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Articles 1351 - 1380 of 2945

Full-Text Articles in Astrophysics and Astronomy

The Detection And Characterization Of Extrasolar Planets, Zachary Richards Jan 2016

The Detection And Characterization Of Extrasolar Planets, Zachary Richards

Legacy Theses & Dissertations (2009 - 2024)

The study of extra-solar planets (exoplanets) is a rapidly expanding field, which aims to detect, characterize, and understand how other planetary systems form and behave. Observing an exoplanet transit its host star allows us to detect the exoplanet in the light curve. As an exoplanet transits, there will be a dip in the total flux (light per unit area) of the host star visible in the light curve. While observing an exoplanet transit, several photometric effects may influence the light curve. We consider the following photometric effects: reflected light, Doppler boosting (beaming), thermal emission, and ellipsoidal variation. This study relies …

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Bayesian Model Testing Of Models For Ellipsoidal Variation On Stars Due To Hot Jupiters, Anthony Gai Jan 2016

Bayesian Model Testing Of Models For Ellipsoidal Variation On Stars Due To Hot Jupiters, Anthony Gai

Legacy Theses & Dissertations (2009 - 2024)

A massive planet closely orbiting its host star creates tidal forces that distort the typically spherical stellar surface. These distortions, known as ellipsoidal variations, result in variations in the photometric flux emitted by the star, which can be detected by the Kepler Space Telescope. Currently, there exist several models describing such variations and their effect on the photometric fux [1] [2] [3] [4]. By using Bayesian model testing in conjunction with the Bayesian-based exoplanet characterization software package EXONEST [4] [5] [6], the most probable representation for ellipsoidal variations was determined for synthetic data and two systems with confirmed hot Jupiter …

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Characterizing Crop Photomultiplier Tube Behavior At 1000 Volts, Zachary T. Smith Jan 2016

Characterizing Crop Photomultiplier Tube Behavior At 1000 Volts, Zachary T. Smith

UCARE: Research Products

In an effort to prolong the lifetime of their Photomultiplier tubes (PMTs), the Cosmic Ray Observatory Project (CROP) made the decision to begin operating the PMTs at an operating voltage of 1000 Volts. The aim of this project was to characterize the fundamental behavior of the PMTs at this operating voltage using several tests. These tests include determining the optimal threshold level of the PMTs, the PMT efficiency, and the time stability of the PMT's output.

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Construction Of An Optical Fiber Strian Gauge, Najwa Sulaiman Jan 2016

Construction Of An Optical Fiber Strian Gauge, Najwa Sulaiman

Master's Theses and Doctoral Dissertations

This project is focused on the construction of an optical fiber strain gauge that is based on a strain gauge described by Butter and Hocker. Our gauge is designed to generate an interference pattern from the signals carried on two bare single-mode fibers that are fastened to an aluminum cantilever. When the cantilever experiences flexural stress, the interference pattern should change. By observing this change, it is possible to determine the strain experienced by the cantilever. I describe the design and construction of our optical fiber strain gauge as well as the characterization of different parts of the apparatus.

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Saturn's Rings: Measuring Particle Size Distributions Using Cassini Uvis Occultation Data, Tracy Becker Jan 2016

Saturn's Rings: Measuring Particle Size Distributions Using Cassini Uvis Occultation Data, Tracy Becker

Electronic Theses and Dissertations

Since its arrival to Saturn in 2004, the Cassini spacecraft has utilized its suite of sophisticated instruments to further our understanding of the Saturnian ring system. We analyze occultation data from Cassini's Ultraviolet Imaging Spectrograph (UVIS) in order to measure the particle size distribution and place limits on the minimum particle sizes in Saturn's rings. Throughout the ring system, particle accretion is countered by collisional and tidal disruption and Keplerian shear. Therefore, the particle size distribution of the rings is continually evolving. The presence of sub-centimeter particles, which have short lifetimes due to these processes, is indicative of ongoing dynamics …

