A Tale of Three Galaxies: A "Clumpy" View of the Spectroscopically
  Anomalous Galaxies IRAS F10398+1455, IRAS F21013-0739 and SDSS J0808+3948
  We investigate the dust properties in three spectroscopically anomalous
galaxies (IRAS F10398+1455, IRAS F21013-0739 and SDSS J0808+3948). Their
Spitzer/IRS spectra are characterized by a steep ~5-8 micron emission
continuum, strong emission bands from polycyclic aromatic hydrocarbon (PAH)
molecules, and prominent 10 micron silicate emission. The steep ~5-8 micron
continuum and strong PAH emission features suggest the presence of starbursts,
while the silicate emission is indicative of significant heating from AGNs. The
simultaneous detection of these two observational properties has rarely been
reported on galactic scale. We employ the PAHFIT software to estimate their
starlight contributions, and the CLUMPY model for the components contributed by
the AGN tori. We find that the CLUMPY model is generally successful in
explaining the overall dust infrared emission, although it appears to emit too
flat at the ~5-8 micron continuum to be consistent with that observed in IRAS
F10398+1455 and IRAS F21013-0739. The flat ~5-8 micron continuum calculated
from the CLUMPY model could arise from the adopted specific silicate opacity of
Ossenkopf et al. (1992) which exceeds that of the Draine & Lee (1984)
"astronomical silicate" by a factor up to 2 in the ~5-8 micron wavelength
range. Future models with a variety of dust species incorporated in the CLUMPY
radiation transfer regime are needed for a thorough understanding of the dust
properties of these spectroscopically anomalous galaxies.
