6,492 research outputs found
Suzaku observations of the low surface brightness cluster A76
Context: We present results of Suzaku observations of a nearby galaxy cluster
A76 at z=0.0395. This cluster is characterized by extremely low X-ray surface
brightness and is hereafter referred to as the LSB cluster. Aims: To understand
the nature and thermodynamic evolution of the LSB cluster by studying the
physical properties of the hot intracluster medium in A76. Methods: We
conducted two-pointed Suzaku observations of A76 and examined the global gas
properties of the cluster by XIS spectral analysis. We also performed
deprojection analysis of annular spectra and derived radial profiles of gas
temperature, density and entropy out to approximately 850 kpc (~ 0.6 r_200) and
560 kpc (~0.4 r_200) in A76 East and A76 West, respectively. Results: The
measured global temperature and metal abundance are approximately 3.3 keV and
0.24 solar, respectively. From the deprojection analysis, the entropy profile
is found to be flat with respect to radius. The entropy within the central
region (r < 0.2r_200) is exceptionally high (~400 keV cm^2). This phenomenon is
not readily explained by either gravitational heating or preheating. The X-ray
morphology is clumped and irregular, and the electron density is extremely low
(1e-4 -- 1e-3 cm^-3) for the observed high temperature, suggesting that A76 is
in the early phase of cluster formation and the gas compression due to
gravitational potential confinement is lagging behind the gas heating.Comment: 7 pages, 5 figures, A&A accepte
Discovery of large scale shock fronts correlated with the radio halo and radio relic in the A2163 galaxy cluster
Imprints of galaxy cluster formation processes are visible in the
intracluster medium and can arise in shock fronts, which are detectable via
discontinuities in e.g. the gas temperature and density profiles. In this
study, we investigate the X-ray properties of the intracluster gas and the
radio morphology of the extraordinary cluster A2163. This cluster shows an
irregular morphology in various wavelengths and has one of the most luminous
and extended known radio halos. Additionally, it is one of the hottest clusters
known. We analyze two Suzaku observations of A2163, one in the north-east (NE)
and one in the south-west (SW) direction, and use archival XMM-Newton data to
remove point sources in the field of view. To compare our findings in the X-ray
regime with the radio emission, we obtain radio images of the cluster from an
archival VLA observation at 20cm. We identify three shock fronts in A2163 in
our spectral X-ray study. A clear shock front lies in the NE direction at a
distance of 1.4Mpc from the center, with a Mach number of
, estimated from the temperature discontinuity. This shock
coincides with the position of a known radio relic. We identify two additional
shocks in the SW direction, one with at a distance of
0.7Mpc, which is likely related to a cool core remnant, and a strong shock with
at a distance of 1.3Mpc, which also closely matches the
radio contours. The complex structure of A2163 as well as the different Mach
numbers and shock velocities suggest a merging scenario with two unequal
merging constituents, where two shock fronts emerged in an early stage of the
merger and traveled outwards while an additional shock front developed in front
of the merging cluster cores.Comment: 9 pages, 7 figures, accepted by A&
Suzaku study of gas properties along filaments of A2744
Context: We present the results of Suzaku observations of a massive galaxy
cluster A2744, which is an active merger at . Aims: By using long
X-ray observations of A2744, we aim to understand the growth of the cluster and
the gas heating process through mass accretion along the surrounding filaments.
Methods: We analyzed data from two-pointed Suzaku observations of A2744 to
derive the temperature distribution out to the virial radius in three different
directions. We also performed a deprojection analysis to study radial profiles
of gas temperature, density, and entropy and compared the X-ray results with
multi-wavelength data to investigate correlations with the surface density of
galaxies and with radio relics. Results: The gas temperature was measured out
to the virial radius in the north-east region and to about
in the north-west and south regions. The radial profile of the gas
temperature is rather flat and the temperature is very high (even near
); it is comparable to the mean temperature of this cluster (
keV). These characteristics have not been reported in any other cluster. We
find a hint of temperature jump in the northeast region whose location
coincides with a large radio relic, indicating that the cluster experienced gas
heating because of merger or mass accretion onto the main cluster. The
temperature distribution is anisotropic and shows no clear positive correlation
with the galaxy density, which suggests an inhomogeneous mass structure and a
complex merger history in A2744.Comment: 8 pages, 8 figures, A&A accepte
X-ray observations and mass determinations in the cluster of galaxies Cl0024+17
We present a detailed analysis of the mass distribution in the rich and
distant cluster of galaxies Cl0024+17. X-ray data come from both a deep
ROSAT/HRI image of the field (Bohringer et al. 1999) and ASCA spectral data.
Using a wide field CCD image of the cluster, we optically identify all the
faint X-ray sources, whose counts are compatible with deep X-ray number counts.
