Velocities of red giants in the SMC

The line-of-sight velocity field is dominated by the projection of the orbital motion of the SMC around the Large Magellanic Cloud/Milky Way. The residuals are inconsistent with both a non-rotating spheroid and a nearly face on disc system.

The current sample and previous stellar and Hi kinematics can be reconciled by rotating disc models with line-of-nodes position angle {Theta} ~120{deg}-130{deg}, moderate inclination (25{deg}-70{deg}), and rotation curves rising at 20-40km/s/kpc. The metal-poor stars exhibit a lower velocity gradient and higher velocity dispersion than the metal-rich stars. If our interpretation of the velocity patterns as bulk rotation is appropriate, then some revision to simulations of the SMC orbit is required since these are generally tuned to the SMC disc line of nodes lying in a north-east-south-west (SW) direction.