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Title: Multipole analysis of redshift-space distortions around cosmic voids

Abstract

We perform a comprehensive redshift-space distortion analysis based on cosmic voids in the large-scale distribution of galaxies observed with the Sloan Digital Sky Survey. To this end, we measure multipoles of the void-galaxy cross-correlation function and compare them with standard model predictions in cosmology. Merely considering linear-order theory allows us to accurately describe the data on the entire available range of scales and to probe void-centric distances down to about 2 h {sup −1}Mpc. Common systematics, such as the Fingers-of-God effect, scale-dependent galaxy bias, and nonlinear clustering do not seem to play a significant role in our analysis. We constrain the growth rate of structure via the redshift-space distortion parameter β at two median redshifts, β( z-bar =0.32)=0.599{sup +0.134}{sub −0.124} and β( z-bar =0.54)=0.457{sup +0.056}{sub −0.054}, with a precision that is competitive with state-of-the-art galaxy-clustering results. While the high-redshift constraint perfectly agrees with model expectations, we observe a mild 2σ deviation at z-bar =0.32, which increases to 3σ when the data is restricted to the lowest available redshift range of 0.15< z <0.33.

Authors:
;  [1]; ; ; ;  [2]
  1. Universitäts-Sternwarte München, Fakultät für Physik, Ludwig-Maximilians Universität, Scheinerstr. 1, D-81679 München (Germany)
  2. Aix Marseille Univ., CNRS/IN2P3, CPPM, 163 avenue de Luminy, F-13288, Marseille (France)
Publication Date:
OSTI Identifier:
22676114
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2017; Journal Issue: 07; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCURACY; COMPARATIVE EVALUATIONS; CORRELATION FUNCTIONS; CORRELATIONS; COSMOLOGY; DISTRIBUTION; FORECASTING; GALAXIES; MULTIPOLES; NONLINEAR PROBLEMS; RED SHIFT; SPACE; STANDARD MODEL

