Using Hydrodynamic Simulations to Understand the Structure and Composition of the Circumgalactic Medium of Milky Way-sized Galaxies

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Book Synopsis Using Hydrodynamic Simulations to Understand the Structure and Composition of the Circumgalactic Medium of Milky Way-sized Galaxies by : Munier Salem

Download or read book Using Hydrodynamic Simulations to Understand the Structure and Composition of the Circumgalactic Medium of Milky Way-sized Galaxies written by Munier Salem and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We explore the structure and evolution of baryons within Milky Way-sized halos (M ~ 1012 Msun) via hydrodynamic simulations. First, we employ a two-fluid model to study the dynamics of a relativistic, diffusive cosmic ray proton (CR) fluid interacting with the thermal interstellar medium (ISM). This model was implemented into the eulerian hydrodynamics code enzo, used throughout this dissertation. After testing this model on analytically tractable scenarios in one dimension, it is unleashed upon an idealized disk simulation in a rapidly-star forming setting, where we find evidence for robust, mass-loaded winds driven by the diffusive CR fluid. These winds reduce the galaxy’s star formation rate (SFR) and circulate on order as much mass into winds as into forming stars. We then extend this model to a cosmological setting where the diffuse CR fluid proves capable of redistributing star formation within the forming disk, reducing the overly-peaked rotation curves in non-CR runs and producing thin, extended disks with visible spiral structure.

Understanding the Circumgalactic Medium Through Hydrodynamic Simulations and Hubble's Cosmic Origins Spectrograph

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ISBN 13 :
Total Pages : 228 pages
Book Rating : 4.:/5 (894 download)

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Book Synopsis Understanding the Circumgalactic Medium Through Hydrodynamic Simulations and Hubble's Cosmic Origins Spectrograph by : Amanda Brady Ford

Download or read book Understanding the Circumgalactic Medium Through Hydrodynamic Simulations and Hubble's Cosmic Origins Spectrograph written by Amanda Brady Ford and published by . This book was released on 2014 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: My dissertation focuses on a relatively new field of study: the region immediately around galaxies known as the circumgalactic medium (CGM). The CGM holds vast quantities of mass and metals, yet its connection to galaxies is not well understood. My work uses cosmological hydrodynamic simulations and comparisons to data from Hubble's Cosmic Origins Spectrograph (COS) to understand the CGM's connection to galaxy evolution, gas accretion, outflows, star formation, and baryon cycling. This includes studies of the CGM's extent and physical conditions; the cause and nature of outflows; gas dynamics, including the first comprehensive study of tracers of inflowing and outflowing gas at low redshift (z=0.25); and direct comparison of theoretical results to observational data. Chapter 1 introduces my research and show its connection to galaxy evolution. Chapter 2 investigates hydrogen and metal line absorption around low-redshift galaxies in cosmological hydrodynamic simulations. This chapter studies different models for stellar outflows, physical conditions, and dependencies on halo mass. Chapter 3 examines the flow of gas into, out of, and around galaxies using a novel particle tracking technique. This chapter examines the baryon cycle in detail for our preferred model of stellar outflows. Chapter 4 compares our model results, including two separate prescriptions for outflows, with data from COS. We contrast these wind models, showing how they cycle baryons differently, and show degeneracies in observational diagnostics. In Chapter 5, I summarize and discuss plans for future research in this field, and how it can be more fully leveraged to understand galaxy evolution.

