TY - JOUR
T1 - The hard X-ray luminosity function of high-redshift (3 < z ≲ 5) active galactic nuclei
AU - Vito, F.
AU - Gilli, R.
AU - Vignali, C.
AU - Comastri, A.
AU - Brusa, M.
AU - Cappelluti, N.
AU - Iwasawa, K.
N1 - Publisher Copyright:
© 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
PY - 2014/9/29
Y1 - 2014/9/29
N2 - 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 LX - z plane. The HXLF is fitted in the range log LX ~ 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 LX < 44), high-redshift AGN is necessary to constrain this model. We also estimated the intrinsic fraction of AGN obscured by a column density logNH ≥ 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 (LX > 1044 erg s-1) obscured AGN fraction from z = 0 to z > 3.
AB - 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 LX - z plane. The HXLF is fitted in the range log LX ~ 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 LX < 44), high-redshift AGN is necessary to constrain this model. We also estimated the intrinsic fraction of AGN obscured by a column density logNH ≥ 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 (LX > 1044 erg s-1) obscured AGN fraction from z = 0 to z > 3.
KW - Galaxies: active
KW - Methods: data analysis
KW - Surveys
KW - X-rays: galaxies
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U2 - 10.1093/mnras/stu2004
DO - 10.1093/mnras/stu2004
M3 - Article
AN - SCOPUS:84922985402
VL - 445
SP - 3557
EP - 3574
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 4
ER -