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The HCN-Water Ratio in the Planet Formation Region of Disks

Najita, Joan R. and Carr, John S. and Pontoppidan, Klaus M. and Salyk, Colette and van Dishoeck, Ewine F. and Blake, Geoffrey A. (2013) The HCN-Water Ratio in the Planet Formation Region of Disks. Astrophysical Journal, 766 (2). Art. No. 134. ISSN 0004-637X. doi:10.1088/0004-637X/766/2/134.

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We find a trend between the mid-infrared HCN/H_2O flux ratio and submillimeter disk mass among T Tauri stars in Taurus. While it may seem puzzling that the molecular emission properties of the inner disk (<few AU) are related to the properties of the outer disk (beyond ~20 AU) probed by the submillimeter continuum, an interesting possible interpretation is that the trend is a result of planetesimal and protoplanet formation. Because objects this large are decoupled from the accretion flow, when they form, they can lock up water (and oxygen) beyond the snow line, thereby enhancing the C/O ratio in the inner disk and altering the molecular abundances there. We discuss the assumptions that underlie this interpretation, a possible alternative explanation, and related open questions that motivate future work. Whatever its origin, understanding the meaning of the relation between the HCN/H_2O ratio and disk mass is of interest as trends like this among T Tauri disk properties are relatively rare.

Item Type:Article
Related URLs:
URLURL TypeDescription
Carr, John S.0000-0002-6695-3977
Pontoppidan, Klaus M.0000-0001-7552-1562
Salyk, Colette0000-0003-3682-6632
van Dishoeck, Ewine F.0000-0001-7591-1907
Blake, Geoffrey A.0000-0003-0787-1610
Additional Information:© 2013 American Astronomical Society. Received 2012 September 26; accepted 2013 February 10; published 2013 March 15. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA. Basic research in infrared astrophysics at the Naval Research Laboratory is supported by 6.1 base funding. J.N. thanks Sharmila Dey for assistance with the data analysis.
Group:UNSPECIFIED, Division of Geological and Planetary Sciences
Funding AgencyGrant Number
Subject Keywords:circumstellar matter; protoplanetary disks; stars: pre-main sequence
Issue or Number:2
Record Number:CaltechAUTHORS:20130503-101423988
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Official Citation:The HCN-Water Ratio in the Planet Formation Region of Disks Joan R. Najita et al. 2013 ApJ 766 134
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38259
Deposited By: Ruth Sustaita
Deposited On:03 May 2013 17:52
Last Modified:09 Nov 2021 23:36

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