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

• Published in: Monthly notices of the Royal Astronomical Society 2005-07, Vol.360 (3), p.1040-1054
• Main Authors: da Ângela, J., Outram, P. J., Shanks, T., Boyle, B. J., Croom, S. M., Loaring, N. S., Miller, L., Smith, R. J.
• Format: Article
• Language: English
• Subjects: Astronomy; Correlation analysis; cosmology: observations; large-scale structure of Universe; quasars: general; Stars & galaxies; surveys
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2005.09094.x

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−γ model fits the projected correlation function [ωp(σ)] at small scales, it implies somewhat too shallow a slope for both ωp(σ) and the z-space correlation function, ξ(s), at larger scales (≲20 h−1 Mpc). 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 ωp(σ). The model is parametrized by a slope of γ = 1.45 for 1 < r < 10 h−1 Mpc and γ = 2.30 for 10 < r < 40 h−1 Mpc. 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.