Dark Energy Survey Year 6 results: Clustering redshifts and importance sampling of self-organized-maps 𝑛⁡(𝑧) realizations for 3 × 2 ⁢pt samples

d’Assignies, W. [Institut de Física d’Altes Energies (IFAE); Barcelona Institute of Science and Technology] (ORCID:0000000297191717); Bernstein, G. M. [University of Pennsylvania]; Yin, B. [Duke University Durham]; Giannini, G. [University of Chicago; University of Chicago]; Alarcon, A. [Institute of Space Sciences (ICE, CSIC)]; Manera, M. [Institut de Física d’Altes Energies (IFAE); Barcelona Institute of Science and Technology; Edifici C Facultat de Ciències]; To, C. [University of Chicago]; Yamamoto, M. [Duke University Durham; Princeton University]; Weaverdyck, N. [Lawrence Berkeley National Laboratory; Berkeley Center for Cosmological Physics]; Cawthon, R. [Oxford College of Emory University]; Gatti, M. [University of Chicago]; Amon, A. [Princeton University]; Anbajagane, D. [University of Chicago]; Avila, S. [Medioambientales y Tecnológicas (CIEMAT)]; Becker, M. R. [Argonne National Laboratory]; Bechtol, K. [University of Wisconsin-Madison]; Chang, C. [University of Chicago; University of Chicago]; Crocce, M. [Institute of Space Sciences (ICE, CSIC); Institut d’Estudis Espacials de Catalunya (IEEC)]; De Vicente, J. [Medioambientales y Tecnológicas (CIEMAT)]; Dodelson, S. [University of Chicago; University of Chicago; Fermi National Accelerator Laboratory]; Fang, J. [William Jewell College]; Ferté, A. [SLAC National Accelerator Laboratory]; Gruen, D. [University Observatory]; Legnani, E. [Institut de Física d’Altes Energies (IFAE); Barcelona Institute of Science and Technology]; Porredon, A. [Ruhr University Bochum; Centro de Investigaciones Energéticas]; Prat, J. [University of Chicago; KTH Royal Institute of Technology and Stockholm University]; Rodriguez-Monroy, M. [Universidad Autónoma de Madrid; CNRS Université Paris-Saclay]; Sánchez, C. [Institut de Física d’Altes Energies (IFAE); Barcelona Institute of Science and Technology; Universitat Autònoma de Barcelona (UAB)]; Schutt, T. [SLAC National Accelerator Laboratory; Stanford University; Stanford University]; Sevilla-Noarbe, I. [Centro de Investigaciones Energéticas]; Sanchez Cid, D. [Centro de Investigaciones Energéticas; University of Zürich]; Troxel, M. A. [Duke University Durham]; Abbott, T. M. C. [NSF’s National Optical-Infrared Astronomy Research Laboratory]; Andrade-Oliveira, F. [University of Zürich]; Aguena, M. [Laboratório Interinstitucional de e-Astronomia—LIneA; INAF-Osservatorio Astronomico di Trieste]; Alves, O. [University of Michigan]; Bacon, D. [University of Portsmouth]; Blazek, J. [Northeastern University]; Bocquet, S. [University Observatory]; Brooks, D. [University College London]; Camilleri, R. [University of Queensland]; Carnero Rosell, A. [Laboratório Interinstitucional de e-Astronomia—LIneA; Universidad de La Laguna; Instituto de Astrofisica de Canarias]; Carrasco Kind, M. [National Center for Supercomputing Applications; University of Illinois at Urbana-Champaign]; Carretero, J. [Institut de Física d’Altes Energies (IFAE); Barcelona Institute of Science and Technology]; Castander, F. J. [University of Chicago; Institute of Space Sciences (ICE, CSIC); Institut d’Estudis Espacials de Catalunya (IEEC)]; da Costa, L. N. [Laboratório Interinstitucional de e-Astronomia—LIneA]; da Silva Pereira, M. E. [Universität Hamburg]; Davis, T. M. [University of Queensland]; Desai, S. [IIT Hyderabad]; Doel, P. [University College London]; Doux, C. [Université Grenoble Alpes; University of Pennsylvania]; Drlica-Wagner, A. [University of Chicago; University of Chicago; Fermi National Accelerator Laboratory]; Eifler, T. [University of Arizona; California Institute of Technology]; Elvin-Poole, J. [University of Waterloo]; Everett, S. [California Institute of Technology]; Flaugher, B. [Fermi National Accelerator Laboratory]; Fosalba, P. [Institute of Space Sciences (ICE, CSIC); Institut d’Estudis Espacials de Catalunya (IEEC)]; Frieman, J. [University of Chicago; University of Chicago; Fermi National Accelerator Laboratory]; García-Bellido, J. [Universidad Autonoma de Madrid]; Gaztanaga, E. [Institute of Space Sciences (ICE, CSIC); Institut d’Estudis Espacials de Catalunya (IEEC); University of Portsmouth]; Giles, P. [University of Sussex]; Gutierrez, G. [Fermi National Accelerator Laboratory]; Hinton, S. R. [University of Queensland]; Hollowood, D. L. [Santa Cruz Institute for Particle Physics]; Honscheid, K. [The Ohio State University; The Ohio State University]; Huterer, D. [University of Michigan]; Jain, B. [University of Pennsylvania]; James, D. J. [Center for Astrophysics | Harvard & Smithsonian]; Kuehn, K. [Macquarie University; Lowell Observatory]; Lahav, O. [University College London]; Lee, S. [California Institute of Technology]; Marshall, J. L. [Texas A&M University]; Mena-Fernández, J. [Université Grenoble Alpes]; Menanteau, F. [National Center for Supercomputing Applications; University of Illinois at Urbana-Champaign]; Miquel, R. [Institució Catalana de Recerca i Estudis Avançats; Institut de Física d’Altes Energies (IFAE); Barcelona Institute of Science and Technology]; Muir, J. [University of Cincinnati; Perimeter Institute for Theoretical Physics]; Myles, J. [Princeton University]; Ogando, R. L. C. [Centro de Tecnologia da Informação Renato Archer; Observatório Nacional]; Palmese, A. [Carnegie Mellon University]; Paterno, M. [Fermi National Accelerator Laboratory]; Petravick, P. [National Center for Supercomputing Applications]; Plazas Malagón, A. A. [SLAC National Accelerator Laboratory; Stanford University]; Raveri, M. [University of Genova and INFN]; Roodman, A. [SLAC National Accelerator Laboratory; Stanford University]; Samuroff, S. [Institut de Física d’Altes Energies (IFAE); Barcelona Institute of Science and Technology; Northeastern University]; Sanchez, E. [Medioambientales y Tecnológicas (CIEMAT)]; Sheldon, E. [Brookhaven National Laboratory]; Shin, T. [Stony Brook University]; Smith, M. [Lancaster University]; Suchyta, E. [Oak Ridge National Laboratory]; Swanson, M. E. C. [National Center for Supercomputing Applications]; Tarle, G. [University of Michigan]; Thomas, D. [University of Portsmouth]; Vikram, V. [University of Pennsylvania]; Walker, A. R. [NSF’s National Optical-Infrared Astronomy Research Laboratory]

