Recent Star Formation in Low Metallicities. The Star-Forming Region NGC
  346/N66 in the Small Magellanic Cloud from Near-Infrared VLT/ISAAC
  Observations
  We perform a photometric analysis on deep, seeing-limited near-IR VLT images
of the region NGC 346/N66 and a nearby control field of the SMC in order to
locate the centres of active high- and intermediate-mass star formation through
the identification of near-IR bright objects as candidate stellar sources under
formation.We use archived imaging data obtained with the high-resolution camera
ISAAC at VLT of NGC 346/N66 and we construct the near-IR colour-magnitude (CMD)
and colour-colour diagrams (C-CD) of all detected sources. We investigate the
nature of all stellar populations in the observed CMDs, and we identify all
stellar sources that show significant near-IR excess emission in the observed
C-CD. We select, thus, the best candidates for being young stellar sources.
Based on their near-IR colours we select 263 candidate young stellar sources.
This sample comprises a variety of objects such as intermediate-mass PMS and
Herbig Ae/Be stars and possibly massive YSOs, providing original near-IR
colours for them. The spatial distribution of the selected candidate sources
shows that they are located along the dusty filamentary structures of N66 seen
in mid- and far-IR dust emission and agrees very well with that of previously
detected candidate YSOs and PMS stars. Our study provides an original accurate
set of near-IR colours for candidate young stellar sources. While this adds
significant information on the star formation process in NGC 346/N66, it is
still necessary to reveal the exact nature of these objects, a process that
requires the combination of multi-wavelength data, so that complete Spectral
Energy Distributions can be constructed for individual sources. This would be a
quite important follow-up study to that presented here.
