A5026278907- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Solar and Space Plasma Dynamics
- Atmospheric Ozone and Climate
- Molecular Spectroscopy and Structure
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Ionosphere and magnetosphere dynamics
- Astronomy and Astrophysical Research
- Geomagnetism and Paleomagnetism Studies
- Cosmology and Gravitation Theories
- Spectroscopy and Laser Applications
- Cold Atom Physics and Bose-Einstein Condensates
- Atomic and Molecular Physics
- Geophysics and Gravity Measurements
- Magnetic and Electromagnetic Effects
- Gas Dynamics and Kinetic Theory
- Dust and Plasma Wave Phenomena
- Astronomical Observations and Instrumentation
- Phase Equilibria and Thermodynamics
- Advanced Combustion Engine Technologies
- Quantum Electrodynamics and Casimir Effect
National Astronomical Observatory of Japan
2014-2024
The Graduate University for Advanced Studies, SOKENDAI
2014-2024
National Institutes of Natural Sciences
2004-2022
Niigata University
1990-2000
Michigan United
1992
The University of Tokyo
1986-1988
Hokkaido University
1980-1987
We report Atacama Large Millimeter/submillimeter Array (ALMA) cycle 0 observations of the C18O (J = 2–1), SO (JN 65–54), and 1.3 mm dust continuum toward L1527 IRS, a class solar-type protostar surrounded by an infalling rotating envelope. emission shows strong redshifted absorption against bright associated with strongly suggesting infall motions in The envelope also rotates velocity mostly proportional to r−1, where r is radius, whereas rotation profile at innermost radius (∼54 AU) may be...
We report the first three-dimensional radiation magnetohydrodynamic (RMHD) simulations of protostellar collapse with and without Ohmic dissipation. take into account many physical processes required to study star formation processes, including a realistic equation state. follow evolution from molecular cloud cores until are formed sufficiently high resolutions introducing sink particle. The involved in adopted numerical methods described detail. can calculate only about one year after our...
We have conducted ALMA observations in the 1.3 mm continuum and 12CO (2-1), C18O (2-1) SO (5_6-4_5) lines toward L1489 IRS, a Class I protostar surrounded by Keplerian disk an infalling envelope. The is clearly identified emission, its outer radius (~700 AU) mass (~0.005 Msun) are comparable to those of disks around T Tauri stars. protostellar estimated be 1.6 Msun with inclination angle 66 deg. In addition disk, there blueshifted redshifted off-axis protrusions seen emission pointing north...
We present the first results from B-fields In STar-forming Region Observations (BISTRO) survey, using Sub-millimetre Common-User Bolometer Array 2 (SCUBA-2) camera, with its associated polarimeter (POL-2), on James Clerk Maxwell Telescope (JCMT) in Hawaii. discuss survey's aims and objectives. describe rationale behind questions which survey will aim to answer. The most important of these is role magnetic fields star formation process scale individual filaments cores dense regions. data...
The collapse of rotating magnetized molecular cloud cores is studied with axisymmetric magnetohydrodynamic (MHD) simulations. Because the change equation state interstellar gas, experience several phases during collapse. In earliest isothermal runaway (n ≲ 1010 H2 cm-3), a pseudodisk formed, and it continues to contract until an opaque core formed at center. this disk, number MHD fast slow shock pairs appear whose wave fronts are parallel disk. We assume that gas obeys polytropic exponent Γ...
We performed three-dimensional $N$-body/SPH simulations to study how mass resolution and other model parameters, such as the star-formation efficiency parameter, $C_*$ threshold density for star formation, $n_{\rm th}$ affect structures of galactic gaseous/stellar disk. employed $10^6$–$10^7$ particles resolve a cold ($T \lt$ 100 K) dense ($n_{\rm H} \gt$ cm$^{-3}$) phase well diffuse, hot phases. found that interstellar medium (ISM) distribution young stars were sensitive assumed values...
view Abstract Citations (159) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Equilibria and Evolutions of Magnetized, Rotating, Isothermal Clouds. II. The Extreme Case: Nonrotating Clouds Tomisaka, Kohji ; Ikeuchi, Satoru Nakamura, Takashi Structures nonrotating magnetized clouds are investigated from a standpoint the equilibrium solution cloud confined by an external pressure which is threaded uniform magnetic field at infinity. for wide...
