Improved cosmological constraints from a joint analysis of the SDSS-II and SNLS supernova samples

Betoule, M. and Kessler, R. and Guy, J. and Mosher, J. and Hardin, D. and Biswas, R. and Astier, P. and El-Hage, P. and Konig, M. and Kuhlmann, S. and Marriner, J. and Pain, R. and Regnault, N. and Balland, C. and Bassett, B. A. and Brown, P. J. and Campbell, H. and Carlberg, R. G. and Cellier-Holzern, F. and Cinabro, D. and Conley, A. and D'Andrea, C. B. and DePoy, D. L. and Doi, M. and Ellis, R. S. and Fabbro, S. and Filippenko, A. V. and Foley, R. J. and Frieman, J. A. and Fouchez, D. and Galbany, L. and Goobar, A. and Gupta, R. R. and Hill, G. J. and Hlozek, R. and Hogan, C. J. and Hook, I. M. and Howell, D. A. and Jha, S. W. and Le Guillou, L. and Leloudas, G. and Lidrnan, C. and Marshall, J. L. and Moeller, A. and Mourao, A. M. and Neveu, J. and Nichol, R. and Olmstead, M. D. and Palanque-Delabrouille, N. and Perlinutter, S. and Prieto, J. L. and Pritchet, C. J. and Richinond, M. and Riess, A. G. and Ruhlmann-Kleider, V. and Sako, M. and Sehahmaneche, K. and Schneider, D. P. and Smith, M. and Sollerman, J. and Sullivan, M. and Walton, N. A. and Wheeler, C. J. (2014) Improved cosmological constraints from a joint analysis of the SDSS-II and SNLS supernova samples. Astronomy and Astrophysics, 568. ISSN 1432-0746

Abstract

Aims. We present cosmological constraints from a joint analysis of type la 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-11 (0.05 <z <0.4), and three years from SNLS (0.2 <z <1), and it totals 740 spectroscopically confirmed type la 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: I) the addition of the full SDSS-II spectroscopically-confirmed SN la 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 la light curves. Results. We produce recalibrated SN la light curves and associated distances for the SDSS-II and SNLS samples. The large SOSS-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 ACDM 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 1.8 sigma (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 omega = -1.018 +/- 0,057 (sral+sys) for a fiat universe. Adding baryon acoustic oscillation distance measurements gives similar constraints: omega = 59 -1.027 0.055. Our supernova measurements provide the most stringent constraints to date on the nature of dark energy.