Elucidating the Diversity of Outflows in Tidal Disruption Events

It has long been known that feedback between immense outflows of gas from supermassive black holes (SMBHs) in the center of galaxies and the environment of the galaxies themselves plays a key role in galaxy evolution. However, the mechanism by which these outflows are launched and a definitive model of SMBH accretion have remained elusive. An important opportunity to study these phenomena occurs when a star is scattered onto an orbit that crosses the SMBH’s tidal radius, temporarily increasing the accretion rate by orders of magnitude as the SMBH consumes gas from the disrupted star. A research team from the University of Arizona will use radio observations of these tidal disruption events (TDEs) in combination with supplemental multi-wavelength data to conduct the first systematic investigation of mass ejection from SMBHs in the local Universe. The project also includes a number of related efforts to increase public awareness of astronomy through a partnership with the Flandrau Planetarium and Science Center. These will include public talks, field trips for students from local Title I schools, and a one-week summer camp for children in grades 5-6 focused on black holes. The research team will track the evolution of TDE outflows via radio and millimeter observations of the radio synchrotron emission produced in the shock between the outflow and the ambient interstellar medium. Modeling of the synchrotron radio emission will allow the researchers to calculate the energy carried by the outflow, the density profile of the ambient medium, and other physical parameters that are otherwise difficult to measure observationally. These calculations in turn inform numerical simulations of TDEs and provide critical physical insight into jets, shocks, accretion flows, and SMBH feedback. In the past three years, the discovery rate of TDEs has increased to roughly 10 per year, providing an opportunity to conduct a systematic radio study of a statistically significant population. 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.