Modelling the redshiftspace distortion of galaxy clustering
Abstract
We use a set of large, highresolution cosmological Nbody simulations to examine the redshiftspace distortions of galaxy clustering on scales of order 10200h^1Mpc. Galaxy redshift surveys currently in progress will, on completion, allow us to measure the quadrupole distortion in the 2point correlation function, xi(sigma, pi), or its Fourier transform, the power spectrum P(k, mu), to a high degree of accuracy. On these scales we typically find a positive quadrupole, as expected for coherent infall on to overdense regions and outflow from underdense regions, but the distortion is substantially weaker than that predicted by pure linear theory. We assess two models that may be regarded as refinements to linear theory, the Zel'dovich approximation and a dispersion model in which the nonlinear velocities generated by the formation of virialized groups and clusters are treated as random perturbations to the velocities predicted by linear theory. We find that neither provides an adequate physical description of the clustering pattern. If used to model redshiftspace distortions on scales for 10<lambda<200h1Mpc the estimated value of beta [beta=f(Omega_0)/b where f(Omega_0)~Omega^0.6_0 and b is the galaxy bias parameter] is liable to systematic errors of the order of 10 per cent or more. We discuss how such systematics can be avoided by (i) development of a more complete model of redshift distortions and (ii) the direct use of galaxy catalogues generated from nonlinear Nbody simulations.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 May 1998
 DOI:
 10.1046/j.13658711.1998.01269.x
 arXiv:
 arXiv:astroph/9707186
 Bibcode:
 1998MNRAS.296...10H
 Keywords:

 GALAXIES: CLUSTERS: GENERAL;
 GALAXIES: DISTANCES AND REDSHIFTS;
 COSMOLOGY: THEORY;
 LARGESCALE STRUCTURE OF UNIVERSE;
 Astrophysics
 EPrint:
 13 pages, Latex, uses mn.sty and mnextra.sty (mnextra.sty included here)