Ages and Luminosities of Young SMC/LMC Star Clusters and the recent Star Formation History of the Clouds

TL;DR

This study analyzes the ages, luminosities, and spatial distribution of young star clusters in the Small and Large Magellanic Clouds, revealing two main periods of enhanced cluster formation and their relation to galactic interactions and shell structures.

Contribution

It provides a detailed age and spatial distribution analysis of young clusters in the Magellanic Clouds using isochrone fitting, and links cluster formation to galactic interactions and shell expansion.

Findings

Two periods of enhanced cluster formation at 160Myr and 630Myr (SMC) and 125Myr and 800Myr (LMC)

Young clusters are associated with shells and high Hα regions, indicating formation from shell expansion

No evidence of cluster dissolution was observed.

Abstract

In this paper we discuss the age and spatial distribution of young (age$<$1Gyr) SMC and LMC clusters using data from the Magellanic Cloud Photometric Surveys. Luminosities are calculated for all age-dated clusters. Ages of 324 and 1193 populous star clusters in the Small and the Large Magellanic Cloud have been determined fitting Padova and Geneva isochrone models to their resolved color-magnitude diagrams. The clusters cover an age range between 10Myr and 1Gyr in each galaxy. For the SMC a constant distance modulus of $(m-M)_0$ = 18.90 and a metallicity of Z = 0.004 were adopted. For the LMC, we used a constant distance modulus of $(m-M)_0$ = 18.50 and a metallicity of Z = 0.008. For both galaxies, we used a variable color excess to derive the cluster ages. We find two periods of enhanced cluster formation in both galaxies at 160Myr and 630Myr (SMC) and at 125Myr and 800Myr (LMC). We present the spatially resolved recent star formation history of both Clouds based on young star clusters. The first peak may have been triggered by a close encounter between the SMC and the LMC. In both galaxies the youngest clusters reside in the supergiant shells, giant shells, the inter-shell regions, and toward regions with a high H$\alpha$ content, suggesting that their formation is related to expansion and shell-shell interaction. Most of the clusters are older than the dynamical age of the supergiant shells. No evidence for cluster dissolution was found. Computed V band luminosities show a trend for fainter magnitudes with increasing age as well as a trend for brighter magnitudes with increasing apparent cluster radii.