The shocking arrival of a streamer toward a protostar in Perseus

Streamers, elongated gaseous structures that range from a few hundred to over 10,000 au, have emerged as a novel mechanism of material supply to protostellar and protoplanetary disks. Thanks to advanced millimeter/submillimeter interferometers like ALMA and NOEMA, we now know that streamers are frequently found around protostars, rather than being isolated occurrences. However, their effects on disk composition are only recently being studied in detail. In this talk, I will present detections of sulfur dioxide (SO₂, a known shock tracer) toward the Class I source Per-emb 50, which are located between the streamer detected for this source and its disk. The SO₂ emission consists of several velocity components, tracing part of the disk kinematics as well as the inner envelope, but its emission peaks are offset from the position of the protostar. The different components that SO₂ traces have different temperatures and densities. These results suggest that streamers produce shocks that can change the local conditions of the planet-forming disk.