Very high redshift quasars and the rapid emergence of super-massive black holes

TL;DR

This paper proposes a model where super-massive black holes form rapidly within hyper-massive star-burst clusters or ultra-compact dwarf galaxies shortly after the first stars, explaining the existence of high-redshift quasars.

Contribution

It introduces a new formation scenario for SMBHs via star-burst clusters, linking early galaxy formation to rapid SMBH emergence and high-redshift quasars.

Findings

SMBHs can form within about 200 Myr in star-burst clusters.

High-redshift quasars may be young ultra-compact dwarf galaxies.

The model explains the SMBH-spheroid correlation near-to-exactly.

Abstract

The observation of quasars at very high redshift such as Poniuaena is a challenge for models of super-massive black hole (SMBH) formation. This work presents a study of SMBH formation via known physical processes in star-burst clusters formed at the onset of the formation of their hosting galaxy. While at the early stages hyper-massive star-burst clusters reach the luminosities of quasars, once their massive stars die, the ensuing gas accretion from the still forming host galaxy compresses its stellar black hole (BH) component to a compact state overcoming heating from the BH--BH binaries such that the cluster collapses, forming a massive SMBH-seed within about a hundred Myr. Within this scenario the SMBH--spheroid correlation emerges near-to-exactly. The highest-redshift quasars may thus be hyper-massive star-burst clusters or young ultra-compact dwarf galaxies (UCDs), being the precursors of the SMBHs that form therein within about 200 Myr of the first stars. For spheroid masses <10^9.6 Msun a SMBH cannot form and instead only the accumulated nuclear cluster remains. The number evolution of the quasar phases with redshift is calculated and the possible problem of missing quasars at very high redshift is raised. SMBH-bearing UCDs and the formation of spheroids are discussed critically in view of the high redshift observations. A possible tension is found between the high star-formation rates (SFRs) implied by downsizing and the observed SFRs, which may be alleviated within the IGIMF theory and if the downsizing times are somewhat longer.