Using distant type Ia supernovae to measure the cosmological expansion parameters

A comprehensive analysis of two recent collections of distant Type Ia supernovae is presented. The method used is both simple and rigorous. Correcting the absolute magnitudes for the measured decline rates yields in nearly all cases a dispersion consistent with measurement uncertainties, showing from these data that Type Ia supernovae are remarkably reliable standardized candles. With 26 supernovae between 0.01 < z < 0.1 and a cosmological sample of six supernovae between 0.35 < z < 0.45, the Cepheid-based Type Ia supernova absolute magnitude scale leads to a Hubble constant H0 = 60 ± 5 km s−1 Mpc−1 and a deceleration constant q0 of 0.385 ± 0.36. We note the implications of these results for the age of the universe both with and without the introduction of a cosmological constant. This leads to further constraints on the mass densityΩM of the universe when comparison is made with the age of the universe derived from globular clusters.