A large scale (CO)-C-12 (J=1-0) survey toward the Chamaeleon region with NANTEN

We carried out a large-scale survey for molecular clouds in (CO)-C-12 (J = 1-0) emission toward the Chamaeleon region with the NANTEN 4-meter radio telescope at Las Campanas Observatory in Chile. The survey covered similar to 491 deg(2) toward 284degrees less than or similar to l less than or similar to 320degrees and -34degrees less than or similar to b less than or similar to -6degrees at an 8' grid spacing. The total molecular mass in the observed area is estimated to be similar to 8300 M.. More than 60% of the total mass is concentrated in and around the previously known Cha 1, 11, and III dark clouds. Two cloud complexes having molecular hydrogen masses of similar to 430 M. and similar to 1300 M., respectively, have been found at similar to 10degrees galactic-east of the Chamaeleon major clouds. We have identified a prominent filament extending from Cha I to the galactic-cast direction, which is remarkably long (greater than or similar to 40 pc) compared with filamentary features found in other dark-cloud complexes. A correlation study between the CO distribution and isolated X-ray emitting T Tauri stars (TTSs) indicates that greater than or similar to 65% of the TTSs are located within I pc of the (CO)-C-12 cloud boundaries. This suggests that low-density parental molecular gas still remains around the isolated TTSs, although the dense parts with density greater than 10(3) cm(-3) have almost dissipated. This provides further support for the local formation of isolated T Tauri stars in small clouds.