A dwarf-dwarf merger and dark matter core as a solution to the Globular Cluster problems in the Fornax dSph

Understand

The five globular clusters (GCs) of the Fornax dSph are puzzling for two reasons; the mass in GCs is high with respect to the galaxy's old stellar mass, and their survival and large distance (> 1 kpc) is at odds with naive expectations of dynamical friction.

• We present here a semi-analytic model, simultaneously addressing both problems in a comprehensive evolutionary framework for Fornax.
• Key to the model is inclusion of: 1) hydrodynamical constraints on the GC formation locations, 2) self-consistent velocity distribution functions in the dynamical friction calculations and 3) expansion of GC orbits due to a past dwarf-dwarf merger in the orbit integrations.
• The latter is crucial for reconciling the dynamical survival of the clusters, and their chemical properties with respect to the Fornax field stars.