BVI PHOTOMETRY OF GLOBULAR-CLUSTERS IN M87

We present CCD photometry in B, V, and I for a sample of globular clusters in the Virgo central giant elliptical galaxy M87. Our measured sample comprises ∼ 270 objects brighter than V ≃ 23.4 mag and with distances r ≳ 25″ (≳ 2 kpc) from the center of the galaxy. In agreement with the recent study of Cohen, we find no detectable gradient of mean cluster color (metallicity) in (B - V) or (V - I) with radial distance. The cluster system does, however, display a large dispersion in color at any radius, corresponding to σ[Fe/H] ≃ 0.6 about a mean metallicity 〈Fe/H]〉 = -1.1 according to our color index scale. The difference in mean color between the globular clusters and the underlying halo light of the galaxy itself, found previously by Strom and coworkers and by Cohen, shows up strongly in all of our color indices; we find virtually no clusters as red as the mean color of the halo stars at any radius.