This is the second in a series of papers devoted to explore a set of six dusty models of active galactic nuclei (AGN) with available spectral energy distributions (SEDs). These models are the smooth torus by Fritz et al. (2006), the clumpy torus by Nenkova et al. (2008B), the clumpy torus by , the two phase torus by Siebenmorgen et al. (2015), the two phase torus by Stalevski et al. (2016), and the wind model by Hönig & Kishimoto (2017). The first paper explores discrimination among models and the parameter restriction using synthetic spectra (González-Martín et al. 2019A). 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 (2017) provides good fits for ∼50% of the sample, and the clumpy torus model by Nenkova et al. (2008B) is good at describing ∼30% of the objects. The wind-disk model by Hönig & Kishimoto (2017) 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. 2008B) 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 times smaller for 10 pc tori) for the smooth torus by Fritz et al. (2006) and the two phase torus by Stalevski et al. (2016) than the one derived from the clumpy torus by (Nenkova et al. 2008B). 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.
We studied the circumnuclear MIR emission in a sample of 19 local active galactic nuclei (AGN) with high spatial resolution spectra using T-ReCS (Gemini) and CanariCam (GTC), together with IRS/Spitzer observations. We measured the flux and the equivalent width for the 11.3 µm PAH feature and the [SIV] line emission as a function of galactocentric distance. This allowed to study the star formation (SF) at sub-kpc scales from the nucleus for a large sample of nearby AGN. The [SIV] line emission could be tracing the AGN radiation field within a few thousand times the sublimation radius (R sub ), but it often peaks at distances greater than 1000 R sub . One possibility is that the SF is contributing to the [SIV] 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.
At distances from the active galaxy nucleus (AGN) 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 which surrounds the AGN. This is the first of two papers aiming at comparing six dusty torus models with available SEDs, namely
Several authors have claimed that the less luminous active galactic nuclei (AGN) are not capable of sustaining the dusty torus structure. Thus, a gradual re-sizing of the torus is expected when the AGN luminosity decreases. Our aim is to confront mid-infrared observations of local AGN of different luminosities with the gradual re-sizing and disappearance of the torus. We applied the decomposition method described by Hernán-Caballero et al. (2015) to a sample of about ∼ 100 IRS/Spitzer spectra of LLAGN and powerful Seyferts in order to decontaminate the torus component from other contributors. We have also included Starburst objects to ensure a secure decomposition of the IRS/Spitzer 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 5-15µm range(C torus ) and bolometric luminosity (L bol ). The AP groups show a progressively higher torus contribution and an increase of the bolometric luminosity, from Group 1 (C torus ∼ 0% and log(L bol ) ∼ 41) and up to Group 5 (C torus ∼ 80% and log(L bol ) ∼ 44). 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 the disappearance at low-luminosities. We were able to fit the average spectra for the torus component in Groups 3 (C torus ∼ 40% and log(L bol ) ∼ 42.6), 4 (C torus ∼ 60% and log(L bol ) ∼ 43.7), and 5 to Clumpy torus models. We did not find a good fitting to Clumpy torus models for Group 2 (C torus ∼ 18% and log(L bol ) ∼ 42). This might suggest a different configuration and/or composition of the clouds for Group 2, which is consistent with a different gas content seen in Groups 1, 2, and 3, according to the detections of H 2 molecular lines. Groups 3, 4, and 5 show a trend to decrease of the width of the torus (which yields 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 on the outer radius of the torus for higher luminosities, consistent with a re-sizing of the torus according to the AGN luminosity.
We measure the 10 and 18µm silicate features in a sample of 67 local (z < 0.1) type 1 active galactic nuclei (AGN) with available Spitzer spectra dominated by non-stellar processes. We find that the 10µm silicate feature peaks at 10.3 +0.7 −0.9 µm with a strength (Si p = ln f p (spectrum)/f p (continuum)) of 0.11 +0.15 −0.36 , while the 18µm one peaks at 17.3 +0.4 −0.7 µm with a strength of 0.14 +0.06 −0.06 . We select from this sample sources with the strongest 10µm silicate strength (σ Si10µm > 0.28, 10 objects). We carry out a detailed modeling of the IRS/Spitzer spectra by comparing several models that assume different geometries and dust composition: a smooth torus model, two clumpy torus models, a two-phase medium torus model, and a disk+outflow clumpy model. We find that the silicate features are well modeled by the clumpy model of , and among all models those including outflows and complex dust composition are the best (Hoenig et al. 2017). We note that even in AGN-dominated galaxies it is usually necessary to add stellar contributions to reproduce the emission at the shortest wavelengths.
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