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Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2017

The Flying Saucer: Tomography of the thermal and density gas structure of an edge-on protoplanetary disk

Anne Dutrey
  • Fonction : Auteur
S. Guilloteau
V. Piétu
  • Fonction : Auteur
E. Chapillon
  • Fonction : Auteur
Valentine Wakelam
  • Fonction : Auteur
E. Di Folco
  • Fonction : Auteur
T. Stoecklin
O. Denis-Alpizar
U. Gorti
  • Fonction : Auteur
R. Teague
T. Henning
D. Semenov
  • Fonction : Auteur
N. Grosso

Résumé

Context. Determining the gas density and temperature structures of protoplanetary disks is a fundamental task in order to constrain planet formation theories. This is a challenging procedure and most determinations are based on model-dependent assumptions. Aims. We attempt a direct determination of the radial and vertical temperature structure of the Flying Saucer disk, thanks to its favorable inclination of 90 degrees.Methods. We present a method based on the tomographic study of an edge-on disk. Using ALMA, we observe at 0.5″ resolution the Flying Saucer in CO J = 2–1 and CS J = 5–4. This edge-on disk appears in silhouette against the CO J = 2–1 emission from background molecular clouds in ρ Oph. The combination of velocity gradients due to the Keplerian rotation of the disk and intensity variations in the CO background as a function of velocity provide a direct measure of the gas temperature as a function of radius and height above the disk mid-plane.Results. The overall thermal structure is consistent with model predictions, with a cold (<12−15 K) CO-depleted mid-plane and a warmer disk atmosphere. However, we find evidence for CO gas along the mid-plane beyond a radius of about 200 au, coincident with a change of grain properties. Such behavior is expected in the case of efficient rise of UV penetration re-heating the disk and thus allowing CO thermal desorption or favoring direct CO photo-desorption. CO is also detected at up to 3–4 scale heights, while CS is confined to around 1 scale height above the mid-plane. The limits of the method due to finite spatial and spectral resolutions are also discussed.Conclusions. This method appears to be a very promising way to determine the gas structure of planet-forming disks, provided that the molecular data have an angular resolution which is high enough, on the order of 0.3−0.1″ at the distance of the nearest star-forming regions.
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Dates et versions

hal-01536626 , version 1 (06-10-2020)

Identifiants

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Anne Dutrey, S. Guilloteau, V. Piétu, E. Chapillon, Valentine Wakelam, et al.. The Flying Saucer: Tomography of the thermal and density gas structure of an edge-on protoplanetary disk. Astronomy and Astrophysics - A&A, 2017, 607, pp.A130. ⟨10.1051/0004-6361/201730645⟩. ⟨hal-01536626⟩
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