Old massive clusters (and a nuclear star cluster?) in the tidal tails of NGC 5238

Abstract

New, deep HST photometry allowed us to identify and study eight compact and bright ($M_V -5.8$) star clusters in the outskirts of the star-forming isolated dwarf galaxy NGC 5238 sun $). Five of these clusters are new discoveries, and six appear projected onto and/or aligned with the tidal tails recently discovered around this galaxy. The clusters are partially resolved into stars, and their colour magnitude diagrams reveal a well-developed red giant branch, implying ages older than 1-2 Gyr. Their integrated luminosity and structural parameters are typical of classical globular clusters, and one of them, with $M_V=-10.56 0.07$, is as bright as omega Cen, the brightest globular cluster in the Milky Way. Since the properties of this cluster are in the range spanned by those of nuclear star clusters we suggest that it may be the nuclear remnant of the disrupted satellite of NGC 5238 that produced the observed tidal tails.