Abstract
We study the angular clustering of X-ray selected active galactic nuclei (AGN) in different flux-limited sub-samples of the Chandra Deep Field North (CDF-N) and South (CDF-S) surveys. We find a strong dependence of the clustering strength on the sub-sample flux-limit, a fact which explains most of the disparate clustering results of different XMM and Chandra surveys. At high flux-limits the clustering length increases considerably; for example, at f_{x,limit} ∼ 10^{-15} erg s-1 cm-2, we obtain r_0 ≃ 17+/-5 and 18+/-3 h^-1 Mpc, for the CDF-N and CDF-S, respectively. The flux-limit dependence translates into a luminosity dependent X-ray AGN clustering. Applying the standard formalism relating the theoretical CDM model clustering to the data in a flat cosmology (for w=-1 and h=0.72), we find: Ω_{m} ≃ 0.28+/-0.03 and σ_{8}^{} ≃ 0.75+/-0.03; while utilizing also the SN Ia Hubble relation (for σ_{8}^=0.75 and h=0.72), we find: Ω_{m} ≃ 0.26+/-0.04 and w=-0.9+/-0.1.
