University of Cambridge > Talks.cam > Kavli Institute for Cosmology Seminars > New Constraints on Dark Energy from Photometrically Classified Type Ia Supernovae and the Foundation Supernova Survey

New Constraints on Dark Energy from Photometrically Classified Type Ia Supernovae and the Foundation Supernova Survey

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Measurements of the dark energy equation-of-state parameter, w, have been limited by uncertainty in the selection effects and photometric calibration of z < 0.1 Type Ia supernovae (SNe Ia). The Foundation Supernova Survey is designed to lower these uncertainties by creating a new sample of z < 0.1 SNe Ia observed on the Pan-STARRS system. I will discuss combining the Foundation sample with SNe from the Pan-STARRS Medium Deep Survey and measure cosmological parameters with 1,338 SNe from a single telescope and a single, well-calibrated photometric system. For the first time, both the low-z and high-z data are predominantly discovered by surveys that do not target pre-selected galaxies, reducing selection bias uncertainties. The z > 0.1 data include 875 SNe without spectroscopic classifications and we show that we can robustly marginalize over CC SN contamination. Foundation Hubble residuals are fainter than the pre-existing low-z Hubble residuals by 0.046 ± 0.027 mag (stat+sys). By combining the SN Ia data with cosmic microwave background constraints, we find w = −0.938 ± 0.053, consistent with ΛCDM. With 463 spectroscopically classified SNe Ia alone, we measure w=−0.933 ± 0.061. Using the more homogeneous and better-characterized Foundation sample gives a 55% reduction in the systematic uncertainty attributed to SN Ia sample selection biases. Although use of just a single photometric system at low and high redshift increases the impact of photometric calibration uncertainties, previous low-z samples may have correlated calibration uncertainties that were neglected in past studies. The full Foundation sample will observe up to 800 SNe to anchor the LSST and WFIRST Hubble diagrams.

This talk is part of the Kavli Institute for Cosmology Seminars series.

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