21 February 2003 Interferometric studies of nearby galactic centers
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Abstract
We discuss the potential of interferometric studies of nearby galactic nuclei with long-baseline interferometric facilities. Information on the morphology of galactic centers has so far been limited to angular sizes corresponding to the diffraction limit of 6-10 m class telescopes. Optical and near-infrared interferometry could in principle be used to reach significantly higher angular resolution, but has so far only been used for bright objects due to the small collecting areas of existing interferometers. Right now, the first interferometers consisting of 8-10 m class telescopes are starting operations and, hence, will soon allow us for the first time to study galactic centers on angular scales which are of an order of magnitude smaller than ever before, i.e. on scales corresponding to baselines of up to 100 m. We discuss these facilities and report on the observational techniques and strategies which are relevant for interferometric observations of these objects. We review imaging results of nearby galactic centers with highest angular resolution so far, with an emphasis on our bispectrum speckle interferometry studies of the core of the Seyfert galaxy NGC 1068. Employing these results, we analyze how near-infrared interferometry can discriminate between the different scenarios which are consistent with our current knowledge based on observations. In particular, characteristic sizes of the circumnuclear dusty torus can be derived with higher precision, additional dust components and the inner part of the jet can be identified, and radiative transfer models of the torus can be better constrained. Furthermore, the flux contribution of central source components can be separated from those of the torus, and thus they can be modeled in more detail. These investigations may ultimately result in a refinement of the unification scheme of galactic nuclei.
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Markus Wittkowski, Wolfgang Duschl, Karl-Heinz Hofmann, Alexander B. Men'shchikov, Gerd Weigelt, "Interferometric studies of nearby galactic centers", Proc. SPIE 4838, Interferometry for Optical Astronomy II, (21 February 2003); doi: 10.1117/12.457964; https://doi.org/10.1117/12.457964
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