HST's hunt for intermediate-mass black holes in star clusters

TL;DR

This paper discusses the search for intermediate-mass black holes in star clusters, emphasizing the potential of combining proper motion measurements with advanced dynamical models to detect or constrain their presence.

Contribution

It introduces a new observational and analytical approach using HST data and dynamical models to identify or limit intermediate-mass black holes in star clusters.

Findings

Proper motion measurements can reveal IMBH presence.

Dynamical models enhance detection sensitivity.

HST observations are crucial for this approach.

Abstract

Establishing or ruling out, either through solid mass measurements or upper limits, the presence of intermediate-mass black holes (IMBHs) at the centers of star clusters would profoundly impact our understanding of problems ranging from the formation and long-term dynamical evolution of stellar systems, to the nature of the seeds and the growth mechanisms of supermassive black holes. While there are sound theoretical arguments both for and against their presence in today's clusters, observational studies have so far not yielded truly conclusive IMBH detections nor upper limits. We argue that the most promising approach to solving this issue is provided by the combination of measurements of the proper motions of stars at the centers of Galactic globular clusters and dynamical models able to take full advantage of this type of data set. We present a program based on HST observations and recently developed tools for dynamical analysis designed to do just that.