Angela BONGIORNO
(INAF - Rome Observatory)
Super massive black holes (SMBHs) seem to be the galaxies' beating hearts. While many observational discoveries support a close link between SMBH activity and the assembly of the host galaxy, the physical processes behind this interplay remain unclear. One of the most efficient way to constrain the physical models of AGN/galaxy co-evolution is to study the effect of accreting SMBHs in the galaxies that host them. Using the rich multi-band photometry in the COSMOS field we explore the host galaxy properties of a large, complete, sample of X-ray and spectroscopically selected AGN. Based on a two-components fit to their SED we derive rest-frame magnitudes, colors, stellar masses and star formation rates up to z~3. We find that the probability for a galaxy to host a black hole growing at any given specific accretion rate (the ratio of X-ray luminosity to the host stellar mass) is independent of the galaxy mass and follows a power-law distribution in L_X/M. By looking at the normalization of such a probability distribution, we show how the incidence of AGN increases with redshift as rapidly as (1+z)^4.2, in close resemblance with the overall evolution of the specific star formation rate (SFR). Although AGN activity and star formation appear to have a common triggering mechanism, we do not find any 'smoking gun' signalling powerful AGN influence on the global properties of their host galaxies.<br>We also analyzed the dependence of optical obscuration on the host galaxy mass and SFR finding no relationship between the fraction of absorbed AGN and the stellar masses and SFR of their host galaxies, once objects of the same luminosity are compared. This result indicates that the physical properties of the medium responsible for optical obscuration in AGN are mainly determined by the environment in the small region close to the central SMBH, but are insensitive to the larger scale galactic conditions.