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Equation Of State Of A Dense And Magnetized Neutron System, Md Masud Jan 2016

Equation Of State Of A Dense And Magnetized Neutron System, Md Masud

Open Access Theses & Dissertations

Neutron stars (NSs) are the windows to check the validation of physical laws at extreme conditions, for example, at very high densities and strong magnetic fields and thus to reach the equations of state (EoS) for a better understanding of the structure as well as the composition of the NSs. In our investigations, it is found that the system's (NSs) pressure becomes anisotropic due to the breaking of rotational symmetry in the presence of strong magnetic fields, which even can be significantly sufficient to lead into the deformation of NSs or to destroy itself.

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First Measurement Of The Helicity Asymmetry E In Ƞ Photoproduction On The Proton, I. Senderovich, B.T. Morrison, M. Dugger, B.G. Ritchie, E. Pasyuk, R. Tucker, J. Brock, C. Carlin, C.D. Keith, D. G. Meekins, Y. Prok Jan 2016

First Measurement Of The Helicity Asymmetry E In Ƞ Photoproduction On The Proton, I. Senderovich, B.T. Morrison, M. Dugger, B.G. Ritchie, E. Pasyuk, R. Tucker, J. Brock, C. Carlin, C.D. Keith, D. G. Meekins, Y. Prok

Physics Faculty Publications

Results are presented for the first measurement of the double-polarization helicity asymmetry E for the ƞ photoproduction reaction ɣp -> ηp. Data were obtained using the FROzen Spin Target (FROST) with the CLAS spectrometer in Hall B at Jefferson Lab, covering a range of center-of-mass energy W from threshold to 2.15 GeV and a large range in center-of-mass polar angle. As an initial application of these data, the results have been incorporated into the Jülich-Bonn model to examine the case for the existence of a narrow N* resonance between 1.66 and 1.70 GeV. The addition of these data to the …

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Measurements Of Dⁿ² And Aⁿ¹: Probing The Neutron Spin Structure, D. Flay, M. Posik, D. S. Parno, K. Allada, M. Canan, C. Hyde, Jefferson Lab Hall A Collaboration Jan 2016

Measurements Of Dⁿ² And Aⁿ¹: Probing The Neutron Spin Structure, D. Flay, M. Posik, D. S. Parno, K. Allada, M. Canan, C. Hyde, Jefferson Lab Hall A Collaboration

Physics Faculty Publications

We report on the results of the E06-014 experiment performed at Jefferson Lab in Hall A, where a precision measurement of the twist-3 matrix element d2 of the neutron dⁿ2 was conducted. The quantity dⁿ2 represents the average color Lorentz force a struck quark experiences in a deep inelastic electron scattering event off a neutron due to its interaction with the hadronizing remnants. This color force was determined from a linear combination of the third moments of the 3He spin structure functions, g1 and g2, after nuclear corrections had been applied to these …

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Dynamical Formation Of Protoplanetesimals, Akbar Whizin Jan 2016

Dynamical Formation Of Protoplanetesimals, Akbar Whizin

Electronic Theses and Dissertations

The seeds of planetesimals that formed in the gaseous protoplanetary disk (PPD) have many barriers to overcome in their growth from millimeter to meter-sized and larger bodies. Centimeter-sized aggregates are weakly bound and self-gravity is almost non-existent so surface forces play a critical role in holding small loosely-bound rubble-piles together. Their orbital motions and effects form disk processes impart relative velocities leading to collisions so understanding the macroscopic disk environment is also necessary. To this end we analyze the dynamics of particles in Saturn's F ring as an analogue to understanding the orbital evolution of proto-planetesimals embedded in a PPD. …

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Spectroscopic And Spectro-Astrometric Analysis Of T Tauri Stars, Logan Ryan Brown Jan 2016

Spectroscopic And Spectro-Astrometric Analysis Of T Tauri Stars, Logan Ryan Brown

