THE TILT OF THE HALO VELOCITY ELLIPSOID AND THE SHAPE OF THE MILKY WAY HALO
International Nuclear Information System (INIS)
Smith, Martin C.; Wyn Evans, N.; An, Jin H.
2009-01-01
A sample of ∼1800 halo subdwarf stars with radial velocities and proper motions is assembled from Bramich et al.'s light-motion catalog of 2008. This is based on the repeated multiband Sloan Digital Sky Survey photometric measurements in Stripe 82. Our sample of halo subdwarfs is extracted via a reduced proper motion diagram and distances are obtained using photometric parallaxes, thus giving full phase-space information. The tilt of the velocity ellipsoid with respect to the spherical polar coordinate system is computed and found to be consistent with zero for two of the three tilt angles, and very small for the third. We prove that if the inner halo is in a steady state and the triaxial velocity ellipsoid is everywhere aligned in spherical polar coordinates, then the potential must be spherically symmetric. The detectable, but very mild, misalignment with spherical polars is consistent with the perturbative effects of the Galactic disk on a spherical dark halo. Banana orbits are generated at the 1:1 resonance (in horizontal and vertical frequencies) by the disk. They populate Galactic potentials at the typical radii of our subdwarf sample, along with the much more dominant short-axis tubes. However, on geometric grounds alone, the tilt cannot vanish for the banana orbits and this leads to a slight, but detectable, misalignment. We argue that the tilt of the stellar halo velocity ellipsoid therefore provides a hitherto largely neglected but important line of argument that the Milky Way's dark halo, which dominates the potential, must be nearly spherical.
Collisionless analogs of Riemann S ellipsoids with halo
International Nuclear Information System (INIS)
Abramyan, M.G.
1987-01-01
A spheroidal halo ensures equilibrium of the collisionless analogs of the Riemann S ellipsoids with oscillations of the particles along the direction of their rotation. Sequences of collisionless triaxial ellipsoids begin and end with dynamically stable members of collisionless embedded spheroids. Both liquid and collisionless Riemann S ellipsoids with weak halo have properties that resemble those of bars of SB galaxies
Radial velocity curves of ellipsoidal red giant binaries in the Large Magellanic Cloud
International Nuclear Information System (INIS)
Nie, J. D.; Wood, P. R.
2014-01-01
Ellipsoidal red giant binaries are close binary systems where an unseen, relatively close companion distorts the red giant, leading to light variations as the red giant moves around its orbit. These binaries are likely to be the immediate evolutionary precursors of close binary planetary nebula and post-asymptotic giant branch and post-red giant branch stars. Due to the MACHO and OGLE photometric monitoring projects, the light variability nature of these ellipsoidal variables has been well studied. However, due to the lack of radial velocity curves, the nature of their masses, separations, and other orbital details has so far remained largely unknown. In order to improve this situation, we have carried out spectral monitoring observations of a large sample of 80 ellipsoidal variables in the Large Magellanic Cloud and we have derived radial velocity curves. At least 12 radial velocity points with good quality were obtained for most of the ellipsoidal variables. The radial velocity data are provided with this paper. Combining the photometric and radial velocity data, we present some statistical results related to the binary properties of these ellipsoidal variables.
Accurate mass and velocity functions of dark matter haloes
Comparat, Johan; Prada, Francisco; Yepes, Gustavo; Klypin, Anatoly
2017-08-01
N-body cosmological simulations are an essential tool to understand the observed distribution of galaxies. We use the MultiDark simulation suite, run with the Planck cosmological parameters, to revisit the mass and velocity functions. At redshift z = 0, the simulations cover four orders of magnitude in halo mass from ˜1011M⊙ with 8783 874 distinct haloes and 532 533 subhaloes. The total volume used is ˜515 Gpc3, more than eight times larger than in previous studies. We measure and model the halo mass function, its covariance matrix w.r.t halo mass and the large-scale halo bias. With the formalism of the excursion-set mass function, we explicit the tight interconnection between the covariance matrix, bias and halo mass function. We obtain a very accurate (function. We also model the subhalo mass function and its relation to the distinct halo mass function. The set of models obtained provides a complete and precise framework for the description of haloes in the concordance Planck cosmology. Finally, we provide precise analytical fits of the Vmax maximum velocity function up to redshift z publicly available in the Skies and Universes data base.
Stellar Velocity Dispersion: Linking Quiescent Galaxies to their Dark Matter Halos
Zahid, H. Jabran; Sohn, Jubee; Geller, Margaret J.
2018-01-01
We analyze the Illustris-1 hydrodynamical cosmological simulation to explore the stellar velocity dispersion of quiescent galaxies as an observational probe of dark matter halo velocity dispersion and mass. Stellar velocity dispersion is proportional to dark matter halo velocity dispersion for both central and satellite galaxies. The dark matter halos of central galaxies are in virial equilibrium and thus the stellar velocity dispersion is also proportional to dark matter halo mass. This prop...
Effects of tidal distortion on binary-star velocity curves and ellipsoidal variation
International Nuclear Information System (INIS)
Wilson, R.E.; Sofia, S.
1976-01-01
Radial velocity curves for the more massive components of binaries with extreme mass ratios can show a large distortion due to tides, as first recognized by Sterne. Binaries in which the effect is large should be rare because nearly all such binaries would be in the rapid phase of mass transfer. However, the optical counterparts of some X-ray binaries may show the effect, which would then serve as a new means of extracting considerable information from the observations. The essential parts of the computational procedure are given. Light curves for ellipsoidal variables with extreme mass ratios were also computed, and were found to be less sinusoidal than those with normal mass ratios
Revisiting the stellar velocity ellipsoid-Hubble-type relation: observations versus simulations
Pinna, F.; Falcón-Barroso, J.; Martig, M.; Martínez-Valpuesta, I.; Méndez-Abreu, J.; van de Ven, G.; Leaman, R.; Lyubenova, M.
2018-04-01
The stellar velocity ellipsoid (SVE) in galaxies can provide important information on the processes that participate in the dynamical heating of their disc components (e.g. giant molecular clouds, mergers, spiral density waves, and bars). Earlier findings suggested a strong relation between the shape of the disc SVE and Hubble type, with later-type galaxies displaying more anisotropic ellipsoids and early types being more isotropic. In this paper, we revisit the strength of this relation using an exhaustive compilation of observational results from the literature on this issue. We find no clear correlation between the shape of the disc SVE and morphological type, and show that galaxies with the same Hubble type display a wide range of vertical-to-radial velocity dispersion ratios. The points are distributed around a mean value and scatter of σz/σR = 0.7 ± 0.2. With the aid of numerical simulations, we argue that different mechanisms might influence the shape of the SVE in the same manner and that the same process (e.g. mergers) does not have the same impact in all the galaxies. The complexity of the observational picture is confirmed by these simulations, which suggest that the vertical-to-radial axis ratio of the SVE is not a good indicator of the main source of disc heating. Our analysis of those simulations also indicates that the observed shape of the disc SVE may be affected by several processes simultaneously and that the signatures of some of them (e.g. mergers) fade over time.
The velocity ellipsoid in the Galactic disc using Gaia DR1
Anguiano, Borja; Majewski, Steven R.; Freeman, Kenneth C.; Mitschang, Arik W.; Smith, Martin C.
2018-02-01
The stellar velocity ellipsoid of the solar neighbour (d Standard of Rest in Galactic rotation to be V⊙ = 13.9 ± 3.4 km s-1. A relation is found between the vertex deviation and the chemical abundances for the thin disc, ranging from -5 to +40° as iron abundance increases. For the thick disc we find a vertex deviation of luv ˜- 15°. The tilt angle (luw) in the U-W plane for the thin disc groups ranges from -10 to +15°, but there is no evident relation between luw and the mean abundances. However, we find a weak relation for luw as a function of iron abundances and α-elements for most of the groups in the thick disc, where the tilt angle decreases from -5 to -20° when [Fe/H] decreases and [α/Fe] increases. The velocity anisotropy parameter is independent of the chemical group abundances and its value is nearly constant for both discs (β ˜ 0.5), suggesting that the combined disc is dynamically relaxed.
Stellar Velocity Dispersion: Linking Quiescent Galaxies to Their Dark Matter Halos
Zahid, H. Jabran; Sohn, Jubee; Geller, Margaret J.
2018-06-01
We analyze the Illustris-1 hydrodynamical cosmological simulation to explore the stellar velocity dispersion of quiescent galaxies as an observational probe of dark matter halo velocity dispersion and mass. Stellar velocity dispersion is proportional to dark matter halo velocity dispersion for both central and satellite galaxies. The dark matter halos of central galaxies are in virial equilibrium and thus the stellar velocity dispersion is also proportional to dark matter halo mass. This proportionality holds even when a line-of-sight aperture dispersion is calculated in analogy to observations. In contrast, at a given stellar velocity dispersion, the dark matter halo mass of satellite galaxies is smaller than virial equilibrium expectations. This deviation from virial equilibrium probably results from tidal stripping of the outer dark matter halo. Stellar velocity dispersion appears insensitive to tidal effects and thus reflects the correlation between stellar velocity dispersion and dark matter halo mass prior to infall. There is a tight relation (≲0.2 dex scatter) between line-of-sight aperture stellar velocity dispersion and dark matter halo mass suggesting that the dark matter halo mass may be estimated from the measured stellar velocity dispersion for both central and satellite galaxies. We evaluate the impact of treating all objects as central galaxies if the relation we derive is applied to a statistical ensemble. A large fraction (≳2/3) of massive quiescent galaxies are central galaxies and systematic uncertainty in the inferred dark matter halo mass is ≲0.1 dex thus simplifying application of the simulation results to currently available observations.
THE ROCKSTAR PHASE-SPACE TEMPORAL HALO FINDER AND THE VELOCITY OFFSETS OF CLUSTER CORES
International Nuclear Information System (INIS)
Behroozi, Peter S.; Wechsler, Risa H.; Wu, Hao-Yi
2013-01-01
We present a new algorithm for identifying dark matter halos, substructure, and tidal features. The approach is based on adaptive hierarchical refinement of friends-of-friends groups in six phase-space dimensions and one time dimension, which allows for robust (grid-independent, shape-independent, and noise-resilient) tracking of substructure; as such, it is named ROCKSTAR (Robust Overdensity Calculation using K-Space Topologically Adaptive Refinement). Our method is massively parallel (up to 10 5 CPUs) and runs on the largest current simulations (>10 10 particles) with high efficiency (10 CPU hours and 60 gigabytes of memory required per billion particles analyzed). A previous paper has shown ROCKSTAR to have excellent recovery of halo properties; we expand on these comparisons with more tests and higher-resolution simulations. We show a significant improvement in substructure recovery compared to several other halo finders and discuss the theoretical and practical limits of simulations in this regard. Finally, we present results that demonstrate conclusively that dark matter halo cores are not at rest relative to the halo bulk or substructure average velocities and have coherent velocity offsets across a wide range of halo masses and redshifts. For massive clusters, these offsets can be up to 350 km s –1 at z = 0 and even higher at high redshifts. Our implementation is publicly available at http://code.google.com/p/rockstar.
Large-scale structure after COBE: Peculiar velocities and correlations of cold dark matter halos
Zurek, Wojciech H.; Quinn, Peter J.; Salmon, John K.; Warren, Michael S.
1994-01-01
Large N-body simulations on parallel supercomputers allow one to simultaneously investigate large-scale structure and the formation of galactic halos with unprecedented resolution. Our study shows that the masses as well as the spatial distribution of halos on scales of tens of megaparsecs in a cold dark matter (CDM) universe with the spectrum normalized to the anisotropies detected by Cosmic Background Explorer (COBE) is compatible with the observations. We also show that the average value of the relative pairwise velocity dispersion sigma(sub v) - used as a principal argument against COBE-normalized CDM models-is significantly lower for halos than for individual particles. When the observational methods of extracting sigma(sub v) are applied to the redshift catalogs obtained from the numerical experiments, estimates differ significantly between different observation-sized samples and overlap observational estimates obtained following the same procedure.
Dependence of the velocity ellipsoid for nearby stars upon metallicity and spectral type
International Nuclear Information System (INIS)
Suchkov, A.A.
1983-01-01
For nearby dwarf stars the ratios of the dispersions in the velocity components along the axes of a rectangular galactic coordinate system depend on spectral type and chemical composition (metal abundance). Relationships are established which could provide clues to such problems as whether the component populations of the Galaxy are relaxing to a steady state and how stars come to be formed with differing mass at different times
A HIGH-VELOCITY BULGE RR LYRAE VARIABLE ON A HALO-LIKE ORBIT
International Nuclear Information System (INIS)
Kunder, Andrea; Storm, J.; Rich, R. M.; Hawkins, K.; Poleski, R.; Johnson, C. I.; Shen, J.; Li, Z.-Y.; Cordero, M. J.; Nataf, D. M.; Bono, G.; Walker, A. R.; Koch, A.; De Propris, R.; Udalski, A.; Szymanski, M. K.; Soszynski, I.; Pietrzynski, G.; Ulaczyk, K.; Wyrzykowski, Ł.
2015-01-01
We report on the RR Lyrae variable star, MACHO 176.18833.411, located toward the Galactic bulge and observed within the data from the ongoing Bulge RR Lyrae Radial Velocity Assay, which has the unusual radial velocity of −372 ± 8 km s −1 and true space velocity of −482 ± 22 km s −1 relative to the Galactic rest frame. Located less than 1 kpc from the Galactic center and toward a field at (l, b) = (3, −2.5), this pulsating star has properties suggesting it belongs to the bulge RR Lyrae star population, yet a velocity indicating it is abnormal, at least with respect to bulge giants and red clump stars. We show that this star is most likely a halo interloper and therefore suggest that halo contamination is not insignificant when studying metal-poor stars found within the bulge area, even for stars within 1 kpc of the Galactic center. We discuss the possibility that MACHO 176.18833.411 is on the extreme edge of the bulge RR Lyrae radial velocity distribution, and also consider a more exotic scenario in which it is a runaway star moving through the Galaxy
A HIGH-VELOCITY BULGE RR LYRAE VARIABLE ON A HALO-LIKE ORBIT
Energy Technology Data Exchange (ETDEWEB)
Kunder, Andrea; Storm, J. [Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); Rich, R. M. [Department of Physics and Astronomy, University of California at Los Angeles, Los Angeles, CA 90095-1562 (United States); Hawkins, K. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Poleski, R. [Department of Astronomy, Ohio State University, 140 W. 18th Avenue, Columbus, OH 43210 (United States); Johnson, C. I. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Shen, J.; Li, Z.-Y. [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Cordero, M. J. [Astronomisches Rechen-Institut: Zentrum für Astronomie, Mönchhofstr. 12-14, D-69120 Heidelberg (Germany); Nataf, D. M. [Research School of Astronomy and Astrophysics, The Australian National University, Canberra, ACT 2611 (Australia); Bono, G. [Dipartimento di Fisica, Universita di Roma Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Roma (Italy); Walker, A. R. [Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603, La Serena (Chile); Koch, A. [Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, D-69117 Heidelberg (Germany); De Propris, R. [Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Turku (Finland); Udalski, A.; Szymanski, M. K.; Soszynski, I.; Pietrzynski, G.; Ulaczyk, K.; Wyrzykowski, Ł. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); and others
2015-07-20
We report on the RR Lyrae variable star, MACHO 176.18833.411, located toward the Galactic bulge and observed within the data from the ongoing Bulge RR Lyrae Radial Velocity Assay, which has the unusual radial velocity of −372 ± 8 km s{sup −1} and true space velocity of −482 ± 22 km s{sup −1} relative to the Galactic rest frame. Located less than 1 kpc from the Galactic center and toward a field at (l, b) = (3, −2.5), this pulsating star has properties suggesting it belongs to the bulge RR Lyrae star population, yet a velocity indicating it is abnormal, at least with respect to bulge giants and red clump stars. We show that this star is most likely a halo interloper and therefore suggest that halo contamination is not insignificant when studying metal-poor stars found within the bulge area, even for stars within 1 kpc of the Galactic center. We discuss the possibility that MACHO 176.18833.411 is on the extreme edge of the bulge RR Lyrae radial velocity distribution, and also consider a more exotic scenario in which it is a runaway star moving through the Galaxy.
Using velocity dispersion to estimate halo mass: Is the Local Group in tension with ΛCDM?
Elahi, Pascal J.; Power, Chris; Lagos, Claudia del P.; Poulton, Rhys; Robotham, Aaron S. G.
2018-06-01
Satellite galaxies are commonly used as tracers to measure the line-of-sight (LOS)velocity dispersion (σLOS) of the dark matter halo associated with their central galaxy, and thereby to estimate the halo's mass. Recent observational dispersion estimates of the Local Group, including the Milky Way and M31, suggest σ ˜50 km s-1, which is surprisingly low when compared to the theoretical expectation of σ ˜100 km s-1 for systems of their mass. Does this pose a problem for Lambda cold dark matter (ΛCDM)? We explore this tension using the SURFS suite of N-body simulations, containing over 10000 (sub)haloes with well tracked orbits. We test how well a central galaxy's host halo velocity dispersion can be recovered by sampling σLOS of subhaloes and surrounding haloes. Our results demonstrate that σLOS is biased mass proxy. We define an optimal window in vLOS and projected distance (Dp) - 0.5 ≲ Dp/Rvir ≲ 1.0 and vLOS ≲ 0.5Vesc, where Rvir is the virial radius and Vesc is the escape velocity - such that the scatter in LOS to halo dispersion is minimized - σLOS = (0.5 ± 0.1)σv, H. We argue that this window should be used to measure LOS dispersions as a proxy for mass, as it minimises scatter in the σLOS-Mvir relation. This bias also naturally explains the results from McConnachie (2012), who used similar cuts when estimating σLOS, LG, producing a bias of σLG = (0.44 ± 0.14)σv, H. We conclude that the Local Group's velocity dispersion does not pose a problem for ΛCDM and has a mass of log M_{LG, vir}/M_{⊙}=12.0^{+0.8}_{-2.0}.
International Nuclear Information System (INIS)
Trujillo-Gomez, Sebastian; Klypin, Anatoly; Primack, Joel; Romanowsky, Aaron J.
2011-01-01
It has long been regarded as difficult if not impossible for a cosmological model to account simultaneously for the galaxy luminosity, mass, and velocity distributions. We revisit this issue using a modern compilation of observational data along with the best available large-scale cosmological simulation of dark matter (DM). We find that the standard cosmological model, used in conjunction with halo abundance matching (HAM) and simple dynamical corrections, fits—at least on average—all basic statistics of galaxies with circular velocities V circ > 80 km s –1 calculated at a radius of ∼10 kpc. Our primary observational constraint is the luminosity-velocity (LV) relation—which generalizes the Tully-Fisher and Faber-Jackson relations in allowing all types of galaxies to be included, and provides a fundamental benchmark to be reproduced by any theory of galaxy formation. We have compiled data for a variety of galaxies ranging from dwarf irregulars to giant ellipticals. The data present a clear monotonic LV relation from ∼50 km s –1 to ∼500 km s –1 , with a bend below ∼80 km s –1 and a systematic offset between late- and early-type galaxies. For comparison to theory, we employ our new ΛCDM 'Bolshoi' simulation of DM, which has unprecedented mass and force resolution over a large cosmological volume, while using an up-to-date set of cosmological parameters. We use HAM to assign rank-ordered galaxy luminosities to the DM halos, a procedure that automatically fits the empirical luminosity function and provides a predicted LV relation that can be checked against observations. The adiabatic contraction of DM halos in response to the infall of the baryons is included as an optional model ingredient. The resulting predictions for the LV relation are in excellent agreement with the available data on both early-type and late-type galaxies for the luminosity range from M r = –14 to M r = –22. We also compare our predictions for the 'cold' baryon mass (i
Figueroa-Vinas, Adolfo; Gurgiolo, Chris A.; Nieves-Chinchilla, Teresa; Goldstein, Melvyn L.
2010-01-01
It has been suggested by a number of authors that the solar wind electron halo can be formed by the scattering of the strahl. On frequent occasions we have observed in electron angular skymaps (Phi/Theta-plots) of the electron 3D velocity distribution functions) a bursty-filament of particles connecting the strahl to the solar wind core-halo. These are seen over a very limited energy range. When the magnetic field is well off the nominal solar wind flow direction such filaments are inconsistent with any local forces and are probably the result of strong scattering. Furthermore, observations indicates that the strahl component is frequently and significantly anisotropic (Tper/Tpal approx.2). This provides a possible free energy source for the excitation of whistler waves as a possible scattering mechanism. The empirical observational evidence between the halo and the strahl suggests that the strahl population may be, at least in part, the source of the halo component.
Asymmetric Velocity Distributions from Halo Density Profiles in the Eddington Approach
International Nuclear Information System (INIS)
Vergados, J. D.
2015-01-01
We show how to obtain the energy distribution f(E) in our vicinity starting from WIMP density profiles in a self-consistent way by employing the Eddington approach and adding reasonable angular momentum dependent terms in the expression of the energy. We then show how we can obtain the velocity dispersions and the asymmetry parameter β in terms of the parameters describing the angular momentum dependence. From this expression, for f(E), we proceed to construct an axially symmetric WIMP a velocity distribution, which, for a gravitationally bound system, automatically has a velocity upper bound and is characterized by the same asymmetriy β. This approach is tested and clarified by constructing analytic expressions in a simple model, with adequate structure. We then show how such velocity distributions can be used in determining the event rates, including modulation, in both the standard and the directional WIMP searches.
Energy Technology Data Exchange (ETDEWEB)
Nishioka, S., E-mail: nishioka@ppl.appi.keio.ac.jp; Goto, I.; Hatayama, A. [Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Miyamoto, K. [School of Natural and Living Sciences Education, Naruto University of Education, 748 Nakashima, Takashima, Naruto-cho, Naruto-shi, Tokushima 772-8502 (Japan); Okuda, S.; Fukano, A. [Toshiba, 33 Isogo-chou, Isogo-ku, Yokohama-shi, Kanagawa 235-001 (Japan)
2014-02-15
Our previous study by two dimension in real space and three dimension in velocity space-particle in cell model shows that the curvature of the plasma meniscus causes the beam halo in the negative ion sources. The negative ions extracted from the periphery of the meniscus are over-focused in the extractor due to the electrostatic lens effect, and consequently become the beam halo. The purpose of this study is to verify this mechanism with the full 3D model. It is shown that the above mechanism is essentially unchanged even in the 3D model, while the fraction of the beam halo is significantly reduced to 6%. This value reasonably agrees with the experimental result.
International Nuclear Information System (INIS)
Nishioka, S.; Goto, I.; Hatayama, A.; Miyamoto, K.; Okuda, S.; Fukano, A.
2014-01-01
Our previous study by two dimension in real space and three dimension in velocity space-particle in cell model shows that the curvature of the plasma meniscus causes the beam halo in the negative ion sources. The negative ions extracted from the periphery of the meniscus are over-focused in the extractor due to the electrostatic lens effect, and consequently become the beam halo. The purpose of this study is to verify this mechanism with the full 3D model. It is shown that the above mechanism is essentially unchanged even in the 3D model, while the fraction of the beam halo is significantly reduced to 6%. This value reasonably agrees with the experimental result
Triaxial Ellipsoidal Quantum Billiards
Waalkens, Holger; Wiersig, Jan; Dullin, Holger R.
1999-01-01
The classical mechanics, exact quantum mechanics and semiclassical quantum mechanics of the billiard in the triaxial ellipsoid are investigated. The system is separable in ellipsoidal coordinates. A smooth description of the motion is given in terms of a geodesic flow on a solid torus, which is a
Gilbert, Karoline M.; Tollerud, Erik; Beaton, Rachael L.; Guhathakurta, Puragra; Bullock, James S.; Chiba, Masashi; Kalirai, Jason S.; Kirby, Evan N.; Majewski, Steven R.; Tanaka, Mikito
2018-01-01
We present the velocity dispersion of red giant branch stars in M31’s halo, derived by modeling the line-of-sight velocity distribution of over 5000 stars in 50 fields spread throughout M31’s stellar halo. The data set was obtained as part of the Spectroscopic and Photometric Landscape of Andromeda’s Stellar Halo (SPLASH) Survey, and covers projected radii of 9 to 175 kpc from M31’s center. All major structural components along the line of sight in both the Milky Way (MW) and M31 are incorporated in a Gaussian Mixture Model, including all previously identified M31 tidal debris features in the observed fields. The probability that an individual star is a constituent of M31 or the MW, based on a set of empirical photometric and spectroscopic diagnostics, is included as a prior probability in the mixture model. The velocity dispersion of stars in M31’s halo is found to decrease only mildly with projected radius, from 108 km s‑1 in the innermost radial bin (8.2 to 14.1 kpc) to ∼80 to 90 km s‑1 at projected radii of ∼40–130 kpc, and can be parameterized with a power law of slope ‑0.12 ± 0.05. The quoted uncertainty on the power-law slope reflects only the precision of the method, although other sources of uncertainty we consider contribute negligibly to the overall error budget. The data presented herein were obtained 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 Observatory was made possible by the generous financial support of the W.M. Keck Foundation.
Reference Ellipsoid and Geoid in Chronometric Geodesy
Kopeikin, Sergei M.
2016-02-01
Chronometric geodesy applies general relativity to study the problem of the shape of celestial bodies including the earth, and their gravitational field. The present paper discusses the relativistic problem of construction of a background geometric manifold that is used for describing a reference ellipsoid, geoid, the normal gravity field of the earth and for calculating geoid's undulation (height). We choose the perfect fluid with an ellipsoidal mass distribution uniformly rotating around a fixed axis as a source of matter generating the geometry of the background manifold through the Einstein equations. We formulate the post-Newtonian hydrodynamic equations of the rotating fluid to find out the set of algebraic equations defining the equipotential surface of the gravity field. In order to solve these equations we explicitly perform all integrals characterizing the interior gravitational potentials in terms of elementary functions depending on the parameters defining the shape of the body and the mass distribution. We employ the coordinate freedom of the equations to choose these parameters to make the shape of the rotating fluid configuration to be an ellipsoid of rotation. We derive expressions of the post-Newtonian mass and angular momentum of the rotating fluid as functions of the rotational velocity and the parameters of the ellipsoid including its bare density, eccentricity and semi-major axes. We formulate the post-Newtonian Pizzetti and Clairaut theorems that are used in geodesy to connect the parameters of the reference ellipsoid to the polar and equatorial values of force of gravity. We expand the post-Newtonian geodetic equations characterizing the reference ellipsoid into the Taylor series with respect to the eccentricity of the ellipsoid, and discuss the small-eccentricity approximation. Finally, we introduce the concept of relativistic geoid and its undulation with respect to the reference ellipsoid, and discuss how to calculate it in chronometric
Reference ellipsoid and geoid in chronometric geodesy
Directory of Open Access Journals (Sweden)
Sergei M Kopeikin
2016-02-01
Full Text Available Chronometric geodesy applies general relativity to study the problem of the shape of celestial bodies including the earth, and their gravitational field. The present paper discusses the relativistic problem of construction of a background geometric manifold that is used for describing a reference ellipsoid, geoid, the normal gravity field of the earth and for calculating geoid's undulation (height. We choose the perfect fluid with an ellipsoidal mass distribution uniformly rotating around a fixed axis as a source of matter generating the geometry of the background manifold through the Einstein equations. We formulate the post-Newtonian hydrodynamic equations of the rotating fluid to find out the set of algebraic equations defining the equipotential surface of the gravity field. In order to solve these equations we explicitly perform all integrals characterizing the interior gravitational potentials in terms of elementary functions depending on the parameters defining the shape of the body and the mass distribution. We employ the coordinate freedom of the equations to choose these parameters to make the shape of the rotating fluid configuration to be an ellipsoid of rotation. We derive expressions of the post-Newtonian mass and angular momentum of the rotating fluid as functions of the rotational velocity and the parameters of the ellipsoid including its bare density, eccentricity and semi-major axes. We formulate the post-Newtonian Pizzetti and Clairaut theorems that are used in geodesy to connect the parameters of the reference ellipsoid to the polar and equatorial values of force of gravity. We expand the post-Newtonian geodetic equations characterizing the reference ellipsoid into the Taylor series with respect to the eccentricity of the ellipsoid, and discuss the small-eccentricity approximation. Finally, we introduce the concept of relativistic geoid and its undulation with respect to the reference ellipsoid, and discuss how to calculate it
Reference Ellipsoid and Geoid in Chronometric Geodesy
Energy Technology Data Exchange (ETDEWEB)
Kopeikin, Sergei M., E-mail: kopeikins@missouri.edu [Department of Physics and Astronomy, University of Missouri, Columbia, MO (United States); Department of Physical Geodesy and Remote Sensing, Siberian State University of Geosystems and Technologies, Novosibirsk (Russian Federation)
2016-02-25
Chronometric geodesy applies general relativity to study the problem of the shape of celestial bodies including the earth, and their gravitational field. The present paper discusses the relativistic problem of construction of a background geometric manifold that is used for describing a reference ellipsoid, geoid, the normal gravity field of the earth and for calculating geoid's undulation (height). We choose the perfect fluid with an ellipsoidal mass distribution uniformly rotating around a fixed axis as a source of matter generating the geometry of the background manifold through the Einstein equations. We formulate the post-Newtonian hydrodynamic equations of the rotating fluid to find out the set of algebraic equations defining the equipotential surface of the gravity field. In order to solve these equations we explicitly perform all integrals characterizing the interior gravitational potentials in terms of elementary functions depending on the parameters defining the shape of the body and the mass distribution. We employ the coordinate freedom of the equations to choose these parameters to make the shape of the rotating fluid configuration to be an ellipsoid of rotation. We derive expressions of the post-Newtonian mass and angular momentum of the rotating fluid as functions of the rotational velocity and the parameters of the ellipsoid including its bare density, eccentricity and semi-major axes. We formulate the post-Newtonian Pizzetti and Clairaut theorems that are used in geodesy to connect the parameters of the reference ellipsoid to the polar and equatorial values of force of gravity. We expand the post-Newtonian geodetic equations characterizing the reference ellipsoid into the Taylor series with respect to the eccentricity of the ellipsoid, and discuss the small-eccentricity approximation. Finally, we introduce the concept of relativistic geoid and its undulation with respect to the reference ellipsoid, and discuss how to calculate it in
Effect of ion velocity on creation of point defects halos of latent tracks in LiF
Czech Academy of Sciences Publication Activity Database
Volkov, A.E.; Schwartz, K.; Medvedev, Nikita; Trautmann, C.
2017-01-01
Roč. 407, Sep (2017), s. 80-85 ISSN 0168-583X R&D Projects: GA MŠk LG15013; GA MŠk(CZ) LM2015083 Institutional support: RVO:68378271 Keywords : swift heavy ion * electronic stopping * track * LiF * color centers * defect halo Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 1.109, year: 2016
Ellipsoidal basis for isotropic oscillator
International Nuclear Information System (INIS)
Kallies, W.; Lukac, I.; Pogosyan, G.S.; Sisakyan, A.N.
1994-01-01
The solutions of the Schroedinger equation are derived for the isotropic oscillator potential in the ellipsoidal coordinate system. The explicit expression is obtained for the ellipsoidal integrals of motion through the components of the orbital moment and Demkov's tensor. The explicit form of the ellipsoidal basis is given for the lowest quantum numbers. 10 refs.; 1 tab. (author)
Post-Newtonian reference ellipsoid for relativistic geodesy
Kopeikin, Sergei; Han, Wenbiao; Mazurova, Elena
2016-02-01
We apply general relativity to construct the post-Newtonian background manifold that serves as a reference spacetime in relativistic geodesy for conducting a relativistic calculation of the geoid's undulation and the deflection of the plumb line from the vertical. We chose an axisymmetric ellipsoidal body made up of a perfect homogeneous fluid uniformly rotating around a fixed axis, as a source generating the reference geometry of the background manifold through Einstein's equations. We then reformulate and extend hydrodynamic calculations of rotating fluids done by a number of previous researchers for astrophysical applications to the realm of relativistic geodesy to set up algebraic equations defining the shape of the post-Newtonian reference ellipsoid. To complete this task, we explicitly perform all integrals characterizing gravitational field potentials inside the fluid body and represent them in terms of the elementary functions depending on the eccentricity of the ellipsoid. We fully explore the coordinate (gauge) freedom of the equations describing the post-Newtonian ellipsoid and demonstrate that the fractional deviation of the post-Newtonian level surface from the Maclaurin ellipsoid can be made much smaller than the previously anticipated estimate based on the astrophysical application of the coordinate gauge advocated by Bardeen and Chandrasekhar. We also derive the gauge-invariant relations of the post-Newtonian mass and the constant angular velocity of the rotating fluid with the parameters characterizing the shape of the post-Newtonian ellipsoid including its eccentricity, a semiminor axis, and a semimajor axis. We formulate the post-Newtonian theorems of Pizzetti and Clairaut that are used in geodesy to connect the geometric parameters of the reference ellipsoid to the physically measurable force of gravity at the pole and equator of the ellipsoid. Finally, we expand the post-Newtonian geodetic equations describing the post-Newtonian ellipsoid to
Galactic Subsystems on the Basis of Cumulative Distribution of Space Velocities
Directory of Open Access Journals (Sweden)
Vidojević, S.
2008-12-01
Full Text Available A sample containing $4,614$ stars with available space velocities and high-quality kinematical data from the Arihip Catalogue is formed. For the purpose of distinguishing galactic subsystems the cumulative distribution of space velocities is studied. The fractions of the three subsystems are found to be: thin disc 92\\%, thick disc 6\\% and halo 2\\%. These results are verified by analysing the elements of velocity ellipsoids and the shape and size of the galactocentric orbits of the sample stars, i.e. the planar and vertical eccentricities of the orbits.
International Nuclear Information System (INIS)
Kwak, Kyujin; Shelton, Robin L.; Raley, Elizabeth A.
2009-01-01
In the Galactic fountain scenario, supernovae and/or stellar winds propel material into the Galactic halo. As the material cools, it condenses into clouds. By using FLASH three-dimensional magnetohydrodynamic simulations, we model and study the dynamical evolution of these gas clouds after they form and begin to fall toward the Galactic plane. In our simulations, we assume that the gas clouds form at a height of z = 5 kpc above the Galactic midplane, then begin to fall from rest. We investigate how the cloud's evolution, dynamics, and interaction with the interstellar medium (ISM) are affected by the initial mass of the cloud. We find that clouds with sufficiently large initial densities (n ≥ 0.1 H atoms cm -3 ) accelerate sufficiently and maintain sufficiently large column densities as to be observed and identified as high-velocity clouds (HVCs) even if the ISM is weakly magnetized (1.3 μG). However, the ISM can provide noticeable resistance to the motion of a low-density cloud (n ≤ 0.01 H atoms cm -3 ) thus making it more probable that a low-density cloud will attain the speed of an intermediate-velocity cloud rather than the speed of an HVC. We also investigate the effects of various possible magnetic field configurations. As expected, the ISM's resistance is greatest when the magnetic field is strong and perpendicular to the motion of the cloud. The trajectory of the cloud is guided by the magnetic field lines in cases where the magnetic field is oriented diagonal to the Galactic plane. The model cloud simulations show that the interactions between the cloud and the ISM can be understood via analogy to the shock tube problem which involves shock and rarefaction waves. We also discuss accelerated ambient gas, streamers of material ablated from the clouds, and the cloud's evolution from a sphere-shaped to a disk- or cigar-shaped object.
Shape matters: The case for Ellipsoids and Ellipsoidal Water
Energy Technology Data Exchange (ETDEWEB)
Tillack, Andreas F. [ORNL; Robinson, Bruce H. [University of Washington, Seattle
2017-11-01
We describe the shape potentials used for the van der Waals interactions between soft-ellipsoids used to coarse-grain molecular moieties in our Metropolis Monte-Carlo simulation software. The morphologies resulting from different expressions for these van der Waals interaction potentials are discussed for the case of a prolate spheroid system with a strong dipole at the ellipsoid center. We also show that the calculation of ellipsoids is, at worst, only about fivefold more expensive computationally when compared to a simple Lennard- Jones sphere. Finally, as an application of the ellipsoidal shape we parametrize water from the original SPC water model and observe – just through the difference in shape alone – a significant improvement of the O-O radial distribution function when compared to experimental data.
The Excursion Set Theory of Halo Mass Functions, Halo Clustering, and Halo Growth
Zentner, Andrew R.
I review the excursion set theory with particular attention toward applications to cold dark matter halo formation and growth, halo abundance, and halo clustering. After a brief introduction to notation and conventions, I begin by recounting the heuristic argument leading to the mass function of bound objects given by Press and Schechter. I then review the more formal derivation of the Press-Schechter halo mass function that makes use of excursion sets of the density field. The excursion set formalism is powerful and can be applied to numerous other problems. I review the excursion set formalism for describing both halo clustering and bias and the properties of void regions. As one of the most enduring legacies of the excursion set approach and one of its most common applications, I spend considerable time reviewing the excursion set theory of halo growth. This section of the review culminates with the description of two Monte Carlo methods for generating ensembles of halo mass accretion histories. In the last section, I emphasize that the standard excursion set approach is the result of several simplifying assumptions. Dropping these assumptions can lead to more faithful predictions and open excursion set theory to new applications. One such assumption is that the height of the barriers that define collapsed objects is a constant function of scale. I illustrate the implementation of the excursion set approach for barriers of arbitrary shape. One such application is the now well-known improvement of the excursion set mass function derived from the "moving" barrier for ellipsoidal collapse. I also emphasize that the statement that halo accretion histories are independent of halo environment in the excursion set approach is not a general prediction of the theory. It is a simplifying assumption. I review the method for constructing correlated random walks of the density field in the more general case. I construct a simple toy model to illustrate that excursion set
Magnetostatics of anisotropic superconducting ellipsoid
International Nuclear Information System (INIS)
Saif, A.G.
1987-09-01
The magnetization and the magnetic field distribution inside (outside) an anisotropic type II superconducting ellipsoid, with filamentary structure, is formulated. We have shown that the magnetic field in this case is different from that of the general anisotropic one. The nucleations of the flux lines for specimens with large demagnetization factors are theoretically studied. We have shown that the nucleations of the flux lines, for specimens with large demagnetization factor, appears at a field larger than that of ellipsoidal shape. (author). 15 refs
Stability of congruent Darwin ellipsoids
International Nuclear Information System (INIS)
Tassoul, M.
1975-01-01
The problem of synchronous oscillations of congruent Darwin ellipsoids is reconsidered. Contrary to results obtained by Chandrasekhar, it is shown that along a Darwin sequence the configurations remain stable with respect to ellipsoidal disturbances until they become too closely spaced. The precise limit which separates stable from unstable systems is found. Apart from some minor differences the Darwin sequence is the exact analog of the Roche sequence
Simonson, S. Christian
2018-04-01
Two anomalous-velocity H I features, High-Velocity Cloud Complex H (HVC H) (Blitz et al. 1999), and Weaver's "jet" (Weaver 1974), appear to be good candidates for dwarf satellites. In this work they are modeled as H I disks in dark matter halos that move in 3D orbits in the combined time-dependent gravitational fields of the Milky Way and M31. As they orbit in the Local Group they develop tidal distortions and produce debris. The current l,b,V appearance of the tidal features as they approach the Milky Way indicate distances of 27 ± 9 kpc for HVC H and 108 ± 36 kpc for Weaver's "jet". As these are within the distances to known Milky Way satellites, finding stellar components would be of interest for the star formation history of the Milky Way. This work uses recent Hubble Space Telescope results on M31 (van der Marel et al. 2012) to calculate the center-of-mass (COM) locations and the dark matter mass distributions of the Milky-Way—M31 system since the Big Bang. Time-dependent COM orbits of the satellites have been computed in 3D, along with rings of test particles representing their disks. Tidal effects that develop on these rings have been compared with published 21-cm line data from Lockman (2003) and Simonson (1975). For HVC H at l = 130.5°, b = +1.5°, V = -200 km/s, the dark matter mass (in solar masses) is estimated as 5.2 ± 3.5E8. The previously estimated H I mass is 6.4E6, or 1.2% of the newly derived satellite mass. For Weaver's "jet", which covers 2° by 7° at l = 197.3°, b = +2.1°, V = -30 to -87 km/s, the dark matter mass is estimated as 1.8 ± 0.6E9. The H I mass is 1.8 ± 1.1E8, or 6% to 12% of the satellite mass. In the case of HVC H, owing to its disk angle of 45°, tidal debris is thrown upward. This would presumably contribute to a halo star stream. In the case of Weaver's "jet", the streamer represents accreting material for the disk. I am grateful to Leo Blitz for bringing Lockman's work on HVC H to my attention and for many helpful
Attractive ellipsoids in robust control
Poznyak, Alexander; Azhmyakov, Vadim
2014-01-01
This monograph introduces a newly developed robust-control design technique for a wide class of continuous-time dynamical systems called the “attractive ellipsoid method.” Along with a coherent introduction to the proposed control design and related topics, the monograph studies nonlinear affine control systems in the presence of uncertainty and presents a constructive and easily implementable control strategy that guarantees certain stability properties. The authors discuss linear-style feedback control synthesis in the context of the above-mentioned systems. The development and physical implementation of high-performance robust-feedback controllers that work in the absence of complete information is addressed, with numerous examples to illustrate how to apply the attractive ellipsoid method to mechanical and electromechanical systems. While theorems are proved systematically, the emphasis is on understanding and applying the theory to real-world situations. Attractive Ellipsoids in Robust Control will a...
Effective ellipsoidal models for wavefield extrapolation in tilted orthorhombic media
Waheed, Umair Bin
2016-04-22
Wavefield computations using the ellipsoidally anisotropic extrapolation operator offer significant cost reduction compared to that for the orthorhombic case, especially when the symmetry planes are tilted and/or rotated. However, ellipsoidal anisotropy does not provide accurate wavefield representation or imaging for media of orthorhombic symmetry. Therefore, we propose the use of ‘effective ellipsoidally anisotropic’ models that correctly capture the kinematic behaviour of wavefields for tilted orthorhombic (TOR) media. We compute effective velocities for the ellipsoidally anisotropic medium using kinematic high-frequency representation of the TOR wavefield, obtained by solving the TOR eikonal equation. The effective model allows us to use the cheaper ellipsoidally anisotropic wave extrapolation operators. Although the effective models are obtained by kinematic matching using high-frequency asymptotic, the resulting wavefield contains most of the critical wavefield components, including frequency dependency and caustics, if present, with reasonable accuracy. The proposed methodology offers a much better cost versus accuracy trade-off for wavefield computations in TOR media, particularly for media of low to moderate anisotropic strength. Furthermore, the computed wavefield solution is free from shear-wave artefacts as opposed to the conventional finite-difference based TOR wave extrapolation scheme. We demonstrate applicability and usefulness of our formulation through numerical tests on synthetic TOR models. © 2016 Institute of Geophysics of the ASCR, v.v.i
Ellipsoid analysis of calvarial shape.
Jacobsen, Petra A; Becker, Devra; Govier, Daniel P; Krantz, Steven G; Kane, Alex
2009-09-01
The purpose of this research was to develop a novel quantitative method of describing calvarial shape by using ellipsoid geometry. The pilot application of Ellipsoid Analysis was to compare calvarial form among individuals with untreated unilateral coronal synostosis, metopic synostosis, and sagittal synostosis and normal subjects. The frontal, parietal, and occipital bones of 10 preoperative patients for each of the four study groups were bilaterally segmented into six regions using three-dimensional skull reconstructions generated by ANALYZE imaging software from high-resolution computed tomography scans. Points along each segment were extracted and manipulated using a MATLAB-based program. The points were fit to the least-squares nearest ellipsoid. Relationships between the six resultant right and left frontal, parietal, and occipital ellipsoidal centroids (FR, FL, PR, PL, OR, and OL, respectively) were tested for association with a synostotic group. Results from the pilot study showed meaningful differences between length ratio, angular, and centroid distance relationships among synostotic groups. The most substantial difference was exhibited in the centroid distance PL-PR between patients with sagittal synostosis and metopic synostosis. The measures most commonly significant were centroid distances FL-PR and FL-PL and the angle OR-FR-PR. Derived centroid relationships were reproducible. Ellipsoid Analysis may offer a more refined approach to quantitative analysis of cranial shape. Symmetric and asymmetric forms can be compared directly. Relevant shape information between traditional landmarks is characterized. These techniques may have wider applicability in quantifying craniofacial morphology with increase in both specificity and general applicability over current methods.
The shape of the invisible halo: N-body simulations on parallel supercomputers
Energy Technology Data Exchange (ETDEWEB)
Warren, M.S.; Zurek, W.H. (Los Alamos National Lab., NM (USA)); Quinn, P.J. (Australian National Univ., Canberra (Australia). Mount Stromlo and Siding Spring Observatories); Salmon, J.K. (California Inst. of Tech., Pasadena, CA (USA))
1990-01-01
We study the shapes of halos and the relationship to their angular momentum content by means of N-body (N {approximately} 10{sup 6}) simulations. Results indicate that in relaxed halos with no apparent substructure: (i) the shape and orientation of the isodensity contours tends to persist throughout the virialised portion of the halo; (ii) most ({approx}70%) of the halos are prolate; (iii) the approximate direction of the angular momentum vector tends to persist throughout the halo; (iv) for spherical shells centered on the core of the halo the magnitude of the specific angular momentum is approximately proportional to their radius; (v) the shortest axis of the ellipsoid which approximates the shape of the halo tends to align with the rotation axis of the halo. This tendency is strongest in the fastest rotating halos. 13 refs., 4 figs.
Intersection of a Sure Ellipsoid and a Random Ellipsoid
Directory of Open Access Journals (Sweden)
Arjun K. Gupta
2012-07-01
Full Text Available Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";} An Expression for the expected value of the intersection of a sure sphere and a random sphere has been derived by Laurent (1974. In the present paper we derive the expression for the expected intersection volume of a sure ellipsoid and a random ellipsoid
Ellipsoidal fuzzy learning for smart car platoons
Dickerson, Julie A.; Kosko, Bart
1993-12-01
A neural-fuzzy system combined supervised and unsupervised learning to find and tune the fuzzy-rules. An additive fuzzy system approximates a function by covering its graph with fuzzy rules. A fuzzy rule patch can take the form of an ellipsoid in the input-output space. Unsupervised competitive learning found the statistics of data clusters. The covariance matrix of each synaptic quantization vector defined on ellipsoid centered at the centroid of the data cluster. Tightly clustered data gave smaller ellipsoids or more certain rules. Sparse data gave larger ellipsoids or less certain rules. Supervised learning tuned the ellipsoids to improve the approximation. The supervised neural system used gradient descent to find the ellipsoidal fuzzy patches. It locally minimized the mean-squared error of the fuzzy approximation. Hybrid ellipsoidal learning estimated the control surface for a smart car controller.
Halo star streams in the solar neighborhood
Kepley, Amanda A.; Morrison, Heather L.; Helmi, Amina; Kinman, T. D.; Van Duyne, Jeffrey; Martin, John C.; Harding, Paul; Norris, John E.; Freeman, Kenneth C.
2007-01-01
We have assembled a sample of halo stars in the solar neighborhood to look for halo substructure in velocity and angular momentum space. Our sample ( 231 stars) includes red giants, RR Lyrae variable stars, and red horizontal branch stars within 2.5 kpc of the Sun with [Fe/H] less than -1.0. It was
GRAVITATIONALLY CONSISTENT HALO CATALOGS AND MERGER TREES FOR PRECISION COSMOLOGY
International Nuclear Information System (INIS)
Behroozi, Peter S.; Wechsler, Risa H.; Wu, Hao-Yi; Busha, Michael T.; Klypin, Anatoly A.; Primack, Joel R.
2013-01-01
We present a new algorithm for generating merger trees and halo catalogs which explicitly ensures consistency of halo properties (mass, position, and velocity) across time steps. Our algorithm has demonstrated the ability to improve both the completeness (through detecting and inserting otherwise missing halos) and purity (through detecting and removing spurious objects) of both merger trees and halo catalogs. In addition, our method is able to robustly measure the self-consistency of halo finders; it is the first to directly measure the uncertainties in halo positions, halo velocities, and the halo mass function for a given halo finder based on consistency between snapshots in cosmological simulations. We use this algorithm to generate merger trees for two large simulations (Bolshoi and Consuelo) and evaluate two halo finders (ROCKSTAR and BDM). We find that both the ROCKSTAR and BDM halo finders track halos extremely well; in both, the number of halos which do not have physically consistent progenitors is at the 1%-2% level across all halo masses. Our code is publicly available at http://code.google.com/p/consistent-trees. Our trees and catalogs are publicly available at http://hipacc.ucsc.edu/Bolshoi/.
Imbalance in the Local Galactic halo?
International Nuclear Information System (INIS)
Croswell, K.; Latham, D.W.; Carney, B.W.; North Carolina Univ., Chapel Hill)
1987-01-01
In a kinematically biased sample of 119 single halo stars, 65 percent of the stars are traveling away from the plane of the Galaxy. Halo spectroscopic binaries do not show this imbalance. Other kinematically biased halo surveys exhibit the same effect. Combining these samples with those of the authors' results in 223 halo stars, 63 percent of which are heading away from the plane of the Galaxy. The probability that the first result could be obtained from a symmetric w velocity distribution is 0.2 percent; the probability that the second result could be so obtained is 0.02 percent. Single halo stars traveling away from the disk appear to have a larger w velocity dispersion than those traveling toward it. Selection effects are analyzed and rejected as the cause of the observed asymmetry. Possible mechanisms for producing the imbalance are discussed, but each has serious difficulties accounting for the observations. 28 references
Ellipsoids and matrix-valued valuations
Ludwig, Monika
2003-01-01
We obtain a classification of Borel measurable, GL(n) covariant, symmetric-matrix-valued valuations on the space of n-dimensional convex polytopes. The only ones turn out to be the moment matrix corresponding to the classical Legendre ellipsoid and the matrix corresponding to the ellipsoid recently discovered by E. Lutwak, D. Yang, and G. Zhang.
Quantum Monodromy in Prolate Ellipsoidal Billiards
Waalkens, Holger; Dullin, Holger R.
2002-01-01
This is the third in a series of three papers on quantum billiards with elliptic and ellipsoidal boundaries. In the present paper we show that the integrable billiard inside a prolate ellipsoid has an isolated singular point in its bifurcation diagram and, therefore, exhibits classical and quantum
Energy Technology Data Exchange (ETDEWEB)
Orr, Nigel [Lab. de Physique Corpusculaire, Caen Univ., 14 (France); Collaboration: La Direction des Sciences de la Matiere du CEA (FR); Le Fonds National de la Recherche Scientifique de Belgique (BE)
1998-12-31
A brief overview of the nuclear halo is presented. Following some historical remarks the general characteristics of the halo systems are discussed with reference to a simple model. The conditions governing the formation of halos are also explored, as are two subjects of current interest - low-lying resonances of halo nucleon correlations. (author) 54 refs., 16 figs., 1 tabs.
How do stars affect ψDM halos?
Chan, James H. H.; Schive, Hsi-Yu; Woo, Tak-Pong; Chiueh, Tzihong
2018-04-01
Wave dark matter (ψDM) predicts a compact soliton core and a granular halo in every galaxy. This work presents the first simulation study of an elliptical galaxy by including both stars and ψDM, focusing on the systematic changes of the central soliton and halo granules. With the addition of stars in the inner halo, we find the soliton core consistently becomes more prominent by absorbing mass from the host halo than that without stars, and the halo granules become "non-isothermal", "hotter" in the inner halo and "cooler" in the outer halo, as opposed to the isothermal halo in pure ψDM cosmological simulations. Moreover, the composite (star+ψDM) mass density is found to follow a r-2 isothermal profile near the half-light radius in most cases. Most striking is the velocity dispersion of halo stars that increases rapidly toward the galactic center by a factor of at least 2 inside the half-light radius caused by the deepened soliton gravitational potential, a result that compares favorably with observations of elliptical galaxies and bulges in spiral galaxies. However in some rare situations we find a phase segregation turning a compact distribution of stars into two distinct populations with high and very low velocity dispersions; while the high-velocity component mostly resides in the halo, the very low-velocity component is bound to the interior of the soliton core, resembling stars in faint dwarf spheroidal galaxies.
Erratum: ``Stellar Halo Parameters from 4588 Subdwarfs'' (ApJ, 583, 765 [2003])
Gould, Andrew
2004-06-01
An error has been discovered in the computer program that determined the stellar halo parameters using ~4500 halo stars drawn from the revised New Luyten Two-Tenths catalog. None of the major scientific conclusions of that paper are qualitatively altered. In particular, five of the nine velocity-ellipsoid parameters remain consistent with zero within their small errors. However, many individual parameters have changed their values by 1 or 2 σ and a few by more. I explain the nature of the error and give corrected values for the parameters. The ~4500 halo stars analyzed were selected from the revised New Luyten Two-Tenths catalog (A. Gould & S. Salim, ApJ, 583, 765 [2003]; S. Salim & A. Gould, ApJ, 583, 765 [2003]) by demanding that the reduced proper motion (RPM) discriminator,η≡V-5log(μ)-3.1(V-J)-1.47|sinb|-2.73,(1)lie within the secure halo range, 1expressed by a break at a virtually unchanged Vbreak=18.27, but with the completeness at this break point rising to 50%+/-6%. In particular, the motion of the local standard of rest (LSR) relative to the halo isV1=1.5+/-2.2kms-1,V3=0.3+/-2.4kms-1.(3)Hence, as originally claimed, all five velocity-ellipsoid parameters in equations (2) and (3) are consistent with zero. Thus, χ2=3.43 for 5 degrees of freedom, slightly less than the previous value (3.97). This implies that the limits on stellar-halo granularity derived in a subsequent paper from this statistic remain essentially unaltered, being about 2% tighter (see eq. [9] of A. Gould, ApJ, 583, 765 [2003]). Four of the 27 parameters do change by more than 2 σ. Both (c11+Δc11)1/2 and (c22+Δc22)1/2 increase by 4 σ. However, because the Δcii are poorly constrained, these parameter-combination measurements did not give any useful information about the halo, and this remains so with the new determinations. The LF bins at MV=10 and MV=11 each decline by 3 σ, which leaves a somewhat lower but still pronounced peak in the LF at these magnitudes (see Fig. 2). It
Indentation of Ellipsoidal and Cylindrical Elastic Shells
Vella, Dominic; Ajdari, Amin; Vaziri, Ashkan; Boudaoud, Arezki
2012-01-01
Thin shells are found in nature at scales ranging from viruses to hens' eggs; the stiffness of such shells is essential for their function. We present the results of numerical simulations and theoretical analyses for the indentation of ellipsoidal
Ellipsoidal prediction regions for multivariate uncertainty characterization
DEFF Research Database (Denmark)
Golestaneh, Faranak; Pinson, Pierre; Azizipanah-Abarghooee, Rasoul
2018-01-01
, for classes of decision-making problems based on robust, interval chance-constrained optimization, necessary inputs take the form of multivariate prediction regions rather than scenarios. The current literature is at very primitive stage of characterizing multivariate prediction regions to be employed...... in these classes of optimization problems. To address this issue, we introduce a new class of multivariate forecasts which form as multivariate ellipsoids for non-Gaussian variables. We propose a data-driven systematic framework to readily generate and evaluate ellipsoidal prediction regions, with predeﬁned...... probability guarantees and minimum conservativeness. A skill score is proposed for quantitative assessment of the quality of prediction ellipsoids. A set of experiments is used to illustrate the discrimination ability of the proposed scoring rule for potential misspeciﬁcation of ellipsoidal prediction regions...
Ellipsoidal bag model for heavy quark system
International Nuclear Information System (INIS)
Bi Pinzhen; Fudan Univ., Shanghai
1991-01-01
The ellipsoidal bag model is used to describe heavy quark systems such as Qanti Q, Qanti Qg and Q 2 anti Q 2 . Instead of two step model, these states are described by an uniform picture. The potential derived from the ellipsoidal bag for Qanti Q is almost equivalent to the Cornell potential. For a Q 2 anti Q 2 system with large quark pair separation, an improvement of 70 MeV is obtained comparing with the spherical bag. (orig.)
Simple and Multi-collision of an Ellipsoid with Planar Surfaces. Part I: Theory
Directory of Open Access Journals (Sweden)
Nicolae–Doru Stănescu
2017-11-01
Full Text Available This paper discusses the problem of simultaneous collisions between an ellipsoid and some planar surfaces. The approach is one based on the theory of screws and uses the notion of inertance. The authors consider that the coefficients of restitution are different for each planar surface and they obtain the velocities after the collision. An example concludes the theory.
Dark matter haloes: a multistream view
Ramachandra, Nesar S.; Shandarin, Sergei F.
2017-09-01
Mysterious dark matter constitutes about 85 per cent of all masses in the Universe. Clustering of dark matter plays a dominant role in the formation of all observed structures on scales from a fraction to a few hundreds of Mega-parsecs. Galaxies play a role of lights illuminating these structures so they can be observed. The observations in the last several decades have unveiled opulent geometry of these structures currently known as the cosmic web. Haloes are the highest concentrations of dark matter and host luminous galaxies. Currently the most accurate modelling of dark matter haloes is achieved in cosmological N-body simulations. Identifying the haloes from the distribution of particles in N-body simulations is one of the problems attracting both considerable interest and efforts. We propose a novel framework for detecting potential dark matter haloes using the field unique for dark matter-multistream field. The multistream field emerges at the non-linear stage of the growth of perturbations because the dark matter is collisionless. Counting the number of velocity streams in gravitational collapses supplements our knowledge of spatial clustering. We assume that the virialized haloes have convex boundaries. Closed and convex regions of the multistream field are hence isolated by imposing a positivity condition on all three eigenvalues of the Hessian estimated on the smoothed multistream field. In a single-scale analysis of high multistream field resolution and low softening length, the halo substructures with local multistream maxima are isolated as individual halo sites.
THE BLACK HOLE–DARK MATTER HALO CONNECTION
International Nuclear Information System (INIS)
Sabra, Bassem M.; Saliba, Charbel; Akl, Maya Abi; Chahine, Gilbert
2015-01-01
We explore the connection between the central supermassive black holes (SMBH) in galaxies and the dark matter halo through the relation between the masses of the SMBHs and the maximum circular velocities of the host galaxies, as well as the relationship between stellar velocity dispersion of the spheroidal component and the circular velocity. Our assumption here is that the circular velocity is a proxy for the mass of the dark matter halo. We rely on a heterogeneous sample containing galaxies of all types. The only requirement is that the galaxy has a direct measurement of the mass of its SMBH and a direct measurement of its circular velocity and its velocity dispersion. Previous studies have analyzed the connection between the SMBH and dark matter halo through the relationship between the circular velocity and the bulge velocity dispersion, with the assumption that the bulge velocity dispersion stands in for the mass of the SMBH, via the well-established SMBH mass–bulge velocity dispersion relation. Using intermediate relations may be misleading when one is studying them to decipher the active ingredients of galaxy formation and evolution. We believe that our approach will provide a more direct probe of the SMBH and the dark matter halo connection. We find that the correlation between the mass of SMBHs and the circular velocities of the host galaxies is extremely weak, leading us to state the dark matter halo may not play a major role in regulating the black hole growth in the present Universe
THE BLACK HOLE–DARK MATTER HALO CONNECTION
Energy Technology Data Exchange (ETDEWEB)
Sabra, Bassem M. [Department of Physics and Astronomy, Notre Dame University-Louaize, P.O. Box 72 Zouk Mikael, Zouk Mosbeh (Lebanon); Saliba, Charbel; Akl, Maya Abi; Chahine, Gilbert, E-mail: bsabra@ndu.edu.lb [Department of Physics, Lebanese University II, Fanar (Lebanon)
2015-04-10
We explore the connection between the central supermassive black holes (SMBH) in galaxies and the dark matter halo through the relation between the masses of the SMBHs and the maximum circular velocities of the host galaxies, as well as the relationship between stellar velocity dispersion of the spheroidal component and the circular velocity. Our assumption here is that the circular velocity is a proxy for the mass of the dark matter halo. We rely on a heterogeneous sample containing galaxies of all types. The only requirement is that the galaxy has a direct measurement of the mass of its SMBH and a direct measurement of its circular velocity and its velocity dispersion. Previous studies have analyzed the connection between the SMBH and dark matter halo through the relationship between the circular velocity and the bulge velocity dispersion, with the assumption that the bulge velocity dispersion stands in for the mass of the SMBH, via the well-established SMBH mass–bulge velocity dispersion relation. Using intermediate relations may be misleading when one is studying them to decipher the active ingredients of galaxy formation and evolution. We believe that our approach will provide a more direct probe of the SMBH and the dark matter halo connection. We find that the correlation between the mass of SMBHs and the circular velocities of the host galaxies is extremely weak, leading us to state the dark matter halo may not play a major role in regulating the black hole growth in the present Universe.
Dimension of the Earth's general ellipsoid
Czech Academy of Sciences Publication Activity Database
Burša, Milan; Kenyon, S.; Kouba, J.; Raděj, K.; Šíma, Zdislav; Vatrt, V.; Vojtíšková, M.
2002-01-01
Roč. 91, č. 1 (2002), s. 31-41 ISSN 0167-9295 Institutional research plan: CEZ:AV0Z1003909 Keywords : Earth's dimensions * Earth's ellipsoid * fundamental constants Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 1.364, year: 2002
On computing ellipsoidal harmonics using Jekeli's renormalization
Czech Academy of Sciences Publication Activity Database
Sebera, Josef; Bouman, J.; Bosch, W.
2012-01-01
Roč. 86, č. 9 (2012), s. 713-726 ISSN 0949-7714 Institutional support: RVO:67985815 Keywords : Earth's gravitational field * spherical and ellipsoidal harmonics * hypergeometric function Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 2.808, year: 2012
An ellipsoidal calculus based on propagation and fusion.
Ros, L; Sabater, A; Thomas, F
2002-01-01
Presents an ellipsoidal calculus based solely on two basic operations: propagation and fusion. Propagation refers to the problem of obtaining an ellipsoid that must satisfy an affine relation with another ellipsoid, and fusion to that of computing the ellipsoid that tightly bounds the intersection of two given ellipsoids. These two operations supersede the Minkowski sum and difference, affine transformation and intersection tight bounding of ellipsoids on which other ellipsoidal calculi are based. Actually, a Minkowski operation can be seen as a fusion followed by a propagation and an affine transformation as a particular case of propagation. Moreover, the presented formulation is numerically stable in the sense that it is immune to degeneracies of the involved ellipsoids and/or affine relations. Examples arising when manipulating uncertain geometric information in the context of the spatial interpretation of line drawings are extensively used as a testbed for the presented calculus.
Theory of coherent transition radiation generated by ellipsoidal electron bunches
Root, op 't W.P.E.M.; Smorenburg, P.W.; Oudheusden, van T.; Wiel, van der M.J.; Luiten, O.J.
2007-01-01
We present the theory of coherent transition radiation (CTR) generated by ellipsoidal electron bunches. We calculate analytical expressions for the electric field spectrum, the power spectrum, and the temporal electric field of CTR, generated by cylindrically symmetric ellipsoidal electron bunches
International Nuclear Information System (INIS)
Helmi, Amina; White, Simon D.M.; Springel, Volker
2002-01-01
We study the phase-space structure of a dark-matter halo formed in a high resolution simulation of a ΛCDM cosmology. Our goal is to quantify how much substructure is left over from the inhomogeneous growth of the halo, and how it may affect the signal in experiments aimed at detecting the dark matter particles directly. If we focus on the equivalent of 'solar vicinity', we find that the dark matter is smoothly distributed in space. The probability of detecting particles bound within dense lumps of individual mass less than 10 7 M · h -1 is small, less than 10 -2 . The velocity ellipsoid in the solar neighborhood deviates only slightly from a multivariate Gaussian, and can be thought of as a superposition of thousands of kinematically cold streams. The motions of the most energetic particles are, however, strongly clumped and highly anisotropic. We conclude that experiments may safely assume a smooth multivariate Gaussian distribution to represent the kinematics of dark-matter particles in the solar neighborhood. Experiments sensitive to the direction of motion of the incident particles could exploit the expected anisotropy to learn about the recent merging history of our Galaxy
Cosmology and cluster halo scaling relations
Araya-Melo, Pablo A.; van de Weygaert, Rien; Jones, Bernard J. T.
2009-01-01
We explore the effects of dark matter and dark energy on the dynamical scaling properties of galaxy clusters. We investigate the cluster Faber-Jackson (FJ), Kormendy and Fundamental Plane (FP) relations between the mass, radius and velocity dispersion of cluster-sized haloes in cosmological N-body
Ellipsoids (v1.0): 3-D magnetic modelling of ellipsoidal bodies
Takahashi, Diego; Oliveira, Vanderlei C., Jr.
2017-09-01
A considerable amount of literature has been published on the magnetic modelling of uniformly magnetized ellipsoids since the second half of the nineteenth century. Ellipsoids have flexibility to represent a wide range of geometrical forms, are the only known bodies which can be uniformly magnetized in the presence of a uniform inducing field and are the only finite bodies for which the self-demagnetization can be treated analytically. This property makes ellipsoids particularly useful for modelling compact orebodies having high susceptibility. In this case, neglecting the self-demagnetization may strongly mislead the interpretation of these bodies by using magnetic methods. A number of previous studies consider that the self-demagnetization can be neglected for the case in which the geological body has an isotropic susceptibility lower than or equal to 0.1 SI. This limiting value, however, seems to be determined empirically and there has been no discussion about how this value was determined. In addition, the geoscientific community lacks an easy-to-use tool to simulate the magnetic field produced by uniformly magnetized ellipsoids. Here, we present an integrated review of the magnetic modelling of arbitrarily oriented triaxial, prolate and oblate ellipsoids. Our review includes ellipsoids with both induced and remanent magnetization, as well as with isotropic or anisotropic susceptibility. We also discuss the ambiguity between confocal ellipsoids with the same magnetic moment and propose a way of determining the isotropic susceptibility above which the self-demagnetization must be taken into consideration. Tests with synthetic data validate our approach. Finally, we provide a set of routines to model the magnetic field produced by ellipsoids. The routines are written in Python language as part of the Fatiando a Terra, which is an open-source library for modelling and inversion in geophysics.
