Enhancing weak lensing redshift distribution characterization by optimizing the Dark Energy Survey Self-Organizing Map Photo-z method

Characterization of the redshift distribution of ensembles of galaxies is pivotal for large scale structure cosmological studies. In this work, we focus on improving the Self-Organizing Map (SOM) methodology for photometric redshift estimation (SOMPZ), specifically in anticipation of the Dark Energy Survey Year 6 (DES Y6) data. This data set, featuring deeper and fainter galaxies than DES Year 3 (DES Y3), demands adapted techniques to ensure accurate recovery of the underlying redshift distribution. We investigate three strategies for enhancing the existing SOM-based approach used in DES Y3: 1) Replacing the Y3 SOM algorithm with one tailored for redshift estimation challenges; 2) Incorporating <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mtext mathvariant="italic">𝑔</mml:mtext> </mml:math> -band flux information to refine redshift estimates (i.e. using <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mtext mathvariant="italic">𝑔𝑟𝑖𝑧</mml:mtext> </mml:math> fluxes as opposed to only <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mtext mathvariant="italic">𝑟𝑖𝑧</mml:mtext> </mml:math> ); 3) Augmenting redshift data for galaxies where available. These methods are applied to DES Y3 data, and results are compared to the Y3 fiducial ones. Our analysis indicates significant improvements with the first two strategies, notably reducing the overlap between redshift bins. By combining strategies 1 and 2, we have successfully managed to reduce redshift bin overlap in DES Y3 by up to 66 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>%</mml:mi> </mml:math> . Conversely, the third strategy, involving the addition of redshift data for selected galaxies as an additional feature in the method, yields inferior results and is abandoned. Our findings contribute to the advancement of weak lensing redshift characterization and lay the groundwork for better redshift characterization in DES Year 6 and future stage IV surveys, like the Rubin Observatory.

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Journal
The Open Journal of Astrophysics
Published
2026-07-28
DOI
https://doi.org/10.33232/001c.165871
Primary Topic
CCD and CMOS Imaging Sensors
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article
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0.00

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article

Enhancing weak lensing redshift distribution characterization by optimizing the Dark Energy Survey Self-Organizing Map Photo-z method

A. Roodman, M. Paterno, K. Herner, S. Everett et al.
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The Open Journal of Astrophysics
CCD and CMOS Imaging Sensors
article

Enhancing weak lensing redshift distribution characterization by optimizing the Dark Energy Survey Self-Organizing Map Photo-z method

A. Roodman, M. Paterno, K. Herner, S. Everett, I. Ferrero, J. Cordero, S. R. Hinton, J. Myles, T. N. Varga, H. Camacho, M. Gatti, J. Carretero, B. Yin, I. Harrison, J. García-Bellido, S. Bocquet, J. L. Marshall, L. N. da Costa, M. R. Becker, A. Drlica-Wagner, G. Giannini, L. F. Secco, D. J. James, J. Frieman, Francisco Javier Castander, D. L. Burke, A. A. Plazas, Gregory Tarlé, E. Suchyta, J. Prat, E. Sheldon, A. Amon, K. Eckert, A. Porredon, R. Chen, A Navarro-Alsina, Eric Huff, Hung-Jin Huang, R. A. Gruendl, J. Zuntz, O. Alves, Xiao Fang, I. Tutusaus, N. MacCrann, G. M. Bernstein, C. Chang, E. S. Rykoff, E. Krause, Scott Dodelson, K. Honscheid, T. Shin, S. Samuroff, J. Elvin-Poole, J. McCullough, D. Sanchez Cid, D. Gruen, Eusebio Sanchez, Javier Sánchez, J. Mena-Fernández, A. Campos, I. Sevilla-Noarbe, Ashley J. Ross, V. Vikram, A. Carnero Rosell, J. De Vicente, ENRIQUE GAZTAÑAGA, Marco Raveri, T. F. Eifler, K. Kuehn, P.-F. Léget, C. To, N. Kuropatkin, J. García-Bellido, F. Menanteau, A. Ferté, Mike Jarvis, Joseph DeRose, J. Blazek, N. Weaverdyck, C. Sánchez, R. L. C. Ogando, Shivam Pandey, A. Choi, M. Lima, R. Miquel, A. Alarcon, M. E. S. Pereira, R. P. Rollins, H. T. Diehl, F. Andrade-Oliveira, A. Pieres, C. Doux, R. Cawthon, Risa H. Wechsler, M. Costanzi, E. S. Rykoff, M. Smith, H. Lin, B. Flaugher, M. A. Troxel, D. Brooks, Y. Zhang, M. Carrasco Kind, J. Frieman, M. E. C. Swanson, B Yanny, O. Friedrich, W. G. Hartley, D. Bacon, M. Aguena, Peter Doel, K. Bechtol, James Annis, R G Rosenfeld, C. Davis, G. Gutiérrez
article en

