Polar Dust, Nuclear Obscuration and IR SED Diversity in Type-1 AGNs
  Despite the hypothesized similar face-on viewing angles, the infrared
emission of type-1 AGNs has diverse spectral energy distribution (SED) shapes
that deviate substantially from the well-characterized quasar templates.
Motivated by the commonly-seen UV-optical obscuration and the discovery of
parsec-scale mid-IR polar dust emission in some nearby AGNs, we develop
semi-empirical SED libraries for reddened type-1 AGNs built on the quasar
intrinsic templates, assuming low-level extinction caused by an extended
distribution of large dust grains. We demonstrate that this model can reproduce
the nuclear UV-to-IR SED and the strong mid-IR polar dust emission of NGC 3783,
the type-1 AGN with the most relevant and robust observational constraints. In
addition, we compile 64 low-$z$ Seyfert-1 nuclei with negligible mid-IR star
formation contamination and satisfactorily fit the individual IR SEDs as well
as the composite UV to mid-IR composite SEDs. Given the success of these fits,
we characterize the possible infrared SED of AGN polar dust emission and
utilize a simple but effective strategy to infer its prevalence among type-1
AGNs. The SEDs of high-$z$ peculiar AGNs, including the extremely red quasars,
mid-IR warm-excess AGNs, and hot dust-obscured galaxies, can be also reproduced
by our model. These results indicate that the IR SEDs of most AGNs, regardless
of redshift or luminosity, arise from similar circumnuclear torus properties
but differ mainly due to the optical depths of extended obscuring dust
components.
