Updated on 2024/10/03

Information

 

写真a

 
MACHIDA MASAHIRO
 
Organization
Faculty of Science Department of Earth and Planetary Sciences Professor
School of Sciences Department of Earth and Planetary Sciences(Joint Appointment)
Graduate School of Sciences Department of Earth and Planetary Sciences(Joint Appointment)
Title
Professor
Profile
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.
Homepage

Research Areas

  • Natural Science / Astronomy

Degree

  • Doctor of Philosophy

  • Doctor of Philosophy

Research History

  • 国立天文台(助教)

Research Interests・Research Keywords

  • Research theme:Theoretical study about black hole binary formation

    Keyword:Black hole

    Research period: 2018.5 - 2023.3

  • Research theme:Satellite Formation

    Keyword:Satellite, Circum-planetary disk, Gas giant planet

    Research period: 2008.4

  • Research theme:Formation of Gas Giant Planet

    Keyword:Numerical simulation, Protoplanetary Disk, Planet

    Research period: 2006.4

  • Research theme:Star Formation

    Keyword:MHD, Jet, Outflow

    Research period: 2003.4

  • Research theme:Star Formation in the Early Universe, First Star Formation

    Keyword:Cosmology, Primordial gas

    Research period: 2000.4

Awards

  • 平成28年度 HPCI 優秀成果賞

    2017.10   磁気流体多層格子法のコードを開発し計算を進め、分子雲コアから星が形成する過程の大規模シミュレーションを行い、成果として2016年度に査読付き論文3編が出版された。この成果によって平成28年度 HPCI 優秀成果賞を受賞した。従来、星が誕生した直後までしか行われていなかった数値シミュレーションを星誕生後の段階まで拡張し、星形成後の長時間進化を複数のスーパーコンピュータを用いて計算した。シミュレーションによって得られた惑星が誕生する母体と考えられる原始惑星系円盤は、近年 ALMA(Atacama Large Millimeter/submillimeter Array)望遠鏡で観測された原始星周りの円盤と物理的特性がよく一致しており、星や惑星の形成過程を解明する手がかりを得ることが出来た。この研究は、九州大学理学研究院の町田正博准教授と博士1年の樋口公紀の他、大阪大学、国立天文台、法政大学のグループで行われた。

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    磁気流体多層格子法のコードを開発し計算を進め、分子雲コアから星が形成する過程の大規模シミュレーションを行い、成果として2016年度に査読付き論文3編が出版された。この成果によって平成28年度 HPCI 優秀成果賞を受賞した。

  • 日本天文学会欧文研究報告論文賞

    2017.3   日本天文学会   日本天文学会刊行の欧文研究報告誌Publications of the Astronomical Society of Japan (PASJ)において過去5年以内に掲載された論文の中から、最も独創的で天文学分野に寄与の大きい、特に優れた論文として授与された。

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    日本天文学会刊行の欧文研究報告誌Publications of the Astronomical Society of Japan (PASJ)において過去5年以内に掲載された論文の中から、最も独創的で天文学分野に寄与の大きい、特に優れた論文として「Effect of Magnetic Braking on Circumstellar Disk Formation in a Strongly Magnetized Cloud (Machida, M. N., Inutsuka, S., & Matsumoto, T.)」が受賞した。

  • 平成24年度 科学技術分野の文部科学大臣表彰 若手科学賞

    2012.4   文部科学省   分子雲コア中での星と惑星形成の研究

Papers

  • A centrally concentrated sub-solar-mass starless core in the Taurus L1495 filamentary complex Reviewed

    Publications of the Astronomical Society of Japan   71 ( 4 )   2019.8

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1093/pasj/psz051

  • The First Bird's-eye View of a Gravitationally Unstable Accretion Disk in High-mass Star Formation Reviewed

    Kazuhito Motogi, Tomoya Hirota, Masahiro Machida, Yoshinori Yonekura, Mareki Honma, Shigehisa Takakuwa, Satoki Matsushita

    Astrophysical Journal Letters   877 ( 2 )   2019.6

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.3847/2041-8213/ab212f

  • The First Two Thousand Years of Star Formation Reviewed

    Masahiro N. Machida, Shantanu Basu

    Astrophysical Journal   876 ( 2 )   2019.5

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.3847/1538-4357/ab18a7

  • ALMA High Angular Resolution Polarization Study An Extremely Young Class 0 Source, OMC-3/MMS 6 Reviewed

    Satoko Takahashi, Masahiro Machida, Kohji Tomisaka, Paul T.P. Ho, Edward B. Fomalont, Kouichiro Nakanishi, Josep Miquel Girart

    Astrophysical Journal   872 ( 1 )   2019.2

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    DOI: 10.3847/1538-4357/aaf6ed

  • Extremely High Excitation SiO Lines in Disk-outflow Systems in Orion Source i Reviewed

    Mi Kyoung Kim, Tomoya Hirota, Masahiro Machida, Yuko Matsushita, Kazuhito Motogi, Naoko Matsumoto, Mareki Honma

    Astrophysical Journal   872 ( 1 )   2019.2

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    DOI: 10.3847/1538-4357/aafb6b

  • Dependence of Hall coefficient on grain size and cosmic ray rate and implication for circumstellar disc formation Reviewed

    Shunta Koga, Yusuke Tsukamoto, Satoshi Okuzumi, Masahiro Machida

    Monthly Notices of the Royal Astronomical Society   484 ( 2 )   2119 - 2136   2019.1

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1093/mnras/sty3524

  • Driving conditions of protostellar outflows in different star-forming environments Reviewed

    Koki Higuchi, Masahiro N. Machida, Hajime Susa

    Monthly Notices of the Royal Astronomical Society   486 ( 3 )   3741 - 3754   2019.1

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1093/mnras/stz1079

  • Does Misalignment between Magnetic Field and Angular Momentum Enhance or Suppress Circumstellar Disk Formation? Reviewed

    Y. Tsukamoto, S. Okuzumi, K. Iwasaki, Masahiro Machida, S. Inutsuka

    Astrophysical Journal   868 ( 1 )   2018.11

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    DOI: 10.3847/1538-4357/aae4dc

  • The Distinct Evolutionary Nature of Two Class 0 Protostars in Serpens Main SMM4 Reviewed

    Yusuke Aso, Naomi Hirano, Yuri Aikawa, Masahiro Machida, Shigehisa Takakuwa, Hsi Wei Yen, Jonathan P. Williams

    Astrophysical Journal   863 ( 1 )   2018.8

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    DOI: 10.3847/1538-4357/aacf9b

  • Warm CO Gas Generated by Possible Turbulent Shocks in a Low-mass Star-forming Dense Core in Taurus Reviewed

    Kazuki Tokuda, Toshikazu Onishi, Kazuya Saigo, Tomoaki Matsumoto, Tsuyoshi Inoue, Shu Ichiro Inutsuka, Yasuo Fukui, Masahiro Machida, Kengo Tomida, Takashi Hosokawa, Akiko Kawamura, Kengo Tachihara

    Astrophysical Journal   862 ( 1 )   2018.7

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.3847/1538-4357/aac898

  • Massive outflows driven by magnetic effects - II. Comparison with observations Reviewed

    Yuko Matsushita, Yuya Sakurai, Takash Hosokawa, Masahiro Machida

    Monthly Notices of the Royal Astronomical Society   475 ( 1 )   391 - 403   2018.3

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1093/mnras/stx3070

  • Different modes of star formation Gravitational collapse of magnetically subcritical cloud Reviewed

    Masahiro Machida, Koki Higuchi, Satoshi Okuzumi

    Monthly Notices of the Royal Astronomical Society   473 ( 3 )   3080 - 3094   2018.1

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    DOI: 10.1093/mnras/stx2589

  • A Detached Protostellar Disk around a ∼0.2 M o Protostar in a Possible Site of a Multiple Star Formation in a Dynamical Environment in Taurus Reviewed

    849 ( 2 )   2017.11

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    We report ALMA observations in 0.87 mm continuum and 12CO (J = 3-2) toward a very low-luminosity (<0.1 L o) protostar, which is deeply embedded in one of the densest cores, MC27/L1521F, in Taurus with an indication of multiple star formation in a highly dynamical environment. The beam size corresponds to ∼20 au, and we have clearly detected blueshifted/redshifted gas in 12CO associated with the protostar. The spatial/velocity distributions of the gas show there is a rotating disk with a size scale of ∼10 au, a disk mass of ∼10-4 M o, and a central stellar mass of ∼0.2 M o. The observed disk seems to be detached from the surrounding dense gas, although it is still embedded at the center of the core whose density is ∼106 cm-3. The current low-outflow activity and the very low luminosity indicate that the mass accretion rate onto the protostar is extremely low in spite of a very early stage of star formation. We may be witnessing the final stage of the formation of ∼0.2 M o protostar. However, we cannot explain the observed low luminosity with the standard pre-main-sequence evolutionary track unless we assume cold accretion with an extremely small initial radius of the protostar (∼0.65 ). These facts may challenge our current understanding of the low mass star formation, in particular the mass accretion process onto the protostar and the circumstellar disk.

    DOI: 10.3847/1538-4357/aa8e9e

  • ALMA Observations of the Protostar L1527 IRS Probing Details of the Disk and the Envelope Structures Reviewed

    Yusuke Aso, Nagayoshi Ohashi, Yuri Aikawa, Masahiro Machida, Kazuya Saigo, Masao Saito, Shigehisa Takakuwa, Kengo Tomida, Kohji Tomisaka, Hsi Wei Yen

    Astrophysical Journal   849 ( 1 )   2017.11

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    DOI: 10.3847/1538-4357/aa8264

  • ALMA Observations of SMM11 Reveal an Extremely Young Protostar in Serpens Main Cluster Reviewed

    Yusuke Aso, Nagayoshi Ohashi, Yuri Aikawa, Masahiro Machida, Kazuya Saigo, Masao Saito, Shigehisa Takakuwa, Kengo Tomida, Kohji Tomisaka, Hsi Wei Yen, Jonathan P. Williams

    Astrophysical Journal Letters   850 ( 1 )   2017.11

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.3847/2041-8213/aa9701

  • Massive outflows driven by magnetic effects in star-forming clouds with high mass accretion rates Reviewed

    Yuko Matsushita, Masahiro Machida, Yuya Sakurai, Takashi Hosokawa

    Monthly Notices of the Royal Astronomical Society   470 ( 1 )   1026 - 1049   2017.9

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    DOI: 10.1093/mnras/stx893

  • Circumstellar Disks and Outflows in Turbulent Molecular Cloud Cores Possible Formation Mechanism for Misaligned Systems Reviewed

    Tomoaki Matsumoto, Masahiro Machida, Shu Ichiro Inutsuka

    Astrophysical Journal   839 ( 1 )   2017.4

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    DOI: 10.3847/1538-4357/aa6a1c

  • Disk-driven rotating bipolar outflow in Orion Source i Reviewed

    Tomoya Hirota, Masahiro Machida, Yuko Matsushita, Kazuhito Motogi, Naoko Matsumoto, Mi Kyoung Kim, Ross A. Burns, Mareki Honma

    Nature Astronomy   1   2017.3

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1038/s41550-017-0146

  • Grand-design Spiral Arms in a Young Forming Circumstellar Disk Reviewed

    Kengo Tomida, Masahiro Machida, Takashi Hosokawa, Yuya Sakurai, Chia Hui Lin

    Astrophysical Journal Letters   835 ( 1 )   2017.1

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    DOI: 10.3847/2041-8213/835/1/L11

  • The impact of the Hall effect during cloud core collapse Implications for circumstellar disk evolution Reviewed

    Yusuke Tsukamoto, Satoshi Okuzumi, Kazunari Iwasaki, Masahiro Machida, Shu Ichiro Inutsuka

    Publications of the Astronomical Society of Japan   69 ( 6 )   2017.1

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1093/pasj/psx113

  • ALMA BAND 8 CONTINUUM EMISSION from ORION SOURCE i Reviewed

    Tomoya Hirota, Masahiro Machida, Yuko Matsushita, Kazuhito Motogi, Naoko Matsumoto, Mi Kyoung Kim, Ross A. Burns, Mareki Honma

    Astrophysical Journal   833 ( 2 )   2016.12

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    DOI: 10.3847/1538-4357/833/2/238

  • The origin of rotation profiles in star-forming clouds Reviewed

    Sanemichi Z. Takahashi, Kengo Tomida, Masahiro Machida, Shu Ichiro Inutsuka

    Monthly Notices of the Royal Astronomical Society   463 ( 2 )   1390 - 1399   2016.12

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    DOI: 10.1093/MNRAS/STW1994

  • Revealing a detailed mass distribution of a high-density core MC27/L1521F in Taurus with ALMA Reviewed

    Astrophysical Journal   826 ( 1 )   2016.7

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    DOI: 10.3847/0004-637X/826/1/26

  • Conditions for circumstellar disc formation - II. Effects of initial cloud stability and mass accretion rate Reviewed

    Masahiro Machida, Tomoaki Matsumoto, Shu Ichiro Inutsuka

    Monthly Notices of the Royal Astronomical Society   463 ( 4 )   4246 - 4267   2016.1

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    DOI: 10.1093/mnras/stw2256

  • Alma observations of the transition from infall motion to keplerian rotation around the late-phase protostar tmc-1a Reviewed

    Yusuke Aso, Nagayoshi Ohashi, Kazuya Saigo, Shin Koyamatsu, Yuri Aikawa, Masahiko Hayashi, Masahiro Machida, Masao Saito, Shigehisa Takakuwa, Kengo Tomida, Kohji Tomisaka, Hsi Wei Yen

    Astrophysical Journal   812 ( 1 )   2015.10

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    DOI: 10.1088/0004-637X/812/1/27

  • Bimodality of Circumstellar Disk Evolution Induced by the Hall Current

    Tsukamoto, Y, Iwasaki, K, Okuzumi, S., Masahiro N Machida, Inutsuka, S.

    The Astrophysical Journal Letters   810 ( 2 )   2015.9

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    DOI: 10.1088/2041-8205/810/2/L26

  • Effects of Ohmic and ambipolar diffusion on formation and evolution of first cores, protostars, and circumstellar discs

    Tsukamoto, Y, Iwasaki, K, Okuzumi, S., Masahiro N Machida, Inutsuka, S.

    Monthly Notices of the Royal Astronomical Society   452 ( 1 )   2015.9

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    DOI: 10.1093/mnras/stv1290

  • Accretion phase of star formation in clouds with different metallicities Reviewed International journal

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   448 ( 2 )   1405 - 1429   2015.4

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1093/mnras/stu2633

    Other Link: http://ads.nao.ac.jp/abs/2015MNRAS.448.1405M

  • RADIATION MAGNETOHYDRODYNAMIC SIMULATIONS OF PROTOSTELLAR COLLAPSE: NONIDEAL MAGNETOHYDRODYNAMIC EFFECTS AND EARLY FORMATION OF CIRCUMSTELLAR DISKS

    Tomida, Kengo, Okuzumi, Satoshi, Masahiro N Machida

    ASTROPHYSICAL JOURNAL   801 ( 2 )   2015.3

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    DOI: 10.1088/0004-637X/801/2/117

  • Effects of radiative transfer on the structure of self-gravitating discs, their fragmentation and the evolution of the fragments

    Tsukamoto, Y, Takahashi, S. Z., Masahiro N Machida, Inutsuka, S.

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   446 ( 2 )   2015.1

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    DOI: 10.1093/mnras/stu2160

  • FORMATION OF A KEPLERIAN DISK IN THE INFALLING ENVELOPE AROUND L1527 IRS: TRANSFORMATION FROM INFALLING MOTIONS TO KEPLER MOTIONS

    Ohashi, Nagayoshi et al., Masahiro N Machida

    ASTROPHYSICAL JOURNAL   796 ( 2 )   2014.12

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    DOI: 10.1088/0004-637X/796/2/131

  • PROTOSTELLAR JETS ENCLOSED BY LOW-VELOCITY OUTFLOWS

    Masahiro N Machida

    ASTROPHYSICAL JOURNAL LETTERS   796 ( 1 )   2014.11

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    DOI: 10.1088/2041-8205/796/1/L17

  • ALMA OBSERVATIONS OF INFALLING FLOWS TOWARD THE KEPLERIAN DISK AROUND THE CLASS I PROTOSTAR L1489 IRS

    Yen, Hsi-Wei, et al., Masahiro N Machida

    ASTROPHYSICAL JOURNAL   793 ( 1 )   2014.9

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    DOI: 10.1088/0004-637X/793/1/1

  • ALMA OBSERVATIONS OF A HIGH-DENSITY CORE IN TAURUS: DYNAMICAL GAS INTERACTION AT THE POSSIBLE SITE OF A MULTIPLE STAR FORMATION

    Tokuda, Kazuki, et al., Masahiro N Machida

    ASTROPHYSICAL JOURNAL LETTERS   789 ( 1 )   2014.7

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    DOI: 10.1088/2041-8205/789/1/L4

  • Accretion of Solid Materials onto Circumplanetary Disks from Protoplanetary Disks Reviewed International journal

    Tanigawa, Takayuki, Maruta, Akito, Masahiro N Machida

    The Astrophysical Journal   784 ( 109 )   2014.4

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    DOI: 10.1088/0004-637X/784/2/109

    Other Link: http://ads.nao.ac.jp/abs/2014ApJ...784..109T

  • Conditions for circumstellar disc formation: effects of initial cloud configuration and sink treatment Reviewed International journal

    Masahiro N Machida, Inutsuka Shu-ichiro, Matsumoto Tomoaki

    Monthly Notices of the Royal Astronomical Society   438 ( 3 )   2278 - 2306   2014.3

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    DOI: 10.1093/mnras/stt2343

    Other Link: http://ads.nao.ac.jp/abs/2014MNRAS.438.2278M

  • Formation, orbital and thermal evolution, and survival of planetary-mass clumps in the early phase of circumstellar disc evolution Reviewed International journal

    Monthly Notices of the Royal Astronomical Society   436 ( 2 )   1667 - 1673   2013.12

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.1093/mnras/stt1684

    Other Link: http://ads.nao.ac.jp/abs/2013MNRAS.436.1667T

  • The formation of Population III stars in gas accretion stage: effects of magnetic fields Reviewed International journal

    Masahiro N Machida, Kentaro Doi

    Monthly Notices of the Royal Astronomical Society   435 ( 5 )   3283 - 3305   2013.11

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    DOI: 10.1093/mnras/stt1524

    Other Link: http://ads.nao.ac.jp/abs/2013MNRAS.435.3283M

  • A Semi-analytical Description for the Formation and Gravitational Evolution of Protoplanetary Disks Reviewed International journal

    Sanemichi Z Takahashi, Inutsuka Shu-ichiro, Masahiro N Machida

    The Astrophysical Journal   770 ( 1 )   71 - 80   2013.6

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    DOI: 10.1088/0004-637X/770/1/71

    Other Link: http://ads.nao.ac.jp/abs/2013ApJ...770...71T

  • Evolution of protostellar outflow around low-mass protostar Reviewed International journal

    Monthly Notices of the Royal Astronomical Society   2013.3

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  • Formation and early evolution of circumstellar discs in turbulent molecular cloud cores Reviewed International journal

    Monthly Notices of the Royal Astronomical Society   428 ( 2 )   2013.1

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  • Radiation Magnetohydrodynamic Simulations of Protostellar Collapse: Protostellar Core Formation Reviewed International journal

    The Astrophysical Journal   763 ( 1 )   2013.1

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  • Exploring Magnetic Field Structure in Star-forming Cores with Polarization of Thermal Dust Emission Reviewed International journal

    The Astrophysical Journal   761 ( 1 )   2012.12

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  • Magnetic Field in the Isolated Massive Dense Clump IRAS 20126+4104 Reviewed International journal

    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

    The Astrophysical Journal Letters   750 ( 2 )   2012.5

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    DOI: 10.1088/2041-8205/750/2/L29

    Other Link: http://ads.nao.ac.jp/abs/2012ApJ...750L..29S

  • Impact of protostellar outflow on star formation: effects of the initial cloud mass Reviewed International journal

    Machida, Masahiro N.; Matsumoto, Tomoaki

    Monthly Notices of the Royal Astronomical Society   421 ( 1 )   2012.3

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    DOI: 10.1111/j.1365-2966.2011.20336.x

    Other Link: http://ads.nao.ac.jp/abs/2012MNRAS.421..588M

  • Distribution of Accreting Gas and Angular Momentum onto Circumplanetary Disks Reviewed International journal

    Tanigawa, Takayuki; Ohtsuki, Keiji; Machida, Masahiro N.

    The Astrophysical Journal, Volume   747 ( 1 )   2012.3

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    DOI: 10.1088/0004-637X/747/1/47

    Other Link: http://ads.nao.ac.jp/abs/2012ApJ...747...47T

  • Classification of the circumstellar disc evolution during the main accretion phase Reviewed International journal

    Tsukamoto, Yusuke; Machida, Masahiro N.

