The 8-13 microns (mid-IR) spectral range has proven to be exceptionally rich in spectral features that can be used to characterize the dust emission properties of active galactic nuclei (AGN). At longer wavelengths (> 20 microns), the moderate angular resolution (>10 arcsec) observations available by space-based telescopes have made the characterization of nearby AGN very challenging. This is because of the large contribution of the host galaxy at longer wavelengths and the difficulties to isolate the AGN emission from other components within these moderate angular resolution observations. From the ground, IR observations at wavelengths > 20 microns are impossible due to the atmosphere. Thus, the cold dust of the torus is poorly constrained as well as the turn-over of the torus emission. The Stratospheric Observatory For Infrared Astronomy (SOFIA) has opened a new window to explore AGN in the range of 20-300 microns with angular resolution < 10arcsec. We here present newly 20-53 um imaging observations using FORCAST and HAWC+ onboard SOFIA of NGC 1068 that, in conjunction with high-angular resolution 1-13 um and sub-mm observations, allow us to characterize the obscuring torus. Using CLUMPY torus models, we inferred the best torus model parameters and we computed 2D images of the dust emission and cloud distribution at several wavelengths from 2 to 432 um. We found that 1) the 1-20 um wavelength range solely is not able to probe the full extend of the torus; 2) the turn-over of the torus emission occurs in the 30-40 um which is sensitive to the detection of cold dust in the torus, and 3) the morphology of the dust emission in our 2D image at 432 um is spatially coincident with the cloud distribution of the torus using 432 um ALMA observations. We also found that the dust emission from our 2D clumpy torus image at 12 um shows an elongated morphology perpendicular to the cloud distribution, and can produce comparable results to those observed using IR interferometry.
The Dust and Cloud Distribution of the Torus of NGC 1068
Enrique Lopez Rodriguez
SOFIA Science Center