Seeds of Life in Space (SOLIS)

VI. Chemical evolution of sulfuretted species along the outflows driven by the low-mass protostellar binary NGC 1333-IRAS4A^★

¹ INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
e-mail: taquet@arcetri.astro.it
² Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
³ Institut de Radioastronomie Millimétrique, 38406 Saint-Martin d’Hères, France
⁴ Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstr. 1, 85748 Garching, Germany
⁵ Laboratoire de Physique de l’ENS, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, Paris, France
⁶ Observatoire de Paris, Université PSL, Sorbonne Université, LERMA, 75014 Paris, France
⁷ Department of Space, Earth, and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
⁸ IRAP, Université de Toulouse, CNRS, CNES, UPS, Toulouse, France
⁹ Department of Physics, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
¹⁰ RIKEN Cluster for Pioneering Research, 2-1, Hirosawa, Wako-shi, Saitama 351-0198, Japan
¹¹ IGN, Observatorio Astronómico Nacional, Calle Alfonso XII, 28004 Madrid, Spain
¹² Dipartimento di Chimica, Biologia e Biotecnologie, Via Elce di Sotto 8, 06123 Perugia, Italy
¹³ LERMA, Université de Cergy-Pontoise, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC, Univ. Paris 06, 95000 Cergy Pontoise, France
¹⁴ National Astronomical Observatory of China, Datun Road 20, Chaoyang, Beijing 100012, PR China
¹⁵ CAS Key Laboratory of FAST, NAOC, Chinese Academy of Sciences, Beijing, PR China
¹⁶ Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, UK
¹⁷ University of AL-Muthanna, College of Science, Physics Department, AL-Muthanna, Iraq
¹⁸ Centro de Astrobiología (CSIC, INTA), Ctra. de Ajalvir, km. 4, Torrejón de Ardoz, 28850 Madrid, Spain
¹⁹ Ural Federal University, 620002, 19 Mira street, Yekaterinburg, Russia
²⁰ Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia, Spain
²¹ Univ. Rennes, CNRS, IPR (Institut de Physique de Rennes) – UMR 6251, 35000 Rennes, France
²² ESO, Karl Schwarzchild Srt. 2, 85478 Garching bei München, Germany
²³ Aix–Marseille Université, PIIM UMR-CNRS 7345, 13397 Marseille, France
²⁴ Università degli Studi di Torino, Dipartimento Chimica Via Pietro Giuria 7, 10125 Torino, Italy
²⁵ Engineering Research Institute Ventspils International Radio Astronomy Centre of Ventspils University of Applied Sciences, Inženieru 101, Ventspils LV-3601, Latvia

Received: 7 November 2019
Accepted: 12 January 2020

Abstract

Context. Low-mass protostars drive powerful molecular outflows that can be observed with millimetre and submillimetre telescopes. Various sulfuretted species are known to be bright in shocks and could be used to infer the physical and chemical conditions throughout the observed outflows.

Aims. The evolution of sulfur chemistry is studied along the outflows driven by the NGC 1333-IRAS4A protobinary system located in the Perseus cloud to constrain the physical and chemical processes at work in shocks.

Methods. We observed various transitions from OCS, CS, SO, and SO₂ towards NGC 1333-IRAS4A in the 1.3, 2, and 3 mm bands using the IRAM NOrthern Extended Millimeter Array and we interpreted the observations through the use of the Paris-Durham shock model.

Results. The targeted species clearly show different spatial emission along the two outflows driven by IRAS4A. OCS is brighter on small and large scales along the south outflow driven by IRAS4A1, whereas SO₂ is detected rather along the outflow driven by IRAS4A2 that is extended along the north east–south west direction. SO is detected at extremely high radial velocity up to + 25 km s⁻¹ relative to the source velocity, clearly allowing us to distinguish the two outflows on small scales. Column density ratio maps estimated from a rotational diagram analysis allowed us to confirm a clear gradient of the OCS/SO₂ column density ratio between the IRAS4A1 and IRAS4A2 outflows. Analysis assuming non Local Thermodynamic Equilibrium of four SO₂ transitions towards several SiO emission peaks suggests that the observed gas should be associated with densities higher than 10⁵ cm⁻³ and relatively warm (T > 100 K) temperatures in most cases.

Conclusions. The observed chemical differentiation between the two outflows of the IRAS4A system could be explained by a different chemical history. The outflow driven by IRAS4A1 is likely younger and more enriched in species initially formed in interstellar ices, such as OCS, and recently sputtered into the shock gas. In contrast, the longer and likely older outflow triggered by IRAS4A2 is more enriched in species that have a gas phase origin, such as SO₂.