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For refcode 2014A&A...568A..22B:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
2014A&A...568A..22B Improved cosmological constraints from a joint analysis of the SDSS-II and SNLS supernova samples Betoule, M.; Kessler, R.; Guy, J.; Mosher, J.; Hardin, D.; Biswas, R.; Astier, P.; El-Hage, P.; Konig, M.; Kuhlmann, S.; Marriner, J.; Pain, R.; Regnault, N.; Balland, C.; Bassett, B. A.; Brown, P. J.; Campbell, H.; Carlberg, R. G.; Cellier-Holzem, F.; Cinabro, D.; Conley, A.; D'Andrea, C. B.; DePoy, D. L.; Doi, M.; Ellis, R. S.; Fabbro, S.; Filippenko, A. V.; Foley, R. J.; Frieman, J. A.; Fouchez, D.; Galbany, L.; Goobar, A.; Gupta, R. R.; Hill, G. J.; Hlozek, R.; Hogan, C. J.; Hook, I. M.; Howell, D. A.; Jha, S. W.; Le Guillou, L.; Leloudas, G.; Lidman, C.; Marshall, J. L.; Moller, A.; Mourao, A. M.; Neveu, J.; Nichol, R.; Olmstead, M. D.; Palanque-Delabrouille, N.; Perlmutter, S.; Prieto, J. L.; Pritchet, C. J.; Richmond, M.; Riess, A. G.; Ruhlmann-Kleider, V.; Sako, M.; Schahmaneche, K.; Schneider, D. P.; Smith, M.; Sollerman, J.; Sullivan, M.; Walton, N. A.; Wheeler, C. J. 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 LambdaCDM cosmology, we find Omega_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 1.8sigma (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. Key words: cosmology: observations, distance scale, dark energy
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