On the intensity of rotational lines of H2 and HD from dense interstellar clouds.
Abstract
Summary. It is shown that the intensities of rotational lines of molecular hydrogen and hydrogen deuteride at 12.3, 17.0, 28.2 and 28. can be appreciably lower than earlier predictions, if realistic excitation and deexcitation rates by collisions are taken into account. Furthermore, dust always concomitant with these molecular species in a dense cloud will absorb most of the line emission so that no reliable values on the absolute amount of the molecules will be obtained. A detailed study of atmospheric transmissions yields, however, that the lines at 17 and 28.2 can be recorded from airplane altitudes, so that at least rotational temperatures in the cloud's boundary layer may be obtained with presently available techniques. Key words: interstellar H2 - dense clouds infrared astronomy
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 1974
- Bibcode:
- 1974A&A....36..211D
- Keywords:
-
- Hydrogen Clouds;
- Infrared Astronomy;
- Interstellar Matter;
- Line Spectra;
- Molecular Rotation;
- Radiant Flux Density;
- Absorption Cross Sections;
- Absorption Spectra;
- Cosmic Dust;
- Deuterides;
- Emission Spectra;
- Interstellar Extinction;
- Molecular Excitation;
- Molecular Ions;
- Optical Thickness;
- Astrophysics