The Mystery of The Red, Dead & Gassy Galaxies

Observations of galaxies across the universe reveal a persistent bimodality; characterized by star-forming blue spiral galaxies, and quenched red elliptical galaxies. Traditionally, the latter population of quenched “red and dead” galaxies were believed to be devoid of molecular hydrogen, essential for star formation. However, recent observations by the ALMA interferometer have challenged this notion, showing quenched galaxies harboring significant reservoirs of molecular gas. In our study, we use the cosmological simulation SIMBA to investigate the mechanisms that allow quenched galaxies to retain molecular gas, focusing on processes directly impacting the molecular gas rather than indirect effects like mergers or the local environment. In total our study will investigate four hypotheses, two intrinsic and two observational. While many studies have investigated the various effects that could lead to detections of molecular gas in quenched galaxies, our study is meant to build upon such literature by holistically investigating the relative impact of each across time within a singular simulation.