MINDS: The DR Tau disk
Astronomy and Astrophysics, vol. 689, pp. A330
Abstract
Context. The Medium Resolution Spectrometer (MRS) of the Mid-InfraRed Instrument (MIRI) on the James Webb Space Telescope (JWST) gives insights into the chemical richness and complexity of the inner regions of planet-forming disks. Several disks that are compact in the millimetre dust emission have been found by Spitzer to be particularly bright in H 2 O, which is thought to be caused by the inward drift of icy pebbles. Here, we analyse the H 2 O-rich spectrum of the compact disk DR Tau using high-quality JWST-MIRI observations. Aims. We infer the H 2 O column densities (in cm −2 ) using methods presented in previous works, as well as introducing a new method to fully characterise the pure rotational spectrum. We aim to further characterise the abundances of H 2 O in the inner regions of this disk and its abundance relative to CO. We also search for emission of other molecular species, such as CH 4 , NH 3 , CS, H 2 , SO 2 , and larger hydrocarbons; commonly detected species, such as CO, CO 2 , HCN, and C 2 H 2 , have been investigated in our previous paper. Methods. We first use 0D local thermodynamic equilibrium (LTE) slab models to investigate the excitation properties observed in different wavelength regions across the entire spectrum, probing both the ro-vibrational and rotational transitions. To further analyse the pure rotational spectrum (≥10 μm), we use the spectrum of a large, structured disk (CI Tau) as a template to search for differences with our compact disk. Finally, we fit multiple components to characterise the radial (and vertical) temperature gradient(s) present in the spectrum of DR Tau. Results. The 0D slab models indicate a radial gradient in the disk, as the excitation temperature (emitting radius) decreases (increases) with increasing wavelength, which is confirmed by the analysis involving the large disk template. To explain the derived emitting radii, we need a larger inclination for the inner disk ( i ~ 10–23°), agreeing with our previous analysis on CO. From our multi-component fit, we find that at least three temperature components ( T 1 ~800 K, T 2 ~470 K, and T 3 ~180 K) are required to reproduce the observed rotational spectrum of H 2 O arising from the inner R em ~0.3–8 au. By comparing line ratios, we derived an upper limit on the column densities (in cm −2 ) for the first two components of log 10 ( N ) ≤18.4 within ~1.2 au. We note that the models with a pure temperature gradient provide as robust results as the more complex models, which include spatial line shielding. No robust detection of the isotopologue H 2 18 O can be made and upper limits are provided for other molecular species. Conclusions. Our analysis confirms the presence of a pure radial temperature gradient present in the inner disk of DR Tau, which can be described by at least three components. This gradient scales roughly as ∼ R -0.5 em in the emitting layers, in the inner 2 au. As the observed H 2 O is mainly optically thick, a lower limit on the abundance ratio of H 2 O/CO~0.17 is derived, suggesting a potential depletion of H 2 O. Similarly to previous work, we detect a cold H 2 O component ( T ~ 180 K) originating from near the snowline, now with a multi-component analysis. Yet, we cannot conclude whether an enhancement of the H 2 O reservoir is observed following radial drift. A consistent analysis of a larger sample is necessary to study the importance of drift in enhancing the H 2 O abundances.
Authors 16
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Leiden University · Leiden Observatory
Affiliation as printed
Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
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Leiden University · Max Planck Institute for Extraterrestrial Physics · Leiden Observatory
Affiliation as printed
Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße 1, 85748 Garching, Germany
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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 · Institut National des Sciences de l'Univers
Affiliation as printed
Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, 91405 Orsay, France
IAS - Institut d'astrophysique spatiale (Bâtiment 121 91405 ORSAY CEDEX - France)
INSU - CNRS - Institut national des sciences de l'Univers (INSU-CNRS 3 rue Michel-Ange, 75794 Paris Cedex 16 - France)
Université Paris-Saclay (Bâtiment Bréguet, 3 Rue Joliot Curie 2e ét, 91190 Gif-sur-Yvette - France)
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University of Vienna · ETH Zurich · Institute for Particle Physics and Astrophysics
Affiliation as printed
Department of Astrophysics, University of Vienna, Türkenschanzstr. 17, 1180 Vienna, Austria
ETH Zürich, Institute for Particle Physics and Astrophysics, Wolfgang-Pauli-Str. 27, 8093 Zürich, Switzerland
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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
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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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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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
Kapteyn Astronomical Institute, Rijksuniversiteit Groningen, Postbus 800, 9700AV Groningen, The Netherlands
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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
Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands
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Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße 1, 85748 Garching, 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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Max Planck Institute for Astronomy
Affiliation as printed
Max-Planck-Institut für Astronomie (MPIA), Königstuhl 17, 69117 Heidelberg, Germany
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Leiden University · Leiden Observatory
Affiliation as printed
Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
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