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The purpose of this thesis was to explore computationally the three dimensional hydrodynamics of extragalactic radio jets. This entailed putting together a large number of numerical tools before such simulations could be performed. The thesis was structured to be a set of papers, each addressing a computational or astrophysical issue that was important in completing the objective of this thesis. Three chapters on numerical techniques are presented testing out both particle and grid-based methods for computational fluid dynamics. Then follow four chapters of astrophysical applications. The first of those considers the flow of a supersonic jet in a transonic cross-wind as a model for narrow angle tails. The second considers jet-shock interactions as a model for wide angle tails. The third tries out jet-cloud interactions as a model for t...
Several three dimensional, multi-species, cosmological hydrodynamic simulations of the formation and evolution of Ly$\alpha$ forest absorbers were performed in three CDM-like cosmological models: the standard CDM model (SCDM), the flat CDM model with a nonzero cosmological constant ($\Lambda$CDM) and the open CDM model (OCDM). Synthetic spectra along random lines-of-sight were generated and analyzed by using a powerful spectrum analysis method designed to mimic observational data reduction. The SCDM model was studied in great detail and found to be in excellent agreement with observations in: the slope and shape of the column density distribution, the value and distribution of the Doppler parameter and the equivalent width, the evolution of line density, effective opacity and flux decrement, etc. A number of sensitive tests were devise...
Comment: 13 pages, 16 figures, To appear in "Proceedings of First Stars III," Eds. Brian W. O'Shea, Alexander Heger & Tom Abel, AIP Conference Series
Comment: 40 pages, 26 figures, Enrico Fermi Summer School "Astrophysics of Galaxy Clusters" held in Varenna, Italy July 15-25, 2008
Comment: 11 pages, 3 figures, Proceedings of "The First Stars and Galaxies: Challenges for the Next Decade", Austin, TX, March 8-11, 2010
This contribution contains the introductory remarks that I presented at IAU Symposium 270 on ``Computational Star Formation" held in Barcelona, Spain, May 31 -- June 4, 2010. I discuss the historical development of numerical MHD methods in astrophysics from a personal perspective. The recent advent of robust, higher order-accurate MHD algorithms and adaptive mesh refinement numerical simulations promises to greatly improve our understanding of the role of magnetic fields in star formation.
Comment: 21 pages, 107 refs., to appear in "Adaptive Mesh Refinement - Theory and Applications", Eds. T. Plewa, T. Linde & V. G. Weirs, Springer Lecture Notes in Computational Science and Engineering, 2004
Comment: 16 pages, 5 figures. in "Matter and Energy in Clusters of Galaxies", Eds. S. Bowyer & C.-Y. Hwuang, PASP Conference Series Vol. 301 (2003)
Comment: 33 pages, 18 figures, to appear in "Background Microwave Radiation and Intracluster Cosmology", Eds. F. Melchiorri and Y. Rephaeli, proceedings of Varenna Summer School, July 2004
Our goal is to develop software libraries and applications for astrophysical fluid dynamics simulations in multidimensions that will enable us to resolve the large spatial and temporal variations that inevitably arise due to gravity, fronts and microphysical phenomena. The software must run efficiently on parallel computers and be general enough to allow the incorporation of a wide variety of physics. Cosmological structure formation with realistic gas physics is the primary application driver in this work. Accurate simulations of e.g. galaxy formation require a spatial dynamic range (i.e., ratio of system scale to smallest resolved feature) of 104 or more in three dimensions in arbitrary topologies. We take this as our technical requirement. We have achieved, and in fact, surpassed these goals.
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