12:00–1:00 pm ERC 501
Dhayaa Anbajagane "Painting baryons onto halos: accessing small-scale astrophysics from large-scale datasets"
Simulations are a staple tool in interpreting our observations of the late-time Universe. Dark matter-only simulations provide us with an easy, approximate model for inferring cosmological information from these observations, while hydrodynamical simulations with galaxy formation are more accurate given their inclusion of baryon evolution, and are also necessary to study any astrophysics from these observations. The question of developing a "realistic" hydro simulation model, however, is complicated and has yet to be resolved. I will explain the process of "painting" baryons onto DM halos, and describe how it provides a complementary model through which we can use observations on cosmological distance scales to infer astrophysics on galactic/sub-galactic scales.
Rich Kron "Time-domain Science from Early Photographs"
The collection of photographic glass plates associated with Yerkes Observatory, dating from 1900, records both images and spectra. It is one of a number of large repositories of such material that can in principle be used for time-domain astronomy, specifically for establishing the flux of a source as it was a century or so ago.
The Yerkes collection features two wide-field (~15 deg on a side) series of blue-sensitive plates (1905 and 1935) that each cover > 80% of the sky north of -20 deg. Both series feature the northern Milky Way. Star images are measurable to at least B = 17.0 with S/N ~ 10, depending on how crowded the field is. Astrometric precision is better 1.4 arcsec, which is generally good enough to match a source reliably to current photometric catalogs. The collection also includes plates that Edwin Hubble took for his UChicago PhD dissertation with George Ritchey's 24-inch reflector to determine the size distribution of faint nebulae.
A group of undergraduate students is studying the ability of inexpensive digitizers to extract photometric measurements from this material. Two publications have demonstrated effective ways to do this. A third publication, in preparation, explores what can be done with early spectrograms. Summer 2023 will feature a production run to complete the digitization of one of the Milky Way Atlases, yielding publicly accessible image files that record useful data on ~10 million stars.
The Yerkes plate collection is valuable not just for scientific purposes, but for historical research on the people who took the plates and the scientific questions of the time. Accordingly, the team now includes historians, librarians, and archivists as well as students in A&A. Some of the history-of-science work will be featured in upcoming related events:
- Kathleen Zar Symposium, 13 - 16 September 2023: "Invisible Labor in Astronomy" https://www.lib.uchicago.edu/conferences/zar-symposium/
- Special Collections Research Center exhibit, 18 September - 17 December 2023: "Untold Story of Women at Yerkes Observatory 1900 - 1930"
