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Recent Merger (recent + merger)
Selected AbstractsShock heating in the group atmosphere of the radio galaxy B2 0838+32AMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2008Nazirah N. Jetha ABSTRACT We present Chandra and radio observations, and analysis of Sloan Digital Sky Survey data, of the radio galaxy B2 0838+32A (4C 32.26) and its environment. The radio galaxy is at the centre of a nearby group that has often been identified with the cluster Abell 695, but we argue that the original Abell cluster is likely to be an unrelated and considerably more distant system. The radio source is a restarting radio galaxy and, using our Chandra data, we argue that the currently active lobes are expanding supersonically, driving a shock with Mach number 2.4+1.0,0.5 into the interstellar medium. This would be only the third strong shock round a young radio source to be discovered, after Centaurus A and NGC 3801. However, in contrast to both these systems, the host galaxy of B2 0838+32A shows no evidence for a recent merger, while the active galactic nuclei (AGN) spectrum shows no evidence for the dusty torus that would imply a large reservoir of cold gas close to the central black hole. On the contrary, the AGN spectrum is of a type that has been associated with the presence of a radiatively inefficient accretion flow that could be controlled by an AGN heating and subsequent cooling of the hot, X-ray emitting gas. If correct, this means that B2 0838+32A is the first source in which we can directly see entropy-increasing processes (shocks) driven by accretion from the hot phase of the interstellar medium. [source] Ly, excess in high-redshift radio galaxies: a signature of star formation,MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007M. Villar-Martín ABSTRACT About 54 per cent of radio galaxies at z, 3 and 8 per cent of radio galaxies at 2 ,z < 3 show unusually strong Ly, emission, compared with the general population of high-redshift (z, 2) radio galaxies. These Ly,-excess objects (LAEs) show Ly,/He ii values consistent with or above standard photoionization model predictions. We reject with confidence several scenarios to explain the unusual strength of Ly, in these objects: shocks, low nebular metallicities, high gas densities and absorption/scattering effects. We show that the most successful explanation is the presence of a young stellar population which provides the extra supply of ionizing photons required to explain the Ly, excess in at least the most extreme LAEs (probably in all of them). This interpretation is strongly supported by the tentative trend found by other authors for z, 3 radio galaxies to show lower ultraviolet rest-frame polarization levels, or the dramatic increase in the detection rate at submm wavelengths of z > 2.5 radio galaxies. The enhanced star formation activity in LAEs could be a consequence of a recent merger which has triggered both the star formation and the active galactic nucleus/radio activities. The measurement of unusually high Ly, ratios in the extended gas of some high-redshift radio galaxies suggests that star formation activity occurs in spatial scales of tens of kpc. We argue that, although the fraction of LAEs may be incompletely determined, both at 2 ,z < 3 and at z, 3, the much larger fraction of LAEs found at z, 3 is a genuine redshift evolution and not due to selection effects. Therefore, our results suggest that the radio galaxy phenomenon is more often associated with a massive starburst at z > 3 than at z < 3. [source] The build-up of haloes within Press,Schechter theoryMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2001Will J. Percival Modelling the build-up of haloes is important for linking the formation of galaxies with cosmological models. A simple model of halo growth is provided by Press,Schechter (PS) theory, where the initial field of density fluctuations is smoothed using spherically symmetric filters centred on a given position to obtain information about the likelihood of later collapse on varying scales. In this paper the predicted halo mass growth is compared for three filter shapes: Gaussian, top-hat and sharp k -space. Preliminary work is also presented analysing the build-up of haloes within numerical simulations using a friends-of-friends group finder. The best-fit to the simulation mass function was obtained using PS theory with a top-hat filter. By comparing both the backwards conditional mass function, which gives the distribution of halo progenitors, and the distribution of halo mergers in time, the build-up of haloes in the simulations is shown to be better fitted by PS theory with a sharp k -space filter. This strengthens previous work, which also found the build-up of haloes in simulations to be well matched to PS theory with a sharp k -space filter by providing a direct comparison of different filters and by extending the statistical tools used to analyse halo mass growth. The usefulness of this work is illustrated by showing that the cosmological evolution in the proportion of haloes that have undergone recent merger is predicted to be independent of mass and power spectrum and to only depend upon cosmology. Recent results from observations of field galaxies are shown to match the evolution expected, but are not sufficiently accurate to distinguish usefully between cosmological parameters. [source] IC 1370: A merger candidate at the periphery of a z , 0.05 cluster,ASTRONOMISCHE NACHRICHTEN, Issue 9-10 2009S. Temporin Abstract Recent studies show evidence of galaxy pre-processing within groups and/or filaments before infall in galaxy clusters. We present VIMOS/IFU observations of IC1370, a galaxy that shows morphological signatures of a recent merger and is located at a projected distance of ,1.2 Mpc to