Alba Vega Alonso TetillaUniversity of SouthamptonCONTRIBUTED TALKProbing the relative roles of orientation and multi-scale gas distributions in shaping the obscuration of Black Holes through cosmic timeThe nature of obscuration in Active Galactic Nuclei (AGN) is still an open debate. It is unclear what are the relative contributions to the line-of-sight Hydrogen column densities from galaxy-scale obscuration and from torus-like obscuration. The latter source is expected to play a significant role in Unification Models, while the former is relevant in Evolutionary Models.

In this work we make use of a combination of both semi-analytic models (GAEA) and semi-empirical models of galaxies and supermassive black holes in a cosmological context to comprehensively probe obscuration properties. To each AGN in our mocks we assign a light-curve which is fine-tuned to reproduce the observed bolometric luminosity function at different epochs. We consider a detailed object-by-object modelling of obscuration, in which for each AGN we assign a gas fraction with a certain profile. Irrespective of our assumptions, we find that galaxy-scale obscuration can hardly reproduce the fraction of sources with logNH>=24, which require an additional torus-like component with a column density that decreases with increasing luminosity to match the data on obscured fractions. The torus-like component should be present in all evolutionary stages of a visible AGN in our models to be effective. On the other hand, galaxy-scale gas obscuration is sufficient to reproduce the fraction of obscured AGN with 22<logNH<24, also highlighting that the strong luminosity and time dependence of Compton-thin AGN (logNH<24) is not a consequence of AGN feedback, but rather of the gas reservoirs becoming more compact with decreasing stellar mass and increasing redshift.
Andy LawrenceUniversity of EdinburghCONTRIBUTED TALKDelayed appearance of coronal lines, Balmer lines, and MIR in AT2019qiz In a survey of late-time spectra of TDEs, we detected the delayed response of narrow emission lines, dust emission, and X-rays in AT2019qiz. Two and a half years after the outburst, coronal lines have peaked, but Balmer lines and MIR emission are still rising. This confirms earlier speculation that extreme coronal line emitters in apparently non-active galaxies are caused by previously missed TDEs. It also demonstrates the existence of circumnuclear material connected to previous activity, on a scale similar to the expected "torus", tracked by a kind of slow-scale reverberation. We will report modelling of the surrounding material.
Ari LaorTechnionCONTRIBUTED TALKThe Free-Free emission. Theory and ObservationsSee The effect of radiation pressure compression (RPC) on ionized gas in active galactic nuclei (AGNs) likely sets the photoionized gas density structure. The photoionized gas free-free absorption and emission are therefore uniquely set by the incident ionizing flux. We use the photoionization code CLOUDY RPC model results to derive the expected relations between the free-free emission and absorption properties and the distance from the AGN centre, for a given AGN luminosity. The free-free absorption frequency of RPC gas is predicted to increase from ~100 MHz on the kpc scale to ~100 GHz on the sub-pc scale, consistent with observations of spatially resolved free-free absorption. The free-free emission at 5 GHz is predicted to yield a radio loudness (R) of ~0.03, below the typical observed values of R ~ 0.1-1 in radio-quiet AGNs. However, the flat free-free radio continuum may become dominant above 100 GHz. The suggested detection of optically thin free-free emission in NGC 1068, on the sub-pc torus scale, is excluded as the brightness temperature is too high for optically thin free-free emission. However, excess emission observed with Atacama Large Millimeter/submillimeter Array (ALMA) above 150 GHz in NGC 1068 is consistent with the predicted free-free emission from gas just outside the broad-line region, a region that overlaps the hot dust disc resolved with GRAVITY. Extended ~100 pc-scale free-free emission is also likely present in NGC 1068. Future sub-mm observation of radio-quiet AGNs with ALMA may allow to image the free-free emission of warm photoionized gas in AGNs down to the 30 mas scale, including highly absorbed AGNs.
Atsushi TanimotoKagoshima UniversityCONTRIBUTED TALK NuSTAR Observations of 52 Compton-thick Active Galactic Nucleus Candidates Selected by the Swift/Burst Alert Telescope All-sky Hard X-Ray SurveyWe present a systematic broadband X-ray spectral analysis of 52 Compton-thick active galactic nucleus (AGN) candidates selected by the Swift/Burst Alert Telescope all-sky hard X-ray survey observed with Chandra, XMM-Newton, Swift, Suzaku, and NuSTAR. To determine the torus properties, we use an X-ray spectral model from a clumpy torus (XClumpy). As a result, the hydrogen column density along the line of sight obtained from the XClumpy model indicates that 24 objects are Compton-thin AGNs and 28 objects are Compton-thick AGNs in a 90% confidence interval. This is because the torus models and observational data applied are different. The hydrogen column density along the equatorial direction of Compton-thick AGNs inferred from the XClumpy model is larger than that of less obscured AGNs. The Compton-thin torus covering factor $C_{22}$ obtained from the XClumpy model is consistent with that of Ricci et al. (2017) in the low Eddington ratio ($\log R_{\mathrm{Edd}} \leq -1.0$), whereas $C_{22}$ inferred from the XClumpy model is larger than that of Ricci et al. (2017) in the high Eddington ratio ($-1.0 \leq \log R_{\mathrm{Edd}}$). The average value of the Compton-thick torus covering factor $C_{24}$ obtained from the XClumpy model is $36_{-4}^{+4}$%. This value is larger than that of Ricci et al. (2017) based on the assumption that all AGNs have intrinsically the same torus structure. These results suggest that the structure of Compton-thick AGNs may be intrinsically different from that of less obscured AGNs.
Bernd VollmerCDS, Observatoire astronomique de StrasbourgCONTRIBUTED TALKModels of thick turbulent gas disks around supermassive black holes and their application to the Galactic Center and NGC 1068The gas disk in the nucleus of NGC1068 has several properties in common with the Circumnuclear Disk (CND) in the Galactic Center: both are thick rotating gas rings, which are kinematically perturbed. To interpret observations of these regions and determine the physical properties of their gas distribution, we present a modeling effort that includes the following: (i) simple dynamical simulations involving partially inelastic collisions between disk gas clouds; (ii) an analytical model of a turbulent clumpy gas disk calibrated by the dynamical model and observations; (iii) local turbulent and cosmic ray gas heating and cooling via H_2O, H_2, and CO emission; and (iv) determination of the molecular abundances. We also consider photodissociation regions (PDRs) where gas is directly illuminated by the central engine. We compare the resulting model data cubes of the CO, HCN, HCO+, and CS brightness temperatures to available observations. In both cases the gas kinematics can be explained by one or two clouds colliding with a preexisting ring. With only dense disk clouds, the observed line fluxes can be reproduced to within a factor of about two. Our models indicate that turbulent mechanical energy input is the dominant gas-heating mechanism within the thick gas disks. Turbulence is maintained by the gain of potential energy via radial gas accretion, which is itself enhanced by the collision of the infalling cloud. Our models support the scenario of infalling gas clouds onto preexisting gas rings in galactic centers.
Bert Vander MeulenGhent UniversityCONTRIBUTED TALKFull-3D X-ray "torus" models with SKIRTDetailed radiative transfer dust modelling suggests that circumnuclear AGN media are complex with clumps and filaments, while recent MIR-observations hint towards polar extended structures of gas and dust, as opposed to the classical dusty torus paradigm. Observations of reprocessed X-ray emission could form a powerful probe to dissect the central parsec structure of AGN, given that advanced X-ray models are available to handle their precise distribution of gas and dust, consistent with the "torus" models used in IR.

We present the new X-ray functionalities of the established SKIRT code —a high-performance Monte Carlo simulation code modelling radiation transport in full 3D— and demonstrate how X-ray radiative transfer is used to model multi-phase “torus” media with complex geometries. Notably, SKIRT includes an advanced treatment of dust extinction and bound-electron scattering in full 3D, allowing for realistic model predictions and X-ray data interpretation. Extended with a complete set of X-ray physics, the SKIRT code can now be used to make self-consistent model predictions over the IR to X-ray range.

