Events: Colloquia

A&A Colloquium: Claude-André Faucher-Giguere (Northwestern)

3:30–4:30 pm Zoom - for link, please contact, Laticia 

“How do galaxies form? New insights from FIRE and into the role of the circumgalactic medium”

Abstract: Galaxies are remarkably diverse in their properties, ranging from irregular to disky to elliptical in morphology, and from blue to red in color. At the same time, when analyzed systematically, galaxy populations exhibit striking regularities, with clear trends with mass and redshift. How does this “regular complexity” emerge from the hot Big Bang? I will present results from the FIRE simulations which shed some light onto the processes that shape galaxies. The FIRE zoom-in simulations resolve the multiphase interstellar medium of galaxies and model several different feedback processes (including Type II/Ia supernovae, stellar winds, and radiation) while including the cosmological environment. I will highlight recent results on the formation of disk galaxies, the “burstiness” of star formation, and galactic winds. Our new results indicate that transitions in each of these important phenomena can be simultaneously explained by a phase transition in the inner circumgalactic medium, “inner CGM virialization” (ICV), and arise from the interplay between feedback energy produced on small scales and the physics of halo gas on larger scales.

Jan 20
Feb 3

A&A Colloquium: Kate Alexander (Northwestern University)

12:00–1:00 pm Zoom

“Cosmic Extremes: Time-Domain Astrophysics in a Multi-Messenger World”

Time-domain astrophysics provides a unique opportunity to study the most extreme physical processes in the Universe, including the deaths of massive stars, the destruction and creation of compact objects like neutron stars and black holes, and the tidal disruption of stars by supermassive black holes. I will discuss my recent and ongoing work to reveal the formation and structure of relativistic jets and outflows in the most extreme astrophysical transients, including gamma-ray bursts (GRBs) and tidal disruption events (TDEs). I will further show that radio data provide the best constraints on the immediate environments of these transients, probing models of black hole growth and accretion (TDEs) and stellar evolution models (GRBs). Finally, I will discuss the bright future of time-domain astrophysics. With the pioneering detections of gravitational waves, astronomers and physicists have gained a new, complementary tool to study compact object mergers, with implications for fields as wide-ranging as general relativity, nuclear physics, cosmology, and shock physics. Collaboration with LIGO and its successor gravitational wave observatories will enable precision constraints on merger physics, while wide-field surveys like DES and Rubin Observatory’s LSST will provide the first large samples of rare, relativistic events and move transient science into the statistical realm. Simultaneously, new radio interferometers like the ngVLA and the Square Kilometer Array together with high-cadence survey experiments like CMB-S4 are poised to transform radio astronomy, revealing the radio sky in unprecedented depth and leading to the discovery of relativistic transient populations in the radio band.

Feb 24