Faculty Profiles - TSUKAMOTO Yusuke

Papers - TSUKAMOTO Yusuke

Division display 21 - 40 of about 45 ／ All the affair displays >>

Chakali E. . The JCMT BISTRO Survey: Revealing the Diverse Magnetic Field Morphologies in Taurus Dense Cores with Sensitive Submillimeter Polarimetry . Astrophysical Journal Letters912 ( 2 ) 2021.5Reviewed International coauthorship

Language：Japanese Publisher：Astrophysical Journal Letters

We have obtained sensitive dust continuum polarization observations at 850 μm in the B213 region of Taurus using POL-2 on SCUBA-2 at the James Clerk Maxwell Telescope as part of the B-fields in STar-forming Region Observations (BISTRO) survey. These observations allow us to probe magnetic field (B-field) at high spatial resolution (∼2000 au or ∼0.01 pc at 140 pc) in two protostellar cores (K04166 and K04169) and one prestellar core (Miz-8b) that lie within the B213 filament. Using the Davis-Chandrasekhar-Fermi method, we estimate the B-field strengths in K04166, K04169, and Miz-8b to be 38 ± 14, 44 ± 16, and 12 ± 5 μG, respectively. These cores show distinct mean B-field orientations. The B-field in K04166 is well ordered and aligned parallel to the orientations of the core minor axis, outflows, core rotation axis, and large-scale uniform B-field, in accordance with magnetically regulated star formation via ambipolar diffusion taking place in K04166. The B-field in K04169 is found to be ordered but oriented nearly perpendicular to the core minor axis and large-scale B-field and not well correlated with other axes. In contrast, Miz-8b exhibits a disordered B-field that shows no preferred alignment with the core minor axis or large-scale field. We found that only one core, K04166, retains a memory of the large-scale uniform B-field. The other two cores, K04169 and Miz-8b, are decoupled from the large-scale field. Such a complex B-field configuration could be caused by gas inflow onto the filament, even in the presence of a substantial magnetic flux.

DOI： 10.3847/2041-8213/abeb1c

Scopus

Wada K. . Formation of "Blanets"from Dust Grains around the Supermassive Black Holes in Galaxies . Astrophysical Journal909 ( 1 ) 2021.3Reviewed

Language：Japanese Publisher：Astrophysical Journal

In Wada et al. (2019), we proposed for the first time that a new class of planets, blanets, can be formed around supermassive black holes in the galactic center. Here, we investigate the dust coagulation processes and physical conditions of the blanet formation outside the snowline (r snow ∼ several parsecs) in more detail, especially considering the effect of the radial drift of the dust aggregates. We found that a dimensionless parameter, where v t is the turbulent velocity and c s is the sound velocity, describing the turbulent viscosity should be smaller than 0.04 in the circumnuclear disk to prevent the destruction of the aggregates due to collision. The formation timescale of blanets τ GI at r snow is, τ GI ≃ 70-80 Myr for α = 0.01 - 0.04 and M BH = 106 M o˙. The mass of the blanets ranges from ∼20M E to 3000M E in r < 4 pc for α = 0.02 (M E is the Earth mass), which is in contrast with 4M E-6M E for the case without the radial drift. Our results suggest that blanets could be formed around relatively low-luminosity active galactic nuclei (L bol ∼ 1042 erg s-1) during their lifetime (≲108 yr).

DOI： 10.3847/1538-4357/abd40a

Scopus

Arzoumanian D. . Dust polarized emission observations of NGC 6334: BISTRO reveals the details of the complex but organized magnetic field structure of the high-mass star-forming hub-filament network . Astronomy and Astrophysics647 2021.3Reviewed International coauthorship

