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|Title:||Volatile-carbon locking and release in protoplanetary disks. A study of TW Hya and HD 100546||Authors:||Kama, M.
van Dishoeck, E. F.
Folsom, C. P.
FEDELE , DAVIDE
|Issue Date:||2016||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||592||First Page:||A83||Abstract:||Aims: The composition of planetary solids and gases is largely rooted in the processing of volatile elements in protoplanetary disks. To shed light on the key processes, we carry out a comparative analysis of the gas-phase carbon abundance in two systems with a similar age and disk mass, but different central stars: HD 100546 and TW Hya. <BR /> Methods: We combine our recent detections of C<SUP>0</SUP> in these disks with observations of other carbon reservoirs (CO, C<SUP>+</SUP>, C<SUB>2</SUB>H) and gas-mass and warm-gas tracers (HD, O<SUP>0</SUP>), as well as spatially resolved ALMA observations and the spectral energy distribution. The disks are modelled with the DALI 2D physical-chemical code. Stellar abundances for HD 100546 are derived from archival spectra. <BR /> Results: Upper limits on HD emission from HD 100546 place an upper limit on the total disk mass of ≤0.1 M<SUB>☉</SUB>. The gas-phase carbon abundance in the atmosphere of this warm Herbig disk is, at most, moderately depleted compared to the interstellar medium, with [C]/[H]<SUB>gas</SUB> = (0.1-1.5) × 10<SUP>-4</SUP>. HD 100546 itself is a λBoötis star, with solar abundances of C and O but a strong depletion of rock-forming elements. In the gas of the T Tauri disk TW Hya, both C and O are strongly underabundant, with [C]/[H]<SUB>gas</SUB> = (0.2-5.0) × 10<SUP>-6</SUP> and C / O > 1. We discuss evidence that the gas-phase C and O abundances are high in the warm inner regions of both disks. Our analytical model, including vertical mixing and a grain size distribution, reproduces the observed [C]/[H]<SUB>gas</SUB> in the outer disk of TW Hya and allows to make predictions for other systems. <P />Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 093.C-0926, 093.F-0015, 077.D-0092, 084.A-9016, and 085.A-9027.Spectra and models are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (<A href="http://184.108.40.206">http://220.127.116.11</A>) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/592/A83">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/592/A83||URI:||http://hdl.handle.net/20.500.12386/26082||URL:||https://www.aanda.org/articles/aa/abs/2016/08/aa26991-15/aa26991-15.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201526991||Bibcode ADS:||2016A&A...592A..83K||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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