Hydrogen Two-Photon Continuum Emission from the Horseshoe Filament in NGC 1275

Far ultraviolet emission has been detected from a knot of Halpha emission in the Horseshoe filament, far out in the NGC 1275 nebula. The flux detected relative to the brightness of the Halpha line in the same spatial region is very close to that expected from Hydrogen two-photon continuum emission in the particle heating model of Ferland et al. (2009) if reddening internal to the filaments is taken into account. We find no need to invoke other sources of far ultraviolet emission such as hot stars or emission lines from CIV in intermediate temperature gas to explain these data.Comment: 9 pages, 8 figures. Accepted for publication in MNRA

A SINFONI view of flies in the Spiderweb: a galaxy cluster in the making

The environment of the high-z radio galaxy PKS 1138-262 at z~2.2 is a prime example of a forming galaxy cluster. We use deep SINFONI data to perform a detailed study of the kinematics of the galaxies within 60 kpc of the radio core and we link this to the kinematics of the protocluster on the megaparsec scale. Identification of optical emission lines shows that 11 galaxies are at the redshift of the protocluster. The density of line emitters is more than an order of magnitude higher in the core of the protocluster than the larger scale environment. This implies a matter overdensity in the core of delta_m~70 which is similar to the outskirts of local galaxy clusters. The velocity distribution of the confirmed satellite galaxies shows a broad, double-peaked velocity structure with sigma=1360+/-206 km/s. A similar broad, double-peaked distribution was found in a previous study targeting the large scale protocluster structure, indicating that a common process is acting on both small and large scales. Including all spectroscopically confirmed protocluster galaxies, a velocity dispersion of 1013+/-87 km/s is found. We show that the protocluster has likely decoupled from the Hubble flow and is a dynamically evolved structure. Comparison to the Millenium simulation indicates that the protocluster velocity distribution is consistent with that of the most massive haloes at z~2, but we rule out that the protocluster is a fully virialized structure based on dynamical arguments and its X-ray luminosity. Comparison to merging haloes in the Millennium simulation shows that the structure as observed in and around the Spiderweb galaxy is best interpreted as being the result of a merger between two massive haloes. We propose that this merger can result in an increase in star formation and AGN activity in the protocluster core and is possibly an important stage in the evolution of massive cD galaxies.Comment: 12 pages, 7 figures. Accepted for publication in MNRA

Binding and activation of host plasminogen on the surface of Francisella tularensis

<p>Abstract</p> <p>Background</p> <p><it>Francisella tularensis </it>(FT) is a gram-negative facultative intracellular coccobacillus and is the causal agent of a life-threatening zoonotic disease known as tularemia. Although FT preferentially infects phagocytic cells of the host, recent evidence suggests that a significant number of bacteria can be found extracellularly in the plasma fraction of the blood during active infection. This observation suggests that the interaction between FT and host plasma components may play an important role in survival and dissemination of the bacterium during the course of infection. Plasminogen (PLG) is a protein zymogen that is found in abundance in the blood of mammalian hosts. A number of both gram-positive and gram-negative bacterial pathogens have the ability to bind to PLG, giving them a survival advantage by increasing their ability to penetrate extracellular matrices and cross tissue barriers.</p> <p>Results</p> <p>We show that PLG binds to the surface of FT and that surface-bound PLG can be activated to plasmin in the presence of tissue PLG activator <it>in vitro</it>. In addition, using Far-Western blotting assays coupled with proteomic analyses of FT outer membrane preparations, we have identified several putative PLG-binding proteins of FT.</p> <p>Conclusions</p> <p>The ability of FT to acquire surface bound PLG that can be activated on its surface may be an important virulence mechanism that results in an increase in initial infectivity, survival, and/or dissemination of this bacterium <it>in vivo</it>.</p

Modeling electron temperature profiles in the pedestal with simple formulas for ETG transport

This paper reports on the refinement (building on Ref.~\cite{hatch_22}) and application of simple formulas for electron heat transport from electron temperature gradient (ETG) driven turbulence in the pedestal. The formulas are improved by (1) improving the parameterization for certain key parameters and (2) carefully accounting for the impact of geometry and shaping in the underlying gyrokinetic simulation database. Comparisons with nonlinear gyrokinetic simulations of ETG transport in the MAST pedestal demonstrate the model's applicability to spherical tokamaks in addition to standard aspect ratio tokamaks. We identify bounds for model applicability: the model is accurate in the steep gradient region, where the ETG turbulence is largely slab-like, but accuracy decreases as the temperature gradient becomes weaker in the pedestal top and the instabilities become increasingly toroidal in nature. We use the formula to model the electron temperature profile in the pedestal for four experimental scenarios while extensively varying input parameters to represent uncertainties. In all cases, the predicted electron temperature pedestal exhibits extreme sensitivity to separatrix temperature and density, which has implications for core-edge integration. The model reproduces the electron temperature profile for high $\eta_e = L_{ne}/L_{Te}$ scenarios but not for low $\eta_e$ scenarios in which microtearing modes have been identified. We develop a proof-of-concept model for MTM transport and explore the relative roles of ETG and MTM in setting the electron temperature profile. We propose that pedestal scenarios predicted for future devices should be tested for compatibility with ETG transport