Ellipsoids (v1.0: 3-D magnetic modelling of ellipsoidal bodies
Directory of Open Access Journals (Sweden)
D. Takahashi
2017-09-01
Full Text Available A considerable amount of literature has been published on the magnetic modelling of uniformly magnetized ellipsoids since the second half of the nineteenth century. Ellipsoids have flexibility to represent a wide range of geometrical forms, are the only known bodies which can be uniformly magnetized in the presence of a uniform inducing field and are the only finite bodies for which the self-demagnetization can be treated analytically. This property makes ellipsoids particularly useful for modelling compact orebodies having high susceptibility. In this case, neglecting the self-demagnetization may strongly mislead the interpretation of these bodies by using magnetic methods. A number of previous studies consider that the self-demagnetization can be neglected for the case in which the geological body has an isotropic susceptibility lower than or equal to 0.1 SI. This limiting value, however, seems to be determined empirically and there has been no discussion about how this value was determined. In addition, the geoscientific community lacks an easy-to-use tool to simulate the magnetic field produced by uniformly magnetized ellipsoids. Here, we present an integrated review of the magnetic modelling of arbitrarily oriented triaxial, prolate and oblate ellipsoids. Our review includes ellipsoids with both induced and remanent magnetization, as well as with isotropic or anisotropic susceptibility. We also discuss the ambiguity between confocal ellipsoids with the same magnetic moment and propose a way of determining the isotropic susceptibility above which the self-demagnetization must be taken into consideration. Tests with synthetic data validate our approach. Finally, we provide a set of routines to model the magnetic field produced by ellipsoids. The routines are written in Python language as part of the Fatiando a Terra, which is an open-source library for modelling and inversion in geophysics.
QUANTIFYING KINEMATIC SUBSTRUCTURE IN THE MILKY WAY'S STELLAR HALO
International Nuclear Information System (INIS)
Xue Xiangxiang; Zhao Gang; Luo Ali; Rix, Hans-Walter; Bell, Eric F.; Koposov, Sergey E.; Kang, Xi; Liu, Chao; Yanny, Brian; Beers, Timothy C.; Lee, Young Sun; Bullock, James S.; Johnston, Kathryn V.; Morrison, Heather; Rockosi, Constance; Weaver, Benjamin A.
2011-01-01
We present and analyze the positions, distances, and radial velocities for over 4000 blue horizontal-branch (BHB) stars in the Milky Way's halo, drawn from SDSS DR8. We search for position-velocity substructure in these data, a signature of the hierarchical assembly of the stellar halo. Using a cumulative 'close pair distribution' as a statistic in the four-dimensional space of sky position, distance, and velocity, we quantify the presence of position-velocity substructure at high statistical significance among the BHB stars: pairs of BHB stars that are close in position on the sky tend to have more similar distances and radial velocities compared to a random sampling of these overall distributions. We make analogous mock observations of 11 numerical halo formation simulations, in which the stellar halo is entirely composed of disrupted satellite debris, and find a level of substructure comparable to that seen in the actually observed BHB star sample. This result quantitatively confirms the hierarchical build-up of the stellar halo through a signature in phase (position-velocity) space. In detail, the structure present in the BHB stars is somewhat less prominent than that seen in most simulated halos, quite possibly because BHB stars represent an older sub-population. BHB stars located beyond 20 kpc from the Galactic center exhibit stronger substructure than at r gc < 20 kpc.
Anisotropic hypersonic phonon propagation in films of aligned ellipsoids.
Beltramo, Peter J; Schneider, Dirk; Fytas, George; Furst, Eric M
2014-11-14
A material with anisotropic elastic mechanical properties and a direction-dependent hypersonic band gap is fabricated using ac electric field-directed convective self-assembly of colloidal ellipsoids. The frequency of the gap, which is detected in the direction perpendicular to particle alignment and entirely absent parallel to alignment, and the effective sound velocities can be tuned by the particle aspect ratio. We hypothesize that the band gap originates from the primary eigenmode peak, the m-splitted (s,1,2) mode, of the particle resonating with the effective medium. These results reveal the potential for powerful control of the hypersonic phononic band diagram by combining anisotropic particles and self-assembly.
Discrete ellipsoidal statistical BGK model and Burnett equations
Zhang, Yu-Dong; Xu, Ai-Guo; Zhang, Guang-Cai; Chen, Zhi-Hua; Wang, Pei
2018-06-01
A new discrete Boltzmann model, the discrete ellipsoidal statistical Bhatnagar-Gross-Krook (ESBGK) model, is proposed to simulate nonequilibrium compressible flows. Compared with the original discrete BGK model, the discrete ES-BGK has a flexible Prandtl number. For the discrete ES-BGK model in the Burnett level, two kinds of discrete velocity model are introduced and the relations between nonequilibrium quantities and the viscous stress and heat flux in the Burnett level are established. The model is verified via four benchmark tests. In addition, a new idea is introduced to recover the actual distribution function through the macroscopic quantities and their space derivatives. The recovery scheme works not only for discrete Boltzmann simulation but also for hydrodynamic ones, for example, those based on the Navier-Stokes or the Burnett equations.
Ellipsoidal prediction regions for multivariate uncertainty characterization
DEFF Research Database (Denmark)
Golestaneh, Faranak; Pinson, Pierre; Azizipanah-Abarghooee, Rasoul
2018-01-01
While substantial advances are observed in probabilistic forecasting for power system operation and electricity market applications, most approaches are still developed in a univariate framework. This prevents from informing about the interdependence structure among locations, lead times and vari......While substantial advances are observed in probabilistic forecasting for power system operation and electricity market applications, most approaches are still developed in a univariate framework. This prevents from informing about the interdependence structure among locations, lead times...... probability guarantees and minimum conservativeness. A skill score is proposed for quantitative assessment of the quality of prediction ellipsoids. A set of experiments is used to illustrate the discrimination ability of the proposed scoring rule for potential misspeciﬁcation of ellipsoidal prediction regions...
Elastic buckling of ellipsoids of revolution
International Nuclear Information System (INIS)
Solal, Roger; Hoffmann, Alain; Roche, Roland.
1976-02-01
The CEASEMT system of calculation by finite elements is used to determine critical internal pressures on a flattened ellipsoid of revolution. This case resembles that of an ellipsoidal head of a thin pressure vessel fitted onto a flexible colla. The calculations are performed assuming the geometry perfect, the deformations slight and the behaviour of the material perfectly elastic. The results obtained are presented favourably by plotting a reduced pressure p* against the geometry. A good definition of p* would be: p*=pπ 2 E/1-μ 2 .e 2 b 2 /a 4 (p* critical pressure, E Young's modulus, μ Poisson's coefficient, e thickness, a half large axis, b half small axis). When a/b is above 2 the p value remains close to 1. For lower a/b values the p value rises considerably with a/b [fr
Circulation of a triaxial, charged ellipsoidal droplet
International Nuclear Information System (INIS)
Graber, J.L.; Rosensteel, G.
2002-01-01
The Kelvin circulation, which is the Casimir invariant of the general collective motion gcm(3) Lie algebra, is determined for a rapidly rotating triaxial nucleus in the classical domain. The potential energy is approximated by the sum of Coulomb repulsion and attractive surface energy terms, and the kinetic energy is adopted from the Riemann ellipsoidal model. An accurate approximation valid for both small and large deformations is reported for the potential energy. The Riemann ellipsoid theory allows for collective rotation in the continuum from rigid body motion to irrotational flow; the rigidity parametrizes this kinematical continuum. Analytic formulas are derived for the circulation, angular momentum, and energy as functions of the axis lengths, fissility, and rigidity. In particular, the bifurcation point to Jacobi triaxial shapes from noncollective oblate spheroids is given by a simple analytic formula. For a given fissility, the bifurcation point depends sensitive- ly on the rigidity. The Kelvin circulation remains approximately constant for triaxial ellipsoids as the angular momentum increases. This implies that gcm(3) is an approximate partial dynamical symmetry for rapidly rotating triaxial nuclei
Directory of Open Access Journals (Sweden)
Zoran Gojković
2017-01-01
Full Text Available The physical surface of the earth has irregular shape which is not mathematically defined, therefore the shape of the Earth is approximated with mathematically defined surfaces such as ellipsoid and sphere. The developing of a global positioning systems, thus and modern navigation systems, as effect produce large amounts of data which contain the problem of homogeneity. This problem could be exceed if all the data are store in the same coordinate system. Hence the need for data transformation from local coordinate systems to the global coordinate systems. Global level implies WGS84 ellipsoid and UTM projection while national coordinate system of Republic Serbia is Gauss-Kruger with Bessel ellipsoid. This coordinate system of Republic Serbia on a global level has a local character. Applying appropriate mathematical models and functions it is possible to transform coordinates from one system to another and vice versa. The paper describes coordinate transformations from Gauss-Kruger coordinate system ellipsoid Bessel to UTM projection WGS84 ellipsoid and vice versa, and also an application which provides transformation of its kind that is made using open source environment. Name of the application is TRANS7_GK_UTM_GK and it can be found and used on the web page of the faculty for Mining and Geology under the link http://gk2utm.rgf.bg.ac.rs with a user guide.
Eccentricity samples: Implications on the potential and the velocity distribution
Directory of Open Access Journals (Sweden)
Cubarsi R.
2017-01-01
Full Text Available Planar and vertical epicycle frequencies and local angular velocity are related to the derivatives up to the second order of the local potential and can be used to test the shape of the potential from stellar disc samples. These samples show a more complex velocity distribution than halo stars and should provide a more realistic test. We assume an axisymmetric potential allowing a mixture of independent ellipsoidal velocity distributions, of separable or Staeckel form in cylindrical or spherical coordinates. We prove that values of local constants are not consistent with a potential separable in addition in cylindrical coordinates and with a spherically symmetric potential. The simplest potential that fits the local constants is used to show that the harmonical and non-harmonical terms of the potential are equally important. The same analysis is used to estimate the local constants. Two families of nested subsamples selected for decreasing planar and vertical eccentricities are used to borne out the relation between the mean squared planar and vertical eccentricities and the velocity dispersions of the subsamples. According to the first-order epicycle model, the radial and vertical velocity components provide accurate information on the planar and vertical epicycle frequencies. However, it is impossible to account for the asymmetric drift which introduces a systematic bias in estimation of the third constant. Under a more general model, when the asymmetric drift is taken into account, the rotation velocity dispersions together with their asymmetric drift provide the correct fit for the local angular velocity. The consistency of the results shows that this new method based on the distribution of eccentricities is worth using for kinematic stellar samples. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. No 176011: Dynamics and Kinematics of Celestial Bodies and Systems
MAPPING THE GALACTIC HALO. VIII. QUANTIFYING SUBSTRUCTURE
International Nuclear Information System (INIS)
Starkenburg, Else; Helmi, Amina; Van Woerden, Hugo; Morrison, Heather L.; Harding, Paul; Frey, Lucy; Oravetz, Dan; Mateo, Mario; Dohm-Palmer, R. C.; Olszewski, Edward W.; Sivarani, Thirupathi; Norris, John E.; Freeman, Kenneth C.; Shectman, Stephen A.
2009-01-01
We have measured the amount of kinematic substructure in the Galactic halo using the final data set from the Spaghetti project, a pencil-beam high-latitude sky survey. Our sample contains 101 photometrically selected and spectroscopically confirmed giants with accurate distance, radial velocity, and metallicity information. We have developed a new clustering estimator: the '4distance' measure, which when applied to our data set leads to the identification of one group and seven pairs of clumped stars. The group, with six members, can confidently be matched to tidal debris of the Sagittarius dwarf galaxy. Two pairs match the properties of known Virgo structures. Using models of the disruption of Sagittarius in Galactic potentials with different degrees of dark halo flattening, we show that this favors a spherical or prolate halo shape, as demonstrated by Newberg et al. using the Sloan Digital Sky Survey data. One additional pair can be linked to older Sagittarius debris. We find that 20% of the stars in the Spaghetti data set are in substructures. From comparison with random data sets, we derive a very conservative lower limit of 10% to the amount of substructure in the halo. However, comparison to numerical simulations shows that our results are also consistent with a halo entirely built up from disrupted satellites, provided that the dominating features are relatively broad due to early merging or relatively heavy progenitor satellites.
African Journals Online (AJOL)
Prof. Adipala Ekwamu
INHERITANCE OF HALO BLIGHT RESISTANCE IN COMMON BEAN ... pv phaseolicola (Psp) is a serious seed-borne disease of common bean ... a toxin produced by the Psp bacterium when ... stakes or in association with maize for support.
THE EFFECTS OF ANGULAR MOMENTUM ON HALO PROFILES
Energy Technology Data Exchange (ETDEWEB)
Lentz, Erik W; Rosenberg, Leslie J [Physics Department, University of Washington, Seattle, WA 98195-1580 (United States); Quinn, Thomas R, E-mail: lentze@phys.washington.edu, E-mail: ljrosenberg@phys.washington.edu, E-mail: trq@astro.washington.edu [Astronomy Department, University of Washington, Seattle, WA 98195-1580 (United States)
2016-05-10
The near universality of DM halo density profiles provided by N -body simulations proved to be robust against changes in total mass density, power spectrum, and some forms of initial velocity dispersion. Here we study the effects of coherently spinning up an isolated DM-only progenitor on halo structure. Halos with spins within several standard deviations of the simulated mean ( λ ≲ 0.20) produce profiles with negligible deviations from the universal form. Only when the spin becomes quite large ( λ ≳ 0.20) do departures become evident. The angular momentum distribution also exhibits a near universal form, which is also independent of halo spin up to λ ≲ 0.20. A correlation between these epidemic profiles and the presence of a strong bar in the virialized halo is also observed. These bar structures bear resemblance to the radial orbit instability in the rotationless limit.
Phase models of galaxies consisting of disk and halo
International Nuclear Information System (INIS)
Osipkov, L.P.; Kutuzov, S.A.
1987-01-01
A method of finding the phase density of a two-component model of mass distribution is developed. The equipotential surfaces and the potential law are given. The equipotentials are lenslike surfaces with a sharp edge in the equatorial plane, which provides the existence of an imbedded thin disk in halo. The equidensity surfaces of the halo coincide with the equipotentials. Phase models for the halo and the disk are constructed separately on the basis of spatial and surface mass densities by solving the corresponding integral equations. In particular the models for the halo with finite dimensions can be constructed. The even part of the phase density in respect to velocities is only found. For the halo it depends on the energy integral as a single argument
Libration-driven flows in ellipsoidal shells
Lemasquerier, D.; Grannan, A. M.; Vidal, J.; Cébron, D.; Favier, B.; Le Bars, M.; Aurnou, J. M.
2017-09-01
Planets and satellites can undergo physical librations, which consist of forced periodic variations in their rotation rate induced by gravitational interactions with nearby bodies. This mechanical forcing may drive turbulence in interior fluid layers such as subsurface oceans and metallic liquid cores through a libration-driven elliptical instability (LDEI) that refers to the resonance of two inertial modes with the libration-induced base flow. LDEI has been studied in the case of a full ellipsoid. Here we address for the first time the question of the persistence of LDEI in the more geophysically relevant ellipsoidal shell geometries. In the experimental setup, an ellipsoidal container with spherical inner cores of different sizes is filled with water. Direct side view flow visualizations are made in the librating frame using Kalliroscope particles. A Fourier analysis of the light intensity fluctuations extracted from recorded movies shows that the presence of an inner core leads to spatial heterogeneities but does not prevent LDEI. Particle image velocimetry and direct numerical simulations are performed on selected cases to confirm our results. Additionally, our survey at a fixed forcing frequency and variable rotation period (i.e., variable Ekman number, E) shows that the libration amplitude at the instability threshold varies as ˜E0.65. This scaling is explained by a competition between surface and bulk dissipation. When extrapolating to planetary interior conditions, this leads to the E1/2 scaling commonly considered. We argue that Enceladus' subsurface ocean and the core of the exoplanet 55 CnC e should both be unstable to LDEI.
User defined function for transformation of ellipsoidal coordinates
Directory of Open Access Journals (Sweden)
Ganić Aleksandar
2014-01-01
Full Text Available The topographic plane of the Earth has irregular shape, and for the purpose of mathematical defining, it is to be approximated by rotational ellipsoid. As local geodetic datum, rotational ellipsoids of various sizes are used in the world. More widely usage of the GPS while performing surveying tasks has resulted in the need to define global geodetic datum in order to obtain the best approximation the entire Earth. For this purpose, geocentric rotational ellipsoid WGS84 was defined and the results of the GPS measurements are shown in relation to it. By applying the appropriate equations, the ellipsoidal coordinates are being transformed from WGS84 into the coordinates on the local rotational ellipsoid, i.e. on the view plane. The paper shows User Defined Function created for Excel, by which the coordinates in the territory of Belgrade are being transformed from WGS84 of rotational ellipsoid into the Gauss-Krüger projection plane.
Internal ellipsoidal estimates of reachable set of impulsive control systems
Energy Technology Data Exchange (ETDEWEB)
Matviychuk, Oksana G. [Institute of Mathematics and Mechanics, Russian Academy of Sciences, 16 S. Kovalevskaya str., Ekaterinburg, 620990, Russia and Ural Federal University, 19 Mira str., Ekaterinburg, 620002 (Russian Federation)
2014-11-18
A problem of estimating reachable sets of linear impulsive control system with uncertainty in initial data is considered. The impulsive controls in the dynamical system belong to the intersection of a special cone with a generalized ellipsoid both taken in the space of functions of bounded variation. Assume that an ellipsoidal state constraints are imposed. The algorithms for constructing internal ellipsoidal estimates of reachable sets for such control systems and numerical simulation results are given.
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.
ZOMG - III. The effect of halo assembly on the satellite population
Garaldi, Enrico; Romano-Díaz, Emilio; Borzyszkowski, Mikolaj; Porciani, Cristiano
2018-01-01
We use zoom hydrodynamical simulations to investigate the properties of satellites within galaxy-sized dark-matter haloes with different assembly histories. We consider two classes of haloes at redshift z = 0: 'stalled' haloes that assembled at z > 1 and 'accreting' ones that are still forming nowadays. Previously, we showed that the stalled haloes are embedded within thick filaments of the cosmic web, while the accreting ones lie where multiple thin filaments converge. We find that satellites in the two classes have both similar and different properties. Their mass spectra, radial count profiles, baryonic and stellar content, and the amount of material they shed are indistinguishable. However, the mass fraction locked in satellites is substantially larger for the accreting haloes as they experience more mergers at late times. The largest difference is found in the satellite kinematics. Substructures fall towards the accreting haloes along quasi-radial trajectories whereas an important tangential velocity component is developed, before accretion, while orbiting the filament that surrounds the stalled haloes. Thus, the velocity anisotropy parameter of the satellites (β) is positive for the accreting haloes and negative for the stalled ones. This signature enables us to tentatively categorize the Milky Way halo as stalled based on a recent measurement of β. Half of our haloes contain clusters of satellites with aligned orbital angular momenta corresponding to flattened structures in space. These features are not driven by baryonic physics and are only found in haloes hosting grand-design spiral galaxies, independently of their assembly history.
DEFF Research Database (Denmark)
Riisager, Karsten
2013-01-01
The halo structure originated from nuclear physics but is now encountered more widely. It appears in loosely bound, clustered systems where the spatial extension of the system is significantly larger than that of the binding potentials. A review is given on our current understanding of these stru......The halo structure originated from nuclear physics but is now encountered more widely. It appears in loosely bound, clustered systems where the spatial extension of the system is significantly larger than that of the binding potentials. A review is given on our current understanding...... of these structures, with an emphasis on how the structures evolve as more cluster components are added and on the experimental situation concerning halo states in light nuclei....
Caraban Gonzalez, Noemi
2018-01-01
In 2015, the artists participated in a research residency at CERN and began to work with data captured by ATLAS, one of the four detectors at the Large Hadron Collider (LHC) that sits in a cavern 100 metres below ground near the main site of CERN, in Meyrin (Switzerland). For Art Basel, they created HALO, an installation that surrounds visitors with data collected by the ATLAS experiment at the LHC. HALO consists of a 10 m wide cylinder defined by vertical piano wires, within which a 4-m tall screen displays particle collisions. The data also triggers hammers that strike the vertical wires and set up vibrations to create a truly multisensory experience. More info: https://arts.cern/event/unveiling-halo-art-basel
Spreading Dynamics of an Ellipsoidal Drop Impacting on a Heated Substrate
Energy Technology Data Exchange (ETDEWEB)
Yun, Sungchan [Korea Nat’l. Univ. of Transportation, Chungju (Korea, Republic of)
2017-03-15
Unlike spherical drop impact, ellipsoidal drop impact can control the bouncing height on a heated surface by significantly altering impact behavior. To scrutinize the effect of the aspect ratio (AR) of the drop on the bounce suppression, in this study, non-axisymmetric spreading behaviors are observed from two side views and characterized based on the spreading width of the drop for horizontal principal axes. In addition, the maximum spreading width is investigated for various ARs. The results show that as the AR increases, the maximum spreading width of the minor axis increases, whereas that of the major axis shows no significant variation. In the regime of high AR and high impact velocity, liquid fragmentations by three parts are observed during bouncing. These fragmentations are discussed in this work. The hydrodynamic features of ellipsoidal drop impact will help understand bouncing control on non-wetting surfaces for several applications, such as self-cleaning and spray cooling.
International Nuclear Information System (INIS)
Lunney, D.
2009-01-01
Weak binding energy is one of the fundamental criteria characterizing the unique properties of nuclear halos. As such, it must be known with great accuracy and is best obtained through direct mass measurements. The global mass market is now a competitive one. Of the many investment vehicles, the Penning trap has emerged as providing the best rate of return and reliability. We examine mass-market trends, highlighting the recent cases of interest. We also hazard a prediction for the halo futures market. (author)
Indentation of Ellipsoidal and Cylindrical Elastic Shells
Vella, Dominic
2012-10-01
Thin shells are found in nature at scales ranging from viruses to hens\\' eggs; the stiffness of such shells is essential for their function. We present the results of numerical simulations and theoretical analyses for the indentation of ellipsoidal and cylindrical elastic shells, considering both pressurized and unpressurized shells. We provide a theoretical foundation for the experimental findings of Lazarus etal. [following paper, Phys. Rev. Lett. 109, 144301 (2012)PRLTAO0031-9007] and for previous work inferring the turgor pressure of bacteria from measurements of their indentation stiffness; we also identify a new regime at large indentation. We show that the indentation stiffness of convex shells is dominated by either the mean or Gaussian curvature of the shell depending on the pressurization and indentation depth. Our results reveal how geometry rules the rigidity of shells. © 2012 American Physical Society.
Halo-independent direct detection analyses without mass assumptions
International Nuclear Information System (INIS)
Anderson, Adam J.; Fox, Patrick J.; Kahn, Yonatan; McCullough, Matthew
2015-01-01
Results from direct detection experiments are typically interpreted by employing an assumption about the dark matter velocity distribution, with results presented in the m χ −σ n plane. Recently methods which are independent of the DM halo velocity distribution have been developed which present results in the v min −g-tilde plane, but these in turn require an assumption on the dark matter mass. Here we present an extension of these halo-independent methods for dark matter direct detection which does not require a fiducial choice of the dark matter mass. With a change of variables from v min to nuclear recoil momentum (p R ), the full halo-independent content of an experimental result for any dark matter mass can be condensed into a single plot as a function of a new halo integral variable, which we call h-til-tilde(p R ). The entire family of conventional halo-independent g-tilde(v min ) plots for all DM masses are directly found from the single h-tilde(p R ) plot through a simple rescaling of axes. By considering results in h-tilde(p R ) space, one can determine if two experiments are inconsistent for all masses and all physically possible halos, or for what range of dark matter masses the results are inconsistent for all halos, without the necessity of multiple g-tilde(v min ) plots for different DM masses. We conduct a sample analysis comparing the CDMS II Si events to the null results from LUX, XENON10, and SuperCDMS using our method and discuss how the results can be strengthened by imposing the physically reasonable requirement of a finite halo escape velocity
Czech Academy of Sciences Publication Activity Database
Gordillo-Vázquez, F.J.; Luque, A.; Šimek, Milan
2011-01-01
Roč. 116, č. 9 (2011), A09319-A09319 ISSN 0148-0227 Institutional research plan: CEZ:AV0Z20430508 Keywords : sprites * halos * spectroscopy Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.021, year: 2011 http://www.trappa.iaa.es/sites/all/files/papers/isi_journal_papers/2011/2011_08.pdf
Universal Dark Halo Scaling Relation for the Dwarf Spheroidal Satellites
Hayashi, Kohei; Ishiyama, Tomoaki; Ogiya, Go; Chiba, Masashi; Inoue, Shigeki; Mori, Masao
2017-07-01
Motivated by a recently found interesting property of the dark halo surface density within a radius, {r}\\max , giving the maximum circular velocity, {V}\\max , we investigate it for dark halos of the Milky Way’s and Andromeda’s dwarf satellites based on cosmological simulations. We select and analyze the simulated subhalos associated with Milky-Way-sized dark halos and find that the values of their surface densities, {{{Σ }}}{V\\max }, are in good agreement with those for the observed dwarf spheroidal satellites even without employing any fitting procedures. Moreover, all subhalos on the small scales of dwarf satellites are expected to obey the universal relation, irrespective of differences in their orbital evolutions, host halo properties, and observed redshifts. Therefore, we find that the universal scaling relation for dark halos on dwarf galaxy mass scales surely exists and provides us with important clues for understanding fundamental properties of dark halos. We also investigate orbital and dynamical evolutions of subhalos to understand the origin of this universal dark halo relation and find that most subhalos evolve generally along the {r}\\max \\propto {V}\\max sequence, even though these subhalos have undergone different histories of mass assembly and tidal stripping. This sequence, therefore, should be the key feature for understanding the nature of the universality of {{{Σ }}}{V\\max }.
Testing approximate predictions of displacements of cosmological dark matter halos
Energy Technology Data Exchange (ETDEWEB)
Munari, Emiliano; Monaco, Pierluigi; Borgani, Stefano [Department of Physics, Astronomy Unit, University of Trieste, via Tiepolo 11, I-34143 Trieste (Italy); Koda, Jun [INAF – Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate (Italy); Kitaura, Francisco-Shu [Instituto de Astrofísica de Canarias, 38205 San Cristóbal de La Laguna, Santa Cruz de Tenerife (Spain); Sefusatti, Emiliano, E-mail: munari@oats.inaf.it, E-mail: monaco@oats.inaf.it, E-mail: jun.koda@brera.inaf.it, E-mail: fkitaura@iac.es, E-mail: sefusatti@oats.inaf.it, E-mail: borgani@oats.inaf.it [INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, I-34143 Trieste (Italy)
2017-07-01
We present a test to quantify how well some approximate methods, designed to reproduce the mildly non-linear evolution of perturbations, are able to reproduce the clustering of DM halos once the grouping of particles into halos is defined and kept fixed. The following methods have been considered: Lagrangian Perturbation Theory (LPT) up to third order, Truncated LPT, Augmented LPT, MUSCLE and COLA. The test runs as follows: halos are defined by applying a friends-of-friends (FoF) halo finder to the output of an N-body simulation. The approximate methods are then applied to the same initial conditions of the simulation, producing for all particles displacements from their starting position and velocities. The position and velocity of each halo are computed by averaging over the particles that belong to that halo, according to the FoF halo finder. This procedure allows us to perform a well-posed test of how clustering of the matter density and halo density fields are recovered, without asking to the approximate method an accurate reconstruction of halos. We have considered the results at z =0,0.5,1, and we have analysed power spectrum in real and redshift space, object-by-object difference in position and velocity, density Probability Distribution Function (PDF) and its moments, phase difference of Fourier modes. We find that higher LPT orders are generally able to better reproduce the clustering of halos, while little or no improvement is found for the matter density field when going to 2LPT and 3LPT. Augmentation provides some improvement when coupled with 2LPT, while its effect is limited when coupled with 3LPT. Little improvement is brought by MUSCLE with respect to Augmentation. The more expensive particle-mesh code COLA outperforms all LPT methods, and this is true even for mesh sizes as large as the inter-particle distance. This test sets an upper limit on the ability of these methods to reproduce the clustering of halos, for the cases when these objects are
Testing approximate predictions of displacements of cosmological dark matter halos
Munari, Emiliano; Monaco, Pierluigi; Koda, Jun; Kitaura, Francisco-Shu; Sefusatti, Emiliano; Borgani, Stefano
2017-07-01
We present a test to quantify how well some approximate methods, designed to reproduce the mildly non-linear evolution of perturbations, are able to reproduce the clustering of DM halos once the grouping of particles into halos is defined and kept fixed. The following methods have been considered: Lagrangian Perturbation Theory (LPT) up to third order, Truncated LPT, Augmented LPT, MUSCLE and COLA. The test runs as follows: halos are defined by applying a friends-of-friends (FoF) halo finder to the output of an N-body simulation. The approximate methods are then applied to the same initial conditions of the simulation, producing for all particles displacements from their starting position and velocities. The position and velocity of each halo are computed by averaging over the particles that belong to that halo, according to the FoF halo finder. This procedure allows us to perform a well-posed test of how clustering of the matter density and halo density fields are recovered, without asking to the approximate method an accurate reconstruction of halos. We have considered the results at z=0,0.5,1, and we have analysed power spectrum in real and redshift space, object-by-object difference in position and velocity, density Probability Distribution Function (PDF) and its moments, phase difference of Fourier modes. We find that higher LPT orders are generally able to better reproduce the clustering of halos, while little or no improvement is found for the matter density field when going to 2LPT and 3LPT. Augmentation provides some improvement when coupled with 2LPT, while its effect is limited when coupled with 3LPT. Little improvement is brought by MUSCLE with respect to Augmentation. The more expensive particle-mesh code COLA outperforms all LPT methods, and this is true even for mesh sizes as large as the inter-particle distance. This test sets an upper limit on the ability of these methods to reproduce the clustering of halos, for the cases when these objects are
Effective Dark Matter Halo Catalog in f(R) Gravity.
He, Jian-Hua; Hawken, Adam J; Li, Baojiu; Guzzo, Luigi
2015-08-14
We introduce the idea of an effective dark matter halo catalog in f(R) gravity, which is built using the effective density field. Using a suite of high resolution N-body simulations, we find that the dynamical properties of halos, such as the distribution of density, velocity dispersion, specific angular momentum and spin, in the effective catalog of f(R) gravity closely mimic those in the cold dark matter model with a cosmological constant (ΛCDM). Thus, when using effective halos, an f(R) model can be viewed as a ΛCDM model. This effective catalog therefore provides a convenient way for studying the baryonic physics, the galaxy halo occupation distribution and even semianalytical galaxy formation in f(R) cosmologies.
Phase models of galaxies consisting of a disk and halo
International Nuclear Information System (INIS)
Osipkov, L.P.; Kutuzov, S.A.
1988-01-01
A method is developed for finding the phase density of a two-component model of a distribution of masses. The equipotential surfaces and potential law are given. The equipotentials are lenslike surfaces with a sharp edge in the equatorial plane, this ensuring the existence of a vanishingly thin embedded disk. The equidensity surfaces of the halo coincide with the equipotentials. Phase models are constructed separately for the halo and for the disk on the basis of the spatial and surface mass densities by the solution of the corresponding integral equations. In particular, models with a halo having finite dimensions can be constructed. For both components, the part of the phase density even with respect to the velocities is found. For the halo, it depends only on the energy integral. Two examples, for which exact solutions are found, are considered
Magnetic spiral arms in galaxy haloes
Henriksen, R. N.
2017-08-01
We seek the conditions for a steady mean field galactic dynamo. The parameter set is reduced to those appearing in the α2 and α/ω dynamo, namely velocity amplitudes, and the ratio of sub-scale helicity to diffusivity. The parameters can be allowed to vary on conical spirals. We analyse the mean field dynamo equations in terms of scale invariant logarithmic spiral modes and special exact solutions. Compatible scale invariant gravitational spiral arms are introduced and illustrated in an appendix, but the detailed dynamical interaction with the magnetic field is left for another work. As a result of planar magnetic spirals `lifting' into the halo, multiple sign changes in average rotation measures forming a regular pattern on each side of the galactic minor axis, are predicted. Such changes have recently been detected in the Continuum Halos in Nearby Galaxies-an EVLA Survey (CHANG-ES) survey.
Antonella Del Rosso
2015-01-01
In the LHC, beams of 25-ns-spaced proton bunches travel at almost the speed of light and pass through many different devices installed along the ring that monitor their properties. During their whirling motion, beam particles might interact with the collimation instrumentation or with residual gas in the vacuum chambers and this creates the beam halo – an annoying source of background for the physics data. Newly installed CMS sub-detectors are now able to monitor it. The Beam Halo Monitors (BHM) are installed around the CMS rotating shielding. The BHM are designed and built by University of Minnesota, CERN, Princeton University, INFN Bologna and the National Technical University of Athens. (Image: Andrea Manna). The Beam Halo Monitor (BHM) is a set of 20 Cherenkov radiators – 10-cm-long quartz crystals – installed at each end of the huge CMS detector. Their design goal is to measure the particles that can cause the so-called “machine-induced...
International Nuclear Information System (INIS)
Pinsonneault, M. H.; Walker, T. P.; Steigman, G.; Narayanan, Vijay K.
1999-01-01
The depletion of lithium during the pre-main-sequence and main-sequence phases of stellar evolution plays a crucial role in the comparison of the predictions of big bang nucleosynthesis with the abundances observed in halo stars. Previous work has indicated a wide range of possible depletion factors, ranging from minimal in standard (nonrotating) stellar models to as much as an order of magnitude in models that include rotational mixing. Recent progress in the study of the angular momentum evolution of low-mass stars permits the construction of theoretical models capable of reproducing the angular momentum evolution of low-mass open cluster stars. The distribution of initial angular momenta can be inferred from stellar rotation data in young open clusters. In this paper we report on the application of these models to the study of lithium depletion in main-sequence halo stars. A range of initial angular momenta produces a range of lithium depletion factors on the main sequence. Using the distribution of initial conditions inferred from young open clusters leads to a well-defined halo lithium plateau with modest scatter and a small population of outliers. The mass-dependent angular momentum loss law inferred from open cluster studies produces a nearly flat plateau, unlike previous models that exhibited a downward curvature for hotter temperatures in the 7Li-Teff plane. The overall depletion factor for the plateau stars is sensitive primarily to the solar initial angular momentum used in the calibration for the mixing diffusion coefficients. Uncertainties remain in the treatment of the internal angular momentum transport in the models, and the potential impact of these uncertainties on our results is discussed. The 6Li/7Li depletion ratio is also examined. We find that the dispersion in the plateau and the 6Li/7Li depletion ratio scale with the absolute 7Li depletion in the plateau, and we use observational data to set bounds on the 7Li depletion in main-sequence halo
International Nuclear Information System (INIS)
Cameron, Peter
2003-01-01
Tune-based halo diagnostics can be divided into two categories -- diagnostics for halo prevention, and diagnostics for halo measurement. Diagnostics for halo prevention are standard fare in accumulators, synchrotrons, and storage rings, and again can be divided into two categories -- diagnostics to measure the tune distribution (primarily to avoid resonances), and diagnostics to identify instabilities (which will not be discussed here). These diagnostic systems include kicked (coherent) tune measurement, phase-locked loop (PLL) tune measurement, Schottky tune measurement, beam transfer function (BTF) measurements, and measurement of transverse quadrupole mode envelope oscillations. We refer briefly to tune diagnostics used at RHIC and intended for the SNS, and then present experimental results. Tune-based diagnostics for halo measurement (as opposed to prevention) are considerably more difficult. We present one brief example of tune-based halo measurement
Mulchaey, John
Most galaxy formation models predict that massive low-redshift disk galaxies are embedded in extended hot halos of externally accreted gas. Such gas appears necessary to maintain ongoing star formation in isolated spirals like the Milky Way. To explain the large population of red galaxies in rich groups and clusters, most galaxy evolution models assume that these hot gas halos are stripped completely when a galaxy enters a denser environment. This simple model has been remarkably successful at reproducing many observed properties of galaxies. Although theoretical arguments suggest hot gas halos are an important component in galaxies, we know very little about this gas from an observational standpoint. In fact, previous observations have failed to detect soft X-ray emission from such halos in disk galaxies. Furthermore, the assumption that hot gas halos are stripped completely when a galaxy enters a group or cluster has not been verified. We propose to combine proprietary and archival XMM-Newton observations of galaxies in the field, groups and clusters to study how hot gas halos are impacted by environment. Our proposed program has three components: 1) The deepest search to date for a hot gas halo in a quiescent spiral galaxy. A detection will confirm a basic tenet of disk galaxy formation models, whereas a non-detection will seriously challenge these models and impose new constraints on the growth mode and feedback history of disk galaxies. 2) A detailed study of the hot gas halos properties of field early-type galaxies. As environmental processes such as stripping are not expected to be important in the field, a study of hot gas halos in this environment will allow us to better understand how feedback and other internal processes impact hot gas halos. 3) A study of hot gas halos in the outskirts of groups and clusters. By comparing observations with our suite of simulations we can begin to understand what role the stripping of hot gas halos plays in galaxy
Needlelike motion of prolate ellipsoids in the sea of spheres
Vasanthi, R.; Ravichandran, S.; Bagchi, Biman
2001-05-01
Molecular dynamics simulations of translational motion of isolated prolate ellipsoids in the sea of spheres have been carried out for several different values of the aspect ratio (κ), obtained by changing either the length or the diameter of the ellipsoids, at several different solvent densities. The interaction among the spheres is given by the Lennard-Jones pair potential while that between spheres and ellipsoids is given by a modified Gay-Berne potential. Both the mean-square displacements of the center of mass of the ellipsoids and their orientational time correlation function have been calculated. It is found that at short to intermediate times, the motion of ellipsoids is anisotropic and primarily needlelike—the molecules prefer to move parallel to their long axis. The ratio of these two diffusion constants (D∥ and D⊥) approaches κ, suggesting a decoupling of D∥ from the length of the ellipsoid. The diffusion becomes isotropic in the long time with the total diffusion coefficient given by D∥+2D⊥. The crossover from the anisotropic to the isotropic diffusion is surprisingly sharp and clear in most cases.
Recoiling black holes in static and evolving dark matter halo potential
Directory of Open Access Journals (Sweden)
Smole M.
2015-01-01
Full Text Available We follow trajectories of kicked black holes in static and evolving dark matter halo potential. We explore both NFW and Einasto dark matter density distributions. Considered dark matter halos represent hosts of massive spiral and elliptical field galaxies. We study critical amplitude of kick velocity necessary for complete black hole ejection at various redshifts and find that ~40% lower kick velocities can remove black holes from their host haloes at z = 7 compared to z = 1. The greatest difference between static and evolving potential occurs near the critical velocity for black hole ejection and at high redshifts. When NFW and Einasto density distributions are compared ~30% higher kick velocities are needed for complete removal of BHs from dark matter halo described by NFW profile. [Projekat Ministarstva nauke Republike Srbije, br. 176021: Visible and invisible matter in nearby galaxies: Theory and observations
IDENTIFYING STAR STREAMS IN THE MILKY WAY HALO
Energy Technology Data Exchange (ETDEWEB)
King, Charles III; Brown, Warren R.; Geller, Margaret J.; Kenyon, Scott J., E-mail: cking@cfa.harvard.edu, E-mail: wbrown@cfa.harvard.edu, E-mail: mgeller@cfa.harvard.edu, E-mail: skenyon@cfa.harvard.edu [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)
2012-05-01
We develop statistical methods for identifying star streams in the halo of the Milky Way that exploit observed spatial and radial velocity distributions. Within a great circle, departures of the observed spatial distribution from random provide a measure of the likelihood of a potential star stream. Comparisons between the radial velocity distribution within a great circle and the radial velocity distribution of the entire sample also measure the statistical significance of potential streams. The radial velocities enable construction of a more powerful joint statistical test for identifying star streams in the Milky Way halo. Applying our method to halo stars in the Hypervelocity Star (HVS) survey, we detect the Sagittarius stream at high significance. Great circle counts and comparisons with theoretical models suggest that the Sagittarius stream comprises 10%-17% of the halo stars in the HVS sample. The population of blue stragglers and blue horizontal branch stars varies along the stream and is a potential probe of the distribution of stellar populations in the Sagittarius dwarf galaxy prior to disruption.
IDENTIFYING STAR STREAMS IN THE MILKY WAY HALO
International Nuclear Information System (INIS)
King, Charles III; Brown, Warren R.; Geller, Margaret J.; Kenyon, Scott J.
2012-01-01
We develop statistical methods for identifying star streams in the halo of the Milky Way that exploit observed spatial and radial velocity distributions. Within a great circle, departures of the observed spatial distribution from random provide a measure of the likelihood of a potential star stream. Comparisons between the radial velocity distribution within a great circle and the radial velocity distribution of the entire sample also measure the statistical significance of potential streams. The radial velocities enable construction of a more powerful joint statistical test for identifying star streams in the Milky Way halo. Applying our method to halo stars in the Hypervelocity Star (HVS) survey, we detect the Sagittarius stream at high significance. Great circle counts and comparisons with theoretical models suggest that the Sagittarius stream comprises 10%-17% of the halo stars in the HVS sample. The population of blue stragglers and blue horizontal branch stars varies along the stream and is a potential probe of the distribution of stellar populations in the Sagittarius dwarf galaxy prior to disruption.
The Extended Baryonic Halo of NGC 3923
Directory of Open Access Journals (Sweden)
Bryan W. Miller
2017-07-01
Full Text Available Galaxy halos and their globular cluster systems build up over time by the accretion of small satellites. We can learn about this process in detail by observing systems with ongoing accretion events and comparing the data with simulations. Elliptical shell galaxies are systems that are thought to be due to ongoing or recent minor mergers. We present preliminary results of an investigation of the baryonic halo—light profile, globular clusters, and shells/streams—of the shell galaxy NGC 3923 from deep Dark Energy Camera (DECam g and i-band imaging. We present the 2D and radial distributions of the globular cluster candidates out to a projected radius of about 185 kpc, or ∼ 37 R e , making this one of the most extended cluster systems studied. The total number of clusters implies a halo mass of M h ∼ 3 × 10 13 M ⊙ . Previous studies had identified between 22 and 42 shells, making NGC 3923 the system with the largest number of shells. We identify 23 strong shells and 11 that are uncertain. Future work will measure the halo mass and mass profile from the radial distributions of the shell, N-body models, and line-of-sight velocity distribution (LOSVD measurements of the shells using the Multi Unit Spectroscopic Explorer (MUSE.
Cold dark matter. 1: The formation of dark halos
Gelb, James M.; Bertschinger, Edmund
1994-01-01
We use numerical simulations of critically closed cold dark matter (CDM) models to study the effects of numerical resolution on observable quantities. We study simulations with up to 256(exp 3) particles using the particle-mesh (PM) method and with up to 144(exp 3) particles using the adaptive particle-particle-mesh (P3M) method. Comparisons of galaxy halo distributions are made among the various simulations. We also compare distributions with observations, and we explore methods for identifying halos, including a new algorithm that finds all particles within closed contours of the smoothed density field surrounding a peak. The simulated halos show more substructure than predicted by the Press-Schechter theory. We are able to rule out all omega = 1 CDM models for linear amplitude sigma(sub 8) greater than or approximately = 0.5 because the simulations produce too many massive halos compared with the observations. The simulations also produce too many low-mass halos. The distribution of halos characterized by their circular velocities for the P3M simulations is in reasonable agreement with the observations for 150 km/s less than or = V(sub circ) less than or = 350 km/s.
Deconstructing Disk Velocity Distribution Functions in the Disk-Mass Survey
Westfall, K. B.; Bershady, M. A.; Verheijen, M. A. W.; Andersen, D. R.; Swaters, R. A.
2008-01-01
We analyze integral-field ionized gas and stellar line-of-sight kinematics in the context of determining the stellar velocity ellipsoid for spiral galaxies observed by the Disk-Mass Survey. Our new methodology enables us to measure, for the first time, a radial gradient in the ellipsoid ratio
Halo-Independent Direct Detection Analyses Without Mass Assumptions
Anderson, Adam J.; Kahn, Yonatan; McCullough, Matthew
2015-10-06
Results from direct detection experiments are typically interpreted by employing an assumption about the dark matter velocity distribution, with results presented in the $m_\\chi-\\sigma_n$ plane. Recently methods which are independent of the DM halo velocity distribution have been developed which present results in the $v_{min}-\\tilde{g}$ plane, but these in turn require an assumption on the dark matter mass. Here we present an extension of these halo-independent methods for dark matter direct detection which does not require a fiducial choice of the dark matter mass. With a change of variables from $v_{min}$ to nuclear recoil momentum ($p_R$), the full halo-independent content of an experimental result for any dark matter mass can be condensed into a single plot as a function of a new halo integral variable, which we call $\\tilde{h}(p_R)$. The entire family of conventional halo-independent $\\tilde{g}(v_{min})$ plots for all DM masses are directly found from the single $\\tilde{h}(p_R)$ plot through a simple re...
THE SEGUE K GIANT SURVEY. III. QUANTIFYING GALACTIC HALO SUBSTRUCTURE
Energy Technology Data Exchange (ETDEWEB)
Janesh, William; Morrison, Heather L.; Ma, Zhibo; Harding, Paul [Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106 (United States); Rockosi, Constance [UCO/Lick Observatory, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Starkenburg, Else [Department of Physics and Astronomy, University of Victoria, P.O. Box 1700, STN CSC, Victoria BC V8W 3P6 (Canada); Xue, Xiang Xiang; Rix, Hans-Walter [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Beers, Timothy C. [Department of Physics and JINA Center for the Evolution of the Elements, University of Notre Dame, Notre Dame, IN 46556 (United States); Johnson, Jennifer [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Lee, Young Sun [Department of Astronomy and Space Science, Chungnam National University, Daejeon 34134 (Korea, Republic of); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)
2016-01-10
We statistically quantify the amount of substructure in the Milky Way stellar halo using a sample of 4568 halo K giant stars at Galactocentric distances ranging over 5–125 kpc. These stars have been selected photometrically and confirmed spectroscopically as K giants from the Sloan Digital Sky Survey’s Sloan Extension for Galactic Understanding and Exploration project. Using a position–velocity clustering estimator (the 4distance) and a model of a smooth stellar halo, we quantify the amount of substructure in the halo, divided by distance and metallicity. Overall, we find that the halo as a whole is highly structured. We also confirm earlier work using blue horizontal branch (BHB) stars which showed that there is an increasing amount of substructure with increasing Galactocentric radius, and additionally find that the amount of substructure in the halo increases with increasing metallicity. Comparing to resampled BHB stars, we find that K giants and BHBs have similar amounts of substructure over equivalent ranges of Galactocentric radius. Using a friends-of-friends algorithm to identify members of individual groups, we find that a large fraction (∼33%) of grouped stars are associated with Sgr, and identify stars belonging to other halo star streams: the Orphan Stream, the Cetus Polar Stream, and others, including previously unknown substructures. A large fraction of sample K giants (more than 50%) are not grouped into any substructure. We find also that the Sgr stream strongly dominates groups in the outer halo for all except the most metal-poor stars, and suggest that this is the source of the increase of substructure with Galactocentric radius and metallicity.
Ardalan, A. A.; Safari, A.
2004-09-01
An operational algorithm for computation of terrain correction (or local gravity field modeling) based on application of closed-form solution of the Newton integral in terms of Cartesian coordinates in multi-cylindrical equal-area map projection of the reference ellipsoid is presented. Multi-cylindrical equal-area map projection of the reference ellipsoid has been derived and is described in detail for the first time. Ellipsoidal mass elements with various sizes on the surface of the reference ellipsoid are selected and the gravitational potential and vector of gravitational intensity (i.e. gravitational acceleration) of the mass elements are computed via numerical solution of the Newton integral in terms of geodetic coordinates {λ,ϕ,h}. Four base- edge points of the ellipsoidal mass elements are transformed into a multi-cylindrical equal-area map projection surface to build Cartesian mass elements by associating the height of the corresponding ellipsoidal mass elements to the transformed area elements. Using the closed-form solution of the Newton integral in terms of Cartesian coordinates, the gravitational potential and vector of gravitational intensity of the transformed Cartesian mass elements are computed and compared with those of the numerical solution of the Newton integral for the ellipsoidal mass elements in terms of geodetic coordinates. Numerical tests indicate that the difference between the two computations, i.e. numerical solution of the Newton integral for ellipsoidal mass elements in terms of geodetic coordinates and closed-form solution of the Newton integral in terms of Cartesian coordinates, in a multi-cylindrical equal-area map projection, is less than 1.6×10-8 m2/s2 for a mass element with a cross section area of 10×10 m and a height of 10,000 m. For a mass element with a cross section area of 1×1 km and a height of 10,000 m the difference is less than 1.5×10-4m2/s2. Since 1.5× 10-4 m2/s2 is equivalent to 1.5×10-5m in the vertical
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.
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.
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.
HALOE test and evaluation software
Edmonds, W.; Natarajan, S.
1987-01-01
Computer programming, system development and analysis efforts during this contract were carried out in support of the Halogen Occultation Experiment (HALOE) at NASA/Langley. Support in the major areas of data acquisition and monitoring, data reduction and system development are described along with a brief explanation of the HALOE project. Documented listings of major software are located in the appendix.
Neutron halo in deformed nuclei
International Nuclear Information System (INIS)
Zhou Shangui; Meng Jie; Ring, P.; Zhao Enguang
2010-01-01
Halo phenomena in deformed nuclei are investigated within a deformed relativistic Hartree Bogoliubov (DRHB) theory. These weakly bound quantum systems present interesting examples for the study of the interdependence between the deformation of the core and the particles in the halo. Contributions of the halo, deformation effects, and large spatial extensions of these systems are described in a fully self-consistent way by the DRHB equations in a spherical Woods-Saxon basis with the proper asymptotic behavior at a large distance from the nuclear center. Magnesium and neon isotopes are studied and detailed results are presented for the deformed neutron-rich and weakly bound nucleus 44 Mg. The core of this nucleus is prolate, but the halo has a slightly oblate shape. This indicates a decoupling of the halo orbitals from the deformation of the core. The generic conditions for the occurrence of this decoupling effects are discussed.
X-ray microfocusing with off-axis ellipsoidal mirror
Energy Technology Data Exchange (ETDEWEB)
Yumoto, Hirokatsu, E-mail: yumoto@spring8.or.jp; Koyama, Takahisa [Japan Synchrotron Radiation Research Institute/SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Matsuyama, Satoshi; Yamauchi, Kazuto [Department of Precision Science and Technology, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan); Kohmura, Yoshiki; Ishikawa, Tetsuya [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Ohashi, Haruhiko [Japan Synchrotron Radiation Research Institute/SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan)
2016-07-27
High-precision ellipsoidal mirrors for two-dimensionally focusing X-rays to nanometer sizes have not been realized because of technical problems in their fabrication processes. The objective of the present study is to develop fabrication techniques for ellipsoidal focusing mirrors in the hard-X-ray region. We design an off-axis ellipsoidal mirror for use under total reflection conditions up to the X-ray energy of 8 keV. We fabricate an ellipsoidal mirror with a surface roughness of 0.3 nm RMS (root-mean-square) and a surface figure error height of 3.0 nm RMS by utilizing a surface profiler and surface finishing method developed by us. The focusing properties of the mirror are evaluated at the BL29XUL beamline in SPring-8. A focusing beam size of 270 nm × 360 nm FWHM (full width at half maximum) at an X-ray energy of 7 keV is observed with the use of the knife-edge scanning method. We expect to apply the developed fabrication techniques to construct ellipsoidal nanofocusing mirrors.
The Hubble IR cutoff in holographic ellipsoidal cosmologies
Energy Technology Data Exchange (ETDEWEB)
Cataldo, Mauricio [Universidad del Bio-Bio, Departamento de Fisica, Facultad de Ciencias, Concepcion (Chile); Cruz, Norman [Grupo de Cosmologia y Gravitacion-UBB, Concepcion (Chile)
2018-01-15
It is well known that for spatially flat FRW cosmologies, the holographic dark energy disfavors the Hubble parameter as a candidate for the IR cutoff. For overcoming this problem, we explore the use of this cutoff in holographic ellipsoidal cosmological models, and derive the general ellipsoidal metric induced by a such holographic energy density. Despite the drawbacks that this cutoff presents in homogeneous and isotropic universes, based on this general metric, we developed a suitable ellipsoidal holographic cosmological model, filled with a dark matter and a dark energy components. At late time stages, the cosmic evolution is dominated by a holographic anisotropic dark energy with barotropic equations of state. The cosmologies expand in all directions in accelerated manner. Since the ellipsoidal cosmologies given here are not asymptotically FRW, the deviation from homogeneity and isotropy of the universe on large cosmological scales remains constant during all cosmic evolution. This feature allows the studied holographic ellipsoidal cosmologies to be ruled by an equation of state ω = p/ρ, whose range belongs to quintessence or even phantom matter. (orig.)
Transverse mixing of ellipsoidal particles in a rotating drum
Directory of Open Access Journals (Sweden)
He Siyuan
2017-01-01
Full Text Available Rotating drums are widely used in industry for mixing, milling, coating and drying processes. In the past decades, mixing of granular materials in rotating drums has been extensively investigated, but most of the studies are based on spherical particles. Particle shape has an influence on the flow behaviour and thus mixing behaviour, though the shape effect has as-yet received limited study. In this work, discrete element method (DEM is employed to study the transverse mixing of ellipsoidal particles in a rotating drum. The effects of aspect ratio and rotating speed on mixing quality and mixing rate are investigated. The results show that mixing index increases exponentially with time for both spheres and ellipsoids. Particles with various aspect ratios are able to reach well-mixed states after sufficient revolutions in the rolling or cascading regime. Ellipsoids show higher mixing rate when rotational speed is set between 25 and 40 rpm. The relationship between mixing rate and aspect ratio of ellipsoids is established, demonstrating that, particles with aspect ratios of 0.5 and 2.0 achieve the highest mixing rates. Increasing rotating speed from 15 rpm to 40 rpm does not necessarily increase the mixing speed of spheres, while monotonous increase is observed for ellipsoids.
Black Hole Space-time In Dark Matter Halo
Xu, Zhaoyi; Hou, Xian; Gong, Xiaobo; Wang, Jiancheng
2018-01-01
For the first time, we obtain the analytical form of black hole space-time metric in dark matter halo for the stationary situation. Using the relation between the rotation velocity (in the equatorial plane) and the spherical symmetric space-time metric coefficient, we obtain the space-time metric for pure dark matter. By considering the dark matter halo in spherical symmetric space-time as part of the energy-momentum tensors in the Einstein field equation, we then obtain the spherical symmetr...
Hess, Robert V; Gardner, Clifford S
1947-01-01
By using the Prandtl-Glauert method that is valid for three-dimensional flow problems, the value of the maximum incremental velocity for compressible flow about thin ellipsoids at zero angle of attack is calculated as a function of the Mach number for various aspect ratios and thickness ratios. The critical Mach numbers of the various ellipsoids are also determined. The results indicate an increase in critical Mach number with decrease in aspect ratio which is large enough to explain experimental results on low-aspect-ratio wings at zero lift.
Monten, Ruben; Toldo, Chiara
2018-02-01
We present new AdS4 black hole solutions in N =2 gauged supergravity coupled to vector and hypermultiplets. We focus on a particular consistent truncation of M-theory on the homogeneous Sasaki–Einstein seven-manifold M 111, characterized by the presence of one Betti vector multiplet. We numerically construct static and spherically symmetric black holes with electric and magnetic charges, corresponding to M2 and M5 branes wrapping non-contractible cycles of the internal manifold. The novel feature characterizing these nonzero temperature configurations is the presence of a massive vector field halo. Moreover, we verify the first law of black hole mechanics and we study the thermodynamics in the canonical ensemble. We analyze the behavior of the massive vector field condensate across the small-large black hole phase transition and we interpret the process in the dual field theory.
Ellipsoidal all-dielectric Fano resonant core-shell metamaterials
Reena, Reena; Kalra, Yogita; Kumar, Ajeet
2018-06-01
In this paper, ellipsoidal core (Si) and shell (SiO2) metamaterial has been proposed for highly directional properties. At the wavelength of magnetic resonance, Fano dip occurs in the backward scattering cross section and forward scattering enhancement takes place at the same wavelength so that there is an increment in the directivity. Effect on the directivity by changing the length of ellipsoidal nanoparticle along semi-axes has been analyzed. Two Fano resonances have been observed by decreasing the length of the nanoparticle along the semi-axis having electric polarization, where first and second Fano resonances are attributed to the dipole and quadrupole moments, respectively. These Fano resonant wavelengths in ellipsoidal nanoparticle exhibit higher directivity than the Kerker's type scattering or forward scattering shown by symmetrical structures like sphere. So, this core-shell metamaterial can act as an efficient directional nanoantenna.
Dislocation pile-ups, slip-bands, ellipsoids, and cracks
International Nuclear Information System (INIS)
Brown, Lawrence M.
2005-01-01
The classic theories of dislocation pile-ups, initiated by Eshelby, Frank and Nabarro, and by Leibfried, can be greatly simplified if it is recognised that the dislocations in the pile-up will experience uniform stress if they are lodged in an ellipsoidal interface. Elementary algebra then produces the familiar results from continuum theory. It seems possible that the ellipsoid construction may represent physical reality if it is taken to represent a three-dimensional slip-band. If so, there are concentrated forces spreading the band perpendicular to the slip band as well as parallel to it. Such ellipsoids also represent Mode II and Mode III cracks, and give a method for dealing with the more complicated Mode I cracks
HOBBY-EBERLY TELESCOPE OBSERVATIONS OF THE DARK HALO IN NGC 821
International Nuclear Information System (INIS)
Forestell, Amy D.; Gebhardt, Karl
2010-01-01
We present stellar line-of-sight velocity distributions (LOSVDs) of elliptical galaxy NGC 821 obtained to approximately 100'' (over two effective radii) with long-slit spectroscopy from the Hobby-Eberly Telescope. Our measured stellar LOSVDs are larger than the planetary nebulae measurements at similar radii. We fit axisymmetric orbit-superposition models with a range of dark halo density profiles, including two-dimensional kinematics at smaller radii from SAURON data. Within our assumptions, the best-fitted model gives a total enclosed mass of 2.0 x 10 11 M sun within 100'', with an accuracy of 2%; this mass is equally divided between halo and stars. At 1 R e , the best-fitted dark matter halo accounts for 13% of the total mass in the galaxy. This dark halo is inconsistent with previous claims of little to no dark matter halo in this galaxy from planetary nebula measurements. We find that a power-law dark halo with a slope 0.1 is the best-fitted model; both the no dark halo and Navarro-Frenk-White models are worse fits at a greater than 99% confidence level. NGC 821 does not appear to have the expected dark halo density profile. The internal moments of the stellar velocity distribution show that the model with no dark halo is radially anisotropic at small radii and tangentially isotropic at large radii, while the best-fitted halo models are slightly radially anisotropic at all radii. We test the potential effects of model smoothing and find that there are no effects on our results within the errors. Finally, we run models using the planetary nebula kinematics and assuming our best-fitted halos and find that the planetary nebulae require radial orbits throughout the galaxy.
Microscopic analysis of Hopper flow with ellipsoidal particles
Liu, Sida; Zhou, Zongyan; Zou, Ruiping; Pinson, David; Yu, Aibing
2013-06-01
Hoppers are widely used in process industries. With such widespread application, difficulties in achieving desired operational behaviors have led to extensive experimental and mathematical studies in the past decades. Particularly, the discrete element method has become one of the most important simulation tools for design and analysis. So far, most studies are on spherical particles for computational convenience. In this work, ellipsoidal particles are used as they can represent a large variation of particle shapes. Hopper flow with ellipsoidal particles is presented highlighting the effect of particle shape on the microscopic properties.
Halo-independent methods for inelastic dark matter scattering
International Nuclear Information System (INIS)
Bozorgnia, Nassim; Schwetz, Thomas; Herrero-Garcia, Juan; Zupan, Jure
2013-01-01
We present halo-independent methods to analyze the results of dark matter direct detection experiments assuming inelastic scattering. We focus on the annual modulation signal reported by DAMA/LIBRA and present three different halo-independent tests. First, we compare it to the upper limit on the unmodulated rate from XENON100 using (a) the trivial requirement that the amplitude of the annual modulation has to be smaller than the bound on the unmodulated rate, and (b) a bound on the annual modulation amplitude based on an expansion in the Earth's velocity. The third test uses the special predictions of the signal shape for inelastic scattering and allows for an internal consistency check of the data without referring to any astrophysics. We conclude that a strong conflict between DAMA/LIBRA and XENON100 in the framework of spin-independent inelastic scattering can be established independently of the local properties of the dark matter halo
ZOMG - I. How the cosmic web inhibits halo growth and generates assembly bias
Borzyszkowski, Mikolaj; Porciani, Cristiano; Romano-Díaz, Emilio; Garaldi, Enrico
2017-07-01
The clustering of dark matter haloes with fixed mass depends on their formation history, an effect known as assembly bias. We use zoom N-body simulations to investigate the origin of this phenomenon. For each halo at redshift z = 0, we determine the time in which the physical volume containing its final mass becomes stable. We consider five examples for which this happens at z ˜ 1.5 and two that do not stabilize by z = 0. The zoom simulations show that early-collapsing haloes do not grow in mass at z = 0 while late-forming ones show a net inflow. The reason is that 'accreting' haloes are located at the nodes of a network of thin filaments feeding them. Conversely, each 'stalled' halo lies within a prominent filament that is thicker than the halo size. Infalling material from the surroundings becomes part of the filament while matter within it recedes from the halo. We conclude that assembly bias originates from quenching halo growth due to tidal forces following the formation of non-linear structures in the cosmic web, as previously conjectured in the literature. Also the internal dynamics of the haloes change: the velocity anisotropy profile is biased towards radial (tangential) orbits in accreting (stalled) haloes. Our findings reveal the cause of the yet unexplained dependence of halo clustering on the anisotropy. Finally, we extend the excursion-set theory to account for these effects. A simple criterion based on the ellipticity of the linear tidal field combined with the spherical-collapse model provides excellent predictions for both classes of haloes.
Exploring the liminality: properties of haloes and subhaloes in borderline f(R) gravity
Shi, Difu; Li, Baojiu; Han, Jiaxin; Gao, Liang; Hellwing, Wojciech A.
2015-09-01
We investigate the properties of dark matter haloes and subhaloes in an f(R) gravity model with |fR0| = 10-6, using a very-high-resolution N-body simulation. The model is a borderline between being cosmologically interesting and yet still consistent with current data. We find that the halo mass function in this model has a maximum 20 per cent enhancement compared with the Λ-cold-dark-matter (ΛCDM) predictions between z = 1 and 0. Because of the chameleon mechanism which screens the deviation from standard gravity in dense environments, haloes more massive than 1013 h-1 M⊙ in this f(R) model have very similar properties to haloes of similar mass in ΛCDM, while less massive haloes, such as that of the Milky Way, can have steeper inner density profiles and higher velocity dispersions due to their weaker screening. The halo concentration is remarkably enhanced for low-mass haloes in this model due to a deepening of the total gravitational potential. Contrary to the naive expectation, the halo formation time zf is later for low-mass haloes in this model, a consequence of these haloes growing faster than their counterparts in ΛCDM at late times and the definition of zf. Subhaloes, especially those less massive than 1011 h-1 M⊙, are substantially more abundant in this f(R) model for host haloes less massive than 1013 h-1 M⊙. We discuss the implications of these results for the Milky Way satellite abundance problem. Although the overall halo and subhalo properties in this borderline f(R) model are close to their ΛCDM predictions, our results suggest that studies of the Local Group and astrophysical systems, aided by high-resolution simulations, can be valuable for further tests of it.
Energy Technology Data Exchange (ETDEWEB)
Hayashi, Kohei [Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), The University of Tokyo, Chiba 277-8583 (Japan); Chiba, Masashi, E-mail: kohei.hayashi@ipmu.jp, E-mail: chiba@astr.tohoku.ac.jp [Astronomical Institute, Tohoku University, Aoba-ku, Sendai 980-8578 (Japan)
2015-09-01
We investigate the non-spherical density structure of dark halos of the dwarf spheroidal (dSph) galaxies in the Milky Way and Andromeda galaxies based on revised axisymmetric mass models from our previous work. The models we adopt here fully take into account velocity anisotropy of tracer stars confined within a flattened dark halo. Applying our models to the available kinematic data of the 12 bright dSphs, we find that these galaxies associate with, in general, elongated dark halos, even considering the effect of this velocity anisotropy of stars. We also find that the best-fit parameters, especially for the shapes of dark halos and velocity anisotropy, are susceptible to both the availability of velocity data in the outer regions and the effect of the lack of sample stars in each spatial bin. Thus, to obtain more realistic limits on dark halo structures, we require photometric and kinematic data over much larger areas in the dSphs than previously explored. The results obtained from the currently available data suggest that the shapes of dark halos in the dSphs are more elongated than those of ΛCDM subhalos. This mismatch needs to be solved by theory including baryon components and the associated feedback to dark halos as well as by further observational limits in larger areas of dSphs. It is also found that more diffuse dark halos may have undergone consecutive star formation history, thereby implying that dark-halo structure plays an important role in star formation activity.
Dynamical behaviour of gaseous halo in a disk galaxy
International Nuclear Information System (INIS)
Ikeuchi, S.; Habe, A.
1981-01-01
Assuming that the gas in the halo of a disk galaxy is supplied from the disk as a hot gas, the authors have studied its dynamical and thermal behaviour by means of a time dependent, two-dimensional hydrodynamic code. They suppose the following boundary conditions at the disk. (i) The hot gas with the temperature Tsub(d) and the density nsub(d) is uniform at r=4-12 kpc in the disk and it is time independent. (ii) This hot gas rotates with the stellar disk in the same velocity. (iii) This hot gas can escape freely from the disk to the halo. These conditions will be verified if the filling factor of hot gas is so large as f=0.5-0.8, as proposed by McKee and Ostriker (1977). The gas motion in the halo has been studied for wider ranges of gas temperature and its density at the disk than previously studied. At the same time, the authors have clarified the observability of various types of gaseous haloes and discuss the roles of gaseous halo on the evolution of galaxies. (Auth.)
