Deep Submillimeter Imaging of Dust Structures in Centaurus A

Abstract

Images covering the central 450 by 100 arcsecond (about 8.0 by 2.0 kpc) of NGC 5128 (Centaurus A) obtained using SCUBA at 850 and 450 micron with beam sizes of 14.5 and 8 arcsecond 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 micron 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 roughly 90 arcsecond, and colder outer dust. The inner disk has a high surface brightness, reverse-S-shaped feature in the 850 and 450 micron images that coincides with the regions of intense 7 and 15 micron continuum and a region of active star-formation. The infrared (IR) and submm images appear to reveal the same material as predicted by a geometric warped disk model consisting of tilted rings. We suggest this scenario is more plausible than that recently proposed in literature suggesting that 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 million solar masses has been calculated within a radius of 225 arcsecond, 45% of which is in the star-forming region of radius about 90 arcsecond about the nucleus.