The dust-gas AGN torus as constrained from X-ray and mid-infrared
  observations
  In the last decades, several multiwavelength studies have been dedicated to
exploring the properties of the obscuring material in active galactic nuclei
(AGN). Various models have been developed to describe the structure and
distribution of this material and constrain its physical and geometrical
parameters through spectral fitting techniques. However, questions, including
how the torus mid-infrared (mid-IR) and X-ray emission are related remain
unanswered. In this work, we study whether the dust continuum at mid-IR and gas
reflection at X-rays have the same distribution in a sample of AGN. We
carefully selected a sample of 36 nearby AGN with NuSTAR and Spitzer spectra
available in both archives. We derived the properties of the nuclear dust and
gas through a spectral fitting, using models developed for mid-IR and X-ray
wavelengths assuming smooth and clumpy distributions for this structure. We
found that a combination of smooth and clumpy distributions of gas and dust,
respectively, is preferred for ~80% of sources with good spectral fits
according to the Akaike criterion. However, considering extra information about
each individual source, such as the absorption variability, we found that ~50%
of our sources are best described by a clumpy distribution of both dust and
gas. The remaining ~50% of our sources can still be explained with a smooth
distribution of gas and a clumpy distribution of dust. The results presented in
this paper suggest that the distribution of the gas and dust in AGN is complex.
We find at least six scenarios to explain the observed properties of our
sample. In these scenarios, three gas-dust distribution combinations are
possible: clumpy-clumpy, smooth-smooth, and smooth-clumpy. Most of them are in
agreement with the notion that gas could also be located in the dust-free
region, which is consistent with the dust-to-gas ratio found.