    Monthly Notices of the Royal Astronomical Society   416 ( 1 )   2011.9

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    DOI: 10.1111/j.1365-2966.2011.19081.x

    Other Link: http://ads.nao.ac.jp/abs/2011MNRAS.416..591T

  • Effect of Magnetic Braking on Circumstellar Disk Formation in a Strongly Magnetized Cloud Reviewed International journal

    Machida, Masahiro N.; Inutsuka, Shu-Ichiro; Matsumoto, Tomoaki

    Publications of the Astronomical Society of Japan   63 ( 3 )   2011.6

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    Other Link: http://ads.nao.ac.jp/abs/2011PASJ...63..555M

  • Recurrent Planet Formation and Intermittent Protostellar Outflows Induced by Episodic Mass Accretion Reviewed International journal

    Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki

    The Astrophysical Journal   2011.3

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  • The origin and formation of the circumstellar disc Reviewed International journal

    Machida, Masahiro N.; Matsumoto, Tomoaki

    Monthly Notices of the Royal Astronomical Society   2011.3

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  • Formation Process of the Circumstellar Disk: Long-term Simulations in the Main Accretion Phase of Star Formation Reviewed International journal

    Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki

    The Astrophysical Journal   2010.12

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  • Exposed Long-lifetime First Core: A New Model of First Cores Based on Radiation Hydrodynamics Reviewed International journal

    Tomida, Kengo; Machida, Masahiro N.; Saigo, Kazuya; Tomisaka, Kohji; Matsumoto, Tomoaki

    2010.12

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  • Emergence of Protoplanetary Disks and Successive Formation of Gaseous Planets by Gravitational Instability  Reviewed International journal

    2010.8

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  • Gas accretion onto a protoplanet and formation of a gas giant planet Reviewed International journal

    Machida, Masahiro N.; Kokubo, Eiichiro; Inutsuka, Shu-Ichiro; Matsumoto, Tomoaki

    Monthly Notices of the Royal Astronomical Society   2010.6

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  • Radiation Magnetohydrodynamics Simulation of Proto-stellar Collapse: Two-component Molecular Outflow Reviewed International journal

    Tomida, Kengo; Tomisaka, Kohji; Matsumoto, Tomoaki; Ohsuga, Ken; Machida, Masahiro N.; Saigo, Kazuya

    The Astrophysical Journal Letters   2010.5

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  • Star Formation in Relic H II Regions of the First Stars: Binarity and Outflow Driving Reviewed International journal

    Machida, Masahiro N.; Omukai, Kazuyuki; Matsumoto, Tomoaki

    The Astrophysical Journal   2009.11

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  • Binary formation with different metallicities: dependence on initial conditions Reviewed International journal

    Machida, Masahiro N.; Omukai, Kazuyuki; Matsumoto, Tomoaki; Inutsuka, Shu-Ichiro

    Monthly Notices of the Royal Astronomical Society   2009.11

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  • The Circumbinary Outflow: A Protostellar Outflow Driven by a Circumbinary Disk Reviewed International journal

    Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki

    The Astrophysical Journal Letters   2009.10

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  • Emission from a Young Protostellar Object. I. Signatures of Young Embedded Outflows Reviewed International journal

    Yamada, Masako; Machida, Masahiro N.; Inutsuka, Shu-ichiro; Tomisaka, Kohji

    The Astrophysical Journal   2009.9

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  • First Direct Simulation of Brown Dwarf Formation in a Compact Cloud Core Reviewed International journal

    Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki

    The Astrophysical Journal Letters   2009.7

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  • Thermal effects of circumplanetary disc formation around proto-gas giant planets Reviewed International journal

    Machida, M. N.

    Monthly Notices of the Royal Astronomical Society   2009.1

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  • Angular Momentum Accretion onto a Gas Giant Planet Reviewed International journal

    Machida, Masahiro N.; Kokubo, Eiichiro; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki

    The Astrophysical Journal   2008.10

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  • Magnetohydrodynamics of Population III Star Formation Reviewed International journal

    Machida, Masahiro N.; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro

    The Astrophysical Journal   2008.10

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  • Binary Formation in Star-forming Clouds with Various Metallicities Reviewed International journal

    Machida, Masahiro N.

    The Astrophysical Journal   2008.7

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  • The Effect of Poloidal Magnetic Field on Type I Planetary Migration: Significance of Magnetic Resonance Reviewed International journal

    Muto, Takayuki; Machida, Masahiro N.; Inutsuka, Shu-ichiro

    The Astrophysical Journal   2008.5

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  • High- and Low-Velocity Magnetized Outflows in the Star Formation Process in a Gravitationally Collapsing Cloud Reviewed International journal

    Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki

    The Astrophysical Journal   2008.4

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  • Formation Scenario for Wide and Close Binary Systems Reviewed International journal

    Machida, Masahiro N.; Tomisaka, Kohji; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro

    The Astrophysical Journal   2008.4

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  • Conditions for the Formation of First-Star Binaries Reviewed International journal

    Machida, Masahiro N.; Omukai, Kazuyuki; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro

    The Astrophysical Journal   2008.4

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  • Magnetic Fields and Rotations of Protostars Reviewed International journal

    Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki

    The Astrophysical Journal   2007.12

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  • Outflows Driven by Giant Protoplanets Reviewed International journal

    Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki

    The Astrophysical Journal   2006.10

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  • Second Core Formation and High-Speed Jets: Resistive Magnetohydrodynamic Nested Grid Simulations Reviewed International journal

    Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki

    The Astrophysical Journal   2006.8

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  • The First Jets in the Universe: Protostellar Jets from the First Stars Reviewed International journal

    Machida, Masahiro N.; Omukai, Kazuyuki; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro

    The Astrophysical Journal   2006.8

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  • Evolution of Rotating Molecular Cloud Core with Oblique Magnetic Field Reviewed International journal

    Machida, Masahiro N.; Matsumoto, Tomoaki; Hanawa, Tomoyuki; Tomisaka, Kohji

    The Astrophysical Journal   2006.7

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  • Collapse and fragmentation of rotating magnetized clouds - II. Binary formation and fragmentation of first cores Reviewed International journal

    Machida, Masahiro N.; Matsumoto, Tomoaki; Hanawa, Tomoyuki; Tomisaka, Kohji

    Monthly Notices of the Royal Astronomical Society   2005.9

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  • Collapse and fragmentation of rotating magnetized clouds - I. Magnetic flux-spin relation Reviewed International journal

    Machida, Masahiro N.; Matsumoto, Tomoaki; Tomisaka, Kohji; Hanawa, Tomoyuki

    Monthly Notices of the Royal Astronomical Society   2005.9

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  • Low-Mass Star Formation Triggered by Supernovae in Primordial Clouds Reviewed International journal

    Machida, M. N., Tomisaka, K., Nakamura, F., Fujimoto, M. Y.

    The Astrophysical Journal   2005.3

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  • Is HE 0107-5240 A Primordial Star? The Characteristics of Extremely Metal-Poor Carbon-Rich Stars Reviewed International journal

    Suda, Takuma; Aikawa, Masayuki; Machida, Masahiro N.; Fujimoto, Masayuki Y.; Iben, Icko, Jr.

    The Astrophysical Journal   2004.8

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  • First MHD simulation of collapse and fragmentation of magnetized molecular cloud cores Reviewed International journal

    Machida, Masahiro N.; Tomisaka, Kohji; Matsumoto, Tomoaki

    Monthly Notices of the Royal Astronomical Society   2004.2

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  • Cloud Dissipation and Disk Wind in the Late Phase of Star Formation

    Machida, MN; Basu, S

    ASTROPHYSICAL JOURNAL   970 ( 1 )   2024.7   ISSN:0004-637X eISSN:1538-4357

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    We perform a long-term simulation of star and disk formation using three-dimensional nonideal magnetohydrodynamics. The simulation starts from a prestellar cloud and proceeds through the long-term evolution of the circumstellar disk until ∼1.5 × 105 yr after protostar formation. The disk has size ≲50 au and little substructure in the main accretion phase because of the action of magnetic braking and the magnetically driven outflow to remove angular momentum. The main accretion phase ends when the outflow breaks out of the cloud, causing the envelope mass to decrease rapidly. The outflow subsequently weakens as the mass accretion rate also weakens. While the envelope-to-disk accretion continues, the disk grows gradually and develops transient spiral structures, due to gravitational instability. When the envelope-to-disk accretion ends, the disk becomes stable and reaches a size ≳300 au. In addition, about 30% of the initial cloud mass has been ejected by the outflow. A significant finding of this work is that after the envelope dissipates a revitalization of the wind occurs, and there is mass ejection from the disk surface that lasts until the end of the simulation. This mass ejection (or disk wind) is generated because the magnetic pressure significantly dominates both the ram pressure and thermal pressure above and below the disk at this stage. Using the angular momentum flux and mass-loss rate estimated from the disk wind, the disk dissipation timescale is estimated to be ∼106 yr.

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  • HCN as a probe of the inner disc in a candidate proto-brown dwarf

    Riaz B., Thi W.F., Machida M.N.

    Monthly Notices of the Royal Astronomical Society: Letters   532 ( 1 )   L36 - L41   2024.7

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    The detection of Keplerian rotation is rare among Class 0 protostellar systems. We have investigated the high-density tracer HCN as a probe of the inner disc in a Class 0 proto-brown dwarf candidate. Our ALMA high angular resolution observations show the peak in the HCN (3-2) line emission arises from a compact component near the proto-brown dwarf with a small bar-like structure and a deconvolved size of ∼50 au. Radiative transfer modelling indicates that this HCN feature is tracing the innermost, dense regions in the proto-brown dwarf where a small Keplerian disc is expected to be present. The limited velocity resolution of the observations, however, makes it difficult to confirm the rotational kinematics of this feature. A brightening in the HCN emission towards the core centre suggests that HCN can survive in the gas phase in the inner, dense regions of the proto-brown dwarf. In contrast, modelling of the HCO+ (3-2) line emission indicates that it originates from the outer pseudo-disc/envelope region and is centrally depleted. HCN line emission can reveal the small-scale structures and can be an efficient observational tool to study the inner disc properties in such faint compact objects where spatially resolving the disc is nearly impossible.

    DOI: 10.1093/mnrasl/slae044

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  • Atomic-Scale 3D Structure of a Supported Pd Nanoparticle Revealed by Electron Tomography with Convolution Neural Network-Based Image Inpainting

    Iwai, H; Nishino, F; Yamamoto, T; Kudo, M; Tsushida, M; Yoshida, H; Machida, M; Ohyama, J

    SMALL METHODS   8 ( 7 )   e2301163   2024.7   ISSN:2366-9608

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  • Internal 1000 au Scale Structures of the R CrA Cluster-forming Cloud. I. Filamentary Structures

    Tachihara, K; Fukaya, N; Tokuda, K; Yamasaki, Y; Nishioka, T; Abe, D; Inoue, T; Harada, N; Shoshi, A; Nozaki, S; Sato, A; Omura, M; Fujishiro, K; Fukagawa, M; Machida, MN; Kanai, T; Oasa, Y; Onishi, T; Saigo, K; Fukui, Y

    ASTROPHYSICAL JOURNAL   968 ( 2 )   2024.6   ISSN:0004-637X eISSN:1538-4357

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    We report Atacama Large Millimeter/submillimeter Array/Atacama Compact Array observations of a high-density region of the Corona Australis cloud forming a young star cluster, and the results of resolving internal structures. In addition to embedded Class 0/I protostars in the continuum, a number of complex dense filamentary structures are detected in the C18O and SO lines by the 7 m array. These are substructures of the molecular clump that are detected by the total power array as extended emission. We identify 101 and 37 filamentary structures with widths of a few thousand astronomical units in C18O and SO, respectively, which are called feathers. The typical column density of the feathers in C18O is about 1022 cm−2, and the volume density and line mass are ∼105 cm−3 and a few M ☉ pc−1, respectively. This line mass is significantly smaller than the critical line mass expected for cold and dense gas. These structures have complex velocity fields, indicating a turbulent interior. The number of feathers associated with Class 0/I protostars is only ∼10, indicating that most of them do not form stars but rather are transient structures. The formation of feathers can be interpreted as a result of colliding gas flow because the morphology is well reproduced by MHD simulations, and this is supported by the presence of H i shells in the vicinity. The colliding gas flows may accumulate gas and form filaments and feathers, and trigger the active star formation of the R CrA cluster.

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  • Delivery of Dust Particles from Protoplanetary Disks onto Circumplanetary Disks of Giant Planets

    Natsuho Maeda, Keiji Ohtsuki, Ryo Suetsugu, Yuhito Shibaike, Takayuki Tanigawa, Masahiro N. Machida

    The Astrophysical Journal   968 ( 2 )   62 - 62   2024.6   ISSN:0004-637X eISSN:1538-4357

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    The principal regular satellites of gas giants are thought to be formed by the accumulation of solid materials in circumplanetary disks (CPDs). While there has been significant progress in the study of satellite formation in CPDs, details of the supply of satellite building blocks to CPDs remain unclear. We perform the orbital integration of solid particles in the protoplanetary disk (PPD) approaching a planet, considering the gas drag force by using the results of three-dimensional hydrodynamical simulations of a local region around the planet. We investigate the planetary mass dependence of the capture positions and the capture rates of dust particles accreting onto the CPD. We also examine the degree of dust retention in the accreting gas onto the CPD, which is important for determining the ratio of the dust-to-gas inflow rates, a key parameter in satellite formation. We find that the degree of dust retention increases with increasing planetary mass for a given dust scale height in the PPD. In the case of a small planet (M <sub>p</sub> = 0.2M <sub>Jup</sub>), most particles with insufficient initial altitudes in the PPD are isolated from the gas in the accreting region. On the other hand, in the case of a massive planet (M <sub>p</sub> = 1M <sub>Jup</sub>), dust particles can be coupled to the vertically accreting gas, even when the dust scale height is about 10%–30% of the gas scale height. The results of this study can be used for models of dust delivery and satellite formation in the CPDs of gas giants of various masses, including exoplanets.

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  • Multiple Outflows around a Single Protostar IRAS 15398−3359

    Jinshi 崔 Sai 英 薩, Hsi-Wei Yen, Masahiro N. Machida, Nagayoshi Ohashi, Yusuke Aso, Anaëlle J. Maury, Sébastien Maret

    The Astrophysical Journal   966 ( 2 )   2024.5   ISSN:0004-637X eISSN:1538-4357

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  • Discovery of Asymmetric Spike-like Structures of the 10 au Disk around the Very Low-luminosity Protostar Embedded in the Taurus Dense Core MC 27/L1521F with ALMA

    Kazuki Tokuda, Naoto Harada, Mitsuki Omura, Tomoaki Matsumoto, Toshikazu Onishi, Kazuya Saigo, Ayumu Shoshi, Shingo Nozaki, Kengo Tachihara, Naofumi Fukaya, Yasuo Fukui, Shu Ichiro Inutsuka, Masahiro N. Machida

    Astrophysical Journal   965 ( 2 )   2024.4   ISSN:0004-637X eISSN:1538-4357

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    Recent Atacama Large Millimeter/submillimeter Array (ALMA) observations have revealed an increasing number of compact protostellar disks with radii of less than a few tens of astronomical units and that young Class 0/I objects have an intrinsic size diversity. To deepen our understanding of the origin of such tiny disks, we have performed highest-resolution configuration observations with ALMA at a beam size of ∼0.″03 (4 au) on the very low-luminosity Class 0 protostar embedded in the Taurus dense core MC 27/L1521F. The 1.3 mm continuum measurement successfully resolved a tiny, faint (∼1 mJy) disk with a major axis length of ∼10 au, one of the smallest examples in the ALMA protostellar studies. In addition, we detected spike-like components in the northeastern direction at the disk edge. Gravitational instability or other fragmentation mechanisms cannot explain the structures, given the central stellar mass of ∼0.2 M ⊙ and the disk mass of ≳10−4 M ⊙. Instead, we propose that these small spike structures were formed by a recent dynamic magnetic flux transport event due to interchange instability that would be favorable to occur if the parental core has a strong magnetic field. The presence of complex arc-like structures on a larger (∼2000 au) scale in the same direction as the spike structures suggests that the event was not single. Such episodic, dynamical events may play an important role in maintaining the compact nature of the protostellar disk in the complex gas envelope during the main accretion phase.

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  • Outflows Driven from a Magnetic Pseudodisk

    Shantanu Basu, Mahmoud Sharkawi, Masahiro N. Machida

    The Astrophysical Journal   964 ( 2 )   2024.4   ISSN:0004-637X eISSN:1538-4357

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  • Observations of spiral and streamer on a candidate proto-brown dwarf

    Riaz, B; Stamatellos, D; Machida, MN

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   529 ( 4 )   3601 - 3609   2024.3   ISSN:0035-8711 eISSN:1365-2966

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    Spirals and streamers are the hallmarks of mass accretion during the early stages of star formation. We present the first observations of a large-scale spiral and a streamer towards a very young brown dwarf candidate in its early formation stages. These observations show, for the first time, the influence of external environment that results in asymmetric mass accretion via feeding filaments on to a candidate proto-brown dwarf in the making. The impact of the streamer has produced emission in warm carbon-chain species close to the candidate proto-brown dwarf. Two contrasting scenarios, a pseudo-disc twisted by core rotation and the collision of dense cores, can both explain these structures. The former argues for the presence of a strong magnetic field in brown dwarf formation while the latter suggests that a minimal magnetic field allows large-scale spirals and clumps to form far from the candidate proto-brown dwarf.

    DOI: 10.1093/mnras/stae724

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  • Revealing Multiple Nested Molecular Outflows with Rotating Signatures in HH270mms1-A with ALMA

    Mitsuki Omura, Kazuki Tokuda, Masahiro N. Machida

    The Astrophysical Journal   963 ( 1 )   2024.3   ISSN:0004-637X eISSN:1538-4357

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    DOI: 10.3847/1538-4357/ad19ce

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  • An Extremely Young Protostellar Core, MMS 1/OMC-3: Episodic Mass Ejection History Traced by the Micro SiO Jet

    Satoko Takahashi, Masahiro N. Machida, Mitsuki Omura, Doug Johnstone, Kazuya Saigo, Naoto Harada, Kohji Tomisaka, Paul T. P. Ho, Luis A. Zapata, Steve Mairs, Gregory J. Herczeg, Kotomi Taniguchi, Yuhua Liu, Asako Sato

    The Astrophysical Journal   964 ( 1 )   2024.3   ISSN:0004-637X eISSN:1538-4357

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    DOI: 10.3847/1538-4357/ad2268

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  • Dust Polarization of Prestellar and Protostellar Sources in OMC-3

    Yuhua Liu, Satoko Takahashi, Masahiro Machida, Kohji Tomisaka, Josep Miquel Girart, Paul T. P. Ho, Kouichiro Nakanishi, Asako Sato

    The Astrophysical Journal   963 ( 2 )   2024.3   ISSN:0004-637X eISSN:1538-4357

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  • Ring Gap Structure around Class I Protostar WL 17

    Ayumu Shoshi, Naoto Harada, Kazuki Tokuda, Yoshihiro Kawasaki, Hayao Yamasaki, Asako Sato, Mitsuki Omura, Masayuki Yamaguchi, Kengo Tachihara, Masahiro N. Machida

    The Astrophysical Journal   961 ( 2 )   2024.2   ISSN:0004-637X eISSN:1538-4357

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  • Uranium-plutonium-americium cation interdiffusion in polycrystalline (U, Pu,Am)O2±x mixed oxides

    Vauchy, R; Matsumoto, T; Hirooka, S; Uno, H; Tamura, T; Arima, T; Inagaki, Y; Idemitsu, K; Nakamura, H; Machida, M; Murakami, T; Kato, M

    JOURNAL OF NUCLEAR MATERIALS   588   2024.1   ISSN:0022-3115 eISSN:1873-4820

  • Simulations of two-temperature jets in galaxy clusters II. X-ray properties of the forward shock

    Ohmura, T; Machida, M; Akamatsu, H

    ASTRONOMY & ASTROPHYSICS   679   2023.11   ISSN:0004-6361 eISSN:1432-0746

  • Simulations of two-temperature jets in galaxy clusters: I. Effect of jet magnetization on dynamics and electron heating

    Ohmura, T; Machida, M

    ASTRONOMY & ASTROPHYSICS   679   2023.11   ISSN:0004-6361 eISSN:1432-0746

  • Secondary Outflow Driven by the Protostar Ser-emb 15 in Serpens

    Asako Sato, Kazuki Tokuda, Masahiro N. Machida, Kengo Tachihara, Naoto Harada, Hayao Yamasaki, Shingo Hirano, Toshikazu Onishi, Yuko Matsushita

    The Astrophysical Journal   958 ( 2 )   102 - 102   2023.11   ISSN:0004-637X eISSN:1538-4357

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    We present the detection of a secondary outflow associated with a Class I source, Ser-emb 15, in the Serpens Molecular Cloud. We reveal two pairs of molecular outflows consisting of three lobes, that is, primary and secondary outflows, using Atacama Large Millimeter/submillimeter Array <sup>12</sup>CO and SiO line observations at a resolution of ∼318 au. The secondary outflow is elongated approximately perpendicular to the axis of the primary outflow in the plane of the sky. We also identify two compact structures, Sources A and B, within an extended structure associated with Ser-emb 15 in the 1.3 mm continuum emission at a resolution of ∼40 au. The projected sizes of Sources A and B are 137 au and 60 au, respectively. Assuming a dust temperature of 20 K, we estimate the dust mass to be 2.4 × 10<sup>−3</sup>M<sub>⊙</sub> for Source A and 3.3 × 10<sup>−4</sup>M<sub>⊙</sub> for Source B. C<sup>18</sup>O line data imply rotational motion around the extended structure, but we cannot resolve rotational motion in Source A and/or B because the angular and frequency resolutions are insufficient. Therefore, we cannot conclude whether Ser-emb 15 is a single or binary system. Thus, either Source A or Source B could drive the secondary outflow. We discuss two scenarios that might explain the driving mechanism of the primary and secondary outflows: the Ser-emb 15 system is (1) a binary system composed of Sources A and B, or (2) a single-star system composed of Source A alone. In either case, the system could be a suitable target for investigating the disk and/or binary formation processes in complicated environments. Detecting these outflows should contribute to understanding complex star-forming environments, which may be common in the star formation processes.

