The VMC survey XXX. Stellar proper motions in the central parts of the
  Small Magellanic Cloud
  We present the first spatially resolved map of stellar proper motions within
the central ($\sim$3.1 $\times$ 2.4 kpc) regions of the Small Magellanic Cloud
(SMC). The data used for this study encompasses four tiles from the ongoing
near-infrared VISTA survey of the Magellanic Clouds system and covers a total
contiguous area on the sky of $\sim$6.81 deg$^2$. Proper motions have been
calculated independently in two dimensions from the spatial offsets in the
$K_s$ filter over time baselines between 22 and 27 months. The reflex motions
of $\sim$33~000 background galaxies are used to calibrate the stellar motions
to an absolute scale. The resulting catalog is composed of more than 690 000
stars which have been selected based on their position in the $(J-K_s, K_s)$
color-magnitude diagram. For the median absolute proper motion of the SMC, we
find ($\mu_{\alpha}\mathrm{cos}(\delta)$, $\mu_{\delta}$) = (1.087 $\pm$ 0.192
(sys.) $\pm$ 0.003 (stat.), $-$1.187 $\pm$ 0.008 (sys.) $\pm$ 0.003 (stat.))
mas yr$^{-1}$, consistent with previous studies. Mapping the proper motions as
a function of position within the SMC reveals a non uniform velocity pattern
indicative of a tidal feature behind the main body of the SMC and a flow of
stars in the South-East moving predominantly along the line-of-sight.
