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- Numerical methods (5)
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- Ring Nebula NGC 6720 (3)
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Articles 1 - 30 of 35
Full-Text Articles in Physics
Evolution Of Magnetism In The Single-Crystal Honeycomb Iridates (Na1−XLiX)2Iro3, Gang Cao, Tongfei Qi, L. Li, Jsaminka Terzic, Vincent Shian Cao, Shujuan Yuan, M. Tovar, Ganpathy Murthy, Ribhu K. Kaul
Evolution Of Magnetism In The Single-Crystal Honeycomb Iridates (Na1−XLiX)2Iro3, Gang Cao, Tongfei Qi, L. Li, Jsaminka Terzic, Vincent Shian Cao, Shujuan Yuan, M. Tovar, Ganpathy Murthy, Ribhu K. Kaul
Physics and Astronomy Faculty Publications
We report the successful synthesis of single crystals of the layered iridate (Na1−xLix)2IrO3, 0 ≤ x ≤ 0.9, and a thorough study of its structural, magnetic, thermal, and transport properties. This compound allows a controlled interpolation between Na2IrO3 and Li2IrO3, while maintaining the quantum magnetism of the honeycomb Ir4+ planes. The measured phase diagram demonstrates a suppression of the Néel temperature TN at an intermediate x, indicating that the magnetic orders in Na2IrO3 and Li2IrO3 …
Molecular Hydrogen Regulated Star Formation In Cosmological Smoothed Particle Hydrodynamics Simulations, Robert Thompson, Kentaro Nagamine, Jason Jaacks, Jun-Hwan Choi
Molecular Hydrogen Regulated Star Formation In Cosmological Smoothed Particle Hydrodynamics Simulations, Robert Thompson, Kentaro Nagamine, Jason Jaacks, Jun-Hwan Choi
Physics and Astronomy Faculty Publications
Some observations have shown that star formation (SF) correlates tightly with the presence of molecular hydrogen (H2); therefore, it is important to investigate its implication on galaxy formation in a cosmological context. In the present work, we implement a sub-grid model (hereafter H2-SF model) that tracks the H2 mass fraction within our cosmological smoothed particle hydrodynamics code GADGET-3 by using an equilibrium analytic model of Krumholz et al. This model allows us to regulate the SF in our simulation by the local abundance of H2 rather than the total cold gas density, which naturally …
Atomic Data For S Ii—Toward Better Diagnostics Of Chemical Evolution In High-Redshift Galaxies, Romas Kisielius, Varsha P. Kulkarni, Gary J. Ferland, Pavel Bogdanovich, Matt L. Lykins
Atomic Data For S Ii—Toward Better Diagnostics Of Chemical Evolution In High-Redshift Galaxies, Romas Kisielius, Varsha P. Kulkarni, Gary J. Ferland, Pavel Bogdanovich, Matt L. Lykins
Physics and Astronomy Faculty Publications
Absorption-line spectroscopy is a powerful tool used to estimate element abundances in both the nearby and distant universe. The accuracy of the abundances thus derived is naturally limited by the accuracy of the atomic data assumed for the spectral lines. We have recently started a project to perform new extensive atomic data calculations used for optical/UV spectral lines in the plasma modeling code Cloudy using state of the art quantal calculations. Here, we demonstrate our approach by focussing on S II, an ion used to estimate metallicities for Milky Way interstellar clouds as well as distant damped Lyman-alpha (DLA) and …
The Progenitors Of The Compact Early-Type Galaxies At High Redshift, Christina C. Williams, Mauro Giavalisco, Paolo Cassata, Elena Tundo, Tommy Wiklind, Yicheng Guo, Bomee Lee, Guillermo Barro, Stijn Wuyts, Eric F. Bell, Christopher J. Conselice, Avishai Dekel, Sandra M. Faber, Henry C. Ferguson, Norman A. Grogin, Nimish Hathi, Kuang-Han Huang, Dalibor D. Kocevski, Anton M. Koekemoer, David C. Koo, Swara Ravindranath, Sarah Salimbeni
The Progenitors Of The Compact Early-Type Galaxies At High Redshift, Christina C. Williams, Mauro Giavalisco, Paolo Cassata, Elena Tundo, Tommy Wiklind, Yicheng Guo, Bomee Lee, Guillermo Barro, Stijn Wuyts, Eric F. Bell, Christopher J. Conselice, Avishai Dekel, Sandra M. Faber, Henry C. Ferguson, Norman A. Grogin, Nimish Hathi, Kuang-Han Huang, Dalibor D. Kocevski, Anton M. Koekemoer, David C. Koo, Swara Ravindranath, Sarah Salimbeni
