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

5.4 The SMC

Many of the papers mentioned in the previous paragraph also discuss the evolutionary history of the SMC, which is connected to the LMC by a bridge of H I and probably also by a common set of intergalactic experiences. Most studies indicate a somewhat more homogeneous and more uniform rate of star and heavy-element formation compared with the LMC, but this may be at least partly the result of there being significantly less information for the SMC, which has many fewer old clusters and fewer well-studied young clusters. There is general agreement, however, that the present mean heavy-element abundances in the SMC are smaller than those in the LMC by about a factor of two (98, 105, and many other references). The rate of cluster formation in the two Clouds differs by a factor of 8 (69), which is roughly the ratio of their masses, suggesting that the star formation rates of the two are very similar when normalized by mass.