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Masahiro N Machida Last modified date:2019.11.30

Associate Professor / Material Science of Solar Planets
Department of Earth and Planetary Sciences
Faculty of Sciences

Graduate School
Undergraduate School

Formation and Evolution of Planetary Systems, Masahiro Machida's HP .
Academic Degree
Doctor of Philosophy
Country of degree conferring institution (Overseas)
Field of Specialization
Total Priod of education and research career in the foreign country
Outline Activities
Theoretical Astronomy and Astrophysics.
I focus on the following topics with numerical simulation.

(1) Gas-giant Planet and its Satellite Formation
It is considered that the gas giant planet such as Jupiter and Saturn in our solar
system is formed after the gas accretes onto a solid core with several earth mass.
However, we cannot well understand the gas accretion process and growth process
of the gas giant planet. This study focuses on the formation and evolution of the
gas giant planet and its circumplanetary disk using numerical simulation. In addition,
the formation process of regular satellites around the gas giant planet is investigated.

(2) Planet Formation by Gravitational Instability
Recently, direct imaging of exo-planet showed that several planets orbit in the region
much far from the central star. It is difficult to form such planets by classical planet
formation scenario (core accretion scenario). In this study, I investigate the planet
formation by gravitational instability of the disk. In this scenario, fragmentation occurs
in the protoplantary disk by gravitational instability and protoplanet appears. To discuss
validity of this scenario, I calculate the formation and evolution of star, disk and planet
from prestellar cloud stage with nested grid simulation code.

(3) Protostellar Jet and Star Formation Efficiency
The star at its formation ejects a large fraction of the mass in the parent cloud by
protostellar outflow. The protostellar outflow transfers an excess angular momentum
of the molecular cloud. In this study, I calculate the formation of the star and propagation
of protostellar outflow to determine the star formation efficiency. In addition, we compare
the results by ALMA with simulations.

(4) First Star Formation and Effect of the Magnetic Field
It is considered that only a massive star forms in the early universe. The magnetic field is
very important in the present-day star formation process because it controls the star
formation efficiency and determines resulting stellar mass. In the early universe, it is
expected that the magnetic field is extremely weak and hardly affects the star formation.
The magnetic field largely dissipates in the collapsing gas in the present day star formation,
while the magnetic field is always coupled with neutral gas in the primordial collapsing cloud.
Thus, the magnetic field continues to be amplified and may affect the star formation even
in the early universe. In this study, we calculate the evolution of the magnetized primordial
gas cloud and investigate the effect of the magnetic field on the first star formation.
Research Interests
  • Theoretical study about black hole binary formation
    keyword : Black hole
  • Formation of Gas Giant Planet
    keyword : Numerical simulation, Protoplanetary Disk, Planet
  • Satellite Formation
    keyword : Satellite, Circum-planetary disk, Gas giant planet
  • Star Formation
    keyword : MHD, Jet, Outflow
  • Star Formation in the Early Universe, First Star Formation
    keyword : Cosmology, Primordial gas
Academic Activities
1. Masahiro N. Machida, Shantanu Basu, The First Two Thousand Years of Star Formation, Astrophysical Journal, 10.3847/1538-4357/ab18a7, 876, 2, 2019.05, Starting from a prestellar core with a size of 1.2 ×104 au, we calculate the evolution of a gravitationally collapsing core until ∼2000 yr after protostar formation using a three-dimensional resistive magnetohydrodynamic simulation in which the protostar is resolved with a spatial resolution of 5.6 ×10-3 au. Following protostar formation, a rotationally supported disk is formed. Although the disk size is as small as ∼2-4 au, it remains present until the end of the simulation. Since the magnetic field dissipates and the angular momentum is then not effectively transferred by magnetic effects, the disk surface density gradually increases, and spiral arms develop due to gravitational instability. The disk angular momentum is then transferred mainly by gravitational torques, which induce an episodic mass accretion onto the central protostar. The episodic accretion causes a highly time-variable mass ejection (the high-velocity jet) near the disk inner edge, where the magnetic field is well coupled with the neutral gas. As the mass of the central protostar increases, the jet velocity gradually increases and exceeds ∼100 . The jet opening angle widens with time at its base, while the jet keeps a very good collimation on a large scale. In addition, a low-velocity outflow is driven from the disk outer edge. A cavity-like structure, a bow shock, and several knots, all of which are usually observed in star-forming regions, are produced in the outflowing region..
