Formation of massive black holes via collisions and accretion

TL;DR

This paper uses numerical simulations to explore how massive black holes of 10^4-10^5 solar masses can form through stellar and gas dynamical processes, addressing challenges in direct collapse models.

Contribution

It introduces a new simulation approach incorporating gas effects to study black hole formation, highlighting the importance of fragmentation and accretion processes.

Findings

Massive black holes of 10^4-10^5 solar masses can form under certain conditions.

Fragmentation and gas accretion significantly influence black hole seed growth.

Simulations suggest alternative pathways to direct collapse for black hole formation.

Abstract

To explain the observed population of supermassive black holes at z~7, very massive seed black holes or, alternatively, super-Eddington scenarios are needed to reach final masses of the order of 10^9 solar masses. A popular explanation for massive seeds has been the direct collapse model, which predicts the formation of a single massive object due to the direct collapse of a massive gas cloud. Simulations over the last years have however shown that such a scenario is very difficult to achieve. A realistic model of black hole formation should therefore take fragmentation into account, and consider the interaction between stellar-dynamical and gas-dynamical processes. We present here numerical simulations pursued with the AMUSE code, employing an approximate treatment of the gas. Based on these simulations, we show that very massive black holes of 10^4-10^5 solar masses may form depending on the gas supply and the accretion onto the protostars.