WoU-MMA: Multi-Messenger Signatures of Hot Accretion Flows around Supermassive Black Hole Binaries

About This Grant

An entirely new perspective on the Universe emerged with humanity’s first observations of gravitational waves a decade ago. These messengers of gravity are ripples in the fabric of spacetime launched from the extreme environments of colliding black holes and detected on Earth for the first time in 2015 by the Laser Interferometer Gravitational Wave Observatory (LIGO). Over the past decade astronomers have used this gravitational messenger, along with traditional astronomical observations of light, to uncover many long-held secrets in physics and astronomy. We have, however, only just begun to learn about our Universe from this new discipline of multi-messenger astronomy. In only the last few years we have begun to break open a new realm of gravitational wave observations from merging black holes that are up to billions of times larger than the merging black holes detected by LIGO. These supermassive black holes probe different physical regimes and stand to again open the flood gates of discovery. This research program will build-up necessary theoretical frameworks needed to describe the astrophysical processes which generate multi-messenger signatures from these monstrous black hole mergers. The aim is to predict observational signatures of these supermassive black hole binaries interacting with their environments. To do so the program will pioneer new models of these interactions to facilitate their discovery and interpretation. In this way the program will advance the state-of-the art in this quickly moving field of multi-messenger astrophysics. It will furthermore contribute to education and training of a graduate student and undergraduate students. Supermassive black holes are the focus of this research program and the subject of a long-standing mystery: will they merge? What can that tell us about the environments that shape them? What are the consequences for the low-frequency gravitational wave sky that is now being probed by the Pulsar Timings Arrays, and in the future by the LISA observatory? The research program will advance the state of the art in modeling binary+gas interactions by laying the theoretical groundwork for a so-far-unexplored regime of binary accretion: hot accretion flows, as opposed to standard thin disk accretion. This program will utilize results established for single-black-hole hot accretion flows, apply them to the binary problem, and make much needed predictions for multi-messenger signatures of accreting supermassive binaries. 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.