Hydrodynamic Simulations and Tomographic Reconstructions of the Intergalactic Medium

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ISBN 13 :
Total Pages : 178 pages
Book Rating : 4.:/5 (919 download)

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Book Synopsis Hydrodynamic Simulations and Tomographic Reconstructions of the Intergalactic Medium by : Casey William Stark

Download or read book Hydrodynamic Simulations and Tomographic Reconstructions of the Intergalactic Medium written by Casey William Stark and published by . This book was released on 2015 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Intergalactic Medium (IGM) is the dominant reservoir of matter in the Universe from which the cosmic web and galaxies form. The structure and physical state of the IGM provides insight into the cosmological model of the Universe, the origin and timeline of the reionization of the Universe, as well as being an essential ingredient in our understanding of galaxy formation and evolution. Our primary handle on this information is a signal known as the Lyman-alpha forest (or Ly-alpha forest) -- the collection of absorption features in high-redshift sources due to intervening neutral hydrogen, which scatters HI Ly-alpha photons out of the line of sight. The Ly-alpha forest flux traces density fluctuations at high redshift and at moderate overdensities, making it an excellent tool for mapping large-scale structure and constraining cosmological parameters. Although the computational methodology for simulating the Ly-alpha forest has existed for over a decade, we are just now approaching the scale of computing power required to simultaneously capture large cosmological scales and the scales of the smallest absorption systems. My thesis focuses on using simulations at the edge of modern computing to produce precise predictions of the statistics of the Ly-alpha forest and to better understand the structure of the IGM. In the first part of my thesis, I review the state of hydrodynamic simulations of the IGM, including pitfalls of the existing under-resolved simulations. Our group developed a new cosmological hydrodynamics code to tackle the computational challenge, and I developed a distributed analysis framework to compute flux statistics from our simulations. I present flux statistics derived from a suite of our large hydrodynamic simulations and demonstrate convergence to the per cent level. I also compare flux statistics derived from simulations using different discretizations and hydrodynamic schemes (Eulerian finite volume vs. smoothed particle hydrodynamics) and discuss differences in their convergence behavior, their overall agreement, and the implications for cosmological constraints. In the second part of my thesis, I present a tomographic reconstruction method that allows us to make 3D maps of the IGM with Mpc resolution. In order to make reconstructions of large surveys computationally feasible, I developed a new Wiener Filter application with an algorithm specialized to our problem, which significantly reduces the space and time complexity compared to previous implementations. I explore two scientific applications of the maps: finding protoclusters by searching the maps for large, contiguous regions of low flux and finding cosmic voids by searching the maps for regions of high flux. Using a large N-body simulation, I identify and characterize both protoclusters and voids at z = 2.5, in the middle of the redshift range being mapped by ongoing surveys. I provide simple methods for identifying protocluster and void candidates in the tomographic flux maps, and then test them on mock surveys and reconstructions. I present forecasts for sample purity and completeness and other scientific applications of these large, high-redshift objects.

Unveiling the Circumgalactic Medium Using a Cloud-by-cloud, Multiphase, Bayesian Ionization Modeling Approach

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ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (134 download)

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Book Synopsis Unveiling the Circumgalactic Medium Using a Cloud-by-cloud, Multiphase, Bayesian Ionization Modeling Approach by : Sameer

