We present the first direct measurement of the mean halo occupation distribution (HOD) of X-ray-selected active galactic nuclei (AGNs) in the COSMOS field at z â¤ 1, based on the association of 41 XMM and 17 C-COSMOS AGNs with member galaxies of 189 X-ray-detected galaxy groups from XMM-Newton and Chandra data. We model the mean AGN occupation in the halo mass range log M200[Mâ] = 13-14.5 with a rolling-off power law with the best-fit index Î± = 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 by a softened step function at logMh>logMmin= 12.75(12.10, 12.95)Mâwhile for the satellite AGN HOD we find a preference for an increasing AGN fraction with Mh, suggesting that the average number of AGNs in satellite galaxies grows slower (Î±s< 0.6) than the linear proportion (Î±s= 1) observed for the satellite HOD of samples of galaxies. We present an estimate of the projected autocorrelation function (ACF) of galaxy groups over the range of rp= 0.1-40 h-1Mpc at ãzã = 0.5. We use the large-scale clustering signal to verify the agreement between the group bias estimated by using the observed galaxy groups ACF and the value derived from the group mass estimates. We perform a measurement of the projected AGN-galaxy-group cross-correlation function, excluding from the analysis AGNs that are within galaxy groups and we model the two-halo term of the clustering signal with the mean AGN HOD based on our results. Â© 2012. The American Astronomical Society. All rights reserved.
|Titolo:||Occupation of X-ray-selected galaxy groups by X-ray active galactic nuclei|
|Data di pubblicazione:||2012|
|Parole Chiave:||dark matter; galaxies: active; large-scale structure of universe; quasars: general; surveys; X-rays: general; Astronomy and Astrophysics; Space and Planetary Science|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1088/0004-637X/758/1/47|
|Appare nelle tipologie:||1.1 Articolo in rivista|