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  • An ALMA-resolved View of 7000 au Protostellar Gas Ring around the Class I Source CrA-IRS 2 as a Possible Sign of Magnetic Flux Advection

    Kazuki Tokuda, Naofumi Fukaya, Kengo Tachihara, Mitsuki Omura, Naoto Harada, Shingo Nozaki, Ayumu Shoshi, Masahiro N. Machida

    The Astrophysical Journal Letters   956 ( 1 )   2023.10   ISSN:2041-8205 eISSN:2041-8213

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  • Gravitational wave physics and astronomy in the nascent era

    Arimoto, M; Asada, H; Cherry, ML; Fujii, MS; Fukazawa, Y; Harada, A; Hayama, K; Hosokawa, T; Ioka, K; Itoh, Y; Kanda, N; Kawabata, KS; Kawaguchi, K; Kawai, N; Kobayashi, T; Kohri, K; Koshio, Y; Kotake, K; Kumamoto, J; Machida, MN; Matsufuru, H; Mihara, T; Mori, M; Morokuma, T; Mukohyama, S; Nakano, H; Narikawa, T; Negoro, H; Nishizawa, A; Ohgami, T; Omukai, K; Sakamoto, T; Sako, S; Sasada, M; Sekiguchi, Y; Serino, M; Soda, J; Sugita, S; Sumiyoshi, K; Susa, H; Suyama, T; Takahashi, H; Takahashi, K; Takiwaki, T; Tanaka, T; Tanaka, M; Tanikawa, A; Tominaga, N; Uchikata, N; Utsumi, Y; Vagins, MR; Yamada, K; Yoshida, M

    PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS   2023 ( 10 )   2023.10   ISSN:2050-3911

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    The detections of gravitational waves (GW) by the LIGO/Virgo collaborations provide various possibilities for both physics and astronomy. We are quite sure that GW observations will develop a lot, both in precision and in number, thanks to the continuous work on the improvement of detectors, including the expected new detector, KAGRA, and the planned detector, LIGO-India. On this occasion, we review the fundamental outcomes and prospects of gravitational wave physics and astronomy. We survey the development, focusing on representative sources of gravitational waves: binary black holes, binary neutron stars, and supernovae. We also summarize the role of gravitational wave observations as a probe of new physics.

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  • An ALMA Glimpse of Dense Molecular Filaments Associated with High-mass Protostellar Systems in the Large Magellanic Cloud Reviewed

    Kazuki Tokuda, Naoto Harada, Kei E. I. Tanaka, Tsuyoshi Inoue, Takashi Shimonishi, Yichen Zhang, Marta Sewiło, Yuri Kunitoshi, Ayu Konishi, Yasuo Fukui, Akiko Kawamura, Toshikazu Onishi, Masahiro N. Machida

    The Astrophysical Journal   955 ( 1 )   52 - 52   2023.9   ISSN:0004-637X eISSN:1538-4357

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    Recent millimeter/submillimeter facilities have revealed the physical properties of filamentary molecular clouds in relation to high-mass star formation. A uniform survey of the nearest, face-on star-forming galaxy, the Large Magellanic Cloud (LMC), complements the Galactic knowledge. We present ALMA survey data with a spatial resolution of ∼0.1 pc in the 0.87 mm continuum and HCO<sup>+</sup> (4–3) emission toward 30 protostellar objects with luminosities of 10<sup>4</sup>–10<sup>5.5</sup>L<sub>⊙</sub> in the LMC. The spatial distributions of the HCO<sup>+</sup> (4–3) line and thermal dust emission are well correlated, indicating that the line effectively traces dense, filamentary gas with an H<sub>2</sub> volume density of ≳10<sup>5</sup> cm<sup>−3</sup> and a line mass of ∼10<sup>3</sup>–10<sup>4</sup>M<sub>⊙</sub> pc<sup>−1</sup>. Furthermore, we obtain an increase in the velocity line widths of filamentary clouds, which follows a power-law dependence on their H<sub>2</sub> column densities with an exponent of ∼0.5. This trend is consistent with observations toward filamentary clouds in nearby star-forming regions within ≲1 kpc from us and suggests enhanced internal turbulence within the filaments due to surrounding gas accretion. Among the 30 sources, we find that 14 are associated with hub-filamentary structures, and these complex structures predominantly appear in protostellar luminosities exceeding ∼5 × 10<sup>4</sup>L<sub>⊙</sub>. The hub-filament systems tend to appear in the latest stages of their natal cloud evolution, often linked to prominent H ii regions and numerous stellar clusters. Our preliminary statistics suggest that the massive filaments accompanied by hub-type complex features may be a necessary intermediate product in forming extremely luminous high-mass stellar systems capable of ultimately dispersing the parent cloud.

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  • Exact Calculation of Nonideal Fields Demonstrates Their Dominance of Injection in Relativistic Reconnection

    Totorica, SR; Zenitani, S; Matsukiyo, S; Machida, M; Sekiguchi, K; Bhattacharjee, A

    ASTROPHYSICAL JOURNAL LETTERS   952 ( 1 )   2023.7   ISSN:2041-8205 eISSN:2041-8213

  • Co-evolution of dust grains and protoplanetary disks Reviewed

    Yusuke Tsukamoto, Masahiro N. Machida, Shu-ichiro Inutsuka

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   75 ( 5 )   835 - 852   2023.7   ISSN:0004-6264 eISSN:2053-051X

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    We propose a new evolutionary process for protoplanetary disks, the co-evolution of dust grains and protoplanetary disks, revealed by dust-gas two-fluid non-ideal magnetohydrodynamics simulations considering the growth of dust grains and associated changes in magnetic resistivity. We found that the dust growth significantly affects disk evolution by changing the coupling between the gas and the magnetic field. Moreover, once the dust grains grow sufficiently large and the adsorption of charged particles on to them becomes negligible, the physical quantities (e.g., density and magnetic field) of the disk are well described by characteristic power laws. In this disk structure, the radial profile of density is steeper and the disk mass is smaller than those of the model ignoring dust growth. We analytically derive these power laws from the basic equations of non-ideal magnetohydrodynamics. The analytical power laws are determined only by observable physical quantities, e.g., central stellar mass and mass accretion rate, and do not include difficult-to-determine parameters, e.g., the viscous parameter & alpha;. Therefore, our model is observationally testable and this disk structure is expected to provide a new perspective for future studies on protostar and disk evolution.

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  • Magnetic Effects Promote Supermassive Star Formation in Metal-enriched Atomic-cooling Halos Reviewed

    Shingo Hirano, Masahiro N. Machida, Shantanu Basu

    Astrophysical Journal   952 ( 1 )   56 - 56   2023.7   ISSN:0004-637X eISSN:1538-4357

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    Intermediate-mass black holes (with ≥10<sup>5</sup>M<sub>⊙</sub>) are promising candidates for the origin of supermassive black holes (with ∼10<sup>9</sup>M<sub>⊙</sub>) in the early universe (redshift z ∼ 6). Chon &amp; Omukai first pointed out direct collapse black hole (DCBH) formation in metal-enriched atomic-cooling halos (ACHs), which relaxes the DCBH formation criterion. On the other hand, Hirano et al. showed that magnetic effects promote DCBH formation in metal-free ACHs. We perform a set of magnetohydrodynamical simulations to investigate star formation in magnetized ACHs with metallicities Z/Z<sub>⊙</sub> = 0, 10<sup>−5</sup>, and 10<sup>−4</sup>. Our simulations show that the mass accretion rate onto the protostars becomes lower in metal-enriched ACHs than in metal-free ACHs. However, many protostars form from gravitationally and thermally unstable metal-enriched gas clouds. Under such circumstances, the magnetic field rapidly increases as magnetic field lines wind up due to the spin of protostars. The region with the amplified magnetic field expands outwards due to the orbital motion of protostars and the rotation of the accreting gas. The amplified magnetic field extracts angular momentum from the accreting gas, promotes the coalescence of low-mass protostars, and increases the mass growth rate of the primary protostar. We conclude that the magnetic field amplification is always realized in metal-enriched ACHs regardless of the initial magnetic field strength, which affects the DCBH formation criterion. In addition, we find a qualitatively different trend from the previous unmagnetized simulations in that the mass growth rate is maximal for extremely metal-poor ACHs with Z/Z<sub>⊙</sub> = 10<sup>−5</sup>.

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  • Impact of turbulence intensity and fragmentation velocity on dust particle size evolution and non-ideal magnetohydrodynamics effects Reviewed

    Yoshihiro Kawasaki, Masahiro N. Machida

    Monthly Notices of the Royal Astronomical Society   522 ( 3 )   3679 - 3692   2023.7   ISSN:0035-8711 eISSN:1365-2966

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    We investigate the influence of dust particle size evolution on non-ideal magnetohydrodynamic (MHD) effects during the collapsing phase of star-forming cores, taking both the turbulence intensity in the collapsing cloud core and the fragmentation velocity of dust particles as parameters. When the turbulence intensity is small, the dust particles do not grow significantly, and the non-ideal MHD effects work efficiently in high-density regions. The dust particles rapidly grow in a strongly turbulent environment, while the efficiency of non-ideal MHD effects in such an environment depends on the fragmentation velocity of the dust particles. When the fragmentation velocity is small, turbulence promotes coagulation growth and collisional fragmentation of dust particles, producing small dust particles. In this case, the adsorption of charged particles on the dust particle surfaces becomes efficient and the abundance of charged particles decreases, making non-ideal MHD effects effective at high densities. On the other hand, when the fragmentation velocity is high, dust particles are less likely to fragment, even if the turbulence is strong. In this case, the production of small dust particles becomes inefficient and non-ideal MHD effects become less effective. We also investigate the effect of the dust composition on the star and disc formation processes. We constrain the turbulence intensity of a collapsing core and the fragmentation velocity of dust for circumstellar disc formation due to the dissipation of the magnetic field.

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  • First observations of warm and cold methanol in Class 0/I proto-brown dwarfs Reviewed

    B. Riaz, W. F. Thi, M. N. Machida

    Monthly Notices of the Royal Astronomical Society   522 ( 4 )   4934 - 4954   2023.7   ISSN:0035-8711 eISSN:1365-2966

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    We present results from the first molecular line survey to search for the fundamental complex organic molecule, methanol (CH3OH), in 14 Class 0/I proto-brown dwarfs (proto-BDs). IRAM 30-m observations over the frequency range of 92-116 and 213-280 GHz have revealed emission in 14 CH3OH transition lines, at upper state energy level, Eupper ∼7-49 K, and critical densities, ncrit of 105-109 cm−3. The most commonly detected lines are at Eupper < 20 K, while 11 proto-BDs also show emission in the higher excitation lines at Eupper ∼21-49 K and ncrit ∼ 105 to 108 cm−3. In comparison with the brown dwarf formation models, the high excitation lines likely probe the warm (∼25-50 K) corino region at ∼10-50 au in the proto-BDs, while the low-excitation lines trace the cold (<20 K) gas at ∼50-150 au. The column density for the cold component is an order of magnitude higher than the warm component. The CH3OH ortho-to-para ratios range between ∼0.3 and 2.3. The volume-averaged CH3OH column densities show a rise with decreasing bolometric luminosity among the proto-BDs, with the median column density higher by a factor of ∼3 compared to low-mass protostars. Emission in high-excitation (Eupper > 25 K) CH3OH lines together with the model predictions suggest that a warm corino is present in ∼78 per cent of the proto-BDs in our sample. The remaining shows evidence of only the cold component, possibly due to the absence of a strong, high-velocity jet that can stir up the warm gas around it.

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  • Direct Imaging Explorations for Companions around Mid-Late M Stars from the Subaru/IRD Strategic Program Reviewed

    Taichi Uyama, Charles Beichman, Masayuki Kuzuhara, Markus Janson, Takayuki Kotani, Dimitri Mawet, Bun’ei Sato, Motohide Tamura, Hiroyuki Tako Ishikawa, Bryson Cale, Thayne Currie, Hiroki Harakawa, Thomas Henning, Teruyuki Hirano, Klaus Hodapp, Yasunori Hori, Masato Ishizuka, Shane Jacobson, Yui Kasagi, Eiichiro Kokubo, Mihoko Konishi, Tomoyuki Kudo, Takashi Kurokawa, Nobuhiko Kusakabe, Jungmi Kwon, Masahiro Machida, Takao Nakagawa, Norio Narita, Jun Nishikawa, Masahiro Ogihara, Masashi Omiya, Takuma Serizawa, Akitoshi Ueda, Sébastien Vievard, Ji Wang

    Astronomical Journal   165 ( 4 )   2023.4   ISSN:0004-6256 eISSN:1538-3881

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    The Subaru telescope is currently performing a strategic program (SSP) using the high-precision near-infrared (NIR) spectrometer IRD to search for exoplanets around nearby mid/late M dwarfs via radial velocity (RV) monitoring. As part of the observing strategy for the exoplanet survey, signatures of massive companions such as RV trends are used to reduce the priority of those stars. However, this RV information remains useful for studying the stellar multiplicity of nearby M dwarfs. To search for companions around such "deprioritized" M dwarfs, we observed 14 IRD-SSP targets using Keck/NIRC2 with pyramid wave-front sensing at NIR wavelengths, leading to high sensitivity to substellar-mass companions within a few arcseconds. We detected two new companions (LSPM J1002+1459 B and LSPM J2204+1505 B) and two new candidates that are likely companions (LSPM J0825+6902 B and LSPM J1645+0444 B), as well as one known companion. Including two known companions resolved by the IRD fiber injection module camera, we detected seven (four new) companions at projected separations between similar to 2 and 20 au in total. A comparison of the colors with the spectral library suggests that LSPM J2204+1505 B and LSPM J0825+6902 B are located at the boundary between late M and early L spectral types. Our deep high-contrast imaging for targets where no bright companions were resolved did not reveal any additional companion candidates. The NIRC2 detection limits could constrain potential substellar-mass companions (similar to 10-75 M (Jup)) at 10 au or further. The failure with Keck/NIRC2 around the IRD-SSP stars having significant RV trends makes these objects promising targets for further RV monitoring or deeper imaging with the James Webb Space Telescope to search for smaller-mass companions below the NIRC2 detection limits.

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  • Crescent-shaped Molecular Outflow from the Intermediate-mass Protostar DK Cha Revealed by ALMA Reviewed

    Naoto Harada, Kazuki Tokuda, Hayao Yamasaki, Asako Sato, Mitsuki Omura, Shingo Hirano, Toshikazu Onishi, Kengo Tachihara, Masahiro N. Machida

    The Astrophysical Journal   945 ( 1 )   63 - 63   2023.3   ISSN:0004-637X eISSN:1538-4357

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    We report on an Atacama Large Millimeter/submillimeter Array study of the Class I or II intermediate-mass protostar DK Cha in the Chamaeleon II region. The <sup>12</sup>CO(J = 2–1) images have an angular resolution of ∼1″ (∼250 au) and show high-velocity blueshifted (≳70 km s<sup>−1</sup>) and redshifted (≳50 km s<sup>−1</sup>) emissions, which have 3000 au scale crescent-shaped structures around the protostellar disk traced in the 1.3 mm continuum. Because the high-velocity components of the CO emission are associated with the protostar, we concluded that the emission traces the pole-on outflow. The blueshifted outflow lobe has a clear layered velocity gradient with a higher-velocity component located on the inner side of the crescent shape, which can be explained by a model of an outflow with a higher velocity in the inner radii. Based on the directly driven outflow scenario, we estimated the driving radii from the observed outflow velocities and found that the driving region extends over 2 orders of magnitude. The <sup>13</sup>CO emission traces a complex envelope structure with arc-like substructures with lengths of ∼1000 au. We identified the arc-like structures as streamers because they appear to be connected to a rotating infalling envelope. DK Cha is useful for understanding characteristics that are visible by looking at nearly face-on configurations of young protostellar systems, providing an alternative perspective for studying the star formation process.

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  • Environmental effects of star-forming cores on mass accretion rate Reviewed

    Shingo Nozaki, Masahiro N. Machida

    Monthly Notices of the Royal Astronomical Society   519 ( 4 )   5017 - 5030   2023.3   ISSN:0035-8711 eISSN:1365-2966

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    We calculate the evolution of cloud cores embedded in different envelopes to investigate environmental effects on the mass accretion rate on to protostars. As the initial state, we neglect the magnetic field and cloud rotation, and adopt star-forming cores composed of two parts: a centrally condensed core and an outer envelope. The inner core has a critical Bonnor-Ebert density profile and is enclosed by the outer envelope. We prepare 15 star-forming cores with different outer envelope densities and gravitational radii, within which the gas flows into the collapsing core, and calculate their evolution until ∼2 × 105 yr after protostar formation. The mass accretion rate decreases as the core is depleted when the outer envelope density is low. In contrast, the mass accretion rate is temporarily enhanced when the outer envelope density is high and the resultant protostellar mass exceeds the initial mass of the centrally condensed core. Some recent observations indicate that the mass of pre-stellar cores is too small to reproduce the stellar mass distribution. Our simulations show that the mass inflow from outside the core contributes greatly to protostellar mass growth when the core is embedded in a high-density envelope, which could explain the recent observations.

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  • Effects of depolarizing intervening galaxies on background radio emission. I. Global disk magnetic field

    Omae, R; Akahori, T; Machida, M

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   75 ( SUPP1 )   S108 - S122   2023.2   ISSN:0004-6264 eISSN:2053-051X

  • Pseudo-observation of spiral galaxies in the radio band to verify depolarization models

    Tashima, Y; Ohmura, T; Machida, M

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   75   S123 - S137   2023.2   ISSN:0004-6264 eISSN:2053-051X

  • ALMA Fragmented Source Catalog in Orion (FraSCO). I. Outflow Interaction within an Embedded Cluster in OMC-2/FIR 3, FIR 4, and FIR 5 Reviewed International journal

    Asako Sato, Satoko Takahashi, Shun Ishii, Paul T.P. Ho, Masahiro N. Machida, John Carpenter, Luis A. Zapata, Paula Stella Teixeira, Sümeyye Suri

    The Astrophysical Journal   944 ( 1 )   92 - 92   2023.2   ISSN:0004-637X eISSN:1538-4357

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    We present a high-angular resolution (∼1″) and wide-field ($2\buildrel{\,\prime}\over{.} 9\times 1\buildrel{\,\prime}\over{.} 9$) image of the 1.3 mm continuum, CO(J = 2–1) and SiO(J = 5–4) line emissions toward an embedded protocluster, FIR 3, FIR 4, and FIR 5, in the Orion Molecular Cloud 2 obtained from the Atacama Large Millimeter/submillimeter Array. We identify 51 continuum sources, 36 of which are newly identified in this study. Their dust masses, projected sizes, and H<sub>2</sub> gas number densities are estimated to be 3.8 × 10<sup>−5</sup>–1.1 × 10<sup>−2</sup>M<sub>⊙</sub>, 290–2000 au, and 6.4 × 10<sup>6</sup>–3.3 × 10<sup>8</sup> cm<sup>−3</sup>, respectively. The results of a Jeans analysis show that ∼80% of the protostellar sources and ∼15% of the prestellar sources are gravitationally bound. We identify 12 molecular outflows traced in the CO(J = 2–1) emission, six of which are newly detected. We spatially resolve shocked gas structures traced by the SiO(J = 5–4) emission in this region for the first time. We identify shocked gas originating from outflows and other shocked regions. These results provide direct evidence of an interaction between dust condensation, FIR 4, and an energetic outflow driven by HOPS-370 located within FIR 3. A comparison of the outflow dynamical timescales, fragmentation timescales, and protostellar ages shows that the previously proposed triggered star formation scenario in FIR 4 is not strongly supported. We also discuss the spatial distribution of filaments identified in our continuum image by comparing it with a previously identified hub-fiber system in the N<sub>2</sub>H<sup>+</sup> line.

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  • Dust motion and possibility of dust growth in a growing circumstellar disk

    Koga, S; Machida, MN

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   519 ( 3 )   3595 - 3610   2023.1   ISSN:0035-8711 eISSN:1365-2966

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    We calculate the evolution of a star-forming cloud core using a three-dimensional resistive magnetohydrodynamics simulation, treating dust grains as Lagrangian particles, to investigate the dust motion in the early star formation stage. We prepare six different-sized set of dust particles in the range ad = 0.01-1000 μm, where ad is the dust grain size. In a gravitationally collapsing cloud, a circumstellar disk forms around a protostar and drives a protostellar outflow. Almost all the small dust grains (ad 10-100 μm) initially distributed in the region θ0 45° are ejected from the center by the outflow, where θ0 is the initial zenith angle relative to the rotation axis, whereas only a small number of the large dust grains (a d gtrsim 100 μm) distributed in the region are ejected. All other grains fall onto either the protostar or disk without being ejected by the outflow. Regardless of the dust grain size, the behavior of the dust motion is divided into two trends after dust particles settle into the circumstellar disk. The dust grains reaching the inner disk region from the upper envelope preferentially fall onto the protostar, while those reaching the outer disk region or disk outer edge from the envelope can survive without an inward radial drift. These surviving grains can induce dust growth. Thus, we expect that the outer disk regions could be a favored place of planet formation.

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  • The water and methanol masers in the face-on accretion system around the high-mass protostar G353.273+0.641

    Kazuhito Motogi, Tomoya Hirota, Masahiro N. Machida, Kei E. I. Tanaka, Yoshinori Yonekura

    Proceedings of the International Astronomical Union   18 ( S380 )   172 - 176   2022.12   ISSN:1743-9213 eISSN:1743-9221

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    We report on a direct comparison of VLBI maser data and ALMA thermal-emission data for the high-mass protostar G353.273+0.641. We detected a gravitationally-unstable disk by dust and a high-velocity jet traced by a thermal CO line by ALMA long-baselines (LB). 6.7 GHz CH<sub>3</sub>OH masers trace infalling streamlines inside the disk. The innermost maser ring indicates another compact accretion disk of 30 au. Such a nested system could be caused by angular momentum transfer by the spiral arms. 22 GHz H<sub>2</sub>O masers trace the jet-accelerating region, which are directly connecting the CO jet and the protostar. The recurrent maser flares imply episodic jet ejections per 1–2 yr, while typical separation of CO knots indicates a variation of outflow rate per 100 yr. Our study demonstrates that VLBI maser observations are still a powerful tool to explore detailed structures nearby high-mass protostars by combining ALMA LB.

