The Three Hundred project: shapes and radial alignment of satellite, infalling, and backsplash galaxies

TL;DR

This study analyzes the shapes and orientations of satellite, infalling, and backsplash galaxies in galaxy clusters, revealing how their alignments depend on their position and orbital history, with implications for understanding galaxy evolution.

Contribution

It provides new insights into the radial and shape alignments of satellite galaxies and dark matter subhaloes, especially highlighting differences among backsplash and infalling populations.

Findings

Radial alignment varies with distance from cluster center.

Backsplash galaxies show stronger radial alignment than infalling ones.

Some galaxies on radial orbits pass very close to the cluster center.

Abstract

Using 324 numerically modelled galaxy clusters we investigate the radial and galaxy-halo alignment of dark matter subhaloes and satellite galaxies orbiting within and around them. We find that radial alignment depends on distance to the centre of the galaxy cluster but appears independent of the dynamical state of the central host cluster. Furthermore, we cannot find a relation between radial alignment of the halo or galaxy shape with its own mass. We report that backsplash galaxies, i.e. objects that have already passed through the cluster radius but are now located in the outskirts, show a stronger radial alignment than infalling objects. We further find that there exists a population of well radially aligned objects passing very close to the central cluster's centre which were found to be on highly radial orbit.