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Uncovering the origins of spiral structure through the measurement of pattern speeds and their radial variation


Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/9832

Uncovering the origins of spiral structure through the measurement of pattern speeds and their radial variation

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dc.contributor.author Meidt, Sharon
dc.date.accessioned 2009-08-27T21:40:45Z
dc.date.available 2009-08-27T21:40:45Z
dc.date.issued 2009-08-27T21:40:45Z
dc.date.submitted July 2009
dc.identifier.uri http://hdl.handle.net/1928/9832
dc.description.abstract At the intersection of galactic dynamics, evolution and global structure, unresolved issues in the nature and origin of spirals can be addressed through the characterization of the angular speeds of the patterns and their possible radial variation. In this thesis I describe the development, testing, and application of the Radial Tremaine-Weinberg (TWR) Method, a generalized version of the continuity-based TW method wherein the pattern speed is allowed to vary arbitrarily with radius. I will address the utility of, and caveats in applying, the TWR calculation together with a standard regularization technique in a series of tests on N-body simulations. The regularization, which smooths otherwise intrinsically noisy solutions based on a priori assumptions for the radial dependence of the pattern speed, proves to be essential for achieving the radial precision necessary for accurate measurement. I also present results from applications of the TWR method to observations of real galaxies, where the possible sources and sinks in the continuity equation are well understood. Using CO observations of the grand design galaxy M51, the TWR method reveals a heretofore un-measured inner spiral pattern speed for the bright two-armed spiral structure, with a value significantly higher than conventional estimates. In addition, the radial dependence implied in the TWR solution suggests a possible resonant link between the inner and outer regions of the bright spiral arms. These findings signify an advance in observational investigations into the nature and origin of grand-design spiral structure. By analyzing high-quality HI and CO data cubes available for four other spiral galaxies, the characteristic signatures of the processes that drive spiral structure are likewise identifiable; within this small sample, the first direct evidence for the presence of resonant coupling of multiple distinct patterns is found in some galaxies, while a simple single pattern speed is measured in others. I conclude with a summary of future avenues for investigation with the TWR method and propose additional modifications of the TW calculation with which the influence of bar and spiral structure on the evolution of galaxy disks can be directly characterized. en_US
dc.description.sponsorship NASA New Mexico Space Grant Consortium; National Science Foundation grant AST 03-06958 to R. J. R. en_US
dc.language.iso en_US en_US
dc.subject pattern speeds en_US
dc.subject spiral structure en_US
dc.subject.lcsh Spiral galaxies--Structure.
dc.subject.lcsh Barred galaxies--Structure.
dc.subject.lcsh Density wave theory.
dc.subject.lcsh Resonance.
dc.title Uncovering the origins of spiral structure through the measurement of pattern speeds and their radial variation en_US
dc.type Dissertation en_US
dc.description.degree Physics en_US
dc.description.level Doctoral en_US
dc.description.department University of New Mexico. Dept. of Physics & Astronomy en_US
dc.description.advisor Rand, Richard
dc.description.committee-member Rand, Richard
dc.description.committee-member Henning, Patricia
dc.description.committee-member Loomba, Dinesh
dc.description.committee-member Roy, Mousumi

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