Download or read book Unveiling the Circumgalactic Medium Using a Cloud-by-cloud, Multiphase, Bayesian Ionization Modeling Approach written by Sameer and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis investigates the physicochemical nature of the gaseous structures in the vicinity of galaxies. Intervening absorption systems seen in the spectra of background quasars probe the circumgalactic medium (CGM) around galaxies and can provide insights into the nature of the gas. The CGM is a dynamic and multiphase interface between a galaxy and its surroundings. Unraveling the origin of the multiphase gas in the CGM is important because it potentially allows us to learn about the processes that supply inflowing gas to the galaxy, enrich the surroundings with metal-rich outflows, and send enriched material back to the galaxy as recycled accretion. First, I present a new method aimed at improving the efficiency of component-by-component ionization modeling of intervening quasar absorption line systems. I carry out cloud-by-cloud, multiphase modeling making use of CLOUDY and Bayesian methods to extract physical properties from an ensemble of absorption profiles. As a demonstration of the method, I focus on four weak, low ionization absorbers at low redshift, because they are multi-phase but relatively simple to constrain. We place errors on the inferred metallicities and ionization parameters for individual clouds and show that the values vary from component to component across the absorption profile. This method requires user input on the number of phases and relies on an optimized transition for each phase, one observed with high resolution and signal-to-noise. The measured Doppler parameter, b, of the optimized transition provides a constraint on the Doppler parameter of HI, thus providing leverage in metallicity measurements even when hydrogen lines are saturated. I present several tests of this methodology, demonstrating that I can recover the input parameters from simulated profiles. I also consider how the model results are affected by which radiative transitions are covered by observations (for example how many HI transitions) and by uncertainties in the $b$ parameters of optimized transitions. I discuss the successes and limitations of the method, and consider its potential for large statistical studies. This improved methodology will help to establish direct connections between the diverse properties derived from characterizing the absorbers and the multiple physical processes at play in the CGM. Next, I present an absorption line study of the physical and chemical properties of the Leo HI Ring and the Leo I Group as traced by 11 quasar sightlines spread over a ~ 600 kpc x 800 kpc region. Using HST/COS G130/G160 archival observations as constraints, I couple cloud-by-cloud, multiphase, Bayesian ionization modeling with galaxy property information to determine the plausible origin of the absorbing gas along these sightlines. I find absorption plausibly associated with the Leo Ring towards five sightlines. The absorption along these five sightlines is stronger in metal lines than expected from individual galaxies, indicative of multiple contributions, and of the complex kinematics of the region. Along three other sightlines, I find absorption likely to be associated with individual galaxies, intragroup gas, and/or large-scale filamentary structure. I also identify three sightlines within a 7° x6° field around the Leo Ring, along which I do not find any absorption. I find that the metallicities associated with the Leo Ring are generally high, with values between solar and several times solar. The inferred high metallicities are consistent with the origin of the ring as tidal debris from a major galaxy merger. Next, I analyze archival ultraviolet quasar spectra from HST/COS covering 47 absorption line systems produced by the CGM of galaxies that have galaxy imaging with HST with known impact parameters and orientations. I conducted a large statistical study with this sample to determine if the metallicities of any of the multiple structures depend on orientation. Cloud-by-cloud, multiphase Bayesian modeling was applied to provide constraints on metallicity, density, and temperature of multiple regions along the sightline. I find that the high metallicity clouds span a large range of velocities while the low metallicity clouds are found close to the systemic velocity of the galaxy. I also find that clouds close to the systemic velocity show a full range of metallicities. High-velocity clouds, on the other hand, show a tendency for tracing high metallicities. I do not find metallicity trends with azimuthal angle, inclination, impact parameter, or galaxy type. Despite the lack of a link between azimuthal angle and metallicity, the independent effects of inflows and outflows are seen in absorption systems using cloud-by-cloud modeling. Finally, I employ the same techniques that I have developed with real absorption systems to investigate absorption systems in cosmological simulations in order to assess the efficacy of the methods in extracting true properties from simulations. I find that the assumption of photoionization thermal equilibrium should be relaxed, particularly for the high ionization gas phases, and this assumption only holds in a particular regime of the CGM phase space. For a discrete distribution of clouds, the inferred posterior distributions contain the actual values in the simulations. For a complex and continuous distribution of clouds in simulations, I find that the properties of the best-constrained clouds agree well with the true values. These findings strengthen our confidence in reliably extracting the properties of the CGM from observational datasets.

