Statistical Analysis of Interacting Dark Matter Halos: On two physically distinct interaction types

  • An, Sung-Ho (Department of Astronomy& Center for Galaxy Evolution Research, Yonsei University) ;
  • Kim, Juhan (Center for Advanced Computation, Korea Institute for Advanced Study) ;
  • Moon, Jun-Sung (Department of Astronomy& Center for Galaxy Evolution Research, Yonsei University) ;
  • Yoon, Suk-Jin (Department of Astronomy& Center for Galaxy Evolution Research, Yonsei University)
  • Published : 2021.04.13

Abstract

We present a statistical analysis of dark matter halos with interacting neighbors using a set of cosmological simulations. We classify the neighbors into two groups based on the total energy (E12) of the target-neighbor system; flybying neighbors (E12 ≥ 0) and merging ones (E12 < 0). First, we find a different trend between the flyby and merger fractions in terms of the halo mass and large-scale density. The flyby fraction highly depends on the halo mass and environment, while the merger fraction show little dependence. Second, we measure the spin-orbit alignment, which is the angular alignment between the spin of a target halo (${\vec{S}}$ ) and the orbital angular momentum of its neighbor (${\vec{L}}$). In the spin-orbit angle distribution, the flybying neighbors show a weaker prograde alignment with their target halos than the merging neighbors do. With respect to the nearest filament, the flybying neighbor has a behavior different from that of the merging neighbor. Finally, we discuss the physical origin of two interaction types.

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