We use SKIRT to make model predictions in X-rays and IR for various "torus" setups. We demonstrate the full-3D capabilities of our code by post-processing hydrodynamical torus simulations with complex polar components. Finally, we present mock observations demonstrating how geometry effects will appear in current XMM-Newton and forthcoming XRISM observations.
Brivael LalouxNational Observatory of AthensCONTRIBUTED TALKA new look through AGN obscuration: X-ray spectroscopy guided by multi-wavelength informationA complete census of Active Galactic Nuclei (AGN) is necessary to understand the growth of supermassive black holes across cosmic time.
In this approach, the surrounding clumpy torus of gas and dust hardens the task by obscuring the central photon source, making the identification of obscured AGN more challenging, especially in the case of Compton-thick sources.
We propose a new Bayesian approach to characterise the level of obscuration of AGNs in deep extragalactic surveys. This methodology uses multiwavelength priors on the bolometric AGN luminosity to guide the X-ray spectral analysis and yield improved constraints on the physical properties of the AGN.
We apply this method to the deep multiwavelength observations in the Chandra COSMOS-Legacy field to provide a new sample of heavily obscured and Compton-thick AGNs. We are using the BXA package with the physically-motivated UXCLUMPY torus model for the X-ray spectral analysis.
This is further combined with an accurate characterisation of the X-ray selection function to estimate in a non-parametric manner the X-ray AGN space density as a function of the redshift, accretion X-ray luminosity and line-of-sight obscuration.
We compute the AGN obscuration fraction and its evolution, which are intrinsically related to the torus coverage of the AGN.
Our analysis also provides new constraints on the Compton thick AGN fraction out to $z \sim2$, and our results deviate from popular X-ray luminosity functions in the literature. It highlights the importance of using multiwavelength information as prior to guide X-ray spectral fitting, especially for the faintest and most obscured sources.
Calvin SykesUniversity of SouthamptonCONTRIBUTED TALKCasting light on new AGN observations with RHD simulationsRadiation-hydrodynamic simulations have proven to be an effective tool for modelling the ~parsec-scale structure surrounding active galactic nuclei, yielding insight into the formation and evolution of the outflows AGN produce, and providing evidence for the hypothesis that obscuration due to the dust content of these winds is responsible for the polar IR emission found in interferometric observations.

The model we have developed at Southampton combines Lagrangian hydrodynamics with accurate thermochemistry and radiative transfer, permitting the interaction between gas and AGN to be faithfully captured. It is also flexible, allowing for both high-resolution calculations that directly resolve the wind-launching process; and calculations performed in a larger simulated domain at lower resolution and with winds launched by a subgrid model which allow the long-term evolution of the wind to be tested.

I will show how a combination of results from these two classes of simulation can help interpret new AGN observations from JWST and GRAVITY+, in particular through the generation of realistic mock images from the simulation outputs.

A limitation of existing simulations is that they impose a torus geometry, typically a differentially-rotating thin disk, in the initial conditions, such that the simulated evolution represents the transient response to the AGN radiation field. Accordingly, I will also present initial results from an extension of the model, in which a torus structure is instead dynamically built from the accretion of individual gas clouds, as is suggested by observations of the central region of the Milky Way.
Carolina AndonieDurham UniversityCONTRIBUTED TALKLocalizing narrow Fe Kα emission within bright AGNThe 6.4 keV Fe Ka emission line is a ubiquitous feature in X-ray spectra of Active Galactic Nuclei (AGN), and its properties track the interaction between the variable primary X-ray continuum and the surrounding structure from which it arises. In this project, we have investigated the nature and origin of the narrow Fe Ka emission using X-ray spectral, timing and imaging constraints for 38 bright nearby AGN (z < 0.5) from the BAT AGN Spectroscopic Survey, using Chandra and XMM-Newton data. We found that for 90% of AGN with FWHM measurements, the virial RFeKa is smaller than the dust sublimation radius (Rsub). Despite a wide range of variability properties, the constraints on the FeKa photon reprocessor size from the timing analysis independently confirm that RFeKa is smaller than Rsub in 83% of AGN. Finally, the imaging analysis yields loose upper limits for all but two sources; Circinus Galaxy and NGC 1068 show significant but subdominant Fe Ka emission extended up to hundreds of parsecs. We conclude that the bulk of narrow Fe Ka emission in typical AGN predominantly arises from regions smaller than and presumably inside Rsub, and thus is associated either with the outer broad-line region or outer accretion disk. However, the large diversity of continuum and narrow Fe Ka variability properties are not easily accommodated by a universal scenario. I will discuss the implications of our work for future studies and how facilities such as XRIMS and Athena will improve our understanding of the Fe Ka emission.
Claudio RicciUniversidad Diego Portales (Chile)INVITED TALKX-ray observations of the close environments of AGNIn my talk I will review recent developments in the study of the circumnuclear environments of accreting supermassive black holes in the X-ray band. I will discuss studies focussed on both absorbed and reflected X-ray radiation, and present newly developed X-ray models. Finally, I will discuss some of the exciting future developments that can be expected in the next years with the advent of XRISM.
David J. RosarioNewcastle UniversityINVITED TALKThe Torus and its environment as seen in the InfraredThe torus is a creature of dust and gas, intimately connected to the cycle of inflow and outflow that sustains an AGN. In the last decade, our field has been witness to astounding improvements in infrared observational capabilities, including resolution, sensitivity, and stability, culminating with JWST in the past several months. This has finally allowed us to directly view the torus and its immediate environment through a multitude of IR tracers. We have been able to outline the major structural components, their interplay, and, presentely, their variety. I will review our best understanding of the nuclear and circumnuclear regions of nearby AGN, starting with the picture developed before the first JWST observations. I will then present a summary of new JWST results and discuss them in the context of our existing understanding. I will end with some thoughts on whether we need a drastically new model for the nuclear environment of AGN.
Donaji Esparza ArredondoInstituto de Astrofísica de CanariasINVITED TALKThe connection between mid-infrared dust emission and the X-ray reflector component in AGNsIn recent decades, several multiwavelength studies have been dedicated to exploring the properties of the obscuring material in active galactic nuclei (AGN), which is key for understanding the class diversity of these sources. Mainly, various models at mid-IR and X-ray wavelengths have been developed to describe the structure and distribution of this material and constrain its physical and geometrical parameters through spectral fitting techniques. However, questions around how torus mid-infrared and X-ray emission are related remain unanswered. In this talk, I will present the results obtained from a comparison of the dust and gas distributions in a sample of nearby AGNs with NuSTAR and Spitzer spectra available. We find that a combination of smooth and clumpy distributions of gas and dust, respectively, is preferred for ∼80% of sources. However, considering other available information about each source, such as the absorption variability, we find that ∼50% of our sources are best described by a clumpy distribution of both dust and gas. The remaining ∼50% of our sources can still be explained by a smooth gas distribution and a clumpy dust distribution. At least six alternative scenarios could resolve the observed properties of our sample. In this talk, I will also describe how a simultaneous fitting technique, which combines data and models of both ranges of wavelengths, is helpful in exploring the complexity of this torus and improving the constrain of the physical parameters of this structure.
In this talk, I will present the role of magnetic fields (B-fields) in the unification scenario of active galaxies and how we can detect the signature of these B-fields in the dusty and molecular tori. I will present a review of what we have learned from infrared (IR) and sub-mm polarimetric observations of Seyfert galaxies and the prospects of this analysis using upcoming ALMA polarimetric observations and future extremely large telescopes.
