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tokens: We are grateful to the referee for thoughtful comments that improved the content and clarity of the paper. We thank Andrew Siemion for assistance observing remotely with the GBT, and Carl Heiles and Leo Blitz for useful discussions. JM received support from a National Science Foundation Graduate Research Fellowship. KA is supported by funding through Herschel , a European Space Agency Cornerstone Mission with significant participation by NASA, through an award issued by JPL/Caltech. This research used NASA Astrophysics Data System Bibliographic Services, the SIMBAD data base, operated at CDS, Strasbourg, France, and the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.