Photodissociation and the HI Content of Galaxies: Atomic Hydrogen as a Tracer for Molecular Gas
Ron Allen
STScI Baltimore
Young massive stars produce Far-UV photons which dissociate the molecular gas on the
surfaces of their parent molecular clouds. Of the many dissociation products which
result from this unavoidable ``back-reaction'', atomic hydrogen is arguably the
easiest to observe through its radio 21-cm hyperfine line emission. In this talk, I
briefly review the physics of the process by which H2 is photodissociated into HI,
and describe a simple model which has been used to estimate the column density N(HI)
of photodissociated HI which appears on the surfaces of molecular clouds. Several HI
features observed in the Galaxy are ascribed to this process. Recent applications of
the model using FUV and HI images of several nearby galaxies yield new ways of
studying global star formation and the properties of giant molecular clouds over
large areas of the galaxy disks.
Date: | Mardi, le 6 avril 2010 |
Heure: | 11:30 |
Lieu: | Université Laval |
| Pavillon Alexandre-Vachon, local 1661 |
Contact: | Jonathan Heiner |
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