Gravitational wave inference of star cluster properties from intermediate-mass black hole mergers

TL;DR

This paper explores whether gravitational wave observations of IMBH mergers can reveal properties of their host star clusters, using models and next-generation detectors, despite challenges from model degeneracy.

Contribution

It introduces an analytic model linking IMBH mergers to cluster properties and assesses the feasibility of inferring cluster characteristics from gravitational wave data.

Findings

Cluster property inference is challenging due to model degeneracy.

Redshift posteriors are relatively narrow, aiding in formation history inference.

Population studies may help overcome individual event limitations.

Abstract

Next-generation ground-based gravitational wave observatories will observe mergers of intermediate-mass black holes (IMBHs) out to high redshift. Such IMBHs can form through runaway tidal encounters in the cores of dense stellar clusters. In this paper, we ask if the gravitational wave observation of a single merger event between two IMBHs, occurring in the aftermath of the coalescence of the clusters in which they formed, can be used to infer the properties of their host clusters, such as mass, redshift, and half-mass radius. We implement an astrophysically motivated analytic model for cluster evolution and IMBH growth, and we perform IMBH binary parameter estimation using a network of three next-generation detectors. We find that inferring the structural properties of clusters in this way is challenging due to model degeneracy. However, the posteriors on the cluster formation redshifts have relatively narrow peaks, and it may still be possible to infer the cluster formation history by measuring a whole population of IMBH binary merger events.