No preferential spatial distribution for massive stars expected from
  their formation
  We analyse N-body and Smoothed Particle Hydrodynamic (SPH) simulations of
young star-forming regions to search for differences in the spatial
distributions of massive stars compared to lower-mass stars. The competitive
accretion theory of massive star formation posits that the most massive stars
should sit in deeper potential wells than lower-mass stars. This may be
observable in the relative surface density or spatial concentration of the most
massive stars compared to other, lower-mass stars. Massive stars in
cool--collapse N-body models do end up in significantly deeper potentials, and
are mass segregated. However, in models of warm (expanding) star-forming
regions, whilst the massive stars do come to be in deeper potentials than
average stars, they are not mass segregated. In the purely hydrodynamical SPH
simulations, the massive stars do come to reside in deeper potentials, which is
due to their runaway growth. However, when photoionisation and stellar winds
are implemented in the simulations, these feedback mechanisms regulate the mass
of the stars and disrupt the inflow of gas into the clouds' potential wells.
This generally makes the potential wells shallower than in the control runs,
and prevents the massive stars from occupying deeper potentials. This in turn
results in the most massive stars having a very similar spatial concentration
and surface density distribution to lower-mass stars. Whilst massive stars do
form via competitive accretion in our simulations, this rarely translates to a
different spatial distribution and so any lack of primordial mass segregation
in an observed star-forming region does not preclude competitive accretion as a
viable formation mechanism for massive stars.
