Dark Matter Halos And Evolution Of Bars In Disk Galaxies: Varying Gas Fraction And Gas Spatial Resolution,
2010
Georgia Southern University
Dark Matter Halos And Evolution Of Bars In Disk Galaxies: Varying Gas Fraction And Gas Spatial Resolution, Jorge Villa-Vargas, Isaac Shlosman, Clayton Heller
Physics & Astronomy: Faculty Publications
We conduct numerical experiments by evolving gaseous/stellar disks embedded in live dark matter halos aiming at quantifying the effect of gas spatial resolution and gas content on the bar evolution. Three model sequences have been constructed using different resolutions, and the gas fraction has been varied along each sequence within the range of f g = 0%-50%, but keeping the disk and halo properties unchanged. We find that the spatial resolution becomes important with an increase in the gas content. For the higher resolution model sequences, we observe a bimodal behavior in the bar evolution with respect to the gas …
Plans For The First Balloon Flight Of The Gamma-Ray Polarimeter Experiment (Grape),
2010
University of New Hampshire - Manchester
Plans For The First Balloon Flight Of The Gamma-Ray Polarimeter Experiment (Grape), Taylor Connor, Chris Bancroft, Peter F. Bloser, Jason S. Legere, Mark L. Mcconnell, James M. Ryan
Space Science Center
We have developed a design for a hard X-ray polarimeter operating in the energy range from 50 to 500 keV. This modular design, known as GRAPE (Gamma-Ray Polarimeter Experiment), has been successfully demonstrated in the lab using partially polarized gamma-ray sources and using fully polarized photon beams at Argonne National Laboratory. In June of 2007, a GRAPE engineering model, consisting of a single detector module, was flown on a high altitude balloon flight to further demonstrate the design and to collect background data. We are currently preparing a much larger balloon payload for a flight in the fall of 2011. …
Development Of The Advance Energetic Pair Telescope (Adept) For Medium-Energy Gamma-Ray Astronomy,
2010
NASA Goddard Space Flight Ctr
Development Of The Advance Energetic Pair Telescope (Adept) For Medium-Energy Gamma-Ray Astronomy, Stanley D. Hunter, Peter F. Bloser, Michael P. Dion, Mark L. Mcconnell, Georgia A. Denolfo, Seunghee Son, James M. Ryan, Floyd Stecker
Space Science Center
Progress in high-energy gamma-ray science has been dramatic since the launch of INTEGRAL, AGILE and FERMI. These instruments, however, are not optimized for observations in the medium-energy (~0.3< Eγ < ~200 MeV) regime where many astrophysical objects exhibit unique, transitory behavior, such as spectral breaks, bursts, and flares. We outline some of the major science goals of a medium-energy mission. These science goals are best achieved with a combination of two telescopes, a Compton telescope and a pair telescope, optimized to provide significant improvements in angular resolution and sensitivity. In this paper we describe the design of the Advanced Energetic Pair Telescope (AdEPT) based on the Three-Dimensional Track Imager (3-DTI) detector. This technology achieves excellent, mediumenergy sensitivity, angular resolution near the kinematic limit, and gamma-ray polarization sensitivity, by high resolution 3-D electron tracking. We describe the performance of a 30×30×30 cm3 prototype of the AdEPT instrument.
