Astrophysics and Astronomy Commons^™

Effects Of Radiation On Neurite Morphology And Cytoskeleton Structure, Melissa Sassman

Student Scholarship

Long-term manned space exploration to the moon, Mars, and other areas beyond Earth's protective magnetic field poses possible acute and late central nervous systems (CNS) risks. Of particular concern for astronauts is exposure to high atomic number, high energy particles known as HZE particles, a component of galactic cosmic radiation (GCR). Although NASA has radiation safety requirements, the possible effects of GCR and HZE particles on the central nervous systems of astronauts remains unknown. Understanding the risks and effects of galactic cosmic radiation and HZE particles on the central nervous system will allow for safer space exploration.

Additionally, and perhaps …

Some Results From The Lariat Experiment, Derek Walker

Honors Capstones

No abstract provided.

Galaxy And Mass Assembly (Gama): The Effect Of Galaxy Group Environment On Active Galactic Nuclei, Yjan A. Gordon, Kevin A. Pimbblet, Matt S. Owers, Joss Bland-Hawthorn, Sarah Brough, Michael J.I. Brown, Michelle E. Cluver, Scott M. Croom, Benne W. Holwerda, Jonathan Loveday, Smriti Mahajan, Lingyu Wang

Faculty and Staff Scholarship

In galaxy clusters, efficiently accreting active galactic nuclei (AGNs) are preferentially located in the infall regions of the cluster projected phase-space, and are rarely found in the cluster core. This has been attributed to both an increase in triggering opportunities for infalling galaxies, and a reduction of those mechanisms in the hot, virialized, cluster core. Exploiting the depth and completeness (98 per cent at r < 19.8mag) of the Galaxy And Mass Assembly survey (GAMA), we probe down the group halo mass function to assess whether AGNs are found in the same regions in groups as they are in clusters. We select 451 optical AGNs from 7498 galaxies with log10(M*/M⊙) > 9.9 in 695 groups with 11.53 ≤ log10(M200/M⊙) ≤ 14.56 at < 0.15. By analysing the projected phase-space positions of these galaxies, we demonstrate that when split both radially, and into physically derived infalling and core populations, AGN position within group projected phase-space is dependent on halo mass. For groups with log10(M200/M⊙) > 13.5,AGNs are preferentially found in the infalling galaxy populationwith 3.6s confidence. At lower halo masses, we observe no difference in AGN fraction between core …

An Enigmatic Population Of Luminous Globular Clusters In A Galaxy Lacking Dark Matter, Pieter Van Dokkum, Yotam Cohen, Shany Danieli, J. Diederik Kruijssen, Aaron Romanowsky, Allison Merritt, Roberto Abraham, Jean Brodie, Charlie Conroy, Deborah Lokhorst, Lamiya Mowla, Ewan O'Sullivan, Jielai Zhang

Faculty Publications

We recently found an ultra diffuse galaxy (UDG) with a half-light radius of R e  = 2.2 kpc and little or no dark matter. The total mass of NGC1052–DF2 was measured from the radial velocities of bright compact objects that are associated with the galaxy. Here, we analyze these objects using a combination of Hubble Space Telescope (HST) imaging and Keck spectroscopy. Their average size is  pc and their average ellipticity is . From a stacked Keck spectrum we derive an age of 9 Gyr and a metallicity of [Fe/H] = −1.35 ± 0.12. Their properties are similar to ωCentauri, …

Thin Film Carbon Nanofuses For Permanent Data Storage, Kevin Robert Laughlin

Theses and Dissertations

We have fabricated nanofuses from thin-film, arc-evaporation carbon for use in permanent data storage. Thin film carbon fuses have fewer fabrication barriers and retain the required resistivity and structural stability to work as a data storage medium. Carbon thin films were characterized for their electrical, microstructural, and chemical bonding properties. Annealing the thin-film carbon in an argon environment at 400°C reduced the resistivity from about 4*10^-2 Ω cm as deposited down to about 5*10^-4 Ω cm, allowing a lower blowing voltage. Nanofuses with widths ranging from 200 nm down to 60 nm were fabricated and tested. They blow …

Development Of A Real-Time Auralization System For Assessment Of Vocal Effort In Virtual-Acoustic Environments, Jennifer Kay Whiting

