The Globular Cluster Systems in the Coma Ellipticals. I. The Luminosity Function in NGC 4874 and Implications for Hubble’s Constant**Based on observations obtained 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.

We have used deep Hubble Space Telescope WFPC2 images in V (F606W) and I (F814W) to measure the luminosity distribution of the globular clusters in NGC 4874, the central cD galaxy of the Coma cluster. We find the "turnover" point of the globular cluster luminosity function (GCLF) to lie at V = 27.88 ± 0.12, while the overall GCLF shape matches the standard Gaussian-like form with dispersion σV = 1.49 ± 0.12. We use the GCLF as a standard candle …