Massive Star Formation via the Collapse of Subvirial and Virialized Turbulent Massive Cores

Similar to their low-mass counterparts, massive stars likely form via the collapse of pre-stellar molecular cores. Recent observations suggest that most massive cores are subvirial (i.e., not supported by turbulence) and therefore are likely unstable to gravitational collapse. Here we perform radiation hydrodynamic simulations to follow the collapse of turbulent massive pre-stellar cores with subvirial and virialized initial conditions to explore how their dynamic state affects the formation of massive stars and core fragmentation into companion stars. We find that subvirial cores undergo rapid monolithic collapse and no fragmentation resulting in massive stars greater in mass as compared to those produced from the collapse of virialized cores that have the same physical properties. In contrast, we find that virialized cores undergo a slower, gradual collapse and turbulent fragmentation at early times resulting in numerous companion stars. We find that in the absence of strong magnetic fields the faster growth rate of massive stars that are born out of subvirial cores leads to an increase in the radiative heating of the core thereby further suppressing fragmentation at early times when turbulent fragmentation occurs for virialized cores. Our results suggest that the most massive stars likely form from the rapid collapse of subvirial cores whereas massive stars born with a large number of companion stars likely form from the slow collapse of highly turbulent cores.