Detection of CH4 in the GV TAU N protoplanetary disk

Abstract

T Tauri stars are low mass young stars that may serve as analogs to the early solar system. Observations of organic molecules in the protoplanetary disks surrounding T Tauri stars are important for characterizing the chemical and physical processes that lead to planet formation. Searches for undetected molecules, particularly in the inner, planet forming regions of these disks are important for testing protoplanetary disk chemical models and for understanding the evolution of volatiles through the star and planet formation process. We used NIRSPEC on Keck 2 to perform a high resolution (λ/Δλ ∼ 25,000) L-band survey of T Tauri star GV Tau N. This object is one of two in which the simple organic molecules HCN and C2 H2 have been reported in absorption in the warm molecular layer of the protoplanetary disk. In this Letter, we report the first detection of methane, CH4, in a protoplanetary disk. Specifically, we detected the ν3 band in absorption. We determined a rotational temperature of 750 ± 50 K and column density of (2.8 ± 0.2) × 1017 cm-2. Our results imply that CH4 originates in the warm molecular layer of the inner protoplanetary disk. © 2013. The American Astronomical Society. All rights reserved.