Astrophysics and Astronomy Commons^™

Rethinking The Polar Cap: Eccentric Dipole Structuring Of Ulf Power At The Highest Corrected Geomagnetic Latitudes, Kevin D. Urban, Andrew J. Gerrard, Louis J. Lanzerotti, Allan T. Weatherwax

Physics Faculty Publications

The day-to-day evolution and statistical features of Pc3-Pc7 band ultralow frequency (ULF) power throughout the southern polar cap suggest that the corrected geomagnetic (CGM) coordinates do not adequately organize the observed hydromagnetic spatial structure. It is shown that that the local-time distribution of ULF power at sites along CGM latitudinal parallels exhibit fundamental differences and that the CGM latitude of a site in general is not indicative of the site's projection into the magnetosphere. Thus, ULF characteristics observed at a single site in the polar cap cannot be freely generalized to other sites of similar CGM latitude but separated in …

Energy Quantity Estimation In Radiated Acoustic Fields, Eric B. Whiting

Theses and Dissertations

Energy quantities, which are calculated from pressure and particle velocity, yield a great deal of information about acoustic fields. Errors in pressure or particle velocity estimation lead to bias errors the estimation of energy quantities. The bias errors arise from different probe configurations and processing methods. Two processing methods are examined: the traditional method and the recently developed Phase and Amplitude Gradient Estimation (PAGE) method. These two methods are compared to investigate how each estimates pressure and particle velocity and the subsequent bias errors in a plane wave, standing wave, and spherical spreading wave field. Analytical expressions are derived for …

The Subject Librarian Newsletter, Physics, Fall 2016, Patti Mccall

Libraries' Newsletters

No abstract provided.

Modeling X-Ray Emission Line Profiles From Massive Star Winds - A Review, Richard Igance

ETSU Faculty Works

The Chandra and XMM-Newton X-ray telescopes have led to numerous advances in the study and understanding of astrophysical X-ray sources. Particularly important has been the much increased spectral resolution of modern X-ray instrumentation. Wind-broadened emission lines have been spectroscopically resolved for many massive stars. This contribution reviews approaches to the modeling of X-ray emission line profile shapes from single stars, including smooth winds, winds with clumping, optically thin versus thick lines, and the effect of a radius-dependent photoabsorption coefficient.

Increasing The Computational Efficiency Of Combinatoric Searches, Wiley Spencer Morgan

Theses and Dissertations

A new algorithm for the enumeration of derivative superstructures of a crystal is presented. The algorithm will help increase the efficiency of computational material design methods such as cluster expansion by increasing the size and diversity of the types of systems that can be modeled. Modeling potential alloys requires the exploration of all possible configurations of atoms. Additionally, modeling the thermal properties of materials requires knowledge of the possible ways of displacing the atoms. One solution to finding all symmetrically unique configurations and displacements is to generate the complete list of possible configurations and remove those that are symmetrically equivalent. …

Directional Excitation Without Breaking Reciprocity, Hamidreza Ramezani, Marc Dubois, Yuan Wang, Y. Ron Shen, Xiang Zhang

Physics & Astronomy Faculty Publications

We propose a mechanism for directional excitation without breaking reciprocity. This is achieved by embedding an impedance matched parity-time symmetric potential in a three-port system. The amplitude distribution within the gain and loss regions is strongly influenced by the direction of the incoming field. Consequently, the excitation of the third port is contingent on the direction of incidence while transmission in the main channel is immune. Our design improves the four-port directional coupler scheme, as there is no need to implement an anechoic termination to one of the ports.

