Keynote Presentation

Demographics of Supermassive Black Holes

Author(s): Luis C. Ho (KIAA/PKU)

Presenter: Luis Ho (KIAA / Peking University)

Supermassive black holes, weighing between millions to billions times the mass of the Sun, are believed to power quasars and other energetic activity in the centers of galaxies. With the help of advanced telescopes from the ground and in space, operating across the electromagnetic spectrum, astronomers have now discovered that supermassive black holes not only exist, but that they are very common and play a critical role in the formation and evolution of galaxies in the Universe. A class of intermediate-mass black holes has also been found. These "seeds" help us understand the formation and growth of supermassive black holes and the origin of quasars in the early Universe. Mergers of seed black holes will provide an important source of gravitational wave radiation that can be detected with upcoming experiments. I review the observational landscape, concentrating on updates of the current census of black holes detected by direct spatially resolved kinematical observations of nearby inactive galaxies, the extension of virial mass estimators to active galaxies and quasars based on reverberation mapping and extensions thereof, new probes afforded by ALMA, and, finally, traditional indicators based on radiative signatures of nuclear activity. I discuss the status of the scaling relations between black hole mass and host galaxy properties, and their possible evolution with redshift. Finally, I test the efficacy of AGN feedback based on observations of the cool gas content in AGN host galaxies.