WorldWideScience

Sample records for equal-mass halo mergers

  1. EVOLUTION OF DARK MATTER PHASE-SPACE DENSITY DISTRIBUTIONS IN EQUAL-MASS HALO MERGERS

    International Nuclear Information System (INIS)

    Vass, Ileana M.; Kazanzidis, Stelios; Valluri, Monica; Kravtsov, Andrey V.

    2009-01-01

    We use dissipationless N-body simulations to investigate the evolution of the true coarse-grained phase-space density distribution f(x, v) in equal-mass mergers between dark matter (DM) halos. The halo models are constructed with various asymptotic power-law indices ρ ∝ r -γ ranging from steep cusps to core-like profiles and we employ the phase-space density estimator 'EnBid' developed by Sharma and Steinmetz to compute f(x, v). The adopted force resolution allows robust phase-space density profile estimates in the inner ∼1% of the virial radii of the simulated systems. We confirm that merger events result in a decrease of the coarse-grained phase-space density in accordance with expectations from Mixing Theorems for collisionless systems. We demonstrate that binary mergers between identical DM halos produce remnants that retain excellent memories of the inner slopes and overall shapes of the phase-space density distribution of their progenitors. The robustness of the phase-space density profiles holds for a range of orbital energies, and a variety of encounter configurations including sequences of several consecutive merger events, designed to mimic hierarchical merging, and collisions occurring at different cosmological epochs. If the progenitor halos are constructed with appreciably different asymptotic power-law indices, we find that the inner slope and overall shape of the phase-space density distribution of the remnant are substantially closer to that of the initial system with the steepest central density cusp. These results explicitly demonstrate that mixing is incomplete in equal-mass mergers between DM halos, as it does not erase memory of the progenitor properties. Our results also confirm the recent analytical predictions of Dehnen regarding the preservation of merging self-gravitating central density cusps.

  2. DARK MATTER HALO MERGERS: DEPENDENCE ON ENVIRONMENT

    International Nuclear Information System (INIS)

    Hester, J. A.; Tasitsiomi, A.

    2010-01-01

    This paper presents a study of the specific major merger rate as a function of group membership, local environment, and redshift in a very large, 500 h -1 Mpc, cosmological N-body simulation, the Millennium Simulation. The goal is to provide environmental diagnostics of major merger populations in order to test simulations against observations and provide further constraints on major merger driven galaxy evolution scenarios. A halo sample is defined using the maximum circular velocity, which is both well defined for subhalos and closely correlated with galaxy luminosity. Subhalos, including the precursors of major mergers, are severely tidally stripped. Major mergers between subhalos are therefore rare compared to mergers between subhalos and their host halos. Tidal stripping also suppresses dynamical friction, resulting in long major merger timescales when the more massive merger progenitor does not host other subhalos. When other subhalos are present, however, major merger timescales are several times shorter. This enhancement may be due to inelastic unbound collisions between subhalos, which deplete their orbital angular momentum and lead to faster orbital decay. Following these results, we predict that major mergers in group environments are dominated by mergers involving the central galaxy, that the specific major merger rate is suppressed in groups when all group members are considered together, and that the frequency of fainter companions is enhanced for major mergers and their remnants. We also measure an 'assembly bias' in the specific major merger rate in that major mergers of galaxy-like halos are slightly suppressed in overdense environments while major mergers of group-like halos are slightly enhanced. A dynamical explanation for this trend is advanced which calls on both tidal effects and interactions between bound halos beyond the virial radii of locally dynamically dominant halos.

  3. Inspiral, merger, and ring-down of equal-mass black-hole binaries

    International Nuclear Information System (INIS)

    Buonanno, Alessandra; Cook, Gregory B.; Pretorius, Frans

    2007-01-01

    We investigate the dynamics and gravitational-wave (GW) emission in the binary merger of equal-mass black holes as obtained from numerical relativity simulations. The simulations were performed with an evolution code based on generalized harmonic coordinates developed by Pretorius, and used quasiequilibrium initial-data sets constructed by Cook and Pfeiffer. Results from the evolution of three sets of initial data are explored in detail, corresponding to different initial separations of the black holes, and exhibit between 2-8 GW cycles before coalescence. We find that to a good approximation the inspiral phase of the evolution is quasicircular, followed by a 'blurred, quasicircular plunge' lasting for about 1-1.5 GW cycles. After this plunge the GW frequency decouples from the orbital frequency, and we define this time to be the start of the merger phase. Roughly 10-15 M separates the time between the beginning of the merger phase and when we are able to extract quasinormal ring-down modes from gravitational waves emitted by the newly formed black hole. This suggests that the merger lasts for a correspondingly short amount of time, approximately 0.5-0.75 of a full GW cycle. We present first-order comparisons between analytical models of the various stages of the merger and the numerical results--more detailed and accurate comparisons will need to await numerical simulations with higher accuracy, better control of systemic errors (including coordinate artifacts), and initial configurations where the binaries are further separated. During the inspiral, we find that if the orbital phase is well modeled, the leading order Newtonian quadrupole formula is able to match both the amplitude and phase of the numerical GW quite accurately until close to the point of merger. We provide comparisons between the numerical results and analytical predictions based on the adiabatic post-Newtonian (PN) and nonadiabatic resummed-PN models (effective-one-body and Pade models). For all

  4. Convergence properties of halo merger trees; halo and substructure merger rates across cosmic history

    Science.gov (United States)

    Poole, Gregory B.; Mutch, Simon J.; Croton, Darren J.; Wyithe, Stuart

    2017-12-01

    We introduce GBPTREES: an algorithm for constructing merger trees from cosmological simulations, designed to identify and correct for pathological cases introduced by errors or ambiguities in the halo finding process. GBPTREES is built upon a halo matching method utilizing pseudo-radial moments constructed from radially sorted particle ID lists (no other information is required) and a scheme for classifying merger tree pathologies from networks of matches made to-and-from haloes across snapshots ranging forward-and-backward in time. Focusing on SUBFIND catalogues for this work, a sweep of parameters influencing our merger tree construction yields the optimal snapshot cadence and scanning range required for converged results. Pathologies proliferate when snapshots are spaced by ≲0.128 dynamical times; conveniently similar to that needed for convergence of semi-analytical modelling, as established by Benson et al. Total merger counts are converged at the level of ∼5 per cent for friends-of-friends (FoF) haloes of size np ≳ 75 across a factor of 512 in mass resolution, but substructure rates converge more slowly with mass resolution, reaching convergence of ∼10 per cent for np ≳ 100 and particle mass mp ≲ 109 M⊙. We present analytic fits to FoF and substructure merger rates across nearly all observed galactic history (z ≤ 8.5). While we find good agreement with the results presented by Fakhouri et al. for FoF haloes, a slightly flatter dependence on merger ratio and increased major merger rates are found, reducing previously reported discrepancies with extended Press-Schechter estimates. When appropriately defined, substructure merger rates show a similar mass ratio dependence as FoF rates, but with stronger mass and redshift dependencies for their normalization.

  5. THE HALO MERGER RATE IN THE MILLENNIUM SIMULATION AND IMPLICATIONS FOR OBSERVED GALAXY MERGER FRACTIONS

    International Nuclear Information System (INIS)

    Genel, Shy; Genzel, Reinhard; Bouche, Nicolas; Naab, Thorsten; Sternberg, Amiel

    2009-01-01

    We have developed a new method to extract halo merger rates from the Millennium Simulation. First, by removing superfluous mergers that are artifacts of the standard friends-of-friends (FOF) halo identification algorithm, we find a lower merger rate compared to previous work. The reductions are more significant at lower redshifts and lower halo masses, and especially for minor mergers. Our new approach results in a better agreement with predictions from the extended Press-Schechter model. Second, we find that the FOF halo finder overestimates the halo mass by up to 50% for halos that are about to merge, which leads to an additional ∼20% overestimate of the merger rate. Therefore, we define halo masses by including only particles that are gravitationally bound to their FOF groups. We provide new best-fitting parameters for a global formula to account for these improvements. In addition, we extract the merger rate per progenitor halo, as well as per descendant halo. The merger rate per progenitor halo is the quantity that should be related to observed galaxy merger fractions when they are measured via pair counting. At low-mass/redshift, the merger rate increases moderately with mass and steeply with redshift. At high enough mass/redshift (for the rarest halos with masses a few times the 'knee' of the mass function), these trends break down, and the merger rate per progenitor halo decreases with mass and increases only moderately with redshift. Defining the merger rate per progenitor halo also allows us to quantify the rate at which halos are being accreted onto larger halos, in addition to the minor and major merger rates. We provide an analytic formula that converts any given merger rate per descendant halo into a merger rate per progenitor halo. Finally, we perform a direct comparison between observed merger fractions and the fraction of halos in the Millennium Simulation that have undergone a major merger during the recent dynamical friction time, and find a

  6. Gravitationally Consistent Halo Catalogs and Merger Trees for Precision Cosmology

    Science.gov (United States)

    Behroozi, Peter S.; Wechsler, Risa H.; Wu, Hao-Yi; Busha, Michael T.; Klypin, Anatoly A.; Primack, Joel R.

    2013-01-01

    We present a new algorithm for generating merger trees and halo catalogs which explicitly ensures consistency of halo properties (mass, position, and velocity) across time steps. Our algorithm has demonstrated the ability to improve both the completeness (through detecting and inserting otherwise missing halos) and purity (through detecting and removing spurious objects) of both merger trees and halo catalogs. In addition, our method is able to robustly measure the self-consistency of halo finders; it is the first to directly measure the uncertainties in halo positions, halo velocities, and the halo mass function for a given halo finder based on consistency between snapshots in cosmological simulations. We use this algorithm to generate merger trees for two large simulations (Bolshoi and Consuelo) and evaluate two halo finders (ROCKSTAR and BDM). We find that both the ROCKSTAR and BDM halo finders track halos extremely well; in both, the number of halos which do not have physically consistent progenitors is at the 1%-2% level across all halo masses. Our code is publicly available at http://code.google.com/p/consistent-trees. Our trees and catalogs are publicly available at http://hipacc.ucsc.edu/Bolshoi/.

  7. Galaxy Mergers and Dark Matter Halo Mergers in LCDM: Mass, Redshift, and Mass-Ratio Dependence

    International Nuclear Information System (INIS)

    Stewart, K.

    2009-01-01

    We employ a high-resolution LCDM N-body simulation to present merger rate predictions for dark matter halos and investigate how common merger-related observables for galaxies - such as close pair counts, starburst counts, and the morphologically disturbed fraction - likely scale with luminosity, stellar mass, merger mass ratio, and redshift from z = 0 to z = 4. We provide a simple 'universal' fitting formula that describes our derived merger rates for dark matter halos a function of dark halo mass, merger mass ratio, and redshift, and go on to predict galaxy merger rates using number density-matching to associate halos with galaxies. For example, we find that the instantaneous merger rate of m/M > 0.3 mass ratio events into typical L ∼> fL * galaxies follows the simple relation dN/dt ≅ 0.03(1+f)Gyr -1 (1+z) 2.1 . Despite the rapid increase in merger rate with redshift, only a small fraction of > 0.4L * high-redshift galaxies (∼ 3% at z = 2) should have experienced a major merger (m/M > 0.3) in the very recent past (t 0.3) in the last 700 Myr and conclude that mergers almost certainly play an important role in delivering baryons and influencing the kinematic properties of Lyman Break Galaxies (LBGs)

  8. Particle ejection during mergers of dark matter halos

    Energy Technology Data Exchange (ETDEWEB)

    Carucci, Isabella P.; Sparre, Martin; Hansen, Steen H. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, Copenhagen, 2100 Denmark (Denmark); Joyce, Michael, E-mail: carucci@dark-cosmology.dk, E-mail: sparre@dark-cosmology.dk, E-mail: hansen@dark-cosmology.dk, E-mail: joyce@lpnhe.in2p3.fr [Laboratoire de Physique Nucléaire et Hautes Énergies, Université Pierre et Marie Curie - Paris 6, CNRS IN2P3 UMR 7585, 4 Place Jussieu, Paris Cedex 05, 75752 France (France)

    2014-06-01

    Dark matter halos are built from accretion and merging. During merging some of the dark matter particles may be ejected with velocities higher than the escape velocity. We use both N-body simulations and single-particle smooth-field simulations to demonstrate that rapid changes to the mean field potential are responsible for such ejection, and in particular that dynamical friction plays no significant role in it. Studying a range of minor mergers, we find that typically between 5–15% of the particles from the smaller of the two merging structures are ejected. We also find that the ejected particles originate essentially from the small halo, and more specifically are particles in the small halo which pass later through the region in which the merging occurs.

  9. GALAXY MERGERS AND DARK MATTER HALO MERGERS IN ΛCDM: MASS, REDSHIFT, AND MASS-RATIO DEPENDENCE

    International Nuclear Information System (INIS)

    Stewart, Kyle R.; Bullock, James S.; Barton, Elizabeth J.; Wechsler, Risa H.

    2009-01-01

    We employ a high-resolution ΛCDM N-body simulation to present merger rate predictions for dark matter (DM) halos and investigate how common merger-related observables for galaxies-such as close pair counts, starburst counts, and the morphologically disturbed fraction-likely scale with luminosity, stellar mass, merger mass ratio, and redshift from z = 0 to z = 4. We investigate both rate at which subhalos first enter the virial radius of a larger halo (the 'infall rate'), and the rate at which subhalos become destroyed, losing 90% of the mass they had at infall (the d estruction rate ) . For both merger rate definitions, we provide a simple 'universal' fitting formula that describes our derived merger rates for DM halos a function of dark halo mass, merger mass ratio, and redshift, and go on to predict galaxy merger rates using number density matching to associate halos with galaxies. For example, we find that the instantaneous (destruction) merger rate of m/M > 0.3 mass-ratio events into typical L ∼> f L * galaxies follows the simple relation dN/dt ≅ 0.03(1 + f) Gyr -1 (1 + z) 2.1 . Despite the rapid increase in merger rate with redshift, only a small fraction of >0.4 L * high-redshift galaxies (∼3% at z = 2) should have experienced a major merger (m/M > 0.3) in the very recent past (t 0.3) in the previous 700 Myr and conclude that mergers almost certainly play an important role in delivering baryons and influencing the kinematic properties of Lyman break galaxies (LBGs).

  10. The mass function of unprocessed dark matter haloes and merger tree branching rates

    Science.gov (United States)

    Benson, Andrew J.

    2017-05-01

    A common approach in semi-analytic modelling of galaxy formation is to construct Monte Carlo realizations of merger histories of dark matter haloes whose masses are sampled from a halo mass function. Both the mass function itself and the merger rates used to construct merging histories are calibrated to N-body simulations. Typically, 'backsplash' haloes (those which were once subhaloes within a larger halo, but which have since moved outside of the halo) are counted in both the halo mass functions and in the merger rates (or, equivalently, progenitor mass functions). This leads to a double counting of mass in Monte Carlo merger histories, which will bias results relative to N-body results. We measure halo mass functions and merger rates with this double counting removed in a large, cosmological N-body simulation with cosmological parameters consistent with current constraints. Furthermore, we account for the inherently noisy nature of N-body halo mass estimates when fitting functions to N-body data, and show that ignoring these errors leads to a significant systematic bias given the precision statistics available from state-of-the-art N-body cosmological simulations.

  11. Mergers and mass accretion for infalling halos both end well outside cluster virial radii

    Energy Technology Data Exchange (ETDEWEB)

    Behroozi, Peter S. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Wechsler, Risa H.; Lu, Yu; Busha, Michael T. [Physics Department, Stanford University, Department of Particle and Particle Astrophysics, SLAC National Accelerator Laboratory, Kavli Institute for Particle Astrophysics and Cosmology Stanford, CA 94305 (United States); Hahn, Oliver [Institute for Astronomy, ETH Zurich, 8093-CH Zurich (Switzerland); Klypin, Anatoly [Astronomy Department, New Mexico State University, Las Cruces, NM 88003 (United States); Primack, Joel R., E-mail: behroozi@stsci.edu [Department of Physics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States)

    2014-06-01

    We find that infalling dark matter halos (i.e., the progenitors of satellite halos) begin losing mass well outside the virial radius of their eventual host halos. The peak mass occurs at a range of clustercentric distances, with median and 68th percentile range of 1.8{sub −1.0}{sup +2.3} R{sub vir,host} for progenitors of z = 0 satellites. The peak circular velocity for infalling halos occurs at significantly larger distances (3.7{sub −2.2}{sup +3.3} R{sub vir,host} at z = 0). This difference arises because different physical processes set peak circular velocity (typically, ∼1:5 and larger mergers which cause transient circular velocity spikes) and peak mass (typically, smooth accretion) for infalling halos. We find that infalling halos also stop having significant mergers well before they enter the virial radius of their eventual hosts. Mergers larger than a 1:40 ratio in halo mass end for infalling halos at similar clustercentric distances (∼1.9 R {sub vir,} {sub host}) as the end of overall mass accretion. However, mergers larger than 1:3 typically end for infalling halos at more than four virial radial away from their eventual hosts. This limits the ability of mergers to affect quenching and morphology changes in clusters. We also note that the transient spikes which set peak circular velocity may lead to issues with abundance matching on that parameter, including unphysical galaxy stellar mass growth profiles near clusters; we propose a simple observational test to check if a better halo proxy for galaxy stellar mass exists.

  12. Mergers and mass accretion for infalling halos both end well outside cluster virial radii

    Energy Technology Data Exchange (ETDEWEB)

    Behroozi, Peter S.; Wechsler, Risa H.; Lu, Yu; Hahn, Oliver; Busha, Michael T.; Klypin, Anatoly; Primack, Joel R.

    2014-05-14

    We find that infalling dark matter halos (i.e., the progenitors of satellite halos) begin losing mass well outside the virial radius of their eventual host halos. The peak mass occurs at a range of clustercentric distances, with median and 68th percentile range of $1.8^{+2.3}_{-1.0} \\,R_\\mathrm{vir,host}$ for progenitors of z = 0 satellites. The peak circular velocity for infalling halos occurs at significantly larger distances ($3.7^{+3.3}_{-2.2} \\,R_\\mathrm{vir,host}$ at z = 0). This difference arises because different physical processes set peak circular velocity (typically, ~1:5 and larger mergers which cause transient circular velocity spikes) and peak mass (typically, smooth accretion) for infalling halos. We find that infalling halos also stop having significant mergers well before they enter the virial radius of their eventual hosts. Mergers larger than a 1:40 ratio in halo mass end for infalling halos at similar clustercentric distances (~1.9 R vir, host) as the end of overall mass accretion. However, mergers larger than 1:3 typically end for infalling halos at more than four virial radial away from their eventual hosts. This limits the ability of mergers to affect quenching and morphology changes in clusters. We also note that the transient spikes which set peak circular velocity may lead to issues with abundance matching on that parameter, including unphysical galaxy stellar mass growth profiles near clusters; we propose a simple observational test to check if a better halo proxy for galaxy stellar mass exists.

  13. The effects of a hot gaseous halo on disc thickening in galaxy minor mergers

    Science.gov (United States)

    Moster, Benjamin P.; Macciò, Andrea V.; Somerville, Rachel S.; Naab, Thorsten; Cox, T. J.

    2012-07-01

    We employ hydrodynamical simulations to study the effects of dissipational gas physics on the vertical heating and thickening of disc galaxies during minor mergers. For the first time we present a suite of simulations that includes a diffuse, rotating, cooling, hot gaseous halo, as predicted by cosmological hydrodynamical simulations as well as models of galaxy formation. We study the effect of this new gaseous component on the vertical structure of a Milky Way-like stellar disc during 1:10 and 1:5 mergers. For 1:10 mergers, we find no increased final thin disc scale height compared to the isolated simulation, leading to the conclusion that thin discs can be present even after a 1:10 merger if a reasonable amount of hot gas is present. The reason for this is the accretion of new cold gas, leading to the formation of a massive new thin stellar disc that dominates the surface brightness profile. In a previous study, in which we included only cold gas in the disc, we showed that the presence of cold gas decreased the thickening by a minor merger relative to the no-gas case. Here, we show that the evolution of the scale height in the presence of a cooling hot halo is dominated by the formation of the new stellar disc. In this scenario, the thick disc is the old stellar disc that has been thickened in a minor merger at z≳ 1, while the thin disc is the new stellar disc that reforms after this merger. When galactic winds are also considered, the final scale height is larger due to two effects. First, the winds reduce the star formation rate, leading to a less massive new stellar disc, such that the thickened old disc still dominates. Secondly, the winds exert a pressure force on the gas in the disc, leading to a shallower gas profile and thus to a thicker new stellar disc. In addition, we study the evolution of the scale height during a 1:5 merger and find that a thin disc can be present even after this merger, provided enough hot gas is available. The final scale

  14. Cumulative Neutrino and Gamma-Ray Backgrounds from Halo and Galaxy Mergers

    Science.gov (United States)

    Yuan, Chengchao; Mészáros, Peter; Murase, Kohta; Jeong, Donghui

    2018-04-01

    The merger of dark matter halos and the gaseous structures embedded in them, such as protogalaxies, galaxies, and groups and clusters of galaxies, results in strong shocks that are capable of accelerating cosmic rays (CRs) to ≳10 PeV. These shocks will produce high-energy neutrinos and γ-rays through inelastic pp collisions. In this work, we study the contributions of these halo mergers to the diffuse neutrino flux and to the nonblazar portion of the extragalactic γ-ray background. We formulate the redshift dependence of the shock velocity, galactic radius, halo gas content, and galactic/intergalactic magnetic fields over the dark matter halo distribution up to a redshift z = 10. We find that high-redshift mergers contribute a significant amount of the CR luminosity density, and the resulting neutrino spectra could explain a large part of the observed diffuse neutrino flux above 0.1 PeV up to several PeV. We also show that our model can somewhat alleviate tensions with the extragalactic γ-ray background. First, since a larger fraction of the CR luminosity density comes from high redshifts, the accompanying γ-rays are more strongly suppressed through γγ annihilations with the cosmic microwave background and the extragalactic background light. Second, mildly radiative-cooled shocks may lead to a harder CR spectrum with spectral indices of 1.5 ≲ s ≲ 2.0. Our study suggests that halo mergers, a fraction of which may also induce starbursts in the merged galaxies, can be promising neutrino emitters without violating the existing Fermi γ-ray constraints on the nonblazar component of the extragalactic γ-ray background.

  15. Momentum flow in black-hole binaries. II. Numerical simulations of equal-mass, head-on mergers with antiparallel spins

    International Nuclear Information System (INIS)

    Lovelace, Geoffrey; Chen Yanbei; Cohen, Michael; Kaplan, Jeffrey D.; Keppel, Drew; Matthews, Keith D.; Nichols, David A.; Scheel, Mark A.; Sperhake, Ulrich

    2010-01-01

    Research on extracting science from binary-black-hole (BBH) simulations has often adopted a 'scattering matrix' perspective: given the binary's initial parameters, what are the final hole's parameters and the emitted gravitational waveform? In contrast, we are using BBH simulations to explore the nonlinear dynamics of curved spacetime. Focusing on the head-on plunge, merger, and ringdown of a BBH with transverse, antiparallel spins, we explore numerically the momentum flow between the holes and the surrounding spacetime. We use the Landau-Lifshitz field-theory-in-flat-spacetime formulation of general relativity to define and compute the density of field energy and field momentum outside horizons and the energy and momentum contained within horizons, and we define the effective velocity of each apparent and event horizon as the ratio of its enclosed momentum to its enclosed mass-energy. We find surprisingly good agreement between the horizons' effective and coordinate velocities. During the plunge, the holes experience a frame-dragging-induced acceleration orthogonal to the plane of their spins and their infall ('downward'), and they reach downward speeds of order 1000 km/s. When the common apparent horizon forms (and when the event horizons merge and their merged neck expands), the horizon swallows upward field momentum that resided between the holes, causing the merged hole to accelerate in the opposite ('upward') direction. As the merged hole and the field energy and momentum settle down, a pulsational burst of gravitational waves is emitted, and the merged hole has a final effective velocity of about 20 km/s upward, which agrees with the recoil velocity obtained by measuring the linear momentum carried to infinity by the emitted gravitational radiation. To investigate the gauge dependence of our results, we compare generalized harmonic and Baumgarte-Shapiro-Shibata-Nakamura-moving-puncture evolutions of physically similar initial data; although the generalized

  16. A machine learning approach to galaxy-LSS classification - I. Imprints on halo merger trees

    Science.gov (United States)

    Hui, Jianan; Aragon, Miguel; Cui, Xinping; Flegal, James M.

    2018-04-01

    The cosmic web plays a major role in the formation and evolution of galaxies and defines, to a large extent, their properties. However, the relation between galaxies and environment is still not well understood. Here, we present a machine learning approach to study imprints of environmental effects on the mass assembly of haloes. We present a galaxy-LSS machine learning classifier based on galaxy properties sensitive to the environment. We then use the classifier to assess the relevance of each property. Correlations between galaxy properties and their cosmic environment can be used to predict galaxy membership to void/wall or filament/cluster with an accuracy of 93 per cent. Our study unveils environmental information encoded in properties of haloes not normally considered directly dependent on the cosmic environment such as merger history and complexity. Understanding the physical mechanism by which the cosmic web is imprinted in a halo can lead to significant improvements in galaxy formation models. This is accomplished by extracting features from galaxy properties and merger trees, computing feature scores for each feature and then applying support vector machine (SVM) to different feature sets. To this end, we have discovered that the shape and depth of the merger tree, formation time, and density of the galaxy are strongly associated with the cosmic environment. We describe a significant improvement in the original classification algorithm by performing LU decomposition of the distance matrix computed by the feature vectors and then using the output of the decomposition as input vectors for SVM.

  17. Simulations of galaxy mergers

    International Nuclear Information System (INIS)

    Villumsen, J.V.; Yale Univ., New Haven, CT

    1982-01-01

    A number of N-body simulations of mergers of equal and unequal galaxies are presented. A new code is presented which determines the potential from a mass distribution by a fourth-order expansion in Tesseral harmonics in three dimensions as an approximation to a collisionless system. The total number of particles in the system is 1200. Two galaxies, each a spherical non-rotating system with isothermal or Hubble density profile, are put in orbit around each other where tidal effects and dynamical friction lead to merging. The final system has a Hubble profile, and in some mergers an 'isothermal' halo forms as found in cD galaxies. Equal mass mergers are more flattened than unequal mass mergers. The central surface brightness decreases except in a merger of isothermal galaxies which shows a major redistribution of energy towards a Hubble profile. Mixing is severe in equal mass mergers, where radial gradients are weakened, while in unequal mass encounters gradients can build up due to less mixing and the formation of a halo. Oblate systems with strong rotation form in high angular momentum encounters while prolate systems with little rotation are formed in near head-on collisions. (author)

  18. Simulations of galaxy mergers

    International Nuclear Information System (INIS)

    Villumsen, J.V.

    1982-01-01

    This work is a theoretical investigation of the mechanisms and results of mergers of elliptical galaxies. An N-body code is developed to simulate the dynamics of centrally concentrated collisionless systems. It is used for N-body simulations of the mergers of galaxies with mass ratios of 1:1, 2:1 and 3:1 with a total of 1200 or 2400 particles. The initial galaxies are spherical and non-rotating with Hubble type profiles and isotropic velocity distributions. The remnants are flattened (up to E4) and are oblate, triaxial or prolate depending on the impact parameter. Equal mass mergers are more flattened than unequal mass mergers and have significant velocity anisotropies. The remnants have Hubble type profiles with decreased central surface brightness and increased core radii and tidal radii. In some unequal mass mergers ''isothermal'' haloes tend to form. The density profiles are inconsistent with De Vaucouleurs profiles even though the initial profiles were not. The central velocity dispersion increases in 1:1 and 2:1 mass mergers but decreases in 3:1 mass mergers. Near head-on mergers lead to prolate systems with little rotation while high angular momentum mergers lead to oblate systems with strong rotation. The rotation curves show solid body rotation out to the half mass radius followed by a slow decline. Radial mixing is strong in equal mass mergers where it will weaken radial gradients. In unequal mass mergers there is little radial mixing but matter from the smaller galaxy ends up in the outer parts of the system where it can give rise to colour gradient

  19. Dark-matter halo mergers as a fertile environment for low-mass Population III star formation

    DEFF Research Database (Denmark)

    Bovino, S.; Latif, M. A.; Grassi, Tommaso

    2014-01-01

    While Population III (Pop III) stars are typically thought to be massive, pathways towards lower mass Pop III stars may exist when the cooling of the gas is particularly enhanced. A possible route is enhanced HD cooling during the merging of dark-matter haloes. The mergers can lead to a high...

  20. Simulated galaxy remnants produced by binary and multiple mergers

    Science.gov (United States)

    Novak, Gregory S.

    2008-10-01

    I compute simulated integral field kinematic data for the remnants produced in a large suite of hydrodynamic binary galaxy merger simulations in order to compare to the galaxies observed as part of the SAURON survey. I find that binary mergers are plausibly the formation mechanism for the ~80% of SAURON galaxies with fast rotation velocities, in agreement with previous studies. However, the simulations of gas-rich binary mergers produce virtually no slow rotators observed to make up ~20% of the SAURON galaxies. In order to identify the origin of these slow rotators, I perform a new set of galaxy merger simulations involving merger histories more complex than single binary mergers of disk galaxies. I set up simple, idealized simulations with four or eight progenitor galaxies in order to build intuition about how a simulated galaxy's merger history affects its kinematic structure. I find that if the merger tree consists solely of roughly equal mass binary mergers, then the remnant is a fast rotator similar to that produced by a single binary merger of disk galaxies. However, if the progenitors merge with the central galaxy one after another in a sequence of mergers with decreasing mass ratios, then the remnant does not rotate. This is a plausible formation scenario for the observed SAURON slowly-rotating galaxies. To see how frequently this happens with realistic initial conditions, I extract halos from a large-scale cosmological simulation and re-simulate the region with higher resolution. These simulations include intergalactic gas that is able to replenish the galaxies' gas supply as the simulation runs. In all cases, I get rapidly rotating remnant galaxies in spite of having several halos with diverse merger histories.

  1. Decoding Galactic Merger Histories

    Directory of Open Access Journals (Sweden)

    Eric F. Bell

    2017-12-01

    Full Text Available Galaxy mergers are expected to influence galaxy properties, yet measurements of individual merger histories are lacking. Models predict that merger histories can be measured using stellar halos and that these halos can be quantified using observations of resolved stars along their minor axis. Such observations reveal that Milky Way-mass galaxies have a wide range of stellar halo properties and show a correlation between their stellar halo masses and metallicities. This correlation agrees with merger-driven models where stellar halos are formed by satellite galaxy disruption. In these models, the largest accreted satellite dominates the stellar halo properties. Consequently, the observed diversity in the stellar halos of Milky Way-mass galaxies implies a large range in the masses of their largest merger partners. In particular, the Milky Way’s low mass halo implies an unusually quiet merger history. We used these measurements to seek predicted correlations between the bulge and central black hole (BH mass and the mass of the largest merger partner. We found no significant correlations: while some galaxies with large bulges and BHs have large stellar halos and thus experienced a major or minor merger, half have small stellar halos and never experienced a significant merger event. These results indicate that bulge and BH growth is not solely driven by merger-related processes.

  2. Tidal Tales of Minor Mergers: Star Formation in the Tidal Tails of Minor Mergers

    Science.gov (United States)

    Knierman, Karen; Monkiewicz, Jacqueline; Scowen, Paul; Groppi, Christopher

    2018-01-01

    While major mergers and their tidal debris are well studied, equal mass galaxy mergers are relatively rare compared to minor mergers (mass ratio HI for 15 minor mergers, are providing a larger sample of environments to study the threshold for star formation that can inform star formation models, particularly at low densities.

  3. Merger relics of cluster galaxies

    Science.gov (United States)

    Yi, S. K.; Lee, J.; Jung, I.; Ji, I.; Sheen, Y.-K.

    2013-06-01

    Context. Sheen and collaborators recently found that a surprisingly large portion (38%) of massive early-type galaxies in heavy clusters show strong merger-related disturbed features. This contradicts the general understanding that massive clusters are hostile environments for galaxy mergers. Considering the significance of mergers in galaxy evolution, it is important to understand this. Aims: We aim to present a theoretical foundation that explains galaxy mergers in massive clusters. Methods: We used the N-body simulation technique to perform a cosmological-volume simulation and derive dark-halo merger trees. Then, we used the semi-analytic modeling technique to populate each halo with galaxies. We ran hydrodynamic simulations of galaxy mergers to estimate the lifetime of merger features for the imaging condition used by Sheen and collaborators. We applied this merger feature lifetime to our semi-analytic models. Finally, we counted the massive early-type galaxies in heavy model clusters that would show strong merger features. Results: While there still are substantial uncertainties, our preliminary results are remarkably close to the observed fraction of galaxies with merger features. Key ingredients for the success are twofold: firstly, the subhalo motion in dark haloes has been accurately traced, and, second, the lifetime of merger features has been properly estimated. As a result, merger features are expected to last very long in cluster environments. Many massive early-type galaxies in heavy clusters therefore show merger features not because they experience mergers in the current clusters in situ, but because they still carry their merger features from their previous halo environments. Conclusions: Investigating the merger relics of cluster galaxies is potentially important, because it uniquely allows us to backtrack the halo merger history.

  4. Accurate evolutions of inspiralling and magnetized neutron stars: Equal-mass binaries

    International Nuclear Information System (INIS)

    Giacomazzo, Bruno; Rezzolla, Luciano; Baiotti, Luca

    2011-01-01

    By performing new, long and numerically accurate general-relativistic simulations of magnetized, equal-mass neutron-star binaries, we investigate the role that realistic magnetic fields may have in the evolution of these systems. In particular, we study the evolution of the magnetic fields and show that they can influence the survival of the hypermassive neutron star produced at the merger by accelerating its collapse to a black hole. We also provide evidence that, even if purely poloidal initially, the magnetic fields produced in the tori surrounding the black hole have toroidal and poloidal components of equivalent strength. When estimating the possibility that magnetic fields could have an impact on the gravitational-wave signals emitted by these systems either during the inspiral or after the merger, we conclude that for realistic magnetic-field strengths B 12 G such effects could be detected, but only marginally, by detectors such as advanced LIGO or advanced Virgo. However, magnetically induced modifications could become detectable in the case of small-mass binaries and with the development of gravitational-wave detectors, such as the Einstein Telescope, with much higher sensitivities at frequencies larger than ≅2 kHz.

  5. Bar formation in Cosmological Haloes

    Science.gov (United States)

    Curir, A.; Mazzei, P.; Murante, G.

    2003-06-01

    We investigate the growth of bar instability in stellar disks embedded in fully cosmological halos. We choose a Lambda -CDM cosmology (i.e. Omega_Λ() = 0.7, Omegam() = 0.3, H[0] = 70 km/s/Mpc) with 25h-1 Mpc of box size. The halo was selected from a low-resolution run (128^3 particles), it doesn't suffer major mergers since z = 5 and it lives in a low-density environment. Then we re-simulate the halo at 8 times higher resolution, following the whole simulation box with a multi-mass tecnique to account for the large-scale tidal forces. The stellar disk is embedded in the halo at a redshift z = 2. The evolution of the system spans more than 10 Gyr down to z = 0.

  6. MERGERS IN ΛCDM: UNCERTAINTIES IN THEORETICAL PREDICTIONS AND INTERPRETATIONS OF THE MERGER RATE

    International Nuclear Information System (INIS)

    Hopkins, Philip F.; Bundy, Kevin; Wetzel, Andrew; Ma, Chung-Pei; Croton, Darren; Khochfar, Sadegh; Hernquist, Lars; Genel, Shy; Van den Bosch, Frank; Somerville, Rachel S.; Keres, Dusan; Stewart, Kyle; Younger, Joshua D.

    2010-01-01

    Different theoretical methodologies lead to order-of-magnitude variations in predicted galaxy-galaxy merger rates. We examine how this arises and quantify the dominant uncertainties. Modeling of dark matter and galaxy inspiral/merger times contribute factor of ∼2 uncertainties. Different estimates of the halo-halo merger rate, the subhalo 'destruction' rate, and the halo merger rate with some dynamical friction time delay for galaxy-galaxy mergers, agree to within this factor of ∼2, provided proper care is taken to define mergers consistently. There are some caveats: if halo/subhalo masses are not appropriately defined the major-merger rate can be dramatically suppressed, and in models with 'orphan' galaxies and under-resolved subhalos the merger timescale can be severely over-estimated. The dominant differences in galaxy-galaxy merger rates between models owe to the treatment of the baryonic physics. Cosmological hydrodynamic simulations without strong feedback and some older semi-analytic models (SAMs), with known discrepancies in mass functions, can be biased by large factors (∼5) in predicted merger rates. However, provided that models yield a reasonable match to the total galaxy mass function, the differences in properties of central galaxies are sufficiently small to alone contribute small (factor of ∼1.5) additional systematics to merger rate predictions. But variations in the baryonic physics of satellite galaxies in models can also have a dramatic effect on merger rates. The well-known problem of satellite 'over-quenching' in most current SAMs-whereby SAM satellite populations are too efficiently stripped of their gas-could lead to order-of-magnitude under-estimates of merger rates for low-mass, gas-rich galaxies. Models in which the masses of satellites are fixed by observations (or SAMs adjusted to resolve this 'over-quenching') tend to predict higher merger rates, but with factor of ∼2 uncertainties stemming from the uncertainty in those

  7. MERGERS AND BULGE FORMATION IN ΛCDM: WHICH MERGERS MATTER?

    International Nuclear Information System (INIS)

    Hopkins, Philip F.; Bundy, Kevin; Wetzel, Andrew; Croton, Darren; Hernquist, Lars; Keres, Dusan; Younger, Joshua D.; Khochfar, Sadegh; Stewart, Kyle

    2010-01-01

    We use a suite of semi-empirical models to predict the galaxy-galaxy merger rate and relative contributions to bulge growth as a function of mass (both halo and stellar), redshift, and mass ratio. The models use empirical constraints on the halo occupation distribution, evolved forward in time, to robustly identify where and when galaxy mergers occur. Together with the results of high-resolution merger simulations, this allows us to quantify the relative contributions of mergers with different properties (e.g., mass ratios, gas fractions, redshifts) to the bulge population. We compare with observational constraints, and find good agreement. We also provide useful fitting functions and make public a code to reproduce the predicted merger rates and contributions to bulge mass growth. We identify several robust conclusions. (1) Major mergers dominate the formation and assembly of ∼L * bulges and the total spheroid mass density, but minor mergers contribute a non-negligible ∼30%. (2) This is mass dependent: bulge formation and assembly is dominated by more minor mergers in lower-mass systems. In higher-mass systems, most bulges originally form in major mergers near ∼L * , but assemble in increasingly minor mergers. (3) The minor/major contribution is also morphology dependent: higher B/T systems preferentially form in more major mergers, with B/T roughly tracing the mass ratio of the largest recent merger; lower B/T systems preferentially form in situ from minor mergers. (4) Low-mass galaxies, being gas-rich, require more mergers to reach the same B/T as high-mass systems. Gas-richness dramatically suppresses the absolute efficiency of bulge formation, but does not strongly influence the relative contribution of major versus minor mergers. (5) Absolute merger rates at fixed mass ratio increase with galaxy mass. (6) Predicted merger rates agree well with those observed in pair and morphology-selected samples, but there is evidence that some morphology

  8. Giant Radio Halos in Galaxy Clusters as Probes of Particle ...

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... Giant radio halos in galaxy clusters probe mechanisms of particle acceleration connected with cluster merger events. Shocks and turbulence are driven in the inter-galactic medium (IGM) during clusters mergers and may have a deep impact on the non-thermal properties of galaxy clusters. Models of ...

  9. Mergers & Acquisitions

    DEFF Research Database (Denmark)

    Fomcenco, Alex

    MERGERS & ACQUISITIONS: Counseling and Choice of Method describes and analyzes the current state of law in Europe in regard to some relevant selected elements related to mergers and acquisitions, and the adviser’s counsel in this regard. The focus is aimed and maintained at application...

  10. New (theoretical) Perspectives on the Galactic Halo

    NARCIS (Netherlands)

    Helmi, A.; Turon, C; Meynadier, F; Arenou, F

    1 discuss recent progress in our understanding of the formation of the stellar halo of the Milky Way in the context of the concordance cosmological model. The Gaia mission will provide unique insights especially into the early assembly of the Galaxy and likely be key in unraveling its merger

  11. WFIRST: Surveying galactic halos within 10Mpc

    Science.gov (United States)

    Courtney, Sol; Johnston, Kathryn; Sanderson, Robyn; WINGS Team

    2018-01-01

    Three aims of a WFIRST Infrared Nearby Galaxy Survey (WINGS) of stellar halos are: (i) to look at the global properties of the halos (e.g. radial profile and total content); (ii) to find and interpret structures that are signatures of accretion histories (including luminosity functions, merger rates and orbits); (iii) to find features at widest possible separations in order to constrain the distribution of dark matter. For all of the above purposes, the halos should be observed to the greatest radial extent possible. The extent to which this is possible or interesting will depend on expected densities of the stellar halos as well as contamination by background galaxies at faint magnitudes. This study “observes" the Bullock/Johnston stellar halo models as a guide for these expectations.

  12. Shape space figure-8 solution of three body problem with two equal masses

    Science.gov (United States)

    Yu, Guowei

    2017-06-01

    In a preprint by Montgomery (https://people.ucsc.edu/~rmont/Nbdy.html), the author attempted to prove the existence of a shape space figure-8 solution of the Newtonian three body problem with two equal masses (it looks like a figure 8 in the shape space, which is different from the famous figure-8 solution with three equal masses (Chenciner and Montgomery 2000 Ann. Math. 152 881-901)). Unfortunately there is an error in the proof and the problem is still open. Consider the α-homogeneous Newton-type potential, 1/rα, using action minimization method, we prove the existence of this solution, for α \\in (1, 2) ; for α=1 (the Newtonian potential), an extra condition is required, which unfortunately seems hard to verify at this moment.

  13. Action minimizers under topological constraints in the planar equal-mass four-body problem

    Science.gov (United States)

    Yan, Duokui

    2018-04-01

    It is shown that in the planar equal-mass four-body problem, there exist two sets of action minimizers connecting two planar boundary configurations with fixed symmetry axes and specific order constraints: a double isosceles configuration and an isosceles trapezoid configuration, while order constraints are introduced on the boundary configurations. By applying the level estimate method, these minimizers are shown to be collision-free and they can be extended to two new sets of periodic or quasi-periodic orbits.

  14. POST-MERGER SIGNATURES OF RED-SEQUENCE GALAXIES IN RICH ABELL CLUSTERS AT z ∼< 0.1

    International Nuclear Information System (INIS)

    Sheen, Yun-Kyeong; Yi, Sukyoung K.; Lee, Jaehyun; Ree, Chang H.

    2012-01-01

    We have investigated the post-merger signatures of red-sequence galaxies in rich Abell clusters at z ∼ r < –20) cluster red-sequence galaxies show post-merger signatures in four clusters consistently. Most (∼71%) of the featured galaxies were found to be bulge dominated, and for the subsample of bulge-dominated red-sequence galaxies, the post-merger fraction rises to ∼38%. We also found that roughly 4% of bulge-dominated red-sequence galaxies interact (ongoing merger). A total of 42% (38% post-merger, 4% ongoing merger) of galaxies show merger-related features. Compared to a field galaxy study with a similar limiting magnitude by van Dokkum in 2005, our cluster study presents a similar post-merger fraction but a markedly lower ongoing merger fraction. The merger fraction derived is surprisingly high for the high density of our clusters, where the fast internal motions of galaxies are thought to play a negative role in galaxy mergers. The fraction of post-merger and ongoing merger galaxies can be explained as follows. Most of the post-merger galaxies may have carried over their merger features from their previous halo environment, whereas interacting galaxies interact in the current cluster in situ. According to our semi-analytic calculation, massive cluster halos may very well have experienced tens of halo mergers over the last 4-5 Gyr; post-merger features last that long, allowing these features to be detected in our clusters today. The apparent lack of dependence of the merger fraction on the clustocentric distance is naturally explained this way. In this scenario, the galaxy morphology and properties can be properly interpreted only when the halo evolution characteristics are understood first.

  15. Mergers + acquisitions.

    Science.gov (United States)

    Hoppszallern, Suzanna

    2002-05-01

    The hospital sector in 2001 led the health care field in mergers and acquisitions. Most deals involved a network augmenting its presence within a specific region or in a market adjacent to its primary service area. Analysts expect M&A activity to increase in 2002.

  16. Mergers & Acquisitions

    DEFF Research Database (Denmark)

    Fomcenco, Alex

    This dissertation is a legal dogmatic thesis, the goal of which is to describe and analyze the current state of law in Europe in regard to some relevant selected elements related to mergers and acquisitions, and the adviser’s counsel in this regard. Having regard to the topic of the dissertation...

  17. Observing Mergers of Non-Spinning Black-Hole Binaries

    Science.gov (United States)

    McWilliams, Sean T.; Boggs, William D.; Baker, John G.; Kelly, Bernard J.

    2010-01-01

    Advances in the field of numerical relativity now make it possible to calculate the final, most powerful merger phase of binary black-hole coalescence for generic binaries. The state of the art has advanced well beyond the equal-mass case into the unequal-mass and spinning regions of parameter space. We present a study of the nonspinning portion of parameter space, primarily using an analytic waveform model tuned to available numerical data, with an emphasis on observational implications. We investigate the impact of varied m8BS ratio on merger signal-to-noise ratios (SNR) for several detectors, and compare our results with expectations from the test-mass limit. We note a striking similarity of the waveform phasing of the merger waveform across the available mass ratios. Motivated by this, we calculate the match between our equal-mass and 4:1 mass-ratio waveforms during the merger as a function of location on the source sky, using a new formalism for the match that accounts for higher harmonics. This is an indicator of the amount of degeneracy in mass ratio for mergers of moderate mass ratio systems.

  18. Satellite dwarf galaxies in a hierarchical universe: the prevalence of dwarf-dwarf major mergers

    International Nuclear Information System (INIS)

    Deason, Alis; Wetzel, Andrew; Garrison-Kimmel, Shea

    2014-01-01

    Mergers are a common phenomenon in hierarchical structure formation, especially for massive galaxies and clusters, but their importance for dwarf galaxies in the Local Group remains poorly understood. We investigate the frequency of major mergers between dwarf galaxies in the Local Group using the ELVIS suite of cosmological zoom-in dissipationless simulations of Milky Way- and M31-like host halos. We find that ∼10% of satellite dwarf galaxies with M star > 10 6 M ☉ that are within the host virial radius experienced a major merger of stellar mass ratio closer than 0.1 since z = 1, with a lower fraction for lower mass dwarf galaxies. Recent merger remnants are biased toward larger radial distance and more recent virial infall times, because most recent mergers occurred shortly before crossing within the virial radius of the host halo. Satellite-satellite mergers also occur within the host halo after virial infall, catalyzed by the large fraction of dwarf galaxies that fell in as part of a group. The merger fraction doubles for dwarf galaxies outside of the host virial radius, so the most distant dwarf galaxies in the Local Group are the most likely to have experienced a recent major merger. We discuss the implications of these results on observable dwarf merger remnants, their star formation histories, the gas content of mergers, and massive black holes in dwarf galaxies.

  19. MERGER SIGNATURES IN THE DYNAMICS OF STAR-FORMING GAS

    International Nuclear Information System (INIS)

    Hung, Chao-Ling; Sanders, D. B.; Hayward, Christopher C.; Smith, Howard A.; Ashby, Matthew L. N.; Martínez-Galarza, Juan R.; Zezas, Andreas; Lanz, Lauranne

    2016-01-01

    The recent advent of integral field spectrographs and millimeter interferometers has revealed the internal dynamics of many hundreds of star-forming galaxies. Spatially resolved kinematics have been used to determine the dynamical status of star-forming galaxies with ambiguous morphologies, and constrain the importance of galaxy interactions during the assembly of galaxies. However, measuring the importance of interactions or galaxy merger rates requires knowledge of the systematics in kinematic diagnostics and the visible time with merger indicators. We analyze the dynamics of star-forming gas in a set of binary merger hydrodynamic simulations with stellar mass ratios of 1:1 and 1:4. We find that the evolution of kinematic asymmetries traced by star-forming gas mirrors morphological asymmetries derived from mock optical images, in which both merger indicators show the largest deviation from isolated disks during strong interaction phases. Based on a series of simulations with various initial disk orientations, orbital parameters, gas fractions, and mass ratios, we find that the merger signatures are visible for ∼0.2–0.4 Gyr with kinematic merger indicators but can be approximately twice as long for equal-mass mergers of massive gas-rich disk galaxies designed to be analogs of z ∼ 2–3 submillimeter galaxies. Merger signatures are most apparent after the second passage and before the black holes coalescence, but in some cases they persist up to several hundred Myr after coalescence. About 20%–60% of the simulated galaxies are not identified as mergers during the strong interaction phase, implying that galaxies undergoing violent merging process do not necessarily exhibit highly asymmetric kinematics in their star-forming gas. The lack of identifiable merger signatures in this population can lead to an underestimation of merger abundances in star-forming galaxies, and including them in samples of star-forming disks may bias the measurements of disk

  20. Radio halos in SZ-selected clusters of galaxies: the making of a halo?

    OpenAIRE

    Bonafede, A.; Intema, H. T.; Brüggen, M.; Vazza, F.; Basu, K.; Sommer, M.; Ebeling, H.; de Gasperin, F.; Röttgering, H. J. A.; van Weeren, R. J.; Cassano, R.

    2015-01-01

    Radio halos are synchrotron radio sources detected in some massive galaxy clusters. Their Mpc-size indicates that (re)acceleration processes are taking place in the host cluster. X-ray catalogues of galaxy clusters have been used in the past to search for radio halos and to understand their connection with cluster-cluster mergers and with the thermal component of the intra-cluster medium. More recently, the Sunyaev-Zel'dovich effect has been proven to be a better route to search for massive c...

  1. Exotic nuclei: Halos

    Energy Technology Data Exchange (ETDEWEB)

    Orr, Nigel [Lab. de Physique Corpusculaire, Caen Univ., 14 (France); Collaboration: La Direction des Sciences de la Matiere du CEA (FR); Le Fonds National de la Recherche Scientifique de Belgique (BE)

    1998-12-31

    A brief overview of the nuclear halo is presented. Following some historical remarks the general characteristics of the halo systems are discussed with reference to a simple model. The conditions governing the formation of halos are also explored, as are two subjects of current interest - low-lying resonances of halo nucleon correlations. (author) 54 refs., 16 figs., 1 tabs.

  2. Galaxy mergers

    International Nuclear Information System (INIS)

    Roos, N.

    1981-01-01

    This thesis contains a series of four papers dealing with the effects of interactions among galaxies during the epoch of cluster formation. Galaxy interactions are investigated and the results incorporated in numerical simulations of the formation of groups and clusters of galaxies. The role of galaxy interactions is analysed in the more general context of simulations of an expanding universe. The evolution of galaxies in rich clusters is discussed. The results of the investigations are presented and their relation to other work done in the field are briefly reviewed and an attempt is made to link galaxy mergers to the occurrence of activity in galactic nuclei. (Auth.)

  3. Radio haloes in Sunyaev-Zel'dovich-selected clusters of galaxies: the making of a halo?

    Science.gov (United States)

    Bonafede, A.; Intema, H.; Brüggen, M.; Vazza, F.; Basu, K.; Sommer, M.; Ebeling, H.; de Gasperin, F.; Röttgering, H. J. A.; van Weeren, R. J.; Cassano, R.

    2015-12-01

    Radio haloes are synchrotron radio sources detected in some massive galaxy clusters. Their size of Mpc indicates that (re)acceleration processes are taking place in the host cluster. X-ray catalogues of galaxy clusters have been used in the past to search for radio haloes and to understand their connection with cluster-cluster mergers and with the thermal component of the intracluster medium. More recently, the Sunyaev-Zel'dovich effect has been proven to be a better route to search for massive clusters in a wider redshift range. With the aim of discovering new radio haloes and understanding their connection with cluster-cluster mergers, we have selected the most massive clusters from the Planck early source catalogue and we have observed with the Giant Metrewave Radio Telescope at 323 MHz those objects for which deep observations were not available. We have discovered new peculiar radio emission in three of the observed clusters, finding (i) a radio halo in the cluster RXCJ0949.8+1708, (ii) extended emission in Abell 1443 that we classify as a radio halo plus a radio relic, with a bright filament embedded in the radio halo, and (iii) low-power radio emission in CIZA J1938.3+5409 that is ten times below the radio-X-ray correlation and represents the first direct detection of the radio emission in the `upper-limit' region of the radio-X-ray diagram. We discuss the properties of these new radio haloes in the framework of theoretical models for the radio emission.

  4. Observational evidence for mergers

    International Nuclear Information System (INIS)

    Schweizer, F.

    1983-01-01

    Theory has long suggested that dynamical friction between colliding galaxies must lead to mergers. The problem for observers has been to find which galaxies are mergers. The author first reviews the available evidence for mergers in various kinds of galaxies, then proposes a tentative classification scheme for mergers, and finally discusses mergers in giant ellipticals and their relation to the evolution and perhaps even the formation of ellipticals. (Auth.)

  5. Galaxy mergers moulding the circum-galactic medium - I. The impact of a major merger

    Science.gov (United States)

    Hani, Maan H.; Sparre, Martin; Ellison, Sara L.; Torrey, Paul; Vogelsberger, Mark

    2018-03-01

    Galaxies are surrounded by sizeable gas reservoirs which host a significant amount of metals: the circum-galactic medium (CGM). The CGM acts as a mediator between the galaxy and the extragalactic medium. However, our understanding of how galaxy mergers, a major evolutionary transformation, impact the CGM remains deficient. We present a theoretical study of the effect of galaxy mergers on the CGM. We use hydrodynamical cosmological zoom-in simulations of a major merger selected from the Illustris project such that the z = 0 descendant has a halo mass and stellar mass comparable to the Milky Way. To study the CGM we then re-simulated this system at a 40 times better mass resolution, and included detailed post-processing ionization modelling. Our work demonstrates the effect the merger has on the characteristic size of the CGM, its metallicity, and the predicted covering fraction of various commonly observed gas-phase species, such as H I, C IV, and O VI. We show that merger-induced outflows can increase the CGM metallicity by 0.2-0.3 dex within 0.5 Gyr post-merger. These effects last up to 6 Gyr post-merger. While the merger increases the total metal covering fractions by factors of 2-3, the covering fractions of commonly observed UV ions decrease due to the hard ionizing radiation from the active galactic nucleus, which we model explicitly. Our study of the single simulated major merger presented in this work demonstrates the significant impact that a galaxy interaction can have on the size, metallicity, and observed column densities of the CGM.

  6. Surviving mergers & acquisitions.

    Science.gov (United States)

    Dixon, Diane L

    2002-01-01

    Mergers and acquisitions are never easy to implement. The health care landscape is a minefield of failed mergers and uneasy alliances generating great turmoil and pain. But some mergers have been successful, creating health systems that benefit the communities they serve. Five prominent leaders offer their advice on minimizing the difficulties of M&As.

  7. Modelling giant radio halos. Doctoral Thesis Award Lecture 2012

    Science.gov (United States)

    Donnert, J. M. F.

    2013-06-01

    We review models for giant radio halos in clusters of galaxies, with a focus on numerical and theoretical work. After summarising the most important observations of these objects, we present an introduction to the theoretical aspects of hadronic models. We compare these models with observations using simulations and find severe problems for hadronic models. We give a short introduction to reacceleration models and show results from the first simulation of CRe reacceleration in cluster mergers. We find that in-line with previous theoretical work, reacceleration models are able to elegantly explain main observables of giant radio halos.

  8. What sets the central structure of dark matter haloes?

    Science.gov (United States)

    Ogiya, Go; Hahn, Oliver

    2018-02-01

    Dark matter (DM) haloes forming near the thermal cut-off scale of the density perturbations are unique, since they are the smallest objects and form through monolithic gravitational collapse, while larger haloes contrastingly have experienced mergers. While standard cold dark matter (CDM) simulations readily produce haloes that follow the universal Navarro-Frenk-White (NFW) density profile with an inner slope, ρ ∝ r-α, with α = 1, recent simulations have found that when the free-streaming cut-off expected for the CDM model is resolved, the resulting haloes follow nearly power-law density profiles of α ∼ 1.5. In this paper, we study the formation of density cusps in haloes using idealized N-body simulations of the collapse of proto-haloes. When the proto-halo profile is initially cored due to particle free-streaming at high redshift, we universally find ∼r-1.5 profiles irrespective of the proto-halo profile slope outside the core and large-scale non-spherical perturbations. Quite in contrast, when the proto-halo has a power-law profile, then we obtain profiles compatible with the NFW shape when the density slope of the proto-halo patch is shallower than a critical value, αini ∼ 0.3, while the final slope can be steeper for αini ≳ 0.3. We further demonstrate that the r-1.5 profiles are sensitive to small-scale noise, which gradually drives them towards an inner slope of -1, where they become resilient to such perturbations. We demonstrate that the r-1.5 solutions are in hydrostatic equilibrium, largely consistent with a simple analytic model, and provide arguments that angular momentum appears to determine the inner slope.

  9. Mergers of black-hole binaries with aligned spins: Waveform characteristics

    International Nuclear Information System (INIS)

    Kelly, Bernard J.; Baker, John G.; Centrella, Joan; Boggs, William D.; McWilliams, Sean T.

    2011-01-01

    We conduct a descriptive analysis of the multipolar structure of gravitational-radiation waveforms from equal-mass aligned-spin mergers, following an approach first presented in the complementary context of nonspinning black holes of varying mass ratio [J. G. Baker et al., Phys. Rev. D 78, 044046 (2008).]. We find that, as with the nonspinning mergers, the dominant waveform mode phases evolve together in lock-step through inspiral and merger, supporting the previous waveform description in terms of an adiabatically rigid rotator driving gravitational-wave emission--an implicit rotating source. We further apply the late-time merger-ringdown model for the rotational frequency introduced in [J. G. Baker et al., Phys. Rev. D 78, 044046 (2008).], along with an improved amplitude model appropriate for the dominant (2, ±2) modes. This provides a quantitative description of the merger-ringdown waveforms, and suggests that the major features of these waveforms can be described with reference only to the intrinsic parameters associated with the state of the final black hole formed in the merger. We provide an explicit model for the merger-ringdown radiation, and demonstrate that this model agrees to fitting factors better than 95% with the original numerical waveforms for system masses above ∼150M · . This model may be directly applicable to gravitational-wave detection of intermediate-mass black-hole mergers.

  10. ZOMG - III. The effect of halo assembly on the satellite population

    Science.gov (United States)

    Garaldi, Enrico; Romano-Díaz, Emilio; Borzyszkowski, Mikolaj; Porciani, Cristiano

    2018-01-01

    We use zoom hydrodynamical simulations to investigate the properties of satellites within galaxy-sized dark-matter haloes with different assembly histories. We consider two classes of haloes at redshift z = 0: 'stalled' haloes that assembled at z > 1 and 'accreting' ones that are still forming nowadays. Previously, we showed that the stalled haloes are embedded within thick filaments of the cosmic web, while the accreting ones lie where multiple thin filaments converge. We find that satellites in the two classes have both similar and different properties. Their mass spectra, radial count profiles, baryonic and stellar content, and the amount of material they shed are indistinguishable. However, the mass fraction locked in satellites is substantially larger for the accreting haloes as they experience more mergers at late times. The largest difference is found in the satellite kinematics. Substructures fall towards the accreting haloes along quasi-radial trajectories whereas an important tangential velocity component is developed, before accretion, while orbiting the filament that surrounds the stalled haloes. Thus, the velocity anisotropy parameter of the satellites (β) is positive for the accreting haloes and negative for the stalled ones. This signature enables us to tentatively categorize the Milky Way halo as stalled based on a recent measurement of β. Half of our haloes contain clusters of satellites with aligned orbital angular momenta corresponding to flattened structures in space. These features are not driven by baryonic physics and are only found in haloes hosting grand-design spiral galaxies, independently of their assembly history.

  11. Revisiting Scaling Relations for Giant Radio Halos in Galaxy Clusters

    Science.gov (United States)

    Cassano, R.; Ettori, S.; Brunetti, G.; Giacintucci, S.; Pratt, G. W.; Venturi, T.; Kale, R.; Dolag, K.; Markevitch, Maxim L.

    2013-01-01

    Many galaxy clusters host megaparsec-scale radio halos, generated by ultrarelativistic electrons in the magnetized intracluster medium. Correlations between the synchrotron power of radio halos and the thermal properties of the hosting clusters were established in the last decade, including the connection between the presence of a halo and cluster mergers. The X-ray luminosity and redshift-limited Extended GMRT Radio Halo Survey provides a rich and unique dataset for statistical studies of the halos. We uniformly analyze the radio and X-ray data for the GMRT cluster sample, and use the new Planck Sunyaev-Zel'dovich (SZ) catalog to revisit the correlations between the power of radio halos and the thermal properties of galaxy clusters. We find that the radio power at 1.4 GHz scales with the cluster X-ray (0.1-2.4 keV) luminosity computed within R(sub 500) as P(sub 1.4) approx. L(2.1+/-0.2) - 500). Our bigger and more homogenous sample confirms that the X-ray luminous (L(sub 500) > 5 × 10(exp 44) erg/s)) clusters branch into two populations-radio halos lie on the correlation, while clusters without radio halos have their radio upper limits well below that correlation. This bimodality remains if we excise cool cores from the X-ray luminosities. We also find that P(sub 1.4) scales with the cluster integrated SZ signal within R(sub 500), measured by Planck, as P(sub 1.4) approx. Y(2.05+/-0.28) - 500), in line with previous findings. However, contrary to previous studies that were limited by incompleteness and small sample size, we find that "SZ-luminous" Y(sub 500) > 6×10(exp -5) Mpc(exp 2) clusters show a bimodal behavior for the presence of radio halos, similar to that in the radio-X-ray diagram. Bimodality of both correlations can be traced to clusters dynamics, with radio halos found exclusively in merging clusters. These results confirm the key role of mergers for the origin of giant radio halos, suggesting that they trigger the relativistic particle acceleration.

