare the absorption behavior with redshift with the pattern expected if the diffuse intergalactic medium (IGM) is responsible for the observed absorption. We also compare the absorption with a comparison sample of gamma-ray burst (GRB) X-ray afterglows. Although the z > 2 quasar opacity is consistent with diffuse IGM absorption, many intermediate-z (0.45 < z < 2) quasars are not sufficiently absorbed for this scenario, and are appreciably less absorbed than GRBs. Only 10/37 quasars at z < 2 are absorbed, and only 5/30 radio-quiet quasars are absorbed. We find a weak correlation between {tau} and z, and an even weaker correlation between {tau} and radio luminosity. These findings lead to the conclusion that although a diffuse IGM origin for the quasar absorption is unlikely, the optical depth does seem to increase with redshift, roughly as (1 + z){sup 2.2{+-}0.6}, tending to {tau} Almost-Equal-To 0.4 at high redshifts, similar to the high-z GRBs. This result can be explained by an ionized and clumpy IGM at z < 2, and a cold, diffuse IGM at higher redshift. If, conversely, the absorption occurs at the quasar, and owing to the steep L{sub x} {proportional_to}(1 + z){sup 7.1{+-}0.5} correlation in the present sample, the host column density scales as N{sub H}{proportional_to}L{sub x}{sup 0.7{+-}0.1}.

Eitan, Assaf; Behar, Ehud, E-mail: sassafe@tx.technion.ac.il, E-mail: behar@physics.technion.ac.il [Physics Department, Technion, Haifa 32000 (Israel)

2013-09-01T23:59:59.000Z

129

Role of cooperative lattice distortion in the charge, orbital, and spin ordering in doped manganites  

Science Journals Connector (OSTI)

The role of lattice distortion in the charge, orbital, and spin ordering in half-doped manganites has been investigated. For fixed magnetic ordering, we show that the cooperative lattice distortion stabilize the experimentally observed ordering even when the strong onsite electronic correlation is taken into account. Furthermore, without invoking the magnetic interactions, the cooperative lattice distortion alone may lead to the correct charge and orbital ordering including the charge stacking effect, and the magnetic ordering can be the consequence of such a charge and orbital ordering. We propose that the cooperative nature of the lattice distortion is essential to understand the complicated charge, orbital, and spin ordering observed in doped manganites.

R. Y. Gu and C. S. Ting

2002-06-07T23:59:59.000Z

130

A Study of Harmonic Distortion Limit Change During the Reconfiguration Process of the Smart Grid.  

E-Print Network [OSTI]

??On the purpose to find out if harmonic distortion limits of customer installations will change during a smart grid reconfiguration process, the thesis was completed.… (more)

Yang, Wenyue

2014-01-01T23:59:59.000Z

131

Role of Distortion Energy and Steric Effects on Cycloadditions in Bioorthogonal Chemistry  

E-Print Network [OSTI]

reacting carbon atoms of the tetrazine are all in a straightmethyl azide, and dimethyl tetrazine viii   LIST OF SCHEMESthe reaction with the tetrazine or azide is distortion-

Lopez, Steven Alexander

2012-01-01T23:59:59.000Z

132

Testing a new luminosity/redshift indicator for $?$-ray bursts  

E-Print Network [OSTI]

We have tested a relative spectral lag (RSL) method suggested earlier as a luminosity/redshift (or distance) estimator, using the generalized method by Schaefer & Collazzi. We find the derivations from the luminosity/redshift-RSL (L/R-RSL) relation are comparable with the corresponding observations. Applying the luminosity-RSL relation to two different GRB samples, we find that there exist no violators from the generalized test, namely the Nakar & Piran test and Li test. We also find that about 36 per cent of Schaefer's sample are outliers for the L/R-RSL relation within 1$\\sigma$ confidence level, but no violators at 3$\\sigma$ level within the current precision of L/R-RSL relation. An analysis of several potential outliers for other luminosity relations shows they can match the L/R-RSL relation well within an acceptable uncertainty. All the coincident results seem to suggest that this relation could be a potential tool for cosmological study.

Zhi-Bin Zhang; Guang-Zhong Xie

2007-11-09T23:59:59.000Z

133

ROSAT Public PSPC Observations in the Las Campanas Redshift Survey  

E-Print Network [OSTI]

The Las Campanas Redshift Survey, an optically selected survey which contains 26,418 galaxy redshifts, has been correlated with ``The First ROSAT Source Catalogue of Pointed Observations with the PSPC,'' which contains 50,408 sources from 2876 ROSAT pointed observations. Ten matches were found. The optical spectra of most of the ten matches show weak narrow emission lines. Due to their high x-ray luminosities, their high x-ray--to--optical flux ratios, and the evidence of rapid x-ray variability in the two brightest matches, we interpret the majority of these objects to be narrow-line Seyfert galaxies or ``hidden'' active galactic nuclei. Of the ten matches, only one galaxy shows the characteristics of a bona fide starburst.

D. L. Tucker; G. Hasinger; H. Lin

1997-04-22T23:59:59.000Z

134

Spectroscopic Needs for Training of LSST Photometric Redshifts  

E-Print Network [OSTI]

This white paper summarizes those conclusions of the Snowmass White Paper "Spectroscopic Needs for Imaging Dark Energy Experiments" (arXiv:1309.5384) which are relevant to the training of LSST photometric redshifts; i.e., the use of spectroscopic redshifts to improve algorithms and reduce photo-z errors. The larger and more complete the available training set is, the smaller the RMS error in photo-z estimates should be, increasing LSST's constraining power. Among the better US-based options for this work are the proposed MANIFEST fiber feed for the Giant Magellan Telescope or (with lower survey speed) the WFOS spectrograph on the Thirty Meter Telescope (TMT). Due to its larger field of view and higher multiplexing, the PFS spectrograph on Subaru would be able to obtain a baseline training sample faster than TMT; comparable performance could be achieved with a highly-multiplexed spectrograph on Gemini with at least a 20 arcmin diameter field of view.

Abate, Alexandra; Schmidt, Samuel J

2014-01-01T23:59:59.000Z

135

Close-spaced thermionic converters with active spacing control and heat-pipe isothermal emitters  

SciTech Connect (OSTI)

Thermionic converters with interelectrode gaps smaller than 10 microns are capable of substantial performance improvements over conventional ignited mode diodes. Previous devices which have demonstrated operation at such small gaps have done so at low power densities and emitter temperatures. Higher power operation requires overcoming two primary design issues: thermal distortion of the emitter due to temperature gradients and degradation of the in-gap spacers at higher emitter temperatures. This work describes two innovations for solution of these issues. The issue of thermal distortion was addressed by an isothermal emitter incorporating a heat-pipe into its structure. Such a heat-pipe emitter, with a single-crystal emitting surface, was fabricated and characterized. Finite-element computational modeling was used to analyze its distortion with an applied heat flux. The calculations suggested that thermal distortion would be significantly reduced as compared with a solid emitter. Ongoing work and preliminary experimental results are described for a system of active interelectrode gap control. In the present design an integral transducer determines the interelectrode gap of the converter. Initial designs for spacing actuators and their required cesium vapor seals are discussed. A novel hot-shell converter design incorporating active spacing control and low-temperature seals is presented. A converter incorporating the above features would be capable of near ideal-converter performance at high power densities. In addition, active spacing control can potentially completely eliminate short-circuit failures in thermionic converter systems.

Fitzpatrick, G.O.; Koester, J.K.; Chang, J.; Britt, E.J.; McVey, J.B. [Space Power, Inc., San Jose, CA (United States)

1996-12-31T23:59:59.000Z

136

Powerful evidences for supporting the claim that gamma-ray burst redshifts are gravity-generated  

E-Print Network [OSTI]

At present, it is widely believed that the phenomenon of the gamma-ray burst redshift is cosmological origin. From a theoretical point of view, this redshift has either a cosmological or a cause that is related to gravity. However, the question of whether the gamma-ray burst redshift has a cosmological origin or not should be answerable in no uncertain terms because both the spectrum characteristics and the count distribution law arising from the two distinct settings are completely different. If the redshift of GRB is generated by gravity, then the afterglow spectrum will certainly contain both the gravitational redshits (containing emission and absorption feature) and Doppler absorption redshift, and hold a definite relation between the two redshifts. In this paper, we present nine direct and decisive evidences to show that the gamma-ray burst redshift is indeed generated by gravity of neutron stars in their merging process; in which, 114 GRBs' redshifts showed that the statistical count distribution law for the two kinds redshift is the same (with errors less than 1.5%), and 74 spectral line redshifts of two GRBs showed that the relation between the two kinds redshift is completely correct (with errors less than 0.0061%).

Fu-Gao Song

2008-05-22T23:59:59.000Z

137

Can Population III Stars at High Redshifts produce GRB's?  

E-Print Network [OSTI]

Gamma ray bursts are the most luminous physical phenomena in the universe, consisting of flashes of gamma rays that last from seconds to hours. There have been attempts to observe gamma ray bursts, for example, from population III stars of about 500 solar mass at high redshifts. Here we argue that collapse of such high mass stars does not lead to gamma ray burst as their core collapse temperatures are not sufficient to produce gamma rays, leading to GRBs.

C. Sivaram; Kenath Arun

2010-08-24T23:59:59.000Z

138

Time, Distance, Velocity, Redshift: a personal guided tour  

E-Print Network [OSTI]

An attempt to answer the question 'Can we observe galaxies that recede faster than light ?' led to a re-examination of the notions of time, distance, velocity and redshift as they occur in newtonian physics, special relativity, general relativity and cosmology. A number of misconceptions were uncovered. It was found that, once freed of special relativity preconceptions, the above question is easily and unequivocally answered

T. Kiang

2003-08-01T23:59:59.000Z

139

A survey for redshifted molecular and atomic absorption lines I  

E-Print Network [OSTI]

We are currently undertaking a large survey for redshifted atomic and molecular absorption ... only one clear and one tentative detection were obtained: HI absorption at z = 0.097 in PKS 1555-140 and OH absorption at z =0.126 in PKS 2300-189, respectively... In order to determine why no clear molecular absorption was detected in any of the 13 sources searched, we investigate the properties of the five redshifted systems currently known to exhibit OH absorption. In four of these, molecules were first detected via millimetre-wave transitions and the flat radio spectra indicate compact background continuum sources, which may suggest a high degree of coverage of the background source by the molecular clouds in the absorber. Furthermore, for these systems we find a relationship between the molecular line strength and red optical--near infrared (V-K) colours, thus supporting the notion that the reddening of these sources is due to dust, which provides an environment conducive to the formation of molecules. Upon comparison with the V-K colours of our sample, this relationship suggests that, presuming the reddening occurs at the host galaxy redshift at least in some of the targets, many of our observations still fall short of the sensitivityrequired to detect OH absorption, although a confirmation of the ``detection'' of OH in 2300-189 could contravene this.

S. J. Curran; M. T. Whiting; M. T. Murphy; J. K. Webb; S. N. Longmore; Y. M. Pihlstroem; R. Athreya; C. Blake

2006-07-26T23:59:59.000Z

140

Can a galaxy redshift survey measure dark energy clustering?  

Science Journals Connector (OSTI)

A wide-field galaxy redshift survey allows one to probe galaxy clustering at largest spatial scales, which carries invaluable information on horizon-scale physics complementarily to the cosmic microwave background (CMB). Assuming the planned survey consisting of z?1 and z?3 surveys with areas of 2000 and 300??deg2, respectively, we study the prospects for probing dark energy clustering from the measured galaxy power spectrum, assuming the dynamical properties of dark energy are specified in terms of the equation of state and the effective sound speed ce in the context of an adiabatic cold dark dominated matter model. The dark energy clustering adds a power to the galaxy power spectrum amplitude at spatial scales greater than the sound horizon, and the enhancement is sensitive to redshift evolution of the net dark energy density, i.e. the equation of state. We find that the galaxy survey, when combined with CMB expected from the Planck satellite mission, can distinguish dark energy clustering from a smooth dark energy model such as the quintessence model (ce=1), when ce?0.04 (0.02) in the case of the constant equation of state w0=-0.9 (-0.95). An ultimate full-sky survey of z?1 galaxies allows the detection when ce?0.08 (0.04) for w0=0.9 (-0.95). These forecasts show a compatible power with an all-sky CMB and galaxy cross correlation that probes the integrated Sachs-Wolfe effect. We also investigate a degeneracy between the dark energy clustering and the nonrelativistic neutrinos implied from the neutrino oscillation experiments, because the two effects both induce a scale-dependent modification in the galaxy power spectrum shape at largest spatial scales accessible from the galaxy survey. It is shown that a wider redshift coverage can efficiently separate the two effects by utilizing the different redshift dependences, where dark energy clustering is apparent only at low redshifts z?1.

Masahiro Takada

2006-08-04T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Space Microbiology  

Science Journals Connector (OSTI)

...2010 ARTICLE REVIEWS Space Microbiology Gerda Horneck...2005. Metagenomic libraries from uncultured microorganisms...environments. Gravit. Space Biol. 18: 85-86...rendering plant process. Public Health Rep. 72: 176...bacteriophage. Life Sci. Space Res. 13: 143-149...

Gerda Horneck; David M. Klaus; Rocco L. Mancinelli

2010-03-01T23:59:59.000Z

142

SLOS242D -SEPTEMBER 2002 -REVISED JANUARY 2004 2 GHz, LOW DISTORTION, CURRENT FEEDBACK AMPLIFIERS  

E-Print Network [OSTI]

PAD packages. RELATED DEVICES AND DESCRIPTIONS THS3001 ±15-V 420-MHz Low Distortion CFB Amplifier THS3061/2 ±15-V 300-MHz Low Distortion CFB Amplifier THS3122 ±15-V Dual CFB Amplifier With 350 mA Drive THS4271

Berns, Hans-Gerd

143

Layered Video Coding Offset Distortion Traces for Trace-Based Evaluation of Video Quality after  

E-Print Network [OSTI]

1 Layered Video Coding Offset Distortion Traces for Trace-Based Evaluation of Video Quality after video traces for scalable encoded video with more than one layer are a convenient representation of the encoded video for the evaluation of networking mechanisms. The video distortion (RMSE) or quality (PSNR

Reisslein, Martin

144

Coding into a source: an inverse rate-distortion Anant Sahai  

E-Print Network [OSTI]

Sahai (UC Berkeley) Inverse Rate Distortion Sep 27, 2006 1 / 27 #12;Suppose the aliens landed. . . Your Distortion Sep 27, 2006 2 / 27 #12;Suppose the aliens landed. . . Your mission: reverse 27, 2006 2 / 27 #12;Suppose the aliens landed. . . Your mission: reverse

Sahai, Anant

145

An iterative longest matching segment approach to speech enhancement with additive noise and channel distortion  

Science Journals Connector (OSTI)

This paper presents a new approach to speech enhancement from single-channel measurements involving both noise and channel distortion (i.e., convolutional noise), and demonstrates its applications for robust speech recognition and for improving noisy ... Keywords: Channel distortion, Corpus-based speech modeling, Longest matching segment, Noisy speech, Speech enhancement, Speech recognition

Ji Ming, Danny Crookes

2014-11-01T23:59:59.000Z

146

A LOW-DISTORTION CLASS-AB AUDIO AMPLIFIER WITH HIGH POWER EFFICIENCY  

E-Print Network [OSTI]

A LOW-DISTORTION CLASS-AB AUDIO AMPLIFIER WITH HIGH POWER EFFICIENCY BY CHAITANYA MOHAN, B of Sciences, Engineering Specialization in: Electrical Engineering New Mexico State University Las Cruces, New Mexico March 2011 #12;"A Low-Distortion Class-AB Audio Amplifier with High Power Efficiency," a the- sis

Furth, Paul

147

Percolation Galaxy Groups and Clusters in the SDSS Redshift Survey: Identification, Catalogs, and the Multiplicity Function  

E-Print Network [OSTI]

We identify galaxy groups and clusters in volume-limited samples of the SDSS redshift survey, using a redshift-space friends-of-friends algorithm. We optimize the friends-of-friends linking lengths to recover galaxy systems that occupy the same dark matter halos, using a set of mock catalogs created by populating halos of N-body simulations with galaxies. Extensive tests with these mock catalogs show that no combination of perpendicular and line-of-sight linking lengths is able to yield groups and clusters that simultaneously recover the true halo multiplicity function, projected size distribution, and velocity dispersion. We adopt a linking length combination that yields, for galaxy groups with ten or more members: a group multiplicity function that is unbiased with respect to the true halo multiplicity function; an unbiased median relation between the multiplicities of groups and their associated halos; a spurious group fraction of less than ~1%; a halo completeness of more than ~97%; the correct projected size distribution as a function of multiplicity; and a velocity dispersion distribution that is ~20% too low at all multiplicities. These results hold over a range of mock catalogs that use different input recipes of populating halos with galaxies. We apply our group-finding algorithm to the SDSS data and obtain three group and cluster catalogs for three volume-limited samples that cover 3495.1 square degrees on the sky. We correct for incompleteness caused by fiber collisions and survey edges, and obtain measurements of the group multiplicity function, with errors calculated from realistic mock catalogs. These multiplicity function measurements provide a key constraint on the relation between galaxy populations and dark matter halos.

Andreas A. Berlind; Joshua A. Frieman; David H. Weinberg; Michael R. Blanton; Michael S. Warren; Kevork Abazajian; Ryan Scranton; David W. Hogg; Roman Scoccimarro; Neta A. Bahcall; J. Brinkmann; J. Richard Gott III; S. J. Kleinman; J. Krzesinski; Brian C. Lee; Christopher J. Miller; Atsuko Nitta; Donald P. Schneider; Douglas L. Tucker; Idit Zehavi; for the SDSS Collaboration

2006-01-16T23:59:59.000Z

148

The 2dF Galaxy Redshift Survey: stochastic relative biasing between galaxy populations  

E-Print Network [OSTI]

It is well known that the clustering of galaxies depends on galaxy type.Such relative bias complicates the inference of cosmological parameters from galaxy redshift surveys, and is a challenge to theories of galaxy formation and evolution. In this paper we perform a joint counts-in-cells analysis on galaxies in the 2dF Galaxy Redshift Survey, classified by both colour and spectral type, eta, as early or late type galaxies. We fit three different models of relative bias to the joint probability distribution of the cell counts, assuming Poisson sampling of the galaxy density field. We investigate the nonlinearity and stochasticity of the relative bias, with cubical cells of side 10Mpc \\leq L \\leq 45Mpc (h=0.7). Exact linear bias is ruled out with high significance on all scales. Power law bias gives a better fit, but likelihood ratios prefer a bivariate lognormal distribution, with a non-zero `stochasticity' - i.e. scatter that may result from physical effects on galaxy formation other than those from the local density field. Using this model, we measure a correlation coefficient in log-density space (r_LN) of 0.958 for cells of length L=10Mpc, increasing to 0.970 by L=45Mpc. This corresponds to a stochasticity sigma_b/bhat of 0.44\\pm0.02 and 0.27\\pm0.05 respectively. For smaller cells, the Poisson sampled lognormal distribution presents an increasingly poor fit to the data, especially with regard to the fraction of completely empty cells. We compare these trends with the predictions of semianalytic galaxy formation models: these match the data well in terms of overall level of stochasticity, variation with scale, and fraction of empty cells.

Vivienne Wild; John A. Peacock; Ofer Lahav; Edward Conway; Steve Maddox; I. K. Baldry; C. M. Baugh; J. Bland-Hawthorn; T. Bridges; R. Cannon; S. Cole; M. Colless; C. Collins; W. Couch; G. Dalton; R. De Propris; S. P. Driver; G. Efstathiou; R. S. Ellis; C. S. Frenk; K. Glazebrook; C. Jackson; I. Lewis; S. Lumsden; D. Madgwick; P. Norberg; B. A. Peterson; W. Sutherland; K. Taylor

2004-11-26T23:59:59.000Z

149

Workload induced spatio-temporal distortions and safety of flight  

SciTech Connect (OSTI)

A theoretical analysis of the relationship between cognitive complexity and the perception of time and distance is presented and experimentally verified. Complex tasks produce high rates of mental representation which affect the subjective sense of duration and, through the subjective time scale, the percept of distance derived from dynamic visual cues (i.e., visual cues requiring rate integration). The analysis of the interrelationship of subjective time and subjective distance yields the prediction that, as a function of cognitive complexity, distance estimates derived from dynamic visual cues will be longer than the actual distance whereas estimates based on perceived temporal duration will be shorter than the actual distance. This prediction was confirmed in an experiment in which subjects (both pilots and non-pilots) estimated distances using either temporal cues or dynamic visual cues. The distance estimation task was also combined with secondary loading tasks in order to vary the overall task complexity. The results indicated that distance estimates based on temporal cues were underestimated while estimates based on visual cues were overestimated. This spatio-temporal distortion effect increased with increases in overall task complexity. 30 refs., 6 figs., 1 tab.

Barrett, C.L.; Weisgerber, S.A. (Los Alamos National Lab., NM (USA); Naval Weapons Center, China Lake, CA (USA))

1989-01-01T23:59:59.000Z

150

Accuracy of photometric redshifts for future weak lensing surveys from space  

Science Journals Connector (OSTI)

......Survey Telescope (LSST), Pan-STARRS and Dark Energy Survey (DES). The results highlight the importance...ground-based telescopes [e.g. Kilo-Degree Survey, Pan-STARRS, Dark Energy Survey (DES), Large Synoptic Survey Telescope......

F. Bellagamba; M. Meneghetti; L. Moscardini; M. Bolzonella

2012-05-01T23:59:59.000Z

151

Gravitational red-shift and deflection of slow light  

E-Print Network [OSTI]

We explore the nature of the classical propagation of light through media with strong frequency-dependent dispersion in the presence of a gravitational field. In the weak field limit, gravity causes a redshift of the optical frequency, which the slow-light medium converts into a spatially-varying index of refraction. This results in the bending of a light ray in the medium. We further propose experimental techniques to amplify and detect the phenomenon using weak value measurements. Independent heuristic and rigorous derivations of this effect are given.

J. Dressel; S. G. Rajeev; J. C. Howell; A. N. Jordan

2008-10-27T23:59:59.000Z

152

THE MULTIWAVELENGTH SURVEY BY YALE-CHILE (MUSYC): DEEP MEDIUM-BAND OPTICAL IMAGING AND HIGH-QUALITY 32-BAND PHOTOMETRIC REDSHIFTS IN THE ECDF-S  

SciTech Connect (OSTI)

We present deep optical 18-medium-band photometry from the Subaru telescope over the {approx}30' x 30' Extended Chandra Deep Field-South, as part of the Multiwavelength Survey by Yale-Chile (MUSYC). This field has a wealth of ground- and space-based ancillary data, and contains the GOODS-South field and the Hubble Ultra Deep Field. We combine the Subaru imaging with existing UBVRIzJHK and Spitzer IRAC images to create a uniform catalog. Detecting sources in the MUSYC 'BVR' image we find {approx}40,000 galaxies with R {sub AB} < 25.3, the median 5{sigma} limit of the 18 medium bands. Photometric redshifts are determined using the EAzY code and compared to {approx}2000 spectroscopic redshifts in this field. The medium-band filters provide very accurate redshifts for the (bright) subset of galaxies with spectroscopic redshifts, particularly at 0.1 < z < 1.2 and at z {approx}> 3.5. For 0.1 < z < 1.2, we find a 1{sigma} scatter in {Delta}z/(1 + z) of 0.007, similar to results obtained with a similar filter set in the COSMOS field. As a demonstration of the data quality, we show that the red sequence and blue cloud can be cleanly identified in rest-frame color-magnitude diagrams at 0.1 < z < 1.2. We find that {approx}20% of the red sequence galaxies show evidence of dust emission at longer rest-frame wavelengths. The reduced images, photometric catalog, and photometric redshifts are provided through the public MUSYC Web site.

Cardamone, Carolin N.; Van Dokkum, Pieter G.; Urry, C. Megan; Brammer, Gabriel [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Taniguchi, Yoshi [Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho 2-5, Matsuyama 790-8577 (Japan); Gawiser, Eric; Bond, Nicholas [Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854-8019 (United States); Taylor, Edward; Damen, Maaike [Sterrewacht Leiden, Leiden University, NL-2300 RA Leiden (Netherlands); Treister, Ezequiel [Institute for Astronomy, 2680 Woodlawn Drive, University of Hawaii, Honolulu, HI 96822 (United States); Cobb, Bethany E. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Schawinski, Kevin [Yale Center for Astronomy and Astrophysics, Yale University, P.O. Box 208121, New Haven, CT 06520 (United States); Lira, Paulina [Departamento de Astronoma, Universidad de Chile, Casilla 36-D, Santiago (Chile); Murayama, Takashi [Astronomical Institute, Graduate School of Science, Tohoku University, Aramaki, Aoba, Sendai 980-8578 (Japan); Saito, Tomoki [Institute for Physics and Mathematics of the Universe, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Sumikawa, Kentaro, E-mail: carolin.cardamone@astro.yale.ed [Graduate School of Science and Engineering, Ehime University, Bunkyo-cho, Matsuyama 790-8577 (Japan)

2010-08-15T23:59:59.000Z

153

A novel direct torque control for induction motor drive system with low torque ripple and current distortion utilising FPGA  

Science Journals Connector (OSTI)

The conventional Direct Torque Control (DTC) is known to produce quick and robust response in ac drives. However, during steady state, notable torque and current pulsations occur. They are reflected in speed estimation, torque response and also produce acoustic noise. In this paper, a novel Space Vector Modulated Direct Torque Control (SVM-DTC) with Low Pass Filter (LPF) for induction motor drive system is proposed, which features low torque ripple, low current distortion and fixed switching frequency. The proposed scheme has been implemented on the Xilinx Spartan 3E FPGA, both simulation and experimental results show that the proposed system can dramatically improve the steady state performance while preserving the dynamic performance of the conventional DTC.

R. Rajendran; N. Devarajan

2013-01-01T23:59:59.000Z

154

Strong-field tidal distortions of rotating black holes: Formalism and results for circular, equatorial orbits  

E-Print Network [OSTI]

Tidal coupling between members of a compact binary system can have an interesting and important influence on that binary's dynamical inspiral. Tidal coupling also distorts the binary's members, changing them (at lowest order) from spheres to ellipsoids. At least in the limit of fluid bodies and Newtonian gravity, there are simple connections between the geometry of the distorted ellipsoid and the impact of tides on the orbit's evolution. In this paper, we develop tools for investigating tidal distortions of rapidly rotating black holes using techniques that are good for strong-field, fast-motion binary orbits. We use black hole perturbation theory, so our results assume extreme mass ratios. We develop tools to compute the distortion to a black hole's curvature for any spin parameter, and for tidal fields arising from any bound orbit, in the frequency domain. We also develop tools to visualize the horizon's distortion for black hole spin $a/M \\le \\sqrt{3}/2$ (leaving the more complicated $a/M > \\sqrt{3}/2$ case to a future analysis). We then study how a Kerr black hole's event horizon is distorted by a small body in a circular, equatorial orbit. We find that the connection between the geometry of tidal distortion and the orbit's evolution is not as simple as in the Newtonian limit.

Stephen O'Sullivan; Scott A. Hughes

2014-07-25T23:59:59.000Z

155

DETERMINING THE LUMINOSITY FUNCTION OF SWIFT LONG GAMMA-RAY BURSTS WITH PSEUDO-REDSHIFTS  

SciTech Connect (OSTI)

The determination of the luminosity function (LF) of gamma-ray bursts (GRBs) is an important role for the cosmological applications of the GRBs, which, however, is seriously hindered by some selection effects due to redshift measurements. In order to avoid these selection effects, we suggest calculating pseudo-redshifts for Swift GRBs according to the empirical L-E{sub p} relationship. Here, such a L-E{sub p} relationship is determined by reconciling the distributions of pseudo- and real redshifts of redshift-known GRBs. The values of E{sub p} taken from Butler's GRB catalog are estimated with Bayesian statistics rather than observed. Using the GRB sample with pseudo-redshifts of a relatively large number, we fit the redshift-resolved luminosity distributions of the GRBs with a broken-power-law LF. The fitting results suggest that the LF could evolve with redshift by a redshift-dependent break luminosity, e.g., L{sub b} = 1.2 Multiplication-Sign 10{sup 51}(1 + z){sup 2} erg s{sup -1}. The low- and high-luminosity indices are constrained to 0.8 and 2.0, respectively. It is found that the proportional coefficient between the GRB event rate and the star formation rate should correspondingly decrease with increasing redshifts.

Tan Weiwei; Yu Yunwei [Institute of Astrophysics, Central China Normal University, Wuhan (China); Cao Xiaofeng, E-mail: yuyw@phy.ccnu.edu.cn [School of Physics, Huazhong University of Science and Technology, Wuhan (China)

2013-07-20T23:59:59.000Z

156

A WFC3 Grism Emission Line Redshift Catalog in the GOODS-South Field  

E-Print Network [OSTI]

We combine HST/WFC3 imaging and G141 grism observations from the CANDELS and 3D-HST surveys to produce a catalog of grism spectroscopic redshifts for galaxies in the CANDELS/GOODS-South field. The WFC3/G141 grism spectra cover a wavelength range of 1.1 0.6. The resulting spectra are visually inspected to identify emission lines and redshifts are determined using cross-correlation with empirical spectral templates. To establish the accuracy of our redshifts, we compare our results against high-quality spectroscopic redshifts from the literature. Using a sample of 411 control galaxies, this analysis yields a precision of sigma_NMAD=0.0028 for the grism-derived redshifts, which is consistent with the accuracy reported by the 3D-HST team. Our final catalog covers an area of 153 square arcmin and contains 1019 redshifts for galaxies in GOODS-S. Roughly 60% (608/1019) of these redshifts are for galaxies with no previously published spectroscopic redshift. These new redshifts span a range of 0.677 1.5. In addition, ...

Morris, Aaron M; Trump, Jonathan R; Weiner, Benjamin J; Hathi, Nimish P; Barro, Guillermo; Dahlen, Tomas; Faber, Sandra M; Finkelstein, Steven L; Fontana, Adriano; Ferguson, Henry C; Grogin, Norman A; Grützbauch, Ruth; Guo, Yicheng; Hsu, Li-Ting; Koekemoer, Anton M; Koo, David C; Mobasher, Bahram; Pforr, Janine; Salvato, Mara; Wiklind, Tommy; Wuyts, Stijn

2015-01-01T23:59:59.000Z

157

Accessing the population of high redshift Gamma Ray Bursts  

E-Print Network [OSTI]

Gamma Ray Bursts (GRBs) are a powerful probe of the high redshift Universe. We present a tool to estimate the detection rate of high-z GRBs by a generic detector with defined energy band and sensitivity. We base this on a population model that reproduces the observed properties of GRBs detected by Swift, Fermi and CGRO in the hard X-ray and gamma-ray bands. We provide the expected cumulative distributions of the flux and fluence of simulated GRBs in different energy bands. We show that scintillator detectors, operating at relatively high energies (e.g. tens of keV to the MeV), can detect only the most luminous GRBs at high redshifts due to the link between the peak spectral energy and the luminosity (Ep-Liso) of GRBs. We show that the best strategy for catching the largest number of high-z bursts is to go softer (e.g. in the soft X-ray band) but with a very high sensitivity. For instance, an imaging soft X-ray detector operating in the 0.2-5 keV energy band reaching a sensitivity, corresponding to a fluence o...

Ghirlanda, G; Ghisellini, G; Mereghetti, S; Tagliaferri, G; Campana, S; Osborne, J P; O'Brien, P; Tanvir, N; Willingale, R; Amati, L; Basa, S; Bernardini, M G; Burlon, D; Covino, S; D'Avanzo, P; Frontera, F; Gotz, D; Melandri, A; Nava, L; Piro, L; Vergani, S D

2015-01-01T23:59:59.000Z

158

Frank Masci (1)MIPS D/L Review (S6), August 7, 2001 Optical Distortion and its Representation  

E-Print Network [OSTI]

-imaged focal planes. l Distortion is significant. Code-V optical ray trace models: 4.7% (24µm), 7.9% (70µm No re-gridding is done to make the BCD and correct for distortion. Instead, the distortion

Masci, Frank

159

The 2dF Galaxy Redshift Survey: Power-spectrum analysis of the final dataset and cosmological implications  

E-Print Network [OSTI]

We present a power spectrum analysis of the final 2dF Galaxy Redshift Survey, employing a direct Fourier method. The sample used comprises 221,414 galaxies with measured redshifts. We investigate in detail the modelling of the sample selection. A new angular mask is derived, based on revisions to the photometric calibration. The redshift selection function is determined by dividing the survey according to rest-frame colour, and deducing a self-consistent treatment of k-corrections and evolution for each population. The covariance matrix for the power-spectrum estimates is determined using two different approaches to the construction of mock surveys which are used to demonstrate that the input cosmological model can be correctly recovered. We are confident that the 2dFGRS power spectrum can be used to infer the matter content of the universe. On large scales, our estimated power spectrum shows evidence for the `baryon oscillations' that are predicted in CDM models. Fitting to a CDM model, assuming a primordial $n_{s}=1$ spectrum, $h=0.72$ and negligible neutrino mass, the preferred parameters are $\\Omega_{M} h = 0.168 \\pm 0.016$ and a baryon fraction $\\Omega_{b} /\\Omega_{M} = 0.185\\pm0.046$ (1$\\sigma$ errors). The value of $\\Omega_{M} h$ is $1\\sigma$ lower than the $0.20 \\pm 0.03$ in our 2001 analysis of the partially complete 2dFGRS. This shift is largely due to the signal from the newly-sampled regions of space, rather than the refinements in the treatment of observational selection. This analysis therefore implies a density significantly below the standard $\\Omega_{M} =0.3$: in combination with CMB data from WMAP, we infer $\\Omega_{M} =0.231\\pm 0.021$. (Abridged.)

S. Cole; W. J. Percival; J. A. Peacock; P. Norberg; C. M. Baugh; C. S. Frenk; I. Baldry; J. Bland-Hawthorn; T. Bridges; R. Cannon; M. Colless; C. Collins; W. Couch; N. J. G. Cross; G. Dalton; V. R. Eke; R. De Propris; S. P. Driver; G. Efstathiou; R. S. Ellis; K. Glazebrook; C. Jackson; A. Jenkins; O. Lahav; I. Lewis; S. Lumsden; S. Maddox; D. Madgwick; B. A. Peterson; W. Sutherland; K. Taylor

2005-08-05T23:59:59.000Z

160

Innovation Spaces  

E-Print Network [OSTI]

Innovation ecosystems today are the lifeblood or the great hope of many major economies, but at the heart of these ecosystems, there are places and spaces. Silicon Valley is not just a place, but a cluster of spaces where ...

Schneider-Sikorsky, Patrick A

2014-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

Analytical and Experimental Investigation for Distortion-Induced Fatigue in Steel Bridges  

E-Print Network [OSTI]

Distortion-induced fatigue has been extensively studied; however, retrofit techniques currently used are expensive and/or time consuming to implement. These retrofit techniques primarily fall into two categories--stiffening or softening the weak web...

Hartman, Amanda

2013-08-31T23:59:59.000Z

162

Repair of Steel Bridge Girders Damaged by Distortion-Induced Fatigue  

E-Print Network [OSTI]

Several studies have identified distortion-induced fatigue as the leading cause of cracks in steel bridges built prior to the mid-1980s. Experimental and computer simulations of 914-mm (36-in.) deep girder-cross frame subassemblies subjected...

Nagati, Amr Daniel

2012-08-31T23:59:59.000Z

163

Towards unifying multi-resolution and multi-description : a distortion-diversity perspective  

E-Print Network [OSTI]

We consider codec structures that exploit diversity in both source coding and channel coding components. We propose to study source-channel schemes using the tradeoff between end-to-end distortion level and the outage ...

Jing, Sheng, Ph. D. Massachusetts Institute of Technology

2009-01-01T23:59:59.000Z

164

E-Print Network 3.0 - artificial grid distortion Sample Search...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

2007; 18(1): 11-34 Evolution of visually guided behavior in artificial agents BYRON BOOTS, SURAJIT... images and the sources of the images in either novel or distorted...

165

Comparison of resonant current regulators for DFIG during grid voltage distortion  

Science Journals Connector (OSTI)

We investigate two different kinds of resonant current regulators for a doubly fed induction generator (DFIG) under distorted grid voltage conditions: proportional ... part. Based on the mathematical model of DFIG

Yi-peng Song; Heng Nian

2013-12-01T23:59:59.000Z

166

Analysis of harmonic distortion in an Integrated Power System for naval applications  

E-Print Network [OSTI]

This research quantifies the voltage distortion over the broad range of operating conditions experienced by a Naval warship. A steady state model of an Integrated Power System (IPS) was developed in a commercially available ...

West, Edward G., S.M. Massachusetts Institute of Technology

2005-01-01T23:59:59.000Z

167

Disk clamping distortion and slider crown sensitivity induced flying height variation  

Science Journals Connector (OSTI)

The disk clamping distortion and slider crown sensitivity induced flying height (FH) variation is investigated. The experimental results which were measured with in situ method were compared with simulated numerical results. Both results indicate that the disk clamping distortion has significant influence on the FH variation. Crown sensitivity of the sliders is one of the factors that determine the amplitude of the FH variation. Higher crown sensitivity sliders exhibit greater FH variation.

Ng Ka Wei; Yuan Zhimin; Liu Bo

2006-01-01T23:59:59.000Z

168

The 2dF Galaxy Redshift Survey: The power spectrum and the matter content of the universe  

E-Print Network [OSTI]

The 2dF Galaxy Redshift Survey has now measured in excess of 160000 galaxy redshifts. This paper presents the power spectrum of the galaxy distribution, calculated using a direct FFT-based technique. We argue that, within the k-space region 0.02

Will J. Percival; Carlton M. Baugh; Joss Bland-Hawthorn; Terry Bridges; Russell Cannon; Shaun Cole; Matthew Colless; Chris Collins; Warrick Couch; Gavin Dalton; Roberto De Propris; Simon P. Driver; George Efstathiou; Richard S. Ellis; Carlos S. Frenk; Karl Glazebrook; Carole Jackson; Ofer Lahav; Ian Lewis; Stuart Lumsden; Steve Maddox; Stephen Moody; Peder Norberg; John A. Peacock; Bruce A. Peterson; Will Sutherland; Keith Taylor

2001-05-15T23:59:59.000Z

169

Cluster scaling and its redshift evolution from XMM-Newton  

E-Print Network [OSTI]

We put together the results of XMM-Newton observations of a number of representative group and cluster samples at low and high redshifts. These results confirm the entropy ramp as an explanation of the observed scaling relations. We observe a mild evolution in the entropy of clusters. The observed degree of evolution is consistent with expectations of the shock heating at a fixed overdensity (500) with respect to the critical density in LCDM. The study of the evolution in the pressure scaling imposes strong requirements in the definition of the average temperature of the cluster. The scaling temperature should be consistent to better than the 10% level. Once such a consistency is achieved, no additional evolution in the pressure has been detected in addition to the prediction of the shock heating in the LCDM Universe.

A. Finoguenov; H. Boehringer; J. P. F. Osmond; T. J. Ponman; A. J. R. Sanderson; Y. -Y. Zhang; M. Zimer

2005-05-19T23:59:59.000Z

170

Distance-redshift relations in an anisotropic cosmological model  

SciTech Connect (OSTI)

In this paper we study an anisotropic model generated from a particular Bianchi type-III metric, which is a generalization of Gödel's metric and an exact solution of Einstein's field equations. We analyse type Ia supernova data, namely the SDSS sample calibrated with the MLCS2k2 fitter, and we verify in which ranges of distances and redshifts the anisotropy could be observed. We also consider, in a joint analysis, the position of the first peak in the CMB anisotropy spectrum, as well as current observational constraints on the Hubble constant. We conclude that a small anisotropy is permitted by the data, and that more accurate measurements of supernova distances above z = 2 might indicate the existence of such anisotropy in the universe.