Does SEGUE/SDSS indicate a dual galactic halo?
International Nuclear Information System (INIS)
Schönrich, Ralph; Asplund, Martin; Casagrande, Luca
2014-01-01
We re-examine recent claims of observational evidence for a dual Galactic halo in SEGUE/SDSS data, and trace them back to improper error treatment and neglect of selection effects. In particular, the detection of a vertical abundance gradient in the halo can be explained as a metallicity bias in distance. A similar bias and the impact of disk contamination affect the sample of blue horizontal branch stars. These examples highlight why non-volume complete samples require forward modeling from theoretical models or extensive bias-corrections. We also show how observational uncertainties produce the specific non-Gaussianity in the observed azimuthal velocity distribution of halo stars, which can be erroneously identified as two Gaussian components. A single kinematic component yields an excellent fit to the observed data, when we model the measurement process including distance uncertainties. Furthermore, we show that sample differences in proper motion space are the direct consequence of kinematic cuts and are enhanced when distance estimates are less accurate. Thus, their presence is neither proof of a separate population nor a measure of reliability for the applied distances. We conclude that currently there is no evidence from SEGUE/SDSS that would favor a dual Galactic halo over a single halo that is full of substructure.
Halo shapes, initial shear field, and cosmic web
International Nuclear Information System (INIS)
Rossi, G
2014-01-01
The ellipsoidal collapse model, combined with the excursion set theory, allows one to estimate the shapes of dark matter halos as seen in high-resolution numerical simulations. The same theoretical framework predicts a quasi-universal behaviour for the conditional axis ratio distributions at later times, set by initial conditions and unaltered by non-linear evolution. The formalism for halo shapes is also useful in making the connection with the initial shear field of the cosmic web, which plays a crucial role in the formation of large-scale structures. The author has briefly discussed the basic aspects of the modelling, as well as the implications of a new formula for the constrained eigenvalues of the initial shear field, given the fact that positions are peaks or dips in the corresponding density field – and not random locations. This formula leads to a new generalized excursion set algorithm for peaks in Gaussian random fields. The results highlighted, here, are relevant for a number of applications, especially for weak lensing studies and for devising algorithms to find and classify structures in the cosmic web
GAVINO ROSELLÓ, AARÓN
2017-01-01
The halo effect is one of the most classic cognitive biases of psychology, and one that we can observe frequently in everyday life. It consists in the realization of an erroneous generalization from a single characteristic or quality of an object or a person, that is, we make a previous judgment from which, we generalize the rest of characteristics. The halo effect manifests itself as continuous in our life. For example, if someone is very handsome or attractive we attribute another series...
Computing the maximum volume inscribed ellipsoid of a polytopic projection
Zhen, Jianzhe; den Hertog, Dick
We introduce a novel scheme based on a blending of Fourier-Motzkin elimination (FME) and adjustable robust optimization techniques to compute the maximum volume inscribed ellipsoid (MVE) in a polytopic projection. It is well-known that deriving an explicit description of a projected polytope is
Computing the Maximum Volume Inscribed Ellipsoid of a Polytopic Projection
Zhen, J.; den Hertog, D.
2015-01-01
We introduce a novel scheme based on a blending of Fourier-Motzkin elimination (FME) and adjustable robust optimization techniques to compute the maximum volume inscribed ellipsoid (MVE) in a polytopic projection. It is well-known that deriving an explicit description of a projected polytope is
Ramification of Datum and Ellipsoidal Parameters on Post ...
African Journals Online (AJOL)
Michael
2015-06-01
Jun 1, 2015 ... also post processed using Ghana War Office datum and ellipsoidal parameters. The results for the two ... rely on the datum (Kotzev, 2013). It is equally ..... Microsoft Excel spreadsheet (MS excel) was used for analysis of the ...
Absorbed fractions for alpha particles in ellipsoidal volumes
International Nuclear Information System (INIS)
Amato, Ernesto; Baldari, Sergio; Italiano, Antonio
2013-01-01
Internal dosimetry of alpha particles is gaining attention due to the increasing applications in cancer treatment and also for the assessment of environmental contamination from radionuclides. We developed a Monte Carlo simulation in GEANT4 in order to calculate the absorbed fractions for monoenergetic alpha particles in the energy interval between 0.1 and 10 MeV, uniformly distributed in ellipsoids made of soft tissue. For each volume, we simulated a spherical shape, three oblate and three prolate ellipsoids, and one scalene shape. For each energy and for every geometrical configuration, an analytical relationship between the absorbed fraction and a ‘generalized radius’ was found; and the dependence of the fit parameters on the alpha energy is discussed and fitted by parametric functions. With the proposed formulation, the absorbed fraction for alpha particles in the energy range explored can be calculated for volumes and for ellipsoidal shapes of practical interest. This method can be applied to the evaluation of absorbed fraction from alpha-emitting radionuclides. The contribution to the deposited energy coming from electron and photon emissions can be accounted for exploiting the specific formulations previously introduced. As an example of application, the dosimetry of 213 Bi and its decay chain in ellipsoids is reported. (paper)
Lue, H F; Meng, J; Zhou, S G
2003-01-01
Properties of single-LAMBDA and double-LAMBDA hypernuclei for even-N Ca isotopes ranging from the proton dripline to the neutron dripline are studied using the relativistic continuum Hartree-Bogolyubov theory with a zero-range pairing interaction. Compared with ordinary nuclei, the addition of one or two LAMBDA-hyperons lowers the Fermi level. The predicted neutron dripline nuclei are, respectively, sup 7 sup 5 subLAMBDA Ca and sup 7 sup 6 sub 2 subLAMBDA Ca, as the additional attractive force provided by the LAMBDA-N interaction shifts nuclei from outside to inside the dripline. Therefore, the last bound hypernuclei have two more neutrons than the corresponding ordinary nuclei. Based on the analysis of two-neutron separation energies, neutron single-particle energy levels, the contribution of continuum and nucleon density distribution, giant halo phenomena due to the pairing correlation, and the contribution from the continuum are suggested to exist in Ca hypernuclei similar to those that appear in ordinary ...
Waheed, Umair bin; Alkhalifah, Tariq Ali
2014-01-01
The wavefield extrapolation operator for ellipsoidally anisotropic (EA) media offers significant cost reduction compared to that for the orthorhombic case, especially when the symmetry planes are tilted and/or rotated. However, ellipsoidal anisotropy does not provide accurate focusing for media of orthorhombic anisotropy. Therefore, we develop effective EA models that correctly capture the kinematic behavior of the wavefield for tilted orthorhombic (TOR) media. Specifically, we compute effective source-dependent velocities for the EA model using kinematic high-frequency representation of the TOR wavefield. The effective model allows us to use the cheaper EA wavefield extrapolation operator to obtain approximate wavefield solutions for a TOR model. Despite the fact that the effective EA models are obtained by kinematic matching using high-frequency asymptotic, the resulting wavefield contains most of the critical wavefield components, including the frequency dependency and caustics, if present, with reasonable accuracy. The methodology developed here offers a much better cost versus accuracy tradeoff for wavefield computations in TOR media, particularly for media of low to moderate complexity. We demonstrate applicability of the proposed approach on a layered TOR model.
Waheed, Umair bin
2014-08-01
The wavefield extrapolation operator for ellipsoidally anisotropic (EA) media offers significant cost reduction compared to that for the orthorhombic case, especially when the symmetry planes are tilted and/or rotated. However, ellipsoidal anisotropy does not provide accurate focusing for media of orthorhombic anisotropy. Therefore, we develop effective EA models that correctly capture the kinematic behavior of the wavefield for tilted orthorhombic (TOR) media. Specifically, we compute effective source-dependent velocities for the EA model using kinematic high-frequency representation of the TOR wavefield. The effective model allows us to use the cheaper EA wavefield extrapolation operator to obtain approximate wavefield solutions for a TOR model. Despite the fact that the effective EA models are obtained by kinematic matching using high-frequency asymptotic, the resulting wavefield contains most of the critical wavefield components, including the frequency dependency and caustics, if present, with reasonable accuracy. The methodology developed here offers a much better cost versus accuracy tradeoff for wavefield computations in TOR media, particularly for media of low to moderate complexity. We demonstrate applicability of the proposed approach on a layered TOR model.
Classical studies of the ellipsoidal shapes for dynamical deformation theories of the nucleus
International Nuclear Information System (INIS)
Remaud, B.
1978-01-01
The shape-dependent functions of the Liquid Drop and the Droplet Models are analytically calculated for an ellipsoid. Using the ellipsoidal symmetries, these functions (including the curvature function) are written in terms of three basic expressions. The nuclear deformation energy can be calculated in a simple way for axially symmetric and asymmetric ellipsoidal nuclei whatever the magnitude of the deformation is
Halo modelling in chameleon theories
Energy Technology Data Exchange (ETDEWEB)
Lombriser, Lucas; Koyama, Kazuya [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth, PO1 3FX (United Kingdom); Li, Baojiu, E-mail: lucas.lombriser@port.ac.uk, E-mail: kazuya.koyama@port.ac.uk, E-mail: baojiu.li@durham.ac.uk [Institute for Computational Cosmology, Ogden Centre for Fundamental Physics, Department of Physics, University of Durham, Science Laboratories, South Road, Durham, DH1 3LE (United Kingdom)
2014-03-01
We analyse modelling techniques for the large-scale structure formed in scalar-tensor theories of constant Brans-Dicke parameter which match the concordance model background expansion history and produce a chameleon suppression of the gravitational modification in high-density regions. Thereby, we use a mass and environment dependent chameleon spherical collapse model, the Sheth-Tormen halo mass function and linear halo bias, the Navarro-Frenk-White halo density profile, and the halo model. Furthermore, using the spherical collapse model, we extrapolate a chameleon mass-concentration scaling relation from a ΛCDM prescription calibrated to N-body simulations. We also provide constraints on the model parameters to ensure viability on local scales. We test our description of the halo mass function and nonlinear matter power spectrum against the respective observables extracted from large-volume and high-resolution N-body simulations in the limiting case of f(R) gravity, corresponding to a vanishing Brans-Dicke parameter. We find good agreement between the two; the halo model provides a good qualitative description of the shape of the relative enhancement of the f(R) matter power spectrum with respect to ΛCDM caused by the extra attractive gravitational force but fails to recover the correct amplitude. Introducing an effective linear power spectrum in the computation of the two-halo term to account for an underestimation of the chameleon suppression at intermediate scales in our approach, we accurately reproduce the measurements from the N-body simulations.
Halo modelling in chameleon theories
International Nuclear Information System (INIS)
Lombriser, Lucas; Koyama, Kazuya; Li, Baojiu
2014-01-01
We analyse modelling techniques for the large-scale structure formed in scalar-tensor theories of constant Brans-Dicke parameter which match the concordance model background expansion history and produce a chameleon suppression of the gravitational modification in high-density regions. Thereby, we use a mass and environment dependent chameleon spherical collapse model, the Sheth-Tormen halo mass function and linear halo bias, the Navarro-Frenk-White halo density profile, and the halo model. Furthermore, using the spherical collapse model, we extrapolate a chameleon mass-concentration scaling relation from a ΛCDM prescription calibrated to N-body simulations. We also provide constraints on the model parameters to ensure viability on local scales. We test our description of the halo mass function and nonlinear matter power spectrum against the respective observables extracted from large-volume and high-resolution N-body simulations in the limiting case of f(R) gravity, corresponding to a vanishing Brans-Dicke parameter. We find good agreement between the two; the halo model provides a good qualitative description of the shape of the relative enhancement of the f(R) matter power spectrum with respect to ΛCDM caused by the extra attractive gravitational force but fails to recover the correct amplitude. Introducing an effective linear power spectrum in the computation of the two-halo term to account for an underestimation of the chameleon suppression at intermediate scales in our approach, we accurately reproduce the measurements from the N-body simulations
International Nuclear Information System (INIS)
Diaz Madriz, Jose Esteban; Granados Quesada, Maria Pamela; Lopez Chacon, Angelica Maria; Monge Cantillo, Carol Paola; Munoz Aguero, Geiner Andres; Vargas Vargas, Jorge Andres
2013-01-01
The halo effect was determined from the consumption of potatoes from Tierra Blanca de Cartago and Palmira de Zarcero. Seminars were held to get to know the topic of fluorosis. A mini health fair was held to explain the effects of fluoride in a population affected by it. Samples of water and forest type potato were collected in the area of Zarcero and San Juan de Chicoa. Measurements of the samples were made in the Chemistry Laboratory of the Universidad de Costa Rica. 20 mg of potato from each zone and 80 ml of distilled water were weighed and then liquefied. Each shake was dispensed in 2 clean test tubes and 7 samples were obtained, of which, 2 test tubes contained the liquefied 1, 2 tubes the liquefied 2, 1 tube with the Rio Reventado water centrifuged. 1 tube with Zarcero irrigation water and 1 tube with distilled water, for the subsequent analysis of fluoride concentration. The samples were taken to the LAMBDA Chemical Laboratory, where the ion chromatography test was performed on each of the samples. A concentration of fluorides of 0.73 ppm was obtained in the water of the Rio Reventado, while a concentration of less than 0.60 ppm was obtained in the water collected in Zarcero. The highest concentration of fluoride was presented in the potato from the area of Palmira de Zarcero with 2.41 ppm compared to that obtained in Cartago, with a lower concentration of 1.34 ppm. The maximum recommended concentration was exceeded in both results. A concentration less than 0.02 ppm was obtained in the analysis of distilled water as a control test [es
Modified circular velocity law
Djeghloul, Nazim
2018-05-01
A modified circular velocity law is presented for a test body orbiting around a spherically symmetric mass. This law exhibits a distance scale parameter and allows to recover both usual Newtonian behaviour for lower distances and a constant velocity limit at large scale. Application to the Galaxy predicts the known behaviour and also leads to a galactic mass in accordance with the measured visible stellar mass so that additional dark matter inside the Galaxy can be avoided. It is also shown that this circular velocity law can be embedded in a geometrical description of spacetime within the standard general relativity framework upon relaxing the usual asymptotic flatness condition. This formulation allows to redefine the introduced Newtonian scale limit in term of the central mass exclusively. Moreover, a satisfactory answer to the galactic escape speed problem can be provided indicating the possibility that one can also get rid of dark matter halo outside the Galaxy.
Disc-halo interactions in ΛCDM
Bauer, Jacob S.; Widrow, Lawrence M.; Erkal, Denis
2018-05-01
We present a new method for embedding a stellar disc in a cosmological dark matter halo and provide a worked example from a Λ cold dark matter zoom-in simulation. The disc is inserted into the halo at a redshift z = 3 as a zero-mass rigid body. Its mass and size are then increased adiabatically while its position, velocity, and orientation are determined from rigid-body dynamics. At z = 1, the rigid disc (RD) is replaced by an N-body disc whose particles sample a three-integral distribution function (DF). The simulation then proceeds to z = 0 with live disc (LD) and halo particles. By comparison, other methods assume one or more of the following: the centre of the RD during the growth phase is pinned to the minimum of the halo potential, the orientation of the RD is fixed, or the live N-body disc is constructed from a two rather than three-integral DF. In general, the presence of a disc makes the halo rounder, more centrally concentrated, and smoother, especially in the innermost regions. We find that methods in which the disc is pinned to the minimum of the halo potential tend to overestimate the amount of adiabatic contraction. Additionally, the effect of the disc on the subhalo distribution appears to be rather insensitive to the disc insertion method. The LD in our simulation develops a bar that is consistent with the bars seen in late-type spiral galaxies. In addition, particles from the disc are launched or `kicked up' to high galactic latitudes.
Beyond assembly bias: exploring secondary halo biases for cluster-size haloes
Mao, Yao-Yuan; Zentner, Andrew R.; Wechsler, Risa H.
2018-03-01
Secondary halo bias, commonly known as `assembly bias', is the dependence of halo clustering on a halo property other than mass. This prediction of the Λ Cold Dark Matter cosmology is essential to modelling the galaxy distribution to high precision and interpreting clustering measurements. As the name suggests, different manifestations of secondary halo bias have been thought to originate from halo assembly histories. We show conclusively that this is incorrect for cluster-size haloes. We present an up-to-date summary of secondary halo biases of high-mass haloes due to various halo properties including concentration, spin, several proxies of assembly history, and subhalo properties. While concentration, spin, and the abundance and radial distribution of subhaloes exhibit significant secondary biases, properties that directly quantify halo assembly history do not. In fact, the entire assembly histories of haloes in pairs are nearly identical to those of isolated haloes. In general, a global correlation between two halo properties does not predict whether or not these two properties exhibit similar secondary biases. For example, assembly history and concentration (or subhalo abundance) are correlated for both paired and isolated haloes, but follow slightly different conditional distributions in these two cases. This results in a secondary halo bias due to concentration (or subhalo abundance), despite the lack of assembly bias in the strict sense for cluster-size haloes. Due to this complexity, caution must be exercised in using any one halo property as a proxy to study the secondary bias due to another property.
Simulation and application of micro X-ray fluorescence based on an ellipsoidal capillary
Yang, Jing; Li, Yude; Wang, Xingyi; Zhang, Xiaoyun; Lin, Xiaoyan
2017-06-01
A micro X-ray fluorescence setup was presented, based on an ellipsoidal capillary and a traditional laboratorial X-ray source. Using Ray-tracing principle, we have simulated the transmission path of X-ray beam in the ellipsoidal capillary and designed the optimal parameters of the ellipsoidal capillary for the micro X-ray fluorescence setup. We demonstrate that ellipsoidal capillary is well suited as condenser for the micro X-ray fluorescence based on traditional laboratorial X-ray source. Furthermore, we obtain the 2D mapping image of the leaf blade sample by using the ellipsoidal capillary we designed.
Are baryonic galactic halos possible
International Nuclear Information System (INIS)
Olive, K.A.; Hegyi, D.J.
1986-01-01
There is little doubt from the rotation curves of spiral galaxies that galactic halos must contain large amounts of dark matter. In this contribution, the authors review arguments which indicate that it is very unlikely that galactic halos contain substantial amounts of baryonic matter. While the authors would like to be able to present a single argument which would rule out baryonic matter, at the present time they are only able to present a collection of arguments each of which argues against one form of baryonic matter. These include: 1) snowballs; 2) gas; 3) low mass stars and Jupiters; 4) high mass stars; and 5) high metalicity objects such as rooks or dust. Black holes, which do not have a well defined baryon number, are also a possible candidate for halo matter. They briefly discuss black holes
Richardson, J K; Ross, A D; Riley, B; Rhodes, R L
2000-03-01
To determine the effect of a halo vest, a cervical orthosis, on clinically relevant balance parameters. Subjects performed unipedal stance (with eyes open and closed, on both firm and soft surfaces) and functional reach, with and without the application of a halo vest. A convenience sample of 12 healthy young subjects, with an equal number of men and women. Seconds for unipedal stance (maximum 45); inches for functional reach. Both unipedal stance times and functional reach (mean +/- standard deviation) were significantly decreased with the halo vest as compared to without it (29.1+/-5.8 vs. 32.8+/-6.4 seconds, p = .002; 12.9+/-1.4 vs. 15.1+/-2.1 inches, prisk for a fall, which could have devastating consequences.
Effects of dipole magnet inhomogeneities on the beam ellipsoid
International Nuclear Information System (INIS)
Tsoupas, N.; Colman, J.; Levine, M.; McKenzie-Wilson, R.; Ward, T.; Grand, P.
1986-01-01
The RAYTRACE computer code has been modified to accept magnetic fields measured in the median plane of a dipole magnet. This modification allows one to study the effects of a non-ideal dipole magnet on the beam ellipsoid (as defined by the TRANSPORT code manual). The effects on the beam ellipsoid are due to: field inhomogeneities in the interior region of the dipole, and discrepancies from design conditions of the magnetic field values in the fringe field region. The results of the RAYTRACE code calculations based on experimentally measured fields will be compared with the results derived using both an ideal (no inhomogeneities) dipole with SCOFF boundaries and an ideal dipole with perfect (according to design) fringe fields
Hybrid ellipsoidal fuzzy systems in forecasting regional electricity loads
Energy Technology Data Exchange (ETDEWEB)
Pai, Ping-Feng [Department of Information Management, National Chi Nan University, 1 University Road, Puli, Nantou 545, Taiwan (China)
2006-09-15
Because of the privatization of electricity in many countries, load forecasting has become one of the most crucial issues in the planning and operations of electric utilities. In addition, accurate regional load forecasting can provide the transmission and distribution operators with more information. The hybrid ellipsoidal fuzzy system was originally designed to solve control and pattern recognition problems. The main objective of this investigation is to develop a hybrid ellipsoidal fuzzy system for time series forecasting (HEFST) and apply the proposed model to forecast regional electricity loads in Taiwan. Additionally, a scaled conjugate gradient learning method is employed in the supervised learning phase of the HEFST model. Subsequently, numerical data taken from the existing literature is used to demonstrate the forecasting performance of the HEFST model. Simulation results reveal that the proposed model has better forecasting performance than the artificial neural network model and the regression model. Thus, the HEFST model is a valid and promising alternative for forecasting regional electricity loads. (author)
Uncertainties, confidence ellipsoids and security polytopes in LSA
Grabe, Michael
1992-05-01
For a given error model, the uncertainties of and the couplings between parameters estimated by a least-squares adjustment (LSA) are formalized. The error model is restricted to normally distributed random errors and to systematic errors that remain constant during measurement, but whose magnitudes and signs are unknown. An outline of the associated, new formalism for estimating measurement uncertainties is sketched as regards its function as a measure of the consistency between theory and experiment. The couplings due to random errors lead to ellipsoids stemming from singular linear mappings of Hotelling's ellipsoids. Those introduced by systematic errors create convex polytopes, so-called security polytopes, which are singular linear mappings of hyperblocks caused by a ldworst-case treatment” of systematic errors.
Electroencephalography in ellipsoidal geometry with fourth-order harmonics.
Alcocer-Sosa, M; Gutierrez, D
2016-08-01
We present a solution to the electroencephalographs (EEG) forward problem of computing the scalp electric potentials for the case when the head's geometry is modeled using a four-shell ellipsoidal geometry and the brain sources with an equivalent current dipole (ECD). The proposed solution includes terms up to the fourth-order ellipsoidal harmonics and we compare this new approximation against those that only considered up to second- and third-order harmonics. Our comparisons use as reference a solution in which a tessellated volume approximates the head and the forward problem is solved through the boundary element method (BEM). We also assess the solution to the inverse problem of estimating the magnitude of an ECD through different harmonic approximations. Our results show that the fourth-order solution provides a better estimate of the ECD in comparison to lesser order ones.
The first all-sky view of the Milky Way stellar halo with Gaia+2MASS RR Lyrae
Iorio, G.; Belokurov, V.; Erkal, D.; Koposov, S. E.; Nipoti, C.; Fraternali, F.
2018-02-01
We exploit the first Gaia data release to study the properties of the Galactic stellar halo as traced by RR Lyrae. We demonstrate that it is possible to select a pure sample of RR Lyrae using only photometric information available in the Gaia+2MASS catalogue. The final sample contains about 21 600 RR Lyrae covering an unprecedented fraction ( ˜ 60 per cent) of the volume of the Galactic inner halo (R < 28 kpc). We study the morphology of the stellar halo by analysing the RR Lyrae distribution with parametric and non-parametric techniques. Taking advantage of the uniform all-sky coverage, we test halo models more sophisticated than usually considered in the literature, such as those with varying flattening, tilts and/or offset of the halo with respect to the Galactic disc. A consistent picture emerges: the inner halo is well reproduced by a smooth distribution of stars settled on triaxial density ellipsoids. The shortest axis is perpendicular to the Milky Way's disc, while the longest axis forms an angle of ˜70° with the axis connecting the Sun and the Galactic Centre. The elongation along the major axis is mild (p = 1.27), and the vertical flattening is shown to evolve from a squashed state with q ≈ 0.57 in the centre to a more spherical q ≈ 0.75 at the outer edge of our data set. Within the radial range probed, the density profile of the stellar halo is well approximated by a single power law with exponent α = -2.96. We do not find evidence of tilt or offset of the halo with respect to the Galaxy's disc.
A THEOREM ON CENTRAL VELOCITY DISPERSIONS
International Nuclear Information System (INIS)
An, Jin H.; Evans, N. Wyn
2009-01-01
It is shown that, if the tracer population is supported by a spherical dark halo with a core or a cusp diverging more slowly than that of a singular isothermal sphere (SIS), the logarithmic cusp slope γ of the tracers must be given exactly by γ = 2β, where β is their velocity anisotropy parameter at the center unless the same tracers are dynamically cold at the center. If the halo cusp diverges faster than that of the SIS, the velocity dispersion of the tracers must diverge at the center too. In particular, if the logarithmic halo cusp slope is larger than two, the diverging velocity dispersion also traces the behavior of the potential. The implication of our theorem on projected quantities is also discussed. We argue that our theorem should be understood as a warning against interpreting results based on simplifying assumptions such as isotropy and spherical symmetry.
ALEGRA-MHD Simulations for Magnetization of an Ellipsoidal Inclusion
2017-08-01
The findings in this report are not to be construed as an official Department of the Army position unless so designated by other authorized...diffusion has saturated. The simplicity of the interior solution lends itself well to verification of computational electromagnetic simulations...via computation with ALEGRA. The computed solution in the interior core of the ellipsoid converges to the exact solution at first order, as expected
Simulation and application of micro X-ray fluorescence based on an ellipsoidal capillary
Energy Technology Data Exchange (ETDEWEB)
Yang, Jing; Li, Yude; Wang, Xingyi; Zhang, Xiaoyun; Lin, Xiaoyan, E-mail: yangjing_928@126.com
2017-06-15
Highlights: • A micro X-ray fluorescence setup based on an ellipsoidal capillary was presented. • The optimal parameters of ellipsoidal capillary were designed. • The 2D mapping image of biological sample was obtained. - Abstract: A micro X-ray fluorescence setup was presented, based on an ellipsoidal capillary and a traditional laboratorial X-ray source. Using Ray-tracing principle, we have simulated the transmission path of X-ray beam in the ellipsoidal capillary and designed the optimal parameters of the ellipsoidal capillary for the micro X-ray fluorescence setup. We demonstrate that ellipsoidal capillary is well suited as condenser for the micro X-ray fluorescence based on traditional laboratorial X-ray source. Furthermore, we obtain the 2D mapping image of the leaf blade sample by using the ellipsoidal capillary we designed.
Dynamic cluster generation for a fuzzy classifier with ellipsoidal regions.
Abe, S
1998-01-01
In this paper, we discuss a fuzzy classifier with ellipsoidal regions that dynamically generates clusters. First, for the data belonging to a class we define a fuzzy rule with an ellipsoidal region. Namely, using the training data for each class, we calculate the center and the covariance matrix of the ellipsoidal region for the class. Then we tune the fuzzy rules, i.e., the slopes of the membership functions, successively until there is no improvement in the recognition rate of the training data. Then if the number of the data belonging to a class that are misclassified into another class exceeds a prescribed number, we define a new cluster to which those data belong and the associated fuzzy rule. Then we tune the newly defined fuzzy rules in the similar way as stated above, fixing the already obtained fuzzy rules. We iterate generation of clusters and tuning of the newly generated fuzzy rules until the number of the data belonging to a class that are misclassified into another class does not exceed the prescribed number. We evaluate our method using thyroid data, Japanese Hiragana data of vehicle license plates, and blood cell data. By dynamic cluster generation, the generalization ability of the classifier is improved and the recognition rate of the fuzzy classifier for the test data is the best among the neural network classifiers and other fuzzy classifiers if there are no discrete input variables.
Simulation of halo particles with Simpsons
International Nuclear Information System (INIS)
Machida, Shinji
2003-01-01
Recent code improvements and some simulation results of halo particles with Simpsons will be presented. We tried to identify resonance behavior of halo particles by looking at tune evolution of individual macro particle
Simulation of halo particles with Simpsons
Machida, Shinji
2003-12-01
Recent code improvements and some simulation results of halo particles with Simpsons will be presented. We tried to identify resonance behavior of halo particles by looking at tune evolution of individual macro particle.
Bose-Einstein condensate haloes embedded in dark energy
Membrado, M.; Pacheco, A. F.
2018-04-01
Context. We have studied clusters of self-gravitating collisionless Newtonian bosons in their ground state and in the presence of the cosmological constant to model dark haloes of dwarf spheroidal (dSph) galaxies. Aim. We aim to analyse the influence of the cosmological constant on the structure of these systems. Observational data of Milky Way dSph galaxies allow us to estimate the boson mass. Methods: We obtained the energy of the ground state of the cluster in the Hartree approximation by solving a variational problem in the particle density. We have also developed and applied the virial theorem. Dark halo models were tested in a sample of 19 galaxies. Galaxy radii, 3D deprojected half-light radii, mass enclosed within them, and luminosity-weighted averages of the square of line-of-sight velocity dispersions are used to estimate the particle mass. Results: Cosmological constant repulsive effects are embedded in one parameter ξ. They are appreciable for ξ > 10-5. Bound structures appear for ξ ≤ ξc = 1.65 × 10-4, what imposes a lower bound for cluster masses as a function of the particle mass. In principle, these systems present tunnelling through a potential barrier; however, after estimating their mean lifes, we realize that their existence is not affected by the age of the Universe. When Milky Way dSph galaxies are used to test the model, we obtain 3.5-1.0+1.3 × 10-22 eV for the particle mass and a lower limit of 5.1-2.8+2.2 × 106 M⊙ for bound haloes. Conclusions: Our estimation for the boson mass is in agreement with other recent results which use different methods. From our particle mass estimation, the treated dSph galaxies would present dark halo masses 5-11 ×107 M⊙. With these values, they would not be affected by the cosmological constant (ξ 10-5) would already feel their effects. Our model that includes dark energy allows us to deal with these dark haloes. Assuming quantities averaged in the sample of galaxies, 10-5 < ξ ≤ ξc dark
Dynamical Constraints On The Galaxy-Halo Connection
Desmond, Harry
2017-07-01
Dark matter halos comprise the bulk of the universe's mass, yet must be probed by the luminous galaxies that form within them. A key goal of modern astrophysics, therefore, is to robustly relate the visible and dark mass, which to first order means relating the properties of galaxies and halos. This may be expected not only to improve our knowledge of galaxy formation, but also to enable high-precision cosmological tests using galaxies and hence maximise the utility of future galaxy surveys. As halos are inaccessible to observations - as galaxies are to N-body simulations - this relation requires an additional modelling step.The aim of this thesis is to develop and evaluate models of the galaxy-halo connection using observations of galaxy dynamics. In particular, I build empirical models based on the technique of halo abundance matching for five key dynamical scaling relations of galaxies - the Tully-Fisher, Faber-Jackson, mass-size and mass discrepancy-acceleration relations, and Fundamental Plane - which relate their baryon distributions and rotation or velocity dispersion profiles. I then develop a statistical scheme based on approximate Bayesian computation to compare the predicted and measured values of a number of summary statistics describing the relations' important features. This not only provides quantitative constraints on the free parameters of the models, but also allows absolute goodness-of-fit measures to be formulated. I find some features to be naturally accounted for by an abundance matching approach and others to impose new constraints on the galaxy-halo connection; the remainder are challenging to account for and may imply galaxy-halo correlations beyond the scope of basic abundance matching.Besides providing concrete statistical tests of specific galaxy formation theories, these results will be of use for guiding the inputs of empirical and semi-analytic galaxy formation models, which require galaxy-halo correlations to be imposed by hand. As
Mismatch and misalignment: dark haloes and satellites of disc galaxies
Deason, A. J.; McCarthy, I. G.; Font, A. S.; Evans, N. W.; Frenk, C. S.; Belokurov, V.; Libeskind, N. I.; Crain, R. A.; Theuns, T.
2011-08-01
mass from the line-of-sight velocities and projected positions of satellite galaxies. We quantify the effects of such systematics in estimates of the host halo mass from the satellite population.
FASHIONABLY LATE? BUILDING UP THE MILKY WAY'S INNER HALO
International Nuclear Information System (INIS)
Morrison, Heather L.; Harding, Paul; Helmi, Amina
2009-01-01
Using a sample of 246 metal-poor stars (RR Lyraes, red giants, and red horizontal branch stars) which is remarkable for the accuracy of its six-dimensional kinematical data, we find, by examining the distribution of stellar orbital angular momenta, a new component for the local halo which has an axial ratio c/a ∼ 0.2, a similar flattening to the thick disk. It has a small prograde rotation but is supported by velocity anisotropy, and contains more intermediate-metallicity stars (with -1.5 < [Fe/H] < -1.0) than the rest of our sample. We suggest that this component was formed quite late, during or after the formation of the disk. It formed either from the gas that was accreted by the last major mergers experienced by the Galaxy, or by dynamical friction of massive infalling satellite(s) with the halo and possibly the stellar disk or thick disk. The remainder of the halo stars in our sample, which are less closely confined to the disk plane, exhibit a clumpy distribution in energy and angular momentum, suggesting that the early, chaotic conditions under which the inner halo formed were not violent enough to erase the record of their origins. The clumpy structure suggests that a relatively small number of progenitors were responsible for building up the inner halo, in line with theoretical expectations. We find a difference in mean binding energy between the RR Lyrae variables and the red giants in our sample, suggesting that more of the RR Lyraes in the sample belong to the outer halo, and that the outer halo may be somewhat younger, as first suggested by Searle and Zinn. We also find that the RR Lyrae mean rotation is more negative than the red giants, which is consistent with the recent result of Carollo et al. that the outer halo has a retrograde rotation and with the difference in kinematics seen between RR Lyraes and blue horizontal branch stars by Kinman et al. (2007).
Does the galaxy-halo connection vary with environment?
Dragomir, Radu; Rodríguez-Puebla, Aldo; Primack, Joel R.; Lee, Christoph T.
2018-05-01
(Sub)halo abundance matching (SHAM) assumes that one (sub) halo property, such as mass Mvir or peak circular velocity Vpeak, determines properties of the galaxy hosted in each (sub) halo such as its luminosity or stellar mass. This assumption implies that the dependence of galaxy luminosity functions (GLFs) and the galaxy stellar mass function (GSMF) on environmental density is determined by the corresponding halo density dependence. In this paper, we test this by determining from a Sloan Digital Sky Survey sample the observed dependence with environmental density of the ugriz GLFs and GSMF for all galaxies, and for central and satellite galaxies separately. We then show that the SHAM predictions are in remarkable agreement with these observations, even when the galaxy population is divided between central and satellite galaxies. However, we show that SHAM fails to reproduce the correct dependence between environmental density and g - r colour for all galaxies and central galaxies, although it better reproduces the colour dependence on environmental density of satellite galaxies.
Non-Gaussian halo assembly bias
International Nuclear Information System (INIS)
Reid, Beth A.; Verde, Licia; Dolag, Klaus; Matarrese, Sabino; Moscardini, Lauro
2010-01-01
The strong dependence of the large-scale dark matter halo bias on the (local) non-Gaussianity parameter, f NL , offers a promising avenue towards constraining primordial non-Gaussianity with large-scale structure surveys. In this paper, we present the first detection of the dependence of the non-Gaussian halo bias on halo formation history using N-body simulations. We also present an analytic derivation of the expected signal based on the extended Press-Schechter formalism. In excellent agreement with our analytic prediction, we find that the halo formation history-dependent contribution to the non-Gaussian halo bias (which we call non-Gaussian halo assembly bias) can be factorized in a form approximately independent of redshift and halo mass. The correction to the non-Gaussian halo bias due to the halo formation history can be as large as 100%, with a suppression of the signal for recently formed halos and enhancement for old halos. This could in principle be a problem for realistic galaxy surveys if observational selection effects were to pick galaxies occupying only recently formed halos. Current semi-analytic galaxy formation models, for example, imply an enhancement in the expected signal of ∼ 23% and ∼ 48% for galaxies at z = 1 selected by stellar mass and star formation rate, respectively
Caustic ring model of the Milky Way halo
International Nuclear Information System (INIS)
Duffy, L. D.; Sikivie, P.
2008-01-01
We present a proposal for the full phase-space distribution of the Milky Way halo. The model is axially and reflection symmetric and its time evolution is self-similar. It describes the halo as a set of discrete dark matter flows with stated densities and velocity vectors everywhere. We first discuss the general conditions under which the time evolution of a cold collisionless self-gravitating fluid is self-similar, and show that symmetry is not necessary for self-similarity. When spherical symmetry is imposed, the model is the same as described by Fillmore and Goldreich, and by Bertschinger, twenty-three years ago. The spherically symmetric model depends on one dimensionless parameter ε and two dimensionful parameters. We set ε=0.3, a value consistent with the slope of the power spectrum of density perturbations on galactic scales. The dimensionful parameters are determined by the galactic rotation velocity (220 km/s) at the position of the Sun and by the age of the Galaxy (13.7 Gyr). The properties of the outer caustics are derived in the spherically symmetric model. The structure of the inner halo depends on the angular momentum distribution of the dark matter particles. We assume that distribution to be axial and reflection symmetric, and dominated by net overall rotation. The inner caustics are rings whose radii are determined in terms of a single additional parameter j max . We summarize the observational evidence in support of the model. The evidence is consistent with j max =0.18 in Concordance cosmology, equivalent to j max,old =0.26 in Einstein-de Sitter cosmology. We give formulas to estimate the flow densities and velocity vectors anywhere in the Milky Way halo. The properties of the first 40 flows at the location of the Earth are listed.
Halo Mitigation Using Nonlinear Lattices
Sonnad, Kiran G
2005-01-01
This work shows that halos in beams with space charge effects can be controlled by combining nonlinear focusing and collimation. The study relies on Particle-in-Cell (PIC) simulations for a one dimensional, continuous focusing model. The PIC simulation results show that nonlinear focusing leads to damping of the beam oscillations thereby reducing the mismatch. It is well established that reduced mismatch leads to reduced halo formation. However, the nonlinear damping is accompanied by emittance growth causing the beam to spread in phase space. As a result, inducing nonlinear damping alone cannot help mitigate the halo. To compensate for this expansion in phase space, the beam is collimated in the simulation and further evolution of the beam shows that the halo is not regenerated. The focusing model used in the PIC is analysed using the Lie Transform perturbation theory showing that by averaging over a lattice period, one can reuduce the focusing force to a form that is identical to that used in the PIC simula...
ULTRAVIOLET HALOS AROUND SPIRAL GALAXIES. I. MORPHOLOGY
Energy Technology Data Exchange (ETDEWEB)
Hodges-Kluck, Edmund; Cafmeyer, Julian; Bregman, Joel N., E-mail: hodgeskl@umich.edu [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)
2016-12-10
We examine ultraviolet halos around a sample of highly inclined galaxies within 25 Mpc to measure their morphology and luminosity. Despite contamination from galactic light scattered into the wings of the point-spread function, we find that ultraviolet (UV) halos occur around each galaxy in our sample. Around most galaxies the halos form a thick, diffuse disk-like structure, but starburst galaxies with galactic superwinds have qualitatively different halos that are more extensive and have filamentary structure. The spatial coincidence of the UV halos above star-forming regions, the lack of consistent association with outflows or extraplanar ionized gas, and the strong correlation between the halo and galaxy UV luminosity suggest that the UV light is an extragalactic reflection nebula. UV halos may thus represent 10{sup 6}–10{sup 7} M {sub ⊙} of dust within 2–10 kpc of the disk, whose properties may change with height in starburst galaxies.
The halo current in ASDEX Upgrade
International Nuclear Information System (INIS)
Pautasso, G.; Giannone, L.; Gruber, O.; Herrmann, A.; Maraschek, M.; Schuhbeck, K.H.
2011-01-01
Due to the complexity of the phenomena involved, a self-consistent physical model for the prediction of the halo current is not available. Therefore the ITER specifications of the spatial distribution and evolution of the halo current rely on empirical assumptions. This paper presents the results of an extensive analysis of the halo current measured in ASDEX Upgrade with particular emphasis on the evolution of the halo region, on the magnitude and time history of the halo current, and on the structure and duration of its toroidal and poloidal asymmetries. The effective length of the poloidal path of the halo current in the vessel is found to be rather insensitive to plasma parameters. Large values of the toroidally averaged halo current are observed in both vertical displacement events and centred disruptions but last a small fraction of the current quench; they coincide typically with a large but short-lived MHD event.
The halo current in ASDEX Upgrade
Pautasso, G.; Giannone, L.; Gruber, O.; Herrmann, A.; Maraschek, M.; Schuhbeck, K. H.; ASDEX Upgrade Team
2011-04-01
Due to the complexity of the phenomena involved, a self-consistent physical model for the prediction of the halo current is not available. Therefore the ITER specifications of the spatial distribution and evolution of the halo current rely on empirical assumptions. This paper presents the results of an extensive analysis of the halo current measured in ASDEX Upgrade with particular emphasis on the evolution of the halo region, on the magnitude and time history of the halo current, and on the structure and duration of its toroidal and poloidal asymmetries. The effective length of the poloidal path of the halo current in the vessel is found to be rather insensitive to plasma parameters. Large values of the toroidally averaged halo current are observed in both vertical displacement events and centred disruptions but last a small fraction of the current quench; they coincide typically with a large but short-lived MHD event.
Brown dwarfs as dark galactic halos
International Nuclear Information System (INIS)
Adams, F.C.; Walker, T.P.
1990-01-01
The possibility that the dark matter in galactic halos can consist of brown dwarf stars is considered. The radiative signature for such halos consisting solely of brown dwarfs is calculated, and the allowed range of brown dwarf masses, the initial mass function (IMF), the stellar properties, and the density distribution of the galactic halo are discussed. The prediction emission from the halo is compared with existing observations. It is found that, for any IMF of brown dwarfs below the deuterium burning limit, brown dwarf halos are consistent with observations. Brown dwarf halos cannot, however, explain the recently observed near-IR background. It is shown that future satellite missions will either detect brown dwarf halos or place tight constraints on the allowed range of the IMF. 30 refs
Libration-Driven Elliptical Instability Experiments in Ellipsoidal Shells
Grannan, A. M.; Lemasquerier, D. G.; Favier, B.; Cebron, D.; Le Bars, M.; Aurnou, J. M.
2016-12-01
Planets and satellites can be subjected to physical libration, which consists in forced periodic variations in their rotation rate induced by gravitational interactions with nearby bodies. These librations may mechanically drive turbulence in interior liquid layers such as subsurface oceans and metallic liquid cores. One possible driving-process is called the Libration-Driven Elliptical Instability (LDEI) and refers to the resonance of two inertial modes with the libration induced base flow. LDEI has been experimentally and numerically studied in the case of a full ellipsoid (e.g. Cébron et al. [2012c], Grannan et al. [2014] and Favier et al. [2015]). In this study, we address the question of the persistence of the LDEI in the theoretically complex case of an ellipsoidal shell which is more geophysically relevant to model planetary liquid layers. We use an ellipsoidal acrylic container filled with water and add spherical inner cores of different sizes. We perform direct side-view visualizations of the flow in the librating frame using Kalliroscope particles. A Fourier analysis of the light intensity extracted from the recorded movies shows that LDEI persists in a shell geometry for a libration frequency which is 4 and 2.4 time the rotation rate, and allows an identification of the mode coupling. Particle Image Velocimetry (PIV) is performed in vertical and horizontal planes on a selected case to confirm our light intensity results. Additionaly, our survey at a fixed forcing-frequency and variable Ekman number (E) allows a comparison with a local stability analysis, and shows that the libration amplitude at the threshold of the instability varies as ≈[E0.63, E0.72]. When extrapolating to planetary interiors conditions, such a scaling leads to an easier excitation of the elliptical instability than the E0.5 scaling commonly considered.
Reionization histories of Milky Way mass halos
International Nuclear Information System (INIS)
Li, Tony Y.; Wechsler, Risa H.; Abel, Tom; Alvarez, Marcelo A.
2014-01-01
We investigate the connection between the reionization era and the present-day universe by examining the mass reionization histories of z = 0 dark matter halos. In a 600 3 Mpc 3 volume, we combine a dark matter N-body simulation with a three-dimensional seminumerical reionization model. This tags each particle with a reionization redshift, so that individual present-day halos can be connected to their reionization histories and environments. We find that the vast majority of present-day halos with masses larger than ∼ few × 10 11 M ☉ reionize earlier than the rest of the universe. We also find significant halo-to-halo diversity in mass reionization histories, and find that in realistic inhomogeneous models, the material within a given halo is not expected to reionize at the same time. In particular, the scatter in reionization times within individual halos is typically larger than the scatter among halos. From our fiducial reionization model, we find that the typical 68% scatter in reionization times within halos is ∼115 Myr for 10 12±0.25 M ☉ halos, decreasing slightly to ∼95 Myr for 10 15±0.25 M ☉ halos. We find a mild correlation between reionization history and environment: halos with shorter reionization histories are typically in more clustered environments, with the strongest trend on a scale of ∼20 Mpc. Material in Milky Way mass halos with short reionization histories is preferentially reionized in relatively large H II regions, implying reionization mostly by sources external to the progenitors of the present-day halo. We investigate the impact on our results of varying the reionization model parameters, which span a range of reionization scenarios with varying timing and morphology.
Relation Between Initial Cosmological Conditions and the Properties of Dark Matter Haloes
International Nuclear Information System (INIS)
Semenov, Vadim
2013-01-01
The core-cusp problem is one of the essential issues in modern cosmology. The Entropy Theory of haloes Evolution recently suggested by Lukash, Doroshkevich and Mikheeva is one of the possible solutions to this problem. This work compares some results of numerical simulation of Large-Scale Structure with the conclusions of the Entropy Theory in order to verify this theory. The numerical simulation was performed in a volume 100 Mpc/h in a side using ∼ 17 million particles. Dark matter particles, which then form virialized haloes, were found in the initial perturbation field. This work investigates the distribution of these dark matter particles and measures the velocity dispersion profiles. It also traces evolution of haloes entropy profiles. On the whole, simulation results correspond to Entropy Theory of haloes evolution
New solutions of the generalized ellipsoidal wave equation
Directory of Open Access Journals (Sweden)
Harold Exton
1999-10-01
Full Text Available Certain aspects and a contribution to the theory of new forms of solutions of an algebraic form of the generalized ellipsoidal wave equation are deduced by considering the Laplace transform of a soluble system of linear differential equations. An ensuing system of non-linear algebraic equations is shown to be consistent and is numerically implemented by means of the computer algebra package MAPLE V. The main results are presented as series of hypergeometric type of there and four variables which readily lend themselves to numerical handling although this does not indicate all of the detailedanalytic properties of the solutions under consideration.
Ellipsoidal reflector for measuring oto-acoustic emissions
DEFF Research Database (Denmark)
Epp, Bastian; Pulkki, Ville; Heiskanen, Vesa
2014-01-01
A truncated prolate ellipsoidal reflector having the ear canal of a listener at one focal point and large- diaphragm low-noise microphone at the other focal point is proposed for free-field recordings of oto-acoustic emissions. A prototype reflector consisting of three pieces is presented, which...... enables measuring the response of the system with different truncations. The response of the system is measured with a miniature loud- speaker, and proof-of-concept measurements of oto-acoustic emissions are presented. The effect of truncation and other physical parameters to the performance of the system...
Mass models for disk and halo components in spiral galaxies
International Nuclear Information System (INIS)
Athanassoula, E.; Bosma, A.
1987-01-01
The mass distribution in spiral galaxies is investigated by means of numerical simulations, summarizing the results reported by Athanassoula et al. (1986). Details of the modeling technique employed are given, including bulge-disk decomposition; computation of bulge and disk rotation curves (assuming constant mass/light ratios for each); and determination (for spherical symmetry) of the total halo mass out to the optical radius, the concentration indices, the halo-density power law, the core radius, the central density, and the velocity dispersion. Also discussed are the procedures for incorporating galactic gas and checking the spiral structure extent. It is found that structural constraints limit disk mass/light ratios to a range of 0.3 dex, and that the most likely models are maximum-disk models with m = 1 disturbances inhibited. 19 references
The design and test of ellipsoidal glass capillaries as condensers for X-ray microscope
International Nuclear Information System (INIS)
Tian Jinping; Li Wenjie; Chen Jie; Liu Gang; Xiong Ying; Liu Longhua; Huang Xinlong; Tian Yangchao
2008-01-01
A high resolution X-ray microscope endstation was constructed on a wiggler beamline at the National Synchrotron Radiation Laboratory (NSRL). Parameters of the ellipsoidal glass capillaries as condensers were calculated and designed based on the illumination requests in the X-ray microscope system. Performance of the ellipsoidal glass capillaries was tested. The results indicate that the beam size agrees with the designed parameters and focus efficiencies of the ellipsoidal glass capillary condensers are better than 85%. (authors)
Lattice ellipsoidal statistical BGK model for thermal non-equilibrium flows
Meng, Jianping; Zhang, Yonghao; Hadjiconstantinou, Nicolas G.; Radtke, Gregg A.; Shan, Xiaowen
2013-03-01
A thermal lattice Boltzmann model is constructed on the basis of the ellipsoidal statistical Bhatnagar-Gross-Krook (ES-BGK) collision operator via the Hermite moment representation. The resulting lattice ES-BGK model uses a single distribution function and features an adjustable Prandtl number. Numerical simulations show that using a moderate discrete velocity set, this model can accurately recover steady and transient solutions of the ES-BGK equation in the slip-flow and early transition regimes in the small Mach number limit that is typical of microscale problems of practical interest. In the transition regime in particular, comparisons with numerical solutions of the ES-BGK model, direct Monte Carlo and low-variance deviational Monte Carlo simulations show good accuracy for values of the Knudsen number up to approximately 0.5. On the other hand, highly non-equilibrium phenomena characterized by high Mach numbers, such as viscous heating and force-driven Poiseuille flow for large values of the driving force, are more difficult to capture quantitatively in the transition regime using discretizations chosen with computational efficiency in mind such as the one used here, although improved accuracy is observed as the number of discrete velocities is increased.
International Nuclear Information System (INIS)
Heitz, Eric
2017-01-01
We present a geometric method for computing an ellipse that subtends the same solid-angle domain as an arbitrarily positioned ellipsoid. With this method we can extend existing analytical solid-angle calculations of ellipses to ellipsoids. Our idea consists of applying a linear transformation on the ellipsoid such that it is transformed into a sphere from which a disk that covers the same solid-angle domain can be computed. We demonstrate that by applying the inverse linear transformation on this disk we obtain an ellipse that subtends the same solid-angle domain as the ellipsoid. We provide a MATLAB implementation of our algorithm and we validate it numerically.
Energy Technology Data Exchange (ETDEWEB)
Heitz, Eric, E-mail: eheitz.research@gmail.com
2017-04-21
We present a geometric method for computing an ellipse that subtends the same solid-angle domain as an arbitrarily positioned ellipsoid. With this method we can extend existing analytical solid-angle calculations of ellipses to ellipsoids. Our idea consists of applying a linear transformation on the ellipsoid such that it is transformed into a sphere from which a disk that covers the same solid-angle domain can be computed. We demonstrate that by applying the inverse linear transformation on this disk we obtain an ellipse that subtends the same solid-angle domain as the ellipsoid. We provide a MATLAB implementation of our algorithm and we validate it numerically.
Galaxy and Mass Assembly (GAMA): halo formation times and halo assembly bias on the cosmic web
Tojeiro, Rita; Eardley, Elizabeth; Peacock, John A.; Norberg, Peder; Alpaslan, Mehmet; Driver, Simon P.; Henriques, Bruno; Hopkins, Andrew M.; Kafle, Prajwal R.; Robotham, Aaron S. G.; Thomas, Peter; Tonini, Chiara; Wild, Vivienne
2017-09-01
We present evidence for halo assembly bias as a function of geometric environment (GE). By classifying Galaxy and Mass Assembly (GAMA) galaxy groups as residing in voids, sheets, filaments or knots using a tidal tensor method, we find that low-mass haloes that reside in knots are older than haloes of the same mass that reside in voids. This result provides direct support to theories that link strong halo tidal interactions with halo assembly times. The trend with GE is reversed at large halo mass, with haloes in knots being younger than haloes of the same mass in voids. We find a clear signal of halo downsizing - more massive haloes host galaxies that assembled their stars earlier. This overall trend holds independently of GE. We support our analysis with an in-depth exploration of the L-Galaxies semi-analytic model, used here to correlate several galaxy properties with three different definitions of halo formation time. We find a complex relationship between halo formation time and galaxy properties, with significant scatter. We confirm that stellar mass to halo mass ratio, specific star formation rate (SFR) and mass-weighed age are reasonable proxies of halo formation time, especially at low halo masses. Instantaneous SFR is a poor indicator at all halo masses. Using the same semi-analytic model, we create mock spectral observations using complex star formation and chemical enrichment histories, which approximately mimic GAMA's typical signal-to-noise ratio and wavelength range. We use these mocks to assert how well potential proxies of halo formation time may be recovered from GAMA-like spectroscopic data.
Halo scale predictions of symmetron modified gravity
Energy Technology Data Exchange (ETDEWEB)
Clampitt, Joseph; Jain, Bhuvnesh; Khoury, Justin, E-mail: clampitt@sas.upenn.edu, E-mail: bjain@physics.upenn.edu, E-mail: jkhoury@sas.upenn.edu [Center for Particle Cosmology and Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd St., Philadelphia, PA 19104 (United States)
2012-01-01
We offer predictions of symmetron modified gravity in the neighborhood of realistic dark matter halos. The predictions for the fifth force are obtained by solving the nonlinear symmetron equation of motion in the spherical NFW approximation. In addition, we compare the three major known screening mechanisms: Vainshtein, Chameleon, and Symmetron around such dark matter halos, emphasizing the significant differences between them and highlighting observational tests which exploit these differences. Finally, we demonstrate the host halo environmental screening effect (''blanket screening'') on smaller satellite halos by solving for the modified forces around a density profile which is the sum of satellite and approximate host components.
Unbound particles in dark matter halos
Energy Technology Data Exchange (ETDEWEB)
Behroozi, Peter S.; Loeb, Abraham; Wechsler, Risa H.
2013-06-13
We investigate unbound dark matter particles in halos by tracing particle trajectories in a simulation run to the far future (a = 100). We find that the traditional sum of kinetic and potential energies is a very poor predictor of which dark matter particles will eventually become unbound from halos. We also study the mass fraction of unbound particles, which increases strongly towards the edges of halos, and decreases significantly at higher redshifts. We discuss implications for dark matter detection experiments, precision calibrations of the halo mass function, the use of baryon fractions to constrain dark energy, and searches for intergalactic supernovae.
Prescod-Weinstein, Chanda; Afshordi, Niayesh
2011-01-01
Structure formation provides a strong test of any cosmic acceleration model because a successful dark energy model must not inhibit or overpredict the development of observed large-scale structures. Traditional approaches to studies of structure formation in the presence of dark energy or a modified gravity implement a modified Press-Schechter formalism, which relates the linear overdensities to the abundance of dark matter haloes at the same time. We critically examine the universality of the Press-Schechter formalism for different cosmologies, and show that the halo abundance is best correlated with spherical linear overdensity at 94% of collapse (or observation) time. We then extend this argument to ellipsoidal collapse (which decreases the fractional time of best correlation for small haloes), and show that our results agree with deviations from modified Press-Schechter formalism seen in simulated mass functions. This provides a novel universal prescription to measure linear density evolution, based on current and future observations of cluster (or dark matter) halo mass function. In particular, even observations of cluster abundance in a single epoch will constrain the entire history of linear growth of cosmological of perturbations.
KINEMATICS OF OUTER HALO GLOBULAR CLUSTERS IN M31
International Nuclear Information System (INIS)
Veljanoski, J.; Ferguson, A. M. N.; Bernard, E. J.; Peñarrubia, J.; Mackey, A. D.; Huxor, A. P.; Irwin, M. J.; Chapman, S. C.; Côté, P.; Tanvir, N. R.; McConnachie, A.; Ibata, R. A.; Martin, N. F.; Fardal, M.; Lewis, G. F.
2013-01-01
We present the first kinematic analysis of the far outer halo globular cluster (GC) population in the Local Group galaxy M31. Our sample contains 53 objects with projected radii of ∼20-130 kpc, 44 of which have no previous spectroscopic information. GCs with projected radii ∼> 30 kpc are found to exhibit net rotation around the minor axis of M31, in the same sense as the inner GCs, albeit with a smaller amplitude of 79 ± 19 km s –1 . The rotation-corrected velocity dispersion of the full halo GC sample is 106 ± 12 km s –1 , which we observe to decrease with increasing projected radius. We find compelling evidence for kinematic coherence among GCs that project on top of halo substructure, including a clear signature of infall for GCs lying along the northwest stream. Using the tracer mass estimator, we estimate the dynamical mass of M31 within 200 kpc to be M M31 = (1.2-1.5) ± 0.2 × 10 12 M ☉ . This value is highly dependent on the chosen model and assumptions within.
On the core-halo structure of NGC 604
Melnick, Yu M
1980-01-01
A detailed study is presented of the core-halo structure of the largest H II region in M 33, NGC 604, using newly obtained multi- aperture H/sub beta / photometry and Fabry-Perot interferometry, in conjunction with published radio continuum observations. Based on a comparison between the radio continuum and H/sub beta / luminosities of NGC 604, a dust density of rho /sub d/=6 10/sup -25/ g cm/sup -3/ is derived for the nebular core, in good agreement with published far- infrared results. By contrast, the halo of NGC 604 appears to contain virtually no dust. It is also shown that the turbulent component of the H/sub alpha /-line profile width of the halo of NGC 604 is significantly lower than that of the nebular core. This result is found to be inconsistent with models in which the highly supersonic velocities implied by the observed emission line profile widths in both nebular components are interpreted in terms of expansion motions. (14 refs).
What to expect from dynamical modelling of galactic haloes - II. The spherical Jeans equation
Wang, Wenting; Han, Jiaxin; Cole, Shaun; More, Surhud; Frenk, Carlos; Schaller, Matthieu
2018-06-01
The spherical Jeans equation (SJE) is widely used in dynamical modelling of the Milky Way (MW) halo potential. We use haloes and galaxies from the cosmological Millennium-II simulation and hydrodynamical APOSTLE (A Project of Simulations of The Local Environment) simulations to investigate the performance of the SJE in recovering the underlying mass profiles of MW mass haloes. The best-fitting halo mass and concentration parameters scatter by 25 per cent and 40 per cent around their input values, respectively, when dark matter particles are used as tracers. This scatter becomes as large as a factor of 3 when using star particles instead. This is significantly larger than the estimated statistical uncertainty associated with the use of the SJE. The existence of correlated phase-space structures that violate the steady-state assumption of the SJE as well as non-spherical geometries is the principal source of the scatter. Binary haloes show larger scatter because they are more aspherical in shape and have a more perturbed dynamical state. Our results confirm that the number of independent phase-space structures sets an intrinsic limiting precision on dynamical inferences based on the steady-state assumption. Modelling with a radius-independent velocity anisotropy, or using tracers within a limited outer radius, result in significantly larger scatter, but the ensemble-averaged measurement over the whole halo sample is approximately unbiased.
Entropies from Coarse-graining: Convex Polytopes vs. Ellipsoids
Directory of Open Access Journals (Sweden)
Nikos Kalogeropoulos
2015-09-01
Full Text Available We examine the Boltzmann/Gibbs/Shannon SBGS and the non-additive Havrda-Charvát/Daróczy/Cressie-Read/Tsallis Sq and the Kaniadakis κ-entropy Sκ from the viewpoint of coarse-graining, symplectic capacities and convexity. We argue that the functional form of such entropies can be ascribed to a discordance in phase-space coarse-graining between two generally different approaches: the Euclidean/Riemannian metric one that reflects independence and picks cubes as the fundamental cells in coarse-graining and the symplectic/canonical one that picks spheres/ellipsoids for this role. Our discussion is motivated by and confined to the behaviour of Hamiltonian systems of many degrees of freedom. We see that Dvoretzky’s theorem provides asymptotic estimates for the minimal dimension beyond which these two approaches are close to each other. We state and speculate about the role that dualities may play in this viewpoint.
Analytic modeling of axisymmetric disruption halo currents
International Nuclear Information System (INIS)
Humphreys, D.A.; Kellman, A.G.
1999-01-01
Currents which can flow in plasma facing components during disruptions pose a challenge to the design of next generation tokamaks. Induced toroidal eddy currents and both induced and conducted poloidal ''halo'' currents can produce design-limiting electromagnetic loads. While induction of toroidal and poloidal currents in passive structures is a well-understood phenomenon, the driving terms and scalings for poloidal currents flowing on open field lines during disruptions are less well established. A model of halo current evolution is presented in which the current is induced in the halo by decay of the plasma current and change in enclosed toroidal flux while being convected into the halo from the core by plasma motion. Fundamental physical processes and scalings are described in a simplified analytic version of the model. The peak axisymmetric halo current is found to depend on halo and core plasma characteristics during the current quench, including machine and plasma dimensions, resistivities, safety factor, and vertical stability growth rate. Two extreme regimes in poloidal halo current amplitude are identified depending on the minimum halo safety factor reached during the disruption. A 'type I' disruption is characterized by a minimum safety factor that remains relatively high (typically 2 - 3, comparable to the predisruption safety factor), and a relatively low poloidal halo current. A 'type II' disruption is characterized by a minimum safety factor comparable to unity and a relatively high poloidal halo current. Model predictions for these two regimes are found to agree well with halo current measurements from vertical displacement event disruptions in DIII-D [T. S. Taylor, K. H. Burrell, D. R. Baker, G. L. Jackson, R. J. La Haye, M. A. Mahdavi, R. Prater, T. C. Simonen, and A. D. Turnbull, open-quotes Results from the DIII-D Scientific Research Program,close quotes in Proceedings of the 17th IAEA Fusion Energy Conference, Yokohama, 1998, to be published in
THE PSEUDO-EVOLUTION OF HALO MASS
International Nuclear Information System (INIS)
Diemer, Benedikt; Kravtsov, Andrey V.; More, Surhud
2013-01-01
A dark matter halo is commonly defined as a spherical overdensity of matter with respect to a reference density, such as the critical density or the mean matter density of the universe. Such definitions can lead to a spurious pseudo-evolution of halo mass simply due to redshift evolution of the reference density, even if its physical density profile remains constant over time. We estimate the amount of such pseudo-evolution of mass between z = 1 and 0 for halos identified in a large N-body simulation, and show that it accounts for almost the entire mass evolution of the majority of halos with M 200ρ-bar ≲ 10 12 h -1 M ☉ and can be a significant fraction of the apparent mass growth even for cluster-sized halos. We estimate the magnitude of the pseudo-evolution assuming that halo density profiles remain static in physical coordinates, and show that this simple model predicts the pseudo-evolution of halos identified in numerical simulations to good accuracy, albeit with significant scatter. We discuss the impact of pseudo-evolution on the evolution of the halo mass function and show that the non-evolution of the low-mass end of the halo mass function is the result of a fortuitous cancellation between pseudo-evolution and the absorption of small halos into larger hosts. We also show that the evolution of the low-mass end of the concentration-mass relation observed in simulations is almost entirely due to the pseudo-evolution of mass. Finally, we discuss the implications of our results for the interpretation of the evolution of various scaling relations between the observable properties of galaxies and galaxy clusters and their halo masses.
UARS Halogen Occultation Experiment (HALOE) Level 2 V001
National Aeronautics and Space Administration — The HALOE home page on the WWW is http://haloe.gats-inc.com/home/index.php The Halogen Occultation Experiment (HALOE) on NASA's Upper Atmosphere Research Satellite...
INTERACTION BETWEEN DARK MATTER SUB-HALOS AND A GALACTIC GASEOUS DISK
International Nuclear Information System (INIS)
Kannan, Rahul; Macciò, Andrea V.; Walter, Fabian; Pasquali, Anna; Moster, Benjamin P.
2012-01-01
We investigate the idea that the interaction of dark matter (DM) sub-halos with the gaseous disks of galaxies can be the origin for the observed holes and shells found in their neutral hydrogen (H I) distributions. We use high-resolution hydrodynamic simulations to show that pure DM sub-halos impacting a galactic disk are not able to produce holes; on the contrary, they result in high-density regions in the disk. However, sub-halos containing a small amount of gas (a few percent of the total DM mass of the sub-halo) are able to displace the gas in the disk and form holes and shells. The sizes and lifetimes of these holes depend on the sub-halo gas mass, density, and impact velocity. A DM sub-halo, of mass 10 8 M ☉ and a gas mass fraction of ∼3%, is able to create a kiloparsec-scale hole with a lifetime similar to those observed in nearby galaxies. We also register an increase in the star formation rate at the rim of the hole, again in agreement with observations. Even though the properties of these simulated structures resemble those found in observations, we find that the number of predicted holes (based on mass and orbital distributions of DM halos derived from cosmological N-body simulations) falls short compared to the observations. Only a handful of holes are produced per gigayear. This leads us to conclude that DM halo impact is not the major channel through which these holes are formed.
Galaxy formation with BECDM - I. Turbulence and relaxation of idealized haloes.
Mocz, Philip; Vogelsberger, Mark; Robles, Victor H; Zavala, Jesús; Boylan-Kolchin, Michael; Fialkov, Anastasia; Hernquist, Lars
2017-11-01
We present a theoretical analysis of some unexplored aspects of relaxed Bose-Einstein condensate dark matter (BECDM) haloes. This type of ultralight bosonic scalar field dark matter is a viable alternative to the standard cold dark matter (CDM) paradigm, as it makes the same large-scale predictions as CDM and potentially overcomes CDM's small-scale problems via a galaxy-scale de Broglie wavelength. We simulate BECDM halo formation through mergers, evolved under the Schrödinger-Poisson equations. The formed haloes consist of a soliton core supported against gravitational collapse by the quantum pressure tensor and an asymptotic r -3 NFW-like profile. We find a fundamental relation of the core-to-halo mass with the dimensionless invariant Ξ ≡ | E |/ M 3 /( Gm/ħ ) 2 or M c / M ≃ 2.6Ξ 1/3 , linking the soliton to global halo properties. For r ≥ 3.5 r c core radii, we find equipartition between potential, classical kinetic and quantum gradient energies. The haloes also exhibit a conspicuous turbulent behaviour driven by the continuous reconnection of vortex lines due to wave interference. We analyse the turbulence 1D velocity power spectrum and find a k -1.1 power law. This suggests that the vorticity in BECDM haloes is homogeneous, similar to thermally-driven counterflow BEC systems from condensed matter physics, in contrast to a k -5/3 Kolmogorov power law seen in mechanically-driven quantum systems. The mode where the power spectrum peaks is approximately the soliton width, implying that the soliton-sized granules carry most of the turbulent energy in BECDM haloes.
