First results of a CO survey of the Large Magellanic Cloud with NANTEN; Giant molecular clouds as formation sites of populous clusters

A new survey of the LMC has been completed in 2.6 mm carbon monoxide emissi on with NANTEN. This survey has revealed 107 giant molecular clouds, the fi rst complete sample of giant molecular clouds in a single galaxy at a linea r resolution of similar to 40 pc. The cloud mass ranges from similar to 6 x 10(4) to 2 x 10(6) M., and the total molecular mass has been estimated to be 4-7 x 10(7) M. for a molecular column density of greater than or similar to 1.0 x 10(21) cm(-2), corresponding to 5-10% of the atomic mass. The mol ecular clouds exhibit a good spatial correlation with the youngest stellar clusters whose ages are less than or similar to 10 Myr, demonstrating that cluster formation is on-going in these clouds. On the other hand, they show little correlation with older clusters or with supernova remnants, suggest ing that the molecular clouds are being rapidly dissipated in several Myrs, probably due to the UV photons of massive stars in clusters.