Gravitational wave background from primordial black holes in globular clusters

TL;DR

This paper investigates the gravitational wave background produced by primordial black holes in globular clusters, showing their potential to significantly contribute to detectable signals and impact dark matter research.

Contribution

It models globular clusters to estimate the merger rate of primordial black holes and highlights their role in the gravitational wave background, a novel aspect in dark matter studies.

Findings

Primordial black holes in globular clusters can produce a detectable GW background.

Their contribution to the GW background is comparable to other known sources.

Including this channel enhances the prospects for primordial black hole detection.

Abstract

Primordial black holes still represent a viable candidate for a significant fraction, if not for the totality, of dark matter. If these compact objects have masses of order tens of solar masses, their coalescence can be observed by current and future ground-based gravitational wave detectors. Therefore, finding new gravitational wave signatures associated with this dark matter candidate can either lead to their detection or help constraining their abundance. In this work we consider the phenomenology of primordial black holes in dense environments, in particular globular clusters. We model the internal structure of globular clusters in a semi-analytical fashion, and we derive the expected merger rate. We show that, if primordial black holes are present in globular clusters, their contribution to the GW background can be comparable to other well-known channels, such as early- and late-time binaries, thus enhancing the detectability prospects of primordial black holes and demonstrating that this contribution needs to be taken into account.