A multiwavelength study of young massive star forming regions. II. The dust environment

Abstract

We present observations of 1.2 mm dust continuum emission made with the Swedish-ESO Submillimeter Telescope toward 18 luminous IRAS point sources, all with colors typical of compact H II regions and associated with CS(2 -> 1) emission, thought to be representative of young massive star forming regions. Emission was detected toward all the IRAS objects. We find that the 1.2 mm sources associated with them have distinct physical parameters, namely sizes of similar to 0.4 pc, dust temperatures of similar to 30 K, masses of similar to 2 x 10(3) M-circle dot, column densities of similar to 3 x 1023 cm(-2), and densities of similar to 4 x 10(5)cm(-3). We refer to these dust structures as massive and dense cores. Most of the 1.2 mm sources show single-peaked structures, several of which exhibit a bright compact peak surrounded by a weaker extended envelope. The observed radial intensity profiles of sources with this type of morphology are well fitted with power-law intensity profiles with power-law indices in the range of 1.0-1.7. This result indicates that massive and dense cores are centrally condensed, having radial density profiles with power-law indices in the range of 1.5-2.2. We also find that the UC H II regions detected with ATCA toward the IRAS sources investigated here (Paper I) are usually projected at the peak position of the 1.2 mm dust continuum emission, suggesting that massive stars are formed at the center of the centrally condensed massive and dense cores.