Astronomy Tea Talk
Speaker 1: Dr. Keerthi Vasan
Title: Spatially Resolved Galactic Winds at Cosmic Noon
Abstract: Outflows play a crucial role in regulating galaxy growth by modulating the amount of gas available in a galaxy's interstellar medium, thereby influencing star formation and, ultimately, galaxy evolution. Understanding the nature and impact of these outflows across cosmic time is essential to constraining feedback processes that shape galaxies. Strong gravitational lensing aided by sensitive Integral Field Spectroscopy (IFS) enables us to conduct detailed studies of the inhomogeneous outflow properties in galaxies at high-redshifts.
In this talk, I will discuss results from our resolved kinematic study of outflowing gas in lensed star-forming galaxies at cosmic noon observed with Keck/KCWI. These IFS observations enable measurements of key outflow properties—including velocity structure, mass loss rates, and mass loading factors across individual galaxy halos. These measurements serve as critical benchmarks for characterizing feedback processes during a pivotal epoch in galaxy evolution. I will also briefly highlight our ongoing efforts to probe the connection between galaxies and their extended environments by studying the Circumgalactic Medium (CGM) through lensed arc tomography. This novel technique leverages the continuous background provided by giant gravitational arcs to spatially map the CGM in detail, offering new insights into how galaxies interact with their surroundings during the course of their evolution.
Speaker 2: Dr. Wuji Wang
Title: ALMA+JWST Discovers Companions at < 18 kpc Around z~3.5 Radio AGN
Abstract: Mergers are important in stellar mass buildup and triggering feedback, especially in the high-redshift universe. High-z radio galaxies (z > 2, radio loud type-2 quasars) are known to trace the dense protocluster environment and be hosted by M_star ~ 10^11 M_solar galaxies. The view on tens of kpc scales was elusive until recent high sensitivity observatories came by. In this talk, I will present our joint ALMA+JWST/NIRSpec IFU view around the center of four z ~ 3.5 radio AGN. We ubiquitously discover ~12 companion systems at distances of < 18 kpc using two independent methods: (i) peculiar [OIII] kinematics; (ii) [CII] emission. We estimate that these systems have M_dyn~10^9-11 M_solar, which indicates a minor merger scenario. All [CII] emitting blobs that were detected are offset from the AGN position, suggesting that cold gas does not reside in the massive host. Our results indicate that these mergers could be the trigger of the most powerful AGN jets at the beginning of Cosmic Noon. They bring gas to the supermassive black holes in the gas-poor host and ignite the AGN feedback. We also find that they can impact the propagation of the jet, e.g., by deflecting the jet. Overall, they play an important role in the evolution of the progenitors of massive galaxy clusters. Our new discovery is an important guide to tens of kpc scale galaxy evolution (galaxy-galaxy mergers) in the early universe.
Besides the main topic, I will also briefly introduce JWST IFU PAH observations at high-redshift.