Physics and Astronomy Faculty Publications
We use GOODS and CANDELS images to identify progenitors of massive (M > 1010 M ☉) compact early-type galaxies (ETGs) at z ~ 1.6. Because merging and accretion increase the size of the stellar component of galaxies, if the progenitors are among known star-forming galaxies, these must be compact themselves. We select candidate progenitors among compact Lyman-break galaxies at z ~ 3 on the basis of their mass, star-formation rate (SFR), and central stellar density, and we find that these account for a large fraction of, and possibly all, compact ETGs at z ~ 1.6. We find that …
Effects Of External Radiation Fields On Line Emission—Application To Star-Forming Regions, Marios Chatzikos, Gary J. Ferland, R. J. R. Williams, Ryan Porter, P. A. M. Vanhoof
Effects Of External Radiation Fields On Line Emission—Application To Star-Forming Regions, Marios Chatzikos, Gary J. Ferland, R. J. R. Williams, Ryan Porter, P. A. M. Vanhoof
Physics and Astronomy Faculty Publications
A variety of astronomical environments contain clouds irradiated by a combination of isotropic and beamed radiation fields. For example, molecular clouds may be irradiated by the isotropic cosmic microwave background, as well as by a nearby active galactic nucleus. These radiation fields excite atoms and molecules and produce emission in different ways. We revisit the escape probability theorem and derive a novel expression that accounts for the presence of external radiation fields. We show that when the field is isotropic the escape probability is reduced relative to that in the absence of external radiation. This is in agreement with previous …
Detecting The Rapidly Expanding Outer Shell Of The Crab Nebula: Where To Look, Xiang Wang, Gary J. Ferland, J. A. Baldwin, E. D. Loh, C. T. Richardson
Detecting The Rapidly Expanding Outer Shell Of The Crab Nebula: Where To Look, Xiang Wang, Gary J. Ferland, J. A. Baldwin, E. D. Loh, C. T. Richardson
Physics and Astronomy Faculty Publications
We present a range of steady-state photoionization simulations, corresponding to different assumed shell geometries and compositions, of the unseen postulated rapidly expanding outer shell to the Crab Nebula. The properties of the shell are constrained by the mass that must lie within it, and by limits to the intensities of hydrogen recombination lines. In all cases the photoionization models predict very strong emissions from high ionization lines that will not be emitted by the Crab's filaments, alleviating problems with detecting these lines in the presence of light scattered from brighter parts of the Crab. The near-NIR [Ne VI] λ7.652 μ …
The Deep2 Galaxy Redshift Survey: Design, Observations, Data Reduction, And Redshifts, Jeffery A. Newman, Michael C. Cooper, Marc Davis, S. M. Faber, Alison L. Coil, Puragra Guhathakurta, David C. Koo, Andrew C. Phillips, Charlie Conroy, Aaron A. Dutton, Douglas P. Finkbeiner, Brian F. Gerke, David J. Rosario, Benjamin J. Weiner, Renbin Yan, Justin J. Harker, Susan A. Kassin, N. P. Konidaris, Kamson Lai, Darren S. Madgwick, K. G. Noeske, Gregory D. Wirth, A. J. Connolly, N. Kaiser, Evan N. Kirby, Brian C. Lemaux, Lihwai Lin, Jennifer M. Lotz, G. A. Luppino, C. Marinoni
The Deep2 Galaxy Redshift Survey: Design, Observations, Data Reduction, And Redshifts, Jeffery A. Newman, Michael C. Cooper, Marc Davis, S. M. Faber, Alison L. Coil, Puragra Guhathakurta, David C. Koo, Andrew C. Phillips, Charlie Conroy, Aaron A. Dutton, Douglas P. Finkbeiner, Brian F. Gerke, David J. Rosario, Benjamin J. Weiner, Renbin Yan, Justin J. Harker, Susan A. Kassin, N. P. Konidaris, Kamson Lai, Darren S. Madgwick, K. G. Noeske, Gregory D. Wirth, A. J. Connolly, N. Kaiser, Evan N. Kirby, Brian C. Lemaux, Lihwai Lin, Jennifer M. Lotz, G. A. Luppino, C. Marinoni
Physics and Astronomy Faculty Publications
