Gravity Seminar: Challenges and opportunities in the first EHT results of the galactic center, Boris Georgiev, University of Waterloo and Perimeter Institute

On May 12, 2022 the Event Horizon Telescope announces its first scientific release about the Milky Way galactic center. The EHT is a global radio interferometric array with resolution of about 10 microarcseconds and at its observing frequency, it is expected to resolve the emission structure of two supermassive black hole candidates (M87* and Sgr A*) on event-horizon scales. M87* data analysis required novel imaging and modelling techniques and revealed a ring of emission and shadow consistent with expectations from General Relativity. The galactic center comes with two additional difficulties: (1) gas in the Milky Way galactic plane both scatters and blurs the radio emission and (2) the mass of Sgr A* implies variability on timescales of 20 seconds, much smaller than an observational night. However, the galactic center also benefits from decades of observations at all frequencies promising a better understanding of the interaction of a black hole with its environment. In this talk, I’ll focus on the challenges in this first-of-a-kind data set, the techniques developed to overcome them, and the new scientific constraints hidden inside those difficulties.