2. 町田 正博, 中村 鉄平, Accretion phase of star formation in clouds with different metallicities, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 10.1093/mnras/stu2633, 448, 2, 1405-1429, 2015.04, [URL], The main accretion phase of star formation is investigated in clouds with different metallicities in the range 0 ≤ Z ≤ Z⊙, resolving the protostellar radius. Starting from a near-equilibrium prestellar cloud, we calculate the cloud evolution up to ˜100 yr after the first protostar forms. Star formation differs considerably between clouds with lower (Z ≤ 10-4 Z⊙) and higher (Z > 10-4 Z⊙) metallicities. Fragmentation frequently occurs and many protostars appear without a stable circumstellar disc in lower-metallicity clouds. In these clouds, although protostars mutually interact and some are ejected from the cloud centre, many remain as a small stellar cluster. In contrast, higher-metallicity clouds produce a single protostar surrounded by a nearly stable rotation-supported disc. In these clouds, although fragmentation occasionally occurs in the disc, the fragments migrate inwards and finally fall on to the central protostar. The difference in cloud evolution is due to different thermal evolutions and mass accretion rates. The thermal evolution of the cloud determines the emergence and lifetime of the first core. The first core develops prior to the formation of a protostar in higher-metallicity clouds, whereas no (obvious) first core appears in lower-metallicity clouds. The first core evolves into a circumstellar disc with a spiral pattern, which effectively transfers the angular momentum outwards and suppresses frequent fragmentation. In lower-metallicity clouds, the higher mass accretion rate increases the disc surface density within a very short time, rendering the disc unstable to self-gravity and inducing vigorous fragmentation..
3. Tanigawa, Takayuki, Maruta, Akito, Masahiro N Machida, Accretion of Solid Materials onto Circumplanetary Disks from Protoplanetary Disks, The Astrophysical Journal, 10.1088/0004-637X/784/2/109, 784, 109, 2014.04, [URL], We investigate the accretion of solid materials onto circumplanetary disks from heliocentric orbits rotating in protoplanetary disks, which is a key process for the formation of regular satellite systems. In the late stage of the gas-capturing phase of giant planet formation, the accreting gas from protoplanetary disks forms circumplanetary disks. Since the accretion flow toward the circumplanetary disks affects the particle motion through gas drag force, we use hydrodynamic simulation data for the gas drag term to calculate the motion of solid materials. We consider a wide range of size for the solid particles (10-2-106 m), and find that the accretion efficiency of the solid particles peaks around 10 m sized particles because energy dissipation of drag with circum-planetary disk gas in this size regime is most effective. The efficiency for particles larger than 10 m becomes lower because gas drag becomes less effective. For particles smaller than 10 m, the efficiency is lower because the particles are strongly coupled with the background gas flow, which prevents particles from accretion. We also find that the distance from the planet where the particles are captured by the circumplanetary disks is in a narrow range and well described as a function of the particle size..
4. Masahiro N Machida, Inutsuka Shu-ichiro, Matsumoto Tomoaki, Conditions for circumstellar disc formation: effects of initial cloud configuration and sink treatment, Monthly Notices of the Royal Astronomical Society, 10.1093/mnras/stt2343, 438, 3, 2278-2306, 2014.03, [URL], The formation of a circumstellar disc in collapsing cloud cores is investigated with three-dimensional magnetohydrodynamic simulations. We prepare four types of initial cloud having different density profiles and calculate their evolution with or without a sink. To investigate the effect of magnetic dissipation on disc formation, Ohmic dissipation is considered in some models. Calculations show that disc formation is very sensitive to both the initial cloud configuration and the sink treatment. The disc size considerably differs in clouds with different density profiles even when the initial clouds have almost the same mass-to-flux ratio. Only a very small disc (˜10 au in size) appears in clouds with a uniform density profile, whereas a large disc (˜100 au in size) forms in clouds with a Bonnor-Ebert density profile. In addition, a large sink accretion radius numerically impedes disc formation during the main accretion phase and tends to foster the misleading notion that disc formation is completely suppressed by magnetic braking. The protostellar outflow is also greatly affected by the sink properties. A sink accretion radius of ≲1 au and sink threshold density of ≳1013 cm-3 are necessary for investigating disc formation during the main accretion phase..
