Study of Torus Structures in Low-luminosity Active Galactic Nuclei with Suzaku

We report the results from a systematic study of the broad band X-ray spectra of low-luminosity active galactic nuclei (LLAGN) obtained with Suzaku and Swift/BAT.Our targets consist of NGC 1566, NGC 3718, NGC 4138, NGC 4941, and NGC 5273, all of which have the hard X-ray luminosities below 10 42 erg s -1 in the 14-195 keV band.Most of the spectra of the nucleus are well reproduced by a sum of partially or fully covered transmitted emission and its reflection from the accretion disk, reprocessed emission from the torus accompanied by a strong narrow iron-Kα line, and a scattered component (for type-2 AGN).The equivalent width of the narrow iron-Kα line enables us to constrain the covering fraction of the torus by comparing with a model prediction.We find that they generally agree with the obscured AGN fraction obtained from hard X-ray at similar luminosities.Our results support the implication that the averaged covering fraction of AGN tori is peaked at L ∼ 10 42-43 erg s -1 but decreases toward lower luminosities. 10th INTEGRAL Workshop: "A Synergistic View of the High Energy Sky" -Integral2014, 15-19 September