On the existence of molecular hydrogen along lines of sight with low reddening.
Abstract
The existence of molecular hydrogen along lines of sight with low reddening (B-V color excesses not exceeding 0.03) is discussed for the stars HD 28497, Mu Col, Alpha Vir, Beta Cen, and Lambda Sco. The main observations are of the R(1) features, which for effective rotational temperatures above 200 K are the dominant source of H2 transitions. If the formation process for molecular hydrogen is similar to that for regions of greater reddening, the observations indicate that the neutral gas outside standard clouds may be partially in small clouds, though a more diffuse component seems to exist in some cases. Extremely high rotational temperatures are inferred for the H2 toward HD 28497. The possibility of formation of H2 through the reaction H(-) + H yields H2 + e(-) is briefly discussed. In any case, only small regions seem to contribute to the observed H2 column density.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1976
- DOI:
- 10.1086/154222
- Bibcode:
- 1976ApJ...204..750Y
- Keywords:
-
- H Lines;
- Hydrogen Clouds;
- Interstellar Gas;
- Molecular Energy Levels;
- Molecular Rotation;
- Stellar Spectra;
- Gas Density;
- Interstellar Extinction;
- Molecular Gases;
- Oao 3;
- Spectral Line Width;
- Tables (Data);
- Astrophysics