Global structure and dynamics of slowly rotating accretion flows

TL;DR

This paper investigates the global properties of slowly rotating accretion flows around supermassive black holes, analyzing how boundary conditions, angular momentum, and galaxy potential influence flow regimes and accretion rates.

Contribution

It provides a detailed numerical analysis of transonic accretion flows, distinguishing between Bondi-like and Disk-like regimes based on angular momentum, and explores the effects of hydrostatic equilibrium and galaxy potential.

Findings

Hydrostatic equilibrium reduces mass accretion rate.

Flow regime depends on angular momentum at Bondi radius.

Galaxy potential significantly influences accretion dynamics.

Abstract

We study the global solutions of slowly rotating accretion flows around the supermassive black hole in the nucleus of an elliptical galaxy. The velocity of accreted gas surrounding the black hole is initially subsonic and then falls onto the black hole supersonically, so accretion flow must be transonic. We numerically solve equations from the Bondi radius to near the black hole. The focus of our discussion will be on the properties of slightly rotating accretion flows in which radiative losses have been ignored. This study discusses how outer boundary conditions (the temperature and specific angular momentum at the outer boundary) influence accretion flow dynamics. We investigate two physically discontinuous regimes: The Bondi-like type accretion and the Disk-like type accretion. A Bondi-like accretion occurs when the specific angular momentum at the Bondi radius $ \ell_{B} $ is smaller than the specific angular momentum at the marginally stable orbit $ \ell_{ms} $. In comparison, a Disk-like accretion occurs when the specific angular momentum at the Bondi radius $ \ell_{B} $ is larger than the specific angular momentum of the marginally stable orbit $ \ell_{ms} $. We also keep the assumption of hydrostatic equilibrium and compare our results with the case in which it is not considered. According to this study, considering the assumption of hydrostatic equilibrium reduces the mass accretion rate. Additionally, we find our solution for different ranges of the viscosity parameter $\alpha$. Finally, we study the effect of galaxy potential on slowly rotating accretion flows.