Cosmological Results from High-z Supernovae**Based in part on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5-26555. This research is primarily associated with proposal GO-8177, but also uses and reports results from proposals GO-7505, 7588, 8641, and 9118. ****CFHT: Based in part on observations taken with the Canada-France-Hawaii Telescope, operated by the National Research Council of Canada, le Centre National de la Recherche Scientifique de France, and the University of Hawaii. CTIO: Based in part on observations taken at the Cerro Tololo Inter-American Observatory. Keck: Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space
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The High-z Supernova Search Team has discovered and observed eight new supernovae in the redshift interval z = 0.3-1.2. These independent observations, analyzed by similar but distinct methods, confirm the results of Riess and Perlmutter and coworkers that supernova luminosity distances imply an accelerating universe. More importantly, they extend the redshift range of consistently observed Type Ia supernovae (SNe Ia) to z 1, where the signature of cosmological effects has the opposite sign of some plausible systematic effects. Consequently, these measurements not only provide another quantitative confirmation of the importance of dark energy, but also constitute a powerful qualitative test for the cosmological origin of cosmic acceleration. We find a rate for SN Ia of (1.4 0.5) 10-4 h 3 Mpc-3 yr-1 at a mean redshift of 0.5. We present distances and host extinctions for 230 SN Ia. These place the following constraints on cosmological quantities: if the equation of state parameter of the dark energy is w = -1, then H0t0 = 0.96 0.04, and - 1.4M = 0.35 0.14. Including the constraint of a flat universe, we find M = 0.28 0.05, independent of any large-scale structure measurements. Adopting a prior based on the Two Degree Field (2dF) Redshift Survey constraint on M and assuming a flat universe, we find that the equation of state parameter of the dark energy lies in the range -1.48 < w < -0.72 at 95% confidence. If we further assume that w > -1, we obtain w < -0.73 at 95% confidence. These constraints are similar in precision and in value to recent results reported using the WMAP satellite, also in combination with the 2dF Redshift Survey.
Tonry, J. L., Schmidt, B. P., Barris, B., Candia, P., Challis, P., Clocchiatti, A., ... Suntzeff, N. B.
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Tonry, John L||Schmidt, Brian P||Barris, Brian||Candia, Pablo||Challis, Peter||Clocchiatti, Alejandro||Coil, Alison L||Filippenko, Alexei V||Garnavich, Peter||Hogan, Craig||Holland, Stephen T||Jha, Saurabh||Kirshner, Robert P||Krisciunas, Kevin||Leibundgut, Bruno||Li, Weidong||Matheson, Thomas||Phillips, Mark M||Riess, Adam G||Schommer, Robert||Smith, R Chris||Sollerman, Jesper||Spyromilio, Jason||Stubbs, Christopher W||Suntzeff, Nicholas B