Measurements of [Omega] and [Lambda] from 42 High-Redshift Supernovae
- Institute for Nuclear and Particle Astrophysics, E. O. Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)
- European Southern Observatory, La Silla (Chile)
- Institute of Astronomy, Cambridge, England (United Kingdom)
- Department of Astronomy, University of Barcelona, Barcelona (Spain)
- Isaac Newton Group, La Palma (Spain)
- Department of Astronomy, Yale University, New Haven, CT (United States)
- Anglo-Australian Observatory, Sydney (Australia)
- Department of Astronomy, University of California, Berkeley, CA (United States)
- Space Telescope Science Institu
We report measurements of the mass density, [Omega][sub M], and cosmological-constant energy density, [Omega][sub [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 Cal[acute a]n/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][sub M] [minus]0.6[Omega][sub [Lambda]] [approx][minus]0.2[plus minus]0.1 in the region of interest ([Omega][sub M] [approx lt]1.5). For a flat ([Omega][sub M] [plus][Omega][sub [Lambda]] =1) cosmology we find [Omega][sup flat] [sub M] =0.28[sup [plus]0.09] [sub [minus]0.08] (1 [sigma] statistical) [sup [plus]0.05] [sub [minus]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 nonzero and positive, with a confidence of P([Lambda][gt]0)=99[percent], including the identified systematic uncertainties. The best-fit age of the universe relative to the Hubble time is t[sup flat] [sub 0] =14.9[sup [plus]1.4] [sub [minus]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 Cal[acute a]n/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. [copyright] [ital [copyright] 1999.] [ital The American Astronomical Society]
- OSTI ID:
- 6466094
- Journal Information:
- The Astrophysical Journal, Vol. 517:2; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Measurements of the cosmological parameters {Omega} and {Lambda} from the first seven supernovae at z{ge}0.35
Systematic corrections to the measured cosmological constant as a result of local inhomogeneity
Related Subjects
GENERAL PHYSICS
COSMOLOGICAL CONSTANT
COSMOLOGY
ENERGY DENSITY
GALAXIES
GRAVITATIONAL COLLAPSE
PROBABILITY
RED SHIFT
SUPERNOVA REMNANTS
SUPERNOVAE
UNIVERSE
COSMIC RADIO SOURCES
ERUPTIVE VARIABLE STARS
STARS
VARIABLE STARS
661300* - Other Aspects of Physical Science- (1992-)