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Measurements of the Cosmological Parameters $\Omega$ and $\Lambda$ from the First 7 Supernovae at $z \geq$ 0.35

Abstract : We have developed a technique to systematically discover and study high-redshift supernovae that can be used to measure the cosmological parameters. We report here results based on the initial seven of >28 supernovae discovered to date in the high-redshift supernova search of the Supernova Cosmology Project. We find a dispersion in peak magnitudes of sigma_{M_B} = 0.27 this dispersion narrows to sigma_{M_B,corr} = 0.19 after "correcting" the magnitudes using the light-curve "width-luminosity" relation found for nearby (z <= 0.1) type Ia supernovae from the Calan/Tololo survey (Hamuy et al. 1996). Comparing lightcurve-width-corrected magnitudes as a function of redshift of our distant (z = 0.35-0.46) supernovae to those of nearby type Ia supernovae yields a global measurement of the mass density, Omega_M = 0.88^{+0.69}_{-0.60} for a Lambda = 0 cosmology. For a spatially flat universe (i.e., Omega_M +Omega_Lambda = 1), we find Omega_M = 0.94 ^{+0.34}_{-0.28} or, equivalently, a measurement of the cosmological constant, Omega_Lambda = 0.06 ^{+0.28}_{-0.34} (<0.51 at the 95% confidence level). For the more general Friedmann-Lemaitre cosmologies with independent Omega_M and Omega_Lambda, the results are presented as a confidence region on the Omega_M-Omega_Lambda plane. This region does not correspond to a unique value of the deceleration parameter q_0. We present analyses and checks for statistical and systematic errors, and also show that our results do not depend on the specifics of the width-luminosity correction. The results for Omega_Lambda-versus-Omega_M are inconsistent with Lambda-dominated, low density, flat cosmologies that have been proposed to reconcile the ages of globular cluster stars with higher Hubble constant values.
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Contributor : Dominique Girod <>
Submitted on : Wednesday, February 14, 2007 - 3:49:58 PM
Last modification on : Saturday, April 11, 2020 - 1:53:16 AM

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S. Perlmutter, S. Gabi, G. Goldhaber, D. E. Groom, I. M. Hook, et al.. Measurements of the Cosmological Parameters $\Omega$ and $\Lambda$ from the First 7 Supernovae at $z \geq$ 0.35. The Astrophysical Journal, American Astronomical Society, 1997, 483, pp.565. ⟨10.1086/304265⟩. ⟨in2p3-00130961⟩



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