Astrophysics Colloquium schedule
Wednesdays, 3:30-4:30 pm
The Astronomy Colloquia Meetings are held in the P&A building, room 1-434. Zoom information sent in email.
The UCLA Department of Physics & Astronomy Astrophysics group established the Astrophysics Colloquium speaking series 20+ year ago. Throughout the academic year, distinguished speakers travel to UCLA to share their latest research. The department sponsors and organizes these events to encourage collaboration within the field. This exposure is critical for our graduate students particular. The content shared in these events broaden their academic horizons. Additionally, the colloquium provide opportunities for our students to network with other specialists and peers.
Can’t make these times? Watch the Astrophysics Colloquium recordings on our newly minted YouTube channel here! Big thanks to our to our donor and program alumnus, Robert J. Altizer '70 BA Astronomy & Astrophysics, for making this repository possible.
Help us continue this enriching speaking series by making a donation online here. Gifts to the Astronomy and Colloquium Fund offset event costs including those related to speaker travel. Support from our event attendees and donors is greatly appreciated. For check instructions or other giving related questions, please contact Madeleine Martin at mmartin@support.ucla.edu or (310) 882-3633.
Fall 2026
Oct. 7 2026
Betsy Mills (University of Kansas)
Resolving the Activity Cycle in the Nearest Galaxy centers
Abstract:Galaxy centers are powerful laboratories for studying the secular processes that shape galaxies across cosmic time, from large-scale gas flows and star formation to stellar feedback and interaction with a central supermassive black hole. While the proximity of the Milky Way center enables detailed study of its contents, its quiescence limits the processes that can be probed. Now, however, ALMA is allowing us to observe gas in the centers of more active nearby galaxies at parsec to sub-parsec scales. In this talk, I will focus on our recent work with ALMA and JWST to probe the early evolution of some of the most extreme star clusters in the present-day universe, and their role in launching galaxy-scale winds. I will also present initial results from an ALMA sample of nearby galaxies, including both starburst and Seyfert galaxies. With this sample, we make detailed comparisons of gas properties that allow us to isolate the physical, chemical, and kinematic conditions during different stages of activity in a galaxy nucleus. Finally, I will end with a brief discussion of the science prospects for PRIMA-- the first in a new class of NASA astrophysics missions.
Oct. 14 2026
Adam Leroy (Ohio State University)
Oct. 21 2025
TBD
Oct. 28 2026
Nick Choksi (Caltech)
Nov. 4 2026
NO COLLOQUIUM
Nov. 11 2026
NO COLLOQUIUM
Nov. 18 2026
Joel Leja (Penn State University)
Again! - but faster, better, and with more physics: ML-accelerated inference of galaxy properties in deep and wide surveys of the universe
Abstract: The inference of the physical properties of galaxies at cosmological distance requires modeling a wide range of physics, including e.g. stellar evolution and atmospheres; dust attenuation and re-emission; nebular physics; AGN emission; and more. Bayesian inference is often used to map this space, and the wide range of physics and large parameter space (30-40 dimensions!) means these codes are not fast. Yet current and near-future surveys of the universe yield spectra for millions of galaxies, and imaging for billions. I will introduce the next-generation solutions, ranging from neural net emulators of key physics (photoionization modeling; stellar spectra) to efficient gradient-enhanced GPU-accelerated high-dimensional sampling to rapid simulation-based inference. These yield speed-ups of somewhere between hundreds and millions, with different trade-offs in flexibility and accuracy. In addition to permitting sophisticated high-dimensional modeling on the industrial scales of modern surveys, I will discuss qualitatively new science directions enabled by these breakthroughs — as modeling entire galaxy populations rather than one-at-a-time approaches, extremely high dimensional modeling of individual systems, e.g. spatially resolved modeling, and new data-driven modeling with the promise to finally address critical systematics in this field.
Nov. 25 2026
NO COLLOQUIUM
Dec. 2 2026
Mike Blanton (Carnegie Observatories)
Do active galactic nuclei behave the way galaxy formation theorists need them to?
Abstract: I discuss what can be learned about galaxy formation theories from studying how active galactic nuclei (AGN) occupy galaxies. In simulations, AGN play the role of quenching and preventing further star formation in the most massive galaxies, preventing them from becoming even higher stellar mass than they are. The cosmological simulations require subgrid physics to describe star formation processes as well as black hole growth and feedback, both of which are complicated, nonlinear processes occurring at AU scales, within simulations with at best about 10 to 100 pc resolution. Among the major cosmological simulation codes, there are many different implementations of this subgrid physics that all lead to predictions of the stellar mass function and star formation rates of galaxies that agree with observations, and this agreement is taken very seriously as validation of the basic picture. These different implementations nevertheless lead to quite different predictions for how AGN populate galaxies as a function of mass and star formation rate. These predictions, in contrast to those regarding stellar properties of galaxies, are almost never compared against observations. I describe a research program to perform these tests. This program requires a major revision of the statistics of AGN demographics in local galaxies, which in many cases have been performed previously without regard to the dramatic selection effects on AGN samples in galaxies. Although there are many methodological difficulties in interpreting the AGN predictions from galaxy formation simulations, I argue that observations of the AGN population can be used to distinguish between the simulations.