Generalized Bondi Accretion Flow with and without Outflow

TL;DR

This paper explores how gas angular momentum and outflows influence accretion rates onto black holes, revealing that the effects vary with Bondi radius and outflow strength, impacting black hole growth.

Contribution

It provides a comprehensive analysis of rotating polytropic accretion flows across a wide parameter space, incorporating outflows with a viscosity model suitable for various angular momenta.

Findings

Mass accretion rate decreases steeply with angular momentum for small Bondi radius.

Mass accretion rate decreases gradually with angular momentum for large Bondi radius.

Stronger outflows reduce the actual mass accreted into the black hole.

Abstract

The properties of accretion flows are affected by the angular momentum of the accreting gas. M.-G. Park found that the mass accretion rate, specifically, decreases significantly as the gas angular momentum increases. However, R. Narayan & A. C. Fabian found the decrease modest. We investigate global solutions for rotating polytropic flows in a much wider parameter space to understand their general properties within the slim disk approximation and a viscosity description suitable for both low- and high-angular-momentum flows. We find that the mass accretion rate for flows with a small Bondi radius decreases steeply as the gas angular momentum increases, while for those with a large Bondi radius, it decreases gradually. Therefore, the decrease of mass accretion rate due to gas rotation can be significant or mild depending on the Bondi radius. We further investigate global solutions of accretion with outflows using the ADIOS model of R. D. Blandford & M. C. Begelman. Stronger outflows in general slightly increase the mass inflow rate at the outer boundary, but the actual mass accreted into the black hole decreases by orders of magnitude. Stronger outflows also weaken the dependence of the mass accretion rate on the gas angular momentum when the viscosity parameter {\alpha} is small. The intricate dependence of the mass inflow rate at the outer boundary and the mass accretion rate into the black hole on gas angular momentum will have interesting implications for the growth of black holes and their energy output.