1998ApJ...507L..83M

We have completed a ¹³CO (J=1-0) survey for molecular clouds toward the Chamaeleon-Musca Dark Cloud Complex, covering an ∼16°x17° area with the NANTEN millimeter-wave telescope. The major result is a discovery of 25 small dense clouds widely distributed over ∼11°x13° (∼28x33 pc at ∼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 (∼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, ≳10³ cm^–3, and mass, ∼20 M_☉, of the small clouds are large enough to form stars in them. The apparent lack of the associated molecular gas for the remaining TTSs is plausibly explained as a result of cloud dissipation due to 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 that it is not necessary to invoke a runaway TTS hypothesis.