Astrophysics and Astronomy Commons^™

Variability Of The Coronal Line Region In Ngc 4151, Hermine Landt, Martin J. Ward, Katrien C. Steenbrugge, Gary J. Ferland

Physics and Astronomy Faculty Publications

We present the first extensive study of the coronal line variability in an active galaxy. Our data set for the nearby source NGC 4151 consists of six epochs of quasi-simultaneous optical and near-infrared spectroscopy spanning a period of about 8 yr and five epochs of X-ray spectroscopy overlapping in time with it. None of the coronal lines showed the variability behaviour observed for the broad emission lines and hot dust emission. In general, the coronal lines varied only weakly, if at all. Using the optical [Fe vii] and X-ray O vii emission lines we estimate that the coronal line gas …

A Statistical Study Of The Dawn-Dusk Asymmetry Of Ion Temperature Anistrophy And Mirror Mode Occurrence In The Terrestrial Dayside Magnetosheath Using Themis Data, A. P. Dimmock, A. Osmane, T. I. Pulkkinen, K. Nykyri

Publications

We present a statistical study of ion temperature anisotropy and mirror mode activity in the Earth's dayside magnetosheath using 6 years of Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations focusing on the quantification of dawn-dusk asymmetry as a function of upstream conditions and distance from the magnetopause. Our statistical data show a pronounced dusk favored asymmetry of T⊥/T∥ which drives a similar asymmetry of mirror mode activity. T⊥/T∥ decreases with increasing solar wind Alfvén Mach number, whereas mirror mode occurrence increases. In both cases, the relative asymmetry between the dawn and dusk flanks decrease with increasing …

Simulation Of Energetic Particle Precipitation Effects During The 2003-2004 Arctic Winter, C. E. Randall, V. L. Harvey, L. A. Holt, D. R. Marsh, D. Kinnison, B. Funke, P. F. Bernath

Chemistry & Biochemistry Faculty Publications

Energetic particle precipitation (EPP) during the 2003-2004 Arctic winter led to the production and subsequent transport of reactive odd nitrogen (NO_x=NO+NO₂) from the mesosphere and lower thermosphere (MLT) into the stratosphere. This caused NO_x enhancements in the polar upper stratosphere in April 2004 that were unprecedented in the satellite record. Simulations of the 2003-2004 Arctic winter with the Whole Atmosphere Community Climate Model using Specified Dynamics (SD-WACCM) are compared to satellite measurements to assess our understanding of the observed NO_x enhancements. The comparisons show that SD-WACCM clearly displays the descent of NO_x produced …

Characterization Of Order-Disorder Phase Transition Temperature For Select Nanoparticles, Gregory J. Sutherland

Theses and Dissertations

A method was found for creating ordered nanoparticles whose size and theoretical order-disorder temperature are ideal for study in the TEM. Specifically FePt, NiPt, FeNiPt and AuCu nanoparticles were studied. We were able to show how a nanoparticle's size affects its order-disorder temperature (Tod). When the particles were around 6 nm in diameter there was a shift downward of the Tod of 10-15 percent compared to the bulk. While particles around 10 nm in diameter experienced a downward shift of 0-6 percent compared to the bulk. One can approximate that particles less than 10-15 nm in diameter would show significant …

Galaxy And Mass Assembly (Gama) Blended Spectra Catalogue : Strong Galaxy–Galaxy Lens And Occulting Galaxy Pair Candidates., Benne W. Holwerda, I. K. Baldry, M. Alpaslan, A. E. Bauer, J. Bland-Hawthorn, S. Brough, M. J. I. Brown, M. E. Cluver, C. J. Conselice, S. P. Driver, A. M. Hopkins, D. H. Jones, Angel R. Lopez-Sanchez, J. Loveday, M. J. Meyer, A. Moffett

