Seeding Supermassive Black Holes with Self-Interacting Dark Matter: A Unified Scenario with Baryons

TL;DR

This paper proposes a novel scenario where self-interacting dark matter halos undergo gravothermal collapse, forming seed black holes that can explain the early existence of supermassive black holes at high redshifts, integrating dark matter and baryonic effects.

Contribution

It introduces a unified model linking self-interacting dark matter halo collapse with SMBH formation, incorporating baryonic influence and conditions for relativistic instability.

Findings

Self-interacting dark matter halos can collapse into seed black holes.

Baryons accelerate gravothermal evolution and collapse.

High-density fluctuation tails are necessary for early SMBH formation.

Abstract

Observations show that supermassive black holes (SMBHs) with a mass of $\sim10^9 M_\odot$ exist when the Universe is just $6\%$ of its current age. We propose a scenario where a self-interacting dark matter halo experiences gravothermal instability and its central region collapses into a seed black hole. The presence of baryons in protogalaxies could significantly accelerate the gravothermal evolution of the halo and shorten collapse timescales. The central halo could dissipate its angular momentum remnant via viscosity induced by the self-interactions. The host halo must be on high tails of density fluctuations, implying that high-$z$ SMBHs are expected to be rare in this scenario. We further derive conditions for triggering general relativistic instability of the collapsed region. Our results indicate that self-interacting dark matter can provide a unified explanation for diverse dark matter distributions in galaxies today and the origin of SMBHs at redshifts $z\sim6-7$.