Download or read book Cosmological Simulations of Galactic Disc Assembly written by Elisa House and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We address the issue of kinematic heating in disc galaxies by analysing a suite of cosmological Milky Way-type disc simulations run with different particle-and grid-based hydrodynamical codes and different resolution, and compare them with observations of the Milky Way. By studying the kinematics of disc stars in these simulations, we seek to determine whether or not the existence of a fragile thin disc is possible within a cosmological framework, where multiple mergers and interactions are the essence of galaxy formation. We study the velocity dispersion-age relation for disc stars at $z=0$ and find that four of the simulations, the stellar disc appears to undergo continual/secular heating. Two other simulations suggest a "saturation" in the heating profile for young stars in the disc. None of the simulations have thin discs as old as that of the Milky Way. We also analyse the kinematics of disc stars at the time of their birth, and find that in some simulations old stars are born cold within the disc and are subsequently heated, while other simulations possess old stellar populations, which are born relatively hot. The models which are in better agreement with observations of the Milky Way's stellar disc undergo significantly lower minor-merger/assembly activity after the last major merger. By running a set of isolated Milky Way-type simulations with different resolution and different density thresholds for star formation we conclude that, on top of the effects of mergers, there exists a ``floor'' in the dispersion that is related to the underlying treatment of the heating and cooling of the interstellar medium, and the low density threshold which such codes use for star formation. A persistent issue in simulations of disc galaxies is the formation of large spheroidal components, and disc galaxies with larger bulge to disc ratios than is observed. This problem is alleviated by supernova feedback. We found that by increasing the feedback in the simulations, we decrease the amount of stars that are accreted onto the main galaxy. The star formation is quenched more efficiently in low mass satellites when stronger feedback is implemented as well as in the main halo. These effects result in a disc galaxy, which has formed less stars overall, but more importantly, contains less accreted stars. As the strong stellar feedback quenches the star formation in the small building blocks, the metallicity of the accreted stars is lower than in the case where less feedback was used. In the context of hierarchical formation, mass assembly is expected to be scale free. Yet the properties of galaxies depend strongly on their mass. We examine how baryonic physics has different effects at different mass scales by analysing three cosmological simulations using the same initial conditions that are scaled to three different masses. Despite their identical dark matter merger history, we show that the simulated galaxies have significantly different stellar accretion histories. As we go down in mass, the lowest mass progenitors are unable to form stars, resulting in a low mass galaxy with less accreted stars. The overall chemical properties are also distinct at the different mass scales, as one might expect from the mass-metallicity relation of observed galaxies. We examine gradients of chemical abundances with radius and with height above the disc, and look for properties that are retained at different mass scales and properties which change, often dramatically. We analyse the kinematic and chemical properties of their accreted and in-situ populations. Again, trends can be found that persist at all mass scales, providing signatures of hierarchical structure formation. We find that accreted populations in the high mass simulation did not resemble any of the populations in the lower mass galaxies, showing that the chemical properties of proto-galaxies, which merge at high redshift to form massive galaxies, differ from the properties of low mass galaxies that survive at z=0. We probe further the signatures of hierarchical structure formation at smaller scales, in dwarf galaxies. We analysed the morphologies, kinematics and chemical properties of two simulated dwarf galaxies with different merger histories. We again analyse the accreted and in-situ populations. Observations of dwarf galaxies have found that they are comprised of multiple components. Our simulated dwarfs indicate that such populations may indeed be a manifestation of the hierarchical formation process in action in these lower mass galaxies. In one simulated dwarf, the in-situ stellar component forms a thin disc and a thick disc. We show that the thick disc in this simulation forms from in-situ stars that are born kinematically hot in the disc from early gas-rich mergers. The thin disc is formed quiescently from the later infall of gas. The accreted stars in the simulation were found to form an extended stellar halo. Chemical signatures of the three populations are also explored. The second dwarf we analysed has different galactic components, a result found to be due to the different merger history of this galaxy. The last major merger in this simulation occurs early on in the formation process between two proto-galaxies of similar mass. The result is a dwarf galaxy comprised of a disc formed of in-situ stars and a flattened rotating stellar halo formed of accreted stars. The angular momentum of the accreted and old in-insitu stars is obtained from the last major merger. We discuss the resemblance of this flattened rotating stellar halo to fast rotating flattened elliptical galaxies, and propose that such structures may explain some of the observed extra-galactic thick discs. These studies show that galactic properties emerge through the complex inter-play between hierarchical structure formation, star formation, and feedback from supernovae. Different modelling of these processes will alter the simulated galaxy's properties, and detailed comparisons with observations can then be made to determine the dominant processes responsible for different galactic properties. We remain optimistic that further improvement in modelling will allow deeper insights into the processes of galaxy formation and evolution.