the center of the cluster II Zw108 at z , 0.05. This galaxy shows two opposite tidal tails, a boxy bulge with a de Vaucouleurs light profile, and a disk component that contributes ,50 % of the total luminosity. We investigate the history of the galaxy by applying the spectral synthesis technique to the integral field observations and combining the resulting information with morphological and photometric parameters. The same observations allow us to investigate a background (z , 0.09) compact group of 6 galaxies, ofwhich IC 1370 was initially thought to be the central, brightest member (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Union Formation through Merger: The Case of Ver.di in GermanyBRITISH JOURNAL OF INDUSTRIAL RELATIONS, Issue 2 2005Berndt Keller This article is concerned with the recent merger of five German unions to form the new multi-industry union, ver.di. Its focus is on the effects of the merger and on developments in the post-merger phase. The article explores the various internal problems of the new union, concentrating on those that flow from the adoption of a matrix form of organisation. It deals also with the external relations of ver.di, with other unions and with the central organisation of German trade unions, the DGB. Central conclusions here are that the creation of ver.di is likely to exacerbate competition amongst German unions and further erode the position of the peak association. [source] The European single market and the regulation of the legal profession: an economic analysisMANAGERIAL AND DECISION ECONOMICS, Issue 3 2002Frank H. StephenArticle first published online: 3 APR 200 The article analyses the effect of removing barriers between two autarkic legal markets with different technologies. Firms using the more efficient technology penetrate the other market. The result is mergers between firms from the efficient jurisdictions and those in the inefficient jurisdictions. Social welfare increases from reduced resource costs in the production of legal services even if prices remain regulated. This leads to pressure for prices for legal services to be reduced. Recent trends in the penetration of EU legal markets by English solicitors firms are discussed, particularly recent mergers involving English and German law firms. Implications for future market regulation are drawn. Copyright © 2002 John Wiley & Sons, Ltd. [source] Simulations of strong gravitational lensing with substructureMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006Adam Amara ABSTRACT Galactic-sized gravitational lenses are simulated by combining a cosmological N -body simulation and models for the baryonic component of the galaxy. The lens caustics, critical curves, image locations and magnification ratios are calculated by ray shooting on an adaptive grid. When the source is near a cusp in a smooth lens' caustic, the sum of the magnifications of the three closest images should be close to zero. It is found that in the observed cases this sum is generally too large to be consistent with the simulations, implying that there is not enough substructure in the simulations. This suggests that other factors play an important role. These may include limited numerical resolution, lensing by structure outside the halo, selection bias and the possibility that a randomly selected galaxy halo may be more irregular, for example, due to recent mergers, than the isolated halo used in this study. It is also shown that, with the level of substructure computed from the N -body simulations, the image magnifications of the Einstein cross-type lenses are very weak functions of source size up to 1 kpc. This is also true for the magnification ratios of widely separated images in the fold and cusp,caustic lenses. This means that selected magnification ratios for the different emission regions of a lensed quasar should agree with each other, barring microlensing by stars. The source size dependence of the magnification ratio between the closest pair of images is more sensitive to substructure. [source] The Urge to Merge: A Multiple-Case StudyNONPROFIT MANAGEMENT & LEADERSHIP, Issue 2 2002Martha Golensky The authors undertook a comparative study of three recent mergers of nonprofit organizations in a Midwestern urban center, within the context of political-economy theory. The research explored the impact of the same environmental factor, managed care, on the initial decisions by organizational leaders and the effects of these early decisions on subsequent actions taken to implement the merger. The study tested the authors' model of the motivations for merging, which proposes that the relationship between the decision-making style of the leadership and the internal and external resources of the prospective partners determines whether the merger is driven primarily by mission, practicality, stability, or fear. Although the findings provide initial support for the hypotheses derived from the model, a demonstration of the differences in the approach to the merger by each organization indicated that other factors emerged as important driving forces during the various phases of the process. [source] SEQUENTIAL MERGERS WITH DIFFERING DIFFERENTIATION LEVELS,AUSTRALIAN ECONOMIC PAPERS, Issue 3 2009TAKESHI EBINA We study sequential merger incentives under presence of product differentiation. Two sets of firms produce closely related goods, whereas each set produces more differentiated goods. Merger incentives under product differentiation are found to be stronger for two firms producing closely related goods than more differentiated goods. Also, after one merger, other firms are willing to follow with their own merger, resulting in sequential mergers. This result is consistent with the recent mergers in the video game software industry in Japan. [source] | |||||||||||||