• Betoule, M.
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• Kessler, R.
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• Guy, J.
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• Mosher, J.
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• Hardin, D.
;
• Biswas, R.
;
• Astier, P.
;
• El-Hage, P.
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• Konig, M.
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• Kuhlmann, S.
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• Marriner, J.
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• Pain, R.
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• Regnault, N.
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• Balland, C.
;
• Bassett, B. A.
;
• Brown, P. J.
;
• Campbell, H.
;
• Carlberg, R. G.
;
• Cellier-Holzem, F.
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• Cinabro, D.
;
• Conley, A.
;
• D'Andrea, C. B.
;
• DePoy, D. L.
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• Doi, M.
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• Ellis, R. S.
;
• Fabbro, S.
;
• Filippenko, A. V.
;
• Foley, R. J.
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• Frieman, J. A.
;
• Fouchez, D.
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• Galbany, L.
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• Goobar, A.
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• Gupta, R. R.
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• Hill, G. J.
;
• Hlozek, R.
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• Hogan, C. J.
;
• Hook, I. M.
;
• Howell, D. A.
;
• Jha, S. W.
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• Le Guillou, L.
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• Leloudas, G.
;
• Lidman, C.
;
• Marshall, J. L.
;
• Möller, A.
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• Mourão, A. M.
;
• Neveu, J.
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• Nichol, R.
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• Olmstead, M. D.
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• Palanque-Delabrouille, N.
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• Perlmutter, S.
• and 13 more

Abstract

Aims: We present cosmological constraints from a joint analysis of type Ia supernova (SN Ia) observations obtained by the SDSS-II and SNLS collaborations. The dataset includes several low-redshift samples (z< 0.1), all three seasons from the SDSS-II (0.05 <z< 0.4), and three years from SNLS (0.2 <z< 1), and it totals 740 spectroscopically confirmed type Ia supernovae with high-quality light curves.
Methods: We followed the methods and assumptions of the SNLS three-year data analysis except for the following important improvements: 1) the addition of the full SDSS-II spectroscopically-confirmed SN Ia sample in both the training of the SALT2 light-curve model and in the Hubble diagram analysis (374 SNe); 2) intercalibration of the SNLS and SDSS surveys and reduced systematic uncertainties in the photometric calibration, performed blindly with respect to the cosmology analysis; and 3) a thorough investigation of systematic errors associated with the SALT2 modeling of SN Ia light curves.
Results: We produce recalibrated SN Ia light curves and associated distances for the SDSS-II and SNLS samples. The large SDSS-II sample provides an effective, independent, low-z anchor for the Hubble diagram and reduces the systematic error from calibration systematics in the low-z SN sample. For a flat ΛCDM cosmology, we find Ω_m =0.295 ± 0.034 (stat+sys), a value consistent with the most recent cosmic microwave background (CMB) measurement from the Planck and WMAP experiments. Our result is 1.8σ (stat+sys) different than the previously published result of SNLS three-year data. The change is due primarily to improvements in the SNLS photometric calibration. When combined with CMB constraints, we measure a constant dark-energy equation of state parameter w =-1.018 ± 0.057 (stat+sys) for a flat universe. Adding baryon acoustic oscillation distance measurements gives similar constraints: w =-1.027 ± 0.055. Our supernova measurements provide the most stringent constraints to date on the nature of dark energy.

Appendices are available in electronic form at http://www.aanda.orgFull Table F.3 and covariance matrix are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/568/A22