Numerical Simulations of Galaxy Formation: Angular Momentum Distribution and Phase Space Structure of Galactic Halos

Persistent Link:
http://hdl.handle.net/10150/194718
Title:
Numerical Simulations of Galaxy Formation: Angular Momentum Distribution and Phase Space Structure of Galactic Halos
Author:
Sharma, Sanjib
Issue Date:
2005
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Within the past decade, the CDM model has emerged as a standard paradigm of structure formation. While it has been very successful in explaining the structure of the Universe on large scales, on smaller (galactic) scales problems have surfaced. In this thesis, we investigate several of these problems in more detail. The thesis is organized as follows. In Chapter 1, we give a brief introduction about structure formation in the universe and discuss some of the problems being faced by the current CDM paradigm of galaxy formation.In Chapter 2, we analyze the angular momentum properties of virialized halos obtained from hydrodynamical simulations. We describe an analytical function that can be used to describe a wide variety of angular momentum distributions (AMDs), with just one parameter α. About $90-95% of halos turn out to haveα < 1.3, while exponential disks in cosmological halos would require 1.3 < α < 1.6. This implies that a typical halo in simulations has an excess of low angular momentum material as compared to that of observed exponential disks, a result which is consistent with the findings of earlier works.In Chapter 3, we perform controlled numerical experiments of merging galactic halos in order to shed light on the results obtained in cosmological simulations. We explore the properties of shape parameter α of AMDs and the spin ratio λGas/λDM in merger remnants and also their dependence on orbital parameters. We find that the shape parameter α is typically close to 1 for a wide range of orbital parameters, less than what is needed to form an exponential disk.The last chapter of the thesis (Chapter 4) is devoted to the analysis of phase space structure of dark matter halos. We first present a method to numerically estimate the densities of discretely sampled data based on a binary space partitioning tree. We implement an entropy-based node splitting criterion that results in a significant improvement in the estimation of densities compared to earlier work. We use this technique to analyze the phase space structure of halos.
Type:
text; Electronic Dissertation
Keywords:
galaxies; halos; dark matter; cosmology; data analysis
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Physics; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Steinmetz, Matthias; Fang, Li-Zhi
Committee Chair:
Steinmetz, Matthias; Fang, Li-Zhi

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleNumerical Simulations of Galaxy Formation: Angular Momentum Distribution and Phase Space Structure of Galactic Halosen_US
dc.creatorSharma, Sanjiben_US
dc.contributor.authorSharma, Sanjiben_US
dc.date.issued2005en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractWithin the past decade, the CDM model has emerged as a standard paradigm of structure formation. While it has been very successful in explaining the structure of the Universe on large scales, on smaller (galactic) scales problems have surfaced. In this thesis, we investigate several of these problems in more detail. The thesis is organized as follows. In Chapter 1, we give a brief introduction about structure formation in the universe and discuss some of the problems being faced by the current CDM paradigm of galaxy formation.In Chapter 2, we analyze the angular momentum properties of virialized halos obtained from hydrodynamical simulations. We describe an analytical function that can be used to describe a wide variety of angular momentum distributions (AMDs), with just one parameter α. About $90-95% of halos turn out to haveα < 1.3, while exponential disks in cosmological halos would require 1.3 < α < 1.6. This implies that a typical halo in simulations has an excess of low angular momentum material as compared to that of observed exponential disks, a result which is consistent with the findings of earlier works.In Chapter 3, we perform controlled numerical experiments of merging galactic halos in order to shed light on the results obtained in cosmological simulations. We explore the properties of shape parameter α of AMDs and the spin ratio λGas/λDM in merger remnants and also their dependence on orbital parameters. We find that the shape parameter α is typically close to 1 for a wide range of orbital parameters, less than what is needed to form an exponential disk.The last chapter of the thesis (Chapter 4) is devoted to the analysis of phase space structure of dark matter halos. We first present a method to numerically estimate the densities of discretely sampled data based on a binary space partitioning tree. We implement an entropy-based node splitting criterion that results in a significant improvement in the estimation of densities compared to earlier work. We use this technique to analyze the phase space structure of halos.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectgalaxiesen_US
dc.subjecthalosen_US
dc.subjectdark matteren_US
dc.subjectcosmologyen_US
dc.subjectdata analysisen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplinePhysicsen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorSteinmetz, Matthiasen_US
dc.contributor.advisorFang, Li-Zhien_US
dc.contributor.chairSteinmetz, Matthiasen_US
dc.contributor.chairFang, Li-Zhien_US
dc.contributor.committeememberSarcevic, Inaen_US
dc.contributor.committeememberShupe, Michael A.en_US
dc.contributor.committeememberEisenstein, Danielen_US
dc.contributor.committeememberDave, Romeelen_US
dc.identifier.proquest1413en_US
dc.identifier.oclc137355536en_US
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