Annu. Rev. Astron. Astrophys. 1981. 19: 77-113 Copyright © 1981 by Annual Reviews. All rights reserved

5.3. Dwarf Spheroidal Systems

The dwarf spheroidal systems are probably satellites of the Galaxy, but represent small elliptical galaxies (-13 M_v < -8) in their own right since the spheroidals are morphologically distinct, being much less concentrated than Galactic globular clusters, and the Fornax system has its own globular clusters - all of which are metal poor (van den Bergh 1969, Danziger 1973). The proximity of these galaxies allows resolution of individual stars, and Demers, Kunkel & Hardy (1979) deduce [Fe/H] ~ - 0.5 for Fornax from the mean height of the giant branch, although recalibration of metal-rich globulars may lower this to perhaps -1.0. A planetary nebula found in Fornax (Danziger et al. 1978) yields [O/H] = - 0.6, [N/H] = - 0.7 [assuming uniform temperature and using solar values of Lambert (1978)], which may be consistent with an overall metallicity near -1.0 since O generally varies less than metals and N may be affected by self-enrichment. Other results for dwarf spheroidal systems are listed in Table 3.

In summary these are all metal-poor systems, as might be expected from the general abundance versus absolute magnitude relationship for elliptical galaxies (cf. Figure 7), and indeed the most massive (Fornax) is also the least metal poor.