H0=43 +/- 11 KM S(-1) MPC(-1) BASED ON ANGULAR DIAMETERS OF HIGH-LUMINOSITY FIELD SPIRAL GALAXIES

Eight methods that favor the long extragalactic distance scale with H-0 near 50 km s-1 Mpc-1 are contrasted with two methods that require the short distance scale with H-0 near 85 km s-1 Mpc-1. A ninth method is developed in this paper that requires the long scale, based on relative linear diameters of luminous field spirals compared with the known linear diameter of M101. Eighty-six field galaxies with a similar morphology to M101 have been identified in the Revised Shapley-Ames Catalog. The linear diameter distribution of this sample shows the expected Malmquist bias as a function of redshift because the galaxies are selected from the flux-limited rather than a distance-limited catalog. The mean relative linear diameter of the sample, based on an arbitrary Hubble constant and corrected for Malmquist bias, is compared with the linear diameter of M101, known from its Cepheid distance. If the mean diameter of the unbiased field galaxy sample is the same as the linear diameter of M101, then H = 43 +/- 11 km s-1 Mpc-1. The correction of this local value ([v0] = 3000 km s-1) to the global cosmological Machian expansion frame is small, giving H-0 (global) < 50 km s-1 Mpc-1 by this method. If H-0 were in fact as high as 85, either (1) our adopted distance to M101 is too large by a factor of 2 or (2) M101 must be among the largest several Sc I galaxies within a distance of approximately 4000 km s-1. The first is impossible because of the known Cepheid distance. The second is unlikely because similar analysis of angular diameter data for field galaxies similar to M31 give the same result, showing either that M101 is not abnormal or that M101 and M31 are both equally abnormal, being among the largest galaxies of their class within the available distance-limited sample.