Embedded Clusters and Their Environments in Massive Star-Forming Region S233IR
Chi-Hung Yan, Young-Chol Minh, Yu-Nang Su, Jennifer Karr, Shiang-Yu Wang, Yi-Jehng Kuan

Abstract: Massive star formation takes place more dramatically compared to the low-mass case. The dynamical processes governing high-mass star formation are much more complex and less understood than those of low-mass star formation. Especially next generation star formation is thought to be triggered in the interacting ambient GMC by expanding HII regions. S233IR is one of the prominent HII regions where embedded massive stars near HII regions have been found in clusters associated with dense molecular cloud. Based on WIRCam images of CFHT and IRAC images of Spitzer, the stellar content and extended emission in S233IR was studied. The ages of the two young stellar clusters in S233IR, from K-band luminosity function, are determined to be 0.5 and 0.8 Myr, respectively, which implies that these regions harbor recent sequential star formation. The IMF slope derived (%25A3F = 1.67) is consistent with the values of other embedded clusters. Applying the gas mass estimated from CO observations, we estimate the star formation efficiency to be 0.14. S233IR dust emission showing PAH spectral feature is consistent with the dust emission from the galactic plane. In addition, new H2 bow shocks spatially distributed over a 2' are discovered.