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arXiv · 2107.04830

Accretion of a Vlasov gas on to a black hole from a sphere of finite radius and the role of angular momentum

Aldo Gamboa·Carlos Gabarrete·Paola Domínguez-Fernández·Darío Núñez·Olivier Sarbach
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Abstract

The accretion of a spherically symmetric, collisionless kinetic gas cloud on to a Schwarzschild black hole is analysed. Whereas previous studies have treated this problem by specifying boundary conditions at infinity, here the properties of the gas are given at a sphere of finite radius. The corresponding steady-state solutions are computed using four different models with an increasing level of sophistication, starting with the purely radial infall of Newtonian particles and culminating with a fully general relativistic calculation in which individual particles have angular momentum. The resulting mass accretion rates are analysed and compared with previous models, including the standard Bondi model for a hydrodynamic flow. We apply our models to the supermassive black holes Sgr A* and M87*, and we discuss how their low luminosity could be partially explained by a kinetic description involving angular momentum. Furthermore, we get results consistent with previous model-dependent bounds for the accretion rate imposed by rotation measures of the polarised light coming from Sgr A* and with estimations of the accretion rate of M87* from the Event Horizon Telescope collaboration. Our methods and results could serve as a first approximation for more realistic black hole accretion models in various astrophysical scenarios in which the accreted material is expected to be nearly collisionless.

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Aldo Gamboa, Carlos Gabarrete, Paola Domínguez-Fernández, Darío Núñez, Olivier Sarbach. 2021-07-10. Accretion of a Vlasov gas on to a black hole from a sphere of finite radius and the role of angular momentum. https://doi.org/10.1103/physrevd.104.083001

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