We present the spatial clustering properties of 1466 X-ray selected AGN compiled from the Chandra CDF-N , CDF-S , eCDF-S , COSMOS and AEGIS fields in the 0.5 - 8 keV band .
The X-ray sources span the redshift interval 0 < z < 3 and have a median value of \bar { z } = 0.976 .
We employ the projected two-point correlation function to infer the spatial clustering and find a clustering length of r _ { 0 } = 7.2 \pm 0.6 h ^ { -1 } Mpc and a slope of \gamma = 1.48 \pm 0.12 , which corresponds to a bias of b ( \bar { z } ) = 2.26 \pm 0.16 .
Using two different halo bias models , we consistently estimate an average dark-matter host halo mass of M _ { h } \simeq 1.3 ( \pm 0.3 ) \times 10 ^ { 13 } h ^ { -1 } M _ { \odot } .
The X-ray AGN bias and the corresponding dark-matter host halo mass , are significantly higher than the corresponding values of optically selected AGN ( at the same redshifts ) .
The redshift evolution of the X-ray selected AGN bias indicates , in agreement with other recent studies , that a unique dark-matter halo mass does not fit well the bias at all the different redshifts probed .
Furthermore , we investigate if there is a dependence of the clustering strength on X-ray luminosity .
To this end we consider only 650 sources around z \sim 1 and we apply a procedure to disentangle the dependence of clustering on redshift .
We find indications for a positive dependence of the clustering length on X-ray luminosity , in the sense that the more luminous sources have a larger clustering length and hence a higher dark-matter halo mass .
In detail we find for an average luminosity difference of \delta \log _ { 10 } L _ { x } \simeq 1 a halo mass difference of a factor of \sim 3 .

These findings appear to be consistent with a galaxy-formation model where the gas accreted onto the supermassive black hole in intermediate luminosity AGN comes mostly from the hot-halo atmosphere around the host galaxy .