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We encourage you to perform a real-time search of NLEBeta
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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

A METHOD TO EXTRACT THE REDSHIFT DISTORTION {beta} PARAMETER IN CONFIGURATION SPACE FROM MINIMAL COSMOLOGICAL ASSUMPTIONS  

SciTech Connect (OSTI)

We present a method to extract the redshift-space distortion {beta} parameter in configuration space with a minimal set of cosmological assumptions. We show that a novel combination of the observed monopole and quadrupole correlation functions can remove efficiently the impact of mild nonlinearities and redshift errors. The method offers a series of convenient properties: it does not depend on the theoretical linear correlation function, the mean galaxy density is irrelevant, only convolutions are used, and there is no explicit dependence on linear bias. Analyses based on dark matter N-body simulations and Fisher matrix demonstrate that errors of a few percent on {beta} are possible with a full-sky, 1 (h {sup -1} Gpc){sup 3} survey centered at a redshift of unity and with negligible shot noise. We also find a baryonic feature in the normalized quadrupole in configuration space that should complicate the extraction of the growth parameter from the linear theory asymptote, but that does not have a major impact on our method.

Tocchini-Valentini, Domenico; Barnard, Michael; Bennett, Charles L.; Szalay, Alexander S., E-mail: dtv@pha.jhu.edu [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218-2686 (United States)

2012-10-01T23:59:59.000Z

4

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

5

Redshift Distortions as a Probe of Gravity  

E-Print Network [OSTI]

Redshift distortion measurements from galaxy surveys include sensitivity to the gravitational growth index distinguishing other theories from Einstein gravity. This gravitational sensitivity is substantially free from uncertainty in the effective equation of state of the cosmic expansion history. We also illustrate the bias in the traditional application to matter density determination using f=Omega_m(a)^{0.6}, and how to avoid it.

Eric V. Linder

2007-09-07T23:59:59.000Z

6

Distortion of the luminosity function of high-redshift galaxies by gravitational lensing  

E-Print Network [OSTI]

The observed properties of high redshift galaxies depend on the underlying foreground distribution of large scale structure, which distorts their intrinsic properties via gravitational lensing. We focus on the regime where the dominant contribution originates from a single lens and examine the statistics of gravitational lensing by a population of virialized and non-virialized structures using sub-mm galaxies at z ~ 2.6 and Lyman-break galaxies at redshifts z ~ 6-15 as the background sources. We quantify the effect of lensing on the luminosity function of the high redshift sources, focusing on the intermediate and small magnifications (mu < 3) which affect the majority of the background galaxies. We show that depending on the intrinsic properties of the background galaxies, gravitational lensing can significantly affect the observed luminosity function even when no obvious strong lenses are present. Finally, we find that in the case of the Lyman-break galaxies it is important to account for the surface bri...

Fialkov, Anastasia

2015-01-01T23:59:59.000Z

7

Nonlinear stochastic growth rates and redshift space distortions  

E-Print Network [OSTI]

The linear growth rate is commonly defined through a simple deterministic relation between the velocity divergence and the matter overdensity in the linear regime. Here we introduce a formalism that extends this to a nonlinear, stochastic relation between $\\theta = \

Jennings, Elise

2015-01-01T23:59:59.000Z

8

Using Perturbative Least Action (PLA) to Reconstruct Redshift Space Distortions  

E-Print Network [OSTI]

In this paper, we apply the Perturbative Least Action Method to model the Local Group of galaxies for various Cosmological models. We show that though the galaxy masses are theoretically good discriminators of $\\Omega_M$ given some observed MW and M31 separation and radial velocity, current estimates of the masses are insufficient to make any cosmological claims. We then discuss additional complications to expand this analysis.

Goldberg, D M

2000-01-01T23:59:59.000Z

9

Beyond the plane-parallel and Newtonian approach: wide-angle redshift distortions and convergence in general relativity  

SciTech Connect (OSTI)

We extend previous analyses of wide-angle correlations in the galaxy power spectrum in redshift space to include all general relativistic effects. These general relativistic corrections to the standard approach become important on large scales and at high redshifts, and they lead to new terms in the wide-angle correlations. We show that in principle the new terms can produce corrections of nearly 10% on Gpc scales over the usual Newtonian approximation. General relativistic corrections will be important for future large-volume surveys such as SKA and Euclid, although the problem of cosmic variance will present a challenge in observing this.

Bertacca, Daniele; Maartens, Roy [Physics Department, University of the Western Cape, Cape Town 7535 (South Africa); Raccanelli, Alvise [Jet Propulsion Laboratory, California Institute of Technology, Pasadena CA 91109 (United States); Clarkson, Chris, E-mail: daniele.bertacca@pd.infn.it, E-mail: Roy.Maartens@port.ac.uk, E-mail: Alvise@caltech.edu, E-mail: Clarkson@maths.uct.ac.za [Centre for Astrophysics, Cosmology and Gravitation and Department of Mathematics and Applied Mathematics, University of Cape Town, Cape Town 7701 (South Africa)

2012-10-01T23:59:59.000Z

10

Testing the Accuracy of Redshift Space Group Finding Algorithms  

E-Print Network [OSTI]

Using simulated redshift surveys generated from a high resolution N-body cosmological structure simulation, we study algorithms used to identify groups of galaxies in redshift space. Two algorithms are investigated; both are friends-of-friends schemes with variable linking lengths in the radial and transverse dimensions. The chief difference between the algorithms is in the redshift linking length. The algorithm proposed by Huchra \\& Geller (1982) uses a generous linking length designed to find ``fingers of god'' while that of Nolthenius \\& White (1987) uses a smaller linking length to minimize contamination by projection. We find that neither of the algorithms studied is intrinsically superior to the other; rather, the ideal algorithm as well as the ideal algorithm parameters depend on the purpose for which groups are to be studied. The Huchra/Geller algorithm misses few real groups, at the cost of including some spurious groups and members, while the Nolthenius/White algorithm misses high velocity dispersion groups and members but is less likely to include interlopers in its group assignments. In a companion paper we investigate the accuracy of virial mass estimates and clustering properties of groups identified using these algorithms.

James J. Frederic

1994-09-07T23:59:59.000Z

11

Estimation problems in the space of distorted stochastic processes  

E-Print Network [OSTI]

300 400 500 600 700 800 900 1000 (b) 800 600 400 200 100 200 300 400 500 600 700 800 900 1000 (c) 0 100 200 300 400 500 600 700 800 900 1000 Figure 1. Doppler effect on a stationary process. (a) Stationary process, X(t). (b) Distortion... variable with zero mean, variance o. Then, py(t, t + h) = o cos(kih + kah + 2tkzh) since the autocovariance function depends on t, the process is not stationary. How- ever, the process X defined by: X(t) = A cos{t) + B sin(t) is stationary. Therefore...

Moutran, Cyril

1996-01-01T23:59:59.000Z

12

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

13

Measuring Galaxy Environments with Deep Redshift Surveys  

E-Print Network [OSTI]

We study the applicability of several galaxy environment measures (n^th-nearest-neighbor distance, counts in an aperture, and Voronoi volume) within deep redshift surveys. Mock galaxy catalogs are employed to mimic representative photometric and spectroscopic surveys at high redshift (z ~ 1). We investigate the effects of survey edges, redshift precision, redshift-space distortions, and target selection upon each environment measure. We find that even optimistic photometric redshift errors (\\sigma_z = 0.02) smear out the line-of-sight galaxy distribution irretrievably on small scales; this significantly limits the application of photometric redshift surveys to environment studies. Edges and holes in a survey field dramatically affect the estimation of environment, with the impact of edge effects depending upon the adopted environment measure. These edge effects considerably limit the usefulness of smaller survey fields (e.g. the GOODS fields) for studies of galaxy environment. In even the poorest groups and clusters, redshift-space distortions limit the effectiveness of each environment statistic; measuring density in projection (e.g. using counts in a cylindrical aperture or a projected n^th-nearest-neighbor distance measure) significantly improves the accuracy of measures in such over-dense environments. For the DEEP2 Galaxy Redshift Survey, we conclude that among the environment estimators tested the projected n^th-nearest-neighbor distance measure provides the most accurate estimate of local galaxy density over a continuous and broad range of scales.

Michael C. Cooper; Jeffrey A. Newman; Darren S. Madgwick; Brian F. Gerke; Renbin Yan; Marc Davis

2005-06-21T23:59:59.000Z

14

Trans-Planckian redshifts and the substance of the space-time river  

E-Print Network [OSTI]

Trans-Planckian redshifts in cosmology and outside black holes may provide windows on a hypothetical short distance cutoff on the fundamental degrees of freedom. In cosmology, such a cutoff seems to require a growing Hilbert space, but for black holes, Unruh's sonic analogy has given rise to both field theoretic and lattice models demonstrating how such a cutoff in a fixed Hilbert space might be compatible with a low energy effective quantum field theory of the Hawking effect. In the lattice case, the outgoing modes arise via a Bloch oscillation from ingoing modes. A short distance cutoff on degrees of freedom is incompatible with local Lorentz invariance, but may nevertheless be compatible with general covariance if the preferred frame is defined non-locally by the cosmological background. Pursuing these ideas in a different direction, condensed matter analogs may eventually allow for laboratory observations of the Hawking effect. This paper introduces and gives a fairly complete but brief review of the work that has been done in these areas, and tries to point the way to some future directions.

Ted Jacobson

2000-02-16T23:59:59.000Z

15

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 0.3

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

2015-01-01T23:59:59.000Z

16

A TYPE Ia SUPERNOVA AT REDSHIFT 1.55 IN HUBBLE SPACE TELESCOPE INFRARED OBSERVATIONS FROM CANDELS  

SciTech Connect (OSTI)

We report the discovery of a Type Ia supernova (SN Ia) at redshift z = 1.55 with the infrared detector of the Wide Field Camera 3 (WFC3-IR) on the Hubble Space Telescope (HST). This object was discovered in CANDELS imaging data of the Hubble Ultra Deep Field and followed as part of the CANDELS+CLASH Supernova project, comprising the SN search components from those two HST multi-cycle treasury programs. This is the highest redshift SN Ia with direct spectroscopic evidence for classification. It is also the first SN Ia at z > 1 found and followed in the infrared, providing a full light curve in rest-frame optical bands. The classification and redshift are securely defined from a combination of multi-band and multi-epoch photometry of the SN, ground-based spectroscopy of the host galaxy, and WFC3-IR grism spectroscopy of both the SN and host. This object is the first of a projected sample at z > 1.5 that will be discovered by the CANDELS and CLASH programs. The full CANDELS+CLASH SN Ia sample will enable unique tests for evolutionary effects that could arise due to differences in SN Ia progenitor systems as a function of redshift. This high-z sample will also allow measurement of the SN Ia rate out to z Almost-Equal-To 2, providing a complementary constraint on SN Ia progenitor models.

Rodney, Steven A.; Riess, Adam G.; Jones, David O. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Dahlen, Tomas; Ferguson, Henry C.; Casertano, Stefano; Grogin, Norman A. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Strolger, Louis-Gregory [Department of Physics, Western Kentucky University, Bowling Green, KY 42101 (United States); Hjorth, Jens; Frederiksen, Teddy F. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Weiner, Benjamin J. [Department of Astronomy, University of Arizona, Tucson, AZ 85721 (United States); Mobasher, Bahram [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Challis, Peter; Kirshner, Robert P. [Harvard/Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Faber, S. M. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 92064 (United States); Filippenko, Alexei V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Garnavich, Peter; Hayden, Brian [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Graur, Or [Department of Astrophysics, Tel Aviv University, 69978 Tel Aviv (Israel); Jha, Saurabh W. [Department of Physics and Astronomy, Rutgers, State University of New Jersey, Piscataway, NJ 08854 (United States); and others

2012-02-10T23:59:59.000Z

17

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

18

Redshift and Energy Conservation  

E-Print Network [OSTI]

It has always been considered a serious error to treat the cosmological redshift as a Doppler velocity effect rather than the result of space expansion. It is demonstrated here that in practical terms this is not the case, and that the apparent distance - redshift relation derived from a Doppler interpretation is reasonably consistent with supernova data (though not as good as the standard model with dark energy). The normal Doppler effect is examined in detail and shown to conserve energy as expected. Because of the equivalence between the general relativistic space expansion paradigm and the Doppler effect (as demonstrated) the long-standing problem of energy loss associated with the expansion of the Universe is treated in a similar manner to the normal well-behaved Doppler effect. The mechanism by which energy is conserved with the normal Doppler shift is applied to the cosmological redshift and the energy violation disappears. However, an additional luminosity-dependent recession factor is introduced. The effect on astronomical objects is examined and it is found to add only a small additional redshift to a body generating power by nuclear means but can be very large for objects powered by gravity. A possible connection to the claimed anomalous redshift of quasars is considered.

Alasdair Macleod

2004-08-06T23:59:59.000Z

19

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

20

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

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

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

22

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

23

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.

24

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

25

Magnitude-Redshift Relation for SNe Ia, Time Dilation, and Plasma Redshift  

E-Print Network [OSTI]

We have previously shown that the type Ia supernovae data by Riess et al. match the prediction of the magnitude-redshift relation in the plasma-redshift cosmology. In this article, we also show that the recent SNLS data, which have a slightly narrower distribution as reported by Astier et al. in 2005, match the predictions of the plasma-redshift cosmology. The standard deviation of the SNLS-magnitude from the predicted curve is only about 0.14. The data indicate that there is no cosmic time dilation. The big-bang cosmology therefore appears false. The plasma redshift, which follows from exact evaluation of photons interaction with hot sparse electron plasma, leads to a quasi-static, infinite, and everlasting universe. It does not need big bang, dark energy, or dark matter for describing the observations. It predicts intrinsic redshifts of galaxies consistent with what is observed. The Hubble constant that best fits the SNLS data is about 63 km per sec per Mpc. This corresponds to an average electron density of about 0.0002 per cubic centimeter in intergalactic space. This density together with the plasma redshift heating to an average plasma temperature in intergalactic space of about 3 million K explains the observed isotropic cosmic microwave background (CMB) and the cosmic X-ray background.

Ari Brynjolfsson

2006-02-22T23:59:59.000Z

26

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

27

Galaxy Redshifts: Improved Techniques  

E-Print Network [OSTI]

This paper analyses the effects of random noise in determining errors and confidence levels for galaxy redshifts obtained by cross-correlation techniques. The main finding is that confidence levels have previously been overestimated, and errors inaccurately calculated in certain applications. New formul\\ae\\ are presented.

A. F. Heavens

1993-05-26T23:59:59.000Z

28

Two Phase Dynamics as the Origin to: 0.25 keV and 0.1 keV X-ray Diffuse Backgrounds, CMB, Global Quantized Redshift, 10 Mpc Space distributions and 30 Myr Cycles at Earth Phenomena  

E-Print Network [OSTI]

An Alternative to explain the origin of matter-background connections from the paper "Do Cosmic Backgrounds Cyclical Renew by Matter and Quanta Emissions?..." proposed: A sequence of discontinuous small changes of light speed in time as the cause, which provoke that criticality processes take place every 26-30 million years. Then, matter particles and quanta reach at one threshold value, and are compelled to reorganize their internal energy and make emissions that later becomes in current cosmic backgrounds. The small discontinues relative decreasing of c of about 10 -5) should do some small effects on planet and living bodies. Cyclic small reorganization of matter particles is consider as the astrophysical origin of Earth cyclic catastrophes. And at space global distribution: quantized redshift, change of galaxy fractal distribution at 10 Mpc scale, galaxy average luminosity and the luminosity fluctuation of galaxy pairs are enhanced out to separations near 10 Mpc. Also proposed: Like the Universe is observed flat in distance and time, the gravitational constant G might decrease with time, which may originate the Earth orbit eccentricity cycle of 100000 yr and, provoke the former mentioned sequence of c decrease in time. And, every 6 million years, the accumulation of G relative decrease of about 10-5 in G compelled space-time to reach at one threshold value that, trigger small relative decrease of light speed c of about 10-5 cyclically. This is interpreted as the Universe has two dynamical phases following one each other cyclically with intervals of 26-30 million years respectively: One of about 0.1 million years, called "activation phase", at which the critical processes take place, follows by longer "inhibition phase". The present approach indicates the existence of a subtle non linear dynamics, which could also contribute to the origin of galaxy fractal distribution.

Eduardo del Pozo Garcia

2015-02-25T23:59:59.000Z

29

Source Coding with Mismatched Distortion Measures  

E-Print Network [OSTI]

We consider the problem of lossy source coding with a mismatched distortion measure. That is, we investigate what distortion guarantees can be made with respect to distortion measure $\\tilde{\\rho}$, for a source code designed such that it achieves distortion less than $D$ with respect to distortion measure $\\rho$. We find a single-letter characterization of this mismatch distortion and study properties of this quantity. These results give insight into the robustness of lossy source coding with respect to modeling errors in the distortion measure. They also provide guidelines on how to choose a good tractable approximation of an intractable distortion measure.

Niesen, Urs; Wornell, Gregory

2008-01-01T23:59:59.000Z

30

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

31

Harmonic distortion correction in pipelined analog to digital converters  

E-Print Network [OSTI]

Background Correction of Harmonic Distortion in PipelinedBackground Correction of Harmonic Distortion in PipelinedADC with 69dB SNDR Enabled by Digital Harmonic Distortion

Panigada, Andrea

2009-01-01T23:59:59.000Z

32

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

33

Galactosynthesis Predictions at High Redshift  

E-Print Network [OSTI]

We predict the Tully-Fisher (TF) and surface-brightness--magnitude relation for disk galaxies at z=3 and discuss the origin of these scaling relations and their scatter. We show that the variation of the TF relation with redshift can be a potentially powerful discriminator of galaxy-formation models. In particular, the TF relation at high redshift might be used to break parameter degeneracies among galactosynthesis models at z=0, as well as to constrain the redshift distribution of collapsing dark-matter halos, the star-formation history and baryon fraction in the disk, and the distribution of halo spins.

Ari Buchalter; Raul Jimenez; Marc Kamionkowski

2001-02-02T23:59:59.000Z

34

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

35

Southern Sky Redshift Survey  

SciTech Connect (OSTI)

The general characteristics of the space distribution of galaxies in the SSRS sample, covering the southern Galactic cap, are examined, and maps of the space distribution are presented. The sample consists of 2028 galaxies in an area of 1.75 sr with declination south of -17.5 deg and galactic latitude below -30 deg. The survey provides useful information on large-scale structure to a depth of 120/h Mpc. The galaxy distribution exhibits prominent filaments, sheets, and voids. Some large-scale structures are highly subclustered; others are much more diffuse. 21 references.

Da Costa, L.N.; Pellegrini, P.S.; Sargent, W.L.W.; Tonry, J.; Davis, M.

1988-04-01T23:59:59.000Z

36

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

37

A faint galaxy redshift survey behind massive clusters  

SciTech Connect (OSTI)

This thesis is concerned with the gravitational lensing effect by massive galaxy clusters. We have explored a new technique for measuring galaxy masses and for detecting high-z galaxies by their optical colors. A redshift survey has been obtained at the Keck for a magnitude limited sample of objects (I<23) behind three clusters, A1689, A2390, and A2218 within a radius of 0.5M pc. For each cluster we see both a clear trend of increasing flux and redshift towards the center. This behavior is the result of image magnifications, such that at fixed redshift one sees further down the luminosity function. The gradient of this magnification is, unlike measurements of image distortion, sensitive to the mass profile, and found to depart strongly from a pure isothermal halo. We have found that V RI color selection can be used effectively as a discriminant for finding high-z galaxies behind clusters and present five 4.1 < z < 5.1 spectra which are of very high quality due to their high mean magnification of {approximately}20, showing strong, visibly-saturated interstellar metal lines in some cases. We have also investigated the radio ring lens PKS 1830-211, locating the source and multiple images and detected molecular absorption at mm wavelengths. Broad molecular absorption of width 1/40kms is found toward the southwest component only, where surprisingly it does not reach the base of the continuum, which implies incomplete coverage of the SW component by molecular gas, despite the small projected size of the source, less than 1/8h pc at the absorption redshift.

Frye, Brenda

1999-12-01T23:59:59.000Z

38

DATABASE AUTHENTICATION BY DISTORTION FREE WATERMARKING  

E-Print Network [OSTI]

DATABASE AUTHENTICATION BY DISTORTION FREE WATERMARKING Sukriti Bhattacharya and Agostino Cortesi@dsi.unive.it, cortesi@unive.it Keywords: Database watermarking, ZAW, Public key watermark, Abstract interpretation the verification of integrity of the relational databases by using a public zero distortion authentication

Cortesi, Tino

39

An Analysis of Gravitational Redshift from Rotating Body-II: The Effect of Electro and Magneto Static Field  

E-Print Network [OSTI]

It is well known fact that gravitational mass can alter the space time structure and gravitational redshift is its one example. Static electric or magnetic charge can also alter the space-time similar to gravitational mass. So Static electric or magnetic charge can also give rise to an effect of same kind on redshift (analogous to gravitational redshift). This can be considered as electro and magneto static redshift. Gravitational redshift has been reported by most of the authors without consideration of static electric and / or magnetic charge present on the rotating body. As a continuation of our previous work [1], in the present paper we will discuss combined gravitational and electro-magneto-static redshift for rotating by using Kerr - Newman - Kasuya metric.

Dubey, Anuj Kumar

2015-01-01T23:59:59.000Z

40

Space  

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Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
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41

Old Galaxies at High Redshift  

E-Print Network [OSTI]

The most passive galaxies at high redshift are unlikely to be identified by either narrow-band emission-line searches, or by Lyman limit searches (both techniques which have been highlighted at this meeting) simply because such selection methods rely on the presence of a strong ultraviolet component. Selection on the basis of extreme radio power has also proved to yield optically active objects with the majority of high-redshift objects studied to date displaying complex elongated optical/UV morphologies, relatively blue optical-ultraviolet continuum colours, and strong emission lines. These features, coupled with the failure to detect any spectral signatures of old stars at $z > 1$, has led to the suggestion that these galaxies are being observed close to or even during a general epoch of formation. However, we have recently demonstrated that radio selection at significantly fainter (mJy) flux densities can be used to identify apparently passively evolving elliptical galaxies at high redshift. Deep Keck spectra have now been obtained for two such objects yielding absorption line redshifts $z \\simeq 1.5$; 53W091 at $z = 1.552$ (Dunlop et al. 1996) and most recently 53W069 at $z = 1.432$. The ultraviolet SEDs of these galaxies indicate minimum ages $> 3$ Gyr while, as stressed in this article, the strength of the reddenning-independent ultraviolet spectral breaks actually indicate a greater minimum age of 5 Gyr for both objects assuming solar metallicity. Since the spectra comprise the integrated light of each galaxy to radii greater than $r_e$, I argue that it is difficult to justify the adoption of significantly super-solar metallicity in interpreting these data. It thus seems hard to escape the conclusion that $\\Omega_0 5$).

James Dunlop

1997-05-13T23:59:59.000Z

42

Tax distortions and global climate policy  

E-Print Network [OSTI]

We consider the efficiency implications of policies to reduce global carbon emissions in a world with pre-existing tax distortions. We first show that the weak double dividend, the proposition that the welfare improvement ...

Babiker, Mustafa H.M.; Metcalf, Gilbert E.; Reilly, John M.

43

Optimal risk sharing under distorted probabilities  

E-Print Network [OSTI]

theory of risk. Geneva Pap. Risk Insurance Theory 25, 141–A. : Two-persons ef?cient risk-sharing and equilibria for36(2), 189–223 (2008) Optimal risk sharing under distorted

Ludkovski, Michael; Young, Virginia R.

2009-01-01T23:59:59.000Z

44

The Galaxy Structure-Redshift Relationship  

E-Print Network [OSTI]

There exists a gradual, but persistent, evolutionary effect in the galaxy population such that galaxy structure and morphology change with redshift. This galaxy structure-redshift relationship is such that an increasingly large fraction of all bright and massive galaxies at redshifts 2 < z < 3 are morphologically peculiar at wavelengths from rest-frame ultraviolet to rest-frame optical. There are however examples of morphologically selected spirals and ellipticals at all redshifts up to z ~ 3. At lower redshift, the bright galaxy population smoothly transforms into normal ellipticals and spirals. The rate of this transformation strongly depends on redshift, with the swiftest evolution occurring between 1 < z < 2. This review characterizes the galaxy structure-redshift relationship, discusses its various physical causes, and how these are revealing the mechanisms responsible for galaxy formation.

Christopher Conselice

2004-07-21T23:59:59.000Z

45

Coulomb Distortion in the Inelastic Regime  

SciTech Connect (OSTI)

The Coulomb distortion effects have been for a long time neglected in deep inelastic scattering for the good reason that the incident energies were very high. But for energies in the range of earlier data from SLAC or at JLab, the Coulomb distortion could have the potential consequence of affecting the A-dependence of the EMC effect and of the longitudinal to transverse virtual photon absorption cross section ratio $R(x,Q^2)$.

Patricia Solvignon, Dave Gaskell, John Arrington

2009-09-01T23:59:59.000Z

46

Coulomb distortion in the inelastic regime  

SciTech Connect (OSTI)

The Coulomb distortion effects have been for a long time neglected in deep inelastic scattering for the good reason that the incident energies were very high. But for energies in the range of earlier data from SLAC or at JLab, the Coulomb distortion could have the potential consequence of affecting the A-dependence of the EMC effect and of the longitudinal to transverse virtual photon absorption cross section ratio R(x,Q{sup 2}).

Solvignon, P.; Arrington, J. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Gaskell, D. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States)

2009-09-02T23:59:59.000Z

47

Coulomb distortion in the inelastic regime.  

SciTech Connect (OSTI)

The Coulomb distortion effects have been for a long time neglected in deep inelastic scattering for the good reason that the incident energies were very high. But for energies in the range of earlier data from SLAC or at JLab, the Coulomb distortion could have the potential consequence of affecting the A-dependence of the EMC effect and of the longitudinal to transverse virtual photon absorption cross section ratio R(x,Q{sup 2}).

Solvignon, P.; Gaskell, D.; Arrington, J.; Physics; Thomas Jefferson National Accelerator Facility

2009-01-01T23:59:59.000Z

48

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

49

Redshift of photons penetrating a hot plasma  

E-Print Network [OSTI]

A new interaction, plasma redshift, is derived, which is important only when photons penetrate a hot, sparse electron plasma. The derivation of plasma redshift is based entirely on conventional axioms of physics. When photons penetrate a cold and dense plasma, they lose energy through ionization and excitation, Compton scattering on the individual electrons, and Raman scattering on the plasma frequency. But in sparse hot plasma, such as in the solar corona, the photons lose energy also in plasma redshift. The energy loss per electron in the plasma redshift is about equal to the product of the photon's energy and one half of the Compton cross-section per electron. In quiescent solar corona, this heating starts in the transition zone to the corona and is a major fraction of the coronal heating. Plasma redshift contributes also to the heating of the interstellar plasma, the galactic corona, and the intergalactic plasma. Plasma redshift explains the solar redshifts, the redshifts of the galactic corona, the cosmological redshifts, the cosmic microwave background, and the X-ray background. The plasma redshift explains the observed magnitude-redshift relation for supernovae SNe Ia without the big bang, dark matter, or dark energy. There is no cosmic time dilation. The universe is not expanding. The plasma redshift, when compared with experiments, shows that the photons' classical gravitational redshifts are reversed as the photons move from the Sun to the Earth. This is a quantum mechanical effect. As seen from the Earth, a repulsion force acts on the photons. This means that there is no need for Einstein's Lambda term. The universe is quasi-static, infinite, and everlasting.

Ari Brynjolfsson

2005-10-07T23:59:59.000Z

50

The effects of output transformers on distortion in audio amplifiers  

E-Print Network [OSTI]

Introduction ~. . . . . . . . , . . . . . . ~. . . . . 7 Frequency Discrimination. . . . . . . . . . . . . . . . 9 Harmonic Distortion. ~ ~. . . . ~ 21 Distortion by the Intermodulationmethod. . . . . . . . 47 Comparison of Harmonic and Intermodulation... current in the primary as a function of frequency . 19 Output voltage of transformer 3 without direct current in the primary as a function of frequency 20 Block diagram for measuring distortion by the harmonic method 26 Per cent harmonic distortion...

Lanier, Ross Edwin

1949-01-01T23:59:59.000Z

51

RESEARCH ARTICLE Distortions of perceived auditory and visual space following  

E-Print Network [OSTI]

Ross W. Deas � Neil W. Roach � Paul V. McGraw Received: 18 February 2008 / Accepted: 4 August 2008 on these cues (King 1993). R. W. Deas (&) Á N. W. Roach Á P. V. McGraw Visual Neuroscience Group, School

Nottingham, University of

52

Constraints of Dark Energy at High Redshift  

E-Print Network [OSTI]

Constrains of dark energy (DE) at high redshift from current and mock future observational data are obtained. It is found that present data give poor constraints of DE even beyond redshift z=0.4, and mock future 2298 type Ia supernove data only give a little improvement of the constraints. We analyze in detail why constraints of DE decrease rapidly with the increasing of redshift. Then we try to improve the constraints of DE at high redshift. It is shown that the most efficient way is to improve the error of observations.

Qiping Su; Rong-Gen Cai

2014-08-24T23:59:59.000Z

53

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

54

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

55

Reflective optical imaging systems with balanced distortion  

DOE Patents [OSTI]

Optical systems compatible with extreme ultraviolet radiation comprising four reflective elements for projecting a mask image onto a substrate are described. The four optical elements comprise, in order from object to image, convex, concave, convex and concave mirrors. The optical systems are particularly suited for step and scan lithography methods. The invention enables the use of larger slit dimensions associated with ring field scanning optics, improves wafer throughput, and allows higher semiconductor device density. The inventive optical systems are characterized by reduced dynamic distortion because the static distortion is balanced across the slit width.

Hudyma, Russell M. (San Ramon, CA)

2001-01-01T23:59:59.000Z

56

Reflective optical imaging system with balanced distortion  

DOE Patents [OSTI]

An optical system compatible with short wavelength (extreme ultraviolet) An optical system compatible with short wavelength (extreme ultraviolet) radiation comprising four reflective elements for projecting a mask image onto a substrate. The four optical elements comprise, in order from object to image, convex, concave, convex and concave mirrors. The optical system is particularly suited for step and scan lithography methods. The invention enables the use of larger slit dimensions associated with ring field scanning optics, improves wafer throughput and allows higher semiconductor device density. The inventive optical system is characterized by reduced dynamic distortion because the static distortion is balanced across the slit width.

