Force-feeding Black Holes

TL;DR

This paper proposes a model where supermassive black holes grow through brief hyperaccretion episodes, with matter forming an envelope that regulates growth and explains the observed black hole mass-velocity dispersion relation.

Contribution

It introduces a new hyperaccretion model involving matter envelopes and ejection mechanisms that account for the M_BH-sigma relation in galaxy centers.

Findings

Black hole growth linked to hyperaccretion episodes.

Ejection of matter occurs when opacity drops, influencing black hole mass limits.

The model reproduces the empirical M_BH-sigma relation.

Abstract

We propose that the growth of supermassive black holes is associated mainly with brief episodes of highly super-Eddington infall of gas ("hyperaccretion"). This gas is not swallowed in real time, but forms an envelope of matter around the black hole that can be swallowed gradually, over a much longer timescale. However, only a small fraction of the black hole mass can be stored in the envelope at any one time. We argue that any infalling matter above a few per cent of the hole's mass is ejected as a result of the plunge in opacity at temperatures below a few thousand degrees K, corresponding to the Hayashi track. The speed of ejection of this matter, compared to the velocity dispersion (sigma) of the host galaxy's core, determines whether the ejected matter is lost forever or returns eventually to rejoin the envelope, from which it can be ultimately accreted. The threshold between matter recycling and permanent loss defines a relationship between the maximum black hole mass and sigma that resembles the empirical M_BH-sigma relation.