We describe the design and data analysis of the DEEP2 Galaxy Redshift Survey, the densest and largest high-precision redshift survey of galaxies at z ~ 1 completed to date. The survey was designed to conduct a comprehensive census of massive galaxies, their properties, environments, and large-scale structure down to absolute magnitude MB = –20 at z ~ 1 via ~90 nights of observation on the Keck telescope. The survey covers an area of 2.8 deg2 divided into four separate fields observed to a limiting apparent magnitude of RAB = 24.1. Objects with z ≲ 0.7 are readily …
Supermassive Black Hole Formation At High Redshifts Via Direct Collapse: Physical Processes In The Early Stage, Jun-Hwan Choi, Isaac Shlosman, Mitchell C. Begelman
Supermassive Black Hole Formation At High Redshifts Via Direct Collapse: Physical Processes In The Early Stage, Jun-Hwan Choi, Isaac Shlosman, Mitchell C. Begelman
Physics and Astronomy Faculty Publications
We use numerical simulations to explore whether direct collapse can lead to the formation of supermassive black hole (SMBH) seeds at high redshifts. Using the adaptive mesh refinement code ENZO, we follow the evolution of gas within slowly tumbling dark matter (DM) halos of Mvir ~ 2 × 108 M☉ and Rvir ~ 1 kpc. For our idealized simulations, we adopt cosmologically motivated DM and baryon density profiles and angular momentum distributions. Our principal goal is to understand how the collapsing flow overcomes the centrifugal barrier and whether it is subject to fragmentation which can potentially …
Controlled Magnetic Reversal In Permalloy Films Patterned Into Artificial Quasicrystals, Vinayak Shantaram Bhat, J. Sklenar, B. Farmer, J. Woods, Jeffrey Todd Hastings, S. J. Lee, J. B. Ketterson, Lance E. De Long
Controlled Magnetic Reversal In Permalloy Films Patterned Into Artificial Quasicrystals, Vinayak Shantaram Bhat, J. Sklenar, B. Farmer, J. Woods, Jeffrey Todd Hastings, S. J. Lee, J. B. Ketterson, Lance E. De Long
Physics and Astronomy Faculty Publications
We have patterned novel Permalloy thin films with quasicrystalline Penrose P2 tilings and measured their dc magnetization and ferromagnetic resonance absorption. Reproducible anomalies in the hysteretic, low-field data signal a series of abrupt transitions between ordered magnetization textures, culminating in a smooth evolution into a saturated state. Micromagnetic simulations compare well to experimental dc hysteresis loops and ferromagnetic resonance spectra and indicate that systematic control of magnetic reversal and domain wall motion can be achieved via tiling design, offering a new paradigm of magnonic quasicrystals.
Long-Term Spectral Evolution Of Tidal Disruption Candidates Selected By Strong Coronal Lines, Chen-Wei Yang, Ting-Gui Wang, Gary J. Ferland, Weimin Yuan, Hong-Yan Zhou, Peng Jiang
Long-Term Spectral Evolution Of Tidal Disruption Candidates Selected By Strong Coronal Lines, Chen-Wei Yang, Ting-Gui Wang, Gary J. Ferland, Weimin Yuan, Hong-Yan Zhou, Peng Jiang
Physics and Astronomy Faculty Publications
We present results of follow-up optical spectroscopic Multi-Mirror Telescope (MMT) observations of seven rare, extreme coronal line-emitting galaxies reported by Wang et al. Large variations in coronal lines are found in four objects, making them strong candidates for tidal disruption events (TDEs). For the four TDE candidates, all the coronal lines with ionization states higher than [Fe VII] disappear within 5-9 yr. The [Fe VII] line faded by a factor of about five in one object (J0952+2143) within 4 yr, whereas the line emerged in another two objects that previously did not show the line. A strong increment in the …
Constraints On Oh Megamaser Excitation From A Survey Of Oh Satellite Lines, James Mcbride, Carl Heiles, Moshe Elitzur
Constraints On Oh Megamaser Excitation From A Survey Of Oh Satellite Lines, James Mcbride, Carl Heiles, Moshe Elitzur
Physics and Astronomy Faculty Publications
We report the results of a full-Stokes survey of all four 18 cm OH lines in 77 OH megamasers (OHMs) using the Arecibo Observatory. This is the first survey of OHMs that included observations of the OH satellite lines; only four of the 77 OHMs have existing satellite line observations in the literature. Satellite line emission is detected in five sources, three of which are redetections of previously published sources. The two sources with new detections of satellite line emission are IRAS F10173+0829, which was detected at 1720 MHz, and IRAS F15107+0724, for which both the 1612 MHz and 1720 …
