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A&A 447, 31-48 (2006)
DOI: 10.1051/0004-6361:20054185

The Supernova Legacy Survey: measurement of $\Omega_{\mathsf$, $\Omega_\mathsf{\Lambda}$ and w from the first year data set

P. Astier1, J. Guy1, N. Regnault1, R. Pain1, E. Aubourg2, 3, D. Balam4, S. Basa5, R. G. Carlberg6, S. Fabbro7, D. Fouchez8, I. M. Hook9, D. A. Howell6, H. Lafoux3, J. D. Neill4, N. Palanque-Delabrouille3, K. Perrett6, C. J. Pritchet4, J. Rich3, M. Sullivan6, R. Taillet1, 10, G. Aldering11, P. Antilogus1, V. Arsenijevic7, C. Balland1, 2, S. Baumont1, 12, J. Bronder9, H. Courtois13, R. S. Ellis14, M. Filiol5, A. C. Gonçalves15, A. Goobar16, D. Guide1, D. Hardin1, V. Lusset3, C. Lidman12, R. McMahon17, M. Mouchet15, 2, A. Mourao7, S. Perlmutter11, 18, P. Ripoche8, C. Tao8 and N. Walton17

1  LPNHE, CNRS-IN2P3 and Universités Paris VI & VII, 4 place Jussieu, 75252 Paris Cedex 05, France;
    e-mail: astier@in2p3.fr
2  APC, Collège de France, 11 place Marcellin Berthelot, 75005 Paris, France
3  DSM/DAPNIA, CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France
4  Department of Physics and Astronomy, University of Victoria, PO Box 3055, Victoria, BC VSW 3P6, Canada
5  LAM, CNRS, BP8, Traverse du Siphon, 13376 Marseille Cedex 12, France
6  Department of Astronomy and Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8, Canada
7  CENTRA-Centro M. de Astrofisica and Department of Physics, IST, Lisbon, Portugal
8  CPPM, CNRS-IN2P3 and Université Aix-Marseille II, Case 907, 13288 Marseille Cedex 9, France
9  University of Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
10  Université de Savoie, 73000 Chambery, France
11  LBNL, 1 Cyclotron Rd, Berkeley, CA 94720, USA
12  ESO, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago 19, Chile
13  CRAL, 9 avenue Charles André, 69561 Saint-Genis-Laval cedex, France
14  California Institute of Technology, Pasadena, California, USA
15  LUTH, UMR 8102, CNRS and Observatoire de Paris, 92195 Meudon, France
16  Department of Physics, Stockholm University, Sweden
17  IoA, University of Cambridge, Madingley Road, Cambridge CB3 0EZ, UK
18  Department of Physics, University of California Berkeley, Berkeley, CA 94720, USA

(Received 9 September 2005 / Accepted 11 October 2005 )

Abstract
We present distance measurements to 71 high redshift type Ia supernovae discovered during the first year of the 5-year Supernova Legacy Survey (SNLS). These events were detected and their multi-color light-curves measured using the MegaPrime/MegaCam instrument at the Canada-France-Hawaii Telescope (CFHT), by repeatedly imaging four one-square degree fields in four bands, as part of the CFHT Legacy Survey (CFHTLS). Follow-up spectroscopy was performed at the VLT, Gemini and Keck telescopes to confirm the nature of the supernovae and to measure their redshift. With this data set, we have built a Hubble diagram extending to z=1, with all distance measurements involving at least two bands. Systematic uncertainties are evaluated making use of the multi-band photometry obtained at CFHT. Cosmological fits to this first year SNLS Hubble diagram give the following results: $\Omega_{\rm M}= 0.263 \pm 0.042\;(stat) \pm 0.032\;(sys)$ for a flat $\Lambda$CDM model; and $w = -1.023 \pm 0.090\;(stat) \pm 0.054\;(sys)$ for a flat cosmology with constant equation of state w when combined with the constraint from the recent Sloan Digital Sky Survey measurement of baryon acoustic oscillations.


Key words: supernovae: general -- cosmology: observations -- cosmological parameters

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