W49A


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W49A = IRAS 19078+0901 -- the most massive and luminous star-forming region in our Galaxy, associated with a H II region.

  • (Roberts et al., 2011A&A...525A.107R)
    Facts: They mapped J = 4-3 transitions of HCN, H13CN, HC15N, HCO+, H13CO+, HC18O+, and HNC to check if W49A is a representative star forming regions in other galaxies.
    Results: The source is a complex mixture of infall and outflows. The main species are mostly optically thick and thus line ratios do not yield abundance ratios. Two clumps of infalling gas is at ~40K, less than the temperature of 100K at the cloud center.
    Conclusions: W 49A is a useful template of starburst galaxies. HCN/HNC/HCO+ line ratios can not be used as abundance ratios due to opacity effects. J=4-3 lines of HCN and HCO+ are better tracers of dense star-forming gas than 1-0 lines.
 

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