We present the angular correlation function of the X-ray population of 1063 XMM-Newton observations at high Galactic latitudes , comprising up to \sim 30000 sources over a sky area of \sim 125 sq .
degrees in the energy bands : soft ( 0.5-2 keV ) and hard ( 2-10 keV ) .
This is the largest sample of serendipitous X-ray sources ever used for clustering analysis purposes to date and the results have been determined with unprecedented accuracy .
We detect significant clustering signals in the soft and hard bands ( \sim 10 \sigma and \sim 5 \sigma , respectively ) .
We deproject the angular correlation function via Limber ’ s equation and calculate the typical spatial lengths .
We infer that AGN at redshifts \sim 1 are embedded in dark matter halos with typical masses of \log M \sim 12.6 h ^ { -1 } M _ { \odot } and lifetimes in the range \sim 3 - 5 \times 10 ^ { 8 } years , which indicates that AGN activity is a transient phase in the life of galaxies .