Language：Japanese Publisher：Astronomy and Astrophysics

Context. Molecular filaments and hubs have received special attention recently thanks to new studies showing their key role in star formation. While the (column) density and velocity structures of both filaments and hubs have been carefully studied, their magnetic field (B-field) properties have yet to be characterized. Consequently, the role of B-fields in the formation and evolution of hub-filament systems is not well constrained. Aims. We aim to understand the role of the B-field and its interplay with turbulence and gravity in the dynamical evolution of the NGC 6334 filament network that harbours cluster-forming hubs and high-mass star formation. Methods. We present new observations of the dust polarized emission at 850 μm toward the 2 pc × 10 pc map of NGC 6334 at a spatial resolution of 0.09 pc obtained with the James Clerk Maxwell Telescope (JCMT) as part of the B-field In STar-forming Region Observations (BISTRO) survey. We study the distribution and dispersion of the polarized intensity (PI), the polarization fraction (PF), and the plane-of-The-sky B-field angle (χB_POS) toward the whole region, along the 10 pc-long ridge and along the sub-filaments connected to the ridge and the hubs. We derived the power spectra of the intensity and χBPOS along the ridge crest and compared them with the results obtained from simulated filaments. Results. The observations span 3 orders of magnitude in Stokes I and PI and 2 orders of magnitude in PF (from 0.2 to 20%). A large scatter in PI and PF is observed for a given value of I. Our analyses show a complex B-field structure when observed over the whole region ( 10 pc); however, at smaller scales (1 pc), χBPOS varies coherently along the crests of the filament network. The observed power spectrum of χBPOS can be well represented with a power law function with a slope of-1.33 ± 0.23, which is 20% shallower than that of I. We find that this result is compatible with the properties of simulated filaments and may indicate the physical processes at play in the formation and evolution of star-forming filaments. Along the sub-filaments, χBPOS rotates frombeing mostly perpendicular or randomly oriented with respect to the crests to mostly parallel as the sub-filaments merge with the ridge and hubs. This variation of the B-field structure along the sub-filaments may be tracing local velocity flows of infalling matter in the ridge and hubs. Our analysis also suggests a variation in the energy balance along the crests of these sub-filaments, from magnetically critical or supercritical at their far ends to magnetically subcritical near the ridge and hubs. We also detect an increase in PF toward the high-column density (NH2 â 1023 cm-2) star cluster-forming hubs. These latter large PF values may be explained by the increase in grain alignment efficiency due to stellar radiation from the newborn stars, combined with an ordered B-field structure. Conclusions. These observational results reveal for the first time the characteristics of the small-scale (down to 0.1 pc) B-field structure of a 10 pc-long hub-filament system. Our analyses show variations in the polarization properties along the sub-filaments that may be tracing the evolution of their physical properties during their interaction with the ridge and hubs. We also detect an impact of feedback from young high-mass stars on the local B-field structure and the polarization properties, which could put constraints on possible models for dust grain alignment and provide important hints as to the interplay between the star formation activity and interstellar B-fields.

DOI： 10.1051/0004-6361/202038624

Scopus

Ngoc N.B. . Observations of magnetic fields surrounding LkHa 101 taken by the BISTRO survey with JCMT-POL-2 . Astrophysical Journal908 ( 1 ) 2021.2Reviewed

Language：Japanese Publisher：Astrophysical Journal

We report the first high spatial resolution measurement of magnetic fields surrounding LkHa 101, part of the Auriga- California molecular cloud. The observations were taken with the POL-2 polarimeter on the James Clerk Maxwell Telescope within the framework of the B-fields In Star-forming Region Observations (BISTRO) survey. Observed polarization of thermal dust emission at 850 μm is found to be mostly associated with the redshifted gas component of the cloud. The magnetic field displays a relatively complex morphology. Two variants of the Davis-Chandrasekhar- Fermi method, unsharp masking and structure function, are used to calculate the strength of magnetic fields in the plane of the sky, yielding a similar result of BPOS~ 115 μG. The mass-to-magnetic-flux ratio in critical value units, λ~0.3, is the smallest among the values obtained for other regions surveyed by POL-2. This implies that the LkHa 101 region is subcritical, and the magnetic field is strong enough to prevent gravitational collapse. The inferred dB/B0~0.3 implies that the large-scale component of the magnetic field dominates the turbulent one. The variation of the polarization fraction with total emission intensity can be fitted by a power law with an index of a =0.82±0.03, which lies in the range previously reported for molecular clouds. We find that the polarization fraction decreases rapidly with proximity to the only early B star (LkHa 101) in the region. Magnetic field tangling and the joint effect of grain alignment and rotational disruption by radiative torques can potentially explain such a decreasing trend.

