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Paper: Buried AGNs in Nearby Ultraluminous Infrared Galaxies
Volume: 381, The Second Annual Spitzer Science Center Conference: Infrared Diagnostics of Galaxy Evolution
Page: 478
Authors: Imanishi, M.
Abstract: We present infrared L-band (3–4 μm) nuclear spectra of a large sample of nearby ultraluminous infrared galaxies (ULIRGs). Using the 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission and absorption features found at 3–4 μm, we search for signatures of optically elusive powerful active galactic nuclei (AGNs) deeply buried in dust in all directions. Among ULIRGs classified optically as “non-Seyfert”, the signatures of powerful buried AGNs are found in a much higher fraction of optical LINER ULIRGs than in HII-region ULIRGs. The evidence of AGNs is found in optical non-Seyfert ULIRGs with both warm and cool far-infrared colors. The overall spectral properties suggest that the total amount of dust around buried AGNs in optical non-Seyfert ULIRGs is systematically larger than that around AGNs in optical Seyfert 2 ULIRGs.
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