The formation of compact dwarf ellipticals through merging star clusters

Abstract

In the past decades, extended old stellar clusters have been observed. These extended objects cover a large range in masses, from extended clusters or faint fuzzies to ultracompact dwarf galaxies. It has been demonstrated that these extended objects can be the result of the merging of star clusters in cluster complexes (small regions in which dozens to hundreds of star clusters form). This formation channel is called the 'Merging Star Cluster Scenario'. This work tries to explain the formation of compact ellipticals in the same theoretical framework. Compact ellipticals are a comparatively rare class of spheroidal galaxies, possessing very small effective radii and high central surface brightnesses. With the use of numerical simulations we show that the merging star cluster scenario, adopted for higher masses, as found with those galaxies, can reproduce all major characteristics and the dynamics of these objects. This opens up a new formation channel to explain the existence of compact elliptical galaxies.