Using final black hole spins and masses to infer the formation history of the observed population of gravitational wave sources

TL;DR

This paper introduces a new method to analyze the formation history of binary black holes by examining the spins and masses of merged black holes, aiming to distinguish between different formation channels.

Contribution

It proposes a novel technique using remnant black hole properties to infer the origins of gravitational wave sources, highlighting differences between dynamical and isolated formation models.

Findings

Dynamically formed BBHs show distinct mass-spin distributions from isolated ones.

Stellar evolution models significantly influence remnant mass predictions.

Current constraints on formation channels are weak but improve with more detections.

Abstract

In this paper we propose a novel technique to constrain the progenitor binary black hole (BBH) formation history using the remnant masses and spins of merged black holes (BHs). Exploring different models, we found that dynamically formed BBHs are distributed differently in the mass-spin plane than those that have formed in isolation. Stellar evolution recipes crucially affect the remnant mass distribution, suggesting that future efforts should be devoted to finding a common way of modelling the evolutionary phases of single and binary stars. Our simple approach has allowed us to place weak constraints on the origin of the presently observed population of merged BHs, although with high uncertainties. Our results show that the fingerprints of different BBH formation channels will emerge as soon as LIGO detects more than $\sim 10^2$ merger events. This work provides a way of thinking that can be easily used both by people working on isolated and on dynamical BBH formation and evolution.