13Ci in high-mass star-forming clouds

A. R. Tieftrunk, K. Jacobs, C. L. Martin, O. Siebertz, A. A. Stark, J. Stutzki, C. K. Walker, G. A. Wright

Research output: Contribution to journalLetter

6 Scopus citations

Abstract

We report measurements of the 12C/13C abundance ratio in the three galactic regions G 333.0-0.4, NGC 6334 A and G 351.6-1.3 from observations of the 12CI 3P23P1 transition and the hyperfine components of the corresponding 13CI transition near 809 GHz. These transitions were observed simultaneously with the CO 7-6 line emission at 806 GHz with the AST/RO telescope located at the South Pole. From a simultaneous fit to the 12CI 3P23P1 transition and the HF components of the corresponding 13CI transition and an independent estimate of an upper limit to the optical depth of the 12CI emission we determine intrinsic 12CI/13CI column density ratios of 23 ± 1 for G 333.0-0.4, 56 ± 14 for NGC 6334 A and 69 ± 12 for G 351.6-1.3. As the regions observed are photon dominated, we argue that the apparent enhancement in the abundance of 13C towards G 333.0-0.4 may be due to strong isotope-selective photodissociation of 13CO, outweighing the effects of chemical isotopic fractionation as suggested by models of PDRs. Towards NGC 6334 A and G 351.6-1.3 these effects appear to be balanced, similar to the situation for the Orion Bar region observed by Keene et al. (1998).

Original languageEnglish (US)
Pages (from-to)L23-L26
JournalAstronomy and astrophysics
Volume375
Issue number2
DOIs
StatePublished - Jan 1 2001

Keywords

  • Atoms
  • Clouds
  • H II regions
  • ISM: abundances
  • Submillimeter

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Tieftrunk, A. R., Jacobs, K., Martin, C. L., Siebertz, O., Stark, A. A., Stutzki, J., Walker, C. K., & Wright, G. A. (2001). 13Ci in high-mass star-forming clouds. Astronomy and astrophysics, 375(2), L23-L26. https://doi.org/10.1051/0004-6361:20010939