3,454 research outputs found
Redefining the Torus: A unifying view of AGNs in the infrared and submillimeter
No full textThe advent of high-angular-resolution IR and submillimeter interferometry allows for spatially resolved observations of the parsec-scale environment of active galactic nuclei (AGNs), commonly referred to as the "torus." While molecular lines show the presence of large, massive disks, the IR observations appear to be dominated by a strong polar component that has been interpreted as a dusty wind. This paper aims at using characteristics shared by AGNs in each of the wavebands and a set of simple physical principles to form a unifying view of these seemingly contradictory observations: dusty molecular gas flows in from galactic scales of ~100 pc to the subparsec environment via a disk with small to moderate scale height. The hot, inner part of the disk puffs up due to IR radiation pressure and unbinds a large amount of the inflowing gas from the black hole's gravitational potential, providing the conditions to launch a wind driven by the radiation pressure from the AGN. The dusty wind feeds back mass into the galaxy at a rate of the order of ~0.1–100 M ⊙ yr−1, depending on the AGN luminosity and Eddington ratio. Angle-dependent obscuration as required by AGN unification is provided by a combination of disk, wind, and wind-launching region
Dust reverberation mapping in the era of big optical surveys and its cosmological application
No full textThe time lag between optical and near-infrared (IR) flux variability can be taken as a means to determine the sublimation radius of the dusty "torus" around supermassive black holes in active galactic nuclei (AGNs). I will show that data from large optical survey telescopes, e.g., the Large Synoptic Survey Telescope (LSST), can be used to measure dust sublimation radii as well. The method makes use of the fact that the Wien tail of the hot dust emission reaches into the optical and can be reliably recovered with high-quality photometry. Simulations show that dust sublimation radii for a large sample of AGNs can be reliably established out to redshift z ~ 0.1-0.2 with the LSST. Due to the ubiquitous presence of AGNs up to high redshifts, they have been studied as cosmological probes. Here, I discuss how optically determined dust time lags fit into the suggestion of using the dust sublimation radius as a "standard candle" and propose an extension of the dust time lags as "standard rulers" in combination with IR interferometry
Dataset in support of the Southampton doctoral thesis 'Probing the inner regions of Active Galactic Nuclei through variability analysis'
No full textThis dataset contains the optical and IR light curves for Zw229-015 observed with ground based optical, Kepler and Spitzer telescopes between 2010-2015, and optical and NIR light curves in the grizJKs bands for PKS 0027-426 observed with DES, VEILS and VOILETTE telescope surveys between 2013-2020.</span
Radiation hydrodynamics models of active galactic nuclei: beyond the central parsec
No full textWe produce radiation hydrodynamics models of an active galactic nucleus torus plus outflow on 1–100 pc scales. This large scale permits direct comparison with observations, provides justification for configurations used in radiation transfer models, and tests the sensitivity of results of smaller scale dynamical models. We find that anisotropic radiation from an active galactic nucleus accretion disk can cause an outflow to evolve to become more polar, agreeing with the ubiquity of polar extended mid-infrared emission, and the general geometry predicted by radiative transfer models. We also find that the velocity maps can reproduce many features of observations, including apparent counterrotation
The subarcsecond mid-infrared view of local active galactic nuclei.III. Polar dust emission
No full textRecent mid-infrared (MIR) interferometric observations have shown that in a few active galactic nuclei (AGNs) the bulk of the infrared emission originates from the polar region above the putative torus, where only a little dust should be present. Here, we investigate whether such strong polar dust emission is common in AGNs. Out of 149 Seyferts in the MIR atlas of local AGNs, 21 show extended MIR emission on single-dish images. In 18 objects, the extended MIR emission aligns with the position angle (PA) of the system axis, established by [O iii], radio, polarization, and maser-based PA measurements. The relative amount of resolved MIR emission is at least 40% and scales with the [O iv] fluxes, implying a strong connection between the extended continuum and [O iv] emitters. These results together with the radio-quiet nature of the Seyferts support the scenario that the bulk of MIR emission is emitted by dust in the polar region and not by the torus, which would demand a new paradigm for the infrared emission structure in AGNs. The current low detection rate of polar dust in the AGNs of the MIR atlas is explained by the lack of sufficient high-quality MIR data and the requirements on the orientation, strength of narrow-line region, and distance of the AGNs. The James Webb Space Telescope will enable much deeper nuclear MIR studies with comparable angular resolution, allowing us to resolve the polar emission and surroundings in most of the nearby AGNs
