Occupation of X-Ray-Selected Galaxy Groups by X-Ray Active Galactic Nuclei

We present the first direct measurement of the mean halo occupation (HOD) of X-ray-selected active galactic nuclei (AGNs) in COSMOS field at z <= 1, based on the association of 41 XMM and 17 -COSMOS AGNs with member galaxies of 189 X-ray-detected galaxy groups XMM-Newton and Chandra data. We model the mean AGN occupation in halo mass range log M ₂₀₀ [M ⊙] = 13-14.5 a rolling-off power law with the best-fit index α = 0.06(- 0.22; 0.36) and normalization parameter fa = 0.05(0.04; 0.06). We find the mean HOD of AGNs among central galaxies to be modeled a softened step function at log Mh > log M = 12.75(12.10, 12.95) M ⊙ while for the AGN HOD we find a preference for an increasing AGN fraction Mh , suggesting that the average number of AGNs in galaxies grows slower (αs < 0.6) than linear proportion (αs = 1) observed for the HOD of samples of galaxies. We present an estimate of the autocorrelation function (ACF) of galaxy groups over the range rp = 0.1-40 h ⁻¹ Mpc at langzrang = 0.5. We use large-scale clustering signal to verify the agreement between the bias estimated by using the observed galaxy groups ACF and the derived from the group mass estimates. We perform a measurement of projected AGN-galaxy-group cross-correlation function, excluding the analysis AGNs that are within galaxy groups and we model the -halo term of the clustering signal with the mean AGN HOD based on results.