ACCRETION OF THE MAGELLANIC SYSTEM ONTO THE GALAXY

Abstract

Our Galaxy is surrounded by a large family of dwarf galaxies of which the\nmost massive are the Large and Small Magellanic Clouds (LMC and SMC). Recent\nevidence suggests that systems with the mass of the Local Group accrete\ngalaxies in smaller groups rather than individually. If so, at least some of\nthe Galaxy's dwarfs may have fallen in with the LMC and SMC, and were formed as\npart of the Magellanic system in the nearby universe. We use the latest\nmeasurements of the proper motions of the LMC and SMC and a multicomponent\nmodel of the Galactic potential to explore the evolution of these galaxy\nconfigurations under the assumption that the Magellanic system may once have\ncontained a number of bound dwarf galaxies. We compare our results to the\navailable kinematic data for the local dwarf galaxies, and examine whether this\nmodel can account for recently discovered stellar streams and the planar\ndistribution of Milky Way satellites. We find that in situations where the LMC\nand SMC are bound to the Milky Way, the kinematics of Draco, Sculptor, Sextans,\nUrsa Minor and the Sagittarius Stream are consistent with having fallen in\nalong with the Magellanic system. These dwarfs, if so associated, will likely\nhave been close to the tidal radius of the LMC originally and are unlikely to\nhave affected each other throughout the orbit. However there are clear cases,\nsuch as Carina and Leo I, that cannot be explained this way\n