Edge-On Disk Study (EODS)

Context . Investigating the vertical distribution of molecular content in protoplanetary disks remains difficult in most disks mildly inclined along the line of sight. In contrast, edge-on disks provide a direct (tomographic) view of the 2D molecular brightness. Aims . We study the radial and vertical molecular distribution as well as the gas temperature and density by observing the Keplerian edge-on disk surrounding the Flying Saucer, a Class II object located in Ophiuchus. Methods . We used new and archival ALMA data to perform a tomography of 12 CO, 13 CO, C 18 O, CN, HCN, CS, H 2 CO, c-C 3 H 2 , N 2 D + , DCN, and 13 CS. We analyzed molecular tomographies and modeled data using the radiative transfer code D ISK F IT . Results . We directly measured the altitude above the mid-plane for each observed species. For the first time, we unambiguously demonstrate the presence of a common molecular layer and measure its thickness. Most molecules are located at the same altitude versus radius. Beyond CO, as predicted by chemical models, the CN emission traces the upper boundary of the molecular layer, whereas the deuterated species (DCN and N 2 D + ) reside below one scale height. Our best fits from D ISK F IT show that most observed transitions in the molecular layer are thermalized because their excitation temperature is the same, around ~17-20K. Conclusions . These long-integration observations clearly reveal a molecular layer predominantly located around one to two scale heights at a temperature above the CO freeze-out temperature. The deuterated molecules are closer to the mid-plane, and N 2 D + may be a good proxy for the CO snowline. Some molecules, such as CN and H 2 CO, are likely influenced by the disk environment, at least beyond the millimeter dust disk radius. The direct observation of the molecular stratification opens the door to detailed chemical modeling in a disk that appears representative of T Tauri disks.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2025-11-26
DOI
https://doi.org/10.1051/0004-6361/202555641
Citations
1
Primary Topic
Astrophysics and Star Formation Studies
Type
article
Field-Weighted Citation Impact
1.15

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article

Edge-On Disk Study (EODS)

Raphaël Meshaka, E. Dartois, Uma Gorti, Otoniel Denis‐Alpizar et al.
1 citations
Astronomy and Astrophysics
Astrophysics and Star Formation Studies
1.15
article

Edge-On Disk Study (EODS)

Raphaël Meshaka, E. Dartois, Uma Gorti, Otoniel Denis‐Alpizar, Sacha Gavino, S. Guilloteau, Á. Kóspál, Maxime Ruaud, Liton Majumdar, S. Wolf, Hideko Nomura, D. Semenov, L. Testi, J.-M. Huré, A. Dutrey, E. Di Folco, Cristina San Juan - Foucher, Nguyễn Thị Phương, Kenji Furuya, Franck Le Petit, Edwige Chapillon, N. Grosso, Ya‐Wen Tang, V. Piétu, Th. Henning
article en
1 citations

Abstract

Context . Investigating the vertical distribution of molecular content in protoplanetary disks remains difficult in most disks mildly inclined along the line of sight. In contrast, edge-on disks provide a direct (tomographic) view of the 2D molecular brightness. Aims . We study the radial and vertical molecular distribution as well as the gas temperature and density by observing the Keplerian edge-on disk surrounding the Flying Saucer, a Class II object located in Ophiuchus. Methods . We used new and archival ALMA data to perform a tomography of 12 CO, 13 CO, C 18 O, CN, HCN, CS, H 2 CO, c-C 3 H 2 , N 2 D + , DCN, and 13 CS. We analyzed molecular tomographies and modeled data using the radiative transfer code D ISK F IT . Results . We directly measured the altitude above the mid-plane for each observed species. For the first time, we unambiguously demonstrate the presence of a common molecular layer and measure its thickness. Most molecules are located at the same altitude versus radius. Beyond CO, as predicted by chemical models, the CN emission traces the upper boundary of the molecular layer, whereas the deuterated species (DCN and N 2 D + ) reside below one scale height. Our best fits from D ISK F IT show that most observed transitions in the molecular layer are thermalized because their excitation temperature is the same, around ~17-20K. Conclusions . These long-integration observations clearly reveal a molecular layer predominantly located around one to two scale heights at a temperature above the CO freeze-out temperature. The deuterated molecules are closer to the mid-plane, and N 2 D + may be a good proxy for the CO snowline. Some molecules, such as CN and H 2 CO, are likely influenced by the disk environment, at least beyond the millimeter dust disk radius. The direct observation of the molecular stratification opens the door to detailed chemical modeling in a disk that appears representative of T Tauri disks.

Astronomy and AstrophysicsVol. 704
Eötvös Loránd University (HU), Centre National de la Recherche Scientifique (FR), Institute of Astronomy and Astrophysics, Academia Sinica (TW), Pioneer (United States) (US), Université de Bordeaux (FR), National Institute of Science Education and Research (IN), Queen Mary University of London (GB), Homi Bhabha National Institute (IN), Aix-Marseille Université (FR), Heidelberg University (DE), Université Paris Sciences et Lettres (FR), Université Paris-Saclay (FR), Konkoly Observatory (HU), Christian-Albrechts-Universität zu Kiel (DE), Sorbonne Université (FR), Osservatorio astronomico di Bologna (IT), Laboratoire d'Astrophysique de Bordeaux (FR), Pioneer (Japan) (JP), Max Planck Institute for Astronomy (DE), RIKEN (JP), Institute of Astronomy (RU), Institut des Sciences Moléculaires d'Orsay (FR), HUN-REN Research Centre for Astronomy and Earth Sciences (HU), Astronomical Observatory (RS), Ausonius Institut de Recherche sur l'Antiquité et le Moyen age (FR), National Astronomical Observatory of Japan (JP), University of Chile (CL), Vietnam Academy of Science and Technology (VN), Heidelberg University (US), Search for Extraterrestrial Intelligence (US), University of Bologna (IT)
National Science Foundation, Vietnam Academy of Science and Technology, 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, Nemzeti Kutatási Fejlesztési és Innovációs Hivatal, National Science and Technology Council, National Institutes of Natural Sciences
Openalex Percentile: Top 15%
Astrophysics and Star Formation Studies
1.15
DOIOpen Access PDFOpenAlex
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