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Wednesday 03 Jul 2019[Seminar] Shining Light on the Dark ISM

Dr Joanne Dawson - Macquarie University

4th Floor, Physics Building 14:00-15:00

It is now known that a significant fraction of the Milky Way ISM resides in a so-called "dark" phase, usually defined as a mixture of cold, optically thick HI and diffuse molecular hydrogen with densities that are insufficient to form and shield CO. However, open questions abound: How much dark gas exists in the Milky Way? How does it participate in the gas-to-stars cycle? How does environment affect the dark gas fraction? What are its characteristic physical and chemical conditions? I will discuss work that has aimed to detect, characterise and quantify dark gas in the Milky Way, with particular focus on the potential of alternative spectral line tracers such as OH and CH, and the importance of radio-frequency absorption measurements.

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