The First Multi-Messenger Study of Supermassive Black Hole Growth

Simon Joseph, Milwaukee WI

Investigators

Abstract

Joseph Simon is awarded an NSF Astronomy and Astrophysics Fellowship to carry out a program of research and education at the University of Colorado. Combining pulsar timing array (PTA) measurements of the gravitational wave (GW) background with electromagnetic observations of galaxy mergers, Simon will model how black holes (BH) merge to form supermassive black holes (SMBH). Results from this project will allow astronomers to better understand how SMBH grow in mass. Simon will also provide research mentoring to undergraduate students and engage them in a program of outreach activities to local middle schools and high schools serving under resourced communities. Hints of the GW background emerging in PTA data appear inconsistent with theoretical predictions neglecting the contributions from BH-BH mergers and imply that SMBHs are more massive, or merge more frequently than previously thought. In this project, Simon will incorporate the best available observations of galaxy mergers and the SMBH mass function alongside a new prescription for the binary evolution timescale into his modeling framework for the binary SMBH population and the GW background. He will first use his refined models to extract the binary evolution timescale from PTA data. He will then combine the electromagnetic observations of galaxy mergers and the SMBH mass function with PTA observations to conduct the first multi-messenger measurement of SMBH mass growth due to BH-BH mergers. This project advances the goals of the NSF Windows on the Universe Big Idea. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.