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Paper: Photometric Calibration of the Supernova Legacy Survey Fields
Volume: 364, The Future of Photometric, Spectrophotometric, and Polarimetric Standardization
Page: 587
Authors: Regnault, N.
Abstract: The 5-year project Supernova Legacy Survey (SNLS) delivers ∼ 100 Type-Ia supernovae (SNe Ia) per year, in the redshift range 0.3 < z < 1.0, with well-sampled g′r′i′z′ lightcurves. The SNLS Collaboration uses the 1 deg2 MegaCam imager (36 2048×4612 thinned CCDs) mounted on the 3.6-m Canada- France-Hawaii Telescope (CFHT) to observe four fields around the sky, in four filters. The primary goal of the project is to measure the dark energy equation of state with a final statistical precision of 0:05. We have shown, using the first year dataset that the calibration uncertainties are currently the dominant contribution to the systematic error budget.

The calibration of the SNLS dataset is challenging in several aspects. Mega- Cam is a wide-field imager, and only a handful of its 36 CCDs can be directly calibrated using standard star observations. Then, measuring the rest-frame B-band luminosity of SNe Ia over the 0.3 < z < 1.0 redshift range requires an excellent flux intercalibration of the MegaCam bands. Finally, the SN Ia SED differs significantly from that of stars and transfering the stellar calibration to the SNLS data requires a precise knowledge of the SN Ia spectra and the instrument transmissions.

We present and discuss the SNLS calibration strategy. We present the calibration aspects which impact most the cosmological measurements. We also discuss the intercalibration of the SNLS with other surveys, such as the CFHTLS-Wide and the SDSS.

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