Download or read book The Formation and Evolution of Disk Galaxies written by Jonathan C. Bird and published by . This book was released on 2012 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Current and next generation surveys of the Milky Way promise to revolutionize our observational perspective of the Galaxy. My dissertation uses a suite of N-body and SPH simulations of disk galaxies to make testable predictions of the assembly history of the Milky Way and identify observational probes that take advantage of the forthcoming data. APOGEE, an infrared survey of the Galaxy and a component of the SDSS-III, will measure the distance, radial velocity, and multi-element chemistry of 10^5 stars located throughout the Galaxy, making it particularly well suited for comparison with simulations. We first use a fuel-consumption argument to constrain the integrated luminosity of the TP-AGB phase; the energy release in this phase is a major uncertainty in stellar population synthesis models. Our initial numerical investigation explores how the minor mergers expected in Lambda-CDM and inherent properties of stellar disks affect the dynamics of stellar radial migration- an essential ingredient in understanding the evolution of the Milky Way and disk galaxies in general. We discover that the resonances and mechanisms responsible for migration are different in isolated and satellite-bombarded galaxies, resulting in distinct migration patterns and potential observational signatures of accretion events. Continuing our development of tools to describe the chemo-dynamics of the disk, we construct statistics to measure overdensities and characterize outliers in the distance, radial velocity projection of phase space. I discuss mock APOGEE observations of our numerical simulations and demonstrate that our statistics can begin to discriminate between significant galaxy formation mechanisms given the data available in the near term. Finally, we use a state of the art cosmological simulation to describe the evolution of mono-age stellar populations and their eventual assembly into a galaxy resembling the Milky Way. Galaxy formation theory faces the exciting challenge of an unprecedented level of statistical scrutiny: imminent and ongoing surveys such as SEGUE, RAVE, APOGEE, LAMOST, and HERMES offer an extraordinary opportunity to unravel the formation history of the Milky Way.
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:
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)"
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.
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.
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.
Download or read book Fundamentals of Galaxy Dynamics Formation and Evolution written by Ignacio Ferreras and published by UCL Press. This book was released on 2019-04-02 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: Galaxies, along with their underlying dark matter halos, constitute the building blocks of structure in the Universe. Of all fundamental forces, gravity is the dominant one that drives the evolution of structures from small density seeds at early times to the galaxies we see today. The interactions among myriads of stars, or dark matter particles, in a gravitating structure produce a system with fascinating connotations to thermodynamics, with some analogies and some fundamental differences. Ignacio Ferreras presents a concise introduction to extragalactic astrophysics, with emphasis on stellar dynamics, and the growth of density fluctuations in an expanding Universe. Additional chapters are devoted to smaller systems (stellar clusters) and larger ones (galaxy clusters). Fundamentals of Galaxy Dynamics, Formation and Evolution is written for advanced undergraduates and beginning postgraduate students, providing a useful tool to get up to speed in a starting research career. Some of the derivations for the most important results are presented in detail to enable students appreciate the beauty of maths as a tool to understand the workings of galaxies. Each chapter includes a set of problems to help the student advance with the material.
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.
Download or read book Galaxy Evolution Across the Hubble Time IAU S235 written by International Astronomical Union. Symposium and published by Cambridge University Press. This book was released on 2007-05-17 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: This last decade has witnessed a revolution in our observations of galaxies; in particular deep imaging with HST and spectroscopy with 10m-class ground-based telescopes have uncovered many objects that are difficult to place along the Hubble sequence. High resolution spectroscopy of extremely faint objects has enabled the study of the kinematic evolution and, hence, the mass assembly of galaxies to unprecedented look-back times for direct comparison with cosmological structure formation scenarios. Thus, it is now possible to study all three aspects of galaxy evolution - their morphological-dynamical, chemical and spectral evolution out to redshift larger than six, exploring more than 95% of the age of the universe. These Proceedings of the IAU Symposium 235 report the considerable progress made in recent years on galaxy formation and evolution, and look forward to the expected breakthroughs in the domain of remote galaxies, with ALMA, the ELT and the next generation space telescopes.
