High redshift formation and evolution of central massive objects I: model description

TL;DR

This paper models the early formation of nuclear star clusters and seed black holes in high-redshift galactic discs, proposing a connection between them based on starburst-driven cluster formation and runaway stellar collisions.

Contribution

It introduces a model linking nuclear star cluster formation and seed black hole creation in high-redshift galaxies with metal-enriched gas inflows.

Findings

Nuclear star clusters at z~10 have masses 10^4-10^6 solar masses.

Black hole seeds formed in these clusters range from ~300 to 2000 solar masses.

Clusters have half-mass radii less than 0.5 parsecs.

Abstract

Galactic nuclei host central massive objects either in the form of supermassive black holes or nuclear stellar clusters. Recent investigations have shown that both components co-exist in at least a few galaxies. In this paper we explore the possibility of a connection between nuclear star clusters and black holes that establishes at the moment of their formation. We here model the evolution of high redshift discs, hosted in dark matter halos with virial temperatures 10^4 K, whose gas has been polluted with metals just above the critical metallicity for fragmentation. A nuclear cluster forms as a result of a central starburst from gas inflowing from the unstable disc. The nuclear stellar cluster provides a suitable environment for the formation of a black hole seed, ensuing from runaway collisions among the most massive stars. Typical masses for the nuclear stellar clusters at the time of black hole formation (z~10) are inthe range 10^4-10^6 solar masses and have half mass radii < 0.5 pc. The black holes forming in these dense, high redshift clusters can have masses in the range ~300-2000 solar masses.