Modeling IR Spectral Energy Distributions: A Pilot Study of Starburst
  Parameters and Silicate Absorption Curves for Some GOALS Galaxies
  This paper describes a pilot study into the spectral energy distribution
(SED) fitting and the derivation of physical parameters for 19 galaxies
observed as part of the Great Observatories All-sky LIRG Survey (GOALS) survey
as observed with the \emph{Spitzer Space Telescope}. For this we have used the
pan-spectral fitting tools developed in a series of papers by Dopita and his
co-workers. We show that the standard Lee and Draine `astronomical silicate'
model cannot provide a good fit to the silicate absorption features as observed
in the heavily dust-extinguished ($A_{\rm V} \sim 50$mag.) starbursts. We have
derived an empirical fit to the `starburst silicate' absorption in these
objects. This absorption curve is consistent with the silicate grains being
systematically larger in starburst environments than in the local Galactic
interstellar medium. We demonstrate the sensitivity of the SED fitting to each
of the fitted parameters, and derive these parameters for those galaxies which
do not have an embedded AGN. This technique is simple and provides reasonably
robust and uniform parameters for the starburst, especially as far as the star
formation rate, population of old stars, compactness of the starburst region
and total foreground extinction are concerned. However, the chemical abundances
and the optical extinction cannot be reliably determined by this analysis, and
optical SEDs will also be required to provide a complete characterization of
the starburst region and of the surrounding galaxy.
