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 .
We find that in order for four of the GCs to survive at their observed projected location , a dark matter core of size r _ { \mathrm { c } } > 1.5 kpc and a dwarf merger with dynamical mass ratio of 1:5 \leq \eta \leq 1:2 with Fornax is required .
We support the merger scenario by showing that aspects of the field star metallicity distribution function and anomalous chemical properties of GC5 , are representative of a merging galaxy which is \sim 1/3 less massive than Fornax .
Together the chemical and dynamical models suggest a scenario where three in-situ GCs in proto-Fornax were ejected to the outskirts during the merger , a GC4 formed during the merger at about 10 Gyrs ago , with GC5 being brought in by the merging galaxy to Fornax .