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S. Brittain, T. Rettig (U. Notre Dame), T. Simon (U. Hawaii), C. Kulesa (U. Arizona), J. Haywood (U. Notre Dame)
To determine the nature of the disks around protostars, it is critical to obtain high-resolution spectral information that can be used to constrain the abundance and location of gas phase molecules prior to and during planetesimal formation. Theoretical models of disks predict that dust preferentially settles to the mid-plane, leaving behind a predominantly gaseous atmosphere at higher vertical scale heights. These theoretical predictions set the stage for models of planet formation -- but have not been observationally tested. The vertical distribution of dust and gas in disks can be assessed by simultaneous comparison of infrared CO absorption lines with infrared extinction. We will present results for 12CO, 13CO, and C18O line absorption in several young disks. The absorbing gas is determined to be cool and located at larger radii, where the line of sight apparently intersects the flared portion of the disk(s). Interestingly, the dust extinction is insufficient to explain the very large columns of absorbing gas. The most straightforward interpretation of the existing data would confirm the stratification of dust and gas in circumstellar disks as predicted by theoretical models.
This work was supported by NSF Astronomy grant 02-05881. Data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.