On the mass distribution of the LIGO-Virgo-KAGRA events

TL;DR

This paper analyzes the mass distribution of black hole mergers detected by LIGO-Virgo-KAGRA, combining stellar-origin and primordial black hole models to better fit observed data and explore black hole formation scenarios.

Contribution

It introduces a method to derive the black hole mass distribution from GW data and demonstrates that a combined stellar and Gaussian distribution fits observations better.

Findings

Combined distribution fits LVK data more accurately.

Stellar and primordial black hole populations can explain observed mass distribution.

Supports the presence of multiple black hole formation channels.

Abstract

The merging black hole binaries detected by the LIGO-Virgo-KAGRA (LVK) gravitational-wave observatories, may help us shed light on how such binaries form. In addition, these detections can help us probe the hypothesized primordial black holes, a candidate for the observed abundance of dark matter. In this work, we study the black-hole mass distribution obtained from the LVK binary black hole merger events. We obtain that distribution by first associating a skewed normal distribution to each event detected with a signal to noise ratio (SNR) $>$ 8 and then summing all such distributions. We also simulate black hole binaries from two separate populations of merging binaries. One of these is a stellar-origin population that follows a mass-distribution similar to the zero-age mass function of stars. The second population of black holes follows a Gaussian mass-distribution. Such a distribution could approximate a population of black hole binaries formed from earlier black hole mergers in dense stellar environments, or binaries of primordial black holes. For those populations, we evaluate the number of detectable events and fit their combination to the LVK observations. In our work, we rely on a wide range of stellar-origin black-hole mass distributions. We find that the observed LVK events can be fitted much better by the combination of such a stellar-origin mass distribution and a Gaussian distribution, than by the stellar-origin mass distribution alone.