Redshift-space distortions with the halo occupation distribution - I. Numerical simulations

We show how redshift-space distortions of the galaxy correlation function or power spectrum can constrain the matter density parameter Ωm and the linear matter fluctuation amplitude σ8. 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 Ωm and σ8 and find paramters 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 halos of large N-body simulations, from which we measure redshift-space distortions on small and large scales. We include a velocity bias parameter αv that allows the velocity dispersions of satellite galaxies in halos to be systematically higher or lower than those of dark matter. Large-scale distortions are determined by the parameter combination β ≡ Ω0.6 m /bg, where bg is the bias factor