A determination of the carbon and oxygen isotopic ratios in the local interstellar medium.
Abstract
Isotopic abundance ratios of carbon and oxygen have been determined for the local interstellar medium by observations of carbon monoxide in three dark clouds. The 12C/13C ratio is obtained by measurements of the optically thin species 12C18O and 13C18O. The weighted mean ratio for the sources B5, B335, and L1262 is found to be 75+-8 (1 sigma), close to the solar system value of 89. From C17O data we find that 18O/17O = 2.8+-0.2, a factor of 2 smaller than the solar system value. The weighted mean double ratio (13C/12C)(16O/18O) is determined from the J=1-0 and J=2-1 13CO and C18O lines to be 7.0+-0.1 and 3.7+-0.4, respectively. Based on these observations, there is no conclusive evidence for a nonterrestrial 16O/18O ratio.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 1981
- DOI:
- 10.1086/183440
- Bibcode:
- 1981ApJ...243L..47W
- Keywords:
-
- Abundance;
- Carbon Isotopes;
- Interstellar Matter;
- Oxygen Isotopes;
- Carbon 13;
- Mass Ratios;
- Oxygen 17;
- Oxygen 18;
- Astrophysics