Studying dark matter haloes with weak lensing
Velander, Malin Barbro Margareta
2012-01-01
Our Universe is comprised not only of normal matter but also of unknown components: dark matter and dark energy. This Thesis recounts studies of dark matter haloes, using a technique known as weak gravitational lensing, in order to learn more about the nature of these dark components. The haloes
THE UNORTHODOX ORBITS OF SUBSTRUCTURE HALOS
Ludlow, Aaron D.; Navarro, Julio F.; Springel, Volker; Jenkins, Adrian; Frenk, Carlos S.; Helmi, Amina
2009-01-01
We use a suite of cosmological N-body simulations to study the properties of substructure halos (subhalos) in galaxy-sized cold dark matter halos. We extend prior work on the subject by considering the whole population of subhalos physically associated with the main system. These are defined as
Efimov effect in 2-neutron halo nuclei
Indian Academy of Sciences (India)
This paper presents an overview of our theoretical investigations in search of Efimov states in light 2-neutron halo nuclei. The calculations have been carried out within a three-body formalism, assuming a compact core and two valence neutrons forming the halo. The calculations provide strong evidence for the occurrence ...
Beam halo studies using a three-dimensional particle-core model
Directory of Open Access Journals (Sweden)
Ji Qiang
2000-06-01
Full Text Available In this paper we present a study of beam halo based on a three-dimensional particle-core model of an ellipsoidal bunched beam in a constant focusing channel including the effects of nonlinear rf focusing. For an initially mismatched beam, three linear envelope modes—a high frequency mode, a low frequency mode, and a quadrupole mode—are identified for an azimuthally symmetric bunched beam. The high frequency mode has three components all in phase; the low frequency mode has the transverse components in phase and the longitudinal component 180° out of phase; the quadrupole mode has no longitudinal component, and the two transverse components in the mode are 180° out of phase. We also study the case of an ellipsoidal bunched beam without azimuthal symmetry and find that the high frequency mode and the low frequency mode are still present but the quadrupole mode is replaced by a new mode with transverse components 180° out of phase and a nonzero longitudinal component. Previous studies, which generally addressed the situation where the longitudinal-to-transverse focusing strength is roughly 0.6 or less, conclude that the oscillation of the high frequency mode is predominantly transverse, and that of the low frequency mode is predominantly longitudinal. In this paper we present a systematic study of the features of the modes as a function of the longitudinal-to-transverse focusing strength ratio. We find that, when the ratio is greater than unity, the high frequency mode may contain a significant longitudinal component. Thus, excitation of the high frequency mode in this situation can be responsible for the formation of longitudinal beam halo. Furthermore, while previous studies have observed halo amplitudes roughly 2–3 times the matched beam edge, for the present parameters we observe much larger amplitudes (5 times or more. This is due to the fact that the longitudinal-to-transverse focusing ratio used here is greater than that of previous
Yang, Jaw-Yen; Yan, Chih-Yuan; Diaz, Manuel; Huang, Juan-Chen; Li, Zhihui; Zhang, Hanxin
2014-01-08
The ideal quantum gas dynamics as manifested by the semiclassical ellipsoidal-statistical (ES) equilibrium distribution derived in Wu et al. (Wu et al . 2012 Proc. R. Soc. A 468 , 1799-1823 (doi:10.1098/rspa.2011.0673)) is numerically studied for particles of three statistics. This anisotropic ES equilibrium distribution was derived using the maximum entropy principle and conserves the mass, momentum and energy, but differs from the standard Fermi-Dirac or Bose-Einstein distribution. The present numerical method combines the discrete velocity (or momentum) ordinate method in momentum space and the high-resolution shock-capturing method in physical space. A decoding procedure to obtain the necessary parameters for determining the ES distribution is also devised. Computations of two-dimensional Riemann problems are presented, and various contours of the quantities unique to this ES model are illustrated. The main flow features, such as shock waves, expansion waves and slip lines and their complex nonlinear interactions, are depicted and found to be consistent with existing calculations for a classical gas.
Yang, Jaw-Yen; Yan, Chih-Yuan; Diaz, Manuel; Huang, Juan-Chen; Li, Zhihui; Zhang, Hanxin
2014-01-01
The ideal quantum gas dynamics as manifested by the semiclassical ellipsoidal-statistical (ES) equilibrium distribution derived in Wu et al. (Wu et al. 2012 Proc. R. Soc. A 468, 1799–1823 (doi:10.1098/rspa.2011.0673)) is numerically studied for particles of three statistics. This anisotropic ES equilibrium distribution was derived using the maximum entropy principle and conserves the mass, momentum and energy, but differs from the standard Fermi–Dirac or Bose–Einstein distribution. The present numerical method combines the discrete velocity (or momentum) ordinate method in momentum space and the high-resolution shock-capturing method in physical space. A decoding procedure to obtain the necessary parameters for determining the ES distribution is also devised. Computations of two-dimensional Riemann problems are presented, and various contours of the quantities unique to this ES model are illustrated. The main flow features, such as shock waves, expansion waves and slip lines and their complex nonlinear interactions, are depicted and found to be consistent with existing calculations for a classical gas. PMID:24399919
Halo formation in three-dimensional bunches
International Nuclear Information System (INIS)
Gluckstern, R.L.; Fedotov, A.V.; Kurennoy, S.; Ryne, R.
1998-01-01
We have constructed, analytically and numerically, a class of self-consistent six-dimensional (6D) phase space stationary distributions. Stationary distributions allow us to study the halo development mechanism without it being obscured by beam redistribution and its effect on halo formation. The beam is then mismatched longitudinally and/or transversely, and we explore the formation of longitudinal and transverse halos in 3D axisymmetric beam bunches. We find that the longitudinal halo forms first for comparable longitudinal and transverse mismatches because the longitudinal tune depression is more severe than the transverse one for elongated bunches. Of particular importance is the result that, due to the coupling between longitudinal and transverse motion, a longitudinal or transverse halo is observed for a mismatch less than 10% if the mismatch in the other plane is large. copyright 1998 The American Physical Society
KIC 7599132: an ellipsoidal variable in a close SB1 system
Catanzaro, G.; Frasca, A.; Giarrusso, M.; Ripepi, V.; Leone, F.; Tognelli, E.; Munari, M.; Scuderi, S.
2018-03-01
In this paper we present a spectroscopic and photometric analysis of the suspected ellipsoidal variable star KIC 7599132. New spectroscopic observations have been obtained with Catania Astrophysical Observatory Spectropolarimeter (CAOS). From the fit of Hα and Hβ we determined the effective temperature and gravity of the primary component, Teff = 10200 ± 150 K and log g = 4.1 ± 0.1, while from a number of metal lines we derive the rotational velocity, vesin i = 60 ± 2 km s-1. We found almost solar abundances with the exception of silicon (0.50 dex) overabundance. A Bayesian analysis, based on the comparison between observational data and theoretical predictions of PROSECCO evolutionary models, allows us to estimate the mass and the age of the primary. We obtained M1 = 2.4 ± 0.2 M⊙ and τs = 3.8 _{-0.7}^{+0.9} Myr. A new model for the system was obtained combining Kepler photometric time-series (Q0-Q17) and our radial velocities by using the code PHOEBE. As a result, the system appears to be a detached binary system with a mass ratio q = 0.30 ± 0.01, a semi-major axis a = 7.3 ± 0.1 R⊙ and an inclination angle i = 35° ± 2°. This modelling allowed us to derive: M2 = 0.7 ± 0.1 M⊙, R1 = 3.0 ± 0.2 R⊙ and R2 = 1.5 ± 0.2 R⊙. Numerical simulations show that if the secondary star had been hotter than 4000 K we would have observed its spectral features in our spectra.
KIC 7599132: an ellipsoidal variable in a close SB1 system
Catanzaro, G.; Frasca, A.; Giarrusso, M.; Ripepi, V.; Leone, F.; Tognelli, E.; Munari, M.; Scuderi, S.
2018-06-01
In this paper, we present a spectroscopic and photometric analysis of the suspected ellipsoidal variable star KIC 7599132. New spectroscopic observations have been obtained with Catania Astrophysical Observatory Spectropolarimeter. From the fit of Hα and Hβ, we determined the effective temperature and gravity of the primary component, Teff = 10200 ± 150 K and log g = 4.1 ± 0.1, while from a number of metal lines, we derive the rotational velocity, v esin i = 60 ± 2 km s-1. We found almost solar abundances with the exception of silicon (0.50 dex) overabundance. A Bayesian analysis, based on the comparison between observational data and theoretical predictions of PROSECCO evolutionary models, allows us to estimate the mass and the age of the primary. We obtained M1 = 2.4 ± 0.2 M⊙ and τs = 3.8 _{-0.7}^{+0.9} Myr. A new model for the system was obtained combining Kepler photometric time series (Q0-Q17) and our radial velocities by using the code PHOEBE. As a result, the system appears to be a detached binary system with a mass ratio q = 0.30 ± 0.01, a semimajor axis a = 7.3 ± 0.1 R⊙ and an inclination angle i = 35° ± 2°. This modelling allowed us to derive: M2 = 0.7 ± 0.1 M⊙, R1 = 3.0 ± 0.2 R⊙, and R2 = 1.5 ± 0.2 R⊙. Numerical simulations show that if the secondary star had been hotter than 4000 K, we would have observed its spectral features in our spectra.
VELOCITY VARIATIONS IN THE PHOENIX–HERMUS STAR STREAM
Energy Technology Data Exchange (ETDEWEB)
Carlberg, R. G. [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Grillmair, C. J., E-mail: carlberg@astro.utoronto.ca, E-mail: carl@ipac.caltech.edu [Spitzer Science Center, 1200 E. California Blvd., Pasadena, CA 91125 (United States)
2016-10-20
Measurements of velocity and density perturbations along stellar streams in the Milky Way provide a time-integrated measure of dark matter substructure at larger galactic radius than the complementary instantaneous inner-halo strong lensing detection of dark matter sub-halos in distant galaxies. An interesting case to consider is the proposed Phoenix–Hermus star stream, which is long, thin, and on a nearly circular orbit, making it a particular good target to study for velocity variations along its length. In the presence of dark matter sub-halos, the stream velocities are significantly perturbed in a manner that is readily understood with the impulse approximation. A set of simulations shows that only sub-halos above a few 10{sup 7} M {sub ⊙} lead to reasonably long-lived observationally detectable velocity variations of amplitude of order 1 km s{sup −1}, with an average of about one visible hit per (two-armed) stream over a 3 Gyr interval. An implication is that globular clusters themselves will not have a visible impact on the stream. Radial velocities have the benefit of being completely insensitive to distance errors. Distance errors scatter individual star velocities perpendicular and tangential to the mean orbit, but their mean values remain unbiased. Calculations like these help build the quantitative case to acquire large, fairly deep, precision velocity samples of stream stars.
Palomar 13: An Unusual Stellar System in the Galactic Halo
Côté, Patrick; Djorgovski, S. G.; Meylan, G.; Castro, Sandra; McCarthy, J. K.
2002-08-01
We report the first results of a program to study the internal kinematics of globular clusters in the outer halo of the Milky Way. Using the Keck telescope and High Resolution Echelle Spectrometer, we have measured precise radial velocities for 30 candidate red giants in the direction of Palomar 13, an object traditionally cataloged as a compact, low-luminosity globular cluster. We have combined these radial velocities with published proper motion membership probabilities and new CCD photometry from the Keck and Canada-France-Hawaii telescopes to isolate a sample of 21 probable members. We find a systemic velocity of s=24.1+/-0.5 km s-1 and a projected, intrinsic velocity dispersion of σp=2.2+/-0.4 km s-1. Although modest, this dispersion is nevertheless several times larger than that expected for a globular cluster of this luminosity and central concentration. Taken at face value, it implies a mass-to-light ratio of ΥV=40+24-17 based on the best-fit King-Michie model. The surface density profile of Palomar 13 also appears unusual compared to most Galactic globular clusters; depending upon the details of background subtraction and model-fitting, Palomar 13 either contains a substantial population of ``extratidal'' stars, or is considerably more spatially extended than previously suspected. The full surface density profile is equally well fitted by a King-Michie model having a high concentration and large tidal radius, or by a Navarro-Frenk-White model. We examine-and tentatively reject-a number of possible origins for the observed characteristics of Palomar 13 (e.g., velocity ``jitter'' among the red giant branch stars, spectroscopic binary stars, nonstandard mass functions, modified Newtonian dynamics) and conclude that the two leading explanations are either catastrophic heating during a recent perigalacticon passage or the presence of a dark matter halo. The available evidence therefore suggests that Palomar 13 is either a globular cluster that is now in the
Dark matter halos with cores from hierarchical structure formation
International Nuclear Information System (INIS)
Strigari, Louis E.; Kaplinghat, Manoj; Bullock, James S.
2007-01-01
We show that dark matter emerging from late decays (z or approx. 0.1 Mpc), and simultaneously generates observable constant-density cores in small dark matter halos. We refer to this class of models as meta-cold dark matter (mCDM), because it is born with nonrelativistic velocities from the decays of cold thermal relics. The constant-density cores are a result of the low phase-space density of mCDM at birth. Warm dark matter cannot produce similar size phase-space limited cores without saturating the Lyα power spectrum bounds. Dark matter-dominated galaxy rotation curves and stellar velocity dispersion profiles may provide the best means to discriminate between mCDM and CDM. mCDM candidates are motivated by the particle spectrum of supersymmetric and extra dimensional extensions to the standard model of particle physics
Halo assembly bias and the tidal anisotropy of the local halo environment
Paranjape, Aseem; Hahn, Oliver; Sheth, Ravi K.
2018-05-01
We study the role of the local tidal environment in determining the assembly bias of dark matter haloes. Previous results suggest that the anisotropy of a halo's environment (i.e. whether it lies in a filament or in a more isotropic region) can play a significant role in determining the eventual mass and age of the halo. We statistically isolate this effect, using correlations between the large-scale and small-scale environments of simulated haloes at z = 0 with masses between 1011.6 ≲ (m/h-1 M⊙) ≲ 1014.9. We probe the large-scale environment, using a novel halo-by-halo estimator of linear bias. For the small-scale environment, we identify a variable αR that captures the tidal anisotropy in a region of radius R = 4R200b around the halo and correlates strongly with halo bias at fixed mass. Segregating haloes by αR reveals two distinct populations. Haloes in highly isotropic local environments (αR ≲ 0.2) behave as expected from the simplest, spherically averaged analytical models of structure formation, showing a negative correlation between their concentration and large-scale bias at all masses. In contrast, haloes in anisotropic, filament-like environments (αR ≳ 0.5) tend to show a positive correlation between bias and concentration at any mass. Our multiscale analysis cleanly demonstrates how the overall assembly bias trend across halo mass emerges as an average over these different halo populations, and provides valuable insights towards building analytical models that correctly incorporate assembly bias. We also discuss potential implications for the nature and detectability of galaxy assembly bias.
Effective field theory description of halo nuclei
Hammer, H.-W.; Ji, C.; Phillips, D. R.
2017-10-01
Nuclear halos emerge as new degrees of freedom near the neutron and proton driplines. They consist of a core and one or a few nucleons which spend most of their time in the classically-forbidden region outside the range of the interaction. Individual nucleons inside the core are thus unresolved in the halo configuration, and the low-energy effective interactions are short-range forces between the core and the valence nucleons. Similar phenomena occur in clusters of 4He atoms, cold atomic gases near a Feshbach resonance, and some exotic hadrons. In these weakly-bound quantum systems universal scaling laws for s-wave binding emerge that are independent of the details of the interaction. Effective field theory (EFT) exposes these correlations and permits the calculation of non-universal corrections to them due to short-distance effects, as well as the extension of these ideas to systems involving the Coulomb interaction and/or binding in higher angular-momentum channels. Halo nuclei exhibit all these features. Halo EFT, the EFT for halo nuclei, has been used to compute the properties of single-neutron, two-neutron, and single-proton halos of s-wave and p-wave type. This review summarizes these results for halo binding energies, radii, Coulomb dissociation, and radiative capture, as well as the connection of these properties to scattering parameters, thereby elucidating the universal correlations between all these observables. We also discuss how Halo EFT's encoding of the long-distance physics of halo nuclei can be used to check and extend ab initio calculations that include detailed modeling of their short-distance dynamics.
Entropy production of a Brownian ellipsoid in the overdamped limit.
Marino, Raffaele; Eichhorn, Ralf; Aurell, Erik
2016-01-01
We analyze the translational and rotational motion of an ellipsoidal Brownian particle from the viewpoint of stochastic thermodynamics. The particle's Brownian motion is driven by external forces and torques and takes place in an heterogeneous thermal environment where friction coefficients and (local) temperature depend on space and time. Our analysis of the particle's stochastic thermodynamics is based on the entropy production associated with single particle trajectories. It is motivated by the recent discovery that the overdamped limit of vanishing inertia effects (as compared to viscous fricion) produces a so-called "anomalous" contribution to the entropy production, which has no counterpart in the overdamped approximation, when inertia effects are simply discarded. Here we show that rotational Brownian motion in the overdamped limit generates an additional contribution to the "anomalous" entropy. We calculate its specific form by performing a systematic singular perturbation analysis for the generating function of the entropy production. As a side result, we also obtain the (well-known) equations of motion in the overdamped limit. We furthermore investigate the effects of particle shape and give explicit expressions of the "anomalous entropy" for prolate and oblate spheroids and for near-spherical Brownian particles.
Quantifying the Rate of Ellipsoid Zone Loss in Stargardt Disease.
Cai, Cindy X; Light, Jacob G; Handa, James T
2018-02-01
To determine a reliable method of using the ellipsoid zone (EZ) on optical coherence tomography (OCT) to track disease progression in Stardgardt disease (STGD). Retrospective reliability study. STGD patients with genetically confirmed ABCA4 gene mutations seen at the Wilmer Eye Institute with follow-up visits separated by at least 12 months were identified. Spectral-domain optical coherence tomography (SD-OCT) macula volume scans centered at the fovea and fundus autofluorescence (FAF) images were obtained. The area of EZ loss was calculated from the SD-OCT and the area of retinal pigment epithelium (RPE) loss from the FAF. Scans were reanalyzed by the primary grader to assess intragrader reliability, and reanalyzed by a second grader to assess intergrader reliability. Sixteen STGD patients (total of 31 eyes) were followed for a mean of 2 years (range 1-4.7 years). The mean rate of EZ loss, 0.31 ± 0.31 mm 2 /year, was similar to the average rate of RPE loss, 0.33 ± 0.38 mm 2 /year. The average area of EZ loss at the initial examination, 4.18 ± 1.91 mm 2 , was larger than the initial area of RPE loss, 2.25 ± 1.66 mm 2 (P disease progression in STGD. This could be used as a sensitive anatomic outcome measure in clinical trials related to STGD. Copyright © 2017 Elsevier Inc. All rights reserved.
Electromagnetic characteristics of systems of prolate and oblate ellipsoids
Karimi, Pouyan; Amiri-Hezaveh, Amirhossein; Ostoja-Starzewski, Martin; Jin, Jian-Ming
2017-11-01
The present study suggests a novel model for simulating electromagnetic characteristics of spheroidal nanofillers. The electromagnetic interference shielding efficiency of prolate and oblate ellipsoids in the X-band frequency range is studied. Different multilayered nanocomposite configurations incorporating carbon nanotubes, graphene nanoplatelets, and carbon blacks are fabricated and tested. The best performance for a specific thickness is observed for the multilayered composite with a gradual increase in the thickness and electrical conductivity of layers. The simulation results based on the proposed model are shown to be in good agreement with the experimental data. The effect of filler alignment on shielding efficiency is also studied by using the nematic order parameter. The ability of a nanocomposite to shield the incident power is found to decrease by increasing alignment especially for high volume fractions of prolate fillers. The interaction of the electromagnetic wave and the fillers is mainly affected by the polarization of the electric field; when the electric field is perpendicular to the equatorial axis of a spheroid, the interaction is significantly reduced and results in a lower shielding efficiency. Apart from the filler alignment, size polydispersity is found to have a significant effect on reflected and transmitted powers. It is demonstrated that the nanofillers with a higher aspect ratio mainly contribute to the shielding performance. The results are of interest in both shielding structures and microwave absorbing materials.
Dark halos formed via dissipationless collapse. I - Shapes and alignment of angular momentum
Warren, Michael S.; Quinn, Peter J.; Salmon, John K.; Zurek, Wojciech H.
1992-11-01
We use N-body simulations on highly parallel supercomputers to study the structure of Galactic dark matter halos. The systems form by gravitational collapse from scale-free and more general Gaussian initial density perturbations in an expanding 400 Mpc-cubed spherical slice of an Einstein-deSitter universe. We analyze the structure and kinematics of about 100 of the largest relaxed halos in each of 10 separate simulations. A typical halo is a triaxial spheroid which tends to be more often prolate than oblate. These shapes are maintained by anisotropic velocity dispersion rather than by angular momentum. Nevertheless, there is a significant tendency for the total angular momentum vector to be aligned with the minor axis of the density distribution.
Vacuum pumping by the halo plasma
International Nuclear Information System (INIS)
Barr, W.L.
1985-01-01
An estimate is made of the effective vacuum pumping speed of the halo plasma in a tandem mirror fusion reactor, and it is shown that, if the electron temperature and line density are great enough, the halo can be a very good vacuum pump. One can probably obtain the required density by recycling the ions at the halo dumps. An array of small venting ports in the dump plates allows local variation of the recycle fraction and local removal of the gas at a conveniently high pressure. This vented-port concept could introduce more flexibility in the design of pumped limiters for tokamaks
Isospin quantum number and structure of the excited states in halo nuclei. Halo-isomers
International Nuclear Information System (INIS)
Izosimov, I.N.
2015-01-01
It has been shown that isobar-analog (IAS), double isobar-analog (DIAS), configuration (CS), and double configuration states (DCS) can simultaneously have n-n, n-p, and p-p halo components in their wave functions. Differences in halo structure of the excited and ground states can result in the formation of isomers (halo-isomers). Both the Borromean and tango halo types can be observed for n-p configurations of atomic nuclei. The structure of the ground and excited states with different isospin quantum number in halo-like nuclei is discussed. B(Mλ) and B(Eλ) for γ-transitions in 6-8 Li, 8-10 Be, 8,10,11 B, 10-14 C, 13-17 N, 15-17,19 O, and 17 F are analyzed. Special attention is given to nuclei whose ground state does not exhibit halo structure, but the excited state may have one.
Metallicity and Kinematics of M31's Outer Stellar Halo from a Keck Spectroscopic Survey
Reitzel, David B.; Guhathakurta, Puragra
2002-07-01
We present first results from a spectroscopic survey designed to examine the metallicity and kinematics of individual red giant branch stars in the outer halo of the Andromeda spiral galaxy (M31). This study is based on multislit spectroscopy with the Keck II 10 m telescope and Low Resolution Imaging Spectrograph of the Ca II near-infrared triplet in 99 M31 halo candidates in a field at R=19 kpc on the southeast minor axis with brightnesses from 20intermediate-velocity stars (-160~2 dex range over which the abundance measurement methods are calibrated. The mean/median metallicity of the M31 halo is about =-1.9 to -1.1 dex (depending on the details of metallicity calibration and sample selection) and possibly higher: the high-metallicity end of the distribution is poorly constrained by our data since the selection function for the secure M31 sample excludes over 80% of the giants in solar/supersolar metallicity range. Possible reasons are explored for the apparent discrepancy between the mean [Fe/H] found in our spectroscopic survey (corrected for metallicity selection bias) and the slightly higher mean values found in earlier photometric studies. Field halo red giants in M31 appear to be somewhat more metal-rich on average than their Milky Way counterparts. The M31 halo [Fe/H] distribution is comparable to that of M31 globular clusters, Galactic globular clusters, and Local Group dwarf satellite galaxies. The data in this 19 kpc outer halo field are broadly consistent with a scenario in which the halo is built from the accretion of small stellar subsystems. There are four stars in the secure M31 sample that have particularly strong Ca II lines, indicating solar metallicity, at a common velocity of ~-340 km s-1 close to the galaxy's systemic velocity, similar to what might be expected for M31 disk giants on the minor axis. An extrapolation of the inner disk brightness profile, however, falls far short of accounting for these four stars-the disk would instead have to
The growth of galaxies and their gaseous haloes
Voort, Frederieke van de
2012-01-01
Galaxies grow by accreting gas, which they need to form stars, from their surrounding haloes. These haloes, in turn, accrete gas from the diffuse intergalactic medium. Feedback from stars and black holes returns gas from the galaxy to the halo and can even expel it from the halo. This cycle of gas
On the absence of radio haloes in clusters with double relics
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.
The Structure and Dark Halo Core Properties of Dwarf Spheroidal Galaxies
Burkert, A.
2015-08-01
The structure and dark matter halo core properties of dwarf spheroidal galaxies (dSphs) are investigated. A double-isothermal (DIS) model of an isothermal, non-self-gravitating stellar system embedded in an isothermal dark halo core provides an excellent fit to the various observed stellar surface density distributions. The stellar core scale length a* is sensitive to the central dark matter density ρ0,d. The maximum stellar radius traces the dark halo core radius {r}c,d. The concentration c* of the stellar system, determined by a King profile fit, depends on the ratio of the stellar-to-dark-matter velocity dispersion {σ }*/{σ }d. Simple empirical relationships are derived that allow us to calculate the dark halo core parameters ρ0,d, {r}c,d, and σd given the observable stellar quantities σ*, a*, and c*. The DIS model is applied to the Milky Way’s dSphs. All dSphs closely follow the same universal dark halo scaling relations {ρ }0,d× {r}c,d={75}-45+85 M⊙ pc-2 that characterize the cores of more massive galaxies over a large range in masses. The dark halo core mass is a strong function of core radius, {M}c,d˜ {r}c,d2. Inside a fixed radius of ˜400 pc the total dark matter mass is, however, roughly constant with {M}d=2.6+/- 1.4× {10}7 M⊙, although outliers are expected. The dark halo core densities of the Galaxy’s dSphs are very high, with {ρ }0,d ≈ 0.2 M⊙ pc-3. dSphs should therefore be tidally undisturbed. Evidence for tidal effects might then provide a serious challenge for the CDM scenario.
Equilibrium and dynamics of uniform density ellipsoidal non-neutral plasmas
International Nuclear Information System (INIS)
Dubin, D.H.E.
1993-01-01
When a single-species plasma is confined in a harmonic Penning trap at cryogenic temperature, the thermal equilibrium is approximately a uniform density spheroid (ellipsoid of revolution). Normal modes corresponding to quadrupole excitations of this plasma have recently been measured. In this paper, nonlinear equations of motion are derived for these quadrupole oscillations. For large amplitudes, the oscillations deform a spheroidal plasma into a triaxial ellipsoid with time-dependent shape and orientation. The integrals of the motion are found and the cylindrically symmetric finite-amplitude oscillations of a spheroid are studied. An analysis of all possible ellipsoidal equilibria is also carried out. New equilibria are discovered which correspond to finite-amplitude versions of the noncylindrically symmetric linear quadrupole oscillations. The equilibria are shown to fall into two classes in which the ellipsoids are either tilted or aligned with respect to the magnetic field. Some of these equilibria have densities well above the Brillouin limit
International Nuclear Information System (INIS)
Masyukov, V.V.; Tsvetkov, V.P.
1990-01-01
The analytical representations of the gravitational potential of perturbed inhomogeneous ellipsoidal configurations with the account of the 'fifth' force are obtained in the form of the series in the parameter of perturbation. 11 refs
Longitudinal phase-space manipulation of ellipsoidal electron bunches in realistic fields
Directory of Open Access Journals (Sweden)
S. B. van der Geer
2006-04-01
Full Text Available Since the recent publication of a practical recipe to create “pancake” electron bunches which evolve into uniformly filled ellipsoids, a number of papers have addressed both an alternative method to create such ellipsoids as well as their behavior in realistic fields. So far, the focus has been on the possibilities to preserve the initial “thermal” transverse emittance. This paper addresses the linear longitudinal phase space of ellipsoidal bunches. It is shown that ellipsoidal bunches allow ballistic compression at subrelativistic energies, without the detrimental effects of nonlinear space-charge forces. This in turn eliminates the need for the large correlated energy spread normally required for longitudinal compression of relativistic particle beams, while simultaneously avoiding all problems related to magnetic compression. Furthermore, the linear space-charge forces of ellipsoidal bunches can be used to reduce the remaining energy spread even further, by carefully choosing the beam transverse size, in a process that is essentially the time-reversed process of the creation of an ellipsoid at the cathode. The feasibility of compression of ellipsoidal bunches is illustrated with a relatively simple setup, consisting of a half-cell S-band photogun and a two-cell booster compressor. Detailed GPT simulations in realistic fields predict that 100 pC ellipsoidal bunches can be ballistically compressed to 100 fs, at a transverse emittance of 0.7 μm, with a final energy of 3.7 MeV and an energy spread of only 50 keV.
Self-consistent Analysis of Three-dimensional Uniformly Charged Ellipsoid with Zero Emittance
International Nuclear Information System (INIS)
Batygin, Yuri K.
2001-01-01
A self-consistent treatment of a three-dimensional ellipsoid with negligible emittance in time-dependent external field is performed. Envelope equations describing the evolution of an ellipsoid boundary are discussed. For a complete model it is required that the initial particle momenta be a linear function of the coordinates. Numerical example and verification of the problem by a 3-dimensional particle-in-cell simulations are given
Remapping simulated halo catalogues in redshift space
Mead, Alexander; Peacock, John
2014-01-01
We discuss the extension to redshift space of a rescaling algorithm, designed to alter the effective cosmology of a pre-existing simulated particle distribution or catalogue of dark matter haloes. The rescaling approach was initially developed by Angulo & White and was adapted and applied to halo catalogues in real space in our previous work. This algorithm requires no information other than the initial and target cosmological parameters, and it contains no tuned parameters. It is shown here ...
On physical scales of dark matter halos
International Nuclear Information System (INIS)
Zemp, Marcel
2014-01-01
It is common practice to describe formal size and mass scales of dark matter halos as spherical overdensities with respect to an evolving density threshold. Here, we critically investigate the evolutionary effects of several such commonly used definitions and compare them to the halo evolution within fixed physical scales as well as to the evolution of other intrinsic physical properties of dark matter halos. It is shown that, in general, the traditional way of characterizing sizes and masses of halos dramatically overpredicts the degree of evolution in the last 10 Gyr, especially for low-mass halos. This pseudo-evolution leads to the illusion of growth even though there are no major changes within fixed physical scales. Such formal size definitions also serve as proxies for the virialized region of a halo in the literature. In general, those spherical overdensity scales do not coincide with the virialized region. A physically more precise nomenclature would be to simply characterize them by their very definition instead of calling such formal size and mass definitions 'virial'. In general, we find a discrepancy between the evolution of the underlying physical structure of dark matter halos seen in cosmological structure formation simulations and pseudo-evolving formal virial quantities. We question the importance of the role of formal virial quantities currently ubiquitously used in descriptions, models, and relations that involve properties of dark matter structures. Concepts and relations based on pseudo-evolving formal virial quantities do not properly reflect the actual evolution of dark matter halos and lead to an inaccurate picture of the physical evolution of our universe.
MODIFIED GRAVITY SPINS UP GALACTIC HALOS
Energy Technology Data Exchange (ETDEWEB)
Lee, Jounghun [Astronomy Program, Department of Physics and Astronomy, FPRD, Seoul National University, Seoul 151-747 (Korea, Republic of); Zhao, Gong-Bo [National Astronomy Observatories, Chinese Academy of Science, Beijing 100012 (China); Li, Baojiu [Institute of Computational Cosmology, Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Koyama, Kazuya, E-mail: jounghun@astro.snu.ac.kr [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, PO1 3FX (United Kingdom)
2013-01-20
We investigate the effect of modified gravity on the specific angular momentum of galactic halos by analyzing the halo catalogs at z = 0 from high-resolution N-body simulations for a f(R) gravity model that meets the solar-system constraint. It is shown that the galactic halos in the f(R) gravity model tend to acquire significantly higher specific angular momentum than those in the standard {Lambda}CDM model. The largest difference in the specific angular momentum distribution between these two models occurs for the case of isolated galactic halos with mass less than 10{sup 11} h {sup -1} M {sub Sun }, which are likely least shielded by the chameleon screening mechanism. As the specific angular momentum of galactic halos is rather insensitive to other cosmological parameters, it can in principle be an independent discriminator of modified gravity. We speculate a possibility of using the relative abundance of low surface brightness galaxies (LSBGs) as a test of general relativity given that the formation of the LSBGs occurs in fast spinning dark halos.
ANGULAR MOMENTUM ACQUISITION IN GALAXY HALOS
International Nuclear Information System (INIS)
Stewart, Kyle R.; Brooks, Alyson M.; Bullock, James S.; Maller, Ariyeh H.; Diemand, Jürg; Wadsley, James; Moustakas, Leonidas A.
2013-01-01
We use high-resolution cosmological hydrodynamic simulations to study the angular momentum acquisition of gaseous halos around Milky-Way-sized galaxies. We find that cold mode accreted gas enters a galaxy halo with ∼70% more specific angular momentum than dark matter averaged over cosmic time (though with a very large dispersion). In fact, we find that all matter has a higher spin parameter when measured at accretion than when averaged over the entire halo lifetime, and is well characterized by λ ∼ 0.1, at accretion. Combined with the fact that cold flow gas spends a relatively short time (1-2 dynamical times) in the halo before sinking to the center, this naturally explains why cold flow halo gas has a specific angular momentum much higher than that of the halo and often forms ''cold flow disks.'' We demonstrate that the higher angular momentum of cold flow gas is related to the fact that it tends to be accreted along filaments.
Role of 'core' and 'halo' solar electrons in ionization of the interstellar medium
International Nuclear Information System (INIS)
Askew, S.D.; Kunc, J.A.; University of Southern California, Los Angeles
1984-01-01
The probability of the interstellar wind atoms (H and He) to survive ionization by solar wind electrons is presented. For the first time a dual temperature electron distribution is used to model the effects of ''core'' (10 eV) and ''halo'' (60 eV) solar electrons on the probabilities. Survival probability distributions as a function of heliocentric distance were calculated for variations in the electron temperature, solar radiation force, and the interstellar wind flow velocity. These probabilities are important in determining the radial density distributions of the interstellar atoms. It has been found that the interstellar wind has a distinctively higher probability of surviving ''halo'' rather than ''core'' electron ionization only at heliocentric distances, rho, smaller than about 0.5 a.u. For distances larger than 0.5 a.u., the probabilities of surviving ''halo'' electrons are close to the probabilities of surviving ''core'' electrons. Also, the probabilities for both ''core'' and ''halo'' electrons are relatively insensitive to changes in μsub(proportional to) (interstellar wind velocity at infinity), μ(the solar ratio of radiation to gravitational force) and α (a model parameter for solar electron temperature) for rho > 0.5. For distances smaller than that, the sensitivity increases significantly. (author)
Disk Heating, Galactoseismology, and the Formation of Stellar Halos
Directory of Open Access Journals (Sweden)
Kathryn V. Johnston
2017-08-01
Full Text Available Deep photometric surveys of the Milky Way have revealed diffuse structures encircling our Galaxy far beyond the “classical” limits of the stellar disk. This paper reviews results from our own and other observational programs, which together suggest that, despite their extreme positions, the stars in these structures were formed in our Galactic disk. Mounting evidence from recent observations and simulations implies kinematic connections between several of these distinct structures. This suggests the existence of collective disk oscillations that can plausibly be traced all the way to asymmetries seen in the stellar velocity distribution around the Sun. There are multiple interesting implications of these findings: they promise new perspectives on the process of disk heating; they provide direct evidence for a stellar halo formation mechanism in addition to the accretion and disruption of satellite galaxies; and, they motivate searches of current and near-future surveys to trace these oscillations across the Galaxy. Such maps could be used as dynamical diagnostics in the emerging field of “Galactoseismology”, which promises to model the history of interactions between the Milky Way and its entourage of satellites, as well examine the density of our dark matter halo. As sensitivity to very low surface brightness features around external galaxies increases, many more examples of such disk oscillations will likely be identified. Statistical samples of such features not only encode detailed information about interaction rates and mergers, but also about long sought-after dark matter halo densities and shapes. Models for the Milky Way’s own Galactoseismic history will therefore serve as a critical foundation for studying the weak dynamical interactions of galaxies across the universe.
Ardalan, A.; Safari, A.; Grafarend, E.
2003-04-01
A new ellipsoidal gravimetric-satellite altimetry boundary value problem has been developed and successfully tested. This boundary value problem has been constructed for gravity observables of the type (i) gravity potential (ii) gravity intensity (iii) deflection of vertical and (iv) satellite altimetry data. The developed boundary value problem is enjoying the ellipsoidal nature and as such can take advantage of high precision GPS observations in the set-up of the problem. The highlights of the solution are as follows: begin{itemize} Application of ellipsoidal harmonic expansion up to degree/order and ellipsoidal centrifugal field for the reduction of global gravity and isostasy effects from the gravity observable at the surface of the Earth. Application of ellipsoidal Newton integral on the equal area map projection surface for the reduction of residual mass effects within a radius of 55 km around the computational point. Ellipsoidal harmonic downward continuation of the residual observables from the surface of the earth down to the surface of reference ellipsoid using the ellipsoidal height of the observation points derived from GPS. Restore of the removed effects at the application points on the surface of reference ellipsoid. Conversion of the satellite altimetry derived heights of the water bodies into potential. Combination of the downward continued gravity information with the potential equivalent of the satellite altimetry derived heights of the water bodies. Application of ellipsoidal Bruns formula for converting the potential values on the surface of the reference ellipsoid into the geoidal heights (i.e. ellipsoidal heights of the geoid) with respect to the reference ellipsoid. Computation of the high-resolution geoid of Iran has successfully tested this new methodology!
Cold dark matter. 2: Spatial and velocity statistics
Gelb, James M.; Bertschinger, Edmund
1994-01-01
We examine high-resolution gravitational N-body simulations of the omega = 1 cold dark matter (CDM) model in order to determine whether there is any normalization of the initial density fluctuation spectrum that yields acceptable results for galaxy clustering and velocities. Dense dark matter halos in the evolved mass distribution are identified with luminous galaxies; the most massive halos are also considered as sites for galaxy groups, with a range of possibilities explored for the group mass-to-light ratios. We verify the earlier conclusions of White et al. (1987) for the low-amplitude (high-bias) CDM model-the galaxy correlation function is marginally acceptable but that there are too many galaxies. We also show that the peak biasing method does not accurately reproduce the results obtained using dense halos identified in the simulations themselves. The Cosmic Background Explorer (COBE) anisotropy implies a higher normalization, resulting in problems with excessive pairwise galaxy velocity dispersion unless a strong velocity bias is present. Although we confirm the strong velocity bias of halos reported by Couchman & Carlberg (1992), we show that the galaxy motions are still too large on small scales. We find no amplitude for which the CDM model can reconcile simultaneously and galaxy correlation function, the low pairwise velocity dispersion, and the richness distribution of groups and clusters. With the normalization implied by COBE, the CDM spectrum has too much power on small scales if omega = 1.
Evidence for halo kinematics among cool carbon-rich dwarfs
Farihi, J.; Arendt, A. R.; Machado, H. S.; Whitehouse, L. J.
2018-04-01
This paper reports preliminary yet compelling kinematical inferences for N ≳ 600 carbon-rich dwarf stars that demonstrate around 30% to 60% are members of the Galactic halo. The study uses a spectroscopically and non-kinematically selected sample of stars from the SDSS, and cross-correlates these data with three proper motion catalogs based on Gaia DR1 astrometry to generate estimates of their 3-D space velocities. The fraction of stars with halo-like kinematics is roughly 30% for distances based on a limited number of parallax measurements, with the remainder dominated by the thick disk, but close to 60% of the sample lie below an old, metal-poor disk isochrone in reduced proper motion. An ancient population is consistent with an extrinsic origin for C/O >1 in cool dwarfs, where a fixed mass of carbon pollution more readily surmounts lower oxygen abundances, and with a lack of detectable ultraviolet-blue flux from younger white dwarf companions. For an initial stellar mass function that favors low-mass stars as in the Galactic disk, the dC stars are likely to be the dominant source of carbon-enhanced, metal-poor stars in the Galaxy.
Revealing the Cosmic Web-dependent Halo Bias
Yang, Xiaohu; Zhang, Youcai; Lu, Tianhuan; Wang, Huiyuan; Shi, Feng; Tweed, Dylan; Li, Shijie; Luo, Wentao; Lu, Yi; Yang, Lei
2017-10-01
Halo bias is the one of the key ingredients of the halo models. It was shown at a given redshift to be only dependent, to the first order, on the halo mass. In this study, four types of cosmic web environments—clusters, filaments, sheets, and voids—are defined within a state-of-the-art high-resolution N-body simulation. Within these environments, we use both halo-dark matter cross correlation and halo-halo autocorrelation functions to probe the clustering properties of halos. The nature of the halo bias differs strongly between the four different cosmic web environments described here. With respect to the overall population, halos in clusters have significantly lower biases in the {10}11.0˜ {10}13.5 {h}-1 {M}⊙ mass range. In other environments, however, halos show extremely enhanced biases up to a factor 10 in voids for halos of mass ˜ {10}12.0 {h}-1 {M}⊙ . Such a strong cosmic web environment dependence in the halo bias may play an important role in future cosmological and galaxy formation studies. Within this cosmic web framework, the age dependency of halo bias is found to be only significant in clusters and filaments for relatively small halos ≲ {10}12.5 {h}-1 {M}⊙ .
Halo Intrinsic Alignment: Dependence on Mass, Formation Time, and Environment
Energy Technology Data Exchange (ETDEWEB)
Xia, Qianli; Kang, Xi; Wang, Peng; Luo, Yu [Purple Mountain Observatory, the Partner Group of MPI für Astronomie, 2 West Beijing Road, Nanjing 210008 (China); Yang, Xiaohu; Jing, Yipeng [Center for Astronomy and Astrophysics, Shanghai Jiao Tong University, Shanghai 200240 (China); Wang, Huiyuan [Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026 (China); Mo, Houjun, E-mail: kangxi@pmo.ac.cn [Astronomy Department and Center for Astrophysics, Tsinghua University, Beijing 10084 (China)
2017-10-10
In this paper we use high-resolution cosmological simulations to study halo intrinsic alignment and its dependence on mass, formation time, and large-scale environment. In agreement with previous studies using N -body simulations, it is found that massive halos have stronger alignment. For the first time, we find that for a given halo mass older halos have stronger alignment and halos in cluster regions also have stronger alignment than those in filaments. To model these dependencies, we extend the linear alignment model with inclusion of halo bias and find that the halo alignment with its mass and formation time dependence can be explained by halo bias. However, the model cannot account for the environment dependence, as it is found that halo bias is lower in clusters and higher in filaments. Our results suggest that halo bias and environment are independent factors in determining halo alignment. We also study the halo alignment correlation function and find that halos are strongly clustered along their major axes and less clustered along the minor axes. The correlated halo alignment can extend to scales as large as 100 h {sup −1} Mpc, where its feature is mainly driven by the baryon acoustic oscillation effect.
International Nuclear Information System (INIS)
Jameson, R.A.
1994-01-01
Beam halos are formed via self-consistent motion of the beam particles. Interactions of single particles with time-varying density distributions of other particles are a major source of halo. Aspects of these interactions are studied for an initially equilibrium distribution in a radial, linear, continuous focusing system. When there is a mismatch, it is shown that in the self-consistent system, there is a threshold in space-charge and mismatch, above which a halo is formed that extends to ∼1.5 times the initial maximum mismatch radius. Tools are sought for characterizing the halo dynamics. Testing the particles against the width of the mismatch driving resonance is useful for finding a conservative estimate of the threshold. The exit, entering and transition times, and the time evolution of the halo, are also explored using this technique. Extension to higher dimensions is briefly discussed
CARBON-ENHANCED METAL-POOR STARS IN THE INNER AND OUTER HALO COMPONENTS OF THE MILKY WAY
International Nuclear Information System (INIS)
Carollo, Daniela; Norris, John E.; Freeman, Ken C.; Beers, Timothy C.; Lee, Young Sun; Kennedy, Catherine R.; Bovy, Jo; Sivarani, Thirupathi; Aoki, Wako
2012-01-01
Carbon-enhanced metal-poor (CEMP) stars in the halo components of the Milky Way are explored, based on accurate determinations of the carbon-to-iron ([C/Fe]) abundance ratios and kinematic quantities for over 30,000 calibration stars from the Sloan Digital Sky Survey. Using our present criterion that low-metallicity stars exhibiting [C/Fe] ratios ( c arbonicity ) in excess of [C/Fe] =+0.7 are considered CEMP stars, the global frequency of CEMP stars in the halo system for [Fe/H] 5 kpc, the CarDF exhibits a strong tail toward high values, up to [C/Fe] > +3.0. We also find a clear increase in the CEMP frequency with |Z|. For stars with –2.0 < [Fe/H] <–1.5, the frequency grows from 5% at |Z| ∼2 kpc to 10% at |Z| ∼10 kpc. For stars with [Fe/H] <–2.0, the frequency grows from 8% at |Z| ∼2 kpc to 25% at |Z| ∼10 kpc. For stars with –2.0 < [Fe/H] <–1.5, the mean carbonicity is ([C/Fe]) ∼+1.0 for 0 kpc < |Z| < 10 kpc, with little dependence on |Z|; for [Fe/H] <–2.0, ([C/Fe]) ∼+1.5, again roughly independent of |Z|. Based on a statistical separation of the halo components in velocity space, we find evidence for a significant contrast in the frequency of CEMP stars between the inner- and outer-halo components—the outer halo possesses roughly twice the fraction of CEMP stars as the inner halo. The carbonicity distribution also differs between the inner-halo and outer-halo components—the inner halo has a greater portion of stars with modest carbon enhancement ([C/Fe] ∼+0.5]); the outer halo has a greater portion of stars with large enhancements ([C/Fe] ∼+2.0), although considerable overlap still exists. We interpret these results as due to the possible presence of additional astrophysical sources of carbon production associated with outer-halo stars, beyond the asymptotic giant-branch source that may dominate for inner-halo stars, with implications for the progenitors of these populations.
THE BLACK HOLE MASS, STELLAR MASS-TO-LIGHT RATIO, AND DARK HALO IN M87
International Nuclear Information System (INIS)
Gebhardt, Karl; Thomas, Jens
2009-01-01
We model the dynamical structure of M87 (NGC4486) using high spatial resolution long-slit observations of stellar light in the central regions, two-dimensional stellar light kinematics out to half of the effective radius, and globular cluster velocities out to eight effective radii. We simultaneously fit for four parameters: black hole mass, dark halo core radius, dark halo circular velocity, and stellar mass-to-light (M/L) ratio. We find a black hole mass of 6.4(±0.5) x 10 9 M sun (the uncertainty is 68% confidence marginalized over the other parameters). The stellar M/L V = 6.3 ± 0.8. The best-fit dark halo core radius is 14 ± 2 kpc, assuming a cored logarithmic potential. The best-fit dark halo circular velocity is 715 ± 15 km s -1 . Our black hole mass is over a factor of 2 larger than previous stellar dynamical measures, and our derived stellar M/L ratio is two times lower than previous dynamical measures. When we do not include a dark halo, we measure a black hole mass and stellar M/L ratio that is consistent with previous measures, implying that the major difference is in the model assumptions. The stellar M/L ratio from our models is very similar to that derived from stellar population models of M87. The reason for the difference in the black hole mass is because we allow the M/L ratio to change with radius. The dark halo is degenerate with the stellar M/L ratio, which is subsequently degenerate with the black hole mass. We argue that dynamical models of galaxies that do not include the contribution from a dark halo may produce a biased result for the black hole mass. This bias is especially large for a galaxy with a shallow light profile such as M87, and may not be as severe in galaxies with steeper light profiles unless they have a large stellar population change with radius.
International Nuclear Information System (INIS)
Marsakov, V.A.; Suchkov, A.A.
1978-01-01
The distributions of orbits eccentricities and of angular momenta for the halo stars and for the old disk population are considered. The distributions have gaps separating the halo from the disk and diving the halo population into three groups. From the point of view of star formation during the collapse at the earliy stages of evolution the gaps evidence that threre were in the Galaxy long periods of suppression of star formation. The kinematics and the orbit elements of the halo stars and of the old disk population allow to conclude that there was no significant relaxation in the halo; the halo subsystems are not stationary, they perform radial oscillations with respect to the galactic centre; the velocity dispersion in the galactic rotation direction for the halo stars having the same age does not exceed 20-40 km/s; the dispersion of the velocity component along the galactic radius is symmetrically higher for the subsystems with a greater eccentrically and reaches 215 km/s for the stars with the greatest eccentricaities; the sing of the angular momentum in the protogalactic gas cloud probably changed at some distance form the galactic centre
An analytic distribution function for a mass-less cored stellar system in a cuspy dark-matter halo
Breddels, Maarten A.; Helmi, Amina
2013-01-01
We demonstrate the existence of a distribution function that can be used to represent spherical mass-less cored stellar systems having constant mildly tangential velocity anisotropy embedded in cuspy dark-matter halos. In particular, we derived analytically the functional form of the distribution
Smooth halos in the cosmic web
International Nuclear Information System (INIS)
Gaite, José
2015-01-01
Dark matter halos can be defined as smooth distributions of dark matter placed in a non-smooth cosmic web structure. This definition of halos demands a precise definition of smoothness and a characterization of the manner in which the transition from smooth halos to the cosmic web takes place. We introduce entropic measures of smoothness, related to measures of inequality previously used in economy and with the advantage of being connected with standard methods of multifractal analysis already used for characterizing the cosmic web structure in cold dark matter N-body simulations. These entropic measures provide us with a quantitative description of the transition from the small scales portrayed as a distribution of halos to the larger scales portrayed as a cosmic web and, therefore, allow us to assign definite sizes to halos. However, these ''smoothness sizes'' have no direct relation to the virial radii. Finally, we discuss the influence of N-body discreteness parameters on smoothness
Smooth halos in the cosmic web
Energy Technology Data Exchange (ETDEWEB)
Gaite, José, E-mail: jose.gaite@upm.es [Physics Dept., ETSIAE, IDR, Universidad Politécnica de Madrid, Pza. Cardenal Cisneros 3, E-28040 Madrid (Spain)
2015-04-01
Dark matter halos can be defined as smooth distributions of dark matter placed in a non-smooth cosmic web structure. This definition of halos demands a precise definition of smoothness and a characterization of the manner in which the transition from smooth halos to the cosmic web takes place. We introduce entropic measures of smoothness, related to measures of inequality previously used in economy and with the advantage of being connected with standard methods of multifractal analysis already used for characterizing the cosmic web structure in cold dark matter N-body simulations. These entropic measures provide us with a quantitative description of the transition from the small scales portrayed as a distribution of halos to the larger scales portrayed as a cosmic web and, therefore, allow us to assign definite sizes to halos. However, these ''smoothness sizes'' have no direct relation to the virial radii. Finally, we discuss the influence of N-body discreteness parameters on smoothness.
A novel approach to derive halo-independent limits on dark matter properties
Ferrer, Francesc; Ibarra, Alejandro; Wild, Sebastian
2015-01-01
We propose a method that allows to place an upper limit on the dark matter elastic scattering cross section with nucleons which is independent of the velocity distribution. Our approach combines null results from direct detection experiments with indirect searches at neutrino telescopes, and goes beyond previous attempts to remove astrophysical uncertainties in that it directly constrains the particle physics properties of the dark matter. The resulting halo-independent upper limits on the sc...
Optimized velocity distributions for direct dark matter detection
Energy Technology Data Exchange (ETDEWEB)
Ibarra, Alejandro; Rappelt, Andreas, E-mail: ibarra@tum.de, E-mail: andreas.rappelt@tum.de [Physik-Department T30d, Technische Universität München, James-Franck-Straße, 85748 Garching (Germany)
2017-08-01
We present a method to calculate, without making assumptions about the local dark matter velocity distribution, the maximal and minimal number of signal events in a direct detection experiment given a set of constraints from other direct detection experiments and/or neutrino telescopes. The method also allows to determine the velocity distribution that optimizes the signal rates. We illustrate our method with three concrete applications: i) to derive a halo-independent upper limit on the cross section from a set of null results, ii) to confront in a halo-independent way a detection claim to a set of null results and iii) to assess, in a halo-independent manner, the prospects for detection in a future experiment given a set of current null results.
Dark energy and dark matter in galaxy halos
International Nuclear Information System (INIS)
Tetradis, N.
2006-01-01
We consider the possibility that the dark matter is coupled through its mass to a scalar field associated with the dark energy of the Universe. In order for such a field to play a role at the present cosmological distances, it must be effectively massless at galactic length scales. We discuss the effect of the field on the distribution of dark matter in galaxy halos. We show that the profile of the distribution outside the galaxy core remains largely unaffected and the approximately flat rotation curves persist. The dispersion of the dark matter velocity is enhanced by a potentially large factor relative to the case of zero coupling between dark energy and dark matter. The counting rates in terrestrial dark matter detectors are similarly enhanced. Existing bounds on the properties of dark matter candidates can be extended to the coupled case, by taking into account the enhancement factor
Two distinct halo populations in the solar neighborhood. III
DEFF Research Database (Denmark)
Schuster, W. J.; Moreno, E.; Nissen, Poul Erik
2012-01-01
spectroscopic analyses, but possible systematic errors in Teff and log g are considered and corrected. With space velocities from Paper I as initial conditions, orbital integrations have been carried out using a detailed, observationally constrained Milky Way model including a bar and spiral arms. Results...... populations in the formation and evolution of the Galaxy. Methods. Ages are derived by comparing the positions of stars in the log Teff–log g diagram with isochrones from the Y2 models interpolated to the exact [Fe/H] and [α/Fe] values of each star. The stellar parameters have been adopted from the preceding...... explains the existence and characteristics of these two metal-rich halo populations, but one remaining defect is that this model is not consistent regarding the rmax’s obtained for the in situ “high-alpha” component; the predicted values are too small. It appears that ω Cen may have contributed...
Parameters of the CGCS 2000 Ellipsoid and Comparisons with GRS 80 and WGS 84
Directory of Open Access Journals (Sweden)
CHENG Pengfei
2016-02-01
Full Text Available According to the definition of China Geodetic Coordinate System 2000(CGCS 2000 and defined constants of the ellipsoid adopted by CGCS 2000,the other geometrical and physical parameters of this ellipsoid are derived and compared with that from GRS 80 and WGS 84,respectively.Meanwhile the coordinates and normal gravity on the CGCS 2000 ellipsoid are compared with that on WGS 84 and GRS 80.The difference between the normal gravity on CGCS 2000 ellipsoid and that on GRS 80 is about -143.54×10-8 m/s2,while it is 0.02×10-8 m/s2 compared to WGS 84.The longitudes of a point on these three ellipsoids are the same,but the maximum difference of latitude between CGCS 2000 and GRS 80 is 8.26×10-11 arc seconds,which is about 2.5×10-6 mm,and the maximum difference of latitude between CGCS 2000 and WGS 84 is 3.6×10-6 arc seconds,which is about 0.11 mm.
CdMoO{sub 4} micro-ellipsoids: controllable synthesis, growth mechanism, and photocatalytic activity
Energy Technology Data Exchange (ETDEWEB)
Dai, Ke; Gao, Tianyu [College of Resources and Environment, Huazhong Agricultural University, Hubei, Wuhan (China); Liu, Hui; Chen, Hao, E-mail: hchenhao@mail.hzau.edu.cn [College of Science, Huazhong Agricultural University, Hubei, Wuhan (China); Wang, Qi, E-mail: hchenhao@mail.hzau.edu.cn [School of Environment Sciences and Engineering, Zhejiang Gongshang University, Zhejiang, Hangzhou (China)
2017-01-15
CdMoO{sub 4} micro-ellipsoids were synthesized by a simple hydrothermal route with the assistance of nonionic surfactant Triton X-100 and characterized by X-ray diffraction, scanning electron microscopy and UV-Vis diffuse reflectance spectroscopy. The effects of hydrothermal pH, temperature, and time on the morphology and photocatalytic activity of CdMoO{sub 4} were investigated. With an initial hydrothermal pH of 5.00, CdMoO{sub 4} micro-ellipsoids were obtained at 180 °C for 24 h and found to possess the highest photocatalytic activity - 89% Rhodamine B can be degraded for 30 minutes presented in the 0.4 g/L CdMoO{sub 4} suspension. The formation mechanism of the CdMoO{sub 4} micro-ellipsoids was initiated by the formation of small nanoparticles and bulk structures afterwards, which was followed by the growth of micro-ellipsoids. Experiment results showed that the evolution of the micro-ellipsoids was an Ostwald ripening process. (author)
Directory of Open Access Journals (Sweden)
Panayiotis Vafeas
2017-01-01
Full Text Available This contribution deals with the scattering by a metallic ellipsoidal target, embedded in a homogeneous conductive medium, which is stimulated when a 3D time-harmonic magnetic dipole is operating at the low-frequency realm. The incident, the scattered, and the total three-dimensional electromagnetic fields, which satisfy Maxwell’s equations, yield low-frequency expansions in terms of positive integral powers of the complex-valued wave number of the exterior medium. We preserve the static Rayleigh approximation and the first three dynamic terms, while the additional terms of minor contribution are neglected. The Maxwell-type problem is transformed into intertwined potential-type boundary value problems with impenetrable boundary conditions, whereas the environment of a genuine ellipsoidal coordinate system provides the necessary setting for tackling such problems in anisotropic space. The fields are represented via nonaxisymmetric infinite series expansions in terms of harmonic eigenfunctions, affiliated with the ellipsoidal system, obtaining analytical closed-form solutions in a compact fashion. Until nowadays, such problems were attacked by using the very few ellipsoidal harmonics exhibiting an analytical form. In the present article, we address this issue by incorporating the full series expansion of the potentials and utilizing the entire subspace of ellipsoidal harmonic eigenfunctions.
En-face imaging of the ellipsoid zone in the retina from optical coherence tomography B-scans
Holmes, T.; Larkin, S.; Downing, M.; Csaky, K.
2015-03-01
It is generally believed that photoreceptor integrity is related to the ellipsoid zone appearance in optical coherence tomography (OCT) B-scans. Algorithms and software were developed for viewing and analyzing the ellipsoid zone. The software performs the following: (a), automated ellipsoid zone isolation in the B-scans, (b), en-face view of the ellipsoid-zone reflectance, (c), alignment and overlay of (b) onto reflectance images of the retina, and (d), alignment and overlay of (c) with microperimetry sensitivity points. Dataset groups were compared from normal and dry age related macular degeneration (DAMD) subjects. Scalar measurements for correlation against condition included the mean and standard deviation of the ellipsoid zone's reflectance. The imageprocessing techniques for automatically finding the ellipsoid zone are based upon a calculation of optical flow which tracks the edges of laminated structures across an image. Statistical significance was shown in T-tests of these measurements with the population pools separated as normal and DAMD subjects. A display of en-face ellipsoid-zone reflectance shows a clear and recognizable difference between any of the normal and DAMD subjects in that they show generally uniform and nonuniform reflectance, respectively, over the region near the macula. Regions surrounding points of low microperimetry (μP) sensitivity have nonregular and lower levels of ellipsoid-zone reflectance nearby. These findings support the idea that the photoreceptor integrity could be affecting both the ellipsoid-zone reflectance and the sensitivity measurements.
The dependence of cosmic ray-driven galactic winds on halo mass
Jacob, Svenja; Pakmor, Rüdiger; Simpson, Christine M.; Springel, Volker; Pfrommer, Christoph
2018-03-01
Galactic winds regulate star formation in disc galaxies and help to enrich the circum-galactic medium. They are therefore crucial for galaxy formation, but their driving mechanism is still poorly understood. Recent studies have demonstrated that cosmic rays (CRs) can drive outflows if active CR transport is taken into account. Using hydrodynamical simulations of isolated galaxies with virial masses between 1010 and 1013 M⊙, we study how the properties of CR-driven winds depend on halo mass. CRs are treated in a two-fluid approximation and their transport is modelled through isotropic or anisotropic diffusion. We find that CRs are only able to drive mass-loaded winds beyond the virial radius in haloes with masses below 1012 M⊙. For our lowest examined halo mass, the wind is roughly spherical and has velocities of ˜20 km s-1. With increasing halo mass, the wind becomes biconical and can reach 10 times higher velocities. The mass loading factor drops rapidly with virial mass, a dependence that approximately follows a power law with a slope between -1 and -2. This scaling is slightly steeper than observational inferences, and also steeper than commonly used prescriptions for wind feedback in cosmological simulations. The slope is quite robust to variations of the CR injection efficiency or the CR diffusion coefficient. In contrast to the mass loading, the energy loading shows no significant dependence on halo mass. While these scalings are close to successful heuristic models of wind feedback, the CR-driven winds in our present models are not yet powerful enough to fully account for the required feedback strength.
Population II brown dwarfs and dark haloes
International Nuclear Information System (INIS)
Zinnecker, H.
1986-01-01
Opacity-limited fragmentation is investigated as a function of the dust-to-gas ratio and it is found that the characteristic protostellar mass Msub(*) is metallicity-dependent. This dependence is such that, for the low metallicity gas out of which the stars of Population II formed in the halo, Msub(*) is less than 0.1 M solar mass. If applicable, these theoretical considerations would predict that substellar masses have formed more frequently under the metal-poor conditions in the early Galaxy (Population II brown dwarfs). Thus the missing mass in the Galactic halo and in the dark haloes around other spirals may well reside in these metal-poor Population II brown dwarfs. (author)
Beam halo in high-intensity beams
International Nuclear Information System (INIS)
Wangler, T.P.
1993-01-01
In space-charge dominated beams the nonlinear space-charge forces produce a filamentation pattern, which in projection to the 2-D phase spaces results in a 2-component beam consisting of an inner core and a diffuse outer halo. The beam-halo is of concern for a next generation of cw, high-power proton linacs that could be applied to intense neutron generators for nuclear materials processing. The author describes what has been learned about beam halo and the evolution of space-charge dominated beams using numerical simulations of initial laminar beams in uniform linear focusing channels. Initial results are presented from a study of beam entropy for an intense space-charge dominated beam
Stability of BEC galactic dark matter halos
Energy Technology Data Exchange (ETDEWEB)
Guzmán, F.S.; Lora-Clavijo, F.D.; González-Avilés, J.J.; Rivera-Paleo, F.J., E-mail: guzman@ifm.umich.mx, E-mail: fadulora@ifm.umich.mx, E-mail: javiles@ifm.umich.mx, E-mail: friverap@ifm.umich.mx [Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio C-3, Cd. Universitaria, 58040 Morelia, Michoacán (Mexico)
2013-09-01
In this paper we show that spherically symmetric BEC dark matter halos, with the sin r/r density profile, that accurately fit galactic rotation curves and represent a potential solution to the cusp-core problem are unstable. We do this by introducing back the density profiles into the fully time-dependent Gross-Pitaevskii-Poisson system of equations. Using numerical methods to track the evolution of the system, we found that these galactic halos lose mass at an approximate rate of half of its mass in a time scale of dozens of Myr. We consider this time scale is enough as to consider these halos are unstable and unlikely to be formed. We provide some arguments to show that this behavior is general and discuss some other drawbacks of the model that restrict its viability.
Chemical enrichment in halo planetary nebulae
Energy Technology Data Exchange (ETDEWEB)
Torres-Peimbert, S; Rayo, J F; Peimbert, M [Universidad Nacional Autonoma de Mexico, Mexico City. Inst. de Astronomia
1981-01-01
Photoelectric spectrophotometry of emission lines in the 3400-7400 A region is presented for the planetary nebulae 108-76/sup 0/1(BB1). From these observations the relative abundances of H, He, C, N, O and Ne are derived. The abundances of the halo PN (BB1, H4-1 and K648) are compared to those predicted by stellar evolution theory under the assumption that the envelope has the chemical composition of the matter located between the H burning shell and the surface. The observed He/H and C/O values are higher than predicted which implies that halo PN contain matter from deeper layers than the H burning shell. Furthermore, the O/Ar, N/Ar and Ne/Ar values in halo PN are higher than in the solar neighbourhood, at least part of this enrichment is produced by the PN progenitors.
Galaxy halo occupation at high redshift
Bullock, James S.; Wechsler, Risa H.; Somerville, Rachel S.
2002-01-01
We discuss how current and future data on the clustering and number density of z~3 Lyman-break galaxies (LBGs) can be used to constrain their relationship to dark matter haloes. We explore a three-parameter model in which the number of LBGs per dark halo scales like a power law in the halo mass: N(M)=(M/M1)S for M>Mmin. Here, Mmin is the minimum mass halo that can host an LBG, M1 is a normalization parameter, associated with the mass above which haloes host more than one observed LBG, and S determines the strength of the mass-dependence. We show how these three parameters are constrained by three observable properties of LBGs: the number density, the large-scale bias and the fraction of objects in close pairs. Given these three quantities, the three unknown model parameters may be estimated analytically, allowing a full exploration of parameter space. As an example, we assume a ΛCDM cosmology and consider the observed properties of a recent sample of spectroscopically confirmed LBGs. We find that the favoured range for our model parameters is Mmin~=(0.4-8)×1010h- 1Msolar, M1~=(6-10)×1012h- 1Msolar, and 0.9acceptable if the allowed range of bg is permitted to span all recent observational estimates. We also discuss how the observed clustering of LBGs as a function of luminosity can be used to constrain halo occupation, although because of current observational uncertainties we are unable to reach any strong conclusions. Our methods and results can be used to constrain more realistic models that aim to derive the occupation function N(M) from first principles, and offer insight into how basic physical properties affect the observed properties of LBGs.
