Gas expulsion in MOND: the possible origin of diffuse globular clusters
  and ultra-faint dwarf galaxies
  We study the evolution of star clusters located in the outer regions of a
galaxy undergoing a sudden mass loss through gas expulsion in the framework of
Milgromian dynamics (MOND) by means of N-body simulations. We find that, to
leave a bound star cluster, the star formation efficiency (SFE) of an embedded
cluster dominated by deep MOND gravity can be reduced down to $2.5\%$. For a
given SFE, the star clusters that survive in MOND can bind a larger fraction of
mass compared to the Newtonian dynamics. Moreover, the more diffuse the
embedded cluster is, the less substantial the size expansion of the final star
cluster is. The density profiles of a surviving star cluster are more cuspy in
the centre for more massive embedded clusters, and the central density profiles
are flatter for less massive embedded clusters or for lower SFE. This work may
help to understand the low concentration and extension of the distant
low-density globular clusters (GCs) and ultra-faint and diffuse satellite
galaxies around the Milky Way.
