The Chemical Enrichment History of the Small Magellanic Cloud and Its Gradients

TL;DR

This study maps the metallicity distribution of stars in the Small Magellanic Cloud, revealing a gradient where central regions are more metal-rich and younger, indicating a link between chemical enrichment and stellar age.

Contribution

First detection of a metallicity gradient in the SMC, connecting chemical enrichment with spatial and age distributions of stars.

Findings

Metallicity decreases with distance from the center.

Younger, more metal-rich stars are concentrated centrally.

A clear metallicity gradient correlates with an age gradient.

Abstract

We present stellar metallicities derived from Ca II triplet spectroscopy in over 350 red giant branch stars in 13 fields distributed in different positions in the SMC, ranging from $\sim$1\arcdeg\@ to $\sim$4\arcdeg\@ from its center. In the innermost fields the average metallicity is [Fe/H] $\sim -1$. This value decreases when we move away towards outermost regions. This is the first detection of a metallicity gradient in this galaxy. We show that the metallicity gradient is related to an age gradient, in the sense that more metal-rich stars, which are also younger, are concentrated in the central regions of the galaxy.