5. Masahiro N Machida, Kentaro Doi, The formation of Population III stars in gas accretion stage: effects of magnetic fields, Monthly Notices of the Royal Astronomical Society, 10.1093/mnras/stt1524, 435, 5, 3283-3305, 2013.11, [URL], The formation of Population III stars is investigated using resistive magnetohydrodynamic simulations. Starting from a magnetized primordial prestellar cloud, we calculate the cloud evolution several hundreds of years after first protostar formation, resolving the protostellar radius. When the natal minihalo field strength is weaker than B ≲ 10-13(n/1 cm-3)-2/3 G (n is the hydrogen number density), magnetic effects can be ignored. In this case, fragmentation occurs frequently and a stellar cluster forms, in which stellar mergers and mass exchange between protostars contribute to the mass growth of these protostars. During the early gas accretion phase, the most massive protostar remains near the cloud centre, whereas some of the less massive protostars are ejected. The magnetic field significantly affects Population III star formation when B ≳ 10-12(n/1 cm-3)-2/3 G. In this case, because the angular momentum around the protostar is effectively transferred by both magnetic braking and protostellar jets, the gas falls directly on to the protostar without forming a disc, and only a single massive star forms. In addition, a massive binary stellar system appears when 10- 13(n/1 cm- 3)- 2/3 ≲ B ≲ 10- 12(n/1 cm- 3)- 2/3 G. Therefore, the magnetic field determines the end result of the formation process (cluster, binary or single star) for Population III stars. Moreover, no persistent circumstellar disc appears around the protostar regardless of the magnetic field strength, which may influence the further evolution of Population III stars..
6. 富田賢吾, 富阪幸治, 町田 正博, Radiation Magnetohydrodynamic Simulations of Protostellar Collapse: Protostellar Core Formation, The Astrophysical Journal, 763, 1, 2013.01, We report the first three-dimensional radiation magnetohydrodynamic (RMHD) simulations of protostellar collapse with and without Ohmic dissipation. We take into account many physical processes required to study star formation processes, including a realistic equation of state. We follow the evolution from molecular cloud cores until protostellar cores are formed with sufficiently high resolutions without introducing a sink particle. The physical processes involved in the simulations and adopted numerical methods are described in detail. We can calculate only about one year after the formation of the protostellar cores with our direct three-dimensional RMHD simulations because of the extremely short timescale in the deep interior of the formed protostellar cores, but successfully describe the early phase of star formation processes. The thermal evolution and the structure of the first and second (protostellar) cores are consistent with previous one-dimensional simulations using full radiation transfer, but differ considerably from preceding multi-dimensional studies with the barotropic approximation. The protostellar cores evolve virtually spherically symmetric in the ideal MHD models because of efficient angular momentum transport by magnetic fields, but Ohmic dissipation enables the formation of the circumstellar disks in the vicinity of the protostellar cores as in previous MHD studies with the barotropic approximation. The formed disks are still small (less than 0.35 AU) because we simulate only the earliest evolution. We also confirm that two different types of outflows are naturally launched by magnetic fields from the first cores and protostellar cores in the resistive MHD models..
7. Shinnaga, Hiroko; Novak, Giles; Vaillancourt, John E.; Machida, Masahiro N.; Kataoka, Akimasa; Tomisaka, Kohji; Davidson, Jacqueline; Phillips, Thomas G.; Dowell, C. Darren; Leeuw, Lerothodi; Houde, Martin, Magnetic Field in the Isolated Massive Dense Clump IRAS 20126+4104, The Astrophysical Journal Letters, 10.1088/2041-8205/750/2/L29, 750, 2, 2012.05, [URL], We measured polarized dust emission at 350 μm toward the high-mass star-forming massive dense clump IRAS 20126+4104 using the SHARC II Polarimeter, SHARP, at the Caltech Submillimeter Observatory. Most of the observed magnetic field vectors agree well with magnetic field vectors obtained from a numerical simulation for the case when the global magnetic field lines are inclined with respect to the rotation axis of the dense clump. The results of the numerical simulation show that rotation plays an important role on the evolution of the massive dense clump and its magnetic field. The direction of the cold CO 1-0 bipolar outflow is parallel to the observed magnetic field within the dense clump as well as the global magnetic field, as inferred from optical polarimetry data, indicating that the magnetic field also plays a critical role in an early stage of massive star formation. The large-scale Keplerian disk of the massive (proto)star rotates in an almost opposite sense to the clump's envelope. The observed magnetic field morphology and the counterrotating feature of the massive dense clump system provide hints to constrain the role of magnetic fields in the process of high-mass star formation..
