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Formation of Water in the Warm Atmospheres of Protoplanetary Disks

Glassgold, A. E. and Meijerink, R. and Najita, J. R. (2009) Formation of Water in the Warm Atmospheres of Protoplanetary Disks. Astrophysical Journal, 701 (1). pp. 142-153. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20090808-142505220

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Abstract

The gas-phase chemistry of water in protoplanetary disks is analyzed with a model based on X-ray heating and ionization of the disk atmosphere. Several uncertain processes appear to play critical roles in generating the column densities of warm water that are detected from disks at infrared wavelengths. The dominant factors are the reactions that form molecular hydrogen, including formation on warm grains, and the ionization and heating of the atmosphere. All of these can work together to produce a region of high water abundances in the molecular transition layer of the inner disk atmosphere, where atoms are transformed into molecules, the temperature drops from thousands to hundreds of Kelvins, and the ionization begins to be dominated by the heavy elements. Grain formation of molecular hydrogen and mechanical heating of the atmosphere can play important roles in this region and directly affect the amount of warm water in protoplanetary disk atmospheres. Thus, it may be possible to account for the existing measurements of water emission from T Tauri disks without invoking transport of water from cooler to warmer regions. The hydroxyl radical OH is underabundant in this model of disk atmospheres and requires consideration of additional production and excitation processes.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0004-637X/701/1/142DOIUNSPECIFIED
http://www.iop.org/EJ/abstract/0004-637X/701/1/142/PublisherUNSPECIFIED
Additional Information:© 2009. The American Astronomical Society. Received 2009 February 10; accepted 2009 May 26; published 2009 July 21. Print publication: Issue 1 (2009 August 10). This work has been supported by NSF grant AST-0507423, NASA grants NNG06GF88G and 1322305 to UC Berkeley. We would like to thank John Black, David Hollenbach, and Xander Tielens for discussions of chemical processes in disks and David and Xander for helpful comments on our manuscript.
Funders:
Funding AgencyGrant Number
NSFAST-0507423
NASANNG06GF88G
NASA1322305
Subject Keywords:The gas-phase chemistry of water in protoplanetary disks is analyzed with a model based on X-ray heating and ionization of the disk atmosphere. Several uncertain processes appear to play critical roles in generating the column densities of warm water that are detected from disks at infrared wavelengths. The dominant factors are the reactions that form molecular hydrogen, including formation on warm grains, and the ionization and heating of the atmosphere. All of these can work together to produce a region of high water abundances in the molecular transition layer of the inner disk atmosphere, where atoms are transformed into molecules, the temperature drops from thousands to hundreds of Kelvins, and the ionization begins to be dominated by the heavy elements. Grain formation of molecular hydrogen and mechanical heating of the atmosphere can play important roles in this region and directly affect the amount of warm water in protoplanetary disk atmospheres. Thus, it may be possible to account for the existing measurements of water emission from T Tauri disks without invoking transport of water from cooler to warmer regions. The hydroxyl radical OH is underabundant in this model of disk atmospheres and requires consideration of additional production and excitation processes.
Record Number:CaltechAUTHORS:20090808-142505220
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20090808-142505220
Official Citation:Formation of Water in the Warm Atmospheres of Protoplanetary Disks A. E. Glassgold, R. Meijerink, and J. R. Najita 2009 ApJ 701 142-153 doi: 10.1088/0004-637X/701/1/142
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14906
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:01 Sep 2009 23:19
Last Modified:27 Mar 2014 04:27

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