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Evidence for a Snow Line beyond the Transitional Radius in the TW Hya Protoplanetary Disk

Zhang, K. and Pontoppidan, K. M. and Salyk, C. and Blake, G. A. (2013) Evidence for a Snow Line beyond the Transitional Radius in the TW Hya Protoplanetary Disk. Astrophysical Journal, 766 (2). Art. No. 82. ISSN 0004-637X. doi:10.1088/0004-637X/766/2/82.

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We present an observational reconstruction of the radial water vapor content near the surface of the TW Hya transitional protoplanetary disk, and report the first localization of the snow line during this phase of disk evolution. The observations are comprised of Spitzer-IRS, Herschel-PACS, and Herschel-HIFI archival spectra. The abundance structure is retrieved by fitting a two-dimensional disk model to the available star+disk photometry and all observed H_2O lines, using a simple step-function parameterization of the water vapor content near the disk surface. We find that water vapor is abundant (~10^(–4) per H_2) in a narrow ring, located at the disk transition radius some 4 AU from the central star, but drops rapidly by several orders of magnitude beyond 4.2 AU over a scale length of no more than 0.5 AU. The inner disk (0.5-4 AU) is also dry, with an upper limit on the vertically averaged water abundance of 10^(–6) per H_2. The water vapor peak occurs at a radius significantly more distant than that expected for a passive continuous disk around a 0.6 M_☉ star, representing a volatile distribution in the TW Hya disk that bears strong similarities to that of the solar system. This is observational evidence for a snow line that moves outward with time in passive disks, with a dry inner disk that results either from gas giant formation or gas dissipation and a significant ice reservoir at large radii. The amount of water present near the snow line is sufficient to potentially catalyze the (further) formation of planetesimals and planets at distances beyond a few AU.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Zhang, K.0000-0002-0661-7517
Pontoppidan, K. M.0000-0001-7552-1562
Salyk, C.0000-0003-3682-6632
Blake, G. A.0000-0003-0787-1610
Additional Information:© 2013 American Astronomical Society. Received 2012 June 4; accepted 2013 February 9; published 2013 March 12. This work is based in part 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. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Funding for this work (to G.B.) was provided by the NASA Astrobiology/Origins of Solar Systems programs and NSF Astronomy & Astrophysics. C.S. gratefully acknowledges NOAO Leo Goldberg Postdoctoral Fellowship support. We also thank the anonymous referee for a thorough and insightful report, which helped to improve this paper.
Group:UNSPECIFIED, Division of Geological and Planetary Sciences
Funding AgencyGrant Number
National Optical Astronomy Observatory (NOAO)UNSPECIFIED
Subject Keywords:astrochemistry; planetary systems; protoplanetary disks; stars: individual (TW Hya)
Issue or Number:2
Record Number:CaltechAUTHORS:20130503-091059917
Persistent URL:
Official Citation:Evidence for a Snow Line beyond the Transitional Radius in the TW Hya Protoplanetary Disk K. Zhang et al. 2013 ApJ 766 82
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38254
Deposited By: Ruth Sustaita
Deposited On:03 May 2013 17:02
Last Modified:09 Nov 2021 23:36

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