Star Formation Efficiencies and Lifetimes of Giant Molecular Clouds in the Milky Way - Astrophysics > Astrophysics of GalaxiesReport as inadecuate




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Abstract: We use a sample of the 13 most luminous WMAP Galactic free-free sources,responsible for 33% of the free- free emission of the Milky Way, to investigatestar formation. The sample contains 40 star forming complexes; we combine thissample with giant molecular cloud GMC catalogs in the literature, to identifythe host GMCs of 32 of the complexes. We estimate the star formation efficiencyepsilon GMC and star formation rate per free-fall time epsilon ff. We find thatepsilon GMC ranges from 0.002 to 0.2, with an ionizing luminosity-weightedaverage epsilon GMC = 0.08, compared to the Galactic average = 0.005. Turningto the star formation rate per free-fall time, we find values that range up toepsilon ff = 1. Weighting by ionizing luminosity, we find an average ofepsilon ff = 0.16 - 0.24 depending on the estimate of the age of the system.Once again, this is much larger than the Galaxy-wide average value epsilon ff =0.008. We show that the lifetimes of giant molecular clouds at the mean massfound in our sample is 17 plus or minus 4 Myr, about two free-fall times. TheGMCs hosting the most luminous clusters are being disrupted by those clusters.Accordingly, we interpret the range in epsilon ff as the result of atime-variable star formation rate; the rate of star formation increases withthe age of the host molecular cloud, until the stars disrupt the cloud. Theseresults are inconsistent with the notion that the star formation rate in MilkyWay GMCs is determined by the properties of supersonic turbulence



Author: Norman Murray

Source: https://arxiv.org/







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