MINDS
Astronomy and Astrophysics, vol. 679, pp. A117
Abstract
Context. The Mid-InfraRed Instrument (MIRI) Medium Resolution Spectrometer (MRS) on board the James Webb Space Telescope (JWST) allows us to probe the inner regions of protoplanetary disks, where the elevated temperatures result in an active chemistry and where the gas composition may dictate the composition of planets forming in this region. The disk around the classical T Tauri star Sz 98, which has an unusually large dust disk in the millimetre with a compact core, was observed with the MRS, and we examine its spectrum here. Aims. We aim to explain the observations and put the disk of Sz 98 in context with other disks, with a focus on the H2O emission through both its ro-vibrational and pure rotational emission. Furthermore, we compare our chemical findings with those obtained for the outer disk from Atacama Large Millimeter/submillimeter Array (ALMA) observations. Methods. In order to model the molecular features in the spectrum, the continuum was subtracted and local thermodynamic equilibrium (LTE) slab models were fitted. The spectrum was divided into different wavelength regions corresponding to H2O lines of different excitation conditions, and the slab model fits were performed individually per region. Results. We confidently detect CO, H2O, OH, CO2, and HCN in the emitting layers. Despite the plethora of H2O lines, the isotopo-logue H218O is not detected. Additionally, no other organics, including C2H2, are detected. This indicates that the C/O ratio could be substantially below unity, in contrast with the outer disk. The H2O emission traces a large radial disk surface region, as evidenced by the gradually changing excitation temperatures and emitting radii. Additionally, the OH and CO2 emission is relatively weak. It is likely that H2O is not significantly photodissociated, either due to self-shielding against the stellar irradiation, or UV shielding from small dust particles. While H2O is prominent and OH is relatively weak, the line fluxes in the inner disk of Sz 98 are not outliers compared to other disks. Conclusions. The relative emitting strength of the different identified molecular features points towards UV shielding of H2O in the inner disk of Sz 98, with a thin layer of OH on top. The majority of the organic molecules are either hidden below the dust continuum, or not present. In general, the inferred composition points to a sub-solar C/O ratio (<0.5) in the inner disk, in contrast with the larger than unity C/O ratio in the gas in the outer disk found with ALMA.
Authors 42
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Affiliation as printed
Institute of Astronomy , KU Leuven , Celestijnenlaan 200D , 3001 Leuven , Belgium
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Leiden University · Max Planck Institute for Extraterrestrial Physics · Leiden Observatory
Affiliation as printed
Leiden Observatory , Leiden University , 2300 RA Leiden , The Netherlands
Max-Planck Institut für Extraterrestrische Physik (MPE) , Giessenbachstr. 1 , 85748 Garching , Germany
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Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max-Planck Institut für Extraterrestrische Physik (MPE) , Giessenbachstr. 1 , 85748 Garching , Germany
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Leiden University · Leiden Observatory
Affiliation as printed
Leiden Observatory , Leiden University , 2300 RA Leiden , The Netherlands
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Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut d'Astrophysique Spatiale
Affiliation as printed
Université Paris-Saclay , CNRS , Institut d'Astrophysique Spatiale , 91405 Orsay , France
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Max Planck Institute for Astronomy
Affiliation as printed
Max-Planck-Institut für Astronomie (MPIA) , Königstuhl 17 , 69117 Heidelberg , Germany
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Affiliation as printed
Kapteyn Astronomical Institute , Rijksuniversiteit Groningen , Postbus 800 , 9700AV Groningen , The Netherlands
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Centre National de la Recherche Scientifique · Université Paris Cité · Commissariat à l'Énergie Atomique et aux Énergies Alternatives · Université Paris-Saclay · Astrophysique, Instrumentation et Modélisation
Affiliation as printed
Université Paris-Saclay , Université Paris Cité , CEA , CNRS , AIM , 91191 Gif-sur-Yvette , France
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Max Planck Institute for Astronomy
Affiliation as printed
Max-Planck-Institut für Astronomie (MPIA) , Königstuhl 17 , 69117 Heidelberg , Germany
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Affiliation as printed
STAR Institute , Université de Liège , Allée du Six Août 19c , 4000 Liège , Belgium
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Max Planck Institute for Astronomy
Affiliation as printed
Max-Planck-Institut für Astronomie (MPIA) , Königstuhl 17 , 69117 Heidelberg , Germany
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Affiliation as printed
Kapteyn Astronomical Institute , Rijksuniversiteit Groningen , Postbus 800 , 9700AV Groningen , The Netherlands
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Affiliation as printed
Institute of Astronomy , KU Leuven , Celestijnenlaan 200D , 3001 Leuven , Belgium
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Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut d'Astrophysique Spatiale
Affiliation as printed
Université Paris-Saclay , CNRS , Institut d'Astrophysique Spatiale , 91405 Orsay , France
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Affiliation as printed
STAR Institute , Université de Liège , Allée du Six Août 19c , 4000 Liège , Belgium
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Affiliation as printed
