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

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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 omega Centauri.