The Discovery of a Population of Pre-Main Sequence Stars in N66/NGC346   from Deep HST/ACS Image
  We report the discovery of a rich population of low mass stars in the young, massive star forming region N66/NGC346 in the Small Magellanic Cloud, from deep V, I and H alpha images taken with the HST/ACS. These stars have likely formed together with the NGC346 cluster, ~3-5 Myr ago. Their magnitude and colors are those of pre-main sequence stars in the mass range 0.6-3 Mo, mostly concentrated in the main cluster, but with secondary subclusters spread over a region across ~45 pc. These subclusters appear to be spatially coincident with previously known knots of molecular gas identified in ground based and ISO observations. We show that N66/NGC346 is a complex region, being shaped by its massive stars, and the observations presented here represent a key step towards the understanding of how star formation occurred and has progressed in this low metallicity environment. 
A. Nota, M. Sirianni, E. Sabbi, M. Tosi, M. Clampin, J. Gallagher, M.   Meixner, S. Oey, A. Pasquali, L. J. Smith, R. Walter...