Galaxy And Mass Assembly (Gama) : Galaxy Colour Gradients Versus Colour, Structure, And Luminosity., Rebecca Kennedy, Steven P. Bamford, Boris Haußler, Sarah Brough, Benne W. Holwerda, Andrew M. Hopkins, Marina Vika, Benedetta Vulcani

Faculty and Staff Scholarship

Using single-component fits to SDSS/UKIDSS images of galaxies in the G09 region of the GAMA survey we study radial colour gradients across the galaxy population. We use the multi-wavelength information provided by MegaMorph analysis of galaxy light profiles to calculate intrinsic colour gradients, and divide into six subsamples split by overall Sérsic index (n) and galaxy colour. We find a bimodality in the colour gradients of high- and low-n galaxies in all wavebands which varies with overall galaxy luminosity. Global trends in colour gradients therefore result from combining the contrasting behaviour of a number of different galaxy populations. The ubiquity …

The Mass Discrepancy Acceleration Relation In Early-Type Galaxies: Extended Mass Profiles And The Phantom Menace To Mond, Joachim Janz, Michele Cappellari, Aaron Romanowsky, Luca Ciotti, Adebusola Alabi, Duncan Forbes

Faculty Publications

The dark matter (DM) haloes around spiral galaxies appear to conspire with their baryonic content: empirically, significant amounts of DM are inferred only below a universal characteristic acceleration scale. Moreover, the discrepancy between the baryonic and dynamical mass, which is usually interpreted as the presence of DM, follows a very tight mass discrepancy acceleration (MDA) relation. Its universality, and its tightness in spiral galaxies, poses a challenge for the DM interpretation and was used to argue in favour of MOdified Newtonian Dynamics (MOND). Here, we test whether or not this applies to early-type galaxies. We use the dynamical models of …

All Nirspec Needs Is Hst/Wfc3 Pre-Imaging? : The Use Of Milky Way Stars In Wfc3 Imaging To Register Nirspec Msa Observations., Benne W. Holwerda, R. J. Bouwens, M. Trenti, M. A. Kenworthy

Faculty and Staff Scholarship

The James Webb Space Telescope (JWST) will be an exquisite new near-infrared observatory with imaging and multi-object spectroscopy through ESA’s NIRspec instrument with its unique Micro-Shutter Array (MSA), allowing for slits to be positioned on astronomical targets by opening specific 0′′.20′′.2-wide micro shutter doors. To ensure proper Target Acquisition (TA), the on-sky position of the MSA needs to be verified before spectroscopic observations start. An onboard centroiding program registers the position of pre-identified guide stars in a TA image, a short pre-spectroscopy exposure without dispersion (image mode) through the MSA with all shutters open. The outstanding issue is the availability …

Book Review: How Do You Find An Exoplanet?, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of How Do You Find an Exoplanet? by John Asher Johnson. Princeton, 2016 178p bibl index afp, 9780691156811 $35.00, 9781400873999

Lunar Stories: The Violence Of Creation, Channon Visscher

Faculty Work Comprehensive List

"Tales of the moon’s creation abound in myth, legend, history and science. Given its conspicuous brightness and nearness, we should not be surprised that the moon has captured the imagination since the dawn of human consciousness."

Posting about how the moon was made ­­­­­­­­from In All Things - an online hub committed to the claim that the life, death, and resurrection of Jesus Christ has implications for the entire world.

http://inallthings.org/lunar-stories-the-violence-of-creation/

Resting-State Connectivity Dynamics In The Human Brain Using High-Speed Fmri, Kishore Vakamudi

Physics & Astronomy ETDs

Resting-state fMRI using seed-based connectivity analysis (SCA) typically involves regression of the confounding signals resulting from movement and physiological noise sources. This not only adds additional complexity to the analysis but may also introduce possible regression bias. We recently introduced a computationally efficient real-time SCA approach without confound regression, which employs sliding-window correlation analysis with running mean and standard deviation (meta-statistics). The present study characterizes the confound tolerance of this windowed seed-based connectivity analysis (wSCA), which combines efficient decorrelation of confounding signal events with high-pass filter characteristics that reduce sensitivity to drifts. The confound suppression and the strength of resting-state …

New Halo White Dwarf Candidates In The Sloan Digital Sky Survey, Kyra Dame, A. Gianninas, Mukremin Kilic, Jeffrey A. Munn, Warren R. Brown, Kurtis A. Williams, Ted Von Hippel, Hugh C. Harris

