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A. C. Quillen (Steward Observatory), A. Alonso-Herrero (U of Hertfordshire), A. Lee, G.H. Rieke (Steward Observatory)
We recently discovered that 100% and 50% of the Seyferts 1.0-1.9s and Seyfert 2s, respectively imaged by NICMOS on HST display unresolved continuum emission associated with an AGN. By compiling measurements from 0.5-10 microns we have measured spectral energy distributions of the CfA sample of Seyferts 2s. Half of these nuclei have spectral energy distributions intermediate between those expected from Seyfert 1 and Seyfert 2 nuclei. Because of the high opacities of the torus models a dichotomy of spectra is predicted and few are expected to have intermediate properties, in contradiction to our observations. With an obscuration model it is difficult to explain the coincidence that objects with unresolved 1.6 micron emission tend to display broad line components. We find that there is a good correlation between the hard X-ray and mid-IR luminosity, though this also is in contradiction to the highly orientation dependent torus models. Recent infrared spectra have shown that PAH emission features caused previous work to mis-interpret the older mid-IR spectra in terms of a strong silicate emission absorption feature. The torus models were incorrectly motivated to require high infrared opacities. To reconcile the contradictions posed by the torus models and the new observations we propose new class of models. The infrared emission arises from an unobscurred low opacity cone shaped region that is illuminated by the collimated central optical and UV radiation. The hotest dust illuminated is capable of reflecting the broad line region so that we would predict that intermediate Seyferts are more likely to have polarized optical continuum. The bulk of the energy escapes at 10-30 microns. We expect that counterparts to Chandra and XMM X-ray sources will be discovered with future mid-IR imaging programs.
The author(s) of this abstract have provided an email address for comments about the abstract: aquillen@as.arizona.edu