The Highly Collimated Radio Jet of HH 80-81: Structure and Non-Thermal
  Emission
  Radio emission from protostellar jets is usually dominated by free-free
emission from thermal electrons. However, in some cases, it has been proposed
that non-thermal emission could also be present. This additional contribution
from non-thermal emission has been inferred through negative spectral indices
at centimeter wavelengths in some regions of the radio jets. In the case of HH
80-81, one of the most powerful protostellar jets known, linearly polarized
emission has also been detected, revealing that the non-thermal emission is of
synchrotron nature from a population of relativistic particles in the jet. This
result implies that an acceleration mechanism should be taking place in some
parts of the jet. Here, we present new high sensitivity and high angular
resolution radio observations at several wavelengths (in the 3-20 cm range) of
the HH80-81 radio jet. These new observations represent an improvement in
sensitivity and angular resolution by a factor of $\sim$10 with respect to
previous observations. This allows us to resolve the morphology of the radio
jet, and to study the different emission mechanisms involved through spectral
index maps. We conclude that synchrotron emission in this jet arises from an
extended component detected at low frequencies and from the termination points
of the jet, where strong shocks against the ambient medium can produce
efficient particle acceleration.
