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Sample records for proton halos

  1. Reactions induced by beams of neutron and proton halo nuclei

    NASA Astrophysics Data System (ADS)

    Penionzhkevich, Yu. E.

    1997-02-01

    Within the collaboration Dubna-GANIL (Caen, France) - IPN (Orsay, France) - NPI (Rez, Czech Republic) - IAP (Bucharest, Romania) at GANIL and the Dubna U400M accelerator, experiments have been carried out to study elastic scattering, fusion and fission using secondary ion beams of 6He, 11Li and 8B. The fission cross-section for the 6He isotopes has been found to be significantly higher than for the 4He nuclei. This enhancement depends mainly on the entrance channel and it is connected with the neutron skin of the 6He nuclei. Also, investigation of the elastic scattering of 11Li (neutron halo), 7Be and 8B (proton halo) has been performed. The microscopic analysis supports the existence of a neutron halo in 11Li and the proton skin in 8B and 7Be. Perspectives for investigations in this field at the Laboratory of Nuclear Reactions JINR are also discussed.

  2. The effect of proton halo on fusion reactions

    NASA Astrophysics Data System (ADS)

    Lay, J. A.; Kumar, Raj; Vitturi, A.

    2015-04-01

    In a recent brief report [Kumar et al., Phys. Rev. C 89, 027601 (2014)] we proposed a method to include the effect of a large break up in fusion reactions with neutron and proton halo nuclei. A stronger enhancement on the total fusion cross section was found for the proton case. However, neither complete nor incomplete fusion was studied and only one target was considered. Here, we revisit the problem in order to address the importance of complete and incomplete fusion. The sensitivity of the cross section to the target is also explored.

  3. Near-Barrier Fusion of the {sup 8}B+{sup 58}Ni Proton-Halo System

    SciTech Connect

    Aguilera, E. F.; Amador-Valenzuela, P.; Martinez-Quiroz, E.; Lizcano, D.; Rosales, P.; Garcia-Martinez, H.; Gomez-Camacho, A.; Kolata, J. J.; Roberts, A.; Lamm, L. O.; Rogachev, G.; Guimaraes, V.; Becchetti, F. D.; Villano, A.; Ojaruega, M.; Febbraro, M.; Chen, Y.; Jiang, H.; DeYoung, P. A.; Peaslee, G. F.

    2011-08-26

    Fusion cross sections were measured for the exotic proton-halo nucleus {sup 8}B incident on a {sup 58}Ni target at several energies near the Coulomb barrier. This is the first experiment to report on the fusion of a proton-halo nucleus. The resulting excitation function shows a striking enhancement with respect to expectations for normal projectiles. Evidence is presented that the sum of the fusion and breakup yields saturates the total reaction cross section.

  4. Higher order mode beams mitigate halos in high intensity proton linacs

    NASA Astrophysics Data System (ADS)

    Pathak, Abhishek; Krishnagopal, Srinivas

    2017-01-01

    High intensity proton linacs (HIPLs) for applications such as Accelerator Driven Reactor Systems (ADRS) have serious beam dynamics issues related to beam halo formation. This can lead to particle loss and radioactivation of the surroundings which consequently limit the beam current. Beam halos are largely driven by the nonlinear space-charge force of the beam, which depends strongly on the beam distribution and also on the initial beam mismatch. We propose here the use of a higher order mode beam (HOMB), that has a weaker nonlinear force, to mitigate beam halos. We first show how the nonlinear space-charge force can itself be exploited in the presence of nonlinear solenoid fields, to produce a HOMB in the low energy beam transport (LEBT) line. We then study the transport of such a beam through a radio frequency quadrupole (RFQ), and show that the HOMB has a significant advantage in terms of emittance blow-up, halo formation and beam loss, over a Gaussian beam, even with a finite initial mismatch. For example, for the transport of a 30 mA beam through the RFQ, with an initial beam mismatch of 45%, the Gaussian beam sees an emittance blow-up of 125%, while the HOMB sees a blow-up of only 35% (relative to the initial emittance of 0.2 π mm -mrad ). Similarly, the beam halo parameter and beam loss are 0.95 and 25% respectively for a Gaussian beam, but only 0.35 and 15% for a HOMB. The beam dynamics of the HOMB agrees quite well with the particle-core model, because of the more linear space-charge force, while for the Gaussian beam there are additional particle loss mechanisms arising from nonlinear resonances. Therefore, the HOMB suppresses emittance blow-up and halo formation, and can make high current ADRS systems more viable.

  5. Primary-cosmic-ray protons above 1015 eV derived from the observation of superhigh-energy halo events

    NASA Astrophysics Data System (ADS)

    Ren, J. R.; Huo, A. X.; Lu, S. L.; Su, S.; Wang, C. R.; Zhang, N. J.; Cao, P. Y.; Zou, B. T.; Li, J. Y.; Wang, S. Z.; Bai, G. Z.; Liu, Z. H.; Li, G. J.; Geng, Q. X.; Zhou, W. D.; He, R. D.; Amenomori, M.; Nanjo, H.; Hotta, N.; Ohta, I.; Mizutani, K.; Kasahara, K.; Yuda, T.; Shibata, M.; Shirai, T.; Tateyama, N.; Torii, S.; Sugimoto, H.; Taira, K.

    1988-09-01

    The primary-cosmic-ray proton flux >1015 eV is derived through analyses on superhigh-energy halo events observed by the Mt. Fuji and Mt. Kanbala emulsion-chamber experiments. Interpretations are made for the origin of halo events based on Monte Carlo simulation, which clarifies the sensitivity of the halo events to the primary-composition and nuclear-interaction models. It is shown that the intensity of the halo events is most sensitive to the primary proton flux and the feature of the fragmentation region of the multiple production. The proton flux >1015 eV is estimated as nearly 3 times less than the extrapolated low-energy measurement by Ryan et al. suggesting the heavy-nuclei dominance above the knee energy of the total spectrum.

  6. Proton Distribution Radii of 12-19C Illuminate Features of Neutron Halos

    SciTech Connect

    Kanungo, R.; Horiuchi, W.; Hagen, Gaute; Jansen, Gustav R.; Navratil, Petr; Ameil, F.; Atkinson, J.; Ayyad, Y.; Cortina-Gil, D.; Dillmann, I.; Estradé, A.; Evdokimov, A.; Farinon, F.; Geissel, H.; Guastalla, G.; Janik, R.; Kimura, M.; Knöbel, R.; Kurcewicz, J.; Litvinov, Yu. A.; Marta, M.; Mostazo, M.; Mukha, I.; Nociforo, C.; Ong, H. J.; Pietri, S.; Prochazka, A.; Scheidenberger, C.; Sitar, B.; Strmen, P.; Suzuki, Y.; Takechi, M.; Tanaka, J.; Tanihata, I.; Terashima, S.; Vargas, J.; Weick, H.; Winfield, J. S.

    2016-09-02

    We report proton radii of 12-19C densities derived from first accurate charge changing cross section measurements at 900A MeV with a carbon target. A thick neutron surface evolves from ~0.5 fm in 15C to ~1 fm in 19C. Also, the halo radius in 19C is found to be 6.4±0.7 fm as large as 11Li. Ab initio calculations based on chiral nucleon-nucleon and three-nucleon forces reproduce the radii well.

  7. Proton Distribution Radii of ^{12-19}C Illuminate Features of Neutron Halos.

    PubMed

    Kanungo, R; Horiuchi, W; Hagen, G; Jansen, G R; Navratil, P; Ameil, F; Atkinson, J; Ayyad, Y; Cortina-Gil, D; Dillmann, I; Estradé, A; Evdokimov, A; Farinon, F; Geissel, H; Guastalla, G; Janik, R; Kimura, M; Knöbel, R; Kurcewicz, J; Litvinov, Yu A; Marta, M; Mostazo, M; Mukha, I; Nociforo, C; Ong, H J; Pietri, S; Prochazka, A; Scheidenberger, C; Sitar, B; Strmen, P; Suzuki, Y; Takechi, M; Tanaka, J; Tanihata, I; Terashima, S; Vargas, J; Weick, H; Winfield, J S

    2016-09-02

    Proton radii of ^{12-19}C densities derived from first accurate charge changing cross section measurements at 900A  MeV with a carbon target are reported. A thick neutron surface evolves from ∼0.5  fm in ^{15}C to ∼1  fm in ^{19}C. The halo radius in ^{19}C is found to be 6.4±0.7  fm as large as ^{11}Li. Ab initio calculations based on chiral nucleon-nucleon and three-nucleon forces reproduce the radii well.

  8. Proton Distribution Radii of 12-19C Illuminate Features of Neutron Halos

    SciTech Connect

    Kanungo, R.; Horiuchi, W.; Hagen, Gaute; Jansen, Gustav R.; Navratil, Petr; Ameil, F.; Atkinson, J.; Ayyad, Y.; Cortina-Gil, D.; Dillmann, I.; Estradé, A.; Evdokimov, A.; Farinon, F.; Geissel, H.; Guastalla, G.; Janik, R.; Kimura, M.; Knöbel, R.; Kurcewicz, J.; Litvinov, Yu. A.; Marta, M.; Mostazo, M.; Mukha, I.; Nociforo, C.; Ong, H. J.; Pietri, S.; Prochazka, A.; Scheidenberger, C.; Sitar, B.; Strmen, P.; Suzuki, Y.; Takechi, M.; Tanaka, J.; Tanihata, I.; Terashima, S.; Vargas, J.; Weick, H.; Winfield, J. S.

    2016-09-02

    We report proton radii of 12-19C densities derived from first accurate charge changing cross section measurements at 900A MeV with a carbon target. A thick neutron surface evolves from ~0.5 fm in 15C to ~1 fm in 19C. Also, the halo radius in 19C is found to be 6.4±0.7 fm as large as 11Li. Ab initio calculations based on chiral nucleon-nucleon and three-nucleon forces reproduce the radii well.

  9. Proton Distribution Radii of 12-19C Illuminate Features of Neutron Halos

    DOE PAGES

    Kanungo, R.; Horiuchi, W.; Hagen, Gaute; ...

    2016-09-02

    We report proton radii of 12-19C densities derived from first accurate charge changing cross section measurements at 900A MeV with a carbon target. A thick neutron surface evolves from ~0.5 fm in 15C to ~1 fm in 19C. Also, the halo radius in 19C is found to be 6.4±0.7 fm as large as 11Li. Ab initio calculations based on chiral nucleon-nucleon and three-nucleon forces reproduce the radii well.

  10. On the nuclear halo of a proton pencil beam stopping in water

    NASA Astrophysics Data System (ADS)

    Gottschalk, Bernard; Cascio, Ethan W.; Daartz, Juliane; Wagner, Miles S.

    2015-07-01

    The dose distribution of a proton beam stopping in water has components due to basic physics and may have others from beam contamination. We propose the concise terms core for the primary beam, halo (see Pedroni et al 2005 Phys. Med. Biol. 50 541-61) for the low dose region from charged secondaries, aura for the low dose region from neutrals, and spray for beam contamination. We have measured the dose distribution in a water tank at 177 MeV under conditions where spray, therefore radial asymmetry, is negligible. We used an ADCL calibrated thimble chamber and a Faraday cup calibrated integral beam monitor so as to obtain immediately the absolute dose per proton. We took depth scans at fixed distances from the beam centroid rather than radial scans at fixed depths. That minimizes the signal range for each scan and better reveals the structure of the core and halo. Transitions from core to halo to aura are already discernible in the raw data. The halo has components attributable to coherent and incoherent nuclear reactions. Due to elastic and inelastic scattering by the nuclear force, the Bragg peak persists to radii larger than can be accounted for by Molière single scattering. The radius of the incoherent component, a dose bump around midrange, agrees with the kinematics of knockout reactions. We have fitted the data in two ways. The first is algebraic or model dependent (MD) as far as possible, and has 25 parameters. The second, using 2D cubic spline regression, is model independent. Optimal parameterization for treatment planning will probably be a hybrid of the two, and will of course require measurements at several incident energies. The MD fit to the core term resembles that of the PSI group (Pedroni et al 2005), which has been widely emulated. However, we replace their T(w), a mass stopping power which mixes electromagnetic (EM) and nuclear effects, with one that is purely EM, arguing that protons that do not undergo hard single scatters continue to lose

  11. On the nuclear halo of a proton pencil beam stopping in water.

    PubMed

    Gottschalk, Bernard; Cascio, Ethan W; Daartz, Juliane; Wagner, Miles S

    2015-07-21

    The dose distribution of a proton beam stopping in water has components due to basic physics and may have others from beam contamination. We propose the concise terms core for the primary beam, halo (see Pedroni et al 2005 Phys. Med. Biol. 50 541-61) for the low dose region from charged secondaries, aura for the low dose region from neutrals, and spray for beam contamination. We have measured the dose distribution in a water tank at 177 MeV under conditions where spray, therefore radial asymmetry, is negligible. We used an ADCL calibrated thimble chamber and a Faraday cup calibrated integral beam monitor so as to obtain immediately the absolute dose per proton. We took depth scans at fixed distances from the beam centroid rather than radial scans at fixed depths. That minimizes the signal range for each scan and better reveals the structure of the core and halo. Transitions from core to halo to aura are already discernible in the raw data. The halo has components attributable to coherent and incoherent nuclear reactions. Due to elastic and inelastic scattering by the nuclear force, the Bragg peak persists to radii larger than can be accounted for by Molière single scattering. The radius of the incoherent component, a dose bump around midrange, agrees with the kinematics of knockout reactions. We have fitted the data in two ways. The first is algebraic or model dependent (MD) as far as possible, and has 25 parameters. The second, using 2D cubic spline regression, is model independent. Optimal parameterization for treatment planning will probably be a hybrid of the two, and will of course require measurements at several incident energies. The MD fit to the core term resembles that of the PSI group (Pedroni et al 2005), which has been widely emulated. However, we replace their T(w), a mass stopping power which mixes electromagnetic (EM) and nuclear effects, with one that is purely EM, arguing that protons that do not undergo hard single scatters continue to lose

  12. Electromagnetic strength of neutron and proton single-particle halo nuclei

    NASA Astrophysics Data System (ADS)

    Typel, S.; Baur, G.

    2005-09-01

    Electromagnetic strength functions of halo nuclei exhibit universal features that can be described in terms of characteristic scale parameters. For a nucleus with nucleon + core structure the reduced transition probability, as determined, e.g., by Coulomb dissociation experiments, shows a typical shape that depends on the nucleon separation energy and the orbital angular momenta in the initial and final states. The sensitivity to the final-state interaction (FSI) between the nucleon and the core can be studied systematically by varying the strength of the interaction in the continuum. In the case of neutron + core nuclei analytical results for the reduced transition probabilities are obtained by introducing the effective-range expansion. The scaling with the relevant parameters is found explicitly. General trends are observed by studying several examples of neutron + core and proton + core nuclei in a single-particle model assuming Woods-Saxon potentials. Many important features of the neutron halo case can be obtained from a square-well model. Rather simple analytical formulas are found. The nucleon-core interaction in the continuum affects the determination of astrophysical S factors at zero energy in the method of asymptotic normalisation coefficients (ANC). It is also relevant for the extrapolation of radiative capture cross sections to low energies.

  13. Electric quadrupole moment of the proton halo nucleus {sup 8}B

    SciTech Connect

    Sumikama, T.; Nagatomo, T.; Ogura, M.; Iwakoshi, T.; Nakashima, Y.; Fujiwara, H.; Matsuta, K.; Fukuda, M.; Mihara, M.; Minamisono, T.

    2006-08-15

    The {beta}-NQR (nuclear quadrupole resonance) signals of {sup 8}B (I{sup {pi}}=2{sup +},T{sub 1/2}=770 ms) implanted in TiO{sub 2} (rutile) have been detected to determine the electric quadrupole moment of {sup 8}B with high precision. The ratio of the quadrupole moments of {sup 8}B and {sup 12}B was determined as |Q({sup 8}B)/Q({sup 12}B)|=4.88{+-}0.04. Combined with the known sign, the quadrupole moment of {sup 8}B was obtained as Q({sup 8}B)=+(64.5{+-}1.4) mb, which is consistent with and more precise than the previously reported value. The experimental values of the Q moment, the proton and neutron radii and the density distribution of {sup 8}B were compared with several theoretical predictions and were found to be best reproduced by a microscopic cluster model, which suggests the existence of a proton halo.

  14. Possibilities of studying the structure of halo nuclei in reactions of quasifree proton scattering at low energies

    SciTech Connect

    Zuyev, S. V. Kasparov, A. A.; Konobeevski, E. S.

    2015-07-15

    The possibility of experimentally studying the structure of halo nuclei in reactions induced by quasifree proton scattering on clusters of these nuclei is considered. Quasifree proton scattering on {sup 6}He, {sup 4}He, {sup 4}n, {sup 2}n, and n clusters in inverse kinematics is considered for the example of the {sup 8}He nucleus. Angular and energy distributions of secondaries are obtained for various representations of the cluster structure of the {sup 8}He nucleus. It is clearly shown that, in the angular and energy distributions of secondaries, one can single out regions that receive dominant contributions from reactions on specific clusters and which correspond to concrete cluster configurations of halo nuclei. Possible relevant experiments are proposed.

  15. Technical Note: Validation of halo modeling for proton pencil beam spot scanning using a quality assurance test pattern

    SciTech Connect

    Lin, Liyong Huang, Sheng; Kang, Minglei; Solberg, Timothy D.; McDonough, James E.; Ainsley, Christopher G.

    2015-09-15

    Purpose: The purpose of this paper is to demonstrate the utility of a comprehensive test pattern in validating calculation models that include the halo component (low-dose tails) of proton pencil beam scanning (PBS) spots. Such a pattern has been used previously for quality assurance purposes to assess spot shape, position, and dose. Methods: In this study, a scintillation detector was used to measure the test pattern in air at isocenter for two proton beam energies (115 and 225 MeV) of two IBA universal nozzles (UN #1 and UN #2). Planar measurements were compared with calculated dose distributions based on the weighted superposition of location-independent (UN #1) or location-dependent (UN #2) spot profiles, previously measured using a pair-magnification method and between two nozzles. Results: Including the halo component below 1% of the central dose is shown to improve the gamma-map comparison between calculation and measurement from 94.9% to 98.4% using 2 mm/2% criteria for the 115 MeV proton beam of UN #1. In contrast, including the halo component below 1% of the central dose does not improve the gamma agreement for the 115 MeV proton beam of UN #2, due to the cutoff of the halo component at off-axis locations. When location-dependent spot profiles are used for calculation instead of spot profiles at central axis, the gamma agreement is improved from 98.0% to 99.5% using 2 mm/2% criteria. The two nozzles clearly have different characteristics, as a direct comparison of measured data shows a passing rate of 89.7% for the 115 MeV proton beam. At 225 MeV, the corresponding gamma comparisons agree better between measurement and calculation, and between measurements in the two nozzles. Conclusions: In addition to confirming the primary component of individual PBS spot profiles, a comprehensive test pattern is useful for the validation of the halo component at off-axis locations, especially for low energy protons.

  16. Technical Note: Validation of halo modeling for proton pencil beam spot scanning using a quality assurance test pattern.

    PubMed

    Lin, Liyong; Huang, Sheng; Kang, Minglei; Solberg, Timothy D; McDonough, James E; Ainsley, Christopher G

    2015-09-01

    The purpose of this paper is to demonstrate the utility of a comprehensive test pattern in validating calculation models that include the halo component (low-dose tails) of proton pencil beam scanning (PBS) spots. Such a pattern has been used previously for quality assurance purposes to assess spot shape, position, and dose. In this study, a scintillation detector was used to measure the test pattern in air at isocenter for two proton beam energies (115 and 225 MeV) of two IBA universal nozzles (UN #1 and UN #2). Planar measurements were compared with calculated dose distributions based on the weighted superposition of location-independent (UN #1) or location-dependent (UN #2) spot profiles, previously measured using a pair-magnification method and between two nozzles. Including the halo component below 1% of the central dose is shown to improve the gamma-map comparison between calculation and measurement from 94.9% to 98.4% using 2 mm/2% criteria for the 115 MeV proton beam of UN #1. In contrast, including the halo component below 1% of the central dose does not improve the gamma agreement for the 115 MeV proton beam of UN #2, due to the cutoff of the halo component at off-axis locations. When location-dependent spot profiles are used for calculation instead of spot profiles at central axis, the gamma agreement is improved from 98.0% to 99.5% using 2 mm/2% criteria. The two nozzles clearly have different characteristics, as a direct comparison of measured data shows a passing rate of 89.7% for the 115 MeV proton beam. At 225 MeV, the corresponding gamma comparisons agree better between measurement and calculation, and between measurements in the two nozzles. In addition to confirming the primary component of individual PBS spot profiles, a comprehensive test pattern is useful for the validation of the halo component at off-axis locations, especially for low energy protons.

  17. Characterization of the dose distribution in the halo region of a clinical proton pencil beam using emulsion film detectors

    NASA Astrophysics Data System (ADS)

    Ariga, A.; Ariga, T.; Braccini, S.; Ereditato, A.; Giacoppo, F.; Nesteruk, K. P.; Pistillo, C.; Scampoli, P.

    2015-01-01

    Proton therapy is a high precision technique in cancer radiation therapy which allows irradiating the tumor with minimal damage to the surrounding healthy tissues. Pencil beam scanning is the most advanced dose distribution technique and it is based on a variable energy beam of a few millimeters FWHM which is moved to cover the target volume. Due to spurious effects of the accelerator, of dose distribution system and to the unavoidable scattering inside the patient's body, the pencil beam is surrounded by a halo that produces a peripheral dose. To assess this issue, nuclear emulsion films interleaved with tissue equivalent material were used for the first time to characterize the beam in the halo region and to experimentally evaluate the corresponding dose. The high-precision tracking performance of the emulsion films allowed studying the angular distribution of the protons in the halo. Measurements with this technique were performed on the clinical beam of the Gantry1 at the Paul Scherrer Institute. Proton tracks were identified in the emulsion films and the track density was studied at several depths. The corresponding dose was assessed by Monte Carlo simulations and the dose profile was obtained as a function of the distance from the center of the beam spot.

  18. Unique decay process: {beta}-delayed emission of a proton and a neutron by the {sup 11}Li halo nucleus

    SciTech Connect

    Baye, D.; Descouvemont, P.; Tursunov, E. M.

    2010-11-15

    The neutron-rich {sup 11}Li halo nucleus is unique among nuclei with known separation energies in its ability to emit a proton and a neutron in a {beta}-decay process. The branching ratio toward this rare decay mode is evaluated within a three-body model for the initial bound state and with Coulomb three-body final scattering states. The branching ratio should be comprised between two extreme cases, i.e., a lower bound 6x10{sup -12} obtained with a pure Coulomb wave and an upper bound 5x10{sup -10} obtained with a plane wave. A simple model with modified Coulomb waves provides plausible values between 0.8x10{sup -10} and 2.2x10{sup -10}, with most probable total energies of the proton and neutron between 0.15 and 0.3 MeV.

  19. Masses and Charge Radii of {sup 17-22}Ne and the Two-Proton-Halo Candidate {sup 17}Ne

    SciTech Connect

    Geithner, W.; Kappertz, S.; Keim, M.; Neugart, R.; Wilbert, S.; Neff, T.; Feldmeier, H.; Herfurth, F.; Yazidjian, C.; Audi, G.; Guenaut, C.; Lunney, D.; Blaum, K.; George, S.; Delahaye, P.; Kellerbauer, A.; Kowalska, M.; Herlert, A.; Kluge, H.-J.; Lievens, P.

    2008-12-19

    High-precision mass and charge radius measurements on {sup 17-22}Ne, including the proton-halo candidate {sup 17}Ne, have been performed with Penning trap mass spectrometry and collinear laser spectroscopy. The {sup 17}Ne mass uncertainty is improved by factor 50, and the charge radii of {sup 17-19}Ne are determined for the first time. The fermionic molecular dynamics model explains the pronounced changes in the ground-state structure. It attributes the large charge radius of {sup 17}Ne to an extended proton configuration with an s{sup 2} component of about 40%. In {sup 18}Ne the smaller radius is due to a significantly smaller s{sup 2} component. The radii increase again for {sup 19-22}Ne due to cluster admixtures.

  20. [ital E]2 properties of nuclei far from stability and the proton-halo problem of [sup 8]B

    SciTech Connect

    Nakada, H.; Otsuka, T. Department of Physics, Faculty of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113 Institute for Nuclear Theory, University of Washington, NH-12, Seattle, Washington 98195 )

    1994-02-01

    [ital E]2 properties of [ital A]=6--10 nuclei, including those of nuclei far from stability, are studied by a (0+2)[h bar][omega] shell-model calculation which includes [ital E]2 core-polarization effects explicitly. The quadrupole moments and the [ital E]2 transition strengths in [ital A]=6--10 nuclei are described quite well by the present cal- culation. This result indicates that the relatively large value of the quadrupole moment of [sup 8]B can be understood without introducing the proton halo in [sup 8]B. An interesting effect of the 2[h bar][omega] core-polarization is found for effective charges used in the 0[h bar][omega] shell model; although isoscalar effective charges are almost constant as a function of nucelus, appreciable variations are needed for isovector effective charges which play important roles in nuclei with high isospin values.

  1. Core excitation contributions to the breakup of the one-neutron halo nucleus {sup 11}Be on a proton

    SciTech Connect

    Crespo, R.; Deltuva, A.; Moro, A. M.

    2011-04-15

    The effect of the core excitation in the breakup of a one-neutron halo nucleus is studied within two different reaction formalisms, namely, the core excited model and the single-scattering approximation of the three-body Faddeev-Alt-Grassberger-Sandhas equations with target-core potential allowing for the core excitation. As an example, we consider the breakup of {sup 11}Be on a proton target at 63.7 MeV/nucleon incident energy and calculate the semi-inclusive cross section in the excitation energy interval E{sub x}=3.0-5.5 MeV (E{sub rel}=2.5-5 MeV) containing the 3/2{sup +} resonance with dominant contribution of the {sup 10}Be(2{sup +}) core excited state. The effect of the core excitation to the breakup cross section integrated around this resonance is found to be very significant. Moreover, when resonant and nonresonant contributions are added, the resulting semi-inclusive cross section is in reasonable agreement with the existing data, demonstrating the relevance of the core excitation mechanism for this observable. The present calculations also show the importance of incorporating the energy dependence of the core-target transition operators in the reaction formalism.

  2. Ab-initio Computation of the 17F Proton-Halo State and Resonances in A=17 Nuclei

    SciTech Connect

    Hagen, Gaute; Papenbrock, T.; Hjorth-Jensen, M.

    2010-01-01

    We perform coupled-cluster calculations of the energies and lifetimes of single-particle states around the doubly magic nucleus ^{16}O based on chiral nucleon-nucleon interactions at next-to-next-to-next-to-leading order. To incorporate effects from the scattering continuum, we solve the coupled-cluster equations with a Gamow-Hartree-Fock basis. Our calculations for the J^{pi} = 1/2^{+} proton-halo state in ^{17}F and the 1/2^{+} state in ^{17}O agree well with experiment, while the calculated spin-orbit splitting between d_{5/2} and d_{3/2} states is too small due to the lack of three-nucleon forces. We find that continuum effects yield a significant amount of additional binding energy for the 1/2^{+} and 3/2^{+} states in ^{17}O and ^{17}F.

  3. Probing nucleon-nucleon interactions in breakup of the one-neutron halo nucleus {sup 11}Be on a proton target

    SciTech Connect

    Cravo, E.; Deltuva, A.; Crespo, R.; Moro, A. M.

    2010-03-15

    A comparison between full few-body Faddeev/Alt-Grassberger-Sandhas (Faddeev/AGS) and continuum-discretized coupled-channels calculations is made for the resonant and nonresonant breakup of {sup 11}Be on proton target at 63.7 MeV/u incident energy. A simplified two-body model is used for {sup 11}Be which involves an inert {sup 10}Be(0{sup +}) core and a valence neutron. The sensitivity of the calculated observables to the nucleon-nucleon potential dynamical input is analyzed. We show that with the present NN and N-core dynamics the results remain a puzzle for the few-body problem of scattering from light exotic halo nuclei.

  4. SOLAR INTERACTING PROTONS VERSUS INTERPLANETARY PROTONS IN THE CORE PLUS HALO MODEL OF DIFFUSIVE SHOCK ACCELERATION AND STOCHASTIC RE-ACCELERATION

    SciTech Connect

    Kocharov, L.; Laitinen, T.; Vainio, R.; Afanasiev, A.; Mursula, K.; Ryan, J. M.

    2015-06-10

    With the first observations of solar γ-rays from the decay of pions, the relationship of protons producing ground level enhancements (GLEs) on the Earth to those of similar energies producing the γ-rays on the Sun has been debated. These two populations may be either independent and simply coincident in large flares, or they may be, in fact, the same population stemming from a single accelerating agent and jointly distributed at the Sun and also in space. Assuming the latter, we model a scenario in which particles are accelerated near the Sun in a shock wave with a fraction transported back to the solar surface to radiate, while the remainder is detected at Earth in the form of a GLE. Interplanetary ions versus ions interacting at the Sun are studied for a spherical shock wave propagating in a radial magnetic field through a highly turbulent radial ray (the acceleration core) and surrounding weakly turbulent sector in which the accelerated particles can propagate toward or away from the Sun. The model presented here accounts for both the first-order Fermi acceleration at the shock front and the second-order, stochastic re-acceleration by the turbulence enhanced behind the shock. We find that the re-acceleration is important in generating the γ-radiation and we also find that up to 10% of the particle population can find its way to the Sun as compared to particles escaping to the interplanetary space.

  5. β -delayed γ decay of P26 : Possible evidence of a proton halo

    NASA Astrophysics Data System (ADS)

    Pérez-Loureiro, D.; Wrede, C.; Bennett, M. B.; Liddick, S. N.; Bowe, A.; Brown, B. A.; Chen, A. A.; Chipps, K. A.; Cooper, N.; Irvine, D.; McNeice, E.; Montes, F.; Naqvi, F.; Ortez, R.; Pain, S. D.; Pereira, J.; Prokop, C. J.; Quaglia, J.; Quinn, S. J.; Sakstrup, J.; Santia, M.; Schwartz, S. B.; Shanab, S.; Simon, A.; Spyrou, A.; Thiagalingam, E.

    2016-06-01

    Background: Measurements of β decay provide important nuclear structure information that can be used to probe isospin asymmetries and inform nuclear astrophysics studies. Purpose: To measure the β -delayed γ decay of P26 and compare the results with previous experimental results and shell-model calculations. Method: A P26 fast beam produced using nuclear fragmentation was implanted into a planar germanium detector. Its β -delayed γ -ray emission was measured with an array of 16 high-purity germanium detectors. Positrons emitted in the decay were detected in coincidence to reduce the background. Results: The absolute intensities of P26 β -delayed γ rays were determined. A total of six new β -decay branches and 15 new γ -ray lines have been observed for the first time in P26 β decay. A complete β -decay scheme was built for the allowed transitions to bound excited states of Si26 . f t values and Gamow-Teller strengths were also determined for these transitions and compared with shell-model calculations and the mirror β decay of Na26 , revealing significant mirror asymmetries. Conclusions: A very good agreement with theoretical predictions based on the USDB shell model is observed. The significant mirror asymmetry observed for the transition to the first excited state (δ =51 (10 )% ) may be evidence for a proton halo in P26 .

  6. An Unusual Lunar Halo

    ERIC Educational Resources Information Center

    Cardon, Bartley L.

    1977-01-01

    Discusses a photograph of an unusual combination of lunar halos: the 22-degree refraction halo, the circumscribed halo, and a reflection halo. Deduces the form and orientations of the ice crystals responsible for the observed halo features. (MLH)

  7. An Unusual Lunar Halo

    ERIC Educational Resources Information Center

    Cardon, Bartley L.

    1977-01-01

    Discusses a photograph of an unusual combination of lunar halos: the 22-degree refraction halo, the circumscribed halo, and a reflection halo. Deduces the form and orientations of the ice crystals responsible for the observed halo features. (MLH)

  8. Nuclear Halos

    SciTech Connect

    Vogt, Erich

    2010-07-27

    We show that extreme nuclear halos are caused only by pairs of s-wave neutrons (or single s-wave neutrons) and that such states occur much more frequently in the periodic table than previously believed. Besides lingering long near zero neutron separation energy such extreme halos have very remarkable properties: they can contribute significantly to the nuclear density at more than twice the normal nuclear radius and their spreading width can be very narrow. The properties of these states are primarily determined by the ''thickness'' of the nuclear surface in the mean-free nuclear potential and thus their importance increases greatly as we approach the neutron drip line. We discuss what such extreme halos are, where they occur, what their properties are and some of their impact on nuclear observations.

  9. Effective field theory description of halo nuclei

    NASA Astrophysics Data System (ADS)

    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.

  10. Borromean halo, Tango halo, and halo isomers in atomic nuclei

    NASA Astrophysics Data System (ADS)

    Izosimov, Igor

    2016-01-01

    Structure of the ground and excited states in halo-like nuclei is discussed. Both the Borromean and tango halo types can be observed for n-p configurations of atomic nuclei.Structure of the halo may be different for the different levels and resonances in atomic nuclei. Isobar analog, double isobar analog, configuration, and double configuration states can simultaneously have n-n, n-p, and p-p halo components in their wave functions. When the halo structure of the excited state differs from that of the ground state, or the ground state has non-halo structure, the γ-transition from the excited state to the ground state can be essentially hindered, i.e. the formation of a specific type of isomers (halo isomers) becomes possible. B(Mγ) and B(Eγ) values for γ-transitions in 6,7,8Li, 8,9,10Be, 8,10,11B, 10,11,12,13,14C, 13,14,15,16,17N, 15,16,17,19O, and 17F are analyzed. Special attention is given to nuclei which ground state does not exhibit halo structure but the excited state (halo isomer) may have one.

  11. Single-Proton Pickup Reaction of the Halo Nucleus 6He on a 9Be Target at 25 MeV/nucleon

    NASA Astrophysics Data System (ADS)

    Pang, Dan-Yang; Ye, Yan-Lin; Jiang, Dong-Xing; Zheng, Tao; Li, Zhi-Huan; Li, Xiang-Qing; Ge, Yu-Cheng; Hua, Hui; Wu, Cui-E.; Lou, Jian-Ling; Lu, Fei; Fan, Feng-Ying; Ozawa, A.; Yamaguchi, Y.; Kanungo, R.; D., Fang; Tanihata, I.

    2007-10-01

    The inclusive differential cross sections of the 7Li nucleus in a reaction induced by 6He on a 9Be target are measured at an incident energy of 25 MeV/nucleon. Finite-range distorted-wave Born approximation calculations suggest that these 7Li particles are formed in a direct single-proton pickup reaction 9Be(6He,7Li)8Li. The experimental data can be well reproduced by taking into account of the contributions of both the ground states and the first excited states of 7Li and 8Li.

  12. The Halo

    NASA Image and Video Library

    2013-12-23

    NASA's Cassini spacecraft looks towards the dark side of Saturn's largest moon, Titan, capturing the blue halo caused by a haze layer that hovers high in the moon's atmosphere. The haze that permeates Titan's atmosphere scatters sunlight and produces the orange color seen here. More on Titan's orange and blue hazes can be found at PIA14913. This view looks towards the side of Titan (3,200 miles or 5,150 kilometers across) that leads in its orbit around Saturn. North on Titan is up and rotated 40 degrees to the left. Images taken using red, green and blue spectral filters were combined to create this natural-color view. The images were taken with the Cassini spacecraft narrow-angle camera on Nov. 3, 2013. The view was acquired at a distance of approximately 2.421 million miles (3.896 million kilometers) from Titan. Image scale is 14 miles (23 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA17180

  13. "Invisible" Galactic Halos.

    ERIC Educational Resources Information Center

    Lugt, Karel Vander

    1993-01-01

    Develops a simple core-halo model of a galaxy that exhibits the main features of observed rotation curves and quantitatively illustrates the need to postulate halos of dark matter. Uses only elementary mechanics. (Author/MVL)

  14. "Invisible" Galactic Halos.

    ERIC Educational Resources Information Center

    Lugt, Karel Vander

    1993-01-01

    Develops a simple core-halo model of a galaxy that exhibits the main features of observed rotation curves and quantitatively illustrates the need to postulate halos of dark matter. Uses only elementary mechanics. (Author/MVL)

  15. Halo CME

    NASA Image and Video Library

    2017-09-28

    A giant cloud appears to expand outward from the sun in all directions in this image from Sept. 28, 2012, which is called a halo CME. This kind of image occurs when a CME moves toward Earth – as here – or directly away from it. Credit: ESA/NASA/SOHO CME WEEK: What To See in CME Images Two main types of explosions occur on the sun: solar flares and coronal mass ejections. Unlike the energy and x-rays produced in a solar flare – which can reach Earth at the speed of light in eight minutes – coronal mass ejections are giant, expanding clouds of solar material that take one to three days to reach Earth. Once at Earth, these ejections, also called CMEs, can impact satellites in space or interfere with radio communications. During CME WEEK from Sept. 22 to 26, 2014, we explore different aspects of these giant eruptions that surge out from the star we live with. When a coronal mass ejection blasts off the sun, scientists rely on instruments called coronagraphs to track their progress. Coronagraphs block out the bright light of the sun, so that the much fainter material in the solar atmosphere -- including CMEs -- can be seen in the surrounding space. CMEs appear in these images as expanding shells of material from the sun's atmosphere -- sometimes a core of colder, solar material (called a filament) from near the sun's surface moves in the center. But mapping out such three-dimensional components from a two-dimensional image isn't easy. Watch the slideshow to find out how scientists interpret what they see in CME pictures. The images in the slideshow are from the three sets of coronagraphs NASA currently has in space. One is on the joint European Space Agency and NASA Solar and Heliospheric Observatory, or SOHO. SOHO launched in 1995, and sits between Earth and the sun about a million miles away from Earth. The other two coronagraphs are on the two spacecraft of the NASA Solar Terrestrial Relations Observatory, or STEREO, mission, which launched in 2006. The two

  16. Farside Halo

    NASA Image and Video Library

    2017-09-28

    There's no way to tell from this SOHO image whether the halo CME on March 5, 2013, originated from the front or far of the sun. But the STEREO spacecraft were watching the sun from the sides and showed it was from the far side. The bright planet is Venus. Credit: NASA/SOHO CME WEEK: What To See in CME Images Two main types of explosions occur on the sun: solar flares and coronal mass ejections. Unlike the energy and x-rays produced in a solar flare – which can reach Earth at the speed of light in eight minutes – coronal mass ejections are giant, expanding clouds of solar material that take one to three days to reach Earth. Once at Earth, these ejections, also called CMEs, can impact satellites in space or interfere with radio communications. During CME WEEK from Sept. 22 to 26, 2014, we explore different aspects of these giant eruptions that surge out from the star we live with. When a coronal mass ejection blasts off the sun, scientists rely on instruments called coronagraphs to track their progress. Coronagraphs block out the bright light of the sun, so that the much fainter material in the solar atmosphere -- including CMEs -- can be seen in the surrounding space. CMEs appear in these images as expanding shells of material from the sun's atmosphere -- sometimes a core of colder, solar material (called a filament) from near the sun's surface moves in the center. But mapping out such three-dimensional components from a two-dimensional image isn't easy. Watch the slideshow to find out how scientists interpret what they see in CME pictures. The images in the slideshow are from the three sets of coronagraphs NASA currently has in space. One is on the joint European Space Agency and NASA Solar and Heliospheric Observatory, or SOHO. SOHO launched in 1995, and sits between Earth and the sun about a million miles away from Earth. The other two coronagraphs are on the two spacecraft of the NASA Solar Terrestrial Relations Observatory, or STEREO, mission, which

  17. Dwarf Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Colín, P.; Klypin, A.; Valenzuela, O.; Gottlöber, Stefan

    2004-09-01

    We study properties of dark matter halos at high redshifts z=2-10 for a vast range of masses with the emphasis on dwarf halos with masses of 107-109 h-1 Msolar. We find that the density profiles of relaxed dwarf halos are well fitted by the Navarro, Frenk, & White (NFW) profile and do not have cores. We compute the halo mass function and the halo spin parameter distribution and find that the former is very well reproduced by the Sheth & Tormen model, while the latter is well fitted by a lognormal distribution with λ0=0.042 and σλ=0.63. We estimate the distribution of concentrations for halos in a mass range that covers 6 orders of magnitude, from 107 to 1013 h-1 Msolar, and find that the data are well reproduced by the model of Bullock et al. The extrapolation of our results to z=0 predicts that present-day isolated dwarf halos should have a very large median concentration of ~35. We measure the subhalo circular velocity functions for halos with masses that range from 4.6×109 to 1013 h-1 Msolar and find that they are similar when normalized to the circular velocity of the parent halo. Dwarf halos studied in this paper are many orders of magnitude smaller than well-studied cluster- and Milky Way-sized halos. Yet, in all respects the dwarfs are just downscaled versions of the large halos. They are cuspy and, as expected, more concentrated. They have the same spin parameter distribution and follow the same mass function that was measured for large halos.

  18. Halo and space charge issues in the SNS Ring

    SciTech Connect

    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.

  19. Halos around planetary nebulae

    NASA Technical Reports Server (NTRS)

    Jewitt, D. C.; Danielson, G. E.; Kupferman, P. N.

    1986-01-01

    Preliminary results of a CCD survey designed to detect and investigate faint halos around planetary nebulae are reported. A TI 800 x 800 pixel CCD was used to take deep exposures of 44 planetary nebulae. The exposures were obtained through an H-alpha filter at the Cassegrain focus of the Palomar 1.5 m telescope. Spatial resolutions of 1 to 2 arcsec were obtained across 400 arcsec wide fields. The images, which are in many cases considerably deeper than any previously taken, reveal numerous planetary nebula halos. About two-thirds of the studied nebulae possess extensive outer halos, here defined as any extended emission beyond the 10 percent isophote. Ionized sulphur electron density measurements show that in some nebulae, the mass in the halo is comparable to the mass contained in the primary H II region. The data have been used to place constraints on the mode of origin of the halos. It is likely that the halos originate either by dynamical separation of a single ejected shell of gas or by the ejection of two or more such shells from the central star. It is possible but less likely that the halos are caused by excitation of the preplanetary stellar wind and improbable that the halos represent reflection nebulae.

  20. The halo fixator.

    PubMed

    Bono, Christopher M

    2007-12-01

    The halo fixator may be used for the definitive treatment of cervical spine trauma, preoperative reduction in the patient with spinal deformity, and adjunctive postoperative stabilization following cervical spine surgery. Halo fixation decreases cervical motion by 30% to 96%. Absolute contraindications include cranial fracture, infection, and severe soft-tissue injury at the proposed pin sites. Relative contraindications include severe chest trauma, obesity, advanced age, and a barrel-shaped chest. In children, a computed tomography scan of the head should be obtained before pin placement to determine cranial bone thickness. Complications of halo fixation include pin loosening, pin site infection, and skin breakdown. A concerning rate of life-threatening complications, such as respiratory distress, has been reported in elderly patients. Despite a paucity of contemporary data, recent retrospective studies have demonstrated acceptable results for halo fixation in managing some upper and lower cervical spine injuries.

  1. AHF: AMIGA'S HALO FINDER

    SciTech Connect

    Knollmann, Steffen R.; Knebe, Alexander

    2009-06-15

    Cosmological simulations are the key tool for investigating the different processes involved in the formation of the universe from small initial density perturbations to galaxies and clusters of galaxies observed today. The identification and analysis of bound objects, halos, is one of the most important steps in drawing useful physical information from simulations. In the advent of larger and larger simulations, a reliable and parallel halo finder, able to cope with the ever-increasing data files, is a must. In this work we present the freely available MPI parallel halo finder AHF. We provide a description of the algorithm and the strategy followed to handle large simulation data. We also describe the parameters a user may choose in order to influence the process of halo finding, as well as pointing out which parameters are crucial to ensure untainted results from the parallel approach. Furthermore, we demonstrate the ability of AHF to scale to high-resolution simulations.

  2. Halo vest instrumentation

    NASA Astrophysics Data System (ADS)

    Huston, Dryver R.; Krag, Martin

    1996-05-01

    The halo vest is a head and neck immobilization system that is often used on patients that are recovering from cervical trauma or surgery. The halo vest system consists of a rigid halo that is firmly attached to the skull, an upright support structure for stabilization and immobilization, and a torso-enveloping vest. The main purpose of this study was to measure the forces that are carried by the halo-vest structure as the subject undergoes various activities of daily living and external loading for different vest designs. A tethered strain gage load cell based instrumentation system was used to take these load measurements on ten different subjects. Three different halo-vest systems were evaluated. The primary difference between the vests was the amount of torso coverage and the use of shoulder straps. The loads were measured, analyzed and used to compare the vests and to create a model of halo-vest-neck mechanics. Future applications of this technology to standalone data logging, pin-load measuring and biofeedback applications are discussed.

  3. The HALO / HALO-2 Supernova Neutrino Detectors

    NASA Astrophysics Data System (ADS)

    Yen, Stanley; HALO Collaboration; HALO-2 Collaboration

    2016-09-01

    The Helium and Lead Observatory (HALO) is a dedicated supernova neutrino detector in SNOLAB, which is built from 79 tons of surplus lead and the helium-3 neutron detectors from the SNO experiment. It is sensitive primarily to electron neutrinos, and is thus complementary to water Cerenkov and organic scintillation detectors which are primarily sensitive to electron anti-neutrinos. A comparison of the rates in these complementary detectors will enable a flavor decomposition of the neutrino flux from the next galactic core-collapse supernova. We have tentative ideas to build a 1000-ton HALO-2 detector in the Gran Sasso laboratory by using the lead from the decommissioned OPERA detector. We are exploring several neutron detector technologies to supplement the existing helium-3 detectors. We welcome new collaborators to join us. This research is supported by the NRC and NSERC (Canada), the US DOE and NSF, and the German RISE program.

  4. Renormalized halo bias

    SciTech Connect

    Assassi, Valentin; Baumann, Daniel; Green, Daniel; Zaldarriaga, Matias E-mail: dbaumann@damtp.cam.ac.uk E-mail: matiasz@ias.edu

    2014-08-01

    This paper provides a systematic study of renormalization in models of halo biasing. Building on work of McDonald, we show that Eulerian biasing is only consistent with renormalization if non-local terms and higher-derivative contributions are included in the biasing model. We explicitly determine the complete list of required bias parameters for Gaussian initial conditions, up to quartic order in the dark matter density contrast and at leading order in derivatives. At quadratic order, this means including the gravitational tidal tensor, while at cubic order the velocity potential appears as an independent degree of freedom. Our study naturally leads to an effective theory of biasing in which the halo density is written as a double expansion in fluctuations and spatial derivatives. We show that the bias expansion can be organized in terms of Galileon operators which aren't renormalized at leading order in derivatives. Finally, we discuss how the renormalized bias parameters impact the statistics of halos.

  5. Halo Nonlinear Reconstruction

    NASA Astrophysics Data System (ADS)

    Yu, Yu; Zhu, Hong-Ming; Pen, Ue-Li

    2017-10-01

    We apply the nonlinear reconstruction method to simulated halo fields. For halo number density 2.77 × {10}-2 {({h}-1{Mpc})}-3 at z = 0, corresponding to the SDSS main sample density, we find that the scale where the noise saturates the linear signal is improved to k≳ 0.36 h {{Mpc}}-1, which is a factor of 2.29 improvement in scale, or 12 in number of linear modes. The improvement is less for higher redshift or lower halo density. We expect this to substantially improve the BAO accuracy of dense, low-redshift surveys, including the SDSS main sample, 6dFGS and 21 cm intensity mapping initiatives.

  6. Origins of Stellar Halos

    NASA Astrophysics Data System (ADS)

    Johnston, Kathryn V.

    2016-08-01

    This contribution reviews ideas about the origins of stellar halos. It includes discussion of the theoretical understanding of and observational evidence for stellar populations formed ``in situ'' (meaning formed in orbits close to their current ones), ``kicked-out'' (meaning formed in the inner galaxy in orbits unlike their current ones) and ``accreted'' (meaning formed in a dark matter halo other than the one they currently occupy). At this point there is general agreement that a significant fraction of any stellar halo population is likely ``accreted''. There is modest evidence for the presence of a ``kicked-out'' population around both the Milky Way and M31. Our theoretical understanding of and the observational evidence for an ``in situ'' population are less clear.

  7. The Outer Halo -- Halo Origins and Mass of the Galaxy

    NASA Astrophysics Data System (ADS)

    Morrison, Heather; Arabadjis, John; Dohm-Palmer, Robbie; Freeman, Ken; Harding, Paul; Mateo, Mario; Norris, John; Olszewski, Ed; Sneden, Chris

    2000-02-01

    Through our detection of distant halo stars, we are now well placed to map the regions of the Galactic halo where previously only satellite galaxies and a few globular clusters were known. Mapping this region is crucial for answering questions like: How and over what timescales was the Milky Way's stellar halo assembled? What is the total mass and shape of its dark halo? The Sagittarius dwarf has demonstrated that at least some of the stellar halo was accreted. But, HOW MUCH of the halo was accreted? Our previous efforts have proven that the Washington photometric system, in conjuction with spectroscopy, is capable of efficiently and unambiguously identifying halo stars out to 100 kpc or more. We require followup spectroscopy to map velocity substructure, which is more likely visible in the outer halo because of the long dynamical timescales, and to identify the rare objects in the extreme outer halo which will constrain the shape and size of its dark halo. We are applying for 4m/RCSP time at both CTIO and KPNO to observe faint outer-halo giant and BHB candidates.

  8. What's a Halo?

    MedlinePlus

    ... to school, doing schoolwork, and participating in extracurricular clubs, as long as they're feeling up to it and the doctor says it's OK. Your child's doctor will tell you what activities your child should avoid while in a halo brace. Sports will have to be put on hold for ...

  9. Stability of halo orbits.

    PubMed

    Howard, J E; Dullin, H R; Horányi, M

    2000-04-10

    We predict new populations of trapped nonequatorial ("halo") orbits of charged dust grains about an arbitrary axisymmetric planet. Simple equilibrium and stability conditions are derived, revealing dramatic differences between positively and negatively charged grains in prograde or retrograde orbits. Implications for the Cassini mission to Saturn are discussed.

  10. Halos in Martian Sandstone

    NASA Image and Video Library

    2017-05-30

    Pale zones called "halos" border bedrock fractures visible in this 2015 image from NASA's Curiosity Mars rover which has been darkened (a previously released image can be seen at PIA20268). Measurements overlaid on the image offer a sense of scale for the size of these fractures. The rover team determined that the halos are rich in silica, a clue to the duration of wet environmental conditions long ago. The location is on the lower slope of Mars' Mount Sharp. Curiosity's Navigation Camera (Navcam) acquired the component images of this mosaic on Aug. 23, 2015, during the 1.083rd Martian day, or sol, of the mission. The location is along the rover's path between "Marias Pass" and "Bridger Basin." In this region, the rover has found fracture zones to be associated with rock compositions enriched in silica, relative to surrounding bedrock. https://photojournal.jpl.nasa.gov/catalog/PIA21649

  11. GALACTIC WARPS IN TRIAXIAL HALOS

    SciTech Connect

    Jeon, Myoungwon; Kim, Sungsoo S.; Ann, Hong Bae E-mail: sungsoo.kim@khu.ac.kr

    2009-05-10

    We study the behavior of galactic disks in triaxial halos both numerically and analytically to see if warps can be excited and sustained in triaxial potentials. We consider the following two scenarios: (1) galactic disks that are initially tilted relative to the equatorial plane of the halo (for a pedagogical purpose), and (2) tilted infall of dark matter relative to the equatorial plane of the disk and the halo. With numerical simulations of 100,000 disk particles in a fixed halo potential, we find that in triaxial halos, warps can be excited and sustained just as in spherical or axisymmetric halos but they show some oscillatory behavior and even can be transformed to a polar-ring system if the halo has a prolate-like triaxiality. The nonaxisymmetric component of the halo causes the disk to nutate, and the differential nutation between the inner and outer parts of the disk generally makes the magnitude of the warp slightly diminish and fluctuate. We also find that warps are relatively weaker in oblate and oblate-like triaxial halos, and since these halos are the halo configurations of disk galaxies inferred by cosmological simulations, our results are consistent with the fact that most of the observed warps are quite weak. We derive approximate formulae for the torques exerted on the disk by the triaxial halo and the dark matter torus, and with these formulae we successfully describe the behavior of the disks in our simulations. The techniques used in deriving these formulae could be applied for realistic halos with more complex structures.

  12. Search for Halo Axions

    SciTech Connect

    Daw, E. J.,; van Bibber, K.

    1998-01-01

    A collaboration of MIT, LLNL, Univ. of Florida, FNAL, UC Berkeley and INR Moscow have built a large-scale RF cavity axion detector. The experiment has been taking production data since February of 1996 and is sensitive enough to detect plausible dark matter axions comprising a reasonable fraction of the mass in our galactic halo. After a brief introduction to axion physics, I discuss details of our instrumentation, our analysis methodology, our run plan and future goals of the experiments.

  13. Rainbows, halos, and glories.

    NASA Astrophysics Data System (ADS)

    Greenler, R.

    Paperback edition of the book first published in 1980 (31.003.052). Contents: 1. Rainbows. 2. Ice-crystal refraction effects: halos, arcs, and spots. 3. Ice-crystal reflection effects: pillars, circles, and crosses. 4. Complex displays, past and present. 5. Scattering: light in the sky and color in the clouds. 6. Diffraction: the corona, the glory, and the specter of the Brocken. 7. Atmospheric refraction: mirages, twinkling stars, and the green flash.

  14. Halo Star Lithium Depletion

    SciTech Connect

    Pinsonneault, M. H.; Walker, T. P.; Steigman, G.; Narayanan, Vijay K.

    1999-12-10

    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

  15. Nuclear Halos and Borromeans in the Primordial Nucleosynthesis Process and in Astrophysical Nuclear Reactions

    NASA Astrophysics Data System (ADS)

    Yilmaz, M.; Özer, O.

    2007-04-01

    Nuclear halo structures and Borromean nuclei have been intensely studied almost two decades. They have a cloud of neutrons and protons extended well beyond the surface of tightly bound core of neutrons and protons which is classically forbidden. Since the extended tail of the valance neutron wave-function of the neutron halos the cross-sections are much larger and their sizes become substantially much larger than the ordinary nuclei. Inferred expectations of halo and Borroeman nuclei in astrophysics due to their novel structures have been suggested to influence the astrophysical reactions, especially in the primordial furnace during the Standard Big Bang Nucleosynthesis (SBBN) process. It is seen that the large spatial extension directly implies that both elastic and absorption cross-sections are large for the reactions involving halo nuclei. The Trojan Horse Method (THM) and the Distorted Wave Born Approximation (DWBA) reaction cross-sections calculations are discussed for low energies.

  16. Nuclear Halos and Borromeans in the Primordial Nucleosynthesis Process and in Astrophysical Nuclear Reactions

    SciTech Connect

    Yilmaz, M.; Oezer, O.

    2007-04-23

    Nuclear halo structures and Borromean nuclei have been intensely studied almost two decades. They have a cloud of neutrons and protons extended well beyond the surface of tightly bound core of neutrons and protons which is classically forbidden. Since the extended tail of the valance neutron wave-function of the neutron halos the cross-sections are much larger and their sizes become substantially much larger than the ordinary nuclei. Inferred expectations of halo and Borroeman nuclei in astrophysics due to their novel structures have been suggested to influence the astrophysical reactions, especially in the primordial furnace during the Standard Big Bang Nucleosynthesis (SBBN) process. It is seen that the large spatial extension directly implies that both elastic and absorption cross-sections are large for the reactions involving halo nuclei. The Trojan Horse Method (THM) and the Distorted Wave Born Approximation (DWBA) reaction cross-sections calculations are discussed for low energies.

  17. "Halo nevi" and UV radiation.

    PubMed

    Pustisek, Nives; Sikanić-Dugić, Nives; Hirsl-Hećej, Vlasta; Domljan, Mislav Luka

    2010-04-01

    Halo nevi, also termed Sutton nevi, are defined as benign melanocytic nevi that are surrounded by an area of depigmentation resembling a halo. Halo nevi are common in children and young adults, with a mean age at onset of 15 years. The incidence in the population is estimated to be approximately 1%. Affected individuals frequently have multiple lesions which are usually localized on the back. A familial tendency for halo nevi has been reported. The etiology of halo nevi is unknown. It is an autoimmune response and T lymphocytes are considered to play a key role in the progressive destruction of nevus cells. Halo nevi may be associated with autoimmune disorders such as vitiligo, Hashimoto thyroiditis, alopecia areata, celiac disease, atopic dermatitis and others. It has been proved that halo nevi are detected after an intense sun exposure especially after sunburns. The etiology of halo nevi, association with malignant melanoma and the role of sun exposure in the development of halo nevi are discussed.

  18. Transverse Beam Halo Measurements at High Intensity Neutrino Source (HINS) using Vibrating Wire Monitor

    SciTech Connect

    Chung, M.; Hanna, B.; Scarpine, V.; Shiltsev, V.; Steimel, J.; Artinian, S.; Arutunian, S.

    2015-02-26

    The measurement and control of beam halos will be critical for the applications of future high-intensity hadron linacs. In particular, beam profile monitors require a very high dynamic range when used for the transverse beam halo measurements. In this study, the Vibrating Wire Monitor (VWM) with aperture 60 mm was installed at the High Intensity Neutrino Source (HINS) front-end to measure the transverse beam halo. A vibrating wire is excited at its resonance frequency with the help of a magnetic feedback loop, and the vibrating and sensitive wires are connected through a balanced arm. The sensitive wire is moved into the beam halo region by a stepper motor controlled translational stage. We study the feasibility of the vibrating wire for the transverse beam halo measurements in the low-energy front-end of the proton linac.

  19. Matter density distributions and elastic form factors of some two-neutron halo nuclei

    NASA Astrophysics Data System (ADS)

    Abdullah, Ahmed N.

    2017-09-01

    The Skyrme-Hartree-Fock (SHF) method with MSK7 Skyrme parameter has been used to investigate the ground-state properties for two-neutron halo nuclei 6He, ^{11}Li, ^{12}Be and ^{14}Be. These ground-state properties include the proton, neutron and matter density distributions, the corresponding rms radii, the binding energy per nucleon and the charge form factors. These calculations clearly reveal the long tail characterizing the halo nuclei as a distinctive feature.

  20. Jupiter's Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow.

    A faint mist of particles can be seen above and below the main rings; this vertically extended, toroidal 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces which can push small grains out of the ring plane. Halo material is present across this entire image, implying that it reaches more than 27,000 km above the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. In order to accentuate faint features in the image, different brightnesses are shown through color, with the brightest

  1. Jupiter's Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow.

    A faint mist of particles can be seen above and below the main rings; this vertically extended, toroidal 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces which can push small grains out of the ring plane. Halo material is present across this entire image, implying that it reaches more than 27,000 km above the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. In order to accentuate faint features in the image, different brightnesses are shown through color, with the brightest

  2. Jupiter Ring Halo

    NASA Image and Video Library

    1998-03-26

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age. Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. A faint mist of particles can be seen above and below the main rings; this vertically extended, toroidal "halo" is unusual in planetary rings, and is probably caused by electromagnetic forces which can push small grains out of the ring plane. Halo material is present across this entire image, implying that it reaches more than 27,000 km above the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. In order to accentuate faint features in the image, different brightnesses are shown through color, with the brightest being

  3. HALOE test and evaluation software

    NASA Technical Reports Server (NTRS)

    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.

  4. Neutron halo in deformed nuclei

    SciTech Connect

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

    2010-07-15

    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 {sup 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.

