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Detection of C2H in cold dark clouds
Wootten, A.; Bozyan, E. P.; Garrett, D. B.; Loren, R. B.; Snell, R. L.
AA(Texas, University, Austi; Millimeter Wave Observatory, Fort Davis, Tex; Owens Valley Radio Observatory, Pasadena, Calif.), AB(Texas, University, Austin, Tex.), AC(Texas, University, Austin, Tex.), AD(Millimeter Wave Observatory; McDonald Observatory, Fort Davis, Tex.), AE(Texas, University, Austin; Millimeter Wave Observatory, Fort Davis, Tex.)
Astrophysical Journal, Part 1, vol. 239, Aug. 1, 1980, p. 844-854. Research supported by the Robert A. Welch Foundation (ApJ Homepage)
Publication Date:
NASA/STI Keywords:
Astronomical Spectroscopy, Free Radicals, Interstellar Gas, Nebulae, Abundance, Astronomical Catalogs, Cosmic Dust, Hydrocarbons, Hydrogen Clouds, Spatial Distribution
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We have surveyed a wide variety of interstellar clouds for the radical C2H including a number of cold dust clouds in which star formation is not known to be occurring (yet). We have also examined small dust clouds with single infrared sources or Herbig-Haro objects. Definite detections of C2H were made in 19 of the 30 regions examined with a further 3 possible detections. C2H was detected in 8 cold dust clouds. We have made extensive maps of the unusual dust cloud L1534 (TMC 1) and of the M17SW star-formation region. Smaller maps of B227, L43, and L134N were also made. The L1534 and M17SW maps show that the C2H distribution is well correlated with that of other molecular species in these clouds. The fractional abundance of C2H in cold clouds is typically found to be X(C2H) ≈ 6 × 10-9. The molecule HC3N is thought to have the same chemical precursor, C2H2+, as the C2H molecule. The ratio of abundances X(C2H)/X(HC3N) tests the chemical formation path, and it falls in the range of 3-10, consistent with the ratio expected from gas phase molecule formation models. There is no evidence, however, for a greater abundance decrease of X(C2H) with increasing density than for other molecular species in any of the clouds we have examined.

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