Mathematics – Logic
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008phdt........13g&link_type=abstract
Proquest Dissertations And Theses 2008. Section 0004, Part 0606 290 pages; [Ph.D. dissertation].United States -- Alabama: The U
Mathematics
Logic
1
Ringed Galaxies, Spiral Galaxies, Nonbarred Ringed Galaxies, Counter-Winding Structure
Scientific paper
This dissertation focusses on a specific morphological class of galaxies: the nonbarred ringed galaxies. These are normal disk galaxies showing prominent, rings ill the absence of prominent bars. We chose this group as the subject of a survey because theoretical studies have suggested that the presence of a non- axisymmetric perturbation, typically in the form of a bar, is required to drive the creation of ring features. By their very nature, these galaxies are either weakly barred or completely nonbarred, making the origin of their rings a mystery. Our goal was to study this morphological group more systematically in order to better understand their mode of ring formation. We obtained broadband images of 25 nonbarred ringed galaxies in the southern sky and narrowband images of 20 of these same galaxies in order to quantify the basic properties of the galaxies, including integrated magnitudes and colors, structural parameters and star formation rates. This is a diverse group with a wide range of metric ring properties. We found one nonbarred ringed galaxy in our sample, ESO 297-27, as a definitive case with rare counter-winding spiral structure. Through a multidimensional decomposition program, we found that the majority of the galaxies have pseudobulges, which may have implications for evolving bars within these galaxies. We also found that the star formation rates within galactic rings are not dependent on the strength of the bar or the shape of the ring. This finding implies that contrary to current belief, the bar of a galaxy may not in fact trigger the star formation that characterizes both barred and nonbarred galaxy rings. We have tried to delineate the properties of this group based on the broadband and narrowband images; however, there are many questions yet to address. This dissertation is just a beginning to understanding this diverse and interesting group of galaxies.
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