  5. Haloes gone MAD: The Halo-Finder Comparison Project

    NASA Astrophysics Data System (ADS)

    Knebe, Alexander; Knollmann, Steffen R.; Muldrew, Stuart I.; Pearce, Frazer R.; Aragon-Calvo, Miguel Angel; Ascasibar, Yago; Behroozi, Peter S.; Ceverino, Daniel; Colombi, Stephane; Diemand, Juerg; Dolag, Klaus; Falck, Bridget L.; Fasel, Patricia; Gardner, Jeff; Gottlöber, Stefan; Hsu, Chung-Hsing; Iannuzzi, Francesca; Klypin, Anatoly; Lukić, Zarija; Maciejewski, Michal; McBride, Cameron; Neyrinck, Mark C.; Planelles, Susana; Potter, Doug; Quilis, Vicent; Rasera, Yann; Read, Justin I.; Ricker, Paul M.; Roy, Fabrice; Springel, Volker; Stadel, Joachim; Stinson, Greg; Sutter, P. M.; Turchaninov, Victor; Tweed, Dylan; Yepes, Gustavo; Zemp, Marcel

    2011-08-01

    We present a detailed comparison of fundamental dark matter halo properties retrieved by a substantial number of different halo finders. These codes span a wide range of techniques including friends-of-friends, spherical-overdensity and phase-space-based algorithms. We further introduce a robust (and publicly available) suite of test scenarios that allow halo finder developers to compare the performance of their codes against those presented here. This set includes mock haloes containing various levels and distributions of substructure at a range of resolutions as well as a cosmological simulation of the large-scale structure of the universe. All the halo-finding codes tested could successfully recover the spatial location of our mock haloes. They further returned lists of particles (potentially) belonging to the object that led to coinciding values for the maximum of the circular velocity profile and the radius where it is reached. All the finders based in configuration space struggled to recover substructure that was located close to the centre of the host halo, and the radial dependence of the mass recovered varies from finder to finder. Those finders based in phase space could resolve central substructure although they found difficulties in accurately recovering its properties. Through a resolution study we found that most of the finders could not reliably recover substructure containing fewer than 30-40 particles. However, also here the phase-space finders excelled by resolving substructure down to 10-20 particles. By comparing the halo finders using a high-resolution cosmological volume, we found that they agree remarkably well on fundamental properties of astrophysical significance (e.g. mass, position, velocity and peak of the rotation curve). We further suggest to utilize the peak of the rotation curve, vmax, as a proxy for mass, given the arbitrariness in defining a proper halo edge. Airport code for Madrid, Spain

  6. Proton radii of neutron-rich B isotopes and neutron surface thickness in 17B

    NASA Astrophysics Data System (ADS)

    Kanungo, Rituparna; Estrade, Alfredo; Horiuchi, Wataru

    2014-09-01

    As the neutron to proton asymmetry increases nuclei develop exotic structures such as neutron skin and halo. It is important to investigate how this asymmetry affects the proton distribution. The matter and proton radii have started unfolding a complete picture of the halo. For two-neutron halos the correlation between the halo neutrons and their distance from the core can be derived to define the average halo geometry. The proton radii are crucial information to extract the neutron skin thickness to constrain the equation of state of asymmetric nuclear matter. Very limited information is available on the proton radii of very neutron-rich nuclei. In this presentation, we will describe the new technique of extracting proton radii from charge changing cross sections using relativistic beams at GSI, Germany. The presentation will show first measurements of proton radii of the neutron-rich boron isotopes. The implications of the results in understanding the neutron surface thickness in the Borromean 17B and its possible halo structure will be discussed. As the neutron to proton asymmetry increases nuclei develop exotic structures such as neutron skin and halo. It is important to investigate how this asymmetry affects the proton distribution. The matter and proton radii have started unfolding a complete picture of the halo. For two-neutron halos the correlation between the halo neutrons and their distance from the core can be derived to define the average halo geometry. The proton radii are crucial information to extract the neutron skin thickness to constrain the equation of state of asymmetric nuclear matter. Very limited information is available on the proton radii of very neutron-rich nuclei. In this presentation, we will describe the new technique of extracting proton radii from charge changing cross sections using relativistic beams at GSI, Germany. The presentation will show first measurements of proton radii of the neutron-rich boron isotopes. The implications

  7. Halo Shape and its Relation to Environment

    NASA Astrophysics Data System (ADS)

    Gottlöber, S.; Turchaninov, V.

    Using high resolution DM simulations we study the shape of dark matter halos. Halos become more spherical with decreasing mass. This trend is even more pronounced for the inner part of the halo. Angular momentum and shape are correlated. The angular momenta of neighboring halos are correlated.

  8. The surface density of haloes

    NASA Astrophysics Data System (ADS)

    Del Popolo, A.; Lee, Xi-Guo

    We study the correlation between the central surface density and the core radius of the dark matter haloes of galaxies and clusters of galaxies. We find that the surface density within the halo characteristic radius r* is not a universal quantity as claimed by some authors (e.g., Milgrom 2009), but it correlates with several physical quantities (e.g., the halo mass M200, and the magnitude MB). The slope of the surface density-mass relation is 0.18 ± 0.05, leaving small room to the possibility of a constant surface density. Finally, we compare the results with MOND predictions.

  9. Halo model and halo properties in Galileon gravity cosmologies

    SciTech Connect

    Barreira, Alexandre; Li, Baojiu; Hellwing, Wojciech A.; Baugh, Carlton M.; Lombriser, Lucas; Pascoli, Silvia E-mail: baojiu.li@durham.ac.uk E-mail: llo@roe.ac.uk E-mail: silvia.pascoli@durham.ac.uk

    2014-04-01

    We investigate the performance of semi-analytical modelling of large-scale structure in Galileon gravity cosmologies using results from N-body simulations. We focus on the Cubic and Quartic Galileon models that provide a reasonable fit to CMB, SNIa and BAO data. We demonstrate that the Sheth-Tormen mass function and linear halo bias can be calibrated to provide a very good fit to our simulation results. We also find that the halo concentration-mass relation is well fitted by a power law. The nonlinear matter power spectrum computed in the halo model approach is found to be inaccurate in the mildly nonlinear regime, but captures reasonably well the effects of the Vainshtein screening mechanism on small scales. In the Cubic model, the screening mechanism hides essentially all of the effects of the fifth force inside haloes. In the case of the Quartic model, the screening mechanism leaves behind residual modifications to gravity, which make the effective gravitational strength time-varying and smaller than the standard value. Compared to normal gravity, this causes a deficiency of massive haloes and leads to a weaker matter clustering on small scales. For both models, we show that there are realistic halo occupation distributions of Luminous Red Galaxies that can match both the observed large-scale clustering amplitude and the number density of these galaxies.

  10. Halo modelling in chameleon theories

    SciTech Connect

    Lombriser, Lucas; Koyama, Kazuya; Li, Baojiu E-mail: kazuya.koyama@port.ac.uk

    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.

  11. The abundance of boron in three halo stars

    NASA Technical Reports Server (NTRS)

    Duncan, Douglas K.; Lambert, David L.; Lemke, Michael

    1992-01-01

    B abundances for three halo stars: HD 140283, HD 19445, and HD 201891 are presented. Using recent determinations of the Be abundance in HD 140283, B/Be of 10 +5/-4 is found for this star, and similar ratios are inferred for HD 19445 and HD 201891. This ratio is equal to the minimum value of 10 expected from a synthesis of B and Be by high-energy cosmic-ray spallation reactions in the interstellar medium. It is shown that the accompanying synthesis of Li by alpha on alpha fusion reactions is probably a minor contributor to the observed 'primordial' Li of halo stars. The observed constant ratios of B/O and Be/O are expected if the principal channel of synthesis involves cosmic-ray CNO nuclei from the supernovae colliding with interstellar protons.

  12. Fermionic Molecular Dynamics for Clusters, Halos and S-Factors

    NASA Astrophysics Data System (ADS)

    Feldmeier, Hans; Neff, Thomas

    2015-11-01

    Antisymmetrized products of Gaussian wave packets projected on total angular momentum, linear momentum, and parity span the FMD many-body Hilbert space in which the nuclear Hamiltonian is diagonalized. The wave packet parameters -- position, momentum, width and spin -- are obtained by variation under constraints. The great flexibility of this basis allows to describe not only shell-model like states but also exotic states like halos, e.g. the two-proton halo in 17Ne, or cluster states as they appear for example in 12C close to the α breakup threshold where the Hoyle state is located. Even a fully microscopic calculation of the 3He(α,γ)7Be capture reaction is possible and yields an astrophysical S-factor that compares very well with newer data.

  13. The abundance of boron in three halo stars

    NASA Technical Reports Server (NTRS)

    Duncan, Douglas K.; Lambert, David L.; Lemke, Michael

    1992-01-01

    B abundances for three halo stars: HD 140283, HD 19445, and HD 201891 are presented. Using recent determinations of the Be abundance in HD 140283, B/Be of 10 +5/-4 is found for this star, and similar ratios are inferred for HD 19445 and HD 201891. This ratio is equal to the minimum value of 10 expected from a synthesis of B and Be by high-energy cosmic-ray spallation reactions in the interstellar medium. It is shown that the accompanying synthesis of Li by alpha on alpha fusion reactions is probably a minor contributor to the observed 'primordial' Li of halo stars. The observed constant ratios of B/O and Be/O are expected if the principal channel of synthesis involves cosmic-ray CNO nuclei from the supernovae colliding with interstellar protons.

  14. Galactic Halos of Hydrogen

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This image shows two companion galaxies, NGC 4625 (top) and NGC 4618 (bottom), and their surrounding cocoons of cool hydrogen gas (purple). The huge set of spiral arms on NGC 4625 (blue) was discovered by the ultraviolet eyes of NASA's Galaxy Evolution Explorer. Though these arms are nearly invisible when viewed in optical light, they glow brightly in ultraviolet. This is because they are bustling with hot, newborn stars that radiate primarily ultraviolet light.

    The vibrant spiral arms are also quite lengthy, stretching out to a distance four times the size of the galaxy's core. They are part of the largest ultraviolet galactic disk discovered so far.

    Astronomers do not know why NGC 4625 grew arms while NGC 4618 did not. The purple nebulosity shown here illustrates that hydrogen gas - an ingredient of star formation - is diffusely distributed around both galaxies. This means that other unknown factors led to the development of the arms of NGC 4625.

    Located 31 million light-years away in the constellation Canes Venatici, NGC 4625 is the closest galaxy ever seen with such a young halo of arms. It is slightly smaller than our Milky Way, both in size and mass. However, the fact that this galaxy's disk is forming stars very actively suggests that it might evolve into a more massive and mature galaxy resembling our own.

    The image is composed of ultraviolet, visible-light and radio data, from the Galaxy Evolution Explorer, the California Institute of Technology's Digitized Sky Survey, and the Westerbork Synthesis Radio Telescope, the Netherlands, respectively. Near-ultraviolet light is colored green; far-ultraviolet light is colored blue; and optical light is colored red. Radio emissions are colored purple.

  15. Building Halos by Digesting Satellites

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-05-01

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

  16. Reliability of the hypernephroma halo

    SciTech Connect

    Wong, W.S.; Cochran, S.T.; Waisman, J.

    1981-11-01

    The excretory urograms and renal arteriograms of 68 patients with renal adenocarcinoma and 84 patients with renal masses other than renal adenocarcinoma were reviewed. The radiographs were examined for the presence or absence of the ''hypernephroma halo.'' The sensitivity of this sign was observed to be only 6% and 35% on excretory urography and arteriography, respectively. The specificity was 92% and 77%. However, the overall accuracy for this sign was only 54% and 59%. The relation between the halo and its postulated structural correlate, the tumor capsule, was also examined. There was no significant association demonstrable. It was concluded that the hypernephroma halo is not a reliable sign for diagnosing renal adenocarcinoma and that it probably does not represent the tumor capsule.

  17. Universality in Molecular Halo Clusters

    NASA Astrophysics Data System (ADS)

    Stipanović, P.; Markić, L. Vranješ; Bešlić, I.; Boronat, J.

    2014-12-01

    The ground state of weakly bound dimers and trimers with a radius extending well into the classically forbidden region is explored, with the goal to test the predicted universality of quantum halo states. The focus of the study is molecules consisting of T ↓ , D ↓ , 3He, 4He, and alkali atoms, where the interaction between particles is much better known than in the case of nuclei, which are traditional examples of quantum halos. The study of realistic systems is supplemented by model calculations in order to analyze how low-energy properties depend on the interaction potential. The use of variational and diffusion Monte Carlo methods enabled a very precise calculation of both the size and binding energy of the trimers. In the quantum halo regime, and for large values of scaled binding energies, all clusters follow almost the same universal line. As the scaled binding energy decreases, Borromean states separate from tango trimers.

  18. Accretion in the galactic halo

    NASA Astrophysics Data System (ADS)

    Stephens, Alex Courtney

    2000-10-01

    The Milky Way disk is enveloped in a diffuse, dynamically-hot collection of stars and star clusters collectively known as the ``stellar halo''. Photometric and chemical analyses suggest that these stars are ancient fossils of the galaxy formation epoch. Yet, little is known about the origin of this trace population. Is this system merely a vestige of the initial burst of star formation within the decoupled proto-Galaxy, or is it the detritus of cannibalized satellite galaxies? In an attempt to unravel the history of the Milky Way's stellar halo, I performed a detailed spectroscopic analysis of 55 metal-poor stars possessing ``extreme'' kinematic properties. It is thought that stars on orbits that either penetrate the remote halo or exhibit large retrograde velocities could have been associated with assimilated (or ``accreted'') dwarf galaxies. The hallmark of an accreted halo star is presumed to be a deficiency (compared with normal stars) of the α-elements (O, Mg, Si, Ca, Ti) with respect to iron, a consequence of sporadic bursts of star formation within the diminutive galaxies. Abundances for a select group of light metals (Li, Na, Mg, Si, Ca, Ti), iron-peak nuclides (Cr, Fe, Ni), and neutron-capture elements (Y, Ba) were calculated using line-strengths measured from high-resolution, high signal-to-noise spectral observations collected with the Keck I 10-m and KPNO 4-m telescopes. The abundances extracted from the spectra reveal: (1)The vast majority of outer halo stars possess supersolar [α/Fe] > 0.0) ratios. (2)The [α/Fe] ratio appears to decrease with increasing metallicity. (3)The outer halo stars have lower ratios of [α/Fe] than inner halo stars at a given metallicity. (4)At the largest metallicities, there is a large spread in the observed [α/Fe] ratios. (5)[α/Fe] anti-correlates with RAPO. (6)Only one star (BD+80° 245) exhibits the peculiar abundances expected of an assimilated star. The general conclusion extracted from these data is that the

  19. Core excitation effects in the breakup of halo nuclei

    SciTech Connect

    Moro, A. M.; Diego, R. de; Lay, J. A.; Crespo, R.; Johnson, R. C.; Arias, J. M.; Gomez-Camacho, J.

    2012-10-20

    The role of core excitation in the structure and dynamics of two-body halo nuclei is investigated. We present calculations for the resonant breakup of {sup 11}Be on protons at an incident energy of 63.7 MeV/nucleon, where core excitation effects were shown to be important. To describe the reaction, we use a recently developed extension of the DWBA formalism which incorporates these core excitation effects within the no-recoil approximation. The validity of the no-recoil approximation is also examined by comparing with DWBA calculations which take into account core recoil. In addition, calculations with two different continuum representations are presented and compared.

  20. White Dwarfs in the Galaxy's Halo

    NASA Astrophysics Data System (ADS)

    Oppenheimer, B.; Murdin, P.

    2002-12-01

    The Galaxy's large spherical halo (see GALACTICMETAL-POOR HALO and HALO, GALACTIC) may harboras many as several hundred billion WHITE DWARFS, apopulation as large in number as the total number of stars in theGalaxy's disk (see DISK GALAXIES and GALACTIC THIN DISK). Although this assertion iscontroversial, several astronomical surveys provide strong support for it andthe implications affect fields ...

  1. Dermoscopy of halo nevus in own observation

    PubMed Central

    Szymszal, Jan

    2014-01-01

    Introduction Halo nevus (HN) is a rare dermatologic entity characterized by a typical whitish rim encircling the existing melanocytic nevus resembling a halo. The clinical picture is suggesting its diagnosis, but so far only several dermoscopic descriptions of halo nevus have existed in the PubMed database. Aim To present the clinical and dermoscopic characteristics of halo nevus observed in dermoscopy. Material and methods Fifteen patients were diagnosed clinically and dermoscopically with halo nevus during planned routine dermoscopic examinations of all melanocytic lesions in 2007–2013. All digital images stored in the computer database were analyzed retrospectively according to the procedure described in the study. The clinical and dermoscopic parameters such as the dermoscopic pattern, color of nevus, special features and description of the surrounding halo were analyzed statistically. Results We analyzed 22 halo nevi (9 in females, 13 in males) in 15 patients (7 females, 8 males) diagnosed during the dermoscopic examination. The mean age of patients during dermoscopic examinations was 18.2 years. Mean patients’ age at HN onset was 15.7 years. Halo nevi occurred the most often as a solitary lesion. The ratio of multiple halo nevi to solitary halo nevus was 5 : 10. Every third halo nevus was located on the posterior trunk upper. In 68.2% of HN cases, the surrounding rim (halo) was characterized by its homogenous, whitish color. Conclusions Dermoscopic patterns such as uniform globular and structureless constituted one-third each of them in all analyzed patterns. PMID:25097486

  2. Dermoscopy of halo nevus in own observation.

    PubMed

    Kamińska-Winciorek, Grażyna; Szymszal, Jan

    2014-06-01

    Halo nevus (HN) is a rare dermatologic entity characterized by a typical whitish rim encircling the existing melanocytic nevus resembling a halo. The clinical picture is suggesting its diagnosis, but so far only several dermoscopic descriptions of halo nevus have existed in the PubMed database. To present the clinical and dermoscopic characteristics of halo nevus observed in dermoscopy. Fifteen patients were diagnosed clinically and dermoscopically with halo nevus during planned routine dermoscopic examinations of all melanocytic lesions in 2007-2013. All digital images stored in the computer database were analyzed retrospectively according to the procedure described in the study. The clinical and dermoscopic parameters such as the dermoscopic pattern, color of nevus, special features and description of the surrounding halo were analyzed statistically. We analyzed 22 halo nevi (9 in females, 13 in males) in 15 patients (7 females, 8 males) diagnosed during the dermoscopic examination. The mean age of patients during dermoscopic examinations was 18.2 years. Mean patients' age at HN onset was 15.7 years. Halo nevi occurred the most often as a solitary lesion. The ratio of multiple halo nevi to solitary halo nevus was 5 : 10. Every third halo nevus was located on the posterior trunk upper. In 68.2% of HN cases, the surrounding rim (halo) was characterized by its homogenous, whitish color. Dermoscopic patterns such as uniform globular and structureless constituted one-third each of them in all analyzed patterns.

  3. Non-Gaussian halo assembly bias

    SciTech Connect

    Reid, Beth A.; Verde, Licia; Dolag, Klaus; Matarrese, Sabino; Moscardini, Lauro E-mail: liciaverde@icc.ub.edu E-mail: sabino.matarrese@pd.infn.it

    2010-07-01

    The strong dependence of the large-scale dark matter halo bias on the (local) non-Gaussianity parameter, f{sub 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.

  4. Halo Coronal Mass Ejections and Geomagnetic Storms

    NASA Technical Reports Server (NTRS)

    Gopalswamy, Nat

    2009-01-01

    In this letter, I show that the discrepancies in the geoeffectiveness of halo coronal mass ejections (CMEs) reported in the literature arise due to the varied definitions of halo CMEs used by different authors. In particular, I show that the low geoeffectiveness rate is a direct consequence of including partial halo CMEs. The geoeffectiveness of partial halo CMEs is lower because they are of low speed and likely to make a glancing impact on Earth. Key words: Coronal mass ejections, geomagnetic storms, geoeffectiveness, halo CMEs.

  5. Halo Coronal Mass Ejections and Geomagnetic Storms

    NASA Technical Reports Server (NTRS)

    Gopalswamy, Nat

    2009-01-01

    In this letter, I show that the discrepancies in the geoeffectiveness of halo coronal mass ejections (CMEs) reported in the literature arise due to the varied definitions of halo CMEs used by different authors. In particular, I show that the low geoeffectiveness rate is a direct consequence of including partial halo CMEs. The geoeffectiveness of partial halo CMEs is lower because they are of low speed and likely to make a glancing impact on Earth. Key words: Coronal mass ejections, geomagnetic storms, geoeffectiveness, halo CMEs.

  6. Proton Therapy

    MedlinePlus

    ... Proton Therapy Alternative & Integrative Medicine Clinical Trials GBM AGILE TTFields – Optune™ Brain Tumor Treatment Locations Treatment Side ... Proton Therapy Alternative & Integrative Medicine Clinical Trials GBM AGILE TTFields – Optune™ Brain Tumor Treatment Locations Treatment Side ...

  7. Halo Density Reduction by Baryonic Settling?

    NASA Astrophysics Data System (ADS)

    Jardel, J. R.; Sellwood, J. A.

    2009-02-01

    We test the proposal by El-Zant et al. that the dark matter density of halos could be reduced through dynamical friction acting on heavy baryonic clumps in the early stages of galaxy formation. Using N-body simulations, we confirm that the inner halo density cusp is flattened to 0.2 of the halo break radius by the settling of a single clump of mass gsim0.5% of the halo mass. We also find that an ensemble of 50 clumps, each having masses gsim0.2%, can flatten the cusp to almost the halo break radius on a timescale of ~9 Gyr, for a Navarro-Frenk-White profile halo of concentration 15. We summarize some of the difficulties that need to be overcome if this mechanism is to resolve the apparent conflict between the observed inner densities of galaxy halos and the predictions of ΛCDM.

  8. Ultraviolet Halos around Spiral Galaxies. I. Morphology

    NASA Astrophysics Data System (ADS)

    Hodges-Kluck, Edmund; Cafmeyer, Julian; Bregman, Joel N.

    2016-12-01

    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 106-107 M ⊙ of dust within 2-10 kpc of the disk, whose properties may change with height in starburst galaxies.

  9. Enantioselective Protonation

    PubMed Central

    Mohr, Justin T.; Hong, Allen Y.; Stoltz, Brian M.

    2010-01-01

    Enantioselective protonation is a common process in biosynthetic sequences. The decarboxylase and esterase enzymes that effect this valuable transformation are able to control both the steric environment around the proton acceptor (typically an enolate) and the proton donor (typically a thiol). Recently, several chemical methods to achieve enantioselective protonation have been developed by exploiting various means of enantiocontrol in different mechanisms. These laboratory transformations have proven useful for the preparation of a number of valuable organic compounds. PMID:20428461

  10. Reionization histories of Milky Way mass halos

    SciTech Connect

    Li, Tony Y.; Wechsler, Risa H.; Abel, Tom; Alvarez, Marcelo A. E-mail: rwechsler@stanford.edu E-mail: malvarez@cita.utoronto.ca

    2014-04-20

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

  11. Clouds Dominate the Galactic Halo

    NASA Astrophysics Data System (ADS)

    2003-01-01

    Using the exquisite sensitivity of the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT), astronomer Jay Lockman of the National Radio Astronomy Observatory (NRAO) in Green Bank, W. Va., has produced the best cross-section ever of the Milky Way Galaxy's diffuse halo of hydrogen gas. This image confirms the presence of discrete hydrogen clouds in the halo, and could help astronomers understand the origin and evolution of the rarefied atmosphere that surrounds our Galaxy. Lockman presented his findings at the American Astronomical Society meeting in Seattle, WA. Hydrogen Clouds Graphic Artist's Rendering of the Milky Way (background) with insert showing GBT image of cross-section of neutral atomic Hydrogen Credit: Kirk Woellert/National Science Foundation Patricia Smiley, NRAO. "The first observations with the Green Bank Telescope suggested that the hydrogen in the lower halo, the transition zone between the Milky Way and intergalactic space, is very clumpy," said Lockman. "The latest data confirm these results and show that instead of trailing away smoothly from the Galactic plane, a significant fraction of the hydrogen gas in the halo is concentrated in discrete clouds. There are even some filaments." Beyond the star-filled disk of the Milky Way, there exists an extensive yet diffuse halo of hydrogen gas. For years, astronomers have speculated about the origin and structure of this gas. "Even the existence of neutral hydrogen in the halo has been somewhat of a puzzle," Lockman remarked. "Unlike the Earth's atmosphere, which is hot enough to hold itself up against the force of gravity, the hydrogen in the halo is too cool to support itself against the gravitational pull of the Milky Way." Lockman points out that some additional factor has to be involved to get neutral hydrogen to such large distances from the Galactic plane. "This force could be cosmic rays, a supersonic wind, the blast waves from supernovae, or something we have not thought of

  12. Ultra-High Intensity Proton Accelerators and their Applications

    SciTech Connect

    Weng, W. T.

    1997-12-31

    The science and technology of proton accelerators have progressed considerably in the past three decades. Three to four orders of magnitude increase in both peak intensity and average flux have made it possible to construct high intensity proton accelerators for modern applications, such as: spallation neutron sources, kaon factory, accelerator production of tritium, energy amplifier and muon collider drivers. The accelerator design focus switched over from intensity for synchrotrons, to brightness for colliders to halos for spallation sources. An overview of this tremendous progress in both accelerator science and technology is presented, with special emphasis on the new challenges of accelerator physics issues such as: H(-) injection, halo formation and reduction of losses.

  13. The Anemic Stellar Halo of M101

    NASA Astrophysics Data System (ADS)

    Holwerda, Benne

    2014-10-01

    Models of galaxy formation in a cosmological context predict that massive disk galaxies should have richly-structured extended stellar halos, containing ~10% of a galaxy's stars, originating in large part from the tidal disruption of dwarf galaxies. Observations of a number of nearby disk galaxies have generally agreed with these expectations. Recent new observations in integrated light with a novel array of low scattered-light telephoto lenses have failed to convincingly detect a stellar halo in the nearby massive face-on disk galaxy M101 (van Dokkum et al. 2014). They argue that any halo has to have <0.3% of the mass of the galaxy. This halo would be the least massive of any massive disk galaxy in the local Universe (by factors of several) -- such a halo is not predicted or naturally interpreted by the models, and would present a critical challenge to the picture of ubiquitous stellar halos formed from the debris of disrupting dwarf galaxies.We propose to resolve the stellar populations of this uniquely anemic stellar halo for 6 orbits with HST (ACS and WFC3), allowing us to reach surface brightness limits sufficient to clearly detect and characterize M101's stellar halo if it carries more than 0.1% of M101's mass. With resolved stellar populations, we can use the gradient of stellar populations as a function of radius to separate stellar halo from disk, which is impossible using integrated light observations. The resolved stellar populations will reveal the halo mass to much greater accuracy, measure the halo radial profile, constrain any halo lopsidedness, estimate the halo's stellar metallicity, and permit an analysis of outer disk stellar populations.

  14. Galaxy and Mass Assembly (GAMA): halo formation times and halo assembly bias on the cosmic web

    NASA Astrophysics Data System (ADS)

    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.

  15. Halo Microlensing and Dark Baryons

    NASA Astrophysics Data System (ADS)

    Crotts, A. P. S.

    1993-12-01

    (While Pierce lectures review past accomplishments, customarily, this talk concerns efforts which we have pursued for some years and which are now reaching fruition. We present elsewhere at this meeting results from research cited for the Prize.) Dark matter exists in the halos of spiral galaxies, and the least radical alternative for its identity is normal matter produced by primordial nucleosynthesis. This matter could easily be hidden in large, condensed objects. Paczynski pointed out in 1986 that if condensations of Galactic halo matter are sufficiently massive, they will produce detectable amplification of background starlight by gravitational lensing. Several groups recently reported possible detections of this effect after surveying large numbers of stars in the Galactic Bulge and LMC. The connection between these events and massive, dark halos is unclear and likely to remain so for some time, given the rate at which they are detected. Following Paczynski's realization, we stressed that a much higher event rate, a statistical control sample, sensitivity to a much broader mass range, and modulation of the predicted lensing rate with galactocentric distance can all be realized by a different experiment: observing the halo of M31 (and the Galaxy) using stars in M31. In some ways, M31 is a more difficult target than the LMC or the Bulge, given the faintness of its stars, but our observations in 1991 and 1993 indicate that these problems have been surmounted. We can detect stellar variability even under extremely crowded conditions like those in M31's inner disk, and can monitor a sufficient number of stars to study halo lensing. We present results from our initial survey which indicates that the required sensitivity can be reached to confirm or reject the hypothesis that sub-solar masses like those detected in our Galaxy make up the missing spiral galaxy mass. It is possible that we may use the data already obtained (and still being analyzed) to place

  16. Historical halo displays as past weather indicator

    NASA Astrophysics Data System (ADS)

    Neuhäuser, Dagmar; Neuhäuser, Ralph

    2017-04-01

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

  17. Dark energy and dark matter haloes

    NASA Astrophysics Data System (ADS)

    Kuhlen, Michael; Strigari, Louis E.; Zentner, Andrew R.; Bullock, James S.; Primack, Joel R.

    2005-02-01

    We investigate the effect of dark energy on the density profiles of dark matter haloes with a suite of cosmological N-body simulations and use our results to test analytic models. We consider constant equation of state models, and allow both w>=-1 and w < -1. Using five simulations with w ranging from -1.5 to -0.5, and with more than ~1600 well-resolved haloes each, we show that the halo concentration model of Bullock et al. accurately predicts the median concentrations of haloes over the range of w, halo masses and redshifts that we are capable of probing. We find that the Bullock et al. model works best when halo masses and concentrations are defined relative to an outer radius set by a cosmology-dependent virial overdensity. For a fixed power spectrum normalization and fixed-mass haloes, larger values of w lead to higher concentrations and higher halo central densities, both because collapse occurs earlier and because haloes have higher virial densities. While precise predictions of halo densities are quite sensitive to various uncertainties, we make broad comparisons to galaxy rotation curve data. At fixed power spectrum normalization (fixed σ8), w > -1 quintessence models seem to exacerbate the central density problem relative to the standard w=-1 model. For example, models with w~=- 0.5 seem disfavoured by the data, which can be matched only by allowing extremely low normalizations, σ8<~ 0.6. Meanwhile w < -1 models help to reduce the apparent discrepancy. We confirm that the halo mass function of Jenkins et al. provides an excellent approximation to the abundance of haloes in our simulations and extend its region of validity to include models with w < -1.

  18. Halo scale predictions of symmetron modified gravity

    SciTech Connect

    Clampitt, Joseph; Jain, Bhuvnesh; Khoury, Justin E-mail: bjain@physics.upenn.edu

    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.

  19. The prodigious halo of the other Huygens.

    PubMed

    Können, Gunther P

    2015-02-01

    At the height of the ceremony in the Principality of Orange of the restoration of the sovereignty of the House of Nassau in 1665, a ceremony led by Christiaan's father, Constantijn Huygens, a "solar crown" appeared in the sky, apparently a divine sign of approval. A nearly forgotten contemporary color engraving of this miraculous event has survived. Constantijn seized the opportunity by using to his advantage the general euphoria among the citizens caused by the appearance. We argue that Constantijn knew exactly what was going on in the sky because of his son's work on halo theory. Given its brightness and its time of appearance, it seems plausible that the most prominent halo in the Orange halo display was a circumscribed halo rather than the more familiar but bleaker circular 22° halo. The same probably holds for most of the other high-sun halos that caused general consternation, dating from the Octavian halo of 44 BC, to the Chernobyl halo of 1986, and indeed up to bright high-sun halos of the present.

  20. The total mass of dark matter haloes

    NASA Astrophysics Data System (ADS)

    Anderhalden, Donnino; Diemand, Jürg

    2011-07-01

    The simple, conventional dark matter halo mass definitions commonly used in cosmological simulations ('virial' mass, FoF mass, M50, 100, 200, …) only capture part of the collapsed material and are therefore inconsistent with the halo mass concept used in analytical treatments of structure formation. Simulations have demonstrated that typical dark matter particle orbits extend out to about 90 per cent of their turnaround radius, which results in apocentre passages outside of the current 'virial' radius on the first and also on the second orbit. Here we describe how the formation history of haloes can be used to identify those particles which took part in the halo collapse, but are missed by conventional group finders because of their remote present location. These particles are added to the part of the halo already identified by FoF. The corrected masses of dark haloes are significantly higher (the median mass increase is 25 per cent) and there is a considerable shift of the halo mass function towards the Press and Schechter form. We conclude that meaningful quantitative comparisons between (semi-)analytic predictions of halo properties (e.g. mass functions, mass accretion rates, merger rates, spatial clustering, etc.) and simulation results will require using the same halo definition in both approaches.

  1. Unbound particles in dark matter halos

    SciTech Connect

    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.

  2. Progress in understanding halo current at JET

    NASA Astrophysics Data System (ADS)

    Riccardo, V.; Arnoux, G.; Beaumont, P.; Hacquin, S.; Hobirk, J.; Howell, D.; Huber, A.; Joffrin, E.; Koslowski, R.; Lam, N.; Leggate, H.; Rachlew, E.; Sergienko, G.; Stephen, A.; Todd, T.; Zerbini, M.; Delogu, R.; Grando, L.; Marcuzzi, D.; Peruzzo, S.; Pomaro, N.; Sonato, P.; JET EFDA Contributors

    2009-05-01

    The poloidal distribution of the halo current density on the top dump plate in JET can now be measured thanks to a new set of Rogowskii coils. These are the first measurements in JET able to offer an insight in the width of the halo current interaction with the wall. Therefore they offer both validation of the assumption made for JET disruption design criteria and one additional point in the extrapolation of the expected halo current width, and hence halo current density (and related local electro-mechanical loads on in-vessel components) for ITER. During upward events, the measured current density is consistent with the measured total poloidal halo current. The halo footprint extends over most of the upper dump plate, converting to a halo current flux tube width of ~100 mm. A set of four toridal field pick-up coils installed 90° apart now allows a more accurate measurement of the poloidal halo current, in particular its toroidal peaking factor, and direct comparison between halo and plasma asymmetries.

  3. Shell closures, loosely bound structures, and halos in exotic nuclei

    SciTech Connect

    Saxena, G.; Singh, D.

    2013-04-15

    Inspired by the recent experiments indicating doubly magic nuclei that lie near the drip-line and encouraged by the success of our relativistic mean-field (RMF) plus state-dependent BCS approach to the description of the ground-state properties of drip-line nuclei, we develop this approach further, across the entire periodic table, to explore magic nuclei, loosely bound structures, and halo formation in exotic nuclei. In our RMF+BCS approach, the single-particle continuum corresponding to the RMF is replaced by a set of discrete positive-energy states for the calculations of pairing energy. Detailed analysis of the single-particle spectrum, pairing energies, and densities of the nuclei predict the unusual proton shell closures at proton numbers Z = 6, 14, 16, 34, and unusual neutron shell closures at neutron numbers N = 6, 14, 16, 34, 40, 70, 112. Further, in several nuclei like the neutron-rich isotopes of Ca, Zr, Mo, etc., the gradual filling of lowlying single-particle resonant state together with weakly bound single-particle states lying close to the continuum threshold helps accommodate more neutrons but with an extremely small increase in the binding energy. This gives rise to the occurrence of loosely bound systems of neutron-rich nuclei with a large neutron-to-proton ratio. In general, the halo-like formation, irrespective of the existence of any resonant state, is seen to be due to the large spatial extension of the wave functions for the weakly bound single-particle states with low orbital angular momentum having very small or no centrifugal barriers.

  4. Stellar haloes in Milky Way mass galaxies: from the inner to the outer haloes

    NASA Astrophysics Data System (ADS)

    Tissera, Patricia B.; Beers, Timothy C.; Carollo, Daniela; Scannapieco, Cecilia

    2014-04-01

    We present a comprehensive study of the chemical properties of the stellar haloes of Milky Way mass galaxies, analysing the transition between the inner to the outer haloes. We find the transition radius between the relative dominance of the inner-halo and outer-halo stellar populations to be ˜15-20 kpc for most of our haloes, similar to that inferred for the Milky Way from recent observations. While the number density of stars in the simulated inner-halo populations decreases rapidly with distance, the outer-halo populations contribute about 20-40 per cent in the fiducial solar neighbourhood, in particular at the lowest metallicities. We have determined [Fe/H] profiles for our simulated haloes; they exhibit flat or mild gradients, in the range [-0.002, -0.01] dex kpc-1. The metallicity distribution functions exhibit different features, reflecting the different assembly history of the individual stellar haloes. We find that stellar haloes formed with larger contributions from massive subgalactic systems have steeper metallicity gradients. Very metal-poor stars are mainly contributed to the halo systems by lower mass satellites. There is a clear trend among the predicted metallicity distribution functions that a higher fraction of low-metallicity stars are found with increasing radius. These properties are consistent with the range of behaviours observed for stellar haloes of nearby galaxies.

  5. Haloes seen in UVIS reflectance

    NASA Astrophysics Data System (ADS)

    Esposito, L. W.; Bradley, E. T.; Colwell, J. E.; Sremcevic, M.

    2012-12-01

    UVIS SOI reflectance spectra show bright 'haloes' around the locations of some of the strongest resonances in Saturn's A ring (Esposito etal 2005). UV spectra constrain the size and composition of the icy ring particles (Bradley etal 2010, 2012). We investigate the Janus 4:3, 5:3, 6:5 and Mimas 5:3 inner Lindblad resonances as well as at the Mimas 5:3 vertical resonance (bending wave location). Models of ring particle regolith evolution (Elliott and Esposito 2010) indicate the deeper regolith is made of older and purer ice. The strong resonances can cause streamline crowding (Lewis and Stewart 2005) which damps the interparticle velocity, allowing temporary clumps to grow, which in turn increase the velocity, eroding the clumps and releasing smaller particles and regolith (see the predator-prey model of Esposito etal 2012). This cyclic behavior, driven by the resonant perturbation from the moon, can yield collision velocities at particular azimuths greater than 1m/sec, sufficient to erode the aggregates (Blum 2006), exposing older, purer materials. Thus, the radial location of the strongest resonances can be where we find both large aggregates and disrupted fragments, in a balance maintained by the periodic moon forcing. If this stirring exposes older, and purer ice, the velocity threshold for eroding the aggregates can explain why only the strongest Lindblad resonances show haloes. Diffusion can explain the morphology of these haloes, although they are not well-resolved spatially by UVIS. Spectra determine the relative contributions of particle size and purity at these locations, for comparison to estimates from the regolith evolution models.

  6. Halo and reverse halo signs in canine pulmonary computed tomography.

    PubMed

    Secrest, Scott; Sakamoto, Kaori

    2014-01-01

    The halo sign (HS) and reverse halo sign (RHS) are radiologic signs identified on pulmonary computed tomography (CT) in people. The HS is described as a circular area of ground-glass attenuation surrounding a pulmonary nodule or mass. The RHS is defined as a focal, rounded area of ground-glass attenuation surrounded by a more or less complete ring of consolidation. These signs have been identified in a variety of diseases in people. The purpose of this retrospective study was to determine if the HS and RHS occur in dogs with pulmonary disease and to determine if they are associated with a particular disease process. In addition, the appearance of the HS and RHS was correlated with the histopathologic changes. Our results indicate that the HS and RHS are not common signs identified in dogs with pulmonary disease with an HS noted in five cases and an RHS in 4 of the 33 dogs that met the inclusion criteria. An association between the HS (P-value 0.8163) or RHS (P-value 0.5988) and neoplasia, infectious/inflammatory, and other disease processes was not identified using a Fisher's exact test. The HS was identified in neoplastic, infectious, and inflammatory conditions, with the RHS identified in neoplastic and infectious diseases and a lung lobe torsion. Histologically, the HS and RHS were caused by tumor extension, necrosis, and/or hemorrhage of the pulmonary parenchyma. © 2014 American College of Veterinary Radiology.

  7. The Dual Origin Of Stellar Halos

    NASA Astrophysics Data System (ADS)

    Zolotov, Adi

    In the dominant Lambda+Cold Dark Matter cosmological paradigm, galaxy stellar halos are thought to form hierarchically from multiple accretion events, starting from the first structures to collapse in the Universe. This dissertation aims to make the first detailed theoretical predictions for the origin of galactic stellar halos. We focus on understanding the physical processes involved in halo formation using high-resolution, N-body + Smooth Particle Hydrodynamic simulations of disk galaxies in a cosmological context. These self-consistent simulations are used to study the competing importance of dissipative processes and dissipationless mergers in the formation of stellar halos. The relative contribution of each mechanism, and its specific role in assembling the inner and outer regions of halos is explored, as a function of galaxy mass and merging history. We show that the presence of both accreted and in situ stars in halos is a generic feature of galaxy formation. For L* galaxies, the relative contribution of each stellar population to a halo is shown to be a function of a galaxy's accretion history. Galaxies with recent mergers, like M31, will host relatively few in situ stars, while galaxies with more quiescent recent histories, like the Milky Way, will likely have a larger relative contribution from an in situ population. We show that in situ halo stars are more [alpha/Fe]-rich than accreted stars at the high [Fe/H] end of a halo's metallicity distribution function. In lower mass galaxies, M ˜ 1010 M, in situ stars dominate the stellarmass of halos. In these galaxies, in situ halo stars are, on average, younger and more metal-rich than accreted halo stars. Because in situ stars are dominant, these trends result in halos that are more metal-rich than simple accretion models predict. The halos of low mass galaxies do not extend out to the virial radii of the primary, as they do in more massive galaxies. We find that the ratio of luminous-halo mass to total

  8. THE PSEUDO-EVOLUTION OF HALO MASS

    SciTech Connect

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

    2013-03-20

    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{sub 200{rho}-bar} Less-Than-Or-Equivalent-To 10{sup 12} h{sup -1} M{sub Sun} 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.

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

    NASA Astrophysics Data System (ADS)

    Kaaret, Philip

    2017-08-01

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

  10. Correlates of Halo Error in Teacher Evaluation.

    ERIC Educational Resources Information Center

    Moritsch, Brian G.; Suter, W. Newton

    1988-01-01

    An analysis of 300 undergraduate psychology student ratings of teachers was undertaken to assess the magnitude of halo error and a variety of rater, ratee, and course characteristics. The raters' halo errors were significantly related to student effort in the course, previous experience with the instructor, and class level. (TJH)

  11. Confounding among Measures of Leniency and Halo.

    ERIC Educational Resources Information Center

    Alliger, George M.; Williams, Kevin J.

    1989-01-01

    The interrelationships among halo and leniency rating errors were examined using simulated rating data. As leniency increased, halo decreased when measured by dimension intercorrelations but increased when measured by standard deviations across dimensions. Implications of these results for the use of the various measures are discussed. (SLD)

  12. Comments on the Measurement of Halo.

    ERIC Educational Resources Information Center

    Fisicaro, Sebastiano A.; Vance, Robert J.

    1994-01-01

    This article presents arguments that the correlation measure "r" of halo is not conceptually more appropriate than the standard deviation (SD) measure. It also describes conditions under which halo effects occur and when the SD and r measures can be used. Neither measure is uniformly superior to the other. (SLD)

  13. Confounding among Measures of Leniency and Halo.

    ERIC Educational Resources Information Center

    Alliger, George M.; Williams, Kevin J.

    1989-01-01

    The interrelationships among halo and leniency rating errors were examined using simulated rating data. As leniency increased, halo decreased when measured by dimension intercorrelations but increased when measured by standard deviations across dimensions. Implications of these results for the use of the various measures are discussed. (SLD)

  14. Comments on the Measurement of Halo.

    ERIC Educational Resources Information Center

    Fisicaro, Sebastiano A.; Vance, Robert J.

    1994-01-01

    This article presents arguments that the correlation measure "r" of halo is not conceptually more appropriate than the standard deviation (SD) measure. It also describes conditions under which halo effects occur and when the SD and r measures can be used. Neither measure is uniformly superior to the other. (SLD)

  15. Correlates of Halo Error in Teacher Evaluation.

    ERIC Educational Resources Information Center

    Moritsch, Brian G.; Suter, W. Newton

    1988-01-01

    An analysis of 300 undergraduate psychology student ratings of teachers was undertaken to assess the magnitude of halo error and a variety of rater, ratee, and course characteristics. The raters' halo errors were significantly related to student effort in the course, previous experience with the instructor, and class level. (TJH)

  16. Analytical halo model of galactic conformity

    NASA Astrophysics Data System (ADS)

    Pahwa, Isha; Paranjape, Aseem

    2017-09-01

    We present a fully analytical halo model of colour-dependent clustering that incorporates the effects of galactic conformity in a halo occupation distribution framework. The model, based on our previous numerical work, describes conformity through a correlation between the colour of a galaxy and the concentration of its parent halo, leading to a correlation between central and satellite galaxy colours at fixed halo mass. The strength of the correlation is set by a tunable 'group quenching efficiency', and the model can separately describe group-level correlations between galaxy colour (1-halo conformity) and large-scale correlations induced by assembly bias (2-halo conformity). We validate our analytical results using clustering measurements in mock galaxy catalogues, finding that the model is accurate at the 10-20 per cent level for a wide range of luminosities and length-scales. We apply the formalism to interpret the colour-dependent clustering of galaxies in the Sloan Digital Sky Survey (SDSS). We find good overall agreement between the data and a model that has 1-halo conformity at a level consistent with previous results based on an SDSS group catalogue, although the clustering data require satellites to be redder than suggested by the group catalogue. Within our modelling uncertainties, however, we do not find strong evidence of 2-halo conformity driven by assembly bias in SDSS clustering.

  17. Milky Way halo gas kinematics

    NASA Technical Reports Server (NTRS)

    Danly, L.

    1986-01-01

    Measurements of high resolution, short wavelength absorption data taken by IUE toward high latitude O and B stars are presented in a discussion of the large scale kinematic properties of Milky Way Halo gas. An analysis of these data demonstrates that: (1) the obsrved absorption widths (FWHM) of Si II are very large, ranging up to 150 Km/s for the most distant halo star; this is much larger than is generally appreciated from optical data; (2) the absorption is observed to be systematically negative in radial velocity, indicating that cool material is, on the whole, flowing toward the disk of the galaxy; (3) there is some evidence for asymmetry between the northern and southern galactic hemispheres, in accordance with the HI 21 cm data toward the galactic poles; (4) low column density gas with highly negative radial LSR velocity (V less than -70 km/s) can be found toward stars beyond 1-3 kpc in the northern galactic hemisphere in all four quadrants of galactic longitude; and (5) only the profiles toward stars in the direction of known high velocity HI features show a clear two component structure.

  18. Proton Transport

    NASA Technical Reports Server (NTRS)

    Pohorille, Andrew; DeVincenzi, Donald L. (Technical Monitor)

    2001-01-01

    The transport of protons across membranes is an essential process for both bioenergetics of modern cells and the origins of cellular life. All living systems make use of proton gradients across cell walls to convert environmental energy into a high-energy chemical compound, adenosine triphosphate (ATP), synthesized from adenosine diphosphate. ATP, in turn, is used as a source of energy to drive many cellular reactions. The ubiquity of this process in biology suggests that even the earliest cellular systems were relying on proton gradient for harvesting environmental energy needed to support their survival and growth. In contemporary cells, proton transfer is assisted by large, complex proteins embedded in membranes. The issue addressed in this Study was: how the same process can be accomplished with the aid of similar but much simpler molecules that could have existed in the protobiological milieu? The model system used in the study contained a bilayer membrane made of phospholipid, dimyristoylphosphatidylcholine (DMPC) which is a good model of the biological membranes forming cellular boundaries. Both sides of the bilayer were surrounded by water which simulated the environment inside and outside the cell. Embedded in the membrane was a fragment of the Influenza-A M$_2$ protein and enough sodium counterions to maintain system neutrality. This protein has been shown to exhibit remarkably high rates of proton transport and, therefore, is an excellent model to study the formation of proton gradients across membranes. The Influenza M$_2$ protein is 97 amino acids in length, but a fragment 25 amino acids long. which contains a transmembrane domain of 19 amino acids flanked by three amino acids on each side. is sufficient to transport protons. Four identical protein fragments, each folded into a helix, aggregate to form small channels spanning the membrane. Protons are conducted through a narrow pore in the middle of the channel in response to applied voltage. This

  19. Probing the galactic halo with ROSAT

    NASA Technical Reports Server (NTRS)

    Burrows, David N.; Mendenhall, J. A.

    1992-01-01

    We discuss the current status of ROSAT shadowing observations designed to search for emission from million degree gas in the halo of the Milky Way galaxy. Preliminary results indicate that million degree halo gas is observed in the 1/4 keV band in some directions, most notably toward the Draco cloud at (l,b) = (92 deg, +38 deg), but that the halo emission is patchy and highly anisotropic. Our current understanding of this halo emission is based on a small handful of observations which have been analyzed to date. Many more observations are currently being analyzed or are scheduled for observation within the next year, and we expect our understanding of this component of the galactic halo to improve dramatically in the near future.

  20. Probing the galactic halo with ROSAT

    NASA Technical Reports Server (NTRS)

    Burrows, D. N.; Mendenhall, J. A.

    1993-01-01

    We discuss the current status of ROSAT shadowing observations designed to search for emission from million degree gas in the halo of the Milky Way galaxy. Preliminary results indicate that million degree halo gas is observed in the 1/4 keV band in some directions, most notably toward the Draco cloud at (l,b) = (92 deg, +38 deg), but that the halo emission is patchy and highly anisotropic. Our current understanding of this halo emission is based on a small handful of observations which have been analyzed to date. Many more observations are currently being analyzed or are scheduled for observation within the next year, and we expect our understanding of this component of the galactic halo to improve dramatically in the near future.

  1. Smooth halos in the cosmic web

    NASA Astrophysics Data System (ADS)

    Gaite, José

    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.

  2. Where have all the cluster halos gone?

    NASA Technical Reports Server (NTRS)

    Burns, Jack O.; Sulkanen, Martin E.; Gisler, Galen R.; Perley, Rick A.

    1992-01-01

    A new LF (330 MHz) VLA image of the Perseus cluster confirms the presence of a miniradio halo with diameter of about 430 kpc (H0 = 75 km/s Mpc) surrounding 3C 84. A careful comparison with the Coma cluster shows that there is no evidence for a similar, very extended halo in Perseus despite the large number of cluster radio galaxies which could power such a halo. These two clusters represent two classes of radio halos which differ by the absence (Coma) or presence (Perseus) of cooling inflows. It is argued that smaller halos as in Perseus result form insufficient clusterwide magnetic fields. A simple model is presented which suggests that cooling flows can suppress the diffusion of turbulently amplified B-fields outward from the cluster core. Such a suppression leads to the development of minihalos which are confined to the cores of cooling flow clusters.

  3. Smooth halos in the cosmic web

    SciTech Connect

    Gaite, José

    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.

  4. Halo-free Phase Contrast Microscopy

    PubMed Central

    Nguyen, Tan H.; Kandel, Mikhail; Shakir, Haadi M.; Best-Popescu, Catherine; Arikkath, Jyothi; Do, Minh N.; Popescu, Gabriel

    2017-01-01

    We present a new approach for retrieving halo-free phase contrast microscopy (hfPC) images by upgrading the conventional PC microscope with an external interferometric module, which generates sufficient data for reversing the halo artifact. Acquiring four independent intensity images, our approach first measures haloed phase maps of the sample. We solve for the halo-free sample transmission function by using a physical model of the image formation under partial spatial coherence. Using this halo-free sample transmission, we can numerically generate artifact-free PC images. Furthermore, this transmission can be further used to obtain quantitative information about the sample, e.g., the thickness with known refractive indices, dry mass of live cells during their cycles. We tested our hfPC method on various control samples, e.g., beads, pillars and validated its potential for biological investigation by imaging live HeLa cells, red blood cells, and neurons. PMID:28338086

  5. Concentrations of Simulated Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Child, Hillary

    2017-01-01

    We present the concentration-mass (c-M) relation of dark matter halos in two new high-volume high-resolution cosmological N-body simulations, Q Continuum and Outer Rim. Concentration describes the density of the central regions of halos; it is highest for low-mass halos at low redshift, decreasing at high mass and redshift. The shape of the c-M relation is an important probe of cosmology. We discuss the redshift dependence of the c-M relation, several different methods to determine concentrations of simulated halos, and potential sources of bias in concentration measurements. To connect to lensing observations, we stack halos, which also allows us to assess the suitability of the Navarro-Frenk-White profile and other profiles, such as Einasto, with an additional shape parameter. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144082.

  6. Halo-free Phase Contrast Microscopy.

    PubMed

    Nguyen, Tan H; Kandel, Mikhail; Shakir, Haadi M; Best-Popescu, Catherine; Arikkath, Jyothi; Do, Minh N; Popescu, Gabriel

    2017-03-24

    We present a new approach for retrieving halo-free phase contrast microscopy (hfPC) images by upgrading the conventional PC microscope with an external interferometric module, which generates sufficient data for reversing the halo artifact. Acquiring four independent intensity images, our approach first measures haloed phase maps of the sample. We solve for the halo-free sample transmission function by using a physical model of the image formation under partial spatial coherence. Using this halo-free sample transmission, we can numerically generate artifact-free PC images. Furthermore, this transmission can be further used to obtain quantitative information about the sample, e.g., the thickness with known refractive indices, dry mass of live cells during their cycles. We tested our hfPC method on various control samples, e.g., beads, pillars and validated its potential for biological investigation by imaging live HeLa cells, red blood cells, and neurons.

  7. Halo-free Phase Contrast Microscopy

    NASA Astrophysics Data System (ADS)

    Nguyen, Tan H.; Kandel, Mikhail; Shakir, Haadi M.; Best-Popescu, Catherine; Arikkath, Jyothi; Do, Minh N.; Popescu, Gabriel

    2017-03-01

    We present a new approach for retrieving halo-free phase contrast microscopy (hfPC) images by upgrading the conventional PC microscope with an external interferometric module, which generates sufficient data for reversing the halo artifact. Acquiring four independent intensity images, our approach first measures haloed phase maps of the sample. We solve for the halo-free sample transmission function by using a physical model of the image formation under partial spatial coherence. Using this halo-free sample transmission, we can numerically generate artifact-free PC images. Furthermore, this transmission can be further used to obtain quantitative information about the sample, e.g., the thickness with known refractive indices, dry mass of live cells during their cycles. We tested our hfPC method on various control samples, e.g., beads, pillars and validated its potential for biological investigation by imaging live HeLa cells, red blood cells, and neurons.

  8. Orbital anisotropy in cosmological haloes revisited

    NASA Astrophysics Data System (ADS)

    Wojtak, Radosław; Gottlöber, Stefan; Klypin, Anatoly

    2013-09-01

    The velocity anisotropy of particles inside dark matter (DM) haloes is an important physical quantity, which is required for the accurate modelling of mass profiles of galaxies and clusters of galaxies. It is typically measured using the ratio of the radial to tangential velocity dispersions at a given distance from the halo centre. However, this measure is insufficient to describe the dynamics of realistic haloes, which are not spherical and are typically quite elongated. Studying the velocity distribution in massive DM haloes in cosmological simulations, we find that in the inner parts of the haloes, the local velocity ellipsoids are strongly aligned with the major axis of the halo, the alignment being stronger for more relaxed haloes. In the outer regions of the haloes, the alignment becomes gradually weaker and the orientation is more random. These two distinct regions of different degree of the alignment coincide with two characteristic regimes of the DM density profile: a shallow inner cusp and a steep outer profile that are separated by a characteristic radius at which the density declines as ρ ∝ r-2. This alignment of the local velocity ellipsoids requires reinterpretation of features found in measurements based on the spherically averaged ratio of the radial to tangential velocity dispersions. In particular, we show that the velocity distribution in the central halo regions is highly anisotropic. For cluster-size haloes with mass 1014-1015 h-1 M⊙, the velocity anisotropy along the major axis is nearly independent of radius and is equal to β = 1 - σ ^2_perp/σ ^2_radial≈ 0.4, which is significantly larger than the previously estimated spherically averaged velocity anisotropy. The alignment of density and velocity anisotropies and the radial trends may also have some implications for the mass modelling based on kinematical data of objects such as galaxy clusters or dwarf spheroidals, where the orbital anisotropy is a key element in an unbiased mass

  9. Nuclear structure investigation of some neutron-rich halo nuclei

    NASA Astrophysics Data System (ADS)

    Abdullah, Ahmed N.

    The ground state proton, neutron and matter densities, the corresponding rms radii and charge form factors of a dripline nuclei 6He, 11Li, 12Be and 14Be have been studied via a three-body model of (Core + n + n). The core-neutron interaction takes the form of Woods-Saxon (WS) potential. The two valence neutrons of 6He, 11Li and 12Be interact by the realistic interaction of ZBMII while those of 14Be interact via the realistic interaction of VPNP. The core and valence (halo) density distributions are described by the single-particle wave functions of the WS potential. The calculated results are discussed and compared with the experimental data. The long tail performance is clearly noticed in the calculated neutron and matter density distributions of these nuclei. The structure of the two valence neutrons in 6He, 11Li and 12Be is found to be mixed configurations with dominant (1p1/2)2 while that for 14Be is mixed configurations with dominant (2s1/2)2. The analysis of the present study supports the halo structure of these nuclei.

  10. Neutron density distribution and the halo structure of C22

    NASA Astrophysics Data System (ADS)

    Sharma, Manjari; Bhagwat, A.; Khan, Z. A.; Haider, W.; Gambhir, Y. K.

    2011-03-01

    The recently measured reaction cross sections for the neutron-rich carbon isotopes (C19, C20, and C22) on a proton target at 40 A MeV are analyzed using the finite range Glauber model (FRGM) and the microscopic optical potential calculated within the Brueckner-Hartree-Fock formalism (BHF). In FRGM nucleon-nucleon cross sections are used, while in the latter (BHF), Hamada-Johnston, Urbana v-14, and the Argonne v-18 internucleon potentials are employed to calculate the microscopic optical potential. The required nucleon density distributions are calculated within the relativistic mean-field (RMF) framework. To test the halo structure, the extended neutron density distribution for C22 is also used. The analysis reveals that the BHF results of all three internucleon potentials are very close to each other, and also agree with the corresponding results of the FRGM. Our results, using RMF densities, are in agreement with the experimental data for all isotopes of carbon except C22, for which we require extended neutron density distribution, indicating a halo structure.

  11. Proton Therapy

    MedlinePlus

    ... effects of the treatment. top of page What equipment is used? Proton beam therapy uses special machines, ... tumor cells. top of page Who operates the equipment? With backgrounds in mechanical, electrical, software, hardware and ...

  12. Ophthalmic halo reduced lenses design

    NASA Astrophysics Data System (ADS)

    Limon, Ofer; Zalevsky, Zeev

    2015-05-01

    The halo effect is a very problematic visual artifact occurring in extended depth of focus or multi-focal ophthalmic lenses such as e.g. intra-ocular (after cataract surgery) or contact lenses when used in dark illumination conditions. This artifact is generated due to surface structures added on top of those lenses in order to increase their depth of focus or to realize multiple focal lengths. In this paper we present novel solution that can resolve this major problem of ophthalmic lenses. The proposed solution involves modification to the surface structure that realizes the extended depth of focus. Our solution is fabricated and numerically and experimentally validated also in preliminary in-vivo trials.

  13. NUBEAM developments and 3d halo modeling

    NASA Astrophysics Data System (ADS)

    Gorelenkova, M. V.; Medley, S. S.; Kaye, S. M.

    2012-10-01

    Recent developments related to the 3D halo model in NUBEAM code are described. To have a reliable halo neutral source for diagnostic simulation, the TRANSP/NUBEAM code has been enhanced with full implementation of ADAS atomic physic ground state and excited state data for hydrogenic beams and mixed species plasma targets. The ADAS codes and database provide the density and temperature dependence of the atomic data, and the collective nature of the state excitation process. To be able to populate 3D halo output with sufficient statistical resolution, the capability to control the statistics of fast ion CX modeling and for thermal halo launch has been added to NUBEAM. The 3D halo neutral model is based on modification and extension of the ``beam in box'' aligned 3d Cartesian grid that includes the neutral beam itself, 3D fast neutral densities due to CX of partially slowed down fast ions in the beam halo region, 3D thermal neutral densities due to CX deposition and fast neutral recapture source. More details on the 3D halo simulation design will be presented.

  14. Halo assembly bias from Separate Universe simulations

    NASA Astrophysics Data System (ADS)

    Paranjape, Aseem; Padmanabhan, Nikhil

    2017-07-01

    We present a calibration of halo assembly bias using the Separate Universe technique. Specifically, we measure the response of halo abundances at fixed mass and concentration to the presence of an infinite-wavelength initial perturbation. We develop an analytical framework for describing the concentration dependence of this peak-background split halo bias - a measure of assembly bias - relying on the near-lognormal distribution of halo concentration at fixed halo mass. The combination of this analytical framework and the Separate Universe technique allows us to achieve very high precision in the calibration of the linear assembly bias b1, and qualitatively reproduces known trends such as the monotonic decrease (increase) of b1 with halo concentration at large (small) masses. The same framework extends to the concentration dependence of higher order bias parameters bn, and we present the first calibration of assembly bias in b2. Our calibrations are directly applicable in analytical Halo Model calculations that seek to robustly detect galaxy assembly bias in observational samples. We detect a non-universality in the b1-b2 relation arising from assembly bias, and suggest that simultaneous measurements of these bias parameters could be used to both detect the signature of assembly bias as well as mitigate its effects in cosmological analyses.

