Title: The origin of the silicate emission in a type 2 AGN
Author(s): R. Mason, N. Levenson, Y. Shi, C. Packham, V. Gorjian, K. Cleary, J. Rhee, M. Werner
Abstract:

We use high spatial resolution IR data to investigate the origin of the unexpected silicate emission in a Seyfert 2 AGN. The unified model of AGN predicts silicate emission features at 10 and 18 Êm in type 1 AGNs, and such features have now been observed in objects ranging from distant quasars to nearby LINERs. More surprising, however, is the detection of the silicate features in emission in several type 2 AGN. In NGC 2110, the closest known type 2 AGN with silicate emission features, mid-IR imaging and spectroscopy enable us to set tight constraints on the location of the emitting material (within 32 pc of the nucleus). This is consistent with a narrow-line region origin for the silicate emission, but clumpy torus model fits to the data show that the emission features may in fact arise in an edge-on torus. Many questions remain regarding the chemistry, structure and origin of the AGN torus, and the true extent of its role in unifying the various classes of AGN. Measurements such as these, on small spatial scales, remain essential to characterising the structures in the cores of active galaxies.