161 research outputs found
Study of the Intracluster and Intergalactic Medium in the Sculptor Supercluster with Suzaku
We studied the high temperature plasma in the direction of the Sculptor
supercluster at z=0.108 with Suzaku. Suzaku carried out four observations in
the supercluster: namely, A2811, A2811 offset, A2804, A2801 regions in 2005
Nov.--Dec., including the regions beyond the virial radii of these clusters.
The study needed precise background estimation because the measured intensity
of the redshifted lines, especially those from oxygen, were strongly affected
by the the Galactic emission. The spectra taken in the regions outside of the
virial radii of the member clusters were used as the background which included
both the Galactic and Cosmic X-ray Background (CXB) components. We also used
the background data which were taken near the Sculptor supercluster.
Temperature and metal abundance profiles were determined to the virial radii of
the member clusters, and then we searched for the oxygen line emission in the
region outside of the virial radii of the clusters. As a result, the
temperature of the clusters decreased toward the virial radii, and the spectral
fits for the filament region did not require extra component other than the
Galactic and CXB components. We constrained the intensities of O VII and O VIII
lines to be less than 8.1 and 5.1 photons cm^-2 s^-1 arcmin^-2, respectively,
as 2-sigma upper limits. The intensity of O VII indicates n_H < 1.6e-5 cm^-3
(Z/0.1 Z_solar)^-1/2 (L/25 Mpc)^-1/2, which corresponds to an over density,
delta < 60 (Z/0.1 Z_solar)^-1/2 (L/25 Mpc)^-1/2.Comment: 11 pages, 8 figures, accepted for publication in PAS
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
C1B domain peptide of protein kinase Cγ significantly suppresses growth of human colon cancer cells in vitro and in an in vivo mouse xenograft model through induction of cell cycle arrest and apoptosis
Two peptides derived from the C1B domain of protein kinase Cγ (PKCγ) were shown to
associate with classical PKC isozymes and modulate their activities. These C1B peptides are designated C1B1 (amino acid residues 101-112) and C1B5 (residues 141-151). Since PKC enzyme activity is shown to be involved in colon cancer development, the effect of C1B peptides on the growth of various human colon cancer cell lines was examined in vitro and in vivo. Sub-micromolar to micromolar levels of both C1B peptides induced approximately 60-70% growth attenuation in multiple colon cancer cell lines in a soft agar tumor colony assay; however, C1B5 peptide was not cytotoxic to normal colon epithelial cells in two dimensional culture. The effect of C1B5 peptide on colony growth of COLO205 cells was reversed by treatment with the PKCα/β inhibitor, Ro-32-0432. C1B peptide treatment attenuated COLO205 cells via two mechanisms: 1) cell cycle arrest and 2) stimulation of apoptosis. This is evident in G[subscript 2] arrest and increases in levels of cleaved caspase 3 and p53 phosphorylated at serine 20. Intratumoral injection of C1B5 peptide (20 mg/kg/day, every three days) markedly attenuated the growth of subcutaneous xenografts of COLO205 cells in SCID mice by 76% compared to the control. Taken together, these results strongly suggest that C1B peptides have negligible effects on normal tissues but are potentially effective chemotherapeutic agents for colon cancer
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
Discovery of the Central Excess Brightness in Hard X-rays in the Cluster of Galaxies Abell 1795
Using the X-ray data from \ASCA, spectral and spatial properties of the
intra-cluster medium (ICM) of the cD cluster Abell 1795 are studied, up to a
radial distance of ( kpc). The ICM
temperature and abundance are spatially rather constant, although the cool
emission component is reconfirmed in the central region. The azimuthally-
averaged radial X-ray surface brightness profiles are very similar between soft
(0.7--3 keV) and hard (3--10 keV) energy bands, and neither can be fitted with
a single- model due to a strong data excess within of the
cluster center. In contrast, double- models can successfully reproduce
the overall brightness profiles both in the soft and hard energy bands, as well
as that derived with the \ROSAT PSPC. Properties of the central excess
brightness are very similar over the 0.2--10 keV energy range spanned by \ROSAT
and \ASCA. Thus, the excess X-ray emission from the core region of this cluster
is confirmed for the first time in hard X-rays above 3 keV. This indicates that
the shape of the gravitational potential becomes deeper than the King-type one
towards the cluster center. Radial profiles of the total gravitating matter,
calculated using the double- model, reveal an excess mass of within kpc of the cluster
center. This suggests a hierarchy in the gravitational potential corresponding
to the cD galaxy and the entire cluster.Comment: 27 pages, 8 figures; to appear ApJ 500 (June 20, 1998
In-Orbit Demonstration of Propellant-Less Formation Flight with Momentum Exchange of Jointed Multiple CubeSats in the MAGNARO Mission
Recently, small satellites such as CubeSats have been applied to a variety of missions such as scientific observations and remote sensing. One of attractive applications that can be relatively easily achieved by small satellites are multi-satellite missions such as formation flight and constellation. As a new method to realize these multi-satellite missions, we propose a method to separate jointed multiple satellite magnetically to generate ΔV without thrusters. To demonstrate the proposed method, we are developing a 3U sized CubeSat called MAGNARO (MAGnetically separating NAnosatellite with Rotation for Orbit control)
Suzaku Observations of the cluster of galaxies Abell 2052
The results from Suzaku XIS observations of the relaxed cluster of galaxies
Abell2052 are presented. Offset pointing data are used to estimate the Galactic
foreground emission in the direction to the cluster. Significant soft X-ray
excess emission above this foreground, the intra-cluster medium emission, and
other background components is confirmed and resolved spectroscopically and
radially. This excess can be described either by (a) local variations of known
Galactic emission components or (b) an additional thermal component with
temperature of about 0.2 keV, possibly associated with the cluster. The radial
temperature and metal abundance profiles of the intra-cluster medium are
measured within \sim 20 in radius (about 60% of the virial radius) from the
cluster center . The temperature drops radially to 0.5-0.6 of the peak value at
a radius of \sim 15'. The gas-mass-weighted metal abundance averaged over the
observed region is found to be 0.21 +- 0.05 times solar.Comment: Accepted for publication in PASJ (2008), 19 pages, postscript figure
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