  15. Dark matter haloes: a multistream view

    NASA Astrophysics Data System (ADS)

    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.

  16. Anisotropic halo model: implementation and numerical results

    NASA Astrophysics Data System (ADS)

    Sgró, Mario A.; Paz, Dante J.; Merchán, Manuel

    2013-07-01

    In the present work, we extend the classic halo model for the large-scale matter distribution including a triaxial model for the halo profiles and their alignments. In particular, we derive general expressions for the halo-matter cross-correlation function. In addition, by numerical integration, we obtain instances of the cross-correlation function depending on the directions given by halo shape axes. These functions are called anisotropic cross-correlations. With the aim of comparing our theoretical results with the simulations, we compute averaged anisotropic correlations in cones with their symmetry axis along each shape direction of the centre halo. From these comparisons we characterize and quantify the alignment of dark matter haloes on the Λcold dark matter context by means of the presented anisotropic halo model. Since our model requires multidimensional integral computation we implement a Monte Carlo method on GPU hardware which allows us to increase the precision of the results and it improves the performance of the computation.

  17. Halo bias in mixed dark matter cosmologies

    NASA Astrophysics Data System (ADS)

    LoVerde, Marilena

    2014-10-01

    The large-scale distribution of cold dark matter halos is generally assumed to trace the large-scale distribution of matter. In a universe with multiple types of matter fluctuations, as is the case with massive neutrinos, the relation between the halo field and the matter fluctuations may be more complicated. We develop a method for calculating the linear bias factor relating fluctuations in the halo number density to fluctuations in the mass density in the presence of multiple fluctuating components of the energy density. In the presence of massive neutrinos we find a small but pronounced feature in the halo bias near the neutrino free-streaming scale. The neutrino feature is a small step with amplitude that increases with halo mass and neutrino mass density. The scale-dependent halo bias lessens the suppression of the small-scale halo power spectrum and should therefore weaken constraints on neutrino mass from the galaxy autopower spectrum and correlation function. On the other hand, the feature in the bias is itself a novel signature of massive neutrinos that can be studied independently.

  18. Population Gradients in Stellar Halos from GHOSTS

    NASA Astrophysics Data System (ADS)

    Bailin, Jeremy; Monachesi, Antonela; Bell, Eric F.; de Jong, Roelof S.; Ghosts Survey

    2015-01-01

    We report on recent results from the Galaxy Halos, Outer disks, Substructure, Thick disks, and Star clusters (GHOSTS) survey, an HST ACS+WFC3 imaging survey to study stellar populations in and around 16 nearby spiral galaxies. By using HST resolution to resolve the stellar halos into individual red giant branch (RGB) stars, we are able to detect distinct stellar populations at several points throughout the halo of the half dozen massive highly-inclined galaxies in the sample. In approximately half of these galaxies, we detect a gradient in the color of the RGB; which we interpret as a metallicity gradient. Stellar halo formation models predict a wide variety of metallicity gradients: those in which the halos are dominated by stars formed in situ predict stronger gradients than we observe, while accretion-dominated halo models predict weaker or nonexistent gradients. Our measurements therefore provide a useful discriminator between stellar halo models, and at first look appear most consistent with the accretion-based model of Cooper et al. (2010).

  19. THE DUAL ORIGIN OF STELLAR HALOS

    SciTech Connect

    Zolotov, Adi; Hogg, David W.; Willman, Beth; Brooks, Alyson M.; Brook, Chris B.; Stinson, Greg E-mail: bwillman@haverford.edu

    2009-09-10

    We investigate the formation of the stellar halos of four simulated disk galaxies using high-resolution, cosmological SPH + N-body simulations. These simulations include a self-consistent treatment of all the major physical processes involved in galaxy formation. The simulated galaxies presented here each have a total mass of {approx}10{sup 12} M{sub sun}, but span a range of merger histories. These simulations allow us to study the competing importance of in situ star formation (stars formed in the primary galaxy) and accretion of stars from subhalos in the building of stellar halos in a {lambda}CDM universe. All four simulated galaxies are surrounded by a stellar halo, whose inner regions (r < 20 kpc) contain both accreted stars, and an in situ stellar population. The outer regions of the galaxies' halos were assembled through pure accretion and disruption of satellites. Most of the in situ halo stars formed at high redshift out of smoothly accreted cold gas in the inner 1 kpc of the galaxies' potential wells, possibly as part of their primordial disks. These stars were displaced from their central locations into the halos through a succession of major mergers. We find that the two galaxies with recently quiescent merger histories have a higher fraction of in situ stars ({approx}20%-50%) in their inner halos than the two galaxies with many recent mergers ({approx}5%-10% in situ fraction). Observational studies concentrating on stellar populations in the inner halo of the Milky Way will be the most affected by the presence of in situ stars with halo kinematics, as we find that their existence in the inner few tens of kpc is a generic feature of galaxy formation.

  20. The Dual Origin of Galactic Stellar Halos

    NASA Astrophysics Data System (ADS)

    Zolotov, Adi

    2011-01-01

    Accreted stellar halos are a natural consequence of galaxy formation in a Lambda-CDM Universe, and contain unique fossil records of hierarchical galaxy formation. The properties of local Milky Way halo stars, however, suggest that the Galaxy's halo is composed of at least two distinct stellar populations, each exhibiting different spatial distributions, orbits, and metallicities. This observed dichotomy is the result of the assembly history of the halo, which likely formed through a process more complex than pure hierarchical accretions. In this talk I will describe the formation of stellar halos surrounding Milky Way-massed disk galaxies simulated using high-resolution cosmological Smooth Particle Hydrodynamics + N-Body simulations. We find that two competing physical processes - accretion of dwarf galaxies and in situ star formation - contribute to the formation of every stellar halo. While the outer regions (r > 20 kpc) of the halos were assembled solely through the accretion and disruption of satellites, in situ star formation supplements accretion in the formation of inner halos. The relative contribution of each stellar population to a halo is shown to be a function of a galaxy's merging history. Galaxies with recent mergers, like M31, will host relatively few in situ stars, while galaxies with more quiescent recent histories, like the Milky Way, will likely have a larger population of such stars. We show how the chemical abundance trends ([Fe/H] vs. [alpha/Fe]) of accreted and in situ stars diverge at the high [Fe/H] end of the metallicity distribution function, and discuss how such trends can be used to study and identify the observable imprints of the Milky Way's formation history.

  1. COSMIC VORTICITY AND THE ORIGIN HALO SPINS

    SciTech Connect

    Libeskind, Noam I.; Steinmetz, Matthias; Gottloeber, Stefan; Hess, Steffen; Hoffman, Yehuda; Knebe, Alexander

    2013-04-01

    In the standard model of cosmology, structure emerges out of a non-rotational flow and the angular momentum of collapsing halos is induced by tidal torques. The growth of angular momentum in the linear and quasi-linear phases is associated with a shear, curl-free, flow and it is well described within the linear framework of tidal torque theory (TTT). However, TTT ceases to be applicable as halos approach turnaround when their ambient flow field becomes rotational. Subsequently, halos become embedded in a vortical flow field and the growth of their angular momentum is affected by the vorticity of their ambient velocity field. Using a cosmological simulation, we have examined the importance of the curl of the velocity field in determining halo spin, finding a significant alignment between the two: the vorticity tends to be perpendicular to the axis of the fastest collapse of the velocity shear tensor (e{sub 1}). This is independent of halo masses and cosmic web environment. Our results agree with previous findings on the tendency of halo spin to be perpendicular to e{sub 1}, and of the spin of (simulated) halos and (observed) galaxies to be aligned with the large-scale structure. It follows that angular momentum growth proceeds in two distinct phases. First, the angular momentum emerges out of a shear, curl-free, potential flow, as described by TTT. In the second phase, in which halos approach virialization, the angular momentum emerges out of a vortical flow and halo spin becomes partially aligned with the vorticity of the ambient flow field.

  2. The statistics of Λ CDM halo concentrations

    NASA Astrophysics Data System (ADS)

    Neto, Angelo F.; Gao, Liang; Bett, Philip; Cole, Shaun; Navarro, Julio F.; Frenk, Carlos S.; White, Simon D. M.; Springel, Volker; Jenkins, Adrian

    2007-11-01

    We use the Millennium Simulation (MS) to study the statistics of Λ cold dark matter (ΛCDM) halo concentrations at z = 0. Our results confirm that the average halo concentration declines monotonically with mass; the concentration-mass relation is well fitted by a power law over three decades in mass, up to the most massive objects that form in a ΛCDM universe (~ 1015h-1Msolar). This is in clear disagreement with the predictions of the model proposed by Bullock et al. for these rare objects, and agrees better with the original predictions of Navarro, Frenk & White. The large volume surveyed, together with the unprecedented numerical resolution of the MS, allows us to estimate with confidence the distribution of concentrations and, consequently, the abundance of systems with unusual properties. About one in a hundred cluster haloes (M200 >~ 3 × 1014h-1Msolar) have concentrations exceeding c200 = 7.5, a result that may be useful in interpreting the likelihood of unusually strong massive gravitational lenses, such as Abell 1689, in the ΛCDM cosmogony. A similar fraction of about 1 per cent of galaxy-sized haloes (M200 ~ 1012h-1Msolar) have c200 < 4.5 and this could be relevant to models that attempt to reconcile the ΛCDM cosmology with rotation curves of low surface brightness galaxies by appealing to haloes of unexpectedly low concentration. We find that halo concentrations are independent of spin once haloes manifestly out of equilibrium have been removed from the sample. Compared to their relaxed brethren, the concentrations of out-of-equilibrium haloes tend to be lower and have more scatter, while their spins tend to be higher. A number of previously noted trends within the halo population are induced primarily by these properties of unrelaxed systems. Finally, we compare the result of predicting halo concentrations using the mass assembly history of the main progenitor with predictions based on simple arguments regarding the assembly time of all progenitors

  3. Halo Mergers in Phase-space

    NASA Astrophysics Data System (ADS)

    Taylor, J. E.

    I consider a very simple model for the evolution of the real space and phase-space density profiles of a dark matter halo as it acquires its mass. I show that this model, which assumes slow growth through gradual accretion, predicts structures much more concentrated than those found in self-consistent simulations of halo formation. By implication, major mergers must act to reduce the concentration of dark matter haloes, adding the orbital energy of the infalling satellite to the internal energy of the pre-existing system and causing it to expand at intermediate radii. This effect should be easy to detect in numerical simulations.

  4. Haloes around the Moon and the Sun

    NASA Astrophysics Data System (ADS)

    Gaina, Alex; Gaina, Danielle A.

    2008-10-01

    The authors observations of the Haloes around the Moon and the Sun during few last years are reported. A Historical review of the phenomenon is given since the observations by Benvenuto Cellini and Gaston Tissandier is given. A photograph (from eight available) of the Halo around the Sun observed in Chisinau on 21 May 2007 is included. The Halo from 21 May 2007 occured after a very fast increasing of the air temperature during one day by more than 15 Deg. The authors consider, that the phenomenon is due to scattering of light on Cirri clouds(7 km altitude), present on the sky during that day. They formed due to very fast heating.

  5. The diagnostic value of halo and reversed halo signs for invasive mold infections in compromised hosts.

    PubMed

    Georgiadou, Sarah P; Sipsas, Nikolaos V; Marom, Edith M; Kontoyiannis, Dimitrios P

    2011-05-01

    The halo sign is a CT finding of ground-glass opacity surrounding a pulmonary nodule or mass. The reversed halo sign is a focal rounded area of ground-glass opacity surrounded by a crescent or complete ring of consolidation. In severely immunocompromised patients, these signs are highly suggestive of early infection by an angioinvasive fungus. The halo sign and reversed halo sign are most commonly associated with invasive pulmonary aspergillosis and pulmonary mucormycosis, respectively. Many other infections and noninfectious conditions, such as neoplastic and inflammatory processes, may also manifest with pulmonary nodules associated with either sign. Although nonspecific, both signs can be useful for preemptive initiation of antifungal therapy in the appropriate clinical setting. This review aims to evaluate the diagnostic value of the halo sign and reversed halo sign in immunocompromised hosts and describes the wide spectrum of diseases associated with them.

  6. The Diagnostic Value of Halo and Reversed Halo Signs for Invasive Mold Infections in Compromised Hosts

    PubMed Central

    Georgiadou, Sarah P.; Sipsas, Nikolaos V.; Marom, Edith M.

    2011-01-01

    The halo sign is a CT finding of ground-glass opacity surrounding a pulmonary nodule or mass. The reversed halo sign is a focal rounded area of ground-glass opacity surrounded by a crescent or complete ring of consolidation. In severely immunocompromised patients, these signs are highly suggestive of early infection by an angioinvasive fungus. The halo sign and reversed halo sign are most commonly associated with invasive pulmonary aspergillosis and pulmonary mucormycosis, respectively. Many other infections and noninfectious conditions, such as neoplastic and inflammatory processes, may also manifest with pulmonary nodules associated with either sign. Although nonspecific, both signs can be useful for preemptive initiation of antifungal therapy in the appropriate clinical setting. This review aims to evaluate the diagnostic value of the halo sign and reversed halo sign in immunocompromised hosts and describes the wide spectrum of diseases associated with them. PMID:21467021

  7. Charge form factors of two-neutron halo nuclei in halo EFT

    NASA Astrophysics Data System (ADS)

    Hagen, P.; Hammer, H.-W.; Platter, L.

    2013-09-01

    We set up a formalism to calculate the charge form factors of two-neutron halo nuclei with S -wave neutron-core interactions in the framework of the halo effective field theory. The method is applied to some known and suspected halo nuclei. In particular, we calculate the form factors and charge radii relative to the core to leading order in the halo EFT and compare to experiments where they are available. Moreover, we investigate the general dependence of the charge radius on the core mass and the one- and two-neutron separation energies.

  8. Dark matter particles in the galactic halo

    SciTech Connect

    Bernabei, R. Belli, P.; Montecchia, F.; Nozzoli, F.; Cappella, F.; D'Angelo, A.; Incicchitti, A.; Prosperi, D.; Cerulli, R.; Dai, C. J.; He, H. L.; Kuang, H. H.; Ma, J. M.; Sheng, X. D.; Ye, Z. P.

    2009-12-15

    Arguments on the investigation of the DarkMatter particles in the galactic halo are addressed. Recent results obtained by exploiting the annual modulation signature are summarized and the perspectives are discussed.

  9. Studying stellar halos with future facilities

    NASA Astrophysics Data System (ADS)

    Greggio, Laura; Falomo, Renato; Uslenghi, Michela

    2016-08-01

    Stellar halos around galaxies retain fundamental evidence of the processes which lead to their build up. Sophisticated models of galaxy formation in a cosmological context yield quantitative predictions about various observable characteristics, including the amount of substructure, the slope of radial mass profiles and three dimensional shapes, and the properties of the stellar populations in the halos. The comparison of such models with the observations provides constraints on the general picture of galaxy formation in the hierarchical Universe, as well as on the physical processes taking place in the halos formation. With the current observing facilities, stellar halos can be effectively probed only for a limited number of nearby galaxies. In this paper we illustrate the progress that we expect in this field with the future ground based large aperture telescopes (E-ELT) and with space based facilities as JWST.

  10. Quantum Halo States in Helium Tetramers.

    PubMed

    Stipanović, Petar; Vranješ Markić, Leandra; Boronat, Jordi

    2017-01-12

    The universality of quantum halo states enables a comparison of systems from different fields of physics, as demonstrated in two- and three-body clusters. In the present work, we studied weakly bound helium tetramers in order to test whether some of these four-body realistic systems qualify as halos. Their ground-state binding energies and structural properties were thoroughly estimated using the diffusion Monte Carlo method with pure estimators. Helium tetramer properties proved to be less sensitive on the potential model than previously evaluated trimer properties. We predict the existence of realistic four-body halo (4)He2(3)He2, whereas (4)He4 and (4)He3(3)He are close to the border and thus can be used as prototypes of quasi-halo systems. Our results could be tested by the experimental determination of the tetramers' structural properties using a setup similar to the one developed for the study of helium trimers.

  11. Genesis Halo Orbit Station Keeping Design

    NASA Technical Reports Server (NTRS)

    Lo, M.; Williams, K.; Wilson, R.; Howell, K.; Barden, B.

    2000-01-01

    As the fifth mission of NASA's Directory Program, Genesis is designed to collect solar wind samples for approximately two years in a halo orbit near the Sun-Earth L(sub 1) Lagrange point for return to the Earth.

  12. Genesis Halo Orbit Station Keeping Design

    NASA Technical Reports Server (NTRS)

    Lo, M.; Williams, K.; Wilson, R.; Howell, K.; Barden, B.

    2000-01-01

    As the fifth mission of NASA's Directory Program, Genesis is designed to collect solar wind samples for approximately two years in a halo orbit near the Sun-Earth L(sub 1) Lagrange point for return to the Earth.

  13. Large Halos of Missing Baryons Around Galaxies

    NASA Astrophysics Data System (ADS)

    Bregman, Joel

    2009-10-01

    If galaxies had the cosmological baryon-to-dark matter ratio, they would have 3-30 times their observed baryon mass. These missing baryons are undetected, but some fraction may surround a galaxy with a hot diffuse halo extending to R_virial (250 kpc). A loosely bound gaseous halo could be stripped in a cluster or group environment, but should be relatively undisturbed around isolated late-type spirals. Existing observations of spirals are mainly of nearby systems, where only the inner parts fit in a field of view so a halo on the scale of R_virial would pass unnoticed. To detect or place limits on a large halo of missing baryons, we propose to observe isolated L* spirals sufficiently distant that we can detect emission to at least R_virial.

  14. The Vertical Structure of the Halo Rotation

    NASA Astrophysics Data System (ADS)

    Kinman, T. D.; Cacciari, C.; Bragaglia, A.; Buzzoni, A.; Spagna, A.

    New GSC-II proper motions of RR Lyrae and Blue Horizontal Branch (BHB) stars near the North Galactic Pole are used to show that the Galactic Halo 5 kpc above the Plane has a significantly retrograde galactic rotation.

  15. Solar Back-sided Halo CME

    NASA Image and Video Library

    The Sun erupted with several CMEs (coronal mass ejections) during a period just over a day (Nov. 8-9, 2012), the largest of which was a halo CME. This CME appears to have originated from an active ...

  16. Two-parameter Fermi function fits to experimental charge and point-proton densities for 208Pb

    NASA Astrophysics Data System (ADS)

    Jones, Adam B.; Brown, B. Alex

    2014-12-01

    We use the model-independent experimental charge density for 208Pb to determine a model-independent point-proton density. An improved two-parameter Fermi function representation for the this point-proton density provides input for the analysis of experiments for the neutron density interpreted in terms of neutron skin and halo properties of 208Pb.

  17. Foxp3(+) regulatory T cells are increased in the early stages of halo nevi: clinicopathological features of 30 halo nevi.

    PubMed

    Park, H S; Jin, S A; Choi, Y-D; Shin, M-H; Lee, S E; Yun, S J

    2012-01-01

    There have been few clinical studies of the role of regulatory T cells (Tregs) in halo formation of halo nevus. To evaluate the clinicopathologic features and the presence of Tregs in halo nevi. We analyzed 30 halo nevi and performed immunohistochemical analysis using antibodies against CD4, CD8, CD25 and Foxp3. We also performed double immunohistochemical staining for Foxp3 and CD25. We found significant increases in Foxp3(+) Tregs, and the shorter the halo nevus duration, the more Foxp3(+) Tregs were detected. Also, the ratio of Foxp3 to CD8 T cells was increased in early stages of halo nevi. Double immunohistochemical staining suggested that the Tregs in the halo nevi were CD25(+)Foxp3(+) T cells. Foxp3(+) Tregs were greatly increased in the halo nevi. The shorter the halo nevi duration, the more Foxp3(+) Tregs were involved in the earlier developmental stages of halo nevi. Copyright © 2012 S. Karger AG, Basel.

  18. Contribution of globular clusters to halos

    NASA Astrophysics Data System (ADS)

    Bragaglia, Angela

    2017-03-01

    The contribution of massive star clusters to their hosting halo dramatically depends on their formation mechanism and their early evolution. Massive globular clusters in the Milky Way (and in other galaxies) have been shown to display peculiar chemical patterns (light-elements correlations and anti-correlations) indicative of a complex star formation, confirmed by photometric evidence (spread or split sequences). I use these chemical signatures to try to understand what is the fraction of halo stars originally born in globular clusters.

  19. On physical scales of dark matter halos

    SciTech Connect

    Zemp, Marcel

    2014-09-10

    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.

  20. Conceptual design of hollow electron lenses for beam halo control in the Large Hadron Collider

    SciTech Connect

    Stancari, Giulio; Previtali, Valentina; Valishev, Alexander; Bruce, Roderik; Redaelli, Stefano; Rossi, Adriana; Salvachua Ferrando, Belen

    2014-06-26

    Collimation with hollow electron beams is a technique for halo control in high-power hadron beams. It is based on an electron beam (possibly pulsed or modulated in intensity) guided by strong axial magnetic fields which overlaps with the circulating beam in a short section of the ring. The concept was tested experimentally at the Fermilab Tevatron collider using a hollow electron gun installed in one of the Tevatron electron lenses. We are proposing a conceptual design for applying this technique to the Large Hadron Collider at CERN. A prototype hollow electron gun for the LHC was built and tested. The expected performance of the hollow electron beam collimator was based on Tevatron experiments and on numerical tracking simulations. Halo removal rates and enhancements of halo diffusivity were estimated as a function of beam and lattice parameters. Proton beam core lifetimes and emittance growth rates were checked to ensure that undesired effects were suppressed. Hardware specifications were based on the Tevatron devices and on preliminary engineering integration studies in the LHC machine. Required resources and a possible timeline were also outlined, together with a brief discussion of alternative halo-removal schemes and of other possible uses of electron lenses to improve the performance of the LHC.

  1. Marrying ab initio calculations and Halo-EFT: 7Li and 7Be radiative nucleon captures

    NASA Astrophysics Data System (ADS)

    Zhang, Xilin; Nollett, Kenneth; Phillips, Daniel

    2013-10-01

    We combine ab initio quantum-Monte-Carlo (QMC) calculations with the Halo-Effective-Field-Theory (Halo-EFT) framework, in order to study low-energy radiative nucleon capture to a weakly bound (halo) nucleus. Here we focus on the reactions 7Li(n, γ)8Li and 7Be(p, γ)8B, which are subjects of long-standing interest for astrophysics. In the low-energy region we can approximate 8Li (8B) as composed of a 7Li (7Be) core (and also its excitation), and a neutron (proton) with an anomalously extended wave function. The scattering and bound states can be studied in Halo-EFT, in which both core and the nucleon are treated as fundamental degrees of freedom. In our leading order calculation, we use asymptotic normalization coefficients from QMC calculations to fix the parameters in the Lagrangian, which we then apply to study radiative captures. This obviates computing the captures by directly using numerically intensive QMC methods, while still incorporating the nuclear dynamics that these methods provide. In addition, the model-independent EFT framework provides novel insights into the manner in which these two nucleon-capture processes are related to one another. This work is supported by US Department of Energy under grant DE-FG02-93ER-40756.

  2. ANGULAR MOMENTUM ACQUISITION IN GALAXY HALOS

    SciTech Connect

    Stewart, Kyle R.; Brooks, Alyson M.; Bullock, James S.; Maller, Ariyeh H.; Diemand, Juerg; Wadsley, James; Moustakas, Leonidas A.

    2013-05-20

    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 {approx}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 {lambda} {approx} 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.

  3. New views of the distant stellar halo

    NASA Astrophysics Data System (ADS)

    Sanderson, Robyn E.; Secunda, Amy; Johnston, Kathryn V.; Bochanski, John J.

    2017-10-01

    Currently, only a small number of Milky Way (MW) stars are known to exist beyond 100 kpc from the Galactic Centre. Though the distribution of these stars in the outer halo is believed to be sparse, they can provide evidence of more recent accretion events than in the inner halo and help map out the MW's dark matter halo to its virial radius. We have re-examined the outermost regions of 11 existing stellar halo models with two synthetic surveys: one mimicking present-day searches for distant M giants and another mimicking RR Lyra (RRL) projections for the Large Synoptic Survey Telescope (LSST). Our models suggest that colour and proper motion cuts currently used to select M giant candidates for follow-up successfully remove nearly all self-contamination from foreground halo dwarf stars and are useful for focusing observations on distant M giants, of which there are thousands to tens of thousands beyond 100 kpc in our models. We likewise expect that LSST will identify comparable numbers of RRLe at these distances. We demonstrate that several observable properties of both tracers, such as proximity of neighbouring stars, proper motions and distances (for RRLe), could help us separate different accreted dwarf galaxies from one another in the distant MW halo. We also discuss prospects for using ratios of M giants to RRLe as a proxy for accretion time, which in the future could provide new constraints on the recent accretion history of our Galaxy.

  4. MODIFIED GRAVITY SPINS UP GALACTIC HALOS

    SciTech Connect

    Lee, Jounghun; Zhao, Gong-Bo; Li, Baojiu; Koyama, Kazuya

    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.

  5. The Splashback Radius as a Physical Halo Boundary and the Growth of Halo Mass

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    The boundaries of cold dark matter halos are commonly defined to enclose a density contrast Δ relative to a reference (mean or critical) density. We argue that a more physical halo boundary choice is the radius at which accreted matter reaches its first orbital apocenter after turnaround. This splashback radius, {R}{sp}, manifests itself as a sharp density drop in the halo outskirts, at a location that depends upon the mass accretion rate. We present calibrations of {R}{sp} and the enclosed mass, {M}{sp}, as a function of mass accretion rate and peak height. We find that {R}{sp} is in the range ≈ 0.8-1{R}200{{m}} for rapidly accreting halos and is ≈ 1.5{R}200{{m}} for slowly accreting halos. Thus, halos and their environmental effects can extend well beyond the conventionally defined “virial” radius. We show that {M}{sp} and {R}{sp} evolve relatively strongly compared to other commonly used definitions. In particular, {M}{sp} evolves significantly even for the smallest dwarf-sized halos at z = 0. We also contrast {M}{sp} with the mass enclosed within four scale radii of the halo density profile, {M}\\lt 4{r{{s}}}, which characterizes the inner halo. During the early stages of halo assembly, {M}{sp} and {M}\\lt 4{r{{s}}} evolve similarly, but in the late stages {M}\\lt 4{r{{s}}} stops increasing while {M}{sp} continues to grow significantly. This illustrates that halos at low z can have “quiet” interiors while continuing to accrete mass in their outskirts. We discuss potential observational estimates of the splashback radius and show that it may already have been detected in galaxy clusters.

  6. Halo occupation numbers and galaxy bias

    NASA Astrophysics Data System (ADS)

    Peacock, J. A.; Smith, R. E.

    2000-11-01

    We propose a heuristic model that displays the main features of realistic theories for galaxy bias. We first show that the low-order clustering statistics of the dark-matter distribution depend almost entirely on the locations and density profiles of dark-matter haloes. The quasi-linear mass correlations are in fact reproduced well by a model of independent randomly-placed haloes. The distribution of galaxies within the halo density field depends on: (i) the efficiency of galaxy formation, as manifested by the halo occupation number - the number of galaxies brighter than some sample limit contained in a halo of a given mass; (ii) the location of these galaxies within their halo. The first factor is constrained by the empirical luminosity function of groups. For the second factor, we assume that one galaxy marks the halo centre, with any remaining galaxies acting as satellites that trace the halo mass. This second assumption is essential if small-scale galaxy correlations are to remain close to a single power law, rather than flattening in the same way as the correlations of the overall density field. These simple assumptions amount to a recipe for non-local bias, in which the probability of finding a galaxy is not a simple function of its local mass density. We have applied this prescription to some CDM models of current interest, and find that the predictions are close to the observed galaxy correlations for a flat Ω=0.3 model (ΛCDM), but not for an Ω=1 model with the same power spectrum (τCDM). This is an inevitable consequence of cluster normalization for the power spectra: cluster-scale haloes of given mass have smaller core radii for high Ω, and hence display enhanced small-scale clustering. Finally, the pairwise velocity dispersion of galaxies in the ΛCDM model is lower than that of the mass, allowing cluster-normalized models to yield a realistic Mach number for the peculiar velocity field. This is largely due to the strong variation of galaxy

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

    NASA Astrophysics Data System (ADS)

    Kaaret, Philip

    We propose to develop, build, and fly HaloSat, a CubeSat capable of measuring the oxygen line emission from the hot Galactic halo. A dedicated CubeSat enables an instrument design and observing strategy to maximize the halo signal while minimizing foregrounds from solar wind charge exchange interactions within the solar system. We will use HaloSat to map the distribution of hot gas in the Milky Way and determine whether it fills an extended, and thus massive halo, or whether the halo is compact, and thus does not contribute significantly to the total mass of the Milky Way. HaloSat can be accomplished at modest cost using a CubeSat, a novel platform for space astrophysics missions. We will use a commercially available CubeSat bus and commercially available X-ray detectors to reduce development risk and minimize overall mission cost. HaloSat builds on the initiatives of GSFC/Wallops Flight Facility (WFF) in the development of CubeSats for low cost access to space and relies on the technical expertise of WFF personnel for spacecraft and mission design and operations. The team, from University of Iowa (UI), GSFC, Johns Hopkins, and CNRS (France), contains experts in X-ray detector development and data analysis and the astrophysics of hot plasmas and Galactic structure. The UI team will include a number of junior researchers (undergraduates, graduate students, and a postdoc) and help train them for future leadership roles on NASA space flight missions.

  8. Proton Therapy

    MedlinePlus

    ... Liver Breast Esophagus Rectum Skull base sarcomas Pediatric brain tumors Head and neck - see the Head and Neck Cancer page Eye ... Intensity-Modulated Radiation Therapy (IMRT) Brain Tumor Treatment Brain Tumors Prostate Cancer Lung Cancer ... related to Proton Therapy Videos related ...

  9. Proton geriatrics

    NASA Astrophysics Data System (ADS)

    Kephart, Thomas W.; Nakagawa, Norio

    1984-07-01

    An SO(10) model with particle spectrum and low energy gauge group identical to that of minimal SU (5) below MX but with a nonstandard charge assignment is shown to agree with the experimental best value of sin2θw(Mw) and the lower bound on the proton lifetime.

  10. Proton Radiobiology

    PubMed Central

    Tommasino, Francesco; Durante, Marco

    2015-01-01

    In addition to the physical advantages (Bragg peak), the use of charged particles in cancer therapy can be associated with distinct biological effects compared to X-rays. While heavy ions (densely ionizing radiation) are known to have an energy- and charge-dependent increased Relative Biological Effectiveness (RBE), protons should not be very different from sparsely ionizing photons. A slightly increased biological effectiveness is taken into account in proton treatment planning by assuming a fixed RBE of 1.1 for the whole radiation field. However, data emerging from recent studies suggest that, for several end points of clinical relevance, the biological response is differentially modulated by protons compared to photons. In parallel, research in the field of medical physics highlighted how variations in RBE that are currently neglected might actually result in deposition of significant doses in healthy organs. This seems to be relevant in particular for normal tissues in the entrance region and for organs at risk close behind the tumor. All these aspects will be considered and discussed in this review, highlighting how a re-discussion of the role of a variable RBE in proton therapy might be well-timed. PMID:25686476

  11. Simulating Halos with the Caterpillar Project

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-04-01

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

  12. GRAVITATIONALLY CONSISTENT HALO CATALOGS AND MERGER TREES FOR PRECISION COSMOLOGY

    SciTech Connect

    Behroozi, Peter S.; Wechsler, Risa H.; Wu, Hao-Yi; Busha, Michael T.; Klypin, Anatoly A.; Primack, Joel R. E-mail: rwechsler@stanford.edu

    2013-01-20

    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/.

  13. Halo Spin Parameter in Cosmological Simulations

    NASA Astrophysics Data System (ADS)

    Ahn, Jieun; Kim, Juhan; Shin, Jihye; Kim, Sungsoo S.; Choi, Yun-Young

    2014-04-01

    Using a cosmological ΛCDM simulation, we analyze the differences between the widely-used spin parameters suggested by Peebles and Bullock. The dimensionless spin parameter λ proposed by Peebles is theoretically well-justified but includes an annoying term, the potential energy, which cannot be directly obtained from observations and is computationally expensive to calculate in numerical simulations. The Bullock's spin parameter λ^' avoids this problem assuming the isothermal density profile of a virialized halo in the Newtonian potential model. However, we find that there exists a substantial discrepancy between λ and λ^' depending on the adopted potential model (Newtonian or Plummer) to calculate the halo total energy and that their redshift evolutions differ to each other significantly. Therefore, we introduce a new spin parameter, λ^{''}, which is simply designed to roughly recover the value of λ but to use the same halo quantities as used in λ^'. If the Plummer potential is adopted, the λ^{''} is related to the Bullock's definition as λ^{''} = 0.80× (1 + z)^{-1/12} λ^'. Hence, the new spin parameter λ^{''} distribution becomes consistent with a log-normal distribution frequently seen for the λ^' while its mean value is much closer to that of λ. On the other hand, in case of the Newtonian potential model, we obtain the relation of λ^{''}=(1+z)^{-1/8}λ^{'}; there is no significant difference at z = 0 as found by others but λ^{'} becomes more overestimated than λ or λ^{''} at higher redshifts. We also investigate the dependence of halo spin parameters on halo mass and redshift. We clearly show that although the λ^' for small-mass halos with M_h < 2× 10^{12} M_odot seems redshift independent after z=1, all the spin parameters explored, on the whole, show a stronger correlation with the increasing halo mass at higher redshifts.

  14. Dark Matter Properties and Halo Central Densities

    NASA Astrophysics Data System (ADS)

    Alam, S. M. Khairul; Bullock, James S.; Weinberg, David H.

    2002-06-01

    Using an analytic model calibrated against numerical simulations, we calculate the central densities of dark matter halos in a ``conventional'' cold dark matter model with a cosmological constant (LCDM) and in a ``tilted'' model (TLCDM) with slightly modified parameters motivated by recent analyses of Lyα forest data. We also calculate how warm dark matter (WDM) would modify these predicted densities by delaying halo formation and imposing phase-space constraints. As a measure of central density, we adopt the quantity ΔV/2, the density within the radius RV/2 at which the halo rotation curve falls to half of its maximum value, in units of the critical density. We compare the theoretical predictions to values of ΔV/2 estimated from the rotation curves of dark matter-dominated disk galaxies. Assuming that dark halos are described by Navarro-Frenk-White profiles, our results suggest that the conventional LCDM model predicts excessively high dark matter densities, unless there is some selection bias in the data toward the low-concentration tail of the halo distribution. A WDM model with particle mass 0.5-1 keV provides a better match to the observational data. However, the modified cold dark matter model, TLCDM, fits the data equally well, suggesting that the solution to the ``halo cores'' problem might lie in moderate changes to cosmological parameters rather than radical changes to the properties of dark matter. If cold dark matter halos have the steeper density profiles found by Moore et al., then neither conventional LCDM nor TLCDM can reproduce the observed central densities.

  15. The Milky Way, the Galactic Halo, and the Halos of Galaxies

    NASA Astrophysics Data System (ADS)

    Gerhard, Ortwin

    2016-08-01

    The Milky Way, ``our'' Galaxy, is currently the subject of intense study with many ground-based surveys, in anticipation of upcoming results from the Gaia mission. From this work we have been learning about the full three-dimensional structure of the Galactic box/peanut bulge, the distribution of stars in the bar and disk, and the many streams and substructures in the Galactic halo. The data indicate that a large fraction of the Galactic halo has been accreted from outside. Similarly, in many external galaxy halos there is now evidence for tidal streams and accretion of satellites. To study these features requires exquisite, deep photometry and spectroscopy. These observations illustrate how galaxy halos are still growing, and sometimes can be used to ``time'' the accretion events. In comparison with cosmological simulations, the structure of galaxy halos gives us a vivid illustration of the hierarchical nature of our Universe.

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

    NASA Astrophysics Data System (ADS)

    Kaaret, Philip

    2017-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Kaaret, Philip

    2016-04-01

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

  18. Electric Properties of One-Neutron Halo Nuclei in Halo EFT

    NASA Astrophysics Data System (ADS)

    Braun, Jonas; Hammer, Hans-Werner

    2017-03-01

    We exploit the separation of scales in weakly-bound nuclei to compute E2 transitions and electric form factors in a halo effective field theory (EFT) framework. The relevant degrees of freedom are the core and the halo neutron. The EFT expansion is carried out in powers of R_{core}/R_{halo}, where R_{core} and R_{halo} denote the length scales of the core and halo, respectively. We include the strong s-wave and d-wave interactions by introducing dimer fields. The dimer propagators are regulated by employing the power divergence subtraction scheme and matched to the effective range expansion in the respective channel. Electromagnetic interactions are included via minimal substitution in the Lagrangian. We demonstrate that, depending on the observable and respective partial wave, additional local gauge-invariant operators contribute in LO, NLO and higher orders.

  19. AUTOMATED CONTROL AND REAL-TIME DATA PROCESSING OF WIRE SCANNER/HALO SCRAPER MEASUREMENTS

    SciTech Connect

    L.A. DAY; J.D. GILPATRICK; ET AL

    2001-06-01

    The Low-Energy Demonstration Accelerator (LEDA), assembled and operating at Los Alamos National Laboratory, provides the platform for obtaining measurements of high-power proton beam-halo formation. Control system software and hardware have been integrated and customized to enable the production of real-time beam-halo profiles. The Experimental Physics and Industrial Control System (EPICS) hosted on a VXI platform, Interactive Data Language (IDL) programs hosted on UNIX platforms, and LabVIEW (LV) Virtual Instruments hosted on a PC platform have been integrated and customized to provide real-time, synchronous motor control, data acquisition, and data analysis of data acquired through specialized DSP instrumentation. These modules communicate through EPICS Channel Access (CA) communication protocol extensions to control and manage execution flow ensuring synchronous data acquisition and real-time processing of measurement data. This paper describes the software integration and management scheme implemented to produce these real-time beam profiles.

  20. Statistical Aspects of X-Class Halo and Non-Halo Events, 1996-2014

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    2016-01-01

    Of the 166 X-class events that occurred during the interval 1996-2014, 80 had associations with halo events, 68 had no associations with halo events, and 18 occurred during LASCO (Large Angle and Spectrometric COronagraph) data gaps. Both the duration and location of the X-class halo events proved to be statistically important parameters with respect to the geo-effectiveness of the events. Forty-four of the 80 X-class halo events occurred within 45 degrees of the Sun's central meridian and 47 of the 80 had duration greater than or equal to 30 minutes, whereas only 28 of the 68 X-class non-halo events occurred within 45 degrees of the Sun's central meridian (2 events have unknown location) and 22 of the 68 had duration greater than or equal to 30 minutes. Ignoring the 4 largest X-class flares greater than or equal to X4.0 during the LASCO data gaps, 17 of the remaining 20 were associated with halo events, and 14 of the 17 had at least one geo-magnetically disturbed day (Ap (i.e. NOAA's Ap* (ApStar)index: the major magnetic storms going back to 1932) greater than or equal to 25 nanotesias) within 1-5 days following the X-class halo event. Based on the hourly Dst (Disturbance storm time) index, the most geo-effective X-class halo event during the interval 1996-2014 was that of an X1.7 flare that occurred on 2001 March 29 at 0957, having an hourly Disturbance storm time minimum equal to minus 387 nanotesias. On average, the X-class halo events (80 events) were found to have a mean duration (42 minutes) slightly longer than the mean duration (29 minutes) of the X-class non-halo events (68 events) with the difference in the means being statistically important at the 1 percent level of significance.

  1. Sun-Earth L1 Region Halo-To-Halo Orbit and Halo-To-LisaJous Orbit Transfers

    NASA Technical Reports Server (NTRS)

    Roberts, Craig E.; DeFazio, Robert

    2004-01-01

    Practical techniques for designing transfer trajectories between Libration Point Orbits (LPOs) are presented. Motivation for development of these techniques was provided by a hardware contingency experienced by the Solar Heliospheric Observatory (SOHO), a joint mission of the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA) orbiting the L1 point of the Sun-Earth system. A potential solution to the problem involved a transfer from SOHO s periodic halo orbit to a new LPO of substantially different dimensions. Assuming the SOHO halo orbit as the departure orbit, several practical LPO transfer techniques were developed to obtain new Lissajous or periodic halo orbits that satisfy mission requirements and constraints. While not implemented for the SOHO mission, practical LPO transfer techniques were devised that are generally applicable to current and future LPO missions.

  2. Why are halo coronal mass ejections faster?

    NASA Astrophysics Data System (ADS)

    Zhang, Qing-Min; Guo, Yang; Chen, Peng-Fei; Ding, Ming-De; Fang, Cheng

    2010-05-01

    Halo coronal mass ejections (CMEs) have been to be significantly faster than normal CMEs, which is a long-standing puzzle. In order to solve the puzzle, we first investigate the observed properties of 31 limb CMEs that clearly display loop-shaped frontal loops. The observational results show a strong tendency that slower CMEs are weaker in white-light intensity. Then, we perform a Monte Carlo simulation of 20000 artificial limb CMEs that have an average velocity of ~523 km s-1. The Thomson scattering of these events is calculated when they are assumed to be observed as limb and halo events, respectively. It is found that the white-light intensity of many slow CMEs becomes remarkably reduced when they turn from being viewed as a limb event to being viewed as a halo event. When the intensity is below the background solar wind fluctuation, it is assumed that they would be missed by coronagraphs. The average velocity of “detectable" halo CMEs is ~922 km s-1 very close to the observed value. This also indicates that wider events are more likely to be recorded. The results soundly suggest that the higher average velocity of halo CMEs is due to that a majority of slow events and some of narrow fast events carrying less material are so faint that they are blended with the solar wind fluctuations, and therefore are not observed.

  3. A ''LIGHT'', CENTRALLY CONCENTRATED MILKY WAY HALO?

    SciTech Connect

    Rashkov, Valery; Pillepich, Annalisa; Deason, Alis J.; Madau, Piero; Rockosi, Constance M.; Mayer, Lucio

    2013-08-20

    We discuss a novel approach to ''weighing'' the Milky Way (MW) dark matter halo, one that combines the latest samples of halo stars selected from the Sloan Digital Sky Survey (SDSS) with state of the art numerical simulations of MW analogs. The fully cosmological runs employed in the present study include ''Eris'', one of the highest resolution hydrodynamical simulations of the formation of a M{sub vir} = 8 Multiplication-Sign 10{sup 11} M{sub Sun} late-type spiral, and the dark-matter-only M{sub vir} = 1.7 Multiplication-Sign 10{sup 12} M{sub Sun} ''Via Lactea II'' (VLII) simulation. Eris provides an excellent laboratory for creating mock SDSS samples of tracer halo stars, and we successfully compare their density, velocity anisotropy, and radial velocity dispersion profiles with the observational data. Most mock SDSS realizations show the same ''cold veil'' recently observed in the distant stellar halo of the MW, with tracers as cold as {sigma}{sub los} Almost-Equal-To 50 km s{sup -1} between 100 and 150 kpc. Controlled experiments based on the integration of the spherical Jeans equation as well as a particle tagging technique applied to VLII show that a ''heavy'' M{sub vir} Almost-Equal-To 2 Multiplication-Sign 10{sup 12} M{sub Sun} realistic host produces a poor fit to the kinematic SDSS data. We argue that these results offer added evidence for a ''light'', centrally concentrated MW halo.

  4. The angular momentum distribution in galactic halos

    NASA Astrophysics Data System (ADS)

    Quinn, P. J.; Zurek, W. H.

    1988-08-01

    N-body simulations are used to model the formation of individual galactic halos from scale-free density perturbations in universes dominated by cold, nondissipative dark matter. In well-mixed halos, the angular momentum distribution is shown to have a systematic behavior with power law index n corresponding to that found for circular rotation curves. For a given n, the distribution of angular momentum has the same trend with radius and energy as that implied for a halo in which all the matter has its maximum possible angular momentum. Dynamical mixing during the relaxation of the halo redistributes both angular momentum and binding energy in an orderly manner. The organized nature of the collapse means that relaxation is not completely violent and that the secondary infall paradigm, in its simplest form, needs to be modified to include the organizing effects of dynamical friction. It is shown that the Mestel hypothesis is not consistent with the final collapsed state of halos, but may be applicable to the collapse of the disks of spirals.

  5. A UNIVERSAL MODEL FOR HALO CONCENTRATIONS

    SciTech Connect

    Diemer, Benedikt; Kravtsov, Andrey V.

    2015-01-20

    We present a numerical study of dark matter halo concentrations in ΛCDM and self-similar cosmologies. We show that the relation between concentration, c, and peak height, ν, exhibits the smallest deviations from universality if halo masses are defined with respect to the critical density of the universe. These deviations can be explained by the residual dependence of concentration on the local slope of the matter power spectrum, n, which affects both the normalization and shape of the c-ν relation. In particular, there is no well-defined floor in the concentration values. Instead, the minimum concentration depends on redshift: at fixed ν, halos at higher z experience steeper slopes n, and thus have lower minimum concentrations. We show that the concentrations in our simulations can be accurately described by a universal seven-parameter function of only ν and n. This model matches our ΛCDM results to ≲ 5% accuracy up to z = 6, and matches scale-free Ω{sub m} = 1 models to ≲ 15%. The model also reproduces the low concentration values of Earth-mass halos at z ≈ 30, and thus correctly extrapolates over 16 orders of magnitude in halo mass. The predictions of our model differ significantly from all models previously proposed in the literature at high masses and redshifts. Our model is in excellent agreement with recent lensing measurements of cluster concentrations.

  6. Static galactic halo and galactic wind

    NASA Technical Reports Server (NTRS)

    Ko, Chung-Ming

    1993-01-01

    Although the exact state of the interstellar medium (ISM) in our Galaxy (other galaxies as well) is not clear at all, the 'common consensus' is that a rough pressure balance (or equipartition of energy) exists between different components and phases: cold, warm, hot phases of the ISM, magnetic field, cosmic rays, etc. If the halo of a galaxy is taken to be an extension of the ISM, then its structure is influenced by various ISM components. A 'complete' description of the halo is evidently very complicated. This paper gives a brief account on cosmic ray halo, which emphasizes the role played by cosmic rays. The interaction between cosmic rays and thermal plasma is facilitated by magnetic field. The cosmic rays are scattered by hydromagnetic waves (e.g., Alfven waves) which in turn can be generated by cosmic ray streaming instability. This constitutes a self-consistent picture. Since we are interested in the structure of the halo, we adopted a hydrodynamic model in which the cosmic rays and waves are described by their pressures. In general there are two classes of halos: static and dynamic.

  7. A "Light," Centrally Concentrated Milky Way Halo?

    NASA Astrophysics Data System (ADS)

    Rashkov, Valery; Pillepich, Annalisa; Deason, Alis J.; Madau, Piero; Rockosi, Constance M.; Guedes, Javiera; Mayer, Lucio

    2013-08-01

    We discuss a novel approach to "weighing" the Milky Way (MW) dark matter halo, one that combines the latest samples of halo stars selected from the Sloan Digital Sky Survey (SDSS) with state of the art numerical simulations of MW analogs. The fully cosmological runs employed in the present study include "Eris," one of the highest resolution hydrodynamical simulations of the formation of a M vir = 8 × 1011 M ⊙ late-type spiral, and the dark-matter-only M vir = 1.7 × 1012 M ⊙ "Via Lactea II" (VLII) simulation. Eris provides an excellent laboratory for creating mock SDSS samples of tracer halo stars, and we successfully compare their density, velocity anisotropy, and radial velocity dispersion profiles with the observational data. Most mock SDSS realizations show the same "cold veil" recently observed in the distant stellar halo of the MW, with tracers as cold as σlos ≈ 50 km s-1 between 100 and 150 kpc. Controlled experiments based on the integration of the spherical Jeans equation as well as a particle tagging technique applied to VLII show that a "heavy" M vir ≈ 2 × 1012 M ⊙ realistic host produces a poor fit to the kinematic SDSS data. We argue that these results offer added evidence for a "light," centrally concentrated MW halo.

  8. A Universal Model for Halo Concentrations

    NASA Astrophysics Data System (ADS)

    Diemer, Benedikt; Kravtsov, Andrey V.

    2015-01-01

    We present a numerical study of dark matter halo concentrations in ΛCDM and self-similar cosmologies. We show that the relation between concentration, c, and peak height, ν, exhibits the smallest deviations from universality if halo masses are defined with respect to the critical density of the universe. These deviations can be explained by the residual dependence of concentration on the local slope of the matter power spectrum, n, which affects both the normalization and shape of the c-ν relation. In particular, there is no well-defined floor in the concentration values. Instead, the minimum concentration depends on redshift: at fixed ν, halos at higher z experience steeper slopes n, and thus have lower minimum concentrations. We show that the concentrations in our simulations can be accurately described by a universal seven-parameter function of only ν and n. This model matches our ΛCDM results to <~ 5% accuracy up to z = 6, and matches scale-free Ωm = 1 models to <~ 15%. The model also reproduces the low concentration values of Earth-mass halos at z ≈ 30, and thus correctly extrapolates over 16 orders of magnitude in halo mass. The predictions of our model differ significantly from all models previously proposed in the literature at high masses and redshifts. Our model is in excellent agreement with recent lensing measurements of cluster concentrations.

  9. Globular Cluster Contributions to the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Martell, Sarah; Grebel, Eva; Lai, David

    2010-08-01

    The goal of this project is to confirm chemically that globular clusters are the source of as much as half the population of the Galactic halo. Using moderate-resolution spectroscopy from the SEGUE survey, we have identified a previously unknown population of halo field giants with distinctly strong CN features. CN variations are typically only observed in globular clusters, so these stars are interpreted as immigrants to the halo that originally formed in globular clusters. In one night of Keck/HIRES time, we will obtain high-quality, high- resolution spectra for five such stars, and determine abundances of O, Na, Mg, Al, alpha, iron-peak and neutron-capture elements. With this information we can state clearly whether these unusual CN-strong halo stars carry the full abundance pattern seen in CN-strong globular cluster stars, with depleted C, O, and Mg and enhanced N, Na, and Al. This type of coarse ``chemical tagging'' will allow a clearer division of the Galactic halo into contributions from globular clusters and from dwarf galaxies, and will place constraints on theoretical models of globular cluster formation and evolution.

  10. The settling of warped disks in oblate dark halos

    NASA Technical Reports Server (NTRS)

    Dubinski, John; Kuijken, Konrad

    1995-01-01

    When a galaxy forms, the disk may initially be tilted with respect to a flattened dark halo. The misalignment between the disk and the halo is a common explanation for galactic disk warps, since in this state disks have precessing bending modes which resemble real warps. The gravitational response of the halo has often been ignored, and its strength and effect on possible bending modes is unknown. We therefore calculate the response of an oblate halo to a precessing inclined exponential disk using a variety of techniques. We construct models with a rigid exponential disk precessing in a particle halo, a particle disk precessing inside a static bulge/halo potential, and a self-consistent model with a particle disk, bulge, and halo. When the disk: halo mass ratio is small (approximately 10%) within 5 exponential scale radii, the disk settles to the equatorial plane of the halo within five orbital times. When the disk and halo mass are comparable, the halo rapidly aligns with the disk within a few orbital times, while the disk inclination drops. The rapid response of the halo to an inclined precessing disk suggests that the warps seen in galactic disks are not due to a misalignment between the disk and the inner halo. If a galaxy forms inclined to the principal plane of a dark halo, either the disk will settle to a pricipal plane or the inner halo will twist to align with the disk. The outer halo will remain misaligned for a much longer time and therefore may still exert a torque. Warped bending modes may still exist if the misalignment of the outer halo persists for a Hubble time.

  11. The settling of warped disks in oblate dark halos

    NASA Technical Reports Server (NTRS)

    Dubinski, John; Kuijken, Konrad

    1995-01-01

    When a galaxy forms, the disk may initially be tilted with respect to a flattened dark halo. The misalignment between the disk and the halo is a common explanation for galactic disk warps, since in this state disks have precessing bending modes which resemble real warps. The gravitational response of the halo has often been ignored, and its strength and effect on possible bending modes is unknown. We therefore calculate the response of an oblate halo to a precessing inclined exponential disk using a variety of techniques. We construct models with a rigid exponential disk precessing in a particle halo, a particle disk precessing inside a static bulge/halo potential, and a self-consistent model with a particle disk, bulge, and halo. When the disk: halo mass ratio is small (approximately 10%) within 5 exponential scale radii, the disk settles to the equatorial plane of the halo within five orbital times. When the disk and halo mass are comparable, the halo rapidly aligns with the disk within a few orbital times, while the disk inclination drops. The rapid response of the halo to an inclined precessing disk suggests that the warps seen in galactic disks are not due to a misalignment between the disk and the inner halo. If a galaxy forms inclined to the principal plane of a dark halo, either the disk will settle to a pricipal plane or the inner halo will twist to align with the disk. The outer halo will remain misaligned for a much longer time and therefore may still exert a torque. Warped bending modes may still exist if the misalignment of the outer halo persists for a Hubble time.

  12. Proton maser

    NASA Astrophysics Data System (ADS)

    Ensley, D. L.

    1988-01-01

    New calculations are reported which confirm the ability of an a priori random, initial-phase proton beam to drive a simple, single-stage microwave cavity maser or transit-time oscillator (TTO) to saturation conversion efficiencies of about 11 percent. The required initial TE(011) mode field can be provided from beam ramp-up bandwidth of excitation to a low level from an external source. A saturation field of 45 tesla and output power of 0.2 TW are calculated using an electron insulation field of 10 tesla and a 3 MeV, 400 Ka/sq cm beam. Results are compared to those for an electron beam of the same energy and geometry, and it is shown that proton beams potentially can provide a three order of magnitude increase in overall microwave power production density over that obtainable from electron beam TTOs.

  13. Stability of BEC galactic dark matter halos

    NASA Astrophysics Data System (ADS)

    Guzmán, F. S.; Lora-Clavijo, F. D.; González-Avilés, J. J.; Rivera-Paleo, F. J.

    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.

  14. Systematic Problems With Stellar Halo Modelling

    NASA Astrophysics Data System (ADS)

    Bailin, Jeremy

    2012-05-01

    Stellar halos contain a small fraction of the stellar mass of a galaxy. The dynamic range required to model the substructure within this small component while simultaneously modeling the main galaxy is currently unobtainable, which has lead to the prevalence of stellar halo models that tag stellar content onto dark matter particles in pure dark matter simulations, making it computationally feasible (e.g. Bullock & Johnston 2005; Cooper et al. 2010). Using paired simulations with identical initial conditions, we estimate the magnitude of the systematic effects these simplifications have on the structure of the halos. We find that (1) "painting" and (2) neglecting baryonic processes each introduce factor-of-several changes to the amount of substructure predicted. We therefore urge caution when interpreting differences between models and observations that are at this level.

  15. The Implication of MOND for Dark Haloes

    NASA Astrophysics Data System (ADS)

    Huang, Yi-Cheng; Kosowsky, A.

    2006-12-01

    It is always interesting that how much implication that Milgrom's relation could provide, even phenomenologically. With just one assumption that the gravitational acceleration goes like 1/r instead of Newton's law, 1/r2, when the acceleration is smaller than the value $10-10m/sec2, it is well known that MOND can give a better description of the rotational curves in spiral galaxies. In this research, we explore the configuration of the parameter space for the dark haloes by fitting the rotation curves of halo profiles with the exponential disk for stellar mass to that of MOND. In addition, we find that the baryon mass to the halo mass ratio is lower than the primordial ratio which gives that the total baryon mass is about 15% of the dark matter, and which is consistent with what we generally expect today.

  16. Polypoid Spitz Nevus With a Halo Reaction.

    PubMed

    Fernandez-Flores, Angel; Saeb-Lima, Marcela; Rodriguez-Peralto, José Luis

    2017-02-01

    Approximately, 2% of Spitz nevi are polypoid; between 3.6% and 7.4% present with a halo reaction. In tandem, these low percentages make the presence of a polypoid Spitz nevus with a halo reaction uncommon; we have not found reports of any previous cases. In the current report, we present a polypoid Spitz nevus with a halo reaction on the back of a 10-year-old male and discuss the morphologic findings. The lesion showed preserved nuclear expression of BAP1. There was no immunohistochemical expression of BRAF and ALK, while the melanocytic cells expressed p16. Comparative genomic hybridization was performed, and no significant aberrations were found. Only 2 small losses were evidenced in chromosome 8. The patient has been followed now for 2 years with no recurrence.

  17. Halo cold dark matter and microlensing

    SciTech Connect

    Gates, Evalyn; Turner, Michael S.

    1993-12-01

    There is good evidence that most of the baryons in the Universe are dark and some evidence that most of the matter in the Universe is nonbaryonic with cold dark matter (cdm) being a promising possibility. We discuss expectations for the abundance of baryons and cdm in the halo of our galaxy and locally. We show that in plausible cdm models the local density of cdm is at least $10^{-25}\\gcmm3$. We also discuss what one can learn about the the local cdm density from microlensing of stars in the LMC by dark stars in the halo and, based upon a suite of reasonable two-component halo models, conclude that microlensing is not a sensitive probe of the local cdm density.

  18. Coulomb dissociation of one- and two-neutron halos in halo EFT

    NASA Astrophysics Data System (ADS)

    Acharya, Bijaya; Phillips, Daniel

    2013-10-01

    In neutron halo nuclei the neutron distribution extends significantly beyond the region occupied by the nuclear ``core.'' Halo effective field theory (Halo-EFT) exploits the consequent separation of scales in order to predict relationships between low-energy observables in these systems as a systematic expansion in Rcore /Rhalo . This talk will discuss results for the Coulomb dissociation of neutron halo nuclei in this framework. In particular, we consider the Coulomb dissociation of 19C. We compute the reduced transition probability (dB (E 1) / dE) for excitation of the bound-state neutrons to the continuum up to N2LO in the Halo-EFT expansion. By comparing the predcition with data from RIKEN we are able to extract accurate results for 19C's one-neutron separation energy and asymptotic normalization coefficient. Good agreement between data and Halo-EFT is also found for the longitudinal momentum distribution of 19C. Results from ongoing work to extend ths calculation to two-neutron halos will also be presented. Supported by the US Department of Energy under grant DE-FG02- 93ER40756.

  19. A hadronic-leptonic model for the Fermi bubbles: Cosmic-rays in the galactic halo and radio emission

    SciTech Connect

    Fujita, Yutaka; Ohira, Yutaka; Yamazaki, Ryo

    2014-07-01

    We investigate non-thermal emission from the Fermi bubbles in a hadronic model. Cosmic-ray (CR) protons are accelerated at the forward shock of the bubbles. They interact with the background gas in the Galactic halo and create π{sup 0}-decay gamma-rays and secondary electrons through proton-proton interaction. We follow the evolution of the CR protons and electrons by calculating their distribution functions. We find that the spectrum and the intensity profiles of π{sup 0}-decay gamma-rays are consistent with observations. We predict that the shock front is located far ahead of the gamma-ray boundary of the Fermi bubbles. This naturally explains the fact that a clear temperature jump of thermal gas was not discovered at the gamma-ray boundary in recent Suzaku observations. We also consider re-acceleration of the background CRs in the Galactic halo at the shock front. We find that it can significantly affect the gamma-rays from the Fermi bubbles, unless the density of the background CRs is ≲ 10% of that in the Galactic disk. We indicate that secondary electrons alone cannot produce the observed radio emission from the Fermi bubbles. However, the radio emission from the outermost region of the bubbles can be explained if electrons are directly accelerated at the shock front with an efficiency of ∼0.1% of that of protons.

  20. Galaxy halo occupation at high redshift

    NASA Astrophysics Data System (ADS)

    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 0.9<~S<~1.1. The preferred region in Mmin expands by an order of magnitude, and slightly shallower slopes are acceptable 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.

