Semi-analytic Modeling of Stellar Populations in Astrophysical Simulations PDF Download
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Author: Brian David Crosby
Publisher:
ISBN: 9781339974927
Category : Electronic dissertations
Languages : en
Pages : 233
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Book Description
Author: Brian David Crosby
Publisher:
ISBN: 9781339974927
Category : Electronic dissertations
Languages : en
Pages : 233
Get Book Here
Book Description
Author: Tilmann Piffl
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Numerical simulations of galaxy formation and observational Galactic Astronomy are two fields of research that study the same objects from different perspectives. Simulations try to understand galaxies like our Milky Way from an evolutionary point of view while observers try to disentangle the current structure and the building blocks of our Galaxy. Due to great advances in computational power as well as in massive stellar surveys we are now able to compare resolved stellar populations in simulations and in observations. In this thesis we use a number of approaches to relate the results of the two fields to each other. The major observational data set we refer to for this work comes from the Radial Velocity Experiment (RAVE), a massive spectroscopic stellar survey that observed almost half a million stars in the Galaxy. In a first study we use three different models of the Galaxy to generate synthetic stellar surveys that can be directly compared to the RAVE data. To do this we evaluate the RAVE selection function to great detail. Among the Galaxy models is the widely used Besancon model that performs well when individual parameter distribution are considered, but fails when we study chemodynamic correlations. The other two models are based on distributions of mass particles instead of analytical distribution functions. This is the first time that such models are converted to the space of observables and are compared to a stellar survey. We show that these models can be competitive and in some aspects superior to analytic models, because of their self-consistent dynamic history. In the case of a full cosmological simulation of disk galaxy formation we can recover features in the synthetic survey that relate to the known issues of the model and hence proof that our technique is sensitive to the global structure of the model. We argue that the next generation of cosmological galaxy formation simulations will deliver valuable models for our Galaxy. Testing these models with our approach will provide a direct connection between stellar Galactic astronomy and physical cosmology. In the second part of the thesis we use a sample of high-velocity halo stars from the RAVE data to estimate the Galactic escape speed and the virial mass of the Milky Way. In the course of this study cosmological simulations of galaxy formation also play a crucial role. Here we use them to calibrate and extensively test our analysis technique. We find the local Galactic escape speed to be 533 (+54/-41) km/s (90% confidence). With this result in combination with a simple mass model of the Galaxy we then construct an estimate of the virial mass of the Galaxy. For the mass profile of the dark matter halo we use two extreme models, a pure Navarro, Frenk & White (NFW) profile and an adiabatically contracted NFW profile. When we use statistics on the concentration parameter of these profile taken from large dissipationless cosmological simulations we obtain an estimate of the virial mass that is almost independent of the choice of the halo profile. For the mass M_340 enclosed within R_340 = 180 kpc we find 1.3 (+0.4/-0.3) x 10^12 M_sun. This value is in very good agreement with a number of other mass estimates in the literature that are based on independent data sets and analysis techniques. In the last part of this thesis we investigate a new possible channel to generate a population of Hypervelocity stars (HVSs) that is observed in the stellar halo. Commonly, it is assumed that the velocities of these stars originate from an interaction with the super-massive black hole in the Galactic center. It was suggested recently that stars stripped-off a disrupted satellite galaxy could reach similar velocities and leave the Galaxy. Here we study in detail the kinematics of tidal debris stars to investigate the probability that the observed sample of HVSs could partly originate from such a galaxy collision. We use a suite of $N$-body simulations following the encounter of a satellite galaxy with its Milky Way-type host galaxy. We quantify the typical pattern in angular and phase space formed by the debris stars and develop a simple model that predicts the kinematics of stripped-off stars. We show that the distribution of orbital energies in the tidal debris has a typical form that can be described quite accurately by a simple function. The main parameters determining the maximum energy kick a tidal debris star can get is the initial mass of the satellite and only to a lower extent its orbit. Main contributors to an unbound stellar population created in this way are massive satellites (M_sat > 10^9 M_sun). The probability that the observed HVS population is significantly contaminated by tidal debris stars appears small in the light of our results
Author: Ignacio Ferreras
Publisher: Springer Science & Business Media
ISBN: 3642202853
Category : Science
Languages : en
Pages : 236
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Book Description
The publication of the morphology - density relation by Alan Dressler in 1980 brought into the limelight the role played by environment in the formation and evolution of galaxies. The symposium Environment and the Formation of Galaxies: 30 years later, was organised with the purpose of establishing the environmental impact on the evolution of galaxies and its dependence on look-back time. Special emphasis was placed on the physical mechanisms that are responsible for transforming galaxies once they are accreted by a group or a cluster, including the observable imprint left in the galaxy HI distribution. Other major topics of the symposium were the environmental dependence of galaxy properties at z ≥ 1 and the implementation of environmental effects in cosmological models of galaxy formation and evolution. This book presents the edited proceedings of this stimulating meeting.
