WorldWideScience

Sample records for cluster merger shocks

  1. Nonthermal Particles and Radiation Produced by Cluster Merger Shocks

    Science.gov (United States)

    2003-09-10

    NONTHERMAL PARTICLES AND RADIATION PRODUCED BY CLUSTER MERGER SHOCKS Robert C. Berrington and Charles D. Dermer Naval Research Laboratory, Code 7653...of the merging cluster and is assumed to be constant as the shock propagates outward from the cluster center. In this paper , we model the cluster ...emission in the60–250 eV band for a number of clus- ters. These clusters include Virgo , Coma, Fornax, A2199, A1795, and A4059 (Lieu et al. 1996a, 1996b

  2. Properties of Merger Shocks in Merging Galaxy Clusters

    Science.gov (United States)

    Ha, Ji-Hoon; Ryu, Dongsu; Kang, Hyesung

    2018-04-01

    X-ray shocks and radio relics detected in the cluster outskirts are commonly interpreted as shocks induced by mergers of subclumps. We study the properties of merger shocks in merging galaxy clusters, using a set of cosmological simulations for the large-scale structure formation of the universe. As a representative case, we focus on the simulated clusters that undergo almost head-on collisions with mass ratio ∼2. Due to the turbulent nature of the intracluster medium, shock surfaces are not smooth, but composed of shocks with different Mach numbers. As the merger shocks expand outward from the core to the outskirts, the average Mach number, , increases in time. We suggest that the shocks propagating along the merger axis could be manifested as X-ray shocks and/or radio relics. The kinetic energy through the shocks, F ϕ , peaks at ∼1 Gyr after their initial launching, or at ∼1–2 Mpc from the core. Because of the Mach number dependent model adopted here for the cosmic-ray (CR) acceleration efficiency, their CR-energy-weighted Mach number is higher with }CR}∼ 3{--}4, compared to the kinetic-energy-weighted Mach number, }φ ∼ 2{--}3. Most energetic shocks are to be found ahead of the lighter dark matter (DM) clump, while the heavier DM clump is located on the opposite side of clusters. Although our study is limited to the merger case considered, the results such as the means and variations of shock properties and their time evolution could be compared with the observed characteristics of merger shocks, constraining interpretations of relevant observations.

  3. 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

  4. Cooking a `Sausage': the impact of merger shocks in cluster gas and galaxy evolution

    Science.gov (United States)

    Stroe, Andra; Sobral, David; Harwood, Jeremy; Van Weeren, Reinout J.; Rumsey, Clare; Intema, Huib; Röttgering, Huub; Brüggen, Marcus; Saunders, Richard; Hardcastle, Martin; Hoeft, Matthias

    2015-01-01

    Galaxy clusters mainly grow through mergers with other clusters and groups. Major mergers give rise to important astrophysical phenomena such as the segregation of dark and luminous matter and the formation of cluster-wide traveling shocks and also drive galaxy evolution. The observable effects of shock waves can be seen at radio wavelengths as relics: elongated, diffuse synchrotron emitting areas located at the periphery of merging clusters. Despite the great interest in relics, candidates with simple geometry, undisturbed morphology and high surface brightness are scarce. The `Sausage' cluster hosts an extraordinary Mpc-wide relic, which enables us to study to study particle acceleration and the effects of shocks on cluster galaxies. We use a unique combination of facilities (INT, WHT, Keck, Subaru, CFHT, GMRT, WSRT, AMI) to obtain the first cluster-wide, multi-wavelength, multi-method analysis aimed at giving a complete picture of a merging cluster with relics. Using the radio data, we derive shock properties and the magnetic field structure for the relic. Using spectral modeling, we test acceleration and electron energy-loss mechanisms and resolve the discrepancy between the Mach number calculated from the radio and X-rays. Our results indicate that particles are shock-accelerated, but turbulent re-acceleration or unusually efficient transport of particles in the downstream area and line-of-sight mixing are important effects. We demonstrate the feasibility of high-frequency observations of radio relics, by presenting a 16 GHz detection of the `Sausage' relic. The radio analysis is complemented by Hα mapping of the cluster volume, aimed at providing the first direct test as to whether the shock drives or prohibits star formation. We find numerous Hα emitting galaxies in close proximity to the radio relic which are extremely massive, metal-rich, mostly star-forming with evidence for gas mass loss though outflows. We speculate that the complex interaction

  5. SHOCKING TAILS IN THE MAJOR MERGER ABELL 2744

    Energy Technology Data Exchange (ETDEWEB)

    Owers, Matt S.; Couch, Warrick J. [Center for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122 (Australia); Nulsen, Paul E. J.; Randall, Scott W., E-mail: mowers@aao.gov.au [Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2012-05-01

    We identify four rare 'jellyfish' galaxies in Hubble Space Telescope imagery of the major merger cluster Abell 2744. These galaxies harbor trails of star-forming knots and filaments which have formed in situ in gas tails stripped from the parent galaxies, indicating they are in the process of being transformed by the environment. Further evidence for rapid transformation in these galaxies comes from their optical spectra, which reveal starburst, poststarburst, and active galactic nucleus features. Most intriguingly, three of the jellyfish galaxies lie near intracluster medium features associated with a merging 'Bullet-like' subcluster and its shock front detected in Chandra X-ray images. We suggest that the high-pressure merger environment may be responsible for the star formation in the gaseous tails. This provides observational evidence for the rapid transformation of galaxies during the violent core passage phase of a major cluster merger.

  6. EVOLUTION OF THE MERGER-INDUCED HYDROSTATIC MASS BIAS IN GALAXY CLUSTERS

    International Nuclear Information System (INIS)

    Nelson, Kaylea; Nagai, Daisuke; Rudd, Douglas H.; Shaw, Laurie

    2012-01-01

    In this work, we examine the effects of mergers on the hydrostatic mass estimate of galaxy clusters using high-resolution Eulerian cosmological simulations. We utilize merger trees to isolate the last merger for each cluster in our sample and follow the time evolution of the hydrostatic mass bias as the systems relax. We find that during a merger, a shock propagates outward from the parent cluster, resulting in an overestimate in the hydrostatic mass bias. After the merger, as a cluster relaxes, the bias in hydrostatic mass estimate decreases but remains at a level of –5%-10% with 15%-20% scatter within r 500 . We also investigate the post-merger evolution of the pressure support from bulk motions, a dominant cause of this residual mass bias. At r 500 , the contribution from random motions peaks at 30% of the total pressure during the merger and quickly decays to ∼10%-15% as a cluster relaxes. Additionally, we use a measure of the random motion pressure to correct the hydrostatic mass estimate. We discover that 4 Gyr after mergers, the direct effects of the merger event on the hydrostatic mass bias have become negligible. Thereafter, the mass bias is primarily due to residual bulk motions in the gas which are not accounted for in the hydrostatic equilibrium equation. We present a hydrostatic mass bias correction method that can recover the unbiased cluster mass for relaxed clusters with 9% scatter at r 500 and 11% scatter in the outskirts, within r 200 .

  7. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Cordero, Juan P.; Campusano, Luis E.; Haines, Christopher P. [Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago (Chile); De Propris, Roberto [Finnish Centre for Astronomy with ESO, University of Turku, Vaisalantie 20, Piikkio, FI-21500 (Finland); Weinzirl, Tim [School of Physics and Astronomy, The University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom); Jogee, Shardha, E-mail: jcordero@das.uchile.cl [Department of Astronomy, The University of Texas at Austin, Austin, TX 78712-1205 (United States)

    2016-01-20

    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{sub 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. 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%

  10. Galaxy-Wide Shocks in the H$\\alpha$ Emission of Nearby Galaxy Mergers

    Science.gov (United States)

    Mortazavi, S. Alireza; Lotz, Jennifer M.

    2018-01-01

    We examine the properties of shocked gas produced as a result of binary galaxy interactions, using H$\\alpha$ emission in a sample 22 mergers observed with SparsePak Integral Field Unit (IFU) at Kitt Peak National Observatory (KPNO). Our sample consists of major and minor tidally interacting galaxies (mass ratio $1text{f}_\\text{shocked}$, and examine the spatial distribution of shocks. We find that close galaxy pairs have, on average, a higher shock fraction than wide pairs, and our coalesced mergers have the highest average $\\text{f}_\\text{shocked}$. Additionally, we find for the first time, correlations between mass ratio, mass of the companion, and $\\text{f}_\\text{shocked}$ in tidally interacting galaxy pairs. Among the non-coalesced systems in our sample, the galaxy pairs with more equal light ratio (stellar mass ratio) tend to have a higher average $\\text{f}_\\text{shocked}$. Also, the primary (more massive) companions are on average slightly more shocked than the secondary (less massive) ones. Utilizing dynamical models in the literature and this work, we inspect trends between $\\text{f}_\\text{shocked}$ and the reconstructed encounter parameters. In this very limited sample, we find that the orbital pericentric separation is correlated with shock fraction, consistent with shocks being produced by the chain of events caused by the tidal impulse during the first passage. These results lay a basis for furture analysis using the higher statistics provided by the on-going and future IFU galaxy surveys.

  11. Merger types forming the Virgo cluster in recent gigayears

    Science.gov (United States)

    Olchanski, M.; Sorce, J. G.

    2018-06-01

    Context. As our closest cluster-neighbor, the Virgo cluster of galaxies is intensely studied by observers to unravel the mysteries of galaxy evolution within clusters. At this stage, cosmological numerical simulations of the cluster are useful to efficiently test theories and calibrate models. However, it is not trivial to select the perfect simulacrum of the Virgo cluster to fairly compare in detail its observed and simulated galaxy populations that are affected by the type and history of the cluster. Aims: Determining precisely the properties of Virgo for a later selection of simulated clusters becomes essential. It is still not clear how to access some of these properties, such as the past history of the Virgo cluster from current observations. Therefore, directly producing effective simulacra of the Virgo cluster is inevitable. Methods: Efficient simulacra of the Virgo cluster can be obtained via simulations that resemble the local Universe down to the cluster scale. In such simulations, Virgo-like halos form in the proper local environment and permit assessing the most probable formation history of the cluster. Studies based on these simulations have already revealed that the Virgo cluster has had a quiet merging history over the last seven gigayears and that the cluster accretes matter along a preferential direction. Results: This paper reveals that in addition such Virgo halos have had on average only one merger larger than about a tenth of their mass at redshift zero within the last four gigayears. This second branch (by opposition to main branch) formed in a given sub-region and merged recently (within the last gigayear). These properties are not shared with a set of random halos within the same mass range. Conclusions: This study extends the validity of the scheme used to produce the Virgo simulacra down to the largest sub-halos of the Virgo cluster. It opens up great prospects for detailed comparisons with observations, including substructures and

  12. Major cluster mergers and the location of the brightest cluster galaxy

    International Nuclear Information System (INIS)

    Martel, Hugo; Robichaud, Fidèle; Barai, Paramita

    2014-01-01

    Using a large N-body cosmological simulation combined with a subgrid treatment of galaxy formation, merging, and tidal destruction, we study the formation and evolution of the galaxy and cluster population in a comoving volume (100 Mpc) 3 in a ΛCDM universe. At z = 0, our computational volume contains 1788 clusters with mass M cl > 1.1 × 10 12 M ☉ , including 18 massive clusters with M cl > 10 14 M ☉ . It also contains 1, 088, 797 galaxies with mass M gal ≥ 2 × 10 9 M ☉ and luminosity L > 9.5 × 10 5 L ☉ . For each cluster, we identified the brightest cluster galaxy (BCG). We then computed two separate statistics: the fraction f BNC of clusters in which the BCG is not the closest galaxy to the center of the cluster in projection, and the ratio Δv/σ, where Δv is the difference in radial velocity between the BCG and the whole cluster and σ is the radial velocity dispersion of the cluster. We found that f BNC increases from 0.05 for low-mass clusters (M cl ∼ 10 12 M ☉ ) to 0.5 for high-mass clusters (M cl > 10 14 M ☉ ) with very little dependence on cluster redshift. Most of this result turns out to be a projection effect and when we consider three-dimensional distances instead of projected distances, f BNC increases only to 0.2 at high-cluster mass. The values of Δv/σ vary from 0 to 1.8, with median values in the range 0.03-0.15 when considering all clusters, and 0.12-0.31 when considering only massive clusters. These results are consistent with previous observational studies and indicate that the central galaxy paradigm, which states that the BCG should be at rest at the center of the cluster, is usually valid, but exceptions are too common to be ignored. We built merger trees for the 18 most massive clusters in the simulation. Analysis of these trees reveal that 16 of these clusters have experienced 1 or several major or semi-major mergers in the past. These mergers leave each cluster in a non-equilibrium state, but eventually the cluster

  13. 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.

  14. The Hierarchical Spectral Merger Algorithm: A New Time Series Clustering Procedure

    KAUST Repository

    Euá n, Carolina; Ombao, Hernando; Ortega, Joaquí n

    2018-01-01

    We present a new method for time series clustering which we call the Hierarchical Spectral Merger (HSM) method. This procedure is based on the spectral theory of time series and identifies series that share similar oscillations or waveforms

  15. Binary Black Hole Mergers from Globular Clusters: Implications for Advanced LIGO.

    Science.gov (United States)

    Rodriguez, Carl L; Morscher, Meagan; Pattabiraman, Bharath; Chatterjee, Sourav; Haster, Carl-Johan; Rasio, Frederic A

    2015-07-31

    The predicted rate of binary black hole mergers from galactic fields can vary over several orders of magnitude and is extremely sensitive to the assumptions of stellar evolution. But in dense stellar environments such as globular clusters, binary black holes form by well-understood gravitational interactions. In this Letter, we study the formation of black hole binaries in an extensive collection of realistic globular cluster models. By comparing these models to observed Milky Way and extragalactic globular clusters, we find that the mergers of dynamically formed binaries could be detected at a rate of ∼100 per year, potentially dominating the binary black hole merger rate. We also find that a majority of cluster-formed binaries are more massive than their field-formed counterparts, suggesting that Advanced LIGO could identify certain binaries as originating from dense stellar environments.

  16. Accretion of satellites on to central galaxies in clusters: merger mass ratios and orbital parameters

    Science.gov (United States)

    Nipoti, Carlo; Giocoli, Carlo; Despali, Giulia

    2018-05-01

    We study the statistical properties of mergers between central and satellite galaxies in galaxy clusters in the redshift range 0 identify dark-matter haloes, we construct halo merger trees for different values of the overdensity Δc. While the virial overdensity definition allows us to probe the accretion of satellites at the cluster virial radius rvir, higher overdensities probe satellite mergers in the central region of the cluster, down to ≈0.06rvir, which can be considered a proxy for the accretion of satellite galaxies on to central galaxies. We find that the characteristic merger mass ratio increases for increasing values of Δc: more than 60 per cent of the mass accreted by central galaxies since z ≈ 1 comes from major mergers. The orbits of satellites accreting on to 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.

  17. Curved Radio Spectra of Weak Cluster Shocks

    Science.gov (United States)

    Kang, Hyesung; Ryu, Dongsu

    2015-08-01

    In order to understand certain observed features of arc-like giant radio relics such as the rareness, uniform surface brightness, and curved integrated spectra, we explore a diffusive shock acceleration (DSA) model for radio relics in which a spherical shock impinges on a magnetized cloud containing fossil relativistic electrons. Toward this end, we perform DSA simulations of spherical shocks with the parameters relevant for the Sausage radio relic in cluster CIZA J2242.8+5301, and calculate the ensuing radio synchrotron emission from re-accelerated electrons. Three types of fossil electron populations are considered: a delta-function like population with the shock injection momentum, a power-law distribution, and a power law with an exponential cutoff. The surface brightness profile of the radio-emitting postshock region and the volume-integrated radio spectrum are calculated and compared with observations. We find that the observed width of the Sausage relic can be explained reasonably well by shocks with speed {u}{{s}}˜ 3× {10}3 {km} {{{s}}}-1 and sonic Mach number {M}{{s}}˜ 3. These shocks produce curved radio spectra that steepen gradually over (0.1-10){ν }{br} with a break frequency {ν }{br}˜ 1 GHz if the duration of electron acceleration is ˜60-80 Myr. However, the abrupt increase in the spectral index above ˜1.5 GHz observed in the Sausage relic seems to indicate that additional physical processes, other than radiative losses, operate for electrons with {γ }{{e}}≳ {10}4.

  18. The radio relics and halo of El Gordo, a massive z = 0.870 cluster merger

    Energy Technology Data Exchange (ETDEWEB)

    Lindner, Robert R.; Baker, Andrew J.; Hughes, John P. [Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854-8019 (United States); Battaglia, Nick [McWilliams Center for Cosmology, Wean Hall, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, PA 15213 (United States); Gupta, Neeraj [ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo (Netherlands); Knowles, Kenda; Moodley, Kavilan [Astrophysics and Cosmology Research Unit, University of KwaZulu-Natal, Durban 4041 (South Africa); Marriage, Tobias A. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218-2686 (United States); Menanteau, Felipe [National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, 1205 W. Clark St., Urbana, IL 61801 (United States); Reese, Erik D. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd St., Philadelphia, PA 19104 (United States); Srianand, Raghunathan, E-mail: rlindner@astro.wisc.edu [IUCAA, Ganeshkhind, Pune 411007 (India)

    2014-05-01

    We present 610 MHz and 2.1 GHz imaging of the massive Sunyaev-Zel'dovich Effect selected z = 0.870 cluster merger ACT-CL J0102–4915 ({sup E}l Gordo{sup )}, obtained with the Giant Metrewave Radio Telescope and the Australia Telescope Compact Array (ATCA), respectively. We detect two complexes of radio relics separated by 3.'4 (1.6 Mpc) along the system's northwest-to-southeast collision axis that have high integrated polarization fractions (33%) and steep spectral indices (α between 1 and 2; S {sub ν}∝ν{sup –α}), consistent with creation via Fermi acceleration by shocks in the intracluster medium triggered by the cluster collision. From the spectral index of the relics, we compute a Mach number M=2.5{sub −0.3}{sup +0.7} and shock speed of 2500{sub −300}{sup +400} km s{sup −1}. With our wide-bandwidth, full-polarization ATCA data, we compute the Faraday depth φ across the northwest relic and find a range of values spanning Δφ = 30 rad m{sup –2}, with a mean value of (φ) = 11 rad m{sup –2} and standard deviation σ{sub φ} = 6 rad m{sup –2}. With the integrated line-of-sight gas density derived from new Chandra X-ray observations, our Faraday depth measurement implies B {sub ∥} ∼ 0.01 μG in the cluster outskirts. The extremely narrow shock widths in the relics (d {sub shock} ≤ 23 kpc), caused by the short synchrotron cooling timescale of relativistic electrons at z = 0.870, prevent us from placing a meaningful constraint on the magnetic field strength B using cooling time arguments. In addition to the relics, we detect a large (r {sub H} ≅ 1.1 Mpc radius), powerful (log (L {sub 1.4}/W Hz{sup –1}) = 25.66 ± 0.12) radio halo with a shape similar to El Gordo's 'bullet'-like X-ray morphology. The spatially resolved spectral-index map of the halo shows the synchrotron spectrum is flattest near the relics, along the system's collision axis, and in regions of high T {sub gas}, all locations associated

  19. Search for low-frequency diffuse radio emission around a shock in the massive galaxy cluster MACS J0744.9+3927

    Science.gov (United States)

    Wilber, A.; Brüggen, M.; Bonafede, A.; Rafferty, D.; Savini, F.; Shimwell, T.; van Weeren, R. J.; Botteon, A.; Cassano, R.; Brunetti, G.; De Gasperin, F.; Wittor, D.; Hoeft, M.; Birzan, L.

    2018-05-01

    Merging galaxy clusters produce low-Mach-number shocks in the intracluster medium. These shocks can accelerate electrons to relativistic energies that are detectable at radio frequencies. MACS J0744.9+3927 is a massive [M500 = (11.8 ± 2.8) × 1014 M⊙], high-redshift (z = 0.6976) cluster where a Bullet-type merger is presumed to have taken place. Sunyaev-Zel'dovich maps from MUSTANG indicate that a shock, with Mach number M = 1.0-2.9 and an extension of ˜200 kpc, sits near the centre of the cluster. The shock is also detected as a brightness and temperature discontinuity in X-ray observations. To search for diffuse radio emission associated with the merger, we have imaged the cluster with the LOw Frequency ARray (LOFAR) at 120-165 MHz. Our LOFAR radio images reveal previously undetected AGN emission, but do not show clear cluster-scale diffuse emission in the form of a radio relic nor a radio halo. The region of the shock is on the western edge of AGN lobe emission from the brightest cluster galaxy. Correlating the flux of known shock-induced radio relics versus their size, we find that the radio emission overlapping the shocked region in MACS J0744.9+3927 is likely of AGN origin. We argue against the presence of a relic caused by diffusive shock acceleration and suggest that the shock is too weak to accelerate electrons from the intracluster medium.

  20. 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.

  1. Shock Acceleration of Electrons and Synchrotron Emission from the Dynamical Ejecta of Neutron Star Mergers

    Science.gov (United States)

    Lee, Shiu-Hang; Maeda, Keiichi; Kawanaka, Norita

    2018-05-01

    Neutron star mergers (NSMs) eject energetic subrelativistic dynamical ejecta into circumbinary media. Analogous to supernovae and supernova remnants, the NSM dynamical ejecta are expected to produce nonthermal emission by electrons accelerated at a shock wave. In this paper, we present the expected radio and X-ray signals by this mechanism, taking into account nonlinear diffusive shock acceleration (DSA) and magnetic field amplification. We suggest that the NSM is unique as a DSA site, where the seed relativistic electrons are abundantly provided by the decays of r-process elements. The signal is predicted to peak at a few 100–1000 days after the merger, determined by the balance between the decrease of the number of seed electrons and the increase of the dissipated kinetic energy, due to the shock expansion. While the resulting flux can ideally reach the maximum flux expected from near-equipartition, the available kinetic energy dissipation rate of the NSM ejecta limits the detectability of such a signal. It is likely that the radio and X-ray emission are overwhelmed by other mechanisms (e.g., an off-axis jet) for an observer placed in a jet direction (i.e., for GW170817). However, for an off-axis observer, to be discovered once a number of NSMs are identified, the dynamical ejecta component is predicted to dominate the nonthermal emission. While the detection of this signal is challenging even with near-future facilities, this potentially provides a robust probe of the creation of r-process elements in NSMs.

  2. THE BURST CLUSTER: DARK MATTER IN A CLUSTER MERGER ASSOCIATED WITH THE SHORT GAMMA-RAY BURST, GRB 050509B

    International Nuclear Information System (INIS)

    Dahle, H.; Sarazin, C. L.; Lopez, L. A.; Kouveliotou, C.; Patel, S. K.; Rol, E.; Van der Horst, A. J.; Wijers, R. A. M. J.; Fynbo, J.; Michałowski, M. J.; Burrows, D. N.; Grupe, D.; Gehrels, N.; Ramirez-Ruiz, E.

    2013-01-01

    We have identified a merging galaxy cluster with evidence of two distinct subclusters. The X-ray and optical data suggest that the subclusters are presently moving away from each other after closest approach. This cluster merger was discovered from observations of the first well-localized short-duration gamma-ray burst (GRB), GRB 050509B. The Swift/Burst Alert Telescope error position of the source is coincident with a cluster of galaxies ZwCl 1234.0+02916, while the subsequent Swift/X-Ray Telescope localization of the X-ray afterglow found the GRB coincident with 2MASX J12361286+2858580, a giant red elliptical galaxy in the cluster. Deep multi-epoch optical images were obtained in this field to constrain the evolution of the GRB afterglow, including a total of 27,480 s exposure in the F814W band with Hubble Space Telescope Advanced Camera for Surveys, among the deepest imaging ever obtained toward a known galaxy cluster in a single passband. We perform a weak gravitational lensing analysis based on these data, including mapping of the total mass distribution of the merger system with high spatial resolution. When combined with Chandra X-ray Observatory Advanced CCD Imaging Spectrometer and Swift/XRT observations, we are able to investigate the dynamical state of the merger to better understand the nature of the dark matter component. Our weak gravitational lensing measurements reveal a separation of the X-ray centroid of the western subcluster from the center of the mass and galaxy light distributions, which is somewhat similar to that of the famous 'Bullet cluster', and we conclude that this 'Burst cluster' adds another candidate to the previously known merger systems for determining the nature of dark matter, as well as for studying the environment of a short GRB. Finally, we discuss potential connections between the cluster dynamical state and/or matter composition, and compact object mergers, which is currently the leading model for the origin of short GRBs

  3. THE BURST CLUSTER: DARK MATTER IN A CLUSTER MERGER ASSOCIATED WITH THE SHORT GAMMA-RAY BURST, GRB 050509B

    Energy Technology Data Exchange (ETDEWEB)

    Dahle, H. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, NO-0315 Oslo (Norway); Sarazin, C. L. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States); Lopez, L. A. [MIT-Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, 37-664H, Cambridge, MA 02139 (United States); Kouveliotou, C. [Space Science Office, ZP12, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Patel, S. K. [Optical Sciences Corporation, 6767 Old Madison Pike, Suite 650, Huntsville, AL 35806 (United States); Rol, E.; Van der Horst, A. J.; Wijers, R. A. M. J. [Astronomical Institute ' Anton Pannekoek' , University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam (Netherlands); Fynbo, J.; Michalowski, M. J. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30, DK-2100 Copenhagen (Denmark); Burrows, D. N.; Grupe, D. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Gehrels, N. [NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Ramirez-Ruiz, E., E-mail: hdahle@astro.uio.no [Department of Astronomy and Astrophysics, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95060 (United States)

    2013-07-20

    We have identified a merging galaxy cluster with evidence of two distinct subclusters. The X-ray and optical data suggest that the subclusters are presently moving away from each other after closest approach. This cluster merger was discovered from observations of the first well-localized short-duration gamma-ray burst (GRB), GRB 050509B. The Swift/Burst Alert Telescope error position of the source is coincident with a cluster of galaxies ZwCl 1234.0+02916, while the subsequent Swift/X-Ray Telescope localization of the X-ray afterglow found the GRB coincident with 2MASX J12361286+2858580, a giant red elliptical galaxy in the cluster. Deep multi-epoch optical images were obtained in this field to constrain the evolution of the GRB afterglow, including a total of 27,480 s exposure in the F814W band with Hubble Space Telescope Advanced Camera for Surveys, among the deepest imaging ever obtained toward a known galaxy cluster in a single passband. We perform a weak gravitational lensing analysis based on these data, including mapping of the total mass distribution of the merger system with high spatial resolution. When combined with Chandra X-ray Observatory Advanced CCD Imaging Spectrometer and Swift/XRT observations, we are able to investigate the dynamical state of the merger to better understand the nature of the dark matter component. Our weak gravitational lensing measurements reveal a separation of the X-ray centroid of the western subcluster from the center of the mass and galaxy light distributions, which is somewhat similar to that of the famous 'Bullet cluster', and we conclude that this 'Burst cluster' adds another candidate to the previously known merger systems for determining the nature of dark matter, as well as for studying the environment of a short GRB. Finally, we discuss potential connections between the cluster dynamical state and/or matter composition, and compact object mergers, which is currently the leading model for the

  4. 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.

  5. Evolution of the Black Hole Mass Function in Star Clusters from Multiple Mergers

    Science.gov (United States)

    Christian, Pierre; Mocz, Philip; Loeb, Abraham

    2018-05-01

    We investigate the effects of black hole (BH) mergers in star clusters on the black hole mass function (BHMF). As BHs are not produced in pair-instability supernovae, it is suggested that there is a dearth of high-mass stellar BHs. This dearth generates a gap in the upper end of the BHMF. Meanwhile, parameter fitting of X-ray binaries suggests the existence of a gap in the mass function under 5 solar masses. We show, through evolving a coagulation equation, that BH mergers can appreciably fill the upper mass gap, and that the lower mass gap generates potentially observable features at larger mass scales. We also explore the importance of ejections in such systems and whether dynamical clusters can be formation sites of intermediate-mass BH seeds.

  6. 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.

  7. 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.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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 −1.0 +2.3 R vir,host for progenitors of z = 0 satellites. The peak circular velocity for infalling halos occurs at significantly larger distances (3.7 −2.2 +3.3 R 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.

  9. 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

  10. Shock Heating of the Merging Galaxy Cluster A521

    Science.gov (United States)

    Bourdin, H.; Mazzotta, P.; Markevitch, M.; Giacintucci, S.; Brunetti, G.

    2013-01-01

    A521 is an interacting galaxy cluster located at z = 0.247, hosting a low-frequency radio halo connected to an eastern radio relic. Previous Chandra observations hinted at the presence of an X-ray brightness edge at the position of the relic, which may be a shock front. We analyze a deep observation of A521 recently performed with XMM-Newton in order to probe the cluster structure up to the outermost regions covered by the radio emission. The cluster atmosphere exhibits various brightness and temperature anisotropies. In particular, two cluster cores appear to be separated by two cold fronts. We find two shock fronts, one that was suggested by Chandra and that is propagating to the east, and another to the southwestern cluster outskirt. The two main interacting clusters appear to be separated by a shock-heated region, which exhibits a spatial correlation with the radio halo. The outer edge of the radio relic coincides spatially with a shock front, suggesting that this shock is responsible for the generation of cosmic-ray electrons in the relic. The propagation direction and Mach number of the shock front derived from the gas density jump, M = 2.4 +/- 0.2, are consistent with expectations from the radio spectral index, under the assumption of Fermi I acceleration mechanism.

  11. Post-Newtonian Dynamics in Dense Star Clusters: Highly Eccentric, Highly Spinning, and Repeated Binary Black Hole Mergers.

    Science.gov (United States)

    Rodriguez, Carl L; Amaro-Seoane, Pau; Chatterjee, Sourav; Rasio, Frederic A

    2018-04-13

    We present models of realistic globular clusters with post-Newtonian dynamics for black holes. By modeling the relativistic accelerations and gravitational-wave emission in isolated binaries and during three- and four-body encounters, we find that nearly half of all binary black hole mergers occur inside the cluster, with about 10% of those mergers entering the LIGO/Virgo band with eccentricities greater than 0.1. In-cluster mergers lead to the birth of a second generation of black holes with larger masses and high spins, which, depending on the black hole natal spins, can sometimes be retained in the cluster and merge again. As a result, globular clusters can produce merging binaries with detectable spins regardless of the birth spins of black holes formed from massive stars. These second-generation black holes would also populate any upper mass gap created by pair-instability supernovae.

  12. Post-Newtonian Dynamics in Dense Star Clusters: Highly Eccentric, Highly Spinning, and Repeated Binary Black Hole Mergers

    Science.gov (United States)

    Rodriguez, Carl L.; Amaro-Seoane, Pau; Chatterjee, Sourav; Rasio, Frederic A.

    2018-04-01

    We present models of realistic globular clusters with post-Newtonian dynamics for black holes. By modeling the relativistic accelerations and gravitational-wave emission in isolated binaries and during three- and four-body encounters, we find that nearly half of all binary black hole mergers occur inside the cluster, with about 10% of those mergers entering the LIGO/Virgo band with eccentricities greater than 0.1. In-cluster mergers lead to the birth of a second generation of black holes with larger masses and high spins, which, depending on the black hole natal spins, can sometimes be retained in the cluster and merge again. As a result, globular clusters can produce merging binaries with detectable spins regardless of the birth spins of black holes formed from massive stars. These second-generation black holes would also populate any upper mass gap created by pair-instability supernovae.

  13. The Hierarchical Spectral Merger Algorithm: A New Time Series Clustering Procedure

    KAUST Repository

    Euán, Carolina

    2018-04-12

    We present a new method for time series clustering which we call the Hierarchical Spectral Merger (HSM) method. This procedure is based on the spectral theory of time series and identifies series that share similar oscillations or waveforms. The extent of similarity between a pair of time series is measured using the total variation distance between their estimated spectral densities. At each step of the algorithm, every time two clusters merge, a new spectral density is estimated using the whole information present in both clusters, which is representative of all the series in the new cluster. The method is implemented in an R package HSMClust. We present two applications of the HSM method, one to data coming from wave-height measurements in oceanography and the other to electroencefalogram (EEG) data.

  14. 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 ...

  15. The Dynamic Quasiperpendicular Shock: Cluster Discoveries

    Czech Academy of Sciences Publication Activity Database

    Krasnoselskikh, V.; Balikhin, M.; Walker, S. N.; Schwartz, S.; Sundkvist, D.; Lobzin, V.; Gedalin, M.; Bale, S. D.; Mozer, F.; Souček, Jan; Hobara, Y.; Comisel, H.

    2013-01-01

    Roč. 178, 2-4 (2013), s. 535-598 ISSN 0038-6308 Institutional support: RVO:68378289 Keywords : collisionless shocks * waves in plasmas * nonstationarity * shock scales * plasma heating and acceleration * wave-particle interactions Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 5.874, year: 2013 http://link.springer.com/article/10.1007%2Fs11214-013-9972-y

  16. Effects of Alfvénic Drift on Diffusive Shock Acceleration at Weak Cluster Shocks

    Science.gov (United States)

    Kang, Hyesung; Ryu, Dongsu

    2018-03-01

    Non-detection of γ-ray emission from galaxy clusters has challenged diffusive shock acceleration (DSA) of cosmic-ray (CR) protons at weak collisionless shocks that are expected to form in the intracluster medium. As an effort to address this problem, we here explore possible roles of Alfvén waves self-excited via resonant streaming instability during the CR acceleration at parallel shocks. The mean drift of Alfvén waves may either increase or decrease the scattering center compression ratio, depending on the postshock cross-helicity, leading to either flatter or steeper CR spectra. We first examine such effects at planar shocks, based on the transport of Alfvén waves in the small amplitude limit. For the shock parameters relevant to cluster shocks, Alfvénic drift flattens the CR spectrum slightly, resulting in a small increase of the CR acceleration efficiency, η. We then consider two additional, physically motivated cases: (1) postshock waves are isotropized via MHD and plasma processes across the shock transition, and (2) postshock waves contain only forward waves propagating along with the flow due to a possible gradient of CR pressure behind the shock. In these cases, Alfvénic drift could reduce η by as much as a factor of five for weak cluster shocks. For the canonical parameters adopted here, we suggest η ∼ 10‑4–10‑2 for shocks with sonic Mach number M s ≈ 2–3. The possible reduction of η may help ease the tension between non-detection of γ-rays from galaxy clusters and DSA predictions.

  17. Clustering impact regime with shocks in freely evolving granular gas

    Science.gov (United States)

    Isobe, Masaharu

    2017-06-01

    A freely cooling granular gas without any external force evolves from the initial homogeneous state to the inhomogeneous clustering state, at which the energy decay deviates from the Haff's law. The asymptotic behavior of energy in the inelastic hard sphere model have been predicted by several theories, which are based on the mode coupling theory or extension of inelastic hard rods gas. In this study, we revisited the clustering regime of freely evolving granular gas via large-scale molecular dynamics simulation with up to 16.7 million inelastic hard disks. We found novel regime regarding on collisions between "clusters" spontaneously appearing after clustering regime, which can only be identified more than a few million particles system. The volumetric dilatation pattern of semicircular shape originated from density shock propagation are well characterized on the appearing of "cluster impact" during the aggregation process of clusters.

  18. Merger and Acquisition Activity as Driver of Spatial Clustering : The Spatial Evolution of the Dutch Banking Industry, 1850-1993

    NARCIS (Netherlands)

    Boschma, Ron; Hartog, Matté

    2014-01-01

    This article investigates the extent to which merger and acquisition (M&A) activity contributed to the spatial clustering of the Dutch banking industry in Amsterdam. This analysis is based on a unique database of all banks in the Netherlands that existed in the period 1850-1993. We found that

  19. Understanding the radio spectral indices of galaxy cluster relics by superdiffusive shock acceleration

    Science.gov (United States)

    Zimbardo, Gaetano; Perri, Silvia

    2018-06-01

    Galaxy cluster merger shocks are the likely source of relativistic electrons, but many observations do not fit into the standard acceleration models. In particular, there is a long-standing discrepancy between the radio derived Mach numbers M_radio and the Mach numbers derived from X-ray measurements, M_X. Here, we show how superdiffusive electron transport and superdiffusive shock acceleration (SSA) can help to solve this problem. We present a heuristic derivation of the superlinear time growth of the mean square displacement of particles, ⟨Δx2⟩∝tβ, and of the particle energy spectral index in the framework of SSA. The resulting expression for the radio spectral index α is then used to determine the superdiffusive exponent β from the observed values of α and of the compression ratio for a number of radio relics. Therefore, the fact that M_radio>M_X can be explained by SSA without the need to make assumptions on the energy spectrum of the seed electrons to be re-accelerated. We also consider the acceleration times obtained in the diffusive case, based both on the Bohm diffusion coefficient and on the quasilinear diffusion coefficient. While in the latter case the acceleration time is consistent with the estimated electron energy loss time, the former case it is much shorter.

  20. The x ray morphology of the relaxed cluster of galaxies A2256. 1: Evidence for a merger event

    Science.gov (United States)

    Briel, U. G.; Henry, J. Patrick; Schwarz, Raimund A.; Boehringer, Hans; Ebeling, Harald; Edge, Alastair C.; Hartner, Gisela D.; Schindler, Sabine; Truemper, Joachim E.; Voges, Wolfgang

    1991-01-01

    The rich cluster of galaxies A2256 was studied utilizing the imaging proportional counter (PSPC (Position Sensitive Proportional Counters)) on board the x-ray observatory ROSAT. A2256 is considered to be a relaxed, Comalike cluster which is dynamically well evolved. However, clear evidence for substructure in A2256 was found. The x-ray surface brightness distribution reveals two separate maxima in the center, one of which is coincident with the central cD galaxy while the morphology of the other shows indications that it is merging with the main cluster body. The x-ray temperatures of the two maxima are different; the probable merging object being about a factor of five cooler than the cluster. The previously measured broad velocity distribution supports the idea that a merger in this cluster is being observed.

  1. The X-ray morphology of the relaxed cluster of galaxies A2256. I - Evidence for a merger event

    Science.gov (United States)

    Briel, U. G.; Henry, J. P.; Schwarz, R. A.; Boehringer, H.; Ebeling, H.

    1991-01-01

    The rich cluster of galaxies A2256 are studied by utilizing the imaging proportional counter on board the X-ray observatory ROSAT. A2256 is considered to be a relaxed Coma-like cluster which is dynamically well evolved. Cleara evidence, however, is found for substructure in A2256. The X-ray surface brightness distribution reveals two separate maxima in the center; one of which is coincident with the central cD galaxy while the morphology of the other shows indications that it is merging with the main cluster body. The X-ray temperatures of the two maxima are different; the probable merging object being about a factor of five cooler than the cluster. The previously measured broad velocity distribution supports the idea that a merger is occurring in this cluster.

  2. Gemini/GMOS Spectroscopy of Globular Clusters in the Merger Remnant Galaxy M85

    Science.gov (United States)

    Ko, Youkyung; Lee, Myung Gyoon; Park, Hong Soo; Sohn, Jubee; Lim, Sungsoon; Hwang, Narae

    2018-06-01

    M85 is a peculiar S0 galaxy in Virgo and a well-known merger remnant. We present the first spectroscopic study of globular clusters (GCs) in M85. We obtain spectra for 21 GC candidates and the nucleus of M85 using the Gemini Multi-Object Spectrograph on the Gemini North 8.1 m telescope. From their radial velocities, 20 of the GCs are found to be members of M85. We find a strong rotation signal of the M85 GC system with a rotation amplitude of 235 km s‑1. The rotation axis of the GC system has a position angle of about 161°, which is 51.°5 larger than that of the stellar light. The rotation-corrected radial velocity dispersion of the GC system is estimated to be {σ }{{r},{cor}}=160 km s‑1. The rotation parameter {{Ω }}{R}icor}/{σ }{{r},{cor}} of the GC system is derived to be {1.47}-0.48+1.05, which is one of the largest among known early-type galaxies. The ages and metallicities of the GCs, which show the same trend as the results based on Lick indices, are derived from full spectrum fitting (ULySS). About half of the GCs are an intermediate-age population whose mean age is ∼3.7 ± 1.9 Gyr, having a mean [Fe/H] value of ‑0.26. The other half are old and metal-poor. These results suggest that M85 experienced a wet merging event about 4 Gyr ago, forming a significant population of star clusters. The strong rotational feature of the GC system can be explained by an off-center major merging.

