Download or read book Shapes Of Galaxies And Their Dark Halos The Proceedings Of The Yale Cosmology Workshop written by Priyamvada Natarajan and published by World Scientific. This book was released on 2002-03-28 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the proceedings of a very topical workshop aimed at understanding the shapes of the baryonic and dark matter components of galaxies. Several groups presented their recent results from observations and numerical N-body simulations.
Download or read book The Shapes of Galaxies and Their Dark Halos written by Priyamvada Natarajan and published by World Scientific. This book was released on 2002 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the proceedings of a very topical workshop aimed at understanding the shapes of the baryonic and dark matter components of galaxies. Several groups presented their recent results from observations and numerical N-body simulations.
Download or read book Exploring the Dynamics and Dark Halos of Elliptical Galaxies at Large Radii written by Amy Dove Forestell and published by . This book was released on 2009 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dark matter is now accepted as an integral part of our universe, and galaxy dynamics have long provided the most convincing observational evidence for dark matter. Spiral galaxies have traditionally been used for these studies because of their more simple kinematics, however elliptical galaxies need to be understood as well. In this dissertation I present deep long-slit spectroscopy from the University of Texas' Hobby-Eberly Telescope for a sample of elliptical galaxies. For a subsample of galaxies I fit axisymmetric orbit-superposition models with a range of dark halo density profiles. I find that all three galaxies modeled require a significant dark halo to explain their motions. However, the shape of the dark halo is not the expected NFW profile, but rather a profile with a flat central slope. I also discuss the galaxy masses, anisotropies, and stellar mass-to-light ratios.
Download or read book Satellite Galaxies as Probes of Dark Matter Halos written by Ingolfur Agustsson and published by . This book was released on 2012 with total page 578 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Dark matter cannot be observed directly at any wavelength of light, but it can be detected through its gravitational effects on luminous material. At present, all large galaxies are thought to be surrounded by "halos" of dark matter; however, the physical parameters of these halos are not well-constrained by observations. The favored theory of galaxy formation, Cold Dark Matter (CDM), ties together many diverse observations into a self-consistent picture of structure formation in the Universe. CDM has been very successful on large length scales (>1 Mpc), but its viability remains in doubt on smaller scales. My dissertation focuses on comparisons of CDM theory to observations of the Universe on these small scales. Here I use satellite galaxies to study the dark matter halos that surround large "host" galaxies. The hosts are the brightest galaxies in their regions of space and are relatively isolated compared to typical galaxies. A single observed host has too few satellites to provide strong constraints on the halo that surrounds it. However, large numbers of host galaxies and their satellites can be collected from modern redshift surveys. This makes it possible to study the hosts' halos using ensemble averages over many host-satellite systems. Using these ensemble averages, I determine the ways in which the locations and motions of the satellites are connected to properties of their hosts (e.g., morphology, color, stellar mass, star formation rate). In order to mimic the way in which the Universe is actually observed, I create an artificial imaging and redshift survey from a CDM computer simulation. This makes it possible to compare results obtained from observed host-satellite systems with host-satellite systems in CDM simulations. The main results of my dissertation are: 1) the locations of satellite galaxies reflect the shapes of the dark matter halos surrounding their hosts, 2) elliptical and spiral host galaxies are embedded within their halos in fundamentally different ways, and 3) the use of the motions of satellite galaxies to constrain the gravitational potentials of their hosts' halos is much less straightforward than has been assumed in previous work.
