Resolving the galactic ridge x-ray background

We use Chandra deep observations of the Galactic Center ( GC) region to improve the constraints on the unresolved fraction of the Galactic ridge X-ray background in the 4-8 keV band. We emphasize the importance of correcting the measured source counts at low fluxes for bias associated with Poisson noise. We find that at distances of 2 '-4 ' from Sgr A* at least similar to 40% of the total X-ray emission in the energy band 4-8 keV originates from point sources with luminosities L2-10 keV > 10(31) erg s(-1). From a comparison of the source number-flux function in the GC region with the known luminosity function of faint X-ray sources in the Solar vicinity, we infer that Chandra has already resolved a large fraction of the cumulative contribution of cataclysmic variables to the total X-ray flux from the GC region. This comparison further indicates that most of the yet unresolved X-ray flux from the GC region (similar to 60%) is likely produced by weak cataclysmic variables and coronally active stars with L2-10 keV < 10(31) erg s(-1). We conclude that the bulk of the high energy Galactic X-ray background in this direction is produced by discrete sources, and that this is likely to be the case for the rest of the Galactic ridge.