  12. Characterizing Black Hole Mergers

    Science.gov (United States)

    Baker, John; Boggs, William Darian; Kelly, Bernard

    2010-01-01

    Binary black hole mergers are a promising source of gravitational waves for interferometric gravitational wave detectors. Recent advances in numerical relativity have revealed the predictions of General Relativity for the strong burst of radiation generated in the final moments of binary coalescence. We explore features in the merger radiation which characterize the final moments of merger and ringdown. Interpreting the waveforms in terms of an rotating implicit radiation source allows a unified phenomenological description of the system from inspiral through ringdown. Common features in the waveforms allow quantitative description of the merger signal which may provide insights for observations large-mass black hole binaries.

  13. The Extended Baryonic Halo of NGC 3923

    Directory of Open Access Journals (Sweden)

    Bryan W. Miller

    2017-07-01

    Full Text Available Galaxy halos and their globular cluster systems build up over time by the accretion of small satellites. We can learn about this process in detail by observing systems with ongoing accretion events and comparing the data with simulations. Elliptical shell galaxies are systems that are thought to be due to ongoing or recent minor mergers. We present preliminary results of an investigation of the baryonic halo—light profile, globular clusters, and shells/streams—of the shell galaxy NGC 3923 from deep Dark Energy Camera (DECam g and i-band imaging. We present the 2D and radial distributions of the globular cluster candidates out to a projected radius of about 185 kpc, or ∼ 37 R e , making this one of the most extended cluster systems studied. The total number of clusters implies a halo mass of M h ∼ 3 × 10 13 M ⊙ . Previous studies had identified between 22 and 42 shells, making NGC 3923 the system with the largest number of shells. We identify 23 strong shells and 11 that are uncertain. Future work will measure the halo mass and mass profile from the radial distributions of the shell, N-body models, and line-of-sight velocity distribution (LOSVD measurements of the shells using the Multi Unit Spectroscopic Explorer (MUSE.

  14. ALFA beam halo

    CERN Document Server

    Komarek, Tomas

    2014-01-01

    This note serves as a final report about CERN Summer Student Programme 2014 project. The beam halo is an undesired phenomenon for physics analyses on particle accelerators. It surrounds the beam core and constitutes an important part of background for signal measurements on some detectors, eg. in the forward region. In this study, the data from the ALFA detector were used, specifically from the run 191373 ($\\beta^*=90\\unit{m}$) and the run 213268 ($\\beta^*=1\\unit{km}$). Using the ROOT framework, a software for beam halo events selection was created and beam halo properties were examined. In the run 213268, excessive beam halo is suspected to be the reason for multiple beam scrapings that occurred. A kinematic reconstruction of beam halo particles is attempted in order to understand beam halo properties in the interaction point. Some further simulations are employed to find constraints for beam halo particles in order to survive in the accelerator for a longer time/many revolutions. This work represents a st...

  15. Merger rate of primordial black-hole binaries

    Science.gov (United States)

    Ali-Haïmoud, Yacine; Kovetz, Ely D.; Kamionkowski, Marc

    2017-12-01

    Primordial black holes (PBHs) have long been a candidate for the elusive dark matter (DM), and remain poorly constrained in the ˜20 - 100 M⊙ mass range. PBH binaries were recently suggested as the possible source of LIGO's first detections. In this paper, we thoroughly revisit existing estimates of the merger rate of PBH binaries. We compute the probability distribution of orbital parameters for PBH binaries formed in the early Universe, accounting for tidal torquing by all other PBHs, as well as standard large-scale adiabatic perturbations. We then check whether the orbital parameters of PBH binaries formed in the early Universe can be significantly affected between formation and merger. Our analytic estimates indicate that the tidal field of halos and interactions with other PBHs, as well as dynamical friction by unbound standard DM particles, do not do significant work on nor torque PBH binaries. We estimate the torque due to baryon accretion to be much weaker than previous calculations, albeit possibly large enough to significantly affect the eccentricity of typical PBH binaries. We also revisit the PBH-binary merger rate resulting from gravitational capture in present-day halos, accounting for Poisson fluctuations. If binaries formed in the early Universe survive to the present time, as suggested by our analytic estimates, they dominate the total PBH merger rate. Moreover, this merger rate would be orders of magnitude larger than LIGO's current upper limits if PBHs make a significant fraction of the dark matter. As a consequence, LIGO would constrain ˜10 - 300 M⊙ PBHs to constitute no more than ˜1 % of the dark matter. To make this conclusion fully robust, though, numerical study of several complex astrophysical processes—such as the formation of the first PBH halos and how they may affect PBH binaries, as well as the accretion of gas onto an extremely eccentric binary—is needed.

  16. The Connection between Radio Halos and Cluster Mergers and the ...

    Indian Academy of Sciences (India)

    (2008) suggested that the behavior of clusters in the. P1.4 − LX diagram is connected with their dynamical state. 2.2 The dynamical state of GMRT clusters ..... (e.g., Cassano et al. 2008) and were used to derive expectations for the planned. LOFAR surveys. Accordingly to these predictions the Tier 1 'Large Area Survey' at.

  17. The Connection between Radio Halos and Cluster Mergers and the ...

    Indian Academy of Sciences (India)

    1Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127, Bologna, Italy. 2IRA-INAF, via Gobetti 101, 40129 Bologna, Italy. ∗ e-mail: rcassano@ira.inaf. .... Chandra archive X-ray data of a sub-sample of GMRT clusters provided a quantita- tive measure of the degree of the cluster disturbance adopting three ...

  18. Mergers at z = 1

    Science.gov (United States)

    Kao, Lancelot L.

    1993-01-01

    Multiband images of nearby interacting pairs of galaxies, mergers, and normal field galaxies are used to simulate images of high redshift mergers by identifying distinctive morphological features. Preliminary results indicate that it is feasible for the HST to detect these high redshift objects.

  19. Mergers and Acquisitions

    DEFF Research Database (Denmark)

    Risberg, Annette

    , employee experiences and communication. Mergers and acquisitions remain one of the most common forms of growth, yet they present considerable challenges for the companies and management involved. The effects on stakeholders, including shareholders, managers and employees, must be considered as well......Introduction to the study of mergers and acquisitions. This book provides an understanding of the mergers and acquisitions process, how and why they occur, and also the broader implications for organizations. It presents issues including motives and planning, partner selection, integration...... by editorial commentaries and reflects the important organizational and behavioural aspects which have often been ignored in the past. By providing this in-depth understanding of the mergers and acquisitions process, the reader understands not only how and why mergers and acquisitions occur, but also...

  20. Mergers and Acquisitions

    DEFF Research Database (Denmark)

    Risberg, Annette

    Introduction to the study of mergers and acquisitions. This book provides an understanding of the mergers and acquisitions process, how and why they occur, and also the broader implications for organizations. It presents issues including motives and planning, partner selection, integration......, employee experiences and communication. Mergers and acquisitions remain one of the most common forms of growth, yet they present considerable challenges for the companies and management involved. The effects on stakeholders, including shareholders, managers and employees, must be considered as well...... by editorial commentaries and reflects the important organizational and behavioural aspects which have often been ignored in the past. By providing this in-depth understanding of the mergers and acquisitions process, the reader understands not only how and why mergers and acquisitions occur, but also...

  1. Mergers: Success versus failure

    International Nuclear Information System (INIS)

    Carley, G. R.

    1997-01-01

    Successful mergers in the context of long-term value creation, as measured by return realized on investor-provided capital, were discussed. In essence, a successful merger is characterized by being motivated by a sound business reason and strategy for the merger, a reasonable price and sound execution. The acquiror's pre-merger success in managing a company is a good indicator of future success. Poorly managed companies that acquire other companies generally continue to be poorly managed with no significant increase in shareholder value. Prior to the acquisition, identification of the potential target, assessment of the people involved on both sides of the transaction, thorough knowledge of the target's potential for value creation, financial implications (debt, equity, terms and demand, tax implications, the potential effect of the proposed acquisition on the acquiror's business plan) and finally the execution of the process itself, are the important determinants of successful mergers

  2. Runaway stars from young star clusters containing initial binaries. I. Equal-mass, equal-energy binaries

    Energy Technology Data Exchange (ETDEWEB)

    Leonard, P.J.T.; Duncan, M.J.

    1988-07-01

    The production of runaway stars by the dynamical-ejection mechanism in an open star cluster containing 50 percent binaries of equal mass and energy is investigated theoretically by means of numerical simulations using the NBODY5 code of Aarseth (1985). The construction of the models is outlined, and the results are presented graphically and characterized in detail. It is shown that binary-binary collisions capable of producing runaways can occur (via formation and disruption, with some stellar collisions, of hierarchical double binaries) in clusters of relatively low density (e.g., pc-sized clusters of O or B stars). The frequency of binaries in the runaway population is found to vary between 0 and 50 percent, with the majority of runaways being unevolved early-type stars. 38 references.

  3. HALO: Wearable Lighting

    OpenAIRE

    Zhao, Nan; Paradiso, Joseph A.

    2015-01-01

    What if lighting were not fixed to our architecture but becomes part of our body? Light would be only where it is needed. Buildings would light up brightly when busy, and dim down when people leave. Lighting would become more energy efficient, more personal, and colorful, tailored to individual needs. What applications beyond illumination would be possible in such a scenario? Halo is a wearable lighting device that aims to investigate this question. More specifically Halo explores the potenti...

  4. RECOILING MASSIVE BLACK HOLES IN GAS-RICH GALAXY MERGERS

    International Nuclear Information System (INIS)

    Guedes, Javiera; Madau, Piero; Mayer, Lucio; Callegari, Simone

    2011-01-01

    The asymmetric emission of gravitational waves produced during the coalescence of a massive black hole (MBH) binary imparts a velocity 'kick' to the system that can displace the hole from the center of its host. Here, we study the trajectories and observability of MBHs recoiling in three (one major, two minor) gas-rich galaxy merger remnants that were previously simulated at high resolution, and in which the pairing of the MBHs had been shown to be successful. We run new simulations of MBHs recoiling in the major merger remnant with Mach numbers in the range 1≤M≤6 and use simulation data to construct a semi-analytical model for the orbital evolution of MBHs in gas-rich systems. We show the following. (1) In major merger remnants the energy deposited by the moving hole into the rotationally supported, turbulent medium makes a negligible contribution to the thermodynamics of the gas. This contribution becomes significant in minor merger remnants, potentially allowing for an electromagnetic signature of MBH recoil. (2) In major merger remnants, the combination of both deeper central potential well and drag from high-density gas confines even MBHs with kick velocities as high as 1200 km s -1 within 1 kpc from the host's center. (3) Kinematically offset nuclei may be observable for timescales of a few Myr in major merger remnants in the case of recoil velocities in the range 700-1000 km s -1 . (4) In minor merger remnants the effect of gas drag is weaker, and MBHs with recoil speeds in the range 300-600 km s -1 will wander through the host halo for longer timescales. When accounting for the probability distribution of kick velocities, however, we find that the likelihood of observing recoiling MBHs in gas-rich galaxy mergers is very low even in the best-case scenario.

  5. Gas-Rich Mergers in LCDM: Disk Survivability and the Baryonic Assembly of Galaxies

    International Nuclear Information System (INIS)

    Stewart, K.

    2009-01-01

    We use N-body simulations and observationally-normalized relations between dark matter halo mass, stellar mass, and cold gas mass to derive robust expectations about the baryonic content of major mergers out to redshift z ∼ 2. First, we find that the majority of major mergers (m/M > 0.3) experienced by Milky Way size dark matter halos should have been gas-rich, and that gas-rich mergers are increasingly common at high redshift. Though the frequency of major mergers into galaxy halos in our simulations greatly exceeds the observed late-type galaxy fraction, the frequency of gas-poor major mergers is consistent with the observed fraction of bulge-dominated galaxies across the halo mass range M DM ∼ 10 11 - 10 13 M · . These results lend support to the conjecture that mergers with high baryonic gas fractions play an important role in building and/or preserving disk galaxies in the universe. Secondly, we find that there is a transition mass below which a galaxy's past major mergers were primarily gas-rich and above which they were gas poor. The associated stellar mass scale corresponds closely to that marking the observed bimodal division between blue, star-forming, disk-dominated systems and red, bulge-dominated systems with old populations. Finally, we find that the overall fraction of a galaxy's cold baryons deposited directly via major mergers is substantial. Approximately 30% of the cold baryonic material in M star ∼ 10 10 M · (M DM ∼ 10 11.5 M · ) galaxies is accreted as cold gas in major mergers. For more massive galaxies with M star ∼ 10 11 M · (M DM ∼ 10 13 M · the fraction of baryons amassed in mergers is even higher, ∼ 50%, but most of these accreted baryons are delivered directly in the form of stars. This baryonic mass deposition is almost unavoidable, and provides a limit on the fraction of a galaxy's cold baryons that can originate in cold flows or from hot halo cooling

  6. Gas-Rich Mergers in LCDM: Disk Survivability and the Baryonic Assembly of Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, Kyle R.; Bullock, James S.; /UC, Irvine; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC; Maller, Ariyeh H.; /New York City Coll. Tech.

    2009-08-03

    We use N-body simulations and observationally-normalized relations between dark matter halo mass, stellar mass, and cold gas mass to derive robust expectations about the baryonic content of major mergers out to redshift z {approx} 2. First, we find that the majority of major mergers (m/M > 0.3) experienced by Milky Way size dark matter halos should have been gas-rich, and that gas-rich mergers are increasingly common at high redshift. Though the frequency of major mergers into galaxy halos in our simulations greatly exceeds the observed late-type galaxy fraction, the frequency of gas-poor major mergers is consistent with the observed fraction of bulge-dominated galaxies across the halo mass range M{sub DM} {approx} 10{sup 11} - 10{sup 13} M{sub {circle_dot}}. These results lend support to the conjecture that mergers with high baryonic gas fractions play an important role in building and/or preserving disk galaxies in the universe. Secondly, we find that there is a transition mass below which a galaxy's past major mergers were primarily gas-rich and above which they were gas poor. The associated stellar mass scale corresponds closely to that marking the observed bimodal division between blue, star-forming, disk-dominated systems and red, bulge-dominated systems with old populations. Finally, we find that the overall fraction of a galaxy's cold baryons deposited directly via major mergers is substantial. Approximately 30% of the cold baryonic material in M{sub star} {approx} 10{sup 10} M{sub {circle_dot}} (M{sub DM} {approx} 10{sup 11.5} M{sub {circle_dot}}) galaxies is accreted as cold gas in major mergers. For more massive galaxies with M{sub star} {approx} 10{sup 11} M{sub {circle_dot}} (M{sub DM} {approx} 10{sup 13} M{sub {circle_dot}} the fraction of baryons amassed in mergers is even higher, {approx} 50%, but most of these accreted baryons are delivered directly in the form of stars. This baryonic mass deposition is almost unavoidable, and provides a

  7. Mergers of Black-Hole Binaries with Aligned Spins: Waveform Characteristics

    Science.gov (United States)

    Kelly, Bernard J.; Baker, John G.; vanMeter, James R.; Boggs, William D.; McWilliams, Sean T.; Centrella, Joan

    2011-01-01

    "We apply our gravitational-waveform analysis techniques, first presented in the context of nonspinning black holes of varying mass ratio [1], to the complementary case of equal-mass spinning black-hole binary systems. We find that, as with the nonspinning mergers, the dominant waveform modes phases evolve together in lock-step through inspiral and merger, supporting the previous model of the binary system as an adiabatically rigid rotator driving gravitational-wave emission - an implicit rotating source (IRS). We further apply the late-merger model for the rotational frequency introduced in [1], along with a new mode amplitude model appropriate for the dominant (2, plus or minus 2) modes. We demonstrate that this seven-parameter model performs well in matches with the original numerical waveform for system masses above - 150 solar mass, both when the parameters are freely fit, and when they are almost completely constrained by physical considerations."

  8. Hospital mergers: a panacea?

    Science.gov (United States)

    Weil, Thomas

    2010-10-01

    Hospital mergers in Europe and North America have been launched to scale down expenditure, enhance the delivery of health care and elevate quality. However, the outcome of mergers suggest that they neither generated cost savings nor improved the quality of care. Almost all consolidations fall short, since those in leadership positions lack the necessary understanding and appreciation of the differences in culture, values and goals of the existing facilities. In spite of these shortcomings, hospital mergers will continue to be pursued in order to improve market share, eliminate excess capacity, gain access to capital and enhance the personal egos of the organizations' leaders.

  9. MERGER ACCOUTING FOR COMPANIES

    Directory of Open Access Journals (Sweden)

    SUCIU GHEORGHE

    2014-05-01

    Full Text Available Companies, especially nowadays, are characterized through great mobility, fast circulation of capital, occurring in their chase for profit. In this context, companies look for alliances, economical and political assistance. These objectives can materialize through merging of companies. The merger can be internal (between Romanian companies or transboundary, which includes foreign companies. In order to correctly reflect these events, the merger operations must be regulated and must respect national and international regulations. One important request concerning the merger operations is that the accounting values of the assets, debts and ownership equity must be brought to the present financial value.

  10. Driving the growth of the earliest supermassive black holes with major mergers of host galaxies

    International Nuclear Information System (INIS)

    Tanaka, Takamitsu L

    2014-01-01

    The formation mechanism of supermassive black holes (SMBHs) in general, and of ∼10 9  m ⊙ SMBHs observed as luminous quasars at redshifts z>6 in particular, remains an open fundamental question. The presence of such massive BHs at such early times, when the Universe was less than a billion years old, implies that they grew via either super-Eddington accretion, or nearly uninterrupted gas accretion near the Eddington limit; the latter, at first glance, is at odds with empirical trends at lower redshifts, where quasar episodes associated with rapid BH growth are rare and brief. In this work, I examine whether and to what extent the growth of the z>6 quasar SMBHs can be explained within the standard quasar paradigm, in which major mergers of host galaxies trigger episodes of rapid gas accretion below or near the Eddington limit. Using a suite of Monte Carlo merger tree simulations of the assembly histories of 40 likely z>6 quasar host halos, I investigate (i) their growth and major merger rates out to z∼40, and (ii) how long the feeding episodes induced by host mergers must last in order to explain the observed z≳6 quasar population without super-Eddington accretion. The halo major merger rate scales roughly as ∝ (1+z) 5/2 , consistent with cosmological simulations at lower redshifts, with quasar hosts typically experiencing ≳10 major mergers between 15>z>6 (≈650 Myr), compared to ∼1 for typical massive galaxies at 3>z>0 (≈11 Gyr). The high rate of major mergers allows for nearly continuous SMBH growth if (for example) a merger triggers feeding for a duration comparable to the halo dynamical time. These findings suggest that the growth mechanisms of the earliest quasar SMBHs need not have been drastically different from their counterparts at lower redshifts. (paper)

  11. Earth-mass haloes and the emergence of NFW density profiles

    Science.gov (United States)

    Angulo, Raul E.; Hahn, Oliver; Ludlow, Aaron D.; Bonoli, Silvia

    2017-11-01

    We simulate neutralino dark matter (χDM) haloes from their initial collapse, at ˜ earth mass, up to a few percent solar. Our results confirm that the density profiles of the first haloes are described by a ˜r-1.5 power law. As haloes grow in mass, their density profiles evolve significantly. In the central regions, they become shallower and reach on average ˜r-1, the asymptotic form of an NFW profile. Using non-cosmological controlled simulations, we observe that temporal variations in the gravitational potential caused by major mergers lead to a shallowing of the inner profile. This transformation is more significant for shallower initial profiles and for a higher number of merging systems. Depending on the merger details, the resulting profiles can be shallower or steeper than NFW in their inner regions. Interestingly, mergers have a much weaker effect when the profile is given by a broken power law with an inner slope of -1 (such as NFW or Hernquist profiles). This offers an explanation for the emergence of NFW-like profiles: after their initial collapse, r-1.5 χDM haloes suffer copious major mergers, which progressively shallows the profile. Once an NFW-like profile is established, subsequent merging does not change the profile anymore. This suggests that halo profiles are not universal but rather a combination of (1) the physics of the formation of the microhaloes and (2) their early merger history - both set by the properties of the dark matter particle - as well as (3) the resilience of NFW-like profiles to perturbations.

  12. Dark influences II. Gas and star formation in minor mergers of dwarf galaxies with dark satellites

    NARCIS (Netherlands)

    Starkenburg, T. K.; Helmi, A.; Sales, L. V.

    2016-01-01

    Context. It has been proposed that mergers induce starbursts and lead to important morphological changes in galaxies. Most studies so far have focused on large galaxies, but dwarfs might also experience such events, since the halo mass function is scale-free in the concordance cosmological model.

  13. Discriminating strange star mergers from neutron star mergers by gravitational-wave measurements

    International Nuclear Information System (INIS)

    Bauswein, A.; Oechslin, R.; Janka, H.-T.

    2010-01-01

    We perform three-dimensional relativistic hydrodynamical simulations of the coalescence of strange stars and explore the possibility to decide on the strange matter hypothesis by means of gravitational-wave measurements. Self-binding of strange quark matter and the generally more compact stars yield features that clearly distinguish strange star from neutron star mergers, e.g. hampering tidal disruption during the plunge of quark stars. Furthermore, instead of forming dilute halo structures around the remnant as in the case of neutron star mergers, the coalescence of strange stars results in a differentially rotating hypermassive object with a sharp surface layer surrounded by a geometrically thin, clumpy high-density strange quark matter disk. We also investigate the importance of including nonzero temperature equations of state in neutron star and strange star merger simulations. In both cases we find a crucial sensitivity of the dynamics and outcome of the coalescence to thermal effects, e.g. the outer remnant structure and the delay time of the dense remnant core to black hole collapse depend on the inclusion of nonzero temperature effects. For comparing and classifying the gravitational-wave signals, we use a number of characteristic quantities like the maximum frequency during inspiral or the dominant frequency of oscillations of the postmerger remnant. In general, these frequencies are higher for strange star mergers. Only for particular choices of the equation of state the frequencies of neutron star and strange star mergers are similar. In such cases additional features of the gravitational-wave luminosity spectrum like the ratio of energy emitted during the inspiral phase to the energy radiated away in the postmerger stage may help to discriminate coalescence events of the different types. If such characteristic quantities could be extracted from gravitational-wave signals, for instance with the upcoming gravitational-wave detectors, a decision on the

  14. Power plays - global mergers

    International Nuclear Information System (INIS)

    Allen, Simon

    1997-01-01

    This article focuses on the increasing number of mergers and acquisitions by electric utilities in the face of growing competition in home markets. The liberalisation of the UK and Scandinavian electricity markets, the impact in Europe of the EU directive on liberalisation, mergers in Switzerland, the selling of Australian generators to UK electric utilities, the globalisation of the industry, and the growing trend for deals between gas and electric utilities are discussed. (UK)

  15. High-velocity streams in the Milky Way halo with the SDSS and GSC-II kinematic survey

    OpenAIRE

    Spagna A.; Smart R.L.; Lattanzi M.G.; Re Fiorentin P.; Beers T.C.; Curir A.

    2012-01-01

    We explore the stellar halo of the Milky Way to search for fossil signatures of past mergers, consisting of streams of particles torn from their progenitors during the process of hierarchical merging. We examine a representative sample of about 2 700 halo subdwarfs in the solar neighborhood, selected from a new kinematic survey produced by means of spectrophotometric data from the Sloan Digital Sky Survey, and high-quality proper motions derived from multi-epoch positions using the Guide Star...

  16. Gas infall into atomic cooling haloes: on the formation of protogalactic disks and supermassive black holes at z > 10

    CERN Document Server

    Prieto, Joaquin; Haiman, Zoltan

    2013-01-01

    We have performed cosmo-hydro simulations using the RAMSES code to study atomic cooling (ACHs) haloes at z=10 with masses 5E7Msun10 to date. We examine the morphology, angular momentum (AM), thermodynamic, and turbulence of these haloes, in order to assess the prevalence of disks and supermassive black holes (SMBHs). We find no correlation between either the magnitude or the direction of the AM of the gas and its parent DM halo. Only 3 haloes form rotationally supported cores. Two of the most massive haloes form massive, compact overdense blobs. These blobs have an accretion rate ~0.5 Msun/yr (at a distance of 100 pc), and are possible sites of SMBH formation. Our results suggest that the degree of rotational support and the fate of the gas in a halo is determined by its large-scale environment and merger history. In particular, the two haloes forming blobs are located at knots of the cosmic web, cooled early on, and experienced many mergers. The gas in these haloes is lumpy and highly turbulent, with Mach N....

  17. ENVIRONMENTAL DEPENDENCE OF THE GALAXY MERGER RATE IN A ΛCDM UNIVERSE

    International Nuclear Information System (INIS)

    Jian, Hung-Yu; Chiueh, Tzihong; Lin Lihwai

    2012-01-01

    We make use of four galaxy catalogs based on four different semi-analytical models (SAMs) implemented in the Millennium Simulation to study the environmental effects and the model dependence of the galaxy merger rate. We begin the analyses by finding that the galaxy merger rate in SAMs has a mild redshift evolution with luminosity-selected samples in the evolution-corrected B-band magnitude range,–21 ≤ M e B ≤ –19, consistent with the results of previous works. To study the environmental dependence of the galaxy merger rate, we adopt two estimators, the local overdensity (1 + δ n ), defined as the surface density from the nth nearest neighbor (n = 6 is chosen in this study), and the host halo mass M h . We find that the galaxy merger rate F mg shows a strong dependence on the local overdensity (1 + δ n ) and the dependence is similar at all redshifts. For the overdensity estimator, the merger rate F mg is found to be about twenty times larger in the densest regions than in underdense ones in two of the four SAMs, while it is roughly four times higher in the other two. In other words, the discrepancies of the merger rate difference between the two extremes can differ by a factor of ∼5 depending on the SAMs adopted. On the other hand, for the halo mass estimator, F mg does not monotonically increase with the host halo mass M h but peaks in the M h range between 10 12 and 10 13 h –1 M ☉ , which corresponds to group environments. The high merger rate in high local density regions corresponds primarily to the high merger rate in group environments. In addition, we also study the merger probability of 'close pairs' identified using the projected separation and the line-of-sight velocity difference C mg and the merger timescale T mg ; these are two important quantities for observations to convert the pair fraction N c into the galaxy merger rate. We discover that T mg has a weak dependence on environment and different SAMs, and is about 2 Gyr old at z

  18. Orbit classification in an equal-mass non-spinning binary black hole pseudo-Newtonian system

    Science.gov (United States)

    Zotos, Euaggelos E.; Dubeibe, F. L.; González, Guillermo A.

    2018-04-01

    The dynamics of a test particle in a non-spinning binary black hole system of equal masses is numerically investigated. The binary system is modeled in the context of the pseudo-Newtonian circular restricted three-body problem, such that the primaries are separated by a fixed distance and move in a circular orbit around each other. In particular, the Paczyński-Wiita potential is used for describing the gravitational field of the two non-Newtonian primaries. The orbital properties of the test particle are determined through the classification of the initial conditions of the orbits, using several values of the Jacobi constant, in the Hill's regions of possible motion. The initial conditions are classified into three main categories: (i) bounded, (ii) escaping and (iii) displaying close encounters. Using the smaller alignment index (SALI) chaos indicator, we further classify bounded orbits into regular, sticky or chaotic. To gain a complete view of the dynamics of the system, we define grids of initial conditions on different types of two-dimensional planes. The orbital structure of the configuration plane, along with the corresponding distributions of the escape and collision/close encounter times, allow us to observe the transition from the classical Newtonian to the pseudo-Newtonian regime. Our numerical results reveal a strong dependence of the properties of the considered basins with the Jacobi constant as well as with the Schwarzschild radius of the black holes.

  19. Universality and Halo Nuclei

    Directory of Open Access Journals (Sweden)

    Tomio L.

    2010-04-01

    Full Text Available Universal aspects of few-body systems will be reviewed motivated by recent interest in atomic and nuclear physics. The critical conditions for the existence of excited states in three-body systems with two-identical particles will be explored. In particular, we consider halo nuclei that can be modeled as three-body nuclear systems, with two halo neutrons and a core. In this context, we also discuss the low-energy neutron−19C elastic scattering, near the conditions for the app earance of an Efimov state.

  20. Prompt electromagnetic transients from binary black hole mergers

    Science.gov (United States)

    Kelly, Bernard J.; Baker, John G.; Etienne, Zachariah B.; Giacomazzo, Bruno; Schnittman, Jeremy

    2017-12-01

    Binary black hole (BBH) mergers provide a prime source for current and future interferometric gravitational wave observatories. Massive BBH mergers may often take place in plasma-rich environments, leading to the exciting possibility of a concurrent electromagnetic (EM) signal observable by traditional astronomical facilities. However, many critical questions about the generation of such counterparts remain unanswered. We explore mechanisms that may drive EM counterparts with magnetohydrodynamic simulations treating a range of scenarios involving equal-mass black-hole binaries immersed in an initially homogeneous fluid with uniform, orbitally aligned magnetic fields. We find that the time development of Poynting luminosity, which may drive jetlike emissions, is relatively insensitive to aspects of the initial configuration. In particular, over a significant range of initial values, the central magnetic field strength is effectively regulated by the gas flow to yield a Poynting luminosity of 1 045-1046ρ-13M8 2 erg s-1 , with BBH mass scaled to M8≡M /(108 M⊙) and ambient density ρ-13≡ρ /(10-13 g cm-3) . We also calculate the direct plasma synchrotron emissions processed through geodesic ray-tracing. Despite lensing effects and dynamics, we find the observed synchrotron flux varies little leading up to merger.

  1. Searching for the full symphony of black hole binary mergers

    Science.gov (United States)

    Harry, Ian; Bustillo, Juan Calderón; Nitz, Alex

    2018-01-01

    Current searches for the gravitational-wave signature of compact binary mergers rely on matched-filtering data from interferometric observatories with sets of modeled gravitational waveforms. These searches currently use model waveforms that do not include the higher-order mode content of the gravitational-wave signal. Higher-order modes are important for many compact binary mergers and their omission reduces the sensitivity to such sources. In this work we explore the sensitivity loss incurred from omitting higher-order modes. We present a new method for searching for compact binary mergers using waveforms that include higher-order mode effects, and evaluate the sensitivity increase that using our new method would allow. We find that, when evaluating sensitivity at a constant rate-of-false alarm, and when including the fact that signal-consistency tests can reject some signals that include higher-order mode content, we observe a sensitivity increase of up to a factor of 2 in volume for high mass ratio, high total-mass systems. For systems with equal mass, or with total mass ˜50 M⊙, we see more modest sensitivity increases, applicable in searches for generic compact binaries.

  2. Anti- versus Pro-Competitive Mergers

    OpenAIRE

    Fridolfsson, Sven-Olof

    2007-01-01

    In a framework where mergers are mutually excluding, I show that firms pursue anti- rather than (alternative) pro-competitive mergers. Potential outsiders to anti-competitive mergers refrain from pursuing pro-competitive mergers if the positive externalities from anti-competitive mergers are strong enough. Potential outsiders to pro-competitive mergers pursue anti-competitive mergers if the negative externalities from the pro-competitive mergers are strong enough. Potential participants in an...

  3. Coronae, Haloes and Glories

    Indian Academy of Sciences (India)

    A point source of monochromatic light viewed through a cloud of particles would appear surrounded by a corona or halo due to diffraction by the particles. The radiations. Fig. 66. Diffraction corona due to. Lycopodium spores showing. a). Granular structure in monochromatic light, and b) radial streaks in white light. diffracted ...

  4. Coronae, Haloes and Glories

    Indian Academy of Sciences (India)

    surrounded by a corona or halo due to diffraction by the particles. The radiations. Fig. 66. Diffraction corona due to. Lycopodium spores showing. a). Granular structure in monochromatic light, and b) radial streaks in white light. diffracted by the particles and reaching the retina of the eye and focussed there~n are superposed.

  5. Spectrum of Sprite Halos

    Czech Academy of Sciences Publication Activity Database

    Gordillo-Vázquez, F.J.; Luque, A.; Šimek, Milan

    2011-01-01

    Roč. 116, č. 9 (2011), A09319-A09319 ISSN 0148-0227 Institutional research plan: CEZ:AV0Z20430508 Keywords : sprites * halos * spectroscopy Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.021, year: 2011 http://www.trappa.iaa.es/sites/all/files/papers/isi_journal_papers/2011/2011_08.pdf

  6. Nonmarket strategy for merger reviews

    NARCIS (Netherlands)

    Clougherty, J.A.

    2003-01-01

    Mergers and acquisitions can involve a significant review by antitrust authorities; however, neither the business strategy not the corporate political strategy literature has fully explored the antitrust dimensions of merger activity. This article considers the ability of corporate political

  7. STELLAR MASS-GAP AS A PROBE OF HALO ASSEMBLY HISTORY AND CONCENTRATION: YOUTH HIDDEN AMONG OLD FOSSILS

    Energy Technology Data Exchange (ETDEWEB)

    Deason, A. J.; Conroy, C. [Department of Astronomy and Astrophysics, University of California Santa Cruz, Santa Cruz, CA 95064 (United States); Wetzel, A. R. [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); Tinker, J. L., E-mail: alis@ucolick.org [Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, NY 10013 (United States)

    2013-11-10

    We investigate the use of the halo mass-gap statistic—defined as the logarithmic difference in mass between the host halo and its most massive satellite subhalo—as a probe of halo age and concentration. A cosmological N-body simulation is used to study N ∼ 25, 000 group/cluster-sized halos in the mass range 10{sup 12.5} < M{sub halo}/M{sub ☉} < 10{sup 14.5}. In agreement with previous work, we find that halo mass-gap is related to halo formation time and concentration. On average, older and more highly concentrated halos have larger halo mass-gaps, and this trend is stronger than the mass-concentration relation over a similar dynamic range. However, there is a large amount of scatter owing to the transitory nature of the satellite subhalo population, which limits the use of the halo mass-gap statistic on an object-by-object basis. For example, we find that 20% of very large halo mass-gap systems (akin to {sup f}ossil groups{sup )} are young and have likely experienced a recent merger between a massive satellite subhalo and the central subhalo. We relate halo mass-gap to the observable stellar mass-gap via abundance matching. Using a galaxy group catalog constructed from the Sloan Digital Sky Survey Data Release 7, we find that the star formation and structural properties of galaxies at fixed mass show no trend with stellar mass-gap. This is despite a variation in halo age of ≈2.5 Gyr over ≈1.2 dex in stellar mass-gap. Thus, we find no evidence to suggest that the halo formation history significantly affects galaxy properties.

  8. Understanding FE Mergers. Research Report

    Science.gov (United States)

    Calvert, Natasha

    2009-01-01

    This report presents research findings and discussion to help develop an understanding of what gives rise to mergers and, when they do happen, what makes them work. The research has focused on merger activity between further education (FE) colleges since incorporation in 1993. Mergers are highly contextual, and part of ensuring success is…

  9. Accretion of satellites onto central galaxies in clusters: merger mass ratios and orbital parameters

    Science.gov (United States)

    Nipoti, Carlo; Giocoli, Carlo; Despali, Giulia

    2018-02-01

    We study the statistical properties of mergers between central and satellite galaxies in galaxy clusters in the redshift range 0 central region of the cluster, down to ≈0.06rvir, which can be considered a proxy for the accretion of satellite galaxies onto central galaxies. We find that the characteristic merger mass ratio increases for increasing values of Δc: more than 60% of the mass accreted by central galaxies since z ≈ 1 comes from major mergers. The orbits of satellites accreting onto central galaxies tend to be more tangential and more bound than orbits of haloes accreting at the virial radius. The obtained distributions of merger mass ratios and orbital parameters are useful to model the evolution of the high-mass end of the galaxy scaling relations without resorting to hydrodynamic cosmological simulations.

  10. Anisotropy in Dynamical Models of Elliptical Galaxy Dark Halos

    Science.gov (United States)

    Forestell, Amy; Gebhardt, K.

    2013-07-01

    Abstract (2,250 Maximum Characters): We discuss the orbital anisotropy results of axisymmetric orbit-superposition dynamical models of elliptical galaxies NGC 821 and NGC 4697. For NGC 821 stellar kinematics are used to determine the best-fitted dark halo (Forestell 2010), then we determine the orbital properties required for planetary nebulae to match the observed kinematic data (Romanowsky et al. 2003) in that assumed dark halo. For NGC 4697 we use both stellar and planetary nebula kinematics (Pinkney et al. 2003, Mendez et al. 2009) to model the galaxy dark halo. In both galaxies we find that the planetary nebulae, which are located at large radii, show radial anisotropy. This is consistent with the results of Dekel et al. (2005), who use disk galaxy merger simulations to show that large anisotropies can be created in the resulting elliptical galaxies and that this anisotropy in combination with the different density profile of a young population could explain how the low dispersions from planetary nebulae measurements are also consistent with typical dark matter halos.

  11. Structure of stable binary neutron star merger remnants: Role of initial spin

    Science.gov (United States)

    Kastaun, W.; Ciolfi, R.; Endrizzi, A.; Giacomazzo, B.

    2017-08-01

    We present general relativistic numerical simulations of binary neutron star (BNS) mergers with different initial spin configurations. We focus on models with stars of mass 1.4 M⊙ each, which employ the equation of state (EOS) by Shen, Horowitz, and Teige, and which result in stable NSs as merger remnants. For comparison, we consider two irrotational equal mass (M =1.35 M⊙) and unequal mass (M =1.29 , 1.42 M⊙ ) BNS models using the APR4 EOS, which result in a supramassive merger remnant. We present visualizations of the fluid flow and temperature distribution and find a strong impact of the spin on vortex structure and nonaxisymmetric deformation. We compute the radial mass distribution and the rotation profile in the equatorial plane using recently developed measures independent of spatial gauge, revealing slowly rotating cores that can be well approximated by the cores of spherical stars. We also study the influence of the spin on the inspiral phase and the gravitational wave (GW) signal. Using a newly developed analysis method, we further show that gravitational waveforms from BNS mergers can exhibit one or more phase jumps after merger, which occur together with minima of the strain amplitude. We provide a natural explanation in terms of the remnant's quadrupole moment, and show that cancellation effects due to phase jumps can have a strong impact on the GW power spectrum. Finally, we discuss the impact of the spin on the amount of ejected matter.

  12. Diffuse X-Ray-emitting Gas in Major Mergers

    Science.gov (United States)

    Smith, Beverly J.; Campbell, Kristen; Struck, Curtis; Soria, Roberto; Swartz, Douglas; Magno, Macon; Dunn, Brianne; Giroux, Mark L.

    2018-02-01

    Using archived data from the Chandra X-ray telescope, we have extracted the diffuse X-ray emission from 49 equal-mass interacting/merging galaxy pairs in a merger sequence, from widely separated pairs to merger remnants. After the removal of contributions from unresolved point sources, we compared the diffuse thermal X-ray luminosity from hot gas (L X(gas)) with the global star formation rate (SFR). After correction for absorption within the target galaxy, we do not see a strong trend of L X(gas)/SFR with the SFR or merger stage for galaxies with SFR > 1 M ⊙ yr‑1. For these galaxies, the median L X(gas)/SFR is 5.5 × 1039 ((erg s‑1)/M ⊙ yr‑1)), similar to that of normal spiral galaxies. These results suggest that stellar feedback in star-forming galaxies reaches an approximately steady-state condition, in which a relatively constant fraction of about 2% of the total energy output from supernovae and stellar winds is converted into X-ray flux. Three late-stage merger remnants with low SFRs and high K-band luminosities (L K ) have enhanced L X(gas)/SFR; their UV/IR/optical colors suggest that they are post-starburst galaxies, perhaps in the process of becoming ellipticals. Systems with L K < 1010 L ⊙ have lower L X(gas)/SFR ratios than the other galaxies in our sample, perhaps due to lower gravitational fields or lower metallicities. We see no relation between L X(gas)/SFR and Seyfert activity in this sample, suggesting that feedback from active galactic nuclei is not a major contributor to the hot gas in our sample galaxies.

  13. Late-stage galaxy mergers in cosmos to z ∼ 1

    International Nuclear Information System (INIS)

    Lackner, C. N.; Silverman, J. D.; Salvato, M.; Kampczyk, P.; Kartaltepe, J. S.; Sanders, D.; Lee, N.; Capak, P.; Scoville, N.; Civano, F.; Halliday, C.; Ilbert, O.; Le Fèvre, O.; Jahnke, K.; Koekemoer, A. M.; Liu, C. T.; Sheth, K.; Toft, S.

    2014-01-01

    The role of major mergers in galaxy and black hole formation is not well-constrained. To help address this, we develop an automated method to identify late-stage galaxy mergers before coalescence of the galactic cores. The resulting sample of mergers is distinct from those obtained using pair-finding and morphological indicators. Our method relies on median-filtering of high-resolution images to distinguish two concentrated galaxy nuclei at small separations. This method does not rely on low surface brightness features to identify mergers, and is therefore reliable to high redshift. Using mock images, we derive statistical contamination and incompleteness corrections for the fraction of late-stage mergers. The mock images show that our method returns an uncontaminated (<10%) sample of mergers with projected separations between 2.2 and 8 kpc out to z∼1. We apply our new method to a magnitude-limited (m FW 814 <23) sample of 44,164 galaxies from the COSMOS HST/ACS catalog. Using a mass-complete sample with logM ∗ /M ⊙ >10.6 and 0.25mergers. Correcting for incompleteness and contamination, the fractional merger rate increases strongly with redshift as r merge ∝(1+z) 3.8±0.9 , in agreement both with earlier studies and with dark matter halo merger rates. Separating the sample into star-forming and quiescent galaxies shows that the merger rate for star-forming galaxies increases strongly with redshift, (1+z) 4.5±1.3 , while the merger rate for quiescent galaxies is consistent with no evolution, (1+z) 1.1±1.2 . The merger rate also becomes steeper with decreasing stellar mass. Limiting our sample to galaxies with spectroscopic redshifts from zCOSMOS, we find that the star formation rates and X-ray selected active galactic nucleus (AGN) activity in likely late-stage mergers are higher by factors of ∼2 relative to those of a control sample. Combining our sample with more widely separated pairs, we find that 8

  14. Tracking the LHC halo

    CERN Multimedia

    Antonella Del Rosso

    2015-01-01

    In the LHC, beams of 25-ns-spaced proton bunches travel at almost the speed of light and pass through many different devices installed along the ring that monitor their properties. During their whirling motion, beam particles might interact with the collimation instrumentation or with residual gas in the vacuum chambers and this creates the beam halo – an annoying source of background for the physics data. Newly installed CMS sub-detectors are now able to monitor it.   The Beam Halo Monitors (BHM) are installed around the CMS rotating shielding. The BHM are designed and built by University of Minnesota, CERN, Princeton University, INFN Bologna and the National Technical University of Athens. (Image: Andrea Manna). The Beam Halo Monitor (BHM) is a set of 20 Cherenkov radiators – 10-cm-long quartz crystals – installed at each end of the huge CMS detector. Their design goal is to measure the particles that can cause the so-called “machine-induced...

  15. ZOMG - II. Does the halo assembly history influence central galaxies and gas accretion?

    Science.gov (United States)

    Romano-Díaz, Emilio; Garaldi, Enrico; Borzyszkowski, Mikolaj; Porciani, Cristiano

    2017-08-01

    The growth rate and the internal dynamics of galaxy-sized dark-matter haloes depend on their location within the cosmic web. Haloes that sit at the nodes grow in mass till the present time and are dominated by radial orbits. Conversely, haloes embedded in prominent filaments do not change much in size and are dominated by tangential orbits. Using zoom hydrodynamical simulations including star formation and feedback, we study how gas accretes on to these different classes of objects, which, for simplicity, we dub 'accreting' and 'stalled' haloes. We find that all haloes get a fresh supply of newly accreted gas in their inner regions, although this slowly decreases with time, in particular for the stalled haloes. The inflow of new gas is always higher than (but comparable with) that of recycled material. Overall, the cold-gas fraction increases (decreases) with time for the accreting (stalled) haloes. In all cases, a stellar disc and a bulge form at the centre of the simulated haloes. The total stellar mass is in excellent agreement with expectations based on the abundance-matching technique. Many properties of the central galaxies do not seem to correlate with the large-scale environment in which the haloes reside. However, there are two notable exceptions that characterize stalled haloes with respect to their accreting counterparts: (I) The galaxy disc contains much older stellar populations. (II) Its vertical scaleheight is larger by a factor of 2 or more. This thickening is likely due to the heating of the long-lived discs by mergers and close flybys.

  16. HBT+: an improved code for finding subhaloes and building merger trees in cosmological simulations

    Science.gov (United States)

    Han, Jiaxin; Cole, Shaun; Frenk, Carlos S.; Benitez-Llambay, Alejandro; Helly, John

    2018-02-01

    Dark matter subhalos are the remnants of (incomplete) halo mergers. Identifying them and establishing their evolutionary links in the form of merger trees is one of the most important applications of cosmological simulations. The HBT (Hierachical Bound-Tracing) code identifies haloes as they form and tracks their evolution as they merge, simultaneously detecting subhaloes and building their merger trees. Here we present a new implementation of this approach, HBT+ , that is much faster, more user friendly, and more physically complete than the original code. Applying HBT+ to cosmological simulations, we show that both the subhalo mass function and the peak-mass function are well fitted by similar double-Schechter functions. The ratio between the two is highest at the high-mass end, reflecting the resilience of massive subhaloes that experience substantial dynamical friction but limited tidal stripping. The radial distribution of the most-massive subhaloes is more concentrated than the universal radial distribution of lower mass subhaloes. Subhalo finders that work in configuration space tend to underestimate the masses of massive subhaloes, an effect that is stronger in the host centre. This may explain, at least in part, the excess of massive subhaloes in galaxy cluster centres inferred from recent lensing observations. We demonstrate that the peak-mass function is a powerful diagnostic of merger tree defects, and the merger trees constructed using HBT+ do not suffer from the missing or switched links that tend to afflict merger trees constructed from more conventional halo finders. We make the HBT+ code publicly available.

  17. SATELLITE DWARF GALAXIES IN A HIERARCHICAL UNIVERSE: THE PREVALENCE OF DWARF-DWARF MAJOR MERGERS

    OpenAIRE

    Deason, A; Wetzel, A; Garrison-Kimmel, S

    2014-01-01

    Mergers are a common phenomenon in hierarchical structure formation, especially for massive galaxies and clusters, but their importance for dwarf galaxies in the Local Group remains poorly understood. We investigate the frequency of major mergers between dwarf galaxies in the Local Group using the ELVIS suite of cosmological zoom-in dissipationless simulations of Milky Way- and M31-like host halos. We find that ~10% of satellite dwarf galaxies with M_star > 10^6 M_sun that are within the host...

  18. Host galaxy properties of mergers of stellar binary black holes and their implications for advanced LIGO gravitational wave sources

    Science.gov (United States)

    Cao, Liang; Lu, Youjun; Zhao, Yuetong

    2018-03-01

    Understanding the host galaxy properties of stellar binary black hole (SBBH) mergers is important for revealing the origin of the SBBH gravitational wave sources detected by advanced LIGO and helpful for identifying their electromagnetic counterparts. Here, we present a comprehensive analysis of the host galaxy properties of SBBHs by implementing semi-analytical recipes for SBBH formation and merger into cosmological galaxy formation model. If the time delay between SBBH formation and merger ranges from ≲ Gyr to the Hubble time, SBBH mergers at redshift z ≲ 0.3 occur preferentially in big galaxies with stellar mass M* ≳ 2 × 1010 M⊙ and metallicities Z peaking at ˜0.6 Z⊙. However, the host galaxy stellar mass distribution of heavy SBBH mergers (M•• ≳ 50 M⊙) is bimodal with one peak at ˜109 M⊙ and the other peak at ˜2 × 1010 M⊙. The contribution fraction from host galaxies with Z ≲ 0.2 Z⊙ to heavy mergers is much larger than that to less heavy mergers. If SBBHs were formed in the early Universe (e.g. z > 6), their mergers detected at z ≲ 0.3 occur preferentially in even more massive galaxies with M* > 3 × 1010 M⊙ and in galaxies with metallicities mostly ≳ 0.2 Z⊙ and peaking at Z ˜ 0.6 Z⊙, due to later cosmic assembly and enrichment of their host galaxies. SBBH mergers at z ≲ 0.3 mainly occur in spiral galaxies, but the fraction of SBBH mergers that occur in elliptical galaxies can be significant if those SBBHs were formed in the early Universe; and about two-thirds of those mergers occur in the central galaxies of dark matter haloes. We also present results on the host galaxy properties of SBBH mergers at higher redshift.

  19. Mixing processes in galaxy mergers

    International Nuclear Information System (INIS)

    White, S.D.M.

    1980-01-01

    Previously published simulations of mergers between galaxies are used to examine the degree to which population gradients are weakened during the coalescence of two or more stellar systems. Although substantial mixing occurs during a merger, its effect on such gradients is quite moderate and can be overwhelmed by the effect of changes in structure. Experiment suggests that the centre-to-edge population difference in a merger remnant will be 20 per cent smaller than that in its progenitor galaxies if these are identical centrally concentrated systems. A sequence of three binary mergers is thus required to reduce such differences by a factor of 2. Because of changes in radial structure, population gradients are, in general, reduced more rapidly than is suggested by these numbers. Mixing is more efficient in mergers between less concentrated systems. In real merger remnants any weakening of gradients may often be masked by star-formation in residual interstellar gas. (author)

  20. Binary Neutron Star Mergers

    Directory of Open Access Journals (Sweden)

    Joshua A. Faber

    2012-07-01

    Full Text Available We review the current status of studies of the coalescence of binary neutron star systems. We begin with a discussion of the formation channels of merging binaries and we discuss the most recent theoretical predictions for merger rates. Next, we turn to the quasi-equilibrium formalisms that are used to study binaries prior to the merger phase and to generate initial data for fully dynamical simulations. The quasi-equilibrium approximation has played a key role in developing our understanding of the physics of binary coalescence and, in particular, of the orbital instability processes that can drive binaries to merger at the end of their lifetimes. We then turn to the numerical techniques used in dynamical simulations, including relativistic formalisms, (magneto-hydrodynamics, gravitational-wave extraction techniques, and nuclear microphysics treatments. This is followed by a summary of the simulations performed across the field to date, including the most recent results from both fully relativistic and microphysically detailed simulations. Finally, we discuss the likely directions for the field as we transition from the first to the second generation of gravitational-wave interferometers and while supercomputers reach the petascale frontier.

  1. Observing Galaxy Mergers in Simulations

    Science.gov (United States)

    Snyder, Gregory

    2018-01-01

    I will describe results on mergers and morphology of distant galaxies. By mock-observing 3D cosmological simulations, we aim to contrast theory with data, design better diagnostics of physical processes, and examine unexpected signatures of galaxy formation. Recently, we conducted mock surveys of the Illustris Simulations to learn how mergers would appear in deep HST and JWST surveys. With this approach, we reconciled merger rates estimated using observed close galaxy pairs with intrinsic merger rates predicted by theory. This implies that the merger-pair observability time is probably shorter in the early universe, and therefore that major mergers are more common than implied by the simplest arguments. Further, we show that disturbance-based diagnostics of late-stage mergers can be improved significantly by combining multi-dimensional image information with simulated merger identifications to train automated classifiers. We then apply these classifiers to real measurements from the CANDELS fields, recovering a merger fraction increasing with redshift in broad agreement with pair fractions and simulations, and with statistical errors smaller by a factor of two than classical morphology estimators. This emphasizes the importance of using robust training sets, including cosmological simulations and multidimensional data, for interpreting observed processes in galaxy evolution.

  2. Overcooled haloes at z ≥ 10: a route to form low-mass first stars

    CERN Document Server

    Prieto, Joaquin; Verde, Licia

    2014-01-01

    It has been shown by Shchekinov & Vasiliev2006 (SV06) that HD molecules can be an important cooling agent in high redshift z >10 haloes if they undergo mergers under specific conditions so suitable shocks are created. Here we build upon Prieto et al. (2012) who studied in detail the merger-generated shocks, and show that the conditions for HD cooling can be studied by combining these results with a suite of dark-matter only simulations. We have performed a number of dark matter only simulations from cosmological initial conditions inside boxes with sizes from 1 to 4 Mpc. We look for haloes with at least two progenitors of which at least one has mass M > M_cr (z), where M_cr (z) is the SV06 critical mass for HD over-cooling. We find that the fraction of over-cooled haloes with mass between M_cr (z) and 10^{0.2} M_cr (z), roughly below the atomic cooling limit, can be as high as ~ 0.6 at z ~ 10 depending on the merger mass ratio. This fraction decreases at higher redshift reaching a value ~0.2 at z ~ 15. Fo...

  3. CHARACTERIZING THE FORMATION HISTORY OF MILKY WAY LIKE STELLAR HALOS WITH MODEL EMULATORS

    International Nuclear Information System (INIS)

    Gómez, Facundo A.; O'Shea, Brian W.; Coleman-Smith, Christopher E.; Tumlinson, Jason; Wolpert, Robert L.

    2012-01-01

    We use the semi-analytic model ChemTreeN, coupled to cosmological N-body simulations, to explore how different galaxy formation histories can affect observational properties of Milky Way like galaxies' stellar halos and their satellite populations. Gaussian processes are used to generate model emulators that allow one to statistically estimate a desired set of model outputs at any location of a p-dimensional input parameter space. This enables one to explore the full input parameter space orders of magnitude faster than could be done otherwise. Using mock observational data sets generated by ChemTreeN itself, we show that it is possible to successfully recover the input parameter vectors used to generate the mock observables if the merger history of the host halo is known. However, our results indicate that for a given observational data set, the determination of 'best-fit' parameters is highly susceptible to the particular merger history of the host. Very different halo merger histories can reproduce the same observational data set, if the 'best-fit' parameters are allowed to vary from history to history. Thus, attempts to characterize the formation history of the Milky Way using these kind of techniques must be performed statistically, analyzing large samples of high-resolution N-body simulations.

  4. HALOE test and evaluation software

    Science.gov (United States)

    Edmonds, W.; Natarajan, S.

    1987-01-01

    Computer programming, system development and analysis efforts during this contract were carried out in support of the Halogen Occultation Experiment (HALOE) at NASA/Langley. Support in the major areas of data acquisition and monitoring, data reduction and system development are described along with a brief explanation of the HALOE project. Documented listings of major software are located in the appendix.

  5. THE CONTRIBUTION OF HALOS WITH DIFFERENT MASS RATIOS TO THE OVERALL GROWTH OF CLUSTER-SIZED HALOS

    Energy Technology Data Exchange (ETDEWEB)

    Lemze, Doron; Ford, Holland C.; Medezinski, Elinor [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Postman, Marc; Koekemoer, Anton [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21208 (United States); Genel, Shy [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Balestra, Italo; Nonino, Mario; Biviano, Andrea [INAF/Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, I-34143 Trieste (Italy); Donahue, Megan [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824-2320 (United States); Kelson, Daniel; Voit, G. Mark [Carnegie Institute for Science, Carnegie Observatories, Pasadena, CA (United States); Mercurio, Amata [INAF/Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli (Italy); Rosati, Piero [European Southern Observatory, Karl-Schwarzschild Strasse 2, D-85748 Garching (Germany); Umetsu, Keiichi [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Sand, David [Department of Physics, Texas Tech University, Box 41051, Lubbock, TX 79409-1051 (United States); Meneghetti, Massimo [INAF, Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Melchior, Peter [Center for Cosmology and Astro-Particle Physics, The Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210 (United States); Newman, Andrew B. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States); Bhatti, Waqas A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); and others

    2013-10-20

    We provide a new observational test for a key prediction of the ΛCDM cosmological model: the contributions of mergers with different halo-to-main-cluster mass ratios to cluster-sized halo growth. We perform this test by dynamically analyzing 7 galaxy clusters, spanning the redshift range 0.13 < z{sub c} < 0.45 and caustic mass range 0.4-1.5 10{sup 15} h{sub 0.73}{sup -1} M{sub ☉}, with an average of 293 spectroscopically confirmed bound galaxies to each cluster. The large radial coverage (a few virial radii), which covers the whole infall region, with a high number of spectroscopically identified galaxies enables this new study. For each cluster, we identify bound galaxies. Out of these galaxies, we identify infalling and accreted halos and estimate their masses and their dynamical states. Using the estimated masses, we derive the contribution of different mass ratios to cluster-sized halo growth. For mass ratios between ∼0.2 and ∼0.7, we find a ∼1σ agreement with ΛCDM expectations based on the Millennium simulations I and II. At low mass ratios, ∼< 0.2, our derived contribution is underestimated since the detection efficiency decreases at low masses, ∼2 × 10{sup 14} h{sub 0.73}{sup -1} M{sub ☉}. At large mass ratios, ∼> 0.7, we do not detect halos probably because our sample, which was chosen to be quite X-ray relaxed, is biased against large mass ratios. Therefore, at large mass ratios, the derived contribution is also underestimated.

  6. Neutron halo in deformed nuclei

    International Nuclear Information System (INIS)

    Zhou Shangui; Meng Jie; Ring, P.; Zhao Enguang

    2010-01-01

    Halo phenomena in deformed nuclei are investigated within a deformed relativistic Hartree Bogoliubov (DRHB) theory. These weakly bound quantum systems present interesting examples for the study of the interdependence between the deformation of the core and the particles in the halo. Contributions of the halo, deformation effects, and large spatial extensions of these systems are described in a fully self-consistent way by the DRHB equations in a spherical Woods-Saxon basis with the proper asymptotic behavior at a large distance from the nuclear center. Magnesium and neon isotopes are studied and detailed results are presented for the deformed neutron-rich and weakly bound nucleus 44 Mg. The core of this nucleus is prolate, but the halo has a slightly oblate shape. This indicates a decoupling of the halo orbitals from the deformation of the core. The generic conditions for the occurrence of this decoupling effects are discussed.

  7. Null Environmental Effects of the Cosmic Web on Dark Matter Halo Properties

    Science.gov (United States)

    Goh, Tze; Primack, Joel; Aragon-Calvo, Miguel; Hellinger, Doug; Rodriguez-Puebla, Aldo; Lee, Christoph; Eckleholm, Elliot; Johnston, Kathryn

    2018-01-01

    We study the effects of the cosmic web environment (filaments, voids and walls) and environmental density on key properties of dark matter halos at redshift z = 0 using the Bolshoi-Planck ΛCDM. The z=0 Bolshoi-Planck simulation is analysed into filaments, voids and walls using the SpineWeb method, as well as VIDE method, both of which use Voronoi tessellation and the watershed transform. The key halo properties that we study are the mass accretion rate, spin parameter, concentration, prolateness, scale factor of the last major merger, and scale factor when the halo had half of its z=0 mass. For all these properties, we find that there is no discernible difference between the halo properties in filaments, walls or voids when compared at the same environmental density. As a result, we conclude that environmental density is the core attribute that affects these properties. This conclusion is in line with recent findings that properties of galaxies in redshift surveys are independent of their cosmic web environment at the same environmental density. We also find that the local web environment of the Milky Way and the Andromeda galaxy near the centre of a cosmic wall does not appear to have any effect on the key properties of these galaxies' dark matter halos, although we find that it is rather rare to have such massive halos near the centre of a relatively small cosmic wall.

  8. Black holes with halos

    Science.gov (United States)

    Monten, Ruben; Toldo, Chiara

    2018-02-01

    We present new AdS4 black hole solutions in N =2 gauged supergravity coupled to vector and hypermultiplets. We focus on a particular consistent truncation of M-theory on the homogeneous Sasaki–Einstein seven-manifold M 111, characterized by the presence of one Betti vector multiplet. We numerically construct static and spherically symmetric black holes with electric and magnetic charges, corresponding to M2 and M5 branes wrapping non-contractible cycles of the internal manifold. The novel feature characterizing these nonzero temperature configurations is the presence of a massive vector field halo. Moreover, we verify the first law of black hole mechanics and we study the thermodynamics in the canonical ensemble. We analyze the behavior of the massive vector field condensate across the small-large black hole phase transition and we interpret the process in the dual field theory.

  9. Cosmic web type dependence of halo clustering

    Science.gov (United States)

    Fisher, J. D.; Faltenbacher, A.

    2018-01-01

    We use the Millennium Simulation to show that halo clustering varies significantly with cosmic web type. Haloes are classified as node, filament, sheet and void haloes based on the eigenvalue decomposition of the velocity shear tensor. The velocity field is sampled by the peculiar velocities of a fixed number of neighbouring haloes, and spatial derivatives are computed using a kernel borrowed from smoothed particle hydrodynamics. The classification scheme is used to examine the clustering of haloes as a function of web type for haloes with masses larger than 1011 h- 1 M⊙. We find that node haloes show positive bias, filament haloes show negligible bias and void and sheet haloes are antibiased independent of halo mass. Our findings suggest that the mass dependence of halo clustering is rooted in the composition of web types as a function of halo mass. The substantial fraction of node-type haloes for halo masses ≳ 2 × 1013 h- 1 M⊙ leads to positive bias. Filament-type haloes prevail at intermediate masses, 1012-1013 h- 1 M⊙, resulting in unbiased clustering. The large contribution of sheet-type haloes at low halo masses ≲ 1012 h- 1 M⊙ generates antibiasing.

  10. Welfare standards in hospital mergers.

    Science.gov (United States)

    Katona, Katalin; Canoy, Marcel

    2013-08-01

    There is a broad literature on the consequences of applying different welfare standards in merger control. Total welfare is usually defined as the sum of consumer and provider surplus, i.e., potential external effects are not considered. The general result is then that consumer welfare is a more restrictive standard than total welfare, which is advantageous in certain situations. This relationship between the two standards is not necessarily true when the merger has significant external effects. We model mergers on hospital markets and allow for not-profit-maximizing behavior of providers and mandatory health insurance. Mandatory health insurance detaches the financial and consumption side of health care markets, and the concept consumer in merger control becomes non-evident. Patients not visiting the merging hospitals still are affected by price changes through their insurance premiums. External financial effects emerge on not directly affected consumers. We show that applying a restricted interpretation of consumer (neglecting externality) in health care merger control can reverse the relation between the two standards; consumer welfare standard can be weaker than total welfare. Consequently, applying the wrong standard can lead to both clearing socially undesirable and to blocking socially desirable mergers. The possible negative consequences of applying a simple consumer welfare standard in merger control can be even stronger when hospitals maximize quality and put less weight on financial considerations. We also investigate the implications of these results for the practice of merger control.

  11. Competition and Mergers among Nonprofits

    NARCIS (Netherlands)

    Prüfer, J.

    2007-01-01

    Should mergers among nonprofit organizations be regulated differently than mergers among for-profit firms? The relevant empirical literature is highly controversial, the theoretical literature is scarce. We analyze the question by modeling duopoly competition with quality-differentiated goods. We

  12. Competition and Mergers among Nonprofits

    NARCIS (Netherlands)

    Prüfer, J.

