Primordial mass segregation in simulations of star formation?
  We take the end result of smoothed particle hydrodynamics (SPH) simulations
of star formation which include feedback from photoionisation and stellar winds
and evolve them for a further 10Myr using $N$-body simulations. We compare the
evolution of each simulation to a control run without feedback, and to a run
with photoionisation feedback only. In common with previous work, we find that
the presence of feedback prevents the runaway growth of massive stars, and the
resulting star-forming regions are less dense, and preserve their initial
substructure for longer. The addition of stellar winds to the feedback produces
only marginal differences compared to the simulations with just photoionisation
feedback.
  We search for mass segregation at different stages in the simulations; before
feedback is switched on in the SPH runs, at the end of the SPH runs (before
$N$-body integration) and during the $N$-body evolution. Whether a simulation
is primordially mass segregated (i.e. before dynamical evolution) depends
extensively on how mass segregation is defined, and different methods for
measuring mass segregation give apparently contradictory results. Primordial
mass segregation is also less common in the simulations when star formation
occurs under the influence of feedback. Further dynamical mass segregation can
also take place during the subsequent (gas-free) dynamical evolution. Taken
together, our results suggest that extreme caution should be exercised when
interpreting the spatial distribution of massive stars relative to low-mass
stars in simulations.
