Inter-cluster velocity structures of star cluster complexes

Star clusters are often born as star-cluster systems, which include several stellar clumps. Such star-cluster complexes could have formed from turbulent molecular clouds. Since Gaia Data Release 2 provided us high quality velocity data of individual stars in known star-cluster complexes, we now can compare the velocity structures of the observed star-cluster complexes with simulated ones. We performed a series of N-body simulations for the formation of star-cluster complexes starting from turbulent molecular clouds. We measured the inter-cluster velocity dispersions of our simulated star-cluster complexes and compared them with the Carina region and NGC 2264. We found that the Carina region and NGC 2264 formed from molecular clouds with a mass of ∼4 × 10⁵M_⊙ and ∼4 × 10⁴M_⊙, respectively. In our simulations, we also found that the maximum cluster mass (M_c,max) in the complex follows ${M_{{{c}},{{max}}}} = 0.{{2}}0M_g^{0.76}$, where M_g is the initial gas mass.