Carbon Monoxide Observations of Dense Interstellar Clouds
Abstract
Millimeter observations of the J = Ol transition of 12C' have been made in 12 dark interstellar clouds. In four of these we have observed 11C1 lines at approximately one-third the intensity of the 12C1 lines. The high apparent 13C/12C ratio in carbon monoxide is due to large optical depth. Column densities of CO are about 1016 in these clouds. Theoretical arguments are presented showing that the J = Ol transition will be thermalized and the observed flux is used to obtain kinetic temperatures. is in the range K, with most of the clouds near 60 K. The temperature determined by the CO agrees with earlier values obtained for two clouds by Heiles, who used OH intensities.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1972
- DOI:
- 10.1086/180945
- Bibcode:
- 1972ApJ...174L..43P