Color gradients in the spheroids of galaxies.
Abstract
Photoelectric surface photometry designed to measure colors at low-brightness levels is presented for the stellar spheroids in galaxies of various morphological types. Radial color gradients of varying sizes are found in all galaxies examined. From a comparison of these data with integrated colors for composite stellar systems, it is concluded that metallicity is the dominant factor controlling the broadband colors of the stellar spheroids. Interpreting the color gradients as a metallicity effect, we show that disk-dominated spiral galaxies display the same metal-rich bulge, metal-poor halo structure seen in the Milky Way. Luminous spheroids, whether in spiral, S0, or elliptical galaxies, have smaller metallicity gradients than those in disk-dominated systems. Further, the metallicity in these giant spheroids is at or above solar out to radii of at least 50 kpc. The relation of these observations to current galaxy-formation theories is briefly discussed.
- Publication:
-
The Astronomical Journal
- Pub Date:
- July 1981
- DOI:
- 10.1086/112973
- Bibcode:
- 1981AJ.....86..981W
- Keywords:
-
- Abundance;
- Color;
- Galactic Structure;
- Stellar Spectrophotometry;
- Electrophotometry;
- Elliptical Galaxies;
- Galactic Evolution;
- Halos;
- Metallic Stars;
- Spiral Galaxies;
- Stellar Systems;
- Astronomy