We present new large field observations of molecular clouds with NANTEN2 toward the super star cluster NGC3603 in the transitions 12 CO(J=2-1, J=1-0) and 13 CO(J=2-1, J=1-0). We suggest that two molecular clouds at 13 km s −1 and 28 km s −1 are associated with NGC3603 as evidenced by higher temperatures toward the H II region as well as morphological correspondence. The mass of the clouds is too small to gravitationally bind them, given their relative motion of ∼20 km s −1 . We suggest that the two clouds collided with each other a Myr ago to trigger the formation of the super star cluster. This scenario is able to explain the origin of the highest mass stellar population in the cluster which is as young as a Myr and is segregated within the central sub-pc of the cluster. This is the second super star cluster along side Westerlund2 where formation may have been triggered by a cloud-cloud collision. Subject headings: ISM: clouds -open clusters and associations -individual: (NGC3603)the large turbulence excited by the shock interaction. This is the second case of formation of a super star cluster by triggering in a cloud-cloud collision along side Westerlund2 NANTEN2 is an international collaboration of ten universities, Nagoya University,

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A large-scale study of the molecular clouds toward the Trifid nebula, M20, has been made in the J=2-1 and J=1-0 transitions of 12 CO and 13 CO. M20 is ionized predominantly by an O7.5 star HD164492. The study has revealed that there are two molecular components at separate velocities peaked toward the center of M20 and that their temperatures -30-50 K as derived by an LVG analysis -are significantly higher than the 10 K of their surroundings.We identify that the two clouds as the parent clouds of the first generation stars in M20. The mass of each cloud is estimated to be ∼ 10 3 M ⊙ and their separation velocity is ∼ 8 km s −1 over ∼1-2 pc. We find the total mass of stars and molecular gas in M20 is less than ∼ 3.2 × 10 3 M ⊙ , which is too small by an order of magnitude to gravitationally bind the system. We argue that the formation of the first generation stars, including the main ionizing O7.5 s tar, was triggered by the collision between the two clouds in a short time scale of ∼1 Myrs, a second example alongside Westerlund 2, where a super star cluster may have been formed due to cloud-cloud collision triggering. Subject headings: ISM: clouds -Radio lines: ISM -open clusters and associations: individual: M20NANTEN2 is an international collaboration of ten universities, Nagoya University,

Furukawa et al. (2009) reported the existence of a large mass of molecular gas associated with the super star cluster Westerlund 2 and the surrounding HII region RCW49, based on a strong morphological correspondence between NAN-TEN2 12 CO(J=2-1) emission and Spitzer IRAC images of the HII region. We here present temperature and density distributions in the associated molecular gas at ∼3.5 pc resolution, as derived from an LVG analysis of the 12 CO(J=2-1), 12 CO(J=1-0) and 13 CO(J=2-1) transitions. The kinetic temperature is as high as ∼60-150 K within a projected distance of ∼5-10 pc from Westerlund 2 and decreases to as low as ∼10 K away from the cluster. The high temperature provides robust verification that the molecular gas is indeed physically associated with the HII region, supporting Furukawa et al.'s conclusion. The derived temperature is also roughly consistent with theoretical calculations of photo dissociation regions (PDRs), while the low spatial resolution of the present study does not warrant a more detailed comparison with PDR models. We suggest that the molecular clouds presented here will serve as an ideal laboratory to test theories on PDRs in future higher resolution studies. Subject headings: ISM: clouds -open clusters and associations: individual (Westerlund 2) -HII regions: individual (RCW 49)