Menezes, R. S. Jr. [Instituto Federal da Bahia, Salvador, BA (Brazil); Pigozzo, C.; Carneiro, S., E-mail: rsmjr@ifba.edu.br, E-mail: cpigozzo@ufba.br, E-mail: saulo.carneiro.ufba@gmail.com [Instituto de Física, Universidade Federal da Bahia, Salvador, Bahia (Brazil)

2013-03-01T23:59:59.000Z

171

Main Sequence Masses and Radii from Gravitational Redshifts  

E-Print Network [OSTI]

Modern instrumentation makes it possible to measure the mass to radius ratio for main sequence stars in open clusters from gravitational redshifts. For stars where independent information is available for either the mass or the radius, this application of general relativity directly determines the other quantity. Applicable examples are: 1) measuring the radii of solar metallicity main sequence stars for which the mass - luminosity relation is well known, 2) measuring the radii for stars where model atmospheres can be used to determine the surface gravity (the mass to radius squared ratio), 3) refining the mass - radius relation for main sequence stars, and 4) measuring the change in radius as stars evolve off the main sequence and up the giant branch.

Ted von Hippel

1995-12-02T23:59:59.000Z

172

Redshift drift in varying speed of light cosmology  

Science Journals Connector (OSTI)

Abstract We derive a redshift drift formula within the framework of varying speed of light (VSL) theory using the specific ansatz for the variability of c ( t ) = c 0 a n ( t ) . We show that negative values of the parameter n, which correspond to diminishing value of the speed of light during the evolution of the universe, effectively rescale dust matter to become little negative pressure matter, and the cosmological constant to became phantom. Positive values of n (growing c ( t ) ) make VSL model to become more like Cold Dark Matter (CDM) model. Observationally, there is a distinction between the VSL model and the ?CDM model for the admissible values of the parameter n ? ? 10 ? 5 , though it will be rather difficult to detect by planned extremely large telescopes (EELT, TMT, GMT) within their accuracy.

Adam Balcerzak; Mariusz P. Da?browski

2014-01-01T23:59:59.000Z

173

A Group of Galaxies at Redshift 2.38  

E-Print Network [OSTI]

We report the discovery of a group of galaxies at redshift 2.38. We imaged about 10% of a claimed supercluster of QSO absorption-lines at z=2.38 (Francis & Hewett 1993). In this small field (2 arcmin radius) we detect two Ly-alpha emitting galaxies. The discovery of two such galaxies in our tiny field supports Francis & Hewett's interpretation of the absorption-line supercluster as a high redshift "Great Wall". One of the Ly-alpha galaxies lies 22 arcsec from a background QSO, and may be associated with a multi-component Ly-alpha absorption complex seen in the QSO spectrum. This galaxy has an extended (50kpc) lumpy Ly-alpha morphology, surrounding a compact IR-bright nucleus. The nucleus shows a pronounced break in its optical-UV colors at about 4000 A (rest-frame), consistent with a stellar population of mass about 7E11 solar masses, an age of more than 500 Myr, and little on-going star-formation. C IV emission is detected, suggesting that a concealed AGN is present. Extended H-alpha emission is also detected; the ratio of Ly-alpha flux to H-alpha is abnormally low (about 0.7), probable evidence for extended dust. This galaxy is surrounded by a number of very red (B-K>5) objects, some of which have colors suggesting that they too are at z=2.38. We hypothesize that this galaxy, its neighbors and a surrounding lumpy gas cloud may be a giant elliptical galaxy in the act of bottom-up formation.

Paul Francis; Bruce Woodgate; Steve Warren; Palle Moller; Marg Mazzolini; Andy Bunker; James Lowenthal; Ted Williams; Takeo Minezaki; Yukiyasu Kobayashi; Yuzuru Yoshii

1995-11-10T23:59:59.000Z

174

Results on Galaxy Evolution from the CNOC2 Field Galaxy Redshift Survey  

E-Print Network [OSTI]

The CNOC2 Field Galaxy Redshift Survey presently contains some 5000 galaxy redshifts, plus extensive UBgRI photometry, and is the largest galaxy sample at moderate redshifts 0.1 < z < 0.6. Here we present some preliminary results on the galaxy luminosity function (LF) and its redshift evolution, using a sample of R < 21.5 CNOC2 galaxies, subdivided into early, intermediate, and late types based on their B-R colors relative to non-evolving galaxy models. We find a significant steepening in the faint-end slope alpha of the LF as one proceeds from early to late types. Also, for all galaxy types we find a rate of M* evolution consistent with that from passively evolving galaxy models. Finally, late-type galaxies show positive density evolution with redshift, in contrast to negative or no density evolution for earlier types.

H. Lin; H. K. C. Yee; R. G. Carlberg; S. L. Morris; M. Sawicki; D. R. Patton; G. D. Wirth; C. W. Shepherd; E. Ellingson; D. Schade; R. O. Marzke; C. J. Pritchet

1997-12-18T23:59:59.000Z

175

High Redshift Gamma-Ray Bursts: Observational Signatures of Superconducting Cosmic Strings?  

E-Print Network [OSTI]

The high-redshift gamma-ray bursts (GRBs), GRBs 080913 and 090423, challenge the conventional GRB progenitor models by their short durations, typical for short GRBs, and their high energy releases, typical for long GRBs. Meanwhile, the GRB rate inferred from high-redshift GRBs also remarkably exceeds the prediction of the collapsar model, with an ordinary star formation history. We show that all these contradictions could be eliminated naturally, if we ascribe some high-redshift GRBs to electromagnetic bursts of superconducting cosmic strings. High-redshift GRBs could become a reasonable way to test the superconducting cosmic string model, because the event rate of cosmic string bursts increases rapidly with increasing redshifts, whereas the collapsar rate decreases.

K. S. Cheng; Yun-Wei Yu; T. Harko

2010-06-11T23:59:59.000Z

176

The Apm Galaxy Survey IV: Redshifts of Rich Clusters of Galaxies  

E-Print Network [OSTI]

We present redshifts for a sample of 229 clusters selected from the APM Galaxy Survey, 189 of which are new redshift determinations. Non-cluster galaxy redshifts have been rejected from this sample using a likelihood ratio test based on the projected and apparent magnitude distributions of the cluster fields. We test this technique using cluster fields in which redshifts have been measured for more than 10 galaxies. Our redshift sample is nearly complete and has been used in previous papers to study the three dimensional distribution of rich clusters of galaxies. 157 of the clusters in our sample are listed in the Abell catalogue or supplement, and the remainder are new cluster identifications.

G. B. Dalton; G. Efstathiou; S. J. Maddox; W. J. Sutherland

1993-11-16T23:59:59.000Z

177

The Dynamics of Rapid Redshifted and Blueshifted Excursions in the Solar Halpha line  

E-Print Network [OSTI]

We analyse high temporal and spatial resolution time-series of spectral scans of the Halpha line obtained with the CRisp Imaging SpectroPolarimeter (CRISP) instrument mounted on the Swedish Solar Telescope. The data reveal highly dynamic, dark, short-lived structures known as Rapid Redshifted and Blueshifted Excursions (RREs, RBEs) that are on-disk absorption features observed in the red and blue wings of spectral lines formed in the chromosphere. We study the dynamics of RREs and RBEs by tracking their evolution in space and time, measuring the speed of the apparent motion, line-of-sight Doppler velocity, and transverse velocity of individual structures. A statistical study of their measured properties shows that RREs and RBEs have similar occurrence rates, lifetimes, lengths, and widths. They also display non-periodic, non-linear transverse motions perpendicular to their axes at speeds of 4 - 31 km/s. Furthermore, both types of structures either appear as high speed jets and blobs that are directed outwardl...

Kuridze, D; Mathioudakis, M; Erdélyi, R; Zaqarashvili, T V; Shelyag, S; Keys, P H; Keenan, F P

2015-01-01T23:59:59.000Z

178

The 2dF Galaxy Redshift Survey: voids and hierarchical scaling models  

E-Print Network [OSTI]

We measure the redshift space reduced void probability function (VPF) for 2dFGRS volume limited galaxy samples covering the absolute magnitude range M_bJ-5logh=-18 to -22. Theoretically, the VPF connects the distribution of voids to the moments of galaxy clustering of all orders, and can be used to discriminate clustering models in the weakly non-linear regime. The reduced VPF measured from the 2dFGRS is in excellent agreement with the paradigm of hierarchical scaling of the galaxy clustering moments. The accuracy of our measurement is such that we can rule out, at a very high significance, popular models for galaxy clustering, including the lognormal distribution. We demonstrate that the negative binomial model gives a very good approximation to the 2dFGRS data over a wide range of scales, out to at least 20h-1Mpc. Conversely, the reduced VPF for dark matter in a LambdaCDM universe does appear to be lognormal on small scales but deviates significantly beyond \\approx 4h-1Mpc. We find little dependence of the 2dFGRS reduced VPF on galaxy luminosity. Our results hold independently in both the north and south Galactic pole survey regions.

D. J. Croton; M. Colless; E. Gaztanaga; C. M. Baugh; P. Norberg; I. K. Baldry; J. Bland-Hawthorn; T. Bridges; R. Cannon; S. Cole; C. Collins; W. Couch; G. Dalton; R. De Propris; S. P. Driver; G. Efstathiou; R. S. Ellis; C. S. Frenk; K. Glazebrook; C. Jackson; O. Lahav; I. Lewis; S. Lumsden; S. Maddox; D. Madgwick; J. A. Peacock; B. A. Peterson; W. Sutherland; K. Taylor

2004-08-23T23:59:59.000Z

179

Space Nuclear  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

a "Group Achievement Award" by the National Aeronautics and Space Administration (NASA) for their efforts as part of the New Horizons mission launch in 2006. More....

180

A NEW POPULATION OF HIGH-REDSHIFT SHORT-DURATION GAMMA-RAY BURSTS E. Berger,1,2,3  

E-Print Network [OSTI]

A NEW POPULATION OF HIGH-REDSHIFT SHORT-DURATION GAMMA-RAY BURSTS E. Berger,1,2,3 D. B. Fox,4 P. A The redshift distribution of the short-duration gamma-ray bursts (GRBs) is a crucial, but currently fragmentary rays: bursts Online material: color figures 1. INTRODUCTION The redshift distribution of the short

Sheppard, Scott S.

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

A Red-Shifted, Fast-Relaxing Azobenzene Photoswitch for Visible Light Control of an Ionotropic Glutamate Receptor  

E-Print Network [OSTI]

A Red-Shifted, Fast-Relaxing Azobenzene Photoswitch for Visible Light Control of an Ionotropic cores with a red-shifted cis-to-trans isomerization have been previously described, they have not yet ligand (PTL) approach. We report the synthesis and characterization of a red-shifted PTL, L-MAG0460

Trauner, Dirk

182

High Redshift X-Ray Selected Quasars: CXOCY J125304.0-090737 joins the club  

E-Print Network [OSTI]

We present a new X-ray selected high redshift quasar CXOCY J125304.0-090737 at z=4.179, discovered by the Calan-Yale Deep Extragalactic Research (CYDER) Survey. This quasar is the fifth X-ray selected high redshift radio quiet quasar ($z>4$) found so far. Here, we present its observed properties which are characterized by its relative optical and X-ray faintness, its X-ray hardness and its X-ray strength compared to optically selected quasars at high redshift. We also compare the X-ray selected high redshift radio quiet quasars to their optically selected counterparts. We find that the optical to X-ray spectral slope, $\\alpha_{ox}$, is statistically harder (more X-ray luminous) for the X-ray selected radio quiet quasars than for the optically selected ones. This result, given the different range of rest frame ultraviolet luminosities studied and the selection of the samples, is consistent with the previously found correlation between X-ray and rest frame ultraviolet luminosities and would extend that result to a much wider luminosity range at high redshift. Finally, we discuss the prospects of unveiling the quasar luminosity function at high redshifts using X-ray surveys. The discovery of a high redshift object in the first field of our survey program provides suggestive evidence that X-ray selected surveys may identify more such objects than would be expected from an extrapolation of the optical luminosity function.

F. J. Castander; E. Treister; T. J. Maccarone; P. S. Coppi; J. Maza; S. E. Zepf; R. Guzman

2003-01-29T23:59:59.000Z

183

Beyond the Lone-Pair Model for Structurally Distorted Metal Oxides  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Beyond the Lone-Pair Model for Structurally Distorted Metal Oxides Print Beyond the Lone-Pair Model for Structurally Distorted Metal Oxides Print "Ferroelectricity," by analogy to ferromagnetism, is defined as the presence of spontaneous electrical polarization in a material, often arising from distortions in the material's crystal structure. In oxides of the metals lead and bismuth, such distortions were for many years attributed to the existence of "lone pair" electrons: pairs of chemically inert, nonbonding valence electrons in hybrid orbitals that leave noticeable voids in the crystal structure. At the ALS, researchers from the U.K., Ireland, and the U.S. have now obtained definitive experimental evidence that this lone-pair model must be revised. High-resolution x-ray photoemission spectroscopy (XPS) and soft x-ray emission spectroscopy (XES) have clarified the subtle electronic origins of the prototypical distortions in these crystal structures. The results have important implications for the tantalizing possibility of spintronic or superconducting devices combining ferroelectric and ferromagnetic properties.

184

Beyond the Lone-Pair Model for Structurally Distorted Metal Oxides  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Beyond the Lone-Pair Model for Structurally Distorted Metal Oxides Print Beyond the Lone-Pair Model for Structurally Distorted Metal Oxides Print "Ferroelectricity," by analogy to ferromagnetism, is defined as the presence of spontaneous electrical polarization in a material, often arising from distortions in the material's crystal structure. In oxides of the metals lead and bismuth, such distortions were for many years attributed to the existence of "lone pair" electrons: pairs of chemically inert, nonbonding valence electrons in hybrid orbitals that leave noticeable voids in the crystal structure. At the ALS, researchers from the U.K., Ireland, and the U.S. have now obtained definitive experimental evidence that this lone-pair model must be revised. High-resolution x-ray photoemission spectroscopy (XPS) and soft x-ray emission spectroscopy (XES) have clarified the subtle electronic origins of the prototypical distortions in these crystal structures. The results have important implications for the tantalizing possibility of spintronic or superconducting devices combining ferroelectric and ferromagnetic properties.

185

Relativistic distorted-wave analysis of quasielastic proton-nucleus scattering  

SciTech Connect (OSTI)

A relativistic distorted-wave impulse approximation formalism is presented for the calculation of quasielastic proton-nucleus scattering. It is shown that the double differential cross section may be written as a contraction between the hadronic tensor (describing the projectile and ejectile) and the polarization tensor (describing the nuclear target) and that this mathematical structure also holds for the case where distortions are included. The eikonal approximation is used to introduce distortions in the wave functions, and the nuclear response is described using a Fermi gas model. The highly oscillatory nine-dimensional integrand contained in the expression for the double differential cross section is computed using a novel technique based on combining traditional Gaussian integration methods with the powerful fitting functions in the matlab programming language. This work has successfully calculated the distorted-wave quasielastic differential cross section for proton-nucleus scattering within a fully relativistic framework. It is found that the distortions lead to a reduction in the double differential cross section and have a negligible effect on the computed spin observables.

Titus, N. P.; Ventel, B. I. S. van der; Niekerk, D. D. van; Hillhouse, G. C. [Department of Physics, University of Stellenbosch, Private Bag X1, Matieland 7602 (South Africa); University for Information Science and Technology, Partizanska Street, Ohrid 6000 (Macedonia, The Former Yugoslav Republic of)

2011-04-15T23:59:59.000Z

186

Space Weather  

E-Print Network [OSTI]

magnetic field that enshrouds Earth is subject to a continuing low dose of galactic cosmic radiation. The best available estimates predict that exposure to such radiation for as little as a year may-inducing radiation in space. Eugene N. Parker 18 August 2005 Any space traveler far removed from the protective

Shepherd, Simon

187

The Nature of Nearby Counterparts to Intermediate-Redshift Luminous Compact Blue Galaxies. III. Interferometric Observations of Neutral Atomic and Molecular Gas  

E-Print Network [OSTI]

We present the results of a VLA and OVRO-MMA follow-up to our single-dish surveys of the neutral atomic and molecular gas in a sample of nearby Luminous Compact Blue Galaxies (LCBGs). These luminous, blue, high surface brightness, starbursting galaxies were selected using criteria similar to that used to define LCBGs at higher redshifts. The surveys were undertaken to study the nature and evolutionary possibilities of LCBGs, using dynamical masses and gas depletion time scales as constraints. Here we present nearly resolved VLA H I maps of four LCBGs, as well as results from the literature for a fifth LCBG. In addition, we present OVRO-MMA maps of CO(J=1-0) in two of these LCBGs. We have used the resolved H I maps to separate the H I emission from target galaxies and their companions to improve the accuracy of our gas and dynamical mass estimates. For this sub-sample of LCBGs, we find that the dynamical masses measured with the single-dish telescope and interferometer are in agreement. However, we find that we have overestimated the mass of H I in two galaxies by a significant amount, possibly as much as 75%, when compared to the single-dish estimates. These two galaxies have companions within a few arc minutes; we find that our single-dish and interferometric measurements of H I masses are in reasonable agreement for galaxies with more distant companions. The H I velocity fields indicate that all five galaxies are clearly rotating yet distorted, likely due to recent interactions. Our measurements of the gas and dynamical masses of LCBGs point towards evolution into low mass galaxies such as dwarf ellipticals, irregulars, and low mass spirals, consistent with studies of LCBGs at higher redshifts.

C. A. Garland; D. J. Pisano; J. P. Williams; R. Guzman; F. J. Castander; L. J. Sage

2007-08-20T23:59:59.000Z

188

A viscoplasticity model with an enhanced control of the yield surface distortion  

E-Print Network [OSTI]

A new model of metal viscoplasticity, which takes combined isotropic, kinematic, and distortional hardening into account, is presented. The basic modeling assumptions are illustrated using a new two-dimensional rheological analogy. This demonstrative rheological model is used as a guideline for the construction of constitutive relations. The nonlinear kinematic hardening is captured using the well-known Armstrong-Frederick approach. The distortion of the yield surface is described with the help of a so-called distortional backstress. A distinctive feature of the model is that any smooth convex saturated form of the yield surface which is symmetric with respect to the loading direction can be captured. In particular, an arbitrary sharpening of the saturated yield locus in the loading direction combined with a flattening on the opposite side can be covered. Moreover, the yield locus evolves smoothly and its convexity is guaranteed at each hardening stage. A strict proof of the thermodynamic consistency is provi...

Shutov, A V

2012-01-01T23:59:59.000Z

189

Micropulse slippage and optical mode distortion in the Boeing APLE amplifier  

Science Journals Connector (OSTI)

In the Boeing Average Power Laser Experiment (APLE), the free electron laser (FEL) oscillator produces short optical pulses for input to the amplifier section. Micropulse slippage can become significant in the amplifier, competing with the effects of high gain and optical mode distortion. A two-dimensional simulation is used to study pulse slippage, and a three-dimensional simulation is used to study mode distortion. A four-dimensional simulation is used to simultaneously study these effects, and to look at the sensitivity of the efficiency to changes in various FEL parameters. We find that high gain and mode distortion effects dominate the pulse slippage effects. The amplifier is fairly insensitice to beam quality degradation and changes in the initial optical field, but a significant improvement in efficiency could be achieved by shortening the electron pulse.

J. Blau; D.J. Frost; W.B. Colson

1993-01-01T23:59:59.000Z

190

Harmonic and interharmonic distortion analysis in the grid-connected wind electric generator  

Science Journals Connector (OSTI)

The operation of wind turbines has an impact on the power quality at the connected electric network. The integration of wind electric generators with the power grid becomes a headache for power engineers in several aspects. Harmonic distortion is one of the most important phenomena which affect the grid performance. This paper provides an in-depth discussion on harmonic and interharmonic distortion taking place on the low-voltage side of the wind generator, as well as in the power grid side. A case study, to determine where a significant amount of harmonic currents or voltages exists in the system, is performed using a power quality analyser. From these measurements and subsequent calculations, the levels of harmonics and interharmonics are analysed. It is found that the harmonic distortion is invariably present on the generator side as well as on the grid side, depending on the wind turbine technology.

V. Suresh Kumar; P.S. Kannan

2007-01-01T23:59:59.000Z

191

Neutral chlorine and molecular hydrogen at high redshift  

E-Print Network [OSTI]

Chlorine and molecular hydrogen are known to be tightly linked together in the cold phase of the local interstellar medium through rapid chemical reactions. We present here the first systematic study of this relation at high redshifts using H$_2$-bearing damped Ly$\\alpha$ systems (DLAs) detected along quasar lines of sight. Using high-resolution spectroscopic data from VLT/UVES and Keck/HIRES, we report the detection of Cl$\\,$I in 9 DLAs (including 5 new detections) out of 18 high-$z$ DLAs with $N($H$_2) \\ge 10^{17.3}\\,$cm$^{-2}$ (including a new H$_2$ detection at $z=3.09145$ towards J$\\,$2100$-$0641) and present upper limits for the remaining 9 systems. We find a $\\sim$5$\\,\\sigma$ correlation between $N$(Cl$\\,$I) and $N$(H$_2$) with only $\\sim$0.2$\\,$dex dispersion over the range 18.1$\\,<\\,$log$\\,N$(H$_2$)$\\,<\\,$20.1, thus probing column densities 10 times lower those seen towards nearby stars, roughly following the relation $N$(Cl$\\,$I$) \\approx 1.5\\times10^{-6} \\times N($H$_2)$. This relation betwee...

Balashev, S A; Klimenko, V V; Petitjean, P; Srianand, R; Ledoux, C; Ivanchik, A V; Varshalovich, D A

2015-01-01T23:59:59.000Z

192

Clusters and Superclusters in the Las Campanas Redshift Survey  

E-Print Network [OSTI]

Two-dimensional high-resolution density field of galaxies of the Las Campanas Redshift Survey (LCRS) with a smoothing length 0.8 Mpc/h is used to extract clusters and groups of galaxies, and a low-resolution field with a smoothing length 10 Mpc/h to find superclusters of galaxies. Properties of these density field (DF) clusters and superclusters are studied and compared with the properties of Abell clusters and superclusters, and LCRS loose groups. We calculate the DF-cluster luminosity function, and show that most luminous clusters in high-density environments are about ten times brighter than most luminous clusters in low-density environments. We present a catalogue of DF-superclusters and show that superclusters that contain Abell clusters are richer and more luminous than superclusters without Abell clusters. A pdf file of the paper with high-resolution figures is available in Tartu Observatory web-site (http://www.aai.ee/~maret/cosmoweb.html)

J. Einasto; M. Einasto; G. H"utsi; E. Saar; D. L. Tucker; E. Tago; V. M"uller; P. Hein"am"aki; S. S. Allam

2003-04-30T23:59:59.000Z

193

Testing and selecting dark energy models with lens redshift data  

Science Journals Connector (OSTI)

In this paper, we compare seven popular dark energy models under the assumption of a flat universe by using the latest observational data of gravitationally-lensed image separations observed in the Cosmic Lens All-Sky Survey (CLASS), the PMN-NVSS Extragalactic Lens Survey (PANELS), the Sloan Digital Sky Survey (SDSS) and other surveys, which are (nearly) complete for the image separation range 0??.3????7??. We combine the 29 lens redshift data with the cosmic microwave background (CMB) observation from the Wilkinson Microwave Anisotropy Probe (WMAP7) results, the baryonic acoustic oscillation (BAO) observation from the spectroscopic Sloan Digital Sky Survey (SDSS) Data Release. The model comparison statistic, the Bayesian information criterion is also applied to assess the worth of the models. This statistic favors models that give a good fit with fewer parameters. Based on this analysis, we find that the simplest cosmological constant model that has only one free parameter is still preferred by the current data. For the other dynamical dark energy models, we find that some of them, such as the Ricci dark energy model, the Affine equation-of-state dark energy, and the generalized Chaplygin gas, can provide good fits to the current data. The Dvali-Gabadadze-Porrati model is the only one-parameter model that can give a rather good fit but also nest ? while the three-parameter model, namely, the interactive dark energy, is clearly disfavored by the data, as it is unable to provide a good fit.

Shuo Cao; Zong-Hong Zhu; Ren Zhao

2011-07-07T23:59:59.000Z

194

 

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

function approach to redshift space distortions: N-body function approach to redshift space distortions: N-body simulations Teppei Okumura IEU, Institute for the Early Universe Abstract: Galaxy redshift surveys are one of the most powerful tools to probe cosmological models. Particularly measurement of redshift space distortions (RSD), caused by peculiar velocities of galaxies, offers an attractive method to directly probe the cosmic growth history of density perturbations. A distribution function approach where RSD can be written as a sum over density weighted velocity moment correlators has recently been developed. In this talk I present the redshift-space power spectrum based on this approach using N-body simulations and show that this formalism predicts the true power spectrum up to sufficiently small scales. Although

195

An on-going multi-wavelength survey of Ly-alpha emitters at redshifts z = 2 - 8  

E-Print Network [OSTI]

In the last decade, the technique of finding Ly-alpha emitters through narrow-band imaging has become a promising method of detecting high redshift galaxies. Ly-alpha emitters have been found from redshifts z ~ 2, up to the highest redshift source known to date at z = 6.96. Several surveys are also underway to find z = 7 - 9 sources. But these very high redshift sources are too faint to be studied in great detail, and more information can be found from studying the same class of objects at lower redshifts. Here we present our survey strategy to determine the nature of Ly-alpha emitters at lower redshifts, through multi-wavelength surveys, and our plans to extend the survey to redshift z = 8.8.

Kim K. Nilsson; Johan P. U. Fynbo; Palle Moller; Alvaro Orsi

2006-11-08T23:59:59.000Z

196

Optical distortions and birefringence in high power laser windows: model and computer code  

SciTech Connect (OSTI)

A general optical model is given which predicts optical wave front distortions and birefringence due to stress and temperature variations in laser heated and pressure loaded windows for cubic lattice window materials. A computer code is described that integrates stress and thermal computations with an optical model to predict the wave front distortions. Restrictive approximations, which have been used previously to predict window temperatures and stress distributions, are avoided by using stress and thermal codes to predict these distributions within the windows. Comparisons between code predictions and experimental results are given.

Greninger, C.E.; Needham, G.A.; Rebar J. Jr.

1985-09-01T23:59:59.000Z

197

The distortion of a uniform flow field due to a finite flat plate  

E-Print Network [OSTI]

THE DISTORTION OI' A UNIFORM FLON FIELD DUE TO A FINITE FLAT PLATE A Thesis Lawrence Michael Zull Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE May... 1970 Major Subject: Mechanical F~nin~eerin THE DISTORTION OF A UNIFORM FLOV FIELD DUE TO A FINITE FLAT PLATE A Thesis by Lawrence Michael Zull Approved as to style and content by: (Ch (Head of De artment) (Member) (Member) ~Ma 19 70 AB...

Zull, Lawrence Michael

2012-06-07T23:59:59.000Z

198

Influence of Harmonic Distortions of Driving Signal on Chirp Parameter Measurement of Mach-Zehnder Modulator - Experimental Verification -  

Science Journals Connector (OSTI)

In this paper, we describe the influence of harmonic distortions of RF driving signal on chirp parameter measurement of a Mach-Zehnder modulator. The influence was experimentally...

Hayashi, Takahiro; Toda, Hiroyuki; Kawanishi, Tetsuya

199

Probing cosmic opacity at high redshifts with gamma-ray bursts  

Science Journals Connector (OSTI)

Probing the evolution of the universe at high redshifts with standard candles is a powerful way to discriminate dark energy models, where an open question nowadays is whether this component is constant or evolves with time. One possible source of ambiguity in this kind of analysis comes from cosmic opacity, which can mimic a dark energy behavior. However, most tests of cosmic opacity have been restricted to the redshift range zgamma-ray bursts, given the validity of the Amati relation, and the latest H(z) data we determine constraints on the cosmic opacity at high redshifts (z>2) for a flat ?CDM model. A possible degeneracy of the results with the adopted cosmological model is also investigated by considering a flat XCDM model. The limits on cosmic opacity in the redshift range 0gamma ray bursts samples are compatible with a transparent universe at 1? level and the results are independent of the dark energy equation of state parameter w.

R.?F.?L. Holanda and V.?C. Busti

2014-05-16T23:59:59.000Z

200

Photometric redshift requirements for lens galaxies in galaxy–galaxy lensing analyses  

Science Journals Connector (OSTI)

......Collister et al. (2007). Footnotes 1 http://www.astro-wise.org/projects/KIDS/ 2 https://www.darkenergysurvey...PRIMUS team for sharing their redshift catalogue, and thank Alison Coil and John Moustakas for help with using the PRIMUS data......

R. Nakajima; R. Mandelbaum; U. Seljak; J. D. Cohn; R. Reyes; R. Cool

2012-03-11T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

Photometric redshifts for the Dark Energy Survey and VISTA and implications for large-scale structure  

Science Journals Connector (OSTI)

......Photometric redshifts for the Dark Energy Survey and VISTA and implications for...requirements for the proposed Dark Energy Survey (DES) using two sets of mock...of dark energy. The proposed Dark Energy Survey (DES) is one such experiment......

Manda Banerji; Filipe B. Abdalla; Ofer Lahav; Huan Lin

2008-05-21T23:59:59.000Z

202

Baryonic acoustic oscillations in 21-cm emission: a probe of dark energy out to high redshifts  

Science Journals Connector (OSTI)

......Galaxy redshift surveys are best suited to studies of the dark energy at relatively late...parameters in models of dark energy, with the ability of a survey to discriminate among different models of dark energy governed by the accuracy......

J. Stuart B. Wyithe; Abraham Loeb; Paul M. Geil

2008-01-21T23:59:59.000Z

203

Comment on "The Cosmic Time in Terms of the Redshift", by Carmeli et al  

E-Print Network [OSTI]

The time-redshift relation of Carmeli et al. differs from that of the standard flat LambdaCDM model by more than 500 million years for 1 < z < 4.5.

Alan Macdonald

2006-06-08T23:59:59.000Z

204

Space Research  

Science Journals Connector (OSTI)

In the two years since the last SPIE meeting on this topic there has been much activity in both ground and space based interferometry. The author reviews those developments. He also summarizes the Strawman Sci...

G. Burkhardt; U. Esser; H. Hefele; I. Heinrich; W. Hofmann…

1998-01-01T23:59:59.000Z

205

Space Microbiology  

Science Journals Connector (OSTI)

...membranes under conditions of free fall (in a drop tower) and hypergravity (in a centrifuge). This...operation in the International Space Station. SAE technical paper 2006-01-2157. SAE, Warrendale, PA. 225 Rothschild, L., and...

Gerda Horneck; David M. Klaus; Rocco L. Mancinelli

2010-03-01T23:59:59.000Z

206

A DETAILED STUDY OF PHOTOMETRIC REDSHIFTS FOR GOODS-SOUTH GALAXIES  

SciTech Connect (OSTI)

We use the deepest and the most comprehensive photometric data currently available for GOODS-South (GOODS-S) galaxies to measure their photometric redshifts. The photometry includes VLT/VIMOS (U band), HST/ACS (F435W, F606W, F775W, and F850LP bands), VLT/ISAAC (J, H, and K{sub s} bands), and four Spitzer/IRAC channels (3.6, 4.5, 5.8, and 8.0 {mu}m). The catalog is selected in the z band (F850LP) and photometry in each band is carried out using the recently completed TFIT algorithm, which performs point-spread function (PSF) matched photometry uniformly across different instruments and filters, despite large variations in PSFs and pixel scales. Photometric redshifts are derived using the GOODZ code, which is based on the template fitting method using priors. The code also implements 'training' of the template spectral energy distribution (SED) set, using available spectroscopic redshifts in order to minimize systematic differences between the templates and the SEDs of the observed galaxies. Our final catalog covers an area of 153 arcmin{sup 2} and includes photometric redshifts for a total of 32,505 objects. The scatter between our estimated photometric and spectroscopic redshifts is {sigma} = 0.040 with 3.7% outliers to the full z-band depth of our catalog, decreasing to {sigma} = 0.039 and 2.1% outliers at a magnitude limit m{sub z} < 24.5. This is consistent with the best results previously published for GOODS-S galaxies, however, the present catalog is the deepest yet available and provides photometric redshifts for significantly more objects to deeper flux limits and higher redshifts than earlier works. Furthermore, we show that the photometric redshifts estimated here for galaxies selected as dropouts are consistent with those expected based on the Lyman break technique.

Dahlen, Tomas; Ferguson, Henry C.; Grogin, Norman A.; Koekemoer, Anton [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Mobasher, Bahram [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Dickinson, Mark [NOAO, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Giavalisco, Mauro; Guo, Yicheng; Salimbeni, Sara [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Lee, Kyoung-Soo [Yale Center for Astronomy and Astrophysics, Departments of Physics and Astronomy, Yale University, New Haven, CT 06520 (United States); Lee, Seong-Kook; Riess, Adam G. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Nonino, Mario, E-mail: dahlen@stsci.ed [INAF - Osservatorio Astronomico di Trieste, Via Tiepolo 11, I-34131 Trieste (Italy)

2010-11-20T23:59:59.000Z

207

ON THE EFFECT OF THE COSMIC MICROWAVE BACKGROUND IN HIGH-REDSHIFT (SUB-)MILLIMETER OBSERVATIONS  

SciTech Connect (OSTI)

Modern (sub-)millimeter interferometers enable the measurement of the cool gas and dust emission of high-redshift galaxies (z > 5). However, at these redshifts the cosmic microwave background (CMB) temperature is higher, approaching, and even exceeding, the temperature of cold dust and molecular gas observed in the local universe. In this paper, we discuss the impact of the warmer CMB on (sub-)millimeter observations of high-redshift galaxies. The CMB affects the observed (sub-)millimeter dust continuum and the line emission (e.g., carbon monoxide, CO) in two ways: (1) it provides an additional source of (both dust and gas) heating and (2) it is a non-negligible background against which the line and continuum emission are measured. We show that these two competing processes affect the way we interpret the dust and gas properties of high-redshift galaxies using spectral energy distribution models. We quantify these effects and provide correction factors to compute what fraction of the intrinsic dust (and line) emission can be detected against the CMB as a function of frequency, redshift, and temperature. We discuss implications on the derived properties of high-redshift galaxies from (sub-)millimeter data. Specifically, the inferred dust and molecular gas masses can be severely underestimated for cold systems if the impact of the CMB is not properly taken into account.

Da Cunha, Elisabete; Groves, Brent; Walter, Fabian; Decarli, Roberto; Rix, Hans-Walter [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)] [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Weiss, Axel [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany)] [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Bertoldi, Frank [Argelander Institute for Astronomy, University of Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany)] [Argelander Institute for Astronomy, University of Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany); Carilli, Chris [National Radio Astronomy Observatory, Pete V. Domenici Array Science Center, P.O. Box O, Socorro, NM 87801 (United States)] [National Radio Astronomy Observatory, Pete V. Domenici Array Science Center, P.O. Box O, Socorro, NM 87801 (United States); Daddi, Emanuele; Sargent, Mark [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, Irfu/Service d'Astrophysique, CEA Saclay, Orme des Merisiers, F-91191 Gif-sur-Yvette Cedex (France)] [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, Irfu/Service d'Astrophysique, CEA Saclay, Orme des Merisiers, F-91191 Gif-sur-Yvette Cedex (France); Elbaz, David; Ivison, Rob [UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom)] [UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Maiolino, Roberto [Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Avenue, Cambridge, CB3 0HE (United Kingdom)] [Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Avenue, Cambridge, CB3 0HE (United Kingdom); Riechers, Dominik [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States)] [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States); Smail, Ian, E-mail: cunha@mpia.de [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom)] [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom)

2013-03-20T23:59:59.000Z

208

Probing Dark Energy with Baryonic Acoustic Oscillations from Future Large Galaxy Redshift Surveys  

E-Print Network [OSTI]

We show that the measurement of the baryonic acoustic oscillations in large high redshift galaxy surveys offers a precision route to the measurement of dark energy. The cosmic microwave background provides the scale of the oscillations as a standard ruler that can be measured in the clustering of galaxies, thereby yielding the Hubble parameter and angular diameter distance as a function of redshift. This, in turn, enables one to probe dark energy. We use a Fisher matrix formalism to study the statistical errors for redshift surveys up to z=3 and report errors on cosmography while marginalizing over a large number of cosmological parameters including a time-dependent equation of state. With redshifts surveys combined with cosmic microwave background satellite data, we achieve errors of 0.037 on Omega_x, 0.10 on w(z=0.8), and 0.28 on dw(z)/dz for cosmological constant model. Models with less negative w(z) permit tighter constraints. We test and discuss the dependence of performance on redshift, survey conditions, and fiducial model. We find results that are competitive with the performance of future supernovae Ia surveys. We conclude that redshift surveys offer a promising independent route to the measurement of dark energy.

Hee-Jong Seo; Daniel J. Eisenstein

2003-07-26T23:59:59.000Z

209

Redshift propagation equations in the {beta}{sup '{ne}}0 Szekeres models  

SciTech Connect (OSTI)

The set of differential equations obeyed by the redshift in the general {beta}{sup '{ne}}0 Szekeres spacetimes is derived. Transversal components of the ray's momentum have to be taken into account, which leads to a set of 3 coupled differential equations. It is shown that in a general Szekeres model, and in a general Lemaitre-Tolman (L-T) model, generic light rays do not have repeatable paths (RLPs): two rays sent from the same source at different times to the same observer pass through different sequences of intermediate matter particles. The only spacetimes in the Szekeres class in which all rays are RLPs are the Friedmann models. Among the proper Szekeres models, RLPs exist only in the axially symmetric subcases, and in each one the RLPs are the null geodesics that intersect each t=constant space on the symmetry axis. In the special models with a 3-dimensional symmetry group (L-T among them), the only RLPs are radial geodesics. This shows that RLPs are very special and in the real Universe should not exist. We present several numerical examples which suggest that the rate of change of positions of objects in the sky, for the studied configuration, is 10{sup -6}-10{sup -7} arc sec per year. With the current accuracy of direction measurement, this drift would become observable after approximately 10 years of monitoring. More precise future observations will be able, in principle, to detect this effect, but there are basic problems with determining the reference direction that does not change.

Krasinski, Andrzej [N. Copernicus Astronomical Centre, Polish Academy of Sciences, Bartycka 18, 00 716 Warszawa (Poland); Bolejko, Krzysztof [Astrophysics Department, University of Oxford, Oxford OX1 3RH (United Kingdom)

2011-04-15T23:59:59.000Z

210

POTATO - a program for generating perovskite structures distorted by tilting of rigid octahedra  

Science Journals Connector (OSTI)

A program that, given the tilt system, tilt angles and octahedral bond distances, will calculate the ideal crystal structure for AMO3 and A2MM'O6 perovskites distorted by octahedral tilting is presented. See the Journal of Applied Crystallography Software List 1997.

Woodward, P.M.

1997-04-01T23:59:59.000Z

211

Magnetic field distortions produced by protective cages around sea turtle nests: unintended consequences for orientation  

E-Print Network [OSTI]

Magnetic field distortions produced by protective cages around sea turtle nests: unintended January 2003; received in revised form 8 July 2003; accepted 21 July 2003 Abstract The EarthÃ?s magnetic in cages has a high magnetic per- meability and might therefore affect the nearby field. Here we report

Lohmann, Kenneth J.

212

Effects of attenuation, dispersion, and high sound?pressure levels on acoustic wave distortion in horns  

Science Journals Connector (OSTI)

High?power sound sources have received a lot of attention in the past few years due to renewed interest in industrial applications of high?intensity sounds such as the acoustic agglomeration of aerosols or combustion enhancement. Most high?power sound sources require a horn to match the source impedance to the medium where the sound is radiated. Such horns introduce distortion in the initial waveform which can be detrimental to the agglomeration or combustion enhancement process. Boundary?layer attenuation smooths the wave shape while dispersion breaks up the symmetry of the waveform. Horn?induced dispersion is usually the dominant dispersion mechanism resulting in strong peaks in the waveform. Finally due to the very high acoustic levels at the horn throat finite?amplitude effects are responsible for a significant amount of distortion at high frequencies. Simple examples of waveform distortion due to these various mechanisms are shown. The effects of sound?pressure level horn design and frequency on distortion are illustrated for an exponential horn and several initial wave shapes. Experimental results are presented that compare very well with theory.