8. Machida, Masahiro N.; Matsumoto, Tomoaki , Impact of protostellar outflow on star formation: effects of the initial cloud mass, Monthly Notices of the Royal Astronomical Society, 10.1111/j.1365-2966.2011.20336.x, 421, 1, 588-607, 2012.03, [URL], The effects of a protostellar outflow on the star formation in a single cloud core are investigated by three-dimensional resistive magnetohydrodynamic (MHD) simulations. Starting from the pre-stellar cloud core, the star formation process is calculated until the end of the main accretion phase. In the calculations, the mass of the pre-stellar cloud is parametrized. During the star formation, the protostellar outflow is driven by the circumstellar disc. The outflow extends also in the transverse direction until its width becomes comparable to the initial cloud scale, and thus the outflow has a wide opening angle of ≳40°. As a result, the protostellar outflow sweeps up a large fraction of the infalling material and ejects it into the interstellar space. The outflow can eject at most over half of the host cloud mass, significantly decreasing the star formation efficiency. The outflow power is stronger in clouds with a greater initial mass. Thus, the protostellar outflow effectively suppresses the star formation efficiency in a massive cloud. The outflow weakens significantly and disappears in several free-fall time-scales of the initial cloud after the cloud begins to collapse. The natal pre-stellar core influences the lifetime and size of the outflow. At the end of the main accretion phase, a massive circumstellar disc comparable in mass to the protostar remains. Calculations show that ˜26-54 per cent of the initial cloud mass is converted into the protostar and ˜8-40 per cent remains in the circumstellar disc, while ˜8-49 per cent can be ejected into the interstellar space by the protostellar outflow. Therefore, the protostellar outflow can decrease the star formation efficiency to ˜50 per cent at the maximum..
9. Tanigawa, Takayuki; Ohtsuki, Keiji; Machida, Masahiro N., Distribution of Accreting Gas and Angular Momentum onto Circumplanetary Disks, The Astrophysical Journal, Volume, 10.1088/0004-637X/747/1/47, 747, 1, 2012.03, [URL], We investigate gas accretion flow onto a circumplanetary disk from a protoplanetary disk in detail by using high-resolution three-dimensional nested-grid hydrodynamic simulations, in order to provide a basis of formation processes of satellites around giant planets. Based on detailed analyses of gas accretion flow, we find that most of gas accretion onto circumplanetary disks occurs nearly vertically toward the disk surface from high altitude, which generates a shock surface at several scale heights of the circumplanetary disk. The gas that has passed through the shock surface moves inward because its specific angular momentum is smaller than that of the local Keplerian rotation, while gas near the midplane in the protoplanetary disk cannot accrete to the circumplanetary disk. Gas near the midplane within the planet's Hill sphere spirals outward and escapes from the Hill sphere through the two Lagrangian points L1 and L2. We also analyze fluxes of accreting mass and angular momentum in detail and find that the distributions of the fluxes onto the disk surface are well described by power-law functions and that a large fraction of gas accretion occurs at the outer region of the disk, i.e., at about 0.1 times the Hill radius. The nature of power-law functions indicates that, other than the outer edge, there is no specific radius where gas accretion is concentrated. These source functions of mass and angular momentum in the circumplanetary disk would provide us with useful constraints on the structure and evolution of the circumplanetary disk, which is important for satellite formation..
10. Tsukamoto, Yusuke; Machida, Masahiro N. , Classification of the circumstellar disc evolution during the main accretion phase, Monthly Notices of the Royal Astronomical Society, 10.1111/j.1365-2966.2011.19081.x, 416, 1, 591-600, 2011.09, [URL], We performed hydrodynamical simulations to investigate the formation and evolution of protostars and circumstellar discs from the pre-stellar cloud. As the initial state, we adopted the molecular cloud core with two non-dimensional parameters representing the thermal and rotational energies. With these parameters, we derived 17 models and calculated the cloud evolution ˜104 yr after the protostar formation. We found that early evolution of the star-disc system can be qualitatively classified into four modes: the massive-disc, early-fragmentation, late-fragmentation, and protostar-dominant modes. In the 'massive-disc mode', to which the majority of models belong, the disc mass is greater than the protostellar mass for over 104 yr and no fragmentation occurs in the circumstellar disc. The collapsing cloud shows fragmentation before the protostar formation in the 'early-fragmentation mode'. The circumstellar disc shows fragmentation after the protostar formation in the 'late-fragmentation mode', in which the secondary star gains most of its mass from the circumstellar disc after fragmentation and has a mass comparable to that of the primary star. The protostellar mass rapidly increases and exceeds the circumstellar disc mass in the 'protostar-dominant mode'. This mode appears only when the initial molecular cloud core has a very small rotational energy. Comparison of our results with observations indicates that the majority of protostars have a fairly massive disc during the main accretion phase: the circumstellar disc mass is comparable to or more massive than the protostar mass. It is expected that such a massive disc promotes gas-giant formation by gravitational instability in a subsequent evolutionary stage..
