Abstract
A growing body of evidence has been supporting the existence of so-called “dark molecular gas” (DMG), which is invisible in the most common tracer of molecular gas, i.e., CO rotational emission. DMG is be-lieved to be the main gas component of the intermediate extinction region from Av~0.05-2, roughly corresponding to the self-shielding threshold of H2 and 13 CO. To quantify DMG relative to HI and CO, we are pursuing three observational techniques; HI self-absorption, OH absorption, and THz C + emission. In this paper, we focus on preliminary results from a CO and OH absorption survey of DMG candidates. Our analysis shows that the OH excitation temperature is close to that of the Galactic continuum back-ground and that OH is a good DMG tracer co-existing with molecular hydrogen in regions without CO. Through systematic “absorption mapping” by the Square Kilometer Array (SKA) and ALMA, we will have unprecedented, comprehensive knowledge of the ISM components including DMG in terms of their temperature and density, which will impact our understanding of galaxy evolution and star formation profoundly.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