The Redshift And Mass Dependence On The Formation Of The Hubble Sequence At Z > 1 From Candels/Uds, Alice Mortlock, Christopher J. Conselice, William G. Hartley, Jamie R. Ownsworth, Caterina Lani, Asa F. L. Bluck, Omar Almaini, Kenneth Duncan, Arjen Van Der Wel, Anton M. Koekemoer, Avishai Dekel, Romeel Davé, Harry C. Ferguson, Duilia F. De Mello, Jeffrey A. Newman, Sandra M. Faber, Norman A. Grogin, Dalibor D. Kocevski, Kamson Lai
The Redshift And Mass Dependence On The Formation Of The Hubble Sequence At Z > 1 From Candels/Uds, Alice Mortlock, Christopher J. Conselice, William G. Hartley, Jamie R. Ownsworth, Caterina Lani, Asa F. L. Bluck, Omar Almaini, Kenneth Duncan, Arjen Van Der Wel, Anton M. Koekemoer, Avishai Dekel, Romeel Davé, Harry C. Ferguson, Duilia F. De Mello, Jeffrey A. Newman, Sandra M. Faber, Norman A. Grogin, Dalibor D. Kocevski, Kamson Lai
Physics and Astronomy Faculty Publications
In this paper we present a detailed study of the structures and morphologies of a sample of 1188 massive galaxies with M* ≥ 1010 M⊙between redshifts z = 1 and 3 within the Ultra Deep Survey (UDS) region of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) field. Using this sample we determine how galaxy structure and morphology evolve with time, and investigate the nature of galaxy structure at high redshift. We visually classify our sample into discs, ellipticals and peculiar systems and correct for redshift effects on these classifications through simulations. We find significant …
Interstellar H2O Masers From J Shocks, David Hollenbach, Moshe Elitzur, Christopher F. Mckee
Interstellar H2O Masers From J Shocks, David Hollenbach, Moshe Elitzur, Christopher F. Mckee
Physics and Astronomy Faculty Publications
We present a model in which the 22 GHz H2O masers observed in star-forming regions occur behind shocks propagating in dense regions (preshock density n 0 ~ 106-108 cm–3). We focus on high-velocity (vs ≳ 30 km s–1) dissociative J shocks in which the heat of H2 re-formation maintains a large column of ~300-400 K gas; at these temperatures the chemistry drives a considerable fraction of the oxygen not in CO to form H2O. The H2O column densities, the hydrogen densities, and the warm …
The Importance Of Major Mergers In The Build Up Of Stellar Mass In Brightest Cluster Galaxies At Z = 1, C. Lidman, G. Iacobuta, A. E. Bauer, L. F. Barrientos, P. Cerulo, W. J. Couch, L. Delaye, R. Demarco, E. Ellingson, A. J. Faloon, D. Gilbank, M. Huertas-Company, S. Mei, J. Meyers, A. Muzzin, A. Noble, J. Nantais, A. Rettura, P. Rosati, R. Sánchez-Janssen, V. Strazzullo, T. M. A. Webb, G. Wilson, Renbin Yan, H. K. C. Yee
The Importance Of Major Mergers In The Build Up Of Stellar Mass In Brightest Cluster Galaxies At Z = 1, C. Lidman, G. Iacobuta, A. E. Bauer, L. F. Barrientos, P. Cerulo, W. J. Couch, L. Delaye, R. Demarco, E. Ellingson, A. J. Faloon, D. Gilbank, M. Huertas-Company, S. Mei, J. Meyers, A. Muzzin, A. Noble, J. Nantais, A. Rettura, P. Rosati, R. Sánchez-Janssen, V. Strazzullo, T. M. A. Webb, G. Wilson, Renbin Yan, H. K. C. Yee
Physics and Astronomy Faculty Publications
Recent independent results from numerical simulations and observations have shown that brightest cluster galaxies (BCGs) have increased their stellar mass by a factor of almost 2 between z ∼ 0.9 and z ∼ 0.2. The numerical simulations further suggest that more than half this mass is accreted through major mergers. Using a sample of 18 distant galaxy clusters with over 600 spectroscopically confirmed cluster members between them, we search for observational evidence that major mergers do play a significant role. We find a major merger rate of 0.38 ± 0.14 mergers per Gyr at z ∼ 1. While the uncertainties, …
Tuning The JEff = 1/2 Insulating State Via Electron Doping And Pressure In The Double-Layered Iridate Sr3Ir2O7, L. Li, P. P. Kong, Tongfei Qi, C. Q. Jin, Shujuan Yuan, Lance E. Delong, P. Schlottmann, Gang Cao