    2007-01-01

    Should mergers among nonprofit organizations be regulated differently than mergers among for-profit firms? The relevant empirical literature is highly controversial, the theoretical literature is scarce. I analyze the question by modeling duopoly competition with quality-differentiated goods. I

  13. Welfare Standards in Hospital Mergers

    NARCIS (Netherlands)

    Katona, K.; Canoy, M.F.M.

    2011-01-01

    There is a broad literature on the consequences of applying different welfare standards in merger control. Specific aspects of health care mergers, however, have not yet been considered. Two features of the health care sector are especially relevant. First, health care providers are possi-bly not

  14. On universality in ergoregion mergers

    International Nuclear Information System (INIS)

    Elvang, Henriette; Figueras, Pau; Hubeny, Veronika E; Rangamani, Mukund; Horowitz, Gary T

    2009-01-01

    We study non-dynamical mergers of ergoregions in d + 1-dimensional vacuum gravity. At the merger point, where the ergosurfaces bounding each ergoregion just touch, solutions exhibit universal behavior when there is rotation only in one plane: the angle between the merging ergosurfaces depends only on the symmetries of the solution, not on any other details of the configuration. We show that universality follows from the fact that the relevant component of Einstein's equation reduces to Laplace's equation at the point of merger. Thus ergoregion mergers mimic mergers of Newtonian equipotentials and have similar universal behavior. For solutions with rotation in more than one plane, universality is lost. We demonstrate universality and non-universality in several explicit examples.

  15. The Excursion Set Theory of Halo Mass Functions, Halo Clustering, and Halo Growth

    Science.gov (United States)

    Zentner, Andrew R.

    I review the excursion set theory with particular attention toward applications to cold dark matter halo formation and growth, halo abundance, and halo clustering. After a brief introduction to notation and conventions, I begin by recounting the heuristic argument leading to the mass function of bound objects given by Press and Schechter. I then review the more formal derivation of the Press-Schechter halo mass function that makes use of excursion sets of the density field. The excursion set formalism is powerful and can be applied to numerous other problems. I review the excursion set formalism for describing both halo clustering and bias and the properties of void regions. As one of the most enduring legacies of the excursion set approach and one of its most common applications, I spend considerable time reviewing the excursion set theory of halo growth. This section of the review culminates with the description of two Monte Carlo methods for generating ensembles of halo mass accretion histories. In the last section, I emphasize that the standard excursion set approach is the result of several simplifying assumptions. Dropping these assumptions can lead to more faithful predictions and open excursion set theory to new applications. One such assumption is that the height of the barriers that define collapsed objects is a constant function of scale. I illustrate the implementation of the excursion set approach for barriers of arbitrary shape. One such application is the now well-known improvement of the excursion set mass function derived from the "moving" barrier for ellipsoidal collapse. I also emphasize that the statement that halo accretion histories are independent of halo environment in the excursion set approach is not a general prediction of the theory. It is a simplifying assumption. I review the method for constructing correlated random walks of the density field in the more general case. I construct a simple toy model to illustrate that excursion set

  16. Endogenous mergers: bidder momentum and market reaction

    NARCIS (Netherlands)

    Kling, G.; Weitzel, G.U.

    2010-01-01

    Recent empirical studies on stock misvaluation as a possible determinant of mergers are inconclusive concerning the central hypothesis that over (under) valuation is negatively (positively) associated with merger announcement returns in stock mergers, but not in cash mergers. We provide empirical

  17. Endogenous mergers: Bidder momentum and market reaction

    NARCIS (Netherlands)

    Kling, G.; Weitzel, U.

    Recent empirical studies on stock misvaluation as a possible determinant of mergers are inconclusive concerning the central hypothesis that over(under)valuation is negatively (positively) associated with merger announcement returns in stock mergers, but not in cash mergers. We provide empirical

  18. El halo de la memoria

    OpenAIRE

    GAVINO ROSELLÓ, AARÓN

    2017-01-01

    The halo effect is one of the most classic cognitive biases of psychology, and one that we can observe frequently in everyday life. It consists in the realization of an erroneous generalization from a single characteristic or quality of an object or a person, that is, we make a previous judgment from which, we generalize the rest of characteristics. The halo effect manifests itself as continuous in our life. For example, if someone is very handsome or attractive we attribute another series...

  19. Galaxy Mergers Moulding the CGM

    Science.gov (United States)

    Hani, Maan H.; Sparre, Martin; Ellison, Sara L.; Torrey, Paul; Vogelsberger, Mark

    2017-07-01

    Galaxies are surrounded by sizeable gas reservoirs which host a significant amount of metals: the circum-galactic medium (CGM). The CGM acts as a mediator between the galaxy and the extra-galactic medium. However, our understanding of how galaxy mergers, a major evolutionary transformation, impact the CGM remains deficient. We present a theoretical study of the effect of galaxy mergers on the CGM: We use hydrodynamical cosmological zoom-in simulations of a major merger selected from the Illustris project such that the z=0 descendant is a Milky Way-like galaxy, and then re-simulated at a 40 times higher mass resolution. We include post-processing ionization modelling. This work demonstrates the effect the merger has on the characteristic size of the CGM, its metallicity and the predicted covering fraction of various commonly observed gas-phase species, such as H I, C IV and O VI. We show that merger-induced outflows can increase the CGM metallicity by 0.2-0.3 dex within 0.5 Gyr post-merger. These effects last up to 6 Gyr post-merger. While the merger increases the total metal covering fractions by factors of 2-3, the covering fractions of commonly observed UV ions decrease due to the hard ionizing radiation from the active galactic nucleus. The case study of the single simulated major merger presented in this work demonstrates the significant impact that a galaxy interaction can have on the size, metallicity and observed column densities of the CGM (Hani et al. in prep).

  20. Halo modelling in chameleon theories

    Energy Technology Data Exchange (ETDEWEB)

    Lombriser, Lucas; Koyama, Kazuya [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth, PO1 3FX (United Kingdom); Li, Baojiu, E-mail: lucas.lombriser@port.ac.uk, E-mail: kazuya.koyama@port.ac.uk, E-mail: baojiu.li@durham.ac.uk [Institute for Computational Cosmology, Ogden Centre for Fundamental Physics, Department of Physics, University of Durham, Science Laboratories, South Road, Durham, DH1 3LE (United Kingdom)

    2014-03-01

    We analyse modelling techniques for the large-scale structure formed in scalar-tensor theories of constant Brans-Dicke parameter which match the concordance model background expansion history and produce a chameleon suppression of the gravitational modification in high-density regions. Thereby, we use a mass and environment dependent chameleon spherical collapse model, the Sheth-Tormen halo mass function and linear halo bias, the Navarro-Frenk-White halo density profile, and the halo model. Furthermore, using the spherical collapse model, we extrapolate a chameleon mass-concentration scaling relation from a ΛCDM prescription calibrated to N-body simulations. We also provide constraints on the model parameters to ensure viability on local scales. We test our description of the halo mass function and nonlinear matter power spectrum against the respective observables extracted from large-volume and high-resolution N-body simulations in the limiting case of f(R) gravity, corresponding to a vanishing Brans-Dicke parameter. We find good agreement between the two; the halo model provides a good qualitative description of the shape of the relative enhancement of the f(R) matter power spectrum with respect to ΛCDM caused by the extra attractive gravitational force but fails to recover the correct amplitude. Introducing an effective linear power spectrum in the computation of the two-halo term to account for an underestimation of the chameleon suppression at intermediate scales in our approach, we accurately reproduce the measurements from the N-body simulations.

  1. Halo modelling in chameleon theories

    International Nuclear Information System (INIS)

    Lombriser, Lucas; Koyama, Kazuya; Li, Baojiu

    2014-01-01

    We analyse modelling techniques for the large-scale structure formed in scalar-tensor theories of constant Brans-Dicke parameter which match the concordance model background expansion history and produce a chameleon suppression of the gravitational modification in high-density regions. Thereby, we use a mass and environment dependent chameleon spherical collapse model, the Sheth-Tormen halo mass function and linear halo bias, the Navarro-Frenk-White halo density profile, and the halo model. Furthermore, using the spherical collapse model, we extrapolate a chameleon mass-concentration scaling relation from a ΛCDM prescription calibrated to N-body simulations. We also provide constraints on the model parameters to ensure viability on local scales. We test our description of the halo mass function and nonlinear matter power spectrum against the respective observables extracted from large-volume and high-resolution N-body simulations in the limiting case of f(R) gravity, corresponding to a vanishing Brans-Dicke parameter. We find good agreement between the two; the halo model provides a good qualitative description of the shape of the relative enhancement of the f(R) matter power spectrum with respect to ΛCDM caused by the extra attractive gravitational force but fails to recover the correct amplitude. Introducing an effective linear power spectrum in the computation of the two-halo term to account for an underestimation of the chameleon suppression at intermediate scales in our approach, we accurately reproduce the measurements from the N-body simulations

  2. Creating lenticular galaxies with mergers

    Science.gov (United States)

    Querejeta, Miguel; Eliche-Moral, M. Carmen; Tapia, Trinidad; Borlaff, Alejandro; van de Ven, Glenn; Lyubenova, Mariya; Martig, Marie; Falcón-Barroso, Jesús; Méndez-Abreu, Jairo; Zamorano, Jaime; Gallego, Jesús

    2017-03-01

    Lenticular galaxies (S0s) represent the majority of early-type galaxies in the local Universe, but their formation channels are still poorly understood. While galaxy mergers are obvious pathways to suppress star formation and increase bulge sizes, the marked parallelism between spiral and lenticular galaxies (e.g. photometric bulge-disc coupling) seemed to rule out a potential merger origin. Here, we summarise our recent work in which we have shown, through N-body numerical simulations, that disc-dominated lenticulars can emerge from major mergers of spiral galaxies, in good agreement with observational photometric scaling relations. Moreover, we show that mergers simultaneously increase the light concentration and reduce the angular momentum relative to their spiral progenitors. This explains the mismatch in angular momentum and concentration between spirals and lenticulars recently revealed by CALIFA observations, which is hard to reconcile with simple fading mechanisms (e.g. ram-pressure stripping).

  3. 76 FR 37895 - Merger Applications

    Science.gov (United States)

    2011-06-28

    ....treas.gov . OTS will post comments and the related index on the OTS Internet Site at http://www.ots... Act. OTS merger regulations are found at 12 CFR 563.22(a), and corporate governance requirements are...

  4. The correlation between the sizes of globular cluster systems and their host dark matter haloes

    Science.gov (United States)

    Hudson, Michael J.; Robison, Bailey

    2018-04-01

    The sizes of entire systems of globular clusters (GCs) depend on the formation and destruction histories of the GCs themselves, but also on the assembly, merger and accretion history of the dark matter (DM) haloes that they inhabit. Recent work has shown a linear relation between total mass of globular clusters in the globular cluster system and the mass of its host dark matter halo, calibrated from weak lensing. Here we extend this to GC system sizes, by studying the radial density profiles of GCs around galaxies in nearby galaxy groups. We find that radial density profiles of the GC systems are well fit with a de Vaucouleurs profile. Combining our results with those from the literature, we find tight relationship (˜0.2 dex scatter) between the effective radius of the GC system and the virial radius (or mass) of its host DM halo, for halos with masses greater than ˜1012M⊙. The steep non-linear dependence of this relationship (R_{{e, GCS}} ∝ R_{200}^{2.5 - 3} ∝ M_{200}^{0.8 - 1}) is currently not well understood, but is an important clue regarding the assembly history of DM haloes and of the GC systems that they host.

  5. EVOLUTION OF SHOCKS AND TURBULENCE IN MAJOR CLUSTER MERGERS

    International Nuclear Information System (INIS)

    Paul, S.; Mannheim, K.; Iapichino, L.; Miniati, F.; Bagchi, J.

    2011-01-01

    We performed a set of cosmological simulations of major mergers in galaxy clusters, in order to study the evolution of merger shocks and the subsequent injection of turbulence in the post-shock region and in the intra-cluster medium (ICM). The computations have been performed with the grid-based, adaptive mesh refinement hydrodynamical code Enzo, using a refinement criterion especially designed for refining turbulent flows in the vicinity of shocks. When a major merger event occurs, a substantial amount of turbulence energy is injected in the ICM of the newly formed cluster. Our simulations show that the shock launched after a major merger develops an ellipsoidal shape and gets broken by the interaction with the filamentary cosmic web around the merging cluster. The size of the post-shock region along the direction of shock propagation is of the order of 300 kpc h -1 , and the turbulent velocity dispersion in this region is larger than 100 km s -1 . We performed a scaling analysis of the turbulence energy within our cluster sample. The best fit for the scaling of the turbulence energy with the cluster mass is consistent with M 5/3 , which is also the scaling law for the thermal energy in the self-similar cluster model. This clearly indicates the close relation between virialization and injection of turbulence in the cluster evolution. As for the turbulence in the cluster core, we found that within 2 Gyr after the major merger (the timescale for the shock propagation in the ICM), the ratio of the turbulent to total pressure is larger than 10%, and after about 4 Gyr it is still larger than 5%, a typical value for nearly relaxed clusters. Turbulence at the cluster center is thus sustained for several gigayears, which is substantially longer than typically assumed in the turbulent re-acceleration models, invoked to explain the statistics of observed radio halos. Striking similarities in the morphology and other physical parameters between our simulations and the

  6. THE DIRT ON DRY MERGERS

    International Nuclear Information System (INIS)

    Desai, Vandana; Soifer, B. T.; Dey, Arjun; Cohen, Emma; Le Floc'h, Emeric

    2011-01-01

    Using data from the Spitzer Space Telescope, we analyze the mid-infrared (3-70 μm) spectral energy distributions of dry merger candidates in the Booetes field of the NOAO Deep Wide-Field Survey. These candidates were selected by previous authors to be luminous, red, early-type galaxies with morphological evidence of recent tidal interactions. We find that a significant fraction of these candidates exhibit 8 and 24 μm excesses compared to expectations for old stellar populations. We estimate that a quarter of dry merger candidates have mid-infrared-derived star formation rates greater than ∼1 M sun yr -1 . This represents a 'frosting' on top of a large old stellar population, and has been seen in previous studies of elliptical galaxies. Further, the dry merger candidates include a higher fraction of star-forming galaxies relative to a control sample without tidal features. We therefore conclude that the star formation in these massive ellipticals is likely triggered by merger activity. Our data suggest that the mergers responsible for the observed tidal features were not completely dry, and may be minor mergers involving a gas-rich dwarf galaxy.

  7. Building Halos by Digesting Satellites

    Science.gov (United States)

    Kohler, Susanna

    2016-05-01

    We think galactic halos are built through the addition of material from the smaller subhalos of satellites digested by their hosts. Though most of the stars in Milky-Way-mass halos were probably formed in situ, many were instead accumulated over time, as orbiting dwarf galaxies were torn apart and their stars flung throughout the host galaxy. A recent set of simulations has examined this brutal formation process.In the authors simulations, a subhalo first falls into the host halo. At this point, it can either survive to present day as a satellite galaxy, or it can be destroyed, its stars scattering throughout the host halo. [Deason et al. 2016]Subhalo FateThere are many open questions about the growth of Milky-Way-mass halos from the accretion of subhalos. Which subhalos are torn apart and accreted, and which ones survive intact? Are more small or large subhalos accreted? Does subhalo accretion affect the host galaxys metallicity? And what can we learn from all of this about the Milky Ways formation history?In a recently published study, a team of scientists from Stanford University and SLAC National Accelerator Laboratory set out to answer these questions using a suite of 45 zoom-in simulations of Milky-Way-mass halos. Led by Alis Deason, the team tracked the accretion history of these 45 test galaxies to determine how their halos were built.Piecing Together HistoryDeason and collaborators reach several new and interesting conclusions based on the outcomes of their simulations.Average accreted stellar mass from destroyed dwarfs for each host halo, as a function of the time of the last major accretion event. More stellar mass is accreted in more recent accretion events. [Deason et al. 2016]Most of the stellar mass accreted by the Milky-Way-mass halos typically comes from only one or two destroyed dwarfs. The accreted dwarfs are usually low-mass if they were accreted early on in the simulation (i.e., in the early universe), and high-mass if they were accreted

  8. Beyond assembly bias: exploring secondary halo biases for cluster-size haloes

    Science.gov (United States)

    Mao, Yao-Yuan; Zentner, Andrew R.; Wechsler, Risa H.

    2018-03-01

    Secondary halo bias, commonly known as `assembly bias', is the dependence of halo clustering on a halo property other than mass. This prediction of the Λ Cold Dark Matter cosmology is essential to modelling the galaxy distribution to high precision and interpreting clustering measurements. As the name suggests, different manifestations of secondary halo bias have been thought to originate from halo assembly histories. We show conclusively that this is incorrect for cluster-size haloes. We present an up-to-date summary of secondary halo biases of high-mass haloes due to various halo properties including concentration, spin, several proxies of assembly history, and subhalo properties. While concentration, spin, and the abundance and radial distribution of subhaloes exhibit significant secondary biases, properties that directly quantify halo assembly history do not. In fact, the entire assembly histories of haloes in pairs are nearly identical to those of isolated haloes. In general, a global correlation between two halo properties does not predict whether or not these two properties exhibit similar secondary biases. For example, assembly history and concentration (or subhalo abundance) are correlated for both paired and isolated haloes, but follow slightly different conditional distributions in these two cases. This results in a secondary halo bias due to concentration (or subhalo abundance), despite the lack of assembly bias in the strict sense for cluster-size haloes. Due to this complexity, caution must be exercised in using any one halo property as a proxy to study the secondary bias due to another property.

  9. Trade Union Mergers: A Survey of the Literature.

    Science.gov (United States)

    Michelson, Grant

    2000-01-01

    Examines trade union mergers highlighting merger forms, merger motivation, role played by union officers, and merger waves. Discusses the consequences of mergers on members and union performance and concludes that union merger activity has had little impact. (Contains 74 references.) (JOW)

  10. Non-Gaussian halo assembly bias

    International Nuclear Information System (INIS)

    Reid, Beth A.; Verde, Licia; Dolag, Klaus; Matarrese, Sabino; Moscardini, Lauro

    2010-01-01

    The strong dependence of the large-scale dark matter halo bias on the (local) non-Gaussianity parameter, f NL , offers a promising avenue towards constraining primordial non-Gaussianity with large-scale structure surveys. In this paper, we present the first detection of the dependence of the non-Gaussian halo bias on halo formation history using N-body simulations. We also present an analytic derivation of the expected signal based on the extended Press-Schechter formalism. In excellent agreement with our analytic prediction, we find that the halo formation history-dependent contribution to the non-Gaussian halo bias (which we call non-Gaussian halo assembly bias) can be factorized in a form approximately independent of redshift and halo mass. The correction to the non-Gaussian halo bias due to the halo formation history can be as large as 100%, with a suppression of the signal for recently formed halos and enhancement for old halos. This could in principle be a problem for realistic galaxy surveys if observational selection effects were to pick galaxies occupying only recently formed halos. Current semi-analytic galaxy formation models, for example, imply an enhancement in the expected signal of ∼ 23% and ∼ 48% for galaxies at z = 1 selected by stellar mass and star formation rate, respectively

  11. University Mergers in Finland: Mediating Global Competition

    Science.gov (United States)

    Välimaa, Jussi; Aittola, Helena; Ursin, Jani

    2014-01-01

    University mergers have become a common strategy for increasing global competitiveness. In this chapter, the authors analyze the implementation of mergers in Finnish universities from the perspective of social justice as conceived within Finland and other Nordic countries.

  12. Halo Mitigation Using Nonlinear Lattices

    CERN Document Server

    Sonnad, Kiran G

    2005-01-01

    This work shows that halos in beams with space charge effects can be controlled by combining nonlinear focusing and collimation. The study relies on Particle-in-Cell (PIC) simulations for a one dimensional, continuous focusing model. The PIC simulation results show that nonlinear focusing leads to damping of the beam oscillations thereby reducing the mismatch. It is well established that reduced mismatch leads to reduced halo formation. However, the nonlinear damping is accompanied by emittance growth causing the beam to spread in phase space. As a result, inducing nonlinear damping alone cannot help mitigate the halo. To compensate for this expansion in phase space, the beam is collimated in the simulation and further evolution of the beam shows that the halo is not regenerated. The focusing model used in the PIC is analysed using the Lie Transform perturbation theory showing that by averaging over a lattice period, one can reuduce the focusing force to a form that is identical to that used in the PIC simula...

  13. Bundling and mergers in energy markets

    International Nuclear Information System (INIS)

    Granier, Laurent; Podesta, Marion

    2010-01-01

    Does bundling trigger mergers in energy industries? We observe mergers between firms belonging to various energy markets, for instance between gas and electricity providers. These mergers enable firms to bundle. We consider two horizontally differentiated markets. In this framework, we show that bundling strategies in energy markets create incentives to form multi-market firms in order to supply bi-energy packages. Moreover, we find that this type of merger is detrimental to social welfare. (author)

  14. Merger Activity and Radio Emission Within A2061

    Science.gov (United States)

    Bailey, Avery; Sarazin, Craig L.; Clarke, Tracy E.; Chatzikos, Marios; Hogge, Taylor; Wik, Daniel R.; Rudnick, Lawrence; Farnsworth, Damon; Van Weeren, Reinout J.; Brown, Shea

    2015-01-01

    Abell 2061 is a galaxy cluster located in the Corona Borealis Supercluster that boasts radio and X-ray structures indicative of a merger. A2061 is located at a redshift z = .0784, contains two brightest cluster galaxies, and has another cluster (A2067) about 2.5 Mpc to the NE, falling towards it. Within A2061, there exists an elongated structure of soft X-ray emission extending to the NE of cluster's center (referred to as the 'Plume') along with a hard X-ray shock region (the 'Shock') located just NE of the cluster's center. Previous observations in the radio have indicated the presence of a extended, central radio halo/relic accompanying the cluster's main X-ray emission but with slight NE displacement and further NE extension. Also emitting in the radio, to the SW of A2061, is a radio relic. The X-ray structures of A2061 were previously examined in 2009 by a Chandra observation. Here we present the results of an August 2013 XMM-Newton observation of the cluster. This XMM-Newton observation, imaged by three detectors, covers a greater field of view with a longer exposure (48.6 ks) than the previous Chandra observation. We will present images and spectra of various regions of the cluster. In addition, we will discuss the dynamics of the cluster, the nature of the Plume, Shock and other features, and origin of the central diffuse radio halo/relic and SW radio relic. These X-ray observations will also be compared to a numerical simulation from the Simulation Library of Astrophysics cluster Mergers (SLAM).

  15. Nurse Executive Leadership During Organizational Mergers.

    Science.gov (United States)

    Piper, Letty Roth; Schneider, Maureen

    2015-12-01

    The recent growth in hospital mergers and the resultant mergers of nursing service departments (NSDs) have produced a need for chief nursing officers (CNOs) to be aware of implications and anticipated dynamic changes. This article addresses the major issues raised by mergers for NSDs and presents an operational step-by-step checklist for CNOs.

  16. 12 CFR 708b.101 - Mergers generally.

    Science.gov (United States)

    2010-01-01

    ... 12 Banks and Banking 6 2010-01-01 2010-01-01 false Mergers generally. 708b.101 Section 708b.101 Banks and Banking NATIONAL CREDIT UNION ADMINISTRATION REGULATIONS AFFECTING CREDIT UNIONS MERGERS OF FEDERALLY-INSURED CREDIT UNIONS; VOLUNTARY TERMINATION OR CONVERSION OF INSURED STATUS Mergers § 708b.101...

  17. 7 CFR 3575.89 - Mergers.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 15 2010-01-01 2010-01-01 false Mergers. 3575.89 Section 3575.89 Agriculture... GENERAL Community Programs Guaranteed Loans § 3575.89 Mergers. (a) General. The Agency may approve mergers or consolidations (herein referred to as “mergers”) when the resulting organization will be eligible...

  18. 7 CFR 1779.89 - Mergers.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 12 2010-01-01 2010-01-01 false Mergers. 1779.89 Section 1779.89 Agriculture... (CONTINUED) WATER AND WASTE DISPOSAL PROGRAMS GUARANTEED LOANS § 1779.89 Mergers. (a) General. The Agency may approve mergers or consolidations (herein referred to as “mergers”) when the resulting organization will...

  19. Is Education Getting Lost in University Mergers?

    Science.gov (United States)

    Ursin, Jani; Aittola, Helena; Henderson, Charles; Valimaa, Jussi

    2010-01-01

    Mergers are common phenomena in higher education institutions. Improving educational quality is typically one of the stated goals of university mergers. Yet, little information exists about how merging institutions approach this goal. This paper presents results from a study of planning documents created prior to four mergers in the Finnish higher…

  20. Accounting for distress in bank mergers

    NARCIS (Netherlands)

    Koetter, M.; Bos, J. W. B.; Heid, F.; Kolari, J. W.; Kool, C. J. M.; Porath, D.

    2007-01-01

    Most bank merger studies do not control for hidden bailouts, which may lead to biased results. In this study we employ a unique data set of approximately 1000 mergers to analyze the determinants of bank mergers. We use undisclosed information on banks' regulatory intervention history to distinguish

  1. Cross-border merger and domestic welfare

    OpenAIRE

    Arijit Mukherjee

    2006-01-01

    We consider the welfare effect of cross-border merger in presence of international R&D competition. Cross-border merger increases domestic welfare if the bargaining power of the foreign firm and the slope of the marginal cost of R&D are sufficiently low. Otherwise, domestic welfare is lower under cross-border merger.

  2. Matter in compact binary mergers

    Science.gov (United States)

    Read, Jocelyn; LIGO Scientific Collaboration, Virgo Scientific Collaboration

    2018-01-01

    Mergers of binary neutron stars or neutron-star/black-hole systems are promising targets for gravitational-wave detection. The dynamics of merging compact objects, and thus their gravitational-wave signatures, are primarily determined by the mass and spin of the components. However, the presence of matter can make an imprint on the final orbits and merger of a binary system. I will outline efforts to understand the impact of neutron-star matter on gravitational waves, using both theoretical and computational input, so that gravitational-wave observations can be used to measure the properties of source systems with neutron-star components.

  3. Halo effects in grading student projects.

    Science.gov (United States)

    Dennis, Ian

    2007-07-01

    Halo effects in rating specific pieces of work, as in educational grading, have received little attention. Grades awarded by 2 independent graders to undergraduate projects were analyzed with a correlated uniqueness model. Grades showed substantial halo despite being awarded by expert assessors at the time of reading the work. There was greater halo between different grades applying to the same section of the project than between grades applying to different sections. Supervisors who had regular contact with the student whose work they were grading showed no more halo than other graders. More reliable graders showed less within-section halo than graders of lower reliability but equal between-sections halo. The halo effects observed cannot be entirely attributable to a unitary general impression.

  4. Brown dwarfs as dark galactic halos

    International Nuclear Information System (INIS)

    Adams, F.C.; Walker, T.P.

    1990-01-01

    The possibility that the dark matter in galactic halos can consist of brown dwarf stars is considered. The radiative signature for such halos consisting solely of brown dwarfs is calculated, and the allowed range of brown dwarf masses, the initial mass function (IMF), the stellar properties, and the density distribution of the galactic halo are discussed. The prediction emission from the halo is compared with existing observations. It is found that, for any IMF of brown dwarfs below the deuterium burning limit, brown dwarf halos are consistent with observations. Brown dwarf halos cannot, however, explain the recently observed near-IR background. It is shown that future satellite missions will either detect brown dwarf halos or place tight constraints on the allowed range of the IMF. 30 refs

  5. ULTRAVIOLET HALOS AROUND SPIRAL GALAXIES. I. MORPHOLOGY

    Energy Technology Data Exchange (ETDEWEB)

    Hodges-Kluck, Edmund; Cafmeyer, Julian; Bregman, Joel N., E-mail: hodgeskl@umich.edu [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)

    2016-12-10

    We examine ultraviolet halos around a sample of highly inclined galaxies within 25 Mpc to measure their morphology and luminosity. Despite contamination from galactic light scattered into the wings of the point-spread function, we find that ultraviolet (UV) halos occur around each galaxy in our sample. Around most galaxies the halos form a thick, diffuse disk-like structure, but starburst galaxies with galactic superwinds have qualitatively different halos that are more extensive and have filamentary structure. The spatial coincidence of the UV halos above star-forming regions, the lack of consistent association with outflows or extraplanar ionized gas, and the strong correlation between the halo and galaxy UV luminosity suggest that the UV light is an extragalactic reflection nebula. UV halos may thus represent 10{sup 6}–10{sup 7} M {sub ⊙} of dust within 2–10 kpc of the disk, whose properties may change with height in starburst galaxies.

  6. A DISTANT RADIO MINI-HALO IN THE PHOENIX GALAXY CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Van Weeren, R. J.; Andrade-Santos, F.; Forman, W. R.; Jones, C. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Intema, H. T. [National Radio Astronomy Observatory, 1003 Lopezville Road, Socorro, NM 87801-0387 (United States); Lal, D. V. [National Centre for Radio Astrophysics, TIFR, Pune University Campus, Post Bag 3, Pune 411 007 (India); Brüggen, M.; De Gasperin, F. [Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg (Germany); Hoeft, M. [Thüringer Landessternwarte Tautenburg, Sternwarte 5, D-07778, Tautenburg (Germany); Nuza, S. E. [Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); Röttgering, H. J. A.; Stroe, A., E-mail: rvanweeren@cfa.harvard.edu [Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands)

    2014-05-10

    We report the discovery of extended radio emission in the Phoenix cluster (SPT-CL J2344-4243, z = 0.596) with the Giant Metrewave Radio Telescope (GMRT) at 610 MHz. The diffuse emission extends over a region of at least 400-500 kpc and surrounds the central radio source of the Brightest Cluster Galaxy, but does not appear to be directly associated with it. We classify the diffuse emission as a radio mini-halo, making it the currently most distant mini-halo known. Radio mini-halos have been explained by synchrotron emitting particles re-accelerated via turbulence, possibly induced by gas sloshing generated from a minor merger event. Chandra observations show a non-concentric X-ray surface brightness distribution, which is consistent with this sloshing interpretation. The mini-halo has a flux density of 17 ± 5 mJy, resulting in a 1.4 GHz radio power of (10.4 ± 3.5) × 10{sup 24} W Hz{sup –1}. The combined cluster emission, which includes the central compact radio source, is also detected in a shallow GMRT 156 MHz observation and together with the 610 MHz data we compute a spectral index of –0.84 ± 0.12 for the overall cluster radio emission. Given that mini-halos typically have steeper radio spectra than cluster radio galaxies, this spectral index should be taken as an upper limit for the mini-halo.

  7. Reionization histories of Milky Way mass halos

    Energy Technology Data Exchange (ETDEWEB)

    Li, Tony Y.; Wechsler, Risa H.; Abel, Tom [Kavli Institute for Particle Astrophysics and Cosmology, Physics Department, Stanford University, Stanford, CA 94305 (United States); Alvarez, Marcelo A., E-mail: tonyyli@stanford.edu, E-mail: rwechsler@stanford.edu, E-mail: tabel@stanford.edu, E-mail: malvarez@cita.utoronto.ca [CITA, University of Toronto, Toronto, Ontario M5S 3H8 (Canada)

    2014-04-20

    We investigate the connection between the reionization era and the present-day universe by examining the mass reionization histories of z = 0 dark matter halos. In a 600{sup 3} Mpc{sup 3} volume, we combine a dark matter N-body simulation with a three-dimensional seminumerical reionization model. This tags each particle with a reionization redshift, so that individual present-day halos can be connected to their reionization histories and environments. We find that the vast majority of present-day halos with masses larger than ∼ few × 10{sup 11} M {sub ☉} reionize earlier than the rest of the universe. We also find significant halo-to-halo diversity in mass reionization histories, and find that in realistic inhomogeneous models, the material within a given halo is not expected to reionize at the same time. In particular, the scatter in reionization times within individual halos is typically larger than the scatter among halos. From our fiducial reionization model, we find that the typical 68% scatter in reionization times within halos is ∼115 Myr for 10{sup 12±0.25} M {sub ☉} halos, decreasing slightly to ∼95 Myr for 10{sup 15±0.25} M {sub ☉} halos. We find a mild correlation between reionization history and environment: halos with shorter reionization histories are typically in more clustered environments, with the strongest trend on a scale of ∼20 Mpc. Material in Milky Way mass halos with short reionization histories is preferentially reionized in relatively large H II regions, implying reionization mostly by sources external to the progenitors of the present-day halo. We investigate the impact on our results of varying the reionization model parameters, which span a range of reionization scenarios with varying timing and morphology.

  8. Medical group mergers: strategies for success.

    Science.gov (United States)

    Latham, Will

    2014-01-01

    As consolidation sweeps over the healthcare industry, many medical groups are considering mergers with other groups as an alternative to employment. While mergers are challenging and fraught with risk, an organized approach to the merger process can dramatically increase the odds for success. Merging groups need to consider the benefits they seek from a merger, identify the obstacles that must be overcome to merge, and develop alternatives to overcome those obstacles. This article addresses the benefits to be gained and issues to be addressed, and provides a tested roadmap that has resulted in many successful medical group mergers.

  9. Orbital decay of supermassive black hole binaries in clumpy multiphase merger remnants

    Science.gov (United States)

    Roškar, Rok; Fiacconi, Davide; Mayer, Lucio; Kazantzidis, Stelios; Quinn, Thomas R.; Wadsley, James

    2015-05-01

    We simulate an equal-mass merger of two Milky Way-size galaxy discs with moderate gas fractions at parsec-scale resolution including a new model for radiative cooling and heating in a multiphase medium, as well as star formation and feedback from supernovae. The two discs initially have a 2.6 × 106 M⊙ supermassive black hole (SMBH) embedded in their centres. As the merger completes and the two galactic cores merge, the SMBHs form a pair with a separation of a few hundred pc that gradually decays. Due to the stochastic nature of the system immediately following the merger, the orbital plane of the binary is significantly perturbed. Furthermore, owing to the strong starburst the gas from the central region is completely evacuated, requiring ˜10 Myr for a nuclear disc to rebuild. Most importantly, the clumpy nature of the interstellar medium has a major impact on the dynamical evolution of the SMBH pair, which undergo gravitational encounters with massive gas clouds and stochastic torquing by both clouds and spiral modes in the disc. These effects combine to greatly delay the decay of the two SMBHs to separations of a few parsecs by nearly two orders of magnitude, ˜108 yr, compared to previous work. In mergers of more gas-rich, clumpier galaxies at high redshift stochastic torques will be even more pronounced and potentially lead to stronger modulation of the orbital decay. This suggests that SMBH pairs at separations of several tens of parsecs should be relatively common at any redshift.

  10. Kinematic and Chemical Constraints on the Formation of M31's Inner and Outer Halo

    Science.gov (United States)

    Koch, Andreas; Rich, R. Michael; Reitzel, David B.; Martin, Nicolas F.; Ibata, Rodrigo A.; Chapman, Scott C.; Majewski, Steven R.; Mori, Masao; Loh, Yeong-Shang; Ostheimer, James C.; Tanaka, Mikito

    2008-12-01

    The halo of M31 shows a wealth of substructures, some of which are consistent with assembly from satellite accretion. Here we report on kinematic and abundance results from Keck DEIMOS spectroscopy in the near-infrared calcium triplet region of over 3500 red giant star candidates along the minor axis and in off-axis spheroid fields of M31. These data reach out to large radial distances of about 160 kpc. The derived radial velocity distributions show an indication of a kinematically cold substructure around ~17 kpc, which has been reported before. We devise a new and improved method to measure spectroscopic metallicities from the calcium triplet in low signal-to-noise ratio spectra using a weighted co-addition of the individual lines. The resulting distribution (accurate to ~0.3 dex down to signal-to-noise ratios of 5) leads us to note an even stronger gradient in the abundance distribution along M31's minor axis and in particular toward the outer halo fields than previously detected. The mean metallicity in the outer fields reaches below -2 dex, with individual values as low as lesssim-2.6 dex. This is the first time such a metal-poor halo has been detected in M31. In the fields toward the inner spheroid, we find a sharp decline of ~0.5 dex in metallicity in a region at ~20 kpc, which roughly coincides with the edge of an extended disk, previously detected from star count maps. A large fraction of red giants that we detect in the most distant fields are likely members of M33's overlapping halo. A comparison of our velocities with those predicted by new N-body simulations argues that the event responsible for the Giant Stream is most likely not responsible for the full population of the inner halo. We show further that the abundance distribution of the Stream is different from that of the inner halo, from which it becomes evident, in turn, that the merger event that formed the Stream and the outer halo cannot have contributed any significant material to the inner

  11. Essays on mergers and acquisitions

    NARCIS (Netherlands)

    Faelten, A.I.

    2016-01-01

    “Essays on Mergers and Acquisitions" tackles some of the most prominent business challenges related to M&A activity. The Introduction examines the reasons why deals fail through well-known case studies; Chapter 1 presents a new index measuring countries M&A maturity worldwide; Chapter 2 focus on the

  12. THE ROLE OF DRY MERGERS FOR THE FORMATION AND EVOLUTION OF BRIGHTEST CLUSTER GALAXIES

    International Nuclear Information System (INIS)

    Ruszkowski, M.; Springel, V.

    2009-01-01

    Using a resimulation technique, we perform high-resolution cosmological simulations of dry mergers in a massive (10 15 M sun ) galaxy cluster identified in the Millennium Run. Our initial conditions include well resolved compound galaxy models consisting of dark matter halos and stellar bulges that are used to replace the most massive cluster progenitor halos at redshift z = 3, allowing us to follow the subsequent dry merger processes that build up the cluster galaxies in a self-consistent cosmological setting. By construction, our galaxy models obey the stellar mass-size relation initially. Also, we study both galaxy models with adiabatically contracted and uncompressed halos. We demonstrate that the brightest cluster galaxy (BCG) evolves away from the Kormendy relation as defined by the smaller mass galaxies (i.e., the relation bends). This is accompanied by a significantly faster dark matter mass growth within the half-light radius of the BCG compared to the increase in the stellar mass inside the same radius. As a result of the comparatively large number of mergers the BCG experiences, its total mass-to-light ratio becomes significantly higher than in typical elliptical galaxies. We also show that the mixing processes between dark matter and stars lead to a small but numerically robust tilt in the fundamental plane and that the BCG lies on the tilted plane. Our model is consistent with the observed steepening of the logarithmic mass-to-light gradient as a function of the stellar mass. As we have not included effects from gas dynamics or star formation, these trends are exclusively due to N-body and stellar dynamical effects. Surprisingly, we find only tentative weak distortion in the Faber-Jackson relation that depends on the aperture size, unlike expected based on studies of isolated merger simulations. This may be due to differences in the distribution of galaxy orbits, which is given in our approach directly by the cosmological context while it has to be

  13. Historical halo displays as past weather indicator

    Science.gov (United States)

    Neuhäuser, Dagmar; Neuhäuser, Ralph

    2017-04-01

    Certain halo displays like the 22° circle were known to indicate specific weather pattern since millennia - as specified in Babylonian omina, Aristotle's Meteorology, farmers' weather lore, etc. Today, it is known that halo phenomena are due to refraction and reflection of sun and moon light in ice crystals in cirrus and cirrostratus, so that halo observations do indicate atmospheric conditions like temperature, humidity, pressure etc. in a few km height. The Astronomical Diaries of Babylonia have recorded both halo phenomena (circles, parhelia, etc.) and weather conditions (rain, clouds, etc.), so that we can use them to show statistically, whether, which and how fast halo phenomena are related to weather - for the last few centuries BC for Babylonia. We can then also compare the observations of Babylonian priests in the given BC epoch (without air and light pollution) with the last few decades of the modern epoch (with air and light pollution), where amateur halo observers have systematically recorded such phenomena (in Europe). Weather and climate are known to be partly driven by solar activity. Hence, one could also consider whether there is an indirect relation between halo displays as weather proxy and aurorae as solar activity proxy - if low solar activity leads to low pressure systems, one could expect more halos, preliminary studies show such a hint. For the last few decades, we have many halo observations, satellite imaging of the aurora oval, and many data on solar activity. A statistically sufficient amount of aurora and halo observations should be available for the historic time to investigate such a possible connection: halos were recorded very often in antiquity and the medieval times (as found in chronicles etc.), and modern scholarly catalogs of aurorae also often contain unrecognized halo displays.

  14. An Unlikely Radio Halo in the Low X-Ray Luminosity Galaxy Cluster RXCJ1514.9-1523

    Science.gov (United States)

    Marketvitch, M.; ZuHone, J. A.; Lee, D.; Giacintucci, S.; Dallacasa, D.; Venturi, T.; Brunetti, G.; Cassano, R.; Markevitch, M.; Athreya, R. M.

    2011-01-01

    Aims: We report the discovery of a giant radio halo in the galaxy cluster RXCJ1514,9-1523 at z=0.22 with a relatively low X-ray luminosity, L(sub X) (0.1-2.4kev) approx. 7 x 10(exp 44) ergs/s. Methods: This faint, diffuse radio source is detected with the Giant Meterwave Radio Telescope at 327 MHz. The source is barely detected at 1.4 GHz in a NVSS pointing that we have reanalyzed. Results: The integrated radio spectrum of the halo is quite steep, with a slope alpha = 1.6 between 327 MHz and 1.4 GHz. While giant radio halos are common in more X-ray luminous cluster mergers, there is a less than 10% probability to detect a halo in systems with L(sub X) origin of ultrarelativistic electrons in clusters. Furthermore, if our steep radio spectral index is confirmed by future deeper radio observations, this cluster would provide another example of the very rare, new class of ultra-steep spectrum radio halos, predicted by the model in which the cluster cosmic ray electrons are produced by turbulent reacceleration.

  15. Unbound particles in dark matter halos

    Energy Technology Data Exchange (ETDEWEB)

    Behroozi, Peter S.; Loeb, Abraham; Wechsler, Risa H.

    2013-06-13

    We investigate unbound dark matter particles in halos by tracing particle trajectories in a simulation run to the far future (a = 100). We find that the traditional sum of kinetic and potential energies is a very poor predictor of which dark matter particles will eventually become unbound from halos. We also study the mass fraction of unbound particles, which increases strongly towards the edges of halos, and decreases significantly at higher redshifts. We discuss implications for dark matter detection experiments, precision calibrations of the halo mass function, the use of baryon fractions to constrain dark energy, and searches for intergalactic supernovae.

  16. HI Absorption in Merger Remnants

    Science.gov (United States)

    Teng, Stacy H.; Veileux, Sylvain; Baker, Andrew J.

    2012-01-01

    It has been proposed that ultraluminous infrared galaxies (ULIRGs) pass through a luminous starburst phase, followed by a dust-enshrouded AGN phase, and finally evolve into optically bright "naked" quasars once they shed their gas/dust reservoirs through powerful wind events. We present the results of our recent 21- cm HI survey of 21 merger remnants with the Green Bank Telescope. These remnants were selected from the QUEST (Quasar/ULIRG Evolution Study) sample of ULIRGs and PG quasars; our targets are all bolometrically dominated by AGN and sample all phases of the proposed ULIRG -> IR-excess quasar -> optical quasar sequence. We explore whether there is an evolutionary connection between ULIRGs and quasars by looking for the occurrence of HI absorption tracing neutral gas outflows; our results will allow us to identify where along the sequence the majority of a merger's gas reservoir is expelled.

  17. Mergers in European Higher Education

    DEFF Research Database (Denmark)

    Rocha, Vera; Teixeira, Pedro N.; Biscaia, Ricardo

    2018-01-01

    In recent years, mergers have been widely used in higher education (HE) to achieve a variety of purposes, ranging from problems of institutional fragmentation to the lack of financial and academic viability, and low institutional efficiency and quality. However, despite a large stream of HE...... experience of 25 European countries with these processes, aiming at identifying main patterns regarding key drivers and motivations. We also analyze the main difficulties identified, the role of funding and financial incentives and, whenever possible, the main impacts and economic gains associated with those...... literature addressing those issues, there has been little attention to the link between funding-related problems and merger processes. Moreover, there is very little comparative research among different higher education systems experiencing those processes. In this paper, we map and characterize the recent...

  18. ACCURATE UNIVERSAL MODELS FOR THE MASS ACCRETION HISTORIES AND CONCENTRATIONS OF DARK MATTER HALOS

    International Nuclear Information System (INIS)

    Zhao, D. H.; Jing, Y. P.; Mo, H. J.; Boerner, G.

    2009-01-01

    cosmological parameters and the power index of the initial density fluctuation spectrum have changed dramatically. Our model predictions also match the PINOCCHIO mass accretion histories very well, which are much independent of our numerical simulations and our definitions of halo merger trees. These models are also simple and easy to implement, making them very useful in modeling the growth and structure of dark matter halos. We provide appendices describing the step-by-step implementation of our models. A calculator which allows one to interactively generate data for any given cosmological model is provided on the Web, together with a user-friendly code to make the relevant calculations and some tables listing the expected concentration as a function of halo mass and redshift in several popular cosmological models. We explain why ΛCDM and open CDM halos on nearly all mass scales show two distinct phases in their mass growth histories. We discuss implications of the universal relations we find in connection to the formation of dark matter halos in the cosmic density field.

  19. Beta Dips in the Gaia Era: Simulation Predictions of the Galactic Velocity Anisotropy Parameter (β) for Stellar Halos

    Science.gov (United States)

    Loebman, Sarah R.; Valluri, Monica; Hattori, Kohei; Debattista, Victor P.; Bell, Eric F.; Stinson, Greg; Christensen, Charlotte R.; Brooks, Alyson; Quinn, Thomas R.; Governato, Fabio

    2018-02-01

    The velocity anisotropy parameter, β, is a measure of the kinematic state of orbits in the stellar halo, which holds promise for constraining the merger history of the Milky Way (MW). We determine global trends for β as a function of radius from three suites of simulations, including accretion-only and cosmological hydrodynamic simulations. We find that the two types of simulations are consistent and predict strong radial anisotropy ( ∼ 0.7) for Galactocentric radii greater than 10 kpc. Previous observations of β for the MW’s stellar halo claim a detection of an isotropic or tangential “dip” at r ∼ 20 kpc. Using the N-body+SPH simulations, we investigate the temporal persistence, population origin, and severity of “dips” in β. We find that dips in the in situ stellar halo are long-lived, while dips in the accreted stellar halo are short-lived and tied to the recent accretion of satellite material. We also find that a major merger as early as z ∼ 1 can result in a present-day low (isotropic to tangential) value of β over a broad range of radii and angles. While all of these mechanisms are plausible drivers for the β dip observed in the MW, each mechanism in the simulations has a unique metallicity signature associated with it, implying that future spectroscopic surveys could distinguish between them. Since an accurate knowledge of β(r) is required for measuring the mass of the MW halo, we note that significant transient dips in β could cause an overestimate of the halo’s mass when using spherical Jeans equation modeling.

  20. Can consumers bank on mergers?

    OpenAIRE

    Kerton, Robert / R

    2003-01-01

    How big do banks need to be to gain all the economies of scale? The largest Canadian banks already achieve scale economies and further increases in size can make them "too big to fail." Available evidence indicates normal monopoly risks will be passed on to Canadian firms and consumers if the largest banks merge. Improved service will make Canada's banks world competitive. Despite the banks' enthusiasm for heft to enter the US market, policy measures exist to prevent mergers that are contr...

  1. Disclosure requirements for merger and acquisition transactions

    International Nuclear Information System (INIS)

    Holm, D.I.

    1998-01-01

    The legal disclosure requirements for merger and acquisition transactions involving Canadian public companies are described. The focus is on issues regarding merger and acquisition related disclosure, including the potential consequences of failing to provide proper information, Ontario Securities Commission Policy 9.1 considerations regarding valuation, review, and approval, cross border considerations and financing a merger and acquisition transaction. Legal and practical consequences for failing to provide proper disclosure, including the steps involved in establishing the due diligence defence, are also discussed

  2. Mergers and acquisitions: valuation and risk assessment

    International Nuclear Information System (INIS)

    McVeigh, C.A.

    1996-01-01

    An overview of various aspects of mergers and acquisition transactions in the petroleum industry were presented. Incentives to mergers and acquisitions were reviewed and discussed, among them value opportunity, critical size, incremental tax pools, financial distress, shareholder dissatisfaction, strategic infrastructure position, complementary assets, and undeveloped land inventory. Current trends in mergers and acquisitions were highlighted. An industry checklist for risk assessments discussing financial position, engineering forecasts, and taxation was also included

  3. Sky Localization of Complete Inspiral-Merger-Ringdown Signals for Nonspinning Black Hole Binaries with LISA

    Science.gov (United States)

    McWilliams, Sean T.; Lang, Ryan N.; Baker, John G.; Thorpe, James Ira

    2011-01-01

    We investigate the capability of LISA to measure the sky position of equal-mass, nonspinning black hole binaries, including for the first time the entire inspiral-merger-ringdown signal, the effect of the LISA orbits, and the complete three-channel LISA response. For an ensemble of systems near the peak of LISA's sensitivity band, with total rest mass of 2 x l0(exp 6) Stellar Mass at a redshift of z = 1 with random orientations and sky positions, we find median sky localization errors of approximately approx. 3 arcminutes. This is comparable to the field of view of powerful electromagnetic telescopes, such as the James Webb Space Telescope, that could be used to search for electromagnetic signals associated with merging black holes. We investigate the way in which parameter errors decrease with measurement time, focusing specifically on the additional information provided during the merger-ringdown segment of the signal. We find that this information improves all parameter estimates directly, rather than through diminishing correlations with any subset of well-determined parameters.

  4. Analytic modeling of axisymmetric disruption halo currents

    International Nuclear Information System (INIS)

    Humphreys, D.A.; Kellman, A.G.

    1999-01-01

    Currents which can flow in plasma facing components during disruptions pose a challenge to the design of next generation tokamaks. Induced toroidal eddy currents and both induced and conducted poloidal ''halo'' currents can produce design-limiting electromagnetic loads. While induction of toroidal and poloidal currents in passive structures is a well-understood phenomenon, the driving terms and scalings for poloidal currents flowing on open field lines during disruptions are less well established. A model of halo current evolution is presented in which the current is induced in the halo by decay of the plasma current and change in enclosed toroidal flux while being convected into the halo from the core by plasma motion. Fundamental physical processes and scalings are described in a simplified analytic version of the model. The peak axisymmetric halo current is found to depend on halo and core plasma characteristics during the current quench, including machine and plasma dimensions, resistivities, safety factor, and vertical stability growth rate. Two extreme regimes in poloidal halo current amplitude are identified depending on the minimum halo safety factor reached during the disruption. A 'type I' disruption is characterized by a minimum safety factor that remains relatively high (typically 2 - 3, comparable to the predisruption safety factor), and a relatively low poloidal halo current. A 'type II' disruption is characterized by a minimum safety factor comparable to unity and a relatively high poloidal halo current. Model predictions for these two regimes are found to agree well with halo current measurements from vertical displacement event disruptions in DIII-D [T. S. Taylor, K. H. Burrell, D. R. Baker, G. L. Jackson, R. J. La Haye, M. A. Mahdavi, R. Prater, T. C. Simonen, and A. D. Turnbull, open-quotes Results from the DIII-D Scientific Research Program,close quotes in Proceedings of the 17th IAEA Fusion Energy Conference, Yokohama, 1998, to be published in

  5. THE PSEUDO-EVOLUTION OF HALO MASS

    International Nuclear Information System (INIS)

    Diemer, Benedikt; Kravtsov, Andrey V.; More, Surhud

    2013-01-01

    A dark matter halo is commonly defined as a spherical overdensity of matter with respect to a reference density, such as the critical density or the mean matter density of the universe. Such definitions can lead to a spurious pseudo-evolution of halo mass simply due to redshift evolution of the reference density, even if its physical density profile remains constant over time. We estimate the amount of such pseudo-evolution of mass between z = 1 and 0 for halos identified in a large N-body simulation, and show that it accounts for almost the entire mass evolution of the majority of halos with M 200ρ-bar ≲ 10 12 h -1 M ☉ and can be a significant fraction of the apparent mass growth even for cluster-sized halos. We estimate the magnitude of the pseudo-evolution assuming that halo density profiles remain static in physical coordinates, and show that this simple model predicts the pseudo-evolution of halos identified in numerical simulations to good accuracy, albeit with significant scatter. We discuss the impact of pseudo-evolution on the evolution of the halo mass function and show that the non-evolution of the low-mass end of the halo mass function is the result of a fortuitous cancellation between pseudo-evolution and the absorption of small halos into larger hosts. We also show that the evolution of the low-mass end of the concentration-mass relation observed in simulations is almost entirely due to the pseudo-evolution of mass. Finally, we discuss the implications of our results for the interpretation of the evolution of various scaling relations between the observable properties of galaxies and galaxy clusters and their halo masses.

  6. UARS Halogen Occultation Experiment (HALOE) Level 2 V001

    Data.gov (United States)

    National Aeronautics and Space Administration — The HALOE home page on the WWW is http://haloe.gats-inc.com/home/index.php The Halogen Occultation Experiment (HALOE) on NASA's Upper Atmosphere Research Satellite...

  7. HaloSat - A CubeSat to Study the Hot Galactic Halo

    Science.gov (United States)

    Kaaret, Philip

    2017-08-01

    Observations of the nearby universe fail to locate about half of the normal matter (baryons) observed in the early universe. The missing baryons may be in hot galactic halos. HaloSat is a CubeSat designed to map oxygen line emission (O VII and O VIII) around the Milky Way in order to constrain the mass and spatial distribution of hot gas in the halo. HaloSat has a grasp competitive with current X-ray observatories. Its observing program will be optimized to minimize contributions from solar wind charge exchange (SWCX) emission that limit the accuracy of current measurements. We describe the current status of HaloSat.

  8. Two cases of halo scalp ring.

    Science.gov (United States)

    Douri, Thaer Hasan

    2016-11-15

    Halo scalp ring (HSR) is a rare form of non-scarring annular alopecia that is attributed to caput succedaneum. It arises perinatally because of prolonged pressure on the scalp by the cervix during or before the delivery. We report two new cases of halo scalp ring in full term pregnancy - newborns.

  9. Two cases of halo scalp ring

    OpenAIRE

    Douri, Thaer Hasan

    2016-01-01

    Halo scalp ring (HSR) is a rare form of non-scarring annular alopecia that is attributed to caput succedaneum. It arises perinatally because of prolonged pressure on the scalp by the cervix during or before the delivery. We report two new cases of halo scalp ring in full term pregnancy - newborns.

  10. Halo abundances and shear in void models

    DEFF Research Database (Denmark)

    Alonso, David; García-Bellido, Juan; Haugbølle, Troels

    2012-01-01

    We study the non-linear gravitational collapse of dark matter into halos through numerical N-body simulations of Lemaitre-Tolman-Bondi void models. We extend the halo mass function formalism to these models in a consistent way. This extension not only compares well with the simulated data at all...

  11. Studying dark matter haloes with weak lensing

    NARCIS (Netherlands)

    Velander, Malin Barbro Margareta

    2012-01-01

    Our Universe is comprised not only of normal matter but also of unknown components: dark matter and dark energy. This Thesis recounts studies of dark matter haloes, using a technique known as weak gravitational lensing, in order to learn more about the nature of these dark components. The haloes

  12. Efimov effect in 2-neutron halo nuclei

    Indian Academy of Sciences (India)

    This paper presents an overview of our theoretical investigations in search of Efimov states in light 2-neutron halo nuclei. The calculations have been carried out within a three-body formalism, assuming a compact core and two valence neutrons forming the halo. The calculations provide strong evidence for the occurrence ...

  13. Halo formation in three-dimensional bunches

    International Nuclear Information System (INIS)

    Gluckstern, R.L.; Fedotov, A.V.; Kurennoy, S.; Ryne, R.

    1998-01-01

    We have constructed, analytically and numerically, a class of self-consistent six-dimensional (6D) phase space stationary distributions. Stationary distributions allow us to study the halo development mechanism without it being obscured by beam redistribution and its effect on halo formation. The beam is then mismatched longitudinally and/or transversely, and we explore the formation of longitudinal and transverse halos in 3D axisymmetric beam bunches. We find that the longitudinal halo forms first for comparable longitudinal and transverse mismatches because the longitudinal tune depression is more severe than the transverse one for elongated bunches. Of particular importance is the result that, due to the coupling between longitudinal and transverse motion, a longitudinal or transverse halo is observed for a mismatch less than 10% if the mismatch in the other plane is large. copyright 1998 The American Physical Society

  14. The influence of Massive Black Hole Binaries on the Morphology of Merger Remnants

    Science.gov (United States)

    Bortolas, E.; Gualandris, A.; Dotti, M.; Read, J. I.

    2018-03-01

    Massive black hole (MBH) binaries, formed as a result of galaxy mergers, are expected to harden by dynamical friction and three-body stellar scatterings, until emission of gravitational waves (GWs) leads to their final coalescence. According to recent simulations, MBH binaries can efficiently harden via stellar encounters only when the host geometry is triaxial, even if only modestly, as angular momentum diffusion allows an efficient repopulation of the binary loss cone. In this paper, we carry out a suite of N-body simulations of equal-mass galaxy collisions, varying the initial orbits and density profiles for the merging galaxies and running simulations both with and without central MBHs. We find that the presence of an MBH binary in the remnant makes the system nearly oblate, aligned with the galaxy merger plane, within a radius enclosing 100 MBH masses. We never find binary hosts to be prolate on any scale. The decaying MBHs slightly enhance the tangential anisotropy in the centre of the remnant due to angular momentum injection and the slingshot ejection of stars on nearly radial orbits. This latter effect results in about 1% of the remnant stars being expelled from the galactic nucleus. Finally, we do not find any strong connection between the remnant morphology and the binary hardening rate, which depends only on the inner density slope of the remnant galaxy. Our results suggest that MBH binaries are able to coalesce within a few Gyr, even if the binary is found to partially erase the merger-induced triaxiality from the remnant.

  15. Potential gains from hospital mergers in Denmark.

    Science.gov (United States)

    Kristensen, Troels; Bogetoft, Peter; Pedersen, Kjeld Moeller

    2010-12-01

    The Danish hospital sector faces a major rebuilding program to centralize activity in fewer and larger hospitals. We aim to conduct an efficiency analysis of hospitals and to estimate the potential cost savings from the planned hospital mergers. We use Data Envelopment Analysis (DEA) to estimate a cost frontier. Based on this analysis, we calculate an efficiency score for each hospital and estimate the potential gains from the proposed mergers by comparing individual efficiencies with the efficiency of the combined hospitals. Furthermore, we apply a decomposition algorithm to split merger gains into technical efficiency, size (scale) and harmony (mix) gains. The motivation for this decomposition is that some of the apparent merger gains may actually be available with less than a full-scale merger, e.g., by sharing best practices and reallocating certain resources and tasks. Our results suggest that many hospitals are technically inefficient, and the expected "best practice" hospitals are quite efficient. Also, some mergers do not seem to lower costs. This finding indicates that some merged hospitals become too large and therefore experience diseconomies of scale. Other mergers lead to considerable cost reductions; we find potential gains resulting from learning better practices and the exploitation of economies of scope. To ensure robustness, we conduct a sensitivity analysis using two alternative returns-to-scale assumptions and two alternative estimation approaches. We consistently find potential gains from improving the technical efficiency and the exploitation of economies of scope from mergers.

  16. Relics as Probes of Galaxy Cluster Mergers

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... http://www.ias.ac.in/article/fulltext/joaa/032/04/0505-0508. Keywords. Cosmology: large-scale structure of Universe; galaxies: clusters: general, intracluster medium. Abstract. Galaxy clusters grow by mergers with other clusters and galaxy groups. These mergers create shocks within the intracluster medium ...

  17. The NGC 454 system: anatomy of a mixed ongoing merger

    Science.gov (United States)

    Plana, H.; Rampazzo, R.; Mazzei, P.; Marino, A.; Amram, Ph.; Ribeiro, A. L. B.

    2017-12-01

    This paper focuses on NGC 454, a nearby interacting pair of galaxies (AM 0112-554, RR23), composed of an early-type (NGC 454 E) and a star-forming late-type companion (NGC 454 W). We aim at characterizing this wet merger candidate via a multi-λ analysis, from near-UV (NUV) to optical using Swift UV/Optical Telescope (UVOT), and mapping the H α intensity (I) distribution, velocity (Vr) and velocity dispersion (σ) fields with SAM+Fabry-Perot@SOAR observations. Luminosity profiles suggest that NGC 454 E is an S0. Distortions in its outskirts caused by the ongoing interaction are visible in both optical and NUV frames. In NGC 454 W, the NUV-UVOT images and the H α show a set of star-forming complexes connected by a faint tail. H α emission is detected along the line connecting NGC 454 E to the NGC 454 main H II complex. We investigate the (I-σ), (I-Vr) and (Vr-σ) diagnostic diagrams of the H II complexes, most of which can be interpreted in a framework of expanding bubbles. In the main H II complex, enclosed in the UV brightest region, the gas velocity dispersion is highly supersonic reaching 60 km s-1. However, H α emission profiles are mostly asymmetric indicating the presence of multiple components with an irregular kinematics. Observations point towards an advanced stage of the encounter. Our smoothed particle hydrodynamic simulations with chemo-photometric implementation suggest that this mixed pair can be understood in terms of a 1:1 gas/halo encounter giving rise to a merger in about 0.2 Gyr from the present stage.

  18. Mergers and integrated care: the Quebec experience

    Directory of Open Access Journals (Sweden)

    Louis Demers

    2013-02-01

    Full Text Available As a researcher, I have studied the efforts to increase the integration of health and social services in Quebec, as well as the mergers in the Quebec healthcare system. These mergers have often been presented as a necessary transition to break down the silos that compartmentalize the services dispensed by various organisations. A review of the studies about mergers and integrated care projects in the Quebec healthcare system, since its inception, show that mergers cannot facilitate integrated care unless they are desired and represent for all of the actors involved an appropriate way to deal with service organisation problems. Otherwise, mergers impede integrated care by creating increased bureaucratisation and standardisation and by triggering conflicts and mistrust among the staff of the merged organisations. It is then preferable to let local actors select the most appropriate organisational integration model for their specific context and offer them resources and incentives to cooperate.

