How the super-Eddington regime regulates black hole growth in high-redshift galaxies

TL;DR

This study uses hydrodynamical simulations to explore how super-Eddington feedback, especially jets, regulates black hole growth in early galaxies, showing that feedback can both suppress and allow growth depending on jet strength.

Contribution

It demonstrates that super-Eddington feedback, particularly jet efficiency, critically influences black hole growth in high-redshift galaxies, a novel insight into early universe black hole evolution.

Findings

Super-Eddington feedback prevents rapid BH growth within a few Myr.

Jets in the super-Eddington regime can eject gas up to galactic scales.

Weaker jets permit more frequent super-Eddington accretion episodes.

Abstract

Super-Eddington accretion is one scenario that may explain the rapid assembly of $\sim 10^9\rm\, M_\odot$ supermassive black holes (BHs) within the first billion year of the Universe. This critical regime is associated with radiatively inefficient accretion and accompanied by powerful outflows in the form of winds and jets. By means of hydrodynamical simulations of BH evolution in an isolated galaxy and its host halo with 12 pc resolution, we investigate how super-Eddington feedback affects the mass growth of the BH. It is shown that super-Eddington feedback efficiently prevents BH growth within a few Myr. The super-Eddington accretion events remain relatively mild with typical rates of about 2-3 times the Eddington limit, because of the efficient regulation by jets in that regime. We find that these jets are powerful enough to eject gas from the centre of the host galaxy all the way up to galactic scales at a few kpc, but do not significantly impact gas inflows at those large scales. By varying the jet feedback efficiency, we find that weaker super-Eddington jets allow for more significant BH growth through more frequent episodes of super-Eddington accretion. We conclude that effective super-Eddington growth is possible, as we find that simulations with weak jet feedback efficiencies provide a slightly larger BH mass evolution over long periods of time ($\sim 80\,\rm Myr$) than that for a BH accreting at the Eddington limit.