Bibcode
Mateos, S.; Carrera, F. J.; Alonso-Herrero, A.; Hernán-Caballero, A.; Barcons, X.; Asensio Ramos, A.; Watson, M. G.; Blain, A.; Caccianiga, A.; Ballo, L.; Braito, V.; Ramos Almeida, C.
Referencia bibliográfica
The Astrophysical Journal, Volume 819, Issue 2, article id. 166, 12 pp. (2016).
Fecha de publicación:
3
2016
Revista
Número de citas
47
Número de citas referidas
46
Descripción
We present the distributions of the geometrical covering factors of the
dusty tori (f2) 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 1042 and 1046
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 f2 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 f2 are
preferred at high AGN luminosities, as postulated by simple receding
torus models, although for type 2 AGNs the effect is certainly small.
f2 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 f2 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.