In general, to explain the transfer of energy surrounding supermassive black holes (SMBH), most of the theoretical models, if not all, must incorporate magnetic fields (B-fields). Advected B-fields are required in all models to explain the launching and collimation of jets and accretion flow. This is the main physical mechanism for powering the core of galaxies that contain active nuclei. Although this process can explain the dynamics of matter at sub-pc scales around the black hole, there is still no clear understanding of how the matter from the host galaxy, which contains kpc-scale B-fields in close equipartition with the diffuse interstellar medium, feeds SMBHs at scales of 10-100 pc.
We have observed the signature of magnetically aligned dust grains at distances of a few tens-pc at infrared/sub-mm wavelengths in a sample of radio-loud (RL) and radio-quiet (RQ) active galactic nuclei (AGN). We found that RQ AGN are low polarized (<0.4%), while RL AGN are highly polarized (5-11%) at 10-100 um. These results are particularly interesting because the dusty torus represents the AGN accretion flow on pc-scales, and this result, besides the radio differences, may be the most telling and dramatic empirical difference between RL versus RQ AGN. For RQ AGN, our results are consistent with the outer region (5 − 120 pc) of the dusty obscuring material being filled with an unmagnetized or highly turbulent, disk and/or expanding outflow at scales. For RL AGN, the measured 89 μm polarization arises primarily from magnetically aligned dust grains associated with a 5 − 120 pc-scale dusty obscuring structure with a toroidal B-field orientation highly offset, 65 ± 22◦, with respect to the jet axis. These findings have profound implications for how we classify and study the evolution of active galaxies.
Francesco SalvestriniINAF - Astrophysical Observatory of ArcetriCONTRIBUTED TALKUnveiling Compton-thick AGN with NuSTAR and mid-IR observationA multi-wavelength strategy is necessary to achieve an accurate characterization of the AGN emission and the properties of the surrounding material, especially in the case of heavy obscuration or weak emission. Coupling the nearly unbiased mid-IR selection with the observations in the X-rays, which are able to penetrate and measure large columns of obscuring material, is crucial to obtain a complete picture of the AGN emission and the surrounding material. Here, we present the results from a complete and systematic study of the hard X-ray properties for 35 mid-IR selected local Seyferts 2, by exploiting the focusing power of NuSTAR at energies above 10 keV.
By modelling the spectral shape of emission reprocessed by the torus (absorbed, reflected and fluorescent emission line components), we put constrains on the shape and the properties (e.g., clumpiness) of the torus.
We present i) the first accurate determination of the intrinsic power and column density of the obscuring material for an almost complete Type 2 AGN sample, with new and archival NuSTAR observations; ii) constrains on the properties of the obscuring torus with physically motivated models (e.g., MyTorus) in the X-rays. iii) The comparison of the level of obscuration in the X-rays with that derived in the mid-IR with different proxies (e.g., the silicate absorption feature, PAH WE).
Our results allow us to investigate the population of nearby heavily-obscured AGN, as well as the multi-wavelength properties of the obscuring torus, crucial to design future campaign with larger samples.
Francesco UrsiniUniversità Roma TreCONTRIBUTED TALKIXPE measurement of the X-ray polarization of the torus in the Circinus GalaxyWe present the Imaging X-ray Polarimetry Explorer (IXPE) observation of the Circinus Galaxy, the closest and X-ray brightest Compton-thick AGN. We find the source to be significantly polarized in the 2–6 keV band. From previous studies, the X-ray spectrum is known to be dominated by reflection components, both neutral (torus) and ionized (outflow cone). Our spectropolarimetric analysis of IXPE and Chandra data indicates that the polarization degree is 28 ± 7 per cent (1-sigma confidence level) for the neutral reflector, with a polarization angle of 18° ± 5°, roughly perpendicular to the radio jet. A comparison with Monte Carlo simulations shows that the neutral reflector is consistent with being an equatorial torus with a half-opening angle of 40°–50°. This is the first X-ray polarization detection in a Seyfert galaxy, confirming the basic predictions of the Unification Model and paving the way for future multiwavelength polarimetric studies of AGNs.
Gaia GasparObservatorio Astronómico de CórdobaCONTRIBUTED TALKCircumnuclear hot dust in Seyfert 2 nucleiThe extent, geometry and temperature distribution of hot dust (T approx. 700-1500 K) detected in the Near Infrared (NIR) is under a strong debate recently fueled by the now available high resolution interferometry data that can target the sub-parsec regions of the torus. In larger extensions, red excesses have been detected in the NIR K-band (1.9 - 2.5 microns) up to some hundred of parsecs and different explanations have been postulated for the heating source. Using NIR spectroscopy, obtained with Flamingos-2 at Gemini South, we have explored the circumnuclear regions of nearby AGNs with resolutions under 0.5". In this talk I will present evidence for hot dust (T approx. 1000 K) at resolved radii up to 100 pc in NGC 6300 and NGC 4945 nuclei and I will compare it to the case of NGC 5128 (Centaurus A) where we have found hot dust only at the unresolved core. I will discuss the different heating mechanisms that have been postulated in the literature in the context of the results for these three Seyfert 2 nuclei. Additionally, I will present Nirdust, a python package recently developed to detect dust and measure its temperature using K-band spectra.
Georgios DimopoulosUniversidad Diego Portales, Santiago, ChileCONTRIBUTED TALKExploring the circumnuclear environment of SMBHs using ray-tracing simulations in the X-ray bandX-ray photons are produced within a few gravitational radii from the SMBH. This X-ray radiation is then reprocessed by neutral and ionized gas around the AGN, and therefore it carries information about the properties of the circumnuclear material. By running ray-tracing simulations in the X-rays with the RefleX platform (Paltani & Ricci 2017), we show that the shape of the spectrum is highly sensitive to the physical and geometrical properties of the circumnuclear material. RefleX is the first platform that considers dust in the X-ray band, which is included in our simulations.

We have developed geometrical models of the AGN environment, including all the most important components: accretion disk, broad-line region, torus and polar dust. We have explored different properties of each component (e.g., column density, metallicity, dust percentage, geometrical properties) and tested how they affect the shape of the X-ray spectrum. We have then applied these new, realistic, models to state-of-the-art X-ray data (e.g., Chandra, XMM-Newton, NuSTAR). In my talk, I will discuss our findings and show how this complex modelling will be particularly important in the next few years, with the advent of high-resolution X-ray instruments, such as that on-board XRISM.
Ismael Garcia-BerneteUniversity of OxfordCONTRIBUTED TALKTorus and dusty polar outflow dependence on AGN properties: results from modelling the high angular resolution IR emissionIn this talk, I will summarise our recent results on the modelling of the nuclear IR emission of an ultra-hard X-ray volume-limited sample of 24 Seyferts by using, for the first time, subarcsecond resolution data and different torus models. We find that the best-fitted models depend on the NH, which is related to the X-ray and optical classification. In particular, smooth, clumpy and two-phase torus models (i.e. without including the polar dusty wind component) best reproduce the IR emission of AGN with relatively high hydrogen column density (i.e. Sy2). However, clumpy disc+wind models provide the best fits to the nuclear IR SEDs of Sy1/1.8/1.9 (with low NH), specifically in the near-IR (NIR) range. The success of the disc+wind models in fitting the NIR emission 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 Seyferts having unfavourable (favourable) conditions for launching IR dusty polar outflows are best-fitted with smooth, clumpy and two-phase torus (disk+wind) models confirming the predictions from simulations. Thus, our results indicate that the nature of the inner dusty structure depend on the intrinsic AGN properties. The advent of JWST has ushered a new era in studies of the central region of local galaxies, and its observations will be crucial to better understand the nuclear dusty region of AGN.
Ivano Saccheo University of Roma 3CONTRIBUTED TALKMean SED of hyper-luminous QSOsIn this talk, I will present the characterization of the mean SED of a sample composed of the most luminous type 1 QSOs (the WISSH sample, Lbol>1047 erg/s) at z~2-4.5, focusing on the differences we find with respect to the typical SED of less luminous sources. I will also present the mean SED derived from different sub-samples of QSOs showing peculiar spectral features (BAL vs non-BAL QSO and CIV weak vs non CIV weak QSOs) and the bolometric corrections obtained for 5100 A° and 3 micron luminosities.
