Can dynamic dark energy explain the $S_8$ tension, the `lensing is low' effect, or strong baryon feedback?

TL;DR

This paper explores whether dynamic dark energy models can address the $S_8$ tension, lensing anomalies, and baryonic feedback effects, finding partial explanations for two of these issues through changes in cosmological distances and lensing signals.

Contribution

It demonstrates that dynamic dark energy can partially explain the $S_8$ tension and lensing anomalies by affecting distance measures and lensing signals, but is less effective for baryonic feedback.

Findings

Galaxy-galaxy lensing signal reduced by up to 7%.

Cosmic shear suppressed by 14%.

Dynamic dark energy increases the tSZ signal by about 15%.

Abstract

We investigate the impact of a DESI motivated dynamic dark energy cosmology on three cosmological anomalies, the $S_8$ tension, the `lensing is low' effect, and observations of strong baryonic feedback. We analyze how these observations vary in $\Lambda$CDM versus dynamic dark energy. We find that the galaxy-galaxy lensing signal is reduced by up to 7% with respect to galaxy clustering and that cosmic shear is suppressed by 14%. These differences are primarily caused by changes to cosmological distance measures which enter the lensing efficiency kernels. In contrast, we find that dynamic dark energy increases the thermal Sunyaev Zeldovich signal by about 15%, but that this is insufficient to substantially reduce the magnitude of baryonic effects. Thus, we find that dynamic dark energy may help explain two out of these three cosmological anomalies. DESI's dynamic dark energy has an important impact on cosmic expansion at $z\lesssim 0.5$, a regime where baryon acoustic oscillations are limited by the small volume. Because lensing is sensitive to distances, in addition to growth, we argue that lensing measurements are a promising alternative to constrain expansion deviations from $\Lambda$ at low redshifts.