716 research outputs found
Discovery of Enhanced Radiative Recombination Continua of He-like Iron and Calcium from IC 443 and Its Implications
We present deep observations of the Galactic supernova remnant IC 443 with
the {\it Suzaku X-ray satellite}. We find prominent K-shell lines from iron and
nickel, together with a triangle residual at 8--10~keV, which corresponds to
the energy of the radiative recombination continuum (RRC) of He-like iron. In
addition, the wavy residuals have been seen at 5.1 and 5.5~keV. We
confirm that the residuals show the first enhanced RRCs of He- and H-like
calcium found in supernova remnants. These facts provide robust evidence for
the recombining plasma. We reproduce the plasma in the 3.7--10~keV band using a
recombining plasma model at the electron temperature 0.65~keV. The
recombination parameter ( is electron density and
is elapsed time after formation of a recombining plasma) and abundances of iron
and nickel are strongly correlated, and hence the errors are large. On the
other hand, the ratio of nickel to iron relative to the solar abundances is
well constrained to 11 (1). A possibility is that the large
abundance ratio is a result of an asymmetric explosion of the progenitor star.Comment: 4 pages, 5 figures, published in Ap
A Complete Survey of the Central Molecular Zone in NH3
We present a map of the major part of the central molecular zone (CMZ) of
simultaneous observations in the NH3 (J,K) = (1,1) and (2,2) lines using the
Kagoshima 6-m telescope. The mapped area is -1.000 < l < 1.625 deg, -0.375 < b
< +0.250 deg. The kinetic temperatures derived from the (2,2) to (1,1)
intensity ratios are 20--80 K or exceed 80 K. The gases corresponding to
temperature of 20--80 K and > 80 K contain 75% and 25% of the total NH3 flux,
respectively. These temperatures indicate that the dense molecular gas in the
CMZ is dominated by gas that is warmer than the majority of the dust present
there. A comparison with the CO survey by Sawada et al. (2001) shows that the
NH3 emitting region is surrounded by a high pressure region on the l-v plane.
Although NH3 emission traces dense gas, it is not extended into a high pressure
region. Therefore, the high pressure region is less dense and has to be hotter.
This indicates that the molecular cloud complex in the Galactic center region
has a ``core'' of dense and warm clouds which are traced by the NH3 emission,
and an ``envelope'' of less dense and hotter gas clouds. Besides heating by
ambipolar diffusion, the hot plasma gas emitting the X-ray emission may heat
the hot ``envelope''.Comment: 21 pages, 14 figures, accepted for PAS
Risk factors for primary open-angle glaucoma in Japanese subjects attending community health screenings
Makoto Ishikawa, Yu Sawada, Noriko Sato, Takeshi YoshitomiDepartment of Ophthalmology, Akita Graduate University School of Medicine, Akita, JapanBackground/aims: To describe risk factors associated with primary open-angle glaucoma (POAG) in Japanese subjects who participated in community health screenings.Methods: Residents of Akita, Japan, participating in a community health checkup were selected to undergo a comprehensive ophthalmic examination. Glaucoma was diagnosed based on optic disk appearance, perimetric results, and other ocular findings. Systemic blood pressure and intraocular pressure were measured and ocular perfusion pressure was calculated. Logistic regression analysis was performed to determine risk factors for POAG patients.Results and conclusion: Of the 710 subjects examined, 26 had POAG. The estimated prevalence of POAG was 3.7%. After adjusting for age, the prevalence of POAG was similar to that found in the Tajimi Study of Japanese subjects. Multivariate logistic regression analysis demonstrated that older age (&ge;60 years, odds ratio [OR]: 3.49), lower diastolic blood pressure (&le;58 mmHg, OR: 2.11), higher intraocular pressure (&ge;19 mmHg, OR: 4.12), and lower ocular perfusion pressure (&le;34 mmHg, OR: 5.78) were associated with increased risk of having POAG. These findings may be relevant for identifying high risk groups.Keywords: glaucoma, community health screening, risk factor
Suzaku Discovery of Twin Thermal Plasma from the Tornado Nebula
The Tornado nebula (G357.7-0.1) is a mysterious radio source with bright
"head" and faint "tail" located in the direction of the Galactic center (GC)
region. We here report the discovery of two diffuse X-ray sources at the head
and tail of the Tornado with the Suzaku satellite. We found emission lines from
highly ionized atoms in the two sources. The spectra are reproduced by an
optically thin thermal plasma with a common temperature of 0.6-0.7 keV. The
interstellar absorption (NH) of these sources are the same and are slightly
larger than that of the GC distance. Since the estimated distance using the NH
value is consistent with the radio observation of the Tornado, these X-ray
sources are likely associated with the Tornado nebula. The twin-plasma
morphology at the both ends of the Tornado suggests that the system is a
bipolar/outflow source.Comment: Accepted for publication in PASJ (7 pages, 4 figures
Recombining Plasma and Hard X-ray Filament in the Mixed-Morphology Supernova Remnant W44
We report new features of the typical mixed-morphology (MM) supernova remnant
(SNR) W44. In the X-ray spectra obtained with Suzaku, radiative recombination
continua (RRCs) of highly ionized atoms are detected for the first time. The
spectra are well reproduced by a thermal plasma in a recombining phase. The
best-fit parameters suggest that the electron temperature of the shock-heated
matters cooled down rapidly from ,keV to ,keV, possibly due to
adiabatic expansion (rarefaction) occurred years ago. We also
discover hard X-ray emission which shows an arc-like structure
spatially-correlated with a radio continuum filament. The surface brightness
distribution shows a clear anti-correlation with CO (J=2-1) emission
from a molecular cloud observed with NANTEN2. While the hard X-ray is most
likely due to a synchrotron enhancement in the vicinity of the cloud, no
current model can quantitatively predict the observed flux.Comment: 10 pages, 5 figures, accepted for publication in PAS
Screening for Narrow Angles in the Japanese Population Using Scanning Peripheral Anterior Chamber Depth Analyzer
Structural changes in the lacrimal sac epithelium and associated lymphoid tissue during experimental dacryocystitis
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