The mass function of local active black holes.

We present estimated black hole masses and accretion rates for a well defined sample of local (z<0.3) broad line AGN from the Hamburg/ESO Survey. We use these black hole masses to determine the active black hole mass function (BHMF) in the local universe. We find indications for anti-hierarchical growth of black holes, in the sense that the fraction of black holes in a high accretion stage significantly decreases with increasing mass. A comparison with the BHMF at higher redshifts also indicates that, at the high mass end, black holes are now in a less active stage than at earlier cosmic epochs. This strengthens the picture of cosmic downsizing of AGN activity, where the most massive black holes grew at early cosmic times, whereas at present mainly smaller mass black holes accrete at a significant rate.