A study of 42 type Ia supernovae and a resulting measurement of ΩM and ΩΛ

A search for cosmological supernovae has discovered over 75, most of which are type Ia supernovae. There is strong evidence from measurements of nearby type Ia supernovae that they can be considered as distance indicators or "standard candles" after correction for the width (time scale stretch parameter) of the individual light curves. Measurements and analysis are completed on 42 of these distant, z = 0.18 to 0.83, supernovae. These supernovae, together with 18 "nearby", z < 0.1 supernovae from the Calan/Tololo Supernova Survey allow us to measure the ratio of the matter density of the universe to the critical density Omega(M), together with the normalized cosmological constant Omega(Lambda), the energy density of the vacuum. For a flat universe, i.e. Omega(M) + Omega(Lambda) = 1, we obtain Omega(M) = 0.28(-0.08)(+0.09) (statistical) (+0.05)(-0.04) (systematic). The data are strongly inconsistent with a Lambda = 0 flat cosmology, the simplest inflationary universe model. An open, Lambda = 0 cosmology also does not fit the data well: the data strongly suggest that the cosmological constant is non-zero and positive, with a confidence of P(Lambda > 0) > 99%. (C) 1998 Elsevier Science B.V. All rights reserved.