Dark Energy Survey Year 6 Results: improved mitigation of spatially varying observational systematics with masking for the MagLim++ lens sample
Abstract
As photometric surveys reach unprecedented statistical precision, systematic uncertainties increasingly dominate large-scale structure probes relying on galaxy number density. Defining the final survey footprint is critical, as it excludes regions affected by artefacts or suboptimal observing conditions. For galaxy clustering, spatially varying observational systematics, such as seeing, are a leading source of bias. Template maps of contaminants are used to derive spatially dependent corrections, but extreme values may fall outside the applicability range of mitigation methods, compromising correction reliability. The complexity and accuracy of systematics modelling depend on footprint conservativeness, with aggressive masking enabling simpler, robust mitigation. We present a unified approach to define the DES Y6 JOINT footprint, integrating observational systematics templates and artefact indicators that degrade mitigation performance. This removes extreme values from an initial footprint, leading to the final JOINT evaluating the DES Y6 lens sample MagLim++ on this footprint, we enhance the Iterative Systematics Decontamination (ISD) method, detecting non-linear systematic contamination and improving correction accuracy. While the mask’s impact on clustering is less significant than systematics decontamination, it remains non-negligible, comparable to statistical uncertainties in certain w(theta) scales and redshift bins. Supporting coherent analyses of galaxy clustering and cosmic shear, the final footprint spans 4,031.04 deg^2, setting the basis for DES Y6 1x2pt, 2x2pt, and 3x2pt analyses. This work highlights how targeted masking strategies optimise the balance between statistical power and systematic control in Stage-III and -IV surveys.
Related
- Demonstrating the Use of the Spherical Fourier Bessel Basis for Large Scale Clustering Systematics Discovery and Mitigation with eBOSS
- The dust in Sauron's eye - Observational and experimental results on the debris disk around HR 4796
- Mitigating scanning-induced systematics in Hipparcos andimplications for Gaia astrometry
- CERES: a cryogenic experiment to reconstruct energy systematics in TeO2 bolometers
- Scalable Dark Siren Cosmology with gwcosmo: GPU Acceleration, Validation and Systematics
BibTeX
@article{rodriguezmonroy2026dark,
title = {{Dark Energy Survey Year 6 Results: improved mitigation of spatially varying observational systematics with masking for the MagLim++ lens sample}},
author = {M. Rodríguez-Monroy and N. Weaverdyck and J. Elvin-Poole and I. Sevilla-Noarbe and S. Avila and A. Porredon and A. Carnero Rosell and A. Drlica-Wagner and D. Anbajagane and E. Sanchez and M. R. Becker and K. Bechtol and M. Crocce and A. Ferté and M. Gatti and J. Mena-Fernández and D. Sanchez Cid and M. Yamamoto and M. Aguena and S. S. Allam and O. Alves and F. Andrade-Oliveira and D. Bacon and J. Blazek and S. Bocquet and D. Brooks and R. Camilleri and J. Carretero and R. Cawthon and C. Chang and L. N. da Costa and M. E. da Silva Pereira and S. Desai and H. T. Diehl and P. Doel and C. Doux and S. Everett and B. Flaugher and P. Fosalba and J. Frieman and J. García-Bellido and R. A. Gruendl and K. Herner and S. R. Hinton and D. L. Hollowood and K. Honscheid and D. Huterer and D. J. James and K. Kuehn and O. Lahav and S. Lee and J. L. Marshall and R. Miquel and J. Muir and J. Myles and R. L. C. Ogando and A. A. Plazas Malagón and J. Prat and T. Schutt and M. Smith},
journal = {The Open Journal of Astrophysics},
year = {2026},
month = oct,
doi = {10.33232/001c.172767},
url = {https://astro.theoj.org/article/172767-dark-energy-survey-year-6-results-improved-mitigation-of-spatially-varying-observational-systematics-with-masking-for-the-maglim-lens-sample},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Dark Energy Survey Year 6 Results: improved mitigation of spatially varying observational systematics with masking for the MagLim++ lens sample
AU - M. Rodríguez-Monroy
AU - N. Weaverdyck
AU - J. Elvin-Poole
AU - I. Sevilla-Noarbe
AU - S. Avila
AU - A. Porredon
AU - A. Carnero Rosell
AU - A. Drlica-Wagner
AU - D. Anbajagane
AU - E. Sanchez
AU - M. R. Becker
AU - K. Bechtol
AU - M. Crocce
AU - A. Ferté
AU - M. Gatti
AU - J. Mena-Fernández
AU - D. Sanchez Cid
AU - M. Yamamoto
AU - M. Aguena
AU - S. S. Allam
AU - O. Alves
AU - F. Andrade-Oliveira
AU - D. Bacon
AU - J. Blazek
AU - S. Bocquet
AU - D. Brooks
AU - R. Camilleri
AU - J. Carretero
AU - R. Cawthon
AU - C. Chang
AU - L. N. da Costa
AU - M. E. da Silva Pereira
AU - S. Desai
AU - H. T. Diehl
AU - P. Doel
AU - C. Doux
AU - S. Everett
AU - B. Flaugher
AU - P. Fosalba
AU - J. Frieman
AU - J. García-Bellido
AU - R. A. Gruendl
AU - K. Herner
AU - S. R. Hinton
AU - D. L. Hollowood
AU - K. Honscheid
AU - D. Huterer
AU - D. J. James
AU - K. Kuehn
AU - O. Lahav
AU - S. Lee
AU - J. L. Marshall
AU - R. Miquel
AU - J. Muir
AU - J. Myles
AU - R. L. C. Ogando
AU - A. A. Plazas Malagón
AU - J. Prat
AU - T. Schutt
AU - M. Smith
PY - 2026
DA - 2026/10/21
JO - The Open Journal of Astrophysics
DO - 10.33232/001c.172767
UR - https://astro.theoj.org/article/172767-dark-energy-survey-year-6-results-improved-mitigation-of-spatially-varying-observational-systematics-with-masking-for-the-maglim-lens-sample
AB - As photometric surveys reach unprecedented statistical precision, systematic uncertainties increasingly dominate large-scale structure probes relying on galaxy number density. Defining the final survey footprint is critical, as it excludes regions affected by artefacts or suboptimal observing conditions. For galaxy clustering, spatially varying observational systematics, such as seeing, are a leading source of bias. Template maps of contaminants are used to derive spatially dependent corrections, but extreme values may fall outside the applicability range of mitigation methods, compromising correction reliability. The complexity and accuracy of systematics modelling depend on footprint conservativeness, with aggressive masking enabling simpler, robust mitigation. We present a unified approach to define the DES Y6 JOINT footprint, integrating observational systematics templates and artefact indicators that degrade mitigation performance. This removes extreme values from an initial footprint, leading to the final JOINT evaluating the DES Y6 lens sample MagLim++ on this footprint, we enhance the Iterative Systematics Decontamination (ISD) method, detecting non-linear systematic contamination and improving correction accuracy. While the mask’s impact on clustering is less significant than systematics decontamination, it remains non-negligible, comparable to statistical uncertainties in certain w(theta) scales and redshift bins. Supporting coherent analyses of galaxy clustering and cosmic shear, the final footprint spans 4,031.04 deg^2, setting the basis for DES Y6 1x2pt, 2x2pt, and 3x2pt analyses. This work highlights how targeted masking strategies optimise the balance between statistical power and systematic control in Stage-III and -IV surveys.
SN - 2565-6120
ER -