In addition we marginally detect the X-ray counter-part of the gravitational
shear perturbation detected by Bonnet et al. (1994) at a 2.5 level. A
careful spectral analysis of ASCA data is also presented. In particular, we
extract a low resolution spectrum of the cluster free from the contamination by
a nearby point source located 1.2 arcmin from the center. The X-ray temperature
deduced from this analysis is keV at the 90%
confidence level. The comparison between the mass derived from a standard X-ray
analysis and from other methods such as the Virial Theorem or the gravitational
lensing effect lead to a mass discrepancy of a factor 1.5 to 3. We discuss all
the possible sources of uncertainties in each method of mass determination and
give some indications on the way to reduce them. A complementary study of
optical data is in progress and may solve the X-ray/optical discrepancy through
a better understanding of the dynamics of the cluster.Comment: Revised version, accepted in Astronomy and Astrophysics (Main
Journal). Few changes in the discussio
Investigating the hard X-ray emission from the hottest Abell cluster A2163 with Suzaku
We present the results from Suzaku observations of the hottest Abell galaxy
cluster A2163 at . To study the physics of gas heating in cluster
mergers, we investigated hard X-ray emission from the merging cluster A2163,
which hosts the brightest synchrotron radio halo. We analyzed hard X-ray
spectra accumulated from two-pointed Suzaku observations. Non-thermal hard
X-ray emission should result from the inverse Compton (IC) scattering of
relativistic electrons by the CMB photons. To measure this emission, the
dominant thermal emission in the hard X-ray band must be modeled in detail. To
this end, we analyzed the combined broad-band X-ray data of A2163 collected by
Suzaku and XMM-Newton, assuming single- and multi-temperature models for
thermal emission and the power-law model for non-thermal emission. From the
Suzaku data, we detected significant hard X-ray emission from A2163 in the
12-60 keV band at the level (or at the level if a
systematic error is considered). The Suzaku HXD spectrum alone is consistent
with the single-T thermal model of gas temperature keV. From the XMM
data, we constructed a multi-T model including a very hot ( keV)
component in the NE region. Incorporating the multi-T and the power-law models
into a two-component model with a radio-band photon index, the 12-60 keV energy
flux of non-thermal emission is constrained within . The 90% upper limit of detected IC
emission is marginal ( in the
12-60 keV). The estimated magnetic field in A2163 is .
While the present results represent a three-fold increase in the accuracy of
the broad band spectral model of A2163, more sensitive hard X-ray observations
are needed to decisively test for the presence of hard X-ray emission due to IC
emission.Comment: 7 pages, 7 figures, A&A accepted. Minor correctio
X-Ray Study of the Outer Region of Abell 2142 with Suzaku
We observed outer regions of a bright cluster of galaxies A2142 with Suzaku.
Temperature and brightness structures were measured out to the virial radius
() with good sensitivity. We confirmed the temperature drop from 9 keV
around the cluster center to about 3.5 keV at , with the density
profile well approximated by the model with . Within
0.4\r_{200}, the entropy profile agrees with , as predicted by the
accretion shock model. The entropy slope becomes flatter in the outer region
and negative around . These features suggest that the intracluster
medium in the outer region is out of thermal equilibrium. Since the relaxation
timescale of electron-ion Coulomb collision is expected to be longer than the
elapsed time after shock heating at , one plausible reason of the low
entropy is the low electron temperature compared to that of ions. Other
possible explanations would be gas clumpiness, turbulence and bulk motions of
ICM\@. We also searched for a warm-hot intergalactic medium around
and set an upper limit on the oxygen line intensity. Assuming a line-of-sight
depth of 2 Mpc and oxygen abundance of 0.1 solar, the upper limit of an
overdensity is calculated to be 280 or 380, depending on the foreground
assumption.Comment: 14 pages, 8 figure
Single-dot spectroscopy via elastic single-electron tunneling through a pair of coupled quantum dots
We study the electronic structure of a single self-assembled InAs quantum dot
by probing elastic single-electron tunneling through a single pair of weakly
coupled dots. In the region below pinch-off voltage, the non-linear threshold
voltage behavior provides electronic addition energies exactly as the linear,
Coulomb blockade oscillation does. By analyzing it, we identify the s and p
shell addition spectrum for up to six electrons in the single InAs dot, i.e.
one of the coupled dots. The evolution of shell addition spectrum with magnetic
field provides Fock-Darwin spectra of s and p shell.Comment: 7 pages, 3 figures, Accepted for publication in Phys. Rev. Let
Accumulation and Circulation of the Knowledge Needed for Biotech Business Promotion by Engineers of R&D Section in an IT Enterprise: the Case of Hitachi Software Engineering Co., Ltd
Much research has been carried out on the accumulation and effective use of knowledge as a company-specific form of intellectual property. However, insufficient attention has been given to research focusing on the effects of micro-level knowledge absorption and its effective use. In this paper, we try to demonstrate what should be done in order to promote new biotech business from the perspective of each engineer\u27s knowledge, through a micro-level investigation focusing on the life science business section of one IT enterprise. Based on the results of a questionnaire survey of engineers, interviews of several engineers, and patent data analysis, we discuss the progress of the biotech business in an IT enterprise from the aspect of accumulation and circulation of knowledge in a core technology field, the IT business, and a technology field of new entry, the biotech business. This paper reports that the positive growth cycle of biotech business promotion in an IT enterprise, using Hitachi Software Engineering Co., Ltd. as a case, attained by incorporating the latest biotech knowledge from junior engineers and utilizing IT knowledge from middle engineers leads to the recruiting of qualified students
Stabilization of collapse and revival dynamics by a non-Markovian phonon bath
Semiconductor quantum dots (QDs) have been demonstrated to be versatile
candidates to study the fundamentals of light-matter interaction [1-3]. In
contrast with atom optics, dissipative processes are induced by the inherent
coupling to the environment and are typically perceived as a major obstacle
towards stable performances in experiments and applications [4].
In this paper we show that this is not necessarily the case. In fact, the
memory of the environment can enhance coherent quantum optical effects. In
particular, we demonstrate that the non-Markovian coupling to an incoherent
phonon bath has a stabilizing effect on the coherent QD cavity-quantum
electrodynamics (cQED) by inhibiting irregular oscillations and boosting
regular collapse and revival patterns. For low photon numbers we predict QD
dynamics that deviate dramatically from the well-known atomic Jaynes-Cummings
model. Our proposal opens the way to a systematic and deliberate design of
photon quantum effects via specifically engineered solid-state environments.Comment: 5 pages, 4 figure
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