# Dark matter heating of gas accreting onto Sgr A$^*$

## TL;DR

This paper investigates how dark matter annihilation heating influences gas accretion onto Sgr A*, suggesting it could significantly reduce accretion rates and explain the observed low activity of the black hole.

## Contribution

It introduces a detailed analysis of dark matter heating effects on Bondi accretion, highlighting potential impacts on supermassive black hole growth models.

## Key findings

- Heating reduces accretion rates in transonic solutions.
- Many plausible parameters lead to the absence of steady-state solutions.
- Dark matter heating may explain Sgr A*'s low accretion rate.

## Abstract

We study effects of heating by dark matter (DM) annihilation on black hole gas accretion. We observe that, for reasonable assumptions about DM densities in spikes around supermassive black holes, as well as DM masses and annihilation cross-sections within the standard WIMP model, heating by DM annihilation may have an appreciable effect on the accretion onto Sgr A$^*$ in the Galactic center. Motivated by this observation we study the effects of such heating on Bondi accretion, i.e. spherically symmetric, steady-state Newtonian accretion onto a black hole. We consider different adiabatic indices for the gas, and different power-law exponents for the DM density profile. We find that typical transonic solutions with heating have a significantly reduced accretion rate. However, for many plausible parameters, transonic solutions do not exist, suggesting a breakdown of the underlying assumptions of steady-state Bondi accretion. Our findings indicate that heating by DM annihilation may play an important role in the accretion onto supermassive black holes at the center of galaxies, and may help explain the low accretion rate observed for Sgr A$^*$.