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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



ID: 719995.0, MPI für Astronomie / Publikationen_mpia
Supercal: cross-calibration of multiple photometric systems to improve cosmological measurements with type Ia supernovae
Authors: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.
Date of Publication (YYYY-MM-DD):2015
Title of Journal:The Astrophysical Journal
Volume:815
Issue / Number:2
Start Page:id. 117 (15 pp)
Audience:Not Specified
Abstract / Description: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.
Free Keywords:dark energy; supernovae: general; surveys
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-637X
URL:http://cdsads.u-strasbg.fr/abs/2015ApJ...815..117S
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