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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.
Author : Kristian Markwart Finlator
Publisher :
ISBN 13 :
Total Pages : 714 pages
Book Rating : 4.:/5 (659 download)
Download or read book Comparing Cosmological Hydrodynamic Simulations with Observations of High-Redshift Galaxy Formation written by Kristian Markwart Finlator and published by . This book was released on 2009 with total page 714 pages. Available in PDF, EPUB and Kindle. Book excerpt: We use cosmological hydrodynamic simulations to study the impact ofoutflows and radiative feedback on high-redshift galaxies. For outflows, we consider simulations that assume (i) no winds, (ii) a c̀̀onstant-wind"model in which the mass-loading factor and outflow speed areconstant, and (iii) m̀̀omentum-driven" winds in which both parametersvary smoothly with mass. In order to treat radiative feedback, wedevelop a moment-based radiative transfer technique that operates inboth post-processing and coupled radiative hydrodynamic modes. We first ask how outflows impact the broadband spectral energydistributions (SEDs) of six observed reionization-epoch galaxies. Simulations reproduce five regardless of the outflow prescription, while the sixth suggests an unusually bursty star formation history. We conclude that (i) simulations broadly account for available constraintson reionization-epoch galaxies, (ii) individual SEDs do not constrainoutflows, and (iii) SED comparisons efficiently isolate objects thatchallenge simulations. We next study how outflows impact the galaxy mass metallicity relation(MZR). Momentum-driven outflows uniquely reproduce observations at z=2. In this scenario, galaxies obey two equilibria: (i) The rate at which agalaxy processes gas into stars and outflows tracks its inflow rate; and(ii) The gas enrichment rate owing to star formation balances the dilutionrate owing to inflows. Combining these conditions indicates that the MZRis dominated by the (instantaneous) variation of outflows with mass, withmore-massive galaxies driving less gas into outflows per unit stellar massformed. Turning to radiative feedback, we use post-processing simulations to studythe topology of reionization. Reionization begins in overdensities andthen l̀̀eaks" directly into voids, with filaments reionizing last owing totheir high density and low emissivity. This result conflicts withprevious findings that voids ionize last. We argue that it owes to theuniqely-biased emissivity field produced by our star formation prescriptions, which have previously been shown to reproduce numerous post-reionizationconstraints. Finally, preliminary results from coupled radiative hydrodynamicsimulations indicate that reionization suppresses the star formation ratedensity by at most 10--20% by z=5. This is much less than previousestimates, which we attribute to our unique reionization topology althoughconfirmation will have to await more detailed modeling.
Author : Francis Joseph Summers
Publisher :
ISBN 13 :
Total Pages : 774 pages
Book Rating : 4.:/5 (28 download)
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:
Author : Jacob Richard Vander Vliet
Publisher :
ISBN 13 :
Total Pages : 348 pages
Book Rating : 4.:/5 (1 download)
Download or read book Observing the Baryon Cycle in Hydrodynamic Cosmological Simulations written by Jacob Richard Vander Vliet and published by . This book was released on 2017 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: An understanding of galaxy evolution requires an understanding of the flow of baryons in and out of a galaxy. The accretion of baryons is required for galaxies to form stars, while stars eject baryons out of the galaxy through stellar feedback mechanisms such as supernovae, stellar winds, and radiation pressure. The interplay between outflowing and infalling material form the circumgalactic medium (CGM). Hydrodynamic simulations provide understanding of the connection between stellar feedback and the distribution and kinematics of baryons in the CGM. To compare simulations and observations properly the simulated CGM must be observed in the same manner as the real CGM. I have developed the Mockspec code to generate synthetic quasar absorption line observations of the CGM in cosmological hydrodynamic simulations. Mockspec generates synthetic spectra based on the phase, metallicity, and kinematics of CGM gas and mimics instrumental effects. Mockspec includes auomated analysis of the spectra and identifies the gas responsible for the absorption. Mockspec was applied to simulations of dwarf galaxies at low redshift to examine the observable effect different feedback models have on the CGM. While the different feedback models had strong effects on the galaxy, they all produced a similar CGM that failed match observations. Mockspec was applied to the VELA simulation suite of high redshift, high mass galaxies to examine the variance of the CGM across different galaxies in different environments. The observed CGM showed little variation between the different galaxies and almost no evolution from z=4 to z=1. The VELAs were not able to generate a CGM to match the observations. The properties of cells responsible for the absorption were compared to the derived properties from Voigt Profile decomposition. VP modeling was found to accurately describe the HI and MgII absorbing gas but failed for high ionization species such as CIV and OVI, which do not arise in the coherent structures assumed by modelling. The technique of mock QAL is useful for testing the accuracy of the simulated CGM and for verifying observational techniques, but not for differentiating between feedback prescriptions in dwarf galaxies.