Author: Andreas Zezas
Publisher: Cambridge University Press
ISBN: 1316877523
Category : Science
Languages : en
Pages : 318
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Book Description
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.
Author: Maurizio Salaris
Publisher: John Wiley & Sons
ISBN: 9780470092224
Category : Science
Languages : en
Pages : 386
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Book Description
Evolution of Stars and Stellar Populations is a comprehensive presentation of the theory of stellar evolution and its application to the study of stellar populations in galaxies. Taking a unique approach to the subject, this self-contained text introduces first the theory of stellar evolution in a clear and accessible manner, with particular emphasis placed on explaining the evolution with time of observable stellar properties, such as luminosities and surface chemical abundances. This is followed by a detailed presentation and discussion of a broad range of related techniques, that are widely applied by researchers in the field to investigate the formation and evolution of galaxies. This book will be invaluable for undergraduates and graduate students in astronomy and astrophysics, and will also be of interest to researchers working in the field of Galactic, extragalactic astronomy and cosmology. comprehensive presentation of stellar evolution theory introduces the concept of stellar population and describes "stellar population synthesis" methods to study ages and star formation histories of star clusters and galaxies presents stellar evolution as a tool for investigating the evolution of galaxies and of the universe in general
Author: Francesca Matteucci
Publisher: Springer Science & Business Media
ISBN: 3642224911
Category : Science
Languages : en
Pages : 237
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Book Description
The term “chemical evolution of galaxies” refers to the evolution of abundances of chemical species in galaxies, which is due to nuclear processes occurring in stars and to gas flows into and out of galaxies. This book deals with the chemical evolution of galaxies of all morphological types (ellipticals, spirals and irregulars) and stresses the importance of the star formation histories in determining the properties of stellar populations in different galaxies. The topic is approached in a didactical and logical manner via galaxy evolution models which are compared with observational results obtained in the last two decades: The reader is given an introduction to the concept of chemical abundances and learns about the main stellar populations in our Galaxy as well as about the classification of galaxy types and their main observables. In the core of the book, the construction and solution of chemical evolution models are discussed in detail, followed by descriptions and interpretations of observations of the chemical evolution of the Milky Way, spheroidal galaxies, irregular galaxies and of cosmic chemical evolution. The aim of this book is to provide an introduction to students as well as to amend our present ideas in research; the book also summarizes the efforts made by authors in the past several years in order to further future research in the field.
Author: Peter Schneider
Publisher: Springer
ISBN: 364254083X
Category : Science
Languages : en
Pages : 637
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Book Description
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.
Author: V. Di Ges
Publisher: World Scientific
ISBN: 9812779442
Category : Science
Languages : en
Pages : 350
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Book Description
This proceedings volume contains results presented at the Sixth International Workshop on Data Analysis in Astronomy ? ?Modeling and Simulation in Science? held on April 15-22, 2007, at the Ettore Majorana Foundation and Center for Scientific Culture, Erice, Italy. Recent progress and new trends in the field of simulation and modeling in three branches of science ? astrophysics, biology, and climatology ? are described in papers presented by outstanding scientists. The impact of new technologies on the design of novel data analysis systems and the interrelation among different fields are foremost in scientists' minds in the modern era. This book therefore focuses primarily on data analysis methodologies and techniques.
Author: Claire Kopenhafer
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 0
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Book Description
One of the primary concerns in galaxy evolution is how galaxies form their stars: what keeps that star formation going over cosmic time, and what causes it to stop in a processes called "quenching". Galaxies with mass similar to our own Milky Way occupy a sweet spot between abundance and brightness that makes them easy to find in the sky, and such galaxies also populate a transitionary regime in behavior that make them interesting for studying galaxy evolution. Numerical modeling-from semi-analytic models to numerical simulations-are valuable tools for understanding the multiple intersecting physical processes that drive galaxy evolution. These processes act both within and around individual galaxies such that numerical models must necessarily encompass a range of spatial and temporal scales. Multiple approaches are commonly used in order for this modeling to be physically insightful. In this dissertation I will present my efforts to unravel the mechanisms of galaxy evolution affect Milky Way-like galaxies using a variety of numerical models.Addressing the issue of what causes galaxies to stop forming stars, I first investigate an unusual population of galaxies called the "break BRDs" (Tuttle and Tonnesen 2020). Within the dominant framework for galaxy quenching, galaxies first stop forming stars in their centers and later in their outskirts. This is the "inside-out" quenching paradigm. The break BRD galaxies possess observational markers that run counter to this narrative. We used the Illustris TNG cosmological simulation(Pillepich et al. 2018b) to find a set of simulated galaxies that are analogous to the observed breakBRDs in order to better understand their evolution. We found that the breakBRD analogues are galaxies that ultimately become fully quenched, but found no clear cause for the "outside-in" modality. This is not the dominant channel for quenching in the IllustrisTNG simulation, but roughly 10% of quiescent galaxies with 10
Author: Nickolay Y. Gnedin
Publisher: Springer
ISBN: 3662478900
Category : Science
Languages : en
Pages : 375
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Book Description
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.
