Contribution
Resolving the nuclear dust structure in Centaurus A
Presenter: Leonard Burtscher (Max-Planck-Institut für Astronomie)
Abstract: Interferometric observations in the mid-infrared made studies of the central dusty tori of Active Galactic Nuclei (AGNs) possible and proved their existence in a number of nearby AGNs. Our first results on Centaurus A (NGC 5128) showed that nuclear dust also exists in the innermost parsec of this galaxy (Meisenheimer et al. 2007). From new observations with an improved (u,v)-coverage and resolution, it is now possible to determine the size, orientation and the physical nature of the mid-infrared emitters in the nucleus more precisely. We find that the extended component that accounts for about half of the mid-IR emission has a size of 0.6 × 0.2 pc (FWHM) and is consistent with an inclined, disk-like dust structure. Its minor axis is oriented almost perfectly parallel to the radio jet. With a bolometric luminosity of Ldust ∼ 3 × 1034 W the disk is much less luminous than the nuclear dust emission from other nearby AGNs, e.g. the torus in the Seyfert 2 galaxy Circinus with Ldust ∼ 2 × 1036 W. The rest of the mid-IR emission of Centaurus A stems from an unresolved core, the radio-to-mid-infrared spectrum of which can be explained by synchrotron emission from the base of the jet.