| Summary: | 碩士 === 國立中央大學 === 天文研究所 === 105 === The missing mass problem was first discussed in the 1930s. However, not until the 1970s and 1980s that the flat rotation curve of spiral galaxies was confirmed in quite a number of galaxies before the astronomy community realized that the missing mass problem is a genuine problem. The mainstream idea is Newtonian dynamics is intact and there is some form of matter which possesses mass but does not interact electromagnetically. It is usually called the dark matter model (or dark matter paradigm). Besides successful in resolving the missing mass problem, dark matter is also an important ingredient in modern cosmology. Nonetheless, it still faces some challenging problems. On the other hand, there is no lack of non-mainstream ideas tossing around. Particularly satisfactory is modified Newtonian dynamics (MOND), which maintains that gravity is stronger than Newtonian when the acceleration is small. It is very successful in explaining the flat rotation curve of spiral galaxies. Many studies of MOND were devoted to spiral galaxies. Recently, some more attentions are paid to elliptical galaxies. We are interested in the relativistic phenomenon gravitational lensing by elliptical galaxies. Base on a recent analysis on slightly deformed spherical systems in the framework of MOND, we investigate their strong lensing images. We develop a numerical code to solve for the image positions under the Bekenstein form (one commonly used MOND interpolation function). The numerical results agree well with the available analytical results. We do an extensive parameter space survey which includes the source position, the lens ellipticity and its orientation, and the degree of MOND. Our aim is to provide a library of cases and a systematic way to study real observations.
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