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Paper: Detection of Hidden Starburst in Active Galactic Nuclei by Means of Near-Infrared Spectroscopy
Volume: 408, The Starburst−AGN Connection
Page: 203
Authors: Rodríguez-Ardila, A.; Riffel, R.; Pastoriza, M.G.; Maraston, C.; Carvalho, E.A.
Abstract: We report results of an ongoing work aimed at developing robust diagnostics for the presence of hidden starburst in active galactic nuclei (AGN) by means of both the underlying near-infrared (NIR) continuum and the line emission spectrum. We found that the 1.1 μm CN absorption band can be taken as unambiguous evidence of young/intermediate stellar populations (SPs). This is confirmed by the analysis of the SPs in four starburst galaxies displaying prominent CN absorption. The spectra are best explained by stellar templates containing a sizable amount (20% to 56% by mass) of 1 Gyr old stars at the Thermally Pulsing-Asymptotic Giant Branch phase. Diagnostic diagrams involving emission line ratios in the NIR were also tested with the goal of separating objects according to the level of nuclear activity. [Fe II] 1.257μm/Paβ vs H2 2.121μm/Brγ and [S III] 0.953μm/Paβ vs He I 1.083μm/Paβ successfully separate starbursts from AGNs and LINERs. They are proposed as useful tools to find out hidden starburst activity.
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