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Paper: High Resolution Millimeter-Wave to Infrared Spectroscopy of Circumstellar Disks
Volume: 324, Debris Disks and the Formation of Planets: A Symposium in Memory of Fred Gillett
Page: 79
Authors: Blake, G.A.
Abstract: The role of high spectral and spatial resolution spectroscopy in understanding the evolution of the gaseous component of circumstellar accretion disks is described. Millimeter-wave emission lines from trace constituents such as CO, CN, HCO+, and HCN can be used to probe the kinematic and physicochemical properties in the near-surface regions of disks beyond 100 AU, but, thanks to extensive molecular depletion in the midplane, they are not a reliable proxy for the disk mass. Mid-infrared observations of the pure rotational transitions of molecular hydrogen would alleviate many of these concerns, and results from the ISO SWS instrument on several "transitional" disks are presented. The measurements of these weak lines used beams substantially larger than the disk angular diameter, and so must be verified or refuted by high angular resolution spectroscopy from the ground. Finally, the high resolution M-band (5 μm) spectroscopy of CO in disks is outlined. Emission lines that are likely optically pumped by hot dust in the inner disk (R ≤ 1 AU) are seen toward inclined systems, while the absorption spectra of edge-on disks clearly reveal the molecular depletion inferred at millimeter-wavelengths.
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