Radio halo sources in clusters of galaxies
International Nuclear Information System (INIS)
Hanisch, R.J.
1986-01-01
Radio halo sources remain one of the most enigmatic of all phenomena related to radio emission from galaxies in clusters. The morphology, extent, and spectral structure of these sources are not well known, and the models proposed to explain them suffer from this lack of observational detail. However, recent observations suggest that radio halo sources may be a composite of relic radio galaxies. The validity of this model could be tested using current and planned high resolutions, low-frequency radio telescopes. 31 references
Blazars with arcminute-scale radio halos
International Nuclear Information System (INIS)
Ulvestad, J.S.; Antonucci, R.R.J.; Space Telescope Science Institute, Baltimore, MD)
1986-01-01
About 10-arcsec resolution 20-cm wavelength maps are presented for three nearby BL Lac objects: Mkn 180, whose halo has a linear size of 85 kpc, 2155-304, with a halo about 375 kpc across, and 1727 + 502, whose one-sided diffuse emission extends to a distance of about 145 kpc from its radio core. Little evidence is found for strong radio variability in the cores of the three blazars; these and other results obtained are consistent with the assertion that the three objects should be classified as normal low luminosity double radio galaxies with optically dull nuclei, if seen from other directions. 20 references
Structure study in the 19C halo
International Nuclear Information System (INIS)
Angelique, J.C.; Le Brun, C.; Liegard, E.; Marques, F.M.; Orr, N.A.
1997-01-01
The halo nuclei are nuclei which have one or more neutrons (or protons) with very weak binding energy what results in a spatial extension beyond the core containing the other nucleons. This important spatial extension is related via the Heisenberg principle to a narrow momentum distribution which signs the halo structure of the nucleus under consideration. To extend our understanding of this phenomenon an experiment has been carried out with the DEMON multidetector in the frame of the collaboration E133. The subject was the study of 19 C, a nucleus susceptible of having a neutron halo due to the low binding energy of its last neutron (S n = 240 ± 100 keV). The 19 C secondary beam was produced by fragmentation of a primary 40 Ar beam in a carbon target between the two solenoids of SISSI and than directed to a GANIL experimental room. A silicon detector telescope was used to detect the charged particles issued from the reaction of 19 C nuclei with the tantalum target while the DEMON detection modular assembly separated by four meters from the target allowed the neutron detection between 0 and 42 degrees. The first results of this analysis are favorable to a halo structure for this nucleus for the reaction channel in which the 18 C core is destroyed. We have compared the angular distribution of the neutrons of 19 C with those obtained from the breakup reactions of other exotic nuclei ( 21 N, 22 O and 24 F) but having no halo structure. A net different behavior of these nuclei indicate a clear difference in structure. Actually, the 19 C distribution corresponds to the superposition of a broad distribution and narrow distribution. The last one having width of 42 ± 12 MeV/c, compatible with an important spatial extension, corresponds to neutrons coming from the halo. It is argued that the model in which the halo neutron moves on a s orbital cannot described the structure of 19 C halo. A more adequate description would be a mixture of s and d orbitals which would also
Dark energy and extended dark matter halos
Chernin, A. D.; Teerikorpi, P.; Valtonen, M. J.; Dolgachev, V. P.; Domozhilova, L. M.; Byrd, G. G.
2012-03-01
The cosmological mean matter (dark and baryonic) density measured in the units of the critical density is Ωm = 0.27. Independently, the local mean density is estimated to be Ωloc = 0.08-0.23 from recent data on galaxy groups at redshifts up to z = 0.01-0.03 (as published by Crook et al. 2007, ApJ, 655, 790 and Makarov & Karachentsev 2011, MNRAS, 412, 2498). If the lower values of Ωloc are reliable, as Makarov & Karachentsev and some other observers prefer, does this mean that the Local Universe of 100-300 Mpc across is an underdensity in the cosmic matter distribution? Or could it nevertheless be representative of the mean cosmic density or even be an overdensity due to the Local Supercluster therein. We focus on dark matter halos of groups of galaxies and check how much dark mass the invisible outer layers of the halos are able to host. The outer layers are usually devoid of bright galaxies and cannot be seen at large distances. The key factor which bounds the size of an isolated halo is the local antigravity produced by the omnipresent background of dark energy. A gravitationally bound halo does not extend beyond the zero-gravity surface where the gravity of matter and the antigravity of dark energy balance, thus defining a natural upper size of a system. We use our theory of local dynamical effects of dark energy to estimate the maximal sizes and masses of the extended dark halos. Using data from three recent catalogs of galaxy groups, we show that the calculated mass bounds conform with the assumption that a significant amount of dark matter is located in the invisible outer parts of the extended halos, sufficient to fill the gap between the observed and expected local matter density. Nearby groups of galaxies and the Virgo cluster have dark halos which seem to extend up to their zero-gravity surfaces. If the extended halo is a common feature of gravitationally bound systems on scales of galaxy groups and clusters, the Local Universe could be typical or even
Distances, metallicities and origins of high-velocity clouds
van Woerden, H; Wakker, BP; Peletier, RF; Schwarz, UJ; KraanKorteweg, RC; Henning, PA; Andernach, H
2000-01-01
A review is given of distances of high-velocity clouds (HVCs) derived from absorption-line measurements, and of the metallicities of HVCs. Chain A definitely lies in the Galactic halo, between 2.5 and 7 kpc above the plane. The distance limits available for other HVCs allow a variety of locations:
Minimization of stress concentration factor in cylindrical pressure vessels with ellipsoidal heads
International Nuclear Information System (INIS)
Magnucki, K.; Szyc, W.; Lewinski, J.
2002-01-01
The paper presents the problem of stress concentration in a cylindrical pressure vessel with ellipsoidal heads subject to internal pressure. At the line, where the ellipsoidal head is adjacent to the circular cylindrical shell, a shear force and bending moment occur, disturbing the membrane stress state in the vessel. The degree of stress concentration depends on the ratio of thicknesses of both the adjacent parts of the shells and on the relative convexity of the ellipsoidal head, with the range for radius-to-thickness ratio between 75 and 125. The stress concentration was analytically described and, afterwards, the effect of these values on the stress concentration ratio was numerically examined. Results of the analysis are shown on charts
The microwave properties of composites including lightweight core–shell ellipsoids
International Nuclear Information System (INIS)
Yuan, Liming; Xu, Yonggang; Dai, Fei; Liao, Yi; Zhang, Deyuan
2016-01-01
In order to study the microwave properties of suspensions including lightweight core–shell ellipsoids, the calculation formula was obtained by substituting an equivalent ellipsoid for the original core–shell ellipsoid. Simulations for Fe-coated diatomite/paraffin suspensions were performed. Results reveal that the calculated results fitted the measured results very well when the inclusion concentration was no more than 15 vol%, but there was an obvious deviation when the inclusion concentration reached 24 vol%. By comparisons, the formula for less diluted suspensions was more suitable for calculating the electromagnetic parameter of suspensions especially when the ratio was smaller between the electromagnetic parameter of the inclusion and that of the host medium. - Highlights: • The microwave properties of suspensions with core-shell inclusions were studied. • Less diluted suspensions were considered. • Flaky Fe-coated diatomite/paraffin suspensions were studied. • The microwave properties could be simulated successfully.
Plug and Play Robust Distributed Control with Ellipsoidal Parametric Uncertainty System
Directory of Open Access Journals (Sweden)
Hong Wang-jian
2016-01-01
Full Text Available We consider a continuous linear time invariant system with ellipsoidal parametric uncertainty structured into subsystems. Since the design of a local controller uses only information on a subsystem and its neighbours, we combine the plug and play idea and robust distributed control to propose one distributed control strategy for linear system with ellipsoidal parametric uncertainty. Firstly for linear system with ellipsoidal parametric uncertainty, a necessary and sufficient condition for robust state feedback control is proposed by means of linear matrix inequality. If this necessary and sufficient condition is satisfied, this robust state feedback gain matrix can be easily derived to guarantee robust stability and prescribed closed loop performance. Secondly the plug and play idea is introduced in the design process. Finally by one example of aircraft flutter model parameter identification, the efficiency of the proposed control strategy can be easily realized.
The microwave properties of composites including lightweight core–shell ellipsoids
Energy Technology Data Exchange (ETDEWEB)
Yuan, Liming, E-mail: lming_y@163.com [Science and Technology on Electromagnetic Scattering Laboratory, Shanghai 200438 (China); Xu, Yonggang; Dai, Fei; Liao, Yi [Science and Technology on Electromagnetic Scattering Laboratory, Shanghai 200438 (China); Zhang, Deyuan [School of Mechanical Engineering and Automation, Beihang University, Beijing 100191 (China)
2016-12-01
In order to study the microwave properties of suspensions including lightweight core–shell ellipsoids, the calculation formula was obtained by substituting an equivalent ellipsoid for the original core–shell ellipsoid. Simulations for Fe-coated diatomite/paraffin suspensions were performed. Results reveal that the calculated results fitted the measured results very well when the inclusion concentration was no more than 15 vol%, but there was an obvious deviation when the inclusion concentration reached 24 vol%. By comparisons, the formula for less diluted suspensions was more suitable for calculating the electromagnetic parameter of suspensions especially when the ratio was smaller between the electromagnetic parameter of the inclusion and that of the host medium. - Highlights: • The microwave properties of suspensions with core-shell inclusions were studied. • Less diluted suspensions were considered. • Flaky Fe-coated diatomite/paraffin suspensions were studied. • The microwave properties could be simulated successfully.
Dynamical or static radio halo - Is there a galactic wind
International Nuclear Information System (INIS)
Lerche, I.; Schlickeiser, R.
1981-01-01
The effect of a galactic wind on a radio halo can be best observed at frequencies smaller than about 1 GHz. At higher frequencies static halo models predict the same features as dynamical halo models. External galaxies, which exhibit a break by 0.5 in their high frequency nonthermal integral flux spectrum, are the best candidates for studying the influence of galactic winds on the formation of relativistic electron haloes around these systems. Several such cases are presented
The Discovery of Ellipsoidal Variations in the Kepler Light Curve of HAT-P-7
Welsh, William F.; Orosz, Jerome A.; Seager, Sara; Fortney, Jonathan J.; Jenkins, Jon; Rowe, Jason F.; Koch, David; Borucki, William J.
2010-01-01
We present an analysis of the early Kepler observations of the previously discovered transiting planet HAT-P-7b. The light curve shows the transit of the star, the occultation of the planet, and the orbit phase-dependent light from the planet. In addition, phase-dependent light from the star is present, known as "ellipsoidal variations". The very nearby planet (only 4 stellar radii away) gravitationally distorts the star and results in a flux modulation twice per orbit. The ellipsoidal variat...
Directory of Open Access Journals (Sweden)
M. Moradi
2007-06-01
Full Text Available In this paper, a uniform classical fluid mixture comprising ellipsoidal molecules is studied. This mixture is composed of two types of ellipsoidal molecules interacting through the Gay-Berne potential with different sizes at temperature T. For this system, the Ornstein-Zernike equation using the Percus-Yevick closure relation is solved. Then the direct correlation function, pair correlation function and the pressure of the fluid at temperature T are calculated. The obtained results are in agreement with the previous theories and the results of molecular dynamic computer simulation.
Bäcklund transformations for the Jacobi system on an ellipsoid
Tsiganov, A. V.
2017-09-01
We consider analogues of auto- and hetero-Bäcklund transformations for the Jacobi system on a threeaxis ellipsoid. Using the results in a Weierstrass paper, where the change of times reduces integrating the equations of motion to inverting the Abel mapping, we construct the differential Abel equations and auto-Bäcklund transformations preserving the Poisson bracket with respect to which the equations of motion written in the Weierstrass form are Hamiltonian. Transforming this bracket to the canonical form, we can construct a new integrable system on the ellipsoid with a Hamiltonian of the natural form and with a fourth-degree integral of motion in momenta.
Tsang, L.; Kubacsi, M. C.; Kong, J. A.
1981-01-01
The radiative transfer theory is applied within the Rayleigh approximation to calculate the backscattering cross section of a layer of randomly positioned and oriented small ellipsoids. The orientation of the ellipsoids is characterized by a probability density function of the Eulerian angles of rotation. The radiative transfer equations are solved by an iterative approach to first order in albedo. In the half space limit the results are identical to those obtained via the approach of Foldy's and distorted Born approximation. Numerical results of the theory are illustrated using parameters encountered in active remote sensing of vegetation layers. A distinctive characteristic is the strong depolarization shown by vertically aligned leaves.
The Ongoing Growth of the M87 Halo through Accretion Events
Directory of Open Access Journals (Sweden)
Alessia Longobardi
2015-12-01
Full Text Available Planetary nebulas (PNs offer a unique tool to investigate the outer regions of massive galaxies because their strong [OIII]λ5007Å emission line makes them detectable out to several effective radii from the galaxy’s centre. We use a deep and extended spectroscopic survey of PNs (∼300 objects to study the spatial distribution, the kinematics and the stellar populations in the extended outer halo of the bright elliptical galaxy M87 (NGC 4486 in the Virgo cluster. We show that in the Virgo core, M87 stellar halo and the intracluster light are two distinct dynamical components, with different velocity distributions. Moreover the synergy of the PN kinematical information and the deep V/B-band photometry revealed an ongoing accretion event in the outer regions of M87. This satellite accretion represents a non-negligible perturbation of the halo properties: beyond 60 kpc the M87 halo is still growing with 60% of its light being added by the accretion event at the distance where it is detected.
Energy Technology Data Exchange (ETDEWEB)
Vlah, Zvonimir; Seljak, Uroš [Institute for Theoretical Physics, University of Zürich, Zürich (Switzerland); Okumura, Teppei [Institute for the Early Universe, Ewha Womans University, Seoul, S. Korea (Korea, Republic of); Desjacques, Vincent, E-mail: zvlah@physik.uzh.ch, E-mail: seljak@physik.uzh.ch, E-mail: teppei@ewha.ac.kr, E-mail: Vincent.Desjacques@unige.ch [Département de Physique Théorique and Center for Astroparticle Physics (CAP) Université de Genéve, Genéve (Switzerland)
2013-10-01
Numerical simulations show that redshift space distortions (RSD) introduce strong scale dependence in the power spectra of halos, with ten percent deviations relative to linear theory predictions even on relatively large scales (k < 0.1h/Mpc) and even in the absence of satellites (which induce Fingers-of-God, FoG, effects). If unmodeled these effects prevent one from extracting cosmological information from RSD surveys. In this paper we use Eulerian perturbation theory (PT) and Eulerian halo biasing model and apply it to the distribution function approach to RSD, in which RSD is decomposed into several correlators of density weighted velocity moments. We model each of these correlators using PT and compare the results to simulations over a wide range of halo masses and redshifts. We find that with an introduction of a physically motivated halo biasing, and using dark matter power spectra from simulations, we can reproduce the simulation results at a percent level on scales up to k ∼ 0.15h/Mpc at z = 0, without the need to have free FoG parameters in the model.
Carlesi, Edoardo; Knebe, Alexander; Lewis, Geraint F.; Wales, Scott; Yepes, Gustavo
2014-04-01
We present the results of a series of adiabatic hydrodynamical simulations of several quintessence models (both with a free and an interacting scalar field) in comparison to a standard Λ cold dark matter cosmology. For each we use 2 × 10243 particles in a 250 h-1 Mpc periodic box assuming 7-year Wilkinson Microwave Anisotropy Probe cosmology. In this work we focus on the properties of haloes in the cosmic web at z = 0. The web is classified into voids, sheets, filaments and knots depending on the eigenvalues of the velocity shear tensor, which are an excellent proxy for the underlying overdensity distribution. We find that the properties of objects classified according to their surrounding environment show a substantial dependence on the underlying cosmology; for example, while Vmax shows average deviations of ≈5 per cent across the different models when considering the full halo sample, comparing objects classified according to their environment, the size of the deviation can be as large as 20 per cent. We also find that halo spin parameters are positively correlated to the coupling, whereas halo concentrations show the opposite behaviour. Furthermore, when studying the concentration-mass relation in different environments, we find that in all cosmologies underdense regions have a larger normalization and a shallower slope. While this behaviour is found to characterize all the models, differences in the best-fitting relations are enhanced in (coupled) dark energy models, thus providing a clearer prediction for this class of models.
Yuan, Sihan; Eisenstein, Daniel J.; Garrison, Lehman H.
2018-04-01
We present the GeneRalized ANd Differentiable Halo Occupation Distribution (GRAND-HOD) routine that generalizes the standard 5 parameter halo occupation distribution model (HOD) with various halo-scale physics and assembly bias. We describe the methodology of 4 different generalizations: satellite distribution generalization, velocity bias, closest approach distance generalization, and assembly bias. We showcase the signatures of these generalizations in the 2-point correlation function (2PCF) and the squeezed 3-point correlation function (squeezed 3PCF). We identify generalized HOD prescriptions that are nearly degenerate in the projected 2PCF and demonstrate that these degeneracies are broken in the redshift-space anisotropic 2PCF and the squeezed 3PCF. We also discuss the possibility of identifying degeneracies in the anisotropic 2PCF and further demonstrate the extra constraining power of the squeezed 3PCF on galaxy-halo connection models. We find that within our current HOD framework, the anisotropic 2PCF can predict the squeezed 3PCF better than its statistical error. This implies that a discordant squeezed 3PCF measurement could falsify the particular HOD model space. Alternatively, it is possible that further generalizations of the HOD model would open opportunities for the squeezed 3PCF to provide novel parameter measurements. The GRAND-HOD Python package is publicly available at https://github.com/SandyYuan/GRAND-HOD.
Interactions between massive dark halos and warped disks
Kuijken, K; Persic, M; Salucci, P
1997-01-01
The normal mode theory for warping of galaxy disks, in which disks are assumed to be tilted with respect to the equator of a massive, flattened dark halo, assumes a rigid, fixed halo. However, consideration of the back-reaction by a misaligned disk on a massive particle halo shows there to be strong
SIMULATIONS OF RECOILING MASSIVE BLACK HOLES IN THE VIA LACTEA HALO
International Nuclear Information System (INIS)
Guedes, J.; Madau, P.; Diemand, J.; Kuhlen, M.; Zemp, M.
2009-01-01
The coalescence of a massive black hole (MBH) binary leads to the gravitational-wave recoil of the system and its ejection from the galaxy core. We have carried out N-body simulations of the motion of a M BH = 3.7 x 10 6 M sun MBH remnant in the 'Via Lactea I' simulation, a Milky Way-sized dark matter halo. The black hole receives a recoil velocity of V kick = 80, 120, 200, 300, and 400 km s -1 at redshift 1.5, and its orbit is followed for over 1 Gyr within a 'live' host halo, subject only to gravity and dynamical friction against the dark matter background. We show that, owing to asphericities in the dark matter potential, the orbit of the MBH is highly nonradial, resulting in a significantly increased decay timescale compared to a spherical halo. The simulations are used to construct a semi-analytic model of the motion of the MBH in a time-varying triaxial Navarro-Frenk-White dark matter halo plus a spherical stellar bulge, where the dynamical friction force is calculated directly from the velocity dispersion tensor. Such a model should offer a realistic picture of the dynamics of kicked MBHs in situations where gas drag, friction by disk stars, and the flattening of the central cusp by the returning black hole are all negligible effects. We find that MBHs ejected with initial recoil velocities V kick ∼> 500 km s -1 do not return to the host center within a Hubble time. In a Milky Way-sized galaxy, a recoiling hole carrying a gaseous disk of initial mass ∼M BH may shine as a quasar for a substantial fraction of its 'wandering' phase. The long decay timescales of kicked MBHs predicted by this study may thus be favorable to the detection of off-nuclear quasar activity.
Inelastic dark matter, non-standard halos and the DAMA/LIBRA results
International Nuclear Information System (INIS)
March-Russell, John; McCabe, Christopher; McCullough, Matthew
2009-01-01
The DAMA collaboration have claimed to detect particle dark matter (DM) via an annual modulation in their observed recoil event rate. This appears to be in strong disagreement with the null results of other experiments if interpreted in terms of elastic DM scattering, while agreement for a small region of parameter space is possible for inelastic DM (iDM) due to the altered kinematics of the collision. To date most analyses assume a simple galactic halo DM velocity distribution, the Standard Halo Model, but direct experimental support for the SHM is severely lacking and theoretical studies indicate possible significant differences. We investigate the dependence of DAMA and the other direct detection experiments on the local DM velocity distribution, utilizing the results of the Via Lactea and Dark Disc numerical simulations. We also investigate effects of varying the solar circular velocity, the DM escape velocity, and the DAMA quenching factor within experimental limits. Our data set includes the latest ZEPLIN-III results, as well as full publicly available data sets. Due to the more sensitive dependence of the inelastic cross section on the velocity distribution, we find that with Via Lactea the DAMA results can be consistent with all other experiments over an enlarged region of iDM parameter space, with higher mass particles being preferred, while Dark Disc does not lead to an improvement. A definitive test of DAMA for iDM requires heavy element detectors.
Binary White Dwarfs in the Galactic Halo
van Oirschot, Pim; Nelemans, Gijs; Helmi, Amina; Starkenburg, Else; Pols, Onno; Brown, Anthony G. A.
We use the stellar population synthesis code SeBa (Portegies Zwart & Verbunt (1996), Toonen, Nelemans & Portegies Zwart (2012)) to study the halo white dwarf population. Here we assume a Kroupa initial mass function and compare 4 models, varying two parameters: the star formation (SF) history of the
Numerical experiments on galactic halo formation
International Nuclear Information System (INIS)
Quinn, P.J.; Salmon, J.K.; Zurek, W.H.
1986-01-01
We have used a hybrid N-body-FFT approach to solving Poisson's equation in a cosmological setting. Using this method, we have explored the connection between the form of the initial Gaussian density perturbations that by today have grown into galaxies and the internal properties of the individual galactic halos that are formed. 19 refs., 4 figs
Reflection halo twins : subsun and supersun
Konnen, Gunther P.; van der Werf, Siebren Y.
2011-01-01
From an aircraft, a short distinct vertical structure is sometimes seen above the setting sun. Such a feature can be understood as a halo, which is the counterpart of the well-known subsun. Whereas the latter arises from reflections off basal faces of plate-oriented ice crystals illuminated from
Baryonic pinching of galactic dark matter halos
International Nuclear Information System (INIS)
Gustafsson, Michael; Fairbairn, Malcolm; Sommer-Larsen, Jesper
2006-01-01
High resolution cosmological N-body simulations of four galaxy-scale dark matter halos are compared to corresponding N-body/hydrodynamical simulations containing dark matter, stars and gas. The simulations without baryons share features with others described in the literature in that the dark matter density slope continuously decreases towards the center, with a density ρ DM ∝r -1.3±0.2 , at about 1% of the virial radius for our Milky Way sized galaxies. The central cusps in the simulations which also contain baryons steepen significantly, to ρ DM ∝r -1.9±0.2 , with an indication of the inner logarithmic slope converging. Models of adiabatic contraction of dark matter halos due to the central buildup of stellar/gaseous galaxies are examined. The simplest and most commonly used model, by Blumenthal et al., is shown to overestimate the central dark matter density considerably. A modified model proposed by Gnedin et al. is tested and it is shown that, while it is a considerable improvement, it is not perfect. Moreover, it is found that the contraction parameters in their model not only depend on the orbital structure of the dark-matter-only halos but also on the stellar feedback prescription which is most relevant for the baryonic distribution. Implications for dark matter annihilation at the galactic center are discussed and it is found that, although our simulations show a considerable reduced dark matter halo contraction as compared to the Blumenthal et al. model, the fluxes from dark matter annihilation are still expected to be enhanced by at least a factor of a hundred, as compared to dark-matter-only halos. Finally, it is shown that, while dark-matter-only halos are typically prolate, the dark matter halos containing baryons are mildly oblate with minor-to-major axis ratios of c/a=0.73±0.11, with their flattening aligned with the central baryonic disks
THE HALO OCCUPATION DISTRIBUTION OF SDSS QUASARS
International Nuclear Information System (INIS)
Richardson, Jonathan; Chatterjee, Suchetana; Nagai, Daisuke; Zheng Zheng; Shen Yue
2012-01-01
We present an estimate of the projected two-point correlation function (2PCF) of quasars in the Sloan Digital Sky Survey (SDSS) over the full range of one- and two-halo scales, 0.02 h –1 Mpc p –1 Mpc. This was achieved by combining data from SDSS DR7 on large scales and Hennawi et al. (with appropriate statistical corrections) on small scales. Our combined clustering sample is the largest spectroscopic quasar clustering sample to date, containing ∼48, 000 quasars in the redshift range 0.4 ∼ sat = (7.4 ± 1.4) × 10 –4 , be satellites in dark matter halos. At z ∼ 1.4, the median masses of the host halos of central and satellite quasars are constrained to be M cen = 4.1 +0.3 –0.4 × 10 12 h –1 M ☉ and M sat = 3.6 +0.8 –1.0 × 10 14 h –1 M ☉ , respectively. To investigate the redshift evolution of the quasar-halo relationship, we also perform HOD modeling of the projected 2PCF measured by Shen et al. for SDSS quasars with median redshift 3.2. We find tentative evidence for an increase in the mass scale of quasar host halos—the inferred median mass of halos hosting central quasars at z ∼ 3.2 is M cen = 14.1 +5.8 –6.9 × 10 12 h –1 M ☉ . The cutoff profiles of the mean occupation functions of central quasars reveal that quasar luminosity is more tightly correlated with halo mass at higher redshifts. The average quasar duty cycle around the median host halo mass is inferred to be f q = 7.3 +0.6 –1.5 × 10 –4 at z ∼ 1.4 and f q = 8.6 +20.4 –7.2 × 10 –2 at z ∼ 3.2. We discuss the implications of our results for quasar evolution and quasar-galaxy co-evolution.
Zhang, Lei; Wu, Hao Bin; Lou, Xiong Wen
2012-07-14
Unusual CoS(2) ellipsoids with anisotropic tube-like cavities have been synthesized from the simultaneous thermal decomposition and sulfidation of a preformed cobalt carbonate precursor. The as-prepared CoS(2) ellipsoids show interesting supercapacitive properties with high capacitance and good cycling performance.
Ardalan, A.; Safari, A.; Grafarend, E.
2003-04-01
An operational algorithm for computing the ellipsoidal terrain correction based on application of closed form solution of the Newton integral in terms of Cartesian coordinates in the cylindrical equal area map projected surface of a reference ellipsoid has been developed. As the first step the mapping of the points on the surface of a reference ellipsoid onto the cylindrical equal area map projection of a cylinder tangent to a point on the surface of reference ellipsoid closely studied and the map projection formulas are computed. Ellipsoidal mass elements with various sizes on the surface of the reference ellipsoid is considered and the gravitational potential and the vector of gravitational intensity of these mass elements has been computed via the solution of Newton integral in terms of ellipsoidal coordinates. The geographical cross section areas of the selected ellipsoidal mass elements are transferred into cylindrical equal area map projection and based on the transformed area elements Cartesian mass elements with the same height as that of the ellipsoidal mass elements are constructed. Using the close form solution of the Newton integral in terms of Cartesian coordinates the potential of the Cartesian mass elements are computed and compared with the same results based on the application of the ellipsoidal Newton integral over the ellipsoidal mass elements. The results of the numerical computations show that difference between computed gravitational potential of the ellipsoidal mass elements and Cartesian mass element in the cylindrical equal area map projection is of the order of 1.6 × 10-8m^2/s^2 for a mass element with the cross section size of 10 km × 10 km and the height of 1000 m. For a 1 km × 1 km mass element with the same height, this difference is less than 1.5 × 10-4 m^2}/s^2. The results of the numerical computations indicate that a new method for computing the terrain correction based on the closed form solution of the Newton integral in
Optical alignment and confinement of an ellipsoidal nanorod in optical tweezers: a theoretical study
Czech Academy of Sciences Publication Activity Database
Trojek, Jan; Chvátal, Lukáš; Zemánek, Pavel
2012-01-01
Roč. 29, č. 7 (2012), s. 1224-1236 ISSN 1084-7529 R&D Projects: GA ČR GA202/09/0348; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : ellipsoidal nanorod * optical tweezers * Rayleigh approximation Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.665, year: 2012
A DEEP CUT ELLIPSOID ALGORITHM FOR CONVEX-PROGRAMMING - THEORY AND APPLICATIONS
FRENK, JBG; GROMICHO, J; ZHANG, S
1994-01-01
This paper proposes a deep cut version of the ellipsoid algorithm for solving a general class of continuous convex programming problems. In each step the algorithm does not require more computational effort to construct these deep cuts than its corresponding central cut version. Rules that prevent
The hard ellipsoid-of-revolution fluid II. The y-expansion equation of state
Mulder, B.M.; Frenkel, D.
1985-01-01
The γ-expansion as introduced by Barboy and Gelbart is applied to a system of hard ellipsoids-of-revolution. The expansion is truncated after the third order term yielding an approximate theory requiring the second- and third-virial coefficients as inputs. As the third virial coefficient is not
International Nuclear Information System (INIS)
Jamali Esfahlan, D.; Madani, H.; Tahmaseb Nazemi, M. T.; Mahdavi, F.; Ghaderi, M. R.; Najafi, M.
2010-01-01
Various methods of Kriging and nonlinear geostatistical methods considered as acceptable methods for resource and reserve estimations have characters such as the least estimation variance in their nature, and accurate results in the acceptable confidence levels range could be achieved if the required parameters for the estimation are determined accurately. If the determined parameters don't have the sufficient accuracy, 3-D geostatistical estimations will not be reliable any more, and by this, all the quantitative parameters of the mineral deposit (e.g. grade-tonnage variations) will be misinterpreted. One of the most significant parameters for 3-D geostatistical estimation is the anisotropy ellipsoid. The anisotropy ellipsoid is important for geostatistical estimations because it determines the samples in different directions required for accomplishing the estimation. The aim of this paper is to illustrate a more simple and time preserving analytical method that can apply geophysical or geochemical analysis data from the core-length of boreholes for modeling the anisotropy ellipsoid. By this method which is based on the distribution of covariance clouds in a 3-D sampling space of a deposit, quantities, ratios, azimuth and plunge of the major-axis, semi-major axis and the minor-axis determine the ore-grade continuity within the deposit and finally the anisotropy ellipsoid of the deposit will be constructed. A case study of an uranium deposit is also analytically discussed for illustrating the application of this method.
Jamari, Jamari; Schipper, Dirk J.
2007-01-01
This paper presents theoretical and experimental results of the residual or plastic deformation and the plastic contact area of an elastic–plastic contact of ellipsoid bodies after unloading. There are three regime responses of the deformation and contact area: elastic, elastic–plastic and fully
Orientational dynamics of a triaxial ellipsoid in simple shear flow: Influence of inertia.
Rosén, Tomas; Kotsubo, Yusuke; Aidun, Cyrus K; Do-Quang, Minh; Lundell, Fredrik
2017-07-01
The motion of a single ellipsoidal particle in simple shear flow can provide valuable insights toward understanding suspension flows with nonspherical particles. Previously, extensive studies have been performed on the ellipsoidal particle with rotational symmetry, a so-called spheroid. The nearly prolate ellipsoid (one major and two minor axes of almost equal size) is known to perform quasiperiodic or even chaotic orbits in the absence of inertia. With small particle inertia, the particle is also known to drift toward this irregular motion. However, it is not previously understood what effects from fluid inertia could be, which is of highest importance for particles close to neutral buoyancy. Here, we find that fluid inertia is acting strongly to suppress the chaotic motion and only very weak fluid inertia is sufficient to stabilize a rotation around the middle axis. The mechanism responsible for this transition is believed to be centrifugal forces acting on fluid, which is dragged along with the rotational motion of the particle. With moderate fluid inertia, it is found that nearly prolate triaxial particles behave similarly to the perfectly spheroidal particles. Finally, we also are able to provide predictions about the stable rotational states for the general triaxial ellipsoid in simple shear with weak inertia.
Chalian, Hamid; Seyal, Adeel Rahim; Rezai, Pedram; Töre, Hüseyin Gürkan; Miller, Frank H; Bentrem, David J; Yaghmai, Vahid
2014-01-10
The accuracy for determining pancreatic cyst volume with commonly used spherical and ellipsoid methods is unknown. The role of CT volumetry in volumetric assessment of pancreatic cysts needs to be explored. To compare volumes of the pancreatic cysts by CT volumetry, spherical and ellipsoid methods and determine their accuracy by correlating with actual volume as determined by EUS-guided aspiration. Setting This is a retrospective analysis performed at a tertiary care center. Patients Seventy-eight pathologically proven pancreatic cysts evaluated with CT and endoscopic ultrasound (EUS) were included. Design The volume of fourteen cysts that had been fully aspirated by EUS was compared to CT volumetry and the routinely used methods (ellipsoid and spherical volume). Two independent observers measured all cysts using commercially available software to evaluate inter-observer reproducibility for CT volumetry. The volume of pancreatic cysts as determined by various methods was compared using repeated measures analysis of variance. Bland-Altman plot and intraclass correlation coefficient were used to determine mean difference and correlation between observers and methods. The error was calculated as the percentage of the difference between the CT estimated volumes and the aspirated volume divided by the aspirated one. CT volumetry was comparable to aspirated volume (P=0.396) with very high intraclass correlation (r=0.891, Pvolumetry. There was excellent inter-observer correlation in volumetry of the entire cohort (r=0.997, Pvolumetry is accurate and reproducible. Ellipsoid and spherical volume overestimate the true volume of pancreatic cysts.
Acoustic wave focusing in an ellipsoidal reflector for extracorporeal shock-wave lithotripsy
Lottati, Itzhak; Eidelman, Shmuel
1993-07-01
Simulations of acoustic wave focusing in an ellipsoidal reflector for extracorporeal shock-wave lithotripsy (ESWL) are presented. The simulations are done on a structured/unstructured grid with a modified Tait equation of state for water. The Euler equations are solved by applying a second-order Godunov method. The computed results compare very well with the experimental results.
DEFF Research Database (Denmark)
Katerinopoulou, Anna; Balic Zunic, Tonci; Lundegaard, Lars Fahl
2012-01-01
Anisotropic broadening correction in X-ray powder diffraction by an ellipsoidal formula is applied on samples with nanosized crystals. Two cases of minerals with largely anisotropic crystallite shapes are presented. The properly applied formalism not only improves the fitting of the theoretical...
A Deep Cut Ellipsoid Algorithm for convex Programming: theory and Applications
Frenk, J.B.G.; Gromicho Dos Santos, J.A.; Zhang, S.
1994-01-01
This paper proposes a deep cut version of the ellipsoid algorithm for solving a general class of continuous convex programming problems. In each step the algorithm does not require more computational effort to construct these deep cuts than its corresponding central cut version. Rules that prevent
A deep cut ellipsoid algorithm for convex programming : Theory and applications
J.B.G. Frenk (Hans); J.A.S. Gromicho (Joaquim); S. Zhang (Shuzhong)
1994-01-01
textabstractThis paper proposes a deep cut version of the ellipsoid algorithm for solving a general class of continuous convex programming problems. In each step the algorithm does not require more computational effort to construct these deep cuts than its corresponding central cut version. Rules
DISCOVERY OF A HALO AROUND THE HELIX NEBULA NGC 7293 IN THE WISE ALL-SKY SURVEY
International Nuclear Information System (INIS)
Zhang Yong; Hsia, Chih-Hao; Kwok, Sun
2012-01-01
We report the discovery of an extended halo (∼40' in diameter) around the planetary nebula NGC 7293 (the Helix Nebula) observed in the 12 μm band from the Wide-field Infrared Survey Explorer all-sky survey. The mid-infrared halo has an axisymmetric structure with a sharp boundary to the northeast and a more diffuse boundary to the southwest, suggesting an interaction between the stellar wind and the interstellar medium (ISM). The symmetry axis of the halo is well aligned with that of a northeast arc, suggesting that the two structures are physically associated. We have attempted to fit the observed geometry with a model of a moving steady-state stellar wind interacting with the ISM. Possible combinations of the ISM density and the stellar velocity are derived from these fittings. The discrepancies between the model and the observations suggest that the stellar mass loss has a more complicated history, including possible time and angle dependences.
Characteristic time for halo current growth and rotation
Energy Technology Data Exchange (ETDEWEB)
Boozer, Allen H., E-mail: ahb17@columbia.edu [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)
2015-10-15
A halo current flows for part of its path through the plasma edge and for part through the chamber walls and during tokamak disruptions can be as large as tenths of the plasma current. The primary interest in halo currents is the large force that they can exert on machine components particularly if the toriodal rotation of the halo current resonates with a natural oscillation frequency of the tokamak device. Halo currents arise when required to slow down the growth of a kink that is too unstable to be stabilized by the chamber walls. The width of the current channel in the halo plasma is comparable to the amplitude of the kink, and the halo current grows linearly, not exponentially, in time. The current density in the halo is comparable to that of the main plasma body. The rocket force due to plasma flowing out of the halo and recombining on the chamber walls can cause the non-axisymmetric magnetic structure produced by the kink to rotate toroidally at a speed comparable to the halo speed of sound. Gerhardt's observations of the halo current in NSTX shot 141 687 [Nucl. Fusion 53, 023005 (2013)] illustrate many features of the theory of halo currents and are discussed as a summary of the theory.
MINIMARS interim report appendix halo model and computer code
International Nuclear Information System (INIS)
Santarius, J.F.; Barr, W.L.; Deng, B.Q.; Emmert, G.A.
1985-01-01
A tenuous, cool plasma called the halo shields the core plasma in a tandem mirror from neutral gas and impurities. The neutral particles are ionized and then pumped by the halo to the end tanks of the device, since flow of plasma along field lines is much faster than radial flow. Plasma reaching the end tank walls recombines, and the resulting neutral gas is vacuum pumped. The basic geometry of the MINIMARS halo is shown. For halo modeling purposes, the core plasma and cold gas regions may be treated as single radial zones leading to halo source and sink terms. The halo itself is differential into two major radial zones: halo scraper and halo dump. The halo scraper zone is defined by the radial distance required for the ion end plugging potential to drop to the central cell value, and thus have no effect on axial confinement; this distance is typically a sloshing plug ion Larmor diameter. The outer edge of the halo dump zone is defined by the last central cell flux tube to pass through the choke coil. This appendix will summarize the halo model that has been developed for MINIMARS and the methodology used in implementing that model as a computer code
ORIGAMI: DELINEATING HALOS USING PHASE-SPACE FOLDS
Energy Technology Data Exchange (ETDEWEB)
Falck, Bridget L.; Neyrinck, Mark C.; Szalay, Alexander S. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)
2012-08-01
We present the ORIGAMI method of identifying structures, particularly halos, in cosmological N-body simulations. Structure formation can be thought of as the folding of an initially flat three-dimensional manifold in six-dimensional phase space. ORIGAMI finds the outer folds that delineate these structures. Halo particles are identified as those that have undergone shell-crossing along three orthogonal axes, providing a dynamical definition of halo regions that is independent of density. ORIGAMI also identifies other morphological structures: particles that have undergone shell-crossing along 2, 1, or 0 orthogonal axes correspond to filaments, walls, and voids, respectively. We compare this method to a standard friends-of-friends halo-finding algorithm and find that ORIGAMI halos are somewhat larger, more diffuse, and less spherical, though the global properties of ORIGAMI halos are in good agreement with other modern halo-finding algorithms.
ORIGAMI: DELINEATING HALOS USING PHASE-SPACE FOLDS
International Nuclear Information System (INIS)
Falck, Bridget L.; Neyrinck, Mark C.; Szalay, Alexander S.
2012-01-01
We present the ORIGAMI method of identifying structures, particularly halos, in cosmological N-body simulations. Structure formation can be thought of as the folding of an initially flat three-dimensional manifold in six-dimensional phase space. ORIGAMI finds the outer folds that delineate these structures. Halo particles are identified as those that have undergone shell-crossing along three orthogonal axes, providing a dynamical definition of halo regions that is independent of density. ORIGAMI also identifies other morphological structures: particles that have undergone shell-crossing along 2, 1, or 0 orthogonal axes correspond to filaments, walls, and voids, respectively. We compare this method to a standard friends-of-friends halo-finding algorithm and find that ORIGAMI halos are somewhat larger, more diffuse, and less spherical, though the global properties of ORIGAMI halos are in good agreement with other modern halo-finding algorithms.
Research Progresses of Halo Streams in the Solar Neighborhood
Xi-long, Liang; Jing-kun, Zhao; Yu-qin, Chen; Gang, Zhao
2018-01-01
The stellar streams originated from the Galactic halo may be detected when they pass by the solar neighborhood, and they still keep some information at their birth times. Thus, the investigation of halo streams in the solar neighborhood is very important for understanding the formation and evolution of our Galaxy. In this paper, the researches of halo streams in the solar neighborhood are briefly reviewed. We have introduced the methods how to detect the halo streams and identify their member stars, summarized the progresses in the observation of member stars of halo streams and in the study of their origins, introduced in detail how to analyze the origins of halo streams in the solar neighborhood by means of numerical simulation and chemical abundance, and finally discussed the prospects of the LAMOST and GAIA in the research of halo streams in the solar neighborhood.
Milgrom Relation Models for Spiral Galaxies from Two-Dimensional Velocity Maps
Barnes, Eric I.; Kosowsky, Arthur; Sellwood, Jerry A.
2007-01-01
Using two-dimensional velocity maps and I-band photometry, we have created mass models of 40 spiral galaxies using the Milgrom relation (the basis of modified Newtonian dynamics, or MOND) to complement previous work. A Bayesian technique is employed to compare several different dark matter halo models to Milgrom and Newtonian models. Pseudo-isothermal dark matter halos provide the best statistical fits to the data in a majority of cases, while the Milgrom relation generally provides good fits...
Cumulative Neutrino and Gamma-Ray Backgrounds from Halo and Galaxy Mergers
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.
A study of acoustic halos in active region NOAA 11330 using multi-height SDO observations
Tripathy, S. C.; Jain, K.; Kholikov, S.; Hill, F.; Rajaguru, S. P.; Cally, P. S.
2018-01-01
We analyze data from the Helioseismic Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA) instruments on board the Solar Dynamics Observatory (SDO) to characterize the spatio-temporal acoustic power distribution in active regions as a function of the height in the solar atmosphere. For this, we use Doppler velocity and continuum intensity observed using the magnetically sensitive line at 6173 Å as well as intensity at 1600 Å and 1700 Å. We focus on the power enhancements seen around AR 11330 as a function of wave frequency, magnetic field strength, field inclination and observation height. We find that acoustic halos occur above the acoustic cutoff frequency and extends up to 10 mHz in HMI Doppler and AIA 1700 Å observations. Halos are also found to be strong functions of magnetic field and their inclination angle. We further calculate and examine the spatially averaged relative phases and cross-coherence spectra and find different wave characteristics at different heights.
Halo-independent determination of the unmodulated WIMP signal in DAMA: the isotropic case
Energy Technology Data Exchange (ETDEWEB)
Gondolo, Paolo [Department of Physics, University of Utah, 115 South 1400 East #201, Salt Lake City, Utah 84112-0830 (United States); Scopel, Stefano, E-mail: paolo.gondolo@utah.edu, E-mail: scopel@sogang.ac.kr [Department of Physics, Sogang University, Seoul 121-742 (Korea, Republic of)
2017-09-01
We present a halo-independent determination of the unmodulated signal corresponding to the DAMA modulation if interpreted as due to dark matter weakly interacting massive particles (WIMPs). First we show how a modulated signal gives information on the WIMP velocity distribution function in the Galactic rest frame from which the unmodulated signal descends. Then we describe a mathematically-sound profile likelihood analysis in which the likelihood is profiled over a continuum of nuisance parameters (namely, the WIMP velocity distribution). As a first application of the method, which is very general and valid for any class of velocity distributions, we restrict the analysis to velocity distributions that are isotropic in the Galactic frame. In this way we obtain halo-independent maximum-likelihood estimates and confidence intervals for the DAMA unmodulated signal. We find that the estimated unmodulated signal is in line with expectations for a WIMP-induced modulation and is compatible with the DAMA background+signal rate. Specifically, for the isotropic case we find that the modulated amplitude ranges between a few percent and about 25% of the unmodulated amplitude, depending on the WIMP mass.
Gravitational lens effect and pregalactic halo objects
International Nuclear Information System (INIS)
Bontz, R.J.
1979-01-01
The changes in flux, position, and size of a distant extended (galaxy, etc.) source that result from the gravitational lens action of a massive opaque object are discussed. The flux increase is described by a single function of two parameters. One of these parameters characterizes the strength of the gravitational lens, the other describes the alignment of source and lens object. This function also describes the relative intensity of the images formed by lens. ( A similar formalism is discussed by Bourassa et al. for a point source). The formalism is applied to the problem of the galactic halo. It appears that a massive (10 1 2 M/sub sun/) spherical halo surrounding the visible part of the galaxy is consistent with the observable properties of extragalactic sources
Structure and reactions of quantum halos
International Nuclear Information System (INIS)
Jensen, A.S.; Riisager, K.; Fedorov, D.V.; Garrido, E.
2004-01-01
This article provides an overview of the basic principles of the physics of quantum halo systems, defined as bound states of clusters of particles with a radius extending well into classically forbidden regions. Exploiting the consequences of this definition, the authors derive the conditions for occurrence in terms of the number of clusters, binding energy, angular momentum, cluster charges, and excitation energy. All these quantities must be small. The article discusses the transitions between different cluster divisions and the importance of thresholds for cluster or particle decay, with particular attention to the Efimov effect and the related exotic states. The pertinent properties can be described by the use of dimensionless variables. Then universal and specific properties can be distinguished, as shown in a series of examples selected from nuclear, atomic, and molecular systems. The neutron dripline is especially interesting for nuclei and negative ions for atoms. For molecules, in which the cluster division comes naturally, a wider range of possibilities exists. Halos in two dimensions have very different properties, and their states are easily spatially extended, whereas Borromean systems are unlikely and spatially confined. The Efimov effect and the Thomas collapse occur only for dimensions between 2.3 and 3.8 and thus not for 2. High-energy reactions directly probe the halo structure. The authors discuss the reaction mechanisms for high-energy nuclear few-body halo breakup on light, intermediate, and heavy nuclear targets. For light targets, the strong interaction dominates, while for heavy targets, the Coulomb interaction dominates. For intermediate targets these processes are of comparable magnitude. As in atomic and molecular physics, a geometric impact-parameter picture is very appropriate. Finally, the authors briefly consider the complementary processes involving electroweak probes available through beta decay, electromagnetic transitions, and
Total dissociation cross section of halo nuclei
Energy Technology Data Exchange (ETDEWEB)
Formanek, J. [Karlova Univ., Prague (Czech Republic). Fakulta Matematicko-Fyzikalni; Lombard, R.J. [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire
1996-10-01
Calculations of the total dissociation cross section is performed in the impact parameter representation. The case of {sup 11}Be and {sup 11}Li loosing one and two neutron(s), respectively, by collision on a {sup 12}C target, which remains in its ground state are discussed. The results are found to depend essentially on the rms radius of the halo wave function. (author). 12 refs.
Gorzynski, Mark; Derocher, Mike; Mitchell, April Slayden
Research underway at Hewlett-Packard on remote communication resulted in the identification of three important components typically missing in existing systems. These missing components are: group nonverbal communication capabilities, high-resolution interactive data capabilities, and global services. Here we discuss some of the design elements in these three areas as part of the Halo program at HP, a remote communication system shown to be effective to end-users.
Photoionization in the halo of the Galaxy
Bregman, Joel N.; Harrington, J. Patrick
1986-01-01
The ionizing radiation field in the halo is calculated and found to be dominated in the 13.6-45 eV range by light from O-B stars that escapes the disk, by planetary nebulae at 45-54 eV, by quasars and the Galactic soft X-ray background at 54-2000 eV, and by the extragalactic X-ray background at higher energies. Photoionization models are calculated with this radiation field incident on halo clouds of constant density for a variety of densities, for normal and depleted abundances, and with variations of the incident spectrum. For species at least triply ionized, such as Si IV, C IV, N V, and O VI, the line ratios are determined by intervening gas with the greatest volume, which is not necessarily the greatest mass component. Column densities from doubly ionized species like Si III should be greater than from triply ionized species. The role of photoionized gas in cosmic ray-supported halos and Galactic fountains is discussed. Observational tests of photoionization models are suggested.
Self-consistent construction of virialized wave dark matter halos
Lin, Shan-Chang; Schive, Hsi-Yu; Wong, Shing-Kwong; Chiueh, Tzihong
2018-05-01
Wave dark matter (ψ DM ), which satisfies the Schrödinger-Poisson equation, has recently attracted substantial attention as a possible dark matter candidate. Numerical simulations have, in the past, provided a powerful tool to explore this new territory of possibility. Despite their successes in revealing several key features of ψ DM , further progress in simulations is limited, in that cosmological simulations so far can only address formation of halos below ˜2 ×1011 M⊙ and substantially more massive halos have become computationally very challenging to obtain. For this reason, the present work adopts a different approach in assessing massive halos by constructing wave-halo solutions directly from the wave distribution function. This approach bears certain similarities with the analytical construction of the particle-halo (cold dark matter model). Instead of many collisionless particles, one deals with one single wave that has many noninteracting eigenstates. The key ingredient in the wave-halo construction is the distribution function of the wave power, and we use several halos produced by structure formation simulations as templates to determine the wave distribution function. Among different models, we find the fermionic King model presents the best fits and we use it for our wave-halo construction. We have devised an iteration method for constructing the nonlinear halo and demonstrate its stability by three-dimensional simulations. A Milky Way-sized halo has also been constructed, and the inner halo is found to be flatter than the NFW profile. These wave-halos have small-scale interferences both in space and time producing time-dependent granules. While the spatial scale of granules varies little, the correlation time is found to increase with radius by 1 order of magnitude across the halo.
The Outer Halo of the Milky Way as Probed by RR Lyr Variables from the Palomar Transient Facility
Cohen, Judith G.; Sesar, Branimir; Bahnolzer, Sophianna; He, Kevin; Kulkarni, Shrinivas R.; Prince, Thomas A.; Bellm, Eric; Laher, Russ R.
2017-11-01
RR Lyrae stars are ideal massless tracers that can be used to study the total mass and dark matter content of the outer halo of the Milky Way (MW). This is because they are easy to find in the light-curve databases of large stellar surveys and their distances can be determined with only knowledge of the light curve. We present here a sample of 112 RR Lyr stars beyond 50 kpc in the outer halo of the MW, excluding the Sgr streams, for which we have obtained moderate-resolution spectra with Deimos on the Keck II Telescope. Four of these have distances exceeding 100 kpc. These were selected from a much larger set of 447 candidate RR Lyr stars that were data-mined using machine-learning techniques applied to the light curves of variable stars in the Palomar Transient Facility database. The observed radial velocities taken at the phase of the variable corresponding to the time of observation were converted to systemic radial velocities in the Galactic standard of rest. From our sample of 112 RR Lyr stars we determine the radial velocity dispersion in the outer halo of the MW to be ˜90 km s-1 at 50 kpc, falling to about 65 km s-1 near 100 kpc once a small number of major outliers are removed. With reasonable estimates of the completeness of our sample of 447 candidates and assuming a spherical halo, we find that the stellar density in the outer halo declines as {r}-4. Based in part on observations obtained at the W. M. Keck Observatory, which is operated jointly by the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration.
Osteocyte Lacunae are Lenticular/Ellipsoid Spaces or Spiral/Helical Tubules
Directory of Open Access Journals (Sweden)
Bijit Kanti Guha
2017-10-01
Full Text Available Introduction: According to the current concept of bone structure, the osteocyte lacunae are lenticular or ellipsoid spaces occupied by osteocytes. These osteocytes are thought to communicate with each other through a tubular system made up of Canaliculi. The rest of the structures i.e., Haversian canal, and Volkmann’s canal are also tubular in shape. Considering this existing concept of bone microstructure described by various authors, it is highly unlikely that the lacunae alone would be lenticular/ellipsoid structure. In the present study author wanted to know that amongst the all tubular spaces, what is the reason that only the osteocyte lacunae are lenticular or ellipsoid structure? Also to investigate whether these lenticular spaces are really lenticular/ellipsoid or they are cut sections of tubes, which are lying helically or spirally. It is well known from various previous studies that Haversian canal, Volkmann’s canal and Canaliculi are tubular shaped structures and how it is possible that lenticular/ellipsoid structure can present amongst them. So we thought that, it may be possible that these lenticular spaces are not actually lenticular but this lenticular shape is due to the cut sections of any type of tubule in various possible planes (i.e., transverse, longitudinal and various degrees of oblique plane. Aim: The present study was carried out to reinvestigate the shape of the osteocyte lacunae amongst the tubular system (i.e., Haversian canal, Volkmann’s canal and Canaliculi of compact bone. Materials and Methods: The study is carried out by preparing thin sections of adult bones (ground glass preparation and visualizing them under binocular light microscope and scanelectron microscope after following proper procedure. Results: We observed that the lacunae are actually spirally/helically placed tubules with several branching. These branching are considered as canaliculi. These branching are of various diameters and they
The Halo of NGC 2438 scrutinized
Oettl, Silvia; Kimeswenger, Stefan
2015-08-01
Haloes and multiple shells around planetary nebulae trace the mass-loss history of the central star. The haloes provide us with information about abundances, ionization or kinematics. Detailed investigations of these haloes can be used to study the evolution of the old stellar population in our galaxy and beyond.Different observations show structures in the haloes like radial rays, blisters and rings (e.g., Ramos-Larios et al. 2012, MNRAS 423, 3753 or Matsuura et al. 2009, ApJ, 700, 1067). The origin of these features has been associated with ionization shadows (Balick 2004, AJ, 127, 2262). They can be observed in regions, where dense knots are opaque to stellar ionizing photons. In this regions we can see leaking UV photons.In this work, we present a detailed investigation of the multiple shell PN NGC 2438. We derive a complete data set of the main nebula. This allows us to analize the physical conditions from photoionization models, such as temperature, density and ionization, and clumping.Data from ESO (3.6m telescope - EFOSC1 - direct imaging and long slit spectroscopy) and from SAAO (spectroscopic observations using a small slit) were available. These data were supplemented by imaging data from the HST archive and by archival VLA observations. The low-excitation species are found to be dominated by clumps. The emission line ratios show no evidence for shocks. We find the shell in ionization equilibrium: a significant amount of UV radiation infiltrates the inner nebula. Thus the shell still seems to be ionized.The photoionization code CLOUDY was used to model the nebular properties and to derive a more accurate distance and ionized mass. The model supports the hypothesis that photoionization is the dominant process in this nebula, far out into the shell.If we want to use extragalactic planetary nebulae as probes of the old stellar population, we need to assess the potential impact of a halo on the evolution. Also the connection of observations and models must
Exploring the Milky Way halo with SDSS-II SN survey RR Lyrae stars
De Lee, Nathan
This thesis details the creation of a large catalog of RR Lyrae stars, their lightcurves, and their associated photometric and kinematic parameters. This catalog contains 421 RR Lyrae stars with 305 RRab and 116 RRc. Of these, 241 stars have stellar spectra taken with either the Blanco 4m RC spectrograph or the SDSS/SEGUE survey, and in some cases taken by both. From these spectra and photometric methods derived from them, an analysis is conducted of the RR lyrae's distribution, metallicity, kinematics, and photometric properties within the halo. All of these RR Lyrae originate from the SDSS-II Supernova Survey. The SDSS-II SN Survey covers a 2.5 degree equatorial stripe ranging from -60 to +60 degrees in RA. This corresponds to relatively high southern galactic latitudes in the anti-center direction. The full catalog ranges from g 0 magnitude 13 to 20 which covers a distance of 3 to 95 kpc from the sun. Using this sample, we explore the Oosterhoff dichotomy through the D log P method as a function of | Z | distance from the plane. This results in a clear division of the RRab stars into OoI and OoII groups at lower | Z |, but the population becomes dominated by OoI stars at higher | Z |. The idea of a dual halo is explored primarily in the context of radial velocity distributions as a function of | Z |. In particular, V gsr , the radial velocity in the galactic standard of rest, is used as a proxy for V [straight phi] , the cylindrical rotational velocity. This is then compared against a single halo model galaxy, which results in very similar V gsr histograms for both at low to medium | Z |. However, at high | Z | there is a clear separation into two distinct velocity groups for the data without a corresponding separation in the model, suggesting that at least a two-component model for the halo is necessary. The final part of the analysis involves [Fe/H] measurements from both spectra and photometric relations cut in both | Z | and radial velocity. In this case
Nuclear halo and its related reactions
International Nuclear Information System (INIS)
Zhang Huanqiao
2005-01-01
In order to search proton halo, the reaction cross sections of 27,28 P, 29 S and the corresponding isotones on Si target were measured at intermediate energies. The measured reaction cross sections of the N=12 and 13 isotones show an abrupt increase at Z=15. The experimental results for the isotones with Z=14 as well as 28 P can be well described by the modified Glauber theory of the optical limit approach. The enhancement of the reaction cross sections for 28 P could be explained in the modified Glauber theory with an enlarged core. Theoretical analysis with the modified Glauber theory of the optical limit and few-body approaches underpredicted the experimental data of 27 P. Our theoretical analysis shows that an enlarged core together with proton halo is probably the mechanism responsible for the enhancement of the cross sections for the reaction of 27 P+ 28 Si. In addition, we find from the experimental results that 29 S may have a moderate proton halo structure. Except the nuclei near or at drop-lines, halo may appear in the excited states of stable nuclei. By means of the asymptotic normalization coefficients (ANC's) extracted from transfer reactions of 11 B(d, p) 12 B, 12 C(d, p) 13 C, and H( 6 He, n) 6 Li, we have verified that the second ( Jπ = 2 - ) and third (Jπ = 1 - ) excited states in 12 B and the first (Jπ =1/2 + ) excited state in 13 C are the neutron halo states, while the second excited state (3.56 MeV, Jπ = 0 + ) in 6 Li is a proton-neutron halo state. We have proposed a procedure to extract the probability for valence particle being out of the binding potential from the measured nuclear asymptotic normalization coefficients. With this procedure, available data regarding the nuclear halo candidates are systematically analyzed and a number of halo nuclei are confirmed. Based on these results we have got a much relaxed condition for nuclear halo occurrence. Furthermore, we have presented the scaling laws for the dimensionless quantity 2 >/R 2 of
Dark matter halo properties from galaxy-galaxy lensing
International Nuclear Information System (INIS)
Brimioulle, Fabrice
2013-01-01
redshift and galaxy shape catalogs. The complete galaxy sample consists of a total number of 5 x 10 6 lens galaxies within a redshift range of 0.05 phot ≤1 and 1.7 x 10 6 corresponding source galaxies with redshifts of 0.05 phot ≤2 and successfully extracted shapes. Assuming that the galaxy halos can be described by analytic profiles, the scaling relations with absolute luminosity for the galaxy masses, their mass-to-light ratios and the corresponding halo parameters have been extracted. Based on the obtained scaling relations, the average values for the corresponding halo parameters and the mean galaxy masses for a given luminosity were derived as a function of considered halo model, the galaxy SED and the local environment density. We obtain a total mass of M total =23.2 +2.8 -2.5 x 10 11 h -1 M s un for an average galaxy with chosen reference luminosity of L * =1.6 x 10 10 h -2 L s un. In contrast, the mean total masses for red galaxies of same luminosity exceed the value of the average galaxy about 130%, while the mass of a blue galaxy is about 65% below the value of an average fiducial galaxy. Investigating the influence of the environmental density on the galaxy properties we observe a significant increase of the total integrated masses with galaxy density, however the velocity dispersions are not affected. This indicates that the central galaxy matter density mostly depends on the galaxy luminosity but not on the environment. Simulations based on the extracted scientific results were built, verifying the robustness of the scientific results. They give a clear hint that multiple deflections on different lens galaxies have to be properly accounted for in order to avoid systematically biased results.
The “Building Blocks” of Stellar Halos
Directory of Open Access Journals (Sweden)
Kyle A. Oman
2017-08-01
Full Text Available The stellar halos of galaxies encode their accretion histories. In particular, the median metallicity of a halo is determined primarily by the mass of the most massive accreted object. We use hydrodynamical cosmological simulations from the apostle project to study the connection between the stellar mass, the metallicity distribution, and the stellar age distribution of a halo and the identity of its most massive progenitor. We find that the stellar populations in an accreted halo typically resemble the old stellar populations in a present-day dwarf galaxy with a stellar mass ∼0.2–0.5 dex greater than that of the stellar halo. This suggests that had they not been accreted, the primary progenitors of stellar halos would have evolved to resemble typical nearby dwarf irregulars.
New fabrication method for an ellipsoidal neutron focusing mirror with a metal substrate.
Guo, Jiang; Takeda, Shin; Morita, Shin-ya; Hino, Masahiro; Oda, Tatsuro; Kato, Jun-ichi; Yamagata, Yutaka; Furusaka, Michihiro
2014-10-06
We propose an ellipsoidal neutron focusing mirror using a metal substrate made with electroless nickel-phosphorus (NiP) plated material for the first time. Electroless NiP has great advantages for realizing an ellipsoidal neutron mirror because of its amorphous structure, good machinability and relatively large critical angle of total reflection for neutrons. We manufactured the mirror by combining ultrahigh precision cutting and fine polishing to generate high form accuracy and low surface roughness. The form accuracy of the mirror was estimated to be 5.3 μm P-V and 0.8 μm P-V for the minor-axis and major-axis direction respectively, while the surface roughness was reduced to 0.2 nm rms. The effect of form error on focusing spot size was evaluated by using a laser beam and the focusing performance of the mirror was verified by neutron experiments.
Quark self-energy in an ellipsoidally anisotropic quark-gluon plasma
Kasmaei, Babak S.; Nopoush, Mohammad; Strickland, Michael
2016-12-01
We calculate the quark self-energy in a quark-gluon plasma that possesses an ellipsoidal momentum-space anisotropy in the local rest frame. By introducing additional transverse-momentum anisotropy parameters into the parton distribution functions, we generalize previous results which were obtained for the case of a spheroidal anisotropy. Our results demonstrate that the presence of anisotropies in the transverse directions affects the real and imaginary parts of quark self-energy and, consequently, the self-energy depends on both the polar and azimuthal angles in the local rest frame of the matter. Our results for the quark self-energy set the stage for the calculation of the effects of ellipsoidal momentum-space anisotropy on quark-gluon plasma photon spectra and collective flow.
Harris, Madison; Cunningham, Emily; Guhathakurta, Puragra; Cheshire, Ishani; Gupta, Nandita
2018-01-01
White dwarf (WD) stars represent the final phase in the life of solar-mass stars. The extreme low luminosity of WDs means that most detailed measurements of such stars are limited to samples in the immediate neighborhood of the Sun in the thin disk of the Milky Way galaxy. We present spectra, line-of-sight (LOS) velocities, and proper motions (PMs) of a sample of faint (m_V ~ 19.0–24.5) white dwarfs (WDs) from the HALO7D survey. HALO7D is a Keck II/DEIMOS spectroscopic survey of unprecedented depth (8–24 hour integrations) in the CANDELS fields of main sequence turnoff stars in the Milky Way's outer halo. Faint WD stars are rare but useful by-products of this survey. We identify the sample of WDs based on their characteristic broad spectral Balmer absorption features, and present a Bayesian method for measuring their LOS velocities. Using their broadband colors, LOS velocities and PMs measured with the Hubble Space Telescope, we identify candidate halo members among the WDs based on the predicted velocity distributions from the Besançon numerical model of stellar populations in the Milky Way galaxy. The WDs found in the HALO7D survey will yield new insights on the old stellar population associated with the Milky Way's thick disk and halo. Funding for this research was provided by the National Science Foundation and NASA/STScI. NG and IC's participation in this research was under the auspices of the Science Internship Program at the University of California Santa Cruz.
Measuring stone volume - three-dimensional software reconstruction or an ellipsoid algebra formula?
Finch, William; Johnston, Richard; Shaida, Nadeem; Winterbottom, Andrew; Wiseman, Oliver
2014-04-01
To determine the optimal method for assessing stone volume, and thus stone burden, by comparing the accuracy of scalene, oblate, and prolate ellipsoid volume equations with three-dimensional (3D)-reconstructed stone volume. Kidney stone volume may be helpful in predicting treatment outcome for renal stones. While the precise measurement of stone volume by 3D reconstruction can be accomplished using modern computer tomography (CT) scanning software, this technique is not available in all hospitals or with routine acute colic scanning protocols. Therefore, maximum diameters as measured by either X-ray or CT are used in the calculation of stone volume based on a scalene ellipsoid formula, as recommended by the European Association of Urology. In all, 100 stones with both X-ray and CT (1-2-mm slices) were reviewed. Complete and partial staghorn stones were excluded. Stone volume was calculated using software designed to measure tissue density of a certain range within a specified region of interest. Correlation coefficients among all measured outcomes were compared. Stone volumes were analysed to determine the average 'shape' of the stones. The maximum stone diameter on X-ray was 3-25 mm and on CT was 3-36 mm, with a reasonable correlation (r = 0.77). Smaller stones (15 mm towards scalene ellipsoids. There was no difference in stone shape by location within the kidney. As the average shape of renal stones changes with diameter, no single equation for estimating stone volume can be recommended. As the maximum diameter increases, calculated stone volume becomes less accurate, suggesting that larger stones have more asymmetric shapes. We recommend that research looking at stone clearance rates should use 3D-reconstructed stone volumes when available, followed by prolate, oblate, or scalene ellipsoid formulas depending on the maximum stone diameter. © 2013 The Authors. BJU International © 2013 BJU International.
ORTEP-III: Oak Ridge Thermal Ellipsoid Plot Program for crystal structure illustrations
Energy Technology Data Exchange (ETDEWEB)
Burnett, M.N.; Johnson, C.K.
