Isotopologues of dense gas tracers in nearby infrared bright galaxies
AffiliationUniv Arizona, Dept Astron
Keywordsgalaxies: individual: M 82, NGC 3079, NGC 3504, IC 694, NGC 4418, MrK 231, NGC 6946, NGC 6240
MetadataShow full item record
PublisherOXFORD UNIV PRESS
CitationLi, F., Wang, J., Fang, M., Li, S., Zhang, Z. Y., Gao, Y., & Kong, M. (2020). Isotopologues of dense gas tracers in nearby infrared bright galaxies. Monthly Notices of the Royal Astronomical Society, 494(1), 1095-1113.
Rights©2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.
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AbstractWe present 1 and 3 mm observations of the C-13- and N-15-bearing isotopologues of dense gas tracers towards eight nearby infrared-bright galaxies. With the Institut de Radioastronomie Millimetrique 30-m telescope, we observed the J = 1-0 transitions of (HCN)-C-13, (HCN)-N-15, (HCO+)-C-13 , (HNC)-C-13, and (HNC)-N-15 towards M 82, NGC 3079, IC 694, Mrk 231, and NGC 6240. The J = 3-2 transition of (HCN)-C-13 was obtained in M 82, NGC 3079, NGC 3504, NGC 4418, NGC 6240, and NGC 6946, using the 10-m Submillimeter Telescope (SMT). We report the first detections of (HNC)-C-13 J = 1-0 and (HCN)-C-13 J = 3-2 in M 82, and (HCN)-C-13 J = 3-2 in NGC 6240 and NGC 3079. We find different line profiles between the J = 1-0 and 3-2 transitions of (HCN)-C-13 in both M 82 and NGC 3079. The optical depths of HCN show significant variations among the sample, indicating that dense gas masses estimated from the line luminosities of HCN J = 1-0 and 3-2 should be treated with caution for individual galaxies. Optical depth of HCN J = 3-2 is found to be higher than that of HCN J = 1-0 in M 82, NGC 3079, NGC 4418, and NGC 6240, which indicates that ground state transitions of dense gas tracers might better trace the star-forming gas than the high-J transitions. Based on the (HCN)-C-13/(HCN)-N-15 line ratios, with the double-isotopic method, low N-14/N-15 abundance ratios of 120 and 140 are found in NGC 3079 and Mrk 231, respectively.
VersionFinal published version
SponsorsNational Key Research and Development Program of China