The luminosity of supernovae of type Ia from TRGB distances and the value of H_0

Abstract

Distances from the tip of the red-giant branch (TRGB) in the halo Population of galaxies - calibrated through RR Lyr stars as well as tied to Hipparcos parallaxes and further supported by stellar models - are used to determine the luminosity of six nearby type Ia supernovae (SN 2011fe, 2007sr, 1998bu, 1989B, 1972E, and 1937C). The result is M_V^corr = -19.41 +/- 0.05. If this value is applied to 62 SNe Ia with 3000< v < 20,000 km/s a large-scale value of the Hubble constant follows of H_0 = 64.0 +/- 1.6 +/- 2.0. The SN HST Project gave H_0 = 62.3 +/- 1.3 +/- 5.0 from ten Cepheid-calibrated SNe Ia (Sandage et al. 2006). The agreement of young Population I (Cepheids) and old, metal-poor Population II (TRGB) distance indicators is satisfactory. The combined weighted result is H_0 = 63.7 +/- 2.3 (i.e. +/-3.6%). The result can also be reconciled with WMAP5 data (Reid et al. 2010).