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Hyper-Eddington Black Hole Growth in Star-Forming Molecular Clouds and Galactic Nuclei: Can It Happen?

Shi, Yanlong and Kremer, Kyle and Grudić, Michael Y. and Gerling-Dunsmore, Hannalore J. and Hopkins, Philip F. (2022) Hyper-Eddington Black Hole Growth in Star-Forming Molecular Clouds and Galactic Nuclei: Can It Happen? . (Unpublished)

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Formation of supermassive black holes (BHs) remains a theoretical challenge. In many models, especially beginning from stellar relic "seeds," this requires sustained super-Eddington accretion. While studies have shown BHs can violate the Eddington limit on accretion disk scales given sufficient "fueling" from larger scales, what remains unclear is whether or not BHs can actually capture sufficient gas from their surrounding ISM. We explore this in a suite of multi-physics high-resolution simulations of BH growth in magnetized, star-forming dense gas complexes including dynamical stellar feedback from radiation, stellar mass-loss, and supernovae, exploring populations of seeds with masses ∼1−10⁴ M_⊙. In this initial study, we neglect feedback from the BHs: so this sets a strong upper limit to the accretion rates seeds can sustain. We show that stellar feedback plays a key role. Complexes with gravitational pressure/surface density below ∼10³ M_⊙ pc⁻² are disrupted with low star formation efficiencies so provide poor environments for BH growth. But in denser cloud complexes, early stellar feedback does not rapidly destroy the clouds but does generate strong shocks and dense clumps, allowing ∼1% of randomly-initialized seeds to encounter a dense clump with low relative velocity and produce runaway, hyper-Eddington accretion (growing by orders of magnitude). Remarkably, mass growth under these conditions is almost independent of initial BH mass, allowing rapid IMBH formation even for stellar-mass seeds. This defines a necessary (but perhaps not sufficient) set of criteria for runaway BH growth: we provide analytic estimates for the probability of runaway growth under different ISM conditions.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper ItemGIZMO code
Shi, Yanlong0000-0002-0087-3237
Kremer, Kyle0000-0002-4086-3180
Grudić, Michael Y.0000-0002-1655-5604
Hopkins, Philip F.0000-0003-3729-1684
Additional Information:Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0). We thank Xiangcheng Ma and Linhao Ma for useful discussions and revisions of this draft. Support for the authors was provided by NSF Research Grants 1911233, 20009234, 2108318, NSF CAREER grant 1455342, NASA grants 80NSSC18K0562, HST-AR-15800. Numerical calculations were run on the Caltech compute cluster “Wheeler,” allocations AST21010 and AST20016 supported by the NSF and TACC, and NASA HEC SMD-16-7592. DATA AVAILABILITY STATEMENT. The data supporting the plots within this article are available on reasonable request to the corresponding author. A public version of the GIZMO code is available at
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
Texas Advanced Computing Center (TACC)UNSPECIFIED
Subject Keywords:black hole physics – accretion, accretion discs – quasars: supermassive black holes – galaxies: star formation
Record Number:CaltechAUTHORS:20220816-221958140
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:116328
Deposited By: George Porter
Deposited On:18 Aug 2022 22:54
Last Modified:18 Aug 2022 22:54

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