Publications

We present optical spectroscopy and near-infrared photometry of 57 faint (g = 19–22) high proper motion white dwarfs identified through repeat imaging of ≈3100 deg² of the Sloan Digital Sky Survey footprint by Munn et al. We use ugriz and JHphotometry to perform a model atmosphere analysis, and identify 10 ultracool white dwarfs with T_eff < 4000 K, including the coolest pure H atmosphere white dwarf currently known, J1657+2638, with T_eff = 3550 ± 100 K. The majority of the objects with cooling ages larger than 9 Gyr display thick disc kinematics and constrain the age of the thick disc to ≥11 Gyr. There are four white dwarfs in our sample with …

Sdss-Iv Manga: Properties Of Galaxies With Kinematically Decoupled Stellar And Gaseous Components, Yifei Jin, Yanmei Chen, Yong Shi, C. A. Tremonti, M. A. Bershady, M. Merrifield, E. Emsellem, Hai Fu, D. Wake, K. Bundy, Lihwai Lin, M. Argudo-Fernandez, Song Huang, D. V. Stark, T. Storchi-Bergmann, D. Bizyaev, J. Brownstein, J. Chisholm, Qi Guo, Lei Hao, Jian Hu, Cheng Li, Ran Li, K. L. Masters, E. Malanushenko, Kaike Pan, R. A. Riffel, A. Roman-Lopes, A. Simmons, D. Thomas, Renbin Yan

Physics and Astronomy Faculty Publications

We study the properties of 66 galaxies with kinematically misaligned gas and stars from MaNGA survey. The fraction of kinematically misaligned galaxies varies with galaxy physical parameters, i.e. M_*, SFR and sSFR. According to their sSFR, we further classify these 66 galaxies into three categories, 10 star-forming, 26 ‘Green Valley’ and 30 quiescent ones. The properties of different types of kinematically misaligned galaxies are different in that the star-forming ones have positive gradient in D_n4000 and higher gas-phase metallicity, while the green valley/quiescent ones have negative D_n4000 gradients and lower gas-phase metallicity on average. …

Comprehensive All-Sky Search For Periodic Gravitational Waves In The Sixth Science Run Ligo Data, B. P. Abbott, R. Abbott, T. D. Abbott, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Malik Rakhmanov, Joseph D. Romano

Physics & Astronomy Faculty Publications

We report on a comprehensive all-sky search for periodic gravitational waves in the frequency band 100-1500 Hz and with a frequency time derivative in the range of [-1.18,+1.00]×10-8 Hz/s. Such a signal could be produced by a nearby spinning and slightly nonaxisymmetric isolated neutron star in our galaxy. This search uses the data from the initial LIGO sixth science run and covers a larger parameter space with respect to any past search. A Loosely Coherent detection pipeline was applied to follow up weak outliers in both Gaussian (95% recovery rate) and non-Gaussian (75% recovery rate) bands. No gravitational wave signals …

Combined Search For Lorentz Violation In Short-Range Gravity, Cheng-Gang Shao, Yu-Jie Tan, Wen-Hai Tan, Shan-Qing Yang, Jun Luo, Michael Edmund Tobar, Quentin G. Bailey, Et Al.

Publications

Short-range experiments testing the gravitational inverse-square law at the submillimeter scale offer uniquely sensitive probes of Lorentz invariance. (See article for remainder of abstract.)

