IRAS16547-4247: A New Candidate of a Protocluster Unveiled with ALMA

TL;DR

This study uses ALMA observations to identify multiple outflows and structures in IRAS16547-4247, indicating it is an early-stage protocluster formation with complex outflow interactions.

Contribution

First detailed ALMA imaging of IRAS16547-4247 revealing multiple outflows and structures, proposing scenarios for its protocluster formation.

Findings

Detection of two high-velocity outflows within the dust continuum peak.

Identification of an hourglass structure associated with outflow cavity walls.

Evidence suggesting IRAS16547-4247 is in an early protocluster formation stage.

Abstract

We present the results of continuum and 12CO(3-2) and CH3OH(7-6) line observations of IRAS16547-4247 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 do not coincide with that of the wide-angle, large scale, bipolar outflow detected with APEX 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 IRAS16547-4247: (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 IRAS16547-4247 represents an early formation phase of a protocluster.