  We present 1.3-mm subarcsecond SMA observations of the prototypical Class 0
protostar VLA1623. We report the detection of 1.3-mm continuum emission both
from the central protostellar component VLA1623 and two additional sources,
Knot-A and Knot-B, which have been already detected at longer wavelengths.
Knot-A and Knot-B are both located along the western cavity wall opened by the
protostellar outflow from VLA1623. Our SMA observations moreover show that
these two continuum sources are associated with bright, high-velocity 12CO(2-1)
emission, slightly shifted downstream of the outflow propagation direction with
respect to the 1.3-mm continuum emission peaks. The alignment of Knot-A and
Knot-B along the protostellar outflow cavity, the compactness of their 1.3-mm
continuum emission and the properties of the associated CO emission suggest
that these two sources trace outflow features due to shocks along the cavity
wall, rather than protostellar objects. While it was considered as one of the
best examples of a close protobinary system so far, the present analysis
suggests that the prototypical Class 0, VLA1623, is single on the scales a>100
AU probed by our SMA observations. Moreover, we present here the second robust
case of compact millimeter continuum emission produced by interactions between
the protostellar jet and the envelope of a Class 0 protostar, which suggests a
high occurrence of these outflow features during the embedded phase.
