NED Abstract 
Copyright by American Astronomical Society.
Reproduced by permission

1999ApJ...517..565P

   Measurements of {OMEGA} and {LAMBDA} from 42 High-Redshift Supernovae

     S. PERLMUTTER, G. ALDERING, G. GOLDHABER, R. A. KNOP, P. NUGENT,
       P. G. CASTRO, S. DEUSTUA, S. FABBRO, A. GOOBAR, D. E. GROOM,
         I. M. HOOK, A. G. KIM, M. Y. KIM, J. C. LEE, N. J. NUNES,
                 R. PAIN, C. R. PENNYPACKER, AND R. QUIMBY
 Institute for Nuclear and Particle Astrophysics, E. O. Lawrence Berkeley
                  National Laboratory, Berkeley, CA 94720

                                 C. LIDMAN
              European Southern Observatory, La Silla, Chile

                 R. S. ELLIS, M. IRWIN, AND R. G. MCMAHON
              Institute of Astronomy, Cambridge, England, UK

                             P. RUIZ-LAPUENTE
    Department of Astronomy, University of Barcelona, Barcelona, Spain

                                 N. WALTON
                    Isaac Newton Group, La Palma, Spain

                                B. SCHAEFER
          Department of Astronomy, Yale University, New Haven, CT

                                B. J. BOYLE
              Anglo-Australian Observatory, Sydney, Australia

                     A. V. FILIPPENKO AND T. MATHESON
      Department of Astronomy, University of California, Berkeley, CA

                      A. S. FRUCHTER AND N. PANAGIA
             Space Telescope Science Institute, Baltimore, MD

                             H. J. M. NEWBERG
                  Fermi National Laboratory, Batavia, IL

                                    AND

                                W. J. COUCH
             University of New South Wales, Sydney, Australia

                      THE SUPERNOVA COSMOLOGY PROJECT
           Received 1998 September 8; accepted 1998 December 17

                                  ABSTRACT
   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 supernovae, at 
redshifts between 0.18 and 0.83, are fitted jointly with a set of 
supernovae from the Calan/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 
0.8{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_^flat^ = 0.28_-0.08_^+-.09^(1 {sigma} 
statistical)_-0.04_^+0.05^ (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 nonzero 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_^flat^ = 14.9_-1.1_^+1.4^(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. 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.

Subject headings: cosmology: observations-distance scale-supernovae: 
general