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Gemini Spectroscopy of Supernovae from the Supernova Legacy Survey: Improving High-Redshift Supernova Selection and Classification
Howell D.A., Sullivan M., Perrett K., Bronder T.J., Hook I.M. et al
Astrophysical Journal 634 (2005) 1190-1201 - http://hal.in2p3.fr/in2p3-00455317
Physique/Astrophysique/Cosmologie et astrophysique extra-galactique
Planète et Univers/Astrophysique/Cosmologie et astrophysique extra-galactique
Gemini Spectroscopy of Supernovae from the Supernova Legacy Survey: Improving High-Redshift Supernova Selection and Classification
D.A. Howell1, M. Sullivan1, K. Perrett1, T. J. Bronder, I. M. Hook2, P. Astier3, E. Aubourg4, 5, D. Balam1, S. Basa6, R.G. Carlberg1, S. Fabbro3, D. Fouchez7, J. Guy3, H. Lafoux8, J.D. Neill, R. Pain3, N. Palanque-Delabrouille4, C.J. Pritchet9, N. Regnault3, J. Rich4, Richard Taillet ()10, R. Knop, R.G. Mcmahon, S. Perlmutter11, N.A. Walton
1 :  Department of Astronomy and Astrophysics
University of Toronto
Department of Astronomy and Astrophysics, University of Toronto, 50 St. George St, Room 1403, Toronto, ON M5S 3H4, Canada
2 :  University of Oxford Astrophysics
University of Oxford Astrophysics
University of Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK.
3 :  LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
CNRS : UMR7585 – IN2P3 – Université Pierre et Marie Curie (UPMC) - Paris VI – Université Paris VII - Paris Diderot
Barre 12-22, 1er étage 4 Place Jussieu 75252 Paris Cedex 05
4 :  IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers (ex DAPNIA)
5 :  APC - UMR 7164 - AstroParticule et Cosmologie
CNRS : UMR7164 – IN2P3 – Observatoire de Paris – Université Paris VII - Paris Diderot – CEA : DSM/IRFU
APC - UMR 7164, Université Paris Diderot, 10 rue Alice Domon et Léonie Duquet, case postale 7020, F-75205 Paris Cedex 13
6 :  LAM - Laboratoire d'Astrophysique de Marseille
CNRS : UMR6110 – INSU – Université de Provence - Aix-Marseille I
Pôle de l'Étoile Site de Château-Gombert 38, rue Frédéric Joliot-Curie 13388 Marseille cedex 13
7 :  CPPM - Centre de Physique des Particules de Marseille
CNRS : UMR7346 – IN2P3 – Université de la Méditerranée - Aix-Marseille II
163, avenue de Luminy - Case 902 - 13288 Marseille cedex 09
8 :  DAPNIA - Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée
9 :  Department of Physics and Astronomy, University of Victoria
University of Victoria
Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, Victoria, BC V8W 3P6, Canada.
10 :  LAPTH - Laboratoire d'Annecy-le-Vieux de Physique Théorique
CNRS : UMR5108 – Université de Savoie
9 Chemin de Bellevue - BP 110 74941 ANNECY LE VIEUX CEDEX
11 :  LBNL - Lawrence Berkeley National Laboratory
Lawrence Berkeley National Lab
Lawrence Berkeley National Lab MS 50F Cyclotron Rd., Berkeley, CA 94720
APC - Cosmologie et Gravitation
We present new techniques for improving the efficiency of supernova (SN) classification at high redshift using 64 candidates observed at Gemini North and South during the first year of the Supernova Legacy Survey (SNLS). The SNLS is an ongoing 5 year project with the goal of measuring the equation of state of dark energy by discovering and following over 700 high-redshift SNe Ia using data from the Canada-France-Hawaii Telescope Legacy Survey. We achieve an improvement in the SN Ia spectroscopic confirmation rate: at Gemini 71% of candidates are now confirmed as SNe Ia, compared to 54% using the methods of previous surveys. This is despite the comparatively high redshift of this sample, in which the median SN Ia redshift is z=0.81 (0.155<=z<=1.01). These improvements were realized because we use the unprecedented color coverage and light curve sampling of the SNLS to predict whether a candidate is a SN Ia and to estimate its redshift, before obtaining a spectrum, using a new technique called the ''SN photo-z.'' In addition, we have improved techniques for galaxy subtraction and SN template χ2 fitting, allowing us to identify candidates even when they are only 15% as bright as the host galaxy. The largest impediment to SN identification is found to be host galaxy contamination of the spectrum-when the SN was at least as bright as the underlying host galaxy the target was identified more than 90% of the time. However, even SNe in bright host galaxies can be easily identified in good seeing conditions. When the image quality was better than 0.55", the candidate was identified 88% of the time. Over the 5 year course of the survey, using the selection techniques presented here, we will be able to add ~170 more confirmed SNe Ia than would be possible using previous methods. APC, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France. DSM/DAPNIA, CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France.

Articles dans des revues avec comité de lecture
Astrophysical Journal (Astrophys. J.)
Publisher American Astronomical Society
ISSN 0004-637X 

Cosmology: Observations – Methods: Data Analysis – Stars: Supernovae: General – Techniques: Spectroscopic – Surveys
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