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Coupling Semi-analytic Models and N-body Simulations

Coupling Semi-analytic Models and N-body Simulations
Author: Krista McCord
Publisher:
Total Pages: 208
Release: 2017
Genre: Electronic dissertations
ISBN:

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Stellar halos give insight into the initial conditions that existed when a host galaxy first formed and provide details on disrupted satellites via their different stellar populations. An algorithm that is computationally inexpensive compared to hydrodynamic simulations is necessary in order to theoretically study the structure and formation of galactic stellar halos in sufficient detail to probe substructure. CoSANG (Coupling Semi-Analytic/N-body Galaxies) is a new computational method that we are developing which couples pure dark matter N-body simulations with a semi-analytic galaxy formation model. At each timestep, results from the N-body simulation feed into the semi-analytic code, whose results feed back into the N-body code making the evolution of the dark matter and baryonic matter dependent on one another. CoSANG will enable a variety of galaxy formation science, including analysis of stellar populations, halo merging, satellite accretion, supermassive black holes, and indirect and direct dark matter detection. In this dissertation, I will describe the new simulation code CoSANG. The results from the extensive testing phase on CoSANG will be presented which indicate CoSANG is properly simulating feedback from galaxies within a dark matter halo. I used this validated code to analyze a CoSANG zoom simulation of a $10^12 M⊙ dark matter halo. Results showed a flatter inner halo near the disk and a more spherical outer halo which is expected when a galaxy exists at the center of a dark matter halo. A comparison is made with a simulation run with the same initial conditions, but with the baryonic component simulated using a hydrodynamic algorithm. The semi-analytic model predicted galaxy types better than the hydrodynamic simulation leading to the conclusion that the CoSANG halo is more accurate. I also present a dark matter direct detection analysis on the CoSANG zoom halo to measure the dark matter velocity distributions and modulation amplitudes. The CoSANG results show that the dark matter velocity distribution does not fit well to a Maxwell Boltzmann distribution and the modulation amplitudes derived indicate an anisotropic dark matter velocity distribution. Future work will include tagging dark matter particles with stellar properties to build and evolve a stellar halo.


Structure Formation in Modified Gravity Cosmologies

Structure Formation in Modified Gravity Cosmologies
Author: Alexandre Barreira
Publisher: Springer
Total Pages: 234
Release: 2016-05-03
Genre: Science
ISBN: 3319336967

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This unique thesis covers all aspects of theories of gravity beyond Einstein’s General Relativity, from setting up the equations that describe the evolution of perturbations, to determining the best-fitting parameters using constraints like the microwave background radiation, and ultimately to the later stages of structure formation using state-of-the-art N-body simulations and comparing them to observations of galaxies, clusters and other large-scale structures. This truly ground-breaking work puts the study of modified gravity models on the same footing as the standard model of cosmology. Since the discovery of the accelerating expansion of the Universe, marked by the awarding of the 2011 Nobel Prize in Physics, there has been a growing interest in understanding what drives that acceleration. One possible explanation lies in theories of gravity beyond Einstein’s General Relativity. This thesis addresses all aspects of the problem, an approach that is crucial to avoiding potentially catastrophic biases in the interpretation of upcoming observational missions.


Handbook of Gravitational Wave Astronomy

Handbook of Gravitational Wave Astronomy
Author: Cosimo Bambi
Publisher: Springer Nature
Total Pages: 1895
Release: 2022-07-02
Genre: Science
ISBN: 9811643067

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This handbook provides an updated comprehensive description of gravitational wave astronomy. In the first part, it reviews gravitational wave experiments, from ground and space based laser interferometers to pulsar timing arrays and indirect detection from the cosmic microwave background. In the second part, it discusses a number of astrophysical and cosmological gravitational wave sources, including black holes, neutron stars, possible more exotic objects, and sources in the early Universe. The third part of the book reviews the methods to calculate gravitational waveforms. The fourth and last part of the book covers techniques employed in gravitational wave astronomy data analysis. This book represents both a valuable resource for graduate students and an important reference for researchers in gravitational wave astronomy.


From the Realm of the Nebulae to Populations of Galaxies

From the Realm of the Nebulae to Populations of Galaxies
Author: Mauro D'Onofrio
Publisher: Springer
Total Pages: 809
Release: 2016-07-26
Genre: Science
ISBN: 3319310062

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In order to outline possible future directions in galaxy research, this book wants to be a short stopover, a moment of self-reflection of the past century of achievements in this area. Since the pioneering years of galaxy research in the early 20th century, the research on galaxies has seen a relentless advance directly connected to the parallel exponential growth of new technologies. Through a series of interviews with distinguished astronomers the editors provide a snapshot of the achievements obtained in understanding galaxies. While many initial questions about their nature have been addressed, many are still open and require new efforts to achieve a solution. The discussions may reveal paradigms worthwhile revisiting. With the help of some of those scientists who have contributed to it, the editors sketch the history of this scientific journey and ask them for inspirations for future directions of galaxy research.


