Details

Autor(en) / Beteiligte

• Vito, F.
• Gilli, R.
• Vignali, C.
• Comastri, A.
• Brusa, M.
• Cappelluti, N.
• Iwasawa, K.

Titel

The hard X-ray luminosity function of high-redshift (3 < z ≲ 5) active galactic nuclei

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2014-12, Vol.445 (4), p.3557-3574

Ort / Verlag

London: Oxford University Press

Erscheinungsjahr

2014

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• We present the hard-band (2–10 keV) X-ray luminosity function (HXLF) of 0.5–2 keV band selected active galactic nuclei (AGN) at high redshift. We have assembled a sample of 141 AGN at 3 < z ≲ 5 from X-ray surveys of different size and depth, in order to sample different regions in the L X − z plane. The HXLF is fitted in the range log L X ∼ 43–45 with standard analytical evolutionary models through a maximum likelihood procedure. The evolution of the HXLF is well described by a pure density evolution, with the AGN space density declining by a factor of ∼10 from z = 3 to 5. A luminosity-dependent density evolution model, which, normally, best represents the HXLF evolution at lower redshift, is also consistent with the data, but a larger sample of low-luminosity (log L X < 44), high-redshift AGN is necessary to constrain this model. We also estimated the intrinsic fraction of AGN obscured by a column density log N H ≥ 23 to be 0.54 ± 0.05, with no strong dependence on luminosity. This fraction is higher than the value in the Local Universe, suggesting an evolution of the luminous (L X > 1044 erg s−1) obscured AGN fraction from z = 0 to z > 3.