Abstract
The triple radio source detected in association with the luminous infrared source IRAS 16547-4247 has previously been studied with high angular resolution and high sensitivity with the Very Large Array at 3.6 cm wavelength. In this paper, we present new 3.6 cm observations taken 2.68 years after the first epoch that allow a search for variability and proper motions, as well as the detection of additional faint sources in the region. We do not detect proper motions along the axis of the outflow in the outer lobes of this source at a 4σ upper limit of ∼160 km s−1. This suggests that these lobes are probably working surfaces where the jet is interacting with a denser medium. However, the brightest components of the lobes show evidence of precession, at a rate of 008 yr−1 clockwise in the plane of the sky. It may be possible to understand the distribution of almost all the identified sources as the result of ejecta from a precessing jet. The core of the thermal jet shows significant variations in flux density and morphology. We compare this source with other jets in low- and high-mass young stars and suggest that the latter can be understood as a scaled-up version of the former.
Highlights
A successful model of low-mass star formation, based on accretion via a circumstellar disk and a collimated outflow in the form of jets (Shu et al 1987), has been developed and found to be consistent with the observations
The three radio components are aligned in a northwest–southeast direction, with the outer lobes symmetrically separated from the central source by an angular distance of ∼10, equivalent to a
Brooks et al (2003) reported a chain of H2 2.12 μm emission knots that trace a collimated flow extending over 1.5 pc that emanates from close to the central component of the triple radio source and has a position angle (P.A.) very similar to that defined by the outer lobes of the triple radio source
Summary
A successful model of low-mass star formation, based on accretion via a circumstellar disk and a collimated outflow in the form of jets (Shu et al 1987), has been developed and found to be consistent with the observations. The triple system is centered on the position of the IRAS source and is coincident within the measurement error with a 1.2 mm dust continuum and a molecular line emission core whose mass is on the order of 103 M (Garay et al 2003). Brooks et al (2003) reported a chain of H2 2.12 μm emission knots that trace a collimated flow extending over 1.5 pc that emanates from close to the central component of the triple radio source and has a position angle (P.A.) very similar to that defined by the outer lobes of the triple radio source. The molecular observations of Garay et al (2007) revealed the presence of a collimated bipolar outflow with lobes ∼0.7 pc in extent and aligned with the thermal jet located at the center of the core. We present new sensitive high-angularresolution VLA observations that provide new information on the characteristics of the radio triple source in IRAS 16547-4247 as well as other sources in the field
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