83 research outputs found
Efficacy and Safety of Endoscopic Ultrasound-guided Ethanol Ablation Therapy for Pancreatic Neuroendocrine Tumors
Recently, endoscopic ultrasonography (EUS)-guided ethanol ablation for small pancreatic neuroendocrine tumors (p-NETs) has been reported. However, the efficacy and safety of the technique remain unclear. We have launched a prospective pilot study of EUS-guided ethanol ablation for p-NETs. The major eligibility criteria are the presence of a pathologically diagnosed grade (G) 1 or G2 p-NET, a tumor size of 2cm, and being a poor candidate for surgery. A total of 5 patients will be treated. The primary endpoint will be the complete ablation rate at 1 month after treatment
EMPRESS. II. Highly Fe-Enriched Metal-poor Galaxies with (Fe/O) and (O/H) : Possible Traces of Super Massive () Stars in Early Galaxies
We present element abundance ratios and ionizing radiation of local young
low-mass (~ M_sun) extremely metal poor galaxies (EMPGs) with a 2%
solar oxygen abundance (O/H)_sun and a high specific star-formation rate
(sSFR~300 Gyr), and other (extremely) metal poor galaxies, which are
compiled from Extremely Metal-Poor Representatives Explored by the Subaru
Survey (EMPRESS) and the literature. Weak emission lines such as [FeIII]4658
and HeII4686 are detected in very deep optical spectra of the EMPGs taken with
8m-class telescopes including Keck and Subaru (Kojima et al. 2019, Izotov et
al. 2018), enabling us to derive element abundance ratios with photoionization
models. We find that neon- and argon-to-oxygen ratios are comparable to those
of known local dwarf galaxies, and that the nitrogen-to-oxygen abundance ratios
(N/O) are lower than 20% (N/O)_sun consistent with the low oxygen abundance.
However, the iron-to-oxygen abundance ratios (Fe/O) of the EMPGs are generally
high; the EMPGs with the 2%-solar oxygen abundance show high Fe/O ratios of
~90-140% (Fe/O)_sun, which are unlikely explained by suggested scenarios of
Type Ia supernova iron productions, iron's dust depletion, and metal-poor gas
inflow onto previously metal-riched galaxies with solar abundances. Moreover,
these EMPGs have very high HeII4686/H ratios of ~1/40, which are not
reproduced by existing models of high-mass X-ray binaries whose progenitor
stellar masses are less than 120 M_sun. Comparing stellar-nucleosynthesis and
photoionization models with a comprehensive sample of EMPGs identified by this
and previous EMPG studies, we propose that both the high Fe/O ratios and the
high HeII4686/H ratios are explained by the past existence of super
massive (300 M_sun) stars, which may evolve into intermediate-mass black
holes (100 M_sun).Comment: ApJ in press. 23 pages, 7 Figures, 6 Table
Extremely Metal-Poor Representatives Explored by the Subaru Survey (EMPRESS). I. A Successful Machine Learning Selection of Metal-Poor Galaxies and the Discovery of a Galaxy with M*<10^6 M_sun and 0.016 Z_sun
We have initiated a new survey for local extremely metal-poor galaxies
(EMPGs) with Subaru/Hyper Suprime-Cam (HSC) large-area (~500 deg^2) optical
images reaching a 5 sigma limit of ~26 magnitude, about 100 times deeper than
the Sloan Digital Sky Survey (SDSS). To select Z/Z_sun<0.1 EMPGs from ~40
million sources detected in the Subaru images, we first develop a
machine-learning (ML) classifier based on a deep neural network algorithm with
a training data set consisting of optical photometry of galaxy, star, and QSO
models. We test our ML classifier with SDSS objects having spectroscopic
metallicity measurements, and confirm that our ML classifier accomplishes
86%-completeness and 46%-purity EMPG classifications with photometric data.
Applying our ML classifier to the photometric data of the Subaru sources as
well as faint SDSS objects with no spectroscopic data, we obtain 27 and 86 EMPG
candidates from the Subaru and SDSS photometric data, respectively. We conduct
optical follow-up spectroscopy for 10 out of our EMPG candidates with
Magellan/LDSS-3+MagE, Keck/DEIMOS, and Subaru/FOCAS, and find that the 10 EMPG
candidates are star-forming galaxies at z=0.007-0.03 with large H_beta
equivalent widths of 104-265 A, stellar masses of log(M*/M_sun)=5.0-7.1, and
high specific star-formation rates of ~300 Gyr^{-1}, which are similar to those
of early galaxies at z>6 reported recently. We spectroscopically confirm that 3
out of 10 candidates are truly EMPGs with Z/Z_sun<0.1, one of which is HSC
J1631+4426, the most metal-poor galaxy with Z/Z_sun=0.016 reported ever.Comment: 30 pages, 26 figures, and 8 tables; (Revision: metallicities changed
due to the use of a more pricise dust correction method, but conclusion does
not change, Minor: a table, some figures, and sentences are added for a clear
explanation.
EMPRESS. IX. Extremely Metal-Poor Galaxies are Very Gas-Rich Dispersion-Dominated Systems: Will JWST Witness Gaseous Turbulent High-z Primordial Galaxies?
We present kinematics of 6 local extremely metal-poor galaxies (EMPGs) with
low metallicities () and low stellar masses
(). Taking deep medium-high resolution
() integral-field spectra with 8.2-m Subaru, we resolve the small
inner velocity gradients and dispersions of the EMPGs with H emission.
Carefully masking out sub-structures originated by inflow and/or outflow, we
fit 3-dimensional disk models to the observed H flux, velocity, and
velocity-dispersion maps. All the EMPGs show rotational velocities () of 5--23 km s smaller than the velocity dispersions
() of 17--31 km s, indicating dispersion-dominated () systems affected by inflow and/or outflow. Except
for two EMPGs with large uncertainties, we find that the EMPGs have very large
gas-mass fractions of . Comparing our results with
other H kinematics studies, we find that
decreases and increases with decreasing metallicity, decreasing
stellar mass, and increasing specific star-formation rate. We also find that
simulated high- () forming galaxies have gas fractions and dynamics
similar to the observed EMPGs. Our EMPG observations and the simulations
suggest that primordial galaxies are gas-rich dispersion-dominated systems,
which would be identified by the forthcoming James Webb Space Telescope (JWST)
observations at .Comment: Submitted to ApJ; After revisio
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