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Advances in Astronomy
Volume 2012 (2012), Article ID 271502, 7 pages
Research Article

Demography of High-Redshift AGN

1Fabrizio Fiore INAF-Osservatorio Astronomico di Roma, via Frascati 33, I00040 Monteporzio Catone, Italy
2Simonetta Puccetti ASI Science Data Center, via Galileo Galilei, 00044 Frascati, Italy
3Smita Mathur Astronomy Department, Ohio State University, Columbus, OH 43210, USA

Received 21 September 2011; Accepted 9 November 2011

Academic Editor: Angela Bongiorno

Copyright © 2012 Fabrizio Fiore et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


High-redshift AGN holds the key to understanding early structure formation and to probe the Universe during its infancy. We review the latest searches for high-z AGN in the deepest X-ray field so far, the Chandra Deep Field South (CDFS) 4 Msecond exposure. We do not confirm the positive detection of a signal in the stacked Chandra images at the position of z~6 galaxies recently reported by Treister and collaborators (2011). We present z>3 X-ray sources number counts in the 0.5–2 keV band, obtained joining CDFS faint detections (see Fiore et al. (2011)), with Chandra-COSMOS and XMM-COSMOS detections. We use these number counts to make predictions for surveys with three mission concepts: Athena, WFXT, and a Super-Chandra.