Size diversity of old Large Magellanic Cloud clusters as determined by
  internal dynamical evolution
  The distribution of size as a function of age observed for star clusters in
the Large Magellanic Cloud (LMC) is very puzzling: young clusters are all
compact, while the oldest systems show both small and large sizes. It is
commonly interpreted as due to a population of binary black holes driving a
progressive expansion of cluster cores. Here we propose, instead, that it is
the natural consequence of the fact that only relatively low-mass clusters have
formed in the last ~3 Gyr in the LMC and only the most compact systems survived
and are observable. The spread in size displayed by the oldest (and most
massive) clusters, instead, can be explained in terms of initial conditions and
internal dynamical evolution. To quantitatively explore the role of the latter,
we selected a sample of five coeval and old LMC clusters with different sizes,
and we estimated their dynamical age from the level of central segregation of
blue straggler stars (the so-called dynamical clock). Similarly to what found
in the Milky Way, we indeed measure different levels of dynamical evolution
among the selected coeval clusters, with large-core systems being dynamically
younger than those with small size. This behaviour is fully consistent with
what expected from internal dynamical evolution processes over timescales
mainly set by the structure of each system at formation.
