Age -- Metallicity relation in the MCs clusters (Based on observations made with the Danish 1.54 m and ESO 3.6m Telescopes at La Silla Observatory, Chile)

TL;DR

This study investigates the age-metallicity relation in Magellanic Clouds star clusters using Strömgren photometry, revealing gradients and possible interaction effects, and compares spatial distributions of metallicity and age.

Contribution

It provides new photometric measurements of clusters in the Magellanic Clouds and analyzes their age-metallicity relation, highlighting gradients and interaction-related metallicity jumps.

Findings

The LMC shows a metallicity gradient with younger clusters being more metal-rich.

A possible metallicity jump occurs around 600 million years, linked to galaxy interactions.

SMC clusters are generally more metal-poor, consistent with its status as a metal-poor galaxy.

Abstract

Aims: To investigate a possible dependence between age and metallicity in the Magellanic Clouds (MCs) from a study of small open star clusters, using Str\"{o}mgren photometry. Our goal is to trace evidence of an age metallicity relation (AMR) and correlate it with the mutual interactions of the two MCs. Our aim is also to correlate the AMR with the spatial distribution of the clusters. In the Large Magellanic Cloud (LMC), the majority of the selected clusters are young (up to 1 Gyr) and our aim is to search for an AMR at this epoch which has not been much studied. Methods: We report on results for 15 LMC and 8 Small Magellanic Cloud (SMC) clusters, scattered all over the area of these galaxies, to cover a wide spatial distribution and metallicity range. The selected LMC clusters were observed with the 1.54m Danish Telescope in Chile, using the Danish Faint Object Spectrograph and Camera (DFOSC) with a single 2kx2k CCD, whereas the SMC clusters were observed with the ESO 3.6m Telescope also in Chile with the ESO Faint Object Spectrograph and Camera (EFOSC). The obtained frames were analysed with the conventional DAOPHOT and IRAF software. We used Str\"{o}mgren filters in order to achieve reliable metallicities from photometry. Isochrone fitting was used in order to determine the ages and metallicities. Results: The AMR for the LMC displays a metallicity gradient, with higher metallicities for the younger ages. The AMR for LMC-SMC star clusters shows a possible jump in metallicity and a considerable increase at about 6x10^8 yr. It is possible that this is connected to the latest LMC-SMC interaction. The AMR for the LMC also displays a metallicity gradient with distance from the centre. The metallicities in SMC are lower, as expected for a metal poor host galaxy.