On van den Bergh's Method for Measuring the Hubble Constant from Type Ia Supernovae

Abstract

In a recent Letter, van den Bergh used the explosion-model light-curve calculations of Hoflich & Khokhlov to calibrate the Hamuy et al. sample of remote Type Ia supernovae (SNe Ia) and obtained low values of H0 in the range 55-60 km s-1 Mpc-1. Citing a higher value of H0 obtained from Cepheid-based distance determinations to a few galaxies in the Virgo Cluster complex, van den Bergh concluded that unless the Cepheid distance scale is wrong, the models of Hoflich & Khokhlov must be much too bright or much too red. Here we calibrate the same sample of remote SNe Ia in the same way as was suggested by van den Bergh, but now relying on Cepheid-based determinations of the distances to SN Ia parent galaxies instead of the explosion-model light-curve calculations. No corrections for extinction of the SNe Ia are required, and no SNe Ia need be excluded on grounds of peculiarity. We obtain H0 = 57 ± 5 km s-1 Mpc-1. Various subsamples of the data give H0 in the range 54-60 km s-1 Mpc-1. This shows that the fault lies not with the SN Ia models, nor with Cepheids, but with the hazardous route through the Virgo complex.