Tuning The JEff = 1/2 Insulating State Via Electron Doping And Pressure In The Double-Layered Iridate Sr3Ir2O7, L. Li, P. P. Kong, Tongfei Qi, C. Q. Jin, Shujuan Yuan, Lance E. Delong, P. Schlottmann, Gang Cao
Physics and Astronomy Faculty Publications
Sr3Ir2O7 exhibits a novel Jeff = 1/2 insulating state that features a splitting between Jeff = 1/2 and 3/2 bands due to spin-orbit interaction. We report a metal-insulator transition in Sr3Ir2O7 via either dilute electron doping (La3+ for Sr2+) or application of high pressure up to 35 GPa. Our study of single-crystal Sr3Ir2O7 and (Sr1−xLax)3Ir2O7 reveals that application of high hydrostatic pressure P leads to a drastic reduction in the electrical resistivity by as much …
Estimations Of The Magnetic Field Strength In The Torus Of Ic 5063 Using Near-Infrared Polarimetry, E. Lopez-Rodriguez, C. Packham, S. Young, Moshe Elitzur, N. A. Levenson, R. E. Mason, C. Ramos Almeida, A. Alonso-Herrero, T. J. Jones, E. Perlman
Estimations Of The Magnetic Field Strength In The Torus Of Ic 5063 Using Near-Infrared Polarimetry, E. Lopez-Rodriguez, C. Packham, S. Young, Moshe Elitzur, N. A. Levenson, R. E. Mason, C. Ramos Almeida, A. Alonso-Herrero, T. J. Jones, E. Perlman
Physics and Astronomy Faculty Publications
An optically and geometrically thick torus obscures the central engine of active galactic nuclei (AGN) from some lines of sight. From a magnetohydrodynamical framework, the torus can be considered to be a particular region of clouds surrounding the central engine where the clouds are dusty and optically thick. In this framework, the magnetic field plays an important role in the creation, morphology and evolution of the torus. If the dust grains within the clouds are assumed to be aligned by paramagnetic alignment, then the ratio of the intrinsic polarization and visual extinction, P(per cent)/Av, is a …
The X-Ray Properties Of Optically Selected Clusters Of Galaxies, A. K. Hicks, G. W. Pratt, M. Donahue, E. Ellingson, M. Gladders, H. Böhringer, H. K. C. Yee, Renbin Yan, J. H. Croston, D. G. Gilbank
The X-Ray Properties Of Optically Selected Clusters Of Galaxies, A. K. Hicks, G. W. Pratt, M. Donahue, E. Ellingson, M. Gladders, H. Böhringer, H. K. C. Yee, Renbin Yan, J. H. Croston, D. G. Gilbank
Physics and Astronomy Faculty Publications
We present the results of Chandra and Suzaku X-ray observations of nine moderate-redshift (0.16 < z < 0.42) clusters discovered via the Red-sequence Cluster Survey (RCS). Surface brightness profiles are fitted to β-models, gas masses are determined, integrated spectra are extracted within R2500, and X-ray temperatures and luminosities are inferred. TheLX–TX relationship expected from self-similar evolution is tested by comparing this sample to our previous X-ray investigation of nine high-redshift (0.6 < z < 1.0) optically selected clusters. We find that optically selected clusters are systematically less luminous than X-ray selected clusters of similar X-ray temperature at both moderate and high z. We are unable to constrain evolution in the LX–TX relation with these data, but find it consistent with no evolution, within relatively large uncertainties. To investigate selection effects, we compare the X-ray properties of our sample to those of clusters in the …
Studies Of Ngc 6720 With Calibrated Hst/Wfc3 Emission-Line Filter Images. Iii. Tangential Motions Using Astrodrizzle Images, C. R. O'Dell, Gary J. Ferland, W. J. Henney, M. Peimbert
Studies Of Ngc 6720 With Calibrated Hst/Wfc3 Emission-Line Filter Images. Iii. Tangential Motions Using Astrodrizzle Images, C. R. O'Dell, Gary J. Ferland, W. J. Henney, M. Peimbert
Physics and Astronomy Faculty Publications
We have been able to compare with astrometric precision AstroDrizzle processed images of NGC 6720 (the Ring Nebula) made using two cameras on the Hubble Space Telescope. The time difference of the observations was 12.925 yr. This large time base allowed the determination of tangential velocities of features within this classic planetary nebula. Individual features were measured in [N II] images as were the dark knots seen in silhouette against background nebular [O III] emission. An image magnification and matching technique was also used to test the accuracy of the usual assumption of homologous expansion. We found that homologous …