1996-07-01
This report describes a computer program for drawing crystal structure illustrations. Ball-and-stick type illustrations of a quality suitable for publication are produced with either spheres or thermal-motion probability ellipsoids on the atomic sites. The program can also produce stereoscopic pairs of illustrations which aid in the visualization of complex packing arrangements of atoms and thermal motion patterns. Interatomic distances, bond angles, and principal axes of thermal motion are also calculated to aid the structural study.
Directory of Open Access Journals (Sweden)
M. A. Bezuglyi
2018-01-01
Full Text Available The correct accounting of laser emitter parameters for improvement of diagnostic authenticity of methods of optical biomedical diagnostic is important problem for applied biophotonic tasks. The purpose of the current research is estimation of influence of energy distribution profile in transversal section of laser beam on light scattering by human skin layers at photometry by ellipsoidal reflectors.Biomedical photometer with ellipsoidal reflectors for investigation of biological tissue specimens in transmitted and reflected light uses laser probing radiation with infinitely thin, Gauss-type and uniform cross-section profile. Distribution of beams with denoted profiles, which consist of 20 million photons with wavelength 632.8 nm, was modeled by using of Monte-Carlo simulation in human skin layers (corneous layer, epidermis, derma and adipose tissue of various anatomic thickness and with ellipsoidal reflectors with focal parameter equal to 16.875 mm and eccentricity of 0.66.The modeling results represent that illuminance distribution in zones of photometric imaging is significantly influenced by the laser beam cross-section profile for various thickness of corneous layer and epidermis in transmitted and reflected light, and also derma in reflected light. Illuminance distribution for adipose tissue in reflected and transmitted light, and also derma in transmitted light, practically do not depend of laser beam profile for anatomic thicknesses, which are appropriate for human skin on various sections of body.There are represented results of modified Monte-Carlo simulation method for biomedical photometer with ellipsoidal reflectors during biometry of human skin layers. For highly scattered corneous layer and epidermis the illumination of middle and external rings of photometric images changes depending from the laser beam profile for more than 50 % in transmitted and 30 % in reflected light. For weakly scattering skin layers (derma and adipose layer
LAVERGNE, Francis; SAB, Karam; SANAHUJA, Julien; BORNERT, Michel; TOULEMONDE, Charles
2016-01-01
A multi-scale homogenization scheme is proposed to estimate the time-dependent strains of fiber-reinforced concrete. This material is modeled as an aging linear viscoelastic composite material featuring ellipsoidal inclusions embedded in a viscoelastic cementitious matrix characterized by a time-dependent Poisson's ratio. To this end, the homogenization scheme proposed in Lavergne et al. [1] is adapted to the case of a time-dependent Poisson's ratio and it is successfully validated on a non-a...
Experimental study of the moment of inertia of a cone-angular variation and inertia ellipsoid
International Nuclear Information System (INIS)
Pintao, Carlos A F; Souza de Filho, Moacir P; Usida, Wesley F; Xavier, Jose A
2007-01-01
In this paper, an experimental set-up which differs from the traditional ones is established in order to determine the moment of inertia of a right circular cone. Its angular variation and inertia ellipsoid are determined by means of an experimental study. In addition, a system that allows for the evaluation of the angular acceleration and torque through electric current or frequency measurement is utilized
Manufacturing method for hard x-ray focusing mirrors with ellipsoidal surface
International Nuclear Information System (INIS)
Yumoto, Hirokatsu; Koyama, Takahisa; Ohashi, Haruhiko; Matsuyama, Satoshi; Yamauchi, Kazuto
2014-01-01
The aim of this study is to establishing the manufacturing method for hard x-ray nano-focusing mirrors with ellipsoidal surface. Ellipsoidal mirror optics, which can produce point focus with a mirror, has a noticeable feature of a high focusing efficiency, although an ultra-precise surface figure with an accuracy of a few nanometers is required for nano-focusing mirrors. Here, we examined the effectiveness of the manufacturing process for ellipsoidal mirrors, which is consisted of a precision grinding process, a removal process of surface roughness, and a computer-controlled shape correction. The precision processing machine for both a removal of surface roughness and a shape correction was developed. This validated the utility of removing surface roughness with a spatial wavelength of 40 μm, which is the tool mark of the grinding process. The developed process achieved the improvement of surface roughness from 1.6 nm to 0.1 nm (RMS), and the figure correction with a high accuracy of < 10 nm and a spatial resolution of < 2 mm. (author)
Measurement of self-shaped ellipsoidal bunches from a photoinjector with postacceleration
Directory of Open Access Journals (Sweden)
Brendan O’Shea
2011-01-01
Full Text Available Recent work has shown the possibility of generating self-shaped ellipsoidal beams with properties commensurate with the requirements of future light sources such as free-electron lasers and inverse Compton sources. In this so-termed “blowout” regime, short laser bunches are transformed via photoemission into short electron bunches which then self-consistently evolve into nearly uniform-density ellipsoids under space-charge forces. We report here on the first blowout studies conducted in collaboration between the UCLA Particle Beam Physics Lab and the Photo Injector Test Facility, Zeuthen (PITZ. The measurements conducted at the PITZ photoinjector facility examine the evolution of 750 pC, 2.7 ps FWHM electron bunches born in an L-band photoinjector and subsequently accelerated through a nine-cell L-band booster for a resulting energy of 12 MeV. These measurements represent the first observations of self-shaped ellipsoid evolution under postinjector acceleration, a key step in demonstrating the utility of such self-shaped beams at higher energy, where the advantages in both transverse and longitudinal and transverse phase space may be exploited in creating very high brightness beams.
The TMS-1 corneal topography measurement applied to calibrated ellipsoidal convex surfaces.
Douthwaite, W A; Matilla, M T
1996-03-01
The purpose of this report is to assess the accuracy of the TMS-1 videokeratoscope (Computed Anatomy Inc.) by using convex ellipsoidal surfaces. The ellipsoids were calibrated using Form Talysurf analysis, which allowed for subsequent calculation of the vertex radius and p value. The videokeratoscope was used to examine the same ellipsoids. The data provided by the instrument software were used to plot a graph of r2 verses y2, where r is the measured radius at y, the distance from the corneal point being measured to the optical axis of the instrument. The intercept on the ordinate of this graph gives the vertex radius, and the slope give the p value. The results arising from the Talysurf and the TMS-1 techniques were compared. The TMS-1 videokeratoscope gave readings for the vertex radius that were generally higher than those of the Talysurf analysis. The vertex radius was up to 0.09 mm greater. The p value results were similar by the two methods for p values of approximately 0.8; however, the TMS-1 results were higher, and the discrepancy increased as the p value approached that of a paraboloid. Although the videokeratoscope may be useful in comparative studies of the cornea, there must be some doubt about the absolute values displayed as the surface becomes increasingly aspheric.
Directory of Open Access Journals (Sweden)
Zhengchun Du
2016-05-01
Full Text Available The use of three-dimensional (3D data in the industrial measurement field is becoming increasingly popular because of the rapid development of laser scanning techniques based on the time-of-flight principle. However, the accuracy and uncertainty of these types of measurement methods are seldom investigated. In this study, a mathematical uncertainty evaluation model for the diameter measurement of standard cylindroid components has been proposed and applied to a 3D laser radar measurement system (LRMS. First, a single-point error ellipsoid analysis for the LRMS was established. An error ellipsoid model and algorithm for diameter measurement of cylindroid components was then proposed based on the single-point error ellipsoid. Finally, four experiments were conducted using the LRMS to measure the diameter of a standard cylinder in the laboratory. The experimental results of the uncertainty evaluation consistently matched well with the predictions. The proposed uncertainty evaluation model for cylindrical diameters can provide a reliable method for actual measurements and support further accuracy improvement of the LRMS.
Kushch, Volodymyr I.; Sevostianov, Igor; Giraud, Albert
2017-11-01
An accurate semi-analytical solution of the conductivity problem for a composite with anisotropic matrix and arbitrarily oriented anisotropic ellipsoidal inhomogeneities has been obtained. The developed approach combines the superposition principle with the multipole expansion of perturbation fields of inhomogeneities in terms of ellipsoidal harmonics and reduces the boundary value problem to an infinite system of linear algebraic equations for the induced multipole moments of inhomogeneities. A complete full-field solution is obtained for the multi-particle models comprising inhomogeneities of diverse shape, size, orientation and properties which enables an adequate account for the microstructure parameters. The solution is valid for the general-type anisotropy of constituents and arbitrary orientation of the orthotropy axes. The effective conductivity tensor of the particulate composite with anisotropic constituents is evaluated in the framework of the generalized Maxwell homogenization scheme. Application of the developed method to composites with imperfect ellipsoidal interfaces is straightforward. Their incorporation yields probably the most general model of a composite that may be considered in the framework of analytical approach.
The Halo Dynamics of NGC 3379: A Normal Elliptical Galaxy with No Dark Matter
Ciardullo, R.; Jacoby, G. H.
1993-05-01
We present the results of a radial velocity survey of planetary nebulae in the normal, non-interacting, elliptical galaxy NGC 3379. In two half-nights with the Kitt Peak 4-m telescope and the NESSIE multifiber spectrograph, we measured the velocities of 29 PNe with projected galactocentric distances between 0.4 and 3.8 effective radii (1 kpc < R < 10 kpc). These data, which have an observational uncertainty of ~ 7 km s(-1) , extend 3 times further into the halo than any previous absorption line study, and allow us for the first time, to examine the kinematics of halo stars in a normal E0 galaxy. The observed velocity dispersion and photometric profile of NGC 3379 agrees extremely well with that expected from a constant mass-to-light, isotropic orbit Jaffe model with a mass-to-light ratio M/L_B ~ 7. A simple c = 2.33 King model with M/L_B ~ 7 also fits the data reasonably well, but models with purely radial or circular orbits are ruled out. The data strongly suggest that NGC 3379 is a galaxy with little or no dark matter within 3.5 effective radii of its nucleus.
The kinematic footprints of five stellar streams in Andromeda's halo
Chapman, S. C.; Ibata, R.; Irwin, M.; Koch, A.; Letarte, B.; Martin, N.; Collins, M.; Lewis, G. F.; McConnachie, A.; Peñarrubia, J.; Rich, R. M.; Trethewey, D.; Ferguson, A.; Huxor, A.; Tanvir, N.
2008-11-01
We present a spectroscopic analysis of five stellar streams (`A', `B', `Cr', `Cp' and `D') as well as the extended star cluster, EC4, which lies within Stream`C', all discovered in the halo of M31 from our Canada-France-Hawaii Telescope/MegaCam survey. These spectroscopic results were initially serendipitous, making use of our existing observations from the DEep Imaging Multi-Object Spectrograph mounted on the Keck II telescope, and thereby emphasizing the ubiquity of tidal streams that account for ~70 per cent of the M31 halo stars in the targeted fields. Subsequent spectroscopy was then procured in Stream`C' and Stream`D' to trace the velocity gradient along the streams. Nine metal-rich ([Fe/H] ~ -0.7) stars at vhel = -349.5kms-1,σv,corr ~ 5.1 +/- 2.5km s-1 are proposed as a serendipitous detection of Stream`Cr', with follow-up kinematic identification at a further point along the stream. Seven metal-poor ([Fe/H] ~-1.3) stars confined to a narrow, 15 km s-1 velocity bin centred at vhel = -285.6, σv,corr = 4.3+1.7-1.4 km s-1 represent a kinematic detection of Stream`Cp', again with follow-up kinematic identification further along the stream. For the cluster EC4, candidate member stars with average [Fe/H] ~-1.4, are found at vhel = -282 suggesting it could be related to Stream`Cp'. No similarly obvious cold kinematic candidate is found for Stream`D', although candidates are proposed in both of two spectroscopic pointings along the stream (both at ~ -400km s-1). Spectroscopy near the edge of Stream`B' suggests a likely kinematic detection at vhel ~ -330, σv,corr ~ 6.9km s-1, while a candidate kinematic detection of Stream`A' is found (plausibly associated to M33 rather than M31) with vhel ~ -170, σv,corr = 12.5km s-1. The low dispersion of the streams in kinematics, physical thickness and metallicity makes it hard to reconcile with a scenario whereby these stream structures as an ensemble are related to the giant southern stream. We conclude that the M31 stellar
International Nuclear Information System (INIS)
Sun, Weiyuan; Liu, Zhiguo; Sun, Tianxi; Peng, Song; Ma, Yongzhong; Ding, Xunliang
2014-01-01
A new device using an ellipsoidal single-bounce monocapillary X-ray optics was numerically designed to realize in-line X-ray phase-contrast imaging by using conventional laboratory X-ray source with a large spot. Numerical simulation results validated the effectiveness of the proposed device and approach. The ellipsoidal single-bounce monocapillary X-ray optics had potential applications in the in-line phase contrast imaging with polychromatic X-rays
Energy Technology Data Exchange (ETDEWEB)
Sun, Weiyuan; Liu, Zhiguo [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Sun, Tianxi, E-mail: stx@bnu.edu.cn [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Peng, Song [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Ma, Yongzhong [Center for Disease Control and Prevention of Beijing, Beijing 100013 (China); Ding, Xunliang [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China)
2014-05-11
A new device using an ellipsoidal single-bounce monocapillary X-ray optics was numerically designed to realize in-line X-ray phase-contrast imaging by using conventional laboratory X-ray source with a large spot. Numerical simulation results validated the effectiveness of the proposed device and approach. The ellipsoidal single-bounce monocapillary X-ray optics had potential applications in the in-line phase contrast imaging with polychromatic X-rays.
Haloes, molecules and multi-neutrons
Energy Technology Data Exchange (ETDEWEB)
Marques Moreno, F.M
2003-01-01
Away from the equilibrium between protons and neutrons within stable nuclei, many exotic nuclei exist. Most of the known nuclear properties evolve smoothly with exoticism, but some extreme proton-neutron combinations have revealed during the last decade completely new concepts. They will be illustrated through three examples: the extended and dilute halo formed by very weakly bound neutrons, the molecular-like neutron orbitals found in nuclei exhibiting a clustering, and the recently revived debate on the possible existence of neutral nuclei. The different experimental results will be reviewed, and we will see how several properties of these new phenomena can be well understood within relatively simple theoretical approaches. (author)
Sub-Coulomb fusion with halo nuclei
International Nuclear Information System (INIS)
Fekou-Youmbi, V.; Sida, J.L.; Alamanos, N.; Auger, F.; Bazin, D.; Borcea, C.; Cabot, C.; Cunsolo, A.; Foti, A.; Gillibert, A.; Lepine, A.; Lewitowicz, M.; Liguori-Neto, R.; Mittig, W.; Pollacco, E.; Roussel-Chomaz, P.; Volant, C.; Yong Feng, Y.
1995-01-01
The nuclear structure of halo nuclei may have strong influence on the fusion cross section at sub-barrier energies. The actual theoretical debate is briefly reviewed and sub-barrier fusion calculations for the system 11 Be+ 238 U are presented. An experimental program on sub-barrier fusion for the systems 7,9,10,11 Be+ 238 U is underway at GANIL. First results with 9 Be and 11 Be beams were obtained using the F.U.S.ION detector. Relative fission cross sections are presented. ((orig.))
Project ECHO: Electronic Communications from Halo Orbit
Borrelli, Jason; Cooley, Bryan; Debole, Marcy; Hrivnak, Lance; Nielsen, Kenneth; Sangmeister, Gary; Wolfe, Matthew
1994-01-01
The design of a communications relay to provide constant access between the Earth and the far side of the Moon is presented. Placement of the relay in a halo orbit about the L2 Earth-Moon Lagrange point allows the satellite to maintain constant simultaneous communication between Earth and scientific payloads on the far side of the Moon. The requirements of NASA's Discovery-class missions adopted and modified for this design are: total project cost should not exceed $150 million excluding launch costs, launch must be provided by Delta-class vehicle, and the satellite should maintain an operational lifetime of 10 to 15 years. The spacecraft will follow a transfer trajectory to the L2 point, after launch by a Delta II 7925 vehicle in 1999. Low-level thrust is used for injection into a stationkeeping-free halo orbit once the spacecraft reaches the L2 point. The shape of this halo orbit is highly elliptical with the maximum excursion from the L2 point being 35000 km. A spun section and despun section connected through a bearing and power transfer assembly (BAPTA) compose the structure of the spacecraft. Communications equipment is placed on the despun section to provide for a stationary dual parabolic offset-feed array antenna system. The dual system is necessary to provide communications coverage during portions of maximum excursion on the halo orbit. Transmissions to the NASA Deep Space Network 34 m antenna include six channels (color video, two voice, scientific data from lunar payloads, satellite housekeeping and telemetry and uplinked commands) using the S- and X-bands. Four radioisotope thermoelectric generators (RTG's) provide a total of 1360 W to power onboard systems and any two of the four Hughes 13 cm ion thrusters at once. Output of the ion thrusters is approximately 17.8 mN each with xenon as the propellant. Presence of torques generated by solar pressure on the antenna dish require the addition of a 'skirt' extending from the spun section of the satellite
X-ray haloes around supernova remnants
International Nuclear Information System (INIS)
Morfill, G.E.; Aschenbach, B.
1984-01-01
Recent observations of the Cas-A supernova remnant have shown X-ray emissions not only from the interior, but also from a fainter 'halo' extending beyond what is normally regarded as the outer boundary, or shock front. The authors suggest that this may be due to the diffusion of energetic, charged particles out of the remnant giving rise to precursor structure of the type predicted by the theory of diffusive shock acceleration. If this is the case we are seeing thermal emission from ambient gas heated by compression and wave dissipation. (author)
X-ray haloes around supernova remnants
Energy Technology Data Exchange (ETDEWEB)
Morfill, G.E.; Aschenbach, B. (Max-Planck-Institut fuer Physik und Astrophysik, Garching (Germany, F.R.). Inst. fuer Extraterrestrische Physik); Drury, L.O' C. (Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany, F.R.))
1984-09-27
Recent observations of the Cas-A supernova remnant have shown X-ray emissions not only from the interior, but also from a fainter 'halo' extending beyond what is normally regarded as the outer boundary, or shock front. The authors suggest that this may be due to the diffusion of energetic charged particles out of the remnant giving rise to precursor structure of the type predicted by the theory of diffusive shock acceleration. If this is the case we are seeing thermal emission from ambient gas heated by compression and wave dissipation.
Li, Ming-Hua; Zhu, Weishan; Zhao, Dong
2018-05-01
The gas is the dominant component of baryonic matter in most galaxy groups and clusters. The spatial offsets of gas centre from the halo centre could be an indicator of the dynamical state of cluster. Knowledge of such offsets is important for estimate the uncertainties when using clusters as cosmological probes. In this paper, we study the centre offsets roff between the gas and that of all the matter within halo systems in ΛCDM cosmological hydrodynamic simulations. We focus on two kinds of centre offsets: one is the three-dimensional PB offsets between the gravitational potential minimum of the entire halo and the barycentre of the ICM, and the other is the two-dimensional PX offsets between the potential minimum of the halo and the iterative centroid of the projected synthetic X-ray emission of the halo. Haloes at higher redshifts tend to have larger values of rescaled offsets roff/r200 and larger gas velocity dispersion σ v^gas/σ _{200}. For both types of offsets, we find that the correlation between the rescaled centre offsets roff/r200 and the rescaled 3D gas velocity dispersion, σ _v^gas/σ _{200} can be approximately described by a quadratic function as r_{off}/r_{200} ∝ (σ v^gas/σ _{200} - k_2)2. A Bayesian analysis with MCMC method is employed to estimate the model parameters. Dependence of the correlation relation on redshifts and the gas mass fraction are also investigated.
THE INNER STRUCTURE OF DWARF-SIZED HALOS IN WARM AND COLD DARK MATTER COSMOLOGIES
Energy Technology Data Exchange (ETDEWEB)
González-Samaniego, A.; Avila-Reese, V. [Instituto de Astronomía, Universidad Nacional Autónoma de México, A.P. 70-264, 04510, México, D.F., México (Mexico); Colín, P. [Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, A.P. 72-3 (Xangari), Morelia, Michoacán 58089, México (Mexico)
2016-03-10
By means of N-body + hydrodynamic zoom-in simulations we study the evolution of the inner dark matter and stellar mass distributions of central dwarf galaxies formed in halos of virial masses M{sub v} = (2–3) × 10{sup 10} h{sup −1} M{sub ⊙} at z = 0, both in a warm dark matter (WDM) and cold dark matter (CDM) cosmology. The half-mode mass in the WDM power spectrum of our simulations is M{sub f} = 2 × 10{sup 10} h{sup −1} M{sub ⊙}. In the dark matter (DM) only simulations halo density profiles are well described by the Navarro–Frenk–White parametric fit in both cosmologies, though the WDM halos have concentrations lower by factors of 1.5–2.0 than their CDM counterparts. In the hydrodynamic simulations, the effects of baryons significantly flatten the inner density, velocity dispersion, and pseudo phase space density profiles of the WDM halos but not of the CDM ones. The density slope, measured at ≈0.02R{sub v}, α{sub 0.02}, becomes shallow in periods of 2–5 Gyr in the WDM runs. We explore whether this flattening process correlates with the global star formation (SF), M{sub s}/M{sub v} ratio, gas outflow, and internal specific angular momentum histories. We do not find any clear trends, but when α{sub 0.02} is shallower than −0.5, M{sub s}/M{sub v} is always between 0.25% and 1%. We conclude that the main reason for the formation of the shallow core is the presence of strong gas mass fluctuations inside the inner halo, which are a consequence of the feedback driven by a very bursty and sustained SF history in shallow gravitational potentials. Our WDM halos, which assemble late and are less concentrated than the CDM ones, obey these conditions. There are also (rare) CDM systems with extended mass assembly histories that obey these conditions and form shallow cores. The dynamical heating and expansion processes behind the DM core flattening apply also to the stars in such a way that the stellar age and metallicity gradients of the
Energy Technology Data Exchange (ETDEWEB)
Zhu, Bida [Department of Mechanics, Huazhong University of Science and Technology, Wuhan 430074 (China); Huang, Minsheng, E-mail: mshuang@hust.edu.cn [Department of Mechanics, Huazhong University of Science and Technology, Wuhan 430074 (China); Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment, Luoyu Road 1037, Wuhan 430074 (China); Li, Zhenhuan [Department of Mechanics, Huazhong University of Science and Technology, Wuhan 430074 (China); Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment, Luoyu Road 1037, Wuhan 430074 (China)
2017-04-15
High concentrations of vacancies tend to be formed inside the metal materials under irradiation, and then accumulate and cluster together gradually to promote the formation of nanovoids. Generally, these voids act as obstacles for dislocation glide and thereby change/degrade the mechanical behavior of irradiated materials. In this work, the interaction between ellipsoidal nanovoids with edge dislocations in alpha-iron has been studied by atomic simulations. The results illuminate that the ellipsoidal void’s semi-major axis on the slip plane and parallel to the dislocation line is the dominant factor controlling the obstacle strength of ellipsoidal nanovoids. Two other semi-major axes, which are perpendicular to the glide plane and parallel to the Burgers vector, respectively, can also influence the critical resolved shear stress (CRSS) for dislocation shearing the ellipsoidal void. The intrinsic atomic mechanisms controlling above phenomena, such as nanovoid-geometry spatial constraint and nanovoid-surface curvature on dislocation evolution, have been discussed carefully. The classical continuum model has been amended to describe the dislocation-ellipsoidal nanovoid interaction base on current results. In addition, the influence of temperature on the CRSS of ellipsoidal nanovoids has also been investigated.
International Nuclear Information System (INIS)
Mihiretie, Besira; Loudet, Jean-Christophe; Pouligny, Bernard
2013-01-01
Radiation pressure forces from a moderately focused vertical laser beam are used to levitate transparent particles, a few micrometers in size. Having recalled basic results about levitation of spheres, and applications to long-working distance trapping, we turn to ellipsoid-shaped particles. Experiments are carried out with polystyrene particles, inside a glass chamber filled with water. The particles are lifted up to contact with the chamber top surface. We examine particle equilibrium in such conditions and show that the system “bifurcates” between static on-axis equilibrium with short ellipsoids, to sustained oscillations with longer ones. A similar Hopf bifurcation is found using a simple ray-optics model of the laser-ellipsoid interaction, providing a qualitative account of the observed oscillations. -- Highlights: ► We study optical levitation of non-spherical micrometer-sized particles. ► Short ellipsoids get trapped on laser beam axis, similarly to spheres. ► Long ellipsoids oscillate, through coupled translation and tilt motions. ► We propose a simple ray-optics model of light interaction with an ellipsoid. ► From computed radiation pressure forces, we explain the observed oscillations
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.
Subhalo demographics in the Illustris simulation: effects of baryons and halo-to-halo variation
Chua, Kun Ting Eddie; Pillepich, Annalisa; Rodriguez-Gomez, Vicente; Vogelsberger, Mark; Bird, Simeon; Hernquist, Lars
2017-12-01
We study the abundance of subhaloes in the hydrodynamical cosmological simulation Illustris, which includes both baryons and dark matter in a cold dark matter volume 106.5 Mpc a side. We compare Illustris to its dark-matter only (DMO) analogue, Illustris-Dark and quantify the effects of baryonic processes on the demographics of subhaloes in the host mass range 1011-3 × 1014 M⊙. We focus on both the evolved (z = 0) subhalo cumulative mass functions (SHMF) and the statistics of subhaloes ever accreted, i.e. infall SHMF. We quantify the variance in subhalo abundance at fixed host mass and investigate the physical reasons responsible for such scatter. We find that in Illustris, baryonic physics impacts both the infall and z = 0 subhalo abundance by tilting the DMO function and suppressing the abundance of low-mass subhaloes. The breaking of self-similarity in the subhalo abundance at z = 0 is enhanced by the inclusion of baryonic physics. The non-monotonic alteration of the evolved subhalo abundances can be explained by the modification of the concentration-mass relation of Illustris hosts compared to Illustris-Dark. Interestingly, the baryonic implementation in Illustris does not lead to an increase in the halo-to-halo variation compared to Illustris-Dark. In both cases, the normalized intrinsic scatter today is larger for Milky Way-like haloes than for cluster-sized objects. For Milky Way-like haloes, it increases from about eight per cent at infall to about 25 per cent at the current epoch. In both runs, haloes of fixed mass formed later host more subhaloes than early formers.
Constraining self-interacting dark matter with scaling laws of observed halo surface densities
Bondarenko, Kyrylo; Boyarsky, Alexey; Bringmann, Torsten; Sokolenko, Anastasia
2018-04-01
The observed surface densities of dark matter halos are known to follow a simple scaling law, ranging from dwarf galaxies to galaxy clusters, with a weak dependence on their virial mass. Here we point out that this can not only be used to provide a method to determine the standard relation between halo mass and concentration, but also to use large samples of objects in order to place constraints on dark matter self-interactions that can be more robust than constraints derived from individual objects. We demonstrate our method by considering a sample of about 50 objects distributed across the whole halo mass range, and by modelling the effect of self-interactions in a way similar to what has been previously done in the literature. Using additional input from simulations then results in a constraint on the self-interaction cross section per unit dark matter mass of about σ/mχlesssim 0.3 cm2/g. We expect that these constraints can be significantly improved in the future, and made more robust, by i) an improved modelling of the effect of self-interactions, both theoretical and by comparison with simulations, ii) taking into account a larger sample of objects and iii) by reducing the currently still relatively large uncertainties that we conservatively assign to the surface densities of individual objects. The latter can be achieved in particular by using kinematic observations to directly constrain the average halo mass inside a given radius, rather than fitting the data to a pre-selected profile and then reconstruct the mass. For a velocity-independent cross-section, our current result is formally already somewhat smaller than the range 0.5‑5 cm2/g that has been invoked to explain potential inconsistencies between small-scale observations and expectations in the standard collisionless cold dark matter paradigm.
Periportal halo on CT: spectrum of causes
International Nuclear Information System (INIS)
Volpacchio, Mariano; Baltazar, Alberto D.; Santamarina, Mario G.; Casetta, Liliana; Cione, Rodrigo; Sanchez, Gimena; Vallejos, Nancy
2003-01-01
Purpose: A periportal hypodense halo is a relatively frequent CT finding. This halo is attributed to the presence of edema or ecstatic lymphatic channels. In our series we illustrate the CT appearance of periportal edema and analyze its causes. Material and Methods: In a retrospective study we analyze a 78 patients series who showed periportal edema on e.v. contrast-enhanced abdominal CTs. The different causes of hepatic periportal edema (demonstrated on CT exams), were established by clinical, laboratory, surgical and anatomo-pathologic correlation. Results: In this study, 49 cases were diagnosed as having congestive heart failure (62,8%), 14 patients had viral hepatitis (18%), 5 patients had recently undergone orthotopic liver transplantation (6.4%), 3 patients had a diagnosis of infectious cholangitis (3.8%), 3 patients had abdominal trauma (3.8%), 2 patients had neoplastic disease (2.6%) and 2 patients had toxic hepatitis (2.6%). Conclusion: Periportal edema is a frequent and nonspecific finding associated with systemic diseases as well as liver specific entities. The integration of CT findings and clinical picture of periportal edema leads to a confident diagnosis of the main cause in most patients. (author)
The CMS Beam Halo Monitor Detector System
CMS Collaboration
2015-01-01
A new Beam Halo Monitor (BHM) detector system has been installed in the CMS cavern to measure the machine-induced background (MIB) from the LHC. This background originates from interactions of the LHC beam halo with the final set of collimators before the CMS experiment and from beam gas interactions. The BHM detector uses the directional nature of Cherenkov radiation and event timing to select particles coming from the direction of the beam and to suppress those originating from the interaction point. It consists of 40 quartz rods, placed on each side of the CMS detector, coupled to UV sensitive PMTs. For each bunch crossing the PMT signal is digitized by a charge integrating ASIC and the arrival time of the signal is recorded. The data are processed in real time to yield a precise measurement of per-bunch-crossing background rate. This measurement is made available to CMS and the LHC, to provide real-time feedback on the beam quality and to improve the efficiency of data taking. In this talk we will describ...
Halo's production in vitro on brachytherapy experiments
International Nuclear Information System (INIS)
Cuperschmid, Ethel M.; Sarmento, Eduardo V.; Campos, Tarcisio P.R.
2011-01-01
Since earlier of 1960, one of the most significant contributions of radiation biology has been the theory of cell killing as a function of increasing doses of a cytotoxic agent, as well as the demonstration of repair of sublethal or potentially lethal damage after irradiation. The impact of cellular and molecular radiobiology, by exploitation of cellular mechanisms related to apoptosis, may be the cell killing with irradiation by including changes other than unrepaired DNA damage. Based on the understanding of the tumor microenvironment and how growth factors and proteins produced by irradiated cells may alter cellular processes, improved combined-modality strategies may emerge. This effect was show since 1960's, but here we propose to demonstrate this phenomenon in Brachytherapy. The present goal is to verify the macroscopic response through the production and analysis of clonogenic control based on halos generation by radioactive seeds of Ho-165 and Sm-153, aiming to study the effect of this type of irradiation. Confluent cell culture flasks with HeLa cell line were subjected to radiation in a period up to five half-lives of radionuclide, respectively. Devices were introduced which set the polymer-ceramic Ho-165 and Sm-153 seeds in the vials. After a period of exposure, the flasks were stained with violet Gensiana. The results showed the formation of halos control of confluent cancer cells. This paper will describe these experiments in the current stage of the research and report the implications of this new way of therapy for cancer treatment. (author)
Remarks on the spherical scalar field halo in galaxies
International Nuclear Information System (INIS)
Nandi, Kamal K.; Valitov, Ildar; Migranov, Nail G.
2009-01-01
Matos, Guzman, and Nunez proposed a model for the galactic halo within the framework of scalar field theory. We argue that an analysis involving the full metric can reveal the true physical nature of the halo only when a certain condition is maintained. We fix that condition and also calculate its impact on observable parameters of the model.
Double folding model analysis of elastic scattering of halo nucleus ...
Indian Academy of Sciences (India)
carried out which provide valuable insight for improving our understanding of nuclear reactions. One of the interesting aspects is to understand the effect of the halo structure, on elastic scattering cross-sections at near-Coulomb barrier energies in reactions induced by neutron halo nuclei and weakly bound radioactive ...
The prolate dark matter halo of the Andromeda galaxy
Energy Technology Data Exchange (ETDEWEB)
Hayashi, Kohei; Chiba, Masashi, E-mail: k.hayasi@astr.tohoku.ac.jp, E-mail: chiba@astr.tohoku.ac.jp [Astronomical Institute, Tohoku University, Aoba-ku, Sendai 980-8578 (Japan)
2014-07-01
We present new limits on the global shape of the dark matter halo in the Andromeda galaxy using and generalizing non-spherical mass models developed by Hayashi and Chiba and compare our results with theoretical predictions of cold dark matter (CDM) models. This is motivated by the fact that CDM models predict non-spherical virialized dark halos, which reflect the process of mass assembly in the galactic scale. Applying our models to the latest kinematic data of globular clusters and dwarf spheroidal galaxies in the Andromeda halo, we find that the most plausible cases for Andromeda yield a prolate shape for its dark halo, irrespective of assumed density profiles. We also find that this prolate dark halo in Andromeda is consistent with theoretical predictions in which the satellites are distributed anisotropically and preferentially located along major axes of their host halos. It is a reflection of the intimate connection between galactic dark matter halos and the cosmic web. Therefore, our result is profound in understanding internal dynamics of halo tracers in Andromeda, such as orbital evolutions of tidal stellar streams, which play important roles in extracting the abundance of CDM subhalos through their dynamical effects on stream structures.
Characteristics of halo current in JT-60U
International Nuclear Information System (INIS)
Neyatani, Y.; Nakamura, Y.; Yoshino, R.; Hatae, T.
1999-01-01
Halo currents and their toroidal peaking factor (TPF) have been measured in JT-60U by Rogowski coil type halo current sensors. The electron temperature in the halo region was around 10 eV at 1 ms before the timing of the maximum halo current. The maximum TPF*I h /I p0 was 0.52 in the operational range of I p = 0.7 ∼ 1.8 MA, B T = 2.2 ∼ 3.5 T, including ITER design parameters of κ > 1.6 and q 95 = 3, which was lower than that of the maximum value of ITER data base (0.75). The magnitude of halo currents tended to decrease with the increase in stored energy just before the energy quench and with the line integrated electron density at the time of the maximum halo current. A termination technique in which the current channel remains stationary was useful to avoid halo current generation. Intense neon gas puffing during the VDE was effective for reducing the halo currents. (author)
Characteristics of halo current in JT-60U
International Nuclear Information System (INIS)
Neyatani, Y.; Nakamura, Y.; Yoshino, R.; Hatae, T.
2001-01-01
Halo currents and their toroidal peaking factor (TPF) have been measured in JT-60U by Rogowski coil type halo current sensors. The electron temperature in the halo region was around 10 eV at 1 ms before the timing of the maximum halo current. The maximum TPF *I h /I p0 was 0.52 in the operational range of I p =0.7∼1.8MA, B T =2.2∼3.5T, including ITER design parameters of κ>1.6 and q 95 =3, which was lower than that of the maximum value of ITER data base (0.75). The magnitude of halo currents tended to decrease with the increase in stored energy just before the energy quench and with the line integrated electron density at the time of the maximum halo current. A termination technique in which the current channel remains stationary was useful to avoid halo current generation. Intense neon gas puffing during the VDE was effective for reducing the halo currents. (author)
A two-point correlation function for Galactic halo stars
Cooper, A. P.; Cole, S.; Frenk, C. S.; Helmi, A.
2011-01-01
We describe a correlation function statistic that quantifies the amount of spatial and kinematic substructure in the stellar halo. We test this statistic using model stellar halo realizations constructed from the Aquarius suite of six high-resolution cosmological N-body simulations, in combination
The edges of dark matter halos: theory and observations
More, Surhud
2017-01-01
I discuss recent theoretical advances which have led us to suggest a physical definition for the boundary of dark matter halos. We propose using the "splashback radius" which corresponds to the apocenter of recently infalling material as a physical boundary for dark matter halos. We also present how the splashback radius can be detected in observations.
The Edges Of Dark Matter Halos: Theory And Observations
More, Surhud
2017-06-01
I discuss recent theoretical advances which have led us to suggest a physical definition for the boundary of dark matter halos. We propose using the "splashback radius" which corresponds to the apocenter of recently infalling material as a physical boundary for dark matter halos. We also present how the splashback radius can be detected in observations.
The f ( R ) halo mass function in the cosmic web
Energy Technology Data Exchange (ETDEWEB)
Braun-Bates, F. von; Winther, H.A.; Alonso, D.; Devriendt, J., E-mail: francesca.vonbraun-bates@physics.ox.ac.uk, E-mail: hans.a.winther@physics.ox.ac.uk, E-mail: david.alonso@physics.ox.ac.uk, E-mail: julien.devriendt@physics.ox.ac.uk [Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom)
2017-03-01
An important indicator of modified gravity is the effect of the local environment on halo properties. This paper examines the influence of the local tidal structure on the halo mass function, the halo orientation, spin and the concentration-mass relation. We use the excursion set formalism to produce a halo mass function conditional on large-scale structure. Our simple model agrees well with simulations on large scales at which the density field is linear or weakly non-linear. Beyond this, our principal result is that f ( R ) does affect halo abundances, the halo spin parameter and the concentration-mass relationship in an environment-independent way, whereas we find no appreciable deviation from \\text(ΛCDM) for the mass function with fixed environment density, nor the alignment of the orientation and spin vectors of the halo to the eigenvectors of the local cosmic web. There is a general trend for greater deviation from \\text(ΛCDM) in underdense environments and for high-mass haloes, as expected from chameleon screening.
The prolate dark matter halo of the Andromeda galaxy
International Nuclear Information System (INIS)
Hayashi, Kohei; Chiba, Masashi
2014-01-01
We present new limits on the global shape of the dark matter halo in the Andromeda galaxy using and generalizing non-spherical mass models developed by Hayashi and Chiba and compare our results with theoretical predictions of cold dark matter (CDM) models. This is motivated by the fact that CDM models predict non-spherical virialized dark halos, which reflect the process of mass assembly in the galactic scale. Applying our models to the latest kinematic data of globular clusters and dwarf spheroidal galaxies in the Andromeda halo, we find that the most plausible cases for Andromeda yield a prolate shape for its dark halo, irrespective of assumed density profiles. We also find that this prolate dark halo in Andromeda is consistent with theoretical predictions in which the satellites are distributed anisotropically and preferentially located along major axes of their host halos. It is a reflection of the intimate connection between galactic dark matter halos and the cosmic web. Therefore, our result is profound in understanding internal dynamics of halo tracers in Andromeda, such as orbital evolutions of tidal stellar streams, which play important roles in extracting the abundance of CDM subhalos through their dynamical effects on stream structures.
Influence of halo doping profiles on MOS transistor mismatch
Andricciola, P.; Tuinhout, H.
2009-01-01
Halo implants are used in modern CMOS technology to reduce the short channel effect. However, the lateral non-uniformity of the channel doping has been proven to degenerate the mismatch performance. With this paper we want to discuss the influence of the halo profile on MOS transistor mismatch. The
Evolution of velocity dispersion along cold collisionless flows
International Nuclear Information System (INIS)
Banik, Nilanjan; Sikivie, Pierre
2016-01-01
We found that the infall of cold dark matter onto a galaxy produces cold collisionless flows and caustics in its halo. If a signal is found in the cavity detector of dark matter axions, the flows will be readily apparent as peaks in the energy spectrum of photons from axion conversion, allowing the densities, velocity vectors and velocity dispersions of the flows to be determined. We also discuss the evolution of velocity dispersion along cold collisionless flows in one and two dimensions. A technique is presented for obtaining the leading behaviour of the velocity dispersion near caustics. The results are used to derive an upper limit on the energy dispersion of the Big Flow from the sharpness of its nearby caustic, and a prediction for the dispersions in its velocity components
Chaudhury, Soumini; Bhattacharjee, Pijushpani; Cowsik, Ramanath
2010-09-01
Direct detection of Weakly Interacting Massive Particle (WIMP) candidates of Dark Matter (DM) is studied within the context of a self-consistent truncated isothermal model of the finite-size dark halo of the Galaxy. The halo model, based on the ``King model'' of the phase space distribution function of collisionless DM particles, takes into account the modifications of the phase-space structure of the halo due to the gravitational influence of the observed visible matter in a self-consistent manner. The parameters of the halo model are determined by a fit to a recently determined circular rotation curve of the Galaxy that extends up to ~ 60 kpc. Unlike in the Standard Halo Model (SHM) customarily used in the analysis of the results of WIMP direct detection experiments, the velocity distribution of the WIMPs in our model is non-Maxwellian with a cut-off at a maximum velocity that is self-consistently determined by the model itself. For our halo model that provides the best fit to the rotation curve data, the 90% C.L. upper limit on the WIMP-nucleon spin-independent cross section from the recent results of the CDMS-II experiment, for example, is ~ 5.3 × 10-8 pb at a WIMP mass of ~ 71 GeV. We also find, using the original 2-bin annual modulation amplitude data on the nuclear recoil event rate seen in the DAMA experiment, that there exists a range of small WIMP masses, typically ~ 2-16 GeV, within which DAMA collaboration's claimed annual modulation signal purportedly due to WIMPs is compatible with the null results of other experiments. These results, based as they are on a self-consistent model of the dark matter halo of the Galaxy, strengthen the possibility of low-mass (lsim10 GeV) WIMPs as a candidate for dark matter as indicated by several earlier studies performed within the context of the SHM. A more rigorous analysis using DAMA bins over smaller intervals should be able to better constrain the ``DAMA regions'' in the WIMP parameter space within the context of
Bimodal Formation Time Distribution for Infall Dark Matter Halos
Shi, Jingjing; Wang, Huiyuan; Mo, H. J.; Xie, Lizhi; Wang, Xiaoyu; Lapi, Andrea; Sheth, Ravi K.
2018-04-01
We use a 200 {h}-1 {Mpc} a-side N-body simulation to study the mass accretion history (MAH) of dark matter halos to be accreted by larger halos, which we call infall halos. We define a quantity {a}nf}\\equiv (1+{z}{{f}})/(1+{z}peak}) to characterize the MAH of infall halos, where {z}peak} and {z}{{f}} are the accretion and formation redshifts, respectively. We find that, at given {z}peak}, their MAH is bimodal. Infall halos are dominated by a young population at high redshift and by an old population at low redshift. For the young population, the {a}nf} distribution is narrow and peaks at about 1.2, independent of {z}peak}, while for the old population, the peak position and width of the {a}nf} distribution both increase with decreasing {z}peak} and are both larger than those of the young population. This bimodal distribution is found to be closely connected to the two phases in the MAHs of halos. While members of the young population are still in the fast accretion phase at z peak, those of the old population have already entered the slow accretion phase at {z}peak}. This bimodal distribution is not found for the whole halo population, nor is it seen in halo merger trees generated with the extended Press–Schechter formalism. The infall halo population at {z}peak} are, on average, younger than the whole halo population of similar masses identified at the same redshift. We discuss the implications of our findings in connection to the bimodal color distribution of observed galaxies and to the link between central and satellite galaxies.
What sets the central structure of dark matter haloes?
Ogiya, Go; Hahn, Oliver
2018-02-01
Dark matter (DM) haloes forming near the thermal cut-off scale of the density perturbations are unique, since they are the smallest objects and form through monolithic gravitational collapse, while larger haloes contrastingly have experienced mergers. While standard cold dark matter (CDM) simulations readily produce haloes that follow the universal Navarro-Frenk-White (NFW) density profile with an inner slope, ρ ∝ r-α, with α = 1, recent simulations have found that when the free-streaming cut-off expected for the CDM model is resolved, the resulting haloes follow nearly power-law density profiles of α ∼ 1.5. In this paper, we study the formation of density cusps in haloes using idealized N-body simulations of the collapse of proto-haloes. When the proto-halo profile is initially cored due to particle free-streaming at high redshift, we universally find ∼r-1.5 profiles irrespective of the proto-halo profile slope outside the core and large-scale non-spherical perturbations. Quite in contrast, when the proto-halo has a power-law profile, then we obtain profiles compatible with the NFW shape when the density slope of the proto-halo patch is shallower than a critical value, αini ∼ 0.3, while the final slope can be steeper for αini ≳ 0.3. We further demonstrate that the r-1.5 profiles are sensitive to small-scale noise, which gradually drives them towards an inner slope of -1, where they become resilient to such perturbations. We demonstrate that the r-1.5 solutions are in hydrostatic equilibrium, largely consistent with a simple analytic model, and provide arguments that angular momentum appears to determine the inner slope.
Comparison of Intra-cluster and M87 Halo Orphan Globular Clusters in the Virgo Cluster
Louie, Tiffany Kaye; Tuan, Jin Zong; Martellini, Adhara; Guhathakurta, Puragra; Toloba, Elisa; Peng, Eric; Longobardi, Alessia; Lim, Sungsoon
2018-01-01
We present a study of “orphan” globular clusters (GCs) — GCs with no identifiable nearby host galaxy — discovered in NGVS, a 104 deg2 CFHT/MegaCam imaging survey. At the distance of the Virgo cluster, GCs are bright enough to make good spectroscopic targets and many are barely resolved in good ground-based seeing. Our orphan GC sample is derived from a subset of NGVS-selected GC candidates that were followed up with Keck/DEIMOS spectroscopy. While our primary spectroscopic targets were candidate GC satellites of Virgo dwarf elliptical and ultra-diffuse galaxies, many objects turned out to be non-satellites based on a radial velocity mismatch with the Virgo galaxy they are projected close to. Using a combination of spectral characteristics (e.g., absorption vs. emission), Gaussian mixture modeling of radial velocity and positions, and extreme deconvolution analysis of ugrizk photometry and image morphology, these non-satellites were classified into: (1) intra-cluster GCs (ICGCs) in the Virgo cluster, (2) GCs in the outer halo of M87, (3) foreground Milky Way stars, and (4) background galaxies. The statistical distinction between ICGCs and M87 halo GCs is based on velocity distributions (mean of 1100 vs. 1300 km/s and dispersions of 700 vs. 400 km/s, respectively) and radial distribution (diffuse vs. centrally concentrated, respectively). We used coaddition to increase the spectral SNR for the two classes of orphan GCs and measured the equivalent widths (EWs) of the Mg b and H-beta absorption lines. These EWs were compared to single stellar population models to obtain mean age and metallicity estimates. The ICGCs and M87 halo GCs have = –0.6+/–0.3 and –0.4+/–0.3 dex, respectively, and mean ages of >~ 5 and >~ 10 Gyr, respectively. This suggests the M87 halo GCs formed in relatively high-mass galaxies that avoided being tidally disrupted by M87 until they were close to the cluster center, while IGCCs formed in relatively low-mass galaxies that were
Directory of Open Access Journals (Sweden)
Kadaj Roman
2016-12-01
Full Text Available The adjustment problem of the so-called combined (hybrid, integrated network created with GNSS vectors and terrestrial observations has been the subject of many theoretical and applied works. The network adjustment in various mathematical spaces was considered: in the Cartesian geocentric system on a reference ellipsoid and on a mapping plane. For practical reasons, it often takes a geodetic coordinate system associated with the reference ellipsoid. In this case, the Cartesian GNSS vectors are converted, for example, into geodesic parameters (azimuth and length on the ellipsoid, but the simple form of converted pseudo-observations are the direct differences of the geodetic coordinates. Unfortunately, such an approach may be essentially distorted by a systematic error resulting from the position error of the GNSS vector, before its projection on the ellipsoid surface. In this paper, an analysis of the impact of this error on the determined measures of geometric ellipsoid elements, including the differences of geodetic coordinates or geodesic parameters is presented. Assuming that the adjustment of a combined network on the ellipsoid shows that the optimal functional approach in relation to the satellite observation, is to create the observational equations directly for the original GNSS Cartesian vector components, writing them directly as a function of the geodetic coordinates (in numerical applications, we use the linearized forms of observational equations with explicitly specified coefficients. While retaining the original character of the Cartesian vector, one avoids any systematic errors that may occur in the conversion of the original GNSS vectors to ellipsoid elements, for example the vector of the geodesic parameters. The problem is theoretically developed and numerically tested. An example of the adjustment of a subnet loaded from the database of reference stations of the ASG-EUPOS system was considered for the preferred functional
Novel design for centrifugal counter-current chromatography: VI. Ellipsoid column.
Gu, Dongyu; Yang, Yi; Xin, Xuelei; Aisa, Haji Akber; Ito, Yoichiro
2015-01-01
A novel ellipsoid column was designed for centrifugal counter-current chromatography. Performance of the ellipsoid column with a capacity of 3.4 mL was examined with three different solvent systems composed of 1-butanol-acetic acid-water (4:1:5, v/v) (BAW), hexane-ethyl acetate-methanol-0.1 M HCl (1:1:1:1, v/v) (HEMH), and 12.5% (w/w) PEG1000 and 12.5% (w/w) dibasic potassium phosphate in water (PEG-DPP) each with suitable test samples. In dipeptide separation with BAW system, both stationary phase retention (Sf) and peak resolution (Rs) of the ellipsoid column were much higher at 0° column angle (column axis parallel to the centrifugal force) than at 90° column angle (column axis perpendicular to the centrifugal force), where elution with the lower phase at a low flow rate produced the best separation yielding Rs at 2.02 with 27.8% Sf at a flow rate of 0.07 ml/min. In the DNP-amino acid separation with HEMW system, the best results were obtained at a flow rate of 0.05 ml/min with 31.6% Sf yielding high Rs values at 2.16 between DNP-DL-glu and DNP-β-ala peaks and 1.81 between DNP-β-ala and DNP-L-ala peaks. In protein separation with PEG-DPP system, lysozyme and myolobin were resolved at Rs of 1.08 at a flow rate of 0.03 ml/min with 38.9% Sf. Most of those Rs values exceed those obtained from the figure-8 column under similar experimental conditions previously reported.
Self-consistent imbedding and the ellipsoidal model model for porous rocks
International Nuclear Information System (INIS)
Korringa, J.; Brown, R.J.S.; Thompson, D.D.; Runge, R.J.
1979-01-01
Equations are obtained for the effective elastic moduli for a model of an isotropic, heterogeneous, porous medium. The mathematical model used for computation is abstract in that it is not simply a rigorous computation for a composite medium of some idealized geometry, although the computation contains individual steps which are just that. Both the solid part and pore space are represented by ellipsoidal or spherical 'grains' or 'pores' of various sizes and shapes. The strain of each grain, caused by external forces applied to the medium, is calculated in a self-consistent imbedding (SCI) approximation, which replaces the true surrounding of any given grain or pore by an isotropic medium defined by the effective moduli to be computed. The ellipsoidal nature of the shapes allows us to use Eshelby's theoretical treatment of a single ellipsoidal inclusion in an infiinte homogeneous medium. Results are compared with the literature, and discrepancies are found with all published accounts of this problem. Deviations from the work of Wu, of Walsh, and of O'Connell and Budiansky are attributed to a substitution made by these authors which though an identity for the exact quantities involved, is only approximate in the SCI calculation. This reduces the validity of the equations to first-order effects only. Differences with the results of Kuster and Toksoez are attributed to the fact that the computation of these authors is not self-consistent in the sense used here. A result seems to be the stiffening of the medium as if the pores are held apart. For spherical grains and pores, their calculated moduli are those given by the Hashin-Shtrikman upper bounds. Our calculation reproduces, in the case of spheres, an early result of Budiansky. An additional feature of our work is that the algebra is simpler than in earlier work. We also incorporate into the theory the possibility that fluid-filled pores are interconnected
Effects of deformations and orientations on neutron-halo structure of light-halo nuclei
International Nuclear Information System (INIS)
Sawhney, Gudveen; Gupta, Raj K.; Sharma, Manoj K.
2013-01-01
The availability of radioactive nuclear beams have enabled to study the structure of nuclei far from the stability line, which in turn led to the discovery of neutron-halo nuclei. These nuclei, located near the neutron drip-line exhibit a high probability of presence of one or two loosely bound neutrons at a large distance from the rest of nucleons. The fragmentation behavior is studied for 13 cases of 1n-halo nuclei, which include 11 Be, 14 B, 15 C, 17 C, 19 C, 22 N, 22 O, 23 O, 24 O, 24 F, 26 F, 29 Ne and 31 Ne, using the cluster-core model (CCM) extended to include the deformations and orientations of nuclei
[Halos and multifocal intraocular lenses: origin and interpretation].
Alba-Bueno, F; Vega, F; Millán, M S
2014-10-01
To present the theoretical and experimental characterization of the halo in multifocal intraocular lenses (MIOL). The origin of the halo in a MIOL is the overlaying of 2 or more images. Using geometrical optics, it can be demonstrated that the diameter of each halo depends on the addition of the lens (ΔP), the base power (P(d)), and the diameter of the IOL that contributes to the «non-focused» focus. In the image plane that corresponds to the distance focus, the halo diameter (δH(d)) is given by: δH(d)=d(pn) ΔP/P(d), where d(pn) is the diameter of the IOL that contributes to the near focus. Analogously, in the near image plane the halo diameter (δH(n)) is: δH(n)=d(pd) ΔP/P(d), where d(pd) is the diameter of the IOL that contributes to the distance focus. Patients perceive halos when they see bright objects over a relatively dark background. In vitro, the halo can be characterized by analyzing the intensity profile of the image of a pinhole that is focused by each of the foci of a MIOL. A comparison has been made between the halos induced by different MIOL of the same base power (20D) in an optical bench. As predicted by theory, the larger the addition of the MIOL, the larger the halo diameter. For large pupils and with MIOL with similar aspheric designs and addition (SN6AD3 vs ZMA00), the apodized MIOL has a smaller halo diameter than a non-apodized one in distance vision, while in near vision the size is very similar, but the relative intensity is higher in the apodized MIOL. When comparing lenses with the same diffractive design, but with different spherical-aspheric base design (SN60D3 vs SN6AD3), the halo in distance vision of the spherical MIOL is larger, while in near vision the spherical IOL induces a smaller halo, but with higher intensity due to the spherical aberration of the distance focus in the near image. In the case of a trifocal-diffractive IOL (AT LISA 839MP) the most noticeable characteristic is the double-halo formation due to the 2 non
Towards high resolution polarisation analysis using double polarisation and ellipsoidal analysers
Martin-Y-Marero, D
2002-01-01
Classical polarisation analysis methods lack the combination of high resolution and high count rate necessary to cope with the demand of modern condensed-matter experiments. In this work, we present a method to achieve high resolution polarisation analysis based on a double polarisation system. Coupling this method with an ellipsoidal wavelength analyser, a high count rate can be achieved whilst delivering a resolution of around 10 mu eV. This method is ideally suited to pulsed sources, although it can be adapted to continuous sources as well. (orig.)
Three-dimensional nonstationary dynamics of a charged bunches-ellipsoids
International Nuclear Information System (INIS)
Budanov, Yu.A.
2000-01-01
The work is aimed at studying the changes in the beam dynamics at the beginning of acceleration, when the zero longitudinal emittance is transformed into the final longitudinal phase volume. This process is studied on the bunch-ellipsoid self-consistent model with the charge uniform distribution. The results obtained present the evaluation of the parameters, whereby the longitudinal dynamics in the bunch significantly changes, namely, the particles bunch with increase in the spatial charge transfers into a new state with doubled frequency of the longitudinal oscillations [ru
Shape matters: Near-field fluid mechanics dominate the collective motions of ellipsoidal squirmers.
Kyoya, K; Matsunaga, D; Imai, Y; Omori, T; Ishikawa, T
2015-12-01
Microswimmers show a variety of collective motions. Despite extensive study, questions remain regarding the role of near-field fluid mechanics in collective motion. In this paper, we describe precisely the Stokes flow around hydrodynamically interacting ellipsoidal squirmers in a monolayer suspension. The results showed that various collective motions, such as ordering, aggregation, and whirls, are dominated by the swimming mode and the aspect ratio. The collective motions are mainly induced by near-field fluid mechanics, despite Stokes flow propagation over a long range. These results emphasize the importance of particle shape in collective motion.
OR TEP-II: a FORTRAN Thermal-Ellipsoid Plot Program for crystal structure illustrations
International Nuclear Information System (INIS)
Johnson, C.K.
1976-03-01
A computer program is described for drawing crystal structure illustrations using a mechanical plotter. Ball-and-stick type illustrations of a quality suitable for publication are produced with either spheres or thermal-motion probability ellipsoids on the atomic sites. The program can produce stereoscopic pairs of illustrations which aid in the visualization of complex packing arrangements of atoms and thermal motion patterns. Interatomic distances, bond angles, and principal axes of thermal motion are also calculated to aid the structural study. The most recent version of the program, OR TEP-II, has a hidden-line-elimination feature to omit those portions of atoms or bonds behind other atoms or bonds
Ellipsoidal diffraction grating as output coupler for quasi-optical gyrotrons
International Nuclear Information System (INIS)
Hogge, J.P.; Cao, H.; Tran, T.M.; Tran, M.Q.; Paris, P.J.; Kasparek, W.
1991-01-01
The use of a diffraction grating arranged in the -1 Littrow mount as an output coupler for a quasi-optical Fabry-Perot resonator at microwave frequencies (100 GHz) was suggested in 1990. A planar grating with curvilinear grooves (in order to match the Littrow condition everywhere on the surface for a given Gaussian beam) gives a power coupling efficiency of 85% which is limited by the depolarization but gave approximately the same global efficiency because of distortion. We report low power tests on an improvement of the second scheme, based on curved grooves on an ellipsoidal surface, which gives a global efficiency of 94%. (author) 3 figs., 3 refs
OR TEP-II: a FORTRAN Thermal-Ellipsoid Plot Program for crystal structure illustrations
Energy Technology Data Exchange (ETDEWEB)
Johnson, C.K.
1976-03-01
A computer program is described for drawing crystal structure illustrations using a mechanical plotter. Ball-and-stick type illustrations of a quality suitable for publication are produced with either spheres or thermal-motion probability ellipsoids on the atomic sites. The program can produce stereoscopic pairs of illustrations which aid in the visualization of complex packing arrangements of atoms and thermal motion patterns. Interatomic distances, bond angles, and principal axes of thermal motion are also calculated to aid the structural study. The most recent version of the program, OR TEP-II, has a hidden-line-elimination feature to omit those portions of atoms or bonds behind other atoms or bonds.
THE OVERDENSITY AND MASSES OF THE FRIENDS-OF-FRIENDS HALOS AND UNIVERSALITY OF HALO MASS FUNCTION
International Nuclear Information System (INIS)
More, Surhud; Kravtsov, Andrey V.; Dalal, Neal; Gottloeber, Stefan
2011-01-01
The friends-of-friends algorithm (hereafter FOF) is a percolation algorithm which is routinely used to identify dark matter halos from N-body simulations. We use results from percolation theory to show that the boundary of FOF halos does not correspond to a single density threshold but to a range of densities close to a critical value that depends upon the linking length parameter, b. We show that for the commonly used choice of b = 0.2, this critical density is equal to 81.62 times the mean matter density. Consequently, halos identified by the FOF algorithm enclose an average overdensity which depends on their density profile (concentration) and therefore changes with halo mass, contrary to the popular belief that the average overdensity is ∼180. We derive an analytical expression for the overdensity as a function of the linking length parameter b and the concentration of the halo. Results of tests carried out using simulated and actual FOF halos identified in cosmological simulations show excellent agreement with our analytical prediction. We also find that the mass of the halo that the FOF algorithm selects crucially depends upon mass resolution. We find a percolation-theory-motivated formula that is able to accurately correct for the dependence on number of particles for the mock realizations of spherical and triaxial Navarro-Frenk-White halos. However, we show that this correction breaks down when applied to the real cosmological FOF halos due to the presence of substructures. Given that abundance of substructure depends on redshift and cosmology, we expect that the resolution effects due to substructure on the FOF mass and halo mass function will also depend on redshift and cosmology and will be difficult to correct for in general. Finally, we discuss the implications of our results for the universality of the mass function.
Metal enriched gaseous halos around distant radio galaxies: Clues to feedback in galaxy formation
Energy Technology Data Exchange (ETDEWEB)
Reuland, M; van Breugel, W; de Vries, W; Dopita, A; Dey, A; Miley, G; Rottgering, H; Venemans, B; Stanford, S A; Lacy, M; Spinrad, H; Dawson, S; Stern, D; Bunker, A
2006-08-01
We present the results of an optical and near-IR spectroscopic study of giant nebular emission line halos associated with three z > 3 radio galaxies, 4C 41.17, 4C 60.07 and B2 0902+34. Previous deep narrow band Ly{alpha} imaging had revealed complex morphologies with sizes up to 100 kpc, possibly connected to outflows and AGN feedback from the central regions. The outer regions of these halos show quiet kinematics with typical velocity dispersions of a few hundred km s{sup -1}, and velocity shears that can mostly be interpreted as being due to rotation. The inner regions show shocked cocoons of gas closely associated with the radio lobes. These display disturbed kinematics and have expansion velocities and/or velocity dispersions >1000 km s{sup -1}. The core region is chemically evolved, and we also find spectroscopic evidence for the ejection of enriched material in 4C 41.17 up to a distance of {approx} 60 kpc along the radio-axis. The dynamical structures traced in the Ly{alpha} line are, in most cases, closely echoed in the Carbon and Oxygen lines. This shows that the Ly{alpha} line is produced in a highly clumped medium of small filling factor, and can therefore be used as a tracer of the dynamics of HzRGs. We conclude that these HzRGs are undergoing a final jet-induced phase of star formation with ejection of most of their interstellar medium before becoming 'red and dead' Elliptical galaxies.
DARK MATTER SUB-HALO COUNTS VIA STAR STREAM CROSSINGS
International Nuclear Information System (INIS)
Carlberg, R. G.
2012-01-01
Dark matter sub-halos create gaps in the stellar streams orbiting in the halos of galaxies. We evaluate the sub-halo stream crossing integral with the guidance of simulations to find that the linear rate of gap creation, R U , in a typical cold dark matter (CDM) galactic halo at 100 kpc is R U ≅0.0066 M-hat 8 -0.35 kpc -1 Gyr -1 , where M-hat 8 (≡ M-hat /10 8 M ☉ ) is the minimum mass halo that creates a visible gap. The relation can be recast entirely in terms of observables, as R U ≅0.059w -0.85 kpc -1 Gyr -1 , for w in kpc, normalized at 100 kpc. Using published data, the density of gaps is estimated for M31's NW stream and the Milky Way Pal 5 stream, Orphan stream, and Eastern Banded Structure. The estimated rates of gap creation all have errors of 50% or more due to uncertain dynamical ages and the relatively noisy stream density measurements. The gap-rate-width data are in good agreement with the CDM-predicted relation. The high density of gaps in the narrow streams requires a total halo population of 10 5 sub-halos above a minimum mass of 10 5 M ☉ .
Historic halo displays as weather indicator: Criteria and examples
Neuhäuser, Dagmar L.; Neuhäuser, Ralph
2016-04-01
There are numerous celestial signs reported in historic records, many of them refer to atmospheric ("sub-lunar") phenomena, such as ice halos and aurorae. In an interdisciplinary collaboration between astrophysics and cultural astronomy, we noticed that celestial observations including meteorological phenomena are often misinterpreted, mostly due to missing genuine criteria: especially ice crystal halos were recorded frequently in past centuries for religious reasons, but are mistaken nowadays often for other phenomena like aurorae. Ice halo displays yield clear information on humidity and temperature in certain atmospheric layers, and thereby indicate certain weather patterns. Ancient so-called rain makers used halo observations for weather forecast; e.g., a connection between certain halo displays and rain a few day later is statistically significant. Ice halos exist around sun and moon and are reported for both (they can stay for several days): many near, middle, and far eastern records from day- and night-time include such observations with high frequency. (Partly based on publications on halos by D.L. Neuhäuser & R. Neuhäuser, available at http://www.astro.uni-jena.de/index.php/terra-astronomy.html)
International Nuclear Information System (INIS)
Bardhan, Jaydeep P; Knepley, Matthew G
2012-01-01
We present two open-source (BSD) implementations of ellipsoidal harmonic expansions for solving problems of potential theory using separation of variables. Ellipsoidal harmonics are used surprisingly infrequently, considering their substantial value for problems ranging in scale from molecules to the entire solar system. In this paper, we suggest two possible reasons for the paucity relative to spherical harmonics. The first is essentially historical—ellipsoidal harmonics developed during the late 19th century and early 20th, when it was found that only the lowest-order harmonics are expressible in closed form. Each higher-order term requires the solution of an eigenvalue problem, and tedious manual computation seems to have discouraged applications and theoretical studies. The second explanation is practical: even with modern computers and accurate eigenvalue algorithms, expansions in ellipsoidal harmonics are significantly more challenging to compute than those in Cartesian or spherical coordinates. The present implementations reduce the 'barrier to entry' by providing an easy and free way for the community to begin using ellipsoidal harmonics in actual research. We demonstrate our implementation using the specific and physiologically crucial problem of how charged proteins interact with their environment, and ask: what other analytical tools await re-discovery in an era of inexpensive computation?
Chemical Cartography. I. A Carbonicity Map of the Galactic Halo
Energy Technology Data Exchange (ETDEWEB)
Lee, Young Sun; Kim, Young Kwang [Department of Astronomy and Space Science, Chungnam National University, Daejeon 34134 (Korea, Republic of); Beers, Timothy C.; Placco, Vinicius; Yoon, Jinmi [Department of Physics and JINA Center for the Evolution of the Elements, University of Notre Dame, Notre Dame, IN 46556 (United States); Carollo, Daniela [Research School of Astronomy and Astrophysics, The Australian National University, Canberra, ACT 2611 (Australia); Masseron, Thomas [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Jung, Jaehun, E-mail: youngsun@cnu.ac.kr [Department of Astronomy, Space Science, and Geology, Chungnam National University, Daejeon 34134 (Korea, Republic of)
2017-02-10
We present the first map of carbonicity, [C/Fe], for the halo system of the Milky Way, based on a sample of over 100,000 main-sequence turnoff stars with available spectroscopy from the Sloan Digital Sky Survey. This map, which explores distances up to 15 kpc from the Sun, reveals clear evidence for the dual nature of the Galactic halo, based on the spatial distribution of stellar carbonicity. The metallicity distribution functions of stars in the inner- and outer-halo regions of the carbonicity map reproduce those previously argued to arise from contributions of the inner- and outer-halo populations, with peaks at [Fe/H] = −1.5 and −2.2, respectively. From consideration of the absolute carbon abundances for our sample, A (C), we also confirm that the carbon-enhanced metal-poor (CEMP) stars in the outer-halo region exhibit a higher frequency of CEMP-no stars (those with no overabundances of heavy neutron-capture elements) than of CEMP- s stars (those with strong overabundances of elements associated with the s -process), whereas the stars in the inner-halo region exhibit a higher frequency of CEMP- s stars. We argue that the contrast in the behavior of the CEMP-no and CEMP- s fractions in these regions arises from differences in the mass distributions of the mini-halos from which the stars of the inner- and outer-halo populations formed, which gives rise in turn to the observed dichotomy of the Galactic halo.
