Young star clusters in the extended UV disk of M83

Abstract

The process of star formation in a low-metallicity environment and whether it differs from star formation in the solar neighbourhood is an open topic. Recently, CO clumps were identified within the extended ultraviolet (XUV) disk of M83 despite the low metallicity and distance from the galaxy center which allows a search for any recent star formation in the clumps. We aim to probe whether active star formation is occurring within the CO clumps in the XUV disk, and to assess its implications for star formation in such environments. We analyse deep Subaru Suprime-Cam Halpha, Hyper Suprime-Cam g, r, & i, and Gemini/FLAMINGOS 2 J and Ks band imaging to search for evidence of star formation within the ALMA-identified CO clumps. We identify sources within the CO clump contours, and we evaluate the probability that these sources are associated with the CO clumps rather than being chance alignments. Based on their magnitudes and adopting single-age stellar population models, we estimate their masses. Four of the clumps have an associated near-infrared counterpart. Based on their magnitude, color, and the general source density in the field, two of these could be chance alignments. One counterpart is associated with the most massive clump in the sample, while another is an unresolved cluster near-infrared source with an estimated age of 5 Myr and a mass of 2000 Msun. The other, an extended complex, is consistent with an age of 6Myr and a mass of 700Msun. The near-infrared photometry is sensitive to young clusters with masses down to a few hundred of Msun for a fully sampled IMF. Star formation is ongoing in a few of the CO clumps, and despite their location on the outskirts of M83, favourable conditions for star formation persist in at least a few clusters. One of the detected sources appears to be interacting with an adjacent molecular clump, which could trigger further star formation.