Theses and Dissertations

This thesis describes the development of the real-time convolution system (RTCS) for a little-studied talker/listener in virtual acoustic environments. We include descriptions of the high-resolution directivity measurements of human speech, the RTCS system components, the measurement and characterization of oral-binaural room impulse responses (OBRIRs) for a variety of acoustic environments, and the compensation filter necessary for its validity. In addition to incorporating the high-resolution directivity measurements, this RTCS improved on that developed by Cabrera et al. [1] through the derivation and inclusion of the compensation filter. Objective measures in the time- and frequency-domains, as well as subjective measures, were developed …

Experimental Investigation Of A New Spiral Wingtip, Naseeb Ahmed Siddiqui, Mohammed Aldheeb, Waqar Asrar, Erwin Sulaeman

International Journal of Aviation, Aeronautics, and Aerospace

Experiments on the relative merits and demerits of slotted wingtips mimicking a bird’s primary feathers have been performed. The real emargination length of feather tips, their flexibility and curved shapes during cruise are considered in the present study. The experiments were performed at a Reynolds number of 3.7 x 10⁵ on a symmetric flat plate half wing of aspect ratio 3. Lift, drag and pitching moments were measured using a six component aerodynamic balance. Four different shapes inspired by bird primary feathers have been analysed. The rigid curved tip performed the best increasing the L/D ratio by 20%. This …

Multiwavelength Observations Of The Blazar Bl Lacertae: A New Fast Tev Gamma-Ray Flare, P. T. Reynolds, Et Al

Physical Sciences Publications

Combined with measurements made by very-long-baseline interferometry, the observations of fast TeV gamma-ray flares probe the structure and emission mechanism of blazar jets. However, only a handful of such flares have been detected to date, and only within the last few years have these flares been observed from lower-frequency-peaked BL Lac objects and flat-spectrum radio quasars. We report on a fast TeV gamma-ray flare from the blazar BL Lacertae observed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS). with a rise time of ~2.3 hr and a decay time of ~36 min. The peak flux above 200 GeV …

Intermediate-Line Emission In Agns: The Effect Of Prescription Of The Gas Density, T. P. Adhikari, K. Hryniewicz, A. Różańska, B. Czerny, Gary J. Ferland

Physics and Astronomy Faculty Publications

The requirement of an intermediate-line component in the recently observed spectra of several active galactic nuclei (AGNs) points to the possible existence of a physically separate region between the broad-line region (BLR) and narrow-line region (NLR). In this paper we explore the emission from the intermediate-line region (ILR) by using photoionization simulations of the gas clouds distributed radially from the center of the AGN. The gas clouds span distances typical for the BLR, ILR, and NLR, and the appearance of dust at the sublimation radius is fully taken into account in our model. The structure of a single cloud is …

Sdss-Iv Manga: The Spatially Resolved Stellar Initial Mass Function In ~400 Early-Type Galaxies, Taniya Parikh, Daniel Thomas, Claudia Maraston, Kyle B. Westfall, Daniel Goddard, Jianhui Lian, Sofia Meneses-Goytia, Amy Jones, Sam Vaughan, Brett H. Andrews, Matthew Bershady, Dmitry Bizyaev, Jonathan Brinkmann, Joel R. Brownstein, Kevin Bundy, Niv Drory, Eric Emsellem, David R. Law, Jeffrey A. Newman, Alexandre Roman-Lopes, David Wake, Renbin Yan, Zheng Zheng

Physics and Astronomy Faculty Publications

Mapping Nearby Galaxies at Apache Point Observatory provides the opportunity to make precise spatially resolved measurements of the IMF slope in galaxies owing to its unique combination of spatial resolution, wavelength coverage, and sample size. We derive radial gradients in age, element abundances, and IMF slope analysing optical and near-infrared absorption features from stacked spectra out to the half-light radius of 366 early-type galaxies with masses 9.9–10.8 log M/M_⊙. We find flat gradients in age and [α/Fe] ratio, as well as negative gradients in metallicity, consistent with the literature. We further derive significant negative gradients …

Near Earth Space Object Detection Utilizing Parallax As Multi-Hypothesis Test Criterion, Joseph C. Tompkins

