It's not ${\sigma }_8$ : constraining the non-linear matter power spectrum with the Dark Energy Survey Year-5 supernova sample

Abstract

The weak gravitational lensing magnification of Type Ia supernovae (SNe Ia) is sensitive to the matter power spectrum on scales $k>1h$ 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 $A_{\mathrm{mod}}$ 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 $A_{\mathrm{mod}}=0.77_{-0.40}^{+0.69}$ (68\% credible interval around the median). Although the median is consistent with unity there are hints of power suppression, with $A_{\mathrm{mod}}<1.09$ at 68\% credibility.

12 pages, submitted to MNRAS. arXiv admin note: text overlap with arXiv:2410.07956