Constraining beta(z) and Omega_m from redshift-space distortions in z~3 galaxy surveys

We use 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 them derive confidence levels in the [Omega_m,beta(z=3)] plane. We model the z-space distortions in the shape of the correlation function measured in orthogonal directions, xi(sigma,pi). This modeling requires an accurate description of the real-space correlation function to be given as an input. From the projection of xi(sigma,pi) in the angular direction, w_p(sigma), 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 gamma=1.76(+0.08)(-0.09) (xi(r)= (r/r_0)^-gamma). A comparison between the shape of xi(s) and w_p(sigma) suggests that xi(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(sigma) results are limited to sigma < 10 h(-1) Mpc. Assuming this double power-law model, and by analysing the shape distortions in xi(sigma,pi), we find the following constraints: beta(z=3) = 0.15 (+0.20)(-0.15), Omega_m = 0.35 (+0.65)(-0.22). Combining these results with orthogonal constraints from linear evolution of density perturbations, we find that beta(z=3) = 0.25 (+0.05)(-0.06), Omega_m = 0.55 (+0.45)(-0.16).