The Observed Rate of Binary Black Hole Mergers can be Entirely Explained by Globular Clusters

TL;DR

This paper demonstrates that the observed rate of binary black hole mergers detected by LIGO and Virgo can be fully explained by dynamical processes within globular clusters, challenging the need for multiple formation channels.

Contribution

It shows that the current BBH merger rate is consistent with a purely globular cluster origin, providing a new perspective on black hole binary formation mechanisms.

Findings

The merger rate fits a globular cluster dynamical origin.

Current LVC BBH merger rate can be explained by globular clusters.

Multiple formation scenarios may contribute to observed rates.

Abstract

Since the first signal in 2015, the gravitational-wave detections of merging binary black holes (BBHs) by the LIGO and Virgo collaborations (LVC) have completely transformed our understanding of the lives and deaths of compact object binaries, and have motivated an enormous amount of theoretical work on the astrophysical origin of these objects. We show that the phenomenological fit to the redshift-dependent merger rate of BBHs from Abbott et al. (2020) is consistent with a purely dynamical origin for these objects, and that the current merger rate of BBHs from the LVC could be explained entirely with globular clusters alone. While this does not prove that globular clusters are the dominant formation channel, we emphasize that many formation scenarios could contribute a significant fraction of the current LVC rate, and that any analysis that assumes a single (or dominant) mechanism for producing BBH mergers is implicitly using a specious astrophysical prior.