SYSTEMATIC UNCERTAINTIES ASSOCIATED WITH THE COSMOLOGICAL ANALYSIS OF THE FIRST PAN-STARRS1 TYPE Ia SUPERNOVA SAMPLE

Abstract

We probe the systematic uncertainties from 113 Type Ia supernovae (SNIa) in\nthe Pan-STARRS1 (PS1) sample along with 197 SN Ia from a combination of\nlow-redshift surveys. The companion paper by Rest et al. (2013) describes the\nphotometric measurements and cosmological inferences from the PS1 sample. The\nlargest systematic uncertainty stems from the photometric calibration of the\nPS1 and low-z samples. We increase the sample of observed Calspec standards\nfrom 7 to 10 used to define the PS1 calibration system. The PS1 and SDSS-II\ncalibration systems are compared and discrepancies up to ~0.02 mag are\nrecovered. We find uncertainties in the proper way to treat intrinsic colors\nand reddening produce differences in the recovered value of w up to 3%. We\nestimate masses of host galaxies of PS1 supernovae and detect an insignificant\ndifference in distance residuals of the full sample of 0.037\\pm0.031 mag for\nhost galaxies with high and low masses. Assuming flatness in our analysis of\nonly SNe measurements, we find $w = {-1.120^{+0.360}_{-0.206}\\textrm{(Stat)}\n^{+0.269}_{-0.291}\\textrm{(Sys)}}$. With additional constraints from BAO,\nCMB(Planck) and H0 measurements, we find $w = -1.166^{+0.072}_{-0.069}$ and\n$\\Omega_M=0.280^{+0.013}_{-0.012}$ (statistical and systematic errors added in\nquadrature). Significance of the inconsistency with $w=-1$ depends on whether\nwe use Planck or WMAP measurements of the CMB:\n$w_{\\textrm{BAO+H0+SN+WMAP}}=-1.124^{+0.083}_{-0.065}$.\n