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In order to understand the diversity of classes observed in active galactic nuclei (AGNs), a geometrically and optically thick torus of gas and dust is required to obscure the central engine depending on the line of sight to the observer. We perform a simultaneous fitting of X-ray and mid-infrared (mid-IR) spectra to investigate whether the same structure could produce both emissions and, if this the case, to obtain better constraints for the physical parameters of the torus. In this case we take advantage of the fact that both emissions show important signatures of obscuration. We used the nearby type 2 active nucleus IC 5063 as a test object. This object is ideal because of the wealth of archival data, including some high-resolution data. It also has a relatively high AGN luminosity that dominates at both X-ray and mid-IR frequencies. We use high spectral resolution NuSTAR and Spitzer/IRS spectra. The AGN dusty models used several physically motivated models. We found that the combination of the smooth torus models at mid-IR by Fritz et al. and at X-rays by Baloković et al., with the viewing and half-opening angles linked to the same value, is the best choice to fit the spectra at both wavelengths. This allows us to determine all the parameters of its torus. This result suggests that the structure producing the continuum emission at mid-IR and the reflection component at X-ray is the same. Therefore, we prove that this technique can be used to infer the physical properties of the torus, at least when AGN dust dominates the mid-IR emission and the reflection component is significant at X-rays. [ABSTRACT FROM AUTHOR]

This is the second in a series of papers devoted to exploring a set of six dusty models of active galactic nuclei (AGN) with available spectral energy distributions. These models are the smooth torus by Fritz et al., the clumpy torus by Nenkova et al., the clumpy torus by Hönig & Kishimoto, the two-phase torus by Siebenmorgen et al., the two-phase torus by Stalevski et al., and the wind model by Hönig & Kishimoto. The first paper explores discrimination among models and the parameter restriction using synthetic spectra. Here we perform spectral fitting of a sample of 110 AGN drawn from the Swift/BAT survey with Spitzer/IRS spectroscopic data. The aim is to explore which is the model that describes better the data and the resulting parameters. The clumpy wind–disk model by Hönig & Kishimoto provides good fits for ∼50% of the sample, and the clumpy torus model by Nenkova et al. is good at describing ∼30% of the objects. The wind–disk model by Hönig & Kishimoto is better for reproducing the mid-infrared spectra of type 1 Seyferts (with 60% of the type 1 Seyferts well reproduced by this model compared to the 10% well represented by the clumpy torus model by Nenkova et al.), while type 2 Seyferts are equally fitted by both models (roughly 40% of the type 2 Seyferts). Large residuals are found irrespective of the model used, indicating that the AGN dust continuum emission is more complex than predicted by the models or that the parameter space is not well sampled. We found that all the resulting parameters for our AGN sample are roughly constrained to 10%–20% of the parameter space. Contrary to what is generally assumed, the derived outer radius of the torus is smaller (reaching up to a factor of ∼5 smaller for 10 pc tori) for the smooth torus by Fritz et al. and the two-phase torus by Stalevski et al. than the one derived from the clumpy torus by Nenkova et al. Covering factors and line-of-sight viewing angles strongly depend on the model used. The total dust mass is the most robust derived quantity, giving equivalent results for four of these models. [ABSTRACT FROM AUTHOR]

At distances from the active galaxy nucleus where the ambient temperature falls below ∼1500–1800 K, dust is able to survive. It is thus possible to have a large dusty structure present that surrounds the active galaxy nucleus. This is the first of two papers aiming at comparing six dusty torus models with available spectral energy distributions, namely, Fritz et al., Nenkova et al., Hönig & Kishimoto, Siebenmorgen et al., Stalevski et al., and Hönig & Kishimoto. In this first paper we use synthetic spectra to explore the discrimination between these models and under which circumstances they allow us to restrict the torus parameters, while our second paper analyzes the best model to describe the mid-infrared spectroscopic data. We have produced synthetic spectra from current instruments GTC/CanariCam and Spitzer/IRS and future James Webb Space Telescope (JWST)/MIRI and JWST/NIRSpec instruments. We find that for a reasonable brightness (F12 μm > 100 mJy) we can actually distinguish among models except for the two pairs of parent models. We show that these models can be distinguished based on the continuum slopes and the strength of the silicate features. Moreover, their parameters can be constrained within 15% of error, irrespective of the instrument used, for all the models except Hönig & Kishimoto. However, the parameter estimates are ruined when more than 50% of circumnuclear contributors are included. Therefore, future high spatial resolution spectra such as those expected from JWST will provide enough coverage and spatial resolution to tackle this topic. [ABSTRACT FROM AUTHOR]

