Characterization of the Molecular Gas of Dusty Star Forming Galaxies across different Environments

The ground-state carbon monoxide (CO) J = 1 → 0 is the most direct tracer of total molecular gas in galaxies, which is the raw material for star formation. This line is also the indispensable anchor to establish the CO spectral line energy distributions (CO SLEDs) of galaxies. The CO SLED provides information about physical properties such as gas density, temperature, and excitation. In our work, we construct the CO SLEDs for a sample of 10 unlensed field SMGs selected
from the ALESS survey at z=1.6 to 2.7. Our work is based on ATCA CO J = 1 → 0 data from the large program COALAS and higher-J CO lines from our recent ALMA observations. We also compare the CO SLEDs of our field SMGs with those of field and (proto)cluster galaxies from the literature to get an insight into the excitation of CO lines in galaxies at different environments. Finally, we derive the sizes of the molecular gas at different transitions and compare them with rest-frame UV/optical/NIR measurements from HST and/or JWST. This study allows us to get insight into the build-up of early-type galaxies in the distant universe