Nuclear clusters in dwarf irregular galaxies and their connection to massive galactic clusters

We compare nuclear globular clusters (nGCs) in dwarf galaxies and Galactic GCs with extended (hot) horizontal branches (EHB-GCs) to test the suggested external origin of the latter and the conditions under which GC self-enrichment can operate. We show that the present-day escape velocity (v_esc) of stellar ejecta to reach the cluster tidal radius compares with those of EHB-GCs. For EHB-GCs, we find a correlation between the present-day v_esc and their metallicity as well as (V - I) colour. The similar v_esc and (V - I) distribution of nGCs and EHB-GCs implies that nGCs could also have complex stellar populations. The v_esc-[Fe/H] relation could reflect the known relation of increasing stellar-wind velocity with metallicity, which in turn explains why more metal-poor clusters typically show more peculiarities in their stellar population than more metal-rich clusters of the same mass.