Chapman, Henry N. (Sunol, CA); Hudyma, Russell M. (San Ramon, CA); Shafer, David R. (Fairfield, CT); Sweeney, Donald W. (San Ramon, CA)

1999-01-01T23:59:59.000Z

57

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

58

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

59

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

60

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

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

Element Abundances at High Redshifts  

E-Print Network [OSTI]

I review measurements of element abundances in different components of the high redshift universe, including the Lyman alpha forest, damped Lyman alpha systems, and Lyman break galaxies. Although progress is being made in all three areas, recent work has also produced some surprises and shown that established ideas about the nature of the damped Lyman alpha systems in particular may be too simplistic. Overall, our knowledge of metal abundances at high z is still very sketchy. Most significantly, there seems to be an order of magnitude shortfall in the comoving density of metals which have been measured up to now compared with those produced by the star formation activity seen in Lyman break galaxies. At least some of the missing metals are likely to be in hot gas in galactic halos and proto-clusters.

Max Pettini

1999-02-11T23:59:59.000Z

62

Surface brightness in plasma-redshift cosmology  

E-Print Network [OSTI]

In 2001 Lori M. Lubin and Allan Sandage, using big-bang cosmology for interpreting the data, found the surface brightness of galaxies to be inversely proportional to about the third power of (1+z), while the contemporary big-bang cosmology predicts that the surface brightness is inversely proportional to the fourth power of (1+z). In contrast, these surface brightness observations are in agreement with the predictions of the plasma-redshift cosmology. Lubin and Sandage (2001) and Barden et al. (2005), who surmised the big-bang expansion, interpreted the observations to indicate that the diameters of galaxies are inversely proportional to (1+z). In contrast, when assuming plasma-redshift cosmology, the diameters of galaxies are observed to be constant independent of redshift and any expansion. Lubin and Sandage (2001) and Barden et al. (2005), when using big-bang cosmology, observed the average absolute magnitude of galaxies to decrease with redshift; while in plasma redshift cosmology it is a constant. Lubin and Sandage and Barden et al. suggested that a coherent evolution could explain the discrepancy between the observed relations and those predicted in the big-bang cosmology. We have failed to find support for this explanation. We consider the observed relations between the redshift and the surface-brightness, the galaxy diameter, and the absolute magnitude to be robust confirmations of plasma-redshift cosmology.

Ari Brynjolfsson

2006-05-31T23:59:59.000Z

63

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

64

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

65

Multi-object spectroscopy of low redshift EIS clusters. III. Properties of optically selected clusters  

E-Print Network [OSTI]

We have carried out an investigation of the properties of low redshift EIS clusters using both spectroscopy and imaging data. We present new redshifts for 738 galaxies in 21 ESO Imaging Survey (EIS) Cluster fields. We use the ``gap''-technique to search for significant overdensities in redshift space and to identify groups/clusters of galaxies corresponding to the original EIS matched filter cluster candidates. In this way we spectroscopically confirm 20 of the 21 cluster candidates with a matched-filter estimated redshift z_MF=0.2. We have now obtained spectroscopic redshifts for 34 EIS cluster candidates with z_MF=0.2 (see also Hansen et al., 2002; Olsen et al., 2003). Of those we spectroscopically confirm 32 with redshifts ranging from z=0.064 to 0.283. We find that: 1) the velocity dispersions of the systems range from sigma_v<=130km/s to sigma_v=1200km/s, typical of galaxy groups to rich clusters; 2) richnesses corresponding to Abell classes R<=1; and 3) concentration indices ranging from C=0.2 to C=1.2. From the analysis of the colours of the galaxy populations we find that 53% of the spectroscopically confirmed systems have a ``significant'' red sequence. These systems are on average richer and have higher velocity dispersions. We find that the colour of the red sequence galaxies matches passive stellar evolution predictions.

L. F. Olsen; C. Benoist; L. da Costa; L. Hansen; H. E. Jorgensen

2005-02-25T23:59:59.000Z

66

CORRECTION OF BUTT-WELDING INDUCED DISTORTIONS BY LASER FORMING  

E-Print Network [OSTI]

CORRECTION OF BUTT-WELDING INDUCED DISTORTIONS BY LASER FORMING Peng Cheng, Andrew J. Birnbaum, Y Egland Technology and Solutions Division Caterpillar Inc. Peoria, IL KEYWORDS Welding, Distortion, Correction, Laser Forming ABSTRACT Welding-induced distortion is an intrinsic phenomenon arising due

Yao, Y. Lawrence

67

PSYCHOACOUSTICALLY CONSTRAINED AND DISTORTION MINIMIZED SPEECH ENHANCEMENT ALGORITHM  

E-Print Network [OSTI]

PSYCHOACOUSTICALLY CONSTRAINED AND DISTORTION MINIMIZED SPEECH ENHANCEMENT ALGORITHM Seokhwan Jo minimized speech enhancement algorithm is considered. In general, noise reduction leads to speech distortion, and thus, the goal of an enhancement al- gorithm should reduce noise and speech distortion so that both

Yoo, Chang D.

68

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

69

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

70

High redshift star-forming galaxies in absorption and emission  

E-Print Network [OSTI]

-forming galaxies in the redshift range 1 emission filling of absorption lines which has implications...

Quider, Anna Marie

2011-07-12T23:59:59.000Z

71

Cosmic Streaming Field at Low Redshift  

E-Print Network [OSTI]

We study the expansion of the nearby Universe using a sample of Type Ia supernovae at redshifts below 0.08. These supernovae allow peculiar velocities to be measured at unprecedented precision. We have investigated in detail the possibility of a varying Hubble constant with redshift and found no evidence of a monopole term for the nearby Universe. A large scale streaming motion is found at an amplitude of about $340^{63}_{-71}$ km/sec, aligned in the direction of $(l_0, b_0) = (312^{\\rm o}.0^{13.5}_{-7.4}, 25^{\\rm o}.7^{8.0}_{-9.2})$, which is close to the direction of the center of Shapley supercluster of galaxies. The large scale streaming motion is best fit by a function involving a strong bipolar term. The streaming velocity field extends from the lowest redshift ($\\sim 0.007$) to beyond 0.025 and likely out to even higher redshifts. The velocity field at redshift below 0.01 can be equally well described by a dipole field or by the same bipolar streaming velocity field that reaches out to beyond $z \\sim 0.025$. We are also able to deduce a robust estimate of the random velocity component of the peculiar velocity field. Within the volume of redshift below 0.01 (weighted average redshift of $\\sim$ 0.067), this thermal component is found to be about 270 km/sec. After correcting this smooth streaming motion, we are able to significantly improve the Hubble expansion fits of these supernovae. The CMAGIC method gives a dramatic decrease of $\\chi^2$ from 90 to 63 for 69 degrees of freedom, and yields a residual scatter of only 0.12 magnitude; the maximum light method gives also a moderate improvement.

Lifan Wang

2007-05-04T23:59:59.000Z

72

CMB and Molecules at High Redshift  

E-Print Network [OSTI]

It becomes possible now to detect cold molecules at high redshift in the millimeter domain. Since the first discovery in 1992 by Brown and van den Bout of CO lines at z=2.28 in a gravitationally lensed starburst galaxy, nearly ten objects are now known to possess large quantities of molecular gas beyond z=1 and up to z = 5, through millimeter and sub-millimeter emission lines. The continuum dust emission is the most easily detected: in the mm domain, the emission is stronger for the more redshifted objects. For the CO lines, the situation is less favorable, and the reported detections are helped by gravitational amplification. The increase of the CMB temperature T_{bg} with redshift helps the rotational line excitation (especially at high z), but not its detection. Absorption in front of quasars is a more sensitive probe of cold gas at high redshift, able to detect individual clouds of a few solar masses (instead of 10^{10} Mo for emission). From the diffuse components, one can measure the cosmic black body temperature as a function of redshift. The high column densities component allow to observe important molecules not observable from the ground, like O2, H2O and LiH for example.

F. Combes

1999-01-17T23:59:59.000Z

73

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

74

Redshifts of Emission Line Objects in the Hubble Ultra Deep Field  

E-Print Network [OSTI]

We present redshifts for 115 emission line objects in the Hubble Ultra Deep Field (HUDF) identified through the GRism ACS Program for Extragalactic Science (GRAPES) project using the slitless grism spectroscopy mode of the ACS Camera on the Hubble Space Telescope (HST). The sample was selected by an emission line search on all extracted 1-dimensional GRAPES spectra. We identify the emission lines using line wavelength ratios where multiple lines are detected in the grism wavelength range (5800A 25 mag). Such emission lines would likely remain undiscovered without our deep survey. The emission line objects fall into 3 categories: 1) Most are low to moderate redshift galaxies (0 star forming galaxies with strong HII regions; 2) 9 are high redshift (4 < z < 7) Lyman-alpha emitters; and 3) at least 3 are candidate AGNs.

Chun Xu; Norbert Pirzkal; Sangeeta Malhotra; James E. Rhoads; Bahram Mobasher; Emanuele Daddi; Caryl Gronwall; Nimish P. Hathi; Nino Panagia; Henry C. Ferguson; Anton M. Koekemoer; Martin Kuemmel; Leonidas A. Moustakas; Anna Pasquali; Sperello di Serego Alighieri; Joel Vernet; Jeremy R. Walsh; Rogier Windhorst; Haojing Yan

2007-01-30T23:59:59.000Z

75

Atom Interferometers and the Gravitational Redshift  

E-Print Network [OSTI]

From the principle of equivalence, Einstein predicted that clocks slow down in a gravitational field. Since the general theory of relativity is based on the principle of equivalence, it is essential to test this prediction accurately. Muller, Peters and Chu claim that a reinterpretation of decade old experiments with atom interferometers leads to a sensitive test of this gravitational redshift effect at the Compton frequency. Wolf et al dispute this claim and adduce arguments against it. In this article, we distill these arguments to a single fundamental objection: an atom is NOT a clock ticking at the Compton frequency. We conclude that atom interferometry experiments conducted to date do not yield such sensitive tests of the gravitational redshift. Finally, we suggest a new interferometric experiment to measure the gravitational redshift, which realises a quantum version of the classical clock "paradox".

Supurna Sinha; Joseph Samuel

2011-05-16T23:59:59.000Z

76

Hubble constant from lensing in plasma-redshift cosmology, and intrinsic redshift of quasars  

E-Print Network [OSTI]

In a series of articles, we have shown that the newly discovered plasma-redshift cosmology gives a simpler, more accurate and consistent explanation of many cosmological phenomena than the big-bang cosmology. The SNe Ia observations are in better agreement with the magnitude-redshift relation predicted by the plasma redshift than that predicted by the multi-parameter big-bang cosmology. No deceleration or expansion parameters are needed. The plasma-redshift cosmology is flat and quasi-static on a large scale. The Hubble constant is no longer an expansion parameter, but is instead a measure of the average electron density along the line of sight towards an object. Perusal of the SNe Ia data and quasar data has shown that there is no time dilation. The conventional estimates of the Hubble constant from gravitational lensing observations use the big-bang cosmology for interpreting the observations. This has lead to a large spread and discordant estimates of the Hubble constant. The purpose of the present article is to show that the gravitational lensing observations are in agreement with the plasma-redshift cosmology, and to show how to evaluate the lensing observations based on the new plasma-redshift cosmology. The lensing observations also indicate that the quasars have large intrinsic redshifts.

Ari Brynjolfsson

2004-12-02T23:59:59.000Z

77

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

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

the efficiency of solid oxide fuel cells can be improved. Citation: Edmondson PD, WJ Weber, F Namavar, and Y Zhang.2011."Lattice Distortions and Oxygen Vacancies Produced in...

78

The inferred redshift distribution of the faint blue excess  

E-Print Network [OSTI]

We infer the redshift distribution of the faint blue galaxy excess (FBE) at B=23.5 by subtracting the predicted distribution of giant/normal galaxies from the observed N(z) distribution for all types. This is possible because of the recent deep {\\it Hubble Space Telescope} (HST) WFPC2 morphological number counts which have convincingly demonstrated that little evolution of the giant population is seen to B=26.0. The mean redshift of the FBE at B=23.5 is found to be _{FBE}=0.40 +/- 0.07 with upper and lower quartiles defined by z_{0.75}=0.58 +/- 0.05 and z_{0.25}=0.28 +/- 0.05, respectively. We compare this inferred FBE N(z) distribution to the predictions from three generic faint galaxy models: dwarf dominated (no evolution), pure luminosity evolution, and evolving dwarfs. The inferred FBE N(z) distribution strongly supports a hybrid evolving dwarf--rich model wherein a large population of dwarfs present at z=0.5 has subsequently faded to obscurity. The total integrated number density of dwarfs (down to M_{B}...

Driver, S P; Phillipps, S; Windhorst, R A; Driver, Simon P; Couch, Warrick J; Phillipps, Steven; Windhorst, Rogier A

1996-01-01T23:59:59.000Z

79

The inferred redshift distribution of the faint blue excess  

E-Print Network [OSTI]

We infer the redshift distribution of the faint blue galaxy excess (FBE) at B=23.5 by subtracting the predicted distribution of giant/normal galaxies from the observed N(z) distribution for all types. This is possible because of the recent deep {\\it Hubble Space Telescope} (HST) WFPC2 morphological number counts which have convincingly demonstrated that little evolution of the giant population is seen to B=26.0. The mean redshift of the FBE at B=23.5 is found to be _{FBE}=0.40 +/- 0.07 with upper and lower quartiles defined by z_{0.75}=0.58 +/- 0.05 and z_{0.25}=0.28 +/- 0.05, respectively. We compare this inferred FBE N(z) distribution to the predictions from three generic faint galaxy models: dwarf dominated (no evolution), pure luminosity evolution, and evolving dwarfs. The inferred FBE N(z) distribution strongly supports a hybrid evolving dwarf--rich model wherein a large population of dwarfs present at z=0.5 has subsequently faded to obscurity. The total integrated number density of dwarfs (down to M_{B}=-11) is estimated to be a factor of 20 times greater than that of E---Sc galaxies and the estimated fading to be 1.0 < \\Delta m < 1.4 mags. Thus, the dwarf population is estimated to be responsible for ~30% of the luminosity density locally, rising to ~57% at z=0.5.

Simon P. Driver; Warrick J. Couch; Steven Phillipps; Rogier A. Windhorst

1996-05-10T23:59:59.000Z

80

Plasma Redshift, Time Dilation, and Supernovas Ia  

E-Print Network [OSTI]

The measurements of the absolute magnitudes and redshifts of supernovas Ia show that conventional physics, which includes plasma redshift, fully explains the observed magnitude-redshift relation of the supernovas. The only parameter that is required is the Hubble constant, which in principle can be measured independently. The contemporary theory of the expansion of the universe (Big Bang) requires in addition to the Hubble constant several adjustable parameters, such as an initial explosion, the dark matter parameter, and a time adjustable dark energy parameter for explaining the supernova Ia data. The contemporary Big Bang theory also requires time dilation of distant events as an inherent premise. The contention is usually that the light curves of distant supernovas show or even prove the time dilation. In the present article, we challenge this assertion. We document and show that the previously reported data in fact indicate that there is no time dilation. The data reported by Riess et al. in the Astrophysical Journal in June 2004 confirm the plasma redshift, the absence of time dilation, dark matter, and dark energy.

Ari Brynjolfsson

2004-07-20T23:59:59.000Z

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.


81

High redshift Gamma-Ray Bursts  

E-Print Network [OSTI]

Ten years of operations of the Swift satellite have allow us to collect a small sample of long Gamma-Ray Bursts (GRBs) at redshift larger than six. I will review here the present status of this research field and discuss the possible use of GRBs as a fundamental new tool to explore the early Universe, complementary to quasar and galaxy surveys.

Salvaterra, R

2015-01-01T23:59:59.000Z

82

Dust and Molecules at High Redshift  

E-Print Network [OSTI]

In the last years, progress has been very rapid in the domain of molecules at high redshift, and we know in better detail now the molecular and dust content in several systems beyond z=1 and up to z = 5. The first discovery in 1992 by Brown and van den Bout of CO lines at z=2.28 in a gravitationally lensed starburst galaxy, strongly stimulated searches of other systems, but these were harder than foreseen, and less than 10 other systems have been discovered in CO emission. Redshifts range between 2 and 5, the largest being BR1202-0725 at z=4.69. Most of these systems, if not all, are gravitationally amplified objects. Some have been discovered first through their dust emission, relatively easy to detect because of the negative K-correction effect. The detection of all these systems could give an answer about the debated question of the star-formation rate as a function of redshift. The maximum of star-formation rate, found around z=2 from optical studies, could shift to higher z if the most remote objects are hidden by dust. Absorption in front of quasars can also probe cold gas at high redshift, taking advantage of very high spatial (milli arcsec) and spectral (30m/s) resolutions. From the diffuse components, one can measure the cosmic black body temperature as a function of redshift. All these preliminary studies will be carried out at large scales with future millimeter instruments, and some perspectives are given.

F. Combes

1998-12-23T23:59:59.000Z

83

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

84

Simulation of Heat Treatment Distortion R.A. Hardin1  

E-Print Network [OSTI]

quenched in water and in oil. Unfortunately, due to the lack of documentation on the heat treatment processSimulation of Heat Treatment Distortion R.A. Hardin1 and C. Beckermann2 1 Research Engineer, 2 Abstract This paper gives an overview of the problem of heat treatment stress and distortion and a review

Beckermann, Christoph

85

Minimization of welding residual stress and distortion in large structures  

E-Print Network [OSTI]

1 Minimization of welding residual stress and distortion in large structures P. Michaleris at Champaign Urbana, Urbana, IL Abstract Welding distortion in large structures is usually caused by buckling due to the residual stress. In cases where the design is fixed and minimum weld size requirements

Michaleris, Panagiotis

86

Stable radial distortion calibration by polynomial matrix inequalities programming  

E-Print Network [OSTI]

polynomials. Further, we show how to model these nonnegativities using polynomial matrix inequalities (PMI) and how to estimate the radial distortion parameters subject to PMI constraints using semidefinite to stabilize the shape of the distortion function. It is based on polynomial matrix inequalities (PMI

Henrion, Didier

87

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

88

Special Relativity in Quantum Phase Space  

E-Print Network [OSTI]

A phase space treatment of special relativity of quantum systems is developed. In this approach a quantum particle remains localized if subject to inertial transformations, the localization occurring in a finite phase space area. Unlike non-relativistic transformations, relativistic transformations generally distort the phase space distribution function, being equivalent to aberrations in optics.

Daniela Dragoman

2008-03-06T23:59:59.000Z

89

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

90

Chemical Elements at High and Low Redshifts  

E-Print Network [OSTI]

The past few years have seen a steady progress in the determination of element abundances at high redshifts, with new and more accurate measures of metallicities in star-forming galaxies, in QSO absorbers, and in the intergalactic medium. We have also become more aware of the limitations of the tools at our disposal in such endeavours. I summarise these recent developments and--in tune with the theme of this meeting--consider the clues which chemical abundance studies offer to the links between the high redshift galaxy populations and today's galaxies. The new data are `fleshing out' the overall picture of element abundances at redshifts z = 2 - 3 which has been gradually coming into focus over the last decade. In particular, we can now account for at least 40% of the metals produced by the global star formation activity in the universe from the Big Bang to z = 2.5, and we have strong indications of where the remainder are likely to be found.

Max Pettini

2006-03-02T23:59:59.000Z

91

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

92

Strain Accommodation By Facile WO6 Octahedral Distortion and...  

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

to other BO6 octahedra in ABO3 structured perovskite oxides, the WO6 octahedra in tungsten trioxide (WO3) can withstand a much larger degree of distortion and tilting to...

93

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

94

Statistics of Voids in the 2dF Galaxy Redshift Survey  

E-Print Network [OSTI]

We present a statistical analysis of voids in the 2dF galaxy redshift survey (2dFGRS). In order to detect the voids, we have developed two robust algorithms. We define voids as non-overlapping maximal spheres empty of halos or galaxies with mass or luminosity above a given one. We search for voids in cosmological $N$-Body simulations to test the performance of our void finders. We obtain and analyze the void statistics for several volume-limited samples for the North Galactic Strip (NGP) and the South Galactic Strip (SGP) constructed from the 2dFGRS full data release. We find that the results obtained from the NGP and the SGP are statistically compatible. From the results of several statistical tests we conclude that voids are essentially uncorrelated, with at most a mild anticorrelation and that there is a dependence of the void number density on redshift at least at the 99.5% confidence level. We develop a technique to correct the distortion caused by the fact that we use the redshift as the radial coordinate. We calibrate this technique with mock catalogues and find that the correction might be of some relevance to carry out accurate inferences from void statistics. We study the statistics of the galaxies inside nine nearby voids. We find that galaxies in voids are not randomly distributed: they form structures like filaments. We also obtain the galaxy number density profile in voids. This profile follow a similar but steeper trend to that follow by halos in voids.

Santiago G. Patiri; Juan Betancort-Rijo; Francisco Prada; Anatoly Klypin; Stefan Gottlöber

2006-10-27T23:59:59.000Z

95

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

96

A vector field method on the distorted Fourier side and decay for wave equations with potentials  

E-Print Network [OSTI]

We study the Cauchy problem for the one-dimensional wave equation with an inverse square potential. We derive dispersive estimates, energy estimates, and estimates involving the scaling vector field, where the latter are obtained by employing a vector field method on the "distorted" Fourier side. In addition, we prove local energy decay estimates. Our results have immediate applications in the context of geometric evolution problems. The theory developed in this paper is fundamental for the proof of the co-dimension 1 stability of the catenoid under the vanishing mean curvature flow in Minkowski space.

Roland Donninger; Joachim Krieger

2014-06-03T23:59:59.000Z

97

Is a Classical Language Adequate in Assessing the Detectability of the Redshifted 21cm Signal from the Early Universe?  

E-Print Network [OSTI]

The classical radiometer equation is commonly used to calculate the detectability of the 21cm emission by diffuse cosmic hydrogen at high redshifts. However, the classical description is only valid in the regime where the occupation number of the photons in phase space is much larger than unity and they collectively behave as a classical electromagnetic field. At redshifts zenergy, of 68/(1+z) mK, the occupation number of the signal photons is smaller than unity. Neverethless, the radiometer equation can still be used in this regime because the weak signal is accompanied by a flood of foreground photons with a high occupation number (involving the synchrotron Galactic...

Loeb, Abraham

2008-01-01T23:59:59.000Z

98

Chemical Consequences of Heme Distortion and the Role of Heme Distortion in Signal Transduction of H-NOX Proteins  

E-Print Network [OSTI]

of wild-type Tt H-NOX as well as energy minimizations 19with energy minimizations and visual inspection of the wild-high- energy frontier orbitals. 81 Heme distortion in wild-

Olea, Jr., Charles

2010-01-01T23:59:59.000Z

99

HI at a Redshift of Zero  

E-Print Network [OSTI]

While LOFAR and the SKA will enable the study of HI at the epoch of reionization for the first time, expectations for the distribution of HI at that redshift depend on our understanding of the cosmological HI mass density at the present epoch and its variation with environment. We exploit a complete optical diameter and HI flux limited sample of galaxies in the local universe to derive a robust measurement of the HIMF for masses log(M / M_{Sun}) > 7.4 which takes into account the effects of local large scale structure.

Christopher M. Springob

2004-11-17T23:59:59.000Z

100

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

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

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

102

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

103

Redshift Limits of BL Lacertae Objects from Optical Spectroscopy  

E-Print Network [OSTI]

Context: BL Lacertae objects have been the targets for numerous recent multiwavelength campaigns, continuum spectral variability studies, and theoretical spectral and variability modeling. A meaningful interpretation of the results of such studies requires a reliable knowledge of the objects' redshifts; however, the redshifts for many are still unknown or uncertain. Aims: Therefore, we hope to determine or constrain the redshifts of six BL Lac objects with unknown or poorly known redshifts. Methods: Observations were made of these objects with the MDM 2.4 m Hiltner telescope. Although no spectral features were detected, and thus no redshifts could be measured, lower redshift limits were assigned to the objects based on the expected equivalent widths of absorption features in their host galaxies. Redshifts were also estimated for some objects by assuming the host galaxies are standard candles and using host galaxy apparent magnitudes taken from the literature. Results: The commonly used redshift of $z=0.102$ for 1219+285 is almost certainly wrong, while the redshifts of the other objects studied remain undetermined.

J. D. Finke; J. C. Shields; M. Boettcher; S. Basu

2007-11-13T23:59:59.000Z

104

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

105

Absorption features of high redshift galactic winds  

E-Print Network [OSTI]

The environment of high-redshift galaxies is characterized by both wind-driven outflowing gas and gravitationally infalling streams. To investigate such galaxy-IGM interplay we have generated synthetic optical absorption line spectra piercing the volume surrounding a starbursting analog of a Lyman Break Galaxy selected in a $z \\approx 3$ output from a SPH simulation, including a detailed treatment of mechanical feedback from winds. Distributions for several observable species (HI, CIII, CIV, SiII, SiIII, SiIV, OVI, OVII, and OVIII) have been derived by post-processing the simulation outputs. The hot wind material is characterized by the presence of high-ionization species such as OVI, OVII, and OVIII (the latter two observable only in X-ray bands); the colder ($Tgas clumps. However, both line profile and Pixel Optical Depth analysis of the synthetic spectra show that the intergalactic filament in which the wind-blowing galaxy is embedded produces absorption signatures that closely mimic those of the wind environment. We conclude that may be difficult to clearly identify wind-blowing galaxies and their complex gaseous environment at high redshift in optical QSO absorption-line spectra based solely on the observed ion absorption patterns.

A. P. M. Fangano; A. Ferrara; P. Richter

2007-06-11T23:59:59.000Z

106

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

107

Multi-object spectroscopy of low-redshift EIS clusters IV. Reliability of matched-filter results at z~0.3-0.4  

E-Print Network [OSTI]

abridged) In this paper we present new redshifts for 747 galaxies in 23 ESO Imaging Survey (EIS) cluster fields. We use the "gap"-technique to search for significant overdensities in redshift space for identifying groups/clusters of galaxies. In this way we spectroscopically confirm systems in 10 of the 23 cluster candidate fields with a matched-filter estimated redshift z_MF=0.3-0.4 and with spectroscopic redshifts in the range from z=0.158 to z=0.534. We find that the systems identified in the present paper span a broad range of one-dimensional velocity dispersion (175-497 km/s) and richness (12L*EIS cluster candidates with estimated redshifts z<=0.4. We have measured a total of 1954 galaxy redshifts in the range z=0.0065 to z=0.6706. Of the 58 systems we confirm 42 (~75%) with redshifts between z=0.095 and z=0.534.

L. F. Grove; L. da Costa; C. Benoist

2008-09-26T23:59:59.000Z

108

Neutrino signal of supernova shock wave propagation:MSW distortion of the spectra and neucleosynthesis  

E-Print Network [OSTI]

Neutrino signal of supernova shock wave propagation:MSW distortion of the spectra and neucleosynthesis

Kawagoe, S; Sumiyoshi, K; Yamada, H; Kajino, T

2006-01-01T23:59:59.000Z

109

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

110

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

111

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

112

Low thermal distortion extreme-UV lithography reticle  

DOE Patents [OSTI]

Thermal distortion of reticles or masks can be significantly reduced by emissivity engineering, i.e., the selective placement or omission of coatings on the reticle. Reflective reticles so fabricated exhibit enhanced heat transfer thereby reducing the level of thermal distortion and ultimately improving the quality of the transcription of the reticle pattern onto the wafer. Reflective reticles include a substrate having an active region that defines the mask pattern and non-active region(s) that are characterized by a surface that has a higher emissivity than that of the active region. The non-active regions are not coated with the radiation reflective material.

Gianoulakis, Steven E. (Albuquerque, NM); Ray-Chaudhuri, Avijit K. (Livermore, CA)

2001-01-01T23:59:59.000Z

113

Low thermal distortion extreme-UV lithography reticle  

DOE Patents [OSTI]

Thermal distortion of reticles or masks can be significantly reduced by emissivity engineering, i.e., the selective placement or omission of coatings on the reticle. Reflective reticles so fabricated exhibit enhanced heat transfer thereby reducing the level of thermal distortion and ultimately improving the quality of the transcription of the reticle pattern onto the wafer. Reflective reticles include a substrate having an active region that defines the mask pattern and non-active region(s) that are characterized by a surface that has a higher emissivity than that of the active region. The non-active regions are not coated with the radiation reflective material.

Gianoulakis, Steven E. (Albuquerque, NM); Ray-Chaudhuri, Avijit K. (Livermore, CA)

2002-01-01T23:59:59.000Z

114

Low thermal distortion Extreme-UV lithography reticle and method  

DOE Patents [OSTI]

Thermal distortion of reticles or masks can be significantly reduced by emissivity engineering, i.e., the selective placement or omission of coatings on the reticle. Reflective reticles so fabricated exhibit enhanced heat transfer thereby reducing the level of thermal distortion and ultimately improving the quality of the transcription of the reticle pattern onto the wafer. Reflective reticles include a substrate having an active region that defines the mask pattern and non-active region(s) that are characterized by a surface that has a higher emissivity than that of the active region. The non-active regions are not coated with the radiation reflective material.

Gianoulakis, Steven E. (Albuquerque, NM); Ray-Chaudhuri, Avijit K. (Livermore, CA)

2002-01-01T23:59:59.000Z

115

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

116

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

117

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

118

Tariff Reform in the Presence of Sector-specific Distortions  

E-Print Network [OSTI]

chosen the highest or lowest tariff. gives: ASSUMPTION 1'.the optimal .distortion (tariff, or (tQ dZ T dt - sQ d y Tsensitive to existing fixed tariffs t = in f i nr.s a and

BEGHIN, JOHN C; Karp, Larry

1990-01-01T23:59:59.000Z

119

System for interferometric distortion measurements that define an optical path  

DOE Patents [OSTI]

An improved phase-shifting point diffraction interferometer can measure both distortion and wavefront aberration. In the preferred embodiment, the interferometer employs an object-plane pinhole array comprising a plurality of object pinholes located between the test optic and the source of electromagnetic radiation and an image-plane mask array that is positioned in the image plane of the test optic. The image-plane mask array comprises a plurality of test windows and corresponding reference pinholes, wherein the positions of the plurality of pinholes in the object-plane pinhole array register with those of the plurality of test windows in image-plane mask array. Electromagnetic radiation that is directed into a first pinhole of object-plane pinhole array thereby creating a first corresponding test beam image on the image-plane mask array. Where distortion is relatively small, it can be directly measured interferometrically by measuring the separation distance between and the orientation of the test beam and reference-beam pinhole and repeating this process for at least one other pinhole of the plurality of pinholes of the object-plane pinhole array. Where the distortion is relative large, it can be measured by using interferometry to direct the stage motion, of a stage supporting the image-plane mask array, and then use the final stage motion as a measure of the distortion.