  19. Mergers and integrated care: the Quebec experience.

    Science.gov (United States)

    Demers, Louis

    2013-01-01

    As a researcher, I have studied the efforts to increase the integration of health and social services in Quebec, as well as the mergers in the Quebec healthcare system. These mergers have often been presented as a necessary transition to break down the silos that compartmentalize the services dispensed by various organisations. A review of the studies about mergers and integrated care projects in the Quebec healthcare system, since its inception, show that mergers cannot facilitate integrated care unless they are desired and represent for all of the actors involved an appropriate way to deal with service organisation problems. Otherwise, mergers impede integrated care by creating increased bureaucratisation and standardisation and by triggering conflicts and mistrust among the staff of the merged organisations. It is then preferable to let local actors select the most appropriate organisational integration model for their specific context and offer them resources and incentives to cooperate.

  20. Impact of bank mergers on shareholders’ wealth

    Directory of Open Access Journals (Sweden)

    Odero Naor Juma

    2013-07-01

    Full Text Available Mergers and acquisitions (M&As perform a vital role in corporate finance in enabling firms achieve varied objectives and financial strategies. This study sought to comprehend the impacts that previous bank mergers have had on the shareholders’ wealth. The study location was in Kenya and it adopted the descriptive survey and correlation design in which the success of mergers was measured based on the objective oriented model using the annual accounts. The study computed the return on assets (ROA, return on equity (ROE and the efficiency ratio (EFF as indicators of shareholder value. The results of the commercial banks were analysed for a five-year period (2006-2010. The study reveals that mergers significantly influence shareholder value with banks that have undertaken mergers creating more value than those that have not. Such banks were ascertained to have posted better results than the overall sector.

  1. Risks of Mergers and Acquisitions Processes

    Directory of Open Access Journals (Sweden)

    Skitsko Volodymyr I.

    2017-06-01

    Full Text Available Despite structural changes both in the economies of individual countries and in the world at large, the size of the merger/acquisition market is not declining and is tending to grow further. However, uncertainty in the global environment increases the importance of proper analysis, assessment and risk management in merger/acquisition transactions. Using the relevant research and publications by various authors, we have built a general ranking of the significance of merger and acquisition risks according to phases of the indicated process, with comparison of individual risk ratings, based on the publications by authors from Central and Eastern Europe and other countries around the world. The ranking of risks and threats of mergers/acquisitions proposed in this work can be considered one of the most complete for today. Further research needs to focus on the analysis, evaluation, and modeling of merger/acquisition risks, which occupy the top of the ranking, presented by the article.

  2. Halo assembly bias and the tidal anisotropy of the local halo environment

    Science.gov (United States)

    Paranjape, Aseem; Hahn, Oliver; Sheth, Ravi K.

    2018-02-01

    We study the role of the local tidal environment in determining the assembly bias of dark matter haloes. Previous results suggest that the anisotropy of a halo's environment (i.e, whether it lies in a filament or in a more isotropic region) can play a significant role in determining the eventual mass and age of the halo. We statistically isolate this effect using correlations between the large-scale and small-scale environments of simulated haloes at z = 0 with masses between 1011.6 ≲ (m/h-1M⊙) ≲ 1014.9. We probe the large-scale environment using a novel halo-by-halo estimator of linear bias. For the small-scale environment, we identify a variable αR that captures the tidal anisotropy in a region of radius R = 4R200b around the halo and correlates strongly with halo bias at fixed mass. Segregating haloes by αR reveals two distinct populations. Haloes in highly isotropic local environments (αR ≲ 0.2) behave as expected from the simplest, spherically averaged analytical models of structure formation, showing a negative correlation between their concentration and large-scale bias at all masses. In contrast, haloes in anisotropic, filament-like environments (αR ≳ 0.5) tend to show a positive correlation between bias and concentration at any mass. Our multi-scale analysis cleanly demonstrates how the overall assembly bias trend across halo mass emerges as an average over these different halo populations, and provides valuable insights towards building analytical models that correctly incorporate assembly bias. We also discuss potential implications for the nature and detectability of galaxy assembly bias.

  3. On mini-halo encounters with stars

    Science.gov (United States)

    Green, Anne M.; Goodwin, Simon P.

    2007-03-01

    We study, analytically and numerically, the energy input into dark matter mini-haloes by interactions with stars. We find that the fractional energy input in simulations of Plummer spheres agrees well with the impulse approximation for small and large impact parameters, with a rapid transition between these two regimes. Using the impulse approximation, the fractional energy input at large impact parameters is fairly independent of the mass and density profiles of the mini-halo; however, low-mass mini-haloes experience a greater fractional energy input in close encounters. We formulate a fitting function which encodes these results and use it to estimate the disruption time-scales of mini-haloes, taking into account the stellar velocity dispersion and mass distribution. For mini-haloes with mass on typical orbits which pass through the disc, we find that the estimated disruption time-scales are independent of mini-halo mass, and are of the order of the age of the Milky Way. For more massive mini-haloes, the estimated disruption time-scales increase rapidly with increasing mass.

  4. Dark matter haloes: a multistream view

    Science.gov (United States)

    Ramachandra, Nesar S.; Shandarin, Sergei F.

    2017-09-01

    Mysterious dark matter constitutes about 85 per cent of all masses in the Universe. Clustering of dark matter plays a dominant role in the formation of all observed structures on scales from a fraction to a few hundreds of Mega-parsecs. Galaxies play a role of lights illuminating these structures so they can be observed. The observations in the last several decades have unveiled opulent geometry of these structures currently known as the cosmic web. Haloes are the highest concentrations of dark matter and host luminous galaxies. Currently the most accurate modelling of dark matter haloes is achieved in cosmological N-body simulations. Identifying the haloes from the distribution of particles in N-body simulations is one of the problems attracting both considerable interest and efforts. We propose a novel framework for detecting potential dark matter haloes using the field unique for dark matter-multistream field. The multistream field emerges at the non-linear stage of the growth of perturbations because the dark matter is collisionless. Counting the number of velocity streams in gravitational collapses supplements our knowledge of spatial clustering. We assume that the virialized haloes have convex boundaries. Closed and convex regions of the multistream field are hence isolated by imposing a positivity condition on all three eigenvalues of the Hessian estimated on the smoothed multistream field. In a single-scale analysis of high multistream field resolution and low softening length, the halo substructures with local multistream maxima are isolated as individual halo sites.

  5. Chandra's Find of Lonely Halo Raises Questions About Dark Matter

    Science.gov (United States)

    2004-10-01

    4555 DSS Optical Image of NGC 4555 Most large elliptical galaxies are found in groups and clusters of galaxies, and are likely the product of the merger of two spiral galaxies. In such an environment, the dark matter halos can be stripped away by gravitational tidal force and added to other galaxies or the group as a whole. Therefore, it is difficult to determine how much dark matter the original galaxies had, and how much they have lost to the group as a whole through interactions with their environment. The importance of the issue of the intrinsic amount of dark matter associated with an elliptical galaxy has recently increased owing to a report by an international team of astronomers led by Aaron Romanowsky of the University of Nottingham, United Kingdom. This team found little, if any evidence of dark matter in three relatively nearby elliptical galaxies. Two of these were in loose galaxy groups, and one was isolated. Their result, based on optical data from the 4.2 meter William Herschel Telescope on the Spanish island of La Palma, is in clear conflict with the X-ray data on NGC 4555. The optical technique used to search for dark matter in the nearby elliptical galaxies could not be applied to NGC 4555 because it is more than 3 times as far away from Earth. 2MASS Infrared Image of NGC 4555 2MASS Infrared Image of NGC 4555 Either the galaxies observed by Romanowsky and colleagues have lost their dark matter halos through earlier interactions with other galaxies, or their dark matter halos are much more extended, or they formed without dark matter halos. The first option is possible for the galaxies in groups, but very unlikely for the isolated galaxy. The second and third options are still open, but would require a modification - perhaps a major modification - of the cold dark matter theory of galaxy formation. "This is clearly a question which deserves further consideration," said O'Sullivan. "It seems likely that much more theoretical and observational work on

  6. High-velocity streams in the Milky Way halo with the SDSS and GSC-II kinematic survey

    Directory of Open Access Journals (Sweden)

    Spagna A.

    2012-02-01

    Full Text Available We explore the stellar halo of the Milky Way to search for fossil signatures of past mergers, consisting of streams of particles torn from their progenitors during the process of hierarchical merging. We examine a representative sample of about 2 700 halo subdwarfs in the solar neighborhood, selected from a new kinematic survey produced by means of spectrophotometric data from the Sloan Digital Sky Survey, and high-quality proper motions derived from multi-epoch positions using the Guide Star Catalog II. We find statistical evidence for discrete overdensities, likely possible accretion remnants. This methodology and the quality of the selected sample are an efficient means to discover new members of known streams and to identify new streams themselves, and set the basis for future studies.

  7. Efimov effect in 2-neutron halo nuclei

    Indian Academy of Sciences (India)

    4.0. 0. 100. 200. 300. 400. 500. 600. 700. 250 keV σσσσ el (b. ) 300 keV. Ei (keV). 350 keV. 250 keV. 300 keV. 350 keV. Figure 1. The peak structures in the scattering cross-sections for (right) one very heavy core and two valence neutrons and (left) three equal masses. have also noticed a clear dependence of the formation ...

  8. 7 CFR 1782.15 - Mergers and consolidations.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 12 2010-01-01 2010-01-01 false Mergers and consolidations. 1782.15 Section 1782.15... AGRICULTURE (CONTINUED) SERVICING OF WATER AND WASTE PROGRAMS § 1782.15 Mergers and consolidations. Mergers... transaction under consideration and the unique facts involved in each transaction. Mergers occur when two or...

  9. An assessment of bank merger success in Germany

    NARCIS (Netherlands)

    Koetter, Michael

    German banks have experienced a merger wave since the early 1990s. However, the success or bank mergers remains a continuous matter or debate. This paper suggests a taxonomy to evaluate post-merger performance on the basis of cost and profit efficiency (CE and PE). I identify successful mergers as

  10. The growth of galaxies and their gaseous haloes

    NARCIS (Netherlands)

    Voort, Frederieke van de

    2012-01-01

    Galaxies grow by accreting gas, which they need to form stars, from their surrounding haloes. These haloes, in turn, accrete gas from the diffuse intergalactic medium. Feedback from stars and black holes returns gas from the galaxy to the halo and can even expel it from the halo. This cycle of gas

  11. Analysis of International Mergers and Acquisitions in the Pharmaceutical Industry

    Directory of Open Access Journals (Sweden)

    Božo Matić

    2011-07-01

    Full Text Available There are numerous researches which analyze mergers and acquisitions, but most of them do not focus on a certain industry, but their sample considers companies from different industries. This paper focuses on mergers and acquisitions in the pharmaceutical industry. It is assumed that pharmaceutical companies with no experience in mergers and acquisitions achieve better results in relatively small and domestic mergers and acquisitions while pharmaceutical companies with greater experience in mergers and acquisitions are successful even in bigger and international mergers and acquisitions. Bigger mergers and acquisitions and international mergers and acquisitions are more risky for the companies so lack of experience in mergers and acquisitions additionally increases risks during the process of mergers and acquisitions. On average, such increase of the risk results in lower returns for stock owners of pharmaceutical companies.

  12. Cost effects of hospital mergers in Portugal.

    Science.gov (United States)

    Azevedo, Helda; Mateus, Céu

    2014-12-01

    The Portuguese hospital sector has been restructured by wide-ranging hospital mergers, following a conviction among policy makers that bigger hospitals lead to lower average costs. Since the effects of mergers have not been systematically evaluated, the purpose of this article is to contribute to this area of knowledge by assessing potential economies of scale to explore and compare these results with realized cost savings after mergers. Considering the period 2003-2009, we estimate the translog cost function to examine economies of scale in the years preceding restructuring. Additionally, we use the difference-in-differences approach to evaluate hospital centres (HC) that occurred between 2004 and 2007, comparing the years after and before mergers. Our findings suggest that economies of scale are present in the pre-merger configuration with an optimum hospital size of around 230 beds. However, the mergers between two or more hospitals led to statistically significant post-merger cost increases, of about 8 %. This result indicates that some HC become too large to explore economies of scale and suggests the difficulty of achieving efficiencies through combining operations and service specialization.

  13. Exact Relativistic Magnetized Haloes around Rotating Disks

    Directory of Open Access Journals (Sweden)

    Antonio C. Gutiérrez-Piñeres

    2015-01-01

    Full Text Available The study of the dynamics of magnetic fields in galaxies is one of important problems in formation and evolution of galaxies. In this paper, we present the exact relativistic treatment of a rotating disk surrounded by a magnetized material halo. The features of the halo and disk are described by the distributional energy-momentum tensor of a general fluid in canonical form. All the relevant quantities and the metric and electromagnetic potentials are exactly determined by an arbitrary harmonic function only. For instance, the generalized Kuzmin-disk potential is used. The particular class of solutions obtained is asymptotically flat and satisfies all the energy conditions. Moreover, the motion of a charged particle on the halo is described. As far as we know, this is the first relativistic model describing analytically the magnetized halo of a rotating disk.

  14. Wide-field kinematic structure of early-type galaxy halos

    Science.gov (United States)

    Arnold, Jacob Antony

    2013-12-01

    The stellar halos of nearby galaxies bare the signatures of the mass-assembly processes that have driven galaxy evolution over the last ˜10 Gyr. Finding and interpreting these relict clues in galaxies within and beyond the local group offers one of the most promising avenues for understanding how galaxies accumulate their stars over time. To tackle this problem we have performed a systematic study of the wide-field kinematic structure of nearby (Dspectroscopy out to several effective radii (˜3 R e). The 22 galaxies presented here span a range of environments (field, group, and cluster), intrinsic luminosities (-22.4 infrared Calcium II triplet. For each spectrum, we parameterize the line-of-sight velocity distribution (LOSVD) as a truncated Gauss-Hermite series convolved with an optimally weighted combination of stellar templates. These kinematic measurements (V, sigma, h3, and h4) are combined with literature values to construct spatially resolved maps of large-scale kinematic structure. A variety of kinematic behaviors are observed beyond ~1 Re, potentially reflecting the stochastic and chaotic assembly of stellar bulges and halos in early-type galaxies. Next, we describe a global analysis (out to 5 Re) of kinematics and metallicity in the nearest S0 galaxy, NGC 3115, along with implications for its assembly history. The data include high-quality wide-field imaging and multi-slit spectra of the field stars and globular clusters (GCs). Within two effective radii, the bulge (as traced by the stars and metal-rich GCs) is flattened and rotates rapidly. At larger radii, the rotation declines dramatically, while the characteristic GC metallicities also decrease with radius. We argue that this pattern is not naturally explained by a binary major merger, but instead by a two-phase assembly process where the inner regions have formed in an early violent, dissipative phase, followed by the protracted growth of the outer parts via minor mergers. To test this hypothesis

  15. Getting cold feet?: Why health care mergers are abandoned.

    Science.gov (United States)

    Roos, Anne-Fleur; Postma, Jeroen

    2016-01-01

    Despite the frequent occurrence and sizeable consequences of merger abandonment in other sectors, there is no thorough understanding of merger abandonment in health care. The purpose of this study is to improve the understanding of determinants of health care merger abandonment. On the basis of the literature on merger abandonment, we formulated a framework on potential determinants of health care merger abandonment. We then constructed a survey that was sent to 70% of all executives of Dutch health care organizations (response rate = 35%, n = 291). We provide descriptive overviews of open, multiple-response, and multiple-choice questions on merger abandonment and use chi-square tests and Fisher's exact tests to test whether abandoned and completed merger processes differ. About 62% of the respondents were involved in at least one merger process during the period of 2005-2012. Thirty-eight percent of these respondents reported that their last merger case ended prematurely (n = 53). The most frequently mentioned determinants of merger abandonment are changing insights on the desirability and feasibility during merger processes, incompatibilities between executives, and insufficient support for the merger from internal stakeholders. We did not find significant relationships between merger abandonment and executives' previous merger experience, degree of organizational diversification, health care sector, size differences, or other organizational differences. Our findings partially confirm results from previous studies, especially with regard to the importance of changing insights and incompatibilities between the involved executives in merger abandonment. We also find that pressure from internal stakeholders, particularly nonexecutive directors, and distrust, fear, and animosity play an important role in merger abandonment. To minimize the organizational and societal costs of abandoned mergers, we advise executives who engage in mergers to construct backup plans with

  16. Do municipal mergers improve fiscal outcomes?

    DEFF Research Database (Denmark)

    Hansen, Sune Welling; Houlberg, Kurt; Pedersen, Lene Holm

    2014-01-01

    relationship between municipal mergers and fiscal outcomes is analysed. Measured on the balance between revenues and expenses, liquid assets and debts, municipal mergers improve the fiscal outcomes of the municipalities in a five-year perspective, although the pre-reform effects tend to be negative....... For liquidity and debt, however, the improvement only entails re-establishing the levels prior to the reform. The testing ground is the recent mergers of Danish municipalities, which, it is argued, constitute a quasi-experiment. This forms the basis of a Difference-in-Difference design, allowing the alleviation...

  17. Beam halo studies in LEHIPA DTL

    Science.gov (United States)

    Roy, S.; Pande, R.; Rao, S. V. L. S.; Krishnagopal, S.; Singh, P.

    2015-11-01

    The Low Energy High Intensity Proton Accelerator (LEHIPA) project at Bhabha Atomic Research Centre (BARC) consists of a 20 MeV, 30 mA proton linac. The accelerator comprises of a 3 MeV Radio Frequency Quadrupole (RFQ) and a 20 MeV Drift Tube Linac (DTL). In such high intensity accelerators, beam halos are of concern as they not only cause an increase in emittance, but also lead to beam loss and radio activation. We have studied the effect of beam mismatch at the DTL input on halo formation and propagation. The particle core model is used to excite the three envelope eigen modes; the quadrupole mode, the fast mode and the slow mode by giving input beam mismatch. These modes get damped as the beam progresses through the DTL. The damping mechanism is clearly Landau damping and leads to increase in rms emittance of the beam. The evolution of these modes and the corresponding increase in beam emittance and maximum beam extent, as the beam propagates through the DTL, has been studied for different space charge tunes. The halo parameter based on the definition of Allen and Wangler has been calculated. It is seen that beam halos are very important for LEHIPA DTL, even at 20 MeV and leads to emittance and beam size increase and also to beam loss in some cases. The longitudinal halo is present even without mismatch and transverse halos arise in the presence of beam mismatch.

  18. MODIFIED GRAVITY SPINS UP GALACTIC HALOS

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jounghun [Astronomy Program, Department of Physics and Astronomy, FPRD, Seoul National University, Seoul 151-747 (Korea, Republic of); Zhao, Gong-Bo [National Astronomy Observatories, Chinese Academy of Science, Beijing 100012 (China); Li, Baojiu [Institute of Computational Cosmology, Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Koyama, Kazuya, E-mail: jounghun@astro.snu.ac.kr [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, PO1 3FX (United Kingdom)

    2013-01-20

    We investigate the effect of modified gravity on the specific angular momentum of galactic halos by analyzing the halo catalogs at z = 0 from high-resolution N-body simulations for a f(R) gravity model that meets the solar-system constraint. It is shown that the galactic halos in the f(R) gravity model tend to acquire significantly higher specific angular momentum than those in the standard {Lambda}CDM model. The largest difference in the specific angular momentum distribution between these two models occurs for the case of isolated galactic halos with mass less than 10{sup 11} h {sup -1} M {sub Sun }, which are likely least shielded by the chameleon screening mechanism. As the specific angular momentum of galactic halos is rather insensitive to other cosmological parameters, it can in principle be an independent discriminator of modified gravity. We speculate a possibility of using the relative abundance of low surface brightness galaxies (LSBGs) as a test of general relativity given that the formation of the LSBGs occurs in fast spinning dark halos.

  19. A 2-3 billion year old major merger paradigm for the Andromeda galaxy and its outskirts

    Science.gov (United States)

    Hammer, F.; Yang, Y. B.; Wang, J. L.; Ibata, R.; Flores, H.; Puech, M.

    2018-04-01

    Recent observations of our neighbouring galaxy M31 have revealed that its disc was shaped by widespread events. The evidence for this includes the high dispersion (V/σ ≤ 3) of stars older than 2 Gyr, and a global star formation episode, 2-4 Gyr ago. Using the modern hydrodynamical code, GIZMO, we have performed 300 high-resolution simulations to explore the extent to which these observed properties can be explained by a single merger. We find that the observed M31 disc resembles models having experienced a 4:1 merger, in which the nuclei coalesced 1.8-3 Gyr ago, and where the first passage took place 7-10 Gyr ago at a large pericentre distance (32 kpc). We also show that within a family of orbital parameters, the Giant Stream (GS) can be formed with various merger mass ratios, from 2:1 to 300:1. A recent major merger may be the only way to create the very unusual age-dispersion relation in the disc. It reproduces and explains the long-lived 10 kpc ring, the widespread and recent star formation event, the absence of a remnant of the GS progenitor, the apparent complexity of the 3D spatial distribution of the GS, the NE and G Clumps and their formation process, and the observed slope of the halo profile. These modelling successes lead us to propose that the bulk of the substructure in the M31 halo, as well as the complexity of the inner galaxy, may be attributable to a single major interaction with a galaxy that has now fully coalesced with Andromeda.

  20. Reduction and processing of astrophysical data by visualization and creation of merger trees from dark matter particle simulations

    International Nuclear Information System (INIS)

    Riser, T.

    2012-01-01

    State of the art dark matter particle simulations of galaxy clusters produce vast amounts of raw data that need to be interpreted and scientifically understood. In this thesis two cornerstones involved in this process are presented. First, a unique and robust algorithm is shown, which extracts a so called ''merger tree'' from dark matter particle data. It represents the development and history of every galaxy that lives within the gravitational potential of the dark matter halos formed by the simulated structure formation process, with a special focus on the merging of smaller halos into bigger ones through the course of time. Second, a modern approach is discussed that facilitates the massively parallel calculative power of state of the art graphics cards to greatly improve the image quality of real-time particle visualizations without the requirement of additional geometric data. (author)

  1. Using r-process enhanced galaxies to estimate the neutron star merger rate at high redshift

    Science.gov (United States)

    Roederer, Ian

    2018-01-01

    The rapid neutron-capture process, or r-process, is one of the fundamental ways that stars produce heavy elements. I describe a new approach that uses the existence of r-process enhanced galaxies, like the recently discovered ultra-faint dwarf galaxy Reticulum II, to derive a rate for neutron star mergers at high redshift. This method relies on three assertions. First, several lines of reasoning point to neutron star mergers as a rare yet prolific producer of r-process elements, and one merger event is capable of enriching most of the stars in a low-mass dwarf galaxy. Second, the Local Group is cosmologically representative of the halo mass function at the mass scales of low-luminosity dwarf galaxies, and the volume that their progenitors spanned at high redshifts can be estimated from simulations. Third, many of these dwarf galaxies are extremely old, and the metals found in their stars today date from the earliest times at high redshift. These galaxies occupy a quantifiable volume of the Universe, from which the frequency of r-process enhanced galaxies can be estimated. This frequency may be interpreted as lower limit to the neutron star merger rate at a redshift (z ~ 5-10) that is much higher than is accessible to gravitational wave observatories. I will present a proof of concept demonstration using medium-resolution multi-object spectroscopy from the Michigan/Magellan Fiber System (M2FS) to recover the known r-process galaxy Reticulum II, and I will discuss future plans to apply this method to other Local Group dwarf galaxies.

  2. Mergers and acquisitions: a most strategic decision.

    Science.gov (United States)

    Laine, Mike; Tyler, David

    2007-11-01

    Five steps are basic to successfully concluding (or deciding not to conclude) a merger or acquisition: Identify targets. Begin with the end in mind. Choose a transaction team. Perform due diligence. Commit to the deal--or to no deal.

  3. DATA MINING THE GALAXY ZOO MERGERS

    Data.gov (United States)

    National Aeronautics and Space Administration — DATA MINING THE GALAXY ZOO MERGERS STEVEN BAEHR, ARUN VEDACHALAM, KIRK BORNE, AND DANIEL SPONSELLER Abstract. Collisions between pairs of galaxies usually end in the...

  4. French bank mergers and acquisitions performance

    Directory of Open Access Journals (Sweden)

    Houda Ben Said

    2017-11-01

    Full Text Available In this paper, we empirically investigate the impact of mergers and acquisitions on French bank performance. Performance is measured by potential gains in efficiency and value creation. We first analyzed efficiency using the data envelopment analysis (DEA under input oriented with variable returns to scale to obtain the efficiency scores. Second, we analyzed the impact on French bank value creation following mergers-acquisitions operations of a set of control variables (model 1 and explicative variables measuring strategic similarities between bidders and targets (model 2. The sample studied is composed of French bank mergers-acquisitions happening between 1996 and 2006 and implying one of the 14 greatest French banking groups. Empirical result showed that mergers and acquisitions have been traduced by an improvement in the overall efficiency by 17.82% and a shareholder value reduction by 5.14%

  5. Avoiding potential pitfalls in mergers and acquisitions.

    Science.gov (United States)

    Glanstein, J; Sallis, M

    1992-01-01

    The single most important factor in determining the success of mergers and acquisitions, write Joy Glanstein, Ph.D., and Mary Sallis, is the human equation and in particular benefit plans--the focus of this article.

  6. Multiemployer Pension Plan Terminations, Mergers, and Insolvencies

    Data.gov (United States)

    Pension Benefit Guaranty Corporation — A listing of multiemployer pension plan terminations, mergers, and insolvencies reported to the PBGC for the current fiscal year. This data set will be updated...

  7. Simulating Halos with the Caterpillar Project

    Science.gov (United States)

    Kohler, Susanna

    2016-04-01

    The Caterpillar Project is a beautiful series of high-resolution cosmological simulations. The goal of this project is to examine the evolution of dark-matter halos like the Milky Ways, to learn about how galaxies like ours formed. This immense computational project is still in progress, but the Caterpillar team is already providing a look at some of its first results.Lessons from Dark-Matter HalosWhy simulate the dark-matter halos of galaxies? Observationally, the formation history of our galaxy is encoded in galactic fossil record clues, like the tidal debris from disrupted satellite galaxies in the outer reaches of our galaxy, or chemical abundance patterns throughout our galactic disk and stellar halo.But to interpret this information in a way that lets us learn about our galaxys history, we need to first test galaxy formation and evolution scenarios via cosmological simulations. Then we can compare the end result of these simulations to what we observe today.This figure illustrates the difference that mass resolution makes. In the left panel, the mass resolution is 1.5*10^7 solar masses per particle. In the right panel, the mass resolution is 3*10^4 solar masses per particle [Griffen et al. 2016]A Computational ChallengeDue to how computationally expensive such simulations are, previous N-body simulations of the growth of Milky-Way-like halos have consisted of only one or a few halos each. But in order to establish a statistical understanding of how galaxy halos form and find out whether the Milky Ways halo is typical or unusual! it is necessary to simulate a larger number of halos.In addition, in order to accurately follow the formation and evolution of substructure within the dark-matter halos, these simulations must be able to resolve the smallest dwarf galaxies, which are around a million solar masses. This requires an extremely high mass resolution, which adds to the computational expense of the simulation.First OutcomesThese are the challenges faced by

  8. Managing Employees’ Adaptation in Mergers: Theoretical Issues

    Directory of Open Access Journals (Sweden)

    Stravinskienė Inga

    2017-06-01

    Full Text Available On the basis of scientific literature analysis, the article focuses on the conceptual framework of adaptation of employees and management of this adaptation in the merged organisations. The article reasons the aspect of change and transition in the post-merger context. The author discusses psychological and behavioural responses of organisation staff towards the post-merger and introduces transition phases of employees. There are also highlighted specific features of staff adaptation management in the merged organisations.

  9. SMBH accretion and mergers: removing the symmetries

    International Nuclear Information System (INIS)

    King, Andrew; Nixon, Chris

    2013-01-01

    We review recent progress in studying accretion flows on to supermassive black holes (SMBH). Much of this removes earlier assumptions of symmetry and regularity, such as aligned and prograde disc rotation. This allows a much richer variety of effects, often because cancellation of angular momentum allows rapid infall. Potential applications include lower SMBH spins allowing faster mass growth and suppressing gravitational-wave reaction recoil in mergers, gas-assisted SMBH mergers, and near-dynamical accretion in galaxy centres. (paper)

  10. TAX ASPECTS REGARDING THE MERGER AND DIVISION

    Directory of Open Access Journals (Sweden)

    BRAGĂ FILOFTEIA VIORICA

    2014-05-01

    Full Text Available In this paper, we want to present the tax issues that influencing the merger and division starting from the economic context characterized by a lack of liquidity, business reorganization to streamline the business and from the advantages and disadvantages of this operation achievement. The documentation was performed by consulting the Tax Code, the Methodological Norms regarding the accounting operations of merger, division, liquidation and professional literature.

  11. Double neutron stars: merger rates revisited

    Science.gov (United States)

    Chruslinska, Martyna; Belczynski, Krzysztof; Klencki, Jakub; Benacquista, Matthew

    2018-03-01

    We revisit double neutron star (DNS) formation in the classical binary evolution scenario in light of the recent Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo DNS detection (GW170817). The observationally estimated Galactic DNS merger rate of R_MW = 21^{+28}_{-14} Myr-1, based on three Galactic DNS systems, fully supports our standard input physics model with RMW = 24 Myr-1. This estimate for the Galaxy translates in a non-trivial way (due to cosmological evolution of progenitor stars in chemically evolving Universe) into a local (z ≈ 0) DNS merger rate density of Rlocal = 48 Gpc-3 yr-1, which is not consistent with the current LIGO/Virgo DNS merger rate estimate (1540^{+3200}_{-1220} Gpc-3 yr-1). Within our study of the parameter space, we find solutions that allow for DNS merger rates as high as R_local ≈ 600^{+600}_{-300} Gpc-3 yr-1 which are thus consistent with the LIGO/Virgo estimate. However, our corresponding BH-BH merger rates for the models with high DNS merger rates exceed the current LIGO/Virgo estimate of local BH-BH merger rate (12-213 Gpc-3 yr-1). Apart from being particularly sensitive to the common envelope treatment, DNS merger rates are rather robust against variations of several of the key factors probed in our study (e.g. mass transfer, angular momentum loss, and natal kicks). This might suggest that either common envelope development/survival works differently for DNS (˜10-20 M⊙ stars) than for BH-BH (˜40-100 M⊙ stars) progenitors, or high black hole (BH) natal kicks are needed to meet observational constraints for both types of binaries. Our conclusion is based on a limited number of (21) evolutionary models and is valid within this particular DNS and BH-BH isolated binary formation scenario.

  12. Black hole mergers in the universe

    OpenAIRE

    Zwart, Simon Portegies; McMillan, Stephen

    1999-01-01

    Mergers of black-hole binaries are expected to release large amounts of energy in the form of gravitational radiation. However, binary evolution models predict merger rates too low to be of observational interest. In this paper we explore the possibility that black holes become members of close binaries via dynamical interactions with other stars in dense stellar systems. In star clusters, black holes become the most massive objects within a few tens of millions of years; dynamical relaxation...

  13. What Drive the Damage to Post-Merger Operating Performance?

    Directory of Open Access Journals (Sweden)

    Soegiharto Soegiharto

    2010-05-01

    Full Text Available This study examines whether bidders’ post-merger operat-ing performance are affected by their CEO behavior, premiumspaid to the target firms, the period of mergers, the method ofpayment, the industry of merged firms, capital liquidity, andtheir pre-merger operating performance. Testing the U.S. suc-cessful merger and acquisition data for the period of 1990s, thisstudy finds that in-wave mergers, intra-industry mergers, thepayment of lower premiums, and better pre-merger operatingperformance drive the bidders to produce better post-mergeroperating performance. Three measures of CEO behavior—themain predictor scrutinezed in this study—are proposed andexamined, and the results demonstrate that the effects of thesemeasures on post-merger operating performance are mixed,suggesting that each of the behavioral measures designed in thisstudy may capture CEO behavior in different ways. Keywords: capital liquidity; CEO overconfidence; merger waves, method of pay-ment operating performance

  14. Revealing the Cosmic Web-dependent Halo Bias

    Science.gov (United States)

    Yang, Xiaohu; Zhang, Youcai; Lu, Tianhuan; Wang, Huiyuan; Shi, Feng; Tweed, Dylan; Li, Shijie; Luo, Wentao; Lu, Yi; Yang, Lei

    2017-10-01

    Halo bias is the one of the key ingredients of the halo models. It was shown at a given redshift to be only dependent, to the first order, on the halo mass. In this study, four types of cosmic web environments—clusters, filaments, sheets, and voids—are defined within a state-of-the-art high-resolution N-body simulation. Within these environments, we use both halo-dark matter cross correlation and halo-halo autocorrelation functions to probe the clustering properties of halos. The nature of the halo bias differs strongly between the four different cosmic web environments described here. With respect to the overall population, halos in clusters have significantly lower biases in the {10}11.0˜ {10}13.5 {h}-1 {M}⊙ mass range. In other environments, however, halos show extremely enhanced biases up to a factor 10 in voids for halos of mass ˜ {10}12.0 {h}-1 {M}⊙ . Such a strong cosmic web environment dependence in the halo bias may play an important role in future cosmological and galaxy formation studies. Within this cosmic web framework, the age dependency of halo bias is found to be only significant in clusters and filaments for relatively small halos ≲ {10}12.5 {h}-1 {M}⊙ .

  15. Halo Intrinsic Alignment: Dependence on Mass, Formation Time, and Environment

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Qianli; Kang, Xi; Wang, Peng; Luo, Yu [Purple Mountain Observatory, the Partner Group of MPI für Astronomie, 2 West Beijing Road, Nanjing 210008 (China); Yang, Xiaohu; Jing, Yipeng [Center for Astronomy and Astrophysics, Shanghai Jiao Tong University, Shanghai 200240 (China); Wang, Huiyuan [Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026 (China); Mo, Houjun, E-mail: kangxi@pmo.ac.cn [Astronomy Department and Center for Astrophysics, Tsinghua University, Beijing 10084 (China)

    2017-10-10

    In this paper we use high-resolution cosmological simulations to study halo intrinsic alignment and its dependence on mass, formation time, and large-scale environment. In agreement with previous studies using N -body simulations, it is found that massive halos have stronger alignment. For the first time, we find that for a given halo mass older halos have stronger alignment and halos in cluster regions also have stronger alignment than those in filaments. To model these dependencies, we extend the linear alignment model with inclusion of halo bias and find that the halo alignment with its mass and formation time dependence can be explained by halo bias. However, the model cannot account for the environment dependence, as it is found that halo bias is lower in clusters and higher in filaments. Our results suggest that halo bias and environment are independent factors in determining halo alignment. We also study the halo alignment correlation function and find that halos are strongly clustered along their major axes and less clustered along the minor axes. The correlated halo alignment can extend to scales as large as 100 h {sup −1} Mpc, where its feature is mainly driven by the baryon acoustic oscillation effect.

  16. Self-consistent beam halo studies ampersand halo diagnostic development in a continuous linear focusing channel

    International Nuclear Information System (INIS)

    Jameson, R.A.

    1994-01-01

    Beam halos are formed via self-consistent motion of the beam particles. Interactions of single particles with time-varying density distributions of other particles are a major source of halo. Aspects of these interactions are studied for an initially equilibrium distribution in a radial, linear, continuous focusing system. When there is a mismatch, it is shown that in the self-consistent system, there is a threshold in space-charge and mismatch, above which a halo is formed that extends to ∼1.5 times the initial maximum mismatch radius. Tools are sought for characterizing the halo dynamics. Testing the particles against the width of the mismatch driving resonance is useful for finding a conservative estimate of the threshold. The exit, entering and transition times, and the time evolution of the halo, are also explored using this technique. Extension to higher dimensions is briefly discussed

  17. The Magellanic Analog Dwarf Companions and Stellar Halos (MADCASH) Survey: Near-Field Cosmology with Resolved Stellar Populations Around Local Volume LMC Stellar-Mass Galaxies

    Science.gov (United States)

    Carlin, Jeffrey L.; Sand, David J.; Willman, Beth; Brodie, Jean P.; Crnojevic, Denija; Peter, Annika; Price, Paul A.; Romanowsky, Aaron J.; Spekkens, Kristine; Strader, Jay

    2017-01-01

    We discuss the first results of our observational program to comprehensively map nearly the entire virial volumes of roughly LMC stellar mass galaxies at distances of ~2-4 Mpc. The MADCASH (Magellanic Analog Dwarf Companions And Stellar Halos) survey will deliver the first census of the dwarf satellite populations and stellar halo properties within LMC-like environments in the Local Volume. These will inform our understanding of the recent DES discoveries of dwarf satellites tentatively affiliated with the LMC/SMC system. We will detail our discovery of the faintest known dwarf galaxy satellite of an LMC stellar-mass host beyond the Local Group, based on deep Subaru+HyperSuprimeCam imaging reaching ~2 magnitudes below its TRGB. We will summarize the survey results and status to date, highlighting some challenges encountered and lessons learned as we process the data for this program through a prototype LSST pipeline. Our program will examine whether LMC stellar mass dwarfs have extended stellar halos, allowing us to assess the relative contributions of in-situ stars vs. merger debris to their stellar populations and halo density profiles. We outline the constraints on galaxy formation models that will be provided by our observations of low-mass galaxy halos and their satellites.

  18. Smooth halos in the cosmic web

    International Nuclear Information System (INIS)

    Gaite, José

    2015-01-01

    Dark matter halos can be defined as smooth distributions of dark matter placed in a non-smooth cosmic web structure. This definition of halos demands a precise definition of smoothness and a characterization of the manner in which the transition from smooth halos to the cosmic web takes place. We introduce entropic measures of smoothness, related to measures of inequality previously used in economy and with the advantage of being connected with standard methods of multifractal analysis already used for characterizing the cosmic web structure in cold dark matter N-body simulations. These entropic measures provide us with a quantitative description of the transition from the small scales portrayed as a distribution of halos to the larger scales portrayed as a cosmic web and, therefore, allow us to assign definite sizes to halos. However, these ''smoothness sizes'' have no direct relation to the virial radii. Finally, we discuss the influence of N-body discreteness parameters on smoothness

  19. The EAGLE simulations of galaxy formation: Public release of halo and galaxy catalogues

    Science.gov (United States)

    McAlpine, S.; Helly, J. C.; Schaller, M.; Trayford, J. W.; Qu, Y.; Furlong, M.; Bower, R. G.; Crain, R. A.; Schaye, J.; Theuns, T.; Dalla Vecchia, C.; Frenk, C. S.; McCarthy, I. G.; Jenkins, A.; Rosas-Guevara, Y.; White, S. D. M.; Baes, M.; Camps, P.; Lemson, G.

    2016-04-01

    We present the public data release of halo and galaxy catalogues extracted from the EAGLE suite of cosmological hydrodynamical simulations of galaxy formation. These simulations were performed with an enhanced version of the GADGET code that includes a modified hydrodynamics solver, time-step limiter and subgrid treatments of baryonic physics, such as stellar mass loss, element-by-element radiative cooling, star formation and feedback from star formation and black hole accretion. The simulation suite includes runs performed in volumes ranging from 25 to 100 comoving megaparsecs per side, with numerical resolution chosen to marginally resolve the Jeans mass of the gas at the star formation threshold. The free parameters of the subgrid models for feedback are calibrated to the redshift z = 0 galaxy stellar mass function, galaxy sizes and black hole mass-stellar mass relation. The simulations have been shown to match a wide range of observations for present-day and higher-redshift galaxies. The raw particle data have been used to link galaxies across redshifts by creating merger trees. The indexing of the tree produces a simple way to connect a galaxy at one redshift to its progenitors at higher redshift and to identify its descendants at lower redshift. In this paper we present a relational database which we are making available for general use. A large number of properties of haloes and galaxies and their merger trees are stored in the database, including stellar masses, star formation rates, metallicities, photometric measurements and mock gri images. Complex queries can be created to explore the evolution of more than 105 galaxies, examples of which are provided in the Appendix. The relatively good and broad agreement of the simulations with a wide range of observational datasets makes the database an ideal resource for the analysis of model galaxies through time, and for connecting and interpreting observational datasets.

  20. Change commitment in low-status merger partners: The role of information processing, relative ingroup prototypicality, and merger patterns.

    Science.gov (United States)

    Rosa, Miriam; Kavanagh, Eithne; Kounov, Pavel; Jarosz, Sywlia; Waldzus, Sven; Collins, Elizabeth C; Giessner, Steffen

    2017-09-01

    Merger announcements cause stress among employees, often leading to low change commitment, especially among employees from the lower-status merger partner. Such stress influences how deeply employees process merger-relevant information. Previous research examined how merger patterns that preserve versus change status differences impact merger support, but did not address how employees' information processing may influence this relationship. The current research addresses this gap through a scenario experiment, focusing on the low-status merger partner. The interplay between merger patterns and information processing was examined regarding employees' prototypicality claims in relation to merger support. Results suggest that an integration-equality merger pattern increases change commitment via prototypicality claims in the new organization, conditional to employees' systematic information processing. © 2017 The British Psychological Society.

  1. When Mergers Fail: A Case Study on the Critical Role of External Stakeholders in Merger Initiatives

    Science.gov (United States)

    Stensaker, Bjørn; Persson, Mats; Pinheiro, Rómulo

    2016-01-01

    One can, in principle, identify numerous arguments for mergers in higher education (HE), including efficiency, diversity, quality, and regional needs. This diversity can be explained by the growing societal interest in the sector, not least concerning the contributions from HE to society at large. However, research on merger processes has tended…

  2. The challenge of merging : Merger patterns, premerger status, and merger support

    NARCIS (Netherlands)

    Giessner, [No Value; Täuber, Susanne; Viki, GT; Otten, S; Terry, DJ; Giessner, S.R

    Employees of merging organizations often show resistance to the merger. The employees' support depends on the companies' premerger status and on the merger pattern. Based on an inter-group perspective, three studies were conducted to investigate the influence of premerger status (high, low) and

  3. Binary neutron star merger simulations

    Energy Technology Data Exchange (ETDEWEB)

    Bruegmann, Bernd [Jena Univ. (Germany)

    2016-11-01

    Our research focuses on the numerical tools necessary to solve Einstein's equations. In recent years we have been particularly interested in spacetimes consisting of two neutron stars in the final stages of their evolution. Because of the emission of gravitational radiation, the objects are driven together to merge; the emitted gravitational wave signal is visualized. This emitted gravitational radiation carries energy and momentum away from the system and contains information about the system. Late last year the Laser Interferometer Gravitational-wave Observatory (LIGO) began searches for these gravitational wave signals at a sensitivity at which detections are expected. Although such systems can radiate a significant amount of their total mass-energy in gravitational waves, the gravitational wave signals one expects to receive on Earth are not strong, since sources of gravitational waves are often many millions of light years away. Therefore one needs accurate templates for the radiation one expects from such systems in order to be able to extract them out of the detector's noise. Although analytical models exist for compact binary systems when the constituents are well separated, we need numerical simulation to investigate the last orbits before merger to obtain accurate templates and validate analytical approximations. Due to the strong nonlinearity of the equations and the large separation of length scales, these simulations are computationally demanding and need to be run on large supercomputers. When matter is present the computational cost as compared to pure black hole (vacuum) simulations increases even more due to the additional matter fields. But also more interesting astrophysical phenomena can happen. In fact, there is the possibility for a strong electromagnetic signal from the merger (e.g., a short gamma-ray burst or lower-energy electromagnetic signatures from the ejecta) and significant neutrino emission. Additionally, we can expect that

  4. Chandra Observations of Galaxy Zoo Mergers: Frequency of Binary Active Nuclei in Massive Mergers

    Science.gov (United States)

    Teng, Stacy H.; Schawinski, Kevin; Urry, C. Megan; Darg, Dan W.; Kaviraj, Sugata; Oh, Kyuseok; Bonning, Erin W.; Cardamone, Carolin N.; Keel, William C.; Lintott, Chris J.; hide

    2012-01-01

    We present the results from a Chandra pilot study of 12 massive galaxy mergers selected from Galaxy Zoo. The sample includes major mergers down to a host galaxy mass of 1011 M that already have optical AGN signatures in at least one of the progenitors. We find that the coincidences of optically selected active nuclei with mildly obscured (N(sub H) approx merger is found to have confirmed binary X-ray nuclei, though the X-ray emission from its southern nucleus could be due solely to star formation. Thus, the occurrences of binary AGN in these mergers are rare (0-8%), unless most merger-induced active nuclei are very heavily obscured or Compton thick.

  5. Mapping substructures in dark matter haloes

    Science.gov (United States)

    Knebe, Alexander; Gill, Stuart P. D.; Kawata, Daisuke; Gibson, Brad K.

    2005-02-01

    We present a detailed study of the real and integrals-of-motion space distributions of a disrupting satellite obtained from a fully self-consistent high-resolution cosmological simulation of a galaxy cluster. The satellite has been re-simulated using various analytical halo potentials, and we find that its debris appears as a coherent structure in integrals-of-motion space in all models (`live' and analytical potential), although the distribution is significantly smeared for the live host halo. The primary mechanism for the dispersion is the mass growth of the host. However, when quantitatively comparing the effects of `live' and time-varying host potentials, we conclude that not all of the dispersion can be accounted for by the steady growth of the mass of the host. We ascribe the remaining discrepancies to additional effects in the `live' halo such as non-sphericity of the host and interactions with other satellites which have not been modelled analytically.

  6. Beam halo in high-intensity beams

    International Nuclear Information System (INIS)

    Wangler, T.P.

    1993-01-01

    In space-charge dominated beams the nonlinear space-charge forces produce a filamentation pattern, which in projection to the 2-D phase spaces results in a 2-component beam consisting of an inner core and a diffuse outer halo. The beam-halo is of concern for a next generation of cw, high-power proton linacs that could be applied to intense neutron generators for nuclear materials processing. The author describes what has been learned about beam halo and the evolution of space-charge dominated beams using numerical simulations of initial laminar beams in uniform linear focusing channels. Initial results are presented from a study of beam entropy for an intense space-charge dominated beam

  7. Stability of BEC galactic dark matter halos

    Energy Technology Data Exchange (ETDEWEB)

    Guzmán, F.S.; Lora-Clavijo, F.D.; González-Avilés, J.J.; Rivera-Paleo, F.J., E-mail: guzman@ifm.umich.mx, E-mail: fadulora@ifm.umich.mx, E-mail: javiles@ifm.umich.mx, E-mail: friverap@ifm.umich.mx [Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio C-3, Cd. Universitaria, 58040 Morelia, Michoacán (Mexico)

    2013-09-01

    In this paper we show that spherically symmetric BEC dark matter halos, with the sin r/r density profile, that accurately fit galactic rotation curves and represent a potential solution to the cusp-core problem are unstable. We do this by introducing back the density profiles into the fully time-dependent Gross-Pitaevskii-Poisson system of equations. Using numerical methods to track the evolution of the system, we found that these galactic halos lose mass at an approximate rate of half of its mass in a time scale of dozens of Myr. We consider this time scale is enough as to consider these halos are unstable and unlikely to be formed. We provide some arguments to show that this behavior is general and discuss some other drawbacks of the model that restrict its viability.

  8. Risk Management in Mergers and Acquisitions

    Directory of Open Access Journals (Sweden)

    Dmitry O. Verdiev

    2015-01-01

    Full Text Available M&A statistics show that less than a third of newly merged companies has realized their planned synergistic effects and increased shareholder value. According to the author, such disgusting situation is due to improper planning and failure of corporate management to understand the importance of risk management in M&A. Lack of practice in identification, evaluation, mitigation and regular monitoring of risks leads to the situation when many companies merge despite the fact that the merger bears substantial risks. Corporate management fails to include risk mitigation expenses in merger costs. In many cases, risk mitigation expenses may be so substantive that the merger loses its attractiveness. Only few companies implement risk management methodology while planning M&A activity. This methodology may anticipate and minimize the consequences of various risk factors that negatively influence integration process. The article suggests an implementation of risk management best practice. This risk management best practice may act as an effective tool of successful realization of synergistic effects in M&A and may be helpful in increasing shareholder value in post-merger period. Risk management is conducted throughout the stages of merger and includes identification, analysis, assessment, management and monitoring of risks. Implementation of risk management at early stages of merger planning significantly decreases uncertainty in relation to achievement of financial and operational goals of newly merged company. The article provides with typical M&A risk matrix that may be adapted for specific M&A project. Risk matrix includes a register of risks sorted by stages of M&A deal, quality assessment of their probability, influence and impact on merger as well as risk mitigation methods.

  9. Radioactively powered emission from black hole-neutron star mergers

    International Nuclear Information System (INIS)

    Tanaka, Masaomi; Wanajo, Shinya; Hotokezaka, Kenta; Kyutoku, Koutarou; Kiuchi, Kenta; Sekiguchi, Yuichiro; Shibata, Masaru

    2014-01-01

    Detection of the electromagnetic counterparts of gravitational wave (GW) sources is important to unveil the nature of compact binary coalescences. We perform three-dimensional, time-dependent, multi-frequency radiative transfer simulations for radioactively powered emission from the ejecta of black hole (BH)-neutron star (NS) mergers. Depending on the BH to NS mass ratio, spin of the BH, and equations of state of dense matter, BH-NS mergers can eject more material than NS-NS mergers. In such cases, radioactively powered emission from the BH-NS merger ejecta can be more luminous than that from NS-NS mergers. We show that, in spite of the expected larger distances to BH-NS merger events, the observed brightness of BH-NS mergers can be comparable to or even higher than that of NS-NS mergers. We find that, when the tidally disrupted BH-NS merger ejecta are confined to a small solid angle, the emission from BH-NS merger ejecta tends to be bluer than that from NS-NS merger ejecta for a given total luminosity. Thanks to this property, we might be able to distinguish BH-NS merger events from NS-NS merger events by multi-band observations of the radioactively powered emission. In addition to the GW observations, such electromagnetic observations can potentially provide independent information on the progenitors of GW sources and the nature of compact binary coalescences.

  10. Galaxy halo occupation at high redshift

    Science.gov (United States)

    Bullock, James S.; Wechsler, Risa H.; Somerville, Rachel S.

    2002-01-01

    We discuss how current and future data on the clustering and number density of z~3 Lyman-break galaxies (LBGs) can be used to constrain their relationship to dark matter haloes. We explore a three-parameter model in which the number of LBGs per dark halo scales like a power law in the halo mass: N(M)=(M/M1)S for M>Mmin. Here, Mmin is the minimum mass halo that can host an LBG, M1 is a normalization parameter, associated with the mass above which haloes host more than one observed LBG, and S determines the strength of the mass-dependence. We show how these three parameters are constrained by three observable properties of LBGs: the number density, the large-scale bias and the fraction of objects in close pairs. Given these three quantities, the three unknown model parameters may be estimated analytically, allowing a full exploration of parameter space. As an example, we assume a ΛCDM cosmology and consider the observed properties of a recent sample of spectroscopically confirmed LBGs. We find that the favoured range for our model parameters is Mmin~=(0.4-8)×1010h- 1Msolar, M1~=(6-10)×1012h- 1Msolar, and 0.9acceptable if the allowed range of bg is permitted to span all recent observational estimates. We also discuss how the observed clustering of LBGs as a function of luminosity can be used to constrain halo occupation, although because of current observational uncertainties we are unable to reach any strong conclusions. Our methods and results can be used to constrain more realistic models that aim to derive the occupation function N(M) from first principles, and offer insight into how basic physical properties affect the observed properties of LBGs.

  11. Two Stellar Components in the Halo of the Milky Way

    National Research Council Canada - National Science Library

    Carollo, Daniela; Beers, Timothy C; Lee, Young-Sun; Chiba, Masashi; Norris, John E; Wilhelm, Ronald; Sivarani, Thirupathi; Marsteller, Brian; Munn, Jeffrey A; Bailer-Jones, Coryn A

    2007-01-01

    ... of galaxy formation and evolution. Although the halo was once considered a single component, evidence for its dichotomy has slowly emerged in recent years from inspection of small samples of halo objects...

  12. A double potential model for neutron halo nuclei

    OpenAIRE

    Abbas, Afsar

    2003-01-01

    It is shown here that loosely bound halo structure of neutron rich nuclei and the ground state spin of single neutron halo nuclei are correlated and are consistently explained if one assumes a double potential shell model for these nuclei.

  13. Spin Complicates Eccentric BH-NS Mergers

    Science.gov (United States)

    Kohler, Susanna

    2015-08-01

    When a neutron star (NS) has a glancing encounter with a black hole (BH), its spin has a significant effect on the outcome, according to new simulations run by William East of Stanford University and his collaborators. Spotting an Eccentric Merger. In a traditional BH-NS merger, the two objects orbit each other quasi-circularly as they spiral in. But there's another kind of merger that's possible in high-density environments like galactic nuclei or globular clusters: a dynamical capture merger, in which a NS and BH pass each other just close enough that the gravity of the black hole "catches" the NS, leading the two objects to merge with very eccentric orbits. During an eccentric merger, the NS can be torn apart -- at which point some fraction of the tidally-disrupted material will escape the system, while some fraction instead accretes back onto the BH. Knowing these fractions is important for being able to model the expected electromagnetic signatures for the merger: the unbound material can power transients like kilonovae, whereas the accreting material may be the cause of short gamma-ray bursts. The amount of material available for events like these would change their observable strengths. Testing the Effects of Spin. To see whether NS spin has an impact on the behavior of the merger, East and collaborators use a general-relativistic hydrodynamic code to simulate the glancing encounter of a BH and a NS with dimensionless spin between a=0 (non-spinning) and a=0.756 (rotation period of 1 ms). They also vary the separation of the first encounter. The group finds that changing the NS's spin can change a number of outcomes of the merger. To start with, it can affect whether the NS is captured by the BH, or if the encounter is glancing and then both objects carry on their merry way. And if the NS is trapped by the BH and torn apart, then the higher the NS's spin, the more matter outside of the BH ends up unbound, instead of getting trapped into an accretion disk

  14. Quadratic genetic modifications: a streamlined route to cosmological simulations with controlled merger history

    Science.gov (United States)

    Rey, Martin P.; Pontzen, Andrew

    2018-02-01

    Recent work has studied the interplay between a galaxy's history and its observable properties using `genetically modified' cosmological zoom simulations. The approach systematically generates alternative histories for a halo, while keeping its cosmological environment fixed. Applications to date altered linear properties of the initial conditions, such as the mean overdensity of specified regions; we extend the formulation to include quadratic features, such as local variance, that determines the overall importance of smooth accretion relative to mergers in a galaxy's history. We introduce an efficient algorithm for this new class of modification and demonstrate its ability to control the variance of a region in a one-dimensional toy model. Outcomes of this work are twofold: (i) a clarification of the formulation of genetic modifications and (ii) a proof of concept for quadratic modifications leading the way to a forthcoming implementation in cosmological simulations.

  15. No evidence for large-scale outflows in the extended ionized halo of ULIRG Mrk273

    Science.gov (United States)

    Spence, R. A. W.; Zaurín, J. Rodríguez; Tadhunter, C. N.; Rose, M.; Cabrera-Lavers, A.; Spoon, H.; Muñoz-Tuñón, C.

    2016-06-01

    We present deep new Gran Telescopio Canarias (GTC) narrow-band images and William Herschel Telescope (WHT) long-slit spectroscopy of the merging system Mrk273 that show a spectacular extended halo of warm ionized gas out to a radius of ˜45 kpc from the system nucleus. Outside of the immediate nuclear regions (r > 6 kpc), there is no evidence for kinematic disturbance in the ionized gas: in the extended regions covered by our spectroscopic slits the emission lines are relatively narrow (full width at half-maximum, FWHM ≲ 350 km s-1) and velocity shifts small (|ΔV| ≲ 250 km s-1). This is despite the presence of powerful near-nuclear outflows (FWHM > 1000 km s-1; |ΔV| > 400 km s-1; r < 6 kpc). Diagnostic ratio plots are fully consistent with Seyfert 2 photoionization to the NE of the nuclear region, however to the SW the plots are more consistent with low-velocity radiative shock models. The kinematics of the ionized gas, combined with the fact that the main structures are aligned with low-surface-brightness tidal continuum features, are consistent with the idea that the ionized halo represents tidal debris left over from a possible triple-merger event, rather than a reservoir of outflowing gas.

  16. [Effects of hospital mergers on health economy].

    Science.gov (United States)

    Ingebrigtsen, Tor

    2010-05-06

    Norwegian hospitals have been characterised by increasing activity, expansion of services and increasing costs for a long time. Differences in quality and accessibility have been documented between hospitals in various geographic locations. Transferral of hospital ownership to the state (from 2002) aimed at increasing capacities and improving quality of services, but also at restricting the increase of costs. These goals have only been partly met. The structure of hospital trusts and organisation of services are therefore continuously debated. This literature review aims at examining whether hospital mergers can reduce costs and at the same time increase the quality of services offered. Literature was identified through a Medline search using the terms "hospital", "merger" and "cost saving". The results are summarized and discussed. Seven original studies of totally 476 hospital mergers (in the USA, Great Britain and Norway) were identified in the period 1982 - 2000. The literature indicates that hospital mergers have a potential to reduce costs by about 10 % if the process achieves complete fusion of previously independent organisations, with a more optimal dimensioning of services and development of a common organizational culture. Collaboration between top management and the professional bureaucracy are prerequisites for success. Mergers are associated with a significant risk of unexpected problems and temporary reduced quality of the services.

  17. Can mergers make slowly rotating elliptical galaxies

    International Nuclear Information System (INIS)

    White, S.D.M.

    1979-01-01

    The results of numerical experiments are used to guide an analytic discussion of hyperbolic mergers among an uncorrelated galaxy population. The expected merger rate is derived as a function of progenitor mass and relative angular momentum, and is used to predict the distribution of the parameter V/sub c//sigma 0 for merger products where V/sub c/ is the maximum observed rotation velocity in a galaxy and sigma 0 is its central velocity dispersion. The median value of this parameter for mergers between comparable galaxies is estimated to be 0.65 and is higher than the observed value in any of the 14 galaxies for which data are available. It seems unlikely that most elliptical galaxies are the result of single or multiple mergers between initially unbound stellar systems; further observational and theoretical work is suggested which should lead to a conclusive test of this picture. The present arguments cannot, however, exclude formation from low angular momentum elliptical orbits

  18. BPASS predictions for binary black hole mergers

    Science.gov (United States)

    Eldridge, J. J.; Stanway, E. R.

    2016-11-01

    Using the Binary Population and Spectral Synthesis code, BPASS, we have calculated the rates, time-scales and mass distributions for binary black hole (BH) mergers as a function of metallicity. We consider these in the context of the recently reported first Laser Interferometer Gravitational-Wave Observatory (LIGO) event detection. We find that the event has a very low probability of arising from a stellar population with initial metallicity mass fraction above Z = 0.010 (Z ≳ 0.5 Z⊙). Binary BH merger events with the reported masses are most likely in populations below 0.008 (Z ≲ 0.4 Z⊙). Events of this kind can occur at all stellar population ages from 3 Myr up to the age of the Universe, but constitute only 0.1-0.4 per cent of binary BH mergers between metallicities of Z = 0.001 and 0.008. However at metallicity Z = 10-4, 26 per cent of binary BH mergers would be expected to have the reported masses. At this metallicity, the progenitor merger times can be close to ≈10 Gyr and rotationally mixed stars evolving through quasi-homogeneous evolution, due to mass transfer in a binary, dominate the rate. The masses inferred for the BHs in the binary progenitor of GW 150914 are amongst the most massive expected at anything but the lowest metallicities in our models. We discuss the implications of our analysis for the electromagnetic follow-up of future LIGO event detections.

  19. Merger 1980: The Organizational Integration of College Mental Health Services.

    Science.gov (United States)

    Foster, Thomas V., Jr.

    1982-01-01

    The merger of a traditional counseling center with a traditional comprehensive student health center at Indiana University, Bloomington is described. Important variables, costs and benefits, suggestions for similar mergers, and the outcome of the Indiana University program are discussed. (CJ)

  20. Financial Synergy in Mergers and Acquisitions in Saudi Arabia

    OpenAIRE

    Basmah Al Qudaiby; Muhammad Rahatullah Khan

    2013-01-01

    Businesses today consider mergers and acquisitions a new strategy for their company’s growth. Companies aim to grow through sales’ increase, assets purchase, profits’ accumulation and market share gains. The better way for achieving these targets is by getting into either a Merger or an Acquisition. As a matter of fact, growth through mergers and acquisitions has been a critical part of the success of many companies operating in the new economy. Mergers and Acquisitions are an important facto...

  1. Interactions between massive dark halos and warped disks

    NARCIS (Netherlands)

    Kuijken, K; Persic, M; Salucci, P

    1997-01-01

    The normal mode theory for warping of galaxy disks, in which disks are assumed to be tilted with respect to the equator of a massive, flattened dark halo, assumes a rigid, fixed halo. However, consideration of the back-reaction by a misaligned disk on a massive particle halo shows there to be strong

  2. Extended and filamentary Lyα emission from the formation of a protogalactic halo at z = 2.63

    Science.gov (United States)

    Rauch, Michael; Becker, George D.; Haehnelt, Martin G.; Gauthier, Jean-Rene; Sargent, Wallace L. W.

    2013-02-01

    We report the observation of a further asymmetric, extended Lyα emitting halo at z = 2.63, from our ultra-deep, long-slit spectroscopic survey of faint high-redshift emitters, undertaken with Magellan LDSS3 in the GOODS-S field. The Lyα emission, detected over more than 30 kpc, is spatially coincident with a statistically significant concentration of galaxies visible in deep broad-band imaging. While these faint galaxies without spectroscopic redshifts cannot all with certainty be associated with one another or with the Lyα emission, there are a number of compelling reasons why they very probably form a Milky Way halo-mass group at the Lyα redshift. Filamentary structure, possibly consisting of Lyα emission with very high equivalent width, blue stellar continua and evidence for disturbed stellar populations, suggest that the properties of the emitting region reflect ongoing galaxy assembly, with recent galaxy mergers and star formation occurring in the group. The Lyα emission may be powered by cooling radiation or spatially extended star formation in the halo, but is unlikely to be fluorescence driven by either an active galactic nucleus or one of the galaxies. A comparison with the Lyα surface brightness profiles of more typical, bright Lyα emitters or Lyman break galaxies from similarly deep two-dimensional spectra shows them to be conspicuously different from the extended, asymmetric object studied here. This is consistent with the picture that typical Lyα emitters represent Lyα resonantly scattering from single, kinematically quiescent, compact sources of ionizing radiation, whereas extended emission of the kind seen in the current halo reflect a more active, kinematically disturbed stage in the galaxy formation process. Hence, unusual Lyα emission as observed here may provide unique insights into what is probably a key mode of galaxy formation at high redshifts. Our observations provide further, circumstantial evidence that galaxy mergers may

  3. Halo white dwarfs in the Gaia era

    NARCIS (Netherlands)

    van Oirschot, P.; Nelemans, G.; Pols, O.; Helmi, A.; Tolstoy, E.; Brown, A. G. A.; Pugliese, G.; de Koter, A.; Wijburg, M.