Theses and Dissertations

The US Strategic Command (USSTRATCOM) operated Space Surveillance Network (SSN) is tasked with Space Situational Awareness (SSA) for the US military. This system is made up of Electro-Optic sensors such as the Space Surveillance Telescope (SST) and Ground-based Electro-Optical Deep Space Surveillance (GEODSS) as well as RADAR based sensors such as the Space Fence. While Lockheed Martin’s Space Fence is very adept at detecting & tracking objects in Low Earth Orbit (LEO) below 3000 Km in height [1], gaps remain in the tracking of Resident Space Objects (RSO’s) in Geosynchronous Orbits (GEO) due to limitations associated with the implementation of …

Sdss Iv Manga – Ssfr Profiles And The Slow Quenching Of Discs In Green Valley Galaxies, Francesco Belfiore, Roberto Maiolino, Kevin Bundy, Karen Masters, Matthew Bershady, Grecco A. Oyarzún, Lihwai Lin, Mariana Cano-Diaz, David Wake, Ashley Spindler, Daniel Thomas, Joel R. Brownstein, Niv Drory, Renbin Yan

Physics and Astronomy Faculty Publications

We study radial profiles in H α equivalent width and specific star formation rate (sSFR) derived from spatially resolved SDSS-IV MaNGA spectroscopy to gain insight on the physical mechanisms that suppress star formation and determine a galaxy’s location in the SFR-M_⋆ diagram. Even within the star-forming ‘main sequence’, the measured sSFR decreases with stellar mass, in both an integrated and spatially resolved sense. Flat sSFR radial profiles are observed for log(M_⋆/M_⊙) < 10.5, while star-forming galaxies of higher mass show a significant decrease in sSFR in the central regions, a likely consequence of both larger bulges and an inside-out growth history. Our primary focus is the green valley, constituted by galaxies lying below the star formation main sequence, but not fully passive. In the green valley we find sSFR profiles that are suppressed with respect to star-forming galaxies of the same mass at all galactocentric distances out to 2 effective radii. The responsible quenching mechanism therefore appears to affect the entire galaxy, not simply an …

Using An Astrophysical Model To Characterize Nuclear Dust, Anita N. Dunsmore

Theses and Dissertations

Dust clouds resulting from nuclear explosions are complex phenomena, and knowledge on how they form is lacking. Noting the similarities between supernovae and nuclear explosions led to the concept of modeling a nuclear dust cloud using a supernova simulation. MOCASSIN uses a Monte Carlo approach to model photons traveling through a dust cloud, allowing the cloud's characteristics to be discovered by comparing an observed spectrum to a calculated one and then changing input values to make the spectra match. Data files describing two nuclear fireballs of varying yields were created and analyzed using MOCASSIN, but yielded zero energy spectra. After …

Galaxy And Mass Assembly (Gama): Blue Spheroids Within 87 Mpc, Smriti Mahajan, Michael J. Drinkwater, S. Driver, A. M. Hopkins, Alister W. Graham, S. Brough, Michael J.I. Brown, Benne W. Holwerda, Matt S. Owers, Kevin A. Pimbblet

Faculty and Staff Scholarship

In this paper, we test if nearby blue spheroid (BSph) galaxies may become the progenitors of star-forming spiral galaxies or passively evolving elliptical galaxies. Our sample comprises 428 galaxies of various morphologies in the redshift range 0.002 < Ζ < 0.02 (8-87 Mpc) with panchromatic data from the Galaxy and Mass Assembly survey. We find that BSph galaxies are structurally (mean effective surface brightness, effective radius) very similar to their passively evolving red counterparts. However, their star formation and other properties such as colour, age, and metallicity are more like star-forming spirals than spheroids (ellipticals and lenticulars). We show that BSph galaxies are statistically distinguishable from other spheroids as well as spirals in the multidimensional space mapped by luminosity-weighted age, metallicity, dust mass, and specific star formation rate. We use HI data to reveal that some of the BSphs are (further) developing their discs, hence their blue colours. They may eventually become spiral galaxies - if sufficient gas accretion occurs - or more likely fade into low-mass red galaxies.

