Astrophysics and Astronomy Commons^™

Orbital-Dependent Polaron Formation In The Relativistic Mott Insulator Sr2Iro4, C. H. Sohn, Min-Cheol Lee, H. J. Park, Kyung Joo Noh, H. K. Yoo, S. J. Moon, K. W. Kim, T. F. Qi, Gang Cao, Deok-Yong Cho, T. W. Noh

Physics and Astronomy Faculty Publications

We use optical spectroscopy to investigate the electron-phonon interaction in Sr₂IrO₄, a well-known 5d transition metal oxide with spin-orbit entangled states. The temperature evolution in the optical spectra is well described by the Fröhlich polaron model, indicating a large electron-phonon interaction. We further find that electrons in different orbitals selectively couple with different phonon modes. While J_eff = 3/2 holes do not seem to couple with any phonons, J_eff = 1/2 and 3z²−r² electrons mainly couple with in-plane and out-of-plane Ir-O bending modes, respectively. The symmetries of the …

Measurement Of The Target-Normal Single-Spin Asymmetry In Deep-Inelastic Scattering From The Reaction 3He↑(E,E′)X, K. Allada, C. Dutta, A. Kolarkar, Wolfgang Korsch, J. Katich, X. Qian, Y. X. Zhao, K. Aniol, J. R. M. Annand, T. Averett, F. Benmokhtar, W. Bertozzi, P. C. Bradshaw, P. Bosted

Physics and Astronomy Faculty Publications

We report the first measurement of the target-normal single-spin asymmetry in deep-inelastic scattering from the inclusive reaction ³He^↑(e,e′)X on a polarized ³He gas target. Assuming time-reversal invariance, this asymmetry is strictly zero in the Born approximation but can be nonzero if two-photon-exchange contributions are included. The experiment, conducted at Jefferson Lab using a 5.89 GeV electron beam, covers a range of 1.7<W<2.9 GeV, 1.0<Q²<4.0 GeV² and 0.16<x<6.5. Neutron asymmetries were extracted using the effective nucleon polarization and measured proton-to-³He cross-section ratios. The measured neutron asymmetries are negative with an average value of (−1.09±0.38)×10⁻² for invariant mass W>2 …

Local Density Of States Study Of A Spin-Orbit-Coupling Induced Mott Insulator Sr2Iro4, Jixia Dai, Eduardo Calleja, Gang Cao, Kyle Mcelroy

Physics and Astronomy Faculty Publications

We present scanning tunneling microscopy and spectroscopy experiments on the novel J_eff=1/2 Mott insulator Sr₂IrO₄. Local density of states (LDOS) measurements show an intrinsic insulating gap of 620 meV that is asymmetric about the Fermi level and is larger than previously reported values. The size of this gap suggests that Sr₂IrO₄ is likely a Mott rather than Slater insulator. In addition, we found a small number of native defects which create in-gap spectral weight. Atomically resolved LDOS measurements on and off the defects show that this energy gap is quite fragile. …

Dielectron Mass Spectra From Au+Au Collisions At √SNn<=200  Gev, J. Kevin Adkins, Renee Fatemi, Wolfgang Korsch, Suvarna Ramachandran, G. Webb, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, E. C. Aschenauer

Physics and Astronomy Faculty Publications

We report the STAR measurements of dielectron (e⁺e⁻) production at midrapidity (|y_ee|^S_NN=200  GeV. The measurements are evaluated in different invariant mass regions with a focus on 0.30–0.76 (ρ-like), 0.76–0.80 (ω-like), and 0.98–1.05 (ϕ-like)   GeV/c². The spectrum in the ω-like and ϕ-like regions can be well described by the hadronic cocktail simulation. In the ρ-like region, however, the vacuum ρ spectral function cannot describe the shape of the dielectron excess. In this range, an enhancement of 1.77±0.11(stat)±0.24(syst)±0.33(cocktail) is determined …

The Inside-Out Growth Of The Most Massive Galaxies At 0.3 < Z < 0.9, Lei Bai, H. K. C. Yee, Renbin Yan, Eve Lee, David G. Gilbank, E. Ellingson, L. F. Barrientos, M. D. Gladders, B. C. Hsieh, I. H. Li

Physics and Astronomy Faculty Publications

We study the surface brightness profiles of a sample of brightest cluster galaxies (BCGs) with 0.3 < z < 0.9.

