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 resulting in higher accretion rates at early times as
compared to the collapse of virialized cores that have the same physical
properties. In contrast, we find that virialized cores undergo a slower,
gradual collapse and significant turbulent fragmentation at early times
resulting in numerous companion stars. In the absence of strong magnetic fields
and protostellar outflows we find that 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. Regardless of initial
condition, we find that the massive accretion disks that form around massive
stars dominant the accretion flow onto the star at late times and eventually
become gravitationally unstable and fragment to form companion stars at late
times.
