Use of gravitational waves to probe the formation channels of compact binaries

TL;DR

This paper explores how gravitational-wave observations can distinguish between different formation channels of compact binaries by analyzing spin orientations, with simulations showing accurate estimates of the fraction of aligned systems after detecting 100-200 sources.

Contribution

It introduces a method to estimate the fraction of binary systems formed via common envelope evolution using Bayesian analysis of gravitational-wave data.

Findings

Bayesian estimation can determine the fraction of aligned systems with about 10% uncertainty after 100-200 detections.

Simulations show distinguishable spin orientation distributions for different formation channels.

The approach helps clarify the dominant formation mechanisms of compact binaries in gravitational-wave observations.

Abstract

With the discovery of the binary black hole coalescence GW150914, the era of gravitational-wave astrophysics has started. Gravitational-wave signals emitted by compact binary coalescences will be detected in large number by LIGO and Virgo in the coming months and years. Much about compact binaries is still uncertain, including some key details about their formation channels. The two scenarios which are typically considered, common envelope evolution and dynamical capture, result in different distributions for the orientation of the black hole spins. In particular, common envelope evolution is expected to be highly efficient in aligning spins with the orbital angular momentum. In this paper we simulate catalogs of gravitational-wave signals in which a given fraction of events comes from common envelop evolution, and has spins nearly aligned with the orbital angular momentum. We show how the fraction of aligned systems can be accurately estimated using Bayesian parameter estimation, with 1 $\sigma$ uncertainties of the order of 10% after 100-200 sources are detected.