An X-Ray Imaging Survey Of Quasar Jets: The Complete Survey, H. L. Marshall, J. M. Gelbord, D. M. Worrall, M. Birkinshaw, D. A. Schwartz, D. L. Jauncey, G. Griffiths, D. W. Murphy, J. E. J. Lovell, E. S. Perlman, L. Godfrey

Aerospace, Physics, and Space Science Faculty Publications

We present Chandra X-ray imaging of a flux-limited sample of flat spectrum radio-emitting quasars with jet-like structure. X-rays are detected from 59% of 56 jets. No counter-jets were detected. The core spectra are fitted by power-law spectra with a photon index Γx, whose distribution is consistent with a normal distribution, with a mean of 1.61+0.04 and dispersion of 0.15+0.04. We show that the distribution of α , the spectral index between the X-ray −0.05 −0.03 rx and radio band jet fluxes, fits a Gaussian with a mean of 0.974 ± 0.012 and dispersion of 0.077 ± 0.008. We test the …

Data From: Polar Topside Ionosphere During Geomagnetic Storms: Comparison Of Isis-Ii With Tdim, Jan J. Sojka, Dan Rice, Michael David, Robert W. Schunk, Robert Benson, H. G. James

Browse all Datasets

Output files from runs of the TDIM ionospheric model used for calculations and electron density profiles from ISIS-II and TDIM used in figures in the article in Radio Science.

Anomalous Electromagnetic Transport In Compact Stars, Efrain J. Ferrer, Vivian De La Incera

Physics & Astronomy Faculty Publications

We study the anomalous electromagnetic transport properties of a quark-matter phase that can be realized in the presence of a magnetic field in the low-temperature/moderate-high-density region of the Quantum Chromodynamics (QCD) phase map. In this so-called Magnetic Dual Chiral Density Wave phase, an inhomogeneous condensate is dynamically induced producing a nontrivial topology, a consequence of the asymmetry of the lowest Landau level modes of the quasiparticles in this phase. The nontrivial topology manifests in the electromagnetic effective action via a chiral anomaly term ����������˜���� , with an axion field �� given by the phase of the Dual Chiral Density Wave …

Anomalous Electromagnetic Transport In Compact Stars, Efrain J. Ferrer, Vivian De La Incera

Publications and Research

We study the anomalous electromagnetic transport properties of a quark-matter phase that can be realized in the presence of a magnetic field in the low-temperature/moderate-high-density region of the Quantum Chromodynamics (QCD) phase map. In this so-called Magnetic Dual Chiral Density Wave phase, an inhomogeneous condensate is dynamically induced producing a nontrivial topology, a consequence of the asymmetry of the lowest Landau level modes of the quasiparticles in this phase. The nontrivial topology manifests in the electromagnetic effective action via a chiral anomaly term θF^µνF˜_µν, with an axion field θ given by the phase of the Dual …

Patterns Of Variation For The Sun And Sun-Like Stars, Richard R. Radick, G. Wesley Lockwood, Gregory W. Henry, Jeffrey C. Hall, Alexei A. Pevtsov

Information Systems and Engineering Management Research Publications

We compare patterns of variation for the Sun and 72 Sun-like stars by combining total and spectral solar irradiance measurements between 2003 and 2017 from the SORCE satellite, Strömgren b, y stellar photometry between 1993 and 2017 from Fairborn Observatory, and solar and stellar chromospheric Ca ii H+K emission observations between 1992 and 2016 from Lowell Observatory. The new data and their analysis strengthen the relationships found previously between chromospheric and brightness variability on the decadal timescale of the solar activity cycle. Both chromospheric H+K and photometric b, y variability among Sun-like stars are related to average chromospheric activity by …

High Order Entropy Conservative Central Schemes For Wide Ranges Of Compressible Gas Dynamics And Mhd Flows, Björn Sjögreen, H.C. Yee

United States National Aeronautics and Space Administration: Publications

The Sjogreen and Yee [31]high order entropy conservative numerical method for compressible gas dynamics is extended to include discontinuities and also extended to equations of ideal magnetohydrodynamics (MHD). The basic idea is based on Tadmor’s [40]original work for inviscid perfect gas flows. For the MHD four formulations of the MHD are considered: (a) the conservative MHD, (b) the Godunov [14]non-conservative form, (c) the Janhunen [19]– MHD with magnetic field source terms, and (d) a MHD with source terms by Brackbill and Barnes[5]. Three forms of the high order entropy numerical fluxes for the MHD in the finite difference framework are …