Abstract
We present griz_{P1} light curves of 146 spectroscopically confirmed Type Ia supernovae (SNe Ia; 0.03 < z < 0.65) discovered during the first 1.5 yr of the PanSTARRS1 Medium Deep Survey. The PanSTARRS1 natural photometric system is determined by a combination of onsite measurements of the instrument response function and observations of spectrophotometric standard stars. We find that the systematic uncertainties in the photometric system are currently 1.2% without accounting for the uncertainty in the Hubble Space Telescope Calspec definition of the AB system. A Hubble diagram is constructed with a subset of 113 out of 146 SNe Ia that pass our light curve quality cuts. The cosmological fit to 310 SNe Ia (113 PS1 SNe Ia + 222 light curves from 197 lowz SNe Ia), using only supernovae (SNe) and assuming a constant dark energy equation of state and flatness, yields w = 1.120^{+0.360}_{0.206}(Stat)^{+0.269}_{0.291}(Sys). When combined with BAO+CMB(Planck)+H_{0}, the analysis yields Ω_{M} = 0.280^{+0.013}_{0.012} and w = 1.166^{+0.072}_{0.069} including all identified systematics. The value of w is inconsistent with the cosmological constant value of 1 at the 2.3σ level. Tension endures after removing either the baryon acoustic oscillation (BAO) or the H_{0} constraint, though it is strongest when including the H_{0} constraint. If we include WMAP9 cosmic microwave background (CMB) constraints instead of those from Planck, we find w = 1.124^{+0.083}_{0.065}, which diminishes the discord to <2σ. We cannot conclude whether the tension with flat ΛCDM is a feature of dark energy, new physics, or a combination of chance and systematic errors. The full PanSTARRS1 SN sample with ∼three times as many SNe should provide more conclusive results.
Original language  English 

Article number  44 
Journal  Astrophysical Journal 
Volume  795 
Issue number  1 
DOIs  
Publication status  Published  01 Nov 2014 
Keywords
 cosmological parameters
 cosmology: observations
 dark energy
 supernovae: general
ASJC Scopus subject areas
 Space and Planetary Science
 Astronomy and Astrophysics
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Stephen Smartt
Person: Academic