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  • Twisted magnetic field in star formation processes of L1521 F revealed by submillimeter dual band polarimetry using James Clerk Maxwell Telescope Reviewed

    Sakiko Fukaya, Hiroko Shinnaga, Ray S. Furuya, Kohji Tomisaka, Masahiro N. Machida, Naoto Harada

    Publications of the Astronomical Society of Japan   75 ( 1 )   120 - 127   2022.11   ISSN:0004-6264 eISSN:2053-051X

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    Understanding the initial conditions of star formation requires both
    observational studies and theoretical works taking into account the magnetic
    field, which plays an important role in star formation processes. Herein, we
    study the young nearby dense cloud core L1521 F ($n$(H$_2$) $\sim 10^{4-6}$
    cm$^{-3}$) in the Taurus Molecular Cloud. This dense core hosts a 0.2 $M_\odot$
    protostar, categorized as a Very Low Luminosity Objects with complex velocity
    structures, particularly in the vicinity of the protostar. To trace the
    magnetic field within the dense core, we conducted high sensitivity
    submillimeter polarimetry of the dust continuum at $\lambda$= 850 $\mu$m and
    450 $\mu$m using the POL-2 polarimeter situated in front of the SCUBA-2
    submillimeter bolometer camera on James Clerk Maxwell Tetescope. This was
    compared with millimeter polarimetry taken at $\lambda$= 3.3 mm with ALMA. The
    magnetic field was detected at $\lambda$= 850 $\mu$m in the peripheral region,
    which is threaded in a north-south direction, while the central region traced
    at $\lambda$= 450 $\mu$m shows a magnetic field with an east-west direction,
    i.e., orthogonal to that of the peripheral region. Magnetic field strengths are
    estimated to be $\sim$70 $\mu$G and 200 $\mu$G in the peripheral- and
    central-regions, respectively, using the Davis-Chandrasekhar-Fermi method. The
    resulting mass-to-flux ratio of 3 times larger than that of magnetically
    critical state for both regions indicates that L1521 F is magnetically
    supercritical, i.e., gravitational forces dominate over magnetic turbulence
    forces. Combining observational data with MHD simulations, detailed parameters
    of the morphological properties of this puzzling object are derived for the
    first time.

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  • Implementation of dust particles in three-dimensional magnetohydrodynamics simulation: dust dynamics in a collapsing cloud core Reviewed

    Yoshihiro Kawasaki, Yoshihiro Kawasaki, Masahiro N. Machida

    Monthly Notices of the Royal Astronomical Society   515 ( 4 )   6073 - 6092   2022.10   ISSN:0035-8711 eISSN:1365-2966

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    The aim of this study is to examine dust dynamics on a large scale and investigate the coupling of dust with gas fluid in the star formation process. We propose a method for calculating the dust trajectory in a gravitationally collapsing cloud, where the dust grains are treated as Lagrangian particles and are assumed to be neutral. We perform the dust trajectory calculations in combination with non-ideal magnetohydrodynamics simulation. Our simulation shows that dust particles with a size of $\le 10\, {\rm \mu m}$ are coupled with gas in a star-forming cloud core. We investigate the time evolution of the dust-to-gas mass ratio and the Stokes number, which is defined as the stopping time normalized by the freefall time-scale, and show that large dust grains ($\gtrsim 100\, {\rm \mu m}$) have a large Stokes number (close to unity) and tend to concentrate in the central region (i.e. protostar and rotationally supported disc) faster than do small grains ($\lesssim 10\, {\rm \mu m}$). Thus, large grains significantly increase the dust-to-gas mass ratio around and inside the disc. We also confirm that the dust trajectory calculations, which trace the physical quantities of each dust particle, reproduce previously reported results obtained using the Eulerian approach.

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  • The First Detection of a Protostellar CO Outflow in the Small Magellanic Cloud with ALMA Reviewed

    Kazuki Tokuda, Sarolta Zahorecz, Yuri Kunitoshi, Kosuke Higashino, Kei E. I. Tanaka, Ayu Konishi, Taisei Suzuki, Naoya Kitano, Naoto Harada, Takashi Shimonishi, Naslim Neelamkodan, Yasuo Fukui, Akiko Kawamura, Toshikazu Onishi, Masahiro N. Machida

    The Astrophysical Journal Letters   936 ( 1 )   L6 - L6   2022.9   ISSN:2041-8205 eISSN:2041-8213

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    Protostellar outflows are one of the most outstanding features of star formation. Observational studies over the last several decades have successfully demonstrated that outflows are ubiquitously associated with low- and high-mass protostars in solar-metallicity Galactic conditions. However, the environmental dependence of protostellar outflow properties is still poorly understood, particularly in the low-metallicity regime. Here we report the first detection of a molecular outflow in the Small Magellanic Cloud with 0.2 Z<sub>⊙</sub>, using Atacama Large Millimeter/submillimeter Array observations at a spatial resolution of 0.1 pc toward the massive protostar Y246. The bipolar outflow is nicely illustrated by high-velocity wings of CO(3–2) emission at ≳15 km s<sup>−1</sup>. The evaluated properties of the outflow (momentum, mechanical force, etc.) are consistent with those of the Galactic counterparts. Our results suggest that the molecular outflows, i.e., the guidepost of the disk accretion at the small scale, might be universally associated with protostars across the metallicity range of ∼0.2–1 Z<sub>⊙</sub>.

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  • Synthetic Polarization Maps of an Outflow Zone from Magnetohydrodynamic Simulations Reviewed

    Gianfranco Bino, Shantanu Basu, Masahiro N. Machida, Aris Tritsis, Mahmoud Sharkawi, Kundan Kadam, Indrani Das

    Astrophysical Journal   936 ( 1 )   2022.9   ISSN:0004-637X eISSN:1538-4357

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    The canonical theory of star formation in a magnetized environment predicts the formation of hourglass-shaped magnetic fields during the prestellar collapse phase. In protostellar cores, recent observations reveal complex and strongly distorted magnetic fields in the inner regions that are sculpted by rotation and outflows. We conduct resistive, nonideal magnetohydrodynamic simulations of a protostellar core and employ the radiative transfer code POLARIS to produce synthetic polarization segment maps. A comparison of our mock-polarization maps based on the toroidal-dominated magnetic field in the outflow zone with the observed polarization vectors of SiO lines in Orion Source I shows a reasonable agreement when the magnetic axis is tilted at an angle θ = 15° with respect to the plane of the sky and if the SiO lines have a net polarization parallel to the local magnetic field. Although the observed polarization is from SiO lines and our synthetic maps are due to polarized dust emission, a comparison is useful and allows us to resolve the ambiguity of whether the line polarization is parallel or perpendicular to the local magnetic field direction.

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  • Dust coagulation and fragmentation in a collapsing cloud core and their influence on non-ideal magnetohydrodynamic effects Reviewed

    Yoshihiro Kawasaki, Shunta Koga, Masahiro N. MacHida

    Monthly Notices of the Royal Astronomical Society   515 ( 2 )   2072 - 2087   2022.9   ISSN:0035-8711 eISSN:1365-2966

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    We determine the time-evolution of the dust particle size distribution during the collapse of a cloud core, accounting for both dust coagulation and dust fragmentation, to investigate the influence of dust growth on non-ideal magnetohydrodynamic (MHD) effects. The density evolution of the collapsing core is given by a one-zone model. We assume two types of dust model: dust composed only of silicate (silicate dust) and dust with a surface covered by H2O ice (H2O ice dust). When only considering collisional coagulation, the non-ideal MHD effects are not effective in the high-density region for both the silicate and H2O ice dust cases. This is because dust coagulation reduces the abundance of small dust particles, resulting in less efficient adsorption of charged particles on the dust surface. For the silicate dust case, when collisional fragmentation is included, the non-ideal MHD effects do apply at a high density of nH > 1012 cm-3 because of the abundant production of small dust particles. On the other hand, for the H2O ice dust case, the production of small dust particles due to fragmentation is not efficient. Therefore, for the H2O ice dust case, non-ideal magnetohydrodynamic effects apply only in the range nH ≳ 1014 cm-3, even when collisional fragmentation is considered. Our results suggest that it is necessary to consider both dust collisional coagulation and fragmentation to activate non-ideal magnetohydrodynamic effects, which should play a significant role in the star and disc formation processes.

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  • Delivery of Gas onto the Circumplanetary Disk of Giant Planets: Planetary-mass Dependence of the Source Region of Accreting Gas and Mass Accretion Rate Reviewed

    Natsuho Maeda, Keiji Ohtsuki, Takayuki Tanigawa, Masahiro N. Machida, Ryo Suetsugu

    The Astrophysical Journal   935 ( 1 )   56 - 56   2022.8   ISSN:0004-637X eISSN:1538-4357

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    Abstract

    Gas accretion onto the circumplanetary disks and the source region of accreting gas are important to reveal dust accretion that leads to satellite formation around giant planets. We performed local three-dimensional high-resolution hydrodynamic simulations of an isothermal and inviscid gas flow around a planet to investigate the planetary-mass dependence of the gas accretion bandwidth and gas accretion rate onto circumplanetary disks. We examined cases with various planetary masses corresponding to M<sub>p</sub> = 0.05–1M<sub>Jup</sub> at 5.2 au, where M<sub>Jup</sub> is the current Jovian mass. We found that the radial width of the gas accretion band is proportional to ${M}_{ { \rm{p } } }^{1/6}$ for the low-mass regime with M<sub>p</sub> ≲ 0.2M<sub>Jup</sub> while it is proportional to M<sub>p</sub> for the high-mass regime with M<sub>p</sub> ≳ 0.2M<sub>Jup</sub>. We found that the ratio of the mass accretion rate onto the circumplanetary disk to that into the Hill sphere is about 0.4 regardless of the planetary mass for the cases we examined. Combining our results with the gap model obtained from global hydrodynamic simulations, we derive a semi-analytical formula of mass accretion rate onto circumplanetary disks. We found that the mass dependence of our three-dimensional accretion rates is the same as the previously obtained two-dimensional case, although the qualitative behavior of accretion flow onto the circumplanetary disk is quite different between the two cases.

    DOI: 10.3847/1538-4357/ac7ddf

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  • Exponentially Amplified Magnetic Field Eliminates Disk Fragmentation around Population III Protostars Reviewed

    Shingo Hirano, Masahiro N. Machida

    The Astrophysical Journal Letters   935 ( 1 )   L16 - L16   2022.8   ISSN:2041-8205 eISSN:2041-8213

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    Abstract

    One critical remaining issue that is unclear in the initial mass function of the first (Population III) stars is the final fate of secondary protostars that formed in the accretion disk—specifically, whether they merge or survive. We focus on the magnetic effects on the formation of the first star under a cosmological magnetic field. We perform a suite of ideal magnetohydrodynamic simulations for 1000 yr after the first protostar formation. Instead of the sink particle technique, we employ a stiff equation of state approach to represent the magnetic field structure connecting protostars. Ten years after the first protostar formation in the cloud initialized with B<sub>0</sub> = 10<sup>−20</sup> G at n<sub>0</sub> = 10<sup>4</sup> cm<sup>−3</sup>, the magnetic field strength around the protostars has amplified from pico- to kilo-Gauss, which is the same strength as the present-day star. The magnetic field rapidly winds up since the gas in the vicinity of the protostar (≤10 au) has undergone several tens of orbital rotations in the first decade after protostar formation. As the mass accretion progresses, the vital magnetic field region extends outward, and magnetic braking eliminates the fragmentation of the disk that would happen in an unmagnetized model. On the other hand, assuming a gas cloud with a small angular momentum, this amplification might not work because the rotation would be slower. However, disk fragmentation would not occur in that case. We conclude that the exponential amplification of the cosmological magnetic field strength, about 10<sup>−18</sup> G, eliminates disk fragmentation around Population III protostars.

    DOI: 10.3847/2041-8213/ac85e0

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  • Selective Oxidation of Methane to Formaldehyde over a Silica-Supported Cobalt Single-Atom Catalyst

    Ohyama, J; Abe, D; Hirayama, A; Iwai, H; Tsuchimura, Y; Sakamoto, K; Irikura, M; Nakamura, Y; Yoshida, H; Machida, M; Nishimura, S; Yamamoto, T; Matsumura, S; Takahashi, K

    JOURNAL OF PHYSICAL CHEMISTRY C   126 ( 4 )   1785 - 1792   2022.2   ISSN:1932-7447 eISSN:1932-7455

  • Elemental Abundances of nearby M Dwarfs Based on High-resolution Near-infrared Spectra Obtained by the Subaru/IRD Survey: Proof of Concept Reviewed

    Hiroyuki Tako Ishikawa, Wako Aoki, Teruyuki Hirano, Takayuki Kotani, Masayuki Kuzuhara, Masashi Omiya, Yasunori Hori, Eiichiro Kokubo, Tomoyuki Kudo, Takashi Kurokawa, Nobuhiko Kusakabe, Norio Narita, Jun Nishikawa, Masahiro Ogihara, Akitoshi Ueda, Thayne Currie, Thomas Henning, Yui Kasagi, Jared R. Kolecki, Jungmi Kwon, Masahiro N. Machida, Michael W. McElwain, Takao Nakagawa, Sebastien Vievard, Ji Wang, Motohide Tamura, Bun'ei Sato

    ASTRONOMICAL JOURNAL   163 ( 2 )   2022.2   ISSN:0004-6256 eISSN:1538-3881

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    Detailed chemical analyses of M dwarfs are scarce but necessary to constrain the formation environment and internal structure of planets being found around them. We present elemental abundances of 13 M dwarfs (2900 < T (eff) < 3500 K) observed in the Subaru/IRD planet search project. They are mid- to late-M dwarfs whose abundance of individual elements has not been well studied. We use the high-resolution (similar to 70,000) near-infrared (970-1750 nm) spectra to measure the abundances of Na, Mg, Si, K, Ca, Ti, V, Cr, Mn, Fe, and Sr by the line-by-line analysis based on model atmospheres, with typical errors ranging from 0.2 dex for [Fe/H] to 0.3-0.4 dex for other [X/H]. We measure radial velocities from the spectra and combine them with Gaia astrometry to calculate the Galactocentric space velocities UVW. The resulting [Fe/H] values agree with previous estimates based on medium-resolution K-band spectroscopy, showing a wide distribution of metallicity (-0.6 < [Fe/H] < +0.4). The abundance ratios of individual elements [X/Fe] are generally aligned with the solar values in all targets. While the [X/Fe] distributions are comparable to those of nearby FGK stars, most of which belong to the thin-disk population, the most metal-poor object, GJ 699, could be a thick-disk star. The UVW velocities also support this. The results raise the prospect that near-infrared spectra of M dwarfs obtained in the planet search projects can be used to grasp the trend of elemental abundances and the Galactic stellar population of nearby M dwarfs.

    DOI: 10.3847/1538-3881/ac3ee0

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  • The Role of Magnetic Fields in the Formation of Protostars, Disks, and Outflows

    Yusuke Tsukamoto, Anaëlle Maury, Benoît Commerçon, Felipe O. Alves, Erin G. Cox, Nami Sakai, Tom Ray, Bo Zhao, Masahiro N. Machida

    2022

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    We present our current understanding of the formation and early evolution of protostars, protoplanetary disks, and the driving of outflows as dictated by the interplay of magnetic fields and partially ionized gas in molecular cloud cores. In recent years, the field has witnessed enormous development through sub-millimeter observations which in turn have constrained models of protostar formation. As a result of these observations % that the observations provided, the state-of-the-art theoretical understanding of the formation and evolution of young stellar objects is described. In particular, we emphasize the importance of the coupling, decoupling, and re-coupling between weakly ionized gas and the magnetic field on appropriate scales. This highlights the complex and intimate relationship between gravitational collapse and magnetic fields in young protostars.

    DOI: 10.48550/ARXIV.2209.13765

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  • "Ash-fall" induced by molecular outflow in protostar evolution Reviewed

    Tsukamoto, Yusuke, Machida, Masahiro N., Inutsuka, Shu-ichiro

    The Astrophysical Journal Letters   2021.9

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    DOI: 10.3847/2041-8213/ac2b2f

  • Impact of Magnetic Braking on High-mass Close Binary Formation Reviewed

    Harada, Naoto, Hirano, Shingo, Machida, Masahiro N., Hosokawa, Takashi

    2021.9

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  • Can High-velocity Protostellar Jets Help to Drive Low-velocity Outflow? Reviewed

    Masahiro Machida

    Monthly Notices of the Royal Astronomical Society   2021.9

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    DOI: 10.1093/mnras/stab2626

  • ALMA Observations toward the S-shaped Outflow and the Envelope around NGC 1333 IRAS 4A2 Reviewed

    Chen-Yu Chuang, Yusuke Aso, Naomi Hirano, Shingo Hirano, Masahiro N. Machida

    The Astrophysical Journal   916 ( 2 )   82 - 82   2021.8

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    DOI: 10.3847/1538-4357/abfdbb

  • Supermassive Star Formation in Magnetized Atomic-cooling Gas Clouds: Enhanced Accretion, Intermittent Fragmentation, and Continuous Mergers Reviewed

    Shingo Hirano, Masahiro N. Machida, Shantanu Basu

    The Astrophysical Journal   917 ( 1 )   34 - 34   2021.8

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    DOI: 10.3847/1538-4357/ac0913

  • Super-fast Rotation in the OMC 2/FIR 6b Jet Reviewed

    Matsushita, Y., Takahashi, S., Ishii, S., Tomisaka, K., Ho, P.T.P., Carpenter, J.M., Machida, M.N.

    Astrophysical Journal   916 ( 1 )   2021.7

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    DOI: 10.3847/1538-4357/ac069f

  • Conditions for Justifying Single-fluid Approximation for Charged and Neutral Dust Fluids and a Smoothed Particle Magnetohydrodynamics Method for Dust–Gas Mixture Reviewed

    913 ( 2 )   2021.6

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    DOI: 10.3847/1538-4357/abf5db

  • Misaligned Twin Molecular Outflows from the Class 0 Protostellar Binary System VLA 1623A Unveiled by ALMA Reviewed

    Chihomi Hara, Ryohei Kawabe, Fumitaka Nakamura, Naomi Hirano, Shigehisa Takakuwa, Yoshito Shimajiri, Takeshi Kamazaki, James Di Francesco, Masahiro N. Machida, Motohide Tamura, Kazuya Saigo, Tomoaki Matsumoto, Kengo Tomida

    The Astrophysical Journal   912 ( 1 )   34 - 34   2021.5

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    DOI: 10.3847/1538-4357/abb810

  • Revealing a Centrally Condensed Structure in OMC-3/MMS 3 with ALMA High-resolution Observations Reviewed

    Kaho Morii, Satoko Takahashi, Masahiro N. Machida

    The Astrophysical Journal   910 ( 2 )   148 - 148   2021.4

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    DOI: 10.3847/1538-4357/abe61c

  • Gravitational Wave Physics and Astronomy in the nascent era

    Arimoto, Makoto, Asada, Hideki, Cherry, Michael L., Fujii, Michiko S., Fukazawa, Yasushi, Harada, Akira, Hayama, Kazuhiro, Hosokawa, Takashi, Ioka, Kunihito, Itoh, Yoichi, Kanda, Nobuyuki, Kawabata, Koji S., Kawaguchi, Kyohei, Kawai, Nobuyuki, Kobayashi, Tsutomu, Kohri, Kazunori, Koshio, Yusuke, Kotake, Kei, Kumamoto, Jun, Machida, Masahiro N., Matsufuru, Hideo, Mihara, Tatehiro, Mori, Masaki, Morokuma, Tomoki, Mukohyama, Shinji, Nakano, Hiroyuki, Narikawa, Tatsuya, Negoro, Hitoshi, Nishizawa, Atsushi, Ohgami, Takayuki, Omukai, Kazuyuki, Sakamoto, Takanori, Sako, Shigeyuki, Sasada, Mahito, Sekiguchi, Yuichiro, Serino, Motoko, Soda, Jiro, Sugita, Satoshi, Sumiyoshi, Kohsuke, Susa, Hajime, Suyama, Teruaki, Takahashi, Hirotaka, Takahashi, Kazuya, Takiwaki, Tomoya, Tanaka, Takahiro, Tanaka, Masaomi, Tanikawa, Ataru, Tominaga, Nozomu, Uchikata, Nami, Utsumi, Yousuke, Vagins, Mark R., Yamada, Kei, Yoshida, Michitoshi

    2021.4

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  • Testing Disk Identification Methods through Numerical Simulations of Protostellar Evolution Reviewed

    Yusuke Aso, Masahiro N. Machida

    The Astrophysical Journal   2020.12

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    DOI: 10.3847/1538-4357/abc6fc

  • Delivery of Pebbles from the Protoplanetary Disk into Circumplanetary Disks

    Toru Homma, Keiji Ohtsuki, Natsuho Maeda, Ryo Suetsugu, Masahiro N. Machida, Takayuki Tanigawa

    The Astrophysical Journal   903 ( 2 )   98 - 98   2020.11

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    DOI: 10.3847/1538-4357/abbc08

  • A Low-velocity Bipolar Outflow from a Deeply Embedded Object in Taurus Revealed by the Atacama Compact Array Reviewed

    The Astrophysical Journal   899 ( 1 )   L10 - L10   2020.8

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    DOI: 10.3847/2041-8213/ab9ca8

