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Decomposition of the Globular Cluster NGC 6397

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Title: Decomposition of the Globular Cluster NGC 6397
Author: Tsui, Hong
Subject Keywords NGC 6397;white dwarf;rotation;galactic bulge;velocity distribution;globular cluster;Jeans mass;Jeans length;anisotropy;Milky Way
Issue Date: 2008-06
Publicly Available in cIRcle 2008-06-06
Citation: Tsui, Hong. 2008. Decomposition of the Globular Cluster NGC 6397. Undergraduate Honours Thesis. Department of Physics and Astronomy. University of British Columbia.
Series/Report no. Undergraduate Honours Theses
Abstract: The kinematics and white dwarf distribution have been studied for the Globular Cluster NGC 6397. The data was obtained from NASA’s Hubble Space Telescope in 2005. In particular, we used the images of a field 5’ Southeast of the core of NGC 6397 from Advanced Camera for Surveys to conduct our analyses. The first part of the study is about the kinematics of the globular cluster. Isotropy of velocity distribution and cluster rotation have been considered. As anticipated, this relaxed cluster exhibited no strong signs of anisotropy. However, there appears to be some level of rotation. The rotational motion turns out to be mu sub alpha cos(delta) = 3.88 ± 1.41 mas yr −1 and mu sub delta = −14.83 ± 0.58 mas yr −1. This result is not entirely expected and deserves further investigation in future studies. The second of the thesis is based on white dwarf populations in the globular cluster and the Galactic Bulge. As a first glance, there appears to be a lacking of white dwarfs at the age of approximately 0.6 Gyr. Further investigation reveals this to be statistically insignificant. Through this analysis, another pattern of white dwarf abundance is discovered. There appeared to be much more stars at the age between 0.9 − 2.0 Gyr. This could be a manifestation of modeling error. As the final consideration of this thesis, white dwarf candidates in the Galactic Bulge are illustrated. Approximately 10 candidates are found at the most probable location of stars in the Bulge. The analyses conducted in this thesis set stage for further development in understanding of globular clusters. In particular, the rotation analysis raises curiosity about the dynamics of NGC 6397 in the plane of the sky. Moreover, the velocity distribution analysis confirms properties and theories pertaining to globular clusters.
Affiliation: Physics and Astronomy, Dept of
URI: http://hdl.handle.net/2429/869
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