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Paper: The Distribution of Silicate Strength of AGNs and ULIRGs
Volume: 373, The Central Engine of Active Galactic Nuclei
Page: 574
Authors: Hao, L.; Weedman, D.W.; Spoon, H.W.W.; Marshall, J.A.; Levenson, N.A.; Elitzur, M.; Houck, J.R.
Abstract: A sample of 196 AGNs and ULIRGs observed by the Infrared Spectrograph (IRS) on Spitzer is analyzed to study the distribution of the strength of the 9.7 μm silicate feature. Average spectra are derived for quasars, Seyfert 1 and Seyfert 2 AGNs, and ULIRGs. We find that quasars, Seyfert 2s and ULIRGs are characterized by silicate features in emission, weak absorption, and strong absorption, respectively, and Seyfert 1s equally by emission or weak absorption. The distributions of their spectral characteristics and luminosities are compared to those of optically faint infrared sources at z ~ 2 being discov- ered by the IRS. It is found that local ULIRGs are a similar population, with lower luminosities and somewhat stronger absorption. Refer to Hao et al. (2007) for more complete results.
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