Dark Matter Halos in Interacting Dark Energy Models: Formation History, Density Profile, Spin and Shape

TL;DR

This study uses N-body simulations to analyze how interacting dark energy models influence dark matter halo properties, revealing significant differences from standard cosmology that can help constrain such models.

Contribution

It provides the first detailed comparison of dark matter halo formation and properties in interacting dark energy models versus $\Lambda$CDM using N-body simulations.

Findings

IDE models with dark matter decaying into dark energy slow structure formation.

Halos in IDE models have lower mass, higher spin, and more anisotropy.

Halo concentration ratios depend on interaction strength, offering a new constraint method.

Abstract

The interacting dark energy (IDE) model, which considers the interaction between dark energy and dark matter, provides a natural mechanism to alleviate the coincidence problem and can also relieve the observational tensions under the $\Lambda$CDM model. Previous studies have put constraints on IDE models by observations of cosmic expansion history, cosmic microwave background and large-scale structures. However, these data are not yet enough to distinguish IDE models from $\Lambda$CDM effectively. Because the non-linear structure formation contains rich cosmological information, it can provide additional means to differentiate alternative models. In this paper, based on a set of $N$-body simulations for IDE models, we investigate the formation histories and properties of dark matter halos, and compare with their $\Lambda$CDM counterparts. For the model with dark matter decaying into dark energy and the parameters being the best-fit values from previous constraints, the structure formation is markedly slowed down, and the halos have systematically lower mass, looser internal structure, higher spin and anisotropy. This is inconsistent with the observed structure formation, and thus this model can be safely ruled out from the perspective of non-linear structure formation. Moreover, we find that the ratio of halo concentrations between IDE and $\Lambda$CDM counterparts depends sensitively on the interaction parameter and is independent of halo mass. This can act as a powerful probe to constrain IDE models. Our results concretely demonstrate that the interaction of the two dark components can affect the halo formation considerably, and therefore the constraints from non-linear structures are indispensable.