IRAS 16547−4247: A New Candidate of a Protocluster Unveiled with ALMA

Abstract

We present the results of continuum and 12CO(3–2) and CH3OH(7–6) line observations of IRAS 16547−4247 made with the Atacama Large Millimeter/submillimeter Array (ALMA) at an angular resolution of ∼0. 5. The 12CO(3–2) emission shows two high-velocity outflows whose driving sources are located within the dust continuum peak. The alignment of these outflows does not coincide with that of the wide-angle, large-scale, bipolar outflow detected with the Atacama Pathfinder Experiment in previous studies. The CH3OH(7–6) line emission traces an hourglass structure associated with the cavity walls created by the outflow lobes. Taking into account our results together with the position of the H2O and class I CH3OH maser clusters, we discuss two possible scenarios that can explain the hourglass structure observed in IRAS 16547−4247: (1) precession of a biconical jet, (2) multiple, or at least two, driving sources powering intersecting outflows. Combining the available evidence, namely, the presence of two cross-aligned bipolar outflows and two different H2O maser groups, we suggest that IRAS 16547−4247 represents an early formation phase of a protocluster.