**Constraining β(z) and Ω ^{0}_{m} from redshift-space distortions in z~ 3 galaxy surveys**

__J. da Ângela__, P. J. Outram, T. Shanks

**Abstract**

We use a sample of 813 Lyman-break galaxies (LBGs) with 2.6 < z < 3.4 to perform a detailed analysis of the redshift-space (z-space)distortions in their clustering pattern, and from that derive confidencelevels in the [Ω^{0}_{m}, β(z= 3)] plane. We model the z-space distortions in the shape of the correlation function measured in orthogonal directions, ξ(σ, π). This modelling requires an accurate description of the real-space correlation function to be given as an input. From the projection of ξ(σ, π) in the angular direction, w_{p} (σ), we derive the best-fitting amplitude and slope for the LBG real-space correlation function: r_{0}= 4.48^{+0.17}_{-0.18}h^{-1} Mpc and = 1.76^{+0.08}_{-0.09}[ξ(r) = (r/r_{0})^{-γ}]. A comparison between the shape of ξ(s) and w_{p} (σ) suggests that ξ(r) deviates from a simple power-law model, with a break at ~9 h^{-1} Mpc. This model is consistent with the observed projected correlation function. However, due to the limited size of the fields used, the w_{p}(σ) results are limited to σ<~ 10 h^{-1} Mpc. Assuming this double-power-law model, and by analysing the shape distortions in ξ(σ, π), we find the following constraints: β(z= 3) = 0.15^{+0.20}_{-0.15}, Ω^{0}_{m}=
0.35^{+0.65}_{-0.22}. Combining these results with orthogonal constraints from linear evolution of density perturbations, we find that β(z= 3) = 0.25^{+0.05}_{-0.06},
Ω^{0}_{m}= 0.55^{+0.45}_{-0.16}.

**Monthly Notices of the Royal Astronomical Society**

Volume 361, Page 879

August 2005