HST observations of the LMC compact HII region N11A

We present a study of the LMC compact H II region N11A using Hubble Space T elescope imaging observations which resolve N11A and reveal its unknown neb ular and stellar features. The presence of a sharp ionization front extendi ng over more than 4" (1 pc) and fine structure filaments as well as larger loops indicate an environment typical of massive star formation regions, in agreement with high [O III]/H beta line ratios. N11A is a young region, as deduced from its morphology, reddening, and especially high local concentr ation of dust, as indicated by the Balmer decrement map. Our observations a lso reveal a cluster of stars lying towards the central part of N11A. Five of the stars are packed in an area less than 2" (0.5 pc), with the most lum inous one being a mid O type star. N11A appears to be the most evolved comp act Hii region in the Magellanic Clouds so far studied.