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Center for Astrophysics Research and Technologies Seminar Series Information


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New Demographic Insights into Massive Star and Cluster Formation

Thursday November 29, 2018
2:00 pm

 Presenter:  Peter Barnes (UFL)
 Series:  Center for Astrophysics Research and Technologies Seminar Series
 Abstract:  The formation, evolution, and lifetime of molecular clouds, and the corresponding timescale for star formation (SF) within them, has been debated for over 40 years. The chief issue has been whether SF is “fast” (meaning clouds form stars in just a few free-fall times, and are promptly disrupted by feedback) or “slow” (meaning that clouds exist for many free-fall times, and persist in one form or another despite SF).

I will describe a consistent set of results from the CHaMP+ThrUMMS surveys, based on high-quality molecular-line and continuum imaging and analysis of large numbers of molecular clouds, which seems to reconcile these two perspectives. This includes new mass conversion laws and SF tracers that reveal 2-3x more mass available for SF in molecular clouds than previously deduced, a long latency period before SF begins in a given cloud, and a locally semi-random mass accretion/dispersal pattern onto/from molecular clumps ("sedimentation"), but one which is a globally strong function of mass surface density ∑. Over a long enough time period, mass accretion dominates over dispersal, but the growth is near exponential, meaning that observable SF above a presumed ∑ threshold is concentrated in time to the last few Myr.

We are beginning to test this new sedimentation picture with numerical models, including forward-modelling of radiative transfer in CO isotopologues (upon which this interpretation is based). This new paradigm supports arguments for long clump lifetimes mediated by pressure confinement, with a terminal crescendo of star formation, suggesting a resolution to the 40-yr-old puzzle of the dynamical state of molecular clouds and their low star formation efficiency. This and ongoing work also has implications for the cosmic history of star formation and galaxy evolution, and refines our view of the typical environment of planet and solar system formation.
 Host:  Gregory Taylor
 Location:  Room 190, Physics & Astronomy

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