1,992 research outputs found

    Subsidiary capability upgrading and parent-subsidiary relationship: insights from a Chinese acquisition in the UK

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    Purpose: - This study aims to explore capability upgrading of EMNE’s subsidiaries in developed countries and how the parent-subsidiary relationship influences such upgrading. Design/methodology/approach: - The study adopts an interdisciplinary approach to capability upgrading of EMNEs subsidiaries in developed countries. It employs a single case study to explore this under-research area. Finding: - the analysis challenges the orthodox view and suggests broad based capability upgrading has taken place in the EMNE acquired subsidiaries ranging from product, process, functional to intersectoral. In addition, the capability upgrading was contingent on the degree of subsidiary autonomy and subsidiary mandates. Originality/value: - This study represents one of the first to examine capability upgrading and parent-subsidiary relationship in the context of EMNEs’ internationalisation activities

    Galaxy gas ejection in radio galaxies: the case of 3C 35

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    We report results from XMM-Newton and Chandra observations of the nearby (z = 0.067) giant radio galaxy 3C 35. We find evidence for an X-ray emitting gas belt, orthogonal to and lying between the lobes of 3C 35, which we interpret as fossil-group gas driven outwards by the expanding radio lobes. We also detect weak emission from a second, more extended group-type environment, as well as inverse-Compton X-ray emission from the radio lobes. The morphological structure of the radio lobes and gas belt point to co-evolution. Furthermore, the radio source is powerful enough to eject galaxy-scale gas out to distances of 100kpc, and the ages of the two features are comparable (tsynch~140Myr, tbelt~80 Myr). The destruction of 3C 35's atmosphere may offer clues as to how fossil systems are regulated: radio galaxies need to be of power comparable to 3C 35 to displace and regulate fossil-group gas. We discuss the implications of the gas belt in 3C 35 in terms of AGN fuelling and feedback.Comment: 18 pages, accepted to MNRA

    The Infrared Jet In 3C66B

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    We present images of infrared emission from the radio jet in 3C66B. Data at three wavelengths (4.5, 6.75 and 14.5 microns) were obtained using the Infrared Space Observatory. The 6.75 micron image clearly shows an extension aligned with the radio structure. The jet was also detected in the 14.5 micron image, but not at 4.5 micron. The radio-infrared-optical spectrum of the jet can be interpreted as synchrotron emission from a population of electrons with a high-energy break of 4e11 eV. We place upper limits on the IR flux from the radio counter-jet. A symmetrical, relativistically beamed twin-jet structure is consistent with our results if the jets consist of multiple components.Comment: 7 pages, 4 figure

    3-D Simulations of Protostellar Jets in Stratified Ambient Media

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    We present fully three-dimensional hydrodynamical simulations of radiative cooling jets propagating into stratified isothermal ambient media with power-law density and pressure distributions. The parameters used are mainly suitable for protostellar jets but results applicable to extragalactic jets are also presented. Comparisons are made with previous simulations of jets through homogeneous media. We find that for radiative cooling jets propagating into regions where the ambient medium has an increasing density (and pressure) gradient, the ambient gas tends to compress the cold, low-pressure cocoon of shocked material that surrounds the beam and destroy the bow shock-like structure at the head. The compressing medium collimates the jet and promotes the development of Kelvin-Helmholtz instabilities which cause beam focusing, wiggling and the formation of internal traveling shocks, closeclose toto thethe headhead, via pinching along the beam. This remarkably resembles the structure of some observed systems (e.g. Haro 6-5B northern and HH 24G jets). These effects are larger for jets with smaller density ratio between jet and environment η\eta (tested for η\eta =1, 3, and 10) and larger Mach number Ma=vj/caM_a=v_j/c_a (tested for Ma=M_a=12 and 24, where vjv_j is the jet velocity and cac_a the ambient sound speed). In an ambient medium of decreasing density (and pressure), the beam is poorly collimated and relaxes, becoming faint. This could explain ''invisible'' jet sections, like the gap between the parent source and collimated beam (e.g., in HH30 jet). Although, on average, jets propagating into an increasing (decreasing) density environment are decelerated (accelerated) by the increasing (decreasing) ram pressure of the ambient medium, we find that their propagation velocities have an oscillating pattern.Comment: 33 pp, LaTeX file, 13 figures upon request. To appear in the Astrophys. J., vol 471, nov. 10t