For the remainder of the abstract, please download this article or visit https://doi.org/10.1088/0004-637X/789/2/134

Optical-Faint, Far-Infrared-Bright Herschel Sources In The Candels Fields: Ultra-Luminous Infrared Galaxies At Z > 1 And The Effect Of Source Blending, Haojing Yan, Mauro Stefanon, Zhiyuan Ma, S. P. Willner, Rachel Somerville, Matthew L.N. Ashby, Romeel Davé, Pablo G. Pérez-González, Antonio Cava, Tommy Wiklind, Dale D. Kocevski, Marc Rafelski, Jeyhan Kartaltepe, Asantha Cooray, Anton M. Koekemoer, Norman A. Grogin

Physics and Astronomy Faculty Publications

The Herschel very wide field surveys have charted hundreds of square degrees in multiple far-IR (FIR) bands. While the Sloan Digital Sky Survey (SDSS) is currently the best resource for optical counterpart identifications over such wide areas, it does not detect a large number of Herschel FIR sources and leaves their nature undetermined. As a test case, we studied seven "SDSS-invisible," very bright 250 μm sources (S ₂₅₀ > 55 mJy) in the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey fields where we have a rich multi-wavelength data set. We took a new approach to decompose the FIR sources, using …

Type Ia Supernova Rate Measurements To Redshift 2.5 From Candels: Searching For Prompt Explosions In The Early Universe, Steven A. Rodney, Adam G. Riess, Louis-Gregory Strolger, Tomas Dahlen, Or Graur, Stefano Casertano, Mark E. Dickinson, Henry C. Ferguson, Peter Garnavich, Brian Hayden, Saurabh W. Jha, David O. Jones, Robert P. Kirshner, Anton M. Koekemoer, Curtis Mccully, Bahram Mobasher, Brandon Patel, Benjamin J. Weiner, S. Bradley Cenko, Kelsey I. Clubb, Michael Cooper, Alexei V. Filippenko, Teddy F. Frederiksen, Jens Hjorth, Bruno Leibundgut, Thomas Matheson, Hooshang Nayyeri, Kyle Penner, Jonathan Trump, Jeffrey M. Silverman, Vivian U, K. Azalee Bostroem, Peter Challis, Abhijith Rajan, Schuyler Wolff, S. M. Faber, Norman A. Grogin, Dale D. Kocevski

Physics and Astronomy Faculty Publications

The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) was a multi-cycle treasury program on the Hubble Space Telescope (HST) that surveyed a total area of ~0.25 deg² with ~900 HST orbits spread across five fields over three years. . . .

For the remainder of the abstract, please visit:

http://dx.doi.org/10.1088/0004-6256/148/1/13

Radiative Cooling Ii: Effects Of Density And Metallicity, Ye Wang, Gary J. Ferland, Matt Lykins, R. L. Porter, Peter A. M. Van Hoof, R. J. R. Williams

Physics and Astronomy Faculty Publications

This work follows Lykins et al. discussion of classic plasma cooling function at low density and solar metallicity. Here, we focus on how the cooling function changes over a wide range of density (n_H <10¹² cm⁻³) and metallicity (Z < 30 Z_⊙). We find that high densities enhance the ionization of elements such as hydrogen and helium until they reach local thermodynamic equilibrium. By charge transfer, the metallicity changes the ionization of hydrogen when it is partially ionized. We describe the total cooling function as a sum of four parts: those due to H&He, the heavy …

