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Paper: Redshift Dependence of AGN Activity in SMGs
Volume: 408, The Starburst−AGN Connection
Page: 457
Authors: Watabe, Y.; Risaliti, G.; Salvati, M.; Nardini, E.; Sani, E.; Marconi, A.
Abstract: To make clear the origin of energy source of Submillimeter and 24 μm-selected ULIRGs at high redshift (z = 1−3), we disentangle the active galactic nucleus (AGN) and starburst contributions by using the mid-infrared spectra observed with Spitzer-IRS spectrometer and the AGN/starburst decomposition model. We quantitatively estimate the average AGN contribution to the stacked 6-8 μm rest-frame spectra of these sources, and, under the assumption of similar infrared-to-bolometric ratios as in local ULIRGs, the relative AGN/starburst contributions to the total infrared luminosity. As a result, while overall the starburst component is dominant in submillimeter galaxies, we find a significant increase of the AGN contribution at redshift z > 2.3 with respect to objects at z < 2.3. Although the mid-infrared emission of 24 μm-ULIRGs is dominated by the AGN component, the starburst component contributes significantly to the bolometric luminosity.
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