Oral Presentation

The Statistical Analysis of Interacting Dark Matter Halos

Sung-Ho An, Jeonghwan Kim, Kiyun Yun (Yonsei University), Juhan Kim (Korea Institute for Advanced Study), and Suk-Jin Yoon (Yonsei University)

Although hard to identify observationally, fly-by encounters between galaxies are believed to play an important role in galaxy evolution. Using a tree-particle-mesh code GOTPM, we performe cosmological N-body simulations and examine the statistical properties of the fly-by interactions as functions of halo masses and ambient environments. Impulsive fly-by pairs are discerned from eventual merger candidates based on the total energy of the two halos of interest. We focus on interactions between Milky Way-sized halos (0.1-2.0 MMW) and with mass ratio of 1:1 - 1:3. Our results are as follows; (1) In clusters, the fly-by interactions are 5 - 10 times (i.e., 1.1 - 1.5 times in case of the mergers) more frequent than in fields, and (2) halos at high redshift experience more fly-by interactions (i.e., less mergers) than those at the lower redshift.