The effect of stellar feedback on the formation and evolution of gas and dust tori in AGN

Abstract

Recently, the existence of geometrically thick dust structures in Active Galactic Nuclei (AGN) has been directly proven with the help of mid-infrared interferometry. The observations are consistent with a two-component model made up of a geometrically thin and warm central disk, surrounded by a colder, fluffy torus component. In an exploratory study, we investigate one possible physical mechanism, which could produce such a structure, namely the effect of stellar feedback from a young nuclear star cluster on the interstellar medium in centres of AGN. The model is realised with the help of the hydrodynamics code TRAMP. We follow the evolution of the interstellar medium by taking discrete mass loss and energy ejection due to stellar processes, as well as optically thin radiative cooling into account. In a post-processing step, we calculate observable quantities (spectral energy distributions and images) with the help of the radiative transfer code MC3D. The interplay between injection of mass, supernova explosions and radiative cooling leads to a two-component structure made up of a cold geometrically thin, but optically thick and very turbulent disk residing in the vicinity of the angular momentum barrier, surrounded by a filamentary structure. The latter consists of cold long radial filaments flowing towards the disk and a hot tenuous medium in between, which shows both inwards and outwards directed motions. This modelling is able to reproduce the range of observed neutral hydrogen column densities of a sample of Seyfert galaxies as well as the relation between them and the strength of the silicate 10 micron spectral feature. Despite being quite crude, our mean Seyfert galaxy model is even able to describe the SEDs of two intermediate type Seyfert galaxies observed with the Spitzer Space Telescope.

16 pages, 11 figures, accepted by MNRAS, high resolution version can be downloaded from: http://www.mpe.mpg.de/~mschartm/papers/schartmann_2008b.pdf

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• Parsec-scale dust distributions in Seyfert galaxies - Results of the MIDI AGN snapshot survey
• Obscuration in AGNs: near-infrared luminosity relations and dust colors
• Unobscured Type 2 AGNs
• Time-resolved infrared emission from radiation-driven central obscuring structures in Active Galactic Nuclei
• The narrow Fe K$\alpha$ line and the molecular torus in active galactic nuclei - an IR/X-ray view
• Spitzer Space Telescope Measurements of Dust Reverberation Lags in the Seyfert 1 Galaxy NGC 6418
• On the evolution of gas clouds exposed to AGN radiation. I. Three-dimensional radiation hydrodynamic simulations
• Unshifted Metastable He I* Mini-Broad Absorption Line System in the Narrow Line Type 1 Quasar SDSS J080248.18$+$551328.9
• Chandra Reveals Heavy Obscuration and Circumnuclear Star Formation in Seyfert 2 Galaxy NGC 4968
• Multi-phase environment of compact galactic nuclei: the role of the Nuclear Star Cluster
• Radiative transfer modelling of parsec-scale dusty warped discs