Stellar Birth Radii in the LMC: Insights into Chemodynamics, Radial Migration, and Star Formation Across the Disk

TL;DR

This study infers stellar birth radii in the LMC to understand its chemodynamical evolution, revealing episodic star formation, radial migration, and chemical enrichment patterns influenced by interactions with the SMC.

Contribution

It introduces a method to infer stellar birth radii in the LMC and applies it to reveal detailed chemodynamical history influenced by galaxy interactions.

Findings

Metallicity gradient steepened at 5, 3, and 1 Gyr ago.

Star formation episodes showed distinct spatial patterns over time.

Radial migration was enhanced at specific epochs.

Abstract

The LMC and SMC are interacting dwarf galaxies that offer a valuable testbed for studying the effects of galactic mergers. We investigate the chemodynamic history of the LMC in the context of its interaction with the SMC by inferring stellar birth radii, first validated on a hydrodynamical simulation tailored to reproduce their interaction history. Using inferred birth radii and stellar ages, we identify signatures of dynamical and chemical evolution across the LMC disk. We find that the LMC's metallicity gradient steepened around 5, 3, and 1 Gyr ago, coinciding with enhanced star formation (SF) episodes. These events exhibit distinct spatial patterns -- initially concentrated in the inner disk at 5 Gyr, expanding outward by 3 Gyr, and becoming widespread with renewed central activity at 1 Gyr -- likely reflecting changes in spin alignment between the interacting disks if the enhancements of SF tracks the pericenter passages of the SMC to the LMC. The inferred radial migration strength of the LMC shows notable enhancements at 0.5, 2, and 5 Gyr. The most $\alpha$-enriched stars form 2-3 Gyr ago at birth radii of 2-4 kpc, the only epoch when star formation is broadly distributed across the disk. Finally, unlike the Milky Way, the LMC lacks a clear [$\alpha$/M]-[Fe/H] bimodality. This is likely due to its more centrally concentrated star formation during these periods, compared to the MW's more extended outer-disk star formation enhancements. These findings place strong constraints on the LMC's assembly history and its interaction with the SMC.