Bokor, Jeffrey; Naulleau, Patrick

2003-05-06T23:59:59.000Z

120

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

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.


121

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

122

RATE DISTORTION OPTIMIZED DOCUMENT CODING USING RESOLUTION ENHANCED RENDERING  

E-Print Network [OSTI]

RATE DISTORTION OPTIMIZED DOCUMENT CODING USING RESOLUTION ENHANCED RENDERING Guotong Feng , Hui at a fixed bit rate. This method, which we call resolution enhanced rendering (RER), works by adaptively enhanced rendering (RER) for jointly optimizing the THIS WORK IS SUPPORTED BY THE XEROX FOUNDATION. MRC

123

Wouthuysen-Field coupling strength and application to high-redshift 21 cm radiation  

E-Print Network [OSTI]

The first UV sources in the universe are expected to have coupled the HI spin temperature to the gas kinetic temperature via scattering in the Lyman-alpha resonance [the Wouthuysen-Field (WF) effect]. By establishing an HI spin temperature different from the temperature of the CMB, the WF effect should allow observations of HI during the reionization epoch in the redshifted 21 cm line. This paper investigates four mechanisms that can affect the strength of the WF effect that were not previously considered: (1) Photons redshifting into the HI Lyman resonances may excite an H atom and result in a radiative cascade terminating in two-photon 2s->1s emission, rather than always degrading to Lyman-alpha as usually assumed. (2) The fine structure of the Lyman-alpha resonance alters the photon frequency distribution and leads to a suppression of the scattering rate. (3) The spin-flip scatterings change the frequency of the photon and cause the photon spectrum to relax not to the kinetic temperature of the gas but to a temperature between the kinetic and spin temperatures, effectively reducing the strength of the Wouthuysen-Field coupling. (4) Near line centre, a photon can change its frequency by several times the line width in a single scattering event, thus potentially invalidating the usual calculation of the Lyman-alpha spectral distortion based on the diffusion approximation. It is shown that (1) suppresses the WF coupling strength by a factor of up to ~2, while (2) and (3) are important only at low kinetic temperatures. Effect (4) has a =2K. If the pre-reionization IGM was efficiently heated by X-rays, only effect (1) is important. Fitting formulae are provided for the range of T_k>=2K and Gunn-Peterson optical depth 10^5--10^7. [ABRIDGED

Christopher M. Hirata

2005-12-05T23:59:59.000Z

124

Liquid crystal-enabled electroosmosis through spatial charge separation in distorted regions as a novel mechanism of electrokinetics  

E-Print Network [OSTI]

Electrically-controlled dynamics of fluids and particles at microscales is a fascinating area of research with applications ranging from microfluidics and sensing to sorting of biomolecules. The driving mechanisms are electric forces acting on spatially separated charges in an isotropic medium such as water. Here we demonstrate that anisotropic conductivity of liquid crystals enables new mechanism of highly efficient electro-osmosis rooted in space charging of regions with distorted orientation. The electric field acts on these distortion-separated charges to induce liquid crystal-enabled electro-osmosis (LCEO). LCEO velocities grow with the square of the field, which allows one to use an AC field to drive steady flows and to avoid electrode damage. Ionic currents in liquid crystals that have been traditionally considered as an undesirable feature in displays, offer a broad platform for versatile applications such as liquid crystal enabled electrokinetics, micropumping and mixing.

Israel Lazo; Chenhui Peng; Jie Xiang; Sergij V. Shiyanovskii; Oleg D. Lavrentovich

2014-08-11T23:59:59.000Z

125

Discrete Intrinsic Redshifts from Quasars to Normal Galaxies  

E-Print Network [OSTI]

It is pointed out that the discrete velocities found by Tifft in galaxies are harmonically related to the discrete intrinsic redshifts found in quasars. All are harmonically related to the constant 0.062 +/- 0.001, and this is the fourth independent analysis in which the redshift increment 0.062 has been shown to be significant. It is concluded that there is a quantized component in the redshift of both quasars and galaxies that has a common origin and is unlikely to be Doppler-related.

M. B. Bell

2002-11-05T23:59:59.000Z

126

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

127

Welding Induced Alignment Distortion in Dual-in-Line LD Packages  

SciTech Connect (OSTI)

The tolerance for the movement of a single mode fiber relative to the laser is extremely tight, a submicron movement can often lead to a significant misalignment and thus the reduction in the power coupled into the fiber. Among various fiber pigtailing assembly technologies, pulsed laser welding is the method with submicron accuracy and is most conducive to automation. However, the melting-solidification process during laser welding can often distort the pre-achieved fiber-optic alignment. This Welding-Induced-Alignment-Distortion (WIAD) is a serious concern and significantly affects the yield for single mode fiber pigtailing to a semiconductor laser. In this paper, effect of laser welding sequence on WIAD in a dual-in-line packager is numerically investigated by means of Finite Element Method (FEM). Optimal welding sequence may minimize WIAD in dual-in-line package. Additionally, unsymmetrical space between fiber and U-channel induced by laser welding of U-channel–to-plate in DIP LD packages is found to have obvious effect on WIAD.

Liu, Wenning N.; Sun, Xin; Khaleel, Mohammad A.; Shi, Frank G.

2007-11-11T23:59:59.000Z

128

The Environment of Galaxies at Low Redshift  

E-Print Network [OSTI]

We compare environmental effects in two analogous samples of galaxies, one from the Sloan Digital Sky Survey (SDSS) and the other from a semi-analytic model (SAM) based on the Millennium Simulation (MS), to test to what extent current SAMs of galaxy formation are reproducing environmental effects. We estimate the large-scale environment of each galaxy using a Bayesian density estimator based on distances to all ten nearest neighbors and compare broad-band photometric properties of the two samples as a function of environment. The feedbacks implemented in the semi-analytic model produce a qualitatively correct galaxy population with similar environmental dependence as that seen in SDSS galaxies. In detail, however, the colors of MS galaxies exhibit an exaggerated dependence on environment: the field contains too many blue galaxies while clusters contain too many red galaxies, compared to the SDSS sample. We also find that the MS contains a population of highly clustered, relatively faint red galaxies with velocity dispersions comparable to their Hubble flow. Such high-density galaxies, if they exist, would be overlooked in any low-redshift survey since their membership to a cluster cannot be determined due to the "Fingers of God" effect.

Nicolas B. Cowan; Zeljko Ivezic

2008-01-15T23:59:59.000Z

129

System to estimate ages and redshifts for radio galaxies  

E-Print Network [OSTI]

The system allowing a user to operate with simulated curves of spectral energy distribution (SED) and to estimate ages and redshifts by photometric data at server {\\bf sed.sao.ru} is described.

O. V. Verkhodanov; A. I. Kopylov; N. V. Verkhodanova; O. P. Zhelenkova; V. N. Chernenkov; Yu. N. Parijskij; N. S. Soboleva; A. V. Temirova

2001-12-06T23:59:59.000Z

130

Structure and kinematics of galaxy clusters I. The redshift catalogue  

E-Print Network [OSTI]

An extensive redshift survey has been conducted on a sample of 15 nearby (0.01 < z < 0.05) clusters of galaxies. A total number of 860 redshifts were determined by fitting of emission--lines and/or cross-correlation techniques. Of this sample, 735 galaxies are within 0.2--0.8 Mpc ($H_0$ = 50 km/s/Mpc) of the center of clusters. Approximate morphological types are available for most of the galaxies. A comparison of the present redshifts with published data allows an extensive error analysis. The agreement is excellent with the most modern data, showing a zero point error of 5 km/s and an overall consistency of the measurements and their uncertainties. We estimate our redshifts to have mean random errors around 30 km/s. A population analysis of the clusters will be given in a forthcoming paper.

P. Stein

1996-01-12T23:59:59.000Z

131

Prediction of Welding Distortion Panagiotis Michaleris and Andrew DeBiccari  

E-Print Network [OSTI]

1 Prediction of Welding Distortion Panagiotis Michaleris and Andrew DeBiccari Edison Welding Institute Columbus, Ohio ABSTRACT. This paper presents a numerical analysis technique for predicting welding induced distortion. The technique combines two dimensional welding simulations with three dimensional

Michaleris, Panagiotis

132

Modelling Thermoelastic Distortion of Optics Using Elastodynamic Reciprocity  

E-Print Network [OSTI]

Thermoelastic distortion resulting from optical absorption by transmissive and reflective optics can cause unacceptable changes in optical systems that employ high power beams. In advanced-generation laser-interferometric gravitational wave detectors for example, optical absorption is expected to result in wavefront distortions that would compromise the sensitivity of the detector; thus necessitating the use of adaptive thermal compensation. Unfortunately, these systems have long thermal time constants and so predictive feed-forward control systems could be required - but the finite-element analysis is computationally expensive. We describe here the use of the Betti-Maxwell elastodynamic reciprocity theorem to calculate the response of linear elastic bodies (optics) to heating that has arbitrary spatial distribution. We demonstrate using a simple example, that it can yield accurate results in computational times that are significantly less than those required for finite-element analyses.

King, Eleanor; Veitch, Peter; Levin, Yuri

2015-01-01T23:59:59.000Z

133

The Hubble series: Convergence properties and redshift variables  

E-Print Network [OSTI]

In cosmography, cosmokinetics, and cosmology it is quite common to encounter physical quantities expanded as a Taylor series in the cosmological redshift z. Perhaps the most well-known exemplar of this phenomenon is the Hubble relation between distance and redshift. However, we now have considerable high-z data available, for instance we have supernova data at least back to redshift z=1.75. This opens up the theoretical question as to whether or not the Hubble series (or more generally any series expansion based on the z-redshift) actually converges for large redshift? Based on a combination of mathematical and physical reasoning, we argue that the radius of convergence of any series expansion in z is less than or equal to 1, and that z-based expansions must break down for z>1, corresponding to a universe less than half its current size. Furthermore, we shall argue on theoretical grounds for the utility of an improved parameterization y=z/(1+z). In terms of the y-redshift we again argue that the radius of convergence of any series expansion in y is less than or equal to 1, so that y-based expansions are likely to be good all the way back to the big bang y=1, but that y-based expansions must break down for y<-1, now corresponding to a universe more than twice its current size.

Celine Cattoen; Matt Visser

2007-10-10T23:59:59.000Z

134

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

135

CMB distortions from damping of acoustic waves produced by cosmic strings  

SciTech Connect (OSTI)

We study diffusion damping of acoustic waves in the photon-baryon fluid due to cosmic strings, and calculate the induced ?- and y-type spectral distortions of the cosmic microwave background. For cosmic strings with tension within current bounds, their contribution to the spectral distortions is subdominant compared to the distortions from primordial density perturbations.

Tashiro, Hiroyuki; Sabancilar, Eray; Vachaspati, Tanmay, E-mail: Hiroyuki.Tashiro@asu.edu, E-mail: Eray.Sabancilar@asu.edu, E-mail: tvachasp@asu.edu [Physics Department, Arizona State University, Tempe, Arizona 85287 (United States)

2013-08-01T23:59:59.000Z

136

The redshifts of bright sub-mm sources  

E-Print Network [OSTI]

One of the key goals in observational cosmology over the next few years will be to establish the redshift distribution of the recently-discovered sub-mm source population. In this brief review I discuss and summarize the redshift information which has been gleaned to date for the ~ 50 bright sub-mm sources which have been uncovered via the six main classes of survey performed with SCUBA on the JCMT over the last 2-3 years. Despite the biases inherent in some of these surveys, and the crudeness of the redshift information available in others, I conclude that all current information suggests that only 10-15 % of luminous sub-mm sources lie at z < 2, and that the median redshift of this population is z ~ 3. I suggest that such a high median redshift is arguably not unexpected given current theories designed to explain the correlation between black-hole mass and spheroid mass found at low redshift. In such scenarios, peak AGN emission is expected to correspond to, or even to cause termination of major star-formation activity in the host spheroid. In contrast, maximum dust emission is expected to occur roughly half-way through the star-formation process. Given that optical emission from bright quasars peaks at z = 2.5, dust-emission from massive ellipticals might be reasonably expected to peak at some point in the preceding ~ 1 Gyr, at z ~ 3. Confirmation or refutation of this picture requires significantly-improved redshift information on bright samples of SCUBA sources.

James S. Dunlop

2001-01-17T23:59:59.000Z

137

Data augmentation for machine learning redshifts applied to SDSS galaxies  

E-Print Network [OSTI]

We present analyses of data augmentation for machine learning redshift estimation. Data augmentation makes a training sample more closely resemble a test sample, if the two base samples differ, in order to improve measured statistics of the test sample. We perform two sets of analyses by selecting 800k (1.7M) SDSS DR8 (DR10) galaxies with spectroscopic redshifts. We construct a base training set by imposing an artificial r band apparent magnitude cut to select only bright galaxies and then augment this base training set by using simulations and by applying the K-correct package to artificially place training set galaxies at a higher redshift. We obtain redshift estimates for the remaining faint galaxy sample, which are not used during training. We find that data augmentation reduces the error on the recovered redshifts by 40% in both sets of analyses, when compared to the difference in error between the ideal case and the non augmented case. The outlier fraction is also reduced by at least 10% and up to 80% u...

Hoyle, Ben; Bonnett, Christopher; Seitz, Stella; Weller, Jochen

2015-01-01T23:59:59.000Z

138

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

139

Is a Classical Language Adequate in Assessing the Detectability of the Redshifted 21cm Signal from the Early Universe?  

E-Print Network [OSTI]

The classical radiometer equation is commonly used to calculate the detectability of the 21cm emission by diffuse cosmic hydrogen at high redshifts. However, the classical description is only valid in the regime where the occupation number of the photons in phase space is much larger than unity and they collectively behave as a classical electromagnetic field. At redshifts zenergy, of 68/(1+z) mK, the occupation number of the signal photons is smaller than unity. Neverethless, the radiometer equation can still be used in this regime because the weak signal is accompanied by a flood of foreground photons with a high occupation number (involving the synchrotron Galactic emission and the cosmic microwave background). As the signal photons are not individually distinguishable, the combined signal+foreground population of photons has a high occupation number, thus justifying the use of the radiometer equation.

Abraham Loeb

2008-03-26T23:59:59.000Z

140

Near-Infrared Imaging of a Group or Cluster of Galaxies at a Redshift of 2.39  

E-Print Network [OSTI]

At z=2.39, the cluster around 53W002 is one of the most distant groups or clusters of galaxies known to date. At this redshift the 4000A-break falls between the J and H bands, thus our infrared observations are designed to identify cluster members by a red J-H colour. Out of the 42 objects we have detected in the field, we find ten galaxies with J-H>1.0 and K>18.8, redder and fainter than the radio galaxy, and consistent with the presence of a 4000A-break at the cluster redshift. Two of these reddest galaxies have been confirmed spectroscopically. The colours, sizes and location of these infrared-selected galaxies suggest a cluster much more similar to those nearby than revealed by Hubble Space Telescope observations alone.

Ian Waddington

1998-01-15T23:59:59.000Z

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
to obtain the most current and comprehensive results.


141

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

142

Ice emission and the redshifts of submillimeter sources  

E-Print Network [OSTI]

Observations at submillimeter wavelengths have revealed a population of sources thought to be at relatively large redshifts. The position of the 850 $\\mu$m passband on the Rayleigh-Jeans portion of the Planck function leads to a maximum redshift estimate of $z\\sim$4.5 since sources will not retain their redshift independent brightness close to the peak of the Planck function and thus drop out of surveys. Here we review evidence that ice absorption is present in the spectra of local ultraluminous infrared galaxies which are often taken as analogs for the 850 $\\mu$m source population. We consider the implication of this absorption for ice induced spectral structure at far infrared wavelengths and present marginal astronomical evidence that amorphous ice may have a feature similar to crystalline ice near 150 $\\mu$m. Recent corroborative laboratory evidence is supportive of this conclusion. It is argued that early metal enrichment by pair instability SN may lead to a high ice content relative to refractory dust at high redshift and a fairly robust detection of ice emission in a $z=6.42$ quasar is presented. It is further shown that ice emission is needed to understand the 450 $\\mu$m sources observed in the GOODS-N field. We are thus encouraged to apply far infrared ice emission models to the available observations of HDF 850.1, the brightest submillimeter source in the {\\it Hubble Deep Field}. We suggest that a redshift as large as 13 may need to be considered for this source, nearly a factor of three above the usual top estimate. Inclusion of the possibility of far infrared ice emission in the spectral energy distributions of model sources generally broadens the range of redshifts to be considered for submillimeter sources compared to models without ice emission.

C. C. Dudley; M. Imanishi; P. R. Maloney

2008-02-12T23:59:59.000Z

143

The characteristic stellar mass as a function of redshift  

E-Print Network [OSTI]

We present a model for the star formation process during the initial collapse of dark matter haloes at redshifts z=0-30. We derive a simple expression for the characteristic stellar mass scale during this initial burst of star formation. In our picture, this characteristic scale reflects both the minimum temperature to which the gas can cool (determined by the metallicity and the temperature of the cosmic microwave background) and the pressure of overlying baryons in the collapsing halo. This prescription reproduces both the large mass scales found in simulations of Population III star formation and the near solar values observed for star formation at low redshift.

Cathie J. Clarke; Volker Bromm

2003-05-11T23:59:59.000Z

144

Multi-object spectroscopy of low redshift EIS clusters. II  

E-Print Network [OSTI]

We present the results of carrying out multi-object spectroscopy in 10 EIS cluster fields. Based on the list of 345 galaxy redshifts we identify significant 3D-density enhancements. For 9 of the EIS clusters we identify significant 3D-concentrations corresponding to the originally detected cluster candidate. We find redshifts in the range 0.097<=z<=0.257 which is in good agreement with the matched filter estimate of z_MF=0.2. We estimate velocity dispersions in the range 219-1160 km/s for the confirmed clusters.

L. F. Olsen; L. Hansen; H. E. Joergensen; C. Benoist; L. da Costa; M. Scodeggio

2003-08-01T23:59:59.000Z

145

Multi-object spectroscopy of low redshift EIS clusters. I  

E-Print Network [OSTI]

We report the results of the first multi-object spectroscopic observations at the Danish 1.54m telescope at La Silla, Chile. Observations of five cluster candidates from the ESO Imaging Survey Cluster Candidate Catalog are described. From these observations we confirm the reality of the five clusters with measured redshifts of 0.11<=z<=0.35. We estimate velocity dispersions in the range 294-621km/s indicating rather poor clusters. This, and the measured cluster redshifts are consistent with the results of the matched filter procedure applied to produce the Cluster Candidate Catalog.

L. Hansen; L. F. Olsen; H. E. Jorgensen

2002-04-23T23:59:59.000Z

146

LMFBR fuel bundle distortion characterization using neutron tomography and potting  

SciTech Connect (OSTI)

A standard liquid metal fast breeder reactor (LMFBR) subassembly used in the Experimental Breeder Reactor II (EBRII) was investigated for fuel bundle distortion by both nondestructive and destructive methods, and the results from both methods were compared. The nondestructive method employed neutron tomography to reconstruct the locations of fuel elements through the use of a maximum entropy reconstruction algorithm known as MENT. The destructive method consisted of ''potting'' (a technique that embeds and permanently fixes the fuel elements in a solid matrix) the subassembly and then cutting and polishing the individual sections. The comparison indicated that the tomography reconstruction provided good results in describing the bundle geometry and spacer-wire locations, with the overall resolution being on the order of a spacer-wire diameter. A dimensional consistency check indicated that the element and spacer-wire dimensions were accurately reproduced in the reconstruction. It was found that in situ fuel elements deform axially in a helical spiral and that the reconstruction was able to identify this helical distortion to within approximately half of a spacerwire diameter.

Betten, P.R.; Tow, D.M.

1984-05-01T23:59:59.000Z

147

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

148

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

149

The Wolf effect and the redshift of quasars  

SciTech Connect (OSTI)

We consider a simple model, based on currently accepted models for active galactic nuclei, for a quasi-stellar object (QSO or "quasar") and examine the influence that correlation-induced spectral changes ("The Wolf Effect") may have upon the redshifts of the optical emission lines.

James, Daniel F.V.

1998-01-23T23:59:59.000Z

150

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

151

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

152

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

153

RVSAO 2.0: Digital Redshifts and Radial Velocities  

E-Print Network [OSTI]

RVSAO is a set of programs to obtain redshifts and radial velocities from digital spectra. RVSAO operates in the IRAF(Tody 1986, 1993) environment. The heart of the system is xcsao, which implements the cross-correlation method, and is a direct descendant of the system built by Tonry and Davis (1979). emsao uses intelligent heuristics to search for emission lines in spectra, then fits them to obtain a redshift. sumspec shifts and sums spectra to build templates for cross-correlation. linespec builds synthetic spectra given a list of spectral lines. bcvcorr corrects velocities for the motion of the earth. We discuss in detail the parameters necessary to run xcsao and emsao properly. We discuss the reliability and error associated with xcsao derived redshifts. We develop an internal error estimator, and we show how large, stable surveys can be used to develop more accurate error estimators. We develop a new methodology for building spectral templates for galaxy redshifts. We show how to obtain correlation velocities using emission line templates. Emission line correlations are substantially more efficient than the previous standard technique, automated emission line fitting. We compare the use of RVSAO with new methods, which use Singular Value Decomposition and $\\chi^2$ fitting techniques.

Michael J. Kurtz; Douglas J. Mink

1998-03-25T23:59:59.000Z

154

The Wolf effect and the Redshift of Quasars  

E-Print Network [OSTI]

We consider a simple model, based on currently accepted models for active galactic nuclei, for a quasi-stellar object (QSO or ``quasar'') and examine the influence that correlation- induced spectral changes (``The Wolf Effect'') may have upon the redshifts of the optical emission lines.

Daniel F. V. James

1998-07-20T23:59:59.000Z

155

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

156

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

157

UV Spectroscopy of Type Ia Supernovae at Low- and High-Redshift  

E-Print Network [OSTI]

Spectroscopy of Type Ia Supernovae at Low- and High-RedshiftUV properties of Type Ia Supernovae. The low-redshift studyULDA Access Guide No. 6: Supernovae, The Netherlands: ESA

Nugent, Peter

2005-01-01T23:59:59.000Z

158

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

159

Coexistence of Weak Ferromagnetism and Polar Lattice Distortion...  

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

that are isostructural with acentric LiNbO3 (space group R3c). Optical second harmonic generation and magnetometry demonstrate lattice polarization at room temperature and...

160

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

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

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

162

The Canada-France Deep Fields III: Photometric Redshift Distribution to I(AB) ~ 24  

E-Print Network [OSTI]

We compute accurate redshift distributions to I(AB) = 24 and R(AB) = 24.5 using photometric redshifts estimated from six-band UBVRIZ photometry in the Canada-France Deep Fields-Photometric Redshift Survey (CFDF-PRS). Our photometric redshift algorithm is calibrated using hundreds of CFRS spectroscopic redshifts in the same fields. The dispersion in redshift is \\sigma/(1+z) \\la 0.04 to the CFRS depth of I(AB) = 22.5, rising to \\sigma/(1+z) \\la 0.06 at our nominal magnitude and redshift limits of I(AB) = 24 and z \\le 1.3, respectively. We describe a new method to compute N(z) that incorporates the full redshift likelihood functions in a Bayesian iterative analysis and we demonstrate in extensive Monte Carlo simulations that it is superior to distributions calculated using simple maximum likelihood redshifts. The field-to-field differences in the redshift distributions, while not unexpected theoretically, are substantial even on 30' scales. We provide I(AB) and R(AB) redshift distributions, median redshifts, and parametrized fits of our results in various magnitude ranges, accounting for both random and systematic errors in the analysis.

M. Brodwin; S. J. Lilly; C. Porciani; H. J. McCracken; O. Le Fevre; S. Foucaud; D. Crampton; Y. Mellier

2006-07-21T23:59:59.000Z

163

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

164

Space of Spaces  

E-Print Network [OSTI]

Wheeler emphasized the study of Superspace - the space of 3-geometries on a spatial manifold of fixed topology. This is a configuration space for GR; knowledge of configuration spaces is useful as regards dynamics and QM.In this Article I consider furthmore generalized configuration spaces to all levels within the conventional `equipped sets' paradigm of mathematical structure used in fundamental Theoretical Physics. This covers A) the more familiar issue of topology change in the sense of topological manifolds (tied to cobordisms), including via pinched manifolds. B) The less familiar issue of not regarding as fixed the yet deeper levels of structure: topological spaces themselves (and their metric space subcase), collections of subsets and sets. Isham has previously presented quantization schemes for a number of these. I consider some classical preliminaries for this program, aside from the most obvious (classical dynamics for each). Rather, I provide I) to all levels Relational and Background Independence criteria, which have Problem of Time facets as consequences. I demonstrate that many of these issues descend all the way down, whilst also documenting at which level the others cease to apply. II) Probability theory on configuration spaces. In fact such a stochastic treatment is how to further mathematize the hitherto fairly formal and sketchy subject of records theory (a type of formultion of quantum gravity). Along these lines I provide a number of further examples of records theories. This is in addition to Kendall's shape statistics being the example corresponding to relational mechanics models. To this example I now add 1) Cech cohomology, 2) Kendall's random sets, 3) the lattice of topologies on a fixed set. I finally consider 4) sheaves, both as a generalization of Cech cohomology and in connection to the study of stratified manifolds such as Superspace itself.

Edward Anderson

2014-11-30T23:59:59.000Z

165

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

166

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

167

Virtually distortion-free imaging system for large field, high resolution lithography  

DOE Patents [OSTI]

Virtually distortion free large field high resolution imaging is performed using an imaging system which contains large field distortion or field curvature. A reticle is imaged in one direction through the optical system to form an encoded mask. The encoded mask is then imaged back through the imaging system onto a wafer positioned at the reticle position.

Hawryluk, A.M.; Ceglio, N.M.

1993-01-05T23:59:59.000Z

168

MULTIZONE NEAR-END SPEECH ENHANCEMENT UNDER OPTIMAL SECOND-ORDER MAGNITUDE DISTORTION  

E-Print Network [OSTI]

MULTIZONE NEAR-END SPEECH ENHANCEMENT UNDER OPTIMAL SECOND-ORDER MAGNITUDE DISTORTION Jo~ao B.c.hendriks@tudelft.nl ABSTRACT In this article, we address near-end speech enhancement for a sce- nario where there are several-end speech enhancement, multizone, second-order magnitude distortion, public address system 1. INTRODUCTION

169

PREDICTION OF HEAT TREATMENT DISTORTION OF CAST STEEL C-RINGS  

E-Print Network [OSTI]

PREDICTION OF HEAT TREATMENT DISTORTION OF CAST STEEL C-RINGS Brandon Elliott Brooks1 and Christoph extensive rework or redesign, recasting, or through additional machining steps. Predicting heat treatment. There has been extensive interest in the prediction of heat treatment distortion via computer simulation

Beckermann, Christoph

170

BLIND COMPENSATION OF NONLINEAR DISTORTIONS VIA SPARSITY RECOVERY Leonardo T. Duarte1  

E-Print Network [OSTI]

BLIND COMPENSATION OF NONLINEAR DISTORTIONS VIA SPARSITY RECOVERY Leonardo T. Duarte1 , Ricardo.jutten@gipsa-lab.grenoble-inp.fr ABSTRACT In this work, we address the problem of compensating a non- linear memoryless system in a blind a representative set of experiments on synthetic data. Index Terms-- Blind compensation, nonlinear distortion

Paris-Sud XI, Université de

171

Blind Compensation of Nonlinear Distortions : Application to Source Separation of Post-Nonlinear  

E-Print Network [OSTI]

1 Blind Compensation of Nonlinear Distortions : Application to Source Separation of Post of blind compensation of nonlinear distortions. Our approach relies on the assumption that the input approached is considered in the development of a two-stage method for blind source separation (BSS) in post

Paris-Sud XI, Université de

172

Matrix Decomposition-Based Data Distortion Techniques for Privacy Preservation in Data Mining  

E-Print Network [OSTI]

. The second is to modify the data mining algorithms so that they allow data mining operations on distributedMatrix Decomposition-Based Data Distortion Techniques for Privacy Preservation in Data Mining Jun-Based Data Distortion Techniques for Privacy Preservation in Data Mining Jun Zhang and Jie Wang, University

Zhang, Jun

173

Transition redshift in $f(T)$ cosmology and observational constraints  

E-Print Network [OSTI]

We extract constraints on the transition redshift $z_{tr}$, determining the onset of cosmic acceleration, predicted by an effective cosmographic construction, in the framework of $f(T)$ gravity. In particular, employing cosmography we obtain bounds on the viable $f(T)$ forms and their derivatives. Since this procedure is model independent, as long as the scalar curvature is fixed, we are able to determine intervals for $z_{tr}$. In this way we guarantee that the Solar-System constraints are preserved and moreover we extract bounds on the transition time and the free parameters of the scenario. We find that the transition redshifts predicted by $f(T)$ cosmology, although compatible with the standard $\\Lambda$CDM predictions, are slightly smaller. Finally, in order to obtain observational constraints on $f(T)$ cosmology, we perform a Monte Carlo fitting using supernova data, involving the most recent union 2.1 data set.

