2015A&A...579A..62G


C.D.S. - SIMBAD4 rel 1.7 - 2019.07.23CEST21:09:12

2015A&A...579A..62G - Astronomy and Astrophysics, volume 579A, 62-62 (2015/7-1)

Chaotic cold accretion on to black holes in rotating atmospheres.

GASPARI M., BRIGHENTI F. and TEMI P.

Abstract (from CDS):

The fueling of black holes is one key problem in the evolution of baryons in the universe. Chaotic cold accretion (CCA) profoundly differs from classic accretion models, as Bondi and thin disc theories. Using 3D high-resolution hydrodynamic simulations, we now probe the impact of rotation on the hot and cold accretion flow in a typical massive galaxy. In the hot mode, with or without turbulence, the pressure-dominated flow forms a geometrically thick rotational barrier, suppressing the black hole accretion rate to ∼1/3 of the spherical case value. When radiative cooling is dominant, the gas loses pressure support and quickly circularizes in a cold thin disk; the accretion rate is decoupled from the cooling rate, although it is higher than that of the hot mode. In the more common state of a turbulent and heated atmosphere, CCA drives the dynamics if the gas velocity dispersion exceeds the rotational velocity, i.e., turbulent Taylor number Tat<1. Extended multiphase filaments condense out of the hot phase via thermal instability (TI) and rain toward the black hole, boosting the accretion rate up to 100 times the Bondi rate ({dot}(M)o~{dot}(M)cool). Initially, turbulence broadens the angular momentum distribution of the hot gas, allowing the cold phase to condense with prograde or retrograde motion. Subsequent chaotic collisions between the cold filaments, clouds, and a clumpy variable torus promote the cancellation of angular momentum, leading to high accretion rates. As turbulence weakens (Tat>1), the broadening of the distribution and the efficiency of collisions diminish, damping the accretion rate ∝Tat–1, until the cold disk drives the dynamics. This is exacerbated by the increased difficulty to grow TI in a rotating halo. The simulated sub-Eddington accretion rates cover the range inferred from AGN cavity observations. CCA predicts inner flat X-ray temperature and r–1 density profiles, as recently discovered in M 87 and NGC 3115. The synthetic Hα images reproduce the main features of cold gas observations in massive ellipticals, as the line fluxes and the filaments versus disk morphology. Such dichotomy is key for the long-term AGN feedback cycle. As gas cools, filamentary CCA develops and boosts AGN heating; the cold mode is thus reduced and the rotating disk remains the sole cold structure. Its consumption leaves the atmosphere in hot mode with suppressed accretion and feedback, reloading the cycle.

Abstract Copyright:

Journal keyword(s): accretion, accretion disks - black hole physics - hydrodynamics - galaxies: ISM - instabilities - turbulence

Simbad objects: 10

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Number of rows : 10

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 NGC 1332 GiP 03 26 17.321 -21 20 07.33   11.45   9.84   ~ 290 0
2 Cl Melotte 22 OpC 03 47 00 +24 07.0           ~ 2885 0
3 NGC 3115 GiG 10 05 13.978 -07 43 06.89   11   9.37   ~ 896 2
4 NGC 4261 LIN 12 19 23.21607184 +05 49 29.7000920   13.92 12.87     ~ 1080 0
5 M 87 BiC 12 30 49.42338230 +12 23 28.0438581 10.16 9.59 8.63   7.49 ~ 5979 3
6 M 60 GiP 12 43 40.008 +11 33 09.40   10.3       ~ 1215 0
7 NGC 5044 BiC 13 15 23.969 -16 23 08.00   11.9   10.74   ~ 434 0
8 NGC 6868 GiP 20 09 54.082 -48 22 46.25   11.58 9.22 10.01 7.91 ~ 197 1
9 NGC 7049 GiP 21 19 00.249 -48 33 43.24   11.28 10.74 9.77   ~ 124 1
10 NAME Phoenix Cluster ClG 23 44 40.9 -42 41 54           ~ 102 0

    Equat.    Gal    SGal    Ecl

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2019.07.23-21:09:12

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