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Register a new userInsights on the Dusty Torus and Neutral Torus from Optical and X-ray Obscuration in a Complete Volume Limited Hard X-ray AGN Sample
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We describe a complete volume limited sample of nearby active galaxies selected by their 14-195keV luminosity, and outline its rationale for studying the mechanisms regulating gas inflow and outflow. We describe also a complementary sample of inactive galaxies, selected to match the AGN host galaxy properties. The active sample appears to have no bias in terms of AGN type, the only difference being the neutral absorbing column which is two orders of magnitude greater for the Seyfert 2s. In the luminosity range spanned by the sample, log L_{14-195keV} [erg/s] = 42.4-43.7, the optically obscured and X-ray absorbed fractions are 50-65%. The similarity of these fractions to more distant spectroscopic AGN samples, although over a limited luminosity range, suggests that the torus does not strongly evolve with redshift. Our sample confirms that X-ray unabsorbed Seyfert 2s are rare, comprising not more than a few percent of the Seyfert 2 population. At higher luminosities, the optically obscured fraction decreases (as expected for the increasing dust sublimation radius), but the X-ray absorbed fraction changes little. We argue that the cold X-ray absorption in these Seyfert 1s can be accounted for by neutral gas in clouds that also contribute to the broad line region (BLR) emission; and suggest that a geometrically thick neutral gas torus co-exists with the BLR and bridges the gap to the dusty torus.
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Context: We investigate mid-infrared and X-ray properties of the dusty torus invoked in the unification scenario for active galactic nuclei. Aims: We use the relation between mid IR and hard X-ray luminosities to constrain the geometry and physical state of the dusty torus. Methods: We present new VISIR observations of 17 nearby AGN and combine these with our earlier VISIR sample of 8 Seyfert galaxies. Combining these observations with X-ray data from the literature we study the correlation between their mid IR and hard X-ray luminosities. Results: A statistically highly significant correlation between the rest frame 12.3 mircon (L_MIR) and 2-10 keV (L_X) luminosities is found. Furthermore, with a probability of 97%, we find that Sy 1 and Sy 2 have the same distribution of L_MIR over L_X. Conclusions: The high resolution of our MIR imaging allows us to exclude any significant non-torus contribution to the AGN mid IR continuum,thereby implying that the similarity in the L_MIR / L_X ratio between Sy 1s and Sy 2s is intrinsic to AGN. We argue that this is best explained by clumpy torus models. The slope of the correlation is in good agreement with the expectations from the unified scenario and indicates little to no change of the torus geometry with luminosity. In addition, we demonstrate that the high angular resolution is crucial for AGN studies in the IR regime.
The location of the obscuring torus in an active galactic nucleus (AGN) is still an unresolved issue. The line widths of X-ray fluorescence lines originated from the torus, particularly Fe K$alpha$, carry key information on the radii of line emitting regions. Utilizing XCLUMPY (Tanimoto et al. 2019), an X-ray clumpy torus model, we develop a realistic model of emission line profiles from an AGN torus where we take into account line broadening due to the Keplerian motion around the black hole. Then, we apply the updated model to the best available broadband spectra (3-100 keV) of the Circinus galaxy observed with Suzaku, XMM-Newton, Nuclear Spectroscopic Telescope Array (NuSTAR), and Chandra, including 0.62 Ms Chandra/HETG data. We confirm that the torus is Compton-thick (hydrogen column-density along the equatorial plane is $N_mathrm{H}^mathrm{Equ}=2.16^{+0.24}_{-0.16}times 10^{25} mathrm{cm}^{-2}$), geometrically thin (torus angular width $sigma=10.3^{+0.7}_{-0.3} mathrm{degrees}$), viewed edge-on (inclination $i=78.3^{+0.4}_{-0.9} mathrm{degrees}$), and has super-solar abundance ($1.52^{+0.04}_{-0.06}$ times solar). Simultaneously analyzing the Chandra/HETG first, second, and third order spectra with consideration of the spatial extent of the Fe K$alpha$ line emitting region, we constrain the inner radius of the torus to be $1.9^{+3.1}_{-0.8}times 10^5$ times the gravitational radius, or $1.6^{+1.5}_{-0.9}times 10^{-2} mathrm{pc}$ for a black hole mass of $(1.7pm 0.3)times 10^6 M_{odot}$. This is about 3 times smaller than that estimated from the dust sublimation radius, suggesting that the inner side of the dusty region of the torus is composed of dust-free gas.
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.
The central engines of Active Galactic Nuclei (AGNs) are powered by accreting supermassive black holes, and while AGNs are known to play an important role in galaxy evolution, the key physical processes occur on scales that are too small to be resolved spatially (aside from a few exceptional cases). Reverberation mapping is a powerful technique that overcomes this limitation by using echoes of light to determine the geometry and kinematics of the central regions. Variable ionizing radiation from close to the black hole drives correlated variability in surrounding gas/dust, but with a time delay due to the light travel time between the regions, allowing reverberation mapping to effectively replace spatial resolution with time resolution. Reverberation mapping is used to measure black hole masses and to probe the innermost X-ray emitting region, the UV/optical accretion disk, the broad emission line region and the dusty torus. In this article we provide an overview of the technique and its varied applications.
Using the latest 70 month Swift-BAT catalog we examined hard X-ray selected Seyfert I galaxies which are relatively little known and little studied, and yet potentially promising to test the ionized relativistic reflection model. From this list we chose 13 sources which have been observed by XMM-Newton for less than 20 ks, in order to explore the broad band soft to hard X-ray properties with the analysis of combined XMM-Newton and Swift data. Out of these we found seven sources which exhibit potentially promising features of the relativistic disc reflection, such as a strong soft excess, a large Compton hump and/or a broadened Fe line. Longer observations of four of these sources with the currently operating satellite missions, such as Suzaku, XMM-Newton and NuStar and two others by such future missions as ASTRO-H, will be invaluable, in order to better understand the relativistic disc reflection closest to the central black hole and constrain such important effects of strong gravity as the black hole spin.
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