Faculty and Staff Scholarship

We present the catalogue of blended galaxy spectra from the Galaxy And Mass Assembly (GAMA) survey. These are cases where light from two galaxies are significantly detected in a single GAMA fibre. Galaxy pairs identified from their blended spectrum fall into two principal classes: they are either strong lenses, a passive galaxy lensing an emission-line galaxy; or occulting galaxies, serendipitous overlaps of two galaxies, of any type. Blended spectra can thus be used to reliably identify strong lenses for follow-up observations (high-resolution imaging) and occulting pairs, especially those that are a late-type partly obscuring an early-type galaxy which are of …

Book Review: The Scientific Exploration Of Venus, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of The Scientific Exploration of Venus, by Fredric W. Taylor. Cambridge, 2014 295p bibl index, 9781107023482 $48.00

Magnetic Flux Circulation In The Rotationally Driven Giant Magnetospheres, P. A. Delamere, A. Otto, X. Ma, F. Bagenal, R. J. Wilson

Publications

The giant‐planet magnetodiscs are shaped by the radial transport of plasma originating in the inner magnetosphere. Magnetic flux transport is a key aspect of the stretched magnetic field configuration of the magnetodisc. While net mass transport is outward (ultimately lost to the solar wind), magnetic flux conservation requires a balanced two‐way transport process. Magnetic reconnection is a critical aspect of the balanced flux transport. We present a comprehensive analysis of current sheet crossings in Saturn's magnetosphere using Cassini magnetometer data from 2004 to 2012 in an attempt to quantify the circulation of magnetic flux, emphasizing local time dependence. A key …

Defining The Circumstellar Habitable Zone, Blake Cervetti, Joanna Mccall

DePaul Discoveries

The study of habitable exoplanets is a rapidly expanding field in astronomy. Exoplanets are planets that orbit stars other than our own sun. One of the keys to knowing whether or not an exoplanet is habitable is by studying the circumstellar habitable zone, or CHZ. Over the past several years, the defined limits of the CHZ have become susceptible to change as new parameters and factors are found to affect a planets habitability. There are many factors that affect its habitability, including the composition of the star, the mass of the planet, the planets atmosphere, etc. Our focus is divided …

Detection Of Baryonic Acoustic Oscillations In The Matter Power Spectrum, Spencer Everett, Ian Johnson, Jon Murphy, Mary Tarpley

DePaul Discoveries

Using the spectra of 22,923 high-redshift quasars from the Baryon Oscillation Spectrosocpic Survey (BOSS) subset of the Sloan Digital Sky Survey (SDSS), the authors detect evidence of the primordial baryonic acoustic oscillations (BAOs) in the matter power spectrum. The detection further endorses the currently accepted Lambda-CDM model of cosmology based upon the existence of dark energy (Lambda) and cold dark matter (CDM). Additionally, the use of the continuous wavelet transform to calculate the power spectrum has many advantages over traditional Fourier methods and independently corroborates previous detections.

Crystal Growth And Electronic Phase Diagram Of 4D-Doped Na1-ΔFe1-XRhXAs In Comparison To 3D-Doped Na1-ΔFe1-XCoXAs, Frank Steckel, Maria Roslova, Robert Beck, Igor Morozov, Saicharan Aswartham, Daniil Evtushinsky, Christian G. F. Blum, Mahmoud Abdel-Hafiez, Dirk Bombor, Janek Maletz, Sergey Borisenko, Andrei V. Shevelkov, Anja U. B. Wolter, Christian Hess, Sabine Wurmehl, Bernd Büchner

Physics and Astronomy Faculty Publications

Single crystals of Na_1−δFe_1−xT_xAs with T = Co, Rh have been grown using a self-flux technique. The crystals were thoroughly characterized by powder x-ray diffraction, magnetic susceptibility, and electronic transport with particular focus on the Rh-doped samples. Measurements of the specific heat and ARPES were conducted exemplarily for the optimally doped compositions. The spin-density wave transition (SDW) observed for samples with low Rh concentration (0≤x≤0.013) is fully suppressed in the optimally doped sample. The superconducting transition temperature (T_c) is enhanced from 10 K in Na_1−δFeAs to 21 …