The Origin of Molecular Hydrogen Emission in Cooling-Flow Filaments

The optical filaments found in many cooling flows in galaxy clusters consist of low-density (∼103 cm−3) cool (∼103 K) gas surrounded by significant amounts of cosmic-ray and magnetic field energy. Their spectra show anomalously strong low-ionization and molecular emission lines when compared with Galactic molecular clouds exposed to ionizing radiation such as the Orion complex. Previous studies have shown that the spectra cannot be produced by O-star photoionization. Here, we calculate the physical conditions in dusty gas that is well shielded from external sources of ionizing photons and is energized either by cosmic rays or dissipative magnetohydrodynamics waves. Strong molecular hydrogen lines, with relative intensities similar to those observed, are produced. Selection effects introduced by the microphysics produce a correlation between the H2 line upper level energy and the population temperature. These selection effects allow a purely collisional gas to produce H2emission that masquerades as starlight-pumped H2 but with intensities that are far stronger. This physics may find application to any environment where a broad range of gas densities or heating rates occur

Galaxy protocluster candidates around z ~ 2.4 radio galaxies

We study the environments of 6 radio galaxies at 2.2 < z < 2.6 using wide-field near-infrared images. We use colour cuts to identify galaxies in this redshift range, and find that three of the radio galaxies are surrounded by significant surface overdensities of such galaxies. The excess galaxies that comprise these overdensities are strongly clustered, suggesting they are physically associated. The colour distribution of the galaxies responsible for the overdensity are consistent with those of galaxies that lie within a narrow redshift range at z ~ 2.4. Thus the excess galaxies are consistent with being companions of the radio galaxies. The overdensities have estimated masses in excess of 10^14 solar masses, and are dense enough to collapse into virizalised structures by the present day: these structures may evolve into groups or clusters of galaxies. A flux-limited sample of protocluster galaxies with K < 20.6 mag is derived by statistically subtracting the fore- and background galaxies. The colour distribution of the protocluster galaxies is bimodal, consisting of a dominant blue sequence, comprising 77 +/- 10% of the galaxies, and a poorly populated red sequence. The blue protocluster galaxies have similar colours to local star-forming irregular galaxies (U -V ~ 0.6), suggesting most protocluster galaxies are still forming stars at the observed epoch. The blue colours and lack of a dominant protocluster red sequence implies that these cluster galaxies form the bulk of their stars at z < 3.Comment: Accepted for publication in MNRA

Collisional Heating as the Origin of Filament Emission in Galaxy Clusters

It has long been known that photoionization, whether by starlight or other sources, has difficulty in accounting for the observed spectra of the optical filaments that often surround central galaxies in large clusters. This paper builds on the first of this series in which we examined whether heating by energetic particles or dissipative magnetohydrodynamic (MHD) wave can account for the observations. The first paper focused on the molecular regions which produce strong H2 and CO lines. Here we extend the calculations to include atomic and low-ionization regions. Two major improvements to the previous calculations have been made. The model of the hydrogen atom, along with all elements of the H-like iso-electronic sequence, is now fully nl-resolved. This allows us to predict the hydrogen emission-line spectrum including excitation by suprathermal secondary electrons and thermal electrons or nuclei. We show how the predicted H Ispectrum differs from the pure-recombination case. The second update is to the rates for H0–H2 inelastic collisions. We now use the values computed by Wrathmall et al. The rates are often much larger and allow the ro–vibrational H2 level populations to achieve a thermal distribution at substantially lower densities than previously thought. We calculate the chemistry, ionization, temperature, gas pressure and emission-line spectrum for a wide range of gas densities and collisional heating rates. We assume that the filaments are magnetically confined. The gas is free to move along field lines so that the gas pressure is equal to that of the surrounding hot gas. A mix of clouds, some being dense and cold and others hot and tenuous, can exist. The observed spectrum will be the integrated emission from clouds with different densities and temperatures but the same pressure P/k=nT. We assume that the gas filling factor is given by a power law in density. The power-law index, the only free parameter in this theory, is set by matching the observed intensities of infrared H2 lines relative to optical H I lines. We conclude that the filaments are heated by ionizing particles, either conducted in from surrounding regions or produced in situ by processes related to MHD waves

Branding the nation: Towards a better understanding

This paper aims to clarify some misunderstanding about nation branding. It examines the origins and interpretations of the concept, and draws a comparison between nation branding and commercial branding. A new definition is offered that emphasises the need to shift from “branding” the nation to nation image management

Characterizing the Performance of Liquid Oxygen in a Magnetic Fluid Management System

The strong paramagnetic susceptibility of liquid oxygen (LOX) has established it as a good candidate for a cryogenic magnetic fluid system. While these properties have been defined for several decades, the continuing advancement and requirements of space technology will soon find a suitable application for a magnetic fluid system which can operate reliably and efficiently. Testing has begun on the dynamics of LOX when applied to electrically-induced steady and varying magnetic fields within a solenoid. The performance of LOX as a working fluid was characterized by its operability and sustainable pressure before breakdown. This paper presents numerical and experimental data on the performance characteristics of LOX in a magnetic fluid management system