Chemical and kinematic structure of extremely high-velocity molecular
  jets in the Serpens Main star-forming region
  The fastest molecular component to the protostellar outflows -- extremely
high-velocity (EHV) molecular jets -- are still puzzling since they are seen
only rarely. The first aim is to analyze the interaction between the EHV jet
and the slow outflow by comparing their outflow force content. The second aim
is to analyze the chemical composition of the different outflow velocity
components and to reveal the spatial location of molecules. ALMA 3 mm and 1.3
mm observations of five outflow sources at 130 -- 260 au resolution in the
Serpens Main cloud are presented. Observations of CO, SiO, H$_2$CO and HCN
reveal the kinematic and chemical structure of those flows. Three velocity
components are distinguished: the slow and the fast wing, and the EHV jet. Out
of five sources, three have the EHV component. Comparison of outflow forces
reveals that only the EHV jet in the youngest source Ser-emb 8 (N) has enough
momentum to power the slow outflow. The SiO abundance is generally enhanced
with velocity, while HCN is present in the slow and the fast wing, but
disappears in the EHV jet. For Ser-emb 8 (N), HCN and SiO show a bow-shock
shaped structure surrounding one of the EHV peaks suggesting sideways ejection
creating secondary shocks upon interaction with the surroundings. Also, the SiO
abundance in the EHV gas decreases with distance from this protostar, whereas
that in the fast wing increases. H$_2$CO is mostly associated with low-velocity
gas but also appears surprisingly in one of the bullets in the Ser-emb~8~(N)
EHV jet. The high detection rate suggests that the presence of the EHV jet may
be more common than previously expected. The origin and temporal evolution of
the abundances of SiO, HCN and H$_2$CO through high-temperature chemistry are
discussed. The data are consistent with a low C/O ratio in the EHV gas versus
high C/O ratio in the fast and slow wings.
