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标题：“Zombie” or active? An alternative explanation to the properties of star-forming galaxies at high redshift
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作者：F. G. Saturni ; M. Mancini ; E. Pezzulli 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2018
卷号：617
DOI：10.1051/0004-6361/201833261
语种：English
出版社：EDP Sciences
摘要：Context. Star-forming galaxies at high redshift show anomalous values of infrared excess, which can be described only by extremizing the existing relations between the shape of their ultraviolet continuum emission and their infrared-to-ultraviolet luminosity ratio, or by constructing ad hoc models of star formation and dust distribution.Aims.We present an alternative explanation, based on unveiled AGN activity, of the existence of such galaxies. The scenario of a weak AGN lends itself naturally to explain the observed spectral properties of these high-zobjects in terms of a continuum slope distribution and not altered infrared excesses.Methods. To this end, we directly compare the infrared-to-ultraviolet properties of high-redshift galaxies to those of known categories of AGN (quasars and Seyferts). We also infer the characteristics of their possible X-ray emission.Results. We find a strong similarity between the spectral shapes and luminosity ratios of AGN with the corresponding properties of such galaxies. In addition, we derive expected X-ray fluxes that are compatible with the energetics from AGN activity.Conclusions. We conclude that a moderate AGN contribution to the UV emission of such high-zobjects is a valid alternative to explain their spectral properties. Even the presence of an active nucleus in each source would not violate the expected quasar statistics. Furthermore, we suggest that the observed similarities between anomalous star-forming galaxies and quasars may provide a benchmark for future theoretical and observational studies on the galaxy population in the early Universe.
关键词：engalaxies: ISMgalaxies: photometryinfrared: galaxiesultraviolet: galaxiesgalaxies: activequasars: general