Abstract
We characterize for the first time the torus properties of an ultra-hard X-ray (14-195 keV) volume-limited (DL<40 Mpc) sample of 24 Seyfert (Sy) galaxies (BCS40 sample). The sample was selected from the Swift/BAT nine month catalog. We use high angular resolution nuclear infrared (IR) photometry and N-band spectroscopy, the CLUMPY torus models and a Bayesian tool to characterize the properties of the nuclear dust. In the case of the Sy1s we estimate the accretion disk contribution to the subarcsecond resolution nuclear IR SEDs (~0.4'') which is, on average, 46+-28, 23+-13 and 11+-5% in the J-, H- and K-bands, respectively. This indicates that the accretion disk templates that assume a steep fall for longer wavelengths than 1 micron might underestimate its contribution to the near-IR emission. Using both optical (broad vs narrow lines) and X-ray (unabsorbed vs absorbed) classifications, we compare the global posterior distribution of the torus model parameters. We confirm that Sy2s have larger values of the torus covering factor (CT~0.95) than Sy1s (CT~0.65) in our volume-limited Seyfert sample. These findings are independent of whether we use an optical or X-ray classification. We find that the torus covering factor remains essentially constant within the errors in our luminosity range and there is no clear dependence with the Eddington ratio. Finally, we find tentative evidence that even an ultra hard X-ray selection is missing a significant fraction of highly absorbed type 2 sources with very high covering factor tori.
Highlights
Active galactic nuclei (AGNs) are powered by accretion of material onto supermassive black holes (SMBHs), which release energy in the form of radiation and/or mechanical outflows to the host galaxy interstellar medium
In Appendix A, we present the results of the nuclear IR SED fitting process with the CLUMPY models, which are the marginal posterior distributions of the six parameters that define these models plus the foreground extinction and vertical shift
We found that the gas masses inferred from the fit of the nuclear IR SEDs in a smaller radius (∼0.5–15 pc) are smaller than those measured in the inner ∼30 pc
Summary
Active galactic nuclei (AGNs) are powered by accretion of material onto supermassive black holes (SMBHs), which release energy in the form of radiation and/or mechanical outflows to the host galaxy interstellar medium. Atacama Large Millimeter/submillimeter Array (ALMA) observations of the archetypal Seyfert 2 galaxy NGC 1068 have spatially resolved for the first time the submillimetre (sub-mm) counterpart of the putative torus (Gallimore et al 2016; Garcıa-Burillo et al 2016; Imanishi et al 2018) This is a disc of ∼7–10 pc diameter. Honig & Kishimoto 2017) This polar emission has been detected so far in 6 Seyfert galaxies of the 23 observed using IR interferometry (Lopez-Gonzaga et al 2016; Leftley et al 2018) and more observations are needed in order to study whether this is a common feature in AGNs. The physical models are more realistic since they include important processes, such as supernovae and AGN feedback.
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