"Halo mergers, AGN and downsizing"

We propose a simple analytic model of active galactic nuclei (AGN) triggered by major mergers of dark matter haloes. The model consists of two main ingredients: (1) the halo merger rate as the main triggering agent, and (2) the quasar light curve, which describes the evolution of individual quasars. The light curve has two components: an exponential ascending phase and a power-law descending phase that depends on mass of the host. The descending phase is modelled such that AGN in more massive haloes shut down faster than in less massive ones. This is compatible with downsizing, since observations reveal little or no sign of recent star formation in massive early-type galaxies. Our results match the luminosity function, the quasar clustering, the local black hole mass function, and the Eddington-ratio distribution. Lastly, we also explore the consequences of extending our model to include minor mergers, less massive hosts and massive black hole seeds.

Coauthors: Francesco Shankar, David Weinberg, Ravi Sheth, Cheng Li, Raul Angulo & Martin Crocce.