PRODIGE – Envelope to disk with NOEMA

VII. (Complex) organic molecules in the NGC1333 IRAS 4B1 outflow: A new laboratory for shock chemistry

¹ Max-Planck-Institut für extraterrestrische Physik, Gießenbachstraße 1, 85748 Garching bei München, Germany
² Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA
³ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁴ Taiwan Astronomical Research Alliance (TARA), Taiwan
⁵ Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, Taipei 106, Taiwan
⁶ European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany
⁷ Institute de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, 38406, Saint-Martin d’Hères, France
⁸ Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany
⁹ Centro de Astrobiología (CAB), CSIC-INTA, Ctra. de Ajalvir Km. 4, 28850, Torrejón de Ardoz, Madrid, Spain
¹⁰ Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
¹¹ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
¹² Department of Astronomy, University of Illinois, 1002 W Green St., Urbana, IL 61801, USA
¹³ Department of Earth, Environment and Physics, Worcester State University, Worcester, MA 01602, USA
¹⁴ Observatorio Astronómico Nacional (IGN), Alfonso XII 3, 28014 Madrid, Spain
¹⁵ Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hilaire, 33615 Pessac, France
¹⁶ Department of Earth Science Education, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea
¹⁷ SNU Astronomy Research Center, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea

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

Received: 15 January 2026
Accepted: 18 February 2026

Abstract

Context. Shock chemistry is an excellent tool for shedding light on the formation and destruction mechanisms of complex organic molecules (COMs). The L1157-mm outflow is the only low-mass protostellar outflow that has extensively been studied in this regard.

Aims. We mapped COM emission and derived the molecular composition of the protostellar outflow driven by the Class 0 protostar NGC 1333 IRAS 4B1 to introduce it as a new laboratory for studying the effect of shocks on COM chemistry.

Methods. We used the data taken as part of the PROtostars & DIsks: Global Evolution (PRODIGE) large program to compute integrated-intensity maps of outflow emission to identify spatial differences between species. The emission spectra were then analysed towards two positions, one in each outflow lobe, by deriving synthetic spectra and population diagrams assuming conditions of local thermodynamic equilibrium.

Results. In addition to typical outflow tracers such as SiO and CO, outflow emission is seen from H₂CO, HNCO, and HC₃N, as well as from the COMs CH₃OH, CH₃CN, and CH₃CHO, and even from deuterated species such as DCN, D₂CO, and CH₂DOH. The maps of integrated-intensity ratios between CH₃OH and DCN, D₂CO, and CH₃CHO reveal gradients with distance from the protostar. For DCN and D₂CO, this may reflect their pre-stellar abundance profile, provided the outflow is young enough, while an explanation is still required for CH₃CHO. Intensity ratio maps of HC₃N and CH₃CN with respect to CH₃OH peak in the southern lobe where the temperatures are highest. This might indicate enhanced HC₃N and CH₃CN formation at this location, potentially in the warmer gas phase. Rotational temperatures are found in the range ∼50-100K, which is warmer on average than for the L1157-B1 shock spot (≲ 30K). The abundances with respect to CH₃OH are higher by factors of a few than for L1157-B1.

Conclusions. For the first time, we securely detected the COMs CH₃CN, CH₃CHO, and CH₂DOH in the IRAS 4B1 outflow, serendipitously with a limited sensitivity and bandwidth. Targeted observations will enable the discovery of new COMs and a more detailed analysis of their emission. The morphological differences between the molecules in the IRAS 4B1 outflow lobes and their relative abundances provide first proof that this outflow is a promising new laboratory for shock chemistry, which will offer crucial information on COM formation and destruction as well as on outflow structure and kinematics.