Super Star Cluster Formation via Cluster Collisions: N-body/SPH Simulations of SSC-N in II Zw 40

Super Star Clusters (SSCS) are thought to be the precursors of globular clusters and their formation is currently a mystery. Are the massive clusters observed today the result of single collapsing clumps, or are they assembled from multiple sub-clusters and sub-clouds? The bright embedded star cluster SSC-N in the post-collision dwarf starburst galaxy II Zw 40 is a good candidate for the model of sub-cluster assembly: high resolution JVLA maps of the supernebula excited by the SSC show intriguing spatial sub-structure, and a 3 km/s resolution spectral data cube of the [SIV] mid-infrared emission line finds two kinematically distinct, spatially co-extensive emission features. To test this possibility, we simulate collisions of two clusters using the AMUSE software framework, including 3D N-Body (ph4, BHTree), SPH (GADGET2), stellar evolution (SeBa) and stellar wind modules. We find a range of collision angles and impact parameters that can reproduce the observed HII structure and 3-D kinematics, supporting the sub-cluster assembly model for SSC-N. We plan further AMUSE simulations to test models for other young extra-galactic SSCs for which we have high resolution data.