2020ApJ...904..185O

We have observed the Class 0 protostellar source IRAS 16293-2422 A in the C¹⁷O and H₂CS lines as well as the 1.3 mm dust continuum with the Atacama Large Millimeter/submillimeter Array at an angular resolution of ∼0.''1 (14 au). The continuum emission of the binary component, Source A, reveals the substructure consisting of five intensity peaks within 100 au from the protostar. The C¹⁷O emission mainly traces the circummultiple structure on a 300 au scale centered at the intensity centroid of the continuum, while it is very weak within a radius of 50 au from the centroid. The H₂CS emission, by contrast, traces the rotating disk structure around one of the continuum peaks (A1). Therefore, it seems that the rotation centroid of the circummultiple structure is slightly different from that of the disk around A1. We derive the rotation temperature by using the multiple lines of H₂CS. Approaching the protostar A1, the rotation temperature steeply rises up to 300 K or higher at the radius of 50 au from the protostar. It is likely due to a local accretion shock and/or the preferential protostellar heating of the transition zone from the circummultiple structure to the disk around A1. This position corresponds to the place where the organic molecular lines are reported to be enhanced. Since the rise of the rotation temperature of H₂CS most likely represents the rise of the gas and dust temperatures, it would be related to the chemical characteristics of this prototypical hot corino.