Capozziello, Salvatore; Saridakis, Emmanuel N

2015-01-01T23:59:59.000Z

174

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

175

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

176

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

2012-06-24T23:59:59.000Z

177

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

178

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

179

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

180

POPULATION III STARS AND REMNANTS IN HIGH-REDSHIFT GALAXIES  

SciTech Connect (OSTI)

Recent simulations of Population III star formation have suggested that some fraction form in binary systems, in addition to having a characteristic mass of tens of solar masses. The deaths of metal-free stars result in the initial chemical enrichment of the universe and the production of the first stellar-mass black holes. Here we present a cosmological adaptive mesh refinement simulation of an overdense region that forms a few 10{sup 9} M{sub Sun} dark matter halos and over 13,000 Population III stars by redshift 15. We find that most halos do not form Population III stars until they reach M{sub vir} {approx} 10{sup 7} M{sub Sun} because this biased region is quickly enriched from both Population III and galaxies, which also produce high levels of ultraviolet radiation that suppress H{sub 2} formation. Nevertheless, Population III stars continue to form, albeit in more massive halos, at a rate of {approx}10{sup -4} M{sub Sun} yr{sup -1} Mpc{sup -3} at redshift 15. The most massive starless halo has a mass of 7 Multiplication-Sign 10{sup 7} M{sub Sun }, which could host massive black hole formation through the direct gaseous collapse scenario. We show that the multiplicity of the Population III remnants grows with halo mass above 10{sup 8} M{sub Sun }, culminating in 50 remnants located in 10{sup 9} M{sub Sun} halos on average. This has implications that high-mass X-ray binaries and intermediate-mass black holes that originate from metal-free stars may be abundant in high-redshift galaxies.

Xu Hao; Norman, Michael L. [Center for Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093 (United States); Wise, John H., E-mail: hxu@ucsd.edu, E-mail: mlnorman@ucsd.edu, E-mail: jwise@gatech.edu [Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, GA 30332 (United States)

2013-08-20T23:59:59.000Z

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.


181

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

182

Is space expanding in the Friedmann universe models?  

E-Print Network [OSTI]

The interpretation of the expanding universe as an expansion of space has recently been challenged. From the geodesic equation in Friedmann universe models and the empty Milne model, we argue that a Newtonian or special relativistic analysis is not applicable on large scales, and the general relativistic interpretation in terms of expanding space has the advantage of being globally consistent. We also show that the cosmic redshift, interpreted as an expansion effect, containts both the Doppler effect and the gravitational frequency shift.

Oyvind Gron; Oystein Elgaroy

2006-09-18T23:59:59.000Z

183

A Spectroscopic Survey of the Fields of 28 Strong Gravitational Lenses: The Redshift Catalog  

E-Print Network [OSTI]

We present the spectroscopic redshift catalog from a wide-field survey of the fields of 28 galaxy-mass strong gravitational lenses. We discuss the acquisition and reduction of the survey data, collected over 40 nights of 6.5m MMT and Magellan time, employing four different multi-object spectrographs. We determine that no biases are introduced by combining datasets obtained with different instrument/spectrograph combinations. Special care is taken to determine redshift uncertainties using repeat observations. The redshift catalog consists of 9768 new and unique galaxy redshifts. 82.4% of the catalog redshifts are between z=0.1 and z=0.7, and the catalog median redshift is z=0.36. The data from this survey will be used to study the lens environments and line-of-sight structures to gain a better understanding of the effects of large scale structure on lens statistics and lens-derived parameters.

Momcheva, Ivelina; Cool, Richard J; Keeton, Charles R; Zabludoff, Ann I

2015-01-01T23:59:59.000Z

184

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

185

6 Equalization of Channels with ISI Many practical channels are bandlimited and linearly distort the  

E-Print Network [OSTI]

244 6 Equalization of Channels with ISI Many practical channels are bandlimited and linearly distort the transmit signal. In this case, the resulting ISI channel has to be equalized for reliable

Pulfrey, David L.

186

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...

187

A restoration model of distorted electron density in wave-cutoff probe measurement  

SciTech Connect (OSTI)

This study investigates the problem of electron density distortion and how the density can be restored in a wave-cutoff probe. Despite recent plasma diagnostics research using a wave-cutoff probe, the problem of electron density distortion caused by plasma conditions has not been resolved. Experimental results indicate that electron density measured using the wave-cutoff method is highly susceptible to variations in the probe tip gap. This electron density distortion is caused by the bulk plasma disturbance between probe tips, and it must be removed for calculating the absolute electron density. To do this, a detailed analytic model was developed using the power balance equation near probe tips. This model demonstrates the characteristics of plasma distortion in wave-cutoff probe measurement and successfully restored the absolute value of electron density with varying probe tip gaps.

Jun, Hyun-Su, E-mail: mtsconst@kaist.ac.kr; Lee, Yun-Seong [Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of)] [Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of)

2014-02-15T23:59:59.000Z

188

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

189

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

E-Print Network [OSTI]

The primary focus of this thesis is to present a framework to develop higher order global differentiability local approximations for 2-D and 3-D distorted element geometries. The necessity and superiority of higher order global differentiability...

Maduri, Rajesh Kumar

2008-02-01T23:59:59.000Z

190

Progress in studies of Electron-Cloud-Induced Optics Distortions at CESRTA  

E-Print Network [OSTI]

OF ELECTRON-CLOUD-INDUCED OPTICS DISTORTIONS AT CESRTA J.A.beam emittance, lattice optics,and the secondary-electronlinear colliders. linear optics arising from electron cloud

Crittenden, J.A.

2010-01-01T23:59:59.000Z

191

Relative stereociliary motion in a hair bundle opposes amplification at distortion frequencies  

E-Print Network [OSTI]

Direct gating of mechanoelectrical-transduction channels by mechanical force is a basic feature of hair cells that assures fast transduction and underpins the mechanical amplification of acoustic inputs. But the associated nonlinearity - the gating compliance - inevitably distorts signals. Because reducing distortion would make the ear a better detector, we sought mechanisms with that effect. Mimicking in vivo stimulation, we used stiff probes to displace individual hair bundles at physiological amplitudes and measured the coherence and phase of the relative stereociliary motions with a dual-beam differential interferometer. Although stereocilia moved coherently and in phase at the stimulus frequencies, large phase lags at the frequencies of the internally generated distortion products indicated dissipative relative motions. Tip links engaged these relative modes and decreased the coherence in both stimulated and free hair bundles. These results show that a hair bundle breaks into a highly dissipative serial arrangement of stereocilia at distortion frequencies, precluding their amplification.

Andrei S. Kozlov; Thomas Risler; Armin J. Hinterwirth; A. J. Hudspeth

2012-03-08T23:59:59.000Z

192

Progress Report on the Berkeley/Anglo-Australian Observatory High-Redshift Supernova Search  

E-Print Network [OSTI]

photometry curve for type Ia supernovae and the redshift vsdistributions for observed supernovae. Figure 5 from Millermain efforts related to supernovae in progress at Berkeley.

Goldhaber, G.

2008-01-01T23:59:59.000Z

193

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

194

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

195

Galaxy Bulges at Mid and High-Redshift  

E-Print Network [OSTI]

Bulges are a major galaxy component in the nearby universe, and are one of the primary features that differentiates and defines galaxies. The origin of bulges can be directly probed in part by examining distant galaxies to search for high redshift bulges, and to study the properties of bulges in formation. We review the evidence for bulges at high redshift in this article, and how by studying bulges through a variety of approaches, including morphological, colour, and stellar mass selection, we can determine when and how these systems assembled. We argue that the majority of the most massive 'classical' bulges are in place by z ~ 1.5 - 2, and likely formed very early through major mergers. Other, likely lower mass, bulges form through a secular process along with their disks. Direct observations suggest that these two formation processes are occurring, as spheroids are commonly seen at z > 1, as are disks and spiral galaxies in the form of luminous diffuse objects, clump-clusters, and chain galaxies. However, bulge+disk systems are relatively rare until z ~ 1, suggesting that this structural assembly occurred relatively late.

Christopher J. Conselice

2007-09-28T23:59:59.000Z

196

The SDSS Coadd: A Galaxy Photometric Redshift Catalog  

SciTech Connect (OSTI)

We present and describe a catalog of galaxy photometric redshifts (photo-z's) for the Sloan Digital Sky Survey (SDSS) Coadd Data. We use the Artificial Neural Network (ANN) technique to calculate photo-z's and the Nearest Neighbor Error (NNE) method to estimate photo-z errors for {approx} 13 million objects classified as galaxies in the coadd with r < 24.5. The photo-z and photo-z error estimators are trained and validated on a sample of {approx} 89, 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 (CNOC2), the Deep Extragalactic Evolutionary Probe Data Release 3(DEEP2 DR3), the SDSS-III's Baryon Oscillation Spectroscopic Survey (BOSS), the Visible imaging Multi-Object Spectrograph - Very Large Telescope Deep Survey (VVDS) 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} = 0.036. After presenting our results and quality tests, we provide a short guide for users accessing the public data.

Reis, Ribamar R.R.; /Fermilab /Rio de Janeiro Federal U.; Soares-Santos, Marcelle; /Fermilab /Inst. Geo. Astron., Havana /Sao Paulo U.; Annis, James; /Fermilab; Dodelson, Scott; /Fermilab /Chicago U. /Chicago U., KICP; Hao, Jiangang; /Fermilab; Johnston, David; /Fermilab; Kubo, Jeffrey; /Fermilab; Lin, Huan; /Fermilab; Seo, Hee-Jong; /UC, Berkeley; Simet, Melanie; /Chicago U.

2011-11-01T23:59:59.000Z

197

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

198

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

199

Non-equilibrium Lorentz gas on a curved space  

E-Print Network [OSTI]

The periodic Lorentz gas with external field and iso-kinetic thermostat is equivalent, by conformal transformation, to a billiard with expanding phase-space and slightly distorted scatterers, for which the trajectories are straight lines. A further time rescaling allows to keep the speed constant in that new geometry. In the hyperbolic regime, the stationary state of this billiard is characterized by a phase-space contraction rate, equal to that of the iso-kinetic Lorentz gas. In contrast to the iso-kinetic Lorentz gas where phase-space contraction occurs in the bulk, the phase-space contraction rate here takes place at the periodic boundaries.

Felipe Barra; Thomas Gilbert

2007-01-12T23:59:59.000Z

200

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.


201

Is a classical language adequate in assessing the detectability of the redshifted 21 cm signal from the early Universe?  

SciTech Connect (OSTI)

The classical radiometer equation is commonly used to calculate the detectability of the 21 cm emission by diffuse cosmic hydrogen at high redshifts. However, the classical description is only valid in the regime where the occupation number of the photons in phase space is much larger than unity and they collectively behave as a classical electromagnetic field. At redshifts z{approx}<20, the spin temperature of the intergalactic gas is dictated by the radiation from galaxies and the brightness temperature of the emitting gas is in the range of mK, independently from the existence of the cosmic microwave background. In regions where the observed brightness temperature of the 21 cm signal is smaller than the observed photon energy, h{nu} = 68(1+z){sup -1} mK, the occupation number of the signal photons is smaller than unity. Nevertheless, the radiometer equation can still be used in this regime because the weak signal is accompanied by a flood of foreground photons with a high occupation number (involving the synchrotron galactic emission and the cosmic microwave background). As the signal photons are not individually distinguishable, the combined signal+foreground population of photons has a high occupation number, thus justifying the use of the radiometer equation.

Loeb, Abraham, E-mail: aloeb@cfa.harvard.edu [Astronomy Department, Harvard University, 60 Garden Street, Cambridge, MA 02138 (United States)

2008-04-15T23:59:59.000Z

202

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

203

Space Kimchi  

E-Print Network [OSTI]

Broadcast Transcript: In space, no one can hear you scream... but did you know that in space no one can detect your smell either? The smell-taste connection means that food in space is not only weightless but tasteless, too. What's a flavor...

Hacker, Randi; Oborny, Jaimie; Tsutsui, William

2006-07-05T23:59:59.000Z

204

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

205

Weighing black holes from zero to high redshift  

E-Print Network [OSTI]

The application of the virial theorem provides a tool to estimate supermassive black hole (BH) masses in large samples of active galactic nuclei (AGN) with broad emission lines at all redshifts and luminosities, if the broad line region (BLR) is gravitationally bound. In this paper we discuss the importance of radiation forces on BLR clouds arising from the deposition of momentum by ionizing photons. Such radiation forces counteract gravitational ones and, if not taken into account, BH masses can be severely underestimated. We provide virial relations corrected for the effect of radiation pressure and we discuss their physical meaning and application. If these corrections to virial masses, calibrated with low luminosity objects, are extrapolated to high luminosities then the BLRs of most quasars might be gravitationally unbound. The importance of radiation forces in high luminosity objects must be thoroughly investigated to assess the reliability of quasar BH masses.

A. Marconi; D. Axon; R. Maiolino; T. Nagao; P. Pietrini; A. Robinson; G. Torricelli

2008-09-02T23:59:59.000Z

206

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

207

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

208

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

209

Awakening of The High Redshift Blazar CGRaBS J0809+5341  

E-Print Network [OSTI]

CGRaBS J0809+5341, a high redshift blazar at z = 2.144, underwent a giant optical outburst on 2014 April 19 when it brightened by $\\sim$5 mag and reached an unfiltered apparent magnitude of 15.7 mag. This implies an absolute magnitude of -30.5 mag, making it one of the brightest quasars in the Universe. This optical flaring triggered us to carry out observations during the decaying part of the flare covering a wide energy range using the {\\it Nuclear Spectroscopic Telescope Array}, {\\it Swift}, and ground based optical facilities. For the first time, the source is detected in $\\gamma$-rays by the Large Area Telescope onboard the {\\it Fermi Gamma-Ray Space Telescope}. A high optical polarization of $\\sim$10\\% is also observed. Using the Sloan Digital Sky Survey spectrum, accretion disk luminosity and black hole mass are estimated as $1.5 \\times 10^{45}$ erg s$^{-1}$ and $10^{8.4}~M_{\\odot}$ respectively. Using a single zone leptonic emission model, we reproduce the spectral energy distribution of the source du...

Paliya, Vaidehi S; Stalin, C S; Fabian, A C; Ramya, S; Covino, S; Tagliaferri, G; Sahayanathan, S; Ravikumar, C D

2015-01-01T23:59:59.000Z

210

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

211

CAIRNS: The Cluster And Infall Region Nearby Survey I. Redshifts and Mass Profiles  

E-Print Network [OSTI]

The CAIRNS (Cluster And Infall Region Nearby Survey) project is a spectroscopic survey of the infall regions surrounding eight nearby, rich, X-ray luminous clusters of galaxies. We collect 15665 redshifts (3471 new or remeasured) within \\sim 5-10 Mpc of the centers of the clusters, making it the largest study of the infall regions of clusters. We determine cluster membership and the mass profiles of the clusters based on the phase space distribution of the galaxies. All of the clusters display decreasing velocity dispersion profiles. The mass profiles are fit well by functional forms based on numerical simulations but exclude an isothermal sphere. Specifically, NFW and Hernquist models provide good descriptions of cluster mass profiles to their turnaround radii. Our sample shows that the predicted infall pattern is ubiquitous in rich, X-ray luminous clusters over a large mass range. The caustic mass estimates are in excellent agreement with independent X-ray estimates at small radii and with virial estimates at intermediate radii. The mean ratio of the caustic mass to the X-ray mass is 1.03\\pm0.11 and the mean ratio of the caustic mass to the virial mass (when corrected for the surface pressure term) is 0.93\\pm0.07. We further demonstrate that the caustic technique provides reasonable mass estimates even in merging clusters.

K. Rines; M. J. Geller; M. J. Kurtz; A. Diaferio

2003-06-25T23:59:59.000Z

212

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

213

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

214

$?$--Rindler space  

E-Print Network [OSTI]

In this paper we construct, and investigate some thermal properties of, the non-commutative counterpart of Rindler space, which we call $\\kappa$--Rindler space. This space is obtained by changing variables in the defining commutators of $\\kappa$--Minkowski space. We then re-derive the commutator structure of $\\kappa$--Rindler space with the help of an appropriate star product, obtained from the $\\kappa$--Minkowski one. Using this star product, following the idea of Padmanabhan, we find the leading order, $1/\\kappa$ correction to the Hawking thermal spectrum.

J. Kowalski-Glikman

2009-07-18T23:59:59.000Z

215

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

216

Evaluation of inherent distortions in the IIST facility using the RELAP5/MOD3 code  

SciTech Connect (OSTI)

The Institute of Nuclear Energy Research (INER) integral system test (IIST) facility is a reduced-height, reduced-pressure test facility constructed at INER that is used to simulate the thermal hydraulics of the Maanshan nuclear power plant (NPP). A small-scaled facility is not capable of simulating all the physical phenomena of an NPP because the behavior of an NPP during accidents is very complicated. Proper scaling then plays an important role in the design of a test facility to ensure the usefulness and applicability of experimental data obtained from a small-scaled facility. However, distortions caused by necessary compromises in the design and construction of a small-scaled test facility exist. The analysis here evaluates whether the inherent distortions in the IIST facility will distort the thermal-hydraulic behaviors of a natural-circulation experiment and influence the usefulness and applicability of the experimental data. Based on the current calculations, the IIST experimental results are found to be partially distorted. Appropriate consideration of and correction for these distortion effects are needed before the results of the IIST natural-circulation experiments can be used to reliably investigate the Maanshan NPP behavior expected by way of an appropriate scale-up procedure.

Ferng, Y.M. [Inst. of Nuclear Energy Research, Lung-Tan (Taiwan, Province of China)

1996-06-01T23:59:59.000Z

217

The structural distortion of the anti-perovskite nitride Ca sub 3 AsN  

SciTech Connect (OSTI)

The structure of the distorted anti-perovskite nitride Ca{sub 3}AsN has been studied both by neutron powder diffraction at 305 and 15 K and by X-ray powder diffraction at room temperature. Ca{sub 3}AsN is distorted to an orthorhombic cell with a and b {approximately} {radical}2a{prime} and c{approximately}2a{prime}, where a{prime} is the lattice constant of the ideal undistorted cubic anti-perovskite. The distortion is produced by tilting of octahedra of Ca{sub 6}N and results in six short and six long bond distances of the twelvefold coordinated As atom by Ca atoms.

Chern, M.Y.; DiSalvo, F.J. (Cornell Univ., Ithaca, NY (United States)); Parise, J.B. (State Univ. of New York, Stony Brook, NY (United States)); Goldstone, J.A. (Los Alamos National lab., NM (United States))

1992-02-01T23:59:59.000Z

218

Distortion of Schwarzschild-anti-de Sitter black holes to black strings  

E-Print Network [OSTI]

Motivated by the existence of black holes with various topologies in four-dimensional spacetimes with a negative cosmological constant, we study axisymmetric static solutions describing any large distortions of Schwarzschild-anti-de Sitter black holes parametrized by the mass $m$. Under the approximation such that $m$ is much larger than the anti-de Sitter radius, it is found that a cylindrically symmetric black string is obtained as a special limit of distorted spherical black holes. Such a prolonged distortion of the event horizon connecting a Schwarzschild-anti-de Sitter black hole to a black string is allowed without violating both the usual black hole thermodynamics and the hoop conjecture for the horizon circumference.

A. Tomimatsu

2005-06-25T23:59:59.000Z

219

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

220

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

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221

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.

222

Galaxy sizes as a function of environment at intermediate redshift from the ESO Distant Cluster Survey  

E-Print Network [OSTI]

In order to assess whether the environment has a significant effect on galaxy sizes, we compare the mass--size relations of cluster and field galaxies in the $0.4 1$), with early-type/passive galaxies in higher density environments growing earlier. Such dependence disappears at lower redshifts. Therefore, if the reported difference at higher-$z$ is real, the growth of field galaxies has caught up with that of cluster galaxies by $z\\sim1$. Any putative mechanism responsible for galaxy growth has to account for the existence of environmental differences at high redshift and their absence (or weakening) at lower redshifts.

Kelkar, Kshitija; Gray, Meghan E; Maltby, David; Vulcani, Benedetta; De Lucia, Gabriella; Poggianti, Bianca M; Zaritsky, Dennis

2015-01-01T23:59:59.000Z

223

Quantifying the Cosmic Web in the New Era of Redshift Surveys  

E-Print Network [OSTI]

Two main strategies have been implemented in mapping the local universe: whole-sky 'shallow' surveys and 'deep' surveys over limited parts of the sky. The two approaches complement each other in studying cosmography and statistical properties of the Universe. We summarise some results on the power spectrum of fluctuations and Wiener reconstruction of the density field from the 2dF Galaxy Redshift Survey (2dFGRS) of 230,000 redshifts. We then discuss future challenges in quantifying the web of cosmic structure in the on-going redshift surveys.

Ofer Lahav

2004-11-03T23:59:59.000Z

224

What fraction of stars formed in infrared galaxies at high redshift?  

E-Print Network [OSTI]

Star formation happens in two types of environment: ultraviolet-bright starbursts (like 30 Doradus and HII galaxies at low redshift and Lyman-break galaxies at high redshift) and infrared-bright dust-enshrouded regions (which may be moderately star-forming like Orion in the Galaxy or extreme like the core of Arp 220). In this work I will estimate how many of the stars in the local Universe formed in each type of environment, using observations of star-forming galaxies at all redshifts at different wavelengths and of the evolution of the field galaxy population.

Neil Trentham

2004-11-18T23:59:59.000Z

225

Extremely metal-poor gas at a redshift of 7  

E-Print Network [OSTI]

In typical astrophysical environments, the abundance of heavy elements ranges from 0.001 to 2 times the solar concentration. Lower abundances have been seen in select stars in the Milky Way's halo and in two quasar absorption systems at redshift z=3. These are widely interpreted as relics from the early universe, when all gas possessed a primordial chemistry. Before now there have been no direct abundance measurements from the first Gyr after the Big Bang, when the earliest stars began synthesizing elements. Here we report observations of hydrogen and heavy element absorption in a quasar spectrum at z=7.04, when the universe was just 772 Myr old (5.6% its present age). We detect a large column of neutral hydrogen but no corresponding heavy elements, limiting the chemical abundance to less than 1/10,000 the solar level if the gas is in a gravitationally bound protogalaxy, or less than 1/1,000 solar if it is diffuse and unbound. If the absorption is truly intergalactic, it would imply that the universe was neit...

Simcoe, Robert A; Cooksey, Kathy L; Kao, Melodie M; Matejek, Michael S; Burgasser, Adam J; 10.1038/nature11612

2012-01-01T23:59:59.000Z

226

The Carnegie Supernova Project: The Low-Redshift Survey  

E-Print Network [OSTI]

Supernovae are essential to understanding the chemical evolution of the Universe. Type Ia supernovae also provide the most powerful observational tool currently available for studying the expansion history of the Universe and the nature of dark energy. Our basic knowledge of supernovae comes from the study of their photometric and spectroscopic properties. However, the presently available data sets of optical and near-infrared light curves of supernovae are rather small and/or heterogeneous, and employ photometric systems that are poorly characterized. Similarly, there are relatively few supernovae whose spectral evolution has been well sampled, both in wavelength and phase, with precise spectrophotometric observations. The low-redshift portion of the Carnegie Supernova Project (CSP) seeks to remedy this situation by providing photometry and spectrophotometry of a large sample of supernovae taken on telescope/filter/detector systems that are well understood and well characterized. During a five-year program which began in September 2004, we expect to obtain high-precision u'g'r'i'BVYJHKs light curves and optical spectrophotometry for about 250 supernovae of all types. In this paper we provide a detailed description of the CSP survey observing and data reduction methodology. In addition, we present preliminary photometry and spectra obtained for a few representative supernovae during the first observing campaign.

Mario Hamuy; Gastón Folatelli; Nidia I. Morrell; Mark M. Phillips; Nicholas B. Suntzeff; S. E. Persson; Miguel Roth; Sergio Gonzalez; Wojtek Krzeminski; Carlos Contreras; Wendy L. Freedman; D. C. Murphy; Barry F. Madore; P. Wyatt; José Maza; Alexei V. Filippenko; Weidong Li; P. A. Pinto

2005-12-01T23:59:59.000Z

227

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

228

Deuterium at High Redshifts: Recent Advances and Open Issues  

E-Print Network [OSTI]

Among the light elements created in the Big Bang, deuterium is one of the most difficult to detect but is also the one whose abundance depends most sensitively on the density of baryons. Thus, although we still have only a few positive identifications of D at high redshifts--when the D/H ratio was close to its primordial value--they give us the most reliable determination of the baryon density, in excellent agreement with measures obtained from entirely different probes, such as the anisotropy of the cosmic microwave background temperature and the average absorption of the UV light of quasars by the intergalactic medium. In this review, I relate observations of D/H in distant gas clouds to the large body of data on the local abundance of D obtained in the last few years with the FUSE satellite. I also discuss some of the outstanding problems in light element abundances and consider future prospects for advances in this area.

Max Pettini

2006-01-19T23:59:59.000Z

229

Visually-based temporal distortion in dyslexia Alan Johnston a,b,*, Aurelio Bruno a  

E-Print Network [OSTI]

Visually-based temporal distortion in dyslexia Alan Johnston a,b,*, Aurelio Bruno a , Junji history: Received 11 March 2008 Received in revised form 18 April 2008 Keywords: Time Dyslexia evidence for anomalous cortico-thalamic circuits in dyslexia. Crown Copyright Ã? 2008 Published by Elsevier

Johnston, Alan

230

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

231

P16: A distortion-weighted glimpse-based intelligibility metric for modified and synthetic speech  

E-Print Network [OSTI]

for speech enhancement in known noise conditions," in Proc. Interspeech, pp. 1636-1639. M. Cooke, C. Mayo, CP16: A distortion-weighted glimpse-based intelligibility metric for modified and synthetic speech Yan Tang1 and Martin Cooke2,1 Cassia Valentini-Botinhao3 1 Language and Speech Laboratory, University

Edinburgh, University of

232

Distortion of a Steel Cylinder Casting with a Core D. Galles and C. Beckermann  

E-Print Network [OSTI]

Distortion of a Steel Cylinder Casting with a Core D. Galles and C. Beckermann Mechanical, are studied through a series of in situ casting trials in which a low-carbon steel cylinder with a core to thermal contractions of the steel. 1. Introduction The final dimensions of a steel casting are commonly

Beckermann, Christoph

233

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

234

A Distortion-Theoretic Perspective for Redundant Metering Security in a Smart Grid  

E-Print Network [OSTI]

A Distortion-Theoretic Perspective for Redundant Metering Security in a Smart Grid Mustafa El--In a smart grid environment some customers employ third-party meters and terminals for integrity verification of the smart meter power measurements reported by the electric utility company. We address the security issues

Kundur, Deepa

235

Fractal-driven distortion of resting state functional networks in fMRI: a simulation study  

E-Print Network [OSTI]

Fractal-driven distortion of resting state functional networks in fMRI: a simulation study Wonsang, Magdeburg, Germany E-mail: you@lin-magdeburg.de Fractals are self-similar and scale-invariant patterns found ubiquitously in nature. A lot of evidences implying fractal properties such as 1/f power spectrums have been

236

A Rate-Energy-Distortion Analysis for Compressed-Sensing-Enabled Wireless Video Streaming on  

E-Print Network [OSTI]

A Rate-Energy-Distortion Analysis for Compressed-Sensing-Enabled Wireless Video Streaming. The objective of this paper is to conduct an experiment- driven analysis of the energy links for low-complexity multimedia sensing devices with a limited budget of available energy per video

Melodia, Tommaso

237

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.

238

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.

239

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

240

Quantitative comparison between Type Ia supernova spectra at low and high redshifts: A case study  

E-Print Network [OSTI]

Highlight - The Physics of Supernovae, ESO/MPA/MPE Workshop,Evolution in high-redshift supernovae Fig. 8 “Ca ii H&K”SN 1991T/SN 1999aa-like supernovae. 1. Introduction Type Ia

Garavini, G.; Supernova Cosmology Project

2008-01-01T23:59:59.000Z

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.


241

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

242

Simultaneous Estimation of Photometric Redshifts and SED Parameters: Improved Techniques and a Realistic Error Budget  

E-Print Network [OSTI]

We seek to improve the accuracy of joint galaxy photometric redshift estimation and spectral energy distribution (SED) fitting. By simulating different sources of uncorrected systematic errors, we demonstrate that if the uncertainties on the photometric redshifts are estimated correctly, so are those on the other SED fitting parameters, such as stellar mass, stellar age, and dust reddening. Furthermore, we find that if the redshift uncertainties are over(under)-estimated, the uncertainties in SED parameters tend to be over(under)-estimated by similar amounts. These results hold even in the presence of severe systematics and provide, for the first time, a mechanism to validate the uncertainties on these parameters via comparison with spectroscopic redshifts. We propose a new technique (annealing) to re-calibrate the joint uncertainties in the photo-z and SED fitting parameters without compromising the performance of the SED fitting + photo-z estimation. This procedure provides a consistent estimation of the mu...

Acquaviva, Viviana; Gawiser, Eric

2015-01-01T23:59:59.000Z

243

Probing the epoch of reionization with redshifted 21 cm HI emission  

E-Print Network [OSTI]

Emission and absorption features in the spectrum of the diffuse radio background below 200 MHz due to the 21 cm hyperfine transition line of neutral hydrogen gas in the high redshift intergalactic medium offer a new and ...

Bowman, Judd D. (Judd David)

2007-01-01T23:59:59.000Z

244

Overdensities of SMGs around WISE-selected, ultra-luminous, high-redshift galaxies  

E-Print Network [OSTI]

Submillimetre (submm) observations of WISE-selected, dusty, luminous, high-redshift galaxies have revealed intriguing overdensities around them on arcmin scales. They could be the best signposts of overdense environments on the sky.

Jones, Suzy F

2015-01-01T23:59:59.000Z

245

Climatological conditions for the subpolar North Atlantic during the field campaign of the Greenland Flow Distortion Experiment  

E-Print Network [OSTI]

of the Greenland Flow Distortion Experiment G.W.K. Moore Department of Physics University of Toronto R.S. Pickart January 21, 2009 #12; 2 Abstract: Due to its high topography, Greenland results in significant to help document this flow distortion as part of the international research project called the Greenland

Pickart, Robert S.

