479 research outputs found
Tracking the Complex Absorption in NGC 2110 with Two Suzaku Observations
We present spectral analysis of two Suzaku observations of the Seyfert 2
galaxy, NGC 2110. This source has been known to show complex, variable
absorption which we study in depth by analyzing these two observations set
seven years apart and by comparing to previously analyzed observations with the
XMM-Newton and Chandra observatories. We find that there is a relatively
stable, full-covering absorber with a column density of ~3
cm, with an additional patchy absorber that is likely variable in both
column density and covering fraction over timescales of years, consistent with
clouds in a patchy torus or in the broad line region. We model a soft emission
line complex, likely arising from ionized plasma and consistent with previous
studies. We find no evidence for reflection from an accretion disk in this
source with no contribution from relativistically broadened Fe Ka line emission
nor from a Compton reflection hump.Comment: Accepted to ApJ: March, 201
Online multiscale dynamic topic models
We propose an online topic model for sequentially analyzing the time evolution of topics in document collections. Topics naturally evolve with multiple timescales. For example, some words may be used consistently over one hundred years, while other words emerge and disappear over periods of a few days. Thus, in the proposed model, current topicspecific distributions over words are assumed to be generated based on the multiscale word distributions of the previous epoch. Considering both the long-timescale dependency as well as the short-timescale dependency yields a more robust model. We derive efficient online inference procedures based on a stochastic EM algorithm, in which the model is sequentially updated using newly obtained data; this means that past data are not required to make the inference. We demonstrate the effectiveness of the proposed method in terms of predictive performance and computational efficiency by examining collections of real documents with timestamps
Cool core disturbed: Observational evidence for coexistence of sub-sonic sloshing gas and stripped shock-heated gas around the core of RX J1347.5-1145
RXJ1347.5-1145 (z = 0.451) is one of the most luminous X-ray galaxy clusters,
which hosts a prominent cool core and exhibits a signature of a major merger.
We present the first direct observational evidence for sub-sonic nature of
sloshing motion of the cool core. We find that a residual X-ray image from the
Chandra X-ray Observatory after removing the global emission shows a clear
dipolar pattern characteristic of gas sloshing, whereas we find no significant
residual in the Sunyaev-Zel'dovich effect (SZE) image from the Atacama Large
Millimeter/submillimeter Array (ALMA). We estimate the equation of state of
perturbations in the gas from the X-ray and SZE residual images. The inferred
velocity is 420 +310 -420 km s-1, which is much lower than the adiabatic sound
speed of the intracluster medium in the core. We thus conclude that the
perturbation is nearly isobaric, and gas sloshing motion is consistent with
being in pressure equilibrium. Next, we report evidence for gas stripping of an
infalling subcluster, which likely shock-heats gas to high temperature well in
excess of 20 keV. Using mass distribution inferred from strong lensing images
of the Hubble Space Telescope (HST), we find that the mass peak is located away
from the peak position of stripped gas with statistical significance of >
5{\sigma}. Unlike for the gas sloshing, the velocity inferred from the equation
of state of the excess hot gas is comparable to the adiabatic sound speed
expected for the 20 keV intracluster medium. All of the results support that
the southeast substructure is created by a merger. On the other hand, the
positional offset between the mass and the gas limits the self-interaction
cross section of dark matter to be less than 3.7 h-1 cm2 g-1 (95% CL).Comment: 18 pages, 10 figures, accepted for publication in Ap
Cerebral amyloid angiopathy-related inflammation presenting with steroid-responsive higher brain dysfunction: case report and review of the literature
A 56-year-old man noticed discomfort in his left lower limb, followed by convulsion and numbness in the same area. Magnetic resonance imaging (MRI) showed white matter lesions in the right parietal lobe accompanied by leptomeningeal or leptomeningeal and cortical post-contrast enhancement along the parietal sulci. The patient also exhibited higher brain dysfunction corresponding with the lesions on MRI. Histological pathology disclosed β-amyloid in the blood vessels and perivascular inflammation, which highlights the diagnosis of cerebral amyloid angiopathy (CAA)-related inflammation. Pulse steroid therapy was so effective that clinical and radiological findings immediately improved
Fe-K line probing of material around the AGN central engine with Suzaku
We systematically analyzed the high-quality Suzaku data of 88 Seyfert
galaxies. We obtained a clear relation between the absorption column density
and the equivalent width of the 6.4 keV line above 10 cm,
suggesting a wide-ranging column density of cm with a
similar solid and a Fe abundance of 0.7--1.3 solar for Seyfert 2 galaxies. The
EW of the 6.4 keV line for Seyfert 1 galaxies are typically 40--120 eV,
suggesting the existence of Compton-thick matter like the torus with a column
density of cm and a solid angle of , and no
difference of neutral matter is visible between Seyfert 1 and 2 galaxies. An
absorber with a lower column density of cm for Compton-thin
Seyfert 2 galaxies is suggested to be not a torus but an interstellar medium.
