Speaker
Description
The Atacama Large Aperture Submillimeter Telescope (AtLAST) will open a new window on the cold molecular gas content of galaxies across cosmic time. With its wide-field mapping, high surface-brightness sensitivity, and ability to detect low-J CO emission, AtLAST will trace diffuse, extended molecular gas in dense environments at high redshift. This is key to understanding how environmental processes shape galaxy evolution and revealing the origin of the intracluster medium.
We demonstrate the feasibility of this approach using deep CO(1–0) observations with the Australian Telescope Compact Array (ATCA). In the Spiderweb protocluster (z=2.2), we discovered massive (>40 kpc), extended molecular gas reservoirs in star-forming galaxies - unexpected given predictions of environmental suppression.
Within our ATCA Large Program COALAS, we obtained 475 hours of observations, identifying such reservoirs in a significant fraction of galaxies and assembling the largest sample to date. These reservoirs likely trace early stages of the proto-intracluster medium, indicating that dense environments at z=2 host diffuse molecular gas.
Such detections remain observationally challenging. AtLAST will overcome these limitations through sensitive, large-area surveys, enabling statistical studies across environments. This will allow us to quantify how environment affects gas content, morphology, and star formation, and trace the emergence of the proto-intracluster medium in the early Universe.