308 research outputs found
XMM-Newton Observation of IC 310 in the Outer Region of the Perseus Cluster of Galaxies
We present results from an XMM-Newton observation of the head-tail radio
galaxy IC 310 located in the southwest region of the Perseus cluster. The
spectrum is well-fitted by an absorbed power-law model with a photon index of
with no significant absorption excess. The X-ray image shows a
point-like emission at IC 310 without any signs of a structure correlated with
the radio halo tail. The temperature of the intracluster medium surrounding IC
310 declines as a function of distance from the cluster center, from keV in the northeast corner of the field of view to about 3 keV in the
southwest region. Although we do not find any sharp edges in the surface
brightness profile, a brightness excess over a smooth model by about
20% is seen. The temperature also rises by about 10% in the same region. This
indicates that the IC 310 region is a subcluster probably infalling into the
Perseus cluster, and the gas in front of IC 310 towards the Perseus cluster is
likely to be compressed by the large-scale motion, which supports the view that
the IC 310 system is undergoing a merger.Comment: 7 pages, 8 figures (including color), accepted for publication in
PAS
Chandra observation of the core of the galaxy cluster AWM7
We present results from a Chandra observation of the core region of the
nearby X-ray bright galaxy cluster AWM7. There are blob-like substructures,
which are seen in the energy band 2--10 keV, within 10 kpc (20'') of the cD
galaxy NGC1129, and the brightest sub-peak has a spatial extent more than 4
kpc. We also notice that the central soft X-ray peak is slightly offset from
the optical center by 1 kpc. These structures have no correlated features in
optical, infrared, or radio band. Energy spectrum of the hard sub-peak
indicates a temperature higher than 3 keV with a metallicity less than 0.3
solar, or a power-law spectrum with photon index 1.2. A hardness ratio map and
a narrow Fe-K band image jointly indicate two Fe-rich blobs symmetrically
located around the cD galaxy, with the direction perpendicular to the sub-peak
direction. In larger scales (r<60 kpc), the temperature gradually drops from 4
keV to 2 keV toward the cluster center and the metal abundance rises steeply to
a peak of 1.5 solar at r=7 kpc. These results indicate that a dynamical process
is going on in the central region of AWM7, which probably creates heated gas
blobs and drives metal injection.Comment: 12 pages, 7 figures (including color), accepted for publication in
ApJ. Postscript is also available at
http://www-x.phys.metro-u.ac.jp/~furusho/papers.htm
Chandra observation of the central galaxies in A1060 cluster of galaxies
Chandra observation of the central region of the A1060 cluster of galaxies
resolved X-ray emission from two giant elliptical galaxies, NGC 3311 and NGC
3309. The emission from these galaxies consists of two components, namely the
hot interstellar medium (ISM) and the low-mass X-ray binaries (LMXBs). We found
the spatial extent of the ISM component was much smaller than that of stars for
both galaxies, while the ratios of X-ray to optical blue-band luminosities were
rather low but within the general scatter for elliptical galaxies. After
subtracting the LMXB component, the ISM is shown to be in pressure balance with
the intracluster medium of A1060 at the outer boundary of the ISM. These
results imply that the hot gas supplied from stellar mass loss is confined by
the external pressure of the intracluster medium, with the thermal conduction
likely to be suppressed. The cD galaxy NGC 3311 does not exhibit the extended
potential structure which is commonly seen in bright elliptical galaxies, and
we discuss the possible evolution history of the very isothermal cluster A1060.Comment: 12 pages, 7 figures, Latex2e(emulateapj5), accepted in Ap
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
Detection of an X-Ray Hot Region in the Virgo Cluster of Galaxies with ASCA
Based on mapping observations with ASCA, an unusual hot region with a spatial
extent of 1 square degree was discovered between M87 and M49 at a center
coordinate of R. A. = 12h 27m 36s and Dec. = (J2000). The X-ray
emission from the region has a 2-10 keV flux of ergs
s cm and a temperature of keV, which is
significantly higher than that in the surrounding medium of keV. The
internal thermal energy in the hot region is estimated to be ergs with a gas density of cm. A power-law
spectrum with a photon index is also allowed by the data. The hot
region suggests there is an energy input due to a shock which is probably
caused by the motion of the gas associated with M49, infalling toward the M87
cluster with a velocity km s.Comment: 12 pages, 3 figures, accepted to ApJ
Detection of Bulk Motions in the ICM of the Centaurus Cluster
Several recent numerical simulations of off-center cluster mergers predict
that significant angular momentum with associated velocities of a few x 10^{3}
km/s can be imparted to the resulting cluster. Such gas bulk velocities can be
detected by the Doppler shift of X-ray spectral lines with ASCA spectrometers.
Using two ASCA observations of the Centaurus cluster, we produced a velocity
map for the gas in the cluster's central regions. We also detected radial and
azimuthal gradients in temperature and metal abundance distributions, which
seem to be associated with the infalling sub-group centered at NGC 4709 (Cen
45). More importantly, we found a significant (>99.8% confidence level)
velocity gradient along a line near-perpendicular to the direction of the
incoming sub-group and with a maximum velocity difference of ~3.4+-1.1 x 10^{3}
km/s. It is unlikely (P < 0.002) that the observed velocity gradient is
generated by gain fluctuations across the detectors. While the observed
azimuthal temperature and abundance variations can be attributed to the
interaction with Cen 45, we argue that the intracluster gas velocity gradient
is more likely due to a previous off-center merging event in the main body of
the Centaurus cluster.Comment: 13 pages in emulateapj5 style, 8 postscript figures; Accepted by ApJ;
Revised version with minor change
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