Frederic G. Pla; Gerhard Reethof

1988-01-01T23:59:59.000Z

213

Layered Video Coding Offset Distortion Traces for Trace-Based Evaluation of Video Quality after  

E-Print Network [OSTI]

Layered Video Coding Offset Distortion Traces for Trace-Based Evaluation of Video Quality after@kom.aau.dk Abstract-- Currently available video traces for scalable en- coded video with more than one layer are a convenient repre- sentation of the encoded video for the evaluation of networking mechanisms. The video

Reisslein, Martin

214

A Unique FPGA for the Implementation of Neural Strategies for Identifying Harmonic Distortions  

E-Print Network [OSTI]

order harmonics. Injection of compensation currents in the electrical power supply by means of an APF allows sinusoidal current shape recovery as well as reactive power compensation. In the process considerations. Those distortion identification schemes are used in nonlinear loads compensation with Active

Boyer, Edmond

215

Higher order global differentiability local approximations for 2-D and 3-D distorted element geometries  

E-Print Network [OSTI]

: C22 HGDA element,p? = p? = 5 96 4.21 ComparisonofUndistortedandDistorteddiscretizationsversusdegrees of freedom for 2-D Poisson?s equation : C33 HGDA element,p? = p? = 7 97 4.22 ComparisonofCij DistortedHGDAelementsversusdiscretizationlength for 2-D...

Maduri, Rajesh Kumar

2008-02-01T23:59:59.000Z

216

Algorithms for correcting geometric distortions in delay line anodes Erik Wilkinsona  

E-Print Network [OSTI]

Algorithms for correcting geometric distortions in delay line anodes Erik Wilkinsona , Steven V, Baltimore, MD 21218 ABSTRACT Time-delay anodes are typically used in conjunction with microchannel plates to provide photon counting and two- dimensional imaging. The anode and associated electronics are used

Colorado at Boulder, University of

217

The Inability of the White-Juday Warp Field Interferometer to Spectrally Resolve Spacetime Distortions  

E-Print Network [OSTI]

This paper contends that the spacetime distortions resulting from the experimentally obtainable electric field of a parallel plate capacitor configuration cannot be detected by the White-Juday Warp Field Interferometer [1]. Any post-processing results indicating a vanishing, non-zero difference between the charged and uncharged states of the capacitor are due to local effects rather than spacetime perturbations.

Jeff Lee; Gerald Cleaver

2014-07-31T23:59:59.000Z

218

Distortion risk measures, ambiguity aversion and optimal eort Christian Y. ROBERT z  

E-Print Network [OSTI]

as the amount of money that should be added as a bu¤er to a risk so that it becomes acceptable to an internalDistortion risk measures, ambiguity aversion and optimal e¤ort Christian Y. ROBERT z and Pierre risk measures to study how choice is inuenced by the decision-maker's attitude to risk and provide

Paris-Sud XI, Université de

219

Rate-distortion analysis and traffic modeling of scalable video coders  

E-Print Network [OSTI]

performance for video transmission based on the characteristics of existing video traffic. Rate-distortion (R-D) based schemes are often applied to improve and stabilize video quality; however, the lack of R-D modeling of scalable coders limits...

Dai, Min

2006-04-12T23:59:59.000Z

220

Perception of Perspective Distortions of Man-Made Virtual Objects Frank Steinicke and Gerd Bruder  

E-Print Network [OSTI]

: Perspective distortions of a Utah teapot rendered with different geometric fields of view and adapted fixed by a chin-rest, resulting in a DFOV of 26 . We arranged a physical Utah teapot inside the frame virtual replica of the physical teapot that we rendered with different GFOVs. In each trial the subject

Hinrichs, Klaus

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Molecular-scale structural distortion near vacancies in pentacene L. C. Grabow,2  

E-Print Network [OSTI]

Molecular-scale structural distortion near vacancies in pentacene S. Seo,1 L. C. Grabow,2 M Received 16 February 2008; accepted 3 April 2008; published online 18 April 2008 Molecular vacancies form of crystals and for the unambiguous assignment of the position of molecules relative to each vacancy

Evans, Paul G.

222

Method to Filter ECGs and Evaluate Clinical Parameter Distortion using Realistic ECG Model Parameter Fitting  

E-Print Network [OSTI]

Method to Filter ECGs and Evaluate Clinical Parameter Distortion using Realistic ECG Model Abstract By fitting a previously published nonlinear model for generating realistic ECG to waveforms, the authors demonstrate that significant points (P, Q, R, S, and T) on the ECG can be determined

McSharry, Patrick E.

223

VERY STRONG EMISSION-LINE GALAXIES IN THE WFC3 INFRARED SPECTROSCOPIC PARALLEL SURVEY AND IMPLICATIONS FOR HIGH-REDSHIFT GALAXIES  

SciTech Connect (OSTI)

The WFC3 Infrared Spectroscopic Parallel Survey uses the Hubble Space Telescope (HST) infrared grism capabilities to obtain slitless spectra of thousands of galaxies over a wide redshift range including the peak of star formation history of the universe. We select a population of very strong emission-line galaxies with rest-frame equivalent widths (EWs) higher than 200 A. A total of 176 objects are found over the redshift range 0.35 < z < 2.3 in the 180 arcmin{sup 2} area that we have analyzed so far. This population consists of young and low-mass starbursts with high specific star formation rates (sSFR). After spectroscopic follow-up of one of these galaxies with Keck/Low Resolution Imaging Spectrometer, we report the detection at z = 0.7 of an extremely metal-poor galaxy with 12 + log(O/H) =7.47 {+-} 0.11. After estimating the active galactic nucleus fraction in the sample, we show that the high-EW galaxies have higher sSFR than normal star-forming galaxies at any redshift. We find that the nebular emission lines can substantially affect the total broadband flux density with a median brightening of 0.3 mag, with some examples of line contamination producing brightening of up to 1 mag. We show that the presence of strong emission lines in low-z galaxies can mimic the color-selection criteria used in the z {approx} 8 dropout surveys. In order to effectively remove low-redshift interlopers, deep optical imaging is needed, at least 1 mag deeper than the bands in which the objects are detected. Without deep optical data, most of the interlopers cannot be ruled out in the wide shallow HST imaging surveys. Finally, we empirically demonstrate that strong nebular lines can lead to an overestimation of the mass and the age of galaxies derived from fitting of their spectral energy distribution (SED). Without removing emission lines, the age and the stellar mass estimates are overestimated by a factor of 2 on average and up to a factor of 10 for the high-EW galaxies. Therefore, the contribution of emission lines should be systematically taken into account in SED fitting of star-forming galaxies at all redshifts.

Atek, H.; Colbert, J.; Shim, H. [Spitzer Science Center, Caltech, Pasadena, CA 91125 (United States); Siana, B.; Bridge, C. [Department of Astronomy, Caltech, Pasadena, CA 91125 (United States); Scarlata, C. [Department of Astronomy, University of Minnesota-Twin Cities, Minneapolis, MN 55455 (United States); Malkan, M.; Ross, N. R. [Department of Physics and Astronomy, University of California, Los Angeles, CA (United States); McCarthy, P.; Dressler, A.; Hathi, N. P. [Observatories of the Carnegie Institution for Science, Pasadena, CA 91101 (United States); Teplitz, H. [Infrared Processing and Analysis Center, Caltech, Pasadena, CA 91125 (United States); Henry, A.; Martin, C. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Bunker, A. J. [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Fosbury, R. A. E. [Space Telescope-European Coordinating Facility, Garching bei Muenchen (Germany)

2011-12-20T23:59:59.000Z

224

Simulation of Distortion and Residual Stress Development During Heat Treatment of Steel Castings  

SciTech Connect (OSTI)

Heat treatment and associated processing, such as quenching, are critical during high strength steel casting production. These processes must be managed closely to prevent thermal and residual stresses that may result in distortion, cracking (particularly after machining), re-work, and weld repair. The risk of casting distortion limits aggressive quenching that can be beneficial to the process and yield an improved outcome. As a result of these distortions, adjustments must be made to the casting or pattern design, or tie bars must be added. Straightening castings after heat treatments can be both time-consuming and expensive. Residual stresses may reduce a casting���¢��������s overall service performance, possibly resulting in catastrophic failure. Stress relieving may help, but expends additional energy in the process. Casting software is very limited in predicting distortions during heat treatment, so corrective measures most often involve a tedious trial-and-error procedure. An extensive review of existing heat treatment residual stress and distortion modeling revealed that it is vital to predict the phase transformations and microstructure of the steel along with the thermal stress development during heat treatment. After reviewing the state-of-the-art in heat treatment residual stress and distortion modeling, an existing commercial code was selected because of its advanced capabilities in predicting phase transformations, the evolving microstructure and related properties along with thermal stress development during heat treatment. However, this software was developed for small parts created from forgings or machined stock, and not for steel castings. Therefore, its predictive capabilities for heat treatment of steel castings were investigated. Available experimental steel casting heat treatment data was determined to be of insufficient detail and breadth, and so new heat treatment experiments were designed and performed, casting and heat treating modified versions of the Navy-C ring (a classical test shape for heat treatment experiments) for several carbon and low alloy steels in order to generate data necessary to validate the code. The predicted distortions were in reasonable agreement with the experimentally measured values. However, the final distortions in the castings were small, making it difficult to determine how accurate the predictions truly are. It is recommended that further validation of the software be performed with the aid of additional experiments with large production steel castings that experience significant heat treatment distortions. It is apparent from this research that the mechanical properties of the bonded sand used for cores and sand molds are key in producing accurate stress simulation results. Because of this, experiments were performed to determine the temperature-dependent elastic modulus of a resin-bonded sand commonly utilized in the steel casting industry. The elastic modulus was seen to vary significantly with heating and cooling rates. Also, the retained room temperature elastic modulus after heating was seen to degrade significantly when the sand was heated above 125�������°C. The elastic modulus curves developed in this work can readily be utilized in casting simulation software. Additional experiments with higher heating rates are recommended to determine the behavior of the elastic modulus in the sand close to the mold-metal interface. The commercial heat treatment residual stress and distortion code, once fully validated, is expected to result in an estimated energy savings of 2.15 trillion BTU���¢��������s/year. Along with these energy savings, reduction of scrap and improvement in casting yield will result in a reduction of the environmental emissions associated with the melting and pouring of the metal which will be saved as a result of this technology.

Christoph Beckermann; Kent Carlson

2011-07-22T23:59:59.000Z

225

Resonance Raman Analysis of the Mechanism of Energy Storage and Chromophore Distortion in the Primary Visual Photoproduct  

E-Print Network [OSTI]

Resonance Raman Analysis of the Mechanism of Energy Storage and Chromophore Distortion modes and their relation to energy storage in the primary photoproduct. Low-temperature (77 K) resonance interactions of the 9- and 13-methyl groups with surrounding residues. This distortion stores light energy

Chang, Belinda

226

When politicians distort science By Robert Socolow, Roger A. Pielke, Jr. , and Randy Olson | 20 October 2011  

E-Print Network [OSTI]

When politicians distort science By Robert Socolow, Roger A. Pielke, Jr. , and Randy Olson | 20 October 2011 Republican presidential candidate and Texas Gov. Rick Perry recently questioned the science to the political distortion -- or even outright rejection -- of science? In coming weeks, three Bulletin experts

227

Photometric Redshifts for the Dark Energy Survey and VISTA and Implications for Large Scale Structure  

SciTech Connect (OSTI)

We conduct a detailed analysis of the photometric redshift requirements for the proposed Dark Energy Survey (DES) using two sets of mock galaxy simulations and an artificial neural network code-ANNz. In particular, we examine how optical photometry in the DES grizY bands can be complemented with near infra-red photometry from the planned VISTA Hemisphere Survey (VHS) in the JHK{sub s} bands in order to improve the photometric redshift estimate by a factor of two at z > 1. We draw attention to the effects of galaxy formation scenarios such as reddening on the photo-z estimate and using our neural network code, calculate A{sub v} for these reddened galaxies. We also look at the impact of using different training sets when calculating photometric redshifts. In particular, we find that using the ongoing DEEP2 and VVDS-Deep spectroscopic surveys to calibrate photometric redshifts for DES, will prove effective. However we need to be aware of uncertainties in the photometric redshift bias that arise when using different training sets as these will translate into errors in the dark energy equation of state parameter, w. Furthermore, we show that the neural network error estimate on the photometric redshift may be used to remove outliers from our samples before any kind of cosmological analysis, in particular for large-scale structure experiments. By removing all galaxies with a 1{sigma} photo-z scatter greater than 0.1 from our DES+VHS sample, we can constrain the galaxy power spectrum out to a redshift of 2 and reduce the fractional error on this power spectrum by {approx}15-20% compared to using the entire catalogue.

Banerji, Manda; Abdalla, Filipe B.; Lahav, Ofer; /University Coll. London; Lin, Huan; /Fermilab

2007-11-01T23:59:59.000Z

228

Red-Shift Distribution of Gamma-ray Bursts and Their Progenitors  

E-Print Network [OSTI]

Gamma ray bursts have been divided into two classes, long-soft gamma ray burst and short-hard gamma ray burst according to the bimodal distribution in duration time. Due to the harder spectrum and the lack of afterglows of short-hard bursts in optical and radio observations, different progenitors for short-hard bursts and long-soft bursts have been suggested. Based on the X-ray afterglow observation and the cumulative red-shift distribution of short-hard bursts, Nakar et al. (2006) found that the progenitors of short-hard bursts are consistent with old populations, such as mergers of binary neutron stars. Recently, the existence of two subclasses in long-soft bursts has been suggested after considering multiple characteristics of gamma-ray bursts, including fluences and the duration time. In this work, we extended the analysis of cumulative red-shift distribution to two possible subclasses in L-GRBs. We found that two possible subclass GRBs show different red-shift distributions, especially for red-shifts z > 1. Our results indicate that the accumulative red-shift distribution can be used as a tool to constrain the progenitor characteristics of possible subclasses in L-GRBs.

Soomin Jeong; Chang-Hwan Lee

2007-10-08T23:59:59.000Z

229

SHELS: A Complete Galaxy Redshift Survey with R$\\leq$20.6  

E-Print Network [OSTI]

The SHELS (Smithsonian Hectospec Lensing Survey) is a complete redshift survey covering two well-separated fields (F1 and F2) of the Deep Lens Survey to a limiting R = 20.6. Here we describe the redshift survey of the F2 field (R.A.$_{2000}$ = 09$^h$19$^m$32.4$^s$ and Decl.$_{2000}$ = +30$^{\\circ}$00$^{\\prime}$00$^{\\prime\\prime}$). The survey includes 16,294 new redshifts measured with the Hectospec on the MMT. The resulting survey of the 4 deg$^2$ F2 field is 95\\% complete to R = 20.6, currently the densest survey to this magnitude limit. The median survey redshift is $ z = 0.3$; the survey provides a view of structure in the range 0.1 $ \\lesssim z \\lesssim 0.6$. A movie displays the large-scale structure in the survey region. We provide a redshift, spectral index D$_n$4000, and stellar mass for each galaxy in the survey. We also provide a metallicity for each galaxy in the range 0.2 $< z <0. 38$. To demonstrate potential applications of the survey, we examine the behavior of the index D$_n$4000 as a f...

Geller, Margaret J; Fabricant, Daniel G; Kurtz, Michael J; Dell'Antonio, Ian P; Zahid, Harus Jabran

2014-01-01T23:59:59.000Z

230

Constraints on perfect fluid and scalar field dark energy models from future redshift surveys  

E-Print Network [OSTI]

We discuss the constraints that future photometric and spectroscopic redshift surveys can put on dark energy through the baryon oscillations of the power spectrum. We model the dark energy either with a perfect fluid or a scalar field and take into account the information contained in the linear growth function. We show that the growth function helps to break the degeneracy in the dark energy parameters and reduce the errors on $w_0,w_1$ roughly by 30% making more appealing multicolor surveys based on photometric redshifts. We find that a 200 square degrees spectroscopic survey reaching $z = 3$ can constrain $w_0,w_1$ to within $\\Delta w_0=0.21,\\Delta w_1=0.26$ and to $\\Delta w_0=0.39,\\Delta w_1=0.54$ using photometric redshifts with absolute uncertainty of 0.02. In the scalar field case we show that the slope $n$ of the inverse power-law potential for dark energy can be constrained to $\\Delta n=0.26$ (spectroscopic redshifts) or $\\Delta n=0.40$ (photometric redshifts), i.e. better than with future ground-based supernovae surveys or CMB data.

Luca Amendola; Claudia Quercellini; Emanuele Giallongo

2004-04-30T23:59:59.000Z

231

Redshifted and blueshifted photoluminescence emission of InAs/InP quantum dots upon amorphization of phase change material  

Science Journals Connector (OSTI)

We present the mechanisms underlying the redshifted and blueshifted photoluminescence (PL) of quantum dots (QDs) upon amorphization of phase change material (PCM). We calculated the...

Humam, Nurrul Syafawati Binti; Sato, Yu; Takahashi, Motoki; Kanazawa, Shohei; Tsumori, Nobuhiro; Regreny, Philippe; Gendry, Michel; Saiki, Toshiharu

2014-01-01T23:59:59.000Z

232

Animated Space  

E-Print Network [OSTI]

activists returning to the Square over thirty years to protest against diverse injustices, including mine closures, nuclear arms escalation, violence against women, Apartheid in South Africa, the war in Iraq and Afghanistan, repression in Palestine... movement, the protests in Southern Europe against austerity, the uprisings in Ukraine, the demonstrations against wasteful state expenditure in Brazil are the emblems of the new politics of insurgency; their rebellious public spaces tangible expression...

Amin, Ash

2014-01-01T23:59:59.000Z

233

Formula for red-shift of light signals coming from distant galaxies  

E-Print Network [OSTI]

Relying on the obtained results in Rev.[1](physics/0505035), we derive the formula relating the red-shift of light signals coming from distant galaxies to the distance of these galaxies from us and the time of detecting of these light signals. The red-shift coefficient, instead of the Hubble parameter, is introduced. It varies with time and positive at all times. Its nowadays value equals the Hubble parameter. It increases forever as time is running from the past to the future. The derived formula enables us to estimate the nowadays increasing rate of the red-shift coefficient, which is nothing but the nowadays value of the "acceleration of the expansion of the Universe".

Jian-Miin Liu

2005-05-04T23:59:59.000Z

234

Type Ia supernova rate at a redshift of ~;0.1  

SciTech Connect (OSTI)

We present the type Ia rate measurement based on two EROS supernova search campaigns (in 1999 and 2000). Sixteen supernovae identified as type Ia were discovered. The measurement of the detection efficiency, using a Monte Carlo simulation, provides the type Ia supernova explosion rate at a redshift {approx} 0.13. The result is 0.125{sub -0.034-0.028}{sup +0.044+0.028} h{sub 70}{sup 2} SNu where 1 SNu = 1 SN/10{sup 10} L{sub {circle_dot}}{sup B}/century. This value is compatible with the previous EROS measurement (Hardin et al. 2000), done with a much smaller sample, at a similar redshift. Comparison with other values at different redshifts suggests an evolution of the type Ia supernova rate.

Blanc, G.; Afonso, C.; Alard, C.; Albert, J.N.; Aldering, G.; Amadon, A.; Andersen, J.; Ansari, R.; Aubourg, E.; Balland, C.; Bareyre,P.; Beaulieu, J.P.; Charlot, X.; Conley, A.; Coutures, C.; Dahlen, T.; Derue, F.; Fan, X.; Ferlet, R.; Folatelli, G.; Fouque, P.; Garavini, G.; Glicenstein, J.F.; Goldman, B.; Goobar, A.; Gould, A.; Graff, D.; Gros,M.; Haissinski, J.; Hamadache, C.; Hardin, D.; Hook, I.M.; deKat, J.; Kent, S.; Kim, A.; Lasserre, T.; LeGuillou, L.; Lesquoy, E.; Loup, C.; Magneville, C.; Marquette, J.B.; Maurice, E.; Maury, A.; Milsztajn, A.; Moniez, M.; Mouchet, M.; Newberg, H.; Nobili, S.; Palanque-Delabrouille,N.; Perdereau, O.; Prevot, L.; Rahal, Y.R.; Regnault, N.; Rich, J.; Ruiz-Lapuente, P.; Spiro, M.; Tisserand, P.; Vidal-Madjar, A.; Vigroux,L.; Walton, N.A.; Zylberajch, S.

2004-05-11T23:59:59.000Z

235

Submillimetre sources in rich cluster fields - source counts, redshift estimates, and cooling flow limits  

E-Print Network [OSTI]

Recent submillimetre surveys have revealed a population of dusty, high redshift sources of great cosmological significance for understanding dust-enshrouded star formation in distant galaxies, and for determining the origin of the far-IR background. In this paper, we analyze nine rich cluster fields mapped at 850 and 450 microns with the SCUBA array on the James Clerk Maxwell telescope. Lensing models of the clusters are developed in order to derive accurate source counts for our sample. VLA maps of the same clusters are used to help constrain the redshift distribution of our SCUBA detections. Implications for high redshift galaxies and for the far-IR background are discussed. We also provide limits on distributed dust produced by cooling flows in these clusters.

Scott C. Chapman; Douglas Scott; Colin Borys; Gregory G. Fahlman

2000-09-05T23:59:59.000Z

236

The gravitational redshift of photons traversing a collapsing dust cloud and observable consequences  

E-Print Network [OSTI]

We analyze the frequency shift of photons propagating on an asymptotically flat spacetime describing a collapsing, spherical dust cloud. We focus on the case where the interaction of the photons with the matter can be neglected. Under fairly general assumptions on the initial data characterizing the collapse, we show that photons with zero angular momentum which travel from past to future null infinity, crossing the collapsing cloud through its center, are always redshifted with respect to stationary observers. We compute this redshift as a function of proper time of a distant stationary observer and discuss its dependency on the mass distribution of the cloud. Possible implications of this redshift effect for weak cosmic censorship and light propagation in cosmological spacetimes are also briefly discussed.

Néstor Ortiz; Olivier Sarbach

2014-11-24T23:59:59.000Z

237

A viscoplasticity model with an enhanced control of the yield surface distortion  

E-Print Network [OSTI]

A new model of metal viscoplasticity, which takes combined isotropic, kinematic, and distortional hardening into account, is presented. The basic modeling assumptions are illustrated using a new two-dimensional rheological analogy. This demonstrative rheological model is used as a guideline for the construction of constitutive relations. The nonlinear kinematic hardening is captured using the well-known Armstrong-Frederick approach. The distortion of the yield surface is described with the help of a so-called distortional backstress. A distinctive feature of the model is that any smooth convex saturated form of the yield surface which is symmetric with respect to the loading direction can be captured. In particular, an arbitrary sharpening of the saturated yield locus in the loading direction combined with a flattening on the opposite side can be covered. Moreover, the yield locus evolves smoothly and its convexity is guaranteed at each hardening stage. A strict proof of the thermodynamic consistency is provided. Finally, the predictive capabilities of the material model are verified using the experimental data for a very high work hardening annealed aluminum alloy 1100 Al.

A. V. Shutov; J. Ihlemann

2012-03-31T23:59:59.000Z

238

Self-consistent EXAFS PDF Projection Method by Matched Correction of Fourier Filter Signal Distortion  

SciTech Connect (OSTI)

Inverse problem solving computation was performed for solving PDF (pair distribution function) from simulated data EXAFS based on data FEFF. For a realistic comparison with experimental data, we chose a model of the first sub-shell Mn-0 pair showing the Jahn Teller distortion in crystalline LaMnO3. To restore the Fourier filtering signal distortion, involved in the first sub-shell information isolated from higher shell contents, relevant distortion matching function was computed initially from the proximity model, and iteratively from the prior-guess during consecutive regularization computation. Adaptive computation of EXAFS background correction is an issue of algorithm development, but our preliminary test was performed under the simulated background correction perfectly excluding the higher shell interference. In our numerical result, efficient convergence of iterative solution indicates a self-consistent tendency that a true PDF solution is convinced as a counterpart of genuine chi-data, provided that a background correction function is iteratively solved using an extended algorithm of MEPP (Matched EXAFS PDF Projection) under development.

Lee, Jay Min [Beamline Research Division, Pohang Accelerator Laboratory, POSTECH, 790-784 (Korea, Republic of); Yang, Dong-Seok [School of Science Education, Chungbuk National University, 361-763 (Korea, Republic of)

2007-02-02T23:59:59.000Z

239

A CLIPPING METHOD TO MITIGATE THE IMPACT OF CATASTROPHIC PHOTOMETRIC REDSHIFT ERRORS ON WEAK LENSING TOMOGRAPHY  

SciTech Connect (OSTI)

We use a mock catalog of galaxies based on the COSMOS galaxy catalog, including information on photometric redshift (photo-z) and spectral energy distribution types of galaxies, in order to study how to define a galaxy subsample suitable for weak lensing tomography feasible with optical (and near-IR) multi-band data. Since most useful cosmological information arises from the sample variance limited regime for upcoming lensing surveys, a suitable subsample can be obtained by discarding a large fraction of galaxies that have less reliable photo-z estimations. We develop a method to efficiently identify photo-z outliers by monitoring the width of the posterior likelihood function of redshift estimation for each galaxy. This clipping method may allow us to obtain clean tomographic redshift bins (here three bins are considered) that have almost no overlap, by discarding more than {approx}70% of galaxies with ill-defined photo-zs corresponding to the number densities of remaining galaxies less than {approx}20 arcmin{sup -2} for a Subaru-type deep survey. Restricting the ranges of magnitudes and redshifts and/or adding near-IR data help us obtain a cleaner redshift binning. Using the Fisher information matrix formalism, we propagate photo-z errors into biases in the dark energy equation of state parameter w. We find that, by discarding most of the ill-defined photo-z galaxies, the bias in w can be reduced to a level comparable to the marginalized statistical error; however, the residual small systematic bias remains due to asymmetric scatters around the relation between photometric and true redshifts. We also use the mock catalog to estimate the cumulative signal-to-noise ratios (S/Ns) for measuring the angular cross-correlations of galaxies between finer photo-z bins, finding higher S/N values for the bins that include photo-z outliers.

Nishizawa, Atsushi J. [Astronomical Institute, Tohoku University, Aramaki Aobaku, Sendai 980-8578 (Japan); Takada, Masahiro [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa City, Chiba 277-8582 (Japan); Hamana, Takashi; Furusawa, Hisanori, E-mail: nishizawa@astr.tohoku.ac.j [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka City, Tokyo 181-8588 (Japan)

2010-08-01T23:59:59.000Z

240

Redshift z ~ 1 Field Galaxies Observed with the Keck Telescope and the HST  

E-Print Network [OSTI]

We report results based on 35 new spectroscopic redshifts obtained with the Keck Telescope for field galaxies that also have photometry and morphology from survey images taken by the refurbished HST. A sample of 24 redshifts for galaxies fainter than I = 22 has a median redshift of z ~ 0.81. This result is inconsistent with the lower median redshift of z ~ 0.6 predicted by the ``maximal merger models'' of Carlberg (1996), which otherwise fit existing data. The data match an extrapolation of the CFRS, as well as predictions of certain mild luminosity-evolution models. Nearly half of the redshifts lie in two structures at z ~ 0.81 and z ~ 1.0, showing the presence of high density concentrations spanning scales of ~ 1/h Mpc, i.e., the size of groups. We find emission lines or the presence of possible neighbors in 7 of 9 otherwise luminous galaxies with red central regions at redshifts beyond z ~ 0.7. We also note a diversity of morphological types among blue galaxies at z ~ 1, including small compact galaxies, ``chains,'' and ``blue nucleated galaxies.'' These morphologies are found among local, but generally less luminous, galaxies. Distant blue galaxies also include apparently normal late-type spirals. These findings could imply modest bursts of star formation caused by mergers or interactions of small, gas-rich galaxies with each other or with larger, well-formed galaxies. This first glimpse of very faint z ~ 1 field galaxies of diverse colors and morphologies suggests that a mixture of physical processes is at work in the formation and evolution of faint field galaxies.

David C. Koo; Nicole P. Vogt; Andrew C. Phillips; Rafael Guzman; K. L. Wu; S. M. Faber; Caryl Gronwall; Duncan A. Forbes; Garth D. Illingworth; Edward J. Groth; Marc Davis; Richard G. Kron; Alexander S. Szalay

1996-04-19T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

The 2dF Galaxy Redshift Survey: Clustering properties of radio galaxies  

E-Print Network [OSTI]

The clustering properties of local, S_{1.4 GHz} > 1 mJy, radio sources are investigated for a sample of 820 objects drawn from the joint use of the FIRST and 2dF Galaxy Redshift surveys. To this aim, we present 271 new bj < 19.45 spectroscopic counterparts of FIRST radio sources to be added to those already introduced in Magliocchetti et al. (2002). The two-point correlation function for the local radio population is found to be entirely consistent with estimates obtained for the whole sample of 2dFGRS galaxies. We estimate the parameters of the real-space correlation function xi(r)=(r/r_0)^{-\\gamma}, r_0=6.7^{+0.9}_{-1.1} Mpc and \\gamma=1.6\\pm 0.1, where h=0.7 is assumed. Different results are instead obtained if we only consider sources that present signatures of AGN activity in their spectra. These objects are shown to be very strongly correlated, with r_0=10.9^{+1.0}_{-1.2} Mpc and \\gamma=2\\pm 0.1, a steeper slope than has been claimed in other recent works. No difference is found in the clustering properties of radio-AGNs of different radio luminosity. These results show that AGN-fuelled sources reside in dark matter halos more massive than \\sim 10^{13.4} M_{\\sun}},higher the corresponding figure for radio-quiet QSOs. This value can be converted into a minimum black hole mass associated with radio-loud, AGN-fuelled objects of M_{BH}^{min}\\sim 10^9 M_{\\sun}. The above results then suggest -at least for relatively faint radio objects -the existence of a threshold black hole mass associated with the onset of significant radio activity such as that of radio-loud AGNs; however, once the activity is triggered, there appears to be no evidence for a connection between black hole mass and level of radio output. (abridged)

Manuela Magliocchetti; Steve J. Maddox; Ed Hawkins; John A. Peacock; Joss Bland-Hawthorn; Terry Bridges; Russell Cannon; Shaun Cole; Matthew Colless; Chris Collins; Warrick Couch; Gavin Dalton; Roberto de Propris; Simon P. Driver; George Efstathiou; Richard S. Ellis; Carlos S. Frenk; Karl Glazebrook; Carole A. Jackson; Bryn Jones; Ofer Lahav; Ian Lewis; Stuart Lumsden; Peder Norberg; Bruce A. Peterson; Will Sutherland; Keith Taylor

2004-02-21T23:59:59.000Z

242

Assessment of radial image distortion and spherical aberration on three-dimensional synthetic aperture particle image velocimetry measurements  

E-Print Network [OSTI]

This thesis presents a numerical study of the effects of radial image distortion and spherical aberration on reconstruction quality of synthetic aperture particle image velocimetry (SAPIV) measurements. A simulated SAPIV ...

Kubaczyk, Daniel Mark

2013-01-01T23:59:59.000Z

243

Time-frequency analyses of transient-evoked stimulus-frequency and distortion-product otoacoustic emissions: Testing  

E-Print Network [OSTI]

97239and Rush University, Chicago, Illinoisb ,c Douglas H. Keefe Boys Town National Research Hospital-frequency SF and distortion-product DP OAEs to test cochlear model predictions. SFOAEs and DPOAEs were elicited

Allen, Jont

244

The Two-Point Correlation Function of Rich Clusters of Galaxies: Results from an Extended APM Cluster Redshift Survey  

E-Print Network [OSTI]

We present new estimates of the spatial two-point correlation function of rich clusters of galaxies selected from the APM Galaxy Survey. We have measured redshifts for a sample of $364$ clusters out to a depth of $\\sim 450\\hmpc$. The clusters have a mean space density of $\\bar{n} = 3.4\\times 10^{-5}\\hmpccc$. The two-point correlation function, $\\xi_{cc}$, for this sample is equal to unity at a pair-separation of $r_0 = 14.3\\pm1.75\\hmpc$ (2$\\sigma$ errors), consistent with our earlier results from a smaller sample. The new observations provide an accurate determination of the shape of $\\xi_{cc}$ to pair-separations of about $50\\hmpc$. Our results show that $\\xi_{cc}$ has a higher amplitude than expected according to the standard $\\Omega=1$ cold dark matter (CDM) model on spatial scales $2\\simlt s \\simlt 50\\hmpc$, but are in good agreement with scale-invariant fluctuations in either a low density CDM model or a critical density universe made up of a mixture of hot and cold dark matter. Our results provide strong constraints on so called `co-operative' models of galaxy formation in which the galaxy formation process introduces large-scale structure in the galaxy distribution.

G. B. Dalton; R. A. C. Croft; G. Efstathiou; W. J. Sutherland; S. J. Maddox; M. Davis

1994-07-25T23:59:59.000Z

245

Large-scale structure in a new deep IRAS galaxy redshift survey  

Science Journals Connector (OSTI)

......6 per cent; while for the FSS-z II project we have redshifts for 80.4 per cent...studies. It was during the first of these projects that the unique object FI0214 +4724 was...Under our null hypothesis we are at liberty to combine the samples to give a single......

S. J. Oliver; M. Rowan-Robinson; T. J. Broadhurst; R. G. McMahon; W. Saunders; A. Taylor; A. Lawrence; C. J. Lonsdale; P. Hacking; T. Conrow

1996-06-01T23:59:59.000Z

246

Gamma-ray burst rate: high-redshift excess and its possible origins  

Science Journals Connector (OSTI)

......Gamma-ray burst rate: high-redshift...E-mail: virgilif@physics.unlv.edu (FJV...USA 2 Department of Physics and Astronomy, University...gamma-ray burst (GRB) rates and their relationship...an increase in GRB rate as (1 +z)delta...models are able to pass the L and z constraints......

Francisco J. Virgili; Bing Zhang; Kentaro Nagamine; Jun-Hwan Choi

2011-11-11T23:59:59.000Z

247

Photon and neutrino redshift in the field of braneworld compact stars  

SciTech Connect (OSTI)

We study gravitational redshift of photons and neutrinos radiated by the braneworld neutron or quark stars that are considered in the framework of the simple model of the internal spacetime with uniform distribution of energy density, and the external spacetime described by the Reissner-Nordström geometry characterized by the braneworld ''tidal'' charge b. For negative tidal charges, the external spacetime is of the black-hole type, while for positive tidal charges, the external spacetime can be of both black-hole and naked-singularity type. We consider also extremely compact stars allowing existence of trapped null geodesics in their interior. We assume radiation of photons from the surface at radius R, neutrinos from the whole compact star interior, and their motion along radial null geodesics of the spacetime. In dependency on the compact stars parameters b and R, the photon surface redshift is related to the range of the neutrino internal redshift and the signatures of the tidal charge and possible existence of extremely compact stars are discussed. When both surface (photon) and internal (neutrino) redshift are given by observations, both compact star parameters R and b can be determined in the framework of our simple model.

Hladík, Jan; Stuchlík, Zden?k, E-mail: jan.hladik@fpf.slu.cz, E-mail: zdenek.stuchlik@fpf.slu.cz [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezrucovo nám. 13, CZ-746 01 Opava (Czech Republic)

2011-07-01T23:59:59.000Z

248

Gamma-ray bursts: cosmic rulers for the high-redshift universe?  

Science Journals Connector (OSTI)

...research-article Discussion Meeting Issue Gamma-ray bursts organized by Alan Wells, Ralph...J. Wijers and Martin Rees Gamma-ray bursts: cosmic rulers for the high-redshift...into spectral correlations in gamma-ray bursts (GBRs), in the hope that...

2007-01-01T23:59:59.000Z

249

Detecting massive galaxies at high redshift using the Dark Energy Survey  

Science Journals Connector (OSTI)

......galaxies at high redshift using the Dark Energy Survey L. J. M. Davies 1 2 C. Maraston...Porto Alegre, Brazil The Dark Energy Survey (DES) will be unprecedented...galaxy surveys (e.g. the Dark Energy survey, DES), in conjunction with......

L. J. M. Davies; C. Maraston; D. Thomas; D. Capozzi; R. H. Wechsler; M. T. Busha; M. Banerji; F. Ostrovski; C. Papovich; B. X. Santiago; R. Nichol; M. A. G. Maia; L. N. da Costa

2013-01-01T23:59:59.000Z

250

On the gravitational redshifts of spectral lines - A critico-historical study  

E-Print Network [OSTI]

A beautiful, detailed computation by Whittaker has enabled us to prove in a rigorous way that the gravitationally redshifted frequency of a monochromatic e.m. wave sent forth at the surface of a celestial body is propagated unaltered from the emitting source to terrestrial observers. We remark that in the customary treatments only qualitative and inaccurate justifications of this fact are given.

A. Loinger; T. Marsico

2011-02-26T23:59:59.000Z

251

REDSHIFTS, WIDTHS, AND RADIANCES OF SPECTRAL LINES EMITTED BY THE SOLAR TRANSITION REGION  

SciTech Connect (OSTI)

A long-standing problem in understanding the physics of the transition region has been the ubiquitous redshifts of transition region ultraviolet spectral lines relative to chromospheric emission lines, a result known since the Skylab era. Extended spectral scans performed for various regions of the solar disk by the Solar Ultraviolet Measurements of Emitted Radiation spectrometer on the Solar and Heliospheric Observatory contain thousands of line profiles per study and allow a thorough investigation of the redshift phenomenon. In using these data from seven distinct disk areas made in lines spanning the chromosphere to coronal temperature range, we derive a relationship between Doppler wavelength shifts and radiances and a relationship between line widths and radiances. While chromospheric and coronal lines emitted by very bright plasmas may in some cases show pronounced redshifts, transition-region lines predominantly show redshifts everywhere in the quiet Sun and in active regions. In coronal holes, however, they display a reduced shift, which at times altogether disappears. The observations and the findings will be described, and possible explanations will be considered.

Feldman, U. [Artep Inc. 2922 Excelsior Spring Circle, Ellicott City, Columbia, MD 21042 (United States); Dammasch, I. E. [Solar Influences Data Analysis Center, Royal Observatory of Belgium, Circular Avenue 3, 1180 Uccle, Brussels (Belgium); Doschek, G. A. [Space Science Division, Naval Research Laboratory, Washington, DC (United States)

2011-12-20T23:59:59.000Z

252

DISCOVERING BRIGHT QUASARS AT INTERMEDIATE REDSHIFTS BASED ON OPTICAL/NEAR-INFRARED COLORS  

SciTech Connect (OSTI)

The identification of quasars at intermediate redshifts (2.2 < z < 3.5) has been inefficient in most previous quasar surveys since the optical colors of quasars are similar to those of stars. The near-IR K-band excess technique has been suggested to overcome this difficulty. Our recent study also proposed to use optical/near-IR colors for selecting z < 4 quasars. To verify the effectiveness of this method, we selected a list of 105 unidentified bright targets with i ? 18.5 from the quasar candidates of SDSS DR6 with both SDSS ugriz optical and UKIDSS YJHK near-IR photometric data, which satisfy our proposed Y – K/g – z criterion and have photometric redshifts between 2.2 and 3.5 estimated from the nine-band SDSS-UKIDSS data. We observed 43 targets with the BFOSC instrument on the 2.16 m optical telescope at Xinglong station of the National Astronomical Observatory of China in the spring of 2012. We spectroscopically identified 36 targets as quasars with redshifts between 2.1 and 3.4. The high success rate of discovering these quasars in the SDSS spectroscopic surveyed area further demonstrates the robustness of both the Y – K/g – z selection criterion and the photometric redshift estimation technique. We also used the above criterion to investigate the possible stellar contamination rate among the quasar candidates of SDSS DR6, and found that the rate is much higher when selecting 3 < z < 3.5 quasar candidates than when selecting lower redshift candidates (z < 2.2). The significant improvement in the photometric redshift estimation when using the nine-band SDSS-UKIDSS data over the five-band SDSS data is demonstrated and a catalog of 7727 unidentified quasar candidates in SDSS DR6 selected with optical/near-IR colors and having photometric redshifts between 2.2 and 3.5 is provided. We also tested the Y – K/g – z selection criterion with the recently released SDSS-III/DR9 quasar catalog and found that 96.2% of 17,999 DR9 quasars with UKIDSS Y- and K-band data satisfy our criterion. With some available samples of red quasars and type II quasars, we find that 88% and 96.5% of these objects can be selected by the Y – K/g – z criterion, respectively, which supports our claim that using the Y – K/g – z criterion efficiently selects both unobscured and obscured quasars. We discuss the implications of our results on the ongoing and upcoming large optical and near-IR sky surveys.

