The age-metallicity relationship of the Large Magellanic Cloud field star population from wide-field Washington photometry

TL;DR

This study uses wide-field Washington photometry to analyze the age and metallicity distribution of 5.5 million stars in the Large Magellanic Cloud, revealing complex chemical evolution and spatial formation patterns over billions of years.

Contribution

It provides a comprehensive age-metallicity relationship for the LMC, showing a mixed chemical evolution model and spatially dependent star formation history.

Findings

The LMC's chemical evolution is a mix of closed-box and bursting models.

Older, metal-poor stars formed mainly in the outer disk, younger, metal-rich in the inner disk.

Minimal metallicity gradient and variable metallicity range over time.

Abstract

We analyze ages and metallicities for some 5.5 million stars distributed throughout the Large Magellanic Cloud (LMC) main body, obtained from CCD Washington CT1 photometry. We produce a comprehensive field star Age-Metallicity Relationship (AMR) from the earliest epoch until ~1 Gyr ago. This AMR reveals that the LMC has not evolved chemically as either a closed-box or bursting system, exclusively, but as a combination of both scenarios that have varied in relative strength over the lifetime of the galaxy, although the bursting model falls closer to the data in general. Furthermore, while old and metal-poor field stars have been preferentially formed in the outer disk, younger and more metal-rich stars have mostly been formed in the inner disk, confirming an outside-in formation. We provide evidence for the formation of stars between 5 and 12 Gyr, during the cluster age gap, although chemical enrichment during this period was minimal. We find no significant metallicity gradient in the LMC. We also find that the range in the metallicity of an LMC field has varied during the lifetime of the LMC. In particular, we find only a small range of the metal abundance in the outer disk fields, whereas an average range of Delta([Fe/H]) = +0.3\pm0.1 dex appears in the inner disk fields.