University of Victoria

About: University of Victoria is a education organization based out in Victoria, British Columbia, Canada. It is known for research contribution in the topics: Population & Galaxy. The organization has 14994 authors who have published 41051 publications receiving 1447972 citations. The organization is also known as: Victoria College.

The Santa Barbara cluster comparison project: A comparison of cosmological hydrodynamics solutions

Abstract: We have simulated the formation of an X-ray cluster in a cold dark matter universe using 12 different codes. The codes span the range of numerical techniques and implementations currently in use, including smoothed particle hydrodynamics (SPH) and grid methods with fixed, deformable, or multilevel meshes. The goal of this comparison is to assess the reliability of cosmological gasdynamical simulations of clusters in the simplest astrophysically relevant case, that in which the gas is assumed to be nonradiative. We compare images of the cluster at different epochs, global properties such as mass, temperature and X-ray luminosity, and radial profiles of various dynamical and thermodynamical quantities. On the whole, the agreement among the various simulations is gratifying, although a number of discrepancies exist. Agreement is best for properties of the dark matter and worst for the total X-ray luminosity. Even in this case, simulations that adequately resolve the core radius of the gas distribution predict total X-ray luminosities that agree to within a factor of 2. Other quantities are reproduced to much higher accuracy. For example, the temperature and gas mass fraction within the virial radius agree to within about 10%, and the ratio of specific dark matter kinetic to gas thermal energies agree to within about 5%. Various factors, including differences in the internal timing of the simulations, contribute to the spread in calculated cluster properties. Based on the overall consistency of results, we discuss a number of general properties of the cluster we have modeled.

Observation of a Narrow Meson State Decaying to Ds+π0 at a Mass of 2.32 GeV/c2

Abstract: We have observed a narrow state near 2.32 GeV/c(2) in the inclusive D(+)(s)pi(0) invariant mass distribution from e(+)e(-) annihilation data at energies near 10.6 GeV. The observed width is consistent with the experimental resolution. The small intrinsic width and the quantum numbers of the final state indicate that the decay violates isospin conservation. The state has natural spin-parity and the low mass suggests a J(P)=0(+) assignment. The data sample corresponds to an integrated luminosity of 91 fb(-1) recorded by the BABAR detector at the SLAC PEP-II asymmetric-energy e(+)e(-) storage ring.

The Radial Velocity Experiment (RAVE): Fourth Data Release

Abstract: We present the stellar atmospheric parameters (effective temperature, surface gravity, overall metallicity), radial velocities, individual abundances, and distances determined for 425,561 stars, which constitute the fourth public data release of the RAdial Velocity Experiment (RAVE). The stellar atmospheric parameters are computed using a new pipeline, based on the algorithms of MATISSE and DEGAS. The spectral degeneracies and the Two Micron All Sky Survey photometric information are now better taken into consideration, improving the parameter determination compared to the previous RAVE data releases. The individual abundances for six elements (magnesium, aluminum, silicon, titanium, iron, and nickel) are also given, based on a special-purpose pipeline that is also improved compared to that available for the RAVE DR3 and Chemical DR1 data releases. Together with photometric information and proper motions, these data can be retrieved from the RAVE collaboration Web site and the Vizier database.

The effect of alliance network diversity on multinational enterprise performance

Abstract: This paper examines the impact of alliance network diversity on multinational enterprise (MNE) economic performance. We consider competing hypotheses derived, alternatively, from transaction cost theory and network theory. Using a latent variable structural equation modeling approach on a sample of 580 large MNEs, we find that MNEs with more diverse alliance networks experience lower economic performance on average than those with less diverse alliance networks. Copyright © 2005 John Wiley & Sons, Ltd.

Great Circle Tidal Streams: Evidence for a Nearly Spherical Massive Dark Halo around the Milky Way

Abstract: An all-high-latitude sky survey for cool carbon giant stars in the Galactic halo has revealed 75 such stars, of which the majority are new detections. Of these, more than half are clustered on a great circle on the sky that intersects the center of Sagittarius dwarf galaxy and is parallel to its proper-motion vector, while many of the remainder are outlying Magellanic Cloud carbon stars. Previous numerical experiments regarding the disruption of the Sagittarius dwarf galaxy (the closest of the Galactic satellite galaxies) predicted that the effect of the strong tides, during its repeated close encounters with the Milky Way, would be to slowly disrupt that galaxy. Because of the small velocity dispersion of the disrupted particles, these disperse slowly along (approximately) the orbital path of the progenitor, eventually giving rise to a very long stream of tidal debris surrounding our Galaxy. The more recently disrupted fragments of this stream should contain a mix of stellar populations similar to that found in the progenitor, which includes giant carbon stars. Given the measured position and velocity of the Sagittarius dwarf, we first integrate its orbit assuming a standard spherical model for the Galactic potential and find both that the path of the orbit intersects the position of the stream and that the radial velocity of the orbit, as viewed from the solar position, agrees very well with the observed radial velocities of the carbon stars. We also present a pole-count analysis of the carbon star distribution, which clearly indicates that the great circle stream we have isolated is statistically significant, being a 5-6 σ overdensity. These two arguments strongly support our conclusion that a large fraction of the halo carbon stars originated in the Sagittarius dwarf galaxy. The stream orbits the Galaxy between the present location of the Sagittarius dwarf, 16 kpc from the Galactic center, and the most distant stream carbon star, at ~60 kpc. It follows neither a polar nor a Galactic plane orbit, so that a large range in both Galactic R- and z-distances is probed. That the stream is observed as a great circle indicates that the Galaxy does not exert a significant torque on the stream, so the Galactic potential must be nearly spherical in the regions probed by the stream. Furthermore, the radial mass distribution of the halo must allow a particle at the position and with the velocity of the Sagittarius dwarf galaxy to reach the distance of the furthest stream carbon stars. Thus, the Sagittarius dwarf galaxy tidal stream gives a very powerful means to constrain the mass distribution it resides in, that is, the dark halo. We present N-body experiments simulating this disruption process as a function of the distribution of mass in the Galactic halo. A likelihood analysis shows that, in the Galactocentric distance range 16 kpc < R < 60 kpc, the dark halo is most likely almost spherical. We rule out, at high confidence levels, the possibility that the halo is significantly oblate, with isodensity contours of aspect qm < 0.7. This result is quite unexpected and contests currently popular galaxy formation models.