Evolution of central galaxy alignments in simulations

TL;DR

This study investigates how the alignment of central galaxies with their environment and their internal stellar and dark matter components evolves over cosmic time using simulations, revealing differences influenced by galaxy type and assembly history.

Contribution

It provides new insights into the evolution of galaxy alignments and the distinct behaviors of stellar and dark matter components over time in simulated universes.

Findings

Dark matter halo alignment differs from stellar alignment.

Galaxy assembly and mergers influence alignment evolution.

Red and blue galaxies show different alignment evolution patterns.

Abstract

Observations suggest that red central galaxies align closely with their group galaxies and the large-scale environment.This finding was also replicated in simulations, which added information about the alignment of the stars that form the galaxies with the dark matter in the halo they inhabit. These results were obtained for the present universe. Our study aims to build upon previous findings by examining the evolution of central galaxy alignment with their environment, as well as the alignment between their stellar and dark matter components. Based on previous studies, in this work, we describe the evolution of the alignment of bright central galaxies over time and try to understand the process leading to the current observed alignment. By employing the merger trees from the simulation, we track the alignment evolution of the central galaxy sample at z=0 used in a previous study, whose results correspond to the observations. In particular, we exploit the anisotropic correlation function to study the alignment of the central galaxies with the environment and the probability distribution of the angle between the axes of the shape tensor calculated for each component to deepen the analysis of the stellar and dark matter components. A description was given of the evolution of alignment in bright central galaxies with a focus on the distinctions between red and blue galaxies. Furthermore, it was found that the alignment of the dark matter halo differs from that of the stellar material within it. According to the findings, the assembly process and mergers influenced the evolution of alignment