AGN and the demographics of supermassive black holes

High angular resolution observations from WFPC and STIS now allow well-constrained dynamical measurement of the masses of supermassive black holes (SMBH) in nearby galaxies. An initial statistical analysis by Magorrian et al. showed that 97% of bulges host SMBH. Black hole mass is correlated moderately with bulge luminosity and strongly with the velocity dispersion of the whole bulge, suggesting that black hole formation may be an intrinsic aspect of bulge formation. Black hole masses for AGN determined from reverberation mapping fall on the same relationship with bulge velocity dispersion as those determined from stellar dynamical measurements. The prospect is therefore that the large-scale distribution of black hole masses in distant quasars may be determined through relatively straightforward measurement. Integral constraints show consistency between the total AGN luminosity density and the total volume density in SMBH contained in galaxy bulges. The strong peak of the high-luminosity quasar-luminosity function at, early cosmic time is consistent with the association of the build-up of SMBH through accretion and bulge formation.. Alternate scenarios requiring substantial build-up of the most massive black holes at later cosmic times are more difficult to reconcile with the evolution of the LF.