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

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 ∼10² merger events. This work provides a way of thinking that can be easily used by people working on both isolated and dynamical BBH formation and evolution.