Download or read book Galactic Dynamics written by James Binney and published by Princeton University Press. This book was released on 2011-10-30 with total page 902 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since it was first published in 1987, Galactic Dynamics has become the most widely used advanced textbook on the structure and dynamics of galaxies and one of the most cited references in astrophysics. Now, in this extensively revised and updated edition, James Binney and Scott Tremaine describe the dramatic recent advances in this subject, making Galactic Dynamics the most authoritative introduction to galactic astrophysics available to advanced undergraduate students, graduate students, and researchers. Every part of the book has been thoroughly overhauled, and many sections have been completely rewritten. Many new topics are covered, including N-body simulation methods, black holes in stellar systems, linear stability and response theory, and galaxy formation in the cosmological context. Binney and Tremaine, two of the world's leading astrophysicists, use the tools of theoretical physics to describe how galaxies and other stellar systems work, succinctly and lucidly explaining theoretical principles and their applications to observational phenomena. They provide readers with an understanding of stellar dynamics at the level needed to reach the frontiers of the subject. This new edition of the classic text is the definitive introduction to the field. ? A complete revision and update of one of the most cited references in astrophysics Provides a comprehensive description of the dynamical structure and evolution of galaxies and other stellar systems Serves as both a graduate textbook and a resource for researchers Includes 20 color illustrations, 205 figures, and more than 200 problems Covers the gravitational N-body problem, hierarchical galaxy formation, galaxy mergers, dark matter, spiral structure, numerical simulations, orbits and chaos, equilibrium and stability of stellar systems, evolution of binary stars and star clusters, and much more Companion volume to Galactic Astronomy, the definitive book on the phenomenology of galaxies and star clusters
Download or read book Chemodynamical Adaptive Mesh Refinement Simulations of Disk Galaxies written by Christopher Gareth Few and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis I bring together three projects that comprise my postgraduate studies; using numerical simulations of galaxy formation in a cosmological context. The first of these projects involves the simulation of a suite of galaxies in loose group and field environments. This suite of galaxies is used to compare properties such as the metallicity gradients and morphology to determine if systematic differences are apparent as a function of subtle environmental differences. Almost no distinction is seen between galaxies in the field and the loose group environments: individual assembly histories of the galaxies dominate over ambient environmental effects with the exception of the vertical velocity dispersion of the stellar disc where loose group galaxies tend to exhibit a greater number of instances of impulsive heating of the disc. In the second project I present further analysis of this suite of galaxies and a comparison with other galaxies simulated using contrasting methodologies, in ad- dition to several semi-numerical galaxy formation models. The focus of this work is the evolution of metallicity gradients and star formation profiles, finding that galaxies form in an inside-out fashion. This leads to steeper metallicity gradients in young stellar populations at high redshift compared with the present day. By considering present day stellar populations with different ages in these galaxies the converse is found, older populations have flatter gradients. This suggests that while the metallicity gradient starts out steep, it flattens over time due to stellar migra- tion/mixing. This flattening due to stellar migration happens at a faster rate than the flattening of the gas phase metallicity gradient. Finally, I present an update to the N-body and adaptive mesh refinement hydrodynamical code ramses that introduces a more sophisticated feedback treatment, this code is dubbed ramses-ch. Under the new scheme, energetic and elemental feedback is contributed by stars throughout their lifetime rather than (as previously) in a single burst. This relaxation of the 'instantaneous feedback approximation' in ramses-ch opens up the opportunity for studying chemical evolution using adaptive mesh refinement hydrodynamics where previous studies were limited to smoothed particle hydrodynamical codes or semi-numerical models. The new code is applied to the simulation of a typical disc galaxy using different stellar initial mass functions and supernovae type-Ia progenitor models. The influence of these model inputs on the ratio of elemental abundances and supernovae rates in the simulated galaxies are compared as a means of constraining chemical evolution models. The conclu- sions drawn from this work are discussed in the broader context of galaxy formation simulations.
