Isotropic Mid-Infrared Emission from the Central 100 pc of Active
  Galaxies
  Dust reprocesses the intrinsic radiation of active galactic nuclei (AGNs) to
emerge at longer wavelengths. The observed mid-infrared (MIR) luminosity
depends fundamentally on the luminosity of the central engine, but in detail it
also depends on the geometric distribution of the surrounding dust. To quantify
this relationship, we observe nearby normal AGNs in the MIR to achieve spatial
resolution better than 100 pc, and we use absorption-corrected X-ray luminosity
as a proxy for the intrinsic AGN emission. We find no significant difference
between optically classified Seyfert 1 and 2 galaxies. Spectroscopic
differences, both at optical and IR wavelengths, indicate that the immediate
surroundings of AGNs is not spherically symmetric, as in standard unified AGN
models. A quantitative analysis of clumpy torus radiative transfer models shows
that a clumpy local environment can account for this dependence on viewing
geometry while producing MIR continuum emission that remains nearly isotropic,
as we observe, although the material is not optically thin at these
wavelengths. We find some luminosity dependence on the X-ray/MIR correlation in
the smallest scale measurements, which may indicate enhanced dust emission
associated with star formation, even on these sub-100 pc scales.
