TY - JOUR
T1 - The 2-degree Field Lensing Survey
T2 - Photometric redshifts from a large new training sample to r < 19.5
AU - Wolf, C.
AU - Johnson, A. S.
AU - Bilicki, M.
AU - Blake, C.
AU - Amon, A.
AU - Erben, T.
AU - Glazebrook, K.
AU - Heymans, C.
AU - Hildebrandt, H.
AU - Joudaki, S.
AU - Klaes, D.
AU - Kuijken, K.
AU - Lidman, C.
AU - Marin, F.
AU - Parkinson, D.
AU - Poole, G.
N1 - Funding Information:
CW was supported by Australian Research Council Laureate Grant FL0992131. Parts of this research were conducted by the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020. MB is supported by the Netherlands Organization for Scientific Research, NWO, through grant number 614.001.451, through FP7 grant number 279396 from the European Research Council and by the Polish National Science Center under contract #UMO-2012/07/D/ST9/02785. CB acknowledges the support of the Australian Research Council through the award of a Future Fellowship. CH acknowledges support from the European Research Council under grant number 647112. HH was supported by the Deutsche Forschungsgemeinschaft under Emmy Noether grant Hi 1495/2-1. TE and DK are supported by the Deutsche Forschungsgemeinschaft in the framework of the TR33 'The Dark Universe'. This study is based in part on data acquired at the Australian Astronomical Observatory, through program A/2014B/08. KK acknowledges support by the Alexander von Humboldt Foundation. DP is supported by the Australian Research Council Future Fellowship Grant FT130101086. This publication used data obtained by the ESO VST-ATLAS survey under program ID 177.A-3011. It also makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration.
Publisher Copyright:
© 2016 The Authors.
PY - 2017/4/11
Y1 - 2017/4/11
N2 - We present a new training set for estimating empirical photometric redshifts of galaxies, which was created as part of the 2-degree Field Lensing Survey project. This training set is located in a ~700 deg2 area of the Kilo-Degree-Survey South field and is randomly selected and nearly complete at r < 19.5. We investigate the photometric redshift performance obtained with ugriz photometry from VST-ATLAS and W1/W2 fromWISE, based on several empirical and template methods. The best redshift errors are obtained with kernel-density estimation (KDE), as are the lowest biases, which are consistent with zero within statistical noise. The 68th percentiles of the redshift scatter for magnitude-limited samples at r < (15.5, 17.5, 19.5) are (0.014, 0.017, 0.028). In this magnitude range, there are no known ambiguities in the colour-redshift map, consistent with a small rate of redshift outliers. In the fainter regime, the KDE method produces p(z) estimates per galaxy that represent unbiased and accurate redshift frequency expectations. The p(z) sum over any subsample is consistent with the true redshift frequency plus Poisson noise. Further improvements in redshift precision at r < 20 would mostly be expected from filter sets with narrower passbands to increase the sensitivity of colours to small changes in redshift.
AB - We present a new training set for estimating empirical photometric redshifts of galaxies, which was created as part of the 2-degree Field Lensing Survey project. This training set is located in a ~700 deg2 area of the Kilo-Degree-Survey South field and is randomly selected and nearly complete at r < 19.5. We investigate the photometric redshift performance obtained with ugriz photometry from VST-ATLAS and W1/W2 fromWISE, based on several empirical and template methods. The best redshift errors are obtained with kernel-density estimation (KDE), as are the lowest biases, which are consistent with zero within statistical noise. The 68th percentiles of the redshift scatter for magnitude-limited samples at r < (15.5, 17.5, 19.5) are (0.014, 0.017, 0.028). In this magnitude range, there are no known ambiguities in the colour-redshift map, consistent with a small rate of redshift outliers. In the fainter regime, the KDE method produces p(z) estimates per galaxy that represent unbiased and accurate redshift frequency expectations. The p(z) sum over any subsample is consistent with the true redshift frequency plus Poisson noise. Further improvements in redshift precision at r < 20 would mostly be expected from filter sets with narrower passbands to increase the sensitivity of colours to small changes in redshift.
KW - Methods: statistical
KW - Surveys
KW - galaxies: distances and redshifts
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U2 - 10.1093/mnras/stw3151
DO - 10.1093/mnras/stw3151
M3 - Article
AN - SCOPUS:85019246310
SN - 0035-8711
VL - 466
SP - 1582
EP - 1159
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -