The Supernova Legacy Survey 3-year sample: Type Ia Supernovae photometric distances and cosmological constraints

TL;DR

This paper presents a comprehensive analysis of 252 high-redshift Type Ia supernovae from the SNLS, measuring their photometric properties and deriving cosmological parameters, with careful consideration of systematic uncertainties.

Contribution

It provides a large, well-calibrated dataset of high-redshift supernovae and assesses systematic uncertainties in photometric distance measurements for cosmology.

Findings

Omega_M = 0.211 +/- 0.034 (stat) +/- 0.069 (sys)

Systematic uncertainties are dominated by photometric calibration

No evidence for evolution of the color-luminosity relation with redshift

Abstract

We present photometric properties and distance measurements of 252 high redshift Type Ia supernovae (0.15 < z < 1.1) discovered during the first three years of the Supernova Legacy Survey (SNLS). These events were detected and their multi-colour light curves measured using the MegaPrime/MegaCam instrument at the Canada-France-Hawaii Telescope (CFHT), by repeatedly imaging four one-square degree fields in four bands. Follow-up spectroscopy was performed at the VLT, Gemini and Keck telescopes to confirm the nature of the supernovae and to measure their redshifts. Systematic uncertainties arising from light curve modeling are studied, making use of two techniques to derive the peak magnitude, shape and colour of the supernovae, and taking advantage of a precise calibration of the SNLS fields. A flat LambdaCDM cosmological fit to 231 SNLS high redshift Type Ia supernovae alone gives Omega_M = 0.211 +/- 0.034(stat) +/- 0.069(sys). The dominant systematic uncertainty comes from uncertainties in the photometric calibration. Systematic uncertainties from light curve fitters come next with a total contribution of +/- 0.026 on Omega_M. No clear evidence is found for a possible evolution of the slope (beta) of the colour-luminosity relation with redshift.