Old massive clusters (and a nuclear star cluster?) in the tidal tails of NGC5238

TL;DR

This study identifies and characterizes eight bright star clusters in NGC5238, revealing some are old globular clusters and possibly remnants of a disrupted satellite galaxy, with implications for galaxy interaction history.

Contribution

First detailed analysis of star clusters in NGC5238's tidal tails, suggesting a nuclear star cluster origin for one and providing insights into galaxy disruption processes.

Findings

Six clusters aligned with tidal tails, indicating a link to galaxy interactions.

One cluster as bright as Omega Cen, possibly a nuclear remnant.

Clusters are older than 1-2 Gyr, typical of globular clusters.

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 NGC5238 (M_*= 10^8 M_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 has M_V=-10.56 +/- 0.07, as bright as Omega Cen, the brightest globular cluster of 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 NGC5238 that produced the observed tidal tails.