Populations and mass distributions in spiral galaxies.
Abstract
The structure of spiral galaxies is investigated on the basis of luminous-population distributions, and the implications for the mass distribution in the disks and for hypothetical dark halos are considered. Two distinct populations (but no significant intermediate components) are identified: a disk with relatively narrow abundance range, mass/luminosity ratio 5-10 solar-mass/solar-B-luminosity, and velocity dispersion (of older stars) caused by molecular-cloud encounters; and a spheroid (with a small age range but kinematic and chemical inhomogeneities) which may have formed before the collapse of the protogalaxy. It is shown that a dark halo containing at least half the mass out to the optical radius is required to stabilize the disk. The significance of the dark halo for the process of chemical enrichment in the early history of galaxies depends on whether it is formed along with the luminous halo stars, represents a separate star population, or consists of massive neutrinos.
- Publication:
-
Publications of the Astronomical Society of Australia
- Pub Date:
- 1983
- DOI:
- 10.1017/S1323358000016660
- Bibcode:
- 1983PASA....5..136V
- Keywords:
-
- Galactic Rotation;
- Galactic Structure;
- Mass Distribution;
- Spiral Galaxies;
- Disks;
- Mass To Light Ratios;
- Milky Way Galaxy;
- Stellar Motions;
- Astrophysics