An observer's guide to the (Local Group) dwarf galaxies: predictions for their own dwarf satellite populations

A recent surge in the discovery of new ultrafaint dwarf satellitesof the Milky Wayhas inspired the idea of searching for faint satellites, $10^3\, \mathrm{M_{\odot}} 99\%$ chance that at least one satellitewith stellar mass$M_*> 10^5 \, \mathrm{M_{\odot}}$ exists around the combined five Local Groupfield dwarf galaxieswith the largest stellar mass. When considering satelliteswith $M_*> 10^4 \, \mathrm{M_{\odot}}$, we predict a combined $5-25$ satellitesfor the five largest field dwarfs, and $10-50$ for the whole Local Groupfield dwarfpopulation. Because of the relatively small number of predicted dwarfs, and their extended spatial distribution, a large fraction each Local Groupdwarf's virial volume will need to be surveyed to guarantee discoveries. We compute the predicted number of satellitesin a given field of view of specific Local Groupgalaxies, as a function of minimum satelliteluminosity, and explicitly obtain such values for the Solitary Local dwarfssurvey. Uncertainties in abundance matching and reionizationmodels are large, implying that comprehensive searches could lead to refinements of both models.