During the years 1922-1936, Hubble studied the morphologies of thousands of nearby galaxies and proposed Hubble's Morphological Sequence. Later, people found some special morphology that can hardly be categorized into the standard Hubble's Sequence. Some galaxies have long tidal tails and showed irregular shapes. Finally, the model of TT (Toomre & Toomre 1972) pointed out that those of galaxies were produced by merging between galaxies. Merger galaxies have important roles in individual galaxy evolution and population of galaxies. Some merging processes may have triggered series of phenomena like starburst and Active Galactic Nuclei (AGN). In addition, modeling of disk-galaxy mergers suggests that morphological types of the participants can be irreversibly changed. Mergers do occur in widely considered peculiar-galaxy populations such as Markarian galaxies and ULIRGs, and even the hosts of QSOs. Images of distant galaxies have implicated strong interaction and subsequent mergers are among the mechanism of the Butcher-Oemler effect. For lacking a complete merger sample in study of interaction and evolution of galaxies, my adviser, under my help, has compiled a sample of mergers based on SDSS high-quality images. We used computer algorithms to coadd images for enhancing the signal-to noise-ratios (SNR), which enables my adviser to visually identify a complete sample of nearby mergers. Based on the obtained sample, with my adviser's help, I finished a study of frequencies and activities of AGN in the nearby mergers. In the result of statistic frequencies, I have found that, the frequencies of either Seyfert/LINER or starburst galaxies in mergers are about twice of those in normal galaxies. As for activities, there is evidence that merging has affected the Seyfert and LINER little. Under the common perception that in AGN, a substantial amount of energy is emitted by X-rays, I have downloaded the X-ray data of nearby galaxies from the XMM-Newton satellite, and carried out a study of AGN activities. The results show that merging enhances the Seyfert, LINER activities slightly if any. Through the analysis of Mayer and Hopkins's merging-galaxy simulation, I find out that my results do not fit their simulated result. From existing knowledge of galaxies and stars, my results suggest that the roles of super-galactic wind can not be ignored during the merging processes.
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