Doctoral Dissertations

"To understand our own solar origins, we must investigate the composition of the protoplanetary disk from which the solar system formed. To infer this, we study analogs to the early solar system called T Tauri stars. These objects are low-mass, pre-main sequence stars surrounded by circumstellar disks of material from which planets are believed to form. We present high-resolution, near-infrared spectroscopic data for the T Tauri stars DR Tau and AA Tau using NIRSPEC at the Keck II telescope. For DR Tau, a spectro-astrometric analysis was performed, obtaining sub-seeing spatial information on water emission. Alongside a disk model, we constrained …

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Mapping Gravitational-Wave Backgrounds Of Arbitrary Polarisation Using Pulsar Timing Arrays, Jonathan Gair, Joseph D. Romano, Stephen R. Taylor Dec 2015

Mapping Gravitational-Wave Backgrounds Of Arbitrary Polarisation Using Pulsar Timing Arrays, Jonathan Gair, Joseph D. Romano, Stephen R. Taylor

Physics & Astronomy Faculty Publications

We extend our previous work on mapping gravitational-wave backgrounds using techniques borrowed from the analysis of cosmic microwave background data to backgrounds which have non-general-relativity (non-GR) polarisations. Our analysis and results are presented in the context of pulsar timing array observations, but the overarching methods are general, and can be easily applied to LIGO or eLISA observations using appropriately modified response functions. Analytic expressions for the pulsar timing response to gravitational waves with non-GR polarisation are given for each mode of a spin-weighted spherical-harmonic decomposition of the background, which permit the signal to be mapped across the sky to any …

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Sdss-Iv/Manga: Spectrophotometric Calibration Technique, Renbin Yan, Christy Tremonti, Matthew A. Bershady, David R. Law, David J. Schlegel, Kevin Bundy, Niv Drory, Nicholas Macdonald, Dmitry Bizyaev, Guillermo A. Blanc, Michael R. Blanton, Brian Cherinka, Arthur Eigenbrot, James E. Gunn, Paul Harding, David W. Hogg, José R. Sánchez-Gallego, Sebastian F. Sánchez, David A. Wake, Anne-Marie Weijmans, Ting Xiao, Kai Zhang Dec 2015

Sdss-Iv/Manga: Spectrophotometric Calibration Technique, Renbin Yan, Christy Tremonti, Matthew A. Bershady, David R. Law, David J. Schlegel, Kevin Bundy, Niv Drory, Nicholas Macdonald, Dmitry Bizyaev, Guillermo A. Blanc, Michael R. Blanton, Brian Cherinka, Arthur Eigenbrot, James E. Gunn, Paul Harding, David W. Hogg, José R. Sánchez-Gallego, Sebastian F. Sánchez, David A. Wake, Anne-Marie Weijmans, Ting Xiao, Kai Zhang

Physics and Astronomy Faculty Publications

Mapping Nearby Galaxies at Apache Point Observatory (MaNGA), one of three core programs in the Sloan Digital Sky Survey-IV, is an integral-field spectroscopic survey of roughly 10,000 nearby galaxies. It employs dithered observations using 17 hexagonal bundles of 2'' fibers to obtain resolved spectroscopy over a wide wavelength range of 3600–10300 Å. To map the internal variations within each galaxy, we need to perform accurate spectral surface photometry, which is to calibrate the specific intensity at every spatial location sampled by each individual aperture element of the integral field unit. The calibration must correct only for the flux loss due …

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A Deep Look At The Nuclear Region Of Ugc 5101 Through High Angular Resolution Mid-Ir Data With Gtc/Canaricam, M. Martínez-Paredes, Almudena Alonso-Herrero, Itziar Aretxaga, C. Ramos Almeida, A. Hernán-Caballero, O. González-Martín, M. Pereira-Santaella, Christopher Packham, A. Asensio Ramos, T. Díaz-Santos, Moshe Elitzur, P. Esquej, I. García-Bernete, Masatoshi Imanishi, Nancy A. Levenson, José Miguel Rodríguez Espinosa Dec 2015