Spin Switching And Magnetization Reversal In Single-Crystal Ndfeo3, Shujuan Yuan, W. Ren, F. Hong, Y. B. Wang, J. C. Zhang, L. Bellaiche, Gang Cao
Spin Switching And Magnetization Reversal In Single-Crystal Ndfeo3, Shujuan Yuan, W. Ren, F. Hong, Y. B. Wang, J. C. Zhang, L. Bellaiche, Gang Cao
Physics and Astronomy Faculty Publications
We report an experimental and computational study of single-crystal NdFeO3, which features two inequivalent magnetic sublattices, namely, Fe and Nd sublattices that are coupled in an antiparallel fashion. This paper reveals that a strong interaction between 3d and 4f electrons of the two sublattices along with a spin-lattice coupling drives an extremely interesting magnetic state that is highly sensitive to the orientation and history of weak magnetic field. The following phenomena are particularly remarkable: (1) sharply contrasting magnetization M(T) along the a and c axes; (2) a first-order spin switching along the a …
Magnetic And Crystal Structures Of Sr2Iro4: A Neutron Diffraction Study, Feng Ye, Songxue Chi, Bryan C. Chakoumakos, Jaime A. Fernandez-Baca, Tongfei Qi, Gang Cao
Magnetic And Crystal Structures Of Sr2Iro4: A Neutron Diffraction Study, Feng Ye, Songxue Chi, Bryan C. Chakoumakos, Jaime A. Fernandez-Baca, Tongfei Qi, Gang Cao
Center for Advanced Materials Faculty Publications
We report a single-crystal neutron diffraction study of the layered Sr2IrO4. This work unambiguously determines the magnetic structure of the system and reveals that the spin orientation rigidly tracks the staggered rotation of the IrO6 octahedra in Sr2IrO4. The long-range antiferromagnetic order has a canted spin configuration with an ordered moment of 0.208(3) μB/Ir site within the basal plane; a detailed examination of the spin canting yields 0.202(3) and 0.049(2) μB/site for the a axis and the b axis, respectively. It is intriguing that forbidden nuclear reflections …
Classification And Analysis Of Emission-Line Galaxies Using Mean Field Independent Component Analysis, James T. Allen, Paul C. Hewett, Chris T. Richardson, Gary J. Ferland, Jack A. Baldwin
Classification And Analysis Of Emission-Line Galaxies Using Mean Field Independent Component Analysis, James T. Allen, Paul C. Hewett, Chris T. Richardson, Gary J. Ferland, Jack A. Baldwin
Physics and Astronomy Faculty Publications
We present an analysis of the optical spectra of narrow emission-line galaxies, based on mean field independent component analysis (MFICA), a blind source separation technique. Samples of galaxies were drawn from the Sloan Digital Sky Survey (SDSS) and used to generate compact sets of ‘continuum’ and ‘emission-line’ component spectra. These components can be linearly combined to reconstruct the observed spectra of a wider sample of galaxies. Only 10 components – five continuum and five emission line – are required to produce accurate reconstructions of essentially all narrow emission-line galaxies to a very high degree of accuracy; the median absolute deviations …
Strongly Localized Magnetization Modes In Permalloy Antidot Lattices, J. Sklenar, V. S. Bhat, Lance E. De Long, O. Heinonen, J. B. Ketterson
Strongly Localized Magnetization Modes In Permalloy Antidot Lattices, J. Sklenar, V. S. Bhat, Lance E. De Long, O. Heinonen, J. B. Ketterson
Physics and Astronomy Faculty Publications
Antidot lattices (ADLs) patterned into soft magnetic thin films exhibit rich ferromagnetic resonance (FMR) spectra corresponding to many different magnetization modes. One of the predicted modes is highly localized at the edges of the antidots; this mode is difficult to detect experimentally. Here we present FMR data for a permalloy thin film patterned into a square array of square antidots. Comparison of these data with micromagnetic simulations permits identification of several edge modes. Our simulations also reveal the effect of the antidot shape on the mode dispersion.
