Radiative feedback from massive black holes in elliptical galaxies: AGN flaring and central starburst fueled by recycled gas

We show how the observed AGN radiative output from massive black holes at the centers of elliptical galaxies affects the hot ISM of these systems with the aid of a high-resolution hydrodynamical code, where the cooling and heating functions include photoionization plus Compton heating. Radiative heating is a key factor in the self-regulated coevolution of massive BHs and their host galaxies, and (1) the mass accumulated by the central BH is limited by feedback to the range observed today and (2) relaxation instabilities occur so that duty cycles are small enough (less than or similar to 0.03) to account for the very small fraction of massive ellipticals observed to be in the on'' QSO phase, when the accretion luminosity approaches the Eddington luminosity. The duty cycle of the hot bubbles inflated at the galactic center during major accretion episodes is of the order of greater than or similar to 0.1-0.4. Major accretion episodes caused by cooling flows in the recycled gas produced by normal stellar evolution trigger nuclear starbursts coincident with AGN flaring. Overall, in the bursting phase (1 less than or similar to z less than or similar to 3), the duty cycle of the BH in its on'' phase is of the order of percents and is unobscured approximately one-third of the time, the obscuration occurring during dusty starbursts. Roughly half of the recycled gas from dying stars is ejected as galactic winds, half is consumed in central starbursts, and less than 1% is accreted onto the central BH. Mechanical energy output from nonrelativistic gas winds integrates to 2:3 x 10(59) ergs, with most of it caused by broad-line AGN outflows. We predict the typical properties of the very metal-rich poststarburst central regions and show that the resulting surface density profiles are well described by Sersic profiles.