4,547 research outputs found
Optical phonons in new ordered perovskite Sr2Cu(Re0.69Ca0.31) Oy system observed by infrared reflectance spectroscopy
We report infrared reflectivity spectra for a new correlated cupric oxide
system Sr2Cu(Re0.69Ca0.31)Oy with y ~ 0.6 at several temperatures ranging
between 8 and 380 K. The reflectivity spectrum at 300 K comprises of several
optical phonons. A couple of residual bands located around 315 and 653 cm-1
exhibit exceptionally large intensity as compared to the other ones. The
overall reflectivity spectrum lifts up slightly with increasing temperature.
The energy and damping factor of transverse-optical phonons are determined by
fitting the imaginary dielectric constant by Lorentz oscillator model and
discussed as a function of temperature in terms of lattice anharmonicity.Comment: 9 pages, 3 figures, presented at ISS2005, to appear in Physica
The energetics of giant radio galaxy lobes from inverse Compton scattering observations
Giant radio galaxy (GRG) lobes are excellent laboratories to study the
evolution of the particle and B-field energetics. However, these results are
based on assumptions of the shape and extension of the GRG lobe electron
spectrum. We re-examine the energetics of GRG lobes as derived by inverse
Compton scattering of CMB photons (ICS-CMB) by relativistic electrons in RG
lobes to assess the physical conditions of RG lobes, their energetics and their
radiation regime. We consider the GRG DA 240 recently observed by Suzaku as a
reference case and we also discuss other RG lobes observed with Chandra and
XMM. We model the spectral energy distribution of the DA 240 East lobe to get
constraint on the shape and the extension of the electron spectrum in the lobe
by using multi-frequency information from radio to gamma-rays. We use radio and
X-ray data to constrain the shape and normalization of the electron spectrum
and we then calculate the SZ effect expected in GRG lobes that is sensitive to
the total electron energy density. We show that the electron energy density U_e
derived form X-ray observations yields only a rough lower limit to its actual
value and that most of the estimates of U_e based on X-ray measurements have to
be increased even by a large factor by considering realistic estimates of the
lower electron momentum p_1. This brings RG lobes away from the equipartition
condition towards a particle-dominated and Compton power dominance regime. We
use the distribution of RG lobes in the U_e/U_B vs. U_e/U_CMB plane as a
further divide between different physical regimes of particle and field
dominance, and radiation mechanism dominance in RG lobes. We conclude that the
SZ effect produced by ICS-CMB mechanism observable in RG lobes provides
reliable estimate of p_1 and U_e and is the best tool to determine the total
energy density of RG lobes and to assess their physical regime.Comment: 9 pages, 6 figures, A&A in pres
Suzaku diagnostics of the energetics in the lobes of the giant radio galaxy 3C 35
The Suzaku observation of a giant radio galaxy 3C 35 revealed faint extended
X-ray emission, associated with its radio lobes and/or host galaxy. After
careful subtraction of the X-ray and non-X-ray background and contaminating
X-ray sources, the X-ray spectrum of the faint emission was reproduced by a sum
of the power-law (PL) and soft thermal components. The soft component was
attributed to the thermal plasma emission from the host galaxy. The photon
index of the PL component,
where the first and second errors represent the statistical and systematic
ones, was found to agree with the synchrotron radio index from the lobes,
. Thus, the PL component was attributed to the inverse
Compton (IC) X-rays from the synchrotron electrons in the lobes. The X-ray flux
density at 1 keV was derived as nJy with the photon
index fixed at the radio value. The X-ray surface brightness from these lobes
( nJy arcmin) is lowest among the lobes studied through the IC
X-ray emission. In combination with the synchrotron radio flux density, Jy at 327.4 MHz, the electron energy density spatially averaged over
the lobes was evaluated to be the lowest among those radio galaxies, as ergs cm over the
electron Lorentz factor of -- . The magnetic energy density
was calculated as ergs cm, corresponding to the magnetic field strength of
G. These results suggest that the
energetics in the 3C 35 lobes are nearly consistent with equipartition between
the electrons and magnetic fields.Comment: 10 pages, 8 figures, accepted for Ap
Small coupling limit and multiple solutions to the Dirichlet Problem for Yang Mills connections in 4 dimensions - Part I
In this paper (Part I) and its sequels (Part II and Part III), we analyze the
structure of the space of solutions to the epsilon-Dirichlet problem for the
Yang-Mills equations on the 4-dimensional disk, for small values of the
coupling constant epsilon. These are in one-to-one correspondence with
solutions to the Dirichlet problem for the Yang Mills equations, for small
boundary data. We prove the existence of multiple solutions, and, in
particular, non minimal ones, and establish a Morse Theory for this non-compact
variational problem. In part I, we describe the problem, state the main
theorems and do the first part of the proof. This consists in transforming the
problem into a finite dimensional problem, by seeking solutions that are
approximated by the connected sum of a minimal solution with an instanton, plus
a correction term due to the boundary. An auxiliary equation is introduced that
allows us to solve the problem orthogonally to the tangent space to the space
of approximate solutions. In Part II, the finite dimensional problem is solved
via the Ljusternik-Schirelman theory, and the existence proofs are completed.
