A search for non-thermal radio emission from jets of massive young stellar objects

Abstract

Massive young stellar objects (MYSOs) have recently been shown to drive jets whose particles can interact with either the magnetic fields of the jet or ambient medium to emit non-thermal radiation. We report a search for non-thermal radio emission from a sample of 15 MYSOs to establish the prevalence of the emission in the objects. We used their spectra across the L-, C- and Q-bands along with spectral index maps to characterise their emission. We find that about 50% of the sources show evidence for non-thermal emission with 40% showing clear non-thermal lobes, especially sources of higher bolometric luminosity. The common or IRAS names of the sources that manifest non-thermal lobes are; V645Cyg, IRAS 22134+5834, NGC 7538 IRS 9, IRAS 23262+640, AFGL 402d and AFGL 490. All the central cores of the sources are thermal with corresponding mass-loss rates that lie in the range 3X10^{-7} to 7X10^{-6} solar masses per year. Given the presence of non-thermal lobes in some of the sources and the evidence of non-thermal emission from some spectral index maps, it seems that magnetic fields play a significant role in the jets of massive protostars. Also noted is that some of the sources show evidence of binarity and variability.