Did massive black holes in globular clusters initially satisfy galactic scaling relations?

TL;DR

This study investigates whether initial black hole masses in globular clusters aligned with galactic scaling relations and how dynamical evolution affects this relationship, providing insights into black hole growth universality.

Contribution

The paper demonstrates that initial IMBHs in globular clusters followed galactic SMBH scaling relations before evolving away due to cluster dynamics.

Findings

IMBHs initially followed galactic SMBH scaling relations

Dynamical evolution causes IMBHs to move off these relations

Results support a universal growth pattern for massive black holes

Abstract

The masses of supermassive black holes (SMBHs, M_BH=10^6-10^11 Msun) in the centres of galaxies are related to the host stellar spheroid mass and velocity dispersion. A key question is how these relations originate, and over which range of black hole masses they hold. It has been speculated that intermediate-mass black holes (IMBHs, M_BH=10^2-10^5 Msun) could play a fundamental role in the growth of SMBHs. A handful of IMBHs has recently been detected in Galactic globular clusters (GCs), but their masses are inconsistent with the galactic scaling relations of SMBHs. In this Letter, we derive the initial properties of the GCs using a standard analytical evolutionary model, of which the free parameters are fixed by independent constraints. We find that the observed IMBH masses initially followed the galactic SMBH scaling relations, and subsequently moved off these relations due to the dynamical evolution of their host GCs. This work is concluded with a brief discussion of the uncertainties and the implications of our results for the possible universality of massive black hole growth.