Magellanic cloud periphery carbon stars. IV. The SMC

The kinematics of 150 carbon stars observed at moderate dispersion on the p eriphery of the Small Magellanic Cloud are compared with the motions of neu tral hydrogen and early-type stars in the intercloud region. The distributi on of radial velocities implies a cofiguration of these stars as a sheet in clined at 73 degrees +/- 4 degrees to the plane of the sky. The near side, to the south, is dominated by a stellar component; to the north, the far si de contains fewer carbon stars and is dominated by the neutral gas. The upp er velocity envelope of the stars is closely the same as that of the gas. T his configuration is shown to be consistent with the known extension of the SMC along the line of sight and is attributed to a tidally induced disrupt ion of the SMC that originated in a close encounter with the LMC some 0.3 t o 0.4 Gyr ago. The dearth of gas on the near side of the sheet is attribute d to ablation processes akin to those inferred in 1996 by Weiner & Williams to collisional excitation of the leading edges of Magellanic Stream clouds . Comparison with the 1989 kinematic data of Hardy, Suntzeff, & Azzopardi a nd Maurice, Martin, & Bouchet and the 1986 and 1988 data of Mathewson et al . leaves little doubt that forces other than gravity play a role in the dyn amics of the H I.