  1. The dark halo of the milky Way

    PubMed

    Alcock

    2000-01-07

    Most of the matter in the Milky Way is invisible to astronomers. Precise numbers are elusive, but it appears that the dark component is 20 times as massive as the visible disk of stars and gas. This dark matter is distributed in space differently than the stars, forming a vast, diffuse halo, more spherical than disklike, which occupies more than 1000 times the volume of the disk of stars. The composition of this dark halo is unknown, but it may comprise a mixture of ancient, degenerate dwarf stars and exotic, hypothetical elementary particles.

  2. Dark energy and extended dark matter halos

    NASA Astrophysics Data System (ADS)

    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

  3. Rockstar: Phase-space halo finder

    NASA Astrophysics Data System (ADS)

    Behroozi, Peter; Wechsler, Risa; Wu, Hao-Yi

    2012-10-01

    Rockstar (Robust Overdensity Calculation using K-Space Topologically Adaptive Refinement) identifies 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. 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). Rockstar offers significant improvement in substructure recovery as compared to several other halo finders.

  4. PHYSICAL PROPERTIES OF COMPLEX C HALO CLOUDS

    SciTech Connect

    Hsu, W.-H.; Putman, M. E.; Peek, J. E. G.; Heitsch, F.; Clark, S. E.; Stanimirovic, S.

    2011-02-15

    Observations from the Galactic Arecibo L-band Feed Array H I (GALFA-H I) Survey of the tail of Complex C are presented and the halo clouds associated with this complex are cataloged. The properties of the Complex C clouds are compared to clouds cataloged at the tail of the Magellanic Stream to provide insight into the origin and destruction mechanism of Complex C. Magellanic Stream and Complex C clouds show similarities in their mass distributions (slope = -0.7 and -0.6 log (N( log (mass)))/ log (mass), respectively) and have a common line width of 20-30 km s{sup -1} (indicative of a warm component), which may indicate a common origin and/or physical process breaking down the clouds. The clouds cataloged at the tail of Complex C extend over a mass range of 10{sup 1.1}-10{sup 4.8} M{sub sun}, sizes of 10{sup 1.2}-10{sup 2.6} pc, and have a median volume density and pressure of 0.065 cm{sup -3} and (P/k) = 580 K cm{sup -3}. We do not see a prominent two-phase structure in Complex C, possibly due to its low metallicity and inefficient cooling compared to other halo clouds. Assuming that the Complex C clouds are in pressure equilibrium with a hot halo medium, we find a median halo density of 5.8 x 10{sup -4} cm{sup -3}, which given a constant distance of 10 kpc is at a z-height of {approx}3 kpc. Using the same argument for the Stream results in a median halo density of 8.4 x 10-{sup 5} (60 kpc/d) cm{sup -3}. These densities are consistent with previous observational constraints and cosmological simulations. We also assess the derived cloud and halo properties with three-dimensional grid simulations of halo H I clouds and find that the temperature is generally consistent within a factor of 1.5 and the volume densities, pressures, and halo densities are consistent within a factor of three.

  5. On the halo events observed by Mount Fuji and Mount Kanbala Emulsion Chamber Experiments

    NASA Technical Reports Server (NTRS)

    Ren, J. R.; Kuang, H. H.; Huo, A. X.; Lu, S. L.; Su, S.; Wang, Y. X.; Xue, Y. G.; Wang, C. R.; He, M.; Zhang, N. J.

    1985-01-01

    The intensity of big gamma-ray families associated by halo is obtained from Mt. Fuji experiment (650 g/sq.cm. atmospheric depth) and Mt. Kanbala experiment (515 g/sq.cm.). The results are compared with Monte Carlo calculation based on several assumptions on interaction mechanisms and the primary cosmic ray composition. The results suggest more than 3 times lower proton abundance among primaries than that of 10 to the 12th to 10 to the 13th eV region within the framework of quasi-scaling model of multiple production.

  6. Search for and analysis of radioactive halos in lunar material

    NASA Technical Reports Server (NTRS)

    Gentry, R. V.

    1976-01-01

    The lunar halo search was conducted because halos in terrestrial minerals serve as pointers to localized radioactivity, and make possible analytical studies on the problems of isotopic dating and mode of crystallization of the host mineral. Ancillary studies were conducted on terrestrial halos and on certain samples of special origin such as tektites and meteorites.

  7. The Constant Error of the Halo in Educational Outcomes Research.

    ERIC Educational Resources Information Center

    Pike, Gary R.

    1999-01-01

    Research suggests correlations between student gains and college experiences may be an artifact of halo effect. A study examined whether halo error underlies students' self-reported gains, significance of the error, and its effect on the relationship between college experiences and educational outcomes. Results confirm halo error may be an…

  8. Comment on Halo Effects in Rating and Evaluation Research.

    ERIC Educational Resources Information Center

    Feeley, Thomas Hugh

    2002-01-01

    Considers the existence of halo effects in individuals' evaluations of target communicators across different dimensions. Notes that halo effects result from raters' inability to discriminate among conceptually distinct and theoretically independent aspects of a target's behavior. Discusses current conceptions of halo error and suggests several…

  9. Comment on Halo Effects in Rating and Evaluation Research.

    ERIC Educational Resources Information Center

    Feeley, Thomas Hugh

    2002-01-01

    Considers the existence of halo effects in individuals' evaluations of target communicators across different dimensions. Notes that halo effects result from raters' inability to discriminate among conceptually distinct and theoretically independent aspects of a target's behavior. Discusses current conceptions of halo error and suggests several…

  10. The Constant Error of the Halo in Educational Outcomes Research.

    ERIC Educational Resources Information Center

    Pike, Gary R.

    1999-01-01

    Research suggests correlations between student gains and college experiences may be an artifact of halo effect. A study examined whether halo error underlies students' self-reported gains, significance of the error, and its effect on the relationship between college experiences and educational outcomes. Results confirm halo error may be an…

  11. Proton-driven electromagnetic instabilities in high-speed solar wind streams

    NASA Technical Reports Server (NTRS)

    Abraham-Shrauner, B.; Asbridge, J. R.; Bame, S. J.; Feldman, W. C.

    1979-01-01

    Electromagnetic instabilities of the field-aligned, right-hand circularly polarized magnetosonic wave and the left-hand circularly polarized Alfven wave driven by two drifted proton components are analyzed for model parameters determined from Imp 7 solar wind proton data measured during high-speed flow conditions. Growth rates calculated using bi-Lorentzian forms for the main and beam proton as well as core and halo electron velocity distributions do not differ significantly from those calculated using bi-Maxwellian forms. Using distribution parameters determined from 17 measured proton spectra, we show that considering the uncertainties the magnetosonic wave may be linearly stable and the Alfven wave is linearly unstable. Because proton velocity distribution function shapes are observed to persist for times long compared to the proton gyroperiod, the latter result suggests that linear stability theory fails for proton-driven ion cyclotron waves in the high-speed solar wind.

  12. Proton-driven electromagnetic instabilities in high-speed solar wind streams

    NASA Technical Reports Server (NTRS)

    Abraham-Shrauner, B.; Asbridge, J. R.; Bame, S. J.; Feldman, W. C.

    1979-01-01

    Electromagnetic instabilities of the field-aligned, right-hand circularly polarized magnetosonic wave and the left-hand circularly polarized Alfven wave driven by two drifted proton components are analyzed for model parameters determined from Imp 7 solar wind proton data measured during high-speed flow conditions. Growth rates calculated using bi-Lorentzian forms for the main and beam proton as well as core and halo electron velocity distributions do not differ significantly from those calculated using bi-Maxwellian forms. Using distribution parameters determined from 17 measured proton spectra, we show that considering the uncertainties the magnetosonic wave may be linearly stable and the Alfven wave is linearly unstable. Because proton velocity distribution function shapes are observed to persist for times long compared to the proton gyroperiod, the latter result suggests that linear stability theory fails for proton-driven ion cyclotron waves in the high-speed solar wind.

  13. Proton scaling

    SciTech Connect

    Canavan, Gregory H

    2009-01-01

    This note presents analytic estimates of the performance of proton beams in remote surveillance for nuclear materials. The analysis partitions the analysis into the eight steps used by a companion note: (1) Air scattering, (2) Neutron production in the ship and cargo, (3) Target detection probability, (4) Signal produced by target, (5) Attenuation of signal by ship and cargo, (6) Attenuation of signal by air, (7) Geometric dilution, and (8) Detector Efficiency. The above analyses indicate that the dominant air scattering and loss mechanisms for particle remote sensing are calculable with reliable and accepted tools. They make it clear that the conversion of proton beams into neutron sources rapidly goes to completion in all but thinnest targets, which means that proton interrogation is for all purposes executed by neutrons. Diffusion models and limiting approximations to them are simple and credible - apart from uncertainty over the cross sections to be used in them - and uncertainty over the structure of the vessels investigated. Multiplication is essentially unknown, in part because it depends on the details of the target and its shielding, which are unlikely to be known in advance. Attenuation of neutron fluxes on the way out are more complicated due to geometry, the spectrum of fission neutrons, and the details of their slowing down during egress. The attenuation by air is large but less uncertain. Detectors and technology are better known. The overall convolution of these effects lead to large but arguably tolerable levels of attenuation of input beams and output signals. That is particularly the case for small, mobile sensors, which can more than compensate for size with proximity to operate reliably while remaining below flux limits. Overall, the estimates used here appear to be of adequate accuracy for decisions. That assessment is strengthened by their agreement with companion calculations.

  14. Structure of Halo and Quasi-halo Helium-Helium-Alkali Trimers

    NASA Astrophysics Data System (ADS)

    Stipanović, Petar; Markić, Leandra Vranješ; Boronat, Jordi

    2017-05-01

    We report a diffusion Monte Carlo study of A^4He_2 and A^4He^3He trimers' structural properties, were A is one of the alkali atoms ^{6,7}Li, ^{23}Na, ^{39}K, ^{85}Rb or ^{133}Cs. Some of them are in a pure halo state, characterized by large spatial extent and universality, while some are close to the halo limit. The theoretical analysis of these trimers enables insight on how structural properties of weakly bound systems change when approaching the halo edge. For that purpose, two-variable distributions of inter-particle separations and angles were calculated. Extreme spatial extensions of some trimers with ^3He confirm their halo nature. Although all the considered systems are floppy, trimers with all bound dimer subsystems are less spread and have significantly lower percentage of quasi-linear configurations than those which have at least one unbound dimer subsystem.

  15. Reputation, Halo, and Ratings of Counseling Programs

    ERIC Educational Resources Information Center

    Thoreson, Richard W.; And Others

    1975-01-01

    This study tests the hypothesis that previous ratings of programs in psychology reflect both an experimental psychology and general institutional halo bias. It was found that applied programs in counseling psychology do receive ratings that differ from overall ratings of psychology in general. Programs ranked as strong, good, and adequate are…

  16. Reputation, Halo, and Ratings of Counseling Programs

    ERIC Educational Resources Information Center

    Thoreson, Richard W.; And Others

    1975-01-01

    This study tests the hypothesis that previous ratings of programs in psychology reflect both an experimental psychology and general institutional halo bias. It was found that applied programs in counseling psychology do receive ratings that differ from overall ratings of psychology in general. Programs ranked as strong, good, and adequate are…

  17. The Hot Gaseous Halos of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Bregman, J.

    2016-06-01

    In the Milky Way, absorption and emission line measurements of O VII and O VIII show that the halo environment is dominated by a nearly spherical halo of temperature 2 × 10^6 K, metallicity of 0.3-0.5 solar, and with a density decreasing as r^{-3/2}. The mass of the hot gas, estimated through extrapolation to the virial radius, is comparable to the stellar mass, but does not account for the missing mass. The Milky Way hot halo appears to be rotating at about 180 km/s, which is consistent with model expectations, depending on the time of infall. Around massive spiral galaxies, hot halos are seen in emission out to about 70 kpc in the best cases. These show similar gas density laws and metallicities in the range 0.1-0.5 solar. The gas mass is comparable to the stellar mass, but does not account for the missing baryons within the virial radius. If the density law can be extrapolated to about three virial radii, the missing baryons would be accounted for.

  18. Substructure of fuzzy dark matter haloes

    NASA Astrophysics Data System (ADS)

    Du, Xiaolong; Behrens, Christoph; Niemeyer, Jens C.

    2017-02-01

    We derive the halo mass function (HMF) for fuzzy dark matter (FDM) by solving the excursion set problem explicitly with a mass-dependent barrier function, which has not been done before. We find that compared to the naive approach of the Sheth-Tormen HMF for FDM, our approach has a higher cutoff mass and the cutoff mass changes less strongly with redshifts. Using merger trees constructed with a modified version of the Lacey & Cole formalism that accounts for suppressed small-scale power and the scale-dependent growth of FDM haloes and the semi-analytic GALACTICUS code, we study the statistics of halo substructure including the effects from dynamical friction and tidal stripping. We find that if the dark matter is a mixture of cold dark matter (CDM) and FDM, there will be a suppression on the halo substructure on small scales which may be able to solve the missing satellites problem faced by the pure CDM model. The suppression becomes stronger with increasing FDM fraction or decreasing FDM mass. Thus, it may be used to constrain the FDM model.

  19. WEIGHING THE GALACTIC DARK MATTER HALO: A LOWER MASS LIMIT FROM THE FASTEST HALO STAR KNOWN

    SciTech Connect

    Przybilla, Norbert; Tillich, Alfred; Heber, Ulrich; Scholz, Ralf-Dieter

    2010-07-20

    The mass of the Galactic dark matter halo is under vivid discussion. A recent study by Xue et al. revised the Galactic halo mass downward by a factor of {approx}2 relative to previous work, based on the line-of-sight velocity distribution of {approx}2400 blue horizontal-branch (BHB) halo stars. The observations were interpreted with a statistical approach using cosmological galaxy formation simulations, as only four of the six-dimensional phase-space coordinates were determined. Here we concentrate on a close investigation of the stars with the highest negative radial velocity from that sample. For one star, SDSSJ153935.67+023909.8 (J1539+0239 for short), we succeed in measuring a significant proper motion, i.e., full phase-space information is obtained. We confirm the star to be a Population II BHB star from an independent quantitative analysis of the Sloan Digital Sky Survey (SDSS) spectrum-providing the first non-LTE (NLTE) study of any halo BHB star-and reconstruct its three-dimensional trajectory in the Galactic potential. J1539+0239 turns out to be the fastest halo star known to date, with a Galactic rest-frame velocity of 694{sup +300}{sub -221} km s{sup -1} (full uncertainty range from Monte Carlo error propagation) at its current position. The extreme kinematics of the star allows a significant lower limit to be put on the halo mass in order to keep it bound, of M {sub halo} {>=} 1.7{sup +2.3}{sub -1.1} x 10{sup 12} M{sub sun}. We conclude that the Xue et al. results tend to underestimate the true halo mass as their most likely mass value is consistent with our analysis only at a level of 4%. However, our result confirms other studies that make use of the full phase-space information.

  20. Non-Gaussian halo mass function and non-spherical halo collapse: theory vs. simulations

    SciTech Connect

    Achitouv, Ixandra E.; Corasaniti, Pier Stefano E-mail: Pier-Stefano.Corasaniti@obspm.fr

    2012-02-01

    The mass distribution of dark matter halos is a sensitive probe of primordial non-Gaussianity (NG). We derive an analytical formula of the halo mass function by perturbatively computing excursion set path-integrals for a non-Gaussian density field with non-vanishing skewness, f{sub NL}. We assume a stochastic barrier model which captures the main features of the ellipsoidal collapse of halos. Contrary to previous results based on extensions of the Press-Schechter formalism to NG initial conditions, we find that the non-spherical collapse of halos directly alter the signature of primordial NG. This points toward a potential degeneracy between the effect of primordial non-Gaussianity and that of non-linear halo collapse. The inferred mass function is found to be in remarkable agreement with N-body simulations of NG local type. Deviations are well within numerical uncertainties for all values of f{sub NL}{sup loc} in the range of validity of the perturbative calculation (|f{sub nl}{sup loc}|∼<200). Moreover, the comparison with simulation results suggests that for |f{sub NL}|∼>30 the non-linear collapse of halos, as described by our barrier model, strongly deviates from that of Gaussian initial conditions. This is not surprising since the effect of non-linear gravitational processes may be altered by initially large NG. Hence, in the lack of prior theoretical knowledge, halo collapse model parameters should be included in statistical halo mass function data analysis which aim to constrain the signature of primordial NG.

  1. The velocity shear tensor: tracer of halo alignment

    NASA Astrophysics Data System (ADS)

    Libeskind, Noam I.; Hoffman, Yehuda; Forero-Romero, Jaime; Gottlöber, Stefan; Knebe, Alexander; Steinmetz, Matthias; Klypin, Anatoly

    2013-01-01

    The alignment of dark matter (DM) haloes and the surrounding large-scale structure (LSS) is examined in the context of the cosmic web. Halo spin, shape and the orbital angular momentum of subhaloes are investigated relative to the LSS using the eigenvectors of the velocity shear tensor evaluated on a grid with a scale of 1 Mpc h-1, deep within the non-linear regime. Knots, filaments, sheets and voids are associated with regions that are collapsing along 3, 2, 1 or 0 principal directions simultaneously. Each halo is tagged with a web classification (i.e. knot halo, filament halo, etc.) according to the nature of the collapse at the halo position. The full distribution of shear eigenvalues is found to be substantially different from that tagged to haloes, indicating that the observed velocity shear is significantly biased. We find that larger mass haloes live in regions where the shear is more isotropic, namely the expansion or collapse is more spherical. A correlation is found between the halo shape and the eigenvectors of the shear tensor, with the longest (shortest) axis of the halo shape being aligned with the slowest (fastest) collapsing eigenvector. This correlation is web independent, suggesting that the velocity shear is a fundamental tracer of the halo alignment. A similar result is found for the alignment of halo spin with the cosmic web. It has been shown that high-mass haloes exhibit a spin flip with respect to the LSS: we find that the mass at which this spin flip occurs is web dependent and not universal as suggested previously. Although weaker than haloes, subhalo orbits too exhibit an alignment with the LSS, providing a possible insight into the highly correlated corotation of the Milky Way's satellite system. The present study suggests that the velocity shear tensor constitutes the natural framework for studying the directional properties of the non-linear LSS and those of haloes and galaxies.

  2. Stellar discs in Aquarius dark matter haloes

    NASA Astrophysics Data System (ADS)

    DeBuhr, Jackson; Ma, Chung-Pei; White, Simon D. M.

    2012-10-01

    We investigate the gravitational interactions between live stellar discs and their dark matter haloes, using Λ cold dark matter haloes similar in mass to that of the Milky Way taken from the Aquarius Project. We introduce the stellar discs by first allowing the haloes to respond to the influence of a growing rigid disc potential from z = 1.3 to 1.0. The rigid potential is then replaced with star particles which evolve self-consistently with the dark matter particles until z = 0.0. Regardless of the initial orientation of the disc, the inner parts of the haloes contract and change from prolate to oblate as the disc grows to its full size. When the disc's normal is initially aligned with the major axis of the halo at z = 1.3, the length of the major axis contracts and becomes the minor axis by z = 1.0. Six out of the eight discs in our main set of simulations form bars, and five of the six bars experience a buckling instability that results in a sudden jump in the vertical stellar velocity dispersion and an accompanying drop in the m = 2 Fourier amplitude of the disc surface density. The bars are not destroyed by the buckling but continue to grow until the present day. Bars are largely absent when the disc mass is reduced by a factor of 2 or more; the relative disc-to-halo mass is therefore a primary factor in bar formation and evolution. A subset of the discs is warped at the outskirts and contains prominent non-coplanar material with a ring-like structure. Many discs reorient by large angles between z = 1 and 0, following a coherent reorientation of their inner haloes. Larger reorientations produce more strongly warped discs, suggesting a tight link between the two phenomena. The origins of bars and warps appear independent: some discs with strong bars show little disturbances at the outskirts, while the discs with the weakest bars show severe warps.

  3. Mapping Dark Matter Halos with Stellar Kinematics

    NASA Astrophysics Data System (ADS)

    Murphy, Jeremy; Gebhardt, K.; Greene, J. E.; Graves, G.

    2013-07-01

    Galaxies of all sizes form and evolve in the centers of dark matter halos. As these halos constitute the large majority of the total mass of a galaxy, dark matter certainly plays a central role in the galaxy's formation and evolution. Yet despite our understanding of the importance of dark matter, observations of the extent and shape of dark matter halos have been slow in coming. The paucity of data is particularly acute in elliptical galaxies. Happily, concerted effort over the past several years by a number of groups has been shedding light on the dark matter halos around galaxies over a wide range in mass. The development of new instrumentation and large surveys, coupled with the tantalizing evidence for a direct detection of dark matter from the AMS experiment, has brought on a golden age in the study of galactic scale dark matter halos. I report on results using extended stellar kinematics from integrated light to dynamically model massive elliptical galaxies in the local universe. I use the integral field power of the Mitchell Spectrograph to explore the kinematics of stars to large radii (R > 2.5 r_e). Once the line-of-sight stellar kinematics are measured, I employ orbit-based, axisymmetric dynamical modeling to explore a range of dark matter halo parameterizations. Globular cluster kinematics at even larger radii are used to further constrain the dynamical models. The dynamical models also return information on the anisotropy of the stars which help to further illuminate the primary formation mechanisms of the galaxy. Specifically, I will show dynamical modeling results for the first and second rank galaxies in the Virgo Cluster, M49 and M87. Although similar in total luminosity and ellipticity, these two galaxies show evidence for different dark matter halo shapes, baryon to dark matter fractions, and stellar anisotropy profiles. Moreover, the stellar velocity dispersion at large radii in M87 is significantly higher than the globular clusters at the same

  4. THE HALO OCCUPATION DISTRIBUTION OF SDSS QUASARS

    SciTech Connect

    Richardson, Jonathan; Chatterjee, Suchetana; Nagai, Daisuke; Zheng Zheng; Shen Yue

    2012-08-10

    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{sup -1} Mpc < r{sub p} < 120 h{sup -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 {approx}48, 000 quasars in the redshift range 0.4 {approx}< z {approx}< 2.5 with median redshift 1.4. We interpret these precise 2PCF measurements within the halo occupation distribution (HOD) framework and constrain the occupation functions of central and satellite quasars in dark matter halos. In order to explain the small-scale clustering, the HOD modeling requires that a small fraction of z {approx} 1.4 quasars, f{sub sat} = (7.4 {+-} 1.4) Multiplication-Sign 10{sup -4}, be satellites in dark matter halos. At z {approx} 1.4, the median masses of the host halos of central and satellite quasars are constrained to be M{sub cen} = 4.1{sup +0.3}{sub -0.4} Multiplication-Sign 10{sup 12} h{sup -1} M{sub Sun} and M{sub sat} = 3.6{sup +0.8}{sub -1.0} Multiplication-Sign 10{sup 14} h{sup -1} M{sub Sun }, 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 {approx} 3.2 is M{sub cen} = 14.1{sup +5.8}{sub -6.9} Multiplication-Sign 10{sup 12} h{sup -1} M{sub Sun }. 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{sub q

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

    SciTech Connect

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

    2010-06-04

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

  6. Comparing halo bias from abundance and clustering

    NASA Astrophysics Data System (ADS)

    Hoffmann, K.; Bel, J.; Gaztañaga, E.

    2015-06-01

    We model the abundance of haloes in the ˜(3 Gpc h-1)3 volume of the MICE Grand Challenge simulation by fitting the universal mass function with an improved Jackknife error covariance estimator that matches theory predictions. We present unifying relations between different fitting models and new predictions for linear (b1) and non-linear (c2 and c3) halo clustering bias. Different mass function fits show strong variations in their performance when including the low mass range (Mh ≲ 3 × 1012 M⊙ h-1) in the analysis. Together with fits from the literature, we find an overall variation in the amplitudes of around 10 per cent in the low mass and up to 50 per cent in the high mass (galaxy cluster) range (Mh > 1014 M⊙ h-1). These variations propagate into a 10 per cent change in b1 predictions and a 50 per cent change in c2 or c3. Despite these strong variations, we find universal relations between b1 and c2 or c3 for which we provide simple fits. Excluding low-mass haloes, different models fitted with reasonable goodness in this analysis, show per cent level agreement in their b1 predictions, but are systematically 5-10 per cent lower than the bias directly measured with two-point halo-mass clustering. This result confirms previous findings derived from smaller volumes (and smaller masses). Inaccuracies in the bias predictions lead to 5-10 per cent errors in growth measurements. They also affect any halo occupation distribution fitting or (cluster) mass calibration from clustering measurements.

  7. Parametrizing the stellar haloes of galaxies

    NASA Astrophysics Data System (ADS)

    D'Souza, Richard; Kauffman, Guinevere; Wang, Jing; Vegetti, Simona

    2014-09-01

    We study the stellar haloes of galaxies out to 70-100 kpc as a function of stellar mass and galaxy type by stacking aligned r- and g-band images from a sample of 45 508 galaxies from Sloan Digital Sky Survey Data Release 9 in the redshift range 0.06 ≤ z ≤ 0.1 and in the mass range 1010.0 M⊙ < M* < 1011.4 M⊙. We derive surface brightness profiles to a depth of almost μr ˜ 32 mag arcsec-2. We find that the ellipticity of the stellar halo is a function of galaxy stellar mass and that the haloes of high-concentration galaxies are more elliptical than those of low-concentration galaxies. Where the g - r colour of the stellar halo can be measured, we find that the stellar light is always bluer than in the main galaxy. The colour of the stellar halo is redder for more massive galaxies. We further demonstrate that the full two-dimensional surface intensity distribution of our galaxy stacks can only be fit through multicomponent Sérsic models. Using the fraction of light in the outer component of the models as a proxy for the fraction of accreted stellar light, we show that this fraction is a function of stellar mass and galaxy type. The fraction of accreted stellar light rises from 30 to 70 per cent and from 2 to 25 per cent for high- and low-concentration galaxies, respectively, over the mass range 1010.0-1011.4 M⊙.

  8. PEEK-Halo effect in interbody fusion.

    PubMed

    Phan, Kevin; Hogan, Jarred A; Assem, Yusuf; Mobbs, Ralph J

    2016-02-01

    Recent developments have seen poly[aryl-ether-ether-ketone] (PEEK) being increasingly used in vertebral body fusion. More novel approaches to improve PEEK have included the introduction of titanium-PEEK (Ti-PEEK) composites and coatings. This paper aims to describe a potential complication of PEEK based implants relating to poorer integration with the surrounding bone, producing a "PEEK-Halo" effect which is not seen in Ti-PEEK composite implants. We present images from two patients undergoing anterior lumbar interbody fusion (ALIF). The first patient underwent an L5/S1 ALIF using a PEEK implant whilst the second patient underwent L4/L5 ALIF using a Ti-PEEK composite implant. Evidence of osseointegration was sought using CT imaging and confirmed using histological preparations of a sheep tibia model. The PEEK-Halo effect is demonstrated by a halo effect between the PEEK implant and the bone graft on CT imaging. This phenomenon is secondary to poor osseointegration of PEEK implants. The PEEK-Halo effect was not demonstrated in the second patient who received a Ti-PEEK composite graft. Histological analysis of graft/bone interface surfaces in PEEK versus Ti-PEEK implants in a sheep model further confirmed poorer osseointegration of the PEEK implant. In conclusion, the PEEK-Halo effect is seen secondary to minimal osseointegration of PEEK at the adjacent vertebral endplate following a PEEK implant insertion. This effect is not seen with Ti-PEEK implants, and may support the role of titanium in improving the bone-implant interface of PEEK substrates. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. The Circumgalactic Medium in Massive Halos

    NASA Astrophysics Data System (ADS)

    Chen, Hsiao-Wen

    This chapter presents a review of the current state of knowledge on the cool (T ˜ 104 K) halo gas content around massive galaxies at z ≈ 0. 2-2. Over the last decade, significant progress has been made in characterizing the cool circumgalactic gas in massive halos of M h ≈ 1012-14 M⊙ at intermediate redshifts using absorption spectroscopy. Systematic studies of halo gas around massive galaxies beyond the nearby universe are made possible by large spectroscopic samples of galaxies and quasars in public archives. In addition to accurate and precise constraints for the incidence of cool gas in massive halos, detailed characterizations of gas kinematics and chemical compositions around massive quiescent galaxies at z ≈ 0. 5 have also been obtained. Combining all available measurements shows that infalling clouds from external sources are likely the primary source of cool gas detected at d 100 d\\gtrsim 100 kpc from massive quiescent galaxies. The origin of the gas closer in is currently less certain, but SNe Ia driven winds appear to contribute significantly to cool gas found at d < 100 kpc. In contrast, cool gas observed at d 200 d\\lesssim 200 kpc from luminous quasars appears to be intimately connected to quasar activities on parsec scales. The observed strong correlation between cool gas covering fraction in quasar host halos and quasar bolometric luminosity remains a puzzle. Combining absorption-line studies with spatially resolved emission measurements of both gas and galaxies is the necessary next step to address remaining questions.

  10. Dark Matter Halos with VIRUS-P

    NASA Astrophysics Data System (ADS)

    Murphy, Jeremy; Gebhardt, K.

    2010-05-01

    We present new, two-dimensional stellar kinematic data on several of the most massive galaxies in the local universe. These data were taken with the integral field spectrograph, VIRUS-P, and extend to unprecedented radial distances. Once robust stellar kinematics are in hand, we run orbit-based axisymmetric dynamical models in order to constrain the stellar mass-to-light ratio and dark matter halo parameters. We have run a large set of dynamical models on the second rank galaxy in the Virgo cluster, M87, and find clear evidence for a massive dark matter halo. The two-dimensional stellar kinematics for several of our other targets, all first and second rank galaxies, are also presented. Dark matter halos are known to dominate the mass profile of elliptical galaxies somewhere between one to two effective radii, yet due to the low surface brightness at these radial distances, determining stellar dynamics is technologically challenging. To overcome this, constraints on the dark matter halo are often made with planetary nebulae or globular clusters at large radii. However, as results from different groups have returned contradictory results, it remains unclear whether different dynamical tracers always follow the stellar kinematics. Due to VIRUS-P's large field of view and on-sky fiber diameter, we are able to determine stellar kinematics at radial distances that overlap with other dynamical tracers. Understanding what the dynamics of stars, planetary nebula and globular clusters tell us about both the extent of the dark matter halo profile and the formation histories of the largest elliptical galaxies is a primary science driver for this work.

  11. The role of Dark Matter sub-halos in the non-thermal emission of galaxy clusters

    NASA Astrophysics Data System (ADS)

    Marchegiani, Paolo; Colafrancesco, Sergio

    2016-11-01

    Annihilation of Dark Matter (DM) particles has been recognized as one of the possible mechanisms for the production of non-thermal particles and radiation in galaxy clusters. Previous studies have shown that, while DM models can reproduce the spectral properties of the radio halo in the Coma cluster, they fail in reproducing the shape of the radio halo surface brightness because they produce a shape that is too concentrated towards the center of the cluster with respect to the observed one. However, in previous studies the DM distribution was modeled as a single spherically symmetric halo, while the DM distribution in Coma is found to have a complex and elongated shape. In this work we calculate a range of non-thermal emissions in the Coma cluster by using the observed distribution of DM sub-halos. We find that, by including the observed sub-halos in the DM model, we obtain a radio surface brightness with a shape similar to the observed one, and that the sub-halos boost the radio emission by a factor between 5 and 20%, thus allowing to reduce the gap between the annihilation cross section required to reproduce the radio halo flux and the upper limits derived from other observations, and that this gap can be explained by realistic values of the boosting factor due to smaller substructures. Models with neutralino mass of 9 GeV and composition τ+ τ-, and mass of 43 GeV and composition b bar b can fit the radio halo spectrum using the observed properties of the magnetic field in Coma, and do not predict a gamma-ray emission in excess compared to the recent Fermi-LAT upper limits. These findings make these DM models viable candidate to explain the origin of radio halos in galaxy clusters, avoiding the problems connected to the excessive gamma-ray emission expected from proton acceleration in most of the currently proposed models, where the acceleration of particles is directly or indirectly connected to events related to clusters merging. Therefore, DM models deserve

  12. Halo mass distribution reconstruction across the cosmic web

    NASA Astrophysics Data System (ADS)

    Zhao, Cheng; Kitaura, Francisco-Shu; Chuang, Chia-Hsun; Prada, Francisco; Yepes, Gustavo; Tao, Charling

    2015-08-01

    We study the relation between halo mass and its environment from a probabilistic perspective. We find that halo mass depends not only on local dark matter density, but also on non-local quantities such as the cosmic web environment and the halo-exclusion effect. Given these accurate relations, we have developed the HADRON-code (Halo mAss Distribution ReconstructiON), a technique which permits us to assign halo masses to a distribution of haloes in three-dimensional space. This can be applied to the fast production of mock galaxy catalogues, by assigning halo masses, and reproducing accurately the bias for different mass cuts. The resulting clustering of the halo populations agree well with that drawn from the BigMultiDark N-body simulation: the power spectra are within 1σ up to scales of k = 0.2 h Mpc-1, when using augmented Lagrangian perturbation theory based mock catalogues. Only the most massive haloes show a larger deviation. For these, we find evidence of the halo-exclusion effect. A clear improvement is achieved when assigning the highest masses to haloes with a minimum distance separation. We also compute the two- and three-point correlation functions, and find an excellent agreement with N-body results. Our work represents a quantitative application of the cosmic web classification. It can have further interesting applications in the multitracer analysis of the large-scale structure for future galaxy surveys.

  13. Characteristic time for halo current growth and rotation

    NASA Astrophysics Data System (ADS)

    Boozer, Allen H.

    2015-10-01

    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.

  14. Characteristic time for halo current growth and rotation

    SciTech Connect

    Boozer, Allen H.

    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.

  15. Dynamics of the Disruption Halo Current Toroidal Asymmetry in NSTX

    SciTech Connect

    S.P. Gerhardt

    2012-09-27

    This paper describes the dynamics of disruption halo current non-axisymmetries in the lower divertor of the National Spherical Torus Experiment [M. Ono, et al. Nuclear Fusion 40, 557 (2000)]. While. The halo currents typically have a strongly asymmetric structure where they enter the divertor floor, and this asymmetry has been observed to complete up to 7 toroidal revolutions over the duration of the halo current pulse. However, the rotation speed and toroidal extend of the asymmetry can vary significantly during the pulse. The rotation speed, halo current pulse duration, and total number of revolutions tend to be smaller in cases with large halo currents. The halo current pattern is observed to become toroidally symmetric at the end of the halo current pulse. It is proposed that this symmeterization is due to the loss of most or all of the closed field line geometry in the final phase of the vertical displacement event.

  16. ORIGAMI: DELINEATING HALOS USING PHASE-SPACE FOLDS

    SciTech Connect

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

    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.

  17. Can MACHOs probe the shape of the galaxy halo ?

    NASA Technical Reports Server (NTRS)

    Frieman, Joshua; Scoccimarro, Roman

    1994-01-01

    Microlensing searches in our galaxy have recently discovered several candidates in the direction of the Large Magellanic Cloud (LMC). We study the prospects for such searches to yield useful information about the flattening of the Galaxy dark matter halo, using a self-consistent oblate halo model and allowing for the possibility of misalignment between the disk and halo symmetry axes. The microlensing optical depth for the LMC, tau(LMC), depends sensitively on the disk-halo tilt angle in the Milky Way, as does the ratio tau(SMC)/tau(LMC). If the tilt angle is as large as 30 deg, a much larger spread in values for tau(LMC) is consistent with rotation curve constraints than previously thought. Disk-halo tilt and halo flattening do not significantly affect the massive compact halo object (MACHO) masses inferred from event durations.

  18. The global dark halo structure of the Andromeda galaxy

    NASA Astrophysics Data System (ADS)

    Hayashi, Kohei; Chiba, Masashi

    2014-01-01

    We set new limits on the global shape of the dark halo in the Andromeda galaxy based on axisymmetric mass models constructed by Hayashi & Chiba (2012). 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. Based on the application of our models to latest kinematical data of globular clusters and dwarf spheroidal galaxies in the Andromeda halo, we find that the most plausible cases for Andromeda yield not a spherical but a prolate shape for its dark halo. We also find that the prolate dark halo is consistent with theoretical predictions in which the satellites are distributed anisotropically and preferentially located along major axes of their galactic host halos. It is a reflection of the intimate connection between galactic dark matter halos and the cosmic web.

  19. Low frequency follow up of radio haloes and relics in the GMRT Radio Halo Cluster Survey

    NASA Astrophysics Data System (ADS)

    Venturi, T.; Giacintucci, S.; Dallacasa, D.; Cassano, R.; Brunetti, G.; Macario, G.; Athreya, R.

    2013-03-01

    Aims: To gain insight into the origin of diffuse radio sources in galaxy clusters and their connection with cluster merger processes, we performed GMRT low frequency observations of the radio haloes, relics and new candidates belonging to the GMRT radio Halo cluster sample first observed at 610 MHz. Our main aim was to investigate their observational properties and integrated spectra at frequencies below 610 MHz. Methods: High sensitivity imaging was performed using the GMRT at 325 MHz and 240 MHz. The properties of the diffuse emission in each cluster were compared to our 610 MHz images and/or literature information available at other frequencies, in order to derive the integrated spectra over a wide frequency range. Results: Cluster radio haloes form a composite class in terms of spectral properties. Beyond the classical radio haloes, whose spectral index α is in the range ~1.2 ÷ 1.3 (S ∝ ν- α), we found sources with α ~ 1.6 ÷ 1.9. This result supports the idea that the spectra of the radiating particles in radio haloes is not universal and that inefficient mechanisms of particle acceleration are responsible for their origin. We also found a variety of brightness distributions, i.e. both centrally peaked and clumpy haloes. Even though the thermal and relativistic plasma tend to occupy the same cluster volume, in some cases a positional shift between the radio and X-ray peaks of emission is evident. Our observations also revealed diffuse cluster sources that cannot be easily classified as either haloes or relics. New candidate relics were found in A 1300 and in A 1682, and in some clusters "bridges" of radio emission have been detected, connecting the relic and radio halo emission. Finally, by combining our new data with information in the literature, we derived the Log LX - Log P325 MHz correlation for radio haloes, and investigated the possible correlation of the spectral index of radio haloes with the temperature of the intracluster medium.

  20. A Speeding Binary in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-04-01

    The recent discovery of a hyper-velocity binary star system in the halo of the Milky Way poses a mystery: how was this system accelerated to its high speed?Accelerating StarsUnlike the uniform motion in the Galactic disk, stars in the Milky Ways halo exhibit a huge diversity of orbits that are usually tilted relative to the disk and have a variety of speeds. One type of halo star, so-called hyper-velocity stars, travel with speeds that can approach the escape velocity of the Galaxy.How do these hyper-velocity stars come about? Assuming they form in the Galactic disk, there are multiple proposed scenarios through which they could be accelerated and injected into the halo, such as:Ejection after a close encounter with the supermassive black hole at the Galactic centerEjection due to a nearby supernova explosionEjection as the result of a dynamical interaction in a dense stellar population.Further observations of hyper-velocity stars are necessary to identify the mechanism responsible for their acceleration.J1211s SurpriseModels of J1211s orbit show it did not originate from the Galactic center (black dot). The solar symbol shows the position of the Sun and the star shows the current position of J1211. The bottom two panels show two depictions(x-y plane and r-z plane) of estimated orbits of J1211 over the past 10 Gyr. [Nmeth et al. 2016]To this end, a team of scientists led by Pter Nmeth (Friedrich Alexander University, Erlangen-Nrnberg) recently studied the candidate halo hyper-velocity star SDSS J121150.27+143716.2. The scientists obtained spectroscopy of J1211 using spectrographs at the Keck Telescope in Hawaii and ESOs Very Large Telescope in Chile. To their surprise, they discovered the signature of a companion in the spectra: J1211 is actually a binary!Nmeth and collaborators found that J1211, located roughly 18,000 light-years away, is moving at a rapid ~570 km/s relative to the galactic rest frame. The binary system consists of a hot (30,600 K) subdwarf and a

  1. Hot Stars in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Adelman, Saul J.; Upgren, Arthur R.; Adelman, Carol J.

    2011-03-01

    Participants; Preface; Foreword; Acknowledgements; Part I. Introductory Papers: 1. What is the galaxy's halo population?; 2. Theoretical properties of horizontal-branch stars; 3. A review of A-type horizontal-branch stars; Part II. Surveys: 4. A progress report on the Edinburgh-Cape object survey; 5. A 300 square degree survey of young stars at high galactic latitudes; 6. The isolation of a new sample of B stars in the halo; 7. A northern catalog of FHB/A stars; 8. Recent progress on a continuing survey of galactic globular clusters for blue stragglers; 9. UV observations with FAUST and the galactic model; 10. Hot stars at the South Galactic Pole; Part III. Clusters: 11. Population II horizontal branches: a photometric study of globular clusters; 12. The period-shift effect in Oosterhoff type II globular clusters; 13. UV photometry of hot stars in omega centauri; 14. Spectroscopic and UBV observations of blue stars at the NGP; 15. Population I horizontal branches: probing the halo-to-disk transition; Part IV. Stars: 16. Very hot subdwarf O stars; 17. Quantitative spectroscopy of the very hot subluminous O-stars: K646, PG1159-035, and KPD0005+5106; 18. Analyzing the helium-rich hot sdO stars in the Palomar Green Survey; 19. Late type companions of hot sd O stars; 20. Hot stars in globular clusters; 21. Faint blue stars from the Hamburg Schmidt Survey; 22. Stellar winds and the evolution of sdB's to sdO's; 23. Halo stars in the Vilnius photometric system; 24. Horizontal branch stars in the geneva photometric system; 25. Zeeman observations of FHB stars and hot subdwarf stars; 26. What does a FHB star's spectrum look like?; 27. A technique for distinguishing FHB stars from A-type stars; 28. eEemental abundances of halo A and interloper stars; 29. The mass of blue horizontal branch stars in the globular cluster NGC6397; 30. IUE observations of blue HB stars in the globular clusters M3 and NGC6752; 31. Metallicities and kinematics of the local RR lyraes: lukewarm stars

  2. Hot Stars in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Adelman, Saul J.; Upgren, Arthur R.; Adelman, Carol J.

    1994-08-01

    Participants; Preface; Foreword; Acknowledgements; Part I. Introductory Papers: 1. What is the galaxy's halo population?; 2. Theoretical properties of horizontal-branch stars; 3. A review of A-type horizontal-branch stars; Part II. Surveys: 4. A progress report on the Edinburgh-Cape object survey; 5. A 300 square degree survey of young stars at high galactic latitudes; 6. The isolation of a new sample of B stars in the halo; 7. A northern catalog of FHB/A stars; 8. Recent progress on a continuing survey of galactic globular clusters for blue stragglers; 9. UV observations with FAUST and the galactic model; 10. Hot stars at the South Galactic Pole; Part III. Clusters: 11. Population II horizontal branches: a photometric study of globular clusters; 12. The period-shift effect in Oosterhoff type II globular clusters; 13. UV photometry of hot stars in omega centauri; 14. Spectroscopic and UBV observations of blue stars at the NGP; 15. Population I horizontal branches: probing the halo-to-disk transition; Part IV. Stars: 16. Very hot subdwarf O stars; 17. Quantitative spectroscopy of the very hot subluminous O-stars: K646, PG1159-035, and KPD0005+5106; 18. Analyzing the helium-rich hot sdO stars in the Palomar Green Survey; 19. Late type companions of hot sd O stars; 20. Hot stars in globular clusters; 21. Faint blue stars from the Hamburg Schmidt Survey; 22. Stellar winds and the evolution of sdB's to sdO's; 23. Halo stars in the Vilnius photometric system; 24. Horizontal branch stars in the geneva photometric system; 25. Zeeman observations of FHB stars and hot subdwarf stars; 26. What does a FHB star's spectrum look like?; 27. A technique for distinguishing FHB stars from A-type stars; 28. eEemental abundances of halo A and interloper stars; 29. The mass of blue horizontal branch stars in the globular cluster NGC6397; 30. IUE observations of blue HB stars in the globular clusters M3 and NGC6752; 31. Metallicities and kinematics of the local RR lyraes: lukewarm stars

  3. Intracranial halo pin penetration causing brain injury secondary to poor halo care technique: a case report and literature review

    PubMed Central

    Male, Kishore Reddy; Guha, Abhijit; James, Stuart; Ahuja, Sashin

    2008-01-01

    This is a case report of intra cranial penetration by halo pins resulting in cerebritis and fits secondary to incorrect halo care by the patient and his family. Halo pin penetration into the skull with brain injury is itself a rare incident. Previously documented case reports were in patients with a previous cranioplasties and they were highlight the fact that halo not to be used in cranioplasty patients. Cranial penetration of the halo pins has generally been secondary to a fall/medical condition as epilepsy. This incident how ever highlights the fact the halo care itself along with proper techniques used for tightening the halo pins by the carer plays a crucial role in preventing complications such as this. PMID:19068118

  4. Precise halo orbit design and optimal transfer to halo orbits from earth using differential evolution

    NASA Astrophysics Data System (ADS)

    Nath, Pranav; Ramanan, R. V.

    2016-01-01

    The mission design to a halo orbit around the libration points from Earth involves two important steps. In the first step, we design a halo orbit for a specified size and in the second step, we obtain an optimal transfer trajectory design to the halo orbit from an Earth parking orbit. Conventionally, the preliminary design for these steps is obtained using higher order analytical solution and the dynamical systems theory respectively. Refinements of the design are carried out using gradient based methods such as differential correction and pseudo arc length continuation method under the of circular restricted three body model. In this paper, alternative single level schemes are developed for both of these steps based on differential evolution, an evolutionary optimization technique. The differential evolution based scheme for halo orbit design produces precise halo orbit design avoiding the refinement steps. Further, in this approach, prior knowledge of higher order analytical solutions for the halo orbit design is not needed. The differential evolution based scheme for the transfer trajectory, identifies the precise location on the halo orbit that needs minimum energy for insertion and avoids exploration of multiple points. The need of a close guess is removed because the present scheme operates on a set of bounds for the unknowns. The constraint on the closest approach altitude from Earth is handled through objective function. The use of these schemes as the design and analysis tools within the of circular restricted three body model is demonstrated through case studies for missions to the first libration point of Sun-Earth system.

  5. Proton radiography to improve proton therapy treatment

    NASA Astrophysics Data System (ADS)

    Takatsu, J.; van der Graaf, E. R.; Van Goethem, M.-J.; van Beuzekom, M.; Klaver, T.; Visser, J.; Brandenburg, S.; Biegun, A. K.

    2016-01-01

    The quality of cancer treatment with protons critically depends on an accurate prediction of the proton stopping powers for the tissues traversed by the protons. Today, treatment planning in proton radiotherapy is based on stopping power calculations from densities of X-ray Computed Tomography (CT) images. This causes systematic uncertainties in the calculated proton range in a patient of typically 3-4%, but can become even 10% in bone regions [1,2,3,4,5,6,7,8]. This may lead to no dose in parts of the tumor and too high dose in healthy tissues [1]. A direct measurement of proton stopping powers with high-energy protons will allow reducing these uncertainties and will improve the quality of the treatment. Several studies have shown that a sufficiently accurate radiograph can be obtained by tracking individual protons traversing a phantom (patient) [4,6,10]. Our studies benefit from the gas-filled time projection chambers based on GridPix technology [2], developed at Nikhef, capable of tracking a single proton. A BaF2 crystal measuring the residual energy of protons was used. Proton radiographs of phantom consisting of different tissue-like materials were measured with a 30×30 mm2 150 MeV proton beam. Measurements were simulated with the Geant4 toolkit.First experimental and simulated energy radiographs are in very good agreement [3]. In this paper we focus on simulation studies of the proton scattering angle as it affects the position resolution of the proton energy loss radiograph. By selecting protons with a small scattering angle, the image quality can be improved significantly.

  6. Deformed halo nuclei probed by breakup reactions

    NASA Astrophysics Data System (ADS)

    Nakamura, Takashi

    2013-07-01

    Breakup reactions play important roles in elucidating the structures near the drip lines, such as nuclear halo. The recent experimental results using the Coulomb and nuclear breakup reactions for the neutron-drip-line nuclei at the new-generation RI beam facility, RIBF at RIKEN, are presented. Focuses are put on the results on the newly found halo nucleus 31Ne, which is intriguing also in that this nucleus is in the island-of-inversion and thus could be strongly deformed. The results on other Ne/Mg/Si neutron rich isotopes ranging from N=20 towards N=28 are also briefly reported. The first breakup experiments using SAMURAI facility at RIBF and future perspectives are also presented.

  7. Magnetic spiral arms in galaxy haloes

    NASA Astrophysics Data System (ADS)

    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.

  8. Cool Carbon Stars in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Gigoyan, K. S.

    2016-06-01

    In this paper we report current status of search and study for Faint High Latitude Carbon Stars (FHLCs). Data for more than 1800 spectroscopically confirmed FHLCs are known, which are found thanks to objective prism surveys and photometric selections. More than half of the detected objects belongs to group of dwarf Carbon (dC) stars. Many-sided investigations based on modern astrophysical databases are necessary to study the space distribution of different groups of the FHLC stars and their possible origin in the Halo of our Galaxy. We report about the selection of FHLCs by the spectroscopic surveys: First Byurakan Survey (FBS), Hamburg/ESO Survey (HES), LAMOST Pilot Survey and SDSS, as well as by photometric selection: APM Survey for Cool Carbon Stars in the Galactic Halo, SDSS and 2MASS JHK colours.

  9. Dark-Matter Halos of Tenuous Galaxies

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-03-01

    A series of recent deep-imaging surveys has revealed dozens of lurking ultra-diffuse galaxies (UDGs) in nearby galaxy clusters. A new study provides key information to help us understand the origins of these faint giants.What are UDGs?There are three main possibilities for how UDGs galaxies with the sizes of giants, but luminosities no brighter than those of dwarfs formed:They are tidal dwarfs, created in galactic collisions when streams of matter were pulled away from the parent galaxies and halos to form dwarfs.They are descended from normal galaxies and were then altered by tidal interactions with the galaxy cluster.They are ancient remnant systems large galaxies whose gas was swept away, putting an early halt to star formation. The gas removal did not, however, affect their large dark matter halos, which permitted them to survive in the cluster environment.The key to differentiating between these options is to obtain mass measurements for the UDGs how large are their dark matter halos? In a recent study led by Michael Beasley (Institute of Astrophysics of the Canary Islands, University of La Laguna), a team of astronomers has determined a clever approach for measuring these galaxies masses: examine their globular clusters.Masses from Globular ClustersVCC 1287s mass measurements put it outside of the usual halo-mass vs. stellar-mass relationships for nearby galaxies: it has a significantly higher halo mass than is normal, given its stellar mass. [Adapted from Beasley et al. 2016]Beasley and collaborators selected one UDG, VCC 1287, from the Virgo galaxy cluster, and they obtained spectra of the globular clusters around it using the OSIRIS spectrograph on the Great Canary Telescope. They then determined VCC 1287s total halo mass in two ways: first by using the dynamics of the globular clusters, and then by relying on a relation between total globular cluster mass and halo mass.The two masses they found are in good agreement with each other; both are around 80

  10. Probing satellite haloes with weak gravitational lensing

    NASA Astrophysics Data System (ADS)

    Gillis, Bryan R.; Hudson, Michael J.; Hilbert, Stefan; Hartlap, Jan

    2013-02-01

    We demonstrate the possibility of detecting tidal stripping of dark matter subhaloes within galaxy groups using weak gravitational lensing. We have run ray-tracing simulations on galaxy catalogues from the Millennium Simulation to generate mock shape catalogues. The ray-tracing catalogues assume a halo model for galaxies and groups using various models with different distributions of mass between galaxy and group haloes to simulate different stages of group evolution. Using these mock catalogues, we forecast the lensing signals that will be detected around galaxy groups and satellite galaxies, as well as test two different methods for isolating the satellites' lensing signals. A key challenge is to determine the accuracy to which group centres can be identified. We show that with current and ongoing surveys, it will possible to detect stripping in groups of mass 1012-1015 M⊙.

  11. Stellar halos around Local Group galaxies

    NASA Astrophysics Data System (ADS)

    McConnachie, Alan W.

    2016-08-01

    The Local Group is now home to 102 known galaxies and candidates, with many new faint galaxies continuing to be discovered. The total stellar mass range spanned by this population covers a factor of close to a billion, from the faintest systems with stellar masses of order a few thousand to the Milky Way and Andromeda, with stellar masses of order 1011 M ⊙. Here, I discuss the evidence for stellar halos surrounding Local Group galaxies spanning from dwarf scales (with the case of the Andromeda II dwarf spheroidal), though to intermediate mass systems (M33) and finishing with M31. Evidence of extended stellar populations and merging is seen across the luminosity function, indicating that the processes that lead to halo formation are common at all mass scales.

  12. Accurate mass and velocity functions of dark matter haloes

    NASA Astrophysics Data System (ADS)

    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 (<2 per cent level) model of the distinct halo mass 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 < 2.3 to push for the development of halo occupation distribution using Vmax. The data and the analysis code are made publicly available in the Skies and Universes data base.

  13. Is the Milky Way's hot halo convectively unstable?

    SciTech Connect

    Henley, David B.; Shelton, Robin L.

    2014-03-20

    We investigate the convective stability of two popular types of model of the gas distribution in the hot Galactic halo. We first consider models in which the halo density and temperature decrease exponentially with height above the disk. These halo models were created to account for the fact that, on some sight lines, the halo's X-ray emission lines and absorption lines yield different temperatures, implying that the halo is non-isothermal. We show that the hot gas in these exponential models is convectively unstable if γ < 3/2, where γ is the ratio of the temperature and density scale heights. Using published measurements of γ and its uncertainty, we use Bayes' theorem to infer posterior probability distributions for γ, and hence the probability that the halo is convectively unstable for different sight lines. We find that, if these exponential models are good descriptions of the hot halo gas, at least in the first few kiloparsecs from the plane, the hot halo is reasonably likely to be convectively unstable on two of the three sight lines for which scale height information is available. We also consider more extended models of the halo. While isothermal halo models are convectively stable if the density decreases with distance from the Galaxy, a model of an extended adiabatic halo in hydrostatic equilibrium with the Galaxy's dark matter is on the boundary between stability and instability. However, we find that radiative cooling may perturb this model in the direction of convective instability. If the Galactic halo is indeed convectively unstable, this would argue in favor of supernova activity in the Galactic disk contributing to the heating of the hot halo gas.

  14. Halo naevi with associated vitiligo-like depigmentations: pathogenetic hypothesis.

    PubMed

    van Geel, N; Speeckaert, R; Lambert, J; Mollet, I; De Keyser, S; De Schepper, S; Brochez, L

    2012-06-01

      In analogy with melanoma-associated leucoderma, halo naevi may trigger in some patients the development of additional depigmentations which are in distribution, extent and prognosis not in accordance with classic vitiligo.   The aim of this study was to support the hypothesis that in a subset of halo naevi patients vitiligo-like lesions develop directly linked to the halo phenomenon.   Forty-one patients with halo naevi were examined for the development of depigmentations not corresponding to typical vitiligo lesions.   We identified a subset of five halo naevi patients with additional subtle depigmentations. After the occurrence of multiple halo naevi, they developed leucoderma that showed a different disease pattern than vitiligo (variable asymmetric distribution, limited extent and lack of progression). Moreover, the characteristics of these halo naevi patients with associated leucoderma were different from classic vitiligo patients (high number of halo naevi, absence of family history for vitiligo and absence of autoimmune diseases) and the timing of occurrence of the leucoderma suggested a direct relation with the halo phenomenon.   In this article, we describe in a limited subset of patients with multiple halo naevi discrete depigmentations at distance from halo naevi which may result from a temporary autoimmune process directly linked to the halo phenomenon. This finding illustrates the collateral damage resulting from skin immunosurveillance and may have clinical consequences as the evolution pattern in this subset of patients is less progressive compared with vitiligo. We present clinical data that support this hypothesis and suggest to call it 'halo naevi-associated leucoderma'. © 2011 The Authors. Journal of the European Academy of Dermatology and Venereology © 2011 European Academy of Dermatology and Venereology.

  15. Prognostic value and clinical significance of halo naevi regarding vitiligo.

    PubMed

    van Geel, N; Vandenhaute, S; Speeckaert, R; Brochez, L; Mollet, I; De Cooman, L; Lambert, J

    2011-04-01

    Vitiligo and halo naevi can present together or separately. Whether they are different entities remains unclear. To assess the clinical significance of halo naevi, both with respect to the future development of vitiligo, and to the clinical profile and course of vitiligo. In total, 291 patients were included in this study: patients with only halo naevi (group 1; n=40), patients with generalized vitiligo without halo naevi (group 2; n=173) and patients with generalized vitiligo with halo naevi (group 3; n=78). Patients with only halo naevi (group 1) reported significantly less associated autoimmune disease (P=0·001), were less likely to have a family history of vitiligo (P=0·013) and were less likely to have presence of Koebner phenomenon (P<0·001) compared with patients with generalized vitiligo (groups 2+3). Multiple halo naevi (≥3) were significantly more frequently observed (P=0·002) in patients from group 1 compared with patients from group 3. In group 3, halo naevi were reported prior to the development of vitiligo in 61% (mean±SD time interval of 33·7±5·17months). No significant correlation was observed between the presence of halo naevi and the extent, activity or subtype of vitiligo. However, halo naevi in patients with vitiligo significantly reduced the risk for associated autoimmune diseases, and age at onset of vitiligo was significantly lower compared with patients with vitiligo without halo naevi (P<0·001). Our results support the hypothesis that halo naevi can represent a distinct condition. In a subset of patients, the occurrence of halo naevi may be an initiating factor in the pathogenesis of vitiligo. © 2011 The Authors. BJD © 2011 British Association of Dermatologists.

  16. Dynamic Colloidal Stabilization by Nanoparticle Halos

    NASA Astrophysics Data System (ADS)

    Karanikas, S.; Louis, A. A.

    2004-12-01

    We explore the conditions under which colloids can be stabilized by the addition of smaller particles. The largest repulsive barriers between colloids occur when the added particles repel each other with soft interactions, leading to an accumulation near the colloid surfaces. At lower densities these layers of mobile particles (nanoparticle halos) result in stabilization, but when too many are added, the interactions become attractive again. We systematically study these effects—accumulation repulsion, reentrant attraction, and bridging—by accurate integral equation techniques.

  17. Stellar Spirals in Triaxial Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Hu, Shaoran; Sijacki, Debora

    2017-03-01

    Two-armed grand-design spirals may form if the shape of its dark matter halo changes abruptly enough. The feasibility of such a mechanism is tested in realistic simulations. The interplay of such externally-driven spirals and self-induced transient spirals is then studied. Subhaloes are also found to lead to transient grand-design spiral structures when they impact the disk.

  18. Splashback Shells of Cold Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Mansfield, Philip; Kravtsov, Andrey V.; Diemer, Benedikt

    2017-05-01

    The density field in the outskirts of dark matter halos is discontinuous as a result of a caustic formed by matter at its first apocenter after infall. In this paper, we present an algorithm to identify the “splashback shell” formed by these apocenters in individual simulated halos using only a single snapshot of the density field. We implement this algorithm in the code Shellfish (SHELL Finding In Spheroidal Halos) and demonstrate that the code identifies splashback shells correctly and measures their properties with an accuracy of < 5 % for halos with more than 50,000 particles and mass accretion rates of {{{Γ }}}{DK14}> 0.5. Using Shellfish, we present the first estimates for several basic properties of individual splashback shells, such as radius, {R}{sp}, mass, and overdensity, and provide fits to the distribution of these quantities as functions of {{{Γ }}}{DK14}, {ν }200{{m}}, and z. We confirm previous findings that {R}{sp} decreases with increasing {{{Γ }}}{DK14}, but we show that, independent of accretion rate, it also decreases with increasing {ν }200{{m}}. We also study the 3D structures of these shells and find that they generally have non-ellipsoidal oval shapes. We find that splashback radii estimated by Shellfish are 20%-30% larger than those estimated in previous studies from stacked density profiles at high accretion rates. We demonstrate that the latter are biased low owing to the contribution of high-mass subhalos to these profiles, and we show that using the median instead of mean density in each radial bin mitigates the effect of substructure on density profiles and removes the bias.

  19. The Halo B2B Studio

    NASA Astrophysics Data System (ADS)

    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.