Subsequent to Paper I, the evolution and fragmentation of a rotating magnetized cloud are studied with use three-dimensional MHD nested-grid simulations. After isothermal runaway collapse, an adiabatic gas forms protostellar first core at center cloud. When is stable for in contracting disk, often breaks into several fragments. Conditions binary formation studied. All cores which show fragmentations geometrically thin, as diameter-to-thickness ratio larger than 3. Two patterns found. (1)...
Fragmentation and binary formation processes are studied using three-dimensional resistive MHD nested grid simulations. Starting with a Bonnor-Ebert isothermal cloud rotating in uniform magnetic field, we calculate the evolution from molecular core (n = 104 cm −3) to stellar (n≃ 1022 −3), where n denotes central density. We calculated 147 models different initial magnetic, rotational, thermal energies amplitudes of nonaxisymmetric perturbation. In collapsing cloud, fragmentation is mainly...
We investigated the evolution of interacting disk galaxies using high-resolution $N$-body/SPH simulations, taking into account multiphase nature interstellar medium (ISM). In our a large-scale starburst occurred naturally at collision interface between two gas disks first encounter, resulting in formation star clusters. This is consistent with observations galaxies. The probability distribution function (PDF) density showed clear change during galaxy-galaxy encounter. compression appears as...
We perform a three-dimensional nested-grid radiation magneto-hydrodynamics (RMHD) simulation with self-gravity to study the early phase of low-mass star formation process from rotating molecular cloud core first adiabatic just before second collapse begins. Radiation transfer is handled flux-limited diffusion approximation, operator-splitting and implicit time-integrator. In RMHD simulation, outer region attains higher entropy size larger than that in magnetohydrodynamics simulations...
Abstract The mechanisms causing millimeter-wave polarization in protoplanetary disks are under debate. To disentangle the mechanisms, we observe disk around HL Tau at 3.1 mm with Atacama Large Millimeter/submillimeter Array (ALMA), which had detected CARMA 1.3 mm. We successfully detect ring-like azimuthal polarized emission This indicates that dust grains aligned major axis being direction, is consistent theory of radiative alignment elongated grains, where perpendicular to radiation flux....
The collapse of slowly rotating molecular cloud cores threaded by magnetic fields is investigated high-resolution numerical simulation. Outflow formation in the collapsing also followed. In models examined, core and parent rotate rigidly are initially a uniform field. simulations show that collapses along field lines. dense region rotates faster than as consequence spin-up central during collapse. exhibits significant precession rotation axis, field, disk orientation, with highest low...
Dynamical collapses of magnetized molecular cloud cores are studied with magnetohydrodynamic simulations from the runaway collapse phase to accretion phase. In phase, a disk threaded by magnetic field lines is contracting owing its self-gravity, and evolution well expressed self-similar solution. The central density increases greatly in finite timescale reaches at which an opaque core formed center. After that, matter accretes newly (accretion phase). this stage, rotationally supported...
view Abstract Citations (164) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Starburst Nucleus: Galactic Scale Bipolar Flow Tomisaka, Kohji ; Ikeuchi, Satoru The galactic scale bipolar outflow from the nucleus of a starburst galaxy is studied. A large wind bubble with size few hundred parsecs at nuclear region results frequent supernova explosions as 0.1 supernovae in year or more. By two-dimensional hydrodynamical simulation, it shown that...
