A First Look at Galaxy Flyby Interactions: I. Characterizing the Frequency of Flybys in a Cosmological Context

Details A First Look at Galaxy Flyby Interactions: I. Characterizing the Frequency of Flybys in a Cosmological Context A First Look at Galaxy Flyby Interactions: I. Characterizing the Frequency of Flybys in a Cosmological Context

2011-03-09

arxiv.org/abs/1103.1675v1

Astronomy and Astrophysics

Astrophysics

Cosmology and Extragalactic Astrophysics

Submitted to ApJ. Figure resolution degraded for arXiv limits, full resolution paper available at http://people.vanderbilt.e

Scientific paper

Galaxy evolution is intricately tied to the dynamical interactions of the host halo and depends crucially on the accuracy of reconstructed interaction history of halos. We characterize the frequency of close flyby interactions in the Universe using cosmological N-body simulations. We present a careful method of identifying and tracking a dark matter halo that resolves the typical classes of anomalies that occur in N-body data. This technique allows us to robustly follow halos and several hierarchical levels of subhalos as they grow, dissolve, merge, and flyby one another -- thereby constructing both a census of the dynamical interactions in a volume and an archive of the dynamical evolution of an individual halo. We find that the number of close flyby interactions is comparable to, or even surpasses, the number of mergers for all halo masses. Halo flybys occur so frequently to high mass halos that they are continually perturbed, unable to reach a dynamical equilibrium. At high redshift, $z \gtrsim 10$, we find that flybys are as frequent as mergers. Our results suggest that close halo flybys can play an important role in the evolution of the earliest dark matter halos and their galaxies, and can still influence galaxy evolution at the present epoch. Our companion paper quantifies the effect of close flyby interactions on galaxies and their dark matter hosts.

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