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The Global Star Formation Laws in Star-forming Galaxies

Time:2015-11-20 09:35Source:未知 Duty editor:administrator

Title:The Global Star Formation Laws in Star-forming Galaxies

Speaker:Yu Gao (Purple Mountain Observatory)

Time:2015-11-20 09:35

Place:Room 212, Astronomy Building

The global star formation (SF) law — the relation between star-forming gas
and SF rate (SFR) — is 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. The ΣSFR is a steeper
function of the total gas Σgas (molecular gas with atomic gas) 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 in our Milky Way 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 the active SF, and thus the basic
units in contributing to the 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 and on most SF
scales.

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