THE HALO OCCUPATION DISTRIBUTION OF X-RAY-BRIGHT ACTIVE GALACTIC NUCLEI: A COMPARISON WITH LUMINOUS QUASARS

We perform halo occupation distribution (HOD) modeling of the projected two-point correlation function (2PCF) of high-redshift (z similar to 1.2) X-ray-bright active galactic nuclei (AGNs) in the XMM-COSMOS field measured by Allevato et al. The HOD parameterization is based on low-luminosity AGNs in cosmological simulations. At the median redshift of z similar to 1.2, we derive a median mass of 1.02(-0.23)(+0.21) x 10(13) h(-1) M-circle dot for halos hosting central AGNs and an upper limit of similar to 10% on the AGN satellite fraction. Our modeling results indicate (at the 2.5 sigma level) that X-ray AGNs reside in more massive halos compared to more bolometrically luminous, optically selected quasars at similar redshift. The modeling also yields constraints on the duty cycle of the X-ray AGN, and we find that at z similar to 1.2 the average duration of the X-ray AGN phase is two orders of magnitude longer than that of the quasar phase. Our inferred mean occupation function of X-ray AGNs is similar to recent empirical measurements with a group catalog and suggests that AGN halo occupancy increases with increasing halo mass. We project the XMM-COSMOS 2PCF measurements to forecast the required survey parameters needed in future AGN clustering studies to enable higher precision HOD constraints and determinations of key physical parameters like the satellite fraction and duty cycle. We find that N-2/A similar to 5 x 10(6) deg(-2) (with N the number of AGNs in a survey area of A deg(2)) is sufficient to constrain the HOD parameters at the 10% level, which is easily achievable by upcoming and proposed X-ray surveys.