    The Galactic Halo is the oldest and most metal-poor component of the Galaxy. It is studied in detail both to understand the formation and evolution of galaxies, as well as the formation and evolution of the earliest stars. With this aim in mind, we plan to couple a population synthesis model to a

  4. Reflection halo twins : subsun and supersun

    NARCIS (Netherlands)

    Konnen, Gunther P.; van der Werf, Siebren Y.

    2011-01-01

    From an aircraft, a short distinct vertical structure is sometimes seen above the setting sun. Such a feature can be understood as a halo, which is the counterpart of the well-known subsun. Whereas the latter arises from reflections off basal faces of plate-oriented ice crystals illuminated from

  5. Cosmology and cluster halo scaling relations

    NARCIS (Netherlands)

    Araya-Melo, Pablo A.; van de Weygaert, Rien; Jones, Bernard J. T.

    2009-01-01

    We explore the effects of dark matter and dark energy on the dynamical scaling properties of galaxy clusters. We investigate the cluster Faber-Jackson (FJ), Kormendy and Fundamental Plane (FP) relations between the mass, radius and velocity dispersion of cluster-sized haloes in cosmological N-body

  6. Halo nucleus and double-λ hypernucleus

    Indian Academy of Sciences (India)

    It appears that the halo phenomenon is a delicately balanced threshold effect and neglect of the details of many-body system may not be crucial. Our neglect of the angular momentum of the extra core neutrons does not seem to affect the results in a significant way. We can infer that the choice of the depth of the core-n.

  7. 7 CFR 1735.62 - Approval of acquisitions and mergers.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 11 2010-01-01 2010-01-01 false Approval of acquisitions and mergers. 1735.62 Section 1735.62 Agriculture Regulations of the Department of Agriculture (Continued) RURAL UTILITIES SERVICE... Mortgage Controls on Acquisitions and Mergers § 1735.62 Approval of acquisitions and mergers. (a) If a...

  8. 7 CFR 1717.152 - Required documentation for all mergers.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 11 2010-01-01 2010-01-01 false Required documentation for all mergers. 1717.152... ELECTRIC LOANS Mergers and Consolidations of Electric Borrowers § 1717.152 Required documentation for all mergers. In order for RUS to advance funds, send bills, and otherwise conduct business with a successor...

  9. 29 CFR 4231.3 - Requirements for mergers and transfers.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 9 2010-07-01 2010-07-01 false Requirements for mergers and transfers. 4231.3 Section 4231..., REORGANIZATION, TERMINATION, AND OTHER RULES APPLICABLE TO MULTIEMPLOYER PLANS MERGERS AND TRANSFERS BETWEEN MULTIEMPLOYER PLANS § 4231.3 Requirements for mergers and transfers. (a) General requirements. A plan sponsor...

  10. 7 CFR 1735.19 - Mergers and consolidations.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 11 2010-01-01 2010-01-01 false Mergers and consolidations. 1735.19 Section 1735.19... Basic Policies § 1735.19 Mergers and consolidations. RUS does not make loans for the sole purpose of merging or consolidating telephone organizations. After a merger or consolidation, RUS will consider...

  11. 7 CFR 1710.108 - Mergers and consolidations.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 11 2010-01-01 2010-01-01 false Mergers and consolidations. 1710.108 Section 1710.108... and Basic Policies § 1710.108 Mergers and consolidations. (a) RUS encourages its borrowers to consider... operating efficiency and financial soundness. (b) After a merger or consolidation, RUS will give priority...

  12. 29 CFR 4011.6 - Mergers, consolidations, and spinoffs.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 9 2010-07-01 2010-07-01 false Mergers, consolidations, and spinoffs. 4011.6 Section 4011... REPORTING AND DISCLOSURE REQUIREMENTS DISCLOSURE TO PARTICIPANTS § 4011.6 Mergers, consolidations, and spinoffs. In the case of a plan involved in a merger, consolidation, or spinoff transaction that becomes...

  13. 7 CFR 1717.615 - Consolidations and mergers.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 11 2010-01-01 2010-01-01 false Consolidations and mergers. 1717.615 Section 1717.615... Controls § 1717.615 Consolidations and mergers. A distribution or power supply borrower may without the..., merger, conveyance or transfer shall be on such terms as shall fully preserve the lien and security of...

  14. Rethinking and re-imagining mergers in further and higher ...

    African Journals Online (AJOL)

    Higher and Further Education in South Africa has been characterized by major changes regarding the shape and size of the system. One of these changes has been the so-called mergers. This article addresses the scenario which contributed to the mergers. An overview of various frameworks or models for mergers is ...

  15. Effective field theory for halo nuclei

    International Nuclear Information System (INIS)

    Hagen, Philipp Robert

    2014-01-01

    We investigate properties of two- and three-body halo systems using effective field theory. If the two-particle scattering length a in such a system is large compared to the typical range of the interaction R, low-energy observables in the strong and the electromagnetic sector can be calculated in halo EFT in a controlled expansion in R/ vertical stroke a vertical stroke. Here we focus on universal properties and stay at leading order in the expansion. Motivated by the existence of the P-wave halo nucleus 6 He, we first set up an EFT framework for a general three-body system with resonant two-particle P-wave interactions. Based on a Lagrangian description, we identify the area in the effective range parameter space where the two-particle sector of our model is renormalizable. However, we argue that for such parameters, there are two two-body bound states: a physical one and an additional deeper-bound and non-normalizable state that limits the range of applicability of our theory. With regard to the three-body sector, we then classify all angular-momentum and parity channels that display asymptotic discrete scale invariance and thus require renormalization via a cut-off dependent three-body force. In the unitary limit an Efimov effect occurs. However, this effect is purely mathematical, since, due to causality bounds, the unitary limit for P-wave interactions can not be realized in nature. Away from the unitary limit, the three-body binding energy spectrum displays an approximate Efimov effect but lies below the unphysical, deep two-body bound state and is thus unphysical. Finally, we discuss possible modifications in our halo EFT approach with P-wave interactions that might provide a suitable way to describe physical three-body bound states. We then set up a halo EFT formalism for two-neutron halo nuclei with resonant two-particle S-wave interactions. Introducing external currents via minimal coupling, we calculate observables and universal correlations for such

  16. The Fate of Neutron Star Binary Mergers

    Energy Technology Data Exchange (ETDEWEB)

    Piro, Anthony L. [The Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Giacomazzo, Bruno [Physics Department, University of Trento, via Sommarive 14, I-38123 Trento (Italy); Perna, Rosalba, E-mail: piro@carnegiescience.edu [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (United States)

    2017-08-01

    Following merger, a neutron star (NS) binary can produce roughly one of three different outcomes: (1) a stable NS, (2) a black hole (BH), or (3) a supramassive, rotationally supported NS, which then collapses to a BH following angular momentum losses. Which of these fates occur and in what proportion has important implications for the electromagnetic transient associated with the mergers and the expected gravitational wave (GW) signatures, which in turn depend on the high density equation of state (EOS). Here we combine relativistic calculations of NS masses using realistic EOSs with Monte Carlo population synthesis based on the mass distribution of NS binaries in our Galaxy to predict the distribution of fates expected. For many EOSs, a significant fraction of the remnants are NSs or supramassive NSs. This lends support to scenarios in which a quickly spinning, highly magnetized NS may be powering an electromagnetic transient. This also indicates that it will be important for future GW observatories to focus on high frequencies to study the post-merger GW emission. Even in cases where individual GW events are too low in signal to noise to study the post merger signature in detail, the statistics of how many mergers produce NSs versus BHs can be compared with our work to constrain the EOS. To match short gamma-ray-burst (SGRB) X-ray afterglow statistics, we find that the stiffest EOSs are ruled out. Furthermore, many popular EOSs require a significant fraction of ∼60%–70% of SGRBs to be from NS–BH mergers rather than just binary NSs.

  17. The Impact of Theoretical Uncertainties in the Halo Mass Function and Halo

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Hao-Yi; Zentner, Andrew R.; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC /Pittsburgh U. /KIPAC, Menlo Park /SLAC

    2010-06-04

    We study the impact of theoretical uncertainty in the dark matter halo mass function and halo bias on dark energy constraints from imminent galaxy cluster surveys. We find that for an optical cluster survey like the Dark Energy Survey, the accuracy required on the predicted halo mass function to make it an insignificant source of error on dark energy parameters is {approx}1%. The analogous requirement on the predicted halo bias is less stringent ({approx}5%), particularly if the observable-mass distribution can be well constrained by other means. These requirements depend upon survey area but are relatively insensitive to survey depth. The most stringent requirements are likely to come from a survey over a significant fraction of the sky that aims to observe clusters down to relatively low mass, M{sub th}{approx} 10{sup 13.7} h{sup -1} M{sub sun}; for such a survey, the mass function and halo bias must be predicted to accuracies of {approx}0.5% and {approx}1%, respectively. These accuracies represent a limit on the practical need to calibrate ever more accurate halo mass and bias functions. We find that improving predictions for the mass function in the low-redshift and low-mass regimes is the most effective way to improve dark energy constraints.

  18. A Giant Radio Halo in a Low-Mass Sz-selected Galaxy Cluster: ACT-CLJ0256.5+0006

    Science.gov (United States)

    Knowles, Kendra; Intema, H. T.; Baker, A. J.; Bharadwaj, V.; Bond, J. R.; Cress, C.; Gupta, N.; Hajian, A.; Hilton, M.; Hincks, A. D.; hide

    2016-01-01

    We present the detection of a giant radio halo (GRH) in the Sunyaev-Zel'dovich (SZ)- selected merging galaxy cluster ACT-CL J0256.5+ 0006 (z = 0.363), observed with the Giant Metrewave Radio Telescope at 325 and 610 MHz. We find this cluster to host a faint (S610 = 5.6 +/- 1.4mJy) radio halo with an angular extent of 2.6 arcmin, corresponding to 0.8 Mpc at the cluster redshift, qualifying it as a GRH. J0256 is one of the lowest mass systems, M500, SZ = (5.0 +/- 1.2) × 10(exp14) M, found to host a GRH. We measure the GRH at lower significance at 325 MHz (S325 = 10.3 +/- 5.3mJy), obtaining a spectral index measurement of a610 325 = 1.0+ 0.7 - 0.9. This result is consistent with the mean spectral index of the population of typical radio haloes, alpha = 1.2 +/- 0.2. Adopting the latter value, we determine a 1.4 GHz radio power of P1.4 GHz = (1.0 +/- 0.3) × 10(exp 24)W/Hz, placing this cluster within the scatter of known scaling relations. Various lines of evidence, including the intracluster medium morphology, suggest that ACT-CL J0256.5+ 0006 is composed of two subclusters. We determine a merger mass ratio of 7:4, and a line-of-sight velocity difference of v? = 1880 +/- 210 km/s. We construct a simple merger model to infer relevant time-scales in the merger. From its location on the P1.4GHz-LX scaling relation, we infer that we observe ACT-CL J0256.5+ 0006 just before first core crossing.

  19. The remnant of a merger between two dwarf galaxies in Andromeda II.

    Science.gov (United States)

    Amorisco, N C; Evans, N W; van de Ven, G

    2014-03-20

    Driven by gravity, massive structures like galaxies and clusters of galaxies are believed to grow continuously through hierarchical merging and accretion of smaller systems. Observational evidence of accretion events is provided by the coherent stellar streams crossing the outer haloes of massive galaxies, such as the Milky Way or Andromeda. At similar mass scales, around 10(11) solar masses in stars, further evidence of merging activity is also ample. Mergers of lower-mass galaxies are expected within the hierarchical process of galaxy formation, but have hitherto not been seen for galaxies with less than about 10(9) solar masses in stars. Here we report the kinematic detection of a stellar stream in one of the satellite galaxies of Andromeda, the dwarf spheroidal Andromeda II, which has a mass of only 10(7) solar masses in stars. The properties of the stream show that we are observing the remnant of a merger between two dwarf galaxies. This had a drastic influence on the dynamics of the remnant, which is now rotating around its projected major axis. The stellar stream in Andromeda II illustrates the scale-free character of the formation of galaxies, down to the lowest galactic mass scales.

  20. Dynamics of merging: post-merger mixing and relaxation of an Illustris galaxy

    Science.gov (United States)

    Young, Anthony M.; Williams, Liliya L. R.; Hjorth, Jens

    2018-02-01

    During the merger of two galaxies, the resulting system undergoes violent relaxation and seeks stable equilibrium. However, the details of this evolution are not fully understood. Using Illustris simulation, we probe two physically related processes, mixing and relaxation. Though the two are driven by the same dynamics—global time-varying potential for the energy, and torques caused by asymmetries for angular momentum—we measure them differently. We define mixing as the redistribution of energy and angular momentum between particles of the two merging galaxies. We assess the degree of mixing as the difference between the shapes of their energy distributions, N(E)s, and their angular momentum distributions, N(L2)s. We find that the difference is decreasing with time, indicating mixing. To measure relaxation, we compare N(E) of the newly merged system to N(E) of a theoretical prediction for relaxed collisionless systems, DARKexp, and witness the system becoming more relaxed, in the sense that N(E) approaches DARKexp N(E). Because the dynamics driving mixing and relaxation are the same, the timescale is similar for both. We measure two sequential timescales: a rapid, 1 Gyr phase after the initial merger, during which the difference in N(E) of the two merging halos decreases by ~ 80%, followed by a slow phase, when the difference decreases by ~ 50% over ~ 8.5 Gyrs. This is a direct measurement of the relaxation timescale. Our work also draws attention to the fact that when a galaxy has reached Jeans equilibrium it may not yet have reached a fully relaxed state given by DARKexp, in that it retains information about its past history. This manifests itself most strongly in stars being centrally concentrated. We argue that it is particularly difficult for stars, and other tightly bound particles, to mix because they have less time to be influenced by the fluctuating potential, even across multiple merger events.

  1. Mergers and acquisitions in the oil and gas industries

    International Nuclear Information System (INIS)

    Corlay, C.; Huby, D.

    1999-01-01

    This paper focuses on mergers and acquisitions in the oil and gas industries, and lists the most important mergers in terms of transaction value for the period 1981-1997, and plots oil and gas mergers and acquisitions activity by sector and by major region. The mean operation indicator in 1998 in terms of reserves, production and refining capacity of the major companies are tabulated. The impact of the mergers on the oil and gas markets are examined, and issues concerning these mergers and acquisitions are explored. (UK)

  2. Galaxy and Mass Assembly (GAMA): probing the merger histories of massive galaxies via stellar populations

    Science.gov (United States)

    Ferreras, I.; Hopkins, A. M.; Gunawardhana, M. L. P.; Sansom, A. E.; Owers, M. S.; Driver, S.; Davies, L.; Robotham, A.; Taylor, E. N.; Konstantopoulos, I.; Brough, S.; Norberg, P.; Croom, S.; Loveday, J.; Wang, L.; Bremer, M.

    2017-06-01

    The merging history of galaxies can be traced with studies of dynamically close pairs. These consist of a massive primary galaxy and a less massive secondary (or satellite) galaxy. The study of the stellar populations of secondary (lower mass) galaxies in close pairs provides a way to understand galaxy growth by mergers. Here we focus on systems involving at least one massive galaxy - with stellar mass above 1011M⊙ in the highly complete Galaxy and Mass Assembly (GAMA) survey. Our working sample comprises 2692 satellite galaxy spectra (0.1 ≤ z ≤ 0.3). These spectra are combined into high S/N stacks, and binned according to both an 'internal' parameter, the stellar mass of the satellite galaxy (I.e. the secondary), and an 'external' parameter, selecting either the mass of the primary in the pair, or the mass of the corresponding dark matter halo. We find significant variations in the age of the populations with respect to environment. At fixed mass, satellites around the most massive galaxies are older and possibly more metal-rich, with age differences ˜1-2 Gyr within the subset of lower mass satellites (˜1010 M⊙). These variations are similar when stacking with respect to the halo mass of the group where the pair is embedded. The population trends in the lower mass satellites are consistent with the old stellar ages found in the outer regions of massive galaxies.

  3. Research Progresses of Halo Streams in the Solar Neighborhood

    Science.gov (United States)

    Xi-long, Liang; Jing-kun, Zhao; Yu-qin, Chen; Gang, Zhao

    2018-01-01

    The stellar streams originated from the Galactic halo may be detected when they pass by the solar neighborhood, and they still keep some information at their birth times. Thus, the investigation of halo streams in the solar neighborhood is very important for understanding the formation and evolution of our Galaxy. In this paper, the researches of halo streams in the solar neighborhood are briefly reviewed. We have introduced the methods how to detect the halo streams and identify their member stars, summarized the progresses in the observation of member stars of halo streams and in the study of their origins, introduced in detail how to analyze the origins of halo streams in the solar neighborhood by means of numerical simulation and chemical abundance, and finally discussed the prospects of the LAMOST and GAIA in the research of halo streams in the solar neighborhood.

  4. ORIGAMI: DELINEATING HALOS USING PHASE-SPACE FOLDS

    International Nuclear Information System (INIS)

    Falck, Bridget L.; Neyrinck, Mark C.; Szalay, Alexander S.

    2012-01-01

    We present the ORIGAMI method of identifying structures, particularly halos, in cosmological N-body simulations. Structure formation can be thought of as the folding of an initially flat three-dimensional manifold in six-dimensional phase space. ORIGAMI finds the outer folds that delineate these structures. Halo particles are identified as those that have undergone shell-crossing along three orthogonal axes, providing a dynamical definition of halo regions that is independent of density. ORIGAMI also identifies other morphological structures: particles that have undergone shell-crossing along 2, 1, or 0 orthogonal axes correspond to filaments, walls, and voids, respectively. We compare this method to a standard friends-of-friends halo-finding algorithm and find that ORIGAMI halos are somewhat larger, more diffuse, and less spherical, though the global properties of ORIGAMI halos are in good agreement with other modern halo-finding algorithms.

  5. ORIGAMI: DELINEATING HALOS USING PHASE-SPACE FOLDS

    Energy Technology Data Exchange (ETDEWEB)

    Falck, Bridget L.; Neyrinck, Mark C.; Szalay, Alexander S. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)

    2012-08-01

    We present the ORIGAMI method of identifying structures, particularly halos, in cosmological N-body simulations. Structure formation can be thought of as the folding of an initially flat three-dimensional manifold in six-dimensional phase space. ORIGAMI finds the outer folds that delineate these structures. Halo particles are identified as those that have undergone shell-crossing along three orthogonal axes, providing a dynamical definition of halo regions that is independent of density. ORIGAMI also identifies other morphological structures: particles that have undergone shell-crossing along 2, 1, or 0 orthogonal axes correspond to filaments, walls, and voids, respectively. We compare this method to a standard friends-of-friends halo-finding algorithm and find that ORIGAMI halos are somewhat larger, more diffuse, and less spherical, though the global properties of ORIGAMI halos are in good agreement with other modern halo-finding algorithms.

  6. THE POPULATION OF HELIUM-MERGER PROGENITORS: OBSERVATIONAL PREDICTIONS

    International Nuclear Information System (INIS)

    Fryer, Chris L.; Belczynski, Krzysztof; Bulik, Tomasz; Berger, Edo; Thöne, Christina; Ellinger, Carola

    2013-01-01

    The helium-merger gamma-ray burst (GRB) progenitor is produced by the rapid accretion onto a compact remnant (neutron star or black hole) when it undergoes a common envelope inspiral with its companion's helium core. This merger phase produces a very distinct environment around these outbursts and recent observations suggest that, in some cases, we are detecting the signatures of the past merger in the GRB afterglow. These observations allow us, for the first time, to study the specific features of the helium-merger progenitor. In this paper, we couple population synthesis calculations to our current understanding of GRB engines and common envelope evolution to make observational predictions for the helium-merger GRB population. Many mergers do not produce GRB outbursts and we discuss the implications of these mergers with the broader population of astrophysical transients.

  7. Black Hole Mergers as Probes of Structure Formation

    Science.gov (United States)

    Alicea-Munoz, Emily

    2008-01-01

    Observations of gravitational waves from massive black hole (MBH) mergers can provide us with important clues about the era of structure formation in the early universe. Previous research in this field has been limited to calculating merger rates of MBHs using different models where many assumptions are made about the specific values of physical parameters of the mergers, resulting in merger rate estimates that span 5 to 6 orders of magnitude. We develop a semi-analytical, phenomenological model that includes plausible combinations of several physical parameters involved in the mergers. which we then turn around to determine how well LISA observations will be able to enhance our understanding of the universe during the critical z approximately equal to 5-30 structure formation era. We do this by generating synthetic LISA observable data (masses, redshifts, merger rates), which are then analyzed using a Markov Chain Monte Carlo (MCMC) method. This allows us to constrain the physical parameters of the mergers.

  8. DRY MERGER RATE AND POST-MERGER FRACTION IN THE COMA CLUSTER CORE

    International Nuclear Information System (INIS)

    Cordero, Juan P.; Campusano, Luis E.; Haines, Christopher P.; De Propris, Roberto; Weinzirl, Tim; Jogee, Shardha

    2016-01-01

    We evaluate the dry merger activity in the Coma cluster, using a spectroscopically complete sample of 70 red-sequence (RS) galaxies, most of which (∼75%) are located within 0.2R 200 (∼0.5 Mpc) from the cluster center, with data from the Coma Treasury Survey obtained with the Hubble Space Telescope. The fraction of close galaxy pairs in the sample is the proxy employed for the estimation of the merger activity. We identify 5 pairs and 1 triplet, enclosing a total of 13 galaxies, based on limits on projected separation and line-of-sight velocity difference. Of these systems, none show signs of ongoing interaction, and therefore we do not find any true mergers in our sample. This negative result sets a 1σ upper limit of 1.5% per Gyr for the major dry merger rate, consistent with the low rates expected in present-day clusters. Detailed examination of the images of all the RS galaxies in the sample reveals only one with low surface brightness features identifiable as the remnant of a past merger or interaction, implying a post-merger fraction below 2%

  9. Mergers and acquisitions involving equine veterinary practices.

    Science.gov (United States)

    Jackman, Brad R; McCafferty, Owen E

    2009-12-01

    This article discusses mergers and acquisitions involving equine veterinary practices. Combining practices can be professionally and economically advantageous but requires a great deal of thought, planning, and implementation. If due diligence is performed and true business teamwork is undertaken, the benefits can be enormous and rewarding.

  10. Mergers and alliances the wider view

    CERN Document Server

    Woodsworth, Anne

    2013-01-01

    Volume 36 of Advances in Librarianship seeks to provide a broad review of the factors that lead to mergers and other alliances, the methods used to ensure effective and successful collaborations, and descriptions of the factors which contributed to less successful efforts at consolidation.

  11. Resilience and Coping After Hospital Mergers.

    Science.gov (United States)

    Russo, Cynthia; Calo, Oriana; Harrison, Georgia; Mahoney, Kathleen; Zavotsky, Kathleen Evanovich

    The aim of this study was to explore the relationship between resilience and coping in frontline nurses working in a healthcare system that has recently undergone a merger. Hospital mergers are common in the current healthcare environment. Mergers can provide hospital nurses the opportunity to use and develop positive coping strategies to help remain resilient during times of change. An anonymous-survey, quantitative, exploratory, descriptive study design was used. Data were obtained from an electronic survey that was made available to all nurses working in a 3-hospital system located in the northeast. Overall, the results showed that, when nurses reported using positive coping strategies, they report higher levels of resilience. The levels of resilience also varied from campus to campus. The campus that has been through 2 recent mergers reported the highest levels of resilience. This study suggests that, during times of change in the workplace, if nurses are encouraged to use positive coping strategies, they may have higher levels of resilience. This changing environment provides the clinical nurse specialists/clinical nurse educators the opportunity to foster and support frontline nurses in the use of healthy coping strategies and to help improve and maintain a high level of resilience, which is critical in today's healthcare environment.

  12. Fueling QSOs: the relevance of mergers

    Czech Academy of Sciences Publication Activity Database

    Bennert, N.; Canalizo, G.; Jungwiert, Bruno; Stockton, A.; Schweizer, F.; Peng, Ch.; Lacy, M.

    2008-01-01

    Roč. 79, č. 4 (2008), s. 1247-1250 ISSN 0037-8720 R&D Projects: GA MŠk(CZ) LC06014 Institutional research plan: CEZ:AV0Z10030501 Keywords : galaxy mergers * quasars * photometry Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  13. Mergers and innovation in the pharmaceutical industry.

    Science.gov (United States)

    Comanor, William S; Scherer, F M

    2013-01-01

    Conflicting trends confound the pharmaceutical industry. The productivity of pharmaceutical innovation has declined in recent years. At the same time, the cohort of large companies who are the leading engines of pharmaceutical R&D has become increasingly concentrated. The concurrent presence of these trends is not sufficient to determine causation. In response to lagging innovation prospects, some companies have sought refuge in mergers and acquisitions to disguise their dwindling prospects or gain R&D synergies. On the other hand, the increased concentration brought on by recent mergers may have contributed to the declining rate of innovation. In this paper, we consider the second of these causal relationships: the likely impact of the recent merger wave among the largest pharmaceutical companies on the rate of innovation. In other words, have recent mergers, which may have been taken in response to lagging innovation, represented a self-defeating strategy that only made industry outcomes worse? Copyright © 2012 Elsevier B.V. All rights reserved.

  14. Efficiency Effects of Bank Mergers and Acquisitions

    NARCIS (Netherlands)

    H.P. Huizinga; J.H.M. Nelissen (Jan); R. Vander Vennet

    2001-01-01

    textabstractNext to technological progress and deregulation, the introduction of the euro is widely considered to be an important catalyst for bank consolidation in Europe. In order to assess the public policy issues surrounding bank mergers, this paper analyzes the efficiency effects of 52

  15. Merger and Acquisition in the Banking Sector

    Directory of Open Access Journals (Sweden)

    Anna Szewczyk

    2008-12-01

    Full Text Available The article presents situation on mergers and acquisitions (MA in banking sector during last twenty years. The main motives are selected and analyzed. All is explained on the base on research reports of the Deutsche Bundesbank and the European Central Bank.

  16. Black Hole Mergers in the Universe.

    Science.gov (United States)

    Portegies Zwart SF; McMillan

    2000-01-01

    Mergers of black hole binaries are expected to release large amounts of energy in the form of gravitational radiation. However, binary evolution models predict merger rates that are too low to be of observational interest. In this Letter, we explore the possibility that black holes become members of close binaries via dynamical interactions with other stars in dense stellar systems. In star clusters, black holes become the most massive objects within a few tens of millions of years; dynamical relaxation then causes them to sink to the cluster core, where they form binaries. These black hole binaries become more tightly bound by superelastic encounters with other cluster members and are ultimately ejected from the cluster. The majority of escaping black hole binaries have orbital periods short enough and eccentricities high enough that the emission of gravitational radiation causes them to coalesce within a few billion years. We predict a black hole merger rate of about 1.6x10-7 yr-1 Mpc-3, implying gravity-wave detection rates substantially greater than the corresponding rates from neutron star mergers. For the first-generation Laser Interferometer Gravitational-Wave Observatory (LIGO-I), we expect about one detection during the first 2 years of operation. For its successor LIGO-II, the rate rises to roughly one detection per day. The uncertainties in these numbers are large. Event rates may drop by about an order of magnitude if the most massive clusters eject their black hole binaries early in their evolution.

  17. Synergy disclosures in mergers and acquisitions

    NARCIS (Netherlands)

    M.D.R.P. Dutordoir (Marie); P.G.J. Roosenboom (Peter); M. Teixeira de Vasconcelos (Manuel)

    2013-01-01

    textabstractWe examine bidding firms’ motives for disclosing a synergy forecast when announcing a merger or acquisition. Our sample consists of 1,990 M&A deals, of which 345 announce synergy estimates. Our results suggest that synergy disclosures serve to obtain a more favorable market reception for

  18. Shareholders’ expectations, aspiration levels, and mergers

    NARCIS (Netherlands)

    Diecidue, E.; van de Ven, J.; Weitzel, U.

    This paper offers a new explanation of value-reducing mergers and stock market driven takeovers by introducing recent research on aspiration levels and individual decision making under risk. If market valuation constitutes an aspiration level for managers, we show that managers may be tempted to

  19. A CEO roundtable on making mergers succeed.

    Science.gov (United States)

    Mandl, A; Bohnett, D; Liddy, E; Komansky, D; Kozlowski, D; Leschly, J; Gupta, R; McDonald, M; Avery, B; Moore, N; Krekel, T

    2000-01-01

    The announcement in January of the merger between America Online and Time Warner marked the convergence of the two most important business trends of the last five years--the rise of the Internet and the resurgence of mergers and acquisitions. M&A activity is at a fever pitch, spurred in large part by the breathtaking influx of capital into the Internet space. And all signs indicate the trend will only accelerate. Against this background, an impressive group of experienced deal makers came together to share their experiences of what makes mergers work. They were assembled in Scottsdale, Arizona, under the auspices of the M&A Group, a professional society formed in 1999 for CEOs interested in M&A as a business strategy. Participants included top executives from Internet start-ups like Teligent; venture capital firms like Baroda Ventures; financial institutions like Merrill Lynch and PricewaterhouseCoopers; and major corporations like Allstate, Tyco International, SmithKline Beecham, Rohm and Haas, VF, Crown Cork & Seal, and Hughes Space and Communications. The spirited and surprisingly frank discussion cut a wide swath, considering issues such as whether most mergers fail to pan out as well as expected, how to increase the odds of success, the nuts and bolts of the integration process, the trade-offs between acquiring a company and growing from within, the importance of cultural issues, and why anyone would want to be on the board of a merged company.

  20. DO ROMANIAN MERGERS REALLY CREATE VALUE?

    Directory of Open Access Journals (Sweden)

    Anca-Simona HROMEI

    2015-12-01

    Full Text Available The realities of our modern society demonstrate that businesses operate in a competitive environment, which requires continuous improvement and development of production and sales. In this context, for financial, economic and fiscal reasons, companies resort to a process of concentration, through the merger of all the factors involved in the fulfilment and diversification of their activities. Often, the reasons for engaging in a merger refer to the fact that two merged companies create, in terms of value, an entity that exceeds the individual values of the two participants if they were to continue to activate separately. This paper aims at analysing whether the well-known relationship ‘1+1=3’, which describes merger synergies, applies at the Romanian level. For this reason, each of the values of 77 merged companies were compared with the sum of the individual values of the firms that initially created them. It was found that 56% of the mergers analysed generated added value for shareholders.

  1. Estimating the potential gains from mergers

    DEFF Research Database (Denmark)

    Bogetoft, Peter; Wang, Dexiang

    2005-01-01

    We introduce simple production economic models to estimate the potential gains from mergers. We decompose the gains into technical ef¿ciency, size (scale) and harmony (mix) gains, and we discuss alternative ways to capture these gains. We propose to approximate the production processes using...

  2. Corporate Employee-Engagement and Merger Outcomes

    NARCIS (Netherlands)

    Liang, H.; Renneboog, Luc

    2017-01-01

    Extending the theories of employee incentives and inalienability of human capital, we investigate the link between a firm’s engagement in employee issues and the returns to shareholders around mergers and acquisitions (M&As) and analyze an international sample of 4,565 M&A deals from 48 countries.

  3. Ultraluminous Infrared Mergers: Elliptical Galaxies in Formation?

    Science.gov (United States)

    Genzel, R.; Tacconi, L. J.; Rigopoulou, D.; Lutz, D.; Tecza, M.

    2001-12-01

    We report high-quality near-IR spectroscopy of 12 ultraluminous infrared galaxy mergers (ULIRGs). Our new VLT and Keck data provide ~0.5" resolution, stellar and gas kinematics of these galaxies, most of which are compact systems in the last merger stages. We confirm that ULIRG mergers are ``ellipticals in formation.'' Random motions dominate their stellar dynamics, but significant rotation is common. Gasdynamics and stellar dynamics are decoupled in most systems. ULIRGs fall on or near the fundamental plane of hot stellar systems, and especially on its less evolution-sensitive, reff-σ projection. The ULIRG velocity dispersion distribution, their location in the fundamental plane, and their distribution of vrotsini/σ closely resemble those of intermediate-mass (~L*), elliptical galaxies with moderate rotation. As a group ULIRGs do not resemble giant ellipticals with large cores and little rotation. Our results are in good agreement with other recent studies indicating that disky ellipticals with compact cores or cusps can form through dissipative mergers of gas-rich disk galaxies while giant ellipticals with large cores have a different formation history. Based on observations at the European Southern Observatory, Chile (ESO 65.N-0266, 65.N-0289), and on observations at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, The University of California, and the National Aeronautics and Space Administration. The Keck Observatory was made possible by the general financial support by the W. M. Keck Foundation.

  4. Technology-based Mergers and Acquisitions

    DEFF Research Database (Denmark)

    Wang, Daojuan; Moini, Hamid

    2014-01-01

    The purpose of this chapter is to provide an updated review of what is known about the performance of technology-based mergers and acquisitions (TBM&As) and their determinants. This review brings together papers published from 1990 to 2012 in top-rated academic journals within nearly all fields...

  5. Cross-border Mergers and Acquisitions

    DEFF Research Database (Denmark)

    Wang, Daojuan

    This paper focuses on three topics in cross-border mergers and acquisitions (CBM&As) field: motivations for CBM&As, valuation techniques and CBM&A performance (assessment and the determinants). By taking an overview of what have been found so far in academic field and investigating...

  6. Models for mergers in higher education

    African Journals Online (AJOL)

    creativity. New York: Cambridge University Press. Eggleston J 1992. Teaching design and technology. Buckingham: Open University. Press. Fisher R 1990. Teaching children to ... Creative thinking as a self-regulatory metacognitive process — a model ..... merger between companies with “identical products operating in.

  7. Mergers and acquisitions: valuation and risk assessment

    International Nuclear Information System (INIS)

    Calvin, B.N.

    1996-01-01

    An independent review of all facets of risk management, as it pertains to mergers and acquisitions within the petroleum industry, with no transactional motivation, was provided by a representative of a firm specializing in all phases of risk assessment. The following topics received attention: (1) the forward curve versus industry expectations, (2) investor expectations, (3) financial versus physical transactions, and (4) synthetic debt

  8. FRONTIER FIELDS CLUSTERS: DEEP CHANDRA OBSERVATIONS OF THE COMPLEX MERGER MACS J1149.6+2223

    Energy Technology Data Exchange (ETDEWEB)

    Ogrean, G. A.; Weeren, R. J. van; Jones, C.; Forman, W.; Andrade-Santos, F.; Murray, S. S.; Nulsen, P.; Bulbul, E.; Kraft, R.; Randall, S. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Dawson, W. A. [Lawrence Livermore National Lab, 7000 East Avenue, Livermore, CA 94550 (United States); Golovich, N. [University of California, One Shields Avenue, Davis, CA 95616 (United States); Roediger, E. [Astronomy and Astrophysics Section, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland); Zitrin, A.; Sayers, J. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Goulding, A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Umetsu, K. [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Mroczkowski, T. [U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375 (United States); Bonafede, A. [Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, D-21029 Hamburg (Germany); Churazov, E., E-mail: gogrean@cfa.harvard.edu [Max Planck Institute for Astrophysics, Karl-Schwarzschild-Str. 1, D-85741, Garching (Germany); and others

    2016-03-10

    The Hubble Space Telescope Frontier Fields cluster MACS J1149.6+2223 is one of the most complex merging clusters, believed to consist of four dark matter halos. We present results from deep (365 ks) Chandra observations of the cluster, which reveal the most distant cold front (z  =  0.544) discovered to date. In the cluster outskirts, we also detect hints of a surface brightness edge that could be the bow shock preceding the cold front. The substructure analysis of the cluster identified several components with large relative radial velocities, thus indicating that at least some collisions occur almost along the line of sight. The inclination of the mergers with respect to the plane of the sky poses significant observational challenges at X-ray wavelengths. MACS J1149.6+2223 possibly hosts a steep-spectrum radio halo. If the steepness of the radio halo is confirmed, then the radio spectrum, combined with the relatively regular ICM morphology, could indicate that MACS J1149.6+2223 is an old merging cluster.

  9. Magnetic spiral arms in galaxy haloes

    Science.gov (United States)

    Henriksen, R. N.

    2017-08-01

    We seek the conditions for a steady mean field galactic dynamo. The parameter set is reduced to those appearing in the α2 and α/ω dynamo, namely velocity amplitudes, and the ratio of sub-scale helicity to diffusivity. The parameters can be allowed to vary on conical spirals. We analyse the mean field dynamo equations in terms of scale invariant logarithmic spiral modes and special exact solutions. Compatible scale invariant gravitational spiral arms are introduced and illustrated in an appendix, but the detailed dynamical interaction with the magnetic field is left for another work. As a result of planar magnetic spirals `lifting' into the halo, multiple sign changes in average rotation measures forming a regular pattern on each side of the galactic minor axis, are predicted. Such changes have recently been detected in the Continuum Halos in Nearby Galaxies-an EVLA Survey (CHANG-ES) survey.

  10. Limits on the window for halo phenomena

    International Nuclear Information System (INIS)

    Fleck, S.

    1994-05-01

    We study domain of coupling constants for which a 3-body or 4-body system is bound while none of its subsystems is bound. Limits on the size of the domain are derived from a variant of the Hall-Post inequalities which relate N-body to (N-1)-body energies at given coupling. Possible applications to halo nuclei and hypernuclei are briefly outlined. (authors). 15 refs., 2 figs

  11. Controlling halo-chaos via wavelet-based feedback

    Directory of Open Access Journals (Sweden)

    Jin-Qing Fang

    2002-01-01

    Full Text Available Halo-chaos in high-current accelerator has become one of the key issues because it can cause excessive radioactivity from the accelerators and significantly limits the applications of the new accelerators in industrial and other fields. Some general engineering methods for chaos control have been developed, but they generally are unsuccessful for halo-chaos suppression due to many technical constraints. In this article, controllability condition for beam halo-chaos is analyzed qualitatively. Then Particles-in-Cell (PIC simulations explore the nature of beam halo-chaos formation. A nonlinear control method and wavelet function feedback controller are proposed for controlling beam halo-chaos. After control of beam halo-chaos for initial proton beam with water bag distributions, the beam halo strength factor H is reduced to zero, and other statistical physical quantities of beam halo-chaos are doubly reduced. The results show that the developed methods in this paper are very effective for proton beam halo-chaos suppression. Potential application of the halo-chaos control method is finally pointed out.

  12. Merger mania: mergers and acquisitions in the generic drug sector from 1995 to 2016.

    Science.gov (United States)

    Gagnon, Marc-André; Volesky, Karena D

    2017-08-22

    Drug shortages and increasing generic drug prices are associated with low levels of competition. Mergers and acquisitions impact the level of competition. Record merger and acquisition activity was reported for the pharmaceutical sector in 2014/15, yet information on mergers and acquisitions in the generic drug sector are absent from the literature. This information is necessary to understand if and how such mergers and acquisitions can be a factor in drug shortages and increasing prices. Data on completed merger and acquisition deals that had a generic drug company being taken over (i.e. 'target') were extracted from Bloomberg Finance L.P. The number and announced value of deals are presented globally, for the United States, and globally excluding the United States annually from 1995 to 2016 in United States dollars. Generic drug companies comprised 9.3% of the value of all deals with pharmaceutical targets occurring from 1995 to 2016. Globally, in 1995 there were no deals, in 2014 there were 22 deals worth $1.86 billion, in 2015 there were 34 deals totalling $33.56 billion, and in 2016 there were 42 deals worth in excess of $44 billion. This substantial increase was partially attributed to Teva's 2016 acquisition of Allergan's generic drug business. The surge in mergers and acquisitions for 2015/16 was driven by deals in the United States, where they represented 89.7% of the dollar value of deals in those years. The recent blitz in mergers and acquisitions signals that the generic drug industry is undergoing a transformation, especially in the United States. This restructuring can negatively affect the level of competition that might impact prices and shortages for some products, emphasizing the importance of updating regulations and procurement policies.

  13. Synergic motives and economic success of mergers of Czech companies

    Directory of Open Access Journals (Sweden)

    Jaroslav Sedláček

    2013-01-01

    Full Text Available One of the motives for mergers and acquisitions is the synergy effect, which can take several forms. This paper tries to find out whether mergers implemented at the Czech market bring positive or negative synergies. The basis of our investigation is the database of the companies that implemented a merger within 2001–2009; out of these, the companies that published their financial statements in a digitalized form were selected. We monitored the development of six indicators characterizing the economic status of a company. The values of these indicators were compared for all participating companies before the merger and for the successor company three years after the merger. The hypotheses were formulated so that they expressed an expectation of a positive synergy brought about by mergers. However, hypothesis testing has not provided a clear result. A positive effect of a merger on the key indicator of net assets, whose growth means an increase in the accounting value of the company after the merger, has been proved for small and medium-sized companies only. The effect of mergers on the increase in indicators has been confirmed for retained earnings from past years and personal costs. Further research will concentrate on the relations between the indicators with the aim to create an integral indicator for the economic success of mergers.

  14. Financial Synergy in Mergers and Acquisitions in Saudi Arabia

    Directory of Open Access Journals (Sweden)

    Basmah Al Qudaiby (Basmah, A. Q.,

    2013-11-01

    Full Text Available Businesses today consider mergers and acquisitions a new strategy for their company’s growth. Companies aim to grow through sales’ increase, assets purchase, profits’ accumulation and market share gains. The better way for achieving these targets is by getting into either a Merger or an Acquisition. As a matter of fact, growth through mergers and acquisitions has been a critical part of the success of many companies operating in the new economy. Mergers and Acquisitions are an important factor in building up market capitalization. Based on three detailed and in depth structured interviews with major Saudi Arabian banks it has been found that, Mergers motivated by economies of scale should be approached cautiously. Companies should also approach vertical mergers cautiously because it is often difficult to gain synergy through a vertical merger and firms should also seek out mergers which allow the firm to acquire specialized knowledge. It has also been found that the firms should look for mergers that increase market power and avoid unrelated or conglomerate mergers.

  15. HaloSat - A CubeSat to Study the Hot Galactic Halo

    Science.gov (United States)

    Kaaret, Philip; Jahoda, Keith; Dingwall, Brenda

    2014-08-01

    Observations fail to locate about half of the baryons required in cosmology. One possible reservoir of missing baryons associated with our Milky Way galaxy is an extended halo of X-ray emitting gas at temperatures of several million degrees. We describe a CubeSat capable of measuring the oxygen line emission from the hot, Galactic halo. HaloSat will provide an unprecedented, all sky map of the emission lines of O VII and O VIII. This will improve our understanding of the quantity and distribution of hot gas in the Milky Way and also of solar wind charge exchange interactions within the solar system. The mission can be accomplished at modest cost.

  16. Nuclear halo and its related reactions

    International Nuclear Information System (INIS)

    Zhang Huanqiao

    2005-01-01

    In order to search proton halo, the reaction cross sections of 27,28 P, 29 S and the corresponding isotones on Si target were measured at intermediate energies. The measured reaction cross sections of the N=12 and 13 isotones show an abrupt increase at Z=15. The experimental results for the isotones with Z=14 as well as 28 P can be well described by the modified Glauber theory of the optical limit approach. The enhancement of the reaction cross sections for 28 P could be explained in the modified Glauber theory with an enlarged core. Theoretical analysis with the modified Glauber theory of the optical limit and few-body approaches underpredicted the experimental data of 27 P. Our theoretical analysis shows that an enlarged core together with proton halo is probably the mechanism responsible for the enhancement of the cross sections for the reaction of 27 P+ 28 Si. In addition, we find from the experimental results that 29 S may have a moderate proton halo structure. Except the nuclei near or at drop-lines, halo may appear in the excited states of stable nuclei. By means of the asymptotic normalization coefficients (ANC's) extracted from transfer reactions of 11 B(d, p) 12 B, 12 C(d, p) 13 C, and H( 6 He, n) 6 Li, we have verified that the second ( Jπ = 2 - ) and third (Jπ = 1 - ) excited states in 12 B and the first (Jπ =1/2 + ) excited state in 13 C are the neutron halo states, while the second excited state (3.56 MeV, Jπ = 0 + ) in 6 Li is a proton-neutron halo state. We have proposed a procedure to extract the probability for valence particle being out of the binding potential from the measured nuclear asymptotic normalization coefficients. With this procedure, available data regarding the nuclear halo candidates are systematically analyzed and a number of halo nuclei are confirmed. Based on these results we have got a much relaxed condition for nuclear halo occurrence. Furthermore, we have presented the scaling laws for the dimensionless quantity 2 >/R 2 of

  17. The “Building Blocks” of Stellar Halos

    Directory of Open Access Journals (Sweden)

    Kyle A. Oman

    2017-08-01

    Full Text Available The stellar halos of galaxies encode their accretion histories. In particular, the median metallicity of a halo is determined primarily by the mass of the most massive accreted object. We use hydrodynamical cosmological simulations from the apostle project to study the connection between the stellar mass, the metallicity distribution, and the stellar age distribution of a halo and the identity of its most massive progenitor. We find that the stellar populations in an accreted halo typically resemble the old stellar populations in a present-day dwarf galaxy with a stellar mass ∼0.2–0.5 dex greater than that of the stellar halo. This suggests that had they not been accreted, the primary progenitors of stellar halos would have evolved to resemble typical nearby dwarf irregulars.

  18. Mergers and acquisitions for the radiologist.

    Science.gov (United States)

    Fleishon, Howard B

    2008-05-01

    In 2006 and the first half of 2007, the rapid pace of global activity contributed to the popularity of mergers and acquisitions (M&A). In fact, the medical imaging industry has a significant history in M&A as well. Along with the expectation of continued growth in medical imaging utilization and other industry trends, radiologists may become more involved in M&A transactions. There is little in the radiology literature dealing with the logistics and pitfalls of M&A. This article is an introduction for radiologists who might consider buying or selling their practices or merging with strategic partners. Although there are significant differences in the approaches of buy or sell situations compared with mergers, they do share several concepts that are outlined. One key to success in M&A transactions is the "process" or approach, which is described with some practical guidelines. Some basic terms and suggestions are also presented for reference.

  19. Kilonova Counterparts of Binary Neutron Star Mergers

    Science.gov (United States)

    Metzger, Brian

    2018-01-01

    The merger of a binary neutron star is accompanied by the ejection of neutron-rich matter into space at velocities up to several tenths that of light, which synthesizes rare heavy isotopes through the rapid neutron capture process (r-process). The radioactive decay of these nuclei was predicted by Metzger et al. (2010) to power an optical transient roughly 1000 times more luminous than a classical nova (a "kilonova"), which is among the most promising electromagnetic counterparts to accompany gravitational wave signal from the merger. I will describe how the luminosities, color, and spectra of the kilonova emission inform the properties of the merging binary (neutron star masses/radii and inclination angle) and the long sought origin of the heaviest elements in the Universe. Results will be discussed in the context of recent discoveries by Advanced LIGO/Virgo.

  20. Estimating the potential gains from mergers

    DEFF Research Database (Denmark)

    Bogetoft, Peter; Wang, Dexiang

    2005-01-01

    We introduce simple production economic models to estimate the potential gains from mergers. We decompose the gains into technical ef¿ciency, size (scale) and harmony (mix) gains, and we discuss alternative ways to capture these gains. We propose to approximate the production processes using...... the non-parametric. Data Envelopment Analysis (DEA) approach, and we use the resulting operational approach to estimate the potential gains from merging agricultural extension of¿ces in Denmark....

  1. Maximum Redshift of Gravitational Wave Merger Events

    Science.gov (United States)

    Koushiappas, Savvas M.; Loeb, Abraham

    2017-12-01

    Future generations of gravitational wave detectors will have the sensitivity to detect gravitational wave events at redshifts far beyond any detectable electromagnetic sources. We show that if the observed event rate is greater than one event per year at redshifts z ≥40 , then the probability distribution of primordial density fluctuations must be significantly non-Gaussian or the events originate from primordial black holes. The nature of the excess events can be determined from the redshift distribution of the merger rate.

  2. ACEC and AES Merger Workshop Report

    Science.gov (United States)

    1992-03-01

    AD-A261 194 . WL-TR-93- 1004 ACEC & AES MERGER WORKSHOP REPORT RAYMOND SZYMANSKI WRIGHT LABORATORY AVOINICS DIRECTORATE WL/AAAF-2 WRIGHT-PATTERSON...34-_’ WýAYMOND SZYMANSKI TA 28 WU 53 E--FOI1MJNG ORGANJZATiK2;J AA\\TlES ,’,D -ýDRESS(E(- £’C:.i-NG ORGANIZATION WRIGHT LABORATORY -;EPOT NUMBER AVOINICS

  3. GRAVITATIONAL MEMORY IN BINARY BLACK HOLE MERGERS

    International Nuclear Information System (INIS)

    Pollney, Denis; Reisswig, Christian

    2011-01-01

    In addition to the dominant oscillatory gravitational wave signals produced during binary inspirals, a non-oscillatory component arises from the nonlinear 'memory' effect, sourced by the emitted gravitational radiation. The memory grows significantly during the late-inspiral and merger, modifying the signal by an almost step-function profile, and making it difficult to model by approximate methods. We use numerical evolutions of binary black holes (BHs) to evaluate the nonlinear memory during late-inspiral, merger, and ringdown. We identify two main components of the signal: the monotonically growing portion corresponding to the memory, and an oscillatory part which sets in roughly at the time of merger and is due to the BH ringdown. Counterintuitively, the ringdown is most prominent for models with the lowest total spin. Thus, the case of maximally spinning BHs anti-aligned to the orbital angular momentum exhibits the highest signal-to-noise ratio (S/N) for interferometric detectors. The largest memory offset, however, occurs for highly spinning BHs, with an estimated value of h tot 20 ≅ 0.24 in the maximally spinning case. These results are central to determining the detectability of nonlinear memory through pulsar timing array measurements.

  4. Experimentally, How Dark Are Black Hole Mergers?

    Energy Technology Data Exchange (ETDEWEB)

    Annis, James [Fermilab; Soares-Santos, Marcelle [Fermilab

    2016-09-29

    The first Advanced LIGO observing run detected two black hole merger events with confidence and likely a third. Many groups organized to followup the events in the optical even though the strong theoretical prior that no optical emission should be seen. We carry through the logic of this by asking about the experimental upper limits to the optical light from Advanced LIGO black hole mergere events. We inventory the published optical searches for transient events associated with the black hole mergers. We describe the factors that go into a formal limit on the visibility of an event (sky area coverage, the coverage factor of the camera, the fraction of sky not covered by intervening objects), and list what is known from the literature of the followup teams quantitative assessment of each factor. Where possible we calculate the total probability from each group that the source was imaged. The calculation of confidence level is reviewed for the case of no background. We find that an experimental 95% upper limit on the magnitude of a black hole requires the sum of the total probabilities over all events to be more than 3. In the first Advanced LIGO observing run we were far from reaching that threshold.

  5. Gravitational waves from primordial black hole mergers

    Energy Technology Data Exchange (ETDEWEB)

    Raidal, Martti; Vaskonen, Ville; Veermäe, Hardi, E-mail: martti.raidal@cern.ch, E-mail: ville.vaskonen@kbfi.ee, E-mail: hardi.veermae@cern.ch [NICPB, Rävala 10, 10143 Tallinn (Estonia)

    2017-09-01

    We study the production of primordial black hole (PBH) binaries and the resulting merger rate, accounting for an extended PBH mass function and the possibility of a clustered spatial distribution. Under the hypothesis that the gravitational wave events observed by LIGO were caused by PBH mergers, we show that it is possible to satisfy all present constraints on the PBH abundance, and find the viable parameter range for the lognormal PBH mass function. The non-observation of a gravitational wave background allows us to derive constraints on the fraction of dark matter in PBHs, which are stronger than any other current constraint in the PBH mass range 0.5−30 M {sub ⊙}. We show that the predicted gravitational wave background can be observed by the coming runs of LIGO, and its non-observation would indicate that the observed events are not of primordial origin. As the PBH mergers convert matter into radiation, they may have interesting cosmological implications, for example in the context of relieving the tension between high and low redshift measurements of the Hubble constant. However, we find that these effects are suppressed as, after recombination, no more that 1% of dark matter can be converted into gravitational waves.

  6. Cosmic Collisions: Galaxy Mergers and Evolution

    Science.gov (United States)

    Trouille, Laura; Willett, Kyle; Masters, Karen; Lintott, Christopher; Whyte, Laura; Lynn, Stuart; Tremonti, Christina A.

    2014-08-01

    Over the years evidence has mounted for a significant mode of galaxy evolution via mergers. This process links gas-rich, spiral galaxies; starbursting galaxies; active galactic nuclei (AGN); post-starburst galaxies; and gas-poor, elliptical galaxies, as objects representing different phases of major galaxy mergers. The post-starburst phase is particularly interesting because nearly every galaxy that evolves from star-forming to quiescent must pass through it. In essence, this phase is a sort of galaxy evolution “bottleneck” that indicates that a galaxy is actively evolving through important physical transitions. In this talk I will present the results from the ‘Galaxy Zoo Quench’ project - using post-starburst galaxies to place observational constraints on the role of mergers and AGN activity in quenching star formation. `Quench’ is the first fully collaborative research project with Zooniverse citizen scientists online; engaging the public in all phases of research, from classification to data analysis and discussion to writing the article and submission to a refereed journal.

  7. The benefit of mergers and taking-overs

    International Nuclear Information System (INIS)

    Nillesen, P.H.L.; Keats, K.; Pollitt, M.

    2001-01-01

    Electricity companies can realize considerable efficiency benefits through mergers by using management skills of a more efficient company and the resulting changed mix of inputs. In this article a pattern of thought is introduced by means of which cost savings of mergers can be identified in a strategic and scientific way. Such a way of thinking can be applied, e.g. in a cash flow analysis, in the valuation of companies and in the merger and taking-over process. 7 refs

  8. Value Creation through ICT Integration in Merger & Acquisition Processes

    DEFF Research Database (Denmark)

    Holm Larsen, Michael

    2005-01-01

    As deals are becoming more complex, and as technology, and the people supporting it, are becoming key drivers of merger and acquisition processes, planning of information and communication technologies in early stages of the integration process is vital to the realization of benefits of an Merger...... & Acquisition process. This statement is substantiated through review of literature from academics as well as practitioners, and case exemplifications of the financial service organization, the Nordea Group. Keywords: ICT Integration, Mergers & Acquisitions, Nordea Group....

  9. Strategy and Tactics of International Mergers and Acquisitions

    Directory of Open Access Journals (Sweden)

    Denys Kiriakov

    2011-12-01

    Full Text Available The article reviews contemporary strategy and tactics issues in terms of international mergers and acquisitions, along with displaying cyclical waves of mergers and acquisitions over the last century as well as motivation thereof. Five strategies adhered to by international companies initiating conclusion of such agreements as well as challenges accompanying execution thereof have been analyzed. Modern strategic and tactical tools of international mergers and acquisitions process management have been researched on exemplary buyer (a corporation case-study.

  10. An Empirical Analysis of Post-Merger Organizational Integration

    OpenAIRE

    Smeets, Valerie Anne Rolande; Gibbs, Michael; Ierulli, Kathryn

    2015-01-01

    We study post-merger organizational integration using linked employer-employee data. Integration is implemented by reassigning a small number of high skilled workers, especially in R&D and management. Workforce mixing is concentrated to establishments set up after merger rather than to previously existing establishments. Worker turnover is high after merger, but new hiring yields stable total employment. Target employees have higher turnover and reassignment, particularly if the target fi...

  11. 24 CFR 242.67 - New corporations, subsidiaries, affiliations, and mergers.

    Science.gov (United States)

    2010-04-01

    ..., affiliations, and mergers. 242.67 Section 242.67 Housing and Urban Development Regulations Relating to Housing... Reporting, and Financial Requirements § 242.67 New corporations, subsidiaries, affiliations, and mergers... written approval for all future mergers. ...

  12. When what we get is not what we want-The role of implemented versus desired merger patterns in support for mergers.

    NARCIS (Netherlands)

    Täuber, Susanne; Gleibs, Ilka H.; Viki, G. Tendayi; Giessner, Steffen R.

    2013-01-01

    Integrating an intergroup perspective on mergers with discrepancy theories, we argue that merger partners aim for merger patterns that benefit their group’s standing best. Importantly, we hypothesize and show that the discrepancy between what merger partners want and what they get affects outcomes

  13. Clustering dark energy and halo abundances

    Science.gov (United States)

    Batista, Ronaldo C.; Marra, Valerio

    2017-11-01

    Within the standard paradigm, dark energy is taken as a homogeneous fluid that drives the accelerated expansion of the universe and does not contribute to the mass of collapsed objects such as galaxies and galaxy clusters. The abundance of galaxy clusters—measured through a variety of channels—has been extensively used to constrain the normalization of the power spectrum: it is an important probe as it allows us to test if the standard ΛCDM model can indeed accurately describe the evolution of structures across billions of years. It is then quite significant that the Planck satellite has detected, via the Sunyaev-Zel'dovich effect, less clusters than expected according to the primary CMB anisotropies. One of the simplest generalizations that could reconcile these observations is to consider models in which dark energy is allowed to cluster, i.e., allowing its sound speed to vary. In this case, however, the standard methods to compute the abundance of galaxy clusters need to be adapted to account for the contributions of dark energy. In particular, we examine the case of clustering dark energy—a dark energy fluid with negligible sound speed—with a redshift-dependent equation of state. We carefully study how the halo mass function is modified in this scenario, highlighting corrections that have not been considered before in the literature. We address modifications in the growth function, collapse threshold, virialization densities and also changes in the comoving scale of collapse and mass function normalization. Our results show that clustering dark energy can impact halo abundances at the level of 10%-30%, depending on the halo mass, and that cluster counts are modified by about 30% at a redshift of unity.

  14. Fast low-energy halo-to-halo transfers between Sun–planet systems

    Directory of Open Access Journals (Sweden)

    Shang Haibin

    2014-04-01

    Full Text Available In this paper, the problem of fast low-energy halo-to-halo transfers between Sun–planet systems is discussed under ephemeris constraints. According to the structure of an invariant manifold, employing an invariant manifold and planetary gravity assist to save fuel consumption is analyzed from the view of orbital energy. Then, a pseudo-manifold is introduced to replace the invariant manifold in such a way that more transfer opportunities are allowed. Fast escape and capture can be achieved along the pseudo-manifold. Furthermore, a global searching method that is based on patched-models is proposed to find an appropriate transfer trajectory. In this searching method, the trajectory is divided into several segments that can be designed under simple dynamical models, and an analytical algorithm is developed for connecting the segments. Earth–Mars and Earth–Venus halo-to-halo transfers are designed to demonstrate the proposed approach. Numerical results show that the transfers that combine the pseudo-manifolds and planetary gravity assist can offer significant fuel consumption and flight time savings over traditional transfer schemes.

  15. A BARYONIC EFFECT ON THE MERGER TIMESCALE OF GALAXY CLUSTERS

    International Nuclear Information System (INIS)

    Zhang, Congyao; Yu, Qingjuan; Lu, Youjun

    2016-01-01

    Accurate estimation of the merger timescales of galaxy clusters is important for understanding the cluster merger process and further understanding the formation and evolution of the large-scale structure of the universe. In this paper, we explore a baryonic effect on the merger timescale of galaxy clusters by using hydrodynamical simulations. We find that the baryons play an important role in accelerating the merger process. The merger timescale decreases upon increasing the gas fraction of galaxy clusters. For example, the merger timescale is shortened by a factor of up to 3 for merging clusters with gas fractions of 0.15, compared with the timescale obtained with 0 gas fractions. The baryonic effect is significant for a wide range of merger parameters and is particularly more significant for nearly head-on mergers and high merging velocities. The baryonic effect on the merger timescale of galaxy clusters is expected to have an impact on the structure formation in the universe, such as the cluster mass function and massive substructures in galaxy clusters, and a bias of “no-gas” may exist in the results obtained from the dark matter-only cosmological simulations

  16. Using Black Hole Mergers to Explore Structure Formation

    Science.gov (United States)

    Alicea-Munoz, E.; Miller, M. Coleman

    2009-01-01

    Observations of gravitational waves from massive black hole mergers will open a new window into the era of structure formation in the early universe. Past efforts have concentrated on calculating merger rates using different physical assumptions, resulting in merger rate estimates that span a wide range (0.1 - 10(exp 4) mergers/year). We develop a semi-analytical, phenomenological model of massive black hole mergers that includes plausible combinations of several physical parameters, which we then turn around to determine how well observations with the Laser Interferometer Space Antenna (LISA) will be able to enhance our understanding of the universe during the critical z approximately equal to 5-30 epoch. Our approach involves generating synthetic LISA observable data (total BH masses, BH mass ratios, redshifts, merger rates), which are then analyzed using a Markov Chain Monte Carlo method, thus finding constraints for the physical parameters of the mergers. We find that our method works well at estimating merger parameters and that the number of merger events is a key discriminant among models, therefore making our method robust against observational uncertainties. Our approach can also be extended to more physically-driven models and more general problems in cosmology. This work is supported in part by the Cooperative Education Program at NASA/GSFC.

  17. Role of Human Resources in the Mergers and Acquisitions Processes

    Directory of Open Access Journals (Sweden)

    Anna Szewczyk

    2007-06-01

    Full Text Available The human resources are one of the most important topics when you talk about the value and importance of a company itself. The article tries to show the different aspects where the human resource affects a merger in the different states of a merger process, especially to the pre-merger-phase, and to which problems it can lead when you not pay attention to it. Finally the question, which is indeed the most important aim concerning mergers namely: how and in which degree the human resource effects the goodwill, is tried to answer.

  18. Maximizing value through mergers and acquisitions in the petroleum industry

    International Nuclear Information System (INIS)

    Anon.

