The Collimated Jet Source in IRAS 16547-4247: Time Variation, Possible Precession, and Upper Limits to the Proper Motions Along the Jet Axis

TL;DR

This study investigates the IRAS 16547-4247 jet, finding no proper motions along the lobes, evidence of precession, and flux variability, providing insights into jet-medium interactions and jet dynamics in star-forming regions.

Contribution

It presents new multi-epoch observations revealing jet precession, proper motion limits, and flux variability, advancing understanding of jet behavior in massive star formation.

Findings

No proper motions detected along the jet lobes at ~160 km/s upper limit.

Evidence of jet precession at 0.08° per year.

Flux density and morphology variations in the core.

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 (VLA) 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 4-$\sigma$ upper limit of $\sim$160 km s$^{-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 $0\rlap.^\circ08$ 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 former can be understood as a scaled-up version of the latter.