Wu, Xue-Bing; Zuo, Wenwen; Yang, Jinyi; Yang, Qian; Wang, Feige, E-mail: wuxb@pku.edu.cn [Department of Astronomy, Peking University, Beijing 100871 (China)

2013-10-01T23:59:59.000Z

253

CLUSTER LENSING PROFILES DERIVED FROM A REDSHIFT ENHANCEMENT OF MAGNIFIED BOSS-SURVEY GALAXIES  

SciTech Connect (OSTI)

We report the first detection of a redshift-depth enhancement of background galaxies magnified by foreground clusters. Using 300,000 BOSS survey galaxies with accurate spectroscopic redshifts, we measure their mean redshift depth behind four large samples of optically selected clusters from the Sloan Digital Sky Survey (SDSS) surveys, totaling 5000-15,000 clusters. A clear trend of increasing mean redshift toward the cluster centers is found, averaged over each of the four cluster samples. In addition, we find similar but noisier behavior for an independent X-ray sample of 158 clusters lying in the foreground of the current BOSS sky area. By adopting the mass-richness relationships appropriate for each survey, we compare our results with theoretical predictions for each of the four SDSS cluster catalogs. The radial form of this redshift enhancement is well fitted by a richness-to-mass weighted composite Navarro-Frenk-White profile with an effective mass ranging between M{sub 200} {approx} 1.4-1.8 Multiplication-Sign 10{sup 14} M{sub Sun} for the optically detected cluster samples, and M{sub 200} {approx} 5.0 Multiplication-Sign 10{sup 14} M{sub Sun} for the X-ray sample. This lensing detection helps to establish the credibility of these SDSS cluster surveys, and provides a normalization for their respective mass-richness relations. In the context of the upcoming bigBOSS, Subaru Prime Focus Spectrograph, and EUCLID-NISP spectroscopic surveys, this method represents an independent means of deriving the masses of cluster samples for examining the cosmological evolution, and provides a relatively clean consistency check of weak-lensing measurements, free from the systematic limitations of shear calibration.

Coupon, Jean; Umetsu, Keiichi [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Broadhurst, Tom, E-mail: coupon@asiaa.sinica.edu.tw [Department of Theoretical Physics, University of Basque Country UPV/EHU, P.O. Box 644, E-48080 Bilbao (Spain)

2013-07-20T23:59:59.000Z

254

THE CHEMICAL PROPERTIES OF LOW-REDSHIFT QSOs  

SciTech Connect (OSTI)

We investigate the chemical properties of low-z QSOs, using archival UV spectra obtained with the Hubble Space Telescope and International Ultraviolet Explorer for a sample of 70 Palomar-Green QSOs at z < 0.5. By utilizing the flux ratios of UV emission lines (i.e., N V/C IV, (Si IV+O IV])/C IV, and N V/He II) as metallicity indicators, we compare broad-line region (BLR) gas metallicity with active galactic nucleus (AGN) properties, i.e., black hole (BH) mass, luminosity, and Eddington ratio. We find that BLR metallicity correlates with Eddington ratio while the dependency on BH mass is much weaker. Although these trends of low-z AGNs appear to be different from those of high-z QSOs, the difference between low-z and high-z samples is partly caused by the limited dynamical range of the samples. We find that metal enrichment at the center of galaxies is closely connected to the accretion activity of BHs and that the scatter of metallicity correlations with BH mass increases over cosmic time.

Shin, Jaejin; Woo, Jong-Hak [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of)] [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of); Nagao, Tohru [The Hakubi Center for Advanced Research, Kyoto University, Yoshida-Ushinomiya-cho, Sakyo-ku, Kyoto 606-8302 (Japan)] [The Hakubi Center for Advanced Research, Kyoto University, Yoshida-Ushinomiya-cho, Sakyo-ku, Kyoto 606-8302 (Japan); Kim, Sang Chul [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of)] [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of)

2013-01-20T23:59:59.000Z

255

Aspects of the rate distortion theory of Gaussian sources under spectral uncertainty  

E-Print Network [OSTI]

e Fig. 8 4o. s(~) Fig. 8 illustrates 4?(~) for r = . 8, which is a typical value in speech modeling. By numerical integration, we obtain the R(D) function given by l Ds = ? f min[0, C, (~))d~, 2 (4. 45) l r I C(u) 1 R(Ds) = ? f max 0, log ' due... constraint on the frequency-weighted mean squared error (FWMSE) between ((*} and (rl}. It can be shown [I] that this rate distortion function is given parametrically by De = Di+Ds(0)+D, Rs(De) = R((Ds(8)). (1. 4) Source Optimal Noise Encoder Ideal...

Duchesne, Joe?lle Marie-Odile

2012-06-07T23:59:59.000Z

256

High Average Power Laser Gain Medium With Low Optical Distortion Using A Transverse Flowing Liquid Host  

DOE Patents [OSTI]

A high average power, low optical distortion laser gain media is based on a flowing liquid media. A diode laser pumping device with tailored irradiance excites the laser active atom, ion or molecule within the liquid media. A laser active component of the liquid media exhibits energy storage times longer than or comparable to the thermal optical response time of the liquid. A circulation system that provides a closed loop for mixing and circulating the lasing liquid into and out of the optical cavity includes a pump, a diffuser, and a heat exchanger. A liquid flow gain cell includes flow straighteners and flow channel compression.

Comaskey, Brian J. (Walnut Creek, CA); Ault, Earl R. (Livermore, CA); Kuklo, Thomas C. (Oakdale, CA)

2005-07-05T23:59:59.000Z

257

Composite resonance: A circuit approach to the waveform distortion dynamics of an HVdc converter  

SciTech Connect (OSTI)

A frequency domain analysis is applied to a controlled HVdc converter interconnecting ac and dc networks. The converter is considered as a three port network, and described using transfer functions. Using ac and dc system frequency dependent impedances an equivalent electrical circuit is constructed. The concept of composite resonance is introduced to emphasize the interaction between the ac and dc systems, and a simplified damping factor derived to predict the dynamics of waveform distortion during transient recovery. The frequency domain analysis is verified by dynamic simulation.

Wood, A.R.; Arrillaga, J. [Univ. of Canterbury, Christchurch (New Zealand)] [Univ. of Canterbury, Christchurch (New Zealand)

1995-10-01T23:59:59.000Z

258

IDENTIFICATIONS AND PHOTOMETRIC REDSHIFTS OF THE 2 Ms CHANDRA DEEP FIELD-SOUTH SOURCES  

SciTech Connect (OSTI)

We present reliable multiwavelength identifications and high-quality photometric redshifts for the 462 X-ray sources in the {approx}2 Ms Chandra Deep Field-South (CDF-S) survey. Source identifications are carried out using deep optical-to-radio multiwavelength catalogs, and are then combined to create lists of primary and secondary counterparts for the X-ray sources. We identified reliable counterparts for 442 (95.7%) of the X-ray sources, with an expected false-match probability of {approx} 6.2%; we also selected four additional likely counterparts. The majority of the other 16 X-ray sources appear to be off-nuclear sources, sources associated with galaxy groups and clusters, high-redshift active galactic nuclei (AGNs), or spurious X-ray sources. A likelihood-ratio method is used for source matching, which effectively reduces the false-match probability at faint magnitudes compared to a simple error-circle matching method. We construct a master photometric catalog for the identified X-ray sources including up to 42 bands of UV-to-infrared data, and then calculate their photometric redshifts (photo-z's). High accuracy in the derived photo-z's is accomplished owing to (1) the up-to-date photometric data covering the full spectral energy distributions (SEDs) of the X-ray sources, (2) more accurate photometric data as a result of source deblending for {approx}10% of the sources in the infrared bands and a few percent in the optical and near-infrared bands, (3) a set of 265 galaxy, AGN, and galaxy/AGN hybrid templates carefully constructed to best represent all possible SEDs, (4) the Zurich Extragalactic Bayesian Redshift Analyzer used to derive the photo-z's, which corrects the SED templates to best represent the SEDs of real sources at different redshifts and thus improves the photo-z quality. The reliability of the photo-z's is evaluated using the subsample of 220 sources with secure spectroscopic redshifts. We achieve an accuracy of |{delta}z|/(1 + z) {approx} 1% and an outlier [with |{delta}z|/(1 + z)>0.15] fraction of {approx}1.4% for sources with spectroscopic redshifts. We performed blind tests to derive a more realistic estimate of the photo-z quality for sources without spectroscopic redshifts. We expect there are {approx}9% outliers for the relatively brighter sources (R {approx}< 26), and the outlier fraction will increase to {approx}15%-25% for the fainter sources (R {approx}> 26). The typical photo-z accuracy is {approx}6%-7%. The outlier fraction and photo-z accuracy do not appear to have a redshift dependence (for z {approx} 0-4). These photo-z's appear to be the best obtained so far for faint X-ray sources, and they have been significantly ({approx}>50%) improved compared to previous estimates of the photo-z's for the X-ray sources in the {approx}2 Ms Chandra Deep Field-North and {approx}1 Ms CDF-S.

Luo, B.; Brandt, W. N.; Xue, Y. Q.; Rafferty, D. A.; Schneider, D. P. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Brusa, M. [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching b. Muenchen (Germany); Alexander, D. M.; Lehmer, B. D. [Department of Physics, Durham University, Durham, DH1 3LE (United Kingdom); Bauer, F. E. [Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 (United States); Comastri, A. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, Bologna (Italy); Koekemoer, A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Mainieri, V. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, Garching, D-85748 (Germany); Silverman, J. D. [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8568 (Japan); Vignali, C. [Dipartimento di Astronomia, Universita di Bologna, Via Ranzani 1, Bologna (Italy)

2010-04-01T23:59:59.000Z

259

The Distortion of the Cosmic Microwave Background by the Milky Way  

E-Print Network [OSTI]

The Milky Way can act as a large-scale weak gravitational lens of the cosmic microwave background (CMB). We study this effect using a photon ray-tracing code and a Galactic mass distribution with disk, bulge and halo components. For an observer at the Sun's coordinates in the Galaxy, the bending of CMB photon paths is limited to less than one arcsecond, and only for rays that pass within a few degrees of the Galactic Center. However, the entire sky is affected, resulting in global distortions of the CMB on large angular scales. These distortions can cause the low-order multipoles of a spherical harmonic expansion of the CMB sky temperature to leak into higher-order modes. Thus the component of the CMB dipole that results from the Local Group's motion relative to the local cosmic frame of rest contributes to higher-order moments for an observer in the solar system. With our ray-tracing code we show that the phenomenon is not sensitive to the specific choice of Galactic potential. We also quantitatively rule it...

Czaja, Benjamin

2014-01-01T23:59:59.000Z

260

Prediction of Finite?Amplitude Waveform Distortion with Dissipation and Spreading Loss  

Science Journals Connector (OSTI)

A new technique recently used for solution of the plane?wave Burgers' equation in a lossless medium has led to the development of an approximate analytical solution to Burgers' equation with dissipation for plane cylindrical and spherical sinusoidal waves. The solution is valid for the initial propagation zone prior to sawtooth formation for Gol'dberg numbers larger than 5 as indicated by comparison with a previous numerical solution of Burgers' equation for a plane wave. The approximate solution is expressed as a series that converges rapidly enough to permit calculations of harmonic levels by hand. For more viscous cases where the approximate solution fails the above technique leads easily to a numerical solution of Burgers' equation. By comparing the harmonic levels predicted by the numerical solution with empirical data taken on distorting spherical waves it is concluded that numerical results tend to be below the measured values. It is felt that the numerical method can be of use in predicting distortion levels for practical underwater systems that exploit finite?amplitude effects.

Boyd B. Cary

1968-01-01T23:59:59.000Z

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261

THE CLUSTERING OF GALAXIES IN THE SDSS-III BARYON OSCILLATION SPECTROSCOPIC SURVEY: LUMINOSITY AND COLOR DEPENDENCE AND REDSHIFT EVOLUTION  

SciTech Connect (OSTI)

We measure the luminosity and color dependence and the redshift evolution of galaxy clustering in the Sloan Digital Sky Survey-III Baryon Oscillation Spectroscopic Survey Ninth Data Release. We focus on the projected two-point correlation function (2PCF) of subsets of its CMASS sample, which includes about 260,000 galaxies over {approx}3300 deg{sup 2} in the redshift range 0.43 < z < 0.7. To minimize the selection effect on galaxy clustering, we construct well-defined luminosity and color subsamples by carefully accounting for the CMASS galaxy selection cuts. The 2PCF of the whole CMASS sample, if approximated by a power-law, has a correlation length of r{sub 0} = 7.93 {+-} 0.06 h {sup -1} Mpc and an index of {gamma} = 1.85 {+-} 0.01. Clear dependences on galaxy luminosity and color are found for the projected 2PCF in all redshift bins, with more luminous and redder galaxies generally exhibiting stronger clustering and steeper 2PCF. The color dependence is also clearly seen for galaxies within the red sequence, consistent with the behavior of SDSS-II main sample galaxies at lower redshifts. At a given luminosity (k + e corrected), no significant evolution of the projected 2PCFs with redshift is detected for red sequence galaxies. We also construct galaxy samples of fixed number density at different redshifts, using redshift-dependent magnitude thresholds. The clustering of these galaxies in the CMASS redshift range is found to be consistent with that predicted by passive evolution. Our measurements of the luminosity and color dependence and redshift evolution of galaxy clustering will allow for detailed modeling of the relation between galaxies and dark matter halos and new constraints on galaxy formation and evolution.

Guo Hong; Zehavi, Idit [Department of Astronomy, Case Western Reserve University, OH 44106 (United States); Zheng Zheng [Department of Physics and Astronomy, University of Utah, UT 84112 (United States); Weinberg, David H. [Department of Astronomy and CCAPP, Ohio State University, Columbus, OH 43210 (United States); Berlind, Andreas A. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Blanton, Michael [Center for Cosmology and Particle Physics, New York University, New York, NY 10003 (United States); Chen Yanmei [Department of Astronomy, Nanjing University, Nanjing 210093 (China); Eisenstein, Daniel J.; McBride, Cameron K. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Ho, Shirley; Ross, Nicholas P. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Kazin, Eyal [Center for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, Victoria 3122 (Australia); Manera, Marc; Maraston, Claudia; Percival, Will J.; Ross, Ashley J.; Samushia, Lado [Institute of Cosmology and Gravitation, Dennis Sciama Building, University of Portsmouth, Portsmouth, PO1 3FX (United Kingdom); Nuza, Sebastian E. [Leibniz-Institut fuer Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); Padmanabhan, Nikhil; Parejko, John K. [Department of Physics, Yale University, 260 Whitney Ave, New Haven, CT 06520 (United States); and others

2013-04-20T23:59:59.000Z

262

Lattice distortions in layered type arsenides LnTAs{sub 2} (Ln=La-Nd, Sm, Gd, Tb; T=Ag, Au): Crystal structures, electronic and magnetic properties  

SciTech Connect (OSTI)

The lanthanide coinage-metal diarsenides LnTAs{sub 2} (Ln=La, Ce-Nd, Sm; T=Ag, Au) have been reinvestigated and their structures have been refined from single crystal X-ray data. Two different distortion variants of the HfCuSi{sub 2} type are found: PrAgAs{sub 2}, NdAgAs{sub 2}, SmAgAs{sub 2}, GdAgAs{sub 2}, TbAgAs{sub 2}, NdAuAs{sub 2} and SmAuAs{sub 2} crystallize as twofold superstructures in space group Pmcn with the As atoms of their planar layers forming zigzag chains, whereas LaAgAs{sub 2}, CeAgAs{sub 2} and PrAuAs{sub 2} adopt a fourfold superstructure (space group Pmca) with cis-trans chains of As atoms. The respective atomic positions can be derived from the HfCuSi{sub 2} type by group-subgroup relations. The compounds with zigzag chains of As atoms exhibit metallic behaviour while those with cis-trans chains are semiconducting as measured on powder pellets. The majority of the compounds including 4f elements show antiferromagnetic ordering at T{sub N}<20 K. - Text3: Zigzig vs. cis-trans.

Rutzinger, D.; Bartsch, C. [Anorganische Chemie, Fachrichtung Chemie und Lebensmittelchemie, Technische Universitaet Dresden, D-01062 Dresden (Germany); Doerr, M. [Institut fuer Festkoerperphysik, Technische Universitaet Dresden, D-01062 Dresden (Germany); Rosner, H. [Max-Planck-Institut fuer Chemische Physik fester Stoffe, Noethnitzer Str. 40, D-01187 Dresden (Germany); Neu, V. [IFW Dresden, Institut fuer metallische Werkstoffe, Helmholtzstr. 20, D-01069 Dresden (Germany); Doert, Th., E-mail: thomas.doert@chemie.tu-dresden.d [Anorganische Chemie, Fachrichtung Chemie und Lebensmittelchemie, Technische Universitaet Dresden, D-01062 Dresden (Germany); Ruck, M. [Anorganische Chemie, Fachrichtung Chemie und Lebensmittelchemie, Technische Universitaet Dresden, D-01062 Dresden (Germany)

2010-03-15T23:59:59.000Z

263

Lack of a Jahn-Teller Distortion in La1-xSrxCoO3 Determined by EXAFS and  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Lack of a Jahn-Teller Distortion in Lack of a Jahn-Teller Distortion in La1-xSrxCoO3 Determined by EXAFS and Neutron PDF Studies The transition metal oxides exhibit a wide range of interesting properties, of which superconductivity in the copper oxides and colossal magnetoresistance in the manganese oxides are perhaps the best known. However, the strange magnetic behavior of several cobalt oxides is another example of these unusual properties, although not yet as intensively studied. The cobaltite system La1-xSrxCoO3 (LSCO) has a rich temperature-concentration phase diagram with anti-ferromagnetism and insulating behavior at low Sr concentrations, and ferromagnetism and metallic behavior at higher concentrations. The magnetism for the end compound LaCoO3 (LCO) is particularly unusual; it has no Co spin magnetic moment at low T (and is diamagnetic). As T increases from 4K, the magnetic susceptibility increases dramatically up to roughly 100K, and then decreases as T is increased to 300K. This behavior has been attributed to Co+3 having several different spin configurations. Initially only two were considered, a low spin state (LS, S=0) that is not magnetic and a high spin state (HS, S=2) that is strongly magnetic. In the '90s a third, intermediate spin configuration (IS, S=1) was proposed by Potze, et al. and Korotin, et al; this configuration should result in a distortion of the CoO6 octahedra (called a Jahn-Teller (JT) distortion). In the late '90s, Louca et al. reported neutron PDF results indicating a distorted Co-O environment, comparable to the Mn-O distortions observed in the similar manganite systems La1-yCayMnO3 (LCMO) and La1-zSrzMnO3 (LSMO). However, to date, these neutron PDF data for the cobaltites are the only structural results that support a JT distortion. While some recent experimental results are argued to be consistent with a large Co-O JT distortion and its associated IS state, many others appear to be inconsistent with such an interpretation. Our group at UC Santa Cruz, therefore took a closer look at the possibility of a JT distortion of the CoO6 octahedra, using a combination of the EXAFS and neutron PDF techniques; here we focus on the Co K-edge EXAFS results, for data collected at SSRL.

264

Measuring the Cosmic Shear in Fourier Space  

E-Print Network [OSTI]

We propose to measure the weak cosmic shear using the spatial derivatives of the galaxy surface brightness field. The measurement should be carried out in Fourier space, in which the point spread function (PSF) can be transformed to a desired form with multiplications, and the spatial derivatives can be easily measured. This method is mathematically well defined regardless of the galaxy morphology and the form of the PSF, and involves simple procedures of image processing. Furthermore, with high resolution galaxy images, this approach allows one to probe the shape distortions of galaxy substructures, which can potentially provide much more independent shear measurements than the ellipticities of the whole galaxy. We demonstrate the efficiency of this method using computer-generated mock galaxy images.

Jun Zhang

2006-12-06T23:59:59.000Z

265

Age of High Redshift Objects - a Litmus Test for the Dark Energy Models  

E-Print Network [OSTI]

The discovery of the quasar, the APM 08279+5255 at z = 3.91 whose age is 2-3 Gyr has once again led to ``age crisis''. The noticeable fact about this object is that it cannot be accommodated in a universe with $\\Omega_m = 0.27$, currently accepted value of matter density parameter and $\\omega = \\mathrm{constant}$. In this work, we explore the concordance of various dark energy parameterizations ($w(z)$ models) with the age estimates of the old high redshift objects. It is alarming to note that the quasar cannot be accommodated in any dark energy model even for $\\Omega_m = 0.23$, which corresponds to $1 \\sigma$ deviation below the best fit value provided by WMAP. There is a need to look for alternative cosmologies or some other dark energy parameterizations which allow the existence of the high redshift objects.

Deepak Jain; Abha Dev

2005-09-08T23:59:59.000Z

266

Spectroscopic Gravitational Lens Candidates in the CNOC2 Field Galaxy Redshift Survey  

E-Print Network [OSTI]

We present five candidate gravitational lenses discovered spectroscopically in the Canadian Network for Observational Cosmology Field Galaxy Redshift Survey (CNOC2), along with one found in followup observations. Each has a secure redshift based on several features, plus a discrepant emission line which does not match any known or plausible feature and is visible in multiple direct spectral images. We identify these lines as Lyman-alpha or [OII] emission from galaxies lensed by, or projected onto, the CNOC2 target galaxies. Einstein radii estimated from the candidate deflector galaxy luminosities indicate that for two candidates the lines are probably [OII] from projected z3 galaxies. We estimate that only 1.9+-0.7 [OII]-emitting galaxies are expected to project onto target galaxies in the original CNOC2 sample, consistent with three or four of the six candidates being true gravitational lenses.

Patrick B. Hall; H. K. C. Yee; Huan Lin; Simon L. Morris; Michael D. Gladders; R. G. Carlberg; David R. Patton; Marcin Sawicki; Charles W. Shepherd; Gregory D. Wirth

2000-06-29T23:59:59.000Z

267

The Efficacy of Galaxy Shape Parameters in Photometric Redshift Estimation: A Neural Network Approach  

SciTech Connect (OSTI)

We present a determination of the effects of including galaxy morphological parameters in photometric redshift estimation with an artificial neural network method. Neural networks, which recognize patterns in the information content of data in an unbiased way, can be a useful estimator of the additional information contained in extra parameters, such as those describing morphology, if the input data are treated on an equal footing. We show that certain principal components of the morphology information are correlated with galaxy type. However, we find that for the data used the inclusion of morphological information does not have a statistically significant benefit for photometric redshift estimation with the techniques employed here. The inclusion of these parameters may result in a trade-off between extra information and additional noise, with the additional noise becoming more dominant as more parameters are added.

Singal, J.; Shmakova, M.; Gerke, B.; /KIPAC, Menlo Park /SLAC /Stanford U.; Griffith, R.L.; /Caltech, JPL; Lotz, J.; /NOAO, Tucson

2011-05-20T23:59:59.000Z

268

Photometric redshift estimation based on data mining with PhotoRApToR  

E-Print Network [OSTI]

Photometric redshifts (photo-z) are crucial to the scienti?c exploitation of modern panchromatic digital surveys. In this paper we present PhotoRApToR (Photometric Research Application To Redshift): a Java/C++ based desktop application capable to solve non-linear regression and multi-variate classi?cation problems, in particular specialized for photo-z estimation. It embeds a machine learning algorithm, namely a multilayer neural network trained by the Quasi Newton learning rule, and special tools dedicated to pre- and postprocessing data. PhotoRApToR has been successfully tested on several scienti?c cases. The application is available for free download from the DAME Program web site.

Cavuoti, Stefano; De Stefano, Virgilio; Longo, Giuseppe

2015-01-01T23:59:59.000Z

269

The Intermediate-band Dropout Method: A New Method to Search for High-Redshift Galaxies  

E-Print Network [OSTI]

We propose a new method to search for high-redshift galaxies that is based on an intermediate-band dropout technique rather than the usual broad-band dropout one. In this method, we use an intermediate-band filter whose central wavelength is longer than 7000 \\AA. This new method makes it possible to distinguish both very late-type stars such as L and T dwarfs and dusty galaxies at intermediate redshift from real high-$z$ Lyman break galaxies. The reason for this is that such interlopers do not show strong intermediate-band depression although they have very red broad-band colors that are indicative of Lyman break galaxies. Applying our new method to imaging data sets obtained with the Suprime-Cam on the Subaru Telescope, we find a new sample of Lyman break galaxies at $z \\simeq 5$.

Shioya, Y; Ajiki, M; Nagao, T; Murayama, T; Sasaki, S; Sumiya, R; Hatakeyama, Y; Shioya, Yasuhiro; Taniguchi, Yoshiaki; Ajiki, Masaru; Nagao, Tohru; Murayama, Takashi; Sasaki, Shunji; Sumiya, Ryoko; Hatakeyama, Yuichiro

2005-01-01T23:59:59.000Z

270

Luminosity function and density field of the Sloan and Las Campanas Redshift Survey  

E-Print Network [OSTI]

The luminosity function of galaxies of the Early Data Release of the Sloan Digital Sky Survey (SDSS) and the Las Campanas Redshift Survey (LCRS) is calculated. The luminosity function depends on redshift, density of the environment and is different for the Norther and Southern slice of SDSS. Luminosity functions is used to derive the number and luminosity density fields of galaxies of the SDSS and LCRS surveys with a grid size of 1 h^{-1} Mpc for flat cosmological models with \\Omega_m=0.3 and \\Omega_\\Lambda =0.7. We find that the luminosity function depends on the density of the environment: in high-density regions brightest galaxies are more luminous than in low-density regions by a factor up to 5.

G. Hütsi; J. Einasto; D. L. Tucker; E. Saar; M. Einasto; V. Müller; P. Heinämäki; S. S. Allam

2002-12-13T23:59:59.000Z

271

The Universe on Very Large Scales: A View from the Las Campanas Redshift Survey  

E-Print Network [OSTI]

The Las Campanas Redshift Survey (LCRS) is among the first galaxy redshift surveys to sample a reasonably fair volume of the local Universe. On the largest scales (>> 100/h Mpc), the galaxy distribution appears smooth; on relatively small scales (<10/h Mpc), the LCRS tends to confirm the clustering characteristics observed in previous, shallower surveys. Here, however, we concern ourselves primarily with clustering on scales near the transition to homogeneity (50-200/h Mpc). We conclude that the general evidence tends to support enhanced clustering on ~ 100/h Mpc scales, but that this result should be confirmed with additional analyses of the LCRS dataset (especially 2D analyses) and with investigations of new and upcoming large-scale surveys covering different regions and/or having different selection effects.

D. L. Tucker; H. Lin; S. Shectman

1999-02-01T23:59:59.000Z

272

High redshift AGNs and HI reionisation: limits from the unresolved X-ray background  

E-Print Network [OSTI]

The rapidly declining population of bright quasars at z~3 appears to make an increasingly small contribution to the ionising background at the HI Lyman limit. It is then generally though that massive stars in (pre-)galactic systems may provide the additional ionising flux needed to complete HI reionisation by z>6. A galaxy dominated background, however, may require that the escape fraction of Lyman continuum radiation from high redshift galaxies is as high as 10%, a value somewhat at odds with (admittedly scarce) observational constraints. High escape fractions from dwarf galaxies have been advocated, or, alternatively, a so-far undetected (or barely detected) population of unobscured, high-redshift faint AGNs. Here we question the latter hypothesis, and show that such sources, to be consistent with the measured level of the unresolved X-ray background at z=0, can provide a fraction of the HII filling factor not larger than 13% by z=6. The fraction rises to 10%.

Haardt, Francesco

2015-01-01T23:59:59.000Z

273

The star formation rate at redshift one: H-alpha spectroscopy with CIRPASS  

E-Print Network [OSTI]

We have conducted an H-alpha survey of 38 0.77redshift galaxies. Stacking the spectra in the rest-frame to infer a total SFR for the field, we find a lower limit (uncorrected for dust reddening) on the star formation rate density at redshift z = 1 of 0.04Msol/yr/Mpc^3. This implies rapid evolution in the star formation rate density from z = 0 to z = 1 which is proportional to (1+z)^{3.1}.

Michelle Doherty; Andrew Bunker; Robert Sharp; Gavin Dalton; Ian Parry; Ian Lewis

2006-04-27T23:59:59.000Z

274

The 2dF Galaxy Redshift Survey: Final Data Release  

E-Print Network [OSTI]

The 2dF Galaxy Redshift Survey (2dFGRS) has obtained spectra for 245591 sources, mainly galaxies, brighter than a nominal extinction-corrected magnitude limit of b_J=19.45. Reliable redshifts were measured for 221414 galaxies. The galaxies are selected from the extended APM Galaxy Survey and cover an area of approximately 1500 square degrees in three regions: an NGP strip, an SGP strip and random fields scattered around the SGP strip. This paper describes the 2dFGRS final data release of 30 June 2003 and complements Colless et al. (2001), which described the survey and the initial 100k data release. The 2dFGRS database and full documentation are available on the WWW at http://www.mso.anu.edu.au/2dFGRS/

Matthew Colless; Bruce A. Peterson; Carole Jackson; John A. Peacock; Shaun Cole; Peder Norberg; Ivan K. Baldry; Carlton M. Baugh; Joss Bland-Hawthorn; Terry Bridges; Russell Cannon; Chris Collins; Warrick Couch; Nicholas Cross; Gavin Dalton; Roberto De Propris; Simon P. Driver; George Efstathiou; Richard S. Ellis; Carlos S. Frenk; Karl Glazebrook; Ofer Lahav; Ian Lewis; Stuart Lumsden; Steve Maddox; Darren Madgwick; Will Sutherland; Keith Taylor

2003-06-27T23:59:59.000Z

275

Distance-Redshift in Inhomogeneous $Omega_0=1$ Friedmann-Lemaitre-Robertson-Walker Cosmology  

E-Print Network [OSTI]

Distance--redshift relations are given in terms of associated Legendre functions for partially filled beam observations inspatially flat Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmologies. These models are dynamically pressure-free, flat FLRW on large scales but, due to mass inhomogeneities, differ in their optical properties. The partially filled beam area-redshift equation is a Lame$^{\\prime}$ equation for arbitrary FLRW and is shown to simplify to the associated Legendre equation for the spatially flat, i.e. $\\Omega_0=1$ case. We fit these new analytic Hubble curves to recent supernovae (SNe) data in an attempt to determine both the mass parameter $\\Omega_m$ and the beam filling parameter $\

R. Kantowski; R. C. Thomas

2001-06-18T23:59:59.000Z

276

THE EGNoG SURVEY: MOLECULAR GAS IN INTERMEDIATE-REDSHIFT STAR-FORMING GALAXIES  

SciTech Connect (OSTI)

We present the Evolution of molecular Gas in Normal Galaxies (EGNoG) survey, an observational study of molecular gas in 31 star-forming galaxies from z = 0.05 to z = 0.5, with stellar masses of (4-30) Multiplication-Sign 10{sup 10} M{sub Sun} and star formation rates of 4-100 M{sub Sun} yr{sup -1}. This survey probes a relatively un-observed redshift range in which the molecular gas content of galaxies is expected to have evolved significantly. To trace the molecular gas in the EGNoG galaxies, we observe the CO(J = 1 {yields} 0) and CO(J = 3 {yields} 2) rotational lines using the Combined Array for Research in Millimeter-wave Astronomy (CARMA). We detect 24 of 31 galaxies and present resolved maps of 10 galaxies in the lower redshift portion of the survey. We use a bimodal prescription for the CO to molecular gas conversion factor, based on specific star formation rate, and compare the EGNoG galaxies to a large sample of galaxies assembled from the literature. We find an average molecular gas depletion time of 0.76 {+-} 0.54 Gyr for normal galaxies and 0.06 {+-} 0.04 Gyr for starburst galaxies. We calculate an average molecular gas fraction of 7%-20% at the intermediate redshifts probed by the EGNoG survey. By expressing the molecular gas fraction in terms of the specific star formation rate and molecular gas depletion time (using typical values), we also calculate the expected evolution of the molecular gas fraction with redshift. The predicted behavior agrees well with the significant evolution observed from z {approx} 2.5 to today.

Bauermeister, A.; Blitz, L.; Wright, M. [Department of Astronomy and Radio Astronomy Laboratory, University of California at Berkeley, B-20 Hearst Field Annex, Berkeley, CA 94720 (United States); Bolatto, A.; Teuben, P. [Department of Astronomy and Laboratory for Millimeter-wave Astronomy, University of Maryland, College Park, MD 20742 (United States); Bureau, M. [Sub-department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Leroy, A. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Ostriker, E. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Wong, T., E-mail: amberb@astro.berkeley.edu [Department of Astronomy, University of Illinois, MC-221, 1002 W. Green Street, Urbana, IL 61801 (United States)

2013-05-10T23:59:59.000Z

277

The first detection of [OIII] emission from high-redshift damped Lyman-alpha galaxies  

E-Print Network [OSTI]

We present the detection of [OIII] emission lines from the galaxies responsible for two high-redshift z>1.75 damped Lyman-alpha (DLA) absorption lines. These are the first detections of rest-frame optical emission lines from high-redshift DLA galaxies. Unlike the Lyman-alpha line, the [OIII] line provides a measure of the systemic velocity of the galaxy. We compare the [OIII] redshifts with the velocity profile of the low-ionisation metal lines in these two absorbers, with the goal of distinguishing between the model of Prochaska and Wolfe of DLA absorbers as large rapidly rotating cold thick discs, and the standard hierarchical CDM model of structure formation, in which DLAs arise in protogalactic fragments. We find some discrepancies with the predictions of the former model. Furthermore the image of the DLA galaxy towards Q2206-1958 shows a complex disturbed morphology, which is more in accord with the hierarchical picture. We use the properties of the rest-frame optical emission lines to further explore the question posed by Moller et al.: are high-redshift DLA galaxies Lyman-break galaxies (LBGs) selected by gas cross section? The measured velocity dispersions of the DLA galaxies are in agreement with this picture, while the data on the [OIII] luminosities and the velocity differences between the Lyman-alpha and [OIII] lines are inconclusive, as there are insufficient LBG measurements overlapping in luminosity. Finally we estimate the star formation rates in these two DLA galaxies, using a variety of diagnostics, and include a discussion of the extent to which the [OIII] line is useful for this purpose. (abridged)

S. J. Weatherley; S. J. Warren; P. Moller; S. M. Fall; J. U. Fynbo; S. M. Croom

2005-01-19T23:59:59.000Z

278

Active Galactic Nuclei in the CNOC2 Field Galaxy Redshift Survey  

E-Print Network [OSTI]

We present a sample of 47 confirmed and 14 candidate Active Galactic Nuclei (AGN) discovered in the Canadian Network for Observational Cosmology field galaxy redshift survey (CNOC2). The sample consists of 38 objects identified from broad emission lines, 8 from narrow [NeV] emission, and 15 candidates from FeII or MgII absorption lines, one of which has been confirmed as a broad-line AGN via infrared spectroscopy. Redshifts of these AGN range from z=0.27 to z=4.67, and the average absolute magnitude is M_B=-22.25. No color selection criteria were involved in selecting this spectroscopically discovered sample. The sample is also unbiased against objects with luminous host galaxies since the spectroscopy preferentially targeted extended objects. Simple color-color diagram selection criteria can recover 81+-6% of the CNOC2 AGN, but several of the most unusual objects would be missing from such a color-selected sample. In the subsample with broad emission lines, the average equivalent widths for MgII and CIII] agree with the predictions of previous studies of the Baldwin effect. However, the average equivalent widths for CIV and Ly-alpha are smaller than predicted by previous studies of the Baldwin effect at lower redshift. This may imply that the slopes of the CIV and Ly-alpha Baldwin effects evolve with redshift, steepening with cosmic time. The broad emission line AGN also show a higher incidence of associated MgII and CIV absorption than in most previous surveys. This may arise from strong absorption being anti-correlated with optical luminosity or becoming less frequent with cosmic time, or possibly because our selection method is not biased against objects with resolved spatial structure or reddened by dust associated with the absorbing gas. (Abridged)

Patrick B. Hall; H. K. C. Yee; Huan Lin; Simon L. Morris; David R. Patton; Marcin Sawicki; Charles W. Shepherd; Gregory D. Wirth; R. G. Carlberg; Richard Elston

2000-07-12T23:59:59.000Z

279

Keck Spectroscopy of Redshift z~3 Galaxies in the Hubble Deep Field  

E-Print Network [OSTI]

We have obtained spectra with the 10-m Keck telescope of a sample of 24 galaxies having colors consistent with star-forming galaxies at redshifts 22. Combined with 5 previously confirmed high-redshift galaxies in the HDF, the 16 confirmed sources yield a comoving volume density of n>2.5^-4 h50^3 Mpc^-3 for q0=0.05, or n>1.2^-3 h50^3 Mpc^-3 for q0=0.5. These densities are comparable to estimates of the local volume density of galaxies brighter than L*, and could be almost three times higher still if all 29 of the unconfirmed candidates in our original sample are indeed also at high redshift. The galaxies are small but luminous, with half-light radii 1.8 M_B > -23. The HST images show a wide range of morphologies, including several with very close, small knots of emission embedded in wispy extended structures. Using rest-frame UV continuum fluxes with no dust correction, we calculate star formation rates in the range 7 - 24 or 3 - 9 h50^-2 Msun/yr for q0=0.05 and q0=0.5, respectively. The variety of morphologies and the high number density of z=3 galaxies in the HDF suggest that they represent a range of physical processes and stages of galaxy formation and evolution, rather than any one class of object, such as massive ellipticals. A key issue remains the measurement of masses. These high-redshift objects are likely to be the low-mass, starbursting building blocks of more massive galaxies seen today.

James D. Lowenthal; David C. Koo; Rafael Guzman; Jesus Gallego; Andrew C. Phillips; S. M. Faber; Nicole P. Vogt; Garth D. Illingworth; Caryl Gronwall

1996-12-30T23:59:59.000Z

280

The 2dF Galaxy Redshift Survey: the local E+A galaxy population  

E-Print Network [OSTI]

We select a sample of low-redshift (z ~ 0.1) E+A galaxies from the 2dF Galaxy Redshift Survey (2dFGRS). The spectra of these objects are defined by strong hydrogen Balmer absorption lines (H-delta, H-gamma, H-beta) combined with a lack of [OII] 3727A emission, together implying a recently-truncated burst of star formation. The E+A spectrum is thus a signpost to galaxies in the process of evolution. We quantify the local environments, clustering properties and luminosity function of the E+A galaxies. We find that the environments are consistent with the ensemble of 2dFGRS galaxies: low-redshift E+A systems are located predominantly in the field, existing as isolated objects or in poor groups. However, the luminosity distribution of galaxies selected using three Balmer absorption lines H-delta-gamma-beta appears more typical of ellipticals. Indeed, morphologically these galaxies are preferentially spheroidal (E/S0) systems. In a small but significant number we find evidence for recent major mergers, such as tidal tails. We infer that major mergers are one important formation mechanism for E+A galaxies, as suggested by previous studies. At low redshift the merger probability is high in the field and low in clusters, thus these recently-formed spheroidal systems do not follow the usual morphology-density relation for ellipticals. Regarding the selection of E+A galaxies: we find that basing the Balmer-line criterion solely on H-delta absorption leads to a significant sub-population of disk systems with detectable H-alpha emission. In these objects the [OII] emission is presumably either obscured by dust or present with a low signal-to-noise ratio, whilst the (H-gamma, H-beta) absorption features are subject to emission-filling.