A Fast Scintillator Compton Telescope For Medium-Energy Gamma-Ray Astronomy,
2010
University of New Hampshire
A Fast Scintillator Compton Telescope For Medium-Energy Gamma-Ray Astronomy, Peter F. Bloser, James M. Ryan, Jason S. Legere, Manuel Julien, Chris Bancroft, Mark L. Mcconnell, Mark Wallace, R M. Kippen, Shawn Tornga
Space Science Center
The field of medium-energy gamma-ray astronomy urgently needs a new mission to build on the success of the COMPTEL instrument on the Compton Gamma Ray Observatory. This mission must achieve sensitivity significantly greater than that of COMPTEL in order to advance the science of relativistic particle accelerators, nuclear astrophysics, and diffuse backgrounds, and bridge the gap between current and future hard X-ray missions and the high-energy Fermi mission. Such an increase in sensitivity can only come about via a dramatic decrease in the instrumental background. We are currently developing a concept for a low-background Compton telescope that employs modern scintillator …
Discovery Of Very High Energy Gamma-Ray Emission From The Snr G54.1+0.3,
2010
Department of Physical Sciences, Cork Institute of Technology, Bishopstown, Cork, Ireland
Discovery Of Very High Energy Gamma-Ray Emission From The Snr G54.1+0.3, P. T. Reynolds, Et Al
Physical Sciences Publications
We report the discovery of very high energy (VHE) gamma-ray emission from the direction of the SNR G54.1+0.3 using the VERITAS ground-based gamma-ray observatory. The TeV signal has an overall significance of 6.8σ and appears pointlike given the resolution of the instrument. The integral flux above 1 TeV is 2.5% of the Crab Nebula flux and significant emission is measured between 250 GeV and 4 TeV, well described by a power-law energy spectrum dN/dE ~ E –Γ with a photon index Γ = 2.39 ± 0.23stat ± 0.30sys. We find no evidence of time variability among observations …
The First Vlbi Image Of The Young, Oxygen-Rich Supernova Remnant In Ngc 4449,
2010
York
The First Vlbi Image Of The Young, Oxygen-Rich Supernova Remnant In Ngc 4449, M. F. Bietenholz, N. Bartel, D. Milisavljevic, R. A. Fesen
Dartmouth Scholarship
We report on sensitive 1.4-GHz VLBI radio observations of the unusually luminous supernova remnant SNR 4449-1 in the galaxy NGC 4449, which gave us the first well-resolved image of this object. The remnant's radio morphology consists of two approximately parallel bright ridges, suggesting similarities to the barrel shape seen for many older Galactic supernova remnants or possibly to SN 1987A. The angular extent of the remnant is 65 × 40 mas, corresponding to (3.7 × 2.3) × 1018 (D/3.8 Mpc) cm. We also present a new, high signal-to-noise ratio optical spectrum. By comparing the remnant's linear size …
Sn 2010u: A Luminous Nova In Ngc 4214,
2010
University of Minnesota
Sn 2010u: A Luminous Nova In Ngc 4214, Roberta M. Humphreys, José L. Prieto, Philip Rosenfield, L. Andrew Helton, Christopher S. Kochanek, K. Z. Stanek, Rubab Khan, Dorota Szczygiel, Karen Mogren, Robert A. Fesen
Dartmouth Scholarship
The luminosity, light curve, post-maximum spectrum, and lack of a progenitor on deep pre-outburst images suggest that SN 2010U was a luminous, fast nova. Its outburst magnitude is consistent with that for a fast nova using the maximum magnitude-rate of decline relationship for classical novae.
Observation And Analysis Of The Hydrogen 21-Cm Line Using A Small Radio Telescope,
2010
University of Alabama in Huntsville
Observation And Analysis Of The Hydrogen 21-Cm Line Using A Small Radio Telescope, Lisa Friederich
Honors Capstone Projects and Theses
No abstract provided.
The Cosmos Out Your Back Door,
2010
Utah State University
Prediction And Study Of Binary Alloys Using First-Principles Methods,
2010
Brigham Young University - Provo
Prediction And Study Of Binary Alloys Using First-Principles Methods, Richard Hansen Taylor Ii
Theses and Dissertations
The utility of first-principles methods in the study and prediction of binary alloys is showcased by three detailed studies. In particular, the T = 0K cluster expansion methodology in conjunction with finite temperature statistical modeling by a Monte Carlo method is used to study two systems of practical interest, Mg-Li (magnesium-lithium) and Rh-W (rhodium-tungsten). Also, an empirically-informed, high-throughput approach to crystal structure prediction is shown by a study of the Pt$_8$Ti (the Pietrokowsky phase) phase and a broad and detailed analysis of binary Mg-X phases in 39 systems (X=Ag, Al, Au, Ca, Cd, Cu, Fe, Ga, Ge, Hf, Hg, In, …
Charged, Rotating Black Holes In Higher Dimensions,
2010
Brigham Young University - Provo
Charged, Rotating Black Holes In Higher Dimensions, Christopher Bruce Verhaaren
Theses and Dissertations