The Galaxy Disk in Cosmological Context (IAU S254)

The Galaxy Disk in Cosmological Context (IAU S254)
Author: International Astronomical Union. Symposium
Publisher: Cambridge University Press
Total Pages: 542
Release: 2009-04-16
Genre: Science
ISBN: 9780521889858

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The paradigm of a dark energy- and dark matter-dominated Universe, with the hierarchical merger scenario for the formation of galaxies, has scored impressive successes in matching the observed Universe. However, the theory fails to explain the difficulty in generating ordinary disk galaxies such as the Milky Way, suggesting that some important physics must be missing in current models. IAU Symposium 254 was organized to address this question, gathering researchers from an unusually broad range of fields, from cosmology to interstellar matter, and the formation and evolution of stars. High-class reviews, lectures and posters combine to define the frontiers in the field and point the way to new avenues of research. This volume presents a unique set of succinct overviews illuminating the full range of topics in this very active field. It also honors Danish astrophysicist Bengt Strömgren (1908-1987), who laid much of the foundation for this entire field.


The Role of Halo Substructure in Gamma-Ray Dark Matter Searches

The Role of Halo Substructure in Gamma-Ray Dark Matter Searches
Author: Miguel A. Sánchez-Conde
Publisher: MDPI
Total Pages: 220
Release: 2020-05-28
Genre: Mathematics
ISBN: 3039360442

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An important, open research topic today is to understand the relevance that dark matter halo substructure may have for dark matter searches. In the standard cosmological model, halo substructure or subhalos are predicted to be largely abundant inside larger halos, for example, galaxies such as ours, and are thought to form first and later merge to form larger structures. Dwarf satellite galaxies—the most massive exponents of halo substructure in our own galaxy—are already known to be excellent targets for dark matter searches, and indeed, they are constantly scrutinized by current gamma-ray experiments in the search for dark matter signals. Lighter subhalos not massive enough to have a visible counterpart of stars and gas may be good targets as well, given their typical abundances and distances. In addition, the clumpy distribution of subhalos residing in larger halos may boost the dark matter signals considerably. In an era in which gamma-ray experiments possess, for the first time, the exciting potential to put to test the preferred dark matter particle theories, a profound knowledge of dark matter astrophysical targets and scenarios is mandatory should we aim for accurate predictions of dark matter-induced fluxes for investing significant telescope observing time on selected targets and for deriving robust conclusions from our dark matter search efforts. In this regard, a precise characterization of the statistical and structural properties of subhalos becomes critical. In this Special Issue, we aim to summarize where we stand today on our knowledge of the different aspects of the dark matter halo substructure; to identify what are the remaining big questions, and how we could address these; and, by doing so, to find new avenues for research.


Workshop on Molecular Dynamics on Parallel Computers

Workshop on Molecular Dynamics on Parallel Computers
Author: Rdiger Esser
Publisher: World Scientific
Total Pages: 400
Release: 2000
Genre: Science
ISBN: 9789810242329

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Molecular dynamics is a well-established technique for simulating complex many-particle systems in many areas of physics, chemistry, and astrophysics. The huge computational requirements for simulations of large systems, especially with long-range forces, demand the use of massively parallel computers. Designing efficient algorithms for these problems is a highly non-trivial task. This book contains the invited talks and abstracts presented at a conference by more than 100 researchers from various fields: computer science, solid state physics, high energy physics, polymers, biochemistry, granular materials and astrophysics. Most of the contributions have been written by users of massively parallel computers and deal with practical issues, but there are also contributions tackling more fundamental algorithmic problems.


Clusters of Galaxies: Beyond the Thermal View

Clusters of Galaxies: Beyond the Thermal View
Author: Jelle Kaastra
Publisher: Springer Science & Business Media
Total Pages: 418
Release: 2008-05-01
Genre: Science
ISBN: 0387788751

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The existence of soft excess emission originating from clusters of galaxies, de ned as em- sion detected below 1 keV in excess over the usual thermal emission from hot intracluster gas (hereafter the ICM) has been claimed since 1996. Soft excesses are particularly - portant to detect because they may (at least partly) be due to thermal emission from the Warm-Hot Intergalactic Medium, where as much as half of the baryons of the Universe could be. They are therefore of fundamental cosmological importance. Soft excess emission has been observed (and has also given rise to controversy) in a number of clusters, mainly raising the following questions: (1) Do clusters really show a soft excess? (2) If so, from what spatial region(s) of the cluster does the soft excess or- inate? (3) Is this excess emission thermal, originating from warm-hot intergalactic gas (at 6 temperatures of?10 K), or non-thermal, in which case several emission mechanisms have been proposed. Interestingly, some of the non-thermal mechanisms suggested to account for soft excess emission can also explain the hard X-ray emission detected in some clusters, for example by RXTE and BeppoSAX (also see Petrosian et al. 2008—Chap. 10, this issue; Rephaeli et al. 2008—Chap. 5, this issue).


IUTAM Symposium on Solver-Coupling and Co-Simulation

IUTAM Symposium on Solver-Coupling and Co-Simulation
Author: Bernhard Schweizer
Publisher: Springer
Total Pages: 291
Release: 2019-05-14
Genre: Technology & Engineering
ISBN: 3030148831

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This is the Proceedings of the IUTAM Symposium on Solver Coupling and Co-Simulation that was held in Darmstadt, Germany, September 18-20, 2017. The symposium focused on recent advances in the development of numerical methods for solver coupling, like new explicit, implicit and semi-implicit co-simulation methods, new approaches for realizing variable communication-time grids, and advances in the stability and convergence analysis of solver coupling methods. Recent developments in the practical application of co-simulation methods, for instance new fields of application for solver coupling approaches, new developments in the parallelization of dynamic models with co-simulation techniques, and standardization of co-simulation interfaces, i.e. standardization of data and model exchange were also discussed. The book brings together the research results of leading scientists in applied mathematics, mechanics, and engineering science, thus contributing to further develop numerical methods for coupled simulations.