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Identifier

000428250

Title

Turnaround radius of galaxy clusters in N-body simulations

Alternative Title

Μελέτη της ακτίνας διαφυγής σμηνών γαλαξιών σε προσομοιώσεις Ν-σωμάτων

Author

Κορκίδης, Γεώργιος Μ.

Thesis advisor

Παυλίδου, Βασιλική

Reviewer

Τάσσης, Κωνσταντίνος

Abstract

We use N-body simulations to examine whether a characteristic turnaround radius, as predicted from the spherical collapse model in a ΛCDM Universe, can be meaningfully identified for galaxy clusters, in the presence of full three-dimensional effects. For that purpose we use The Dark Sky Simulations and Illustris-TNG dark-matter--only cosmological runs to calculate radial velocity profiles around collapsed structures, extending out to many times the virial radius R₂₀₀. There, the turnaround radius can be unambiguously identified as the largest non-expanding scale around a center of gravity. We find that: a) Indeed, a single turnaround scale can meaningfully describe strongly non-spherical structures. b) For halos of masses M₂₀₀ > 10¹³M⊙, the turnaround radius R_ta scales with the enclosed mass M_ta as M_ta^1/3 , as predicted by the spherical collapse model. c) The deviation of R_ta in simulated halos from the spherical collapse model prediction is rather insensitive to halo asphericity. Rather, it is sensitive to the tidal forces due to massive neighbors when such are present. d) Halos exhibit a characteristic average density within the turnaround scale. This characteristic density is dependent on cosmology and redshift. For the present cosmic epoch and for concordance cosmological parameters (Ω_m ∼ 0.3; Ω_Λ ∼ 0.7) turnaround structures exhibit an average matter density contrast with the background Universe of δ ∼ 11. Thus R_ta is equivalent to R₁₁ -- in a way analogous to defining the "virial" radius as R₂₀₀ -- with the advantage that R₁₁ is shown in this work to correspond to a kinematically relevant scale in N-body simulations

Language

English

Subject

Large-scale structure of universe

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Issue date

2020-03-27

Collection

School/Department--School of Sciences and Engineering--Department of Physics--Post-graduate theses

Type of Work--Post-graduate theses

Views

611

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