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American Astronomical Society Meeting 207, Washington, DC : États-Unis
SNLS: The Supernova Type Ia Rate at z = 0.47
J. D. Neill, M. Sullivan, D. Balam, P. Astier1, E. Aubourg2, S. Basa, R. G. Carlberg, A. Conley, S. Fabbro, D. Fouchez, J. Guy1, I. Hook, D. A. Howell, H. Lafoux, R. Pain1, N. Palanque-Delabrouille3, K. Perrett, C. J. Pritchet, N. Regnault, J. Rich, Richard Taillet1, S. Baumont1, J. Bronder, M. Graham, E. Hsiao, V. Lusset, P. Ripoche, A. Mourao, S. Perlmutter, C. Tao4
SNLS Collaboration(s)

We present a preliminary measurement of the distant Type Ia supernova rate derived from the Canada -- France -- Hawaii Telescope Supernova Legacy Survey (SNLS). By observing four one-square degree fields with a high temporal frequency (< $\delta$ > ~4 observer-frame days) over large fractions of a year (~6 months each field, with breaks during full moon) and using 8 meter-class telescopes for spectroscopic followup, the survey not only provides the dense time sampling needed to achieve a high completeness, but also enjoys the benefit of high quality spectroscopy to verify the Type Ia candidates and hence reduce contamination from non-Type Ia events. The goal of the survey is to measure ~ 700 Type Ia SNe out to $z ^~ 1$ over a period of 5 years. We use the first two years of survey data to begin characterizing the Type Ia sample and explore a methodology for calculating rates from the survey. We use individual SNLS survey epoch properties to observe Monte Carlo simulations of $10^6 $Type Ia supernovae in the redshift range 0.2 < z < 0.6, and thus derive our survey efficiency. We combine this efficiency with a carefully selected control sample of spectroscopically confirmed SNLS Type Ia SNe to derive a volumetric rate. When comparing our volumetric rate with other ground-based surveys that also use spectroscopic candidate verification, we find no evidence for significant systematic underestimation of the SN Ia rates near z = 0.5. When comparing published SN Ia rates spanning the redshift range 0.0 < z < 1.6 to models of SN Ia production, we find that neither pure delay-time models nor two component models can accommodate all the observed data.
1 :  LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
2 :  APC - UMR 7164 - AstroParticule et Cosmologie
3 :  DAPNIA - Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée
4 :  CPPM - Centre de Physique des Particules de Marseille
Physique/Astrophysique/Cosmologie et astrophysique extra-galactique