Performance Of Phase And Amplitude Gradient Estimator Method For Calculating Energy Quantities In A Plane-Wave Tube Environment, Daxton A. Hawks

Student Works

Acoustic intensity, energy densities, and impedance are useful quantities when considering sound fields. Calculating these energy quantities relies on measurements of acoustic pressure and particle velocity. Pressure and particle velocity can be directly measured, but direct measurements of particle velocity are difficult to make, and are normally inaccurate. A more common and effective way to find particle velocity is to estimate it using pressure measurements from two closely-spaced microphones. The traditional way of estimating particle velocity is severely limited by frequency. The PAGE method, developed at Brigham Young University, extends the frequency bandwidth at which accurate estimations can be made. …

Daxton Hawks Reu Prospectus, Daxton A. Hawks

Student Works

The purpose of my research is to investigate the ability of the PAGE method to improve the frequency bandwidth of calculations of energy-based quantities from multiple pressure microphones. I will accomplish this by investigating sound waves in both plane-wave and standing-wave environments. I will compare the PAGE method calculations for Ia, Ir, Ep, Ek, and Z to those of traditional and analytical expressions, based on careful ambient condition monitoring. Quantifying the bandwidth extension of the PAGE method for these energy-based quantities will lay a foundation for further application.

Examination Of Resonant Modes In Microwave Cavities, Sophia Schwalbe, Gianpaolo Carosi

Student Works

The Axion Dark Matter eXperiment (ADMX) looks to detect dark matter axion particles by using microwave cavities in a high magnetic eld to convert the axion's mass energy to a detectable photon. The photon frequency corresponds to the axion mass. Tuning elements in the cavities allow the resonant frequency to be changed but only certain modes couple to the axion. Interactions with additional resonant modes that do not couple to the axion cause unobservable regions in the frequency range. This research investigated new methods to move the additional resonant modes in order to observe these regions.

Kepler-1647b: The Largest And Longest-Period Kepler Transiting Circumbinary Planet, V. B. Kostov, J. A. Orosz, W. F. Welsh, L. R. Doyle, D. C. Fabrycky, N. Haghighipour, B. Quarles, D. R. Short, W. D. Cochran, M. End, E. B. Ford, J. Gregorio, T. C. Hinse, H. Isaacson, J. M. Jenkins, Eric L.N. Jensen, S. Kane, I. Kull, D. W. Latham, J. J. Lissauer, G. W. Marcy, T. Mazeh, T. W. A. Müller, J. Pepper, S. N. Quinn, D. Ragozzine, A. Shporer, J. H. Steffen, G. Torres, G. Windmiller, W. J. Borucki

Physics & Astronomy Faculty Works

We report the discovery of a new Kepler transiting circumbinary planet (CBP). This latest addition to the still-small family of CBPs defies the current trend of known short-period planets orbiting near the stability limit of binary stars. Unlike the previous discoveries, the planet revolving around the eclipsing binary system Kepler-1647 has a very long orbital period (~1100 days) and was at conjunction only twice during the Kepler mission lifetime. Due to the singular configuration of the system, Kepler-1647b is not only the longest-period transiting CBP at the time of writing, but also one of the longest-period transiting planets. With a …

Preventing Oxidation Of Aluminum Films With Cadmium Of Zinc Barriers, Spencer B. Perry

Student Works

The planned Large UV/Optical/Near-infrared Telescope (LUVOIR) is expected to launch sometime in the 2030s if NASA surveys recommend LUVOIR over several other projects in early developmental stages [1]. As the project title suggests, the proposed telescope would include large mirrors (between 8 and 16 meters) as part of the orbiting reflector telescope. My research focused on the preparation of aluminum mirrors with zinc or cadmium barrier layers that were designed to prevent oxidation of the aluminum.

The Relation Between Stellar And Dynamical Surface Densities In The Central Regions Of Disk Galaxies, Federico Lelli, Stacy S. Mcgaugh, Marcel S. Pawlowski

Faculty Scholarship

We use the Spitzer Photometry and Accurate Rotation Curves (SPARC) database to study the relation between the central surface density of stars and dynamical mass in 135 disk galaxies (S0 to dIrr). We find that correlates tightly with over 4 dex. This central density relation can be described by a double power law. High surface brightness galaxies are consistent with a 1:1 relation, suggesting that they are self-gravitating and baryon dominated in the inner parts. Low surface brightness (LSB) galaxies systematically deviate from the 1:1 line, indicating that the dark matter contribution progressively increases but remains tightly coupled to the …

