Angular diameter determinations of radio supernovae and the distance scale

This paper details a new method of determining extragalactic distances and inferring H/sub 0/. The method combines the determinations of radial expansion velocities of supernovae via optical spectroscopy and the determinations of angular expansion velocities via Very Long Baseline Interferometry (VLBI). The data of two recent supernovae, SN 1979c in the galaxy M100 and SN 1980k in the galaxy NGC 6946, have been analyzed. The author obtained an estimate of the distance, D, to M100 of 11.4αν≤ D [Mpc] ≤24.4αν and a lower limit of the distance to NGC 6946 of D > 2.3αν [Mpc] with the factor αν coupling the expansion velocities of the ''radiosphere'' and the photosphere and being most likely ≥1. These distances are equivalent to 100αν/sup -1/≥H/sub 0/ [km s/sup -1/ Mpc/sup -1/]Δ 40αν/sup -1/ and H/sub 0/ < 230αν/sup -1/ km s/sup -1/ Mpc/sup -1/ for the two measurements, respectively