Possibility of primordial black holes as the source of gravitational wave events in the advanced LIGO detector

TL;DR

This paper investigates whether primordial black holes could explain LIGO gravitational wave events, modeling their merger rates, lensing effects, and comparing predicted distributions with observations, ultimately ruling out PBHs as the primary source.

Contribution

It provides a detailed analysis of PBH binary formation, merger rates, and lensing effects, and compares these predictions with LIGO data to assess PBHs as GW sources.

Findings

Primordial black holes cannot account for all observed GW events.

The best-fit PBH mass function parameters are M_c=25 M_sun and σ=0.6.

The binary PBH scenario is ruled out as the main source of LIGO GW events.

Abstract

The analysis of gravitational Wave (GW) data from advanced LIGO provides the mass of each companion of binary black holes as the source of GWs. The mass of events corresponding to the binary black holes from GW is above $20$ M$_\odot$ which is much larger than the mass of astrophysical black holes detected by x-ray observations. In this work, we examine primordial black holes (PBHs) as the source of LIGO events. Assuming that $100\%$ of the dark matter is made of PBHs, we estimate the rate at which these objects make binaries, merge, and produce GWs as a function of redshift. The gravitational lensing of GWs by PBHs can also enhance the amplitude of the strain. We simulate GWs sourced by binary PBHs, with the detection threshold of $S/N>10$ for both Livingston and Hanford detectors. For the log-normal mass function of PBHs, we generate the expected distribution of events, compare our results with the observed events, and find the best value of the mass function parameters (i.e., $M_c =25 M_\odot$ and $\sigma=0.6$) in the log-normal mass function. Comparing the expected number of events with the number of observed ones rules out the present-Universe binary formation PBH scenario as the candidate for the source of GW events detected by LIGO.