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Title: Measurements of Omega and Lambda from 42 high-redshift supernovae
Author: Perlmutter, S.
Aldering, G.
Goldhaber, G.
Knop, R.A.
Nugent, P.
Castro, P.G.
Deustua, S.
Fabbro, S.
Goobar, A.
Groom, D.E.
Hook, I. M.
Kim, A.G.
Kim, M.Y.
Lee, J.C.
Nunes, N.J.
Pain, R.
Pennypacker, C. R.
Quimby, R.
Lidman, C.
Ellis, R. S.
Irwin, M.
McMahon, R. G.
Ruiz Lapuente, Ma. Pilar
Walton, N.
Schaefer, B.
Boyle, B. J.
Filippenko, A. V.
Matheson, T.
Fruchter, A.S.
Panagia, N.
Newberg, H.J.M.
Couch, W.J.
Keywords: Cosmologia
Issue Date: 1998
Publisher: Institute of Physics (IOP)
Abstract: We report measurements of the mass density, ΩM, and cosmological-constant energy density, ΩΛ, of the universe based on the analysis of 42 type Ia supernovae discovered by the Supernova Cosmology Project. The magnitude-redshift data for these supernovae, at redshifts between 0.18 and 0.83, are fitted jointly with a set of supernovae from the Calán/Tololo Supernova Survey, at redshifts below 0.1, to yield values for the cosmological parameters. All supernova peak magnitudes are standardized using a SN Ia light-curve width-luminosity relation. The measurement yields a joint probability distribution of the cosmological parameters that is approximated by the relation 0.8ΩM-0.6ΩΛ≈-0.2±0.1 in the region of interest (ΩMlesssim1.5). For a flat (ΩM+ΩΛ=1) cosmology we find ΩMflat=0.28+0.09-0.08 (1 σ statistical) +0.05-0.04 (identified systematics). The data are strongly inconsistent with a Λ=0 flat cosmology, the simplest inflationary universe model. An open, Λ=0 cosmology also does not fit the data well: the data indicate that the cosmological constant is nonzero and positive, with a confidence of P(Λ>0)=99%, including the identified systematic uncertainties. The best-fit age of the universe relative to the Hubble time is t0flat=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 Calán/Tololo sample and our high-redshift sample. Excluding those few supernovae that are outliers in color excess or fit residual does not significantly change the results. The conclusions are also robust whether or not a width-luminosity relation is used to standardize the supernova peak magnitudes. We discuss and constrain, where possible, hypothetical alternatives to a cosmological constant.
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It is part of: Astrophysical Journal, 1998, vol. 517, num. 2, p. 565-586
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ISSN: 0004-637X
Appears in Collections:Articles publicats en revistes (Física Quàntica i Astrofísica)

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