    1996-01-01

    An 'Insight' conference was held in February 1996 to help understand the economics of mergers and acquisitions in the petroleum industry. Speaking notes, overhead projection slides and full text of the presentations (where available) from seven contributors at the conference were combined in this volume of proceedings. Specific topics of discussion included a review of the current scene in mergers and acquisitions, assessing management and employees, optimizing tax advantages, looking for synergies, the value of human perspective in mergers and acquisitions, tips on analyzing the engineering report, and the market's perception of merger and acquisition reporting. tabs., figs

  19. Haloes, molecules and multi-neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Marques Moreno, F.M

    2003-01-01

    Away from the equilibrium between protons and neutrons within stable nuclei, many exotic nuclei exist. Most of the known nuclear properties evolve smoothly with exoticism, but some extreme proton-neutron combinations have revealed during the last decade completely new concepts. They will be illustrated through three examples: the extended and dilute halo formed by very weakly bound neutrons, the molecular-like neutron orbitals found in nuclei exhibiting a clustering, and the recently revived debate on the possible existence of neutral nuclei. The different experimental results will be reviewed, and we will see how several properties of these new phenomena can be well understood within relatively simple theoretical approaches. (author)

  20. Sub-Coulomb fusion with halo nuclei

    International Nuclear Information System (INIS)

    Fekou-Youmbi, V.; Sida, J.L.; Alamanos, N.; Auger, F.; Bazin, D.; Borcea, C.; Cabot, C.; Cunsolo, A.; Foti, A.; Gillibert, A.; Lepine, A.; Lewitowicz, M.; Liguori-Neto, R.; Mittig, W.; Pollacco, E.; Roussel-Chomaz, P.; Volant, C.; Yong Feng, Y.

    1995-01-01

    The nuclear structure of halo nuclei may have strong influence on the fusion cross section at sub-barrier energies. The actual theoretical debate is briefly reviewed and sub-barrier fusion calculations for the system 11 Be+ 238 U are presented. An experimental program on sub-barrier fusion for the systems 7,9,10,11 Be+ 238 U is underway at GANIL. First results with 9 Be and 11 Be beams were obtained using the F.U.S.ION detector. Relative fission cross sections are presented. ((orig.))

  1. Statistics of matter distribution from halo dynamics

    International Nuclear Information System (INIS)

    Bonometto, S.A.; Borgani, S.; Persic, M.; Salucci, P.

    1990-01-01

    The galaxy-background correlation function at short distances is explored by means of the observed disk dynamics of spiral galaxies. Using both the sample of galaxies and the analytical method for dark-to-luminous mass decomposition from optical rotation curves presented by Persic and Salucci (1988, 1990), individual sizes and mean densities are worked out for 42 extended halos as functions of both the intensity and the gradient of the central velocity field. The statistics for the expected density enhancements within given distances from galactic centers shows simple properties which strongly tie galaxy-background and galaxy-galaxy correlation functions. 42 refs

  2. Universal properties of dark matter halos.

    Science.gov (United States)

    Boyarsky, A; Neronov, A; Ruchayskiy, O; Tkachev, I

    2010-05-14

    We discuss the universal relation between density and size of observed dark matter halos that was recently shown to hold on a wide range of scales, from dwarf galaxies to galaxy clusters. Predictions of cold dark matter (ΛCDM) N-body simulations are consistent with this relation. We demonstrate that this property of ΛCDM can be understood analytically in the secondary infall model. Qualitative understanding given by this model provides a new way to predict which deviations from ΛCDM or large-scale modifications of gravity can affect universal behavior and, therefore, to constrain them observationally.

  3. Unitarity Bounds and the Cuspy Halo Problem

    International Nuclear Information System (INIS)

    Hui, Lam

    2001-01-01

    Conventional cold dark matter cosmological models predict cuspy halos which are in apparent conflict with observations. We show that unitarity arguments imply interesting constraints on two proposals to address this problem: collisional dark matter and strongly annihilating dark matter. Efficient scattering in both implies m∼<12 GeV and m∼<25 GeV , respectively. We also show that the strong annihilation in the second scenario implies the presence of elastic scattering. Recent evidence suggests a collisional scenario where the cross section scales inversely with velocity -- we argue superelastic processes are likely involved. Exceptions and implications for searches are discussed

  4. Efficiency Gains and Myopic Antitrust Authority in a Dynamic Merger Game

    OpenAIRE

    MOTTA, Massimo; VASCONCELOS, Helder

    2003-01-01

    This Paper models a sequential merger formation game with endogenous efficiency gains in which every merger has to be submitted for approval to the Antitrust Authority (AA). Two different types of AA are studied: first, a myopic AA, which judges a given merger without considering that subsequent mergers may occur; and, second, a forward-looking AA, which anticipates the ultimate market structure a given merger will lead to. By contrasting the decisions of these two types of AA, merger policy ...

  5. Subhalo demographics in the Illustris simulation: effects of baryons and halo-to-halo variation

    Science.gov (United States)

    Chua, Kun Ting Eddie; Pillepich, Annalisa; Rodriguez-Gomez, Vicente; Vogelsberger, Mark; Bird, Simeon; Hernquist, Lars

    2017-12-01

    We study the abundance of subhaloes in the hydrodynamical cosmological simulation Illustris, which includes both baryons and dark matter in a cold dark matter volume 106.5 Mpc a side. We compare Illustris to its dark-matter only (DMO) analogue, Illustris-Dark and quantify the effects of baryonic processes on the demographics of subhaloes in the host mass range 1011-3 × 1014 M⊙. We focus on both the evolved (z = 0) subhalo cumulative mass functions (SHMF) and the statistics of subhaloes ever accreted, i.e. infall SHMF. We quantify the variance in subhalo abundance at fixed host mass and investigate the physical reasons responsible for such scatter. We find that in Illustris, baryonic physics impacts both the infall and z = 0 subhalo abundance by tilting the DMO function and suppressing the abundance of low-mass subhaloes. The breaking of self-similarity in the subhalo abundance at z = 0 is enhanced by the inclusion of baryonic physics. The non-monotonic alteration of the evolved subhalo abundances can be explained by the modification of the concentration-mass relation of Illustris hosts compared to Illustris-Dark. Interestingly, the baryonic implementation in Illustris does not lead to an increase in the halo-to-halo variation compared to Illustris-Dark. In both cases, the normalized intrinsic scatter today is larger for Milky Way-like haloes than for cluster-sized objects. For Milky Way-like haloes, it increases from about eight per cent at infall to about 25 per cent at the current epoch. In both runs, haloes of fixed mass formed later host more subhaloes than early formers.

  6. 77 FR 16264 - Manufacturer of Controlled Substances, Notice of Registration; Halo Pharmaceutical Inc.

    Science.gov (United States)

    2012-03-20

    ... Enforcement Administration Manufacturer of Controlled Substances, Notice of Registration; Halo Pharmaceutical... FR 77850, Halo Pharmaceutical Inc., 30 North Jefferson Road, Whippany, New Jersey 07981, made... determined that the registration of Halo Pharmaceutical Inc. to manufacture the listed basic classes of...

  7. 77 FR 75672 - Manufacturer of Controlled Substances, Notice of Registration, Halo Pharmaceutical, Inc.

    Science.gov (United States)

    2012-12-21

    ... Enforcement Administration Manufacturer of Controlled Substances, Notice of Registration, Halo Pharmaceutical... 47114, Halo Pharmaceutical, Inc., 30 North Jefferson Road, Whippany, New Jersey 07981, made application... determined that the registration of Halo Pharmaceutical, Inc., to manufacture the listed basic classes of...

  8. Alternative techniques for beam halo measurements

    CERN Document Server

    Welsch, CP; Burel, B; Lefèvre, T; Chapman, T; Pilon, MJ

    2006-01-01

    In future high intensity, high energy accelerators it must be ensured that particle losses are minimized, as activation of the vacuum chambers or other components makes maintenance and upgrade work time consuming and costly. It is imperative to have a clear understanding of the mechanisms that can lead to halo formation and to have the possibility to test available theoretical models with an adequate experimental setup. Measurements based on optical transition radiation (OTR) are a well-established technique for measurements of the transverse beam profile. However, in order to be suitable for halo measurements as well, the dynamic range of the final image acquisition system needs to be high, being able to cover at least five orders of magnitude in intensity changes. Here, the performance of a standard acquisition system as it is used in the CLIC test facility (CTF3) is compared to a step-by-step measurement with a small movable photo multiplier tube and an innovative camera system based on charge injection de...

  9. The CMS Beam Halo Monitor Detector System

    CERN Document Server

    CMS Collaboration

    2015-01-01

    A new Beam Halo Monitor (BHM) detector system has been installed in the CMS cavern to measure the machine-induced background (MIB) from the LHC. This background originates from interactions of the LHC beam halo with the final set of collimators before the CMS experiment and from beam gas interactions. The BHM detector uses the directional nature of Cherenkov radiation and event timing to select particles coming from the direction of the beam and to suppress those originating from the interaction point. It consists of 40 quartz rods, placed on each side of the CMS detector, coupled to UV sensitive PMTs. For each bunch crossing the PMT signal is digitized by a charge integrating ASIC and the arrival time of the signal is recorded. The data are processed in real time to yield a precise measurement of per-bunch-crossing background rate. This measurement is made available to CMS and the LHC, to provide real-time feedback on the beam quality and to improve the efficiency of data taking. In this talk we will describ...

  10. The CMS Beam Halo Monitor Detector System

    CERN Document Server

    Stifter, Kelly

    2015-01-01

    A new Beam Halo Monitor (BHM) detector system has been installed in the CMS cavern to measure the machine-induced background (MIB) from the LHC. This background originates from interactions of the LHC beam halo with the final set of collimators before the CMS experiment and from beam gas interactions. The BHM detector uses the directional nature of Cherenkov radiation and event timing to select particles coming from the direction of the beam and to supress those originating from the interaction point. It consists of 40 quartz rods, placed on each side of the CMS detector, coupled to UV sensitive PMTs. For each bunch crossing the PMT signal is digitized by a charge integrating ASIC and the arrival time of the signal is recorded. The data are processed in real time to yield a precise measurement of per-bunch-crossing background rate. This measurement is made available to CMS and the LHC, to provide real-time feedback on the beam quality and to improve the efficiency of data taking. In this talk we will descri...

  11. Eccentric binary black-hole mergers: The transition from inspiral to plunge in general relativity

    International Nuclear Information System (INIS)

    Sperhake, Ulrich; Bruegmann, Bernd; Berti, Emanuele; Cardoso, Vitor; Gonzalez, Jose A.; Ansorg, Marcus

    2008-01-01

    We study the transition from inspiral to plunge in general relativity by computing gravitational waveforms of nonspinning, equal-mass black-hole binaries. We consider three sequences of simulations, starting with a quasicircular inspiral completing 1.5, 2.3 and 9.6 orbits, respectively, prior to coalescence of the holes. For each sequence, the binding energy of the system is kept constant and the orbital angular momentum is progressively reduced, producing orbits of increasing eccentricity and eventually a head-on collision. We analyze in detail the radiation of energy and angular momentum in gravitational waves, the contribution of different multipolar components and the final spin of the remnant, comparing numerical predictions with the post-Newtonian approximation and with extrapolations of point-particle results. We find that the motion transitions from inspiral to plunge when the orbital angular momentum L=L crit ≅0.8M 2 . For L crit the radiated energy drops very rapidly. Orbits with L≅L crit produce our largest dimensionless Kerr parameter for the remnant, j=J/M 2 ≅0.724±0.13 (to be compared with the Kerr parameter j≅0.69 resulting from quasicircular inspirals). This value is in good agreement with the value of 0.72 reported in [I. Hinder, B. Vaishnav, F. Herrmann, D. Shoemaker, and P. Laguna, Phys. Rev. D 77, 081502 (2008).]. These conclusions are quite insensitive to the initial separation of the holes, and they can be understood by extrapolating point-particle results. Generalizing a model recently proposed by Buonanno, Kidder and Lehner [A. Buonanno, L. E. Kidder, and L. Lehner, Phys. Rev. D 77, 026004 (2008).] to eccentric binaries, we conjecture that (1) j≅0.724 is close to the maximal Kerr parameter that can be obtained by any merger of nonspinning holes, and (2) no binary merger (even if the binary members are extremal Kerr black holes with spins aligned to the orbital angular momentum, and the inspiral is highly eccentric) can violate the

  12. INSPIRALLING SUPERMASSIVE BLACK HOLES: A NEW SIGNPOST FOR GALAXY MERGERS

    International Nuclear Information System (INIS)

    Comerford, Julia M.; Gerke, Brian F.; Newman, Jeffrey A.; Davis, Marc; Yan, Renbin; Cooper, Michael C.; Coil, Alison L.; Faber, S. M.; Koo, David C.; Rosario, D. J.; Dutton, Aaron A.

    2009-01-01

    We present a new technique for observationally identifying galaxy mergers spectroscopically rather than through host galaxy imaging. Our technique exploits the dynamics of supermassive black holes (SMBHs) powering active galactic nuclei (AGNs) in merger-remnant galaxies. Because structure in the universe is built up through galaxy mergers and nearly all galaxies host a central SMBH, some galaxies should possess two SMBHs near their centers as the result of a recent merger. These SMBHs spiral to the center of the resultant merger-remnant galaxy, and one or both of the SMBHs may power AGNs. Using the DEEP2 Galaxy Redshift Survey, we have examined 1881 red galaxies, of which 91 exhibit [O III] and Hβ emission lines indicative of Seyfert 2 activity. Of these, 32 AGNs have [O III] emission-line redshifts significantly different from the redshifts of the host galaxies' stars, corresponding to velocity offsets of ∼50 km s -1 to ∼300 km s -1 . Two of these AGNs exhibit double-peaked [O III] emission lines, while the remaining 30 AGNs each exhibit a single set of velocity-offset [O III] emission lines. After exploring a variety of physical models for these velocity offsets, we argue that the most likely explanation is inspiralling SMBHs in merger-remnant galaxies. Based on this interpretation, we find that roughly half of the red galaxies hosting AGNs are also merger remnants, which implies that mergers may trigger AGN activity in red galaxies. The AGN velocity offsets we find imply a merger fraction of ∼30% and a merger rate of ∼3 mergers Gyr -1 for red galaxies at redshifts 0.34 < z < 0.82.

  13. Merger market power analysis: Pacific Enterprises and Enova Corporation

    International Nuclear Information System (INIS)

    Bailey, S.

    1999-01-01

    The Pacific Enterprises - Enova (PE-Enova) merger may be viewed as an example of the new breed of gas and power 'convergence' mergers. The merger involved the combination of a large gas distribution utility and a contiguous gas and electric utility located in Southern California. As with most mergers, the PE-Enova merger was proposed to federal and state regulators as an opportunity to achieve ratepayer savings. However, the merger also presented an issue of vertical market power involving the substantial electric generation capacity served by Southern California Gas Company (SoCalGas) and its potential impact on electric market prices, and the associated revenues for generation assets owned by San Diego Gas and Electric (SDGandE). In order for the merger to proceed, the approval of at least five separate State and federal regulators would be required. Although much of the attention of state regulators, proponents, and intervenors surrounded the division of synergy savings between ratepayers and shareholders, the analysis of the potential for market power abuse was extensive. Intervenors presented numerous complex arguments regarding the potential adverse effects of the merger on competition. In particular, intervenors argued that the combined company would manipulate its storage and transport operations to influence the delivered price of gas to California generators, and therefore, the price of power in the wholesale electric market. The arguments surrounding the existence and impacts of market power in this case are of interest in the understanding the nature and complexity of factors that may be considered in evaluating mergers. The proceeding also provides insight into how regulators are grappling with market power issues associated with convergence mergers, and weigh merger costs and benefits

  14. SECULAR DAMPING OF STELLAR BARS IN SPINNING DARK MATTER HALOS

    Energy Technology Data Exchange (ETDEWEB)

    Long, Stacy; Shlosman, Isaac [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506-0055 (United States); Heller, Clayton [Department of Physics, Georgia Southern University, Statesboro, GA 30460 (United States)

    2014-03-01

    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 momentum exchange between the disk and the halo facilitated by the bar. For the first time we have demonstrated that a dark matter halo can emit and not purely absorb angular momentum. Although the halo as a whole is not found to emit, the net transfer of angular momentum from the disk to the halo is significantly reduced or completely eliminated. The paradigm shift implies that the accepted view that disks serve as sources of angular momentum and halos serve as sinks must be revised. Halos with λ ≳ 0.03 are expected to form a substantial fraction, based on the lognormal distribution of λ. The dependence of secular bar evolution on halo spin, therefore, implies profound corollaries for the cosmological evolution of galactic disks.

  15. A two-point correlation function for Galactic halo stars

    NARCIS (Netherlands)

    Cooper, A. P.; Cole, S.; Frenk, C. S.; Helmi, A.

    2011-01-01

    We describe a correlation function statistic that quantifies the amount of spatial and kinematic substructure in the stellar halo. We test this statistic using model stellar halo realizations constructed from the Aquarius suite of six high-resolution cosmological N-body simulations, in combination

  16. A 500 PARSEC HALO SURROUNDING THE GALACTIC GLOBULAR NGC 1851

    NARCIS (Netherlands)

    Olszewski, Edward W.; Saha, Abhijit; Knezek, Patricia; Subramaniam, Annapurni; de Boer, Thomas; Seitzer, Patrick

    2009-01-01

    Using imaging that shows 4 mag of main-sequence stars, we have discovered that the Galactic globular cluster NGC 1851 is surrounded by a halo that is visible from the tidal radius of 700 arcsec (41 pc) to more than 4500 arcsec (> 250 pc). This halo is symmetric and falls in density as a power law of

  17. Remarks on the spherical scalar field halo in galaxies

    International Nuclear Information System (INIS)

    Nandi, Kamal K.; Valitov, Ildar; Migranov, Nail G.

    2009-01-01

    Matos, Guzman, and Nunez proposed a model for the galactic halo within the framework of scalar field theory. We argue that an analysis involving the full metric can reveal the true physical nature of the halo only when a certain condition is maintained. We fix that condition and also calculate its impact on observable parameters of the model.

  18. Is the dark halo of our Galaxy spherical?

    NARCIS (Netherlands)

    Helmi, A

    2004-01-01

    It has been recently claimed that the confined structure of the debris from the Sagittarius dwarf implies that the dark matter halo of our Galaxy should be nearly spherical, in strong contrast with predictions from cold dark matter simulations, where dark haloes are found to have typical density

  19. Depth-Dependent Halos : Illustrative Rendering of Dense Line Data

    NARCIS (Netherlands)

    Everts, Maarten H.; Bekker, Henk; Roerdink, Jos B.T.M.; Isenberg, Tobias

    2009-01-01

    We present a technique for the illustrative rendering of 3D line data at interactive frame rates. We create depth-dependent halos around lines to emphasize tight line bundles while less structured lines are de-emphasized. Moreover, the depth-dependent halos combined with depth cueing via line width

  20. The prolate dark matter halo of the Andromeda galaxy

    International Nuclear Information System (INIS)

    Hayashi, Kohei; Chiba, Masashi

    2014-01-01

    We present new limits on the global shape of the dark matter halo in the Andromeda galaxy using and generalizing non-spherical mass models developed by Hayashi and Chiba and compare our results with theoretical predictions of cold dark matter (CDM) models. This is motivated by the fact that CDM models predict non-spherical virialized dark halos, which reflect the process of mass assembly in the galactic scale. Applying our models to the latest kinematic data of globular clusters and dwarf spheroidal galaxies in the Andromeda halo, we find that the most plausible cases for Andromeda yield a prolate shape for its dark halo, irrespective of assumed density profiles. We also find that this prolate dark halo in Andromeda is consistent with theoretical predictions in which the satellites are distributed anisotropically and preferentially located along major axes of their host halos. It is a reflection of the intimate connection between galactic dark matter halos and the cosmic web. Therefore, our result is profound in understanding internal dynamics of halo tracers in Andromeda, such as orbital evolutions of tidal stellar streams, which play important roles in extracting the abundance of CDM subhalos through their dynamical effects on stream structures.

  1. A Hidden Radio Halo in the Galaxy Cluster A1682?

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... High sensitivity observations of radio halos in galaxy clusters at frequencies ≤ 330 MHz are still relatively rare, and very little is known compared to the classical 1.4 GHz images. The few radio halos imaged down to 150–240 MHz show a considerable spread in size, morphology and spectral properties.

  2. Characteristics of halo current in JT-60U

    International Nuclear Information System (INIS)

    Neyatani, Y.; Nakamura, Y.; Yoshino, R.; Hatae, T.

    2001-01-01

    Halo currents and their toroidal peaking factor (TPF) have been measured in JT-60U by Rogowski coil type halo current sensors. The electron temperature in the halo region was around 10 eV at 1 ms before the timing of the maximum halo current. The maximum TPF *I h /I p0 was 0.52 in the operational range of I p =0.7∼1.8MA, B T =2.2∼3.5T, including ITER design parameters of κ>1.6 and q 95 =3, which was lower than that of the maximum value of ITER data base (0.75). The magnitude of halo currents tended to decrease with the increase in stored energy just before the energy quench and with the line integrated electron density at the time of the maximum halo current. A termination technique in which the current channel remains stationary was useful to avoid halo current generation. Intense neon gas puffing during the VDE was effective for reducing the halo currents. (author)

  3. The f ( R ) halo mass function in the cosmic web

    Energy Technology Data Exchange (ETDEWEB)

    Braun-Bates, F. von; Winther, H.A.; Alonso, D.; Devriendt, J., E-mail: francesca.vonbraun-bates@physics.ox.ac.uk, E-mail: hans.a.winther@physics.ox.ac.uk, E-mail: david.alonso@physics.ox.ac.uk, E-mail: julien.devriendt@physics.ox.ac.uk [Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom)

    2017-03-01

    An important indicator of modified gravity is the effect of the local environment on halo properties. This paper examines the influence of the local tidal structure on the halo mass function, the halo orientation, spin and the concentration-mass relation. We use the excursion set formalism to produce a halo mass function conditional on large-scale structure. Our simple model agrees well with simulations on large scales at which the density field is linear or weakly non-linear. Beyond this, our principal result is that f ( R ) does affect halo abundances, the halo spin parameter and the concentration-mass relationship in an environment-independent way, whereas we find no appreciable deviation from \\text(ΛCDM) for the mass function with fixed environment density, nor the alignment of the orientation and spin vectors of the halo to the eigenvectors of the local cosmic web. There is a general trend for greater deviation from \\text(ΛCDM) in underdense environments and for high-mass haloes, as expected from chameleon screening.

  4. Influence of halo doping profiles on MOS transistor mismatch

    NARCIS (Netherlands)

    Andricciola, P.; Tuinhout, H.

    2009-01-01

    Halo implants are used in modern CMOS technology to reduce the short channel effect. However, the lateral non-uniformity of the channel doping has been proven to degenerate the mismatch performance. With this paper we want to discuss the influence of the halo profile on MOS transistor mismatch. The

  5. Galactic Angular Momentum in Cosmological Zoom-in Simulations. I. Disk and Bulge Components and the Galaxy-Halo Connection

    Science.gov (United States)

    Sokołowska, Aleksandra; Capelo, Pedro R.; Fall, S. Michael; Mayer, Lucio; Shen, Sijing; Bonoli, Silvia

    2017-02-01

    We investigate the angular momentum evolution of four disk galaxies residing in Milky-Way-sized halos formed in cosmological zoom-in simulations with various sub-grid physics and merging histories. We decompose these galaxies, kinematically and photometrically, into their disk and bulge components. The simulated galaxies and their components lie on the observed sequences in the j *-M * diagram, relating the specific angular momentum and mass of the stellar component. We find that galaxies in low-density environments follow the relation {j}* \\propto {M}* α past major mergers, with α ˜ 0.6 in the case of strong feedback, when bulge-to-disk ratios are relatively constant, and α ˜ 1.4 in the other cases, when secular processes operate on shorter timescales. We compute the retention factors (I.e., the ratio of the specific angular momenta of stars and dark matter) for both disks and bulges and show that they vary relatively slowly after averaging over numerous but brief fluctuations. For disks, the retention factors are usually close to unity, while for bulges, they are a few times smaller. Our simulations therefore indicate that galaxies and their halos grow in a quasi-homologous way.

  6. A forming, dust-enshrouded disk at z = 0.43: the first example of a massive, late-type spiral rebuilt after a major merger?

    Science.gov (United States)

    Hammer, F.; Flores, H.; Yang, Y. B.; Athanassoula, E.; Puech, M.; Rodrigues, M.; Peirani, S.

    2009-03-01

    By combining Ultra Deep Field imagery from HST/ACS with kinematics from VLT/GIRAFFE, we derive a physical model of distant galaxies in a way similar to that achievable for nearby galaxies. A significant part of the evolution in the density of cosmic star formation is related to the rapid evolution of both luminous IR galaxies (LIRGs) and Luminous Compact galaxies: here we study the properties of a distant, compact galaxy, J033245.11-274724.0, which is also a LIRG. Given the photometric and spectrophotometric accuracies of data of all wavelengths, we can decompose the galaxy into sub-components and correct them for reddening. Combination of deep imagery and kinematics provides a reasonable physical model of the galaxy. The galaxy is dominated by a dust-enshrouded disk revealed by UDF imagery. The disk radius is half that of the Milky Way and the galaxy forms stars at a rate of 20 M⊙/yr. Morphology and kinematics show that both gas and stars spiral inwards rapidly to feed the disk and the central regions. A combined system of a bar and two nonrotating spiral arms regulates the material accretion, induces high velocity dispersions, with σ larger than 100 km s-1 and redistributes the angular momentum. The detailed physical properties of J033245.11-274724.0 resemble the expectations of modeling the merger of two equal-mass, gaseous-rich galaxies, 0.5 Gyr after the merger. They cannot be reproduced by any combination of intrinsic disk perturbations alone, given the absence of any significant outflow mechanisms. In its later evolution, J033245.11-274724.0 could become a massive, late-type spiral that evolves to become part of the Tully-Fisher relation, with an angular momentum induced mostly by the orbital angular-momentum of the merger.

  7. a Doorway to Borromean Halo Nuclei:. the Samba Configuration

    Science.gov (United States)

    Yamashita, M. T.; Frederico, T.; Hussein, M. H.

    We exploit the possibility of new configurations in three-body halo nuclei, Samba type (the neutron-core form a bound system) as a doorway to Borromean systems. The nuclei 12Be, 15B, 23N and 27F are of such nature, in particular 23N with a half-life of 37.7 s and a halo radius of 6.07 fm is an excellent example of Samba-halo configuration. The fusion below the barrier of the Samba halo nuclei with heavy targets could reveal the so far elusive enhancement and a dominance of one-neutron over two-neutron transfers, in contrast to what was found recently for the Borromean halo nucleus 6He+238U.

  8. Development of an Automatic Detection Program of Halo CMEs

    Science.gov (United States)

    Choi, K.; Park, M. Y.; Kim, J.

    2017-12-01

    The front-side halo CMEs are the major cause for large geomagnetic storms. Halo CMEs can result in damage to satellites, communication, electrical transmission lines and power systems. Thus automated techniques for detecting and analysing Halo CMEs from coronagraph data are of ever increasing importance for space weather monitoring and forecasting. In this study, we developed the algorithm that can automatically detect and do image processing the Halo CMEs in the images from the LASCO C3 coronagraph on board the SOHO spacecraft. With the detection algorithm, we derived the geometric and kinematical parameters of halo CMEs, such as source location, width, actual CME speed and arrival time at 21.5 solar radii.

  9. Migrating Legacy Systems in the Global Merger & Acquisition Environment

    Science.gov (United States)

    Katerattanakul, Pairin; Kam, Hwee-Joo; Lee, James J.; Hong, Soongoo

    2009-01-01

    The MetaFrame system migration project at WorldPharma, while driven by merger and acquisition, had faced complexities caused by both technical challenges and organizational issues in the climate of uncertainties. However, WorldPharma still insisted on instigating this post-merger system migration project. This project served to (1) consolidate the…

  10. University Mergers in Russia: Four Waves of Educational Policy

    Science.gov (United States)

    Romanenko, K. R.; Lisyutkin, M. A.

    2018-01-01

    This article is aimed at identifying distinctive features of the educational policy of university mergers--their main stages, types, and declared goals. We analyzed cases of university mergers and acquisitions (M&A) from the 1990s to the present, which allowed us to identify and describe four Russia-specific waves of educational policy. Based…

  11. Integrating organizational and human behavior perspectives on mergers and acquisitions

    NARCIS (Netherlands)

    Weber, Yaakov; Drori, Israel

    2011-01-01

    This article presents a conceptual framework for investigating merger and acquisition (M&A) performance through a multistage and multilevel approach. First, human resource challenges during the integration process following a merger are explored to help explain the inconsistencies among empirical

  12. Strategic Mergers of Strong Institutions to Enhance Competitive Advantage

    Science.gov (United States)

    Harman, Grant; Harman, Kay

    2008-01-01

    Strategic mergers are formal combinations or amalgamations of higher education institutions with the aim of enhancing competitive advantage, or merging for "mutual growth". Recently, in a number of countries, there has been a decided shift from mergers initiated by governments, and dealing mainly with "problem" cases, towards…

  13. What Drives Private and Public Merger Waves in Europe?

    DEFF Research Database (Denmark)

    Bartholdy, Jan; Blunck, Benjamin

    What drives merger waves? Harford 2005 argues that mergers are an efficient response to economic shocks to an industry, whereas Rhodes-Kropf, Robinson & Viswanathan 2005 argues that merger waves are driven by overvaluation of the acquiring firm, and to a lesser extent, the target firm. Both paper...... significant differences between driving forces for listed firms and for private firms. Public or listed firm mergers and acquisitions are primarily driven by overvaluation or behavioural factors, whereas private transactions are driven by economic factors.......What drives merger waves? Harford 2005 argues that mergers are an efficient response to economic shocks to an industry, whereas Rhodes-Kropf, Robinson & Viswanathan 2005 argues that merger waves are driven by overvaluation of the acquiring firm, and to a lesser extent, the target firm. Both papers...... are based on empirical analyses of listed US firms. This paper presents additional evidence of merger waves in the European Union (EU). The use of European data allows a more detailed analysis, since firm level data is available for both listed as well as private transactions. This analysis reveals...

  14. Star formation in mergers with comologically motivated initial conditions

    NARCIS (Netherlands)

    Karman, Wouter; Macciò, Andrea V.; Kannan, Rahul; Moster, Benjamin P.; Somerville, Rachel S.

    2015-01-01

    We use semi-analytic models and cosmological merger trees to provide the initial conditions for multimerger numerical hydrodynamic simulations, and exploit these simulations to explore the effect of galaxy interaction and merging on star formation (SF). We compute numerical realizations of 12 merger

  15. MORTUARY MERGERS AND THE INTERNATIONALIZATION OF INTERMENT

    Directory of Open Access Journals (Sweden)

    David O. Whitten

    2001-01-01

    Full Text Available “Mortuary Mergers and the Internationalization of Interment” is a study ofthe death services industry’s response to a changing market. Throughout the industry and across national borders, independent mortuaries and cemeteries are merging or consolidating. International death services firms are structured much as the automobile, oil, and communications multinationals are. Monopolistic competition is increasingly replaced by national and international oligopoly that may well translate into monopoly in isolated markets and lead to antitrust action and regulation. The study develops the historical roots of the death services industry but concentrates on the revolution underway. The prospects for the industry in the twenty-first century conclude the paper.

  16. Performance Assessment of Mergers and Acquisitions

    DEFF Research Database (Denmark)

    Wang, Daojuan; Moini, Hamid

    2012-01-01

    Corporate mergers and acquisitions (M&As) have been increasing popular during these decades. However, a majority of research show failure rate (40% - 80%) has not significantly changed. This “success paradox” triggers us to reflect on performance assessment of M&As: how the performance of M...... on the performance measures and benchmarks adopted in M&A research field and the relevant empirical results. We find that the definitions of performance varied in terms of accounting, financial, operational and perceptual metrics. And performance assessment is sensitive to the definition of performance, methodology...

  17. The human resources in mergers and acquisitions

    Directory of Open Access Journals (Sweden)

    Noemí Martínez Caraballo

    2007-07-01

    Full Text Available In view of intangible resources -and, among them, human capital- play a significant role in the managerial strategy, this article aims to analyze the fit of human resources in companies that has been target of mergers and/or acquisitions processes. In this sense, the present paper will be centered in carrying out a state of the art of this topic and in showing some evidences about the top managers perceptions of the target company with the purpose of better understanding which are the reasons for the departure and the permanence of them.

  18. Sloshing in its cD halo: MUSE kinematics of the central galaxy NGC 3311 in the Hydra I cluster

    Science.gov (United States)

    Barbosa, C. E.; Arnaboldi, M.; Coccato, L.; Gerhard, O.; Mendes de Oliveira, C.; Hilker, M.; Richtler, T.

    2018-01-01

    Context. Early-type galaxies (ETGs) show a strong size evolution with redshift. This evolution is explained by fast "in-situ" star formation at high-z followed by a late mass assembly mostly driven by minor mergers that deposit stars primarily in the outer halo. Aims: We aim to identify the main structural components of the Hydra I cD galaxy NGC 3311 to investigate the connection between the central galaxy and the surrounding stellar halo. Methods: We produce maps of the line-of-sight velocity distribution (LOSVD) moments from a mosaic of MUSE pointings covering NGC 3311 out to 25 kpc. Combining deep photometric and spectroscopic data, we model the LOSVD maps using a finite mixture distribution, including four non-concentric components that are nearly isothermal spheroids, with different line-of-sight systemic velocities V, velocity dispersions σ, and small (constant) values of the higher order Gauss-Hermite moments h3 and h4. Results: The kinemetry analysis indicates that NGC 3311 is classified as a slow rotator, although the galaxy shows a line-of-sight velocity gradient along the photometric major axis. The comparison of the correlations between h3 and h4 with V/σ with simulated galaxies indicates that NGC 3311 assembled mainly through dry mergers. The σ profile rises to ≃ 400 km s-1 at 20 kpc, a significant fraction (0.55) of the Hydra I cluster velocity dispersion, indicating that stars there were stripped from progenitors orbiting in the cluster core. The finite mixture distribution modeling supports three inner components related to the central galaxy and a fourth component with large effective radius (51 kpc) and velocity dispersion (327 km s-1) consistent with a cD envelope. We find that the cD envelope is offset from the center of NGC 3311 both spatially (8.6 kpc) and in velocity (ΔV = 204 km s-1), but coincides with the cluster core X-ray isophotes and the mean velocity of core galaxies. Also, the envelope contributes to the broad wings of the

  19. Impact of HMO mergers and acquisitions on financial performance.

    Science.gov (United States)

    Weech-Maldonado, Robert

    2002-01-01

    This study examines the effect of health maintenance organization (HMO) mergers and acquisitions on financial performance, as indicated by cash flow returns, profitability ratios, and efficiency indicators. Pooled, cross-sectional files of financial performance data were created for HMO mergers occurring in the period of 1988 to 1994. The study uses a time-series design involving the analysis of pre- and post-acquisition financial performance measured over a period of four years. Change scores for the industry-adjusted financial performance measures were calculated and then evaluated using t-tests. The study showed that HMO mergers had a positive effect on financial performance and efficiency. This effect disappeared, however, after adjusting for HMO industry returns. Potential synergies arising from HMO mergers have been largely illusory. Mergers may have been a result of non-value enhancing motives or management overconfidence.

  20. ROLE OF INTERNATIONAL MERGERS AND ACQUISITIONS IN CORPORATE INTEGRATION

    Directory of Open Access Journals (Sweden)

    Lucia P. BLĂJUȚ

    2015-04-01

    Full Text Available This paper highlights the role of international mergers and acquisitions in corporate integration. The factors that stimulate mergers and acquisitions activities bring real changes in the world economy. Mergers and acquisitions are a form of expansion: mergers can take place either as a statutory merger or consolidation and minority, majority or full acquisitions dominate the international market. It is very important to not confuse the meaning of the two terms. Multinational companies are forced by the competitive environment to adopt new strategies to penetrate a particular market and decrease the position of competition on global market or to counteract competitor action on the other market. Cross-border M and A is functionally classified in horizontal, vertical, concentric and conglomerate. The balance between these types of M and A has been changing over time and the distinction among these four categories is not always clear-cut.

  1. Energy mergers, acquisitions and trusts : no end in sight

    International Nuclear Information System (INIS)

    Shiry, J.

    1998-01-01

    An overview of Canadian export of natural gas to the U.S. and mergers in the Canadian gas industry was presented. Issues discussed included: (1) the Canadian role in U.S. gas markets, (2) growth, returns, and reinvestment rates in the Canadian gas industry, (3) current and historical mergers and acquisitions activity, (4) the driving forces of continued mergers, and (5) the role of trusts in mergers and acquisitions. It was stressed that the recent trend of energy industry mergers is reshaping the industry. Canadian gas producers are currently finding themselves in a high risk, low-return, capital intensive industry caught in a 10-year major growth trend driven by U.S. exports. Unfortunately, for the immediate future there is no end in sight. figs

  2. Effects of deformations and orientations on neutron-halo structure of light-halo nuclei

    International Nuclear Information System (INIS)

    Sawhney, Gudveen; Gupta, Raj K.; Sharma, Manoj K.

    2013-01-01

    The availability of radioactive nuclear beams have enabled to study the structure of nuclei far from the stability line, which in turn led to the discovery of neutron-halo nuclei. These nuclei, located near the neutron drip-line exhibit a high probability of presence of one or two loosely bound neutrons at a large distance from the rest of nucleons. The fragmentation behavior is studied for 13 cases of 1n-halo nuclei, which include 11 Be, 14 B, 15 C, 17 C, 19 C, 22 N, 22 O, 23 O, 24 O, 24 F, 26 F, 29 Ne and 31 Ne, using the cluster-core model (CCM) extended to include the deformations and orientations of nuclei

  3. The Greater Impact of Mergers on the Growth of Massive Galaxies: Implications for Mass Assembly and Evolution since z sime 1

    Science.gov (United States)

    Bundy, Kevin; Fukugita, Masataka; Ellis, Richard S.; Targett, Thomas A.; Belli, Sirio; Kodama, Tadayuki

    2009-06-01

    Using deep infrared observations conducted with the MOIRCS imager on the Subaru Telescope in the northern GOODS field combined with public surveys in GOODS-S, we investigate the dependence on stellar mass, M *, and galaxy type of the close pair fraction (5 h -1 kpc implied merger rate. In terms of combined depth and survey area, our publicly available mass-limited sample represents a significant improvement over earlier infrared surveys used for this purpose. In common with some recent studies, we find that the fraction of paired systems that could result in major mergers is low (~4%) and does not increase significantly with redshift to z ≈ 1.2, with vprop(1 + z)1.6±1.6. Our key finding is that massive galaxies with M *>1011 M sun are more likely to host merging companions than less massive systems (M * ~ 1010 M sun). We find evidence for a higher pair fraction for red, spheroidal hosts compared to blue, late-type systems, in line with expectations based on clustering at small scales. The so-called "dry" mergers between early-type galaxies devoid of star formation (SF) represent nearly 50% of close pairs with M *>3 × 1010 M sun at z ~ 0.5, but less than 30% at z ~ 1. This result can be explained by the increasing abundance of red, early-type galaxies at these masses. We compare the volumetric merger rate of galaxies with different masses to mass-dependent trends in galaxy evolution. Our results reaffirm the conclusion of Bundy et al. that major mergers do not fully account for the formation of spheroidal galaxies since z ~ 1. In terms of mass assembly, major mergers contribute little to galaxy growth below M * ~ 3 × 1010 M sun but play a more significant role among galaxies with M * gsim 1011 M sun ~ 30% of which have undergone mostly dry mergers over the observed redshift range. Overall, the relatively rapid and recent coalescence of high-mass galaxies mirrors the expected hierarchical growth of halos and is consistent with recent model predictions, even if

  4. Forming Disk Galaxies in Wet Major Mergers. I. Three Fiducial Examples

    Science.gov (United States)

    Athanassoula, E.; Rodionov, S. A.; Peschken, N.; Lambert, J. C.

    2016-04-01

    Using three fiducial N-body+SPH simulations, we follow the merging of two disk galaxies that each have a hot gaseous halo component, and examine whether the merger remnant can be a spiral galaxy. The stellar progenitor disks are destroyed by violent relaxation during the merging and most of their stars form a classical bulge, while the remaining stars, as well as stars born during the merging times, form a thick disk and its bar. A new stellar disk forms subsequently and gradually in the remnant from the gas accreted mainly from the halo. It is vertically thin and well extended in its equatorial plane. A bar starts forming before the disk is fully in place, which is contrary to what is assumed in idealized simulations of isolated bar-forming galaxies, and has morphological features such as ansae and boxy/peanut bulges. Stars of different ages populate different parts of the box/peanut. A disky pseudobulge also forms, so that by the end of the simulation all three types of bulges coexist. The oldest stars are found in the classical bulge, followed by those of the thick disk, then by those in the thin disk. The youngest stars are in the spiral arms and the disky pseudobulge. The disk surface density profiles are of type II (exponential with downbending); the circular velocity curves are flat and show that the disks are submaximum in these examples: two clearly so and one near-borderline between maximum and submaximum. On average, only roughly between 10% and 20% of the stellar mass is in the classical bulge of the final models, I.e., much less than in previous simulations.

  5. THE OVERDENSITY AND MASSES OF THE FRIENDS-OF-FRIENDS HALOS AND UNIVERSALITY OF HALO MASS FUNCTION

    International Nuclear Information System (INIS)

    More, Surhud; Kravtsov, Andrey V.; Dalal, Neal; Gottloeber, Stefan

    2011-01-01

    The friends-of-friends algorithm (hereafter FOF) is a percolation algorithm which is routinely used to identify dark matter halos from N-body simulations. We use results from percolation theory to show that the boundary of FOF halos does not correspond to a single density threshold but to a range of densities close to a critical value that depends upon the linking length parameter, b. We show that for the commonly used choice of b = 0.2, this critical density is equal to 81.62 times the mean matter density. Consequently, halos identified by the FOF algorithm enclose an average overdensity which depends on their density profile (concentration) and therefore changes with halo mass, contrary to the popular belief that the average overdensity is ∼180. We derive an analytical expression for the overdensity as a function of the linking length parameter b and the concentration of the halo. Results of tests carried out using simulated and actual FOF halos identified in cosmological simulations show excellent agreement with our analytical prediction. We also find that the mass of the halo that the FOF algorithm selects crucially depends upon mass resolution. We find a percolation-theory-motivated formula that is able to accurately correct for the dependence on number of particles for the mock realizations of spherical and triaxial Navarro-Frenk-White halos. However, we show that this correction breaks down when applied to the real cosmological FOF halos due to the presence of substructures. Given that abundance of substructure depends on redshift and cosmology, we expect that the resolution effects due to substructure on the FOF mass and halo mass function will also depend on redshift and cosmology and will be difficult to correct for in general. Finally, we discuss the implications of our results for the universality of the mass function.

  6. Supermassive black holes do not correlate with dark matter haloes of galaxies.

    Science.gov (United States)

    Kormendy, John; Bender, Ralf

    2011-01-20

    Supermassive black holes have been detected in all galaxies that contain bulge components when the galaxies observed were close enough that the searches were feasible. Together with the observation that bigger black holes live in bigger bulges, this has led to the belief that black-hole growth and bulge formation regulate each other. That is, black holes and bulges coevolve. Therefore, reports of a similar correlation between black holes and the dark matter haloes in which visible galaxies are embedded have profound implications. Dark matter is likely to be non-baryonic, so these reports suggest that unknown, exotic physics controls black-hole growth. Here we show, in part on the basis of recent measurements of bulgeless galaxies, that there is almost no correlation between dark matter and parameters that measure black holes unless the galaxy also contains a bulge. We conclude that black holes do not correlate directly with dark matter. They do not correlate with galaxy disks, either. Therefore, black holes coevolve only with bulges. This simplifies the puzzle of their coevolution by focusing attention on purely baryonic processes in the galaxy mergers that make bulges.

  7. The Milky Way Halo in Action Space

    Science.gov (United States)

    Myeong, G. C.; Evans, N. W.; Belokurov, V.; Sanders, J. L.; Koposov, S. E.

    2018-04-01

    We analyze the structure of the local stellar halo of the Milky Way using ∼60000 stars with full phase space coordinates extracted from the SDSS–Gaia catalog. We display stars in action space as a function of metallicity in a realistic axisymmetric potential for the Milky Way Galaxy. The metal-rich population is more distended toward high radial action J R as compared to azimuthal or vertical action, J ϕ or J z . It has a mild prograde rotation ( ≈ 25 {km} {{{s}}}-1), is radially anisotropic and highly flattened, with axis ratio q ≈ 0.6–0.7. The metal-poor population is more evenly distributed in all three actions. It has larger prograde rotation ( ≈ 50 {km} {{{s}}}-1), a mild radial anisotropy, and a roundish morphology (q ≈ 0.9). We identify two further components of the halo in action space. There is a high-energy, retrograde component that is only present in the metal-rich stars. This is suggestive of an origin in a retrograde encounter, possibly the one that created the stripped dwarf galaxy nucleus, ωCentauri. Also visible as a distinct entity in action space is a resonant component, which is flattened and prograde. It extends over a range of metallicities down to [Fe/H] ≈ ‑3. It has a net outward radial velocity ≈ 12 {km} {{{s}}}-1 within the solar circle at | z| < 3.5 {kpc}. The existence of resonant stars at such extremely low metallicities has not been seen before.

  8. DARK MATTER SUB-HALO COUNTS VIA STAR STREAM CROSSINGS

    International Nuclear Information System (INIS)

    Carlberg, R. G.

    2012-01-01

    Dark matter sub-halos create gaps in the stellar streams orbiting in the halos of galaxies. We evaluate the sub-halo stream crossing integral with the guidance of simulations to find that the linear rate of gap creation, R U , in a typical cold dark matter (CDM) galactic halo at 100 kpc is R U ≅0.0066 M-hat 8 -0.35 kpc -1 Gyr -1 , where M-hat 8 (≡ M-hat /10 8 M ☉ ) is the minimum mass halo that creates a visible gap. The relation can be recast entirely in terms of observables, as R U ≅0.059w -0.85 kpc -1 Gyr -1 , for w in kpc, normalized at 100 kpc. Using published data, the density of gaps is estimated for M31's NW stream and the Milky Way Pal 5 stream, Orphan stream, and Eastern Banded Structure. The estimated rates of gap creation all have errors of 50% or more due to uncertain dynamical ages and the relatively noisy stream density measurements. The gap-rate-width data are in good agreement with the CDM-predicted relation. The high density of gaps in the narrow streams requires a total halo population of 10 5 sub-halos above a minimum mass of 10 5 M ☉ .

  9. Stellar Bar Evolution in the Absence of Dark Matter Halo

    Science.gov (United States)

    Roshan, Mahmood

    2018-02-01

    We study the stellar bar growth in high-resolution numerical galaxy models with and without dark matter halos. In all models, the galactic disk is exponential, and the halos are rigid or live Plummer spheres. More specifically, when there is no dark matter halo, we modify the gravitational force between point particles. To do so, we use the weak field limit of an alternative theory of dark matter known as MOG in the literature. The galaxy model in MOG has the same initial conditions as galaxy models with a dark matter halo. On the other hand, the initial random velocities and Toomre’s local stability parameter are the same for all of the models. We show that the evolution and growth of the bar in MOG is substantially different from the standard cases including dark matter halo. More importantly, we find that the bar growth rate and its final magnitude are smaller in MOG. On the other hand, the maximum value of the bar in MOG is smaller than that in the Newtonian models. It is shown that although the live dark matter halo may support bar instability, MOG has stabilizing effects. Furthermore, we show that MOG supports fast pattern speeds, and unlike in the dark matter halo models, the pattern speed does not decrease with time. These differences, combined with the relevant observations, may help to distinguish between dark matter and modified gravity in galactic scales.

  10. Neutron Star Mergers and the R process

    Science.gov (United States)

    Joniak, Ronald; Ugalde, Claudio

    2017-09-01

    About half of the elements of the periodic table that are present today in the Solar System were synthesized before the formation of the Sun via a rapid neutron capture process (r process). However, the astrophysical site of the r process is a longstanding problem that has captivated both experimental and theoretical astrophysicists. Up to date, two possible scenarios for the site of the r process have been suggested: the first involves the high entropy wind of core collapse supernovae, and the second corresponds to the merger of two compact stellar objects such as neutron stars. We will study the robustness of the nucleosynthesis abundance pattern between the second and third r process peaks as produced by neutron star mergers with r process-like neutron exposures. First, we will vary parameters to obtain an understanding of the astrophysical mechanisms that create the r process. Next, we will create a program to obtain the best possible parameters based on a chi-squared test. Once we have the best fits, we will test the effect of fission in the overall isotope abundance pattern distribution. Later on, we will vary the ratio of masses of the two fission fragments and study its effect on elemental abundances. This research was supported by the UIC College of Liberal Arts and Sciences Undergraduate Research Initiative (LASURI).

  11. Pair fireball precursors of neutron star mergers

    Science.gov (United States)

    Metzger, Brian D.; Zivancev, Charles

    2016-10-01

    If at least one neutron star (NS) is magnetized in a binary NS merger, then the orbital motion of the conducting companion during the final inspiral induces a strong voltage and current along the magnetic field lines connecting the NSs. If a modest fraction η of the extracted electromagnetic power extracted accelerates relativistic particles, the resulting gamma-ray emission a compact volume will result in the formation of an electron-positron pair fireball. Applying a steady-state pair wind model, we quantify the detectability of the precursor fireball with gamma-ray satellites. For η ˜ 1 the gamma-ray detection horizon of Dmax ≈ 10(Bd/1014 G)3/4 Mpc is much closer than the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo horizon of 200 Mpc, unless the NS surface magnetic field strength is very large, B_d ≲ 10^{15} G. Given the quasi-isotropic nature of the emission, mergers with weaker NS fields could contribute a nearby population of short gamma-ray bursts. Power not dissipated close to the binary is carried to infinity along the open field lines by a large-scale Poynting flux. Reconnection within this outflow, well outside of the pair photosphere, provides a potential site for non-thermal emission, such as a coherent millisecond radio burst.

  12. Chemical Cartography. I. A Carbonicity Map of the Galactic Halo

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Young Sun; Kim, Young Kwang [Department of Astronomy and Space Science, Chungnam National University, Daejeon 34134 (Korea, Republic of); Beers, Timothy C.; Placco, Vinicius; Yoon, Jinmi [Department of Physics and JINA Center for the Evolution of the Elements, University of Notre Dame, Notre Dame, IN 46556 (United States); Carollo, Daniela [Research School of Astronomy and Astrophysics, The Australian National University, Canberra, ACT 2611 (Australia); Masseron, Thomas [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Jung, Jaehun, E-mail: youngsun@cnu.ac.kr [Department of Astronomy, Space Science, and Geology, Chungnam National University, Daejeon 34134 (Korea, Republic of)

    2017-02-10

    We present the first map of carbonicity, [C/Fe], for the halo system of the Milky Way, based on a sample of over 100,000 main-sequence turnoff stars with available spectroscopy from the Sloan Digital Sky Survey. This map, which explores distances up to 15 kpc from the Sun, reveals clear evidence for the dual nature of the Galactic halo, based on the spatial distribution of stellar carbonicity. The metallicity distribution functions of stars in the inner- and outer-halo regions of the carbonicity map reproduce those previously argued to arise from contributions of the inner- and outer-halo populations, with peaks at [Fe/H] = −1.5 and −2.2, respectively. From consideration of the absolute carbon abundances for our sample, A (C), we also confirm that the carbon-enhanced metal-poor (CEMP) stars in the outer-halo region exhibit a higher frequency of CEMP-no stars (those with no overabundances of heavy neutron-capture elements) than of CEMP- s stars (those with strong overabundances of elements associated with the s -process), whereas the stars in the inner-halo region exhibit a higher frequency of CEMP- s stars. We argue that the contrast in the behavior of the CEMP-no and CEMP- s fractions in these regions arises from differences in the mass distributions of the mini-halos from which the stars of the inner- and outer-halo populations formed, which gives rise in turn to the observed dichotomy of the Galactic halo.

  13. 17 CFR 270.17a-8 - Mergers of affiliated companies.

    Science.gov (United States)

    2010-04-01

    ... 17 Commodity and Securities Exchanges 3 2010-04-01 2010-04-01 false Mergers of affiliated... (CONTINUED) RULES AND REGULATIONS, INVESTMENT COMPANY ACT OF 1940 § 270.17a-8 Mergers of affiliated companies. (a) Exemption of affiliated mergers. A Merger of a registered investment company (or a series thereof...

  14. Galaxy Mergers from the Largest to the Smallest Scales: Introduction and Overview

    Science.gov (United States)

    Centrella, Joan

    2012-01-01

    Galaxy mergers encompass a wide range of astrophysical phenomena, including cosmological considerations, gas and stellar dynamics, AGN evolution, and mergers of the central SMBHs. Astrophysical signatures of galaxy mergers can be observed across most of the electromagnetic spectrum and through gravitational radiation. This talk provides an introduction and overview of the meeting, highlighting the key aspects of galaxy mergers from large to small scales.

  15. 12 CFR 250.182 - Terms defining competitive effects of proposed mergers.

    Science.gov (United States)

    2010-01-01

    ... mergers. 250.182 Section 250.182 Banks and Banking FEDERAL RESERVE SYSTEM (CONTINUED) BOARD OF GOVERNORS... competitive effects of proposed mergers. Under the Bank Merger Act (12 U.S.C. 1828(c)), a Federal Banking agency receiving a merger application must request the views of the other two banking agencies and the...

  16. 7 CFR 1717.159 - Applications for RUS approvals of mergers.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 11 2010-01-01 2010-01-01 false Applications for RUS approvals of mergers. 1717.159... ELECTRIC LOANS Mergers and Consolidations of Electric Borrowers § 1717.159 Applications for RUS approvals of mergers. If a proposed merger requires RUS approval according to RUS regulations and/or the loan...

  17. Connecting Galaxies, Halos, and Star Formation Rates Across Cosmic Time

    Energy Technology Data Exchange (ETDEWEB)

    Conroy, Charlie; Wechsler, Risa H.

    2008-06-02

    A simple, observationally-motivated model is presented for understanding how halo masses, galaxy stellar masses, and star formation rates are related, and how these relations evolve with time. The relation between halo mass and galaxy stellar mass is determined by matching the observed spatial abundance of galaxies to the expected spatial abundance of halos at multiple epochs--i.e. more massive galaxies are assigned to more massive halos at each epoch. This 'abundance matching' technique has been shown previously to reproduce the observed luminosity- and scale-dependence of galaxy clustering over a range of epochs. Halos at different epochs are connected by halo mass accretion histories estimated from N-body simulations. The halo-galaxy connection at fixed epochs in conjunction with the connection between halos across time provides a connection between observed galaxies across time. With approximations for the impact of merging and accretion on the growth of galaxies, one can then directly infer the star formation histories of galaxies as a function of stellar and halo mass. This model is tuned to match both the observed evolution of the stellar mass function and the normalization of the observed star formation rate--stellar mass relation to z {approx} 1. The data demands, for example, that the star formation rate density is dominated by galaxies with M{sub star} {approx} 10{sup 10.0-10.5} M{sub {circle_dot}} from 0 < z < 1, and that such galaxies over these epochs reside in halos with M{sub vir} {approx} 10{sup 11.5-12.5} M{sub {circle_dot}}. The star formation rate--halo mass relation is approximately Gaussian over the range 0 < z < 1 with a mildly evolving mean and normalization. This model is then used to shed light on a number of issues, including (1) a clarification of 'downsizing', (2) the lack of a sharp characteristic halo mass at which star formation is truncated, and (3) the dominance of star formation over merging to the stellar

  18. Evolution of Southern Hemisphere spring air masses observed by HALOE

    Science.gov (United States)

    Pierce, R. Bradley; Grose, William L.; Russell, James M., III; Tuck, Adrian F.

    1994-01-01

    The evolution of Southern Hemisphere air masses observed by the Halogen Occultation Experiment (HALOE) during September 21 through October 15, 1992, is investigated using isentropic trajectories computed from United Kingdom Meteorological Office (UKMO) assimilated winds and temperatures. Maps of constituent concentrations are obtained by accumulation of air masses from previous HALOE occultations. Lagged correlations between initial and subsequent HALOE observations of the same air mass are used to validate the air mass trajectories. High correlations are found for lag times as large as 10 days. Frequency distributions of the air mass constituent concentrations are used to examine constituent distributions in and around the Southern Hemisphere polar vortex.

  19. Stellar halos: a rosetta stone for galaxy formation and cosmology

    Science.gov (United States)

    Inglis Read, Justin

    2015-08-01

    Stellar halos make up about a percent of the total stellar mass in galaxies. Yet their old age and long phase mixing times make them living fossil records of galactic history. In this talk, I review the latest simulations of structure formation in our standard Lambda Cold Dark Matter cosmology. I discuss the latest predictions for stellar halos and the relationship between the stellar halo light and the underlying dark matter. Finally, I discuss how these simulations compare to observations of the Milky Way and Andromeda and, ultimately, what this means for our cosmological model and the formation history of the Galaxy.

  20. Decomposition of potential efficiency gains from hospital mergers in Greece.

    Science.gov (United States)

    Flokou, Angeliki; Aletras, Vassilis; Niakas, Dimitris

    2017-12-01

    This paper evaluates the technical efficiency of 71 Greek public hospitals and examines potential efficiency gains from 13 candidate mergers among them. Efficiency assessments are performed using bootstrapped Data Envelopment Analysis (DEA) whilst merger analysis is conducted by applying the Bogetoft and Wang methodology which allows the overall potential merger gains to be decomposed into three main components of inefficiency, namely technical (or learning), scope (or harmony) and scale (or size) effects. Thus, the analysis provides important insights not only on the magnitude of the potential total efficiency gains but also on their sources. The overall analysis is conducted in the context of a complete methodological framework where methods for outlier detection, returns to scale identification, and bias corrections for DEA estimations are also applied. Mergers are analyzed under the assumptions of constant, variable and non-decreasing returns to scale in an input oriented DEA model with three inputs and three outputs. The main finding of the study indicates that almost all mergers show substantial potential room for efficiency improvement, which is mainly attributed to the pre-merger technical inefficiencies of the individual hospitals and therefore it might be possible to be achieved without the need of implementing full-scale mergers. The same -though, at a lower extent- applies to the harmony effect whilst the size effect shows marginal or even negative gains.

  1. Single and simultaneous binary mergers in Wright-Fisher genealogies.

    Science.gov (United States)

    Melfi, Andrew; Viswanath, Divakar

    2018-04-12

    The Kingman coalescent is a commonly used model in genetics, which is often justified with reference to the Wright-Fisher (WF) model. Current proofs of convergence of WF and other models to the Kingman coalescent assume a constant sample size. However, sample sizes have become quite large in human genetics. Therefore, we develop a convergence theory that allows the sample size to increase with population size. If the haploid population size is N and the sample size is N 1∕3-ϵ , ϵ>0, we prove that Wright-Fisher genealogies involve at most a single binary merger in each generation with probability converging to 1 in the limit of large N. Single binary merger or no merger in each generation of the genealogy implies that the Kingman partition distribution is obtained exactly. If the sample size is N 1∕2-ϵ , Wright-Fisher genealogies may involve simultaneous binary mergers in a single generation but do not involve triple mergers in the large N limit. The asymptotic theory is verified using numerical calculations. Variable population sizes are handled algorithmically. It is found that even distant bottlenecks can increase the probability of triple mergers as well as simultaneous binary mergers in WF genealogies. Copyright © 2018. Published by Elsevier Inc.

  2. On the consequences of low-mass white dwarf mergers

    International Nuclear Information System (INIS)

    Iben, I. Jr.

    1990-01-01

    The theory of binary star evolution suggests that about 10 percent of all main-sequence binary systems should evolve into a close pair of light white dwarfs which merge within a Hubble time. This paper explores the consequences of such mergers on the assumption that a merger can be approximated by a mass-transfer event which occurs on a time scale shorter than that given by the Eddington accretion limit. The evolution of He + He mergers and of CO + He and of hybrid + He mergers are discussed. The birthrate of helium degenerate pairs which merge in less than a Hubble time is estimated, and the space density of low-luminosity merger products currently present in the Galaxy is predicted. It is shown that the evolutionary tracks of models of simulated mergers pass through the region in the H-R diagram occupied by subdwarfs, but that the predicted space density of merger products exceeds by over a factor of three the space density of subdwarf estimated form the known sample of such stars. 61 refs

  3. EUROPEAN CROSS-BORDER MERGERS AND ACQUISITIONS- REALITIES AND PERSPECTIVES

    Directory of Open Access Journals (Sweden)

    Vancea Mariana

    2011-07-01

    Full Text Available This paper analyses the impact of the economic and financial crisis on merger and acquisition activity in Europe and the latest trends manifested on the cross-border merger and acquisition market involving European companies. Thus, a first objective of this research is to reveal the evolution of the European cross-border merger and acquisition activity in terms of dynamics, volume and structure. Another objective of this research is to reveal the short and medium term perspectives on mergers and acquisitions in Europe. Thus, under the continuous economic recovery of the European countries and the other worldwide economies, the recovery of financial markets and the growth of corporate profits, we shall witness an intensive cross-border merger and acquisition activity in Europe. The expansion engine of these operations seems to be represented by the emerging economies. This research is based on a systematic, logical and comparative analysis of scientific literature and statistical data regarding the cross-border mergers and acquisitions that involve European companies in recent years. This paper is part of the doctoral thesis Mergers and acquisitions- strategies of growth and development of enterprises. European and national particularities, coordinated by professor Ph.D. Alina Bădulescu from University of Oradea, Faculty of Economics. The doctoral research is supported by The Sectorial Operational Program for Human Resources Development 2007-2013, Contract POSDRU 59/1.5/S/1- Romanian researchers through modern and efficient doctoral programs.

  4. Properties of Kilonovae from Dynamical and Post-merger Ejecta of Neutron Star Mergers

    Science.gov (United States)

    Tanaka, Masaomi; Kato, Daiji; Gaigalas, Gediminas; Rynkun, Pavel; Radžiūtė, Laima; Wanajo, Shinya; Sekiguchi, Yuichiro; Nakamura, Nobuyuki; Tanuma, Hajime; Murakami, Izumi; Sakaue, Hiroyuki A.