DOI： 10.3847/1538-4357/abd0fc

Scopus

Doi Y. . The JCMT BISTRO Survey: Magnetic Fields Associated with a Network of Filaments in NGC 1333 . Astrophysical Journal899 ( 1 ) 2020.8Reviewed

Hirano S. . The Effect of Misalignment between the Rotation Axis and Magnetic Field on the Circumstellar Disk . Astrophysical Journal898 ( 2 ) 2020.8Reviewed

Tsukamoto Y. . Early Evolution of Disk, Outflow, and Magnetic Field of Young Stellar Objects: Impact of Dust Model . Astrophysical Journal896 ( 2 ) 2020.6Reviewed

Takaishi D. . Star-disc alignment in the protoplanetary discs: SPH simulation of the collapse of turbulent molecular cloud cores . Monthly Notices of the Royal Astronomical Society492 ( 4 ) 5641 - 5654 2020Reviewed

Wada K. . Planet Formation around Supermassive Black Holes in the Active Galactic Nuclei . Astrophysical Journal886 ( 2 ) 2019.12Reviewed

B-Fields In Star-Forming Regions Observations bistro Collaboration T. . The JCMT BISTRO Survey: The Magnetic Field of the Barnard 1 Star-forming Region . Astrophysical Journal877 ( 2 ) 2019.6Reviewed

Liu J. . The JCMT BISTRO Survey: The Magnetic Field in the Starless Core ρ Ophiuchus C . Astrophysical Journal877 ( 1 ) 2019.5Reviewed

Wang J.W. . JCMT BISTRO Survey: Magnetic Fields within the Hub-filament Structure in IC 5146 . Astrophysical Journal876 ( 1 ) 2019.5Reviewed

Koga S. . Dependence of Hall coefficient on grain size and cosmic ray rate and implication for circumstellar disc formation . Monthly Notices of the Royal Astronomical Society484 ( 2 ) 2119 - 2136 2019.4Reviewed

Tanaka Y.A. . Pebble accretion in Class 0/I YSOs as a possible pathway for early planet formation . Monthly Notices of the Royal Astronomical Society484 ( 2 ) 1574 - 1588 2019.4Reviewed

Tsukamoto, Yusuke; Okuzumi, Satoshi; Iwasaki, Kazunari; Machida, Masahiro N.; Inutsuka, Shu-ichiro . Does Misalignment between Magnetic Field and Angular Momentum Enhance or Suppress Circumstellar Disk Formation? . The Astrophysical Journal868 ( 1 ) 2018.11Reviewed

Takakuwa, Shigehisa; Tsukamoto, Yusuke; Saigo, Kazuya; Saito, Masao . Possible Counterrotation between the Disk and Protostellar Envelope around the Class I Protostar IRAS 04169+2702 . The Astrophysical Journal865 ( 1 ) 2018.9Reviewed

Soam et al. . Magnetic Fields toward Ophiuchus-B Derived from SCUBA-2 Polarization Measurements . The Astrophysical Journal861 ( 1 ) 2018.7Reviewed

Kwon et al. . A First Look at BISTRO Observations of the ρ Oph-A core . The Astrophysical Journal,859 ( 1 ) 2018.5Reviewed

Tsukamoto, Yusuke; Okuzumi, Satoshi; Iwasaki, Kazunari; Machida, Masahiro N.; Inutsuka, Shu-ichiro . The impact of the Hall effect during cloud core collapse: Implications for circumstellar disk evolution . Publications of the Astronomical Society of Japan69 ( 6 ) 95 2017.12Reviewed

Ward-Thompson et al . First Results from BISTRO: A SCUBA-2 Polarimeter Survey of the Gould Belt . The Astrophysical Journal842 ( 1 ) 66 - 76 2017.6Reviewed

　 PREV - NEXT 　

<TSUKAMOTO Yusuke>

Papers - TSUKAMOTO Yusuke