Drama of HII regions: Clustered and Triggered Star Formation

TL;DR

This paper investigates how HII regions influence star formation, using multi-wavelength data to analyze physical conditions and evidence of triggered star formation in various regions affected by massive stars.

Contribution

It provides a comprehensive multi-wavelength observational analysis of star formation influenced by HII regions, highlighting signs of triggered star formation and the physical state of the interstellar medium.

Findings

Active star formation in large infrared bubbles with expanding shells

Tentative signs of triggered star formation in smaller bubbles

Possible triggered origin of dense cores in the Rosette Molecular Complex

Abstract

In order to understand the star formation process under the influence of HII regions, we have carried out extensive investigations to well selected star-forming regions which all have been profoundly affected by existing massive O type stars. On the basis of multi-wavelength data from mid-infrared to millimeter collected using $Spitzer$, $Herschel$, and ground based radio telescopes, the physical status of interstellar medium and star formation in these regions have been revealed. In a relatively large infrared dust bubble, active star formation is undergoing and the shell is still expanding. Signs of compressed gas and triggered star formation have been tentatively detected in a relatively small bubble. The dense cores in the Rosette Molecular Complex detected at 1.1 mm using SMA have been speculated to have a likely triggered origin according to their spatial distribution. Although some observational results have been obtained, more efforts are necessary to reach trustworthy conclusions.