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 Title: 

            High-Resolution Near Infrared Spectroscopy of Circumstellar CO around Young Stars

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 Authors:

          Sean Brittain, NOAO

          Terrence W. Rettig, University of Notre Dame

          Craig Kulesa, University of Arizona

          Theodore Simon, University of Hawaii

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 Abstract:

          Gas in the inner 50AU of a young protoplanetary disk comprises most of the mass of the disk and subsequent planets, but it is not clear if gas survives long enough, with sufficient density, to make current theories of planet formation viable. Recent interferometric observations of circumstellar disks have generated useful measurements of the inner radii of the disks. Coupled with the direct measures of H2 provided by the FEPS Spitzer Legacy Project, which provide a more robust measure of the total gas mass, these efforts will guide our understanding of circumstellar evolution.  High-resolution spectra of fundamental CO ro-vibrational lines complement both these observations by providing a sensitive probe of the distribution gas in the inner few AU. Ro-vibrational CO line emission provides the most sensitive probe of excited molecular gas in disks; its diverse excitation mechanisms can be disentangled spectroscopically and provide a unique view into the clearing of !

circumstellar matter due to radiation and planet formation. We present near infrared high-resolution spectra of CO from the circumstellar protoplanetary region around young stars. The spectra of disks in different evolutionary states are compared. We will discuss how the excitation mechanism of the gas can shed light on the evolution of the disk and the implications this might have for planetary formation scenarios.

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