Controlling beam halo-chaos via backstepping design
International Nuclear Information System (INIS)
Gao Yuan; Kong Feng
2008-01-01
A backstepping control method is proposed for controlling beam halo-chaos in the periodic focusing channels (PFCs) of high-current ion accelerator. The analysis and numerical results show that the method, via adjusting an exterior magnetic field, is effective to control beam halo chaos with five types of initial distribution ion beams, all statistical quantities of the beam halo-chaos are largely reduced, and the uniformity of ion beam is improved. This control method has an important value of application, for the exterior magnetic field can be easily adjusted in the periodical magnetic focusing channels in experiment
Is there a composition gradient in the halo
International Nuclear Information System (INIS)
Kraft, R.P.; Trefzger, C.F.; Suntzeff, N.
1979-01-01
In the inner halo (galactocentric distance R < approximately 8 kpc), the Basel RGU photometry should allow the derivation of the shapes and dimensions of the iso-abundance contours. For the outer halo to R approximately 30 kpc, the authors review techniques based on Δs-measurements of RR Lyraes (Lick) and intermediate band-pass photometry of globular-cluster giants (Searle and Zinn, Palomar). Both methods suggest little change in mean [Fe/H] between 10 and 30 kpc; however, both may be biased against the discovery of very metal-poor objects. The conclusion that the outer halo has no abundance gradient may be somewhat premature. (Auth.)
Equidistant map projections of a triaxial ellipsoid with the use of reduced coordinates
Directory of Open Access Journals (Sweden)
Pędzich Paweł
2017-12-01
Full Text Available The paper presents a new method of constructing equidistant map projections of a triaxial ellipsoid as a function of reduced coordinates. Equations for x and y coordinates are expressed with the use of the normal elliptic integral of the second kind and Jacobian elliptic functions. This solution allows to use common known and widely described in literature methods of solving such integrals and functions. The main advantage of this method is the fact that the calculations of x and y coordinates are practically based on a single algorithm that is required to solve the elliptic integral of the second kind. Equations are provided for three types of map projections: cylindrical, azimuthal and pseudocylindrical. These types of projections are often used in planetary cartography for presentation of entire and polar regions of extraterrestrial objects. The paper also contains equations for the calculation of the length of a meridian and a parallel of a triaxial ellipsoid in reduced coordinates. Moreover, graticules of three coordinates systems (planetographic, planetocentric and reduced in developed map projections are presented. The basic properties of developed map projections are also described. The obtained map projections may be applied in planetary cartography in order to create maps of extraterrestrial objects.
Exact reconstruction formula for the spherical mean Radon transform on ellipsoids
International Nuclear Information System (INIS)
Haltmeier, Markus
2014-01-01
Many modern imaging and remote sensing applications require reconstructing a function from spherical averages (mean values). Examples include photoacoustic tomography, ultrasound imaging or SONAR. Several formulas of the back-projection type for recovering a function in n spatial dimensions from mean values over spheres centered on a sphere have been derived by D Finch, S K Patch and Rakesh (2004 SIAM J. Math. Anal. 35 1213–1240) for odd spatial dimension and by D Finch, M Haltmeier and Rakesh (2007 SIAM J. Appl. Math. 68 392–412) for even spatial dimension. In this paper we generalize some of these formulas to the case where the centers of integration lie on the boundary of an arbitrary ellipsoid. For the special cases n = 2 and n = 3 our results have recently been established by Y Salman (2014 J. Math. Anal. Appl. 420 612–20). For the higher dimensional case n>3 we establish proof techniques extending the ones in the above references. Back-projection type inversion formulas for recovering a function from spherical means with centers on an ellipsoid have first been derived by F Natterer (2012 Inverse Problems Imaging 6 315–20) for n = 3 and by V Palamodov (2012 Inverse Problems 28 065014) for arbitrary dimension. The results of Natterer have later been generalized to arbitrary dimension by M Haltmeier (2014 SIAM J. Math. Anal. 46 214–32). Note that these formulas are different from the ones derived in the present paper. (paper)
International Nuclear Information System (INIS)
He Xiang; Tang Chunmei; Chen Jianping; Chen Yudong; Zeng Xiaojun; Zhang Yachun
2015-01-01
Some reports presented that the radar cross section (RCS) from the radar antenna of military airplanes can be reduced by using a low-temperature plasma screen. This paper gives a numerical and experimental analysis of this RCS-reduction method. The shape of the plasma screen was designed as a semi-ellipsoid in order to make full use of the space in the radar dome. In simulations, we discussed the scattering of the electromagnetic (EM) wave by a perfect electric conductor (PEC) covered with this plasma screen using the finite-difference-time-domain (FDTD) method. The variations of their return loss as a function of wave frequency, plasma density profile, and collision frequency were presented. In the experiments, a semi-ellipsoidal shaped plasma screen was produced. Electromagnetic attenuation of 1.5 GHz EM wave was measured for a radio frequency (RF) power of 5 kW at an argon pressure of 200-1150 Pa. A good agreement is found between simulated and experimental results. It can be confirmed that the plasma screen is useful in applications for stealth of radar antenna. (paper)
All-optical temporal fractional order differentiator using an in-fiber ellipsoidal air-microcavity
Zhang, Lihong; Sun, Shuqian; Li, Ming; Zhu, Ninghua
2017-12-01
An all-optical temporal fractional order differentiator with ultrabroad bandwidth (~1.6 THz) and extremely simple fabrication is proposed and experimentally demonstrated based on an in-fiber ellipsoidal air-microcavity. The ellipsoidal air-microcavity is fabricated by splicing a single mode fiber (SMF) and a photonic crystal fiber (PCF) together using a simple arc-discharging technology. By changing the arc-discharging times, the propagation loss can be adjusted and then the differentiation order is tuned. A nearly Gaussian-like optical pulse with 3 dB bandwidth of 8 nm is launched into the differentiator and a 0.65 order differentiation of the input pulse is achieved with a processing error of 2.55%. Project supported by the the National Natural Science Foundation of China (Nos. 61522509, 61377002, 61535012), the National High-Tech Research & Development Program of China (No. SS2015AA011002), and the Beijing Natural Science Foundation (No. 4152052). Ming Li was supported in part by the Thousand Young Talent Program.
Production of quasi ellipsoidal laser pulses for next generation high brightness photoinjectors
Energy Technology Data Exchange (ETDEWEB)
Rublack, T., E-mail: Tino.Rublack@desy.de [DESY, Zeuthen (Germany); Good, J.; Khojoyan, M.; Krasilnikov, M.; Stephan, F. [DESY, Zeuthen (Germany); Hartl, I.; Schreiber, S. [DESY, Hamburg (Germany); Andrianov, A.; Gacheva, E.; Khazanov, E.; Mironov, S.; Potemkin, A.; Zelenogorskii, V.V. [IAP/RAS, Nizhny Novgorod (Russian Federation); Syresin, E. [JINR, Dubna (Russian Federation)
2016-09-01
The use of high brightness electron beams in Free Electron Laser (FEL) applications is of increasing importance. One of the most promising methods to generate such beams is the usage of shaped photocathode laser pulses. It has already demonstrated that temporal and transverse flat-top laser pulses can produce very low emittance beams [1]. Nevertheless, based on beam simulations further improvements can be achieved using quasi-ellipsoidal laser pulses, e.g. 30% reduction in transverse projected emittance at 1 nC bunch charge. In a collaboration between DESY, the Institute of Applied Physics of the Russian Academy of Science (IAP RAS) in Nizhny Novgorod and the Joint Institute of Nuclear Research (JINR) in Dubna such a laser system capable of producing trains of laser pulses with a quasi-ellipsoidal distribution, has been developed. The prototype of the system was installed at the Photo Injector Test facility at DESY in Zeuthen (PITZ) and is currently in the commissioning phase. In the following, the laser system will be introduced, the procedure of pulse shaping will be described and the last experimental results will be shown.
Probability distribution of distance in a uniform ellipsoid: Theory and applications to physics
International Nuclear Information System (INIS)
Parry, Michelle; Fischbach, Ephraim
2000-01-01
A number of authors have previously found the probability P n (r) that two points uniformly distributed in an n-dimensional sphere are separated by a distance r. This result greatly facilitates the calculation of self-energies of spherically symmetric matter distributions interacting by means of an arbitrary radially symmetric two-body potential. We present here the analogous results for P 2 (r;ε) and P 3 (r;ε) which respectively describe an ellipse and an ellipsoid whose major and minor axes are 2a and 2b. It is shown that for ε=(1-b 2 /a 2 ) 1/2 ≤1, P 2 (r;ε) and P 3 (r;ε) can be obtained as an expansion in powers of ε, and our results are valid through order ε 4 . As an application of these results we calculate the Coulomb energy of an ellipsoidal nucleus, and compare our result to an earlier result quoted in the literature. (c) 2000 American Institute of Physics
Photoreceptor inner segment ellipsoid band integrity on spectral domain optical coherence tomography
Directory of Open Access Journals (Sweden)
Saxena S
2014-12-01
Full Text Available Sandeep Saxena,1 Khushboo Srivastav,1 Chui M Cheung,2 Joanne YW Ng,3 Timothy YY Lai3 1Retina Service, Department of Ophthalmology, King George’s Medical University Lucknow, India; 2Singapore National Eye Centre, Singapore; 3Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Kowloon, Hong Kong Abstract: Spectral domain optical coherence tomography cross-sectional imaging of the macula has conventionally been resolved into four bands. However, some doubts were raised regarding authentication of the existence of these bands. Recently, a number of studies have suggested that the second band appeared to originate from the inner segment ellipsoids of the foveal cone photoreceptors, and therefore the previously called inner segment-outer segment junction is now referred to as inner segment ellipsoidband. Photoreceptor dysfunction may be a significant predictor of visual acuity in a spectrum of surgical and medical retinal diseases. This review aims to provide an overview and summarizes the role of the photoreceptor inner segment ellipsoid band in the management and prognostication of various vitreoretinal diseases. Keywords: spectral domain optical coherence tomography, inner segment-outer segment junction, external limiting membrane, macular hole, diabetic macular edema, age relate macular degeneration
Design stresses in probabilistic form for ellipsoidal and toroidal pressure vessels
International Nuclear Information System (INIS)
Smith, C.O.
1979-01-01
Design has customarily been based on applied loading, geometry, and handbook values for strength to give a deterministic solution. The engineering profession, however, has become increasingly concerned with the adequacy of design calculations. This concern indicates a need for critical evaluation of designs based on arbitrary multipliers, such as factors of safety or worst-case treatment. Ellipsoids are frequently used for end closure of cylindrical pressure shells. Toroids of elliptic or circular cross-section, are widely used, e.g., for connecting two parallel legs in a U-shape. This paper gives equations for means and standard deviations of stresses developed in ellipsoids and toroids with internal pressure. Inherent are: (1) design variables are generally characterized by spectra of values (assumed to be normally distributed), rather than by unique values, and (2) a small, but finite, probability of failure must be recognized in any design. By coupling stresses due to applied loading as calculated by the given equations with strength available in a material, reliability (or the alternative probability of failure) can be calculated. Conversely, for a given reliability the appropriate size can be determined. (orig.)
Robe's Restricted Problem of 2 + 2 Bodies with a Roche Ellipsoid - Triaxial System
Aggarwal, Rajiv; Kaur, Bhavneet; Yadav, Sushil
2018-03-01
This paper investigates the motion of two infinitesimal masses on the location and stability of the equilibrium points in Robe's restricted problem of 2 + 2 bodies with the bigger primary a Roche ellipsoid and the smaller a triaxial body. We suppose the bigger primary of mass m 1 to be filled with a homogeneous incompressible fluid of density ρ 1. The third and the fourth bodies (of mass m 3 and m 4 respectively) are small solid spheres of density ρ 3 and ρ 4 respectively inside the ellipsoid, with the assumption that the mass and the radius of the third and the fourth body are infinitesimal. We assume that m 2 is describing a circle around m 1. The masses m 3 and m 4 mutually attract each other, do not influence the motion of m 1 and m 2 but are influenced by them. We have taken into consideration all the three components of the pressure field in deriving the expression for the buoyancy force viz (i) due to the own gravitational field of the fluid (ii) that originating in the attraction of m 2 (iii) that arising from the centrifugal force. In this paper, equilibrium solutions of m 3 and m 4 and their linear stability are analyzed.
Galactic hail: the origin of the high-velocity cloud complex C
Fraternali, F.; Marasco, A.; Armillotta, L.; Marinacci, F.
High-velocity clouds consist of cold gas that appears to be raining down from the halo to the disc of the Milky Way. Over the past 50 years, two competing scenarios have attributed their origin either to gas accretion from outside the Galaxy or to circulation of gas from the Galactic disc powered by
The immitigable nature of assembly bias: the impact of halo definition on assembly bias
Villarreal, Antonio S.; Zentner, Andrew R.; Mao, Yao-Yuan; Purcell, Chris W.; van den Bosch, Frank C.; Diemer, Benedikt; Lange, Johannes U.; Wang, Kuan; Campbell, Duncan
2017-11-01
Dark matter halo clustering depends not only on halo mass, but also on other properties such as concentration and shape. This phenomenon is known broadly as assembly bias. We explore the dependence of assembly bias on halo definition, parametrized by spherical overdensity parameter, Δ. We summarize the strength of concentration-, shape-, and spin-dependent halo clustering as a function of halo mass and halo definition. Concentration-dependent clustering depends strongly on mass at all Δ. For conventional halo definitions (Δ ∼ 200 - 600 m), concentration-dependent clustering at low mass is driven by a population of haloes that is altered through interactions with neighbouring haloes. Concentration-dependent clustering can be greatly reduced through a mass-dependent halo definition with Δ ∼ 20 - 40 m for haloes with M200 m ≲ 1012 h-1M⊙. Smaller Δ implies larger radii and mitigates assembly bias at low mass by subsuming altered, so-called backsplash haloes into now larger host haloes. At higher masses (M200 m ≳ 1013 h-1M⊙) larger overdensities, Δ ≳ 600 m, are necessary. Shape- and spin-dependent clustering are significant for all halo definitions that we explore and exhibit a relatively weaker mass dependence. Generally, both the strength and the sense of assembly bias depend on halo definition, varying significantly even among common definitions. We identify no halo definition that mitigates all manifestations of assembly bias. A halo definition that mitigates assembly bias based on one halo property (e.g. concentration) must be mass dependent. The halo definitions that best mitigate concentration-dependent halo clustering do not coincide with the expected average splashback radii at fixed halo mass.
Davis, Joshua R.; Titus, Sarah J.; Horsman, Eric
2013-11-01
The dynamic theory of deformable ellipsoidal inclusions in slow viscous flows was worked out by J.D. Eshelby in the 1950s, and further developed and applied by various authors. We describe three approaches to computing Eshelby's ellipsoid dynamics and other homogeneous deformations. The most sophisticated of our methods uses differential-geometric techniques on Lie groups. This Lie group method is faster and more precise than earlier methods, and perfectly preserves certain geometric properties of the ellipsoids, including volume. We apply our method to the analysis of naturally deformed clasts from the Gem Lake shear zone in the Sierra Nevada mountains of California, USA. This application demonstrates how, given three-dimensional strain data, we can solve simultaneously for best-fit bulk kinematics of the shear zone, as well as relative viscosities of clasts and matrix rocks.
Water droplet deformation under the motion in gas area with subsonic velocities
Directory of Open Access Journals (Sweden)
Kuibin Pavel A.
2015-01-01
Full Text Available The experimental investigation of water droplet deformation (characteristic dimensions 3 ÷ 6 mm when moving through the gas area (air with 1÷ 5 m/s velocities was carried out. The high-speed (delay time between the frames is less than 100 ns tools of cross-correlation videorecording were used. A cyclic change nature of the droplet shapes (from close to spherical to conditionally ellipsoidal was found. The characteristic times of “deformation cycles” and the maximal deviations of droplet dimensions relative to initial dimensions were determined. The influence of droplet velocities and its dimensions on the deformation characteristics was determined.
Energy Technology Data Exchange (ETDEWEB)
Eichner, Thomas; Seitz, Stella; Monna, Anna [Universitaets-Sternwarte Muenchen, Scheinerstr. 1, D-81679 Muenchen (Germany); Suyu, Sherry H. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Halkola, Aleksi [Institute of Medical Engineering, University of Luebeck, Ratzeburger Allee 160 23562 Luebeck (Germany); Umetsu, Keiichi [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Zitrin, Adi [Institut fuer Theoretische Astrophysik, ZAH, Albert-Ueberle-Strasse 2, D-69120 Heidelberg (Germany); Coe, Dan; Postman, Marc; Koekemoer, Anton; Bradley, Larry [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21208 (United States); Rosati, Piero [ESO-European Southern Observatory, D-85748 Garching bei Muenchen (Germany); Grillo, Claudio; Host, Ole [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Balestra, Italo [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Zheng, Wei; Lemze, Doron [Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Broadhurst, Tom [Department of Theoretical Physics, University of the Basque Country, P.O. Box 644, E-48080 Bilbao (Spain); Moustakas, Leonidas [Jet Propulsion Laboratory, California Institute of Technology, MS 169-327, Pasadena, CA 91109 (United States); Molino, Alberto [Instituto de Astrofisica de Andalucia (CSIC), C/Camino Bajo de Huetor 24, Granada E-18008 (Spain); and others
2013-09-10
In this work, we analyze the mass distribution of MACSJ1206.2-0847, particularly focusing on the halo properties of its cluster members. The cluster appears relaxed in its X-ray emission, but has a significant amount of intracluster light that is not centrally concentrated, suggesting that galaxy-scale interactions are still ongoing despite the overall relaxed state. The cluster lenses 12 background galaxies into multiple images and one galaxy at z = 1.033 into a giant arc and its counterimage. The multiple image positions and the surface brightness (SFB) distribution of the arc, which is bent around several cluster members, are sensitive to the cluster galaxy halo properties. We model the cluster mass distribution with a Navarro-Frenk-White profile and the galaxy halos with two parameters for the mass normalization and the extent of a reference halo assuming scalings with their observed near-infrared light. We match the multiple image positions at an rms level of 0.''85 and can reconstruct the SFB distribution of the arc in several filters to a remarkable accuracy based on this cluster model. The length scale where the enclosed galaxy halo mass is best constrained is about 5 effective radii-a scale in between those accessible to dynamical and field strong-lensing mass estimates on the one hand and galaxy-galaxy weak-lensing results on the other hand. The velocity dispersion and halo size of a galaxy with m{sub 160W,AB} = 19.2 and M{sub B,Vega} = -20.7 are {sigma} = 150 km s{sup -1} and r Almost-Equal-To 26 {+-} 6 kpc, respectively, indicating that the halos of the cluster galaxies are tidally stripped. We also reconstruct the unlensed source, which is smaller by a factor of {approx}5.8 in area, demonstrating the increase in morphological information due to lensing. We conclude that this galaxy likely has star-forming spiral arms with a red (older) central component.
International Nuclear Information System (INIS)
Eichner, Thomas; Seitz, Stella; Monna, Anna; Suyu, Sherry H.; Halkola, Aleksi; Umetsu, Keiichi; Zitrin, Adi; Coe, Dan; Postman, Marc; Koekemoer, Anton; Bradley, Larry; Rosati, Piero; Grillo, Claudio; Høst, Ole; Balestra, Italo; Zheng, Wei; Lemze, Doron; Broadhurst, Tom; Moustakas, Leonidas; Molino, Alberto
2013-01-01
In this work, we analyze the mass distribution of MACSJ1206.2-0847, particularly focusing on the halo properties of its cluster members. The cluster appears relaxed in its X-ray emission, but has a significant amount of intracluster light that is not centrally concentrated, suggesting that galaxy-scale interactions are still ongoing despite the overall relaxed state. The cluster lenses 12 background galaxies into multiple images and one galaxy at z = 1.033 into a giant arc and its counterimage. The multiple image positions and the surface brightness (SFB) distribution of the arc, which is bent around several cluster members, are sensitive to the cluster galaxy halo properties. We model the cluster mass distribution with a Navarro-Frenk-White profile and the galaxy halos with two parameters for the mass normalization and the extent of a reference halo assuming scalings with their observed near-infrared light. We match the multiple image positions at an rms level of 0.''85 and can reconstruct the SFB distribution of the arc in several filters to a remarkable accuracy based on this cluster model. The length scale where the enclosed galaxy halo mass is best constrained is about 5 effective radii—a scale in between those accessible to dynamical and field strong-lensing mass estimates on the one hand and galaxy-galaxy weak-lensing results on the other hand. The velocity dispersion and halo size of a galaxy with m 160W,AB = 19.2 and M B,Vega = –20.7 are σ = 150 km s –1 and r ≈ 26 ± 6 kpc, respectively, indicating that the halos of the cluster galaxies are tidally stripped. We also reconstruct the unlensed source, which is smaller by a factor of ∼5.8 in area, demonstrating the increase in morphological information due to lensing. We conclude that this galaxy likely has star-forming spiral arms with a red (older) central component
A beam halo event of the ATLAS Experiment
ATLAS, Experiment
2014-01-01
Beam halo events: These occur as a single beam of protons is circulating in one direction in LHC, just passing through ATLAS. An outlier particle hits a part of the detector causing a spray of particles.
Possible existence of wormholes in the central regions of halos
Energy Technology Data Exchange (ETDEWEB)
Rahaman, Farook, E-mail: rahaman@iucaa.ernet.in [Department of Mathematics, Jadavpur University, Kolkata 700032, West Bengal (India); Salucci, P., E-mail: salucci@sissa.it [SISSA, International School for Advanced Studies, Via Bonomea 265, 34136, Trieste (Italy); INFN, Sezione di Trieste, Via Valerio 2, 34127, Trieste (Italy); Kuhfittig, P.K.F., E-mail: kuhfitti@msoe.edu [Department of Mathematics, Milwaukee School of Engineering, Milwaukee, WI 53202-3109 (United States); Ray, Saibal, E-mail: saibal@iucaa.ernet.in [Department of Physics, Government College of Engineering and Ceramic Technology, Kolkata 700010, West Bengal (India); Rahaman, Mosiur, E-mail: mosiurju@gmail.com [Department of Mathematics, Meghnad Saha Institute of Technology, Kolkata 700150 (India)
2014-11-15
An earlier study (Rahaman, et al., 2014 and Kuhfittig, 2014) has demonstrated the possible existence of wormholes in the outer regions of the galactic halo, based on the Navarro–Frenk–White (NFW) density profile. This paper uses the Universal Rotation Curve (URC) dark matter model to obtain analogous results for the central parts of the halo. This result is an important compliment to the earlier result, thereby confirming the possible existence of wormholes in most of the spiral galaxies. - Highlights: • Earlier we showed possible existence of wormholes in the outer regions of halo. • We obtain here analogous results for the central parts of the galactic halo. • Our result is an important compliment to the earlier result. • This confirms possible existence of wormholes in most of the spiral galaxies.
First Attempts at using Active Halo Control at the LHC
Energy Technology Data Exchange (ETDEWEB)
Wagner, Joschka [CERN; Bruce, Roderik [CERN; Garcia Morales, Hector [CERN; Höfle, Wolfgang [CERN; Kotzian, Gerd [CERN; Kwee-Hinzmann, Regina [CERN; Langner, Andy [CERN; Mereghetti, Alessio [CERN; Quaranta, Elena [CERN; Redaelli, Stefano [CERN; Rossi, Adriana [CERN; Salvachua, Belen [CERN; Stancari, Giulio [Fermilab; Tomás, Rogelio [CERN; Valentino, Gianluca [CERN; Valuch, Daniel [CERN
2016-06-01
The beam halo population is a non-negligible factor for the performance of the LHC collimation system and the machine protection. In particular this could become crucial for aiming at stored beam energies of 700 MJ in the High Luminosity (HL-LHC) project, in order to avoid beam dumps caused by orbit jitter and to ensure safety during a crab cavity failure. Therefore several techniques to safely deplete the halo, i.e. active halo control, are under development. In a first attempt a novel way for safe halo depletion was tested with particle narrow-band excitation employing the LHC Transverse Damper (ADT). At an energy of 450 GeV a bunch selective beam tail scraping without affecting the core distribution was attempted. This paper presents the first measurement results, as well as a simple simulation to model the underlying dynamics.
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.
Disruption, vertical displacement event and halo current characterization for ITER
International Nuclear Information System (INIS)
Wesley, J.; Fujisawa, N.; Ortolani, S.; Putvinski, S.; Rosenbluth, M.N.
1997-01-01
Characteristics, in ITER, of plasma disruptions, vertical displacement events (VDEs) and the conversion of plasma current to runaway electron current in a disruption are presented. In addition to the well known potential of disruptions to produce rapid thermal energy and plasma current quenches and theoretical predictions that show the likelihood of ∼ 50% runaway conversion, an assessment of VDE and halo current characteristics in vertically elongated tokamaks shows that disruptions in ITER will result in VDEs with peak in-vessel halo currents of up to 50% of the predisruption plasma current and with toroidal peaking factors (peak/average current density) of up to 4:1. However, the assessment also shows an inverse correlation between the halo current magnitude and the toroidal peaking factor; hence, ITER VDEs can be expected to have a product of normalized halo current magnitude times toroidal peaking factor of ≤ 75%. (author). 3 refs, 2 figs, 3 tabs
Summary of the 2014 Beam-Halo Monitoring Workshop
Energy Technology Data Exchange (ETDEWEB)
Fisher, Alan
2015-09-25
Understanding and controlling beam halo is important for high-intensity hadron accelerators, for high-brightness electron linacs, and for low-emittance light sources. This can only be achieved by developing suitable diagnostics. The main challenge faced by such instrumentation is the high dynamic range needed to observe the halo in the presence of an intense core. In addition, measurements must often be made non-invasively. This talk summarizes the one-day workshop on Beam-Halo Monitoring that was held at SLAC on September 19 last year, immediately following IBIC 2014 in Monterey. Workshop presentations described invasive techniques using wires, screens, or crystal collimators, and non-invasive measurements with gas or scattered electrons. Talks on optical methods showed the close links between observing halo and astronomical problems like observing the solar corona or directly observing a planet orbiting another star.
Bouillot, Vincent R.; Alimi, Jean-Michel; Corasaniti, Pier-Stefano; Rasera, Yann
2015-06-01
Observations of colliding galaxy clusters with high relative velocity probe the tail of the halo pairwise velocity distribution with the potential of providing a powerful test of cosmology. As an example it has been argued that the discovery of the Bullet Cluster challenges standard Λ cold dark matter (ΛCDM) model predictions. Halo catalogues from N-body simulations have been used to estimate the probability of Bullet-like clusters. However, due to simulation volume effects previous studies had to rely on a Gaussian extrapolation of the pairwise velocity distribution to high velocities. Here, we perform a detail analysis using the halo catalogues from the Dark Energy Universe Simulation Full Universe Runs (DEUS-FUR), which enables us to resolve the high-velocity tail of the distribution and study its dependence on the halo mass definition, redshift and cosmology. Building upon these results, we estimate the probability of Bullet-like systems in the framework of Extreme Value Statistics. We show that the tail of extreme pairwise velocities significantly deviates from that of a Gaussian, moreover it carries an imprint of the underlying cosmology. We find the Bullet Cluster probability to be two orders of magnitude larger than previous estimates, thus easing the tension with the ΛCDM model. Finally, the comparison of the inferred probabilities for the different DEUS-FUR cosmologies suggests that observations of extreme interacting clusters can provide constraints on dark energy models complementary to standard cosmological tests.
Directory of Open Access Journals (Sweden)
M. Moradi
2004-12-01
Full Text Available The density functional theory analogue of Percus Yevick (PY and Hyper-Netted chain (HNC has been used to write the grand potential of a liquid with cylindrical and ellipsoidal molecules. The integral equations for the density can be obtained by minimizing the grand potential with respect to the density. Some kinds of liquid crystals, can have the cylindrical or ellipsoidal rigid molecules. In this study we have calculated the density profile of this kind of liquids confined between hard walls and we compared the results. As it is seen from the graphs of the density profiles the molecules can be arranged as layers with respect to the walls.
International Nuclear Information System (INIS)
Akhmadeev, Albert A; Kh Salakhov, Myakzyum
2016-01-01
In this work we develop an approach of automatic recognition of ellipsoidal particles on the atomic force microscopy (AFM) image and determination of their size, which is based on image segmentation and the surface approximation by ellipsoids. In addition to the comparative simplicity and rapidity of processing, this method allows us to determine the size of particles, the surface of which is not completely visible on the image. The proposed method showed good results on simulated images including noisy ones. Using this algorithm the size distributions of silica particles on experimental AFM images have been determined. (paper)
SIMULATIONS OF HIGH-VELOCITY CLOUDS. I. HYDRODYNAMICS AND HIGH-VELOCITY HIGH IONS
International Nuclear Information System (INIS)
Kwak, Kyujin; Henley, David B.; Shelton, Robin L.
2011-01-01
We present hydrodynamic simulations of high-velocity clouds (HVCs) traveling through the hot, tenuous medium in the Galactic halo. A suite of models was created using the FLASH hydrodynamics code, sampling various cloud sizes, densities, and velocities. In all cases, the cloud-halo interaction ablates material from the clouds. The ablated material falls behind the clouds where it mixes with the ambient medium to produce intermediate-temperature gas, some of which radiatively cools to less than 10,000 K. Using a non-equilibrium ionization algorithm, we track the ionization levels of carbon, nitrogen, and oxygen in the gas throughout the simulation period. We present observation-related predictions, including the expected H I and high ion (C IV, N V, and O VI) column densities on sightlines through the clouds as functions of evolutionary time and off-center distance. The predicted column densities overlap those observed for Complex C. The observations are best matched by clouds that have interacted with the Galactic environment for tens to hundreds of megayears. Given the large distances across which the clouds would travel during such time, our results are consistent with Complex C having an extragalactic origin. The destruction of HVCs is also of interest; the smallest cloud (initial mass ∼ 120 M sun ) lost most of its mass during the simulation period (60 Myr), while the largest cloud (initial mass ∼ 4 x 10 5 M sun ) remained largely intact, although deformed, during its simulation period (240 Myr).
REVISITING SCALING RELATIONS FOR GIANT RADIO HALOS IN GALAXY CLUSTERS
Energy Technology Data Exchange (ETDEWEB)
Cassano, R.; Brunetti, G.; Venturi, T.; Kale, R. [INAF/IRA, via Gobetti 101, I-40129 Bologna (Italy); Ettori, S. [INAF/Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Giacintucci, S. [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Pratt, G. W. [Laboratoire AIM, IRFU/Service dAstrophysique-CEA/DSM-CNRS-Université Paris Diderot, Bât. 709, CEA-Saclay, F-91191 Gif-sur-Yvette Cedex (France); Dolag, K. [University Observatory Munich, Scheinerstr. 1, D-81679 Munich (Germany); Markevitch, M. [Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
2013-11-10
Many galaxy clusters host megaparsec-scale radio halos, generated by ultrarelativistic electrons in the magnetized intracluster medium. Correlations between the synchrotron power of radio halos and the thermal properties of the hosting clusters were established in the last decade, including the connection between the presence of a halo and cluster mergers. The X-ray luminosity and redshift-limited Extended GMRT Radio Halo Survey provides a rich and unique dataset for statistical studies of the halos. We uniformly analyze the radio and X-ray data for the GMRT cluster sample, and use the new Planck Sunyaev-Zel'dovich (SZ) catalog to revisit the correlations between the power of radio halos and the thermal properties of galaxy clusters. We find that the radio power at 1.4 GHz scales with the cluster X-ray (0.1-2.4 keV) luminosity computed within R{sub 500} as P{sub 1.4}∼L{sup 2.1±0.2}{sub 500}. Our bigger and more homogenous sample confirms that the X-ray luminous (L{sub 500} > 5 × 10{sup 44} erg s{sup –1}) clusters branch into two populations—radio halos lie on the correlation, while clusters without radio halos have their radio upper limits well below that correlation. This bimodality remains if we excise cool cores from the X-ray luminosities. We also find that P{sub 1.4} scales with the cluster integrated SZ signal within R{sub 500}, measured by Planck, as P{sub 1.4}∼Y{sup 2.05±0.28}{sub 500}, in line with previous findings. However, contrary to previous studies that were limited by incompleteness and small sample size, we find that 'SZ-luminous' Y{sub 500} > 6 × 10{sup –5} Mpc{sup 2} clusters show a bimodal behavior for the presence of radio halos, similar to that in the radio-X-ray diagram. Bimodality of both correlations can be traced to clusters dynamics, with radio halos found exclusively in merging clusters. These results confirm the key role of mergers for the origin of giant radio halos, suggesting that they trigger the
Analytical shear and flexion of Einasto dark matter haloes
Retana-Montenegro, E.; Frutos-Alfaro, F.; Baes, M.
2012-01-01
N-body simulations predict that dark matter haloes are described by specific density profiles on both galactic- and cluster-sized scales. Weak gravitational lensing through the measurements of their first and second order properties, shear and flexion, is a powerful observational tool for investigating the true shape of these profiles. One of the three-parameter density profiles recently favoured in the description of dark matter haloes is the Einasto profile. We present exact expressions for...
Possible existence of wormholes in the galactic halo region
Energy Technology Data Exchange (ETDEWEB)
Rahaman, Farook [Jadavpur University, Department of Mathematics, Kolkata, West Bengal (India); Kuhfittig, P.K.F. [Milwaukee School of Engineering, Department of Mathematics, Milwaukee, WI (United States); Ray, Saibal [Government College of Engineering and Ceramic Technology, Department of Physics, Kolkata, West Bengal (India); Islam, Nasarul [Danga High Madrasah, Department of Mathematics, Kolkata, West Bengal (India)
2014-02-15
Two observational results, the density profile from simulations performed in the ΛCDM scenario and the observed flat galactic rotation curves, are taken as input with the aim of showing that the galactic halo possesses some of the characteristics needed to support traversable wormholes. This result should be sufficient to provide an incentive for scientists to seek observational evidence for wormholes in the galactic halo region. (orig.)
One dark matter mystery: halos in the cosmic web
Gaite, Jose
2015-01-01
The current cold dark matter cosmological model explains the large scale cosmic web structure but is challenged by the observation of a relatively smooth distribution of matter in galactic clusters. We consider various aspects of modeling the dark matter around galaxies as distributed in smooth halos and, especially, the smoothness of the dark matter halos seen in N-body cosmological simulations. We conclude that the problems of the cold dark matter cosmology on small scales are more serious than normally admitted.
One dark matter mystery: halos in the cosmic web
International Nuclear Information System (INIS)
Gaite, Jose
2015-01-01
The current cold dark matter cosmological model explains the large scale cosmic web structure but is challenged by the observation of a relatively smooth distribution of matter in galactic clusters. We consider various aspects of modeling the dark matter around galaxies as distributed in smooth halos and, especially, the smoothness of the dark matter halos seen in N-body cosmological simulations. We conclude that the problems of the cold dark matter cosmology on small scales are more serious than normally admitted
Halo and space charge issues in the SNS Ring
International Nuclear Information System (INIS)
Fedotov, A.V.; Abell, D.T.; Beebe-Wang, J.; Lee, Y.Y.; Malitsky, N.; Wei, J.; Gluckstern, R.L.
2000-01-01
The latest designs for high-intensity proton rings require minimizing beam-induced radioactivation of the vacuum chamber. Although the tune depression in the ring is much smaller than in high-intensity linacs, space-charge contributions to halo formation and, hence, beam loss may be significant. This paper reviews our current understanding of halo formation issues for the Spallation Neutron Source (SNS) accumulator ring
Studies of halo distributions under beam-beam interaction
International Nuclear Information System (INIS)
Chen, T.; Irwin, J.; Siemann, R.H.
1995-01-01
The halo distribution due to the beam-beam interaction in circular electron-positron colliders is simulated with a program which uses a technique that saves a factor of hundreds to thousands of CPU time. The distribution and the interference between the beam-beam interaction and lattice nonlinearities has been investigated. The effects on the halo distribution due to radiation damping misalignment at the collision point, and chromatic effect are presented
Halo and space charge issues in the SNS Ring
Energy Technology Data Exchange (ETDEWEB)
Fedotov, A.V.; Abell, D.T.; Beebe-Wang, J.; Lee, Y.Y.; Malitsky, N.; Wei, J.; Gluckstern, R.L.
2000-06-30
The latest designs for high-intensity proton rings require minimizing beam-induced radioactivation of the vacuum chamber. Although the tune depression in the ring is much smaller than in high-intensity linacs, space-charge contributions to halo formation and, hence, beam loss may be significant. This paper reviews our current understanding of halo formation issues for the Spallation Neutron Source (SNS) accumulator ring.
Integrated Marketing Communications (IMC) di PT Halo Rumah Bernyanyi
Rebekka Rismayanti
2017-01-01
Abstract: This research aims to describe the effectiveness of Integrated Marketing Communication (IMC) in PT Halo Rumah Bernyanyi which, from the perspective of marketing strategy, could be studied by analyzing the segmentation, targeting, and positioning. Using case-study method with in-depth interview, the result shows that the implementation of IMC at PT Halo Rumah Bernyayi is arranged in one single strategy and tend to neglect the complexities of running multi-brand family karaoke-house. ...
Integrated Marketing Communications (IMC) Di PT Halo Rumah Bernyanyi
Rismayanti, Rebekka
2016-01-01
: This research aims to describe the effectiveness of Integrated Marketing Communication (IMC) in PT Halo Rumah Bernyanyi which, from the perspective of marketing strategy, could be studied by analyzing the segmentation, targeting, and positioning. Using case-study method with in-depth interview, the result shows that the implementation of IMC at PT Halo Rumah Bernyayi is arranged in one single strategy and tend to neglect the complexities of running multi-brand family karaoke-house. This con...
MD 1691: Active halo control using tune ripple at injection
Garcia Morales, Hector; Bruce, Roderik; Redaelli, Stefano; Fitterer, Miriam; Fiascaris, Maria; Nisbet, David; Thiesen, Hugues; Valentino, Gianluca; Xu, Chen; CERN. Geneva. ATS Department
2017-01-01
In this MD we performed halo excitation through tune ripple. This consists in an excitation that introduces new resonance sidebands around the existing resonance lines. In presence of sufficient detuning with amplitude, these sidebands can in principle affect only the dynamics of the halo particles at large amplitudes. Tune ripple was induced through a current modulation of the warm trim quadrupoles in IR7. This is the first time this method is experimentally tested at the LHC.
Galactic warps and the shape of heavy halos
International Nuclear Information System (INIS)
Sparke, L.S.
1984-01-01
The outer disks of many spiral galaxies are bent away from the plane of the inner disk; the abundance of these warps suggests that they are long-lived. Isolated galactic disks have long been thought to have no discrete modes of vertical oscillation under their own gravity, and so to be incapable of sustaining persistent warps. However, the visible disk contains only a fraction of the galactic mass; an invisible galactic halo makes up the rest. This paper presents an investigation of vertical warping modes in self-gravitating disks, in the imposed potential due to an axisymmetric unseen massive halo. If the halo matter is distributed so that the free precession rate of a test particle decreases with radius near the edge of the disk, then the disk has a discrete mode of vibration; oblate halos which become rapidly more flattened at large radii, and uniformly prolate halos, satisfy this requirement. Otherwise, the disk has no discrete modes and so cannot maintain a long-lived warp, unless the edge is sharply truncated. Computed mode shapes which resemble the observed warps can be found for halo masses consistent with those inferred from galactic rotation curves
Unmixing the Galactic halo with RR Lyrae tagging
Belokurov, V.; Deason, A. J.; Koposov, S. E.; Catelan, M.; Erkal, D.; Drake, A. J.; Evans, N. W.
2018-06-01
We show that tagging RR Lyrae stars according to their location in the period-amplitude diagram can be used to shed light on the genesis of the Galactic stellar halo. The mixture of RR Lyrae of ab type, separated into classes along the lines suggested by Oosterhoff, displays a strong and coherent evolution with Galactocentric radius. The change in the RR Lyrae composition appears to coincide with the break in the halo's radial density profile at ˜25 kpc. Using simple models of the stellar halo, we establish that at least three different types of accretion events are necessary to explain the observed RRab behaviour. Given that there exists a correlation between the RRab class fraction and the total stellar content of a dwarf satellite, we hypothesize that the field halo RRab composition is controlled by the mass of the progenitor contributing the bulk of the stellar debris at the given radius. This idea is tested against a suite of cosmological zoom-in simulations of Milky Way-like stellar halo formation. Finally, we study some of the most prominent stellar streams in the Milky Way halo and demonstrate that their RRab class fractions follow the trends established previously.
Dissipative dark matter halos: The steady state solution. II.
Foot, R.
2018-05-01
Within the mirror dark matter model and dissipative dark matter models in general, halos around galaxies with active star formation (including spirals and gas-rich dwarfs) are dynamical: they expand and contract in response to heating and cooling processes. Ordinary type II supernovae (SNe) can provide the dominant heat source, which is possible if kinetic mixing interaction exists with strength ɛ ˜10-9- 10-10 . Dissipative dark matter halos can be modeled as a fluid governed by Euler's equations. Around sufficiently isolated and unperturbed galaxies the halo can relax to a steady state configuration, where heating and cooling rates locally balance and hydrostatic equilibrium prevails. These steady state conditions can be solved to derive the physical properties, including the halo density and temperature profiles, for model galaxies. Here, we consider idealized spherically symmetric galaxies within the mirror dark particle model, as in our earlier paper [Phys. Rev. D 97, 043012 (2018), 10.1103/PhysRevD.97.043012], but we assume that the local halo heating in the SN vicinity dominates over radiative sources. With this assumption, physically interesting steady state solutions arise which we compute for a representative range of model galaxies. The end result is a rather simple description of the dark matter halo around idealized spherically symmetric systems, characterized in principle by only one parameter, with physical properties that closely resemble the empirical properties of disk galaxies.
Observation and analysis of halo current in EAST
Chen, Da-Long; Shen, Biao; Qian, Jin-Ping; Sun, You-Wen; Liu, Guang-Jun; Shi, Tong-Hui; Zhuang, Hui-Dong; Xiao, Bing-Jia
2014-06-01
Plasma in a typically elongated cross-section tokamak (for example, EAST) is inherently unstable against vertical displacement. When plasma loses the vertical position control, it moves downward or upward, leading to disruption, and a large halo current is generated helically in EAST typically in the scrape-off layer. When flowing into the vacuum vessel through in-vessel components, the halo current will give rise to a large J × B force acting on the vessel and the in-vessel components. In EAST VDE experiment, part of the eddy current is measured in halo sensors, due to the large loop voltage. Primary experimental data demonstrate that the halo current first lands on the outer plate and then flows clockwise, and the analysis of the information indicates that the maximum halo current estimated in EAST is about 0.4 times the plasma current and the maximum value of TPF × Ih/IP0 is 0.65, furthermore Ih/Ip0 and TPF × Ih/Ip0 tend to increase with the increase of Ip0. The test of the strong gas injection system shows good success in increasing the radiated power, which may be effective in reducing the halo current.
Dissipative dark matter halos: The steady state solution
Foot, R.
2018-02-01
Dissipative dark matter, where dark matter particle properties closely resemble familiar baryonic matter, is considered. Mirror dark matter, which arises from an isomorphic hidden sector, is a specific and theoretically constrained scenario. Other possibilities include models with more generic hidden sectors that contain massless dark photons [unbroken U (1 ) gauge interactions]. Such dark matter not only features dissipative cooling processes but also is assumed to have nontrivial heating sourced by ordinary supernovae (facilitated by the kinetic mixing interaction). The dynamics of dissipative dark matter halos around rotationally supported galaxies, influenced by heating as well as cooling processes, can be modeled by fluid equations. For a sufficiently isolated galaxy with a stable star formation rate, the dissipative dark matter halos are expected to evolve to a steady state configuration which is in hydrostatic equilibrium and where heating and cooling rates locally balance. Here, we take into account the major cooling and heating processes, and numerically solve for the steady state solution under the assumptions of spherical symmetry, negligible dark magnetic fields, and that supernova sourced energy is transported to the halo via dark radiation. For the parameters considered, and assumptions made, we were unable to find a physically realistic solution for the constrained case of mirror dark matter halos. Halo cooling generally exceeds heating at realistic halo mass densities. This problem can be rectified in more generic dissipative dark matter models, and we discuss a specific example in some detail.
The gamma-ray-flux PDF from galactic halo substructure
International Nuclear Information System (INIS)
Lee, Samuel K.; Ando, Shin'ichiro; Kamionkowski, Marc
2009-01-01
One of the targets of the recently launched Fermi Gamma-ray Space Telescope is a diffuse gamma-ray background from dark-matter annihilation or decay in the Galactic halo. N-body simulations and theoretical arguments suggest that the dark matter in the Galactic halo may be clumped into substructure, rather than smoothly distributed. Here we propose the gamma-ray-flux probability distribution function (PDF) as a probe of substructure in the Galactic halo. We calculate this PDF for a phenomenological model of halo substructure and determine the regions of the substructure parameter space in which the PDF may be distinguished from the PDF for a smooth distribution of dark matter. In principle, the PDF allows a statistical detection of substructure, even if individual halos cannot be detected. It may also allow detection of substructure on the smallest microhalo mass scales, ∼ M ⊕ , for weakly-interacting massive particles (WIMPs). Furthermore, it may also provide a method to measure the substructure mass function. However, an analysis that assumes a typical halo substructure model and a conservative estimate of the diffuse background suggests that the substructure PDF may not be detectable in the lifespan of Fermi in the specific case that the WIMP is a neutralino. Nevertheless, for a large range of substructure, WIMP annihilation, and diffuse background models, PDF analysis may provide a clear signature of substructure
Remapping dark matter halo catalogues between cosmological simulations
Mead, A. J.; Peacock, J. A.
2014-05-01
We present and test a method for modifying the catalogue of dark matter haloes produced from a given cosmological simulation, so that it resembles the result of a simulation with an entirely different set of parameters. This extends the method of Angulo & White, which rescales the full particle distribution from a simulation. Working directly with the halo catalogue offers an advantage in speed, and also allows modifications of the internal structure of the haloes to account for non-linear differences between cosmologies. Our method can be used directly on a halo catalogue in a self-contained manner without any additional information about the overall density field; although the large-scale displacement field is required by the method, this can be inferred from the halo catalogue alone. We show proof of concept of our method by rescaling a matter-only simulation with no baryon acoustic oscillation (BAO) features to a more standard Λ cold dark matter model containing a cosmological constant and a BAO signal. In conjunction with the halo occupation approach, this method provides a basis for the rapid generation of mock galaxy samples spanning a wide range of cosmological parameters.
Stellar-to-halo mass relation of cluster galaxies
International Nuclear Information System (INIS)
Niemiec, Anna; Jullo, Eric; Limousin, Marceau; Giocoli, Carlo
2017-01-01
In the formation of galaxy groups and clusters, the dark matter haloes containing satellite galaxies are expected to be tidally stripped in gravitational interactions with the host. We use galaxy-galaxy weak lensing to measure the average mass of dark matter haloes of satellite galaxies as a function of projected distance to the centre of the host, since stripping is expected to be greater for satellites closer to the centre of the cluster. We further classify the satellites according to their stellar mass: assuming that the stellar component of the galaxy is less disrupted by tidal stripping, stellar mass can be used as a proxy of the infall mass. We study the stellar to halo mass relation of satellites as a function of the cluster-centric distance to measure tidal stripping. We use the shear catalogues of the DES science veri cation archive, the CFHTLenS and the CFHT Stripe 82 surveys, and we select satellites from the redMaPPer catalogue of clusters. For galaxies located in the outskirts of clusters, we nd a stellar to halo mass relation in good agreement with the theoretical expectations from Moster, Naab & White (2013) for central galaxies. In the centre of the cluster, we nd that this relation is shifted to smaller halo mass for a given stellar mass. We interpret this nding as further evidence for tidal stripping of dark matter haloes in high density environments.
Halo models of HI selected galaxies
Paul, Niladri; Choudhury, Tirthankar Roy; Paranjape, Aseem
2018-06-01
Modelling the distribution of neutral hydrogen (HI) in dark matter halos is important for studying galaxy evolution in the cosmological context. We use a novel approach to infer the HI-dark matter connection at the massive end (m_H{I} > 10^{9.8} M_{⊙}) from radio HI emission surveys, using optical properties of low-redshift galaxies as an intermediary. In particular, we use a previously calibrated optical HOD describing the luminosity- and colour-dependent clustering of SDSS galaxies and describe the HI content using a statistical scaling relation between the optical properties and HI mass. This allows us to compute the abundance and clustering properties of HI-selected galaxies and compare with data from the ALFALFA survey. We apply an MCMC-based statistical analysis to constrain the free parameters related to the scaling relation. The resulting best-fit scaling relation identifies massive HI galaxies primarily with optically faint blue centrals, consistent with expectations from galaxy formation models. We compare the Hi-stellar mass relation predicted by our model with independent observations from matched Hi-optical galaxy samples, finding reasonable agreement. As a further application, we make some preliminary forecasts for future observations of HI and optical galaxies in the expected overlap volume of SKA and Euclid/LSST.
Estimating the tumble rates of galaxy halos
International Nuclear Information System (INIS)
Simonson, G.F.; Tohline, J.E.
1983-01-01
It has previously been demonstrated that cold gas in a static spheroidal galaxy will damp to a preferred plane, in which the angular momentum vector of the gas is aligned with the symmetry axis of the potential, through dissipative processes. We show now that, if the same galaxy rigidly tumbles about a nonsymmetry axis, the preferred orientation of the gas can become a permanently and smoothly warped sheet, in which rings of gas at large radii may be fully orthogonal to those near the galaxy's core. Detailed numerical orbit calculations closely match an analytic prediction made previously for the structure of the warp. This structure depends primarily on the eccentricity, density profile, and tumble rate of the spheroid. We show that the tumble rate can now be determined for a galaxy containing a significantly warped disk. Ordinary observations used in conjunction with graphs such as those we present, yield at least firm lower limits to the tumble periods of these objects. We have applied this method to the two peculiar systems NGC 5128 and NGC 2685 and found that, if they are prolate systems supporting permanently warped gaseous disks, they must tumble with periods near 5 x 10 9 yr and 2 x 10 9 yr respectively. In a preliminary investigation, we also find that the massive, unseen halos surrounding spiral galaxies must tumble with periods longer than or on the same order as those of the elliptical galaxies
Performance of the CMS Beam Halo Monitor
CMS Collaboration
2015-01-01
The CMS Beam Halo Monitor has been successfully installed in the CMS cavern in LHC Long Shutdown 1 for measuring the machine induced background for LHC Run II. The system is based on 40 detector units composed of radiation hard synthetic quartz Cherenkov radiators coupled to fast photomultiplier tubes for a direction sensitive measurement. The readout electronics chain uses many components developed for the Phase 1 upgrade to the CMS Hadronic Calorimeter electronics, with dedicated firmware and readout adapted to the beam monitoring requirements. The PMT signal is digitized by a charge integrating ASIC (QIE10), providing both the signal rise time, with few ns resolution, and the charge integrated over one bunch crossing. The backend electronics uses microTCA technology and received data via a high-speed 5 Gbps asynchronous link. It records histograms with sub-bunch crossing timing resolution and is readout by IPbus using the newly designed CMS data acquisition for non-event based data. The data is processed i...
MAGNIFICATION BY GALAXY GROUP DARK MATTER HALOS
Energy Technology Data Exchange (ETDEWEB)
Ford, Jes; Hildebrandt, Hendrik; Van Waerbeke, Ludovic [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Leauthaud, Alexie; Tanaka, Masayuki [Institute for the Physics and Mathematics of the Universe, University of Tokyo, Chiba 277-8582 (Japan); Capak, Peter [NASA Spitzer Science Center, California Institute of Technology, 220-6 Caltech, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Finoguenov, Alexis [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany); George, Matthew R. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Rhodes, Jason [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
2012-08-01
We report on the detection of gravitational lensing magnification by a population of galaxy groups, at a significance level of 4.9{sigma}. Using X-ray-selected groups in the COSMOS 1.64 deg{sup 2} field, and high-redshift Lyman break galaxies as sources, we measure a lensing-induced angular cross-correlation between the samples. After satisfying consistency checks that demonstrate we have indeed detected a magnification signal, and are not suffering from contamination by physical overlap of samples, we proceed to implement an optimally weighted cross-correlation function to further boost the signal to noise of the measurement. Interpreting this optimally weighted measurement allows us to study properties of the lensing groups. We model the full distribution of group masses using a composite-halo approach, considering both the singular isothermal sphere and Navarro-Frenk-White profiles, and find our best-fit values to be consistent with those recovered using the weak-lensing shear technique. We argue that future weak-lensing studies will need to incorporate magnification along with shear, both to reduce residual systematics and to make full use of all available source information, in an effort to maximize scientific yield of the observations.
The CMS Beam Halo Monitor electronics
International Nuclear Information System (INIS)
Tosi, N.; Fabbri, F.; Montanari, A.; Torromeo, G.; Dabrowski, A.E.; Orfanelli, S.; Grassi, T.; Hughes, E.; Mans, J.; Rusack, R.; Stifter, K.; Stickland, D.P.
2016-01-01
The CMS Beam Halo Monitor has been successfully installed in the CMS cavern in LHC Long Shutdown 1 for measuring the machine induced background for LHC Run II. The system is based on 40 detector units composed of synthetic quartz Cherenkov radiators coupled to fast photomultiplier tubes (PMTs). The readout electronics chain uses many components developed for the Phase 1 upgrade to the CMS Hadronic Calorimeter electronics, with dedicated firmware and readout adapted to the beam monitoring requirements. The PMT signal is digitized by a charge integrating ASIC (QIE10), providing both the signal rise time, with few nanosecond resolution, and the charge integrated over one bunch crossing. The backend electronics uses microTCA technology and receives data via a high-speed 5 Gbps asynchronous link. It records histograms with sub-bunch crossing timing resolution and is read out via IPbus using the newly designed CMS data acquisition for non-event based data. The data is processed in real time and published to CMS and the LHC, providing online feedback on the beam quality. A dedicated calibration monitoring system has been designed to generate short triggered pulses of light to monitor the efficiency of the system. The electronics has been in operation since the first LHC beams of Run II and has served as the first demonstration of the new QIE10, Microsemi Igloo2 FPGA and high-speed 5 Gbps link with LHC data
Halo structure of strange particles in nuclei
International Nuclear Information System (INIS)
Akaishi, Yoshinori; Yamazaki, Toshimitsu.
1997-01-01
Some characteristic behaviors of hyperons in nuclei which have recently been revealed experimentally and theoretically are discussed with the emphasis on the repulsive part of the hyperon-nucleus interaction. The observed Σ 4 He nucleus is a bound state with J π = 0 + and T ≅ 1/2. Its nucleus-Σ potential derived from a realistic ΣN interaction is characterized by inner repulsion and a strong Lane term, which play important roles in forming the Σ-hypernuclear bound state. In 208 Pb a typical Coulomb-assisted bound state is expected, where Σ is trapped in the surface region by the nucleus-Σ potential with the aid of Coulomb and centrifugal interactions. In the double-strangeness (S=-2) sector, there is a possibility that the lightest double-Λ hypernucleus ΛΛ 4 H is abundantly populated by stopping Ξ - on 4 He. Its formation branching amounts to about 15%. A stopped Ξ - on 9 Be will also produce efficiently a variety of double-Λ hyperfragments. Discrete spectra of weak-decay pions from the fragments will provide a means of mass spectroscopy of double-Λ hypernuclei. In the S=-2 five-body system an excited state Ξ 5 H is predicted to appear with 'strangeness halo' and the ground state ΛΛ 5 H with almost pure ΛΛ component. (author)
The CMS Beam Halo Monitor Electronics
AUTHOR|(CDS)2080684; Fabbri, F.; Grassi, T.; Hughes, E.; Mans, J.; Montanari, A.; Orfanelli, S.; Rusack, R.; Torromeo, G.; Stickland, D.P.; Stifter, K.
2016-01-01
The CMS Beam Halo Monitor has been successfully installed in the CMS cavern in LHC Long Shutdown 1 for measuring the machine induced background for LHC Run II. The system is based on 40 detector units composed of synthetic quartz Cherenkov radiators coupled to fast photomultiplier tubes. The readout electronics chain uses many components developed for the Phase 1 upgrade to the CMS Hadronic Calorimeter electronics, with dedicated firmware and readout adapted to the beam monitoring requirements. The PMT signal is digitized by a charge integrating ASIC (QIE10), providing both the signal rise time, with few ns resolution, and the charge integrated over one bunch crossing. The backend electronics uses microTCA technology and receives data via a high-speed 5 Gbps asynchronous link. It records histograms with sub-bunch crossing timing resolution and is readout by IPbus using the newly designed CMS data acquisition for non-event based data. The data is processed in real time and published to CMS and the LHC, providi...
Radio haloes in nearby galaxies modelled with 1D cosmic ray transport using SPINNAKER
Heesen, V.; Krause, M.; Beck, R.; Adebahr, B.; Bomans, D. J.; Carretti, E.; Dumke, M.; Heald, G.; Irwin, J.; Koribalski, B. S.; Mulcahy, D. D.; Westmeier, T.; Dettmar, R.-J.
2018-05-01
We present radio continuum maps of 12 nearby (D ≤ 27 Mpc), edge-on (i ≥ 76°), late-type spiral galaxies mostly at 1.4 and 5 GHz, observed with the Australia Telescope Compact Array, Very Large Array, Westerbork Synthesis Radio Telescope, Effelsberg 100-m, and Parkes 64-m telescopes. All galaxies show clear evidence of radio haloes, including the first detection in the Magellanic-type galaxy NGC 55. In 11 galaxies, we find a thin and a thick disc that can be better fitted by exponential rather than Gaussian functions. We fit our SPINNAKER (SPectral INdex Numerical Analysis of K(c)osmic-ray Electron Radio-emission) 1D cosmic ray transport models to the vertical model profiles of the non-thermal intensity and to the non-thermal radio spectral index in the halo. We simultaneously fit for the advection speed (or diffusion coefficient) and magnetic field scale height. In the thick disc, the magnetic field scale heights range from 2 to 8 kpc with an average across the sample of 3.0 ± 1.7 kpc; they show no correlation with either star formation rate (SFR), SFR surface density (ΣSFR), or rotation speed (Vrot). The advection speeds range from 100 to 700 km s - 1 and display correlations of V∝SFR0.36 ± 0.06 and V∝ Σ _SFR^{0.39± 0.09}; they agree remarkably well with the escape velocities (0.5 ≤ V/Vesc ≤ 2), which can be explained by cosmic ray-driven winds. Radio haloes show the presence of disc winds in galaxies with ΣSFR > 10 - 3 M⊙ yr - 1 kpc - 2 that extend over several kpc and are driven by processes related to the distributed star formation in the disc.
The Interaction of Hot and Cold Gas in the Disk and Halo of Galaxies
Slavin, Jonathan; Salamon, Michael (Technical Monitor)
2004-01-01
Most of the thermal energy in the Galaxy and perhaps most of the baryons in the Universe are found in hot (log T approximately 5.5 - 7) gas. Hot gas is detected in the local interstellar medium, in supernova remnants (SNR), the Galactic halo, galaxy clusters and the intergalactic medium (IGM). In our own Galaxy, hot gas exists in large superbubbles up to several hundred pc in diameter that locally dominate the interstellar medium (ISM) and determine its thermal and dynamic evolution. While X-ray observations using ROSAT, Chandra and XMM have allowed us to make dramatic progress in mapping out the morphology of the hot gas and in understanding some of its spectral characteristics, there remain fundamental questions that are unanswered. Chief among these questions is the way that hot gas interacts with cooler phase gas and the effects these interactions have on hot gas energetics. The theoretical investigations we proposed in this grant aim to explore these interactions and to develop observational diagnostics that will allow us to gain much improved information on the evolution of hot gas in the disk and halo of galaxies. The first of the series of investigations that we proposed was a thorough exploration of turbulent mixing layers and cloud evaporation. We proposed to employ a multi-dimensional hydrodynamical code that includes non-equilibrium ionization (NEI), radiative cooling and thermal conduction. These models are to be applied to high velocity clouds in our galactic halo that are seen to have O VI by FUSE (Sembach et ai. 2000) and other clouds for which sufficient constraining observations exist.
Experimental tests on buckling of ellipsoidal vessel heads subjected to internal pressure
International Nuclear Information System (INIS)
Roche, R.L.; Alix, M.
1980-05-01
Tests were performed on 17 ellipsoidal vessel heads of three different materials and different geometries. The results include the following: 1) Accurate definition of the geometry and particularly a direct measurement of the thickness along the meridian. 2) The properties of the material of each head, obtained from test specimens cut from the head itself after the test. 3) The recording of deflection/pressure curves with indication of the pressure at which buckling occurred. These results can be used for validation and qualification of methods for calculating the buckling load when plasticity occurs before buckling. It was possible to develop an empirical equation representing the experimental results obtained with satisfactory accuracy. This equation may be useful in pressure vessel design
Design of an ellipsoidal mirror for freewave characterization of materials at microwave frequencies
International Nuclear Information System (INIS)
Rojo, M; Muñoz, J; Molina-Cuberos, G J; Margineda, J; García-Collado, Á J
2016-01-01
Free-wave characterization of the electromagnetic properties of materials at microwave frequencies requires that scattering at the edges of the samples and/or holder be minimized. Here, an ellipsoidal mirror is designed and characterized in order to decrease the size of the beam, thereby avoiding the scattering problems, even when relatively small samples are used. In the experimental configuration, both the emitting antenna and sample are located at the mirror focuses. Since both the emitted and reflected (focused) beams are Gaussian in nature, we make use of Gaussian beam theory to carry out the design. The mirror parameters are optimized by numerical simulations (COMSOL Multiphysics ® ) and then experimentally tested. An experimental setup is presented for dielectric, magnetic and chiral measurement in the 4.5–18 GHz band. (paper)
Space-charge calculation for bunched beams with 3-D ellipsoidal symmetry
International Nuclear Information System (INIS)
Garnett, R.W.; Wangler, T.P.
1991-01-01
A method for calculating 3-D space-charge forces has been developed that is suitable for bunched beams of either ions or relativistic electrons. The method is based on the analytic relations between charge-density and electric fields for a distribution with 3-D ellipsoidal symmetry in real space. At each step we use a Fourier-series representation for the smooth particle-density function obtained from the distribution of the macroparticles being tracked through the elements of the system. The resulting smooth electric fields reduce the problem of noise from artificial collisions, associated with small numbers of interacting macroparticles. Example calculations will be shown for comparison with other methods. 4 refs., 2 figs., 1 tab
Ellipsoidal and parabolic glass capillaries as condensers for x-ray microscopes
International Nuclear Information System (INIS)
Zeng Xianghui; Duewer, Fred; Feser, Michael; Huang, Carson; Lyon, Alan; Tkachuk, Andrei; Yun Wenbing
2008-01-01
Single-bounce ellipsoidal and paraboloidal glass capillary focusing optics have been fabricated for use as condenser lenses for both synchrotron and tabletop x-ray microscopes in the x-ray energy range of 2.5-18 keV. The condenser numerical apertures (NAs) of these devices are designed to match the NA of x-ray zone plate objectives, which gives them a great advantage over zone plate condensers in laboratory microscopes. The fabricated condensers have slope errors as low as 20 μrad rms. These capillaries provide a uniform hollow-cone illumination with almost full focusing efficiency, which is much higher than what is available with zone plate condensers. Sub-50 nm resolution at 8 keV x-ray energy was achieved by utilizing this high-efficiency condenser in a laboratory microscope based on a rotating anode generator
Degenerate Quadtree Latitude/Longitude Grid Based on WGS-84 Ellipsoidal Facet
Directory of Open Access Journals (Sweden)
HU Bailin
2016-12-01
Full Text Available For the needs of digital earth development and solving many global problems, a new discrete global grid system-DQLLG (degenerate quadtree latitude/longitude grid was put forward, which was based on WGS-84 ellipsoidal facet. The hierarchical subdivision method, characteristics and grid column/row coordinate system were detailed. The Latitude/Longitude coordinate, area and side length of multi-resolution meshes on different subdivision levels were calculated. Then the changes of mesh areas and side lengths were analyzed and compared that with spherical DQLLG. The research indicates that the DQLLG had many excellent features:uniformity, hierarchy, consistency of direction, extensive data compatibility and so on. It has certain practicality for Global GIS in the future.
Directory of Open Access Journals (Sweden)
Jesus Patricio Ordaz Oliver
2015-01-01
Full Text Available This paper presents a stability analysis for LNDS (Lagrangian nonlinear dynamical systems with dynamic uncertain using a PID controller with external disturbances rejection based on attractive ellipsoid methods, since the PID-CT (proportional integral derivative computed torque compensator has been used for the nonlinear trajectory tracking of an LNDS, when there are external perturbations and system uncertainties. The global system convergence of the trivial solution has not been proved. In this sense, we propose an approach to find the gains of the nonlinear PID-CT controller to guarantee the boundedness of the trivial solution by means of the concept of the UUB (uniform-ultimately bounded stability. In order to show the effectiveness of the methodology proposed, we applied it in a real 2-DoF robot system.
