2019MNRAS.483.1184M

We report continuum GMRT observations aimed to explore the behaviour of the jet associated with IRAS 16547-4247 at very low frequencies (325 MHz and 610 MHz). The obtained maps reveal an elongated morphology in the SE-NW direction. In addition, the 610 MHz map shows three knots associated to the elongated morphology that seems to correspond to the triple radio source identified as the jet seen at higher frequencies. However, at 325 MHz, although an elongated morphology is also observed, only two knots appear in the map. By comparing our knot positions at both frequencies with a precessing jet model used in a previous work, we find that the knots fall closely to the wiggling path and, hence, they likely represent shocks of the material of the precessing jet with the medium. Only the nature of the southernmost knot detected at 325 MHz remains unclear. Besides, we found that the whole emission of the lobes is non-thermal down to very low frequencies and that the possible associated emission mechanisms work differently in both lobes, causing the discrepancies observed between frequencies. To explain these discrepancies we investigate mechanisms such as synchrotron radiative losses in a magnetic field of ∼0.5 mG in the shocks and find this possibility unlikely to occur. Alternatively, we invoke jet interaction with an inhomogeneous medium as the most probable scenario.