A non-linear solution to the $S_8$ tension II: Analysis of DES Year 3 cosmic shear

TL;DR

This paper analyzes DES Year 3 cosmic shear data to explore non-linear matter power spectrum suppression as a solution to the $S_8$ tension, finding it less extreme than KiDS data suggests but still beyond current simulations, with implications for dark matter models.

Contribution

It provides the first detailed analysis of DES Year 3 cosmic shear data in the context of non-linear suppression of the matter power spectrum to address the $S_8$ tension.

Findings

Suppression required is less extreme than KiDS data suggests.

Suppression extends into mildly non-linear scales around $k\,\sim\,0.2 h\mathrm{Mpc}^{-1}$.

Linear scale measurements of $S_8$ should align with Planck $\\Lambda$CDM predictions.

Abstract

Weak galaxy lensing surveys have consistently reported low values of the $S_8$ parameter compared to the $\textit{Planck}\ \Lambda\rm{CDM}$ cosmology. Amon & Efstathiou (2022) used KiDS-1000 cosmic shear measurements to propose that this tension can be reconciled if the matter fluctuation spectrum is suppressed more strongly on non-linear scales than assumed in state-of-the-art hydrodynamical simulations. In this paper, we investigate cosmic shear data from the Dark Energy Survey (DES) Year 3. The non-linear suppression of the matter power spectrum required to resolve the $S_8$ tension between DES and the $\textit{Planck}\ \Lambda\rm{CDM}$ model is not as strong as inferred using KiDS data, but is still more extreme than predictions from recent numerical simulations. An alternative possibility is that non-standard dark matter contributes to the required suppression. We investigate the redshift and scale dependence of the suppression of the matter power spectrum. If our proposed explanation of the $S_8$ tension is correct, the required suppression must extend into the mildly non-linear regime to wavenumbers $k\sim 0.2 h {\rm Mpc}^{-1}$. In addition, all measures of $S_8$ using linear scales should agree with the $\textit{Planck}\ \Lambda\rm{CDM}$ cosmology, an expectation that will be testable to high precision in the near future.