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Dark Energy Survey Year 6 results: Redshift calibration of the MagLim++ lens sample

G. Giannini1,2,*, A. Alarcon1, W. d’Assignies3, G. M. Bernstein4, M. A. Troxel5, C. Chang6,2, B. Yin5, A. Amon7, J. Myles7 et al. (DES Collaboration)

J. Myles7, N. Weaverdyck8,9, A. Porredon10,11, D. Anbajagane2, S. Avila11, K. Bechtol12, M. R. Becker13, J. Blazek14, M. Crocce15,1, D. Gruen16, M. Rodriguez-Monroy17,18, C. Sánchez3,19, I. Sevilla-Noarbe11, M. Aguena20,21, S. Allam22, O. Alves23, F. Andrade-Oliveira24, D. Bacon25, S. Bocquet16, D. Brooks26, R. Camilleri27, A. Carnero Rosell28,21,29, J. Carretero3, R. Cawthon30, L. N. da Costa21, M. E. da Silva Pereira31, T. M. Davis27, J. De Vicente11, D. L. DePoy32, S. Desai33, H. T. Diehl22, S. Dodelson22,6,2, P. Doel26, C. Doux4,34, A. Drlica-Wagner2,22,6, J. Elvin-Poole35, S. Everett36, A. E. Evrard37,23, B. Flaugher22, J. Frieman6,22,2, J. García-Bellido38, M. Gatti2,1, E. Gaztanaga25,1,15, P. Giles39, R. A. Gruendl40,41, G. Gutierrez22, K. Herner22, S. R. Hinton27, D. L. Hollowood42, K. Honscheid43,44, D. Huterer23, D. J. James45, K. Kuehn46,47, O. Lahav26, S. Lee48,49, H. Lin22, J. L. Marshall32, J. Mena-Fernández34,50, F. Menanteau41,40, R. Miquel3,51, J. Muir52,53, R. L. C. Ogando54, D. Petravick41, A. A. Plazas Malagón55,56, J. Prat57,58, M. Raveri59, E. S. Rykoff56,55, S. Samuroff3,14, E. Sanchez11, D. Sanchez Cid24,11, T. Shin60, M. Smith61, E. Suchyta62, M. E. C. Swanson41, G. Tarle23, D. Thomas25, C. To6, D. L. Tucker22, V. Vikram63, and M. Yamamoto5,7 (DES Collaboration)

