Large-scale clustering of sloan digital sky survey quasars: Impact of the baryon density and the cosmological constant

Abstract

We report on the first result from the clustering analysis of SDSS quasars. We computed the two-point correlation function (2PCF) of SDSS quasars in redshift space at 8 h-1 Mpc < s < 500 h-1 Mpc, with particular attention to its baryonic signature. Our sample consisted of 19986 quasars extracted from the SDSS Data Release 4. The redshift range of the sample is 0.72 ≤ z ≤ 2.24 (the mean redshift is z̄ = 1.46) and the reddening-corrected i-band apparent magnitude range is 15.0 ≤ m i.rc ≤ 19.1. Due to the relatively low number density of the quasar sample, the bump in the power spectrum due to the baryon density, Ωb, is not clearly visible. The effect of the baryon density is, however, to distort the overall shape of the 2PCF. The degree of distortion makes it an interesting alternate measure of the baryonic signature. Assuming a scale-independent linear bias and a spatially flat universe, we combined the observed quasar 2PCF and the predicted matter 2PCF to put constraints on Ωb and ΩΛ (the cosmological constant). Our result was fitted as 0.80 -2.8Ωb < Ω Λ < 0.90 - 1.4Ωb at the 2σ confidence level. The "mean" bias parameter of our quasar sample is 1.59 σ8-1 (for Ωb = 0.04 and ΩΛ = 0.7), where σ8 is the top-hat mass fluctuation amplitude at 8 h-1 Mpc. We also estimated the corresponding bias parameter of quasars at z = 0, bQSO.Fry(0), assuming Fry's bias evolution model. For Ωb = 0.04, ΩΛ = 0.73, and Ωd = 0.23, we found bQSO.Fry(0) = 0.54 + 0.83 σ8-1 which is valid for 0.6 < σ8 < 1.0. © 2005. Astronomical Society of Japan.