PROFESSOR CHANGBOM PARK

We study the dependence of galaxy properties on environmental parameters such as the local density, nearest neighbour distance and morphology. We find that a galaxy with an early- or late-type nearest companion within its virial radius tends to be an early or late type, respectively. The morphology of galaxies located in high density regions tends to be the same as that of the ones in low density regions if their luminosity and the nearest neighbor environment are the same. This strongly supports that galaxy morphology and luminosity evolution has been driven mainly by galaxy-galaxy interactions, and the background density affected morphology and luminosity only through the frequency of interactions. Inside the cluster virial radius galaxy morphology depends mainly on the clustercentric radius, but the star formation activity depends on the environment attributed to the nearest neighbor galaxy. Outside the cluster virial radius, the local density-morphology relation appears to exist only though the correlation of morphology with luminosity and the neighbor environment.