We present a method for solving the Einstein-Maxwell equations in a five dimensional, asymptotically flat, black hole spacetime with three commuting Killing vector fields. In particular, we show that by reducing the dimension of the Einstein-Maxwell equations in a Kaluza-Klein like manner we can determine the components of the metric and vector potential which lie in the direction of the Killing vector fields. These components are determined by nine scalar fields each of which satisfy a partial differential equation in two variables. These equations take the form of an elliptic operator set equal to a nonlinear source. We find evidence …
A Mass-Loss Rate Determination For Zeta Puppis From The Quantitative Analysis Of X-Ray Emission-Line Profiles,
2010
Swarthmore College
A Mass-Loss Rate Determination For Zeta Puppis From The Quantitative Analysis Of X-Ray Emission-Line Profiles, David H. Cohen, M. A. Leutenegger, Emma Edwina Wollman , '09, J. Zsargó, D. J. Hillier, R. H.D. Townsend, S. P. Owocki
Physics & Astronomy Faculty Works
We fit every emission line in the high-resolution Chandra grating spectrum of. Pup with an empirical line profile model that accounts for the effects of Doppler broadening and attenuation by the bulk wind. For each of 16 lines or line complexes that can be reliably measured, we determine a best-fitting fiducial optical depth, tau(*) equivalent to kappa(M) over dot/4 pi R(*)upsilon(infinity), and place confidence limits on this parameter. These 16 lines include seven that have not previously been reported on in the literature. The extended wavelength range of these lines allows us to infer, for the first time, a clear …
Quiescent Superhumps Detected In The Dwarf Nova V344 Lyrae By Kepler,
2010
NASA Ames Research Center
Quiescent Superhumps Detected In The Dwarf Nova V344 Lyrae By Kepler, Martin D. Still, Steve B. Howell, Matt A. Wood, John K. Cannizzo, Alan P. Smale
Aerospace, Physics, and Space Science Faculty Publications
The timing capabilities and sensitivity of Kepler, NASA's observatory to find Earth-sized planets within the habitable zone of stars, are well matched to the timescales and amplitudes of accretion disk variability in cataclysmic variables. This instrumental combination provides an unprecedented opportunity to test and refine stellar accretion paradigms with high-precision, uniform data, and containing none of the diurnal or season gaps that limit ground-based observations. We present a 3 month, 1 minute cadence Kepler light curve of V344 Lyr, a faint, little-studied dwarf nova within the Kepler field. The light curve samples V344 Lyr during five full normal outbursts and …
Real-Space Approach To Time Dependent Current Density Functional Theory,
2010
Brigham Young University - Provo
Real-Space Approach To Time Dependent Current Density Functional Theory, Daniel S. Jensen
Theses and Dissertations
A real-space time-domain calculation of the frequency-dependent dielectric constant of nonmetallic crystals is outlined and the integrals required for this calculation are computed. The outline is based on time dependent current density functional theory and is partially implemented in the ab initio density functional theory FIREBALL program. The addition of a vector potential to the Hamiltonian of the system is discussed as well as the need to include the current density in addition to the particle density. The derivation of gradient integrals within a localized atomic-like orbital basis is presented for use in constructing the current density. Due to the …
Colours Of Bulges And Discs Within Galaxy Clusters And The Signature Of Disc Fading On Infall,
2010
University of Waterloo
Colours Of Bulges And Discs Within Galaxy Clusters And The Signature Of Disc Fading On Infall, Michael J. Hudson, Jeffrey B. Stevenson, Russell J. Smith, Gary A. Wegner
Dartmouth Scholarship
The origins of the bulge and disc components of galaxies are of primary importance to understanding galaxy formation. Here bulge–disc decomposition is performed simultaneously in B and R bands for 922 bright galaxies in eight nearby (z < 0.06) clusters with deep redshift coverage using photometry from the National Optical Astronomy Observatory (NOAO) Fundamental Plane Survey. The total galaxy colours follow a universal colour–magnitude relation (CMR). The discs of L* galaxies are 0.24 mag bluer in B−R than bulges. Bulges have a significant CMR slope while the CMR slope of discs is flat. Thus the slope of the CMR of the total light is driven primarily (60 per cent) by the bulge CMR, and to a lesser extent (40 per cent) by the change in the bulge‐to‐total ratio …
In Search Of Empty Places: Voids In The Distribution Of Galaxies,
2010
Brigham Young University - Provo
In Search Of Empty Places: Voids In The Distribution Of Galaxies, Brian K. Bucklein
Theses and Dissertations
