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The ratio of carbon monoxide to molecular hydrogen in interstellar dark clouds
Abstract
LTE (C-13)O column densities are compared with the corresponding values of beam-convolved visual extinction at more than 100 locations within 38 different interstellar dark clouds. A roughly linear correlation is found to exist between these two quantities for visual extinctions in the range from about 1.5 to 5 mag. It is argued that this correlation can be extended up to about 10 mag and that the standard gas-to-extinction ratio can be expected to remain valid in the sources studied. The correlation of LTE (C-13)O column density with visual extinction is used to obtain an equation for the H2 column density associated with a given (C-13)O column density. It is shown that if the clouds studied are assumed to be chemically homogeneous, the equation obtained implies that at least 12% of all gas-phase carbon is in the form of CO. Comparison of the observational data with various theories proposed for molecule formation in dark clouds indicates that Langer's (1977) ion-molecule scheme accounts well for the observations when the fractionation channel of Watson et al. (1976) is included.
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Cited by
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“One can then correlate N(CO) or its isotopes against extinction to determine a conversion factor (Dickman 1978; Frerking et al. 1982).”
BackgroundCool Gas in High-Redshift Galaxies
Carilli, C. L., & Walter, F. (2013) · Annual Review of Astronomy and Astrophysics · doi:10.1146/annurev-astro-082812-140953 · Cited by 1,107
Molecular Gas at High Redshift
Solomon, P. M., & Vanden Bout, P. A. (2005) · Annual Review of Astronomy and Astrophysics · doi:10.1146/annurev.astro.43.051804.102221 · Cited by 868
Calibration of X-ray absorption in our Galaxy
Willingale, R., Starling, R. L. C., Beardmore, A. P., Tanvir, N. R., & O'Brien, P. T. (2013) · Monthly Notices of the Royal Astronomical Society · doi:10.1093/mnras/stt175 · Cited by 799
RE-EXAMINING LARSON'S SCALING RELATIONSHIPS IN GALACTIC MOLECULAR CLOUDS
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Metadata
- Authors
- Dickman, R. L.
- Venue
- The Astrophysical Journal Supplement Series
- Publisher
- American Astronomical Society
- Published
- 1978-08
- Volume
- 37
- Pages
- 407
- ISSN
- 0067-0049 (ISSN-L)
- 1538-4365
- OpenAlex
- W2067542394
- Cited by
- 423
- References
- 0
- Type
- conference abstract
- Language
- en
- Open access
- closed
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- Dickman, R. L. (1978). The ratio of carbon monoxide to molecular hydrogen in interstellar dark clouds. The Astrophysical Journal Supplement Series. https://doi.org/10.1086/190535
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