From Star Clusters to Dwarf Galaxies and Galactic Nuclei

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Intense star formation bursts typically produce massive (super) star clusters (SSCs). In especially intense instances, the SSCs are grouped into clumps, or stellar superclusters, containing from a few-dozen to a few-hundred SSCs within a region spanning only a few hundred pc. Such intense star-formation events may have been typical during early galaxy assembly when gas-rich late-type proto-galaxies interactes profusely. The dynamical evolution of superclusters is dominated initially by the formation mechanism of the constituent SSCs, followed by the successive merging of the SSCs within a few supercluster crossing times. The resulting objects become satellites that may either (i) be expelled from the host galaxy forming isolated dwarf galaxies, (ii) orbit about the host forming low-mass satellites, (iii) continue to orbit within the disk of the host or (iv) fall towards the centre of the host forming a nucleus. The above possibilities (i) & (ii) are exciting in view of (a) recent suggestions that some dwarf irregular galaxies may be related to tidal dwarf galaxies which are observed to form in the tidal tails of interacting galaxies and contain assemblages of SSCs, and (b) the very recent finding of a new class of galaxy, namely the ultra-compact dwarf galaxies (UCDs), in the Fornax galaxy cluster. The very recent detection of a new class of star clusters, the faint fuzzies (FFs), in the disks of two lenticular galaxies is highly for possibility (iii), which is probably also relevant for the enigmatic w Cen globular cluster that orbits within the disk of the Milky Way. The realisation that many late-type disk galaxies have nuclei consisting of relatively young star clusters makes possibility (iv) highly interesting.