doi:10.1103/6lfl-h6dg

DOE OSTI · 3647884

Dark Energy Survey Year 6 results: Clustering redshifts and importance sampling of self-organized-maps 𝑛⁡(𝑧) realizations for 3 × 2 ⁢pt samples

View original source ↗Read source document ↗Export metadata ↓

Abstract

This work is part of a series establishing the redshift framework for the 3 × 2 ⁢pt analysis of the Dark Energy Survey Year 6 (DES Y6). For DES Y6, photometric redshift distributions are estimated using self-organizing maps (SOMs), calibrated with spectroscopic and many-band photometric data. To overcome limitations from color-redshift degeneracies and incomplete spectroscopic coverage, we enhance this approach by incorporating clustering-based redshift constraints (clustering-z, or WZ) from angular cross-correlations with BOSS and eBOSS galaxies and eBOSS quasar samples. We define a WZ likelihood and apply importance sampling to a large ensemble of SOM-derived 𝑛⁡(𝑧) realizations, selecting those consistent with the clustering measurements to produce a posterior sample for each lens and source bin. The analysis uses angular scales corresponding to 1.5–5 Mpc to optimize signal-to-noise ratio while mitigating modeling uncertainties and marginalizes over redshift-dependent galaxy bias and other systematics informed by the N-body simulation CARDINAL . While a sparser spectroscopic reference sample limits WZ constraining power at 𝑧 >1.1, particularly for source bins, we demonstrate that combining SOM with WZ improves redshift accuracy and enhances the overall cosmological constraining power of DES Y6. As a result, we estimate an improvement in 𝑆 8 of approximately 10% for cosmic shear and 3 ×2⁢pt analysis, primarily due to the WZ calibration of the source samples.