Suppression Of Dielectronic Recombination Due To Finite Density Effects, D. Nikolić, T. W. Gorczyca, K. T. Korista, Gary J. Ferland, N. R. Badnell
Suppression Of Dielectronic Recombination Due To Finite Density Effects, D. Nikolić, T. W. Gorczyca, K. T. Korista, Gary J. Ferland, N. R. Badnell
Physics and Astronomy Faculty Publications
We have developed a general model for determining density-dependent effective dielectronic recombination (DR) rate coefficients in order to explore finite-density effects on the ionization balance of plasmas. Our model consists of multiplying by a suppression factor those highly-accurate total zero-density DR rate coefficients which have been produced from state-of-the-art theoretical calculations and which have been benchmarked by experiment. The suppression factor is based upon earlier detailed collision-radiative calculations which were made for a wide range of ions at various densities and temperatures, but used a simplified treatment of DR. A general suppression formula is then developed as a function of …
Erratum: 'Improved He I Emissivities In The Case B Approximation', R. L. Porter, Gary J. Ferland, P. J. Storey, M. J. Detisch
Erratum: 'Improved He I Emissivities In The Case B Approximation', R. L. Porter, Gary J. Ferland, P. J. Storey, M. J. Detisch
Physics and Astronomy Faculty Publications
No abstract provided.
Tuning Electronic Structure Via Exipatial Strain In Sr2Iro4 Thin Films, J. Nichols, Jsaminka Terzic, Emily Geraldine Bittle, Oleksandr B. Korneta, Lance E. De Long, Joseph Brill, Gang Cao, Sung S. Ambrose Seo
Tuning Electronic Structure Via Exipatial Strain In Sr2Iro4 Thin Films, J. Nichols, Jsaminka Terzic, Emily Geraldine Bittle, Oleksandr B. Korneta, Lance E. De Long, Joseph Brill, Gang Cao, Sung S. Ambrose Seo
Physics and Astronomy Faculty Publications
We have synthesized epitaxial Sr2IrO4 thin-films on various substrates and studied their electronic structure as a function of lattice-strain. Under tensile (compressive) strain, increased (decreased) Ir-O-Ir bond-angle is expected to result in increased (decreased) electronic bandwidth. However, we have observed that the two optical absorption peaks near 0.5 eV and 1.0 eV are shifted to higher (lower) energies under tensile (compressive) strain, indicating that the electronic-correlation energy is also affected by in-plane lattice-strain. The effective tuning of electronic structure under lattice-modification provides an important insight into the physics driven by the coexisting strong spin-orbit coupling and electronic …
Expanded Iron Uta Spectra—Probing The Thermal Stability Limits In Agn Clouds, Gary J. Ferland, R. Kisielius, F. P. Keenan, P. A. M. Van Hoof, V. Jonauskas, Matt L. Lykins, R. L. Porter, R. J. R. Williams
Expanded Iron Uta Spectra—Probing The Thermal Stability Limits In Agn Clouds, Gary J. Ferland, R. Kisielius, F. P. Keenan, P. A. M. Van Hoof, V. Jonauskas, Matt L. Lykins, R. L. Porter, R. J. R. Williams
Physics and Astronomy Faculty Publications
The Fe unresolved transition arrays (UTAs) produce prominent features in the ~15-17 Å wavelength range in the spectra of active galactic nuclei (AGNs). Here, we present new calculations of the energies and oscillator strengths of inner-shell lines from Fe XIV, Fe XV, and Fe XVI. These are crucial ions since they are dominant at inflection points in the gas thermal stability curve, and UTA excitation followed by autoionization is an important ionization mechanism for these species. We incorporate these, and data reported in previous papers, into the plasma simulation code Cloudy. This updated physics is subsequently employed to reconsider the …
The Nature Of The H2-Emitting Gas In The Crab Nebula, C. T. Richardson, J. A. Baldwin, Gary J. Ferland, E. D. Loh, C. A. Kuehn, A. C. Fabian, Philippe Salomé
