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The TW Hya Rosetta Stone Project IV: A Hydrocarbon-rich Disk Atmosphere

Cleeves, L. Ilsedore and Loomis, Ryan A. and Teague, Richard and Bergin, Edwin A. and Wilner, David J. and Bergner, Jennifer B. and Blake, Geoffrey A. and Calahan, Jenny K. and Cazzoletti, Paolo and van Dishoeck, Ewine F. and Guzmán, Viviana V. and Hogerheijde, Michiel R. and Huang, Jane and Kama, Mihkel and Öberg, Karin I. and Qi, Chunhua and Terwisscha van Scheltinga, Jeroen and Walsh, Catherine (2021) The TW Hya Rosetta Stone Project IV: A Hydrocarbon-rich Disk Atmosphere. Astrophysical Journal, 911 (1). Art. No. 29. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20210423-164858179

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Abstract

Connecting the composition of planet-forming disks with that of gas giant exoplanet atmospheres, in particular through C/O ratios, is one of the key goals of disk chemistry. Small hydrocarbons like C₂H and C₃H₂ have been identified as tracers of C/O, as they form abundantly under high C/O conditions. We present resolved c–C₃H₂ observations from the TW Hya Rosetta Stone Project, a program designed to map the chemistry of common molecules at 15–20 au resolution in the TW Hya disk. Augmented by archival data, these observations comprise the most extensive multi-line set for disks of both ortho and para spin isomers spanning a wide range of energies, E_u = 29–97 K. We find the ortho-to-para ratio of c–C₃H₂ is consistent with 3 throughout extent of the emission, and the total abundance of both c–C₃H₂ isomers is (7.5–10) × 10⁻¹¹ per H atom, or 1%–10% of the previously published C₂H abundance in the same source. We find c–C₃H₂ comes from a layer near the surface that extends no deeper than z/r = 0.25. Our observations are consistent with substantial radial variation in gas-phase C/O in TW Hya, with a sharp increase outside ~30 au. Even if we are not directly tracing the midplane, if planets accrete from the surface via, e.g., meridional flows, then such a change should be imprinted on forming planets. Perhaps interestingly, the HR 8799 planetary system also shows an increasing gradient in its giant planets' atmospheric C/O ratios. While these stars are quite different, hydrocarbon rings in disks are common, and therefore our results are consistent with the young planets of HR 8799 still bearing the imprint of their parent disk's volatile chemistry.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-4357/abe862DOIArticle
https://arxiv.org/abs/2102.09577arXivDiscussion Paper
ORCID:
AuthorORCID
Cleeves, L. Ilsedore0000-0003-2076-8001
Loomis, Ryan A.0000-0002-8932-1219
Teague, Richard0000-0003-1534-5186
Bergin, Edwin A.0000-0003-4179-6394
Wilner, David J.0000-0003-1526-7587
Bergner, Jennifer B.0000-0002-8716-0482
Blake, Geoffrey A.0000-0003-0787-1610
Calahan, Jenny K.0000-0002-0150-0125
Cazzoletti, Paolo0000-0002-1917-7370
van Dishoeck, Ewine F.0000-0001-7591-1907
Guzmán, Viviana V.0000-0003-4784-3040
Hogerheijde, Michiel R.0000-0001-5217-537X
Huang, Jane0000-0001-6947-6072
Kama, Mihkel0000-0003-0065-7267
Öberg, Karin I.0000-0001-8798-1347
Qi, Chunhua0000-0001-8642-1786
Terwisscha van Scheltinga, Jeroen0000-0002-3800-9639
Walsh, Catherine0000-0001-6078-786X
Additional Information:© 2021. The American Astronomical Society. Received 2020 November 5; revised 2021 February 17; accepted 2021 February 18; published 2021 April 13. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2013.0.00114.S, ADS/JAO.ALMA#2013.0.00198.S, and ADS/JAO.ALMA#2016.0.00311.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST, and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The calculations that were made for this paper were conducted on the Smithsonian Astrophysical Observatory's Hydra High Performance Cluster, for which we are grateful to have access to. L.I.C. gratefully acknowledges support from the David and Lucille Packard Foundation and the Virginia Space Grant Consortium. J.T.v.S. and M.R.H. are supported by the Dutch Astrochemistry II program of the Netherlands Organization for Scientific Research (648.000.025). C.W. acknowledges financial support from the University of Leeds and from the Science and Technology Facilities Council (grant Nos. ST/R000549/1 and ST/T000287/1). J.K.C. acknowledges support from the National Science Foundation Graduate Research Fellowship under grant No. DGE 1256260 and the National Aeronautics and Space Administration FINESST grant, under grant No. 80NSSC19K1534. V.V.G. acknowledges support from FONDECYT Iniciación 11180904. J.H. acknowledges support for this work provided by NASA through the NASA Hubble Fellowship grant #HST-HF2-51460.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. M.K. gratefully acknowledges funding by the University of Tartu ASTRA project 2014-2020.4.01.16-0029 KOMEET, financed by the EU European Regional Development Fund.
Funders:
Funding AgencyGrant Number
David and Lucile Packard FoundationUNSPECIFIED
Virginia Space Grant ConsortiumUNSPECIFIED
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)648.000.025
Science and Technology Facilities Council (STFC)ST/R000549/1
Science and Technology Facilities Council (STFC)ST/T000287/1
NSF Graduate Research FellowshipDGE-1256260
NASA Earth and Space Science Fellowship80NSSC19K1534
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)11180904
NASA Hubble FellowshipHST-HF2-51460.001-A
NASANAS5-26555
University of Tartu2014-2020.4.01.16-0029 KOMEET
European Regional Development FundUNSPECIFIED
Subject Keywords:Protoplanetary disks; Astrochemistry; Exoplanet atmospheric composition
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Protoplanetary disks (1300); Astrochemistry (75); Exoplanet atmospheric composition (2021)
Record Number:CaltechAUTHORS:20210423-164858179
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20210423-164858179
Official Citation:L. Ilsedore Cleeves et al 2021 ApJ 911 29
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108835
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:27 Apr 2021 15:07
Last Modified:24 Aug 2021 20:56

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