Explore related subjects

Cosmological parameters Distances, redshifts, & velocities Large scale structure of the Universe

Keep this discovery

BibTeX RIS

d’Assignies, W. [Institut de Física d’Altes Energies (IFAE); Barcelona Institute of Science and Technology] (ORCID:0000000297191717), Bernstein, G. M. [University of Pennsylvania], Yin, B. [Duke University Durham], Giannini, G. [University of Chicago; University of Chicago], Alarcon, A. [Institute of Space Sciences (ICE, CSIC)], Manera, M. [Institut de Física d’Altes Energies (IFAE); Barcelona Institute of Science and Technology; Edifici C Facultat de Ciències], To, C. [University of Chicago], Yamamoto, M. [Duke University Durham; Princeton University], Weaverdyck, N. [Lawrence Berkeley National Laboratory; Berkeley Center for Cosmological Physics], Cawthon, R. [Oxford College of Emory University], Gatti, M. [University of Chicago], Amon, A. [Princeton University], Anbajagane, D. [University of Chicago], Avila, S. [Medioambientales y Tecnológicas (CIEMAT)], Becker, M. R. [Argonne National Laboratory], Bechtol, K. [University of Wisconsin-Madison], Chang, C. [University of Chicago; University of Chicago], Crocce, M. [Institute of Space Sciences (ICE, CSIC); Institut d’Estudis Espacials de Catalunya (IEEC)], De Vicente, J. [Medioambientales y Tecnológicas (CIEMAT)], Dodelson, S. [University of Chicago; University of Chicago; Fermi National Accelerator Laboratory], Fang, J. [William Jewell College], Ferté, A. [SLAC National Accelerator Laboratory], Gruen, D. [University Observatory], Legnani, E. [Institut de Física d’Altes Energies (IFAE); Barcelona Institute of Science and Technology], Porredon, A. [Ruhr University Bochum; Centro de Investigaciones Energéticas], Prat, J. [University of Chicago; KTH Royal Institute of Technology and Stockholm University], Rodriguez-Monroy, M. [Universidad Autónoma de Madrid; CNRS Université Paris-Saclay], Sánchez, C. [Institut de Física d’Altes Energies (IFAE); Barcelona Institute of Science and Technology; Universitat Autònoma de Barcelona (UAB)], Schutt, T. [SLAC National Accelerator Laboratory; Stanford University; Stanford University], Sevilla-Noarbe, I. [Centro de Investigaciones Energéticas], Sanchez Cid, D. [Centro de Investigaciones Energéticas; University of Zürich], Troxel, M. A. [Duke University Durham], Abbott, T. M. C. [NSF’s National Optical-Infrared Astronomy Research Laboratory], Andrade-Oliveira, F. [University of Zürich], Aguena, M. [Laboratório Interinstitucional de e-Astronomia—LIneA; INAF-Osservatorio Astronomico di Trieste], Alves, O. [University of Michigan], Bacon, D. [University of Portsmouth], Blazek, J. [Northeastern University], Bocquet, S. [University Observatory], Brooks, D. [University College London], Camilleri, R. [University of Queensland], Carnero Rosell, A. [Laboratório Interinstitucional de e-Astronomia—LIneA; Universidad de La Laguna; Instituto de Astrofisica de Canarias], Carrasco Kind, M. [National Center for Supercomputing Applications; University of Illinois at Urbana-Champaign], Carretero, J. [Institut de Física d’Altes Energies (IFAE); Barcelona Institute of Science and Technology], Castander, F. J. [University of Chicago; Institute of Space Sciences (ICE, CSIC); Institut d’Estudis Espacials de Catalunya (IEEC)], da Costa, L. N. [Laboratório Interinstitucional de e-Astronomia—LIneA], da Silva Pereira, M. E. [Universität Hamburg], Davis, T. M. [University of Queensland], Desai, S. [IIT Hyderabad], Doel, P. [University College London], Doux, C. [Université Grenoble Alpes; University of Pennsylvania], Drlica-Wagner, A. [University of Chicago; University of Chicago; Fermi National Accelerator Laboratory], Eifler, T. [University of Arizona; California Institute of Technology], Elvin-Poole, J. [University of Waterloo], Everett, S. [California Institute of Technology], Flaugher, B. [Fermi National Accelerator Laboratory], Fosalba, P. [Institute of Space Sciences (ICE, CSIC); Institut d’Estudis Espacials de Catalunya (IEEC)], Frieman, J. [University of Chicago; University of Chicago; Fermi National Accelerator Laboratory], García-Bellido, J. [Universidad Autonoma de Madrid], Gaztanaga, E. [Institute of Space Sciences (ICE, CSIC); Institut d’Estudis Espacials de Catalunya (IEEC); University of Portsmouth], Giles, P. [University of Sussex], Gutierrez, G. [Fermi National Accelerator Laboratory], Hinton, S. R. [University of Queensland], Hollowood, D. L. [Santa Cruz Institute for Particle Physics], Honscheid, K. [The Ohio State University; The Ohio State University], Huterer, D. [University of Michigan], Jain, B. [University of Pennsylvania], James, D. J. [Center for Astrophysics | Harvard & Smithsonian], Kuehn, K. [Macquarie University; Lowell Observatory], Lahav, O. [University College London], Lee, S. [California Institute of Technology], Marshall, J. L. [Texas A&M University], Mena-Fernández, J. [Université Grenoble Alpes], Menanteau, F. [National Center for Supercomputing Applications; University of Illinois at Urbana-Champaign], Miquel, R. [Institució Catalana de Recerca i Estudis Avançats; Institut de Física d’Altes Energies (IFAE); Barcelona Institute of Science and Technology], Muir, J. [University of Cincinnati; Perimeter Institute for Theoretical Physics], Myles, J. [Princeton University], Ogando, R. L. C. [Centro de Tecnologia da Informação Renato Archer; Observatório Nacional], Palmese, A. [Carnegie Mellon University], Paterno, M. [Fermi National Accelerator Laboratory], Petravick, P. [National Center for Supercomputing Applications], Plazas Malagón, A. A. [SLAC National Accelerator Laboratory; Stanford University], Raveri, M. [University of Genova and INFN], Roodman, A. [SLAC National Accelerator Laboratory; Stanford University], Samuroff, S. [Institut de Física d’Altes Energies (IFAE); Barcelona Institute of Science and Technology; Northeastern University], Sanchez, E. [Medioambientales y Tecnológicas (CIEMAT)], Sheldon, E. [Brookhaven National Laboratory], Shin, T. [Stony Brook University], Smith, M. [Lancaster University], Suchyta, E. [Oak Ridge National Laboratory], Swanson, M. E. C. [National Center for Supercomputing Applications], Tarle, G. [University of Michigan], Thomas, D. [University of Portsmouth], Vikram, V. [University of Pennsylvania], Walker, A. R. [NSF’s National Optical-Infrared Astronomy Research Laboratory]. 2026-06-26. Dark Energy Survey Year 6 results: Clustering redshifts and importance sampling of self-organized-maps 𝑛⁡(𝑧) realizations for 3 × 2 ⁢pt samples. https://doi.org/10.1103/6lfl-h6dg

