[en] We present the distributions of the geometrical covering factors of the dusty tori (f_2) of active galactic nuclei (AGNs) using an X-ray selected complete sample of 227 AGNs drawn from the Bright Ultra-hard XMM-Newton Survey. The AGNs have z from 0.05 to 1.7, 2–10 keV luminosities between 10"4"2 and 10"4"6 erg s"−"1, and Compton-thin X-ray absorption. Employing data from UKIDSS, 2MASS, and the Wide-field Infrared Survey Explorer in a previous work, we determined the rest-frame 1–20 μm continuum emission from the torus, which we model here with the clumpy torus models of Nenkova et al. Optically classified type 1 and type 2 AGNs are intrinsically different, with type 2 AGNs having, on average, tori with higher f_2 than type 1 AGNs. Nevertheless, ∼20% of type 1 AGNs have tori with large covering factors, while ∼23%–28% of type 2 AGNs have tori with small covering factors. Low f_2 are preferred at high AGN luminosities, as postulated by simple receding torus models, although for type 2 AGNs the effect is certainly small. f_2 increases with the X-ray column density, which implies that dust extinction and X-ray absorption take place in material that share an overall geometry and most likely belong to the same structure, the putative torus. Based on our results, the viewing angle, AGN luminosity, and also f_2 determine the optical appearance of an AGN and control the shape of the rest-frame ∼1–20 μm nuclear continuum emission. Thus, the torus geometrical covering factor is a key ingredient of unification schemes

[en] Dedicated searches generally find a decreasing fraction of obscured active galactic nuclei (AGN) with increasing AGN luminosity. This has often been interpreted as evidence for a decrease of the covering factor of the AGN torus with increasing luminosity, the so-called receding torus models. Using a complete flux-limited X-ray selected sample of 199 AGN, from the Bright Ultra-hard XMM-Newton Survey, we determine the intrinsic fraction of optical type-2 AGN at $0.05⩽<!--\; ???\; -->z⩽<!--\; ???\; -->1$ as a function of rest-frame 2–10 keV X-ray luminosity from ${10}^{42}$ to ${10}^{45}\mathrm{e}\mathrm{r}\mathrm{g}{\mathrm{s}}^{-<!--\; ???\; -->1}$. We use the distributions of covering factors of AGN tori derived from CLUMPY torus models. Since these distributions combined over the total AGN population need to match the intrinsic type-2 AGN fraction, we reveal a population of X-ray undetected objects with high-covering factor tori, which are increasingly numerous at higher AGN luminosities. When these “missing” objects are included, we find that Compton-thick AGN account at most for ${37}_{-<!--\; ???\; -->10}^{+9}$% of the total population. The intrinsic type-2 AGN fraction is 58 ± 4% and has a weak, non-significant (less than 2σ) luminosity dependence. This contradicts the results generally reported by AGN surveys and the expectations from receding torus models. Our findings imply that the majority of luminous rapidly accreting supermassive black holes at $z⩽<!--\; ???\; -->1$ reside in highly obscured nuclear environments, but most of them are so deeply embedded that they have so far escaped detection in X-rays in <10 keV wide area surveys.