NLTE Rovibrational Analysis of Hot Disk Tracers in the Massive Binary Protostellar System IRAS 16547 4247

During the embedded phase of massive star formation, the surrounding material of protostars experiences vigorous physics and chemistry, resulting in intense local conditions, such as high temperature and density. As a consequence, various high excitation molecular lines have been detected and used to probe the physical properties of these massive protostellar systems. Recent ALMA observations have unveiled the unusual structure of the inner region of IRAS 16547-4247 (an O-type binary protostellar object) with rovibrationally excited “hot-disk” tracing molecules, e.g., NaCl, SiS, and H₂O. We present non-local thermal equilibrium (NLTE) analysis of the detected species to constrain the physical properties of this circumbinary system. The effects of physical conditions (e.g. temperature, density, and radiation) on the excitation of these detected molecules are explored with NLTE modeling. Such study is essential to the evaluation of the potential of these rovibrationally excited molecules as “disk-tracers”, as well as to the investigation of detailed structures of massive star-forming regions.