Discussion On The Criterion Of "Galaxy Pair" In SDSS DR7

Interaction and merging between galaxies play an important role in the evolution of galaxies. Merging galaxies are also the most attractive objects in the research. Theoretically speaking, the process of interaction and merging propel the evolution of galaxies, they also affect morphological and spectral characteristics, gasdynamics, high energy processes and nuclear activity. Toomre(1997) was one of the first researcher who proposed that the formation of elliptical galaxies stem from interaction of spiral galaxies. Schweizer(1999) did same study about the effect of merging process to early-type disk galaxies and elliptical galaxies. But given different data and selection criteria those researches used to select galaxy pairs, their sample properties existed some statistic differences, and also, the results were not entirely same.Based on the work of Allam et al. (2004) and Ellison et al., we selected two high quality galaxy pairs sample from photometric and spectrometric databases of SDSS DR7 by using their selection criteria. Moreover, we compared these two merging galaxy samples, analyzed the differences of some merging galaxy pairs and discuss the reason for these differences. And we also download many parameters of these galaxies from DR7 and collect their metallicity, star formation rate(SFR) and other data from other databases for further statistical research. We also simulated a number of galaxies with the same redshift, magnitude, and radius distribution of real galaxies to check the projection effect and the completeness of these two samples.