简介: |
The global star formation (SF) laws — the relations between star-forming gas and SF rate (SFR) — are reexamined in a large sample of 181 local star-forming galaxies with infrared luminosities (SFR) spanning almost five orders of magnitude. The surface density of dense molecular gas (as traced by HCN) has the tightest and linear correlation with that of SFR (ΣSFR). The ΣSFR is a steeper function of the total (H2+HI) Σgas than that of molecular gas ΣH2. We further show that the SFR and a variety of dense gas tracers (e.g., HCN, CS, their high-J and high-J CO) are all linearly correlated for both the Galactic dense cores and star-forming galaxies near and far. This has immediate implications on the modes of SF in galaxies because the dense cores are the sites of active SF, and thus the basic units in contributing to SF. The SFR should depend linearly upon the mass of dense molecular gas (the SF law!). These ground-based observations of last decade and recent Herschel results highlight what the ALMA is delivering on the studies of "SF laws" across large redshift ranges over wide SF scales.
Bio: Professor Yu Gao is an astronomer and group leader in the Purple Mountain Observatory. His research focuses on observations of star formation and molecular gas in nearby galaxies. Prof. Gao received his B.S. from the University of Science and Technology of China in 1984, and his Ph.D. from Stony Brook University in 1996. He was a postdoc fellow in the University of Illinois, University of Toronto, Caltech/JPL, and later became a scientist at Caltech and later at the University of Massachusetts. Since 2004, he joined the Purple Mountain Observatory as a leading professor. Prof. Gao has published over 100 papers which have been cited more than 2600 times. He serves as an associate editor for Ap&SS, Sci. China, and is on the editorial board of PASJ and RAA. He is a recipient of the China NSFC Distinguished Young Scholar, and CAS Hundred Talents award. |