Investigating The Correlation Between Inclination Of Coronal Loops And Solar Flare Activity, John-Paul Mann

Symposium Of University Research and Creative Expression (SOURCE)

The purpose of this research is to investigate changes in the coronal loop structures during the life cycle of a solar flare. Coronal loops are intricate and complicated magnetic features on the solar surface that are the source of large solar flares. Understanding the dynamics of these coronal loops provides better models for predicting solar flare activity. By obtaining the magnetogram, or magnetic field strength, along with the inclination of these coronal loops, the full structure of the coronal loop can be obtained. Therefore, we studied how the coronal loops inclination angle, as it emerges from the photosphere, changes in …

Predicting Solar Sigmoid Lifetimes Based On Shearing In The Photosphere, Austen Stone

Symposium Of University Research and Creative Expression (SOURCE)

This project’s purpose was to study how the speed at which the plasma in the photosphere of the sun affects the lifetime and shape of a solar sigmoid. Solar sigmoids are S-shaped, twisted magnetic structures that are due to the shifting magnetic field lines emerging from the surface of the sun. The photosphere is the visible layer of the sun’s surface and is made up of cells of plasma that are highly conductive and influenced by the magnetic field of the sun. Sigmoids form when shearing (a lateral shift between two objects in directions opposite each other) occurs in the …

New Constraints On Quantum Gravity From X-Ray And Gamma-Ray Observations, Eric S. Perlman, Saul A. Rappaport, Wayne A. Christiansen, Yeejack Ng, John G. Devore, David A. Pooley

Aerospace, Physics, and Space Science Faculty Publications

One aspect of the quantum nature of spacetime is its “foaminess” at very small scales. Many models for spacetime foam are defined by the accumulation power α, which parameterizes the rate at which Planck-scale spatial uncertainties (and the phase shifts they produce) may accumulate over large path lengths. Here α is defined by the expression for the path-length fluctuations, dℓ, of a source at distance ℓ, wherein dℓ  ℓ1-aℓ a P , with ℓP being the Planck length. We reassess previous proposals to use astronomical observations of distant quasars and active galactic nuclei to test models of spacetime foam. …

Metal-Poor, Strongly Star-Forming Galaxies In The Deep2 Survey: The Relationship Between Stellar Mass, Temperature-Based Metallicity, And Star Formation Rate, Chun Ly, Jane R. Rigby, Michael Cooper, Renbin Yan

Physics and Astronomy Faculty Publications

We report on the discovery of 28 z ≈ 0.8 metal-poor galaxies in DEEP2.

For the remainder of the abstract, please download this article or visit https://doi.org/10.1088/0004-637X/805/1/45.

Isolation Of Flow And Nonflow Correlations By Two- And Four-Particle Cumulant Measurements Of Azimuthal Harmonics In √SNn=200 Gev Au+Au Collisions, James K. Adkins, Renee H. Fatemi, Suvarna Ramachandran, N. M. Abdelwahab, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin

Physics and Astronomy Faculty Publications

A data-driven method was applied to Au+Au collisions at √sNN = 200 GeV made with the STAR detector at RHIC to isolate pseudorapidity distance Δη-dependent and Δη-independent correlations by using two- and four-particle azimuthal cumulant measurements. We identified a Δη-independent component of the correlation, which is dominated by anisotropic flow and flow fluctuations. It was also found to be independent of η within the measured range of pseudorapidity |η| < 1. In 20–30% central Au+Au colli- sions, the relative flow fluctuation was found to be 34% ± 2%(stat.) ± 3%(sys.) for particles with transverse momentum P_T less than 2 GeV/c. The Δη-dependent part, attributed to nonflow correlations, is found to be 5% ± 2%(sys.) relative to the flow …

