Bibcode
Fernández-Ontiveros, J. A.; Prieto, M. A.; Acosta-Pulido, J. A.; Montes, M.
Bibliographical reference
Journal of Physics: Conference Series, Volume 372, Issue 1, pp. 012006 (2012).
Advertised on:
7
2012
Citations
23
Refereed citations
20
Description
The inner structure of AGNs is expected to change below a certain
luminosity limit. The big blue bump, footprint of the accretion disk, is
absent for the majority of low-luminosity AGNs (LLAGNs). Moreover,
recent simulations suggest that the torus, a keystone in the Unified
Model, vanishes for nuclei with Lbol lesssim 1042
erg s-1 . However, the study of LLAGN is a complex task
due to the contribution of the host galaxy, which light swamps these
faint nuclei. This is specially critical in the IR range, at the maximum
of the torus emission, due to the contribution of the old stellar
population and/or dust in the nuclear region. Adaptive optics imaging in
the NIR (VLT/NaCo) together with diffraction limited imaging in the
mid-IR (VLT/VISIR) permit us to isolate the nuclear emission for some of
the nearest LLAGNs in the Southern Hemisphere. These data were extended
to the optical/UV range (HST), radio (VLA, VLBI) and X-rays (Chandra,
XMM-Newton, Integral), in order to build a genuine spectral energy
distribution (SED) for each AGN with a consistent spatial resolution
(< 0''.5) across the whole spectral range. From the individual SEDs,
we construct an average SED for LLAGNs sampled in all the wavebands
mentioned before. Compared with previous multiwavelength studies of
LLAGNs, this work covers the mid-IR and NIR ranges with high-spatial
resolution data. The LLAGNs in the sample present a large diversity in
terms of SED shapes. Some of them are very well described by a
self-absorbed synchrotron (e.g. NGC 1052), while some other present a
thermal-like bump at ~ 1 μm (NGC 4594). All of them are significantly
different when compared with bright Seyferts and quasars, suggesting
that the inner structure of AGNs (i.e. the torus and the accretion disk)
suffers intrinsic changes at low luminosities.