The Distribution of Dense Cores near HII Regions

George Bobotsis, Michel Fich

Published 2019-08-15Version 1

An investigation of dust emission associated with a large sample of HII regions has been carried out. Stacked results from this sample suggest that each HII region is at or near the center of a cluster of dense cores, that extends far beyond the HII region, and has volume density that decreases as r^(-3). The data also shows evidence for enhanced numbers of cores near the boundary of the HII regions. At the same time, a significant decrease in the number of cores, consistent with no cores, is observed in the interior of these HII regions. Neither these HII regions, nor their associated massive OB stars were found to have a significant heating effect on their associated dusty clumps. Clouds, or the outermost layers of the clumps in which the cores are embedded, are found to exert a strong shielding effect to external heating sources. Despite this, a large portion of the identified cores was found to be warmer than their surrounding cloud and consequently may be in the initial stages of star formation. The star formation efficiency of the 7 HII region systems with the most reliable mass budgets ranged between 1% and 9%.