Constrained simulations of the Local Group: on the radial distribution
  of substructures
  We examine the properties of satellites found in high resolution simulations
of the local group. We use constrained simulations designed to reproduce the
main dynamical features that characterize the local neighborhood, i.e. within
tens of Mpc around the Local Group (LG). Specifically, a LG-like object is
found located within the 'correct' dynamical environment and consisting of
three main objects which are associated with the Milky Way, M31 and M33. By
running two simulations of this LG from identical initial conditions - one with
and one without baryons modeled hydrodynamically - we can quantify the effect
of gas physics on the $z=0$ population of subhaloes in an environment similar
to our own. We find that above a certain mass cut, $M_{\rm sub} >
2\times10^{8}h^{-1} M_{\odot}$ subhaloes in hydrodynamic simulations are more
radially concentrated than those in simulations with out gas. This is caused by
the collapse of baryons into stars that typically sit in the central regions of
subhaloes, making them denser. The increased central density of such a subhalo,
results in less mass loss due to tidal stripping than the same subhalo
simulated with only dark matter. The increased mass in hydrodynamic subhaloes
with respect to dark matter ones, causes dynamical friction to be more
effective, dragging the subhalo towards the centre of the host. This results in
these subhaloes being effectively more radially concentrated then their dark
matter counterparts.
