Complex Organic Molecules tracing shocks along the outflow cavity in the
  high-mass protostar IRAS20126+4104
  We report on subarcsecond observations of complex organic molecules (COMs) in
the high-mass protostar IRAS20126+4104 with the Plateau de Bure Interferometer
in its most extended configurations. In addition to the simple molecules SO,
HNCO and H2-13CO, we detect emission from CH3CN, CH3OH, HCOOH, HCOOCH3,
CH3OCH3, CH3CH2CN, CH3COCH3, NH2CN, and (CH2OH)2. SO and HNCO present a
X-shaped morphology consistent with tracing the outflow cavity walls. Most of
the COMs have their peak emission at the putative position of the protostar,
but also show an extension towards the south(east), coinciding with an H2 knot
from the jet at about 800-1000 au from the protostar. This is especially clear
in the case of H2-13CO and CH3OCH3. We fitted the spectra at representative
positions for the disc and the outflow, and found that the abundances of most
COMs are comparable at both positions, suggesting that COMs are enhanced in
shocks as a result of the passage of the outflow. By coupling a parametric
shock model to a large gas-grain chemical network including COMs, we find that
the observed COMs should survive in the gas phase for about 2000 yr, comparable
to the shock lifetime estimated from the water masers at the outflow position.
Overall, our data indicate that COMs in IRAS20126+4104 may arise not only from
the disc, but also from dense and hot regions associated with the outflow.
