Star clusters in the dwarf irregular galaxy Leo A

TL;DR

This study reports the discovery of four new star clusters in the dwarf irregular galaxy Leo A, expanding the known cluster sample to five, with detailed photometric analysis revealing their ages and low masses.

Contribution

First identification of multiple star clusters in Leo A using HST data, providing insights into their ages, masses, and spatial distribution in this isolated galaxy.

Findings

Four new star clusters discovered in Leo A

Clusters are of low mass and varied ages

Detailed photometric analysis of cluster stellar populations

Abstract

Leo A is an isolated gas-rich dwarf irregular galaxy of low stellar mass and metallicity residing at the outskirts of the Local Group. Ages of the stellar populations in Leo A range from $\sim$10 Myr to $\sim$10 Gyr. So far, only one star cluster has been discovered in this galaxy. Our aim is to search for star cluster candidates in the Leo A galaxy. We performed photometry of star-like objects on HST ACS archive observation frames in the $F475W$ and $F814W$ passbands and studied the spatial clustering of the Leo A stars down to the turn-off point of the old stellar populations. We report the discovery of four star clusters in the Leo A galaxy. This means that now a sample of five star clusters is known in Leo A. Two clusters are of a young age ($\sim$20 Myr; overlapping with HII regions) and low in mass ($\gtrsim$400 M$_\odot$ and $\gtrsim$150 M$_\odot$), the other three clusters are older ($\gtrsim$100 Myr) and also of low mass ($\gtrsim$300 M$_\odot$). These rough estimates are made assuming the isochrones of a metallicity derived for HII regions ($Z=0.0007$). Colour-magnitude diagrams of the stars residing in the circular areas of a 2.5arcsec radius around the clusters and integrated aperture photometry results of the clusters are presented.