Radio Recombination Line Observations of the Ionized Gas in the Galactic Center.
Abstract
We present radio recombination line observations of the various components of ionized gas in the galactic center. We find Sgr B2 to have a HeII zone with radius about 80% of that of the HII zone. This explains the beam-dependent He+/H+ variations. The smaller HeII zone could be due to preferential absorption of helium-ionizing photons by dust having a smoothly increasing absorptivity shortward of 912 Angstroms. The ionized gas in the extended thermal component is characterized by a low degree of excitation, as indicated by the observed upper limits to the once- and twice-ionized helium abundances. The ionizing agent was favored to be a large number of early B-type stars remaining from a huge burst of star formation that could have occurred at the Galactic Center about 10 to the 7th power years ago. Finally, we also studied Sgr A West, the HII region coincident with the kinematic nucleus of our Galaxy. The dynamics of the region are consistent with Keplerian rotation caused by the normal stellar population plus a 5 million solar mass non-stellar source at the center.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- December 1978
- Bibcode:
- 1978PhDT........12R
- Keywords:
-
- Physics: Astronomy and Astrophysics;
- Galactic Radiation;
- Interstellar Radiation;
- Ionized Gases;
- Radio Astronomy;
- Celestial Mechanics;
- Helium;
- Hydrogen;
- Kepler Laws;
- Photons;
- Spectrum Analysis;
- Astrophysics