Type Ia Supernovae Rate as a Function of Redshift from the First 3 Years of the SuperNovae Legacy Survey

Pascal Ripoche
Lawrence Berkeley National Laboratory


I will present a measurement of the Type Ia supernova (SN\,Ia) rate as a function of redshift, based on the first 3 years of the SuperNova Legacy Survey (SNLS). Supernova candidates were detected and light-curves derived on images obtained for the deep survey of the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS), covering four 1 square degree fields, while spectroscopy of Sn Ia candidates was obtained at VLT, Gemini and Keck telescopes. A complete re-processing of the imaging survey was performed with an automated procedure, producing an unbiased sample of about 400 Sn Ia candidates. About 200 of these candidates were spectroscopically followed and identified during the "real-time" operations. A detailed "on image" Sn Ia simulation was performed to derive precise detection and identification efficiencies. Using both photometric and spectroscopic redshift, we have derived a Sn Ia explosion rate in redshift bins of 0.1 between z=0.2 and z=1.2 and compared this measurement with predictions based on cosmic star formation history models.