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Abstract:
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The subject of this dissertation is to study the effects of galaxy flybys on the structural
evolution of galaxies. Galaxy flybys are very close interactions that do not result in a merger.
With the high frequency in the late Universe, their role in the evolution of galaxies is significant.
Earlier studies focused on equal-mass flybys, which are extremely rare. We focus on typical
flybys with a lower mass ratio. We aim to explore the structure and evolution of galaxies in
greater detail and demonstrate that these flybys are just as important as equal-mass ones.
We performed a series of N body simulations of typical flybys with varying impact para-
meters. We demonstrated the applicability and importance of isolated N body simulations and
developed an efficient method for reliable bar detection in galaxy discs.
For the first time, we examined the evolution of the secondary galaxy, focusing on its dark
matter mass loss. The results show that the leftover mass follows logarithmic growth law with
impact parameter and suggest that flybys contribute to the formation of dark matter-deficient
galaxies.
The primary galaxy is affected in a similar way as in equal-mass flybys. Bars form in closer
flybys, two-armed spirals form during all flybys, and the dark matter halo spins up. Most of
the parameters of these structures are correlated or anti-correlated with the impact parameter.
We also noticed that a double bar could form as evolving spirals wrap around the early-formed
bar.
We successfully demonstrated that frequent, typical flybys with lower mass ratios signifi-
cantly affect the evolution of galaxies, producing various observed effects. Our results should
serve as a warning not to disregard these interactions in future studies. |