Annu. Rev. Astron. Astrophys. 1989. 27: 139-59 Copyright © 1989 by Annual Reviews. All rights reserved

5.12 Sculptor

Smaller and less luminous than Fornax, Sculptor is also somewhat simpler. It contains no globular clusters, but also none of the various indicators of recent star formation (HII regions, O and B stars). Its CMD (29, 59, 83, 95) shows a well-populated giant branch with a main sequence turnoff that DaCosta (29) detects and interprets as indicating either a low helium abundance or a slightly younger age than that of Galactic globular clusters. In addition, there are a few stars on the main sequence above the turnoff; these are either ``blue stragglers'' like those found in some Galactic globular clusters, or else they are young stars that represent a population similar to but much smaller than the intermediate-age stars of Fornax. Eskridge (40), from a global luminosity function for Sculptor, similarly concluded that there are blue strugglers, and he detected a range in the brightness of the turnoff suggesting that star formation occupied an interval of a few billion years before it stopped.

An additional matter of interest is the chemical inhomogeneity of the Sculptor giants. The spectra of Norris & Bessell (95) showed that either [Fe/H] or [Ca/H] varies, or both. Subsequent panoramic photometry by Smith & Dopita (114) confirmed the inhomogeneity and suggested that CN and Ca variations were correlated, similar to the case for Centauri.