Title: Radial distribution of HI in disk-dominated galaxies
Speaker: Jing Wang, Kavli Institute for Astronomy and Astrophysics, Peking University
Host: Jianfeng Wu
Time: 14:30-16:30, Thursday, Oct 29 2020
Location: Physics Building 552
Abstract: HI is an important part of the bayonic cycle of galaxies, and sensitive sensor of environmental effects. We investigate how it is distributed in galaxies, and what clues it carries about galaxy evolution. We compiled a sample of more than 500 nearby galaxies covering over five orders of magnitude in H I mass and more than 10 B-band magnitudes to study the radial distribution of HI. The HI size-mass relation is remarkably tight with a scatter σ ∼ 0.06 dex, or 14 per cent. The scatter does not change as a function of galaxy luminosity, H I richness or morphological type. The relation is linked to the fact that dwarf and spiral galaxies have a homogeneous radial profile of H I surface density in the outer regions when the radius is normalized by DHI. It puts a strong constraint on the way that different processes, including gas inflow, star formation and feedback, balance in numerical models of galaxies. Based on the relation and homogeneous profile shape, we reasonably well predict the HI radial distribution based on the total HI mass for disk-dominated galaxies. This is good news, because HI has a different radial extension than stars, while it is very hard for radio observations to spatially resolve it. With predicted HI radial distributions for observed galaxies, we study how the HI within the stellar disks fuel star formation, and find a much tighter link than considering the whole HI disk. We also study how the HI beyond the stellar disks feels ram pressure when galaxies travel through clusters, and find that 40% of infalling HI rich galaxies in Coma-like clusters feel ram pressure in the HI outer disks at 2R200.
Jing Wang’s research interests are gas accretion onto galaxies; the cold gas and stellar structure of galaxies; the morphological transformation of galaxies; the relation between star formation and cold gas; the effect of cluster and group environments on galaxies.
Her research replies on multi-wavelength observational analysis, especially the 21 cm emission line data that probes atomic hydrogen gas. She has been actively involved in several large HI surveys, including GASS (and also its follow-up survey for molecular hydrogen, COLD GASS), Bluedisk, LVHIS, WALLABY, IMAGING, Apertif-shallow and MALS.