Physical processes in the ISM

The Star Formation Law: Dense Cores and Star-Forming Galaxies Connection

Not scheduled

20m

MPE

contributed talk

Speaker

Yu Gao (Purple Mountain Observatory)

Description

We first show that the disk-averaged surface star formation rate (SFR) density has the tightest linear correlation with that of the dense molecular gas (traced by HCN), not the molecular gas (H2) or total gas (HI+H2). This is consistent with the tight FIR-HCN correlation established globally for both dense cores and star-forming galaxies near and far. The Kennicutt-Schmidt law that relates the disk-averaged surface densities of total gas and SFR appears to have no unique power-law slope with larger scatters since the correlation slopes change from ~1 for normal spirals to ~1.5 when (U)LIRGs are included. New observations using other dense molecular gas tracers, such as multi-transition CS lines, as well as high-J CO lines from Herschel SPIRE/FTS observations, further reveal that the SFR and dense gas relationship is linear. Additionally, the locally resolved SFR-HCN correlation in M51 is also consistent with the linear SFR-HCN correlation established globally in galaxies. All of these suggest that dense cores are the basic units contributing to the SFR and SFR might depend linearly upon the mass of dense molecular gas.