Dynamical friction in globular cluster-rich ultra-diffuse galaxies: the
  case of NGC5846-UDG1
  Ultra-diffuse galaxies that contain a large sample of globular clusters (GCs)
offer an opportunity to test the predictions of galactic dynamics theory.
NGC5846-UDG1 is an excellent example, with a high-quality sample of dozens of
GC candidates. We show that the observed distribution of GCs in NGC5846-UDG1 is
suggestive of mass segregation induced by gravitational dynamical friction. We
present simple analytic calculations, backed by a series of numerical
simulations, that naturally explain the observed present-day pattern of GC
masses and radial positions. Subject to some assumptions on the GC population
at birth, the analysis supports the possibility that NGC5846-UDG1 resides in a
massive dark matter halo. This is an example for the use of GC-rich systems as
dynamical (in addition to kinematical) tracers of dark matter.
