A (CO)-C-13 (J=1-0) search for small molecular clouds toward the Chamaeleon-Musca Dark Cloud Complex

We have completed a (CO)-C-13 (J = 1-0) survey for molecular clouds toward the Chamaeleon-Musca Dark Cloud Complex, covering an similar to 16 degrees x 17 degrees area with the NANTEN millimeter-wave telescope. The major resu lt is a discovery of 25 small dense clouds widely distributed over similar to 11 degrees x 13 degrees (similar to 28 x 33 pc at similar to 140 pc), in addition to the four previously known large dark clouds. The small clouds show a good spatial correlation with the 33 isolated X-ray-emitting T Tauri stars (TTSs), and most (similar to 70%) of the 33 TTSs located within 4 pc of the small clouds' boundaries are likely formed in the small clouds. It is argued that the average density, greater than or similar to 10(3) cm(-3) , and mass, similar to 20 M-., of the small clouds are large enough to form stars in them. The apparent lack of the associated molecular gas for the r emaining TTSs is plausibly explained as a result of cloud dissipation due t o the outflow activity of the X-ray TTSs. Based on the present findings, we conclude that the X-ray TTSs were formed in the small dense clouds and tha t it is not necessary to invoke a runaway TTS hypothesis.