A Distant HII Region In The Galaxy
- 1 January 1965
- journal article
- research article
- Published by CSIRO Publishing in Australian Journal of Physics
- Vol. 18 (1) , 91-96
- https://doi.org/10.1071/ph650091
Abstract
It has long been realized that 21 cm absorption studies can provide information about the distance of unidentified radio sources. When the radiation from a continuum source is absorbed by neutral hydrogen clouds in the foreground, an observation of the radial velocity range over which the absorption occurs indicates the position of the source in relation to the various hydrogen features along the line of sight. Whenever absorption effects can be seen, we can immediately tell whether the source concerned is galactic or extragalactic; if it is galactic, we can then place limits on its distance.Keywords
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