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Open Access Dissertation
Doctor of Philosophy (PhD)
Year Degree Awarded
Month Degree Awarded
External Galaxies | Other Astrophysics and Astronomy | Physical Processes
The study of barred galaxy dynamics has had many successes explaining observed phenomena in barred galaxies both locally and distant, including our own Milky Way, a barred galaxy. However, the majority of this knowledge arises from either (a) analytic linear theory, which by definition cannot inform nonlinear processes, or (b) simulations which are subject to an unconstrained host of evolutionary mechanisms, including `real' dynamical processes and `artificial' numerical processes, and are thus difficult to interpret. This work chooses a path which attempts to take the best of both techniques, employing n-body simulations in the Lambda cold dark matter paradigm designed to isolate dynamical mechanisms responsible for the evolution and observed features of barred galaxies. We develop techniques to analyze the simulations: (1) an algorithm to classify orbit families in an evolving system, (2) a method to compute the area of orbit trajectories, (3) a technique to measure the angular momentum flow through specific channels, and (4) a parameterization of bar evolutionary phases based on harmonic decompositions. Using these simulations, we elucidate a wide range of dynamical processes important for barred galaxy evolution including (1) the shadow bar, which inhibits angular momentum transfer between the disc and the dark matter halo and may reduce the amount of angular momentum transferred by a factor of three, (2) the presence specific orbit families that support the growth of the bar whose role had not been previously understood, (3) harmonic--locking, which alters and/or stalls the evolution of the bar pattern, and (4) the role of the dark matter halo relative to the disc in determining the evolution. We present observational diagnostics including (1) a method to measure the dynamical length of the bar including descriptions of how traditional metrics overestimate the bar length, (2) predictions for the rate of radial mixing and the mechanisms responsible, (3) predictions for the mechanisms important for bulge formation, such that bulges with may form solely through secular processes, and (4) predictions for the flux of dark matter density at the solar radius for direct-detection experiments, where the flux may double from the naive model typically used.
Petersen, Michael, "The Non-linear Dynamics of Barred Galaxy Evolution in LCDM" (2019). Doctoral Dissertations. 1494.