246

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

247

The Environments of Low and High Luminosity Radio Galaxies at Moderate Redshifts  

E-Print Network [OSTI]

In the local Universe, high-power radio galaxies live in lower density environments than low-luminosity radio galaxies. If this trend continues to higher redshifts, powerful radio galaxies would serve as efficient probes of moderate redshift groups and poor clusters. Photometric studies of radio galaxies at 0.3 environment correlation disappears at moderate redshifts, though this could be the result of foreground/background contamination affecting the photometric measures of environment. We have obtained multi-object spectroscopy of in the fields of 14 lower luminosity (L_1.4GHz 1.2x10^25 W/Hz) radio galaxies at z ~ 0.3 to spectroscopically investigate the link between the environment and the radio luminosity of radio galaxies at moderate redshifts. Our results support the photometric analyses; there does not appear to be a correlation between the luminosity of a radio galaxy and its environment at moderate redshifts. Hence, radio galaxies are not efficient signposts for group environments at moderate redshifts.

M. W. Auger; R. H. Becker; C. D. Fassnacht

2008-01-02T23:59:59.000Z

248

THE PRISM MULTI-OBJECT SURVEY (PRIMUS). II. DATA REDUCTION AND REDSHIFT FITTING  

SciTech Connect (OSTI)

The PRIsm MUlti-object Survey (PRIMUS) is a spectroscopic galaxy redshift survey to z {approx} 1 completed with a low-dispersion prism and slitmasks allowing for simultaneous observations of {approx}2500 objects over 0.18 deg{sup 2}. The final PRIMUS catalog includes {approx}130,000 robust redshifts over 9.1 deg{sup 2}. In this paper, we summarize the PRIMUS observational strategy and present the data reduction details used to measure redshifts, redshift precision, and survey completeness. The survey motivation, observational techniques, fields, target selection, slitmask design, and observations are presented in Coil et al. Comparisons to existing higher-resolution spectroscopic measurements show a typical precision of {sigma}{sub z}/(1 + z) = 0.005. PRIMUS, both in area and number of redshifts, is the largest faint galaxy redshift survey completed to date and is allowing for precise measurements of the relationship between active galactic nuclei and their hosts, the effects of environment on galaxy evolution, and the build up of galactic systems over the latter half of cosmic history.

Cool, Richard J. [MMT Observatory, Tucson, AZ 85721 (United States); Moustakas, John [Department of Physics, Siena College, 515 Loudon Rd., Loudonville, NY 12211 (United States); Blanton, Michael R.; Hogg, David W. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Burles, Scott M. [D.E. Shaw and Co. L.P, 20400 Stevens Creek Blvd., Suite 850, Cupertino, CA 95014 (United States); Coil, Alison L.; Aird, James; Mendez, Alexander J. [Department of Physics, Center for Astrophysics and Space Sciences, University of California, 9500 Gilman Dr., La Jolla, San Diego, CA 92093 (United States); Eisenstein, Daniel J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St, MS 20, Cambridge, MA 02138 (United States); Wong, Kenneth C. [Steward Observatory, The University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States); Zhu, Guangtun [Center for Astrophysical Sciences, Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Bernstein, Rebecca A. [Department of Astronomy and Astrophysics, UCA/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Bolton, Adam S. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States)

2013-04-20T23:59:59.000Z

249

$?$--PhotoZ: Photometric Redshifts by Inverting the Tolman Surface Brightness Test  

E-Print Network [OSTI]

Surface brightness is a fundamental observational parameter of galaxies. We show, for the first time in detail, how it can be used to obtain photometric redshifts for galaxies, the $\\mu$-PhotoZ method. We demonstrate that the Tolman surface brightness relation, $\\mu \\propto (1+z)^{-4}$, is a powerful tool for determining galaxy redshifts from photometric data. We develop a model using $\\mu$ and a color percentile (ranking) measure to demonstrate the $\\mu$-PhotoZ method. We apply our method to a set of galaxies from the SHELS survey, and demonstrate that the photometric redshift accuracy achieved using the surface brightness method alone is comparable with the best color-based methods. We show that the $\\mu$-PhotoZ method is very effective in determining the redshift for red galaxies using only two photometric bands. We discuss the properties of the small, skewed, non-gaussian component of the error distribution. We calibrate $\\mu_r, (r-i)$ from the SDSS to redshift, and tabulate the result, providing a simple, but accurate look up table to estimate the redshift of distant red galaxies.

Michael J. Kurtz; Margaret J. Geller; Daniel G. Fabricant; William F. Wyatt; Ian P. Dell'Antonio

2007-07-03T23:59:59.000Z

250

THE MICRO-ARCSECOND SCINTILLATION-INDUCED VARIABILITY (MASIV) SURVEY. III. OPTICAL IDENTIFICATIONS AND NEW REDSHIFTS  

SciTech Connect (OSTI)

Intraday variability (IDV) of the radio emission from active galactic nuclei is now known to be predominantly due to interstellar scintillation (ISS). The MASIV (The Micro-Arcsecond Scintillation-Induced Variability) survey of 443 flat spectrum sources revealed that the IDV is related to the radio flux density and redshift. A study of the physical properties of these sources has been severely handicapped by the absence of reliable redshift measurements for many of these objects. This paper presents 79 new redshifts and a critical evaluation of 233 redshifts obtained from the literature. We classify spectroscopic identifications based on emission line properties, finding that 78% of the sources have broad emission lines and are mainly FSRQs. About 16% are weak lined objects, chiefly BL Lacs, and the remaining 6% are narrow line objects. The gross properties (redshift, spectroscopic class) of the MASIV sample are similar to those of other blazar surveys. However, the extreme compactness implied by ISS favors FSRQs and BL Lacs in the MASIV sample as these are the most compact object classes. We confirm that the level of IDV depends on the 5 GHz flux density for all optical spectral types. We find that BL Lac objects tend to be more variable than broad line quasars. The level of ISS decreases substantially above a redshift of about two. The decrease is found to be generally consistent with ISS expected for beamed emission from a jet that is limited to a fixed maximum brightness temperature in the source rest frame.

Pursimo, Tapio [Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma (Spain)] [Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma (Spain); Ojha, Roopesh [NVI Inc./U. S. Naval Observatory, 3450 Massachusetts Ave NW, Washington DC (United States)] [NVI Inc./U. S. Naval Observatory, 3450 Massachusetts Ave NW, Washington DC (United States); Jauncey, David L. [CSIRO Astronomy and Space Science and Mount Stromlo Observatory, Canberra ACT 0200 (Australia)] [CSIRO Astronomy and Space Science and Mount Stromlo Observatory, Canberra ACT 0200 (Australia); Rickett, Barney J. [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, CA 92093 (United States)] [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, CA 92093 (United States); Dutka, Michael S. [The Catholic University of America, 620 Michigan Ave., N.E., Washington DC 20064 (United States)] [The Catholic University of America, 620 Michigan Ave., N.E., Washington DC 20064 (United States); Koay, Jun Yi; Bignall, Hayley E.; Macquart, Jean-Pierre [ICRAR, Curtin University, Bentley, WA 6845 (Australia)] [ICRAR, Curtin University, Bentley, WA 6845 (Australia); Lovell, James E. J. [School of Mathematics and Physics, University of Tasmania, TAS 7001 (Australia)] [School of Mathematics and Physics, University of Tasmania, TAS 7001 (Australia); Kedziora-Chudczer, Lucyna, E-mail: tpursimo@not.iac.es [School of Physics and Astrophysics, UNSW, Sydney NSW 2052 (Australia)] [School of Physics and Astrophysics, UNSW, Sydney NSW 2052 (Australia)

2013-04-10T23:59:59.000Z

251

Space Nuclear  

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

Space Nuclear Today the INL is preparing to assist with the Multi-Mission RTG (MMRTG). The INL is assigned the final assembly and testing of the RTG for the project which is...

252

Radiative Feedback in Relic HII Regions at High-Redshift  

E-Print Network [OSTI]

UV radiation from early astrophysical sources could have a large impact on subsequent star formation in nearby protogalaxies. Here we study the radiative feedback from the first, short-lived stars using hydrodynamical simulations with transient UV backgrounds (UVBs) and persistent Lyman-Werner backgrounds (LWBs) of varying intensity. We extend our prior work in Mesinger et al. (2006), by studying a more typical region whose proto-galaxies form at lower redshifts, z~13-20, in the epoch likely preceding the bulk of reionization. We confirm our previous results that feedback in the relic HII regions resulting from such transient radiation, is itself transient. Feedback effects dwindle away after ~30% of the Hubble time, and the same critical specific intensity of J_UV~0.1 x 10^{-21} ergs/s/cm^2/Hz/sr separates positive and negative feedback regimes. Additionally, we discover a second episode of eventual positive feedback in halos which have not yet collapsed when their progenitor regions were exposed to the transient UVB. This eventual positive feedback appears in all runs, regardless of the strength of the UVB. However, this feedback regime is very sensitive to the presence of Lyman-Werner radiation, and notable effects disappear under fairly modest background intensities of J_LW>10^{-3} x 10^{-21} ergs/s/cm^2/Hz/sr. We conclude that UV radiative feedback in relic HII regions, although a complicated process, seems unlikely to have a major impact on the progress of cosmological reionization, provided that present estimates of the lifetime and luminosity of a PopIII star are accurate. More likely is that the build-up of the LWB ultimately governs the feedback strength until a persistent UV background can be established. [abridged

Andrei Mesinger; Greg L. Bryan; Zoltan Haiman

2009-09-13T23:59:59.000Z

253

Analytical Model of Tidal Distortion and Dissipation for a Giant Planet with a Viscoelastic Core  

E-Print Network [OSTI]

We present analytical expressions for the tidal Love numbers of a giant planet with a solid core and a fluid envelope. We model the core as a uniform, incompressible, elastic solid, and the envelope as a non-viscous fluid satisfying the $n=1$ polytropic equation of state. We discuss how the Love numbers depend on the size, density, and shear modulus of the core. We then model the core as a viscoelastic Maxwell solid and compute the tidal dissipation rate in the planet as characterized by the imaginary part of the Love number $k_2$. Our results improve upon existing calculations based on planetary models with a solid core and a uniform ($n=0$) envelope. Our analytical expressions for the Love numbers can be applied to study tidal distortion and viscoelastic dissipation of giant planets with solid cores of various rheological properties, and our general method can be extended to study tidal distortion/dissipation of super-earths.

Storch, Natalia I

2015-01-01T23:59:59.000Z

254

Distortions of Experimental Muon Arrival Time Distributions of Extensive Air Showers by the Observation Conditions  

E-Print Network [OSTI]

Event-by-event measured arrival time distributions of Extensive Air Shower (EAS) muons are affected and distorted by various interrelated effects which originate from the time resolution of the timing detectors, from fluctuations of the reference time and the number (multiplicity) of detected muons spanning the arrival time distribution of the individual EAS events. The origin of these effects is discussed, and different correction procedures, which involve detailed simulations, are proposed and illustrated. The discussed distortions are relevant for relatively small observation distances (R < 200 m) from the EAS core. Their significance decreases with increasing observation distance and increasing primary energies. Local arrival time distributions which refer to the observed arrival time of the first local muon prove to be less sensitive to the mass of the primary. This feature points to the necessity of arrival time measurements with additional information on the curvature of the EAS disk.

R. Haeusler; A. F. Badea; H. Rebel; I. M. Brancus; J. Oehlschlaeger

2001-10-17T23:59:59.000Z

255

Space Sciences  

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

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmosphericNuclear Security Administrationcontroller systemsBiSite CulturalDepartment2)isomeraseUSChargeSpace Sciences Space

256

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

257

Optic for industrial endoscope/borescope with narrow field of view and low distortion  

DOE Patents [OSTI]

An optic for the imaging optics on the distal end of a flexible fiberoptic endoscope or rigid borescope inspection tool. The image coverage is over a narrow (<20 degrees) field of view with very low optical distortion (<5% pin cushion or barrel distortion), compared to the typical <20% distortion. The optic will permit non-contact surface roughness measurements using optical techniques. This optic will permit simultaneous collection of selected image plane data, which data can then be subsequently optically processed. The image analysis will yield non-contact surface topology data for inspection where access to the surface does not permit a mechanical styles profilometer verification of surface topology. The optic allows a very broad spectral band or range of optical inspection. It is capable of spectroscopic imaging and fluorescence induced imaging when a scanning illumination source is used. The total viewing angle for this optic is 10 degrees for the full field of view of 10 degrees, compared to 40-70 degrees full angle field of view of the conventional gradient index or GRIN's lens systems.

Stone, Gary F.; Trebes, James E.

2005-08-16T23:59:59.000Z

258

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

259

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

260

The Swift Gamma-Ray Burst Host Galaxy Legacy Survey - I. Sample Selection and Redshift Distribution  

E-Print Network [OSTI]

We introduce the Swift Gamma-Ray Burst Host Galaxy Legacy Survey ("SHOALS"), a multi-observatory high-redshift galaxy survey targeting the largest unbiased sample of long-duration gamma-ray burst hosts yet assembled (119 in total). We describe the motivations of the survey and the development of our selection criteria, including an assessment of the impact of various observability metrics on the success rate of afterglow-based redshift measurement. We briefly outline our host-galaxy observational program, consisting of deep Spitzer/IRAC imaging of every field supplemented by similarly-deep, multi-color optical/NIR photometry, plus spectroscopy of events without pre-existing redshifts. Our optimized selection cuts combined with host-galaxy follow-up have so far enabled redshift measurements for 110 targets (92%) and placed upper limits on all but one of the remainder. About 20% of GRBs in the sample are heavily dust-obscured, and at most 2% originate from z>5.5. Using this sample we estimate the redshift-depen...

Perley, D A; Schulze, S; Postigo, A de Ugarte; Hjorth, J; Berger, E; Cenko, S B; Chary, R; Cucchiara, A; Ellis, R; Fong, W; Fynbo, J P U; Gorosabel, J; Greiner, J; Jakobsson, P; Laskar, T; Levan, A J; Micha?owski, M J; Milvang-Jensen, B; Tanvir, N R; Thöne, C C; Wiersema, K

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.


261

The environments of intermediate-redshift QSOs: 0.3 < z < 0.7  

E-Print Network [OSTI]

An angular correlation of low significance (2 sigma) is observed between 0.3 0.5 QSOs. After converting to an excess of galaxies physically associated with the QSO, this lack of strong correlation is shown to be consistent with the clustering of normal galaxies at the same moderate redshifts. Combined with previous observations, these results imply that the environments of radio-quiet QSOs do not undergo significant evolution with respect to the galaxy population over a wide range of redshifts (0 < z < 1.5). This is in marked contrast to the rapid increase in the richness of the environments associated with radio-loud QSOs over the same redshift range.

R. J. Smith; B. J. Boyle; S. J. Maddox

1999-11-22T23:59:59.000Z

262

Type Ia supernova rate at a redshift of ~ 0.1  

E-Print Network [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 ~ 0.13. The result is $0.125^{+0.044+0.028}_{-0.034-0.028} h_{70}^2$ SNu where 1 SNu = 1 SN / $10^{10} L_{sun}^B$ / 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; 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; Fouqué, P; Garavini, G; Glicenstein, J F; Goldman, B; Goobar, A; Gould, A; Graff, D; Gros, M; Haïssinski, J; Hamadache, C; Hardin, D; Hook, I M; De Kat, J; Kent, S; Kim, A; Lasserre, T; Le Guillou, Laurent; 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, Nathalie; Perdereau, O; Prévôt, 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

2004-01-01T23:59:59.000Z

263

Type Ia supernova rate at a redshift of ~ 0.1  

E-Print Network [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 ~ 0.13. The result is $0.125^{+0.044+0.028}_{-0.034-0.028} h_{70}^2$ SNu where 1 SNu = 1 SN / $10^{10} L_{sun}^B$ / 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.

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

2004-05-11T23:59:59.000Z

264

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

265

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

266

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

267

Redshift evolution of the dynamical properties of massive galaxies from SDSS-III/BOSS  

E-Print Network [OSTI]

We study the redshift evolution of the dynamical properties of ~180,000 massive galaxies from SDSS-III/BOSS combined with a local early-type galaxy sample from SDSS-II in the redshift range 0.12sigma significance. By combining our sample with high-redshift literature data we find that this evolution of the dynamical to stellar mass ratio continues beyond z~0.7 up to z>2 as Mdyn/Mstar~ (1+z)^{-0.30+/- 0.12} further strengthening the evidence for an increase of Mdyn/Mstar with cosmic time. This result is in line with recent predictions from galaxy formation simulations based on minor merger driven mass growth, in which the dark matter fraction within the half-light radius increases with cosmic time.

Beifiori, Alessandra; Maraston, Claudia; Steele, Oliver; Masters, Karen L; Pforr, Janine; Saglia, Roberto P; Bender, Ralf; Tojeiro, Rita; Chen, Yan-Mei; Bolton, Adam; Brownstein, Joel R; Johansson, Jonas; Leauthaud, Alexie; Nichol, Robert C; Schneider, Donald P; Senger, Robert; Skibba, Ramin; Wake, David; Pan, Kaike; Snedden, Stephanie; Bizyaev, Dmitry; Brewington, Howard; Malanushenko, Viktor; Malanushenko, Elena; Oravetz, Daniel; Simmons, Audrey; Shelden, Alaina; Ebelke, Garrett

2014-01-01T23:59:59.000Z

268

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

269

Design and analysis of a scanning beam interference lithography system for patterning gratings with nanometer-level distortions  

E-Print Network [OSTI]

This thesis describes the design and analysis of a system for patterning large-area gratings with nanometer level phase distortions. The novel patterning method, termed scanning beam interference lithography (SBIL), uses ...

Konkola, Paul Thomas, 1973-

2003-01-01T23:59:59.000Z

270

Verification of d-wave pairing symmetry by microwave intermodulation distortion measurements in yttrium barium copper oxide  

E-Print Network [OSTI]

We report measurements of the temperature and power dependence of the microwave frequency intermodulation distortion (IMD) in high quality pulsed laser deposition (PLD) Yttrium Barium Copper Oxide (YBCO) on LaAlO3 substrate. ...

Park, Sang-Hoon, Ph. D. Massachusetts Institute of Technology

2004-01-01T23:59:59.000Z

271

The fate of high redshift massive compact galaxies in dense environments  

SciTech Connect (OSTI)

Massive compact galaxies seem to be more common at high redshift than in the local universe, especially in denser environments. To investigate the fate of such massive galaxies identified at z {approx} 2 we analyse the evolution of their properties in three cosmological hydrodynamical simulations that form virialized galaxy groups of mass {approx} 10{sup 13} M{sub {circle_dot}} hosting a central massive elliptical/S0 galaxy by redshift zero. We find that at redshift {approx} 2 the population of galaxies with M{sub *} > 2 x 10{sup 10} M{sub {circle_dot}} is diverse in terms of mass, velocity dispersion, star formation and effective radius, containing both very compact and relatively extended objects. In each simulation all the compact satellite galaxies have merged into the central galaxy by redshift 0 (with the exception of one simulation where one of such satellite galaxy survives). Satellites of similar mass at z = 0 are all less compact than their high redshift counterparts. They form later than the galaxies in the z = 2 sample and enter the group potential at z < 1, when dynamical friction times are longer than the Hubble time. Also, by z = 0 the central galaxies have increased substantially their characteristic radius via a combination of in situ star formation and mergers. Hence in a group environment descendants of compact galaxies either evolve towards larger sizes or they disappear before the present time as a result of the environment in which they evolve. Since the group-sized halos that we consider are representative of dense environments in the {Lambda}CDM cosmology, we conclude that the majority of high redshift compact massive galaxies do not survive until today as a result of the environment.

Kaufmann, Tobias; /Zurich, ETH; Mayer, Lucio; /Zurich U.; Carollo, Marcella; /Zurich, ETH; Feldmann, Robert; /Fermilab /Chicago U., KICP

2012-01-01T23:59:59.000Z

272

Conduction-Band-Offset Rule Governing J-V Distortion in CdS/CI(G)S Solar Cells  

E-Print Network [OSTI]

Conduction-Band-Offset Rule Governing J-V Distortion in CdS/CI(G)S Solar Cells A. Kanevce, MV at the n/p interface of a solar cell can lead to significant distortion of the current-voltage (J-V) curve-layer [TCO/CdS/CI(G)S] approximation for the solar cell. The parameters that influence the barrier height

Sites, James R.

273

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

274

Structural distortion in RPt sub 2 Sn sub 2 compounds (R = rare earth)  

SciTech Connect (OSTI)

CeM{sub 2}X{sub 2} compounds (M-transition metals, X = Si, Ge, Sn) exhibit very exotic properties such as intermediate valence state, heavy fermion, magnetism, and superconductivity. Most of them crystallize in the ThCr{sub 2}Si{sub 2} type structure (14/nmm) while a few adopt the CeBe{sub 2}Ge{sub 2} primitive one (P4/nmmm). Among these compounds, CePt{sub 2}Sn{sub 2} has the heaviest known specific heat coefficient ({gamma} = 3.5 J/mol-K{sup 2}) and orders antiferromagnetically at T{sub N} = 0.88 K. Samples of CePt{sub 2}Sn{sub 2}, Ce{sub 0.e}La{sub 0.2}Pt{sub 2}Sn{sub 2}, and LaPt{sub 2}Sn{sub 2} have been studied by X-ray powder diffraction experiments including Rietveld calculations before and after annealing. As-cast samples can be indexed in the tetragonal primitive cell; however, re- examination of annealed samples (1 3 days at 800{degrees}C and 3 weeks at 700{degrees}C) reveals a monoclinic distortion of the lattice. Such a distortion has already been observed for CeNi{sub 2}Sn{sub 2}. Furthermore, our diffraction patterns show evidence for superlattice lines at twice the unit cell parameters, which was verified by transmission electron microscopy. Microprobes analysis on these samples show that the Pt sublattice is slightly substoichiometric (97.5%). Thus strains due to large atomic radii and ordering of Pt vacancies could be responsible for the monoclinic distortion and superlattice lines. 13 refs., 3 figs., 1 tab.

Latroche, M.; Selsane, M.; Godart, C.; Schiffmacher, G. (Centre National de la Recherche Scientifique (CNRS), 92 - Meudon-Bellevue (France)); Beyerman, W.P.; Thompson, J.D. (Los Alamos National Lab., NM (USA))

1991-01-01T23:59:59.000Z

275

Space Videos  

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

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr May JunDatastreamsmmcrcalgovInstrumentsrucLas ConchasPassiveSubmittedStatus Tom Fletcher,Future |Carlos ValenciaSpace Dust

276

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

277

Anisotropies in Non-Thermal Distortions of Cosmic Light from Photon-Axion Conversion  

E-Print Network [OSTI]

Ultralight axions which couple sufficiently strongly to photons can leave imprints on the sky at diverse frequencies by mixing with cosmic light in the presence of background magnetic fields. We explore such direction dependent grey-body distortions of the CMB spectrum, enhanced by resonant conditions in the IGM plasma. We also find that if such axions are produced in the early universe and represent a subdominant dark radiation component today, they could convert into X-rays in supervoids, and brighten them at X-ray frequencies.

Guido D'Amico; Nemanja Kaloper

2015-01-07T23:59:59.000Z

278

Anisotropies in Non-Thermal Distortions of Cosmic Light from Photon-Axion Conversion  

E-Print Network [OSTI]

Ultralight axions which couple sufficiently strongly to photons can leave imprints on the sky at diverse frequencies by mixing with cosmic light in the presence of background magnetic fields. We explore such direction dependent grey-body distortions of the CMB spectrum, enhanced by resonant conditions in the IGM plasma. We also find that if such axions are produced in the early universe and represent a subdominant dark radiation component today, they could convert into X-rays in supervoids, and brighten them at X-ray frequencies.

D'Amico, Guido

2015-01-01T23:59:59.000Z

279

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

280

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

Note: This page contains sample records for the topic "redshift space distortions" from the National Library of EnergyBeta (NLEBeta).
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281

I. Apples to apples $A^2$: photometric redshift predictions for next-generation surveys  

E-Print Network [OSTI]

This is the first of a series of papers where we compare the expected performance of two of the largest stage IV next-generation surveys in the optical and infrared (LSST and Euclid), with a particular focus on cluster surveys. In this first paper, we introduce the mock catalogues we have utilized in this work, an N-body simulation+semi-analytical cone with a posterior modification with PhotReal, a technique which modifies the original photometry to make it more realistic by using an empirical library of spectral templates. We have confirmed the reliability of the mock catalogue by comparing the obtained color-magnitude relation, the luminosity and mass function and the angular correlation function with those of real data. We also analyze the behavior of the expected photometric redshifts for each different survey, in terms of photometric redshift resolution, photometric redshift bias and fraction of outliers. In addition, we discuss the benefits of using the BPZ \\emph{odds} photometric redshift quality param...

Ascaso, Begoña; Benítez, Narciso

2015-01-01T23:59:59.000Z

282

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

283

The 160 Square Degree ROSAT Survey: the Revised Catalog of 201 Clusters with Spectroscopic Redshifts  

E-Print Network [OSTI]

We present the revised catalog of galaxy clusters detected as extended X-ray sources in the 160 Square Degree ROSAT Survey, including spectroscopic redshifts and X-ray luminosities for 200 of the 201 members. The median redshift is z~0.25 and the median X-ray luminosity is 4.2e+43 erg/s/h50^2 (0.5-2.0 keV). This is the largest high-redshift sample of X-ray selected clusters published to date. There are 73 objects at z>0.3 and 22 objects at z>0.5 drawn from a statistically complete flux-limited survey with a median object flux of 1.4d-13 erg/cm^2/s. We describe the optical follow-up of these clusters with an emphasis on our spectroscopy which has yielded 155 cluster redshifts, 110 of which are presented here for the first time. These measurements combined with 45 from the literature and other sources provide near-complete spectroscopic coverage for our survey. We discuss the final optical identifications for the extended X-ray sources in the survey region and compare our results to similar X-ray cluster search...

Mullis, C R; Quintana, H; Vikhlinin, A; Henry, J P; Gioia, I M; Hornstrup, A; Forman, W; Jones, C

2003-01-01T23:59:59.000Z

284

Supernova rates from the Southern inTermediate Redshift ESO Supernova Search (STRESS)  

E-Print Network [OSTI]

To measure the supernova (SN) rates at intermediate redshift we performed the Southern inTermediate Redshift ESO Supernova Search (STRESS). Unlike most of the current high redshift SN searches, this survey was specifically designed to estimate the rate for both type Ia and core collapse (CC) SNe. We counted the SNe discovered in a selected galaxy sample measuring SN rate per unit blue band luminosity. Our analysis is based on a sample of ~43000 galaxies and on 25 spectroscopically confirmed SNe plus 64 selected SN candidates. Our approach is aimed at obtaining a direct comparison of the high redshift and local rates and at investigating the dependence of the rates on specific galaxy properties, most notably their colour. The type Ia SN rate, at mean redshift z=0.3, amounts to 0.22^{+0.10+0.16}_{-0.08 -0.14} h_{70}^2 SNu, while the CC SN rate, at z=0.21, is 0.82^{+0.31 +0.30}_{-0.24 -0.26} h_{70}^2 SNu. The quoted errors are the statistical and systematic uncertainties. With respect to local value, the CC SN rate at z=0.2 is higher by a factor of ~2 already at redshift, whereas the type Ia SN rate remains almost constant. This implies that a significant fraction of SN Ia progenitors has a lifetime longer than 2-3 Gyr. We also measured the SN rates in the red and blue galaxies and found that the SN Ia rate seems to be constant in galaxies of different colour, whereas the CC SN rate seems to peak in blue galaxies, as in the local Universe. SN rates per unit volume were found to be consistent with other measurements showing a steeper evolution with redshift for CC SNe with respect to SNe Ia. Finally we have exploited the link between star formation (SF) and SN rates to predict the evolutionary behaviour of the SN rates and compare it with the path indicated by observations.

M. T. Botticella; M. Riello; E. Cappellaro; S. Benetti; G. Altavilla; A. Pastorello; M. Turatto; L. Greggio; F. Patat; S. Valenti; L. Zampieri; A. Harutyunyan; G. Pignata; S. Taubenberger

2007-10-19T23:59:59.000Z

285

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

286

Contestation of Space  

E-Print Network [OSTI]

Volume 25, 2012 Contestation of Space A Photo Essay by Nuraoccurring in Ramallah between refugee and non-refugee space.Keywords: Divided spaces Introduction This study was

Alkhalili, Nura

2012-01-01T23:59:59.000Z

287

Competing for Shelf Space.  

E-Print Network [OSTI]

Retailers, and Shelf Space. ” Journal of Marketing, 26(3),Model for Optimizing Retail Space Allocations. ” ManagementMethods to Estimate Shelf Space Elasticities. ” Quant.

Martínez-de-Albéniz, V.; Roels, G.

2007-01-01T23:59:59.000Z

288

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

289

AGN Environments in the Sloan Digital Sky Survey I: Dependence on Type, Redshift, and Luminosity  

E-Print Network [OSTI]

We explore how the local environment is related to the redshift, type, and luminosity of active galactic nuclei (AGN). Recent simulations and observations are converging on the view that the extreme luminosity of quasars is fueled in major mergers of gas-rich galaxies. In such a picture, quasars are expected to be located in regions with a higher density of galaxies on small scales where mergers are more likely to take place. However, in this picture, the activity observed in low-luminosity AGN is due to secular processes that are less dependent on the local galaxy density. To test this hypothesis, we compare the local photometric galaxy density on kiloparsec scales around spectroscopic Type I and Type II quasars to the local density around lower luminosity spectroscopic Type I and Type II AGN. To minimize projection effects and evolution in the photometric galaxy sample we use to characterize AGN environments, we place our random control sample at the same redshift as our AGN and impose a narrow redshift window around both the AGN and control targets. We find that higher luminosity AGN have more overdense environments compared to lower luminosity AGN on all scales out to our $2\\Mpchseventy$ limit. Additionally, in the range $0.3\\leqslant z\\leqslant 0.6$, Type II quasars have similarly overdense environments to those of bright Type I quasars on all scales out to our $2\\Mpchseventy$ limit, while the environment of dimmer Type I quasars appears to be less overdense than the environment of Type II quasars. We see increased overdensity for Type II AGN compared to Type I AGN on scales out to our limit of $2\\Mpchseventy$ in overlapping redshift ranges. We also detect marginal evidence for evolution in the number of galaxies within $2\\Mpchseventy$ of a quasar with redshift.