  • 1Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans, s/n, 08193 Barcelona, Spain
  • 2Kavli Institute for Cosmological Physics, University of Chicago, Chicago, Illinois 60637, USA
  • 3Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Campus UAB, 08193 Bellaterra (Barcelona) Spain
  • 4Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
  • 5Department of Physics, Duke University, Durham, North Carolina 27708, USA
  • 6Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60637, USA
  • 7Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, New Jersey 08544, USA
  • 8Berkeley Center for Cosmological Physics, Department of Physics, University of California, Berkeley, California 94720, USA
  • 9Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA
  • 10Ruhr University Bochum, Faculty of Physics and Astronomy, Astronomical Institute, German Centre for Cosmological Lensing, 44780 Bochum, Germany
  • 11Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain
  • 12Physics Department, 2320 Chamberlin Hall, University of Wisconsin-Madison, 1150 University Avenue Madison, Wisconsin 53706-1390, USA
  • 13Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, USA
  • 14Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA
  • 15Institut d’Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain
  • 16University Observatory, LMU Faculty of Physics, Scheinerstraße 1, 81679 Munich, Germany
  • 17Instituto de Física Teórica UAM/CSIC, Universidad Autónoma de Madrid, 28049 Madrid, Spain
  • 18Laboratoire de physique des 2 infinis Irène Joliot-Curie, CNRS Université Paris-Saclay, Bât. 100, F-91405 Orsay Cedex, France
  • 19Departament de Física, Universitat Autònoma de Barcelona (UAB), 08193 Bellaterra, Barcelona, Spain
  • 20INAF-Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, I-34143 Trieste, Italy
  • 21Laboratório Interinstitucional de e-Astronomia—LIneA, Avenida Pastor Martin Luther King Jr, 126 Del Castilho, Nova América Offices, Torre 3000/sala 817 CEP: 20765-000, Brazil
  • 22Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, Illinois 60510, USA
  • 23Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
  • 24Physik-Institut, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
  • 25Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, PO1 3FX, United Kingdom
  • 26Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, United Kingdom
  • 27School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia
  • 28Universidad de La Laguna, Departamento de Astrofísica, E-38206 La Laguna, Tenerife, Spain
  • 29Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife, Spain
  • 30Oxford College of Emory University, Oxford, Georgia 30054, USA
  • 31Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
  • 32George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, and Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843, USA
  • 33Department of Physics, IIT Hyderabad, Kandi, Telangana 502285, India
  • 34Université Grenoble Alpes, CNRS, LPSC-IN2P3, 38000 Grenoble, France
  • 35Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
  • 36California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, California 91125, USA
  • 37Department of Astronomy, University of Michigan, Ann Arbor, Michigan 48109, USA
  • 38Instituto de Fisica Teorica UAM/CSIC, Universidad Autonoma de Madrid, 28049 Madrid, Spain
  • 39Department of Physics and Astronomy, Pevensey Building, University of Sussex, Brighton, BN1 9QH, United Kingdom
  • 40Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, Illinois 61801, USA
  • 41Center for Astrophysical Surveys, National Center for Supercomputing Applications, 1205 West Clark Street, Urbana, Illinois 61801, USA
  • 42Santa Cruz Institute for Particle Physics, Santa Cruz, California 95064, USA
  • 43Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
  • 44Center for Cosmology and Astro-Particle Physics, The Ohio State University, Columbus, Ohio 43210, USA
  • 45Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, Massachusetts 02138, USA
  • 46Australian Astronomical Optics, Macquarie University, North Ryde, NSW 2113, Australia
  • 47Lowell Observatory, 1400 Mars Hill Road, Flagstaff, Arizona 86001, USA
  • 48Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, California 91109, USA
  • 49Department of Physics and Astronomy, Ohio University, Clippinger Labs, Athens, Ohio 45701
  • 50Aix Marseille University, CNRS/IN2P3, CPPM, Marseille, France
  • 51Institució Catalana de Recerca i Estudis Avançats, E-08010 Barcelona, Spain
  • 52Perimeter Institute for Theoretical Physics, 31 Caroline St. North, Waterloo, Ontario N2L 2Y5, Canada
  • 53Department of Physics, University of Cincinnati, Cincinnati, Ohio 45221, USA
  • 54Observatório Nacional, Rua Gal. José Cristino 77, Rio de Janeiro, Rio de Janeiro—20921-400, Brazil
  • 55Kavli Institute for Particle Astrophysics and Cosmology, P.O. Box 2450, Stanford University, Stanford, California 94305, USA
  • 56SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
  • 57Nordita, KTH Royal Institute of Technology and Stockholm University, Hannes Alfvéns väg 12, SE-10691 Stockholm, Sweden
  • 58University of Copenhagen, Dark Cosmology Centre, Juliane Maries Vej 30, 2100 Copenhagen O, Denmark
  • 59Department of Physics, University of Genova and INFN, Via Dodecaneso 33, 16146, Genova, Italy
  • 60Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
  • 61Physics Department, Lancaster University, Lancaster, LA1 4YB, United Kingdom
  • 62Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
  • 63Central University of Kerala, Periye, Kerala 671320, India

  • *Contact author: giulia.giannini15@gmail.com
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Phys. Rev. D 114, 023520 – Published 7 July, 2026

DOI: https://doi.org/10.1103/mkwr-bfls

Abstract

In this work, we derive and calibrate the redshift distribution of the MagLim++ lens galaxy sample used in the Dark Energy Survey Year 6 (DES Y6) 3×2  pt cosmology analysis. The 3×2  pt analysis combines galaxy clustering from the lens galaxy sample and weak gravitational lensing. The redshift distributions are inferred using the SOMPZ method—a self-organizing map framework that combines deep-field multiband photometry, wide-field data, and a synthetic source injection (balrog) catalog. Key improvements over the DES Year 3 (Y3) calibration include a noise-weighted SOM metric, an expanded balrog catalog, and an improved scheme for propagating systematic uncertainties, which allows us to generate O(108) redshift realizations that collectively span the dominant sources of uncertainty. These realizations are then combined with independent clustering-redshift measurements via importance sampling. The resulting calibration achieves typical uncertainties on the mean redshift of 1%–2%, corresponding to a 20%–30% average reduction relative to DES Y3. We compress the n(z) uncertainties into a small number of orthogonal modes for use in cosmological inference. Marginalizing over these modes leads to only a minor degradation in cosmological constraints. This analysis establishes the MagLim++ sample as a robust lens sample for precision cosmology with DES Y6 and provides a scalable framework for future surveys.

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Phys. Rev. D 114, 023520– Published 7 July, 2026
  • Received 25 March 2026
  • Accepted 26 May 2026
Article part of CHORUS
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