40 research outputs found
Suzaku observations of the Hydra A cluster out to the virial radius
We report Suzaku observations of the northern half of the Hydra A cluster out
to ~1.4 Mpc, reaching the virial radius. This is the first Suzaku observations
of a medium-size (kT ~3 keV) cluster out to the virial radius. Two observations
were conducted, north-west and north-east offsets, which continue in a filament
direction and a void direction of the large-scale structure of the Universe,
respectively. The X-ray emission and distribution of galaxies elongate in the
filament direction. The temperature profiles in the two directions are mostly
consistent with each other within the error bars and drop to 1.5 keV at 1.5
r_500. As observed by Suzaku in hot clusters, the entropy profile becomes
flatter beyond r_500, in disagreement with the r^1.1 relationship that is
expected from accretion shock heating models. When scaled with the average
intracluster medium (ICM) temperature, the entropy profiles of clusters
observed with Suzaku are universal and do not depend on system mass. The
hydrostatic mass values in the void and filament directions are in good
agreement, and the Navarro, Frenk, and White universal mass profile represents
the hydrostatic mass distribution up to ~ 2 r_500. Beyond r_500, the ratio of
gas mass to hydrostatic mass exceeds the result of the Wilkinson microwave
anisotropy probe, and at r_100, these ratios in the filament and void
directions reach 0.4 and 0.3, respectively. We discuss possible deviations from
hydrostatic equilibrium at cluster outskirts. We derived radial profiles of the
gasmass- to-light ratio and iron-mass-to-light ratio out to the virial radius.
Within r_500, the iron-mass-to-light ratio of the Hydra A cluster was compared
with those in other clusters observed with Suzaku.Comment: 16 pages, 15 figures; Accepted for publication in PAS
Suzaku and Chandra observations of the galaxy cluster RXC J1053.7+5453 with a radio relic
We present the results of Suzaku and Chandra observations of the galaxy
cluster RXC J1053.7+5453 (), which contains a radio relic. The radio
relic is located at the distance of kpc from the X-ray peak toward
the west. We measured the temperature of this cluster for the first time. The
resultant temperature in the center is keV, which is lower than the
value expected from the X-ray luminosity - temperature and the velocity
dispersion - temperature relation. Though we did not find a significant
temperature jump at the outer edge of the relic, our results suggest that the
temperature decreases outward across the relic. Assuming the existence of the
shock at the relic, its Mach number becomes . A possible spatial
variation of Mach number along the relic is suggested. Additionally, a sharp
surface brightness edge is found at the distance of kpc from the
X-ray peak toward the west in the Chandra image. We performed X-ray spectral
and surface brightness analyses around the edge with Suzaku and Chandra data,
respectively. The obtained surface brightness and temperature profiles suggest
that this edge is not a shock but likely a cold front. Alternatively, it cannot
be ruled out that thermal pressure is really discontinuous across the edge. In
this case, if the pressure across the surface brightness edge is in
equilibrium, other forms of pressure sources, such as cosmic-rays, are
necessary. We searched for the non-thermal inverse Compton component in the
relic region. Assuming the photon index , the resultant upper
limit of the flux is for
area in the 0.3-10 keV band, which
implies that the lower limit of magnetic field strength becomes $ 0.7 {\rm \
\mu G}$.Comment: 13page, 8 figures, accepted for publication in PASJ. arXiv admin
note: text overlap with arXiv:1508.0584
Suzaku Observation of HCG 62: Temperature, Abundance, and Extended Hard X-ray Emission Profiles
We present results of 120 ks observation of a compact group of galaxies
HCG~62 () with Suzaku XIS and HXD-PIN\@. The XIS spectra for four
annular regions were fitted with two temperature {\it vapec} model with
variable abundance, combined with the foreground Galactic component. The
Galactic component was constrained to have a common surface brightness among
the four annuli, and two temperature {\it apec} model was preferred to single
temperature model. We confirmed the multi-temperature nature of the intra-group
medium reported with Chandra and XMM-Newton, with a doughnut-like high
temperature ring at radii 3.3--6.5 in a hardness image. We found Mg, Si, S,
and Fe abundances to be fairly robust. We examined the possible
``high-abundance arc'' at southwest from the center, however Suzaku
data did not confirm it. We suspect that it is a misidentification of an excess
hot component in this region as the Fe line. Careful background study showed no
positive detection of the extended hard X-rays previously reported with ASCA,
in 5--12 keV with XIS and 12--40 keV with HXD-PIN, although our upper limit did
not exclude the ASCA result. There is an indication that the X-ray intensity in
region is % higher than the nominal CXB level (5--12 keV),
and Chandra and Suzaku data suggest that most of this excess could be due to
concentration of hard X-ray sources with an average photon index of
. Cumulative mass of O, Fe and Mg in the group gas and the
metal mass-to-light ratio were derived and compared with those in other groups.
Possible role of AGN or galaxy mergers in this group is also discussed.Comment: 29 pages with 9 figures, accepted for publication in PASJ Vol 60,
second Suzaku special issu
Suzaku Observations of the Centaurus Cluster: Absence of Bulk Motions in the Intracluster Medium
The Centaurus cluster (z=0.0104) was observed with the X-ray Imaging
Spectrometer (XIS) onboard the Suzaku X-ray satellite in three pointings, one
centered on the cluster core and the other two offset by +-8' in declination.