Chris Blake; Michael Pracy; Warrick Couch; Kenji Bekki; Ian Lewis; Karl Glazebrook; Ivan Baldry; Carlton Baugh; Joss Bland-Hawthorn; Terry Bridges; Russell Cannon; Shaun Cole; Matthew Colless; Chris Collins; Gavin Dalton; Roberto De Propris; Simon Driver; George Efstathiou; Richard Ellis; Carlos Frenk; Carole Jackson; Ofer Lahav; Stuart Lumsden; Steve Maddox; Darren Madgwick; Peder Norberg; John Peacock; Bruce Peterson; Will Sutherland; Keith Taylor

2004-08-29T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

Cosmographic bounds on the cosmological deceleration-acceleration transition redshift in $f(\\mathcal{R})$ gravity  

E-Print Network [OSTI]

We examine the observational viability of a class of $f(\\mathcal{R})$ gravity cosmological models. Particular attention is devoted to constraints from the recent observational determination of the redshift of the cosmological deceleration-acceleration transition. Making use of the fact that the Ricci scalar is a function of redshift $z$ in these models, $\\mathcal {R=R}(z)$, and so is $f(z)$, we use cosmography to relate a $f(z)$ test function evaluated at higher $z$ to late-time cosmographic bounds. First, we consider a model independent procedure to build up a numerical $f(z)$ by requiring that at $z=0$ the corresponding cosmological model reduces to standard $\\Lambda$CDM. We then infer late-time observational constraints on $f(z)$ in terms of bounds on the Taylor expansion cosmographic coefficients. In doing so we parameterize possible departures from the standard $\\Lambda$CDM model in terms of a two-parameter logarithmic correction. The physical meaning of the two parameters is also discussed in terms of the post Newtonian approximation. Second, we provide numerical estimates of the cosmographic series terms by using Type Ia supernova apparent magnitude data and Hubble parameter measurements. Finally, we use these estimates to bound the two parameters of the logarithmic correction. We find that the deceleration parameter in our model changes sign at a redshift consistent with what is observed.

Salvatore Capozziello; Omer Farooq; Orlando Luongo; Bharat Ratra

2014-03-06T23:59:59.000Z

282

Constraining galaxy cluster temperatures and redshifts with eROSITA survey data  

E-Print Network [OSTI]

The nature of dark energy is imprinted in the large-scale structure of the Universe and thus in the mass and redshift distribution of galaxy clusters. The upcoming eROSITA mission will exploit this method of probing dark energy by detecting roughly 100,000 clusters of galaxies in X-rays. For a precise cosmological analysis the various galaxy cluster properties need to be measured with high precision and accuracy. To predict these characteristics of eROSITA galaxy clusters and to optimise optical follow-up observations, we estimate the precision and the accuracy with which eROSITA will be able to determine galaxy cluster temperatures and redshifts from X-ray spectra. Additionally, we present the total number of clusters for which these two properties will be available from the eROSITA survey directly. During its four years of all-sky surveys, eROSITA will determine cluster temperatures with relative uncertainties of Delta(T)/T<10% at the 68%-confidence level for clusters up to redshifts of z~0.16 which corr...

Borm, Katharina; Mohammed, Irshad; Lovisari, Lorenzo

2014-01-01T23:59:59.000Z

283

Multimedia Phase-Spaces  

Science Journals Connector (OSTI)

Dynamic phase-spaces are suggested as a way of designing and implementing interactive multimedia systems. A dynamic phase-space is a space of properties overlayed with dynamics. The space is “decorated” with multimedia resources such ... Keywords: catastrophe theory, dynamics, installation, interactive narrative, museums, phase-space

Peter Bøgh Andersen

1998-05-01T23:59:59.000Z

284

The luminosity distance-redshift relation up to second order in the Poisson gauge with anisotropic stress  

E-Print Network [OSTI]

We present the generalization of previously published results, about the perturbed redshift and the luminosity-redshift relation up to second order in perturbation theory, for the case of the Poisson gauge with anisotropic stress. The results are therefore valid for general dark energy models and (most) modify gravity models. We use an innovative approach based on the recently proposed "geodesic light-cone" gauge. We then compare our finding with other results, which recently appeared in the literature, for the particular case of vanishing anisotropic stress. To arrive at a common accepted expression for the non-linear and relativistic corrections to the redshift and distance-redshift relation is of fundamental importance in view of future cosmological surveys. Thanks to these surveys the Universe will be further probed with high precision and at very different scales, where non-linear and relativistic effects can play a key role.

Marozzi, Giovanni

2014-01-01T23:59:59.000Z

285

The luminosity distance-redshift relation up to second order in the Poisson gauge with anisotropic stress  

E-Print Network [OSTI]

We present the generalization of previously published results, about the perturbed redshift and the luminosity-redshift relation up to second order in perturbation theory, for the case of the Poisson gauge and in the presence of anisotropic stress. The results are therefore valid for general dark energy models and (most) modified gravity models. We use an innovative approach based on the recently proposed "geodesic light-cone" gauge. We then compare our finding with other results, which recently appeared in the literature, for the particular case of vanishing anisotropic stress. Arriving at a common accepted expression for the non-linear and relativistic corrections to the redshift and distance-redshift relation is of fundamental importance in view of future cosmological surveys. Thanks to these surveys the Universe will be further probed with high precision and at very different scales, where non-linear and relativistic effects can play a key role.

Giovanni Marozzi

2014-06-04T23:59:59.000Z

286

A REDSHIFT SURVEY OF HERSCHEL FAR-INFRARED SELECTED STARBURSTS AND IMPLICATIONS FOR OBSCURED STAR FORMATION  

SciTech Connect (OSTI)

We present Keck spectroscopic observations and redshifts for a sample of 767 Herschel-SPIRE selected galaxies (HSGs) at 250, 350, and 500 {mu}m, taken with the Keck I Low Resolution Imaging Spectrometer and the Keck II DEep Imaging Multi-Object Spectrograph. The redshift distribution of these SPIRE sources from the Herschel Multitiered Extragalactic Survey peaks at z = 0.85, with 731 sources at z < 2 and a tail of sources out to z {approx} 5. We measure more significant disagreement between photometric and spectroscopic redshifts (({Delta}z/(1 + z{sub spec})) = 0.29) than is seen in non-infrared selected samples, likely due to enhanced star formation rates and dust obscuration in infrared-selected galaxies. The infrared data are used to directly measure integrated infrared luminosities and dust temperatures independent of radio or 24 {mu}m flux densities. By probing the dust spectral energy distribution (SED) at its peak, we estimate that the vast majority (72%-83%) of z < 2 Herschel-selected galaxies would drop out of traditional submillimeter surveys at 0.85-1 mm. We find that dust temperature traces infrared luminosity, due in part to the SPIRE wavelength selection biases, and partially from physical effects. As a result, we measure no significant trend in SPIRE color with redshift; if dust temperature were independent of luminosity or redshift, a trend in SPIRE color would be expected. Composite infrared SEDs are constructed as a function of infrared luminosity, showing the increase in dust temperature with luminosity, and subtle change in near-infrared and mid-infrared spectral properties. Moderate evolution in the far-infrared (FIR)/radio correlation is measured for this partially radio-selected sample, with q{sub IR}{proportional_to}(1 + z){sup -0.30{+-}0.02} at z < 2. We estimate the luminosity function and implied star formation rate density contribution of HSGs at z < 1.6 and find overall agreement with work based on 24 {mu}m extrapolations of the LIRG, ULIRG, and total infrared contributions. This work significantly increased the number of spectroscopically confirmed infrared-luminous galaxies at z >> 0 and demonstrates the growing importance of dusty starbursts for galaxy evolution studies and the build-up of stellar mass throughout cosmic time.

Casey, C. M.; Budynkiewicz, J. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Berta, S.; Lutz, D.; Magnelli, B. [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany); Bethermin, M.; Le Floc'h, E.; Magdis, G. [Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu - CNRS - Universite Paris Diderot, CE-Saclay, pt courrier 131, F-91191 Gif-sur-Yvette (France); Bock, J.; Bridge, C. [California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Burgarella, D. [Laboratoire d'Astrophysique de Marseille - LAM, Universite d'Aix-Marseille and CNRS, UMR7326, 38 rue F. Joliot-Curie, 13388 Marseille Cedex 13 (France); Chapin, E. [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Chapman, S. C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Clements, D. L. [Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom); Conley, A. [Center for Astrophysics and Space Astronomy 389-UCB, University of Colorado, Boulder, CO 80309 (United States); Conselice, C. J. [School of Physics and Astronomy, University of Nottingham, NG7 2RD (United Kingdom); Cooray, A. [Dept. of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Farrah, D. [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Hatziminaoglou, E. [ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei Muenchen (Germany); Ivison, R. J. [UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); and others

2012-12-20T23:59:59.000Z

287

Sculpting space through sound  

E-Print Network [OSTI]

How does one experience space? What kind of information do humans collect in the process of constructing space in their mind? How does one begin to understand volume, light, texture, material, smell and sense of space? The ...

Nakagawa, Junko, 1975-

2002-01-01T23:59:59.000Z

288

The Impact of Star Formation and Gamma-Ray Burst Rates at High Redshift on Cosmic Chemical Evolution and Reionization  

E-Print Network [OSTI]

Recent observations in the total luminosity density have led to significant progress in establishing the star formation rate (SFR) at high redshift. Concurrently observed gamma-ray burst rates have also been used to extract the SFR at high redshift. The SFR in turn can be used to make a host of predictions concerning the ionization history of the Universe, the chemical abundances, and supernova rates. We compare the predictions made using a hierarchical model of cosmic chemical evolution based on three recently proposed SFRs: two based on extracting the SFR from the observed gamma-ray burst rate at high redshift, and one based on the observed galaxy luminosity function at high redshift. Using the WMAP/Planck data on the optical depth and epoch of reionization, we find that only the SFR inferred from gamma-ray burst data at high redshift suffices to allow a single mode (in the initial mass function) of star formation which extends from z = 0 to redshifts > 10. For the case of the more conservative SFR based on...

Vangioni, E; Prestegard, T; Silk, J; Petitjean, P; Mandic, V

2014-01-01T23:59:59.000Z

289

Quantum estimation of the Schwarzschild space-time parameters of the Earth  

E-Print Network [OSTI]

We propose a quantum experiment to measure with high precision the Schwarzschild space-time parameters of the Earth. The scheme can also be applied to measure distances by taking into account the curvature of the Earth's space-time. As a wave-packet of (entangled) light is sent from the Earth to a satellite it is red-shifted and deformed due to the curvature of space-time. Measurements after the propagation enable the estimation of the space-time parameters. We compare our results with the state of the art, which involves classical measurement methods, and discuss what developments are required in space-based quantum experiments to improve on the current measurement of the Schwarzschild radius of the Earth.

David Edward Bruschi; Animesh Datta; Rupert Ursin; Timothy C. Ralph; Ivette Fuentes

2014-08-31T23:59:59.000Z

290

Joint source channel coding for non-ergodic channels: the distortion signal-to-noise ratio (SNR) exponent perspective  

E-Print Network [OSTI]

. . . . . . . . . . . . . . . 8 II DISTORTION SNR EXPONENT FOR THE AWGN CHANNEL 10 A. Introduction and Problem Statement . . . . . . . . . . . . 10 B. Informed Transmitter Upper Bound . . . . . . . . . . . . . 12 C. Prior Work... mean square error, a simple joint source channel coding scheme that involves just transmitting the source over the channel with appropriate power scaling is optimal [1,2]. Some advantages and disadvantages of joint source channel coding are discussed...

Bhattad, Kapil

2008-10-10T23:59:59.000Z

291

Cooperative effect of monoclinic distortion and sinusoidal modulation in the martensitic structure of Ni{sub 2}FeGa  

SciTech Connect (OSTI)

The structural features of the '5M' martensitic phase in Ni{sub 2}FeGa alloys have been determined by electron diffraction using the multi-slice least-squares (MSLS) method. The results demonstrate that the '5M' phase contains an evident cooperative effect of monoclinic distortion and sinusoidal modulation along the [110]{sub c} direction. Theoretical simulations based on our refined data suggest that the '5M' martensitic phase observed in Ni-Fe-Ga and Ni-Mn-Ga has visible common behaviors in both stacking sequence and local structural distortion. Considering the cooperative effect of monoclinic distortion and sinusoidal modulation, we demonstrate that the '7M' martensitic phase could adopt two equivalent structural phases corresponding with the stacking sequences of (43{sup -}){sub 2} and (52{sup -}){sub 2}, respectively. - Graphical abstract: The structural model of the '5M' Ni{sub 2}FeGa martensite viewed along the [001]{sub c} (i.e. [010]{sub m}) zone axis, demonstrating the cooperative effect of monoclinic distortion and sinusoidal modulation along the [110]{sub c} direction.

Lu, J.B.; Yang, H.X.; Tian, H.F.; Zeng, L.J.; Ma, C.; Feng, L.; Wu, G.H. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Li, J.Q., E-mail: LJQ@aphy.iphy.ac.c [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Jansen, J. [National Center for HREM, Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Lorentzweg 1, Delft (Netherlands)

2010-02-15T23:59:59.000Z

292

The effect of plasma channel on the self-distortion of laser pulse propagating through the collisional plasma channel  

Science Journals Connector (OSTI)

Abstract In the present paper, laser pulse distortion/breakup and the effect of the plasma channel on the laser propagation through the collisional plasma have been studied by using moment theory approach. Second order nonlinear differential equations of the beam width parameter have been derived for the propagation of the laser through uniform homogenous plasma and preformed plasma channel having parabolic density profile. Differential equations of beam width parameter have been solved numerically using Runge Kutta method. It has been observed from analysis that when the laser pulse propagates through the homogenous plasma, the low intensity front and rear parts of the laser get defocused/diffracted and the high intensity central/main portion of the laser pulse gets self-guided. As a result of this, the laser pulse gets distorted. This distortion of the laser has not been observed when the laser pulse is propagated through the plasma channel having density minimum at the axis and maximum at the edges. The laser pulse is guided as a whole, even the low intensity front and rear parts of the laser are also guided. Therefore, the plasma channel is useful to prevent the distortion/breakup of the laser.

Navpreet Singh; Arvinder Singh

2014-01-01T23:59:59.000Z

293

In Outer Space without a Space Suit?  

E-Print Network [OSTI]

The author proposes and investigates his old idea - a living human in space without the encumbrance of a complex space suit. Only in this condition can biological humanity seriously attempt to colonize space because all planets of Solar system (except the Earth) do not have suitable atmospheres. Aside from the issue of temperature, a suitable partial pressure of oxygen is lacking. In this case the main problem is how to satiate human blood with oxygen and delete carbonic acid gas (carbon dioxide). The proposed system would enable a person to function in outer space without a space suit and, for a long time, without food. That is useful also in the Earth for sustaining working men in an otherwise deadly atmosphere laden with lethal particulates (in case of nuclear, chemical or biological war), in underground confined spaces without fresh air, under water or a top high mountains above a height that can sustain respiration.

Alexander Bolonkin

2008-06-24T23:59:59.000Z

294

In Outer Space without a Space Suit?  

E-Print Network [OSTI]

The author proposes and investigates his old idea - a living human in space without the encumbrance of a complex space suit. Only in this condition can biological humanity seriously attempt to colonize space because all planets of Solar system (except the Earth) do not have suitable atmospheres. Aside from the issue of temperature, a suitable partial pressure of oxygen is lacking. In this case the main problem is how to satiate human blood with oxygen and delete carbonic acid gas (carbon dioxide). The proposed system would enable a person to function in outer space without a space suit and, for a long time, without food. That is useful also in the Earth for sustaining working men in an otherwise deadly atmosphere laden with lethal particulates (in case of nuclear, chemical or biological war), in underground confined spaces without fresh air, under water or a top high mountains above a height that can sustain respiration.

Bolonkin, Alexander

2008-01-01T23:59:59.000Z

295

Space System Architecture  

E-Print Network [OSTI]

Final Report of SSPARC: the Space Systems, Policy, and Architecture Research Consortium (Thrust II and III)

McManus, Dr. Hugh

296

Robust Machine Learning Applied to Astronomical Datasets III: Probabilistic Photometric Redshifts for Galaxies and Quasars in the SDSS and GALEX  

E-Print Network [OSTI]

We apply machine learning in the form of a nearest neighbor instance-based algorithm (NN) to generate full photometric redshift probability density functions (PDFs) for objects in the Fifth Data Release of the Sloan Digital Sky Survey (SDSS DR5). We use a conceptually simple but novel application of NN to generate the PDFs - perturbing the object colors by their measurement error - and using the resulting instances of nearest neighbor distributions to generate numerous individual redshifts. When the redshifts are compared to existing SDSS spectroscopic data, we find that the mean value of each PDF has a dispersion between the photometric and spectroscopic redshift consistent with other machine learning techniques, being sigma = 0.0207 +/- 0.0001 for main sample galaxies to r < 17.77 mag, sigma = 0.0243 +/- 0.0002 for luminous red galaxies to r < ~19.2 mag, and sigma = 0.343 +/- 0.005 for quasars to i < 20.3 mag. The PDFs allow the selection of subsets with improved statistics. For quasars, the improvement is dramatic: for those with a single peak in their probability distribution, the dispersion is reduced from 0.343 to sigma = 0.117 +/- 0.010, and the photometric redshift is within 0.3 of the spectroscopic redshift for 99.3 +/- 0.1% of the objects. Thus, for this optical quasar sample, we can virtually eliminate 'catastrophic' photometric redshift estimates. In addition to the SDSS sample, we incorporate ultraviolet photometry from the Third Data Release of the Galaxy Evolution Explorer All-Sky Imaging Survey (GALEX AIS GR3) to create PDFs for objects seen in both surveys. For quasars, the increased coverage of the observed frame UV of the SED results in significant improvement over the full SDSS sample, with sigma = 0.234 +/- 0.010. We demonstrate that this improvement is genuine. [Abridged

Nicholas M. Ball; Robert J. Brunner; Adam D. Myers; Natalie E. Strand; Stacey L. Alberts; David Tcheng

2008-04-21T23:59:59.000Z

297

The Fundamental Plane of field early-type galaxies at intermediate redshift  

E-Print Network [OSTI]

We present preliminary results on the evolution of the stellar populations of field early-type galaxies (E/S0) from z=0.4 to z=0. The diagnostic tool used in this study is the Fundamental Plane (FP), a tight empirical correlation between their central velocity dispersion (sigma), effective radius (Re), and effective surface brightness (SBe), which is observed to hold in the local Universe. Using HST-WFPC2 archive images and spectra obtained at the ESO-3.6m telescope we measured the FP parameters for a sample of ~30 field E/S0s at z=0.2-0.4. Remarkably, field E/S0s at intermediate redshift also define a tight FP, with scatter unchanged with respect to that of local samples. The intermediate redshift FP is offset from the local one, in the sense that, for given RE and sigma, galaxies are brighter at z=0.4 than at z=0. The implication of the offset of the FP in terms of passive evolution of the stellar population depends on its star formation history. In a single burst scenario, the stellar populations of field E/S0s were formed at z=0.8-1.6 (Omega=0.3; Omega_{Lambda}=0.7; H_0=50 km/s/Mpc). Alternatively, the bulk of stars (90% in mass) can be formed at high redshift (z~3), and the rest in a secondary burst occurred more recently (z~0.5-0.8).

T. Treu; M. Stiavelli; S. Casertano; P. Moller; G. Bertin

2000-07-18T23:59:59.000Z

298

On Synthesis of the Big Bang Model with Freundlich's Redshift and its Cosmological Consequences  

E-Print Network [OSTI]

We derive exact theoretical value of the constant cosmic background radiation (CBR) temperature $T_0$ using the interconnections between the Gamow, Alpher and Herman (GAH) hot Big Bang cosmology model of the expanding Universe and the modified Freundlich redshift. As a result of this confluence an astonishing relationship between $T_0$ and the four fundamental physical constants $c$,$\\hbar$,$k$,$G$ is found including also the Melvin's value of the Freundlich constant $A_s$.Then the resulting predicted the CBR temperature is $T_0=2.76626 K$. This prediction show excellent agreement with the data obtained from ground-based and balloon-borne observations and also with a mean of the perfect black-body spectrum CMB temperature $2.725 K$ measured COBE in 1992. Using a new cosmological model we determine the horizon scale, age and mass of the present observable Universe. The calculations based on discrete redshift equations for the electromagnetic, electroweak phases and Planck epoch of the Universe predicts a graviton and string masses, which are originated beyond on Planck time. The predicted graviton mass $m_Gr$ is about five orders of magnitude less than the present "the best possible upper bounds on the mass of the graviton", which may be "discovered" in the proposed LISA observations. We present quantitative new results for the different quantum-cosmological parameters. Finally, it is showed that the mystery largeness and smallness dimensionless combination of the Quantum Cosmological constant $\\Lambda_0$ and Planck length $l_Pl$ may be derived as their ratio from the Trans-Planck redshift relation. Thus is found the meaning a famous largeness cosmological number $c^3/\\hbarG\\Lambda_0=2.8*10^{125}$ that is inverse of $\\Lambda_0 l_Pl^2=3.6*10^{-126}$, and "which in 1930s was a regarded as a major problem by Eddington and Dirac".

Asger G. Gasanalizade

2010-09-24T23:59:59.000Z

299

Measurements of the UV Upturn in Local and Intermediate-Redshift Ellipticals  

E-Print Network [OSTI]

The rest-frame UV contains the most sensitive indicators of age for elliptical galaxies. While the near-UV flux from young ellipticals isolates the main sequence turnoff, the far-UV flux in old ellipticals is dominated by hot horizontal branch (HB) stars. This evolved population was first revealed by early UV observations showing a sharp flux increase shortward of rest-frame 2500 A, subsequently dubbed the "UV upturn." The phenomenon has since been characterized in many local ellipticals, and measurements at intermediate redshifts are now underway. Once ellipticals reach ages of 5-10 Gyr, stellar and galactic evolution theories predict that the UV-to-optical flux ratio can increase by orders of magnitude over timescales of a few Gyr, making the UV upturn the most rapidly evolving feature of these galaxies. It is thus expected to fade dramatically with increasing redshift. I review the imaging and spectroscopic evidence for the nature of the UV upturn in nearby ellipticals, and then present observations that measure the UV upturn at an epoch significantly earlier than our own. Far-UV data from the HUT demonstrate that the spectra of nearby ellipticals are dominated by hot HB stars. FOC UV imaging of M32 and the M31 bulge detected the UV-bright phases of post-HB stars, but did not reach the HB itself. Recent STIS observations were the first to image the hot HB and post-HB stars in the center of the nearest elliptical galaxy, M32; these observations also show a striking lack of UV-bright post-AGB stars. FOC observations of Abell 370, a rich galaxy cluster at z=0.375, show that giant ellipticals at a lookback time of 4 Gyr can exhibit strong UV luminosity, with no evidence of evolution in the UV upturn between this epoch and our own, thus implying a high redshift of formation (z_f > 4).

Thomas M. Brown

1999-05-28T23:59:59.000Z

300

Weighing the Universe with Photometric Redshift Surveys and the Impact on Dark Energy Forecasts  

E-Print Network [OSTI]

With a wariness of Occam's razor awakened by the discovery of cosmic acceleration, we abandon the usual assumption of zero mean curvature and ask how well it can be determined by planned surveys. We also explore the impact of uncertain mean curvature on forecasts for the performance of planned dark energy probes. We find that weak lensing and photometric baryon acoustic oscillation data, in combination with CMB data, can determine the mean curvature well enough that the residual uncertainty does not degrade constraints on dark energy. We also find that determinations of curvature are highly tolerant of photometric redshift errors.

Lloyd Knox; Yong-Seon Song; Hu Zhan

2006-05-21T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
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they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Low red-shift formula for the luminosity distance in a LTB model with cosmological constant  

E-Print Network [OSTI]

We calculate the low red-shift Taylor expansion for the luminosity distance for an observer at the center of a spherically symmetric matter inhomogeneity with a non vanishing cosmological constant. We then test the accuracy of the formulas comparing them to the numerical calculation for different cases for both the luminosity distance and the radial coordinate. The formulas can be used as a starting point to understand the general non linear effects of a local inhomogeneity in presence of a cosmological constant, without making any special assumption about the inhomogeneity profile.

Antonio Enea Romano; Pisin Chen

2014-05-08T23:59:59.000Z

302

Star formation trends in high-redshift galaxy surveys: the elephant or the tail?  

E-Print Network [OSTI]

Star formation rate and accummulated stellar mass are two fundamental physical quantities that describe the evolutionary state of a forming galaxy. Two recent attempts to determine the relationship between these quantities, by interpreting a sample of star-forming galaxies at redshift of z~4, have led to opposite conclusions. We use a model galaxy population to investigate possible causes for this discrepancy and conclude that minor errors in the conversion from observables to physical quantities can lead to major misrepresentation when applied without awareness of sample selection. We also investigate, in a general way, the physical origin of the correlation between star formation rate and stellar mass within hierarchical galaxy formation theory.

Stringer, Martin; Frenk, Carlos S; Stark, Daniel P

2010-01-01T23:59:59.000Z

303

The infinite red-shift surfaces of the Kerr and Kerr-Newman solutions of the Einstein field equations  

E-Print Network [OSTI]

In contrast to the Schwarzschild solution, the infinite red-shift surfaces and null surfaces of the Kerr solution to the axially-symmetric Einstein field equations are distinct. Some three-dimensional depictions of these surfaces are presented here for observers following the time-like Killing vector of the Kerr and Kerr-Newman solutions. Some similarities of the latter to the Reissner-Nordstrom solution are also discussed. In the case of the Kerr solution, the inner infinite red-shift surface terminates at the ring singularity. This is not the case for the Kerr-Newman solution where the infinite red-shift surface and the ring singularity have no points in common. The presence of charge severs the relation between the singularity and the infinite red-shift surface. This paper is also intended to fill a void in the literature where few, if any, adequate representations of the infinite red-shift surfaces and their relation to the singularity and horizons exist.

Gerald E. Marsh

2007-07-12T23:59:59.000Z

304

High Redshift Intergalactic C IV Abundance Measurements from the Near-Infrared Spectra of Two z~6 QSOs  

E-Print Network [OSTI]

New measurements of the z~6 intergalactic CIV abundance are presented, using moderate resolution IR spectra of two QSOs taken with GNIRS on Gemini South. These data were systematically searched for high redshift CIV absorption lines, using objective selection criteria. Comprehensive tests were performed to quantify sample incompleteness, as well as the rate of false positive CIV identifications. The trend of constant $\\Omega_{CIV}(z)$ observed at z~2-5 appears to continue to z~6, the highest observed redshift. The CIV sample is also consistent with the redshift-invariant form of the CIV column density distribution reported by Songaila (2001) at lower redshift, although with fairly large uncertainties due to a smaller sample size and noisier infrared data. The constant value of $\\Omega_{CIV}$ does not necessarily imply that the IGM was infused with an early metallicity ``floor,'' but the presence of early CIV does indicate that heavy-element enrichment began < 1 Gyr after the Big Bang. The lack of a decline in $\\Omega_{CIV}$ at high redshift may indicate that integrated CIV measurements are sensitive to the instantaneous rate of feedback from galaxy formation at each epoch. Alternatively, it could result from a balance in the evolution of the intergalactic gas density, ionization conditions, and heavy-element abundance over time.

Robert A. Simcoe

2006-05-30T23:59:59.000Z

305

Space: Dreams of the new space race  

Science Journals Connector (OSTI)

... new-space sector has been booming, thanks to a change in its business model. Private spaceflight has always been a business for dreamers, and now one group of dreamers ... , Virginia, pioneered the marketplace for space tourism. Since 2001, it has sent five private individuals into orbit on Russian spacecraft, at US$20 million a trip. Then, ...

David Chandler

2007-08-29T23:59:59.000Z

306

Dynamically Close Galaxy Pairs and Merger Rate Evolution in the CNOC2 Redshift Survey  

E-Print Network [OSTI]

We investigate redshift evolution in the galaxy merger and accretion rates, using a well-defined sample of 4184 galaxies with 0.12 < z < 0.55 and R_C < 21.5. We identify 88 galaxies in close (5 < r_p < 20 h^{-1} kpc) dynamical (delta v < 500 km/s) pairs. These galaxies are used to compute global pair statistics, after accounting for selection effects resulting from the flux limit, k-corrections, luminosity evolution, and spectroscopic incompleteness. We find that the number of companions per galaxy (for -21 < M_B^{k,e} < -18) is Nc = 0.0321 +/- 0.0077 at z=0.3. The luminosity in companions, per galaxy, is Lc = 0.0294 +/- 0.0084 x 10^10 h^2 L_sun. We assume that Nc is proportional to the galaxy merger rate, while Lc is directly related to the mass accretion rate. After increasing the maximum pair separation to 50 h^{-1} kpc, and comparing with the low redshift SSRS2 pairs sample, we infer evolution in the galaxy merger and accretion rates of (1+z)^{2.3 +/- 0.7} and (1+z)^{2.3 +/- 0.9} respectively. These are the first such estimates to be made using only confirmed dynamical pairs. When combined with several additional assumptions, this implies that approximately 15% of present epoch galaxies with -21 < M_B < -18 have undergone a major merger since z=1.

D. R. Patton; C. J. Pritchet; R. G. Carlberg; R. O. Marzke; H. K. C. Yee; P. B. Hall; H. Lin; S. L. Morris; M. Sawicki; C. W. Shepherd; G. D. Wirth

2001-09-24T23:59:59.000Z

307

THE SLOAN DIGITAL SKY SURVEY CO-ADD: A GALAXY PHOTOMETRIC REDSHIFT CATALOG  

SciTech Connect (OSTI)

We present and describe a catalog of galaxy photometric redshifts (photo-z) for the Sloan Digital Sky Survey (SDSS) Co-add Data. We use the artificial neural network (ANN) technique to calculate the photo-z and the nearest neighbor error method to estimate photo-z errors for {approx}13 million objects classified as galaxies in the co-add with r < 24.5. The photo-z and photo-z error estimators are trained and validated on a sample of {approx}83,000 galaxies that have SDSS photometry and spectroscopic redshifts measured by the SDSS Data Release 7 (DR7), the Canadian Network for Observational Cosmology Field Galaxy Survey, the Deep Extragalactic Evolutionary Probe Data Release 3, the VIsible imaging Multi-Object Spectrograph-Very Large Telescope Deep Survey, and the WiggleZ Dark Energy Survey. For the best ANN methods we have tried, we find that 68% of the galaxies in the validation set have a photo-z error smaller than {sigma}{sub 68} = 0.031. After presenting our results and quality tests, we provide a short guide for users accessing the public data.

Reis, Ribamar R. R.; Soares-Santos, Marcelle; Annis, James; Dodelson, Scott; Hao Jiangang; Johnston, David; Kubo, Jeffrey; Lin Huan [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Seo, Hee-Jong [Berkeley Center for Cosmological Physics, LBL and Department of Physics, University of California, Berkeley, CA 94720 (United States); Simet, Melanie [Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637 (United States)

2012-03-01T23:59:59.000Z

308

QUENCHING STAR FORMATION AT INTERMEDIATE REDSHIFTS: DOWNSIZING OF THE MASS FLUX DENSITY IN THE GREEN VALLEY  

SciTech Connect (OSTI)

The bimodality in galaxy properties has been observed at low and high redshifts, with a clear distinction between star-forming galaxies in the blue cloud and passively evolving objects in the red sequence; the absence of galaxies with intermediate properties indicates that the quenching of star formation and subsequent transition between populations must happen rapidly. In this paper, we present a study of over 100 transiting galaxies in the so-called green valley at intermediate redshifts (z {approx} 0.8). By using very deep spectroscopy with the DEIMOS instrument at the Keck telescope we are able to infer the star formation histories of these objects and measure the stellar mass flux density transiting from the blue cloud to the red sequence when the universe was half its current age. Our results indicate that the process happened more rapidly and for more massive galaxies in the past, suggesting a top-down scenario in which the massive end of the red sequence is forming first. This represents another aspect of downsizing, with the mass flux density moving toward smaller galaxies in recent times.

Goncalves, Thiago S.; Menendez-Delmestre, Karin [Observatorio do Valongo, Universidade Federal do Rio de Janeiro, Ladeira Pedro Antonio, 43, Saude 20080-090 Rio de Janeiro (Brazil); Martin, D. Christopher; Wyder, Ted K. [California Institute of Technology, MC 278-17, Pasadena, CA 91125 (United States); Koekemoer, Anton, E-mail: tsg@astro.ufrj.br [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2012-11-01T23:59:59.000Z

309

Stellar Masses of Luminous Compact Blue Galaxies at Redshifts z=0.4-1.2  

E-Print Network [OSTI]

We present stellar mass measurements for a sample of 36 Luminous Compact Blue Galaxies (LCBGs) at redshifts z = 0.4-1.2 in the Flanking Fields around the Hubble Deep Field North. The technique is based on fitting a two-component galaxy population model to multi-broadband photometry. Best-fit models are found to be largely independent on the assumed values for the IMF and the metallicity of the stellar populations, but are sensitive to the amount of extinction and the extinction law adopted. On average, the best-fit model corresponds to a LMC extinction law with E(B-V)=0.5. Stellar mass estimates, however, are remarkably independent on the final model choice. Using a Salpeter IMF, the derived median stellar mass for this sample is 5 x 10^9 Mo, i.e., ~2 times smaller than previous virial mass estimates. Despite uncertainties of a factor 2-3, our results strengthen prior claims that L* CBGs at intermediate redshifts are, on average, about 10 times less massive than a typical L* galaxy today.

R. Guzman; G. Ostlin; D. Kunth; M. Bershady; D. Koo; M. Pahre

2003-02-12T23:59:59.000Z

310

Star Formation at Redshift One: Preliminary results from an H-alpha Survey  

E-Print Network [OSTI]

We present the first successful demonstration of multi-object near-infrared spectroscopy on high redshift galaxies. Our objective is to address the true star formation history of the universe at z~1, a crucial epoch which some have suggested is the peak of star formation activity. By using H-alpha -the same robust star formation indicator used at low-z - redshifted into the J- and H-bands, we can trace star formation without the systematic uncertainties of different calibrators, or the extreme dust extinction in the rest-UV, which have plagued previous efforts. We are using the instrument CIRPASS (the Cambridge Infra-Red PAnoramic Survey Spectrograph), in multi-object mode, which has been successfully demonstrated on the Anglo-Australian Telescope (AAT) and the William Herschel Telescope (WHT). CIRPASS has 150 fibres deployable over \\~40arcmin on the AAT and ~15arcmin on the WHT. Here we present preliminary results from one of our fields observed with the WHT: H-alpha detections of z~1 galaxies in the Hubble Deep Field North.

M. Doherty; A. Bunker; R. Sharp; G. Dalton; I. Parry; I. Lewis; E. MacDonald; C. Wolf

2004-07-12T23:59:59.000Z

311

Solar Concentration in Space  

Science Journals Connector (OSTI)

Solar concentrators go space. Lens and mirror-based solar concentrators have recently begun to boost photovoltaic power supplies for satellites in space. In 1998, the first mission carrying solar concentrators...

Dr. Ralf Leutz; Dr. Akio Suzuki

2001-01-01T23:59:59.000Z

312

Space-based detectors  

Science Journals Connector (OSTI)

The parallel session C5 on Space-Based Detectors gave a broad overview over the planned space missions related to gravitational wave detection. Overviews of the revolutionary science to be expected from LISA was ...

A. Sesana; W. J. Weber; C. J. Killow…

2014-11-01T23:59:59.000Z

313

Quotients of Metric Spaces  

E-Print Network [OSTI]

the properties of quotient spaces of metric spaces. We will use "iff" as an abbreviation for "if and only if". If f is a function from X onto Y, we will write f: X --->> Y....

Herman, Robert A.

1968-01-01T23:59:59.000Z

314

Architecting space communication networks  

E-Print Network [OSTI]

Reliable communication and navigation services are critical to robotic and human space missions. NASA currently provides them through three independent and uncoordinated network that consist of both Earth-based and space-based ...

Sanchez Net, Marc

2014-01-01T23:59:59.000Z

315

Space Shuttle Program Status  

E-Print Network [OSTI]

Brigham City, Utah Space Shuttle Main Engines Pratt & Whitney/Rocketdyne Canoga Park, CA NASA JSC Houston

Waliser, Duane E.

316

Cubature on Wiener space  

Science Journals Connector (OSTI)

...research-article Cubature on Wiener space Terry Lyons Nicolas Victoir...a cubature formula on Wiener space of degree m.R eferences Ben...M. 1996 CarnotCarath eodory spaces seen from within: sub-Riemannian...North-Holland Mathematical Library. Kloeden, P. E. & Platen...

2004-01-01T23:59:59.000Z

317

Whither design space?  

Science Journals Connector (OSTI)

Design space exploration is a long-standing focus in computational design research. Its three main threads are accounts of designer action, development of strategies for amplification of designer action in exploration, and discovery of computational ... Keywords: Design Space Exploration, Knowledge Representation, Search, State Space, Typed Feature Structures

Robert F. Woodbury; Andrew L. Burrow

2006-04-01T23:59:59.000Z

318

Developments in space engineering and space science  

Science Journals Connector (OSTI)

...geostationary satellite INSAT, which provides both weather observation and...of results in satellite missions monitoring space weather as for those...At that time satellite data were only...on numerical weather predictions...

2003-01-01T23:59:59.000Z

319

TANK SPACE OPTIONS REPORT  

SciTech Connect (OSTI)

Since this report was originally issued in 2001, several options proposed for increasing double-shell tank (DST) storage space were implemented or are in the process of implementation. Changes to the single-shell tank (SST) waste retrieval schedule, completion of DST space saving options, and the DST space saving options in progress have delayed the projected shortfall of DST storage space from the 2007-2011 to the 2018-2025 timeframe (ORP-11242, River Protection Project System Plan). This report reevaluates options from Rev. 0 and includes evaluations of new options for alleviating projected restrictions on SST waste retrieval beginning in 2018 because of the lack of DST storage space.

WILLIS WL; AHRENDT MR

2009-08-11T23:59:59.000Z

320

ON THE INJECTION SPECTRUM OF RELATIVISTIC ELECTRONS IN HIGH-REDSHIFT RADIO GALAXIES  

SciTech Connect (OSTI)

We point out that the remarkable linearity of the ultra-steep radio spectra of high-redshift radio galaxies reflects a previously reported general trend for powerful radio galaxies, according to which the spectral curvature is less for sources having steeper spectra (measured near rest-frame 1 GHz). We argue based on existing theoretical and observational evidence that it is premature to conclude that the particle acceleration mechanism in sources having straight, ultra-steep radio spectra gives rise to an ultra-steep injection spectrum of the radiating electrons. In empirical support for this we show that the estimated injection spectral indices available for a representative sample of 35 compact steep spectrum radio sources are not correlated with their rest-frame (intrinsic) rotation measures, which are known to be typically large, indicating a dense environment, as is also the case for high-z radio galaxies.

Gopal-Krishna; Mhaskey, Mukul [National Centre for Radio Astrophysics/TIFR, Pune University Campus, Pune 411007 (India); Mangalam, A., E-mail: krishna@ncra.tifr.res.in, E-mail: wmu3@gmail.com, E-mail: mangalam@iiap.res.in [Indian Institute of Astrophysics, Sarjapur Road, Koramangala 2nd Block, Bangalore 560034 (India)

2012-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

Properties of Ly-alpha and Gamma Ray Burst selected starbursts at high redshifts  

E-Print Network [OSTI]

Selection of starbursts through either deep narrow band imaging of redshifted Ly-alpha emitters, or localisation of host galaxies of gamma-ray bursts both give access to starburst galaxies that are significantly fainter than what is currently available from selection techniques based on the continuum (such as Lyman-break selection). We here present results from a survey for Ly-alpha emitters at z=3, conducted at the European Southern Observatory's Very Large Telescope. Furthermore, we briefly describe the properties of host galaxies of gamma-ray bursts at z>2. The majority of both Ly-alpha and gamma-ray burst selected starbursts are fainter than the flux limit of the Lyman-break galaxy sample, suggesting that a significant fraction of the integrated star formation at z~3 is located in galaxies at the faint end of the luminosity function.

