Halo spin and orientation in Interacting Dark Matter Dark Energy Cosmology

TL;DR

This paper investigates how interactions between dark matter and dark energy influence the shape and spin orientation of dark matter halos using N-body simulations, revealing different alignment behaviors depending on the direction of energy transfer.

Contribution

It introduces a simulation-based analysis of halo shape and spin alignments in interacting dark matter-dark energy models, providing fitted functions for these alignment signals.

Findings

Enhanced shape alignment in IDE I models

Decreased spin alignment in IDE I models

Opposite effects in IDE II models

Abstract

In recent years, the interaction between dark matter (DM) and dark energy (DE) has become a topic of interest in cosmology. Interacting dark matter-dark energy (IDE) models have a substantial impact on the formation of cosmological large-scale structures, which serve as the background for DM halo evolution. This impact can be examined through the shape and spin orientation of halos in numerical simulations incorporating IDE effects. In our work, we use the N-body simulation pipeline ME-GADGET to simulate and study the halo spin and orientation in IDE models. We found that in models where DM transfers into DE (IDE I), the alignment of halo shapes with the surrounding tidal field is enhanced, while the alignment of halo spins with the tidal field is decreased compared to $\Lambda$CDM. Conversely, in models where DE transfers into DM (IDE II), the opposite occurs. We have provided fitted functions to describe these alignment signals. Our study provides the foundation for more accurate modeling of observations in the future such as China Space Station Telescope.