Star Formation in Galaxy Evolution: Connecting Numerical Models to Reality

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Publisher : Springer
ISBN 13 : 3662478900
Total Pages : 375 pages
Book Rating : 4.6/5 (624 download)

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Book Synopsis Star Formation in Galaxy Evolution: Connecting Numerical Models to Reality by : Nickolay Y. Gnedin

Download or read book Star Formation in Galaxy Evolution: Connecting Numerical Models to Reality written by Nickolay Y. Gnedin and published by Springer. This book was released on 2015-09-09 with total page 375 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains the elaborated and updated versions of the 24 lectures given at the 43rd Saas-Fee Advanced Course. Written by four eminent scientists in the field, the book reviews the physical processes related to star formation, starting from cosmological down to galactic scales. It presents a detailed description of the interstellar medium and its link with the star formation. And it describes the main numerical computational techniques designed to solve the equations governing self-gravitating fluids used for modelling of galactic and extra-galactic systems. This book provides a unique framework which is needed to develop and improve the simulation techniques designed for understanding the formation and evolution of galaxies. Presented in an accessible manner it contains the present day state of knowledge of the field. It serves as an entry point and key reference to students and researchers in astronomy, cosmology, and physics.

Galaxy Formation and Mergers with Stars and Massive Black Holes

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Publisher : Stanford University
ISBN 13 :
Total Pages : 189 pages
Book Rating : 4.F/5 ( download)

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Book Synopsis Galaxy Formation and Mergers with Stars and Massive Black Holes by : Chi-hun Kim

Download or read book Galaxy Formation and Mergers with Stars and Massive Black Holes written by Chi-hun Kim and published by Stanford University. This book was released on 2011 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: While mounting observational evidence suggests the coevolution of galaxies and their embedded massive black holes (MBHs), a comprehensive astrophysical understanding which incorporates both galaxies and MBHs has been missing. To tackle the nonlinear processes of galaxy formation, we develop a state-of-the-art numerical framework which self-consistently models the interplay between galactic components: dark matter, gas, stars, and MBHs. Utilizing this physically motivated tool, we present an investigation of a massive star-forming galaxy hosting a slowly growing MBH in a cosmological LCDM simulation. The MBH feedback heats the surrounding gas and locally suppresses star formation in the galactic inner core. In simulations of merging galaxies, the high-resolution adaptive mesh allows us to observe widespread starbursts via shock-induced star formation, and the interplay between the galaxies and their embedding medium. Fast growing MBHs in merging galaxies drive more frequent and powerful jets creating sizable bubbles at the galactic centers. We conclude that the interaction between the interstellar gas, stars and MBHs is critical in understanding the star formation history, black hole accretion history, and cosmological evolution of galaxies. Expanding upon our extensive experience in galactic simulations, we are well poised to apply this tool to other challenging, yet highly rewarding tasks in contemporary astrophysics, such as high-redshift quasar formation.

Cosmological Simulations of Galaxy Formation Including Hydrodynamics

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ISBN 13 :
Total Pages : 774 pages
Book Rating : 4.:/5 (28 download)

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Book Synopsis Cosmological Simulations of Galaxy Formation Including Hydrodynamics by : Francis Joseph Summers

Download or read book Cosmological Simulations of Galaxy Formation Including Hydrodynamics written by Francis Joseph Summers and published by . This book was released on 1993 with total page 774 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Simulations of Galaxy Formation and Large Scale Structure

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Publisher : Sudwestdeutscher Verlag Fur Hochschulschriften AG
ISBN 13 : 9783838108841
Total Pages : 212 pages
Book Rating : 4.1/5 (88 download)

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Book Synopsis Simulations of Galaxy Formation and Large Scale Structure by : Felix Stoehr

Download or read book Simulations of Galaxy Formation and Large Scale Structure written by Felix Stoehr and published by Sudwestdeutscher Verlag Fur Hochschulschriften AG. This book was released on 2009-12 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work we use the N-body resimulation technique to address aspects of structure formation. In the first chapter we study the influence of the local environment of DM haloes on their properties. In the second chapter we address the so-called "substructure problem" which is one of the major challenges of the CDM model of cosmology. We perform ultra-high resolution simulations of the assembly of a Milky Way type dark matter halo within its full cosmological context and propose a new analytical fitting formula (SWTS) which provides a better fit to the simulated Milky Way halo than the NFW or Moore profiles do. In the third chapter we use our ultra-high resolution simulations to study the possible -ray signal from dark matter annihilation. If such a signal was detected, the nature of the dark matter, the answer to one of the most important questions of modern cosmology, would be known. (urn: nbn: de: bvb:19-16446)"