J. P. U. Fynbo; B. Krog; K. Nilsson; G. Bjornsson; J. Hjorth; P. Jakobsson; C. Ledoux; P. Moller; B. Thomsen

2004-12-14T23:59:59.000Z

322

The star formation history inferred from long gamma-ray bursts with high pseudo-redshifts  

E-Print Network [OSTI]

By employing a simple semi-analytical star formation model where the formation rates of Population (Pop) I/II and III stars can be calculated, respectively, we account for the number distribution of gamma-ray bursts (GRBs) with high pseudo-redshifts that was derived from an empirical luminosity-indictor relationship. It is suggested that a considerable number of Pop III GRBs could exist in the present sample of Swift GRBs. By further combining the implication for the star formation history from the optical depth of the CMB photons, it is also suggested that only a very small fraction 0.6% of Pop III GRBs could have triggered the Swift BAT. These results could provide an useful basis for estimating future detectability of Pop III stars and their produced transient phenomena.

Tan, Wei-Wei; Yu, Yun-Wei

2015-01-01T23:59:59.000Z

323

The red-shift effect and radiation decay on black hole spacetimes  

E-Print Network [OSTI]

We consider solutions to the linear wave equation on a (maximally extended) Schwarzschild spacetime, assuming only that the solution decays suitably at spatial infinity on a complete Cauchy hypersurface. (In particular, we allow the support of the solution to contain the bifurcate event horizon.) We prove uniform decay bounds for the solution in the exterior regions, including the uniform bound Cv_+^{-1}, where v_+ denotes max{v,1} and v denotes Eddington-Finkelstein advanced time. We also prove uniform decay bounds for the flux of energy through the event horizon and null infinity. The estimates near the event horizon exploit an integral energy identity normalized to local observers. This estimate can be thought to quantify the celebrated red-shift effect. The results in particular give an independent proof of the classical uniform boundedness theorem of Kay and Wald, without recourse to the discrete isometries of spacetime.

Mihalis Dafermos; Igor Rodnianski

2005-12-21T23:59:59.000Z

324

The UV to FIR spectral energy distribution of star-forming galaxies in the redshift desert  

E-Print Network [OSTI]

We analyze the rest-frame UV-to-near-IR spectral energy distribution (SED) of Lyman break galaxies (LBGs), star-forming (SF) BzK (sBzK), and UV-selected galaxies at 1.5 deep FIR data taken within the framework of the GOODS-Herschel project. According to their best-fitted SED-derived properties we find that, due to their selection criterion involving UV measurements, LBGs tend to be UV-brighter, bluer, have less prominent Balmer break (are younger), and have higher dust-corrected total SFR than sBzK galaxies. In a color versus stellar mass diagram, LBGs at z ~ 2 tend to be mostly located over the blue cloud of galaxies at their redshift, although galaxies with older ages, higher dust attenuation, and redder UV continuum slope deviate to the green valley and red sequence. We find PACS (100um or 160um) individual detection...

Oteo, I; Magdis, G; Pérez-García, A M; Cepa, J; Cedrés, B; Sánchez, H Domínguez; Ederoclite, A; Sánchez-Portal, M; Pérez-Martínez, R; Pintos-Castro, I; Polednikova, J

2013-01-01T23:59:59.000Z

325

A step towards testing general relativity using weak gravitational lensing and redshift surveys  

E-Print Network [OSTI]

Using the linear theory of perturbations in General Relativity, we express a set of consistency relations that can be observationally tested with current and future large scale structure surveys. We then outline a stringent model-independent program to test gravity on cosmological scales. We illustrate the feasibility of such a program by jointly using several observables like peculiar velocities, galaxy clustering and weak gravitational lensing. After addressing possible observational or astrophysical caveats like galaxy bias and redshift uncertainties, we forecast in particular how well one can predict the lensing signal from a cosmic shear survey using an over-lapping galaxy survey. We finally discuss the specific physics probed this way and illustrate how $f(R)$ gravity models would fail such a test.

Yong-Seon Song; Olivier Doré

2008-12-01T23:59:59.000Z

326

The effect of dark matter resolution on the collapse of baryons in high redshift numerical simulations  

E-Print Network [OSTI]

We examine the impact of dark matter particle resolution on the formation of a baryonic core in high resolution adaptive mesh refinement simulations. We test the effect that both particle smoothing and particle splitting have on the hydrodynamic properties of a collapsing halo at high redshift (z > 20). Furthermore, we vary the background field intensity, with energy below the Lyman limit ( 100.0$ be satisfied, where ${M_{\\rm{core}}}$ is the enclosed baryon mass within the core and $M_{\\rm{DM}}$ is the minimum dark matter particle mass. This ratio should provide a very useful starting point for conducting convergence tests before any production run simulations. We find that dark matter particle smoothing is a useful adjunct to already highly resolved simulations.

Regan, John A; Wise, John H

2015-01-01T23:59:59.000Z

327

Generalized Chaplygin gas model: constraints from Hubble parameter versus Redshift Data  

E-Print Network [OSTI]

We examine observational constraints on the generalized Chaplygin gas (GCG) model for dark energy from the 9 Hubble parameter data points, the 115 SNLS Sne Ia data and the size of baryonic acoustic oscillation peak at redshift, $z=0.35$. At a 95.4% confidence level, a combination of three data sets gives $0.67\\leq A_s\\leq 0.83$ and $-0.21\\leq \\alpha\\leq 0.42$, which is within the allowed parameters ranges of the GCG as a candidate of the unified dark matter and dark energy. It is found that the standard Chaplygin gas model ($\\alpha=1$) is ruled out by these data at the 99.7% confidence level.

Puxun Wu; Hongwei Yu

2006-12-09T23:59:59.000Z

328

Constraints on (Omega_m,Omega_Lambda) using distributions of inclination angles for high redshift filaments  

E-Print Network [OSTI]

In this paper we present a scale free method to determine the cosmological parameters (Omega_m, Omega_Lambda). The method is based on the requirement of isotropy of the distribution of orientations of cosmological filaments. The current structure formation paradigm predicts that the first structures to form are voids and filaments, causing a web-like structure of the matter distribution at high redshifts. Recent observational evidence suggests that the threads, or filaments, of the cosmic web most easily are mapped in Ly-alpha emission. We describe how such a 3D map can be used to constrain the cosmological parameters in a way which, contrary to most other cosmological tests, does not require the use of a standard rod or a standard candle. We perform detailed simulations in order to define the optimal survey parameters for the definition of an observing programme aimed to address this test, and to investigate how statistical and observational errors will influence the results. We conclude that observations should target filaments of comoving size 15-50 Mpc in the redshift range 2-4, and that each filament must be defined by at least four Ly-alpha emitters. Detection of 20 filaments will be sufficient to obtain a result, while 50 filaments will make it possible to place significant new constraints on the values of Omega_m and Omega_Lambda permitted by the current supernova observations. In a future paper we study how robust these conclusions are to systematic velocities in the survey box.

M. Weidinger; P. Moller; J. P. U. Fynbo; B. Thomsen; M. P. Egholm

2002-05-24T23:59:59.000Z

329

Current Dark Matter Annihilation Constraints from CMB and Low-Redshift Data  

E-Print Network [OSTI]

Updated constraints on dark matter cross section and mass are presented combining CMB power spectrum measurements from Planck, WMAP9, ACT, and SPT as well as several low-redshift datasets (BAO, HST, supernovae). For the CMB datasets, we combine WMAP9 temperature and polarization data for l 2500, and Planck CMB four-point lensing measurements. We allow for redshift-dependent energy deposition from dark matter annihilation by using a `universal' energy absorption curve. We also include an updated treatment of the excitation, heating, and ionization energy fractions, and provide updated deposition efficiency factors (f_eff) for 41 different dark matter models. Assuming perfect energy deposition (f_eff = 1) and a thermal cross section, dark matter masses below 26 GeV are excluded at the 2-sigma level. Assuming a more generic efficiency of f_eff = 0.2, thermal dark matter masses below 5 GeV are disfavored at the 2-sigma level. These limits are a factor of ~2 improvement over those from WMAP9 data alone. These current constraints probe, but do not exclude, dark matter as an explanation for reported anomalous indirect detection observations from AMS-02/PAMELA and the Fermi Gamma-ray Inner Galaxy data. They also probe relevant models that would explain anomalous direct detection events from CDMS, CRESST, CoGeNT, and DAMA, as originating from a generic thermal WIMP. Projected constraints from the full Planck release should improve the current limits by another factor of ~2, but will not definitely probe these signals. The proposed CMB Stage IV experiment will more decisively explore the relevant regions and improve upon the Planck constraints by another factor of ~2.

Mathew S. Madhavacheril; Neelima Sehgal; Tracy R. Slatyer

2014-11-28T23:59:59.000Z

330

The 2dF Galaxy Redshift Survey: Galaxy luminosity functions per spectral type  

E-Print Network [OSTI]

We calculate the optical bj luminosity function of the 2dF Galaxy Redshift Survey (2dFGRS) for different subsets defined by their spectral properties. These spectrally selected subsets are defined using a new parameter, eta, which is a linear combination of the first two projections derived from a Principal Component Analysis. This parameter eta identifies the average emission and absorption line strength in the galaxy rest-frame spectrum and hence is a useful indicator of the present star formation. We use a total of 75,000 galaxies in our calculations, chosen from a sample of high signal-to-noise ratio, low redshift galaxies observed before January 2001. We find that there is a systematic steepening of the faint end slope (alpha) as one moves from passive (alpha = -0.54) to active (alpha = -1.50) star-forming galaxies, and that there is also a corresponding faintening of the rest-frame characteristic magnitude M* - 5\\log_10(h) (from -19.6 to -19.2). We also show that the Schechter function provides a poor fit to the quiescent (Type 1) LF for very faint galaxies (M - 5log_10(h) fainter than -16.0), perhaps suggesting the presence of a significant dwarf population. The luminosity functions presented here give a precise confirmation of the trends seen previously in a much smaller preliminary 2dFGRS sample, and in other surveys. We also present a new procedure for determining self-consistent K-corrections and investigate possible fibre-aperture biases.

D. S. Madgwick; O. Lahav; I. K. Baldry; C. M. Baugh; J. Bland-Hawthorn; T. Bridges; R. Cannon; S. Cole; M. Colless; C. Collins; W. Couch; G. Dalton; R. De Propris; S. P. Driver; G. Efstathiou; R. S. Ellis; C. S. Frenk; K. Glazebrook; C. Jackson; I. Lewis; S. Lumsden; S. Maddox; P. Norberg; J. A. Peacock; B. A. Peterson; W. Sutherland; K. Taylor

2002-02-06T23:59:59.000Z

331

ESTIMATING PHOTOMETRIC REDSHIFTS OF QUASARS VIA THE k-NEAREST NEIGHBOR APPROACH BASED ON LARGE SURVEY DATABASES  

SciTech Connect (OSTI)

We apply one of the lazy learning methods, the k-nearest neighbor (kNN) algorithm, to estimate the photometric redshifts of quasars based on various data sets from the Sloan Digital Sky Survey (SDSS), the UKIRT Infrared Deep Sky Survey (UKIDSS), and the Wide-field Infrared Survey Explorer (WISE; the SDSS sample, the SDSS-UKIDSS sample, the SDSS-WISE sample, and the SDSS-UKIDSS-WISE sample). The influence of the k value and different input patterns on the performance of kNN is discussed. kNN performs best when k is different with a special input pattern for a special data set. The best result belongs to the SDSS-UKIDSS-WISE sample. The experimental results generally show that the more information from more bands, the better performance of photometric redshift estimation with kNN. The results also demonstrate that kNN using multiband data can effectively solve the catastrophic failure of photometric redshift estimation, which is met by many machine learning methods. Compared with the performance of various other methods of estimating the photometric redshifts of quasars, kNN based on KD-Tree shows superiority, exhibiting the best accuracy.

Zhang Yanxia; Ma He; Peng Nanbo; Zhao Yongheng [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, 100012 Beijing (China); Wu Xuebing, E-mail: zyx@bao.ac.cn [Department of Astronomy, Peking University, 100871 Beijing (China)

2013-08-01T23:59:59.000Z

332

The CNOC2 Field Galaxy Redshift Survey I: The Survey and the Catalog for the Patch CNOC 0223+00  

E-Print Network [OSTI]

The Canadian Network for Observational Cosmology (CNOC2) Field Galaxy Redshift Survey is a spectroscopic/photometric survey of faint galaxies over 1.5 square degrees of sky with a nominal spectroscopic limit of R_c=21.5 mag. The primary goals of the survey are to investigate the evolution of galaxy clustering and galaxy populations over the redshift range of approximately 0.1 to 0.6. The survey area contains four widely separated patches on the sky with a total spectroscopic sample of over 6000 redshifts and a photometric sample of over 40,000 galaxies with 5-color photometry. We describe the survey and observational strategies, multi-object spectroscopy mask design procedure, and data reduction techniques for creating the spectroscopic-photometric catalogs. We also discuss the derivations of various statistical weights for the redshift sample which allow it to be used as a complete sample. As the initial release of the survey data, we present the data set and some statistics for the Patch CNOC0223+00.

H. K. C. Yee; S. L. Morris; H. Lin; R. G. Carlberg; P. B. Hall; M. Sawicki; D. R. Patton; G. D. Wirth; E. Ellingson; C. W. Shepherd

2000-04-03T23:59:59.000Z

333

MUSE integral-field spectroscopy towards the Frontier Fields Cluster Abell S1063: I. Data products and redshift identifications  

E-Print Network [OSTI]

We present the first observations of the Frontier Fields Cluster Abell S1063, taken with the newly commissioned Multi Unit Spectroscopic Explorer (MUSE) integral field spectrograph. Because of the relatively large field of view (1 arcmin^2), MUSE is ideal to simultaneously target multiple galaxies in blank and cluster fields over the full optical spectrum. We analysed the four hours of data obtained in the Science Verification phase on this cluster and measured redshifts for 60 objects. We confirm the redshift of five cluster galaxies, and determine the redshift of 28 other cluster members. Behind the cluster, we find 16 galaxies at higher redshift, including three previously unknown Lyman-alpha emitters at z>3, and five multiply-lensed galaxies. We report the detection of a new z=4.113 multiply lensed galaxy, with images that are consistent with lensing model predictions derived for the Fronter Fields. We detect CIII], C IV and He II emission in a multiply lensed galaxy at z=3.116, suggesting the likely pres...

Karman, W; Grillo, C; Balestra, I; Rosati, P; Vanzella, E; Coe, D; Christensen, L; Koekemoer, A M; Kruehler, T; Lombardi, M; Mercurio, A; Nonino, M; van der Wel, A

2014-01-01T23:59:59.000Z

334

The WiggleZ Dark Energy Survey: direct constraints on blue galaxy intrinsic alignments at intermediate redshifts  

Science Journals Connector (OSTI)

......research-article Papers The WiggleZ Dark Energy Survey: direct constraints on blue...spectroscopic redshifts from the WiggleZ Dark Energy Survey. Our null detection allows...shape measurements, the WiggleZ Dark Energy Survey (Drinkwater et al. 2010......

Rachel Mandelbaum; Chris Blake; Sarah Bridle; Filipe B. Abdalla; Sarah Brough; Matthew Colless; Warrick Couch; Scott Croom; Tamara Davis; Michael J. Drinkwater; Karl Forster; Karl Glazebrook; Ben Jelliffe; Russell J. Jurek; I-hui Li; Barry Madore; Chris Martin; Kevin Pimbblet; Gregory B. Poole; Michael Pracy; Rob Sharp; Emily Wisnioski; David Woods; Ted Wyder

2011-01-11T23:59:59.000Z

335

The WiggleZ Dark Energy Survey: mapping the distance–redshift relation with baryon acoustic oscillations  

Science Journals Connector (OSTI)

......research-article Papers The WiggleZ Dark Energy Survey: mapping the distance-redshift...final data set of the WiggleZ Dark Energy Survey. We combine our correlation...6: the SDSS, the WiggleZ Dark Energy Survey and the 6-degree Field Galaxy......

Chris Blake; Eyal A. Kazin; Florian Beutler; Tamara M. Davis; David Parkinson; Sarah Brough; Matthew Colless; Carlos Contreras; Warrick Couch; Scott Croom; Darren Croton; Michael J. Drinkwater; Karl Forster; David Gilbank; Mike Gladders; Karl Glazebrook; Ben Jelliffe; Russell J. Jurek; I-hui Li; Barry Madore; D. Christopher Martin; Kevin Pimbblet; Gregory B. Poole; Michael Pracy; Rob Sharp; Emily Wisnioski; David Woods; Ted K. Wyder; H. K. C. Yee

2011-12-11T23:59:59.000Z

336

High Redshift Intergalactic C IV Abundance Measurements from the Near-Infrared Spectra of Two z~6 QSOs  

E-Print Network [OSTI]

New measurements of the z~6 intergalactic CIV abundance are presented, using moderate resolution IR spectra of two QSOs taken with GNIRS on Gemini South. These data were systematically searched for high redshift CIV absorption lines, using objective selection criteria. Comprehensive tests were performed to quantify sample incompleteness, as well as the rate of false positive CIV identifications. The trend of constant $\\Omega_{CIV}(z)$ observed at z~2-5 appears to continue to z~6, the highest observed redshift. The CIV sample is also consistent with the redshift-invariant form of the CIV column density distribution reported by Songaila (2001) at lower redshift, although with fairly large uncertainties due to a smaller sample size and noisier infrared data. The constant value of $\\Omega_{CIV}$ does not necessarily imply that the IGM was infused with an early metallicity ``floor,'' but the presence of early CIV does indicate that heavy-element enrichment began < 1 Gyr after the Big Bang. The lack of a decline...

Simcoe, R A

2006-01-01T23:59:59.000Z

337

A simple varying-speed-of-light hypothesis is enough for explaining high-redshift supernovae data  

E-Print Network [OSTI]

The hypothesis that the speed of light decreases by nearly 2 cm per sec and per year is discussed within the frame of a simple phenomenological model. It is shown that this hypothesis can provide an alternative explanation for the redshift-distance relationship of type Ia supernovae, which is nowadays given in terms of a new form of (dark) energy of unknown origin.

Yves-Henri Sanejouand

2005-09-20T23:59:59.000Z

338

Model of thermally induced wavefront distortion and birefringence in side-pumped Nd-doped YAG and phosphate glass heat capacity rod lasers  

Science Journals Connector (OSTI)

We develop an analytic model to describe the dynamic average thermal distortion and phase difference between the two principal polarizations in side-pumped Nd:YAG and Nd:glass heat...

Liu, Liang; Wang, Xiaobo; Guo, Shaofeng; Xu, Xiaojun; Lu, Qisheng

2010-01-01T23:59:59.000Z

339

Space Systems Finland 1 Deployment in the Space Sector  

E-Print Network [OSTI]

© Space Systems Finland 1 Deployment in the Space Sector #12;© Space Systems Finland 2 SW Constraints Design Requirements User Requirements SW Requirements #12;© Space Systems Finland 3 The space, but there is no viable alternative · Many requirements are not testable #12;© Space Systems Finland 4 SSF OBJECTIVES

Southampton, University of

340

RAPID, MACHINE-LEARNED RESOURCE ALLOCATION: APPLICATION TO HIGH-REDSHIFT GAMMA-RAY BURST FOLLOW-UP  

SciTech Connect (OSTI)

As the number of observed gamma-ray bursts (GRBs) continues to grow, follow-up resources need to be used more efficiently in order to maximize science output from limited telescope time. As such, it is becoming increasingly important to rapidly identify bursts of interest as soon as possible after the event, before the afterglows fade beyond detectability. Studying the most distant (highest redshift) events, for instance, remains a primary goal for many in the field. Here, we present our Random Forest Automated Triage Estimator for GRB redshifts (RATE GRB-z ) for rapid identification of high-redshift candidates using early-time metrics from the three telescopes onboard Swift. While the basic RATE methodology is generalizable to a number of resource allocation problems, here we demonstrate its utility for telescope-constrained follow-up efforts with the primary goal to identify and study high-z GRBs. For each new GRB, RATE GRB-z provides a recommendation-based on the available telescope time-of whether the event warrants additional follow-up resources. We train RATE GRB-z using a set consisting of 135 Swift bursts with known redshifts, only 18 of which are z > 4. Cross-validated performance metrics on these training data suggest that {approx}56% of high-z bursts can be captured from following up the top 20% of the ranked candidates, and {approx}84% of high-z bursts are identified after following up the top {approx}40% of candidates. We further use the method to rank 200 + Swift bursts with unknown redshifts according to their likelihood of being high-z.

Morgan, A. N.; Richards, Joseph W.; Butler, Nathaniel R.; Bloom, Joshua S. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Long, James; Broderick, Tamara, E-mail: amorgan@astro.berkeley.edu [Department of Statistics, University of California, Berkeley, CA 94720-3860 (United States)

2012-02-20T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

CONTAMINATION OF BROADBAND PHOTOMETRY BY NEBULAR EMISSION IN HIGH-REDSHIFT GALAXIES: INVESTIGATIONS WITH KECK'S MOSFIRE NEAR-INFRARED SPECTROGRAPH  

SciTech Connect (OSTI)

Earlier work has raised the potential importance of nebular emission in the derivation of the physical characteristics of high-redshift Lyman break galaxies. Within certain redshift ranges, and especially at z ? 6-7, such lines may be strong enough to reduce estimates of the stellar masses and ages of galaxies compared with those derived assuming the broadband photometry represents stellar light alone. To test this hypothesis at the highest redshifts where such lines can be probed with ground-based facilities, we examine the near-infrared spectra of a representative sample of 28 3.0 < z < 3.8 Lyman break galaxies using the newly commissioned MOSFIRE near-infrared spectrograph at the Keck I telescope. We use these data to derive the rest-frame equivalent widths (EWs) of [O III] emission and show that these are comparable with estimates derived using the spectral energy distribution (SED) fitting technique introduced for sources of known redshift by Stark et al. Although our current sample is modest, its [O III] EW distribution is consistent with that inferred for H? based on SED fitting of Stark et al.'s larger sample of 3.8 < z < 5 galaxies. For a subset of survey galaxies, we use the combination of optical and near-infrared spectroscopy to quantify kinematics of outflows in z ? 3.5 star-forming galaxies and discuss the implications for reionization measurements. The trends we uncover underline the dangers of relying purely on broadband photometry to estimate the physical properties of high-redshift galaxies and emphasize the important role of diagnostic spectroscopy.

Schenker, Matthew A; Ellis, Richard S; Konidaris, Nick P [Department of Astrophysics, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Stark, Daniel P, E-mail: schenker@astro.caltech.edu [Department of Astronomy and Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)

2013-11-01T23:59:59.000Z

342

Berkeley Lab Space  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Space Space Committee Charter Articles Presentations Feedback Contact Us ANNOUNCEMENTS Space Planning Advisory Committee (SPAC) The LBNL Space Planning Advisory Committee (SPAC) was chartered in January 2010 to help manage the growth, both in the short term as well as long term. Specifically, SPAC will recommend to senior laboratory management policies and procedures for the allocation and utilization of space and opportunities for increased efficiency. (For the complete charter, click here.)We welcome comments and suggestions. Our email is: SPAC@lbl.gov. SPAC (Space Planning Advisory Committee) SPAC Members Telephone Number Email Rich Diamond 510-486-4459 RCDiamond@lbl.gov Rich McClure 510-486-4486 RMMcClure@lbl.gov Diana Attia 510-486-7399 DMAttia@lbl.gov Rebecca Rishell 510-486-6689

343

Isolating relativistic effects in large-scale structure  

E-Print Network [OSTI]

We present a fully relativistic calculation of the observed galaxy number counts in the linear regime. We show that besides the density fluctuations and redshift-space distortions, various relativistic effects contribute to observations at large scales. These effects all have the same physical origin: they result from the fact that our coordinate system, namely the galaxy redshift and the incoming photons' direction, is distorted by inhomogeneities in our universe. We then discuss the impact of the relativistic effects on the angular power spectrum and on the two-point correlation function in configuration space. We show that the latter is very well adapted to isolate the relativistic effects since it naturally makes use of the symmetries of the different contributions. In particular, we discuss how the Doppler effect and the gravitational redshift distortions can be isolated by looking for a dipole in the cross-correlation function between a bright and a faint population of galaxies.

Bonvin, Camille

2014-01-01T23:59:59.000Z

344

AB Space Engine  

E-Print Network [OSTI]

On 4 January 2007 the author published the article Wireless Transfer of Electricity in Outer Space in http://arxiv.org wherein he offered and researched a new revolutionary method of transferring electric energy in space. In that same article, he offered a new engine which produces a large thrust without throwing away large amounts of reaction mass (unlike the conventional rocket engine). In the current article, the author develops the theory of this kind of impulse engine and computes a sample project which shows the big possibilities opened by this new AB-Space Engine. The AB-Space Engine gets the energy from ground-mounted power; a planet electric station can transfer electricity up to 1000 millions (and more) of kilometers by plasma wires. Author shows that AB-Space Engine can produce thrust of 10 tons (and more). That can accelerate a space ship to some thousands of kilometers/second. AB-Space Engine has a staggering specific impulse owing to the very small mass expended. The AB-Space Engine reacts not by expulsion of its own mass (unlike rocket engine) but against the mass of its planet of origin (located perhaps a thousand of millions of kilometers away) through the magnetic field of its plasma cable. For creating this plasma cable the AB-Space Engine spends only some kg of hydrogen.

Alexander Bolonkin

2008-03-02T23:59:59.000Z

345

Passive solar space heating  

SciTech Connect (OSTI)

An overview of passive solar space heating is presented indicating trends in design, new developments, performance measures, analytical design aids, and monitored building results.

Balcomb, J.D.

1980-01-01T23:59:59.000Z

346

Total Space Heat-  

Annual Energy Outlook 2013 [U.S. Energy Information Administration (EIA)]

Buildings Energy Consumption Survey: Energy End-Use Consumption Tables Total Space Heat- ing Cool- ing Venti- lation Water Heat- ing Light- ing Cook- ing Refrig- eration...

347

Neutron Tomography and Space  

E-Print Network [OSTI]

Kevin Shields, “Optimization of neutron tomography for rapidNEUTRON TOMOGRAPHY AND SPACE Hal Egbert, Ronald Walker, R.industrial applications[1]. Neutron Computed Tomography was

Egbert, Hal; Walker, Ronald; Flocchini, R.

2007-01-01T23:59:59.000Z

348

Dynamical 3-Space: Alternative Explanation of the `Dark Matter Ring'  

E-Print Network [OSTI]

NASA has claimed the discovery of a `Ring of Dark Matter' in the galaxy cluster CL 0024+17, see Jee M.J. et al. arXiv:0705.2171, based upon gravitational lensing data. Here we show that the lensing can be given an alternative explanation that does not involve `dark matter'. This explanation comes from the new dynamics of 3-space. This dynamics involves two constant G and alpha - the fine structure constant. This dynamics has explained the bore hole anomaly, spiral galaxy flat rotation speeds, the masses of black holes in spherical galaxies, gravitational light bending and lensing, all without invoking `dark matter', and also the supernova redshift data without the need for `dark energy'.

Reginald T Cahill

2007-05-20T23:59:59.000Z

349

Today's Space Weather Space Weather Case Studies  

E-Print Network [OSTI]

tank on Space ShuQle trips alarms Impacts #12;Quebec electrical blackout: "GIC" (ground-induced current) Quebec sits on are large sheet of bedrock [rock shield], and grounding is difficult Hydro-Quebec's power grid is, within 90-sec of storm onset

350

National Aeronautics and Space Administration International Space  

E-Print Network [OSTI]

sustainability and ensure their early incorporation in the architecture ­ Apply a phased approach to exploration Partnerships Strategy · NASA leadership of a sustainable and affordable human space exploration of many costs (not LCC) or obtain funding or resource offsets 2. Enhance sustainability thru interdependent

Waliser, Duane E.

351

Cobalt–Zinc Molybdates as New Blue Pigments Involving Co2+ in Distorted Trigonal Bipyramids and Octahedra  

Science Journals Connector (OSTI)

(11) Dark purple coloration is found in the adamite-type family, such as phosphates (Zn,Co)2(OH)PO4. ... Two new adamite-type phases, Co2(OH)PO4 and Zn2(OH)PO4: structure-directing effect of organic additives ... Both materials are isomorphous with the adamite-type M2(OH)XO4 structure, and consist of a condensed vertex- and edge-sharing network of MO5, distorted MO6(M = Co, Zn), and PO4 subunits. ...

L. Robertson; M. Duttine; M. Gaudon; A. Demourgues

2011-04-13T23:59:59.000Z

352

Observations of spheromak equilibria which differ from the minimum-energy state and have internal kink distortions  

Science Journals Connector (OSTI)

Experimental spheromak magnetic equilibria are measured which differ significantly from the minimum-energy state, and are well described by a numerical model where j?/B has a linear dependence on the poloidal flux function. Equilibria are determined in a nonperturbing manner by the combination of measurements of flux-conserver image currents with calculations from this model. These equilibria are corroborated by the observation of nondisruptive rotating internal kink distortions (with toroidal mode numbers n=1, 2, and 3), coupled with theoretical thresholds for the onset of these modes.

S. O. Knox; Cris W. Barnes; G. J. Marklin; T. R. Jarboe; I. Henins; H. W. Hoida; B. L. Wright

1986-02-24T23:59:59.000Z

353

Space Plasma Physics  

Science Journals Connector (OSTI)

...W.D., BEAM-PLASMA DISCHARGE - BUILDUP...DURING ELECTRON BEAM-PLASMA INTERACTIONS, GEOPHYSICAL...ELECTRON-BEAM IN THE ATMOSPHERE, PLANETARY AND SPACE...1980 ). Space plasma physics: electron...regula' occurred at large pitch angles. Note...in quite different areas. (i) There is...

KLAUS WILHELM; WOLFGANG STÜDEMANN; WILLIBALD RIEDLER

1984-07-13T23:59:59.000Z

354

SPACE RESOURCES ROUNDTABLE IX  

E-Print Network [OSTI]

in developing the resources of space, including the Moon, Mars, asteroids, comets, and other bodies organizations. The ninth Space Resources Roundtable solicits presentations about: · Orbital or landed measurements of the Moon, Mars, and/or asteroids and comets to identify and characterize potential resources

Rathbun, Julie A.

355

Towards interactive smart spaces  

Science Journals Connector (OSTI)

Recently, we have been witnessing how various social applications and networking services are being integrated more deeply into our daily lives. Until now, social interaction has been attributed exclusively to humans, while resources and the smart space ... Keywords: Context-Awareness, Knowledge-Based Systems, Smart Spaces, Social Interaction

Ekaterina Gilman; Oleg Davidyuk; Xiang Su; Jukka Riekki

2013-01-01T23:59:59.000Z

356

AB Space Engine  

E-Print Network [OSTI]

On 4 January 2007 the author published the article Wireless Transfer of Electricity in Outer Space in http://arxiv.org wherein he offered and researched a new revolutionary method of transferring electric energy in space. In that same article, he offered a new engine which produces a large thrust without throwing away large amounts of reaction mass (unlike the conventional rocket engine). In the current article, the author develops the theory of this kind of impulse engine and computes a sample project which shows the big possibilities opened by this new AB-Space Engine. The AB-Space Engine gets the energy from ground-mounted power; a planet electric station can transfer electricity up to 1000 millions (and more) of kilometers by plasma wires. Author shows that AB-Space Engine can produce thrust of 10 tons (and more). That can accelerate a space ship to some thousands of kilometers/second. AB-Space Engine has a staggering specific impulse owing to the very small mass expended. The AB-Space Engine reacts not b...

Bolonkin, Alexander

2008-01-01T23:59:59.000Z

357

SPACE TECHNOLOGY Actual Estimate  

E-Print Network [OSTI]

SPACE TECHNOLOGY TECH-1 Actual Estimate Budget Authority (in $ millions) FY 2011 FY 2012 FY 2013 FY.7 247.0 Exploration Technology Development 144.6 189.9 202.0 215.5 215.7 214.5 216.5 Notional SPACE TECHNOLOGY OVERVIEW .............................. TECH- 2 SBIR AND STTR

358

DUST EXTINCTION BIAS IN THE COLUMN DENSITY DISTRIBUTION OF GAMMA-RAY BURSTS: HIGH COLUMN DENSITY, LOW-REDSHIFT GRBs ARE MORE HEAVILY OBSCURED  

SciTech Connect (OSTI)

The afterglows of gamma-ray bursts (GRBs) have more soft-X-ray absorption than expected from the foreground gas column in the Galaxy. While the redshift of the absorption can in general not be constrained from current X-ray observations, it has been assumed that the absorption is due to metals in the host galaxy of the GRB. The large sample of X-ray afterglows and redshifts now available allows the construction of statistically meaningful distributions of the metal column densities. We construct such a sample and show, as found in previous studies, that the typical absorbing column density (N{sub H{sub X}}) increases substantially with redshift, with few high column density objects found at low-to-moderate redshifts. We show, however, that when highly extinguished bursts are included in the sample, using redshifts from their host galaxies, high column density sources are also found at low-to-moderate redshift. We infer from individual objects in the sample and from observations of blazars that the increase in column density with redshift is unlikely to be related to metals in the intergalactic medium or intervening absorbers. Instead we show that the origin of the apparent increase with redshift is primarily due to dust extinction bias: GRBs with high X-ray absorption column densities found at z {approx}< 4 typically have very high dust extinction column densities, while those found at the highest redshifts do not. It is unclear how such a strongly evolving N{sub H{sub X}}/A{sub V} ratio would arise, and based on current data, remains a puzzle.

Watson, Darach [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen O (Denmark); Jakobsson, Pall, E-mail: darach@dark-cosmology.dk, E-mail: pja@raunvis.hi.is [Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhaga 5, IS-107 Reykjavik (Iceland)

2012-08-01T23:59:59.000Z

359

SCP06F6: A carbon-rich extragalactic transient at redshift z~0.14?  

E-Print Network [OSTI]

We show that the spectrum of the unusual transient SCP06F6 is consistent with emission from a cool, optically thick and carbon-rich atmosphere if the transient is located at a redshift of z~0.14. The implied extragalactic nature of the transient rules out novae, shell flashes, and V838 Mon-like events as cause of the observed brightening. The distance to SCP06F6 implies a peak magnitude of M_I ~- 18, in the regime of supernovae. While the morphology of the light curve of SCP06F6 around the peak in brightness resembles the slowly evolving Type IIn supernovae SN1994Y and SN2006gy its spectroscopic appearence differs from all previous observed supernovae. We further report the detection of an X-ray source co-incident with SCP06F6 in a target of opportunity XMM-Newton observation made during the declining phase of the transient. The X-ray luminosity of L_X ~- (5+-1)e42 erg/s is two orders of magnitude higher than observed to date from supernovae. If related to a supernova event, SCP06F6 may define a new class. An alternative, though less likely, scenario is the tidal disruption of a carbon-rich star.

B. T. Gaensicke; A. J. Levan; T. R. Marsh; P. J. Wheatley

2008-09-15T23:59:59.000Z

360

INTERPRETING THE GLOBAL 21 cm SIGNAL FROM HIGH REDSHIFTS. I. MODEL-INDEPENDENT CONSTRAINTS  

SciTech Connect (OSTI)

The sky-averaged (global) 21 cm signal is a powerful probe of the intergalactic medium (IGM) prior to the completion of reionization. However, so far it has been unclear whether it will provide more than crude estimates of when the universe's first stars and black holes formed, even in the best case scenario in which the signal is accurately extracted from the foregrounds. In contrast to previous work, which has focused on predicting the 21 cm signatures of the first luminous objects, we investigate an arbitrary realization of the signal and attempt to translate its features to the physical properties of the IGM. Within a simplified global framework, the 21 cm signal yields quantitative constraints on the Ly? background intensity, net heat deposition, ionized fraction, and their time derivatives without invoking models for the astrophysical sources themselves. The 21 cm absorption signal is most easily interpreted, setting strong limits on the heating rate density of the universe with a measurement of its redshift alone, independent of the ionization history or details of the Ly? background evolution. In a companion paper, we extend these results, focusing on the confidence with which one can infer source emissivities from IGM properties.

Mirocha, Jordan; Harker, Geraint J. A.; Burns, Jack O., E-mail: jordan.mirocha@colorado.edu [Center for Astrophysics and Space Astronomy, University of Colorado, Campus Box 389, Boulder, CO 80309 (United States)

2013-11-10T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

An Intermediate-band imaging survey for high-redshift Lyman Alpha Emitters: The Mahoroba-11  

E-Print Network [OSTI]

We present results of our intermediate-band optical imaging survey for high-$z$ Ly$\\alpha$ emitters (LAEs) using the prime focus camera, Suprime-Cam, on the 8.2m Subaru Telescope. In our survey, we use eleven filters; four broad-band filters ($B$, $R_{\\rm c}$, $i^\\prime$, and $z^\\prime$) and seven intermediate-band filters covering from 500 nm to 720 nm; we call this imaging program as the Mahoroba-11. The seven intermediate-band filters are selected from the IA filter series that is the Suprime-Cam intermediate-band filter system whose spectral resolution is $R = 23$. Our survey has been made in a $34^\\prime \\times 27^\\prime$ sky area in the Subaru XMM Newton Deep Survey field. We have found 409 IA-excess objects that provide us a large photometric sample of strong emission-line objects. Applying the photometric redshift method to this sample, we obtained a new sample of 198 LAE candidates at $3 42.67$ between $z \\sim 3$ and 5.

Yamada, S F; Sumiya, R; Umeda, K; Shioya, Y; Ajiki, M; Nagao, T; Murayama, T; Taniguchi, Y; Yamada, Sanae F.; Sasaki, Shunji S.; Sumiya, Ryoko; Umeda, Kazuyoshi; Shioya, Yasuhiro; Ajiki, Masaru; Nagao, Tohru; Murayama, Takashi; Taniguchi, Yoshiaki

2005-01-01T23:59:59.000Z

362

ON THE CORRELATION OF LOW-ENERGY SPECTRAL INDICES AND REDSHIFTS OF GAMMA-RAY BURSTS  

SciTech Connect (OSTI)

It was found by Amati et al. in 2002 that for a small sample of nine gamma-ray bursts (GRBs), more distant events appear to be systematically harder in the soft gamma-ray band. Here, we have collected a larger sample of 65 GRBs, whose time-integrated spectra are well established and can be well fitted with the so-called Band function. It is confirmed that a correlation between the redshifts (z) and the low-energy indices ({alpha}) of the Band function does exist, though it is a bit more scattered than the result of Amati et al. This correlation cannot be simply attributed to the effect of photon reddening. Furthermore, correlations between {alpha} and E {sub peak} (the peak energy in the {nu}F {sub {nu}} spectrum in the rest frame), {alpha} and E {sub iso} (the isotropic energy release), and {alpha} and L {sub iso} (the isotropic luminosity) are also found, which indicate that these parameters are somehow connected. The results may provide useful constraints on the physics of GRBs.

