2025/11/03 by Gingras, Marie-Joëlle, McNamara, B. R., Coil, Alison L. +5
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena
paper · doi:10.48550/arxiv.2511.01986
openalex publication_date 2025/11/03 · openalex created_date 2025/11/06 · openalex updated_date 2026/07/28
We present Keck Cosmic Web Imager observations of stellar populations in three galaxies lying at the centers of cooling flow clusters. All three host rich molecular gas reservoirs and show prominent Balmer absorption from 30-100 Myr-old stars consistent with long lasting star formation. Two systems, A1835 and PKS 0745-191, have spatially extended young stellar populations in their centers with recent star formation rates of 100 M\odot yr-1 and 8 M\odot yr-1, respectively. In A1835 we uncover a blueshifted clump of young stars moving at high speed with respect to the gas and central galaxy. We suggest these stars formed in a gaseous outflow and have since detached from their natal gas and are now falling inward. This result indicates that star formation is proceeding in a dynamically complex environment shaped by the central galaxy's motion relative to cooling clouds and the feedback from radio jets. In RX J0820.9+0752 intermediate-age stars are found in a filament outside the nucleus with no discernible star formation at the center of the galaxy. All projected galaxies consist of old stellar populations with deep D4000 breaks and lack detectable warm gas. While they may interact gravitationally with the central galaxy, they cannot have donated the upward of 1010~ M\odot of molecular gas found in these systems. These results highlight the importance of analyzing spatially resolved stellar kinematics and star formation histories in brightest cluster galaxies, an approach that remains relatively understudied.