We find that these hyper-luminous QSOs have a harder optical continuum and an enhanced near IR emission which we observe both as a more prominent red bump and as a shift to higher frequencies of the typical dip between nuclear and torus emission. We attribute this result to the presence of an extra hot dust component close to its sublimation temperature. By extending this analysis to the more heterogeneous SDSS QSO catalog, I will discuss whether our results can be generalized to the entire population of hyper-luminous QSOs. Finally, I will discuss the location of WISSH QSOs in the recently proposed star-forming vs AGN dominated galaxy diagnostic diagram (Symeonidis & Page 2021) and its possible extension up to z = 4.5.
Jacob IsbellMPIACONTRIBUTED TALKSubparsec Imaging of the Circumnuclear Dust in Circinus using MATISSEThe Circinus Galaxy is the nearest Seyfert 2 and serves as an ideal laboratory for studying AGN obscuration, fueling, and feedback. Previous infrared observations revealed complex structures and polar dust emission in Circinus, challenging the idea of the simple obscuring torus from the Unified Model. We observed Circinus with the new instrument, VLTI/MATISSE, producing 150 correlated flux and 100 closure phase spectra between 3 and 13μm. The novel inclusion of closure phases makes infrared interferometric imaging of this source possible for the first time. We use IRBis to reconstruct images in the LMN-bands at ~10mas (= 0.19pc) resolution. The thermal dust emission is clearly separated into several components: an unresolved source, a thin disk 1.5pc in diameter along PA~30°, and polar emission extending >2pc perpendicular to the disk and exhibiting significant substructure. We fit blackbody functions with dust extinction to several apertures extracted from the images to produce a temperature distribution. Steep temperature gradients along the disk (~360K to ~210K in 0.72pc) and low LM fluxes show that the disk is composed of dense material which completely obscures the sublimation zone. High temperatures (>230K) far from the central engine in the polar direction indicate significant dust clumpiness and lower density. Comparisons to radiative transfer modeling attest to the dusty nature of the sub-pc scale environment in Circinus. The morphology and temperature distribution reinforce disk+wind models and thus these images give an unprecedented simultaneous view of both AGN fueling and feedback channels.
James AgostinoUniversity of Toledo (Ohio, US)CONTRIBUTED TALKQuantifying Nuclear Molecular Gas Content with High Resolution ALMA CO Observations of Luminous Infrared GalaxiesBlack hole mass scaling relations have been a hot topic in the past few decades due to the apparent impact that black holes have on global galaxy properties despite their small gravitational regions of influence. In this project we utilize state of the art CO observations from ALMA of several luminous infrared galaxies to reach 10s of parsec resolution, allowing us to both quantify the amount of cold nuclear molecular gas and take a closer look at the detailed structure of these extreme environments in which we may resolve a torus. Black hole masses in these galaxies have been measured dynamically from AO-assisted integral-field spectroscopy in the past, but the spatial resolution was still not high enough to account for the nuclear structure we now see. Our ALMA data reveal a significant amount of cold molecular gas very close to these black holes, which had made its way into previous dynamical measurements as part of the black hole mass. We find this molecular gas can contribute as much as 10% to the dynamical measurements originally attributed solely to the black hole. We use these data to provide corrected black hole masses and examine their resulting positions on black hole scaling relations, which have strong implications for fueling and feedback within galactic nuclei.
James LeftleyOCACONTRIBUTED TALKAn mid-infrared interferometric survey of nearby AGNAGN image reconstructions in the IR created from MATISSE and GRAVITY data have shown their dusty central regions are very complex and, at times, difficult to interpret. However, for example in the case of Circinus, the overarching geometry uncovered at longer wavelengths by the reconstruction agrees with the initial simplistic models from limited datasets acquired with MIDI. Multiple AGN have now been observed with MATISSE, often with insufficient coverage for image reconstruction. However, a single MATISSE snapshot contains enough information to fit simplistic models. In this presentation, we will show the observations of these AGN as well as simplistic modelling to the interferometric data in an attempt to understand the distribution of dust at their centres.
Keiichi WadaKagoshima UniversityINVITED TALKHydrodynamical pictures of the torus and other components in AGNsI will overview recent progress in the physics-motivated models of the obscuring tori and other primary components of AGNs, such as NLRs, polar dust emission and BLRs. The numerical models and radiative transfer simulations allow us to make realistic comparisons with high-resolution multi-wavelength observations from radio to X-ray over a wide range of spatial scales.
Konrad TristramEuropean Southern ObservatoryCONTRIBUTED TALKThe Sy 2 nucleus of Circinus -- the ALMA submm pictureThe Seyfert 2 nucleus of the Circinus galaxy is one of the best laboratories to study the physics of AGN in great detail.
I will present the most recent submm ALMA results for this nucleus and compare them to the findings in the infrared and at radio wavelengths. While the infrared mainly traces warm (T ~ 300K) dust in the polar direction on parsec scales, the cold (T < 100K) and dense molecular and dusty material seen in the submm is located in a relatively thin, disk-like structure. This material is clearly dominated by rotation with only little signs of an outflow. High gas density tracers show a strong, yet unresolved (∼4pc) concentration of the emission at the nucleus, pointing at a very small “torus”. While the gas gets denser and higher excited towards the centre, there is no clear evidence for any special chemistry. Circinus does not show a clear HCN enhancement due to an X-ray dominated region as observed in other AGN. In summary, a clear two components structure is found, composed of a dense molecular disk plus a dusty polar wind or "fountain", i.e. in general agreement to recent models of the torus.
Kyoko OnishiChalmers University of TechnologyCONTRIBUTED TALKCON-quest: on the properties of dense molecular gas in relation with moderately active galactic nucleiWe present ALMA observations of dense molecular gas at molecular torus (~50pc) scale resolution in 15 galaxies moderately luminous in infrared (10^10-11 Lsun; subLIRGs; Onishi et al. 2022ab in prep.).
Recent observations are revealing suggestive evidence of AGN activities affecting the surrounding molecular gas. Many of such projects aimed to observe a sample of galaxies with AGN, and nuclei with weaker activities are often not included.
Our sample includes 3 AGN hosts, 4 LINER hosts and 8 galaxies with star-forming regions. This enables us to directly compare the correlation of host galaxy properties and black hole properties from strong AGN hosts to galaxies without AGN.
From the obtained data, we firstly compare dense molecular gas distributions such as gas concentration, to the activity such as Eddington ratio or X-ray.
We then discuss the kinematic features, especially streaming motions of gas, and its correlation to the black hole mass and their activity.
Then we present spatially resolved HCN/HCO+ line intensity maps in our sample, and discuss the correlation between the kinematics and the AGN existence.
We also discuss the continuum distribution and its connection to the black hole activity.
Marko StalevskiAstronomical Observatory of BelgradeCONTRIBUTED TALKThrough the smoke and mirrors of the AGN in Circinus galaxyCircinus is the closest Seyfert 2 galaxy and harbors the second brightest active galactic nucleus (AGN) in the mid-infrared (MIR). Recent MIR interferometry and single dish imaging have cast this galaxy in a major role as a prototype of the newly recognized population of ‘polar dust AGN’. In this picture, a major fraction of the MIR emission is associated with dusty winds blown away from the sublimation zone by radiation pressure. I will present our recent and ongoing efforts to understand the obscuring and outflowing structures in Circinus using MIR imaging, optical polarimetry and IFS data, tied together by state-of-the-art radiative transfer simulations. All the evidence paints a consistent picture of a compact dusty disk responsible for the obscuration and feeding of the black hole, and a dusty outflow in the polar direction.