The dust sublimation radius as an outer envelope to the bulk of the narrow Fe Kα line emission in type 1 AGNs
No full textThe Fe Kα emission line is the most ubiquitous feature in the X-ray spectra of active galactic nuclei (AGNs), but the origin of its narrow core remains uncertain. Here, we investigate the connection between the sizes of the Fe Kα core emission regions and the measured sizes of the dusty tori in 13 local Type 1 AGNs. The observed Fe Kα emission radii (RFe) are determined from spectrally resolved line widths in X-ray grating spectra, and the dust sublimation radii (Rdust) are measured either from optical/near-infrared (NIR) reverberation time lags or from resolved NIR interferometric data. This direct comparison shows, on an object-by-object basis, that the dust sublimation radius forms an outer envelope to the bulk of the Fe Kα emission. RFe matches Rdust well in the AGNs, with the best constrained line widths currently. In a significant fraction of objects without a clear narrow line core, RFe is similar to, or smaller than, the radius of the optical broad line region. These facts place important constraints on the torus geometries for our sample. Extended tori in which the solid angle of fluorescing gas peaks at well beyond the dust sublimation radius can be ruled out. We also test for luminosity scalings of RFe, finding that the Eddington ratio is not a prime driver in determining the line location in our sample. We also discuss in detail potential caveats of data analysis and instrumental limitations, simplistic line modeling, uncertain black hole masses, and sample selection, showing that none of these is likely to bias our core result. The calorimeter on board Astro-H will soon vastly increase the parameter space over which line measurements can be made, overcoming many of these limitations
Radiation Hydrodynamics Models of Active Galactic Nuclei: Beyond the Central Parsec: SPH RHD AGN Cloudy tables
No full textDataset to support publications in Astrophysical Journal. Tables of dust properties, radiation pressure, heating & cooling rates, for dusty gas impacted by AGN radiation.</span
3D radiation hydrodynamics of a dynamical torus
No full textWe have developed a new dynamical model of the torus region in active galactic nuclei (AGNs), using a three-dimensional radiation hydrodynamics algorithm. These new simulations have the specific aim to explore the role of radiatively driven outflows, which is hotly debated in current literature as a possible explanation for the observed IR emission from the polar regions of AGNs. In this first paper, we only consider radiative effects induced by the primary radiation from the AGN. The simulations generate a disk and outflow structure that qualitatively agrees with observations, although the outflow is radial rather than polar, likely due to the lack of radiation pressure from hot dust. We find cutoffs between the wind and disk at gas temperatures of 1000 K and dust temperatures of 100 K, producing kinematic signatures that can be used for interpretation of high-resolution IR observations. We also produce line emission maps to aid in the interpretation of recent ALMA observations and future James Webb Space Telescope observations. We investigate a number of simulation parameters and find that the anisotropy of the radiation field is equally important to the Eddington factor, despite the anisotropy often being assumed to have a single, sometimes arbitrary form in many previous works. We also find that supernovae can have a small but significant impact, but only at extremely high star formation rates
Education & Covid-19 Related Health Behavior
No full textThis OSF project contains supplementary material for the article Hoenig & Wenz (2020).
Hoenig, K., & Wenz, S. E. (2020). Education, health behavior, and working conditions during the pandemic: Evidence from a German sample. European Societies, 1–14. https://doi.org/10.1080/14616696.2020.182400
Education & Covid-19 Related Health Behavior
No full textThis OSF project contains supplementary material for the article Hoenig & Wenz (2020).
Hoenig, K., & Wenz, S. E. (2020). Education, health behavior, and working conditions during the pandemic: Evidence from a German sample. European Societies, 1–14. https://doi.org/10.1080/14616696.2020.182400
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