In both panels the dark and light gray areas represent the spectrum of the unresolved and resolved CXRB, respectively. Left panel: the yellow dashed and continuous lines show the expectations of the G07 model for the two components. Right panel: the shaded area represents the total CXRB emission. Blue lines show the G07 model output with the CT (any z, any L, nH > 24) contribution enhanced by a factor 2. Green lines show the G07 model with the only heavily CT contribution enhanced by a factor 5. Red lines show the case where the contribution of high z CT has been enhanced assuming a linear evolution with redshift. Continuous, long-dashed, and short-dashed lines are for CDFS unresolved, CDFS resolved, and total CXRB, respectively.