Interplay of Galactic Winds and Circumgalactic Media

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ISBN 13 :
Total Pages : 130 pages
Book Rating : 4.:/5 (16 download)

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Book Synopsis Interplay of Galactic Winds and Circumgalactic Media by : Drummond Fielding

Download or read book Interplay of Galactic Winds and Circumgalactic Media written by Drummond Fielding and published by . This book was released on 2018 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: The flow of gas through the circumgalactic medium (CGM) regulates galaxy growth over cosmic time. Observations have recently revealed a complex multi-phase structure in the CGM that has challenged many of the established theories and highlights significant gaps in our understanding of this critical aspect of galaxy formation. The spatial scales relevant to the CGM span a huge range with its structure and evolution determined by small-scale processes—such as the launching of galactic winds by clustered supernovae and thermal instability in the hydrostatic halo—and large-scale processes—such as cosmological accretion. I will describe my efforts to use controlled numerical simulations to understand the details and interplay of these multi-scale processes in order to develop a coherent picture of the CGM that is consistent with observations.

The Circumgalactic Medium of Nearby Galaxies

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ISBN 13 :
Total Pages : 206 pages
Book Rating : 4.:/5 (17 download)

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Book Synopsis The Circumgalactic Medium of Nearby Galaxies by : David Matthew French

Download or read book The Circumgalactic Medium of Nearby Galaxies written by David Matthew French and published by . This book was released on 2018 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: Current Lambda Cold-Dark-Matter cosmology predicts the growth of large scale structure from small, initial perturbations in the dark matter potential distribution. Gas in the Universe follows this dark matter potential, collapsing along a series of filaments and knots, and eventually forming galaxies. The present-day Universe is left with a rich kaleidoscope of galaxies of different types, colors, and sizes. Observations suggest, however, that the gas from which these galaxies are built continues to play a pivotal role in their evolution. Numerous studies have already found strong evidence for the spatial correlation of neutral hydrogen (\HI; $\rm Ly\alpha$ absorption being our tracer of choice here) in the intergalactic medium (IGM) and galaxies. This thesis examines how intergalactic \HI~interacts with, is influenced by, and depends on the nearby galaxies lying within it. This study is made possible by correlating the positions of archival Cosmic Origins Spectrograph (COS; Hubble Space Telescope) sightlines toward background quasi-stellar objects (QSOs) with the distributions of known galaxies within the nearby, $cz \leq 10,000$ \kms~Universe. To enable this, I compile a catalog of all known galaxies in this redshift range, and homogenized measurements of their diameters, axis ratios, position angles, and magnitudes. This effort ensures that I can compare galaxy measurements from different sources with confidence. I introduce a novel likelihood method to automate the process of matching galaxies from this catalog with nearby absorption and also to quantify the relative isolation of these absorbers versus their proximity to galaxies. To test this method, I built a pilot sample with 33 QSO sightines chosen for their proximity to large ($D \ge 25$ kpc) galaxies. In each I identify all $\rm Ly\alpha$ lines within $cz \leq 10,000$ \kms~and match each line with the highest-likelihood galaxy. I discover a preference for $\rm Ly\alpha$ to be detected near high inclination galaxies at a $3.6\sigma$ significance level. I attribute this to the combination of a $

Comparing Simulations and Observations of Galaxy Evolution

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ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (867 download)

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Book Synopsis Comparing Simulations and Observations of Galaxy Evolution by : Cameron Bryce Hummels

