Speaker
Description
We investigate the differences between several proposed formation scenarios for binary black holes (BBHs), including isolated stellar evolution, dynamical assembly in dense clusters and active galactic nuclei (AGN) disks, and primordial BHs. Our approach exploits the distinguishing spin features of each formation channel, and focuses on the models' predicted correlations between the spin magnitudes (and orientations) with their mass. Using hierarchical Bayesian inference on the recent GWTC-4.0 dataset, we compare these features across all models and assess how well each scenario explains the data. We find that the data strongly favor the presence of a positive correlation between mass and spin magnitude, in agreement with previous studies. Furthermore, we find that the hierarchical scenario provides a better fit to the observations, due to the inclusion of second-generation mergers leading to higher spins at larger masses. The current dataset does not allow us to distinguish orientation properties: cluster (random orientations) and AGN (aligned orientations) scenarios show similar Bayesian evidence. Finally, we find that the mass–spin correlation predicted by the primordial scenario gives a poor fit to the data and can only account for a subset of the observed events.