Cluster formation induced by a cloud--cloud collision in [DBS2003]179.

[DBS2003]179 is a super star cluster in the Galaxy discovered by deep near infrared observations. We carried out CO J=1-0 and J=3-2 observations of the region of [DBS2003]179 with NANTEN2, ASTE and the Mopra 22m telescope. We identified and mapped two molecular clouds which are likely associated with the cluster. The association is evidenced by the spatial correlation with the 8 micron Spitzer image, and a high ratio of the two transitions of 12CO (J=3-2 to J=1-0). The two clouds show complementary distribution in space and bridge features connecting them in velocity. We frame a hypothesis that the two clouds collided with each other 1-2 Myr ago, and the collision compressed the interface layer, triggering the formation of the cluster. This offers an additional piece of evidence for a super star cluster formed by cloud--cloud collision alongside of the four super star clusters including Wd2, NGC3603, RCW38 and R136. The findings indicate that the known super star clusters having closely associated dust emission are formed by cloud-cloud collision, lending support for the important role of cloud--cloud collision in high-mass star formation.