Studying magnetic fields, dynamics, and fundamental physics near a black hole with current and future mm-VLBI instruments

The Event Horizon Telescope (EHT) has imaged the black hole shadows of the supermassive black hole at the center of the galaxy M87 (M87*) and at the center of the Milky Way (Sgr A*). Polarimetric imaging of M87* with the EHT enabled significantly stronger inferences on the black hole and accretion parameters than total intensity data alone. Geometric modeling was a central tool for studying the structure of M87* and Sgr A* in total intensity. In the first part of the talk, I will show the results of fitting a new polarimetric “m-ring” geometric model to EHT observations of M87*. Our geometric modeling results are generally consistent with imaging methods, but they also enable studies of the black hole when imaging methods struggle, such as nights with sparse coverage or weak signals.

In the second part of the talk, I will focus on plans and science goals for future instruments. The Next-Generation EHT (ngEHT) will be a transformative enhancement of the EHT, with array expansions and improvements allowing for, e.g., high dynamic range imaging of AGN jets, and for real-time movie reconstructions of variable sources like Sgr A*. With the ngEHT Analysis Challenges, we explore the science capabilities of the ngEHT, and develop new analysis algorithms capable of analyzing the large and complex ngEHT datasets. Finally, I will give a brief overview of several proposals to image black holes using space-based telescopes, which achieve order-of-magnitude angular resolution improvements compared to what is attainable from the ground and allow for high-precision tests of general relativity.

09/11/2023 - 12:00
Dr. Freek Roelofs
Center for Astrophysics, Harvard & Smithsonian, USA.