Martin WardDurham University, EnglandCONTRIBUTED TALKCoronal line emission from the innermost NLR: Torus or Other? We report on the association of near-infrared coronal line emission with the inner edge of the torus? in NGC 5548. Coronal lines are forbidden transitions arising from highly ionized (> 100 eV) states of heavy metals and were first detected in AGN in the early period of their spectroscopic study. Using spectra obtained in a year-long of NGC 5548 we performed a detailed study of the location, kinematics and variability of the coronal line emitting gas. We observe that the profiles of two near-infrared coronal lines ([Si VI] and [S VIII]) have broad wings in addition to narrow cores, whereas [S IX] and [Si X] have narrow cores only. The wings of [Si VI] and [S VIII] are highly variable but the line cores are not, implying multiple locations (stratification) of coronal line gas. The variability timescale, profile shape and photoionisation modelling indicate that these wings originate in an X-ray heated wind evaporated from the inner edge of the torus. Partial obscuration of the line emitting gas by the near side of the torus could explain the observed line asymmetry. The narrow line cores may be emitted at larger radii, further downstream in this stratified and accelerating wind. In the future, coronal lines may be used together with molecular line studies to better understand the innermost NLR and its connection with the obscuring material.

Mislav BalokovicYale UniversityCONTRIBUTED TALKResolving the Torus Using Broadband X-ray Spectroscopy and Milliarcsecond-scale Observations of Nearby AGNMaking use of sensitive broadband X-ray observations of nearby obscured AGN, recent studies are placing interesting constraints on some basic geometrical parameters of the structures that obscure the innermost regions. Constraints on the covering factor of the obscuring gas can be significantly improved over single-epoch spectral analyses using a self-consistent multi-epoch approach, which I will demonstrate on the nearby low-luminosity AGN NGC 1052. Both the spectral fitting and the line-of-sight column density variability statistics lead to the picture of a nearly uniform, Compton-thin obscurer with a large covering factor in this particular AGN. This is consistent with recent findings for other low-luminosity AGN. However, such a conclusion is model-dependent and in apparent conflict with subparsec-scale measurements of the free-free absorption profile based on multi-frequency VLBI observations with milliarcsecond angular resolution. These spatially resolved measurements inform building of new X-ray spectral models for the structures likely corresponding to the broad line region and the obscuring torus. Sensitive interferometric measurements for nearby AGN now extend down to near-infrared wavelengths. Developing and leveraging novel AGN models that account for spectral or spatial information in multiple spectral bands will provide a critical step forward in understanding the complexity of the structures widely known under the deceptively simple name of the torus.
Nora DrewesUniversity of SouthamptonCONTRIBUTED TALK Infrared Interferometry: The Connection Between the Polar Outflow Cone and the DiscThanks to interferometric studies in the mid-infrared with MIDI, we have revised our view of the dusty ‘torus’ in active galactic nuclei to be a two-part structure, an equatorial cone and a hollow polar outflow cone. Surveys of cool dust shows that the polar cone dominates in the 8 – 13 um wavelength range, giving us little idea about how the disc and cone are connected. The dust disc is thought to be the source of the 3 – 5 um SED bump. To investigate this connection between the dust and the disc, especially in the 3 – 5 um SED bump, we study several type 1 AGN using the MATISSE infrared interferometer. We aim to exploit the L (3.5 um) and M (4.6 um) bands to resolve the warm dust and the N-band (8 - 13 um) to resolve the cooler dust. We look at AGNs covering the parameter space, including the accretion rate, to test radiatively driven outflow models. One of the questions we examine is whether an increase in the accretion rate affects the opening angle of the polar dust cone.
Núria Torres-AlbàClemson UniversityCONTRIBUTED TALKX-ray Absorption variability in a sample of 14 local obscured AGNActive galactic nuclei (AGN) are powered by accreting supermassive black holes, surrounded by a torus of obscuring material. According to the unification theory, this torus is uniform and obscures certain lines of sight. However, more recent observations have brought us to consider a slightly more complex picture: both infrared observations and X-ray eclipsing events suggest the torus is likely to be a patchy structure. Here, we present the analysis of 14 nearby Seyfert 2 galaxies, selected to have at least one NuSTAR observation to accurately constrain parameters such as the torus average column density and covering factor. Our sample consists of a total of 85 X-ray observations at different epochs. We
measure with high accuracy the torus line-of-sight column density in each epoch. Our analysis shows line-of sight column density variability for 9/14 sources, as well as large differences between line-of-sight column densities and average torus column densities for variable sources. This suggests that the material responsible for obscuration and reflection might not be the same, pointing toward added complexities in the torus structure.
Omaira González MartínIRyA - UNAMCONTRIBUTED TALKNEW AGN TORUS MODEL INCLUDING THE ROLE OF GRAIN SIZESpectral fits to the infrared spectra from the nuclear regions of active galactic nuclei (AGN) can place constraints on the dust properties and distributions by comparison with models. However, none of the currently available models fully describe the current observations of AGN available today. Among the aspects least explored, we focus on the role of dust grain size. We offer to the community a new SED library, named [GoMar22] model, which is based on the two-phase torus model developed before, with a parameter space optimization and the inclusion of the maximum grain size as a model parameter. We created 777,600 spectral energy distributions using the SKIRT code, where the grain size can vary within the range Psize= 0.01-10.0um. We also fit this new and several existing libraries to a sample of 68 nearby and luminous AGN with Spitzer/IRS spectra dominated by the AGN dust. We find that the [GoMar22] model can adequately reproduce up to ~85-90% of the spectra. The dust grain size parameter significantly improve the final fit in up to 90% of these spectra. We find that ~1/3 of our sample requires dust grains as large as Psize~10um, suggesting dust grain growth at the proximity of the AGN. Nonetheless, we also remark that the disk+wind or the clumpy torus models are still required to reproduce the spectra of a non-negligible fraction of objects, suggesting the need of several dust geometries to explain the AGN infrared continuum.
Omar Ulises Reyes AmadorInstituto de Radioastronomía y Astrofísica - UNAMCONTRIBUTED TALKExploring an appropriate chemical composition of the dusty torus in a sample of nearby type-1 AGNThe Unified Scheme of AGN is currently the most accepted model that can simultaneously explain the different spectral characteristics observed in type-1 and type-2 AGN. It invokes the existence of a dusty structure that blocks the light coming from the Broad Line Region (BLR) in type-2 AGN. This dusty structure is responsible for the Mid-Infrared (MIR) emission of AGN. The most direct way so far used to study this structure, has been through Spectral Energy Distribution (SED) fitting, using dust emission models calculated through radiative transfer techniques. Among the assumptions considered when calculating such models, those regarding the dust properties are of crucial importance. Nevertheless, limited effort has been put forward to explore the chemical composition, the role of different optical properties and the grain size distribution. All of which can have a substantial impact on the theoretical radiative transfer calculations. In this research, we have thoroughly tackled part of this issue, by exploring the role of the dust chemical composition in the dusty torus through NIR-SED fitting of a sample of nearby type-1 AGN using the popular astronomical silicates and a set of amorphous and crystalline silicates. In this talk, I am going to present preliminary results.
Panayiotis TzanavarisNASA-GSFC / UMBCCONTRIBUTED TALKThin or Thick? Broad or Narrow? Answers, Implications, and ProspectsI will discuss state-of-the art physical modeling with MYTORUS to probe two key AGN properties, Compton thickness and Fe K emission line width, with broad and critical repercussions for galaxy evolution and cosmology. We used a sample of bona fide Compton thin AGN, which due to their expected moderate obscuration are ideal for constraining both torus properties and emission from the accretion disk, imprinted on narrow and broad Fe K emission, and associated continua, respectively. Contrary to our expectations, we found that emission from a torus clumpy geometry is sufficient to model all objects, with no need for a broad line arising in the inner part of the accretion disk. In addition, our modeling showed that, in fact, most of these objects are globally Compton thick. I will highlight how reliable modeling of torus properties, is significant in a broader context: Compton thickness is key for modeling the Cosmic X-ray Background and establishing the contribution from an obscured population; while relativistically broadened Fe K emission can provide insights on supermassive black hole spin, with implications on jet formation and galaxy evolution.
