A Protostellar Jet Emanating from a Hypercompact HII Region
  We present radio continuum observations of the high-mass young stellar object
(HMYSO) G345.4938+01.4677 made using the Australia Telescope Compact Array
(ATCA) at 5, 9, 17, and 19 GHz. These observations provide definite evidence
that the outer and inner pairs of radio lobes consist of shock ionized material
being excited by an underlying collimated and fast protostellar jet emanating
from a hypercompact HII region. By comparing with images taken 6 yr earlier at
5 and 9 GHz using the same telescope, we assess the proper motions of the radio
sources. The outer West and East lobes exhibit proper motions of $64\pm12$ and
$48\pm13$ milliarcsec yr$^{-1}$, indicating velocities projected in the plane
of the sky and receding from G345.4938+01.4677 of $520$ and $390$ km s$^{-1}$,
respectively. The internal radio lobes also display proper motion signals
consistently receding from the HMYSO, with magnitudes of $17\pm11$ and
$35\pm10$ milliarcsec yr$^{-1}$ for the inner West and East lobes,
respectively. The morphology of the outer West lobe is that of a detached bow
shock. At 17 and 19 GHz, the outer East lobe displays an arcuate morphology
also suggesting a bow shock. These results show that disk accretion and jet
acceleration --- possibly occurring in a very similar way compared with
low-mass protostars --- is taking place in G345.4938+01.4677 despite the
presence of ionizing radiation and the associated hypercompact HII region.