  3. MOCCA-SURVEY Database. I. Eccentric Black Hole Mergers during Binary–Single Interactions in Globular Clusters

    Science.gov (United States)

    Samsing, Johan; Askar, Abbas; Giersz, Mirek

    2018-03-01

    We estimate the population of eccentric gravitational wave (GW) binary black hole (BBH) mergers forming during binary–single interactions in globular clusters (GCs), using ∼800 GC models that were evolved using the MOCCA code for star cluster simulations as part of the MOCCA-Survey Database I project. By re-simulating BH binary–single interactions extracted from this set of GC models using an N-body code that includes GW emission at the 2.5 post-Newtonian level, we find that ∼10% of all the BBHs assembled in our GC models that merge at present time form during chaotic binary–single interactions, and that about half of this sample have an eccentricity >0.1 at 10 Hz. We explicitly show that this derived rate of eccentric mergers is ∼100 times higher than one would find with a purely Newtonian N-body code. Furthermore, we demonstrate that the eccentric fraction can be accurately estimated using a simple analytical formalism when the interacting BHs are of similar mass, a result that serves as the first successful analytical description of eccentric GW mergers forming during three-body interactions in realistic GCs.

  4. 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.)

  5. ACCRETION SHOCKS IN CLUSTERS OF GALAXIES AND THEIR SZ SIGNATURE FROM COSMOLOGICAL SIMULATIONS

    International Nuclear Information System (INIS)

    Molnar, Sandor M.; Hearn, Nathan; Haiman, Zoltan; Bryan, Greg; Evrard, August E.; Lake, George

    2009-01-01

    Cold dark matter (CDM) hierarchical structure formation models predict the existence of large-scale accretion shocks between the virial and turnaround radii of clusters of galaxies. Kocsis et al. suggest that the Sunyaev-Zel'dovich signal associated with such shocks might be observable with the next generation radio interferometer, ALMA (Atacama Large Millimeter Array). We study the three-dimensional distribution of accretion shocks around individual clusters of galaxies drawn from adaptive mesh refinement (AMR) and smoothed particle hydrodynamics simulations of ΛCDM (dark energy dominated CDM) models. In relaxed clusters, we find two distinct sets of shocks. One set ('virial shocks'), with Mach numbers of 2.5-4, is located at radii 0.9-1.3 R vir , where R vir is the spherical infall estimate of the virial radius, covering about 40%-50% of the total surface area around clusters at these radii. Another set of stronger shocks ( e xternal shocks ) is located farther out, at about 3 R vir , with large Mach numbers (∼100), covering about 40%-60% of the surface area. We simulate SZ surface brightness maps of relaxed massive galaxy clusters drawn from high-resolution AMR runs, and conclude that ALMA should be capable of detecting the virial shocks in massive clusters of galaxies. More simulations are needed to improve estimates of astrophysical noise and to determine optimal observational strategies.

  6. Enrichment of r-Process Elements by Neutron Star Mergers through the Sub-Halo Clustering

    Science.gov (United States)

    Ishimaru, Yuhri; Ojima, Takuya; Wanajo, Shinya; Prantzos, Nikos

    Neutron star mergers (NSMs) are suggested to be the most plausible site of r-process by nucleosynthesis studies, while previous chemical evolution models pointed out that the long lifetimes of NS binaries are in conflict with the observed [r/Fe] of the Galactic halo stars. We attempt to solve this problem, assuming the Galactic halo was formed from merging sub-halos. We find that [r/Fe] start increasing at [Fe/H] < -3, if the star formation efficiencies are smaller for less massive sub-halos. We also show that small numbers of NSMs for least massive sub-halos could cause the large enhancement of [r/Fe]. Our results support NSMs as the major site of r-process.

  7. Constructing and Monitoring the Infrared SED of the First Known Recent Stellar Merger

    Science.gov (United States)

    McCollum, Bruce; Laine, Seppo; Bruhweiler, Frederick; Rottler, Lee

    2012-12-01

    Stellar mergers have long been thought to be astrophysically important to the evolution and global properties of dense stellar aggregates and even open clusters. However, the study of this phenomenon has until now been severely impeded by the lack of any definite, recent merger with which to compare models. It was recently realized that a 2008 nova was in fact a contact binary which erupted when the two stars finally merged. We have obtained post-merger infrared observations which show a large IR excess and a nonstellar SED which have changed subsantially over time, and near-IR emission lines from shocked material. This object is an important opportunity to learn about the nature and time evolution of recent merger products, and to assemble a unique data set which will be used for many years as a basis for modeling stellar mergers.

  8. Comparison of three methods for the estimation of cross-shock electric potential using Cluster data

    Directory of Open Access Journals (Sweden)

    A. P. Dimmock

    2011-05-01

    Full Text Available Cluster four point measurements provide a comprehensive dataset for the separation of temporal and spatial variations, which is crucial for the calculation of the cross shock electrostatic potential using electric field measurements. While Cluster is probably the most suited among present and past spacecraft missions to provide such a separation at the terrestrial bow shock, it is far from ideal for a study of the cross shock potential, since only 2 components of the electric field are measured in the spacecraft spin plane. The present paper is devoted to the comparison of 3 different techniques that can be used to estimate the potential with this limitation. The first technique is the estimate taking only into account the projection of the measured components onto the shock normal. The second uses the ideal MHD condition E·B = 0 to estimate the third electric field component. The last method is based on the structure of the electric field in the Normal Incidence Frame (NIF for which only the potential component along the shock normal and the motional electric field exist. All 3 approaches are used to estimate the potential for a single crossing of the terrestrial bow shock that took place on the 31 March 2001. Surprisingly all three methods lead to the same order of magnitude for the cross shock potential. It is argued that the third method must lead to more reliable results. The effect of the shock normal inaccuracy is investigated for this particular shock crossing. The resulting electrostatic potential appears too high in comparison with the theoretical results for low Mach number shocks. This shows the variability of the potential, interpreted in the frame of the non-stationary shock model.

  9. Cavitation cluster dynamics in shock-wave lithotripsy: Part I

    NARCIS (Netherlands)

    Arora, M.; Junge, L.; Junge, L.; Ohl, C.D.

    2005-01-01

    The spatiotemporal dynamics of cavitation bubble growth and collapse in shock-wave lithotripsy in a free field was studied experimentally. The lithotripter was equipped with two independently triggerable layers of piezoceramics. The front and back layers generated positive pressure amplitudes of 30

  10. A MULTI-WAVELENGTH STUDY OF THE SUNYAEV-ZEL'DOVICH EFFECT IN THE TRIPLE-MERGER CLUSTER MACS J0717.5+3745 WITH MUSTANG AND BOLOCAM

    International Nuclear Information System (INIS)

    Mroczkowski, Tony; Korngut, Phillip; Bock, James; Zemcov, Michael; Dicker, Simon; Reese, Erik D.; Young, Alexander; Devlin, Mark; Sayers, Jack; Czakon, Nicole; Golwala, Sunil; Mason, Brian; Romero, Charles; Sarazin, Craig; Koch, Patrick M.; Lin, Kai-Yang; Umetsu, Keiichi; Molnar, Sandor M.; Pierpaoli, Elena

    2012-01-01

    We present 90, 140, and 268 GHz subarcminute resolution imaging of the Sunyaev-Zel'dovich effect (SZE) in the disturbed, intermediate-redshift (z 0.5458) galaxy cluster MACS J0717.5+3745, a triple-merger system comprising four distinct, optically detected subclusters. Our 90 GHz SZE data result in a sensitive, 34 μJy beam –1 map of the SZE at 13'' effective resolution using the MUSTANG bolometer array on the Green Bank Telescope (GBT). Our 140 and 268 GHz SZE imaging, with resolutions of 58'' and 31'' and sensitivities of 1.8 and 3.3 mJy beam –1 , respectively, was obtained through observations from the Caltech Submillimeter Observatory using Bolocam. We compare these maps to a two-dimensional pressure map derived from Chandra X-ray observations. Our MUSTANG SZE data confirm previous indications from Chandra of a pressure enhancement due to shock-heated, ∼> 20 keV gas immediately adjacent to extended radio emission seen in low-frequency radio maps of this cluster. MUSTANG also detects pressure substructure that is not well constrained by the Chandra X-ray data in the remnant core of a merging subcluster. We find that the small-scale pressure enhancements in the MUSTANG data amount to ∼2% of the total pressure measured in the 140 GHz Bolocam observations. The X-ray inferred pseudo-pressure template also fails on larger scales to accurately describe the Bolocam data, particularly at the location of the subcluster with a remnant core known to have a high line-of-sight optical velocity of ∼3200 km s –1 . Our Bolocam data are adequately described when we add an additional component—not described by a thermal SZE spectrum—to the X-ray template coincident with this subcluster. Using flux densities extracted from our model fits, and marginalizing over the X-ray spectroscopic temperature constraints for the region, we fit a thermal + kinetic SZE spectrum to our Bolocam data and find that the subcluster has a best-fit line-of-sight proper velocity v z 3600

  11. Hard X-ray emission from accretion shocks around galaxy clusters

    Science.gov (United States)

    Kushnir, Doron; Waxman, Eli

    2010-02-01

    We show that the hard X-ray (HXR) emission observed from several galaxy clusters is consistent with a simple model, in which the nonthermal emission is produced by inverse Compton scattering of cosmic microwave background photons by electrons accelerated in cluster accretion shocks: The dependence of HXR surface brightness on cluster temperature is consistent with that predicted by the model, and the observed HXR luminosity is consistent with the fraction of shock thermal energy deposited in relativistic electrons being lesssim0.1. Alternative models, where the HXR emission is predicted to be correlated with the cluster thermal emission, are disfavored by the data. The implications of our predictions to future HXR observations (e.g. by NuStar, Simbol-X) and to (space/ground based) γ-ray observations (e.g. by Fermi, HESS, MAGIC, VERITAS) are discussed.

  12. Hard X-ray emission from accretion shocks around galaxy clusters

    Energy Technology Data Exchange (ETDEWEB)

    Kushnir, Doron; Waxman, Eli, E-mail: doron.kushnir@weizmann.ac.il, E-mail: eli.waxman@weizmann.ac.il [Physics Faculty, Weizmann Institute of Science, PO Box 26, Rehovot (Israel)

    2010-02-01

    We show that the hard X-ray (HXR) emission observed from several galaxy clusters is consistent with a simple model, in which the nonthermal emission is produced by inverse Compton scattering of cosmic microwave background photons by electrons accelerated in cluster accretion shocks: The dependence of HXR surface brightness on cluster temperature is consistent with that predicted by the model, and the observed HXR luminosity is consistent with the fraction of shock thermal energy deposited in relativistic electrons being ∼<0.1. Alternative models, where the HXR emission is predicted to be correlated with the cluster thermal emission, are disfavored by the data. The implications of our predictions to future HXR observations (e.g. by NuStar, Simbol-X) and to (space/ground based) γ-ray observations (e.g. by Fermi, HESS, MAGIC, VERITAS) are discussed.

  13. Hard X-ray emission from accretion shocks around galaxy clusters

    International Nuclear Information System (INIS)

    Kushnir, Doron; Waxman, Eli

    2010-01-01

    We show that the hard X-ray (HXR) emission observed from several galaxy clusters is consistent with a simple model, in which the nonthermal emission is produced by inverse Compton scattering of cosmic microwave background photons by electrons accelerated in cluster accretion shocks: The dependence of HXR surface brightness on cluster temperature is consistent with that predicted by the model, and the observed HXR luminosity is consistent with the fraction of shock thermal energy deposited in relativistic electrons being ∼<0.1. Alternative models, where the HXR emission is predicted to be correlated with the cluster thermal emission, are disfavored by the data. The implications of our predictions to future HXR observations (e.g. by NuStar, Simbol-X) and to (space/ground based) γ-ray observations (e.g. by Fermi, HESS, MAGIC, VERITAS) are discussed

  14. Shocks and cold fronts in merging and massive galaxy clusters: new detections with Chandra

    Science.gov (United States)

    Botteon, A.; Gastaldello, F.; Brunetti, G.

    2018-06-01

    A number of merging galaxy clusters show the presence of shocks and cold fronts, i.e. sharp discontinuities in surface brightness and temperature. The observation of these features requires an X-ray telescope with high spatial resolution like Chandra, and allows to study important aspects concerning the physics of the intracluster medium (ICM), such as its thermal conduction and viscosity, as well as to provide information on the physical conditions leading to the acceleration of cosmic rays and magnetic field amplification in the cluster environment. In this work we search for new discontinuities in 15 merging and massive clusters observed with Chandra by using different imaging and spectral techniques of X-ray observations. Our analysis led to the discovery of 22 edges: six shocks, eight cold fronts, and eight with uncertain origin. All the six shocks detected have Mdiverse approaches aimed to identify edges in the ICM. A radio follow-up of the shocks discovered in this paper will be useful to study the connection between weak shocks and radio relics.

  15. Another shock for the Bullet cluster, and the source of seed electrons for radio relics

    Science.gov (United States)

    Shimwell, Timothy W.; Markevitch, Maxim; Brown, Shea; Feretti, Luigina; Gaensler, B. M.; Johnston-Hollitt, M.; Lage, Craig; Srinivasan, Raghav

    2015-05-01

    With Australia Telescope Compact Array observations, we detect a highly elongated Mpc-scale diffuse radio source on the eastern periphery of the Bullet cluster 1E 0657-55.8, which we argue has the positional, spectral and polarimetric characteristics of a radio relic. This powerful relic (2.3 ± 0.1 × 1025 W Hz-1) consists of a bright northern bulb and a faint linear tail. The bulb emits 94 per cent of the observed radio flux and has the highest surface brightness of any known relic. Exactly coincident with the linear tail, we find a sharp X-ray surface brightness edge in the deep Chandra image of the cluster - a signature of a shock front in the hot intracluster medium (ICM), located on the opposite side of the cluster to the famous bow shock. This new example of an X-ray shock coincident with a relic further supports the hypothesis that shocks in the outer regions of clusters can form relics via diffusive shock (re-)acceleration. Intriguingly, our new relic suggests that seed electrons for reacceleration are coming from a local remnant of a radio galaxy, which we are lucky to catch before its complete disruption. If this scenario, in which a relic forms when a shock crosses a well-defined region of the ICM polluted with aged relativistic plasma - as opposed to the usual assumption that seeds are uniformly mixed in the ICM - is also the case for other relics, this may explain a number of peculiar properties of peripheral relics.

  16. X-RAY SIGNATURES OF NON-EQUILIBRIUM IONIZATION EFFECTS IN GALAXY CLUSTER ACCRETION SHOCK REGIONS

    International Nuclear Information System (INIS)

    Wong, Ka-Wah; Sarazin, Craig L.; Ji Li

    2011-01-01

    The densities in the outer regions of clusters of galaxies are very low, and the collisional timescales are very long. As a result, heavy elements will be under-ionized after they have passed through the accretion shock. We have studied systematically the effects of non-equilibrium ionization for relaxed clusters in the ΛCDM cosmology using one-dimensional hydrodynamic simulations. We found that non-equilibrium ionization effects do not depend on cluster mass, but depend strongly on redshift which can be understood by self-similar scaling arguments. The effects are stronger for clusters at lower redshifts. We present X-ray signatures such as surface brightness profiles and emission lines in detail for a massive cluster at low redshift. In general, soft emission (0.3-1.0 keV) is enhanced significantly by under-ionization, and the enhancement can be nearly an order of magnitude near the shock radius. The most prominent non-equilibrium ionization signature we found is the O VII and O VIII line ratio. The ratios for non-equilibrium ionization and collisional ionization equilibrium models are different by more than an order of magnitude at radii beyond half of the shock radius. These non-equilibrium ionization signatures are equally strong for models with different non-adiabatic shock electron heating efficiencies. We have also calculated the detectability of the O VII and O VIII lines with the future International X-ray Observatory (IXO). Depending on the line ratio measured, we conclude that an exposure of ∼130-380 ks on a moderate-redshift, massive regular cluster with the X-ray Microcalorimeter Spectrometer (XMS) on the IXO will be sufficient to provide a strong test for the non-equilibrium ionization model.

  17. Complex Structure of Galaxy Cluster Abell 1689: Evidence for a Merger from X-Ray Data?

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, K

    2004-01-29

    Abell 1689 is a galaxy cluster at z = 0:183 where previous measurements of its mass using various techniques gave discrepant results. We present a new detailed measurement of the mass with the data based on X-ray observations with the European Photon Imaging Camera aboard the XMM-Newton Observatory, determined by using an unparameterized deprojection technique. Fitting the total mass profile to a Navarro-Frenk-White model yields halo concentration c = 7.2{sub -2.4}{sup +1.6} and r{sub 200} = 1.13 {+-} 0.21 h{sup -1} Mpc, corresponding to a mass which is less than half of what is found from gravitational lensing. Adding to the evidence of substructure from optical observations, X-ray analysis shows a highly asymmetric temperature profile and a non-uniform redshift distribution implying large scale relative motion of the gas. A lower than expected gas mass fraction f{sub gas} = 0.072 {+-} 0.008 (for a flat {Lambda}CDM cosmology) suggests a complex spatial and/or dynamical structure. We also find no signs of any additional absorbing component previously reported on the basis of the Chandra data, confirming the XMM low energy response using data from ROSAT.

  18. Interplanetary shock transmitted into the Earth's magnetosheath: Cluster and Double Star observations

    Directory of Open Access Journals (Sweden)

    G. Pallocchia

    2010-05-01

    Full Text Available On day 7 May 2005, the plasma instruments on board Double Star TC1 and Cluster SC3 spacecraft register inside the magnetosheath, at 19:15:12 and 19:16:20 UT, respectively, a strong pressure pulse due to the impact of an interplanetary shock wave (IS on the terrestrial bow shock. The analysis of this event provides clear and quantitative evidences confirming and strengthening some results given by past simulations and observational studies. In fact, here we show that the transmitted shock is slowed down with respect to the incident IS (in the Earth's reference frame and that, besides the transmitted shock, the IS – bow shock interaction generates a second discontinuity. Moreover, supported also by a special set three-dimensional magnetohydrodynamic simulation, we discuss, as further effects of the interaction of the IS with the magnetosphere, other two interesting aspects of the present event, that is: the TC1 double crossing of the bow shock (observed few minutes after the impact of the IS and the presence, only in the SC3 data, of a third discontinuity produced inside the magnetosheath.

  19. 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).

  20. Fast and Furious: Shock heated gas as the origin of spatially resolved hard X-ray emission in the central 5 kpc of the galaxy merger NGC 6240

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Junfeng; Nardini, Emanuele; Fabbiano, Giuseppina; Karovska, Margarita; Elvis, Martin; Risaliti, Guido; Zezas, Andreas [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Pellegrini, Silvia [Dipartimento di Astronomia, Universitá di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Max, Claire [Center for Adaptive Optics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); U, Vivian, E-mail: jfwang@northwestern.edu [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2014-01-20

    We have obtained a deep, subarcsecond resolution X-ray image of the nuclear region of the luminous galaxy merger NGC 6240 with Chandra, which resolves the X-ray emission from the pair of active nuclei and the diffuse hot gas in great detail. We detect extended hard X-ray emission from kT ∼ 6 keV (∼70 MK) hot gas over a spatial scale of 5 kpc, indicating the presence of fast shocks with a velocity of ∼2200 km s{sup –1}. For the first time, we obtain the spatial distribution of this highly ionized gas emitting Fe XXV, which shows a remarkable correspondence to the large-scale morphology of H{sub 2}(1-0) S(1) line emission and Hα filaments. Propagation of fast shocks originating in the starburst-driven wind into the ambient dense gas can account for this morphological correspondence. With an observed L {sub 0.5-8} {sub keV} = 5.3 × 10{sup 41} erg s{sup –1}, the diffuse hard X-ray emission is ∼100 times more luminous than that observed in the classic starburst galaxy M82. Assuming a filling factor of 1% for the 70 MK temperature gas, we estimate its total mass (M {sub hot} = 1.8 × 10{sup 8} M {sub ☉}) and thermal energy (E {sub th} = 6.5 × 10{sup 57} erg). The total iron mass in the highly ionized plasma is M {sub Fe} = 4.6 × 10{sup 5} M {sub ☉}. Both the energetics and the iron mass in the hot gas are consistent with the expected injection from the supernovae explosion during the starburst that is commensurate with its high star formation rate. No evidence for fluorescent Fe I emission is found in the CO filament connecting the two nuclei.

  1. Fast and Furious: Shock Heated Gas as the Origin of Spatially Resolved Hard X-Ray Emission in the Central 5 kpc of the Galaxy Merger NGC 6240

    Science.gov (United States)

    Wang, Junfeng; Nardini, Emanuele; Fabbiano, Giuseppina; Karovska, Margarita; Elvis, Martin; Pellegrini, Silvia; Max, Claire; Risaliti, Guido; U, Vivian; Zezas, Andreas

    2014-01-01

    We have obtained a deep, subarcsecond resolution X-ray image of the nuclear region of the luminous galaxy merger NGC 6240 with Chandra, which resolves the X-ray emission from the pair of active nuclei and the diffuse hot gas in great detail. We detect extended hard X-ray emission from kT ~ 6 keV (~70 MK) hot gas over a spatial scale of 5 kpc, indicating the presence of fast shocks with a velocity of ~2200 km s-1. For the first time, we obtain the spatial distribution of this highly ionized gas emitting Fe XXV, which shows a remarkable correspondence to the large-scale morphology of H2(1-0) S(1) line emission and Hα filaments. Propagation of fast shocks originating in the starburst-driven wind into the ambient dense gas can account for this morphological correspondence. With an observed L 0.5-8 keV = 5.3 × 1041 erg s-1, the diffuse hard X-ray emission is ~100 times more luminous than that observed in the classic starburst galaxy M82. Assuming a filling factor of 1% for the 70 MK temperature gas, we estimate its total mass (M hot = 1.8 × 108 M ⊙) and thermal energy (E th = 6.5 × 1057 erg). The total iron mass in the highly ionized plasma is M Fe = 4.6 × 105 M ⊙. Both the energetics and the iron mass in the hot gas are consistent with the expected injection from the supernovae explosion during the starburst that is commensurate with its high star formation rate. No evidence for fluorescent Fe I emission is found in the CO filament connecting the two nuclei.

  2. Fast and Furious: Shock heated gas as the origin of spatially resolved hard X-ray emission in the central 5 kpc of the galaxy merger NGC 6240

    International Nuclear Information System (INIS)

    Wang, Junfeng; Nardini, Emanuele; Fabbiano, Giuseppina; Karovska, Margarita; Elvis, Martin; Risaliti, Guido; Zezas, Andreas; Pellegrini, Silvia; Max, Claire; U, Vivian

    2014-01-01

    We have obtained a deep, subarcsecond resolution X-ray image of the nuclear region of the luminous galaxy merger NGC 6240 with Chandra, which resolves the X-ray emission from the pair of active nuclei and the diffuse hot gas in great detail. We detect extended hard X-ray emission from kT ∼ 6 keV (∼70 MK) hot gas over a spatial scale of 5 kpc, indicating the presence of fast shocks with a velocity of ∼2200 km s –1 . For the first time, we obtain the spatial distribution of this highly ionized gas emitting Fe XXV, which shows a remarkable correspondence to the large-scale morphology of H 2 (1-0) S(1) line emission and Hα filaments. Propagation of fast shocks originating in the starburst-driven wind into the ambient dense gas can account for this morphological correspondence. With an observed L 0.5-8 keV = 5.3 × 10 41 erg s –1 , the diffuse hard X-ray emission is ∼100 times more luminous than that observed in the classic starburst galaxy M82. Assuming a filling factor of 1% for the 70 MK temperature gas, we estimate its total mass (M hot = 1.8 × 10 8 M ☉ ) and thermal energy (E th = 6.5 × 10 57 erg). The total iron mass in the highly ionized plasma is M Fe = 4.6 × 10 5 M ☉ . Both the energetics and the iron mass in the hot gas are consistent with the expected injection from the supernovae explosion during the starburst that is commensurate with its high star formation rate. No evidence for fluorescent Fe I emission is found in the CO filament connecting the two nuclei.

  3. CHARACTERISTICS OF THE SECONDARY BUBBLE CLUSTER PRODUCED BY AN ELECTROHYDRAULIC SHOCK WAVE LITHOTRIPTER

    Science.gov (United States)

    Zhou, Yufeng; Qin, Jun; Zhong, Pei

    2013-01-01

    This study investigated the characteristics of the secondary bubble cluster produced by an electrohydraulic lithotripter using high-speed imaging and passive cavitation detection techniques. The results showed that (i) the discrepancy of the collapse time between near a flat rigid boundary and in a free field of the secondary bubble cluster was not as significant as that by the primary one; (ii) the secondary bubble clusters were small but in a high bubble density and nonuniform in distribution, and they did not expand and aggregate significantly near a rigid boundary; and (iii) the corresponding bubble collapse was weaker with few microjet formation and bubble rebound. By applying a strong suction flow near the electrode tip, the production of the secondary shock wave (SW) and induced bubble cluster could be disturbed significantly, but without influence on the primary ones. Consequently, stone fragmentation efficiency was reduced from 41.2 ± 7.1% to 32.2 ± 3.5% after 250 shocks (p <0.05). Altogether, these observations suggest that the secondary bubble cluster produced by an electrohydraulic lithotripter may contribute to its ability for effective stone fragmentation. PMID:22390990

  4. On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

    Directory of Open Access Journals (Sweden)

    V. V. Lobzin

    2008-09-01

    Full Text Available A new method for remote sensing of the quasiperpendicular part of the bow shock surface is presented. The method is based on analysis of high frequency electric field fluctuations corresponding to Langmuir, upshifted, and downshifted oscillations in the electron foreshock. Langmuir waves usually have maximum intensity at the upstream boundary of this region. All these waves are generated by energetic electrons accelerated by quasiperpendicular zone of the shock front. Nonstationary behavior of the shock, in particular due to rippling, should result in modulation of energetic electron fluxes, thereby giving rise to variations of Langmuir waves intensity. For upshifted and downshifted oscillations, the variations of both intensity and central frequency can be observed. For the present study, WHISPER measurements of electric field spectra obtained aboard Cluster spacecraft are used to choose 48 crossings of the electron foreshock boundary with dominating Langmuir waves and to perform for the first time a statistical analysis of nonstationary behavior of quasiperpendicular zone of the Earth's bow shock. Analysis of hidden periodicities in plasma wave energy reveals shock front nonstationarity in the frequency range 0.33 fBiBi, where fBi is the proton gyrofrequency upstream of the shock, and shows that the probability to observe such a nonstationarity increases with Mach number. The profiles observed aboard different spacecraft and the dominating frequencies of the periodicities are usually different. Hence nonstationarity and/or rippling seem to be rather irregular both in space and time rather than resembling a quasiregular wave propagating on the shock surface.

  5. On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

    Directory of Open Access Journals (Sweden)

    V. V. Lobzin

    2008-09-01

    Full Text Available A new method for remote sensing of the quasiperpendicular part of the bow shock surface is presented. The method is based on analysis of high frequency electric field fluctuations corresponding to Langmuir, upshifted, and downshifted oscillations in the electron foreshock. Langmuir waves usually have maximum intensity at the upstream boundary of this region. All these waves are generated by energetic electrons accelerated by quasiperpendicular zone of the shock front. Nonstationary behavior of the shock, in particular due to rippling, should result in modulation of energetic electron fluxes, thereby giving rise to variations of Langmuir waves intensity. For upshifted and downshifted oscillations, the variations of both intensity and central frequency can be observed. For the present study, WHISPER measurements of electric field spectra obtained aboard Cluster spacecraft are used to choose 48 crossings of the electron foreshock boundary with dominating Langmuir waves and to perform for the first time a statistical analysis of nonstationary behavior of quasiperpendicular zone of the Earth's bow shock. Analysis of hidden periodicities in plasma wave energy reveals shock front nonstationarity in the frequency range 0.33 fBishock, and shows that the probability to observe such a nonstationarity increases with Mach number. The profiles observed aboard different spacecraft and the dominating frequencies of the periodicities are usually different. Hence nonstationarity and/or rippling seem to be rather irregular both in space and time rather than resembling a quasiregular wave propagating on the shock surface.

  6. Non-stationarity of the quasi-perpendicular bow shock: comparison between Cluster observations and simulations

    Directory of Open Access Journals (Sweden)

    H. Comişel

    2011-02-01

    Full Text Available We have performed full particle electromagnetic simulations of a quasi-perpendicular shock. The shock parameters have been chosen to be appropriate for the quasi-perpendicular Earth's bow shock observed by Cluster on 24 January 2001 (Lobzin et al., 2007. We have performed two simulations with different ion to electron mass ratio: run 1 with mi/me=1840 and run 2 with mi/me=100. In run 1 the growth rate of the modified two-stream instability (MTSI is large enough to get excited during the reflection and upstream gyration of part of the incident solar wind ions. The waves due to the MTSI are on the whistler mode branch and have downstream directed phase velocities in the shock frame. The Poynting flux (and wave group velocity far upstream in the foot is also directed in the downstream direction. However, in the density and magnetic field compression region of the overshoot the waves are refracted and the Poynting flux in the shock frame is directed upstream. The MTSI is suppressed in the low mass ratio run 2. The low mass ratio run shows more clearly the non-stationarity of the shock with a larger time scale of the order of an inverse ion gyrofrequency (Ωci: the magnetic field profile flattens and steepens with a period of ~1.5Ωci−1. This non-stationarity is different from reformation seen in previous simulations of perpendicular or quasi-perpendicular shocks. Beginning with a sharp shock ramp the large electric field in the normal direction leads to high reflection rate of solar wind protons. As they propagate upstream, the ion bulk velocity decreases and the magnetic field increases in the foot, which results in a flattening of the magnetic field profile and in a decrease of the normal electric field. Subsequently the reflection rate decreases and the whole shock profile steepens again. Superimposed on this 'breathing' behavior are in the realistic mass ratio case the waves due to the MTSI. The simulations lead us to a re-interpretation of

  7. A NOVEL APPROACH TO CONSTRAIN THE MASS RATIO OF MINOR MERGERS IN ELLIPTICAL GALAXIES: APPLICATION TO NGC 4889, THE BRIGHTEST CLUSTER GALAXY IN COMA

    International Nuclear Information System (INIS)

    Gu Meng; Huang Song; Ho, Luis C.; Peng, Chien Y.

    2013-01-01

    Minor mergers are thought to be important for the buildup and structural evolution of massive elliptical galaxies. In this work, we report the discovery of a system of four shell features in NGC 4889, one of the brightest members of the Coma cluster, using optical images taken with the Hubble Space Telescope and the Sloan Digital Sky Survey. The shells are well aligned with the major axis of the host and are likely to have been formed by the accretion of a small satellite galaxy. We have performed a detailed two-dimensional photometric decomposition of NGC 4889 and of the many overlapping nearby galaxies in its vicinity. This comprehensive model allows us not only to firmly detect the low-surface brightness shells, but, crucially, also to accurately measure their luminosities and colors. The shells are bluer than the underlying stars at the same radius in the main galaxy. We make use of the colors of the shells and the color-magnitude relation of the Coma cluster to infer the luminosity (or mass) of the progenitor galaxy. The shells in NGC 4889 appear to have been produced by the minor merger of a moderate-luminosity (M I ≈ –18.7 mag) disk (S0 or spiral) galaxy with a luminosity (mass) ratio of ∼90:1 with respect to the primary galaxy. The novel methodology presented in this work can be exploited to decode the fossil record imprinted in the photometric substructure of other nearby early-type galaxies

  8. Large carbon cluster thin film gauges for measuring aerodynamic heat transfer rates in hypersonic shock tunnels

    International Nuclear Information System (INIS)

    Srinath, S; Reddy, K P J

    2015-01-01

    Different types of Large Carbon Cluster (LCC) layers are synthesized by a single-step pyrolysis technique at various ratios of precursor mixture. The aim is to develop a fast responsive and stable thermal gauge based on a LCC layer which has relatively good electrical conduction in order to use it in the hypersonic flow field. The thermoelectric property of the LCC layer has been studied. It is found that these carbon clusters are sensitive to temperature changes. Therefore suitable thermal gauges were developed for blunt cone bodies and were tested in hypersonic shock tunnels at a flow Mach number of 6.8 to measure aerodynamic heating. The LCC layer of this thermal gauge encounters high shear forces and a hostile environment for test duration in the range of a millisecond. The results are favorable to use large carbon clusters as a better sensor than a conventional platinum thin film gauge in view of fast responsiveness and stability. (paper)

  9. A Zoo of Radio Relics: Cluster Cores to Filaments Ruta Kale1,2 ...

    Indian Academy of Sciences (India)

    Abstract. Radio relics in galaxy clusters can be electrons accelerated at cluster merger shocks or adiabatically compressed fossil radio cocoons or dying radio galaxies. The spectral evolution of radio relics is affected by the surrounding thermal plasma. We present a low frequency study of three radio relics representing ...

  10. ION INJECTION AT QUASI-PARALLEL SHOCKS SEEN BY THE CLUSTER SPACECRAFT

    International Nuclear Information System (INIS)

    Johlander, A.; Vaivads, A.; Khotyaintsev, Yu. V.; Retinò, A.; Dandouras, I.

    2016-01-01

    Collisionless shocks in space plasma are known to be capable of accelerating ions to very high energies through diffusive shock acceleration (DSA). This process requires an injection of suprathermal ions, but the mechanisms producing such a suprathermal ion seed population are still not fully understood. We study acceleration of solar wind ions resulting from reflection off short large-amplitude magnetic structures (SLAMSs) in the quasi-parallel bow shock of Earth using in situ data from the four Cluster spacecraft. Nearly specularly reflected solar wind ions are observed just upstream of a SLAMS. The reflected ions are undergoing shock drift acceleration (SDA) and obtain energies higher than the solar wind energy upstream of the SLAMS. Our test particle simulations show that solar wind ions with lower energy are more likely to be reflected off the SLAMS, while high-energy ions pass through the SLAMS, which is consistent with the observations. The process of SDA at SLAMSs can provide an effective way of accelerating solar wind ions to suprathermal energies. Therefore, this could be a mechanism of ion injection into DSA in astrophysical plasmas

  11. A NOVEL APPROACH TO CONSTRAIN THE MASS RATIO OF MINOR MERGERS IN ELLIPTICAL GALAXIES: APPLICATION TO NGC 4889, THE BRIGHTEST CLUSTER GALAXY IN COMA

    Energy Technology Data Exchange (ETDEWEB)

    Gu Meng; Huang Song [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Ho, Luis C. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Peng, Chien Y. [Giant Magellan Telescope Organization, 251 South Lake Avenue, Suite 300, Pasadena, CA 91101 (United States)

    2013-08-10

    Minor mergers are thought to be important for the buildup and structural evolution of massive elliptical galaxies. In this work, we report the discovery of a system of four shell features in NGC 4889, one of the brightest members of the Coma cluster, using optical images taken with the Hubble Space Telescope and the Sloan Digital Sky Survey. The shells are well aligned with the major axis of the host and are likely to have been formed by the accretion of a small satellite galaxy. We have performed a detailed two-dimensional photometric decomposition of NGC 4889 and of the many overlapping nearby galaxies in its vicinity. This comprehensive model allows us not only to firmly detect the low-surface brightness shells, but, crucially, also to accurately measure their luminosities and colors. The shells are bluer than the underlying stars at the same radius in the main galaxy. We make use of the colors of the shells and the color-magnitude relation of the Coma cluster to infer the luminosity (or mass) of the progenitor galaxy. The shells in NGC 4889 appear to have been produced by the minor merger of a moderate-luminosity (M{sub I} Almost-Equal-To -18.7 mag) disk (S0 or spiral) galaxy with a luminosity (mass) ratio of {approx}90:1 with respect to the primary galaxy. The novel methodology presented in this work can be exploited to decode the fossil record imprinted in the photometric substructure of other nearby early-type galaxies.

  12. A Novel Approach to Constrain the Mass Ratio of Minor Mergers in Elliptical Galaxies: Application to NGC 4889, the Brightest Cluster Galaxy in Coma

    Science.gov (United States)

    Gu, Meng; Ho, Luis C.; Peng, Chien Y.; Huang, Song

    2013-08-01

    Minor mergers are thought to be important for the buildup and structural evolution of massive elliptical galaxies. In this work, we report the discovery of a system of four shell features in NGC 4889, one of the brightest members of the Coma cluster, using optical images taken with the Hubble Space Telescope and the Sloan Digital Sky Survey. The shells are well aligned with the major axis of the host and are likely to have been formed by the accretion of a small satellite galaxy. We have performed a detailed two-dimensional photometric decomposition of NGC 4889 and of the many overlapping nearby galaxies in its vicinity. This comprehensive model allows us not only to firmly detect the low-surface brightness shells, but, crucially, also to accurately measure their luminosities and colors. The shells are bluer than the underlying stars at the same radius in the main galaxy. We make use of the colors of the shells and the color-magnitude relation of the Coma cluster to infer the luminosity (or mass) of the progenitor galaxy. The shells in NGC 4889 appear to have been produced by the minor merger of a moderate-luminosity (MI ≈ -18.7 mag) disk (S0 or spiral) galaxy with a luminosity (mass) ratio of ~90:1 with respect to the primary galaxy. The novel methodology presented in this work can be exploited to decode the fossil record imprinted in the photometric substructure of other nearby early-type galaxies. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555.

  13. 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.

  14. 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...... and fiscal neutrality, group-related issues, holding-structure issues, employees, stock exchange listing issues, and corporate nationality....

  15. 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.

  16. Clusters of galaxies as tools in observational cosmology : results from x-ray analysis

    International Nuclear Information System (INIS)

    Weratschnig, J.M.

    2009-01-01

    Clusters of galaxies are the largest gravitationally bound structures in the universe. They can be used as ideal tools to study large scale structure formation (e.g. when studying merger clusters) and provide highly interesting environments to analyse several characteristic interaction processes (like ram pressure stripping of galaxies, magnetic fields). In this dissertation thesis, we have studied several clusters of galaxies using X-ray observations. To obtain scientific results, we have applied different data reduction and analysis methods. With a combination of morphological and spectral analysis, the merger cluster Abell 514 was studied in much detail. It has a highly interesting morphology and shows signs for an ongoing merger as well as a shock. using a new method to detect substructure, we have analysed several clusters to determine whether any substructure is present in the X-ray image. This hints towards a real structure in the distribution of the intra-cluster medium (ICM) and is evidence for ongoing mergers. The results from this analysis are extensively used with the cluster of galaxies Abell S1136. Here, we study the ICM distribution and compare its structure with the spatial distribution of star forming galaxies. Cluster magnetic fields are another important topic of my thesis. They can be studied in Radio observations, which can be put into relation with results from X-ray observations. using observational data from several clusters, we could support the theory that cluster magnetic fields are frozen into the ICM. (author)

  17. THE FORMATION OF SECONDARY STELLAR GENERATIONS IN MASSIVE YOUNG STAR CLUSTERS FROM RAPIDLY COOLING SHOCKED STELLAR WINDS

    Energy Technology Data Exchange (ETDEWEB)

    Wünsch, R.; Palouš, J.; Ehlerová, S. [Astronomical Institute, Academy of Sciences of the Czech Republic, Boční II 1401, 141 31 Prague (Czech Republic); Tenorio-Tagle, G. [Instituto Nacional de Astrofísica Optica y Electrónica, AP 51, 72000 Puebla, México (Mexico)

    2017-01-20

    We study a model of rapidly cooling shocked stellar winds in young massive clusters and estimate the circumstances under which secondary star formation, out of the reinserted winds from a first stellar generation (1G), is possible. We have used two implementations of the model: a highly idealized, computationally inexpensive, spherically symmetric semi-analytic model, and a complex, three-dimensional radiation-hydrodynamic, simulation; they are in a good mutual agreement. The results confirm our previous findings that, in a cluster with 1G mass 10{sup 7} M {sub ⊙} and half-mass–radius 2.38 pc, the shocked stellar winds become thermally unstable, collapse into dense gaseous structures that partially accumulate inside the cluster, self-shield against ionizing stellar radiation, and form the second generation (2G) of stars. We have used the semi-analytic model to explore a subset of the parameter space covering a wide range of the observationally poorly constrained parameters: the heating efficiency, η {sub he}, and the mass loading, η {sub ml}. The results show that the fraction of the 1G stellar winds accumulating inside the cluster can be larger than 50% if η {sub he} ≲ 10%, which is suggested by the observations. Furthermore, for low η {sub he}, the model provides a self-consistent mechanism predicting 2G stars forming only in the central zones of the cluster. Finally, we have calculated the accumulated warm gas emission in the H30 α recombination line, analyzed its velocity profile, and estimated its intensity for super star clusters in interacting galaxies NGC4038/9 (Antennae) showing that the warm gas should be detectable with ALMA.