Peter BoormanCaltechCONTRIBUTED TALKIlluminating the densest AGN obscurers with the NuLANDS survey and beyondHigh-energy X-ray spectroscopy of Compton-thick AGN provides a unique testbed for studying the geometry and structure of the densest regions of the AGN torus. However, current estimates of the abundance of Compton-thick AGN remain extremely uncertain, and it is still unclear whether this uncertainty is driven by selection effects, luminosity/accretion rate dependencies, computational struggles with exploring complex parameter spaces or something else entirely. An important handicap of previous works has been the inability to effectively select Compton-thick AGN with approximately equal efficacy relative to the (often brighter) less-obscured AGN population. To investigate such issues, I will present NuLANDS — one of the largest NuSTAR legacy surveys ever performed, combining mid-to-far infrared colour selection with broadband X-ray spectroscopy, aiming to construct an unbiased census of AGN obscuration in the local Universe. Testament to the isotropic selection and comprehensive analysis strategies of the sample, we find a substantial directly observed Compton-thick fraction of 36%, with uncertainties that are consistent with the latest predictions from Cosmic X-ray Background synthesis models. NuLANDS thus marks a major step in completing the local census of AGN accretion activity, but there is still much work to be done. I will conclude with the current challenges faced by X-ray spectroscopic studies of the AGN torus, as well as the prospects for next-generation X-ray facilities to infer the geometry of the obscurer over a wide range of luminosity, redshift and column density.
Pierre VermotAstronomical Institute of the Czech Academy of SciencesCONTRIBUTED TALKThe parsec scale hot dust in NGC 1068I present the analysis of a GRAVITY/VLTI observation of the central region of the famous Seyfert 2 galaxy NGC 1068. The observation probes the smallest spatial scales and hottest temperatures of the dusty structure. It reveals a complex geometry, whose interpretation is not straight forward. Assuming that the observed structure is the innermost sublimation region of a dusty torus, I present a 3D radiative model consistent with all the observables.
Raffaella MorgantiASTRON/Kapteyn Institute Groningen Univ.CONTRIBUTED TALKCold gas in the heart of 3C84We explore the central regions of young and recently restarted radio galaxies using high resolution observations of cold molecular gas and HI (in absorption). In this way we aim at identify not only the presence of rotating structures (circumnuclear discs and tori) but also the presence of gas with disturbed kinematics or high turbulence, tracing the fuelling and feedback processes.

Here we focus on the case of 3C84 one of the most famous radio galaxies, known to have a fast duty cycle and located in the centre of the iconic gas-rich, cool-core Perseus cluster. Two HI absorption systems have been found in this object: one extremely narrow and highly redshifted and one as broad as FWZI~1000 km/s, centred around the systemic velocity. We trace the HI on multiple scales, from the kpc, using the WSRT and VLA, down to pc scales using the VLBA. We connect the properties of the HI with those of the molecular gas (observed in emission) from data available in the ALMA archive and literature.

We report on the results and compare them with what found in other objects located in different and less extreme environments.
Romain G. PETROVUniversity Côte d'AZur, Lagrange LaboratoryCONTRIBUTED TALKAGN dust tori with GRAVITY+, MATISSE Wide and a New Generation Fringe TrackerThe combination of GRAVITY+ and MATISSE Wide upgrades will dramatically increase the number of AGNs for which VLTI fringes would be correctly tracked, both on- and off-axis. The addition of a new generation fringe tracker would further increase this number. The size-luminosity and size-wavelength relationship found in the literature from Reverberation Mapping and MIDI/VLTI observations show that a significant number of these newly observable AGNs would have a torus large enough to be resolved. Here we provide an estimate of the numbers and nature of such targets and discuss the increase in the range of accessible AGN parameters such as the Eddington ratio, the radio-loudness, and the SMBH mass. We also evaluate the range of distances permitting at least spectro-astrometric estimates of torus size and potential eligibility for dust parallax measurements.
Ryosuke UematsuKyoto UniversityCONTRIBUTED TALKX-Ray Constraint on the Location of the AGN Torus in the Circinus GalaxyThe 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 Kα, carry key information on the radii of line emitting regions. Utilizing XCLUMPY, 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. First, we apply the updated model to the best available broadband spectra (3-100 keV) of the Circinus galaxy observed with Suzaku, XMM-Newton, NuSTAR, and Chandra, including 0.62 Ms Chandra/HETG data. We confirm that the torus is Compton-thick, geometrically thin, viewed edge-on, and has super-solar abundance. Subsequently, we perform simultaneous analyses of the Chandra/HETG first, second, and third order spectra with consideration of the spatial extent of the Fe Kα line emitting region. We successfully constrain the inner radius of the torus to be ~1.9×10^5 times the gravitational radius, or ~1.6×10^{-2} pc for a black hole mass of ~1.7×10^6 times solar mass. 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. This demonstrates that high resolution X-ray spectroscopy, especially with forthcoming X-Ray Imaging and Spectroscopy Mission (XRISM), is helpful to reveal the nature of inner regions of AGN tori.
Santiago GARCIA-BURILLOObservatorio de Madrid (OAN--IGN)INVITED TALKNew insights on the structure and kinematics of dusty molecular tori in AGN The advent of state-of-the-art high-angular-resolution NIR, MIR and submillimeter interferometer observations have made possible the obtention of spatially resolved images of the nuclear scale environment of active galactic nuclei (AGNs), commonly referred to in the literature as the “torus”. In the canonical scheme, the torus is expected to be located between the BLR and the NLR, and extend to a few parsec scales. In this talk we will review how these observations, obtained by facilities like VLTI-Gravity, VLTI-MATISSE and ALMA, have revolutionized the field by revealing with unparalled detail in a growing number of nearby AGN the 'many faces' of molecular tori and by imaging their associated dusty winds, which emerge in the shape of polar components.
Sara RosboroughRochester Institute of TechnologyCONTRIBUTED TALKThe Reverberation Response of the AGN Broad Line Region in the Context of the Dusty Torus Nestled within the dusty torus of an active galactic nucleus (AGN) is the broad line region (BLR), where gas clouds are deep within the black hole’s gravitational well and emission line profiles are Doppler broadened to several 1000 km/s. The BLR, therefore, is a crucial probe of the sub-parsec, inner regions of the AGN. However, the challenging task of spatially resolving the BLR means the structure and dynamics is poorly understood. The reverberation mapping technique utilizes the time delay between the variability of the AGN’s continuum source and the response of the broad emission lines to measure distances and kinematics of BLR’s gas clouds. The TOrus Reverberation MApping Code (TORMAC), developed by Almeyda et al. 2017, simulates the responses of the dusty torus clouds to the variability of the AGN's continuum emission. The simulated light curves can be compared to observed light curves to obtain structural information. Here we present results from TORMAC+BLR, which expands upon TORMAC, to simulate and investigate the velocity-resolved reverberation response of the BLR models with various geometries and dynamics. We use TORMAC+BLR to simulate both the torus and BLR light curves of the well-studied AGN, NGC 3783. The combination of BLR and torus reverberation mapping will enable a better understanding of the inter-relations between the two regions.
Satoko Sawada-SatohOsaka Metropolitan UniversityCONTRIBUTED TALKCircumnuclear dense molecular gas in the nearby radio galaxy NGC 4261The cold molecular gas in the circumnuclear disk (CND) of radio galaxies can play a key role in fueling the supermassive black hole (SMBH). High angular resolution images of the molecular gas within the SMBH sphere of influence (SoI) can also be a powerful tool for accurately measuring SMBH masses. However, the distribution of low-J CO lines appears to extend to the edge of CNDs. Alternatively, dense gas tracers such as HCN and HCO+ lines are expected to trace farther into SoI better, thus enabling more accurate measurements of SMBH masses.
