The Effect of Coupled Dark Energy on the Alignment between Dark Matter and Galaxy Distributions in Clusters

TL;DR

This study explores how coupled Dark Energy models influence the alignment between satellite galaxies and matter in clusters, revealing differences from standard cosmology that could help probe dark sector interactions.

Contribution

It demonstrates that coupled Dark Energy affects galaxy-matter alignments in clusters, providing a new observational probe for dark energy interactions.

Findings

cDE models reduce satellite alignment along matter major axes

The null hypothesis of identical distributions is rejected at 99% confidence

Galaxy-matter alignment differences can probe dark sector interactions

Abstract

We investigate the effects of a coupled Dark Energy (cDE) scalar field on the alignment between satellites and matter distributions in galaxy clusters. Using high-resolution N-body simulations for LCDM and cDE cosmological models, we compute the probability density distribution for the alignment angle between the satellite galaxies and underlying matter distributions, finding a difference between the two scenarios. With respect to LCDM, in cDE cosmologies the satellite galaxies are less preferentially located along the major axis of the matter distribution, possibly reducing the tension with obersevational data. A physical explanation is that the coupling between dark matter and dark energy acts as an additional tidal force on the satellite galaxies diminishing the alignments between their distribution and the matter one. Through a Wald test based on the generalized chi-square statistics, the null hypothesis that the two probability distributions come from the same parent population is rejected at the 99 % confidence level. It is concluded that the galaxy-matter alignment in clusters may provide a unique probe of dark sector interactions as well as the nature of dark energy.