    Effect of Gravitational Lensing on Measurements of the Sunyaev-Zel'dovich Effect

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    The Sunyaev-Zel'dovich (SZ) effect of a cluster of galaxies is usually measured after background radio sources are removed from the cluster field. Gravitational lensing by the cluster potential leads to a systematic deficit in the residual intensity of unresolved sources behind the cluster core relative to a control field far from the cluster center. As a result, the measured decrement in the Rayleigh-Jeans temperature of the cosmic microwave background is overestimated. We calculate the associated systematic bias which is inevitably introduced into measurements of the Hubble constant using the SZ effect. For the cluster A2218, we find that observations at 15 GHz with a beam radius of 0'.4 and a source removal threshold of 100 microJy underestimate the Hubble constant by 6-10%. If the profile of the gas pressure declines more steeply with radius than that of the dark matter density, then the ratio of lensing to SZ decrements increases towards the outer part of the cluster.Comment: 11 pages, 3 figures, submitted to ApJ

    Another X-ray-Discovered Poor Cluster of Galaxies Associated with CL 0016+16

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    We report optical spectroscopic observations of RX J0018.8+1602, a ROSAT X-ray source proposed to be an intermediate redshift cluster of galaxies. Our observations confirm the identification of RX J0018.8+1602 and provide measurements of its mean radial velocity (z=0.5406 +/- 0.0006) and velocity dispersion (sigma_p = 200 [+110, -80] km/s). This is the second poor cluster that has been found to be a companion to CL 0016+16 (z=0.5455), the other one being RX J0018.3+1618 (z=0.5506). The 0.2-2 keV band source-frame X-ray luminosity summed over both companion clusters is 5E44 ergs/s, which is a significant fraction, ~23%, of the X-ray luminosity of the main cluster. The companions are located at angular distances of 10 arcmin to 25 arcmin (minimum physical scales of 5 Mpc to 12 Mpc) from CL 0016+16 and we propose that they represent a new large-scale component of the X-ray emission from clusters of galaxies. Similar low X-ray luminosity poor clusters surrounding nearby Abell clusters can explain the excess power observed in the angular cross-correlation function between Abell clusters and the X-ray background on inferred physical scales of 14--20 Mpc (Soltan et al. 1996)

    The Dynamical State fo the Starless Dense Core FeSt 1-457: A Pulsating Globule?

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    High resolution molecular line observations of CS, HCO+, C18O and N2H+ were obtained toward the starless globule FeSt 1-457 in order to investigate its kinematics and chemistry. The HCO+ and CS spectra show clear self-reversed and asymmetric profiles across the face of the globule. The sense of the observed asymmetry is indicative of the global presence of expansion motions in the outer layers of the globule. These motions appear to be subsonic and significantly below the escape velocity of the globule. Comparison of our observations with near-infrared extinction data indicate that the globule is gravitationally bound. Taken together these considerations lead us to suggest that the observed expansion has its origin in an oscillatory motion of the outer layers of the globule which itself is likely in a quasi-stable state near hydrostatic equilibrium. Analysis of the observed linewidths of CO and N2H+ confirm that thermal pressure is the dominant component of the cloud's internal support. A simple calculation suggests that the dominant mode of pulsation would be an l = 2 mode with a period of 0.3 Myr. Deformation of the globule due to the large amplitude l = 2 oscillation may be responsible for the double-peaked structure of the core detected in high resolution extinction maps. Detailed comparison of the molecular-line observations and extinction data provides evidence for significant depletion of C18O and perhaps HCO+ while N2H+ may be undepleted to a cloud depth of about 40 magnitudes of visual extinction.Comment: to appear in ApJ vol 665 20 August 2007

    Discovery of an optical and X-ray synchrotron jet in NGC 7385

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    We report the discovery of optical and X-ray synchrotron emission from the brighter radio jet in galaxy NGC 7385 using data from HST and Chandra. The jet has a projected length of 5 kpc and a similar morphology to other known optical jets in low-power radio galaxies. We also report a strong jet-cloud interaction which appears to be deflecting the counter-jet and causing a reversal in its direction

    Hydrodynamic simulations of AGN jets:The impact of Riemann solvers and spatial reconstruction schemes on jet evolution

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    Numerical simulations play an essential role in helping us to understand the physical processes behind relativistic jets in active galactic nuclei. The large number of hydrodynamic codes available today enables a variety of different numerical algorithms to be utilized when conducting the simulations. Since many of the simulations presented in the literature use different combinations of algorithms it is important to quantify the differences in jet evolution that can arise due to the precise numerical schemes used. We conduct a series of simulations using the FLASH (magneto-)hydrodynamics code in which we vary the Riemann solver and spatial reconstruction schemes to determine their impact on the evolution and dynamics of the jets. For highly refined grids the variation in the simulation results introduced by the different combinations of spatial reconstruction scheme and Riemann solver is typically small. A high level of convergence is found for simulations using third-order spatial reconstruction with the Harten–Lax–Van-Leer with contact and Hybrid Riemann solvers
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