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Supercal: Cross-calibration of Multiple Photometric Systems to Improve Cosmological Measurements with Type Ia Supernovae

Scolnic, D.; Casertano, S.; Riess, A.; Rest, A.; Schlafly, E.; Foley, R.J.; Finkbeiner, D.; Tang, C.; Burgett, W.S.; Chambers, K.C.; Draper, P.W.; Flewelling, H.; Hodapp, K.W.; Huber, M.E.; Kaiser, N.; Kudritzki, R.P.; Magnier, E.A.; Metcalfe, N.; Stubbs, C.W.

Supercal: Cross-calibration of Multiple Photometric Systems to Improve Cosmological Measurements with Type Ia Supernovae Thumbnail


Authors

D. Scolnic

S. Casertano

A. Riess

A. Rest

E. Schlafly

R.J. Foley

D. Finkbeiner

C. Tang

W.S. Burgett

K.C. Chambers

P.W. Draper

H. Flewelling

K.W. Hodapp

M.E. Huber

N. Kaiser

R.P. Kudritzki

E.A. Magnier

C.W. Stubbs



Abstract

Current cosmological analyses, which use Type Ia supernova observations, combine supernova (SN) samples to expand the redshift range beyond that of a single sample and increase the overall sample size. The inhomogeneous photometric calibration between different SN samples is one of the largest systematic uncertainties of the cosmological parameter estimation. To place these different samples on a single system, analyses currently use observations of a small sample of very bright flux standards on the Hubble Space Telescope system. We propose a complementary method, called "Supercal," in which we use measurements of secondary standards in each system, compare these to measurements of the same stars in the Pan-STARRS1 (PS1) system, and determine the offsets for each system relative to PS1, placing all SN observations on a single, consistent photometric system. PS1 has observed 3π of the sky and has a relative calibration of better than 5 mmag (for ~15 < griz < 21 mag), making it an ideal reference system. We use this process to recalibrate optical observations taken by the following SN samples: PS1, Supernova Legacy Survey, SDSS, CSP, and CfA1-4. We measure discrepancies on average of 10 mmag, but up to 35 mmag, in various optical passbands. We find that correcting for these differences changes the recovered values for the dark energy equation of state parameter, w, by an average of 2.6%. This change is roughly half the size of current statistical constraints on w. The size of this effect strongly depends on the error in the B − V calibration of the low-z surveys. The Supercal method will allow future analyses to tie past samples to the best calibrated sample.

Citation

Scolnic, D., Casertano, S., Riess, A., Rest, A., Schlafly, E., Foley, R., …Stubbs, C. (2015). Supercal: Cross-calibration of Multiple Photometric Systems to Improve Cosmological Measurements with Type Ia Supernovae. Astrophysical Journal, 815, https://doi.org/10.1088/0004-637x/815/2/117

Journal Article Type Article
Publication Date Dec 1, 2015
Deposit Date Apr 5, 2016
Publicly Available Date Mar 29, 2024
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 815
DOI https://doi.org/10.1088/0004-637x/815/2/117
Related Public URLs http://arxiv.org/abs/1508.05361

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Copyright Statement
© 2015. The American Astronomical Society. All rights reserved.





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