High-Resolution Mid-Infrared Imaging and Astrometry of the Nucleus of the Seyfert Galaxy NGC 1068

Abstract

We have used the Goddard Infrared Array Camera to obtain a high resolution (0.7" FWHM) image of the nucleus of NGC 1068 at 12.4 microns. The location of the 12.4 micron peak relative to the peak of the optical continuum has also been determined. The brightest part of the infrared nuclear peak is found to be elongated almost N-S (P.A. ~8^deg^), with an extent (corrected for instrumental blurring) ~0.6" FWHM (45 pc). Fainter resolved structure in the deconvolved image extends ~2" (150 pc) to the NE (P.A. ~30^deg^) and probably ~1.5" (110 pc) to the SW (P.A.~200^deg^). Approximately half of the nuclear 12.4 micron flux comes from this extended component. The distribution of 12.4 micron emission is correlated with both the [O II] λ5007 "ionization cone" and the optical continuum emission imaged by HST, and it aligns perpendicular to the plane of a putative molecular torus. The morphology of the extended emission could be accounted for in terms of scattering of nuclear radiation by an extended electron cloud along the torus axis, but the observed polarization is both too low and in the wrong direction for this model. We suggest instead that the extended mid-infrared emission is thermal radiation from dust in circumnuclear clouds heated by the collimated optical/UV AGN source Some or all of the unresolved 12.4 micron emission may still originate from the torus. The infrared emission peak is found to be 0.3" (20 pc) +/- 0.15" south of the optical continuum peak, and it coincides with the apex of the ionization cone, the presumed location of the torus. The observed displacement between the optical continuum and the mid-infrared peaks is similar to that predicted by Miller, Goodrich, & Mathews (1991) for the separation of the electron scattering zone from the nuclear optical/UV source.