Date of Award
Doctor of Philosophy (PhD)
Astrophysical & Planetary Sciences
Jack O. Burns
Brian W. O'Shea
Galaxy clusters are unique astrophysical laboratories that contain many thermal and non-thermal phenomena. In particular, they are hosts to cosmic shocks, which propagate through the intracluster medium as a by-product of structure formation. It is believed that at these shock fronts, magnetic field inhomogeneities in a compressing flow may lead to the acceleration of cosmic ray electrons and ions. These relativistic particles decay and radiate through a variety of mechanisms, and have observational signatures in radio, hard X-ray, and Gamma-ray wavelengths.
We begin this dissertation by developing a method to find shocks in cosmological adaptive mesh refinement simulations of structure formation. After describing the evolution of shock properties through cosmic time, we make estimates for the amount of kinetic energy processed and the total number of cosmic ray protons that could be accelerated at these shocks.
We then use this method of shock finding and a model for the acceleration of and radio synchrotron emission from cosmic ray electrons to estimate the radio emission properties in large scale structures. By examining the time-evolution of the radio emission with respect to the X-ray emission during a galaxy cluster merger, we find that the relative timing of the enhancements in each are important consequences of the shock dynamics. By calculating the radio emission expected from a given mass galaxy cluster, we make estimates for future large-area radio surveys.
Next, we use a state-of-the-art magnetohydrodynamic simulation to follow the electron acceleration in a massive merging galaxy cluster. We use the magnetic field information to calculate not only the total radio emission, but also create radio polarization maps that are compared to recent observations. We find that we can naturally reproduce Mpc-scale radio emission that resemble many of the known double radio relic systems.
Finally, motivated by our previous studies, we develop and introduce a numerical library, CRT, for following cosmic ray transport. Using this new tool, we are able to follow the acceleration and aging of cosmic rays as they flow throughout the intracluster medium. Using synthetic observations, we outline how this new capability will revolutionize our study of galaxy cluster non-thermal populations by allowing comparisons with current and upcoming telescopes.
Skillman, Samuel William, "Adaptive Mesh Refinement Cosmological Simulations of Cosmic Rays in Galaxy Clusters" (2013). Astrophysical & Planetary Sciences Graduate Theses & Dissertations. 30.