  • FRagmentation and Evolution of Dense Cores Judged by ALMA (FREJA). I. Overview: Inner similar to 1000 au Structures of Prestellar/Protostellar Cores in Taurus Reviewed

    Kazuki Tokuda, Kakeru Fujishiro, Kengo Tachihara, Tatsuyuki Takashima, Yasuo Fukui, Sarolta Zahorecz, Kazuya Saigo, Tomoaki Matsumoto, Kengo Tomida, Masahiro N. Machida, Shu-ichiro Inutsuka, Philippe Andre, Akiko Kawamura, Toshikazu Onishi

    ASTROPHYSICAL JOURNAL   899 ( 1 )   2020.8

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    DOI: 10.3847/1538-4357/ab9ca7

  • The Effect of Misalignment between the Rotation Axis and Magnetic Field on the Circumstellar Disk Reviewed

    Shingo Hirano, Yusuke Tsukamoto, Shantanu Basu, Masahiro N. Machida

    The Astrophysical Journal   898 ( 2 )   118 - 118   2020.7

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    DOI: 10.3847/1538-4357/ab9f9d

  • Twin Jets and Close Binary Formation Reviewed

    Yu Saiki, Masahiro N. Machida

    ASTROPHYSICAL JOURNAL LETTERS   897 ( 2 )   2020.7

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    DOI: 10.3847/2041-8213/ab9d86

  • Early Evolution of Disk, Outflow, and Magnetic Field of Young Stellar Objects: Impact of Dust Model Reviewed

    Y. Tsukamoto, M. N. Machida, H. Susa, H. Nomura, S. Inutsuka

    The Astrophysical Journal   2020.6

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    DOI: 10.3847/1538-4357/ab93d0

  • Magnetic Field Structure of Orion Source I Reviewed

    Tomoya Hirota, Richard L. Plambeck, Melvyn C. H. Wright, Masahiro N. Machida, Yuko Matsushita, Kazuhito Motogi, Mi Kyoung Kim, Ross A. Burns, Mareki Honma

    The Astrophysical Journal   2020.6

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    DOI: 10.3847/1538-4357/ab959e

  • Disk Structure around the Class i Protostar L1489 IRS Revealed by ALMA A Warped-disk System Reviewed

    Jinshi Sai, Nagayoshi Ohashi, Kazuya Saigo, Tomoaki Matsumoto, Yusuke Aso, Shigehisa Takakuwa, Yuri Aikawa, Ippei Kurose, Hsi Wei Yen, Kohji Tomisaka, Kengo Tomida, Masahiro N. MacHida

    Astrophysical Journal   893 ( 1 )   2020.4

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    DOI: 10.3847/1538-4357/ab8065

  • Disk Structure around the Class I Protostar L1489 IRS Revealed by ALMA: A Warped-disk System

    Jinshi Sai, Nagayoshi Ohashi, Kazuya Saigo, Tomoaki Matsumoto, Yusuke Aso, Shigehisa Takakuwa, Yuri Aikawa, Ippei Kurose, Hsi-Wei Yen, Kohji Tomisaka, Kengo Tomida, Masahiro N. Machida

    ASTROPHYSICAL JOURNAL   893 ( 1 )   2020.4

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    DOI: 10.3847/1538-4357/ab8065

  • Misalignment of magnetic fields, outflows, and discs in star-forming clouds Reviewed

    Masahiro N. Machida, Shingo Hirano, Hideyuki Kitta

    Monthly Notices of the Royal Astronomical Society   491 ( 2 )   2180 - 2197   2020.1

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    DOI: 10.1093/mnras/stz3159

  • Protostellar Evolution in Serpens Main Possible Origin of Disk-size Diversity Reviewed

    Yusuke Aso, Naomi Hirano, Yuri Aikawa, Masahiro N. Machida, Nagayoshi Ohashi, Masao Saito, Shigehisa Takakuwa, Hsi Wei Yen, Jonathan P. Williams

    Astrophysical Journal   887 ( 2 )   2019.12

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    DOI: 10.3847/1538-4357/ab5284

  • Driving conditions of protostellar outflows in different star-forming environments Reviewed

    Higuchi Koki, Machida Masahiro N, Susa Hajime

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   486 ( 3 )   3741 - 3754   2019.7

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    Driving conditions of protostellar outflows in different star-forming environments

    DOI: 10.1093/mnras/stz1079

  • Origin of misalignments: protostellar jet, outflow, circumstellar disc, and magnetic field Reviewed

    Hirano Shingo, Machida Masahiro N

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   485 ( 4 )   4667 - 4674   2019.6

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    Origin of misalignments: protostellar jet, outflow, circumstellar disc, and magnetic field

    DOI: 10.1093/mnras/stz740

  • A Very Compact Extremely High Velocity Flow toward MMS 5/OMC-3 Revealed with ALMA Reviewed

    Yuko Matsushita, Satoko Takahashi, Masahiro N. Machida, Kohji Tomisaka

    ASTROPHYSICAL JOURNAL   871 ( 2 )   221 - 221   2019.2

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    DOI: 10.3847/1538-4357/aaf1b6

  • ALMA reveals a pseudo-disc in a proto-brown dwarf Reviewed

    B. Riaz, M. N. Machida, D. Stamatellos

    Monthly Notices of the Royal Astronomical Society   486 ( 3 )   4114 - 4129   2019.1

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    DOI: 10.1093/mnras/stz1032

  • Does Misalignment between Magnetic Field and Angular Momentum Enhance or Suppress Circumstellar Disk Formation? Reviewed

    Y. Tsukamoto, S. Okuzumi, K. Iwasaki, M. N. Machida, S. Inutsuka

    The Astrophysical Journal   868 ( 1 )   22 - 22   2018.11

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    DOI: 10.3847/1538-4357/aae4dc

  • Extremely Dense Cores Associated with Chandra Sources in Ophiuchus A Forming Brown Dwarfs Unveiled? Reviewed

    Ryohei Kawabe, Chihomi Hara, Fumitaka Nakamura, Kazuya Saigo, Takeshi Kamazaki, Yoshito Shimajiri, Kengo Tomida, Shigehisa Takakuwa, Yohko Tsuboi, Masahiro N. Machida, James Di Francesco, Rachel Friesen, Naomi Hirano, Yumiko Oasa, Motohide Tamura, Yoichi Tamura, Takashi Tsukagoshi, David Wilner

    Astrophysical Journal   866 ( 2 )   2018.10

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    DOI: 10.3847/1538-4357/aae153

  • Evolution of magnetic fields in collapsing star-forming clouds under different environments Reviewed

    Higuchi Koki, Machida Masahiro N, Susa Hajime

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   475 ( 3 )   3331 - 3347   2018.4

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    Evolution of magnetic fields in collapsing star-forming clouds under different environments

    DOI: 10.1093/mnras/sty046

  • Massive outflows driven by magnetic effects - II. Comparison with observations Reviewed

    Yuko Matsushita, Yuya Sakurai, Takashi Hosokawa, Masahiro N. Machida

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   475 ( 1 )   391 - 403   2018.3

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    DOI: 10.1093/mnras/stx3070

  • Different modes of star formation: Gravitational collapse of magnetically subcritical cloud Reviewed

    Masahiro N. Machida, Koki Higuchi, Satoshi Okuzumi

    Monthly Notices of the Royal Astronomical Society   473 ( 3 )   3080 - 3094   2018.1

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    DOI: 10.1093/mnras/stx2589

  • ALMA Observations of SMM11 Reveal an Extremely Young Protostar in Serpens Main Cluster Reviewed

    Yusuke Aso, Nagayoshi Ohashi, Yuri Aikawa, Masahiro N. Machida, Kazuya Saigo, Masao Saito, Shigehisa Takakuwa, Kengo Tomida, Kohji Tomisaka, Hsi-Wei Yen, Jonathan P. Williams

    The Astrophysical Journal   850 ( 1 )   2017.11

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    DOI: 10.3847/2041-8213/aa9701

  • ALMA observations of submillimeter H2O and SiO lines in Orion Source I

    Tomoya Hirota, Masahiro N. Machida, Yuko Matsushita, Kazuhito Motogi, Naoko Matsumoto, Mikyoung Kim, Ross A. Burns, Mareki Honma

    2017.11

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    ALMA observations of submillimeter H2O and SiO lines in Orion Source I
    We present observational results of the submillimeter H2O and SiO lines<br />
    toward a candidate high-mass young stellar object Orion Source I using ALMA.<br />
    The spatial structures of the high excitation lines at lower-state energies of<br />
    >2500 K show compact structures consistent with the circumstellar disk and/or<br />
    base of the northeast-southwest bipolar outflow with a 100 au scale. The<br />
    highest excitation transition, the SiO (v=4) line at band 8, has the most<br />
    compact structure. In contrast, lower-excitation transitions are more extended<br />
    than 200 au tracing the outflow. Almost all the line show velocity gradients<br />
    perpendicular to the outflow axis suggesting rotation motions of the<br />
    circumstellar disk and outflow. While some of the detected lines show broad<br />
    line profiles and spatially extended emission components indicative of thermal<br />
    excitation, the strong H2O lines at 321 GHz, 474 GHz, and 658 GHz with<br />
    brightness temperatures of >1000 K show clear signatures of maser action.

  • A Detached Protostellar Disk around a similar to 0.2M(circle dot) Protostar in a Possible Site of a Multiple Star Formation in a Dynamical Environment in Taurus Reviewed

    Kazuki Tokuda, Toshikazu Onishi, Kazuya Saigo, Takashi Hosokawa, Tomoaki Matsumoto, Shu-ichiro Inutsuka, Masahiro N. Machida, Kengo Tomida, Masanobu Kunitomo, Akiko Kawamura, Yasuo Fukui, Kengo Tachihara

    ASTROPHYSICAL JOURNAL   849 ( 2 )   101 - 101   2017.11

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    DOI: 10.3847/1538-4357/aa8e9e

  • ALMA Observations of the Protostar L1527 IRS: Probing Details of the Disk and the Envelope Structures Reviewed

    Yusuke Aso, Nagayoshi Ohashi, Yuri Aikawa, Masahiro N. Machida, Kazuya Saigo, Masao Saito, Shigehisa Takakuwa, Kengo Tomida, Kohji Tomisaka, Hsi-Wei Yen

    The Astrophysical Journal   849 ( 1 )   56 - 56   2017.10

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    DOI: 10.3847/1538-4357/aa8264

  • Massive outflows driven by magnetic effects in star-forming clouds with high mass accretion rates Reviewed

    Yuko Matsushita, Masahiro N. Machida, Yuya Sakurai, Takashi Hosokawa

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   470 ( 1 )   1026 - 1049   2017.8

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    DOI: 10.1093/mnras/stx893

  • Disk-driven rotating bipolar outflow in Orion Source I Reviewed

    Tomoya Hirota, Masahiro N. Machida, Yuko Matsushita, Kazuhito Motogi, Naoko Matsumoto, Mi Kyoung Kim, Ross A. Burns, Mareki Honma

    NATURE ASTRONOMY   1 ( 7 )   2017.7

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    DOI: 10.1038/s41550-017-0146

  • Circumstellar Disks and Outflows in Turbulent Molecular Cloud Cores: Possible Formation Mechanism for Misaligned Systems Reviewed

    Tomoaki Matsumoto, Masahiro N. Machida, Shu-ichiro Inutsuka

    The Astrophysical Journal   839 ( 1 )   69 - 69   2017.4

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    DOI: 10.3847/1538-4357/aa6a1c

  • Erratum: “Alma Observations of the Transition from Infall Motion to Keplerian Rotation around the Late-phase Protostar TMC-1A” (2015, ApJ, 812, 27) Reviewed

    836 ( 1 )   148 - 148   2017.2

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    DOI: 10.3847/1538-4357/836/1/148

  • Grand-design Spiral Arms in a Young Forming Circumstellar Disk Reviewed

    Kengo Tomida, Masahiro N. Machida, Takashi Hosokawa, Yuya Sakurai, Chia Hui Lin

    ASTROPHYSICAL JOURNAL LETTERS   835 ( 1 )   2017.1

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    DOI: 10.3847/2041-8213/835/1/L11

  • Conditions for circumstellar disc formation - II. Effects of initial cloud stability and mass accretion rate Reviewed

    Masahiro N. Machida, Tomoaki Matsumoto, Shu-ichiro Inutsuka

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   463 ( 4 )   4246 - 4267   2016.12

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    DOI: 10.1093/mnras/stw2256

  • ALMA BAND 8 CONTINUUM EMISSION FROM ORION SOURCE I Reviewed

    Tomoya Hirota, Masahiro N. Machida, Yuko Matsushita, Kazuhito Motogi, Naoko Matsumoto, Mi Kyoung Kim, Ross A. Burns, Mareki Honma

    ASTROPHYSICAL JOURNAL   833 ( 2 )   2016.12

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    DOI: 10.3847/1538-4357/833/2/238

  • REVEALING A DETAILED MASS DISTRIBUTION OF A HIGH-DENSITY CORE MC27/L1521F IN TAURUS WITH ALMA Reviewed

    Kazuki Tokuda, Toshikazu Onishi, Tomoaki Matsumoto, Kazuya Saigo, Akiko Kawamura, Yasuo Fukui, Shu-ichiro Inutsuka, Masahiro N. Machida, Kengo Tomida, Kengo Tachihara, Philippe Andre

    ASTROPHYSICAL JOURNAL   826 ( 1 )   2016.7

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    DOI: 10.3847/0004-637X/826/1/26

  • ALMA OBSERVATIONS OF THE TRANSITION FROM INFALL MOTION TO KEPLERIAN ROTATION AROUND THE LATE-PHASE PROTOSTAR TMC-1A Reviewed

    Yusuke Aso, Nagayoshi Ohashi, Kazuya Saigo, Shin Koyamatsu, Yuri Aikawa, Masahiko Hayashi, Masahiro N. Machida, Masao Saito, Shigehisa Takakuwa, Kengo Tomida, Kohji Tomisaka, Hsi-Wei Yen

    ASTROPHYSICAL JOURNAL   812 ( 1 )   2015.10

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    DOI: 10.1088/0004-637X/812/1/27

  • BIMODALITY OF CIRCUMSTELLAR DISK EVOLUTION INDUCED BY THE HALL CURRENT

    Y. Tsukamoto, K. Iwasaki, S. Okuzumi, M. N. Machida, S. Inutsuka

    The Astrophysical Journal   810 ( 2 )   2015.9

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    DOI: 10.1088/2041-8205/810/2/L26

  • Accretion phase of star formation in clouds with different metallicities Reviewed

    Masahiro N. Machida, Teppei Nakamura

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   448 ( 2 )   1405 - 1429   2015.4

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    DOI: 10.1093/mnras/stu2633

  • RADIATION MAGNETOHYDRODYNAMIC SIMULATIONS OF PROTOSTELLAR COLLAPSE: NONIDEAL MAGNETOHYDRODYNAMIC EFFECTS AND EARLY FORMATION OF CIRCUMSTELLAR DISKS Reviewed

    Kengo Tomida, Satoshi Okuzumi, Masahiro N. Machida

    ASTROPHYSICAL JOURNAL   801 ( 2 )   2015.3

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    DOI: 10.1088/0004-637X/801/2/117

  • FORMATION OF A KEPLERIAN DISK IN THE INFALLING ENVELOPE AROUND L1527 IRS: TRANSFORMATION FROM INFALLING MOTIONS TO KEPLER MOTIONS Reviewed

    Nagayoshi Ohashi, Kazuya Saigo, Yusuke Aso, Yuri Aikawa, Shin Koyamatsu, Masahiro N. Machida, Masao Saito, Sanemichi Z. Takahashi, Shigehisa Takakuwa, Kengo Tomida, Kohji Tomisaka, Hsi-Wei Yen

    ASTROPHYSICAL JOURNAL   796 ( 2 )   2014.12

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    DOI: 10.1088/0004-637X/796/2/131

  • PROTOSTELLAR JETS ENCLOSED BY LOW-VELOCITY OUTFLOWS Reviewed

    Masahiro N. Machida

    ASTROPHYSICAL JOURNAL LETTERS   796 ( 1 )   2014.11

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    DOI: 10.1088/2041-8205/796/1/L17

  • ALMA OBSERVATIONS OF INFALLING FLOWS TOWARD THE KEPLERIAN DISK AROUND THE CLASS I PROTOSTAR L1489 IRS Reviewed

    Hsi-Wei Yen, Shigehisa Takakuwa, Nagayoshi Ohashi, Yuri Aikawa, Yusuke Aso, Shin Koyamatsu, Masahiro N. Machida, Kazuya Saigo, Masao Saito, Kengo Tomida, Kohji Tomisaka

    ASTROPHYSICAL JOURNAL   793 ( 1 )   2014.9

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    DOI: 10.1088/0004-637X/793/1/1

  • ALMA OBSERVATIONS OF A HIGH-DENSITY CORE IN TAURUS: DYNAMICAL GAS INTERACTION AT THE POSSIBLE SITE OF A MULTIPLE STAR FORMATION Reviewed

    Kazuki Tokuda, Toshikazu Onishi, Kazuya Saigo, Akiko Kawamura, Yasuo Fukui, Tomoaki Matsumoto, Shu-ichiro Inutsuka, Masahiro N. Machida, Kengo Tomida, Kengo Tachihara

    ASTROPHYSICAL JOURNAL LETTERS   789 ( 1 )   2014.7

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    DOI: 10.1088/2041-8205/789/1/L4

  • ACCRETION OF SOLID MATERIALS ONTO CIRCUMPLANETARY DISKS FROM PROTOPLANETARY DISKS Reviewed

    Takayuki Tanigawa, Akito Maruta, Masahiro N. Machida

    ASTROPHYSICAL JOURNAL   784 ( 2 )   2014.4

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    DOI: 10.1088/0004-637X/784/2/109

  • Conditions for circumstellar disc formation: effects of initial cloud configuration and sink treatment Reviewed

    Masahiro N. Machida, Shu-ichiro Inutsuka, Tomoaki Matsumoto

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   438 ( 3 )   2278 - 2306   2014.3

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    DOI: 10.1093/mnras/stt2343

  • Formation, orbital and thermal evolution, and survival of planetary-mass clumps in the early phase of circumstellar disc evolution Reviewed

    Yusuke Tsukamoto, Masahiro N. Machida, Shu-ichiro Inutsuka

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   436 ( 2 )   1667 - 1673   2013.12

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    DOI: 10.1093/mnras/stt1684

  • A SEMI-ANALYTICAL DESCRIPTION FOR THE FORMATION AND GRAVITATIONAL EVOLUTION OF PROTOPLANETARY DISKS Reviewed

    Sanemichi Z. Takahashi, Shu-ichiro Inutsuka, Masahiro N. Machida

    ASTROPHYSICAL JOURNAL   770 ( 1 )   2013.6

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    DOI: 10.1088/0004-637X/770/1/71

  • Formation and early evolution of circumstellar discs in turbulent molecular cloud cores Reviewed

    Yusuke Tsukamoto, Masahiro N. Machida

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   428 ( 2 )   1321 - 1334   2013.1

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    DOI: 10.1093/mnras/sts111

  • RADIATION MAGNETOHYDRODYNAMIC SIMULATIONS OF PROTOSTELLAR COLLAPSE: PROTOSTELLAR CORE FORMATION Reviewed

    Kengo Tomida, Kohji Tomisaka, Tomoaki Matsumoto, Yasunori Hori, Satoshi Okuzumi, Masahiro N. Machida, Kazuya Saigo

    ASTROPHYSICAL JOURNAL   763 ( 1 )   2013.1

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    DOI: 10.1088/0004-637X/763/1/6

  • EXPLORING MAGNETIC FIELD STRUCTURE IN STAR-FORMING CORES WITH POLARIZATION OF THERMAL DUST EMISSION Reviewed

    Akimasa Kataoka, Masahiro N. Machida, Kohji Tomisaka

    ASTROPHYSICAL JOURNAL   761 ( 1 )   2012.12

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    DOI: 10.1088/0004-637X/761/1/40

  • MAGNETIC FIELD IN THE ISOLATED MASSIVE DENSE CLUMP IRAS 20126+4104 Reviewed

    Hiroko Shinnaga, Giles Novak, John E. Vaillancourt, Masahiro N. Machida, Akimasa Kataoka, Kohji Tomisaka, Jacqueline Davidson, Thomas G. Phillips, C. Darren Dowell, Lerothodi Leeuw, Martin Houde

    ASTROPHYSICAL JOURNAL LETTERS   750 ( 2 )   2012.5

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    DOI: 10.1088/2041-8205/750/2/L29

  • DISTRIBUTION OF ACCRETING GAS AND ANGULAR MOMENTUM ONTO CIRCUMPLANETARY DISKS Reviewed

    Takayuki Tanigawa, Keiji Ohtsuki, Masahiro N. Machida

    ASTROPHYSICAL JOURNAL   747 ( 1 )   2012.3

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    DOI: 10.1088/0004-637X/747/1/47

  • Impact of protostellar outflow on star formation: effects of the initial cloud mass Reviewed

    Masahiro N. Machida, Tomoaki Matsumoto

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   421 ( 1 )   588 - 607   2012.3

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    DOI: 10.1111/j.1365-2966.2011.20336.x

  • Classification of the circumstellar disc evolution during the main accretion phase Reviewed

    Yusuke Tsukamoto, Masahiro N. Machida

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   416 ( 1 )   591 - 600   2011.9

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    DOI: 10.1111/j.1365-2966.2011.19081.x

  • Effect of Magnetic Braking on Circumstellar Disk Formation in a Strongly Magnetized Cloud Reviewed

    Masahiro N. Machida, Shu-ichiro Inutsuka, Tomoaki Matsumoto

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   63 ( 3 )   555 - 573   2011.6

