Cosmic Collisions: Galaxies, Black Holes, and Gravitational Waves

Galaxy mergers play an important role in the evolution of the universe, since mergers trigger star formation, build up the mass of supermassive black holes, and drive supermassive black hole mergers that are strong sources of gravitational waves. However, accurate identification of galaxy mergers has been a persistent observational challenge that limits progress in these areas. Here, I will present new approaches to galaxy merger identification, including approaches that use stellar kinematics instead of imaging alone, and approaches that are trained on state-of-the-art cosmological simulations of galaxies. I will summarize the results of our study of galaxy mergers imaged by the Hubble Space Telescope, where we measure the impact of mergers on star formation and supermassive black hole growth. With our new measurements of the galaxy merger rate, we can predict the amplitude of the gravitational wave background produced by merging supermassive black holes. Pulsar timing arrays expect to make the exciting detection of this gravitational wave background within the coming few years.

Host: Laura Blecha