2004/09/28 by C. Vignali, D. M. Alexander, Vignali, C. +3
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0409699
Proceedings of the VI Italian Conference on Active Galactic Nuclei (Volterra, 25-28 May, 2004). 8 pages, 4 figures, Latex macro agn6.cls Electronic edition at http://www.arcetri.astro.it/~agn6/
arxiv created 2004/09/28 · arxiv updated 2009/12/01
Recent X-ray surveys with Chandra and XMM-Newton have found several genuine Type II quasars, the long sought-after population of high-luminosity (high-redshift) Seyfert 2 galaxies, and a sizable number of Type II quasar candidates. However, at present it is hard to know whether the on-going X-ray surveys are providing a reliable and nearly complete census of the Type II quasar population. In order to address this open issue and shed light on the broad-band properties of Type II quasars, we used the sample of 291 high-ionization narrow emission-line AGN at z=0.3-0.83 selected from the Sloan Digital Sky Survey by Zakamska et al. (2003). Using archival X-ray information, we were able to place constraints on the X-ray emission of 17 of these objects (three X-ray detections and 14 upper limits). Using the [O III]5007 line luminosities to predict the intrinsic X-ray power of the AGN, we found that at least 47% of the objects in the observed sample provides evidence for the presence of X-ray absorption (with NH>1022 cm-2), including the four highest luminosity sources with predicted unobscured luminosities of ~1045 erg/s. For the only source with moderate-quality XMM-Newton spectral data, all of the pieces of the puzzle (2-10 keV luminosity of ~4x1044 erg/s, NH~1-3x1022 cm-2, and unobscured magnitude MB=-26 assure that this is a genuine Type II quasar.