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Magnetic fields in the Local Universe
Magnetic fields in the Local Universe
This thesis comprises several research efforts centering around cosmological and astrophysical magnetic fields. In the following summary, these are shortly outlined. References and acknowledgments to the respective works are put in front of each chapter. The first chapter entails the first prediction of today's remnants of a primordial large scale magnetic field both in strength and in three dimensional morphology within a comoving box with edge length of 600 Mpc/h. The general idea here is to translate the matter density field inferred from large scale structure data into the radiation dominated epoch up to the point where the horizon scale is much smaller than the smallest scale resolvable by the data. The density field obtained this way is used as initial conditions for the so called Harrison effect, which results in a magnetic field being generated up to recombination. From there on, magnetic field and matter evolution are simulated via a Magnetohydrodynamics solver up to red-shift z=0, revealing the magnetic field structure today. In chapters two to four several analyses of the Galactic Faraday depth sky are presented. Here, rotation measures of extra-Galactic point sources are used to constrain the Galactic component of the Faraday rotation sky. In a first simple inference model a full sky estimate is build from the scattered data points. A component of the inference, which is intended to model the sky amplitude, is found to have strong resemblance with the Galactic free-free emission measure sky. Hence, building on the simple model, additional data is used to disentangle the Faraday sky into its components. In a first phenomenological model, the signature of the local Galactic arm is discovered with the help of emission measure data. In further attempts, dispersion measure data from Galactic pulsars is additionally used to give a quantitative prediction of the line-of-sight averaged Galactic magnetic field sky. In the last chapter, two research projects revolving around circular polarization in the radio regime are summarized. In the first work, the Faraday depth sky and synchrotron intensity data are used to give a prediction on the Galactic synchrotron circular polarization sky. Due to the sensitivity of circular polarization to the charge of the synchrotron light emitting medium, statements on the leptonic content of the Milky Way can be made. The very same property of circular polarization is used in the second paper in order to show that observations of Stokes V may help to decide whether the content of radio jets is hadronic or leptonic.
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Hutschenreuter, Sebastian
2020
English
Universitätsbibliothek der Ludwig-Maximilians-Universität München
Hutschenreuter, Sebastian (2020): Magnetic fields in the Local Universe. Dissertation, LMU München: Faculty of Physics
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Abstract

This thesis comprises several research efforts centering around cosmological and astrophysical magnetic fields. In the following summary, these are shortly outlined. References and acknowledgments to the respective works are put in front of each chapter. The first chapter entails the first prediction of today's remnants of a primordial large scale magnetic field both in strength and in three dimensional morphology within a comoving box with edge length of 600 Mpc/h. The general idea here is to translate the matter density field inferred from large scale structure data into the radiation dominated epoch up to the point where the horizon scale is much smaller than the smallest scale resolvable by the data. The density field obtained this way is used as initial conditions for the so called Harrison effect, which results in a magnetic field being generated up to recombination. From there on, magnetic field and matter evolution are simulated via a Magnetohydrodynamics solver up to red-shift z=0, revealing the magnetic field structure today. In chapters two to four several analyses of the Galactic Faraday depth sky are presented. Here, rotation measures of extra-Galactic point sources are used to constrain the Galactic component of the Faraday rotation sky. In a first simple inference model a full sky estimate is build from the scattered data points. A component of the inference, which is intended to model the sky amplitude, is found to have strong resemblance with the Galactic free-free emission measure sky. Hence, building on the simple model, additional data is used to disentangle the Faraday sky into its components. In a first phenomenological model, the signature of the local Galactic arm is discovered with the help of emission measure data. In further attempts, dispersion measure data from Galactic pulsars is additionally used to give a quantitative prediction of the line-of-sight averaged Galactic magnetic field sky. In the last chapter, two research projects revolving around circular polarization in the radio regime are summarized. In the first work, the Faraday depth sky and synchrotron intensity data are used to give a prediction on the Galactic synchrotron circular polarization sky. Due to the sensitivity of circular polarization to the charge of the synchrotron light emitting medium, statements on the leptonic content of the Milky Way can be made. The very same property of circular polarization is used in the second paper in order to show that observations of Stokes V may help to decide whether the content of radio jets is hadronic or leptonic.