Subaru Spectroscopy And Spectral Modeling Of Cygnus A, Matthew J. Merlo, Erik S. Perlman, Robert Nikutta, Christopher Packham, Moshe Elitzur, Masatoshi Imanishi, N. A. Levenson, James T. Radomski, Itziar Aretxaga

Physics and Astronomy Faculty Publications

We present high angular resolution (~0.''5) MIR spectra of the powerful radio galaxy, Cygnus A (Cyg A), obtained with the Subaru telescope. The overall shape of the spectra agree with previous high angular resolution MIR observations, as well as previous Spitzer spectra. Our spectra, both on and off nucleus, show a deep silicate absorption feature. The absorption feature can be modeled with a blackbody obscured by cold dust or a clumpy torus. The deep silicate feature is best fit by a simple model of a screened blackbody, suggesting that foreground absorption plays a significant, if not dominant, role in shaping …

On The Observability Of Optically Thin Coronal Hyperfine Structure Lines, Marios Chatzikos, Gary J. Ferland, R. J. R. Williams, A. C. Fabian

Physics and Astronomy Faculty Publications

We present CLOUDY calculations for the intensity of coronal hyperfine lines in various environments. We model indirect collisional and radiative transitions, and quantify the collisionally excited line emissivity in the density-temperature phase space. As an observational aid, we also express the emissivity in units of that in the 0.4-0.7 keV band. For most hyperfine lines, knowledge of the X-ray surface brightness and the plasma temperature is sufficient for rough estimates. We find that the radiation fields of both Perseus A and Virgo A can enhance the populations of highly ionized species within 1 kpc. They can also enhance line emissivity …

Electronic Device Incorporating Memristor Made From Metallic Nanowire, Douglas R. Strachan, Stephen L. Johnson

Physics and Astronomy Faculty Patents

An electronic device includes a first electrode, a second electrode and a nanowire connected between the first and second electrodes to allow electric current flow. The nanowire is made from a conductive material exhibiting a variable resistance due to electromigration. The nanowire is repeatably switchable between two states. A voltage clamp operates through feedback control to maintain the voltage across the nanowire and prevent thermal runaway.

Investigating Evidence For Different Black Hole Accretion Modes Since Redshift Z ∼ 1, A. Georgakakis, P. G. Pérez-González, N. Fanidakis, M. Salvato, J. Aird, H. Messias, J. M. Lotz, G. Barro, Li-Ting Hsu, K. Nandra, D. Rosario, M. C. Cooper, Dalibor D. Kocevski, J. A. Newman

Physics and Astronomy Faculty Publications

Chandra data in the COSMOS, AEGIS-XD and 4 Ms Chandra Deep Field South are combined with multiwavelength photometry available in those fields to determine the rest-frame U − V versus V − J colours of X-ray AGN hosts in the redshift intervals 0.1 < z < 0.6 (mean z¯=0.40) and 0.6 < z < 1.2 (mean z¯=0.85). This combination of colours provides an effective and least model-dependent means of separating quiescent from star-forming, including dust reddened, galaxies. Morphological information emphasizes differences between AGN populations split by theirU − V versus V − J colours. AGN in quiescent galaxies consist almost exclusively of bulges, while star-forming hosts are equally split between early- and late-type hosts. The position of AGN hosts on the U − V versusV − J diagram is then used to set limits on the accretion density of the …

Event-Plane-Dependent Dihadron Correlations With Harmonic VN Subtraction In Au + Au Collisions At √SNn=200 Gev, H Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, D. Arkhipkin, G. S. Averichev, Renee H. Fatemi, Robert G. Fersch, Wolfgang Korsch, G. Webb, Wayne Otto Witzke

