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Physics and Astronomy

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Departmental Colloquium

The Dark Side of H<sup>2</sup> in the Galaxy: ┬áThe Empire Strikes Back  
Guest Speaker
Prof. Loris Magnani  
Guest Affiliation
Department of Physics and Astronomy, The University of Georgia  
Thursday, January 19, 2017 3:30 pm - 4:30 pm  
Physics Auditorium (Rm 202)  
The idea that substantial molecular gas is present in the interstellar medium but is not detectable by the CO(1-0) emission line has become fairly prevalent in the last decade. This component hasbecome known as "dark gas", a term first suggested in a paper describing its properties and extent by Grenier, Casandjian and Terrier (2005). Their main conclusion is that the dark gas mass in the Milky Way is comparable to the molecular mass detected by CO(1-0) emission. More recent studies seem to corroborate this conclusion. A key element in deciding whether molecular gas may be dark or not depends on thesensitivity of the CO observations. Here we present very sensitive CO, OH, and CH observations of the outer regions of diffuse molecular gas which show that most of the dark molecular gas can be spectroscopically detected with sensitive enough observations.