Read Books Online and Download eBooks, EPub, PDF, Mobi, Kindle, Text Full Free.
Cosmological Hydrodynamic Simulations Of The Lyman Alpha Forest
Download Cosmological Hydrodynamic Simulations Of The Lyman Alpha Forest full books in PDF, epub, and Kindle. Read online Cosmological Hydrodynamic Simulations Of The Lyman Alpha Forest ebook anywhere anytime directly on your device. Fast Download speed and no annoying ads. We cannot guarantee that every ebooks is available!
Book Synopsis Cosmological Hydrodynamic Simulations of the Lyman-alpha Forest by : Yu Zhang
Download or read book Cosmological Hydrodynamic Simulations of the Lyman-alpha Forest written by Yu Zhang and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Several three dimensional, multi-species, cosmological hydrodynamic simulations of the formation and evolution of Ly$alpha$ forest absorbers were performed in three CDM-like cosmological models: the standard CDM model (SCDM), the flat CDM model with a nonzero cosmological constant ($Lambda$CDM) and the open CDM model (OCDM). Synthetic spectra along random lines-of-sight were generated and analyzed by using a powerful spectrum analysis method designed to mimic observational data reduction. The SCDM model was studied in great detail and found to be in excellent agreement with observations in: the slope and shape of the column density distribution, the value and distribution of the Doppler parameter and the equivalent width, the evolution of line density, effective opacity and flux decrement, etc. A number of sensitive tests were devised to compare and contrast different cosmological models, and it is found that both the SCDM and the $Lambda$CDM models agree with observations quite well, while the OCDM model fails to match most of the observational data satisfactorily. It is discovered that the low column density (log $Nsb{HI} simeq$ 13.3 and log $Nsb{HeII} simeq$ 14.5) H sc I and He sc II Ly$alpha$ absorbers which are optically-thin at the line center ($tausb0
Book Synopsis The Lyman Alpha Forest in Hierarchical Structure Formation Models by : Romeel S Davé
Download or read book The Lyman Alpha Forest in Hierarchical Structure Formation Models written by Romeel S Davé and published by . This book was released on 1998 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis An Analysis of Astrophysics and Fundamental Physics from the Lyman-alpha Forest by : Aaron Joseph Day
Download or read book An Analysis of Astrophysics and Fundamental Physics from the Lyman-alpha Forest written by Aaron Joseph Day and published by . This book was released on 2013 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Lyman-alpha forest, made up of the cosmologically redshifted hydrogen Lyman-alpha absorption lines in the spectra of distant quasars, is a sensitive probe of cosmology and astrophysics. The shape and distribution of the Lyman-alpha absorption lines is deter- mined by the column densities, peculiar velocities, redshifts, turbulent velocities, temperatures, and the distribution of systems of neutral hydrogen in the space between galaxies known as the intergalactic medium. The Lyman-alpha forest is sensitive to the total cosmological matter power spectrum at the smallest available scales. It provides a long lever arm for constraints on the shape of the matter power spectrum when used in conjunction with measurements at large scales, such as the cosmic microwave background. It also has the potential to be used to detect the small scale matter power suppression caused by the free streaming of fundamental particles including known active light neutrinos or potential warm dark matter candidates. Focusing on the line widths, optical depth, and the power spectrum of the flux of the Lyman-alpha forest, we find that previously published observations do not match the outputs of fully hydrodynamic cosmological computer simulations. We present a new measurement of the power spectrum of the flux of the Lyman-alpha forest, using 91 quasar spectra taken with the Keck HIRES spectrograph. This is the largest high resolution data set to date by a factor of about 3. The high resolution of our data sample gives fully resolved absorption lines. Compared to the low resolution data set from SDSS, the HIRES data allows for more accurate subtraction of metal line contamination, as well as a measurement of the flux power at the smallest scales. Finally, we run a suite of 44 new computer simulations, varying cosmological and astrophysical parameters in an attempt to find a model that matches our observational data. We find that no standard cosmological or astrophysical parameters provide an acceptable match. This calls into question previous constraints on cosmological parameters made from Lyman-alpha forest data sets
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.
