On the origin and dynamics of the Magellanic Stream

Twelve of the 21 globular clusters and dwarf spheroidal galaxies lying between 25 and 250 kpc from the Galaxy lie within a narrow zone not more than 6 deg from a great circle, as seen from the Galactic center. Although this planar distribution is inclined by 35 deg to the Magellanic Stream, it can be shown that both may originate in a single encounter disrupting the outer parts of a low-mass 'victim'. Color-magnitude investigations and RR Lyrae variables of the stellar systems, as well as composition differences between the Magellanic Stream and the planar distribution, point to a considerable age for the major portion of stellar debris, placing the more violent disruptive episode earlier than the current perigalactic pass of the Magellanic Clouds. Given that the Stream itself, as well as the young stellar content of the Wing of the SMC, point to a recent disruptive event, at least two disruptive encounters must have occurred. Computer simulation, following methods developed by Toomre, were used to generate a family of models for the formation of the Magellanic Stream that broadly match both the spatial and the velocity distributions of both the gaseous and the stellar components. Agreement in the scaling of velocity is obtained by deepening the Galactic potential with a massive halo, consistent with the formulations of Ostriker et al. (1974) and Einasto et al. (1974).