212 research outputs found
Spectral Statistics and Luminosity Function of a Hard X-ray Complete Sample of Brightest AGNs
We investigated the statistics of the X-ray spectral properties of a complete
flux-limited sample of bright AGNs from HEAO-1 all-sky catalogs to provide the
bright end constraint of the evolution of AGN hard X-ray luminosity function
(HXLF) and the AGN population synthesis model of the X-ray background. Spectral
studies have been made using ASCA and XMM-Newton observation data for almost
all AGNs in this sample.Comment: PTPTex v0.88, 2 pages with 4 figures, Proceedings of the
"Stellar-Mass, Intermediate -Masss, and Supermassive Black Holes" in Kyoto,
Japa
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&
On why the Iron K-shell absorption in AGN is not a signature of the local Warm/Hot Intergalactic Medium
We present a comparison between the 2001 XMM-Newton and 2005 Suzaku
observations of the quasar, PG1211+143 at z=0.0809. Variability is observed in
the 7 keV iron K-shell absorption line (at 7.6 keV in the quasar frame), which
is significantly weaker in 2005 than during the 2001 XMM-Newton observation.
From a recombination timescale of <4 years, this implies an absorber density
n>0.004 particles/cm3, while the absorber column is 5e22<N_H <1 1e24
particles/cm2. Thus the sizescale of the absorber is too compact (pc scale) and
the surface brightness of the dense gas too high (by 9-10 orders of magnitude)
to arise from local hot gas, such as the local bubble, group or Warm/Hot
Intergalactic Medium (WHIM), as suggested by McKernan et al. (2004, 2005).
Instead the iron K-shell absorption must be associated with an AGN outflow with
mildly relativistic velocities. Finally we show that the the association of the
absorption in PG1211+143 with local hot gas is simply a coincidence, the
comparison between the recession and iron K absorber outflow velocities in
other AGN does not reveal a one to one kinematic correlation.Comment: accepted for publication in MNRAS LETTERS. 5 pages, 4 figure
Locating the Warm-Hot Intergalactic Medium in the Simulated Local Universe
We present an analysis of mock spectral observation of warm-hot intergalactic
medium (WHIM) using a constrained simulation of the local universe. The
simulated map of oxygen emission lines from local WHIM reproduces well the
observed structures traced by galaxies in the real local universe. We further
attempt to perform mock observations of outer parts of simulated Coma cluster
and A3627 adopting the expected performance of DIOS (Diffuse Intergalactic
Oxygen Surveyor), which is proposed as a dedicated soft X-ray mission to search
for cosmic missing baryons. We find that WHIMs surrounding nearby clusters are
detectable with a typical exposure time of a day, and thus constitute realistic
and promising targets for DIOS. We also find that an X-ray emitting clump in
front of Coma cluster, recently reported in the XMM-Newton observation, has a
counterpart in the simulated local universe, and its observed spectrum can be
well reproduced in the simulated local universe if the gas temperature is set
to the observationally estimated value.Comment: 25 pages, 3 tables, 16 figures. Accepted for publication in PASJ.
High resolution PS/PDF files are available at
http://www-utap.phys.s.u-tokyo.ac.jp/~kohji/research/x-ray/index.htm
DIOS: the dark baryon exploring mission
DIOS (Diffuse Intergalactic Oxygen Surveyor) is a small satellite aiming for
a launch around 2020 with JAXA's Epsilon rocket. Its main aim is a search for
warm-hot intergalactic medium with high-resolution X-ray spectroscopy of
redshifted emission lines from OVII and OVIII ions. The superior energy
resolution of TES microcalorimeters combined with a very wide field of view
(30--50 arcmin diameter) will enable us to look into gas dynamics of cosmic
plasmas in a wide range of spatial scales from Earth's magnetosphere to
unvirialized regions of clusters of galaxies. Mechanical and thermal design of
the spacecraft and development of the TES calorimeter system are described. We
also consider revising the payload design to optimize the scientific capability
allowed by the boundary conditions of the small mission.Comment: 10 pages, 11 figures, Proceedings of the SPIE Astronomical
Instrumentation : Space Telescopes and Instrumentation 2014: Ultraviolet to
Gamma Ra
Detection of Excess Hard X-ray Emission from the Group of Galaxies HCG62
From the group of galaxies HCG62, we detected an excess hard X-ray emission
in energies above keV with \A SCA. The excess emission is spatially
extended up to from the group center, and somewhat enhanced toward
north. Its spectrum can be represented by either a power-law of photon index
0.8-2.7, or a Bremsstrahlung of temperature keV. In the 2-10 keV range,
the observed hard X-ray flux, erg cm
s, implies a luminosity of erg s for a
Hubble constant of 50 km s Mpc. The emission is thus too luminous
to be attributed to X-ray binaries in the memb er galaxies. We discuss possible
origin of the hard X-ray emission.Comment: 6 pages, 3 Postscript figures, uses emulateapj.sty. Accepted for
publication in the Astrophysical Journal Letter
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