The 2dF QSO Redshift Survey -: XIII.: A measurement of Λ from the quasi-stellar object power spectrum, PS (k||,k⊥)

We report on measurements of the cosmological constant, Lambda, and the redshift space distortion parameter beta = Ohm(m)(0.6)/b, based on an analysis of the quasi-stellar object (QSO) power spectrum in parallel and perpendicular to the observer's line of sight, P-s(k(parallel to), k(perpendicular to)), from the final catalogue of the Two-Degree Field (2dF) QSO Redshift Survey. We derive a joint <LF>Lambda - beta 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 (Ohm(m) + Ohm(Lambda) = 1) cosmology and a Lambda cosmology r(z) function to convert from redshift into comoving distance, we find best-fitting values of Ohm(Lambda) = 0.71(-0.17)(+0.09) and beta(q)(z similar to 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 Ohm(Lambda) = 0.64(-0.16)(+0.11) and beta(q)(z similar to 1.4) = 0.40(-0.09)(+0.09), is consistent with the Lambda r(z) results, and inconsistent with a Ohm(Lambda) = 0 flat cosmology at over 95 per cent confidence.