  20. The Vertical Structure of the Halo Rotation

    NASA Astrophysics Data System (ADS)

    Kinman, T. D.; Bragaglia, A.; Cacciari, C.; Buzzoni, A.; Spagna, A.

    New GSC-II proper motions and radial velocities of RR Lyrae and Blue Horizontal Branch stars near the North Galactic Pole are used to show that the Galactic Halo 5 kpc above the Plane has a significantly retrograde galactic rotation. Streaming motions cannot be excluded. Based on observations collected at the Kitt Peak and TNG Observatories. Funded by MIUR-Cofin 2001 (PI: Gratton).

  1. Oxygen vs. Age in Halo Field Stars

    NASA Astrophysics Data System (ADS)

    Laird, J. B.; Sneden, C.

    1996-04-01

    Oxygen abundances as a function of age are presented for a sample of halo field stars near the main sequence turn-off. We have measured oxygen abundances using the infrared oxygen triplet, and ages have previously been determined for these stars by Schuster & Nissen and Marquez & Schuster using Stromgren photometry and theoretical isochrones. The age spread observed among globular clusters and among the field stars indicates that the formation of the halo occurred over at least several billion years. The relatively shorter time scale for the contribution of Type Ia supernovae should have produced a significant decrease in the oxygen-to-iron (O/Fe) ratio over this time, leading to a significant variation in [O/Fe] among stars with different ages. We do not find the expected correlation of O/Fe and age. This result suggests that either the timescale for Type Ia supernovae is significantly longer than 1 Gyr or the stars of different ages formed in chemically isolated regions of the halo.

  2. Proton decay theory

    SciTech Connect

    Marciano, W.J.

    1983-01-01

    Topics include minimal SU(5) predictions, gauge boson mediated proton decay, uncertainties in tau/sub p/, Higgs scalar effects, proton decay via Higgs scalars, supersymmetric SU(5), dimension 5 operators and proton decay, and Higgs scalars and proton decay. (WHK)

  3. Synchrotron based proton drivers

    SciTech Connect

    Weiren Chou

    2002-09-19

    Proton drivers are the proton sources that produce intense short proton bunches. They have a wide range of applications. This paper discusses the proton drivers based on high-intensity proton synchrotrons. It gives a review of the high-intensity proton sources over the world and a brief report on recent developments in this field in the U.S. high-energy physics (HEP) community. The Fermilab Proton Driver is used as a case study for a number of challenging technical design issues.

  4. Epicardial halo phenomenon: a guide for pericardiocentesis?

    PubMed

    Ristić, Arsen D; Wagner, Hans-Joachim; Maksimović, Ružica; Maisch, Bernhard

    2013-05-01

    The epicardial halo delineates the heart shadow in fluoroscopy. To establish whether the sign is applicable to pericardiocentesis guidance, three investigators evaluated its intensity as absent = grade 0, indistinct = 0.5, clear = 1, intensive = 2 in posterior-anterior (PA) and lateral fluoroscopies recorded before pericardiocentesis or cardiac catheterization (Philips Integris-II BH3000). Three populations were studied: (a) 32 patients with pericardial effusion (PE group), 53.1 % males, aged 53.9 ± 13.9 years; (b) 14 patients with perimyocarditis (PM group), 64.3 % males, aged 51.6 ± 14.4 years; and (c) 46 coronary patients (CAD group), no PE, 95.6 % males, aged 67.3 ± 11.8 years. The intensity of the halo phenomenon was highest in patients with PE, lowest in patients with CAD, and intermediate in patients with PM (median sum of grades in PA/lateral view: 4/5 vs. 2/2.5 vs. 3/3, respectively) (p < 0.01). The halo phenomenon correlated well with HR and echocardiographic PE size in both angiographic views. The correlation with body mass index (BMI) and age was significant only in the lateral view and with PE volume only in the PA view. The sensitivity of the halo sign for PE was 84.1 % in PA and 92.0 % in lateral views. In 10/32 PE patients, the evaluation of the sign was repeated after PE drainage, revealing lower grades both in PA and in lateral views (p < 0.01). In conclusion, the epicardial halo sign is highly sensitive for the detection of a PE; it correlates well in at least one angiographic projection with the PE volume, HR, age, BMI, and the PE size in echocardiography and could be therefore applied as a safety guide for pericardiocentesis.

  5. The Halo of NGC 2438 scrutinized

    NASA Astrophysics Data System (ADS)

    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

  6. Revisiting the Bulge-Halo Conspiracy. I. Dependence on Galaxy Properties and Halo Mass

    NASA Astrophysics Data System (ADS)

    Shankar, Francesco; Sonnenfeld, Alessandro; Mamon, Gary A.; Chae, Kyu-Hyun; Gavazzi, Raphael; Treu, Tommaso; Diemer, Benedikt; Nipoti, Carlo; Buchan, Stewart; Bernardi, Mariangela; Sheth, Ravi; Huertas-Company, Marc

    2017-05-01

    We carry out a systematic investigation of the total mass density profile of massive ({log} {M}{star}/{M}⊙ ≳ 11.3) early-type galaxies and its dependence on galactic properties and host halo mass with the aid of a variety of lensing/dynamical data and large mock galaxy catalogs. The latter are produced via semi-empirical models that, by design, are based on just a few basic input assumptions. Galaxies with measured stellar masses, effective radii, and Sérsic indices, are assigned, via abundance matching relations, host dark matter halos characterized by a typical ΛCDM profile. Our main results are as follows. (1) In line with observational evidence, our semi-empirical models naturally predict that the total, mass-weighted density slope at the effective radius γ‧ is not universal, steepening for more compact and/or massive galaxies, but flattening with increasing host halo mass. (2) Models characterized by a Salpeter or variable initial mass function (IMF) and uncontracted dark matter profiles are in good agreement with the data, while a Chabrier IMF and/or adiabatic contractions/expansions of the dark matter halos are highly disfavored. (3) Currently available data on the mass density profiles of very massive galaxies ({log} {M}{star}/{M}⊙ ≳ 12), with {M}{halo}≳ 3× {10}14 {M}⊙ , favor instead models with a stellar profile flatter than a Sérsic one in the very inner regions (r ≲ 3-5 kpc), and a cored NFW or Einasto dark matter profile with median halo concentration a factor of ˜2 or ≲1.3, respectively, higher than those typically predicted by N-body numerical simulations.

  7. Resolved Stellar Halos of M87 and NGC 5128

    NASA Astrophysics Data System (ADS)

    Bird, Sarah A.; Harris, William; Flynn, Chris; Blakeslee, John P.; Valtonen, Mauri

    2015-08-01

    We search halo fields of two giant elliptical galaxies: M87, using HST images at 10 kpc from the center, and NGC 5128 (Cen A), using VIMOS VLT images at 65 kpc from the center and archival HST data from 8 to 38 kpc from the center. We resolve thousands of red-giant-branch stars in these stellar halo fields using V and I filters, and, in addition, measure the metallicity using stellar isochrones. In Cen A, we find that the density of metal-rich and metal-poor halo stars falls off with the same slope in the de Vaucouleurs' law profile, from the inner halo of 8 kpc out to 70 kpc, with no sign of a transition to dominance by metal-poor stars. We also find that the metallicity distribution of the inner stellar halo of M87 is most similar to that of NGC 5128's inner stellar halo.

  8. Reaction cross sections of 14B and 8He on proton targets for the separation of proton and neutron density distributions

    NASA Astrophysics Data System (ADS)

    Tanaka, Masaomi; Fukuda, Mitunori; Nishimura, Daiki; Suzuki, Shinji; Takechi, Maya; Mihara, Mototsugu; Matsuta, Kensaku; Oono, Junnichi; Yamaoka, Shintaro; Ohtsubo, Takashi; Izumikawa, Takuji; Nagashima, Masayuki; Suzuki, Takeshi; Yamaguchi, Takayuki; Kitagawa, Atsushi; Fukuda, Shigekazu; Sato, Shinji; Himac H093 Collaboration

    2014-09-01

    In order to discuss the exotic surface structures of neutron- / proton-rich nuclei such as halo and skin in detail, it is important to clarify the distributions of neutron and proton respectively. For this purpose, we utilize the isospin (p-p or p-n) asymmetry of nucleon-nucleon total cross sections in the intermediate energy region. We employed a Proton target as the isospin asymmetric target, which is the most asymmetric one. Also, we employed Be, C, and Al targets which are isospin symmetric to be contrast with Proton target. In the present work, we have measured reaction cross sections for 14B and 8He on Proton, Be, C, and Al targets at intermediate energies. The experiments were carried out at the HIMAC heavy ion synchrotron facility, Japan. We will report results of the analyses.

  9. Proton Therapy - Accelerating Protons to Save Lives

    SciTech Connect

    Keppel, Cynthia

    2011-10-25

    In 1946, physicist Robert Wilson first suggested that protons could be used as a form of radiation therapy in the treatment of cancer because of the sharp drop-off that occurs on the distal edge of the radiation dose. Research soon confirmed that high-energy protons were particularly suitable for treating tumors near critical structures, such as the heart and spinal column. The precision with which protons can be delivered means that more radiation can be deposited into the tumor while the surrounding healthy tissue receives substantially less or, in some cases, no radiation. Since these times, particle accelerators have continuously been used in cancer therapy and today new facilities specifically designed for proton therapy are being built in many countries. Proton therapy has been hailed as a revolutionary cancer treatment, with higher cure rates and fewer side effects than traditional X-ray photon radiation therapy. Proton therapy is the modality of choice for treating certain small tumors of the eye, head or neck. Because it exposes less of the tissue surrounding a tumor to the dosage, proton therapy lowers the risk of secondary cancers later in life - especially important for young children. To date, over 80,000 patients worldwide have been treated with protons. Currently, there are nine proton radiation therapy facilities operating in the United States, one at the Hampton University Proton Therapy Institute. An overview of the treatment technology and this new center will be presented.

  10. Data-Parallel Halo Finder Operator in PISTON

    SciTech Connect

    Widanagamaachchi, W. N.

    2012-08-01

    PISTON is a portable framework which supports the development of visualization and analysis operators using a platform-independent, data-parallel programming model. Operators such as isosurface, cut-surface and threshold have been implemented in this framework, with the exact same operator code achieving good parallel performance on different architectures. An important analysis operator in cosmology is the halo finder. A halo is a cluster of particles and is considered a common feature of interest found in cosmology data. As the number of cosmological simulations carried out in the recent past has increased, the resultant data of these simulations and the required analysis tasks have increased as well. As a consequence, there is a need to develop scalable and efficient tools to carry out the needed analysis. Therefore, we are currently implementing a halo finder operator using PISTON. Researchers have developed a wide variety of techniques to identify halos in raw particle data. The most basic algorithm is the friend-of-friends (FOF) halo finder, where the particles are clustered based on two parameters: linking length and halo size. In a FOF halo finder, all particles which lie within the linking length are considered as one halo and the halos are filtered based on the halo size parameter. A naive implementation of a FOF halo finder compares each and every particle pair, requiring O(n{sup 2}) operations. Our data-parallel halo finder operator uses a balanced k-d tree to reduce this number of operations in the average case, and implements the algorithm using only the data-parallel primitives in order to achieve portability and performance.

  11. The role of primary 16O as a neutron poison in AGB stars and fluorine primary production at halo metallicities.

    NASA Astrophysics Data System (ADS)

    Gallino, R.; Bisterzo, S.; Cristallo, S.; Straniero, O.

    The discovery of a historical bug in the s-post-process AGB code obtained so far by the Torino group forced us to reconsider the role of primary 16O in the 13C-pocket, produced by the 13C(alpha , n)16O reaction, as important neutron poison for the build up of the s-elements at Halo metallicities. The effect is noticeable only for the highest 13C-pocket efficiencies (cases ST*2 and ST). For Galactic disc metallicities, the bug effect is negligible. A comparative analysis of the neutron poison effect of other primary isotopes (12C, 22Ne and its progenies) is presented. The effect of proton captures, by 14N(n, p)14C, boosts a primary production of fluorine in halo AGB stars, with [F/Fe] comparable to [C/Fe], without affecting the s-elements production.

  12. Observation of Parametric X-Rays Produced by 400-GeV/C Protons in Bent Crystals

    SciTech Connect

    Scandale, W.; Arduini, G.; Assmann, R.; Cerutti, F.; Gilardoni, S.; Christiansen, J.; Laface, E.; Losito, R.; Masi, A.; Metral, E.; Mirarchi, D.; Montesano, S.; Previtali, V.; Redaelli, S.; Valentino, G.; Schoofs, P.; Smirnov, G.; Tlustos, L.; Bagli, E.; Baricordi, S.; Dalpiaz, P.; /Ferrara U. /INFN, Ferrara /Ferrara U. /INFN, Ferrara /Ferrara U. /INFN, Ferrara /Ferrara U. /INFN, Ferrara /Frascati /Frascati /Frascati /INFN, Legnaro /INFN, Legnaro /INFN, Legnaro /INFN, Legnaro /INFN, Legnaro /INFN, Legnaro /INFN, Rome /INFN, Rome /INFN, Rome /INFN, Rome /INFN, Naples /Serpukhov, IHEP /Serpukhov, IHEP /Serpukhov, IHEP /Serpukhov, IHEP /Serpukhov, IHEP /Dubna, JINR /Dubna, JINR /St. Petersburg, INP /St. Petersburg, INP /St. Petersburg, INP /St. Petersburg, INP /Imperial Coll., London /Imperial Coll., London /Imperial Coll., London /Imperial Coll., London /Imperial Coll., London /Imperial Coll., London /Imperial Coll., London /Imperial Coll., London /Brookhaven /SLAC /SLAC /SLAC /IPTP, Dubna /Tomsk Polytechnic U. /Tomsk Polytechnic U.

    2012-05-07

    Spectral maxima of parametric X-ray radiation (PXR) produced by 400 GeV/c protons in bent silicon crystals aligned with the beam have been observed in an experiment at the H8 external beam of the CERN SPS. The total yield of PXR photons was about 10{sup -6} per proton. Agreement between calculations and the experimental data shows that the PXR kinematic theory is valid for bent crystals with sufficiently small curvature as used in the experiment. The intensity of PXR emitted from halo protons in a bent crystal used as a primary collimator in a circular accelerator may be considered as a possible tool to control its crystal structure, which is slowly damaged because of irradiation. The intensity distribution of PXR peaks depends on the crystal thickness intersected by the beam, which changes for different orientations of a crystal collimator. This dependence may be used to control crystal collimator alignment by analyzing PXR spectra produced by halo protons.

  13. The Angular Momentum Distribution within Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Chen, D.; Jing, Y.

    We study the angular momentum profile of dark matter halos for a statistical sample drawn from a set of high-resolution cosmological simulations of 2563 particles. Two typical Cold Dark Matter (CDM) models have been analyzed, and the halos are selected to have at least 3× 104 particles in order to reliably measure the angular momentum profile. In contrast with the recent claims of Bullock et al. (2001), we find that the degree of misalignment of angular momentum within a halo is very high. About 50 percent of halos have more than 10 percent of halo mass in the mass of negative angular momentum j. After the mass of negative j is excluded, the cumulative mass function M(halos (˜ 50%) which exhibit systematic deviations from the universal function. Our results, however, are broadly in good agreement with the recent work of van den Bosch et al. (2002). We also study the angular momentum profile of halos in a Warm Dark Matter (WDM) model and a Self-Interacting Dark Matter (SIDM) model. We find that the angular momentum profile of halos in the WDM is statistically indistinguishable from that in the CDM model, but the angular momentum of halos in the SIDM is reduced by the self-interaction of dark matter.

  14. Angular Momentum Profiles of Warm Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Bullock, James S.; Kravtsov, and Andrey V.; Colín, Pedro

    2002-01-01

    We compare the specific angular momentum profiles of virialized dark halos in cold dark matter (CDM) and warm dark matter (WDM) models, using high-resolution dissipationless simulations. The simulations were initialized using the same set of modes, except on small scales, where the power was suppressed in WDM below the filtering length. Remarkably, WDM as well as CDM halos are well described by the two-parameter angular momentum profile of Bullock and coworkers, even though the halo masses are below the filtering scale of the WDM. Although the best-fit shape parameters change quantitatively for individual halos in the two simulations, we find no systematic variation in profile shapes as a function of the dark matter type. The scatter in shape parameters is significantly smaller for the WDM halos, suggesting that substructure and/or merging history plays a role in producing scatter about the mean angular momentum distribution, but that the average angular momentum profiles of halos originate from larger scale phenomena or a mechanism associated with the virialization process. The known mismatch between the angular momentum distributions of dark halos and disk galaxies is, therefore, present in WDM as well as CDM models. Our WDM halos tend to have a less coherent (more misaligned) angular momentum structure and smaller spin parameters than do their CDM counterparts, although we caution that this result is based on a small number of halos.

  15. Two stellar components in the halo of the Milky Way.

    PubMed

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

    2007-12-13

    The halo of the Milky Way provides unique elemental abundance and kinematic information on the first objects to form in the Universe, and this information can be used to tightly constrain models of galaxy formation and evolution. Although the halo was once considered a single component, evidence for its dichotomy has slowly emerged in recent years from inspection of small samples of halo objects. Here we show that the halo is indeed clearly divisible into two broadly overlapping structural components--an inner and an outer halo--that exhibit different spatial density profiles, stellar orbits and stellar metallicities (abundances of elements heavier than helium). The inner halo has a modest net prograde rotation, whereas the outer halo exhibits a net retrograde rotation and a peak metallicity one-third that of the inner halo. These properties indicate that the individual halo components probably formed in fundamentally different ways, through successive dissipational (inner) and dissipationless (outer) mergers and tidal disruption of proto-Galactic clumps.

  16. Squeezing the halo bispectrum: a test of bias models

    NASA Astrophysics Data System (ADS)

    Moradinezhad Dizgah, Azadeh; Chan, Kwan Chuen; Noreña, Jorge; Biagetti, Matteo; Desjacques, Vincent

    2016-09-01

    We study the halo-matter cross bispectrum in the presence of primordial non-Gaussianity of the local type. We restrict ourselves to the squeezed limit, for which the calculation are straightforward, and perform the measurements in the initial conditions of N-body simulations, to mitigate the contamination induced by nonlinear gravitational evolution. Interestingly, the halo-matter cross bispectrum is not trivial even in this simple limit as it is strongly sensitive to the scale-dependence of the quadratic and third-order halo bias. Therefore, it can be used to test biasing prescriptions. We consider three different prescription for halo clustering: excursion set peaks (ESP), local bias and a model in which the halo bias parameters are explicitly derived from a peak-background split. In all cases, the model parameters are fully constrained with statistics other than the cross bispectrum. We measure the cross bispectrum involving one halo fluctuation field and two mass overdensity fields for various halo masses and collapse redshifts. We find that the ESP is in reasonably good agreement with the numerical data, while the other alternatives we consider fail in various cases. This suggests that the scale-dependence of halo bias also is a crucial ingredient to the squeezed limit of the halo bispectrum.

  17. Halo particle confinement in the VLHC using optical stochastic cooling

    SciTech Connect

    Zholents, Alexander; Barletta, W.; Chattopadhyay, S.; Zolotorev, M.

    2000-06-01

    Beam halo particles following the extreme trajectories near the physical aperture limit radiate Smith-Purcell radiation when moving over a diffraction grating. This grating can be used as a pick-up and a kicker for optical stochastic cooling of the halo particles. In this application cooling would have the effect of slowing down the halo particle diffusion onto the aperture. Cooling efficiency would quickly diminish with the distance from the aperture and would only affect the halo particles. A preliminary analysis of this system is considered.

  18. N-body dark matter haloes with simple hierarchical histories

    NASA Astrophysics Data System (ADS)

    Jiang, Lilian; Helly, John C.; Cole, Shaun; Frenk, Carlos S.

    2014-05-01

    We present a new algorithm which groups the subhaloes found in cosmological N-body simulations by structure finders such as SUBFIND into dark matter haloes whose formation histories are strictly hierarchical. One advantage of these `Dhaloes' over the commonly used friends-of-friends (FoF) haloes is that they retain their individual identity in the cases when FoF haloes are artificially merged by tenuous bridges of particles or by an overlap of their outer diffuse haloes. Dhaloes are thus well suited for modelling galaxy formation and their merger trees form the basis of the Durham semi-analytic galaxy formation model, GALFORM. Applying the Dhalo construction to the Λ cold dark matter Millennium II Simulation, we find that approximately 90 per cent of Dhaloes have a one-to-one, bijective match with a corresponding FoF halo. The remaining 10 per cent are typically secondary components of large FoF haloes. Although the mass functions of both types of haloes are similar, the mass of Dhaloes correlates much more tightly with the virial mass, M200, than FoF haloes. Approximately 80 per cent of FoF and bijective and non-bijective Dhaloes are relaxed according to standard criteria. For these relaxed haloes, all three types have similar concentration-M200 relations and, at fixed mass, the concentration distributions are described accurately by log-normal distributions.

  19. Milky Way is Surrounded by Huge Halo of Hot Gas

    NASA Image and Video Library

    2012-09-24

    Astronomers have used Chandra to find evidence that our Milky Way Galaxy is embedded in an enormous halo of hot gas that extends for hundreds of thousands of light years. This artist's illustration shows the halo of hot gas, in blue, around the Milky Way and two small neighboring galaxies. The mass of the halo is estimated to be comparable to the mass of all the stars in the Milky Way galaxy. If the size and mass of this gas halo is confirmed, it could be the solution to the "missing-baryon" problem for the Galaxy.

  20. Reversed Halo Sign: Presents in Different Pulmonary Diseases

    PubMed Central

    Zhan, Xi; Zhang, Lei; Wang, Zheng; Jin, Mulan; Liu, Min; Tong, Zhaohui

    2015-01-01

    Objective To observe the incidence of reversed halo sign in different pulmonary diseases and the pathological correspondence of reversed halo sign. Methods Retrospectively studied the high resolution computer tomography scans of all the patients who were admitted in our department with abnormal pulmonary imaging, from 1st of January 2011 to 31st of December 2013, and all the cases with reversed halo sign on the high resolution computer tomography were collected. Clinical data such as pathological findings and confirmed diagnosis of the patients with reversed halo sign on the high resolution computer tomography scan were collected and summarized. Results Of 1546 abnormal High resolution computer tomography scans 108 had a reverse halo sign present, including 108 cases were observed with reversed halo sign in the high resolution computer tomography, including 40 cases of pulmonary tuberculosis, 43 cases of cryptogenic organizing pneumonia, 16 cases of lung cancer, 7 cases of sarcoidosis, and 1 case of pulmonary cryptococcosis, 1 case of granulomatosis with polyangiitis. Reversed halo sign had a higher incidence in granulomatous diseases (16.28%) compared with non-granulomatous diseases (9.97%). Conclusions Reversed halo sign is relatively non specific; it can be observed in different lung diseases, and different phases of diseases; reversed halo sign is more commonly found in granulomatous diseases compared with non-granulomatous diseases, and is most commonly observed in pulmonary tuberculosis among the granulomatous diseases, and in cryptogenic organizing pneumonia among the non-granulomatous diseases. PMID:26083865

  1. Reversed Halo Sign: Presents in Different Pulmonary Diseases.

    PubMed

    Zhan, Xi; Zhang, Lei; Wang, Zheng; Jin, Mulan; Liu, Min; Tong, Zhaohui

    2015-01-01

    To observe the incidence of reversed halo sign in different pulmonary diseases and the pathological correspondence of reversed halo sign. Retrospectively studied the high resolution computer tomography scans of all the patients who were admitted in our department with abnormal pulmonary imaging, from 1st of January 2011 to 31st of December 2013, and all the cases with reversed halo sign on the high resolution computer tomography were collected. Clinical data such as pathological findings and confirmed diagnosis of the patients with reversed halo sign on the high resolution computer tomography scan were collected and summarized. Of 1546 abnormal High resolution computer tomography scans 108 had a reverse halo sign present, including 108 cases were observed with reversed halo sign in the high resolution computer tomography, including 40 cases of pulmonary tuberculosis, 43 cases of cryptogenic organizing pneumonia, 16 cases of lung cancer, 7 cases of sarcoidosis, and 1 case of pulmonary cryptococcosis, 1 case of granulomatosis with polyangiitis. Reversed halo sign had a higher incidence in granulomatous diseases (16.28%) compared with non-granulomatous diseases (9.97%). Reversed halo sign is relatively non specific; it can be observed in different lung diseases, and different phases of diseases; reversed halo sign is more commonly found in granulomatous diseases compared with non-granulomatous diseases, and is most commonly observed in pulmonary tuberculosis among the granulomatous diseases, and in cryptogenic organizing pneumonia among the non-granulomatous diseases.

  2. Light source halos in night vision goggles: psychophysical assessments

    NASA Astrophysics Data System (ADS)

    Craig, Greg; Macuda, Todd; Thomas, Paul; Allison, Rob; Jennings, Sion

    2005-05-01

    Anecdotal reports by pilots flying with Night Vision Goggles (NVGs) in urban environments suggest that halos produced by bright light sources impact flight performance. The current study developed a methodology to examine the impact of viewing distance on perceived halo size. This was a first step in characterizing the subtle phenomenon of halo. Observers provided absolute size estimates of halos generated by a red LED at several viewing distances. Physical measurements of these halos were also recorded. The results indicated that the perceived halo linear size decreased as viewing distance was decreased. Further, the data showed that halos subtended a constant visual angle on the goggles (1°48", +/-7") irrespective of distance up to 75". This invariance with distance may impact pilot visual performance. For example, the counterintuitive apparent contraction of halo size with decreasing viewing distance may impact estimates of closure rates and of the spatial layout of light sources in the scene. Preliminary results suggest that halo is a dynamic phenomenon that requires further research to characterize the specific perceptual effects that it might have on pilot performance.

  3. Effects of image intensifier halo on perceived layout

    NASA Astrophysics Data System (ADS)

    Zacher, James E.; Brandwood, Tracey; Thomas, Paul; Vinnikov, Margarita; Xu, Gancun; Jennings, Sion; Macuda, Todd; Palmisano, Stephan A.; Craig, Greg; Wilcox, Laurie; Allison, Robert S.

    2007-04-01

    Night vision devices (NVDs) or night-vision goggles (NVGs) based on image intensifiers improve nighttime visibility and extend night operations for military and increasingly civil aviation. However, NVG imagery is not equivalent to daytime vision and impaired depth and motion perception has been noted. One potential cause of impaired perceptions of space and environmental layout is NVG halo, where bright light sources appear to be surrounded by a disc-like halo. In this study we measured the characteristics of NVG halo psychophysically and objectively and then evaluated the influence of halo on perceived environmental layout in a simulation experiment. Halos are generated in the device and are not directly related to the spatial layout of the scene. We found that, when visible, halo image (i.e. angular) size was only weakly dependent on both source intensity and distance although halo intensity did vary with effective source intensity. The size of halo images surrounding lights sources are independent of the source distance and thus do not obey the normal laws of perspective. In simulation experiments we investigated the effect of NVG halo on judgements of observer attitude with respect to the ground during simulated flight. We discuss the results in terms of NVG design and of the ability of human operators to compensate for perceptual distortions.

  4. Mapping stellar content to dark matter haloes - II. Halo mass is the main driver of galaxy quenching

    NASA Astrophysics Data System (ADS)

    Zu, Ying; Mandelbaum, Rachel

    2016-04-01

    We develop a simple yet comprehensive method to distinguish the underlying drivers of galaxy quenching, using the clustering and galaxy-galaxy lensing of red and blue galaxies in Sloan Digital Sky Survey. Building on the iHOD framework developed by Zu & Mandelbaum, we consider two quenching scenarios: (1) a `halo' quenching model in which halo mass is the sole driver for turning off star formation in both centrals and satellites; and (2) a `hybrid' quenching model in which the quenched fraction of galaxies depends on their stellar mass, while the satellite quenching has an extra dependence on halo mass. The two best-fitting models describe the red galaxy clustering and lensing equally well, but halo quenching provides significantly better fits to the blue galaxies above 1011 h-2 M⊙. The halo quenching model also correctly predicts the average halo mass of the red and blue centrals, showing excellent agreement with the direct weak lensing measurements of locally brightest galaxies. Models in which quenching is not tied to halo mass, including an age-matching model in which galaxy colour depends on halo age at fixed M*, fail to reproduce the observed halo mass for massive blue centrals. We find similar critical halo masses responsible for the quenching of centrals and satellites (˜1.5 × 1012 h-1 M⊙), hinting at a uniform quenching mechanism for both, e.g. the virial shock heating of infalling gas. The success of the iHOD halo quenching model provides strong evidence that the physical mechanism that quenches star formation in galaxies is tied principally to the masses of their dark matter haloes rather than the properties of their stellar components.

  5. 77 FR 75672 - Manufacturer of Controlled Substances, Notice of Registration, Halo Pharmaceutical, Inc.

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-21

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

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

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-20

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

  7. The accreted stellar halo as a window on halo assembly in L* galaxies

    NASA Astrophysics Data System (ADS)

    Amorisco, Nicola C.

    2017-07-01

    Theory and observations agree that the accreted stellar haloes (ASHs) of Milky Way-like galaxies display significant scatter. I take advantage of this stochasticity to invert the link between halo assembly history (HAH) and ASH, using mock ASHs corresponding to 750 ΛCDM HAHs, sharing a final virial mass of Mh(z = 0) = 1012.25M⊙. Hosts with poor/rich ASHs assemble following orthogonal growth-patterns. Hosts with rich ASHs experience accretion events (AEs) with high virial mass ratios (HVMRs, Ms/Mh ≳ 0.1) at 0.5 ≲ zinfall ≲ 1.5, in a phase of fast growth. This maximizes the accreted stellar mass under the condition these satellites are disrupted by z = 0. At similar times, hosts with poor ASHs grow slowly through minor mergers, with only very recent HVMR AEs: this results in a globally more abundant satellite population and in distinctive surviving massive satellites (stellar mass log Ms, */M⊙ ≳ 9). Several properties of the Milky Way are in agreement with the predictions of this framework for hosts with poor, concentrated ASHs, including: (i) the recent infall of Sagittarius and Magellanic Clouds, (ii) the likely higher-than-average concentration of its dark halo and (iii) the signatures of fast chemical enrichment of a sizable fraction of its halo stellar populations.

  8. Composition of Low-redshift Halo Gas

    NASA Astrophysics Data System (ADS)

    Cen, Renyue

    2013-06-01

    Halo gas in low-z (z < 0.5) >=0.1 L * galaxies in high-resolution, large-scale cosmological hydrodynamic simulations is examined with respect to three components: cold, warm, and hot with temperatures of <105, 105-6, and >106 K, respectively. Utilizing O VI λλ1032, 1038 absorption lines, the warm component is compared to observations, and agreement is found with respect to the galaxy-O VI line correlation, the ratio of the O VI line incidence rate in blue to red galaxies, and the amount of O VI mass in star-forming galaxies. A detailed account of the sources of warm halo gas (stellar feedback heating, gravitational shock heating, and accretion from the intergalactic medium), inflowing and outflowing warm halo gas metallicity disparities, and their dependencies on galaxy types and environment is also presented. With the warm component securely anchored, our simulations make the following additional predictions. First, cold gas is the primary component in inner regions with its mass comprising 50% of all gas within galactocentric radius r = (30, 150) kpc in (red, blue) galaxies. Second, at r > (30, 200) kpc in (red, blue) galaxies the hot component becomes the majority. Third, the warm component is a perpetual minority, with its contribution peaking at ~30% at r = 100-300 kpc in blue galaxies and never exceeding 5% in red galaxies. The significant amount of cold gas in low-z early-type galaxies, which was found in simulations and in agreement with recent observations (Thom et al.), is intriguing, as is the dominance of hot gas at large radii in blue galaxies.

  9. Baryonic distributions in galaxy dark matter halos

    NASA Astrophysics Data System (ADS)

    Richards, Emily E.

    In our best current understanding of the growth of structure in the Universe, visibly complex distributions of gas and stars form and evolve into a wide range of galaxies inside overdensities of dark matter. Re-creating the observed diversity in the organization of baryonic mass within dark matter halos represents a key challenge for galaxy formation models. In this dissertation, I constrain the distribution of baryonic and non-baryonic matter in a statistically representative sample of 44 nearby galaxies defined from the Extended Disk Galaxy Exploration Science (EDGES) survey to address the growth of galaxy disks in dark matter halos. I trace the gravitational potentials of each galaxy using rotation curves derived from new and archival radio synthesis observations of neutral hydrogen (HI). The measured rotation curves are decomposed into baryonic and dark matter halo components using 3.6 mum images for the stellar content, the HI observations for the atomic gas component, and, when available, CO data from the literature for the molecular gas component. The HI kinematics are supplemented with optical integral field spectroscopic (IFS) observations to measure the central ionized gas kinematics in 26 galaxies. Distributions of baryonic-to-total mass ratios are determined from the rotation curve decompositions under different assumptions about the contribution of the stellar component, and are compared to global and radial properties of the dominant stellar populations extracted from optical and near-infrared photometry. Galaxies are grouped into clusters of similar baryonic-to-total mass distributions to examine whether they also exhibit similar star and gas properties. The radial distribution of baryonic-to-total mass in a galaxy does not appear to correlate with any characteristics of its star formation history. This result encapsulates the challenge facing simulations to create galaxies which evolve with different star formation histories but similar

  10. COMPOSITION OF LOW-REDSHIFT HALO GAS

    SciTech Connect

    Cen Renyue

    2013-06-20

    Halo gas in low-z (z < 0.5) {>=}0.1 L{sub *} galaxies in high-resolution, large-scale cosmological hydrodynamic simulations is examined with respect to three components: cold, warm, and hot with temperatures of <10{sup 5}, 10{sup 5-6}, and >10{sup 6} K, respectively. Utilizing O VI {lambda}{lambda}1032, 1038 absorption lines, the warm component is compared to observations, and agreement is found with respect to the galaxy-O VI line correlation, the ratio of the O VI line incidence rate in blue to red galaxies, and the amount of O VI mass in star-forming galaxies. A detailed account of the sources of warm halo gas (stellar feedback heating, gravitational shock heating, and accretion from the intergalactic medium), inflowing and outflowing warm halo gas metallicity disparities, and their dependencies on galaxy types and environment is also presented. With the warm component securely anchored, our simulations make the following additional predictions. First, cold gas is the primary component in inner regions with its mass comprising 50% of all gas within galactocentric radius r = (30, 150) kpc in (red, blue) galaxies. Second, at r > (30, 200) kpc in (red, blue) galaxies the hot component becomes the majority. Third, the warm component is a perpetual minority, with its contribution peaking at {approx}30% at r = 100-300 kpc in blue galaxies and never exceeding 5% in red galaxies. The significant amount of cold gas in low-z early-type galaxies, which was found in simulations and in agreement with recent observations (Thom et al.), is intriguing, as is the dominance of hot gas at large radii in blue galaxies.

  11. The Halo Stars in NGC 5128. III. An Inner Halo Field and the Metallicity Distribution

    NASA Astrophysics Data System (ADS)

    Harris, William E.; Harris, Gretchen L. H.

    2002-06-01

    We present new Hubble Space Telescope WFPC2 (V,I) photometry for field stars in NGC 5128 at a projected distance of 8 kpc from the galaxy center, which probes a mixture of its inner halo and outer bulge. The color-magnitude diagram shows an old red giant branch that is even broader in color than our two previously studied outer halo fields (at 21 and 31 kpc), with significant numbers of stars extending to solar metallicity and higher. The peak frequency of the metallicity distribution function (MDF) is at [m/H]~=-0.4, with even fewer metal-poor stars than in the outer halo fields. If we use the 21 and 31 kpc fields to define template ``halo'' MDFs and subtract these from the 8 kpc field, the residual ``bulge'' population has a mean [m/H]~=-0.2, similar to the bulges of other large spiral and elliptical galaxies. We find that the main features of the halo MDF can be reproduced by a simple chemical evolution model in which early star formation goes on simultaneously with an initial stage of rapid infall of very metal-poor gas, after which the infall dies away exponentially. Finally, by comparison with the MDFs for the NGC 5128 globular clusters, we find that in all the halo fields we have studied there is a clear decrease of specific frequency SN (number of clusters per unit halo light) with increasing metallicity. At the lowest-metallicity range ([Fe/H]<-1.6) SN is ~4-8, while at metallicities [Fe/H]>-1 it has dropped to ~=1.5. This trend may indicate that globular cluster formation efficiency is a strong function of the metallicity of the protocluster gas. However, we suggest an alternate possibility, which is that globular clusters form preferentially sooner than field stars. If most of the cluster formation within a host giant molecular cloud takes place sooner than most of the distributed field-star formation and if the earliest most metal-poor star-forming clouds are prematurely disrupted by their own first bursts of star formation, then they would leave

  12. HOW WELL DO COSMOLOGICAL SIMULATIONS REPRODUCE INDIVIDUAL HALO PROPERTIES?

    SciTech Connect

    Trenti, Michele; Smith, Britton D.; Hallman, Eric J.; Skillman, Samuel W.; Shull, J. Michael

    2010-03-10

    Cosmological simulations of galaxy formation often rely on prescriptions for star formation and feedback that depend on halo properties such as halo mass, central overdensity, and virial temperature. In this paper, we address the convergence of individual halo properties, based on their number of particles N, focusing, in particular, on the mass of halos near the resolution limit of a simulation. While it has been established that the halo mass function is sampled on average down to N {approx} 20-30 particles, we show that individual halo properties exhibit significant scatter, and some systematic biases, as one approaches the resolution limit. We carry out a series of cosmological simulations using the Gadget2 and Enzo codes with N{sub p} = 64{sup 3} to N{sub p} = 1024{sup 3} total particles, keeping the same large-scale structure in the simulation box. We consider boxes of small (l{sub box} = 8 Mpc h {sup -1}), medium (l{sub box} = 64 Mpc h {sup -1}), and large (l{sub box} = 512 Mpc h {sup -1}) size to probe different halo masses and formation redshifts. We cross-identify dark matter halos in boxes at different resolutions and measure the scatter in their properties. The uncertainty in the mass of single halos depends on the number of particles (scaling approximately as N {sup -1/3}), but the rarer the density peak, the more robust its identification. The virial radius of halos is very stable and can be measured without bias for halos with N {approx}> 30. In contrast, the average density within a sphere containing 25% of the total halo mass is severely underestimated (by more than a factor 2) and the halo spin is moderately overestimated for N {approx}< 100. If sub-grid physics is implemented upon a cosmological simulation, we recommend that rare halos ({approx}3sigma peaks) be resolved with N {approx}> 100 particles and common halos ({approx}1sigma peaks) with N {approx}> 400 particles to avoid excessive numerical noise and possible systematic biases in the

  13. Diverse stellar haloes in nearby Milky Way mass disc galaxies

    NASA Astrophysics Data System (ADS)

    Harmsen, Benjamin; Monachesi, Antonela; Bell, Eric F.; de Jong, Roelof S.; Bailin, Jeremy; Radburn-Smith, David J.; Holwerda, Benne W.

    2017-04-01

    We have examined the resolved stellar populations at large galactocentric distances along the minor axis (from 10 kpc up to between 40 and 75 kpc), with limited major axis coverage, of six nearby highly inclined Milky Way (MW) mass disc galaxies using Hubble Space Telescope data from the Galaxy haloes, Outer discs, Substructure, Thick discs, and Star clusters (GHOSTS) survey. We select red giant branch stars to derive stellar halo density profiles. The projected minor axis density profiles can be approximated by power laws with projected slopes of -2 to -3.7 and a diversity of stellar halo masses of 1-6 × 109 M⊙, or 2-14 per cent of the total galaxy stellar masses. The typical intrinsic scatter around a smooth power-law fit is 0.05-0.1 dex owing to substructure. By comparing the minor and major axis profiles, we infer projected axis ratios c/a at ∼25 kpc between 0.4and0.75. The GHOSTS stellar haloes are diverse, lying between the extremes charted out by the (rather atypical) haloes of the MW and M31. We find a strong correlation between the stellar halo metallicities and the stellar halo masses. We compare our results with cosmological models, finding good agreement between our observations and accretion-only models where the stellar haloes are formed by the disruption of dwarf satellites. In particular, the strong observed correlation between stellar halo metallicity and mass is naturally reproduced. Low-resolution hydrodynamical models have unrealistically high stellar halo masses. Current high-resolution hydrodynamical models appear to predict stellar halo masses somewhat higher than observed but with reasonable metallicities, metallicity gradients, and density profiles.

  14. The Prevalence of the 22 deg Halo in Cirrus Clouds

    NASA Technical Reports Server (NTRS)

    Diedenhoven, vanBastiaan

    2014-01-01

    Halos at 22 deg from the sun attributed to randomly-orientated, pristine hexagonal crystals are frequently observed through ice clouds. These frequent sightings of halos formed by pristine crystals pose an apparent inconsistency with the dominance of distorted, nonpristine ice crystals indicated by in situ and remote sensing data. Furthermore, the 46 deg halo, which is associated with pristine hexagonal crystals as well, is observed far less frequently than the 22 deg halo. Considering that plausible mechanisms that could cause crystal distortion such as aggregation, sublimation, riming and collisions are stochastic processes that likely lead to distributions of crystals with varying distortion levels, here the presence of the 22 deg and 46 deg halo features in phase functions of mixtures of pristine and distorted hexagonal ice crystals is examined. We conclude that the 22 deg halo feature is generally present if the contribution by pristine crystals to the total scattering cross section is greater than only about 10% in the case of compact particles or columns, and greater than about 40% for plates. The 46 deg halo feature is present only if the mean distortion level is low and the contribution of pristine crystals to the total scattering cross section is above about 20%, 50% and 70%, in the case of compact crystals, plates and columns, respectively. These results indicate that frequent sightings of 22 deg halos are not inconsistent with the observed dominance of distorted, non-pristine ice crystals. Furthermore, the low mean distortion levels and large contributions by pristine crystals needed to produce the 461 halo features provide a potential explanation of the common sighting of the 22 deg halo without any detectable 46 deg halo.

  15. Asymmetries in the inner regions of ΛCDM haloes

    NASA Astrophysics Data System (ADS)

    Gao, Liang; White, Simon D. M.

    2006-11-01

    Many galaxies display warps, lopsided images, asymmetric rotation curves or other features which suggest that their immediate dynamical environment is neither static nor in equilibrium. In cold dark matter (CDM) theories, such non-equilibrium features are expected in the inner regions of many dark haloes as a result of recent hierarchical growth. We used the excellent statistics provided by the very large Millennium Simulation to study (i) how the distribution of position and velocity asymmetries predicted for halo cores by the concordance ΛCDM cosmogony depends on halo mass and (ii) how much of the dark matter in the inner core has been added at relatively recent times. Asymmetries are typically larger in more massive haloes. Thus 20 per cent of cluster haloes have density centre separated from barycentre by more than 20 per cent of the virial radius, while only 7 per cent of Milky Way haloes have such large asymmetries. About 40 per cent of all cluster haloes have a mean core velocity which differs from the barycentre velocity by more than a quarter of the characteristic halo circular velocity, whereas only 10 per cent of Milky Way haloes have such large velocity offsets. About 25 per cent of all cluster haloes have acquired more than a quarter of the mass currently in their inner 10 kpc through mergers since z = 1. The corresponding percentage of Milky Way haloes is 15 per cent. These numbers seem quite compatible with the levels of asymmetry seen in the observable regions of galaxies, but quantitative comparison requires more detailed modelling of the observable components.

  16. Halo Properties and Secular Evolution in Barred Galaxies

    NASA Astrophysics Data System (ADS)

    Athanassoula, E.

    The halo plays a crucial role in the evolution of barred galaxies. Its near-resonant material absorbs angular momentum emitted from some of the disc particles and helps the bar become stronger. As a result, a bar (oval) forms in the inner parts of the halo of strongly barred disc galaxies. It is thinner in the inner parts (but still considerably fatter than the disc bar) and tends to spherical at larger radii. Its length increases with time, while always staying shorter than the disc bar. It is roughly aligned with the disc bar, which it trails only slightly, and it turns with roughly the same pattern speed. The bi-symmetric component of the halo density continues well outside the halo bar, where it clearly trails behind the disc bar. The length and strength of the disc and halo bars correlate; the former being always much stronger than the latter. If the halo is composed of weakly interacting massive particles, then the formation of the halo bar, by redistributing the matter in the halo and changing its shape, could influence the expected annihilation signal. This is indeed found to be the case if the halo has a core, but not if it has a steep cusp. The formation and evolution of the bar strongly affect the halo orbits. A fraction of them becomes near-resonant, similar to the disc near-resonant orbits at the same resonance, while another fraction becomes chaotic. Finally, a massive and responsive halo makes it harder for a central mass concentration to destroy the disc bar.

  17. MASS-DEPENDENT BARYON ACOUSTIC OSCILLATION SIGNAL AND HALO BIAS

    SciTech Connect

    Wang Qiao; Zhan Hu

    2013-05-10

    We characterize the baryon acoustic oscillations (BAO) feature in halo two-point statistics using N-body simulations. We find that nonlinear damping of the BAO signal is less severe for halos in the mass range we investigate than for dark matter. The amount of damping depends weakly on the halo mass. The correlation functions show a mass-dependent drop of the halo clustering bias below roughly 90 h {sup -1} Mpc, which coincides with the scale of the BAO trough. The drop of bias is 4% for halos with mass M > 10{sup 14} h {sup -1} M{sub Sun} and reduces to roughly 2% for halos with mass M > 10{sup 13} h {sup -1} M{sub Sun }. In contrast, halo biases in simulations without BAO change more smoothly around 90 h {sup -1} Mpc. In Fourier space, the bias of M > 10{sup 14} h {sup -1} M{sub Sun} halos decreases smoothly by 11% from wavenumber k = 0.012 h Mpc{sup -1} to 0.2 h Mpc{sup -1}, whereas that of M > 10{sup 13} h {sup -1} M{sub Sun} halos decreases by less than 4% over the same range. By comparing the halo biases in pairs of otherwise identical simulations, one with and the other without BAO, we also observe a modulation of the halo bias. These results suggest that precise calibrations of the mass-dependent BAO signal and scale-dependent bias on large scales would be needed for interpreting precise measurements of the two-point statistics of clusters or massive galaxies in the future.

  18. Halos of unified dark matter scalar field

    SciTech Connect

    Bertacca, Daniele; Bartolo, Nicola; Matarrese, Sabino E-mail: nicola.bartolo@pd.infn.it

    2008-05-15

    We investigate the static and spherically symmetric solutions of Einstein's equations for a scalar field with a non-canonical kinetic term, assumed to provide both the dark matter and dark energy components of the Universe. In particular, we give a prescription to obtain solutions (dark halos) whose rotation curve v{sub c}(r) is in good agreement with observational data. We show that there exist suitable scalar field Lagrangians that allow us to describe the cosmological background evolution and the static solutions with a single dark fluid.

  19. Invariant mass spectroscopy of halo nuclei

    SciTech Connect

    Nakamura, Takashi

    2008-11-11

    We have applied the invariant mass spectroscopy to explore the low-lying exited states of halo nuclei at intermediate energies around 70 MeV/nucleon at RIKEN. As examples, we show here the results of Coulomb breakup study for {sup 11}Li using the Pb target, as well as breakup reactions of {sup 14}Be with p and C targets. The former study revealed a strong Coulomb breakup cross section reflecting the large enhancement of E1 strength at low excitation energies (soft E1 excitation). The latter revealed the observation of the first 2{sup +} state in {sup 14}Be.

  20. [A special instrument: the halo fixator].

    PubMed

    Schmolke, Stephan; Gossé, Frank

    2008-03-01

    Installation of an external fixator in combination with a body cast for temporary or definitive immobilization and retention of unstable fractures of the craniocervical junction and upper part of the cervical spine. Further established applications include presurgical extension treatment of paralytic scoliosis and temporary retention within complex spine deformity operations after ventral release or mobilized osteotomies. Closed reposition and temporary retention of unstable injuries of the cervical spine up to operation. Extension treatment for careful reposition of fresh or dated malpositions of the cervical spine. Conservative treatment of injuries of the craniocervical junction and the upper part of the cervical spine. Presurgical extension of paralytic scoliosis. Temporary extension after ventral release. Cranial fractures and intracranial injuries. Soft-tissue infections of the skull. Children < 3 years. Adiposity, chest injuries and paraplegia as relative contraindications using the halo body cast. Halo traction is applied in two stages; first, the head ring is attached to the skull, then, the body cast and suspension assembly are added. Local anesthesia, depending on circumstances. Sizing of the components; the optimal size of the ring is about 1.5" larger than the circumference of the patient's head. Patient in sitting or supine position. The halo ring is held in proper position by stabilizer plates; the lower margin of the ring should be just above the ears and about 0.4" above the eyebrows. The anterior pins are placed in shallow groove on the forehead between supraorbital ridges and frontal protuberances. Threaded skull pins are screwed with defined torque (4-8"/pounds) in the lamina externa of the cranial calotte without perforating the lamina interna. To avoid side-to-side drifting, the diagonally opposite pins should be tightened simultaneously. Finally, connection of the halo ring with a body cast or putting on an extension device. Secure external

  1. Analytical estimation of ATF beam halo distribution

    NASA Astrophysics Data System (ADS)

    Wang, Dou; Philip, Bambade; Kaoru, Yokoya; Gao, Jie

    2014-12-01

    In order to study the backgrounds in the ATF2 beam line and the interaction point (IP), this paper has developed an analytical method to give an estimation of the ATF beam halo distribution based on K. Hirata and K. Yokoya's theory. The equilibrium particle distribution of the beam tail in the ATF damping ring is presented, with each electron affected by several stochastic processes such as beam-gas scattering, beam-gas bremsstrahlung and intra-beam scattering, in addition to the synchrotron radiation damping effects. This is a general method which can also be applied to other electron rings.

  2. Project ECHO: Electronic Communications from Halo Orbit

    NASA Astrophysics Data System (ADS)

    Borrelli, Jason; Cooley, Bryan; Debole, Marcy; Hrivnak, Lance; Nielsen, Kenneth; Sangmeister, Gary; Wolfe, Matthew

    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

  3. Cosmic stellar relics in the Galactic halo

    NASA Astrophysics Data System (ADS)

    Salvadori, Stefania; Schneider, Raffaella; Ferrara, Andrea

    2007-10-01

    We study the stellar population history and chemical evolution of the Milky Way (MW) in a hierarchical Λ cold dark matter model for structure formation. Using a Monte Carlo method based on the semi-analytical extended Press & Schechter formalism, we develop a new code GALAXY MERGER TREE AND EVOLUTION (GAMETE) to reconstruct the merger tree of the Galaxy and follow the evolution of gas and stars along the hierarchical tree. Our approach allows us to compare the observational properties of the MW with model results, exploring different properties of primordial stars, such as their initial mass function and the critical metallicity for low-mass star formation, Zcr. In particular, by matching our predictions to the metallicity distribution function (MDF) of metal-poor stars in the Galactic halo we find that: (i) a strong supernova (SN) feedback is required to reproduce the observed properties of the MW; (ii) stars with [Fe/H] < -2.5 form in haloes accreting Galactic medium (GM) enriched by earlier SN explosions; (iii) the fiducial model (Zcr = 10-4Zsolar, mPopIII = 200 Msolar) provides an overall good fit to the MDF, but cannot account for the two hyper-metal-poor (HMP) stars with [Fe/H] < -5 the latter can be accommodated if Zcr <= 10-6 Zsolar but such model overpopulates the `metallicity desert', that is, the range -5.3 < [Fe/H] < -4 in which no stars have been detected; (iv) the current non-detection of metal-free stars robustly constrains either Zcr > 0 or the masses of the first stars mPopIII > 0.9 Msolar (v) the statistical impact of truly second-generation stars, that is, stars forming out of gas polluted only by metal-free stars, is negligible in current samples; and (vi) independent of Zcr, 60 per cent of metals in the GM are ejected through winds by haloes with masses M < 6 × 109 Msolar, thus showing that low-mass haloes are the dominant population contributing to cosmic metal enrichment. We discuss the limitations of our study and comparison with previous

  4. Project ECHO: Electronic Communications from Halo Orbit

    NASA Technical Reports Server (NTRS)

    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

  5. CALET's sensitivity to Dark Matter annihilation in the galactic halo

    SciTech Connect

    Motz, H.; Asaoka, Y.; Torii, S.; Bhattacharyya, S. E-mail: yoichi.asaoka@aoni.waseda.jp E-mail: saptashwab@ruri.waseda.jp

    2015-12-01

    CALET (Calorimetric Electron Telescope), installed on the ISS in August 2015, directly measures the electron+positron cosmic rays flux up to 20 TeV. With its proton rejection capability of 1 : 10{sup 5} and an aperture of 1200 cm{sup 2·} sr, it will provide good statistics even well above one TeV, while also featuring an energy resolution of 2%, which allows it to detect fine structures in the spectrum. Such structures may originate from Dark Matter annihilation or decay, making indirect Dark Matter search one of CALET's main science objectives among others such as identification of signatures from nearby supernova remnants, study of the heavy nuclei spectra and gamma astronomy. The latest results from AMS-02 on positron fraction and total electron+positron flux can be fitted with a parametrization including a single pulsar as an extra power law source with exponential cut-off, which emits an equal amount of electrons and positrons. This single pulsar scenario for the positron excess is extrapolated into the TeV region and the expected CALET data for this case are simulated. Based on this prediction for CALET data, the sensitivity of CALET to Dark Matter annihilation in the galactic halo has been calculated. It is shown that CALET could significantly improve the limits compared to current data, especially for those Dark Matter candidates that feature a large fraction of annihilation directly into e{sup +} + e{sup −}, such as the LKP (Lightest Kaluza-Klein particle)

  6. The Dependence of the Occupation of Galaxies on the Halo Formation Time

    NASA Astrophysics Data System (ADS)

    Zhu, Guangtun; Zheng, Zheng; Lin, W. P.; Jing, Y. P.; Kang, Xi; Gao, Liang

    2006-03-01

    We study the dependence of the galaxy contents within halos on the halo formation time using two galaxy formation models, one being a semianalytic model utilizing the halo assembly history from a high-resolution N-body simulation and the other being a smoothed particle hydrodynamics simulation including radiative cooling, star formation, and energy feedback from galactic winds. We confirm the finding by Gao et al. that at fixed mass, the clustering of halos depends on the halo formation time, especially for low-mass halos. This age dependence of halo clustering makes it desirable to study the correlation between the occupation of galaxies within halos and the halo age. We find that, in halos of fixed mass, the number of satellite galaxies has a strong dependence on halo age, with fewer satellites in older halos. The youngest one-third of the halos can have an order of magnitude more satellites than the oldest one-third. For central galaxies, in halos that form earlier, they tend to have more stars and thus appear to be more luminous, and the dependence of their luminosity on halo age is not as strong as that of stellar mass. The results can be understood through the star formation history in halos and the merging of satellites onto central galaxies. The age dependence of the galaxy contents within halos would constitute an important ingredient in a more accurate halo-based model of galaxy clustering.

  7. Elastic proton-proton scattering at RHIC

    SciTech Connect

    Yip, K.

    2011-09-03

    Here we describe elastic proton+proton (p+p) scattering measurements at RHIC in p+p collisions with a special optics run of {beta}* {approx} 21 m at STAR, at the center-of-mass energy {radical}s = 200 GeV during the last week of the RHIC 2009 run. We present preliminary results of single and double spin asymmetries.

  8. The Edges Of Dark Matter Halos: Theory And Observations

    NASA Astrophysics Data System (ADS)

    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.

  9. Beam halo definitions based upon moments of the particle distribution

    NASA Astrophysics Data System (ADS)

    Allen, C. K.; Wangler, T. P.

    2002-12-01

    Two different parameters for the quantitative description of beam halo are discussed. Both are based on moments of the particle distribution and represent a convenient and model-independent method for quantifying the magnitude of beam halo observed in either spatial or phase-space projections. One parameter is a measure of spatial profile of the beam and has been defined by Wangler and Crandall previously. The current authors defined a new parameter using kinematic invariants to quantify halo formation in 2D phase space. Here we expand the development and present detailed numerical results. Although the spatial-profile parameter and the phase-space halo parameter both reduce to the same value when the distribution has the elliptical symmetry, in general these parameters are not equal. Halo in the 1D spatial profiles is relatively easily measured, but is variable as the beam distribution evolves and can hide as it rotates in phase space. The 2D phase-space halo is more difficult to measure, but it varies more smoothly as the halo evolves. It provides a more reliable characterization of the halo as an intrinsic property of the beam.

  10. Remarks on the spherical scalar field halo in galaxies

    SciTech Connect

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

    2009-08-15

    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.

  11. Halo-Independent Comparison of Direct Dark Matter Detection Data

    DOE PAGES

    Del Nobile, Eugenio

    2014-01-01

    We review the halo-independent formalism that allows comparing data from different direct dark matter detection experiments without making assumptions on the properties of the dark matter halo. We apply this method to spin-independent WIMP-nuclei interactions, for both isospin-conserving and isospin-violating couplings, and to WIMPs interacting through an anomalous magnetic moment.

  12. Lyman-Werner UV escape fractions from primordial haloes

    NASA Astrophysics Data System (ADS)

    Schauer, Anna T. P.; Whalen, Daniel J.; Glover, Simon C. O.; Klessen, Ralf S.

    2015-12-01

    Population III (Pop III) stars can regulate star formation in the primordial Universe in several ways. They can ionize nearby haloes, and even if their ionizing photons are trapped by their own haloes, their Lyman-Werner (LW) photons can still escape and destroy H2 in other haloes, preventing them from cooling and forming stars. LW escape fractions are thus a key parameter in cosmological simulations of early reionization and star formation but have not yet been parametrized for realistic haloes by halo or stellar mass. To do so, we perform radiation hydrodynamical simulations of LW UV escape from 9-120 M⊙ Pop III stars in 105-107 M⊙ haloes with ZEUS-MP. We find that photons in the LW lines (i.e. those responsible for destroying H2 in nearby systems) have escape fractions ranging from 0 to 85 per cent. No LW photons escape the most massive halo in our sample, even from the most massive star. Escape fractions for photons elsewhere in the 11.18-13.6 eV energy range, which can be redshifted into the LW lines at cosmological distances, are generally much higher, being above 60 per cent for all but the least massive stars in the most massive haloes. We find that shielding of H2 by neutral hydrogen, which has been neglected in most studies to date, produces escape fractions that are up to a factor of 3 smaller than those predicted by H2 self-shielding alone.

  13. The prolate dark matter halo of the Andromeda galaxy

    SciTech Connect

    Hayashi, Kohei; Chiba, Masashi E-mail: chiba@astr.tohoku.ac.jp

    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.

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

    SciTech Connect

    Long, Stacy; Shlosman, Isaac; Heller, Clayton

    2014-03-01

    We demonstrate using numerical simulations of isolated galaxies that growth of stellar bars in spinning dark matter halos is heavily suppressed in the secular phase of evolution. In a representative set of models, we show that for values of the cosmological spin parameter λ ≳ 0.03, bar growth (in strength and size) becomes increasingly quenched. Furthermore, the slowdown of the bar pattern speed weakens considerably with increasing λ until it ceases completely. The terminal structure of the bars is affected as well, including extent and shape of their boxy/peanut bulges. The essence of this effect lies in the modified angular momentum exchange between the disk and the halo facilitated by the bar. For the first time we have demonstrated that a dark matter halo can emit and not purely absorb angular momentum. Although the halo as a whole is not found to emit, the net transfer of angular momentum from the disk to the halo is significantly reduced or completely eliminated. The paradigm shift implies that the accepted view that disks serve as sources of angular momentum and halos serve as sinks must be revised. Halos with λ ≳ 0.03 are expected to form a substantial fraction, based on the lognormal distribution of λ. The dependence of secular bar evolution on halo spin, therefore, implies profound corollaries for the cosmological evolution of galactic disks.

  15. Investigating Halo and Ceiling Effects in Student Evaluations of Instruction

    ERIC Educational Resources Information Center

    Keeley, Jared W.; English, Taylor; Irons, Jessica; Henslee, Amber M.

    2013-01-01

    Many measurement biases affect student evaluations of instruction (SEIs). However, two have been relatively understudied: halo effects and ceiling/floor effects. This study examined these effects in two ways. To examine the halo effect, using a videotaped lecture, we manipulated specific teacher behaviors to be "good" or "bad"…

  16. Detecting Halo Effects in Performance-Based Examinations

    ERIC Educational Resources Information Center

    Bechger, Timo M.; Maris, Gunter; Hsiao, Ya Ping

    2010-01-01

    The main purpose of this article is to demonstrate how halo effects may be detected and quantified using two independent ratings of the same person. A practical illustration is given to show how halo effects can be avoided. (Contains 2 tables, 7 figures, and 2 notes.)

