Probing the Gas in Protoplanetary Disks with TEXES on Gemini-N

The [Ne II] line at 12.81 microns has been suggested as a potential new probe of the planet formation region of circumstellar disks. It is a potentially powerful diagnostic because the neon in disks is expected to be fully in the gas phase and in atomic form. In addition, the 12.81-micron line probes warm, ionized gas, conditions which are believed to characterize the upper atmosphere of the inner disks surrounding classical T Tauri stars (Glassgold et al. 2007) and disk photoevaporative flows (Alexander 2008). Because it is sensitive to low column densities of gas, [Ne II] may also prove useful in identifying any residual gas surrounding weak-line T Tauri stars. Such measurements can potentially probe the dissipation timescale of gaseous disks and, thereby, constrain the timescale for giant planet formation.