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What Controls the Rate of Star Formation: Common Features and Common Myths
Wednesday, December 19, 2018 - 3:30pm PST
University of Texas
The relations between star formation and gas have received renewed attention. We combine studies on scales ranging from local (within 0.5 kpc) to distant galaxies to assess what factors contribute to star formation. These include studies of star forming regions in the Milky Way, the LMC, nearby galaxies with spatially resolved star formation, and integrated galaxy studies. We test which tracers provide the best predictor of star formation rate. The star formation ``efficiency," defined as star formation rate divided by mass, spreads over a large range when the mass refers to molecular gas; the standard deviation of the log of the efficiency decreases by a factor of three when the mass of relatively dense molecular gas is used rather than the mass of all the molecular gas. We suggest ways to further develop the concept of ``dense gas" to incorporate other factors, such as turbulence and magnetic fields. We also consider whether commonly accepted ideas, such as the concept of molecular clouds as bound entities or the idea that the free-fall rate determines the speed of star formation, are actually myths.