Black Holes: Bridging Simulations and Observations

León Salas
University of Wisconsin-Milwaukee

In recent years, General Relativistic Magnetohydrodynamic (GRMHD) simulations, combined with multiwavelength observations have provided critical insights into the nature of radiation from accreting black holes. These simulations have revealed a particularly interesting magnetically arrested disk (MAD) regime whereby the accretion is choked by strong magnetic fields. The higher magnetic flux characteristic of the MAD regime leads to new dynamics, including interchange-type accretion modes and flux eruptions. Polarization measurements by the Event Horizon Telescope (EHT) from the supermassive black holes M87* and Sagittarius A* (Sgr A*) favor MAD states. However, nearly all MAD models exhibit greater 230 GHz flux variability than seen in historical observations of Sgr A*.

In this talk, I will present my investigation on the dynamics of MAD GRMHD simulations and the (sub)millimeter variability of Sgr A* focusing on the poorly understood electron thermodynamics. In addition, I will talk about the multiwavelength signatures of a black hole X-ray binary outburst simulation to understand how synchrotron emission from the accretion disc and jet contribute to the X-ray emission and potentially influence observables such as polarization. Finally, I will show a library of polarized images that will be used for training PRIMO, a machine learning–based image reconstruction code. PRIMO has enabled higher-resolution imaging of M87* using EHT data acquired in 2017, even in the presence of sparse data coverage. We aim to extend these results by imaging polarized data from 2017 to 2025, which are characterized by progressively improved baseline coverage, and to provide essential groundwork for the first multi-month EHT movie campaign of M87*, which has already started this week.