The Binary Black Hole Population after LIGO/Virgo’s O3a Observing Run

Advanced LIGO and Virgo’s O3a observing run has significantly expanded and refined our understanding of the stellar-mass binary black hole (BBH) population. Past detections have, to date, suggested a picture in which BBHs have low spins, masses concentrated below 45 solar masses, and preferentially equal mass ratios. In this talk, I will present the latest lessons learned during O3a, describing LIGO and Virgo’s updated measurements of the spin, mass, and redshift distributions of BBHs. I will additionally speculate about the implications of these measurements for understanding the origin and evolution of compact binary mergers.