The Durham/UKST Galaxy Redshift Survey  VII. Redshiftspace distortions in the power spectrum
Abstract
We investigate the effect of redshiftspace distortions in the power spectrum parallel and perpendicular to the line of sight of the observer, P^{S}(k_{∥},k_{⊥}), using the optically selected Durham/UKST Galaxy Redshift Survey. On small, nonlinear scales anisotropy in the power spectrum is dominated by the galaxy velocity dispersion; the `Finger of God' effect. On larger, linear scales coherent peculiar velocities caused by the infall of galaxies into overdense regions are the main cause of anisotropy. According to gravitational instability theory these distortions depend only on the density and bias parameters via β~Ωm0.6b. Geometrical distortions also occur if the wrong cosmology is assumed, although these would be relatively small given the low redshift of the survey. To quantify these effects, we assume the realspace power spectrum of the APM Galaxy Survey, and fit a simple model for the redshiftspace and geometrical distortions. Assuming a flat Ω_{m}=1 universe, we find values for the onedimensional pairwise velocity dispersion of σ_{p}=410+/170kms^{1}, and β=0.38+/0.17. An open Ω_{m}=0.3, and a flat Ω_{m}=0.3, Ω_{Λ}=0.7 universe yield σ_{p}=420kms^{1}, β=0.40, and σ_{p}=440kms^{1}, β=0.45, respectively, with comparable errors. These results are consistent with estimates using the twopoint galaxy correlation function, ξ(σ,π), and favour either a lowdensity universe with Ω_{m}~0.3 if galaxies trace the underlying mass distribution, or a bias factor of b~2.5 if Ω_{m}=1.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 March 2001
 DOI:
 10.1046/j.13658711.2001.04047.x
 arXiv:
 arXiv:astroph/0009387
 Bibcode:
 2001MNRAS.321..497O
 Keywords:

 SURVEYS;
 COSMOLOGY: OBSERVATIONS;
 LARGESCALE STRUCTURE OF UNIVERSE;
 surveys;
 cosmology: observations;
 largescale structure of Universe;
 Astrophysics
 EPrint:
 5 pages, accepted for publication in MNRAS