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Physical properties of the circumnuclear cloud distribution in Active Galactic Nuclei

Esser, Johannes

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Abstract

In this thesis the structure of the \gls{BLR} and the inner dust torus of \glspl{AGN} is studied. In a first project we have carried out a multiwavelength reverberation mapping campaign of hot dust in \gls{AGN} for a sample of 25 nearby \gls{AGN} with redshifts below 0.2. Reverberation mapping allows to measure the radius of the dust torus which, in relation to the \gls{AD} luminosity, can be used as a cosmological standard candle. Despite the radius the multiwavelength approach allows for the investigation of other dust properties like the temperature. An influence of dust temperatures on the relation between the dust radius and the \gls{AD} luminosity is expected, as hotter dust should be located closer to the heating source at smaller radii. We were able to determine 14 reliable dust radii and 20 reliable dust temperatures for our \gls{AGN}. This is the largest sample of homogeneously reverberation mapped inner dust tori using a multiwavelength approach and among the largest dust reverberation mapping samples overall. We got tighter constraints on the luminosity radius relation when a novel temperature normalization was applied. Especially the slope of the relation is only in good agreement with the expected value of 0.5 if the temperature normalization is taken into account. Additionally we can determine the surface area of the dust only when the temperature is known. We found that the radial extend of the dust torus behaves comparable to the delay with respect to luminosity.

In the second project we compare concurrent changes of the dust radius to shape variations of \glspl{BEL} for NGC~4151 observed from 2004 to 2006. These simultaneous changes are discussed in a variety of dust and \gls{BEL} formation schemes. Furthermore we use the shape variations to assess possible (especially azimuthal) cloud distributions, which could be responsible for the observed variations. A dust inflated \gls{AD} provides the framework best suited to explain our findings. The changes in the \glspl{BEL} suggest that this dusty cloud formation happens in spatially confined areas on rather short timescales.

Item Type: Dissertation
Supervisor: Rix, Prof. Dr. Hans-Walter
Place of Publication: Heidelberg
Date of thesis defense: 18 May 2020
Date Deposited: 29 May 2020 07:35
Date: 2020
Faculties / Institutes: The Faculty of Physics and Astronomy > Dekanat der Fakultät für Physik und Astronomie
Subjects: 520 Astronomy and allied sciences
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