Galactic evolution. II. Disk galaxies with massive halos.
Abstract
Models of galactic evolution are computed in which matter shed by dying halo stars accumulates in a smaller, more rapidly rotating disk. The models are simpler and more successful than one-zone (pure disk) models in that (1) the observed absence of low-metal-abundance low-mass dwarfs is expected, not anomalous and (2) the relative birthrate function (or IMF) need not be a strongly variable function of time in agreement with recent interpretations of observed stellar populations and neutral hydrogen in our own and other galaxies. Even a simple 'Salpeter' IMF for both disk and halo will produce an acceptable model. The model with a halo 'Salpeter' IMF, roughly one-quarter of the mass in the secondary disk, and approximately half the metals produced in the halo seems most compatible with observations of the metal abundance in low-mass stars, the deuterium abundance, halo planetary nebulae, and light from Population II stars, as well as with arguments on the stability of the disk.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1975
- DOI:
- 10.1086/153983
- Bibcode:
- 1975ApJ...202..353O
- Keywords:
-
- Galactic Evolution;
- Galactic Structure;
- Halos;
- Star Distribution;
- Stellar Evolution;
- Astronomical Models;
- Elliptical Galaxies;
- Galactic Radiation;
- Mathematical Models;
- Radio Astronomy;
- Spiral Galaxies;
- Stellar Mass;
- Astrophysics