Author : Giovanni Guidi
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (11 download)
Download or read book Connecting Simulations and Observations in Galaxy Formation Studies written by Giovanni Guidi and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Observational and computational extragalactic astrophysics are two fields of research that study a similar subject from different perspectives. Observational extragalactic astrophysics aims, by recovering the spectral energy distribution of galaxies at different wavelengths, to reliably measure their properties at different cosmic times and in a large variety of environments. Analyzing the light collected by the instruments, observers try to disentangle the different processes occurring in galaxies at the scales of galactic physics, as well as the effect of larger scale processes such as mergers and accretion, in order to obtain a consistent picture of galaxy formation and evolution. On the other hand, hydrodynamical simulations of galaxy formation in cosmological context are able to follow the evolution of a galaxy along cosmic time, taking into account both external processes such as mergers, interactions and accretion, and internal mechanisms such as feedback from Supernovae and Active Galactic Nuclei. Due to the great advances in...
Author : Rahul Vasudev Nair Kannan
Publisher :
ISBN 13 :
Total Pages : 137 pages
Book Rating : 4.:/5 (898 download)
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:
Download or read book Hydrodynamic Simulations of Cosmological Galaxy Merger Trees written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis we use cosmological merger trees and semi-analytic models of galaxy formation to provide the initial conditions for multi-merger hydrodynamic simulations. In this way we exploit the advantages of merger simulations (high resolution and detailed treatment of the gas physics) and semi-analytic models (cosmological background and low computational cost), and integrate them to create a novel tool. This approach allows us to study the evolution of various galaxy properties with an improved treatment of the gas components, including, for the first time, the hot gaseous halo from which gas cools and accretes onto the central disc. Using a suite of minor merger simulations we find that disc thickening is reduced relative to the collisionless case through the absorption of kinetic impact energy by the gas. In a following series of major merger simulations, we show that adding the hot gas component is a key ingredient in order to reproduce several observed properties of elliptical galaxies, like the abundance of fast rotators. Moreover, the presence of a gaseous halo reduces the starburst efficiency. We then focus on the effects of multiple concurrent mergers, which we found to be cosmologically more common than sequences of isolated binary mergers. For this, we investigate, whether accreted satellite stars can be distinguished kinematically from stars formed 'in situ' in the central galaxy, and find that this is only possible for a fraction of the disrupted satellites. Our simulations to date indicate that the combination of a detailed treatment of gas physics, high resolution, and a cosmological background, brings numerical simulations in better agreement with observations. Overall, the novel tool developed in this thesis will be very useful for pursuing a number of questions pertaining to the transformation of galaxy internal structure by mergers and accretion.
Author :
Publisher :
ISBN 13 :
Total Pages : 137 pages
Book Rating : 4.:/5 (931 download)
Download or read book Hydrodynamical Simulations of Galaxy Formation in a Cosmological Context written by and published by . This book was released on 2014 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt:
![Download Out-of-core Hydrodynamic Simulations of Cosmological Structure Formation [microform] PDF Online Free](https://books.google.com/books/content/images/frontcover/74fXAAAACAAJ?fife=w200-h370)
Author : Hy Trac
Publisher : Library and Archives Canada = Bibliothèque et Archives Canada
ISBN 13 : 9780612942400
Total Pages : 328 pages
Book Rating : 4.9/5 (424 download)
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.
Author : Casey William Stark
Publisher :
ISBN 13 :
Total Pages : 178 pages
Book Rating : 4.:/5 (919 download)
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.
Author : Felix Stoehr
Publisher : Sudwestdeutscher Verlag Fur Hochschulschriften AG
ISBN 13 : 9783838108841
Total Pages : 212 pages
Book Rating : 4.1/5 (88 download)
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)"
Author : Amanda Brady Ford
Publisher :
ISBN 13 :
Total Pages : 228 pages
Book Rating : 4.:/5 (894 download)
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.
Author : Cameron Bryce Hummels
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (867 download)
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.
Download or read book Temps de l'advènement à la couronne et du décès des roys de France, depuis Hugues Capet jusques à Louis XIV, à présent régnant written by and published by . This book was released on 1650* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Manuel Corona
Publisher :
ISBN 13 : 9783923200689
Total Pages : 127 pages
Book Rating : 4.2/5 (6 download)
Download or read book Hydrodynamical Approach of Galaxy-formation on the Basis of a Fluid-model of Two and Three Components During the Recombination Era of the Universe written by Manuel Corona and published by . This book was released on 1984 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Jared M. Gabor
Publisher :
ISBN 13 :
Total Pages : 218 pages
Book Rating : 4.:/5 (862 download)
Download or read book Building a Red Sequence in Cosmological Hydrodynamic Simulations written by Jared M. Gabor and published by . This book was released on 2011 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Munier Salem
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (1 download)
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.
