The potential role of NGC 205 in generating Andromeda's vast thin
  co-rotating plane of satellite galaxies
  The Andromeda galaxy is observed to have a system of two large dwarf
ellipticals and ~13 smaller satellite galaxies that are currently co-rotating
in a thin plane, in addition to 2 counter-rotating satellite galaxies. We
explored the consistency of those observations with a scenario where the
majority of the co-rotating satellite galaxies originated from a subhalo group,
where NGC 205 was the host and the satellite galaxies occupied dark matter
sub-subhalos. We ran N-body simulations of a close encounter between NGC 205
and M31. In the simulations, NGC 205 was surrounded by massless particles to
statistically sample the distribution of the sub-subhalos expected in a subhalo
that has a mass similar to NGC 205. We made Monte Carlo samplings and found
that, using a set of reference parameters, the probability of producing a
thinner distribution of sub-subhalos than the observed NGC 205 + 15 smaller
satellites (thus including the 2 counter-rotators, but excluding M32) increased
from <1e-8 for the initial distribution to ~0.01 at pericentre. The probability
of the simulated sub-subhalos occupying the locations of the observed
co-rotating satellites in the line of sight velocity versus projected on-sky
distance plane is at most 0.002 for 11 out of 13 satellites. Increasing the
mass of M31 and the extent of the initial distribution of sub-subhalos gives a
maximum probability of 0.004 for all 13 co-rotating satellites, but the
probability of producing the thinness would drop to ~ 0.001.