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    DOI: 10.1093/pasj/63.3.555

  • EXPOSED LONG-LIFETIME FIRST CORE: A NEW MODEL OF FIRST CORES BASED ON RADIATION HYDRODYNAMICS (vol 725, L239, 2010) Reviewed

    Kengo Tomida, Masahiro N. Machida, Kazuya Saigo, Kohji Tomisaka, Tomoaki Matsumoto

    ASTROPHYSICAL JOURNAL LETTERS   732 ( 1 )   2011.5

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    DOI: 10.1088/2041-8205/732/1/L18

  • RECURRENT PLANET FORMATION AND INTERMITTENT PROTOSTELLAR OUTFLOWS INDUCED BY EPISODIC MASS ACCRETION Reviewed

    Masahiro N. Machida, Shu-ichiro Inutsuka, Tomoaki Matsumoto

    ASTROPHYSICAL JOURNAL   729 ( 1 )   2011.3

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    DOI: 10.1088/0004-637X/729/1/42

  • EXPOSED LONG-LIFETIME FIRST CORE: A NEW MODEL OF FIRST CORES BASED ON RADIATION HYDRODYNAMICS Reviewed

    Kengo Tomida, Masahiro N. Machida, Kazuya Saigo, Kohji Tomisaka, Tomoaki Matsumoto

    ASTROPHYSICAL JOURNAL LETTERS   725 ( 2 )   L239 - L244   2010.12

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    DOI: 10.1088/2041-8205/725/2/L239

  • FORMATION PROCESS OF THE CIRCUMSTELLAR DISK: LONG-TERM SIMULATIONS IN THE MAIN ACCRETION PHASE OF STAR FORMATION Reviewed

    Masahiro N. Machida, Shu-ichiro Inutsuka, Tomoaki Matsumoto

    ASTROPHYSICAL JOURNAL   724 ( 2 )   1006 - 1020   2010.12

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    DOI: 10.1088/0004-637X/724/2/1006

  • EMERGENCE OF PROTOPLANETARY DISKS AND SUCCESSIVE FORMATION OF GASEOUS PLANETS BY GRAVITATIONAL INSTABILITY Reviewed

    Shu-ichiro Inutsuka, Masahiro N. Machida, Tomoaki Matsumoto

    ASTROPHYSICAL JOURNAL LETTERS   718 ( 2 )   L58 - L62   2010.8

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    DOI: 10.1088/2041-8205/718/2/L58

  • Gas accretion onto a protoplanet and formation of a gas giant planet Reviewed

    Masahiro N. Machida, Eiichiro Kokubo, Shu-ichiro Inutsuka, Tomoaki Matsumoto

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   405 ( 2 )   1227 - 1243   2010.6

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    DOI: 10.1111/j.1365-2966.2010.16527.x

  • RADIATION MAGNETOHYDRODYNAMICS SIMULATION OF PROTO-STELLAR COLLAPSE: TWO-COMPONENT MOLECULAR OUTFLOW Reviewed

    Kengo Tomida, Kohji Tomisaka, Tomoaki Matsumoto, Ken Ohsuga, Masahiro N. Machida, Kazuya Saigo

    ASTROPHYSICAL JOURNAL LETTERS   714 ( 1 )   L58 - L63   2010.5

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    DOI: 10.1088/2041-8205/714/1/L58

  • Binary formation with different metallicities: dependence on initial conditions Reviewed

    Masahiro N. Machida, Kazuyuki Omukai, Tomoaki Matsumoto, Shu-ichiro Inutsuka

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   399 ( 3 )   1255 - 1263   2009.11

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    DOI: 10.1111/j.1365-2966.2009.15394.x

  • EMISSION FROM A YOUNG PROTOSTELLAR OBJECT. I. SIGNATURES OF YOUNG EMBEDDED OUTFLOWS Reviewed

    Masako Yamada, Masahiro N. Machida, Shu-ichiro Inutsuka, Kohji Tomisaka

    ASTROPHYSICAL JOURNAL   703 ( 1 )   1141 - 1158   2009.9

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    DOI: 10.1088/0004-637X/703/1/1141

  • FIRST DIRECT SIMULATION OF BROWN DWARF FORMATION IN A COMPACT CLOUD CORE Reviewed

    Masahiro N. Machida, Shu-ichiro Inutsuka, Tomoaki Matsumoto

    ASTROPHYSICAL JOURNAL LETTERS   699 ( 2 )   L157 - L160   2009.7

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    DOI: 10.1088/0004-637X/699/2/L157

  • Angular momentum accretion onto a gas giant planet Reviewed

    Masahiro N. Machida, Eiichiro Kokubo, Shu-Ichiro Inutsuka, Tomoaki Matsumoto

    ASTROPHYSICAL JOURNAL   685 ( 2 )   1220 - 1236   2008.10

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1086/590421

  • Magnetohydrodynamics of population III star formation Reviewed

    Masahiro N. Machida, Tomoaki Matsumoto, Shu-ichiro Inutsuka

    ASTROPHYSICAL JOURNAL   685 ( 2 )   690 - 704   2008.10

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    DOI: 10.1086/591074

  • Binary formation in star-forming clouds with various metallicities Reviewed

    Masahiro N. Machida

    ASTROPHYSICAL JOURNAL LETTERS   682 ( 1 )   L1 - L4   2008.7

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    DOI: 10.1086/590109

  • The effect of poloidal magnetic field on type I planetary migration: Significance of magnetic resonance Reviewed

    Takayuki Muto, Masahiro N. Machida, Shu-Ichiro Inutsuka

    ASTROPHYSICAL JOURNAL   679 ( 1 )   813 - 826   2008.5

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    DOI: 10.1086/587027

  • Conditions for the formation of first-star binaries Reviewed

    Masahiro N. Machida, Kazuyuki Omukai, Tomoaki Matsumoto, Shu-Ichiro Inutsuka

    ASTROPHYSICAL JOURNAL   677 ( 2 )   813 - 827   2008.4

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1086/533434

  • High- and low-velocity magnetized outflows in the star formation process in a gravitationally collapsing cloud Reviewed

    Masahiro N. Machida, Shu-ichiro Inutsuka, Tomoaki Matsumoto

    ASTROPHYSICAL JOURNAL   676 ( 2 )   1088 - 1108   2008.4

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1086/528364

  • Formation scenario for wide and close binary systems Reviewed

    Masahiro N. Machida, Kohji Tomisaka, Tomoaki Matsumoto, Shu-Ichiro Inutsuka

    ASTROPHYSICAL JOURNAL   677 ( 1 )   327 - 347   2008.4

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    DOI: 10.1086/529133

  • Magnetic fields and rotations of protostars Reviewed

    Masahiro N. Machida, Shu-Ichiro Inutsuka, Tomoaki Matsumoto

    ASTROPHYSICAL JOURNAL   670 ( 2 )   1198 - 1213   2007.12

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    DOI: 10.1086/521779

  • The effect of poloidal magnetic field on type i planetary migration Reviewed

    Takayuki Muto, Masahiro N. MacHida, Shu-Ichiro Inutsuka

    Proceedings of the International Astronomical Union   3 ( 249 )   401 - 406   2007.10

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1017/S1743921308016906

  • Evolution of rotating molecular cloud core with oblique magnetic field Reviewed

    Masahiro N. Machida, Tomoaki Matsumoto, Tomoyuki Hanawa, Kohji Tomisaka

    ASTROPHYSICAL JOURNAL   645 ( 2 )   1227 - 1245   2006.7

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    DOI: 10.1086/504423

  • Self-gravitational collapse of a magnetized cloud core: High resolution simulations with three-dimensional MHD nested grid Reviewed

    Tomoaki Matsumoto, Masahiro N. Machida, Kohji Tomisaka, Tomoyuki Hanawa

    Computer Physics Communications   164 ( 1-3 )   229 - 236   2004.12

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    Language:English   Publishing type:Research paper (other academic)  

    DOI: 10.1016/j.cpc.2004.06.033

▼display all

Presentations

  • 星磁場と回転の効果による円盤の方向の空間依存性

    町田 正博

    日本天文学会  2015.9 

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    Event date: 2015.9

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:甲南大学   Country:Japan  

    近年の観測から星形成領域で大局磁場とジェット、アウトフローの向きが異なることが示唆されている。また、星形成領域の偏光観測によって複雑な形状の磁力線が観測されている。磁場は星の形成に関して重大な役割を果たすが、その振る舞いは単純ではない。収縮するガス雲中でローレンツ力と遠心力によって特定の方向の収縮が抑制させることによって円盤状の構造が出来る。磁場によって作られる円盤状構造をpseudo-diskと呼び、回転によって作られる構造を回転円盤と呼ぶ。

  • 星形成初期段階での空間スケールの違いによる角運動量輸送機構

    町田 正博

    日本天文学会  2015.3 

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    Event date: 2015.3

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:大阪大学   Country:Japan  

    星は分子雲コアが重力収縮して誕生する。観測から分子雲コアの角運動量は原始星の角運動量よりも 4−5 桁程
    度大きいことが分かっている。そのため、星が出来る過程でどのようにして角運動量を輸送するかを理解すること
    は星形成過程を解明する上で重要である。先行研究によって、星形成過程で現れるアウトフローによって分子雲コ
    アが持っていた角運動量の多くの割合が星間空間に微量のガスと共に放出されることが示された。しかし、今ま
    での研究では磁場の散逸や原始星形成後に現れるジェットなどによる角運動量輸送過程は調べられていなかった。
    この研究では、星形成前の分子雲コアを初期条件として星形成過程を計算を計算した。その際、分子雲コアか
    ら原始星のスケールまでを空間分解して原始星形成後 500 年以上の計算を行った。この計算の初期の結果は前回
    の天文学会で発表しており、(i) 星周円盤外縁から低速度アウトフローが定常的に現れ、(ii) 原始星近傍からは高
    速度ジェットが非定常に出現することが示された。
    今回は、星の誕生前後での角運動量輸送機構について発表する。星形成直後、星周円盤の外側では主に磁気制
    動によって角運動量が輸送される。他方、円盤の外縁では磁気制動に加えてアウトフローによって角運動量が効率
    的に輸送される。円盤の内側では磁場の散逸のために磁場による角運動量輸送は効果的ではない。そのため、こ
    の領域では円盤の面密度が上昇し重力不安定性によって非軸対称な構造が発達し、円盤中の非軸対称性によって
    生じる重力トルクによる角運動量輸送効率が磁場による輸送効率をはるかに卓越する。また、より小さいスケー
    ル (原始星近傍) では、ジェットによる角運動量輸送が効果的となる。さらに、ジェットの非定常性は円盤中での
    非軸対構造による非定常降着に起因する。ることが分かった。

  • 原始星ジェットの進化

    町田 正博

    日本天文学会  2014.9 

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    Event date: 2014.9

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:山形大学   Country:Japan  

    星形成領域の観測から、星形成過程で高速のジェットと低速のアウトフローが現れることが分かっている。し
    かし、これらのフローの駆動機構は解明されていない。原始星ジェットは、その速度から重力ポテンシャルの深
    い原始星近傍で駆動すると考えられているため、数値シミュレーションによってジェットの駆動を調べるために
    は、駆動領域である原始星を分解する必要がある。原始星は 0.01AU 程度の半径を持つ。原始星 (近傍) へは、星
    周円盤から質量が供給される。そのため、ガス降着とジェットの関係を調べるためには星周円盤を解像する必要
    がある。星周円盤は、1−100AU 程度の大きさを持つ。また、円盤は、分子雲コアから供給されるガスによって成
    長する。分子雲コアは、1 万 AU 以上の大きさを持つ。厳密にジェットの駆動を計算するためには、原始星、星周
    円盤、分子雲コアを空間分解する必要があるが、これらは空間スケールが 6 桁以上も異なる。また、時間尺度も
    大きく異なる。そのため、今までの研究ではジェットの長時間進化を計算することは難しかった。
    この研究では、簡単な原始星モデルと多層格子法を用いてジェットの駆動を計算した。星が出来る前の分子雲
    コアを初期条件として、中心に原始星が誕生してからおよそ 300 年間ジェットの進化を計算した。結果、ジェット
    の駆動は非定常であることが分かった。また、従来考えられていたように、ファーストコアから駆動したアウト
    フローの中をジェットが突き進むことにより星形成の初期段階において二種類のフローが現れることが分かった。
    計算中、原始星からのジェットは、最大 ∼ 100km/s の速度を持ち 300AU 程度まで達した。また、低速のアウト
    フローは ∼ 1km/s の速度を持ち 200AU 程度まで達した。

  • 磁気制動と星周円盤の形成を適切に計算するための条件

    町田 正博

    日本天文学会  2013.9 

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    Event date: 2013.9

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:東北大学   Country:Japan  

    星周円盤は星形成の副産物であり惑星形成の母体であるため、その形成や進化 を理解することは重要である。しかし、理論的に星周円盤がいつ、どのように して形成するのかは未だ理解されていない。 従来、星の母体となる分子雲コアの角運動量は、原始星の角運動量よりも遥かに 大きいために 円盤形成は、収縮するガス中での角運動量保存の自然な帰結だと考えられていた。 しかし、近年、磁場の効果により原始星周囲の角運動量が外層に過剰に輸送され てしまい 回転円盤が出来ないという問題が指摘されている(Magnetic Braking Catastrophe)。 円盤形成過程は、磁場の増幅と散逸、また磁気制動とアウトフローによる角運動 量輸送などが 密接に絡み合っているために数値シミュレーションによる理解が必要となる。 しかし、シミュレーションで中心の原始星まで解像してしまうと計算のタイムス テップが 非常に短くなり円盤形成過程を計算することが出来ない。 そのため原始星近傍領域をマスクしてその内側領域を計算しないという手法(シ ンクセル法) が使用されている。 この手法を用いて円盤形成過程を計算した結果、星形成過程(少なくとも ガス降着初期段階)では回転円盤出来ないということが報告がされた(Li et al. 2011)。 しかし、研究者ごとにシンクセルの大きさや結果が大きく異なっている。
    この研究では星周円盤を適切に計算するための条件を求めるために、 シンクセルの半径や境界条件などを変えて多くの計算を行った。 先ず、他の研究と同様のシンクセルを採用して過去の研究結果を再現した。 その後、シンク半径を徐々に小さくして計算結果が収束するかどうかを調べた。 その結果、ガス収縮段階において形成するファーストコアを十分な空間解像度で 分解すれば円盤形成過程が適切に計算でき、またClass 0段階の原始星周囲でも 円盤が 形成しうることが分かった。 さらに初期の分子雲コアの状態が星周円盤の形成に与える影響も調べた。

  • 原始星の進化とアウトフローの関係

    町田 正博

    日本天文学会  2013.3 

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    Event date: 2013.3

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:埼玉大学   Country:Japan  

    星形成領域の観測は、星はその誕生時に分子アウトフローというガスの放出現象を 伴うことを示唆している。このアウトフローは、広い開口角を持ち原始星周囲の ガスを 星間空間に放出する。そのため、アウトフローは原始星の進化の過程で重要な役割を 果たすと考えられているが、その駆動機構については未だ論争中である。 従来、アウトフローは、高速でコリメーションの良いジェット成分との相互作用 によっ て駆動されると考えられていた。他方、近年の 分子雲コアから原始星が誕生するまでの数値計算は、アウトフ ローは原始星の周囲に形成する円盤状天体から駆動することを示した。 後者の研究では中心星近傍からのガスの放出現象は示せたが、 長時間計算が困難だったために、計算で得られたフローを観測と比較することは 出来なかった。

    この研究では、分子雲コアから原始星の形成を経て、分子雲コアが散逸するまでの 計算を行った。その際、アウトフロー駆動の内側の領域は空間 的に解像せずに分子雲コア全体を計算して、アウトフローの長時間進化を調べた。 また、中心に落下したガスから中心天体への質量降着率を導出して原始星の進化 も同時 に計算し、中心星の進化段階を決定した。 計算の結果、原始星がClass 0段階にある場合には、アウトフローは円盤に降着 するガスから エネルギーを獲得して激しく中心星近傍から放出されるが、原始星がClass I段階に 進化するとアウトフローが新たにエネルギーを獲得することが出来ず徐々に 弱くなることが分かった。 また、計算から得られたアウトフローの質量、運動量、エネルギーの時間進化は 観測と 良く一致した。 さらに、観測から得られている中心星光度とアウトフローの運動量の関係を再現する ことが出来た。 これらの結果は、原始星アウトフローは円盤からの直接駆動されるフローによっ て説明が可能 であることを意味している。

  • 初代星周りの円盤形成と磁場の効果

    町田 正博

    日本天文学会  2012.9 

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    Event date: 2012.9

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:大分大学   Country:Japan  

    初代星の形成・進化を理解することは宇宙の進化を理解する上で重要である。 過去の研究から、一つのダークマターハロー中では単一の大質量初代星 が形成されると考えられてきた。 しかし、過去の研究は球対称を仮定していたために、角運動量の 効果を無視していた。その後の3次元シミュレーションも初代星形成直 後までしか計算していなかったために、初代星形成後の円盤形成段階は 調べられていなかった。 近年、シンクセル法などを用いて複数のグループが初代星形成後の進化 の計算を行った。これらの研究は、原始星誕生後に周囲の円盤が分裂して 複数の星が形成しうることを示した。 しかし、これらの計算では、(i)シンクセルが大きすぎるために分裂が盛ん に起こるであろう円盤の内側領域を計算出来ない、または、 (ii)シンクセルを用いない場合には原始星の内部構造まで計算して しまうために長時間計算が出来ないという問題があった。

    この研究では、シンクセルを用いずに原始星形成後の長時間 計算を実現した。具体的には、過去の初代星の進化計算から得られた質量と 半径の関係をガスの状態方程式に組み込んだ。この手法により中心星 は質量の増加と共に半径を増大させる。そのため原始星の内部構造を計算 することは出来ないが、原始星周囲の構造を長時間計算することが可能である。 計算の結果、磁場が無い場合には、他の計算で示されているように 激しく分裂が起こり、多数の星が誕生することが分かった。 いくつかの原始星は中心近傍の比較的質量の大きな星に落下する。また、いくつかの 原始星は中心部から放出される。放出される星の最小質量は木星質量程度で ある。他方、初期宇宙に非常に弱い磁場が存在する場合には、磁気制動によって 角運動量が輸送され星周円盤が成長しない。そのため、古典的 描像のようにダークマターハローの中心に単一の大質量星が誕生する。

  • 磁気星間雲中での星周円盤の形成

    町田正博

    日本天文学会  2012.3 

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    Event date: 2012.3

    Presentation type:Oral presentation (general)  

    Venue:龍谷大学   Country:Japan  

    星や円盤形成の母体となる分子雲は、磁化されておりマイクロガウス程度 の磁場を保持している。星や円盤は、この磁気星間雲 が重力収縮して形成する。星周円盤は、惑星形成の母体でもあるため、 その形成過程を理解することは星形成のみならず惑星形成の観点からも 重要である。 近年、この重力収縮するガス雲中での円盤の形成について「Magnetic Braking Catastrophe」という困難があると指摘されている。 これは、重力収縮の過程、または星形成後のガス降着段階で、磁場の効果 により角運動量が輸送されてしまい回転円盤が出来ないという問題であ る。 円盤が形成するとその回転によって磁力線が強く捻られる。 すると円盤の角運動量は、この磁力線を捻ることによって星間空間に輸送される。 円盤が回転を続ける限り磁力線が捻られ続け角運動量も輸送され続ける。 そのため、星形成過程では回転円盤が出来ないという主張である。

    我々は、磁気星間雲中での星周円盤の形成過程を調べるために、磁気散逸 MHD多層格子法を用いて、星形成前の分子雲コアから星が誕生して円盤が 出来る過程の計算を行った。その結果、分子雲の磁場が強い場合でも回転円盤が 出来ることが分かった。円盤形成の初期段階では、周囲に十分なガスが 残っているために、円盤の角運動量は磁力線を通じて円盤周囲のガス に輸送される。しかし、分子雲が十分進化して、分子雲内のガスが円盤に落下し 円盤ガスよりも軽くなると角運動量を効率的に輸送できなくなる。従って、 分子雲のガスが枯渇しつつある段階では回転円盤の形成が可能となる。 さらに、初期にガス雲が重力的に非常に不安定であり円盤へのガス降着率が 大きい場合には、磁場による角運動量輸送率よりもガス降着によって持ち込 まれる角運動量の方が大きくなり、中心星が非常に若い段階でも十分に大き く重い円盤が出来ることが分かった。

  • 星周円盤とガス惑星形成における重元素量の影響

    町田正博、松本倫明

    日本天文学会  2011.9 

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    Event date: 2011.9

    Presentation type:Oral presentation (general)  

    Venue:鹿児島大学   Country:Japan  

    系外惑星の観測は、主星の重元素量が多い程、惑星が存在する確率が高いこと を示している。 コア・アクリーションシナリオに従うと、このような 重元素量が多い円盤中では固体コアが出来やすくガス惑星も誕生しやす いことが分かる。そのため、主星の重元素量と惑星頻度の関係は、 惑星がコア・アクリーションによって誕生したことの間接的な証拠であると 考えられている。 他方、もう一つの惑星形成シナリオである重力不安定シナリオでは、ダスト や重元素量の違いは、ガス惑星の形成にはほとんど影響を与えないと考えられ ている。しかし、この重力不安定シナリオを考える場合には、円盤の形成も 考慮する必要がある。 この講演では、円盤のサイズや質量がダストの量(重元素量)と密接に関係しており、 コア・アクリーションシナリオと同様に、金属量が高いほど重い円盤が形成し、 重力不安定によりガス惑星形成が誕生しやすいことを示す。

