TheHubble Space TelescopeKey Project on the Extragalactic Distance Scale. XXIV. The Calibration of Tully‐Fisher Relations and the Value of the Hubble Constant

This paper presents the calibration of BVRIH -0.5 Tully-Fisher relations based on Cepheid distances 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, H 0 , mainly concentrating on an I -band all-sky survey by Giovanelli and collaborators, consisting of total I magnitudes and 50% line width data for ~550 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 H 0 = 71 ± 4 (random) ± 7 (systematic). We have also investigated how the value of H 0 is affected by various systematic uncertainties, such as the internal extinction correction method used, Tully-Fisher slopes and shapes, a possible metallicity dependence of the Cepheid period-luminosity relation, and cluster population incompleteness bias.