Progressive Redshifts In The Late-Time Spectra Of Type Ia Supernovae, C. S. Black, R. A. Fesen, J. T. Parrent

Dartmouth Scholarship

We examine the evolution of late-time, optical nebular features of Type Ia supernovae (SNe Ia) using a sample consisting of 160 spectra of 27 normal SNe Ia taken from the literature as well as unpublished spectra of SN 2008Q and ASASSN-14lp. Particular attention was given to nebular features between 4000-6000 A in terms of temporal changes in width and central wavelength. Analysis of the prominent late-time 4700 A feature shows a progressive central wavelength shift from ~4600 A to longer wavelengths out to at least day +300 for our entire sample. We find no evidence for the feature's red-ward shift …

High Altitude Cosmic Ray Detection, Jordan D. Van Nest

2017 Academic High Altitude Conference

Cosmic rays are high energy atomic nuclei travelling near the speed of light that collide with atoms and molecules in Earth’s upper atmosphere (primarily with nitrogen and oxygen), breaking down into a shower of particles of various energies in the stratosphere. As they travel earthward, these particles continue to break down and lose energy which results in relatively little ionizing radiation reaching the surface. Due to the scattering of cosmic rays, the angle at which the rays enter the atmosphere can affect the number and energies of ionizing particles detected at various altitudes. When using a standard Geiger counter on …

Obscured Agns In Bulgeless Hosts Discovered By Wise : The Case Study Of Sdss J1224+5555, S. Satyapal, N. J. Secrest, B. Rothberg, J. A. O’Connor, S. L. Ellison, R. C. Hickox

Dartmouth Scholarship

There is mounting evidence that supermassive black holes form and grow in bulgeless galaxies. However, a robust determination of the fraction of AGNs in bulgeless galaxies, an important constraint to models of supermassive black hole seed formation and merger-free models of AGN fueling, is unknown, since optical studies have been shown to be incomplete for low mass AGNs. In a recent study using the Wide-field Infrared Survey Explorer, we discovered hundreds of bulgeless galaxies that display mid-infrared signatures of extremely hot dust suggestive of powerful accreting massive black holes, despite having no signatures of black hole activity at optical wavelengths. …

High Efficiency Near Diffraction-Limited Mid-Infrared Flat Lenses Based On Metasurface Reflectarrays, Shuyan Zhang, Myoung Hwan Kim, Francesco Aieta, Alan She, Tobias Mansuripur, Ilan Gabay, Mohammadreza Khorasaninejad, David Rousso, Xiaojun Wang, Mariano Troccoli

Physics & Astronomy Faculty Publications

We report the first demonstration of a mid-IR reflection-based flat lens with high efficiency and near diffraction-limited focusing. Focusing efficiency as high as 80%, in good agreement with simulations (83%), has been achieved at 45° incidence angle at λ = 4.6 μm. The off-axis geometry considerably simplifies the optical arrangement compared to the common geometry of normal incidence in reflection mode which requires beam splitters. Simulations show that the effects of incidence angle are small compared to parabolic mirrors with the same NA. The use of single-step photolithography allows large scale fabrication. Such a device is important in the development …

Spectroscopic Orbits For 15 Late-Type Stars, Daryl W. Willmarth, Francis C. Fekel, Helmut A. Abt, Dimitri Pourbaix

Information Systems and Engineering Management Research Publications

Spectroscopic orbital elements are determined for 15 stars with periods from 8 to 6528 days with six orbits computed for the first time. Improved astrometric orbits are computed for two stars and one new orbit is derived. Visual orbits were previously determined for four stars, four stars are members of multiple systems, and five stars have Hipparcos "G" designations or have been resolved by speckle interferometry. For the nine binaries with previous spectroscopic orbits, we determine improved or comparable elements. For HD 28271 and HD 200790, our spectroscopic results support the conclusions of previous authors that the large values of …

