A DIAMETER EFFECT IN THE TULLY-FISHER RELATION AND ITS CONSEQUENCES

The southern spiral galaxies data of Mathewson et al. are analysed. In the clusters the deviations from an inverse Tully-Fisher relation are correlated with deviations from a diameter-magnitude relation. This i mplies an additional parameter in the Tully-Fisher relation. When this diameter effect is taken into account, regions away from the general direction of the Great Attractor show a smooth Hubble flow out to at l east V(CMB) = 8000 km s-1. The Mathewson et al. data in the general di rection of the Great Attractor are consistent with either a net flow t owards our Galaxy for objects at distances of about 8000 km s-1 or a q uiet Hubble flow at this distance. Direct measurements of all the quan tities required for a definitive application of the diameter term to t he absolute calibration of the Tully-Fisher relation are not yet avail able. However, the use of the best current estimates of the quantities involved leads to a provisional estimate for the Hubble constant of H -0 = 5 3 km s-1 Mpc-1 rather than about 85 km s-1 Mpc-1, the value obt ained when the diameter effect is neglected.