Galaxy Pairs In The Sloan Digital Sky Survey - Xii. The Fuelling Mechanism Of Low-Excitation Radio-Loud Agn, Sara L. Ellison, David R. Patton, Ryan C. Hickox

Dartmouth Scholarship

We investigate whether the fuelling of low-excitation radio galaxies (LERGs) is linked to major galaxy interactions. Our study utilizes a sample of 10 800 spectroscopic galaxy pairs and 97 post-mergers selected from the Sloan Digital Sky Survey with matches to multiwavelength data sets. The LERG fraction amongst interacting galaxies is a factor of 3.5 higher than that of a control sample matched in local galaxy density, redshift and stellar mass. However, the LERG excess in pairs does not depend on projected separation and remains elevated out to at least 500 h70−1" role="presentation">h−170

kpc, suggesting that major mergers are not …

Fermi-Bounce Cosmology And The Fermion Curvaton Mechanism, Stephon Alexander, Yi-Fu Cai, Antonino Marcianò

Dartmouth Scholarship

A nonsingular bouncing cosmology can be achieved by introducing a fermion field with BCS condensation occurring at high energy scales. In this paper we are able to dilute the anisotropic stress near the bounce by means of releasing the gap energy density near the phase transition between the radiation and condensate states. In order to explain the nearly scale-invariant CMB spectrum, another fermion field is required. We investigate one possible curvaton mechanism by involving one another fermion field without condensation where the mass is lighter than the background field. We show that, by virtue of the fermion curvaton mechanism, our …

Disappearance Of Plasmaspheric Hiss Following Interplanetary Shock, Zhenpeng Su, Hui Zhu, Fuliang Xiao, Yuming Wang, Chao Shen, Min Zhang, Shui Wang, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, Harlan E. Spence, Geoffrey Reeves, H. O. Funsten, J. B. Blake, D. N. Baker, J. R. Wygant

Physics & Astronomy

Abstract Plasmaspheric hiss is one of the important plasma waves controlling radiation belt dynamics. Its spatiotemporal distribution and generation mechanism are presently the object of active research. We here give the first report on the shock-induced disappearance of plasmaspheric hiss observed by the Van Allen Probes on 8 October 2013. This special event exhibits the dramatic variability of plasmaspheric hiss and provides a good opportunity to test its generation mechanisms. The origination of plasmaspheric hiss from plasmatrough chorus is suggested to be an appropriate prerequisite to explain this event. The shock increased the suprathermal electron fluxes, and then the enhanced …

Unprecedented Study Of The Broadband Emission Of Mrk 421 During Flaring Activity In March 2010, P. T. Reynolds, Et. Al.

Physical Sciences Publications

Context. Because of its proximity, Mrk 421 is one of the best sources on which to study the nature of BL Lac objects. Its proximity allows us to characterize its broadband spectral energy distribution (SED).

Aims. The goal is to better understand the mechanisms responsible for the broadband emission and the temporal evolution of Mrk 421. These mechanisms may also apply to more distant blazars that cannot be studied with the same level of detail.

Methods. A flare occurring in March 2010 was observed for 13 consecutive days (from MJD 55 265 to MJD 55 277) with unprecedented wavelength coverage …

High-Energy Electronic Excitations In Sr2Iro4 Observed By Raman Scattering, Jhih-An Yang, Yi-Ping Huang, Michael Hermele, Tongfei Qi, Gang Cao, Dmitry Reznik

Physics and Astronomy Faculty Publications

Spin-orbit interaction in Sr₂IrO₄ leads to the realization of the J_eff=1/2 state and also induces an insulating behavior. Using large-shift Raman spectroscopy, we found two high-energy excitations of the d-shell multiplet at 690 and 680 meV with A_1g and B_1g symmetry, respectively. As temperature decreases, the A_1g and B_1g peaks narrow, and the A_1g peak shifts to higher energy while the energy of the B_1g peak remains the same. When 25% of Ir is substituted with Rh the A_1g peak softens by 10% but the B …