The Origin and Detection of High-Redshift Supermassive Black Holes

TL;DR

This paper reviews the origins of high-redshift supermassive black holes, comparing stellar seed growth and direct gas collapse models, and discusses future observational tests to distinguish these scenarios.

Contribution

It provides a comparative analysis of the main theories for SMBH formation at high redshift and discusses potential observational strategies for differentiation.

Findings

Stellar seed growth via Eddington-limited accretion and mergers can produce SMBHs by redshift 6.

Direct collapse of gas offers an alternative rapid formation pathway for early SMBHs.

Future observations by LISA and other instruments can help distinguish between formation scenarios.

Abstract

Supermassive black holes (SMBHs) are common in local galactic nuclei, and SMBHs as massive as several billion solar masses already exist at redshift z=6. These earliest SMBHs may arise by the combination of Eddington-limited growth and mergers of stellar-mass seed BHs left behind by the first generation of metal-free stars, or by the rapid direct collapse of gas in rare special environments where the gas can avoid fragmenting into stars. In this contribution, I review these two competing scenarios. I also briefly mention some more exotic ideas and how the different models may be distinguished in the future by LISA and other instruments.