Speaker
Description
A connection between Supermassive Black Holes (SMBH) and galaxy growth has been suggested by a number of studies, based on empirical correlations between BH mass and integrated galaxy properties as galaxy bulge mass, total stellar mass, velocity dispersion and star formation rate (SFR). In particular current studies show that SFR and AGN activity appear to follow similar patterns with cosmic time (i.e. redshift), indicating that the evolution of galaxies and their central SMBH proceeds in a coherent way.
So far most studies have explored intermediate/high redshift ranges, mainly due to the lack of large, homogeneous X-ray surveys at low redshift. In our work we intend to study the AGN activity as a function of stellar mass and star-formation rate in local Universe. Starting from a parent sample of galaxies from the Sloan Digital Sky Survey (SDSS DR8) with spectroscopic SFR estimates, and applying standard multiwavelength AGN selection criteria (optical BPT-diagrams, X-ray/optical ratio etc) we derived the fraction of efficiently-accreting AGNs and investigated the properties of their host galaxies (star-formation, mass). We then measured the distribution of specific black hole accretion rate (sBHAR) using X-ray detections from the 3XMM-Newton Serendipitous Source Catalogue (3XMM DR8) finding systematically higher values of sBHAR for galaxies with active star-formation than for quiescent ones, for all ranges of stellar masses. Finally, taking into account the variable XMM sensitivity across the sky, we infer the intrinsic sBHAR distribution in the local Universe, showing that nuclear activity in local galaxies peaks at very low accretion rates.
