Breaking the σ8-Ω m Degeneracy Using the Clustering of High-z X-ray Active Galactic Nuclei

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 (0.5-2 keV) 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 et al., we manage to break the σ₈-Ω _m degeneracy. The resulting cosmological constraints are Ω _m = 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 ^-1 M _sun. For the constant Λ model (w = -1) we find Ω _m = 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.