The VMC survey -- XLI. Stellar proper motions within the Small
  Magellanic Cloud
  We used data from the near-infrared VISTA survey of the Magellanic Cloud
system (VMC) to measure proper motions (PMs) of stars within the Small
Magellanic Cloud (SMC). The data analysed in this study comprise 26 VMC tiles,
covering a total contiguous area on the sky of ~40 deg$^2$. Using multi-epoch
observations in the Ks band over time baselines between 13 and 38 months, we
calculated absolute PMs with respect to ~130,000 background galaxies. We
selected a sample of ~2,160,000 likely SMC member stars to model the
centre-of-mass motion of the galaxy. The results found for three different
choices of the SMC centre are in good agreement with recent space-based
measurements. Using the systemic motion of the SMC, we constructed spatially
resolved residual PM maps and analysed for the first time the internal
kinematics of the intermediate-age/old and young stellar populations
separately. We found outward motions that point either towards a stretching of
the galaxy or stripping of its outer regions. Stellar motions towards the North
might be related to the "Counter Bridge" behind the SMC. The young populations
show larger PMs in the region of the SMC Wing, towards the young Magellanic
Bridge. In the older populations, we further detected a coordinated motion of
stars away from the SMC in the direction of the Old Bridge as well as a stream
towards the SMC.
