Constraining multiple compact binary subpopulations with GWTC-2

With the release of the second Gravitational Wave Transient Catalog (GWTC-2), there are now nearly 50 confident compact binary mergers detected by the LIGO and Virgo instruments.  This includes multiple detections consistent with the presence of a neutron star.  Whereas the first such detection, GW170817, was confirmed to contain at least one neutron star by its electromagnetic counterpart, none of these new candidates have counterparts to aid their classification.  GW190814 is of particularly ambiguous origins, as its smaller compact object (2.50-2.67 solar masses at the 90% credible level) is either the largest known neutron star, or the smallest known black hole.

While most previous population studies focus in on a single source category (most frequently binary black holes), the presence of at least one ambiguous event makes it necessary to simultaneously fit all three source categories (binary black holes, binary neutron stars, and neutron star-black hole binaries).  In this talk I will discuss several recent analyses which do precisely this.  I also apply the same techniques to identify subpopulations within the broader binary black hole population.