The Australia Telescope National Facility Colloquium | |||
15:00-16:00 Wed 20 Nov 2013 | |||
Snezana Stanimirovic(University of Wisconsin) Snezana Stanimirovic Colloquium -- Importance of atomic hydrogen in molecule and star formationRecent observations of galaxies on parsec and kilo-parsec scales show a remarkably uniform neutral hydrogen (HI) surface density. The steady-state models for H2 formation explain this HI saturation as a threshold surface density required to shield molecular hydrogen (H2) against photodissociation, and predict it should depend only on metallicity. However, several important questions remain regarding the role of HI in H2 shielding. For example, while the theoretical shielding HI comes purely from the cold neutral medium (CNM), the observed HI is a mixture of both cold and warm HI (CNM and WNM), and could be underestimated due to the presence of high optical depth HI.
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