11. Machida, Masahiro N.; Inutsuka, Shu-Ichiro; Matsumoto, Tomoaki , Effect of Magnetic Braking on Circumstellar Disk Formation in a Strongly Magnetized Cloud, Publications of the Astronomical Society of Japan, 63, 3, 555-573, 2011.06, [URL], Using resistive magnetohydrodynamics simulation, we consider circumstellar disk formation in a strongly magnetized cloud. As the initial state, an isolated cloud core embedded in a low-density interstellar medium with a uniform magnetic field was adopted. The cloud evolution was calculated until almost all gas inside the initial cloud fell onto either the circumstellar disk or a protostar, and a part of the gas was ejected into the interstellar medium by the protostellar outflow driven by the circumstellar disk. In the early main accretion phase, the disk size is limited to ˜10 AU because the angular momentum of the circumstellar disk is effectively transferred by both magnetic braking and the protostellar outflow. In the later main accretion phase, however, the circumstellar disk grows rapidly and exceeds ≳ 100 AU by the end of the main accretion phase. This rapid growth of the circumstellar disk is caused by depletion of the infalling envelope, while magnetic braking is effective when the infalling envelope is more massive than the circumstellar disk. The infalling envelope cannot brake the circumstellar disk when the latter is more massive than the former. In addition, the protostellar outflow weakens and disappears in the later main accretion phase, because the outflow is powered by gas accretion onto the circumstellar disk. Although the circumstellar disk formed in a magnetized cloud is considerably smaller than that in an unmagnetized cloud, a circumstellar disk exceeding 100 AU can form even in a strongly magnetized cloud..
12. Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki, Recurrent Planet Formation and Intermittent Protostellar Outflows Induced by Episodic Mass Accretion, The Astrophysical Journal, 2011.03.
13. Machida, Masahiro N.; Matsumoto, Tomoaki, The origin and formation of the circumstellar disc, Monthly Notices of the Royal Astronomical Society, 2011.03.
14. Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki, Formation Process of the Circumstellar Disk: Long-term Simulations in the Main Accretion Phase of Star Formation, The Astrophysical Journal, 2010.12.
15. Tomida, Kengo; Machida, Masahiro N.; Saigo, Kazuya; Tomisaka, Kohji; Matsumoto, Tomoaki, Exposed Long-lifetime First Core: A New Model of First Cores Based on Radiation Hydrodynamics, The Astrophysical Journal Letters  , 2010.12.
16. Inutsuka, Shu-ichiro; Machida, Masahiro N.; Matsumoto, Tomoaki, Emergence of Protoplanetary Disks and Successive Formation of Gaseous Planets by Gravitational Instability 
, The Astrophysical Journal Letters, 2010.08.
17. Machida, Masahiro N.; Kokubo, Eiichiro; Inutsuka, Shu-Ichiro; Matsumoto, Tomoaki, Gas accretion onto a protoplanet and formation of a gas giant planet, Monthly Notices of the Royal Astronomical Society, 2010.06.
18. Tomida, Kengo; Tomisaka, Kohji; Matsumoto, Tomoaki; Ohsuga, Ken; Machida, Masahiro N.; Saigo, Kazuya, Radiation Magnetohydrodynamics Simulation of Proto-stellar Collapse: Two-component Molecular Outflow, The Astrophysical Journal Letters, 2010.05.
19. Machida, Masahiro N.; Omukai, Kazuyuki; Matsumoto, Tomoaki, Star Formation in Relic H II Regions of the First Stars: Binarity and Outflow Driving, The Astrophysical Journal, 2009.11.
20. Machida, Masahiro N.; Omukai, Kazuyuki; Matsumoto, Tomoaki; Inutsuka, Shu-Ichiro, Binary formation with different metallicities: dependence on initial conditions, Monthly Notices of the Royal Astronomical Society, 2009.11.
21. Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki, The Circumbinary Outflow: A Protostellar Outflow Driven by a Circumbinary Disk, The Astrophysical Journal Letters, 2009.10.
22. Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki, First Direct Simulation of Brown Dwarf Formation in a Compact Cloud Core, The Astrophysical Journal Letters, 2009.07.
23. Machida, M. N., Thermal effects of circumplanetary disc formation around proto-gas giant planets, Monthly Notices of the Royal Astronomical Society, 2009.01.
24. Machida, Masahiro N.; Kokubo, Eiichiro; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki, Angular Momentum Accretion onto a Gas Giant Planet, The Astrophysical Journal, 2008.10.
25. Machida, Masahiro N.; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro, Magnetohydrodynamics of Population III Star Formation, The Astrophysical Journal, 2008.10.
26. Machida, Masahiro N., Binary Formation in Star-forming Clouds with Various Metallicities, The Astrophysical Journal, 2008.07.
27. Muto, Takayuki; Machida, Masahiro N.; Inutsuka, Shu-ichiro, The Effect of Poloidal Magnetic Field on Type I Planetary Migration: Significance of Magnetic Resonance, The Astrophysical Journal, 2008.05.
28. Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki, High- and Low-Velocity Magnetized Outflows in the Star Formation Process in a Gravitationally Collapsing Cloud, The Astrophysical Journal, 2008.04.
29. Machida, Masahiro N.; Omukai, Kazuyuki; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro, Conditions for the Formation of First-Star Binaries, The Astrophysical Journal, 2008.04.
30. Machida, Masahiro N.; Tomisaka, Kohji; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro, Formation Scenario for Wide and Close Binary Systems, The Astrophysical Journal, 2008.04.
31. Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki, Magnetic Fields and Rotations of Protostars, The Astrophysical Journal, 2007.12.
32. Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki, Outflows Driven by Giant Protoplanets, The Astrophysical Journal, 2006.10.
33. Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki, Second Core Formation and High-Speed Jets: Resistive Magnetohydrodynamic Nested Grid Simulations
, The Astrophysical Journal, 2006.08.
34. Machida, Masahiro N.; Omukai, Kazuyuki; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro, The First Jets in the Universe: Protostellar Jets from the First Stars, The Astrophysical Journal, 2006.08.
35. Machida, Masahiro N.; Matsumoto, Tomoaki; Hanawa, Tomoyuki; Tomisaka, Kohji, Evolution of Rotating Molecular Cloud Core with Oblique Magnetic Field, The Astrophysical Journal, 2006.07.
36. Machida, Masahiro N.; Matsumoto, Tomoaki; Hanawa, Tomoyuki; Tomisaka, Kohji, Collapse and fragmentation of rotating magnetized clouds - II. Binary formation and fragmentation of first cores, Monthly Notices of the Royal Astronomical Society, 2005.09.
37. Machida, Masahiro N.; Matsumoto, Tomoaki; Tomisaka, Kohji; Hanawa, Tomoyuki, Collapse and fragmentation of rotating magnetized clouds - I. Magnetic flux-spin relation, Monthly Notices of the Royal Astronomical Society, 2005.09.
38. Machida, M. N., Tomisaka, K., Nakamura, F., Fujimoto, M. Y., Low-Mass Star Formation Triggered by Supernovae in Primordial Clouds, The Astrophysical Journal, 2005.03.
39. Suda, Takuma; Aikawa, Masayuki; Machida, Masahiro N.; Fujimoto, Masayuki Y.; Iben, Icko, Jr., Is HE 0107-5240 A Primordial Star? The Characteristics of Extremely Metal-Poor Carbon-Rich Stars, The Astrophysical Journal, 2004.08.
40. Machida, Masahiro N.; Tomisaka, Kohji; Matsumoto, Tomoaki, First MHD simulation of collapse and fragmentation of magnetized molecular cloud cores, Monthly Notices of the Royal Astronomical Society, 2004.02.
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Membership in Academic Society
  • The Astronomical Society of Japan
  • Star and Planet Formation in Molecular Cloud Cores
Educational Activities
Fluid Dynamics, Comparative Planetology, Thermal Dynamics
Other Educational Activities
  • 2019.10, Lecture at Moji Gakuen high school.
  • 2019.03, Lecture in Workshop collection in Fukuoka.
  • 2017.10, Lecture for high school and junior high school students.