We report on the first detection and maps of HCN J=1-0 and HCO+ J=1-0 emission lines from the circumnuclear region of a nearby radio galaxy NGC4261, using the Northern Extended Millimeter Array. Both molecular lines are detected at a radial velocity of ±700 km/s relative to the systemic velocity of the galaxy, and they arise from a CND with an outer radius of 100 pc. The velocity fields of HCN and HCO+ are fitted with a Keplerian disk rotation, and derived the enclosed mass. The dense gas mass associated with the CND is calculated to be 6.03×10^7 M_solar, which is comparable to a typical CND mass measured in galaxies of various types. It supports a positive correlation between the dense gas mass in the CND and the accretion rate onto the supermassive black hole, though there are uncertainties in the parameters of the correlation.
Satoshi YamadaRIKENCONTRIBUTED TALKLatest Picture of Torus and Polar Dust in Merging Galaxies Revealed by Hard X-ray to Radio Multiwavelength AnalysisWe perform systematic X-ray spectroscopy and the multiwavelength (hard X-ray to radio) SED decomposition of 57 merging systems (84 resolved galaxies) observed with NuSTAR and/or Swift/BAT. Analyzing the broadband X-ray spectra containing available soft X-ray data (Chandra, XMM-Newton, Suzaku, and Swift/XRT) with the clumpy torus model XCLUMPY (Tanimoto+19), we identify 40 hard-X-ray detected AGNs and constrain their torus parameters. The torus covering fractions (CF ~ 0.6) for the AGNs with $\lambda_{Edd}$ ~ 1 are larger than those of Swift/BAT-selected AGNs with similarly high Eddington ratios (Yamada+21, ApJS, 257, 61). For the multiwavelength SED decomposition using 17 instruments (X-ray spectra and 43 filter bands), we modify a SED-fitting code X-CIGALE (Yang+20) by implementing the infrared CLUMPY model with the same geometry as XCLUMPY. By adopting the torus parameters obtained by our X-ray fitting, we report the main results of the torus and outflowing polar dust. The integrated (UV-to-infrared) luminosities of polar dust are ~2 times larger than those of torus, reflecting the apparent covering fractions. The polar dust temperature is lower in late mergers (~130 K) than in early mergers (~170 K). The spatial scales of the polar dust, estimated by the temperature and dust sublimation radius, are consistent with the mid-infrared images (10-1000 pc; Asmus 2019) and increase with AGN luminosity and merger stage. These results suggest that the AGNs in late mergers become buried (large torus covering fraction) and show infrared-luminous kpc-scale dusty winds connected from the pc-scale region (Yamada+22, ApJS, submitted).
Seiji KamenoJoint ALMA Observatory / National Astronomical Observatory of JapanCONTRIBUTED TALKJet-Torus Interaction in the Radio Galaxy NGC 1052We present radio absorption features of sulfur-bearing molecules in the radio galaxy NGC 1052. Using ALMA, we detected SO absorption lines in multiple transitions of the upper levels of $N=2 - 8$ and estimated the rotation temperature of $\sim 500$ K. The high temperature is consistent with the excitation condition of H$_2$O maser emission and presence of vibrationally excited HCN and HCO$^+$ absorption lines. The sulfur-bearing gas is ascribed to evaporation of icy dust component through jet-torus interaction. The absorption line profiles are very different between submm- and mm-wavelengths: while submm features are composed of a single component centered at the systemic velocity, double-peaked profiles appear in mm. The double-peaked profiles may also imply interactions in both approaching and receding jets. Implication of jet-torus interaction supports collimation of the sub-relativistic jets by gas pressure of the torus.
Shoichiro MizukoshiInstitute of Astronomy, Graduate School of Science, The University of TokyoCONTRIBUTED TALKMeasurement of AGN dust extinction based on the near-infrared flux variability of WISE dataWe present the measurement of the line-of-sight extinction of the dusty torus for 463 active galactic nuclei (AGNs) based on the reddening of the color of the variable flux component in near-infrared (NIR). We collected long-term monitoring data by Wide-field Infrared Survey Explorer (WISE) for 513 local AGNs cataloged by the Swift/BAT AGN Spectroscopic Survey (BASS) and found that the multi-epoch NIR flux data in two different bands (WISE W1 and W2) are tightly correlated for most of the targets. The flux variation gradient (FVG) in the W1 and W2 bands was derived by applying linear regression analysis, and we reported that those for unobscured AGNs fall in a relatively narrow range, whereas those for obscured AGNs are distributed in a redder and broader range. The AGN’s line-of-sight dust extinction (Av) is calculated using the amount of the reddening in the FVG and is compared with the neutral hydrogen column density (NH) of the BASS catalog. We found that the NH/Av ratios of obscured AGNs are greater than those of the Galactic diffuse interstellar medium (ISM) and are distributed with a large scatter by at most two orders of magnitude. Furthermore, we found that the lower envelope of the NH/Av of obscured AGNs is comparable to the Galactic diffuse ISM. These properties of the NH/Av can be explained by increase in the NH attributed to the dust-free gas clouds covering the line of sight in the broad-line region. (Mizukoshi et al. 2022, MNRAS, 516, 2876)
Shoji OgawaKyoto UniversityCONTRIBUTED TALKSystematic Study of AGN Clumpy Tori with Broadband X-ray Spectroscopy: Updated Unified Picture of AGN StructureWe present the results of a systematic, broadband X-ray spectral analysis of nearby active galactic nuclei (AGNs) with the X-ray clumpy torus model (XCLUMPY; Tanimoto et al. 2019). By adding 16 AGNs newly analyzed in this paper, we study total 28 AGNs including unabsorbed and absorbed AGNs taken from Ichikawa et al. (2015) and García-Bernete et al. (2019). This is the largest sample whose X-ray and infrared spectra are analyzed by the clumpy torus models XCLUMPY and CLUMPY (Nenkova et al. 2008), respectively. The relation between the Eddington ratio and the torus covering factor determined from the X-ray torus parameters of each object follows the trend found by Ricci et al. (2017) based on a statistical analysis. We confirm the results by Tanimoto et al. (2020) that (1) the torus angular widths determined by the infrared data are larger than those by the X-ray data and that (2) the ratios of the hydrogen column density to V-band extinction ($N_{\rm H}/A_{\rm V}$) along the line of sight in obscured AGNs are similar to the Galactic value on average. Unobscured AGNs show apparently smaller line-of-sight $N_{\rm H}/A_{\rm V}$ ratios than the Galactic one. Our findings can be well explained by an updated unified picture of AGN structure including a dusty torus, dusty polar outflows, and dust-free gas, where the inclination determines the X-ray and optical classifications and observed torus properties in the X-ray and infrared bands.
Shumpei NagoshiKyoto UniversityCONTRIBUTED TALKProbing the origins of broad line region by reverberation mapping and multi-wavelength observations of an extremely variable quasarWhile the unified model of quasar structure provides a concise description of diverse spectra, the components' physical origins are unresolved. To explore the physical origin of the unified model, we focused on Changing-State Quasar as a target because observing structural changes associated with state transitions can provide insight into the origins of each structure. We aimed to understand the central core structure of the Changing-State Quasar and its changes before and after the state transition. As the research target, we selected SDSS J125809.31+351943.0, which exhibited one of the most significant variations in the history of observations. We performed reverberation mapping by optical spectroscopy to investigate the structure of the broad line region as well as the black hole mass. We also measured the time lag between the WISE light curve and optical light curve to estimate the size of the dust torus. In addition, we compared optical to X-ray spectral indices (αox) before and after the state transition to investigate the structure difference of the accretion disk. As a result, the variations in αox and the Eddington ratio were consistent with those predicted from the instability of the accretion disk due to hydrogen ionization. The variation in the shape of the broad lines indicates that two components exist in the broad line region. We suggest that these components originate from rotating/outflowing gases located near the dust torus generated by different processes.
