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

Similar to their low-mass counterparts, massive starslikely form via the collapse of pre-stellar molecular cores. Recent observations suggest that most massive coresare 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 coreswith subvirial and virialized initial conditions to explore how their dynamic state affects the formation of massive starsand corefragmentation into companion stars. We find that subvirial coresundergo rapid monolithic collapse and no fragmentation resulting in massive starsgreater in mass as compared to those produced from the collapse of virialized coresthat have the same physical properties. In contrast, we find that virialized coresundergo 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 starsthat are born out of subvirial coresleads to an increase in the radiative heating of the corethereby further suppressing fragmentation at early times when turbulent fragmentation occurs for virialized cores. Our results suggest that the most massive starslikely form from the rapid collapse of subvirial coreswhereas massive starsborn with a large number of companion starslikely form from the slow collapse of highly turbulent cores.