AAS Meeting #193 - Austin, Texas, January 1999
Session 39. Cosmology/Large Scale Structure
Display, Thursday, January 7, 1999, 9:20am-6:30pm, Exhibit Hall 1

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[39.04] Measurements of \Omega and \Lambda from High-Redshift Supernovae

G. Aldering, S. Perlmutter, R.A. Knop, P. Nugent, G. Goldhaber, D.E. Groom, M.Y. Kim, C.R. Pennypacker, S. Deustua, R. Quimby (LBNL/CfPA, Berkeley), A. Goobar (U. Stockholm), R. Pain, S. Fabbro (CRNS-IN2P3), I.M. Hook, C. Lidman (ESO), A. Kim (College de France), B. E. Schaefer (Yale), R. Ellis, M. Irwin, N. Walton (IoA), P. Ruiz-Lapuente (U. Barcelona), A. S. Fruchter, N. Panagia (STScI), Supernova Cosmology Project Collaboration

We report measurements of the mass density, \Omega\rm M, and cosmological-constant energy density, \Omega\Lambda, of the universe based on the analysis of more than forty Type~Ia supernovae discovered by the Supernova Cosmology Project. The magnitude-redshift data for these high redshift supernovae are fit 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 lightcurve width-luminosity relation. The measurement yields a joint probability distribution of the cosmological parameters that is approximated by the relation 0.8 \,\Omega\rm M- 0.6\,\Omega\Lambda \approx -0.2 ± 0.1 in the region of interest (\Omega\rm M \lesssim 1.5). For a flat (zero curvature) cosmology we find \Omega\rm M = 0.28+0.09-0.08 (statistical) +0.05-0.04 (systematic). The data are strongly inconsistent with a \Lambda = 0 zero-curvature 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 systematic uncertainty. The best-fit age of the universe relative to the Hubble time is t0=14.9+1.4-1.1\,(0.63/h) Gyr for a zero-curvature universe. 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 which 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.

If you would like more information about this abstract, please follow the link to www-supernova.lbl.gov. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

The author(s) of this abstract have provided an email address for comments about the abstract: galdering@lbl.gov

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