Tidally-induced radial migration waves in LMC-like galaxies

TL;DR

This study investigates how tidal interactions between galaxies induce wave-like radial migration and metallicity changes, using high-resolution simulations of LMC-like galaxies to quantify these effects during satellite pericentre passages.

Contribution

It introduces a new model describing tidal interactions as a driver of wave-like radial migration and analyzes its impact on metallicity distribution in LMC-like galaxies.

Findings

Tidal interactions trigger wave-like radial migration fluxes up to 40% of stellar mass per Gyr.

Migration waves occur during pericentre passages, largely independent of the Toomre Q parameter.

Tidal interactions cause a 3-5% metallicity drop in the inner disc compared to isolated galaxies.

Abstract

Stellar radial migration has predominantly been examined in isolated disc galaxies where non-axisymmetric structures drive the process. By contrast, while tidal interactions are known for having an influence, their contribution remains comparatively under explored. The LMC, the nearest disc galaxy to the Milky Way (MW) and currently interacting with the SMC, provides a unique laboratory to investigate this interplay. We aim to quantify the impact of tidal interactions on radial migration and metallicity distribution in high-resolution simulations of LMC-like disc galaxies. We leverage a subsample of KRATOS, a suite of 28 pure $N$-body simulations of the LMC-SMC-MW system. Specifically, we use 6 simulations of both isolated and interacting LMC-like galaxies, exploring different values of the Toomre stellar parameter $Q$. These simulations allow to map the evolution of the stars' guiding radii $R_g(t)$ and compute radial migration fluxes in interacting systems and compare with their isolated counterparts, allowing to quantify the link between tidal interactions, radial migration, non-axisymmetric patterns, disc internal stability, and radial metallicity distribution. We present tidally-triggered wave-like radial migration fluxes reaching up to $\sim40\%$ of disc stellar mass per Gyr. This wave-like migration appears during the satellite's pericentre passages, almost independently of $Q$ and induces a metallicity drop of $\sim$3-5\% of the isolated galaxy's maximum metallicity in the inner disc. Additionally, in the isolated simulations, the extent of variation in the bar's resonance region coincides with the mixing zones in the metallicity distribution. We propose a novel description of a wave-like radial migration flux as a dynamical response of a galaxy undergoing tidal interactions and sketch its impact on the galaxy's metallicity distribution.