A Deep Look At The Nuclear Region Of Ugc 5101 Through High Angular Resolution Mid-Ir Data With Gtc/Canaricam, M. Martínez-Paredes, Almudena Alonso-Herrero, Itziar Aretxaga, C. Ramos Almeida, A. Hernán-Caballero, O. González-Martín, M. Pereira-Santaella, Christopher Packham, A. Asensio Ramos, T. Díaz-Santos, Moshe Elitzur, P. Esquej, I. García-Bernete, Masatoshi Imanishi, Nancy A. Levenson, José Miguel Rodríguez Espinosa

Physics and Astronomy Faculty Publications

We present an analysis of the nuclear infrared (IR, 1.6–18 μm) emission of the ultraluminous IR galaxy UGC 5101 to derive the properties of its active galactic nucleus (AGN) and its obscuring material. We use new mid-IR high angular resolution (0.3–0.5 arcsec) imaging using the Si-2 filter (λC = 8.7 μm) and 7.5–13 μm spectroscopy taken with CanariCam (CC) on the 10.4 m Gran Telescopio CANARIAS. We also use archival Hubble Space Telescope/NICMOS and Subaru/COMICS imaging and Spitzer/IRS spectroscopy. We estimate the near- and mid-IR unresolved nuclear emission by modelling the imaging data with GALFIT. We decompose …

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Strong Variability Of The Coronal Line Region In Ngc 5548, Hermine Landt, Martin J. Ward, Katrien C. Steenbrugge, Gary J. Ferland Dec 2015

Strong Variability Of The Coronal Line Region In Ngc 5548, Hermine Landt, Martin J. Ward, Katrien C. Steenbrugge, Gary J. Ferland

Physics and Astronomy Faculty Publications

We present the second extensive study of the coronal line variability in an active galaxy. Our data set for the well-studied Seyfert galaxy NGC 5548 consists of five epochs of quasi-simultaneous optical and near-infrared spectroscopy spanning a period of about five years and three epochs of X-ray spectroscopy overlapping in time with it. Whereas the broad emission lines and hot dust emission varied only moderately, the coronal lines varied strongly. However, the observed high variability is mainly due to a flux decrease. Using the optical [Fe vii] and X-ray O vii emission lines we estimate that the coronal line gas …

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Di-Hadron Correlations With Identified Leading Hadrons In 200 Gev Au + Au And D + Au Collisions At Star, James K. Adkins, Renee H. Fatemi, Suvarna Ramachandran, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, A. Aparin, D. Arkhipkin, E. C. Aschenauer, G. S. Averichev, X. Bai Dec 2015

Di-Hadron Correlations With Identified Leading Hadrons In 200 Gev Au + Au And D + Au Collisions At Star, James K. Adkins, Renee H. Fatemi, Suvarna Ramachandran, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, A. Aparin, D. Arkhipkin, E. C. Aschenauer, G. S. Averichev, X. Bai

Physics and Astronomy Faculty Publications

The STAR Collaborationpresents for the first time two-dimensional di-hadron correlations with identified leading hadrons in 200 GeV central Au+Au and minimum-bias d+Au collisions to explore hadronization mechanisms in the quark gluon plasma. The enhancement of the jet-like yield for leading pions in Au + Au data with respect to the d + Au reference and the absence of such an enhancement for leading non-pions (protons and kaons) are discussed within the context of a quark recombination scenario. The correlated yield at large angles, specifically in the ridge region, is found to be significantly higher for leading non-pions than pions. …

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On Calculating The Current-Voltage Characteristic Of Multi-Diode Models For Organic Solar Cells, Ken Roberts, Sree Ram Valluri Dec 2015

On Calculating The Current-Voltage Characteristic Of Multi-Diode Models For Organic Solar Cells, Ken Roberts, Sree Ram Valluri

Physics and Astronomy Publications

We provide an alternative formulation of the exact calculation of the current-voltage characteristic of solar cells which have been modeled with a lumped parameters equivalent circuit with one or two diodes. Such models, for instance, are suitable for describing organic solar cells whose current-voltage characteristic curve has an inflection point, also known as an S-shaped anomaly. Our formulation avoids the risk of numerical overflow in the calculation. It is suitable for implementation in Fortran, C or on micro-controllers.

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From JEff=1/2 Insulator To P-Wave Superconductor In Single-Crystal Sr2Ir1−XRuXO4 (0≤X≤1), Shujuan Yuan, Saicharan Aswartham, Jsaminka Terzic, H. Zheng, H. D. Zhao, P. Schlottmann, Gang Cao Dec 2015

From JEff=1/2 Insulator To P-Wave Superconductor In Single-Crystal Sr2Ir1−XRuXO4 (0≤X≤1), Shujuan Yuan, Saicharan Aswartham, Jsaminka Terzic, H. Zheng, H. D. Zhao, P. Schlottmann, Gang Cao

Physics and Astronomy Faculty Publications

Sr2IrO4 is a magnetic insulator assisted by strong spin-orbit coupling (SOC) whereas Sr2RuO4 is a p-wave superconductor. The contrasting ground states have been shown to result from the critical role of the strong SOC in the iridate. Our investigation of structural, transport, and magnetic properties reveals that substituting 4dRu4+(4d4) ions for 5dIr4+(5d5) ions in Sr2IrO4 directly adds holes to the t2g bands, reduces the SOC, and thus rebalances the competing energies in single-crystal Sr …

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Supermassive Black Hole Seed Formation At High Redshifts: Long-Term Evolution Of The Direct Collapse, Isaac Shlosman, Jun-Hwan Choi, Mitchell C. Begelman, Kentaro Nagamine Dec 2015

Supermassive Black Hole Seed Formation At High Redshifts: Long-Term Evolution Of The Direct Collapse, Isaac Shlosman, Jun-Hwan Choi, Mitchell C. Begelman, Kentaro Nagamine

Physics and Astronomy Faculty Publications

We use cosmological adaptive mesh refinement code enzo zoom-in simulations to study the long-term evolution of the collapsing gas within dark matter haloes at z. This direct collapse process is a leading candidate for rapid formation of supermassive black hole (SMBH) seeds. To circumvent the Courant condition at small radii, we apply the sink particle method, focusing on evolution on scales ∼0.01–10 pc. The collapse proceeds in two stages, with the secondary runaway happening within the central 10 pc. The sink particles form when the collapsing gas requires additional refinement of the grid size at the highest refinement level. …

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Observation Of Transverse Spin-Dependent Azimuthal Correlations Of Charged Pion Pairs In P↑+P At √S=200  Gev, James K. Adkins, Renee H. Fatemi, Suvarna Ramachandran, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, A. Aparin, D. Arkhipkin, E. C. Aschenauer, G. S. Averichev Dec 2015

Observation Of Transverse Spin-Dependent Azimuthal Correlations Of Charged Pion Pairs In P↑+P At √S=200  Gev, James K. Adkins, Renee H. Fatemi, Suvarna Ramachandran, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, A. Aparin, D. Arkhipkin, E. C. Aschenauer, G. S. Averichev

Physics and Astronomy Faculty Publications

We report the observation of transverse polarization-dependent azimuthal correlations in charged pion pair production with the STAR experiment in p↑+p collisions at RHIC. These correlations directly probe quark transversity distributions. We measure signals in excess of 5 standard deviations at high transverse momenta, at high pseudorapidities η>0.5, and for pair masses around the mass of the ρ meson. This is the first direct transversity measurement in p+p collisions.

