The Luminosity Function For The Member Galaxies And The Dynamics Of The Clusters

With the expectation of searching for the information about the origin and formation of the large-scale structures in the Universe, such as galaxies and galaxy clusters, and providing observational proof for the previously available or newly proposed theories for the formation and evolution of galaxies or clusters, this thesis mainly concentrates on the luminosity functions (LFs) of 198 member galaxies (including 174 early-type galaxies) in the central region of the nearby cluster of galaxies A2634 in the B , V and R bands, and on dynamics of the binary cluster system A399/A401.Firstly, the LFs of the member galaxies in the central region of A2634 in the B , V and R bands were devived. The Schechter function, Gaussian function and their linear combinations are used in our x2 -minimum fittings. Comparison with other studies for the LFs of galaxies shows that our LFs differ significantly from the LFs for field galaxies and other rich clusters, which may be due to the differences in morphology composition of the member galaxies and in the environmental effects.Convincing evidence of a past interaction between two rich clusters A399 and A401 was found by recent X-ray imaging observations. Based on the updated data for the galaxies in the region of A399 / A401, we examined the structure and dynamics of this binary clusters of galaxies. A mixture-modeling algorithm called the KMM algorithm has been applied to obtain a robust partition into two clusters, which allows us to take a virial estimate of the mass and deblend the velocity distribution for each cluster using the K -test. Assuming that these two clusters follow a linear two-body orbit, we analyzed this system with the two-body gravitational model, As a result, three bound solutions were derived. The X-ray imaging observation and the localized velocity structure favor such a bound-incoming model that these two clusters, with atrue spatial separation of about 6.4 h-1 Mpc, are moving together with a relative velocity of- 664 km s"1 along the direction with a projection angle of 71.5.Additionally, the recent progress on the LFs of galaxies, substructures and dynamics of galaxy clusters is also briefly reviewed.