The Lensing Counter Narrative: An Effective Description of Small-Scale Clustering in Weak Lensing Power Spectra

2025/10/21 by Joseph DeRose, Shi-Fan Chen, DeRose, Joseph +1
Physics and Astronomy · #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #Dark Matter and Cosmic Phenomena #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena

paper · pdf · doi:10.48550/arxiv.2510.18981

openalex publication_date 2025/10/21 · openalex created_date 2025/10/24 · openalex updated_date 2026/07/28

Abstract

We present a new formalism to separate large- and small-scale contributions to cosmic shear through lensing counterterms (LCT) inspired by effective field theory (EFT). Marginalizing over these LCTs isolates the large-scale cosmological signal in weak lensing power spectra while simultaneously constraining the impact of baryonic feedback or new physics (e.g. axion dark matter) at small scales. Our formalism removes the need for hard scale cuts in standard analyses, even when theoretical predictions are limited to below a physical cutoff Λ, resulting in significant improvements in constraining power -- up to 5× smaller in the case of a LSST-Y10-like analysis without marginalizing over baryons when the analysis cutoff is set to Λ= 1.0h Mpc^-1. We conduct a proof-of-principle analysis on the publicly available DES Y3 data, finding S₈= 0.783± 0.029 and S₈ = 0.798± 0.026 for analyses with cutoffs of Λ= 0.5h Mpc^-1 and 1.0 h Mpc^-1, respectively, with no detection of modifications to small-scale clustering at k > Λ beyond the predictions of collisionless dark matter in a ΛCDM universe. We make our JAX-based pipeline, gholax, integrated with intrinsic alignment predictions from the EFT of large-scale structure at 1-loop, publicly available.

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Related

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• Robust cosmic shear with small-scale nulling