The VMC Survey - XIV. First results on the look-back time star-formation
  rate tomography of the Small Magellanic Cloud
  We analyse deep images from the VISTA survey of the Magellanic Clouds in the
YJKs filters, covering 14 sqrdeg (10 tiles), split into 120 subregions, and
comprising the main body and Wing of the Small Magellanic Cloud (SMC). We apply
a colour--magnitude diagram reconstruction method that returns their
best-fitting star formation rate SFR(t), age-metallicity relation (AMR),
distance and mean reddening, together with 68% confidence intervals. The
distance data can be approximated by a plane tilted in the East-West direction
with a mean inclination of 39 deg, although deviations of up to 3 kpc suggest a
distorted and warped disk. After assigning to every observed star a probability
of belonging to a given age-metallicity interval, we build high-resolution
population maps. These dramatically reveal the flocculent nature of the young
star-forming regions and the nearly smooth features traced by older stellar
generations. They document the formation of the SMC Wing at ages <0.2 Gyr and
the peak of star formation in the SMC Bar at 40 Myr. We clearly detect periods
of enhanced star formation at 1.5 Gyr and 5 Gyr. The former is possibly related
to a new feature found in the AMR, which suggests ingestion of metal-poor gas
at ages slightly larger than 1 Gyr. The latter constitutes a major period of
stellar mass formation. We confirm that the SFR(t) was moderately low at even
older ages.
