The CASS Astrophysics Seminar features world-class astrophysicists from around the world speaking on current topics of research. Presentations are aimed at the graduate and post-graduate level, but are open to the general public. CASS seminars take place on Wednesdays from 4:00 - 5:00 p.m. in 383 SERF (Marlar Seminar Room), unless otherwise noted. You can watch a live stream of the talk or prior talks at the CASS Seminar YouTube Channel. The organizers are Prof. Shelley Wright and Prof. George Fuller.
March 29, 2017
- "The Assembly of the First Galaxies: Insights from the Renaissance Simulations"
- Distinguished Professor of Physics, CASS; Director of San Diego Supercomputer Center
The Renaissance Simulations are a suite of high resolution multiphysics cosmological simulations to explore the assembly of the first generation of galaxies. Consuming some 60 million core-hours on the Blue Waters supercomputer over 3 calendar years, the Renaissance Simulations bridge the gap between the formation of Population III stars in minihalos at z ~ 20 and the formation of the first chemically enriched star-forming galaxies at z ~ 10. In this talk I describe how the simulations were performed, and what we have learned about the first generation of galaxies. Topics include the duration of the Pop III epoch as a function of environment; the preprocessing of the IGM by Pop III chemical and radiative feedback; properties of the first galaxies; and their contribution to reionization. The UV luminosity function of our simulated galaxies agree with HST observations over the narrow range of magnitudes where they overlap, giving us some confidence in the results. I present synthetic JWST observations, and conclude by describing our efforts to build a data access portal called the Renaissance Simulations Laboratory so that others may independently explore the first galaxies computationally.
April 12, 2017
- Professor Emeritus, Department of Hydrology & Atmospheric Sciences
- University of Arizona
April 19, 2017
- Professor, Department of Astrophysical & Planetary Sciences
- University of Colorado, Boulder
April 26, 2017
- University of Wisconsin-Madison
May 3, 2017
- "Young Galaxies Forming in the High-Redshift Universe"
- Associate Professor
- Leiden Observatories
Over the last few years, enormous progress has been made in studying galaxies in the first two billion years thanks to the incredible capabilities of the Hubble and Spitzer Space Telescopes. Already, more than 1500 probable galaxies are known at redshifts above z~6, and now the current frontier is at z~9-10, with 50 plausible galaxy identifications to date, and a spectroscopic redshift measurement to z=11.1. Noteworthy advances are also being made in characterizing the physical properties for these distant galaxies, with probes of the nebular emission lines and specific star formation rates to z~8.5 and new constraints on dust-enshrouded star formation at z>~2 from ALMA. One area where there has been particularly exciting activity is in the study of ultra-faint galaxies in the early universe with the Hubble Frontier Fields (HFF) program, combining the power of long exposures with Hubble and Spitzer with gravitational lensing by massive galaxy clusters. In this colloquium, I survey these and other highlights of current research on high redshift galaxies, while looking forward to future work with JWST.
May 10, 2017
- Assistant Professor, Department of Physics & Astronomy
- California State University at Northridge (CSUN)
May 17, 2017
- "The Dynamics of the Local Group: Challenges to Convention in the Era
of Precision Astrometry"
- Assistant Professor
- University of Arizona
Our understanding of the dynamics of our Local Group of galaxies has changed dramatically over the past few years owing to significant advancements in astrometry and our theoretical understanding of galaxy structure. I will provide an overview of key contributions by the Hubble Space Telescope to this evolving picture. In particular, I will highlight the HSTPROMO team’s proper motion measurements of key players in the Local Group, such as the most massive satellites of the Milky Way (the Large and Small Magellanic Clouds), the first ever direct proper motion measurement of M31 and an implied new orbital history for M33. These results have met with controversy, challenging preconceptions of the orbital dynamics and evolution of key members of the Local Group. I will further highlight the importance of HST’s continued role in this field in the era of Gaia.
May 24, 2017
- Millikan Postdoctoral Fellow
May 31, 2017
- NSF Astronomy & Astrophysics Postdoctoral Fellow
- TAPIR, Caltech / Columbia University Dept of Astronomy