Download or read book Dark Matter Halos and Stellar Kinematics of Elliptical Galaxies written by Jeremy David Murphy and published by . This book was released on 2012 with total page 606 pages. Available in PDF, EPUB and Kindle. Book excerpt: The hierarchical assembly of mass, wherein smaller clumps of dark matter, stars, gas, and dust buildup over time to form the galaxies we see today in the local Universe through accretion events with other clumps, is a central tenet of galaxy formation theory. Supported by theoretically motivated simulations, and observations of the distribution of galaxies over a large range of redshift, the theory of hierarchical growth is now well established. However, on the scales of individual galaxies, hierarchical growth struggles to explain a number of observations involving the amount and distribution of dark matter in galaxies, and the timescale of both the formation of stars, and the assembly of those stars into galaxies. In this dissertation I attempt to address some of the central issues of galaxy formation. My work focuses on massive elliptical galaxies and employs the orbit-based, axisymmetric dynamical modeling technique of Schwarzschild to constrain the total mass of a galaxy to large radii. From this starting point a determination of the extent and shape of the dark matter halo profile is possible and can then be compared to the results of simulations of the formation of galaxies. These dynamical models include information on the stellar orbital structure of the galaxy, and can be used as a further point of comparison with N-body simulations and observations from other groups. Dynamical modeling results for both M49 and M87, the first and second rank galaxies in the Virgo Cluster, are presented and compared in Chapters 4 and 2 respectively. Although both galaxies are similar in mass, a closer analysis shows they exhibit very different dark matter halo profiles and stellar orbital structure, and likely followed very different formation pathways. My primary dataset comes from observations carried out on the Mitchell Spectrograph (formally VIRUS-P) at McDonald Observatory.\footnote{The instrument's name was changed over the last year. As some of this work was originally written when the instrument was named VIRUS-P, I have elected to use that name in those sections of this dissertation (Chapters 2 and 5). In Chapters 3, 4, and 6, I use the current name.} The Mitchell Spectrograph is a fiber-fed integral field spectrograph, and allows one to collect spectra at many positions on a galaxy simultaneously. With spectroscopy one is able to not only constrain the kinematics of the stars, but also their integrated chemical abundances. In the introduction I describe recent work I have carried out with my collaborators using the Mitchell Spectrograph to add further constraints to our picture of galaxy formation. In that work we find that the cores of massive elliptical galaxies have been in place for many billions of years, and had their star formation truncated at early times. The stars comprising their outer halos, however, come from less massive systems. Yet unlike the stars of present day, low-mass galaxies, whose star formation is typically extended, these accreted systems had their star formation shut off at high redshift. Although our current sample is relatively small, these observations place a rigid constraint on the timescale of galaxy assembly and indicate the important role of minor mergers in the buildup of the diffuse outer halos of these systems. All of these advances in our understanding of the Universe are driven, in large part, by advances in the instrumentation used to collect the data. The Mitchell Spectrograph is a wonderful example of such an advance, as the instrument has allowed for observations of the outer halo of M87 to unprecedented radial distances (Chapter 3). A significant component of my dissertation research has been focused on characterizing the fiber optics of both the Mitchell Spectrograph and the fiber optics for the VIRUS spectrograph. I cover the results of the work on the Mitchell Spectrograph optical fibers in Chapter 5. The affects of stress and motion on a fiber bundle, critical to the VIRUS spectrograph, are explored in Chapter 6.
Download or read book Spiral Structure in Galaxies written by Marc S Seigar and published by Morgan & Claypool Publishers. This book was released on 2017-06-29 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: How does it happen that billions of stars can cooperate to produce the beautiful spirals that characterize so many galaxies, including ours? This book reviews the history behind the discovery of spiral galaxies and the problems faced when trying to explain the existence of spiral structure within them. In the book, subjects such as galaxy morphology and structure are addressed as well as several models for spiral structure. The evidence in favor or against these models is discussed. The book ends by discussing how spiral structure can be used as a proxy for other properties of spiral galaxies, such as their dark matter content and their central supermassive black hole masses, and why this is important.
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.
Download or read book Gravitational Dynamics written by Ofer Lahav and published by Cambridge University Press. This book was released on 1996-07-13 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gravity plays a central role in the dynamics of all astrophysical systems - from stars to the Universe as a whole. This timely volume examines all aspects of gravitational dynamics - from stellar systems and galaxy disks, to the dynamics of the Local Group, large scale structures and motions, galaxy formation and general relativity. Each chapter is written by a world expert renowned for original contributions to the field. The authors are: James Binney, Roger Blandford, David Burstein, Tim de Zeeuw, George Efstathiou, Steve Gull, Nick Kaiser, J. Katz, Donald Lynden-Bell, Ruth Lynden-Bell, Douglas Lin, Jeremiah Ostriker, T. Padmanabhan, J. Papaloizou, Jim Peebles, Jim Pringle, Martin Rees, Maarteen Schmidt, Scott Tremaine and Simon White. This volume provides a broad, pedagogical introduction to gravitational dynamics for graduate students, and an up-to-date review for researchers in cosmology, astrophysics, mathematical physics and applied mathematics.
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 The Evolution of Galaxies and Their Environment written by David J. Hollenbach and published by . This book was released on 1993 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modern Cosmology and the Dark Matter Problem written by D. W. Sciama and published by Cambridge University Press. This book was released on 1993 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book shows how modern cosmology has led to the idea of dark matter in the universe, and presents a new theory to explain it.
