The origin of star-gas misalignments in simulated galaxies

TL;DR

This study uses the EAGLE simulations to investigate the origins of star-gas misalignments in galaxies, finding that internal galaxy properties significantly influence misalignment persistence despite environmental effects.

Contribution

It demonstrates that internal galaxy properties, such as shape and kinematic state, are key in determining star-gas misalignments, aligning simulation results with observations.

Findings

EAGLE reproduces observed misalignment frequencies across environments.

Internal properties like triaxiality influence misalignment persistence.

Environment affects misalignments but internal dynamics are crucial.

Abstract

We study the origin of misalignments between the stellar and star-forming gas components of simulated galaxies in the EAGLE simulations. We focus on galaxies with stellar masses $\geq 10^9$ M$_\odot$ at 0$\leq$z$\leq$1. We compare the frequency of misalignments with observational results from the SAMI survey and find that overall, EAGLE can reproduce the incidence of misalignments in the field and clusters, as well as the dependence on stellar mass and optical colour within the uncertainties. We study the dependence on kinematic misalignments with internal galaxy properties and different processes related to galaxy mergers and sudden changes in stellar and star-forming gas mass. We found that despite the environment being relevant in setting the conditions to misalign the star-forming gas, the internal galaxy properties play a crucial role in determining whether the gas quickly aligns with the stellar component or not. Hence, galaxies that are more triaxial and more dispersion dominated display more misalignments because they are inefficient at realigning the star-forming gas towards the stellar angular momentum vector.