Feedback-regulated Seed Black Hole Growth in Star-Forming Molecular Clouds and Galactic Nuclei

TL;DR

This study explores how feedback from accreting black holes affects their rapid growth within star-forming molecular clouds, demonstrating that hyper-Eddington accretion can still occur under various feedback conditions, leading to the formation of intermediate-mass black holes.

Contribution

It provides a detailed simulation-based analysis of black hole feedback effects on seed black hole growth in GMCs, including an analytic model for maximum mass growth regulation.

Findings

Hyper-Eddington accretion remains feasible despite feedback.

Maximum black hole mass growth is regulated by feedback momentum deposition.

Rapid formation of ~10^4 solar mass IMBHs from stellar-mass seeds within Myr.

Abstract

The detection of supermassive black holes (SMBHs) in high-redshift luminous quasars may require a phase of rapid accretion, and as a precondition, substantial gas influx toward seed black holes (BHs) from kilo-parsec or parsec scales. Our previous research demonstrated the plausibility of such gas supply for BH seeds within star-forming giant molecular clouds (GMCs) with high surface density ($\sim 10^4\,{\rm {\rm M_\odot}\, pc}^{-2}$), facilitating ``hyper-Eddington'' accretion via efficient feeding by dense clumps which are driven by turbulence and stellar feedback. This article investigates the impacts of feedback from accreting BHs on this process, including radiation, mechanical jets, and highly relativistic cosmic rays. We run a suite of numerical simulations to explore diverse parameter spaces of BH feedback, including the sub-grid accretion model, feedback energy efficiency, mass loading factor, and initial metallicity. Utilizing radiative feedback models inferred from the slim disk, we find that hyper-Eddington accretion is still achievable, yielding BH bolometric luminosities as high as $10^{41}$ -- $10^{44}\,\rm erg/s$, depending on the GMC properties and specific feedback model assumed. We find the maximum possible mass growth of seed BHs ($\Delta M_{\rm BH}^{\rm max}$) is regulated by the momentum deposition rate from BH feedback, $\dot{p}_{\rm feedback}/(\dot{M}_{\rm BH} c)$, which leads to an analytic scaling that agrees well with simulations. This scenario predicts the rapid formation of $\sim 10^4\,\rm M_\odot$ intermediate-massive BHs (IMBHs) from stellar-mass BHs within $\sim \rm Myr$. Furthermore, we examine the impacts of sub-grid accretion models and how BH feedback may influence star formation within these cloud complexes.