Star Cluster Formation in Turbulent, Magnetized Dense Clumps with
  Radiative and Outflow Feedback
  We present three Orion simulations of star cluster formation in a 1000 Msun,
turbulent molecular cloud clump, including the effects of radiative transfer,
protostellar outflows, and magnetic fields. Our simulations all use
self-consistent turbulent initial conditions and vary the mean mass-to-flux
ratio relative to the critical value over 2, 10, and infinity to gauge the
influence of magnetic fields on star cluster formation. We find, in good
agreement with previous studies, that magnetic fields of typically observed
strengths lower the star formation rate by a factor of 2.4 and reduce the
amount of fragmentation by a factor of 2 relative to the zero-field case. We
also find that the field increases the characteristic sink particle mass, again
by a factor of 2.4. The magnetic field also increases the degree of clustering
in our simulations, such that the maximum stellar densities in the strong field
case are higher than the others by again a factor of 2. This clustering tends
to encourage the formation of multiple systems, which are more common in the
rad-MHD runs than the rad-hydro run. The companion frequency in our simulations
is consistent with observations of multiplicity in Class I sources,
particularly for the strong field case. Finally, we find evidence of primordial
mass segregation in our simulations reminiscent of that observed in star
clusters like the Orion Nebula Cluster.
