Series: Astronomy Colloquium
Date: Wednesday 15-Oct-2025
Time: 16:05-17:00 (4:05-5:00 pm)
Location: ATL 2400
Speaker: Prof. Gordon Richards (Drexel University)
Title: An Empirical Look at AGN Accretion with a View Toward LSST
With the start of the Rubin Observatory's Legacy Survey of Space and Time, the LSST AGN Science Collaboration is on the precipice of discovering tens of millions of new quasars and Active Galactic Nuclei. Just as machine learning (ML) applied to SDSS data increased quasar discovery space by an order of magnitude, so too will it for LSST. While lacking representative samples to train on, we are encouraged by the latest advances in ML, which I will discuss. Ultimately the goal is not to simply discover AGNs, but to use them to investigate galaxy evolution and black hole physics. Lacking a spectroscopic component, I will discuss how the LSST team hopes to leverage time-domain information to be able to estimate mass-weighted accretion rates from the photometry alone. How AGNs accrete and vary is a function of their accretion disk physics and geometry. Thus, it is of considerable interest that, while perhaps still a gold standard for X-ray binaries, 2024 saw the demotion of the standard thin accretion disk model as applied to AGNs -- in favor of a much thicker hyper-magnetized, flux-frozen model derived from following galaxy formation processes to small scales. I'll close by considering how AGN astronomers can think about winds and jets within the context of that model.
In-person colloquia are usually preceded by espresso and ice cream at 1:45 pm outside room PSC 1150 and are followed by an informal reception at 5:15 pm in that room. Anyone interested in talking with the speaker, or being added to the colloquium announcement email list, should contact the colloquium organizer Dr. Richard Mushotzky. Lunch will normally be reserved for the speaker to talk to graduate students. Anyone asking a question during a talk is asked to raise their hand and be acknowledged before speaking. Contact Dr. Richard Mushotzky for details.
Colloquium Organizer:
Dr. Richard Mushotzky
Special accommodations for individuals with disabilities can be made by calling (301) 405-3001. It would be appreciated if we are notified at least one week in advance.