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Relative Proper Motions In The Rho Ophiuchi Cluster, Bruce Wilking, Frederick Vrba, Timothy Sullivan Dec 2015

Relative Proper Motions In The Rho Ophiuchi Cluster, Bruce Wilking, Frederick Vrba, Timothy Sullivan

Physics Faculty Works

Near-infrared images optimized for astrometry have been obtained for four fields in the high-density L 1688 cloud core over a 12 year period. The targeted regions include deeply embedded young stellar objects (YSOs) and very low luminosity objects too faint and/or heavily veiled for spectroscopy. Relative proper motions in R.A. and decl. were computed for 111 sources and again for a subset of 65 YSOs, resulting in a mean proper motion of (0,0) for each field. Assuming each field has the same mean proper motion, YSOs in the four fields were combined to yield estimates of the velocity dispersions in …

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An Organic Mixed Ion-Electron Conductor For Power Electronics, Abdellah Malti, Jesper Edberg, Hjalmar Granberg, Zia Ullah Khan, Jens W. Andreasen, Xianjie Liu, Dan Zhao, Hao Zhang, Yulong Yao, Joseph W. Brill, Isak Engquist, Mats Fahlman, Lars Wågberg, Xavier Crispin, Magnus Berggren Dec 2015

An Organic Mixed Ion-Electron Conductor For Power Electronics, Abdellah Malti, Jesper Edberg, Hjalmar Granberg, Zia Ullah Khan, Jens W. Andreasen, Xianjie Liu, Dan Zhao, Hao Zhang, Yulong Yao, Joseph W. Brill, Isak Engquist, Mats Fahlman, Lars Wågberg, Xavier Crispin, Magnus Berggren

Physics and Astronomy Faculty Publications

A mixed ionic–electronic conductor based on nanofibrillated cellulose composited with poly(3,4-ethylene-dioxythio­phene):­poly(styrene-sulfonate) along with high boiling point solvents is demonstrated in bulky electrochemical devices. The high electronic and ionic conductivities of the resulting nanopaper are exploited in devices which exhibit record values for the charge storage capacitance (1F) in supercapacitors and transconductance (1S) in electrochemical transistors.

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Electronic Structure And Insulating Gap In Epitaxial Vo2 Polymorphs, Shinbuhm Lee, Tricia L. Meyer, Changhee Sohn, Donghwa Lee, John Nichols, Dongkyu Lee, Sung S. Ambrose Seo, John W. Freeland, Tae Won Noh, Ho Nyung Lee Dec 2015

Electronic Structure And Insulating Gap In Epitaxial Vo2 Polymorphs, Shinbuhm Lee, Tricia L. Meyer, Changhee Sohn, Donghwa Lee, John Nichols, Dongkyu Lee, Sung S. Ambrose Seo, John W. Freeland, Tae Won Noh, Ho Nyung Lee

Physics and Astronomy Faculty Publications

Determining the origin of the insulating gap in the monoclinic VO2(M1) is a long-standing issue. The difficulty of this study arises from the simultaneous occurrence of structural and electronic transitions upon thermal cycling. Here, we compare the electronic structure of the M1 phase with that of single crystalline insulating VO2(A) and VO2(B) thin films to better understand the insulating phase of VO2. As these A and B phases do not undergo a structural transition upon thermal cycling, we comparatively study the origin of the gap opening in the insulating VO2 phases. …

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Scalable Synthesis And Energy Applications Of Defect Engineered Nano Materials, Mehmet Karakaya Dec 2015

Scalable Synthesis And Energy Applications Of Defect Engineered Nano Materials, Mehmet Karakaya

All Dissertations

Nanomaterials and nanotechnologies have attracted a great deal of attention in a few decades due to their novel physical properties such as, high aspect ratio, surface morphology, impurities, etc. which lead to unique chemical, optical and electronic properties. The awareness of importance of nanomaterials has motivated researchers to develop nanomaterial growth techniques to further control nanostructures properties such as, size, surface morphology, etc. that may alter their fundamental behavior. Carbon nanotubes (CNTs) are one of the most promising materials with their rigidity, strength, elasticity and electric conductivity for future applications. Despite their excellent properties explored by the abundant research works, …

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Dark Matter Halo Concentration And The Evolution Of Spiral Structure In N-Body, Barred Spiral Galaxies, Jazmin Esmeralda Berlanga Medina Dec 2015

