Active galactic nucleus torus models and the puzzling infrared spectrum
  of IRAS F10214+4724
  We present a revised model for the infrared emission of the hyperluminous
infrared galaxy IRAS F10214+4724 which takes into account recent photometric
data from Spitzer and Herschel that sample the peak of its spectral energy
distribution. We first present and discuss a grid of smooth active galactic
nucleus (AGN) torus models computed with the method of Efstathiou &
Rowan-Robinson and demonstrate that the combination of these models and the
starburst models of Efstathiou and coworkers, while able to give an excellent
fit to the average spectrum of Seyfert 2s and spectra of individual type 2
quasars measured by Spitzer, fails to match the spectral energy distribution of
IRAS F10214+4724. This is mainly due to the fact that the nuSnu distribution of
the galaxy falls very steeply with increasing frequency (a characteristic that
is usually indicative of heavy absorption by dust) but shows a silicate feature
in emission. Such emission features are not expected in sources with
optical/near-infrared type 2 AGN spectral signatures. The Herschel data show
that there is more power emitted in the rest-frame 20-50um wavelength range
compared with the model presented by Efstathiou which assumes three components
of emission: an edge-on torus, clouds (at a temperature of 610 and 200K) that
are associated with the narrow-line region (NLR) and a highly obscured
starburst that dominates in the submillimetre. We present a revised version of
that model that assumes an additional component of emission which we associate
with NLR clouds at a temperature of 100K. The 100K dust component could also be
explained by a highly obscured hot starburst. The model suggests that the NLR
of IRAS F10214+4724 has an unusually high covering factor (>= 17%) or more
likely the magnification of the emission from the NLR clouds is significantly
higher than that of the emission from the torus.
