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PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-2135
DTSTART:20110310T213000Z
DURATION:PT1H0M0S
DTSTAMP:20240328T123414Z
LAST-MODIFIED:20110303T140901Z
LOCATION:4421 Sterling Hall
SUMMARY:The Formation of Molecular Clouds and Massive Stars\, Astronom
y Colloquium\, Mordecai-Mark Mac Low\, American Museum of Natural Hist
ory
DESCRIPTION:In this talk I consider two questions. First\, I investig
ate the formation of molecular clouds from diffuse interstellar gas.
It has been argued that the midplane pressure controls the fraction of
molecular hydrogen present\, and thus the star formation rate. Altern
atively\, I and others have suggested that the gravitational instabili
ty of the disk controls both. I present numerical results demonstrati
ng that the observed correlations between midplane pressure\, molecula
r hydrogen fraction\, and star formation rate can be explained within
the gravitational instability picture. Second\, I discuss how ionizat
ion affects the formation of massive stars. Although most distinctive
observables of massive stars can be traced back to their ionizing radi
ation\, it does not appear to have a strong effect on their actual for
mation. Rather\, I present simulations suggesting that stars only ion
ize large volumes after their accretion has already been throttled by
gravitational fragmentation in the accretion flow. At the same time th
ese models can explain many aspects of the observations of ultracompac
t H II regions.<\;br>\;
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URL:https://www.physics.wisc.edu/events/?id=2135
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