Distances to the Virgo and Ursa Major clusters and a determination of H0

Multicolor CCD photometry of spiral galaxies within the Ursa Major and Virgo Clusters is presented and combined with accurate 21 cm H I line-width measurements in order to investigate the luminosity-line-width relations (Tully-Fisher hereafter TF relations) as a distance indicator. There is evidence for a slight morphological-type dependence of the TF relations, although the effect is present only at the 1-2 σ level. No difference in the slope of the TF relations is found between the two clusters, despite the considerable difference in densities and crossing times. A significant reduction in the dispersion of the TF relations is made possible from both accurate total magnitudes and accurate inclinations derived from ellipse fitting to galaxy isophotes. As a result, galaxies with inclinations as low as 30ᵈeg^ can now be included in the sample. In the Ursa Major Cluster, the intrinsic dispersion in the TF relations is found to be only ~0. 25 mag. We show that the use of aperture magnitudes (e. g. , H band data) results in an artificially large slope to the TF relations. The use of total magnitudes yields a slope of ~8 at near-infrared wavelengths, as a result L is proportional to V³. 2^ₘax_. An absolute calibration of the TF relations was obtained by fitting to three nearby galaxies with reasonably accurate distances: M31, M33, and NGC 2403. These systems establish the distance to the Ursa Major Cluster to be 15. 5 +/- 1. 2 Mpc and the mean distance to the Virgo Cluster to be 15. 6 +/- 1. 5 Mpc, with slightly greater uncertainty due to the possible presence of superposed galaxies. A determination of the value of the Hubble Constant was made by assuming a Virgocentric flow of 300 km s^-1^ at the Local Group, yielding a derived value of H₀_ = 85 +/- 10 km s^-1^ Mpc^-1^.