Abstract

Characterization of the redshift distribution of ensembles of galaxies is pivotal for large scale structure cosmological studies. In this work, we focus on improving the Self-Organizing Map (SOM) methodology for photometric redshift estimation (SOMPZ), specifically in anticipation of the Dark Energy Survey Year 6 (DES Y6) data. This data set, featuring deeper and fainter galaxies than DES Year 3 (DES Y3), demands adapted techniques to ensure accurate recovery of the underlying redshift distribution. We investigate three strategies for enhancing the existing SOM-based approach used in DES Y3: 1) Replacing the Y3 SOM algorithm with one tailored for redshift estimation challenges; 2) Incorporating <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mtext mathvariant="italic">𝑔</mml:mtext> </mml:math> -band flux information to refine redshift estimates (i.e. using <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mtext mathvariant="italic">𝑔𝑟𝑖𝑧</mml:mtext> </mml:math> fluxes as opposed to only <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mtext mathvariant="italic">𝑟𝑖𝑧</mml:mtext> </mml:math> ); 3) Augmenting redshift data for galaxies where available. These methods are applied to DES Y3 data, and results are compared to the Y3 fiducial ones. Our analysis indicates significant improvements with the first two strategies, notably reducing the overlap between redshift bins. By combining strategies 1 and 2, we have successfully managed to reduce redshift bin overlap in DES Y3 by up to 66 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>%</mml:mi> </mml:math> . Conversely, the third strategy, involving the addition of redshift data for selected galaxies as an additional feature in the method, yields inferior results and is abandoned. Our findings contribute to the advancement of weak lensing redshift characterization and lay the groundwork for better redshift characterization in DES Year 6 and future stage IV surveys, like the Rubin Observatory.

The Open Journal of AstrophysicsVol. 9
Institució Catalana de Recerca i Estudis Avançats (ES), Nordic Institute for Theoretical Physics (SE), California Institute of Technology (US), Universitat Autònoma de Barcelona (ES), Argonne National Laboratory (US), Oak Ridge National Laboratory (US), Commonwealth Scientific and Industrial Research Organisation (AU), Space Telescope Science Institute (US), University of Wisconsin System (US), Fermi National Accelerator Laboratory (US), Harvard University (US), University of Trieste (IT), University of Waterloo (CA), Universidad de La Laguna (ES), William & Mary (US), The University of Queensland (AU), Universidade Estadual de Campinas (UNICAMP) (BR), Urbana University (US), University of California, Santa Cruz (US), Institute for High Energy Physics (ES), Princeton University (US), University of Michigan (US), Lowell Observatory (US), Trieste Astronomical Observatory (IT), The Ohio State University at Lima (US), Regional Municipality of Waterloo (CA), Valongo Observatory (BR), Institut d'Estudis Espacials de Catalunya (ES), Kavli Institute for Particle Astrophysics and Cosmology (US), Genoa (Brazil) (BR), Excellence Cluster Origins (DE), Menlo School (US), Institut Català de Ciències del Clima (ES), SKA Observatory (GB), IIT@MIT (US), Michigan United (US), Astrobiology Center (JP), California Consortium of Addiction Programs and Professionals (US), Unidades Centrales Científico-Técnicas (ES), Istituto Nazionale di Fisica Nucleare, Sezione di Genova (IT), Institut für Urheber- und Medienrecht (DE), Hamburg Institut (Germany) (DE), Cerro Tololo Inter-American Observatory (CL), Laboratoire de Physique Subatomique et de Cosmologie (FR), ORCID (US), Laboratório Interinstitucional de e-Astronomia (BR), Institute for Fundamental Physics of the Universe (IT), Pierre Auger Observatory (AR), Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (ES), Institut de Recherche en Astrophysique et Planétologie (FR), State Library of Ohio (US), University College London (GB), Stony Brook University (US), University of Portsmouth (GB), Carnegie Mellon University (US), University of Pennsylvania (US), Ruhr University Bochum (DE), Netherlands Institute for Radio Astronomy (NL), Brookhaven College (US)
National Science Foundation, U.S. Department of Energy, University of Pennsylvania, Ohio State University, University of Portsmouth, Centres de Recerca de Catalunya, University College London, European Commission, University of Sussex, Deutsche Forschungsgemeinschaft, Generalitat de Catalunya, Ministério da Ciência, Tecnologia e Inovação, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Financiadora de Estudos e Projetos, Institut de Física d'Altes Energies, University of Illinois at Urbana-Champaign, Office of Science, Science and Technology Facilities Council, European Regional Development Fund, High Energy Physics, Integrated Electronics Engineering Center, Binghamton University, Argonne National Laboratory, Fermilab, Lawrence Berkeley National Laboratory, SLAC National Accelerator Laboratory
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