Deep Submillimeter Imaging of Dust Structures in Centaurus A

Images covering the central 450'' × 100'' (~8.0 kpc × 2.0 kpc) of NGC 5128 (Centaurus A) obtained using SCUBA at 850 and 450 μm with beam sizes of 14.″5 and 8'', respectively, are presented. These data are compared with those obtained at other wavelengths, in particular the optical, mid-infrared, and far-infrared continuum. The sensitive 850 and 450 μm images show that the submillimeter (submm) continuum morphology and spectral index distribution of Centaurus A comprise four regions: an unresolved AGN core, an inner jet interacting with gas in the dust lane, an inner disk of radius ~90'', and colder outer dust. The inner disk has a high surface brightness, reverse-S-shaped feature in the 850 and 450 μm images that coincides with the regions of intense 7 and 15 μm continuum and a region of active star formation. The infrared (IR) and submm images seem to reveal the same material as predicted by a geometric warped-disk model consisting of tilted rings. We suggest that this scenario is more plausible than that recently proposed in literature, in which the mid-IR emission in Centaurus A is primarily from a bar with a structure that is different from the extended warped disk alone. A dust mass total of 2.2 × 106 M☉ has been calculated within a radius of 225'', 45% of which is in the star-forming region of radius ~90'' about the nucleus.