Constraining halo occupation properties of X-ray AGNs using clustering of Chandra sources in the Bootes survey region

We present one of the most precise measurement to date of the spatial clustering of X-ray selected AGNs using a sample derived from the Chandra X-ray Observatory survey in the Boötes field. The real-space twopoint correlation function over a redshift interval from z = 0.17 to z ∼ 3 is well described by the power law, ξ(r) = (r/r0), for comoving separations r . 20 h−1 Mpc. We find γ = 1.84 ± 0.12 and r0 consistent with no redshift trend within the sample (varying between r0 = 5.5 ± 0.6 h−1 Mpc for 〈z〉 = 0.37 and r0 = 6.9 ± 1.0 h−1 Mpc for 〈z〉 = 1.28). Further, we are able to measure the projections of the two-point correlation function both on the sky plane and in the line of sight. We use these measurements to show that the Chandra/Boötes AGNs are predominantly located at the centers of dark matter halos with the circular velocity vmax > 320 km s−1 or M180 > 4.1 × 1012 h−1 M , and tend to avoid satellite galaxies in halos of this or higher mass. The halo occupation properties inferred from the clustering properties of Chandra/Boötes AGNs — the mass scale of the parent dark matter halos, the lack of significant redshift evolution of the clustering length, and the low satellite fraction — are broadly consistent with the Hopkins et al. (2006) scenario of quasar activity triggered by mergers of similarly-sized galaxies.