High Resolution Spectroscopy of [NeII] Emission from AA Tau and GM Aur

TL;DR

This study uses high-resolution spectroscopy to analyze [NeII] emission from the disks of young stars GM Aur and AA Tau, revealing disk rotation as the primary origin and suggesting emission arises from larger radii than CO emission.

Contribution

First high-resolution spectroscopic analysis of [NeII] emission from these young stars, demonstrating disk rotation dominates line broadening and spatially extending the emission region.

Findings

[NeII] emission is centered near stellar velocity and broader than in face-on systems.

[NeII] emission likely originates from larger disk radii than CO emission.

Detected [NeII] equivalent width is less than that in previous Spitzer spectra.

Abstract

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.