Bias Properties of Extragalactic Distance Indicators. VI. Luminosity Functions of M31 and M101 Look-alikes Listed in the RSA2: H0 Therefrom

Galaxies whose morphologies are similar to M 101 (Sc I) and M3 1 (Sb I- II) are listed in two tables. The selection is made by inspecting direct images of Shapley-Ames galaxies in the recent Carnegie Atlas of Galaxies. Absolute magnitudes, calculated from redshifts, give mean values of <M(m)_B_)+5 log(H_0_/50) for the look-alikes in the flux-limited samples of the tables. These kinematic absolute magnitudes are then reduced to the T = 5, L = 1 morphological type and luminosity class of M101, and T = 3, L= 2 type and class of M31 by the tables in Paper V of this series. Reductions are made in parallel using fully corrected apparent magnitudes from both the RSA2 and the RC3 catalogs. Corrections to form a distance- limited sample to account for observational selection bias are made using Spaenhauer diagrams to assess the extent of the bias effect. The intrinsic dispersion of this reduced, look-alike, distance indicator is σ(M)~0.65 mag, similar to the intrinsic dispersion of the Tully- Fisher indicator for field and for cluster galaxies. Calibration of the resulting combined distance-limited look-alike luminosity function is made using the II fundamental calibrators from Paper V. The calibrated data using RSA2 apparent magnitudes for the combined M101 and M31 look- alike sample give H_0_ = 55+/-5 km s^-1^ Mpc^-1^. The data using RC3 apparent magnitudes, which require that we treat the M101 and M31 lists separately, give H_0_ = 53+/-4 km s^-1^ Mpc^-1^ for M101 look-alikes and H_0_= 48+/-4 km s^-1^ Mpc^-1^ for the M31 look-alikes. The short distance scale with H_0_ ~ 85 is impossible at the 6 σ(M) level using the totality of the data here.