Study of Swift/BAT Selected Low-luminosity Active Galactic Nuclei Observed with Suzaku

Abstract

We systematically analyze the broadband (0.5--200 keV) X-ray spectra of hard X-ray ($>10$ keV) selected local low-luminosity active galactic nuclei (LLAGNs) observed with {\it Suzaku} and {\it Swift}/BAT. The sample consists of ten LLAGNs detected with {\it Swift}/BAT with intrinsic 14--195 keV luminosities smaller than $10^{42}$ erg s${}^{-1}$ available in the {\it Suzaku} archive, covering a wide range of the Eddington ratio from $10^{-5}$ to $10^{-2}$. The overall spectra can be reproduced with an absorbed cut-off power law, often accompanied by reflection components from distant cold matter, and/or optically-thin thermal emission from the host galaxy. In all objects, relativistic reflection components from the innermost disk are not required. Eight objects show a significant narrow iron-K$\alpha$ emission line. Comparing their observed equivalent widths with the predictions from the Monte-Carlo based torus model by \cite{Ike09}, we constrain the column density in the equatorial plane to be $\log N_{\mathrm{H}}^{\mathrm{eq}}>22.7$ or the torus half opening angle ${\theta }_{\mathrm{oa}}<70^{\circ }$. We infer that the Eddington ratio (${\lambda }_{\mathrm{Edd}}$) is a key parameter that determines the torus structure of LLAGNs: the torus becomes large at ${\lambda }_{\mathrm{Edd}}\gtrsim 2\times 10^{-4}$, whereas at lower accretion rates it is little developed. The luminosity correlation between the hard X-ray and mid-infrared (MIR) bands of the LLAGNs follows the same one as for more luminous AGNs. This implies that other mechanisms than AGN-heated dust are responsible for the MIR emission in low Eddington ratio LLAGNs.

16 pages, 55 figures, accepted for publication in ApJ

References in corpus (21)

• Toward the Standard Population Synthesis Model of the X-Ray Background: Evolution of X-Ray Luminosity and Absorption Functions of Active Galactic Nuclei Including Compton-Thick Populations
• An XMM-Newton survey of broad iron lines in Seyfert galaxies
• Absorption Properties and Evolution of Active Galactic Nuclei
• Radiatively Inefficient Accretion in Nearby Galaxies
• Obscuration-dependent evolution of Active Galactic Nuclei
• The Hard X-ray Spectrum as a Probe for Black-Hole Growth in Radio-Quiet Active Galactic Nuclei
• Kinematics of the Local Universe XIII. 21-cm line measurements of 452 galaxies with the Nançay radiotelescope, JHK Tully-Fisher relation and preliminary maps of the peculiar velocity field
• The subarcsecond mid-infrared view of local active galactic nuclei: II. The mid-infrared--X-ray correlation
• Seyfert galaxies in the local Universe (z$\le$ 0.1): the average X-ray spectrum as seen by $BeppoSAX$
• The X-Ray to Mid-Infrared Relation of AGN at High Luminosity
• Study on X-ray Spectra of Obscured AGNs based on Monte Carlo simulation - an interpretation of observed wide-band spectra
• Measuring the mass of the central black hole in the bulgeless galaxy NGC 4395 from gas dynamical modeling
• A Search for "Dwarf" Seyfert Nuclei. VII. A Catalog of Central Stellar Velocity Dispersions of Nearby Galaxies
• Revisiting the relationship between 6 μm and 2-10 keV continuum luminosities of AGN
• SFI++ II: A New I-band Tully-Fisher Catalog, Derivation of Peculiar Velocities and Dataset Properties
• The cosmological properties of AGN in the XMM-Newton Hard Bright Survey
• Iron K$\alpha$ emission in type-I and type-II Active Galactic Nuclei
• The Mass of the Central Black Hole in the Nearby Seyfert Galaxy NGC5273
• Simultaneous Estimation of Time Delays and Quasar Structure
• The mid-infrared emission of Seyfert galaxies. A new analysis of ISOCAM data
• X-ray spectral variability of LINERs selected from the Palomar sample

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• Hard X-ray Irradiation Potentially Drives Negative AGN Feedback by Altering Molecular Gas Properties
• Dark Energy Survey Identification of A Low-Mass Active Galactic Nucleus at Redshift 0.823 from Optical Variability
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