Physics and Astronomy Faculty Publications

STAR measurements of dihadron azimuthal correlations (Δϕ) are reported in midcentral (20–60%) Au + Au collisions at √^sNN = 200 GeV as a function of the trigger particle's azimuthal angle relative to the event plane, ϕ_s = |ϕ_t − ^ψEP |. The elliptic (^v2), triangular (^v3), and quadratic (^v4) flow harmonic backgrounds are subtracted using the zero yield at minimum (ZYAM) method. The results are compared to minimum-bias d + Au collisions. It is found that a finite near-side (|Δϕ| < π/2) long-range pseudorapidity correlation (ridge) is present in the in-plane direction (ϕ_s∼0). The …

Ds/Cft At Uniform Energy Density And A De Sitter “Bluewall”, Diptarka Das, Sumit R. Das, K. Narayan

Physics and Astronomy Faculty Publications

We describe a class of spacetimes that are asymptotically de Sitter in the Poincare slicing. Assuming that a dS/CFT correspondence exists, we argue that these are gravity duals to a CFT on a circle leading to uniform energy-momentum density, and are equivalent to an analytic continuation of the Euclidean AdS black brane. These are solutions with a complex parameter which then gives a real energy-momentum density. We also discuss a related solution with the parameter continued to a real number, which we refer to as a de Sitter “bluewall”. This spacetime has two asymptotic de Sitter universes and Cauchy horizons …

Single Spin Asymmetries Of Inclusive Hadrons Produced In Electron Scattering From A Transversely Polarized 3He Target, K. Allada, Y. X. Zhao, K. Aniol, J. R. M. Annand, T. Averett, F. Benmokhtar, W. Bertozzi, P. C. Bradshaw, P. Bosted, A. Camsonne, C. Dutta, Ameya Suresh Kolarkar, Wolfgang Korsch

Physics and Astronomy Faculty Publications

We report the first measurement of target single spin asymmetries (A_N) in the inclusive hadron production reaction, e+³He^↑→h+X, using a transversely polarized ³He target. The experiment was conducted at Jefferson Lab in Hall A using a 5.9-GeV electron beam. Three types of hadrons (π^±, K^±, and proton) were detected in the transverse hadron momentum range 0.54 <p_T< 0.74 GeV/c. The range of x_F for pions was −0.29 <x_F< −0.23 and for kaons was −0.25 <x_F< −0.18. The observed asymmetry strongly depends on the type of hadron. A positive asymmetry is observed for π⁺ and K⁺. A negative asymmetry is observed for π⁻. The …

Jet-Hadron Correlations In √SNn=200 Gev P+P And Central Au+Au Collisions, L. Adamczyk, James K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, Renee H. Fatemi, Suvarna Ramachandran, G. Webb

Physics and Astronomy Faculty Publications

Azimuthal angular correlations of charged hadrons with respect to the axis of a reconstructed (trigger) jet in Au+Au and p+p collisions at √^sNN=200  GeV in STAR are presented. The trigger jet population in Au+Au collisions is biased toward jets that have not interacted with the medium, allowing easier matching of jet energies between Au+Au and p+p collisions while enhancing medium effects on the recoil jet. The associated hadron yield of the recoil jet is significantly suppressed at high transverse momentum (p^assoc_T) and enhanced at low p^assoc_T in 0%–20% central …

Evolution Of Broad-Line Emission From Active Galactic Nuclei, Moshe Elitzur, Luis C. Ho, Jonathan R. Trump

Physics and Astronomy Faculty Publications

Apart from viewing-dependent obscuration, intrinsic broad-line emission from active galactic nuclei (AGN) follows an evolutionary sequence: type 1 → 1.2/1.5 → 1.8/1.9 → 2 as the accretion rate on to the central black hole is decreasing. This spectral evolution is controlled, at least in part, by the parameter L_bol/M^2/3, where L_bol is the AGN bolometric luminosity and M is the black hole mass. Both this dependence and the double-peaked profiles that emerge along the sequence arise naturally in the disc-wind scenario for the AGN broad-line region.

