High-Resolution Mid-Infrared Imaging of the Nucleus of NGC 1068

Abstract

We have obtained mid-infrared images of the nucleus of NGC 1068 from the Hale 5 m telescope at Mount Palomar with diffraction-limited resolution and high sensitivity at λ=8.8, 10.3, and 12.5 μm. Deconvolved images show that the infrared emission extends north to south in the inner 2", consisting of a central peak, a component extending 1" north of the central source, a component extending 1" south of the central source, and several smaller structures located 1" to the northeast. The central peak is extended 0.4" N-S and unresolved (<=0.2") E-W. We find that 50%+/-5% of the flux emerges from the central 0.4" and that a single unresolved point source can account for only 27%+/-5% of the total flux. However, if the central peak arises from optically thick emission, we estimate that the emitting region has a projected area >=2 pc² and thus may contain a compact source such as a parsec-scale torus. We observe a correspondence between the northern extension and northeastern sources appearing on the mid-infrared images and the [O III] clouds A-C and E. We interpret the faint optical counterpart to the mid-infrared southern extension as being due to a partial obscuration by the intervening disk of the host galaxy. The N-S extension of the mid-infrared emission coincides with one wall of the conical narrow-line region and aligns with the N-S orientation of the radio jet close to the nucleus. We interpret the infrared emission as arising from the optically thick dust that lines the walls of the low-density cavity formed by the radio jet and heated by radiation from the central source.