The role of flow geometry in influencing the stability criteria for low angular momentum axisymmetric black hole accretion

Accretion flow on a horizon is supersonic, no matter what the flow angular momentum or the spin of the black hole is. This means that a black hole accretion can always be viewed as a flow in a flat space–time through one or more convergent–divergent ducts. In this paper, we study how the area of cross-sections must vary in order that the flow has the same properties in both systems. We show that the accretion flow experiencing a shock is equivalent to having two ducts connected back-to-back, both with a neck where the flow becomes supersonic. We study the pressure and Mach number variations for corotating, contrarotating flows and flows around a black hole with evolving spin.

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The impact of angular momentum on black hole accretion rates in simulations of galaxy formation

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stv2056 ◽

2015 ◽

Vol 454 (1) ◽

pp. 1038-1057 ◽

Cited By ~ 145

Author(s):

Y. M. Rosas-Guevara ◽

R. G. Bower ◽

J. Schaye ◽

M. Furlong ◽

C. S. Frenk ◽

...

Keyword(s):

Black Hole ◽

Angular Momentum ◽

Galaxy Formation ◽

Black Hole Accretion ◽

Accretion Rates ◽

The Impact ◽

Hole Accretion

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The self-regulated AGN feedback loop: the role of chaotic cold accretion

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315010455 ◽

2015 ◽

Vol 11 (S319) ◽

pp. 17-20

Author(s):

M. Gaspari

Keyword(s):

Black Hole ◽

Feedback Loop ◽

Cosmic Time ◽

Rapid Variability ◽

Cooling Flow ◽

Black Hole Accretion ◽

Tightly Coupled ◽

Hole Accretion ◽

Gaseous Halo

AbstractSupermassive black hole accretion and feedback play central role in the evolution of galaxies, groups, and clusters. I review how AGN feedback is tightly coupled with the formation of multiphase gas and the newly probed chaotic cold accretion (CCA). In a turbulent and heated atmosphere, cold clouds and kpc-scale filaments condense out of the plasma via thermal instability and rain toward the black hole. In the nucleus, the recurrent chaotic collisions between the cold clouds, filaments, and central torus promote angular momentum cancellation or mixing, boosting the accretion rate up to 100 times the Bondi rate. The rapid variability triggers powerful AGN outflows, which quench the cooling flow and star formation without destroying the cool core. The AGN heating stifles the formation of multiphase gas and accretion, the feedback subsides and the hot halo is allowed to cool again, restarting a new cycle. Ultimately, CCA creates a symbiotic link between the black hole and the whole host via a tight self-regulated feedback which preserves the gaseous halo in global thermal equilibrium throughout cosmic time.

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Self-consistent Black Hole Accretion Spectral Models and the Forgotten Role of Coronal Comptonization of Reflection Emission

The Astrophysical Journal ◽

10.3847/1538-4357/836/1/119 ◽

2017 ◽

Vol 836 (1) ◽

pp. 119 ◽

Cited By ~ 17

Author(s):

James F. Steiner ◽

Javier A. García ◽

Wiebke Eikmann ◽

Jeffrey E. McClintock ◽

Laura W. Brenneman ◽

...

Keyword(s):

Black Hole ◽

Black Hole Accretion ◽

Spectral Models ◽

Self Consistent ◽

Hole Accretion

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Real galaxy mergers from galaxy pair catalogues

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa227 ◽

2020 ◽

Vol 493 (1) ◽

pp. 922-929 ◽

Cited By ~ 1

Author(s):

Hugo Pfister ◽

Massimo Dotti ◽

Clotilde Laigle ◽

Yohan Dubois ◽

Marta Volonteri

Keyword(s):

Neural Network ◽

Black Hole ◽

Aspect Ratio ◽

Galaxy Mergers ◽

Exact Role ◽

Black Hole Accretion ◽

Selection Processes ◽

Hole Accretion ◽

Projected Distance

ABSTRACT Mergers of galaxies are extremely violent events shaping their evolution. Such events are thought to trigger starbursts and, possibly, black hole accretion. Nonetheless, it is still not clear how to know the fate of a galaxy pair from the data available at a given time, limiting our ability to constrain the exact role of mergers. In this paper we use the light-cone of the horizon-agn simulation, for which we know the fate of each pair, to test three selection processes aiming at identifying true merging pairs. We find that the simplest one (selecting objects within two thresholds on projected distance d and redshift difference Δz) gives similar results than the most complex one (based on a neural network analysing d, Δz, redshift of the primary, masses/star formation rates/aspect ratio of both galaxies). Our best thresholds are $d_\mathrm{th}\sim 100\, \mathrm{kpc}$ and Δzth ∼ 10−3, in agreement with recent results.

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