1,036 research outputs found
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 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
Properties of the cosmological filament between two clusters: A possible detection of a large-scale accretion shock by
We report on the results of a observation of the plasma in the
filament located between the two massive clusters of galaxies Abell 399 and
Abell 401. Abell 399 (=0.0724) and Abell 401 (=0.0737) are expected to be
in the initial phase of a cluster merger. In the region between the two
clusters, we find a clear enhancement in the temperature of the filament plasma
from 4 keV (expected value from a typical cluster temperature profile) to
6.5 keV. Our analysis also shows that filament plasma is present out to
a radial distance of 15' (1.3 Mpc) from a line connecting the two clusters. The
temperature profile is characterized by an almost flat radial shape with
6-7 keV within 10' or 0.8 Mpc. Across =8'~from the axis, the
temperature of the filament plasma shows a drop from 6.3 keV to 5.1 keV,
indicating the presence of a shock front. The Mach number based on the
temperature drop is estimated to be 1.3. We also successfully
determined the abundance profile up to 15' (1.3 Mpc), showing an almost
constant value (=0.3 solar) at the cluster outskirt. We estimated the
Compton -parameter to be 14.5, which is in
agreement with 's results (14-17 on the filament). The
line of sight depth of the filament is 1.1 Mpc, indicating that the
geometry of filament is likely a pancake shape rather than cylindrical. The
total mass of the filamentary structure is 7.7. We discuss a possible interpretation of the drop of X-ray emission
at the rim of the filament, which was pushed out by the merging activity and
formed by the accretion flow induced by the gravitational force of the
filament.Comment: 8 pages, 8 figures, accepted for publication in A&
Theory and Phenomenology of Heavy Flavor at RHIC
We review the problem of heavy-quark diffusion in the Quark-Gluon Plasma and
its ramifications for heavy-quark spectra in heavy-ion collisions at RHIC. In
particular, we attempt to reconcile underlying mechanisms of several seemingly
different approaches that have been put forward to explain the large
suppression and elliptic flow of non-photonic electron spectra. We also
emphasize the importance of a quantitative description of the bulk medium
evolution to extract reliable values for the heavy-quark diffusion coefficient.Comment: 8 pages latex, including 10 eps figures; plenary talk at SQM08,
Beijing (China), Oct. 06-10, 200
Pathogenic variation of Phakopsora pachyrhizi populations in Brazil.
The obligate basidiomycete Phakopsora pachyrhizi is the causal agent of soybean rust that has potential to reduce the yield of soybean drastically. Soybean production in Brazil has been threatened by the rust since the pathogen was first discovered in 2001. To understand pathogenic variation of the rust populations in South America, an evaluation system for soybean rust resistance has been constructed using a set of 16 differential varieties. In this study, the evaluation system was used to investigate pathogenic variation among the P. pachyrhizi populations in Brazil. Samples of P. pachyrhizi were collected from the diseased soybeans in Brazil in the 2007-2008 and 2008-2009 soybean cultivation seasons. In the first season, two rust samples showed similar pattern of the infection types on the differential set, suggesting that the same or similar pathogen population was present in the two locations. The other samples were likely different pathogenic populations. In the second season, different patterns of the infection types were found among the samples. Comparison of the evaluation data from the two seasons demonstrated that pathogenic variation between the seasons was detected in the populations from Rio Grande do Sul and Paraná but was not remarkable in those from Rondônia. This study provides useful knowledge about P. pachyrhizi populations in Brazil to identify the resistant soybean genotypes and target effective cultivars against certain pathogen populations.Edição do Proceedings of the National Soybean Rust Symposium, New Orleans, 2009
Possible relationship between Helicobacter pylori infection and cap polyposis of the colon
The definitive version is available at www.blackwell-synergy.com.ArticleHELICOBACTER. 9(6): 651-656 (2004)journal articl
X-ray Temperature and Mass Measurements to the Virial Radius of Abell 1413 with Suzaku
We present X-ray observations of the northern outskirts of the relaxed galaxy
cluster A1413 with Suzaku, whose XIS instrument has the low intrinsic
background needed to make measurements of these low surface brightness regions.
We excise 15 point sources superimposed on the image above a flux of \fluxunit (2--10keV) using XMM-Newton and Suzaku images of the
cluster. We quantify all known systematic errors as part of our analysis, and
show our statistical errors encompasses them for the most part. Our results
extend previous measurements with Chandra and XMM-Newton, and show a
significant temperature drop to about 3keV at the virial radius, . Our
entropy profile in the outer region () joins smoothly onto that
of XMM-Newton, and shows a flatter slope compared with simple models, similar
to a few other clusters observed at the virial radius. The integrated mass of
the cluster at the virial radius is approximately
and varies by about 30% depending on the particular method used to measure it.Comment: 32pages, 9 figures, accepted for publication in PAS
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