    観測されているような分子雲コアを初期条件として、ガスに含まれるダストの量 をパラメータとして、円盤形成の計算を行った。ダストの存在量の違いは、ガス の熱進化とイオン化度を通して磁場の散逸に影響を与える。計算の結果、ダスト の量が多いほど、重くサイズの大きな円盤が出来ることが分かった。これは、 以下の2つの理由による。 (1)ダスト量が多い程、ガスが光学的に厚くなる密度が低く、初期により大きな円盤 を形成する。 (2)ガス中にダストが豊富に存在する程、ガスのイオン化度が低く 磁場がより散逸して磁場制動 による角運動量輸送が非効率的になり大きな円盤を成長させる。 これらの結果は、星形成前の分子雲コアが重元素を豊富に含むほど、重力不安定 によってガス惑星 が誕生しやすいことを示唆している。

  • 低金属量下での星周円盤の形成

    町田正博

    日本天文学会2011年春季年会  2011.3 

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    Event date: 2011.3

    Presentation type:Oral presentation (general)  

    Venue:筑波大学   Country:Japan  

    Other Link: http://www.asj.or.jp/nenkai/2011a/

  • 星周円盤の起源とその形成過程

    町田正博

    日本天文学会2010年秋季年会  2010.9 

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    Event date: 2010.9

    Presentation type:Oral presentation (general)  

    Venue:金沢大学   Country:Japan  

    Other Link: http://www.asj.or.jp/nenkai/2010b/

  • 原始星アウトフローと星形成率の関係

    町田正博

    日本天文学会2010年春季年会  2010.3 

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    Event date: 2010.3

    Presentation type:Oral presentation (general)  

    Venue:広島大学   Country:Japan  

    Other Link: http://www.asj.or.jp/nenkai/2010a/

  • 周連星円盤からのアウトフロー

    町田正博

    日本天文学会2009年秋季年会  2009.9 

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    Event date: 2009.9

    Presentation type:Oral presentation (general)  

    Venue:山口大学吉田キャンパス   Country:Japan  

  • 低質量分子雲コア中での褐色矮星の形成可能性

    町田正博

    日本天文学会2009年春季年会  2009.3 

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    Event date: 2009.3

    Presentation type:Oral presentation (general)  

    Venue:大阪府立大学中百舌鳥キャンパス   Country:Japan  

  • 巨大ガス惑星と周惑星円盤の形成過程

    町田正博

    日本天文学会2008年秋季年会  2008.9 

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    Event date: 2008.9

    Presentation type:Oral presentation (general)  

    Venue:岡山理科大学   Country:Japan  

  • 異なる重元素量を持つガス雲中での星形成過程と連星頻度

    町田正博

    日本天文学会2008年春季年会  2008.3 

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    Event date: 2008.3

    Presentation type:Oral presentation (general)  

    Venue:国立オリンピック記念青少年総合センター   Country:Japan  

  • 近接連星と遠隔連星の形成シナリオ

    町田正博

    日本天文学会2007年秋季年会  2007.9 

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    Event date: 2007.9

    Presentation type:Oral presentation (general)  

    Venue:岐阜大学   Country:Japan  

  • 原始惑星系円盤中でのガス惑星の角運動量獲得過程

    町田正博

    日本天文学会2007年春季年会  2007.3 

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    Event date: 2007.3

    Presentation type:Oral presentation (general)  

    Venue:東海大学   Country:Japan  

  • 星形成過程における分子流と光学ジェットの駆動メカニズム

    町田正博

    日本天文学会2006年秋季年会  2006.9 

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    Event date: 2006.9

    Presentation type:Oral presentation (general)  

    Venue:九州国際大学   Country:Japan  

  • 磁気散逸MHDによる第二コアからの高速ジェット駆動機構の解明

    町田正博

    日本天文学会2006年春季年会  2006.3 

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    Event date: 2006.3

    Presentation type:Oral presentation (general)  

    Venue:和歌山大学   Country:Japan  

  • 原始巨大惑星へのガス降着とアウトフロー

    町田正博

    日本天文学会2005年秋季年会  2005.10 

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    Event date: 2005.10

    Presentation type:Oral presentation (general)  

    Venue:北海道大学   Country:Japan  

    Other Link: http://www.asj.or.jp/nenkai/2005b/

  • 原始星形成:磁場と回転が平行/垂直になる場合

    町田正博

    日本天文学会2005年春季年会  2005.3 

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    Event date: 2005.3

    Presentation type:Oral presentation (general)  

    Venue:明星大学   Country:Japan  

  • 分子雲の分裂条件

    町田正博

    日本天文学会2004年秋季年会  2004.9 

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    Event date: 2004.9

    Presentation type:Oral presentation (general)  

    Venue:岩手大学   Country:Japan  

    Other Link: http://www.asj.or.jp/nenkai/2004b/

  • 原始星の磁束と角運動量

    町田正博

    日本天文学会2004年春季年会  2004.3 

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    Event date: 2004.3

    Presentation type:Oral presentation (general)  

    Venue:名古屋大学   Country:Japan  

  • 分子雲コアの分裂を誘発するディスクとバーの形成

    町田正博

    日本天文学会2003年秋季年会  2003.9 

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    Event date: 2003.9

    Presentation type:Oral presentation (general)  

    Venue:愛媛大学   Country:Japan  

  • 分子雲コアからの連星形成過程とアウトフロー

    町田正博

    日本天文学会2003年春季年会  2003.3 

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    Event date: 2003.3

    Presentation type:Oral presentation (general)  

    Venue:東北大学   Country:Japan  

    Other Link: http://www.asj.or.jp/nenkai/2003a/

  • 非軸対称揺らぎを入れた星間分子雲の成長過程

    町田正博

    日本天文学会2002年秋季年会  2002.10 

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    Event date: 2002.10

    Presentation type:Oral presentation (general)  

    Venue:宮崎シーガイア   Country:Japan  

    Other Link: http://www.asj.or.jp/nenkai/2002b/

  • 非軸対称揺らぎにおける星間磁気雲の収縮過程

    町田正博、富阪幸治、松本倫明

    日本天文学会2002年春季年会  2002.3 

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    Event date: 2002.3

    Presentation type:Oral presentation (general)  

    Venue:茨城大学   Country:Japan  

  • 3次元MHD Nested Grid シミュレーションによる星間磁気雲の重力収縮

    町田正博、富阪幸治、松本倫明

    日本天文学会2001年秋季年会  2001.10 

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    Event date: 2001.10

    Presentation type:Oral presentation (general)  

    Venue:イーグレ姫路   Country:Japan  

  • 初期宇宙における低質量星の形成過程

    町田正博、藤本正行、中村文隆

    日本天文学会2001年春季年会  2001.3 

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    Event date: 2001.3

    Presentation type:Oral presentation (general)  

    Venue:千葉大学   Country:Japan  

  • SuperNova Triggered Star-Formation in Early Universe

    2000.10 

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    Event date: 2000.10

    Presentation type:Oral presentation (general)  

    Country:Japan  

  • The infrared Doppler (IRD) instrument for the Subaru telescope Instrument description and commissioning results

    Takayuki Kotani, Motohide Tamura, Jun Nishikawa, Akitoshi Ueda, Masayuki Kuzuhara, Masashi Omiya, Jun Hashimoto, Masato Ishizuka, Teruyuki Hirano, Hiroshi Suto, Takashi Kurokawa, Tsukasa Kokubo, Takahiro Mori, Yosuke Tanaka, Ken Kashiwagi, Mihoko Konishi, Tomoyuki Kudo, Bun'Ei Sato, Shane Jacobson, Klaus W. Hodapp, Donald B. Hall, Wako Aoki, Tomonori Usuda, Shogo Nishiyama, Tadashi Nakajima, Yuji Ikeda, Tomoyasu Yamamuro, Jun Ichi Morino, Haruka Baba, Ko Hosokawa, Hiroyuki Ishikawa, Norio Narita, Eiichiro Kokubo, Yutaka Hayano, Hideyuki Izumiura, Eiji Kambe, Nobuhiko Kusakabe, Jungmi Kwon, Masahiro Ikoma, Yasunori Hori, Hidenori Genda, Akihiko Fukui, Yuka Fujii, Hajime Kawahara, Guyon Olivier, Nemanja Jovanovic, Hiroki Harakawa, Masahiko Hayashi, Masahide Hidai, Masahiro Machida, Taro Matsuo, Tetsuya Nagata, Masahiro Ogihara, Hideki Takami, Naruhisa Takato, Hiroshi Terada, Daehyeon Oh

    Ground-based and Airborne Instrumentation for Astronomy VII 2018  2018.1 

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    Event date: 2018.6

    Language:English  

    Country:United States  

  • Grand design spiral arms in a young forming circumstellar disk

    K. Tomida, Masahiro Machida, T. Hosokawa, Y. Sakurai, C. H. Lin

    2017 Conference Francesco's Legacy: Star Formation in Space and Time  2017.1 

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    Event date: 2017.6

    Language:English  

    Country:Italy  

  • Grand design spiral arms in a young forming circumstellar disk

    K. Tomida, Masahiro Machida, T. Hosokawa, Y. Sakurai, C. H. Lin

    2017 Conference Francesco's Legacy: Star Formation in Space and Time  2017.1 

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    Event date: 2017.6

    Language:English  

    Country:Italy  

  • Grand design spiral arms in a young forming circumstellar disk

    K. Tomida, Masahiro Machida, T. Hosokawa, Y. Sakurai, C. H. Lin

    2017 Conference Francesco's Legacy: Star Formation in Space and Time  2017.1 

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    Event date: 2017.6

    Language:English  

    Country:Italy  

  • Grand design spiral arms in a young forming circumstellar disk

    K. Tomida, Masahiro Machida, T. Hosokawa, Y. Sakurai, C. H. Lin

    2017 Conference Francesco's Legacy: Star Formation in Space and Time  2017.1 

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    Event date: 2017.6

    Language:English  

    Country:Italy  

  • Low-Mass Star Formation From Molecular Cloud Cores to Protostars and Protoplanetary Disks

    S. I. Inutsuka, Masahiro Machida, T. Matsumoto, Y. Tsukamoto, K. Iwasaki

    6th Zermatt Symposium on Conditions and Impact of Star Formation: From Lab to Space 2015  2016.5 

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    Event date: 2015.9

    Language:English  

    Country:Switzerland  

  • Low-Mass Star Formation From Molecular Cloud Cores to Protostars and Protoplanetary Disks

    S. I. Inutsuka, Masahiro Machida, T. Matsumoto, Y. Tsukamoto, K. Iwasaki

    6th Zermatt Symposium on Conditions and Impact of Star Formation: From Lab to Space 2015  2016.5 

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    Event date: 2015.9

    Language:English  

    Country:Switzerland  

  • Low-Mass Star Formation From Molecular Cloud Cores to Protostars and Protoplanetary Disks

    S. I. Inutsuka, Masahiro Machida, T. Matsumoto, Y. Tsukamoto, K. Iwasaki

    6th Zermatt Symposium on Conditions and Impact of Star Formation: From Lab to Space 2015  2016.5 

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    Event date: 2015.9

    Language:English  

    Country:Switzerland  

  • Low-Mass Star Formation From Molecular Cloud Cores to Protostars and Protoplanetary Disks

    S. I. Inutsuka, Masahiro Machida, T. Matsumoto, Y. Tsukamoto, K. Iwasaki

    6th Zermatt Symposium on Conditions and Impact of Star Formation: From Lab to Space 2015  2016.5 

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    Event date: 2015.9

    Language:English  

    Country:Switzerland  

  • Infrared Doppler instrument (IRD) for the Subaru telescope to search for Earth-like planets around nearby M-dwarfs

    Takayuki Kotani, Motohide Tamura, Hiroshi Suto, Jun Nishikawa, Bun'Ei Sato, Wako Aoki, Tomonori Usuda, Takashi Kurokawa, Ken Kashiwagi, Shogo Nishiyama, Yuji Ikeda, Donald B. Hall, Klaus W. Hodapp, Shane Jacobson, Jun Hashimoto, Jun Ichi Morino, Yasushi Okuyama, Yosuke Tanaka, Shota Suzuki, Sadahiro Inoue, Jungmi Kwon, Takuya Suenaga, Dehyun Oh, Haruka Baba, Norio Narita, Eiichiro Kokubo, Yutaka Hayano, Hideyuki Izumiura, Eiji Kambe, Tomoyuki Kudo, Nobuhiko Kusakabe, Masahiro Ikoma, Yasunori Hori, Masashi Omiya, Hidenori Genda, Akihiko Fukui, Yuka Fujii, Olivier Guyon, Hiroki Harakawa, Masahiko Hayashi, Masahide Hidai, Teruyuki Hirano, Masayuki Kuzuhara, Masahiro Machida, Taro Matsuo, Tetsuya Nagata, Hirohi Onuki, Masahiro Ogihara, Hideki Takami, Naruhisa Takato, Yasuhiro H. Takahashi, Chihiro Tachinami, Hiroshi Terada, Hajime Kawahara, Tomoyasu Yamamuro

    Ground-Based and Airborne Instrumentation for Astronomy V  2014.1 

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    Event date: 2014.6

    Language:English  

    Country:Canada  

  • Infrared Doppler instrument (IRD) for the Subaru telescope to search for Earth-like planets around nearby M-dwarfs

    Takayuki Kotani, Motohide Tamura, Hiroshi Suto, Jun Nishikawa, Bun'Ei Sato, Wako Aoki, Tomonori Usuda, Takashi Kurokawa, Ken Kashiwagi, Shogo Nishiyama, Yuji Ikeda, Donald B. Hall, Klaus W. Hodapp, Shane Jacobson, Jun Hashimoto, Jun Ichi Morino, Yasushi Okuyama, Yosuke Tanaka, Shota Suzuki, Sadahiro Inoue, Jungmi Kwon, Takuya Suenaga, Dehyun Oh, Haruka Baba, Norio Narita, Eiichiro Kokubo, Yutaka Hayano, Hideyuki Izumiura, Eiji Kambe, Tomoyuki Kudo, Nobuhiko Kusakabe, Masahiro Ikoma, Yasunori Hori, Masashi Omiya, Hidenori Genda, Akihiko Fukui, Yuka Fujii, Olivier Guyon, Hiroki Harakawa, Masahiko Hayashi, Masahide Hidai, Teruyuki Hirano, Masayuki Kuzuhara, Masahiro Machida, Taro Matsuo, Tetsuya Nagata, Hirohi Onuki, Masahiro Ogihara, Hideki Takami, Naruhisa Takato, Yasuhiro H. Takahashi, Chihiro Tachinami, Hiroshi Terada, Hajime Kawahara, Tomoyasu Yamamuro

    Ground-Based and Airborne Instrumentation for Astronomy V  2014.1 

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    Event date: 2014.6

    Language:English  

    Country:Canada  

  • Infrared Doppler instrument (IRD) for the Subaru telescope to search for Earth-like planets around nearby M-dwarfs

    Takayuki Kotani, Motohide Tamura, Hiroshi Suto, Jun Nishikawa, Bun'Ei Sato, Wako Aoki, Tomonori Usuda, Takashi Kurokawa, Ken Kashiwagi, Shogo Nishiyama, Yuji Ikeda, Donald B. Hall, Klaus W. Hodapp, Shane Jacobson, Jun Hashimoto, Jun Ichi Morino, Yasushi Okuyama, Yosuke Tanaka, Shota Suzuki, Sadahiro Inoue, Jungmi Kwon, Takuya Suenaga, Dehyun Oh, Haruka Baba, Norio Narita, Eiichiro Kokubo, Yutaka Hayano, Hideyuki Izumiura, Eiji Kambe, Tomoyuki Kudo, Nobuhiko Kusakabe, Masahiro Ikoma, Yasunori Hori, Masashi Omiya, Hidenori Genda, Akihiko Fukui, Yuka Fujii, Olivier Guyon, Hiroki Harakawa, Masahiko Hayashi, Masahide Hidai, Teruyuki Hirano, Masayuki Kuzuhara, Masahiro Machida, Taro Matsuo, Tetsuya Nagata, Hirohi Onuki, Masahiro Ogihara, Hideki Takami, Naruhisa Takato, Yasuhiro H. Takahashi, Chihiro Tachinami, Hiroshi Terada, Hajime Kawahara, Tomoyasu Yamamuro

    Ground-Based and Airborne Instrumentation for Astronomy V  2014.1 

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    Event date: 2014.6

    Language:English  

    Country:Canada  

  • Infrared Doppler instrument (IRD) for the Subaru telescope to search for Earth-like planets around nearby M-dwarfs

    Takayuki Kotani, Motohide Tamura, Hiroshi Suto, Jun Nishikawa, Bun'Ei Sato, Wako Aoki, Tomonori Usuda, Takashi Kurokawa, Ken Kashiwagi, Shogo Nishiyama, Yuji Ikeda, Donald B. Hall, Klaus W. Hodapp, Shane Jacobson, Jun Hashimoto, Jun Ichi Morino, Yasushi Okuyama, Yosuke Tanaka, Shota Suzuki, Sadahiro Inoue, Jungmi Kwon, Takuya Suenaga, Dehyun Oh, Haruka Baba, Norio Narita, Eiichiro Kokubo, Yutaka Hayano, Hideyuki Izumiura, Eiji Kambe, Tomoyuki Kudo, Nobuhiko Kusakabe, Masahiro Ikoma, Yasunori Hori, Masashi Omiya, Hidenori Genda, Akihiko Fukui, Yuka Fujii, Olivier Guyon, Hiroki Harakawa, Masahiko Hayashi, Masahide Hidai, Teruyuki Hirano, Masayuki Kuzuhara, Masahiro Machida, Taro Matsuo, Tetsuya Nagata, Hirohi Onuki, Masahiro Ogihara, Hideki Takami, Naruhisa Takato, Yasuhiro H. Takahashi, Chihiro Tachinami, Hiroshi Terada, Hajime Kawahara, Tomoyasu Yamamuro

    Ground-Based and Airborne Instrumentation for Astronomy V  2014.1 

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    Event date: 2014.6

    Language:English  

    Country:Canada  

  • Infrared Doppler instrument for the Subaru telescope (IRD)

    M. Tamura, H. Suto, J. Nishikawa, T. Kotani, B. Sato, W. Aoki, T. Usuda, T. Kurokawa, K. Kashiwagi, S. Nishiyama, Y. Ikeda, D. Hall, K. Hodapp, J. Hashimoto, J. Morino, S. Inoue, Y. Mizuno, Y. Washizaki, Y. Tanaka, S. Suzuki, J. Kwon, T. Suenaga, D. Oh, N. Narita, E. Kokubo, Y. Hayano, H. Izumiura, E. Kambe, T. Kudo, N. Kusakabe, M. Ikoma, Y. Hori, M. Omiya, H. Genda, A. Fukui, Y. Fujii, O. Guyon, H. Harakawa, M. Hayashi, M. Hidai, T. Hirano, M. Kuzuhara, Masahiro Machida, T. Matsuo, T. Nagata, Y. Ohnuki, M. Ogihara, S. Oshino, R. Suzuki, H. Takami, N. Takato, Y. Takahashi, C. Tachinami, H. Terada

    Ground-Based and Airborne Instrumentation for Astronomy IV  2012.12 

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    Event date: 2012.7

    Language:English  

    Country:Netherlands  

  • Infrared Doppler instrument for the Subaru telescope (IRD)

    M. Tamura, H. Suto, J. Nishikawa, T. Kotani, B. Sato, W. Aoki, T. Usuda, T. Kurokawa, K. Kashiwagi, S. Nishiyama, Y. Ikeda, D. Hall, K. Hodapp, J. Hashimoto, J. Morino, S. Inoue, Y. Mizuno, Y. Washizaki, Y. Tanaka, S. Suzuki, J. Kwon, T. Suenaga, D. Oh, N. Narita, E. Kokubo, Y. Hayano, H. Izumiura, E. Kambe, T. Kudo, N. Kusakabe, M. Ikoma, Y. Hori, M. Omiya, H. Genda, A. Fukui, Y. Fujii, O. Guyon, H. Harakawa, M. Hayashi, M. Hidai, T. Hirano, M. Kuzuhara, Masahiro Machida, T. Matsuo, T. Nagata, Y. Ohnuki, M. Ogihara, S. Oshino, R. Suzuki, H. Takami, N. Takato, Y. Takahashi, C. Tachinami, H. Terada

    Ground-Based and Airborne Instrumentation for Astronomy IV  2012.12 

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    Event date: 2012.7

    Language:English  

    Country:Netherlands  

  • Infrared Doppler instrument for the Subaru telescope (IRD)

    M. Tamura, H. Suto, J. Nishikawa, T. Kotani, B. Sato, W. Aoki, T. Usuda, T. Kurokawa, K. Kashiwagi, S. Nishiyama, Y. Ikeda, D. Hall, K. Hodapp, J. Hashimoto, J. Morino, S. Inoue, Y. Mizuno, Y. Washizaki, Y. Tanaka, S. Suzuki, J. Kwon, T. Suenaga, D. Oh, N. Narita, E. Kokubo, Y. Hayano, H. Izumiura, E. Kambe, T. Kudo, N. Kusakabe, M. Ikoma, Y. Hori, M. Omiya, H. Genda, A. Fukui, Y. Fujii, O. Guyon, H. Harakawa, M. Hayashi, M. Hidai, T. Hirano, M. Kuzuhara, Masahiro Machida, T. Matsuo, T. Nagata, Y. Ohnuki, M. Ogihara, S. Oshino, R. Suzuki, H. Takami, N. Takato, Y. Takahashi, C. Tachinami, H. Terada

    Ground-Based and Airborne Instrumentation for Astronomy IV  2012.12 

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    Event date: 2012.7

    Language:English  

    Country:Netherlands  

  • Infrared Doppler instrument for the Subaru telescope (IRD)

