Modeling the Unresolved NIR–MIR SEDs of Local (z &lt; 0.1) QSOs

et al. 2022

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We present a statistical analysis of the properties of the obscuring material around active galactic nuclei (AGN). This study represents the first of its kind for an ultra-hard X-ray (14-195 keV; Swift/BAT), volume-limited (D L <40 Mpc) sample of 24 Seyfert (Sy) galaxies (BCS 40 sample) using high angular resolution infrared data and various torus models: smooth, clumpy, and two-phase torus models and clumpy disc+wind models. We find that torus models (i.e. without including the polar dusty wind component) and disc+wind models provide the best fits for a comparable number of galaxies, 8 out of 24 (33.3%) and 9 out of 24 (37.5%), respectively. We find that the best-fit models depend on the hydrogen column density (N X−ray H ), which is related to the X-ray (unobscured or obscured) and optical (Sy1/Sy2) classification. In particular, smooth, clumpy, and two-phase torus models are best at reproducing the infrared (IR) emission of AGN with relatively high hydrogen column density (median value of log (N X−ray H cm −2 )=23.5±0.8; i.e. Sy2). However, clumpy disc+wind models provide the best fits to the nuclear IR spectral energy distributions (SEDs) of Sy1/1.8/1.9 (median value of log (N X−ray H cm −2 )=21.0±1.0) -specifically, in the near-infrared (NIR) range. The success of the disc+wind models in fitting the NIR emission of Sy1 galaxies is due to the combination of adding large graphite grains to the dust composition and self-obscuration effects caused by the wind at intermediate inclinations. In general, we find that the Seyfert galaxies having unfavourable (favourable) conditions, namely" nuclear hydrogen column density and Eddington ratio, for launching IR dusty polar outflows are best-fitted with smooth, clumpy, and two-phase torus (disk+wind) models, confirming the predictions from simulations. Therefore, our results indicate that the nature of the inner dusty structure in AGN depends on the intrinsic AGN properties.

Section: Sed Fitting Proceduresmentioning

confidence: 99%

Section: Sed Fitting Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Torus and polar dust dependence on active galactic nucleus properties

García-Bernete

González‐Martín²,

et al. 2022

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The Galaxy Activity, Torus, and Outflow Survey (GATOS)

García‐Burillo

Alonso‐Herrero

et al. 2021

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We present the first results of the Galaxy Activity, Torus, and Outflow Survey (GATOS), a project aimed at understanding the properties of the dusty molecular tori and their connection to the host galaxy in nearby Seyfert galaxies. Our project expands the range of active galactic nuclei (AGN) luminosities and Eddington ratios covered by previous surveys of Seyferts conducted by the Atacama Large Millimeter Array (ALMA), allowing us to study the gas feeding and feedback cycle in a combined sample of 19 Seyferts. We used ALMA to obtain new images of the emission of molecular gas and dust using the CO(3–2) and HCO+(4–3) lines as well as their underlying continuum emission at 870 μm with high spatial resolutions (0.1″ ∼ 7 − 13 pc) in the circumnuclear disks (CND) of ten nearby (D < 28 Mpc) Seyfert galaxies selected from an ultra-hard X-ray survey. Our new ALMA observations detect 870 μm continuum and CO line emission from spatially resolved disks located around the AGN in all the sources. The bulk of the 870 μm continuum flux can be accounted for by thermal emission from dust in the majority of the targets. For most of the sources, the disks show a preponderant orientation perpendicular to the AGN wind axes, as expected for dusty molecular tori. The median diameters and molecular gas masses of the tori are ∼42 pc and ∼6 × 105 M⊙, respectively. We also detected the emission of the 4–3 line of HCO+ in four GATOS targets. The order of magnitude differences found in the CO/HCO+ ratios within our combined sample point to a very different density radial stratification inside the dusty molecular tori of these Seyferts. We find a positive correlation between the line-of-sight gas column densities responsible for the absorption of X-rays and the molecular gas column densities derived from CO toward the AGN in our sources. Furthermore, the median values of both column densities are similar. This suggests that the neutral gas line-of-sight column densities of the dusty molecular tori imaged by ALMA significantly contribute to the obscuration of X-rays. The radial distributions of molecular gas in the CND of our combined sample show signs of nuclear-scale molecular gas deficits. We also detect molecular outflows in the sources that show the most extreme nuclear-scale gas deficits in our sample. These observations find for the first time supporting evidence that the imprint of AGN feedback is more extreme in higher luminosity and/or higher Eddington ratio Seyfert galaxies.

The role of grain size in active galactic nuclei torus dust models

González‐Martín

Fritz

et al. 2023

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Context. Active galactic nuclei (AGN) are surrounded by dust within the central parsecs. The dusty circumnuclear structures, referred to as the torus, are mainly heated by radiation from the AGN and emitted at infrared wavelengths, producing the emergent dust continuum and silicate features. Fits to the infrared spectra from the nuclear regions of AGN can place constraints on the dust properties, distribution, and geometry by comparison with models. However, none of the currently available models fully describe the observations of AGN currently available. Aims. Among the aspects least explored, here we focus on the role of dust grain size. We offer the community a new spectral energy distribution (SED) library which is based on the two-phase torus model developed before with the inclusion of the grain size as a model parameter, parameterized by the maximum grain size Psize or equivalently the mass-weighted average grain size ⟨P⟩. Methods. We created 691 200 SEDs using the SKIRT code, where the maximum grain size can vary within the range Psize = 0.01 − 10.0 μm (⟨P⟩ = 0.007 − 3.41 μm). We fit this new library and several existing libraries to a sample of 68 nearby and luminous AGN with Spitzer/IRS spectra dominated by AGN-heated dust. Results. We find that the GoMar23 model can adequately reproduce up to ∼85–88% of the spectra. The dust grain size parameter significantly improves the final fit in up to 90% of these spectra. Statistical tests indicate that the grain size is the third most important parameter in the fitting procedure (after the size and half opening angle of the torus). The requirement of a foreground extinction by our model is lower compared to purely clumpy models. We find that ∼41% of our sample requires that the maximum dust grain size is as large as Psize ∼ 10 μm (⟨P⟩∼3.41 μm). Nonetheless, we also remark that disk+wind and clumpy torus models are still required to reproduce the spectra of a nonnegligible fraction of objects, suggesting the need for several dust geometries to explain the infrared continuum of AGN. Conclusions. This work provides tentative evidence for dust grain growth in the proximity of the AGN.