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Article overview
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A Single Intrinsic Luminosity Function for Both Type-I and Type-II Active Galactic Nuclei | Shuang Nan Zhang
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2 Dec 2004 | Journal: | Astrophys.J. 618 (2004) L79-L82 | Subject: | astro-ph | Abstract: | The luminous electromagnetic emission from distant active galactic nuclei (AGNs) including quasars is believed to be powered by accretion onto super-massive black holes (SMBHs). In the standard unification model for AGNs a dusty torus covers a significant portion of the viewing angles to the accretion disk and the BH. The system is classified as a type-I AGN if the accretion disk is viewed through the opening part; otherwise it is called a type-II AGN. Therefore the ratio of type-II to type-I AGNs serves as a sensitive probe to the unification model. A surprising discovery made from several large sky coverage and/or deep AGN surveys has found a significant anti-correlation between the type-II fraction and the observed X-ray luminosity between 2-10 keV. This suggests two different luminosity functions for the two types of AGNs, thus challenging the AGN unification model. However this observed anti-correlation is a natural consequence of the AGN unification model with only one intrinsic luminosity function if the inclination angle effects of the X-ray emitting accretion disk are taken into account. Thus the AGN unification model survived another critical test. | Source: | arXiv, astro-ph/0412043 | Services: | Forum | Review | PDF | Favorites |
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