2025A&A...695A.278H

Context. While protostellar outflows are important in terms of mass accretion and angular momentum transport in star formation processes, high-resolution observations of outflows in protobinary systems are still sparse.
Aims. We aim to reveal outflow structures traced by millimeter SiO emission in a low-mass protobinary system, L483.
Methods. We observed the SiO (J = 5-4) line in L483 with the Atacama Large Millimeter/submillimeter Array (ALMA) as part of the large program FAUST (Fifty AU STudy of the chemistry in the disk/envelope systems of Solar-like protostars). The spatial and spectral resolutions were 0.39^''×0.30^'' (780 au×60 au) and 122 kHz (0.17 km s^–1 at 217 GHz), respectively. The spectral lines of SO, CS, and C¹⁸O were also used to study the physical and dynamical properties of the SiO emitting regions.
Results. Two SiO emission peaks are identified in the central part of L483, which have offsets of 100 au and 200 au toward the northeast (SiO-peak) and north (SiO-N), respectively, from the continuum peak. The SiO-peak shows only blueshifted emission with a broad linewidth of 5 km s^–1, while that of SiO-N corresponds to the systemic velocity. Furthermore, weak and compact SiO emission components are distributed up to 2400 au away from the continuum position. They have narrow linewidths of ∼1 km s^–1. One of these components is a blueshifted isolated emission feature, 2400 au northeast of the continuum peak, NE-cloud, located outside the east-west outflow lobes. The SiO abundances relative to H₂ are 10^–10-10^–9 and 10^–10 in the central part and more widely distributed components, respectively. These are intermediate values between those of strongly shocked regions caused by high-velocity outflows and quiescent molecular clouds.
Conclusions. The central SiO emission could be interpreted as either two different outflows driven by both protostars or as an outflow ejected from one of the circumstellar disks in the binary system. The NE-cloud region is most likely explained as a remnant of an old shock produced by past outflow activity, as has been proposed for the low-mass protostar IRAS 15398-3359. The complex structures of the outflows traced by the SiO line could reflect dynamical processes of the newly formed protobinary system in L483.