Molecular abundances in the Magellanic Clouds
نویسندگان
چکیده
The first definite discoveries of extragalactic deuterium are reported. DCO has been detected in three and DCN has been measured in one star-forming region of the Large Magellanic Cloud (LMC). While the HCO/DCO abundance ratios are found to be 19± 3, 24 ± 4, and 67 ± 18 for N113, N44BC and N159HW, respectively, a HCN/DCN abundance ratio of 23 ± 5 is obtained for N113. These results are consistent with a gas temperature of about 20K and a D/H ratio of about 1.5× 10, consistent with that observed in the Galaxy. If the cloud temperature is closer to 30K, then a D/H ratio is required to be up to an order of magnitude larger. Because this ratio provides a lower limit to the primordial D/H ratio, it indicates that the baryon mass density alone is unable to close the universe.
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