An Interferometer Investigation of the 21-CENTIMETER Hydrogen-Line Absorption.
Abstract
The brightness distributions across five intense radio sources have been investigated in the hydrogenline absorption features, and the features have been resolved into Gaussian components. In some cases a variation of the absorption across the face of a source has been found, which, with the kinematical distance to the cloud in question, allowed a typical length to be estimated, which in turn allows estimations of densities and masses. Densities range from a few atoms per cubic centimeter to, in the case of a small cloud in front of Orion A, as much as 680 atoms/cm3. Masses range from a few solar masses up to perhaps a thousand solar masses in the cloud causing the deep line in Cas A. The absorption features in several other sources were investigated, and this material is briefly analyzed statistically, from which it is concluded that the distribution law for central optical depths is approximately , and that a line of sight, on the average, intersects 4.1 clouds/kpc in the galactic plane. There is some evidence that the density is up to twice this in the local spiral arm.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 1965
- DOI:
- 10.1086/148426
- Bibcode:
- 1965ApJ...142.1398C