2025A&A...696A.219C

Context. High-velocity collimated jets play a fundamental role in the earliest evolutionary stages of Sun-like protostars. By analysing their chemical composition and spatio-kinematical structure, we can decipher the origins of different molecular species.
Aims. As part of the IRAM Large Program SOLIS, we imaged the SVS13 protostellar system in line emission to kinematically separate jets from the large-scale outflows and static envelopes and to investigate their chemistry.
Methods. Using the NOEMA interferometer, we imaged the protostellar sources SVS13-A and SVS13-B in SiO(2-1), SO(2₃-1₂), CS(2-1), and CH₃ OH(2_k, k_–1k, k_) at a spatial resolution of ∼ 2″-3″(600-900 au). An SiO(2-1) image with a smaller beam (1″.5, i.e. 450 au) was also produced.
Results. The CS and SO emission traces the ∼5000 au envelope that hosts the SVS13-A and VLA3 young stellar objects, and CH₃OH probes the compact hot corino associated with SVS13-A (T∼100-110 K). In addition, CS blue-shifted emission reveals a molecular shell in the direction of the jet driven by SVS13-A that is revealed by high-velocity SiO, SO and low-velocity H₂ emission (PA ∼155^∘). We also imaged the protostellar jet driven by SVS13-B in SiO, and in SO, CS, and CH₃OH for the first time as well, along PA∼167^∘. The molecules peak at different distances from the driving source: SiO(2-1) peaks at ∼1600 au, and SO(2₃-1₂), CS(2-1) and CH₃OH(2_k, k_–1k, k_) peak at ∼2000-2850 au. Moreover, SiO(2-1) emits at larger distances than SiO(5-4), indicating a lower excitation at a larger distance from the protostar. The observed species also show different velocity distributions: SiO peaks at velocities up to +35 km s^–1 (red) and -20 km s^–1 (blue) with respect to the systemic velocity, SO and CS peak at ± 10 km s^–1, and CH₃OH is at low velocities of ± 4 km s^–1.
Conclusions. The multi-species observations revealed a stratified chemical structure in the jet of SVS13-B. A jet-like component with a transversal size ≤450 au is traced by SiO, which is efficiently formed in high-velocity shocks (>25 km s^–1) by sputtering and vaporisation of the grain cores and mantles. A slower and wider (transversal size ∼750 au) component is probed by methanol, which is released from dust mantles at lower shock velocities (<10 km s^–1). The SO and CS emission traces an intermediate component with respect to the components probed by SiO and CH₃ OH. High spatial resolution imaging (down to 10 au) of the jet of SVS13-B in multiple species will aid in reconstructing the chemistry of shocked material in protostellar jets.