These constraints can be understood by the fact that the 6.4 keV line intensity
ratio against the 10--50 keV flux is almost identical within a range of 2--3 in
many Seyfert galaxies. Interestingly, objects exist with a low EW, 10--30 eV,
of the 6.4 keV line, suggesting that those torus subtends only a small solid
angle of . Ionized Fe-K emission or absorption lines are
detected from several percents of AGNs. Considering the ionization state and
equivalent width, emitters and absorbers of ionized Fe-K lines can be explained
by the same origin, and highly ionized matter is located at the broad line
region. The rapid increase in EW of the ionized Fe-K emission lines at
cm is found, like that of the cold material. It is found
that these features seem to change for brighter objects with more than several
erg/s such that the Fe-K line features become weak. We discuss this
feature, together with the torus structure.Comment: 32 pages, 20 figures, ApJ accepte
ASCA observation of Unusually X-ray Hard Radio Quiet QSO Kaz 102
We have observed a radio-quiet QSO Kaz 102 (z=0.136) with ASCA as a part of
our program of complete spectral characterization of hard X-ray selected AGNs.
We found that Kaz 102 shows unusual spectral properties. A simple power-law
with absorption in our galaxy gave a satisfactory description of the spectrum.
However, it showed a very hard photon index of Gamma=1.0 with no sign of deep
absorption or a prominent spectral feature. We further explored the Compton
reflection with Fe K-alpha line and warm absorber models for hardening the
spectrum. Both gave statistically satisfactory fits. However, the Compton
reflection model requires a very low metal abundance (0.03-0.07 in solar
units).The warm absorber model with no direct component is preferred and gave a
very high ionization parameter xi=200. If this is the case, the values of xi,
warm absorber column density, and variability over about 10 years may suggest
that the warm absorber resides in the broad-line region and crosses the line of
sight to the central X-ray source.Comment: 5 pages, 5 figures. Accepted to Publication of the Astronomical
Society of Japan (Letters
Health impact assessment of PM2.5-related mitigation scenarios using local risk coefficient estimates in 9 Japanese cities
Previous studies have highlighted the negative effects of PM2.5 on mortality, expressed in terms of attributable deaths and life years lost. However, there are very few studies assessing the health impacts of air pollution in terms of economic burden/benefits. This study assessed the health impact of two hypothetical interventions among sex- and age-specific risk populations using a robust risk estimation and economic valuation process. We utilized the sex- and age-stratified daily all-cause mortality together with the daily PM2.5 of the 9 Japanese cities from 2002 to 2008 in estimating the relative risks. The estimated risks were then utilized for the economic valuation of co-benefits/burden with respect to the two hypothetical PM2.5-related mitigation scenarios, in comparison to status quo, namely: i) decrease to Japanese standards, and ii) decrease to WHO standards. Impact of these interventions on health were assessed using the following HIA metrics: attributable mortality, attributable years life lost, and environmental health impact. A 10-μg/m3 increase in PM2.5 would increase the risk by 0.52% (95% CI: −0.91% to 1.99%) for all-cause mortality, with varying risk estimates per subgroup. High economic burdens were estimated at status quo, with particularly distinct burden difference for age-specific mortality; 0.40 trillion yen (0–64 y.o.) and 1.50 trillion yen (>64 y.o.). If stricter standards, relative to status quo, were to be enforced, i.e. WHO standard, there is a potential to yield economic benefits in the same risk population; 0.26 trillion yen (0–64 y.o.) and 0.98 trillion yen (>64 y.o.). We did not observe any substantial difference with the burden and benefit related to sex-specific mortality. Using the estimated local risk coefficients complemented with the valuation of the risks, policymaking entities will have the opportunity to operate their own HIA to assess the relevant air pollution-related health impacts
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