Centro de Astrobiología (CAB) , CSIC-INTA , ESAC Campus , Camino Bajo del Castillo s/n , 28692 Villanueva de la Cañada , Madrid , Spain
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Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
Affiliation as printed
LESIA , Observatoire de Paris , Université PSL , CNRS , Sorbonne Université , Université de Paris , 5 place Jules Janssen , 92195 Meudon , France
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Max Planck Institute for Astronomy
Affiliation as printed
Max-Planck-Institut für Astronomie (MPIA) , Königstuhl 17 , 69117 Heidelberg , Germany
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Dublin Institute For Advanced Studies · Astronomical Observatory of Capodimonte
Affiliation as printed
Dublin Institute for Advanced Studies , 31 Fitzwilliam Place , D02 XF86 Dublin , Ireland
INAF-Osservatorio Astronomico di Capodimonte , Salita Moiariello 16 , 80131 Napoli , Italy
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Royal Observatory · UK Astronomy Technology Centre
Affiliation as printed
UK Astronomy Technology Centre , Royal Observatory Edinburgh , Blackford Hill , Edinburgh EH9 3HJ , UK
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ETH Zurich · Institute for Particle Physics and Astrophysics
Affiliation as printed
ETH Zürich , Institute for Particle Physics and Astrophysics , Wolfgang-Pauli-Str. 27 , 8093 Zürich , Switzerland
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Affiliation as printed
Dept. of Astrophysics , University of Vienna , Türkenschanzstr. 17 , 1180 Vienna , Austria
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Affiliation as printed
Department of Astrophysics/IMAPP , Radboud University , PO Box 9010 , 6500 GL Nijmegen , The Netherlands
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Space Research Organisation Netherlands
Affiliation as printed
SRON Netherlands Institute for Space Research , PO Box 800 , 9700 AV Groningen , The Netherlands
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Affiliation as printed
Centro de Astrobiología (CAB) , CSIC-INTA , ESAC Campus , Camino Bajo del Castillo s/n , 28692 Villanueva de la Cañada , Madrid , Spain
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Affiliation as printed
Kapteyn Astronomical Institute , Rijksuniversiteit Groningen , Postbus 800 , 9700AV Groningen , The Netherlands
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Centre National de la Recherche Scientifique · Université Paris Cité · Commissariat à l'Énergie Atomique et aux Énergies Alternatives · Université Paris-Saclay · Astrophysique, Instrumentation et Modélisation
Affiliation as printed
Université Paris-Saclay , Université Paris Cité , CEA , CNRS , AIM , 91191 Gif-sur-Yvette , France
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Stockholm University · AlbaNova
Affiliation as printed
Department of Astronomy , Stockholm University , AlbaNova University Center , 10691 Stockholm , Sweden
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Centre National de la Recherche Scientifique · Université Paris Cité · Commissariat à l'Énergie Atomique et aux Énergies Alternatives · Université Paris-Saclay · Astrophysique, Instrumentation et Modélisation
Affiliation as printed
Université Paris-Saclay , Université Paris Cité , CEA , CNRS , AIM , 91191 Gif-sur-Yvette , France
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University of Vienna · Konkoly Observatory · HUN-REN Research Centre for Astronomy and Earth Sciences · Hungarian Research Network
Affiliation as printed
Dept. of Astrophysics , University of Vienna , Türkenschanzstr. 17 , 1180 Vienna , Austria
Konkoly Observatory , Research Centre for Astronomy and Earth Sciences , Eötvös Loránd Research Network (ELKH) , Konkoly-Thege Miklós út 15-17 , 1121 Budapest , Hungary
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Dublin Institute For Advanced Studies
Affiliation as printed
Dublin Institute for Advanced Studies , 31 Fitzwilliam Place , D02 XF86 Dublin , Ireland
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Max Planck Institute for Astronomy
Affiliation as printed
Max-Planck-Institut für Astronomie (MPIA) , Königstuhl 17 , 69117 Heidelberg , Germany
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Max Planck Institute for Astronomy
Affiliation as printed
Max-Planck-Institut für Astronomie (MPIA) , Königstuhl 17 , 69117 Heidelberg , Germany
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Affiliation as printed
Institute of Astronomy , KU Leuven , Celestijnenlaan 200D , 3001 Leuven , Belgium
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Leiden University · Leiden Observatory
Affiliation as printed
Leiden Observatory , Leiden University , 2300 RA Leiden , The Netherlands
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Radboud University Nijmegen · Space Research Organisation Netherlands
Affiliation as printed
Department of Astrophysics/IMAPP , Radboud University , PO Box 9010 , 6500 GL Nijmegen , The Netherlands
SRON Netherlands Institute for Space Research , PO Box 800 , 9700 AV Groningen , The Netherlands
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Royal Observatory · UK Astronomy Technology Centre
Affiliation as printed
UK Astronomy Technology Centre , Royal Observatory Edinburgh , Blackford Hill , Edinburgh EH9 3HJ , UK
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Affiliation as printed
Centro de Astrobiología (CAB , CSIC-INTA) , Carretera de Ajalvir , 28850 Torrejón de Ardoz , Madrid , Spain
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DTU Space · Technical University of Denmark
Affiliation as printed
DTU Space , Technical University of Denmark , Building 328 , Elektrovej , 2800 Kgs. Lyngby , Denmark
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Stockholm University · AlbaNova
Affiliation as printed
Department of Astronomy , Stockholm University , AlbaNova University Center , 10691 Stockholm , Sweden
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