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J.A. Goetz (College of Wooster)
We have undertaken a complete near-infrared study of three star forming regions to better understand how clusters of pre-main sequence stars and young stars of various ages interact with each other and with their environment. In our study, we attempt to determine the age of each region. The primary mode of interaction for the youngest cluster of massive objects (<< 105 yr) appears to be via jets; jets from the environs of these forming stars encounter dense molecular material and create observable shock-excited gas. Massive stars in more evolved clusters (~ 104 -- 105 yr) interact through photoionization of the gas. The expansion of those HII regions provides additional interaction. Further star formation is stimulated in their wake.
Each program region consists of a core cluster of forming or recently formed stars. To better understand the interaction within each cluster, we have attempted to determine the relative and absolute ages of the members. We determined the ages of the small core cluster of objects in Cep A East, our youngest region, by examining maser emission, shock-excited emission emanating from jets and the dynamical ages of the bipolar outflows. For our other program objects, S88B and S235A/B, we have analyzed an extended stellar population associated with each region to determine its age and compared this with core cluster member ages derived from ZAMS ages and dynamical ages of surrounding HII regions.
In addition to assigning ages to the cluster member objects, we have postulated scenarios for the modes of interaction and to explain the emission observed at radio and infrared wavelengths.