  17. Investigating Halo and Ceiling Effects in Student Evaluations of Instruction

    ERIC Educational Resources Information Center

    Keeley, Jared W.; English, Taylor; Irons, Jessica; Henslee, Amber M.

    2013-01-01

    Many measurement biases affect student evaluations of instruction (SEIs). However, two have been relatively understudied: halo effects and ceiling/floor effects. This study examined these effects in two ways. To examine the halo effect, using a videotaped lecture, we manipulated specific teacher behaviors to be "good" or "bad"…

  18. Detecting Halo Effects in Performance-Based Examinations

    ERIC Educational Resources Information Center

    Bechger, Timo M.; Maris, Gunter; Hsiao, Ya Ping

    2010-01-01

    The main purpose of this article is to demonstrate how halo effects may be detected and quantified using two independent ratings of the same person. A practical illustration is given to show how halo effects can be avoided. (Contains 2 tables, 7 figures, and 2 notes.)

  19. The segregation of baryons and dark matter during halo assembly

    NASA Astrophysics Data System (ADS)

    Liao, Shihong; Gao, Liang; Frenk, Carlos S.; Guo, Qi; Wang, Jie

    2017-09-01

    The standard galaxy formation theory assumes that baryons and dark matter are initially well mixed before becoming segregated due to radiative cooling. We use non-radiative hydrodynamical simulations to explicitly examine this assumption and find that baryons and dark matter can also be segregated due to different characteristics of gas and dark matter during the buildup of the halo. As a result, baryons in many haloes do not originate from the same Lagrangian region as the dark matter. When using the fraction of corresponding dark matter and gas particles in the initial conditions (the 'paired fraction') as a proxy of the dark matter and gas segregation strength of a halo, on average about 25 per cent of the baryonic and dark matter of the final halo are segregated in the initial conditions. This is at odds with the assumption of the standard galaxy formation model. A consequence of this effect is that the baryons and dark matter of the same halo initially experience different tidal torques and thus their angular momentum vectors are often misaligned. The degree of the misalignment is largely preserved during later halo assembly and can be understood with the tidal torque theory. The result challenges the precision of some semi-analytical approaches that utilize dark matter halo merger trees to infer properties of gas associated with dark matter haloes.

  20. Proton pump inhibitors

    MedlinePlus

    Proton pump inhibitors (PPIs) are medicines that work by reducing the amount of stomach acid made by ... Proton pump inhibitors are used to: Relieve symptoms of acid reflux, or gastroesophageal reflux disease (GERD). This ...

  1. What's In a Proton?

    ScienceCinema

    Brookhaven Lab

    2016-07-12

    Physicist Peter Steinberg explains that fundamental particles like protons are themselves made up of still smaller particles called quarks. He discusses how new particles are produced when quarks are liberated from protons...a process that can be observed

  2. What's In a Proton?

    SciTech Connect

    Brookhaven Lab

    2009-07-08

    Physicist Peter Steinberg explains that fundamental particles like protons are themselves made up of still smaller particles called quarks. He discusses how new particles are produced when quarks are liberated from protons...a process that can be observed

  3. Frost halos from supercooled water droplets

    PubMed Central

    Jung, Stefan; Tiwari, Manish K.; Poulikakos, Dimos

    2012-01-01

    Water freezing on solid surfaces is ubiquitous in nature. Even though icing/frosting impairs the performance and safety in many processes, its mechanism remains inadequately understood. Changing atmospheric conditions, surface properties, the complexity of icing physics, and the unorthodox behavior of water are the primary factors that make icing and frost formation intriguing and difficult to predict. In addition to its unquestioned scientific and practical importance, unraveling the frosting mechanism under different conditions is a prerequisite to develop “icephobic” surfaces, which may avoid ice formation and contamination. In this work we demonstrate that evaporation from a freezing supercooled sessile droplet, which starts explosively due to the sudden latent heat released upon recalescent freezing, generates a condensation halo around the droplet, which crystallizes and drastically affects the surface behavior. The process involves simultaneous multiple phase transitions and may also spread icing by initiating sequential freezing of neighboring droplets in the form of a domino effect and frost propagation. Experiments under controlled humidity conditions using substrates differing up to three orders of magnitude in thermal conductivity establish that a delicate balance between heat diffusion and vapor transport determines the final expanse of the frozen condensate halo, which, in turn, controls frost formation and propagation. PMID:23012410

  4. Halogen Occultation Experiment (HALOE) optical filter characterization

    NASA Technical Reports Server (NTRS)

    Harvey, Gale A.

    1989-01-01

    The Halogen Occultation Experiment (HALOE) is a solar occultation experiment that will fly on the Upper Atmosphere Research Satellite to measure mixing ratio profiles of O3, H2O, NO2, NO, CH4, HCl, and HF. The inversion of the HALOE data will be critically dependent on a detailed knowledge of eight optical filters. A filter characterization program was undertaken to measure in-band transmissions, out-of-band transmissions, in-band transmission shifts with temperature, reflectivities, and age stability. Fourier Transform Infrared Spectrometers were used to perform measurements over the spectral interval 400/cm to 6300/cm (25 micrometers to 1.6 micrometers). Very high precision (0.1 percent T) in-band measurements and very high resolution (0.0001 percent T) out-of-band measurements have been made. The measurements revealed several conventional leaks at 0.01 percent transmission and greatly enhanced (1,000) leaks to the 2-element filters when placed in a Fabry-Perot cavity. Filter throughput changes by 5 percent for a 25 C change in filter temperature.

  5. Halo clustering with nonlocal non-Gaussianity

    SciTech Connect

    Schmidt, Fabian; Kamionkowski, Marc

    2010-11-15

    We show how the peak-background split (PBS) can be generalized to predict the effect of nonlocal primordial non-Gaussianity on the clustering of halos. Our approach is applicable to arbitrary primordial bispectra. We show that the scale dependence of halo clustering predicted in the peak-background split agrees with that of the local-biasing model on large scales. On smaller scales, k > or approx. 0.01h Mpc{sup -1}, the predictions diverge, a consequence of the assumption of separation of scales in the peak-background split. Even on large scales, PBS and local biasing do not generally agree on the amplitude of the effect outside of the high-peak limit. The scale dependence of the biasing - the effect that provides strong constraints to the local-model bispectrum - is far weaker for the equilateral and self-ordering-scalar-field models of non-Gaussianity. The bias scale dependence for the orthogonal and folded models is weaker than in the local model ({approx}k{sup -1}), but likely still strong enough to be constraining. We show that departures from scale-invariance of the primordial power spectrum may lead to order-unity corrections, relative to predictions made assuming scale-invariance--to the non-Gaussian bias in some of these nonlocal models for non-Gaussianity. An Appendix shows that a nonlocal model can produce the local-model bispectrum, a mathematical curiosity we uncovered in the course of this investigation.

  6. HALOE Algorithm Improvements for Upper Tropospheric Sounding

    NASA Technical Reports Server (NTRS)

    McHugh, Martin J.; Gordley, Larry L.; Russell, James M., III; Hervig, Mark E.

    1999-01-01

    This report details the ongoing efforts by GATS, Inc., in conjunction with Hampton University and University of Wyoming, in NASA's Mission to Planet Earth UARS Science Investigator Program entitled "HALOE Algorithm Improvements for Upper Tropospheric Soundings." The goal of this effort is to develop and implement major inversion and processing improvements that will extend HALOE measurements further into the troposphere. In particular, O3, H2O, and CH4 retrievals may be extended into the middle troposphere, and NO, HCl and possibly HF into the upper troposphere. Key areas of research being carried out to accomplish this include: pointing/tracking analysis; cloud identification and modeling; simultaneous multichannel retrieval capability; forward model improvements; high vertical-resolution gas filter channel retrievals; a refined temperature retrieval; robust error analyses; long-term trend reliability studies; and data validation. The current (first-year) effort concentrates on the pointer/tracker correction algorithms, cloud filtering and validation, and multi-channel retrieval development. However, these areas are all highly coupled, so progress in one area benefits from and sometimes depends on work in others.

  7. HALOE Algorithm Improvements for Upper Tropospheric Sounding

    NASA Technical Reports Server (NTRS)

    Thompson, Robert E.

    2001-01-01

    This report details the ongoing efforts by GATS, Inc., in conjunction with Hampton University and University of Wyoming, in NASA's Mission to Planet Earth UARS Science Investigator Program entitled "HALOE Algorithm Improvements for Upper Tropospheric Sounding." The goal of this effort is to develop and implement major inversion and processing improvements that will extend HALOE measurements further into the troposphere. In particular, O3, H2O, and CH4 retrievals may be extended into the middle troposphere, and NO, HCl and possibly HF into the upper troposphere. Key areas of research being carried out to accomplish this include: pointing/tracking analysis; cloud identification and modeling; simultaneous multichannel retrieval capability; forward model improvements; high vertical-resolution gas filter channel retrievals; a refined temperature retrieval; robust error analyses; long-term trend reliability studies; and data validation. The current (first year) effort concentrates on the pointer/tracker correction algorithms, cloud filtering and validation, and multichannel retrieval development. However, these areas are all highly coupled, so progress in one area benefits from and sometimes depends on work in others.

  8. HALOE Algorithm Improvements for Upper Tropospheric Soundings

    NASA Technical Reports Server (NTRS)

    Thompson, Robert E.; Douglass, Anne (Technical Monitor)

    2000-01-01

    This report details the ongoing efforts by GATS, Inc., in conjunction with Hampton University and University of Wyoming, in NASA's Mission to Planet Earth UARS Science Investigator Program entitled "HALOE Algorithm Improvements for Upper Tropospheric Sounding." The goal of this effort is to develop and implement major inversion and processing improvements that will extend HALOE measurements further into the troposphere. In particular, O3, H2O, and CH4 retrievals may be extended into the middle troposphere, and NO, HCl and possibly HF into the upper troposphere. Key areas of research being carried out to accomplish this include: pointing/tracking analysis; cloud identification and modeling; simultaneous multichannel retrieval capability; forward model improvements; high vertical-resolution gas filter channel retrievals; a refined temperature retrieval; robust error analyses; long-term trend reliability studies; and data validation. The current (first year) effort concentrates on the pointer/tracker correction algorithms, cloud filtering and validation, and multichannel retrieval development. However, these areas are all highly coupled, so progress in one area benefits from and sometimes depends on work in others.

  9. HALOE Algorithm Improvements for Upper Tropospheric Sounding

    NASA Technical Reports Server (NTRS)

    Thompson, Robert Earl; McHugh, Martin J.; Gordley, Larry L.; Hervig, Mark E.; Russell, James M., III; Douglass, Anne (Technical Monitor)

    2001-01-01

    This report details the ongoing efforts by GATS, Inc., in conjunction with Hampton University and University of Wyoming, in NASA's Mission to Planet Earth Upper Atmospheric Research Satellite (UARS) Science Investigator Program entitled 'HALOE Algorithm Improvements for Upper Tropospheric Sounding.' The goal of this effort is to develop and implement major inversion and processing improvements that will extend Halogen Occultation Experiment (HALOE) measurements further into the troposphere. In particular, O3, H2O, and CH4 retrievals may be extended into the middle troposphere, and NO, HCl and possibly HF into the upper troposphere. Key areas of research being carried out to accomplish this include: pointing/tracking analysis; cloud identification and modeling; simultaneous multichannel retrieval capability; forward model improvements; high vertical-resolution gas filter channel retrievals; a refined temperature retrieval; robust error analyses; long-term trend reliability studies; and data validation. The current (first year) effort concentrates on the pointer/tracker correction algorithms, cloud filtering and validation, and multichannel retrieval development. However, these areas are all highly coupled, so progress in one area benefits from and sometimes depends on work in others.

  10. MACHO (MAssive Compact Halo Objects) Data

    DOE Data Explorer

    The primary aim of the MACHO Project is to test the hypothesis that a significant fraction of the dark matter in the halo of the Milky Way is made up of objects like brown dwarfs or planets: these objects have come to be known as MACHOs, for MAssive Compact Halo Objects. The signature of these objects is the occasional amplification of the light from extragalactic stars by the gravitational lens effect. The amplification can be large, but events are extremely rare: it is necessary to monitor photometrically several million stars for a period of years in order to obtain a useful detection rate. For this purpose MACHO has a two channel system that employs eight CCDs, mounted on the 50 inch telescope at Mt. Stromlo. The high data rate (several GBytes per night) is accommodated by custom electronics and on-line data reduction. The Project has taken more than 27,000 images with this system since June 1992. Analysis of a subset of these data has yielded databases containing light curves in two colors for 8 million stars in the LMC and 10 million in the bulge of the Milky Way. A search for microlensing has turned up four candidates toward the Large Magellanic Cloud and 45 toward the Galactic Bulge. The web page for data provides links to MACHO Project data portals and various specialized interfaces for viewing or searching the data. (Specialized Interface)

  11. Inhomogeneous chemical enrichment in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Kobayashi, Chiaki

    2016-08-01

    In a galaxy, chemical enrichment takes place in an inhomogeneous fashion, and the Galactic Halo is one of the places where the inhomogeneous effects are imprinted and can be constrained from observations. I show this using my chemodynamical simulations of Milky Way type galaxies. The scatter in the elemental abundances originate from radial migration, merging/accretion of satellite galaxies, local variation of star formation and chemical enrichment, and intrinsic variation of nucleosynthesis yields. In the simulated galaxies, there is no strong age-metallicity relation. This means that the most metal-poor stars are not always the oldest stars, and can be formed in chemically unevolved clouds at later times. The long-lifetime sources of chemical enrichment such as asymptotic giant branch stars or neutron star mergers can contribute at low metallicities. The intrinsic variation of yields are important in the early Universe or metal-poor systems such as in the Galactic halo. The carbon enhancement of extremely metal-poor (EMP) stars can be best explained by faint supernovae, the low [α/Fe] ratios in some EMP stars naturally arise from low-mass (~ 13 - 15M ⊙) supernovae, and finally, the [α/Fe] knee in dwarf spheroidal galaxies can be produced by subclasses of Type Ia supernovae such as SN 2002cx-like objects and sub-Chandrasekhar mass explosions.

  12. Detecting Halo Substructure in the Gaia Era

    NASA Astrophysics Data System (ADS)

    Mateu, C.; Aguilar, L.; Bruzual, G.; Brown, A.; Valenzuela, O.; Carigi, L.; Velázquez, H.; Hernández, F.

    2014-06-01

    The observational data expected to come from the Gaia astrometric mission represent an unrivaled opportunity to search for tidal streams using all-sky full phase-space information for nearly a billion stars in our Galaxy. In this contribution we will describe the Modified Great Circle Cell Count (mGC3) method devised for the detection of stellar streams in the galactic halo. This method is based on the GC3 method originally devised by Johnston, Hernquist, & Bolte (1996), modified to include velocity information in order to enhance the contrast of stream signatures with respect to the galactic halo background. We present our results on the efficiency of mGC3, tested by embedding tidal streams from N-body simulations in a mock Gaia catalogue of the galactic background, which includes a realistic realization of the photometric and kinematic properties, errors and completeness limits. We investigate mGC3's efficiency as a function of initial satellite luminosity, star formation history and orbital parameters and find that satellites in the range 10^8-10^9 L_⊙ can be recovered for streams as dynamically old as ~10 Gyr and up to galactocentric distances of ~40 kpc. For some combinations of dynamical ages and orbits, tidal streams with luminosities down to 4-5×10^7 L_⊙ can be recovered.

  13. Constraining the halo mass function with observations

    NASA Astrophysics Data System (ADS)

    Castro, Tiago; Marra, Valerio; Quartin, Miguel

    2016-12-01

    The abundances of dark matter haloes in the universe are described by the halo mass function (HMF). It enters most cosmological analyses and parametrizes how the linear growth of primordial perturbations is connected to these abundances. Interestingly, this connection can be made approximately cosmology independent. This made it possible to map in detail its near-universal behaviour through large-scale simulations. However, such simulations may suffer from systematic effects, especially if baryonic physics is included. In this paper, we ask how well observations can constrain directly the HMF. The observables we consider are galaxy cluster number counts, galaxy cluster power spectrum and lensing of Type Ia supernovae. Our results show that Dark Energy Survey is capable of putting the first meaningful constraints on the HMF, while both Euclid and J-PAS (Javalambre-Physics of the Accelerated Universe Astrophysical Survey) can give stronger constraints, comparable to the ones from state-of-the-art simulations. We also find that an independent measurement of cluster masses is even more important for measuring the HMF than for constraining the cosmological parameters, and can vastly improve the determination of the HMF. Measuring the HMF could thus be used to cross-check simulations and their implementation of baryon physics. It could even, if deviations cannot be accounted for, hint at new physics.

  14. Stellar Streams in the Andromeda Halo

    NASA Astrophysics Data System (ADS)

    Fardal, Mark A.; PAndAS Collaboration

    2011-05-01

    The PAndAS survey detects RGB and AGB stars in our neighbor galaxy M31, out to 150 kpc from the galaxy center with an extension to M33. Maps of this survey display a spectacular collection of stellar streams extending tens to hundreds of kpc in length. Many of these streams overlap with each other or with M31's central regions, making it difficult to disentangle the different streams. I discuss what is currently known about the nature, origin, significance, and eventual fate of these stellar streams. Photometric observations from the PAndAS survey and follow-up work constrain the metallicity, age, luminosity, and stellar mass of the stellar population. I discuss scenarios for how some of these streams formed, while for others their origin remains a mystery. I present observationally constrained numerical simulations for the formation of some of the streams. The streams also are probes of the mass profile and lumpiness of M31's dark matter halo. Spectroscopic samples are used to constrain M31's halo mass at large radius.

  15. Simulating the carbon footprint of galactic haloes

    NASA Astrophysics Data System (ADS)

    Bird, Simeon; Rubin, Kate H. R.; Suresh, Joshua; Hernquist, Lars

    2016-10-01

    We compare simulations, including the Illustris simulations, to observations of C IV and C II absorption at z = 2-4. These are the C IV column density distribution function in the column density range 1012-1015 cm-2, the C IV equivalent width distribution at 0.1-2 Å, and the covering fractions and equivalent widths of C IV1548 Å and C II 1337 Å around damped Lyman α systems (DLAs). In the context of the feedback models that we investigate, all C IV observations favour the use of more energetic wind models, which are better able to enrich the gas surrounding haloes. We propose two ways to achieve this: an increased wind velocity and an increase in wind thermal energy. However, even our most energetic wind models do not produce enough absorbers with C IV equivalent width >0.6 Å, which in our simulations are associated with the most massive haloes. All simulations are in reasonable agreement with the C II covering fraction and equivalent widths around damped Lyman α absorbers, although there is a moderate deficit in one bin 10-100 kpc from the DLA. Finally, we show that the C IV in our simulations is predominantly photoionized.

  16. Proton: the particle.

    PubMed

    Suit, Herman

    2013-11-01

    The purpose of this article is to review briefly the nature of protons: creation at the Big Bang, abundance, physical characteristics, internal components, and life span. Several particle discoveries by proton as the experimental tool are considered. Protons play important roles in science, medicine, and industry. This article was prompted by my experience in the curative treatment of cancer patients by protons and my interest in the nature of protons as particles. The latter has been stimulated by many discussions with particle physicists and reading related books and journals. Protons in our universe number ≈10(80). Protons were created at 10(-6) -1 second after the Big Bang at ≈1.37 × 10(10) years beforethe present. Proton life span has been experimentally determined to be ≥10(34) years; that is, the age of the universe is 10(-24)th of the minimum life span of a proton. The abundance of the elements is hydrogen, ≈74%; helium, ≈24%; and heavier atoms, ≈2%. Accordingly, protons are the dominant baryonic subatomic particle in the universe because ≈87% are protons. They are in each atom in our universe and thus involved in virtually every activity of matter in the visible universe, including life on our planet. Protons were discovered in 1919. In 1968, they were determined to be composed of even smaller particles, principally quarks and gluons. Protons have been the experimental tool in the discoveries of quarks (charm, bottom, and top), bosons (W(+), W(-), Z(0), and Higgs), antiprotons, and antineutrons. Industrial applications of protons are numerous and important. Additionally, protons are well appreciated in medicine for their role in radiation oncology and in magnetic resonance imaging. Protons are the dominant baryonic subatomic particle in the visible universe, comprising ≈87% of the particle mass. They are present in each atom of our universe and thus a participant in every activity involving matter.

  17. Proton: The Particle

    SciTech Connect

    Suit, Herman

    2013-11-01

    The purpose of this article is to review briefly the nature of protons: creation at the Big Bang, abundance, physical characteristics, internal components, and life span. Several particle discoveries by proton as the experimental tool are considered. Protons play important roles in science, medicine, and industry. This article was prompted by my experience in the curative treatment of cancer patients by protons and my interest in the nature of protons as particles. The latter has been stimulated by many discussions with particle physicists and reading related books and journals. Protons in our universe number ≈10{sup 80}. Protons were created at 10{sup −6} –1 second after the Big Bang at ≈1.37 × 10{sup 10} years beforethe present. Proton life span has been experimentally determined to be ≥10{sup 34} years; that is, the age of the universe is 10{sup −24}th of the minimum life span of a proton. The abundance of the elements is hydrogen, ≈74%; helium, ≈24%; and heavier atoms, ≈2%. Accordingly, protons are the dominant baryonic subatomic particle in the universe because ≈87% are protons. They are in each atom in our universe and thus involved in virtually every activity of matter in the visible universe, including life on our planet. Protons were discovered in 1919. In 1968, they were determined to be composed of even smaller particles, principally quarks and gluons. Protons have been the experimental tool in the discoveries of quarks (charm, bottom, and top), bosons (W{sup +}, W{sup −}, Z{sup 0}, and Higgs), antiprotons, and antineutrons. Industrial applications of protons are numerous and important. Additionally, protons are well appreciated in medicine for their role in radiation oncology and in magnetic resonance imaging. Protons are the dominant baryonic subatomic particle in the visible universe, comprising ≈87% of the particle mass. They are present in each atom of our universe and thus a participant in every activity involving matter.

  18. STATISTICS OF DARK MATTER HALOS FROM THE EXCURSION SET APPROACH

    SciTech Connect

    Lapi, A.; Salucci, P.; Danese, L.

    2013-08-01

    We exploit the excursion set approach in integral formulation to derive novel, accurate analytic approximations of the unconditional and conditional first crossing distributions for random walks with uncorrelated steps and general shapes of the moving barrier; we find the corresponding approximations of the unconditional and conditional halo mass functions for cold dark matter (DM) power spectra to represent very well the outcomes of state-of-the-art cosmological N-body simulations. In addition, we apply these results to derive, and confront with simulations, other quantities of interest in halo statistics, including the rates of halo formation and creation, the average halo growth history, and the halo bias. Finally, we discuss how our approach and main results change when considering random walks with correlated instead of uncorrelated steps, and warm instead of cold DM power spectra.

  19. SUBSTRUCTURE IN THE STELLAR HALOS OF THE AQUARIUS SIMULATIONS

    SciTech Connect

    Helmi, Amina; Cooper, A. P.; Cole, S.; Frenk, C. S.; White, S. D. M.; Navarro, J. F.

    2011-05-20

    We characterize the substructure in the simulated stellar halos of Cooper et al. which were formed by the disruption of satellite galaxies within the cosmological N-body simulations of galactic halos of the Aquarius project. These stellar halos exhibit a wealth of tidal features: broad overdensities and very narrow faint streams akin to those observed around the Milky Way. The substructures are distributed anisotropically on the sky, a characteristic that should become apparent in the next generation of photometric surveys. The normalized RMS of the density of stars on the sky appears to be systematically larger for our halos compared with the value estimated for the Milky Way from main-sequence turnoff stars in the Sloan Digital Sky Survey. We show that this is likely to be due in part to contamination by faint QSOs and redder main-sequence stars, and might suggest that {approx}10% of the Milky Way halo stars have formed in situ.

  20. Observations of diffusion in the electron halo and strahl

    NASA Astrophysics Data System (ADS)

    Gurgiolo, Chris; Goldstein, Melvyn L.

    2016-12-01

    Observations of the three-dimensional solar wind electron velocity distribution functions (VDF) using ϕ-θ plots often show a tongue of electrons that begins at the strahl and stretches toward a new population of electrons, termed the proto-halo, that exists near the projection of the magnetic field opposite that associated with the strahl. The energy range in which the tongue and proto-halo are observed forms a "diffusion zone". The tongue first appears in energy generally near the lower-energy range of the strahl and in the absence of any clear core/halo signature. While the ϕ-θ plots give the appearance that the tongue and proto-halo are derived from the strahl, a close examination of their density suggests that their source is probably the upper-energy core/halo electrons which have been scattered by one or more processes into these populations.

  1. A halo and a blow-out in NGC 253

    NASA Technical Reports Server (NTRS)

    Carilli, C. L.; Holdaway, M. A.; Ho, P. T. P.

    1993-01-01

    We present the discovery of a 'synchrotron halo' in NGC 253. NGC 253 is an inclined, dusty, barred Sc galaxy in the Sculptor Group. It is also one of the prototype nuclear star burst galaxies. Very Large Array observations at 327 MHz and 1.4 GHz have revealed a synchrotron emitting 'halo' extending 9 kpc above and below the plane of NGC 253 (assuming a distance of 4 Mpc). The spectral index for the radio emission steepens from -0.7 in the disk to -1.0 in the halo. The fractional polarization at 1.4 GHz increases from less than or equal to 2 percent in the disk up to 20 percent in the halo, and the magnetic field vectors project parallel to the plane over most of the halo.

  2. Interstellar protonated molecular species

    NASA Astrophysics Data System (ADS)

    Etim, Emmanuel E.; Gorai, Prasanta; Das, Ankan; Arunan, Elangannan

    2017-08-01

    Majority of the known interstellar cations are protonated species believed to be the natural precursors for their corresponding neutral analogues formed via the dissociative recombination process. The protonation of a neutral species can occur in more than one position on the molecular structure thus resulting in more than one proton binding energy value and different protonated species for the same neutral species. In the present work, ab initio quantum calculations are employed to calculate accurate proton binding energies for over 100 neutral interstellar molecules of which majority of the neutral molecules are protonated in more than one position. From the results, protonated species resulting from a high proton binding energy prefers to remain protonated rather than transferring a proton and returning to its neutral form as compared to its analogue that gives rise to a lower proton binding energy (PBE) from the same neutral species. For two protonated species resulting from the same neutral molecule, the one that results in a higher PBE is more stable as compared to its counterpart that is responsible for the lower PBE for the same neutral species. Here, the most stable species are highlighted for all the systems considered.

  3. Binary white dwarfs in the halo of the Milky Way

    NASA Astrophysics Data System (ADS)

    van Oirschot, Pim; Nelemans, Gijs; Toonen, Silvia; Pols, Onno; Brown, Anthony G. A.; Helmi, Amina; Portegies Zwart, Simon

    2014-09-01

    Aims: We study single and binary white dwarfs in the inner halo of the Milky Way in order to learn more about the conditions under which the population of halo stars was born, such as the initial mass function (IMF), the star formation history, or the binary fraction. Methods: We simulate the evolution of low-metallicity halo stars at distances up to ~3 kpc using the binary population synthesis code SeBa. We use two different white dwarf cooling models to predict the present-day luminosities of halo white dwarfs. We determine the white dwarf luminosity functions (WDLFs) for eight different halo models and compare these with the observed halo WDLF of white dwarfs in the SuperCOSMOS Sky Survey. Furthermore, we predict the properties of binary white dwarfs in the halo and determine the number of halo white dwarfs that is expected to be observed with the Gaia satellite. Results: By comparing the WDLFs, we find that a standard IMF matches the observations more accurately than a top-heavy one, but the difference with a bottom-heavy IMF is small. A burst of star formation 13 Gyr ago fits slightly better than a star formation burst 10 Gyr ago and also slightly better than continuous star formation 10-13 Gyr ago. Gaia will be the first instument to constrain the bright end of the field halo WDLF, where contributions from binary WDs are considerable. Many of these will have He cores, of which a handful have atypical surface gravities (log g < 6) and reach luminosities log (L/L⊙) > 0 in our standard model for WD cooling. These so called pre-WDs, if observed, can help us to constrain white dwarf cooling models and might teach us something about the fraction of halo stars that reside in binaries. Appendices are available in electronic form at http://www.aanda.org

  4. Kinematic imprint of clumpy disk formation on halo objects

    NASA Astrophysics Data System (ADS)

    Inoue, Shigeki

    2013-02-01

    Context. Clumpy disk galaxies in the distant universe, at redshift of z ≳ 1, have been observed to host several giant clumps in their disks. They are thought to correspond to early formative stages of disk galaxies. On the other hand, halo objects, such as old globular clusters and halo stars, are likely to consist of the oldest stars in a galaxy (age ≳ 10 Gyr), clumpy disk formation can thus be presumed to take place in a pre-existing halo system. Aims: Giant clumps orbit in the same direction in a premature disk and are so massive that they may be expected to interact gravitationally with halo objects and exercise influence on the kinematic state of the halo. Accordingly, I scrutinize the possibility that the clumps leave a kinematic imprint of the clumpy disk formation on a halo system. Methods: I perform a restricted N-body calculation with a toy model to study the kinematic influence on a halo by orbital motions of clumps and the dependence of the results on masses (mass loss), number, and orbital radii of the clumps. Results: I show that halo objects can catch clump motions and acquire disky rotation in a dynamical friction time scale of the clumps, ~0.5 Gyr. The influence of clumps is limited within a region around the disk, while the halo system shows vertical gradients of net rotation velocity and orbital eccentricity. The significance of the kinematic influence strongly depends on the clump masses; the lower limit of postulated clump mass would be ~5 × 108 M⊙. The result also depends on whether the clumps are subjected to rapid mass loss or not, which is an open question under debate in recent studies. The existence of such massive clumps is not unrealistic. I therefore suggest that the imprints of past clumpy disk formation could remain in current galactic halos.

  5. The Origin of Angular Momentum in Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Vitvitska, Maya; Klypin, Anatoly A.; Kravtsov, Andrey V.; Wechsler, Risa H.; Primack, Joel R.; Bullock, James S.

    2002-12-01

    We propose a new explanation for the origin of angular momentum in galaxies and their dark halos, in which the halos obtain their spin through the cumulative acquisition of angular momentum from satellite accretion. In our model, the buildup of angular momentum is a random walk process associated with the mass assembly history of the halo's major progenitor. We assume no correlation between the angular momenta of accreted objects. The main role of tidal torques in this approach is to produce the random tangential velocities of merging satellites. Using the extended Press-Schechter approximation, we calculate the growth of mass, angular momentum, and spin parameter λ for many halos. Our random walk model reproduces the key features of the angular momentum of halos found in ΛCDM N-body simulations: a lognormal distribution in λ with an average of <λ>~0.045 and dispersion σλ=0.56, independent of mass and redshift. The evolution of the spin parameter in individual halos in this model is quite different from the steady increase with time of angular momentum in the tidal torque picture. We find both in N-body simulations and in our random walk model that the value of λ changes significantly with time for a halo's major progenitor. It typically has a sharp increase due to major mergers and a steady decline during periods of gradual accretion of small satellites. The model predicts that, on average, the λ of ~1012 Msolar halos that had major mergers after redshift z=3 should be substantially larger than the λ of those that did not. Perhaps surprisingly, this suggests that halos that host later forming elliptical galaxies should rotate faster than halos of spiral galaxies.

  6. Mapping the Galactic Halo. I. The ``Spaghetti'' Survey

    NASA Astrophysics Data System (ADS)

    Morrison, Heather L.; Mateo, Mario; Olszewski, Edward W.; Harding, Paul; Dohm-Palmer, R. C.; Freeman, Kenneth C.; Norris, John E.; Morita, Miwa

    2000-05-01

    We describe a major survey of the Milky Way halo designed to test for kinematic substructure caused by destruction of accreted satellites. We use the Washington photometric system to identify halo stars efficiently for spectroscopic follow-up. Tracers include halo giants (detectable out to more than 100 kpc), blue horizontal-branch (BHB) stars, halo stars near the main-sequence turnoff, and the ``blue metal-poor stars'' of Preston, Beers, & Shectman. We demonstrate the success of our survey by showing spectra of stars we have identified in all these categories, including giants as distant as 75 kpc. We discuss the problem of identifying the most distant halo giants. In particular, extremely metal-poor halo K dwarfs are present in approximately equal numbers to the distant giants for V>18, and we show that our method will distinguish reliably between these two groups of metal-poor stars. We plan to survey 100 deg2 at high Galactic latitude and expect to increase the numbers of known halo giants, BHB stars, and turnoff stars by more than an order of magnitude. In addition to the strong test that this large sample will provide for the question, Was the Milky Way halo accreted from satellite galaxies? we will improve the accuracy of mass measurements of the Milky Way beyond 50 kpc via the kinematics of the many distant giants and BHB stars we find. We show that one of our first data sets constrains the halo density law over Galactocentric radii of 5-20 kpc and z-heights of 2-15 kpc. The data support a flattened power-law halo with b/a of 0.6 and exponent -3.0. More complex models with a varying axial ratio may be needed with a larger data set.

  7. Zooming in on accretion - I. The structure of halo gas

    NASA Astrophysics Data System (ADS)

    Nelson, Dylan; Genel, Shy; Pillepich, Annalisa; Vogelsberger, Mark; Springel, Volker; Hernquist, Lars

    2016-08-01

    We study the properties of gas in and around 1012 M⊙ haloes at z = 2 using a suite of high-resolution cosmological hydrodynamic `zoom' simulations. We quantify the thermal and dynamical structure of these gaseous reservoirs in terms of their mean radial distributions and angular variability along different sightlines. With each halo simulated at three levels of increasing resolution, the highest reaching a baryon mass resolution of ˜10 000 solar masses, we study the interface between filamentary inflow and the quasi-static hot halo atmosphere. We highlight the discrepancy between the spatial resolution available in the halo gas as opposed to within the galaxy itself, and find that stream morphologies become increasingly complex at higher resolution, with large coherent flows revealing density and temperature structure at progressively smaller scales. Moreover, multiple gas components co-exist at the same radius within the halo, making radially averaged analyses misleading. This is particularly true where the hot, quasi-static, high entropy halo atmosphere interacts with cold, rapidly inflowing, low entropy accretion. Haloes at this mass have a well-defined virial shock, associated with a sharp jump in temperature and entropy at ≳ 1.25 rvir. The presence, radius, and radial width of this boundary feature, however, vary not only from halo to halo, but also as a function of angular direction, covering roughly ˜75 per cent of the 4π sphere. We investigate the process of gas virialization as imprinted in the halo structure, and discuss different modes for the accretion of gas from the intergalactic medium.

  8. HALO384: a halo-based potency prediction algorithm for high-throughput detection of antimicrobial agents.

    PubMed

    Woehrmann, Marcos H; Gassner, Nadine C; Bray, Walter M; Stuart, Joshua M; Lokey, Scott

    2010-02-01

    A high-throughput (HT) agar-based halo assay is described, which allows for rapid screening of chemical libraries for bioactivity in microorganisms such as yeast and bacteria. A pattern recognition algorithm was developed to identify halo-like shapes in plate reader optical density (OD) measurements. The authors find that the total growth inhibition within a detected halo provides an accurate estimate of a compound's potency measured in terms of its EC(50). The new halo recognition method performs significantly better than an earlier method based on single-point OD readings. An assay based on the halo algorithm was used to screen a 21,120-member library of drug-like compounds in Saccharomyces cerevisiae, leading to the identification of novel bioactive scaffolds containing derivatives of varying potencies. The authors also show that the HT halo assay can be performed with the pathogenic bacterium Vibrio cholerae and that liquid culture EC(50) values and halo scores show a good correlation in this organism. These results suggest that the HT halo assay provides a rapid and inexpensive way to screen for bioactivity in multiple microorganisms.

  9. The practical Pomeron for high energy proton collimation

    NASA Astrophysics Data System (ADS)

    Appleby, R. B.; Barlow, R. J.; Molson, J. G.; Serluca, M.; Toader, A.

    2016-10-01

    We present a model which describes proton scattering data from ISR to Tevatron energies, and which can be applied to collimation in high energy accelerators, such as the LHC and FCC. Collimators remove beam halo particles, so that they do not impinge on vulnerable regions of the machine, such as the superconducting magnets and the experimental areas. In simulating the effect of the collimator jaws it is crucial to model the scattering of protons at small momentum transfer t, as these protons can subsequently survive several turns of the ring before being lost. At high energies these soft processes are well described by Pomeron exchange models. We study the behaviour of elastic and single-diffractive dissociation cross sections over a wide range of energy, and show that the model can be used as a global description of the wide variety of high energy elastic and diffractive data presently available. In particular it models low mass diffraction dissociation, where a rich resonance structure is present, and thus predicts the differential and integrated cross sections in the kinematical range appropriate to the LHC. We incorporate the physics of this model into the beam tracking code MERLIN and use it to simulate the resulting loss maps of the beam halo lost in the collimators in the LHC.

  10. SU-E-T-443: Developmental Technique for Proton Pencil Beam Measurements: Depth Dose

    SciTech Connect

    Arjomandy, B; Lee, T; Schultz, T; Hsi, W; Park, S

    2014-06-01

    Purpose: Measurements of depth dose distribution (DDD) of pencil beam in proton therapy can be challenging and time consuming. We have developed a technique that uses two Bragg peak chambers to expedite these measurements with a high accuracy. Methods and Material: We used a PTW water tank and two PTW 10.5 cm3 Bragg peak chambers; one as a field chamber and the other as a reference chamber to measure DDDs for 100–250 MeV proton pencil beams. The reference chamber was positioned outside of the water tank upstream with respect to field chamber. We used Geant4 Monte Carlo Simulation (MCS) to model the ProTom proton beam to generate DDDs. The MCS generated DDDs were used to account for halo effects of proton pencil beam that are not measureable with Bragg peak chambers. We also used PTW PEAKFINDER to measure DDDs for comparison purpose. Results: We compared measured and MCS DDDs with Continuous Slowing Down Approximation (CSDA) ranges to verify the range of proton beams that were supplied by the manufacturer. The agreements between all DDD with respect to CSDA were within ±0.5 mm. The WET for Bragg peak chamber for energies between 100–250 MeV was 12.7 ± 0.5 mm. The correction for halo effect was negligible below 150 MeV and was in order of ∼5-10% for 150–250 MeV. Conclusion: Use of Bragg Peak chamber as a reference chamber can facilitate DDD measurements in proton pencil beam with a high accuracy. Some corrections will be required to account for halo effect in case of high energy proton beams due to physical size of chamber.

  11. Turbulence and particle acceleration in giant radio haloes: the origin of seed electrons

    NASA Astrophysics Data System (ADS)

    Pinzke, Anders; Oh, S. Peng; Pfrommer, Christoph

    2017-03-01

    About one-third of X-ray-luminous clusters show smooth, Mpc-scale radio emission, known as giant radio haloes. One promising model for radio haloes is Fermi-II acceleration of seed relativistic electrons by compressible turbulence. The origin of these seed electrons has never been fully explored. Here, we integrate the Fokker-Planck equation of the cosmic ray (CR) electron and proton distributions when post-processing cosmological simulations of cluster formation and confront them with radio surface brightness and spectral data of Coma. For standard assumptions, structure formation shocks lead to a seed electron population that produces too centrally concentrated radio emission. Matching observations requires modifying properties of the CR population (rapid streaming; enhanced CR electron acceleration at shocks) or turbulence (increasing turbulent-to-thermal energy density with radius), but at the expense of fine-tuning. In a parameter study, we find that radio properties are exponentially sensitive to the amplitude of turbulence, which is inconsistent with small scatter in scaling relations. This sensitivity is removed if we relate the acceleration time to the turbulent dissipation time. In this case, turbulence above a threshold value provides a fixed amount of amplification; observations could thus potentially constrain the unknown CR seed population. To obtain sufficient acceleration, the turbulent magneto-hydrodynamics cascade has to terminate by transit time damping on CRs, i.e. thermal particles must be scattered by plasma instabilities. Understanding the small scatter in radio halo scaling relations may provide a rich source of insight on plasma processes in clusters.

  12. [Halos and multifocal intraocular lenses: origin and interpretation].

    PubMed

    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

  13. The Making of the Milky Way Halo

    NASA Astrophysics Data System (ADS)

    1999-02-01

    The VLT Watches a Dissolving Stellar Cluster A group of ESO astronomers [1] has used new observations, obtained with the first 8.2-m VLT Unit Telescope (UT1) during the "Science Verification" programme, to show that a globular cluster in the Milky Way galaxy is "evaporating" and has already lost its faintest stars. This is the first observational result of its kind and has important implications for future studies. It may be explained by a gradual loss of such stars from the cluster into the Milky Way halo, a roughly spherical region around the much flatter, spiral structure in which most of the stars and nebulae are located. The new result lends strong support to current theories about the evolution of the structure of this halo and also provides insights into the formation of the galaxy in which we live. Globular clusters and the halo of the Milky Way The stars that we observe in the halo of the Milky Way represent only a small fraction of the total mass in this region. Investigations of the motions of stars in our Galaxy have shown that this halo must harbour much more matter, which is hidden from our view. The same phenomenon has been observed in other galaxies, and astronomers refer to it as "dark matter". It is at this moment not known what this matter consists of. The brightest objects in the halo are the globular clusters . They are large groupings of stars that were formed together in the very early evolutionary phases of the Milky Way, some 12,000 - 14,000 million years ago. This happened soon after the moment when the first structures emerged in the large cloud of primordial hydrogen in which our Galaxy was born. A popular scenario describes the first build-up of galactic structure, i.e. of stars and gas, as when normal matter began to collect inside the dark-matter halo, due to its strong gravitational attraction. The globular clusters were most probably the first denizens of this protogalaxy . It is believed that the Milky Way Galaxy subsequently

  14. Neutron Skins and Halo Orbits in the s d and p f Shells

    NASA Astrophysics Data System (ADS)

    Bonnard, J.; Lenzi, S. M.; Zuker, A. P.

    2016-05-01

    The strong dependence of Coulomb energies on nuclear radii makes it possible to extract the latter from calculations of the former. The resulting estimates of neutron skins indicate that two mechanisms are involved. The first one—isovector monopole polarizability—amounts to noting that when a particle is added to a system it drives the radii of neutrons and protons in different directions, tending to equalize the radii of both fluids independently of the neutron excess. This mechanism is well understood and the Duflo-Zuker (small) neutron skin values derived 14 years ago are consistent with recent measures and estimates. The alternative mechanism involves halo orbits whose huge sizes tend to make the neutron skins larger and have a subtle influence on the radial behavior of s d and p f shell nuclei. In particular, they account for the sudden rise in the isotope shifts of nuclei beyond N =28 and the near constancy of radii in the A =40 - 56 region. This mechanism, detected here for the first time, is not well understood and may well go beyond the Efimov physics usually associated with halo orbits.

  15. A new halo-independent approach to dark matter direct detection analysis

    SciTech Connect

    Feldstein, Brian; Kahlhoefer, Felix E-mail: felix.kahlhoefer@physics.ox.ac.uk

    2014-08-01

    Uncertainty in the local dark matter velocity distribution is a key difficulty in the analysis of data from direct detection experiments. Here we propose a new approach for dealing with this uncertainty, which does not involve any assumptions about the structure of the dark matter halo. Given a dark matter model, our method yields the velocity distribution which best describes a set of direct detection data as a finite sum of streams with optimised speeds and densities. The method is conceptually simple and numerically very efficient. We give an explicit example in which the method is applied to determining the ratio of proton to neutron couplings of dark matter from a hypothetical set of future data.

  16. The mass transfer kinetics in columns packed with Halo-ES shell particles.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2011-02-18

    The average mesopore size of the new Halo-ES-Peptide shell particles is 160 Å, markedly larger than that of the classical Halo shell particles (90 Å). We found that this change causes a considerable decrease of the film mass transfer resistance measured for columns packed with these particles. We analyze data obtained by systematic measurements of the C term of the van Deemter equation for the peptide β-lipotropin (MW = 769 Da), the protein insulin (MW = 5800 Da), and a series of non-retained polystyrene standards (MW = 6400 and 13,200). The improvement in column performance is explained by an increase of the fraction of the external surface area of the shell that allows the entrance of the sample molecules inside the particle. The fraction of the shell surface accessible to a probe controls the rate of its external film mass transfer, i.e. its rate of transfer between the interstitial and the stagnant eluent. Although measurable, the increase in sample diffusivity through the porous shells does not account for the better performance of Halo-ES-peptide columns. Furthermore, the analysis of the HETPs data of small molecules (uracil, acetophenone, toluene, and naphthalene, MW< 150) reveals that the eddy diffusion (A) term of these new columns is 25% lower than that of the classical Halo columns. This result is consistent with the impact of intra-particle diffusivity on the eddy diffusion mechanism in packed columns. As shell diffusivity increases, so does the rate of transfer of sample molecules between the eluent stream-paths flowing through the packed particles and across the column diameter. Dispersion through short-range inter-channel and trans-column eddies is reduced. Copyright © 2010 Elsevier B.V. All rights reserved.

  17. Study of proton radioactivities

    SciTech Connect

    Davids, C.N.; Back, B.B.; Henderson, D.J.

    1995-08-01

    About a dozen nuclei are currently known to accomplish their radioactive decay by emitting a proton. These nuclei are situated far from the valley of stability, and mark the very limits of existence for proton-rich nuclei: the proton drip line. A new 39-ms proton radioactivity was observed following the bombardment of a {sup 96}Ru target by a beam of 420-MeV {sup 78}Kr. Using the double-sided Si strip detector implantation system at the FMA, a proton group having an energy of 1.05 MeV was observed, correlated with the implantation of ions having mass 167. The subsequent daughter decay was identified as {sup 166}Os by its characteristic alpha decay, and therefore the proton emitter is assigned to the {sup 167}Ir nucleus. Further analysis showed that a second weak proton group from the same nucleus is present, indicating an isomeric state. Two other proton emitters were discovered recently at the FMA: {sup 171}Au and {sup 185}Bi, which is the heaviest known proton radioactivity. The measured decay energies and half-lives will enable the angular momentum of the emitted protons to be determined, thus providing spectroscopic information on nuclei that are beyond the proton drip line. In addition, the decay energy yields the mass of the nucleus, providing a sensitive test of mass models in this extremely proton-rich region of the chart of the nuclides. Additional searches for proton emitters will be conducted in the future, in order to extend our knowledge of the location of the proton drip line.

  18. Evaluation and evolution of speed for halo and partial halo CMEs

    NASA Astrophysics Data System (ADS)

    Becerril, Carlos; Muñoz Martínez, Guadalupe; Lopez-Lopez, Jose Luis

    Halo CMEs are known to be directed towards the Earth; and therefore are of great interest in space weather forecasting. Two main issues are involved in making good arrival predictions: the precision of the evaluation of the initial parameters near the Sun and an appropriate model for ICME propagation. The initial CME speed and direction are needed to infer the travel time, but these crucial parameters are difficult to obtain for earthward pointed CMEs. In this work we identified halo and partial halo CMES associated to EIT flares and Interplanetary Shocks. Considering the location of the flare and the projection effect we evaluated the initial speed of the CME; using the initial values we calculated the arrival time and speed and compared these values to the ones of the ICME related. We found a good approximation to the actual parameters, showing that the models applied in the evaluation of the initial parameters and the prediction of the final ones are consistent to the real evolution of the phenomena.

  19. Inhomogeneous chemical enrichment in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Kobayashi, Chiaki

    2015-08-01

    In a galaxy, chemical enrichment takes place in an inhomogeneous fashion, and the Galactic Halo is one of the places where the inhomogeneous effects are imprinted and can be constrained from observations. I show this using my chemodynamical simulations of Milky Way type galaxies. The scatter in the elemental abundances is originated from radial migration, merging/accretion of satellite galaxies, local variation of star formation and chemical enrichment, and intrinsic variation of nucleosynthesis yields. In the simulated galaxies, there is no strong age-metallicity relations. This means that the most metal poor stars are not always the oldest stars, and can be formed in chemically unevolved clouds at later times. The long-lifetime sources of chemical enrichment such as asymptotic giant blanch stars or neutron star mergers can contribute the abundance patterns of extremely metal-poor stars, which are in good agreement with observations.

  20. Jupiter's Main Ring/Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (28.5 miles) per picture element (pixel) along Jupiter's rings. Because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow, peering back toward the Sun; the ring was approximately 2.3 million kilometers (1.4 million miles) away. The arc on the far right of the image is produced when sunlight is scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts - - a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, outside the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the figure's far left side. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. Some radial structure is barely visible across the ring's ansa (top image). A faint mist of particles can be seen above and below the main rings. This vertically extended 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces pushing the smallest grains out of the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. To accentuate faint features in the bottom image of the ring halo, different brightnesses are shown through color. Brightest features are white or yellow and the

  1. Jupiter's Main Ring/Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (28.5 miles) per picture element (pixel) along Jupiter's rings. Because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow, peering back toward the Sun; the ring was approximately 2.3 million kilometers (1.4 million miles) away. The arc on the far right of the image is produced when sunlight is scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts - - a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, outside the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the figure's far left side. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. Some radial structure is barely visible across the ring's ansa (top image). A faint mist of particles can be seen above and below the main rings. This vertically extended 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces pushing the smallest grains out of the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. To accentuate faint features in the bottom image of the ring halo, different brightnesses are shown through color. Brightest features are white or yellow and the

  2. The optical halo around NGC 253

    NASA Astrophysics Data System (ADS)

    Beck, R.; Hutschenreiter, G.; Wielebinski, R.

    1982-02-01

    A photographic technique of image enhancement and digital smoothing of P.D.S. scans are used to study the blue light from an extended halo surrounding NGC 253. The photographic technique, described by Malin (1978), is based on the fact that the true image is formed in the topmost surface layer of the emission of a plate, while the fog is found in deeper layers of the emulsion. The investigation made it possible to follow the distribution of light out to 10 kpc from the plane of the galaxy. Synchrotron emission is responsible for the bulk of radio continuum emission in NGC 253 (Beck et al., 1979). Moreover, the radio map at a wavelength of 3.4 cm shows a spur-like feature at the exact position where the diffuse loop of light is seen, indicating a similar emission origin.

  3. The Extent of Hot Gaseous Galaxy Halos

    NASA Astrophysics Data System (ADS)

    Bregman, Joel N.; Anderson, Michael E.; Hodges-Kluck, Edmund J.; Miller, Matthew J.; Dai, Xinyu

    2017-01-01

    There are several constraints on the hot gas distribution around the Milky Way and external galaxies, but they are confined to within about 50 kpc, approximately 0.2R200. Beyond 0.2R200, several density distributions have been proposed, some that contain all the missing baryons within R200 and others that have the baryons extending to 2-3R200 before reaching the cosmological baryon to dark matter ratio. These differences are determined by galaxy formation processes and by feedback from supernovae and AGN. We present the conflicting evidence for the different extended baryon distributions. A clearer picture of the properties of these hot galaxy halos would be provided by high resolution soft X-ray spectroscopy, such as of the O VII and O VIII resonance lines, and the proposed Arcus mission would enable these breakthrough observations.

  4. Particle Dark Matter in the galactic halo

    NASA Astrophysics Data System (ADS)

    Bernabei, R.; Belli, P.; D'Angelo, S.; di Marco, A.; Montecchia, F.; D'Angelo, A.; Incicchitti, A.; Cappella, F.; Caracciolo, V.; Cerulli, R.; Dai, C. J.; He, H. L.; Kuang, H. H.; Ma, X. H.; Sheng, X. D.; Wang, R. G.; Ye, Z. P.

    2015-10-01

    The DAMA/LIBRA-phase1 and the former DAMA/NaI data (cumulative exposure 1.33 ton × yr, corresponding to 14 annual cycles) give evidence at 9.3σ C.L. for the presence of Dark Matter (DM) particles in the galactic halo, on the basis of the exploited model independent DM annual modulation signature by using highly radio-pure NaI(Tl) target. Results and comparisons will be shortly recalled. Recent analyses on possible diurnal effects and on the Earth shadowing effect (the latter holds only for some DM candidates) will be mentioned. The analysis of the time distribution of the low-energy single-hit events in DAMA/LIBRA-phase1 is reported for the first time. Finally, some perspectives of the presently running DAMA/LIBRA-phase2 will be mentioned.

  5. The halo sign: HRCT findings in 85 patients

    PubMed Central

    Alves, Giordano Rafael Tronco; Marchiori, Edson; Irion, Klaus; Nin, Carlos Schuler; Watte, Guilherme; Pasqualotto, Alessandro Comarú; Severo, Luiz Carlos; Hochhegger, Bruno

    2016-01-01

    ABSTRACT Objective: The halo sign consists of an area of ground-glass opacity surrounding pulmonary lesions on chest CT scans. We compared immunocompetent and immunosuppressed patients in terms of halo sign features and sought to identify those of greatest diagnostic value. Methods: This was a retrospective study of CT scans performed at any of seven centers between January of 2011 and May of 2015. Patients were classified according to their immune status. Two thoracic radiologists reviewed the scans in order to determine the number of lesions, as well as their distribution, size, and contour, together with halo thickness and any other associated findings. Results: Of the 85 patients evaluated, 53 were immunocompetent and 32 were immunosuppressed. Of the 53 immunocompetent patients, 34 (64%) were diagnosed with primary neoplasm. Of the 32 immunosuppressed patients, 25 (78%) were diagnosed with aspergillosis. Multiple and randomly distributed lesions were more common in the immunosuppressed patients than in the immunocompetent patients (p < 0.001 for both). Halo thickness was found to be greater in the immunosuppressed patients (p < 0.05). Conclusions: Etiologies of the halo sign differ markedly between immunocompetent and immunosuppressed patients. Although thicker halos are more likely to occur in patients with infectious diseases, the number and distribution of lesions should also be taken into account when evaluating patients presenting with the halo sign. PMID:28117474

  6. The slight spin of the old stellar halo

    NASA Astrophysics Data System (ADS)

    Deason, Alis J.; Belokurov, Vasily; Koposov, Sergey E.; Gómez, Facundo A.; Grand, Robert J.; Marinacci, Federico; Pakmor, Rüdiger

    2017-09-01

    We combine Gaia data release 1 astrometry with Sloan Digital Sky Survey (SDSS) images taken some ∼10-15 years earlier, to measure proper motions of stars in the halo of our Galaxy. The SDSS-Gaia proper motions have typical statistical errors of 2 mas yr-1 down to r ∼ 20 mag, and are robust to variations with magnitude and colour. Armed with this exquisite set of halo proper motions, we identify RR Lyrae, blue horizontal branch (BHB), and K giant stars in the halo, and measure their net rotation with respect to the Galactic disc. We find evidence for a gently rotating prograde signal (〈Vϕ〉 ∼ 5-25 km s-1) in the halo stars, which shows little variation with Galactocentric radius out to 50 kpc. The average rotation signal for the three populations is 〈Vϕ〉 = 14 ± 2 ± 10 (syst.) km s-1. There is also tentative evidence for a kinematic correlation with metallicity, whereby the metal richer BHB and K giant stars have slightly stronger prograde rotation than the metal poorer stars. Using the Auriga simulation suite, we find that the old (T >10 Gyr) stars in the simulated haloes exhibit mild prograde rotation, with little dependence on radius or metallicity, in general agreement with the observations. The weak halo rotation suggests that the Milky Way has a minor in situ halo component, and has undergone a relatively quiet accretion history.

  7. Optimal linear reconstruction of dark matter from halo catalogues

    DOE PAGES

    Cai, Yan -Chuan; Bernstein, Gary; Sheth, Ravi K.

    2011-04-01

    The dark matter lumps (or "halos") that contain galaxies have locations in the Universe that are to some extent random with respect to the overall matter distributions. We investigate how best to estimate the total matter distribution from the locations of the halos. We derive the weight function w(M) to apply to dark-matter haloes that minimizes the stochasticity between the weighted halo distribution and its underlying mass density field. The optimal w(M) depends on the range of masses of halos being used. While the standard biased-Poisson model of the halo distribution predicts that bias weighting is optimal, the simple factmore » that the mass is comprised of haloes implies that the optimal w(M) will be a mixture of mass-weighting and bias-weighting. In N-body simulations, the Poisson estimator is up to 15× noisier than the optimal. Optimal weighting could make cosmological tests based on the matter power spectrum or cross-correlations much more powerful and/or cost effective.« less

  8. Optimal linear reconstruction of dark matter from halo catalogues

    SciTech Connect

    Cai, Yan -Chuan; Bernstein, Gary; Sheth, Ravi K.

    2011-04-01

    The dark matter lumps (or "halos") that contain galaxies have locations in the Universe that are to some extent random with respect to the overall matter distributions. We investigate how best to estimate the total matter distribution from the locations of the halos. We derive the weight function w(M) to apply to dark-matter haloes that minimizes the stochasticity between the weighted halo distribution and its underlying mass density field. The optimal w(M) depends on the range of masses of halos being used. While the standard biased-Poisson model of the halo distribution predicts that bias weighting is optimal, the simple fact that the mass is comprised of haloes implies that the optimal w(M) will be a mixture of mass-weighting and bias-weighting. In N-body simulations, the Poisson estimator is up to 15× noisier than the optimal. Optimal weighting could make cosmological tests based on the matter power spectrum or cross-correlations much more powerful and/or cost effective.

  9. Solar wind halo electrons from 1-4 AU

    NASA Technical Reports Server (NTRS)

    Mccomas, D. J.; Bame, S. J.; Feldman, W. C.; Gosling, J. T.; Phillips, J. L.

    1992-01-01

    Observations from the Ulysses solar wind electron spectrometer are used to make a first examination of the evolution of the solar wind suprathermal or halo electron population as a function of heliocentric distance beyond 1 AU. As the core population cools with increasing heliocentric distance, no gap is formed between the core and halo populations. Rather, the halo electrons extend to increasingly lower energies. As predicted previously on theoretical grounds, the ratio of the core electron temperature to the low energy cutoff of the halo population appears to be roughly constant with a value of about 7.5. The total integrated heat flux drops rapidly with increasing heliocentric distance; a best fit power law of R exp -2.36 is found. In addition, it is found that the ratio of the halo to core densities is roughly constant over heliocentric distance with the halo representing 4 percent of the total electron distribution. These results suggest that the halo population may not consist of truly noninteractive test particles over the heliocentric range of 1-4 AU.

  10. Historic halo displays as weather indicator: Criteria and examples

    NASA Astrophysics Data System (ADS)

    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)

  11. The Halos and Environments of Nearby Galaxies (HERON) Survey

    NASA Astrophysics Data System (ADS)

    Rich, R. Michael; Brosch, Noah; Bullock, James; Burkert, Andreas; Collins, Michelle; de Groot, Laura; Kennefick, Julia; Koch, Andreas; Longstaff, Francis; Sales, Laura

    2017-03-01

    We have used dedicated 0.7m telescopes in California and Israel to image the halos of ~ 200 galaxies in the Local Volume to 29 mag/sq arcsec, the sample mainly drawn from the 2MASS Large Galaxy Atlas (LGA). We supplement the LGA sample with dwarf galaxies and more distant giant ellipticals. Low surface brightness halos exceeding 50 kpc in diameter are found only in galaxies more luminous than L*, and classic interaction signatures are relatively infrequent. Halo diameter is correlated with total galaxy luminosity. Extended low surface brightness halos are present even in galaxies as faint as MV = - 18. Edge-on galaxies with boxy bulges tend to lack extended spheroidal halos, while those with large classical bulges exhibit extended round halos, supporting the notions that boxy or barlike bulges originate from disks. Most face-on spiral galaxies present features that appear to be irregular extensions of spiral arms, although rare cases show smooth boundaries with no sign of star formation. Although we serendipitously discovered a dwarf galaxy undergoing tidal disruption in the halo of NGC 4449, we found no comparable examples in our general survey. A search for similar examples in the Local Volume identified hcc087, a tidally disrupting dwarf galaxy in the Hercules Cluster, but we do not confirm an anomalously large half-light radius reported for the dwarf VCC 1661.

  12. Universal Dark Halo Scaling Relation for the Dwarf Spheroidal Satellites

    NASA Astrophysics Data System (ADS)

    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 }.

