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2001ApJ...551..131C - Astrophys. J., 551, 131-152 (2001/April-2)
Cooling flows and quasars. II. Detailed models of feedback-modulated accretion flows.
CIOTTI L. and OSTRIKER J.P.
Abstract (from CDS):
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 X-ray galaxy emission comes from the coronal gas. For a fixed galaxy total mass and structure, the length and the intensity of the bursts depend sensitively on the accretion efficiency and the SN Ia rate. For high efficiency and SN Ia rate values, short and strong bursts are followed by a degassing of the galaxy, with a consequent shut-off of the BH followed by a long period when the mass loss from the stellar population replenishes the galaxy, and after which a new cooling catastrophe another accretion event takes place. In this case, high accretion rates characterize the BH evolution, but the total mass accreted by the BH is very small. For low efficiency and SN Ia rate values, the luminosity evolution is still characterized by strong intermittencies, but the number of global degassing events is considerably reduced, and for very low efficiency values it completely disappears. The remaining instability is then concentrated in the central galactic regions. We also allow for departures from spherical symmetry by examining scenarios in which the central engine is either an advection-dominated accretion flow or a more conventional accretion disk that is optically thick except for a polar region. The general property of highly unstable accretion remains true, with central BHs growing episodically to the mass range 108-109 M☉ (in contrast to ΔMBH≳1010-1011 M☉, if feedback is ignored). In all cases the duty cycle (fraction of the time that the system will be seen as an AGN) is quite small and in the range fBH≃10–4-2x10–3. Thus, for any reasonable value of the efficiency, the presence of a massive BH at the center of a galaxy seems to be incompatible with the presence of a long-lived cooling flow.
Abstract Copyright: ∼
Journal keyword(s): Galaxies: Cooling Flows - Galaxies: Active - Galaxies: Elliptical and Lenticular, cD - Galaxies: ISM - Galaxies: Nuclei - X-Rays: Galaxies
Simbad objects: 4
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