THE HUBBL E SPACE T EL ESCOPE KEY PROJECT ON THE EXTRAGALACTIC DISTANCE SCALE. XXIV. THE CALIBRATION OF TULLY-FISHER RELATIONS AND THE VALUE OF THE

This paper presents the calibration of Tully-Fisher relations based on Cepheid distances BV RIH ~0.5 to 21 galaxies within 25 Mpc and 23 clusters within 10,000 km s~1. These relations have been applied to several distant cluster surveys in order to derive a value for the Hubble constant, mainly concentrat- H 0 , ing on an I-band all-sky survey by Giovanelli and collaborators, consisting of total I magnitudes and 50% line width data for D550 galaxies in 16 clusters. For comparison, we also derive the values of H 0 using surveys in the B and V bands by Bothun and collaborators, and in H band by Aaronson and collaborators. Careful comparisons with various other databases from the literature suggest that the H-band data, which have isophotal magnitudes extrapolated from aperture magnitudes rather than total magnitudes, are subject to systematic uncertainties. Taking a weighted average of the estimates of Hubble constants from four surveys, we obtain