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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 731622.0, MPI für Astronomie / Publikationen_mpia
The shadow of the Flying Saucer: A very low temperature for large dust grains
Authors:Guilloteau, S.; Piétu, V.; Chapillon, E.; Di Folco, E.; Dutrey, A.; Henning, T.; Semenov, D.; Birnstiel, T.; Grosso, N.
Date of Publication (YYYY-MM-DD):2016
Title of Journal:Astronomy and Astrophysics
Start Page:id. L1 (5 pp)
Audience:Not Specified
Abstract / Description:Context. Dust determines the temperature structure of protoplanetary disks, however, dust temperature determinations almost invariably rely on a complex modeling of the Spectral Energy Distribution. <BR /> Aims: We attempt a direct determination of the temperature of large grains emitting at mm wavelengths. <BR /> Methods: We observe the edge-on dust disk of the Flying Saucer, which appears in silhouette against the CO J = 2-1 emission from a background molecular cloud 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 allows us to directly measure the dust temperature. The dust opacity can then be derived from the emitted continuum radiation. <BR /> Results: The dust disk absorbs the radiation from the CO clouds at several velocities. We derive very low dust temperatures, 5 to 7 K at radii around 100 au, which is much lower than most model predictions. The dust optical depth is >0.2 at 230 GHz, and the scale height at 100 au is at least 8 au (best fit 13 au). However, the dust disk is very flat (flaring index -0.35), which is indicative of dust settling in the outer parts.
Free Keywords:circumstellar matter; protoplanetary disks; radio lines: stars
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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