Compton Scattering From 12C Using Tagged Photons In The Energy Range 65–115 Mev, L. S. Myers, Khayrullo Shoniyozov, M. F. Preston, M. D. Anderson, J. R. M. Annand, M. Boselli, W. J. Briscoe, J. Brudvik, J. I. Capone, G. Feldman, K. G. Fissum, K. Hansen, S. S. Henshaw, L. Isaksson, R. Jebali, Michael A. Kovash, K. Lewis, M. Lundin, I. J. D. Macgregor, D. G. Middleton, D. E. Mittelberger, M. Murray, A. M. Nathan, S. Nutbeam, G. V. O'Rielly, B. Schröder, B. Seitz, S. C. Stave, H. R. Weller

Physics and Astronomy Faculty Publications

Elastic scattering of photons from ¹²C has been investigated using quasimonoenergetic tagged photons with energies in the range 65–115 MeV at laboratory angles of 60^∘, 120^∘, and 150^∘ at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. A phenomenological model was employed to provide an estimate of the sensitivity of the ¹²C(γ,γ)¹²C cross section to the bound-nucleon polarizabilities.

Secular Damping Of Stellar Bars In Spinning Dark Matter Halos, Stacy Long, Isaac Shlosman, Clayton Heller

Physics and Astronomy Faculty Publications

We demonstrate using numerical simulations of isolated galaxies that growth of stellar bars in spinning dark matter halos is heavily suppressed in the secular phase of evolution. In a representative set of models, we show that for values of the cosmological spin parameter λ ≳ 0.03, bar growth (in strength and size) becomes increasingly quenched. Furthermore, the slowdown of the bar pattern speed weakens considerably with increasing λ until it ceases completely. The terminal structure of the bars is affected as well, including extent and shape of their boxy/peanut bulges. The essence of this effect lies in the modified angular …

Two-Neutron Transfer Reaction Mechanisms In 12C(6He, 4He) 14C Using A Realistic Three-Body 6He Model, D. Smalley, F. Sarazin, F. M. Nunes, B. A. Brown, P. Adsley, H. Al-Falou, C. Andreoiu, B. Baartman, G. C. Ball, J. C. Blackmon, H. C. Boston, W. N. Catford, S. Chagnon-Lessard, A. Chester, R. M. Churchman, D. S. Cross, C. Aa. Diget, D. Di Valentino, S. P. Fox, B. R. Fulton, A. Garnsworthy, G. Hackman, U. Hager, R. Kshetri, J. N. Orce, N. A. Orr, E. Paul, M. Pearson, E. T. Rand, J. Rees, S. Sjue, C. E. Svensson, E. Tardiff, A. Diaz Varela, S. J. Williams, Steven W. Yates

Physics and Astronomy Faculty Publications

The reaction mechanisms of the two-neutron transfer reaction ¹²C(⁶He,⁴He) have been studied at E_lab=30 MeV at the TRIUMF ISAC-II facility using the Silicon Highly-segmented Array for Reactions and Coulex (SHARC) charged-particle detector array. Optical potential parameters have been extracted from the analysis of the elastic scattering angular distribution. The new potential has been applied to the study of the transfer angular distribution to the 2+₂ 8.32 MeV state in ¹⁴C, using a realistic three-body ⁶He model and advanced shell-model calculations for the carbon structure, allowing to calculate the relative contributions …

Dilute Magnetism And Spin-Orbital Percolation Effects In Sr2Ir1−XRhXO4, J. P. Clancy, A. Lupascu, H. Gretarsson, Z. Islam, Y. F. Hu, D. Casa, C. S. Nelson, S. C. Lamarra, Gang Cao, Young-June Kim

