Kinematics and Structure of Ionized Gas in the UCHII Regions of W33 Main
  High mass proto-stars create Ultra-Compact Hii regions (UCHII) at the stage
of evolution when most of the accretion is finished but the star is still
heavily embedded in molecular material. The morphologies of UCHII regions
reflect the interactions of stellar winds, stellar motions, and density
structure in the molecular cloud; they are complex and it has been very
difficult to interpret them. We here present data obtained with TEXES on the
NASA IRTF of the [NeII] emission line in the proto-cluster of young OB stars in
W33 Main. The data cube has a spatial resolution of ~ 1.4 arcsec and true
velocity resolution ~ 5 km/s; with A ~ 0.02Av it is relatively unaffected by
extinction. We have run 3D hydrodynamic and line profile simulations, using
PLUTO and RADMC-3D, of the gas structures created by multiple windy stars
moving relative to each other through the ambient cloud. By iterative
comparison of the data cube and the simulations, we arrive at models that
reproduce the different morphology and kinematic structure of each UCHII region
in W33 Main. The results indicate that each sub-source probably holds multiple
exciting stars, permitting an improved view of the stellar population, and
finds the stellar trajectories, which may determine the dynamical development
of the proto-cluster.
