| Abstract | We report on the first determination of the distance to the Coma Cluster from surface brightness fluctuation (SBF) measurements obtained from Hubble Space Telescope WFPC2 observations of the bright E0 galaxy NGC 4881 in the Coma Cluster and ground-based observations of the ``standard'' E1 galaxy NGC 3379 in the Leo-I group. Relative distances based on the I-band fluctuation magnitude, m̄I, are strongly dependent on the metallicity and age of the stellar population. However, the radial changes in the stellar populations of the two giant ellipticals NGC 3379 and NGC 4881 are well described by published Mg2 gradients, and the ground-based measurements of m̄I at several radial points in NGC 3379 are used to calibrate m̄I in terms of the Mg2 index. The distance to NGC 3379, assumed to be identical to the average SBF distance of the Leo-I group, is combined with the new SBF measurements of NGC 4881 to obtain a Coma Cluster distance of 102 +/- 14 Mpc. Combining this distance with the cosmic recession velocity of the Coma Cluster (7186 +/- 428 km s-1), we find the Hubble constant to be H0 = 71 +/- 11 km s-1 Mpc-1. Based on observations with the NASA/ESA Hubble Space Telescope and partially supported by NASA through grant HF-1066.01-94A awarded by the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract No. NAS5-26555. |