International Nuclear Information System (INIS)
Kon, A; Nakatsutsumi, M; Chen, Z L; Kodama, R; Buffechoux, S; Fuchs, J; Jin, Z
2010-01-01
We developed for the first time, very compact ( 3 ) extremely low f-number (f/number = 0.4) confocal ellipsoid focusing systems. Direct measurement of the laser focal spot using a low-energy laser beam indicates 1/5 reduction of the spot size compared to standard focusing (using a f/2.7 optics). Such mirror is thus able to achieve significant enhancement of the focused laser intensity without modifying the laser system itself. The mirror is then used under plasma mirror regime which enables us to compactify the size, to liberate us from the anxiety of protecting the optics from target debris after shots, and to enhance the temporal contrast. In this paper, we focus our attention to designing and optimizing the geometry of such innovative plasma optics.
Direct evidence for a massive galactic halo
International Nuclear Information System (INIS)
Hawkins, M.R.S.
1983-01-01
The discovery of a very distant galactic RR Lyrae star, R15 is reported. Spectroscopic observations of the object show that it has a high negative radial velocity, implying a lower limit to the mass of the galaxy of 1.4 x 10 12 Msun. (author)
International Nuclear Information System (INIS)
Singh, M.R.; Mukund, R.; Sahni, V.C.
1999-01-01
The influence of geometrical shape errors and surface errors on the characteristics and performance of grazing incidence optics used in the design of beamlines at synchrotron radiation facilities is considered. The methodology adopted for the simulation of slope errors is described and results presented for the ellipsoidal focussing mirror used in the design of PGM beamline at Indus-1. (author)
Tan, W.F.; Yu, Y.T.; Wang, M.X.; Liu, F.; Koopal, L.K.
2014-01-01
Spherical, ellipsoidal, and elongated hematite particles have been obtained via a simple chemical precipitation reaction of FeCl3 and NaOH in the presence of ascorbic acid,(AA). The effects of pH, molar ratio of AA/Fe(III), and time on the formation and shape of the hematite particles were
High-velocity runaway stars from three-body encounters
Gvaramadze, V. V.; Gualandris, A.; Portegies Zwart, S.
2010-01-01
We performed numerical simulations of dynamical encounters between hard, massive binaries and a very massive star (VMS; formed through runaway mergers of ordinary stars in the dense core of a young massive star cluster) to explore the hypothesis that this dynamical process could be responsible for the origin of high-velocity (≥ 200 - 400 km s-1) early or late B-type stars. We estimated the typical velocities produced in encounters between very tight massive binaries and VMSs (of mass of ≥ 200 M⊙) and found that about 3 - 4% of all encounters produce velocities ≥ 400 km s-1, while in about 2% of encounters the escapers attain velocities exceeding the Milky Ways's escape velocity. We therefore argue that the origin of high-velocity (≥ 200 - 400 km s-1) runaway stars and at least some so-called hypervelocity stars could be associated with dynamical encounters between the tightest massive binaries and VMSs formed in the cores of star clusters. We also simulated dynamical encounters between tight massive binaries and single ordinary 50 - 100 M⊙ stars. We found that from 1 to ≃ 4% of these encounters can produce runaway stars with velocities of ≥ 300 - 400 km s-1 (typical of the bound population of high-velocity halo B-type stars) and occasionally (in less than 1% of encounters) produce hypervelocity (≥ 700 km s-1) late B-type escapers.
International Nuclear Information System (INIS)
Thompson, Thomas W. J.; Rothschild, Richard E.
2009-01-01
Using two Chandra observations, we have derived estimates of the dust distribution and distance to the eclipsing high-mass X-ray binary Cen X-3 using the energy-resolved dust-scattered X-ray halo. By comparing the observed X-ray halos in 200 eV bands from 2-5 keV to the halo profiles predicted by the Weingartner and Draine interstellar grain model, we find that the vast majority (∼ 70%) of the dust along the line of sight to the system is located within about 300 pc of the Sun, although the halo measurements are insensitive to dust very close to the source. One of the Chandra observations occurred during an egress from eclipse as the pulsar emerged from behind the mass-donating primary. By comparing model halo light curves during this transition to the halo measurements, a source distance of 5.7 ± 1.5 kpc (68% confidence level) is estimated, although we find this result depends on the distribution of dust on very small scales. Nevertheless, this value is marginally inconsistent with the commonly accepted distance to Cen X-3 of 8 kpc. We also find that the energy scaling of the scattering optical depth predicted by the Weingartner and Draine interstellar grain model does not accurately represent the results determined by X-ray halo studies of Cen X-3. Relative to the model, there appears to be less scattering at low energies or more scattering at high energies in Cen X-3.
Mechanical device for enhancing halo density in the TMX-U tandem mirror
International Nuclear Information System (INIS)
Hsu, W.L.; Barr, W.L.; Simonen, T.C.
1984-04-01
The halo recycler, a mechanical device similar to pumped limiters used in tokamaks, is studied as a means of enhancing the halo plasma density in the Tandem Mirror Experiment Upgrade (TMX-U). The recycler structure consists of an annular chamber at each end of the tandem mirror device where the halo plasma is collected. The halo plasma density is increased by recycling the halo ions as they are neutralized by the collector plate. With sufficient power fed into the halo electrons, the recycler can sustain an upstream electron temperature of 30 eV for effective halo shielding while maintaining a low temperature of 5 eV near the collector plate to reduce sputtering. A power flow model has shown that the required power for heating the halo is low enough to make the halo recycler a practical concept
Halo-independent analysis of direct detection data for light WIMPs
International Nuclear Information System (INIS)
Nobile, Eugenio Del; Gelmini, Graciela B.; Huh, Ji-Haeng; Gondolo, Paolo
2013-01-01
We present a halo-independent analysis of direct detection data on ''light WIMPs'', i.e. weakly interacting massive particles with mass close to or below 10 GeV/c 2 . We include new results from silicon CDMS detectors (bounds and excess events), the latest CoGeNT acceptances, and recent measurements of low sodium quenching factors in NaI crystals. We focus on light WIMPs with spin-independent isospin-conserving and isospin-violating interactions with nucleons. For these dark matter candidates we find that a low quenching factor would make the DAMA modulation incompatible with a reasonable escape velocity for the dark matter halo, and that the tension among experimental data tightens in both the isospin-conserving and isospin-violating scenarios. We also find that a new although milder tension appears between the CoGeNT and DAMA annual modulations on one side and the silicon excess events on the other, in that it seems difficult to interpret them as the modulated and unmodulated aspects of the same WIMP dark matter signal
H I Clouds in the Lower Halo. I. The Galactic All-Sky Survey Pilot Region
International Nuclear Information System (INIS)
Ford, H. Alyson; McClure-Griffiths, N. M.; Calabretta, M. R.; Lockman, Felix J.; Pisano, D. J.; Bailin, J.; Kalberla, P. M. W.; Murphy, T.
2008-01-01
We have detected over 400 H I clouds in the lower halo of the Galaxy within the pilot region of the Galactic All-Sky Survey (GASS), a region of the fourth quadrant that spans 18 deg. in longitude, 40 deg. in latitude, and is centered on the Galactic equator. These clouds have a median peak brightness temperature of 0.6 K, a median velocity width of 12.8 km s -1 , and angular sizes ∼ -1 . A sample of clouds likely to be near tangent points was analyzed in detail. These clouds have radii on the order of 30 pc and a median H I mass of 630 M sun . The population has a vertical scale height of 400 pc and is concentrated in Galactocentric radius, peaking at R = 3.8 kpc. This confined structure suggests that the clouds are linked to spiral features, while morphological evidence that many clouds are aligned with loops and filaments is suggestive of a relationship with star formation. The clouds might result from supernovae and stellar winds in the form of fragmenting shells and gas that has been pushed into the halo rather than from a galactic fountain.
Internal Stellar Kinematics of M32 from the SPLASH Survey: Dark Halo Constraints
Howley, K. M.; Guhathakurta, P.; van der Marel, R.; Geha, M.; Kalirai, J.; Yniguez, B.; Kirby, E.; Cuillandre, J.-C.; Gilbert, K.
2013-03-01
As part of the SPLASH survey of the Andromeda (M31) system, we have obtained Keck/DEIMOS spectra of the compact elliptical (cE) satellite M32. This is the first resolved-star kinematical study of any cE galaxy. In contrast to most previous kinematical studies that extended out to r information to account statistically for M31 contamination. The rotation curve and velocity dispersion profile extend well beyond the radius (r ~ 150'') where the isophotes are distorted. Unlike NGC 205, another close dwarf companion of M31, M32's kinematics appear regular and symmetric and do not show obvious sharp gradients across the region of isophotal elongation and twists. We interpret M31's kinematics using three-integral axisymmetric dynamical equilibrium models constructed using Schwarzschild's orbit superposition technique. Models with a constant mass-to-light ratio can fit the data remarkably well. However, since such a model requires an increasing tangential anisotropy with radius, invoking the presence of an extended dark halo may be more plausible. Such an extended dark halo is definitely required to bind a half-dozen fast-moving stars observed at the largest radii, but these stars may not be an equilibrium component of M32. Data herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.
... this page: //medlineplus.gov/ency/article/003927.htm Nerve conduction velocity To use the sharing features on this page, please enable JavaScript. Nerve conduction velocity (NCV) is a test to see ...
International Nuclear Information System (INIS)
Beyer, R.T.
1985-01-01
The paper reviews the work carried out on the velocity of sound in liquid alkali metals. The experimental methods to determine the velocity measurements are described. Tables are presented of reported data on the velocity of sound in lithium, sodium, potassium, rubidium and caesium. A formula is given for alkali metals, in which the sound velocity is a function of shear viscosity, atomic mass and atomic volume. (U.K.)
How Galaxies Acquire their Gas: A Map of Multiphase Accretion and Feedback in Gaseous Galaxy Halos
Tumlinson, Jason
2009-07-01
We propose to address two of the biggest open questions in galaxy formation - how galaxies acquire their gas and how they return it to the IGM - with a concentrated COS survey of diffuse multiphase gas in the halos of SDSS galaxies at z = 0.15 - 0.35. Our chief science goal is to establish a basic set of observational facts about the physical state, metallicity, and kinematics of halo gas, including the sky covering fraction of hot and cold material, the metallicity of infall and outflow, and correlations with galaxy stellar mass, type, and color - all as a function of impact parameter from 10 - 150 kpc. Theory suggests that the bimodality of galaxy colors, the shape of the luminosity function, and the mass-metallicity relation are all influenced at a fundamental level by accretion and feedback, yet these gas processes are poorly understood and cannot be predicted robustly from first principles. We lack even a basic observational assessment of the multiphase gaseous content of galaxy halos on 100 kpc scales, and we do not know how these processes vary with galaxy properties. This ignorance is presently one of the key impediments to understanding galaxy formation in general. We propose to use the high-resolution gratings G130M and G160M on the Cosmic Origins Spectrograph to obtain sensitive column density measurements of a comprehensive suite of multiphase ions in the spectra of 43 z sound map of the physical state and metallicity of gaseous halos, and subsets of the data with cuts on galaxy mass, color, and SFR will seek out predicted variations of gas properties with galaxy properties. Our interpretation of these data will be aided by state-of-the-art hydrodynamic simulations of accretion and feedback, in turn providing information to refine and test such models. We will also use Keck, MMT, and Magellan {as needed} to obtain optical spectra of the QSOs to measure cold gas with Mg II, and optical spectra of the galaxies to measure SFRs and to look for outflows. In
The Angular Momentum of Baryons and Dark Matter Halos Revisited
Kimm, Taysun; Devriendt, Julien; Slyz, Adrianne; Pichon, Christophe; Kassin, Susan A.; Dubois, Yohan
2011-01-01
Recent theoretical studies have shown that galaxies at high redshift are fed by cold, dense gas filaments, suggesting angular momentum transport by gas differs from that by dark matter. Revisiting this issue using high-resolution cosmological hydrodynamics simulations with adaptive-mesh refinement (AMR), we find that at the time of accretion, gas and dark matter do carry a similar amount of specific angular momentum, but that it is systematically higher than that of the dark matter halo as a whole. At high redshift, freshly accreted gas rapidly streams into the central region of the halo, directly depositing this large amount of angular momentum within a sphere of radius r = 0.1R(sub vir). In contrast, dark matter particles pass through the central region unscathed, and a fraction of them ends up populating the outer regions of the halo (r/R(sub vir) > 0.1), redistributing angular momentum in the process. As a result, large-scale motions of the cosmic web have to be considered as the origin of gas angular momentum rather than its virialised dark matter halo host. This generic result holds for halos of all masses at all redshifts, as radiative cooling ensures that a significant fraction of baryons remain trapped at the centre of the halos. Despite this injection of angular momentum enriched gas, we predict an amount for stellar discs which is in fair agreement with observations at z=0. This arises because the total specific angular momentum of the baryons (gas and stars) remains close to that of dark matter halos. Indeed, our simulations indicate that any differential loss of angular momentum amplitude between the two components is minor even though dark matter halos continuously lose between half and two-thirds of their specific angular momentum modulus as they evolve. In light of our results, a substantial revision of the standard theory of disc formation seems to be required. We propose a new scenario where gas efficiently carries the angular momentum generated
HOT GAS HALOS IN EARLY-TYPE FIELD GALAXIES
International Nuclear Information System (INIS)
Mulchaey, John S.; Jeltema, Tesla E.
2010-01-01
We use Chandra and XMM-Newton to study the hot gas content in a sample of field early-type galaxies. We find that the L X -L K relationship is steeper for field galaxies than for comparable galaxies in groups and clusters. The low hot gas content of field galaxies with L K ∼ * suggests that internal processes such as supernovae-driven winds or active galactic nucleus feedback expel hot gas from low-mass galaxies. Such mechanisms may be less effective in groups and clusters where the presence of an intragroup or intracluster medium can confine outflowing material. In addition, galaxies in groups and clusters may be able to accrete gas from the ambient medium. While there is a population of L K ∼ * galaxies in groups and clusters that retain hot gas halos, some galaxies in these rich environments, including brighter galaxies, are largely devoid of hot gas. In these cases, the hot gas halos have likely been removed via ram pressure stripping. This suggests a very complex interplay between the intragroup/intracluster medium and hot gas halos of galaxies in rich environments, with the ambient medium helping to confine or even enhance the halos in some cases and acting to remove gas in others. In contrast, the hot gas content of more isolated galaxies is largely a function of the mass of the galaxy, with more massive galaxies able to maintain their halos, while in lower mass systems the hot gas escapes in outflowing winds.
Deep brain transcranial magnetic stimulation using variable "Halo coil" system
Meng, Y.; Hadimani, R. L.; Crowther, L. J.; Xu, Z.; Qu, J.; Jiles, D. C.
2015-05-01
Transcranial Magnetic Stimulation has the potential to treat various neurological disorders non-invasively and safely. The "Halo coil" configuration can stimulate deeper regions of the brain with lower surface to deep-brain field ratio compared to other coil configurations. The existing "Halo coil" configuration is fixed and is limited in varying the site of stimulation in the brain. We have developed a new system based on the current "Halo coil" design along with a graphical user interface system that enables the larger coil to rotate along the transverse plane. The new system can also enable vertical movement of larger coil. Thus, this adjustable "Halo coil" configuration can stimulate different regions of the brain by adjusting the position and orientation of the larger coil on the head. We have calculated magnetic and electric fields inside a MRI-derived heterogeneous head model for various positions and orientations of the coil. We have also investigated the mechanical and thermal stability of the adjustable "Halo coil" configuration for various positions and orientations of the coil to ensure safe operation of the system.
2MASS J06562998+3002455: Not a Cool White Dwarf Candidate, but a Population II Halo Star
de la Fuente Marcos, Raúl; de la Fuente Marcos, Carlos
2018-06-01
2MASS J06562998+3002455 or PSS 309-6 is a high proper-motion star that was discovered during a survey with the 2.1 m telescope at Kitt Peak National Observatory. Here, we reevaluate the status of this interesting star using Gaia DR2. Our results strongly suggest that PSS 309-6 could be a Population II star as the value of its V component is close to -220 km/s, which is typical for halo stars in the immediate solar neighborhood. Kapteyn's star is the nearest known halo star and PSS 309-6 exhibits similar kinematic and photometric signatures. Its properties also resemble those of 2MASS J15484023-3544254, which was once thought to be the nearest cool white dwarf but was later reclassified as K-type subdwarf. Although it is virtually certain that PSS 309-6 is not a nearby white dwarf but a more distant Population II subdwarf, further spectroscopic information, including radial velocity measurements, is necessary to fully characterize this probable member of the Galactic halo.
Halo-independent direct detection of momentum-dependent dark matter
Energy Technology Data Exchange (ETDEWEB)
Cherry, John F. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Frandsen, Mads T.; Shoemaker, Ian M., E-mail: jcherry@lanl.gov, E-mail: frandsen@cp3-origins.net, E-mail: shoemaker@cp3-origins.net [CP3-Origins and the Danish Institute for Advanced Study, University of Southern Denmark, Campusvej 55, DK-5230 Odense M (Denmark)
2014-10-01
We show that the momentum dependence of dark matter interactions with nuclei can be probed in direct detection experiments without knowledge of the dark matter velocity distribution. This is one of the few properties of DM microphysics that can be determined with direct detection alone, given a signal of dark matter in multiple direct detection experiments with different targets. Long-range interactions arising from the exchange of a light mediator are one example of momentum-dependent DM. For data produced from the exchange of a massless mediator we find for example that the mediator mass can be constrained to be ∼< 10 MeV for DM in the 20-1000 GeV range in a halo-independent manner.
Halo-independent direct detection of momentum-dependent dark matter
International Nuclear Information System (INIS)
Cherry, John F.; Frandsen, Mads T.; Shoemaker, Ian M.
2014-01-01
We show that the momentum dependence of dark matter interactions with nuclei can be probed in direct detection experiments without knowledge of the dark matter velocity distribution. This is one of the few properties of DM microphysics that can be determined with direct detection alone, given a signal of dark matter in multiple direct detection experiments with different targets. Long-range interactions arising from the exchange of a light mediator are one example of momentum-dependent DM. For data produced from the exchange of a massless mediator we find for example that the mediator mass can be constrained to be ∼< 10 MeV for DM in the 20-1000 GeV range in a halo-independent manner
The radial velocities of planetary nebulae in NGC 3379
Ciardullo, Robin; Jacoby, George H.; Dejonghe, Herwig B.
1993-09-01
We present the results of a radial velocity survey of planetary nebulae (PNs) in the normal elliptical galaxy NGC 3379 performed with the Kitt Peak 4 m telescope and the NESSIE multifiber spectrograph. In two half-nights, we measured 29 PNs with projected galactocentric distances between 0.4 and 3.8 effective radii with an observational uncertainty of about 7 km/s. These data extend three times farther into the halo than any previous absorption-line velocity study. The velocity dispersion and photometric profile of the galaxy agrees extremely well with that expected from a constant mass-to-light ratio, isotropic orbit Jaffe model with M/L(B) about 7; the best-fitting anisotropic models from a quadratic programming algorithm also give M/L(B) about 7. The data are consistent with models that contain no dark matter within 3.5 effective radii of the galaxy's nucleus.
Halo substructure in the SDSS-Gaia catalogue: streams and clumps
Myeong, G. C.; Evans, N. W.; Belokurov, V.; Amorisco, N. C.; Koposov, S. E.
2018-04-01
We use the Sloan Digital Sky Survey (SDSS)-Gaia Catalogue to identify six new pieces of halo substructure. SDSS-Gaia is an astrometric catalogue that exploits SDSS data release 9 to provide first epoch photometry for objects in the Gaia source catalogue. We use a version of the catalogue containing 245 316 stars with all phase-space coordinates within a heliocentric distance of ˜10 kpc. We devise a method to assess the significance of halo substructures based on their clustering in velocity space. The two most substantial structures are multiple wraps of a stream which has undergone considerable phase mixing (S1, with 94 members) and a kinematically cold stream (S2, with 61 members). The member stars of S1 have a median position of (X, Y, Z) = (8.12, -0.22, 2.75) kpc and a median metallicity of [Fe/H] = -1.78. The stars of S2 have median coordinates (X, Y, Z) = (8.66, 0.30, 0.77) kpc and a median metallicity of [Fe/H] = -1.91. They lie in velocity space close to some of the stars in the stream reported by Helmi et al. By modelling, we estimate that both structures had progenitors with virial masses ≈1010M⊙ and infall times ≳ 9 Gyr ago. Using abundance matching, these correspond to stellar masses between 106 and 107M⊙. These are somewhat larger than the masses inferred through the mass-metallicity relation by factors of 5 to 15. Additionally, we identify two further substructures (S3 and S4 with 55 and 40 members) and two clusters or moving group (C1 and C2 with 24 and 12) members. In all six cases, clustering in kinematics is found to correspond to clustering in both configuration space and metallicity, adding credence to the reliability of our detections.
Puzzle of the folding potential on the nuclear halo reactions
International Nuclear Information System (INIS)
Ismail, Atef; Lee, Yen Cheong; Mahmoud, Z.M.M.
2015-01-01
Folding potentials of the elastic scattering drip-line nuclei at various incident energies is one method to study nuclear matter density distributions and nuclear radii. The nuclei with density distributions consisting of a bulk (core) and an outer layer (halo), dilute and spatially extended are called the halo nuclei caused for the weak particle binding. Several halo nuclei are studied and many potential candidates are identified. All the cross-sections of the elastic scattering for the drip-line nuclei 11 Be and 6 He, are calculated to understand the exotic properties of these nuclei starting from its structure, extended radius, nuclear size till the large total reaction cross-sections for these nuclei when it interacts with a stable target 12 C. (author)
Properties of the ISM - Gas in the halo
Savage, Blair D.
1990-01-01
The properties of interstellar gas in the galactic halo are reviewed. Halo gas is found to have a wide range of physical conditions with temperatures ranging from less than 170 K to more than 200,000 K. The gas extending away from the plane of the Milky Way has density scale heights ranging from less than 300 pc for certain species in the neutral medium to approximately 3000 pc for the most highly ionized gas. The complex kinematical characteristics of the gas provides important clues about its origin. The gas phase elemental abundances in the neutral halo gas are closer to solar than is found for the highly depleted gas of the Milky Way disk. The possible origin of gas at large distances away from the galactic plane is discussed.
Halos around ellipticals and the environment dependence of Hubble type
International Nuclear Information System (INIS)
Zurek, W.H.; Quinn, P.J.; Salmon, J.K.
1985-01-01
It is not surprising that the baryonic material inside the more compact halos will tend to form a more compact, luminous elliptical. What needs to be explained is the difference in the value of the spin parameter (lambda). It might be tempting to speculate that more compact, dense halos have systematically smaller values of lambda. Such an effect is predicted by linear calculations. Our simulations show that it may exist but it appears to be too small compared to the random scatter of the values of lambda and rho to be decisive. It is more likely that the baryonic material has initially similar lambda both in the future spirals and elliptical but compact halos damp out the lambda of the dissipative, baryonic material more readily
Discovery of a Group of Receding, Variable Halo Stars toward Norma
Energy Technology Data Exchange (ETDEWEB)
Chakrabarti, Sukanya; Sargent, Benjamin; Lipnicky, Andrew [School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623 (United States); Angeloni, Rodolfo [Departamento de Fisica y Astronomia, Universidad de La Serena, Av. Juan Cisternas 1200 N, La Serena (Chile); Freeman, Kenneth [Research School of Astronomy and Astrophysics ANU RSAA Mount Stromlo Observatory (Australia); Simon, Joshua D. [The Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Konorski, Piotr [Warsaw University Observatory, al. Ujazdowskie 4, 00-001 Warszawa (Poland); Gieren, Wolfgang [Universidad de Concepcion, Concepción, Bío Bío Region (Chile); Sesar, Branimir [Max-Planck Institute for Astronomy, Room 332, Könighstuhl 17, D-69117 Heidelberg (Germany); Blitz, Leo; Basri, Gibor [Department of Astronomy, Campbell Hall, #501, Berkeley, CA 94720 (United States); Vacca, William [SOFIA-USRA, NASA Ames Research Center, Mail Stop N232-12, Moffet Field, CA 94035-1000 (United States); Marengo, Massimo [Department of Physics and Astronomy, Iowa State University, Ames, IA 50010 (United States); Guhathakurta, Puragra [Department of Astronomy, UC Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Quillen, Alice [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Chang, Philip, E-mail: chakrabarti@astro.rit.edu [Dept of Physics, PO Box 413, Milwaukee, WI 53201 (United States)
2017-08-01
We present results from spectroscopic observations of a trio of Cepheid candidates identified from K {sub s} -band light curves toward Norma. The spectra show that these stars are moving with a large and similar radial velocity—the heliocentric velocities are 171 ± 32 km s{sup −1}, 164 ± 37 km s{sup −1}, and 173 ± 20 km s{sup −1}. The average radial velocity is ∼169 km s{sup −1}, which is large and distinct from typical stars in the Galaxy’s stellar disk. Given the radial velocities and associated 1 σ error, we find that the combined probability that these three stars are foreground Milky Way disk stars is ∼7 × 10{sup −4}%, and the probability that these are large-amplitude spotted stars in a binary is ∼10{sup −5}%. These objects at l ∼ 333° and b ∼ −1° are therefore associated with the stellar halo. The identification of these sources as Type I Cepheids is not certain, and thus the distances of these sources are not yet well established. Assuming the 3.6 μ m period–luminosity relation of Type I Cepheids gives a distance of ∼78 kpc for these sources.
Discovery of a Group of Receding, Variable Halo Stars toward Norma
International Nuclear Information System (INIS)
Chakrabarti, Sukanya; Sargent, Benjamin; Lipnicky, Andrew; Angeloni, Rodolfo; Freeman, Kenneth; Simon, Joshua D.; Konorski, Piotr; Gieren, Wolfgang; Sesar, Branimir; Blitz, Leo; Basri, Gibor; Vacca, William; Marengo, Massimo; Guhathakurta, Puragra; Quillen, Alice; Chang, Philip
2017-01-01
We present results from spectroscopic observations of a trio of Cepheid candidates identified from K s -band light curves toward Norma. The spectra show that these stars are moving with a large and similar radial velocity—the heliocentric velocities are 171 ± 32 km s −1 , 164 ± 37 km s −1 , and 173 ± 20 km s −1 . The average radial velocity is ∼169 km s −1 , which is large and distinct from typical stars in the Galaxy’s stellar disk. Given the radial velocities and associated 1 σ error, we find that the combined probability that these three stars are foreground Milky Way disk stars is ∼7 × 10 −4 %, and the probability that these are large-amplitude spotted stars in a binary is ∼10 −5 %. These objects at l ∼ 333° and b ∼ −1° are therefore associated with the stellar halo. The identification of these sources as Type I Cepheids is not certain, and thus the distances of these sources are not yet well established. Assuming the 3.6 μ m period–luminosity relation of Type I Cepheids gives a distance of ∼78 kpc for these sources.
The globular cluster-dark matter halo connection
Boylan-Kolchin, Michael
2017-12-01
I present a simple phenomenological model for the observed linear scaling of the stellar mass in old globular clusters (GCs) with z = 0 halo mass in which the stellar mass in GCs scales linearly with progenitor halo mass at z = 6 above a minimum halo mass for GC formation. This model reproduces the observed MGCs-Mhalo relation at z = 0 and results in a prediction for the minimum halo mass at z = 6 required for hosting one GC: Mmin(z = 6) = 1.07 × 109 M⊙. Translated to z = 0, the mean threshold mass is Mhalo(z = 0) ≈ 2 × 1010 M⊙. I explore the observability of GCs in the reionization era and their contribution to cosmic reionization, both of which depend sensitively on the (unknown) ratio of GC birth mass to present-day stellar mass, ξ. Based on current detections of z ≳ 6 objects with M1500 10 are strongly disfavoured; this, in turn, has potentially important implications for GC formation scenarios. Even for low values of ξ, some observed high-z galaxies may actually be GCs, complicating estimates of reionization-era galaxy ultraviolet luminosity functions and constraints on dark matter models. GCs are likely important reionization sources if 5 ≲ ξ ≲ 10. I also explore predictions for the fraction of accreted versus in situ GCs in the local Universe and for descendants of systems at the halo mass threshold of GC formation (dwarf galaxies). An appealing feature of the model presented here is the ability to make predictions for GC properties based solely on dark matter halo merger trees.
The Halo Boundary of Galaxy Clusters in the SDSS
Energy Technology Data Exchange (ETDEWEB)
Baxter, Eric; Jain, Bhuvnesh; Sheth, Ravi K. [Center for Particle Cosmology, Department of Physics, University of Pennsylvania, Philadelphia, PA 19104 (United States); Chang, Chihway; Kravtsov, Andrey [Kavli Institute for Cosmological Physics, The University of Chicago, Chicago, IL 60637 (United States); Adhikari, Susmita; Dalal, Neal [Department of Astronomy, University of Illinois at Urbana-Champaign, Champaign, IL 61801 (United States); More, Surhud [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Tokyo Institutes for Advanced Study, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba, 277-8583 (Japan); Rozo, Eduardo [Department of Physics, University of Arizona, Tucson, AZ 85721 (United States); Rykoff, Eli, E-mail: ebax@sas.upenn.edu [Kavli Institute for Particle Astrophysics and Cosmology, P.O. Box 2450, Stanford University, Stanford, CA 94305 (United States)
2017-05-20
Analytical models and simulations predict a rapid decline in the halo density profile associated with the transition from the “infalling” regime outside the halo to the “collapsed” regime within the halo. Using data from SDSS, we explore evidence for such a feature in the density profiles of galaxy clusters using several different approaches. We first estimate the steepening of the outer galaxy density profile around clusters, finding evidence for truncation of the halo profile. Next, we measure the galaxy density profile around clusters using two sets of galaxies selected on color. We find evidence of an abrupt change in galaxy colors that coincides with the location of the steepening of the density profile. Since galaxies that have completed orbits within the cluster are more likely to be quenched of star formation and thus appear redder, this abrupt change in galaxy color can be associated with the transition from single-stream to multi-stream regimes. We also use a standard model comparison approach to measure evidence for a “splashback”-like feature, but find that this approach is very sensitive to modeling assumptions. Finally, we perform measurements using an independent cluster catalog to test for potential systematic errors associated with cluster selection. We identify several avenues for future work: improved understanding of the small-scale galaxy profile, lensing measurements, identification of proxies for the halo accretion rate, and other tests. With upcoming data from the DES, KiDS, and HSC surveys, we can expect significant improvements in the study of halo boundaries.
Painting galaxies into dark matter halos using machine learning
Agarwal, Shankar; Davé, Romeel; Bassett, Bruce A.
2018-05-01
We develop a machine learning (ML) framework to populate large dark matter-only simulations with baryonic galaxies. Our ML framework takes input halo properties including halo mass, environment, spin, and recent growth history, and outputs central galaxy and halo baryonic properties including stellar mass (M*), star formation rate (SFR), metallicity (Z), neutral (H I) and molecular (H_2) hydrogen mass. We apply this to the MUFASA cosmological hydrodynamic simulation, and show that it recovers the mean trends of output quantities with halo mass highly accurately, including following the sharp drop in SFR and gas in quenched massive galaxies. However, the scatter around the mean relations is under-predicted. Examining galaxies individually, at z = 0 the stellar mass and metallicity are accurately recovered (σ ≲ 0.2 dex), but SFR and H I show larger scatter (σ ≳ 0.3 dex); these values improve somewhat at z = 1, 2. Remarkably, ML quantitatively recovers second parameter trends in galaxy properties, e.g. that galaxies with higher gas content and lower metallicity have higher SFR at a given M*. Testing various ML algorithms, we find that none perform significantly better than the others, nor does ensembling improve performance, likely because none of the algorithms reproduce the large observed scatter around the mean properties. For the random forest algorithm, we find that halo mass and nearby (˜200 kpc) environment are the most important predictive variables followed by growth history, while halo spin and ˜Mpc scale environment are not important. Finally we study the impact of additionally inputting key baryonic properties M*, SFR, and Z, as would be available e.g. from an equilibrium model, and show that particularly providing the SFR enables H I to be recovered substantially more accurately.
Three-body halo nuclei in an effective theory framework
Energy Technology Data Exchange (ETDEWEB)
Canham, David L.
2009-05-20
The universal properties and structure of halo nuclei composed of two neutrons (2n) and a core are investigated within an effective quantum mechanics framework. We construct an effective interaction potential that exploits the separation of scales in halo nuclei and treat the nucleus as an effective three-body system, which to leading order is described by the large S-wave scattering lengths in the underlying two-body subsystems. The uncertainty from higher orders in the expansion is quantified through theoretical error bands. First, we investigate the possibility to observe excited Efimov states in 2n halo nuclei. Based on the experimental data, {sup 20}C is the only halo nucleus candidate to possibly have an Efimov excited state, with an energy less than 7 keV below the scattering threshold. Second, we study the structure of {sup 20}C and other 2n halo nuclei. In particular, we calculate their matter density form factors, radii, and two-neutron opening angles. We then make a systematic improvement upon these calculations by extending the effective potential to the next-to-leading order. To this order, we require an additional two-body parameter, which we tune to the effective range of the interaction. In addition to range corrections to the 2n halo nuclei results, we show corrections to the Efimov effect in the three-boson system. Furthermore, we explore universality in the linear range corrections to the Efimov spectrum. Finally, we study the scattering of D{sup 0} and D{sup *0} mesons and their antiparticles off the X(3872) in an effective field theory for short-range interactions. We present results for the S-wave scattering amplitude, total interaction cross section and S-wave scattering length. (orig.)
The Halo Boundary of Galaxy Clusters in the SDSS
International Nuclear Information System (INIS)
Baxter, Eric; Jain, Bhuvnesh; Sheth, Ravi K.; Chang, Chihway; Kravtsov, Andrey; Adhikari, Susmita; Dalal, Neal; More, Surhud; Rozo, Eduardo; Rykoff, Eli
2017-01-01
Analytical models and simulations predict a rapid decline in the halo density profile associated with the transition from the “infalling” regime outside the halo to the “collapsed” regime within the halo. Using data from SDSS, we explore evidence for such a feature in the density profiles of galaxy clusters using several different approaches. We first estimate the steepening of the outer galaxy density profile around clusters, finding evidence for truncation of the halo profile. Next, we measure the galaxy density profile around clusters using two sets of galaxies selected on color. We find evidence of an abrupt change in galaxy colors that coincides with the location of the steepening of the density profile. Since galaxies that have completed orbits within the cluster are more likely to be quenched of star formation and thus appear redder, this abrupt change in galaxy color can be associated with the transition from single-stream to multi-stream regimes. We also use a standard model comparison approach to measure evidence for a “splashback”-like feature, but find that this approach is very sensitive to modeling assumptions. Finally, we perform measurements using an independent cluster catalog to test for potential systematic errors associated with cluster selection. We identify several avenues for future work: improved understanding of the small-scale galaxy profile, lensing measurements, identification of proxies for the halo accretion rate, and other tests. With upcoming data from the DES, KiDS, and HSC surveys, we can expect significant improvements in the study of halo boundaries.
Three-body halo nuclei in an effective theory framework
International Nuclear Information System (INIS)
Canham, David L.
2009-01-01
The universal properties and structure of halo nuclei composed of two neutrons (2n) and a core are investigated within an effective quantum mechanics framework. We construct an effective interaction potential that exploits the separation of scales in halo nuclei and treat the nucleus as an effective three-body system, which to leading order is described by the large S-wave scattering lengths in the underlying two-body subsystems. The uncertainty from higher orders in the expansion is quantified through theoretical error bands. First, we investigate the possibility to observe excited Efimov states in 2n halo nuclei. Based on the experimental data, 20 C is the only halo nucleus candidate to possibly have an Efimov excited state, with an energy less than 7 keV below the scattering threshold. Second, we study the structure of 20 C and other 2n halo nuclei. In particular, we calculate their matter density form factors, radii, and two-neutron opening angles. We then make a systematic improvement upon these calculations by extending the effective potential to the next-to-leading order. To this order, we require an additional two-body parameter, which we tune to the effective range of the interaction. In addition to range corrections to the 2n halo nuclei results, we show corrections to the Efimov effect in the three-boson system. Furthermore, we explore universality in the linear range corrections to the Efimov spectrum. Finally, we study the scattering of D 0 and D *0 mesons and their antiparticles off the X(3872) in an effective field theory for short-range interactions. We present results for the S-wave scattering amplitude, total interaction cross section and S-wave scattering length. (orig.)
The Milky Way's Circular Velocity Curve and Its Constraint on the Galactic Mass with RR Lyrae Stars
Energy Technology Data Exchange (ETDEWEB)
Ablimit, Iminhaji; Zhao, Gang, E-mail: iminhaji@nao.cas.cn, E-mail: gzhao@nao.cas.cn [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)
2017-09-01
We present a sample of 1148 ab-type RR Lyrae (RRLab) variables identified from Catalina Surveys Data Release 1, combined with SDSS DR8 and LAMOST DR4 spectral data. We first use a large sample of 860 Galactic halo RRLab stars and derive the circular velocity distributions for the stellar halo. With the precise distances and carefully determined radial velocities (the center-of-mass radial velocities) and by considering the pulsation of the RRLab stars in our sample, we can obtain a reliable and comparable stellar halo circular velocity curve. We follow two different prescriptions for the velocity anisotropy parameter β in the Jeans equation to study the circular velocity curve and mass profile. Additionally, we test two different solar peculiar motions in our calculation. The best result we obtained with the adopted solar peculiar motion 1 of ( U , V , W ) = (11.1, 12, 7.2) km s{sup −1} is that the enclosed mass of the Milky Way within 50 kpc is (3.75 ± 1.33) × 10{sup 11} M {sub ⊙} based on β = 0 and the circular velocity 180 ± 31.92 (km s{sup −1}) at 50 kpc. This result is consistent with dynamical model results, and it is also comparable to the results of previous similar works.
A UNIFIED FRAMEWORK FOR THE ORBITAL STRUCTURE OF BARS AND TRIAXIAL ELLIPSOIDS
Energy Technology Data Exchange (ETDEWEB)
Valluri, Monica; Abbott, Caleb [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Shen, Juntai [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Debattista, Victor P., E-mail: mvalluri@umich.edu, E-mail: calebga@umich.edu, E-mail: jshen@shao.ac.cn, E-mail: vpdebattista@uclan.ac.uk [Jeremiah Horrocks Institute, University of Central Lancashire, Preston, PR1 2HE (United Kingdom)
2016-02-20
We examine a large random sample of orbits in two self-consistent simulations of N-body bars. Orbits in these bars are classified both visually and with a new automated orbit classification method based on frequency analysis. The well-known prograde x1 orbit family originates from the same parent orbit as the box orbits in stationary and rotating triaxial ellipsoids. However, only a small fraction of bar orbits (∼4%) have predominately prograde motion like their periodic parent orbit. Most bar orbits arising from the x1 orbit have little net angular momentum in the bar frame, making them equivalent to box orbits in rotating triaxial potentials. In these simulations a small fraction of bar orbits (∼7%) are long-axis tubes that behave exactly like those in triaxial ellipsoids: they are tipped about the intermediate axis owing to the Coriolis force, with the sense of tipping determined by the sign of their angular momentum about the long axis. No orbits parented by prograde periodic x2 orbits are found in the pure bar model, but a tiny population (∼2%) of short-axis tube orbits parented by retrograde x4 orbits are found. When a central point mass representing a supermassive black hole (SMBH) is grown adiabatically at the center of the bar, those orbits that lie in the immediate vicinity of the SMBH are transformed into precessing Keplerian orbits that belong to the same major families (short-axis tubes, long-axis tubes and boxes) occupying the bar at larger radii. During the growth of an SMBH, the inflow of mass and outward transport of angular momentum transform some x1 and long-axis tube orbits into prograde short-axis tubes. This study has important implications for future attempts to constrain the masses of SMBHs in barred galaxies using orbit-based methods like the Schwarzschild orbit superposition scheme and for understanding the observed features in barred galaxies.
An ancient F-type subdwarf from the halo crossing the Galactic plane
Scholz, R.-D.; Heber, U.; Heuser, C.; Ziegerer, E.; Geier, S.; Niederhofer, F.
2015-02-01
Aims: We selected the bluest object, WISE J0725-2351, from Luhman's new high proper motion (HPM) survey based on observations with the Wide-field Infrared Survey Explorer (WISE) for spectroscopic follow-up observations. Our aim was to unravel the nature of this relatively bright (V ~ 12, J ~ 11) HPM star (μ = 267 mas/yr). Methods: We obtained low- and medium-resolution spectra with the European Southern Observatory (ESO) New Technology Telescope (NTT)/EFOSC2 and Very Large Telescope (VLT)/X-Shooter instruments, investigated the radial velocity and performed a quantitative spectral analysis that allowed us to determine physical parameters. The fit of the spectral energy distribution based on the available photometry to low-metallicity model spectra and the similarity of our target to a metal-poor benchmark star (HD 84937) allowed us to estimate the distance and space velocity. Results: As in the case of HD 84937, we classified WISE J0725-2351 as sdF5: or a metal-poor turnoff star with [ Fe/H ] = -2.0 ± 0.2, Teff = 6250 ± 100 K, log g = 4.0 ± 0.2, and a possible age of about 12 Gyr. At an estimated distance of more than 400 pc, its proper motion translates to a tangential velocity of more than 500 km s-1. Together with its constant (on timescales of hours, days, and months) and large radial velocity (about +240 km s-1), the resulting Galactic restframe velocity is about 460 km s-1, implying a bound retrograde orbit for this extreme halo object that currently crosses the Galactic plane at high speed. Based on observations at the La Silla-Paranal Observatory of the European Southern Observatory for programmes 092.D-0040(A) and 093.D-0127(A).
Shirasaki, Masato; Yoshida, Naoki
2018-04-01
Weak lensing three-point statistics are powerful probes of the structure of dark matter haloes. We propose to use the correlation of the positions of galaxies with the shapes of background galaxy pairs, known as the halo-shear-shear correlation (HSSC), to measure the mean halo ellipticity and the abundance of subhaloes in a statistical manner. We run high-resolution cosmological N-body simulations and use the outputs to measure the HSSC for galaxy haloes and cluster haloes. Non-spherical haloes cause a characteristic azimuthal variation of the HSSC, and massive subhaloes in the outer region near the virial radius contribute to ˜ 10 per cent of the HSSC amplitude. Using the HSSC and its covariance estimated from our N-body simulations, we make forecast for constraining the internal structure of dark matter haloes with future galaxy surveys. With 1000 galaxy groups with mass greater than 1013.5 h-1M⊙, the average halo ellipticity can be measured with an accuracy of 10 percent. A spherical, smooth mass distribution can be ruled out at a ˜5σ significance level. The existence of subhaloes whose masses are in 1-10 percent of the main halo mass can be detected with ˜104 galaxies/clusters. We conclude that the HSSC provides valuable information on the structure of dark haloes and hence on the nature of dark matter.
Thomason, L. W.
2012-01-01
Herein, the Halogen Occultation Experiment (HALOE) aerosol extinction coefficient data is evaluated in the low aerosol loading period after 1996 as the first necessary step in a process that will eventually allow the production of a combined HALOE/SAGE II (Stratospheric Aerosol and Gas Experiment) aerosol climatology of derived aerosol products including surface area density. Based on these analyses, it is demonstrated that HALOE's 3.46 microns is of good quality above 19 km and suitable for scientific applications above that altitude. However, it is increasingly suspect at lower altitudes and should not be used below 17 km under any circumstances after 1996. The 3.40 microns is biased by about 10% throughout the lower stratosphere due to the failure to clear NO2 but otherwise appears to be a high quality product down to 15 km. The 2.45 and 5.26 micron aerosol extinction coefficient measurements are clearly biased and should not be used for scientific applications after the most intense parts of the Pinatubo period. Many of the issues in the aerosol data appear to be related to either the failure to clear some interfering gas species or doing so poorly. For instance, it is clear that the 3.40micronaerosol extinction coefficient measurements can be improved through the inclusion of an NO2 correction and could, in fact, end up as the highest quality overall HALOE aerosol extinction coefficient measurement. It also appears that the 2.45 and 5.26 micron channels may be improved by updating the Upper Atmosphere Pilot Database which is used as a resource for the removal of gas species otherwise not available from direct HALOE measurements. Finally, a simple model to demonstrate the promise of mixed visible/infrared aerosol extinction coefficient ensembles for the retrieval of bulk aerosol properties demonstrates that a combined HALOE/SAGE II aerosol climatology is feasible and may represent a substantial improvement over independently derived data sets.
Two clusters of GABAergic ellipsoid body neurons modulate olfactory labile memory in Drosophila.
Zhang, Zhiping; Li, Xiaoting; Guo, Jing; Li, Yan; Guo, Aike
2013-03-20
In Drosophila, aversive olfactory memory is believed to be stored in a prominent brain structure, the mushroom body (MB), and two pairs of MB intrinsic neurons, the dorsal paired medial (DPM) and the anterior paired lateral (APL) neurons, are found to regulate the consolidation of middle-term memory (MTM). Here we report that another prominent brain structure, the ellipsoid body (EB), is also involved in the modulation of olfactory MTM. Activating EB R2/R4m neurons does not affect the learning index, but specifically eliminates anesthesia-sensitive memory (ASM), the labile component of olfactory MTM. We further demonstrate that approximately two-thirds of these EB neurons are GABAergic and are responsible for the suppression of ASM. Using GRASP (GFP reconstitution across synaptic partners), we reveal potential synaptic connections between the EB and MB in regions covering both the presynaptic and postsynaptic sites of EB neurons, suggesting the presence of bidirectional connections between these two important brain structures. These findings suggest the existence of direct connections between the MB and EB, and provide new insights into the neural circuit basis for olfactory labile memory in Drosophila.
Correlation of Macular Focal Electroretinogram with Ellipsoid Zone Extension in Stargardt Disease
Directory of Open Access Journals (Sweden)
Edoardo Abed
2017-01-01
Full Text Available Stargardt disease (STGD1 is the most common cause of inherited juvenile macular degeneration. This disease is characterized by a progressive accumulation of lipofuscin in the outer retina and subsequent loss of photoreceptors and retinal pigment epithelium. The aim of this study was to evaluate the relationship between cone photoreceptor function and structure in STGD1. Macular function was assessed by visual acuity measurement and focal electroretinogram (FERG recording while spectral domain optical coherence tomography (SD-OCT imaging was performed to evaluate the integrity of photoreceptors. FERG amplitude was significantly reduced in patients with Stargardt disease (p<0.0001. The amplitude of FERG showed a negative relationship with interruption of ellipsoid zone (EZ (R2=0.54, p<0.0001 and a positive correlation with average macular thickness (AMT. Conversely, visual acuity was only weakly correlated with central macular thickness (CMT (R2=0.12, p=0.04. In conclusion, this study demonstrates that FERG amplitude is a reliable indicator of macular cone function while visual acuity reflects the activity of the foveal region. A precise assessment of macular cone function by FERG recording may be useful to monitor the progression of STGD1 and to select the optimal candidates to include in future clinical trials to treat this disease.
Wang, Chong; Kou, Xueying; Xie, Ning; Guo, Lanlan; Sun, Yanfeng; Chuai, Xiaohong; Ma, Jian; Sun, Peng; Wang, Yue; Lu, Geyu
2017-05-26
Indium tungsten oxide ellipsoidal nanospheres were prepared with different In/W ratios by using a simple hydrothermal method without any surfactant for the first time. Sensors based on different In/W ratios samples were fabricated, and one of the samples exhibited better response to methanol compared with others. High content of defective oxygen (Ov) and proper output proportion of In to W might be the main reasons for the better gas sensing properties. The length of the nanosphere was about 150-200 nm, and the width was about 100 nm. Various techniques were applied to investigate the nanospheres. Sensing characteristics toward methanol were investigated. Significantly, the sensor exhibited ultrafast response to methanol. The response time to 400 ppm methanol was no more than 2 s and the recovery time was 9 s at 312 °C. Most importantly, the humidity almost had no effect on the response of the sensor fabricated here, which is hard to achieve in gas-sensing applications.
International Nuclear Information System (INIS)
DePuit, Ryan J; Squires, Todd M
2012-01-01
Active and nonlinear microrheology experiments involve a colloidal probe that is forced to move within a material, with the goal of recovering the nonlinear rheological response properties of the material. Various mechanisms cause discrepancies between the nonlinear rheology measured microrheologically and macroscopically, including direct probe-bath collisions, the Lagrangian unsteadiness experienced by the material elements, and the spatially inhomogeneous and rheologically mixed strain field set up around the probe. Here, we perform computational nonlinear microrheology experiments, in which a colloidal probe translates through a dilute suspension of Brownian ellipsoids, whose results we compare against analogous computational experiments on the macroscopic shear rheology of the same model material. The quantitative impact of each of the mechanisms for micro-macro-discrepancy can thus be computed directly, with additional computational experiments performed where the processes in question are ‘turned off’. We show that all three discrepancy mechanisms impact the microrheological measurement quantitatively, and that none can be neglected. This motivates a search for microrheological probes whose geometry or forcing is optimized to minimize these impacts, which we present in a companion article.
Behaviors of ellipsoidal micro-particles within a two-beam optical levitator
International Nuclear Information System (INIS)
Petkov, T.; Yang, M.; Ren, K.F.; Pouligny, B.; Loudet, J.-C.
2017-01-01
The two-beam levitator (TBL) is a standard optical setup made of a couple of counter-propagating beams. Note worthily, TBLs allow the manipulation and trapping of particles at long working distances. While much experience has been accumulated in the trapping of single spherical particles in TBLs, the behaviors of asymmetrical particles turn out to be more complex, and even surprising. Here, we report observations with prolate ellipsoidal polystyrene particles, with varying aspect ratio and ratio of the two beam powers. Generalizing the earlier work by Mihiretie et al. in single beam geometries [JQSRT 126, 61 (2013)], we observe that particles may be either static, or permanently oscillating, and that the two-beam geometry produces new particle responses: some of them are static, but non-symmetrical, while others correspond to new types of oscillations. A two-dimensional model based on ray-optics qualitatively accounts for these configurations and for the “primary” oscillations of the particles. Furthermore, levitation powers measured in the experiments are in fair agreement with those computed from GLMT (Generalized Lorentz Mie Theory), MLFMA (Multilevel Fast Multipole Algorithm) and approximate ray-optics methods. - Highlights: • Spheroids in two-laser beam geometry may stabilize in asymmetric configurations. • Particles undergo different types of oscillations, in polar and azimuthal angles. • Polar angle oscillations and asymmetric equilibriums are predicted by ray-optics. • The basic levitation force decreases with particle aspect ratio. • Experiments, simple ray optics and MLFMA calculations show similar tendencies.
Sokołowski, Damian; Kamiński, Marcin
2018-01-01
This study proposes a framework for determination of basic probabilistic characteristics of the orthotropic homogenized elastic properties of the periodic composite reinforced with ellipsoidal particles and a high stiffness contrast between the reinforcement and the matrix. Homogenization problem, solved by the Iterative Stochastic Finite Element Method (ISFEM) is implemented according to the stochastic perturbation, Monte Carlo simulation and semi-analytical techniques with the use of cubic Representative Volume Element (RVE) of this composite containing single particle. The given input Gaussian random variable is Young modulus of the matrix, while 3D homogenization scheme is based on numerical determination of the strain energy of the RVE under uniform unit stretches carried out in the FEM system ABAQUS. The entire series of several deterministic solutions with varying Young modulus of the matrix serves for the Weighted Least Squares Method (WLSM) recovery of polynomial response functions finally used in stochastic Taylor expansions inherent for the ISFEM. A numerical example consists of the High Density Polyurethane (HDPU) reinforced with the Carbon Black particle. It is numerically investigated (1) if the resulting homogenized characteristics are also Gaussian and (2) how the uncertainty in matrix Young modulus affects the effective stiffness tensor components and their PDF (Probability Density Function).
International Nuclear Information System (INIS)
Basin, A.A.; Vatulin, V.V.; Vakhlamova, L.L.; Vinokurov, P.A.; Dement'ev, Yu.A.; Eliseev, G.M.; Ermolovich, V.F.; Morenko, L.Z.; Morenko, A.I.; Remizov, G.N.; Romanov, Yu.A.; Ryabikina, N.A.; Skrypnik, S.I.; Skidan, G.I.; Tikhomirov, B.P.; Shagaliev, R.M.
1996-01-01
To solve the design problem of an inertial thermonuclear fusion facility requires the united efforts of scientists in various countries. In the field of heavy ion fusion a collaboration between scientists in Germany and Russia is under successful development. VNIIEF possesses advanced software for numerical simulation of the processes in thermonuclear target operation. This paper describes a target design suggested and being studied by scientists of Frankfurt University and GSI which is based on 2D non-stationary calculation of the X-ray energy transport and capsule compression. The target consists of a spherical capsule with DT fuel and an ellipsoidal chamber containment. The ion beam energy is released in two fixed converters located on the chamber axis symmetricall with respect to the capsule. The X-ray field is formed on the capsule surface with a set of special shields. The basic aim of our research is to estimate the effect of gas dynamic expansion of the chamber walls, shields and capsule on the target operation. To increase the reliability of the obtained results and the assessment of probable errors in predicting radiation field parameters and the capsule state, the calculations were accomplished in a kinetic arrangement with various techniques. (orig.)
Numerical solutions of the semiclassical Boltzmann ellipsoidal-statistical kinetic model equation
Yang, Jaw-Yen; Yan, Chin-Yuan; Huang, Juan-Chen; Li, Zhihui
2014-01-01
Computations of rarefied gas dynamical flows governed by the semiclassical Boltzmann ellipsoidal-statistical (ES) kinetic model equation using an accurate numerical method are presented. The semiclassical ES model was derived through the maximum entropy principle and conserves not only the mass, momentum and energy, but also contains additional higher order moments that differ from the standard quantum distributions. A different decoding procedure to obtain the necessary parameters for determining the ES distribution is also devised. The numerical method in phase space combines the discrete-ordinate method in momentum space and the high-resolution shock capturing method in physical space. Numerical solutions of two-dimensional Riemann problems for two configurations covering various degrees of rarefaction are presented and various contours of the quantities unique to this new model are illustrated. When the relaxation time becomes very small, the main flow features a display similar to that of ideal quantum gas dynamics, and the present solutions are found to be consistent with existing calculations for classical gas. The effect of a parameter that permits an adjustable Prandtl number in the flow is also studied. PMID:25104904
Gaze3DFix: Detecting 3D fixations with an ellipsoidal bounding volume.
Weber, Sascha; Schubert, Rebekka S; Vogt, Stefan; Velichkovsky, Boris M; Pannasch, Sebastian
2017-10-26
Nowadays, the use of eyetracking to determine 2-D gaze positions is common practice, and several approaches to the detection of 2-D fixations exist, but ready-to-use algorithms to determine eye movements in three dimensions are still missing. Here we present a dispersion-based algorithm with an ellipsoidal bounding volume that estimates 3D fixations. Therefore, 3D gaze points are obtained using a vector-based approach and are further processed with our algorithm. To evaluate the accuracy of our method, we performed experimental studies with real and virtual stimuli. We obtained good congruence between stimulus position and both the 3D gaze points and the 3D fixation locations within the tested range of 200-600 mm. The mean deviation of the 3D fixations from the stimulus positions was 17 mm for the real as well as for the virtual stimuli, with larger variances at increasing stimulus distances. The described algorithms are implemented in two dynamic linked libraries (Gaze3D.dll and Fixation3D.dll), and we provide a graphical user interface (Gaze3DFixGUI.exe) that is designed for importing 2-D binocular eyetracking data and calculating both 3D gaze points and 3D fixations using the libraries. The Gaze3DFix toolkit, including both libraries and the graphical user interface, is available as open-source software at https://github.com/applied-cognition-research/Gaze3DFix .
Kerins, E; Evans, N W; Baillon, Paul; Carr, B J; Giraud-Héraud, Yannick; Gould, A; Hewett, P C; Kaplan, J; Paulin-Henriksson, S; Smartt, S J; Tsapras, Y; Valls-Gabaud, D
2003-01-01
The POINT-AGAPE collaboration is currently searching for massive compact halo objects (MACHOs) towards the Andromeda galaxy (M31). The survey aims to exploit the high inclination of the M31 disk, which causes an asymmetry in the spatial distribution of M31 MACHOs. Here, we investigate the effects of halo velocity anisotropy and flattening on the asymmetry signal using simple halo models. For a spherically symmetric and isotropic halo, we find that the underlying pixel-lensing rate in far-disk M31 MACHOs is more than 5 times the rate of near-disk events. We find that the asymmetry is increased further by about 30% if the MACHOs occupy radial orbits rather than tangential orbits, but is substantially reduced if the MACHOs lie in a flattened halo. However, even for haloes with a minor-to-major axis ratio q = 0.3, the numbers of M31 MACHOs in the far-side outnumber those in the near-side by a factor of ~2. We show that, if positional information is exploited in addition to number counts, then the number of candid...
Resolution of vitiligo following excision of halo congenital melanocytic nevus: a rare case report.
Wang, Kai; Wang, Zhi; Huang, Weiqing
2016-05-01
Halo congenital melanocytic nevus (CMN) associated with vitiligo is rare, especially with regard to CMN excision. Only two reports of excision of halo CMN following repigmentation of vitiligo are found in the literature. We present a case of a girl with halo CMN and periorbital vitiligo. The halo CMN was excised and followed by spontaneous improvement of vitiligo. The result suggests excision of the inciting lesion may be a promising way to control vitiligo. © 2015 Wiley Periodicals, Inc.
Research Note--Should Consumers Use the Halo to Form Product Evaluations?
Peter Boatwright; Ajay Kalra; Wei Zhang
2008-01-01
In purchase situations where attribute information is either missing or difficult to judge, a well-known heuristic that consumers use to form evaluations is the halo effect. The psychology literature has widely considered the halo a reflection of consumers' inability to discriminate between different attributes and have therefore labeled it the "halo error" or the "logical error." The objective of this paper is to offer a rationale for the halo effect. We use a decision-theory framework to sh...
Clear and Measurable Signature of Modified Gravity in the Galaxy Velocity Field
Hellwing, Wojciech A.; Barreira, Alexandre; Frenk, Carlos S.; Li, Baojiu; Cole, Shaun
2014-06-01
The velocity field of dark matter and galaxies reflects the continued action of gravity throughout cosmic history. We show that the low-order moments of the pairwise velocity distribution v12 are a powerful diagnostic of the laws of gravity on cosmological scales. In particular, the projected line-of-sight galaxy pairwise velocity dispersion σ12(r) is very sensitive to the presence of modified gravity. Using a set of high-resolution N-body simulations, we compute the pairwise velocity distribution and its projected line-of-sight dispersion for a class of modified gravity theories: the chameleon f(R) gravity and Galileon gravity (cubic and quartic). The velocities of dark matter halos with a wide range of masses would exhibit deviations from general relativity at the (5-10)σ level. We examine strategies for detecting these deviations in galaxy redshift and peculiar velocity surveys. If detected, this signature would be a "smoking gun" for modified gravity.
Populating dark matter haloes with galaxies: comparing the 2dFGRS with mock galaxy redshift surveys
Yang, Xiaohu; Mo, H. J.; Jing, Y. P.; van den Bosch, Frank C.; Chu, YaoQuan
2004-06-01
In two recent papers, we developed a powerful technique to link the distribution of galaxies to that of dark matter haloes by considering halo occupation numbers as a function of galaxy luminosity and type. In this paper we use these distribution functions to populate dark matter haloes in high-resolution N-body simulations of the standard ΛCDM cosmology with Ωm= 0.3, ΩΛ= 0.7 and σ8= 0.9. Stacking simulation boxes of 100 h-1 Mpc and 300 h-1 Mpc with 5123 particles each we construct mock galaxy redshift surveys out to a redshift of z= 0.2 with a numerical resolution that guarantees completeness down to 0.01L*. We use these mock surveys to investigate various clustering statistics. The predicted two-dimensional correlation function ξ(rp, π) reveals clear signatures of redshift space distortions. The projected correlation functions for galaxies with different luminosities and types, derived from ξ(rp, π), match the observations well on scales larger than ~3 h-1 Mpc. On smaller scales, however, the model overpredicts the clustering power by about a factor two. Modelling the `finger-of-God' effect on small scales reveals that the standard ΛCDM model predicts pairwise velocity dispersions (PVD) that are ~400 km s-1 too high at projected pair separations of ~1 h-1 Mpc. A strong velocity bias in massive haloes, with bvel≡σgal/σdm~ 0.6 (where σgal and σdm are the velocity dispersions of galaxies and dark matter particles, respectively) can reduce the predicted PVD to the observed level, but does not help to resolve the overprediction of clustering power on small scales. Consistent results can be obtained within the standard ΛCDM model only when the average mass-to-light ratio of clusters is of the order of 1000 (M/L)solar in the B-band. Alternatively, as we show by a simple approximation, a ΛCDM model with σ8~= 0.75 may also reproduce the observational results. We discuss our results in light of the recent WMAP results and the constraints on σ8 obtained
De bepaling van halo-azijnzuren, chloriet en chloraat in drinkwater
Peters RJB; van de Meer-Arp KKM; Versteegh JFM
1990-01-01
A method was developed to determine halo-acetic acids with a detection limit of 0.1 mug/L. Halo-acetic acids were determined in samples drinking water derived from surface- and bankfiltrated water however, not in drinking water derived from groundwater. Halo-acetic acids were found in chlorinated
2012-12-21
..., Notice of Registration, Halo Pharmaceutical, Inc. By Notice dated July 30, 2012, and published in the Federal Register on August 7, 2012, 77 FR 47114, Halo Pharmaceutical, Inc., 30 North Jefferson Road... 21 U.S.C. 823(a), and determined that the registration of Halo Pharmaceutical, Inc., to manufacture...
2012-03-20
..., Notice of Registration; Halo Pharmaceutical Inc. By Notice dated December 2, 2011, and published in the Federal Register on December 14, 2011, 76 FR 77850, Halo Pharmaceutical Inc., 30 North Jefferson Road... considered the factors in 21 U.S.C. 823(a) and determined that the registration of Halo Pharmaceutical Inc...
International Nuclear Information System (INIS)
Berryman, J.G.
1997-01-01
Eshelby close-quote s formula gives the response of a single ellipsoidal elastic inclusion in an elastic whole space to a uniform strain imposed at infinity. Using a linear combination of results from two simple thought experiments, we show how this formula may be generalized to both poroelasticity and thermoelasticity. The resulting new formulas are important for applications to analysis of poroelastic and thermoelastic composites, including but not restricted to rocks. copyright 1997 The American Physical Society
Outer Retinal Changes Including the Ellipsoid Zone Band in Usher Syndrome 1B due to MYO7A Mutations.
Sumaroka, Alexander; Matsui, Rodrigo; Cideciyan, Artur V; McGuigan, David B; Sheplock, Rebecca; Schwartz, Sharon B; Jacobson, Samuel G
2016-07-01
To study transition zones from normal to abnormal retina in Usher syndrome IB (USH1B) caused by myosin 7A (MYO7A) mutations. Optical coherence tomography (OCT) scattering layers in outer retina were segmented in patients (n = 16, ages 2-42; eight patients had serial data, average interval 4.5 years) to quantify outer nuclear layer (ONL) and outer segments (OS) as well as the locus of EZ (ellipsoid zone) edge and its extent from the fovea. Static perimetry was measured under dark-adapted (DA) and light-adapted (LA) conditions. Ellipsoid zone edge in USH1B-MYO7A could be located up to 23° from the fovea. Ellipsoid zone extent constricted at a rate of 0.51°/year with slower rates at smaller eccentricities. A well-defined EZ line could be associated with normal or abnormal ONL and/or OS thickness; detectable ONL extended well beyond EZ edge. At the EZ edge, the local slope of LA sensitivity loss was 2.6 (±1.7) dB/deg for central transition zones. At greater eccentricities, the local slope of cone sensitivity loss was shallower (1.1 ± 0.4 dB/deg for LA) than that of rod sensitivity loss (2.8 ± 1.2 dB/deg for DA). In USH1B-MYO7A, constriction rate of EZ extent depends on the initial eccentricity of the transition. Ellipsoid zone edges in the macula correspond to large local changes in cone vision, but extramacular EZ edges show more pronounced losses on rod-based vision tests. It is advisable to use not only the EZ line but also other structural and functional parameters for estimating natural history of disease and possible therapeutic effects in future clinical trials of USH1B-MYO7A.
Large-scale assembly bias of dark matter halos
Energy Technology Data Exchange (ETDEWEB)
Lazeyras, Titouan; Musso, Marcello; Schmidt, Fabian, E-mail: titouan@mpa-garching.mpg.de, E-mail: mmusso@sas.upenn.edu, E-mail: fabians@mpa-garching.mpg.de [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching (Germany)
2017-03-01
We present precise measurements of the assembly bias of dark matter halos, i.e. the dependence of halo bias on other properties than the mass, using curved 'separate universe' N-body simulations which effectively incorporate an infinite-wavelength matter overdensity into the background density. This method measures the LIMD (local-in-matter-density) bias parameters b {sub n} in the large-scale limit. We focus on the dependence of the first two Eulerian biases b {sup E} {sup {sub 1}} and b {sup E} {sup {sub 2}} on four halo properties: the concentration, spin, mass accretion rate, and ellipticity. We quantitatively compare our results with previous works in which assembly bias was measured on fairly small scales. Despite this difference, our findings are in good agreement with previous results. We also look at the joint dependence of bias on two halo properties in addition to the mass. Finally, using the excursion set peaks model, we attempt to shed new insights on how assembly bias arises in this analytical model.
Constraining the Galaxy's dark halo with RAVE stars
Piffl, T.; Binney, J.; McMillan, P. J.; Steinmetz, M.; Helmi, A.; Wyse, R. F. G.; Bienaymé, O.; Bland-Hawthorn, J.; Freeman, K.; Gibson, B.; Gilmore, G.; Grebel, E. K.; Kordopatis, G.; Navarro, J. F.; Parker, Q.; Reid, W. A.; Seabroke, G.; Siebert, A.; Watson, F.; Zwitter, T.
2014-01-01
We use the kinematics of ˜200 000 giant stars that lie within ˜1.5 kpc of the plane to measure the vertical profile of mass density near the Sun. We find that the dark mass contained within the isodensity surface of the dark halo that passes through the Sun ((6 ± 0.9) × 1010 M⊙), and the surface