The Dwarf Satellites of M31 and the Galaxy

Abstract

The satellite systems of M31 and the Galaxy are compared. It is noted that all five of the suspected stripped dSph cores of M31 companions are located within a projected distance of 40 kpc of from the nucleus of this galaxy, whereas the normal dSph companions to this object have distances > 40 kpc from the center of M31. All companions within 200 kpc < D(M31) < 600 kpc are late-type objects. The companions to the Galaxy appear to exhibit different systematics with the irregular LMC and SMC being located at small R_{gc}. It is speculated that this difference might be accounted for by assuming that the Magellanic Clouds are interlopers that were originally formed in the outer reaches of the Local Group. The radial distribution of the total sample of 40 companions of M31 and the Galaxy, which is shown in Figure 1, may hint at the possibility that these objects contain distinct populations of core (R < 25 kpc) and halo (R > 25 kpc) satellites.)