Download or read book Comparing Simulations and Observations of Galaxy Evolution written by Cameron Bryce Hummels and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: First, we create a method for producing synthetic photometric images of grid-based hydrodynamical models for use in a direct comparison against observations in a variety of filter bands. We apply this method to a simulation of a cluster of galaxies to investigate the nature of the red-sequence/blue-cloud dichotomy in the galaxy color-magnitude diagram. Second, we implement several subgrid models governing the complex behavior of gas and stars on small scales in our galaxy models. Several numerical simulations are conducted with similar initial conditions, where we systematically vary the subgrid models, afterward assessing their efficacy through comparisons of their internal kinematics with observed systems. Third, we generate an additional method to compare observations with simulations, focusing on the tenuous circumgalactic medium. Informed by our previous studies, we investigate the sensitivity of this new mode of comparison to hydrodynamical subgrid prescription. Finally, we synthesize the results of these studies and identify future avenues of research.

Galactic Gas Flows from Halo to Disk

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ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (14 download)

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Book Synopsis Galactic Gas Flows from Halo to Disk by : Hannah V. Bish

Download or read book Galactic Gas Flows from Halo to Disk written by Hannah V. Bish and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The evolution of galaxies is closely linked to the exchange of gas between their disk and the circumgalactic medium (CGM) - the massive, extended, diffuse halo of gas in which galaxies are embedded. Recent advances in high-resolution spectroscopy have enabled observers to firmly establish the key role played by the CGM in the life cycle of galaxies: it is the hiding place of at least half of all galactic baryons, acting as a massive reservoir that replenishes the supply of fuel for star formation via gas accretion onto the disk. However, this nearly-invisible halo gas is challenging to observe, and we are still missing a complete picture of its distribution, kinematics, and multiphase structure. In this thesis, I use the Milky Way as a case study to shed light on the nature of cool and warm CGM gas flows, taking advantage of the abundance of quasar and stellar sightlines which probe the Galactic CGM. In particular, I focus on the behavior of low-velocity gas, which is often overlooked by CGM studies because it is difficult to measure in isolation. I show that local CGM gas is predominantly inflowing, place constraints on the inflowing cloud sizes, and determine that these clouds lie close to the disk. I use a novel spectral differencing technique to correct for foreground absorption along sightlines through the Galactic halo, and present the first unobscured measurements of the Milky Way's extended low-velocity CGM. The results demonstrate that either the warm CGM does not have a spherical morphology, as is often assumed for star-forming galaxies, or that the Milky Way is not a typical star-forming galaxy. Finally, I find that inflow velocities are higher for warmer gas, suggesting a picture in which warm accreting gas slows down and cools as it approaches the disk. The mass accretion rates of these inflows indicate that a significant fraction of star-formation fuel may accrete onto the disk at low velocities.

Dynamics of the Milky Way

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Publisher : Springer
ISBN 13 : 3319187724
Total Pages : 274 pages
Book Rating : 4.3/5 (191 download)

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Book Synopsis Dynamics of the Milky Way by : Jason Sanders

Download or read book Dynamics of the Milky Way written by Jason Sanders and published by Springer. This book was released on 2015-06-15 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work presents a study of methods useful for modeling and understanding dynamical systems in the Galaxy. A natural coordinate system for the study of dynamical systems is the angle-action coordinate system. New methods for the approximation of the action-angle variables in general potentials are presented and discussed. These new tools are applied to the construction of dynamical models for two of the Galaxy’s components: tidal streams and the Galactic disc. Tidal streams are remnants of tidally stripped satellites in the Milky Way that experience the effects of the large scale structure of the Galactic gravitational potential, while the Galactic disc provides insights into the nature of the Galaxy near the Sun. Appropriate action-based models are presented and discussed for these components, and extended to include further information such as the metallicity of stars.

Mapping the Circumgalactic Medium

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ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (14 download)

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Book Synopsis Mapping the Circumgalactic Medium by : Matthew C. Wilde

Download or read book Mapping the Circumgalactic Medium written by Matthew C. Wilde and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work presented in this dissertation provides the groundwork for understanding key unresolved questions in the study of galaxy evolution: the circumgalactic medium (CGM) and the role of environment. I present a new survey that has the power to drastically improve our understanding of the CGM and use it to estimate the size of the CGM as a function of galactic mass. In addition, a novel method to reconstruct the cosmic web using Physarum polycephalum slime mold is presented and applied to the SDSS surveys. This cosmic web reconstruction was released publicly with SDSS DR17 and will allow exciting connections between galaxies and their environments to be illuminated, to distances greater than other previous catalogs.

