The APOSTLE simulations: solutions to the Local Group's cosmic puzzles
  The Local Group of galaxies offer some of the most discriminating tests of
models of cosmic structure formation. For example, observations of the Milky
Way (MW) and Andromeda satellite populations appear to be in disagreement with
N-body simulations of the "Lambda Cold Dark Matter" ({\Lambda}CDM) model: there
are far fewer satellite galaxies than substructures in cold dark matter halos
(the "missing satellites" problem); dwarf galaxies seem to avoid the most
massive substructures (the "too-big-to-fail" problem); and the brightest
satellites appear to orbit their host galaxies on a thin plane (the "planes of
satellites" problem). Here we present results from APOSTLE (A Project Of
Simulating The Local Environment), a suite of cosmological hydrodynamic
simulations of twelve volumes selected to match the kinematics of the Local
Group (LG) members. Applying the Eagle code to the LG environment, we find that
our simulations match the observed abundance of LG galaxies, including the
satellite galaxies of the MW and Andromeda. Due to changes to the structure of
halos and the evolution in the LG environment, the simulations reproduce the
observed relation between stellar mass and velocity dispersion of individual
dwarf spheroidal galaxies without necessitating the formation of cores in their
dark matter profiles. Satellite systems form with a range of spatial
anisotropies, including one similar to that of the MW, confirming that such a
configuration is not unexpected in {\Lambda}CDM. Finally, based on the observed
velocity dispersion, size, and stellar mass, we provide new estimates of the
maximum circular velocity for the halos of nine MW dwarf spheroidals.
