2007A&A...461..983V

We characterize the molecular environment of classical T Tauri stars in Lupus observed with the Spitzer Space Telescope in our search for gas-rich disks toward these sources. Submillimeter observations of ¹²CO, ¹³CO, and C¹⁸O in the J=3-2 and 2-1 lines were obtained with the James Clerk Maxwell Telescope toward a sample of 21 T Tauri stars with disks in the Lupus molecular clouds. Pointings at the sources and at selected off-positions are presented in order to disentangle material associated with disks from ambient cloud material. One source, IM Lup (Sz 82), was found with the double-peaked ¹²CO and ¹³CO profiles characteristic of a large rotating gas disk. The inclination of the disk is found to be ∼20°, with an outer radius of 400-700AU. For most other sources, including GQ Lup with its substellar companion, the single-dish ¹²CO lines are dominated by extended cloud emission with a complex velocity structure. No evidence of molecular outflows is found. Due to dense circumstellar material, compact C¹⁸O emission was detected toward only two sources. Future searches for gas-rich disks in Lupus should either use interferometers or perform very deep single-dish integrations in dense gas tracers to separate the cloud and disk emission.