| Summary: | 博士 === 國立清華大學 === 物理系 === 101 === In this dissertation, we study the formation and evolution of axis-symmetric and asymmetric ring galaxies through the collision scenario. Head-on and non-axisymmetric collisions between the dwarf galaxy and the disk galaxy were performed through N-body simulations to address their origins. It was found that the simulations with smaller initial relative velocities between two galaxies, or in the cases with heavier dwarf galaxies, could produce rings with higher density contrasts. In addition, it was shown that the collisions with larger inclination angle could produce the elliptical rings with the larger eccentricity. The impact parameter has a significant positive correlation with the location of the disk center. Besides, we study the radial velocity and the azimuthal velocity of rings, and concluded that a positive correlation was found between the radial velocity of the ring and the dwarf’s mass. In addition, when the inclination angle of the galaxy pair is larger, the average azimuthal velocity of the ring is lower, but the variations of the radial velocity and the azimuthal velocity of the ring were larger. A positive correlation was also found between the impact parameter and the range of the radial velocity on the ring. Finally, we study the morphology of the gas within two Hi deficient disk galaxies, NGC 4911 and NGC 4921. From the Hi and CO data, these two galaxies might have experienced the ram pressure or the galactic interactions in the Coma Cluster.
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