Out-of-core Hydrodynamic Simulations of Cosmological Structure Formation [microform]

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Publisher : Library and Archives Canada = Bibliothèque et Archives Canada
ISBN 13 : 9780612942400
Total Pages : 328 pages
Book Rating : 4.9/5 (424 download)

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Book Synopsis Out-of-core Hydrodynamic Simulations of Cosmological Structure Formation [microform] by : Hy Trac

Download or read book Out-of-core Hydrodynamic Simulations of Cosmological Structure Formation [microform] written by Hy Trac and published by Library and Archives Canada = Bibliothèque et Archives Canada. This book was released on 2004 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: Astrophysical and cosmological structure formation are challenging problems because they involve dynamical and hydrodynamical processes that can span a large range in scale, mass, and energy. Hydrodynamic and N-body simulations are powerful tools with which to solve the nonlinear physics, and their continuing development and application is the focus of this thesis. I present a new approach to Eulerian computational fluid dynamics that is designed to work at high Mach numbers encountered in astrophysical simulations. The Eulerian conservation equations are solved in an adaptive frame moving with the fluid where Mach numbers are minimized. The Moving Frame code separately tracks local and bulk flow components, allowing thermodynamic variables to be accurately calculated in both subsonic and supersonic fluid. This thesis includes the first astrophysical application of Eulerian hydrodynamic simulations to model the formation of blue stragglers through stellar mergers. The off-axis collision of equal mass stars produces a single merger remnant. The merger of n = 3 polytropes results in substantial chemical mixing throughout the remnant, while the merger of realistic M = 0.8 M & odot; main sequence stars produces significant mixing only outside of the core. The Out-of-core Hydro code is applied to running the largest Eulerian hydrodynamic simulation to date for studying the thermal history of the high redshift 3 & le; z & le; 7 intergalactic medium. The temperature-density and gas-dark matter density relations, as well as the scatter in these relations, are robustly quantified. Reionization and shock heating are observed to influence the temperature of the photoionized gas. An out-of-core hydrodynamic code has been developed for high resolution cosmological simulations. Out-of-core computation refers to the technique of using disk space as virtual memory and transferring data in and out of main memory at high I/O bandwidth. The code is based on a two-level mesh scheme where short-range physics is solved on a high-resolution, localized mesh while long-range physics is captured on a lower resolution, global mesh. Furthermore, a parallel particle-mesh N-body code is applied to simulating the clustering of dark matter halos. The PMFAST simulations show that that several bias parameters are consistent with being scale-invariant, a useful property for doing cosmology with galaxy clustering.

Comparing Cosmological Hydrodynamic Simulations with Observations of High-redshift Galaxy Formation

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ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (612 download)

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Book Synopsis Comparing Cosmological Hydrodynamic Simulations with Observations of High-redshift Galaxy Formation by :

Download or read book Comparing Cosmological Hydrodynamic Simulations with Observations of High-redshift Galaxy Formation written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Comparing cosmological hydrodynamic simulations with observations of high-redshift galaxy formation.

Hydrodynamic Simulations of Galaxy Formation in a Cosmological Context

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Publisher :
ISBN 13 :
Total Pages : 137 pages
Book Rating : 4.:/5 (898 download)

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Book Synopsis Hydrodynamic Simulations of Galaxy Formation in a Cosmological Context by : Rahul Vasudev Nair Kannan

Download or read book Hydrodynamic Simulations of Galaxy Formation in a Cosmological Context written by Rahul Vasudev Nair Kannan and published by . This book was released on 2014 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: