The molecular content of the DMTau and GGTau disks

We report the detection of CN, HCN, HNC, CS, HCO+, C2H and H2CO (ortho and para) in the protoplanetary disks of DM Tau and GG Tau. For the first time organic molecules are observed in objects representative of the presolar nebula. These molecules are underabundant with respect to the standard dense clouds. The depletions in the “outer” disk of DM Tau (100 < r < 900 AU), derived from the line intensities and state of excitation, range from f ' 5 (for CO) to 100 (for H2CO). The relatively large abundances of CN and C2H are typical of a photon-dominated chemistry.