Planet Formation Imager (Pfi): Science Vision And Key Requirements, S. Kraus, J. D. Monnier, M. J. Ireland, G. Duchêne, C. Espaillat, S. Hönig, A. Juhasz, C. Mordasini, J. Olofsson, C. Paladini, K. Stassun, N. Turner, G. Vasisht, T. J. Harries, M. R. Bate, J.-F. Gonzalez, A. Matter, Z. Zhu, O. Panic, Z. Regaly, A. Morbidelli, F. Meru, S. Wolf, J. Ilee, J.-P. Berger, M. Zhao, Q. Kral, A. Morlok, A. Bonsor, D. Ciardi, S. R. Kane, K. Kratter, G. Laughlin, J. Pepper, S. Raymond, L. Labadie, R. P. Nelson, G. Weigelt, T. Ten Brummelaar, A. Pierens, R. Oudmaijer, W. Kley, B. Pope, Eric L.N. Jensen, A. Bayo, M. Smith, T. Boyajian, L. H. Quiroga-Nuñez, R. Millan-Gabet, A. Chiavassa, A. Gallenne, M. Reynolds, W.-J. De Wit, M. Wittkowski, F. Millour, P. Gandhi, C. Ramos Almeida, A. Alonso Herrero, C. Packham, M. Kishimoto, K. R. W. Tristram, J.-U. Pott, J. Surdej, D. Buscher, C. Haniff, S. Lacour, R. Petrov, S. Ridgway, P. Tuthill, G. Van Belle, P. Armitage, C. Baruteau, M. Benisty, B. Bitsch, S.-J. Paardekooper, C. Pinte, F. Masset, G. Rosotti

Physics & Astronomy Faculty Works

The Planet Formation Imager (PFI) project aims to provide a strong scientific vision for ground-based optical astronomy beyond the upcoming generation of Extremely Large Telescopes. We make the case that a breakthrough in angular resolution imaging capabilities is required in order to unravel the processes involved in planet formation. PFI will be optimised to provide a complete census of the protoplanet population at all stellocentric radii and over the age range from 0.1 to ~100 Myr. Within this age period, planetary systems undergo dramatic changes and the final architecture of planetary systems is determined. Our goal is to study the …

The Turning-Off Of Supernova Remnants: The Transition Into The Radiative Phase, Ryan A. Lazur, Rodolfo Barniol Duran, Dimitrios Giannios

The Summer Undergraduate Research Fellowship (SURF) Symposium

Supernovae are amongst the most energetic events in the Universe. Understanding the different stages of the life of a supernova is currently one of the main objectives in astrophysics. During a supernova explosion, material with mass several times that of the Sun is ejected with a speed about 1/10 that of light. In current models, the transition from the Sedov-Taylor to the radiative phase is assumed to be almost instantaneous, which is not entirely accurate. Here the physics of the transition to the radiative phase will be revisited. Observations indicate that the supernova ejecta remains bright in the radio band …

Hst Hot-Jupiter Transmission Spectral Survey: Clear Skies For Cool Saturn Wasp-39b, Patrick D. Fischer, Heather Knutson, David K. Sing, Gregory W. Henry, Michael H. Williamson, Jonathan J. Fortney, Adam S. Burrows, Tiffany Kataria, Nikolay Nikolov, Adam P. Showman, Gilda E. Ballester, Jean-Michel Désert, Suzanne Aigrain, Drake Deming, Alain Lecavelier Des Etangs, Alfred Vidal-Madjar

Information Systems and Engineering Management Research Publications

We present the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) optical transmission spectroscopy of the cool Saturn-mass exoplanet WASP-39b from 0.29-1.025 μm, along with complementary transit observations from Spitzer IRAC at 3.6 and 4.5 μm. The low density and large atmospheric pressure scale height of WASP-39b make it particularly amenable to atmospheric characterization using this technique. We detect a Rayleigh scattering slope as well as sodium and potassium absorption features; this is the first exoplanet in which both alkali features are clearly detected with the extended wings predicted by cloud-free atmosphere models. The full transmission spectrum is well …