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.

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.

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.

"In Einstein’s Telescope, Evalyn Gates, an expert on all that’s dark in the universe, brings dark matter, dark energy, and even black holes to light." —Neil deGrasse Tyson, astrophysicist, American Museum of Natural History, and New York Times best-selling author of Astrophysics for People in a Hurry In 1936, Albert Einstein predicted that gravitational distortions would allow space itself to act as a telescope far more powerful than humans could ever build. Now, cosmologists at the forefront of their field are using this radical technique ("Einstein’s Telescope") to detect the invisible. In fresh, engaging prose, astrophysicist Evalyn Gates explains how this tool is enabling scientists to uncover planets as big as the Earth, discover black holes as they whirl through space, and trace the evolution of cosmic architecture over billions of years. Powerful and accessible, Einstein’s Telescope takes us to the brink of a revolution in our understanding of the deepest mysteries of the Universe.

We study the angular momentum, shape and density structures of dark matter haloes using very large dark matter simulations, and use smaller, higher-resolution simulations to investigate how the distributions of these properties are changed by the physical processes associated with baryons and galaxy formation. We begin with a brief review of the necessary background theory, including the growth of cosmic structures, the origin of their angular momenta, and the techniques used to simulate galaxies, haloes and the large scale structure. In Chapter 2, we use the Millennium Simulation (MS) to investigate the distributions of the spin and shape parameters of millions of dark matter haloes. We compare results for haloes identified using three different algorithms, including one based on the branches of the halo merger trees. In addition to characterising the relationships between halo spin, shape and mass, we also study their impact on halo clustering and bias. We go on in Chapter 3 to investigate the internal angular momentum structure of dark matter haloes. We look at the radial profiles of the dark matter angular momentum in terms of both magnitude and direction, again using large-volume dark matter simulations including the MS. We then directly compare dark matter haloes simulated both with and without baryonic physics, studying how this changes the dark matter angular momentum. After relating the spin orientation of galaxies to their haloes, we consider the shape of the projected, stacked mass distribution of haloes oriented according to their central galaxy, mimicking attempts to measure halo ellipticity by weak gravitational lensing. We consider the density structure of dark matter haloes in Chapter 4. For the dark matter simulations, we focus our interest on the source of the scatter in the distribution of concentration parameters, correlating it with both the halo spin and formation time. We compare different algorithms for predicting the concentration distribution using different aspects of the merger histories. We again go on to directly compare high-resolution haloes in simulations run with and without baryons and galaxy formation, looking at how these additional physical processes transform the density profiles. Finally, we compare the circular velocity curves of the haloes simulated with galaxies to the rotation curves of observed galaxies, using the Universal Rotation Curve model.