Download or read book Astronomy Notes written by Nick Strobel and published by . This book was released on 2010 with total page 556 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Realm of the Nebulae written by Edwin Powell Hubble and published by Yale University Press. This book was released on 1982-01-01 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: No modern astronomer made a more profound contribution to our understanding of the cosmos than did Edwin Hubble, who first conclusively demonstrated that the universe is expanding. Basing his theory on the observation of the change in distanct galaxies, called red shift, Hubble showed that this is a Doppler effect, or alteration in the wavelength of light, resulting from the rapid motion of celestial objects away from Earth. In 1935, Hubble described his principal observations and conclusions in the Silliman lectures at Yale University. These lectures were published the following year as "The Realm of the Nebulae," which quickly became a classic work.
Download or read book Toward a New Millennium in Galaxy Morphology written by David L. Block and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 798 pages. Available in PDF, EPUB and Kindle. Book excerpt: South Africa - a land of paradigm shifts. A land where we are willing to leave behind the old, to bravely accept the new. What do we need to exit the dark ages in the morphology of galaxies? How prevalent is the cherishing of old concepts? Traditional morphology has been `mask-oriented', focusing on masks of dust and gas which may constitute only 5 percent of the dynamical mass of a galaxy. Some of the world's foremost astronomers flew to South Africa to address morphologically related issues at an International Conference, the proceedings of which are contained in this volume. Examine predicted extinction curves for primordial dust at high redshift. Stars evolve; why not dust? Read about the breakdown of the Hubble sequence at a redshift of one. Explore the morphology of rings; the mysteries of metal-rich globular clusters; vigorous star-formation in the Large Magellanic Cloud; the world of secular evolution, where galaxies change their shapes within one Hubble time. And much more. Examine a new kinematical classification scheme of the unmasked, dust-penetrated near-infrared images of spiral galaxies. This volume contains over 80 refereed contributions (including 18 in-depth keynote review articles), 40 pages of questions and answers, a panel discussion transcribed from tape and 24 colour plates. The volume is unique in that contributions from both high and low redshift experts are represented at a level readily accessible to postdoctoral students entering the exciting world of morphology - whether it be of the local, or more distant, Universe.
Download or read book Galaxies written by Francoise Combes and published by John Wiley & Sons. This book was released on 2021-03-05 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: Galaxies are vast ensembles of stars, gas and dust, embedded in dark matter halos. They are the basic building blocks of the Universe, gathered in groups, clusters and super-clusters. They exist in many forms, either as spheroids or disks. Classifications, such as the Hubble sequence (based on mass concentration and gas fraction) and the colormagnitude diagram (which separates a blue cloud from a red sequence) help to understand their formation and evolution. Galaxies spend a large part of their lives in the blue cloud, forming stars as spiral or dwarf galaxies. Then, via a mechanism that is still unclear, they stop forming stars and quietly end in the red sequence, as spheroids. This transformation may be due to galaxy interactions, or because of the feedback of active nuclei, through the energy released by their central super-massive black holes. These mechanisms could explain the history of cosmic star formation, the rate of which was far greater in the first half of the UniverseÂs life. Galaxies delves into all of these surrounding subjects in six chapters written by dedicated, specialist astronomers and researchers in the field, from their numerical simulations to their evolutions.
Download or read book The Dark Matter Halo Shape of Edge on Disk Galaxies written by Jess Clare O'Brien and published by . This book was released on 2007 with total page 215 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Gravitational Lensing written by Scott Dodelson and published by Cambridge University Press. This book was released on 2017-06-08 with total page 245 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gravitational lensing is a consequence of general relativity, where the gravitational force due to a massive object bends the paths of light originating from distant objects lying behind it. Using very little general relativity and no higher level mathematics, this text presents the basics of gravitational lensing, focusing on the equations needed to understand the phenomena. It then applies them to a diverse set of topics, including multiply imaged objects, time delays, extrasolar planets, microlensing, cluster masses, galaxy shape measurements, cosmic shear, and lensing of the cosmic microwave background. This approach allows undergraduate students and others to get quickly up to speed on the basics and the important issues. The text will be especially relevant as large surveys such as LSST and Euclid begin to dominate the astronomical landscape. Designed for a one semester course, it is accessible to anyone with two years of undergraduate physics background.