To search for possible bulk motions of the intracluster medium, the central
energy of He-like Fe-K line (at a rest-frame energy of 6.7 keV) was examined to
look for a positional dependence. Over spatial scales of 50 kpc to 140 kpc
around the cluster core, the central line energy was found to be constant
within the calibration error of 15 eV. The 90% upper limit on the line-of-sight
velocity difference is |Delta_v|< 1400 km/s, giving a tighter constraint than
previous measurements. The significant velocity gradients inferred from a
previous Chandra study were not detected between two pairs of rectangular
regions near the cluster core. These results suggest that the bulk velocity
does not largely exceed the thermal velocity of the gas in the central region
of the Centaurus cluster. The mean redshift of the intracluster medium was
determined to be 0.0097, in agreement with the optical redshift of the cluster
within the calibration uncertainty. Implications of the present results for the
estimation of the cluster mass are briefly discussed.Comment: 9 pages, 4 figures. Accepted for publication in PASJ. Version with
high-quality color figures at
http://cosmic.riken.jp/ota/publications/index.htm
A Galaxy Merger Scenario for the NGC 1550 Galaxy from Metal Distributions in the X-ray Emitting Plasma
The elliptical galaxy NGC 1550 at a redshift of , identified with
an extended X-ray source RX J0419+0225, was observed with {\it XMM-Newton} for
31 ks. From the X-ray data and archival near infra-red data of Two Micron All
Sky survay, we derive the profiles of components constituting the NGC 1550
system; the gas mass, total mass, metal mass, and galaxy luminosity. The metals
(oxygen, silicon, and iron) are extended to kpc from the center,
wherein 70% of the -band luminosity is carried by NGC 1550 itself. As
first revealed with {\it ASCA}, the data reconfirms the presence of a dark
halo, of which the mass () is typical of a galaxy
group rather than of a single galaxy. Within 210 kpc, the -band
mass-to-light ratio reaches , which is comparable to
those of clusters of galaxies. The iron-mass-to-light ratio profile (silicon-
and oxygen mass-to-light ratio profiles as well) exhibits about two orders of
magnitude decrease toward the center. Further studies comparing mass densities
of metals with those of the other cluster components reveal that the iron (as
well as silicon) in the ICM traces very well the total gravitating mass,
whereas the stellar component is significantly more concentrated to within
several tens kpc of the NGC 1550 nucleus. Thus, in the central region, the
amount of metals is significantly depleted for the luminous galaxy light. Among
a few possible explanations of this effect, the most likely scenario is that
galaxies in this system were initially much more extended than today, and
gradually fell to the center and merged into NGC 1550.Comment: 31 pages, 10 figures, 2 table
X-Ray Study of Temperature and Abundance Profiles of the Cluster of Galaxies Abell 1060 with Suzaku
We carried out observations of the central and 20' east offset regions of the
cluster of galaxies Abell 1060 with Suzaku. Spatially resolved X-ray spectral
analysis has revealed temperature and abundance profiles of Abell 1060 out to
27' ~ 380; /h_70 kpc, which corresponded to ~ 0.25; r_180. Temperature decrease
of the intra cluster medium from 3.4 keV at the center to 2.2 keV in the
outskirt region are clearly observed. Abundances of Si, S and Fe also decrease
by more than 50% from the center to the outer, while Mg shows fairly constant
abundance distribution at ~ 0.7 solar within r < 17'. O shows lower abundance
of ~ 0.3 solar in the central region (r~ 6'), and indicates a similar feature
with Mg, however it is sensitive to the estimated contribution of the Galactic
components of kT_1 ~ 0.15 keV and kT_2 ~ 0.7 keV in the outer annuli (r ~ 13').
Systematic effects due to the point spread function tails, contamination on the
XIS filters, instrumental background, cosmic and/or Galactic X-ray background,
and the assumed solar abundance tables are carefully examined. Results on
temperature and abundances of Si, S, and Fe are consistent with those derived
by XMM-Newton at r < 13'. Formation and metal enrichment process of the cluster
are discussed based on the present results.Comment: 20 pages, 19 figures, accepted for publication in PAS
The ASTRO-H X-ray Observatory
The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly
successful X-ray missions initiated by the Institute of Space and Astronautical
Science (ISAS). ASTRO-H will investigate the physics of the high-energy
universe via a suite of four instruments, covering a very wide energy range,
from 0.3 keV to 600 keV. These instruments include a high-resolution,
high-throughput spectrometer sensitive over 0.3-2 keV with high spectral
resolution of Delta E < 7 eV, enabled by a micro-calorimeter array located in
the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers
covering 5-80 keV, located in the focal plane of multilayer-coated, focusing
hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12
keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and
a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the
40-600 keV band. The simultaneous broad bandpass, coupled with high spectral
resolution, will enable the pursuit of a wide variety of important science
themes.Comment: 22 pages, 17 figures, Proceedings of the SPIE Astronomical
Instrumentation "Space Telescopes and Instrumentation 2012: Ultraviolet to
Gamma Ray