Further observations of radio recombination lines from the direction of the Galactic Centre
Abstract
The hydrogen recombination lines H351-alpha, H252-alpha, and H166-alpha have been used to investigate the properties of low-density ionized gas which lies in the direction of the Galactic Center. A limit of less than 5 K antenna temperature was found for the H351-alpha line, which implies that the electron density of the region is not less than 5/cu cm. Limits can be placed on the emission measure of lower density components in the interstellar medium in the direction of the Galactic Center. If T(e) = 5000 K is assumed, the emission measure of this component is less than 50 pc/cm to the 6th for electron densities less than 1/cu cm. H166-alpha and H252-alpha observations show that the low density gas extends over approximately 2.5 deg and coincides with a prominent absorption feature seen on low-frequency (29.9 MHz) continuum maps. It is concluded that the ionized gas arises from evolved H II regions which partially overlap in front of the Galactic Center.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- December 1980
- DOI:
- 10.1093/mnras/193.4.781
- Bibcode:
- 1980MNRAS.193..781H
- Keywords:
-
- Galactic Nuclei;
- H Alpha Line;
- Hydrogen Recombinations;
- Radio Spectra;
- Electron Density Profiles;
- Emission Spectra;
- H Ii Regions;
- Ionized Gases;
- Astrophysics