  18. 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.)

  19. Cluster Physics with Merging Galaxy Clusters

    Directory of Open Access Journals (Sweden)

    Sandor M. Molnar

    2016-02-01

    Full Text Available Collisions between galaxy clusters provide a unique opportunity to study matter in a parameter space which cannot be explored in our laboratories on Earth. In the standard LCDM model, where the total density is dominated by the cosmological constant ($Lambda$ and the matter density by cold dark matter (CDM, structure formation is hierarchical, and clusters grow mostly by merging.Mergers of two massive clusters are the most energetic events in the universe after the Big Bang,hence they provide a unique laboratory to study cluster physics.The two main mass components in clusters behave differently during collisions:the dark matter is nearly collisionless, responding only to gravity, while the gas is subject to pressure forces and dissipation, and shocks and turbulenceare developed during collisions. In the present contribution we review the different methods used to derive the physical properties of merging clusters. Different physical processes leave their signatures on different wavelengths, thusour review is based on a multifrequency analysis. In principle, the best way to analyze multifrequency observations of merging clustersis to model them using N-body/HYDRO numerical simulations. We discuss the results of such detailed analyses.New high spatial and spectral resolution ground and space based telescopeswill come online in the near future. Motivated by these new opportunities,we briefly discuss methods which will be feasible in the near future in studying merging clusters.

  20. On the origin of field-aligned beams at the quasi-perpendicular bow shock: multi-spacecraft observations by Cluster

    Directory of Open Access Journals (Sweden)

    H. Kucharek

    2004-07-01

    Full Text Available Two distinct populations of reflected and accelerated ions are known to originate from quasi-perpendicular shocks, gyrating ions and reflected ion beams. Recent observations under such bow shock conditions with Cluster have shown strong evidence that both particle distributions appear to emerge from the same reflection process. In this paper the basic production mechanism of field-aligned beams has been investigated by using CLUSTER multi-spacecraft measurements. We have analyzed several quasi-perpendicular shocks with the Cluster Ion Spectrometry experiment (CIS and followed the spatial and temporal evolution of the reflected and transmitted ion populations across the shock. These observations show that the field-aligned beams most likely result from effective scattering in pitch angle during reflection in the shock ramp. Investigating a low Mach number shock, leakage of a fraction of the thermalized ion distribution in the downstream region does not appear to be the source as the volume in phase space occupied by beam ions is empty downstream of the shock ramp.

  1. 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.

  2. 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...

  3. The Next Generation of Numerical Modeling in Mergers- Constraining the Star Formation Law

    Science.gov (United States)

    Chien, Li-Hsin

    2010-09-01

    Spectacular images of colliding galaxies like the "Antennae", taken with the Hubble Space Telescope, have revealed that a burst of star/cluster formation occurs whenever gas-rich galaxies interact. A?The ages and locations of these clusters reveal the interaction history and provide crucial clues to the process of star formation in galaxies. A?We propose to carry out state-of-the-art numerical simulations to model six nearby galaxy mergers {Arp 256, NGC 7469, NGC 4038/39, NGC 520, NGC 2623, NGC 3256}, hence increasing the number with this level of sophistication by a factor of 3. These simulations provide specific predictions for the age and spatial distributions of young star clusters. The comparison between these simulation results and the observations will allow us to answer a number of fundamental questions including: 1} is shock-induced or density-dependent star formation the dominant mechanism; 2} are the demographics {i.e. mass and age distributions} of the clusters in different mergers similar, i.e. "universal", or very different; and 3} will it be necessary to include other mechanisms, e.g., locally triggered star formation, in the models to better match the observations?

  4. Large amplitude solitary waves in and near the Earth’s magnetosphere, magnetopause and bow shock: Polar and Cluster observations

    Directory of Open Access Journals (Sweden)

    C. Cattell

    2003-01-01

    Full Text Available Solitary waves with large electric fields (up to 100's of mV/m have been observed throughout the magnetosphere and in the bow shock. We discuss observations by Polar at high altitudes ( ~ 4-8 RE , during crossings of the plasma sheet boundary and cusp, and new measurements by Polar at the equatorial magnetopause and by Cluster near the bow shock, in the cusp and at the plasma sheet boundary. We describe the results of a statistical study of electron solitary waves observed by Polar at high altitudes. The mean solitary wave duration was ~ 2 ms. The waves have velocities from ~ 1000 km/s to  > 2500 km/s. Observed scale sizes (parallel to the magnetic field are on the order of 1-10lD, with eF/kTe from ~ 0.01 to O(1. The average speed of solitary waves at the plasma sheet boundary is faster than the average speed observed in the cusp and at cusp injections. The amplitude increases with both velocity and scale size. These observations are all consistent with the identification of the solitary waves as electron hole modes. We also report the discovery of solitary waves at the magnetopause, observed in Polar data obtained at the subsolar equatorial magnetopause. Both positive and negative potential structures have been observed with amplitudes up to ~ 25 mV/m. The velocities range from 150 km/s to >2500 km/s, with scale sizes the order of a kilometer (comparable to the Debye length. Initial observations of solitary waves by the four Cluster satellites are utilized to discuss the scale sizes and time variability of the regions where the solitary waves occur. Preliminary results from the four Cluster satellites have given a glimpse of the spatial and temporal variability of the occurrence of solitary waves and their association with other wave modes. In all the events studied, significant differences were observed in the waveforms observed simultaneously at the four locations separated by ~ 1000 km. When solitary waves were seen at one satellite, they

  5. Observations of the spatial and temporal structure of field-aligned beam and gyrating ring distributions at the quasi-perpendicular bow shock with Cluster CIS

    Directory of Open Access Journals (Sweden)

    E. Möbius

    2001-09-01

    Full Text Available During the early orbit phase, the Cluster spacecraft have repeatedly crossed the perpendicular Earth’s bow shock and provided the first multi-spacecraft measurements. We have analyzed data from the Cluster Ion Spectrometry experiment (CIS, which observes the 3D-ion distribution function of the major species in the energy range of 5 eV to 40 keV with a 4 s resolution. Beams of reflected ions were observed simultaneously at all spacecraft locations and could be tracked from upstream to the shock itself. They were found to originate from the same distribution of ions that constitutes the reflected gyrating ions, which form a ring distribution in the velocity space immediately upstream and downstream of the shock. This observation suggests a common origin of ring and beam populations at quasi-perpendicular shocks in the form of specular reflection and immediate pitch angle scattering. Generally, the spatial evolution across the shock is very similar on all spacecraft, but phased in time according to their relative location. However, a distinct temporal structure of the ion fluxes in the field-aligned beam is observed that varies simultaneously on all spacecraft. This is likely to reflect the variations in the reflection and scattering efficiencies.Key words. Interplanetary physics (planetary bow shocks; energetic particles; instruments and techniques

  6. 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.

  7. The Stormy Life of Galaxy Clusters

    Science.gov (United States)

    Rudnick, Lawrence

    2018-01-01

    Galaxy clusters, the largest gravitationally bound structures, hold the full history of their baryonic evolution, serve as important cosmological tools and allow us to probe unique physical regimes in their diffuse plasmas. With characteristic dynamical timescales of 107-109 years, these diffuse thermal and relativistic media continue to evolve, as dark matter drives major mergers and more gentle continuing accretion. The history of this assembly is encoded in the plasmas, and a wide range of observational and theoretical investigations are aimed at decoding their signatures. X-ray temperature and density variations, low Mach number shocks, and "cold front" discontinuities all illuminate clusters' continued evolution. Radio structures and spectra are passive indicators of merger shocks, while radio galaxy distortions reveal the complex motions in the intracluster medium. Deep in cluster cores, AGNs associated with brightest cluster galaxies provide ongoing energy, and perhaps even stabilize the intracluster medium. In this talk, we will recount this evolving picture of the stormy ICM, and suggest areas of likely advance in the coming years.

  8. Mergers and Acquisitions

    OpenAIRE

    Frasch, Manfred; Leptin, Maria

    2000-01-01

    Mergers and acquisitions (M&As) are booming a strategy of choice for organizations attempting to maintain a competitive advantage. Previous research on mergers and acquisitions declares that acquirers do not normally benefit from acquisitions. Targets, on the other hand, have a tendency of gaining positive returns in the few days surrounding merger announcements due to several characteristic on the acquisitions deal. The announcement period wealth effect on acquiring firms, however, is as cle...

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. 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...

  14. Predation and Mergers: Is Merger Law Counterproductive?

    OpenAIRE

    Persson, Lars

    1999-01-01

    This Paper shows that predation might help firms overcome the free riding problem of mergers by changing the acquisition situation in the buyer's favour relative to the firms outside the merger. It is also shown that the bidding competition for the prey's assets is most harmful to predators when the use of the prey's assets exerts strong negative externalities on rivals, i.e. when their use severely reduces competitors' profits. The reason is that potential buyers are then willing to pay a hi...

  15. CHANDRA OBSERVATION OF ABELL 1142: A COOL-CORE CLUSTER LACKING A CENTRAL BRIGHTEST CLUSTER GALAXY?

    Energy Technology Data Exchange (ETDEWEB)

    Su, Yuanyuan; Weeren, Reinout van [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Buote, David A. [Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Gastaldello, Fabio, E-mail: yuanyuan.su@cfa.harvard.edu [INAF-IASF-Milano, Via E. Bassini 15, I-20133 Milano (Italy)

    2016-04-10

    Abell 1142 is a low-mass galaxy cluster at low redshift containing two comparable brightest cluster galaxies (BCGs) resembling a scaled-down version of the Coma Cluster. Our Chandra analysis reveals an X-ray emission peak, roughly 100 kpc away from either BCG, which we identify as the cluster center. The emission center manifests itself as a second beta-model surface brightness component distinct from that of the cluster on larger scales. The center is also substantially cooler and more metal-rich than the surrounding intracluster medium (ICM), which makes Abell 1142 appear to be a cool-core cluster. The redshift distribution of its member galaxies indicates that Abell 1142 may contain two subclusters, each of which contain one BCG. The BCGs are merging at a relative velocity of ≈1200 km s{sup −1}. This ongoing merger may have shock-heated the ICM from ≈2 keV to above 3 keV, which would explain the anomalous L{sub X}–T{sub X} scaling relation for this system. This merger may have displaced the metal-enriched “cool core” of either of the subclusters from the BCG. The southern BCG consists of three individual galaxies residing within a radius of 5 kpc in projection. These galaxies should rapidly sink into the subcluster center due to the dynamical friction of a cuspy cold dark matter halo.

  16. 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.

  17. 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.

  18. 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)

  19. MERGER ACCOUTING FOR COMPANIES

    OpenAIRE

    SUCIU GHEORGHE

    2014-01-01

    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 mu...

  20. 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)

  1. Observation of energy-time dispersed ion structures in the magnetosheath by CLUSTER: possible signatures of transient acceleration processes at shock

    Directory of Open Access Journals (Sweden)

    P. Louarn

    Full Text Available We analyse energy-time dispersed ion signatures that have been observed by CLUSTER in the dayside magnetosheath. These events are characterized by sudden increases in the ion flux at energies larger than 10 keV. The high energy ions (30 keV are first detected, with the transition to the low energy ions (5 keV lasting about 100 s. These injections are often associated with transient plasma structures of a few minutes in duration, characterized by a hotter, less dense plasma and a diverted flow velocity, thus presenting similarities with "hot flow anomalies". They also involve modifications of the magnetic field direction, suggesting that the shock interacts with a solar wind discontinuity at the time of the event. The injections can originate from the magnetosphere or the shock region. Studying in detail a particular event, we discuss this last hypothesis. We show that the observed energy/time dispersion can be explained by combining a time-of-flight effect with a drift of the source of energetic particles along the shock. We propose that the acceleration results from a Fermi process linked to the interaction of the discontinuity with a quasi-perpendicular shock. This model explains the observed pitch-angle selection of the accelerated particles. The Fermi process acting on the beam of ions reflected from the shock appears to be sufficiently efficient to accelerate over short time scales (less than 30 s particles at energies above 30 keV.

    Key words. Magnetospheric physics (solar-wind-magnetosphere interaction; magnetosheath – Space plasma physics (shock waves

  2. LOW-VELOCITY SHOCKS TRACED BY EXTENDED SiO EMISSION ALONG THE W43 RIDGES: WITNESSING THE FORMATION OF YOUNG MASSIVE CLUSTERS

    International Nuclear Information System (INIS)

    Nguyen-Luong, Q.; Martin, P. G.; Motte, F.; Louvet, F.; Hill, T.; Hennemann, M.; Didelon, P.; Carlhoff, P.; Schilke, P.; Lesaffre, P.; Gusdorf, A.; Schneider, N.; Bontemps, S.; Duarte-Cabral, A.; Menten, K. M.; Wyrowski, F.; Bendo, G.; Roussel, H.; Bernard, J.-P.; Bronfman, L.

    2013-01-01

    The formation of high-mass stars is tightly linked to that of their parental clouds. Here, we focus on the high-density parts of W43, a molecular cloud undergoing an efficient event of star formation. Using a column density image derived from Herschel continuum maps, we identify two high-density filamentary clouds, called the W43-MM1 and W43-MM2 ridges. Both have gas masses of 2.1 × 10 4 M ☉ and 3.5 × 10 4 M ☉ above >10 23 cm -2 and within areas of ∼6 and ∼14 pc 2 , respectively. The W43-MM1 and W43-MM2 ridges are structures that are coherent in velocity and gravitationally bound, despite their large velocity dispersion measured by the N 2 H + (1-0) lines of the W43-HERO IRAM large program. Another intriguing result is that these ridges harbor widespread (∼10 pc 2 ) bright SiO (2-1) emission, which we interpret to be the result of low-velocity shocks (≤10 km s –1 ). We measure a significant relationship between the SiO (2-1) luminosity and velocity extent and show that it distinguishes our observations from the high-velocity shocks associated with outflows. We use state-of-the-art shock models to demonstrate that a small percentage (10%) of Si atoms in low-velocity shocks, observed initially in gas phase or in grain mantles, can explain the observed SiO column density in the W43 ridges. The spatial and velocity overlaps between the ridges of high-density gas and the shocked SiO gas suggest that ridges could be forming via colliding flows driven by gravity and accompanied by low-velocity shocks. This mechanism may be the initial conditions for the formation of young massive clusters

  3. 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...

  4. Observations and Modeling of Merging Galaxy Clusters

    Science.gov (United States)

    Golovich, Nathan Ryan

    substructures well aligned between the radio relics. Conclusions: Radio relics are efficient triggers for identifying major mergers occurring within the plane of the sky. This is ideal for observing offsets between galaxies and dark matter distributions as well as cluster shocks. Double radio relic systems, in particular, have the simplest geometries, which allow for accurate dynamical models and inferred astrophysics. Comparing and contrasting the dynamical models of MACS J1149.5+2223 and ZwCl 0008.8+5215 with similar studies in the literature (Dawson, 2013b; Ng et al., 2015; van Weeren et al., 2017), a wide range of dynamical phase space (˜ 1500 - 3000 km -1 at pericenter and ˜ 500 - 1500 Myr after pericenter) may be sampled with radio relic mergers. With sufficient samples of bimodal systems, velocity dependence of underlying astrophysics may be uncovered. (Abstract shortened by ProQuest.).

  5. LOFAR discovery of a double radio halo system in Abell 1758 and radio/X-ray study of the cluster pair

    Science.gov (United States)

    Botteon, A.; Shimwell, T. W.; Bonafede, A.; Dallacasa, D.; Brunetti, G.; Mandal, S.; van Weeren, R. J.; Brüggen, M.; Cassano, R.; de Gasperin, F.; Hoang, D. N.; Hoeft, M.; Röttgering, H. J. A.; Savini, F.; White, G. J.; Wilber, A.; Venturi, T.

    2018-05-01

    Radio halos and radio relics are diffuse synchrotron sources that extend over Mpc-scales and are found in a number of merger galaxy clusters. They are believed to form as a consequence of the energy that is dissipated by turbulence and shocks in the intra-cluster medium (ICM). However, the precise physical processes that generate these steep synchrotron spectrum sources are still poorly constrained. We present a new LOFAR observation of the double galaxy cluster Abell 1758. This system is composed of A1758N, a massive cluster hosting a known giant radio halo, and A1758S, which is a less massive cluster whose diffuse radio emission is confirmed here for the first time. Our observations have revealed a radio halo and a candidate radio relic in A1758S, and a suggestion of emission along the bridge connecting the two systems which deserves confirmation. We combined the LOFAR data with archival VLA and GMRT observations to constrain the spectral properties of the diffuse emission. We also analyzed a deep archival Chandra observation and used this to provide evidence that A1758N and A1758S are in a pre-merger phase. The ICM temperature across the bridge that connects the two systems shows a jump which might indicate the presence of a transversal shock generated in the initial stage of the merger.

  6. A VERY DEEP CHANDRA OBSERVATION OF A2052: BUBBLES, SHOCKS, AND SLOSHING

    International Nuclear Information System (INIS)

    Blanton, E. L.; Douglass, E. M.; Randall, S. W.; McNamara, B. R.; Clarke, T. E.; Sarazin, C. L.; McDonald, M.

    2011-01-01

    We present the first results from a very deep (∼650 ks) Chandra X-ray observation of A2052, as well as archival Very Large Array radio observations. The data reveal detailed structure in the inner parts of the cluster, including bubbles evacuated by radio lobes of the active galactic nucleus (AGN), compressed bubble rims, filaments, and loops. Two concentric shocks are seen, and a temperature rise is measured for the innermost one. On larger scales, we report the first detection of an excess surface brightness spiral feature. The spiral has cooler temperatures, lower entropies, and higher abundances than its surroundings, and is likely the result of sloshing gas initiated by a previous cluster-cluster or sub-cluster merger. Initial evidence for previously unseen bubbles at larger radii related to earlier outbursts from the AGN is presented.

  7. College Mergers: An Emerging Alternative.

    Science.gov (United States)

    Breuder, Robert L.

    1989-01-01

    Examines the merger of Williamsport Area Community College (WACC) and the University of Pennsylvania, necessitated by the city of Williamsport's decision to discontinue its sponsorship of WACC. Considers the principles underlying the merger, legal questions, reactions from within WACC and the surrounding community, and the benefits of the merger.…

  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. Dynamical effects of successive mergers on the evolution of spherical stellar systems

    International Nuclear Information System (INIS)

    Lee, H.M.

    1987-01-01

    Numerical investigations are carried out to study the dynamical effects of high-mass stars formed out of successive mergers among tidally captured binaries on the evolution of spherical stellar systems. It is assumed that all tidally captured systems become mergers in order to maximize these effects. Stellar systems with N greater than about 10 to the 7th are susceptible to merger instability which may lead to the formation of a central black hole. It is shown that globular clusters are likely to achieve postcollapse expansion due to three-body binary heating and stellar evolution, while galactic nuclei can easily be overcome by the merger instability in the core. 25 references

  10. Galaxy Cluster Outskirts from the Thermal SZ and Non-Thermal Synchrotron Link

    Directory of Open Access Journals (Sweden)

    Kaustuv Basu

    2016-11-01

    Full Text Available Galaxy cluster merger shocks are the main agent for the thermalization of the intracluster medium and the energization of cosmic ray particles in it. Shock propagation changes the state of the tenuous intracluster plasma, and the corresponding signal variations are measurable with the current generation of X-ray and Sunyaev–Zel’dovich (SZ effect instruments. Additionally, non-thermal electrons (re-energized by the shocks sometimes give rise to extended and luminous synchrotron sources known as radio relics, which are prominent indicators of shocks propagating roughly in the plane of the sky. In this short review, we discuss how the joint modeling of the non-thermal and thermal signal variations across radio relic shock fronts is helping to advance our knowledge of the gas thermodynamical properties and magnetic field strengths in the cluster outskirts. We describe the first use of the SZ effect to measure the Mach numbers of relic shocks, for both the nearest (Coma and the farthest (El Gordo clusters with known radio relics.

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

    Energy Technology Data Exchange (ETDEWEB)

    Deason, Alis [Department of Astronomy and Astrophysics, University of California Santa Cruz, Santa Cruz, CA (United States); Wetzel, Andrew [TAPIR, California Institute of Technology, Pasadena, CA (United States); Garrison-Kimmel, Shea, E-mail: alis@ucolick.org [Center for Cosmology, Department of Physics and Astronomy, University of California, Irvine, CA (United States)

    2014-10-20

    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 {sub star} > 10{sup 6} M {sub ☉} 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.

  12. 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.

  13. Low-velocity Shocks Traced by Extended SiO Emission along the W43 Ridges: Witnessing the Formation of Young Massive Clusters

    Science.gov (United States)

    Nguyen-Lu'o'ng, Q.; Motte, F.; Carlhoff, P.; Louvet, F.; Lesaffre, P.; Schilke, P.; Hill, T.; Hennemann, M.; Gusdorf, A.; Didelon, P.; Schneider, N.; Bontemps, S.; Duarte-Cabral, A.; Menten, K. M.; Martin, P. G.; Wyrowski, F.; Bendo, G.; Roussel, H.; Bernard, J.-P.; Bronfman, L.; Henning, T.; Kramer, C.; Heitsch, F.

    2013-10-01

    The formation of high-mass stars is tightly linked to that of their parental clouds. Here, we focus on the high-density parts of W43, a molecular cloud undergoing an efficient event of star formation. Using a column density image derived from Herschel continuum maps, we identify two high-density filamentary clouds, called the W43-MM1 and W43-MM2 ridges. Both have gas masses of 2.1 × 104 M ⊙ and 3.5 × 104 M ⊙ above >10^{23}\\, {{cm}^{-2}} and within areas of ~6 and ~14 pc2, respectively. The W43-MM1 and W43-MM2 ridges are structures that are coherent in velocity and gravitationally bound, despite their large velocity dispersion measured by the N2H+ (1-0) lines of the W43-HERO IRAM large program. Another intriguing result is that these ridges harbor widespread (~10 pc2) bright SiO (2-1) emission, which we interpret to be the result of low-velocity shocks (models to demonstrate that a small percentage (10%) of Si atoms in low-velocity shocks, observed initially in gas phase or in grain mantles, can explain the observed SiO column density in the W43 ridges. The spatial and velocity overlaps between the ridges of high-density gas and the shocked SiO gas suggest that ridges could be forming via colliding flows driven by gravity and accompanied by low-velocity shocks. This mechanism may be the initial conditions for the formation of young massive clusters.

  14. clusters

    Indian Academy of Sciences (India)

    2017-09-27

    Sep 27, 2017 ... Author for correspondence (zh4403701@126.com). MS received 15 ... lic clusters using density functional theory (DFT)-GGA of the DMOL3 package. ... In the process of geometric optimization, con- vergence thresholds ..... and Postgraduate Research & Practice Innovation Program of. Jiangsu Province ...

  15. clusters

    Indian Academy of Sciences (India)

    environmental as well as technical problems during fuel gas utilization. ... adsorption on some alloys of Pd, namely PdAu, PdAg ... ried out on small neutral and charged Au24,26,27, Cu,28 ... study of Zanti et al.29 on Pdn (n = 1–9) clusters.

  16. NEW OPPORTUNITIES ON THE MARKET OF MERGERS AND ACQUISITIONS FOR 2014

    Directory of Open Access Journals (Sweden)

    Alina MOLDOVAN-MADAN

    2013-12-01

    Full Text Available Mergers and acquisitions activity at global level could begin during 2014. Confidence in the economic environment, the availability of cash and credit, the restoration of confidence in local economies – all of these factors signals new opportunities on mergers and acquisitions market. However, caution still dominate this area and this is understandable, given the occurring of unprecedented economic crisis. In this context, the market remains very sensitive to geopolitical issues - any shock could extend short-term interruptions of the flow of transactions. However, while organic growth measures only provide diminishing returns, mergers and acquisitions activity may be the only practical way of increasing for companies.

  17. 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)

  18. Internationalize Mergers and Acquisitions

    OpenAIRE

    Zhou, Lili

    2017-01-01

    As globalization processes, an increasing number of companies use mergers and acquisitions as a tool to achieve company growth in the international business world. The purpose of this thesis is to investigate the process of an international M&A and analyze the factors leading to success. The research started with reviewing different academic theory. The important aspects in both pre-M&A phase and post-M&A phase have been studied in depth. Because of the complexity in international...

  19. Mergers & Acquisitions and Intangibles

    OpenAIRE

    Ott, Christian

    2012-01-01

    This dissertation explores the disclosure on intangibles acquired in Mergers & Acquisitos. The related empirical analyses are based on a sample of M&As that are accounted for under the International Financial Reporting Standards (IFRS) and United States Generally Accepted Accounting Principles (US-GAAP). In three different research papers I answer three distinct research questions. In order to enable capital providers and other external stakeholders to evaluate the PPA, the International Fina...

  20. The evolution of magnetic fields in clusters of galaxies

    International Nuclear Information System (INIS)

    Stoeckl, J.

    2011-01-01

    Although the observational knowledge base about the properties of magnetic fields in clusters of galaxies has significantly improved in recent years, our understanding of the evolution and influence of the magnetic fields is still limited. We present results from our study on the influence of cluster scale magnetic fields on the structure formation of clusters of galaxies and the evolution of the intra-cluster medium (ICM). The high-resolution simulations employ a self-consistent numerical setup, which includes gravity, cosmology, magnetohydrodynamics and radiative cooling. We find that during structure formation cosmological magnetic seed fields of the order of 10 -1 1 to 10 -9 G are amplified by up to six orders of magnitude, which is in good agreement with observations. Furthermore we find that merger shocks during the cluster formation can have a dispersive effect on the magnetic field in the cluster center, and the outgoing shock waves can lead to magnetic fields of the order of [mu]G even at distances of more than 1 Mpc from the center. We highlight this as a possible explanation for the faint or undetectable radio halos that can be observed together with strong radio relics. (author) [de

  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. 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.

  3. Using communication to oil the wheel of a merger

    International Nuclear Information System (INIS)

    Wallet, Annie; Breyer, Wolfgang

    2002-01-01

    This paper presents a short overview of what has been done up to now for Mental Merger program. It has been decided to concentrate the pilot program on the main culture shock, i.e. the French-German one. The following steps were performed: Perception gathering; Mono-cultural seminars; Bi-cultural workshops. Process of launching the cooperation monitoring body is under way

  4. Radio observations of the double-relic galaxy cluster Abell 1240

    Science.gov (United States)

    Hoang, D. N.; Shimwell, T. W.; van Weeren, R. J.; Intema, H. T.; Röttgering, H. J. A.; Andrade-Santos, F.; Akamatsu, H.; Bonafede, A.; Brunetti, G.; Dawson, W. A.; Golovich, N.; Best, P. N.; Botteon, A.; Brüggen, M.; Cassano, R.; de Gasperin, F.; Hoeft, M.; Stroe, A.; White, G. J.

    2018-05-01

    We present LOFAR 120 - 168 MHz images of the merging galaxy cluster Abell 1240 that hosts double radio relics. In combination with the GMRT 595 - 629 MHz and VLA 2 - 4 GHz data, we characterised the spectral and polarimetric properties of the radio emission. The spectral indices for the relics steepen from their outer edges towards the cluster centre and the electric field vectors are approximately perpendicular to the major axes of the relics. The results are consistent with the picture that these relics trace large-scale shocks propagating outwards during the merger. Assuming diffusive shock acceleration (DSA), we obtain shock Mach numbers of M=2.4 and 2.3 for the northern and southern shocks, respectively. For M≲ 3 shocks, a pre-existing population of mildly relativistic electrons is required to explain the brightness of the relics due to the high (>10 per cent) particle acceleration efficiency required. However, for M≳ 4 shocks the required efficiency is ≳ 1% and ≳ 0.5%, respectively, which is low enough for shock acceleration directly from the thermal pool. We used the fractional polarization to constrain the viewing angle to ≥53 ± 3° and ≥39 ± 5° for the northern and southern shocks, respectively. We found no evidence for diffuse emission in the cluster central region. If the halo spans the entire region between the relics (˜1.8 Mpc) our upper limit on the power is P1.4GHz = (1.4 ± 0.6) × 1023 W Hz-1 which is approximately equal to the anticipated flux from a cluster of this mass. However, if the halo is smaller than this, our constraints on the power imply that the halo is underluminous.

  5. XMM-Newton and Chandra Observations of the Remarkable Dynamics of the Intracluster Medium and Radio Sources in the Clusters Abell 2061 and 3667

    Science.gov (United States)

    Sarazin, C.; Hogge, T.; Chatzikos, M.; Wik, D.; Giacintucci, S.; Clarke, T.; Wong, K.; Gitti, M.; Finoguenov, A.

    2014-07-01

    XMM-Newton and Chandra observations of remarkable dynamic structures in the X-ray gas and connected radio sources in three clusters are presented. Abell 2061 is a highly irregular, merging cluster in the Corona Borealis supercluster. X-ray observations show that there is a plume of very cool gas (˜1 keV) to the NE of the cluster, and a hot (7.6 keV) shock region just NE of the center. There is a very bright radio relic to the far SW of the cluster, and a central radio halo/relic with an extension to the NE. Comparison to SLAM simulations show that this is an offset merger of a ˜5 × 10^{13} M⊙ subcluster with a ˜2.5 × 10^{14} M⊙ cluster seen after first core passage. The plume is the cool-core gas from the subcluster, which has been ``slingshot'' to the NE of the cluster. The plume gas is now falling back into the cluster center, and shocks when it hits the central gas. The model predicts a strong shock to the SW at the location of the bright radio relic, and another shock at the NE radio extension. Time permitting, the observations of Abell 2626 and Abell 3667 will also be presented.

  6. GALAXY CLUSTER RADIO RELICS IN ADAPTIVE MESH REFINEMENT COSMOLOGICAL SIMULATIONS: RELIC PROPERTIES AND SCALING RELATIONSHIPS

    International Nuclear Information System (INIS)

    Skillman, Samuel W.; Hallman, Eric J.; Burns, Jack O.; Smith, Britton D.; O'Shea, Brian W.; Turk, Matthew J.

    2011-01-01

    Cosmological shocks are a critical part of large-scale structure formation, and are responsible for heating the intracluster medium in galaxy clusters. In addition, they are capable of accelerating non-thermal electrons and protons. In this work, we focus on the acceleration of electrons at shock fronts, which is thought to be responsible for radio relics-extended radio features in the vicinity of merging galaxy clusters. By combining high-resolution adaptive mesh refinement/N-body cosmological simulations with an accurate shock-finding algorithm and a model for electron acceleration, we calculate the expected synchrotron emission resulting from cosmological structure formation. We produce synthetic radio maps of a large sample of galaxy clusters and present luminosity functions and scaling relationships. With upcoming long-wavelength radio telescopes, we expect to see an abundance of radio emission associated with merger shocks in the intracluster medium. By producing observationally motivated statistics, we provide predictions that can be compared with observations to further improve our understanding of magnetic fields and electron shock acceleration.

  7. 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

  8. 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

  9. 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.

  10. Knowledge management in international mergers

    NARCIS (Netherlands)

    Grotenhuis, F.D.J.; Weggeman, M.C.D.P.

    2002-01-01

    This paper discusses the need for knowledge management in mergers and acquisitions. In mergers and acquisitions two cultures are combined, and also two systems of knowledge and insights are integrated. In order to develop and sustain competitive advantages for the knowledge-intensive firm, strategic

  11. Indexing mergers and acquisitions

    OpenAIRE

    Gang, Jianhua; Guo, Jie (Michael); Hu, Nan; Li, Xi

    2017-01-01

    We measure the efficiency of mergers and acquisitions by putting forward an index (the ‘M&A Index’) based on stochastic frontier analysis. The M&A Index is calculated for each takeover deal and is standardized between 0 and 1. An acquisition with a higher index encompasses higher efficiency. We find that takeover bids with higher M&A Indices are more likely to succeed. Moreover, the M&A Index shows a strong and positive relation with the acquirers’ post-acquisition stock perfo...

  12. 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.

  13. The formation of secondary stellar generations in massive young star clusters from rapidly cooling shocked stellar winds

    Czech Academy of Sciences Publication Activity Database

    Wünsch, Richard; Palouš, Jan; Tenorio-Tagle, G.; Ehlerová, Soňa

    2017-01-01

    Roč. 835, č. 1 (2017), 60/1-60/15 ISSN 0004-637X R&D Projects: GA ČR GA15-06012S Grant - others:Ga MŠk(CZ) LM2015070 Institutional support: RVO:67985815 Keywords : galaxies * ISM * star clusters Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 5.533, year: 2016

  14. 7 CFR 3575.89 - Mergers.

    Science.gov (United States)

    2010-01-01

    ... merged borrower. Mergers may be approved when: (1) The merger is in the best interest of the Government.... (b) Distinguishing mergers from transfers and assumptions. Mergers occur when one entity combines with another entity in such a way that the first entity ceases to exist as a separate entity while the...

  15. 7 CFR 1779.89 - Mergers.

    Science.gov (United States)

    2010-01-01

    ... of the merged borrower. Mergers may be approved when: (1) The merger is in the best interest of the... borrower. (b) Distinguishing mergers from transfers and assumptions. Mergers occur when one entity combines with another entity in such a way that the first entity ceases to exist as a separate entity while the...

  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. Justice Department Airline Merger Policy

    Science.gov (United States)

    Farmer, D. A.

    1972-01-01

    Justice Department airline merger policy is developed within the context of the Federal Aviation Act, in which there is an unusually explicit reliance on competition as a means of fulfilling statutory goals. The economics of the airline industry appear to indicate that low concentration and vigorous competition are particularly viable and desirable. Several factors, including existing regulatory policy, create incentives for airlines to merge whether or not an individual merger promotes or conflicts with the public interest. Specific benefits to the public should be identified and shown to clearly outweight the detriments, including adverse competitive impact, in order for airline mergers to be approved.

  19. Superdiffusion of relativistic electrons at supernova remnant shocks

    Science.gov (United States)

    Perri, Silvia

    2018-01-01

    Anomalous transport has been observed in various systems as nonlinear systems, numerical simulations of plasma turbulence, in laboratory plasmas, and recently in the propagation of energetic particles in the interplanetary space. Thanks to in situ observations it has been possible to deduce transport properties directly from spacecraft data. This technique has further found applicability to remote observations of relativistic electrons accelerated at supernova remnants (SNRs) shocks, pointing out that far upstream of the blast waves, the x-ray synchrotron emission, as captured by the Chandra spacecraft, is consistent with models of superdiffusive transport (i.e., transport faster than normal diffusive). Here we present and summarize evidences of superdiffusion both in the interplanetary space and upstream of SNRs shock fronts, in particular by analyzing, for the first time in the framework of superdiffusion, the transport properties of electrons accelerated at the young G1.9+0.3 SNR. We also briefly describe how this new model can be used to interpret radio emissions from electrons accelerated at shocks forming during galaxy cluster mergers.

  20. THE UNREASONABLE WEAKNESS OF R -PROCESS COSMIC RAYS IN THE NEUTRON-STAR-MERGER NUCLEOSYNTHESIS SCENARIO

    Energy Technology Data Exchange (ETDEWEB)

    Kyutoku, Koutarou [Interdisciplinary Theoretical Science (iTHES) Research Group, RIKEN, Wako, Saitama 351-0198 (Japan); Ioka, Kunihito, E-mail: koutarou.kyutoku@riken.jp [Center for Gravitational Physics, Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto, 606-8502 (Japan)

    2016-08-10

    We reach the robust conclusion that, by combining the observed cosmic rays of r -process elements with the fact that the velocity of the neutron-star-merger ejecta is much higher than that of the supernova ejecta, either (1) the reverse shock in the neutron-star-merger ejecta is a very inefficient accelerator that converts less than 0.003% of the ejecta kinetic energy to the cosmic-ray energy or (2) the neutron star merger is not the origin of the Galactic r -process elements. We also find that the acceleration efficiency should be less than 0.1% for the reverse shock of the supernova ejecta with observed cosmic rays lighter than the iron.

  1. 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.

  2. THERMODYNAMICS OF THE COMA CLUSTER OUTSKIRTS

    International Nuclear Information System (INIS)

    Simionescu, A.; Werner, N.; Urban, O.; Allen, S. W.; Fabian, A. C.; Sanders, J. S.; Walker, S. A.; Mantz, A.; Matsushita, K.; Sasaki, T.; Sato, T.; Nulsen, P. E. J.; Takei, Y.

    2013-01-01

    We present results from a large mosaic of Suzaku observations of the Coma Cluster, the nearest and X-ray brightest hot (∼8 keV), dynamically active, non-cool core system, focusing on the thermodynamic properties of the intracluster medium on large scales. For azimuths not aligned with an infalling subcluster toward the southwest, our measured temperature and X-ray brightness profiles exhibit broadly consistent radial trends, with the temperature decreasing from about 8.5 keV at the cluster center to about 2 keV at a radius of 2 Mpc, which is the edge of our detection limit. The southwest merger significantly boosts the surface brightness, allowing us to detect X-ray emission out to ∼2.2 Mpc along this direction. Apart from the southwestern infalling subcluster, the surface brightness profiles show multiple edges around radii of 30-40 arcmin. The azimuthally averaged temperature profile, as well as the deprojected density and pressure profiles, all show a sharp drop consistent with an outwardly-propagating shock front located at 40 arcmin, corresponding to the outermost edge of the giant radio halo observed at 352 MHz with the Westerbork Synthesis Radio Telescope. The shock front may be powering this radio emission. A clear entropy excess inside of r 500 reflects the violent merging events linked with these morphological features. Beyond r 500 , the entropy profiles of the Coma Cluster along the relatively relaxed directions are consistent with the power-law behavior expected from simple models of gravitational large-scale structure formation. The pressure is also in agreement at these radii with the expected values measured from Sunyaev-Zel'dovich data from the Planck satellite. However, due to the large uncertainties associated with the Coma Cluster measurements, we cannot yet exclude an entropy flattening in this system consistent with that seen in more relaxed cool core clusters

  3. WHERE DO WET, DRY, AND MIXED GALAXY MERGERS OCCUR? A STUDY OF THE ENVIRONMENTS OF CLOSE GALAXY PAIRS IN THE DEEP2 GALAXY REDSHIFT SURVEY

    International Nuclear Information System (INIS)

    Lin, Lihwai; Cooper, Michael C.; Willmer, Christopher N. A.; Jian, Hung-Yu; Chiueh, Tzihong; Koo, David C.; Guhathakurta, Puragra; Patton, David R.; Yan, Renbin; Coil, Alison L.; Croton, Darren J.; Gerke, Brian F.; Lotz, Jennifer; Newman, Jeffrey A.

    2010-01-01

    We study the environments of wet, dry, and mixed galaxy mergers at 0.75 c ) is observed to increase with overdensity, using N-body simulations, we find that the fraction of pairs that will eventually merge decreases with the local density, predominantly because interlopers are more common in dense environments. After taking into account the merger probability of pairs as a function of local density, we find only marginal environment dependence of the galaxy merger rate for wet mergers. On the other hand, the dry and mixed merger rates increase rapidly with local density due to the increased population of red galaxies in dense environments, implying that the dry and mixed mergers are most effective in overdense regions. We also find that the environment distribution of K+A galaxies is similar to that of wet mergers alone and of wet+mixed mergers, suggesting a possible connection between K+A galaxies and wet and/or wet+mixed mergers. Based on our results, we therefore expect that the properties, including structures and masses, of red-sequence galaxies should be different between those in underdense regions and those in overdense regions since the dry mergers are significantly more important in dense environments. We conclude that, as early as z ∼ 1, high-density regions are the preferred environment in which dry mergers occur, and that present-day red-sequence galaxies in overdense environments have, on average, undergone 1.2 ± 0.3 dry mergers since this time, accounting for (38 ± 10)% of their mass accretion in the last 8 billion years. The main uncertainty in this finding is the conversion from the pair fraction to the galaxy merger rate, which is possibly as large as a factor of 2. Our findings suggest that dry mergers are crucial in the mass assembly of massive red galaxies in dense environments, such as brightest cluster galaxies in galaxy groups and clusters.

  4. Brightest Cluster Galaxies in REXCESS Clusters

    Science.gov (United States)

    Haarsma, Deborah B.; Leisman, L.; Bruch, S.; Donahue, M.

