2016A&A...596L...2S

Aims. We seek to study the physical properties of the ionized jet emission in the vicinity of an O-type young stellar object (YSO) and to estimate the efficiency of the transfer of energy and momentum from small- to large-scale outflows.
Methods. We conducted Karl G. Jansky Very Large Array (VLA) observations, at both 22 and 45GHz, of compact and faint radio continuum emission in the high-mass star-forming region G023.01-00.41 with an angular resolution between 0.3" and 0.1" and a thermal rms on the order of 10µJy/beam.
Results. We discovered a collimated thermal (bremsstrahlung) jet emission with a radio luminosity (L_rad) of 24mJy.kpc² at 45GHz in the inner 1000AU from an O-type YSO. The radio thermal jet has an opening angle of 44° and carries a momentum rate of 8x10^–3(M_☉/yr).km/s. By combining the new data with previous observations of the molecular outflow and water maser shocks, we can trace the outflow emission from its driving source through the molecular clump across more than two orders of magnitude in length (500AU-0.2pc). We find that the momentum-transfer efficiency between the inner jet emission and the extended outflow of entrained ambient gas is near unity. This result suggests that the large-scale flow is swept up by the mechanical force of radio jet emission, which originates from within 1000AU of the high-mass YSO.