Jet multiplicity in the proto-binary system NGC1333-IRAS4A. The detailed
  CALYPSO IRAM-PdBI view
  Owing to the paucity of sub-arcsecond (sub)mm observations required to probe
the innermost regions of newly forming protostars, several fundamental
questions are still being debated, such as the existence and coevality of close
multiple systems. We study the physical and chemical properties of the jets and
protostellar sources in the NGC1333-IRAS4A proto-binary system using continuum
emission and molecular tracers of shocked gas. We observed NGC1333-IRAS4A in
the SiO(6-5), SO(6_5-5_4), and CO(2-1) lines and the continuum emission at 1.3,
1.4, and 3 mm using the IRAM Plateau de Bure Interferometer in the framework of
the CALYPSO large program. We clearly disentangle for the first time the
outflow emission from the two sources A1 and A2. The two protostellar jets have
very different properties: the A1 jet is faster, has a short dynamical
timescale (<10^3 yr), and is associated with H2 shocked emission, whereas the
A2 jet, which dominates the large-scale emission, is associated with diffuse
emission, bends, and emits at slower velocities. The observed bending of the A2
jet is consistent with the change of propagation direction observed at large
scale and suggests jet precession on very short timescales (~200-600 yr). In
addition, a chemically rich spectrum with emission from several COMs (e.g.
HCOOH, CH3OCHO, CH3OCH3) is only detected towards A2. Finally, very
high-velocity shocked emission (~50 km s^-1) is observed along the A1 jet. An
LTE analysis shows that SiO, SO, and H2CO abundances in the gas phase are
enhanced up to (3-4)x10^{-7}, (1.4-1.7)x10^{-6}, and (3-7.9)x10^{-7},
respectively. The intrinsic different properties of the jets and driving
sources in NGC1333-IRAS4A suggest different evolutionary stages for the two
protostars, with A1 being younger than A2, in a very early stage of star
formation previous to the hot-corino phase.
