Precise electrical transport measurements by using bridgman type pressure cell at low temperature

金沢大学理工研究域環境デザイン学系We report a technique for the precise measurement of the electrical resisivity under high pressure at low temperature by using Bridgman anvils made of tungsten carbide. Quasi-hydrostatic pressure is generated up to ∼15 GPa in the relatively large working space which allows the use of large specimens and simple experimental procedures rather than using a standard diamond anvil cell. The application is demonstrated by the measurements of the electrical resistivity of lead in order to describe the effect of pressure on the superconducting transition. © 2010 IOP Publishing Ltd

Study of the Intracluster and Intergalactic Medium in the Sculptor Supercluster with Suzaku

We studied the high temperature plasma in the direction of the Sculptor supercluster at z=0.108 with Suzaku. Suzaku carried out four observations in the supercluster: namely, A2811, A2811 offset, A2804, A2801 regions in 2005 Nov.--Dec., including the regions beyond the virial radii of these clusters. The study needed precise background estimation because the measured intensity of the redshifted lines, especially those from oxygen, were strongly affected by the the Galactic emission. The spectra taken in the regions outside of the virial radii of the member clusters were used as the background which included both the Galactic and Cosmic X-ray Background (CXB) components. We also used the background data which were taken near the Sculptor supercluster. Temperature and metal abundance profiles were determined to the virial radii of the member clusters, and then we searched for the oxygen line emission in the region outside of the virial radii of the clusters. As a result, the temperature of the clusters decreased toward the virial radii, and the spectral fits for the filament region did not require extra component other than the Galactic and CXB components. We constrained the intensities of O VII and O VIII lines to be less than 8.1 and 5.1 photons cm^-2 s^-1 arcmin^-2, respectively, as 2-sigma upper limits. The intensity of O VII indicates n_H < 1.6e-5 cm^-3 (Z/0.1 Z_solar)^-1/2 (L/25 Mpc)^-1/2, which corresponds to an over density, delta < 60 (Z/0.1 Z_solar)^-1/2 (L/25 Mpc)^-1/2.Comment: 11 pages, 8 figures, accepted for publication in PAS

Suzaku observations of the Hydra A cluster out to the virial radius

We report Suzaku observations of the northern half of the Hydra A cluster out to ~1.4 Mpc, reaching the virial radius. This is the first Suzaku observations of a medium-size (kT ~3 keV) cluster out to the virial radius. Two observations were conducted, north-west and north-east offsets, which continue in a filament direction and a void direction of the large-scale structure of the Universe, respectively. The X-ray emission and distribution of galaxies elongate in the filament direction. The temperature profiles in the two directions are mostly consistent with each other within the error bars and drop to 1.5 keV at 1.5 r_500. As observed by Suzaku in hot clusters, the entropy profile becomes flatter beyond r_500, in disagreement with the r^1.1 relationship that is expected from accretion shock heating models. When scaled with the average intracluster medium (ICM) temperature, the entropy profiles of clusters observed with Suzaku are universal and do not depend on system mass. The hydrostatic mass values in the void and filament directions are in good agreement, and the Navarro, Frenk, and White universal mass profile represents the hydrostatic mass distribution up to ~ 2 r_500. Beyond r_500, the ratio of gas mass to hydrostatic mass exceeds the result of the Wilkinson microwave anisotropy probe, and at r_100, these ratios in the filament and void directions reach 0.4 and 0.3, respectively. We discuss possible deviations from hydrostatic equilibrium at cluster outskirts. We derived radial profiles of the gasmass- to-light ratio and iron-mass-to-light ratio out to the virial radius. Within r_500, the iron-mass-to-light ratio of the Hydra A cluster was compared with those in other clusters observed with Suzaku.Comment: 16 pages, 15 figures; Accepted for publication in PAS

Fractional Vortices and Lumps

We study what might be called fractional vortices, vortex configurations with the minimum winding from the viewpoint of their topological stability, but which are characterized by various notable substructures in the transverse energy distribution. The fractional vortices occur in diverse Abelian or non-Abelian generalizations of the Higgs model. The global and local features characterizing these are studied, and we identify the two crucial ingredients for their occurrence - the vacuum degeneracy leading to non-trivial vacuum moduli M, and the BPS nature of the vortices. Fractional vortices are further classified into two kinds. The first type of such vortices appear when M has orbifold Z_n singularities; the second type occurs in systems in which the vacuum moduli space M possesses either a deformed geometry or some singularity. These general features are illustrated with several concrete models.Comment: LaTeX, 46 pages, 12 figures. V2: minor changes, footnote adde

Discovery of the Central Excess Brightness in Hard X-rays in the Cluster of Galaxies Abell 1795

Using the X-ray data from \ASCA, spectral and spatial properties of the intra-cluster medium (ICM) of the cD cluster Abell 1795 are studied, up to a radial distance of $\sim 12'$ ($\sim 1.3$ $h_{50}^{-1}$ kpc). The ICM temperature and abundance are spatially rather constant, although the cool emission component is reconfirmed in the central region. The azimuthally- averaged radial X-ray surface brightness profiles are very similar between soft (0.7--3 keV) and hard (3--10 keV) energy bands, and neither can be fitted with a single-$\beta$ model due to a strong data excess within $\sim5'$ of the cluster center. In contrast, double-$\beta$ models can successfully reproduce the overall brightness profiles both in the soft and hard energy bands, as well as that derived with the \ROSAT PSPC. Properties of the central excess brightness are very similar over the 0.2--10 keV energy range spanned by \ROSAT and \ASCA. Thus, the excess X-ray emission from the core region of this cluster is confirmed for the first time in hard X-rays above 3 keV. This indicates that the shape of the gravitational potential becomes deeper than the King-type one towards the cluster center. Radial profiles of the total gravitating matter, calculated using the double-$\beta$ model, reveal an excess mass of $\sim 3 \times 10^{13}~ M_{\odot}$ within $\sim 150 h^{-1}_{50}$ kpc of the cluster center. This suggests a hierarchy in the gravitational potential corresponding to the cD galaxy and the entire cluster.Comment: 27 pages, 8 figures; to appear ApJ 500 (June 20, 1998