Stefano MarchesiINAF-OAS BolognaCONTRIBUTED TALKThe characterization of the obscuring material in the nearby changing-look Compton thick AGN NGC 1358: results of a NuSTAR-XMM-Newton monitoringIn this talk, I present the results of a multi-epoch monitoring with NuSTAR and XMM-Newton of NGC 1358, a heavily obscured AGN whose properties made it an ideal changing look candidate. The source was indeed found to be highly variable in line-of-sight column density over time-scales from weeks to years, a result that allowed us to confirm its changing-look nature. We also found a tentative anti-correlation between column density and luminosity, which can be understood in the framework of Chaotic Cold Accretion clouds driving recursive AGN feedback. Besides this important result, I will also show how a multi epoch X-ray monitoring is highly effective in simultaneously constraining three otherwise highly degenerate parameters: the torus average column density and covering factor, and the inclination angle between the torus axis and the observer. In summary, he monitoring campaign of NGC 1358 has proven the efficiency of our newly developed method to select candidate NH-variable, heavily obscured AGN, which we plan to soon extend to a larger sample to better characterize the properties of the obscuring material surrounding accreting supermassive black holes, as well as constrain AGN feeding models.
Susanne AaltoChalmers University of Technology, Department of Space Earth and EnnvironmentINVITED TALKAn ALMA view on the chemistry and kinematics of AGN torii.Cold gas plays a central role in feeding and regulating star formation and growth of supermassive black holes (SMBH) in galaxy nuclei. SMBHs and their accretion disks are often surrounded by a dusty torus that obscures the AGN, and serves as a reservoir of gas. The torii are dynamically active regions on scales from sub-pc to tens of pc. They are subject to in- and outflows and may also be actively star forming.

I will give a brief review of recent mm and submm wave studies of the kinematics and chemistry of nearby AGN-torii. Chemistry is an emerging tool to study the evolution of the torus through the interplay between kinematics and radiation and the gas properties. I will also present some recent results from the ALMA CONfirm high-resolution survey of extremely dust obscured nuclei and propose an evolutionary path for extremely thick tori.
Takuma IzumiNAOJCONTRIBUTED TALKResolving supermassive black hole feeding, feedback, and obscuration: multiphase gas flows down to sub-parsecMass accretion is a fundamental process for the growth of supermassive black holes and activating the central engine. However, detailed accretion properties have not been observationally identified at the central ~10 parsec of active galaxies due to its compactness. Here we present the direct detection of parsec-scale dense molecular inflow in the active nucleus of the Circinus galaxy (type-2 AGN) based on high resolution ALMA observations. The dense gas disk is gravitationally unstable and drives accretion down to the central ~1 parsec. Only a tiny portion (< 3%) of this inflow is consumed in the actual black hole growth but a bulk portion is blown-out by multiphase outflows. For example, diffuse atomic gas exhibits AGN-driven slow outflows (< 40 km/s) that eventually fall back to the disk. This vertical gas motion produces a geometrically thick disk (aspect ratio ~0.5) with a sufficiently high gas-column density to obscure the nucleus. We also identified a parsec-scale root part of fast (~200 km/s) ionized outflows that would clarify the origin of the MIR polar dust elongation. Our observations provide a spatially resolved, highly dynamic picture of multiphase AGN feeding, feedback, and consequently obscuration.
Taro ShimizuMax-Planck-Institute for Extraterrestrial PhysicsINVITED TALKImaging and Resolving the Central Parsec: A Revolution from NIR-MIR InterferometryWithin the last half-decade, near- and mid-infrared interferometry has seen a resurgence with the installation of both GRAVITY and MATISSE at the VLTI. Both instruments are capable of combining the light from all four UTs to provide six baseline interferometric measurements from 2-13 micron with a spatial resolution of several milli-arcseconds. In this talk, I will review the latest results from both instruments on the central parsec of AGN with a focus on the torus region but also look inwards to the broad line region. I will compare the results to the latest modern models and simulations of AGN structure and discuss where more input is needed from both theory and observations. Finally I will briefly look to what the future will bring with the upcoming GRAVITY+ upgrade that will not only enhance GRAVITY but also the VLTI infrastructure as a whole.
Tathagata SahaNicolaus Copernicus Astronomical Center of the Polish Academy of SciencesCONTRIBUTED TALKA BXA-driven study of reliability of X-ray Spectral fits in determining AGN torus morpholologyNumerous X-ray spectral models of the AGN torus have been developed over the last decade, (UXCLUMPY, CTORUS, MYTORUS, etc.). They span a range of assumed torus morphologies. The degeneracies in these models can limit reliable constraints of parameters of interest, such as the intrinsic photon index and parameters of the torus morphology. To analyze these effects, we simulate synthetic data under XMM-Newton and NuSTAR response files using six different models. We use the Bayesian X-ray analysis (BXA-Multinest) package to analyze the simulated datasets using the same set of models. For typical exposure times of observation and intrinsic fluxes for nearby Compton-thick AGN, several morphological parameters remain poorly constrained. In addition, the distinction of morphology using BXA is reliably possible only if we have a high intrinsic source flux for given a typical exposure time. Additional challenges regarding the initial modeling of the torus remain, thus IR imaging, X-ray polarimetry, and reverberation mapping can be extremely helpful. These studies can help us simulate arbitrary geometries with the help of generic radiative transfer and ray tracing codes (like REFLEX, XARS, SKIRT, etc.). Our project thus demonstrates the power of BXA both in terms of accuracy in applying the correct torus model and the constraints on the estimated model parameters and makes a case for a multiwavelength study involving support from imaging and timing studies.
Triana AlmeydaUniversity of FloridaINVITED TALKTime Domain studies of the dusty torus regions in AGNOne of the major characteristics of active galactic nuclei (AGN) is their variability. Time domain studies of AGN can aid in our interpretation and understanding of their structure and accretion mechanisms. In particular, due to the small angular sizes of the major AGN components, reverberation mapping has served as the main probe to investigate the structures of AGN, ranging from the accretion disk to the AGN’s innermost surrounding dust in the “torus”. In this talk, I will focus on the current state and future prospects of reverberation mapping the nuclear dust emission in AGN, from modeling to large time domain surveys including LSST.
Yixian CaoMPE (Max Planck Institute for Extraterrestrial Physics)CONTRIBUTED TALKResolved measurements of hot dust structure sizes around AGNs from GRAVITY observationsGRAVITY has demonstrated excellent efficiency in resolving the sizes of hot dust structures around the AGNs. In this talk, I will present our latest measurements of the hot dust structure sizes of nine type 1 AGNs from GRAVITY observations. Combining these new measurements with the other eight samples previously observed by GRAVITY, we study the hot dust structure size-luminosity relation. We find that the slope of this relation is shallower than the expected value of 0.5, which assumes the sublimation radius forms the inner boundary of the hot dust structure. We also find a strong correlation between the size of the hot dust structure and the size of the broad line region, which enables us to infer the BH masses from our direct measurements of the hot dust structure sizes. I will discuss the possible physical causes of these relations and the prospects of measuring hot dust size with future GRAVITY(+) observations.
Yoshihiro UedaKyoto UniversityINVITED TALKProbing Torus Structure with X-Ray Imaging and Spectroscopy Misson (XRISM)X-ray observations are a powerful tool for studying AGN tori, because X-rays trace all matter including gas and dust at various physical conditions, thus providing us with an unbiased view of matter distribution. In this talk, we first present a brief summary of the specifications and latest status of the X-ray Imaging and Spectroscopy Mission (XRISM), planned to be launched in early 2023. XRISM is equipped with an X-ray micro-calorimeter that achieves unprecedented energy resolution of <7 eV in the iron-K band. The observation plan of AGNs in the performance verification phase is introduced. Then, we discuss the prospect of AGN science with XRISM, mainly focusing on investigation of torus structure.