Citation Formats

Hamaus, Nico, Weller, Jochen, Cousinou, Marie-Claude, Pisani, Alice, Aubert, Marie, and Escoffier, Stéphanie, E-mail: hamaus@usm.lmu.de, E-mail: cousinou@cppm.in2p3.fr, E-mail: pisani@cppm.in2p3.fr, E-mail: maubert@cppm.in2p3.fr, E-mail: escoffier@cppm.in2p3.fr, E-mail: jochen.weller@usm.lmu.de. Multipole analysis of redshift-space distortions around cosmic voids. United States: N. p., 2017. Web. doi:10.1088/1475-7516/2017/07/014.
Hamaus, Nico, Weller, Jochen, Cousinou, Marie-Claude, Pisani, Alice, Aubert, Marie, & Escoffier, Stéphanie, E-mail: hamaus@usm.lmu.de, E-mail: cousinou@cppm.in2p3.fr, E-mail: pisani@cppm.in2p3.fr, E-mail: maubert@cppm.in2p3.fr, E-mail: escoffier@cppm.in2p3.fr, E-mail: jochen.weller@usm.lmu.de. Multipole analysis of redshift-space distortions around cosmic voids. United States. doi:10.1088/1475-7516/2017/07/014.
Hamaus, Nico, Weller, Jochen, Cousinou, Marie-Claude, Pisani, Alice, Aubert, Marie, and Escoffier, Stéphanie, E-mail: hamaus@usm.lmu.de, E-mail: cousinou@cppm.in2p3.fr, E-mail: pisani@cppm.in2p3.fr, E-mail: maubert@cppm.in2p3.fr, E-mail: escoffier@cppm.in2p3.fr, E-mail: jochen.weller@usm.lmu.de. Sat . "Multipole analysis of redshift-space distortions around cosmic voids". United States. doi:10.1088/1475-7516/2017/07/014.
@article{osti_22676114,
title = {Multipole analysis of redshift-space distortions around cosmic voids},
author = {Hamaus, Nico and Weller, Jochen and Cousinou, Marie-Claude and Pisani, Alice and Aubert, Marie and Escoffier, Stéphanie, E-mail: hamaus@usm.lmu.de, E-mail: cousinou@cppm.in2p3.fr, E-mail: pisani@cppm.in2p3.fr, E-mail: maubert@cppm.in2p3.fr, E-mail: escoffier@cppm.in2p3.fr, E-mail: jochen.weller@usm.lmu.de},
abstractNote = {We perform a comprehensive redshift-space distortion analysis based on cosmic voids in the large-scale distribution of galaxies observed with the Sloan Digital Sky Survey. To this end, we measure multipoles of the void-galaxy cross-correlation function and compare them with standard model predictions in cosmology. Merely considering linear-order theory allows us to accurately describe the data on the entire available range of scales and to probe void-centric distances down to about 2 h {sup −1}Mpc. Common systematics, such as the Fingers-of-God effect, scale-dependent galaxy bias, and nonlinear clustering do not seem to play a significant role in our analysis. We constrain the growth rate of structure via the redshift-space distortion parameter β at two median redshifts, β( z-bar =0.32)=0.599{sup +0.134}{sub −0.124} and β( z-bar =0.54)=0.457{sup +0.056}{sub −0.054}, with a precision that is competitive with state-of-the-art galaxy-clustering results. While the high-redshift constraint perfectly agrees with model expectations, we observe a mild 2σ deviation at z-bar =0.32, which increases to 3σ when the data is restricted to the lowest available redshift range of 0.15< z <0.33.},
doi = {10.1088/1475-7516/2017/07/014},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 07,
volume = 2017,
place = {United States},
year = {Sat Jul 01 00:00:00 EDT 2017},
month = {Sat Jul 01 00:00:00 EDT 2017}
}
  • Cosmic voids in the large-scale structure of the Universe affect the peculiar motions of objects in their vicinity. Although these motions are difficult to observe directly, the clustering pattern of their surrounding tracers in redshift space is influenced in a unique way. This allows to investigate the interplay between densities and velocities around voids, which is solely dictated by the laws of gravity. With the help of N-body simulations and derived mock-galaxy catalogs we calculate the average density fluctuations around voids identified with a watershed algorithm in redshift space and compare the results with the expectation from general relativity andmore » the ΛCDM model. We find linear theory to work remarkably well in describing the dynamics of voids. Adopting a Bayesian inference framework, we explore the full posterior of our model parameters and forecast the achievable accuracy on measurements of the growth rate of structure and the geometric distortion through the Alcock-Paczyński effect. Systematic errors in the latter are reduced from ∼15% to ∼5% when peculiar velocities are taken into account. The relative parameter uncertainties in galaxy surveys with number densities comparable to the SDSS MAIN (CMASS) sample probing a volume of 1h{sup −3}Gpc{sup 3} yield σ{sub f/b}/(f/b).∼2% (20%) and σ{sub D{sub A{sub H}}}/D{sub AH∼0}.2% (2%), respectively. At this level of precision the linear-theory model becomes systematics dominated, with parameter biases that fall beyond these values. Nevertheless, the presented method is highly model independent; its viability lies in the underlying assumption of statistical isotropy of the Universe.« less
  • Galaxy redshift surveys provide a distorted picture of the universe due to the non-Hubble component of galaxy motions. By measuring such distortions in the linear regime one can constrain the quantity {beta}={Omega}{sup 0.6}/{ital b} where {Omega} is the cosmological density parameter and {ital b} is the (linear) bias factor for optically selected galaxies. In this paper we apply two techniques for estimating {beta} from the Stromlo-APM redshift survey: (1) measuring the anisotropy of the redshift space correlation function in spherical harmonics, and (2) comparing the amplitude of the direction-averaged redshift space correlation function to the real space correlation function. Wemore » test the validity of these techniques, particularly whether the assumption of linear theory is justified, using two sets of large {ital N}-body simulations. We find that the first technique is affected by nonlinearities on scales up to {approximately}30 {ital h}{sup {minus}1}Mpc. The second technique is less sensitive to nonlinear effects and so is more useful for existing redshift surveys. The Stromlo-APM survey data favors a low value for {beta}, with {beta}{approx_lt}0.6. A bias parameter {ital b}{approx_equal}2 is thus required if {Omega}{equivalent_to}1. However, higher-order correlations measured from the APM galaxy survey indicate a low value for the bias parameter {ital b}{approx_equal}1, requiring that {Omega}{approx_lt}0.5. We also measure the relative bias for samples of galaxies of various luminosity and morphological type and find that low-luminosity galaxies are roughly three times less biased than {ital L}{asterisk} galaxies. For the galaxy population as a whole, we measure a real space variance of galaxy counts in 8 {ital h}{sup {minus}1}Mpc spheres of ({sigma}{sup 2}{sub 8}){sub {ital g}}=0.89{plus_minus}0.05. {copyright} {ital 1996 The American Astronomical Society.}« less
  • I extend the usual linear-theory formula for large-scale clustering in redshift-space to include gravitational redshift. The extra contribution to the standard galaxy power spectrum is suppressed by k{sub c}{sup −2}, where k{sub c} = ck/aH (k is the wavevector, a the expansion factor, and H = a-dot /a), and is thus effectively limited to the few largest-scale modes and very difficult to detect; however, a correlation, ∝k{sub c}{sup −1}, is generated between the real and imaginary parts of the Fourier space density fields of two different types of galaxy, which would otherwise be zero, i.e., the cross-power spectrum has anmore » imaginary part: P{sub ab}(k,μ)/P(k) = (b{sub a}+fμ{sup 2})(b{sub b}+fμ{sup 2})−i(3/2)Ω{sub m}(μ/k{sub c})(b{sub a}−b{sub b})+O(k{sub c}{sup −2}), where P(k) is the real-space mass-density power spectrum, b{sub i} are the galaxy biases, μ is the cosine of the angle between the wavevector and line of sight, and f = dln D/dln a (D is the linear growth factor). The total signal-to-noise of measurements of this effect is not dominated by the largest scales — it converges at k ∼ 0.05 h Mpc{sup −1}. This gravitational redshift result is pedagogically interesting, but naive in that it is gauge dependent and there are other effects of similar form and size, related to the transformation between observable and proper coordinates. I include these effects, which add other contributions to the coefficient of μ/k{sub c}, and add a μ{sup 3}/k{sub c} term, but don't qualitatively change the picture. The leading source of noise in the measurement is galaxy shot-noise, not sample variance, so developments that allow higher S/N surveys can make this measurement powerful, although it would otherwise be only marginally detectable in a JDEM-scale survey.« less
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  • We investigate the dynamics of a single spherical void embedded in a Friedmann-Lemaitre universe, and analyze the void shape in the redshift space. We find that the void in the redshift space appears as an ellipse shape elongated along the line of sight (i.e., an opposite deformation to the Kaiser effect). Applying this result to observed void candidates at the redshift z ∼ 1-2, it may provide us with a new method to evaluate the cosmological parameters, in particular the value of a cosmological constant.