    2009-01-01

    Most galaxy clusters contain a Brightest Cluster Galaxy (BCG) which is larger than the other cluster ellipticals and has a more extended profile. In the hierarchical model, the BCG forms through many galaxy mergers in the crowded center of the cluster, and thus its properties give insight into the assembly of the cluster as a whole. In this project, we are working with the Representative XMM-Newton Cluster Structure Survey (REXCESS) team (Boehringer et al 2007) to study BCGs in 33 X-ray luminous galaxy clusters, 0.055 < z < 0.183. We are imaging the BCGs in R band at the Southern Observatory for Astrophysical Research (SOAR) in Chile. In this poster, we discuss our methods and give preliminary measurements of the BCG magnitudes, morphology, and stellar mass. We compare these BCG properties with the properties of their host clusters, particularly of the X-ray emitting gas.

  5. 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)

  6. 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.

  7. The Merger Paradox and R&D

    OpenAIRE

    MIYAGIWA, Kaz; WAN, Jiangyun(Yunyun)

    2015-01-01

    The merger paradox is revisited in the presence of cost-reducing R&D in Cournot oligopoly. Two cases are found, in which merger is profitable without satisfying the 80-percent threshold requirement of Salant et al (1983).

  8. 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.

  9. Mergers, Strategic Investments and Antitrust Policy

    OpenAIRE

    Deneffe, Daniel; Wakker, Peter

    1996-01-01

    textabstractEstablished firms can diversify into new markets in two distinct modes: through internal development or through conglomerate merger. Building on a dynamic three-stage bargaining model with variable threats, this paper shows that a lenient antitrust position toward horizontal mergers can induce established firms that would otherwise not have entered to enter via conglomerate merger. The vigor of antitrust enforcement toward horizontal mergers also affects the conglomerate acquisiti...

  10. The economic impact of merger control legislation

    OpenAIRE

    Carletti, Elena; Hartmann, Philipp; Onega, Steven

    2007-01-01

    We construct a unique dataset of legislative reforms in merger control legislation that occurred in nineteen industrial countries in the period 1987-2004, and investigate the economic impact of these changes on stock prices. In line with the hypothesis that merger control should challenge anticompetitive mergers and thus limit future monopolistic profits, we find that the strengthening of merger control decreases the stock prices of non-financial firms. In contrast, we find that bank stock pr...

  11. 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.

  12. 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)

  13. Assessment of Innovation Effects of Mergers

    OpenAIRE

    Kern, Benjamin René

    2015-01-01

    Summary of Doctoral Dissertation Assessment of Innovation Effects of Mergers The adequate consideration of innovation effects of mergers in merger review was, and still is, one of the most controversially discussed issues between antitrust scholars. In this connection the question has been raised whether the traditional categories in competition law are sufficiently suitable for dealing with innovation aspects or whether new ...

  14. 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.

  15. 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...

  16. 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…

  17. 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

  18. A relationship of polycyclic aromatic hydrocarbon features with galaxy merger in star-forming galaxies at z < 0.2

    Science.gov (United States)

    Murata, Katsuhiro L.; Yamada, Rika; Oyabu, Shinki; Kaneda, Hidehiro; Ishihara, Daisuke; Yamagishi, Mitsuyoshi; Kokusho, Takuma; Takeuchi, Tsutomu T.

    2017-11-01

    Using the AKARI, Wide-field Infrared Survey Explorer (WISE), Infrared Astronomical Satellite (IRAS), Sloan Digital Sky Survey (SDSS) and Hubble Space Telescope (HST) data, we investigated the relation of polycyclic aromatic hydrocarbon (PAH) mass (MPAH), very small grain mass (MVSG), big grain mass (MBG) and stellar mass (Mstar) with galaxy merger for 55 star-forming galaxies at redshift z 0.1, we divided the galaxies into merger galaxies and non-merger galaxies with the morphological parameter asymmetry A, and quantified merging stages of galaxies based on the morphological indicators, the second-order momentum of the brightest 20 per cent region M20 and the Gini coefficient. We find that MPAH/MBG of merger galaxies tend to be lower than that of non-merger galaxies and there are no systematic differences of MVSG/MBG and MBG/Mstar between merger galaxies and non-merger galaxies. We find that galaxies with very low MPAH/MBG seem to be merger galaxies at late stages. These results suggest that PAHs are partly destroyed at late stages of merging processes. Furthermore, we investigated MPAH/MBG variations in radiation field intensity strength G0 and the emission line ratio of [O I] λ 6300/Hα that is a shock tracer for merger galaxies and find that MPAH/MBG decreases with increasing both G0 and [O I]/Hα. PAH destruction is likely to be caused by two processes: strong radiation fields and large-scale shocks during merging processes of galaxies.

  19. 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...... 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...

  20. Mergers and Acquisitions in India

    OpenAIRE

    Agarwal, Ankita

    2009-01-01

    From the past few decades, Mergers and Acquisitions (M&A) have dominated the environment in which the companies operate. Whenever there is an announcement about a merger, there is an excitement and expectation among the shareholders. This expectation may or may not convert into an abnormal return. It is useful to have some kind of research activity on the performance of M&A, as both bidders and target firms will gain from it. The results have revealed that on average, the returns to the targ...

  1. 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.

  2. 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

  3. More Mergers,More Acquisitions

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    China aims to maintain sound development of the national economy through M&As Anew round of corporate mergers and acquisitions (M&As) is on the way. On September 6, the State Council announced that it would require companies in the automobile, iron and steel, cement, machinery manufacturing, electro- lytic aluminum and rare earth industries to accelerate M&As.

  4. More Mergers,More Acquisitions

    Institute of Scientific and Technical Information of China (English)

    LAN XINZHEN

    2010-01-01

    @@ A new round of corporate mergers and acquisitions(M&As)is on the way.On September 6,the State Council announced that it would require companies in the automobile,iron and steel,cement,machinery manufacturing,electrolytic aluminum and rare earth industries to accelerate M&As.

  5. Creating lenticular galaxies with mergers

    NARCIS (Netherlands)

    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

    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

  6. Jellyfish: Observational Properties of Extreme Ram-Pressure Stripping Events in Massive Galaxy Clusters

    Science.gov (United States)

    Conor, McPartland; Ebeling, Harald; Roediger, Elke

    2015-08-01

    We investigate the physical origin and observational signatures of extreme ram-pressure stripping (RPS) in 63 massive galaxy clusters at z=0.3-0.7, based on data in the F606W passband obtained with the Advanced Camera for Surveys aboard the Hubble Space Telescope. Using a training set of a dozen ``jellyfish" galaxies identified earlier in the same imaging data, we define quantitative morphological criteria to select candidate galaxies which are similar to known cases of RPS. Considering a sample of 16 ``jellyfish" galaxies (10 of which we present for the first time), we visually derive estimates of the projected direction of motion based on dynamical features such as apparent compression shocks and debris trails. Our findings suggest that the observed events occur primarily at large distances from the cluster core and involve infall trajectories featuring high impact parameters. Simple models of cluster growth show that such trajectories are consistent with two scenarios: 1) galaxy infall along filaments; and 2) infall at high velocities (≥1000 km/s) characteristic of cluster mergers. The observed distribution of events is best described by timescales of ˜few Myr in agreement with recent numerical simulations of RPS. The broader areal coverage of the Hubble Frontier Fields should provide an even larger sample of RPS events to determine the relative contributions of infall and cluster mergers. Prompted by the discovery of several jellyfish galaxies whose brightness in the F606W passband rivals or exceeds that of the respective brightest cluster galaxy, we attempt to constrain the luminosity function of galaxies undergoing RPS. The observed significant excess at the bright end compared to the luminosity functions of blue cluster members strongly suggests enhanced star formation, thus challenging theoretical and numerical studies according to which RPS merely displaces existing star-forming regions. In-depth studies of individual objects will help test our

  7. Cluster-cluster clustering

    International Nuclear Information System (INIS)

    Barnes, J.; Dekel, A.; Efstathiou, G.; Frenk, C.S.; Yale Univ., New Haven, CT; California Univ., Santa Barbara; Cambridge Univ., England; Sussex Univ., Brighton, England)

    1985-01-01

    The cluster correlation function xi sub c(r) is compared with the particle correlation function, xi(r) in cosmological N-body simulations with a wide range of initial conditions. The experiments include scale-free initial conditions, pancake models with a coherence length in the initial density field, and hybrid models. Three N-body techniques and two cluster-finding algorithms are used. In scale-free models with white noise initial conditions, xi sub c and xi are essentially identical. In scale-free models with more power on large scales, it is found that the amplitude of xi sub c increases with cluster richness; in this case the clusters give a biased estimate of the particle correlations. In the pancake and hybrid models (with n = 0 or 1), xi sub c is steeper than xi, but the cluster correlation length exceeds that of the points by less than a factor of 2, independent of cluster richness. Thus the high amplitude of xi sub c found in studies of rich clusters of galaxies is inconsistent with white noise and pancake models and may indicate a primordial fluctuation spectrum with substantial power on large scales. 30 references

  8. Gas clump formation via thermal instability in high-redshift dwarf galaxy mergers

    Science.gov (United States)

    Arata, Shohei; Yajima, Hidenobu; Nagamine, Kentaro

    2018-04-01

    Star formation in high-redshift dwarf galaxies is a key to understand early galaxy evolution in the early Universe. Using the three-dimensional hydrodynamics code GIZMO, we study the formation mechanism of cold, high-density gas clouds in interacting dwarf galaxies with halo masses of ˜3 × 107 M⊙, which are likely to be the formation sites of early star clusters. Our simulations can resolve both the structure of interstellar medium on small scales of ≲ 0.1 pc and the galactic disc simultaneously. We find that the cold gas clouds form in the post-shock region via thermal instability due to metal-line cooling, when the cooling time is shorter than the galactic dynamical time. The mass function of cold clouds shows almost a power-law initially with an upper limit of thermally unstable scale. We find that some clouds merge into more massive ones with ≳104 M⊙ within ˜ 2 Myr. Only the massive cold clouds with ≳ 103 M⊙ can keep collapsing due to gravitational instability, resulting in the formation of star clusters. We find that the clump formation is more efficient in the prograde-prograde merger than the prograde-retrograde case due to the difference in the degree of shear flow. In addition, we investigate the dependence of cloud mass function on metallicity and H2 abundance, and show that the cases with low metallicities (≲10-2 Z⊙) or high H2 abundance (≳10-3) cannot form massive cold clouds with ≳103 M⊙.

  9. The relative role of galaxy mergers and cosmic flows in feeding black holes

    International Nuclear Information System (INIS)

    Bellovary, Jillian; Brooks, Alyson; Volonteri, Marta; Governato, Fabio; Quinn, Thomas; Wadsley, James

    2013-01-01

    Using a set of zoomed-in cosmological simulations of high-redshift progenitors of massive galaxies, we isolate and trace the history of gas that is accreted by central supermassive black holes. We determine the origins of the accreted gas, in terms of whether it entered the galaxy during a merger event or was smoothly accreted. Furthermore, we designate whether the smoothly accreted gas is accreted via a cold flow or is shocked upon entry into the halo. For moderate-mass (10 6 -10 7 M ☉ ) black holes at z ∼ 4, there is a preference to accrete cold flow gas as opposed to gas of shocked or merger origin. However, this result is a consequence of the fact that the entire galaxy has a higher fraction of gas from cold flows. In general, each black hole tends to accrete the same fractions of smooth- and merger-accreted gas as is contained in its host galaxy, suggesting that once gas enters a halo it becomes well-mixed, and its origins are erased. We find that the angular momentum of the gas upon halo entry is a more important factor; black holes preferentially accrete gas that had low angular momentum when it entered the galaxy, regardless of whether it was accreted smoothly or through mergers.

  10. 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.

  11. Mergers as an Omega estimator

    International Nuclear Information System (INIS)

    Carlberg, R.G.

    1990-01-01

    The redshift dependence of the fraction of galaxies which are merging or strongly interacting is a steep function of Omega and depends on the ratio of the cutoff velocity for interactions to the pairwise velocity dispersion. For typical galaxies the merger rate is shown to vary as (1 + z)exp m, where m is about 4.51 (Omega)exp 0.42, for Omega near 1 and a CDM-like cosmology. The index m has a relatively weak dependence on the maximum merger velocity, the mass of the galaxy, and the background cosmology, for small variations around a cosmology with a low redshift, z of about 2, of galaxy formation. Estimates of m from optical and IRAS galaxies have found that m is about 3-4, but with very large uncertainties. If quasar evolution follows the evolution of galaxy merging and m for quasars is greater than 4, then Omega is greater than 0.8. 21 refs

  12. Mergers, managerial incentives, and efficiencies

    OpenAIRE

    Jovanovic, Dragan

    2014-01-01

    We analyze the effects of synergies from horizontal mergers in a Cournot oligopoly where principals provide their agents with incentives to cut marginal costs prior to choosing output. We stress that synergies come at a cost which possibly leads to a countervailing incentive effect: The merged firm's principal may be induced to stifle managerial incentives in order to reduce her agency costs. Whenever this incentive effect dominates the well-known direct synergy effect, synergies actually red...

  13. Pre and Post Merger Valuation- A Study of Tata Corus Merger Deal

    OpenAIRE

    Sumeet Gupta

    2009-01-01

    Indian Economy being characterized as Global Economy leading to inorganic growth through Mergers, Acquisitions, Takeovers and Joint Ventures. Mergers would affect the company’s inflow and outflow of various variables like sales, expenses and cash position etc. It becomes imperative to evaluate the pre merger and post merger conditions of the firms so that successful deal can be carried out. The deal would also affect the shareholders wealth. The prediction of future forecasted sales and other...

  14. 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

  15. National Versus International Mergers and Trade Liberalization

    OpenAIRE

    Yildiz, Halis Murat

    2003-01-01

    This paper uses an endogenous merger formation approach in a concentrated international oligopoly to examine the effects of trade liberalization on the nature of merger incentives (national vs. international). The effects of unilateral trade liberalization on a country’s industry structure are found to be depending on the other country’s trade policy regime. If the other country practices free trade, unilateral liberalization by a country yields international mergers whereas if it practices a...

  16. 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

  17. LEGAL CONSEQUENCES OF MERGERS AND ACQUISITIONS

    Directory of Open Access Journals (Sweden)

    Amelia-Raluca ONIŞOR

    2016-05-01

    Full Text Available The research analyses the legal effects of mergers and acquisitions from the Romanian Company Law perspective, underlining certain general principles, the procedure of annulment of such a legal transformation of companies and the protection of the employees of companies participating in the merger according to the Law no. 67/2006. These consequences of mergers and acquisions are to be seen in the broader light of the most important purpose of this legal instrument, maximizing financial and organizational efficiencies, thus legal certainty is a desirable goal to be assumed by any merger regulation.

  18. 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

  19. Impact of mergers and acquisitions on the efficiency of banking in Colombia

    Directory of Open Access Journals (Sweden)

    Miguel Sarmiento

    2018-04-01

    Full Text Available This article evaluates the efficiency of Colombian banking using nonparametric border models. The results indicate that there has been a gradual increase in efficiency and that the global financial crisis of 2008 affected this trend. Since 2009 there has been a rapid recovery of efficiency measures, except for cost efficiency. This suggests that, in the face of external shocks, the adjustment costs of banks are greater. Mergers and acquisitions contribute to the increase in banking efficiency.

  20. Globular Clusters - Guides to Galaxies

    CERN Document Server

    Richtler, Tom; Joint ESO-FONDAP Workshop on Globular Clusters

    2009-01-01

    The principal question of whether and how globular clusters can contribute to a better understanding of galaxy formation and evolution is perhaps the main driving force behind the overall endeavour of studying globular cluster systems. Naturally, this splits up into many individual problems. The objective of the Joint ESO-FONDAP Workshop on Globular Clusters - Guides to Galaxies was to bring together researchers, both observational and theoretical, to present and discuss the most recent results. Topics covered in these proceedings are: internal dynamics of globular clusters and interaction with host galaxies (tidal tails, evolution of cluster masses), accretion of globular clusters, detailed descriptions of nearby cluster systems, ultracompact dwarfs, formations of massive clusters in mergers and elsewhere, the ACS Virgo survey, galaxy formation and globular clusters, dynamics and kinematics of globular cluster systems and dark matter-related problems. With its wide coverage of the topic, this book constitute...

  1. UNDERSTANDING BLACK HOLE MASS ASSEMBLY VIA ACCRETION AND MERGERS AT LATE TIMES IN COSMOLOGICAL SIMULATIONS

    International Nuclear Information System (INIS)

    Kulier, Andrea; Ostriker, Jeremiah P.; Lackner, Claire N.; Cen, Renyue; Natarajan, Priyamvada

    2015-01-01

    Accretion is thought to primarily contribute to the mass accumulation history of supermassive black holes (SMBHs) throughout cosmic time. While this may be true at high redshifts, at lower redshifts and for the most massive black holes (BHs) mergers themselves might add significantly to the mass budget. We explore this in two disparate environments—a massive cluster and a void region. We evolve SMBHs from 4 > z > 0 using merger trees derived from hydrodynamical cosmological simulations of these two regions, scaled to the observed value of the stellar mass fraction to account for overcooling. Mass gains from gas accretion proportional to bulge growth and BH-BH mergers are tracked, as are BHs that remain ''orbiting'' due to insufficient dynamical friction in a merger remnant, as well as those that are ejected due to gravitational recoil. We find that gas accretion remains the dominant source of mass accumulation in almost all SMBHs; mergers contribute 2.5% ± 0.1% for all SMBHs in the cluster and 1.0% ± 0.1% in the void since z = 4. However, mergers are significant for massive SMBHs. The fraction of mass accumulated from mergers for central BHs generally increases for larger values of the host bulge mass: in the void, the fraction is 2% at M *, bul = 10 10 M ☉ , increasing to 4% at M *, bul ≳ 10 11 M ☉ , and in the cluster it is 4% at M *, bul = 10 10 M ☉ and 23% at 10 12 M ☉ . We also find that the total mass in orbiting SMBHs is negligible in the void, but significant in the cluster, in which a potentially detectable 40% of SMBHs and ≈8% of the total SMBH mass (where the total includes central, orbiting, and ejected SMBHs) is found orbiting at z = 0. The existence of orbiting and ejected SMBHs requires modification of the Soltan argument. We estimate this correction to the integrated accreted mass density of SMBHs to be in the range 6%-21%, with a mean value of 11% ± 3%. Quantifying the growth due to mergers at these late times

  2. 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...

  3. Mergers, Strategic Investments and Antitrust Policy

    NARCIS (Netherlands)

    D. Deneffe (Daniel); P.P. Wakker (Peter)

    1996-01-01

    textabstractEstablished firms can diversify into new markets in two distinct modes: through internal development or through conglomerate merger. Building on a dynamic three-stage bargaining model with variable threats, this paper shows that a lenient antitrust position toward horizontal mergers can

  4. On Mergers in Consumer Search Markets

    NARCIS (Netherlands)

    M.C.W. Janssen (Maarten); J.L. Moraga-Gonzalez (José Luis)

    2007-01-01

    textabstractWe study mergers in a market where N firms sell a homogeneous good and consumers search sequentially to discover prices. The main motivation for such an analysis is that mergers generally affect market prices and thereby, in a search environment, the search behavior of consumers.

  5. 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.

  6. The University of Johannesburg merger: Academics experience of the pre-merger phase

    Directory of Open Access Journals (Sweden)

    G. A. Goldman

    2006-12-01

    Full Text Available Purpose of the study: The aim of this study is to gain an understanding of the merger experiences academic staff were exposed to during the pre-merger phase of the University of Johannesburg merger. Of particular interest is how these experiences translate into acceptance of the merger amongst academic staff. The study was borne out of the transformation of the higher education landscape in South Africa, which is typified by a spate of mergers between higher education institutions. Design/methodology/approach: As the purpose of the study was, inter alia, aimed at understanding the merger experiences of academic staff, the study was conducted according to an interpretive research paradigm, where interpretation of data calls for an insider perspective, in order to "see things through their eyes" as it were. In this regard, a qualitative methodology was employed. Findings: Findings indicate that academic staff members at the University of Johannesburg experience two distinct mental states during the pre-merger phase. Following the announcement of the merger, reaction and experience tend to be emotionally driven but as merging efforts become more concrete over time, this emotive state is replaced by a more rationally driven disposition. Implications: The distinction between an emotive and rational demeanour during the pre-merger phase of a merger affords managers and leaders the opportunity to plan change interventions in such a way that irrational, emotive responses and behaviour do not hamper progress in terms of merger implementation. In a more general sense, this study highlights the process of transition individual staff members pass through as they have to come to terms with the changes brought about by a merger. Originality / Value: The majority of merger literature, as well as change literature, focuses on the organisational context of change during a merger. Limited literature exists on the personal effects of a change event such as a

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

    Indian Academy of Sciences (India)

    scenario still remain poorly understood. ... to test models with future observations. ... A popular scenario for the origin of radio halos assumes that relativis- ..... based on particle acceleration by merger-driven turbulence in galaxy clusters shows.

  8. Essays on mergers and acquisitions

    OpenAIRE

    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 importance of corporate governance when conducting deals in unknown territories; whilst Chapter 3 and 4 conduct research on companies’ decision to tap capital markets and their subsequent M&A acti...

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. VLA Discovers Giant Rings Around Galaxy Cluster

    Science.gov (United States)

    2006-11-01

    , thanks to its very high sensitivity and unique capability to make images of exceedingly faint radio-emitting objects," Bagchi said. The scientists also used the European Space Agency's XMM-Newton, the world's most sensitive X-ray observatory, to observe this extraordinary cluster of galaxies. "The advanced technical capabilities of the orbiting XMM-Newton revealed a spectacular bullet-like region of X-ray emission in this dynamically active cluster," said Gastao B. Lima Neto, of the Institute of Astronomy and Geophysics in Sao Paulo, Brazil, a co-author of the research paper. "Our X-ray observations strongly suggest a recent collision and merger of two or more smaller clusters. Such a phenomenon is among the most energetic events in the Universe after the Big Bang. Only a tiny fraction of the total energy of this collision, if transferred to electrons, would cause them to emit the radio waves observed by the VLA. However, the main question is, how this is achieved," said Florence Durret of the Astrophysical Institute of Paris, France, another of the researchers. The scientists calculated that the total energy of the colliding groups of galaxies would be enough to keep our Sun shining for more than 20 sextillion years (2 followed by 22 zeros)! "We think the shock waves that sped up these electrons came from the collision of a smaller group of galaxies with the main body of the larger cluster. When two such massive objects crash into each other at supersonic speed, gigantic ripple-like shock waves are created in the surrounding gas, which race out to the outer regions of the forming cluster at a speed of thousands of kilometers per second," Bagchi said. "You can imagine that each cluster is like a supersonic aircraft, moving faster than the speed of sound in the surrounding gas, and just as you hear a sonic boom when shock waves from an airplane pass by you, we believe that the situation in the Abell 3376 cluster is similar, with ringlike radio structures tracing out the

  15. 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)

  16. 7 CFR 1717.152 - Required documentation for all mergers.

    Science.gov (United States)

    2010-01-01

    ... mergers. In order for RUS to advance funds, send bills, and otherwise conduct business with a successor..., borrowers must submit: (1) A transmittal letter on corporate letterhead signed by the manager of each active... evidence the merger pursuant to applicable law. Examples include plan of merger, articles of merger...

  17. 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...

  18. 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

  19. Company Mergers and Acquisitions on the Edge of Unlawful Competition

    Directory of Open Access Journals (Sweden)

    Elena - Mădălina Rotaru

    2016-01-01

    Full Text Available In the field of economy, transactions represent one of the fastest means available for improvingany company’s commercial and strategic position in the market. The context of technologicaldevelopments in recent years and the trend of globalization have largely influenced work in thefields of goods and services. Currently, geographical factors are no longer an obstacle andcompanies can expand their production without being influenced by state frontiers. Internationalmergers and acquisitions are, most often, joined by a true "cultural shock" [1] and must comply withregulations on competition both nationally and internationally. Since the penalties imposed byauthorities in charge of competition regulations are substantial, both internationally andnationally, this means that, when making mergers, one should be very cautious.

  20. 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.

  1. 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.

  2. The E-MOSAICS project: simulating the formation and co-evolution of galaxies and their star cluster populations

    Science.gov (United States)

    Pfeffer, Joel; Kruijssen, J. M. Diederik; Crain, Robert A.; Bastian, Nate

    2018-04-01

    We introduce the MOdelling Star cluster population Assembly In Cosmological Simulations within EAGLE (E-MOSAICS) project. E-MOSAICS incorporates models describing the formation, evolution, and disruption of star clusters into the EAGLE galaxy formation simulations, enabling the examination of the co-evolution of star clusters and their host galaxies in a fully cosmological context. A fraction of the star formation rate of dense gas is assumed to yield a cluster population; this fraction and the population's initial properties are governed by the physical properties of the natal gas. The subsequent evolution and disruption of the entire cluster population are followed accounting for two-body relaxation, stellar evolution, and gravitational shocks induced by the local tidal field. This introductory paper presents a detailed description of the model and initial results from a suite of 10 simulations of ˜L⋆ galaxies with disc-like morphologies at z = 0. The simulations broadly reproduce key observed characteristics of young star clusters and globular clusters (GCs), without invoking separate formation mechanisms for each population. The simulated GCs are the surviving population of massive clusters formed at early epochs (z ≳ 1-2), when the characteristic pressures and surface densities of star-forming gas were significantly higher than observed in local galaxies. We examine the influence of the star formation and assembly histories of galaxies on their cluster populations, finding that (at similar present-day mass) earlier-forming galaxies foster a more massive and disruption-resilient cluster population, while galaxies with late mergers are capable of forming massive clusters even at late cosmic epochs. We find that the phenomenological treatment of interstellar gas in EAGLE precludes the accurate modelling of cluster disruption in low-density environments, but infer that simulations incorporating an explicitly modelled cold interstellar gas phase will overcome

  3. Shock absorber

    International Nuclear Information System (INIS)

    Nemeth, J.D.

    1981-01-01

    A shock absorber for the support of piping and components in a nuclear power plant is described. It combines a high degree of stiffness under sudden shocks, e.g. seismic disturbances, with the ability to allow for thermal expansion without resistance when so required. (JIW)

  4. Mergers and Product Quality: Evidence from the Airline Industry

    OpenAIRE

    Chen, Yongmin; Gayle, Philip

    2013-01-01

    Retrospective studies of horizontal mergers have focused on their price effects, leaving the important question of how mergers affect product quality largely unanswered. This paper empirically investigates this issue for two recent airline mergers: Delta/Northwest and Continental/United. Consistent with the theoretical premise that mergers improve coordination but diminish competitive pressure for quality provision, we find: (i) each merger is associated with a quality increase in markets whe...

  5. ROLE OF INTERNATIONAL MERGERS AND ACQUISITIONS IN CORPORATE INTEGRATION

    OpenAIRE

    Lucia P. BLĂJUȚ

    2015-01-01

    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 fo...

  6. 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

  7. When Worlds Collide: Chandra Observes Titanic Merger

    Science.gov (United States)

    2002-04-01

    NASA's Chandra X-ray Observatory has provided the best X-ray image yet of two Milky Way-like galaxies in the midst of a head-on collision. Since all galaxies - including our own - may have undergone mergers, this provides insight into how the universe came to look as it does today. Astronomers believe the mega-merger in the galaxy known as Arp 220 triggered the formation of huge numbers of new stars, sent shock waves rumbling through intergalactic space, and could possibly lead to the formation of a supermassive black hole in the center of the new conglomerate galaxy. The Chandra data also suggest that merger of these two galaxies began only 10 million years ago, a short time in astronomical terms. "The Chandra observations show that things really get messed up when two galaxies run into each other at full speed," said David Clements of the Imperial College, London, one of the team members involved in the study. "The event affects everything from the formation of massive black holes to the dispersal of heavy elements into the universe." Arp 220 is considered to be a prototype for understanding what conditions were like in the early universe, when massive galaxies and supermassive black holes were presumably formed by numerous galaxy collisions. At a relatively nearby distance of about 250 million light years, Arp 220 is the closest example of an "ultra-luminous" galaxy, one that gives off a trillion times as much radiation as our Sun. The Chandra image shows a bright central region at the waist of a glowing, hour-glass-shaped cloud of multimillion-degree gas. Rushing out of the galaxy at hundreds of thousands of miles per hour, the super-heated as forms a "superwind," thought to be due to explosive activity generated by the formation of hundreds of millions of new stars. Farther out, spanning a distance of 75,000 light years, are giant lobes of hot gas that could be galactic remnants flung into intergalactic space by the early impact of the collision. Whether the

  8. The Impact of Merger Status and Relative Representation on Identification with a Merger Group

    Directory of Open Access Journals (Sweden)

    Filip Boen

    2005-12-01

    Full Text Available This experiment tested to what extent identification with a new merger group is determined by the status of that merger group and by the relative representation of the pre-merger ingroup. One hundred university students were assigned to a team of 'inductive' thinkers, and were later merged with a team of 'deductive' thinkers to form a team of 'analyst' thinkers. The status of the merger group (low, high and the relative representation of the ingroup into the novel merger group (low, high were manipulated. Participants identified more with the merger group in the high than in the low status condition, and they identified more in the high than in the low representation condition. The predicted interaction between relative representation and merger status was not significant. However, relative representation did interact with participants' pre-merger identification: Pre- and post-merger identification were positively related when the ingroup was highly represented, but 'negatively' when the ingroup was lowly represented.

  9. 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

  10. Can this merger be saved?

    Science.gov (United States)

    Cliffe, S

    1999-01-01

    In this fictional case study, a merger that looked like a marriage made in heaven to those at corporate headquarters is feeling like an infernal union to those on the ground. The merger is between Synergon Capital, a U.S. financial-services behemoth, and Beauchamp, Becker & Company, a venerable British financial-services company with strong profits and an extraordinarily loyal client base of wealthy individuals. Beauchamp also boasts a strong group of senior managers led by Julian Mansfield, a highly cultured and beloved patriarch who personifies all that's good about the company. Synergon isn't accustomed to acquiring such companies. It usually encircles a poorly managed turnaround candidate and then, once the deal is done, drops a neutron bomb on it, leaving file cabinets and contracts but no people. Before acquiring Beauchamp, Synergon's macho men offered loud assurances that they would leave the tradition-bound company alone-provided, of course, that Beauchamp met the ambitious target numbers and showed sufficient enthusiasm for cross-selling Synergon's products to its wealthy clients. In charge of making the acquisition work is Nick Cunningham, one of Synergon's more thoughtful executives. Nick, who was against the deal from the start, is the face and voice of Synergon for Julian Mansfield. And Mansfield, in his restrained way, is angry at the constant flow of bureaucratic forms, at the rude demands for instant information, at the peremptory changes. He's even dropping broad hints at retirement. Nick has already been warned: if Mansfield goes, you go. Six commentators advise Nick on how to save his job by bringing peace and prosperity to the feuding couple.

  11. demystifying the shock of shocking

    African Journals Online (AJOL)

    (with a pulse), atrial fibrillation and atrial flutter. The energy dose in cardioversion is less (0.5. - 2 J/kg) than in defibrillation (2 - 4 J/kg). In cardioversion the shock is discharged synchronously with the native R wave of the patient. Without synchronisation,. VF can be induced if a shock is delivered during the refractory period ...

  12. Impact of star formation inhomogeneities on merger rates and interpretation of LIGO results

    International Nuclear Information System (INIS)

    O'Shaughnessy, R; Kopparapu, R K; Belczynski, K

    2012-01-01

    Within the next decade, ground based gravitational-wave detectors are in principle capable of determining the compact object merger rate per unit volume of the local universe to better than 20% with more than 30 detections. These measurements will constrain our models of stellar, binary and star cluster evolution in the nearby present-day and ancient universe. We argue that the stellar models are sensitive to heterogeneities (in age and metallicity at least) in such a way that the predicted merger rates are subject to an additional 30-50% systematic errors unless these heterogeneities are taken into account. Without adding new electromagnetic constraints on massive binary evolution or relying on more information from each merger (e.g., binary masses and spins), as few as the 5 merger detections could exhaust the information available in a naive comparison to merger rate predictions. As a concrete example immediately relevant to analysis of initial and enhanced LIGO results, we use a nearby-universe catalog to demonstrate that no one tracer of stellar content can be consistently used to constrain merger rates without introducing a systematic error of order O(30%) at 90% confidence (depending on the type of binary involved). For example, though binary black holes typically take many Gyr to merge, binary neutron stars often merge rapidly; different tracers of stellar content are required for these two types. More generally, we argue that theoretical binary evolution can depend sufficiently sensitively on star-forming conditions-even assuming no uncertainty in binary evolution model-that the distribution of star-forming conditions must be incorporated to reduce the systematic error in merger rate predictions below roughly 40%. We emphasize that the degree of sensitivity to star-forming conditions depends on the binary evolution model and on the amount of relevant variation in star-forming conditions. For example, if after further comparison with electromagnetic and

  13. BANK MERGERS AND ACQUISITIONS IN ROMANIA AFTER 1989

    Directory of Open Access Journals (Sweden)

    Copil Crina Angela

    2014-07-01

    Full Text Available In this paper I proposed to myself to analyse the main bank acquisitions and mergers from Romania after 1989, causes that led to their appearance, their effects on the bank system and their future perspectives on the Romanian bank market. In the context of adherence to the European bank system a solution for the Romanian banks is the concentration of the bank system by mergers and acquisitions or the increase of the bank capitals because in the period of transition the smaller banks are vulnerable, don’t dispose of an infrastructure that would alow them to offer financial services comparable to those offered by the great bank groups, can’t offer large credits and is addressing to the smaller and average enterprise, which in their turn are exposed to all the shocks that are felt in the economy. The strategies of concentration and consolidation applied by the banks in this period implemented by the transactions with mergers and acquisitions are essential because of their success depends the existence of the bank, the rank it will have on the market, the profit of the bank, the efficiency, the increase of the satisfaction degree of the clients and the increase of the shares’ value. The increase of the interest of the investor in mergers and acquisitions determined the creating of the great financial conglomerates that offer a large range of services, operates simultaneously on many markets and include beside the bank activity insurance, leasing subsidiaries, investment funds, pension funds, subsidiaries specialized in credit saving. In the last decades the Romanian bank financial system suffered significant changes, registering an ample consolidation process, the number of bank institutions decreased and in the context of the present financial crisis, the continuing of the process of restructuring is anticipated.The main reason for choosing this subject if the fact that in the evolution of the concentration the bank mergers and acquisitions

  14. Getting to Yes on a Merger.

    Science.gov (United States)

    Burkhardt, John

    1994-01-01

    The merger of the University of Detroit and Mercy College (Michigan) is chronicled from early conversations through preparation and decision making. Salient issues that had to be addressed, especially persistent conflicts, and lessons learned from the experience are noted. (MSE)

  15. 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.

  16. 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...

  17. 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...

  18. 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%

  19. Models for mergers in higher education

    African Journals Online (AJOL)

    Investing in creativity: Many happy returns. Education Leadership, ... A possible model for higher education mergers, based on such extrapolation, is ..... working styles should be carefully managed from the very beginning of the process.

  20. An Experimental Approach to Merger Evaluation

    OpenAIRE

    Christopher T. Conlon; Julie Holland Mortimer

    2013-01-01

    The 2010 Department of Justice and Federal Trade Commission Horizontal Merger Guidelines lay out a new standard for assessing proposed mergers in markets with differentiated products. This new standard is based on a measure of ``upward pricing pressure,'' (UPP) and the calculation of a ``gross upward pricing pressure index'' (GUPPI) in turn relies on a ``diversion ratio,'' which measures the fraction of consumers of one product that switch to another product when the price of the first produc...

  1. 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.

  2. 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

  3. Hypovolemic shock

    Science.gov (United States)

    ... the person's position unless they are in immediate danger. Do not give fluids by mouth. If person ... the patient with shock. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine . 25th ed. Philadelphia, PA: ...

  4. Organizational Culture and Multinacional Mergers: An Approach to the Case of Maersk Sealand

    Directory of Open Access Journals (Sweden)

    Alberto Vallejo Peña

    2016-01-01

    Full Text Available Within the broad tradition of studies on corporate mergers in the field of the sociology of organisations, the literature has paid special attention to the influence of the organisational cultures and the national origin of the companies involved in such processes. This study addresses the acquisition of Sealand (US company by Maersk (Danish company based on a case study of its terminal in Algeciras, Spain. The employees of both companies underwent a complex integration process in the early 2000s. An inquiry into the factors that caused the culture shock they experienced led to a review of their organisational and national cultures and their impact on the post-merger process. The results suggest that differences in organisation, management style and concept of industrial relations hindered the integration of both groups.

  5. Shock absorber

    International Nuclear Information System (INIS)

    Housman, J.J.

    1978-01-01

    A shock absorber is described for use in a hostile environment at the end of a blind passage for absorbing impact loads. The shock absorber includes at least one element which occupies the passage and which is comprised of a porous brittle material which is substantially non-degradable in the hostile environment. A void volume is provided in the element to enable the element to absorb a predetermined level of energy upon being crushed due to impact loading

  6. 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.

  7. Evolution of the major merger galaxy pair fraction at z < 1

    International Nuclear Information System (INIS)

    Keenan, R. C.; Hsieh, B. C.; Lin, L.; Chou, R. C. Y.; Huang, S.; Lin, J. H.; Chang, K. H.; Foucaud, S.; De Propris, R.

    2014-01-01

    We present a study of the largest available sample of near-infrared selected (i.e., stellar mass selected) dynamically close pairs of galaxies at low redshifts (z < 0.3). We combine this sample with new estimates of the major merger pair fraction for stellar mass selected galaxies at z < 0.8, from the Red Sequence Cluster Survey (RCS1). We construct our low-redshift K-band selected sample using photometry from the UKIRT Infrared Deep Sky Survey and the Two Micron All Sky Survey (2MASS) in the K band (∼2.2 μm). Combined with all available spectroscopy, our K-band selected sample contains ∼250, 000 galaxies and is >90% spectroscopically complete. The depth and large volume of this sample allow us to investigate the low-redshift pair fraction and merger rate of galaxies over a wide range in K-band luminosity. We find the major merger pair fraction to be flat at ∼2% as a function of K-band luminosity for galaxies in the range 10 8 -10 12 L ☉ , in contrast to recent results from studies in the local group that find a substantially higher low-mass pair fraction. This low-redshift major merger pair fraction is ∼40%-50% higher than previous estimates drawn from K-band samples, which were based on 2MASS photometry alone. Combining with the RCS1 sample, we find a much flatter evolution (m = 0.7 ± 0.1) in the relation f pair ∝(1 + z) m than indicated in many previous studies. These results indicate that a typical L ∼ L* galaxy has undergone ∼0.2-0.8 major mergers since z = 1 (depending on the assumptions of merger timescale and percentage of pairs that actually merge).

  8. Evolution of the major merger galaxy pair fraction at z < 1

    Energy Technology Data Exchange (ETDEWEB)

    Keenan, R. C.; Hsieh, B. C.; Lin, L.; Chou, R. C. Y.; Huang, S.; Lin, J. H.; Chang, K. H. [Academia Sinica Institute for Astronomy and Astrophysics, Taipei, Taiwan (China); Foucaud, S. [Shanghai Jiao Tong University, Shanghai (China); De Propris, R. [Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Turku (Finland)

    2014-11-10

    We present a study of the largest available sample of near-infrared selected (i.e., stellar mass selected) dynamically close pairs of galaxies at low redshifts (z < 0.3). We combine this sample with new estimates of the major merger pair fraction for stellar mass selected galaxies at z < 0.8, from the Red Sequence Cluster Survey (RCS1). We construct our low-redshift K-band selected sample using photometry from the UKIRT Infrared Deep Sky Survey and the Two Micron All Sky Survey (2MASS) in the K band (∼2.2 μm). Combined with all available spectroscopy, our K-band selected sample contains ∼250, 000 galaxies and is >90% spectroscopically complete. The depth and large volume of this sample allow us to investigate the low-redshift pair fraction and merger rate of galaxies over a wide range in K-band luminosity. We find the major merger pair fraction to be flat at ∼2% as a function of K-band luminosity for galaxies in the range 10{sup 8}-10{sup 12} L {sub ☉}, in contrast to recent results from studies in the local group that find a substantially higher low-mass pair fraction. This low-redshift major merger pair fraction is ∼40%-50% higher than previous estimates drawn from K-band samples, which were based on 2MASS photometry alone. Combining with the RCS1 sample, we find a much flatter evolution (m = 0.7 ± 0.1) in the relation f {sub pair}∝(1 + z) {sup m} than indicated in many previous studies. These results indicate that a typical L ∼ L* galaxy has undergone ∼0.2-0.8 major mergers since z = 1 (depending on the assumptions of merger timescale and percentage of pairs that actually merge).

