Two of a Kind: Comparing Big and Small Black Holes in Binaries

When modeling the population of merging binary black holes, analyses have generally focused on characterizing the distribution of primary (i.e. more massive) black holes in the binary, while simplistic prescriptions are used for the distribution of secondary masses. However, the secondary mass distribution and its relationship to the primary mass distribution provide a fundamental observational constraint on how coalescing binary black holes are formed. We present the first analysis of the binary black hole population that explicitly fits for the secondary mass distribution. I will discuss the results of this analysis and its implications for the astrophysical formation of binary black hole systems.