    2018-01-01

    Ejected material from neutron star mergers gives rise to electromagnetic emission powered by radioactive decays of r-process nuclei, the so-called kilonova or macronova. While properties of the emission are largely affected by opacities in the ejected material, available atomic data for r-process elements are still limited. We perform atomic structure calculations for r-process elements: Se (Z = 34), Ru (Z = 44), Te (Z = 52), Ba (Z = 56), Nd (Z = 60), and Er (Z = 68). We confirm that the opacities from bound–bound transitions of open f-shell, lanthanide elements (Nd and Er) are higher than those of the other elements over a wide wavelength range. The opacities of open s-shell (Ba), p-shell (Se and Te), and d-shell (Ru) elements are lower than those of open f-shell elements, and their transitions are concentrated in the ultraviolet and optical wavelengths. We show that the optical brightness can be different by > 2 mag depending on the element abundances in the ejecta such that post-merger, lanthanide-free ejecta produce brighter and bluer optical emission. Such blue emission from post-merger ejecta can be observed from the polar directions if the mass of the preceding dynamical ejecta in these regions is small. For the ejecta mass of 0.01 {M}ȯ , observed magnitudes of the blue emission will reach 21.0 mag (100 Mpc) and 22.5 mag (200 Mpc) in the g and r bands within a few days after the merger, which are detectable with 1 m or 2 m class telescopes.

  5. Mergers and acquisitions in the international banking sector

    Directory of Open Access Journals (Sweden)

    Botis, S.

    2013-06-01

    Full Text Available The economic crisis emphasized the risks that banks assume and run. Reducing them is a strong reason for the acceleration of mergers and acquisitions in the international banking field. The merger of banking entities has established itself as a modern method of global credit risk management within every country and internationally. The main objective of this article is to highlight the latest developments on the bank mergers and acquisitions market in the U.S. and EU and on emerging market trends.

  6. An Empirical Analysis of Post-Merger Organizational Integration

    DEFF Research Database (Denmark)

    Smeets, Valerie Anne Rolande; Ierulli, Kathryn; Gibbs, Michael

    2016-01-01

    existing establishments. Worker turnover is high after merger, but new hiring yields stable total employment. Target employees have higher turnover and reassignment, particularly if the target firm is small relative to the acquiring firm. These findings may suggest integration is costly, but can......We study post-merger organizational integration using linked employer-employee data. Integration is implemented by reassigning a small number of high skilled workers, especially in R&D and management. Workforce mixing is concentrated to establishments set up after merger rather than to previously...... be achieved by focusing on key employees. Alternatively, reassigning a few key employees is sufficient for achieving integration....

  7. Effective Dark Matter Halo Catalog in f(R) Gravity.

    Science.gov (United States)

    He, Jian-Hua; Hawken, Adam J; Li, Baojiu; Guzzo, Luigi

    2015-08-14

    We introduce the idea of an effective dark matter halo catalog in f(R) gravity, which is built using the effective density field. Using a suite of high resolution N-body simulations, we find that the dynamical properties of halos, such as the distribution of density, velocity dispersion, specific angular momentum and spin, in the effective catalog of f(R) gravity closely mimic those in the cold dark matter model with a cosmological constant (ΛCDM). Thus, when using effective halos, an f(R) model can be viewed as a ΛCDM model. This effective catalog therefore provides a convenient way for studying the baryonic physics, the galaxy halo occupation distribution and even semianalytical galaxy formation in f(R) cosmologies.

  8. UARS Halogen Occultation Experiment (HALOE) Level 3AT V001

    Data.gov (United States)

    National Aeronautics and Space Administration — The Halogen Occultation Experiment (HALOE) Level 3AT data product consists of daily vertical profiles of temperature, aerosol extinction and concentrations of HCl,...

  9. On the galaxy-halo connection in the EAGLE simulation

    Science.gov (United States)

    Desmond, Harry; Mao, Yao-Yuan; Wechsler, Risa H.; Crain, Robert A.; Schaye, Joop

    2017-10-01

    Empirical models of galaxy formation require assumptions about the correlations between galaxy and halo properties. These may be calibrated against observations or inferred from physical models such as hydrodynamical simulations. In this Letter, we use the EAGLE simulation to investigate the correlation of galaxy size with halo properties. We motivate this analysis by noting that the common assumption of angular momentum partition between baryons and dark matter in rotationally supported galaxies overpredicts both the spread in the stellar mass-size relation and the anticorrelation of size and velocity residuals, indicating a problem with the galaxy-halo connection it implies. We find the EAGLE galaxy population to perform significantly better on both statistics, and trace this success to the weakness of the correlations of galaxy size with halo mass, concentration and spin at fixed stellar mass. Using these correlations in empirical models will enable fine-grained aspects of galaxy scalings to be matched.

  10. A beam halo event of the ATLAS Experiment

    CERN Multimedia

    ATLAS, Experiment

    2014-01-01

    Beam halo events: These occur as a single beam of protons is circulating in one direction in LHC, just passing through ATLAS. An outlier particle hits a part of the detector causing a spray of particles.

  11. Summary of the 2014 Beam-Halo Monitoring Workshop

    Energy Technology Data Exchange (ETDEWEB)

    Fisher, Alan

    2015-09-25

    Understanding and controlling beam halo is important for high-intensity hadron accelerators, for high-brightness electron linacs, and for low-emittance light sources. This can only be achieved by developing suitable diagnostics. The main challenge faced by such instrumentation is the high dynamic range needed to observe the halo in the presence of an intense core. In addition, measurements must often be made non-invasively. This talk summarizes the one-day workshop on Beam-Halo Monitoring that was held at SLAC on September 19 last year, immediately following IBIC 2014 in Monterey. Workshop presentations described invasive techniques using wires, screens, or crystal collimators, and non-invasive measurements with gas or scattered electrons. Talks on optical methods showed the close links between observing halo and astronomical problems like observing the solar corona or directly observing a planet orbiting another star.

  12. Halo Core Tracking for Galaxy Placement in Cosmological Simulations

    Science.gov (United States)

    Korytov, Danila

    2017-01-01

    Synthetic galaxy catalogs are an important product of cosmological simulations. Upcoming surveys, such as LSST, require high volume and high resolution simulations for generating large object catalogs. These catalogs have many uses including testing and improving analysis pipelines, predictions for different cosmologies and investigations of systematic errors. Dark matter (DM) only simulations are able to reach the required volume and resolution but need an accurate prescription for galaxy placement within DM halos. We present a method for galaxy placement. For halos above a characteristic mass, central DM simulation particles are taken as tracer particles for a galaxy. These halo ``cores'' are tracked through the simulation and may merge with other ``cores'' or be ripped apart by halo tidal forces. We examine how accurately we can reproduce galaxy cluster profiles, two point correlation functions and other galaxy statistics.

  13. Analytical Model of Symmetric Halo Doped DG-Tunnel FET

    Directory of Open Access Journals (Sweden)

    S. Nagarajan

    2015-11-01

    Full Text Available Two-dimensional analytical model of symmetric halo doped double gate tunnel field effect transistor has been presented in this work. This model is developed based on the 2-D Poisson’s equation. Some important parameters such that surface potential, vertical and lateral electric field, electric field intensity and band energy have been modelled. The doping concentration and length of halo regions are varied and dependency of various parameters is studied. The halo doping is imparted to improve the ON current and to reduce the intrinsic ambipolarity of the device. Hence we can achieve improved ION/IOFF ratio. The scaling property of halo doped structure is analyzed with various dielectric constants.

  14. Possible existence of wormholes in the central regions of halos

    Energy Technology Data Exchange (ETDEWEB)

    Rahaman, Farook, E-mail: rahaman@iucaa.ernet.in [Department of Mathematics, Jadavpur University, Kolkata 700032, West Bengal (India); Salucci, P., E-mail: salucci@sissa.it [SISSA, International School for Advanced Studies, Via Bonomea 265, 34136, Trieste (Italy); INFN, Sezione di Trieste, Via Valerio 2, 34127, Trieste (Italy); Kuhfittig, P.K.F., E-mail: kuhfitti@msoe.edu [Department of Mathematics, Milwaukee School of Engineering, Milwaukee, WI 53202-3109 (United States); Ray, Saibal, E-mail: saibal@iucaa.ernet.in [Department of Physics, Government College of Engineering and Ceramic Technology, Kolkata 700010, West Bengal (India); Rahaman, Mosiur, E-mail: mosiurju@gmail.com [Department of Mathematics, Meghnad Saha Institute of Technology, Kolkata 700150 (India)

    2014-11-15

    An earlier study (Rahaman, et al., 2014 and Kuhfittig, 2014) has demonstrated the possible existence of wormholes in the outer regions of the galactic halo, based on the Navarro–Frenk–White (NFW) density profile. This paper uses the Universal Rotation Curve (URC) dark matter model to obtain analogous results for the central parts of the halo. This result is an important compliment to the earlier result, thereby confirming the possible existence of wormholes in most of the spiral galaxies. - Highlights: • Earlier we showed possible existence of wormholes in the outer regions of halo. • We obtain here analogous results for the central parts of the galactic halo. • Our result is an important compliment to the earlier result. • This confirms possible existence of wormholes in most of the spiral galaxies.

  15. Halo performance on low light level image intensifiers

    Science.gov (United States)

    Cui, Dongxu; Ren, Ling; Chang, Benkang; Shi, Feng; Shi, Jifang; Qian, Yunsheng; Wang, Honggang; Zhang, Junju

    To analyze the formation mechanism of the halo on low light level image intensifiers and the influencing factors on the halo size, a halo tester has been designed. Under the illumination between 10-2 lx and 10-4 lx, we use the tester to collect a 0.1922 mm hole image directly with CoolSNAPK4 charge-coupled device (CCD) in a darkroom. The practical measurement result shows that the amplification ratio is 343.4. Then we put the super second and third generation image intensifiers after the hole, and the halo sizes of the hole images on the screens are determined as 0.2388 and 0.5533 mm respectively. The results are helpful to improve the quality of the low light level image intensifiers.

  16. First Attempts at using Active Halo Control at the LHC

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, Joschka [CERN; Bruce, Roderik [CERN; Garcia Morales, Hector [CERN; Höfle, Wolfgang [CERN; Kotzian, Gerd [CERN; Kwee-Hinzmann, Regina [CERN; Langner, Andy [CERN; Mereghetti, Alessio [CERN; Quaranta, Elena [CERN; Redaelli, Stefano [CERN; Rossi, Adriana [CERN; Salvachua, Belen [CERN; Stancari, Giulio [Fermilab; Tomás, Rogelio [CERN; Valentino, Gianluca [CERN; Valuch, Daniel [CERN

    2016-06-01

    The beam halo population is a non-negligible factor for the performance of the LHC collimation system and the machine protection. In particular this could become crucial for aiming at stored beam energies of 700 MJ in the High Luminosity (HL-LHC) project, in order to avoid beam dumps caused by orbit jitter and to ensure safety during a crab cavity failure. Therefore several techniques to safely deplete the halo, i.e. active halo control, are under development. In a first attempt a novel way for safe halo depletion was tested with particle narrow-band excitation employing the LHC Transverse Damper (ADT). At an energy of 450 GeV a bunch selective beam tail scraping without affecting the core distribution was attempted. This paper presents the first measurement results, as well as a simple simulation to model the underlying dynamics.

  17. BEAM HALO FORMATION IN HIGH-INTENSITY BEAMS.

    Energy Technology Data Exchange (ETDEWEB)

    FEDOTOV, A.V.

    2005-03-18

    Studies of beam halo became unavoidable feature of high-intensity machines where uncontrolled beam loss should be kept to extremely small level. For a well controlled stable beam such a loss is typically associated with the low density halo surrounding beam core. In order to minimize uncontrolled beam loss or improve performance of an accelerator, it is very important to understand what are the sources of halo formation in a specific machine of interest. The dominant mechanisms are, in fact, different in linear accelerators, circular machines or Energy Recovering Linacs (ERL). In this paper, we summarize basic mechanisms of halo formation in high-intensity beams and discuss their application to various types of accelerators of interest, such as linacs, rings and ERL.

  18. Testing approximate predictions of displacements of cosmological dark matter halos

    Science.gov (United States)

    Munari, Emiliano; Monaco, Pierluigi; Koda, Jun; Kitaura, Francisco-Shu; Sefusatti, Emiliano; Borgani, Stefano

    2017-07-01

    We present a test to quantify how well some approximate methods, designed to reproduce the mildly non-linear evolution of perturbations, are able to reproduce the clustering of DM halos once the grouping of particles into halos is defined and kept fixed. The following methods have been considered: Lagrangian Perturbation Theory (LPT) up to third order, Truncated LPT, Augmented LPT, MUSCLE and COLA. The test runs as follows: halos are defined by applying a friends-of-friends (FoF) halo finder to the output of an N-body simulation. The approximate methods are then applied to the same initial conditions of the simulation, producing for all particles displacements from their starting position and velocities. The position and velocity of each halo are computed by averaging over the particles that belong to that halo, according to the FoF halo finder. This procedure allows us to perform a well-posed test of how clustering of the matter density and halo density fields are recovered, without asking to the approximate method an accurate reconstruction of halos. We have considered the results at z=0,0.5,1, and we have analysed power spectrum in real and redshift space, object-by-object difference in position and velocity, density Probability Distribution Function (PDF) and its moments, phase difference of Fourier modes. We find that higher LPT orders are generally able to better reproduce the clustering of halos, while little or no improvement is found for the matter density field when going to 2LPT and 3LPT. Augmentation provides some improvement when coupled with 2LPT, while its effect is limited when coupled with 3LPT. Little improvement is brought by MUSCLE with respect to Augmentation. The more expensive particle-mesh code COLA outperforms all LPT methods, and this is true even for mesh sizes as large as the inter-particle distance. This test sets an upper limit on the ability of these methods to reproduce the clustering of halos, for the cases when these objects are

  19. Testing approximate predictions of displacements of cosmological dark matter halos

    Energy Technology Data Exchange (ETDEWEB)

    Munari, Emiliano; Monaco, Pierluigi; Borgani, Stefano [Department of Physics, Astronomy Unit, University of Trieste, via Tiepolo 11, I-34143 Trieste (Italy); Koda, Jun [INAF – Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate (Italy); Kitaura, Francisco-Shu [Instituto de Astrofísica de Canarias, 38205 San Cristóbal de La Laguna, Santa Cruz de Tenerife (Spain); Sefusatti, Emiliano, E-mail: munari@oats.inaf.it, E-mail: monaco@oats.inaf.it, E-mail: jun.koda@brera.inaf.it, E-mail: fkitaura@iac.es, E-mail: sefusatti@oats.inaf.it, E-mail: borgani@oats.inaf.it [INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, I-34143 Trieste (Italy)

    2017-07-01

    We present a test to quantify how well some approximate methods, designed to reproduce the mildly non-linear evolution of perturbations, are able to reproduce the clustering of DM halos once the grouping of particles into halos is defined and kept fixed. The following methods have been considered: Lagrangian Perturbation Theory (LPT) up to third order, Truncated LPT, Augmented LPT, MUSCLE and COLA. The test runs as follows: halos are defined by applying a friends-of-friends (FoF) halo finder to the output of an N-body simulation. The approximate methods are then applied to the same initial conditions of the simulation, producing for all particles displacements from their starting position and velocities. The position and velocity of each halo are computed by averaging over the particles that belong to that halo, according to the FoF halo finder. This procedure allows us to perform a well-posed test of how clustering of the matter density and halo density fields are recovered, without asking to the approximate method an accurate reconstruction of halos. We have considered the results at z =0,0.5,1, and we have analysed power spectrum in real and redshift space, object-by-object difference in position and velocity, density Probability Distribution Function (PDF) and its moments, phase difference of Fourier modes. We find that higher LPT orders are generally able to better reproduce the clustering of halos, while little or no improvement is found for the matter density field when going to 2LPT and 3LPT. Augmentation provides some improvement when coupled with 2LPT, while its effect is limited when coupled with 3LPT. Little improvement is brought by MUSCLE with respect to Augmentation. The more expensive particle-mesh code COLA outperforms all LPT methods, and this is true even for mesh sizes as large as the inter-particle distance. This test sets an upper limit on the ability of these methods to reproduce the clustering of halos, for the cases when these objects are

  20. Analytical shear and flexion of Einasto dark matter haloes

    OpenAIRE

    Retana-Montenegro, E.; Frutos-Alfaro, F.; Baes, M.

    2012-01-01

    N-body simulations predict that dark matter haloes are described by specific density profiles on both galactic- and cluster-sized scales. Weak gravitational lensing through the measurements of their first and second order properties, shear and flexion, is a powerful observational tool for investigating the true shape of these profiles. One of the three-parameter density profiles recently favoured in the description of dark matter haloes is the Einasto profile. We present exact expressions for...

  1. clustep: Initial conditions for galaxy cluster halo simulations

    Science.gov (United States)

    Ruggiero, Rafael

    2017-11-01

    clustep generates a snapshot in GADGET-2 (ascl:0003.001) format containing a galaxy cluster halo in equilibrium; this snapshot can also be read in RAMSES (ascl:1011.007) using the DICE patch. The halo is made of a dark matter component and a gas component, with the latter representing the ICM. Each of these components follows a Dehnen density profile, with gamma=0 or gamma=1. If gamma=1, then the profile corresponds to a Hernquist profile.

  2. MD 1691: Active halo control using tune ripple at injection

    CERN Document Server

    Garcia Morales, Hector; Bruce, Roderik; Redaelli, Stefano; Fitterer, Miriam; Fiascaris, Maria; Nisbet, David; Thiesen, Hugues; Valentino, Gianluca; Xu, Chen; CERN. Geneva. ATS Department

    2017-01-01

    In this MD we performed halo excitation through tune ripple. This consists in an excitation that introduces new resonance sidebands around the existing resonance lines. In presence of sufficient detuning with amplitude, these sidebands can in principle affect only the dynamics of the halo particles at large amplitudes. Tune ripple was induced through a current modulation of the warm trim quadrupoles in IR7. This is the first time this method is experimentally tested at the LHC.

  3. Integrated Marketing Communications (IMC) Di PT Halo Rumah Bernyanyi

    OpenAIRE

    Rismayanti, Rebekka

    2016-01-01

    : This research aims to describe the effectiveness of Integrated Marketing Communication (IMC) in PT Halo Rumah Bernyanyi which, from the perspective of marketing strategy, could be studied by analyzing the segmentation, targeting, and positioning. Using case-study method with in-depth interview, the result shows that the implementation of IMC at PT Halo Rumah Bernyayi is arranged in one single strategy and tend to neglect the complexities of running multi-brand family karaoke-house. This con...

  4. Integrated Marketing Communications (IMC) di PT Halo Rumah Bernyanyi

    OpenAIRE

    Rebekka Rismayanti

    2017-01-01

    Abstract: This research aims to describe the effectiveness of Integrated Marketing Communication (IMC) in PT Halo Rumah Bernyanyi which, from the perspective of marketing strategy, could be studied by analyzing the segmentation, targeting, and positioning. Using case-study method with in-depth interview, the result shows that the implementation of IMC at PT Halo Rumah Bernyayi is arranged in one single strategy and tend to neglect the complexities of running multi-brand family karaoke-house. ...

  5. Non-Gaussianity and Excursion Set Theory: Halo Bias

    Energy Technology Data Exchange (ETDEWEB)

    Adshead, Peter [Enrico Fermi Institute, Univ. of Chicago, IL (United States); Baxter, Eric J. [Univ. of Chicago, Chicago, IL (United States); Dodelson, Scott [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Lidz, Adam [Univ. of Pennsylvania, Philadelphia, PA (United States)

    2012-09-01

    We study the impact of primordial non-Gaussianity generated during inflation on the bias of halos using excursion set theory. We recapture the familiar result that the bias scales as $k^{-2}$ on large scales for local type non-Gaussianity but explicitly identify the approximations that go into this conclusion and the corrections to it. We solve the more complicated problem of non-spherical halos, for which the collapse threshold is scale dependent.

  6. Possible existence of wormholes in the galactic halo region

    Energy Technology Data Exchange (ETDEWEB)

    Rahaman, Farook [Jadavpur University, Department of Mathematics, Kolkata, West Bengal (India); Kuhfittig, P.K.F. [Milwaukee School of Engineering, Department of Mathematics, Milwaukee, WI (United States); Ray, Saibal [Government College of Engineering and Ceramic Technology, Department of Physics, Kolkata, West Bengal (India); Islam, Nasarul [Danga High Madrasah, Department of Mathematics, Kolkata, West Bengal (India)

    2014-02-15

    Two observational results, the density profile from simulations performed in the ΛCDM scenario and the observed flat galactic rotation curves, are taken as input with the aim of showing that the galactic halo possesses some of the characteristics needed to support traversable wormholes. This result should be sufficient to provide an incentive for scientists to seek observational evidence for wormholes in the galactic halo region. (orig.)

  7. Halo-independent direct detection analyses without mass assumptions

    International Nuclear Information System (INIS)

    Anderson, Adam J.; Fox, Patrick J.; Kahn, Yonatan; McCullough, Matthew

    2015-01-01

    Results from direct detection experiments are typically interpreted by employing an assumption about the dark matter velocity distribution, with results presented in the m χ −σ n plane. Recently methods which are independent of the DM halo velocity distribution have been developed which present results in the v min −g-tilde plane, but these in turn require an assumption on the dark matter mass. Here we present an extension of these halo-independent methods for dark matter direct detection which does not require a fiducial choice of the dark matter mass. With a change of variables from v min to nuclear recoil momentum (p R ), the full halo-independent content of an experimental result for any dark matter mass can be condensed into a single plot as a function of a new halo integral variable, which we call h-til-tilde(p R ). The entire family of conventional halo-independent g-tilde(v min ) plots for all DM masses are directly found from the single h-tilde(p R ) plot through a simple rescaling of axes. By considering results in h-tilde(p R ) space, one can determine if two experiments are inconsistent for all masses and all physically possible halos, or for what range of dark matter masses the results are inconsistent for all halos, without the necessity of multiple g-tilde(v min ) plots for different DM masses. We conduct a sample analysis comparing the CDMS II Si events to the null results from LUX, XENON10, and SuperCDMS using our method and discuss how the results can be strengthened by imposing the physically reasonable requirement of a finite halo escape velocity

  8. Halo and space charge issues in the SNS Ring

    International Nuclear Information System (INIS)

    Fedotov, A.V.; Abell, D.T.; Beebe-Wang, J.; Lee, Y.Y.; Malitsky, N.; Wei, J.; Gluckstern, R.L.

    2000-01-01

    The latest designs for high-intensity proton rings require minimizing beam-induced radioactivation of the vacuum chamber. Although the tune depression in the ring is much smaller than in high-intensity linacs, space-charge contributions to halo formation and, hence, beam loss may be significant. This paper reviews our current understanding of halo formation issues for the Spallation Neutron Source (SNS) accumulator ring

  9. MAJOR-MERGER GALAXY PAIRS IN THE COSMOS FIELD—MASS-DEPENDENT MERGER RATE EVOLUTION SINCE z = 1

    International Nuclear Information System (INIS)

    Xu, C. Kevin; Zhao, Yinghe; Gao, Y.; Scoville, N.; Capak, P.; Drory, N.

    2012-01-01

    We present results of a statistical study of the cosmic evolution of the mass-dependent major-merger rate since z = 1. A stellar mass limited sample of close major-merger pairs (the CPAIR sample) was selected from the archive of the COSMOS survey. Pair fractions at different redshifts derived using the CPAIR sample and a local K-band-selected pair sample show no significant variations with stellar mass. The pair fraction exhibits moderately strong cosmic evolution, with the best-fitting function of f pair = 10 –1.88(±0.03) (1 + z) 2.2(±0.2) . The best-fitting function for the merger rate is R mg (Gyr –1 ) = 0.053 × (M star /10 10.7 M ☉ ) 0.3 (1 + z) 2.2 /(1 + z/8). This rate implies that galaxies of M star ∼ 10 10 -10 11.5 M ☉ have undergone ∼0.5-1.5 major mergers since z = 1. Our results show that, for massive galaxies (M star ≥ 10 10.5 M ☉ ) at z ≤ 1, major mergers involving star-forming galaxies (i.e., wet and mixed mergers) can account for the formation of both ellipticals and red quiescent galaxies (RQGs). On the other hand, major mergers cannot be responsible for the formation of most low mass ellipticals and RQGs of M star ∼ 10.3 M ☉ . Our quantitative estimates indicate that major mergers have significant impact on the stellar mass assembly of the most massive galaxies (M star ≥ 10 11.3 M ☉ ), but for less massive galaxies the stellar mass assembly is dominated by the star formation. Comparison with the mass-dependent (ultra)luminous infrared galaxies ((U)LIRG) rates suggests that the frequency of major-merger events is comparable to or higher than that of (U)LIRGs.

  10. Electromagnetic Counterparts to Black Hole Mergers

    Science.gov (United States)

    Schnittman, Jeremy D.

    2011-01-01

    During the final moments of a binary black hole (BH) merger, the gravitational wave (GW) luminosity of the system is greater than the combined electromagnetic (EM) output of the entire observable universe. However, the extremely weak coupling between GWs and ordinary matter makes these waves very difficult to detect directly. Fortunately, the inspirating BH system will interact strongly-on a purely Newtonian level-with any surrounding material in the host galaxy, and this matter can in turn produce unique EM signals detectable at Earth. By identifying EM counterparts to GW sources, we will be able to study the host environments of the merging BHs, in turn greatly expanding the scientific yield of a mission like LISA. Here we present a comprehensive review of the recent literature on the subject of EM counterparts, as well as a discussion of the theoretical and observational advances required to fully realize the scientific potential of the field.

  11. Post-Merger Evolution of Betelgeuse

    Science.gov (United States)

    Sullivan, James; Wheeler, J. Craig; Nance, Sarafina; Diaz, Manuel

    2017-01-01

    Betelgeuse appears to rotate anomalously rapidly. One possible explanation is that if merged with a companion of about 1 solar mass when it evolved up the Hyashi track to become a red giant. We have used the MESA evolutionary code to explore the effects of such a merger. We have added a solar mass of matter with angular momentum corresponding to the Keplerian angular velocity at the current radius of Betelgeuse and then followed the evolution of that mass and angular momentum. A wave of angular momentum propagates in toward the core where it is stalled by the composition barrier at the boundary with the helium core. There is also a rearrangement of the envelope material that results in a decrease in the surface gravity, yielding a result in closer agreement with observations than either non-rotating models or models evolved from rotating ZAMS models.

  12. Managing mergers in the petroleum industry

    International Nuclear Information System (INIS)

    Swartout, H. B.

    1997-01-01

    The size and scope of various acquisitions by Precision Drilling Corporation over the last decade were examined from the point of view of the acquiror. Also examined were Precision Drilling's approach to acquisitions and the probable reasons for the Corporation's success in acquiring other companies. In a series of 15 acquisitions from 1985 to 1997, the company went from the initial three drilling rigs to 205 rigs and from $4.5 million in revenues in 1985 to $455 million in 1997. Knowing the drilling business and the customers' business, an informed assessment of the target company's long term potential, decisive action, efficient and knowledgeable negotiators able to assess what is driving the other side, and a flexible, creative approach to financing mergers, were identified as most responsible for the Corporation's success

  13. Dissipative dark matter halos: The steady state solution

    Science.gov (United States)

    Foot, R.

    2018-02-01

    Dissipative dark matter, where dark matter particle properties closely resemble familiar baryonic matter, is considered. Mirror dark matter, which arises from an isomorphic hidden sector, is a specific and theoretically constrained scenario. Other possibilities include models with more generic hidden sectors that contain massless dark photons [unbroken U (1 ) gauge interactions]. Such dark matter not only features dissipative cooling processes but also is assumed to have nontrivial heating sourced by ordinary supernovae (facilitated by the kinetic mixing interaction). The dynamics of dissipative dark matter halos around rotationally supported galaxies, influenced by heating as well as cooling processes, can be modeled by fluid equations. For a sufficiently isolated galaxy with a stable star formation rate, the dissipative dark matter halos are expected to evolve to a steady state configuration which is in hydrostatic equilibrium and where heating and cooling rates locally balance. Here, we take into account the major cooling and heating processes, and numerically solve for the steady state solution under the assumptions of spherical symmetry, negligible dark magnetic fields, and that supernova sourced energy is transported to the halo via dark radiation. For the parameters considered, and assumptions made, we were unable to find a physically realistic solution for the constrained case of mirror dark matter halos. Halo cooling generally exceeds heating at realistic halo mass densities. This problem can be rectified in more generic dissipative dark matter models, and we discuss a specific example in some detail.

  14. Cold dark matter. 1: The formation of dark halos

    Science.gov (United States)

    Gelb, James M.; Bertschinger, Edmund

    1994-01-01

    We use numerical simulations of critically closed cold dark matter (CDM) models to study the effects of numerical resolution on observable quantities. We study simulations with up to 256(exp 3) particles using the particle-mesh (PM) method and with up to 144(exp 3) particles using the adaptive particle-particle-mesh (P3M) method. Comparisons of galaxy halo distributions are made among the various simulations. We also compare distributions with observations, and we explore methods for identifying halos, including a new algorithm that finds all particles within closed contours of the smoothed density field surrounding a peak. The simulated halos show more substructure than predicted by the Press-Schechter theory. We are able to rule out all omega = 1 CDM models for linear amplitude sigma(sub 8) greater than or approximately = 0.5 because the simulations produce too many massive halos compared with the observations. The simulations also produce too many low-mass halos. The distribution of halos characterized by their circular velocities for the P3M simulations is in reasonable agreement with the observations for 150 km/s less than or = V(sub circ) less than or = 350 km/s.

  15. Unmixing the Galactic Halo with RR Lyrae tagging

    Science.gov (United States)

    Belokurov, V.; Deason, A. J.; Koposov, S. E.; Catelan, M.; Erkal, D.; Drake, A. J.; Evans, N. W.

    2018-03-01

    We show that tagging RR Lyrae stars according to their location in the period-amplitude diagram can be used to shed light on the genesis of the Galactic stellar halo. The mixture of RR Lyrae of ab type, separated into classes along the lines suggested by Oosterhoff, displays a strong and coherent evolution with Galactocentric radius. The change in the RR Lyrae composition appears to coincide with the break in the halo's radial density profile at ˜25 kpc. Using simple models of the stellar halo, we establish that at least three different types of accretion events are necessary to explain the observed RRab behavior. Given that there exists a correlation between the RRab class fraction and the total stellar content of a dwarf satellite, we hypothesize that the field halo RRab composition is controlled by the mass of the progenitor contributing the bulk of the stellar debris at the given radius. This idea is tested against a suite of cosmological zoom-in simulations of Milky Way-like stellar halo formation. Finally, we study some of the most prominent stellar streams in the Milky Way halo and demonstrate that their RRab class fractions follow the trends established previously.

  16. QUANTIFYING KINEMATIC SUBSTRUCTURE IN THE MILKY WAY'S STELLAR HALO

    International Nuclear Information System (INIS)

    Xue Xiangxiang; Zhao Gang; Luo Ali; Rix, Hans-Walter; Bell, Eric F.; Koposov, Sergey E.; Kang, Xi; Liu, Chao; Yanny, Brian; Beers, Timothy C.; Lee, Young Sun; Bullock, James S.; Johnston, Kathryn V.; Morrison, Heather; Rockosi, Constance; Weaver, Benjamin A.

    2011-01-01

    We present and analyze the positions, distances, and radial velocities for over 4000 blue horizontal-branch (BHB) stars in the Milky Way's halo, drawn from SDSS DR8. We search for position-velocity substructure in these data, a signature of the hierarchical assembly of the stellar halo. Using a cumulative 'close pair distribution' as a statistic in the four-dimensional space of sky position, distance, and velocity, we quantify the presence of position-velocity substructure at high statistical significance among the BHB stars: pairs of BHB stars that are close in position on the sky tend to have more similar distances and radial velocities compared to a random sampling of these overall distributions. We make analogous mock observations of 11 numerical halo formation simulations, in which the stellar halo is entirely composed of disrupted satellite debris, and find a level of substructure comparable to that seen in the actually observed BHB star sample. This result quantitatively confirms the hierarchical build-up of the stellar halo through a signature in phase (position-velocity) space. In detail, the structure present in the BHB stars is somewhat less prominent than that seen in most simulated halos, quite possibly because BHB stars represent an older sub-population. BHB stars located beyond 20 kpc from the Galactic center exhibit stronger substructure than at r gc < 20 kpc.

  17. Stellar-to-halo mass relation of cluster galaxies

    International Nuclear Information System (INIS)

    Niemiec, Anna; Jullo, Eric; Limousin, Marceau; Giocoli, Carlo

    2017-01-01

    In the formation of galaxy groups and clusters, the dark matter haloes containing satellite galaxies are expected to be tidally stripped in gravitational interactions with the host. We use galaxy-galaxy weak lensing to measure the average mass of dark matter haloes of satellite galaxies as a function of projected distance to the centre of the host, since stripping is expected to be greater for satellites closer to the centre of the cluster. We further classify the satellites according to their stellar mass: assuming that the stellar component of the galaxy is less disrupted by tidal stripping, stellar mass can be used as a proxy of the infall mass. We study the stellar to halo mass relation of satellites as a function of the cluster-centric distance to measure tidal stripping. We use the shear catalogues of the DES science veri cation archive, the CFHTLenS and the CFHT Stripe 82 surveys, and we select satellites from the redMaPPer catalogue of clusters. For galaxies located in the outskirts of clusters, we nd a stellar to halo mass relation in good agreement with the theoretical expectations from Moster, Naab & White (2013) for central galaxies. In the centre of the cluster, we nd that this relation is shifted to smaller halo mass for a given stellar mass. We interpret this nding as further evidence for tidal stripping of dark matter haloes in high density environments.

  18. The CMS Beam Halo Monitor Electronics

    CERN Document Server

    AUTHOR|(CDS)2080684; Fabbri, F.; Grassi, T.; Hughes, E.; Mans, J.; Montanari, A.; Orfanelli, S.; Rusack, R.; Torromeo, G.; Stickland, D.P.; Stifter, K.

    2016-01-01

    The CMS Beam Halo Monitor has been successfully installed in the CMS cavern in LHC Long Shutdown 1 for measuring the machine induced background for LHC Run II. The system is based on 40 detector units composed of synthetic quartz Cherenkov radiators coupled to fast photomultiplier tubes. The readout electronics chain uses many components developed for the Phase 1 upgrade to the CMS Hadronic Calorimeter electronics, with dedicated firmware and readout adapted to the beam monitoring requirements. The PMT signal is digitized by a charge integrating ASIC (QIE10), providing both the signal rise time, with few ns resolution, and the charge integrated over one bunch crossing. The backend electronics uses microTCA technology and receives data via a high-speed 5 Gbps asynchronous link. It records histograms with sub-bunch crossing timing resolution and is readout by IPbus using the newly designed CMS data acquisition for non-event based data. The data is processed in real time and published to CMS and the LHC, providi...

  19. The CMS Beam Halo Monitor electronics

    International Nuclear Information System (INIS)

    Tosi, N.; Fabbri, F.; Montanari, A.; Torromeo, G.; Dabrowski, A.E.; Orfanelli, S.; Grassi, T.; Hughes, E.; Mans, J.; Rusack, R.; Stifter, K.; Stickland, D.P.

    2016-01-01

    The CMS Beam Halo Monitor has been successfully installed in the CMS cavern in LHC Long Shutdown 1 for measuring the machine induced background for LHC Run II. The system is based on 40 detector units composed of synthetic quartz Cherenkov radiators coupled to fast photomultiplier tubes (PMTs). The readout electronics chain uses many components developed for the Phase 1 upgrade to the CMS Hadronic Calorimeter electronics, with dedicated firmware and readout adapted to the beam monitoring requirements. The PMT signal is digitized by a charge integrating ASIC (QIE10), providing both the signal rise time, with few nanosecond resolution, and the charge integrated over one bunch crossing. The backend electronics uses microTCA technology and receives data via a high-speed 5 Gbps asynchronous link. It records histograms with sub-bunch crossing timing resolution and is read out via IPbus using the newly designed CMS data acquisition for non-event based data. The data is processed in real time and published to CMS and the LHC, providing online feedback on the beam quality. A dedicated calibration monitoring system has been designed to generate short triggered pulses of light to monitor the efficiency of the system. The electronics has been in operation since the first LHC beams of Run II and has served as the first demonstration of the new QIE10, Microsemi Igloo2 FPGA and high-speed 5 Gbps link with LHC data

  20. Performance of the CMS Beam Halo Monitor

    CERN Document Server

    CMS Collaboration

    2015-01-01

    The CMS Beam Halo Monitor has been successfully installed in the CMS cavern in LHC Long Shutdown 1 for measuring the machine induced background for LHC Run II. The system is based on 40 detector units composed of radiation hard synthetic quartz Cherenkov radiators coupled to fast photomultiplier tubes for a direction sensitive measurement. The readout electronics chain uses many components developed for the Phase 1 upgrade to the CMS Hadronic Calorimeter electronics, with dedicated firmware and readout adapted to the beam monitoring requirements. The PMT signal is digitized by a charge integrating ASIC (QIE10), providing both the signal rise time, with few ns resolution, and the charge integrated over one bunch crossing. The backend electronics uses microTCA technology and received data via a high-speed 5 Gbps asynchronous link. It records histograms with sub-bunch crossing timing resolution and is readout by IPbus using the newly designed CMS data acquisition for non-event based data. The data is processed i...

  1. Design of CMS Beam Halo Monitor system

    CERN Document Server

    AUTHOR|(CDS)2078842

    2015-01-01

    A fast and directional monitoring system for the CMS experiment is designed to provide an online, bunch-by-bunch measurement of beam background induced by beam halo interactions, separately for each beam. The background detection is based on Cherenkov radiation produced in synthetic fused silica read out by a fast, UV sensitive photomultiplier tube. Twenty detector units per end will be azimuthally distributed around the rotating shielding of CMS, covering ~408 cm2 at 20.6m from the interaction point, at a radius of ~180 cm. The directional and fast response of the system allows the discrimination of the background particles from the dominant flux in the cavern induced by pp collision debris, produced within the 25 ns bunch spacing. A robust multi-layered shielding will enclose each detector unit to protect the photomultiplier tube from the magnetic field and to eliminate the occupancy from low energy particles. The design of the front-end units is validated by experimental results. An overview of the new sy...

  2. Halo structure of strange particles in nuclei

    International Nuclear Information System (INIS)

    Akaishi, Yoshinori; Yamazaki, Toshimitsu.

    1997-01-01

    Some characteristic behaviors of hyperons in nuclei which have recently been revealed experimentally and theoretically are discussed with the emphasis on the repulsive part of the hyperon-nucleus interaction. The observed Σ 4 He nucleus is a bound state with J π = 0 + and T ≅ 1/2. Its nucleus-Σ potential derived from a realistic ΣN interaction is characterized by inner repulsion and a strong Lane term, which play important roles in forming the Σ-hypernuclear bound state. In 208 Pb a typical Coulomb-assisted bound state is expected, where Σ is trapped in the surface region by the nucleus-Σ potential with the aid of Coulomb and centrifugal interactions. In the double-strangeness (S=-2) sector, there is a possibility that the lightest double-Λ hypernucleus ΛΛ 4 H is abundantly populated by stopping Ξ - on 4 He. Its formation branching amounts to about 15%. A stopped Ξ - on 9 Be will also produce efficiently a variety of double-Λ hyperfragments. Discrete spectra of weak-decay pions from the fragments will provide a means of mass spectroscopy of double-Λ hypernuclei. In the S=-2 five-body system an excited state Ξ 5 H is predicted to appear with 'strangeness halo' and the ground state ΛΛ 5 H with almost pure ΛΛ component. (author)

  3. The CMS Beam Halo Monitor electronics

    Science.gov (United States)

    Tosi, N.; Dabrowski, A. E.; Fabbri, F.; Grassi, T.; Hughes, E.; Mans, J.; Montanari, A.; Orfanelli, S.; Rusack, R.; Torromeo, G.; Stickland, D. P.; Stifter, K.

    2016-02-01

    The CMS Beam Halo Monitor has been successfully installed in the CMS cavern in LHC Long Shutdown 1 for measuring the machine induced background for LHC Run II. The system is based on 40 detector units composed of synthetic quartz Cherenkov radiators coupled to fast photomultiplier tubes (PMTs). The readout electronics chain uses many components developed for the Phase 1 upgrade to the CMS Hadronic Calorimeter electronics, with dedicated firmware and readout adapted to the beam monitoring requirements. The PMT signal is digitized by a charge integrating ASIC (QIE10), providing both the signal rise time, with few nanosecond resolution, and the charge integrated over one bunch crossing. The backend electronics uses microTCA technology and receives data via a high-speed 5 Gbps asynchronous link. It records histograms with sub-bunch crossing timing resolution and is read out via IPbus using the newly designed CMS data acquisition for non-event based data. The data is processed in real time and published to CMS and the LHC, providing online feedback on the beam quality. A dedicated calibration monitoring system has been designed to generate short triggered pulses of light to monitor the efficiency of the system. The electronics has been in operation since the first LHC beams of Run II and has served as the first demonstration of the new QIE10, Microsemi Igloo2 FPGA and high-speed 5 Gbps link with LHC data.

  4. Beam halo collimation in heavy ion synchrotrons

    Directory of Open Access Journals (Sweden)

    I. Strašík

    2015-08-01

    Full Text Available This paper presents a systematic study of the halo collimation of ion beams from proton up to uranium in synchrotrons. The projected Facility for Antiproton and Ion Research synchrotron SIS100 is used as a reference case. The concepts are separated into fully stripped (e.g., ^{238}U^{92+} and partially stripped (e.g., ^{238}U^{28+} ion collimation. An application of the two-stage betatron collimation system, well established for proton accelerators, is intended also for fully stripped ions. The two-stage system consists of a primary collimator (a scattering foil and secondary collimators (bulky absorbers. Interaction of the particles with the primary collimator (scattering, momentum losses, and nuclear interactions was simulated by using fluka. Particle-tracking simulations were performed by using mad-x. Finally, the dependence of the collimation efficiency on the primary ion species was determined. The influence of the collimation system adjustment, lattice imperfections, and beam parameters was estimated. The concept for the collimation of partially stripped ions employs a thin stripping foil in order to change their charge state. These ions are subsequently deflected towards a dump location using a beam optical element. The charge state distribution after the stripping foil was obtained from global. The ions were tracked by using mad–x.

  5. Mergers and acquisitions: some implications of cultural change.

    Science.gov (United States)

    Cavanaugh, S J

    1996-01-01

    A result of recent National Health Service reforms is the need to investigate, and possibly change, the culture of the professional working relationship between members of staff and their employer. This is particularly the case in situations of mergers and acquisitions where staff working from different cultural environments must work together. Mergers are becoming a feature of health service provision, perhaps this becomes most obvious with the recent moves by colleges of nursing and midwifery into the higher education sector and amalgamations of some purchasing authorities. Mergers highlight the practical issues of bringing together different organizational and work cultures to deliver a high quality service. This article discusses some aspects of the nature of organizational culture, the human impact of mergers and acquisitions and offers strategies for managing these events.

  6. Black Hole Mergers and Gravitational Waves: Opening the New Frontier

    Science.gov (United States)

    Centrella, Joan

    2012-01-01

    The final merger of two black holes produces a powerful burst of gravitational waves, emitting more energy than all the stars in the observable universe combined. Since these mergers take place in the regime of strong dynamical gravity, computing the gravitational waveforms requires solving the full Einstein equations of general relativity on a computer. For more than 30 years, scientists tried to simulate these mergers using the methods of numerical relativity. The resulting computer codes were plagued by instabilities, causing them to crash well before the black holes in the binary could complete even a single orbit. In the past several years, this situation has changed dramatically, with a series of remarkable breakthroughs. This talk will highlight these breakthroughs and the resulting 'gold rush' of new results that is revealing the dynamics of binary black hole mergers, and their applications in gravitational wave detection, testing general relativity, and astrophysics.

  7. A radio counterpart to a neutron star merger.

    Science.gov (United States)

    Hallinan, G; Corsi, A; Mooley, K P; Hotokezaka, K; Nakar, E; Kasliwal, M M; Kaplan, D L; Frail, D A; Myers, S T; Murphy, T; De, K; Dobie, D; Allison, J R; Bannister, K W; Bhalerao, V; Chandra, P; Clarke, T E; Giacintucci, S; Ho, A Y Q; Horesh, A; Kassim, N E; Kulkarni, S R; Lenc, E; Lockman, F J; Lynch, C; Nichols, D; Nissanke, S; Palliyaguru, N; Peters, W M; Piran, T; Rana, J; Sadler, E M; Singer, L P

    2017-12-22

    Gravitational waves have been detected from a binary neutron star merger event, GW170817. The detection of electromagnetic radiation from the same source has shown that the merger occurred in the outskirts of the galaxy NGC 4993, at a distance of 40 megaparsecs from Earth. We report the detection of a counterpart radio source that appears 16 days after the event, allowing us to diagnose the energetics and environment of the merger. The observed radio emission can be explained by either a collimated ultrarelativistic jet, viewed off-axis, or a cocoon of mildly relativistic ejecta. Within 100 days of the merger, the radio light curves will enable observers to distinguish between these models, and the angular velocity and geometry of the debris will be directly measurable by very long baseline interferometry. Copyright © 2017, American Association for the Advancement of Science.

  8. Efficiency defense and administrative fuzziness in merger regulation

    Czech Academy of Sciences Publication Activity Database

    Medvedev, Andrei

    -, č. 234 (2004), s. 1-42 ISSN 1211-3298 Institutional research plan: CEZ:AV0Z7085904 Keywords : merger regulation * efficiency defense Subject RIV: AH - Economics http://www.cerge-ei.cz/pdf/wp/Wp234.pdf

  9. Quality competition and hospital mergers-An experiment.

    Science.gov (United States)

    Han, Johann; Kairies-Schwarz, Nadja; Vomhof, Markus

    2017-12-01

    On the basis of a Salop model with regulated prices, we investigate quality provision behaviour of competing hospitals before and after a merger. For this, we use a controlled laboratory experiment where subjects decided on the level of treatment quality as head of a hospital. We find that the post-merger average quality is significantly lower than the average pre-merger quality. However, for merger insiders and outsiders, average quality choices are significantly higher than predicted for pure profit-maximising hospitals. This upward deviation is potentially driven by altruistic behaviour towards patients. Furthermore, we find that in the case where sufficient cost synergies are realised by the merged hospitals, there is a significant increase in average quality choices compared to the scenario without synergies. Finally, we find that our results do not change when comparing individual decisions to team decisions. Copyright © 2017 John Wiley & Sons, Ltd.

  10. Modeling the Effects of Mergers in the Retail Sector

    DEFF Research Database (Denmark)

    Blomgren-Hansen, Niels

    2013-01-01

    According to EU competition law, mergers that significantly impedes effective competition, particularly by creating or strengthening a dominant position are prohibited. To identify these cases, authorities need a quantifiable model of the relationship between the variables that are affected...... by the merger and some measure of competition. Furthermore, the authorities must make their decision quickly, rendering deliberate data collection and econometric analyses infeasible in practice. The decision must be based on easily accessible data. In this paper, a simple model of the interaction between...... the retail and wholesale markets is constructed, calibrated and simulated based on a concrete case (the acquisition and merger of 250 shops previously organized in a voluntary chain of shops comprising roughly half of the market for high-end cosmetics in Denmark). Model simulations predicts that the merger...

  11. Black Hole Mergers, Gravitational Waves, and Multi-Messenger Astronomy

    Science.gov (United States)

    Centrella, Joan M.

    2010-01-01

    The final merger of two black holes is expected to be the strongest source of gravitational waves for both ground-based detectors such as LIGO and VIRGO, as well as the space-based LISA. Since the merger takes place in the regime of strong dynamical gravity, computing the resulting gravitational waveforms requires solving the full Einstein equations of general relativity on a computer. Although numerical codes designed to simulate black hole mergers were plagued for many years by a host of instabilities, recent breakthroughs have conquered these problems and opened up this field dramatically. This talk will focus on the resulting gold rush of new results that is revealing the dynamics and waveforms of binary black hole mergers, and their applications in gravitational wave detection, astrophysics, and testing general relativity.

  12. Modeling the Complete Gravitational Wave Spectrum of Neutron Star Mergers.

    Science.gov (United States)

    Bernuzzi, Sebastiano; Dietrich, Tim; Nagar, Alessandro

    2015-08-28

    In the context of neutron star mergers, we study the gravitational wave spectrum of the merger remnant using numerical relativity simulations. Postmerger spectra are characterized by a main peak frequency f2 related to the particular structure and dynamics of the remnant hot hypermassive neutron star. We show that f(2) is correlated with the tidal coupling constant κ(2)^T that characterizes the binary tidal interactions during the late-inspiral merger. The relation f(2)(κ(2)^T) depends very weakly on the binary total mass, mass ratio, equation of state, and thermal effects. This observation opens up the possibility of developing a model of the gravitational spectrum of every merger unifying the late-inspiral and postmerger descriptions.

  13. Horizontal mergers and weak and strong competition commissions

    Directory of Open Access Journals (Sweden)

    Ristić Bojan

    2014-01-01

    Full Text Available In this paper we analyse the horizontal merger of companies in an already concentrated industry. The participants in mergers are obliged to submit notification to the Competition Commission but they also have the option of rejecting the merger. At the time of the notification submission the participants do not know whether the Commission is strong or weak, and they can complain to the Court if the Commission prohibits the merger. We model the strategic interaction between Participants and Commission in a dynamic game of incomplete information and determine weak perfect Bayesian equilibria. The main finding of our paper is that Participants will base their decision to submit notification on their belief in a weak Commission decision and will almost completely ignore the possibility of a strong Commission decision. We also provide a detailed examination of one case from Serbian regulatory practice, which coincides with the results of our game theoretical model.

  14. Black-hole Merger Simulations for LISA Science

    Science.gov (United States)

    Kelly, Bernard J.; Baker, John G.; vanMeter, James R.; Boggs, William D.; Centrella, Joan M.; McWilliams, Sean T.

    2009-01-01

    The strongest expected sources of gravitational waves in the LISA band are the mergers of massive black holes. LISA may observe these systems to high redshift, z>10, to uncover details of the origin of massive black holes, and of the relationship between black holes and their host structures, and structure formation itself. These signals arise from the final stage in the development of a massive black-hole binary emitting strong gravitational radiation that accelerates the system's inspiral toward merger. The strongest part of the signal, at the point of merger, carries much information about the system and provides a probe of extreme gravitational physics. Theoretical predictions for these merger signals rely on supercomputer simulations to solve Einstein's equations. We discuss recent numerical results and their impact on LISA science expectations.

  15. Numerical Relativity Simulations for Black Hole Merger Astrophysics

    Science.gov (United States)

    Baker, John G.

    2010-01-01

    Massive black hole mergers are perhaps the most energetic astronomical events, establishing their importance as gravitational wave sources for LISA, and also possibly leading to observable influences on their local environments. Advances in numerical relativity over the last five years have fueled the development of a rich physical understanding of general relativity's predictions for these events. Z will overview the understanding of these event emerging from numerical simulation studies. These simulations elucidate the pre-merger dynamics of the black hole binaries, the consequent gravitational waveform signatures ' and the resulting state, including its kick velocity, for the final black hole produced by the merger. Scenarios are now being considered for observing each of these aspects of the merger, involving both gravitational-wave and electromagnetic astronomy.

  16. Modeling the Effects of Mergers in the Retail Sector

    DEFF Research Database (Denmark)

    Blomgren-Hansen, Niels

    2013-01-01

    the retail and wholesale markets is constructed, calibrated and simulated based on a concrete case (the acquisition and merger of 250 shops previously organized in a voluntary chain of shops comprising roughly half of the market for high-end cosmetics in Denmark). Model simulations predicts that the merger......According to EU competition law, mergers that significantly impedes effective competition, particularly by creating or strengthening a dominant position are prohibited. To identify these cases, authorities need a quantifiable model of the relationship between the variables that are affected...... by the merger and some measure of competition. Furthermore, the authorities must make their decision quickly, rendering deliberate data collection and econometric analyses infeasible in practice. The decision must be based on easily accessible data. In this paper, a simple model of the interaction between...

  17. Understanding Information Systems Integration Deficiencies in Mergers and Acquisitions

    DEFF Research Database (Denmark)

    Henningsson, Stefan; Kettinger, William J.

    2017-01-01

    Information systems (IS) integration is a critical challenge for value-creating mergers and acquisitions. Appropriate design and implementation of IS integration is typically a precondition for enabling a majority of the anticipated business benefits of a combined organization. Often...

  18. The Role of Occupational Identification During Post-Merger Integration.

    Science.gov (United States)

    Kroon, David P; Noorderhaven, Niels G

    2018-04-01

    Integration processes after mergers are fraught with difficulties, and constitute a main cause of merger failure. This study focuses on the human aspect of post-merger integration, and in particular, on the role of occupational identification. We theorize and empirically demonstrate by means of a survey design that employees' identification with their occupation is positively related to their willingness to cooperate in the post-merger integration process, over and above the effect of organization members' organizational identification. This positive effect of occupational identification is stronger for uniformed personnel but attenuates in the course of the integration process. Qualitative interviews further explore and interpret the results from our statistical analysis. Together, these findings have important practical implications and suggest future research directions.

  19. Synthesis and enzymatic ketonization of the 5-(halo-2-hydroxymuconates and 5-(halo-2-hydroxy-2,4-pentadienoates

    Directory of Open Access Journals (Sweden)

    Tyler M. M. Stack

    2017-05-01

    Full Text Available 5-Halo-2-hydroxymuconates and 5-halo-2-hydroxy-2,4-pentadienoates are stable dienols that are proposed intermediates in bacterial meta-fission pathways for the degradation of halogenated aromatic compounds. The presence of the halogen raises questions about how the bulk and/or electronegativity of these substrates would affect enzyme catalysis or whether some pathway enzymes have evolved to accommodate it. To address these questions, 5-halo-2-hydroxymuconates and 5-halo-2-hydroxy-2,4-pentadienoates (5-halo = Cl, Br, F were synthesized and a preliminary analysis of their enzymatic properties carried out. In aqueous buffer, 5-halo-2-hydroxy-2,4-pentadienoates rapidly equilibrate with the β,γ-unsaturated ketones. For the 5-chloro and 5-bromo derivatives, a slower conversion to the α,β-isomers follows. There is no detectable formation of the α,β-isomer for the 5-fluoro derivative. Kinetic parameters were also obtained for both sets of compounds in the presence of 4-oxalocrotonate tautomerase (4-OT from Pseudomonas putida mt-2 and Leptothrix cholodnii SP-6. For 5-halo-2-hydroxymuconates, there are no major differences in the kinetic parameters for the two enzymes (following the formation of the β,γ-unsaturated ketones. In contrast, the L. cholodnii SP-6 4-OT is ≈10-fold less efficient than the P. putida mt-2 4-OT in the formation of the β,γ-unsaturated ketones and the α,β-isomers from the 5-halo-2-hydroxy-2,4-pentadienoates. The implications of these findings are discussed. The availability of these compounds will facilitate future studies of the haloaromatic catabolic pathways.

  20. COMPANIES’ MERGERS AND AQUISITIONS AS A SOCIAL PROCESS: MODERN REALITIES

    Directory of Open Access Journals (Sweden)

    S. A. Barkov

    2017-01-01

    Full Text Available Mergers and acquisitions have become one of the main business strategies in the past decades. However, as the international experience indicates, the impact of mergers and acquisitions is rather ambiguous. On the one hand, mergers accelerate the evolution of organizations, strengthen their market positions and competitive advantages, create opportunities for the future development. On the other hand, mergers and acquisitions often lead to severe system crises, caused by various confrontations and risks. From the social and administrative point of view, mergers and acquisitions are commonly perceived as troublesome transformation processes instilling distrust and fear in the workers. Fear of the upcoming mergers is typical not only for ordinary employees, but also for senior management, who remains the most vulnerable unit in the M&A process. Mergers are considered as a stress and challenge for all the categories of employees. The employees realize the instability and the vulnerability of their current statuses, the limited ability to influence the situation and job insecurity. The uncertainty and fear lead to the employees’ resistance of different kinds, which eventually destroys the corporate unity, exacerbates the contradictions between various groups of employees and destabilizes the operation of companies. The authors assume that in the post-industrial age the employees’ perceptions of the merger processes can change and study the trends and factors which determine employees’ attitude towards mergers and acquisitions. Nowadays management strategies and the logic of administrative processes change radically, the structure of companies and the relationships in organizations networks undergo crucial transformations. The tendency to the democratization of organizations has received widespread recognition; companies become more flexible and are more frequently perceived and operate as open systems. The companies start to use the project

  1. Analisis Kinerja Keuangan Perusahaan Sebelum dan Sesudah Merger dan Akuisisi

    OpenAIRE

    Esterlina, Prisya; Firdausi, Nila Nuzula

    2017-01-01

    The research aimed to examine the conditions of companies' financial performance before and after conducting merger and acquisition. Indonesia Stock Exchange (IDX known as BEI) noticed that a whole sector in thirty companies did a merger and acquisition during 2010-2012 periods, except financial sector.Using financial ratio as the parameter of financial performance, it turned out to be the variables that used in this research were current ratio, total asset turnover, fixed asset turnover, deb...

  2. Galaxy pairs as a probe for mergers at z ~ 2

    DEFF Research Database (Denmark)

    Man, A.W.S.; Zirm, Andrew Wasmuth; Toft, Sune

    2011-01-01

    In this work I investigate the redshift evolution of pair fraction of a sample of 196 massive galaxies from z = 0 to 3, selected from the COSMOS field. We find that on average a massive galaxy undergoes ~ 1.1 \\pm 0.5 major merger since z = 3. I will review the current limitations of using the pair...... fraction as a probe for quantifying the impact of mergers on galaxy evolution. This work is based on the paper Man et al. (2011)....

  3. Numerical Relativity, Black Hole Mergers, and Gravitational Waves: Part II

    Science.gov (United States)

    Centrella, Joan

    2012-01-01

    This series of 3 lectures will present recent developments in numerical relativity, and their applications to simulating black hole mergers and computing the resulting gravitational waveforms. In this second lecture, we focus on simulations of black hole binary mergers. We hig hlight the instabilities that plagued the codes for many years, the r ecent breakthroughs that led to the first accurate simulations, and the current state of the art.

  4. The Detection and Parameter Estimation of Binary Black Hole Mergers

    Science.gov (United States)

    Biwer, Christopher M.

    In this dissertation we study gravitational-wave data analysis techniques for binary neutron star and black hole mergers. During its first observing run, the Advanced Laser Interferometer Gravitational-wave Observatory (Advanced LIGO) reported the first, direct observations of gravitational waves from two binary black hole mergers. We present the results from the search for binary black hole mergers which unambiguously detected the binary black hole mergers. We determine the effect of calibration errors on the detection statistic of the search. Since the search is not designed to precisely measure the astrophysical parameters of the binary neutron star and black hole mergers, we use Bayesian methods to develop a new parameter estimation analysis. We demonstrate the performance of the analysis on the binary black hole mergers detected during Advanced LIGO's first observing run. We use the parameter estimation analysis to assess the ability of gravitational-wave observatories to observe a gap in the black hole mass distribution between 52 M and 133 M due to pair-instability supernovae. Finally, we use simulated signals added to the Advanced LIGO detectors to validate the search and parameter estimation analyses used to publish the detection of the astrophysical events.

  5. Merger and Industrial Acceleration: Study at Indonesian Islamic Banking Industry

    Directory of Open Access Journals (Sweden)

    Kindy Miftah

    2017-02-01

    Full Text Available The purpose of this research tries to feed the alternatives of merger between Islamic banks which becomes a form of recommendation to optimize the merger result, so it will contribute to the development of Indonesia’s banking sector in particular. Methodolgy of this study is using comparison technique utilize result of calculation valuation based on valuation theory in general with method discounted cash flaw (DCF. Valuation data processing using data past performance sharia banks is to plan future financial performance. Results of valuation will be conducted both with individual banks that will be merged and alternative merger determined. These findings implied from various possibility alternative mergers between sharia banks, there are 5 alternatives that are feasible considering the internal aspect such as tendency shareholder and condition sharia bank to be merged related to internal interest and external aspect namely scale of assets from merger banks and probability success from merger process.DOI:  10.15408/sjie.v6i1.4728

  6. The diversity and similarity of simulated cold dark matter haloes

    Science.gov (United States)

    Navarro, Julio F.; Ludlow, Aaron; Springel, Volker; Wang, Jie; Vogelsberger, Mark; White, Simon D. M.; Jenkins, Adrian; Frenk, Carlos S.; Helmi, Amina

    2010-02-01

    We study the mass, velocity dispersion and anisotropy profiles of Λ cold dark matter (ΛCDM) haloes using a suite of N-body simulations of unprecedented numerical resolution. The Aquarius Project follows the formation of six different galaxy-sized haloes simulated several times at varying numerical resolution, allowing numerical convergence to be assessed directly. The highest resolution simulation represents a single dark matter halo using 4.4 billion particles, of which 1.1 billion end up within the virial radius. Our analysis confirms a number of results claimed by earlier work, and clarifies a few issues where conflicting claims may be found in the recent literature. The mass profile of ΛCDM haloes deviates slightly but systematically from the form proposed by Navarro, Frenk & White. The spherically averaged density profile becomes progressively shallower inwards and, at the innermost resolved radius, the logarithmic slope is γ ≡ - d ln ρ/d ln r universal: different haloes cannot, in general, be rescaled to look identical. Departures from similarity are also seen in velocity dispersion profiles and correlate with those in density profiles so as to preserve a power-law form for the spherically averaged pseudo-phase-space density, ρ/σ3 ~ r-1.875. The index here is identical to that of Bertschinger's similarity solution for self-similar infall on to a point mass from an otherwise uniform Einstein-de Sitter universe. The origin of this striking behaviour is unclear, but its robustness suggests that it reflects a fundamental structural property of ΛCDM haloes. Our conclusions are reliable down to radii below 0.4 per cent of the virial radius, providing well-defined predictions for halo structure when baryonic effects are neglected, and thus an instructive theoretical template against which the modifications induced by the baryonic components of real galaxies can be judged.

  7. A mechanical device for enhancing the halo density in the TMX-U tandem mirror

    International Nuclear Information System (INIS)

    Hsu, W.L.; Barr, W.L.; Simonen, T.C.

