Confronting cosmic shear astrophysical uncertainties: DES Year 3 revisited

2025/12/03 by Leah Bigwood, Bigwood, Leah, J. McCullough +41 · 2 citations
Physics and Astronomy · #Galaxies: Formation, Evolution, Phenomena #Cosmology and Gravitation Theories #Astronomy and Astrophysical Research

paper · pdf · doi:10.48550/arxiv.2512.04209

Abstract

Cosmology from weak gravitational lensing has been limited by astrophysical uncertainties in baryonic feedback and intrinsic alignments. By calibrating these effects using external data, we recover non-linear information, achieving a 2% constraint on the clustering amplitude, S₈, resulting in a factor of two improvement on the ΛCDM constraints relative to the fiducial Dark Energy Survey Year 3 model. The posterior, S₈=0.832^+0.013_-0.017, shifts by 1.5σ to higher values, in closer agreement with the cosmic microwave background result for the standard six-parameter ΛCDM cosmology. Our approach uses a star-forming 'blue' galaxy sample with intrinsic alignment model parameters calibrated by direct spectroscopic measurements, together with a baryonic feedback model informed by observations of X-ray gas fractions and kinematic Sunyaev-Zel'dovich effect profiles that span a wide range in halo mass and redshift. Our results provide a blueprint for next-generation surveys: leveraging galaxy properties to control intrinsic alignments and external gas probes to calibrate feedback, unlocking a substantial improvement in the precision of weak lensing surveys.

Citations

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• The LSST Dark Energy Science Collaboration (DESC) Science Requirements Document

Cited by

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• Early- and late-time constraints on Wald-Gauss-Bonnet topological dark energy and implications for the H₀ and S₈ tensions
• Simulation budgeting for hybrid effective field theories

Related

• Dark Energy Survey Year 3: Blue Shear
• The Dark Energy Camera All Data Everywhere cosmic shear project V: Constraints on cosmology and astrophysics from 270 million galaxies across 13,000 deg² of the sky
• Dark Energy Survey Year 3 Results: Multi-Probe Modeling Strategy and Validation
• Validation of the DESI-DR1 3x2-pt analysis: scale cut and shear ratio tests
• Constraining Baryonic Physics with DES Y1 and Planck data -- Combining Galaxy Clustering, Weak Lensing, and CMB Lensing