Open AccessRedshift‐space distortions with the halo occupation distribution – I. Numerical simulations
Author(s) -
Tinker Jeremy L.,
Weinberg David H.,
Zheng Zheng
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.10114.x
Subject(s) - physics , astrophysics , galaxy , redshift , dark matter , correlation function (quantum field theory) , spectral density , halo , redshift space distortions , peculiar velocity , matter power spectrum , parameter space , galaxy formation and evolution , statistical physics , redshift survey , statistics , quantum mechanics , mathematics , dielectric
We show how redshift‐space distortions of the galaxy correlation function or power spectrum can constrain the matter density parameter Ω m and the linear matter fluctuation amplitude σ 8 . We improve on previous treatments by adopting a fully non‐linear description of galaxy clustering and bias, which allows us to achieve the accuracy demanded by larger galaxy redshift surveys and to break parameter degeneracies by combining large‐scale and small‐scale distortions. Given an observationally motivated choice of the initial power spectrum shape, we consider different combinations of Ω m and σ 8 and find parameters of the galaxy halo occupation distribution (HOD) that yield nearly identical galaxy correlation functions in real space. We use these HOD parameters to populate the dark matter haloes of large N ‐body simulations, from which we measure redshift‐space distortions on small and large scales. We include a velocity bias parameter α v that allows the velocity dispersions of satellite galaxies in haloes to be systematically higher or lower than those of dark matter. Large‐scale distortions are determined by the parameter combination β≡Ω 0.6 m / b g , where b g is the bias factor defined by the ratio of galaxy and matter correlation functions, in agreement with the linear theory prediction of parameter degeneracy. However, linear theory does not accurately describe the distortions themselves on scales accessible to our simulations. We provide fitting formulas to estimate β from measurements of the redshift‐space correlation function or power spectrum, and we show that these formulas are significantly more accurate than those in the existing literature. On small scales, the ‘FOG’ distortions at projected separations ∼0.1 h −1 Mpc depend on Ω m α 2 v but are independent of σ 8 , while at intermediate separations they depend on σ 8 as well. One can thus use measurements of redshift‐space distortions over a wide range of scales to separately determine Ω m , σ 8 , and α v .