The Galactic Halo
Abstract
A survey of observations and analyses of phenomena associated with the theoretical galactic halo (GH) or corona is presented, with a focus on research performed at Queen's University in Belfast. The origin and main features of the GH theory are outlined, and the previous observations supporting it are reviewed, including visible clouds at high Galactic latitudes (z), UV absorption lines in the GH, absorption in the haloes of other galaxies, and early-type stars in the GH. The Queen's University work is based on spectroscopic observations of 18 high-z OB stars obtained at high resolution (lambda/delta lambda = 20,000) in the 389-402 and 576-604-nm bands with the Anglo-Australian Telescope in September 1979 and 1980. The stars are found to be normal, with no evidence of subluminosity, and to lie at z distances of about 0.3-3.5 kpc; hence they are considered good tracers of GH gas. A velocity dependence of the N(Na I)/N(Ca II) ratio is observed and attributed to Ca sputtering from grain surfaces rather than to the collisional ionization of Na I.
- Publication:
-
Irish Astronomical Journal
- Pub Date:
- September 1982
- Bibcode:
- 1982IrAJ...15..309K
- Keywords:
-
- Halos;
- Intergalactic Media;
- Milky Way Galaxy;
- Absorption Spectra;
- Interstellar Gas;
- Quasars;
- Stellar Atmospheres;
- Ultraviolet Astronomy;
- Astrophysics