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The Study of Fossil Galaxy Groups by Excursion Set Theory of Nonlinear Structure Formation

Sattari, Zahra | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51071 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Baghram, Shant; Rahvar, Sohrab
  7. Abstract:
  8. In the standard cold dark matter (CDM) family of cosmological models,the cosmological structures form hierarchically with the assumption of cold dark matter existence. The structure formation in the current CDM paradigm is capable of estimating the distribution function of the structures. It gives us a correct view from our observations of galaxies and structures. One of the successful methods to explain the statistics of cosmlogoical structures and their formation time is Excursion Set Theory. The excursion set theory considers the density field for each point in the universe smoothed with a spatial window function using the physics of random processes. The statistics of the structures can be obtained from the physics of the trajectories with a first upcrossing of the barrier c which is the critical density field.The purpose of this thesis is to study the fossil groups of galaxies by excursion set theory. Fossil systems are galaxy associations dominated by a relatively isolated, bright elliptical galaxy. These groups have a magnitude gap of 2 in the red band between the brightest and the second brightest galaxy. It seems that fossil systems have the history of halo mass assembly at early times. The excursion set theory allows us to statistically study the main progenitor history of haloes, merger rates and merger history of subhaloes of the group. In this thesis, we aim to study the statistics of fossil groups from the point of theory in the standard model of cosmology. Thus, we can find the mass distribution and the magnitude gap for these systems and compare the results with observations and large scale simulations
  9. Keywords:
  10. Cosmology ; Fossil Galaxy Groups ; Galaxies Formation ; Nonlinear Structure Formation ; Excursion Set Theory

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