Results of the fit procedure. We modeled the XRT unresolved spectrum as the sum of five components, each fit by a power law. Colors are the same as in the previous figure: (i) Chandra sources not detected by XRT (blue); x (iii) bright sources PSF residuals (red); (iv) stray-light contamination (green); (iv) X-ray emission of optical/IR sources (violet). The fifth component, the truly unresolved emission, which is our aim, is plotted with its uncertainties as the gray area.