215 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
X-ray Observation of Mars with Suzaku at Solar Minimun
Mars was observed in X-rays during April 3-5 2008 for 82 ksec with the
Japanese Suzaku observatory. Mars has been known to emit X-rays via the
scattering of solar X-rays and via the charge exchange between neutral atoms in
the exosphere and solar wind ions. Past theoretical studies suggest that the
exospheric neutral density may vary by a factor of up to 10 over the solar
cycle. To investigate a potential change of the exospheric charge exchange
emission, Mars was observed with Suzaku at solar minimum. Significant signals
were not detected at the position of Mars in the energy band of 0.2-5 keV. A 2
sigma upper limit of the O VII line flux in 0.5-0.65 keV was 4.3
ph cm s. Comparing this upper limit to the past Chandra and
XMM-Newton observations conducted near solar maximum, it was found that the
exospheric density at solar minimum does not exceed that near solar maximum by
more than 6-70 times.Comment: 17 pages, 7 figures, accepted for publication in PAS
ASCA Compilation of X-Ray Properties of Hot Gas in Elliptical Galaxies and Galaxy Clusters: Two Breaks in the Temperature Dependences
Utilizing ASCA archival data of about 300 objects of elliptical galaxies,
groups, and clusters of galaxies, we performed systematic measurements of the
X-ray properties of hot gas in their systems, and compiled them in this paper.
The steepness of the luminosity--temperature (LT) relation, , in the range of 1.5--15 keV is
, consistent with previous measurements. In the relation,
we find two breaks at around ICM temperatures of 1 keV and 4 keV:
above 4 keV, in 1.5--5 keV, and
below 1.5 keV. Such two breaks are also evident in the
temperature and size relation. The steepness in the LT relation at keV
is consistent with the scale-relation derived from the CDM model, indicating
that the gravitational effect is dominant in richer clusters, while poorer
clusters suffer non-gravity effects. The steep LT relation below 1 keV is
almost attributed to X-ray faint systems of elliptical galaxies and galaxy
groups. We found that the ICM mass within the scaling radius follows
the relation of from X-ray faint galaxies
to rich clusters. Therefore, we speculate that even such X-ray faint systems
contain a large-scale hot gas, which is too faint to detect.Comment: 59 pages, 20 figures, to appear in PASJ 56 No.6 Pdf documents
including complete tables are available as
http://www-heaf.hepl.hiroshima-u.ac.jp/~fukazawa/icmmas-sup.pd
X-Ray View of the Shock Front in the Merging Cluster Abell 3376 with Suzaku
We report on a Suzaku measurement of the shock feature associated with the
western radio relic in the merging cluster A3376. The temperature profile is
characterized by an almost flat radial shape with kT ~ 4 keV within 0.5 r200
and a rise by about 1 keV inside the radio relic. Across the relic region
(0.6-0.8 r200), the temperature shows a remarkable drop from about 4.7 keV to
1.3 keV. This is a clear evidence that the radio relic really corresponds to a
shock front possibly caused by a past major merger. The observed sharp changes
of the temperature and electron density indicate the Mach number M~3. The
radial entropy profile is flatter than the prediction (r^1.1) of numerical
simulations within 0.5 r200}, and becomes steeper around the relic region.
These observed features and time-scale estimation consistently imply that the
ICM around the radio relic has experienced a merger shock and is in the middle
of the process of dynamical and thermal relaxation.Comment: Accepted for publication in PASJ (12 pages, 6 figures
The International X-ray Observatory
The International X-ray Observatory (IXO) is a joint ESA-JAXA-NASA effort to
address fundamental and timely questions in astrophysics: What happens close to
a black hole? How did supermassive black holes grow? How does large scale
structure form? What is the connection between these processes? To address
these questions IXO will employ optics with 3 sq m collecting area and 5 arc
sec angular resolution - 20 times more collecting area at 1 keV than any
previous X-ray observatory. Focal plane instruments will deliver a 100-fold
increase in effective area for high-resolution spectroscopy, deep spectral
imaging over a wide field of view, unprecedented polarimetric sensitivity,
microsecond spectroscopic timing, and high count rate capability. The mission
is being planned for launch in 2021 to an L2 orbit, with a five-year lifetime
and consumables for 10 years.Comment: 6 pages, 3 figures, for conference "X-ray Astronomy 2009 Present
status, multi-wavelength approach and future perspectives
Enhancement of Terrestrial Diffuse X-ray Emission Associated With Coronal Mass Ejection and Geomagnetic Storm
We present an analysis of a Suzaku observation taken during the geomagnetic
storm of 2005 August 23-24. We found time variation of diffuse soft X-ray
emission when a coronal mass ejection hit Earth and caused a geomagnetic storm.
The diffuse emission consists of fluorescent scattering of solar X-rays and
exospheric solarwind charge exchange. The former is characterized by a neutral
oxygen emission line due to strong heating of the upper atmosphere during the
storm time, while the latter is dominated by a sum of C V, C VI, N VI, N VII, O
VII, and O VIII emission lines due to the enhanced solar wind flux in the
vicinity of the exosphere. Using the solar wind data taken with the ACE and
WIND satellites,a time correlation between the solar wind and the strong O VII
line flux were investigated. We estimated necessary column densities for the
solar X-ray scattering and exospheric SWCX. From these results, we argue that a
part of the solar wind ions enter inside the magnetosphere and cause the SWCX
reaction.Comment: 33 pages, 16 figures, accepted for publication in PAS
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