57 research outputs found
Extended Thermal X-ray Emission from the Spiral-Dominant Group of Galaxies HCG 57
We observed a group of galaxies, HCG 57, with ASCA. Regardless that their
member galaxies are dominated by spiral galaxies, we detected extended thermal
X-ray emission that is attributed to hot gas with a temperature of
keV. This is the second clear detection of thermal X-ray emission
from a spiral-dominant group of galaxies after HCG 92. The luminosity of the
thermal emission is about erg s in the 0.5--10 keV
band, which is higher than that of HCG 92, but relatively less luminous among
groups of galaxies. The X-ray emission is extended over several member
galaxies, and is thus associated with the group rather than an individual
galaxy. The metal abundance cannot be well constrained with a lower limit of
0.08 solar. The gas-to-stellar mass ratio is . Although this is
relatively low among groups, the hot gas is also a significant component even
in the spiral-dominant group. We suggest that the X-ray faintness of
spiral-dominant groups is due to the low surface brightness and somewhat low
gas mass, at least in the case of HCG 57.Comment: 12 pages, 4 figures, to appear in PASJ 54 No.
Chandra X-Ray Spectral Analysis of Cooling Flow Clusters, 2A 0335+096 and Abell 2199
We report on a spatially resolved analysis of Chandra X-ray data on a nearby
typical cooling flow cluster of galaxies 2A 0335+096, together with A 2199 for
a comparison. As recently found in the cores of other clusters, the temperature
around the central part of 2A 0335+096 is 1.3--1.5 keV, which is higher than
that inferred from the cooling flow picture. Furthermore, the absorption column
density is almost constant against the radius in 2A 0335+096; there is no
evidence of excess absorption up to 200--250 kpc. This indicates that no
significant amount of cold material, which has cooled down, is present. These
properties are similar to those of A 2199. Since the cooling time in the
central part is much shorter than the age of the clusters, a heating mechanism,
which weakens the effect of radiative cooling, is expected to be present in the
central part of both clusters of galaxies. Both 2A 0335+096 and A 2199 have
radio jets associated with their cD galaxy. We discuss the possibility of
heating processes caused by these radio jets by considering the thermal
conduction and the sound velocity together with the observed disturbance of the
ICM temperature and density. We conclude that the observed radio jets can
produce local heating and/or cooling, but do not sufficiently reduce the
overall radiative cooling. This implies that much more violent jets, whose
emission has now decayed, heated up the cooling gas years ago.Comment: 13 pages, 7 figures, to appear in PASJ 55 No.
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
Hard X-ray Properties of the Merging Cluster Abell 3667 as Observed with Suzaku
Wide-band Suzaku data on the merging cluster Abell 3667 were examined for
hard X-ray emission in excess to the known thermal component. Suzaku detected
X-ray signals in the wide energy band from 0.5 to 40 keV. The hard X-ray (> 10
keV) flux observed by the HXD around the cluster center cannot be explained by
a simple extension of the thermal emission with average temperature of ~7 keV.
The emission is most likely an emission from a very hot (kT > 13.2 keV) thermal
component around the cluster center, produced via a strong heating process in
the merger. In the north-west radio relic, no signature of non-thermal emission
was observed. Using the HXD, the overall upper-limit flux within a 34'x34'
field-of-view around the relic is derived to be 5.3e-12 erg s-1 cm-2 in the
10-40 keV band, after subtracting the ICM contribution estimated using the XIS
or the XMM-Newton spectra. Directly on the relic region, the upper limit is
further tightened by the XIS data to be less than 7.3e-13 erg s-1 cm-2, when
converted into the 10--40 keV band. The latter value suggest that the average
magnetic field within the relic is higher than 1.6 uG. The non-thermal pressure
due to magnetic fields and relativistic electrons may be as large as ~20% of
the thermal pressure in the region.Comment: 18 pages, 13 figures, to be appeared in PASJ 200
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
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
Obstetric Outcomes in Women with Rheumatic Disease and COVID-19 in the Context of Vaccination Status
OBJECTIVE: To describe obstetric outcomes based on COVID-19 vaccination status, in women with rheumatic and musculoskeletal diseases (RMDs) who developed COVID-19 during pregnancy. METHODS: Data regarding pregnant women entered into the COVID-19 Global Rheumatology Alliance registry from 24 March 2020-25 February 2022 were analysed. Obstetric outcomes were stratified by number of COVID-19 vaccine doses received prior to COVID-19 infection in pregnancy. Descriptive differences between groups were tested using the chi -square or Fisher's exact test. RESULTS: There were 73 pregnancies in 73 women with RMD and COVID-19. Overall, 24.7% (18) of pregnancies were ongoing, while of the 55 completed pregnancies 90.9% (50) of pregnancies resulted in livebirths. At the time of COVID-19 diagnosis, 60.3% (n = 44) of women were unvaccinated, 4.1% (n = 3) had received one vaccine dose while 35.6% (n = 26) had two or more doses. Although 83.6% (n = 61) of women required no treatment for COVID-19, 20.5% (n = 15) required hospital admission. COVID-19 resulted in delivery in 6.8% (n = 3) of unvaccinated women and 3.8% (n = 1) of fully vaccinated women. There was a greater number of preterm births (PTB) in unvaccinated women compared with fully vaccinated 29.5% (n = 13) vs 18.2%(n = 2). CONCLUSION: In this descriptive study, unvaccinated pregnant women with RMD and COVID-19 had a greater number of PTB compared with those fully vaccinated against COVID-19. Additionally, the need for COVID-19 pharmacological treatment was uncommon in pregnant women with RMD regardless of vaccination status. These results support active promotion of COVID-19 vaccination in women with RMD who are pregnant or planning a pregnancy
- …