The Physical Conditions in Starbursts Derived from Bayesian Fitting of
  Mid-IR SEDS: 30 Doradus as a Template
  To understand and interpret the observed Spectral Energy Distributions (SEDs)
of starbursts, theoretical or semi-empirical SED models are necessary. Yet,
while they are well-founded in theory, independent verification and calibration
of these models, including the exploration of possible degeneracies between
their parameters, are rarely made. As a consequence, a robust fitting method
that leads to unique and reproducible results has been lacking. Here we
introduce a novel approach based on Bayesian analysis to fit the Spitzer-IRS
spectra of starbursts using the SED models proposed by Groves et al. (2008). We
demonstrate its capabilities and verify the agreement between the derived best
fit parameters and actual physical conditions by modelling the nearby,
well-studied, giant HII region 30 Dor in the LMC. The derived physical
parameters, such as cluster mass, cluster age, ISM pressure and covering
fraction of photodissociation regions, are representative of the 30 Dor region.
The inclusion of the emission lines in the modelling is crucial to break
degeneracies. We investigate the limitations and uncertainties by modelling
sub-regions, which are dominated by single components, within 30 Dor. A
remarkable result for 30 Doradus in particular is a considerable contribution
to its mid-infrared spectrum from hot ({\simeq} 300K) dust. The demonstrated
success of our approach will allow us to derive the physical conditions in more
distant, spatially unresolved starbursts.
