Formation of globular clusters in dwarf galaxies of the Local Group

The existence of globular clusters (GCs) in a few satellite galaxies, and their absence in majority of dwarf galaxies, present a challenge for models attempting to understand the origins of GCs. In addition to GC presence appearing stochastic and difficult to describe with average trends, in the smallest satellite galaxies GCs contribute a substantial fraction of total stellar mass. We investigate the stochasticity and number of GCs in dwarf galaxies using an updated version of our model that links the formation of GCs to the growth of the host galaxy mass. We find that more than 50% of dwarf galaxies with stellar mass $M_\odot\lesssim 2\times10^7 M_\odot$ do not host GCs, whereas dwarfs with $M_\odot\sim10^8 M_\odot$ almost always contain some GCs, with a median number $\sim 10$ at $z=0$. These predictions are in agreement with the observations of the Local Volume dwarfs. We also confirm the near-linear GC system mass--halo mass relation down to $M_{\rm h}\simeq10^8 M_\odot$ under the assumption that GC formation and evolution in galaxies of all mass can be described by the same physical model. A detailed case study of two model dwarfs that resemble the Fornax dwarf spheroidal galaxy shows that observational samples can be notably biased by incompleteness below detection limit and at large radii.