    1984-01-01

    The halo recycler, a mechanical device similar to pump limiters used in tokamaks, is studied as a means of enhancing the halo plasma density in the Tandem Mirror Experiment Upgrade (TMX-U). The recycler structure consists of an annular chamber at each end of the tandem mirror device where the halo plasma is collected. The halo plasma density is increased by recycling the halo ions as they are neutralized by the collector plate. With sufficient power fed into the halo electrons, the recycler can sustain an upstream electron temperature of 30 eV for effective halo shielding while maintaining a low temperature of 5 eV near the collector plate to reduce sputtering. A power flow model has shown that the required power for heating the halo is low enough to make the halo recycler a practical concept. (orig.)

  8. The Angular Momentum of Baryons and Dark Matter Halos Revisited

    Science.gov (United States)

    Kimm, Taysun; Devriendt, Julien; Slyz, Adrianne; Pichon, Christophe; Kassin, Susan A.; Dubois, Yohan

    2011-01-01

    Recent theoretical studies have shown that galaxies at high redshift are fed by cold, dense gas filaments, suggesting angular momentum transport by gas differs from that by dark matter. Revisiting this issue using high-resolution cosmological hydrodynamics simulations with adaptive-mesh refinement (AMR), we find that at the time of accretion, gas and dark matter do carry a similar amount of specific angular momentum, but that it is systematically higher than that of the dark matter halo as a whole. At high redshift, freshly accreted gas rapidly streams into the central region of the halo, directly depositing this large amount of angular momentum within a sphere of radius r = 0.1R(sub vir). In contrast, dark matter particles pass through the central region unscathed, and a fraction of them ends up populating the outer regions of the halo (r/R(sub vir) > 0.1), redistributing angular momentum in the process. As a result, large-scale motions of the cosmic web have to be considered as the origin of gas angular momentum rather than its virialised dark matter halo host. This generic result holds for halos of all masses at all redshifts, as radiative cooling ensures that a significant fraction of baryons remain trapped at the centre of the halos. Despite this injection of angular momentum enriched gas, we predict an amount for stellar discs which is in fair agreement with observations at z=0. This arises because the total specific angular momentum of the baryons (gas and stars) remains close to that of dark matter halos. Indeed, our simulations indicate that any differential loss of angular momentum amplitude between the two components is minor even though dark matter halos continuously lose between half and two-thirds of their specific angular momentum modulus as they evolve. In light of our results, a substantial revision of the standard theory of disc formation seems to be required. We propose a new scenario where gas efficiently carries the angular momentum generated

  9. Halo-Independent Direct Detection Analyses Without Mass Assumptions

    CERN Document Server

    Anderson, Adam J.; Kahn, Yonatan; McCullough, Matthew

    2015-10-06

    Results from direct detection experiments are typically interpreted by employing an assumption about the dark matter velocity distribution, with results presented in the $m_\\chi-\\sigma_n$ plane. Recently methods which are independent of the DM halo velocity distribution have been developed which present results in the $v_{min}-\\tilde{g}$ plane, but these in turn require an assumption on the dark matter mass. Here we present an extension of these halo-independent methods for dark matter direct detection which does not require a fiducial choice of the dark matter mass. With a change of variables from $v_{min}$ to nuclear recoil momentum ($p_R$), the full halo-independent content of an experimental result for any dark matter mass can be condensed into a single plot as a function of a new halo integral variable, which we call $\\tilde{h}(p_R)$. The entire family of conventional halo-independent $\\tilde{g}(v_{min})$ plots for all DM masses are directly found from the single $\\tilde{h}(p_R)$ plot through a simple re...

  10. HOT GAS HALOS IN EARLY-TYPE FIELD GALAXIES

    International Nuclear Information System (INIS)

    Mulchaey, John S.; Jeltema, Tesla E.

    2010-01-01

    We use Chandra and XMM-Newton to study the hot gas content in a sample of field early-type galaxies. We find that the L X -L K relationship is steeper for field galaxies than for comparable galaxies in groups and clusters. The low hot gas content of field galaxies with L K ∼ * suggests that internal processes such as supernovae-driven winds or active galactic nucleus feedback expel hot gas from low-mass galaxies. Such mechanisms may be less effective in groups and clusters where the presence of an intragroup or intracluster medium can confine outflowing material. In addition, galaxies in groups and clusters may be able to accrete gas from the ambient medium. While there is a population of L K ∼ * galaxies in groups and clusters that retain hot gas halos, some galaxies in these rich environments, including brighter galaxies, are largely devoid of hot gas. In these cases, the hot gas halos have likely been removed via ram pressure stripping. This suggests a very complex interplay between the intragroup/intracluster medium and hot gas halos of galaxies in rich environments, with the ambient medium helping to confine or even enhance the halos in some cases and acting to remove gas in others. In contrast, the hot gas content of more isolated galaxies is largely a function of the mass of the galaxy, with more massive galaxies able to maintain their halos, while in lower mass systems the hot gas escapes in outflowing winds.

  11. The Structure and Evolution of Cold Dark Matter Halos

    Science.gov (United States)

    Diemand, Jürg; Moore, Ben

    2011-02-01

    In the standard cosmological model a mysterious cold dark matter (CDM) component dominates the formation of structures. Numerical studies of the f ormation of CDM halos have produced several robust results that allow unique tests of the hierarchical clustering paradigm. Universal properties of halos, including their mass profiles and substructure properties are roughly consistent with observational data from the scales of dwarf galaxies to galaxy clusters. Resolving the fine grained structure of halos has enabled us to make predictions for ongoing and planned direct and indirect dark matter detection experiments. While simulations of pure CDM halos are now very accurate and in good agreement (recently claimed discrepancies are addressed in detail in this review), we are still unable to make robust, quantitative predictions about galaxy formation and about how the dark matter distribution changes in the process. Whilst discrepancies between observations and simulations have been the subject of much debate in the literature, galaxy formation and evolution needs to be understood in more detail in order to fully test the CDM paradigm. Whatever the true nature of the dark matter particle is, its clustering properties must not be too different from a cold neutralino like particle to maintain all the successes of the model in matching large scale structure data and the global properties of halos which are mostly in good agreement with observations.

  12. Two distinct halo populations in the solar neighborhood. III

    DEFF Research Database (Denmark)

    Schuster, W. J.; Moreno, E.; Nissen, Poul Erik

    2012-01-01

    Context. In Papers I and II of this series, we have found clear indications of the existence of two distinct populations of stars in the solar neighborhood belonging to the metal-rich end of the halo metallicity distribution function. Based on high-resolution, high S/N spectra, it is possible...... to distinguish between “high-alpha” and “low-alpha” components using the [α/Fe] versus [Fe/H] diagram. Aims. Precise relative ages and orbital parameters are determined for 67 halo and 16 thick-disk stars having metallicities in the range −1.4 .... The “high-alpha” halo stars have ages 2–3 Gyr larger than the “low-alpha” ones, with some probability that the thick-disk stars have ages intermediate between these two halo components. The orbital parameters show very distinct differences between the “high-alpha” and “low-alpha” halo stars. The “low...

  13. Early halo immobilization of displaced traumatic spondylolisthesis of the axis.

    Science.gov (United States)

    Vaccaro, Alexander R; Madigan, Luke; Bauerle, Wayne B; Blescia, Adam; Cotler, Jerome M

    2002-10-15

    A retrospective study evaluating early halo immobilization of Types II and IIA hangman's fractures. To determine the treatment efficacy of early halo immobilization of Type II and IIA hangman's fractures. The treatment of hangman's fractures with traction reduction is well established, but the time required in traction before the institution of halo-vest immobilization is controversial. A retrospective review of all patients admitted to a level one spinal cord injury center between 1986 and 1999 with either a Type II or IIA hangman's fracture was performed. Initial and final radiographs were measured for translation and angulation. The need for reapplication of traction was also recorded. There were a total of 27 Type II and four Type IIA fractures. Of the Type II fractures, 21 went onto union after early halo immobilization. Six patients required reapplication of traction reduction because of fracture displacement. The Type IIA fractures all progressed to union. The discerning factor between the failure group and the success group was the initial degree of angulation on lateral cervical radiography. The patients requiring reapplication of traction had an initial fracture angulation of 12 degrees or greater. Early halo immobilization after traction reduction of Type II and IIA hangman's fractures is an effective method of management. Type II fractures with an angulation of greater than or equal to 12 degrees may require an extended period of traction to ensure adequate long-term fracture alignment.

  14. HALOGEN: a tool for fast generation of mock halo catalogues

    Science.gov (United States)

    Avila, Santiago; Murray, Steven G.; Knebe, Alexander; Power, Chris; Robotham, Aaron S. G.; Garcia-Bellido, Juan

    2015-06-01

    We present a simple method of generating approximate synthetic halo catalogues: HALOGEN. This method uses a combination of second-order Lagrangian Perturbation Theory (2LPT) in order to generate the large-scale matter distribution, analytical mass functions to generate halo masses, and a single-parameter stochastic model for halo bias to position haloes. HALOGEN represents a simplification of similar recently published methods. Our method is constrained to recover the two-point function at intermediate (10 h-1 Mpc space distortions) with results from N-body simulations to determine the validity of our method for different purposes. One of the benefits of HALOGEN is its flexibility, and we demonstrate this by showing how it can be adapted to varying cosmologies and simulation specifications. A driving motivation for the development of such approximate schemes is the need to compute covariance matrices and study the systematic errors for large galaxy surveys, which requires thousands of simulated realizations. We discuss the applicability of our method in this context, and conclude that it is well suited to mass production of appropriate halo catalogues. The code is publicly available at https://github.com/savila/halogen.

  15. Deep brain transcranial magnetic stimulation using variable "Halo coil" system

    Science.gov (United States)

    Meng, Y.; Hadimani, R. L.; Crowther, L. J.; Xu, Z.; Qu, J.; Jiles, D. C.

    2015-05-01

    Transcranial Magnetic Stimulation has the potential to treat various neurological disorders non-invasively and safely. The "Halo coil" configuration can stimulate deeper regions of the brain with lower surface to deep-brain field ratio compared to other coil configurations. The existing "Halo coil" configuration is fixed and is limited in varying the site of stimulation in the brain. We have developed a new system based on the current "Halo coil" design along with a graphical user interface system that enables the larger coil to rotate along the transverse plane. The new system can also enable vertical movement of larger coil. Thus, this adjustable "Halo coil" configuration can stimulate different regions of the brain by adjusting the position and orientation of the larger coil on the head. We have calculated magnetic and electric fields inside a MRI-derived heterogeneous head model for various positions and orientations of the coil. We have also investigated the mechanical and thermal stability of the adjustable "Halo coil" configuration for various positions and orientations of the coil to ensure safe operation of the system.

  16. THE BLACK HOLE–DARK MATTER HALO CONNECTION

    International Nuclear Information System (INIS)

    Sabra, Bassem M.; Saliba, Charbel; Akl, Maya Abi; Chahine, Gilbert

    2015-01-01

    We explore the connection between the central supermassive black holes (SMBH) in galaxies and the dark matter halo through the relation between the masses of the SMBHs and the maximum circular velocities of the host galaxies, as well as the relationship between stellar velocity dispersion of the spheroidal component and the circular velocity. Our assumption here is that the circular velocity is a proxy for the mass of the dark matter halo. We rely on a heterogeneous sample containing galaxies of all types. The only requirement is that the galaxy has a direct measurement of the mass of its SMBH and a direct measurement of its circular velocity and its velocity dispersion. Previous studies have analyzed the connection between the SMBH and dark matter halo through the relationship between the circular velocity and the bulge velocity dispersion, with the assumption that the bulge velocity dispersion stands in for the mass of the SMBH, via the well-established SMBH mass–bulge velocity dispersion relation. Using intermediate relations may be misleading when one is studying them to decipher the active ingredients of galaxy formation and evolution. We believe that our approach will provide a more direct probe of the SMBH and the dark matter halo connection. We find that the correlation between the mass of SMBHs and the circular velocities of the host galaxies is extremely weak, leading us to state the dark matter halo may not play a major role in regulating the black hole growth in the present Universe

  17. THE BLACK HOLE–DARK MATTER HALO CONNECTION

    Energy Technology Data Exchange (ETDEWEB)

    Sabra, Bassem M. [Department of Physics and Astronomy, Notre Dame University-Louaize, P.O. Box 72 Zouk Mikael, Zouk Mosbeh (Lebanon); Saliba, Charbel; Akl, Maya Abi; Chahine, Gilbert, E-mail: bsabra@ndu.edu.lb [Department of Physics, Lebanese University II, Fanar (Lebanon)

    2015-04-10

    We explore the connection between the central supermassive black holes (SMBH) in galaxies and the dark matter halo through the relation between the masses of the SMBHs and the maximum circular velocities of the host galaxies, as well as the relationship between stellar velocity dispersion of the spheroidal component and the circular velocity. Our assumption here is that the circular velocity is a proxy for the mass of the dark matter halo. We rely on a heterogeneous sample containing galaxies of all types. The only requirement is that the galaxy has a direct measurement of the mass of its SMBH and a direct measurement of its circular velocity and its velocity dispersion. Previous studies have analyzed the connection between the SMBH and dark matter halo through the relationship between the circular velocity and the bulge velocity dispersion, with the assumption that the bulge velocity dispersion stands in for the mass of the SMBH, via the well-established SMBH mass–bulge velocity dispersion relation. Using intermediate relations may be misleading when one is studying them to decipher the active ingredients of galaxy formation and evolution. We believe that our approach will provide a more direct probe of the SMBH and the dark matter halo connection. We find that the correlation between the mass of SMBHs and the circular velocities of the host galaxies is extremely weak, leading us to state the dark matter halo may not play a major role in regulating the black hole growth in the present Universe.

  18. A PETAL OF THE SUNFLOWER: PHOTOMETRY OF THE STELLAR TIDAL STREAM IN THE HALO OF MESSIER 63 (NGC 5055)

    International Nuclear Information System (INIS)

    Chonis, Taylor S.; Martínez-Delgado, David; Gabany, R. Jay; Majewski, Steven R.; Hill, Gary J.; Gralak, Ray; Trujillo, Ignacio

    2011-01-01

    We present deep surface photometry of a very faint, giant arc-loop feature in the halo of the nearby spiral galaxy NGC 5055 (M63) that is consistent with being a part of a stellar stream resulting from the disruption of a dwarf satellite galaxy. This faint feature was first detected in early photographic studies by van der Kruit; more recently, in the study of Martínez-Delgado and as presented in this work, from the loop has been realized to be the result of a recent minor merger through evidence obtained by wide-field, deep images taken with a telescope of only 0.16 m aperture. The stellar stream is clearly confirmed in additional deep images taken with the 0.5 m telescope of the BlackBird Remote Observatory and the 0.8 m telescope of the McDonald Observatory. This low surface brightness (μ R ≈ 26 mag arcsec –2 ) arc-like structure around the disk of the galaxy extends 14.'0 (∼29 kpc projected) from its center, with a projected width of 1.'6 (∼3.3 kpc). The stream's morphology is consistent with that of the visible part of a giant, 'great-circle' type stellar stream originating from the recent accretion of a ∼10 8 M ☉ dwarf satellite in the last few Gyr. The progenitor satellite's current position and final fate are not conclusive from our data. The color of the stream's stars is consistent with dwarfs in the Local Group and is similar to the outer faint regions of M63's disk and stellar halo. From our photometric study, we detect other low surface brightness 'plumes'; some of these may be extended spiral features related to the galaxy's complex spiral structure, and others may be tidal debris associated with the disruption of the galaxy's outer stellar disk as a result of the accretion event. We are able to differentiate between features related to the tidal stream and faint, blue extended features in the outskirts of the galaxy's disk previously detected by the Galaxy Evolution Explorer satellite. With its highly warped H I gaseous disk (∼20

  19. Black Hole Mergers and Recoils in Low-Mass Galaxies

    Science.gov (United States)

    Blecha, Laura; Kelley, Luke; Koss, Michael; Satyapal, Shobita

    2018-01-01

    Mergers between massive black holes (BHs) in the intermediate-mass range are one of the most promising sources of gravitational waves (GWs) detectable with LISA. These highly energetic GW events could be observed out to very high redshift, in the epoch where massive BH seeds are thought to form. Despite recent progress, however, much is still not known about the low-mass BH population even in the local Universe. The rates of BH binary formation, inspiral, and merger are also highly uncertain across the BH mass scale. To address these pressing issues in advance of LISA, cosmological hydrodynamics simulations and semi-analytic modeling are being used to model the formation and evolution of BH binaries, and the GW signals they produce. Efforts are also underway to understand the electromagnetic (EM) signatures of the BH binary population. These have proven largely elusive thus far, but an increasing population of BH pairs has been found, and advances in the coming years will provide important comparisons for models of GW sources. Moreover, asymmetry in the GW emission from BH mergers imparts a recoil kick to the merged BH, which in extreme cases can eject the BH from its host galaxy. This creates additional uncertainty in the BH merger rate, but the remnant recoiling BH could be observed as an offset quasar. Identifications of such objects would provide another EM signature of BH mergers that would help pave the way for LISA. We will review model predictions of the BH inspiral and merger rate across the mass scale. We will also describe how the EM signatures of active, merging BHs can be used to constrain theoretical merger rates. Finally, we will discuss the predicted observability of recoiling BHs and ongoing efforts to identify and confirm candidate recoils.

  20. A comprehensive, holistic people integration process for mergers and acquisitions

    Directory of Open Access Journals (Sweden)

    Rina P. Steynberg

    2011-02-01

    Full Text Available Orientation: Mergers and Acquisitions (M&As are a frequent, alternative strategic growth option to organic growth for organisations. The failure rate of mergers and acquisitions is alarmingly high (70% plus failures. The people factor is seen as one of the main contributors to this failure.Research purpose: To develop and validate a comprehensive, holistic model for the people integration process during mergers and acquisitions.Motivation for the study: The literature on a comprehensive, holistic people integration process for mergers and acquisitions is sparse and fragmented.Research design, approach and method: A qualitative approach was adopted consisting of a three step process which solicited the views of seasoned M&A Practioners; these views were compared against the available literature. Finally, practioners were asked to critique the final model from a practice perspective. The utility of the final model was assessed against two mergers and acquisitions case studies.Main findings: A comprehensive, holistic people integration process model for mergers and acquisitions was developed and validated. However, this model will only significantly enhance mergers and acquisitions value realisation if it is applied from the appropriate vantage point.Practical/managerial implications: The proposed approach will increase the probability of a successful M&A people-wise and M&A value realisation.Contribution/value add: Theoretically, the development and validation of a M&A people process integration model; practically, guidelines for successful people integration; organisationally, significantly enhancing the chances of M&A success; and community wise, the reduction of the negative effects of M&A failure on communities.

  1. Integrated delivery systems: mergers and acquisitions.

    Science.gov (United States)

    Pinkerton, S

    1999-01-01

    Mergers and acquisitions are usually the way an IDS is built. The CNO and/or CNOs/DONs have an integral role in the resolution of the M/A process. During this time of significant change, during which there may even be chaos, the CNOs work to maintain stability so there is as little impact as possible on patient outcomes, a core responsibility of the CNOs. The CNOs should focus on identifying and working with the highly skilled individuals in the organization to get to the recovery stage of the M/A process, at which time a high-performing organization is achieved. To build this new organization or IDS, the old organizations of the M/A must be changed (Moss Kanter, 1994). The successful CNOs will manage the trade-offs and will become experts in collaboration. The CNO's goals are to maximize the quality of patient care, the professional satisfaction of the nurse, and the goals of achieving cost effectiveness for the system (Clifford, 1998), and keeping this focus through the M/A process will yield success.

  2. SHAM beyond clustering: new tests of galaxy–halo abundance matching with galaxy groups

    Energy Technology Data Exchange (ETDEWEB)

    Hearin, Andrew P.; Zentner, Andrew R.; Berlind, Andreas A.; Newman, Jeffrey A.

    2013-05-27

    We construct mock catalogs of galaxy groups using subhalo abundance matching (SHAM) and undertake several new tests of the SHAM prescription for the galaxy-dark matter connection. All SHAM models we studied exhibit significant tension with galaxy groups observed in the Sloan Digital Sky Survey (SDSS). The SHAM prediction for the field galaxy luminosity function (LF) is systematically too dim, and the group galaxy LF systematically too bright, regardless of the details of the SHAM prescription. SHAM models connecting r-band luminosity, Mr, to Vacc, the maximum circular velocity of a subhalo at the time of accretion onto the host, faithfully reproduce galaxy group abundance as a function of richness, g(N). However, SHAM models connecting Mr with Vpeak, the peak value of Vmax over the entire merger history of the halo, over-predict galaxy group abundance. Our results suggest that no SHAM model can simultaneously reproduce the observed g(N) and two-point projected galaxy clustering. Nevertheless, we also report a new success of SHAM: an accurate prediction for Phi(m12), the abundance of galaxy groups as a function of magnitude gap m12, defined as the difference between the r-band absolute magnitude of the two brightest group members. We show that it may be possible to use joint measurements of g(N) and Phi(m12) to tightly constrain the details of the SHAM implementation. Additionally, we show that the hypothesis that the luminosity gap is constructed via random draws from a universal LF provides a poor description of the data, contradicting recent claims in the literature. Finally, we test a common assumption of the Conditional Luminosity Function (CLF) formalism, that the satellite LF need only be conditioned by the brightness of the central galaxy. We find this assumption to be well-supported by the observed Phi(m12).

  3. Revisiting the bulge-halo conspiracy - II. Towards explaining its puzzling dependence on redshift

    Science.gov (United States)

    Shankar, Francesco; Sonnenfeld, Alessandro; Grylls, Philip; Zanisi, Lorenzo; Nipoti, Carlo; Chae, Kyu-Hyun; Bernardi, Mariangela; Petrillo, Carlo Enrico; Huertas-Company, Marc; Mamon, Gary A.; Buchan, Stewart

    2018-04-01

    We carry out a systematic investigation of the total mass density profile of massive (log Mstar/M⊙ ˜ 11.5) early-type galaxies and its dependence on redshift, specifically in the range 0 ≲ z ≲ 1. We start from a large sample of Sloan Digital Sky Survey early-type galaxies with stellar masses and effective radii measured assuming two different profiles, de Vaucouleurs and Sérsic. We assign dark matter haloes to galaxies via abundance matching relations with standard ΛCDM profiles and concentrations. We then compute the total, mass-weighted density slope at the effective radius γ΄, and study its redshift dependence at fixed stellar mass. We find that a necessary condition to induce an increasingly flatter γ΄ at higher redshifts, as suggested by current strong lensing data, is to allow the intrinsic stellar profile of massive galaxies to be Sérsic and the input Sérsic index n to vary with redshift as n(z) ∝ (1 + z)δ, with δ ≲ -1. This conclusion holds irrespective of the input Mstar-Mhalo relation, the assumed stellar initial mass function (IMF), or even the chosen level of adiabatic contraction in the model. Secondary contributors to the observed redshift evolution of γ΄ may come from an increased contribution at higher redshifts of adiabatic contraction and/or bottom-light stellar IMFs. The strong lensing selection effects we have simulated seem not to contribute to this effect. A steadily increasing Sérsic index with cosmic time is supported by independent observations, though it is not yet clear whether cosmological hierarchical models (e.g. mergers) are capable of reproducing such a fast and sharp evolution.

  4. The Galaxy Cluster Merger Catalog: An Online Repository of Mock Observations from Simulated Galaxy Cluster Mergers

    Science.gov (United States)

    ZuHone, J. A.; Kowalik, K.; Öhman, E.; Lau, E.; Nagai, D.

    2018-01-01

    We present the “Galaxy Cluster Merger Catalog.” This catalog provides an extensive suite of mock observations and related data for N-body and hydrodynamical simulations of galaxy cluster mergers and clusters from cosmological simulations. These mock observations consist of projections of a number of important observable quantities in several different wavebands, as well as along different lines of sight through each simulation domain. The web interface to the catalog consists of easily browsable images over epoch and projection direction, as well as download links for the raw data and a JS9 interface for interactive data exploration. The data are presented within a consistent format so that comparison between simulations is straightforward. All of the data products are provided in the standard Flexible Image Transport System file format. The data are being stored on the yt Hub (http://hub.yt), which allows for remote access and analysis using a Jupyter notebook server. Future versions of the catalog will include simulations from a number of research groups and a variety of research topics related to the study of interactions of galaxy clusters with each other and with their member galaxies. The catalog is located at http://gcmc.hub.yt.

  5. A ROBUST MEASURE OF DARK MATTER HALO ELLIPTICITIES

    Energy Technology Data Exchange (ETDEWEB)

    Evslin, Jarah [Institute of Modern Physics, CAS, NanChangLu 509, Lanzhou 730000 (China)

    2016-08-01

    In simulations of the standard cosmological model (ΛCDM), dark matter halos are aspherical. However, so far the asphericity of an individual galaxy’s halo has never been robustly established. We use the Jeans equations to define a quantity that robustly characterizes a deviation from rotational symmetry. This quantity is essentially the gravitational torque and it roughly provides the ellipticity projected along the line of sight. We show that the Thirty Meter Telescope (TMT), with a single epoch of observations combined with those of the Gaia Space Telescope , can distinguish the ΛCDM value of the torque from zero for each Sculptor-like dwarf galaxy with a confidence between 0 and 5 σ , depending on the orientation of each halo. With two epochs of observations, TMT will achieve a 5 σ discovery of torque and thus asphericity for most such galaxies, thus providing a new and powerful test of the ΛCDM model.

  6. Properties of the ISM - Gas in the halo

    Science.gov (United States)

    Savage, Blair D.

    1990-01-01

    The properties of interstellar gas in the galactic halo are reviewed. Halo gas is found to have a wide range of physical conditions with temperatures ranging from less than 170 K to more than 200,000 K. The gas extending away from the plane of the Milky Way has density scale heights ranging from less than 300 pc for certain species in the neutral medium to approximately 3000 pc for the most highly ionized gas. The complex kinematical characteristics of the gas provides important clues about its origin. The gas phase elemental abundances in the neutral halo gas are closer to solar than is found for the highly depleted gas of the Milky Way disk. The possible origin of gas at large distances away from the galactic plane is discussed.

  7. Axionic dark matter signatures in various halo models

    Energy Technology Data Exchange (ETDEWEB)

    Vergados, J.D., E-mail: vergados@uoi.gr [Center for Axion and Precision Physics Research, Institute for Basic Science (IBS), Daejeon 34141 (Korea, Republic of); Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141 (Korea, Republic of); ARC Centre of Excellence in Particle Physics at the Terascale and Centre for the Subatomic Structure of Matter (CSSM), University of Adelaide, Adelaide SA 5005 (Australia); Semertzidis, Y.K. [Center for Axion and Precision Physics Research, Institute for Basic Science (IBS), Daejeon 34141 (Korea, Republic of); Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141 (Korea, Republic of)

    2017-02-15

    In the present work we study possible signatures in the Axion Dark Matter searches. We focus on the dependence of the expected width in resonant cavities for various popular halo models, leading to standard velocity distributions, e.g. Maxwell–Boltzmann, as well as phase-mixed and non-virialized axionic dark matter (flows, caustic rings). We study, in particular, the time dependence of the resonance width (modulation) arising from such models. We find that the difference between the maximum (in June) and the minimum (in December) can vary by about 10% in the case of standard halos. In the case of mixed phase halos the variation is a bit bigger and for caustic rings the maximum is expected to occur a bit later. Experimentally such a modulation is observable with present technology.

  8. Reactions of Proton Halo Nuclei in a Relativistic Optical Potential

    CERN Document Server

    Rashdan, M

    2003-01-01

    The reaction cross section, sigma sub R; of the proton halo nuclei sup 1 sup 7 Ne and sup 1 sup 2 N on Si is calculated using an optical potential derived from the solution of the Dirac-Brueckner-Bethe-Goldstone equation, starting from the one-boson-exchange potential of Bonn. The nuclear densities are generated from self-consistent Hartree-Fock calculations using the recent Skyrme interaction SKRA. It is found that the enhancement in the reaction cross section found experimentally for the sup 1 sup 7 Ne + Si system in comparison to sup 1 sup 5 O + Si, where sup 1 sup 5 O has been considered as a core of sup 1 sup 7 Ne, is mainly due to the proton halo structure of sup 1 sup 7 Ne which increases the interaction, in the surface and tail regions. Glauber model calculations did not produce this enhancement in sigma sub R for proton halo nuclei

  9. Halo-independent methods for inelastic dark matter scattering

    International Nuclear Information System (INIS)

    Bozorgnia, Nassim; Schwetz, Thomas; Herrero-Garcia, Juan; Zupan, Jure

    2013-01-01

    We present halo-independent methods to analyze the results of dark matter direct detection experiments assuming inelastic scattering. We focus on the annual modulation signal reported by DAMA/LIBRA and present three different halo-independent tests. First, we compare it to the upper limit on the unmodulated rate from XENON100 using (a) the trivial requirement that the amplitude of the annual modulation has to be smaller than the bound on the unmodulated rate, and (b) a bound on the annual modulation amplitude based on an expansion in the Earth's velocity. The third test uses the special predictions of the signal shape for inelastic scattering and allows for an internal consistency check of the data without referring to any astrophysics. We conclude that a strong conflict between DAMA/LIBRA and XENON100 in the framework of spin-independent inelastic scattering can be established independently of the local properties of the dark matter halo

  10. Two distinct halo populations in the solar neighborhood. IV

    DEFF Research Database (Denmark)

    Nissen, P. E.; Schuster, W. J.

    2012-01-01

    We investigate if there is a difference in the lithium abundances of stars belonging to two halo populations of F and G main-sequence stars previously found to differ in [alpha/Fe] for the metallicity range -1.4 ...-resolution spectra using MARCS model atmospheres. Furthermore, masses of the stars are determined from the logTeff - logg diagram by interpolating between Yonsei-Yale evolutionary tracks. There is no significant systematic difference in the lithium abundances of high- and low-alpha halo stars. For the large majority...... predicted from standard Big Bang nucleosynthesis calculations and the WMAP baryon density. The relation, however, does not apply to stars with [Fe/H] halo stars were formed with a Li abundance close to the primordial value, and that lithium in their atmospheres has been...

  11. The Halo Boundary of Galaxy Clusters in the SDSS

    Energy Technology Data Exchange (ETDEWEB)

    Baxter, Eric; Jain, Bhuvnesh; Sheth, Ravi K. [Center for Particle Cosmology, Department of Physics, University of Pennsylvania, Philadelphia, PA 19104 (United States); Chang, Chihway; Kravtsov, Andrey [Kavli Institute for Cosmological Physics, The University of Chicago, Chicago, IL 60637 (United States); Adhikari, Susmita; Dalal, Neal [Department of Astronomy, University of Illinois at Urbana-Champaign, Champaign, IL 61801 (United States); More, Surhud [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Tokyo Institutes for Advanced Study, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba, 277-8583 (Japan); Rozo, Eduardo [Department of Physics, University of Arizona, Tucson, AZ 85721 (United States); Rykoff, Eli, E-mail: ebax@sas.upenn.edu [Kavli Institute for Particle Astrophysics and Cosmology, P.O. Box 2450, Stanford University, Stanford, CA 94305 (United States)

    2017-05-20

    Analytical models and simulations predict a rapid decline in the halo density profile associated with the transition from the “infalling” regime outside the halo to the “collapsed” regime within the halo. Using data from SDSS, we explore evidence for such a feature in the density profiles of galaxy clusters using several different approaches. We first estimate the steepening of the outer galaxy density profile around clusters, finding evidence for truncation of the halo profile. Next, we measure the galaxy density profile around clusters using two sets of galaxies selected on color. We find evidence of an abrupt change in galaxy colors that coincides with the location of the steepening of the density profile. Since galaxies that have completed orbits within the cluster are more likely to be quenched of star formation and thus appear redder, this abrupt change in galaxy color can be associated with the transition from single-stream to multi-stream regimes. We also use a standard model comparison approach to measure evidence for a “splashback”-like feature, but find that this approach is very sensitive to modeling assumptions. Finally, we perform measurements using an independent cluster catalog to test for potential systematic errors associated with cluster selection. We identify several avenues for future work: improved understanding of the small-scale galaxy profile, lensing measurements, identification of proxies for the halo accretion rate, and other tests. With upcoming data from the DES, KiDS, and HSC surveys, we can expect significant improvements in the study of halo boundaries.

  12. Three-body halo nuclei in an effective theory framework

    Energy Technology Data Exchange (ETDEWEB)

    Canham, David L.

    2009-05-20

    The universal properties and structure of halo nuclei composed of two neutrons (2n) and a core are investigated within an effective quantum mechanics framework. We construct an effective interaction potential that exploits the separation of scales in halo nuclei and treat the nucleus as an effective three-body system, which to leading order is described by the large S-wave scattering lengths in the underlying two-body subsystems. The uncertainty from higher orders in the expansion is quantified through theoretical error bands. First, we investigate the possibility to observe excited Efimov states in 2n halo nuclei. Based on the experimental data, {sup 20}C is the only halo nucleus candidate to possibly have an Efimov excited state, with an energy less than 7 keV below the scattering threshold. Second, we study the structure of {sup 20}C and other 2n halo nuclei. In particular, we calculate their matter density form factors, radii, and two-neutron opening angles. We then make a systematic improvement upon these calculations by extending the effective potential to the next-to-leading order. To this order, we require an additional two-body parameter, which we tune to the effective range of the interaction. In addition to range corrections to the 2n halo nuclei results, we show corrections to the Efimov effect in the three-boson system. Furthermore, we explore universality in the linear range corrections to the Efimov spectrum. Finally, we study the scattering of D{sup 0} and D{sup *0} mesons and their antiparticles off the X(3872) in an effective field theory for short-range interactions. We present results for the S-wave scattering amplitude, total interaction cross section and S-wave scattering length. (orig.)

  13. A comprehensive, holistic people integration process for mergers and acquisitions

    Directory of Open Access Journals (Sweden)

    Rina P. Steynberg

    2011-03-01

    Research purpose: To develop and validate a comprehensive, holistic model for the people integration process during mergers and acquisitions. Motivation for the study: The literature on a comprehensive, holistic people integration process for mergers and acquisitions is sparse and fragmented. Research design, approach and method: A qualitative approach was adopted consisting of a three step process which solicited the views of seasoned M&A Practioners; these views were compared against the available literature. Finally, practioners were asked to critique the final model from a practice perspective. The utility of the final model was assessed against two mergers and acquisitions case studies. Main findings: A comprehensive, holistic people integration process model for mergers and acquisitions was developed and validated. However, this model will only significantly enhance mergers and acquisitions value realisation if it is applied from the appropriate vantage point. Practical/managerial implications: The proposed approach will increase the probability of a successful M&A people-wise and M&A value realisation. Contribution/value add: Theoretically, the development and validation of a M&A people process integration model; practically, guidelines for successful people integration; organisationally, significantly enhancing the chances of M&A success; and community wise, the reduction of the negative effects of M&A failure on communities.

  14. THE MAIN OPERATIONS OF REORGANIZATION THROUGH MERGERS OF TRADING COMPANIES

    Directory of Open Access Journals (Sweden)

    Alexandra-Gabriela Rolea

    2013-11-01

    Full Text Available Notwithstanding the optimistic forecasts issued by experts a couple of years ago, the economic predicaments of the European Union’s member states, including Romania, are far from being settled. The extension of the economic and financial dowturn, the continuing process of globalization and the financial markets’ volatility have imposed an unparalleled flexibility upon the economic agents, in that the amount of mergers and acquisitions has risen at a both national and international level. This background calls for a detailed but nonetheless approachable study of the reorganization of the trading companies though mergers, aimed mainly at the business environment. In order to reach the aforementioned objectives, the theoretical endeavor seeks to explore the relevant legal provisions, including the European Directives. The juridical and accounting operations of mergers, their legal consequences and concrete implications on the activity of the trading companies will also be analysed. Some particular approaches embraced by the legal practice are to be presented, as in Romania mergers are submitted to the control of the court. The study will have a positive impact on the economic agents, who are fostered to conclude this type of restructuring, by altering the line of thought shaped a few years ago, according to which mergers are difficult, isolated and sometimes even unacceptable operations.

  15. Specification of merger gains in the Norwegian electricity distribution industry

    International Nuclear Information System (INIS)

    Saastamoinen, Antti; Bjørndal, Endre; Bjørndal, Mette

    2017-01-01

    Electricity distribution often exhibits economies of scale. In Norway, a number of smaller distribution system operators exist and thus there is potential to restructure the industry, possibly through mergers. However, the revenue cap regulatory model in Norway does not incentivize firms to merge as merging leads to a stricter revenue cap for the merged company. Thus the regulator compensates the firms in order to create such incentives. The amount of compensation is based on the potential gains of the merger estimated using a data envelopment analysis (DEA) based frontier approach introduced by Bogetoft and Wang (2005). DEA is however only one of many possible frontier estimators that can be used in estimation. Furthermore, the returns to scale assumption, the operating environment of firms and the presence of stochastic noise and outlier observations are all known to affect to the estimation of production technology. In this paper we explore how varying assumptions under two alternative frontier estimators shape the distribution of merger gains within the Norwegian distribution industry. Our results reveal that the restructuring policies of the industry may be significantly altered depending how potential gains from the mergers are estimated. - Highlights: • The merger gains of Norwegian electricity distribution firm are investigated. • Different estimators and model specifications are applied. • Results show that the gains are significantly affected by the model choice. • Incentives to merge may be shaped through the estimation of gains.

  16. Targeting Cislunar Near Rectilinear Halo Orbits for Human Space Exploration

    Science.gov (United States)

    Williams, Jacob; Lee, David E.; Whitley, Ryan J.; Bokelmann, Kevin A.; Davis, Diane C.; Berry, Christopher F.

    2017-01-01

    Part of the challenge of charting a human exploration space architecture is finding locations to stage missions to multiple destinations. To that end, a specific subset of Earth-Moon halo orbits, known as Near Rectilinear Halo Orbits (NRHOs) are evaluated. In this paper, a systematic process for generating full ephemeris based ballistic NRHOs is outlined, different size NRHOs are examined for their favorability to avoid eclipses, the performance requirements for missions to and from NRHOs are calculated, and disposal options are evaluated. Combined, these studies confirm the feasibility of cislunar NRHOs to enable human exploration in the cislunar proving ground.

  17. Signatures of compact halos of sterile-neutrino dark matter

    Science.gov (United States)

    Kühnel, Florian; Ohlsson, Tommy

    2017-11-01

    We investigate compact halos of sterile-neutrino dark matter and examine observable signatures with respect to neutrino and photon emission. Primarily, we consider two cases: primordial black-hole halos and ultracompact minihalos. In both cases, we find that there exists a broad range of possible parameter choices such that detection in the near future with x-ray and gamma-ray telescopes might be well possible. In fact, for energies above 10 TeV, the neutrino telescope IceCube would be a splendid detection machine for such macroscopic dark-matter candidates.

  18. Mismatch and misalignment: dark haloes and satellites of disc galaxies

    Science.gov (United States)

    Deason, A. J.; McCarthy, I. G.; Font, A. S.; Evans, N. W.; Frenk, C. S.; Belokurov, V.; Libeskind, N. I.; Crain, R. A.; Theuns, T.

    2011-08-01

    We study the phase-space distribution of satellite galaxies associated with late-type galaxies in the GIMIC suite of simulations. GIMIC consists of resimulations of five cosmologically representative regions from the Millennium Simulation, which have higher resolution and incorporate baryonic physics. Whilst the disc of the galaxy is well aligned with the inner regions (r˜ 0.1r200) of the dark matter halo, both in shape and angular momentum, there can be substantial misalignments at larger radii (r˜r200). Misalignments of >45° are seen in ˜30 per cent of our sample. We find that the satellite population aligns with the shape (and angular momentum) of the outer dark matter halo. However, the alignment with the galaxy is weak owing to the mismatch between the disc and dark matter halo. Roughly 20 per cent of the satellite systems with 10 bright galaxies within r200 exhibit a polar spatial alignment with respect to the galaxy - an orientation reminiscent of the classical satellites of the Milky Way. We find that a small fraction (˜10 per cent) of satellite systems show evidence for rotational support which we attribute to group infall. There is a bias towards satellites on prograde orbits relative to the spin of the dark matter halo (and to a lesser extent with the angular momentum of the disc). This preference towards co-rotation is stronger in the inner regions of the halo where the most massive satellites accreted at relatively early times are located. We attribute the anisotropic spatial distribution and angular momentum bias of the satellites at z= 0 to their directional accretion along the major axes of the dark matter halo. The satellite galaxies have been accreted relatively recently compared to the dark matter mass and have experienced less phase-mixing and relaxation - the memory of their accretion history can remain intact to z= 0. Understanding the phase-space distribution of the z= 0 satellite population is key for studies that estimate the host halo

  19. Dynamical Constraints On The Galaxy-Halo Connection

    Science.gov (United States)

    Desmond, Harry

    2017-07-01

    Dark matter halos comprise the bulk of the universe's mass, yet must be probed by the luminous galaxies that form within them. A key goal of modern astrophysics, therefore, is to robustly relate the visible and dark mass, which to first order means relating the properties of galaxies and halos. This may be expected not only to improve our knowledge of galaxy formation, but also to enable high-precision cosmological tests using galaxies and hence maximise the utility of future galaxy surveys. As halos are inaccessible to observations - as galaxies are to N-body simulations - this relation requires an additional modelling step.The aim of this thesis is to develop and evaluate models of the galaxy-halo connection using observations of galaxy dynamics. In particular, I build empirical models based on the technique of halo abundance matching for five key dynamical scaling relations of galaxies - the Tully-Fisher, Faber-Jackson, mass-size and mass discrepancy-acceleration relations, and Fundamental Plane - which relate their baryon distributions and rotation or velocity dispersion profiles. I then develop a statistical scheme based on approximate Bayesian computation to compare the predicted and measured values of a number of summary statistics describing the relations' important features. This not only provides quantitative constraints on the free parameters of the models, but also allows absolute goodness-of-fit measures to be formulated. I find some features to be naturally accounted for by an abundance matching approach and others to impose new constraints on the galaxy-halo connection; the remainder are challenging to account for and may imply galaxy-halo correlations beyond the scope of basic abundance matching.Besides providing concrete statistical tests of specific galaxy formation theories, these results will be of use for guiding the inputs of empirical and semi-analytic galaxy formation models, which require galaxy-halo correlations to be imposed by hand. As

  20. Halo Occupation Distribution Modeling of Clustering of Luminous Red Galaxies

    OpenAIRE

    Zheng, Zheng; Zehavi, Idit; Eisenstein, Daniel J.; Weinberg, David H.; Jing, Y. P.

    2008-01-01

    We perform Halo Occupation Distribution (HOD) modeling to interpret small-scale and intermediate-scale clustering of 35,000 luminous early-type galaxies and their cross-correlation with a reference imaging sample of normal L* galaxies in the Sloan Digital Sky Survey. The modeling results show that most of these luminous red galaxies (LRGs) are central galaxies residing in massive halos of typical mass M ~ a few times 10^13 to 10^14 Msun/h, while a few percent of them have to be satellites wit...

  1. Halo-like structures studied by atomic force microscopy

    DEFF Research Database (Denmark)

    Sørensen, Alexis Hammer; Kyhle, Anders; Hansen, L. Theil

    1997-01-01

    Nanometer-sized clusters of copper have been produced in a hollow cathode sputtering source and deposited on SiOx. Halo-like structures consisting of micrometer sized protrusions in the solicon oxide surface surrounded by thin rings of smaller particles are observed. The area in between seems...... to be depleted of particles. We propose that the halo-like structures are a result of electrostatic forces acting between the incoming charged clusters and charged regions on the surface. A simple computer simulation supports this suggestion....

  2. Black Hole Space-time In Dark Matter Halo

    OpenAIRE

    Xu, Zhaoyi; Hou, Xian; Gong, Xiaobo; Wang, Jiancheng

    2018-01-01

    For the first time, we obtain the analytical form of black hole space-time metric in dark matter halo for the stationary situation. Using the relation between the rotation velocity (in the equatorial plane) and the spherical symmetric space-time metric coefficient, we obtain the space-time metric for pure dark matter. By considering the dark matter halo in spherical symmetric space-time as part of the energy-momentum tensors in the Einstein field equation, we then obtain the spherical symmetr...

  3. Mergers between governmental research institutes and Universities in the Danish HE sector

    DEFF Research Database (Denmark)

    Aagaard, Kaare; Hansen, Hanne Foss; Rasmussen, Jørgen Gulddahl

    2016-01-01

    This article presents an analysis of the mergers in the Danish Higher Education (HE)-sector with a particular emphasis on the 2007 mergers involving universities and Government Research Institutes (GRIs). Furthermore, it follows the post-merger processes up to 2014/2015 at two Danish universities...... and the outcomes. Finally, it is shown that it makes a significant difference whether a federal or a unitary structure is implemented after the merger, although each solution has both strengths and weaknesses....

  4. Quantifying the impact of mergers on the angular momentum of simulated galaxies

    Science.gov (United States)

    Lagos, Claudia del P.; Stevens, Adam R. H.; Bower, Richard G.; Davis, Timothy A.; Contreras, Sergio; Padilla, Nelson D.; Obreschkow, Danail; Croton, Darren; Trayford, James W.; Welker, Charlotte; Theuns, Tom

    2018-02-01

    We use EAGLE to quantify the effect galaxy mergers have on the stellar specific angular momentum of galaxies, jstars. We split mergers into dry (gas-poor)/wet (gas-rich), major/minor and different spin alignments and orbital parameters. Wet (dry) mergers have an average neutral gas-to-stellar mass ratio of 1.1 (0.02), while major (minor) mergers are those with stellar mass ratios ≥0.3 (0.1-0.3). We correlate the positions of galaxies in the jstars-stellar mass plane at z = 0 with their merger history, and find that galaxies of low spins suffered dry mergers, while galaxies of normal/high spins suffered predominantly wet mergers, if any. The radial jstars profiles of galaxies that went through dry mergers are deficient by ≈0.3 dex at r ≲ 10 r50 (with r50 being the half-stellar mass radius), compared to galaxies that went through wet mergers. Studying the merger remnants reveals that dry mergers reduce jstars by ≈30 per cent, while wet mergers increase it by ≈10 per cent, on average. The latter is connected to the build-up of the bulge by newly formed stars of high rotational speed. Moving from minor to major mergers accentuates these effects. When the spin vectors of the galaxies prior to the dry merger are misaligned, jstars decreases by a greater magnitude, while in wet mergers corotation and high orbital angular momentum efficiently spun-up galaxies. We predict what would be the observational signatures in the jstars profiles driven by dry mergers: (i) shallow radial profiles and (ii) profiles that rise beyond ≈10 r50, both of which are significantly different from spiral galaxies.

  5. RELICS OF GALAXY MERGING: OBSERVATIONAL PREDICTIONS FOR A WANDERING MASSIVE BLACK HOLE AND ACCOMPANYING STAR CLUSTER IN THE HALO OF M31

    Energy Technology Data Exchange (ETDEWEB)

    Kawaguchi, Toshihiro [Astronomy Data Center, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Saito, Yuriko [Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), Mitaka, Tokyo 181-8588 (Japan); Miki, Yohei; Mori, Masao, E-mail: ts.kawaguti@nao.ac.jp [Center for Computational Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8577 (Japan)

    2014-07-01

    Galaxies and massive black holes (BHs) presumably grow via galactic merging events and subsequent BH coalescence. As a case study, we investigate the merging event between the Andromeda galaxy (M31) and a satellite galaxy. We compute the expected observational appearance of the massive BH that was at the center of the satellite galaxy prior to the merger and is currently wandering in the M31 halo. We demonstrate that a radiatively inefficient accretion flow with a bolometric luminosity of a few tens of solar luminosities develops when Hoyle-Lyttleton accretion onto the BH is assumed. We compute the associated broadband spectrum and show that the radio band (observable with EVLA, ALMA, and the Square Kilometre Array) is the best frequency range in which to detect the emission. We also evaluate the mass and the luminosity of the stars bound by the wandering BH and find that such a star cluster is sufficiently luminous that it could correspond to one of the star clusters found by the PAndAS survey. The discovery of a relic massive BH wandering in a galactic halo will provide a direct means of investigating in detail the coevolution of galaxies and BHs. It also means a new population of BHs (off-center massive BHs) and offers targets for clean BH imaging that avoid strong interstellar scattering in the centers of galaxies.

  6. X-ray surveys - Weighting the dark matter haloes of X-ray AGN: towards a physical description of the accretion history of the Universe

    Science.gov (United States)

    Georgakakis, Antonis; Mountrichas, G.; Fanidakis, N.; Finoguenov, A.; Aegis Collaboration

    2012-09-01

    The masses of the dark matter haloes in which AGN live is powerful diagnostic of the conditions under which supermassive black holes form and evolve across cosmic time. A new clustering estimation method will be presented which requires spectroscopy only for the AGN and uses photometric redshift probability density functions for galaxies to determine the projected real-space AGN/galaxy cross-correlation function. Our method is superior to traditional AGN clustering estimators (e.g. auto-correlation function) because (i) random errors are significantly suppressed when counting AGN/galaxy pairs, (ii) the impact of sample variance is minimized, and (iii) the requirements for spectroscopy are minimal; only spectroscopic redshift measurements for the AGN are needed. This method is applied to the combined AEGIS, COSMOS and ECDFS fields to infer the bias and dark matter halo mass of moderate luminosity (Lx~10^43 erg/s/cm^2) X-ray AGN at z~1 (total of 400). Predictions from the GALFORM semi-analytic model will be compared to the observations to show that a combination of hot and cold-gas accretion (the latter triggered by disk instabilities in spirals rather than mergers) reproduce well the clustering properties of X-ray AGN over a range of redshifts and luminosities.

  7. Toward a Combined SAGE II-HALOE Aerosol Climatology: An Evaluation of HALOE Version 19 Stratospheric Aerosol Extinction Coefficient Observations

    Science.gov (United States)

    Thomason, L. W.

    2012-01-01

    Herein, the Halogen Occultation Experiment (HALOE) aerosol extinction coefficient data is evaluated in the low aerosol loading period after 1996 as the first necessary step in a process that will eventually allow the production of a combined HALOE/SAGE II (Stratospheric Aerosol and Gas Experiment) aerosol climatology of derived aerosol products including surface area density. Based on these analyses, it is demonstrated that HALOE's 3.46 microns is of good quality above 19 km and suitable for scientific applications above that altitude. However, it is increasingly suspect at lower altitudes and should not be used below 17 km under any circumstances after 1996. The 3.40 microns is biased by about 10% throughout the lower stratosphere due to the failure to clear NO2 but otherwise appears to be a high quality product down to 15 km. The 2.45 and 5.26 micron aerosol extinction coefficient measurements are clearly biased and should not be used for scientific applications after the most intense parts of the Pinatubo period. Many of the issues in the aerosol data appear to be related to either the failure to clear some interfering gas species or doing so poorly. For instance, it is clear that the 3.40micronaerosol extinction coefficient measurements can be improved through the inclusion of an NO2 correction and could, in fact, end up as the highest quality overall HALOE aerosol extinction coefficient measurement. It also appears that the 2.45 and 5.26 micron channels may be improved by updating the Upper Atmosphere Pilot Database which is used as a resource for the removal of gas species otherwise not available from direct HALOE measurements. Finally, a simple model to demonstrate the promise of mixed visible/infrared aerosol extinction coefficient ensembles for the retrieval of bulk aerosol properties demonstrates that a combined HALOE/SAGE II aerosol climatology is feasible and may represent a substantial improvement over independently derived data sets.

  8. Hydrodynamic evolution of neutron star merger remnants

    Science.gov (United States)

    Liu, Men-Quan; Zhang, Jie

    2017-11-01

    Based on the special relativistic hydrodynamic equations and updated cooling function, we investigate the long-term evolution of neutron stars merger (NSM) remnants by a one-dimensional hydrodynamic code. Three NSM models from one soft equation of state, SFHo, and two stiff equations of state, DD2 and TM1, are used to compare their influences on the hydrodynamic evolution of remnants. We present the luminosity, mass and radius of remnants, as well as the velocity, temperature and density of shocks. For a typical interstellar medium (ISM) density with solar metallicity, we find that the NSM remnant from the SFHo model makes much more changes to ISM in terms of velocity, density and temperature distributions, compared with the case of DD2 and TM1 models. The maximal luminosity of the NSM remnant from the SFHo model is 3.4 × 1038 erg s-1, which is several times larger than that from DD2 and TM1 models. The NSM remnant from the SFHo model can maintain high luminosity (>1038 erg s-1) for 2.29 × 104 yr. Furthermore, the density and temperature of remnants at the maximal luminosity are not sensitive to the power of the original remnant. For the ISM with the solar metallicity and nH = 1 cm- 3, the density of the first shock ∼10-23 g cm-3 and the temperature ∼3 × 105 K in the maximal luminosity phase; The temperature of the first shock decreases and there is a thin 'dense' shell with density ∼10-21 g cm-3 after the maximal luminosity. These characteristics may be helpful for future observations of NSM remnants.

  9. BRIGHT 'MERGER-NOVA' FROM THE REMNANT OF A NEUTRON STAR BINARY MERGER: A SIGNATURE OF A NEWLY BORN, MASSIVE, MILLISECOND MAGNETAR

    International Nuclear Information System (INIS)

    Yu, Yun-Wei; Zhang, Bing; Gao, He

    2013-01-01

    A massive millisecond magnetar may survive the merger of a neutron star (NS) binary, which would continuously power the merger ejecta. We develop a generic dynamic model for the merger ejecta with energy injection from the central magnetar. The ejecta emission (the m erger-nova ) powered by the magnetar peaks in the UV band and the peak of the light curve, progressively shifts to an earlier epoch with increasing frequency. A magnetar-powered merger-nova could have an optical peak brightness comparable to a supernova, which is a few tens or hundreds times brighter than the radioactive-powered merger-novae (the so-called macro-nova or kilo-nova). On the other hand, such a merger-nova would peak earlier and have a significantly shorter duration than that of a supernova. An early collapse of the magnetar could suppress the brightness of the optical emission and shorten its duration. Such millisecond-magnetar-powered merger-novae may be detected from NS-NS merger events without an observed short gamma-ray burst, and could be a bright electromagnetic counterpart for gravitational wave bursts due to NS-NS mergers. If detected, it suggests that the merger leaves behind a massive NS, which has important implications for the equation-of-state of nuclear matter

  10. Resolution of vitiligo following excision of halo congenital melanocytic nevus: a rare case report.

    Science.gov (United States)

    Wang, Kai; Wang, Zhi; Huang, Weiqing

    2016-05-01

    Halo congenital melanocytic nevus (CMN) associated with vitiligo is rare, especially with regard to CMN excision. Only two reports of excision of halo CMN following repigmentation of vitiligo are found in the literature. We present a case of a girl with halo CMN and periorbital vitiligo. The halo CMN was excised and followed by spontaneous improvement of vitiligo. The result suggests excision of the inciting lesion may be a promising way to control vitiligo. © 2015 Wiley Periodicals, Inc.

  11. Research Note--Should Consumers Use the Halo to Form Product Evaluations?

    OpenAIRE

    Peter Boatwright; Ajay Kalra; Wei Zhang

    2008-01-01

    In purchase situations where attribute information is either missing or difficult to judge, a well-known heuristic that consumers use to form evaluations is the halo effect. The psychology literature has widely considered the halo a reflection of consumers' inability to discriminate between different attributes and have therefore labeled it the "halo error" or the "logical error." The objective of this paper is to offer a rationale for the halo effect. We use a decision-theory framework to sh...

  12. Implications of mergers and acquisitions in gas and electric markets: The role of yardstick competition in merger analysis

    International Nuclear Information System (INIS)

    Reiter, H.L.

    1999-01-01

    There has been no shortage of proposed and consummated mergers of regulated utilities in the electric, natural gas, and telecommunication industries over the last decade. For example, the National Rural Electric Cooperative Association states that there have been thirty electric utility mergers since 1992 and dozens of so-called convergence mergers between electric and gas utilities during that period. Yardstick competition or the competition that occurs when the regulator can compare the relative performances of utilities it regulates with other utilities it regulates or with neighboring utilities in other jurisdictions, places pressure on the regulated utilities to perform better for fear of coming up short in the comparison process. There are three important questions regulators may ask about the importance of yardstick competition as regulatory tool and the weight regulators should give to diminution of yardstick competition in the merger context. First, does it make that much difference? In the electric industry, for example, distribution costs typically comprise less than ten percent of the delivered price of electricity. Second, to preserve theoretical yardstick competition, are regulators then going to block mergers that bring other efficiencies? And finally, are there sound tools at the regulators' disposal should they be inclined to take yardstick competition seriously as a factor in regulation of utilities?

  13. Astrophysics of Super-Massive Black Hole Mergers

    Science.gov (United States)

    Schnittman, Jeremy D.

    2013-01-01

    We present here an overview of recent work in the subject of astrophysical manifestations of super-massive black hole (SMBH) mergers. This is a field that has been traditionally driven by theoretical work, but in recent years has also generated a great deal of interest and excitement in the observational astronomy community. In particular, the electromagnetic (EM) counterparts to SMBH mergers provide the means to detect and characterize these highly energetic events at cosmological distances, even in the absence of a space-based gravitational-wave observatory. In addition to providing a mechanism for observing SMBH mergers, EM counterparts also give important information about the environments in which these remarkable events take place, thus teaching us about the mechanisms through which galaxies form and evolve symbiotically with their central black holes.

  14. Employer-provided health insurance and hospital mergers.

    Science.gov (United States)

    Garmon, Christopher

    2013-07-01

    This paper explores the impact of employer-provided health insurance on hospital competition and hospital mergers. Under employer-provided health insurance, employer executives act as agents for their employees in selecting health insurance options for their firm. The paper investigates whether a merger of hospitals favored by executives will result in a larger price increase than a merger of competing hospitals elsewhere. This is found to be the case even when the executive has the same opportunity cost of travel as her employees and even when the executive is the sole owner of the firm, retaining all profits. This is consistent with the Federal Trade Commission's findings in its challenge of Evanston Northwestern Healthcare's acquisition of Highland Park Hospital. Implications of the model are further tested with executive location data and hospital data from Florida and Texas.

  15. Galaxy pairs as a probe for mergers at z ~ 2

    DEFF Research Database (Denmark)

    Man, A.W.S.; Zirm, Andrew Wasmuth; Toft, Sune

    2011-01-01

    In this work I investigate the redshift evolution of pair fraction of a sample of 196 massive galaxies from z = 0 to 3, selected from the COSMOS field. We find that on average a massive galaxy undergoes ~ 1.1 \\pm 0.5 major merger since z = 3. I will review the current limitations of using the pai...... fraction as a probe for quantifying the impact of mergers on galaxy evolution. This work is based on the paper Man et al. (2011).......In this work I investigate the redshift evolution of pair fraction of a sample of 196 massive galaxies from z = 0 to 3, selected from the COSMOS field. We find that on average a massive galaxy undergoes ~ 1.1 \\pm 0.5 major merger since z = 3. I will review the current limitations of using the pair...

  16. The effects of union mergers and internal restructuring:

    DEFF Research Database (Denmark)

    Navrbjerg, Steen Erik; Larsen, Trine Pernille

    2016-01-01

    Trade union mergers and restructuring are often seen as strategy for union revitalisation and renewal and have been ongoing in the majority of European trade unions. This paper explores how recent union mergers and internal restructuring has affected unions service provision, union democracy...... and interest representation. This is analysed drawing on longitudinal data from two Danish shop steward surveys conducted in 1998 and 2010, comparing shop stewards in merged and non-merged unions respectively. The main results are that although it could be expected that union mergers and internal restructuring...... may entail lower service levels, democratic deficit and weakening of union identities, this is not always the case. Danish shop stewards appear more satisfied with their union’s service provision anno 2010 compared to 1998 and feel more able to influence union politics. However, variations also exist...

  17. How Enterprise Architecture Maturity Enables Post-merger IT Integration

    DEFF Research Database (Denmark)

    Törmer, Robert Lorenz; Henningsson, Stefan

    2017-01-01

    While world-wide Mergers and Acquisitions (M&As) activity continues to accelerate, a substantial proportion of deals fails to yield the expected value. The inability to plan and implement post-merger integration of information technology contributes substantially to these failure rates. This paper...... advances the argument that a company’s pre-existing Enterprise Architecture decisively shapes the capability to implement post-merger IT integration and subsequently realize benefits from M&A. Our multiple-case study investigates three acquisition cases and develops an explanatory theory of how Enterprise...... Architecture maturity enables the implementation of distinct integration strategies. The results do not only enrich the academic literature on M&A, but also show the strategic value of Enterprise Architecture maturity....

  18. Merger Strategy, Cross-Cultural Involvement, and Polyphony

    DEFF Research Database (Denmark)

    Svane, Marita; Boje, David

    2014-01-01

    Structured Abstract: Purpose: The strategy is dynamic, however the cross-cultural polyphonic dynamics were ignored, with dire consequencs. Our purpose is to explore how the organisation tries to make sense of the happening through storytelling and how the leadership practices may change due...... (Aristotle, 350 BCE: 1450b: 25, p. 233). Design: We present a dialogic performance of the cross-cultural dynamics of a merger. The context is a two-year old merger. The merger was strategically a good decision that takes into the consideration that the market is highly competitive with a decreasing number......, the proliferation of ever more living stories, expanding the web of differences (Bakhtin, 1984). Gadamer (1975: 367) makes the point that "to conduct a dialogue requies first of all that the partners do not talk at cross purposes." The living story web expanded in ways that so may cross purpose proliferated...

  19. A Framework for Understanding Post-Merger Information Systems Integration

    DEFF Research Database (Denmark)

    Alaranta, Maria; Kautz, Karlheinz

    2012-01-01

    that researchers and managers of post-merger IS integration should pay particular attention to the IS and organizational merger contexts; the need to build relationships and collaboration between the merging parties; power struggles; and, perhaps most importantly, understanding and treating post......This paper develops a theoretical framework for the integration of information systems (IS) after a merger or an acquisition. The framework integrates three perspectives: a structuralist, an individualist, and an interactive process perspective to analyze and understand such integrations....... The framework is applied to a longitudinal case study of a manufacturing company that grew through an acquisition. The management decided to integrate the production control IS via tailoring a new system that blends together features of existing IS. The application of the framework in the case study confirms...

  20. 17 CFR 230.145 - Reclassification of securities, mergers, consolidations and acquisitions of assets.

    Science.gov (United States)

    2010-04-01

    ..., mergers, consolidations and acquisitions of assets. 230.145 Section 230.145 Commodity and Securities... § 230.145 Reclassification of securities, mergers, consolidations and acquisitions of assets.... A statutory merger or consolidation or similar plan or acquisition in which securities of such...