Lance Miller

Abstract:

The completed 2dF QSO Redshift (2QZ) Survey has been used to search for extreme large-scale cosmological structure (around 200 Mpc) over the redshift range 0100Mpc are in the linear or only weakly non-linear regime and do not represent collapsed non-linear structures. We compare the measurements with the expectation of a standard LCDM model by measuring the variance of counts in cells and find that, provided the distribution of QSOs on large scales exhibits a mild bias with respect to the distribution of dark matter, the observed fluctuations are found to be in good agreement with the model. There is no evidence on such scales for any extreme structures that might require, for example, departures from the assumption of Gaussian initial perturbations. Thus the power-spectrum derived from the 2QZ Survey appears to provide a complete description of the distribution of QSOs. The amount of bias and its redshift dependence that is required is consistent with that found from studying the clustering of 2QZ QSOs on 10 Mpc scales, and may be adequately described by an approximately redshift-invariant power spectrum with normalisation sigma_8=1.0 corresponding to a bias at z=0 of b=1.1 rising to b=2 at the survey's mean redshift z=1.5.

Abstract:

We report on measurements of the cosmological constant, Λ, and the redshift space distortion parameter β= Ωm0.6/b, based on an analysis of the quasi-stellar object (QSO) power spectrum parallel and perpendicular to the observer's line of sight, Ps(k≺, k⊥), from the final catalogue of the Two-Degree Field (2dF) QSO Redshift Survey. We derive a joint Λ - β constraint from the geometric and redshift-space distortions in the power spectrum. By combining this result with a second constraint based on mass clustering evolution, we break this degeneracy and obtain strong constraints on both parameters. Assuming a flat (Ωm + Ωλ = 1) cosmology and a Λ cosmology r(z) function to convert from redshift into comoving distance, we find best-fitting values of Ωλ = 0.71 -0.17+0.09 and βq(z ∼ 1.4) = 0.45 -0.11+0.09 Assuming instead an Einstein-de Sitter cosmology r(z) we find that the best-fitting model obtained, with Ω λ = 0.64+0.16+0.11 and β q(z ∼ 1.4) = 0-40-0.09+0.09, is consistent with the Λ r(z) results, and inconsistent with a Ω λ = 0 flat cosmology at over 95 per cent confidence.