The VMC survey -- XLIV: Mapping metallicity trends in the Large Magellanic Cloud using near-infrared passbands

TL;DR

This study maps the metallicity distribution across the Large Magellanic Cloud using near-infrared data, revealing a shallow gradient and asymmetries likely caused by tidal interactions.

Contribution

It provides high-resolution metallicity maps of the LMC using RGB star analysis and near-infrared passbands, highlighting metallicity gradients and asymmetries.

Findings

Mean metallicity [Fe/H] = -0.42 dex

Shallow metallicity gradient of -0.008 dex/kpc

Asymmetric metallicity distribution influenced by tidal interactions

Abstract

We have derived high-spatial-resolution metallicity maps covering $\sim$105~deg$^2$ across the Large Magellanic Cloud (LMC) using near-infrared passbands from the VISTA Survey of the Magellanic Clouds. We attempt to understand the metallicity distribution and gradients of the LMC up to a radius of $\sim$ 6~kpc. We identify red giant branch (RGB) stars in spatially distinct $Y, (Y-K_{\rm s})$ colour-magnitude diagrams. In any of our selected subregions, the RGB slope is used as an indicator of the average metallicity, based on calibration to metallicity using spectroscopic data. The mean LMC metallicity is [Fe/H] = $-$0.42~dex ($\sigma$[Fe/H] = 0.04~dex). We find the bar to be mildly metal-rich compared with the outer disc, showing evidence of a shallow gradient in metallicity ($-0.008 \pm 0.001$ dex kpc$^{-1}$) from the galaxy's centre to a radius of 6~kpc. Our results suggest that the LMC's stellar bar is chemically similar to the bars found in large spiral galaxies. The LMC's radial metallicity gradient is asymmetric. It is metal-poor and flatter towards the southwest, in the direction of the Bridge. This hints at mixing and/or distortion of the spatial metallicity distribution, presumably caused by tidal interactions between the Magellanic Clouds.