Suppressing hot gas accretion to supermassive black holes by stellar winds

TL;DR

This paper challenges the traditional Bondi accretion model for supermassive black holes, showing stellar winds create hot bubbles that suppress accretion and impact galaxy evolution.

Contribution

It introduces a new mechanism where stellar winds form hot bubbles that significantly reduce SMBH accretion rates, questioning the applicability of Bondi accretion in certain galaxies.

Findings

Hot stellar winds form bubbles that inhibit accretion.

Hot bubbles can lead to cold clump accretion after cooling.

Bondi accretion is ineffective for AGN feedback in some galaxies.

Abstract

We argue that one of the basic assumptions of the Bondi accretion process, that the accreting object has zero pressure, might not hold in many galaxies because of the pressure exerted by stellar winds of star orbiting the central super massive black hole (SMBH). Hence, the Bondi accretion cannot be used in these cases, such as in the galaxy NGC 3115. The winds of these high-velocity stars are shocked to temperatures above the virial temperature of the galaxy, leading to the formation of a hot bubble of size ~0.1-10 pc near the center. This hot bubble can substantially reduce the mass accretion rate by the SMBH. If the density of the hot bubble is lower than that of the interstellar medium (ISM), a density-inversion layer is formed. As the gas loses energy by X-ray radiation, eventually more mass of the cooling shocked stellar winds will be accreted to the SMBH. This accretion will be of cold clumps. After a period of millions of years of low AGN activity, therefore, a stronger AGN activity will occur that will heat and expel gas, much as in cooling flow clusters. Adding to other problems of the Bondi process, our results render the Bondi accretion irrelevant for AGN feedback in cooling flow in galaxies and small groups of galaxies and during galaxy formation.