Аннотация
We present griz light curves of 146 spectroscopically confirmed Type Ia
Supernovae (0.03<z<0.65) discovered during the first 1.5 years of the
Pan-STARRS1 Medium Deep Survey. The Pan-STARRS1 natural photometric system is
determined by a combination of on-site measurements of the instrument response
function and observations of spectrophotometric standard stars. We have
investigated spatial and time variations in the photometry, and we find that
the systematic uncertainties in the photometric system are currently 1.2%
without accounting for the uncertainty in the HST Calspec definition of the AB
system. We discuss our efforts to minimize the systematic uncertainties in the
photometry. A Hubble diagram is constructed with a subset of 112 SNe Ia (out of
the 146) that pass our light curve quality cuts. The cosmological fit to 313
SNe Ia (112 PS1 SNe Ia + 201 low-z SNe Ia), using only SNe and assuming a
constant dark energy equation of state and flatness, yields w =
-1.015^+0.319_-0.201(Stat)+0.164_-0.122(Sys). When combined with
BAO+CMB(Planck)+H0, the analysis yields Ømega_M = 0.277^+0.010_-0.012 and
w = -1.186^+0.076_-0.065 including all identified systematics, as spelled
out in the companion paper by Scolnic et al. (2013a). The value of w is
inconsistent with the cosmological constant value of -1 at the 2.4 sigma level.
This tension has been seen in other high-z SN surveys and endures after
removing either the BAO or the H0 constraint. If we include WMAP9 CMB
constraints instead of those from Planck, we find w = -1.142^+0.076_-0.087,
which diminishes the discord to <2 sigma. We cannot conclude whether the
tension with flat CDM is a feature of dark energy, new physics, or a
combination of chance and systematic errors. The full Pan-STARRS1 supernova
sample will be 3 times as large as this initial sample, which should provide
more conclusive results.
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