Geng, J. J.; Huang, Y. F., E-mail: hyf@nju.edu.cn [Department of Astronomy, Nanjing University, Nanjing 210093 (China)

2013-02-10T23:59:59.000Z

363

Machine learning techniques for astrophysical modelling and photometric redshift estimation of quasars in optical sky surveys  

E-Print Network [OSTI]

Machine learning techniques are utilised in several areas of astrophysical research today. This dissertation addresses the application of ML techniques to two classes of problems in astrophysics, namely, the analysis of individual astronomical phenomena over time and the automated, simultaneous analysis of thousands of objects in large optical sky surveys. Specifically investigated are (1) techniques to approximate the precise orbits of the satellites of Jupiter and Saturn given Earth-based observations as well as (2) techniques to quickly estimate the distances of quasars observed in the Sloan Digital Sky Survey. Learning methods considered include genetic algorithms, particle swarm optimisation, artificial neural networks, and radial basis function networks. The first part of this dissertation demonstrates that GAs and PSO can both be efficiently used to model functions that are highly non-linear in several dimensions. It is subsequently demonstrated in the second part that ANNs and RBFNs can be used as effective predictors of spectroscopic redshift given accurate photometry, especially in combination with other learning-based approaches described in the literature. Careful application of these and other ML techniques to problems in astronomy and astrophysics will contribute to a better understanding of stellar evolution, binary star systems, cosmology, and the large-scale structure of the universe.

N. Daniel Kumar

2008-11-04T23:59:59.000Z

364

WIDESPREAD AND HIDDEN ACTIVE GALACTIC NUCLEI IN STAR-FORMING GALAXIES AT REDSHIFT >0.3  

SciTech Connect (OSTI)

We characterize the incidence of active galactic nuclei (AGNs) in 0.3 < z < 1 star-forming galaxies by applying multi-wavelength AGN diagnostics (X-ray, optical, mid-infrared, radio) to a sample of galaxies selected at 70 {mu}m from the Far-Infrared Deep Extragalactic Legacy survey (FIDEL). Given the depth of FIDEL, we detect 'normal' galaxies on the specific star formation rate (sSFR) sequence as well as starbursting systems with elevated sSFR. We find an overall high occurrence of AGN of 37% {+-} 3%, more than twice as high as in previous studies of galaxies with comparable infrared luminosities and redshifts but in good agreement with the AGN fraction of nearby (0.05 < z < 0.1) galaxies of similar infrared luminosities. The more complete census of AGNs comes from using the recently developed Mass-Excitation (MEx) diagnostic diagram. This optical diagnostic is also sensitive to X-ray weak AGNs and X-ray absorbed AGNs, and reveals that absorbed active nuclei reside almost exclusively in infrared-luminous hosts. The fraction of galaxies hosting an AGN appears to be independent of sSFR and remains elevated both on the sSFR sequence and above. In contrast, the fraction of AGNs that are X-ray absorbed increases substantially with increasing sSFR, possibly due to an increased gas fraction and/or gas density in the host galaxies.

Juneau, Stephanie; Bournaud, Frederic; Daddi, Emanuele; Elbaz, David [CEA-Saclay, DSM/IRFU/SAp, F-91191 Gif-sur-Yvette (France)] [CEA-Saclay, DSM/IRFU/SAp, F-91191 Gif-sur-Yvette (France); Dickinson, Mark; Kartaltepe, Jeyhan S. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)] [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Alexander, David M.; Mullaney, James R. [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom)] [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Magnelli, Benjamin [Max-Planck-Instituet fuer extraterrestrische Physik, Postfach 1312, D-85741 Garching bei Muenchen (Germany)] [Max-Planck-Instituet fuer extraterrestrische Physik, Postfach 1312, D-85741 Garching bei Muenchen (Germany); Hwang, Ho Seong; Willner, S. P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)] [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Coil, Alison L. [Department of Physics, Center for Astrophysics and Space Sciences, University of California, 9500 Gilman Dr., La Jolla, San Diego, CA 92093 (United States)] [Department of Physics, Center for Astrophysics and Space Sciences, University of California, 9500 Gilman Dr., La Jolla, San Diego, CA 92093 (United States); Rosario, David J. [Max-Planck-Instituet fuer extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching bei Muenchen (Germany)] [Max-Planck-Instituet fuer extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching bei Muenchen (Germany); Trump, Jonathan R.; Faber, S. M.; Kocevski, Dale D. [University of California Observatories/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)] [University of California Observatories/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States); Weiner, Benjamin J.; Willmer, Christopher N. A. [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)] [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Cooper, Michael C. [Center for Galaxy Evolution, Department of Physics and Astronomy, University of California-Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States)] [Center for Galaxy Evolution, Department of Physics and Astronomy, University of California-Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Frayer, David T., E-mail: stephanie.juneau@cea.fr [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States); and others

2013-02-20T23:59:59.000Z

365

A 250 GHz Survey of High Redshift QSOs from the Sloan Digital Sky Survey  

E-Print Network [OSTI]

We present observations at 250 GHz (1.2 mm), 43 GHz, and 1.4 GHz of a sample of 41 QSOs at z > 3.7 found in the Sloan Digital Sky Survey. We detect 16 sources with a 250 GHz flux density greater than 1.4 mJy. The combination of centimeter and millimeter wavelength observations indicates that the 250 GHz emission is most likely thermal dust emission. Assuming a dust temperature of 50 K, the implied dust masses for the 16 detected sources are in the range 1.5e8 to 5.9e8 Msun, and the dust emitting regions are likely to be larger than 1 kpc in extent. The radio-through-optical spectral energy distributions for these sources are within the broad range defined by lower redshift, lower optical luminosity QSOs. We consider possible dust heating mechanisms, including UV emission from the active nucleus (AGN) and a starburst concurrent with the AGN, with implied star formation rates between 500 and 2000 Msun/year.

Carilli, C L; Rupen, M P; Fan, X; Strauss, M A; Menten, K M; Kreysa, E; Schneider, D P; Bertarini, A; Yun, M S; Zylka, R; Fan, Xiaohui; Strauss, Michael A.; Schneider, Donald P.

2001-01-01T23:59:59.000Z

366

THE CARNEGIE SUPERNOVA PROJECT: SECOND PHOTOMETRY DATA RELEASE OF LOW-REDSHIFT TYPE Ia SUPERNOVAE  

SciTech Connect (OSTI)

The Carnegie Supernova Project (CSP) was a five-year observational survey conducted at Las Campanas Observatory that obtained, among other things, high-quality light curves of {approx}100 low-redshift Type Ia supernovae (SNe Ia). Presented here is the second data release of nearby SN Ia photometry consisting of 50 objects, with a subset of 45 having near-infrared follow-up observations. Thirty-three objects have optical pre-maximum coverage with a subset of 15 beginning at least five days before maximum light. In the near-infrared, 27 objects have coverage beginning before the epoch of B-band maximum, with a subset of 13 beginning at least five days before maximum. In addition, we present results of a photometric calibration program to measure the CSP optical (uBgVri) bandpasses with an accuracy of {approx}1%. Finally, we report the discovery of a second SN Ia, SN 2006ot, similar in its characteristics to the peculiar SN 2006bt.

Stritzinger, Maximilian D. [The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm (Sweden); Phillips, M. M.; Campillay, Abdo; Morrell, Nidia; Krzeminski, Wojtek; Roth, Miguel [Carnegie Observatories, Las Campanas Observatory, La Serena (Chile); Boldt, Luis N. [Argelander Institut fuer Astronomie, Universitaet Bonn, D-53111 Bonn (Germany); Burns, Chris; Freedman, Wendy L.; Madore, Barry F.; Persson, Sven E. [Observatories of the Carnegie Institution for Science, Pasadena, CA 91101 (United States); Contreras, Carlos [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Victoria 3122 (Australia); Gonzalez, Sergio [Atacama Large Millimeter/Submillimeter Array, European Southern Observatory (Chile); Folatelli, Gaston [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Salgado, Francisco [Leiden Observatory, Leiden University, NL-2300 RA Leiden (Netherlands); DePoy, D. L.; Marshall, J. L.; Rheault, Jean-Philippe; Suntzeff, Nicholas B. [George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States); Hamuy, Mario, E-mail: max.stritzinger@astro.su.se, E-mail: max@dark-cosmology.dk, E-mail: mstritzinger@lco.cl [Departamento de Astronomia, Universidad de Chile, Santiago (Chile)

2011-11-15T23:59:59.000Z

367

The CNOC2 sample of intermediate redshift galaxy groups - the powerhouse of galaxy evolution  

E-Print Network [OSTI]

The evolution of galaxies in groups may have important implications for the global evolution of star formation rate in the Universe, since many processes which operate in groups may suppress star formation, and the fraction of galaxies bound in groups at the present day is as high as ~60%. We present an analysis of our sample of 0.3<=z<=0.55 groups, selected from the CNOC2 redshift survey and supplemented with deep spectroscopy and HST ACS imaging. We find that these groups contain significantly more passive galaxies than the field, with excesses of S0, elliptical and passive spiral galaxy types. The morphological composition is closely matched to that of more massive irregular clusters at a similar epoch. Contrasting with galaxy samples in a variety of environments and epochs, we find that the fraction of passive galaxies (EW[OII]<5A), is strongly evolving in the group environment, with parallel evolution in the (global) field population, whilst little evolution is observed in cluster cores since z~...

Wilman, D J; Bower, R G; Mulchaey, J S; Oemler, A; Carlberg, R G

2005-01-01T23:59:59.000Z

368

The CNOC2 sample of intermediate redshift galaxy groups - the powerhouse of galaxy evolution  

E-Print Network [OSTI]

The evolution of galaxies in groups may have important implications for the global evolution of star formation rate in the Universe, since many processes which operate in groups may suppress star formation, and the fraction of galaxies bound in groups at the present day is as high as ~60%. We present an analysis of our sample of 0.3<=z<=0.55 groups, selected from the CNOC2 redshift survey and supplemented with deep spectroscopy and HST ACS imaging. We find that these groups contain significantly more passive galaxies than the field, with excesses of S0, elliptical and passive spiral galaxy types. The morphological composition is closely matched to that of more massive irregular clusters at a similar epoch. Contrasting with galaxy samples in a variety of environments and epochs, we find that the fraction of passive galaxies (EW[OII]<5A), is strongly evolving in the group environment, with parallel evolution in the (global) field population, whilst little evolution is observed in cluster cores since z~1.

D. J. Wilman; M. L. Balogh; R. G. Bower; J. S. Mulchaey; A. Oemler Jr; R. G. Carlberg

2005-10-04T23:59:59.000Z

369

The Nature of Nearby Counterparts to Intermediate Redshift Luminous Compact Blue Galaxies II. CO Observations  

E-Print Network [OSTI]

We present the results of a single-dish beam-matched survey of the three lowest rotational transitions of CO in a sample of 20 local (D < 70 Mpc) Luminous Compact Blue Galaxies (LCBGs). These ~L*, blue, high surface brightness, starbursting galaxies were selected with the same criteria used to define LCBGs at higher redshifts. Our detection rate was 70%, with those galaxies having Lblue<7e9 Lsun no detected. We find the H2 masses of local LCBGs range from 6.6e6 to 2.7e9 Msun, assuming a Galactic CO-to-H2 conversion factor. Combining these results with our earlier HI survey of the same sample, we find that the ratio of molecular to atomic gas mass is low, typically 5-10%. Using a Large Velocity Gradient model, we find that the average gas conditions of the entire ISM in local LCBGs are similar to those found in the centers of star forming regions in our Galaxy, and nuclear regions of other galaxies. Star formation rates, determined from IRAS fluxes, are a few solar masses per year, much higher per unit dynamical mass than normal spirals. If this rate remains constant, the molecular hydrogen depletion time scales are short, 10-200 Myr.

C. A. Garland; J. P. Williams; D. J. Pisano; R. Guzman; F. J. Castander; J. Brinkmann

2005-02-03T23:59:59.000Z

370

The 2dF Galaxy Redshift Survey: higher order galaxy correlation functions  

E-Print Network [OSTI]

We measure moments of the galaxy count probability distribution function in the two-degree field galaxy redshift survey (2dFGRS). The survey is divided into volume limited subsamples in order to examine the dependence of the higher order clustering on galaxy luminosity. We demonstrate the hierarchical scaling of the averaged p-point galaxy correlation functions, xibar_p, up to p=6. The hierarchical amplitudes, S_p = xibar_p/xibar_2^{p-1}, are approximately independent of the cell radius used to smooth the galaxy distribution on small to medium scales. On larger scales we find the higher order moments can be strongly affected by the presence of rare, massive superstructures in the galaxy distribution. The skewness S_3 has a weak dependence on luminosity, approximated by a linear dependence on log luminosity. We discuss the implications of our results for simple models of linear and non-linear bias that relate the galaxy distribution to the underlying mass.

D. J. Croton; E. Gaztanaga; C. M. Baugh; P. Norberg; M. Colless; I. K. Baldry; J. Bland-Hawthorn; T. Bridges; R. Cannon; S. Cole; C. Collins; W. Couch; G. Dalton; R. De Propris; S. P. Driver; G. Efstathiou; R. S. Ellis; C. S. Frenk; K. Glazebrook; C. Jackson; O. Lahav; I. Lewis; S. Lumsden; S. Maddox; D. Madgwick; J. A. Peacock; B. A. Peterson; W. Sutherland; K. Taylor

2004-08-23T23:59:59.000Z

371

The 2dF Galaxy Redshift Survey: Spectral Types and Luminosity Functions  

E-Print Network [OSTI]

We describe the 2dF Galaxy Redshift Survey (2dFGRS), and the current status of the observations. In this exploratory paper, we apply a Principal Component Analysis to a preliminary sample of 5869 galaxy spectra and use the two most significant components to split the sample into five spectral classes. These classes are defined by considering visual classifications of a subset of the 2dF spectra, and also by comparing to high quality spectra of local galaxies. We calculate a luminosity function for each of the different classes and find that later-type galaxies have a fainter characteristic magnitude, and a steeper faint-end slope. For the whole sample we find M*=-19.7 (for Omega=1, H_0=100 km/sec/Mpc), alpha=-1.3, phi*=0.017. For class 1 (`early-type') we find M*=-19.6, alpha=-0.7, while for class 5 (`late-type') we find M*=-19.0, alpha=-1.7. The derived 2dF luminosity functions agree well with other recent luminosity function estimates.

S. R. Folkes; S. Ronen; I. Price; O. Lahav; M. Colless; S. J. Maddox; K. E. Deeley; K. Glazebrook; J. Bland-Hawthorn; R. D. Cannon; S. Cole; C. A. Collins; W. J. Couch; S. P. Driver; G. Dalton; G. Efstathiou; R. S. Ellis; C. S. Frenk; N. Kaiser; I. J. Lewis; S. L. Lumsden; J. A. Peacock; B. A. Peterson; W. Sutherland; K. Taylor

1999-03-30T23:59:59.000Z

372

The 2dF Galaxy Redshift Survey: The Number and Luminosity Density of Galaxies  

E-Print Network [OSTI]

We present the bivariate brightness distribution (BBD) for the 2dF Galaxy Redshift Survey (2dFGRS) based on a preliminary subsample of 45,000 galaxies. The BBD is an extension of the galaxy luminosity function incorporating surface brightness information. It allows the measurement of the local luminosity density, j_B, and the galaxy luminosity and surface brightness distributions while accounting for surface brightness selection biases. The recovered 2dFGRS BBD shows a strong surface brightness-luminosity relation (M_B~2.4\\mu_e). The luminosity-density is dominated by normal galaxies and the luminosity-density peak lies away from the selection boundaries implying that the 2dFGRS is complete and that luminous low surface brightness galaxies are rare. The final value we derive for the local luminosity-density, inclusive of surface brightness corrections, is: j_B=2.49+/-0.20x10^8 h L_solar Mpc^-3. Representative Schechter function parameters are: M*=-19.75+/-0.05, phi*=2.02+/-0.02x10^-2 and alpha=-1.09+/-0.03. Extending the conventional methodology to incorporate surface brightness selection effects has resulted in an increase in the luminosity-density of 37%.

Nicholas Cross; Simon P. Driver; Warrick Couch; Carlton M. Baugh; Joss Bland-Hawthorn; Terry Bridges; Russell Cannon; Shaun Cole; Matthew Colless; Chris Collins; Gavin Dalton; Kathryn Deeley; Roberto De Propris; George Efstathiou; Richard S. Ellis; Carlos S. Frenk; Karl Glazebrook; Carole Jackson; Ofer Lahav; Ian Lewis; Stuart Lumsden; Steve Maddox; Darren Madgwick; Stephen Moody; Peder Norberg; John A. Peacock; Bruce A. Peterson; Ian Price; Mark Seaborne; Will Sutherland; Helen Tadros; Keith Taylor

2002-02-07T23:59:59.000Z

373

The 2dF Galaxy Redshift Survey: the luminosity function of cluster galaxies  

E-Print Network [OSTI]

We have determined the composite luminosity function (LF) for galaxies in 60 clusters from the 2dF Galaxy Redshift Survey. The LF spans the range $-22.5

Roberto De Propris; M. Colless; S. Driver; W. Couch; J. Peacock; I. Baldry; C. Baugh; C. Collins; J. Bland-Hawthorn; T. Bridges; R. Cannon; S. Cole; N. Cross; G. B. Dalton; G. Efstathiou; R. S. Ellis; C. S. Frenk; K. Glazebrook; E. Hawkins; C. Jackson; O. Lahav; I. Lewis; S. Lumsden; S. Maddox; D. S. Madgwick; P. Norberg; W. Percival; B. Peterson; W. Sutherland; K. Taylor

2002-12-30T23:59:59.000Z

374

Probing the nature of dark energy through galaxy redshift surveys with radio telescopes  

E-Print Network [OSTI]

Galaxy redshift surveys using optical telescopes have, in combination with other cosmological probes, enabled precision measurements of the nature of dark energy. We show that radio telescopes are rapidly becoming competitive with optical facilities in spectroscopic surveys of large numbers of galaxies. Two breakthroughs are driving this change. Firstly, individual radio telescopes are more efficient at mapping the sky thanks to the large field-of-view of new phased-array feeds. Secondly, ever more dishes can be correlated in a cost-effective manner with rapid increases in computing power. The next decade will see the coming of age of the 21cm radio wavelength as a cosmological probe as first the Pathfinders then, ultimately, the Square Kilometre Array is constructed. The latter will determine precise 3D positions for a billion galaxies, mapping the distribution of matter in the Universe over the last 12 billion years. This radio telescope will be able to constrain the equation of state of dark energy, and it...

Duffy, Alan R

2014-01-01T23:59:59.000Z

375

Constraining dynamical dark energy models through the abundance of high-redshift supermassive black holes  

Science Journals Connector (OSTI)

......Constraining dynamical dark energy models through the abundance...its contribution to the energy density would become rapidly...provided by the NASA Joint Dark Energy Mission (JDEM) -Wide-Field Infrared Survey Telescope (WFIRST) space......

A. Lamastra; N. Menci; F. Fiore; C. Di Porto; L. Amendola

2012-03-01T23:59:59.000Z

376

A measurement of the cosmological mass density from clustering in the 2dF Galaxy Redshift Survey  

E-Print Network [OSTI]

The large-scale structure in the distribution of galaxies is thought to arise from the gravitational instability of small fluctuations in the initial density field of the universe. A key test of this hypothesis is that superclusters of galaxies in the process of formation should generate systematic infall of other galaxies. This would be evident in the pattern of recessional velocities, causing an anisotropy in the inferred spatial clustering of galaxies. Here we report a precise measurement of this clustering, using the redshifts of more than 141,000 galaxies from the two-degree-field galaxy redshift survey. We determine the parameter beta = Omega^{0.6}/b = 0.43 +- 0.07, where Omega is the total mass-density parameter and b is a measure of the `bias' of the luminous galaxies in the survey. Combined with the anisotropy of the cosmic microwave background, our results favour a low-density universe with Omega approximately 0.3.

J. A. Peacock; S. Cole; P. Norberg; C. M. Baugh; J. Bland-Hawthorn; T. Bridges; R. D. Cannon; M. Colless; C. Collins; W. Couch; G. Dalton; K. Deeley; R. De Propris; S. P. Driver; G. Efstathiou; R. S. Ellis; C. S. Frenk; K. Glazebrook; C. Jackson; O. Lahav; I. Lewis; S. Lumsden; S. Maddox; W. J. Percival; B. A. Peterson; I. Price; W. Sutherland; K. Taylor

2001-03-09T23:59:59.000Z

377

Black hole mass estimates and emission line properties of a sample of redshift Z > 6:5 quasars  

E-Print Network [OSTI]

), mainly thanks to optical surveys such as the Sloan Digital Sky Survey (SDSS; York et al. 2000), the Canada 1 Based on observations collected at the European Southern Observatory, Chile, programs 286.A-5025, 087.A-0890 and 088.A- 0897. This paper also... ; Latif et al. 2013). At low redshift, elemental abundances estimated from both emission and intrinsic absorption lines show that quasar environments are characterized by solar or super- solar metallicities. Jiang et al. (2007) estimated the BLR...

De Rosa, Gisella; Venemans, Bram P.; Decarli, Roberto; Gennaro, Mario; Simcoe, Robert A.; Dietrich, Matthias; Peterson, Bradley M.; Walter, Fabian; Frank, Stephan; McMahon, Richard G.; Hewett, Paul C.; Mortlock, Daniel J.; Simpson, Chris

2014-07-09T23:59:59.000Z

378

On globally Symmetric Finsler spaces  

E-Print Network [OSTI]

The paper consider the symmetric of Finsler spaces. We give some conditions about globally symmetric Finsler spaces. Then we prove that these spaces can be written as a coset space of Lie group with an invariant Finsler metric. Finally, we prove that such a space must be Berwaldian

Khatamy, R Chavosh

2011-01-01T23:59:59.000Z

379

Space, time and machines  

E-Print Network [OSTI]

The 2nd law of thermodynamics is used to shed light on present-day puzzles in cosmology. The universal law, given as an equation of motion, describes diverse systems when consuming free energy via various mechanisms to attain stationary states in their respective surroundings. Expansion of the Universe, galactic rotation and lensing as well as clustering of red-shifted spectral lines are found as natural consequences of the maximal energy dispersal that satisfies the conservation of energy, in the forms of kinetic, potential and dissipation. The Universe in its entirety is pictured as a giant Riemann resonator in evolution via step-by-step spontaneous breaking of one stationary-state symmetry to another to diminish energy density differences relative to its zero-density "surroundings". The continuum equation of evolution is proven equivalent to the Navier-Stokes equation. The ubiquitous flow equation has no solution because the forces and flows are inseparable when the dissipative process has three or more degrees of freedom. Since an evolving system is without a norm, there is no unitary transformation to solve the characteristic equation, but detailed trajectories remain inherently intractable. Conversely, stationary-state trajectories can be solved.

Arto Annila

2012-06-19T23:59:59.000Z

380

Search for Redshifted 2.2 MeV Neutron Capture Line From A0535+262 in Outburst  

E-Print Network [OSTI]

The Be/X-ray binary system A0535+262 underwent a giant outburst in May-June 2005, followed by a dimmer outburst in August-September 2005. This increased intensity provided an opportunity to search for redshifted neutron-capture lines from the surface of the neutron star. If discovered, such lines would constrain the neutron star equation of state, providing the motivation of this search. The spectrometer (SPI) on board the INTEGRAL satellite observed the dimmer outburst and provided the data for this research. We have not detected a line with enough significance, with the width-dependent upper limits on the broadened and redshifted neutron capture line in the range of (2 - 11) x 10^(-4) photons cm^(-2) s^(-1). To our knowledge, these are the strongest upper limits on the redshifted 2.2 MeV emission from an accreting neutron star. Our analysis of the transparency of the neutron star surface for 2.2 MeV photons shows that photons have a small but finite chance of leaving the atmosphere unscattered, which diminishes the possibility of detection.

Sirin Caliskan; Emrah Kalemci; Matthew G. Baring; Steven E. Boggs; Peter Kretschmar

2008-12-15T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
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381

Simplified Space Conditioning  

Broader source: Energy.gov (indexed) [DOE]

Simplified Space Conditioning Simplified Space Conditioning Duncan Prahl, RA IBACOS, Inc. Building America Technical Update April 29, 2013 Simplified Space Conditioning Rethinking HVAC Design * Traditional Method - Assume envelope losses dictate the load - Room by room load analysis - Pick Equipment and distribute to meet the load in each room * New Method - Consider how the occupants live in the building - Seriously consider internal gains in both heating and cooling - Consider ventilation strategy - Design system Simplified Space Conditioning If you are: * A production builder * Participating in "above code" programs * Following ACCA Manual RS or ASHRAE 55 * Need to prove "delivering heat to each habitable room" * Concerned about litigation * Play it safe, Use Manual J, S & D and condition every

382

Live From Outer Space  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Live from Outer Space: How Cells Influence the Growth of Nanostructures Live from Outer Space: How Cells Influence the Growth of Nanostructures Far above the heads of Earthlings, arrays of single-cell creatures embedded in nanostructures ride on the International Space Station (courtesy of Sandia National Laboratories and the University of New Mexico, NASA, and the U.S. Air Force) to test whether nanostructures whose formations were directed by yeast and other single cells can create more secure homes for their occupants-even in the vacuum and radiation of outer space-than those created by more standard chemical procedures. Cheap, tiny, and very lightweight sensors of chemical or biological agents could be made from long-lived cells that require no upkeep, yet sense and then communicate effectively with each other and their external

383

Astrophysics and Space Instrumentation  

Science Journals Connector (OSTI)

Instrumentation for particle and high-energy photon measurements in space must provide high levels of performance while meeting the severe constraints imposed by flight. Direct measurements are required spanni...

John W. Mitchell; Thomas Hams; Thomas Hams

2012-01-01T23:59:59.000Z

384

Space Flight Requirements  

E-Print Network [OSTI]

Science Glovebox), SpaceDrums (Levitator), EMCS (European Modular Cultivation System), PCDF (Protein MERLIN, HDPCG, PCF, CVDA, VDA2, DCPCG, PCFVG, PCFLST, CRIMM CRIMM Commercial Refrigerator Incubator Growth GLACIER General Laboratory Active Cryogenic ISS Experiment Refrigerator HDPCG High Density

385

Notes on sexuality & space  

E-Print Network [OSTI]

Very little has been written on sexuality in architectural scholarship. Sexuality & Space (Princeton Architectural Press, 1992) contains the proceedings of an eponymous 1990 conference at Princeton University, and was both ...

Jacobson, Samuel Ray

2013-01-01T23:59:59.000Z

386

THE OPTICALLY UNBIASED GRB HOST (TOUGH) SURVEY. V. VLT/X-SHOOTER EMISSION-LINE REDSHIFTS FOR SWIFT GRBs AT z {approx} 2  

SciTech Connect (OSTI)

We present simultaneous optical and near-infrared (NIR) spectroscopy of 19 Swift {gamma}-ray burst (GRB) host galaxies observed with the VLT/X-shooter with the aim of measuring their redshifts. Galaxies were selected from The Optically Unbiased GRB Host (TOUGH) survey (15 of the 19 galaxies) or because they hosted GRBs without a bright optical afterglow. Here we provide emission-line redshifts for 13 of the observed galaxies with brightnesses between F606W > 27 mag and R = 22.9 mag (median R-tilde =24.6 mag). The median redshift is z-tilde =2.1 for all hosts and z-tilde =2.3 for the TOUGH hosts. Our new data significantly improve the redshift completeness of the TOUGH survey, which now stands at 77% (53 out of 69 GRBs). They furthermore provide accurate redshifts for nine prototype dark GRBs (e.g., GRB 071021 at z = 2.452 and GRB 080207 at z = 2.086), which are exemplary of GRBs where redshifts are challenging to obtain via afterglow spectroscopy. This establishes X-shooter spectroscopy as an efficient tool for redshift determination of faint, star-forming, high-redshift galaxies such as GRB hosts. It is hence a further step toward removing the bias in GRB samples that is caused by optically dark events, and provides the basis for a better understanding of the conditions in which GRBs form. The distribution of column densities as measured from X-ray data (N{sub H,X}), for example, is closely related to the darkness of the afterglow and skewed toward low N{sub H,X} values in samples that are dominated by bursts with bright optical afterglows.

Kruehler, Thomas; Malesani, Daniele; Milvang-Jensen, Bo; Fynbo, Johan P. U.; Hjorth, Jens; Sparre, Martin; Watson, Darach J. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Jakobsson, Pall [Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, 107 Reykjavik (Iceland); Levan, Andrew J. [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom); Tanvir, Nial R. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH (United Kingdom)

2012-10-10T23:59:59.000Z

387

Space-charged-induced emittance growth in the transport of high-brightness electron beams  

SciTech Connect (OSTI)

The emittance induced by space charge in a drifting beam of finite length has been investigated, and a scaling law has been obtained from simple considerations of the different rates of expansion of different portions of the beam. The scaling law predicts the initial rate of emittance growth, before the beam shape has distorted significantly, and thus represents an upper bound on the rate of emittance increase. This scaling law has been substantiated by particle-in-cell simulation and the dependence on geometric factors evaluated for specific choices of the beam profile. For long, axially nonuniform beams, the geometric factors have been evaluated explicitly for Gaussian profiles, and other shapes.

Jones, M.E.; Carlsten, B.E.

1987-03-01T23:59:59.000Z

388

Progress in Studies of Electron-Cloud-Induced Optics Distortions at CesrTA  

SciTech Connect (OSTI)

The Cornell Electron Storage Ring Test Accelerator (CesrTA) program has included extensive measurements of coherent betatron tune shifts for a variety of electron and positron beam energies, bunch population levels, and bunch train configurations. The tune shifts have been shown to result primarily from the interaction of the beam with the space-charge field of the beam-induced low-energy electron cloud in the vacuum chamber. Comparison to several advanced electron cloud simulation codes has allowed determination of the sensitivity of these measurements to physical parameters characterizing the synchrotron radiation flux, the production of photo-electrons on the vacuum chamber wall, the beam emittance, lattice optics, and the secondary-electron yield model. We report on progress in understanding the cloud buildup and decay mechanisms in magnetic fields and in field-free regions, addressing quantitatively the precise determination of the physical parameters of the modeling. Validation of these models will serve as essential input in the design of damping rings for future high-energy linear colliders.

Crittenden, James; /Cornell U., CLASSE; Calvey, Joseph; /Cornell U., CLASSE; Dugan, Gerald; /Cornell U., CLASSE; Kreinick, David; /Cornell U., CLASSE; Leong, Zhidong; /Cornell U., CLASSE; Livezey, Jesse; /Cornell U., CLASSE; Palmer, Mark; /Cornell U., CLASSE; Rubin, David; /Cornell U., CLASSE; Sagan, David; /Cornell U., CLASSE; Furman, Miguel; /LBL, Berkeley; Penn, Gregory; /LBL, Berkeley; Venturini, Marco; /LBL, Berkeley; Harkay, Katherine; /Argonne; Holtzapple, Robert; /Cal. Poly.; Pivi, Mauro; /SLAC; Wang, Lanfa; /SLAC

2012-06-25T23:59:59.000Z

389

Robust Machine Learning Applied to Astronomical Datasets II: Quantifying Photometric Redshifts for Quasars Using Instance-Based Learning  

E-Print Network [OSTI]

We apply instance-based machine learning in the form of a k-nearest neighbor algorithm to the task of estimating photometric redshifts for 55,746 objects spectroscopically classified as quasars in the Fifth Data Release of the Sloan Digital Sky Survey. We compare the results obtained to those from an empirical color-redshift relation (CZR). In contrast to previously published results using CZRs, we find that the instance-based photometric redshifts are assigned with no regions of catastrophic failure. Remaining outliers are simply scattered about the ideal relation, in a similar manner to the pattern seen in the optical for normal galaxies at redshifts z < ~1. The instance-based algorithm is trained on a representative sample of the data and pseudo-blind-tested on the remaining unseen data. The variance between the photometric and spectroscopic redshifts is sigma^2 = 0.123 +/- 0.002 (compared to sigma^2 = 0.265 +/- 0.006 for the CZR), and 54.9 +/- 0.7%, 73.3 +/- 0.6%, and 80.7 +/- 0.3% of the objects are within delta z < 0.1, 0.2, and 0.3 respectively. We also match our sample to the Second Data Release of the Galaxy Evolution Explorer legacy data and the resulting 7,642 objects show a further improvement, giving a variance of sigma^2 = 0.054 +/- 0.005, and 70.8 +/- 1.2%, 85.8 +/- 1.0%, and 90.8 +/- 0.7% of objects within delta z < 0.1, 0.2, and 0.3. We show that the improvement is indeed due to the extra information provided by GALEX, by training on the same dataset using purely SDSS photometry, which has a variance of sigma^2 = 0.090 +/- 0.007. Each set of results represents a realistic standard for application to further datasets for which the spectra are representative.

Nicholas M. Ball; Robert J. Brunner; Adam D. Myers; Natalie E. Strand; Stacey L. Alberts; David Tcheng; Xavier Llorà

2006-12-17T23:59:59.000Z

390

A CLOSE-PAIR ANALYSIS OF DAMP MERGERS AT INTERMEDIATE REDSHIFTS  

SciTech Connect (OSTI)

We have studied the kinematics of {approx}2800 candidate close-pair galaxies at 0.1 < z < 1.2 identified from the Canada-France-Hawaii Telescope Legacy Survey fields. Spectra of these systems were obtained using spectrometers on the 6.5 m Magellan and 5 m Hale telescopes. These data allow us to constrain the rate of dry mergers at intermediate redshifts and to test the 'hot halo' model for quenching of star formation. Using virial radii estimated from the correlation between dynamical and stellar masses published by Leauthaud et al., we find that around 1/5 of our candidate pairs are likely to share a common dark matter halo (our metric for close physical association). These pairs are divided into red-red, blue-red, and blue-blue systems using the rest-frame colors classification method introduced in Chou et al.. Galaxies classified as red in our sample have very low star formation rates, but they need not be totally quiescent, and hence we refer to them as 'damp', rather than 'dry', systems. After correcting for known selection effects, the fraction of blue-blue pairs is significantly greater than that of red-red and blue-red pairs. Red-red pairs are almost entirely absent from our sample, suggesting that damp mergers are rare at z {approx} 0.5. Our data support models with a short merging timescale (<0.5 Gyr) in which star formation is enhanced in the early phase of mergers, but quenched in the late phase. Hot halo models may explain this behavior, but only if virial shocks that heat gas are inefficient until major mergers are nearly complete.

Chou, Richard C. Y.; Abraham, Roberto G. [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada); Bridge, Carrie R., E-mail: chou@astro.utoronto.ca, E-mail: abraham@astro.utoronto.ca, E-mail: bridge@astro.caltech.edu [Department of Astronomy, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States)

2012-12-01T23:59:59.000Z

391

Environment and Galaxy Evolution at Intermediate Redshift in the CNOC2 Survey  

E-Print Network [OSTI]

(abridged) The systematic variation of galaxy colors and types with clustering environment could either be the result of local conditions at formation or subsequent environmental effects as larger scale structures draw together galaxies whose stellar mass is largely in place. At z~0.4 the co-moving galaxy correlation length, r_0, measured in the CNOC2 sample is strongly color dependent, rising from 2/h Mpc to nearly 10/h Mpc as the volume-limited subsamples range from blue to red. The luminosity dependence of r_0 at z~0.4 is weak below L_ast although there is an upturn at high luminosity where its interpretation depends on separating it from the r_0-color relation. The dominant effect of the group environment on star formation is seen in the radial gradient of the mean galaxy colors which on the average become redder than the field toward the group centers. The redder-than-field trend applies to groups with a line-of-sight velocity dispersion, sigma_1>150 kms. There is an indication, somewhat statistically insecure, that the high luminosity galaxies in groups with sigma_1<125 kms become bluer toward the group center. We conclude that the higher velocity dispersion groups largely act to suppress star formation relative to the less clustered field, leading to ``embalmed'' galaxies. The tidal fields within the groups appear to be a strong candidate for the physical source of the reduction of star formation in group galaxies relative to field. Tides operate effectively at all velocity dispersions to remove gas rich companions and low density gas in galactic halos. Given that much of the field population is in groups we suggest that this suppression may be the dominant galaxy evolution force at low redshift.

R. G. Carlberg; H. K. C. Yee; S. L. Morris; H. Lin; P. B. Hall; D. R. Patton; M. Sawicki; C. W. Shepherd

2001-06-27T23:59:59.000Z

392

Stellar Populations Found in the Central kpc of Four Luminous Compact Blue Galaxies at Intermediate Redshift  

E-Print Network [OSTI]

We investigate the star formation history of the central regions of four Luminous Compact Blue Galaxies (LCBGs). LCBGs are blue (B-V<0.6), compact (MU_B<21.5 mag arcsec^-2) galaxies with absolute magnitudes M_B brighter than -17.5. The LCBGs analyzed here are located at 0.436redshifts.

C. Hoyos; R. Guzman; A. I. Diaz; D. C. Koo; M. A. Bershady; .

2007-09-28T23:59:59.000Z

393

The 2dF Galaxy Redshift Survey: luminosity functions by density environment and galaxy type  

E-Print Network [OSTI]

We use the 2dF Galaxy Redshift Survey to measure the dependence of the bJ-band galaxy luminosity function on large-scale environment, defined by density contrast in spheres of radius 8h-1Mpc, and on spectral type, determined from principal component analysis. We find that the galaxy populations at both extremes of density differ significantly from that at the mean density. The population in voids is dominated by late types and shows, relative to the mean, a deficit of galaxies that becomes increasingly pronounced at magnitudes brighter than M_bJ-5log10h <-18.5. In contrast, cluster regions have a relative excess of very bright early-type galaxies with M_bJ-5log10h < -21. Differences in the mid to faint-end population between environments are significant: at M_bJ-5log10h=-18 early and late-type cluster galaxies show comparable abundances, whereas in voids the late types dominate by almost an order of magnitude. We find that the luminosity functions measured in all density environments, from voids to clusters, can be approximated by Schechter functions with parameters that vary smoothly with local density, but in a fashion which differs strikingly for early and late-type galaxies. These observed variations, combined with our finding that the faint-end slope of the overall luminosity function depends at most weakly on density environment, may prove to be a significant challenge for models of galaxy formation.

Darren J. Croton; Glennys R. Farrar; Peder Norberg; Matthew Colless; John A. Peacock; I. K. Baldry; C. M. Baugh; J. Bland-Hawthorn; T. Bridges; R. Cannon; S. Cole; C. Collins; W. Couch; G. Dalton; R. De Propris; S. P. Driver; G. Efstathiou; R. S. Ellis; C. S. Frenk; K. Glazebrook; C. Jackson; O. Lahav; I. Lewis; S. Lumsden; S. Maddox; D. Madgwick; B. A. Peterson; W. Sutherland; K. Taylor

2005-02-08T23:59:59.000Z

394

The 2dF Galaxy Redshift Survey: Near Infrared Galaxy Luminosity Functions  

E-Print Network [OSTI]

We combine the 2MASS extended source catalogue and the 2dFGRS to produce an IR selected galaxy catalogue with 17,173 measured redshifts. We use this extensive dataset to estimate the J and K-band galaxy luminosity functions. The LFs are fairly well fit by Schechter functions with J: M*-5log h= -22.36+/-0.02, alpha= -0.93+/-0.04, Phi=0.0104+/-0.0016 h^3/Mpc^3 and K: M*-5log h= -23.44+/-0.03, alpha=-0.96+/-0.05, Phi=0.0108+/-0.0016 h^3/Mpc^3 (2MASS Kron magnitudes). These parameters assume a cosmological model with Omega=0.3 and Lambda=0.7. With datasets of this size, systematic rather than random errors are the dominant source of uncertainty in the determination of the LF. We carry out a careful investigation of possible systematic effects in our data. The surface brightness distribution of the sample shows no evidence that significant numbers of low surface brightness or compact galaxies are missed by the survey. We estimate the present-day distributions of B-K and J-K colours as a function of absolute magnitude and use models of the galaxy stellar populations, constrained by the observed optical and infrared colours, to infer the galaxy stellar mass function. Integrated over all galaxy masses, this yields a total mass fraction in stars (in units of the critical mass density) of Omega_*.h= (1.6+/-0.24)/10^3 for a Kennicutt IMF and Omega_*.h= (2.9+/-0.43)/10^3 for a Salpeter IMF. These values agree with those inferred from observational estimates of the star formation history of the universe provided that dust extinction corrections are modest.

