Modeling Dual Active Galactic Nuclei in Mergers: Unique Probes of Black Hole Inspiral and Growth

University Of Florida, Gainesville FL

Investigators

Abstract

Collisions between galaxies can dramatically change their structure and are key phases in their evolution. These merger events can also strongly influence the supermassive black holes that live in the centers of galaxies. Supermassive black holes grow by consuming gas in their surroundings, and galaxy merger events can funnel a fresh gas supply to the black holes, triggering a phase of rapid growth. Eventually, the black holes from each merging galaxy also form a close black hole binary, which produces powerful gravitational waves---ripples in the fabric of spacetime---that could be detected in the near future. However, the formation timescale for black hole binaries remains highly uncertain, hampering efforts to predict their gravitational wave signals. Moreover, the connection between galaxy mergers and black hole fueling is still actively debated, an issue complicated by the fact that signatures of black hole fueling are often hidden by intervening gas and dust. The Principal Investigator's (PI's) work will address these critical limitations in the understanding of black hole fueling. Using simulations of galaxy and black hole evolution, the PI will determine the connection between mergers and black hole fueling and make predictions for future observations, including observations with the upcoming James Webb Space Telescope (JWST). The PI will also provide new constraints on the timescale for black hole binaries to become detectable gravitational-wave sources. In addition, the PI will initiate a Women in Physics & Astronomy program at Florida, including a multi-level mentoring program and a seminar series on professional development and equity & inclusion topics. This program will encourage retention of junior female scientists, create stronger ties between the physics and astronomy departments, and promote an inclusive climate that is actively welcoming to members of underrepresented groups. Galaxy mergers are key phases in the evolution of galaxies and their central supermassive black holes (BHs). Mergers can dramatically change galaxies' structure and trigger new star formation as well as rapid BH fueling. These events also lead to the formation of close BH binaries, which are powerful sources of gravitational waves (GWs) that should be detectable in the near future. However, BH binary inspiral timescales remain highly uncertain, hampering GW predictions, and the connection between galaxy mergers and BH fueling is still actively debated. Empirical studies are complicated by the fact that signatures of active BH growth are often obscured by intervening gas and dust. The PI's work will address these critical limitations in the ability to interpret observations of BH fueling and inspiral in mergers. JWST will soon transform the view of BH and galaxy evolution, and the advent of the GW era has amplified the need for better constraints on the low-frequency GW source population. Now is the ideal time to undertake a study of BH fueling and inspiral in merging galaxies that makes testable predictions for near-future observations. The PI will use hydrodynamic simulations and radiative transfer calculations to quantify the intrinsic connection between mergers and BH fueling, determine the role of selection biases in surveys of merger-driven BH fueling, and place semi-empirical constraints on BH pair inspiral.