How common is the Milky Way - satellite system alignment?
  The highly flattened distribution of satellite galaxies in the Milky Way
presents a number of puzzles. Firstly, its polar alignment stands out from the
planar alignments commonly found in other galaxies. Secondly, recent proper
motion measurements reveal that the orbital angular momentum of at least 3, and
possibly as many as 8, of the Milky Ways satellites point (within 30 degrees)
along the axis of their flattened configuration, suggesting some form of
coherent motion. In this paper we use a high resolution cosmological simulation
to investigate whether this pattern conflicts with the expectations of the cold
dark matter model of structure formation. We find that this seemingly unlikely
set up occurs often: approximately 35% of the time we find systems in which the
angular momentum of 3 individual satellites point along, or close to, the short
axis of the satellite distribution. In addition, in 30% of the systems we find
that the net angular momentum of the 6 best aligned satellites lies within 35
degrees of the short axis of the satellite distribution, as observed for the
Milky Way.
