Lunch talk on Oct. 12, 2022

The dusty ISM in high-redshift strongly lensed submillimeter galaxies

Speaker: Chentao Yang (Chalmers University of Technology)

Venue: Video Conference

Time: 12:30 PM, Wednesday, Oct. 12, 2022

Abstract: 

The discovery of a population of high-redshift dust-obscured submillimeter galaxies (SMGs) has revolutionized our understanding of galaxy evolution and star formation in extreme conditions. We have thus carefully selected a sample of the brightest strongly lensed SMGs. Using IRAM telescopes, we observed multiple transitions of the CO lines and analyzed the physical conditions of the molecular gas (2017, A&A 608, A144). The first multiple transitions of the submm H2O line survey at high-redshift were also conducted within our sample. Through these water lines, we have studied the properties of the far-IR radiation fields that they trace primarily, which provide us with new constraints of the warm dense, extreme dust-obscured regions (2016, A&A 595, A80). ALMA 0".2-0".4 follow-up of one of the brightest sources at z=3.63 in our sample shows very well agreement of the spatial distribution and kinematics between the CO, H2O, and H2O+ lines (2019, A&A, 624, A138). Interestingly, this merger shows a mismatch between the cold-dust continuum peak and the peak of the line emissions, suggesting a significant amount of cold gas is in the interacting region, similar to the local merger prototype, the Antennae Galaxies. In one of the merger companions, we have detected the 448 GHz H2O(423–330) line for the first time at high redshift (2020, A&A, 634, L3), which can probe into the deeply buried regions of the dusty ISM. Combining detection H2O lines previously, we have decomposed the dusty ISM structure into two components without any spatially resolve maps, one submillimeter optically thick core component with a ~ 0.1 kpc radius, which resembles characteristic properties of a maximum starburst and a ~ 1 kpc disk which dominates the total infrared luminosity. In parallel, we have conducted a series of line surveys in 3mm and 2mm bands with NOEMA and ALMA towards both starburst and quasar host galaxies, which resulted in detections of more than 20 molecular lines from 15 species from their rotational and vibrational spectra in each galaxy. The rich detections of molecules in multiple transitions enable us for the first time to have an unprecedented detailed view of the astrochemical process and reveal rich information about the physical properties and chemical compositions of the molecular gas, as well as the properties of the radiation fields that dominated by UV photons, X-rays and cosmic rays. The data also enables us to directly compare the ISM properties between a starburst and an AGN-dominated environment.