GLOBULAR CLUSTER SYSTEMS IN GIANT ELLIPTICALS: THE MASS/METALLICITY RELATION**Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Data from the Hubble Space Telescope taken with the Advanced Camera for Surveys/WFC camera have been used to investigate the globular cluster (GC) populations around six giant elliptical galaxies that are ∼40 Mpc distant. From these six fields, imaged in B and I, a total of more than 15,000 candidate GCs have been measured, of which 8000 or more are high-probability GCs. The data reach a limiting magnitude near MI ≃ −8, about 0.4 mag fainter …