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C. E. Groppi, G. H. Rieke (Steward Observatory)
A popular unified model for AGNs hypothesizes that their central engines consist of a central super-massive black hole surrounded by a parsec sized accretion disk. Seyfert 1 and Seyfert 2 nuclei are observed in different directions relative to this universal geometry. We present analysis of multi-band photometric data of a sample of 73 Seyfert 1 and Seyfert 2 galaxies that calls this standard AGN model for Seyfert 2s into question. Correlations of 8.4 GHz radio, [OIII] and N band infrared data made with both small and large apertures point toward the conclusion that the thermal infrared emission does not emanate from a parsec sized accretion disk in the nucleus of the galaxy, but is produced much farther away from the nucleus. We show that the existing N band flux should be easily accounted for by the amount of interstellar dust one would expect given the [OIII] line intensities, a standard gas to dust ratio and solar abundances. This flux is probably augmented by mid infrared emission from dust heated by circumnuclear star formation. We believe that the infrared excess in Seyfert 1s is the result of an accretion disk, since our data shows that the nuclear mid infrared emission is strongly correlated with the nuclear [OIII] flux. Thus, the parsec sized accretion disk model can explain Seyfert 1 galaxies, but Seyfert 2 objects are different, not the identical type of object with a different viewing geometry.
The author(s) of this abstract have provided an email address for comments about the abstract: cgroppi@as.arizona.edu