  9. Probing the non-thermal emission in Abell 2146 and the Perseus cluster with the JVLA

    Science.gov (United States)

    Gendron-Marsolais, Marie-Lou; Hlavacek-Larrondo, Julie; van Weeren, Reinout; Clarke, Tracy; Intema, Huib; Russell, Helen; Edge, Alastair; Fabian, Andy; Olamaie, Malak; Rumsey, Clare; King, Lindsay; McNamara, Brian; Fecteau-Beaucage, David; Hogan, Michael; Mezcua, Mar; Taylor, Gregory; Blundell, Katherine; Sanders, Jeremy

    2018-01-01

    Jets created from accretion onto supermassive black holes release relativistic particles on large distances. These strongly affect the intracluster medium when located in the center of a brightest cluster galaxy. The hierarchical merging of subclusters and groups, from which cluster originate, also generates perturbations into the intracluster medium through shocks and turbulence, constituting a potential source of reacceleration for these particles. I will present deep multi-configuration low radio frequency observations from the Karl G. Jansky Very Large Array of two unique clusters, probing the non-thermal emission from the old particle population of the AGN outflows.Recently awarded of 550 hours of Chandra observations, Abell 2146 is one of the rare clusters undergoing a spectacular merger in the plane of the sky. Our recent deep multi-configuration JVLA 1.4 GHz observations have revealed the presence of a structure extending to 850 kpc in size, consisting of one component associated with the upstream shock and classified as a radio relic, and one associated with the subcluster core, consistent with a radio halo bounded by the bow shock. Theses structures have some of the lowest radio powers detected thus far in any cluster. The flux measurements of the halo, its morphology and measurements of the dynamical state of the cluster suggest that the halo was recently created (~ 0.3 Gyr after core passage). This makes A2146 extremely interesting to study, allowing us to probe the complete evolutionary stages of halos.I will also present results on 230-470 MHz JVLA observations of the Perseus cluster. Our observations of this nearby relaxed cool core cluster have revealed a multitude of new structures associated with the mini-halo, extending to hundreds of kpc in size. Its irregular morphology seems to be have been influenced both by the AGN activity and by the sloshing motion of the cluster’ gas. In addition, it has a filamentary structure similar to that seen in

  10. Search for Formation Criteria for Globular Cluster Systems

    Science.gov (United States)

    Nuritdinov, S. N.; Mirtadjieva, K. T.; Tadjibaev, I. U.

    2005-01-01

    Star cluster formation is a major mode of star formation in the extreme conditions of interacting galaxies and violent starbursts. By studying ages and metallicities of young metal-enhanced star clusters in mergers / merger remnants we can learn about the violent star formation history of these galaxies and eventually about galaxy formation and evolution. We will present a new set of evolutionary synthesis models of our GALEV code specially developed to account for the gaseous emission of presently forming star clusters and an advanced tool to compare large model grids with multi-color broad-band observations becoming presently available in large amounts. Such observations are an ecomonic way to determine the parameters of young star clusters as will be shown in the presentation. First results of newly-born clusters in mergers and starburst galaxies are presented and compared to the well-studied old globulars and interpreted in the framework of galaxy formation / evolution.

  11. Star formation and substructure in galaxy clusters

    International Nuclear Information System (INIS)

    Cohen, Seth A.; Hickox, Ryan C.; Wegner, Gary A.; Einasto, Maret; Vennik, Jaan

    2014-01-01

    We investigate the relationship between star formation (SF) and substructure in a sample of 107 nearby galaxy clusters using data from the Sloan Digital Sky Survey. Several past studies of individual galaxy clusters have suggested that cluster mergers enhance cluster SF, while others find no such relationship. The SF fraction in multi-component clusters (0.228 ± 0.007) is higher than that in single-component clusters (0.175 ± 0.016) for galaxies with M r 0.1 <−20.5. In both single- and multi-component clusters, the fraction of star-forming galaxies increases with clustercentric distance and decreases with local galaxy number density, and multi-component clusters show a higher SF fraction than single-component clusters at almost all clustercentric distances and local densities. Comparing the SF fraction in individual clusters to several statistical measures of substructure, we find weak, but in most cases significant at greater than 2σ, correlations between substructure and SF fraction. These results could indicate that cluster mergers may cause weak but significant SF enhancement in clusters, or unrelaxed clusters exhibit slightly stronger SF due to their less evolved states relative to relaxed clusters.

  12. 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…

  13. 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

  14. 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.

  15. 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

  16. The Formation and Evolution of Star Clusters in Interacting Galaxies

    Science.gov (United States)

    Maji, Moupiya; Zhu, Qirong; Li, Yuexing; Charlton, Jane; Hernquist, Lars; Knebe, Alexander

    2017-08-01

    Observations of globular clusters show that they have universal lognormal mass functions with a characteristic peak at ˜ 2× {10}5 {M}⊙ , but the origin of this peaked distribution is highly debated. Here we investigate the formation and evolution of star clusters (SCs) in interacting galaxies using high-resolution hydrodynamical simulations performed with two different codes in order to mitigate numerical artifacts. We find that massive SCs in the range of ˜ {10}5.5{--}{10}7.5 {M}⊙ form preferentially in the highly shocked regions produced by galaxy interactions. The nascent cluster-forming clouds have high gas pressures in the range of P/k˜ {10}8{--}{10}12 {{K}} {{cm}}-3, which is ˜ {10}4{--}{10}8 times higher than the typical pressure of the interstellar medium but consistent with recent observations of a pre-super-SC cloud in the Antennae Galaxies. Furthermore, these massive SCs have quasi-lognormal initial mass functions with a peak around ˜ {10}6 {M}⊙ . The number of clusters declines with time due to destructive processes, but the shape and the peak of the mass functions do not change significantly during the course of galaxy collisions. Our results suggest that gas-rich galaxy mergers may provide a favorable environment for the formation of massive SCs such as globular clusters, and that the lognormal mass functions and the unique peak may originate from the extreme high-pressure conditions of the birth clouds and may survive the dynamical evolution.

  17. 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.

  18. 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.

  19. 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.

  20. Twin radio relics in the nearby low-mass galaxy cluster Abell 168

    Science.gov (United States)

    Dwarakanath, K. S.; Parekh, V.; Kale, R.; George, L. T.

    2018-06-01

    We report the discovery of twin radio relics in the outskirts of the low-mass merging galaxy cluster Abell 168 (redshift=0.045). One of the relics is elongated with a linear extent ˜800 kpc and projected width of ˜80 kpc and is located ˜900 kpc towards the north of the cluster centre, oriented roughly perpendicular to the major axis of the X-ray emission. The second relic is ring-shaped with a size ˜220 kpc and is located near the inner edge of the elongated relic at a distance of ˜600 kpc from the cluster centre. These radio sources were imaged at 323 and 608 MHz with the Giant Meterwave Radio Telescope and at 1520 MHz with the Karl G. Jansky Very Large Array (VLA). The elongated relic was detected at all frequencies, with a radio power of 1.38 ± 0.14 × 1023 W Hz-1 at 1.4 GHz and a power law in the frequency range 70-1500 MHz (S ∝ να, α = -1.1 ± 0.04). This radio power is in good agreement with that expected from the known empirical relation between the radio powers of relics and host cluster masses. This is the lowest mass (M500 = 1.24 × 1014 M⊙) cluster in which relics due to merger shocks are detected. The ring-shaped relic has a steeper spectral index (α) of -1.74 ± 0.29 in the frequency range 100-600 MHz. We propose this relic to be an old plasma, revived due to adiabatic compression by the outgoing shock that produced the elongated relic.

  1. Modeling the formation of globular cluster systems in the Virgo cluster

    International Nuclear Information System (INIS)

    Li, Hui; Gnedin, Oleg Y.

    2014-01-01

    The mass distribution and chemical composition of globular cluster (GC) systems preserve fossil record of the early stages of galaxy formation. The observed distribution of GC colors within massive early-type galaxies in the ACS Virgo Cluster Survey (ACSVCS) reveals a multi-modal shape, which likely corresponds to a multi-modal metallicity distribution. We present a simple model for the formation and disruption of GCs that aims to match the ACSVCS data. This model tests the hypothesis that GCs are formed during major mergers of gas-rich galaxies and inherit the metallicity of their hosts. To trace merger events, we use halo merger trees extracted from a large cosmological N-body simulation. We select 20 halos in the mass range of 2 × 10 12 to 7 × 10 13 M ☉ and match them to 19 Virgo galaxies with K-band luminosity between 3 × 10 10 and 3 × 10 11 L ☉ . To set the [Fe/H] abundances, we use an empirical galaxy mass-metallicity relation. We find that a minimal merger ratio of 1:3 best matches the observed cluster metallicity distribution. A characteristic bimodal shape appears because metal-rich GCs are produced by late mergers between massive halos, while metal-poor GCs are produced by collective merger activities of less massive hosts at early times. The model outcome is robust to alternative prescriptions for cluster formation rate throughout cosmic time, but a gradual evolution of the mass-metallicity relation with redshift appears to be necessary to match the observed cluster metallicities. We also affirm the age-metallicity relation, predicted by an earlier model, in which metal-rich clusters are systematically several billion younger than their metal-poor counterparts.

  2. 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

  3. [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.

  4. PERLINDUNGAN HUKUM TERHADAP KEPENTINGAN PARA PIHAK DI DALAM MERGER BANK

    Directory of Open Access Journals (Sweden)

    Dani Amran Hakim

    2016-04-01

    Full Text Available The legal protection of interests of the parties in the merger of banks, which is formulated into the problem as follows a Is the legal basis for bank mergers? b How is the legal protection of the parties in a bank merger? Merger is one of the company's development and growth. Merger is also one other alternative for capital investment through internal and organic growth. In banking mergers regulated in Law Number 10 of 1998. In the implementation of the merger must also consider the interests of the parties, namely, 1 the interests of the shareholders, 2 the interests of the depositors, 3 the interest of the bank employees, and 4 the interests of officials. Keywords: Protection Law, the Parties, Bank Merger 

  5. 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)

  6. The problems of assessing the value of mergers and acquisitions

    Directory of Open Access Journals (Sweden)

    Borovikov A.D.

    2017-04-01

    Full Text Available the article discusses some questions concerning mergers and acquisitions of companies. The essential foundation of any mergers and acquisitions is always the competitive environment, more precisely, its constant changes.

  7. Cosmological aspects and properties evolution of galaxy clusters

    International Nuclear Information System (INIS)

    Majerowicz, Sebastien

    2003-01-01

    In the standard scenario for galaxy cluster formation, galaxy clusters form by material accretion and violent merger events. Between two merger events, galaxy cluster components which are the dark matter (75 %), the intra-cluster medium (20 %) and the galaxies (5 %), reach for equilibrium. The intra-cluster medium is the main baryonic component. This is a hot optically thin gas and its temperature tells something about the gravitational potential well. This well is essentially the consequence of the dark matter distribution. The intra-cluster medium is so hot than its emission produces only x-ray photons. We studied the properties of the intra-cluster medium for some clusters by using the observations coming from the european satellite XMM-NEWTON [fr

  8. Galaxy mergers and active nuclei. II. Cosmological evolution

    International Nuclear Information System (INIS)

    Roos, N.

    1985-01-01

    Galaxy mergers may produce active galactic nuclei (AGNs) by repopulating stellar loss-cone orbits around a central black hole. In the companion paper we derived a local bolometric luminosity function of AGNs based on this process. In this paper we interpret the observed cosmological evolution of the luminosity function of AGNs as due to evolution of the merging rate among galaxies after their formation at a redshift of approx.3. An important difference between our model and previous (empirical) models is that the evolution depends on galactic (stellar) luminosity instead of central nonthermal luminosity. The radio counts at 1.4 GHz and optical counts are reproduced by the model if the merging rate of the galaxies at the bright end of the galaxy luminosity function evolves considerably faster than the merging rate of the smaller galaxies. The theoretical and observed luminosity functions at high redshift have similar characteristics: (i) at high luminosity the evolution is best described by luminosity evolution, and (2) the luminosity function has a maximum at approx.10 3 Gpc -3 , which is the space density of the most massive galaxies. A large fraction of these galaxies are presumably formed in the precursors of rich clusters. Their merger rate is high initially and declines rapidly on a time scale of a few billion years. If the initial density fluctuation spectrum for protoclusters of mass M/sub cl/ has the form deltarho/rhoproportionalM/sup( -1+n//3)/2/sub cl/, then the steep evolution of the most luminous galaxies suggests nroughly-equal-1.3 at a redshift of approx.3, which is consistent with the observed clustering of galaxies

  9. 29 CFR 4231.7 - De minimis mergers and transfers.

    Science.gov (United States)

    2010-07-01

    ... actuarial valuation. (b) De minimis merger defined. A merger is de minimis if the present value of accrued... market value of all the assets of the transferor plan; (2) The present value of the accrued benefits... value of the plan's assets is the highest. (1) A merger is not de minimis if the total present value of...

  10. 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 ...

  11. 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...

  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. 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...

  15. 7 CFR 1710.108 - Mergers and consolidations.

    Science.gov (United States)

    2010-01-01

    ... operating efficiency and financial soundness. (b) After a merger or consolidation, RUS will give priority... 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...

  16. Toxic shock syndrome

    Science.gov (United States)

    Staphylococcal toxic shock syndrome; Toxic shock-like syndrome; TSLS ... Toxic shock syndrome is caused by a toxin produced by some types of staphylococcus bacteria. A similar problem, called toxic shock- ...

  17. Reconciling mass functions with the star-forming main sequence via mergers

    Science.gov (United States)

    Steinhardt, Charles L.; Yurk, Dominic; Capak, Peter

    2017-06-01

    We combine star formation along the 'main sequence', quiescence and clustering and merging to produce an empirical model for the evolution of individual galaxies. Main-sequence star formation alone would significantly steepen the stellar mass function towards low redshift, in sharp conflict with observation. However, a combination of star formation and merging produces a consistent result for correct choice of the merger rate function. As a result, we are motivated to propose a model in which hierarchical merging is disconnected from environmentally independent star formation. This model can be tested via correlation functions and would produce new constraints on clustering and merging.

  18. 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.

  19. Railroad mergers and acquisitions take shape

    Energy Technology Data Exchange (ETDEWEB)

    Fiscor, S.

    1995-12-01

    This year has been one of the most exciting years in recent history concerning US railroads and coal transportation, as mergers and acquisitions narrow the field for Western coal carriers. The views on the mergers and how they will affect coal transportation are mixed. The coal industry`s growth in the West and its stability in the East is the basis for the most recent changes in the rail industry. Restructuring US coal markets to confirm to environmental policy has had a profound effect on much more than the coal industry itself. Deregulation of rail transport has also been an important factor. 1 fig., 3 tabs.

  20. A HIGH FIDELITY SAMPLE OF COLD FRONT CLUSTERS FROM THE CHANDRA ARCHIVE

    International Nuclear Information System (INIS)

    Owers, Matt S.; Nulsen, Paul E. J.; Markevitch, Maxim; Couch, Warrick J.

    2009-01-01

    This paper presents a sample of 'cold front' clusters selected from the Chandra archive. The clusters are selected based purely on the existence of surface brightness edges in their Chandra images which are modeled as density jumps. A combination of the derived density and temperature jumps across the fronts is used to select nine robust examples of cold front clusters: 1ES0657 - 558, Abell 1201, Abell 1758N, MS1455.0+2232, Abell 2069, Abell 2142, Abell 2163, RXJ1720.1+2638, and Abell 3667. This sample is the subject of an ongoing study aimed at relating cold fronts to cluster merger activity, and understanding how the merging environment affects the cluster constituents. Here, temperature maps are presented along with the Chandra X-ray images. A dichotomy is found in the sample in that there exists a subsample of cold front clusters which are clearly mergers based on their X-ray morphologies, and a second subsample of clusters which harbor cold fronts, but have surprisingly relaxed X-ray morphologies, and minimal evidence for merger activity at other wavelengths. For this second subsample, the existence of a cold front provides the sole evidence for merger activity at X-ray wavelengths. We discuss how cold fronts can provide additional information which may be used to constrain merger histories, and also the possibility of using cold fronts to distinguish major and minor mergers.

  1. Entropy Generation Across Earth's Bow Shock

    Science.gov (United States)

    Parks, George K.; McCarthy, Michael; Fu, Suiyan; Lee E. s; Cao, Jinbin; Goldstein, Melvyn L.; Canu, Patrick; Dandouras, Iannis S.; Reme, Henri; Fazakerley, Andrew; hide

    2011-01-01

    Earth's bow shock is a transition layer that causes an irreversible change in the state of plasma that is stationary in time. Theories predict entropy increases across the bow shock but entropy has never been directly measured. Cluster and Double Star plasma experiments measure 3D plasma distributions upstream and downstream of the bow shock that allow calculation of Boltzmann's entropy function H and his famous H-theorem, dH/dt O. We present the first direct measurements of entropy density changes across Earth's bow shock. We will show that this entropy generation may be part of the processes that produce the non-thermal plasma distributions is consistent with a kinetic entropy flux model derived from the collisionless Boltzmann equation, giving strong support that solar wind's total entropy across the bow shock remains unchanged. As far as we know, our results are not explained by any existing shock models and should be of interests to theorists.

  2. The determinants of merger waves: An international perspective

    Science.gov (United States)

    Gugler, Klaus; Mueller, Dennis C.; Weichselbaumer, Michael

    2012-01-01

    One of the most conspicuous features of mergers is that they come in waves that are correlated with increases in share prices and price/earnings ratios. We use a natural way to discriminate between pure stock market influences on firm decisions and other influences by examining merger patterns for both listed and unlisted firms. If “real” changes in the economy drive merger waves, as some neoclassical theories of mergers predict, both listed and unlisted firms should experience waves. We find significant differences between listed and unlisted firms as predicted by behavioral theories of merger waves. PMID:27346903

  3. 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)

  4. Mergers and acquisitions in the oil and gas industries

    Energy Technology Data Exchange (ETDEWEB)

    Corlay, C.; Huby, D. [Institut Francais du Petrole, Rueil-Malmaison (France)

    1999-07-01

    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)

  5. Simulation of Plasma Jet Merger and Liner Formation within the PLX- α Project

    Science.gov (United States)

    Samulyak, Roman; Chen, Hsin-Chiang; Shih, Wen; Hsu, Scott

    2015-11-01

    Detailed numerical studies of the propagation and merger of high Mach number argon plasma jets and the formation of plasma liners have been performed using the newly developed method of Lagrangian particles (LP). The LP method significantly improves accuracy and mathematical rigor of common particle-based numerical methods such as smooth particle hydrodynamics while preserving their main advantages compared to grid-based methods. A brief overview of the LP method will be presented. The Lagrangian particle code implements main relevant physics models such as an equation of state for argon undergoing atomic physics transformation, radiation losses in thin optical limit, and heat conduction. Simulations of the merger of two plasma jets are compared with experimental data from past PLX experiments. Simulations quantify the effect of oblique shock waves, ionization, and radiation processes on the jet merger process. Results of preliminary simulations of future PLX- alpha experiments involving the ~ π / 2 -solid-angle plasma-liner configuration with 9 guns will also be presented. Partially supported by ARPA-E's ALPHA program.

  6. Binary Black Hole Mergers from Field Triples: Properties, Rates, and the Impact of Stellar Evolution

    Energy Technology Data Exchange (ETDEWEB)

    Antonini, Fabio [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astrophysics, Northwestern University, Evanston, IL 60208 (United States); Toonen, Silvia [Astronomical Institute Anton Pannekoek, University of Amsterdam, P.O. Box 94249, 1090 GE, Amsterdam (Netherlands); Hamers, Adrian S. [Institute for Advanced Study, School of Natural Sciences, Einstein Drive, Princeton, NJ 08540 (United States)

    2017-06-01

    We consider the formation of binary black hole (BH) mergers through the evolution of field massive triple stars. In this scenario, favorable conditions for the inspiral of a BH binary are initiated by its gravitational interaction with a distant companion, rather than by a common-envelope phase invoked in standard binary evolution models. We use a code that follows self-consistently the evolution of massive triple stars, combining the secular triple dynamics (Lidov–Kozai cycles) with stellar evolution. After a BH triple is formed, its dynamical evolution is computed using either the orbit-averaged equations of motion, or a high-precision direct integrator for triples with weaker hierarchies for which the secular perturbation theory breaks down. Most BH mergers in our models are produced in the latter non-secular dynamical regime. We derive the properties of the merging binaries and compute a BH merger rate in the range (0.3–1.3) Gpc{sup −3} yr{sup −1}, or up to ≈2.5 Gpc{sup −3} yr{sup −1} if the BH orbital planes have initially random orientation. Finally, we show that BH mergers from the triple channel have significantly higher eccentricities than those formed through the evolution of massive binaries or in dense star clusters. Measured eccentricities could therefore be used to uniquely identify binary mergers formed through the evolution of triple stars. While our results suggest up to ≈10 detections per year with Advanced-LIGO, the high eccentricities could render the merging binaries harder to detect with planned space based interferometers such as LISA.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Bargaining in Mergers and Termination Fees

    NARCIS (Netherlands)

    Weitzel, U.; Rosenkranz, S.

    We model takeovers as a bargaining process and explain termination fees for, both, the target and the acquirer, subject to parties’ bargaining power and outside options. In equilibrium, termination fees are offered by firms with outside options in exchange for a greater share of merger synergies.

  12. 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.

  13. 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...

  14. 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

  15. 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...

  16. 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

  17. 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.

  18. Using transfer learning to detect galaxy mergers

    Science.gov (United States)

    Ackermann, Sandro; Schawinksi, Kevin; Zhang, Ce; Weigel, Anna K.; Turp, M. Dennis

    2018-05-01

    We investigate the use of deep convolutional neural networks (deep CNNs) for automatic visual detection of galaxy mergers. Moreover, we investigate the use of transfer learning in conjunction with CNNs, by retraining networks first trained on pictures of everyday objects. We test the hypothesis that transfer learning is useful for improving classification performance for small training sets. This would make transfer learning useful for finding rare objects in astronomical imaging datasets. We find that these deep learning methods perform significantly better than current state-of-the-art merger detection methods based on nonparametric systems like CAS and GM20. Our method is end-to-end and robust to image noise and distortions; it can be applied directly without image preprocessing. We also find that transfer learning can act as a regulariser in some cases, leading to better overall classification accuracy (p = 0.02). Transfer learning on our full training set leads to a lowered error rate from 0.0381 down to 0.0321, a relative improvement of 15%. Finally, we perform a basic sanity-check by creating a merger sample with our method, and comparing with an already existing, manually created merger catalogue in terms of colour-mass distribution and stellar mass function.

  19. Merger incentives and the failing firm defense

    NARCIS (Netherlands)

    Bouckaert, J.M.C.; Kort, P.M.

    2014-01-01

    The merger incentives between profitable firms differ fundamentally from the incentives of a profitable firm to merge with a failing firm. We investigate these incentives under different modes of price competition and Cournot behavior. Our main finding is that firms strictly prefer exit of the

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. The AGN Luminosity Fraction in Galaxy Mergers

    Science.gov (United States)

    Dietrich, Jeremy; Weiner, Aaron; Ashby, Matthew; Martinez-Galarza, Juan Rafael; Smith, Howard Alan

    2017-01-01

    Galaxy mergers are key events in galaxy evolution, generally triggering massive starbursts and AGNs. However, in these chaotic systems, it is not yet known what fraction each of these two mechanisms contributes to the total luminosity. Here we measure and model spectral energy distributions (SEDs) using the Code for Investigating Galaxy Emission (CIGALE) in up to 33 broad bands from the UV to the far-IR for 23 IR-luminous galaxies to estimate the fraction of the bolometric IR luminosity that can be attributed to the AGN. The galaxies are split nearly evenly into two subsamples: late-stage mergers, found in the IRAS Revised Bright Galaxy Sample or Faint Source Catalog, and early-stage mergers found in the Spitzer Interacting Galaxy Sample. We find that the AGN contribution to the total IR luminosity varies greatly from system to system, from 0% up to ~90%, but is substantially greater in the later-stage and brighter mergers. This is consistent with what is known about galaxy evolution and the triggering of AGNs.The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. 1262851, and by the Smithsonian Institution.

  5. 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

  6. 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

  7. 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.

  8. Luminous Infrared Galaxies. III. Multiple Merger, Extended Massive Star Formation, Galactic Wind, and Nuclear Inflow in NGC 3256

    Science.gov (United States)

    Lípari, S.; Díaz, R.; Taniguchi, Y.; Terlevich, R.; Dottori, H.; Carranza, G.

    2000-08-01

    We report detailed evidence for multiple merger, extended massive star formation, galactic wind, and circular/noncircular motions in the luminous infrared galaxy NGC 3256, based on observations of high-resolution imaging (Hubble Space Telescope, ESO NTT), and extensive spectroscopic data (more than 1000 spectra, collected at Estación Astrofísica de Bosque Alegre, Complejo Astronómico el Leoncito, Cerro Tololo InterAmerican Observatory, and IUE observatories). We find in a detailed morphological study (resolution ~15 pc) that the extended massive star formation process detected previously in NGC 3256 shows extended triple asymmetrical spiral arms (r~5 kpc), emanating from three different nuclei. The main optical nucleus shows a small spiral disk (r~500 pc), which is a continuation of the external one and reaches the very nucleus. The core shows blue elongated structure (50 pc×25 pc) and harbors a blue stellar cluster candidate (r~8 pc). We discuss this complex morphology in the framework of an extended massive star formation driven by a multiple merger process (models of Hernquist et al. and Taniguchi et al.). We study the kinematics of this system and present a detailed Hα velocity field for the central region (40''×40'' rmax~30''~5 kpc), with a spatial resolution of 1" and errors of +/-15 km s-1. The color and isovelocity maps show mainly (1) a kinematic center of circular motion with ``spider'' shape, located between the main optical nucleus and the close (5") mid-IR nucleus and (2) noncircular motions in the external parts. We obtained three ``sinusoidal rotation curves'' (from the Hα velocity field) around position angle (P.A.) ~55°, ~90°, and ~130°. In the main optical nucleus we found a clear ``outflow component'' associated with galactic winds plus an ``inflow radial motion.'' The outflow component was also detected in the central and external regions (rstandard models of photoionization, shocks, and starbursts). We present four detailed emission

  9. Shock Waves

    CERN Document Server

    Jiang, Z

    2005-01-01

    The International Symposium on Shock Waves (ISSW) is a well established series of conferences held every two years in a different location. A unique feature of the ISSW is the emphasis on bridging the gap between physicists and engineers working in fields as different as gas dynamics, fluid mechanics and materials sciences. The main results presented at these meetings constitute valuable proceedings that offer anyone working in this field an authoritative and comprehensive source of reference.

  10. CAUGHT IN THE ACT: THE ASSEMBLY OF MASSIVE CLUSTER GALAXIES AT z = 1.62

    International Nuclear Information System (INIS)

    Lotz, Jennifer M.; Ferguson, Henry C.; Grogin, Norman; Koekemoer, Anton M.; Papovich, Casey; Tran, Kim-Vy; Faber, S. M.; Guo Yicheng; Kocevski, Dale; Lee, Kyoung-Soo; McIntosh, Daniel; Momcheva, Ivelina; Rudnick, Gregory; Saintonge, Amelie; Van der Wel, Arjen; Willmer, Christopher

    2013-01-01

    We present the recent merger history of massive galaxies in a spectroscopically confirmed proto-cluster at z = 1.62. Using Hubble Space Telescope WFC3 near-infrared imaging from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we select cluster and z ∼ 1.6 field galaxies with M star ≥ 3 × 10 10 M ☉ , to determine the frequency of double nuclei or close companions within projected separations less than 20 kpc co-moving. We find that four out of five spectroscopically confirmed massive proto-cluster galaxies have double nuclei, and 57 +13 -14 % of all M star ≥ 3 × 10 10 M ☉ cluster candidates are observed in either close pair systems or have double nuclei. In contrast, only 11% ± 3% of the field galaxies are observed in close pair/double nuclei systems. After correcting for the contribution from random projections, the implied merger rate per massive galaxy in the proto-cluster is ∼3-10 times higher than the merger rate of massive field galaxies at z ∼ 1.6. Close pairs in the cluster have minor merger stellar mass ratios (M primary : M satellite ≥ 4), while the field pairs consist of both major and minor mergers. At least half of the cluster mergers are gas-poor, as indicated by their red colors and low 24 μm fluxes. Two of the double-nucleated cluster members have X-ray detected active galactic nuclei with L x > 10 43 erg s –1 , and are strong candidates for dual or offset super-massive black holes. We conclude that the massive z = 1.62 proto-cluster galaxies are undergoing accelerated assembly via minor mergers, and discuss the implications for galaxy evolution in proto-cluster environments

  11. The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. VII. Properties of the Host Galaxy and Constraints on the Merger Timescale

    Science.gov (United States)

    Blanchard, P. K.; Berger, E.; Fong, W.; Nicholl, M.; Leja, J.; Conroy, C.; Alexander, K. D.; Margutti, R.; Williams, P. K. G.; Doctor, Z.; Chornock, R.; Villar, V. A.; Cowperthwaite, P. S.; Annis, J.; Brout, D.; Brown, D. A.; Chen, H.-Y.; Eftekhari, T.; Frieman, J. A.; Holz, D. E.; Metzger, B. D.; Rest, A.; Sako, M.; Soares-Santos, M.

    2017-10-01

    We present the properties of NGC 4993, the host galaxy of GW170817, the first gravitational-wave (GW) event from the merger of a binary neutron star (BNS) system and the first with an electromagnetic (EM) counterpart. We use both archival photometry and new optical/near-IR imaging and spectroscopy, together with stellar population synthesis models to infer the global properties of the host galaxy. We infer a star formation history peaked at ≳ 10 {Gyr} ago, with subsequent exponential decline leading to a low current star formation rate of 0.01 {M}⊙ yr-1, which we convert into a binary merger timescale probability distribution. We find a median merger timescale of {11.2}-1.4+0.7 Gyr, with a 90% confidence range of 6.8{--}13.6 {Gyr}. This in turn indicates an initial binary separation of ≈ 4.5 {R}⊙ , comparable to the inferred values for Galactic BNS systems. We also use new and archival Hubble Space Telescope images to measure a projected offset of the optical counterpart of 2.1 kpc (0.64r e ) from the center of NGC 4993 and to place a limit of {M}r≳ -7.2 mag on any pre-existing emission, which rules out the brighter half of the globular cluster luminosity function. Finally, the age and offset of the system indicates it experienced a modest natal kick with an upper limit of ˜200 km s-1. Future GW-EM observations of BNS mergers will enable measurement of their population delay time distribution, which will directly inform their viability as the dominant source of r-process enrichment in the universe.

  12. The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. VII. Properties of the Host Galaxy and Constraints on the Merger Timescale

    Energy Technology Data Exchange (ETDEWEB)

    Blanchard, P. K.; Berger, E.; Fong, W.; Nicholl, M.; Leja, J.; Conroy, C.; Alexander, K. D.; Margutti, R.; Williams, P. K. G.; Doctor, Z.; Chornock, R.; Villar, V. A.; Cowperthwaite, P. S.; Annis, J.; Brout, D.; Brown, D. A.; Chen, H. -Y.; Eftekhari, T.; Frieman, J. A.; Holz, D. E.; Metzger, B. D.; Rest, A.; Sako, M.; Soares-Santos, M.

    2017-10-16

    We present the properties of NGC 4993, the host galaxy of GW170817, the first gravitational wave (GW) event from the merger of a binary neutron star (BNS) system and the first with an electromagnetic (EM) counterpart. We use both archival photometry and new optical/near-IR imaging and spectroscopy, together with stellar population synthesis models to infer the global properties of the host galaxy. We infer a star formation history peaked at $\\gtrsim 10$ Gyr ago, with subsequent exponential decline leading to a low current star formation rate of 0.01 M$_{\\odot}$ yr$^{-1}$, which we convert into a binary merger timescale probability distribution. We find a median merger timescale of $11.2^{+0.7}_{-1.4}$ Gyr, with a 90% confidence range of $6.8-13.6$ Gyr. This in turn indicates an initial binary separation of $\\approx 4.5$ R$_{\\odot}$, comparable to the inferred values for Galactic BNS systems. We also use new and archival $Hubble$ $Space$ $Telescope$ images to measure a projected offset of the optical counterpart of $2.1$ kpc (0.64$r_{e}$) from the center of NGC 4993 and to place a limit of $M_{r} \\gtrsim -7.2$ mag on any pre-existing emission, which rules out the brighter half of the globular cluster luminosity function. Finally, the age and offset of the system indicates it experienced a modest natal kick with an upper limit of $\\sim 200$ km s$^{-1}$. Future GW$-$EM observations of BNS mergers will enable measurement of their population delay time distribution, which will directly inform their viability as the dominant source of $r$-process enrichment in the Universe.

  13. Probing Minor-merger-driven Star Formation In Early-type Galaxies Using Spatially-resolved Spectro-photometric Studies

    Science.gov (United States)

    Kaviraj, Sugata; Crockett, M.; Silk, J.; O'Connell, R. W.; Whitmore, B.; Windhorst, R.; Cappellari, M.; Bureau, M.; Davies, R.

    2012-01-01

    Recent studies that leverage the rest-frame ultraviolet (UV) spectrum have revealed widespread recent star formation in early-type galaxies (ETGs), traditionally considered to be old, passively-evolving systems. This recent star formation builds 20% of the ETG stellar mass after z 1, driven by repeated minor mergers between ETGs and small, gas-rich satellites. We demonstrate how spatially-resolved studies, using a combination of high-resolution UV-optical imaging and integral-field spectroscopy (IFS), is a powerful tool to quantify the assembly history of individual ETGs and elucidate the poorly-understood minor-merger process. Using a combination of WFC3 UV-optical (2500-8200 angstroms) imaging and IFS from the SAURON project of the ETG NGC 4150, we show that this galaxy experienced a merger with mass ratio 1:15 around 0.9 Gyr ago, which formed 3% of its stellar mass and a young kinematically-decoupled core. A UV-optical analysis of its globular cluster system shows that the bulk of the stars locked up in these clusters likely formed 6-7 Gyrs in the past. We introduce a new HST-WFC3 programme, approved in Cycle 19, which will leverage similar UV-optical imaging of a representative sample of nearby ETGs from SAURON to study the recent star formation and its drivers in unprecedented detail and put definitive constraints on minor-merger-driven star formation in massive galaxies at late epochs.

  14. Jellyfish: the origin and distribution of extreme ram-pressure stripping events in massive galaxy clusters

    Science.gov (United States)

    McPartland, Conor; Ebeling, Harald; Roediger, Elke; Blumenthal, Kelly

    2016-01-01

    We investigate the observational signatures and physical origin of ram-pressure stripping (RPS) in 63 massive galaxy clusters at z = 0.3-0.7, based on images obtained with the Hubble Space Telescope. Using a training set of a dozen `jellyfish' galaxies identified earlier in the same imaging data, we define morphological criteria to select 211 additional, less obvious cases of RPS. Spectroscopic follow-up observations of 124 candidates so far confirmed 53 as cluster members. For the brightest and most favourably aligned systems, we visually derive estimates of the projected direction of motion based on the orientation of apparent compression shocks and debris trails. Our findings suggest that the onset of these events occurs primarily at large distances from the cluster core (>400 kpc), and that the trajectories of the affected galaxies feature high-impact parameters. Simple models show that such trajectories are highly improbable for galaxy infall along filaments but common for infall at high velocities, even after observational biases are accounted for, provided the duration of the resulting RPS events is ≲500 Myr. We thus tentatively conclude that extreme RPS events are preferentially triggered by cluster mergers, an interpretation that is supported by the disturbed dynamical state of many of the host clusters. This hypothesis implies that extreme RPS might occur also near the cores of merging poor clusters or even merging groups of galaxies. Finally, we present nine additional `jellyfish" galaxies at z > 0.3 discovered by us, thereby doubling the number of such systems known at intermediate redshift.

  15. Clustering of near clusters versus cluster compactness

    International Nuclear Information System (INIS)

    Yu Gao; Yipeng Jing

    1989-01-01

    The clustering properties of near Zwicky clusters are studied by using the two-point angular correlation function. The angular correlation functions for compact and medium compact clusters, for open clusters, and for all near Zwicky clusters are estimated. The results show much stronger clustering for compact and medium compact clusters than for open clusters, and that open clusters have nearly the same clustering strength as galaxies. A detailed study of the compactness-dependence of correlation function strength is worth investigating. (author)

  16. 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.

  17. 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.

  18. 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.

  19. The Double Galaxy Cluster A2465. III. X-Ray and Weak-lensing Observations

    Energy Technology Data Exchange (ETDEWEB)

    Wegner, Gary A. [Department of Physics and Astronomy, 6127 Wilder Laboratory, Hanover, NH 03745 (United States); Umetsu, Keiichi; Molnar, Sandor M. [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Nonino, Mario [INAF/Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34143 Trieste (Italy); Medezinski, Elinor [Department of Astrophysical Sciences, 4 Ivy Lane, Princeton, NJ 08544 (United States); Andrade-Santos, Felipe; Bogdan, Akos; Lovisari, Lorenzo; Forman, William R.; Jones, Christine, E-mail: gary.wegner@dartmouth.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2017-07-20

    We report Chandra X-ray observations and optical weak-lensing measurements from Subaru/Suprime-Cam images of the double galaxy cluster A2465 ( z = 0.245). The X-ray brightness data are fit to a β model to obtain the radial gas density profiles of the northeast (NE) and southwest (SW) subcomponents, which are seen to differ in structure. We determine core radii, central temperatures, the gas masses within r {sub 500c}, and the total masses for the broader NE and sharper SW components assuming hydrostatic equilibrium. There is no large X-ray excess between the two components. The central entropy of the NE subcluster is about two times higher than the SW. Along with its structural properties and an apparent radio halo that is a sign of a merger, this suggests that the NE component has undergone merging on its own. The weak-lensing analysis gives virial masses for each substructure, which compare well with earlier dynamical results. The derived outer mass contours of the SW sub-component from weak lensing are more irregular and extended than those of the NE. Although there is a weak enhancement and small offsets between X-ray gas and mass centers from weak lensing, the lack of large amounts of gas between the two subclusters indicates that A2465 is in a pre-merger state. We discuss star formation enhancement in this system resulting from its dynamics and shock-induced star formation scenarios. A dynamical model that is consistent with the observed cluster data, based on the FLASH program and the radial infall model, is constructed, where the subclusters currently separated by ∼1.2 Mpc are approaching each other at ∼2000 km s{sup −1} and will meet in ∼0.4 Gyr.

  20. The Double Galaxy Cluster A2465. III. X-Ray and Weak-lensing Observations

    Science.gov (United States)

    Wegner, Gary A.; Umetsu, Keiichi; Molnar, Sandor M.; Nonino, Mario; Medezinski, Elinor; Andrade-Santos, Felipe; Bogdan, Akos; Lovisari, Lorenzo; Forman, William R.; Jones, Christine

    2017-07-01

    We report Chandra X-ray observations and optical weak-lensing measurements from Subaru/Suprime-Cam images of the double galaxy cluster A2465 (z = 0.245). The X-ray brightness data are fit to a β model to obtain the radial gas density profiles of the northeast (NE) and southwest (SW) subcomponents, which are seen to differ in structure. We determine core radii, central temperatures, the gas masses within r 500c, and the total masses for the broader NE and sharper SW components assuming hydrostatic equilibrium. There is no large X-ray excess between the two components. The central entropy of the NE subcluster is about two times higher than the SW. Along with its structural properties and an apparent radio halo that is a sign of a merger, this suggests that the NE component has undergone merging on its own. The weak-lensing analysis gives virial masses for each substructure, which compare well with earlier dynamical results. The derived outer mass contours of the SW sub-component from weak lensing are more irregular and extended than those of the NE. Although there is a weak enhancement and small offsets between X-ray gas and mass centers from weak lensing, the lack of large amounts of gas between the two subclusters indicates that A2465 is in a pre-merger state. We discuss star formation enhancement in this system resulting from its dynamics and shock-induced star formation scenarios. A dynamical model that is consistent with the observed cluster data, based on the FLASH program and the radial infall model, is constructed, where the subclusters currently separated by ˜1.2 Mpc are approaching each other at ˜2000 km s-1 and will meet in ˜0.4 Gyr. Based in part on data collected at the Subaru Telescope, which is operated by the National Astronomical Society of Japan.

  1. THE ASSEMBLY OF GALAXY CLUSTERS

    International Nuclear Information System (INIS)

    Berrier, Joel C.; Stewart, Kyle R.; Bullock, James S.; Purcell, Chris W.; Barton, Elizabeth J.; Wechsler, Risa H.

