It's not $\sigma_8$ : constraining the non-linear matter power spectrum with the Dark Energy Survey Year-5 supernova sample

TL;DR

This paper investigates the non-linear matter power spectrum using supernova lensing data from DES Year-5, introducing an empirical parameter to quantify deviations from standard models, and finds hints of power suppression.

Contribution

It presents a novel analysis of SN Ia lensing to constrain non-linear matter power spectrum modifications with an empirical parameter, using DES Year-5 data.

Findings

Estimated the suppression/enhancement parameter $A_{mod}$ with credible intervals.

Found median $A_{mod}$ consistent with unity but with hints of suppression.

Provided constraints on non-linear matter power spectrum deviations.

Abstract

The weak gravitational lensing magnification of Type Ia supernovae (SNe Ia) is sensitive to the matter power spectrum on scales $k>1 h$ Mpc$^{-1}$, making it unwise to interpret SNe Ia lensing in terms of power on linear scales. We compute the probability density function of SNe Ia magnification as a function of standard cosmological parameters, plus an empirical parameter $A_{\rm mod}$ which describes the suppression or enhancement of matter power on non-linear scales compared to a cold dark matter only model. While baryons are expected to enhance power on the scales relevant to SN Ia lensing, other physics such as neutrino masses or non-standard dark matter may suppress power. Using the Dark Energy Survey Year-5 sample, we find $A_{\rm mod} = 0.77^{+0.69}_{-0.40}$ (68\% credible interval around the median). Although the median is consistent with unity there are hints of power suppression, with $A_{\rm mod} < 1.09$ at 68\% credibility.