Star Cluster collisions - a formation scenario for the Extended Globular Cluster Scl-dE1 GC1

TL;DR

This study uses N-body simulations to investigate the formation of the extended globular cluster Scl-dE1 GC1, exploring star cluster mergers and expansion scenarios, and discusses how future velocity dispersion measurements could differentiate these models.

Contribution

It presents detailed N-body simulations of star cluster mergers and expansion to explain the formation of the extended globular cluster Scl-dE1 GC1, considering dark matter influence and star formation efficiency.

Findings

High star formation efficiency (~33%) is needed for merger remnants.

Low-mass dark matter halos are compatible with observed cluster properties.

Expansion after mass loss is a viable alternative formation scenario.

Abstract

Recent observations of the dwarf elliptical galaxy Scl-dE1 (Sc22) in the Sculptor group of galaxies revealed an extended globular cluster (Scl-dE1 GC1), which exhibits an extremely large core radius of about 21.2 pc. The authors of the discovery paper speculated on whether this object could reside in its own dark matter halo and/or if it might have formed through the merging of two or more star clusters. In this paper, we present N-body simulations to explore thoroughly this particular formation scenario. We follow the merger of two star clusters within dark matter haloes of a range of masses (as well as in the absence of a dark matter halo). In order to obtain a remnant which resembles the observed extended star cluster, we find that the star formation efficiency has to be quite high (around 33 per cent) and the dark matter halo, if present at all, has to be of very low mass, i.e. raising the mass to light ratio of the object within the body of the stellar distribution by at most a factor of a few. We also find that expansion of a single star cluster following mass loss provides another viable formation path. Finally, we show that future measurements of the velocity dispersion of this system may be able to distinguish between the various scenarios we have explored.