Shaun Cole; Peder Norberg; Carlton Baugh; Carlos Frenk; Joss Bland-Hawthorn; Terry Bridges; Russell Cannon; Matthew Colless; Chris Collins; Warrick Couch; Nicholas Cross; Gavin Dalton; Roberto De Propris; Simon Driver; George Efstathiou; Richard Ellis; Karl Glazebrook; Carole Jackson; Ofer Lahav; Ian Lewis; Stuart Lumsden; Steve Maddox; Darren Madgwick; John Peacock; Bruce Peterson; Will Sutherland; Keith Taylor

2001-12-11T23:59:59.000Z

395

Ca40(d, p)Ca41, a Test of the Validity of the Distorted-Wave Born Approximation  

Science Journals Connector (OSTI)

The reaction Ca40(d, p)Ca41 has been studied at deuteron energies of 7.0, 8.0, 9.0, 10.0, 11.0, and 12.0 MeV. Absolute differential cross sections for the four most prominent proton groups were measured and are compared with predictions based on the distorted-wave Born approximation (DWBA). Particular emphasis is placed on the ability of this approach to extract precise spectroscopic factors, which for this reaction are expected to be known a priori. Effects of variation of optical parameters, and of inclusion of spin-orbit and finite-range effects, are discussed in detail. It can be concluded that, if one uses optical potentials which fit elastic-scattering data, spectroscopic factors can be extracted with an accuracy of 20% or better.

L. L. Lee; Jr.; J. P. Schiffer; B. Zeidman; G. R. Satchler; R. M. Drisko; R. H. Bassel

1964-11-23T23:59:59.000Z

396

Determination of projection geometry from quantitative assessment of the distortion of spherical references in single-view projection radiography  

SciTech Connect (OSTI)

A method is introduced, inferring the three-dimensional (3-D) location from the 2-D radiographic shadow of an opaque spherical reference body of known radius by considering its elliptical distortion, the 2-D shadow location and a known source-to-receptor distance. Three noncollinear spheres fixed to a rigid object constitute all possible degrees of freedom, i.e., the entire 3-D imaging geometry. The method may be used (a) to determine the 3-D imaging geometry from a single 2-D view and (b) to correct for foreshortening of object distances coplanar with the plane defined by the sphere triplet. Apart from the mathematical background the article describes a small feasibility experiment, performed with four different sphere diameters and a commercial dental ccd-receptor system (pixel length: 0.0195 mm). The mouse-cursor based image evaluation revealed an average underestimation of the critical depth- (x-) coordinate decreasing with increasing radius (-30.3% for r=0.5 mm to 2.8% for r=2.5 mm). Intraobserver reliability (the standard deviation between three single cursor-based assessments) ranged between 0% and 8% of the actual true depth. The main source of the input error is associated with the assessment of the amount of elliptical distortion, where subpixel accuracy is demanded. Consequently, software-based automated image evaluation is required using available methods for pattern recognition and point-spread correction. Provided sufficient accuracy, the method provides an important tool for foreshortening correction, depth assessment, motion analysis, and 3-D reconstruction from two or more 2-D views.

Schulze, Ralf; Bruellmann, Dan Dominik; Roeder, Felix; D'Hoedt, Bernd [Department of Oral Surgery (and Oral Radiology), Johannes Gutenberg-University, Dental School, Augustusplatz 2, Mainz, 55131 (Germany)

2004-10-01T23:59:59.000Z

397

Earth, Space Sciences  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Earth, Space Sciences Earth, Space Sciences /science-innovation/_assets/images/icon-science.jpg Earth, Space Sciences National security depends on science and technology. The United States relies on Los Alamos National Laboratory for the best of both. No place on Earth pursues a broader array of world-class scientific endeavors. Climate, Ocean and Sea Ice Modeling (COSIM)» Earth A team of scientists is working to understand how local changes in hydrology might bring about major changes to the Arctic landscape, including the possibility of a large-scale carbon release from thawing permafrost. Bryan Travis, an expert in fluid dynamics, is author of the Mars global hydrology numerical computer model, or MAGHNUM, used for calculating heat and fluid transport phenomena. (MAGHNUM was previously

398

Fun in Space  

Science Journals Connector (OSTI)

This after-dinner address attempts to point up in a simplified way the amusing as well as some of the more serious problems which arise in connection with flight into space. Figures are given to challenge some of the more fanciful claims about the value of the moon as a military base noting the very large amounts of fuel required to take weapons up to the moon and then to return them to the earth. Some of the important research problems in physics and astronomy which can be carried out by the use of space vehicles are enumerated. As examples of a space science enterprise the results of the magnetic field measurements by the Pioneer V package are summarized. The impractibility of using the moon and other planets as colonies for the earth's excess population is also demonstrated.

Lee A. DuBridge

1960-01-01T23:59:59.000Z

399

Signatures of Cool Gas Fueling a Star-Forming Galaxy at Redshift 2.3  

Science Journals Connector (OSTI)

...different colors, masses, and environments...properties of galactic winds using background...B. ., MASSIV: Mass Assembly Survey...D. R. ., High velocity dispersion in a rare...excitation in ULIRGs: Maps of diagnostic emission-line...ratios in space and velocity . Astrophys...

N. Bouché; M. T. Murphy; G. G. Kacprzak; C. Péroux; T. Contini; C. L. Martin; M. Dessauges-Zavadsky

2013-07-05T23:59:59.000Z

400

Topology of neutral hydrogen distribution with the Square Kilometer Array  

E-Print Network [OSTI]

Morphology of the complex HI gas distribution can be quantified by statistics like the Minkowski functionals, and can provide a way to statistically study the large scale structure in the HI maps both at low redshifts, and during the epoch of reionization (EoR). At low redshifts, the 21cm emission traces the underlying matter distribution. Topology of the HI gas distribution, as measured by the genus, could be used as a "standard ruler". This enables the determination of distance-redshift relation and also the discrimination of various models of dark energy and of modified gravity. The topological analysis is also sensitive to certain primordial non-Gaussian features. Compared with two-point statistics, the topological statistics are more robust against the nonlinear gravitational evolution, bias, and redshift-space distortion. The HI intensity map observation naturally avoids the sparse sampling distortion, which is an important systematic in optical galaxy survey. The large cosmic volume accessible to SKA w...

Wang, Yougang; Wu, Fengquan; Chen, Xuelei; Wang, Xin; Kim, Juhan; Park, Changbom; Lee, Khee-Gan; Cen, Renyue

2015-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

Nonlinear classification of Banach spaces  

E-Print Network [OSTI]

Hilbert space when p> 2. We then build upon the method of this proof to show that a quasi-Banach space coarsely embeds into a Hilbert space if and only if it is isomorphic to a subspace of L0(??) for some probability space (?,B,??)....

Randrianarivony, Nirina Lovasoa

2005-11-01T23:59:59.000Z

402

Extending the supernova Hubble diagram to z~1.5 with the Euclid space mission  

E-Print Network [OSTI]

We forecast dark energy constraints that could be obtained from a new large sample of Type Ia supernovae where those at high redshift are acquired with the Euclid space mission. We simulate a three-prong SN survey: a zsurveys are assumed to be conducted from the ground, while the high-z is a joint ground- and space-based survey. This latter survey, the "Dark Energy Supernova Infra-Red Experiment" (DESIRE), is designed to fit within 6 months of Euclid observing time, with a dedicated observing program. We simulate the SN events as they would be observed in rolling-search mode by the various instruments, and derive the quality of expected cosmological constraints. We account for known systematic uncertainties, in particular calibration uncertainties including their contribution through the training of the supernova model used to fit the supernovae li...

Astier, P; Brescia, M; Cappellaro, E; Carlberg, R G; Cavuoti, S; Della Valle, M; Gangler, E; Goobar, A; Guy, J; Hardin, D; Hook, I M; Kessler, R; Kim, A; Linder, E; Longo, G; Maguire, K; Mannucci, F; Mattila, S; Nichol, R; Pain, R; Regnault, N; Spiro, S; Sullivan, M; Tao, C; Turatto, M; Wang, X F; Wood-Vasey, W M

2014-01-01T23:59:59.000Z

403

2011 Confined Space Program Update  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Confined Space Entry Program Update Confined Space Entry Program Update IMPORTANT: After reading this document, click the "Get Course Credit" link at the bottom of the page. You will then log in to the EHS training system using your LDAP to get course credit. LBNL's confined space entry program was substantially improved this year. Several new features have been included which improve overall safety for Confined Space Entrants and better align the confined space entry program with the OSHA requirements. As an Activity Lead, Confined Space Entrant or Entry Supervisor, you should be aware of the following: We improved the procedures for safely working in confined spaces. Please review the new Chapter 34 in Publication 3000. Additionally, we have a new planning tool known as the confined space inventory which is a registry of LBNL's confined spaces, their potential hazards and safe work procedures unique to a particular confined space.

404

Space science and policy  

Science Journals Connector (OSTI)

......research-article Features Space science and policy David Southwood David Southwood is a Senior...Moreover, the ESA industrial return policy produced its own problems, as I'll...science in Europe. The industrial return policy is at the heart of ESA and builds in a......

David Southwood

2014-12-01T23:59:59.000Z

405

CHANDRA X-RAY OBSERVATIONS OF THE REDSHIFT 1.53 RADIO-LOUD QUASAR 3C 270.1  

SciTech Connect (OSTI)

Chandra X-ray observations of the high redshift (z = 1.532) radio-loud quasar 3C 270.1 in 2008 February show the nucleus to have a power-law spectrum, {Gamma} = 1.66 {+-} 0.08, typical of a radio-loud quasar, and a marginally detected Fe K{alpha} emission line. The data also reveal extended X-ray emission, about half of which is associated with the radio emission from this source. The southern emission is co-spatial with the radio lobe and peaks at the position of the double radio hot spot. Modeling this hot spot, including Spitzer upper limits, rules out synchrotron emission from a single power-law population of electrons, favoring inverse Compton emission with a field of {approx}11 nT, roughly a third of the equipartition value. The northern emission is concentrated close to the location of a 40 Degree-Sign bend where the radio jet is presumed to encounter an external medium. It can be explained by inverse Compton emission involving cosmic microwave background photons with a field of {approx}3 nT, a factor of 7-10 below the equipartition value. The remaining, more diffuse X-ray emission is harder (HR = -0.09 {+-} 0.22). With only 22.8 {+-} 5.6 counts, the spectral form cannot be constrained. Assuming thermal emission with a temperature of 4 keV yields an estimate for the luminosity of 1.8 Multiplication-Sign 10{sup 44} erg s{sup -1}, consistent with the luminosity-temperature relation of lower-redshift clusters. However, deeper Chandra X-ray observations are required to delineate the spatial distribution and better constrain the spectrum of the diffuse emission to verify that we have detected X-ray emission from a high-redshift cluster.

Wilkes, Belinda J.; Lal, Dharam V.; Willner, S. P.; Ashby, M. L. N.; Fazio, G. G. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Worrall, D. M.; Birkinshaw, Mark [HH Wills Physics Laboratory, University of Bristol, Bristol (United Kingdom); Haas, Martin; Chini, Rolf [Astronomisches Institut, Ruhr-University, Bochum (Germany); Antonucci, Robert [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Avara, Mark [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Barthel, Peter [Kapteyn Astronomical Institute, University of Groningen, Groningen (Netherlands); Hardcastle, Martin [School of Physics and Astronomy, University of Hertfordshire, Hatfield (United Kingdom); Lawrence, Charles [JPL, Pasadena, CA 91109 (United States); Leipski, Christian [MPIA, Heidelberg (Germany); Ogle, Patrick [Spitzer Science Center, Caltech, Pasadena, CA 91125 (United States); Schulz, Bernhard [IPAC, Caltech, Pasadena, CA 91125 (United States)

2012-01-20T23:59:59.000Z

406

The 2dF Galaxy Redshift Survey: The b_J-band galaxy luminosity function and survey selection function  

E-Print Network [OSTI]

We use more than 110500 galaxies from the 2dF galaxy redshift survey (2dFGRS) to estimate the b_J-band galaxy luminosity function at redshift z=0, taking account of evolution, the distribution of magnitude measurement errors and small corrections for incompletenessin the galaxy catalogue. Throughout the interval -16.5>M- 5log h>-22, the luminosity function is accurately described by a Schechter function with M* -5log h =-19.66+/-0.07, alpha=-1.21+/-0.03 and phistar=(1.61+/-0.08) 10^{-2} h^3/Mpc^3, giving an integrated luminosity density of rho_L=(1.82+/-0.17) 10^8 h L_sol/Mpc^3 (assuming an Omega_0=0.3, Lambda_0=0.7 cosmology). The quoted errors have contributions from the accuracy of the photometric zeropoint, large scale structure in the galaxy distribution and, importantly, from the uncertainty in the appropriate evolutionary corrections. Our luminosity function is in excellent agreement with, but has much smaller statistical errors than an estimate from the Sloan Digital Sky Survey (SDSS) data when the SDSS data are accurately translated to the b_J-band and the luminosity functions are normalized in the same way. We use the luminosity function, along with maps describing the redshift completeness of the current 2dFGRS catalogue, and its weak dependence on apparent magnitude, to define a complete description of the 2dFGRS selection function. Details and tests of the calibration of the 2dFGRS photometric parent catalogue are also presented.

P. Norberg; S. Cole; C. Baugh; C. Frenk; I. Baldry; J. Bland-Hawthorn; T. Bridges; R. Cannon; M. Colless; C. Collins; W. Couch; N. Cross; G. Dalton; R. De Propris; S. Driver; G. Efstathiou; R. Ellis; K. Glazebrook; C. Jackson; O. Lahav; I. Lewis; S. Lumsden; S. Maddox; D. Madgwick; J. Peacock; B. Peterson; W. Sutherland; K. Taylor

2002-04-26T23:59:59.000Z

407

Inr .I. Heor Mass Transfer. Vol. 14. pp. 751-766. Pergamon Press 1971 Printed in Great Britain THE EFFECT OF THERMAL DISTORTION ON  

E-Print Network [OSTI]

on the thermal contact resistance between two semi-infinite solids of different materials. Good agreement THE EFFECT OF THERMAL DISTORTION ON CONSTRICTION RESISTANCE J. R. BARBER Department of Mechanical Engineering ; "9 Poisson's ratio ; P, thermal contact resistance ; 0, direct stress. Subscripts 0, interface

Barber, James R.

408

Effect of antiferromagnetic spin correlations on lattice distortion and charge ordering in Pr0.5Ca1.5MnO4  

Science Journals Connector (OSTI)

...correlations on lattice distortion and charge ordering in Pr0.5Ca1.5MnO4 10.1073/pnas.0704303104 Songxue Chi F. Ye Pengcheng Dai J. A. Fernandez-Baca Q. Huang J. W. Lynn E. W. Plummer R. Mathieu Y. Kaneko Y. Tokura *Department of Physics...

Songxue Chi; F. Ye; Pengcheng Dai; J. A. Fernandez-Baca; Q. Huang; J. W. Lynn; E. W. Plummer; R. Mathieu; Y. Kaneko; Y. Tokura

2007-01-01T23:59:59.000Z

409

The richness dependence of galaxy cluster correlations: Results from a redshift survey of rich APM clusters  

E-Print Network [OSTI]

We analyse the spatial clustering properties of a new catalogue of very rich galaxy clusters selected from the APM Galaxy Survey. These clusters are of comparable richness and space density to Abell Richness Class $\\geq 1$ clusters, but selected using an objective algorithm from a catalogue demonstrably free of artificial inhomogeneities. Evaluation of the two-point correlation function $\\xi_{cc}(r)$ for the full sample and for richer subsamples reveals that the correlation amplitude is consistent with that measured for lower richness APM clusters and X-ray selected clusters. We apply a maxmimum likelihood estimator to find the best fitting slope and amplitude of a power law fit to $\\xi_{cc}(r)$, and to estimate the correlation length $r_{0}$ (the value of $r$ at which $\\xi_{cc}(r)$ is equal to unity). For clusters with a mean space density of $1.6\\times 10^{-6}\\hmpccc$ (equivalent to the space density of Abell Richness $\\geq 2$ clusters), we find $r_{0}=21.3^{+11.1}_{-9.3} \\hmpc$ (95% confidence limits). This is consistent with the weak richness dependence of $\\xi_{cc}(r)$ expected in Gaussian models of structure formation. In particular, the amplitude of $\\xi_{cc}(r)$ at all richnesses matches that of $\\xi_{cc}(r)$ for clusters selected in N-Body simulations of a low density Cold Dark Matter model.

Rupert A. C. Croft; Gavin B. Dalton; George Efstathiou; Will Sutherland; Steve Maddox

1997-01-09T23:59:59.000Z

410

Strong Emission-Line Galaxies at Low Redshift in the Field around the Quasar SDSSp J104433.04-012502.2  

E-Print Network [OSTI]

We discuss observational properties of strong emission-line galaxies at low redshift found by our deep imaging survey for high-redshift Ly alpha emitters. In our surveys, we used the narrowband filter, NB816 (lambda_center=8150A with FWHM = 120A), and the intermediate-band filter, IA827 (lambda_center = 8270A with FWHM = 340A). In this survey, 62 NB816-excess (> 0.9 mag) and 21 IA827-excess (> 0.8 mag) objects were found. Among them, we found 20 NB816-excess and 4 IA827-excess Ly alpha emitter candidates. Therefore, it turns out that 42 NB816-excess and 17 IA827-excess objects are strong emission-line objects at lower redshift. Since 4 objects in the two low-z samples are common, the total number of strong low-z emitters is 55. Applying our photometric redshift technique, we identify 7 H alpha emitters at z~0.24, 20 H beta-[OIII] ones at z~0.65, and 11 [OII] ones at z~1.19. However, we cannot determine reliable photometric redshifts of the remaining 17 emitters. The distributions of their rest frame equivalen...

Ajiki, M; Taniguchi, Y; Murayama, T; Nagao, T; Sasaki, S S; Sumiya, R; Morioka, T; Hatakeyama, Y; Yokouchi, A; Takahashi, M I; Koizumi, O; Ajiki, Masaru; Shioya, Yasuhiro; Taniguchi, Yoshiaki; Murayama, Takashi; Nagao, Tohru; Sasaki, Shunji S.; Sumiya, Ryoko; Morioka, Taichi; Hatakeyama, Yuichiro; Yokouchi, Asuka; Takahashi, Mari I.; Koizumi, Osamu

2005-01-01T23:59:59.000Z

411

Hacking Spaces: Place as Interface  

Science Journals Connector (OSTI)

In this article, we analyze the complex rationales—both transparent to us and, at times, made visible—underneath the instructional spaces in which we work and teach. To do so, we first situate space analysis in the larger, national conversations about instructional spaces and then through the work of computers and writing scholars. We conclude with an analysis of instructional spaces at our institution. These are spaces specific to our locale, but spaces we think are quite common at most institutions of higher education. Perhaps more importantly, we situate this space analysis on issues these spaces pose—issues of restricted movement, impaired ability to collaborate, sensory disruption, limited leadership ability, and functional/material constraints. We attempt to return to the roots of hacking and to situate hacking as a particular tool for negotiating and, at times, disrupting the assumptions built under, within, and across instructional spaces.

Douglas M. Walls; Scott Schopieray; Dànielle Nicole DeVoss

2009-01-01T23:59:59.000Z

412

Propagators in Lagrangian space  

SciTech Connect (OSTI)

It has been found recently that propagators, e.g. the cross correlation spectra of the cosmic fields with the initial density field, decay exponentially at large k in an Eulerian description of the dynamics. We explore here similar quantities defined for a Lagrangian space description. We find that propagators in Lagrangian space do not exhibit the same properties: they are found not to be monotonic functions of time, and to track back the linear growth rate at late time (but with a renormalized amplitude). These results have been obtained with a novel method which we describe alongside. It allows the formal resummation of the same set of diagrams as those that led to the known results in Eulerian space. We provide a tentative explanation for the marked differences seen between the Eulerian and the Lagrangian cases, and we point out the role played by the vorticity degrees of freedom that are specific to the Lagrangian formalism. This provides us with new insights into the late-time behavior of the propagators.

Bernardeau, Francis; Valageas, Patrick [Institut de Physique Theorique, CEA/DSM/IPhT, Unite de recherche associee au CNRS, CEA/Saclay, 91191 Gif-sur-Yvette cedex, France and Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, Ontario M5S 3H8 (Canada); Service de Physique Theorique, CEA/DSM/SPhT, Unite de recherche associee au CNRS, CEA/Saclay, 91191 Gif-sur-Yvette cedex (France)

2008-10-15T23:59:59.000Z

413

Graphically oriented method for obtaining atomic displacement fields in crystals from irreducible representations of space groups  

Science Journals Connector (OSTI)

A method for obtaining distortion fields in a crystal from a given irreducible representation of the underlying space group is described. The method, based on projection operators of group theory, is graphically oriented and therefore calculation-free. For an example (space group P4¯21m), complete sets of representation matrices are analytically calculated for all irreducible representations which correspond to all wave vectors of the form k=(q,q,0). All 96 linear independent atomic displacement modes in the (3×3×1) supercell, which are induced by the two irreducible representations with k=(13,13,0), are explicitly determined: the obtained atomic displacement fields are plane waves with wave vector k.

Jürgen K. Gutmann and Horst Böhm

2000-06-01T23:59:59.000Z

414

The Kast Ground Based UV Spectral Survey of 79 QSOs at Redshift 2 for Lyman Alpha Forest and Metal Absorption  

E-Print Network [OSTI]

We present a moderate resolution (~1.15 Angstroms/pixel) survey of 79 quasars obtained using the Kast spectrograph on the Shane 3m telescope at Lick observatory. The spectra span the wavelength range of 3175-5880 Angstroms, and have typical signal to noise of 6-20 in the regions of the spectra showing Lyman alpha forest absorption. The quasars have a mean emission redshift of z=2.17, and nearly all cover the entire Lyman alpha forest between Lyman alpha and Lyman beta. Although the quasars were selected to avoid BAL, two quasars in the survey are BAL, one of which is a new discovery. We list the HI and metal ions observed in a total of 140 absorption systems. We also identify 526 emission lines, and list their observed wavelengths, along with new redshifts of the quasars. We determine the rest wavelengths of 3 emission lines or line blends in the forest to be 1070.95 +/- 1.00, 1123.13 +/- 0.51, and 1175.88 +/- 0.30 Angstroms.

Tytler, D; Suzuki, N; Kirkman, D; Lubin, D; Orin, A; Tytler, David; Meara, John M. O'; Suzuki, Nao; Kirkman, David; Lubin, Dan; Orin, Adam

2004-01-01T23:59:59.000Z

415

The Kast Ground Based UV Spectral Survey of 79 QSOs at Redshift 2 for Lyman Alpha Forest and Metal Absorption  

E-Print Network [OSTI]

We present a moderate resolution (~1.15 Angstroms/pixel) survey of 79 quasars obtained using the Kast spectrograph on the Shane 3m telescope at Lick observatory. The spectra span the wavelength range of 3175-5880 Angstroms, and have typical signal to noise of 6-20 in the regions of the spectra showing Lyman alpha forest absorption. The quasars have a mean emission redshift of z=2.17, and nearly all cover the entire Lyman alpha forest between Lyman alpha and Lyman beta. Although the quasars were selected to avoid BAL, two quasars in the survey are BAL, one of which is a new discovery. We list the HI and metal ions observed in a total of 140 absorption systems. We also identify 526 emission lines, and list their observed wavelengths, along with new redshifts of the quasars. We determine the rest wavelengths of 3 emission lines or line blends in the forest to be 1070.95 +/- 1.00, 1123.13 +/- 0.51, and 1175.88 +/- 0.30 Angstroms.

David Tytler; John M. O'Meara; Nao Suzuki; David Kirkman; Dan Lubin; Adam Orin

2004-05-04T23:59:59.000Z

416

A redshifted Fe K$\\alpha$ line from the unusual gamma-ray source PMN J1603-4904  

E-Print Network [OSTI]

Multiwavelength observations have revealed the highly unusual properties of the gamma-ray source PMN J1603-4904, which are difficult to reconcile with any other well established gamma-ray source class. The object is either a very atypical blazar or compact jet source seen at a larger angle to the line of sight. In order to determine the physical origin of the high-energy emission processes in PMN J1603-4904, we study the X-ray spectrum in detail. We performed quasi-simultaneous X-ray observations with XMM-Newton and Suzaku in 2013 September, resulting in the first high signal-to-noise X-ray spectrum of this source. The 2-10 keV X-ray spectrum can be well described by an absorbed power law with an emission line at 5.44$\\pm$0.05 keV (observed frame). Interpreting this feature as a K{\\alpha} line from neutral iron, we determine the redshift of PMN J1603-4904 to be z=0.18$\\pm$0.01, corresponding to a luminosity distance of 872$\\pm$54 Mpc. The detection of a redshifted X-ray emission line further challenges the or...

Müller, C; Dauser, T; Kreikenbohm, A; Beuchert, T; Kadler, M; Ojha, R; Wilms, J; Böck, M; Carpenter, B; Markowitz, A; McConville, W; Pottschmidt, K; Stawarz, L; Taylor, G B

2015-01-01T23:59:59.000Z

417

National Aeronautics and Space Administration Space Launch System  

E-Print Network [OSTI]

was previously designated the space shuttle main engine and is built by Aerojet Rocketdyne of Sacramento, Calif

Waliser, Duane E.

418

Semiclassical Distorted Wave Model Analysis of Backward Proton Emission from $(p,p^{\\prime}x)$ Reactions at Intermediate Energies  

E-Print Network [OSTI]

A semiclassical distorted wave (SCDW) model with Wigner transform of one-body density matrix is presented for multistep direct $(p,p^{\\prime}x)$ reactions to the continuum. The model uses Wigner distribution functions obtained in methods which include nucleon-nucleon correlations to a different extent, as well as Woods-Saxon (WS) single-particle wave function. The higher momentum components of target nucleons that play a crucial role in reproducing the high-energy part of the backward proton spectra are properly taken into account. This SCDW model is applied to analyses of multistep direct processes in $^{12}$C$(p,p^{\\prime}x)$, $^{40}$Ca$(p,p^{\\prime}x)$ and $^{90}$Zr$(p,p^{\\prime}x)$ in the incident energy range of 150--392 MeV. The double differential cross sections are calculated up to three-step processes. The calculated angular distributions are in good agreement with the experimental data, in particular at backward angles where the previous SCDW calculations with the WS single-particle wave function showed large underestimation. It is found that the result with the Wigner distribution function based on the coherent density fluctuation model provides overall better agreement with the experimental data over the whole emission energies.

M. K. Gaidarov; Y. Watanabe; K. Ogata; M. Kohno; M. Kawai; A. N. Antonov

2003-07-28T23:59:59.000Z

419

National Aeronautics and Space Administration International Space Station  

E-Print Network [OSTI]

and technological endeavor ever undertaken, involving support from five space agencies representing 16 nations. Once's solar panels exceed the wingspan of a Boeing 777 jetliner and harness enough energy from the sunNational Aeronautics and Space Administration NASAfacts International Space Station Clearly

420

E-Print Network 3.0 - achieve efficient transmission Sample Search...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Berkeley National Laboratory, High Redshift Supernova Search Collection: Physics ; Power Transmission, Distribution and Plants 8 Nonlinear Signal Distortion in WDM...

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

The science of space weather  

Science Journals Connector (OSTI)

...magnetic reconnection|space weather| 1. Introduction Fifty...31 January 1958, the satellite Explorer 1 was launched...et al. 2005). (e) Satellite anomalies Space weather can cause a variety of satellite anomalies such as surface...

2008-01-01T23:59:59.000Z

422

Space Contamination and Ecological Problems  

Science Journals Connector (OSTI)

The state-of-the-art theories concerning the problem of pollution by space vehicles are discussed and a variety of mechanical problems’ formulations are considered, as applied to environmental problems in space.

V. M. Fomin; A. M. Kharitonov…

1995-01-01T23:59:59.000Z

423

Europeanizing Territoriality - Towards Soft Spaces?  

E-Print Network [OSTI]

spatial or development planning might provide a way forward. A number of studies across Europe have highlighted and explored the emergence of so called soft spaces as attempts to create hybrids of territorial and relational spaces (see, for example... by creating bespoke spaces for dealing with specific issues such as regeneration, integrating different sectors such as transport, infrastructure, education, etc. in such processes operating at variable scales. Studies of soft spaces have focused upon...

Allmendinger, Phil; Chilla, Tobias; Sielker, Franziska

2014-01-01T23:59:59.000Z

424

Demystifying White Spaces Xuemin Hongl  

E-Print Network [OSTI]

Demystifying White Spaces Xuemin Hongl , Cheng-Xiang Wangl , John Thompson2 , and Yan Zhang3 1Joint.wang@hw.ac.uk.john.thompson@ed.ac.uk. yanzhang@ieee.org Abstract-White spaces refer to the unused frequency voids across time or space. The vast existence of white spaces has been validated by many measurements and is widely regarded as an undesirable

Wang, Cheng-Xiang

425

2012 RAL Space Sarah James  

E-Print Network [OSTI]

are here Chilton Ionosonde #12;© 2012 RAL Space #12;What is the ionosphere? Marconi's transatlantic radio

426

Space, Health and Population Economics  

E-Print Network [OSTI]

Space, Health SHaPE and Population Economics Changing Demographics and Immigration: Implications for IndianaImplications for Indiana Brigitte Waldorf, Purdue University Farm Policy Study Group b 20 07 December 2010 #12;Space, Health SHaPE and Population Economics America is ... ... Aging #12;Space, Health

427

Geodesic spaces : momentum Groups : symmetry  

E-Print Network [OSTI]

Geodesic spaces : momentum :: Groups : symmetry Vaughan Pratt Stanford University BLAST 2010 a · b denoting b rotated 90 degrees about a. End of reprise. 3. This talk; Geodesic spaces At FMCS. as points evenly spaced along a geodesic , right distributivity expresses a symmetry of about an arbitrary

Pratt, Vaughan

428

National Aeronautics and Space Administration  

E-Print Network [OSTI]

really mark the end of outer space as a field for humankind's visions, longings, and projections ccononttiinnuueedd onon nenexxtt ppaagege Berlin Symposium on Outer Space and the End of Utopia in the 1970s By Friederike Mehl, Universiteit van Amsterdam, FriederikeMehl@gmx.de Did the end of the Space Age in the 1970s

429

Policies on Japan's Space Industry  

E-Print Network [OSTI]

as a strategic industry Practical space use in National Security Diplomacy ...etc Policy Administrative Structure on the Basic Space Law legislated in 2008. 1. The government sets space policy as a national strategy utilization environment Develop new markets with small size satellites and rockets Promote the serialization

430

National Aeronautics and Space Administration  

E-Print Network [OSTI]

National Aeronautics and Space Administration Launch Services Program Earth's Bridge to Space 2012 roles, getting rockets and satellites ready for flight, on their way, and all the way to orbit absolutely instrumental for the United States to have access to a dependable and secure Earth-to-space bridge

431

Upgrading Below Grade Spaces  

Broader source: Energy.gov (indexed) [DOE]

Patrick H. Huelman, Sam Breidenbach, Steve Schirber Patrick H. Huelman, Sam Breidenbach, Steve Schirber NorthernSTAR Building America Partnership Upgrading Below Grade Spaces Residential Energy Efficiency Stakeholder March 1, 2012 Austin, TX * Act 1: Technical Challenges & Opportunities - Pat Huelman, University of Minnesota * Act 2: Assessing Homeowner Priorities & Risks - Sam Breidenbach, TDS Custom Construction * Act 3: An Industry Perspective - Steve Schirber, Cocoon Act 1. Upgrade Below Grade * Basement Remodeling: It Doesn't Get Any Riskier! - Combustion safety - Foundation moisture - Radon (& other soil gases) - Biologicals (mold, dust mites, etc.) - Garage gases (if attached) * And front and center are uncontrolled... - negative pressures in basements (beyond stack)

432

space booklet_DOE  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

U U C L E A R E N E R G Y DOE/NE-0071 U . S . D e p a r t m e n t o f E n e r g y O f f i c e o f N u c l e a r E n e r g y , S c i e n c e a n d T e c h n o l o g y N UCLEAR Power in Space 2

433

Hyper Space Issue 2  

E-Print Network [OSTI]

University, Indianapolis, Indiana. Ed.: How real is STAR WARS? Nick: I enjoyed seeing the movie, it was funl I found the story reasonable. The models and special effects were terrificI There were a couple of errors such as the misuaaof the concept... space without any sound may be uninteresting to the audience. Ed.: What about faster than light travel? Nick: Hyper drive is impossible if you use conventional physics starting from a finite position. But if you start in a different place hyperdrive...

1977-01-01T23:59:59.000Z

434

A PUBLIC K{sub s} -SELECTED CATALOG IN THE COSMOS/ULTRAVISTA FIELD: PHOTOMETRY, PHOTOMETRIC REDSHIFTS, AND STELLAR POPULATION PARAMETERS {sup ,}  

SciTech Connect (OSTI)

We present a catalog covering 1.62 deg{sup 2} of the COSMOS/UltraVISTA field with point-spread function (PSF) matched photometry in 30 photometric bands. The catalog covers the wavelength range 0.15-24 {mu}m including the available GALEX, Subaru, Canada-France-Hawaii Telescope, VISTA, and Spitzer data. Catalog sources have been selected from the DR1 UltraVISTA K{sub s} band imaging that reaches a depth of K {sub s,tot} = 23.4 AB (90% completeness). The PSF-matched catalog is generated using position-dependent PSFs ensuring accurate colors across the entire field. Also included is a catalog of photometric redshifts (z {sub phot}) for all galaxies computed with the EAZY code. Comparison with spectroscopy from the zCOSMOS 10k bright sample shows that up to z {approx} 1.5 the z {sub phot} are accurate to {Delta}z/(1 + z) = 0.013, with a catastrophic outlier fraction of only 1.6%. The z {sub phot} also show good agreement with the z {sub phot} from the NEWFIRM Medium Band Survey out to z {approx} 3. A catalog of stellar masses and stellar population parameters for galaxies determined using the FAST spectral energy distribution fitting code is provided for all galaxies. Also included are rest-frame U - V and V - J colors, L {sub 2800} and L {sub IR}. The UVJ color-color diagram confirms that the galaxy bi-modality is well-established out to z {approx} 2. Star-forming galaxies also obey a star-forming 'main sequence' out to z {approx} 2.5, and this sequence evolves in a manner consistent with previous measurements. The COSMOS/UltraVISTA K{sub s} -selected catalog covers a unique parameter space in both depth, area, and multi-wavelength coverage and promises to be a useful tool for studying the growth of the galaxy population out to z {approx} 3-4.

Muzzin, Adam; Franx, Marijn; Labbe, Ivo [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)] [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Marchesini, Danilo [Department of Physics and Astronomy, Tufts University, Medford, MA 06520 (United States)] [Department of Physics and Astronomy, Tufts University, Medford, MA 06520 (United States); Stefanon, Mauro [Physics and Astronomy Department, University of Missouri, Columbia, MO 65211 (United States)] [Physics and Astronomy Department, University of Missouri, Columbia, MO 65211 (United States); Milvang-Jensen, Bo; Fynbo, J. P. U. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark)] [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Dunlop, James S. [SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom)] [SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom); Brammer, Gabriel [European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Vitacura, Santiago (Chile)] [European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Vitacura, Santiago (Chile); Van Dokkum, Pieter [Department of Astronomy, Yale University, New Haven, CT 06520-8101 (United States)] [Department of Astronomy, Yale University, New Haven, CT 06520-8101 (United States)

2013-05-01T23:59:59.000Z

435

SPACE BASED INTERCEPTOR SCALING  

SciTech Connect (OSTI)

Space Based Interceptor (SBI) have ranges that are adequate to address rogue ICBMs. They are not overly sensitive to 30-60 s delay times. Current technologies would support boost phase intercept with about 150 interceptors. Higher acceleration and velocity could reduce than number by about a factor of 3 at the cost of heavier and more expensive Kinetic Kill Vehicles (KKVs). 6g SBI would reduce optimal constellation costs by about 35%; 8g SBI would reduce them another 20%. Interceptor ranges fall rapidly with theater missile range. Constellations increase significantly for ranges under 3,000 km, even with advanced interceptor technology. For distributed launches, these estimates recover earlier strategic scalings, which demonstrate the improved absentee ratio for larger or multiple launch areas. Constellations increase with the number of missiles and the number of interceptors launched at each. The economic estimates above suggest that two SBI per missile with a modest midcourse underlay is appropriate. The SBI KKV technology would appear to be common for space- and surface-based boost phase systems, and could have synergisms with improved midcourse intercept and discrimination systems. While advanced technology could be helpful in reducing costs, particularly for short range theater missiles, current technology appears adequate for pressing rogue ICBM, accidental, and unauthorized launches.

G. CANAVAN

2001-02-01T23:59:59.000Z

436

Magnetic reconnection in space  

SciTech Connect (OSTI)

Models of magnetic reconnection in space plasmas generally consider only a segment of the magnetic field lines. The consideration of only a segment of the lines is shown to lead to paradoxical results in which reconnection can be impossible even in a magnetic field constrained to be curl free or can be at an Alfven rate even when the plasma is a perfect conductor. A model of reconnecting magnetic fields is developed which shows the smallness of the interdiffusion distance {delta}{sub d} of magnetic field lines does not limit the speed of reconnection but does provide a reconnection trigger. When the reconnection region has a natural length L{sub r}, the spatial scale of the gradient of magnetic field across the magnetic field lines must reach L{sub g} Almost-Equal-To 0.3L{sub r}/ln(L{sub r}/{delta}{sub d}) for fast reconnection to be triggered, which implies a current density j Almost-Equal-To B/{mu}{sub 0}L{sub g} that is far lower than that usually thought required for fast reconnection. The relation between magnetic reconnection in space and in toroidal laboratory plasmas is also discussed.

Boozer, Allen H. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

2012-09-15T23:59:59.000Z

437

Dark matter distortions  

Science Journals Connector (OSTI)

... of clumped mass. Einstein showed that the Sun's gravity bends light rays from distant stars, and speculated that a ... , and speculated that a star fortuitously aligned with a distant object would create a ring image2. Zwicky argued3 that ...

J. A. Tyson

1988-07-28T23:59:59.000Z

438

Transportation Market Distortions  

E-Print Network [OSTI]

of Highways, Volpe National Transportation Systems Center (Evaluating Criticism of Transportation Costing, VictoriaFrom Here: Evaluating Transportation Diversity, Victoria

Litman, Todd

2006-01-01T23:59:59.000Z

439

Theoretical prediction of local distortion in an ErO{sub 6} cluster: Stabilization of a C{sub 4v} structure by a rack and pinion effect  

SciTech Connect (OSTI)

As a possible atomic coordination of erbium dopants surrounded by oxygen, a molecular orbital calculation of an ErO{sub 6} cluster can predict a C{sub 4v} pseudo-octahedral structure with Er distortion of {approx}0.1 Aa from the octahedral center. It was found that bond alternation by a 'rack and pinion effect' can minimize the electron transfer from O{sup 2-} to Er{sup 3+} at this distortion range, resulting in stable ionic bonding; the rotation of an O 2p orbital due to Er 5d translation, similar to rack and pinion motion, forms a new O 2p--Er 5d bond, while a dipole moment induced by symmetrical degradation makes an O 2p--Er 6s bond unstable. {copyright} 2001 American Institute of Physics.

Ishii, Masashi; Komukai, Yasuo

2001-08-13T23:59:59.000Z

440

Steric and Electronic Effects Relating to the Cu2+ Jahn?Teller Distortion in Zn1-xCuxAl2O4 Spinels  

Science Journals Connector (OSTI)

Steric and Electronic Effects Relating to the Cu2+ Jahn?Teller Distortion in Zn1-xCuxAl2O4 Spinels§ ... XRD-data refinements on the whole solid solution have allowed defining two critical areas where structural features such as cell parameter and inversion rate as well as cation-oxygen bond distances in 8a and 16d sites of the spinel network exhibit clear unique variations. ...

A. Le Nestour; M. Gaudon; G. Villeneuve; R. Andriessen; A. Demourgues

2007-02-10T23:59:59.000Z