The Emission and Distribution of Dust of the Torus of NGC 1068

Abstract

Abstract We present observations of NGC 1068 covering the 19.7–53.0 μ m wavelength range using FORCAST and HAWC+ on board SOFIA. Using these observations, high-angular-resolution infrared (IR) and submillimeter observations, we find an observational turnover of the torus emission in the 30–40 μ m wavelength range with a characteristic temperature of 70–100 K. This component is clearly different from the diffuse extended emission in the narrow line and star formation regions at 10–100 μ m within the central 700 pc. We compute 2.2–432 μ m 2D images using the best inferred clumpy torus model based on several nuclear spectral energy distribution (SED) coverages. We find that when 1–20 μ m SED is used, the inferred result gives a small torus size (<4 pc radius) and a steep radial dust distribution. The computed torus using the 1–432 μ m SED provides comparable torus sizes, pc radius, and morphology to the recently resolved 432 μ m Atacama Large Millimeter Array observations. This result indicates that the 1–20 μ m wavelength range is not able to probe the full extent of the torus. The characterization of the turnover emission of the torus using the 30–60 μ m wavelength range is sensitive to the detection of cold dust in the torus. The morphology of the dust emission in our 2D image at 432 μ m is spatially coincident with the cloud distribution, while the morphology of the emission in the 1–20 μ m wavelength range shows an elongated morphology perpendicular to the cloud distribution. We find that our 2D clumpy torus image at 12 μ m can produce comparable results to those observed using IR interferometry.