Dark Matter Halo Concentration And The Evolution Of Spiral Structure In N-Body, Barred Spiral Galaxies, Jazmin Esmeralda Berlanga Medina

Graduate Theses and Dissertations

Motivated by the evidence of relationships between pitch angle (the tightness of spiral arm structure in the disk), P, and various indicators of central mass concentration, as well as the theoretical relationship between halo mass concentration and the density of visible matter in the central part of the galaxy, we look at a possible relationship between P and cvir (the virial concentration of the dark matter halo) in N-body simulations of barred, spiral galaxies. We also look at the evolution of pitch angle over time in higher temporal resolution than any data currently available in the literature. We find that …

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Decoupling Of The Antiferromagnetic And Insulating States In Tb-Doped Sr2Iro4, J. C. Wang, Saicharan Aswartham, Feng Ye, Jsaminka Terzic, H. Zheng, Daniel Haskel, Shalinee Chikara, Yong Choi, P. Schlottmann, Radu Custelcean, Shujuan Yuan, Gang Cao Dec 2015

Decoupling Of The Antiferromagnetic And Insulating States In Tb-Doped Sr2Iro4, J. C. Wang, Saicharan Aswartham, Feng Ye, Jsaminka Terzic, H. Zheng, Daniel Haskel, Shalinee Chikara, Yong Choi, P. Schlottmann, Radu Custelcean, Shujuan Yuan, Gang Cao

Physics and Astronomy Faculty Publications

Sr2IrO4 is a spin-orbit-coupled insulator with an antiferromagnetic (AFM) transition at TN=240K. We report results of a comprehensive study of single-crystal Sr2Ir1−xTbxO4(0≤x≤0.03). This study found that a mere 3% (x=0.03) of tetravalent Tb4+(4f7) substituting for Ir4+ (rather than Sr2+) completely suppresses the long-range collinear AFM transition but retains the insulating state, leading to a phase diagram featuring a decoupling of the magnetic interactions and charge gap. The insulating state at x=0.03 is characterized by …

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Evidence For Photoionization-Driven Broad Absorption Line Variability, Tinggui Wang, Chenwei Yang, Huiyuan Wang, Gary J. Ferland Dec 2015

Evidence For Photoionization-Driven Broad Absorption Line Variability, Tinggui Wang, Chenwei Yang, Huiyuan Wang, Gary J. Ferland

Physics and Astronomy Faculty Publications

We present a qualitative analysis of the variability of quasar broad absorption lines using the large multi-epoch spectroscopic data set of the Sloan Digital Sky Survey Data Release 10. We confirm that variations of absorption lines are highly coordinated among different components of the same ion or the same absorption component of different ions for C ɪᴠ, Si ɪᴠ, and N ᴠ. Furthermore, we show that the equivalent widths (EWs) of the lines decrease or increase statistically when the continuum brightens or dims. This is further supported by the synchronized variations of emission and absorption-line EWs when the well-established intrinsic …

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The Inferred Evolution Of The Cold Gas Properties Of Candels Galaxies At 0.5 < Z < 3.0, G. Popping, K. Caputi, S. C. Trager, Rachel S. Somerville, Avishai Dekel, Susan A. Kassin, Dale D. Kocevski, Anton M. Koekemoer, Sandra M. Faber, Henry C. Ferguson, A. Galametz, Norman A. Grogin, Yicheng Guo, Y. Lu, Arjen Van Der Wel, Benjamin J. Weiner Dec 2015

The Inferred Evolution Of The Cold Gas Properties Of Candels Galaxies At 0.5 < Z < 3.0, G. Popping, K. Caputi, S. C. Trager, Rachel S. Somerville, Avishai Dekel, Susan A. Kassin, Dale D. Kocevski, Anton M. Koekemoer, Sandra M. Faber, Henry C. Ferguson, A. Galametz, Norman A. Grogin, Yicheng Guo, Y. Lu, Arjen Van Der Wel, Benjamin J. Weiner

