A5050379623- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Astronomical Observations and Instrumentation
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Solar and Space Plasma Dynamics
- History and Developments in Astronomy
- Nuclear physics research studies
- Astrophysical Phenomena and Observations
- Adaptive optics and wavefront sensing
- Calibration and Measurement Techniques
- Geophysics and Gravity Measurements
- Spacecraft Design and Technology
- Neutrino Physics Research
- Astronomical and nuclear sciences
- CCD and CMOS Imaging Sensors
- Inertial Sensor and Navigation
- Scientific Research and Discoveries
- Phase Equilibria and Thermodynamics
- Cosmology and Gravitation Theories
- Planetary Science and Exploration
National Astronomical Observatory of Japan
2016-2025
The Graduate University for Advanced Studies, SOKENDAI
2010-2017
National Institutes of Natural Sciences
2004-2010
Astronomical Observatory
1999-2009
Center for Astrophysics Harvard & Smithsonian
1996
The University of Tokyo
1990-1993
Tokyo University of Science
1991
The predicted nucleosynthesis products of Type Ia and II supernovae are combined with various parameter ratios compared the solar abundances heavy elements their isotopes, also in LMC SMC. Aided by a reasonable model galactic chemical evolution, ratio total numbers (of all time) to that best reproduces observed is determined be NIa/NII = 0.15 for Galaxy, agreement current observations. For MCs, however, this larger than yielding 0.2–0.3. We discuss several possible star formation history...
We introduce a metallicity dependence of the Type Ia supernova (SN Ia) rate into Galactic and cosmic chemical evolution models. In our SN progenitor scenario, accreting white dwarf (WD) blows strong wind to reach Chandrasekhar mass limit. If iron abundance progenitors is as low [Fe/H] ≲ -1, then too weak for SNe occur. Our model successfully reproduces observed in solar neighborhood. make following predictions that can test this effect:(1) are not found environments such galaxies outskirts...
Abstract A general method and formulae to derive the CO-to-H2 conversion factor in galaxies as a function of metallicity are presented based on an analysis observed data for obtained nearby spiral dwarf irregular galaxies. From CO eight we following formula, which gives (X*) metallicity: log X*= −1.0 (12 +log O/H)+ A, where X* = NH2 / ICO × 10−20 H2/(K km s−1) is constant. Since dependent luminosity galaxies, derived correlation between absolute magnitude We also investigated dependence...
Abstract The Japan Astrometry Satellite Mission for INfrared Exploration (JASMINE) is a planned M-class science space mission by the Institute of Space and Astronautical Science, Aerospace Agency. JASMINE has two main goals. One Galactic archaeology with Center survey, which aims to reveal Milky Way’s central core structure formation history from Gaia-level (∼25 ${\mu} $as) astrometry in near-infrared (NIR) Hw band (1.0–1.6 $m). other an exoplanet discover transiting Earth-like exoplanets...
The origin of r-process elements remains unidentified and still puzzles us. recent discovery evidence for the ejection from a short-duration γ-ray burst singled out neutron star mergers (NSMs) as their origin. In contrast, core-collapse supernovae are ruled main heavy (A > 110) by numerical simulations. However, properties characterizing NSM events – rarity high yield per event have been claimed to be incompatible with observed stellar records on in Galaxy. We add this picture our results,...
We make a prediction of the cosmic supernova rate history as composite rates in spiral and elliptical galaxies. include metallicity effect on evolution Type Ia (SN Ia) progenitors construct detailed models for evolutions galaxies clusters field to meet latest observational constraints. In cluster environment, synthesized star formation (SFR) has an excess at z ≳ 3 corresponding early starburst ellipticals shallower slope from present peak redshift ~ 1.4 compared with Madau's plot. we assume...
view Abstract Citations (136) References (60) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Lifetime of Type Ia Supernova Progenitors Deduced from the Chemical Evolution in Solar Neighborhood Yoshii, Yuzuru ; Tsujimoto, Takuji Nomoto, Ken'ichi Using chemical evolution model which allows material infall outside disk region, we have determined lifetime tIa supernova progenitors and timescale tin that simultaneously reproduce major observational features...
view Abstract Citations (113) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Low-Mass Helium Star Models for Type Ib Supernovae: Light Curves, Mixing, and Nucleosynthesis Shigeyama, Toshikazu ; Nomoto, Ken'ichi Tsujimoto, Takuji Hashimoto, Masa-Aki curves, Rayleigh-Taylor instability, nucleosynthesis of exploding helium stars are examined to look relevant models supernovae, especially SN 1983N 1983I whose light curves decline as fast Ia...
Context . Given their high luminosities ( L ≳ 10 4 ⊙ ), red supergiants (RSGs) are good tracers of the chemical abundances young stellar population in Milky Way and nearby galaxies. However, previous abundance analyses tailored to RSGs suffer some systematic uncertainties originating in, most notably, synthesized molecular spectral lines for RSGs. Aims We establish a new analysis procedure that circumvents difficulties faced works, test with ten observed near-infrared high-resolution...
Abstract The super star cluster NGC1569-B has recently been observed to have an extremely high [Ba/Fe]. We consider that the [Ba/Fe] (∼1.3) is due chemical enrichment of giant molecular clouds by either collapsars, neutron mergers, or magneto-rotational supernovae, and thereby investigate which three polluters can best reproduce Since it found collapsars such Ba abundance, we numerically formation in NGC1569 using chemodynamical simulations merging dwarf galaxies with collapsars. principal...
