The rotating molecular structures and the ionized outflow associated with IRAS 16547-4247

Abstract

We present Very Large Array 1.3 cm radio continuum and water maser observations as well as Submillimeter Array SO 2 (226.300 GHz) and 1.3 mm dust continuum observations toward the massive star formation region IRAS 16547−4247. We find evidence of multiple sources in the central part of the region. There is evidence of a rotating structure associated with the most massive of these sources, traced at small scales (∼50 AU) by the water masers. At large scales (∼1000 AU), we find a velocity gradient in the SO 2 molecular emission with a barely resolved structure that can be modeled as a rotating ring or two separate objects. The velocity gradients of the masers and of the molecular emission have the same sense and may trace the same structure at different size scales. The position angles of the structures associated with the velocity gradients are roughly perpendicular to the outflow axis observed in radio continuum and several molecular tracers. We estimate the mass of the most massive central source to be around 30 solar masses from the velocity gradient in the water maser emission. The main source of error in this estimate is the radius of the rotating structure. We also find water masers that are associated with the large-scale molecular outflow of the system, as well as water masers that are associated with other sources in the region. Our results suggest that the formation of this source, one of the most luminous protostars or protostellar clusters known, is taking place with the presence of ionized jets and disk-like structures.