Bayesian analysis of the spin distribution of LIGO/Virgo black holes

TL;DR

This paper uses Bayesian methods to analyze LIGO/Virgo black hole spin data, finding strong evidence for low spins and supporting the hypothesis that these black holes may be primordial in origin.

Contribution

It provides a Bayesian framework to compare different spin distribution priors for LIGO/Virgo black holes, revealing a preference for low and isotropic spins.

Findings

Strong evidence for low black hole spins.

Significant support for isotropic spin distribution.

Results suggest black holes may be primordial.

Abstract

Gravitational wave detection from binary black hole (BBH) inspirals has become routine thanks to the LIGO/Virgo interferometers. The nature of these back holes remains uncertain. We study here the spin distributions of LIGO/Virgo black holes from the first catalogue GWTC-1 and the first four published BBH events from run O3. We compute the Bayes evidence for several independent priors: flat, isotropic, spin-aligned and anti-aligned. We find strong evidence for low spins in all of the cases, and significant evidence for small isotropic spins versus any other distribution. When considered as a homogeneous population of black holes, these results give support to the idea that LIGO/Virgo BBH are primordial.