In Part III, we prove that the space of gauge equivalence classes of Sobolev
connections with prescribed boundary value is a smooth manifold, as well as
some technical lemmas used in Part I. The methods employed still work when the
4-dimensional disk is replaced by a more general compact manifold with
boundary, and SU(2) is replaced by any compact Lie group
Finite Temperature Effects in One-dimensional Mott-Hubbard Insulator: Angle-Resolved Photoemission Study of Na_{0.96}V_{2}O_{5}
We have made an angle-resolved photoemission study of a one-dimensional (1D)
Mott-Hubbard insulator Na_{0.96}V_{2}O_{5} and found that the spectra of the V
3d lower Hubbard band are strongly dependent on the temperature. We have
calculated the one-particle spectral function of the one-dimensional t-J model
at finite temperatures by exact diagonalization and compared them with the
experimental results. Good overall agreement is obtained between experiment and
theory. The strong finite temperature effects are discussed in terms of the
existence of the ``Fermi surface'' of the spinon band.Comment: 4 pages, 3 figure
Evidence of non-thermal X-ray emission from radio lobes of Cygnus A
Using deep Chandra ACIS observation data for Cygnus A, we report evidence of
non-thermal X-ray emission from radio lobes surrounded by a rich intra-cluster
medium (ICM). The diffuse X-ray emission, which are associated with the eastern
and western radio lobes, were observed in a 0.7--7 keV Chandra$ ACIS image. The
lobe spectra are reproduced with not only a single-temperature Mekal model,
such as that of the surrounding ICM component, but also an additional power-law
(PL) model. The X-ray flux densities of PL components for the eastern and
western lobes at 1 keV are derived as 77.7^{+28.9}_{-31.9} nJy and
52.4^{+42.9}_{-42.4} nJy, respectively, and the photon indices are
1.69^{+0.07}_{-0.13} and 1.84^{+2.90}_{-0.12}, respectively. The non-thermal
component is considered to be produced via the inverse Compton (IC) process, as
is often seen in the X-ray emission from radio lobes. From a re-analysis of
radio observation data, the multiwavelength spectra strongly suggest that the
seed photon source of the IC X-rays includes both cosmic microwave background
radiation and synchrotron radiation from the lobes. The derived parameters
indicate significant dominance of the electron energy density over the magnetic
field energy density in the Cygnus A lobes under the rich ICM environment.Comment: 8 pages, 5 figures, accepted for publication in Ap
Suzaku observation of the giant radio galaxy 3C 326
A Suzaku observation of a giant radio galaxy, 3C 326, which has a physical
size of about 2 Mpc, was conducted on 2008 January 19 -- 21. In addition to
several X-ray sources, diffuse emission was significantly detected associated
with its west lobe, but the east lobe was contaminated by an unidentified X-ray
source WARP J1552.4+2007. After careful evaluation of the X-ray and Non X-ray
background, the 0.4 -- 7 keV X-ray spectrum of the west lobe is described by a
power-law model. The photon index and 1 keV flux density was derived as
and nJy,
respectively, where the first and second errors represent the statistical and
systematic ones. The diffuse X-rays were attributed to be inverse Compton
radiation by the synchrotron radio electrons scattering off the cosmic
microwave background photons. This radio galaxy is the largest among those with
lobes detected through inverse Compton X-ray emission. A comparison of the
radio to X-ray fluxes yields the energy densities of electron and magnetic
field as ergs/cm3 and ergs/cm3, respectively. The galaxy
is suggested to host a low luminosity nucleus with an absorption-corrected 2 --
10 keV luminosity of ergs/s, together with a relatively
weak radio core. The energetics in the west lobe of 3C 326 were compared with
those of moderate radio galaxies with a size of kpc. The west lobe
of 3C 326 is confirmed to agree with the correlations for the moderate radio
