Modeling Intra-Cluster Gas in Triaxial Dark Halos : An Analytical Approach

We present the first physical model for the non-spherical intra-cluster gas distribution in hydrostatic equilibrium under the gravity of triaxial dark matter halos. Adopting the concentric triaxial density profiles of the dark halos with constant axis ratios proposed by Jing & Suto (2002), we derive an analytical expression for the triaxial halo potential on the basis of the perturbation theory, and find the hydrostatic solutions for the gas density and temperature profiles both in isothermal and polytropic equations of state. The resulting iso-potential surfaces are well approximated by triaxial ellipsoids with the eccentricities dependent on the radial distance. We also find a formula for the eccentricity ratio between the intra-cluster gas and the underlying dark halo. Our results allow one to determine the shapes of the underlying dark halos from the observed intra-cluster gas through the X-ray and/or the Sunyaev-Zel'dovich effects clusters.Comment: accepted by ApJ, LaTex file, 22 pages, 8 postscript figure

Reconstructing Three-dimensional Structure of Underlying Triaxial Dark Halos From Xray and Sunyaev-Zel'dovich Effect Observations of Galaxy Clusters

While the use of galaxy clusters as {\it tools} to probe cosmology is established, their conventional description still relies on the spherical and/or isothermal models that were proposed more than 20 years ago. We present, instead, a deprojection method to extract their intrinsic properties from X-ray and Sunyaev--Zel'dovich effect observations in order to improve our understanding of cluster physics. First we develop a theoretical model for the intra-cluster gas in hydrostatic equilibrium in a triaxial dark matter halo with a constant axis ratio. In this theoretical model, the gas density profiles are expressed in terms of the intrinsic properties of the dark matter halos. Then, we incorporate the projection effect into the gas profiles, and show that the gas surface brightness profiles are expressed in terms of the eccentricities and the orientation angles of the dark halos. For the practical purpose of our theoretical model, we provide several empirical fitting formulae for the gas density and temperature profiles, and also for the surface brightness profiles relevant to X-ray and Sunyaev--Zel'dovich effect observations. Finally, we construct a numerical algorithm to determine the halo eccentricities and orientation angles using our model, and demonstrate that it is possible in principle to reconstruct the 3D structures of the dark halos from the X-ray and/or Sunyaev-Zel'dovich effect cluster data alone without requiring priors such as weak lensing informations and without relying on such restrictive assumptions as the halo axial symmetry about the line-of-sight.Comment: Accepted version, new discussions added, typos and minor mistakes corrected, ApJ in press (2004, Feb. 1 scheduled, Vol. 601, No. 2 issue),26 pages, 7 postscript figure

Ultraviolet avalanche in anisotropic non-Abelian plasmas

We present solutions of coupled particle-field evolution in classical U(1) and SU(2) gauge theories in real time on three-dimensional lattices. For strongly anisotropic particle momentum distributions, we find qualitatively different behavior for the two theories when the field strength is high enough that non-Abelian self-interactions matter for SU(2). It appears that the energy drained by a Weibel-like plasma instability from the particles does not build up exponentially in transverse magnetic fields but instead returns, isotropically, to the hard scale via a rapid avalanche into the ultraviolet.Comment: 22 pages, 10 figures; v3: small textual changes; updated to correspond with version to appear in publicatio

Vortex state in double transition superconductors

Novel vortex phase and nature of double transition field are investigated by two-component Ginzburg-Landau theory in a situation where fourfold-twofold symmetric superconducting double transition occurs. The deformation from 60 degree triangular vortex lattice and a possibility of the vortex sheet structure are discussed. In the presence of the gradient coupling, the transition changes to a crossover at finite fields. These characters are important to identify the multiple superconducting phase in PrOs_4_Sb_12.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Let

X-ray Measurements of the Gravitational Potential Profile in the Central Region of the Abell 1060 Cluster of Galaxies

X-ray spectral and imaging data from ASCA and ROSAT were used to measure the total mass profile in the central region of Abell 1060, a nearby and relatively poor cluster of galaxies. The ASCA X-ray spectra, after correcting for the spatial response of the X-ray telescope, show an isothermal distribution of the intra-cluster medium (ICM) within at least $\sim$ 12' (or $160h_{70}^{-1}$ kpc; $H_0 = 70 h_{70}$ km s$^{-1}$Mpc$^{-1}$) in radius of the cluster center. The azimuthally averaged surface brightness profile from the ROSAT PSPC exhibits a central excess above an isothermal $\beta$ model. The ring-sorted ASCA GIS spectra and the radial surface brightness distribution from the ROSAT PSPC were simultaneously utilized to constrain the gravitational potential profile. Some analytic models of the total mass density profile were examined. The ICM density profile was also specified by analytic forms. The ICM temperature distribution was constrained to satisfy the hydrostatic equilibrium, and to be consistent with the data. Then, the total mass distribution was found to be described better by the universal dark halo profile proposed by Navarro, Frenk, and White (1996;1997) than by a King-type model with a flat density core. A profile with a central cusp together with a logarithmic radial slope of $\sim 1.5$ was also consistent with the data. Discussions are made concerning the estimated dark matter distribution around the cluster center.Comment: 32 pages. Accepted: ApJ 2000, 35 pages, Title was correcte

Fundamentals and stock returns in Japan

This paper relates cross-sectional differences in returns on Japanese stocks to the underlying behavior of four fundamental variables: earnings yield, size, book to market ratio, and cash flow yield. Alternative statistical specifications and various estimation methods are applied to a comprehensive, high-quality data set that extends from 1971 to 1988. The sample includes both manufacturing and non-manufacturing firms, companies from both sections of the Tokyo Stock Exchange, and also delisted securities. Our findings reveal a significant relationship between fundamental variables and expected returns in the Japanese market. Of the four fundamental variables considered, the book to market ratio and cash flow yield have the most significant positive impact on expected returns