High Resolution Spectroscopy of [NeII] Emission from AA Tau and GM Aur
  We present high resolution (R=80,000) spectroscopy of [NeII] emission from
two young stars, GM Aur and AA Tau, which have moderate to high inclinations.
The emission from both sources appears centered near the stellar velocity and
is broader than the [NeII] emission measured previously for the face-on disk
system TW Hya. These properties are consistent with a disk origin for the
[NeII] emission we detect, with disk rotation (rather than photoevaporation or
turbulence in a hot disk atmosphere) playing the dominant role in the origin of
the line width. In the non-face-on systems, the [NeII] emission is narrower
than the CO fundamental emission from the same sources. If the widths of both
diagnostics are dominated by Keplerian rotation, this suggests that the [NeII]
emission arises from larger disk radii on average than does the CO emission.
The equivalent width of the [NeII] emission we detect is less than that of the
spectrally unresolved [NeII] feature in the Spitzer spectra of the same
sources. Variability in the [NeII] emission or the mid-infrared continuum, a
spatially extended [NeII] component, or a very (spectrally) broad [NeII]
component might account for the difference in the equivalent widths.
