Vol. 552
In section 13. Astronomical instrumentation

Improved photometric calibration of the SNLS and the SDSS supernova surveys

Substantial efforts over the past few years have brought the photometric calibration accuracy of some large imaging surveys down to the 1% or 2% level. This already impressive level, however, remains a limiting factor in some uses of those surveys, including the measurement of precise cosmological parameters from the Hubble diagram of type Ia supernovae. The authors have used multiple overlapping calibration paths to both cross-calibrate large sets of tertiary standard stars in the fields of the Supernovae Legacy Survey (SNLS) and SDSS supernovae searches and calibrate those standards onto the scale of the HST primary photometric standards. The resulting photometry is calibrated to the HST system with 0.4% accuracy, which is comparable to the external accuracy of the HST primary standards.