Fast molecular jet from L1157-mm
  L1157-mm powers a molecular outflow that is well-known for its shock-induced
chemical activity in several hot-spots. We have studied the molecular emission
toward L1157-mm searching for a jet component responsible for these spots. We
used the IRAM 30m telescope to observe the vicinity of L1157-mm in several
lines of SiO. The SiO(5-4) and SiO(6-5) spectra toward L1157-mm present blue
and red detached components about 45 km/s away from the ambient cloud. These
extremely high-velocity (EHV) components are similar to those found in the
L1448 and IRAS 04166+2706 outflows, and probably arise from a molecular jet
driven by L1157-mm. Observations of off-center positions indicate that the jet
is unresolved in SiO(5-4) (<11"). The EHV jet seen in SiO probably excites
L1157-B1 and the other chemically active spots of the L1157 outflow.
