Colloquium – Lia Medeiros

Lia Medeiros, University of Wisconsin- Milwaukee

black hole images: what they’ve taught us so far and how we can improve them

Abstract: Horizon-scale observations of accreting supermassive black holes with the Event Horizon
Telescope (EHT) have opened a new window onto strong-field gravity and black-hole accretion.
The EHT’s 2022 observations of Sagittarius A* (Sgr A*), the black hole at the center of our
Galaxy, provide a new opportunity to test the Kerr metric in a previously unexplored regime. I
will discuss the EHT observations of Sgr A*, focusing on what they can reveal about
fundamental physics, and briefly compare these results with the earlier observations of M87*. I
will then discuss how improvements in both observations and data analysis can extend these
measurements in the near future. In particular, I will introduce PRIMO, a machine-learning
algorithm for EHT data analysis that uses a large library of high-fidelity simulations as a training
set. I will show a higher-resolution reconstruction of M87* obtained with PRIMO and
demonstrate how improved image reconstruction can provide new constraints on both black-
hole accretion and strong-field gravity.

Bio: Dr. Medeiros has been an Assistant Professor at UWM since Jan 2025. Before arriving at UWM she was a NASA Hubble Fellowship Program, Einstein Fellow at Princeton University, was a member of the Institute for Advanced Study (IAS) from 2019 to 2023 and was a National Science Foundation (NSF) Astronomy and Astrophysics Postdoctoral Fellow from 2019 to 2022. She completed her undergraduate education at the University of California-Berkeley in Physics and Astrophysics, class of 2013. She then received her Masters and PhD (2019) in Physics from the University of California-Santa Barbara. After completing her classes in Santa Barbara, she took advantage of the flexibility allowed by an NSF Graduate Research Fellowship and spent three years at the Steward Observatory at The University of Arizona and one year at the Black Hole Initiative at Harvard. Her PhD thesis was completed in collaboration with University of Arizona Professors Feryal Özel and Dimitrios Psaltis.

September 9, 2026 @ 1:00pm (CST) in Commons Center 237

Host: Steve Taylor