Download or read book The Analysis of Stellar Populations in the Milky Way and Beyond written by Andreia Jessica Arabani Carrillo and published by . This book was released on 2021 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt: No other astronomical object can unlock the mysteries of the Universe more than stars. Studying the crowded, unresolved stellar populations of nearby galaxies aids in understanding what brings about their observed properties, morphology, activity, and assembly history. Studying the Milky Way’s resolved stellar populations, specifically their detailed chemical abundances and kinematics, provides us with an unparalleled, zoomed-in view of galaxy formation. Additionally, understanding Milky Way stellar populations can supplement our knowledge in other fields in Astronomy, such as exoplanet populations, as the gas that forms a star also forms the planets around it. This is the focus of my dissertation: analyzing stellar populations--both resolved in the Milky Way (observed and simulated) and unresolved in a nearby galaxy--to holistically understand galaxy formation, the Milky Way assembly, and the Galactic context of exoplanet demographics. This Thesis is structured going from the largest and farthest of scales e.g. external galaxy, to the smallest of scales e.g. planet-hosting stars. With unresolved, ensemble stellar populations, I investigate the assembly of the different components: the bulge, bar, and disc, of the nearby galaxy NGC 2903, using the VIRUS-P Exploration of Nearby Galaxies (VENGA) Integral Field Spectroscopy (IFS) survey. This work benefited from high signal-to-noise, spatially-resolved spectroscopic data that enabled me to construct a more comprehensive picture of NGC 2903’s formation history by understanding the growth of its different components. Moving closer to the Milky Way and unveiling the history of its halo, I present a detailed chemical study for stars from one of Milky Way’s most significant mergers dubbed Gaia-Enceladus-Sausage (GES), aided by high-resolution optical spectra from McDonald Observatory and Magellan Telescope. I contrast these stars’ abundance trends to those found in the Milky Way and its surviving satellites to understand how its chemical signatures compare to other stellar populations and what this tells us about its star formation history. As emphasized in this Thesis, it is important to investigate galaxy assembly through the lenses of different galaxy components and in an interdisciplinary way. Therefore, I also aim to understand the formation of the Milky Way disc. I do this by turning to a zoom-in cosmological simulation of a Milky Way mass galaxy from the FIRE-2 suite and where I determine how the ages, metallicities, and detailed chemical abundances of stars relate to each other and to their current and birth locations. Specifically, I investigate if the stars in the simulations exhibit a tight age-abundance trend, similar to what is found in observations. Further, I explore how the dispersion found around this trend, at different metallicities and locations in the galaxy, relates to the star formation history of the simulated Milky Way. Lastly, taking advantage of the power of Milky Way large surveys, I kinematically and chemically characterized targets from the Transiting Exoplanet Survey Satellite (TESS) to understand the Galactic context of planet-hosting stars. This is especially important as we find more exoplanets in different parts of the Galaxy, enabling us to understand if and how planet formation and demographics are different for different Milky Way stellar populations. The accomplishments of this Thesis have contributed to a broad range of fields in Astronomy, but all tied together by the analysis of stellar populations in the Milky Way and beyond
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: A comprehensive examination of nearly fourteen billion years of galaxy formation and evolution, from primordial gas to present-day galaxies.
Download or read book Galactic Bulges written by Eija Laurikainen and published by Springer. This book was released on 2015-09-29 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book consists of invited reviews on Galactic Bulges written by experts in the field. A central point of the book is that, while in the standard picture of galaxy formation a significant amount of the baryonic mass is expected to reside in classical bulges, the question what is the fraction of galaxies with no classical bulges in the local Universe has remained open. The most spectacular example of a galaxy with no significant classical bulge is the Milky Way. The reviews of this book attempt to clarify the role of the various types of bulges during the mass build-up of galaxies, based on morphology, kinematics and stellar populations and connecting their properties at low and high redshifts. The observed properties are compared with the predictions of the theoretical models, accounting for the many physical processes leading to the central mass concentration and their destruction in galaxies. This book serves as an entry point for PhD students and non-specialists and as a reference work for researchers in the field.
Download or read book Cosmological Simulations of Galaxy Clusters written by Monique Henson and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
