Cooling Flows and Quasars. II. Detailed Models of Feedback‐modulated Accretion Flows

Abstract

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

Black holes in pseudobulges: demography and models

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The regulation of star formation in cool-core clusters: imprints on the stellar populations of brightest cluster galaxies

“…The BCGs often host radio-loud AGN (Sun 2009), and theoretical estimates have long suggested that the mechanical heating of the intracluster gas by these AGNs plays a key role in counteracting radiative cooling (Binney & Tabor 1995;Ciotti & Ostriker 2001;Soker et al 2001;Babul et al 2002). With imaging X-ray observations showing clear signs of interactions between the AGN outflows and the hot diffuse gas surrounding the BCGs (see Nulsen 2007, 2012 andreferences therein), there is now a broad consensus that in order to make sense of the full range of BCG properties, it is crucial to understand the role of cooling, feedback and gas accretion in cluster cores.…”

The X‐Ray–faint Emission of the Supermassive Nuclear Black Hole of IC 1459

“…Suggested explanations for this lack of nuclear activity have included the presence of Compton-thick obscuring material in the line of sight to the nucleus (e.g. the Circinus galaxy, Matt et al 1999), feedback modulated accretion with a low duty cycle (Binney & Tabor 1995, Ciotti & Ostriker 2001, and inefficient accretion onto the black hole (e.g., Sgr A*, see review by Melia & Falcke 2001. The latter include instability-driven periodic accretion in a thin accretion disk (Siemiginowska & Elvis 1997;Siemiginowska, Czerny & Kostyunin 1996), and the more popular radiatively-inefficient advection dominated accretion flow (ADAF, CDAF, ADIOS) models (see review by Narayan 2002).…”