Stunted accretion growth of black holes by combined effect of the flow angular momentum and radiation feedback

TL;DR

This study uses 2D radiation hydrodynamics simulations to show that gas angular momentum and radiation feedback significantly suppress black hole accretion rates, challenging rapid growth scenarios for early supermassive black holes.

Contribution

It provides a combined analysis of angular momentum and radiation feedback effects on black hole accretion, revealing a substantial reduction in accretion rates and introducing an analytical model for this suppression.

Findings

Accretion rates are reduced to 1-10% of the Bondi rate due to angular momentum and radiation.

Significant suppression persists unless the angular momentum is extremely low.

Rapid black hole growth is hindered by the angular momentum barrier.

Abstract

Accretion on to seed black holes (BHs) is believed to play a crucial role in formation of supermassive BHs observed at high-redshift (z>6). Here, we investigate the combined effect of gas angular momentum and radiation feedback on the accretion flow, by performing 2D axially symmetric radiation hydrodynamics simulations that solve the flow structure across the Bondi radius and the outer part of the accretion disc simultaneously. The accreting gas with finite angular momentum forms a rotationally-supported disc inside the Bondi radius, where the accretion proceeds by the angular momentum transport due to assumed alpha-type viscosity. We find that the interplay of radiation and angular momentum significantly suppresses accretion even if the radiative feedback is weakened in an equatorial shadowing region. The accretion rate is O(alpha)\sim O(0.01-0.1) times the Bondi value, where alpha is the viscosity parameter. By developing an analytical model, we show that such a great reduction of the accretion rate persists unless the angular momentum is so small that the corresponding centrifugal radius is \lesssim 0.04 times the Bondi radius. We argue that BHs are hard to grow quickly via rapid mass accretion considering the angular momentum barrier presented in this paper.