Measurements of Omega and Lambda from 42 high-redshift supernovae
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Open Access Publications from the University of California

Measurements of Omega and Lambda from 42 high-redshift supernovae

  • Author(s): Perlmutter, S
  • Aldering, G
  • Goldhaber, G
  • Knop, RA
  • Nugent, P
  • Castro, PG
  • Deustua, S
  • Fabbro, S
  • Goobar, A
  • Groom, DE
  • Hook, IM
  • Kim, AG
  • Kim, MY
  • Lee, JC
  • Nunes, NJ
  • Pain, R
  • Pennypacker, CR
  • Quimby, R
  • Lidman, C
  • Ellis, RS
  • Irwin, M
  • McMahon, RG
  • Ruiz-Lapuente, P
  • Walton, N
  • Schaefer, B
  • Boyle, BJ
  • Filippenko, AV
  • Matheson, T
  • Fruchter, AS
  • Panagia, N
  • Newberg, HJM
  • Couch, WJ
  • et al.

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We report measurements of the mass density, Omega_M, and cosmological-constant energy density, Omega_Lambda, of the universe based on the analysis of 42 Type Ia supernovae discovered by the Supernova Cosmology Project. The magnitude-redshift data for these SNe, at redshifts between 0.18 and 0.83, are fit jointly with a set of SNe from the Calan/Tololo Supernova Survey, at redshifts below 0.1, to yield values for the cosmological parameters. All SN peak magnitudes are standardized using a SN Ia lightcurve width-luminosity relation. The measurement yields a joint probability distribution of the cosmological parameters that is approximated by the relation 0.8 Omega_M - 0.6 Omega_Lambda ~= -0.2 +/- 0.1 in the region of interest (Omega_M <~ 1.5). For a flat (Omega_M + Omega_Lambda = 1) cosmology we find Omega_M = 0.28{+0.09,-0.08} (1 sigma statistical) {+0.05,-0.04} (identified systematics). 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 indicate that the cosmological constant is non-zero and positive, with a confidence of P(Lambda > 0) = 99%, including the identified systematic uncertainties. The best-fit age of the universe relative to the Hubble time is t_0 = 14.9{+1.4,-1.1} (0.63/h) Gyr for a flat cosmology. The size of our sample allows us to perform a variety of statistical tests to check for possible systematic errors and biases. We find no significant differences in either the host reddening distribution or Malmquist bias between the low-redshift Calan/Tololo sample and our high-redshift sample. The conclusions are robust whether or not a width-luminosity relation is used to standardize the SN peak magnitudes.

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