Author: Andi KronawitterPublisher:
ISBN:
Category :
Languages : en
Pages : 139
Book Description
Orbital Structure and Dark Matter Halos of Elliptical Galaxies
Author: Andi KronawitterDark Matter Halos and Stellar Kinematics of Elliptical Galaxies
Author: Jeremy David MurphyPublisher:
ISBN:
Category :
Languages : en
Pages : 606
Book Description
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.
Mergers of Elliptical Galaxies and Dark Matter Halos
Author: Michael Robert Boylan-KolchinPublisher:
ISBN:
Category : Galaxy mergers
Languages : en
Pages : 424
Book Description
The orbital structure of galaxies and dark matter halos in N-body simulations
Author: The Orbital Structure of Galaxies and Dark Matter Halos in N-body Simulatons
Author: Roland JesseitStructure and Dynamics of Elliptical Galaxies
Author: Tim de ZeeuwPublisher: Springer Science & Business Media
ISBN: 940093971X
Category : Science
Languages : en
Pages : 589
Book Description
IAU Symposium 127 was held in Princeton on May 28-31, 1986, at the Institute for Advanced Study. There were 150 participants from 19 countries. This was the first IAU Symposium devoted exclusively to elliptical galaxies. The last decade has been a period of exceptionally rapid progress regard ing our understanding of elliptical galaxies, driven on the observational side by a wealth of new photometric and spectroscopic data, and on the theoretical side by the recognition that ellipticals are slowly rotating triaxial systems, instead of rotationally flattened bodies. The 30 invited speakers reviewed all aspects of this progress, its consequences, and the major outstanding problems. Nearly 80 poster contributions were displayed for the duration of the meeting. These contained many of the most recent developments. The first part of these Proceedings contains the written versions of the invited reviews and the summary, in the order of their presentation. The accompanying discussions are based on the written versions of questions and answers as handed in by the participants. The second part of this book is devoted to the poster contribu tions. They have been grouped in a thematic order, proceeding from morphology to theory. Indices of objects, subjects, and names are provided. Unfortunately, none of the invited participants from the USSR were able to attend the Symposium. The Proceedings include the written versions of the planned contributions by Popov and Polyachenko.
Two Non-traditional Applications of Orbit-based Modeling
Author: John Raymond JardelPublisher:
ISBN:
Category :
Languages : en
Pages : 102
Book Description
Orbit-based modeling is a powerful way to construct dynamical models of galaxies. It has been used to measure the masses of supermassive black holes (SMBHs), constrain dark matter halos, and to recover information about the orbit structure of galaxies. This type of modeling usually goes hand in hand with the study of elliptical galaxies, however its applicability extends much further than this. In this thesis, I apply the well-studied technique of orbit-based modeling to two different types of galaxies -- NGC 4594 (Sa) and Fornax (dSph). In NGC 4594, I use orbit-based models to update the mass of the central SMBH, place new constraints on its dark matter halo, and analyze the internal moments of its distribution function. For Fornax, the focus is to determine the shape of the dark matter density profile as well as to learn what we can from the internal moments.
The Shapes of Galaxies and Their Dark Halos
Author: Priyamvada NatarajanPublisher: World Scientific
ISBN: 9789810248482
Category : Science
Languages : en
Pages : 286
Book Description
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.
Phase-space Structure of Cold Dark Matter Halos
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 12
Book Description
A galactic halo of cold dark matter particles has a sheet-like structure in phase-space. The energy and momentum spectra of such particles on earth has a set of peaks whose central values and intensities form a record of the formation of the Galaxy. Scattering of the dark matter particles by stars and globular clusters broadens the peaks but does not erase them entirely. The giant shells around some elliptical galaxies may be a manifestation of this structure.
The Orbital Structure of Galaxies and Dark Matter Halos in N-Body Simulations
Author: Publisher:
ISBN:
Category :
Languages : de
Pages :
Book Description
In dieser Arbeit werden zwei Entstehungmechanismen fuer Galaxien in N-Koerper Rechnungen untersucht. Unter der Annahme, dass die Teilchen in einem sphaerischen dunkle Materie Halo sich auf Kreisbahnen bewegen, macht die adiabatische Naeherung genaue Voraussagen ueber das Mass der Kontraktion des Halos waehrend der langsamen Scheibenbildung. Wir finden in N-Koerper Rechnungen, dass die adiabatische Naeherung fuer alle realistischen Massenverhaeltnisse zwischen Scheibe und Halo gilt, und Abweichungen von Kreisbahnen keine groessere Rolle spielen. Im zweiten Teil beschaeftigen wir uns mit der Entstehung von elliptischen Galaxien durch Verschmelzung von Scheibengalaxien. In einem Sample von 150 solcher Kollisionen klassifizieren wir die komplexe orbitale Struktur des Endergebnisses jeder Kollisionsrechnung. Die Klassifikation wird mit der Triaxialitaet und der Laenge der Haupttraegheitsachsen verknuepft, mit denen die Gestalt einer elliptischen Galaxie parametrisiert wird. Wir leiten daraus eine globale Besetzungswahrscheinlichkeit fuer selbstkonsistente triaxiale Galaxien ab, die mit theoretischen Erwartungen uebereinstimmt. Weiterhin finden wir, dass die Isophotenstruktur in den N-Koerperrechnungen nicht von einer Orbitgattung, sondern von einer ueberlagerung verschiedener Gattungen herruehrt. Die Dichotomie zwischen elliptischen Galaxien mit boxfoermigen und scheibenfoermigen Isophoten kann deswegen nicht vollstaendig auf eine Dominanz von box- bzw. scheibenfoermigen Orbits zurueckgefuehrt werden. Bisherige Simulationen koennen nicht beobachtete Korrelationen zwischen dem h_3 Parameter und der mittleren Geschwindigkeit reproduzieren. Als Ursache dieser Diskrepanz werden die box Orbits identifiziert, die in dissipationslosen Simulationen ueberproduziert werden. Z-tube Orbits erfuellen diese Korrelation jedoch sehr gut. Ebenso zeigt diese Komponente dieselbe Korrelation zwischen dem h_3 Parameter und v/sigma_0, wie beobachtete elliptische Galaxien. Wir schliessen darau.