2016MNRAS.462.3221A

The Andromeda galaxy is observed to have a system of two large dwarf ellipticals and ∼13 smaller satellite galaxies that are currently corotating 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 corotating satellite galaxies originated from a subhalo group, where NGC 205 was the host and the satellite galaxies occupied dark matter sub-subhaloes. 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-subhaloes 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-subhaloes than the observed NGC 205 + 15 smaller satellites (thus including the two counter-rotators, but excluding M32) increased from <10^–8 for the initial distribution to ∼10^–2 at pericentre. The probability of the simulated sub-subhaloes occupying the locations of the observed corotating satellites in the line-of-sight velocity versus projected on-sky distance plane is at most 2 x 10^–3 for 11 out of 13 satellites. Increasing the mass of M31 and the extent of the initial distribution of sub-subhaloes gives a maximum probability of 4 x 10^–3 for all 13 corotating satellites, but the probability of producing the thinness would drop to ∼10^–3.