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We have constrained the extragalactic source count distributions over a broadrange of X-ray fluxes and in various energy bands to test whether thepredictions from X-ray background synthesis models agree with the observationalconstraints provided by our measurements. We have used 1129 XMM-Newtonobservations at |b|>20 deg covering a sky area of 132.3 deg^2 to compile thelargest complete samples of X-ray objects to date in the 0.5-1 keV, 1-2 keV,2-4.5 keV, 4.5-10 keV, 0.5-2 keV and 2-10 keV energy bands. Our survey includesin excess of 30,000 sources down to ~10^-15 erg/cm^2/s below 2 keV and down to~10^{-14} erg/cm^2/s above 2 keV. A break in the source count distributions wasdetected in all energy bands except the 4.5-10 keV band. An analytical modelcomprising 2 power-law components cannot adequately describe the curvature seenin the source count distributions. The shape of the logN(>S)-logS is stronglydependent on the energy band with a general steepening apparent as we move tohigher energies. This is due to non-AGN populations, comprised mainly of starsand clusters of galaxies, contribute up to 30% of the source population atenergies <2 keV and at fluxes >10^{-13} erg/cm^2/s, and these populations ofobjects have significantly flatter source count distributions than AGN. We finda substantial increase in the relative fraction of hard X-ray sources at higherenergies, from >55% below 2 keV to >77% above 2 keV. However the majority ofsources detected above 4.5 keV still have significant flux below 2 keV.Comparison with predictions from the synthesis models suggest that the modelsmight be overpredicting the number of faint absorbed AGN, which would call forfine adjustment of some model parameters such as the obscured to unobscured AGNratio and/or the distribution of column densities at intermediate obscuration.

High precision X-ray logN-logS distributions: implications for the obscured AGN population