    2009-01-01

    We study the formation of 53 galaxy cluster-size dark matter halos (M = 10 14.0-14.76 M sun ) formed within a pair of cosmological Λ cold dark matter N-body simulations, and track the accretion histories of cluster subhalos with masses large enough to host ∼0.3 L * galaxies. By associating subhalos with cluster galaxies, we find the majority of galaxies in clusters experience no 'preprocessing' in the group environment prior to their accretion into the cluster. On average, 70% of cluster galaxies fall into the cluster potential directly from the field, with no luminous companions in their host halos at the time of accretion; less than 12% are accreted as members of groups with five or more galaxies. Moreover, we find that cluster galaxies are significantly less likely to have experienced a merger in the recent past (∼<6 Gyr) than a field halo of the same mass. These results suggest that local cluster processes such as ram pressure stripping, galaxy harassment, or strangulation play the dominant role in explaining the difference between cluster and field populations at a fixed stellar mass, and that pre-evolution or past merging in the group environment is of secondary importance for setting cluster galaxy properties for most clusters. The accretion times for z = 0 cluster members are quite extended, with ∼20% incorporated into the cluster halo more than 7 Gyr ago and ∼20% within the last 2 Gyr. By comparing the observed morphological fractions in cluster and field populations, we estimate an approximate timescale for late-type to early-type transformation within the cluster environment to be ∼6 Gyr.

  2. Dynamical history of a binary cluster: Abell 3653

    Science.gov (United States)

    Caglar, Turgay; Hudaverdi, Murat

    2017-12-01

    We study the dynamical structure of a bimodal galaxy cluster Abell 3653 at z = 0.1089 using optical and X-ray data. Observations include archival data from the Anglo-Australian Telescope, X-ray observatories XMM-Newton and Chandra. We draw a global picture for A3653 using galaxy density, X-ray luminosity and temperature maps. The galaxy distribution has a regular morphological shape at the 3 Mpc size. The galaxy density map shows an elongation in the east-west direction, which perfectly aligns with the extended diffuse X-ray emission. We detect two dominant groups around the two brightest cluster galaxies (BCGs). BCG1 (z = 0.1099) can be associated with the main cluster A3653E, and a foreground subcluster A3653W is concentrated at BCG2 (z = 0.1075). Both X-ray peaks are dislocated from the BCGs by ∼35 kpc, which suggest an ongoing merger process. We measure the subcluster gas temperatures of 4.67 and 3.66 keV, respectively. Two-body dynamical analysis shows that A3653E and A3653W are very likely gravitationally bound (93.5 per cent probability). The highly favoured scenario suggests that the two subclusters have a mass ratio of 1.4 and are colliding close to the plane of sky (α = 17.61°) at 2400 km s-1, and will undergo core passage in 380 Myr. The temperature map also significantly shows a shock-heated gas (6.16 keV) between the subclusters, which confirms the supersonic infalling scenario.

  3. CHANDRA OBSERVATIONS OF GALAXY ZOO MERGERS: FREQUENCY OF BINARY ACTIVE NUCLEI IN MASSIVE MERGERS

    Energy Technology Data Exchange (ETDEWEB)

    Teng, Stacy H. [Observational Cosmology Laboratory, NASA/GSFC, Greenbelt, MD 20771 (United States); Schawinski, Kevin; Urry, C. Megan; Bonning, Erin W. [Department of Physics, Yale University, New Haven, CT 06511 (United States); Darg, Dan W.; Kaviraj, Sugata; Lintott, Chris J. [Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH (United Kingdom); Oh, Kyuseok [Department of Astronomy, Yonsei University, Seoul 120-749 (Korea, Republic of); Cardamone, Carolin N. [Harriet W. Sheridan Center for Teaching and Learning, Brown University, P.O. Box 1912, Providence, RI 02912 (United States); Keel, William C. [Department of Physics and Astronomy, 206 Gallalee Hall, 514 University Boulevard, University of Alabama, Tuscaloosa, AL 35487-034 (United States); Simmons, Brooke D. [Yale Center for Astronomy and Astrophysics, Yale University, P.O. Box 208121, New Haven, CT 06520 (United States); Treister, Ezequiel, E-mail: stacy.h.teng@nasa.gov [Departamento de Astronomia, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile)

    2012-07-10

    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 10{sup 11} M{sub Sun} that already have optical active galactic nucleus (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}< 1.1 Multiplication-Sign 10{sup 22} cm{sup -2}) X-ray nuclei are relatively common (8/12), but the detections are too faint (<40 counts per nucleus; f{sub 2-10keV} {approx}< 1.2 Multiplication-Sign 10{sup -13} erg s{sup -1} cm{sup -2}) to reliably separate starburst and nuclear activity as the origin of the X-ray emission. Only one 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 AGNs in these mergers are rare (0%-8%), unless most merger-induced active nuclei are very heavily obscured or Compton thick.

  4. Shock Prevention

    Science.gov (United States)

    1978-01-01

    The electrician pictured is installing a General Electric Ground Fault Interrupter (GFI), a device which provides protection against electrical shock in the home or in industrial facilities. Shocks due to defective wiring in home appliances or other electrical equipment can cause severe burns, even death. As a result, the National Electrical Code now requires GFIs in all new homes constructed. This particular type of GFI employs a sensing element which derives from technology acquired in space projects by SCI Systems, Inc., Huntsville, Alabama, producer of sensors for GE and other manufacturers of GFI equipment. The sensor is based on the company's experience in developing miniaturized circuitry for space telemetry and other spacecraft electrical systems; this experience enabled SCI to package interruptor circuitry in the extremely limited space available and to produce sensory devices at practicable cost. The tiny sensor measures the strength of the electrical current and detects current differentials that indicate a fault in the functioning of an electrical system. The sensing element then triggers a signal to a disconnect mechanism in the GFI, which cuts off the current in the faulty circuit.

  5. 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.

  6. Do Municipal Mergers Improve Fiscal Outcomes?

    DEFF Research Database (Denmark)

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

    2014-01-01

    Improved fiscal management is a frequent justification for promoting boundary consolidations. However, whether or not this is actually the case is rarely placed under rigorous empirical scrutiny. Hence, this article investigates if fiscal outcomes are improved when municipalities are merged....... The basic argument is that the conceptualisation of fiscal management in political science is often too narrow as it focuses on the budget and pays hardly any attention to balances in the final accounts and debts – elements of management which are central to policy making. On this background, the causal...... 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...

  7. The importance of partnerships, mergers and acquisitions

    Energy Technology Data Exchange (ETDEWEB)

    Trabandt, C.A. [Merrill Lynch, New York, NY (United States)

    1998-09-01

    An overview of the electric utility industry was presented. The main factors driving mergers and acquisitions in the industry were identified as being consolidation, disaggregation, convergence and international expansion. To prove the point, statistics from recent merger and acquisition transactions in the U.S. were presented. The importance of disaggregation of the utility business and convergence as the major themes of the electricity and natural gas industries were demonstrated. They are driven by a new competitive marketplace and fewer regulations. The driving forces behind them were explained, buttressing the arguments with recent statistics reflecting an upsurge in convergence transactions. Significant opportunities abroad and recent foreign acquisitions by U. S. utilities were also reviewed. With regard to convergence, it was shown to be occurring in both the generation/wholesale and distribution/retail marketing segment of the electric power industry. 3 figs.

  8. The Merging Galaxy Cluster A520 - A Broken-Up Cool Core, A Dark Subcluster, and an X-Ray Channel

    Science.gov (United States)

    Wang, Qian H.S.; Markevitch, Maxim; Giacintucci, Simona

    2016-01-01

    We present results from a deep Chandra X-ray observation of a merging galaxy cluster A520. A high-resolution gas temperature map reveals a long trail of dense, cool clumpsapparently the fragments of a cool core that has been stripped from the infalling subcluster by ram pressure. The clumps should still be connected by the stretched magnetic field lines. The observed temperature variations imply that thermal conductivity is suppressed by a factor greater than 100 across the presumed direction of the magnetic field (as found in other clusters), and is also suppressed along the field lines by a factor of several. Two massive clumps in the periphery of A520, visible in the weak-lensing mass map and the X-ray image, have apparently been completely stripped of gas during the merger, but then re-accreted the surrounding high-entropy gas upon exit from the cluster. The mass clump that hosted the stripped cool core is also re-accreting hotter gas. An X-ray hydrostatic mass estimate for the clump that has the simplest geometry agrees with the lensing mass. Its current gas mass to total mass ratio is very low, 1.5 percent to 3 percent, which makes it a "dark subcluster." We also found a curious low X-ray brightness channel (likely a low-density sheet in projection) going across the cluster along the direction of an apparent secondary merger. The channel may be caused by plasma depletion in a region of an amplified magnetic field (with plasma Beta approximately equal to 10-20). The shock in A520 will be studied in a separate paper.

  9. 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....

  10. Merger negotiations with stock market feedback

    OpenAIRE

    Betton, Sandra; Eckbo, B. Espen; Thompson, Rex; Thorburn, Karin S.

    2011-01-01

    Merger negotiations routinely occur amidst economically significant a target stock price runups. Since the source of the runup is unobservable (is it a target stand-alone value change and/or deal anticipation?), feeding the runup back into the offer price risks "paying twice" for the target shares. We present a novel structural empirical analysis of this runup feedback hypothesis. We show that rational deal anticipation implies a nonlinear relationship between the runup and the offer price ma...

  11. 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.

  12. A scoreboard of mergers and acquisitions

    Energy Technology Data Exchange (ETDEWEB)

    Parent, L.V

    1989-08-01

    In the late 70s and early 80s when market growth was not a viable alternative and price deregulation was imminent, new strategies were sought that would provide some basis for survival in a deregulated environment, and merger/acquisition strategy took on new significance. According to the author, eight mega gas pipe line companies have evolved. The strategic objectives behind these merges is analyzed.

  13. 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.

  14. 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.

  15. Merger and Innovation Incentives in a Differentiated Industry

    OpenAIRE

    Kesavayuth, Dusanee; Lee, Sang-Ho; Zikos, Vasileios

    2017-01-01

    In this paper, we consider a duopoly with product differentiation and examine the interaction between merger and innovation incentives. The analysis reveals that a merger tends to discourage innovation, unless the investment cost is sufficiently low. This result holds whether or not side payments between firms are allowed. When side payments are permitted, a bilateral merger-to-monopoly is always profitable, a standard result in the literature. When side payments are not permitted, however, w...

  16. 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

  17. VersaCold: Analysis of Change Management in Mergers & Acquisitions

    OpenAIRE

    Eslami, Sara

    2011-01-01

    Many firms use mergers and acquisitions as a corporate strategy to increase shareholder value. Therefore, understanding such a widely exercised strategy and its implications on corporate change would be critical for organizations that wish to pursue this strategy. This study provides an in depth review of mergers and acquisitions and introduces best practices for managing changes that result from mergers and acquisitions. Next, the concepts are applied to two cases of acquisitions in VersaCol...

  18. 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.

  19. 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....

  20. Manufacturers Mergers and Product Variety in Vertically Related Markets

    OpenAIRE

    Chrysovalantou Milliou; Joel Sandonis

    2014-01-01

    We study final product manufacturers’ incentives to introduce new products into the market and how they are affected by a merger among them. We show that when manufacturers distribute their products through multi-product retailers, a manufacturers merger, although it leads to an increase in the wholesale prices, it can enhance product variety. The merger generated product variety efficiencies though arise only when vertical relations are present: when manufacturers sell directly their produ...

  1. of Mergers and Acquisitions on the Human Resource Department

    OpenAIRE

    mohatta, maulshree

    2007-01-01

    Mergers and acquisitions take place in all forms of industries and businesses, however small or large. They have and impact on almost all the areas and departments of business. One department in any business or industry on which a merger or an acquisition has a major impact is the human recourse department or the personnel of the companies which have undergone a merger, or have acquired, or have been acquired. The following dissertation represents an analysis of the research carried out...

  2. 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...

  3. The Fallacies of Mergers Being Acquisitions: Fact or Fiction?

    OpenAIRE

    Maneckji, Hilla Shahpur

    2006-01-01

    The goal of this dissertation study was to examine the fallacies of mergers being acquisitions, which is a very new topic, and that hasn’t been investigated in detail before. The aim of this research was to investigate if major global mergers were acquisitions in camouflage and were only created to portray a false perception. The study was conducted to understand the differences and characteristics between mergers and acquisitions that were further examined taking into account live case studi...

  4. 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. ...

  5. 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.

  6. 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

  7. 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.

  8. The effect of mergers and acquisitions on behavioral health care.

    Science.gov (United States)

    Lazarus, A

    1995-01-01

    The consolidation of America's managed health care industry rivals any corporate raider scenario. Unlike previous merger booms, however, health care unions in the 1990s have been strategically planned. Particular attention is paid to merger activity in the behavioral health care field. Ultimately, the author writes, mergers will bring greater efficiency and lower costs to health care but also less choice for patients. Unless providers and payers pay close attention to the human side of mergers and acquisitions, new alliances are likely to fall short of their goals.

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

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-12-01

    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.

  10. 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.

  11. 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 ...

  12. LIGO Discovers the Merger of Two Black Holes

    Science.gov (United States)

    Kohler, Susanna

    2016-02-01

    Big news: the Laser Interferometer Gravitational-Wave Observatory (LIGO) has detected its first gravitational-wave signal! Not only is the detection of this signal a major technical accomplishment and an exciting confirmation of general relativity, but it also has huge implications for black-hole astrophysics.What did LIGO see?LIGO is designed to detect the ripples in space-time created by two massive objects orbiting each other. These waves can reach observable amplitudes when a binary system consisting of two especially massive objects i.e., black holes or neutron stars reach the end of their inspiral and merge.LIGO has been unsuccessfully searching for gravitational waves since its initial operations in 2002, but a recent upgrade in its design has significantly increased its sensitivity and observational range. The first official observing run of Advanced LIGO began 18 September 2015, but the instruments were up and running in engineering mode several weeks before that. And it was in this time frame before official observing even began! that LIGO spotted its first gravitational wave signal: GW150914.One of LIGOs two detection sites, located near Hanford in eastern Washington. [LIGO]The signal, detected on 14 September, 2015, provides astronomers with a remarkable amount of information about the merger that caused it. From the detection, the LIGO team has extracted the masses of the two black holes that merged, 36+5-4 and 29+4-4 solar masses, as well as the mass of the final black hole formed by the merger, ~62 solar masses. The team also determined that the merger happened roughly a billion light-years away (at a redshift of z~0.1), and the direction of the signal was localized to an area of ~600 square degrees (roughly 1% of the sky).Why is this detection a big deal?This is the firstdirect detection of gravitational waves, providing spectacular further confirmation of Einsteins theory of general relativity. But the implications of GW150914 go far beyond this

  13. On the interplay between cosmological shock waves and their environment

    Science.gov (United States)

    Martin-Alvarez, Sergio; Planelles, Susana; Quilis, Vicent

    2017-05-01

    Cosmological shock waves are tracers of the thermal history of the structures in the Universe. They play a crucial role in redistributing the energy within the cosmic structures and are also amongst the main ingredients of galaxy and galaxy cluster formation. Understanding this important function requires a proper description of the interplay between shocks and the different environments where they can be found. In this paper, an Adaptive Mesh Refinement (AMR) Eulerian cosmological simulation is analysed by means of a shock-finding algorithm that allows to generate shock wave maps. Based on the population of dark matter halos and on the distribution of density contrast in the simulation, we classify the shocks in five different environments. These range from galaxy clusters to voids. The shock distribution function and the shocks power spectrum are studied for these environments dynamics. We find that shock waves on different environments undergo different formation and evolution processes, showing as well different characteristics. We identify three different phases of formation, evolution and dissipation of these shock waves, and an intricate migration between distinct environments and scales. Shock waves initially form at external, low density regions and are merged and amplified through the collapse of structures. Shock waves and cosmic structures follow a parallel evolution. Later on, shocks start to detach from them and dissipate. We also find that most of the power that shock waves dissipate is found at scales of k ˜0.5 Mpc^{-1}, with a secondary peak at k ˜8 Mpc^{-1}. The evolution of the shocks power spectrum confirms that shock waves evolution is coupled and conditioned by their environment.

  14. On the rate of black hole binary mergers in galactic nuclei due to dynamical hardening

    Science.gov (United States)

    Leigh, N. W. C.; Geller, A. M.; McKernan, B.; Ford, K. E. S.; Mac Low, M.-M.; Bellovary, J.; Haiman, Z.; Lyra, W.; Samsing, J.; O'Dowd, M.; Kocsis, B.; Endlich, S.

    2018-03-01

    We assess the contribution of dynamical hardening by direct three-body scattering interactions to the rate of stellar-mass black hole binary (BHB) mergers in galactic nuclei. We derive an analytic model for the single-binary encounter rate in a nucleus with spherical and disc components hosting a super-massive black hole (SMBH). We determine the total number of encounters NGW needed to harden a BHB to the point that inspiral due to gravitational wave emission occurs before the next three-body scattering event. This is done independently for both the spherical and disc components. Using a Monte Carlo approach, we refine our calculations for NGW to include gravitational wave emission between scattering events. For astrophysically plausible models, we find that typically NGW ≲ 10. We find two separate regimes for the efficient dynamical hardening of BHBs: (1) spherical star clusters with high central densities, low-velocity dispersions, and no significant Keplerian component and (2) migration traps in discs around SMBHs lacking any significant spherical stellar component in the vicinity of the migration trap, which is expected due to effective orbital inclination reduction of any spherical population by the disc. We also find a weak correlation between the ratio of the second-order velocity moment to velocity dispersion in galactic nuclei and the rate of BHB mergers, where this ratio is a proxy for the ratio between the rotation- and dispersion-supported components. Because discs enforce planar interactions that are efficient in hardening BHBs, particularly in migration traps, they have high merger rates that can contribute significantly to the rate of BHB mergers detected by the advanced Laser Interferometer Gravitational-Wave Observatory.

  15. TIDAL TAILS OF MINOR MERGERS: STAR FORMATION EFFICIENCY IN THE WESTERN TAIL OF NGC 2782

    Energy Technology Data Exchange (ETDEWEB)

    Knierman, Karen; Scowen, Paul; Jansen, Rolf A. [School of Earth and Space Exploration, Arizona State University, 550 East Tyler Mall, Room PSF-686 (P.O. Box 871404), Tempe, AZ 85287-1404 (United States); Knezek, Patricia M. [WIYN Consortium, Inc., 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Wehner, Elizabeth, E-mail: karen.knierman@asu.edu, E-mail: paul.scowen@asu.edu, E-mail: rolf.jansen@asu.edu, E-mail: pknezek@noao.edu, E-mail: ewehner@haverford.edu [Department of Astronomy, Haverford College, Haverford, PA 19041 (United States)

    2012-04-10

    While major mergers and their tidal debris are well studied, they are less common than minor mergers (mass ratios {approx}< 0.3). The peculiar spiral NGC 2782 is the result of a merger between two disk galaxies with a mass ratio of {approx}4: 1 occurring {approx}200 Myr ago. This merger produced a molecular and H I-rich, optically bright eastern tail and an H I-rich, optically faint western tail. Non-detection of CO in the western tail by Braine et al. suggested that star formation had not yet begun to occur in that tidal tail. However, deep H{alpha} narrowband images show evidence of recent star formation in the western tail. Across the entire western tail, we find the global star formation rate per unit area ({Sigma}{sub SFR}) to be several orders of magnitude less than expected from the total gas density. Together with extended FUV+NUV emission from Galaxy Evolution Explorer along the tail, this indicates a low global star formation efficiency in the tidal tail producing lower mass star clusters. The H II region that we observed has a local (few-kiloparsec scale) {Sigma}{sub SFR} from H{alpha} that is less than that expected from the total gas density, which is consistent with other observations of tidal debris. The star formation efficiency of this H II region inferred from the total gas density is low, but normal when inferred from the molecular gas density. These results suggest the presence of a very small, locally dense region in the western tail of NGC 2782 or of a low-metallicity and/or low-pressure star-forming region.

  16. 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

  17. 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

  18. 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.

  19. Merging Galaxy Clusters: Analysis of Simulated Analogs

    Science.gov (United States)

    Nguyen, Jayke; Wittman, David; Cornell, Hunter

    2018-01-01

    The nature of dark matter can be better constrained by observing merging galaxy clusters. However, uncertainty in the viewing angle leads to uncertainty in dynamical quantities such as 3-d velocities, 3-d separations, and time since pericenter. The classic timing argument links these quantities via equations of motion, but neglects effects of nonzero impact parameter (i.e. it assumes velocities are parallel to the separation vector), dynamical friction, substructure, and larger-scale environment. We present a new approach using n-body cosmological simulations that naturally incorporate these effects. By uniformly sampling viewing angles about simulated cluster analogs, we see projected merger parameters in the many possible configurations of a given cluster. We select comparable simulated analogs and evaluate the likelihood of particular merger parameters as a function of viewing angle. We present viewing angle constraints for a sample of observed mergers including the Bullet cluster and El Gordo, and show that the separation vectors are closer to the plane of the sky than previously reported.

  20. Collisionless electrostatic shocks

    DEFF Research Database (Denmark)

    Andersen, H.K.; Andersen, S.A.; Jensen, Vagn Orla

    1970-01-01

    An attempt was made in the laboratory to observe the standing collisionless electrostatic shocks in connection with the bow shock of the earth......An attempt was made in the laboratory to observe the standing collisionless electrostatic shocks in connection with the bow shock of the earth...

  1. 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).

  2. STRUCTURAL ANALYSIS OF MERGERS AND ACQUISITIONS IN THE FOOD INDUSTRY

    OpenAIRE

    Adams, Wendi L.; Love, H. Alan; Capps, Oral, Jr.

    1997-01-01

    Determinants of merger and acquisition activity in the food industry are analyzed using logit regression analysis. Factors affecting the food processing, food retailing and food service sectors are considered. Results indicate merger and acquisition activity in all three sectors are significantly influenced by antitrust activity, profitability and real gross domestic product.

  3. Transparency and Coordinated Effects in European Merger Control

    DEFF Research Database (Denmark)

    Albæk, Svend; Møllgaard, H. Peter; Overgaard, Per Baltzer

    2010-01-01

    In this paper, we first outline the foundations in economic theory of so-called coordinated effects with a particular view to mergers and with a special focus on transparency. Then, we review a number of seminal merger cases in EU competition policy (Airtours, Sony/BMG, ABF/GBI Business) in light...

  4. 12 CFR 931.5 - Liquidation, merger, or consolidation.

    Science.gov (United States)

    2010-01-01

    ... 12 Banks and Banking 7 2010-01-01 2010-01-01 false Liquidation, merger, or consolidation. 931.5 Section 931.5 Banks and Banking FEDERAL HOUSING FINANCE BOARD FEDERAL HOME LOAN BANK RISK MANAGEMENT AND CAPITAL STANDARDS FEDERAL HOME LOAN BANK CAPITAL STOCK § 931.5 Liquidation, merger, or consolidation. The...

  5. 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…

  6. Mergers and acquisitions's impact on financial performance: an ...

    African Journals Online (AJOL)

    Mergers and acquisitions's impact on financial performance: an evaluation with perspective of time. ... Journal Home > Vol 9, No 5S (2017) > ... are firms are able to convert these qualitative aspects into quantitative form and if yes than ... Keywords: mergers and acquisitions; du pont analysis; long run; financial performance; ...

  7. 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…

  8. 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…

  9. Do Mergers of Potentially Dominant firms foster Innovation?

    NARCIS (Netherlands)

    Cefis, E.; Sabidussi, A.; Schenk, E.J.J.

    2007-01-01

    We investigate the effects of M&A on innovation in the specific context of potential or realized market dominance. Authorities are challenged by balancing both detrimental and beneficial effects of mergers on innovation, especially when a merger threatens to result in market dominance, while

  10. 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

  11. 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

  12. The different growth pathways of Brightest Cluster Galaxies and the Intra-Cluster Light

    Science.gov (United States)

    Contini, E.; Yi, S. K.; Kang, X.

    2018-06-01

    We study the growth pathways of Brightest Central Galaxies (BCGs) and Intra-Cluster Light (ICL) by means of a semi-analytic model. We assume that the ICL forms by stellar stripping of satellite galaxies and violent processes during mergers, and implement two independent models: (1) one considers both mergers and stellar stripping (named STANDARD model), and one considers only mergers (named MERGERS model). We find that BCGs and ICL form, grow and overall evolve at different times and with different timescales, but they show a clear co-evolution after redshift z ˜ 0.7 - 0.8. Around 90% of the ICL from stellar stripping is built-up in the innermost 150 Kpc from the halo centre and the dominant contribution comes from disk-like galaxies (B/Tcluster other than the BCG, at z = 0. We then suggest that this quantity is a valid observable that can shed light on the relative importance of mergers and stellar stripping for the formation of the ICL.

  13. 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.

  14. 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.

  15. Performance Assessment of Mergers and Acquisitions

    DEFF Research Database (Denmark)

    Wang, Daojuan; Moini, Hamid

    2012-01-01

    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......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...

  16. Mergers, Acquisitions, and Access: STM Publishing Today

    Science.gov (United States)

    Robertson, Kathleen

    Electronic publishing is changing the fundamentals of the entire printing/delivery/archive system that has served as the distribution mechanism for scientific research over the last century and a half. The merger-mania of the last 20 years, preprint pools, and publishers' licensing and journals-bundling plans are among the phenomena impacting the scientific information field. Science-Technology-Medical (STM) publishing is experiencing a period of intense consolidation and reorganization. This paper gives an overview of the economic factors fueling these trends, the major STM publishers, and the government regulatory bodies that referee this industry in Europe, Canada, and the USA.

  17. 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.

  18. 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.

  19. 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

  20. Which types of hospital mergers save consumers money?

    Science.gov (United States)

    Connor, R A; Feldman, R D; Dowd, B E; Radcliff, T A

    1997-01-01

    This study analyzes the changes in costs and prices from 1986 to 1994 for more than 3,500 U.S. short-term general hospitals, including 122 horizontal mergers. These mergers were generally financially beneficial to consumers, providing average price reductions of approximately 7 percent. Merger-related price reductions were considerably less in market areas with higher market concentration levels. Merger-related price reductions in areas with higher penetration by health maintenance organizations (HMOs) were approximately twice those in areas with lower HMO penetration. Merger-related price reductions were greater for low-occupancy hospitals, nonteaching hospitals, nonsystem hospitals, similar-size hospitals, and hospitals with greater premerger service duplication.

  1. Merger Strategy, Cross-Cultural Involvement, and Polyphony

    DEFF Research Database (Denmark)

    Svane, Marita; Boje, David

    2014-01-01

    to the learning from the experience. By storytelling we mean the dynamic interplay between grander narratives of the past and more emergent living stories of participants. Living story is ontological in its Being-in-the-world, its aliveness primordially in lived-life from birth to death. In this case...... (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...... of customers and many competitors. The industry is therefore characterised by a high degree of mergers and acquisitions. Despite the strategic advantages the idea of the merger was not equally attractive to both of the organisations. They had a history of being competitors with a good deal of hostility. One...

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

    Energy Technology Data Exchange (ETDEWEB)

    Shiry, J. [Woodside Research Ltd., Calgary, AB (Canada)

    1998-08-01

    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.

  3. TIDAL TAILS OF MINOR MERGERS. II. COMPARING STAR FORMATION IN THE TIDAL TAILS OF NGC 2782

    Energy Technology Data Exchange (ETDEWEB)

    Knierman, Karen A.; Scowen, Paul; Veach, Todd; Groppi, Christopher [School of Earth and Space Exploration, Arizona State University, 550 E. Tyler Mall, Room PSF-686 (P.O. Box 871404), Tempe, AZ 85287-1404 (United States); Mullan, Brendan; Charlton, Jane [Department of Astronomy and Astrophysics, Penn State University, 525 Davey Lab, University Park, PA (United States); Konstantopoulos, Iraklis [Australian Astronomical Observatory, P.O. Box 915, North Ryde NSW 1670 (Australia); Knezek, Patricia M., E-mail: karen.knierman@asu.edu, E-mail: paul.scowen@asu.edu, E-mail: tveach@asu.edu, E-mail: cgroppi@asu.edu, E-mail: mullan@astro.psu.edu, E-mail: iraklis@aao.gov.au, E-mail: pknezek@noao.edu [WIYN Consortium, Inc., 950 N. Cherry Avenue, Tucson, AZ 85719 (United States)

    2013-09-10

    The peculiar spiral NGC 2782 is the result of a minor merger with a mass ratio {approx}4: 1 occurring {approx}200 Myr ago. This merger produced a molecular and H I-rich, optically bright eastern tail and an H I-rich, optically faint western tail. Non-detection of CO in the western tail by Braine et al. suggested that star formation had not yet begun. However, deep UBVR and H{alpha} narrowband images show evidence of recent star formation in the western tail, though it lacks massive star clusters and cluster complexes. Using Herschel PACS spectroscopy, we discover 158 {mu}m [C II] emission at the location of the three most luminous H{alpha} sources in the eastern tail, but not at the location of the even brighter H{alpha} source in the western tail. The western tail is found to have a normal star formation efficiency (SFE), but the eastern tail has a low SFE. The lack of CO and [C II] emission suggests that the western tail H II region may have a low carbon abundance and be undergoing its first star formation. The western tail is more efficient at forming stars, but lacks massive clusters. We propose that the low SFE in the eastern tail may be due to its formation as a splash region where gas heating is important even though it has sufficient molecular and neutral gas to make massive star clusters. The western tail, which has lower gas surface density and does not form high-mass star clusters, is a tidally formed region where gravitational compression likely enhances star formation.

  4. TIDAL TAILS OF MINOR MERGERS. II. COMPARING STAR FORMATION IN THE TIDAL TAILS OF NGC 2782

    International Nuclear Information System (INIS)

    Knierman, Karen A.; Scowen, Paul; Veach, Todd; Groppi, Christopher; Mullan, Brendan; Charlton, Jane; Konstantopoulos, Iraklis; Knezek, Patricia M.

    2013-01-01

    The peculiar spiral NGC 2782 is the result of a minor merger with a mass ratio ∼4: 1 occurring ∼200 Myr ago. This merger produced a molecular and H I-rich, optically bright eastern tail and an H I-rich, optically faint western tail. Non-detection of CO in the western tail by Braine et al. suggested that star formation had not yet begun. However, deep UBVR and Hα narrowband images show evidence of recent star formation in the western tail, though it lacks massive star clusters and cluster complexes. Using Herschel PACS spectroscopy, we discover 158 μm [C II] emission at the location of the three most luminous Hα sources in the eastern tail, but not at the location of the even brighter Hα source in the western tail. The western tail is found to have a normal star formation efficiency (SFE), but the eastern tail has a low SFE. The lack of CO and [C II] emission suggests that the western tail H II region may have a low carbon abundance and be undergoing its first star formation. The western tail is more efficient at forming stars, but lacks massive clusters. We propose that the low SFE in the eastern tail may be due to its formation as a splash region where gas heating is important even though it has sufficient molecular and neutral gas to make massive star clusters. The western tail, which has lower gas surface density and does not form high-mass star clusters, is a tidally formed region where gravitational compression likely enhances star formation

  5. Electromagnetic Signals Following Stellar-mass Black Hole Mergers

    Energy Technology Data Exchange (ETDEWEB)

    Mink, S. E. de; King, A., E-mail: S.E.deMink@uva.nl, E-mail: ark@leicester.ac.uk [Anton Pannekoek Institute for Astronomy, University of Amsterdam, 1090 GE Amsterdam (Netherlands)

    2017-04-10

    It is often assumed that gravitational-wave (GW) events resulting from the merger of stellar-mass black holes are unlikely to produce electromagnetic (EM) counterparts. We point out that the progenitor binary has probably shed a mass ≳10 M {sub ⊙} during its prior evolution. If even a tiny fraction of this gas is retained in a circumbinary disk, the sudden mass loss and recoil of the merged black hole shocks and heats it within hours of the GW event. Whether the resulting EM signal is detectable is uncertain. The optical depth through the disk is likely to be high enough that the prompt emission consists only of photons from its optically thin skin, while the majority may take years to emerge. However, if some mechanism can release more photons in a time comparable to the few-hour energy production time, the peak luminosity of the EM signal could be detectable. For a disk retaining only ∼10{sup −3} of the mass shed in the earlier binary evolution, medium-energy X-rays to infrared emission would be observable hours after the GW event for source distances of ∼500 Mpc. Events like this may already have been observed, but ascribed to unidentified active galactic nuclei. Improved sky localization should eventually allow identification based on spatial coincidence. A detection would provide unique constraints on formation scenarios and potentially offer tests of strong-field general relativity. Accordingly, we argue that the high scientific payoff of an EM detection fully justifies search campaigns.

  6. Geometrical shock dynamics for magnetohydrodynamic fast shocks

    KAUST Repository

    Mostert, W.; Pullin, D. I.; Samtaney, Ravi; Wheatley, V.

    2016-01-01

    We describe a formulation of two-dimensional geometrical shock dynamics (GSD) suitable for ideal magnetohydrodynamic (MHD) fast shocks under magnetic fields of general strength and orientation. The resulting area–Mach-number–shock-angle relation is then incorporated into a numerical method using pseudospectral differentiation. The MHD-GSD model is verified by comparison with results from nonlinear finite-volume solution of the complete ideal MHD equations applied to a shock implosion flow in the presence of an oblique and spatially varying magnetic field ahead of the shock. Results from application of the MHD-GSD equations to the stability of fast MHD shocks in two dimensions are presented. It is shown that the time to formation of triple points for both perturbed MHD and gas-dynamic shocks increases as (Formula presented.), where (Formula presented.) is a measure of the initial Mach-number perturbation. Symmetry breaking in the MHD case is demonstrated. In cylindrical converging geometry, in the presence of an azimuthal field produced by a line current, the MHD shock behaves in the mean as in Pullin et al. (Phys. Fluids, vol. 26, 2014, 097103), but suffers a greater relative pressure fluctuation along the shock than the gas-dynamic shock. © 2016 Cambridge University Press

  7. Geometrical shock dynamics for magnetohydrodynamic fast shocks

    KAUST Repository

    Mostert, W.

    2016-12-12

    We describe a formulation of two-dimensional geometrical shock dynamics (GSD) suitable for ideal magnetohydrodynamic (MHD) fast shocks under magnetic fields of general strength and orientation. The resulting area–Mach-number–shock-angle relation is then incorporated into a numerical method using pseudospectral differentiation. The MHD-GSD model is verified by comparison with results from nonlinear finite-volume solution of the complete ideal MHD equations applied to a shock implosion flow in the presence of an oblique and spatially varying magnetic field ahead of the shock. Results from application of the MHD-GSD equations to the stability of fast MHD shocks in two dimensions are presented. It is shown that the time to formation of triple points for both perturbed MHD and gas-dynamic shocks increases as (Formula presented.), where (Formula presented.) is a measure of the initial Mach-number perturbation. Symmetry breaking in the MHD case is demonstrated. In cylindrical converging geometry, in the presence of an azimuthal field produced by a line current, the MHD shock behaves in the mean as in Pullin et al. (Phys. Fluids, vol. 26, 2014, 097103), but suffers a greater relative pressure fluctuation along the shock than the gas-dynamic shock. © 2016 Cambridge University Press

  8. Mass Ejection from the Remnant of a Binary Neutron Star Merger: Viscous-radiation Hydrodynamics Study

    Science.gov (United States)

    Fujibayashi, Sho; Kiuchi, Kenta; Nishimura, Nobuya; Sekiguchi, Yuichiro; Shibata, Masaru

    2018-06-01

    We perform long-term general relativistic neutrino radiation hydrodynamics simulations (in axisymmetry) for a massive neutron star (MNS) surrounded by a torus, which is a canonical remnant formed after the binary neutron star merger. We take into account the effects of viscosity, which is likely to arise in the merger remnant due to magnetohydrodynamical turbulence. The viscous effect plays key roles for the mass ejection from the remnant in two phases of the evolution. In the first t ≲ 10 ms, a differential rotation state of the MNS is changed to a rigidly rotating state. A shock wave caused by the variation of its quasi-equilibrium state induces significant mass ejection of mass ∼(0.5–2.0) × {10}-2 {M}ȯ for the α-viscosity parameter of 0.01–0.04. For the longer-term evolution with ∼0.1–10 s, a significant fraction of the torus material is ejected. We find that the total mass of the viscosity-driven ejecta (≳ {10}-2 {M}ȯ ) could dominate over that of the dynamical ejecta (≲ {10}-2 {M}ȯ ). The electron fraction, Y e , of the ejecta is always high enough (Y e ≳ 0.25) that this post-merger ejecta is lanthanide-poor; hence, the opacity of the ejecta is likely to be ∼10–100 times lower than that of the dynamical ejecta. This indicates that the electromagnetic signal from the ejecta would be rapidly evolving, bright, and blue if it is observed from a small viewing angle (≲45°) for which the effect of the dynamical ejecta is minor.

  9. 18 GHz SZ Measurements of the Bullet Cluster Siddharth S. Malu ...

    Indian Academy of Sciences (India)

    1E0657-56, known as the 'Bullet cluster', is one of the hottest known clusters. It is a cluster collision/merger event at z ∼0.296, with the larger, westward cluster being ∼10 times the mass of the smaller 'bullet'. It is known to have a strong radio halo (Liang et al. 2000), and the Sunyaev–Zel'dovich effect (Andreani et al. 1999;.

  10. HUBBLE CAPTURES MERGER BETWEEN QUASAR AND GALAXY

    Science.gov (United States)

    2002-01-01

    This NASA Hubble Space Telescope image shows evidence fo r a merger between a quasar and a companion galaxy. This surprising result might require theorists to rethink their explanations for the nature of quasars, the most energetic objects in the universe. The bright central object is the quasar itself, located several billion light-years away. The two wisps on the (left) of the bright central object are remnants of a bright galaxy that have been disrupted by the mutual gravitational attraction between the quasar and the companion galaxy. This provides clear evidence for a merger between the two objects. Since their discovery in 1963, quasars (quasi-stellar objects) have been enigmatic because they emit prodigious amounts of energy from a very compact source. The most widely accepted model is that a quasar is powered by a supermassive black hole in the core of a galaxy. These new observations proved a challenge for theorists as no current models predict the complex quasar interactions unveiled by Hubble. The image was taken with the Wide Field Planetary Camera-2. Credit: John Bahcall, Institute for Advanced Study, NASA.

  11. 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).

  12. The galaxy major merger fraction to {z} 1

    Science.gov (United States)

    López-Sanjuan, C.; Balcells, M.; Pérez-González, P. G.; Barro, G.; García-Dabó, C. E.; Gallego, J.; Zamorano, J.

    2009-07-01

    Aims: The importance of disc-disc major mergers in galaxy evolution remains uncertain. We study the major merger fraction in a SPITZER/IRAC-selected catalogue in the GOODS-S field up to z 1 for luminosity- and mass-limited samples. Methods: We select disc-disc merger remnants on the basis of morphological asymmetries/distortions, and address three main sources of systematic errors: (i) we explicitly apply morphological K-corrections; (ii) we measure asymmetries in galaxies artificially redshifted to zd = 1.0 to deal with loss of morphological information with redshift; and (iii) we take into account the observational errors in z and A, which tend to overestimate the merger fraction, though use of maximum likelihood techniques. Results: We obtain morphological merger fractions (f_m^mph) below 0.06 up to z 1. Parameterizing the merger fraction evolution with redshift as f_m^mph(z) = f_m^mph(0) (1+z)^m, we find that m = 1.8 ± 0.5 for MB ≤ -20 galaxies, while m = 5.4 ± 0.4 for Mstar ≥ 1010 M⊙ galaxies. When we translate our merger fractions to merger rates (Re_m^mph), their evolution, parameterized as Re_m^mph(z) = Re_m^mph(0) (1+z)^n, is quite similar in both cases: n = 3.3 ± 0.8 for MB ≤ -20 galaxies, and n = 3.5 ± 0.4 for Mstar ≥ 1010 M⊙ galaxies. Conclusions: Our results imply that only 8% of today's Mstar ≥ 1010 M⊙ galaxies have undergone a disc-disc major merger since z 1. In addition, 21% of Mstar ≥ 1010 M⊙ galaxies at z 1 have undergone one of these mergers since z 1.5. This suggests that disc-disc major mergers are not the dominant process in the evolution of Mstar ≥ 1010 M⊙ galaxies since z 1, with only 0.2 disc-disc major mergers per galaxy, but may be an important process at z > 1, with ˜1 merger per galaxy at 1 < z < 3.

