New Constraints on $Ω_M$, $Ω_Λ$, and w from an Independent Set of Eleven High-Redshift Supernovae Observed with HST

Details New Constraints on $Ω_M$, $Ω_Λ$, and w from an Independent Set of Eleven High-Redshift Supernovae Observed with HST New Constraints on $Ω_M$, $Ω_Λ$, and w from an Independent Set of Eleven High-Redshift Supernovae Observed with HST

2003-09-12

arxiv.org/abs/astro-ph/0309368v1

Astrophys.J.598:102,2003

Astronomy and Astrophysics

Astrophysics

Accepted for publication in Astrophysical Journal; For data tables and full-resolution figures, see http://supernova.lbl.gov

Scientific paper

10.1086/378560

We report measurements of $\Omega_M$, $\Omega_\Lambda$, and w from eleven supernovae at z=0.36-0.86 with high-quality lightcurves measured using WFPC-2 on the HST. This is an independent set of high-redshift supernovae that confirms previous supernova evidence for an accelerating Universe. Combined with earlier Supernova Cosmology Project data, the new supernovae yield a flat-universe measurement of the mass density $\Omega_M=0.25^{+0.07}_{-0.06}$ (statistical) $\pm0.04$ (identified systematics), or equivalently, a cosmological constant of $\Omega_\Lambda=0.75^{+0.06}_{-0.07}$ (statistical) $\pm0.04$ (identified systematics). When the supernova results are combined with independent flat-universe measurements of $\Omega_M$ from CMB and galaxy redshift distortion data, they provide a measurement of $w=-1.05^{+0.15}_{-0.20}$ (statistical) $\pm0.09$ (identified systematic), if w is assumed to be constant in time. The new data offer greatly improved color measurements of the high-redshift supernovae, and hence improved host-galaxy extinction estimates. These extinction measurements show no anomalous negative E(B-V) at high redshift. The precision of the measurements is such that it is possible to perform a host-galaxy extinction correction directly for individual supernovae without any assumptions or priors on the parent E(B-V) distribution. Our cosmological fits using full extinction corrections confirm that dark energy is required with $P(\Omega_\Lambda>0)>0.99$, a result consistent with previous and current supernova analyses which rely upon the identification of a low-extinction subset or prior assumptions concerning the intrinsic extinction distribution.

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