Natalie E. Strand; Robert J. Brunner; Adam D. Myers

2008-07-24T23:59:59.000Z

290

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

291

A New Determination of the High Redshift Type Ia Supernova Rates with the Hubble Space Telescope Advanced Camera for Surveys  

E-Print Network [OSTI]

Schmidt, B. P. , 2003, in Supernovae and Gamma Ray Bursts,for identifying Type Ia supernovae (although spectroscopicfor future high-statistics supernovae searches in which

2008-01-01T23:59:59.000Z

292

3741SPACE AUDIT PROCEDURE Space audit  

E-Print Network [OSTI]

Page 1 3741SPACE AUDIT PROCEDURE Space audit identified to be conducted Will audit disrupt or disturb occupants of the space Notify Faculty, School or Business Unit of the audit Is the audit for timetabling purposes Is the audit a physical audit Confirm audit requirements Is the audit for other space

293

UNIVERSITY SPACE POLICY ALLOCATION OF UNIVERSITY SPACE  

E-Print Network [OSTI]

UNIVERSITY COLLEGE DUBLIN UNIVERSITY SPACE POLICY #12;ALLOCATION OF UNIVERSITY SPACE I Purpose To provide a methodology for the allocation of space across the University II Background Due to the university's success in attracting research funding, the need for space and facilities has grown

294

COMMERCIAL SPACE ACCOMPLISHMENTS Commercial Cargo Space Accomplishments  

E-Print Network [OSTI]

11/13/2013 COMMERCIAL SPACE ACCOMPLISHMENTS Commercial Cargo Space Accomplishments The Obama Administration's ambitious commercial space program, which has bipartisan support in Congress, has enabled NASA's successful partnership with two American companies now able to resupply the station - SpaceX and Orbital

Waliser, Duane E.

295

Detecting and interpreting distortions in hierarchical organization of complex time series  

E-Print Network [OSTI]

Hierarchical organization is a cornerstone of complexity and multifractality constitutes its central quantifying concept. For model uniform cascades the corresponding singularity spectra are symmetric while those extracted from empirical data are often asymmetric. Using the selected time series representing such diverse phenomena like price changes and inter-transaction times in the financial markets, sentence length variability in the narrative texts, Missouri River discharge and Sunspot Number variability as examples, we show that the resulting singularity spectra appear strongly asymmetric, more often left-sided but in some cases also right-sided. We present a unified view on the origin of such effects and indicate that they may be crucially informative for identifying composition of the time series. One particularly intriguing case of this later kind of asymmetry is detected in the daily reported Sunspot Number variability. This signals that either the commonly used famous Wolf formula distorts the real d...

Dro?d?, Stanis?aw

2015-01-01T23:59:59.000Z

296

Surface alloys of icosahedral AlMnSi with phason distortions  

SciTech Connect (OSTI)

The microstructures produced by electron-beam melting and by ion-beam mixing Al/Mn and Al/Mn/Si layers on Si substrates are examined. The treatments were found to incorporate Si from the substrate into the surface alloy. Several phases formed, depending on treatment, including ..cap alpha..- and ..beta..-AlMnSi, ..mu..-AlMn (epitaxial on Si(111), and amorphous and icosahedral AlMnSi. The observed microstructures relate the novel icosahedral phase to other phases and elucidate its formation kinetics. Diffraction patterns from large icosahedral grains (up to 5 ..mu..m) show distortions in the position and shape of weak (but not strong) reflections, as predicted for phason defects in a quasicrystalline lattice, one of the structures proposed for icosahedral phases.

Follstaedt, D.M.; Knapp, J.A.

1986-12-01T23:59:59.000Z

297

Peierls distorted chain as a quantum data bus for quantum state transfer  

E-Print Network [OSTI]

We systematically study the transfer of quantum state of electron spin as the flying qubit along a half-filled Peierls distorted tight-binding chain described by the Su-Schrieffer-Heeger (SSH) model, which behaves as a quantum data bus. This enables a novel physical mechanism for quantum communication with always-on interaction: the effective hopping of the spin carrier between sites $A$ and $B$ connected to two sites in this SSH chain can be induced by the quasi-excitations of the SSH model. As we prove, it is the Peierls energy gap of the SSH quasi-excitations that plays a crucial role to protect the robustness of the quantum state transfer process. Moreover, our observation also indicates that such a scheme can also be employed to explore the intrinsic property of the quantum system.

M. X. Huo; Ying Li; Z. Song; C. P. Sun

2006-06-01T23:59:59.000Z

298

Charge-induced distortion and stabilization of surface transfer doped porphyrin films  

SciTech Connect (OSTI)

The interaction between zinc-tetraphenylporphyrin (ZnTPP) and fullerenes (C{sub 60} and C{sub 60}F{sub 48}) are studied using ultraviolet photoelectron spectroscopy (UPS) and scanning tunneling microscopy (STM). Low temperature STM reveals highly ordered ZnTPP monolayers on Au(111). In contrast to C{sub 60}, a submonolayer coverage of C{sub 60}F{sub 48} results in long-range disorder of the underlying single ZnTPP layer and distortion of individual ZnTPP molecules. This is induced by substantial charge transfer at the organic-organic interface, revealed by the interface energetics from UPS. However, a second layer of ZnTPP prevents C{sub 60}F{sub 48} guests from breaking the self-assembled porphyrin template. This finding is important for understanding the growth behaviour of “bottom-up” functional nanostructures involving strong donor-acceptor heterojunctions in molecular electronics.

Smets, Y.; Stark, C. B.; Wright, C. A.; Pakes, C. I. [Department of Physics, La Trobe University, Bundoora, Victoria 3086 (Australia)] [Department of Physics, La Trobe University, Bundoora, Victoria 3086 (Australia); Lach, S.; Schmitt, F.; Ziegler, C. [Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern (Germany)] [Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern (Germany); Wanke, M. [Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz (Germany)] [Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz (Germany); Ley, L. [Department of Physics, La Trobe University, Bundoora, Victoria 3086 (Australia) [Department of Physics, La Trobe University, Bundoora, Victoria 3086 (Australia); Institut für Technische Physik, Universität Erlangen-Nürnberg, 91058 Erlangen (Germany)

2013-07-28T23:59:59.000Z

299

Synchrotron Radiation Wake in Free Space  

SciTech Connect (OSTI)

In this paper, we derive the transverse radiation force of a bunch of ultrarelativistic charged particles coherently radiating in free space assuming that the bending radius is much larger than the beam dimensions. In contrast to a similar recent study, where the authors decompose the total transverse force and find only a part that is responsible for the distortion of the beam orbit, we derive a full expression for the force and leave the issues of the beam dynamics for a separate consideration. Another approach to the calculation of the transverse force has been previously developed. In many cases considered in this paper, the calculations are extremely cumbersome; they were systematically performed with the use of symbolic engine of the computer program MATHEMATICA.

Stupakov, G.V.; /SLAC

2011-08-31T23:59:59.000Z

300

Using neural networks to estimate redshift distributions. An application to CFHTLenS  

E-Print Network [OSTI]

We present a novel way of using neural networks (NN) to estimate the redshift distribution of a galaxy sample. We are able to obtain a probability density function (PDF) for each galaxy using a classification neural network. The method is applied to 58714 galaxies in CFHTLenS that have spectroscopic redshifts from DEEP2, VVDS and VIPERS. Using this data we show that the stacked PDF's give an excellent representation of the true $N(z)$ using information from 5, 4 or 3 photometric bands. We show that the fractional error due to using N(z_(phot)) instead of N(z_(truth)) is IPython notebook accompanying this paper is made available here: https://bitbucke...

Bonnett, Christopher

2013-01-01T23:59:59.000Z

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.


301

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

302

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

303

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

304

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

305

The 2dF Galaxy Redshift Survey: Wiener Reconstruction of the Cosmic Web  

E-Print Network [OSTI]

We reconstruct the underlying density field of the 2 degree Field Galaxy Redshift Survey (2dFGRS) for the redshift range 0.035

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

2003-12-19T23:59:59.000Z

306

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

307

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

308

Superclusters of galaxies from the 2df redshift survey. 1. the catalogue  

SciTech Connect (OSTI)

We use the 2dF Galaxy Redshift Survey data to compile catalogues of superclusters for the Northern and Southern regions of the 2dFGRS, altogether 543 superclusters at redshifts 0.009 {le} z {le} 0.2. We analyze methods of compiling supercluster catalogues and use results of the Millennium Simulation to investigate possible selection effects and errors. We find that the most effective method is the density field method using smoothing with an Epanechnikov kernel of radius 8 h{sup -1} Mpc. We derive positions of the highest luminosity density peaks and find the most luminous cluster in the vicinity of the peak, this cluster is considered as the main cluster and its brightest galaxy the main galaxy of the supercluster. In catalogues we give equatorial coordinates and distances of superclusters as determined by positions of their main clusters. We also calculate the expected total luminosities of the superclusters.

Einasto, Jaan; Einasto, M.; Tago, E.; Saar, E.; Huetsi, G.; Joeveer, M.; Liivamagi, L.J.; Suhhonenko, I.; Jaaniste, J.; Heinamaki, P.; Mueller, V.; Knebe, A.; Tucker, D. /Tartu Observ. /Estonian U. /Tuorla Observ. /Potsdam, Astrophys. Inst. /Fermilab

2006-03-01T23:59:59.000Z

309

Extremely Luminous Water Vapor Emission from a Type 2 Quasar at Redshift z = 0.66  

E-Print Network [OSTI]

A search for water masers in 47 Sloan Digital Sky Survey Type 2 quasars using the Green Bank Telescope has yielded a detection at a redshift of z = 0.660. This maser is more than an order of magnitude higher in redshift than any previously known and, with a total isotropic luminosity of 23,000 L_sun, also the most powerful. The presence and detectability of water masers in quasars at z ~ 0.3-0.8 may provide a better understanding of quasar molecular tori and disks, as well as fundamental quasar and galaxy properties such as black hole masses. Water masers at cosmologically interesting distances may also eventually provide, via direct distance determinations, a new cosmological observable for testing the reality and properties of dark energy, currently inferred primarily through Type 1a supernova measurements.

Richard Barvainis; Robert Antonucci

2005-06-10T23:59:59.000Z

310

A high dimensional delay selection for the reconstruction of proper Phase Space with Cross auto-correlation  

E-Print Network [OSTI]

For the purpose of phase space reconstruction from nonlinear time series, delay selection is one of the most vital criteria. This is normally done by using a general measure viz., mutual information (MI). However, in that case, the delay selection is limited to the estimation of a single delay using MI between two variables only. The corresponding reconstructed phase space is also not satisfactory. To overcome the situation, a high-dimensional estimator of the MI is used; it selects more than one delay between more than two variables. The quality of the reconstructed phase space is tested by shape distortion parameter (SD), it is found that even this multidimensional MI sometimes fails to produce a less distorted phase space. In this paper, an alternative nonlinear measure cross autocorrelation (CAC) is introduced. A comparative study is made between the reconstructed phase spaces of a known three dimensional Neuro dynamical model, Lorenz dynamical model and a three dimensional food web model under MI for two and higher dimensions and also under cross auto-correlation separately. It is found that the least distorted phase space is obtained only under the notion of cross autocorrelation.

Sanjay Kumar Palit; Sayan Mukherjee; D. K. Bhattacharya

2014-09-21T23:59:59.000Z

311

Deriving the redshift of distant galaxies with Gamma-Ray Burst transient edges  

E-Print Network [OSTI]

Cosmological Gamma-Ray Bursts (GRBs) offer a unique perspective to probe the evolution of distant galaxies. We discuss one of the multiple benefits of this approach, i.e. the detection of transient edges in the GRB prompt phase emission. These absorption features can be used to directly derive the redshift of GRBs and their host galaxies without the need of any optical spectroscopic follow-up.

Le Floc'h, E; Mirabel, I F

2002-01-01T23:59:59.000Z

312

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

313

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

314

The distribution of neutral hydrogen around high-redshift galaxies and quasars in the EAGLE simulation  

E-Print Network [OSTI]

The observed high covering fractions of neutral hydrogen (HI) with column densities above $\\sim 10^{17} \\rm{cm}^{-2}$ around Lyman-Break Galaxies (LBGs) and bright quasars at redshifts z ~ 2-3 has been identified as a challenge for simulations of galaxy formation. We use the EAGLE cosmological, hydrodynamical simulation, which has been shown to reproduce a wide range of galaxy properties and for which the subgrid feedback was calibrated without considering gas properties, to study the distribution of HI around high-redshift galaxies. We predict the covering fractions of strong HI absorbers ($N_{\\rm{HI}} \\gtrsim 10^{17} \\rm{cm}^{-2}$) inside haloes to increase rapidly with redshift but to depend only weakly on halo mass. For massive ($M_{200} \\gtrsim 10^{12} {\\rm M_{\\odot}}$) halos the covering fraction profiles are nearly scale-invariant and we provide fitting functions that reproduce the simulation results. While efficient feedback is required to increase the HI covering fractions to the high observed values...

Rahmati, Alireza; Bower, Richard G; Crain, Robert A; Furlong, Michelle; Schaller, Matthieu; Theuns, Tom

2015-01-01T23:59:59.000Z

315

Seeding High Redshift QSOs by Collisional Runaway in Primordial Star Clusters  

E-Print Network [OSTI]

We study how runaway stellar collisions in high redshift, metal poor star clusters form very massive stars (VMSs) that can directly collapse to intermediate mass black holes (IMBHs). We follow the evolution of a pair of two neighboring high-redshift mini-halos which are expected to host central nuclear star clusters (NSCs) with very high resolution, cosmological hydrodynamical zoom-in simulations with the adaptive mesh refinement code RAMSES. One of the two mini-halos enriches the central NSC of the other mini-halo to a critical metallicity, sufficient for Pop. II star formation at redshift z~27. We then use the spatial configuration of the flattened, asymmetrical gas cloud forming in the RAMSES simulations at the core of the metal enriched halo to set the initial conditions for simulations of an initially non-spherical star cluster with the direct summation code NBODY6 which are compared to about 2000 NBODY6 simulations of spherical star clusters for a wide range of star cluster parameters. In this way we es...

Katz, Harley; Haehnelt, Martin G

2015-01-01T23:59:59.000Z

316

The DEEP2 Galaxy Redshift Survey: The Relationship Between Galaxy Properties and Environment at z ~ 1  

E-Print Network [OSTI]

We study the mean environment of galaxies in the DEEP2 Galaxy Redshift Survey as a function of rest-frame color, luminosity, and [OII] equivalent width. The local galaxy overdensity for >14,000 galaxies at 0.75 environment is found to depend most strongly on galaxy color; all major features of the correlation between mean overdensity and rest-frame color observed in the local universe were already in place at z ~ 1. In contrast to local results, we find a substantial slope in the mean dependence of environment on luminosity for blue, star-forming galaxies at z ~ 1, with brighter blue galaxies being found on average in regions of greater overdensity. We discuss the roles of galaxy clusters and groups in establishing the observed correlations between environment and galaxy properties at high redshift, and we also explore the evidence for a ``downsizing of quenching'' from z ~ 1 to z ~ 0. Our results add weight to existing evidence that the mechanism(s) that result in star-formation quenching are efficient in group environments as well as clusters. This work is the first of its kind at high redshift and represents the first in a series of papers addressing the role of environment in galaxy formation at 0 < z < 1.

Michael C. Cooper; Jeffrey A. Newman; Darren J. Croton; Benjamin J. Weiner; Christopher N. A. Willmer; Brian F. Gerke; Darren S. Madgwick; S. M. Faber; Marc Davis; Alison L. Coil; Douglas P. Finkbeiner; Puragra Guhathakurta; David C. Koo

2006-04-26T23:59:59.000Z

317

On the Bias of the Distance-Redshift Relation from Gravitational Lensing  

E-Print Network [OSTI]

A long standing question in cosmology is whether gravitational lensing changes the distance-redshift relation $D(z)$ or the mean flux density of sources. Interest in this has been rekindled by recent studies in non-linear relativistic perturbation theory that find biases in both the area of a surface of constant redshift and in the mean distance to this surface, with a fractional bias in both cases on the order of the mean squared convergence $\\langle \\kappa^2 \\rangle$. Any such area bias could alter CMB cosmology, and the corresponding bias in mean flux density could affect supernova cosmology. Here we show that, in an ensemble averaged sense, the perturbation to the area of a surface of constant redshift is in reality much smaller, being on the order of the cumulative bending angle squared, or roughly a part-in-a-million effect. This validates the arguments of Weinberg (1976) that the mean magnification $\\mu$ of sources is unity and of Kibble \\& Lieu (2005) that the mean direction-averaged inverse magni...

Kaiser, Nick

2015-01-01T23:59:59.000Z

318

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

319

The UV, Lyman-alpha, and dark matter halo properties of high redshift galaxies  

E-Print Network [OSTI]

We explore the properties of high-redshift Lyman-alpha emitters (LAE), and their link with the Lyman-Break galaxy population (LBG), using a semi-analytic model of galaxy formation that takes into account resonant scattering of Lya photons in gas outflows. We can reasonably reproduce the abundances of LAEs and LBGs from redshift 3 to 7, as well as most UV LFs of LAEs. The stronger dust attenuation for (resonant) Lya photons compared to UV continuum photons in bright LBGs provides a natural interpretation to the increase of the LAE fraction in LBG samples, X_LAE, towards fainter magnitudes. The redshift evolution of X_LAE seems however very sensitive to UV magnitudes limits and EW cuts. In spite of the apparent good match between the statistical properties predicted by the model and the observations, we find that the tail of the Lya equivalent width distribution (EW > 100 A) cannot be explained by our model, and we need to invoke additional mechanisms. We find that LAEs and LBGs span a very similar dynamical ra...

Garel, T; Guiderdoni, B; Michel-Dansac, L; Hayes, M; Verhamme, A

2015-01-01T23:59:59.000Z

320

A New Contributor to Chemical Evolution in High-Redshift Galaxies  

E-Print Network [OSTI]

The recent discovery of a new population of stars exhibiting unusual elemental abundance patterns characterized by enhanced Ti to Ga elements and low alpha and n-capture elements suggests the contribution of a new class of supernovae, probably a kind of Type Ia supernovae associated with close binary evolution. The role of these supernovae in chemical evolution is negligible in normal galaxies that undergo moderate star formation such as our own. Thus, while the frequency of occurrence would be too low to detect in low-redshift galaxies, it may represent a prominent population in high-redshift objects such as early epoch massive elliptical galaxies and QSOs. The chemical contributor of this proposed type of supernovae in combination with recognized supernovae is shown to be compatible with the recent observational features in the distant universe, successfully reproducing the Type II supernovae-like abundance pattern with enhancement of Ga and Ge in the gas of newborn massive galaxies and high iron abundances in QSOs even at redshifts of around 6.

Takuji Tsujimoto

2004-06-29T23:59:59.000Z

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.


321

An unexpectedly low-redshift excess of Swift gamma-ray burst rate  

E-Print Network [OSTI]

Gamma-ray bursts (GRBs) are the most violent explosions in the Universe and can be used to explore the properties of high-redshift universe. It is believed that the long GRBs are associated with the deaths of massive stars. So it is possible to use GRBs to investigate the star formation rate (SFR). In this paper, we use Lynden-Bell's $c^-$ method to study the luminosity function and rate of \\emph{Swift} long GRBs without any assumptions. We find that the luminosity of GRBs evolves with redshift as $L(z)\\propto g(z)=(1+z)^k$ with $k=2.43_{-0.38}^{+0.41}$. After correcting the redshift evolution through $L_0(z)=L(z)/g(z)$, the luminosity function can be expressed as $\\psi(L_0)\\propto L_0^{-0.14\\pm0.02}$ for dim GRBs and $\\psi(L_0)\\propto L_0^{-0.70\\pm0.03}$ for bright GRBs, with the break point $L_{0}^{b}=1.43\\times10^{51}~{\\rm erg~s^{-1}}$. We also find that the formation rate of GRBs is almost constant at $z1.0$, the formation rate of GRB is consistent with the SFR. Our results are dramatically different from...

Yu, H; Dai, Z G; Cheng, K S

2015-01-01T23:59:59.000Z

322

Restframe I-band Hubble diagram for type Ia supernovae up to redshift z ~; 0.5  

E-Print Network [OSTI]

in STScI Symposium Ser. 13, Supernovae and gamma-ray bursts:Highlight: The Physics of Supernovae, ed. W. Hillebrandt &diagram for type Ia supernovae up to redshift z ? 0.5 ? S.

2005-01-01T23:59:59.000Z

323

Corrected Table for the Parametric Coefficients for the Optical Depth of the Universe to Gamma-rays at Various Redshifts  

E-Print Network [OSTI]

Table 1 in our paper, ApJ 648, 774 (2006) entitled "Intergalactic Photon Spectra from the Far IR to the UV Lyman Limit for 0 Optical Depth of the Universe to High Energy Gamma-Rays" had erroneous numbers for the coefficients fitting the parametric form for the optical depth of the universe to gamma-rays. The correct values for these parameters as described in the original text are given here in a corrected table for various redshifts for the baseline model (upper row) and fast evolution (lower row) for each individual redshift. The parametric approximation is good for optical depths between 0.01 and 100 and for gamma-ray energies up to ~2 TeV for all redshifts but also for energies up to ~10 TeV for redshifts less than 1.

F. W. Stecker; M. A. Malkan; S. T. Scully

2007-02-02T23:59:59.000Z

324

CRYSTALLOGRAPHIC POINT AND SPACE  

E-Print Network [OSTI]

CRYSTALLOGRAPHIC POINT AND SPACE GROUPS Andy Elvin June 10, 2013 #12;Contents Point and Space no reflection axes #12;Cube and Octahedron are dual Symmetries under Oh #12;Space Groups Subgroups of E(3) Point Group + Translation { R | 0 }{ E | t }a = { R | t }a = Ra + t 230 Space Groups 73 symmorphic space

California at Santa Cruz, University of

325

Definitions Numbered Space  

E-Print Network [OSTI]

Definitions · Numbered Space ­ a single space marked with a number and reserved for a single permit 24/7 · Unnumbered Space ­ a space which can be used by any customer allowed to park in that lot. High Low Average Question 4: If I buy a staff permit for an UNNUMBERED* space in a non-gated surface

Behmer, Spencer T.

326

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

327

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

328

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

329

Space Solar Power Program  

SciTech Connect (OSTI)

Information pertaining to the Space Solar Power Program is presented on energy analysis; markets; overall development plan; organizational plan; environmental and safety issues; power systems; space transportation; space manufacturing, construction, operations; design examples; and finance.

Arif, H.; Barbosa, H.; Bardet, C.; Baroud, M.; Behar, A.; Berrier, K.; Berthe, P.; Bertrand, R.; Bibyk, I.; Bisson, J.; Bloch, L.; Bobadilla, G.; Bourque, D.; Bush, L.; Carandang, R.; Chiku, T.; Crosby, N.; De Seixas, M.; De Vries, J.; Doll, S.; Dufour, F.; Eckart, P.; Fahey, M.; Fenot, F.; Foeckersperger, S.; Fontaine, J.E.; Fowler, R.; Frey, H.; Fujio, H.; Gasa, J.M.; Gleave, J.; Godoe, J.; Green, I.; Haeberli, R.; Hanada, T.; Ha

1992-08-01T23:59:59.000Z

330

Quantum Complex Minkowski Space  

E-Print Network [OSTI]

The complex Minkowski phase space has the physical interpretation of the phase space of the scalar massive conformal particle. The aim of the paper is the construction and investigation of the quantum complex Minkowski space.

Grzegorz Jakimowicz; Anatol Odzijewicz

2005-05-06T23:59:59.000Z

331

Space Science and Applications  

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

1 Space Science and Applications Applying world-class expertise in space sciences and associated technologies to detect and characterize national security threats Contacts Group...

332

A CLASS OF ECCENTRIC BINARIES WITH DYNAMIC TIDAL DISTORTIONS DISCOVERED WITH KEPLER  

SciTech Connect (OSTI)

We have discovered a class of eccentric binary systems within the Kepler data archive that have dynamic tidal distortions and tidally induced pulsations. Each has a uniquely shaped light curve that is characterized by periodic brightening or variability at timescales of 4-20 days, frequently accompanied by shorter period oscillations. We can explain the dominant features of the entire class with orbitally varying tidal forces that occur in close, eccentric binary systems. The large variety of light curve shapes arises from viewing systems at different angles. This hypothesis is supported by spectroscopic radial velocity measurements for five systems, each showing evidence of being in an eccentric binary system. Prior to the discovery of these 17 new systems, only four stars, where KOI-54 is the best example, were known to have evidence of these dynamic tides and tidally induced oscillations. We perform preliminary fits to the light curves and radial velocity data, present the overall properties of this class, and discuss the work required to accurately model these systems.

Thompson, Susan E.; Barclay, Thomas; Howell, Steve B.; Still, Martin; Ibrahim, Khadeejah A. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Everett, Mark [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States); Mullally, Fergal; Rowe, Jason; Christiansen, Jessie L.; Twicken, Joseph D.; Clarke, Bruce D. [SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, CA 94043 (United States); Kurtz, Donald W.; Hambleton, Kelly, E-mail: susan.e.thompson@nasa.gov [Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE (United Kingdom)

2012-07-01T23:59:59.000Z

333

Ultra-lightweight telescope with MEMS adaptive optic for distortion correction.  

SciTech Connect (OSTI)

Recent world events have underscored the need for a satellite based persistent global surveillance capability. To be useful, the satellite must be able to continuously monitor objects the size of a person anywhere on the globe and do so at a low cost. One way to satisfy these requirements involves a constellation of satellites in low earth orbit capable of resolving a spot on the order of 20 cm. To reduce cost of deployment, such a system must be dramatically lighter than a traditional satellite surveillance system with a high spatial resolution. The key to meeting this requirement is a lightweight optics system with a deformable primary and secondary mirrors and an adaptive optic subsystem correction of wavefront distortion. This proposal is concerned with development of MEMS micromirrors for correction of aberrations in the primary mirror and improvement of image quality, thus reducing the optical requirements on the deployable mirrors. To meet this challenge, MEMS micromirrors must meet stringent criteria on their performance in terms of flatness, roughness and resolution of position. Using Sandia's SUMMIT foundry which provides the world's most sophisticated surface MEMS technology as well as novel designs optimized by finite element analysis will meet severe requirements on mirror travel range and accuracy.

Spahn, Olga Blum; Cowan, William D.; Shaw, Michael J.; Adams, David Price; Sweatt, William C.; Dagel, Daryl James; Grine, Alejandro J.; Mani, Seethambal S.; Resnick, Paul James; Gass, Fawn Renee; Grossetete, Grant David

2004-12-01T23:59:59.000Z

334

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

335

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

336

The Environment on few Mpc scales of Infrared Luminous Galaxies at Redshifts z~1  

E-Print Network [OSTI]

We investigate the environment of infrared luminous galaxies (L$_{IR}$[8-1000 $\\mu $m$] >10^{11}$L$_{\\sun}$). We focus on the redshift range 0.7 $\\leq$ z $\\leq$ 1, where these galaxies dominate the star formation activity and play a significant role in galaxy evolution. We employ MIPS 24$\\mu$m data to identify infrared galaxies in the Extended Groth Strip (EGS). We use a local density indicator to probe the environment on few Mpc scales and a group member catalog, both of which make use of the DEEP2 spectroscopic redshift catalog, to quantify the environment of these galaxies. We find that the local environment of LIRGs and ULIRGs is intermediate between that of blue and red galaxies. LIRGs and ULIRGs avoid underdense environments and inhabit local environments that are more dense on average than those of other DEEP2 galaxies at similar redshifts. However, when the comparison sample of the non-IR DEEP2 galaxies is restricted to have the same range of stellar mass, color, or luminosity as the IR--galaxies, there is no longer any significant difference in environment; the IR-galaxies follow the same trends in the color-environment and luminosity-environment relations observed at z$\\sim$1. We also find that about 30% of the LIRGs and ULIRGs belong to groups, associated with a minimum dark matter halo of 6$\\times10^{12}$M$_{\\odot}$h$^{-1}$. The group members constitute 20 % of the sources responsible for the IR star formation rate density and comoving energy density at z$\\sim$1.

D. Marcillac; G. H. Rieke; C. Papovich; C. N. A. Willmer; B. J. Weiner; A. L. Coil; M. C. Cooper; B. F. Gerke; J. Woo; J. A. Newman; A. Georgakakis; E. S. Laird; K. Nandra; G. G. Fazio; J. -S. Huang; D. C. Koo

2007-12-01T23:59:59.000Z

337

A blind test of photometric redshifts on ground-based data  

E-Print Network [OSTI]

Aims. We analyse the relative performance of different photo-z codes in blind applications to ground-based data. Methods. We tested the codes on imaging datasets with different depths and filter coverages and compared the results to large spectroscopic catalogues. The photo-z error behaviour was analysed to select cleaner subsamples with more secure photo-z estimates. We consider Hyperz, BPZ, and the code used in the CADIS, COMBO-17, and HIROCS surveys. Results. The photo-z error estimates of the three codes do not correlate tightly with the accuracy of the photo-z's. While very large errors sometimes indicate a true catastrophic photo-z failure, smaller errors are usually not meaningful. For any given dataset, we find significant differences in redshift accuracy and outlier rates between the different codes when compared to spectroscopic redshifts. However, different codes excel in different regimes. The agreement between different sets of photo-z's is better for the subsample with secure spectroscopic redshifts than for the whole catalogue. Conclusions. Running today's photo-z codes on well-calibrated ground-based data can lead to reasonable accuracy. The actual performance on a given dataset is largely dependent on the template choice and on realistic instrumental response curves. It would be desirable to improve the photo-z error estimation for future applications so as to get a better handle on rejecting objects with grossly inaccurate photo-z's. The secure spectroscopic subsamples commonly used for assessments of photo-z accuracy may be biased toward objects for which the photo-z's are easier to estimate than for a complete flux-limited sample, resulting in very optimistic estimates. (abridged)

H. Hildebrandt; C. Wolf; N. Benitez

2008-01-18T23:59:59.000Z

338

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

339

Space Shuttle Program Status  

E-Print Network [OSTI]

1 Space Shuttle Program Status John Casper Associate Manager Space Shuttle Program September 13, 2010 NAC Space Operations Committee #12;2 Operations #12;3 Flown Manifest March 2009 ­ May 2010 #12, 2010 · 132nd Space Shuttle mission · 32nd Flight of Atlantis (120,650,907 statute miles) · 294 Total

Waliser, Duane E.

