The Peak Luminosity of Type Ia Supernovae and its Implications for the Cosmic Expansion Rate

Abstract

Supernovae of type Ia (SNe Ia) are confirmed to be the best distance indicators to derive the cosmic expansion rate. The dispersion of their peak lumi- nosity at optical bands (BV I) is approximate to 0.13mag, after taking into account the eects of the second parameters (i.e., the initial decline rate m15(B) and (B V ) color at maximum light). The local calibrations from HST indicate an absolute magnitude of 19.48 ± 0.08mag (in V band) for SNe Ia in spiral galaxies. The current expansion rate, H0, is found to be 63.6 ± 1.8 (random) ±5.7 (system- atic)kms 1 Mpc 1 . This value will decrease by 3% when the metallicity eect on the cepheid distances is considered. In addition, a marginal local outward flow of 4.0±4.5% within the velocity-distance of 7000km s 1 can be inferred from SNe Ia for the Einstein-de Sitter universe; however, this outward flow is only 2.2±4.4% for an accelerating expansion universe (which is supported by high-z SNe Ia).