Browsing Astronomy by Issue Date
Now showing items 1-20 of 63
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Physical conditions in giant extragalactic H II regions
(1984)Giant Extragalactic H II Regions (GEHRs) in nearby galaxies have been observed at both radio and optical wavelengths. Narrow band optical imaging, large and small aperture optical spectrophotometry, radio continuum imaging ... -
The composition of near-earth objects
(1998)I present reflectance spectra of 34 near-Earth objects (NEOs), 6 main-belt asteroids, and four non-NEO cometary candidates, all obtained with the Apache Point Observatory 3.5m telescope + Double Imaging Spectrograph. The ... -
The optical counterparts of the luminous x-ray binary stars in globular clusters
(1998)Ten percent of our Galaxy's luminous (LX≳1036 ergs-1 ) X-ray point sources are located in globular clusters (GCs), but globular clusters contribute a much smaller fraction of normal stars to the Galaxy. X-ray bursts ... -
The formation and evolution of the large magellanic cloud from selected clusters and star fields
(1998)We have obtained deep Hubble Space Telescope color-magnitude diagrams of fields centered on the six old LMC globular clusters NGC 1754, NGC 1835, WGC 1898, NGC 1916, NGC 2005, and NGC 2019. The data have been carefully ... -
What's happening around Herbig Ae stars?: investigating circumstellar activity in young intermediate mass stars with optical and near-infrared spectroscopy
(2001)We have investigated the optical and near-infrared spectral behavior of the intermediate mass, pre-main sequence Herbig Ae stars, with particular emphasis on variability and evolution. The evolutionary state of Herbig Ae ... -
A hyperbolic tetrad approach to numerical relativity
(2003)An in-depth numerical study using 3 + 1 formulations of the Einstein equations for 1D colliding plane waves reveals factors which increase accuracy and stability: using "mixed" variables, hyperbolicity, satisfying the ... -
The assembly of cluster galaxies
(2004)Clusters of galaxies are the largest bound structures in the universe. As such, they represent an important tool for testing models of structure formation. In addition, because galaxies in clusters span a range of local ... -
HI selected galaxies in the Sloan Digital Sky Survey
(2005)We present the results from a study of HI selected galaxies that fall within both the HI Parkes All Sky Survey (HIPASS) and the Sloan Digital Sky Survey (SDSS). By comparing the optical properties derived from the SDSS ... -
Candidate isolated neutron stars and other stellar x-ray sources from the ROSAT all-sky and Sloan Digital Sky Surveys
(2006)Although extra-solar X-ray sources were first observed almost fifty years ago, the first all-sky imaging X-ray survey was only recently completed. The ROSAT All-Sky Survey (RASS) Bright and Faint Source Catalogs include ... -
The Optical Variability of Quasars as Seen by SDSS
(2012-09-13)I provide a quantitative analysis of the database of 3.5 million photometric measurements for 80,000 spectroscopically confirmed quasars recently assembled by the Sloan Digital Sky Survey (SDSS). This database is an excellent ... -
Activity and Kinematics of Cool and Ultracool Dwarfs
(2013-02-25)The ages of cool and ultracool dwarfs are particularly important. For cool M dwarfs, accurate ages combined with their ubiquity in the stellar disk could lead to a new level of precision in age dating the Galaxy. A better ... -
Time-Resolved Properties and Global Trends in dMe Flares from Simultaneous Photometry and Spectra
(2013-02-25)We present a homogeneous survey of near-ultraviolet (NUV) /optical line and continuum emission during twenty M dwarf flares with simultaneous, high cadence photometry and spectra. These data were obtained to study the ... -
Karhunen-Loeve Analysis for Weak Gravitational Lensing
(2013-02-25)In the past decade, weak gravitational lensing has become an important tool in the study of the universe at the largest scale, giving insights into the distribution of dark matter, the expansion of the universe, and the ... -
A Ground-Based Search for Transit Timing Variations from the Apache Point Observatory
(2013-02-25)The following dissertation presents work done as part of a ground-based transit follow-up program designed to look for transit timing variations in well-known transiting systems called, the Apache Point Survey of Transit ... -
Simulating and Characterizing the Pale Blue Dot
(2013-02-25)The goal of this work is to develop and validate a comprehensive model of Earth's disk-integrated spectrum. Earth is our only example of a habitable planet, or a planet capable of maintaining liquid water on its surface. ... -
Drivers of Turbulence in the Neutral Interstellar Medium of Dwarf Galaxies
(2013-07-23)The cause of HI velocity dispersions in the interstellar medium (ISM) of galaxies is often attributed to star formation, but recent evidence has shown these two quantities are not connected in regions of low star formation. ... -
The Milky Way in SDSS and in N-body Models
(2013-11-14)In this thesis, I present a comparison between recent Sloan Digital Sky Survey (SDSS) Galactic studies and N-body simulations to aid in the interpretation of observed structural features. I investigate the origin of the ... -
X-ray Binary Evolution and the Connection to Star Formation in Nearby Galaxies with the Chandra Local Volume Survey
(2014-02-24)X-ray binaries, especially those with a massive stellar companion, provide a unique probe through which one can study the end-points of high-mass stellar evolution while simultaneously tracing recent star formation. In ... -
Observational Constraints on Models of Rapidly Evolving Luminous Stars
(2014-02-24)Resolved stellar populations in galaxies are excellent laboratories for testing our understanding of galaxy formation, integrated colors and luminosities, supernova progenitor masses, and energy input from stellar feedback. ... -
Star Formation in N-Body + SPH Simulations
(2014-02-24)The primary focus of my thesis work is to study star formation using a series of high resolution cosmological N-body Simulations. Specifically, I have studied the total stellar-to-halo mass ratio as a function of halo mass ...