Cosmology, Relativity, and Gravity Commons^™

Development Of Realistic Simulations Of The Interactions Between Stars And The Interstellar Medium In Disk Galaxies, Thomas M. Zeltwanger

Electronic Theses and Dissertations

fWe have developed GALAXY, a two dimensional, self-consistent N-body plus hydro-dynamic computer program to model and study the behavior of disk galaxies like our Milky Way. Our goal is to better understand how such galaxies maintain their spiral structure for billions of years.

The program utilizes two independent gravitating N-body components. One simulates the collision-less star particles in the galaxy, and the other simulates colliding clouds. A gravitating hydrodynamic code simulates the interstellar medium. Additionally, a static spherical halo and a central black hole interact gravitationally with the other components of the model galaxy. All components interact with each other …

Redshift-Distance Survey Of Early-Type Galaxies: Dipole Of The Velocity Field, L. N. Da Costa, M. Bernardi, M. V. Alonso, G. Wegner

Dartmouth Scholarship

We use the recently completed redshift-distance survey of nearby early-type galaxies (ENEAR) to measure the dipole component of the peculiar velocity field to a depth of cz ~ 6000 km s-1. The sample consists of 1145 galaxies brighter than mB = 14.5 and with cz ≤ 7000 km s-1, uniformly distributed over the whole sky, and 129 fainter cluster galaxies within the same volume. Most of the Dn-σ distances were obtained from new spectroscopic and photometric observations conducted by this project, ensuring the homogeneity of the data over the whole sky. These 1274 galaxies are objectively assigned …

Enear Redshift-Distance Survey: Cosmological Constraints, Stefano Borgani, Mariangela Bernardi, Luiz N. Da Costa, Gary Wegner

Dartmouth Scholarship

We present an analysis of the ENEAR sample of peculiar velocities of field and cluster elliptical galaxies, obtained with Dn-σ distances. We use the velocity correlation function ψ1(r) to analyze the statistics of the field object's velocities, while the analysis of the cluster data is based on the estimate of their rms peculiar velocity Vrms. The results are compared with predictions from cosmological models using linear theory. The statistics of the model velocity field is parameterized by the amplitude η8 = σ8Ω and by the shape parameter Γ of the cold dark matter-like power spectrum. …

A Spectroscopic Redshift For The Cl 0024+16 Multiple Arc System: Implications For The Central Mass Distribution, Tom Broadhurst, Xiaosheng Huang, Brenda Frye, Richard Ellis

Physics and Astronomy

We present a spectroscopic redshift of z = 1.675 for the well-known multiply lensed system of arcs seen in the z = 0.39 cluster Cl 0024+16. In contrast to earlier work, we find that the lensed images are accurately reproduced by a projected mass distribution which traces the locations of the brightest cluster elliptical galaxies, suggesting that the most significant minima of the cluster potential are not dynamically erased. The averaged mass profile is shallow and consistent with predictions of recent numerical simulations. The source redshift enables us to determine an enclosed cluster mass of M(<100 kpc h-1) = …

Book Review: The Birth Of Time: How Astronomers Measured The Age Of The Universe, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of The Birth of Time : How Astronomers Measured the Age of the Universe by John Gribbin. Yale, 2000 237p, 0-300-08346-7 $22.50.

Sensitivity Curves For Spaceborne Gravitational Wave Interferometers, Shane L. Larson, William A. Hiscock, Ronald W. Hellings

All Physics Faculty Publications

To determine whether particular sources of gravitational radiation will be detectable by a specific gravitational wave detector, it is necessary to know the sensitivity limits of the instrument. These instrumental sensitivities are often depicted (after averaging over source position and polarization) by graphing the minimal values of the gravitational wave amplitude detectable by the instrument versus the frequency of the gravitational wave. This paper describes in detail how to compute such a sensitivity curve given a set of specifications for a spaceborne laser interferometer gravitational wave observatory. Minor errors in the prior literature are corrected, and the first (mostly) analytic …

Using Binary Star Observations To Bound The Mass Of The Graviton, Shane L. Larson, William A. Hiscock

All Physics Faculty Publications

Interacting white dwarf binary star systems, including helium cataclysmic variable (HeCV) systems, are expected to be strong sources of gravitational radiation, and should be detectable by proposed space-based laser interferometer gravitational wave observatories such as LISA. Several HeCV star systems are presently known and can be studied optically, which will allow electromagnetic and gravitational wave observations to be correlated. Comparisons of the phases of a gravitational wave signal and the orbital light curve from an interacting binary white dwarf star system can be used to bound the mass of the graviton. Observations of typical HeCV systems by LISA could potentially …

Superstring Cosmology: An Investigation Into Low Temperature Effective Gauss-Bonnet Corrections To The Einstein Field Equations In An Inflationary Scenario, David Dressel

Masters Theses

Several problems with the inflationary cosmological model and the force coupling constants are addressed in the context of superstring theory. In order to simplify the field equations slightly, vacuum solutions are attempted. The solutions for several field equations are analyzed in order to obtain an inflationary universe that leads to a nearly static internal space. A solution is found when Gauss-Bonnet terms, as well as the Einstein terms, are used in the field equations, along with an exponential radii function for a ten dimensional product space. The solutions lead to a three-phase universe that might describe our very early universe. …

Characterization Of Cosmic Microwave Background Temperature Fluctuations For Cosmological Topologies Specified By Topological Betti Numbers, Troy Gobble

Masters Theses

The cosmic microwave background explorer, COBE, and the Balloon Observations of Millimetric Extragalactic Radiation and Geophysics, BOOMERanG, have collected data from the universe and detected relic anisotropies indicative of one of the earliest events of the universe, decoupling. Hidden in the correlation between these temperature fluctuations is the signature of the global shape, or topology, of the early universe. It is possible to calculate the temperature fluctuations as due to primeval adiabatic density temperature fluctuations from the Sachs-Wolfe effect, which contains a topological term. Here we investigate some of the spaces and how they affect the microwave background.

A large …