A5037708825- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Cosmology and Gravitation Theories
- Astro and Planetary Science
- Dark Matter and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Molecular Spectroscopy and Structure
- Astrophysical Phenomena and Observations
- Advanced ceramic materials synthesis
- Smart Materials for Construction
- Atomic and Subatomic Physics Research
- Advanced Thermoelectric Materials and Devices
- Photonic Crystals and Applications
- Photonic and Optical Devices
- Nuclear materials and radiation effects
- Catalytic Processes in Materials Science
- Muon and positron interactions and applications
- Advanced materials and composites
- Optical Coatings and Gratings
- ZnO doping and properties
- Phase Equilibria and Thermodynamics
- Gas Sensing Nanomaterials and Sensors
- Gamma-ray bursts and supernovae
- Radio Astronomy Observations and Technology
The University of Tokyo
2013-2025
Tokyo University of Science
1998-2025
Kanagawa University
2023-2025
Inpex (Japan)
2024
Kyushu University
2018-2023
The University of Texas at Austin
2016-2018
National Hospital Organization
2018
Kavli Institute for the Physics and Mathematics of the Universe
2012
Nagasaki University
2007
Toyota Central Research and Development Laboratories (Japan)
2002-2004
We perform a large set of radiation hydrodynamics simulations primordial star formation in fully cosmological context. Our statistical sample 100 First Stars show that the first generation stars have wide mass distribution M_popIII = 10 ~ 1000 M_sun. run to generate star-forming gas clouds. then follow protostar each cloud and subsequent protostellar evolution until accretion onto is halted by stellar radiative feedback. The rates differ significantly among clouds which largely determine...
We perform a large set of cosmological simulations early structure formation and follow the evolution 1540 star-forming gas clouds to derive mass distribution primordial stars. The star in our is characterized by two distinct populations, so-called Population III.1 stars formed under influence far ultraviolet (FUV) radiation (Population III.2D stars). In this work, we determine stellar masses using dependences on physical properties cloud and/or external photodissociating intensity from...
ABSTRACT We present coupled stellar evolution (SE) and 3D radiation-hydrodynamic (RHD) simulations of the primordial protostars, their immediate environment, dynamic accretion history under influence ionizing dissociating UV feedback. Our SE RHD calculations result in a wide diversity final masses covering 10 <?CDATA ${M}_{\odot }$?> ≲ M * 3 . The formation very massive (≳250 ) stars is possible weak feedback, whereas ordinary (a few ×10 form when feedback can efficiently halt accretion....
We present an overview of the Large Program, ``Early Planet Formation in Embedded Disks (eDisk)'', conducted with Atacama Millimeter/submillimeter Array (ALMA). The ubiquitous detections substructures, particularly rings and gaps, protoplanetary disks around T Tauri stars raise possibility that at least some planet formation may have already started during embedded stages star formation. In order to address exactly how when is initiated, program focuses on searching for substructures 12...
Making the first supermassive black holes Supermassive existed less than a billion years after Big Bang. Because can grow at maximum rate that depends on their current mass, it has been difficult to understand how such massive could have formed so quickly. Hirano et al. developed simulations show streaming motions—velocity offsets between gas and dark matter components—could produced with tens of thousands solar masses in early universe. That's big enough into we observe today. Science ,...
Abstract We study the formation of massive Population III binary stars using a newly developed radiation hydrodynamics code with adaptive mesh refinement and ray-tracing methods. follow evolution typical primordial star-forming cloud obtained from cosmological simulation. Several protostars form as result disk fragmentation grow in mass by gas accretion, which is finally quenched feedback protostars. Our enables us, for first time, to consider both ionizing dissociating multiple protostars,...
We study the formation of massive black holes in first star clusters. locate star-forming gas clouds protogalactic haloes ≳107 M⊙ cosmological hydrodynamics simulations and use them to generate initial conditions for clusters with masses ∼105 M⊙. then perform a series direct-tree hybrid N-body follow runaway stellar collisions dense In all cluster models except one, occur within few million years, mass central, most reaches ∼400–1900 Such very stars collapse leave intermediate-mass (IMBHs)....
Gravitational collapse of a massive primordial gas cloud is thought to be promising path for the formation supermassive blackholes in early universe. We study conditions so-called direct (DC) blackhole fully cosmological context. combine semianalytic model galaxy with halo merger trees constructed from dark matter $N$-body simulations. locate total 68 possible DC sites volume $20\;h^{-1}\;\mathrm{Mpc}$ on side. then perform hydrodynamics simulations 42 selected halos detail evolution clouds...
Abstract We present observations of the Class 0 protostar IRAS 16544–1604 in CB 68 from “Early Planet Formation Embedded Disks (eDisk)” ALMA Large program. The target continuum and lines at 1.3 mm with an angular resolution ∼5 au. image reveals a dusty protostellar disk radius ∼30 au seen close to edge-on asymmetric structures along both major minor axes. While asymmetry axis can be interpreted as effect dust flaring, comes real nonaxisymmetric structure. C 18 O cubes clearly show gas that...
Abstract Recent observations by the James Webb Space Telescope (JWST) discovered unexpectedly abundant luminous galaxies at high redshift, posing possibly a severe challenge to popular galaxy formation models. We study early structure in cosmological model with blue, tilted power spectrum (BTPS) given <?CDATA $P(k)\propto {k}^{{m}_{{\rm{s}}}}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>P</mml:mi> <mml:mo stretchy="false">(</mml:mo>...