  13. Characterization of Polar Mesospheric Clouds Using Infrared Measurements From HALOE

    NASA Technical Reports Server (NTRS)

    Hervig, Mark E.

    2002-01-01

    Measurements from the Halogen Occultation Experiment (HALOE) revealed the infrared signature of polar mesospheric clouds (PMCs), for the first time, HALOE PMC observations at eight wavelengths (2.45 - 10 microns) show remarkable agreement with model PMC spectra based on ice particle extinction, and thus provide the first confirmation that water ice is the primary component of PMCs. Because PMCs respond to changes in temperature and water vapor, they are considered an indicator of global climate change. We propose to further the understanding of PMCs using a decade of infrared measurements form HALOE. This effort will characterize PMC spectral properties, extinction profiles, and size distributions. Using this information, HALOE measurements will be used to make simultaneous retrievals of H2O, O3, and temperature, in the presence of PMCs. The simultaneous retrievals of particle properties, H2O, O3, and temperature will be used with HALOE NO data to provide a significant step forward in the knowledge of PMC characteristics and formation conditions. We will challenge fundamental theories of PMC formation, and investigate changes in PMC properties and related conditions over the length of the HALOE measurement record. HALOE has been operating without flaw since it was launched on October 11, 1991. Consequently, ten southern and ten northern PMC seasons have been observed thus far, providing a wealth of data for the study of PMCs and related parameters.

  14. Characterization of Polar Mesospheric Clouds Using Infrared Measurements from HALOE

    NASA Technical Reports Server (NTRS)

    Hervig, Mark E.

    2002-01-01

    Measurements from the Halogen Occultation Experiment (HALOE) revealed the infrared signature of polar mesospheric clouds (PMCs), for the first time, HALOE PMC observations at eight wavelengths (2.45 - 10 microns) show remarkable agreement with model PMC spectra based on ice particle extinction, and thus provide the first confirmation that water ice is the primary component of PMCs. Because PMCs respond to changes in temperature and water vapor, they are considered an indicator of global climate change. We propose to further the understanding of PMCs using a decade of infrared measurements form HALOE. This effort will characterize PMC spectral properties, extinction profiles, and size distributions. Using this information, HALOE measurements will be used to make simultaneous retrievals of H2O3, and temperature, in the presence of PMCs. The simultaneous retrievals of particle properties, H2O3, and temperature will be used with HALOE NO data to provide a significant step forward in the knowledge of PMC characteristics and formation conditions. We will challenge fundamental theories of PMC formation, and investigate changes in PMC properties and related conditions over the length of the HALOE measurement record. HALOE has been operating without flaw since it was launched on October 11, 1991. Consequently, ten southern and ten northern PMC seasons have been observed thus far, providing a wealth of data for the study of PMC and related parameters.

  15. The Stellar Density Profile of the Distant Galactic Halo

    NASA Astrophysics Data System (ADS)

    Slater, Colin T.; Nidever, David L.; Munn, Jeffrey A.; Bell, Eric F.; Majewski, Steven R.

    2016-12-01

    We use extensive gravity-sensitive DDO 51 photometry over 5100 square degrees, combined with Sloan Digital Sky Survey broadband photometry, to select a catalog of ˜4000 giant stars covering a large fraction of the high Galactic latitude sky and reaching out to ˜80 kpc in the Galactic halo. This sample of bright and unbiased tracers enables us to measure the radial profile and 3D structure of the stellar halo to large distances, which had previously only been measured with sparse tracers or small samples. Using population synthesis models to reproduce the observed giant star luminosity function, we find that the halo maintains a {r}-3.5 profile from 30 to 80 kpc with no signs of a truncation or sharp break over this range. The radial profile measurement is largely insensitive to individual halo substructure components, but we find that attempting to measure the shape of the halo is overwhelmed by the Sagittarius stream such that no elliposidal shape is a satisfactory description in this region. These measurements allow us to begin placing the Milky Way in context with the growing sample of external galaxies where similar halo profile measurements are available, with the goal of further linking the properties of stellar halos to the accretion histories that formed them.

  16. The Stellar Halos of Massive Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Greene, Jenny E.; Murphy, Jeremy D.; Comerford, Julia M.; Gebhardt, Karl; Adams, Joshua J.

    2012-05-01

    We use the Mitchell Spectrograph (formerly VIRUS-P) on the McDonald Observatory 2.7 m Harlan J. Smith Telescope to search for the chemical signatures of massive elliptical galaxy assembly. The Mitchell Spectrograph is an integral-field spectrograph with a uniquely wide field of view (107'' × 107''), allowing us to achieve remarkably high signal-to-noise ratios of ~20-70 pixel-1 in radial bins of 2-2.5 times the effective radii of the eight galaxies in our sample. Focusing on a sample of massive elliptical galaxies with stellar velocity dispersions σ* > 150 km s-1, we study the radial dependence in the equivalent widths (EW) of key metal absorption lines. By twice the effective radius, the Mgb EWs have dropped by ~50%, and only a weak correlation between σ* and Mgb EW remains. The Mgb EWs at large radii are comparable to those seen in the centers of elliptical galaxies that are ~ an order of magnitude less massive. We find that the well-known metallicity gradients often observed within an effective radius continue smoothly to 2.5 Re , while the abundance ratio gradients remain flat. Much like the halo of the Milky Way, the stellar halos of our galaxies have low metallicities and high α-abundance ratios, as expected for very old stars formed in small stellar systems. Our observations support a picture in which the outer parts of massive elliptical galaxies are built by the accretion of much smaller systems whose star formation history was truncated at early times.

  17. Constrained Violent Relaxation to a Spherical Halo

    NASA Astrophysics Data System (ADS)

    Mangalam, A.; Nityananda, R.; Sridhar, S.

    1999-10-01

    Violent relaxation during the collapse of a galaxy halo is known to be incomplete in realistic cases such as cosmological infall or mergers. We adopt a physical picture of strong but short-lived interactions between potential fluctuations and particle orbits, using the broad framework outlined earlier for incorporating incompleteness of the relaxation. We are guided by results from plasma physics, viz., the quasilinear theory of Landau damping, but allow for significant differences in our case. Crucially, wave particle scattering does not drive the system to an equilibrium distribution function of the exponential type, even in regions of phase space allowed by the constraints. The physical process is mixing without friction in ``action'' space, for which the simplest possible model is a constant phase space density modulated by the constraints. Our distribution function does not use the exponential functions of the energy prevalent in other work, which we regard as inappropriate to collisionless systems. The dynamical constraint of a finite short period of the relaxation process is argued to lead to a 1/Tr factor in the distribution function, where Tr is the radial period. The notion of strong potential fluctuations in a core is built in as a cutoff in pericenter (which we find preferable to one angular momentum, the other alternative we explored). The halo of the self-consistent, parameter-free solutions show an r-4 behavior in density at large r, an r1/4 surface brightness profile in the region 0.1re-8re, and a radially anisotropic velocity dispersion profile outside an isotropic core. The energy distribution seen in simulations N(E) singles out the pericenter cutoff model as the most realistic among the variants we have explored. The results are robust to modifications of the period dependence keeping the same asymptotic behavior or to the use of binding energy raised to the power of 3/2 in place of 1/Tr.

  18. Halo Current Simulations for Tokamak Plasmas

    NASA Astrophysics Data System (ADS)

    Paccagnella, R.; Strauss, H. R.; Torasso, R.; Park, W.; Jardin, S.; Breslau, J.; Pletzer, A.; Fu, G. Y.; Sugiyama, L.

    2003-10-01

    A 3D MHD multi-level code, M3D [1], has been used in this work to simulate a tokamak Vertical Displacement Event (VDE) scenario. These simulations are interesting both from the point of view of gaining physical insight on the plasma dynamics during a VDE or a disruption event and are also relevant in order to estimate the amount of non-axisymmetric torques on the vacuum chamber -- a particular important issue for next generation tokamak (like ITER) design. In this work we numerically simulate a single-null ITER-like plasma evolution using a nonlinear single-fluid model interfaced through thin shell resistive wall boundary conditions to the external vacuum solution. A complete reconstruction of the magnetic field time evolution is therefore possible in the plasma and vacuum regions. Work is in progress to benchmark the code with 2D simulations done with the TSC [2] code. We have previously verified the expected linear scaling of the vertical instability growth rate with the wall resistivity. We are studying the effect of different initial tokamak equilibria (i.e. with different q profiles) on the instability growth rate. We are also studying the nonlinear evolution of the VDE for different fault-scenarios involving the relative timing of the disruptive thermal quench and the loss of vertical control, and for different assumptions regarding the conductivity and width of the plasma halo region. An output of this work is a prediction of the Toroidal Peaking Factor (TPF) [3] of the halo currents and associated vessel forces characterizing the non-axisymmetric events. This work was supported in part by the USDOE. [1] PARK, W., et al., Phys.Plasmas 6, 1796 (1999). [2] Sayer, R.O., Peng, Y-K. M., Jardin, S. C., Kellman, A. G., Wesley, J. C., Nuclear Fusion 33, 969 (1993). [3] Pomphrey, N., Bialek, J., Park, W., Nuclear Fusion 38, 449 (1998).

  19. THE STELLAR HALOS OF MASSIVE ELLIPTICAL GALAXIES

    SciTech Connect

    Greene, Jenny E.; Murphy, Jeremy D.; Comerford, Julia M.; Gebhardt, Karl; Adams, Joshua J.

    2012-05-01

    We use the Mitchell Spectrograph (formerly VIRUS-P) on the McDonald Observatory 2.7 m Harlan J. Smith Telescope to search for the chemical signatures of massive elliptical galaxy assembly. The Mitchell Spectrograph is an integral-field spectrograph with a uniquely wide field of view (107'' Multiplication-Sign 107''), allowing us to achieve remarkably high signal-to-noise ratios of {approx}20-70 pixel{sup -1} in radial bins of 2-2.5 times the effective radii of the eight galaxies in our sample. Focusing on a sample of massive elliptical galaxies with stellar velocity dispersions {sigma}{sub *} > 150 km s{sup -1}, we study the radial dependence in the equivalent widths (EW) of key metal absorption lines. By twice the effective radius, the Mgb EWs have dropped by {approx}50%, and only a weak correlation between {sigma}{sub *} and Mgb EW remains. The Mgb EWs at large radii are comparable to those seen in the centers of elliptical galaxies that are {approx} an order of magnitude less massive. We find that the well-known metallicity gradients often observed within an effective radius continue smoothly to 2.5 R{sub e} , while the abundance ratio gradients remain flat. Much like the halo of the Milky Way, the stellar halos of our galaxies have low metallicities and high {alpha}-abundance ratios, as expected for very old stars formed in small stellar systems. Our observations support a picture in which the outer parts of massive elliptical galaxies are built by the accretion of much smaller systems whose star formation history was truncated at early times.

  20. Development of hollow electron beams for proton and ion collimation

    SciTech Connect

    Stancari, G.; Drozhdin, A.I.; Kuznetsov, G.; Shiltsev, V.; Still, D.A.; Valishev, A.; Vorobiev, L.G.; Assmann, R.; Kabantsev, A.; /UC, San Diego

    2010-06-01

    Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams.

  1. Observation of energetic protons penetrating previous shock wave

    NASA Astrophysics Data System (ADS)

    Al-Sawad, A.; Saloniemi, O.; Laitinen, T. L.; Kocharov, L. G.; Valtonen, E.

    2009-12-01

    We report new evidence on energetic protons penetrating previous shock wave. We have chosen four Multi Eruption Solar Energetic Particle (MESEP) events from the list presented by Al-Sawad 2007, and observed by Energetic and Relativistic Nuclei and Electron (ERNE) instrument on the Solar and Heliospheric Observatory (SOHO). Two events were studied in details, the event of 2001 October 19-21, which was in association with two X1.6/2B solar flares and halo CMEs separated by ~15 hours and the event of 2000 April 04, which was associated with two CMEs separated by ~8 hours. The other two new MESEP events were on 2000 February 17-19 and 2005 August 22-25. The first event was associated with two CMEs. The first halo CME was associated with M 1.3 solar flare at S29E07 Hα location from the NOAA AR 8827, and with metric and later D-H type II radio bursts, indicating a formation of shock wave, which was later passed near the Earth's orbit and registered, by SOHO, ACE and Wind spacecrafts. The second CME erupted from the south-west after ~13 hours. The second event was associated with two halo CMEs separated by ~16 and erupted from same NOAA AR 10798 in association with M class solar flares. The first halo was in association with metric type II but both were in association with D-H type II. In both events the first CME was decelerating and both events can be classified as gradual SEP events. Our analysis for proton flux anisotropy data, He/P ratio and possible velocity dispersion in the second peak of the intensity-time profile are related to the second CME in both events. This suggests that the energetic protons > 10 MeV penetrate the first shock waves associated with first CMEs in order to reach 1 AU and thus, these observations indicate that capability of interplanetary shock to accelerate high-energy protons gradually declines as shock travels from near the Sun to beyond 1~AU.

  2. Proton elastic and charge-exchange scattering from exotic nuclei

    SciTech Connect

    Arellano, H.F.; Love, W.G.; Brieva, F.A.

    1993-10-01

    Calculations of elastic and charge-exchange scattering of protons from exotic nuclei are made using density-dependent nucleon-nucleon interactions. These results are compared with similar calculations for nearby nuclei in order to identify signatures of the proposed neutron halos in these processes. In the case of elastic scattering we compare our results with available data. For charge/exchange scattering our calculations are intended to provide a guide of the sizes and shapes of cross sections to be expected for this process. Results over a range of projectile energies are presented and discussed.

  3. THE GROWTH OF GALAXY STELLAR MASS WITHIN DARK MATTER HALOS

    SciTech Connect

    Zehavi, Idit; Patiri, Santiago; Zheng Zheng

    2012-02-20

    We study the evolution of stellar mass in galaxies as a function of host halo mass, using the 'MPA' and 'Durham' semi-analytic models, implemented on the Millennium Run simulation. For both models, the stellar mass of the central galaxies increases rapidly with halo mass at the low-mass end and more slowly in halos of larger masses at the three redshifts probed (z {approx} 0, 1, 2). About 45% of the stellar mass in central galaxies in present-day halos less massive than {approx}10{sup 12} h{sup -1} M{sub Sun} is already in place at z {approx} 1, and this fraction increases to {approx}65% for more massive halos. The baryon conversion efficiency into stars has a peaked distribution with halo mass, and the peak location shifts toward lower mass from z {approx} 1 to z {approx} 0. The stellar mass in low-mass halos grows mostly by star formation since z {approx} 1, while in high-mass halos most of the stellar mass is assembled by mergers, reminiscent of 'downsizing'. We compare our findings to empirical results from the Sloan Digital Sky Survey and DEEP2 surveys utilizing galaxy clustering measurements to study galaxy evolution. The theoretical predictions are in qualitative agreement with these phenomenological results, but there are large discrepancies. The most significant one concerns the number of stars already in place in the progenitor galaxies at z {approx} 1, which is about a factor of two larger in both semi-analytic models. We demonstrate that methods studying galaxy evolution from the galaxy-halo connection are powerful in constraining theoretical models and can guide future efforts of modeling galaxy evolution. Conversely, semi-analytic models serve an important role in improving such methods.

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

    NASA Astrophysics Data System (ADS)

    Lee, Young Sun; Beers, Timothy C.; Kim, Young Kwang; Placco, Vinicius; Yoon, Jinmi; Carollo, Daniela; Masseron, Thomas; Jung, Jaehun

    2017-02-01

    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.

  5. Halo occupation distribution of massive galaxies since z= 1

    NASA Astrophysics Data System (ADS)

    Matsuoka, Y.; Masaki, S.; Kawara, K.; Sugiyama, N.

    2011-01-01

    We present a clustering analysis of ˜60 000 massive (stellar mass M★ > 1011 M⊙) galaxies out to z= 1 drawn from 55.2 deg2 of the UKIRT Infrared Deep Sky Survey (UKIDSS) and the Sloan Digital Sky Survey (SDSS) II Supernova Survey. Strong clustering is detected for all the subsamples of massive galaxies characterized by different stellar masses (M★= 1011.0-11.5 M⊙, 1011.5-12.0 M⊙) or rest-frame colours (blue: U-V < 1.0, red: U-V > 1.0). We find that more mature (more massive or redder) galaxies are more clustered, which implies that the more mature galaxies have started stellar-mass assembly earlier within the highly biased region where the structure formation has also started earlier. By means of halo occupation distribution (HOD) models fitted to the observed angular correlation function, we infer the properties of the underlying host dark haloes. We find that the estimated bias factors and host halo masses are systematically larger for galaxies with larger stellar masses, which is consistent with the general agreement that the capability of hosting massive galaxies depends strongly on halo mass. The estimated effective halo masses are ˜1014 M⊙, which gives the stellar-mass to halo-mass ratios of ˜0.003. The observed evolution of bias factors indicates rapid evolution of spatial distributions of cold dark matter relative to those traced by the massive galaxies, while the transition of host halo masses might imply that the fractional mass growth rate of haloes is less than those of stellar systems. The inferred halo masses and high fractions of central galaxies indicate that the massive galaxies in the current sample are possibly equivalent to central galaxies of galaxy clusters.

  6. Pinless halo in the pediatric population: indications and complications.

    PubMed

    Bakhshi, Hooman; Kushare, Indranil; Banskota, Bibek; Nelson, Christopher; Dormans, John P

    2015-06-01

    The use of the conventional halo is accompanied by the possibility of serious complications, especially in the pediatric population. Complications could include penetration of pin into the skull, pin loosening, pin tract infection, cranial nerve palsies, and vest-related pressure sores. The noninvasive "pinless" halo was introduced in an attempt to mitigate these problems while retaining the effectiveness of the conventional halo. The purpose of this study is to determine the indications and complications related to pinless halo application. We retrospectively reviewed 61 patients, whose treatment included the use of a pinless halo device, presenting to our institution between 2004 and 2012. There were 35 male and 26 female patients with an average age of 6.04 years. Indications of pinless halo application included postoperative immobilization for congenital muscular torticollis in 38 cases, conservative management of atlantoaxial rotatory subluxation in 11 cases, postoperative immobilization following cervical fusion in 10 cases, and immobilization for occipital condyle fracture in 2 cases. The average duration of the pinless halo application was 32.68 days. Thirteen patients had complications, among which major complications were seen in 2 patients, each of whom developed a pressure sore; one on the scalp and the other on the chest. Both the pressure sores responded to local treatment; however, 1 resulted in permanent alopecia. The use of the noninvasive pinless halo was found to be safe with few complications in our study. The complications were infrequent and patients were compliant to treatment, indicating that this modality is patient-friendly. Effectiveness of this treatment in comparison with invasive halos and other cervical orthoses was not determined and is a limitation of this study. Level IV-Case series.

  7. A New Model for Dark Matter Halos Hosting Quasars

    NASA Astrophysics Data System (ADS)

    Cen, Renyue; Safarzadeh, Mohammadtaher

    2015-01-01

    A new model for quasar-hosting dark matter halos, meeting two physical conditions, is put forth. First, significant interactions are taken into consideration to trigger quasar activities. Second, satellites in very massive halos at low redshift are removed from consideration due to their deficiency in cold gas. We analyze the Millennium Simulation to find halos that meet these two conditions and simultaneously match two-point auto-correlation functions of quasars and cross-correlation functions between quasars and galaxies at z = 0.5-3.2. The masses of the quasar hosts found decrease with decreasing redshift, with the mass thresholds being [(2-5) × 1012, (2-5) × 1011, (1-3) × 1011] M ⊙ for median luminosities of ~[1046, 1046, 1045] erg s-1 at z = (3.2, 1.4, 0.53), respectively, an order of magnitude lower than those inferred based on halo occupation distribution modeling. In this model, quasar hosts are primarily massive central halos at z >= 2-3 but increasingly dominated by lower mass satellite halos experiencing major interactions toward lower redshift. However, below z = 1, satellite halos in groups more massive than ~2 × 1013 M ⊙ do not host quasars. Whether for central or satellite halos, imposing the condition of significant interactions substantially boosts the clustering strength compared to the total population with the same mass cut. The inferred lifetimes of quasars at z = 0.5-3.2 of 3-30 Myr are in agreement with observations. Quasars at z ~ 2 would be hosted by halos of mass ~5 × 1011 M ⊙ in this model, compared to ~3 × 1012 M ⊙ previously thought, which would help reconcile with the observed, otherwise puzzling high covering fractions for Lyman limit systems around quasars.

  8. The halo model in a massive neutrino cosmology

    SciTech Connect

    Massara, Elena; Villaescusa-Navarro, Francisco; Viel, Matteo E-mail: villaescusa@oats.inaf.it

    2014-12-01

    We provide a quantitative analysis of the halo model in the context of massive neutrino cosmologies. We discuss all the ingredients necessary to model the non-linear matter and cold dark matter power spectra and compare with the results of N-body simulations that incorporate massive neutrinos. Our neutrino halo model is able to capture the non-linear behavior of matter clustering with a ∼20% accuracy up to very non-linear scales of k = 10 h/Mpc (which would be affected by baryon physics). The largest discrepancies arise in the range k = 0.5 – 1 h/Mpc where the 1-halo and 2-halo terms are comparable and are present also in a massless neutrino cosmology. However, at scales k < 0.2 h/Mpc our neutrino halo model agrees with the results of N-body simulations at the level of 8% for total neutrino masses of < 0.3 eV. We also model the neutrino non-linear density field as a sum of a linear and clustered component and predict the neutrino power spectrum and the cold dark matter-neutrino cross-power spectrum up to k = 1 h/Mpc with ∼30% accuracy. For masses below 0.15 eV the neutrino halo model captures the neutrino induced suppression, casted in terms of matter power ratios between massive and massless scenarios, with a 2% agreement with the results of N-body/neutrino simulations. Finally, we provide a simple application of the halo model: the computation of the clustering of galaxies, in massless and massive neutrinos cosmologies, using a simple Halo Occupation Distribution scheme and our halo model extension.

  9. A Universal Angular Momentum Profile for Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Liao, Shihong; Chen, Jianxiong; Chu, M.-C.

    2017-07-01

    The angular momentum distribution in dark matter halos and galaxies is a key ingredient in understanding their formation. Specifically, the internal distribution of angular momenta is closely related to the formation of disk galaxies. In this article, we use halos identified from a high-resolution simulation, the Bolshoi simulation, to study the spatial distribution of specific angular momenta, j(r,θ ). We show that by stacking halos with similar masses to increase the signal-to-noise ratio, the profile can be fitted as a simple function, j{(r,θ )={j}s{\\sin }2{(θ /{θ }s)(r/{r}s)}2/(1+r/{r}s)}4, with three free parameters, {j}s,{r}s, and {θ }s. Specifically, j s correlates with the halo mass M vir as {j}s\\propto {M}{vir}2/3, r s has a weak dependence on the halo mass as {r}s\\propto {M}{vir}0.040, and {θ }s is independent of M vir. This profile agrees with that from a rigid shell model, though its origin is unclear. Our universal specific angular momentum profile j(r,θ ) is useful in modeling the angular momenta of halos. Furthermore, by using an empirical stellar mass-halo mass relation, we can infer the average angular momentum distribution of a dark matter halo. The specific angular momentum-stellar mass relation within a halo computed from our profile is shown to share a similar shape as that from the observed disk galaxies.

  10. Neutron-halo nuclei in cold synthesis and cluster decay of heavy nuclei: {ital Z}=104 nucleus as an example

    SciTech Connect

    Gupta, R.K.; Singh, S.; Muenzenberg, G.; Scheid, W. ||

    1995-05-01

    Nuclei at the neutron-drip line are studied. The light neutron-halo nuclei are found to play an important role for both cold fusion reactions and exotic cluster decay studies of heavy nuclei at the neutron-drip line. For cold fusion reactions, beams of neutron-halo nuclei are shown to occur as natural extensions of the conventional lighter beams but with the corresponding target nuclei as the heavy neutron-rich radioactive nuclei. Thus, in synthesizing the various isotopes of a neutron-rich cool compound nucleus, both the target and projectile nuclei have to be richer in neutrons, with their proton numbers remaining the same. On the other hand, neutron-halo (cluster) decays are favored for a relatively less neutron-rich parent nucleus. Possible consequences of this work for the shell structure effects in neutron-rich heavy nuclei are also pointed out. This follows from the fact that the so far observed phenomena of both cold fusion and cluster radioactivity are associated with closed or nearly closed shell nuclei. Calculations are made for {sup 274,288}104, using the quantum mechanical fragmentation theory for cold fusion reaction studies and a performed cluster model for cluster decay studies.

  11. Testing gravity using the environmental dependence of dark matter halos.

    PubMed

    Zhao, Gong-Bo; Li, Baojiu; Koyama, Kazuya

    2011-08-12

    In this Letter, we investigate the environmental dependence of dark matter halos in theories which attempt to explain the accelerated expansion of the Universe by modifying general relativity (GR). Using high-resolution N-body simulations in f(R) gravity models which recover GR in dense environments by virtue of the chameleon mechanism, we find a significant difference, which depends on the environment, between the lensing and dynamical masses of dark matter halos. This environmental dependence of the halo properties can be used as a smoking gun to test GR observationally.

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

    SciTech Connect

    Conroy, Charlie; Wechsler, Risa H.

    2008-06-02

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

  13. Halo current diagnostic system of experimental advanced superconducting tokamak

    SciTech Connect

    Chen, D. L.; Shen, B.; Sun, Y.; Qian, J. P. Wang, Y.; Xiao, B. J.; Granetz, R. S.

    2015-10-15

    The design, calibration, and installation of disruption halo current sensors for the Experimental Advanced Superconducting Tokamak are described in this article. All the sensors are Rogowski coils that surround conducting structures, and all the signals are analog integrated. Coils with two different cross-section sizes have been fabricated, and their mutual inductances are calibrated. Sensors have been installed to measure halo currents in several different parts of both the upper divertor (tungsten) and lower divertor (graphite) at several toroidal locations. Initial measurements from disruptions show that the halo current diagnostics are working well.

  14. Complications of halo fixation of the cervical spine.

    PubMed

    Hayes, Victor M; Silber, Jeff S; Siddiqi, Farhan N; Kondrachov, Dmitriy; Lipetz, Jason S; Lonner, Baron

    2005-06-01

    Halo fixators play an integral role in stabilizing the cervical spine. They are most widely used after upper cervical to midcervical spine fractures and dislocations and as a supplement to various surgical fixation techniques. Compared with supine cervical traction techniques, halo fixators allow early patient mobilization and shorten hospital stays. The incidence of halo-fixator complications remains high. Minor complications include pin loosening, localized infection, periorbital edema, superficial pressure sores, and unsightly scars. Major complications include pin penetration, osteomyelitis, subdural abscess, nerve palsies, fracture overdistraction, and persistent instability. Many of these potential complications can be avoided with proper pin placement and meticulous pin care.

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  16. On-orbit calibration of HALOE detector linearity.

    PubMed

    Hervig, Mark; Gordley, Larry; McHugh, Marty; Thompson, Earl; Magill, Brian; Deaver, Lance

    2007-11-10

    The Halogen Occultation Experiment (HALOE) conducted satellite solar occultation measurements for 14 years ending on 21 November 2005. HALOE contained a calibration wheel, which included three neutral density filters that were used to examine response linearity through a combination of ground and on-orbit measurements. Although measurement uncertainties preclude a confident assessment of the true extent of nonlinearity, the on-orbit data lead to the conclusion that any existing response nonlinearity has changed by less than 2% over the mission lifetime. This conclusion eliminates a potentially significant uncertainty when using HALOE data for studies of long-term atmospheric trends.

  17. Halo current diagnostic system of experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Chen, D. L.; Shen, B.; Granetz, R. S.; Sun, Y.; Qian, J. P.; Wang, Y.; Xiao, B. J.

    2015-10-01

    The design, calibration, and installation of disruption halo current sensors for the Experimental Advanced Superconducting Tokamak are described in this article. All the sensors are Rogowski coils that surround conducting structures, and all the signals are analog integrated. Coils with two different cross-section sizes have been fabricated, and their mutual inductances are calibrated. Sensors have been installed to measure halo currents in several different parts of both the upper divertor (tungsten) and lower divertor (graphite) at several toroidal locations. Initial measurements from disruptions show that the halo current diagnostics are working well.

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

    NASA Astrophysics Data System (ADS)

    Inglis Read, Justin

    2015-08-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  20. Halo current diagnostic system of experimental advanced superconducting tokamak.

    PubMed

    Chen, D L; Shen, B; Granetz, R S; Sun, Y; Qian, J P; Wang, Y; Xiao, B J

    2015-10-01

    The design, calibration, and installation of disruption halo current sensors for the Experimental Advanced Superconducting Tokamak are described in this article. All the sensors are Rogowski coils that surround conducting structures, and all the signals are analog integrated. Coils with two different cross-section sizes have been fabricated, and their mutual inductances are calibrated. Sensors have been installed to measure halo currents in several different parts of both the upper divertor (tungsten) and lower divertor (graphite) at several toroidal locations. Initial measurements from disruptions show that the halo current diagnostics are working well.

  1. HaloSat: A CubeSat to Map the Distribution of Baryonic Matter in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Miles, Drew M.

    2016-04-01

    Approximately half of predicted baryonic matter in the Milky Way remains unidentified. One possible explanation for the location of this missing matter is in an extended Galactic halo. HaloSat is a CubeSat that aims to constrain the mass and distribution of the halo’s baryonic matter by obtaining an all-sky map of O VII and O VIII emission in the hot gas associated with the halo of the Milky Way. HaloSat offers an improvement in the quality of measurements of oxygen line emission over existing X-ray observatories and an observation plan dedicated to mapping the hot gas in the Galactic halo. In addition to the missing baryon problem, HaloSat will assign a portion of its observations to the solar wind charge exchange (SWCX) in order to calibrate models of SCWX emission. We present here the current status of HaloSat and the progression of instrument development in anticipation of a 2018 launch.

  2. Reconstruction of halo power spectrum from redshift-space galaxy distribution: cylinder-grouping method and halo exclusion effect

    NASA Astrophysics Data System (ADS)

    Okumura, Teppei; Takada, Masahiro; More, Surhud; Masaki, Shogo

    2017-07-01

    The peculiar velocity field measured by redshift-space distortions (RSD) in galaxy surveys provides a unique probe of the growth of large-scale structure. However, systematic effects arise when including satellite galaxies in the clustering analysis. Since satellite galaxies tend to reside in massive haloes with a greater halo bias, the inclusion boosts the clustering power. In addition, virial motions of the satellite galaxies cause a significant suppression of the clustering power due to non-linear RSD effects. We develop a novel method to recover the redshift-space power spectrum of haloes from the observed galaxy distribution by minimizing the contamination of satellite galaxies. The cylinder-grouping method (CGM) we study effectively excludes satellite galaxies from a galaxy sample. However, we find that this technique produces apparent anisotropies in the reconstructed halo distribution over all the scales which mimic RSD. On small scales, the apparent anisotropic clustering is caused by exclusion of haloes within the anisotropic cylinder used by the CGM. On large scales, the misidentification of different haloes in the large-scale structures, aligned along the line of sight, into the same CGM group causes the apparent anisotropic clustering via their cross-correlation with the CGM haloes. We construct an empirical model for the CGM halo power spectrum, which includes correction terms derived using the CGM window function at small scales as well as the linear matter power spectrum multiplied by a simple anisotropic function at large scales. We apply this model to a mock galaxy catalogue at z = 0.5, designed to resemble Sloan Digital Sky Survey-III Baryon Oscillation Spectroscopic Survey (BOSS) CMASS galaxies, and find that our model can predict both the monopole and quadrupole power spectra of the host haloes up to k < 0.5 {{h Mpc^{-1}}} to within 5 per cent.

  3. Proton Remains Puzzling

    SciTech Connect

    Gao, Haiyan; Liu, Tianbo; Peng, Chao; Ye, Zhihong; Zhao, Zhiwen

    2015-01-01

    Nucleons are building blocks of visible matter, and are responsible for more than 99% of the visible mass in the universe despite the fact that the discovery of the Higgs boson is almost irrelevant to the origin of the proton mass. While major progress has been made in the last two decades in understanding the proton spin puzzle discovered in the late 1980s by the European Muon Collaboration, a new proton puzzle emerged in the last several years concerning the proton charge radius, which is the charge weighted size of the proton. In this paper we will review the latest situation concerning the proton charge radius, mass and spin, and discuss upcoming new experiments addressing these puzzles, as well as implications for new physics.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    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 (Λ CDM ). Thus, when using effective halos, an f (R ) model can be viewed as a Λ CDM 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.

  5. Dark matter annihilation in the first galaxy haloes

    NASA Astrophysics Data System (ADS)

    Schön, S.; Mack, K. J.; Avram, C. A.; Wyithe, J. S. B.; Barberio, E.

    2015-08-01

    We investigate the impact of energy released from self-annihilating dark matter (DM) on heating of gas in the small, high-redshift DM haloes thought to host the first stars. A supersymmetric (SUSY)-neutralino-like particle is implemented as our DM candidate. The PYTHIA code is used to model the final, stable particle distributions produced during the annihilation process. We use an analytic treatment in conjunction with the code MEDEA2 to find the energy transfer and subsequent partition into heating, ionizing and Lyman α photon components. We consider a number of halo density models, DM particle masses and annihilation channels. We find that the injected energy from DM exceeds the binding energy of the gas within a 105-106 M⊙ halo at redshifts above 20, preventing star formation in early haloes in which primordial gas would otherwise cool. Thus we find that DM annihilation could delay the formation of the first galaxies.

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

    PubMed

    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.

  7. Detection of ultraviolet halos around highly inclined galaxies

    SciTech Connect

    Hodges-Kluck, Edmund; Bregman, Joel N.

    2014-07-10

    We report the discovery of diffuse ultraviolet light around late-type galaxies out to 5-20 kpc from the midplane using Swift and GALEX images. The emission is consistent with the stellar outskirts in the early-type galaxies but not in the late-type galaxies, where the emission is quite blue and consistent with a reflection nebula powered by light escaping from the galaxy and scattering off dust in the halo. Our results agree with expectations from halo dust discovered in extinction by Ménard et al. to within a few kpc of the disk and imply a comparable amount of hot and cold gas in galaxy halos (a few× 10{sup 8} M{sub ☉} within 20 kpc) if the dust resides primarily in Mg II absorbers. The results also highlight the potential of UV photometry to study individual galaxy halos.

  8. Visibility of stars, halos, and rainbows during solar eclipses.

    PubMed

    Können, Gunther P; Hinz, Claudia

    2008-12-01

    The visibility of stars, planets, diffraction coronas, halos, and rainbows during the partial and total phases of a solar eclipse is studied. The limiting magnitude during various stages of the partial phase is presented. The sky radiance during totality with respect to noneclipse conditions is revisited and found to be typically 1/4000. The corresponding limiting magnitude is +3.5. At totality, the signal-to-background ratio of diffraction coronas, halos, and rainbows has dropped by a factor of 250. It is found that diffraction coronas around the totally eclipsed Sun may nevertheless occur. Analyses of lunar halo observations during twilight indicate that bright halo displays may also persist during totality. Rainbows during totality seem impossible.

  9. Halo Core Tracking for Galaxy Placement in Cosmological Simulations

    NASA Astrophysics Data System (ADS)

    Korytov, Danila

    2017-01-01

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

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

    SciTech Connect

    Rahaman, Farook; Salucci, P.; Kuhfittig, P.K.F.; Ray, Saibal; Rahaman, Mosiur

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2017-10-01

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

  12. Lithium in halo stars from standard stellar evolution

    NASA Technical Reports Server (NTRS)

    Deliyannis, Constantine P.; Demarque, Pierre; Kawaler, Steven D.

    1990-01-01

    A grid has been constructed of theoretical evolution sequences of models for low-metallicity stars from the premain-sequence to the giant branch phases. The grid is used to study the history of surface Li abundance during standard stellar evolution. The Li-7 observations of halo stars by Spite and Spite (1982) and subsequent observations are synthesized to separate the halo stars by age. The theory of surface Li abundance is illustrated by following the evolution of a reference halo star model from the contracting fully convective premain sequence to the giant branch phase. The theoretical models are compared with observed Li abundances. The results show that the halo star lithium abundances can be explained in the context of standard stellar evolution theory using completely standard assumptions and physics.

  13. Halo Orbit Mission Correction Maneuvers Using Optimal Control

    NASA Technical Reports Server (NTRS)

    Lo, M.; Serban, R.; Petzold, L.; Koon, W.; Ross, S.; Marsden, J.; Wilson, R.

    2000-01-01

    This paper addresses the computation of the required trajectory correction maneuvers (TCM) for a halo orbit space mission to compensate for the launch velocity errors introduced by inaccuracies of the launch vehicle.

  14. Brain Abscess After Halo Fixation for the Cervical Spine.

    PubMed

    Lopes, Arthur; Andrade, Almir; Silva, Igor; Paiva, Wellingson; Brock, Roger; Teixeira, Manoel

    2017-08-01

    Halo fixation is one of the possible treatments for cervical spine fractures. However, improper use of these devices may lead to many complications, such as pin loosening, halo dislocation, pin site infection, and intradural penetration. We report the case of a 43-year-old man who first presented with a seizure and an altered level of consciousness 5 months after halo-vest placement for an odontoid fracture. Brain imaging showed a brain abscess, under the previous left parietal pin. The patient underwent abscess drainage and antibiotics were administered for 12 weeks. On hospital discharge, he presented with only mild impairments. Misapplication of halo fixation devices may lead to serious complications, including intracranial pin penetration and brain abscesses. Proper use of the recommended technique may decrease the risk for complications related to the procedure. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Spontaneous Involution of Congenital Melanocytic Nevus With Halo Phenomenon.

    PubMed

    Lee, Noo Ri; Chung, Hee-Chul; Hong, Hannah; Lee, Jin Wook; Ahn, Sung Ku

    2015-12-01

    Congenital melanocytic nevus (CMN) is a neural crest-derived hamartoma, which appear at or soon after birth. CMN has a dynamic course and may show variable changes over time, including spontaneous involution. Spontaneous involution of CMN is a rare phenomenon and is often reported in association with halo phenomenon or vitiligo. The mechanism of halo phenomenon is yet to be investigated but is suggested to be a destruction of melanocytes by immune responses of cytotoxic T cells or IgM autoantibodies. Here, the authors report an interesting case of spontaneously regressed medium-sized CMN with halo phenomenon and without vitiligo, which provides evidence that cytotoxic T cells account for the halo formation and pigmentary regression of CMN.

  16. Halo Orbit Mission Correction Maneuvers Using Optimal Control

    NASA Technical Reports Server (NTRS)

    Lo, M.; Serban, R.; Petzold, L.; Koon, W.; Ross, S.; Marsden, J.; Wilson, R.

    2000-01-01

    This paper addresses the computation of the required trajectory correction maneuvers (TCM) for a halo orbit space mission to compensate for the launch velocity errors introduced by inaccuracies of the launch vehicle.

  17. EFFECT OF DARK MATTER HALO SUBSTRUCTURES ON GALAXY ROTATION CURVES

    SciTech Connect

    Roy, Nirupam

    2010-11-01

    In this paper, the effect of halo substructures on galaxy rotation curves is investigated using a simple model of dark matter clustering. A dark matter halo density profile is developed based only on the scale-free nature of clustering that leads to a statistically self-similar distribution of the substructures at the galactic scale. A semi-analytical method is used to derive rotation curves for such a clumpy dark matter density profile. It is found that the halo substructures significantly affect the galaxy velocity field. Based on the fractal geometry of the halo, this self-consistent model predicts a Navarro-Frenk-White-like rotation curve and a scale-free power spectrum of the rotation velocity fluctuations.

  18. Summary of the 2014 Beam-Halo Monitoring Workshop

    SciTech Connect

    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.

  19. Halo formation and evolution: unification of structure and physical properties

    NASA Astrophysics Data System (ADS)

    Ernest, Allan D.; Collins, Matthew P.

    2016-08-01

    The assembly of matter in the universe proliferates a wide variety of halo structures, often with enigmatic consequences. Giant spiral galaxies, for example, contain both dark matter and hot gas, while dwarf spheroidal galaxies, with weaker gravity, contain much larger fractions of dark matter, but little gas. Globular clusters, superficially resembling these dwarf spheroidals, have little or no dark matter. Halo temperatures are also puzzling: hot cluster halos contain cooler galaxy halos; dwarf galaxies have no hot gas at all despite their similar internal processes. Another mystery is the origin of the gas that galaxies require to maintain their measured star formation rates (SFRs). We outline how gravitational quantum theory solves these problems, and enables baryons to function as weakly-interacting-massive-particles (WIMPs) in Lambda Cold Dark Matter (LCDM) theory. Significantly, these dark-baryon ensembles may also be consistent with primordial nucleosynthesis (BBN) and cosmic microwave background (CMB) anisotropies.

  20. Terminal Velocity Infall in QSO Absorption Line Halos

    NASA Astrophysics Data System (ADS)

    Benjamin, Robert A.

    We explore the hypothesis that clouds detected in quasar absorption line systems are falling at a terminal velocity toward the center of high redshift gaseous galactic halos. Since both the ionization level and terminal velocity of halo clouds increase with increasing distance from the central galaxy, velocity resolved profiles of highly ionized gas are predicted to have a greater width than low ionization gas. A line of sight passing through the center of gaseous halo (an idealized damped Ly alpha system), yields low ionization absorption at the velocity of the galaxy, flanked by high ionization on either side. Reasonable halo parameters yield total velocity extents for C IV of Delta v_{C IV}=100-200 km s^{-1}, in agreement with many systems observed by Lu et al (1997). The remaining systems may better described by the rotating disk model of Prochaska & Wolfe (1998). Finally, observational tests are suggested for verifying or falsifying the terminal velocity hypothesis for these systems.

  1. DIAGNOSTIC TOOLS FOR BEAM HALO INVESTIGATION IN SNS LINAC

    SciTech Connect

    Aleksandrov, Alexander V; Blokland, Willem; Liu, Yun; Long, Cary D; Zhukov, Alexander P

    2012-01-01

    Uncontrolled beam loss is a major concern in the operation of a high intensity hadron linac. A low density cloud of particles with large oscillation amplitudes, so called halo, can form around the dense regular beam core. This halo can be a direct or indirect cause of beam loss. There is experimental evidence of halo growing in the SNS linac and limiting the further reduction of beam loss. A set of tools is being developed for detecting of the halo and investigating its origin and dynamics. The set includes high resolution emittance measurements in the injector, laser based emittance measurements at 1 GeV, and high resolution profile measurements along the linac. We will present our experience with useful measurement techniques and data analysis algorithms.

  2. Lithium in halo stars from standard stellar evolution

    NASA Technical Reports Server (NTRS)

    Deliyannis, Constantine P.; Demarque, Pierre; Kawaler, Steven D.

    1990-01-01

    A grid has been constructed of theoretical evolution sequences of models for low-metallicity stars from the premain-sequence to the giant branch phases. The grid is used to study the history of surface Li abundance during standard stellar evolution. The Li-7 observations of halo stars by Spite and Spite (1982) and subsequent observations are synthesized to separate the halo stars by age. The theory of surface Li abundance is illustrated by following the evolution of a reference halo star model from the contracting fully convective premain sequence to the giant branch phase. The theoretical models are compared with observed Li abundances. The results show that the halo star lithium abundances can be explained in the context of standard stellar evolution theory using completely standard assumptions and physics.

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

    SciTech Connect

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

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

    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

  6. REVISITING SCALING RELATIONS FOR GIANT RADIO HALOS IN GALAXY CLUSTERS

    SciTech Connect

    Cassano, R.; Brunetti, G.; Venturi, T.; Kale, R.; Pratt, G. W.; Markevitch, M.

    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 relativistic particle

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    Many galaxy clusters host megaparsec-scale radio halos, generated by ultrarelativistic electrons in the magnetized intracluster medium. Correlations between the synchrotron power of radio halos and the thermal properties of the hosting clusters were established in the last decade, including the connection between the presence of a halo and cluster mergers. The X-ray luminosity and redshift-limited Extended GMRT Radio Halo Survey provides a rich and unique dataset for statistical studies of the halos. We uniformly analyze the radio and X-ray data for the GMRT cluster sample, and use the new Planck Sunyaev-Zel'dovich (SZ) catalog to revisit the correlations between the power of radio halos and the thermal properties of galaxy clusters. We find that the radio power at 1.4 GHz scales with the cluster X-ray (0.1-2.4 keV) luminosity computed within R 500 as P_{1.4} \\sim L^{2.1+/- 0.2}_{500}. Our bigger and more homogenous sample confirms that the X-ray luminous (L 500 > 5 × 1044 erg s-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 1.4 scales with the cluster integrated SZ signal within R 500, measured by Planck, as P_{1.4}\\sim Y^{2.05+/- 0.28}_{500}, in line with previous findings. However, contrary to previous studies that were limited by incompleteness and small sample size, we find that "SZ-luminous" Y 500 > 6 × 10-5 Mpc2 clusters show a bimodal behavior for the presence of radio halos, similar to that in the radio-X-ray diagram. Bimodality of both correlations can be traced to clusters dynamics, with radio halos found exclusively in merging clusters. These results confirm the key role of mergers for the origin of giant radio halos, suggesting that they trigger the relativistic particle acceleration.

  8. An Improved Catalog of Halo Wide Binary Candidates

    NASA Astrophysics Data System (ADS)

    Allen, Christine; Monroy-Rodríguez, Miguel A.

    2014-08-01

    We present an improved catalog of halo wide binaries compiled from an extensive literature search. Most of our binaries stem from the common proper motion binary catalogs by Allen et al. and Chanamé & Gould, but we have also included binaries from the lists of Ryan and Zapatero-Osorio & Martín. All binaries were carefully checked and their distances and systemic radial velocities are included when available. Probable membership to the halo population was tested by means of reduced proper motion diagrams for 251 candidate halo binaries. After eliminating obvious disk binaries, we ended up with 211 probable halo binaries, 150 of which have radial velocities available. We compute galactic orbits for these 150 binaries and calculate the time they spend within the galactic disk. Considering the full sample of 251 candidate halo binaries as well as several subsamples, we find that the distribution of angular separations (or expected major semiaxes) follows a power law f(a) ~ a -1 (Oepik's relation) up to different limits. For the 50 most disk-like binaries, those that spend their entire lives within z = ±500 pc, this limit is found to be 19,000 AU (0.09 pc), while for the 50 most halo-like binaries, those that spend on average only 18% of their lives within z = ±500 pc, the limit is 63,000 AU (0.31 pc). In a companion paper, we employ this catalog to establish limits on the masses of the halo massive perturbers (massive compact halo objects).

  9. Halo-independent direct detection analyses without mass assumptions

    SciTech Connect

    Anderson, Adam J.; Fox, Patrick J.; Kahn, Yonatan; McCullough, Matthew E-mail: pjfox@fnal.gov E-mail: matthew.mccullough@cern.ch

    2015-10-01

    Results from direct detection experiments are typically interpreted by employing an assumption about the dark matter velocity distribution, with results presented in the m{sub χ}−σ{sub n} plane. Recently methods which are independent of the DM halo velocity distribution have been developed which present results in the v{sub 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{sub min} to nuclear recoil momentum (p{sub 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-tilde (p{sub R}). The entire family of conventional halo-independent g-tilde (v{sub min}) plots for all DM masses are directly found from the single h-tilde (p{sub R}) plot through a simple rescaling of axes. By considering results in h-tilde (p{sub 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{sub 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.

  10. Halo-independent direct detection analyses without mass assumptions

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    Results from direct detection experiments are typically interpreted by employing an assumption about the dark matter velocity distribution, with results presented in the mχ-σn plane. Recently methods which are independent of the DM halo velocity distribution have been developed which present results in the vmin-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 vmin to nuclear recoil momentum (pR), 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(pR). The entire family of conventional halo-independent tilde g(vmin) plots for all DM masses are directly found from the single tilde h(pR) plot through a simple rescaling of axes. By considering results in tilde h(pR) 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 tilde g(vmin) 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.

  11. Halo-independent direct detection analyses without mass assumptions

    SciTech Connect

    Anderson, Adam J.; Fox, Patrick 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 mχ – σn plane. Recently methods which are independent of the DM halo velocity distribution have been developed which present results in the vmin – 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 vmin to nuclear recoil momentum (pR), 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(pR). The entire family of conventional halo-independent tilde g~(vmin) plots for all DM masses are directly found from the single tilde h~(pR) plot through a simple rescaling of axes. By considering results in tildeh~(pR) 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 tilde g~(vmin) plots for different DM masses. As a result, 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.

  12. Vaporization in comets - The icy grain halo of Comet West

    NASA Technical Reports Server (NTRS)

    Ahearn, M. F.; Cowan, J. J.

    1980-01-01

    The variation with heliocentric distance of the production rates of various species in Comet West (1975n = 1976 VI) is explained with a cometary model consisting of a CO2 dominated nucleus plus a halo of icy grains of H2O or clathrate hydrate. It is concluded that the parents of CN and C3 are released primarily from the nucleus but that the parent of C2 is released primarily from the halo of icy grains.

  13. Halo-independent direct detection analyses without mass assumptions

    SciTech Connect

    Anderson, Adam J.; Fox, Patrick 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{sub χ}−σ{sub n} plane. Recently methods which are independent of the DM halo velocity distribution have been developed which present results in the v{sub 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{sub min} to nuclear recoil momentum (p{sub 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{sub R}). The entire family of conventional halo-independent g-tilde(v{sub min}) plots for all DM masses are directly found from the single h-tilde(p{sub R}) plot through a simple rescaling of axes. By considering results in h-tilde(p{sub 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{sub 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.

  14. THE SEGUE K GIANT SURVEY. III. QUANTIFYING GALACTIC HALO SUBSTRUCTURE

    SciTech Connect

    Janesh, William; Morrison, Heather L.; Ma, Zhibo; Harding, Paul; Rockosi, Constance; Xue, Xiang Xiang; Rix, Hans-Walter; Beers, Timothy C.; Johnson, Jennifer; Lee, Young Sun; Schneider, Donald P.

    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.

  15. The SEGUE K Giant Survey. III. Quantifying Galactic Halo Substructure

    NASA Astrophysics Data System (ADS)

    Janesh, William; Morrison, Heather L.; Ma, Zhibo; Rockosi, Constance; Starkenburg, Else; Xue, Xiang Xiang; Rix, Hans-Walter; Harding, Paul; Beers, Timothy C.; Johnson, Jennifer; Lee, Young Sun; Schneider, Donald P.

    2016-01-01

    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.

  16. Halo-independent direct detection analyses without mass assumptions

    DOE PAGES

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

    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 mχ – σn plane. Recently methods which are independent of the DM halo velocity distribution have been developed which present results in the vmin – 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 vmin to nuclear recoil momentum (pR),more » 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(pR). The entire family of conventional halo-independent tilde g~(vmin) plots for all DM masses are directly found from the single tilde h~(pR) plot through a simple rescaling of axes. By considering results in tildeh~(pR) 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 tilde g~(vmin) plots for different DM masses. As a result, 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.« less

  17. An improved catalog of halo wide binary candidates

    SciTech Connect

    Allen, Christine; Monroy-Rodríguez, Miguel A.

    2014-08-01

    We present an improved catalog of halo wide binaries compiled from an extensive literature search. Most of our binaries stem from the common proper motion binary catalogs by Allen et al. and Chanamé and Gould, but we have also included binaries from the lists of Ryan and Zapatero-Osorio and Martín. All binaries were carefully checked and their distances and systemic radial velocities are included when available. Probable membership to the halo population was tested by means of reduced proper motion diagrams for 251 candidate halo binaries. After eliminating obvious disk binaries, we ended up with 211 probable halo binaries, 150 of which have radial velocities available. We compute galactic orbits for these 150 binaries and calculate the time they spend within the galactic disk. Considering the full sample of 251 candidate halo binaries as well as several subsamples, we find that the distribution of angular separations (or expected major semiaxes) follows a power law f(a) ∼ a {sup –1} (Oepik's relation) up to different limits. For the 50 most disk-like binaries, those that spend their entire lives within z = ±500 pc, this limit is found to be 19,000 AU (0.09 pc), while for the 50 most halo-like binaries, those that spend on average only 18% of their lives within z = ±500 pc, the limit is 63,000 AU (0.31 pc). In a companion paper, we employ this catalog to establish limits on the masses of the halo massive perturbers (massive compact halo objects).

  18. Indications and complications of crown halo vest placement: A review.

    PubMed

    Lee, Dennis; Adeoye, Adeola L; Dahdaleh, Nader S

    2017-06-01

    Crown halo vest placement remains an option for the treatment of a variety of upper and subaxial cervical spinal fractures. While the device remains a useful non-operative option for the treatment of these injuries, it has been associated with a variety of complications. This manuscript represents an up to date narrative review of the indications, complications, and complication avoidance for the placement of crown halo vests. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Abundance analysis of the outer halo globular cluster Palomar 14

    NASA Astrophysics Data System (ADS)

    Çalışkan, Ş.; Christlieb, N.; Grebel, E. K.

    2012-01-01

    We determine the elemental abundances of nine red giant stars belonging to Palomar 14 (Pal 14). Pal 14 is an outer halo globular cluster (GC) at a distance of ~70 kpc. Our abundance analysis is based on high-resolution spectra and one-dimensional stellar model atmospheres. We derived the abundances for the iron peak elements Sc, V, Cr, Mn, Co, Ni, the α-elements O, Mg, Si, Ca, Ti, the light odd element Na, and the neutron-capture elements Y, Zr, Ba, La, Ce, Nd, Eu, Dy, and Cu. Our data do not permit us to investigate light element (i.e., O to Mg) abundance variations. The neutron-capture elements show an r-process signature. We compare our measurements with the abundance ratios of inner and other outer halo GCs, halo field stars, GCs of recognized extragalactic origin, and stars in dwarf spheroidal galaxies (dSphs). The abundance pattern of Pal 14 is almost identical to those of Pal 3 and Pal 4, the next distant members of the outer halo GC population after Pal 14. The abundance pattern of Pal 14 is also similar to those of the inner halo GCs, halo field stars, and GCs of recognized extragalactic origin, but differs from what is customarily found in dSphs field stars. The abundance properties of Pal 14, as well as those of the other outer halo GCs, are thus compatible with an accretion origin from dSphs. Whether or not GC accretion played a role, it seems that the formation conditions of outer halo GCs and GCs in dSphs were similar. Based on observations collected at the European Southern Observatory, Chile (Program IDs 077.B-0769).Tables A.1 and A.2 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/537/A83

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

    SciTech Connect

    Adshead, Peter; Baxter, Eric J.; Dodelson, Scott; Lidz, Adam

    2012-09-01

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

  1. Highly ionized gas in the Galactic halo

    NASA Technical Reports Server (NTRS)

    Shull, J. Michael; Slavin, Jonathan D.

    1994-01-01

    We reexamine the values of electron density n(sub e) and gas pressure P/k in the interstellar medium (ISM) of the Galactic halo, as inferred from C IV emission and absorption lines and using current C IV atomic data. In a homogeneous model with 4.7 less than or equal to log T less than or equal to 5.3, the data are consistent with 0.01 less than or equal to n(sub e) less than or equal to 0.02/cu cm and 2200 less than or equal to P/k less than or equal to 3700/cu cm K, a factor of 2-3 higher than advocated by Martin & Bowyer (1990) and comparable to the thermal pressure in the disk. If some of the C IV absorption arises from nonemitting, photoionized gas, then the inferred density and pressure will increase accordingly. The volume filling factor for homogeneous models ranges from 0.5% to 5%. Because of the constraints arising from filling factor and radiated power, most of the C IV must arise from gas near the peak of the cooling curve, at log t less than or equal to 5.6. We relate both emission-line and absorption-line observations to recent models in which turbulent mixing layers and isobarically cooling supernova remnants (SNRs) provide significant amounts of halo gas at approximately 10(exp 5.3) K and process 20-40 solar mass/yr with a power of approximately 10(exp 41) ergs/sec. Since the observed C IV and N V absorption scale heights have been reported to differ, at 4.9 kpc and 1.6 kpc, respectively, we examine inhomogeneous models with different exponential scale heights of T, P, and SN energy input. The ISM may change its character with distance above the Galactic plane, as superbubbles and mixing layers dominate over isolated SNRs as the source of the C IV. For appropiate scale heights, the midplane pressure is twice the homogeneous values quoted above. The O IV lambda 1034 diffuse emission line, which can be used as a temperature diagnostic of the hot gas, is predicted to be comparable in strength to that of C IV lambda 1549 (approximately 6000 photons

  2. The elusive stellar halo of the Triangulum galaxy

    NASA Astrophysics Data System (ADS)

    McMonigal, B.; Lewis, G. F.; Brewer, B. J.; Irwin, M. J.; Martin, N. F.; McConnachie, A. W.; Ibata, R. A.; Ferguson, A. M. N.; Mackey, A. D.; Chapman, S. C.

    2016-10-01

    The stellar haloes of large galaxies represent a vital probe of the processes of galaxy evolution. They are the remnants of the initial bouts of star formation during the collapse of the protogalactic cloud, coupled with imprint of ancient and ongoing accretion events. Previously, we have reported the tentative detection of a possible, faint, extended stellar halo in the Local Group spiral, the Triangulum galaxy (M33). However, the presence of substructure surrounding M33 made interpretation of this feature difficult. Here, we employ the final data set from the Pan-Andromeda Archaeological Survey, combined with an improved calibration and a newly derived contamination model for the region to revisit this claim. With an array of new fitting algorithms, fully accounting for contamination and the substantial substructure beyond the prominent stellar disc in M33, we reanalyse the surrounds to separate the signal of the stellar halo and the outer halo substructure. Using more robust search algorithms, we do not detect a large-scale smooth stellar halo and place a limit on the maximum surface brightness of such a feature of μV = 35.5 mag arcsec-2, or a total halo luminosity of L < 106 L⊙.

  3. What to expect from dynamical modelling of galactic haloes

    NASA Astrophysics Data System (ADS)

    Wang, Wenting; Han, Jiaxin; Cole, Shaun; Frenk, Carlos; Sawala, Till

    2017-09-01

    Many dynamical models of the Milky Way halo require assumptions that the distribution function of a tracer population should be independent of time (i.e. a steady-state distribution function) and that the underlying potential is spherical. We study the limitations of such modelling by applying a general dynamical model with minimal assumptions to a large sample of galactic haloes from cosmological N-body and hydrodynamical simulations. Using dark matter particles as dynamical tracers, we find that the systematic uncertainties in the measured mass and concentration parameters typically have an amplitude of 25-40 per cent. When stars are used as tracers, however, the systematic uncertainties can be as large as a factor of 2-3. The systematic uncertainties are not reduced by increasing the tracer sample size and vary stochastically from halo to halo. These systematic uncertainties are mostly driven by underestimated statistical noise caused by correlated phase-space structures that violate the steady-state assumption. The number of independent phase-space structures inferred from the uncertainty level sets a limiting sample size beyond which a further increase no longer significantly improves the accuracy of dynamical inferences. The systematic uncertainty level is determined by the halo merger history, the shape and environment of the halo. Our conclusions apply generally to any spherical steady-state model.

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

    DOE PAGES

    Niemiec, Anna; Jullo, Eric; Limousin, Marceau; ...

    2017-07-04

    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 bemore » 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.« less

  5. Concentration, ellipsoidal collapse, and the densest dark matter haloes

    NASA Astrophysics Data System (ADS)

    Okoli, Chiamaka; Afshordi, Niayesh

    2016-03-01

    The smallest dark matter haloes are the first objects to form in the hierarchical structure formation of cold dark matter (CDM) cosmology and are expected to be the densest and most fundamental building blocks of CDM structures in our Universe. Nevertheless, the physical characteristics of these haloes have stayed illusive, as they remain well beyond the current resolution of N-body simulations (at redshift zero). However, they dominate the predictions (and uncertainty) in expected dark matter annihilation signal, amongst other astrophysical observables. Using the conservation of total energy and the ellipsoidal collapse framework, we can analytically find the mean and scatter of concentration c and 1D velocity dispersion σ1d for haloes of different virial mass M200. Both c and σ _1d/M_{200}^{1/3} are in good agreement with numerical results within the regime probed by simulations - slowly decreasing functions of mass that approach constant values at large masses. In particular, the predictions for the 1D velocity dispersion of cluster mass haloes are surprisingly robust as the inverse heat capacity of cosmological haloes crosses zero at M200 ˜ 1014 M⊙. However, we find that current extrapolations from simulations to smallest CDM haloes dramatically depend on the assumed profile (e.g. NFW versus Einasto) and fitting function, which is why theoretical considerations, such as the one presented here, can significantly constrain the range of feasible predictions.

