What Does the Large Magellanic Cloud Look Like? It Depends on [M/H] and Age

TL;DR

This study uses extensive stellar maps based on Gaia DR3 data to analyze how the Large Magellanic Cloud's structure varies with metallicity and age, revealing simple exponential profiles and age-dependent scale lengths.

Contribution

It presents the first area-complete, mono-abundance and mono-age-mono-abundance stellar maps of the LMC, showing how its structure depends on metallicity and age.

Findings

Radial profiles are exponential with scale length decreasing with metallicity.

Bar prominence diminishes at lower metallicities.

Younger populations are more centrally concentrated.

Abstract

We offer a new way to look at the Large Magellanic Cloud through stellar mono-abundance and mono-age-mono-abundance maps. These maps are based on $\gtrsim 500\,000$ member stars with photo-spectroscopic [M/H] and age estimates from Gaia DR3 data, and they are the first area-complete, metallicity- and age-differentiated stellar maps of any disk galaxy. Azimuthally averaged, these maps reveal a surprisingly simple picture of the Milky Way's largest satellite galaxy. For any [M/H] below -0.1 dex, the LMC's radial profile is well described by a simple exponential, but with a scale length that steadily shrinks towards higher metallicities, from nearly 2.3~kpc at [M/H]$=-1.8$ to only 0.75~kpc at [M/H]$=-0.25$. The prominence of the bar decreases dramatically with [M/H], making it barely discernible at [M/H]$\lesssim -1.5$. Yet, even for metal-rich populations, the bar has little impact on the azimuthally averaged profile of the mono-abundance components. Including ages, we find that the scale length is a greater function of age than of metallicity, with younger populations far more centrally concentrated. At old ages, the scale length decreases with increasing metallicity; at young ages, the scale-length is independent of metallicity. These findings provide quantitative support for a scenario where the LMC built its stellar structure effectively outside in.