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SUMMARY:New Constraints on Dark Energy from Photometrically Classified Typ
 e Ia Supernovae and the Foundation Supernova Survey - David Jones (UC Sant
 a Cruz)
DTSTART:20190328T133000Z
DTEND:20190328T143000Z
UID:TALK122224@talks.cam.ac.uk
CONTACT:Steven Brereton
DESCRIPTION:Measurements of the dark energy equation-of-state parameter\, 
 w\, have been limited by uncertainty in the selection effects and photomet
 ric calibration of z < 0.1 Type Ia supernovae (SNe Ia). The Foundation Sup
 ernova Survey is designed to lower these uncertainties by creating a new s
 ample 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 S
 urvey and measure cosmological parameters with 1\,338 SNe from a single te
 lescope and a single\, well-calibrated photometric system. For the first t
 ime\, both the low-z and high-z data are predominantly discovered by surve
 ys that do not target pre-selected galaxies\, reducing selection bias unce
 rtainties. The z > 0.1 data include 875 SNe without spectroscopic classifi
 cations and we show that we can robustly marginalize over CC SN contaminat
 ion.  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 SN
 e Ia alone\, we measure w=−0.933 ± 0.061. Using the more homogeneous an
 d better-characterized Foundation sample gives a 55% reduction in the syst
 ematic uncertainty attributed to SN Ia sample selection biases. Although u
 se of just a single photometric system at low and high redshift increases 
 the impact of photometric calibration uncertainties\, previous low-z sampl
 es may have correlated calibration uncertainties that were neglected in pa
 st studies. The full Foundation sample will observe up to 800 SNe to ancho
 r the LSST and WFIRST Hubble diagrams.
LOCATION:Martin Ryle Meeting Room KICC
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