The Equilibrium Structure of Dark Matter Halos.

Cosmology;Dark Matter;Dark Energy;Large-scale Structure of the Universe;Physics;Science;Physics

Busha, Michael TravisPando Zayas, Leopoldo A. ;

University of Michigan

关键词: Cosmology;    Dark Matter;    Dark Energy;    Large-scale Structure of the Universe;    Physics;    Science;    Physics;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/57651/mbusha_1.pdf?sequence=2&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The far future provides an excellent laboratory for studyingcosmological structures.The eventual dominance of the cosmologicalconstant causes the universe to enter a phase of exponential deSitterexpansion during which dark matter halos are allowed to relax withoutinterruptions from mass accretion.Using of suite of N-bodysimulations evolved to scale factor a = 100 in an LCDM universe,this thesis presents the equilibrium distribution and structure ofhalos and investigates the importance of mergers in setting theinternal halo structure.Using conservation of energy, it is possibleto accurately predict the total amount of mass that will ultimatelyaccrete onto a halo.Once this mass is accreted, the halo quicklyreaches a state of dynamical equilibrium.Halos in this equilibriumhave a greatly simplified radial phase space profile characterized bya single zero-velocity surface that unambiguously defines the haloedge. The radial density profile for such halos is well fit by anNFW profile inside r200, but is steeper at larger radii andbetter fit by a truncated Hernquist profile.In order to study theimportance of hierarchical merging in setting the equilibriumstructure, I also present results form LWDM-like simulations withinitial power spectra that suppress the early formation of smallhalos.Using these simulations, I present a modified fit to the massaccretion form of Wechsler et al. (2002) that better characterizes halogrowth at all epochs.At the end of the simulations, we recoverdensity profiles and phase space structures that are virtuallyunchanged between the CDM and WDM cosmologies.The only difference inthe global halo properties, a systematic concentration shift, can becharacterized in terms of the halo formation epoch.Weconclude that mass accretion is not the driving process for setting theequilibrium halo structure.