2.30 pm Monday 1 October 2001
Supermassive black holes are ubiquitous components of galaxies and have been present since a redshift of 6 or more. Their current masses are a result of two processes: accretion during the quasar epoch; and mergers between galaxies, followed by coalescence of binary black holes via emission of gravitational radiation. I review recent progress in our understanding of "black hole demographics" and show that there is now excellent agreement between black hole masses determined in various ways, in quiescent galaxies, quasars and AGN. I then discuss the merger history of black holes and the consequences for galaxy structure. Binary black holes are efficient at lowering the densities of stellar and dark-matter systems; the observed absence of dark-matter cusps at the centers of galaxies as predicted by CDM may be a consequence of this process. I also discuss the consequences for detection of dark-matter annihilation radiation from the Galactic center.