Physics and Astronomy Faculty Publications

We derive the total cold gas, atomic hydrogen, and molecular gas masses of approximately 24 000 galaxies covering four decades in stellar mass at redshifts 0.5 < z < 3.0, taken from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey survey. Our inferences are based on the inversion of a molecular hydrogen based star formation law, coupled with a prescription to separate atomic and molecular gas. We find that: (1) there is an increasing trend between the inferred cold gas (H i and H2), H i, and H2 mass and the stellar mass of galaxies down to stellar masses of 108 M⊙ already in place at z = 3; (2) the molecular fractions of cold gas increase with increasing stellar mass and look-back time; (3) there is hardly any evolution in the mean H i content of galaxies at fixed stellar mass; (4) the cold gas fraction and relative amount of molecular …

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Construction Of A 408 Nm Laser System For Use In Ion Interferometry, Lawrence Archibald Dec 2015

Construction Of A 408 Nm Laser System For Use In Ion Interferometry, Lawrence Archibald

Theses and Dissertations

This work reports on the construction of a 408 nm laser system designed to drive stimulated Raman transitions between the F = 4 and F = 5 2 S 1/2 states of 87 Sr + using the 2 P 3/2 state as the intermediate state. This laser system will be used as part of a 87 Sr + ion interferometer. This work also includes a discussion of relevant theory describing the interaction of the ions and laser, along with a calculation of the transition rates as a function of laser power and detuning.

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Ultraviolet Emission Lines Of Si Ii In Cool Star And Solar Spectra, Sibasish Laha, Francis P. Keenan, Gary J. Ferland, Catherine A. Ramsbottom, Kanti M. Aggarwal, Thomas R. Ayres, Marios Chatzikos, Peter A. M. Van Hoof, Robin J. R. Williams Nov 2015

Ultraviolet Emission Lines Of Si Ii In Cool Star And Solar Spectra, Sibasish Laha, Francis P. Keenan, Gary J. Ferland, Catherine A. Ramsbottom, Kanti M. Aggarwal, Thomas R. Ayres, Marios Chatzikos, Peter A. M. Van Hoof, Robin J. R. Williams

Physics and Astronomy Faculty Publications

Recent atomic physics calculations for Si ii are employed within the cloudy modelling code to analyse Hubble Space Telescope (HST) STIS ultraviolet spectra of three cool stars, β Geminorum, α Centauri A and B, as well as previously published HST/GHRS observations of α Tau, plus solar quiet Sun data from the High Resolution Telescope and Spectrograph. Discrepancies found previously between theory and observation for line intensity ratios involving the 3s23p 2PJ–3s3p2 4PJ' intercombination multiplet of Si II at ∼ 2335 Å are significantly reduced, as are those for …

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Azimuthal Anisotropy In U+U And Au+Au Collisions At Rhic, James K. Adkins, Renee H. Fatemi, Suvarna Ramachandran, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, A. Aparin, D. Arkhipkin, E. C. Aschenauer, G. S. Averichev Nov 2015

Azimuthal Anisotropy In U+U And Au+Au Collisions At Rhic, James K. Adkins, Renee H. Fatemi, Suvarna Ramachandran, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, A. Aparin, D. Arkhipkin, E. C. Aschenauer, G. S. Averichev

Physics and Astronomy Faculty Publications

Collisions between prolate uranium nuclei are used to study how particle production and azimuthal anisotropies depend on initial geometry in heavy-ion collisions. We report the two- and four-particle cumulants, v2{2} and v2{4}, for charged hadrons from U+U collisions at √sNN=193  GeV and Au+Au collisions at √sNN=200  GeV. Nearly fully overlapping collisions are selected based on the energy deposited by spectators in zero degree calorimeters (ZDCs). Within this sample, the observed dependence of v2{2} on multiplicity demonstrates that ZDC information combined with multiplicity can preferentially select different overlap configurations …

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