Submillimeter and molecular views of three Galactic ring-like HII regions

TL;DR

This study uses submillimeter and CO observations to analyze three Galactic ring-like HII regions, identifying potential sites of triggered star formation and examining the properties of associated dense clumps and YSOs.

Contribution

It provides new insights into the star formation activity at the interfaces of ring-like HII regions using multi-wavelength data and compares these regions to other star-forming environments.

Findings

KR 120 likely hosts embedded YSOs indicating triggered star formation

Masses of dense clumps are around 100 Solar masses

IR luminosity correlates with clump mass over four orders of magnitude

Abstract

We use SCUBA 850 micron and CO observations to analyze the surroundings of three Galactic ring-like HII regions, KR 7, KR 81, and KR 120 (Sh 2-124, Sh 2-165 and Sh 2-187), with the aim of finding sites of triggered star formation. We find one prominent submillimeter (sub-mm) source for each region, located at the interface between the HII region and its neutral surroundings. Using Two Micron All Sky Survey photometry, we find that the prominent sub-mm source for KR 120 probably contains an embedded cluster of young stellar objects (YSOs), making it a likely site for triggered star formation. The KR 7 sub-mm source could possibly contain embedded YSOs, while the KR 81 sub-mm source likely does not. The mass column densities for these dominant sub-mm sources fall in the ~0.1-0.6 g cm^{-2} range. The mass of the cold, dense material (clumps) seen as the three dominant sub-mm sources fall around ~100 Solar masses. We use the SCUBA Legacy catalog to characterize the populations of sub-mm sources around the HII regions, and compare them to the sources found around a previously studied similar ring-like HII region (KR 140) and near a massive star-forming region (W3). Finally, we estimate the IR luminosities of the prominent newly detected sub-mm sources and find that they are correlated with the clump mass, consistent with a previously known luminosity-mass relationship which this study shows to be valid over four orders of magnitude in mass.