  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. 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...

  15. 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.

  16. BRIGHTEST CLUSTER GALAXIES AND CORE GAS DENSITY IN REXCESS CLUSTERS

    International Nuclear Information System (INIS)

    Haarsma, Deborah B.; Leisman, Luke; Donahue, Megan; Bruch, Seth; Voit, G. Mark; Boehringer, Hans; Pratt, Gabriel W.; Pierini, Daniele; Croston, Judith H.; Arnaud, Monique

    2010-01-01

    We investigate the relationship between brightest cluster galaxies (BCGs) and their host clusters using a sample of nearby galaxy clusters from the Representative XMM-Newton Cluster Structure Survey. The sample was imaged with the Southern Observatory for Astrophysical Research in R band to investigate the mass of the old stellar population. Using a metric radius of 12 h -1 kpc, we found that the BCG luminosity depends weakly on overall cluster mass as L BCG ∝ M 0.18±0.07 cl , consistent with previous work. We found that 90% of the BCGs are located within 0.035 r 500 of the peak of the X-ray emission, including all of the cool core (CC) clusters. We also found an unexpected correlation between the BCG metric luminosity and the core gas density for non-cool-core (non-CC) clusters, following a power law of n e ∝ L 2.7±0.4 BCG (where n e is measured at 0.008 r 500 ). The correlation is not easily explained by star formation (which is weak in non-CC clusters) or overall cluster mass (which is not correlated with core gas density). The trend persists even when the BCG is not located near the peak of the X-ray emission, so proximity is not necessary. We suggest that, for non-CC clusters, this correlation implies that the same process that sets the central entropy of the cluster gas also determines the central stellar density of the BCG, and that this underlying physical process is likely to be mergers.

  17. The statistics of foreshock cavities: results of a Cluster survey

    OpenAIRE

    L. Billingham; S. J. Schwartz; D. G. Sibeck

    2008-01-01

    We use Cluster magnetic field, thermal ion, and energetic particle observations upstream of the Earth's bow shock to investigate the occurrence patterns of foreshock cavities. Such cavities are thought to form when bundles of magnetic field connect to the quasi-parallel bow shock. Shock-processed suprathermal ions can then stream along the field, back against the flow of the solar wind. These suprathermals enhance the pressure on shock-connected field lines causing them to expand into th...

  18. On the absence of radio haloes in clusters with double relics

    Science.gov (United States)

    Bonafede, A.; Cassano, R.; Brüggen, M.; Ogrean, G. A.; Riseley, C. J.; Cuciti, V.; de Gasperin, F.; Golovich, N.; Kale, R.; Venturi, T.; van Weeren, R. J.; Wik, D. R.; Wittman, D.

    2017-09-01

    Pairs of radio relics are believed to form during cluster mergers, and are best observed when the merger occurs in the plane of the sky. Mergers can also produce radio haloes, through complex processes likely linked to turbulent re-acceleration of cosmic ray electrons. However, only some clusters with double relics also show a radio halo. Here, we present a novel method to derive upper limits on the radio halo emission, and analyse archival X-ray Chandra data, as well as galaxy velocity dispersions and lensing data, in order to understand the key parameter that switches on radio halo emission. We place upper limits on the halo power below the P1.4 GHz-M500 correlation for some clusters, confirming that clusters with double relics have different radio properties. Computing X-ray morphological indicators, we find that clusters with double relics are associated with the most disturbed clusters. We also investigate the role of different mass-ratios and time-since-merger. Data do not indicate that the merger mass-ratio has an impact on the presence or absence of radio haloes (the null hypothesis that the clusters belong to the same group cannot be rejected). However, the data suggest that the absence of radio haloes could be associated with early and late mergers, but the sample is too small to perform a statistical test. Our study is limited by the small number of clusters with double relics. Future surveys with LOFAR, ASKAP, MeerKat and SKA will provide larger samples to better address this issue.

  19. Economic and organizational determinants of HMO mergers and failures.

    Science.gov (United States)

    Feldman, R; Wholey, D; Christianson, J

    1996-01-01

    This study analyzed data from all operational health maintenance organizations (HMOs) in the United States from 1986 through 1993. Eighty HMOs disappeared through mergers and 149 failed over that period. We estimated a multinomial logit model to predict whether an HMO would merge and survive, merge and disappear, or fail, relative to the probability of no event. We found that enrollment and profitability play a critical role in explaining HMO mergers and failures: large and profitable HMOs were more likely to merge and survive, but less likely to merge and disappear or fail. These results explain why HMO merger and failure rates fell after 1988, as most surviving HMOs became larger and more profitable. Among several market-area variables in the model, state anti-takeover regulations had a negative impact on mergers. Mergers were more likely in markets with more competing HMOs, but the overall market penetration of HMOs had no effect on mergers. This result may have important implications for the current debate over the future of the competitive health care strategy. If public policy successfully stimulates the development of large numbers of new HMOs, another wave of mergers and failures is likely to occur. But it appears that growth in overall HMO penetration will not lead inevitably to increased market concentration.

  20. 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

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

    Science.gov (United States)

    Melfi, Andrew; Viswanath, Divakar

    2018-05-01

    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 Elsevier Inc. All rights reserved.

  2. 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.

  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. Merger of binary neutron stars: Gravitational waves and electromagnetic counterparts

    Energy Technology Data Exchange (ETDEWEB)

    Shibata, Masaru

    2016-12-15

    Late inspiral and merger phases of binary neutron stars are the valuable new experimental fields for exploring nuclear physics because (i) gravitational waves from them will bring information for the neutron-star equation of state and (ii) the matter ejected after the onset of the merger could be the main site for the r-process nucleosynthesis. We will summarize these aspects of the binary neutron stars, describing the current understanding for the merger process of binary neutron stars that has been revealed by numerical-relativity simulations.

  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. 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.

  8. GdF-Suez. The challenges of a merger

    International Nuclear Information System (INIS)

    Lepetit, V.

    2007-01-01

    After 18 months of stamping, the GdF-Suez merger is finally started. This operation will lead to the creation of a major actor of the European energy scene in particular for natural gas and LNG. This paper reviews the stakes of this merger in terms of employment and its impacts on energy prices and markets. One goal of this merger is to gain market shares in electricity and to compete with EdF (Electricite de France), the French electric utility. (J.S.)

  9. Mergers and acquisitions: new arrangements in health care. Part 1.

    Science.gov (United States)

    Grant, E A

    1988-02-01

    Mergers and acquisitions are assuming a more important role in the healthcare industry today. These transactions require various issues be considered, such as valuation, capital planning, and so forth. In this article, the first in a five-part series on mergers and acquisitions, the fundamental methods and techniques of valuation are discussed. Some of these valuation methods, including comparative market transactions and free cash flow, are explained and examples are used to help potential purchasers and sellers to determine an organization's true value. Other articles in this series will include legal issues, tax implications, purchase investigations, and capital planning for mergers and acquisitions.

  10. Miniature shock tube for laser driven shocks.

    Science.gov (United States)

    Busquet, Michel; Barroso, Patrice; Melse, Thierry; Bauduin, Daniel

    2010-02-01

    We describe in this paper the design of a miniature shock tube (smaller than 1 cm(3)) that can be placed in a vacuum vessel and allows transverse optical probing and longitudinal backside extreme ultraviolet emission spectroscopy in the 100-500 A range. Typical application is the study of laser launched radiative shocks, in the framework of what is called "laboratory astrophysics."

  11. Are Credit Shocks Supply or Demand Shocks?

    OpenAIRE

    Bijapur, Mohan

    2013-01-01

    This paper provides new insights into the relationship between the supply of credit and the macroeconomy. We present evidence that credit shocks constitute shocks to aggregate supply in that they have a permanent effect on output and cause inflation to rise in the short term. Our results also suggest that the effects on aggregate supply have grown stronger in recent decades.

  12. Shock absorbing structure

    International Nuclear Information System (INIS)

    Kojima, Naoki; Matsushita, Kazuo.

    1992-01-01

    Small pieces of shock absorbers are filled in a space of a shock absorbing vessel which is divided into a plurality of sections by partitioning members. These sections function to prevent excess deformation or replacement of the fillers upon occurrence of falling accident. Since the shock absorbing small pieces in the shock absorbing vessel are filled irregularly, shock absorbing characteristics such as compression strength is not varied depending on the direction, but they exhibit excellent shock absorbing performance. They surely absorb shocks exerted on a transportation vessel upon falling or the like. If existing artificial fillers such as pole rings made of metal or ceramic and cut pieces such as alumium extrusion molding products are used as the shock absorbing pieces, they have excellent fire-proofness and cold resistance since the small pieces are inflammable and do not contain water. (T.M.)

  13. Melting under shock compression

    International Nuclear Information System (INIS)

    Bennett, B.I.

    1980-10-01

    A simple model, using experimentally measured shock and particle velocities, is applied to the Lindemann melting formula to predict the density, temperature, and pressure at which a material will melt when shocked from room temperature and zero pressure initial conditions

  14. Weighing galaxy clusters with gas. II. On the origin of hydrostatic mass bias in ΛCDM galaxy clusters

    International Nuclear Information System (INIS)

    Nelson, Kaylea; Nagai, Daisuke; Yu, Liang; Lau, Erwin T.; Rudd, Douglas H.

    2014-01-01

    The use of galaxy clusters as cosmological probes hinges on our ability to measure their masses accurately and with high precision. Hydrostatic mass is one of the most common methods for estimating the masses of individual galaxy clusters, which suffer from biases due to departures from hydrostatic equilibrium. Using a large, mass-limited sample of massive galaxy clusters from a high-resolution hydrodynamical cosmological simulation, in this work we show that in addition to turbulent and bulk gas velocities, acceleration of gas introduces biases in the hydrostatic mass estimate of galaxy clusters. In unrelaxed clusters, the acceleration bias is comparable to the bias due to non-thermal pressure associated with merger-induced turbulent and bulk gas motions. In relaxed clusters, the mean mass bias due to acceleration is small (≲ 3%), but the scatter in the mass bias can be reduced by accounting for gas acceleration. Additionally, this acceleration bias is greater in the outskirts of higher redshift clusters where mergers are more frequent and clusters are accreting more rapidly. Since gas acceleration cannot be observed directly, it introduces an irreducible bias for hydrostatic mass estimates. This acceleration bias places limits on how well we can recover cluster masses from future X-ray and microwave observations. We discuss implications for cluster mass estimates based on X-ray, Sunyaev-Zel'dovich effect, and gravitational lensing observations and their impact on cluster cosmology.

  15. Energy shocks and detecting influential industries

    International Nuclear Information System (INIS)

    Kang, Dongsuk; Lee, Duk Hee

    2017-01-01

    An industry's relationship of supply and demand with the energy sector can be a critical factor in the stability of its economic performance. Furthermore, the patterns of industry dependence on energy industries can be a major characteristic of entire industrial structure. This research evaluates industries' impact scores for their overall influence on other industries and vulnerability to supply and demand shocks from the energy sector. The study utilizes a sample of Korea's industrial input–output tables from 2010 to 2012. Using a chain of complementary methodologies, this study finds that among four clusters, energy, services, and raw materials are key members that can spread energy shocks to other industries. Therefore, governments need to prepare effective energy efficiency policies for these target industries. - Highlights: • We analyze an industry's impact score of its vulnerability to energy shock and inter-industrial effects. • We utilize the sample of input-output tables in Korea from 2010 to 2012. • We implement simulation, PCA, TOPSIS, cluster analysis about energy shock and industrial trades. • Subsectors of energy, services, raw material are subject to energy shock and influential to others. • These bridge industries can be targets that require policies for effective energy efficiency.

  16. Biomass shock pretreatment

    Science.gov (United States)

    Holtzapple, Mark T.; Madison, Maxine Jones; Ramirez, Rocio Sierra; Deimund, Mark A.; Falls, Matthew; Dunkelman, John J.

    2014-07-01

    Methods and apparatus for treating biomass that may include introducing a biomass to a chamber; exposing the biomass in the chamber to a shock event to produce a shocked biomass; and transferring the shocked biomass from the chamber. In some aspects, the method may include pretreating the biomass with a chemical before introducing the biomass to the chamber and/or after transferring shocked biomass from the chamber.

  17. 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.

  18. 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.

  19. 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

  20. Analyzing and executing mergers and acquisitions.

    Science.gov (United States)

    Woodard, M A; Lindstrom, K

    1997-05-01

    Healthcare organization are consolidating at an unprecedented rate. With the number of mergers and acquisitions not likely to abate, healthcare organizations will need to become involved in strategic planning to manage the effects of this transaction activity and exert more control over the direction it will take. In particular, healthcare organizations need to know how to respond when their organizations are approached about a consolidation opportunity and how to determine whether a consolidation transaction would be strategically advantageous. Healthcare organizations can increase the chances that a consolidation will be successful by following six steps: performing a business inventory; determining the desire business profile; setting criteria for selecting a partner; identifying potential buyers and sellers; negotiating terms; and closing the transaction.

  1. Relativistic Shock Acceleration

    International Nuclear Information System (INIS)

    Duffy, P.; Downes, T.P.; Gallant, Y.A.; Kirk, J.G.

    1999-01-01

    In this paper we briefly review the basic theory of shock waves in relativistic hydrodynamics and magneto-hydrodynamics, emphasising some astrophysically interesting cases. We then present an overview of the theory of particle acceleration at such shocks describing the methods used to calculate the spectral indices of energetic particles. Recent results on acceleration at ultra-relativistic shocks are discussed. (author)

  2. Neutrino flavor evolution in neutron star mergers

    Science.gov (United States)

    Tian, James Y.; Patwardhan, Amol V.; Fuller, George M.

    2017-08-01

    We examine the flavor evolution of neutrinos emitted from the disklike remnant (hereafter called "neutrino disk") of a binary neutron star (BNS) merger. We specifically follow the neutrinos emitted from the center of the disk, along the polar axis perpendicular to the equatorial plane. We carried out two-flavor simulations using a variety of different possible initial neutrino luminosities and energy spectra and, for comparison, three-flavor simulations in specific cases. In all simulations, the normal neutrino mass hierarchy was used. The flavor evolution was found to be highly dependent on the initial neutrino luminosities and energy spectra; in particular, we found two broad classes of results depending on the sign of the initial net electron neutrino lepton number (i.e., the number of neutrinos minus the number of antineutrinos). In the antineutrino-dominated case, we found that the matter-neutrino resonance effect dominates, consistent with previous results, whereas in the neutrino-dominated case, a bipolar spectral swap develops. The neutrino-dominated conditions required for this latter result have been realized, e.g., in a BNS merger simulation that employs the "DD2" equation of state for neutron star matter [Phys. Rev. D 93, 044019 (2016), 10.1103/PhysRevD.93.044019]. For this case, in addition to the swap at low energies, a collective Mikheyev-Smirnov-Wolfenstein mechanism generates a high-energy electron neutrino tail. The enhanced population of high-energy electron neutrinos in this scenario could have implications for the prospects of r -process nucleosynthesis in the material ejected outside the plane of the neutrino disk.

  3. 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.

  4. 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.

  5. 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.

  6. 76 FR 72823 - Voluntary Mergers of Federal Home Loan Banks

    Science.gov (United States)

    2011-11-28

    ... corporate law, disclosure practices that are required under the federal securities laws, and the approval standards required under federal banking laws relating to mergers of insured depository institutions. D...

  7. 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.

  8. 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.

  9. 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...

  10. 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...

  11. 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......, where union size and less so the union’s recent merger and restructuring history appears to affect shop stewards’ relations with their unions....

  12. 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

  13. 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.

  14. 7 CFR 1735.19 - Mergers and consolidations.

    Science.gov (United States)

    2010-01-01

    ... Basic Policies § 1735.19 Mergers and consolidations. RUS does not make loans for the sole purpose of... making loans to the telephone system to finance the improvement or extension of telephone service in...

  15. Mergers and Acquisitions By China's Petroleum and Chemical Companies

    Institute of Scientific and Technical Information of China (English)

    Peter Zong

    2007-01-01

    @@ In the world of mergers and acquisitions (M&A), deals by Asian players usually account for around 15% of the activity.In 2005 and 2006, however, this proportion increased and was estimated to be 18% - 20%.

  16. AN OVERVIEW ON THE DETERMINANTS OF MERGERS AND ACQUISITIONS WAVES

    Directory of Open Access Journals (Sweden)

    Vancea Mariana

    2012-12-01

    Full Text Available This paper concentrates on the presentation of the economic dimension of the mergers and acquisitions from a macroeconomic perspective. Thus, the objective of this paper is to reveal the main drivers of merger and acquisition activity. These operations take place in waves, which enters the context of changing the competition game marked by economic changes, technological evolutions, changes generated by the phenomenon of globalization, and by regulating changes. On the other side, a series of studies in the literature argue the existence of a connection between evaluating the securities and the merger and acquisition activity. This research is based on a systematic, logical and comparative analysis of scientific literature regarding the macroeconomic determinants of mergers and acquisitions.

  17. 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.

  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. 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

  20. 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.

  1. Imposed Change During Merger: Impact on Psychological Contract of employees

    OpenAIRE

    Mysore, Somashekar Sthaneshwar

    2008-01-01

    Acquisitions, amalgamation or mergers and change have been an ongoing part of the operational strategy of many organisations with the intention of achieving growth or rationalisation (Cartwright & cooper, 1992). Kavanagh and Ashkanasy (2006) have noted that amalgamation or mergers are highly complex events with a number of factors that can lead to success or failure and because they influence so many parts of the participating organisations in such fundamental ways. As such, amalgamation, mer...

  2. 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.

  3. The failing firm defence: merger policy and entry

    OpenAIRE

    Mason, Robin; Weeds, Helen

    2003-01-01

    This Paper considers the 'failing firm defence'. Under this principle, found in most antitrust jurisdictions, a merger that would otherwise be blocked due to its adverse effect on competition is permitted when the firm to be acquired is a failing firm, and an alternative, less detrimental merger is unavailable. Competition authorities have shown considerable reluctance to accept the failing firm defence, and it has been successfully used in just a handful of cases. The Paper considers the def...

  4. Evaluating mergers and acquisitions with a purchase investigation.

    Science.gov (United States)

    Grant, E A; Giniat, E J

    1988-04-01

    Mergers and acquisitions are risk transactions. Therefore, a well-planned and executed purchase investigation that considers financial, personnel, legal and risk management, third-party payer, and medical staff issues is imperative. Organizations that can successfully complete a purchase investigation will be able to make better informed, lower risk, financial decisions, and will have a competitive advantage in achieving strategic goals. This article is the third in a series on mergers and acquisitions. Other articles will include legal issues and capital planning.

  5. Mergers and acquisitions in the natural gas industry

    Energy Technology Data Exchange (ETDEWEB)

    Burkhardt, D.A.; Brown, M.L.

    1984-04-26

    Three examples of natural gas distribution companies involved in merger activity illustrate how the distribution as well as the transmission side of the industry may be attractive to potential acquiring companies seeking diversification. Although the mergers are a new phenonmenon, the acquiring firms are attracted by the overlapping service areas and the operating efficiency of the regulated distributors. They also see a possible outlet for surplus natural gas. 1 table.

  6. Electric utility mergers and acquisitions seen in a larger perspective

    Energy Technology Data Exchange (ETDEWEB)

    Hawes, D.W.

    1995-10-01

    Merger negotiations are intricate and sensitive dances which, far more often than not, may end in failure. The famed prediction of {open_quotes}50 in five{close_quotes} may prove correct - though it may be 50 utilities in 2005. Still, mergers are only a partial hedge against what may, after all, be 10 years of better prices for customers and tougher times for shareholders.

  7. Alfven shock trains

    International Nuclear Information System (INIS)

    Malkov, M.A.; Kennel, C.F.; Wu, C.C.; Pellat, R.; Shapiro, V.D.

    1991-01-01

    The Cohen--Kulsrud--Burgers equation (CKB) is used to consider the nonlinear evolution of resistive, quasiparallel Alfven waves subject to a long-wavelength, plane-polarized, monochromatic instability. The instability saturates by nonlinear steepening, which proceeds until the periodic waveform develops an interior scale length comparable to the dissipation length; a fast or an intermediate shock then forms. The result is a periodic train of Alfven shocks of one or the other type. For propagation strictly parallel to the magnetic field, there will be two shocks per instability wavelength. Numerical integration of the time-dependent CKB equation shows that an initial, small-amplitude growing wave asymptotes to a stable, periodic stationary wave whose analytic solution specifies how the type of shock embedded in the shock train, and the amplitude and speed of the shock train, depend on the strength and phase of the instability. Waveforms observed upstream of the Earth's bowshock and cometary shocks resemble those calculated here

  8. Tracking the Obscured Star Formation Along the Complete Evolutionary Merger Sequence of LIRGs

    Science.gov (United States)

    Diaz-Santos, Tanio

    2014-10-01

    We propose to obtain WFC3 narrow-band Pa-beta imaging of a sample of 24 nearby luminous infrared (IR) galaxies (LIRGs) from the Great Observatories All-sky LIRG survey (GOALS) selected to be in advanced stages of interaction. LIRGs account for half of the obscured star formation of the Universe at z ~ 1-2, and they represent a key population in galaxy formation and evolution. We will use the Pa-beta images to trace the ionized gas in LIRGs and study its spatial distribution from scales of ~ 100 pc to up to several kpc, probing the youngest, massive stars formed in the most buried environments of LIRGs due to the interaction process. This will allow us to measure how the gas in the center of mergers is converted into stars, which eventually leads to the build-up of a nuclear stellar cusp and the "inside-out" growth of bulges. We will also create spatially-resolved Pa-beta equivalent width maps to search for age gradients across the galaxies and correlate the distribution of Pa-beta emission with that of un-obscured star clusters detected in the UV and optical with HST on the same spatial scales. Finally, we will combine our data with previous studies mainly focused on isolated and early-stage interacting LIRG systems to analyze the size and compactness of the starburst along the complete merger sequence of LIRGs. The requested data represent a critical missing piece of information that will allow us to understand both the physics of merger-induced star formation and the applicability of local LIRGs as templates for high-z interacting starburst galaxies.

  9. 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

  10. The γ-rays that accompanied GW170817 and the observational signature of a magnetic jet breaking out of NS merger ejecta

    Science.gov (United States)

    Bromberg, O.; Tchekhovskoy, A.; Gottlieb, O.; Nakar, E.; Piran, T.

    2018-04-01

    We present the first relativistic magnetohydrodynamics numerical simulation of a magnetic jet that propagates through and emerges from the dynamical ejecta of a binary neutron star merger. Generated by the magnetized rotation of the merger remnant, the jet propagates through the ejecta and produces an energetic cocoon that expands at mildly relativistic velocities and breaks out of the ejecta. We show that if the ejecta has a low-mass (˜10-7 M⊙) high-velocity (v ˜ 0.85c) tail, the cocoon shock breakout will generate γ-ray emission that is comparable to the observed short GRB170817A that accompanied the recent gravitational wave event GW170817. Thus, we propose that this gamma-ray burst (GRB), which is quite different from all other short GRBs observed before, was produced by a different mechanism. We expect, however, that such events are numerous and many will be detected in coming LIGO-Virgo runs.

  11. Relics in galaxy clusters at high radio frequencies

    Science.gov (United States)

    Kierdorf, M.; Beck, R.; Hoeft, M.; Klein, U.; van Weeren, R. J.; Forman, W. R.; Jones, C.

    2017-04-01

    fronts that are observed edge-on. The polarization degrees correspond to Mach numbers of >2.2. Polarized emission is also detected in the radio relics in ZwCl 0008+52 and, for the first time, in Abell 1612. The smaller sizes and lower degrees of polarizations of the latter relics indicate a weaker shock and/or an inclination between the relic and the sky plane. Abell 1612 shows a complex X-ray surface brightness distribution, indicating a recent major merger and supporting the classification of the radio emission as a radio relic. In our cluster sample, no wavelength-dependent Faraday depolarization is detected between 4.85 GHz and 8.35 GHz, except for one component of the Toothbrush relic. Faraday depolarization between 1.38 GHz and 8.35 GHz varies with distance from the center of the host cluster 1RXS 06+42, which can be explained by a decrease in electron density and/or in strength of a turbulent (or tangled) magnetic field. Faraday rotation measures show large-scale gradients along the relics, which cannot be explained by variations in the Milky Way foreground. Conclusions: Single-dish telescopes are ideal tools to confirm relic candidates and search for new relic candidates. Measurement of the wavelength-dependent depolarization along the Toothbrush relic shows that the electron density of the intra-cluster medium (ICM) and strength of the tangled magnetic field decrease with distance from the center of the foreground cluster. Large-scale regular fields appear to be present in intergalactic space around galaxy clusters. Based on observations with the 100-m telescope at Effelsberg, operated by the Max-Planck-Institut für Radioastronomie (MPIfR) on behalf of the Max-Planck-Gesellschaft.The reduced Stokes parameter images (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/600/A18

  12. Cluster headache

    Science.gov (United States)

    Histamine headache; Headache - histamine; Migrainous neuralgia; Headache - cluster; Horton's headache; Vascular headache - cluster ... Doctors do not know exactly what causes cluster headaches. They ... (chemical in the body released during an allergic response) or ...

  13. Merging history of three bimodal clusters

    Science.gov (United States)

    Maurogordato, S.; Sauvageot, J. L.; Bourdin, H.; Cappi, A.; Benoist, C.; Ferrari, C.; Mars, G.; Houairi, K.

    2011-01-01

    We present a combined X-ray and optical analysis of three bimodal galaxy clusters selected as merging candidates at z ~ 0.1. These targets are part of MUSIC (MUlti-Wavelength Sample of Interacting Clusters), which is a general project designed to study the physics of merging clusters by means of multi-wavelength observations. Observations include spectro-imaging with XMM-Newton EPIC camera, multi-object spectroscopy (260 new redshifts), and wide-field imaging at the ESO 3.6 m and 2.2 m telescopes. We build a global picture of these clusters using X-ray luminosity and temperature maps together with galaxy density and velocity distributions. Idealized numerical simulations were used to constrain the merging scenario for each system. We show that A2933 is very likely an equal-mass advanced pre-merger ~200 Myr before the core collapse, while A2440 and A2384 are post-merger systems (~450 Myr and ~1.5 Gyr after core collapse, respectively). In the case of A2384, we detect a spectacular filament of galaxies and gas spreading over more than 1 h-1 Mpc, which we infer to have been stripped during the previous collision. The analysis of the MUSIC sample allows us to outline some general properties of merging clusters: a strong luminosity segregation of galaxies in recent post-mergers; the existence of preferential axes - corresponding to the merging directions - along which the BCGs and structures on various scales are aligned; the concomitance, in most major merger cases, of secondary merging or accretion events, with groups infalling onto the main cluster, and in some cases the evidence of previous merging episodes in one of the main components. These results are in good agreement with the hierarchical scenario of structure formation, in which clusters are expected to form by successive merging events, and matter is accreted along large-scale filaments. Based on data obtained with the European Southern Observatory, Chile (programs 072.A-0595, 075.A-0264, and 079.A-0425

  14. System Shock: The Archetype of Operational Shock

    Science.gov (United States)

    2017-05-25

    the battle space. They can also facilitate a much greater understanding of the variables involved in each party’s decision - making process. However...system shock nests within current US Army Unified Land Operations doctrine. In order to test the utility of system shock theory to Gray Zone...23 Neil E. Harrison, “Thinking about the World We Make ” in Chaos Theory in the Social Sciences: Foundations and Applications

  15. TIDAL TAILS OF MINOR MERGERS: STAR FORMATION EFFICIENCY IN THE WESTERN TAIL OF NGC 2782

    International Nuclear Information System (INIS)

    Knierman, Karen; Scowen, Paul; Jansen, Rolf A.; Knezek, Patricia M.; Wehner, Elizabeth

    2012-01-01

    While major mergers and their tidal debris are well studied, they are less common than minor mergers (mass ratios ∼ SFR ) to be several orders of magnitude less than expected from the total gas density. Together with extended FUV+NUV emission from Galaxy Evolution Explorer along the tail, this indicates a low global star formation efficiency in the tidal tail producing lower mass star clusters. The H II region that we observed has a local (few-kiloparsec scale) Σ SFR from Hα that is less than that expected from the total gas density, which is consistent with other observations of tidal debris. The star formation efficiency of this H II region inferred from the total gas density is low, but normal when inferred from the molecular gas density. These results suggest the presence of a very small, locally dense region in the western tail of NGC 2782 or of a low-metallicity and/or low-pressure star-forming region.

  16. Early Soft X-Ray to UV Emission from Double Neutron Star Mergers: Implications from the Long-term Observations of GW170817

    Science.gov (United States)

    Wang, Xiang-Yu; Huang, Zhi-Qiu

    2018-01-01

    Recent long-term radio follow-up observations of GW170817 reveal a simple power-law rising light curve, with a slope of {t}0.78, up to 93 days after the merger. The latest X-ray detection at 109 days is also consistent with such a temporal slope. Such a shallow rise behavior requires a mildly relativistic outflow with a steep velocity gradient profile, so that slower material with larger energy catches up with the decelerating ejecta and re-energizes it. It has been suggested that this mildly relativistic outflow may represent a cocoon of material. We suggest that the velocity gradient profile may form during the stage that the cocoon is breaking out of the merger ejecta, resulting from shock propagation down a density gradient. The cooling of the hot relativistic cocoon material immediately after it breaks out should have produced soft X-ray to UV radiation at tens of seconds to hours after the merger. The soft X-ray emission has a luminosity of {L}{{X}}∼ {10}45 {erg} {{{s}}}-1 over a period of tens of seconds for a merger event like GW170817. The UV emission shows a rise initially and peaks at about a few hours with a luminosity of {L}{UV}∼ {10}42 {erg} {{{s}}}-1. The soft X-ray transients could be detected by future wide-angle X-ray detectors, such as the Chinese mission Einstein Probe. This soft X-ray/UV emission would serve as one of the earliest electromagnetic counterparts of gravitation waves from double neutron star mergers and could provide the earliest localization of the sources.

  17. THE MATRYOSHKA RUN. II. TIME-DEPENDENT TURBULENCE STATISTICS, STOCHASTIC PARTICLE ACCELERATION, AND MICROPHYSICS IMPACT IN A MASSIVE GALAXY CLUSTER

    International Nuclear Information System (INIS)

    Miniati, Francesco

    2015-01-01

    We use the Matryoshka run to study the time-dependent statistics of structure-formation-driven turbulence in the intracluster medium of a 10 15 M ☉ galaxy cluster. We investigate the turbulent cascade in the inner megaparsec for both compressional and incompressible velocity components. The flow maintains approximate conditions of fully developed turbulence, with departures thereof settling in about an eddy-turnover time. Turbulent velocity dispersion remains above 700 km s –1 even at low mass accretion rate, with the fraction of compressional energy between 10% and 40%. The normalization and the slope of the compressional turbulence are susceptible to large variations on short timescales, unlike the incompressible counterpart. A major merger occurs around redshift z ≅ 0 and is accompanied by a long period of enhanced turbulence, ascribed to temporal clustering of mass accretion related to spatial clustering of matter. We test models of stochastic acceleration by compressional modes for the origin of diffuse radio emission in galaxy clusters. The turbulence simulation model constrains an important unknown of this complex problem and brings forth its dependence on the elusive microphysics of the intracluster plasma. In particular, the specifics of the plasma collisionality and the dissipation physics of weak shocks affect the cascade of compressional modes with strong impact on the acceleration rates. In this context radio halos emerge as complex phenomena in which a hierarchy of processes acting on progressively smaller scales are at work. Stochastic acceleration by compressional modes implies statistical correlation of radio power and spectral index with merging cores distance, both testable in principle with radio surveys

  18. Suzaku observations of the outskirts of the galaxy cluster Abell 3395, including a filament toward Abell 3391

    Science.gov (United States)

    Sugawara, Yuuki; Takizawa, Motokazu; Itahana, Madoka; Akamatsu, Hiroki; Fujita, Yutaka; Ohashi, Takaya; Ishisaki, Yoshitaka

    2017-12-01

    The results of Suzaku observations of the outskirts of Abell 3395, including a large-scale structure filament toward Abell 3391, are presented. We measured temperature and abundance distributions from the southern outskirt of A 3395 to the north at the virial radius, where a filament structure has been found in the former X-ray and Sunyaev-Zel'dovich (SZ) effect observations between A 3391 and A 3395. The overall temperature structure is consistent with the universal profile proposed by Okabe, N., et al. 2014, PASJ, 66, 99 for relaxed clusters, except for the filament region. A hint of intracluster medium heating is found between the two clusters, which might be due to their interaction in the early phase of a cluster merger. Although we obtained a relatively low metal abundance of Z=0.169^{+0.164+0.009+0.018}_{-0.150-0.004-0.015} solar, where the first, second, and third errors are statistical, cosmic X-ray background systematic, and non-X-ray background systematic, respectively, at the virial radius in the filament, our results are still consistent with previous results for other clusters (Z ˜ 0.3 solar) within errors. Therefore, our results are also consistent with the early enrichment scenario. We estimated Compton y parameters only from X-ray results in the region between A 3391 and A 3395 assuming a simple geometry. They are smaller than the previous SZ results with the Planck satellite. The difference could be attributed to a more elaborate geometry such as a filament inclined to the line-of-sight direction, or underestimation of the X-ray temperature because of the unresolved multi-temperature structures or undetected hot X-ray emission of the shock-heated gas.

  19. The Nature and Origin of UCDs in the Coma Cluster

    Science.gov (United States)

    Chiboucas, Kristin; Tully, R. Brent; Madrid, Juan; Phillipps, Steven; Carter, David; Peng, Eric

    2018-01-01

    UCDs are super massive star clusters found largely in dense regions but have also been found around individual galaxies and in smaller groups. Their origin is still under debate but currently favored scenarios include formation as giant star clusters, either as the brightest globular clusters or through mergers of super star clusters, themselves formed during major galaxy mergers, or as remnant nuclei from tidal stripping of nucleated dwarf ellipticals. Establishing the nature of these enigmatic objects has important implications for our understanding of star formation, star cluster formation, the missing satellite problem, and galaxy evolution. We are attempting to disentangle these competing formation scenarios with a large survey of UCDs in the Coma cluster. Using ACS two-passband imaging from the HST/ACS Coma Cluster Treasury Survey, we are using colors and sizes to identify the UCD cluster members. With a large size limited sample of the UCD population within the core region of the Coma cluster, we are investigating the population size, properties, and spatial distribution, and comparing that with the Coma globular cluster and nuclear star cluster populations to discriminate between the threshing and globular cluster scenarios. In previous work, we had found a possible correlation of UCD colors with host galaxy and a possible excess of UCDs around a non-central giant galaxy with an unusually large globular cluster population, both suggestive of a globular cluster origin. With a larger sample size and additional imaging fields that encompass the regions around these giant galaxies, we have found that the color correlation with host persists and the giant galaxy with unusually large globular cluster population does appear to host a large UCD population as well. We present the current status of the survey.

  20. 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.

  1. Making operational sense of mergers and acquisitions

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, J.E.

    1999-09-01

    Mergers and acquisitions place a new requirement on many utilities. Not only must they be operationally efficient, but they must also be able to effectively manage internal change projects that results in the integration of new and acquired businesses. Evidence from US industry suggests that this is not an easy feat. However, careful planning of integration strategy, as well as taking the proper steps to design, develop, and implement integrated overhead functions, contribute significantly to successful M and A. Fundamentally, this means choosing the right integration organizational structure, picking the right overhead functions for integration, developing complete plans for integration, and thoroughly executing those plans. For the many utilities that are attempting to develop shared services operations, a number of specific steps can be taken to avoid common pitfalls. Key among these is to develop plans in a manner very similar to the establishment of new ventures. Communicating these efforts to the affected staff and garnering executive buy-in are key aspects of the change effort. Ultimately, utilities must track the impacts of these change efforts in cost savings and service quality improvements.

  2. Simulating The Dynamical Evolution Of Galaxies In Group And Cluster Environments

    Science.gov (United States)

    Vijayaraghavan, Rukmani

    2015-07-01

    Galaxy clusters are harsh environments for their constituent galaxies. A variety of physical processes effective in these dense environments transform gas-rich, spiral, star-forming galaxies to elliptical or spheroidal galaxies with very little gas and therefore minimal star formation. The consequences of these processes are well understood observationally. Galaxies in progressively denser environments have systematically declining star formation rates and gas content. However, a theoretical understanding of of where, when, and how these processes act, and the interplay between the various galaxy transformation mechanisms in clusters remains elusive. In this dissertation, I use numerical simulations of cluster mergers as well as galaxies evolving in quiescent environments to develop a theoretical framework to understand some of the physics of galaxy transformation in cluster environments. Galaxies can be transformed in smaller groups before they are accreted by their eventual massive cluster environments, an effect termed `pre-processing'. Galaxy cluster mergers themselves can accelerate many galaxy transformation mechanisms, including tidal and ram pressure stripping of galaxies and galaxy-galaxy collisions and mergers that result in reassemblies of galaxies' stars and gas. Observationally, cluster mergers have distinct velocity and phase-space signatures depending on the observer's line of sight with respect to the merger direction. Using dark matter only as well as hydrodynamic simulations of cluster mergers with random ensembles of particles tagged with galaxy models, I quantify the effects of cluster mergers on galaxy evolution before, during, and after the mergers. Based on my theoretical predictions of the dynamical signatures of these mergers in combination with galaxy transformation signatures, one can observationally identify remnants of mergers and quantify the effect of the environment on galaxies in dense group and cluster environments. The presence of

  3. Testing Numerical Models of Cool Core Galaxy Cluster Formation with X-Ray Observations

    Science.gov (United States)

    Henning, Jason W.; Gantner, Brennan; Burns, Jack O.; Hallman, Eric J.

    2009-12-01

    Using archival Chandra and ROSAT data along with numerical simulations, we compare the properties of cool core and non-cool core galaxy clusters, paying particular attention to the region beyond the cluster cores. With the use of single and double β-models, we demonstrate a statistically significant difference in the slopes of observed cluster surface brightness profiles while the cluster cores remain indistinguishable between the two cluster types. Additionally, through the use of hardness ratio profiles, we find evidence suggesting cool core clusters are cooler beyond their cores than non-cool core clusters of comparable mass and temperature, both in observed and simulated clusters. The similarities between real and simulated clusters supports a model presented in earlier work by the authors describing differing merger histories between cool core and non-cool core clusters. Discrepancies between real and simulated clusters will inform upcoming numerical models and simulations as to new ways to incorporate feedback in these systems.

  4. The cosmic merger rate of neutron stars and black holes

    Science.gov (United States)

    Mapelli, Michela; Giacobbo, Nicola

    2018-06-01

    Six gravitational wave detections have been reported so far, providing crucial insights on the merger rate of double compact objects. We investigate the cosmic merger rate of double neutron stars (DNSs), neutron star-black hole binaries (NSBHs) and black hole binaries (BHBs) by means of population-synthesis simulations coupled with the Illustris cosmological simulation. We have performed six different simulations, considering different assumptions for the efficiency of common envelope (CE) ejection and exploring two distributions for the supernova (SN) kicks. The current BHB merger rate derived from our simulations spans from ˜150 to ˜240 Gpc-3 yr-1 and is only mildly dependent on CE efficiency. In contrast, the current merger rates of DNSs (ranging from ˜20 to ˜600 Gpc-3 yr-1) and NSBHs (ranging from ˜10 to ˜100 Gpc-3 yr-1) strongly depend on the assumptions on CE and natal kicks. The merger rate of DNSs is consistent with the one inferred from the detection of GW170817 only if a high efficiency of CE ejection and low SN kicks (drawn from a Maxwellian distribution with one dimensional root mean square σ = 15 km s-1) are assumed.

  5. 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.

  6. 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.

  7. 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.

  8. Signatures of Heavy Element Production in Neutron Star Mergers

    Science.gov (United States)

    Barnes, Jennifer

    2018-06-01

    Compact object mergers involving at least one neutron star have long been theorized to be sites of astrophysical nucleosynthesis via rapid neutron capture (the r-process). The observation in light and gravitational waves of the first neutron star merger (GW1701817) this past summer provided a stunning confirmation of this theory. Electromagnetic emission powered by the radioactive decay of freshly synthesized nuclei from mergers encodes information about the composition burned by the r-process, including whether a particular merger event synthesized the heaviest nuclei along the r-process path, or froze out at lower mass number. However, efforts to model the emission in detail must still contend with many uncertainties. For instance, the uncertain nuclear masses far from the valley of stability influence the final composition burned by the r-process, as will weak interactions operating in the merger’s immediate aftermath. This in turn can affect the color electromagnetic emission. Understanding the details of these transients’ spectra will also require a detailed accounting the electronic transitions of r-process elements and ions, in order to identify the strong transitions that underlie spectral formation. This talk will provide an overview of our current understanding of radioactive transients from mergers, with an emphasis on the role of experiment in providing critical inputs for models and reducing uncertainty.

