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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 (P0.03) 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 k0.1Y0.4. 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 P z P 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 ; 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 Sérsic profiles.

Most elliptical galaxies contain central black holes (BHs), and most also contain significant amounts of hot gas capable of accreting on to the central BH due to cooling times short compared to the Hubble time. Why therefore do we not see AGNs at the center of most elliptical galaxies rather than in only (at most) a few per cent of them? We propose here the simple idea that feedback from accretion events heats the ambient gas, retarding subsequent infall, in a follow up of papers by Binney & Tabor (1995, BT95) and Ciotti & Ostriker (1997, CO97). Even small amounts of accretion on a central BH can cause the release of enough energy to reverse the central inflow, when the Compton temperature (T X ) of the emitted radiation is higher than the mean galactic gas temperature, the basic assumption of this paper. Well observed nearby AGN (3C 273, 3C 279), having T X near 5 × 10 8 K, amply satisfy this requirement. In this context, we present a new class of 1D hydrodynamical evolutionary sequences for the gas flows in elliptical galaxies with a massive central BH. The model galaxies are constrained to lie on the Fundamental Plane of elliptical galaxies, and are surrounded by variable amounts of dark matter. Two source terms operate: mass loss from evolving stars, and a secularly declining heating by type Ia supernovae (SNIa). Like the previous models investigated by Ciotti et al. (1991, CDPR) these new models can evolve up to three consecutive evolutionary stages: the wind, outflow, and inflow phases. At this point the presence of the BH alters dramatically the subsequent evolution, because of the energy emitted due to the accreting gas flow. The effect of Compton heating and cooling, of hydrogen and helium photoionization heating, and of bremsstrahlung recycling on the gas flow are investigated by numerical integration of the nonstationary equations of hydrodynamics, in the simplifying assumption of spherical symmetry, and for various values of the accretion efficiency and supernova rates.The resulting evolution is characterized by strong oscillations, in which very fast and energetic bursts from the BH are followed by longer periods during which the

We extend the black hole (BH) feedback models of Ciotti, Ostriker, and Proga to two dimensions. In this paper, we focus on identifying the differences between the one-dimensional and two-dimensional hydrodynamical simulations. We examine a normal, isolated L * galaxy subject to the cooling flow instability of gas in the inner regions. Allowance is made for subsequent star formation, Type Ia and Type II supernovae, radiation pressure, and inflow to the central BH from mildly rotating galactic gas which is being replenished as a normal consequence of stellar evolution. The central BH accretes some of the infalling gas and expels a conical wind with mass, momentum, and energy flux derived from both observational and theoretical studies. The galaxy is assumed to have low specific angular momentum in analogy with the existing one-dimensional case in order to isolate the effect of dimensionality. The code then tracks the interaction of the outflowing radiation and winds with the galactic gas and their effects on regulating the accretion. After matching physical modeling to the extent possible between the one-dimensional and two-dimensional treatments, we find essentially similar results in terms of BH growth and duty cycle (fraction of the time above a given fraction of the Eddington luminosity). In the two-dimensional calculations, the cool shells forming at 0.1-1 kpc from the center are Rayleigh-Taylor unstable to fragmentation, leading to a somewhat higher accretion rate, less effective feedback, and a more irregular pattern of bursting compared to the one-dimensional case.

We discuss the importance of feedback via photoionization and Compton heating on the coevolution of massive black holes (MBHs) at the centre of spheroidal galaxies, and their stellar and gaseous components. We first assess the energetics of the radiative feedback from a typical quasar on the ambient interstellar medium (ISM). We then demonstrate that the observed M BH -σ relation could be established following the conversion of most of the gas of an elliptical progenitor into stars, specifically when the gas-to-stars mass ratio in the central regions has dropped to a low level ∼0.01 or less, so that gas cooling is no longer able to keep up with the radiative heating by the growing central massive black hole (MBH). A considerable amount of the remaining gas will be expelled and both MBH accretion and star formation will proceed at significantly reduced rates thereafter, in agreement with observations of present-day ellipticals. We find further support for this scenario by evolving over an equivalent Hubble time a simple, physically based toy model that additionally takes into account the mass and energy return for the spheroid evolving stellar population, a physical ingredient often neglected in similar approaches.

The deposition of mechanical feedback from a supermassive black hole (SMBH) in an active galactic nucleus (AGN) into the surrounding galaxy occurs via broad-line winds which must carry mass and radial momentum as well as energy. The effect can be summarized by the dimensionless parameteris the efficiency by which accreted matter is turned into wind energy in the disc surrounding the central SMBH. The outflowing mass and momentum are proportional to η, and many prior treatments have essentially assumed that η = 0. We perform one-and two-dimensional simulations and find that the growth of the central SMBH is very sensitive to the inclusion of the mass and momentum driving but is insensitive to the assumed mechanical efficiency. For example in representative calculations, the omission of momentum and mass feedback leads to an hundred fold increase in the mass of the SMBH to over 10 10 M ⊙ . When allowance is made for momentum driving, the final SMBH mass is much lower and the wind efficiencies which lead to the most observationally acceptable results are relatively low with ǫ w 10 −4 .

We find, from high-resolution hydro simulations, that winds from AGN effectively heat the inner parts (≈ 100 pc) of elliptical galaxies, reducing infall to the central black hole; and radiative (photoionization and X-ray) heating reduces cooling flows at the kpc scale. Including both types of feedback with (peak) efficiencies of 3 10 −4 < ∼ ǫ w < ∼ 10 −3 and of ǫ EM ≃ 10 −1.3 respectively, produces systems having duty-cycles, central black hole masses, X-ray luminosities, optical light profiles, and E+A spectra in accord with the broad suite of modern observations of massive elliptical systems. Our main conclusion is that mechanical feedback (including all three of energy, momentum and mass) is necessary but the efficiency, based on several independent arguments must be a factor of 10 lower than is commonly assumed. Bursts are frequent at z > 1 and decline in frequency towards the present epoch as energy and metal rich gas are expelled from the galaxies into the surrounding medium. For a representative galaxy of final stellar mass ≃ 3 10 11 M ⊙ , roughly 3 10 10 M ⊙ of recycled gas has been added to the ISM since z ≃ 2 and, of that, roughly 63% has been expelled from the galaxy, 19% has been converted into new metal rich stars in the central few hundred parsecs, and 2% has been added to the central supermassive black hole, with the remaining 16% in the form hot X-ray emitting ISM. The bursts occupy a total time of ≃ 170 Myr, which is roughly 1.4% of the available time. Of this time, the central SMBH would be seen as an UV or optical source for ≃ 45% and ≃ 71% of the time, respectively. Restricting to the last 8.5 Gyr, the burst occupy ≃ 44 Myr, corresponding to a fiducial duty-cycle of ≃ 5 10 −3 .

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