Letter to the Editor

FAUST

XVII. Super deuteration in the planet-forming system IRS 63 where the streamer strikes the disk

¹ INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy
² Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
³ Department of Astronomy, The University of Texas at Austin, 2515 Speedway, Austin, TX 78712, USA
⁴ Department of Chemistry, Biology, and Biotechnology, The University of Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy
⁵ Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
⁶ Dipartimento di Chimica and Nanostructured Interfaces and Surfaces (NIS) Centre, Università degli Studi di Torino, via P. Giuria 7, I-10125 Torino, Italy
⁷ National Radio Astronomy Observatory, PO Box O Socorro, NM 87801, USA
⁸ RIKEN Cluster for Pioneering Research, 2-1, Hirosawa, Wako-shi, Saitama 351-0198, Japan
⁹ Center for Astrochemical Studies, Max-Planck-Institut für extraterrestrische Physik (MPE), Gie βenbachstr. 1, D-85741 Garching, Germany
¹⁰ European Southern Observatory, Karl-Schwarzschild Str. 2, 85748 Garching bei München, Germany
¹¹ Excellence Cluster ORIGINS, Boltzmannstraße 2, D-85748 Garching bei München, Germany
¹² Department of Physics and Astronomy, Rice University, 6100 Main Street, MS-108, Houston, TX 77005, USA
¹³ Department of Astronomy, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
¹⁴ Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands
¹⁵ IRAP, Univ. de Toulouse, CNRS, CNES, UPS, Toulouse, France
¹⁶ Astrochemistry Laboratory, Code 691, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA
¹⁷ CY Cergy Paris Université, Sorbonne Université, Observatoire de Paris, PSL University, CNRS, LERMA, F-95000 Cergy, France
¹⁸ School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
¹⁹ Department of Astronomy, Xiamen University, Xiamen, Fujian 361005, PR China
²⁰ Komaba Institute for Science, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
²¹ Department of Basic Science, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
²² Center for Frontier Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
²³ Department of Chemistry, University of Virginia, McCormick Road, PO Box 400319 Charlottesville, VA 22904, USA
²⁴ National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka-shi, Tokyo 181-8588, Japan
²⁵ Centro de Astrobiología (CAB), CSIC-INTA, Ctra. de Torrejón a Ajalvir, km 4, 28850 Torrejón de Ardoz, Spain
²⁶ NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
²⁷ Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 5C2, Canada
²⁸ Université de Bordeaux – CNRS Laboratoire d’Astrophysique de Bordeaux, 33600 Pessac, France
²⁹ Institut de Radioastronomie Millimétrique, 38406 Saint-Martin d’Hères, France
³⁰ Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, A.P. 3-72 (Xangari), 8701 Morelia, Mexico
³¹ LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, 92190 Meudon, France
³² Institute of Astronomy and Astrophysics, Academia Sinica, 11F of Astronomy-Mathematics Building, AS/NTU No.1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan, ROC
³³ Division of Science, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
³⁴ Institute of Low Temperature Science, Hokkaido University, N19W8, Kita-ku, Sapporo, Hokkaido 060-0819, Japan
³⁵ Department of Physics, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
³⁶ Yukawa Institute for Theoretical Physics, Kyoto Univ. Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto-shi, Kyoto-fu 606-8502, Japan
³⁷ Graduate School of Informatics and Engineering, The University of Electro-Communications, Chofu, Tokyo 182-8585, Japan
³⁸ Steward Observatory, 933 N Cherry Ave., Tucson, AZ 85721, USA
³⁹ Dipartimento di Fisica e Astronomia “Augusto Righi”, Viale Berti Pichat 6/2, Bologna, Italy
⁴⁰ Materials Science and Engineering, College of Engineering, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548, Japan
⁴¹ Star and Planet Formation Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama 351-0198, Japan
⁴² SOKENDAI (The Graduate University for Advanced Studies), Shonan Village, Hayama, Kanagawa 240-0193, Japan

Received: 16 May 2024
Accepted: 28 June 2024

Abstract

Context. Recent observations suggest that planet formation starts early, in protostellar disks of ≤10⁵ yr, which are characterized by strong interactions with the environment, such as through accretion streamers and molecular outflows.

Aims. To investigate the impact of such phenomena on the physical and chemical properties of a disk, it is key to understand what chemistry planets inherit from their natal environment.

Methods. In the context of the ALMA large program Fifty AU Study of the chemistry in the disk/envelope system of solar-like protostars (FAUST), we present observations on scales from ∼1500 au to ∼60 au of H₂CO, HDCO, and D₂CO toward the young planet-forming disk IRS 63.

Results. The H₂CO probes the gas in the disk as well as in a large scale streamer (∼1500 au) impacting onto the southeast disk side. We detected for the first time deuterated formaldehyde, HDCO and D₂CO, in a planet-forming disk and HDCO in the streamer that is feeding it. These detections allowed us to estimate the deuterium fractionation of H₂CO in the disk: [HDCO]/[H₂CO] ∼ 0.1 − 0.3 and [D₂CO]/[H₂CO] ∼ 0.1. Interestingly, while HDCO follows the H₂CO distribution in the disk and in the streamer, the distribution of D₂CO is highly asymmetric, with a peak of the emission (and [D]/[H] ratio) in the southeast disk side, where the streamer crashes onto the disk. In addition, D₂CO was detected in two spots along the blue- and redshifted outflow. This suggests that (i) in the disk, HDCO formation is dominated by gas-phase reactions in a manner similar to H₂CO, while (ii) D₂CO is mainly formed on the grain mantles during the prestellar phase and/or in the disk itself and is at present released in the gas phase in the shocks driven by the streamer and the outflow.

Conclusions. These findings testify to the key role of streamers in the buildup of the disk concerning both the final mass available for planet formation and its chemical composition.