  9. 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.

  10. Weighted Clustering

    DEFF Research Database (Denmark)

    Ackerman, Margareta; Ben-David, Shai; Branzei, Simina

    2012-01-01

    We investigate a natural generalization of the classical clustering problem, considering clustering tasks in which different instances may have different weights.We conduct the first extensive theoretical analysis on the influence of weighted data on standard clustering algorithms in both...... the partitional and hierarchical settings, characterizing the conditions under which algorithms react to weights. Extending a recent framework for clustering algorithm selection, we propose intuitive properties that would allow users to choose between clustering algorithms in the weighted setting and classify...

  11. University Merger Reforms: Rational, political, institutional or incidental processes? The case of Denmark

    DEFF Research Database (Denmark)

    Aagaard, Kurt; Hansen, Hanne Foss; Rasmussen, Jørgen Gulddahl

    Mergers have for some years been popular within the public sector in many countries this includes mergers between higher education institutions. In the Danish university and Government Research Institutions sector a process of merger took place in 2006. ‘University merger reforms’ is an analysis ...... on an organizational level demands the use of more than one conceptual model for agenda-setting - decision making and institutional restructuring,......-sector and some of the conclusions made from other kinds of merger studies. Important conclusions of the study of the three universities are that mergers and especially post-mergers processes are much more than linear, straight forward rational processes and that understanding merger processes...

  12. EVOLUTION AND DISTRIBUTION OF MAGNETIC FIELDS FROM ACTIVE GALACTIC NUCLEI IN GALAXY CLUSTERS. II. THE EFFECTS OF CLUSTER SIZE AND DYNAMICAL STATE

    International Nuclear Information System (INIS)

    Xu Hao; Li Hui; Collins, David C.; Li, Shengtai; Norman, Michael L.

    2011-01-01

    Theory and simulations suggest that magnetic fields from radio jets and lobes powered by their central super massive black holes can be an important source of magnetic fields in the galaxy clusters. This is Paper II in a series of studies where we present self-consistent high-resolution adaptive mesh refinement cosmological magnetohydrodynamic simulations that simultaneously follow the formation of a galaxy cluster and evolution of magnetic fields ejected by an active galactic nucleus. We studied 12 different galaxy clusters with virial masses ranging from 1 x 10 14 to 2 x 10 15 M sun . In this work, we examine the effects of the mass and merger history on the final magnetic properties. We find that the evolution of magnetic fields is qualitatively similar to those of previous studies. In most clusters, the injected magnetic fields can be transported throughout the cluster and be further amplified by the intracluster medium (ICM) turbulence during the cluster formation process with hierarchical mergers, while the amplification history and the magnetic field distribution depend on the cluster formation and magnetism history. This can be very different for different clusters. The total magnetic energies in these clusters are between 4 x 10 57 and 10 61 erg, which is mainly decided by the cluster mass, scaling approximately with the square of the total mass. Dynamically older relaxed clusters usually have more magnetic fields in their ICM. The dynamically very young clusters may be magnetized weakly since there is not enough time for magnetic fields to be amplified.

  13. Discovery of megaparsec-scale, low surface brightness nonthermal emission in merging galaxy clusters using the green bank telescope

    Energy Technology Data Exchange (ETDEWEB)

    Farnsworth, Damon; Rudnick, Lawrence [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church Street S.E., Minneapolis, MN 55455 (United States); Brown, Shea [Department of Physics and Astronomy, University of Iowa, 203 Van Allen Hall, Iowa City, IA 52242 (United States); Brunetti, Gianfranco [INAF/Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna (Italy)

    2013-12-20

    We present results from a study of 12 X-ray bright clusters at 1.4 GHz with the 100 m Green Bank Telescope. After subtraction of point sources using existing interferometer data, we reach a median (best) 1σ rms sensitivity level of 0.01 (0.006) μJy arcsec{sup –2}, and find a significant excess of diffuse, low surface brightness emission in 11 of 12 Abell clusters observed. We also present initial results at 1.4 GHz of A2319 from the Very Large Array. In particular, we find: (1) four new detections of diffuse structures tentatively classified as two halos (A2065, A2069) and two relics (A2067, A2073); (2) the first detection of the radio halo in A2061 at 1.4 GHz, which qualifies this as a possible ultra-steep spectrum halo source with a synchrotron spectral index of α ∼ 1.8 between 327 MHz and 1.4 GHz; (3) a ∼2 Mpc radio halo in the sloshing, minor-merger cluster A2142; (4) a >2× increase of the giant radio halo extent and luminosity in the merging cluster A2319; (5) a ∼7× increase to the integrated radio flux and >4× increase to the observed extent of the peripheral radio relic in A1367 to ∼600 kpc, which we also observe to be polarized on a similar scale; (6) significant excess emission of ambiguous nature in three clusters with embedded tailed radio galaxies (A119, A400, A3744). Our radio halo detections agree with the well-known X-ray/radio luminosity correlation, but they are larger and fainter than current radio power correlation studies would predict. The corresponding volume-averaged synchrotron emissivities are 1-2 orders of magnitude below the characteristic value found in previous studies. Some of the halo-like detections may be some type of previously unseen, low surface brightness radio halo or blend of unresolved shock structures and sub-Mpc-scale turbulent regions associated with their respective cluster merging activity. Four of the five tentative halos contain one or more X-ray cold fronts, suggesting a possible connection between gas

  14. Adiabatic invariants in stellar dynamics. 2: Gravitational shocking

    Science.gov (United States)

    Weinberg, Martin D.

    1994-01-01

    A new theory of gravitational shocking based on time-dependent perturbation theory shows that the changes in energy and angular momentum due to a slowly varying disturbance are not exponentially small for stellar dynamical systems in general. It predicts significant shock heating by slowly varying perturbations previously thought to be negligible according to the adiabatic criterion. The theory extends the scenarios traditionally computed only with the impulse approximation and is applicable to a wide class of disturbances. The approach is applied specifically to the problem of disk shocking of star clusters.

  15. A Marketing Perspective on Mergers and Acquisitions : How Marketing Integration Affects Postmerger Performance

    OpenAIRE

    Homburg, Christian; Bucerius, Matthias

    2004-01-01

    Previous research on mergers and acquisitions (M&A) has neglected marketing issues by and large. This paper examines the effects of post merger integration (PMI) in marketing (ex tent and speed of marketing integration) on M&A performance mediated by integration outcomes (magnitude of cost savings and market-related performance). Results from a survey of 232 horizontal mergers and acquisitions show that market-related performance after the merger or acquisition has a much stronger impac...

  16. Does Merger Simulation Work? A "Natural Experiment" in the Swedish Analgesics Market Market

    OpenAIRE

    Björnerstedt, Jonas; Verboven, Frank

    2012-01-01

    We exploit a natural experiment associated with a large merger in the Swedish market for analgesics (painkillers). We confront the predictions from a merger simulation study, as conducted during the investigation, with the actual merger effects over a two-year comparison window. The merger simulation model is based on a constant expenditures specification for the nested logit model (as an alternative to the typical unit demand specification). The model predicts a large price increase of 34% b...

  17. 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.

  18. 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

  19. 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?

  20. Implications of mergers and acquisitions in gas and electric markets: The role of yardstick competition in merger analysis

    Energy Technology Data Exchange (ETDEWEB)

    Reiter, H.L.

    1999-06-30

    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?

  1. Hydraulic shock absorbers

    International Nuclear Information System (INIS)

    Thatcher, G.; Davidson, D. F.

    1984-01-01

    A hydraulic shock absorber of the dash pot kind for use with electrically conducting liquid such as sodium, has magnet means for electro magnetically braking a stream of liquid discharged from the cylinder. The shock absorber finds use in a liquid metal cooled nuclear reactor for arresting control rods

  2. Our Favorite Film Shocks

    DEFF Research Database (Denmark)

    Willerslev, Rane; Suhr, Christian

    2014-01-01

    The modern medium of film has long been hailed for its capacity for producing shocks of an entertaining, thought-provoking, or even politically emancipative nature. But what is a shock, how and when does it occur, how long does it last, and are there particular techniques for producing cinematic...

  3. Climate shocks and conflict

    NARCIS (Netherlands)

    Papaioannou, Kostadis J.

    2016-01-01

    This paper offers a historical micro-level analysis of the impact of climate shocks on the incidence of civil conflict in colonial Nigeria (1912-1945). Primary historical sources on court cases, prisoners and homicides are used to capture conflict. To measure climate shocks we use the deviation

  4. 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.

  5. 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.

  6. A Framework for Understanding Post-Merger Information Systems Integration

    DEFF Research Database (Denmark)

    Alaranta, Maria; Kautz, Karlheinz

    2012-01-01

    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...... several known impediments to IS integrations. It also identifies a number of new inhibitors, as well as known and new facilitators that can bring post-merger IS integration to a success. Our findings provide relevant insights to researching and managing post-merger IS integrations. They emphasize...

  7. Managing Key Risks in Post-Merger IS Integration

    DEFF Research Database (Denmark)

    Alaranta, Mar; Mathiassen, L

    2014-01-01

    Mergers and acquisitions (M&A) require organizations to blend together different information system (IS) configurations. Unfortunately, less than 50 percent of M&A's achieve their goals, with IS integration being a major problem. Here, the authors offer a framework to help managers prepare for......, analyze, and mitigate risks during post-merger IS integration. They identify key risks relating to IS integration content, process, and context, and present five strategies for mitigating those risks. Their framework aims to help managers proactively reduce the impact of adverse events. Adopting...... the framework supported by their templates is straightforward and the time and resources required are minimal. When properly executed, adoption increases the likelihood of successful merger outcomes; the framework is thus a valuable addition to the management tool box and can be applied in collaboration...

  8. Cluster management.

    Science.gov (United States)

    Katz, R

    1992-11-01

    Cluster management is a management model that fosters decentralization of management, develops leadership potential of staff, and creates ownership of unit-based goals. Unlike shared governance models, there is no formal structure created by committees and it is less threatening for managers. There are two parts to the cluster management model. One is the formation of cluster groups, consisting of all staff and facilitated by a cluster leader. The cluster groups function for communication and problem-solving. The second part of the cluster management model is the creation of task forces. These task forces are designed to work on short-term goals, usually in response to solving one of the unit's goals. Sometimes the task forces are used for quality improvement or system problems. Clusters are groups of not more than five or six staff members, facilitated by a cluster leader. A cluster is made up of individuals who work the same shift. For example, people with job titles who work days would be in a cluster. There would be registered nurses, licensed practical nurses, nursing assistants, and unit clerks in the cluster. The cluster leader is chosen by the manager based on certain criteria and is trained for this specialized role. The concept of cluster management, criteria for choosing leaders, training for leaders, using cluster groups to solve quality improvement issues, and the learning process necessary for manager support are described.

  9. Towards a Novel Conceptual Framework for Understanding Mergers in Higher Education

    Science.gov (United States)

    Cai, Yuzhuo; Pinheiro, Rómulo; Geschwind, Lars; Aarrevaara, Timo

    2016-01-01

    This paper tries to develop a conceptual framework for a comprehensive understanding of the merger process, which is regarded as a matter of institutionalization of organizational innovation. In the framework, a number of factors affecting merger process or institutionalization of merger are identified, such as those related to environmental…

  10. Discursive "Policy Logics" of Mergers in US Higher Education: Strategy or Tragedy?

    Science.gov (United States)

    Stephenson, Sandria S.

    2011-01-01

    Mergers are part of the historical fabric of US higher education. However, the current economic recession and other policy issues have experts and academicians predicting an increase in higher education mergers in the USA. Consequently, this study analysed the discursive "policy logics" surrounding merger negotiations in US higher…

  11. 7 CFR 1717.158 - Mergers with borrowers who prepaid RUS loans.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 11 2010-01-01 2010-01-01 false Mergers with borrowers who prepaid RUS loans. 1717.158 Section 1717.158 Agriculture Regulations of the Department of Agriculture (Continued) RURAL... GUARANTEED ELECTRIC LOANS Mergers and Consolidations of Electric Borrowers § 1717.158 Mergers with borrowers...

  12. 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...

  13. Mergers in Chinese Higher Education: Lessons for Studies in a Global Context

    Science.gov (United States)

    Cai, Yuzhuo; Yang, Xi

    2016-01-01

    Since the 1990s, there have been more than 400 cases of university mergers in China, representing various types and involving 1000 public institutions. While China has provided good and abundant cases for studies on university mergers, such an opportunity has not yet been fully exploited by international scholars of university merger research.…

  14. Mergers between Governmental Research Institutes and Universities in the Danish HE Sector

    Science.gov (United States)

    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 examines the consequences of the changes seen…

  15. 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...

  16. Creditor-focused corporate governance: Evidence from mergers and acquisitions in Japan

    NARCIS (Netherlands)

    V. Mehrotra (Vikas); D. van Schaik (Dimitri); J. Spronk (Jaap); O.W. Steenbeek (Onno)

    2011-01-01

    textabstractMergers in Japan have the dubious distinction of not creating wealth for shareholders of target firms, in sharp contrast to what occurs in much of the rest of the world. Using a sample of 91 mergers from 1982 through 2003 we document several distinctive features of the merger market in

  17. 12 CFR 611.1125 - Treatment of associations not approving districtwide mergers.

    Science.gov (United States)

    2010-01-01

    ... in a districtwide merger or consolidation: (1) Discriminate in the provision of any financial service... ORGANIZATION Mergers, Consolidations, and Charter Amendments of Associations § 611.1125 Treatment of... certificates of territory for districtwide mergers or consolidations of associations, the Farm Credit...

  18. From discs to bulges: effect of mergers on the morphology of galaxies

    NARCIS (Netherlands)

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

    2015-01-01

    We study the effect of mergers on the morphology of galaxies by means of the simulated merger tree approach first proposed by Moster et al. This method combines N-body cosmological simulations and semi-analytic techniques to extract realistic initial conditions for galaxy mergers. These are then

  19. REPRODUCING THE OBSERVED ABUNDANCES IN RCB AND HdC STARS WITH POST-DOUBLE-DEGENERATE MERGER MODELS-CONSTRAINTS ON MERGER AND POST-MERGER SIMULATIONS AND PHYSICS PROCESSES

    Energy Technology Data Exchange (ETDEWEB)

    Menon, Athira; Herwig, Falk; Denissenkov, Pavel A. [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P5C2 (Canada); Clayton, Geoffrey C.; Staff, Jan [Department of Physics and Astronomy, Louisiana State University, 202 Nicholson Hall, Tower Dr., Baton Rouge, LA 70803-4001 (United States); Pignatari, Marco [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Paxton, Bill [Kavli Institute for Theoretical Physics and Department of Physics, Kohn Hall, University of California, Santa Barbara, CA 93106 (United States)

    2013-07-20

    The R Coronae Borealis (RCB) stars are hydrogen-deficient, variable stars that are most likely the result of He-CO WD mergers. They display extremely low oxygen isotopic ratios, {sup 16}O/{sup 18}O {approx_equal} 1-10, {sup 12}C/{sup 13}C {>=} 100, and enhancements up to 2.6 dex in F and in s-process elements from Zn to La, compared to solar. These abundances provide stringent constraints on the physical processes during and after the double-degenerate merger. As shown previously, O-isotopic ratios observed in RCB stars cannot result from the dynamic double-degenerate merger phase, and we now investigate the role of the long-term one-dimensional spherical post-merger evolution and nucleosynthesis based on realistic hydrodynamic merger progenitor models. We adopt a model for extra envelope mixing to represent processes driven by rotation originating in the dynamical merger. Comprehensive nucleosynthesis post-processing simulations for these stellar evolution models reproduce, for the first time, the full range of the observed abundances for almost all the elements measured in RCB stars: {sup 16}O/{sup 18}O ratios between 9 and 15, C-isotopic ratios above 100, and {approx}1.4-2.35 dex F enhancements, along with enrichments in s-process elements. The nucleosynthesis processes in our models constrain the length and temperature in the dynamic merger shell-of-fire feature as well as the envelope mixing in the post-merger phase. s-process elements originate either in the shell-of-fire merger feature or during the post-merger evolution, but the contribution from the asymptotic giant branch progenitors is negligible. The post-merger envelope mixing must eventually cease {approx}10{sup 6} yr after the dynamic merger phase before the star enters the RCB phase.

  20. REPRODUCING THE OBSERVED ABUNDANCES IN RCB AND HdC STARS WITH POST-DOUBLE-DEGENERATE MERGER MODELS—CONSTRAINTS ON MERGER AND POST-MERGER SIMULATIONS AND PHYSICS PROCESSES

    International Nuclear Information System (INIS)

    Menon, Athira; Herwig, Falk; Denissenkov, Pavel A.; Clayton, Geoffrey C.; Staff, Jan; Pignatari, Marco; Paxton, Bill

    2013-01-01

    The R Coronae Borealis (RCB) stars are hydrogen-deficient, variable stars that are most likely the result of He-CO WD mergers. They display extremely low oxygen isotopic ratios, 16 O/ 18 O ≅ 1-10, 12 C/ 13 C ≥ 100, and enhancements up to 2.6 dex in F and in s-process elements from Zn to La, compared to solar. These abundances provide stringent constraints on the physical processes during and after the double-degenerate merger. As shown previously, O-isotopic ratios observed in RCB stars cannot result from the dynamic double-degenerate merger phase, and we now investigate the role of the long-term one-dimensional spherical post-merger evolution and nucleosynthesis based on realistic hydrodynamic merger progenitor models. We adopt a model for extra envelope mixing to represent processes driven by rotation originating in the dynamical merger. Comprehensive nucleosynthesis post-processing simulations for these stellar evolution models reproduce, for the first time, the full range of the observed abundances for almost all the elements measured in RCB stars: 16 O/ 18 O ratios between 9 and 15, C-isotopic ratios above 100, and ∼1.4-2.35 dex F enhancements, along with enrichments in s-process elements. The nucleosynthesis processes in our models constrain the length and temperature in the dynamic merger shell-of-fire feature as well as the envelope mixing in the post-merger phase. s-process elements originate either in the shell-of-fire merger feature or during the post-merger evolution, but the contribution from the asymptotic giant branch progenitors is negligible. The post-merger envelope mixing must eventually cease ∼10 6 yr after the dynamic merger phase before the star enters the RCB phase

  1. Spatially Offset Active Galactic Nuclei. II. Triggering in Galaxy Mergers

    Energy Technology Data Exchange (ETDEWEB)

    Barrows, R. Scott; Comerford, Julia M. [Department of Astrophysical and Planetary Sciences, University of Colorado Boulder, Boulder, CO 80309 (United States); Greene, Jenny E. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Pooley, David, E-mail: Robert.Barrows@Colorado.edu [Department of Physics and Astronomy, Trinity University, San Antonio, TX 78212 (United States)

    2017-04-01

    Galaxy mergers are likely to play a role in triggering active galactic nuclei (AGNs), but the conditions under which this process occurs are poorly understood. In Paper I, we constructed a sample of spatially offset X-ray AGNs that represent galaxy mergers hosting a single AGN. In this paper, we use our offset AGN sample to constrain the parameters that affect AGN observability in galaxy mergers. We also construct dual-AGN samples with similar selection properties for comparison. We find that the offset AGN fraction shows no evidence for a dependence on AGN luminosity, while the dual-AGN fractions show stronger evidence for a positive dependence, suggesting that the merger events forming dual AGNs are more efficient at instigating accretion onto supermassive black holes than those forming offset AGNs. We also find that the offset and dual-AGN fractions both have a negative dependence on nuclear separation and are similar in value at small physical scales. This dependence may become stronger when restricted to high AGN luminosities, although a larger sample is needed for confirmation. These results indicate that the probability of AGN triggering increases at later merger stages. This study is the first to systematically probe down to nuclear separations of <1 kpc (∼0.8 kpc) and is consistent with predictions from simulations that AGN observability peaks in this regime. We also find that the offset AGNs are not preferentially obscured compared to the parent AGN sample, suggesting that our selection may be targeting galaxy mergers with relatively dust-free nuclear regions.

  2. Valuation of Company Merger from the Shareholders’ Point of View

    Directory of Open Access Journals (Sweden)

    Christian Toll

    2017-08-01

    Full Text Available By means of a company merger formerly legally and economically independent companies are tied up to an economic entity. To order the financial state of affairs after the merger, the current shareholders must revalue their stake in the merged company. The interest is focused on the valuation of shares and, consequently, on the allocation of the future economic benefits of the merged company to each owner. Despite the apparent relevance of company mergers in practice, the scientific literature deals with this topic only in an unsatisfying manner. After some early simple model-oriented approaches with the aim to define an ideal exchange ratio, the valuation problem of a merger was taken up again not earlier than in Hering (2004. Based on his considerations, the aim of our paper is to extend and generalize the valuation methods for a company merger and foremost to set the algebra for the computation of the critical share by using maximization of wealth as target function on a firm foundation. We assign a certain marginal quota to the shareholders representing the minimum share in the merged company which puts them in a financial position no worse than compared to the going concern basis. For this reason, we introduce the state marginal quota model as an innovative valuation approach that considers both existing market imperfections and individual expectations of a specific shareholder. To pinpoint our key finding: If private financial redistributions are available, our extended and generalized model shows that the marginal quota * in question cannot be “trivially” obtained as a ratio of utilities. Instead, it is essential to consider the private decision field of a shareholder to allow a restructuring of the dividend payout stream offered by the merged company in order to reach at least a level of utility which is comparable to the state before the merger.

  3. Spatially Offset Active Galactic Nuclei. II. Triggering in Galaxy Mergers

    Science.gov (United States)

    Barrows, R. Scott; Comerford, Julia M.; Greene, Jenny E.; Pooley, David

    2017-04-01

    Galaxy mergers are likely to play a role in triggering active galactic nuclei (AGNs), but the conditions under which this process occurs are poorly understood. In Paper I, we constructed a sample of spatially offset X-ray AGNs that represent galaxy mergers hosting a single AGN. In this paper, we use our offset AGN sample to constrain the parameters that affect AGN observability in galaxy mergers. We also construct dual-AGN samples with similar selection properties for comparison. We find that the offset AGN fraction shows no evidence for a dependence on AGN luminosity, while the dual-AGN fractions show stronger evidence for a positive dependence, suggesting that the merger events forming dual AGNs are more efficient at instigating accretion onto supermassive black holes than those forming offset AGNs. We also find that the offset and dual-AGN fractions both have a negative dependence on nuclear separation and are similar in value at small physical scales. This dependence may become stronger when restricted to high AGN luminosities, although a larger sample is needed for confirmation. These results indicate that the probability of AGN triggering increases at later merger stages. This study is the first to systematically probe down to nuclear separations of <1 kpc (˜0.8 kpc) and is consistent with predictions from simulations that AGN observability peaks in this regime. We also find that the offset AGNs are not preferentially obscured compared to the parent AGN sample, suggesting that our selection may be targeting galaxy mergers with relatively dust-free nuclear regions.

  4. Black Hole Mergers in Galactic Nuclei Induced by the Eccentric Kozai–Lidov Effect

    Science.gov (United States)

    Hoang, Bao-Minh; Naoz, Smadar; Kocsis, Bence; Rasio, Frederic A.; Dosopoulou, Fani

    2018-04-01

    Nuclear star clusters around a central massive black hole (MBH) are expected to be abundant in stellar black hole (BH) remnants and BH–BH binaries. These binaries form a hierarchical triple system with the central MBH, and gravitational perturbations from the MBH can cause high-eccentricity excitation in the BH–BH binary orbit. During this process, the eccentricity may approach unity, and the pericenter distance may become sufficiently small so that gravitational-wave emission drives the BH–BH binary to merge. In this work, we construct a simple proof-of-concept model for this process, and specifically, we study the eccentric Kozai–Lidov mechanism in unequal-mass, soft BH–BH binaries. Our model is based on a set of Monte Carlo simulations for BH–BH binaries in galactic nuclei, taking into account quadrupole- and octupole-level secular perturbations, general relativistic precession, and gravitational-wave emission. For a typical steady-state number of BH–BH binaries, our model predicts a total merger rate of ∼1–3 {Gpc} ‑3 {yr} ‑1, depending on the assumed density profile in the nucleus. Thus, our mechanism could potentially compete with other dynamical formation processes for merging BH–BH binaries, such as the interactions of stellar BHs in globular clusters or in nuclear star clusters without an MBH.

  5. Impacts of Mergers and Acquisitions on Acquirer Banks’ Performance

    Directory of Open Access Journals (Sweden)

    Burhan Ali Shah

    2017-09-01

    Full Text Available This study investigates the effects of mergers and acquisitions (M & A on the operating performance of the acquirer banks in Pakistan. For this purpose, a sample of 18 transactions, involving acquirer banks, listed on the Karachi Stock Exchange, is used. The Financial Ratio Analysis (FRA is used to determine the effects of M & A. The significance of change in the operating performances is tested through a paired sample t-test. The results indicate deterioration in the performances of the acquirer banks in the post-merger period.

  6. Hospital mergers and acquisitions: does market consolidation harm patients?

    Science.gov (United States)

    Ho, V; Hamilton, B H

    2000-09-01

    Debate continues on whether consolidation in health care markets enhances efficiency or instead facilitates market power, possibly damaging quality. We compare the quality of hospital care before and after mergers and acquisitions in California between 1992 and 1995. We analyze inpatient mortality for heart attack and stroke patients, 90-day readmission for heart attack patients, and discharge within 48 h for normal newborn babies. Recent mergers and acquisitions have not had a measurable impact on inpatient mortality, although the associated standard errors are large. Readmission rates and early discharge increased in some cases. The adverse consequences of increased market power on the quality of care require further substantiation.

  7. MERGERS, ACQUISITIONS AND BANKING CONSOLIDATION IN CENTRAL AND EASTERN EUROPE

    Directory of Open Access Journals (Sweden)

    Andreea Nicoleta Popovici

    2013-12-01

    Full Text Available Acquisitions and mergers are the growth and expansion strategies that are commonly used by the companies in all over the world because of several reasons such as increasing the profit, sales and market share, entering into new markets, operating with economics of scale, coping with managerial problems and so on. This article underlines the characteristics of mergers and acquisitions (M&A, the different types of M&A, the challenges and opportunities for the banking system in Central and Eastern Europe and we analyze the implications of the recently observed sharp expansion of foreign banks in the Central and Eastern European Countries.

  8. Recent mergers and acquisitions changes face of RSA coal

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-10-01

    During the last two years, the South African coal industry has altered dramatically, with several major mergers and acquisitions taking place affecting production and Richards Bay Coal Terminal (RBCT) entitlement. This article summarises the current position, as it happened. Events discussed include: the merger of Trans-Natal and Randcoal; Sasol becoming a member of RBCT; Tavistock`s Shell acquisition; the Duiker Mining-Lonrho acquisition; Amcoal`s purchase of Gold Fields Coal; the sale of Welgedacht Exploration Company to the Kangra Group and the formation of New Coal by Amcoal and Ingwe. 2 tabs., 2 photos.

  9. Antecedents of hospital ownership conversions, mergers, and closures.

    Science.gov (United States)

    Sloan, Frank A; Ostermann, Jan; Conover, Christopher J

    2003-01-01

    This study assesses the determinants of conversions in hospital ownership from 1986 through 1996. To place such changes in context, we also analyze causes of hospital mergers and closures, which are often alternatives to hospital ownership conversion. A consistent result from our analysis is that an important antecedent of ownership conversions is a low profit margin. Conversions from private nonprofit or government ownership to for-profit status are preceded by chronically low margins and high debt-to-asset ratios. By contrast, conversions from for-profit ownership occur quickly following declines in margins. Many mergers seem motivated by a desire to increase market power--a consideration not evident for conversions.

  10. The impact of post-merger cross-shareholdings on South African merger control policy

    Directory of Open Access Journals (Sweden)

    Chris Charter

    2012-10-01

    Full Text Available There is a concentration of EU and US standards in the South African economy. In addition, a number of large industries have been undergoing consolidation. As a result, the phenomenon of cross-holdings, both within and across industries, is not unusual. In cases where the level of cross-holding falls short of joint control, the competition authorities have at times sought to apply the co-ordinated effects doctrine or some variation thereof hoping to lessen potential competition. More recently, the Tribunal has also considered the possible unilateral effects of the acquisition of a minority stake in a rival. A number of cases has emerged that to a greater or lesser degree explores the impact of crossholdings and cross-directorships on the competitive behaviour of the firms concerned. This paper includes a review of some of these decisions with a view to determining whether any clear policy seems likely to emerge from the competition authorities. The authorities’ approach to date, reveals an evolution from reflex suspicion to a more reasoned, fact-based outlook. Cross-holdings and directorships are treated in the same way as any other evidence relevant to an analysis of a given merger. However, despite the Tribunal’s willingness to wrestle with various economic theories, the most recent decision suggests that the acquisition of a non-controlling cross-holding in a company may not fall under the analysis of South African merger regulation at all. Should that position change, following clarification by the Tribunal or an unequivocal ruling of the Competition Appeal Court, the body of case law goes some way to indicating the type and manner of analysis the authorities will employ.

  11. A cocoon shock breakout as the origin of the γ-ray emission in GW170817

    Science.gov (United States)

    Gottlieb, Ore; Nakar, Ehud; Piran, Tsvi; Hotokezaka, Kenta

    2018-06-01

    The short Gamma-Ray Burst, GRB170817A, that followed the binary neutron star merger gravitational waves signal, GW170817, is not a usual sGRB. It is weaker by three orders of magnitude than the weakest sGRB seen before and its spectra, showing a hard early signal followed by a softer thermal spectrum, is unique. We show, first, that the γ-rays must have emerged from at least mildly relativistic outflow, implying that a relativistic jet was launched following the merger. We then show that the observations are consistent with the predictions of a mildly relativistic shock breakout: a minute γ-ray energy as compared with the total energy and a rather smooth light curve with a hard to soft evolution. We present here a novel analytic study and detailed numerical 2D and 3D relativistic hydrodynamic and radiation simulations that support the picture in which the observed γ-rays arose from a shock breakout of a cocoon from the merger's ejecta (Kasliwal et al. 2017). The cocoon can be formed by either a choked jet which does not generate a sGRB (in any direction) or by a successful jet which generates an undetected regular sGRB along the system's axis pointing away from us. Remarkably, for the choked jet model, the macronova signal produced by the ejecta (which is partially boosted to high velocities by the cocoon's shock) and the radio that is produced by the interaction of the shocked cocoon material with the surrounding matter, agree with the observed UV/optical/IR emission and with current radio observations. Finally, we discuss the possibility that the jet propagation within the ejecta may photodissociate some of of the heavy elements and may affect the composition of a fraction of ejecta and, in turn, the opacity and the early macronova light.

  12. Eccentric, nonspinning, inspiral, Gaussian-process merger approximant for the detection and characterization of eccentric binary black hole mergers

    Science.gov (United States)

    Huerta, E. A.; Moore, C. J.; Kumar, Prayush; George, Daniel; Chua, Alvin J. K.; Haas, Roland; Wessel, Erik; Johnson, Daniel; Glennon, Derek; Rebei, Adam; Holgado, A. Miguel; Gair, Jonathan R.; Pfeiffer, Harald P.

    2018-01-01

    We present ENIGMA, a time domain, inspiral-merger-ringdown waveform model that describes nonspinning binary black holes systems that evolve on moderately eccentric orbits. The inspiral evolution is described using a consistent combination of post-Newtonian theory, self-force and black hole perturbation theory. Assuming eccentric binaries that circularize prior to coalescence, we smoothly match the eccentric inspiral with a stand-alone, quasicircular merger, which is constructed using machine learning algorithms that are trained with quasicircular numerical relativity waveforms. We show that ENIGMA reproduces with excellent accuracy the dynamics of quasicircular compact binaries. We validate ENIGMA using a set of Einstein Toolkit eccentric numerical relativity waveforms, which describe eccentric binary black hole mergers with mass-ratios between 1 ≤q ≤5.5 , and eccentricities e0≲0.2 ten orbits before merger. We use this model to explore in detail the physics that can be extracted with moderately eccentric, nonspinning binary black hole mergers. In particular, we use ENIGMA to show that the gravitational wave transients GW150914, GW151226, GW170104, GW170814 and GW170608 can be effectively recovered with spinning, quasicircular templates if the eccentricity of these events at a gravitational wave frequency of 10 Hz satisfies e0≤{0.175 ,0.125 ,0.175 ,0.175 ,0.125 }, respectively. We show that if these systems have eccentricities e0˜0.1 at a gravitational wave frequency of 10 Hz, they can be misclassified as quasicircular binaries due to parameter space degeneracies between eccentricity and spin corrections. Using our catalog of eccentric numerical relativity simulations, we discuss the importance of including higher-order waveform multipoles in gravitational wave searches of eccentric binary black hole mergers.

  13. Isotopic clusters

    International Nuclear Information System (INIS)

    Geraedts, J.M.P.

    1983-01-01

    Spectra of isotopically mixed clusters (dimers of SF 6 ) are calculated as well as transition frequencies. The result leads to speculations about the suitability of the laser-cluster fragmentation process for isotope separation. (Auth.)

  14. Cluster Headache

    Science.gov (United States)

    ... a role. Unlike migraine and tension headache, cluster headache generally isn't associated with triggers, such as foods, hormonal changes or stress. Once a cluster period begins, however, drinking alcohol ...

  15. First measurement of H I 21 cm emission from a GRB host galaxy indicates a post-merger system

    Science.gov (United States)

    Arabsalmani, Maryam; Roychowdhury, Sambit; Zwaan, Martin A.; Kanekar, Nissim; Michałowski, Michał J.

    2015-11-01

    We report the detection and mapping of atomic hydrogen in H I 21 cm emission from ESO 184-G82, the host galaxy of the gamma-ray burst 980425. This is the first instance where H I in emission has been detected from a galaxy hosting a gamma-ray burst (GRB). ESO 184-G82 is an isolated galaxy and contains a Wolf-Rayet region close to the location of the GRB and the associated supernova, SN 1998bw. This is one of the most luminous H II regions identified in the local Universe, with a very high inferred density of star formation. The H I 21 cm observations reveal a high H I mass for the galaxy, twice as large as the stellar mass. The spatial and velocity distribution of the H I 21 cm emission reveals a disturbed rotating gas disc, which suggests that the galaxy has undergone a recent minor merger that disrupted its rotation. We find that the Wolf-Rayet region and the GRB are both located in the highest H I column density region of the galaxy. We speculate that the merger event has resulted in shock compression of the gas, triggering extreme star formation activity, and resulting in the formation of both the Wolf-Rayet region and the GRB. The high H I column density environment of the GRB is consistent with the high H I column densities seen in absorption in the host galaxies of high-redshift GRBs.

  16. Cluster Headache

    OpenAIRE

    Pearce, Iris

    1985-01-01

    Cluster headache is the most severe primary headache with recurrent pain attacks described as worse than giving birth. The aim of this paper was to make an overview of current knowledge on cluster headache with a focus on pathophysiology and treatment. This paper presents hypotheses of cluster headache pathophysiology, current treatment options and possible future therapy approaches. For years, the hypothalamus was regarded as the key structure in cluster headache, but is now thought to be pa...

  17. Categorias Cluster

    OpenAIRE

    Queiroz, Dayane Andrade

    2015-01-01

    Neste trabalho apresentamos as categorias cluster, que foram introduzidas por Aslak Bakke Buan, Robert Marsh, Markus Reineke, Idun Reiten e Gordana Todorov, com o objetivo de categoriíicar as algebras cluster criadas em 2002 por Sergey Fomin e Andrei Zelevinsky. Os autores acima, em [4], mostraram que existe uma estreita relação entre algebras cluster e categorias cluster para quivers cujo grafo subjacente é um diagrama de Dynkin. Para isto desenvolveram uma teoria tilting na estrutura triang...

  18. Collisionless shock waves

    International Nuclear Information System (INIS)

    Sagdeev, R.Z.; Kennel, C.F.

    1991-01-01

    Collisionless shocks cannot occur naturally on the earth, because nearly all matter here consists of electrically neutral atoms and molecules. In space, however, high temperatures and ultraviolet radiation from hot stars decompose atoms into their constituent nuclei and electrons, producing a soup of electrically charged particles known as a plasma. Plasma physicists proposed that the collective electrical and magnetic properties of plasmas could produce interactions that take the place of collisions and permit shocks to form. In 1964 the theoretical work found its first experimental confirmation. Norman F. Ness and his colleagues at the Goddard Space Flight Center, using data collected from the iMP-1 spacecraft, detected clear signs that a collisionless shock exists where the solar wind encounters the earth's magnetic field. More recent research has demonstrated that collisionless shocks appear in a dazzling array of astronomical settings. For example, shocks have been found in the solar wind upstream (sunward) of all the planet and comets that have been visited by spacecraft. Violent flares on the sun generate shocks that propagate to the far reaches of the solar system; tremendous galactic outbursts create disruptions in the intergalactic medium that are trillions of times larger. In addition, many astrophysicists think that shocks from supernova explosions in our galaxy accelerate cosmic rays, a class of extraordinarily energetic elementary particles and atomic nuclei that rain down on the earth from all directions

  19. Two-stream instability in collisionless shocks and foreshock

    International Nuclear Information System (INIS)

    Dieckmann, M E; Eliasson, B; Shukla, P K; Sircombe, N J; Dendy, R O

    2006-01-01

    Shocks play a key role in plasma thermalization and particle acceleration in the near Earth space plasma, in astrophysical plasma and in laser plasma interactions. An accurate understanding of the physics of plasma shocks is thus of immense importance. We give an overview over some recent developments in particle-in-cell simulations of plasma shocks and foreshock dynamics. We focus on ion reflection by shocks and on the two-stream instabilities these beams can drive, and these are placed in the context of experimental observations, e.g. by the Cluster mission. We discuss how we may expand the insight gained from the observation of proton beam driven instabilities at near Earth plasma shocks to better understand their astrophysical counterparts, such as ion beam instabilities triggered by internal and external shocks in the relativistic jets of gamma ray bursts, shocks in the accretion discs of micro-quasars and supernova remnant shocks. It is discussed how and why the peak energy that can be reached by particles that are accelerated by two-stream instabilities increases from keV energies to GeV energies and beyond, as we increase the streaming speed to relativistic values, and why the particle energy spectrum sometimes resembles power law distributions

  20. Two-stream instability in collisionless shocks and foreshock

    Energy Technology Data Exchange (ETDEWEB)

    Dieckmann, M E [Institute of Theoretical Physics IV and Centre for Plasma Science and Astrophysics, Ruhr-University Bochum, D-44780 Bochum (Germany); Eliasson, B [Institute of Theoretical Physics IV and Centre for Plasma Science and Astrophysics, Ruhr-University Bochum, D-44780 Bochum (Germany); Shukla, P K [Institute of Theoretical Physics IV and Centre for Plasma Science and Astrophysics, Ruhr-University Bochum, D-44780 Bochum (Germany); Sircombe, N J [Centre for Fusion, Space and Astrophysics, Department of Physics, Warwick University, Coventry CV4 7AL (United Kingdom); Dendy, R O [Centre for Fusion, Space and Astrophysics, Department of Physics, Warwick University, Coventry CV4 7AL (United Kingdom)

    2006-12-15

    Shocks play a key role in plasma thermalization and particle acceleration in the near Earth space plasma, in astrophysical plasma and in laser plasma interactions. An accurate understanding of the physics of plasma shocks is thus of immense importance. We give an overview over some recent developments in particle-in-cell simulations of plasma shocks and foreshock dynamics. We focus on ion reflection by shocks and on the two-stream instabilities these beams can drive, and these are placed in the context of experimental observations, e.g. by the Cluster mission. We discuss how we may expand the insight gained from the observation of proton beam driven instabilities at near Earth plasma shocks to better understand their astrophysical counterparts, such as ion beam instabilities triggered by internal and external shocks in the relativistic jets of gamma ray bursts, shocks in the accretion discs of micro-quasars and supernova remnant shocks. It is discussed how and why the peak energy that can be reached by particles that are accelerated by two-stream instabilities increases from keV energies to GeV energies and beyond, as we increase the streaming speed to relativistic values, and why the particle energy spectrum sometimes resembles power law distributions.