title: Models of Dust and Gas Tori in Active Galactic Nuclei
creator: Schartmann, Marc
subject: 520
subject: 520 Astronomy and allied sciences
description: The goal of this thesis is to gain theoretical understanding of the distribution of dust and gas in the innermost parsecs of Active Galactic Nuclei. Unified schemes demand a circum-nuclear disk or "torus" to geometrically unify two separate classes of observed objects (face-on and edge-on view onto the torus). In a multi-step approach, we work towards the establishment of realistic simulations of this massive and dense gas and dust reservoir, in order to be able to interpret near- and mid-infrared interferometric observations (MIDI, AMBER), which are able to resolve dust structures in the centres of Seyfert galaxies. In a first step, we investigate an analytical torus model (the so-called "Turbulent Torus Model") with the help of radiative transfer calculations and find gross agreement with large aperture, as well as high-resolution observations of Seyfert galaxies. However, the model SEDs show too pronounced silicate emission features in the face-on case. This can be overcome with the help of three-dimensional clumpy tori, calculated in a second step. Special emphasis is put on the differences of clumpy and continuous dust distributions, also concerning interferometric observations. In a further step, we apply hydrodynamic simulations to trace the evolution of a nuclear star cluster, which provides energy via discrete supernova explosions and mass from stellar mass loss. With these ingredients, a highly dynamical system forms, with gas streaming inward, in form of long filaments, which cool due to radiative energy losses. In the vicinity of the minimum of the effective potential (caused by gravity of the nuclear stellar cluster and black hole, as well as rotation of the gas), a turbulent disk forms, surrounded by a less dense clumpy and filamentary toroidal structure. Subsequent radiative transfer calculations yield good agreement with Seyfert galaxy spectral energy distributions (observed with the Spitzer space telescope). Problems of the comparison of continuous models with the silicate feature strength to H I column density relation can be overcome with the help of our new approach. 
date: 2006
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/7186/1/phd_thesis_schartmann.pdf
identifier: DOI:10.11588/heidok.00007186
identifier: urn:nbn:de:bsz:16-opus-71865
identifier:   Schartmann, Marc  (2006) Models of Dust and Gas Tori in Active Galactic Nuclei.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/7186/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng