Publication details for Prof David AlexanderVito, F., Vignali, C., Gilli, R., Comastri, A., Iwasawa, K., Brandt, W.N., Alexander, D.M., Brusa, M., Lehmer, B., Bauer, F.E., Schneider, D.P., Xue, Y.Q. & Luo, B. (2013). The high-redshift (z > 3) active galactic nucleus population in the 4-Ms Chandra Deep Field-South. Monthly notices of the Royal Astronomical Society 428(1): 354-369.
- Publication type: Journal Article
- ISSN/ISBN: 0035-8711 (print), 1365-2966 (electronic)
- DOI: 10.1093/mnras/sts034
- Keywords: methods: data analysis, techniques: imaging spectroscopy, surveys, galaxies: active, galaxies: high-redshift, X-rays: galaxies
- Further publication details on publisher web site
- Durham Research Online (DRO) - may include full text
Author(s) from Durham
We present results from a spectral analysis of a sample of high-redshift (z > 3) X-ray-selected active galactic nucleus (AGN) in the 4-Ms Chandra Deep Field-South (CDF-S), the deepest X-ray survey to date. The sample is selected using the most recent spectroscopic and photometric information available in this field. It consists of 34 sources with median redshift z = 3.7, 80 median net counts in the 0.5–7 keV band and median rest-frame absorption-corrected luminosity L2-10 keV ≈ 1.5 × 1044 erg s−1. Spectral analysis for the full sample is presented and the intrinsic column density distribution, corrected for observational biases using spectral simulations, is compared with the expectations of X-ray background (XRB) synthesis models. We find that ≈57 per cent of the sources are highly obscured (NH > 1023 cm−2). Source number counts in the 0.5-2 keV band down to flux F0.5-2 keV ≈ 4 × 10−17 erg s−1 cm−2 are also presented. Our results are consistent with a decline of the AGN space density at z > 3 and suggest that, at those redshifts, the AGN obscured fraction is in agreement with the expectations of XRB synthesis models.