The initial mass function of the first, Population III (Pop III), stars plays a vital role in shaping galaxy formation and evolution early Universe. One key remaining issue is final fate secondary protostars formed accretion disc, specifically whether they merge or survive. We perform suite hydrodynamic simulations complex interplay between fragmentation, protostellar accretion, merging inside dark matter minihaloes. Instead traditional sink particle method, we employ stiff equation state...
XMASS, a low-background, large liquid-xenon detector, was used to search for solar axions that would be produced by bremsstrahlung and Compton effects in the Sun. With an exposure of 5.6 ton days liquid xenon, model-independent limit on coupling mass ≪1 keV is |gaee|<5.4×10−11 (90% C.L.), which factor two stronger than existing experimental limit. The bounds axion masses DFSZ KSVZ models are 1.9 250 eV, respectively. In range 10–40 keV, this study most stringent limit, better previously...
Metal enrichment by first-generation (Pop III) stars is the very first step of matter cycle in structure formation and it followed extremely metal-poor (EMP) stars. To investigate process Pop III stars, we carry out a series numerical simulations including feedback effects photoionization supernovae (SNe) with range masses minihaloes (MHs), Mhalo, MPopIII. We find that metal-rich ejecta reach neighbouring haloes external (EE) occurs when H ii region expands before SN explosion. The are only...
In recent years, the discovery of massive quasars at z~7 has provided a striking challenge to our understanding origin and growth supermassive black holes in early Universe. Mounting observational theoretical evidence indicates viability seeds, formed by collapse stars, as progenitor model for such early, accreting holes. Although considerable progress been made understanding, many questions remain regarding how (and often) objects may form, they live die, next generation observatories yield...
Constraining the physical and chemical structure of young embedded disks is crucial to understanding earliest stages planet formation. As part Early Planet Formation in Embedded Disks Atacama Large Millimeter/submillimeter Array Program, we present high spatial resolution ($\sim$0$.\!\!^{\prime\prime}$1 or $\sim$15 au) observations 1.3 mm continuum $^{13}$CO $J=$ 2-1, C$^{18}$O SO $J_N=$ $6_5$-$5_4$ molecular lines toward disk around Class I protostar L1489 IRS. The emission shows a...
ABSTRACT Density inhomogeneity in the intergalactic medium (IGM) can boost recombination rate of ionized gas substantially, affecting growth H ii regions during reionization. Previous attempts to quantify this effect typically failed resolve down Jeans scale preionization IGM, which is important establishing effect, along with hydrodynamical back-reaction reionization on it. Toward that end, we perform a set fully coupled, radiation-hydrodynamics simulations from cosmological initial...
Abstract We report on an Atacama Large Millimeter/submillimeter Array study of the Class I or II intermediate-mass protostar DK Cha in Chamaeleon region. The 12 CO( J = 2–1) images have angular resolution ∼1″ (∼250 au) and show high-velocity blueshifted (≳70 km s −1 ) redshifted (≳50 emissions, which 3000 au scale crescent-shaped structures around protostellar disk traced 1.3 mm continuum. Because components CO emission are associated with protostar, we concluded that traces pole-on outflow....
Abstract We present an analytic description of the spherically symmetric gravitational collapse radiatively cooling gas clouds, which illustrates mechanism by radiative induces instability at a characteristic mass scale determined microphysics gas. The approach is based on developing density-temperature relationship into full dynamical model. convert barotropic equation state, we develop refined criterion and calculate density velocity profiles From these quantities determine time-dependent...
Recent high-resolution observations have enabled detailed investigations of the circumstellar environments around Class 0/I protostars. Several studies reported that infall velocity envelope is a few times smaller than free-fall inferred from protostellar masses estimated via observed rotational their Keplerian disks. To explore physical origins slow infall, we perform set three-dimensional non-ideal magnetohydrodynamic simulations star formation process, extending to $10^5$ yr after...
The formation and mass distribution of the first stars depend on various environmental factors in early universe. We compare 120 cosmological hydrodynamical simulations to explore how baryonic streaming velocity (SV) relative dark matter affects stars. vary SV from zero three times its cosmic root-mean-square value, $v_{\rm SV}/\sigma_{\rm SV}=0-3$, identify 20 representative halos simulations. For each model, we follow evolution a primordial star-forming cloud appearance dense core (with...
We develop a new semi-analytic framework of Population (Pop) III and subsequent galaxy formation designed to run on dark matter halo merger trees. In our framework, we consider the effect Lyman-Werner flux from Pop II stars baryon streaming velocity critical minihalo mass for formation. Our model incorporates feedback in self-consistent way, therefore, spatial variation naturally emerges. The depends properties as reproducing radiative hydrodynamical simulation results. perform statistical...
Abstract We have observed the late Class I protostellar source Elias 29 at a spatial resolution of 70 au with Atacama Large Millimeter/submillimeter Array as part FAUST Program. focus on line emission SO, while that 34 C 18 O, CS, SiO, H 13 CO + , and DCO are used supplementarily. The distribution SO rotational temperature ( T rot (SO)) is evaluated by using intensity ratio its two excitation lines. Besides in vicinity protostar, hot spots found distance 500 from protostar; (SO) locally...
Abstract Recent high-resolution observations have enabled detailed investigations of the circumstellar environments around Class 0/I protostars. Several studies reported that infall velocity envelope is a few times smaller than freefall inferred from protostellar masses estimated via observed rotational their Keplerian disks. To explore physical origins slow infall, we perform set three-dimensional resistive magnetohydrodynamic simulations star formation process, extending to 10 5 yr after...