Dust in the polar region as a major contributor to the IR emission of
  AGN
  (abridged) It is generally assumed that the distribution of dust on parsec
scales forms a geometrically- and optically-thick entity in the equatorial
plane around the accretion disk and broad-line region - dubbed "dust torus" -
that emits the bulk of the sub-arcsecond-scale IR emission and gives rise to
orientation-dependent obscuration. Here we report detailed interferometry
observations of the unobscured (type 1) AGN in NGC 3783 that allow us to
constrain the size, elongation, and direction of the mid-IR emission with high
accuracy. The mid-IR emission is characterized by a strong elongation toward
position angle PA -52 deg, closely aligned with the polar axis (PA -45 deg). We
determine half-light radii along the major and minor axes at 12.5 {\mu}m of
(4.23 +/- 0.63) pc x (1.42 +/- 0.21) pc, which corresponds to
intrinsically-scaled sizes of (69.4 +/- 10.8) rin x (23.3 +/- 3.5) rin for the
inner dust radius of rin = 0.061 pc as inferred from near-IR reverberation
mapping. This implies an axis ratio of 3:1, with about 60-90% of the 8-13
{\mu}m emission associated with the polar-elongated component. These
observations are difficult to reconcile with the standard interpretation that
most of the parsec-scale mid-IR emission in AGN originates from the torus and
challenges the justification of using simple torus models to model the
broad-band IR emission. It is quite likely that the hot-dust emission in NGC
3783 as recently resolved by near-IR interferometry is misaligned with the
mid-IR emitting source, which also finds a correspondence in the two distinct
3-5 {\mu}m and 20 {\mu}m bumps seen in the high-angular resolution spectral
energy distribution (SED). We conclude that these observations support a
scenario where the majority of the mid-IR emission in Seyfert AGN originates
from a dusty wind in the polar region of the AGN.
