Supermassive black hole formation in the initial collapse of axion dark matter

TL;DR

This paper demonstrates that axion dark matter can form supermassive black holes during initial cosmic collapse due to gravitational self-interactions and Bose-Einstein condensation.

Contribution

It reveals a new mechanism for supermassive black hole formation involving axion dark matter rethermalization and angular momentum transport.

Findings

Black holes with masses from 10^5 to 10^{10} solar masses can form during initial collapse.

The process applies to QCD axions and axion-like particles with mass > 10^{-16} eV/c^2.

Axion rethermalization facilitates angular momentum outward transport, enabling black hole formation.

Abstract

Axion dark matter thermalizes by gravitational self-interactions and forms a Bose-Einstein condensate. We show that the rethermalization of the axion fluid during the initial collapse of large scale overdensities near cosmic dawn transports angular momentum outward sufficientlly fast that black holes form with masses ranging from approximately $10^5$ to a few times $10^{10}~M_\odot$. This conclusion holds for QCD axions and for axion-like particles of mass larger than $10^{-16}$ eV/$c^2$.