Supernova Constraints and Systematic Uncertainties from the First 3 Years of the Supernova Legacy Survey

A. Conley (1) , J. Guy (2) , M. Sullivan , N. Regnault (2) , P. Astier (2) , C. Balland (2) , S. Basa (3) , R. G. Carlberg (1) , D. Fouchez (4) , D. Hardin (2) , I. M. Hook , D. A. Howell , R. Pain (2) , N. Palanque-Delabrouille (5) , K. M. Perrett , C. J. Pritchet , J. Rich (6) , V. Ruhlmann-Kleider (6) , D. Balam (1) , S. Baumont (7) , R. S. Ellis , S. Fabbro , H. K. Fakhouri , N. Fourmanoit (2) , S. Gonzalez-Gaitan , M. L. Graham , M. J. Hudson , E. Hsiao , T. Kronborg (2) , C. Lidman (8) , A. M. Mourao , J. D. Neill , S. Perlmutter , P. Ripoche (2) , N. Suzuki , E. S. Walker

1 Department of Astronomy and Astrophysics [Universty of Toronto]
2 LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
3 LAM - Laboratoire d'Astrophysique de Marseille
4 CPPM - Centre de Physique des Particules de Marseille
5 DPhP - Département de Physique des Particules (ex SPP)
6 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
7 LPSC - Laboratoire de Physique Subatomique et de Cosmologie
8 ESO - European Southern Observatory

We combine high redshift Type Ia supernovae from the first 3 years of the Supernova Legacy Survey (SNLS) with other supernova (SN) samples, primarily at lower redshifts, to form a high-quality joint sample of 472 SNe (123 low-$z$, 93 SDSS, 242 SNLS, and 14 {\it Hubble Space Telescope}). SN data alone require cosmic acceleration at >99.9% confidence, including systematic effects. For the dark energy equation of state parameter (assumed constant out to at least $z=1.4$) in a flat universe, we find $w = -0.91^{+0.16}_{-0.20}(\mathrm{stat}) ^{+0.07}_{-0.14} (\mathrm{sys})$ from SNe only, consistent with a cosmological constant. Our fits include a correction for the recently discovered relationship between host-galaxy mass and SN absolute brightness. We pay particular attention to systematic uncertainties, characterizing them using a systematics covariance matrix that incorporates the redshift dependence of these effects, as well as the shape-luminosity and color-luminosity relationships. Unlike previous work, we include the effects of systematic terms on the empirical light-curve models. The total systematic uncertainty is dominated by calibration terms. We describe how the systematic uncertainties can be reduced with soon to be available improved nearby and intermediate-redshift samples, particularly those calibrated onto USNO/SDSS-like systems.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Cosmologie et astrophysique extra-galactique [astro-ph.CO]

A. Conley, J. Guy, M. Sullivan, N. Regnault, P. Astier, et al.. Supernova Constraints and Systematic Uncertainties from the First 3 Years of the Supernova Legacy Survey. The Astrophysical Journal Supplement, 2011, 192, pp.1. ⟨10.1088/0067-0049/192/1/1⟩. ⟨hal-00662099⟩