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|Title:||Observations and modelling of CO and [C I] in protoplanetary disks. First detections of [C I] and constraints on the carbon abundance||Authors:||Kama, M.
van Dishoeck, E. F.
FEDELE , DAVIDE
Perez Beaupuits, J. -P.
van der Marel, N.
van Kempen, T. A.
van Weeren, R. J.
Yıldız, U. A.
|Issue Date:||2016||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||588||First Page:||A108||Abstract:||Context. The gas-solid budget of carbon in protoplanetary disks is related to the composition of the cores and atmospheres of the planets forming in them. The principal gas-phase carbon carriers CO, C<SUP>0</SUP>, and C<SUP>+</SUP> can now be observed regularly in disks. <BR /> Aims: The gas-phase carbon abundance in disks has thus far not been well characterized observationally. We obtain new constraints on the [C]/[H] ratio in a large sample of disks, and compile an overview of the strength of [C I] and warm CO emission. <BR /> Methods: We carried out a survey of the CO 6-5 line and the [C I] 1-0 and 2-1 lines towards 37 disks with the APEX telescope, and supplemented it with [C II] data from the literature. The data are interpreted using a grid of models produced with the DALI disk code. We also investigate how well the gas-phase carbon abundance can be determined in light of parameter uncertainties. <BR /> Results: The CO 6-5 line is detected in 13 out of 33 sources, [C I] 1-0 in 6 out of 12, and [C I] 2-1 in 1 out of 33. With separate deep integrations, the first unambiguous detections of the [C I] 1-0 line in disks are obtained, in TW Hya and HD 100546. <BR /> Conclusions: Gas-phase carbon abundance reductions of a factor of 5-10 or more can be identified robustly based on CO and [C I] detections, assuming reasonable constraints on other parameters. The atomic carbon detection towards TW Hya confirms a factor of 100 reduction of [C]/[H]<SUB>gas</SUB> in that disk, while the data are consistent with an ISM-like carbon abundance for HD 100546. In addition, BP Tau, T Cha, HD 139614, HD 141569, and HD 100453 are either carbon-depleted or gas-poor disks. The low [C I] 2-1 detection rates in the survey mostly reflect insufficient sensitivity for T Tauri disks. The Herbig Ae/Be disks with CO and [C II] upper limits below the models are debris-disk-like systems. An increase in sensitivity of roughly order of magnitude compared to our survey is required to obtain useful constraints on the gas-phase [C]/[H] ratio in most of the targeted systems. <P />The reduced spectra (FITS files) are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://220.127.116.11) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A108">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A108||URI:||http://hdl.handle.net/20.500.12386/26083||URL:||https://www.aanda.org/articles/aa/abs/2016/04/aa26791-15/aa26791-15.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201526791||Bibcode ADS:||2016A&A...588A.108K||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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