@article{10902/4091,
year = {2012},
month = {10},
url = {http://hdl.handle.net/10902/4091},
abstract = {ABSTRACT: We present results on a search of heavily obscured active galaxies z > 1.7 using the rest-frame 9−20 keV excess for X-ray sources detected in the deep XMM-CDFS survey. Out of 176 sources selected with the conservative detection criteria (>8σ) in the first source catalogue of Ranalli et al. (in prep.), 46 objects lie in the redshift range of interest with the median redshift  ≃ 2.5. Their typical rest-frame 10−20 keV luminosity is 1044 erg s-1, as observed. Among optically faint objects that lack spectroscopic redshift, four were found to be strongly absorbed X-ray sources, and the enhanced Fe K emission or absorption features in their X-ray spectra were used to obtain X-ray spectroscopic redshifts. Using the X-ray colour–colour diagram based on the rest-frame 3−5 keV, 5−9 keV, and 9−20 keV bands, seven objects were selected for their 9−20 keV excess and were found to be strongly absorbed X-ray sources with column density of NH ≥ 0.6 × 1024 cm-2, including two possible Compton thick sources. While they are emitting at quasar luminosity, ~3/4 of the sample objects are found to be absorbed by NH > 1022 cm-2. A comparison with local AGN at the matched luminosity suggests an increasing trend of the absorbed source fraction for high-luminosity AGN towards high redshifts.},
organization = {This research made use of the data obtained from XMM-Newton and the Chandra X-ray Observatory. K.I. thanks support from Spanish Ministerio de Ciencia e Innovación (MICINN) through the grant (AYA2010-21782-C03-01). W.N.B. thanks the NASA ADP grant NNX10AC99G. We acknowledge financial contribution from the agreement ASI-INAF I/009/10/0},
publisher = {EDP Sciences},
publisher = {Astronomy and Astrophysics, 2012, 546, A84},
title = {The XMM deep survey in the CDF-S II. A 9–20 keV selection of heavily obscured active galaxies at z  >  1.7},
author = {Iwasawa, Kazushi and Gilli, Roberto and Vignali, Cristian and Comastri, Andrea and Brandt, William Nielsen and Ranalli, Piero and Vito, Fabio and Cappelluti, Nico and Carrera Troyano, Francisco Jesús and Falocco, Serena and Georgantopoulos, Ioannis and Mainieri, Vincenzo and Paolillo, Maurizio},
}