A physical model for the fueling and evolution of quasars in galaxy mergers

We develop an evolutionary model for starbursts, quasars, and spheroidal galaxies in which supermassive black holes play a dominant role. In this picture, mergers between gas-rich galaxies drive nuclear inflows of gas, producing intense starbursts and feeding the growth of supermassive black holes. During this phase, the black hole is heavily obscured (a "buried" quasar), but feedback energy from its growth expels the gas, rendering the black hole briefly visible as a bright, optical source (a "visible" quasar), and eventually halting accretion (a "dead" quasar). The self-regulated growth of the black hole accounts for the observed correlation between black hole mass and stellar velocity dispersion in spheroidal galaxies. We show that the quasar lifetime and obscuring column density depend on both the instantaneous and peak luminosities of the quasar, and determine this dependence using a large set of simulations of galaxy mergers varying the host galaxy properties, orbital geometry, and gas physics. We are able to reproduce and test these models against a wide variety of observational constraints.