**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

**Abstract**

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
[w_{p}(σ)] at small scales, it implies somewhat too
shallow a slope for both w_{p}(σ) and the z-space
correlation function, ξ(s), at larger scales
(>~20h^{-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 w_{p}(σ).
The model is parametrized by a slope of γ= 1.45 for 1 < r <
10h^{-1}Mpc and γ= 2.30 for 10 < r <
40h^{-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
Ω^{0}_{m} and β(z= 1.4), using an improved
version of the method of Hoyle et al. The constraints we derive are
Ω^{0}_{m}= 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