The Hubble Space Telescope Key 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 bas ed 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 clus ter 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 similar to 55 0 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 b and by Aaronson and collaborators. Careful comparisons with various other d atabases from the literature suggest that the H-band data, which have isoph otal magnitudes extrapolated from aperture magnitudes rather than total mag nitudes, 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 intern al extinction correction method used, Tully-Fisher slopes and shapes, a pos sible metallicity dependence of the Cepheid period-luminosity relation, and cluster population incompleteness bias.