340

Space Complexity Algorithms & Complexity  

E-Print Network [OSTI]

Space Complexity Algorithms & Complexity Space Complexity Nicolas Stroppa Patrik Lambert - plambert@computing.dcu.ie CA313@Dublin City University. 2008-2009. December 4, 2008 #12;Space Complexity Hierarchy of problems #12;Space Complexity NP-intermediate Languages If P = NP, then are there languages which neither in P

Way, Andy

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

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

342

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

343

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

344

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

345

Redshifting of cosmological black bodies in BSBM varying-alpha theories  

E-Print Network [OSTI]

the density of photons with frequency ? is N = ?/(~?). The Stefan-Boltzmann law for a decoupled black body is therefore also preserved, with the temperature receiving no new effects due to a varying ? (other than those due to the gravitational effect of ?... term exists for pure radiation, the field ? does not lose or gain energy (other than redshifting like 1/a6 due to its own pressure) and likewise the energy for ra- diation should be defined so that it does not depart from the usual 1/a4 law. Thus...

Barrow, John D.; Magueijo, João

2014-11-04T23:59:59.000Z

346

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

347

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

348

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 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, and 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 = 0.123 +/- 0.002 (compared to sigma = 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...

Ball, N M; Myers, A D; Strand, N E; Alberts, S L; Tcheng, D; Llora, X; Ball, Nicholas M.; Brunner, Robert J.; Myers, Adam D.; Strand, Natalie E.; Alberts, Stacey L.; Tcheng, David; Llor\\`a, Xavier

2006-01-01T23:59:59.000Z

349

Local structure underlying anomalous tetragonal distortions in BiFeO{sub 3}-PbTiO{sub 3} ferroelectrics  

SciTech Connect (OSTI)

The local structure of tetragonal BiFeO{sub 3}-PbTiO{sub 3} solid solutions featuring anomalous lattice distortions has been determined using simultaneous fitting of neutron total scattering and extended X-ray absorption fine structure data. On the local scale, the large tetragonal distortion, promoted by the displacements of the A-cations (Bi and Pb), is accommodated primarily by the [FeO{sub 6}] octahedra, even though both Fe and Ti acquire (5+1)-fold coordination. Bi cations exhibit considerably larger displacements than Pb. The combination of the A-cation displacements and the ability of M-cations to adopt 5-fold coordination is suggested as key for stabilizing the large tetragonality in BiMO{sub 3}-PbTiO{sub 3} systems.

Levin, I.; Krayzman, V.; Woicik, J. C. [Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Tucker, M. G. [ISIS Facility, Rutherford Appleton Laboratory, Didcot (United Kingdom)

2014-06-16T23:59:59.000Z

350

mm-WAVE Op-Amps FOR LOW DISTORTION AMPLIFICATION WITH HIGH OIP3/PDC RATIO > 100 AT 2 GHz  

E-Print Network [OSTI]

mm-WAVE Op-Amps FOR LOW DISTORTION AMPLIFICATION WITH HIGH OIP3/PDC RATIO > 100 AT 2 GHz Zach in bandwidth for an op-amp of any kind, as well as 3Ã? betterment in OIP3/PDC ratio at fs = 2-3 GHz, when dissipation PDC. This very high ratio of third-order-intercept power to DC power consumption POIP 3/PDC > 100

Rodwell, Mark J. W.

351

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

352

The High Redshift Blazar S5 0836+71: A Broadband Study  

E-Print Network [OSTI]

A broadband study of the high redshift blazar S5 0836+71 (z = 2.172) is presented. Multi-frequency light curves show multiple episodes of X-ray and $\\gamma$-ray flares, while optical-UV fluxes show little variations. During the GeV outburst, the highest $\\gamma$-ray flux measured is (5.22 $\\pm$ 1.10) $\\times$ 10$^{-6}$ ph cm$^{-2}$ s$^{-1}$ in the range of 0.1-300 GeV, which corresponds to an isotropic $\\gamma$-ray luminosity of (1.62 $\\pm$ 0.44) $\\times$ 10$^{50}$ erg s$^{-1}$, thereby making this as one of the most luminous $\\gamma$-ray flare ever observed from any blazar. A fast $\\gamma$-ray flux rising time of $\\sim$3 hours is also noticed which is probably the first measurement of hour scale variability detected from a high redshift (z > 2) blazar. The various activity states of S5 0836+71 are reproduced under the assumption of single zone leptonic emission model. In all the states, the emission region is located inside the broad line region, and the optical-UV radiation is dominated by the accretion dis...

Paliya, Vaidehi S

2015-01-01T23:59:59.000Z

353

$XMM-Newton$ $?$ project: III. Gas mass fraction shape in high redshift clusters  

E-Print Network [OSTI]

We study the gas mass fraction, $f\\_{\\rm gas},$ behavior in $XMM-Newton$ $\\Omega$ project. The typical $f\\_{\\rm gas}$ shape of high redshift galaxy clusters follows the global shape inferred at low redshift quite well. This result is consistent with the gravitational instability picture leading to self similar structures for both the dark and baryonic matter. However, the mean $f\\_{\\rm gas} in distant clusters shows some differences to local ones, indicating a departure from strict scaling. This result is consistent with the observed evolution in the luminosity-temperature relation. We quantitatively investigate this departure from scaling laws. Within the local sample we used, a moderate but clear variation of the amplitude of the gas mass fraction with temperature is found, a trend that weakens in the outer regions. These variations do not explain departure from scaling laws of our distant clusters. An important implication of our results is that the gas fraction evolution, a test of the cosmological parameters, can lead to biased values when applied at radii smaller than the virial radius. From our $XMM$ clusters, the apparent gas fraction at the virial radius is consistent with a non-evolving universal value in a high matter density model and not with a concordance.

Rachida Sadat; Alain Blanchard; Sebastien C. Vauclair; David H. Lumb; James Bartlett; A. K. Romer; Jean-Philippe Bernard; Michel Boer; Philippe Marty; Jukka Nevalainen; Douglas J. Burke; C. A. Collins; Robert C. Nichol

2005-03-19T23:59:59.000Z

354

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

355

Feedback Limits Rapid Growth of Seed Black Holes at High Redshift  

E-Print Network [OSTI]

Seed black holes formed in the collapse of population III stars have been invoked to explain the presence of supermassive black holes at high redshift. It has been suggested that a seed black hole can grow up to $10^{5\\sim 6}\\sunm$ through highly super-Eddington accretion for a period of $\\sim 10^{6\\sim 7}$ yr between redshift $z=20\\sim 24$. We studied the feedback of radiation pressure, Compton heating and outflow during the seed black hole growth. It is found that its surrounding medium fueled to the seed hole is greatly heated by Compton heating. For a super-critical accretion onto a $10^3\\sunm$ seed hole, a Compton sphere (with a temperature $\\sim 10^6$K) forms in a timescale of $1.6\\times 10^3$yr so that the hole is only supplied by a rate of $10^{-3}$ Eddington limit from the Compton sphere. Beyond the Compton sphere, the kinetic feedback of the strong outflow heats the medium at large distance, this leads to a dramatical decrease of the outer Bondi accretion onto the black hole and avoid the accumulation of the matter. The highly super-critical accretion will be rapidly halted by the strong feedback. The seed black holes hardly grow up at the very early universe unless the strong feedback can be avoided.

J. -M. Wang; Y. -M. Chen; C. Hu

2005-12-17T23:59:59.000Z

356

A New Contributor to Chemical Evolution in High-Redshift Galaxies  

E-Print Network [OSTI]

The recent discovery of a new population of stars exhibiting unusual elemental abundance patterns characterized by enhanced Ti to Ga elements and low alpha and n-capture elements suggests the contribution of a new class of supernovae, probably a kind of Type Ia supernovae associated with close binary evolution. The role of these supernovae in chemical evolution is negligible in normal galaxies that undergo moderate star formation such as our own. Thus, while the frequency of occurrence would be too low to detect in low-redshift galaxies, it may represent a prominent population in high-redshift objects such as early epoch massive elliptical galaxies and QSOs. The chemical contributor of this proposed type of supernovae in combination with recognized supernovae is shown to be compatible with the recent observational features in the distant universe, successfully reproducing the Type II supernovae-like abundance pattern with enhancement of Ga and Ge in the gas of newborn massive galaxies and high iron abundances...

Tsujimoto, T

2004-01-01T23:59:59.000Z

357

ULTRA STEEP SPECTRUM RADIO SOURCES IN THE LOCKMAN HOLE: SERVS IDENTIFICATIONS AND REDSHIFT DISTRIBUTION AT THE FAINTEST RADIO FLUXES  

SciTech Connect (OSTI)

Ultra steep spectrum (USS) radio sources have been successfully used to select powerful radio sources at high redshifts (z {approx}> 2). Typically restricted to large-sky surveys and relatively bright radio flux densities, it has gradually become possible to extend the USS search to sub-mJy levels, thanks to the recent appearance of sensitive low-frequency radio facilities. Here a first detailed analysis of the nature of the faintest USS sources is presented. By using Giant Metrewave Radio Telescope and Very Large Array radio observations of the Lockman Hole at 610 MHz and 1.4 GHz, a sample of 58 USS sources, with 610 MHz integrated fluxes above 100 {mu}Jy, is assembled. Deep infrared data at 3.6 and 4.5 {mu}m from the Spitzer Extragalactic Representative Volume Survey (SERVS) are used to reliably identify counterparts for 48 (83%) of these sources, showing an average total magnitude of [3.6]{sub AB} = 19.8 mag. Spectroscopic redshifts for 14 USS sources, together with photometric redshift estimates, improved by the use of the deep SERVS data, for a further 19 objects, show redshifts ranging from z = 0.1 to z = 2.8, peaking at z {approx} 0.6 and tailing off at high redshifts. The remaining 25 USS sources, with no redshift estimate, include the faintest [3.6] magnitudes, with 10 sources undetected at 3.6 and 4.5 {mu}m (typically [3.6] {approx}> 22-23 mag from local measurements), which suggests the likely existence of higher redshifts among the sub-mJy USS population. The comparison with the Square Kilometre Array Design Studies Simulated Skies models indicates that Fanaroff-Riley type I radio sources and radio-quiet active galactic nuclei may constitute the bulk of the faintest USS population, and raises the possibility that the high efficiency of the USS technique for the selection of high-redshift sources remains even at the sub-mJy level.

Afonso, J.; Bizzocchi, L.; Grossi, M.; Messias, H.; Fernandes, C. A. C. [Observatorio Astronomico de Lisboa, Faculdade de Ciencias, Universidade de Lisboa, Tapada da Ajuda, 1349-018 Lisbon (Portugal); Ibar, E.; Ivison, R. J. [UK Astronomy Technology Centre, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom); Simpson, C. [Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD (United Kingdom); Chapman, S.; Gonzalez-Solares, E. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Jarvis, M. J. [Centre for Astrophysics, Science and Technology Research Institute, University of Hertfordshire, Hatfield, Herts AL10 9AB (United Kingdom); Rottgering, H. [Leiden Observatory, Leiden University, Oort Gebouw, P.O. Box 9513, 2300 RA Leiden (Netherlands); Norris, R. P. [CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia); Dunlop, J.; Best, P. [SUPA, Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Pforr, J. [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX (United Kingdom); Vaccari, M. [Department of Astronomy, University of Padova, vicolo Osservatorio 3, 35122 Padova (Italy); Seymour, N. [Mullard Space Science Laboratory, UCL, Holmbury St Mary, Dorking, Surrey RH5 6NT (United Kingdom); Farrah, D. [Astronomy Centre, Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH (United Kingdom); Huang, J.-S., E-mail: jafonso@oal.ul.pt [Department of Astrophysics, Oxford University, Keble Road, Oxford OX1 3RH (United Kingdom); and others

2011-12-20T23:59:59.000Z

358

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

359

Analysis of system wide distortion in an integrated power system utilizing a high voltage DC bus and silicon carbide power devices  

E-Print Network [OSTI]

This research investigates the distortion on the electrical distribution system for a high voltage DC Integrated Power System (IPS). The analysis was concentrated on the power supplied to a propulsion motor driven by an ...

Fallier, William F. (William Frederick)

2007-01-01T23:59:59.000Z

360

Ordered involutive operator spaces  

E-Print Network [OSTI]

This is a companion to recent papers of the authors; here we construct the `noncommutative Shilov boundary' of a (possibly nonunital) selfadjoint ordered space of Hilbert space operators. The morphisms in the universal property of the boundary preserve order. As an application, we consider `maximal' and `minimal' unitizations of such ordered operator spaces.

Blecher, David P; Neal, Matthew; Werner, Wend

2007-01-01T23:59:59.000Z

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.


361

SPACE RESOURCES ROUNDTABLE IX  

E-Print Network [OSTI]

SPACE RESOURCES ROUNDTABLE IX Colorado School of Mines October 25-27, 2007 http://www.ISRUinfo.com Sponsored by: Colorado School of Mines Lunar and Planetary Institute Space Resources Roundtable, Inc. First Space Michael B. Duke, Colorado School of Mines Leslie Gertsch, University of Missouri-Rolla Alex

Rathbun, Julie A.

362

Conclusions Fractionated Space Systems  

E-Print Network [OSTI]

Conclusions Fractionated Space Systems There is a growing interest in fractionated space system design. Fractionated space systems are inherently flexible and modular. There are many key technologies of flexibility serves as a source of motivation for system designers to embed flexibility into a system design (i

de Weck, Olivier L.

363

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

364

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

365

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

366

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

367

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

368

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

369

Superclusters of galaxies from the 2dF redshift survey. 2. Comparison with simulations  

SciTech Connect (OSTI)

We investigate properties of superclusters of galaxies found on the basis of the 2dF Galaxy Redshift Survey, and compare them with properties of superclusters from the Millennium Simulation.We study the dependence of various characteristics of superclusters on their distance from the observer, on their total luminosity, and on their multiplicity. The multiplicity is defined by the number of Density Field (DF) clusters in superclusters. Using the multiplicity we divide superclusters into four richness classes: poor, medium, rich and extremely rich.We show that superclusters are asymmetrical and have multi-branching filamentary structure, with the degree of asymmetry and filamentarity being higher for the more luminous and richer superclusters. The comparison of real superclusters with Millennium superclusters shows that most properties of simulated superclusters agree very well with real data, the main differences being in the luminosity and multiplicity distributions.

Einasto, Jaan; Einasto, M.; Saar, E.; Tago, E.; Liivamagi, L.J.; Joeveer, M.J; Suhhonenko, I.; Hutsi, G.; /Tartu Observ.; Jaaniste, J.; /Estonian U.; Heinamaki, P.; /Tuorla; Muller, V.; Knebe, A.; /Potsdam, Astrophys. Inst.; Tucker, D.; /Fermilab

2006-04-01T23:59:59.000Z

370

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

371

COSMIC RAYS CAN DRIVE STRONG OUTFLOWS FROM GAS-RICH HIGH-REDSHIFT DISK GALAXIES  

SciTech Connect (OSTI)

We present simulations of the magnetized interstellar medium (ISM) in models of massive star-forming (40 M {sub ?} yr{sup –1}) disk galaxies with high gas surface densities (?{sub gas} ? 100 M {sub ?} pc{sup –2}) similar to observed star-forming high-redshift disks. We assume that type II supernovae deposit 10% of their energy into the ISM as cosmic rays (CRs) and neglect the additional deposition of thermal energy or momentum. With a typical Galactic diffusion coefficient for CRs (3 × 10{sup 28} cm{sup 2} s{sup –1}), we demonstrate that this process alone can trigger the local formation of a strong low-density galactic wind maintaining vertically open field lines. Driven by the additional pressure gradient of the relativistic fluid, the wind speed can exceed 10{sup 3} km s{sup –1}, much higher than the escape velocity of the galaxy. The global mass loading, i.e., the ratio of the gas mass leaving the galactic disk in a wind to the star formation rate, becomes of order unity once the system has settled into an equilibrium. We conclude that relativistic particles accelerated in supernova remnants alone provide a natural and efficient mechanism to trigger winds similar to observed mass-loaded galactic winds in high-redshift galaxies. These winds also help in explaining the low efficiencies for the conversion of gas into stars in galaxies, as well as the early enrichment of the intergalactic medium with metals. This mechanism may be at least of similar importance to the traditionally considered momentum feedback from massive stars and thermal and kinetic feedback from supernova explosions.

Hanasz, M.; Kowalik, K.; Wólta?ski, D. [Centre for Astronomy, Nicolaus Copernicus University, Faculty of Physics, Astronomy and Informatics, Grudziadzka 5, PL-87100 Toru? (Poland)] [Centre for Astronomy, Nicolaus Copernicus University, Faculty of Physics, Astronomy and Informatics, Grudziadzka 5, PL-87100 Toru? (Poland); Lesch, H. [Universitäts-Sternwarte München, Scheinerstr. 1, D-81679 München (Germany)] [Universitäts-Sternwarte München, Scheinerstr. 1, D-81679 München (Germany); Naab, T. [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching bei München (Germany)] [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching bei München (Germany); Gawryszczak, A., E-mail: mhanasz@astri.uni.torun.pl [Pozna? Supercomputing and Networking Centre, ul. Noskowskiego 10, PL-61-704 Pozna? (Poland)

2013-11-10T23:59:59.000Z

372

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

373

MODELING THE REDSHIFT EVOLUTION OF THE NORMAL GALAXY X-RAY LUMINOSITY FUNCTION  

SciTech Connect (OSTI)

Emission from X-ray binaries (XRBs) is a major component of the total X-ray luminosity of normal galaxies, so X-ray studies of high-redshift galaxies allow us to probe the formation and evolution of XRBs on very long timescales ({approx}10 Gyr). In this paper, we present results from large-scale population synthesis models of binary populations in galaxies from z = 0 to {approx}20. We use as input into our modeling the Millennium II Cosmological Simulation and the updated semi-analytic galaxy catalog by Guo et al. to self-consistently account for the star formation history (SFH) and metallicity evolution of each galaxy. We run a grid of 192 models, varying all the parameters known from previous studies to affect the evolution of XRBs. We use our models and observationally derived prescriptions for hot gas emission to create theoretical galaxy X-ray luminosity functions (XLFs) for several redshift bins. Models with low common envelope efficiencies, a 50% twins mass ratio distribution, a steeper initial mass function exponent, and high stellar wind mass-loss rates best match observational results from Tzanavaris and Georgantopoulos, though they significantly underproduce bright early-type and very bright (L{sub x} > 10{sup 41}) late-type galaxies. These discrepancies are likely caused by uncertainties in hot gas emission and SFHs, active galactic nucleus contamination, and a lack of dynamically formed low-mass XRBs. In our highest likelihood models, we find that hot gas emission dominates the emission for most bright galaxies. We also find that the evolution of the normal galaxy X-ray luminosity density out to z = 4 is driven largely by XRBs in galaxies with X-ray luminosities between 10{sup 40} and 10{sup 41} erg s{sup -1}.

Tremmel, M. [Department of Astronomy, University of Washington, Box 351580, U.W., Seattle, WA 98195-1580 (United States)] [Department of Astronomy, University of Washington, Box 351580, U.W., Seattle, WA 98195-1580 (United States); Fragos, T.; Zezas, A. [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); Lehmer, B. D.; Tzanavaris, P. [The Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States)] [The Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States); Belczynski, K. [Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warsaw (Poland)] [Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warsaw (Poland); Kalogera, V.; Farr, W. M. [Center for Interdisciplinary Research and Exploration in Astrophysics and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States)] [Center for Interdisciplinary Research and Exploration in Astrophysics and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Basu-Zych, A. R.; Hornschemeier, A.; Jenkins, L.; Ptak, A., E-mail: mjt29@astro.washington.edu [NASA Goddard Space Flight Centre, Code 662, Greenbelt, MD 20771 (United States)

2013-03-20T23:59:59.000Z

374

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

375

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

376

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

377

CANDELS/GOODS-S, CDFS, ECDFS: Photometric Redshifts For Normal and for X-Ray-Detected Galaxies  

E-Print Network [OSTI]

We present photometric redshifts and associated probability distributions for all detected sources in the Extended Chandra Deep Field South (ECDFS). The work makes use of the most up-to-date data from the Cosmic Assembly Near-IR Deep Legacy Survey (CANDELS) and the Taiwan ECDFS Near-Infrared Survey (TENIS) in addition to other data. We also revisit multi-wavelength counterparts for published X-ray sources from the 4Ms-CDFS and 250ks-ECDFS surveys, finding reliable counterparts for 1207 out of 1259 sources ($\\sim 96\\%$). Data used for photometric redshifts include intermediate-band photometry deblended using the TFIT method, which is used for the first time in this work. Photometric redshifts for X-ray source counterparts are based on a new library of AGN/galaxy hybrid templates appropriate for the faint X-ray population in the CDFS. Photometric redshift accuracy for normal galaxies is 0.010 and for X-ray sources is 0.014, and outlier fractions are $4\\%$ and $5.4\\%$ respectively. The results within the CANDELS...

Hsu, Li-Ting; Nandra, Kirpal; Brusa, Marcella; Bender, Ralf; Buchner, Johannes; Donley, Jennifer L; Kocevski, Dale D; Guo, Yicheng; Hathi, Nimish P; Rangel, Cyprian; Willner, S P; Brightman, Murray; Georgakakis, Antonis; Budavári, Tamás; Szalay, Alexander S; Ashby, Matthew L N; Barro, Guillermo; Dahlen, Tomas; Faber, Sandra M; Ferguson, Henry C; Galametz, Audrey; Grazian, Andrea; Grogin, Norman A; Huang, Kuang-Han; Koekemoer, Anton M; Lucas, Ray A; McGrath, Elizabeth; Mobasher, Bahram; Peth, Michael; Rosario, David J; Trump, Jonathan R

2014-01-01T23:59:59.000Z

378

Kant's hidden ontology of space  

E-Print Network [OSTI]

Verlag, Cassam, Quassim. “Space and Objective Experience,”John. World Enough and Space-Time (Cambridge, Massachusetts:On the Perception of Space [and Time],” in The Cambridge

Messina, James Anthony

2011-01-01T23:59:59.000Z

379

SPACE: the SPectroscopic All-sky Cosmic Explorer  

E-Print Network [OSTI]

We describe the scientific motivations, the mission concept and the instrumentation of SPACE, a class-M mission proposed for concept study at the first call of the ESA Cosmic-Vision 2015-2025 planning cycle. SPACE aims to produce the largest three-dimensional evolutionary map of the Universe over the past 10 billion years by taking near-IR spectra and measuring redshifts for more than half a billion galaxies at 0SPACE will also target a smaller sky field, performing a deep spectroscopic survey of millions of galaxies to AB~26 and at 2SPACE will use a 1.5m diameter Ritchey-Chretien telescope equipped with a set of arrays of Digital Micro-mirror Devices (DMDs) covering a total field of view of 0.4 deg2, and will perform large-multiplexing multi-object spectroscopy (e.g. ~6000 targets per pointing) at a spectral resolution of R~400 as well as diffraction-limited imaging with continuous coverage from 0.8mum to 1.8mum.

A. Cimatti; M. Robberto; C. M. Baugh; S. V. W. Beckwith; R. Content; E. Daddi; G. De Lucia; B. Garilli; L. Guzzo; G. Kauffmann; M. Lehnert; D. Maccagni; A. Martinez-Sansigre; F. Pasian; I. N. Reid; P. Rosati; R. Salvaterra; M. Stiavelli; Y. Wang; M. Zapatero Osorio; the SPACE team

2008-04-28T23:59:59.000Z

380

zCOSMOS: A Large VLT/VIMOS redshift survey covering 0 < z < 3 in the COSMOS field  

E-Print Network [OSTI]

zCOSMOS is a large redshift survey that is being undertaken in the COSMOS field using 600 hours of observation with the VIMOS spectrograph on the 8-m VLT. The survey is designed to characterise the environments of COSMOS galaxies from the 100 kpc scales of galaxy groups up to the 100 Mpc scale of the cosmic web and to produce diagnostic information on galaxies and active galactic nuclei. The zCOSMOS survey consists of two parts: (a) zCOSMOS-bright, a magnitude-limited I-band IAB designed to mimic the parameters of the 2dfGRS; and (b) zCOSMOS-deep, a survey of approximately 10,000 galaxies selected through colour-selection criteria to have 1.4 design and the construction of the target catalogues, and briefly outlines the observational program and the data pipeline. In the first observing season, spectra of 1303 zCOSMOS-bright targets and of 977 zCOSMOS-deep targets have been obtained. These are briefly analysed to demonstrate the characteristics that may be expected from zCOSMOS, and particularly zCOSMOS-bright, when it is finally completed between 2008-2009. The power of combining spectroscopic and photometric redshifts is demonstrated, especially in correctly identifying the emission line in single-line spectra and in determining which of the less reliable spectroscopic redshifts are correct and which are incorrect. Our zCOSMOS-deep spectra demonstrate the effectiveness of our selection techniques to isolate high redshift galaxies at 1.4 < z < 3.0 and of VIMOS to measure their redshifts using ultraviolet absorption lines.

S. J. Lilly; O. Le Fevre; A. Renzini; G. Zamorani; M. Scodeggio; T. Contini; C. M. Carollo; G. Hasinger; J. -P. Kneib; A. Iovino; V. Le Brun; C. Maier; V. Mainieri; M. Mignoli; J. Silverman; L. A. M. Tasca; M. Bolzonella; A. Bongiorno; D. Bottini; P. Capak; K. Caputi; A. Cimatti; O. Cucciati; E. Daddi; R. Feldmann; P. Franzetti; B. Garilli; L. Guzzo; O. Ilbert; P. Kampczyk; K. Kovac; F. Lamareille; A. Leauthaud; J. -F. Le Borgne; H. J. McCracken; C. Marinoni; R. Pello; E. Ricciardelli; C. Scarlata; D. Vergani; D. B. Sanders; E. Schinnerer; N. Scoville; Y. Taniguchi; other zCOSMOS team members

2006-12-11T23:59:59.000Z

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.


381

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

382

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

383

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

384

space for science, enterprise and environment Bringing Space Into School  

E-Print Network [OSTI]

space for science, enterprise and environment Bringing Space Into School Science The National Space Education Initiative #12;space for science, enterprise and environment National Space Education Initiative the consultations · Recommendations of the report #12;space for science, enterprise and environment Background

385

Quantum-Space Attacks  

E-Print Network [OSTI]

Theoretical quantum key distribution (QKD) protocols commonly rely on the use of qubits (quantum bits). In reality, however, due to practical limitations, the legitimate users are forced to employ a larger quantum (Hilbert) space, say a quhexit (quantum six-dimensional) space, or even a much larger quantum Hilbert space. Various specific attacks exploit of these limitations. Although security can still be proved in some very special cases, a general framework that considers such realistic QKD protocols, as well as} attacks on such protocols, is still missing. We describe a general method of attacking realistic QKD protocols, which we call the `quantum-space attack'. The description is based on assessing the enlarged quantum space actually used by a protocol, the `quantum space of the protocol'. We demonstrate these new methods by classifying various (known) recent attacks against several QKD schemes, and by analyzing a novel attack on interferometry-based QKD.

Ran Gelles; Tal Mor

2007-11-25T23:59:59.000Z

386

Gymnastics in Phase Space  

SciTech Connect (OSTI)

As accelerator technology advances, the requirements on accelerator beam quality become increasingly demanding. Facing these new demands, the topic of phase space gymnastics is becoming a new focus of accelerator physics R&D. In a phase space gymnastics, the beam's phase space distribution is manipulated and precision tailored to meet the required beam qualities. On the other hand, all realization of such gymnastics will have to obey accelerator physics principles as well as technological limitations. Recent examples of phase space gymnastics include Emittance exchanges, Phase space exchanges, Emittance partitioning, Seeded FELs and Microbunched beams. The emittance related topics of this list are reviewed in this report. The accelerator physics basis, the optics design principles that provide these phase space manipulations, and the possible applications of these gymnastics, are discussed. This fascinating new field promises to be a powerful tool of the future.

Chao, Alexander Wu; /SLAC

2012-03-01T23:59:59.000Z

387

Matter: Space without Time  

E-Print Network [OSTI]

While Quantum Gravity remains elusive and Quantum Field Theory retains the interpretational difficulties of Quantum Mechanics, we have introduced an alternate approach to the unification of particles, fields, space and time, suggesting that the concept of matter as space without time provides a framework which unifies matter with spacetime and in which we anticipate the development of complete theories (ideally a single unified theory) describing observed 'particles, charges, fields and forces' solely with the geometry of our matter-space-time universe.

Yousef Ghazi-Tabatabai

2012-11-19T23:59:59.000Z

388

Total Space Heat-  

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

Commercial 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...

389

Total Space Heat-  

Gasoline and Diesel Fuel Update (EIA)

Revised: December, 2008 Total Space Heat- ing Cool- ing Venti- lation Water Heat- ing Light- ing Cook- ing Refrig- eration Office Equip- ment Com- puters Other All Buildings...

390

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

391

Beyond Space-Time  

E-Print Network [OSTI]

These notes, based on the remarks made at the 23 Solvay Conference, collect several speculative ideas concerning gauge/ strings duality, de Sitter spaces, dimensionality and the cosmological constant.

A. M. Polyakov

2006-02-01T23:59:59.000Z

392

Sounds and Space   

E-Print Network [OSTI]

the account I give (in section 1) of what sounds are and (in section 2) of the role of space in auditory perception....

Nudds, Matthew

393

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

394

Space: the final frontier  

E-Print Network [OSTI]

Edited by Markus Eichhorn frontiers of biogeography 6.2,6596 Space: the final frontier Spatial Simulation: Exploringpoints in some places, but frontiers of biogeography 6.2,

Stoll, Peter

2014-01-01T23:59:59.000Z

395

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

396

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.