  6. Halo-free phase contrast microscopy (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Nguyen, Tan H.; Kandel, Mikhail E.; Shakir, Haadi M.; Best, Catherine; Do, Minh N.; Popescu, Gabriel

    2017-02-01

    The phase contrast (PC) method is one of the most impactful developments in the four-century long history of microscopy. It allows for intrinsic, nondestructive contrast of transparent specimens, such as live cells. However, PC is plagued by the halo artifact, a result of insufficient spatial coherence in the illumination field, which limits its applicability. We present a new approach for retrieving halo-free phase contrast microscopy (hfPC) images by upgrading the conventional PC microscope with an external interferometric module, which generates sufficient data for reversing the halo artifact. Measuring four independent intensity images, our approach first measures haloed phase maps of the sample. We solve for the halo-free sample transmission function by using a physical model of the image formation under partial spatial coherence. Using this halo-free sample transmission, we can numerically generate artifact-free PC images. Furthermore, this transmission can be further used to obtain quantitative information about the sample, e.g., the thickness with known refractive indices, dry mass of live cells during their cycles. We tested our hfPC method on various control samples, e.g., beads, pillars and validated its potential for biological investigation by imaging live HeLa cells, red blood cells, and neurons.

  7. DUAL HALOS AND FORMATION OF EARLY-TYPE GALAXIES

    SciTech Connect

    Park, Hong Soo; Lee, Myung Gyoon E-mail: mglee@astro.snu.ac.kr

    2013-08-20

    We present a determination of the two-dimensional shape parameters of the blue and red globular cluster systems (GCSs) in a large number of elliptical galaxies and lenticular galaxies (early-type galaxies, called ETGs). We use a homogeneous data set of the globular clusters in 23 ETGs obtained from the HST/ACS Virgo Cluster Survey. The position angles of both blue and red GCSs show a correlation with those of the stellar light distribution, showing that the major axes of the GCSs are well aligned with those of their host galaxies. However, the shapes of the red GCSs show a tight correlation with the stellar light distribution as well as with the rotation property of their host galaxies, while the shapes of the blue GCSs do much less. These provide clear geometric evidence that the origins of the blue and red globular clusters are distinct and that ETGs may have dual halos: a blue (metal-poor) halo and a red (metal-rich) halo. These two halos show significant differences in metallicity, structure, and kinematics, indicating that they are formed in two distinguishable ways. The red halos might have formed via dissipational processes with rotation, while the blue halos are through accretion.

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  10. The age of the Milky Way inner halo.

    PubMed

    Kalirai, Jason S

    2012-05-30

    The Milky Way galaxy has several components, such as the bulge, disk and halo. Unravelling the assembly history of these stellar populations is often restricted because of difficulties in measuring accurate ages for low-mass, hydrogen-burning stars. Unlike these progenitors, white dwarf stars, the 'cinders' of stellar evolution, are remarkably simple objects and their fundamental properties can be measured with little ambiguity. Here I report observations of newly formed white dwarf stars in the halo of the Milky Way, and a separate analysis of archival data in the well studied 12.5-billion-year-old globular cluster Messier 4. I measure the mass distribution of the remnant stars and invert the stellar evolution process to develop a mathematical relation that links this final stellar mass to the mass of their immediate progenitors, and therefore to the age of the parent population. By applying this technique to a small sample of four nearby and kinematically confirmed halo white dwarf stars, I calculate the age of local field halo stars to be 11.4 ± 0.7 billion years. The oldest globular clusters formed 13.5 billion years ago. Future observations of newly formed white dwarf stars in the halo could be used to reduce the uncertainty, and to probe relative differences between the formation times of the youngest globular clusters and the inner halo.

  11. The abundance and environment of dark matter haloes

    NASA Astrophysics Data System (ADS)

    Metuki, Ofer; Libeskind, Noam I.; Hoffman, Yehuda

    2016-07-01

    An open question in cosmology and the theory of structure formation is to what extent does environment affect the properties of galaxies and haloes. The present paper aims at shedding light on this problem. The paper focuses on the analysis of a dark matter only simulation and it addresses the issue of how the environment affects the abundance of haloes, which are assigned four attributes: their virial mass, an ambient density calculated with an aperture that scales with Rvir (ΔM), a fixed-aperture (ΔR) ambient density, and a cosmic web classification (i.e. voids, sheets, filaments, and knots, as defined by the V-web algorithm). ΔM is the mean density around a halo evaluated within a sphere of a radius of 5Rvir, where Rvir is the virial radius. ΔR is the density field Gaussian smoothed with R = 4 h-1 Mpc, evaluated at the centre of the halo. The main result of the paper is that the difference between haloes in different web elements stems from the difference in their mass functions, and does not depend on their adaptive-aperture ambient density. A dependence on the fixed-aperture ambient density is induced by the cross-correlation between the mass of a halo and its fixed-aperture ambient density.

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

    NASA Astrophysics Data System (ADS)

    Niemiec, Anna; Jullo, Eric; Limousin, Marceau; Giocoli, Carlo; Erben, Thomas; Hildebrant, Hendrik; Kneib, Jean-Paul; Leauthaud, Alexie; Makler, Martin; Moraes, Bruno; Pereira, Maria E. S.; Shan, Huanyuan; Rozo, Eduardo; Rykoff, Eli; Van Waerbeke, Ludovic

    2017-10-01

    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 Dark Energy Survey (DES) science verification archive, the Canada-France-Hawaii Lensing Survey (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 find a stellar-to- halo mass relation in good agreement with the theoretical expectations from Moster et al. for central galaxies. In the centre of the cluster, we find that this relation is shifted to smaller halo mass for a given stellar mass. We interpret this finding as further evidence for tidal stripping of dark matter haloes in high-density environments.

  13. Corrections to halo model in presence of primordial magnetic field

    NASA Astrophysics Data System (ADS)

    Varalakshmi, Cheera; Nigam, Rahul

    2017-01-01

    We study the role played by the primordial magnetic field in the process of structure formation in the early universe. We have compared the halo mass abundance in the presence and absence of the magnetic field. We derive a modified Press-Schechter formula in presence of another source for matter perturbation and use it to study how this extra source affects halo count. This other source is the magnetic field with a given power spectrum. We find the ranges for the magnetic field strength over which the field enhances the halo formation for a mass range for spectral index nb = -2.95. We found that for field strength less than or equal to B = 7.0 nG, which we call the cut-off field strength, the presence of magnetic field enhances halo formation at low mass scale while it disrupts for a stronger field. We further investigate the dependence of halo count on the spectral index of the magnetic field power spectrum. We observe that at the cut-off field strength, halo formation is disrupted for a spectral index larger than -2.9. We carry out similar investigation for the more generic ellipsoidal collapse where the mass function is given by the Sheth-Tormen formula. For this case we find the cut-off field strength is 5.5 nG.

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

    SciTech Connect

    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

    2011-09-01

    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{sub gc} < 20 kpc.

  15. The gamma-ray-flux PDF from galactic halo substructure

    SciTech Connect

    Lee, Samuel K.; Ando, Shin'ichiro; Kamionkowski, Marc E-mail: ando@tapir.caltech.edu

    2009-07-01

    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{sub ⊕}, 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.

  16. Reference dosimetry of proton pencil beams based on dose-area product: a proof of concept.

    PubMed

    Gomà, Carles; Safai, Sairos; Vörös, Sándor

    2017-06-21

    This paper describes a novel approach to the reference dosimetry of proton pencil beams based on dose-area product ([Formula: see text]). It depicts the calibration of a large-diameter plane-parallel ionization chamber in terms of dose-area product in a (60)Co beam, the Monte Carlo calculation of beam quality correction factors-in terms of dose-area product-in proton beams, the Monte Carlo calculation of nuclear halo correction factors, and the experimental determination of [Formula: see text] of a single proton pencil beam. This new approach to reference dosimetry proves to be feasible, as it yields [Formula: see text] values in agreement with the standard and well-established approach of determining the absorbed dose to water at the centre of a broad homogeneous field generated by the superposition of regularly-spaced proton pencil beams.

  17. Reference dosimetry of proton pencil beams based on dose-area product: a proof of concept

    NASA Astrophysics Data System (ADS)

    Gomà, Carles; Safai, Sairos; Vörös, Sándor

    2017-06-01

    This paper describes a novel approach to the reference dosimetry of proton pencil beams based on dose-area product (DAPw ). It depicts the calibration of a large-diameter plane-parallel ionization chamber in terms of dose-area product in a 60Co beam, the Monte Carlo calculation of beam quality correction factors—in terms of dose-area product—in proton beams, the Monte Carlo calculation of nuclear halo correction factors, and the experimental determination of DAPw of a single proton pencil beam. This new approach to reference dosimetry proves to be feasible, as it yields DAPw values in agreement with the standard and well-established approach of determining the absorbed dose to water at the centre of a broad homogeneous field generated by the superposition of regularly-spaced proton pencil beams.

  18. Synthesis and enzymatic ketonization of the 5-(halo)-2-hydroxymuconates and 5-(halo)-2-hydroxy-2,4-pentadienoates.

    PubMed

    Stack, Tyler M M; Jr, William H Johnson; Whitman, Christian P

    2017-01-01

    5-Halo-2-hydroxymuconates and 5-halo-2-hydroxy-2,4-pentadienoates are stable dienols that are proposed intermediates in bacterial meta-fission pathways for the degradation of halogenated aromatic compounds. The presence of the halogen raises questions about how the bulk and/or electronegativity of these substrates would affect enzyme catalysis or whether some pathway enzymes have evolved to accommodate it. To address these questions, 5-halo-2-hydroxymuconates and 5-halo-2-hydroxy-2,4-pentadienoates (5-halo = Cl, Br, F) were synthesized and a preliminary analysis of their enzymatic properties carried out. In aqueous buffer, 5-halo-2-hydroxy-2,4-pentadienoates rapidly equilibrate with the β,γ-unsaturated ketones. For the 5-chloro and 5-bromo derivatives, a slower conversion to the α,β-isomers follows. There is no detectable formation of the α,β-isomer for the 5-fluoro derivative. Kinetic parameters were also obtained for both sets of compounds in the presence of 4-oxalocrotonate tautomerase (4-OT) from Pseudomonas putida mt-2 and Leptothrix cholodnii SP-6. For 5-halo-2-hydroxymuconates, there are no major differences in the kinetic parameters for the two enzymes (following the formation of the β,γ-unsaturated ketones). In contrast, the L. cholodnii SP-6 4-OT is ≈10-fold less efficient than the P. putida mt-2 4-OT in the formation of the β,γ-unsaturated ketones and the α,β-isomers from the 5-halo-2-hydroxy-2,4-pentadienoates. The implications of these findings are discussed. The availability of these compounds will facilitate future studies of the haloaromatic catabolic pathways.

  19. The universality of the virial halo mass function and models for non-universality of other halo definitions

    NASA Astrophysics Data System (ADS)

    Despali, Giulia; Giocoli, Carlo; Angulo, Raul E.; Tormen, Giuseppe; Sheth, Ravi K.; Baso, Giacomo; Moscardini, Lauro

    2016-03-01

    The abundance of galaxy clusters can constrain both the geometry and growth of structure in our Universe. However, this probe could be significantly complicated by recent claims of non-universality-non-trivial dependences with respect to the cosmological model and redshift. In this work, we analyse the dependence of the mass function on the way haloes are identified and establish if this can cause departures from universality. In order to explore this dependence, we use a set of different N-body cosmological simulations (Le SBARBINE simulations), with the latest cosmological parameters from the Planck collaboration; this first suite of simulations is followed by a lower resolution set, carried out with different cosmological parameters. We identify dark matter haloes using a spherical overdensity algorithm with varying overdensity thresholds (virial, 2000, 1000, 500, 200 ρc and 200 ρb) at all redshifts. We notice that, when expressed in terms of the rescaled variable ν, the mass function for virial haloes is a nearly universal as a function of redshift and cosmology, while this is clearly not the case for the other overdensities we considered. We provide fitting functions for the halo mass function parameters as a function of overdensity, that allow us to predict, to within a few per cent accuracy, the halo mass function for a wide range of halo definitions, redshifts and cosmological models. We then show how the departures from universality associated with other halo definitions can be derived by combining the universality of the virial definition with the expected shape of the density profile of haloes.

  20. Haloes Seen In UVIS Reflectance Spectra

    NASA Astrophysics Data System (ADS)

    Esposito, Larry W.; Bradley, E.; Colwell, J.; Sremcevic, M.

    2012-10-01

    UVIS SOI reflectance spectra show bright ‘haloes’ around the locations of some of the strongest resonances in Saturn’s A ring (Esposito etal 2005). UV spectra constrain the size and composition of the icy ring particles (Bradley etal 2010, 2012). We investigate the Janus 4:3, 5:3, 6:5 and Mimas 5:3 inner Lindblad resonances as well as at the Mimas 5:3 vertical resonance (bending wave location). Models of ring particle regolith evolution (Elliott and Esposito 2010) indicate the deeper regolith is made of older and purer ice. The strong resonances cause streamline crowding (Lewis and Stewart 2005) which damps the interparticle velocity, allowing temporary clumps to grow, which in turn increase the velocity, eroding the clumps and releasing smaller particles and regolith (see the predator-prey model of Esposito etal 2012). This cyclic behavior, driven by the resonant perturbation from the moon, can yield collision velocities greater than 1m/sec, sufficient to erode the aggregates (Blum 2006), exposing older, purer materials. Thus, the radial location of the strongest resonances can be where we find both large aggregates and disrupted fragments, in a balance maintained by the periodic moon forcing. If this stirring exposes older, and purer ice, the velocity threshold for eroding the aggregates can explain why only the strongest Lindblad resonances show haloes. UVIS spectra can determine the relative contributions of particle size and purity at these locations, for comparison to estimates from the regolith evolution models.

  1. The extent of the local hi halo

    NASA Technical Reports Server (NTRS)

    Lockman, F. J.; Hobbs, L. M.; Shull, J. M.

    1985-01-01

    Forty-five high-latitude, OB stars have been observed in the Ly alpha and 21 cm lines of HI in an effort to map out the vertical distribution and extent of the local HI halo. The 25 stars for which a reliable HI colum density can be obtained from Ly alpha lie between 60 and 3100 pc from the plane. The principal result is that the total column density of HI at z 1 kpc is, on the average, 5 + or - 3 x 10 the 19th power/sq cm, or 15% of the total sub HI. At relatively low z the data toward some stars suggest a low effective scale height and fairly high average foreground density, while toward others the effective scale height is large and the average density is low. This can be understood as the result of irregularities in the interstellar medium. A model with half of the HI mass in clouds having radii of a few pc and a Gaussian vertical distribution with sigma sub 2 = 135 pc, and half of the mass in an exponential component with a scale height of 500 pc, gives a satisfactory fit to the data. The technique of comparing Ly alpha and 21 cm column densities is also used to discuss the problem of estimating the distance to several possibly subluminous stars.

  2. The CMS Beam Halo Monitor electronics

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  3. HALO VELOCITY GROUPS IN THE PISCES OVERDENSITY

    SciTech Connect

    Sesar, Branimir; Ivezic, Zeljko; Vivas, A. Katherina; Duffau, Sonia E-mail: zi@u.washington.ed E-mail: sonia.duffau@gmail.co

    2010-07-01

    We report spectroscopic observations of five faint (V {approx} 20) RR Lyrae stars associated with the Pisces overdensity conducted with the Gemini South Telescope. At a heliocentric and galactocentric distance of {approx}80 kpc, this is the most distant substructure in the Galactic halo known to date. We combined our observations with literature data and confirmed that the substructure is composed of two different kinematic groups. The main group contains eight stars and has (V{sub gsr}) = 50 km s{sup -1}, while the second group contains four stars at a velocity of (V{sub gsr}) = -52 km s{sup -1}, where V{sub gsr} is the radial velocity in the galactocentric standard of rest. The metallicity distribution of RR Lyrae stars in the Pisces overdensity is centered on [Fe/H] = -1.5 dex and has a width of 0.3 dex. The new data allowed us to establish that both groups are spatially extended making it very unlikely that they are bound systems, and are more likely to be debris of a tidally disrupted galaxy or galaxies. Due to small sky coverage, it is still unclear whether these groups have the same or different progenitors.

  4. Baryonic Distributions in Galaxy Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Richards, Emily E.

    2016-01-01

    Understanding the role and significance of dark matter in the evolution of baryonic components (i.e., conversion of the gaseous disk into stars) is a critical aspect for realistic models of galaxy evolution. In an effort to address fundamental questions regarding the growth and distribution of stellar disks in dark matter halos in a statistical manner, we have undertaken a project correlating structural properties and star formation activity with the dark matter properties of the host galaxy. The project uses a statistical sample of 45 nearby galaxies which are optimally suited for rotation curve decomposition analysis. The dataset includes deep Spitzer 3.6μm images to trace the stellar distribution, neutral and ionized gas rotation curves to trace the total mass distribution, and optical images to examine the dominant stellar populations. Using a sub-set of galaxies from the full sample, we find that the distribution of the baryonic mass relative to the total mass is roughly self-similar in more massive galaxies when normalized by the average stellar disk scale length measured at 3.6μm. We additionally observe an emerging trend between total baryonic mass and the radius at which the total mass distribution transitions from baryon-dominated to dark matter-dominated. However, we find no significant correlation between the distribution of dark matter and structural properties of the stellar disk, such as changes in color or star formation activity.

  5. Experimental searches for galactic halo axions.

    PubMed

    van Bibber, Karl A; Kinion, S Darin

    2003-11-15

    A very light axion would be copiously produced during the Big Bang as a zero-temperature Bose gas, and it would possess vanishingly small couplings to matter and radiation. It thus represents an ideal cold dark matter candidate. Galactic halo axions may be detected by their resonant conversion to microwave photons in a high-Q cavity permeated by a strong magnetic field. A large-scale search for the axion is ongoing in the US with sufficient sensitivity to see axions of plausible model couplings. Dramatic breakthroughs in the development of near-quantum limited superconducting quantum interference device amplifiers promise to improve the sensitivity of the experiment by a factor of 30 in the near future. In Japan, a group has been developing a Rydberg atom single-quantum detector as an alternative to linear amplifiers for a microwave-cavity axion experiment. Should the axion be discovered, the predicted fine structure in the axion signal would be rich in information about the history of galactic formation.

  6. The Halo of the Milky Way

    SciTech Connect

    Newberg, Heidi Jo; Yanny, Brian; /Rensselaer Poly. /Fermilab

    2005-02-01

    The authors show that the star counts in the spheroid of the Milky Way are not symmetric about the l = 0{sup o}, l = 180{sup o} plane. The minimum counts are found towards l = 155{sup o}. The Galactic longitude of maximum star counts depends on the magnitude and color selection of the halo stars. They interpret this as evidence that the spheroid population is triaxial with a major axis oriented 65{sup o} from the line of sight from the Sun to the Galactic center, and approximately perpendicular to the Galactic bar. Large local star concentrations from tidal debris and possible tidal debris are also observed. A full understanding of the Galactic spheroid population awaits position information and three dimensional space velocities for a representative set of stars in every substructure. Tangential velocities for many stars will be provided by current and planned astrometry missions, but no planned mission will measure stars faint enough to unravel the more distant parts of the spheroid, which contain the majority of the spatial substructure. This paper uses data from the Sloan Digital Sky Survey (SDSS) public data release DR3.

  7. Clusters and Halos in Light Nuclei

    SciTech Connect

    Neff, Thomas; Feldmeier, Hans

    2009-08-26

    The structure of light nuclei in the p- and sd-shell features exotic phenomena like halos and clustering. In the Fermionic Molecular Dynamics (FMD) approach we aim at a consistent microscopic description of well bound nuclei and of loosely bound exotic systems. This is possible due to the flexibility of the single-particle basis states using Gaussian wave-packets localized in phase space. Many-body basis states are Slater determinants projected on parity, angular and total linear momentum.The structure of {sup 12}C is discussed. Here the ground state band can be well described within a shell model picture but excited states above the three-{alpha} threshold, including the famous Hoyle state, show a pronounced cluster structure. As another example we study the structure of the Neon isotopes {sup 17-22}Ne. In {sup 17}Ne we find a large s{sup 2} occupation related to a large charge radius. The charge radius decreases for {sup 18}Ne but gets again very large for {sup 19}Ne and {sup 20}Ne which is explained by significant admixtures of {sup 3}He and {sup 4}He cluster components into to the ground state wave functions.

  8. Clusters and Halos in Light Nuclei

    NASA Astrophysics Data System (ADS)

    Neff, Thomas; Feldmeier, Hans

    2009-08-01

    The structure of light nuclei in the p- and sd-shell features exotic phenomena like halos and clustering. In the Fermionic Molecular Dynamics (FMD) approach we aim at a consistent microscopic description of well bound nuclei and of loosely bound exotic systems. This is possible due to the flexibility of the single-particle basis states using Gaussian wave-packets localized in phase space. Many-body basis states are Slater determinants projected on parity, angular and total linear momentum. The structure of 12C is discussed. Here the ground state band can be well described within a shell model picture but excited states above the three-α threshold, including the famous Hoyle state, show a pronounced cluster structure. As another example we study the structure of the Neon isotopes 17-22Ne. In 17Ne we find a large s2 occupation related to a large charge radius. The charge radius decreases for 18Ne but gets again very large for 19Ne and 20Ne which is explained by significant admixtures of 3He and 4He cluster components into to the ground state wave functions.

  9. The Dark Halo of NGC 1399

    NASA Astrophysics Data System (ADS)

    Schuberth, Y.; Richtler, T.; Hilker, M.

    2006-06-01

    NGC 1399 is the central giant elliptical of the nearby Fornax cluster of galaxies. Our sample now consists of 625 GCs with projected galactocentric distances between 6 and 100 kpc, thus increasing by almost a factor of two the radial range in comparison to the study presented by Richtler et al. 2004). We determine the line-of-sight velocity dispersion as a function of radius and compare it to spherical Jeans-models. We find that a massive dark halo is required in order to explain the dynamics of the metal-poor (red) GCs. At 60 kpc, the dark matter fraction is 60%. In accordance with their shallower radial distribution, the metal-rich (blue) GCs show a higher line-of-sight velocity dispersion. Yet, there is reason to believe that the blue cluster population of NGC 1399 is contaminated by intra-cluster GCs which perhaps have been stripped off neighboring early-type galaxies. The center of the Fornax cluster is a complex environment, and a more detailed analysis of our data will allow us to better understand the GC systems of central giant ellipticals and their connection to the galaxy clusters in which they reside.

  10. Do dark matter halos explain lensing peaks?

    NASA Astrophysics Data System (ADS)

    Zorrilla Matilla, José Manuel; Haiman, Zoltán; Hsu, Daniel; Gupta, Arushi; Petri, Andrea

    2016-10-01

    We have investigated a recently proposed halo-based model, Camelus, for predicting weak-lensing peak counts, and compared its results over a collection of 162 cosmologies with those from N-body simulations. While counts from both models agree for peaks with S /N >1 (where S /N is the ratio of the peak height to the r.m.s. shape noise), we find ≈50 % fewer counts for peaks near S /N =0 and significantly higher counts in the negative S /N tail. Adding shape noise reduces the differences to within 20% for all cosmologies. We also found larger covariances that are more sensitive to cosmological parameters. As a result, credibility regions in the {Ωm,σ8} are ≈30 % larger. Even though the credible contours are commensurate, each model draws its predictive power from different types of peaks. Low peaks, especially those with 2 3 ). Our results confirm the importance of using a cosmology-dependent covariance with at least a 14% improvement in parameter constraints. We identified the covariance estimation as the main driver behind differences in inference, and suggest possible ways to make Camelus even more useful as a highly accurate peak count emulator.

  11. The Schwarzschild Proton

    SciTech Connect

    Haramein, Nassim

    2010-11-24

    We review our model of a proton that obeys the Schwarzschild condition. We find that only a very small percentage ({approx}10{sup -39}%) of the vacuum fluctuations available within a proton volume need be cohered and converted to mass-energy in order for the proton to meet the Schwarzschild condition. This proportion is equivalent to that between gravitation and the strong force where gravitation is thought to be {approx}10{sup -38} to 10{sup -40} weaker than the strong force. Gravitational attraction between two contiguous Schwarzschild protons can accommodate both nucleon and quark confinement. We calculate that two contiguous Schwarzschild protons would rotate at c and have a period of 10{sup -23} s and a frequency of 10{sup 22} Hz which is characteristic of the strong force interaction time and a close approximation of the gamma emission typically associated with nuclear decay. We include a scaling law and find that the Schwarzschild proton data point lies near the least squares trend line for organized matter. Using a semi-classical model, we find that a proton charge orbiting at a proton radius at c generates a good approximation to the measured anomalous magnetic moment.

  12. Analytical and numerical studies of dark matter halos

    NASA Astrophysics Data System (ADS)

    Austin, Crystal Gayle

    This dissertation focuses on the evolution and structure of dark matter halos of galaxies, groups and clusters of galaxies. I explore the dependence of the final halo's properties on the initial conditions and the physical processes that guide the halo to equilibrium, with special focus on the power-law nature of the r/s 3 profile, where r is the density profile and s is the velocity dispersion profile. As the astronomy community does not yet fully understand these processes, this research expands our understanding of collisionless, gravitationally-interacting systems. In the initial chapters, I study the collisionless semi-analytic halo simulations and show that the final properties are sensitive to the initial conditions, such as the power-spectra filtering scale, the secondary velocities' magnitudes and directions, and the accretion rate. The general conclusions are that semi-analytic halos are in hydrostatic equilibrium and have a power-law r/s 3 profile. If there were discontinuities in the initial conditions, the power-law feature in r/s 3 breaks. Because of this, hydrostatic equilibrium is a less restrictive condition than the r/s 3 profile. These halos can recover from moderate discontinuities by either correcting a single profile by sacrificing other quantities or by sufficient post-accretion. Finally, I compare collisionless semi-analytic and N-body simulations directly. This novel comparison is useful because these techniques use different physics to collapse the proto-halo. The physical differences between these two methods are used to determine causes of the final halo profiles. Specifically, I find the NFW density profile and power-law r/s 3 are due to the slow rate of evolution, which is determined from the initial conditions and cosmology. The density slope-velocity anisotropy relationship is dependent, rather, on the physical processes (notably the radial orbit instability) and three-dimensional evolution used to collapse the proto-halos. We also

  13. Formation of the Galactic Stellar Halo. I. Structure and Kinematics

    NASA Astrophysics Data System (ADS)

    Bekki, Kenji; Chiba, Masashi

    2001-09-01

    We perform numerical simulations for the formation of the Galactic stellar halo, based on the currently favored cold dark matter theory of galaxy formation. Our numerical models, taking into account both dynamical and chemical evolution processes in a consistent manner, are aimed at explaining the observed structure and kinematics of the stellar halo in the context of hierarchical galaxy formation. The main results of the present simulations are summarized as follows: (1) Basic physical processes involved in the formation of the stellar halo, composed of metal-deficient stars with [Fe/H]<=-1.0, are described by both dissipative and dissipationless merging of subgalactic clumps and their resultant tidal disruption in the course of gravitational contraction of the Galaxy at high redshift (z>1). (2) The simulated halo has a density profile similar to the observed power-law form of ρ(r)~r-3.5 and also has a metallicity distribution similar to the observations. The halo shows virtually no radial gradient for stellar ages and only a small gradient for metallicities. (3) The dual nature of the halo, i.e., its inner flattened and outer spherical density distribution, is reproduced, at least qualitatively, by the present model. The outer spherical halo is formed via essentially dissipationless merging of small subgalactic clumps, whereas the inner flattened one is formed via three different mechanisms, i.e., dissipative merging between larger, more massive clumps, adiabatic contraction due to the growing Galactic disk, and gaseous accretion onto the equatorial plane. (4) For the simulated metal-poor stars with [Fe/H]<=-1.0, there is no strong correlation between metal abundances and orbital eccentricities, in good agreement with the recent observations. Moreover, the observed fraction of the low-eccentricity stars is reproduced correctly for [Fe/H]<=-1.6 and approximately for the intermediate-abundance range of -1.6<[Fe/H]<=-1.0. (5) The mean rotational velocity of the

  14. Surface Protonics Promotes Catalysis

    NASA Astrophysics Data System (ADS)

    Manabe, R.; Okada, S.; Inagaki, R.; Oshima, K.; Ogo, S.; Sekine, Y.

    2016-12-01

    Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando–IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd–CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics.

  15. Electron-proton spectrometer

    NASA Technical Reports Server (NTRS)

    Winckler, J. R.

    1973-01-01

    An electron-proton spectrometer was designed to measure the geomagnetically trapped radiation in a geostationary orbit at 6.6 earth radii in the outer radiation belt. This instrument is to be flown on the Applications Technology Satellite-F (ATS-F). The electron-proton spectrometer consists of two permanent magnet surface barrier detector arrays and associated electronics capable of selecting and detecting electrons in three energy ranges: (1) 30-50 keV, (2) 150-200 keV, and (3) 500 keV and protons in three energy ranges. The electron-proton spectrometer has the capability of measuring the fluxes of electrons and protons in various directions with respect to the magnetic field lines running through the satellite. One magnet detector array system is implemented to scan between EME north and south through west, sampling the directional flux in 15 steps. The other magnet-detector array system is fixed looking toward EME east.

  16. Surface Protonics Promotes Catalysis

    PubMed Central

    Manabe, R.; Okada, S.; Inagaki, R.; Oshima, K.; Ogo, S.; Sekine, Y.

    2016-01-01

    Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando–IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd–CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics. PMID:27905505

  17. The halo sign: HRCT findings in 85 patients.

    PubMed

    Alves, Giordano Rafael Tronco; Marchiori, Edson; Irion, Klaus; Nin, Carlos Schuler; Watte, Guilherme; Pasqualotto, Alessandro Comarú; Severo, Luiz Carlos; Hochhegger, Bruno

    2016-01-01

    The halo sign consists of an area of ground-glass opacity surrounding pulmonary lesions on chest CT scans. We compared immunocompetent and immunosuppressed patients in terms of halo sign features and sought to identify those of greatest diagnostic value. This was a retrospective study of CT scans performed at any of seven centers between January of 2011 and May of 2015. Patients were classified according to their immune status. Two thoracic radiologists reviewed the scans in order to determine the number of lesions, as well as their distribution, size, and contour, together with halo thickness and any other associated findings. Of the 85 patients evaluated, 53 were immunocompetent and 32 were immunosuppressed. Of the 53 immunocompetent patients, 34 (64%) were diagnosed with primary neoplasm. Of the 32 immunosuppressed patients, 25 (78%) were diagnosed with aspergillosis. Multiple and randomly distributed lesions were more common in the immunosuppressed patients than in the immunocompetent patients (p < 0.001 for both). Halo thickness was found to be greater in the immunosuppressed patients (p < 0.05). Etiologies of the halo sign differ markedly between immunocompetent and immunosuppressed patients. Although thicker halos are more likely to occur in patients with infectious diseases, the number and distribution of lesions should also be taken into account when evaluating patients presenting with the halo sign. O sinal do halo consiste em uma área de opacidade em vidro fosco ao redor de lesões pulmonares em imagens de TC de tórax. Pacientes imunocompetentes e imunodeprimidos foram comparados quanto a características do sinal do halo a fim de identificar as de maior valor diagnóstico. Estudo retrospectivo de tomografias realizadas em sete centros entre janeiro de 2011 e maio de 2015. Os pacientes foram classificados de acordo com seu estado imunológico. Dois radiologistas torácicos analisaram os exames a fim de determinar o número de lesões e sua distribui

  18. Ecology of dark matter haloes -II. Effects of interactions on the alignment of halo pairs

    NASA Astrophysics Data System (ADS)

    L'Huillier, Benjamin; Park, Changbom; Kim, Juhan

    2017-01-01

    We use the Horizon Run 4 cosmological N-body simulation to study the effects of distant and close interactions on the alignments of the shapes, spins, and orbits of targets haloes with their neighbours, and their dependence on the local density environment and neighbour separation. Interacting targets have a significantly lower spin and higher sphericity and oblateness than all targets. Interacting pairs initially have anti-parallel spins, but the spins develop parallel alignment as time goes on. Neighbours tend to evolve in the plane of rotation of the target, and in the direction of the major axis of prolate haloes. Moreover, interactions are preferentially radial, while pairs with non-radial orbits are preferentially prograde. The alignment signals are stronger at high-mass and for close separations, and independent on the large-scale density. Positive alignment signals are found at redshifts up to 4, and increase with decreasing redshifts. Moreover, the orbits tend to become prograde at low redshift, while no alignment is found at high redshift (z = 4).

  19. Halo common proper motion stars - Subdwarf distance scale, halo binary fraction, and UBVRI colors

    NASA Technical Reports Server (NTRS)

    Ryan, Sean G.

    1992-01-01

    Common proper motion stars identified by Luyten (1979, 1980) were selected according to reduced proper motion and photometric criteria to produce a list of candidate halo objects. UBVRI photometry was obtained to identify genuine halo parts. About 20 percent of the stars with (Fe/H) less than -1.0 were found to have random errors not less than several x 0.1 mag in distance modulus, in addition to the photometric errors, thought to be due to the existence of close binary companions to some of the common proper motion stars. The implications of these errors for kinematic studies of field Population II stars are considered. Systematic errors of order 16 percent were also detected in distances derived from the U-B,B-V deblanketing technique. It is suggested that Population II field stars did not originate in globular clusters which subsequently disintegrated but formed in less dense environments. Several K subdwarfs were found with very high UV excesses, comparable with those predicted by some synthetic colors.

  20. Ecology of dark matter haloes - II. Effects of interactions on the alignment of halo pairs

    NASA Astrophysics Data System (ADS)

    L'Huillier, Benjamin; Park, Changbom; Kim, Juhan

    2017-04-01

    We use the Horizon Run 4 cosmological N-body simulation to study the effects of distant and close interactions on the alignments of the shapes, spins and orbits of targets haloes with their neighbours, and their dependence on the local density environment and neighbour separation. Interacting targets have a significantly lower spin and higher sphericity and oblateness than all targets. Interacting pairs initially have antiparallel spins, but the spins develop parallel alignment as time goes on. Neighbours tend to evolve in the plane of rotation of the target, and in the direction of the major axis of prolate haloes. Moreover, interactions are preferentially radial, while pairs with non-radial orbits are preferentially prograde. The alignment signals are stronger at high mass and for close separations, and independent of the large-scale density. Positive alignment signals are found at redshifts up to 4, and increase with decreasing redshifts. Moreover, the orbits tend to become prograde at low redshift, while no alignment is found at high redshift (z = 4).

  1. The Case for the Dual Halo of the Milky Way

    NASA Astrophysics Data System (ADS)

    Beers, Timothy C.; Carollo, Daniela; Ivezić, Željko; An, Deokkeun; Chiba, Masashi; Norris, John E.; Freeman, Ken C.; Lee, Young Sun; Munn, Jeffrey A.; Re Fiorentin, Paola; Sivarani, Thirupathi; Wilhelm, Ronald; Yanny, Brian; York, Donald G.

    2012-02-01

    Carollo et al. have recently resolved the stellar population of the Milky Way halo into at least two distinct components, an inner halo and an outer halo. This result has been criticized by Schönrich et al., who claim that the retrograde signature associated with the outer halo is due to the adoption of faulty distances. We refute this claim, and demonstrate that the Schönrich et al. photometric distances are themselves flawed because they adopted an incorrect main-sequence absolute magnitude relationship from the work of Ivezić et al. When compared to the recommended relation from Ivezić et al., which is tied to a Milky Way globular cluster distance scale and accounts for age and metallicity effects, the relation adopted by Schönrich et al. yields up to 18% shorter distances for stars near the main-sequence turnoff (TO). Use of the correct relationship yields agreement between the distances assigned by Carollo et al. and Ivezić et al. for low-metallicity dwarfs to within 6%-10%. Schönrich et al. also point out that intermediate-gravity stars (3.5 <=log g < 4.0) with colors redder than the TO region are likely misclassified, with which we concur. We implement a new procedure to reassign luminosity classifications for the TO stars that require it. New derivations of the rotational behavior demonstrate that the retrograde signature and high velocity dispersion of the outer-halo population remain. We summarize additional lines of evidence for a dual halo, including a test of the retrograde signature based on proper motions alone, and conclude that the preponderance of evidence strongly rejects the single-halo interpretation.

  2. Trigonometric parallaxes of high velocity halo white dwarf candidates

    NASA Astrophysics Data System (ADS)

    Ducourant, C.; Teixeira, R.; Hambly, N. C.; Oppenheimer, B. R.; Hawkins, M. R. S.; Rapaport, M.; Modolo, J.; Lecampion, J. F.

    2007-07-01

    Context: The status of 38 halo white dwarf candidates identified by Oppenheimer et al. (2001, Science, 292, 698) has been intensively discussed by various authors. In analyses undertaken to date, trigonometric parallaxes are crucial missing data. Distance measurements are mandatory to kinematically segregate halo object from disk objects and hence enable a more reliable estimate of the local density of halo dark matter residing in such objects. Aims: We present trigonometric parallax measurements for 15 candidate halo white dwarfs (WDs) selected from the Oppenheimer et al. (2001) list. Methods: We observed the stars using the ESO 1.56-m Danish Telescope and ESO 2.2-m telescope from August 2001 to July 2004. Results: Parallaxes with accuracies of 1-2 mas were determined yielding relative errors on distances of ~5% for 6 objects, ~12% for 3 objects, and ~20% for two more objects. Four stars appear to be too distant (probably farther than 100 pc) to have measurable parallaxes in our observations. Conclusions: Distances, absolute magnitudes and revised space velocities were derived for the 15 halo WDs from the Oppenheimer et al. (2001) list. Halo membership is confirmed unambiguously for 6 objects while 5 objects may be thick disk members and 4 objects are too distant to draw any conclusion based solely on kinematics. Comparing our trigonometric parallaxes with photometric parallaxes used in previous work reveals an overestimation of distance as derived from photometric techniques. This new data set can be used to revise the halo white dwarf space density, and that analysis will be presented in a subsequent publication. Based on observations collected at the European Southern Observatory, Chile (067.D-0107, 069.D-0054, 070.D-0028, 071.D-0005, 072.D-0153, 073.D-0028).

  3. Spatial and Kinematic Alignments between Central and Satellite Halos

    NASA Astrophysics Data System (ADS)

    Faltenbacher, A.; Jing, Y. P.; Li, Cheng; Mao, Shude; Mo, H. J.; Pasquali, Anna; van den Bosch, Frank C.

    2008-03-01

    Based on a cosmological N-body simulation, we analyze spatial and kinematic alignments of satellite halos within 6 times the virial radius of group-sized host halos (rvir). We measure three different types of spatial alignment: halo alignment between the orientation of the group central substructure (GCS) and the distribution of its satellites, radial alignment between the orientation of a satellite and the direction toward its GCS, and direct alignment between the orientation of the GCS and that of its satellites. Analogously, we use the directions of satellite velocities and probe three further types of alignment: the radial velocity alignment between the satellite velocity and the connecting line between the satellite and GCS, the halo velocity alignment between the orientation of the GCS and satellite velocities, and the autovelocity alignment between the satellite orientations and their velocities. We find that satellites are preferentially located along the major axis of the GCS within at least 6rvir (the range probed here). Furthermore, satellites preferentially point toward the GCS. The most pronounced signal is detected on small scales, but a detectable signal extends out to ~6rvir. The direct alignment signal is weaker; however, a systematic trend is visible at distances lesssim2rvir. All velocity alignments are highly significant on small scales. The halo velocity alignment is constant within 2rvir and declines rapidly beyond. The halo and the autovelocity alignments are maximal at small scales and disappear beyond 1rvir and 1.5rvir, respectively. Our results suggest that the halo alignment reflects the filamentary large-scale structure that extends far beyond the virial radii of the groups. In contrast, the main contribution to the radial alignment arises from the adjustment of the satellite orientations in the group tidal field. The projected data reveal good agreement with recent results derived from large galaxy surveys.

  4. Capacity of straylight and disk halo size to diagnose cataract.

    PubMed

    Palomo-Álvarez, Catalina; Puell, María C

    2015-10-01

    To examine the capacity of straylight and disk halo size to diagnose cataract. Faculty of Optics and Optometry, Universidad Complutense de Madrid, Spain. Prospective study. Straylight, disk halo radius, and high-contrast corrected distance visual acuity (CDVA) measurements were compared between patients with age-related cataract and age-matched normal-sighted control subjects by calculating the area under the curve (AUC) receiver operating characteristic. Measurements were made in 53 eyes of 53 patients with a mean age of 67.94 years ± 7.11 (SD) and 31 eyes of 31 controls with a mean age 66.06 ± 5.43 years. Significantly worse (P < .001) mean straylight (1.38 ± 0.24 log[s]), mean disk halo radius (2.40 ± 0.18 log minutes of arc [arcmin]), and mean CDVA (0.17 ± 0.11 logMAR) were recorded in the cataract group than in the control group (1.17 ± 0.11 log[s], 2.10 ± 0.16 log arcmin, and 0.08 ± 0.08 logMAR). Significant differences in AUCs were observed for disk halo radius (0.89 ± 0.04) versus straylight (0.77 ± 0.05) (P = .03) and disk halo radius versus CDVA (0.72 ± 0.05) (P = .001). The comparison of disk halo radius versus the discriminant function with input from CDVA and straylight (0.80 ± 0.05) was at the limit of significance only (0.091 ± 0.05, P = .051). Although all 3 variables discriminated well between normal eyes and eyes with cataract, the disk halo radius showed the best diagnostic capacity. Neither author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  5. The natural history of halo nevi: a retrospective case series.

    PubMed

    Aouthmany, Mouhammad; Weinstein, Mara; Zirwas, Matthew J; Brodell, Robert T

    2012-10-01

    The time period between onset of depigmentation around the halo nevus (HN) to complete resolution of the nevus and halo has not been well studied. We sought to better understand the natural history of the HN. A retrospective chart review of patients with a clinical diagnosis of HN selected from a private practice database (1994-2010) was performed. In all, 52 patients with 80 HN were identified. The current stage of the HN was determined by a follow-up questionnaire and physical examination of 36 patients with 56 HN. Seven HN were excised. Of the remaining 49 HN, 51% (25) demonstrated no change in the halo or nevus after an average of 4.2 years; 14.3% (7) demonstrated partial nevus regression with persistence of the halo after an average of 6.7 years; 4.1% (2) demonstrated complete involution of the nevus with persistent halo depigmentation after an average of 7.7 years; 8.2% (4) demonstrated complete nevus involution with some repigmentation of the halo after an average of 11.8 years; 22.4% (11) demonstrated complete resolution of the nevus with complete repigmentation of the halo after an average of 7.8 years. Some subjects were lost to follow-up. The time of initial HN onset was dependent on patient recall. These results demonstrate that HN typically persist for a decade or longer. A subgroup may progress through stages of involution with a return to normal-appearing skin, but even these lesions persisted for an average of 7.8 years. Education about the prolonged natural history of HN may reassure patients and avoid unnecessary excision. Copyright © 2011 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.

  6. Constraining the Galaxy's dark halo with RAVE stars

    NASA Astrophysics Data System (ADS)

    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.

    2014-12-01

    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 density within 0.9 kpc of the plane ((69 ± 10) M⊙ pc-2) are almost independent of the (oblate) halo's axis ratio q. If the halo is spherical, 46 per cent of the radial force on the Sun is provided by baryons, and only 4.3 per cent of the Galaxy's mass is baryonic. If the halo is flattened, the baryons contribute even less strongly to the local radial force and to the Galaxy's mass. The dark matter density at the location of the Sun is 0.0126 q-0.89 M⊙ pc-3 = 0.48 q-0.89 GeV cm-3. When combined with other literature results we find hints for a mildly oblate dark halo with q ≃ 0.8. Our value for the dark mass within the solar radius is larger than that predicted by cosmological dark-matter-only simulations but in good agreement with simulations once the effects of baryonic infall are taken into account. Our mass models consist of three double-exponential discs, an oblate bulge and a Navarro-Frenk-White dark matter halo, and we model the dynamics of the RAVE (RAdial Velocity Experiment) stars in the corresponding gravitational fields by finding distribution functions f J that depend on three action integrals. Statistical errors are completely swamped by systematic uncertainties, the most important of which are the distance to the stars in the photometric and spectroscopic samples and the solar distance to the Galactic Centre. Systematics other than the flattening of the dark halo yield overall uncertainties ˜15 per cent.

  7. Halo/galaxy bispectrum with equilateral-type primordial trispectrum

    NASA Astrophysics Data System (ADS)

    Mizuno, Shuntaro; Yokoyama, Shuichiro

    2015-06-01

    We investigate the effect of equilateral-type primordial trispectrum on the halo/galaxy bispectrum. We consider three types of equilateral primordial trispectra which are generated by quartic operators naturally appearing in the effective field theory of inflation and can be characterized by three nonlinearity parameters, gNLσ˙ 4 , gNLσ˙ 2(∂σ )2 , and gNL(∂σ )4 . Recently, constraints on these parameters have been investigated from Cosmic Microwave Background (CMB) observations by using WMAP9 data. In order to consider the halo/galaxy bispectrum with the equilateral-type primordial trispectra, we adopt the integrated perturbation theory in which the effects of primordial non-Gaussianity are wholly encapsulated in the linear primordial polyspectrum for the evaluation of the biased polyspectrum. We show the shapes of the halo/galaxy bispectrum with the equilateral-type primordial trispectra and find that the primordial trispectrum characterized by gNLσ˙ 4 provides the same scale dependence as the gravity-induced halo/galaxy bispectrum. Hence, it would be difficult to obtain the constraint on gNLσ˙ 4 from the observations of the halo/galaxy bispectrum. On the other hand, the primordial trispectra characterized by gNLσ˙ 2(∂σ )2 and gNL(∂σ )4 provide the common scale dependence which is different from that of the gravity-induced halo/galaxy bispectrum on large scales. Hence, future observations of the halo/galaxy bispectrum would give constraints on the nonlinearity parameters, gNLσ˙ 2(∂σ )2 and gNL(∂σ )4 independently from CMB observations.

  8. Proton-proton colliding beam facility ISABELLE

    SciTech Connect

    Hahn, H

    1980-01-01

    This paper attempts to present the status of the ISABELLE construction project, which has the objective of building a 400 + 400 GeV proton colliding beam facility. The major technical features of the superconducting accelerators with their projected performance are described. Progress made so far, difficulties encountered, and the program until completion in 1986 is briefly reviewed.

  9. Novel technique for relieving anastomotic tension using halo-vest immobilization after tracheal sleeve resection.

    PubMed

    Imai, Kazuhiro; Minamiya, Yoshihiro; Saito, Hajime; Miyakoshi, Naohisa; Hongo, Michio; Kasukawa, Yuji; Ishikawa, Yoshinori; Motoyama, Satoru; Sato, Yusuke; Shimada, Yoichi; Ogawa, Jun-ichi

    2013-07-01

    We describe a novel technique of using halo-vest-enforced immobilization to relieve anastomotic tension after tracheal sleeve resection. Immediately after the tracheal sleeve resection, four halo titanium pins were inserted in the skulls of the patients to secure the halo-vest. All patients fitted with halo-vests were able to eat and drink and their clinical course was good. Bronchoscopy confirmed the absence of anastomotic leaks and stenoses, and there were no complications associated with the halo-vest. We believe that ensuring neck flexion using a halo-vest after tracheal sleeve resection is an excellent way of relieving anastomotic tension that would predispose the wound to dehiscence.

  10. Rhodium-catalyzed intramolecular hydroarylation of 1-halo-1-alkynes: regioselective synthesis of semihydrogenated aromatic heterocycles.

    PubMed

    Murase, Hirohiko; Senda, Kousuke; Senoo, Masato; Hata, Takeshi; Urabe, Hirokazu

    2014-01-03

    The regioselective intramolecular hydroarylation of (3-halo-2-propynyl)anilines, (3-halo-2-propynyl) aryl ethers, or (4-halo-3-butynyl) aryl ethers was efficiently catalyzed by Rh2(OCOCF3)4 to give semihydrogenated aromatic heterocycles, such as 4-halo-1,2-dihydroquinolines, 4-halo-3-chromenes, or 4-(halomethylene)chromans, in good to excellent yields. Some synthetic applications taking advantage of the halo-substituents of the products are also illustrated. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. A NEW MODEL FOR DARK MATTER HALOS HOSTING QUASARS

    SciTech Connect

    Cen, Renyue; Safarzadeh, Mohammadtaher

    2015-01-10

    A new model for quasar-hosting dark matter halos, meeting two physical conditions, is put forth. First, significant interactions are taken into consideration to trigger quasar activities. Second, satellites in very massive halos at low redshift are removed from consideration due to their deficiency in cold gas. We analyze the Millennium Simulation to find halos that meet these two conditions and simultaneously match two-point auto-correlation functions of quasars and cross-correlation functions between quasars and galaxies at z = 0.5-3.2. The masses of the quasar hosts found decrease with decreasing redshift, with the mass thresholds being [(2-5) × 10{sup 12}, (2-5) × 10{sup 11}, (1-3) × 10{sup 11}] M {sub ☉} for median luminosities of ∼[10{sup 46}, 10{sup 46}, 10{sup 45}] erg s{sup –1} at z = (3.2, 1.4, 0.53), respectively, an order of magnitude lower than those inferred based on halo occupation distribution modeling. In this model, quasar hosts are primarily massive central halos at z ≥ 2-3 but increasingly dominated by lower mass satellite halos experiencing major interactions toward lower redshift. However, below z = 1, satellite halos in groups more massive than ∼2 × 10{sup 13} M {sub ☉} do not host quasars. Whether for central or satellite halos, imposing the condition of significant interactions substantially boosts the clustering strength compared to the total population with the same mass cut. The inferred lifetimes of quasars at z = 0.5-3.2 of 3-30 Myr are in agreement with observations. Quasars at z ∼ 2 would be hosted by halos of mass ∼5 × 10{sup 11} M {sub ☉} in this model, compared to ∼3 × 10{sup 12} M {sub ☉} previously thought, which would help reconcile with the observed, otherwise puzzling high covering fractions for Lyman limit systems around quasars.

  12. The Angular Momentum of Baryons and Dark Matter Halos Revisited

    NASA Technical Reports Server (NTRS)

    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

  13. Halo formation and evolution: unifying physical properties with structure

    NASA Astrophysics Data System (ADS)

    Ernest, Alllan David; Collins, Matthew P.

    2015-08-01

    The assembly of matter in the universe proliferates a variety of structures with diverse properties. For example, massive halos of clusters of galaxies have temperatures often an order of magnitude or more higher than the individual galaxy halos within the cluster, or the temperatures of isolated galaxy halos. Giant spiral galaxies contain large quantities of both dark matter and hot gas while other structures like globular clusters appear to have little or no dark matter or gas. Still others, like the dwarf spheroidal galaxies have low gravity and little hot gas, but ironically contain some of the largest fractions of dark matter in the universe. Star forming rates (SFRs) also vary: compare for example the SFRs of giant elliptical galaxies, globular clusters, spiral and starburst galaxies. Furthermore there is evidence that the various structure types have existed over a large fraction of cosmic history. How can this array of variation in properties be reconciled with galaxy halo formation and evolution?We propose a model of halo formation [1] and evolution [2] that is consistent with both primordial nucleosynthesis (BBN) and the isotropies in the cosmic microwave background (CMB). The model uses two simple parameters, the total mass and size of a structure, to (1) explain why galaxies have the fractions of dark matter that they do (including why dwarf spheroidals are so dark matter dominated despite their weak gravity), (2) enable an understanding of the black hole-bulge/black hole-dark halo relations, (3) explain how fully formed massive galaxies can occur so early in cosmic history, (4) understand the connection between spiral and elliptical galaxies (5) unify the nature of globular clusters, dwarf spheroidal galaxies and bulges and (6) predict the temperatures of hot gas halos and understand how cool galaxy halos can remain stable in the hot environments of cluster-galaxy halos.[1] Ernest, A. D., 2012, in Prof. Ion Cotaescu (Ed) Advances in Quantum Theory, pp

  14. Proton therapy in Japan

    SciTech Connect

    Tsunemoto, H.; Morita, S.; Ishikawa, T.; Furukawa, S.; Kawachi, K.; Kanai, T.; Ohara, H.; Kitagawa, T.; Inada, T.

    1985-01-01

    There are two facilities for clinical trials with protons in Japan: the National Institute of Radiological Sciences (NIRS), Chiba, and the Particle Radiation Medical Science Center (PARMS), University of Tsukuba. At the National Institute of Radiological Sciences, patient treatment with the 70 MeV proton beam began in November 1979, and 29 patients were treated through December 1984. Of 11 patients who received protons only, 9 have had local control of the tumor. Two of the 9 patients, suffering from recurrent tumor after radical photon beam irradiation, developed complications after proton treatment. In the patients treated with photons or neutrons followed by proton boost, tumors were controlled in 12 of 18 patients (66.6%), and no complications were observed in this series. Malignant melanoma could not be controlled with the proton beam. A spot-beam-scanning system for protons has been effectively used in the clinical trials to minimize the dose to the normal tissues and to concentrate the dose in the target volume. At the Particle Radiation Medical Science Center, University of Tsukuba, treatment with a vertical 250 MeV proton beam was begun in April 1983, and 22 patients were treated through February 1984. Local control of the tumor was observed in 14 of 22 patients (63.6%), whereas there was no local control in the treatment of glioblastoma multiforme. There have been no severe complications in patients treated at PARMS. The results suggest that local control of tumors will be better with proton beams than with photon beams, whereas additional modalities are required to manage radioresistant tumors.

  15. HALOGEN: a tool for fast generation of mock halo catalogues

    NASA Astrophysics Data System (ADS)

    Avila, Santiago; Murray, Steven G.; Knebe, Alexander; Power, Chris; Robotham, Aaron S. G.; Garcia-Bellido, Juan

    2015-06-01

    We present a simple method of generating approximate synthetic halo catalogues: HALOGEN. This method uses a combination of second-order Lagrangian Perturbation Theory (2LPT) in order to generate the large-scale matter distribution, analytical mass functions to generate halo masses, and a single-parameter stochastic model for halo bias to position haloes. HALOGEN represents a simplification of similar recently published methods. Our method is constrained to recover the two-point function at intermediate (10 h-1 Mpc < r < 50 h-1 Mpc) scales, which we show is successful to within 2 per cent. Larger scales (˜100 h-1 Mpc) are reproduced to within 15 per cent. We compare several other statistics (e.g. power spectrum, point distribution function, redshift space distortions) with results from N-body simulations to determine the validity of our method for different purposes. One of the benefits of HALOGEN is its flexibility, and we demonstrate this by showing how it can be adapted to varying cosmologies and simulation specifications. A driving motivation for the development of such approximate schemes is the need to compute covariance matrices and study the systematic errors for large galaxy surveys, which requires thousands of simulated realizations. We discuss the applicability of our method in this context, and conclude that it is well suited to mass production of appropriate halo catalogues. The code is publicly available at https://github.com/savila/halogen.

  16. Observations of stratospheric hydrogen fluoride by halogen occultation experiment (HALOE)

    NASA Technical Reports Server (NTRS)

    Luo, M.; Cicerone, R. J.; Russel, J. M., III; Huang, T. Y. W.

    1994-01-01

    The Halogen Occultation Experiment (HALOE) Hydrogen Fluoride (HF) channel on the Upper Atmospheric Research Satellite (UARS) is providing the first global measurements of stratospheric HF, the dominant flourine reservoir in the atmosphere. This paper describes the latitudinal and seasonal variations of HALOE-observed HF in terms of vertical profiles, altitude/latitude cross sections, and column abundances. The HF global distribution shows a 'tracerlike' structure and its column amount increases with latitude, in agreement with previous aircraft measurements of the HF column amount. A comparison between the HALOE HF column above 20 km and the ATMOS 1985 measurements is used to estimate the annual rate of increase of stratospheric HF. Exponential rates of 4.9-6.6%/yr and linear growth rates of 6-8.6%/yr in 1985 and 4.3-5.5%/yr in 1992-1993 are found. HALOE HF measurements during the 1993 Antarctic spring are briefly described. This species behaves like a conserved tracer and its distribution shows an area of enhanced mixing ratios correlated with the polar vortex that has a clear latitude boundary. Finally, simulated HF distributions by the National Center for Atmospheric Research (NCAR) two-dimensional model are used to compare with HALOE observations of HF. Reasonable agreements in the global structure and the absolute amount of HF are found. The differences between the model and the observed results indicate the need for improving treatment of atmospheric dynamics and fluorine-related chemical parameters in the model simulations.

  17. HaloTag technology: a versatile platform for biomedical applications.

    PubMed

    England, Christopher G; Luo, Haiming; Cai, Weibo

    2015-06-17

    Exploration of protein function and interaction is critical for discovering links among genomics, proteomics, and disease state; yet, the immense complexity of proteomics found in biological systems currently limits our investigational capacity. Although affinity and autofluorescent tags are widely employed for protein analysis, these methods have been met with limited success because they lack specificity and require multiple fusion tags and genetic constructs. As an alternative approach, the innovative HaloTag protein fusion platform allows protein function and interaction to be comprehensively analyzed using a single genetic construct with multiple capabilities. This is accomplished using a simplified process, in which a variable HaloTag ligand binds rapidly to the HaloTag protein (usually linked to the protein of interest) with high affinity and specificity. In this review, we examine all current applications of the HaloTag technology platform for biomedical applications, such as the study of protein isolation and purification, protein function, protein-protein and protein-DNA interactions, biological assays, in vitro cellular imaging, and in vivo molecular imaging. In addition, novel uses of the HaloTag platform are briefly discussed along with potential future applications.

  18. Pyramidal ice crystal scattering phase functions and concentric halos

    NASA Astrophysics Data System (ADS)

    Liu, C.; Jonas, P. R.; Saunders, C. P. R.

    1996-11-01

    Phase functions have been calculated using the Monte Carlo/geometric ray tracing method for single hexagonal pyramidal ice crystals (such as solid and hollow bullets) randomly oriented in space and horizontal plane, in order to study the concentric halo formations. Results from three dimensional model calculations show that 9° halo can be as bright as the common 22° halo for pyramidal angle of 28°, and the 18°, 20°, 24° and 35° halos cannot be seen due to the strong 22° halo domination in the scattering phase function between 18° and 35°. For solid pyramidal ice crystals randomly oriented horizontally, the 35° arc can be produced and its intensity depends on the incident ray solar angle and the particle aspect ratio. Acknowledgements. The work done by P. Henelius and E. Vilenius in programme development is gratefully acknowledged. Topical Editor D. Alcayde thanks I. Pryse and A. Vallance-Jones for their help in evaluating this paper.--> Correspondence to: T. Nygrén-->

  19. Does SEGUE/SDSS indicate a dual galactic halo?

    SciTech Connect

    Schönrich, Ralph; Asplund, Martin; Casagrande, Luca

    2014-05-01

    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.

  20. Dynamical evolution of primordial dark matter haloes through mergers

    NASA Astrophysics Data System (ADS)

    Ogiya, Go; Nagai, Daisuke; Ishiyama, Tomoaki

    2016-09-01

    Primordial dark matter (DM) haloes are the smallest gravitationally bound DM structures from which the first stars, black holes and galaxies form and grow in the early universe. However, their structures are sensitive to the free streaming scale of DM, which in turn depends on the nature of DM particles. In this work, we test the hypothesis that the slope of the central cusps in primordial DM haloes near the free streaming scale depends on the nature of merging process. By combining and analysing data from a cosmological simulation with the cutoff in the small-scale matter power spectrum as well as a suite of controlled, high-resolution simulations of binary mergers, we find that (1) the primordial DM haloes form preferentially through major mergers in radial orbits; (2) their central DM density profile is more susceptible to a merging process compared to that of galaxy- and cluster-sized DM haloes; (3) consecutive major mergers drive the central density slope to approach the universal form characterized by the Navarro-Frenk-White profile, which is shown to be robust to the impacts of mergers and serves an attractor solution for the density structure of DM haloes. Our work highlights the importance of dynamical processes on the structure formation during the Dark Ages.