Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 478, Issue 1, Pages 592-610Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/sty957
Keywords
methods: data analysis; catalogues; surveys
Categories
Funding
- NASA through Einstein Postdoctoral Fellowship by the Chandra X-ray Center [PF5-160138]
- NASA [NAS8-03060]
- U.S. Department of Energy
- U.S. National Science Foundation
- Ministry of Science and Education of Spain
- Science and Technology Facilities Council of the United Kingdom
- Higher Education Funding Council for England
- National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign
- Kavli Institute of Cosmological Physics at the University of Chicago
- Center for Cosmology and Astro-Particle Physics at the Ohio State University
- Mitchell Institute for Fundamental Physics and Astronomy at Texas AM University
- Financiadora de Estudos e Projetos
- Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro
- Conselho Nacional de Desenvolvimento Cientifico e Tecnologico
- Ministerio da Ciencia, Tecnologia e Inovacao
- Deutsche Forschungsgemeinschaft
- Argonne National Laboratory
- University of California at Santa Cruz
- University of Cambridge
- Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas-Madrid
- University of Chicago
- University College London
- DES-Brazil Consortium
- University of Edinburgh
- Eidgenossische Technische Hochschule Zurich
- Fermi National Accelerator Laboratory
- University of Illinois at Urbana-Champaign
- Institut de Ciencies de l'Espai (IEEC/CSIC)
- Institut de Fisica d'Altes Energies
- Lawrence Berkeley National Laboratory
- Ludwig-Maximilians Universitat Munchen
- associated Excellence Cluster Universe
- University of Michigan
- National Optical Astronomy Observatory,
- University of Nottingham
- Ohio State University
- University of Pennsylvania
- University of Portsmouth
- SLAC National Accelerator Laboratory
- Stanford University
- University of Sussex
- Texas AM University
- OzDES Membership Consortium
- National Science Foundation [AST-1138766, AST-1536171]
- MINECO [AYA2015-71825, ESP2015-88861, FPA2015-68048, SEV-2012-0234, SEV-2016-0597, MDM-2015-0509]
- ERDF funds from the European Union
- CERCA programme of the Generalitat de Catalunya
- European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013)
- ERC [240672, 291329, 306478]
- Australian Research Council Centre of Excellence for All-sky Astrophysics [CE110001020]
- U.S. Department of Energy, Office of Science, Office of High Energy Physics [DE-AC02-07CH11359]
- Very Large Telescope at the ESO Paranal Observatory [LP175.A-0839]
- STFC [ST/L005573/1, ST/J005428/1, ST/P000649/1, ST/M007030/1, ST/K00090X/1, ST/M002853/1, ST/I001204/1, ST/R000972/1, ST/K006797/1, ST/F002335/1] Funding Source: UKRI
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We describe the derivation and validation of redshift distribution estimates and their uncertainties for the populations of galaxies used as weak-lensing sources in the Dark Energy Survey (DES) Year 1 cosmological analyses. The Bayesian Photometric Redshift (BPZ) code is used to assign galaxies to four redshift bins between z approximate to 0.2 and approximate to 1.3, and to produce initial estimates of the lensing-weighted redshift distributions n(PZ)(i)(z) proportional to d(n)(i)/dz for members of bin i. Accurate determination of cosmological parameters depends critically on knowledge of n(i), but is insensitive to bin assignments or redshift errors for individual galaxies. The cosmological analyses allow for shifts n(i)(z) = n(PZ)(i)(z - Delta z(i)) to correct the mean redshift of n(i)(z) for biases in n(PZ)(i). The Delta z(i) are constrained by comparison of independently estimated 30-band photometric redshifts of galaxies in the Cosmic Evolution Survey (COSMOS) field to BPZ estimates made from the DES griz fluxes, for a sample matched in fluxes, pre-seeing size, and lensing weight to the DES weak-lensing sources. In companion papers, the Delta z(i) of the three lowest redshift bins are further constrained by the angular clustering of the source galaxies around red galaxies with secure photometric redshifts at 0.15 < z < 0.9. This paper details the BPZ and COSMOS procedures, and demonstrates that the cosmological inference is insensitive to details of the n(i)(z) beyond the choice of Delta z(i). The clustering and COSMOS validation methods produce consistent estimates of Delta z(i) in the bins where both can be applied, with combined uncertainties of sigma(i)(Delta z) = 0.015, 0.013, 0.011, and 0.022 in the four bins. Repeating the photo-z procedure instead using the Directional Neighbourhood Fitting algorithm, or using the n(i)(z) estimated from the matched sample in COSMOS, yields no discernible difference in cosmological inferences.
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