PRODIGE – Envelope to disk with NOEMA

VIII. Sulfur oxides trace a shock caused by a streamer in the inner envelope of a protostar

¹ European Southern Observatory, Karl-Schwarzschild-Strasse 2 85748 Garching bei Munchen, Munchen, Germany
² Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
³ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁴ Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627-0171, USA
⁵ Taiwan Astronomical Research Alliance (TARA), Taipei, Taiwan, ROC
⁶ Institute of Astronomy and Astrophysics, Academia Sinica, No.1, Sec. 4, Roosevelt Road, Taipei 106319, Taiwan, ROC
⁷ Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, 38406 Saint-Martin d’Hères, France
⁸ IPAG, Université Grenoble Alpes, CNRS, 38000 Grenoble, France
⁹ Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany
¹⁰ Centro de Astrobiología (CAB), CSIC-INTA, Ctra. de Torrejón a Ajalvir km 4, 28806, Torrejón de Ardoz, Spain
¹¹ SKA Observatory, Jodrell Bank, Lower Withington, Macclesfield SK11 9FT, UK
¹² Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hilaire, 33615 Pessac, France
¹³ Observatorio Astronómico Nacional (IGN), Alfonso XII 3, 28014 Madrid, Spain
¹⁴ Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, 91405 Orsay, France
¹⁵ Space Research Institute, Austrian Academy of Sciences, Schmiedlstr. 6, 8042 Graz, Austria

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 3 November 2025
Accepted: 14 March 2026

Abstract

Context. Recently, streamers have been observed causing shocks at the outer edge of protoplanetary disks. The study of sulfur-bearing species can help us to understand the physical and chemical changes caused by infalling streamers toward their landing positions.

Aims. We study the physical properties traced by the emission of SO₂ and SO toward the Class I protostar Per-emb 50, which is possibly related to the streamer infalling toward its disk.

Methods. We present new NOrthern Extended Millimeter Array (NOEMA) A-array observations as part of the large program “Protostars and Disks: Global Evolution” (PRODIGE). We analyzed the morphology of SO₂ and SO, and complement our interpretations with additional H₂CO and CO data from the same program. We compared the SO₂ and SO morphology with an infalling-rotating model. We applied Bayesian model selection to the brightest SO₂ line to disentangle the different kinematic components traced by this molecule. We used local thermodynamic equilibrium (LTE) and non-LTE analyses to determine the temperature and density of the SO₂ emission.

Results. There are two separate peaks of SO₂ emission offset toward the southwest of Per-emb 50: one brighter (peak 1) at about 180 au from the protostar, and a weaker one (peak 2) at about 400 au. Peak 2 is blueshifted with respect to an infalling-rotating envelope. We propose that this peak is caused by the shock between the inner envelope and the streamer. Peak 1 is consistent with the expected envelope motion, and could thus be caused by shocks at the disk-envelope interface, but potential streamer influence cannot be neglected. Both peaks show abundance ratios consistent with a low-velocity shock (~3–4 km s⁻¹) when compared with shock models.

Conclusions. Streamers can affect the physical and chemical structure of both disks and envelopes, suggesting that streamers can play an important role in shaping both structures in the embedded stages of star formation.