Globular cluster luminosity functions and the Hubble constant from WFPC2 imaging: galaxies in the Coma I cloud

The membership of some galaxies in the nearby (d similar to 12 Mpc) Coma I cloud is uncertain. Here we present globular cluster luminosity functions (GCLFs) from the Hubble Space Telescope for two bright ellipticals which may belong to this group. After fitting the GCLF, we find a turnover magnitude of m(V)(0) = 23.23 +/- 0.11 for NGC 4278 and m(V)(0) = 23.07 +/- 0.13 for NGC 4494. Our limiting magnitude is about two magnitudes fainter than these values, making this data among the most complete GCLFs published to date. The fitted GCLF dispersions (similar to 1.1(m)) are somewhat smaller than typical values for other ellipticals. Assuming an absolute turnover magnitude of M(V)(0) = -7.62, and after applying a small metallicity correction, we derive distance modulii of (m - M) = 30.61 +/- 0.14 for NGC 4278 and 30.50 +/- 0.15 for NGC 4494. These distance estimates are compared to other methods, and lie within the published range of values. We conclude that both galaxies lie at the same distance and are both members of the Coma I cloud