N-body simulations of the Small Magellanic Cloud and the Magellanic Stream

Abstract

An extensive set of N-body simulations has been carried out on the gravitational interaction of the Small Magellanic Cloud (SMC) with the Galaxy and the Large Magellanic Cloud (LMC). The SMC is assumed to have been a barred galaxy with a disc-to-halo mass ratio of unity before interaction and was modelled by a large number of self-gravitating particles, whereas the Galaxy and LMC have been represented by rigid spherical potentials. Our more advanced numerical treatment has enabled us to obtain the most integrated and systematic understanding to date of numerous morphological and kinematical features observed in the Magellanic system (excluding the LMC), which have been dealt with more or less separately in previous studies. The best model we have found succeeded in reproducing the Magellanic Stream (MS) as a tidal plume created by the SMC-LMC-Galaxy close encounter 1.5 Gyr ago. At the same time, we see the formation of a leading counterpart to the Magellanic Stream (the leading arm), on the opposite side of the Magellanic Clouds to the Stream, which mimics the overall distribution of several neutral hydrogen clumps observed in the corresponding region of the sky. A close encounter with the LMC 0.2 Gyr ago created another tidal tail and bridge system, which constitutes the interCloud region in our model. The elongation of the SMC bar along the line-of-sight direction suggested by Cepheid observations has been partially reproduced, alongside its projected appearance on the sky. The model successfully explains some major trends in the kinematics of young populations in the SMC bar and older populations in the ‘halo’ of the SMC, as well as the overall velocity pattern for the gas, young stars, and carbon stars in the interCloud region.