Observations of CO in HI clouds: Correlations with HI and OH
Abstract
A search was made for the CO 2.6-mm line in 76 directions showing strong HI 21-cm absorption. It was detected in 21 directions, most of them corresponding to diffuse clouds. The CO and HI lines approximately coincide in velocity, but there is no apparent correlation between the CO line intensities and HI optical depths, column densities or spin temperatures. The smaller width of the CO line suggests that CO is confined in clumps within the diffuse clouds. The CO velocities are strongly correlated with those of the OH absorption lines; this indicates that the two species coexist within the molecular clumps; the CO lines are somewhat wider, however, which may be attributed to optical depth effects. The ratio of the line widths is used to estimate CO physical conditions within several clouds.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 1981
- Bibcode:
- 1981A&A...101..401K
- Keywords:
-
- Carbon Monoxide;
- Hydrogen Clouds;
- Hydroxyl Emission;
- Interstellar Matter;
- Molecular Clouds;
- Spectral Line Width;
- Extragalactic Radio Sources;
- Optical Thickness;
- Radio Astronomy;
- Astronomy