Figure 8: Ratio of obscured to total AGN as a function of hard X-ray luminosity. The black circles with dashed error bars show the obscured AGN fraction from the extended Chandra deep field south (ECDF-S) alone, while the gray circles show the results obtained using the meta-analysis by Treister and Urry [31]. Black circles with solid error bars show the fraction obtained combining these two samples. The dependence in the AGN population synthesis model of Gilli et al. [39] for the intrinsic and observed fractions of obscured AGN is shown by the dashed and dotted red lines; the dependence used by Treister and Urry [31] is shown by the solid blue line. The dashed magenta line shows the expected dependence for a radiation-limited torus [65], while the dotted green line shows the expectation for the original “receding torus’’ [30], both normalized to the observed value in the  erg s−1 bin. (b) Same as (a) but using an AGN sample at selected in hard X-rays from Swift/BAT observations [37]. The fact that the same luminosity dependence is observed in both samples indicates that it is not due to selection effects.