Physics and Astronomy Faculty Publications

We have used a combination of resonant magnetic x-ray scattering and x-ray absorption spectroscopy to investigate the properties of the doped spin-orbital Mott insulator Sr₂Ir_1−xRh_xO₄ (0.07 ≤ x ≤ 0.70). We show that Sr₂Ir_1−xRh_xO₄ represents a unique model system for the study of dilute magnetism in the presence of strong spin-orbit coupling, and provide evidence of a doping-induced change in magnetic structure and a suppression of magnetic order at x_c ∼ 0.17. We demonstrate that Rh-doping introduces Rh³⁺/Ir⁵⁺ ions which …

Novel Magnetism Of Ir5+(5D4) Ions In The Double Perovskite Sr2Yiro6, Gang Cao, Tongfei Qi, Li Li, Jsaminka Terzic, Shujuan Yuan, Lance E. De Long, Ganpathy Murthy, Ribhu K. Kaul

Physics and Astronomy Faculty Publications

We synthesize and study single crystals of a new double-perovskite Sr₂YIrO₆. Despite two strongly unfavorable conditions for magnetic order, namely, pentavalent Ir⁵⁺(5d⁴) ions which are anticipated to have J_eff=0 singlet ground states in the strong spin-orbit coupling (SOC) limit and geometric frustration in a face-centered cubic structure formed by the Ir⁵⁺ ions, we observe this iridate to undergo a novel magnetic transition at temperatures below 1.3 K. We provide compelling experimental and theoretical evidence that the origin of magnetism is in an unusual interplay between strong noncubic crystal …

Light-By-Light Scattering Nonlogarithmic Corrections To Hyperfine Splitting In Muonium, Michael I. Eides, Valery A. Shelyuto

Physics and Astronomy Faculty Publications

We consider three-loop corrections to hyperfine splitting in muonium generated by the gauge invariant set of diagrams with a virtual light-by-light scattering block. These diagrams produce both recoil and nonrecoil contributions to hyperfine splitting. Recoil corrections are enhanced by large logarithms of the muon-electron mass ratio. Both nonrecoil and logarithmically enhanced radiative-recoil corrections were calculated some time ago. Here we calculate nonlogarithmic radiative-recoil corrections generated by the insertions of the light-by-light scattering block.

Energy Dependence Of Moments Of Net-Proton Multiplicity Distributions At Rhic, James K. Atkins, Renee H. Fatemi, Wolfgang Korsch, Suvarna Ramachandran, G. Webb, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, E. C. Aschenauer, G. S. Averichev, J. Balewski, A. Banerjee, Z. Barnovska, D. R. Beavis, R. Bellwied, A. Bhasin, A. K. Bhati, P. Bhattarai, H. Bichsel, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, W. Borowski

Physics and Astronomy Faculty Publications

We report the beam energy(√⁸NN = 7.7-200 GeV) and collision centrality dependence of the mean (M), standard deviation (σ), skewness (S), and kurtosis (κ) of the net-proton multiplicity distributions in Au+Au collisions. The measurements are carried out by the STAR experiment at midrapidity (|y|<0.5) and within the transverse momentum range 0.4<ρτ<0.8  GeV/c in the first phase of the Beam Energy Scan program at the Relativistic Heavy Ion Collider. These measurements are important for understanding the quantum chromodynamic phase diagram. The products of the moments, Sσ and κσ2, are sensitive to the correlation length of the hot and dense …

Interpreting The Ionization Sequence In Agn Emission-Line Spectra, Chris T. Richardson, James T. Allen, Jack A. Baldwin, Paul C. Hewett, Gary J. Ferland

Physics and Astronomy Faculty Publications

We investigate the physical cause of the great range in the ionization level seen in the spectra of narrow-lined active galactic nuclei (AGN). We used a recently developed technique called mean field independent component analysis to identify examples of individual Sloan Digital Sky Survey galaxies whose spectra are not dominated by emission due to star formation (SF), which we therefore designate as AGN. We assembled high signal-to-noise ratio (S/N) composite spectra of a sequence of these AGN defined by the ionization level of their narrow-line regions (NLR), and extending down to very low ionization cases. We then used a local …

