Primordial Black Hole Scenario for the Gravitational-Wave Event GW150914

TL;DR

This paper proposes that primordial black holes could explain the GW150914 gravitational-wave event, with their merger rates aligning with observational constraints, suggesting a testable dark matter component.

Contribution

It introduces the primordial black hole scenario as an explanation for GW150914 and analyzes its compatibility with existing observational limits.

Findings

PBH merger rate can match GW150914 if PBHs are a fraction of dark matter

PBH abundance aligns with CMB spectral distortion limits

Scenario predicts testable gravitational-wave event rates

Abstract

We point out that the gravitational-wave event GW150914 observed by the LIGO detectors can be explained by the coalescence of primordial black holes (PBHs). It is found that the expected PBH merger rate would exceed the rate estimated by the LIGO scientific Collaboration and Virgo Collaboration if PBHs were the dominant component of dark matter, while it can be made compatible if PBHs constitute a fraction of dark matter. Intriguingly, the abundance of PBHs required to explain the suggested lower bound on the event rate, $> 2$ events ${\rm Gpc}^{-3} {\rm yr}^{-1}$, roughly coincides with the existing upper limit set by the nondetection of the cosmic microwave background spectral distortion. This implies that the proposed PBH scenario may be tested in the not-too-distant future.