Chemical Composition in the IRAS 16562–3959 High-mass Star-forming Region

Abstract

We have analyzed the Atacama Large Millimeter/submillimeter Array cycle 2 data of band 6 toward the G345.4938+01.4677 massive young protostellar object (G345.5+1.47 MYSO) in the IRAS 16562–3959 high-mass star-forming region with an angular resolution of ∼0.″3, corresponding to ∼760 au. We spatially resolve the central region, which consists of three prominent molecular emission cores. A hypercompact H ii region (Core A) and two molecule-rich cores (Core B and Core C) are identified using the moment zero images of the H30 α line and a CH 3 OH line, respectively. Various oxygen-bearing complex organic molecules, such as (CH 3 ) 2 CO and CH 3 OCHO, have been detected toward the positions of Core B and Core C, while nitrogen-bearing species, CH 3 CN, HC 3 N, and its 13 C isotopologues, have been detected toward all of the cores. We discuss the formation mechanisms of H 2 CO by comparing the spatial distribution of C 18 O with that of H 2 CO. The 33 SO emission, on the other hand, shows a ring-like structure surrounding Core A, and it peaks on the outer edge of the H30 α emission region. These results imply that SO is enhanced in a shock produced by the expanding motion of the ionized region.