Shape Analysis of HII Regions -- II. Synthetic Observations
  The statistical shape analysis method developed for probing the link between
physical parameters and morphologies of Galactic HII regions is applied here to
a set of synthetic observations (SOs) of a numerically modelled HII region. The
systematic extraction of HII region shape, presented in the first paper of this
series, allows for a quantifiable confirmation of the accuracy of the numerical
simulation, with respect to the real observational counterparts of the
resulting SOs. A further aim of this investigation is to determine whether such
SOs can be used for direct interpretation of the observational data, in a
future supervised classification scheme based upon HII region shape. The
numerical HII region data was the result of photoionisation and radiation
pressure feedback of a 34 Msun star, in a 1000 Msun cloud. The SOs analysed
herein comprised four evolutionary snapshots (0.1, 0.2, 0.4 and 0.6 Myr), and
multiple viewing projection angles. The shape analysis results provided
conclusive evidence of the efficacy of the numerical simulations. When
comparing the shapes of the synthetic regions to their observational
counterparts, the SOs were grouped in amongst the Galactic HII regions by the
hierarchical clustering procedure. There was also an association between the
evolutionary distribution of regions and the respective groups. This suggested
that the shape analysis method could be further developed for morphological
classification of HII regions by using a synthetic data training set, with
differing initial conditions of well-defined parameters.
