Measuring Robust Pattern Speeds in a Large Sample of Spiral Galaxies

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AST-0306958RandOne of the most elusive measurements associated with spiral density waves is that of the angular frequency with which the pattern rotates. Since many properties of galaxy evolution may depend on how frequently stars and gas encounter density waves, determining pattern speeds is of fundamental importance. The researcher has already shown that the Tremaine-Weinberg method developed some while ago can now be successfully applied to measuring pattern speeds in galaxies with a molecular-dominated interstellar medium (ISM), using observations of carbon monoxide (CO). This project will extend that work to a much larger sample, using archival data from surveys, and will investigate whether galaxies with a neutral-hydrogen-dominated ISM can be analyzed using neutral hydrogen (HI) measurements, also from published surveys. This research will explore whether it is feasible to combine both CO and HI data to study galaxies whose ISM is not dominated by either phase.Where available, morphological and kinematic data for the studied galaxies will be used to investigate the predictions of density-wave theory concerning resonances and the effect of extended haloes. For barred spirals, this work will also test suggested connections between the bar pattern and the spiral pattern.The research will involve at least one doctoral thesis project, and create a new research opportunity at an accredited Minority Institution (Hispanic Serving). The results will be spread widely to the community and beyond, through the principal investigator's continuing local public outreach work.