Cite the original work for its findings. Save a collection to share your selection of sources.

Discover connections

Cosmological parameters subject Distances, redshifts, & velocities subject Large scale structure of the Universe subject

Connections use source metadata and explicit phrase matches, not verified experimental comparisons.

KEEP EXPLORING

Related discoveries

DOE OSTI2025

Evidence for large baryonic feedback at low and intermediate redshifts from kinematic Sunyaev-Zel’dovich observations with ACT and DESI photometric galaxies

Recent advances in cosmological observations have provided an unprecedented opportunity to investigate the distribution of baryons relative to the underlying matter. In this work, we show that the gas is more extended than the dark matter, and the amount of baryonic feedback at $z \lesssim 1$ disfavors low-feedback models such as that of state-of-the-art hydrodynamical simulation IllustrisTNG compared with high-feedback models such as that of the original Illustris simulation. This has important implications for bridging the gap between theory and observations and understanding galaxy formation and evolution. Furthermore, a better grasp of the baryon-dark matter link is critical to future cosmological analyses, which are currently impeded by our limited knowledge of baryonic feedback. Here, we measure the kinematic Sunyaev-Zel'dovich (kSZ) effect from the Atacama Cosmology Telescope (ACT), stacked on the luminous red galaxy (LRG) sample of the Dark Energy Spectroscopic Instrument (DESI) imaging survey. This is the first analysis to use photometric redshifts for reconstructing galaxy velocities. Due to the large number of galaxies comprising the DESI imaging survey, this is the highest signal-to-noise stacked kSZ measurement to date: we detect the signal at 13$σ$, finding strong evidence that the gas is more spread out than the dark matter, as well as a preference for larger feedback compared to some commonly used state-of-the-art hydrodynamical simulations. Here, our work opens up the possibility of recalibrating large hydrodynamical simulations using the kSZ effect. In addition, our findings highlight the importance of properly accounting for baryonic feedback with future surveys such as LSST through direct probes such as the kSZ, and shed light on long-standing enigmas in astrophysics, such as the “missing baryon” problem.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2026

