SIMBAD references

The origin of the black hole mergers detected by LIGO-Virgo remains an open question. While the unusual mass and spin of a few events constrain their possible astrophysical formation mechanisms, it is difficult to classify the bulk of the observed mergers. Here we consider the distribution of masses and spins in LIGO-Virgo's first two observing catalogs. We show that, for black holes in the mass gap, our fiducial active galactic nucleus (AGN) model is preferred over a parametric mass-spin model fit to the full GWTC-2 merger sample (Bayes factor B > 10). This preference, nevertheless, depends on uncertain AGN model parameters. We further show that a 20% fractional contribution of the detected events of an AGN-disk origin reproduces well the observed black hole mass distribution in the pair-instability mass gap, while only marginally contributing to the lower-mass detected population. The overall AGN contribution corresponds to a black hole merger rate of about 2.5 Gpc^–3 yr^–1, comparable to theoretical expectations.