306 research outputs found
An analytical model for the non-linear redshift-space power spectrum
We use N-body simulations to test the predictions of the redshift distortion
in the power spectrum given by the halo model in which the clustering of dark
matter particles is considered as a result both of the clustering of dark halos
in space and of the distribution of dark matter particles in individual dark
halo. The predicted redshift distortion depends sensitively on several model
parameters in a way different from the real-space power spectrum. An accurate
model of the redshift distortion can be constructed if the following properties
of the halo population are modelled accurately: the mass function of dark
halos, the velocity dispersion among dark halos, and the non-linear nature of
halo bias on small scales. The model can be readily applied to interpreting the
clustering properties and velocity dispersion of different populations of
galaxies once a cluster-weighted bias (or equivalently an halo occupation
number model) is specified for the galaxies. Some non-trivial bias features
observed from redshift surveys of optical galaxies and of IRAS galaxies
relative to the standard low-density cold dark matter model can be easily
explained in the cluster weighted bias model. The halo model further indicates
that a linear bias can be a good approximation only on for k <= 0.1 hMpc^{-1}.Comment: 10 pages, 10 figures, accepted for publication in MNRA
Global Power Counting Analysis On Probing Electroweak Symmetry Breaking Mechanism At High Energy Colliders
We develop a precise power counting rule (a generalization of Weinberg's
counting method for the nonlinear sigma model) for the electroweak theories
formulated by chiral Lagrangians. Then we estimate the contributions of ``all''
next-to-leading order (NLO) bosonic operators to the amplitudes of the relevant
scattering processes which can be measured at high energy colliders, such as
the LHC and future Linear Colliders. Based upon these results, we globally
classify the sensitivities of testing all NLO bosonic operators for probing the
electroweak symmetry breaking mechanism at high energy colliders.Comment: Version Published in Physics Letters B. Latex, 12 pages, minor typos
correcte
Two-Phased Intra-Cluster Medium in the Centaurus Cluster of Galaxies
ASCA and ROSAT data of the Centaurus cluster were analyzed. A central excess
in the radial brightness profile is found in the hard energy band up to 10keV.
This requires a deeper central potential than a King-type one. A double-beta
brightness distribution gives a good account of the data. A deprojected energy
spectrum within a spherical region of radius 30 kpc at the cluster center
indicates that the ICM cannot be isothermal there. Simultaneous fitting of the
three (PSPC, GIS, and SIS) energy spectra extracted from the central 3' region
showed that a two-temperature model that has temperatures of 1.4keV and 4.4keV
and a common metallicity of 1.0 solar with the Galactic absorption gives the
best description to the spectra. A cooling-flow spectral model did not give
satisfactory fit. A 3-dimensional cluster model incorporating the two-phase
picture, the double-beta brightness distribution, and the central metallicity
increase reproduced the overall ASCA and ROSAT data successfully. The derived
spatial distribution of the dark matter deviates from a King-type profile
exhibiting a central excess, which is consistent with the Navvaro-Frenk-White
model. The iron is revealed to be more widely spread than stars, which may have
been caused by energetic supernovae and the motion of the cD galaxy. Since the
derived characteristics of the cool phase including the temperature, angular
extent, gas mass, and metallicity, are on a smooth extension of those of
inter-stellar medium (ISM) of elliptical galaxies, the cool phase can be
regarded as the ISM associated with the cD galaxy. The cool-phase X-ray
emission is presumably sustained by energies dissipated by infalling mass to
the cD galaxy in the course of cluster evolution.Comment: accepted for publication in Ap
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