The present-day globular cluster kinematics of lenticular galaxies from the E-MOSAICS simulations and their relation to the galaxy assembly histories

TL;DR

This study uses the E-MOSAICS simulations to analyze the current kinematic profiles of globular clusters in 50 lenticular galaxies, revealing diverse rotation patterns and their links to galaxy assembly histories.

Contribution

It provides new insights into the kinematic behavior of globular clusters in S0 galaxies and their relation to past merger events, based on cosmological simulations.

Findings

82% of GCs are aligned with galaxy major axis, consistent with observations.

No clear correlation between GC kinematics and past mergers for aligned galaxies.

Misaligned GCs often result from recent major mergers or perturbations of in-situ GCs.

Abstract

We study the present-day rotational velocity ($V_{rot}$) and velocity dispersion (${\sigma}$) profiles of the globular cluster (GC) systems in a sample of 50 lenticular (S0) galaxies from the E-MOSAICS galaxy formation simulations. We find that 82% of the galaxies have GCs that are rotating along the photometric major axis of the galaxy ($aligned$), while the remaining 18% of the galaxies do not ($misaligned$). This is generally consistent with the observations from the SLUGGS survey. For the $aligned$ galaxies, classified as $peaked$ $and$ $outwardly$ $decreasing$ (49%), $flat$ (24%) and $increasing$ (27%) based on the $V_{rot}/{\sigma}$ profiles out to large radii, we do not find any clear correlation between these present-day $V_{rot}/{\sigma}$ profiles of the GCs and the past merger histories of the S0 galaxies, unlike in previous simulations of galaxy stars. For just over half of the $misaligned$ galaxies, we find that the GC misalignment is the result of a major merger within the last 10 Gyr so that the $ex$-$situ$ GCs are misaligned by an angle between 0{\deg} (co-rotation) to 180{\deg} (counter-rotation) with respect to the $in$-$situ$ GCs, depending on the orbital configuration of the merging galaxies. For the remaining $misaligned$ galaxies, we suggest that the $in$-$situ$ metal-poor GCs, formed at early times, have undergone more frequent kinematic perturbations than the $in$-$situ$ metal-rich GCs. We also find that the GCs accreted early and the $in$-$situ$ GCs are predominantly located within 0.2 virial radii ($R_{200}$) from the centre of galaxies in 3D phase-space diagrams.