Dust close (∼few pc) to the accretion disk in active galactic nuclei (AGNs) is key to understanding many of their observational signatures, and it is key to tracing how the AGN is fed or even evolves along its duty cycle. With estimated sizes of less than 10 pc, as constrained by mid-IR (MIR) high angular resolution data, only the superb spatial resolution achieved by ALMA is able to actually image this dusty structure. However, the question regarding how the dust at submillimeter wavelengths (sub-mm, typical ALMA band) behaves in the AGN contest, arises. We study the detectability of the emission associated with the AGN dusty structure at submillimeter wavelengths using ALMA, in a theoretical and observational way. Theoretically, we use the Clumpy models from Nenkova et al., together with the MIR to X-ray and radio fundamental plane scaling relations. We find that it is more likely to detect bigger and denser dusty tori at the highest ALMA frequency (666 GHz/450 μm). We also find that with 1 hr at 353 GHz/850 μm and 10 hr at 666 GHz/450 μm we can detect, with a high detection limit, a 1 mJy torus (characteristic of bright AGNs). This means that an object for which the unresolved spectral energy distribution (SED) is at 12 μm has a flux of ∼1 mJy. Observationally, we use four prototypical AGNs: NGC 1052 (low-luminosity AGN), NGC 1068 (type 2), NGC 3516 (type 1.5), and I Zw 1 (QSO), with radio, submillimeter, and MIR data available. All the MIR spectra are best fit with the smooth model reported by Fritz et al. A power law and a single, or a composition of, synchrotron component(s) reproduce the centimeter radio wavelengths. We combined and extrapolated both fits to compare the extrapolation of both torus and jet contributors at submillimeter wavelengths with data at these wavelengths. Our observational results are consistent with our theoretical results. The most promising candidate to detect the torus is the QSO I Zw 1 (therefore, highly accreting sources in general), although it cannot be resolved owing to the distance of this source. We suggest that to explore the detection of a torus at submillimeter wavelengths, it is necessary to perform an SED analysis including radio data, with particular attention to the angular resolution. [ABSTRACT FROM AUTHOR]

We studied the circumnuclear mid-IR emission in a sample of 19 local active galactic nuclei (AGNs) with high spatial resolution spectra using T-ReCS (Gemini) and CanariCam (GTC), together with Spitzer/IRS observations. We measured the flux and the equivalent width for the 11.3 μm PAH feature and the [S iv] line emission as a function of galactocentric distance. This allowed us to study the star formation (SF) at subkiloparsec scales from the nucleus for a large sample of nearby AGNs. The [S iv] line emission could be tracing the AGN radiation field within a few thousand times the sublimation radius (Rsub), but it often peaks at distances greater than 1000 Rsub. One possibility is that the SF is contributing to the [S iv] total flux. We found an 11.3 μm PAH emission deficit within the inner few tens of parsecs from the AGN. This deficit might be due to the destruction of the molecules responsible for this feature or the lack of SF at these distances. We found a sensible agreement in the expected shift of the relation of the AGN bolometric luminosity and the SF rate. This indicates that numerical models attributing the link between AGN activity and host galaxy growth to mergers are in agreement with our data, for most inner galaxy parts. [ABSTRACT FROM AUTHOR]

Several authors have claimed that less luminous active galactic nuclei (AGNs) are not capable of sustaining a dusty torus structure. Thus, a gradual resizing of the torus is expected when the AGN luminosity decreases. Our aim is to examine mid-infrared observations of local AGNs of different luminosities for the gradual resizing and disappearance of the torus. We applied the decomposition method described by Hernán-Caballero et al. to a sample of ∼100 Spitzer/IRS spectra of low-luminosity AGNs and powerful Seyferts in order to decontaminate the torus component from other contributors. We have also included Starburst objects to ensure secure decomposition of the Spitzer/IRS spectra. We have used the affinity propagation (AP) method to cluster the data into five groups within the sample according to torus contribution to the 5–15 μm range () and bolometric luminosity (). The AP groups show a progressively higher torus contribution and an increase of the bolometric luminosity from Group 1 ( and ) up to Group 5 ( and ). We have fitted the average spectra of each of the AP groups to clumpy models. The torus is no longer present in Group 1, supporting its disappearance at low luminosities. We were able to fit the average spectra for the torus component in Groups 3 ( and ), 4 ( and ), and 5 to Clumpy torus models. We did not find a good fitting to Clumpy torus models for Group 2 ( and ). This might suggest a different configuration and/or composition of the clouds for Group 2, which is consistent with the different gas content seen in Groups 1, 2, and 3, according to detections of molecular lines. Groups 3, 4, and 5 show a trend of decreasing torus width (which leads to a likely decrease of the geometrical covering factor), although we cannot confirm it with the present data. Finally, Groups 3, 4, and 5 show an increase of the outer radius of the torus for higher luminosities, consistent with a resizing of the torus according to AGN luminosity. [ABSTRACT FROM AUTHOR]