Bibcode
Mason, R. E.; Lopez-Rodriguez, E.; Packham, C.; Alonso-Herrero, A.; Levenson, N. A.; Radomski, J.; Ramos-Almeida, C.; Colina, L.; Elitzur, M.; Arextaga, I.; Roche, P. F.; Oi, N.
Bibliographical reference
Journal of Physics: Conference Series, Volume 372, Issue 1, pp. 012036 (2012).
Advertised on:
7
2012
Citations
0
Refereed citations
0
Description
We have obtained high-resolution mid-infrared (MIR) imaging, nuclear
spectral energy distributions (SEDs) and archival Spitzer spectra for 22
low-luminosity active galactic nuclei (LLAGN; Lbol < 5
× 1042 erg s-1). Infrared (IR)
observations may advance our understanding of the accretion ows in
LLAGN, the fate of the obscuring torus at low accretion rates, and,
perhaps, the star formation histories of these objects. However, while
comprehensively studied in higher-luminosity Seyferts and quasars, the
nuclear IR properties of LLAGN have not yet been well-determined. In
these proceedings we summarise the results for the LLAGN at the
relatively high-luminosity, high-Eddington ratio end of the sample.
Strong, compact nuclear sources are visible in the MIR images of these
objects, with luminosities consistent with or slightly in execss of that
predicted by the standard MIR/X-ray relation. Their broadband nuclear
SEDs are diverse; some resemble typical Seyfert nuclei, while others
possess less of a well-defined MIR "dust bump". Strong silicate emission
is present in many of these objects. We speculate that this, together
with high ratios of silicate strength to hydrogen column density, could
suggest optically thin dust and low dust-to-gas ratios, in accordance
with model predictions that LLAGN do not host a Seyfert-like obscuring
torus.