The Evolution and Quenching of Galaxies after z ~ 3
I will describe a toy power-law model for the growth of black holes in galaxies and their role in quenching. Galaxies while star-forming are assumed to exist at the centers of relatively undisturbed dark halos,and their stellar masses and radii Re are linked to their halo properties via simple power-law relations. Black hole mass is assumed to correlate with central stellar density, which implies a connection to halo properties via the previous assumptions. Quenching occurs when the total energy emitted by the black hole, Ebh, equals some total energy needed to heat the halo, Ehalo, which is assumed to behave the functional form f(z) Mvir^t, where f(z) is a function of redshift. The functional form of f(z) and the value of t are derived by fitting to the observed distribution of star-forming galaxies in the R_e - M* plane and the ridge line of quenched galaxies in the Sig1- M* plane from z ~ 3 to now. It is further shown that the empirically derived from for Ehalo is virtually to the thermal energy content of the hot gas in the halo as a function of time. The implications are that 1) halos are a 2-parameter family that imprint their properties on the M* and Re of galaxies, 2) halos "know" about their BH masses because the two are connected through the properties of their central galaxy, and 3) galaxies quench when the energy deposited by their BHs approximately doubles the thermal energy in their hot-gas halos.