« HST observations of nuclear star clusters in 41 MATLAS dwarf galaxies: properties and implications in terms of formation scenario »
Debated for decades, the formation of nuclear star clusters (NSCs) –the densest stellar objects in the Universe– currently opposes two main scenarios: the migration and merging of globular clusters (GCs) due to dynamical friction, and the in-situ star-formation from gas infall. Studies of NSC stellar populations suggest that the former prevails in dwarf galaxies, with a possible contribution of the latter. However, timescales are such that up to now, no ongoing GC mergers were caught in the act. I will present a follow-up study of 41 nucleated dwarfs from the MATLAS survey observed with the high resolution ACS camera of the Hubble Space Telescope. About 12% of the galaxies show a complex nuclear region containing multiple star clusters and stellar tails which, I will show, establish a first direct evidence of ongoing star cluster mergers in the center of dwarf galaxies. Structural properties and photometry of the full NSC sample have been derived and compared to NSCs from galaxies in a range of mass and environment. I will showcase the results and discuss them in terms of NSC formation process. I will conclude on the future of NSC studies in the context of upcoming large surveys with deep and high spatial resolution observations, such as the Euclid Wide Survey.