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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:
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:
Author : Vicente Rodriguez-Gomez
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (995 download)
Download or read book Galaxy Mergers and Some Consequences: The Cosmological Context written by Vicente Rodriguez-Gomez and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The last few years have seen enormous progress in the field of galaxy formation and evolution. The latest generation of hydrodynamic cosmological simulations (e.g., the "Illustris" simulation) has been able to produce reasonably realistic populations of galaxies by tracking the evolution of dark matter, gas, stars, and black holes over a cosmological volume "representative" of the large-scale density field.
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 : 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...
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.
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 : 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 : Jeffrey Paul Gardner
Publisher :
ISBN 13 :
Total Pages : 175 pages
Book Rating : 4.:/5 (467 download)
Download or read book Numerical Simulations of Galaxy Formation in a Cosmological Context written by Jeffrey Paul Gardner and published by . This book was released on 2000 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 137 pages
Book Rating : 4.:/5 (873 download)
Download or read book Simulating the Growth of a Disk Galaxy and Its Supermassive Black Hole in a Cosmological Simulating the Growth of a Disk Galaxy and Its Supermassive Black Hole in a Cosmological Context written by and published by . This book was released on 2008 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: Supermassive black holes (SMBHs) are ubiquitous in the centers of galaxies. Their formation and subsequent evolution is inextricably linked to that of their host galaxies, and the study of galaxy formation is incomplete without the inclusion of SMBHs. The present work seeks to understand the growth and evolution of SMBHs through their interaction with the host galaxy and its environment. In the first part of the thesis (Chap. 2 and 3), we combine a simple semi-analytic model of outflows from active galactic nuclei (AGN) with a simulated dark matter density distribution to study the impact of SMBH feedback on cosmological scales. We find that constraints can be placed on the kinetic efficiency of such feedback using observations of the filling fraction of the Ly[alpha] forest. We also find that AGN feedback is energetic enough to redistribute baryons over cosmological distances, having potentially significant effects on the interpretation of cosmological data which are sensitive to the total matter density distribution (e.g. weak lensing). However, truly assessing the impact of AGN feedback in the universe necessitates large-dynamic range simulations with extensive treatment of baryonic physics to first model the fueling of SMBHs. In the second part of the thesis (Chap. 4-6) we use a hydrodynamic adaptive mesh refinement simulation to follow the growth and evolution of a typical disk galaxy hosting a SMBH, in a cosmological context. The simulation covers a dynamical range of 10 million allowing us to study the transport of matter and angular momentum from super-galactic scales all the way down to the outer edge of the accretion disk around the SMBH. Focusing our attention on the central few hundred parsecs of the galaxy, we find the presence of a cold, self-gravitating, molecular gas disk which is globally unstable. The global instabilities drive super-sonic turbulence, which maintains local stability and allows gas to fuel a SMBH without first fragmenting completely into stars. The fueling appears to be a stochastic process, with no preferred timescale for accretion over the duration of the simulation.
Author :
Publisher :
ISBN 13 :
Total Pages : 12 pages
Book Rating : 4.:/5 (727 download)
Download or read book Isolating Triggered Star Formation written by and published by . This book was released on 2007 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Galaxy pairs provide a potentially powerful means of studying triggered star formation from galaxy interactions. We use a large cosmological N-body simulation coupled with a well-tested semi-analytic substructure model to demonstrate that the majority of galaxies in close pairs reside within cluster or group-size halos and therefore represent a biased population, poorly suited for direct comparison to 'field' galaxies. Thus, the frequent observation that some types of galaxies in pairs have redder colors than 'field' galaxies is primarily a selection effect. We use our simulations to devise a means to select galaxy pairs that are isolated in their dark matter halos with respect to other massive subhalos (N= 2 halos) and to select a control sample of isolated galaxies (N= 1 halos) for comparison. We then apply these selection criteria to a volume-limited subset of the 2dF Galaxy Redshift Survey with M{sub B, j} (less-than or equal to) -19 and obtain the first clean measure of the typical fraction of galaxies affected by triggered star formation and the average elevation in the star formation rate. We find that 24% (30.5 %) of these L* and sub-L* galaxies in isolated 50 (30) h−1 kpc pairs exhibit star formation that is boosted by a factor of (almost equal to)> 5 above their average past value, while only 10% of isolated galaxies in the control sample show this level of enhancement. Thus, 14% (20 %) of the galaxies in these close pairs show clear triggered star formation. Our orbit models suggest that 12% (16%) of 50 (30) h−1 kpc close pairs that are isolated according to our definition have had a close ((less-than or equal to) 30 h−1 kpc) pass within the last Gyr. Thus, the data are broadly consistent with a scenario in which most or all close passes of isolated pairs result in triggered star formation. The isolation criteria we develop provide a means to constrain star formation and feedback prescriptions in hydrodynamic simulations and a very general method of understanding the importance of triggered star formation in a cosmological context.
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 : International Astronomical Union. Symposium
Publisher : Cambridge University Press
ISBN 13 : 9780521889858
Total Pages : 542 pages
Book Rating : 4.8/5 (898 download)
Download or read book The Galaxy Disk in Cosmological Context (IAU S254) written by International Astronomical Union. Symposium and published by Cambridge University Press. This book was released on 2009-04-16 with total page 542 pages. Available in PDF, EPUB and Kindle. Book excerpt: The paradigm of a dark energy- and dark matter-dominated Universe, with the hierarchical merger scenario for the formation of galaxies, has scored impressive successes in matching the observed Universe. However, the theory fails to explain the difficulty in generating ordinary disk galaxies such as the Milky Way, suggesting that some important physics must be missing in current models. IAU Symposium 254 was organized to address this question, gathering researchers from an unusually broad range of fields, from cosmology to interstellar matter, and the formation and evolution of stars. High-class reviews, lectures and posters combine to define the frontiers in the field and point the way to new avenues of research. This volume presents a unique set of succinct overviews illuminating the full range of topics in this very active field. It also honors Danish astrophysicist Bengt Strömgren (1908-1987), who laid much of the foundation for this entire field.
Author : Chi-hun Kim
Publisher : Stanford University
ISBN 13 :
Total Pages : 189 pages
Book Rating : 4.F/5 ( download)
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.
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 : 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 : Nickolay Y. Gnedin
Publisher : Springer
ISBN 13 : 3662478900
Total Pages : 375 pages
Book Rating : 4.6/5 (624 download)
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.
