Institute for Advanced Study / Princeton University Joint Astrophysics Colloquium

Abstract: Black hole mergers carry information about some of the least understood stages of stellar evolution, the dynamics of dense stellar systems, and the growth of compact objects through accretion. Gravitational-wave observations offer a way to investigate this physics across cosmic history, and have already produced several surprises. Among the most striking are exceptionally massive and rapidly spinning black holes, whose properties challenge conventional formation scenarios and raise new questions about how much black holes grow after their birth. I will discuss recent results that connect these discoveries to the physics of black hole growth and binary assembly, including the possibility that gas-rich galactic nuclei play an important role. Establishing that connection would have implications beyond merger origins: gravitational waves could probe the interplay of accretion and dynamics in otherwise inaccessible environments. It would also change how we observe these systems, since mergers embedded in gas may reveal themselves through electromagnetic emission as well as gravitational waves.