The Nature Of The H2-Emitting Gas In The Crab Nebula, C. T. Richardson, J. A. Baldwin, Gary J. Ferland, E. D. Loh, C. A. Kuehn, A. C. Fabian, Philippe Salomé
Physics and Astronomy Faculty Publications
Understanding how molecules and dust might have formed within a rapidly expanding young supernova remnant is important because of the obvious application to vigorous supernova activity at very high redshift. In previous papers, we have mapped the Crab nebula (the Crab) in a rotovibrational H2emission line, and then measured the molecular excitation temperature for a few of the brighter H2-emitting knots that we have found to be scattered throughout the Crab's filaments. We found that H2 emission is often quite strong, correlates with optical low-ionization emission lines and has a surprisingly high excitation temperature. Here, …
Radiative Cooling In Collisionally Ionized And Photoionized Plasmas, Matt Lykins, Gary J. Ferland, Ryan L. Porter, Peter A. M. Van Hoof, R. J. R. Williams, Orly Gnat
Radiative Cooling In Collisionally Ionized And Photoionized Plasmas, Matt Lykins, Gary J. Ferland, Ryan L. Porter, Peter A. M. Van Hoof, R. J. R. Williams, Orly Gnat
Physics and Astronomy Faculty Publications
We discuss recent improvements in the calculation of the radiative cooling in both collisionally ionized and photoionized plasmas. We are extending the spectral simulation code CLOUDY so that as much as possible of the underlying atomic data are taken from external data bases, some created by others and some developed by the CLOUDY team. This paper focuses on recent changes in the treatment of many stages of ionization of iron, and discusses its extensions to other elements. The H- and He-like ions are treated in the isoelectronic approach described previously. Fe II is a special case treated with a large …
Studies Of Ngc 6720 With Calibrated Hst/Wfc3 Emission-Line Filter Images. Ii. Physical Conditions, C. R. O'Dell, Gary J. Ferland, W. J. Henney, M. Peimbert
Studies Of Ngc 6720 With Calibrated Hst/Wfc3 Emission-Line Filter Images. Ii. Physical Conditions, C. R. O'Dell, Gary J. Ferland, W. J. Henney, M. Peimbert
Physics and Astronomy Faculty Publications
We have performed a detailed analysis of the electron temperature and density in the Ring Nebula using the calibrated Hubble Space Telescope WFC3 images described in the preceding paper. The electron temperature (Te) determined from [NII] and [O III] rises slightly and monotonically toward the central star. The observed equivalent width (EW) in the central region indicates that Te rises as high as 13,000 K. In contrast, the low EWs in the outer regions are largely due to scattered diffuse Galactic radiation by dust. The images allowed determination of unprecedented small-scale variations in Te. …
Studies Of Ngc 6720 With Calibrated Hst/Wfc3 Emission-Line Filter Images. I. Structure And Evolution, C. R. O'Dell, Gary J. Ferland, W. J. Henney, M. Peimbert
Studies Of Ngc 6720 With Calibrated Hst/Wfc3 Emission-Line Filter Images. I. Structure And Evolution, C. R. O'Dell, Gary J. Ferland, W. J. Henney, M. Peimbert
Physics and Astronomy Faculty Publications
We have performed a detailed analysis of the Ring Nebula (NGC 6720) using Hubble Space Telescope WFC3 images and derived a new three-dimensional model. Existing high spectral resolution spectra played an important supplementary role in our modeling. It is shown that the Main Ring of the nebula is an ionization-bounded irregular non-symmetric disk with a central cavity and perpendicular extended lobes pointed almost toward the observer. The faint outer halos are determined to be fossil radiation, i.e., radiation from gas ionized in an earlier stage of the nebula when it was not ionization bounded. The narrowband WFC3 filters that isolate …