PDRs4All

Astronomy and Astrophysics, vol. 689, pp. L4

Abstract

The gas-phase abundance of carbon, x C = [C/H] gas = x C + + x C 0 + x CO + … , and its depletion factors are essential parameters for understanding the gas and solid compositions that are ultimately incorporated into (exo)planets. The majority of protoplanetary disks are born in clusters and, as a result, are exposed to external far-ultraviolet (FUV) radiation. These FUV photons potentially affect the disk’s evolution, chemical composition, and line excitation. We present the first detection of the [C I ] 609 μm fine-structure ( 3 P 1 – 3 P 0 ) line of neutral carbon (C 0 ), achieved with ALMA, toward one of these disks, d203-506, in the Orion Nebula Cluster. We also report the detection of [C I ] forbidden and C I permitted lines (from electronically excited states up to ∼10 eV) observed with JWST in the near-infrared (NIR). These lines trace the irradiated outer disk and photo-evaporative wind. Contrary to the common belief that these NIR lines are C + recombination lines, we find that they are dominated by FUV-pumping of C 0 followed by fluorescence cascades. They trace the transition from atomic to molecular gas, and their intensities scale with G 0 . The lack of outstanding NIR O I fluorescent emission, however, implies a sharper attenuation of external FUV radiation with E ≳ 12 eV ( λ ≲ Lyman- β ). This is related to a lower effective FUV dust absorption cross section compared to that of interstellar grains, implying a more prominent role for FUV shielding by the C 0 photoionization continuum. The [C I ] 609 μm line intensity is proportional to N (C 0 ) and can be used to infer x C . We derive x C ≃ 1.4 × 10 −4 . This implies that there is no major depletion of volatile carbon compared to x C measured in the natal cloud, hinting at a young disk. We also show that external FUV radiation impacts the outer disk and wind by vertically shifting the water freeze-out depth, which likely results in less efficient grain growth and settling. This shift leads to nearly solar gas-phase C/O abundance ratios in these irradiated layers.

Authors 29

1. Javier R. Goicoechea

   Instituto de Física Fundamental

   Affiliation as printed

   Instituto de Física Fundamental (CSIC), Calle Serrano 121-123, 28006 Madrid, Spain

2. J. Le Bourlot

   Université Paris Cité

   Affiliation as printed

   Université Paris Cité, Paris, France

3. J. H. Black

   Chalmers University of Technology

   Affiliation as printed

   Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden

4. Felipe Alarcón

   University of Michigan

   Affiliation as printed

   Dept. of Astronomy, University of Michigan, Ann Arbor, MI, USA

5. Edwin A. Bergin

   University of Michigan

   Affiliation as printed

   Dept. of Astronomy, University of Michigan, Ann Arbor, MI, USA

6. Olivier Berné

   Centre National de la Recherche Scientifique · Université Toulouse III - Paul Sabatier · Institut de Recherche en Astrophysique et Planétologie

   Affiliation as printed

   Institut de Recherche en Astrophysique et Planétologie, Université Toulouse III - Paul Sabatier, CNRS, CNES, Toulouse, France

7. Émeric Bron

   Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères

   Affiliation as printed

   LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, Paris-Meudon, France

8. Amélie Canin

   Centre National de la Recherche Scientifique · Université Toulouse III - Paul Sabatier · Institut de Recherche en Astrophysique et Planétologie

   Affiliation as printed

   Institut de Recherche en Astrophysique et Planétologie, Université Toulouse III - Paul Sabatier, CNRS, CNES, Toulouse, France

9. E. Chapillon
   Affiliation as printed

   IRAM, 300 rue de la Piscine, 38406 Saint Martin d’Hères, France

10. Ryan Chown

    Western University · The Ohio State University

    Affiliation as printed

    Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA

    Department of Physics and Astronomy, University of Western Ontario, London, Ontario, Canada

    Institute for Earth and Space Exploration, University of Western Ontario, London, Ontario, Canada

11. Emmanuel Dartois

    Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut des Sciences Moléculaires d'Orsay

    Affiliation as printed

    Institut des Sciences Moléculaires d’Orsay, CNRS, Université Paris-Saclay, Orsay, France

12. Maryvonne Gérin

    Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères

    Affiliation as printed

    LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, Paris-Meudon, France

13. E. Habart

    Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut d'Astrophysique Spatiale

    Affiliation as printed

    Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, Orsay, France

14. Thomas J. Haworth

    Queen Mary University of London

    Affiliation as printed

    School of Physics and Astronomy, Queen Mary University of London, London E1 4NS, UK

15. C. Joblin

    Centre National de la Recherche Scientifique · Université Toulouse III - Paul Sabatier · Institut de Recherche en Astrophysique et Planétologie

    Affiliation as printed

    Institut de Recherche en Astrophysique et Planétologie, Université Toulouse III - Paul Sabatier, CNRS, CNES, Toulouse, France

16. Olga Kannavou

    Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut d'Astrophysique Spatiale

    Affiliation as printed

    Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, Orsay, France

17. Franck Le Petit

    Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères

    Affiliation as printed

    LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, Paris-Meudon, France

18. Takashi Onaka

    The University of Tokyo

    Affiliation as printed

    Department of Astronomy, Graduate School of Science, University of Tokyo, Tokyo, Japan

19. E. Peeters

    Western University · Search for Extraterrestrial Intelligence

    Affiliation as printed

    Carl Sagan Center, SETI Institute, Mountain View, CA, USA

    Department of Physics and Astronomy, University of Western Ontario, London, Ontario, Canada

    Institute for Earth and Space Exploration, University of Western Ontario, London, Ontario, Canada

20. Jérôme Pety

    Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères

    Affiliation as printed

    IRAM, 300 rue de la Piscine, 38406 Saint Martin d’Hères, France

    LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, Paris-Meudon, France

21. E. Roueff

    Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères

    Affiliation as printed

    LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, Paris-Meudon, France

22. Ameek Sidhu

    Western University

    Affiliation as printed

    Department of Physics and Astronomy, University of Western Ontario, London, Ontario, Canada

    Institute for Earth and Space Exploration, University of Western Ontario, London, Ontario, Canada

23. Ilane Schroetter

    Centre National de la Recherche Scientifique · Université Toulouse III - Paul Sabatier · Institut de Recherche en Astrophysique et Planétologie

    Affiliation as printed

    Institut de Recherche en Astrophysique et Planétologie, Université Toulouse III - Paul Sabatier, CNRS, CNES, Toulouse, France

24. Benoît Tabone

    Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut d'Astrophysique Spatiale

    Affiliation as printed

    Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, Orsay, France

25. Alexander G. G. M. Tielens Aachen Leiden Observatory

    Leiden University · Leiden Observatory · University of Maryland, College Park

    Affiliation as printed

    Astronomy Department, Univ. of Maryland, College Park, MD, USA

    Leiden Observatory, Leiden University, Leiden, The Netherlands

26. Boris Trahin

    Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut d'Astrophysique Spatiale

    Affiliation as printed

    Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, Orsay, France

27. Dries Van De Putte

    Western University · Space Telescope Science Institute

    Affiliation as printed

    Department of Physics and Astronomy, University of Western Ontario, London, Ontario, Canada

    Institute for Earth and Space Exploration, University of Western Ontario, London, Ontario, Canada

    Space Telescope Science Institute, Baltimore, MD, USA

28. S. Vicente
    Affiliation as printed

    Instituto de Astrofísica e Ciências do Espaçsbon, Lisbon, Portugal

29. Marion Zannese

    Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut d'Astrophysique Spatiale

    Affiliation as printed

    Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, Orsay, France