PDRs4All

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.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2024-08-19
DOI
https://doi.org/10.1051/0004-6361/202450988
Citations
15
Primary Topic
Astrophysics and Star Formation Studies
Type
article
Field-Weighted Citation Impact
4.97

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article

PDRs4All

S. Vicente, Edwin A. Bergin, Émeric Bron, Maryvonne Gérin et al.
15 citations
Astronomy and Astrophysics
Astrophysics and Star Formation Studies
4.97
article

PDRs4All

S. Vicente, Edwin A. Bergin, Émeric Bron, Maryvonne Gérin, E. Dartois, E. Chapillon, J. Pety, Marion Zannese, J. R. Goicoechea, Takashi Onaka, Ryan Chown, Ilane Schroetter, J. H. Black, Felipe Alarcón, O. Berné, E. Peeters, E. Roueff, Boris Trahin, Amélie Canin, Benoît Tabone, E. Habart, A. G. G. M. Tielens, C. Joblin, J. Le Bourlot, Thomas J. Haworth, Dries Van De Putte, Ameek Sidhu, Olga Kannavou, Franck Le Petit
article en
15 citations

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.

Astronomy and AstrophysicsVol. 689
Leiden University (NL), Western University (CA), Centre National de la Recherche Scientifique (FR), Space Telescope Science Institute (US), Université Toulouse III - Paul Sabatier (FR), Queen Mary University of London (GB), Université Paris Cité (FR), Université Paris Sciences et Lettres (FR), Université Paris-Saclay (FR), University of Michigan (US), Observatoire de Paris (FR), Sorbonne Université (FR), Institute of Astrophysics and Space Sciences (PT), Instituto de Física Fundamental (ES), Institut d'Astrophysique Spatiale (FR), Institut des Sciences Moléculaires d'Orsay (FR), Ausonius Institut de Recherche sur l'Antiquité et le Moyen age (FR), Institut de Recherche en Astrophysique et Planétologie (FR), The Ohio State University (US), Chalmers University of Technology (SE), University of Maryland, College Park (US), The University of Tokyo (JP), Search for Extraterrestrial Intelligence (US)
National Science Foundation, National Aeronautics and Space Administration, Space Telescope Science Institute, UK Research and Innovation, National Radio Astronomy Observatory, Centre National d’Etudes Spatiales, Korea Astronomy and Space Science Institute, Centre National de la Recherche Scientifique, National Astronomical Observatory of Japan, National Science and Technology Council, HORIZON EUROPE Framework Programme, Canadian Space Agency, Natural Sciences and Engineering Research Council of Canada, Japan Society for the Promotion of Science, National Institutes of Natural Sciences
Openalex Percentile: Top 5%
Astrophysics and Star Formation Studies
4.97
DOIOpen Access PDFOpenAlex
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