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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 Rta scales with the enclosed mass Mta as Mta1/3 , as predicted by the spherical collapse model. c) The deviation of Rta 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 (Ωm ∼ 0.3; ΩΛ ∼ 0.7) turnaround structures exhibit an average matter density contrast with the background Universe of δ ∼ 11. Thus Rta 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
Μεγάλης δομές στο σύμπαν
Issue date 2020.
Collection   Faculty/Department--Faculty of Sciences and Engineering--Department of Physics--Post-graduate theses
  Type of Work--Post-graduate theses
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