Massive Black Hole formation in proto-stellar clusters via early gas accretion

TL;DR

This paper presents a semi-analytic model showing that early gas accretion in proto-stellar clusters can produce massive black holes, potentially explaining GW signals with black holes above the traditional mass gap.

Contribution

It introduces a new semi-analytic model for black hole growth in proto-stellar clusters during their early stages, highlighting the formation of massive black holes consistent with recent observations.

Findings

Black hole masses can reach and exceed the BH mass gap.

Gas-rich proto-clusters can produce black holes up to ~1000 solar masses.

Results align with recent gravitational-wave detections.

Abstract

We review our semi-analytic model of stellar black hole (BH) mass growth by gas accretion in gas-rich stellar clusters during their birthstage within the first $\sim 10\,{\rm Myr}$ after the first stellar formation event. Such proto-stellar clusters are massive and compact, with typical masses $\sim 10^6\,{\rm M}_\odot$ and sizes $\sim 1\,{\rm pc}$, suggested by recent James Webb Space Telescope (JWST) observations. We find that the BH masses are shifted by the end of gas depletion to values within and above the BH mass gap, well within the range of components of the recent gravitational-wave (GW) signal GW231123, and up to masses $\sim 10^3\,{\rm M}_\odot$.