VRI PHOTOMETRY OF GLOBULAR-CLUSTERS IN VIRGO AND LEO ELLIPTICALS

We present VRI photometry for the globular cluster systems (GCS's) of ten elliptical and SO galaxies in Virgo and Lee. We find that the V-I color (metallicity) distributions are quite different from galaxy to g alaxy. One extreme is represented by NGC 4374 with a narrow, blue dist ribution. NGC 4472 has a very broad, uniform distribution in color, co rresponding to - 1.8<[Fe/H]<+0.47. At the other extreme is NGC 4365, w hich is weighted towards red colors, and possibly has a peculiar lumin osity function. We suggest that this variation of GCS metallicity depe nds on environment, with formation of high metallicity globular cluste rs inhibited in higher density environments. We compare color-color pl ots of the GCS's of these galaxies with the Milky Way GCS and with int egrated isochrones. We find good agreement with the galaxies studied h ere except that the isochrones predict colors which are slightly too b right in the I band for metal-rich clusters. We also consider the radi al GC color distributions in these galaxies. We find evidence for a V- T color gradient only in NGC 4374, in the sense of redder clusters tow ard the center of the galaxy but warn that possible systematic effects must be ruled out with new data. Lastly, using the surface brightness fluctuation distances to these galaxies, we find supporting evidence for the universality of the globular cluster luminosity function.