Neutral Pion Cross Section And Spin Asymmetries At Intermediate Pseudorapidity In Polarized Proton Collisions At √S=200  Gev, L. Adamczyk, James K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, Renee H. Fatemi, Robert G. Fersch, Wolfgang Korsch, Suvarna Ramachandran, G. Webb

Physics and Astronomy Faculty Publications

The differential cross section and spin asymmetries for neutral pions produced within the intermediate pseudorapidity range 0.8<ηp_T/c and is found to agree with a next-to-leading order perturbative QCD calculation. The longitudinal double-spin asymmetry A_LL is measured in the same pseudorapidity range and spans a range of Bjorken-x down to x≈0.01. The measured A_LL is consistent with model predictions for varying degrees of gluon polarization. The parity-violating asymmetry A_L is also measured and found to be consistent with zero. The transverse single-spin asymmetry A_N is measured over a previously unexplored kinematic range in …

Energy Dependence Of The (E,2E) Recoil Peak To Binary Peak Ratio Across He (2P2)1D And (2S2P)1P Autoionizing Levels, B. A. Deharak, K. Bartschat, Nicholas L. S. Martin

Physics and Astronomy Faculty Publications

The (e,2e) recoil peak to binary peak ratio as a function of the ejected-electron energy is reported for helium autoionizing levels (2p²)¹D and (2s2p)¹P. A special out-of-plane geometry is used where the ejected electrons are detected in a plane that includes the momentum transfer axis but is perpendicular to the scattering plane. The measured recoil peak to binary peak ratio is a dimensionless quantity that can be directly compared with calculations. A second-order model in the projectile-target interaction correctly reproduces the observed energy dependence …

A Transition Mass For Black Holes To Show Broad Emission Lines, Susmita Chakravorty, Martin Elvis, Gary J. Ferland

Physics and Astronomy Faculty Publications

Although the supermassive (AGN) and stellar mass (BHBs) black holes have many properties in common, the broad emission lines (BELs) are exclusively signatures of the active galactic nuclei (AGN). Based on the detection of these lines from Sloan Digital Sky Survey (SDSS) data bases, there seems to be no AGN with mass M_BH ≲ 10⁵ M_⊙. In this paper, we investigate if such low-mass black holes are really non-existent or they are undetected because the BELs in them are not produced efficiently. Using the ionizing spectral energy distribution for a wide range of black hole mass, …

Suppression Of Dielectronic Recombination At Finite Densities, T. W. Gorczyca, D. Nikolić, N. R. Badnell, Gary J. Ferland

Physics and Astronomy Faculty Publications

Density-dependent effective dielectronic recombination rate coefficients are determined in order to explore finite-density effects on the ionization balance of plasmas.

Cold Gas Dynamics In Hydra-A: Evidence For A Rotating Disc, S. L. Hamer, A. C. Edge, A. M. Swinbank, J. B. R. Oonk, R. Mittal, B. R. Mcnamara, H. R. Russell, M. N. Bremer, F. Combes, A. C. Fabian, N. P. H. Nesvadba, C. P. O'Dea, S. A. Baum, P. Salomé, G. Tremblay, M. Donahue, Gary J. Ferland, C. L. Sarazin

Physics and Astronomy Faculty Publications

We present multifrequency observations of the radio galaxy Hydra-A (3C218) located in the core of a massive, X-ray luminous galaxy cluster. Integral field unit spectroscopy is used to trace the kinematics of the ionized and warm molecular hydrogen which are consistent with an ∼5 kpc rotating disc. Broad, double-peaked lines of CO(2–1), [C II] 157 μm and [O I] 63 μm are detected. We estimate the mass of the cold gas within the disc to be M_gas = 2.3 ± 0.3 × 10⁹ M_⊙. These observations demonstrate that the complex line profiles found in the cold …