Seeds of Life in Space (SOLIS). VI. Chemical evolution of sulfuretted
  species along the outflows driven by the low-mass protostellar binary
  NGC1333-IRAS4A
  Context. Low-mass protostars drive powerful molecular outflows that can be
observed with mm and sub-mm telescopes. Various sulfuretted species are known
to be bright in shocks and could be used to infer the physical and chemical
conditions throughout the observed outflows. Aims. The evolution of sulfur
chemistry is studied along the outflows driven by the NGC1333-IRAS4A
protobinary system located in the Perseus cloud to constrain the physical and
chemical processes at work in shocks. Methods. We observed various transitions
from OCS, CS, SO, and SO$_2$ towards NGC1333-IRAS4A in the 1.3, 2, and 3mm
bands using the IRAM NOEMA array and we interpreted the observations through
the use of the Paris-Durham shock model. Results. The targeted species clearly
show different spatial emission along the two outflows driven by IRAS4A. OCS is
brighter on small and large scales along the south outflow driven by IRAS4A1,
whereas SO$_2$ is detected rather along the outflow driven by IRAS4A2 that is
extended along the north east - south west (NE-SW) direction. Column density
ratio maps estimated from a rotational diagram analysis allowed us to confirm a
clear gradient of the OCS/SO$_2$ column density ratio between the IRAS4A1 and
IRAS4A2 outflows. SO is detected at extremely high radial velocity up to 25
km/s relative to the source velocity, clearly allowing us to distinguish the
two outflows on small scales. Conclusions. The observed chemical
differentiation between the two outflows of the IRAS4A system could be
explained by a different chemical history. The outflow driven by IRAS4A1 is
likely younger and more enriched in species initially formed in interstellar
ices, such as OCS, and recently sputtered into the shock gas. In contrast, the
longer and likely older outflow triggered by IRAS4A2 is more enriched in
species that have a gas phase origin, such as SO$_2$.
