Laya Ghodsi

Talk: Laya Ghodsi, 3:00pm -  3:30pm
Multiphase circumgalactic medium of MACS1931-26 brightest cluster galaxy
The evolution of galaxies is influenced by the diffuse gas reservoir surrounding them, known as the circumgalactic medium (CGM). The CGM acts as a bridge between galaxies and their cosmological environment, enabling gas flows that fuel star formation and redistribute metals throughout the medium. I will discuss the multiphase circumgalactic medium (CGM) of the brightest cluster galaxy (BCG) in the cool-core cluster MACS1931-26 at z∼0.35, which hosts one of the largest known H₂ reservoirs, exhibits elevated star formation, and contains a radio-loud AGN. We trace cold H₂ (10-100 K) in MACS1931-26 using multiple CO and CI emission lines, revealing that the gas in the BCG is highly excited, comparable to local ULIRGs. In contrast, the CGM gas is much less excited, indicating differing ionization sources in these environments.
Our JWST observations reveal warm H₂ coincident with CO, with the CGM being approximately 20 K warmer than the BCG. The warm-to-cold molecular gas mass ratio is 4% in the CGM and 2% in the BCG, suggesting lower star formation efficiency in the CGM. This ratio is comparable to that observed at the edges of the shock front of Stephan’s Quintet group. Ongoing shock modeling aims to reveal potential gas flows from the CGM to the BCG, which may fuel star formation and correlate with the strong activity of AGN, shedding light on the complex feedback processes governing galaxy evolution.