397

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

398

Phase-space structures II: Hierarchical Structure Finder  

E-Print Network [OSTI]

A new multi-dimensional Hierarchical Structure Finder (HSF) to study the phase-space structure of dark matter in N-body cosmological simulations is presented. The algorithm depends mainly on two parameters, which control the level of connectivity of the detected structures and their significance compared to Poisson noise. By working in 6D phase-space, where contrasts are much more pronounced than in 3D position space, our HSF algorithm is capable of detecting subhaloes including their tidal tails, and can recognise other phase-space structures such as pure streams and candidate caustics. If an additional unbinding criterion is added, the algorithm can be used as a self-consistent halo and subhalo finder. As a test, we apply it to a large halo of the Millennium Simulation, where 19 % of the halo mass are found to belong to bound substructures, which is more than what is detected with conventional 3D substructure finders, and an additional 23-36 % of the total mass belongs to unbound HSF structures. The distribution of identified phase-space density peaks is clearly bimodal: high peaks are dominated by the bound structures and low peaks belong mostly to tidal streams. In order to better understand what HSF provides, we examine the time evolution of structures, based on the merger tree history. Bound structures typically make only up to 6 orbits inside the main halo. Still, HSF can identify at the present time at least 80 % of the original content of structures with a redshift of infall as high as z space.

M. Maciejewski; S. Colombi; V. Springel; C. Alard; F. R. Bouchet

2008-12-01T23:59:59.000Z

399

National Aeronautical and Space Administration (NASA) Johnson...  

Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

Aeronautical and Space Administration (NASA) Johnson Space Flight Center National Aeronautical and Space Administration (NASA) Johnson Space Flight Center Space Shuttle Endeavour,...

400

Atoms for space  

SciTech Connect (OSTI)

Nuclear technology offers many advantages in an expanded solar system space exploration program. These cover a range of possible applications such as power for spacecraft, lunar and planetary surfaces, and electric propulsion; rocket propulsion for lunar and Mars vehicles; space radiation protection; water and sewage treatment; space mining; process heat; medical isotopes; and self-luminous systems. In addition, space offers opportunities to perform scientific research and develop systems that can solve problems here on Earth. These might include fusion and antimatter research, using the Moon as a source of helium-3 fusion fuel, and manufacturing perfect fusion targets. In addition, nuclear technologies can be used to reduce risk and costs of the Space Exploration Initiative. 1 fig.

Buden, D.

1990-10-01T23:59:59.000Z

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

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

402

Chemical Enrichment at High Redshifts: Understanding the Nature of Damped Ly$?$ Systems in Hierarchical Models  

E-Print Network [OSTI]

We use cosmological hydrodynamical simulations including star formation and metal enrichment to study the evolution of the chemical properties of galaxy-like objects at high redshift in the range $0.25Hydrogen column densities with abundances and scatter comparable to those observed in damped Lyman-$\\alpha$ systems (DLAs).The unweighted mean of abundance ratios and least square linear regressions through the simulated DLAs yield intrinsic metallicity evolution for the [Zn/H] and [Fe/H], consistent with results obtained from similar analysis of available observations. Our model statistically reproduces the mild evolution detected in the metallicity of the neutral hydrogen content of the Universe, given by mass-weighted means,if observational constraints are considered (as suggested by Boiss\\'ee et al. 1998). For the $\\alpha$-elements in the simulated DLAs, we find neither enhancement nor dependence on metallicity. Our results support the hypotheses that DLAs trace a variety of galactic objects with different formation histories and that both SNI and SNII are contributing to the chemical enrichment of the gas component at least since $z \\approx 2$. This study indicates that DLAs could be understood as the building blocks that merged to form today normal galaxies within a hierarchical clustering scenario.

P. B. Tissera; D. G. Lambas M. B. Mosconi; S. A. Cora

2001-04-18T23:59:59.000Z

403

Tungsten-incorporation induced red-shift in the bandgap of gallium oxide thin films  

SciTech Connect (OSTI)

Tungsten (W) incorporated Ga{sub 2}O{sub 3} films were produced by co-sputter deposition. W-concentration was varied by the applied sputtering-power. The structure and optical properties of W-incorporated Ga{sub 2}O{sub 3} films were evaluated using X-ray diffraction, scanning electron microscopy, and spectrophotometric measurements. No secondary phase formation was observed in W-incorporated Ga{sub 2}O{sub 3} films. W-induced effects were significant on the structure and optical properties of Ga{sub 2}O{sub 3} films. The bandgap of Ga{sub 2}O{sub 3} films without W-incorporation was {approx}5 eV. Red-shift in the bandgap was noted with increasing W-concentration indicating the electronic structure changes in W-Ga{sub 2}O{sub 3} films. A functional relationship between W-concentration and optical property is discussed.

Rubio, E. J.; Ramana, C. V. [Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas 79968 (United States)] [Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas 79968 (United States)

2013-05-13T23:59:59.000Z

404

Estimation of compact binary coalescense rates from short gamma-ray burst redshift measurements  

E-Print Network [OSTI]

Short gamma-ray bursts are believed to originate from the merger of two compact objects. If this scenario is correct, these bursts will be accompanied by the emission of strong gravitational waves, detectable by current or planned GW detectors, such as LIGO and Virgo. No detection of a gravitational wave has been made up to date. In this paper I will use a set of observed redshift measurements of short gamma-ray bursts to fit a model in order to determine the rate of such merger events in the nearby universe. Various corrections will be included in that calculation, as the field-of-view of the satellite missions, the beaming factors of gamma-ray bursts and other parameters. The computed rate estimations will be compared to other rate estimations, based on observations on binary neutron stars and population synthesis models. Given the upper limit established by LIGO/Virgo measurements, it is possible to draw conclusions on the beaming angle of gamma-ray bursts.

Alexander Dietz

2011-04-15T23:59:59.000Z

405

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

406

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

407

Detection of Gravitational Redshift on the Solar Disk by Using Iodine-Cell Technique  

E-Print Network [OSTI]

With an aim to examine whether the predicted solar gravitational redshift can be observationally confirmed under the influence of the convective Doppler shift due to granular motions, we attempted measuring the absolute spectral line-shifts on a large number of points over the solar disk based on an extensive set of 5188-5212A region spectra taken through an iodine-cell with the Solar Domeless Telescope at Hida Observatory. The resulting heliocentric line shifts at the meridian line (where no rotational shift exists), which were derived by finding the best-fit parameterized model spectrum with the observed spectrum and corrected for the earth's motion, turned out to be weakly position-dependent as ~ +400 m/s near the disk center and increasing toward the limb up to ~ +600 m/s (both with a standard deviation of sigma ~ 100 m/s). Interestingly, this trend tends to disappear when the convectiveshift due to granular motions (~-300 m/s at the disk center and increasing toward the limb; simulated based on the two-c...

Takeda, Yoichi

2012-01-01T23:59:59.000Z

408

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

409

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

410

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

411

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

412

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

413

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

414

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

415

The Volume Fraction of Ionized Intergalactic Gas at Redshift z=6.5  

E-Print Network [OSTI]

The observed number density of Lyman-alpha sources implies a minimum volume of the inter-galactic medium that must be ionized, in order to allow the Lyman-alpha photons to escape attenuation. We estimate this volume by assigning to each Lyman-alpha emitter the minimum Stromgren sphere that would allow half its Lyman-alpha photons to escape. This implies a lower limit to ionized gas volume fraction of 20-50% at redshift z=6.5. This is a lower limit in two ways: First, we conservatively assume that the Lyman-alpha sources seen (at a relatively bright flux limit) are the only ones present; and second, we assume the smallest Stromgren sphere volume that will allow the photons to escape. This limit is completely independent of what ionizing photon sources produced the bubbles. Deeper Lyman-alpha surveys are possible with present technology, and can strengthen these limits by detecting a higher density of Lyman-alpha galaxies.

Sangeeta Malhotra; James Rhoads

2005-11-07T23:59:59.000Z

416

Space-QUEST: Experiments with quantum entanglement in space  

E-Print Network [OSTI]

The European Space Agency (ESA) has supported a range of studies in the field of quantum physics and quantum information science in space for several years, and consequently we have submitted the mission proposal Space-QUEST (Quantum Entanglement for Space Experiments) to the European Life and Physical Sciences in Space Program. We propose to perform space-to-ground quantum communication tests from the International Space Station (ISS). We present the proposed experiments in space as well as the design of a space based quantum communication payload.

Rupert Ursin; Thomas Jennewein; Johannes Kofler; Josep M. Perdigues; Luigi Cacciapuoti; Clovis J. de Matos; Markus Aspelmeyer; Alejandra Valencia; Thomas Scheidl; Alessandro Fedrizzi; Antonio Acin; Cesare Barbieri; Giuseppe Bianco; Caslav Brukner; Jose Capmany; Sergio Cova; Dirk Giggenbach; Walter Leeb; Robert H. Hadfield; Raymond Laflamme; Norbert Lutkenhaus; Gerard Milburn; Momtchil Peev; Timothy Ralph; John Rarity; Renato Renner; Etienne Samain; Nikolaos Solomos; Wolfgang Tittel; Juan P. Torres; Morio Toyoshima; Arturo Ortigosa-Blanch; Valerio Pruneri; Paolo Villoresi; Ian Walmsley; Gregor Weihs; Harald Weinfurter; Marek Zukowski; Anton Zeilinger

2008-06-05T23:59:59.000Z

417

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

418

Overview of Space Business Space & Integrated Defense Systems  

E-Print Network [OSTI]

Overview of Space Business Space & Integrated Defense Systems Mitsubishi Corporation August 26 in Rio de Janeiro and Belo Horizonte #12;MC's Space Business Involved with aerospace business more than 40 years, covering civil/commercial space business, defense related space business and defense

419

Spinorial space-time and privileged space direction (I)  

E-Print Network [OSTI]

Spinorial space-time and privileged space direction (I) Luis Gonzalez-Mestres Abstract Contrary of a privileged space direction are not strange phenomena from the point of view of fundamental space-time geometry. As already emphasized in our previous papers on the subject, the spinorial space-time we

Paris-Sud XI, Université de

420

Space Robotic Capabilities David Kortenkamp (NASA Johnson Space Center)  

E-Print Network [OSTI]

Johnson Space Center Space Robotic Capabilities David Kortenkamp (NASA Johnson Space Center) Liam) David Wettergreen (Carnegie Mellon University) Dan Clancy (NASA Ames) #12;Johnson Space Center 12/18/2001 Space Robotics State-of-Art 2 ! Motivation Science Objectives Mission Concepts Robots Human

Kortenkamp, David

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

"Space Station" Theme: Learning to Work, and Live, in Space  

E-Print Network [OSTI]

"Space Station" IMAX Film Theme: Learning to Work, and Live, in Space The educational value of NASM visit and afterward. See the "Alignment with Standards" table for details regarding how "Space Station in the "Space Station" program: · How astronauts train · What it is like to live and work in Space aboard

Mathis, Wayne N.

422

3742SPACE ISSUES AND RESOLUTION PROCEDURE Space issue or  

E-Print Network [OSTI]

Page 1 3742SPACE ISSUES AND RESOLUTION PROCEDURE Space issue or conflict identified Do any of the strategies mitigate issue/conflict Complete Conflict Resolution Form Submit form to Space Management Office Space Management Office conduct issue/conflict analysis Space Management Office document possible

423

Improved Life of Die Casting Dies of H13 Steel by Attaining Improved Mechanical Properties and Distortion Control During Heat Treatment  

SciTech Connect (OSTI)

The ultimate goal of this project is to increase die casting die life by using fast enough quenching rates to obtain good toughness and fatigue resistance in premium grade H-13 steel dies. The main tasks of the project were to compile a database on physical and mechanical properties of H-13; conduct gas quenching experiments to determine cooling rates of dies in difference vacuum furnaces; measure the as-quenched distortion of dies and the residual stresses; generate finite element analysis models to predict cooling rates, distortion, and residual stress of gas quenched dies; and establish rules and create PC-based expert system for prediction of cooling rates, distortion, and residual stress in vacuum/gas quenched H-13 dies. Cooling curves during gas quenching of H-13 blocks and die shapes have been measured under a variety of gas pressure. Dimensional changes caused by the gas quenching processes have been determined by accurate mapping of all surfaces with coordinate measuring machines before and after the quench. Residual stresses were determined by the ASTM E837 hole-drilling strain gage method. To facilitate the computer modeling work, a comprehensive database of H-13 mechanical and physical properties has been compiled. Finite element analysis of the heat treated shapes has been conducted using the TRAST/ABAQUS codes. There is a good fit between the predicted and measured distortion contours. However, the magnitude of the predicted distortion and residual stresses does not match well the measured values. Further fine tuning of the model is required before it can be used to predict distortion and residual stress in a quantitative manner. This last step is a prerequisite to generating rules for a reliable expert system.

J. F. Wallace; D. Schwam

1998-10-01T23:59:59.000Z

424

Discovery of Very High Energy Gamma Rays from PKS 1424+240 and Multiwavelength Constraints on its Redshift  

SciTech Connect (OSTI)

We report the first detection of very-high-energy (VHE) gamma-ray emission above 140GeV from PKS 1424+240, a BL Lac object with an unknown redshift. The photon spectrum above 140GeV measured by VERITAS is well described by a power law with a photon index of 3.8 {+-}0.5{sub stat} {+-} 0.3{sub syst} and a flux normalization at 200 GeV of (5.1 {+-} 0.9{sub stat} {+-} 0.5{sub syst}) x 10{sup -11} TeV{sup -1} cm{sup -2} s{sup -1}, where stat and syst denote the statistical and systematical uncertainty, respectively. The VHE flux is steady over the observation period between MJD 54881 and 55003 (2009 February 19 to June 21). Flux variability is also not observed in contemporaneous high energy observations with the Fermi Large Area Telescope (LAT). Contemporaneous X-ray and optical data were also obtained from the Swift XRT and MDM observatory, respectively. The broadband spectral energy distribution (SED) is well described by a one-zone synchrotron self-Compton (SSC) model favoring a redshift of less than 0.1. Using the photon index measured with Fermi in combination with recent extragalactic background light (EBL) absorption models it can be concluded from the VERITAS data that the redshift of PKS 1424+240 is less than 0.66.

Acciari, V.A.; /Harvard-Smithsonian Ctr. Astrophys.; Aliu, E.; /Delaware U., Bartol Inst.; Arlen, T.; /UCLA; Aune, T.; /UC, Santa Cruz; Bautista, M.; /McGill U.; Beilicke, M. /Washington U., St. Louis; Benbow, W.; /Harvard-Smithsonian Ctr. Astrophys.; Bottcher, M.; /Ohio U.; Boltuch, D.; /Delaware U., Bartol Inst.; Bradbury, S.M.; /Leeds U.; Buckley, J.H.; /Washington U., St. Louis; Bugaev, V.; /Washington U., St. Louis; Byrum, K.; /Argonne; Cannon, A.; /University Coll., Dublin; Cesarini, A.; /Natl. U. of Ireland, Galway; Chow, Y.C.; /UCLA; Ciupik, L.; /Roosevelt U., Chicago; Cogan, P.; /McGill U.; Cui, W.; /Purdue U.; Duke, C.; /Grinnell Coll.; Falcone, A.; /Penn State U. /Purdue U. /Utah U. /Roosevelt U., Chicago /Harvard-Smithsonian Ctr. Astrophys. /Purdue U. /Natl. U. of Ireland, Galway /Utah U. /University Coll., Dublin /McGill U. /Roosevelt U., Chicago /McGill U. /Delaware U., Bartol Inst. /Utah U. /Chicago U., EFI /Iowa State U. /Roosevelt U., Chicago /DePauw U. /Utah U. /Pittsburg State U. /Washington U., St. Louis /Iowa State U. /Natl. U. of Ireland, Galway /Utah U. /McGill U. /Washington U., St. Louis /McGill U. /McGill U. /Purdue U. /Anderson U. /Galway-Mayo Inst. of Tech. /Iowa State U. /UCLA; /more authors..

2012-04-05T23:59:59.000Z

425

A Spectroscopic Redshift for the Cl0024+16 Multiple Arc System: Implications for the Central Mass Distribution  

E-Print Network [OSTI]

We present a spectroscopic redshift of z=1.675 for the well-known multiply lensed system of arcs seen in the z=0.39 cluster Cl0024+16. In contrast to earlier work, we find that the lensed images are accurately reproduced by a projected mass distribution which traces the locations of the brightest cluster ellipticals, suggesting that the most significant minima of the cluster potential are not fully erased. The averaged mass profile is shallow and consistent with predictions of recent numerical simulations. The source redshift enables us to determine an enclosed cluster mass of M(<100kpc/h)=1.11+/-0.03 x 10^{14}M_{\\odot}/h and a mass-to-light ratio of M/L_B(<100kpc/h)=320h(M/L_B)_{\\odot}, after correction for passive stellar evolution. The arc spectrum contains many ionized absorption lines and closely resembles that of the local Wolf-Rayet galaxy NGC4217. Our lens model predicts a high magnification (~20) for each image and identifies a new pair of multiple images at a predicted redshift of z=1.3.

Tom Broadhurst; Xiaosheng Huang; Brenda Frye; Richard Ellis

1999-02-23T23:59:59.000Z

426

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

427

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.6 29.5 29.5 29.5 29.5 29.5 29.5 Crosscutting Space Tech Development 120.4 187.7 293.8 272.1 266.6 259.7 247.0 Exploration Technology Development 144.6 189.9 202.0 215.5 215.7 214.5 216.5 Notional SPACE

428

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

429

Relativistic helicity and link in Minkowski space-time  

SciTech Connect (OSTI)

A relativistic helicity has been formulated in the four-dimensional Minkowski space-time. Whereas the relativistic distortion of space-time violates the conservation of the conventional helicity, the newly defined relativistic helicity conserves in a barotropic fluid or plasma, dictating a fundamental topological constraint. The relation between the helicity and the vortex-line topology has been delineated by analyzing the linking number of vortex filaments which are singular differential forms representing the pure states of Banach algebra. While the dimension of space-time is four, vortex filaments link, because vorticities are primarily 2-forms and the corresponding 2-chains link in four dimension; the relativistic helicity measures the linking number of vortex filaments that are proper-time cross-sections of the vorticity 2-chains. A thermodynamic force yields an additional term in the vorticity, by which the vortex filaments on a reference-time plane are no longer pure states. However, the vortex filaments on a proper-time plane remain to be pure states, if the thermodynamic force is exact (barotropic), thus, the linking number of vortex filaments conserves.

Yoshida, Z.; Kawazura, Y. [Graduate School of Frontier Sciences, University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan)] [Graduate School of Frontier Sciences, University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Yokoyama, T. [Department of Mathematics, Hokkaido University, Kita 10, Nishi 8, Kita-Ku, Sapporo, Hokkaido 060-0810 (Japan)] [Department of Mathematics, Hokkaido University, Kita 10, Nishi 8, Kita-Ku, Sapporo, Hokkaido 060-0810 (Japan)

2014-04-15T23:59:59.000Z

430

Competing for Shelf Space.  

E-Print Network [OSTI]

the changes in supplier i’s wholesale price and pro?t, i =space despite their lower wholesale prices. Using a di?erentImpact of Manufacturers’ Wholesale Prices a on a Retailer’s

Martínez-de-Albéniz, V.; Roels, G.

2007-01-01T23:59:59.000Z

431

Envisioning creative space  

E-Print Network [OSTI]

This thesis proposes a framework to articulate certain criteria in creative spatial productions such as architecture. I discuss that a conformist and unquestioning adaptation to conventional space conceptions limits ...

Özkâr, Mine, 1976-

1999-01-01T23:59:59.000Z

432

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

433

Hyper Space Complex Number  

E-Print Network [OSTI]

A new kind of numbers called Hyper Space Complex Numbers and its algebras are defined and proved. It is with good properties as the classic Complex Numbers, such as expressed in coordinates, triangular and exponent forms and following the associative and commutative laws of addition and multiplication. So the classic Complex Number is developed from in complex plane with two dimensions to in complex space with N dimensions and the number system is enlarged also.

Shanguang Tan

2007-04-23T23:59:59.000Z

434

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

435

Non-Gaussianity as a Probe of the Physics of the Primordial Universe and the Astrophysics of the Low Redshift Universe  

SciTech Connect (OSTI)

A new and powerful probe of the origin and evolution of structures in the Universe has emerged and been actively developed over the last decade. In the coming decade, non-Gaussianity, i.e., the study of non-Gaussian contributions to the correlations of cosmological fluctuations, will become an important probe of both the early and the late Universe. Specifically, it will play a leading role in furthering our understanding of two fundamental aspects of cosmology and astrophysics: (1) The physics of the very early universe that created the primordial seeds for large-scale structures, and (2) The subsequent growth of structures via gravitational instability and gas physics at later times. To date, observations of fluctuations in the Cosmic Microwave Background (CMB) and the Large-Scale Structure of the Universe (LSS) have focused largely on the Gaussian contribution as measured by the two-point correlations (or the power spectrum) of density fluctuations. However, an even greater amount of information is contained in non-Gaussianity and a large discovery space therefore still remains to be explored. Many observational probes can be used to measure non-Gaussianity, including CMB, LSS, gravitational lensing, Lyman-{alpha} forest, 21-cm fluctuations, and the abundance of rare objects such as clusters of galaxies and high-redshift galaxies. Not only does the study of non-Gaussianity maximize the science return from a plethora of present and future cosmological experiments and observations, but it also carries great potential for important discoveries in the coming decade.

Komatsu, E.; /Texas U. /Tokyo U.; Afshordi, N.; /Perimeter Inst. Theor. Phys.; Bartolo, N.; /Padua U.; Baumann, D.; /Harvard U.; Bond, J.R.; /Toronto U.; Buchbinder, E.I.; /Perimeter Inst. Theor. Phys.; Byrnes, C.T.; /Heidelberg U.; Chen, Xingang; /MIT; Chung, D.J.H.; /Wisconsin U., Madison; Cooray, A.; /UC, Irvine; Creminelli, P.; /ICTP, Trieste; Dalal, N.; /Toronto U.; Dore, O.; /Toronto U.; Easther, R.; /Yale U.; Frolov, A.V.; /Simon Fraser U.; Gorski, K.M.; /Warsaw U.; Khoury, J.; /Pennsylvania U.; Kinney, W.H.; /SUNY, Buffalo; Kofman, L.; /Toronto U.; Koyama, K.; /Portsmouth U.; Leblond, L.; /Texas A-M /Princeton U. /Queen Mary, U. of London /Cambridge U., DAMTP /Columbia U. /Stanford U., Phys. Dept. /Lancaster U. /Princeton, Inst. Advanced Study /Padua U. /INFN, Padua /Cornell U., Phys. Dept. /Toronto U. /Tokyo U. /Pennsylvania U. /Princeton, Inst. Advanced Study /Cambridge U. /INFN, Padua /CERN /Antonio Narino U. /Santander Industrial U. /Kyoto U. /New York U. /Cambridge U., DAMTP /Saclay, SPhT /LBL, Berkeley /Zurich U. /Princeton, Inst. Advanced Study /Queen Mary, U. of London /Cambridge U., DAMTP /Stanford U., Phys. Dept. /SLAC /UC, Berkeley /Cambridge U. /Landau Inst. /Princeton U. /Tokyo U. /MIT /Perimeter Inst. Theor. Phys. /Barcelona, IEEC /Illinois U., Urbana /Portsmouth U. /Texas U. /Perimeter Inst. Theor. Phys. /Harvard U. /Harvard U.

2011-11-14T23:59:59.000Z

436

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

437

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

438

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

439

MASSIVE CLUMPS IN LOCAL GALAXIES: COMPARISONS WITH HIGH-REDSHIFT CLUMPS  

SciTech Connect (OSTI)

Local UV-bright galaxies in the Kiso survey include clumpy systems with kiloparsec-size star complexes that resemble clumpy young galaxies in surveys at high redshift. We compare clump masses and underlying disks in several dozen galaxies from each of these surveys to the star complexes and disks of normal spirals. Photometry and spectroscopy for the Kiso and spiral sample come from the Sloan Digital Sky Survey. We find that the largest Kiso clumpy galaxies resemble Ultra Deep Field (UDF) clumpies in terms of the star formation rates, clump masses, and clump surface densities. Clump masses and surface densities in normal spirals are smaller. If the clump masses are proportional to the turbulent Jeans mass in the interstellar medium, then for the most luminous galaxies in the sequence of normal:Kiso:UDF, the turbulent speeds and surface densities increase in the proportions 1.0:4.7:5.0 and 1.0:4.0:5.1, respectively, for fixed restframe B-band absolute magnitude. For the least luminous galaxies in the overlapping magnitude range, the turbulent speed and surface density trends are 1.0:2.7:7.4 and 1.0:1.4:3.0, respectively. We also find that while all three types have radially decreasing disk intensities when measured with ellipse-fit azimuthal averages, the average profiles are more irregular for UDF clumpies (which are viewed in their restframe UV) than for Kiso galaxies (viewed at g-band), and major axis intensity scans are even more irregular for the UDF than Kiso galaxies. Local clumpy galaxies in the Kiso survey appear to be intermediate between UDF clumpies and normal spirals.

Elmegreen, Bruce G. [IBM Research Division, T. J. Watson Research Center, Yorktown Hts., NY 10598 (United States); Elmegreen, Debra Meloy; Dewberry, J.; Putko, J.; Teich, Y.; Popinchalk, M. [Vassar College, Dept. of Physics and Astronomy, Poughkeepsie, NY 12604 (United States); Sanchez Almeida, J.; Munoz-Tunon, C. [Instituto de Astrof'sica de Canarias, C/via Lactea, s/n, E-38205, La Laguna, Tenerife (Spain)

2013-09-01T23:59:59.000Z

440

Space Physics at UNH FROM THE DAWN OF SPACE EXPLORATION, UNH space scientists, engineers, and  

E-Print Network [OSTI]

Space Physics at UNH FROM THE DAWN OF SPACE EXPLORATION, UNH space scientists, engineers, and students in the Institute for the Study of Earth, Oceans, and Space (EOS) have worked on mission design and modeling. The Space Science Center, housed at EOS, is engaged in research and graduate education in all

Pringle, James "Jamie"

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.


441

China's Space Robotic Arms Programs  

E-Print Network [OSTI]

Blog, “Gen. Chilton on a Space Weapons Treaty,” October 30,archive/2076/general-chilton-on-a-space-weapons-treaty. 31on the military use of space, see Kevin Pollpeter, “China’s

POLLPETER, Kevin

2013-01-01T23:59:59.000Z

442

Space Instrument Realization (ISR-5)  

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

5 Space Instrument Realization Providing expertise to support the design and fabrication of space-based custom instrumentation Contacts Group Leader Amy Regan Email Staff...

443

Generation and growth rates of nonlinear distortions in a traveling wave tube John G. Wohlbier, Ian Dobson, and John H. Booske  

E-Print Network [OSTI]

Generation and growth rates of nonlinear distortions in a traveling wave tube John G. Wo the generation of intermodulation frequencies and calculate their growth rates. The model describes the evolution rates is derived and compared to simulation results. DOI: 10.1103/PhysRevE.66.056504 PACS number s : 52

Dobson, Ian

444

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.

445

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

446

Quantization of empty space  

E-Print Network [OSTI]

We suggest to use "minimal" choice of quantum gravity theory, that is the quantum field theory, in which space-time is seen as Riemannian space and metric (or vierbein field) is the dynamical variable. We then suggest to use the simplest acceptable action, that is the squared curvature action. The correspondent model is renormalizable, has the correct classical limit without matter and can be explored using Euclidian path integral formalism. In order to get nonperturbative results one has to put this model on the lattice. While doing so serious problems with measure over dynamical variables are encountered, which were not solved until present. We suggest to solve them using the representation of Riemannian space as a limiting case of Riemann - Cartan space, where the Poincare group connection plays the role of dynamical variable. We construct manifestly gauge invariant discretization of Riemann - Cartan space. Lattice realization of Poincare gauge transformation naturally acts on the dynamical variables of the constructed discretization. There exists local measure invariant under this gauge transformation, which could be used as a basic element of lattice path integral methods. The correspondent lattice model appears to be useful for numerical simulations.

M. A. Zubkov

2005-11-02T23:59:59.000Z

447

A cascaded model of spectral distortions due to spectral response effects and pulse pileup effects in a photon-counting x-ray detector for CT  

SciTech Connect (OSTI)

Purpose: Energy discriminating, photon-counting detectors (PCDs) are an emerging technology for computed tomography (CT) with various potential benefits for clinical CT. The photon energies measured by PCDs can be distorted due to the interactions of a photon with the detector and the interaction of multiple coincident photons. These effects result in distorted recorded x-ray spectra which may lead to artifacts in reconstructed CT images and inaccuracies in tissue identification. Model-based compensation techniques have the potential to account for the distortion effects. This approach requires only a small number of parameters and is applicable to a wide range of spectra and count rates, but it needs an accurate model of the spectral distortions occurring in PCDs. The purpose of this study was to develop a model of those spectral distortions and to evaluate the model using a PCD (model DXMCT-1; DxRay, Inc., Northridge, CA) and various x-ray spectra in a wide range of count rates. Methods: The authors hypothesize that the complex phenomena of spectral distortions can be modeled by: (1) separating them into count-rate independent factors that we call the spectral response effects (SRE), and count-rate dependent factors that we call the pulse pileup effects (PPE), (2) developing separate models for SRE and PPE, and (3) cascading the SRE and PPE models into a combined SRE+PPE model that describes PCD distortions at both low and high count rates. The SRE model describes the probability distribution of the recorded spectrum, with a photo peak and a continuum tail, given the incident photon energy. Model parameters were obtained from calibration measurements with three radioisotopes and then interpolated linearly for other energies. The PPE model used was developed in the authors’ previous work [K. Taguchi et al., “Modeling the performance of a photon counting x-ray detector for CT: Energy response and pulse pileup effects,” Med. Phys. 38(2), 1089–1102 (2011)]. The agreement between the x-ray spectra calculated by the cascaded SRE+PPE model and the measured spectra was evaluated for various levels of deadtime loss ratios (DLR) and incident spectral shapes, realized using different attenuators, in terms of the weighted coefficient of variation (COV{sub W}), i.e., the root mean square difference weighted by the statistical errors of the data and divided by the mean. Results: At low count rates, when DLR < 10%, the distorted spectra measured by the DXMCT-1 were in agreement with those calculated by SRE only, with COV{sub W}'s less than 4%. At higher count rates, the measured spectra were also in agreement with the ones calculated by the cascaded SRE+PPE model; with PMMA as attenuator, COV{sub W} was 5.6% at a DLR of 22% and as small as 6.7% for a DLR as high as 55%. Conclusions: The x-ray spectra calculated by the proposed model agreed with the measured spectra over a wide range of count rates and spectral shapes. The SRE model predicted the