galaxies, and , where
is their total physical size. This implies that the lobes of 3C 326 are
still being energized by the jet, despite the current weakness of the nucleus.Comment: 11 pages, 10 figures, 6 tables, Accepted for ApJ (v706 issue
Diagnosing Energy Loss: PHENIX Results on High-pT Hadron Spectra
Measurements of inclusive spectra of hadrons at large transverse momentum
over a broad range of energy in different collision systems have been performed
with the PHENIX experiment at RHIC. The data allow to study the energy and
system size dependence of the suppression observed in RAA of high-pT hadrons at
sqrt(s_NN)= 200 GeV. Due to the large energy range from sqrt(s_NN)= 22 GeV to
200 GeV, the results can be compared to results from CERN SPS at a similar
energy. The large Au+Au dataset from the 2004 run of RHIC also allows to
constrain theoretical models that describe the hot and dense matter produced in
such collisions. Investigation of particle ratios such as eta/pi0 helps
understanding the mechanisms of energy loss.Comment: 4 pages, 6 figures. To appear in the proceedings of the 19th
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions
(Quark Matter 2006), Shanghai, China, November 14-20, 200
The Effect of Environment on the X-Ray Emission from Early-Type Galaxies
In order to help understand the phenomena of X-ray emission from early-type
galaxies, we obtained an optically flux-limited sample of 34 early-type
galaxies, observed with ROSAT. A previous analysis of this sample suggested
that the most X-ray luminous galaxies were in rich environments. Here we
investigate environmental influences quantitatively, and find a positive
correlation between L_B/L_X and the local galaxy density. We suggest that this
correlation occurs because the X-ray luminosity is enhanced either through
accretion of the intergalactic gas or because the ambient medium stifles
galactic winds. When the ambient medium is unimportant, partial or global
galactic winds can occur, reducing L_B/L_X. These effects lead to the large
observed dispersion in L_X at fixed L_B. We argue that the transition from
global winds to partial winds is one of the principle reasons for the steep
relationship between L_X and L_B. We discuss details of the data reduction not
previously presented, and examine the dependence of L_X on the choice of outer
source radius and background location. Effects of Malmquist bias are shown not
to be important for the issues addressed. Finally, we compare the temperature
deduced for these galaxies from different analyses of ROSAT and ASCA data.Comment: 29 pages, including 6 figures (ps); AASTeX 12pt,aaspp4 format;
submitted to Ap
Mosaic CCD method: A new technique for observing dynamics of cometary magnetospheres
On April 29, 1990, the plasma tail of Comet Austin was observed with a CCD camera on the 105-cm Schmidt telescope at the Kiso Observatory of the University of Tokyo. The area of the CCD used in this observation is only about 1 sq cm. When this CCD is used on the 105-cm Schmidt telescope at the Kiso Observatory, the area corresponds to a narrow square view of 12 ft x 12 ft. By comparison with the photograph of Comet Austin taken by Numazawa (personal communication) on the same night, we see that only a small part of the plasma tail can be photographed at one time with the CCD. However, by shifting the view on the CCD after each exposure, we succeeded in imaging the entire length of the cometary magnetosphere of 1.6 x 10(exp 6) km. This new technique is called 'the mosaic CCD method'. In order to study the dynamics of cometary plasma tails, seven frames of the comet from the head to the tail region were twice imaged with the mosaic CCD method and two sets of images were obtained. Six microstructures, including arcade structures, were identified in both the images. Sketches of the plasma tail including microstructures are included
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