    M. Tamura, H. Suto, J. Nishikawa, T. Kotani, B. Sato, W. Aoki, T. Usuda, T. Kurokawa, K. Kashiwagi, S. Nishiyama, Y. Ikeda, D. Hall, K. Hodapp, J. Hashimoto, J. Morino, S. Inoue, Y. Mizuno, Y. Washizaki, Y. Tanaka, S. Suzuki, J. Kwon, T. Suenaga, D. Oh, N. Narita, E. Kokubo, Y. Hayano, H. Izumiura, E. Kambe, T. Kudo, N. Kusakabe, M. Ikoma, Y. Hori, M. Omiya, H. Genda, A. Fukui, Y. Fujii, O. Guyon, H. Harakawa, M. Hayashi, M. Hidai, T. Hirano, M. Kuzuhara, Masahiro Machida, T. Matsuo, T. Nagata, Y. Ohnuki, M. Ogihara, S. Oshino, R. Suzuki, H. Takami, N. Takato, Y. Takahashi, C. Tachinami, H. Terada

    Ground-Based and Airborne Instrumentation for Astronomy IV  2012.12 

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    Event date: 2012.7

    Language:English  

    Country:Netherlands  

  • Expected observations of star formation process From molecular cloud core to first hydrostatic core

    Kohji Tomisaka, Akimasa Kataoka, Masahiro Machida, Kengo Tomida, Kazuya Saigo

    Conference on Labyrinth of Star Formation dedicated to Prof. Anthony Whitworth, 2012  2014.1 

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    Event date: 2012.6

    Language:English  

    Country:Greece  

  • The effect of mass accretion for formation and thermal evolution of circumstellar disks

    Yusuke Tsukamoto, Masahiro Machida, Shu Ichiro Inutsuka

    Conference on Labyrinth of Star Formation dedicated to Prof. Anthony Whitworth, 2012  2014.1 

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    Event date: 2012.6

    Language:English  

    Country:Greece  

  • Expected observations of star formation process From molecular cloud core to first hydrostatic core

    Kohji Tomisaka, Akimasa Kataoka, Masahiro Machida, Kengo Tomida, Kazuya Saigo

    Conference on Labyrinth of Star Formation dedicated to Prof. Anthony Whitworth, 2012  2014.1 

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    Event date: 2012.6

    Language:English  

    Country:Greece  

  • The effect of mass accretion for formation and thermal evolution of circumstellar disks

    Yusuke Tsukamoto, Masahiro Machida, Shu Ichiro Inutsuka

    Conference on Labyrinth of Star Formation dedicated to Prof. Anthony Whitworth, 2012  2014.1 

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    Event date: 2012.6

    Language:English  

    Country:Greece  

  • Expected observations of star formation process From molecular cloud core to first hydrostatic core

    Kohji Tomisaka, Akimasa Kataoka, Masahiro Machida, Kengo Tomida, Kazuya Saigo

    Conference on Labyrinth of Star Formation dedicated to Prof. Anthony Whitworth, 2012  2014.1 

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    Event date: 2012.6

    Language:English  

    Country:Greece  

  • The effect of mass accretion for formation and thermal evolution of circumstellar disks

    Yusuke Tsukamoto, Masahiro Machida, Shu Ichiro Inutsuka

    Conference on Labyrinth of Star Formation dedicated to Prof. Anthony Whitworth, 2012  2014.1 

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    Event date: 2012.6

    Language:English  

    Country:Greece  

  • Expected observations of star formation process From molecular cloud core to first hydrostatic core

    Kohji Tomisaka, Akimasa Kataoka, Masahiro Machida, Kengo Tomida, Kazuya Saigo

    Conference on Labyrinth of Star Formation dedicated to Prof. Anthony Whitworth, 2012  2014.1 

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    Event date: 2012.6

    Language:English  

    Country:Greece  

  • The effect of mass accretion for formation and thermal evolution of circumstellar disks

    Yusuke Tsukamoto, Masahiro Machida, Shu Ichiro Inutsuka

    Conference on Labyrinth of Star Formation dedicated to Prof. Anthony Whitworth, 2012  2014.1 

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    Event date: 2012.6

    Language:English  

    Country:Greece  

  • Magnetohy drodynamics of Population III star formation

    Masahiro Machida, Kazuyuki Omukai, Tomoaki Matsumoto

    1st Stars and Galaxies: Challenges for the Next Decade  2010.12 

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    Event date: 2010.3

    Language:English  

    Country:United States  

  • Magnetohy drodynamics of Population III star formation

    Masahiro Machida, Kazuyuki Omukai, Tomoaki Matsumoto

    1st Stars and Galaxies: Challenges for the Next Decade  2010.12 

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    Event date: 2010.3

    Language:English  

    Country:United States  

  • Magnetohy drodynamics of Population III star formation

    Masahiro Machida, Kazuyuki Omukai, Tomoaki Matsumoto

    1st Stars and Galaxies: Challenges for the Next Decade  2010.12 

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    Event date: 2010.3

    Language:English  

    Country:United States  

  • Magnetohy drodynamics of Population III star formation

    Masahiro Machida, Kazuyuki Omukai, Tomoaki Matsumoto

    1st Stars and Galaxies: Challenges for the Next Decade  2010.12 

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    Event date: 2010.3

    Language:English  

    Country:United States  

  • Self-gravitational collapse of a magnetized cloud core High resolution simulations with three-dimensional MHD nested grid

    Tomoaki Matsumoto, Masahiro Machida, Kohji Tomisaka, Tomoyuki Hanawa

    Proceedings of the 18th International Conference  2004.12 

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    Event date: 2003.9

    Language:English  

    Country:United States  

  • Self-gravitational collapse of a magnetized cloud core High resolution simulations with three-dimensional MHD nested grid

    Tomoaki Matsumoto, Masahiro Machida, Kohji Tomisaka, Tomoyuki Hanawa

    Proceedings of the 18th International Conference  2004.12 

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    Event date: 2003.9

    Language:English  

    Country:United States  

  • Self-gravitational collapse of a magnetized cloud core High resolution simulations with three-dimensional MHD nested grid

    Tomoaki Matsumoto, Masahiro Machida, Kohji Tomisaka, Tomoyuki Hanawa

    Proceedings of the 18th International Conference  2004.12 

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    Event date: 2003.9

    Language:English  

    Country:United States  

  • Self-gravitational collapse of a magnetized cloud core High resolution simulations with three-dimensional MHD nested grid

    Tomoaki Matsumoto, Masahiro Machida, Kohji Tomisaka, Tomoyuki Hanawa

    Proceedings of the 18th International Conference  2004.12 

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    Event date: 2003.9

    Language:English  

    Country:United States  

  • Recent developments in simulations of low-mass star formation

    Masahiro Machida

    2011.4 

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    Language:English  

    Country:Other  

  • Recent developments in simulations of low-mass star formation

    Masahiro Machida

    2011.4 

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    Language:English  

    Country:Other  

  • Recent developments in simulations of low-mass star formation

    Masahiro Machida

    2011.4 

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    Language:English  

    Country:Other  

  • Recent developments in simulations of low-mass star formation

    Masahiro Machida

    2011.4 

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    Language:English  

    Country:Other  

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Professional Memberships

  • The Astronomical Society of Japan

Academic Activities

  • Screening of academic papers

    Role(s): Peer review

    2024

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    Type:Peer review 

    Number of peer-reviewed articles in foreign language journals:4

    Number of peer-reviewed articles in Japanese journals:0

    Proceedings of International Conference Number of peer-reviewed papers:0

    Proceedings of domestic conference Number of peer-reviewed papers:0

  • Screening of academic papers

    Role(s): Peer review

    2023

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    Type:Peer review 

    Number of peer-reviewed articles in foreign language journals:3

  • Screening of academic papers

    Role(s): Peer review

    2021

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    Type:Peer review 

    Number of peer-reviewed articles in foreign language journals:3

  • Screening of academic papers

    Role(s): Peer review

    2020

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    Type:Peer review 

    Number of peer-reviewed articles in foreign language journals:2

  • Screening of academic papers

    Role(s): Peer review

    2019

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    Type:Peer review 

    Number of peer-reviewed articles in foreign language journals:2

  • Screening of academic papers

    Role(s): Peer review

    2018

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    Type:Peer review 

    Number of peer-reviewed articles in foreign language journals:3

  • Screening of academic papers

    Role(s): Peer review

    2017

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    Type:Peer review 

    Number of peer-reviewed articles in foreign language journals:3

    Number of peer-reviewed articles in Japanese journals:0

    Proceedings of International Conference Number of peer-reviewed papers:0

    Proceedings of domestic conference Number of peer-reviewed papers:0

  • Screening of academic papers

    Role(s): Peer review

    2016

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    Type:Peer review 

    Number of peer-reviewed articles in foreign language journals:3

    Number of peer-reviewed articles in Japanese journals:0

    Proceedings of International Conference Number of peer-reviewed papers:0

    Proceedings of domestic conference Number of peer-reviewed papers:0

  • 天文月報

    2012.1 - 2017.6

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    Type:Academic society, research group, etc. 

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Research Projects

  • ALMA共同科学研究事業

    2022.4 - 2024.4

    共同研究

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    Authorship:Principal investigator  Grant type:Other funds from industry-academia collaboration

  • 主降着段階における星形成過程の理論的研究

    2021 - 2023

    日本学術振興会  科学研究費助成事業  基盤研究(C)

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    Authorship:Principal investigator  Grant type:Scientific research funding

  • Star formation Process during main accretion phase

    Grant number:21K03617  2021 - 2023

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (C)

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    Authorship:Principal investigator  Grant type:Scientific research funding

    CiNii Research

  • 星周円盤の形成と原始星ジェットの理論研究

    2021 - 2022

    日本学術振興会・文部科学省  科学研究費助成事業  新学術領域研究(研究領域提案型)

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    Authorship:Principal investigator  Grant type:Scientific research funding

  • Theoretical study about circumstellar disks and protostellar jets

    Grant number:21H00046  2021 - 2022

    Japan Society for the Promotion of Science・Ministry of Education, Culture, Sports, Science and Technology  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research on Innovative Areas

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    Authorship:Principal investigator  Grant type:Scientific research funding

    CiNii Research

  • ブラックホール連星形成過程の理論的研究

    Grant number:17H06360  2017 - 2022

    日本学術振興会・文部科学省  科学研究費助成事業  新学術領域研究

    大向 一行, 須佐 元, 町田 正博, 谷川 衝, 細川 隆史, 藤井 通子

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    Authorship:Coinvestigator(s)  Grant type:Scientific research funding

    重力波源天体であるブラックホール(BH)連星の起源を、理論的研究により調べた。
    得られた主な結果の通りである:
    1)孤立大質量連星形成に関して、宇宙初期の低金属量環境において形成されうる大質量連星の性質を調べたところ、初代星は数十質量からなる大質量の連星系として形成されることが分かった。 2)低金属度連星の進化についての解析モデルにより調べた。その結果、重力波観測で見つかっているBH合体のすべてが孤立連星起源であるとしても矛盾がないことを示した。3)星団進化に対する重力多体計算により、星同士の動的相互作用による連星形成割合を見積もった。星数が小さな散開星団でも連星BHが形成可能なことが分かった。

    CiNii Research

  • 極初期宇宙における星形成の研究

    Grant number:17H02869  2017 - 2021

    日本学術振興会  科学研究費助成事業  基盤研究(B)

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    Authorship:Coinvestigator(s)  Grant type:Scientific research funding

  • 星形成後期段階の解明

    Grant number:17K05387  2017 - 2020

    日本学術振興会  科学研究費助成事業  基盤研究(C)

    町田 正博

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    Authorship:Principal investigator  Grant type:Scientific research funding

    数値シミュレーションを用いて原始星形成後の質量降着期の星周円盤の成長と原始星ジェットの駆動機構を解明した。星周円盤の外縁では磁気制動による角運動量輸送が効率的であり円盤のサイズ成長が抑制される。この段階では、定常的に円盤にガスが降着するため、重力不安定により渦状碗が発達する。渦状碗による非軸対称重力トルクによって円盤の角運動量が輸送され、円盤ガスは中心星へ落下する。その後、円盤は重力的に安定となり中心星への質量降着率は下がる。また、中心星に落下するガスの一部がジェットとして原始星近傍から放出される。この研究によって、中心星へのガス降着と中心部からのジェットは非定常であることが分かった。

    CiNii Research

  • 重力不安定によるガス惑星形成と原始惑星系円盤の進化

    Grant number:26103707  2014 - 2015

    日本学術振興会・文部科学省  科学研究費助成事業  新学術領域研究

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    Authorship:Principal investigator  Grant type:Scientific research funding

  • 新しい星形成シナリオの構築

    Grant number:25400232  2013 - 2017

    日本学術振興会  科学研究費助成事業  基盤研究(C)

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    Authorship:Principal investigator  Grant type:Scientific research funding

  • 原始星アウトフローの長時間進化と星周円盤の形成過程

    Grant number:21740136  2009 - 2011

    科学研究費助成事業  若手研究(B)

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    Authorship:Principal investigator  Grant type:Scientific research funding

  • 星間分子雲の収縮から第二コアの形成と高速ジェット現象の解明

    Grant number:18740104  2006 - 2008

    科学研究費助成事業  若手研究(B)

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    Authorship:Principal investigator  Grant type:Scientific research funding

  • 強い磁場を持つ分子雲コア中での星形成過程

    Grant number:17KK0096 

    町田 正博

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    Grant type:Scientific research funding

    観測から星形成の母体となる分子雲コアは強い磁場を持つことが分かっている。これまでの研究では、重力エネルギーが磁気エネルギーを卓越している場合の分子雲コアの進化について研究が行われてきた。しかし、磁気エネルギーが重力エネルギーを卓越している分子雲コアも観測で見つかっている。この研究では、初期に磁場によって支えられている分子雲コア中での星形成過程を調べた。磁場は両極性拡散によって分子雲コアから抜ける。その後、ガスの自己重力により収縮し星が誕生する。しかし、星形成前に磁気制動によって分子雲コアの角運動量の大分部が抜けているため磁場が卓越したガス雲中での星形成過程は通常とは大きく異なることが分かった。

    CiNii Research

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Educational Activities

  • Fluid Dynamics, Comparative Planetology, Thermal Dynamics

Award for Educational Activities

  • なし

       

Class subject

  • 比較惑星学

    2023.12 - 2024.2   Winter quarter

  • 熱力学概論

    2023.12 - 2024.2   Winter quarter

  • 宇宙科学概論

    2023.4 - 2023.9   First semester

  • 流体力学特論

    2023.4 - 2023.9   First semester

  • 地球惑星数理演習

    2023.4 - 2023.9   First semester

  • 比較惑星学

    2022.12 - 2023.2   Winter quarter

  • 熱力学概論

    2022.12 - 2023.2   Winter quarter

  • 地球惑星科学特別講義Ⅵ

    2022.10 - 2023.3   Second semester

  • 宇宙科学概論

    2022.4 - 2022.9   First semester

  • 流体力学特論

    2022.4 - 2022.9   First semester

  • 地球惑星数理演習

    2022.4 - 2022.9   First semester

  • Fluid Dynamics

    2022.4 - 2022.9   First semester

  • 比較惑星学

    2021.12 - 2022.2   Winter quarter

  • 熱力学概論

    2021.12 - 2022.2   Winter quarter

  • 流体力学特論

    2021.4 - 2021.9   First semester

  • 地球惑星数理演習

    2021.4 - 2021.9   First semester

  • 比較惑星学

    2020.12 - 2021.2   Winter quarter

  • 地球惑星数理演習

    2020.4 - 2020.9   First semester

  • 流体力学特論

    2020.4 - 2020.9   First semester

  • Fluid Dynamics

    2020.4 - 2020.9   First semester

  • 物理学概論B

    2019.12 - 2020.2   Winter quarter

  • 比較惑星学

    2019.12 - 2020.2   Winter quarter

  • 流体力学特論

    2019.10 - 2020.3   Second semester

  • 流体力学特論

    2019.10 - 2020.3   Second semester

  • 比較惑星学

    2019.10 - 2020.3   Second semester

  • 地球惑星科学II

    2019.4 - 2019.9   First semester

  • 比較惑星学

    2018.12 - 2019.2   Winter quarter

  • 連続体力学Ⅰ

    2018.10 - 2019.3   Second semester

  • 連続体力学Ⅰ(物理)

    2018.10 - 2019.3   Second semester

  • 連続体力学Ⅰ(地惑)

    2018.10 - 2019.3   Second semester

  • Fluid Dynamics

    2018.4 - 2018.9   First semester

  • Fluid dynamics

    2018.4 - 2018.9   First semester

  • 物理学概論B

    2018.4 - 2018.9   First semester

  • 地球惑星数理演習

    2018.4 - 2018.9   First semester

  • 流体力学特論

    2018.4 - 2018.9   First semester

  • 比較惑星学

    2017.12 - 2018.2   Winter quarter

  • 連続体力学Ⅰ(物理)

    2017.10 - 2018.3   Second semester

  • 連続体力学Ⅰ(地惑)

    2017.10 - 2018.3   Second semester

  • 物理学概論B

    2017.10 - 2018.3   Second semester

  • 地球惑星数理演習

    2017.4 - 2017.9   First semester

  • 流体力学特論

    2017.4 - 2017.9   First semester

  • 物理学概論B

    2016.10 - 2017.3   Second semester

  • 比較惑星学

    2016.10 - 2017.3   Second semester

  • 地球惑星数理演習

    2016.4 - 2016.9   First semester

  • 流体力学特論

    2016.4 - 2016.9   First semester

  • 連続体力学I

    2015.10 - 2016.3   Second semester

  • 物理学概論B

    2015.10 - 2016.3   Second semester

  • 地球惑星科学II

    2015.10 - 2016.3   Second semester

  • 地球惑星数理演習

    2015.4 - 2015.9   First semester

  • 流体力学特論

    2015.4 - 2015.9   First semester

  • 地球惑星科学II

    2014.10 - 2015.3   Second semester

  • 物理学概論B

    2014.10 - 2015.3   Second semester

  • 連続体力学I

    2014.10 - 2015.3   Second semester

  • 比較惑星学

    2014.10 - 2015.3   Second semester

  • 流体力学特論

    2014.4 - 2014.9   First semester

  • 地球惑星数理演習

    2014.4 - 2014.9   First semester

  • 比較惑星学

    2013.10 - 2014.3   Second semester

  • 連続体力学I

    2013.10 - 2014.3   Second semester

  • 自然科学総合実験

    2013.4 - 2013.9   First semester

  • 地球惑星数理演習

    2013.4 - 2013.9   First semester

  • 流体力学特論

    2013.4 - 2013.9   First semester

  • 比較惑星学

    2012.10 - 2013.3   Second semester

  • 連続体力学I

    2012.10 - 2013.3   Second semester

  • コアセミナー

    2012.4 - 2012.9   First semester

  • 流体力学特論

    2012.4 - 2012.9   First semester

  • 地球科学I

    2012.4 - 2012.9   First semester

  • 自然科学総合実験

    2012.4 - 2012.9   First semester

  • 比較惑星学

    2011.10 - 2012.3   Second semester

  • コアセミナー

    2011.4 - 2011.9   First semester

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FD Participation

  • 2022.3   Role:Participation   Title:実験・実習科目の課題と今後のあり方

    Organizer:Undergraduate school department

  • 2016.3   Role:Participation   Title:EEP Seminar

    Organizer:Undergraduate school department

  • 2013.3   Role:Participation   Title:アクティブ・ラーニング:入門と実践

    Organizer:[Undergraduate school/graduate school/graduate faculty]

  • 2013.3   Role:Participation   Title:基幹教育院の新カリキュラムについて

    Organizer:Undergraduate school department

Visiting, concurrent, or part-time lecturers at other universities, institutions, etc.

  • 2021  名古屋大学・理学部  Classification:Intensive course  Domestic/International Classification:Japan 

    Semester, Day Time or Duration:後期

  • 2018  福岡大学  Classification:Intensive course  Domestic/International Classification:Japan 

    Semester, Day Time or Duration:前期

  • 2016  京都大学  Classification:Intensive course  Domestic/International Classification:Japan 

    Semester, Day Time or Duration:前期

  • 2015  筑波大学・理学部  Classification:Intensive course  Domestic/International Classification:Japan 

    Semester, Day Time or Duration:後期

  • 2015  神戸大学・理学部  Classification:Intensive course  Domestic/International Classification:Japan 

    Semester, Day Time or Duration:前期

  • 2015  北海道大学・理学研究院  Classification:Intensive course  Domestic/International Classification:Japan 

    Semester, Day Time or Duration:後期

  • 2004  法政大学・人間環境学部  Classification:Part-time lecturer  Domestic/International Classification:Japan 

  • 2003  法政大学・人間環境学部  Classification:Part-time lecturer  Domestic/International Classification:Japan 

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Other educational activity and Special note

  • 2021  Class Teacher 

  • 2020  Class Teacher 

  • 2019  Special Affairs 

     詳細を見る

    Lecture at Moji Gakuen high school

  • 2018  Special Affairs 

     詳細を見る

    Lecture in Workshop collection in Fukuoka

  • 2017  Special Affairs 

     詳細を見る

    Lecture for high school and junior high school students

  • 2012  Class Teacher 

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Media Coverage

  • コズミックフロント・NEXT TV or radio program

    2020.4

     More details

    コズミックフロント・NEXT

Travel Abroad

  • 2023.8 - 2023.9

    Staying countory name 1:Canada   Staying institution name 1:Western Ontario University

  • 2019.4 - 2019.9

    Staying countory name 1:Canada   Staying institution name 1:Western Ontario University

  • 2018.8 - 2018.9

    Staying countory name 1:Canada   Staying institution name 1:Western Ontario University