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The Earliest Stages of High-Mass Star Formation
Wednesday, November 07, 2018 - 3:30pm PST
Although the formation of low-mass stars is broadly understood, understanding high-mass star formation is much more difficult due to their rarity, their clustered environments, their short time scales, and their ability to disrupt their natal environment. I will discuss recent progress in the study of high-mass star formation. Two competing theories, “competitive accretion” and “turbulent core accretion,” make distinct quantitative predictions about the internal structure of the young, cold clumps from which stars form. Specifically, these predictions address the overall collapse of high-mass molecular clumps, the gravitational boundedness of clumps, and the mass of the youngest progenitor “pre-stellar’’ cores. Molecular line and continuum studies using centimeter, millimeter, and infrared wavelength telescopes have now identified such young clumps and are beginning to test these predictions. Specifically, our team finds (1) asymmetric HCO+ line profiles toward high-mass clumps definitively indicate global collapse, (2) core masses in the youngest clumps are typically ~2-4 Msun, close to the Jeans' mass, and (3) the cores have small virial parameters, so gravity dominates over turbulence. The evidence to date slightly favors the “competitive accretion” model.