Bibcode
Mateos, S.; Carrera, F. J.; Barcons, X.; Alonso-Herrero, A.; Hernán-Caballero, A.; Page, M.; Ramos-Almeida, C.; Caccianiga, A.; Miyaji, T.; Blain, A.
Bibliographical reference
The Astrophysical Journal Letters, Volume 841, Issue 2, article id. L18, 6 pp. (2017).
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6
2017
Citations
40
Refereed citations
35
Description
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≤slant z≤slant 1
as a function of rest-frame 2–10 keV X-ray luminosity from
{10}42 to {10}45 {erg} {{{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≤slant 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.
Related projects
Nuclear Activity in Galaxies: a 3D Perspective from the Nucleus to the Outskirts
This project consists of two main research lines. First, the study of quasar-driven outflows in luminous and nearby obscured active galactic nuclei (AGN) and the impact that they have on their massive host galaxies (AGN feedback). To do so, we have obtained Gran Telescopio CANARIAS (GTC) infrared and optical observations with the instruments
Cristina
Ramos Almeida