Dark Energy Survey year 6 results: Magnification modeling and its impact on galaxy clustering and galaxy-galaxy lensing cosmology

Gravitational lensing magnification alters the observed spatial distribution of galaxies and must be accounted for to prevent biases in cosmological probes of the large-scale structure. We investigate its effects on the Dark Energy Survey Year 6 galaxy clustering and galaxy-galaxy lensing analyses using the fiducial lens (position tracer) sample M ag L im++. Magnification bias is parameterized by a coefficient that describes the response of the number of selected objects per unlensed area element to a change in the lensing convergence. We quantify this coefficient using the BALROG synthetic source injection catalog to account for the complexity of the selection function, and compare these results with simplified estimates. The resulting values of the magnification coefficients for each redshift bin are [3.16 ± 0.08, 2.76 ± 0.21, 4.09 ± 0.15, 4.42 ± 0.16, 4.90 ± 0.29, 4.83 ± 0.25]. Relative to Year 3, this analysis provides more precise and accurate magnification bias estimates through a larger BALROG area and reweighting to better match the data properties. Here, the cosmological results are robust when tested against various magnification parameter prior choices and also when adding cross-clustering between lens redshift bins. Neglecting magnification, however, introduces significant systematic shifts: relative to the fiducial analysis with Gaussian priors centered on the BALROG -derived estimates, we observe shifts of 1.37σ in S 8 and -0.84σ in Ω m (with cosmic shear included: -0.61σ in S 8 and -0.71σ in Ω m ), in agreement with findings from simulated data, demonstrating that magnification must be modeled to avoid biases. Freeing the magnification bias in lens bin 2 leads to unphysical negative values, further justifying its exclusion from the fiducial Year 6 analysis.

Cosmological parameters↗

DOE OSTI2024

SPT clusters with DES and HST weak lensing. II. Cosmological constraints from the abundance of massive halos

We present cosmological constraints from the abundance of galaxy clusters selected via the thermal Sunyaev-Zel’dovich (SZ) effect in South Pole Telescope (SPT) data with a simultaneous mass calibration using weak gravitational lensing data from the Dark Energy Survey (DES) and the Hubble Space Telescope (HST). The cluster sample is constructed from the combined SPT-SZ, SPTpol ECS, and SPTpol 500d surveys, and comprises 1,005 confirmed clusters in the redshift range 0.25–1.78 over a total sky area of 5200 deg 2 . We use DES Year 3 weak-lensing data for 688 clusters with redshifts 𝑧 < 0.95 and HST weak-lensing data for 39 clusters with 0.6 < 𝑧 < 1.7. The weak-lensing measurements enable robust mass measurements of sample clusters and allow us to empirically constrain the SZ observable-mass relation without having to make strong assumptions about, e.g., the hydrodynamical state of the clusters. For a flat Λ⁢ CDM cosmology, and marginalizing over the sum of massive neutrinos, we measure Ω m = 0.286 ± 0.032, 𝜎 8 = 0.817 ± 0.026, and the parameter combination 𝜎 8 ⁢(Ω m /0.3) 0.25 = 0.805 ± 0.016. Our measurement of 𝑆 8 ≡ 𝜎 8 ⁢$\sqrt{Ω_{m}/0.3}$ = 0.795 ± 0.029 and the constraint from Planck CMB anisotropies (2018 TT, TE, EE+lowE) differ by 1.1⁢𝜎. In combination with that Planck dataset, we place a 95% upper limit on the sum of neutrino masses ∑𝑚 𝜈 < 0.18 eV. When additionally allowing the dark energy equation of state parameter 𝑤 to vary, we obtain 𝑤 = −1.45 ± 0.31 from our cluster-based analysis. In combination with Planck data, we measure 𝑤 =−1.3⁢4$^{+0.22}_{−0.15}$, or a 2.2⁢𝜎 difference with a cosmological constant. We use the cluster abundance to measure 𝜎8 in five redshift bins between 0.25 and 1.8, and we find the results to be consistent with structure growth as predicted by the Λ⁢ CDM model fit to Planck primary CMB data.

79 ASTRONOMY AND ASTROPHYSICS↗