Observations and modelling of CO and [C I] in protoplanetary disks. First detections of [C I] and constraints on the carbon abundance
Journal
Date Issued
2016
Author(s)
Kama, M.
•
Bruderer, S.
•
Carney, M.
•
Hogerheijde, M.
•
van Dishoeck, E. F.
•
•
Baryshev, A.
•
Boland, W.
•
Güsten, R.
•
Aikutalp, A.
•
Choi, Y.
•
Endo, A.
•
Frieswijk, W.
•
Karska, A.
•
Klaassen, P.
•
Koumpia, E.
•
Kristensen, L.
•
•
Nagy, Z.
•
Perez Beaupuits, J. -P.
•
Risacher, C.
•
van der Marel, N.
•
van Kempen, T. A.
•
van Weeren, R. J.
•
Wyrowski, F.
•
Yıldız, U. A.
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, C0, and C+ can now be observed regularly in disks.
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.
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.
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.
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]gas 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.
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.
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.
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.
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]gas 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.
The reduced spectra (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A108
Volume
588
Start page
A108
Issn Identifier
0004-6361
Ads BibCode
2016A&A...588A.108K
Rights
open.access
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