Book Synopsis QSO Pairs and the Lyman-alpha Forest: Observations, Simulations, and Cosmological Implications by : Andrew Robert Marble
Download or read book QSO Pairs and the Lyman-alpha Forest: Observations, Simulations, and Cosmological Implications written by Andrew Robert Marble and published by . This book was released on 2007 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: Using a suite of hydrodynamic simulations, anisotropies in the Lyalpha flux correlation function due to redshift-space distortions and spectral smoothing are investigated for 1:8 ≤ z ≤ 3, further enabling future applications of the Alcock-Paczynski test with Lyalpha correlation measurements. Sources of systematic error including limitations in mass-resolution and simulation volume, prescriptions for galactic outflow, and the observationally uncertain mean flux decrement are considered. The latter is found to be dominant. An approximate solution for obtaining the zero-lag cross-correlation for arbitrary spectral resolution is presented, as is a method for implementing the resulting anisotropy corrections while mitigating systematic uncertainty.
Book Synopsis Lyman-alpha as an Astrophysical and Cosmological Tool by : Mark Dijkstra
Download or read book Lyman-alpha as an Astrophysical and Cosmological Tool written by Mark Dijkstra and published by Springer Nature. This book was released on 2019-11-12 with total page 421 pages. Available in PDF, EPUB and Kindle. Book excerpt: The hydrogen Lyman-alpha line is of utmost importance to many fields of astrophysics. This UV line being conveniently redshifted with distance to the visible and even near infrared wavelength ranges, it is observable from the ground, and provides the main observational window on the formation and evolution of high redshift galaxies. Absorbing systems that would otherwise go unnoticed are revealed through the Lyman-alpha forest, Lyman-limit, and damped Lyman-alpha systems, tracing the distribution of baryonic matter on large scales, and its chemical enrichment. We are living an exciting epoch with the advent of new instruments and facilities, on board of satellites and on the ground. Wide field and very sensitive integral field spectrographs are becoming available on the ground, such as MUSE at the ESO VLT. The giant E-ELT and TMT telescopes will foster a quantum leap in sensitivity and both spatial and spectroscopic resolution, to the point of being able, perhaps, to measure directly the acceleration of the Hubble flow. In space, the JWST will open new possibilities to study the Lyman-alpha emission of primordial galaxies in the near infrared. As long as the Hubble Space Telescope will remain available, the UV-restframe properties of nearby galaxies will be accessible to our knowledge. Therefore, this Saas-Fee course appears very timely and should meet the interest of many young researchers.
Book Synopsis Towards Physics Responsible for Large-scale Lyman-[alpha] Forest Bias Parameters by :
Download or read book Towards Physics Responsible for Large-scale Lyman-[alpha] Forest Bias Parameters written by and published by . This book was released on 2016 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: Using a series of carefully constructed numerical experiments based on hydrodynamic cosmological SPH simulations, we attempt to build an intuition for the relevant physics behind the large scale density (b[delta]) and velocity gradient (b[eta]) biases of the Lyman-[alpha] forest. Starting with the fluctuating Gunn-Peterson approximation applied to the smoothed total density field in real-space, and progressing through redshift-space with no thermal broadening, redshift-space with thermal broadening and hydrodynamically simulated baryon fields, we investigate how approximations found in the literature fare. We find that Seljak's 2012 analytical formulae for these bias parameters work surprisingly well in the limit of no thermal broadening and linear redshift-space distortions. We also show that his b[eta] formula is exact in the limit of no thermal broadening. Since introduction of thermal broadening significantly affects its value, we speculate that a combination of large-scale measurements of b[eta] and the small scale flux PDF might be a sensitive probe of the thermal state of the IGM. Lastly, we find that large-scale biases derived from the smoothed total matter field are within 10-20% to those based on hydrodynamical quantities, in line with other measurements in the literature.
