The 2dF QSO Redshift Survey- XV. Correlation analysis of redshift-space distortions

J. da Ângela, P. J. Outram, T. Shanks, B. J. Boyle, S. M. Croom, N. S. Loaring, L. Miller, R. J. Smith

We analyse the redshift-space (z-space) distortions of quasi-stellar object (QSO) clustering in the 2-degree field instrument (2dF) QSO Redshift Survey (2QZ). To interpret the z-space correlation function, ξ(σ, π), we require an accurate model for the QSO real-space correlation function, ξ(r). Although a single power-law ξ(r) ~r model fits the projected correlation function [wp(σ)] at small scales, it implies somewhat too shallow a slope for both wp(σ) and the z-space correlation function, ξ(s), at larger scales (>~20h-1Mpc). Motivated by the form for ξ(r) seen in the 2dF Galaxy Redshift Survey (2dFGRS) and in standard Λ cold dark matter (CDM) predictions, we use a double power-law model for ξ(r), which gives a good fit to ξ(s) and wp(σ). The model is parametrized by a slope of γ= 1.45 for 1 < r < 10h-1Mpc and γ= 2.30 for 10 < r < 40h-1Mpc. As found for the 2dFGRS, the value of β determined from the ratio of ξ(s)/ξ(r) depends sensitively on the form of ξ(r) assumed. With our double power-law form for ξ(r), we measure β(z= 1.4) = 0.32+0.09-0.11. Assuming the same model for ξ(r), we then analyse the z-space distortions in the 2QZ ξ(σ, π) and put constraints on the values of Ω0m and β(z= 1.4), using an improved version of the method of Hoyle et al. The constraints we derive are Ω0m= 0.35+0.19-0.13, β(z= 1.4) = 0.50+0.13-0.15, in agreement with our ξ(s)/ξ(r) results at the ~1σ level.

Monthly Notices of the Royal Astronomical Society
Volume 360, Page 1040
July 2005