We present the hard-band ($2-10,mathrm{keV}$) X-ray luminosity function (HXLF) of $0.5-2,mathrm{keV}$ band selected AGN at high redshift. We have assembled a sample of 141 AGN at $3<zlesssim5$ 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 $mathrm{logL_Xsim43-45}$ 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 $sim10$ 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 ($mathrm{logL_X}<44$), high-redshift AGN is necessary to constrain this model. We also estimated the intrinsic fraction of AGN obscured by a column density $mathrm{logN_H}geq23$ to be $0.54pm0.05$, with no strong dependence on luminosity. This fraction is higher than the value in the Local Universe, suggesting an evolution of the luminous ($mathrm{L_X>10^{44}mathrm{erg,s^{-1}}}$) obscured AGN fraction from $z=0$ to $z>3$.
We list here the contents of the Proceedings of the Wide Field X-ray Telescope conference held in Bologna, Italy on 25-26 Nov 2009. The conference highlighted the scientific potential and discovery space provided by an X-ray mission concept character
ized by a wide field-of-view (1 sq.deg.), large effective area (1 sq.mt.) and approximately constant PSF (~5 arcsec HEW) across the whole FOV. The index is in html form with clickable links to the individual contributions.