We discuss the evolution of magnetic flux density and angular velocity in a molecular cloud core, on basis three-dimensional numerical simulations, which rotating magnetized fragments collapses to form very dense optically thick core >5 × 1010 cm−3. As increases towards formation converge single relationship between two quantities. If is magnetically dominated its approaches 1.5(n/5 cm−3)½ mG, while if rotationally 2.57 10−3 (n/5 yr−1, where n gas. also find that ratio remains nearly...
We followed the collapse of cloud cores with various rotation speed and density frustrations using three-dimensional hydrodynamical simulations by assuming a barotropic equation state examined comprehensive evolution paths from molecule core to stellar core. found that evolutionary depend only on angular velocity initial Ωc0. These agree well predictions Saigo Tomisaka's quasi-equilibrium axisymmetric models SPH calculations Bate. Evolutionary are qualitatively classified into three types....
A first adiabatic core is a transient object formed in the early phase of star formation. The observation believed to be difficult because its short lifetime and low luminosity. On basis radiation hydrodynamic simulations, we propose novel theoretical model cores, Exposed Long-lifetime First (ELF). In very low-mass molecular core, evolves slowly lives longer than 10,000 years accretion rate considerably low. evolution ELFs different from that ordinary cores cooling has significant effect...
We have observed the Class I protostar TMC-1A with Atacama Millimeter/submillimeter Array (ALMA) in 12CO and C18O (J=2-1), 1.3-mm dust continuum emission. Continuum emission a deconvolved size of 0.50"x0.37", perpendicular to outflow, is detected. It most likely traces circumstellar disk around TMC-1A, as previously reported. In contrast, more extended structure detected although it still elongated 3.3"x2.2", indicating that mainly flattened envelope surrounding central protostar. shows...
Abstract We present 850 μ m imaging polarimetry data of the ρ Oph-A core taken with Submillimeter Common-User Bolometer Array-2 (SCUBA-2) and its polarimeter (POL-2) as part our ongoing survey project, <?CDATA ${\boldsymbol{B}}$?> -fields In STar forming RegiOns (BISTRO). The polarization vectors are used to identify orientation magnetic field projected on plane sky at a resolution 0.01 pc. 10 subregions distinct fractions angles in 0.2 pc core; some them can be coherent structure Oph...
We present new observations of the active star-formation region NGC 1333 in Perseus molecular cloud complex from James Clerk Maxwell Telescope B-Fields In Star-forming Region Observations (BISTRO) survey with POL-2 instrument. The BISTRO data cover entire (~1.5 pc x 2 pc) at 0.02 resolution and spatially resolve polarized emission individual filamentary structures for first time. inferred magnetic field structure is as a whole, each filament aligned different position angles relative to...
Abstract We present the Atacama Large Millimeter/submillimeter Array observations of linearly polarized 1.1 mm continuum emission at ∼0.″14 (55 au) resolution and CO ( J = 2−1) ∼1.″5 (590 toward one prestellar (MMS 4), four Class 0 1, MMS 3, 5, 6), I 7), flat-spectrum 2) sources in Orion Molecular Cloud 3 region. The dust disk-like structures clear outflows are detected all except for 4. diameters these structures, ranging from 16 to 97 au, estimated based on deconvolved full width half...
This is the first paper about fragmentation and mass outflow in molecular clouds by using three-dimensional magnetohydrodynamical (MHD) nested-grid simulations. The binary star formation process studied, paying particular attention to of a rotating magnetized cloud. We assume an isothermal cylindrical cloud hydrostatic balance. Non-axisymmetric as well axisymmetric perturbations are added initial state subsequent evolutions studied. evolution characterized three parameters: amplitude...
We investigate the effect of rotation on star formation process quantitatively using axisymmetric numerical calculations. An adiabatic hydrostatic object (the so-called first core) forms in a contracting cloud core, after central region becomes optically thick and continues to contract, driven by mass accretion onto it. The structure rotating core is characterized its total angular momentum Jcore Mcore, both which increase with time. find that evolves constant Jcore/M. Evolutionary paths...