Formation of young massive clusters from turbulent molecular clouds

We simulate the formation and evolution of young star clusters from turbulent molecular clouds using smoothed-particle hydrodynamics and direct N-body methods. We find that the shape of the cluster mass function that originates from an individual molecular cloud is consistent with a Schechter function with power-law slopes of β = -1.73. The superposition of mass functions turn out to have a power-law slope of < -2. The mass of the most massive cluster formed from a single molecular cloud with mass M _g scales with 6.1 M ^0.51 _g. The molecular clouds that tend to form massive clusters are much denser than those typical found in the Milky Way. The velocity dispersion of such molecular clouds reaches 20km s^-1 and it is consistent with the relative velocity of the molecular clouds observed near NGC 3603 and Westerlund 2, for which a triggered star formation by cloud-cloud collisions is suggested.