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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 : 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 : Claudia Del P. Lagos
Publisher : Springer Science & Business Media
ISBN 13 : 3319015265
Total Pages : 252 pages
Book Rating : 4.3/5 (19 download)
Download or read book The Physics of Galaxy Formation written by Claudia Del P. Lagos and published by Springer Science & Business Media. This book was released on 2013-10-15 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis addresses two of the central processes which underpin the formation of galaxies: the formation of stars and the injection of energy into the interstellar medium from supernovae, called feedback. In her work Claudia Lagos has completely overhauled the treatment of these processes in simulations of galaxy formation. Her thesis makes two major breakthroughs, and represents the first major steps forward in these areas in more than a decade. Her work has enabled, for the first time, predictions to be made which can be compared against new observations which probe the neutral gas content of galaxies, opening up a completely novel way to constrain the models. The treatment of feedback from supernovae, and how this removes material from the interstellar medium, is also likely to have a lasting impact on the field. Claudia Lagos Ph.D. thesis was nominated by the Institute for Computational Cosmology at Durham University as an outstanding Ph.D. thesis 2012.
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 : I. Pérez-Fournon
Publisher : Cambridge University Press
ISBN 13 : 9780521825917
Total Pages : 302 pages
Book Rating : 4.8/5 (259 download)
Download or read book Galaxies at High Redshift written by I. Pérez-Fournon and published by Cambridge University Press. This book was released on 2003-03-20 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents lectures of the XI Canary Islands Winter School of Astrophysics written by experts in the field.
Author : Avishai Dekel
Publisher : Cambridge University Press
ISBN 13 : 9780521586320
Total Pages : 492 pages
Book Rating : 4.5/5 (863 download)
Download or read book Formation of Structure in the Universe written by Avishai Dekel and published by Cambridge University Press. This book was released on 1999-04-15 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: This advanced textbook provides an up-to-date and comprehensive introduction to the very active field of structure formation in cosmology. It is written by eleven world-leading authorities. Written in a clear and pedagogical style appropriate for graduate students in astronomy and physics, this textbook introduces the reader to a wide range of exciting topics in contemporary cosmology: from recent advances in redshift surveys, to the latest models in gravitational lensing and cosmological simulations. The authors are all world-renowned experts both for their research and teaching skills. In the fast-moving field of structure formation, this book provides advanced undergraduate and graduate students with a welcome textbook which unites the latest theory and observations.
Author : Andrea Cimatti
Publisher : Cambridge University Press
ISBN 13 : 1108764223
Total Pages : 587 pages
Book Rating : 4.1/5 (87 download)
Download or read book Introduction to Galaxy Formation and Evolution written by Andrea Cimatti and published by Cambridge University Press. This book was released on 2019-10-17 with total page 587 pages. Available in PDF, EPUB and Kindle. Book excerpt: Present-day elliptical, spiral and irregular galaxies are large systems made of stars, gas and dark matter. Their properties result from a variety of physical processes that have occurred during the nearly fourteen billion years since the Big Bang. This comprehensive textbook, which bridges the gap between introductory and specialized texts, explains the key physical processes of galaxy formation, from the cosmological recombination of primordial gas to the evolution of the different galaxies that we observe in the Universe today. In a logical sequence, the book introduces cosmology, illustrates the properties of galaxies in the present-day Universe, then explains the physical processes behind galaxy formation in the cosmological context, taking into account the most recent developments in this field. The text ends on how to find distant galaxies with multi-wavelength observations, and how to extract the physical and evolutionary properties based on imaging and spectroscopic data.
Author : Andreas Zezas
Publisher : Cambridge University Press
ISBN 13 : 1316877523
Total Pages : 318 pages
Book Rating : 4.3/5 (168 download)
Download or read book Star-Formation Rates of Galaxies written by Andreas Zezas and published by Cambridge University Press. This book was released on 2021-04-29 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: Star-formation is one of the key processes that shape the current state and evolution of galaxies. This volume provides a comprehensive presentation of the different methods used to measure the intensity of recent or on-going star-forming activity in galaxies, discussing their advantages and complications in detail. It includes a thorough overview of the theoretical underpinnings of star-formation rate indicators, including topics such as stellar evolution and stellar spectra, the stellar initial mass function, and the physical conditions in the interstellar medium. The authors bring together in one place detailed and comparative discussions of traditional and new star-formation rate indicators, star-formation rate measurements in different spatial scales, and comparisons of star-formation rate indicators probing different stellar populations, along with the corresponding theoretical background. This is a useful reference for students and researchers working in the field of extragalactic astrophysics and studying star-formation in local and higher-redshift galaxies.
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 : 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 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 : J. A. Peacock
Publisher : Cambridge University Press
ISBN 13 : 9780521422703
Total Pages : 700 pages
Book Rating : 4.4/5 (227 download)
Download or read book Cosmological Physics written by J. A. Peacock and published by Cambridge University Press. This book was released on 1999 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive and authoritative introduction to contemporary cosmology for advanced undergraduate and graduate students.
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 : Patrick Petitjean
Publisher : Atlantica Séguier Frontières
ISBN 13 : 9782863322291
Total Pages : 490 pages
Book Rating : 4.3/5 (222 download)
Download or read book Structure and Evolution of the Intergalactic Medium from QSO Absorption Line Systems written by Patrick Petitjean and published by Atlantica Séguier Frontières. This book was released on 1997 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Houjun Mo
Publisher : Cambridge University Press
ISBN 13 : 0521857937
Total Pages : 841 pages
Book Rating : 4.5/5 (218 download)
Download or read book Galaxy Formation and Evolution written by Houjun Mo and published by Cambridge University Press. This book was released on 2010-05-20 with total page 841 pages. Available in PDF, EPUB and Kindle. Book excerpt: A coherent introduction for researchers in astronomy, particle physics, and cosmology on the formation and evolution of galaxies.
