Primordial black hole merger rates: distributions for multiple LIGO observables

TL;DR

This paper calculates the detectable merger rates of primordial black holes across various observables and compares them to astrophysical black hole mergers, highlighting how current data can support or exclude PBH hypotheses.

Contribution

It introduces detailed distributions of PBH merger observables and assesses their compatibility with LIGO data, considering multiple mass functions and selection effects.

Findings

Current LIGO data can be consistent with PBHs when selection effects are included.

Some PBH mass distributions are excluded by existing observations.

Future data could definitively test the primordial black hole origin hypothesis.

Abstract

We have calculated the detectable merger rate of primordial black holes, as a function of the redshift, as well as the binary's mass ratio, total mass and chirp mass (observables that have not previously been explored in great detail for PBHs). We consider both the current and design sensitivity of LIGO and five different primordial black hole mass functions, as well as showing a comparison to a predicted astrophysical black hole merger rate. We show that the empirical preference for nearly equal-mass binaries in current LIGO/Virgo data can be consistent with a PBH hypothesis once observational selection effects are taken into account. However, current data do exclude some PBH mass distributions, and future data may be able to rule out the possibility that all observed BH mergers had a primordial origin.