Protostars and Planets VI, Heidelberg, July 15-20, 2013

Poster 2S022

Molecular Line Surveys of Nearby T Tauri Stars: Late-time Chemistry of Protoplanetary Disks

Kastner, Joel (Rochester Inst. of Technology, Rochester, NY, USA)
Punzi, Kristina (Rochester Inst. of Technology, Rochester, NY, USA)
Rodriguez, David (Universidad de Chile)
Sacco, G. Germano (Arcetri Observatory, Italy)
Hily-Blant, Pierre (IPAG, France)
Forveille, Thierry (IPAG, France)
Zuckerman, Ben (UCLA, USA)

We have conducted mm-wave molecular line surveys of the evolved, irradiated circumstellar disks orbiting the nearby, roughly solar-mass, pre-main sequence (T Tauri) stars TW Hya, V4046 Sgr, T Cha, and LkCa 15. All four are transition disk systems with relatively advanced ages (5-12 Myr), yet display spectral signatures of ongoing stellar accretion. Our radio spectral line surveys were performed with the APEX 12 meter and IRAM 30 meter telescopes. In the cases of the TW Hya, V4046 Sgr, and LkCa 15 disks -- all of which are known to retain significant residual gaseous components, as evidenced by previous radio and infrared detections of molecular and atomic emission lines -- we performed unbiased broad-band observations intended to yield a complete census of bright mm-wave emission lines. Initial results from these survey data include first-time detections of the molecules CCH (in TW Hya and V4046 Sgr) and CS (in all three disks), as well as complete coverage of hyperfine transitions of CN and CCH. In the case of T Cha, we have obtained the first direct detection of its rotating, gaseous disk, in the form of double-peaked emission lines of CO and lines of HCN, CN, and HCO+. Our line survey results thereby provide new constraints on models describing late-stage disk protoplanetary gas dissipation and chemical evolution, and point out future directions for ALMA imaging of these and other, similarly resolvable T Tauri star disks.

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