Dynamical friction in globular cluster-rich ultra-diffuse galaxies: the case of NGC5846-UDG1

Abstract: 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.