Book Synopsis The Intergalactic Medium by : Juna Ariele Kollmeier
Download or read book The Intergalactic Medium written by Juna Ariele Kollmeier and published by . This book was released on 2006 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Two fundamental predictions of modern cosmological models are that i) galaxies form from small perturbations in the cosmic density field and ii) there is a tenuous medium between the galaxies that traces the underlying dark matter distribution in a relatively simple way. This thesis concerns the structure of the intergalactic medium (IGM) and its relation to galaxies. Specifically, I analyze the nature of the IGM, observable via the Lyman-alpha transition of hydrogen, as predicted from cosmological hydrodynamic simulations of a cold dark matter + dark energy universe. I first quantify the relation between galaxies and absorption in the Lyman-alpha forest on large (~10 Megaparsec) and small (~0.5 Megaparsec) scales and show that, in the absence of feedback from the galaxies themselves, observations of this relation can serve as robust tests of the inflationary cold dark matter model. I show that the strong bias of high redshift galaxies toward high density regions imprints a clear signature on the distribution of flux in the Lyman-alpha forest, and these predictions are examined as functions of galaxy baryon mass, star formation rate, and dark matter halo mass and occupation. I then investigate the potential impact of galaxies on the IGM and find that supernova-driven winds (as predicted in cosmological simulations) can substantially impact their local surroundings, particularly via heating, but that only very powerful winds can create easily detectable "holes'" in the IGM. The impact of winds on the Lyman-alpha optical depth near galaxies is less dramatic than their impact on gas temperature because winds heat only a small fraction of the gas present in the turnaround regions surrounding galaxies, all of which contribute to the Lyman-alpha forest near galaxies. Finally, I combine a Monte Carlo radiative transfer code with cosmological hydrodynamic simulations to investigate the signature of fluorescent Lyman-alpha emission from large scale structure due to impinging radiation from the metagalactic ionizing background as well as local bright sources such as quasars. I compare these predictions with current observations and discuss future observing campaigns and realistic strategies for detecting fluorescence from the ambient metagalactic ionization as well as in the vicinity of bright quasars.
Book Synopsis The Lyman Alpha Forest in Hierarchical Structure Formation Models by : Romeel S Davé
Download or read book The Lyman Alpha Forest in Hierarchical Structure Formation Models written by Romeel S Davé and published by . This book was released on 1998 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Cosmological Gas-dynamics, Simulations of the Lyman-Ã Forest by :
Download or read book Cosmological Gas-dynamics, Simulations of the Lyman-Ã Forest written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Building a Red Sequence in Cosmological Hydrodynamic Simulations by : Jared M. Gabor
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:
Book Synopsis Extragalactic Astronomy and Cosmology by : Peter Schneider
Download or read book Extragalactic Astronomy and Cosmology written by Peter Schneider and published by Springer. This book was released on 2014-10-08 with total page 637 pages. Available in PDF, EPUB and Kindle. Book excerpt: This second edition has been updated and substantially expanded. Starting with the description of our home galaxy, the Milky Way, this cogently written textbook introduces the reader to the astronomy of galaxies, their structure, active galactic nuclei, evolution and large scale distribution in the Universe. After an extensive and thorough introduction to modern observational and theoretical cosmology, the focus turns to the formation of structures and astronomical objects in the early Universe. The basics of classical astronomy and stellar astrophysics needed for extragalactic astronomy are provided in the appendix. While this book has grown out of introductory university courses on astronomy and astrophysics and includes a set of problems and solutions, it will not only benefit undergraduate students and lecturers; thanks to the comprehensive coverage of the field, even graduate students and researchers specializing in related fields will appreciate it as a valuable reference work.
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.
Book Synopsis Temps de l'advènement à la couronne et du décès des roys de France, depuis Hugues Capet jusques à Louis XIV, à présent régnant by :
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 :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)
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.
Download or read book Mining the Sky written by A.J. Banday and published by Springer Science & Business Media. This book was released on 2001-09-11 with total page 732 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book reviews methods for the analysis of astronomical datasets, particularly emphasizing very large databases arising from both existing and forthcoming projects, as well as current large-scale computer simulation studies. Leading experts give overviews of cutting-edge methods applicable in the area of astronomical data mining.
Book Synopsis Measuring the Cosmological Constant Through the Lyman-Alpha Forest Using the Alcock-Paczynski Test by : Wen-Ching Lin
Download or read book Measuring the Cosmological Constant Through the Lyman-Alpha Forest Using the Alcock-Paczynski Test written by Wen-Ching Lin and published by . This book was released on 2003 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt:
![Download Towards Physics Responsible for Large-scale Lyman-[alpha] Forest Bias Parameters PDF Online Free](https://books.google.com/books/content/images/frontcover/nndoswEACAAJ?fife=w200-h370)
![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)
