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

TL;DR

This study uses 1.2-mm dust continuum observations to analyze the physical properties and structure of massive star forming regions, revealing centrally condensed cores where massive stars likely form.

Contribution

First detailed millimeter-wave analysis of physical parameters and density profiles of young massive star forming cores associated with IRAS sources.

Findings

Massive cores have sizes ~0.4 pc, masses ~2000 Msun, and densities ~4x10^5 cm^-3.

Radial intensity profiles fit power-laws with indices 1.0-1.7, indicating central condensation.

UC HII regions are located at the peaks of dust emission, implying star formation at core centers.

Abstract

We present observations of 1.2-mm dust continuum emission, made with the Swedish ESO Submillimeter Telescope, towards eighteen luminous IRAS point sources, all with colors typical of compact HII 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 0.4 pc, dust temperatures of 30 K, masses of 2x10^3 Msun, column densities of 3x10^23 cm^-2, and densities of 4x10^5 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 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 1.5-2.2. We also find that the UC HII regions detected with ATCA towards 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.