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Masahiro N Machida Last modified date:2016.07.31

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


Graduate School
Undergraduate School


Homepage
http://jupiter.geo.kyushu-u.ac.jp/machida/index.html
Formation and Evolution of Planetary Systems, Masahiro Machida's HP .
Fax
092-642-4208
Academic Degree
Doctor of Philosophy
Field of Specialization
Astrophysics
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.

(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
Research Interests
  • Formation of Gas Giant Planet
    keyword : Numerical simulation, Protoplanetary Disk, Planet
    2006.04.
  • Satellite Formation
    keyword : Satellite, Circum-planetary disk, Gas giant planet
    2008.04.
  • Star Formation
    keyword : MHD, Jet, Outflow
    2003.04.
  • Star Formation in the Early Universe, First Star Formation
    keyword : Cosmology, Primordial gas
    2000.04.
Academic Activities
Papers
1. 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, 448, 2, 1405-1429, 2015.04, [URL].
2. Tanigawa, Takayuki, Maruta, Akito, Masahiro N Machida, Accretion of Solid Materials onto Circumplanetary Disks from Protoplanetary Disks, The Astrophysical Journal, 784, 109, 2014.04, [URL].
3. 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, 438, 3, 2014.03, [URL].
4. 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, 435, 5, 2013.11, [URL].
5. 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.
6. 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, 750, 2, 2012.05, [URL].
7. 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, 421, 1, 588-607, 2012.03, [URL].
8. Tanigawa, Takayuki; Ohtsuki, Keiji; Machida, Masahiro N., Distribution of Accreting Gas and Angular Momentum onto Circumplanetary Disks, The Astrophysical Journal, Volume, 747, 1, 2012.03, [URL].
9. Tsukamoto, Yusuke; Machida, Masahiro N. , Classification of the circumstellar disc evolution during the main accretion phase, Monthly Notices of the Royal Astronomical Society, 416, 1, 591-600, 2011.09, [URL].
10. 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].
11. 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.
12. Machida, Masahiro N.; Matsumoto, Tomoaki, The origin and formation of the circumstellar disc, Monthly Notices of the Royal Astronomical Society, 2011.03.
13. 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.
14. 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.
15. 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.
16. 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.
17. 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.
18. 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.
19. 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.
20. 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.
21. 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.
22. Machida, M. N., Thermal effects of circumplanetary disc formation around proto-gas giant planets, Monthly Notices of the Royal Astronomical Society, 2009.01.
23. Machida, Masahiro N.; Kokubo, Eiichiro; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki, Angular Momentum Accretion onto a Gas Giant Planet, The Astrophysical Journal, 2008.10.
24. Machida, Masahiro N.; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro, Magnetohydrodynamics of Population III Star Formation, The Astrophysical Journal, 2008.10.
25. Machida, Masahiro N., Binary Formation in Star-forming Clouds with Various Metallicities, The Astrophysical Journal, 2008.07.
26. 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.
27. 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.
28. Machida, Masahiro N.; Omukai, Kazuyuki; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro, Conditions for the Formation of First-Star Binaries, The Astrophysical Journal, 2008.04.
29. Machida, Masahiro N.; Tomisaka, Kohji; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro, Formation Scenario for Wide and Close Binary Systems, The Astrophysical Journal, 2008.04.
30. Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki, Magnetic Fields and Rotations of Protostars, The Astrophysical Journal, 2007.12.
31. Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki, Outflows Driven by Giant Protoplanets, The Astrophysical Journal, 2006.10.
32. 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.
33. 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.
34. Machida, Masahiro N.; Matsumoto, Tomoaki; Hanawa, Tomoyuki; Tomisaka, Kohji, Evolution of Rotating Molecular Cloud Core with Oblique Magnetic Field, The Astrophysical Journal, 2006.07.
35. 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.
36. 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.
37. 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.
38. 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.
39. 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.
Presentations
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Membership in Academic Society
  • The Astronomical Society of Japan
Awards
  • Star and Planet Formation in Molecular Cloud Cores
Educational