The importance of super-Eddington black hole accretion for the emergence of massive quiescent galaxies at high redshift

TL;DR

This study shows that allowing super-Eddington black hole accretion in galaxy formation simulations is crucial for matching JWST observations of massive quiescent galaxies at high redshift, emphasizing black hole growth's role in early galaxy quenching.

Contribution

Demonstrates that super-Eddington black hole accretion is essential in simulations to reproduce the abundance of massive quiescent galaxies at high redshift, clarifying the reason for COLIBRE model's success.

Findings

Super-Eddington accretion accounts for about 50% of black hole mass growth at high redshift.

Only models permitting super-Eddington accretion match JWST constraints at z > 6.

Super-Eddington events, though rare, significantly impact galaxy quenching.

Abstract

Recent JWST observations indicate that massive quiescent galaxies (stellar mass $M_{*}\gtrsim 10^{10}~\mathrm{M_\odot}$) at high redshift ($z\gtrsim 6$) are more abundant than predicted by most existing galaxy formation simulations and semi-analytic models. Notably, the new COLIBRE simulations have succeeded in reconciling this tension, though the precise reason for their improved agreement with JWST data remains unclear. We demonstrate that the improved agreement is largely due to super-Eddington growth of supermassive black holes (BHs) at high redshift. We run a series of $(100~\mathrm{cMpc})^{3}$ simulations with the COLIBRE subgrid physics, varying the maximum allowed BH accretion rate in units of the Eddington rate. We show that only the fiducial COLIBRE model, which permits super-Eddington accretion, is consistent with the JWST constraints at $z \gtrsim 6$. Moreover, we find that in COLIBRE about $50$ per cent of BH mass growth at high redshift occurs in the super-Eddington regime, even though such events are extremely rare in time. Our work highlights the important role of super-Eddington accretion in simulations of galaxy formation for reproducing the observed early emergence of quenching of massive galaxies.