Assembly of the outer Galactic stellar halo in the hierarchical model
  We provide a set of numerical N-body simulations for studying the formation
of the outer Milky Ways's stellar halo through accretion events. After
simulating minor mergers of prograde and retrograde orbiting satellite halo
with a Dark Matter main halo, we analyze the signal left by satellite stars in
the rotation velocity distribution. The aim is to explore the orbital
conditions where a retrograde signal in the outer part of the halo can be
obtained, in order to give a possible explanation of the observed rotational
properties of the Milky Way stellar halo. Our results show that, for satellites
more massive than $\sim 1/40$ of the main halo, the dynamical friction has a
fundamental role in assembling the final velocity distributions resulting from
different orbits and that retrograde satellites moving on low inclination
orbits deposit more stars in the outer halo regions end therefore can produce
the counter-rotating behavior observed in the outer Milky Way halo.
