A Unified Dark-Matter--Driven Relativistic Bondi Route to Black-Hole Growth from Stellar to Supermassive Scales

TL;DR

This paper proposes a dark matter-driven accretion mechanism that can rapidly grow primordial black holes into supermassive black holes by redshift 7, linking dark matter physics to black hole evolution.

Contribution

It introduces a universal super-Eddington accretion model based on self-interacting dark matter that explains early SMBH formation without fine-tuning.

Findings

Bondi accretion rate depends only on SIDM mass in critical regime.

Primordial black holes can grow to supermassive sizes by redshift 7.

The model connects dark matter properties to the observed black hole mass distribution.

Abstract

Observations of luminous quasars at $z\gtrsim7$ reveal supermassive black holes (SMBHs) with inferred masses $M_{\rm BH}\sim10^9 \, M_\odot$ formed within the first $\sim700$~Myr of cosmic history. Standard growth channels \textrm{ -- } Eddington-limited gas accretion and hierarchical mergers \textrm{ -- } face severe timescale restrictions. We consider a super-Eddington accretion mechanism aided by the Bondi accretion of a minimal model of self-interacting dark matter (SIDM). We demonstrate that in a {\it critical regime} with a near-relativistic sound speed, the Bondi accretion yields an accretion rate that depends only on the mass $m$ of SIDM, thus it is universal to the ambient environment. This critical accretion mechanism for $m\gtrsim 10^{-2}\; {\rm eV}$ can grow seeds as small as $10\,M_\odot$ primordial black holes (PBH) in the early Universe into $10^9$ \textrm{--} $10^{10}\,M_\odot$ SMBHs by $z\sim7$ without fine-tuned environments. Therefore, given a mass distribution of PBHs and a value of $m$, the mass function of primary black holes at late time can be fully determined with masses ranging from stellar to SMBHs. This connects the microscopic physics of dark matter to astrophysical observations of black holes.