We investigate several techniques to identify voids in the galaxy distribution of matter in the universe. We utilize galaxy number counts as a function of apparent magnitude and Wolf plots to search a two- or three-dimensional data set in a pencil-beam fashion to locate voids within the field of view. The technique is able to distinguish between voids that represent simply a decrease in density as well as those that show a build up of galaxies on the front or back side of the void. This method turns out to be primarily useable only at relatively short range (out to …
Oh Megamasers In Merging Galaxies: A Multi-Frequency Study Of Iizw096,
2010
Brigham Young University - Provo
Oh Megamasers In Merging Galaxies: A Multi-Frequency Study Of Iizw096, Kirstin Marie Cooprider
Theses and Dissertations
OH Megamasers (OHMs) generally appear in luminous infrared regions i.e. merging galaxies. In this study we assume that OHMs may not be represented by their association with star formation solely, because of the possibility of a compact AGN source in the merging galaxies. In fact, previously classified starburst galaxies where OHMs are found are now optically observed as AGN. OHMs may also serve as a reasonable criterion for the evolutionary stage of the merger. This project focuses on observations from a multi-frequency analysis of merging regions with known OHMs. Optically, Hα and BVRI filters provided an environmental perspective of the …
Evidence For The Supernova-Synthesized Dust From The Rising Afterglow Of Grb071025 At Z ∼ 5,
2010
Department of Astronomy, University of California
Evidence For The Supernova-Synthesized Dust From The Rising Afterglow Of Grb071025 At Z ∼ 5, Daniel A. Perley, J. S. Bloom, C. R. Klein, S. Covino, T. Minezaki, P. Wozniak, W. T. Vestrand, G. G. Williams, P. Milne, N R. Butler, A C. Updike, T Kruhler, P Afonso, A Antonelli, L Cowie, P Ferrero, J Greiner, Dieter H. Hartmann, Y Kakazu, A Küpcü Yoldaş, A N. Morgan, P A. Price, J X. Prochaska, Y Yoshii
Publications
We present observations and analysis of the broad-band afterglow of Swift GRB 071025. Using optical and infrared (RIYJHK) photometry, we derive a photometric redshift of 4.4 < 5.2; at this redshift our simultaneous multicolour observations begin at ∼30 s after the gamma-ray burst trigger in the host frame, during the initial rising phase of the afterglow. We associate the light-curve peak at ∼580 s in the observer frame with the formation of the forward shock, giving an estimate of the initial Lorentz factor 0 ∼ 200. The red spectral energy distribution (even in regions not affected by the Lyman α break) provides secure evidence of a large dust column. However, the inferred extinction curve shows a prominent flat component between 2000 and 3000 Å in the rest frame, inconsistent with any locally observed template but well fitted by models of dust formed by supernovae. Time-dependent fits to the extinction profile reveal no evidence of dust destruction and limit the decrease in the extinction column to A3000 < 0.54 mag after t = 50 s in the rest frame. Together with studies of high-z quasars, our observations suggest a transition in dust properties in the early Universe, possibly associated with a transition between supernova-dominated and asymptotic giant branch-dominated modes of dust production.
Modeling Gas Distribution In Protoplanetary Accretion Disks,
2010
University of Washington
Modeling Gas Distribution In Protoplanetary Accretion Disks, Martin Kronberg, Josiah Lewis, Sean D. Brittain
Publications
Protoplanetary accretion disks are disks of dust and gas which surround and feed material onto a forming star in the earliest stages of its evolution. One of the most useful methods for studying these disks is near infrared spectroscopy of rovibrational CO emission. This paper presents the methods in which synthetically generated spectra are modeled and fit to spectral data gathered from protoplanetary disks. This paper also discussed the methods in which this code can be improved by modifying the code to run a Monte Carlo analysis of best fit across the CONDOR cluster at Clemson University, thereby allowing for …
Probing Protoplanetary Disk Upper Atmospheres For Heating And Dust Settling Using Synthetic Co Spectra,
2010
Covenant College
Probing Protoplanetary Disk Upper Atmospheres For Heating And Dust Settling Using Synthetic Co Spectra, Josiah Lewis, Martin Kronberg, Sean D. Brittain
Publications
CO emission is a useful probe of the warm gas distribution in the planet forming regions of disks around Herbig Ae/Be (HAeBe) stars. We model UV fluoresced and thermally excited CO in the circumstellar disks of several HAeBes. We find indications of dust settling in the upper atmospheres of HD 141569 and HD 97048 and a correlation between PAH luminosity and gas heating in these two systems.
