THE PROTO-GALAXY, GLOBULAR-CLUSTERS, AND QUASARS

Metallicities and horizontal-branch population gradients are used to d istinguish between two populations of Galactic halo globular clusters. The beta population of clusters appears to be almost coeval and occur s mainly at R < RE.. Clusters of the beta population were probably for med during a rapid Eggen, Lynden-Bell, & Sandage (ELS)-type collapse o f the inner proto-Galaxy. Clusters of the alpha population all occur a t R > 8 kpc. Many of these objects are found to lie on plunging retrog rade orbits. This suggests that clusters of the alpha population forme d during an extended Searle-Zinn-type merger and collapse phase. The r elative ages, metallicities, and locations of the alpha and beta popul ations indicate, as has also been suggested by Larson and by Lee, that the Galaxy formed inside out, with the dense proto-Galactic core form ing stars and clusters before its lower density halo. It is very tenta tively suggested that the metal-poor bulge cluster NGC 6287 might be t he oldest Galactic globular cluster. In a massive galaxy the quasar ph enomenon probably takes place after the bulk of its globular cluster s ystem has formed. A quasar outburst may have guillotined cluster forma tion in the nearby S0 galaxy NGC 3115, thus preventing the formation o f a thick-disk globular cluster population.