210 research outputs found
Metal Abundances in the Hot Interstellar Medium in Early-Type Galaxies Observed with ASCA
We have analyzed ASCA data of 27 early-type galaxies, and studied the
properties of their X-ray emitting ISM (Inter Stellar
Medium) in detail. We found that overlapping lines and free-bound continuum
cause strong coupling in the derived abundances of various elements. The
abundance determination is also difficult due to the uncertainties in the Fe-L
atomic physics, because Fe-L lines couple with O and Ne K-lines. However, when
abundances of -elements are fixed, all the plasma codes give similar Fe
abundances with a scattering of only 20-30%. To relax the strong coupling among
the elements, we included 20% systematic errors in the Fe-L region of the
spectra. Then, in X-ray luminous galaxies, the derived abundance of Fe and
-elements both became solar within a factor of 2. This result
relaxes the previous severe discrepancy between the ISM and stellar
metallicities. The ISM metallicity in X-ray fainter galaxies is still
uncertain, but we can at least constrain that contribution from type-Ia SN to
the ISM abundance is lower than in X-ray luminous systems. These results
strongly suggest that a large fraction of SN Ia products have escaped into
intergalactic space.Comment: 48 pages with 20 figures, Latex(PASJadd.sty, PASJ95.sty), accepted
for publication in PAS
Identification of multiple actin-binding sites in cofilin-phosphatase Slingshot-1L
AbstractSlingshot-1L (SSH1L) is a phosphatase that specifically dephosphorylates and activates cofilin, an actin-severing and -depolymerizing protein. SSH1L binds to and is activated by F-actin in vitro, and co-localizes with F-actin in cultured cells. We examined the F-actin-binding activity, F-actin-mediated phosphatase activation, and subcellular distribution of various mutants of SSH1L. We identified three sites involved in F-actin binding of SSH1L: Trp-458 close to the C-terminus of the phosphatase domain, an LHK motif in the N-terminal region, and an LKR motif in the C-terminal region. These sites play unique roles in the control of subcellular localization and F-actin-mediated activation of SSH1L
Metallicity of the Fossil Group NGC 1550 Observed with Suzaku
We studied the temperature and metal abundance distributions of the
intra-cluster medium (ICM) in a group of galaxies NGC 1550 observed with
Suzaku. The NGC 1550 is classified as a fossil group, which have few bright
member galaxies except for the central galaxy. Thus, such a type of galaxy is
important to investigate how the metals are enriched to the ICM. With the
Suzaku XIS instruments, we directly measured not only Si, S, and Fe lines but
also O and Mg lines and obtained those abundances to an outer region of ~0.5
r_180 for the first time, and confirmed that the metals in the ICM of such a
fossil group are indeed extending to a large radius. We found steeper gradients
for Mg, Si, S, and Fe abundances, while O showed almost flat abundance
distribution. Abundance ratios of alpha-elements to Fe were similar to those of
the other groups and poor clusters. We calculated the number ratio of type II
to type Ia supernovae for the ICM enrichment to be 2.9 +- 0.5 within 0.1 r_180,
and the value was consistent with those for the other groups and poor clusters
observed with Suzaku. We also calculated metal mass-to-light ratios (MLRs) for
Fe, O and Mg with B-band and K-band luminosities of the member galaxies of NGC
1550. The derived MLRs were comparable to those of NGC 5044 group in the r<0.1
r_180 region, while those of NGC 1550 are slightly higher than those of NGC
5044 in the outer region.Comment: 11 pages, 7 figures, accepted for publication in PAS
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
Suzaku Observation of Group of Galaxies NGC 507: Temperature and Metal Distributions in the Intra-cluster Medium
Temperature and abundance distributions of the intra-cluster medium (ICM) in
the NGC 507 group of galaxies were studied with Suzaku. Observed concentric
annular spectra were well-represented by a two temperature model for ICM, and
we found steeper abundance gradients for Mg, Si, S, and Fe compared with O in
the central region. Abundance ratios of alpha-elements to iron were found to be
similar to those in other groups and poor clusters. We calculated metal
mass-to-light ratios for Fe, O and Mg (IMLR, OMLR, MMLR) for NGC 507, and
values for different systems were compared. Hotter and richer systems tend to
show higher values of IMLR, OMLR, and MMLR. OMLR and MMLR were measured to an
outer region for the first time with Suzaku, while IMLR was consistent with
that with ASCA. We also looked into 2-dimensional map of the hardness ratio,
but found no significant deviation from the circular symmetry.Comment: 12 pages, 10 figures, accepted for publication in PAS
Suzaku and XMM-Newton Observations of the Fornax cluster: Temperature and Metallicity Distribution
Suzaku observed a central region and five offset regions within 0.2 r180 in
the Fornax cluster, a nearby poor cluster, and XMM-Newton mapped the cluster
with 15 pointings out to 0.3 r180. The distributions of O, Mg, Si, S, and Fe in
the intracluster medium (ICM) were studied with Suzaku, and those of Fe and
temperature were studied with XMM. The temperature of the ICM gradually
decreases with radius from 1.3 keV at 0.04 r180 to 1 keV at 0.2-0.3 r180. If
the new solar abundances of Lodders et al. (2003) and a single-temperature
plasma model are adopted, O, Mg, Si, S, and Fe show similar abundances: 0.4-0.6
solar within 0.02-0.2 r180. This Fe abundance is similar to those at 0.1-0.2
r180 in rich clusters and other groups of galaxies. At 0.2-0.3 r180, the Fe
abundance becomes 0.2-0.3 solar. A two-temperature plasma model yields ICM
abundances that are higher by a factor of 1.2-1.5, but gives similar abundance
ratios among O, Mg, Si, S, and Fe. The northern region has a lower ICM
temperature and higher brightness and Fe abundance, whereas the southern region
has a higher ICM temperature and lower brightness and Fe abundance. These
results indicate that the cD galaxy may have traveled from the north because of
recent dynamical evolution. The cumulative oxygen- and iron-mass-to-light
ratios within 0.3 r180 are more than an order of magnitude lower than those of
rich clusters and some relaxed groups of galaxies. Past dynamical evolution
might have hindered the strong concentration of hot gas in the Fornax cluster's
central region. Scatter in the IMLR and similarity in the element abundances in
the ICM of groups and clusters of galaxies indicate early metal synthesis.Comment: 15 pages, 13 figures, accepted for publication in PAS
THERMAL AND CHEMICAL EVOLUTIONS OF GALAXY CLUSTERS OBSERVED WITH SUZAKU
We studied the properties of the intracluster medium (ICM) of galaxy clusters to outer regions observed with Suzaku. The observed temperature dropped by about ~30% from the central region to the virial radius of the clusters. The derived entropy profile agreed with the expectation from simulations within r500, while the entropy profile in r > r500 indicated a flatter slope than the simulations. This would suggest that the cluster outskirts were out of hydrostatic equilibrium. As for the metallicity, we studied the metal abundances from O to Fe up to ~0.5 times the virial radius of galaxy groups and clusters. Comparing the results with supernova nucleosynthesis models, the number ratio of type II to Ia supernovae is estimated to be ~3.5. We also calculated not only Fe, but also O and Mg mass-to-light ratios (MLRs) with K-band luminosity. The MLRs in the clusters had a similar feature
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