Using results of nucleosynthesis calculations for theoretical core-collapse supernova models with various progenitor's masses, it is shown that abundance patterns C, Mg, Si, Ca, and H seen in extremely metal-deficient stars [Fe/H] < -2.5 follow those the individual first generation remnants (SNRs). This suggests most were made from (SN) events. To obtain ratio heavy elements to hydrogen, a formula derived estimate mass hydrogen swept up by SNR when occurs interstellar matter primordial...
We simulate the dynamical and chemical evolution of a dwarf galaxy embedded in dark matter halo, using three-dimensional N-body/smoothed particle hydrodynamics (SPH) simulation code combined with stellar population synthesis. The initial condition is adopted accord 1010 M☉ virialized sphere 1 σ cold perturbation which contains 10% baryonic mass. A supersonic spherical outflow driven by first starburst near center produces an expanding supershell stars are subsequently formed. Consecutive...
Abstract The stellar record of elemental abundances in satellite galaxies is important to identify the origin r -process because such a small system could have hosted single event, which would distinguish member stars that are formed before and after event through evidence considerable difference elements, as found ultra-faint dwarf galaxy Reticulum II (Ret II). However, limited mass these systems prevents us from collecting information sufficient number individual satellites. Hence, it...
ABSTRACT Recent JWST observations of the z = 10.6 galaxy GN-z11 have revealed a very high gas-phase nitrogen abundance (higher than four times solar value), small half-light radius (≈60 pc), and large stellar mass (Ms ≈ 109 M⊙) for its size. We consider that this object is forming galactic nucleus or ultra-compact dwarf rather proto globular cluster, thereby investigate chemical pattern using one-zone evolution models. The principal results models are as follows. observed log (N/O) &gt;...
Context. Classical Cepheids (CCs) are solid distance indicators and tracers of young stellar populations. Dating back to the beginning 20th century, they have been safely adopted trace rotation, kinematics, chemical enrichment history Galactic thin disk. Aims. The main aim this investigation is provide iron, oxygen, sulfur abundances for largest most homogeneous sample CCs analyzed so far (1118 spectra 356 objects). current sample, containing 70 which spectroscopic metal provided first time,...
A model for Galactic chemical evolution, driven by supernova-induced star formation, is formulated and used to examine the nature of halo at early epochs. In this model, new stars are formed following each supernova event; thus, their abundance pattern determined combination heavy elements ejected from itself those that already present in interstellar gas swept up remnant. The end result a prediction large scatter ratios among low-metallicity stars, reflecting different nucleosynthesis yield...
Results of recent observations the Galactic bulge demand that we discard a simple picture its formation, suggesting presence two stellar populations represented by peaks metallicity distribution (MDF) in bulge. To assess this issue, construct chemical evolution models have been updated respects: First, delay time (DTD) type Ia supernovae (SNe Ia) recently revealed extensive SN surveys is incorporated into models. Second, nucleosynthesis clock, s-processing asymptotic giant branch (AGB)...
Classical Cepheids are useful tracers of the Galactic young stellar population because their distances and ages can be determined from period-luminosity period-age relations. In addition, radial velocities chemical abundance derived spectroscopic observations, providing further insights into structure evolution Galaxy. Here, we report classical near Center, three which were reported in 2011, other for first time. The these suggest that stars orbit within Nuclear Stellar Disk, a group...
ABSTRACT Recent observations have revealed that at least eight globular clusters (GCs) in the Galaxy show internal abundance spreads [Fe/H]. We investigate origin of these “anomalous” GCs using numerical simulations dwarfs orbiting around and chemical evolution model hosting GCs. The principal results are as follows. formed a host dwarf galaxy with total mass <?CDATA $\sim {10}^{10}\,{M}_{\odot }$?> can merge to form single nuclear GC before is completely destroyed by Galaxy, if they massive...
Abstract WINERED is a novel near-infrared (NIR) high-resolution spectrograph (HRS) that pursues the highest possible sensitivity to realize high-precision spectroscopy in NIR as optical wavelength range. covers 0.9–1.35 μ m ( z , Y and J -bands) with three modes (Wide mode two Hires modes) at maximum spectral resolutions of R = 28,000 70,000. For fulfilling objective, designed an unprecedentedly high instrument throughput (up 50% including quantum efficiency array) times or more than other...
Abstract The search for Population III stars has fascinated and eluded astrophysicists decades. One promising place capturing evidence of their presence must be high-redshift objects; signatures should recorded in characteristic chemical abundances. We deduce the Fe Mg abundances broadline region (BLR) from intensities ultraviolet ii emission lines near-infrared spectrum UKIDSS Large Area Survey (ULAS) J1342+0928 at z = 7.54, by advancing our novel flux-to-abundance conversion method...
Abstract Fluxes of the diffuse supernova neutrino background (DSNB) are calculated based on a new modeling galactic chemical evolution, where variable stellar initial mass function (IMF), depending galaxy type, is introduced and black hole (BH) formation from failed considered for progenitors heavier than 18 M ⊙ . The flux calculations performed different combinations star rate, nuclear equation state, hierarchy, to examine systematic effects these factors. In any case, our model predicts...