# Radiation-driven turbulent accretion onto massive black holes

## TL;DR

This study uses high-resolution 3D radiation-hydrodynamic simulations to explore how ionizing radiation from black holes influences surrounding gas, revealing turbulence and oscillations in accretion rates that differ from earlier models.

## Contribution

It introduces 3D simulations of black hole accretion that capture turbulence and more accurate oscillation amplitudes, advancing understanding beyond 1D/2D models.

## Key findings

- Turbulence dominates gas kinetic energy but is less than 10% of thermal energy.
- 3D simulations show smaller accretion rate oscillations (~2-3 orders of magnitude).
- Ionized bubbles shrink during quiescent periods, increasing gas density.

## Abstract

Accretion of gas and interaction of matter and radiation are at the heart of many questions pertaining to black hole (BH) growth and coevolution of massive BHs and their host galaxies. To answer them it is critical to quantify how the ionizing radiation that emanates from the innermost regions of the BH accretion flow couples to the surrounding medium and how it regulates the BH fueling. In this work we use high resolution 3-dimensional (3D) radiation-hydrodynamic simulations with the code Enzo, equipped with adaptive ray tracing module Moray, to investigate radiation-regulated BH accretion of cold gas. Our simulations reproduce findings from an earlier generation of 1D/2D simulations: the accretion powered UV and X-ray radiation forms a highly ionized bubble, which leads to suppression of BH accretion rate characterized by quasi-periodic outbursts. A new feature revealed by the 3D simulations is the highly turbulent nature of the gas flow in vicinity of the ionization front. During quiescent periods between accretion outbursts, the ionized bubble shrinks in size and the gas density that precedes the ionization front increases. Consequently, the 3D simulations show oscillations in the accretion rate of only ~2-3 orders of magnitude, significantly smaller than 1D/2D models. We calculate the energy budget of the gas flow and find that turbulence is the main contributor to the kinetic energy of the gas but corresponds to less than 10% of its thermal energy and thus does not contribute significantly to the pressure support of the gas.