Breaking the σ8-Ωm degeneracy using the clustering of high-z X-ray active galactic nuclei

Abstract

The clustering of X-ray selected active galactic nuclei (AGNs) appears to be a valuable tool for extracting cosmological information. Using the recent high-precision angular clustering results of ∼30,000 XMM-Newton soft (0.5-2keV) X-ray sources, which have a median redshift of z ∼ 1, and assuming a flat geometry, a constant in comoving coordinates AGN clustering evolution, and the AGN bias evolution model of Basilakos etal., we manage to break the σ8-Ωm degeneracy. The resulting cosmological constraints are Ωm = 0.27+0.03-0.05, w = -0.90+0.10-0.16, and σ8 = 0.74+0.14-0.12, while the dark matter host halo mass, in which the X-ray selected AGNs are presumed to reside, is M = 2.50+0.50-1.50 × 1013 h -1M⊙. For the constant Λ model (w = -1) we find Ωm = 0.24 0.06 and σ8 = 0.83 +0.11-0.16, in good agreement with recent studies based on cluster abundances, weak lensing, and the cosmic microwave background, but in disagreement with the recent bulk flow analysis. © 2010 The American Astronomical Society. All rights reserved.