Faculty Profiles - INUTSUKA, Shu-ichiro

Papers - INUTSUKA, Shu-ichiro

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

Tsukamoto, Y; Machida, MN; Susa, H; Nomura, H; Inutsuka, S

ASTROPHYSICAL JOURNAL Vol. 896 ( 2 ) 2020.6

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Astrophysical Journal

The formation and early evolution of low-mass young stellar objects (YSOs) are investigated using three-dimensional non-ideal magnetohydrodynamics simulations. We investigate the evolution of YSOs up to ∼ 104 after protostar formation, at which protostellar mass reaches ∼ 0.1M⊙. We particularly focus on the impact of the dust model on the evolution. We found that a circumstellar disk is formed in all simulations, regardless of the dust model. Disk size is approximately 10 au at the protostar formation epoch, and it increases to several tens of au at ∼ 104 after protostar formation. The disk mass is comparable to the central protostellar mass, and gravitational instability develops. In simulations with small dust sizes, the warp of the pseudodisk develops ∼ 104 after protostar formation. The warp strengthens magnetic braking in the disk and decreases disk size. Ion-neutral drift can occur in the infalling envelope when the typical dust size is ≳ 0.2μ m and the protostar (plus disk) mass is M≳ 0.1M⊙. The outflow activity is anticorrelated to the dust size, and the strong outflow appears with small dust grains.

DOI： 10.3847/1538-4357/ab93d0

The Molecular Cloud Lifecycle International coauthorship Open Access

Chevance, M; Kruijssen, JMD; Vazquez-Semadeni, E; Nakamura, F; Klessen, R; Ballesteros-Paredes, J; Inutsuka, S; Adamo, A; Hennebelle, P

SPACE SCIENCE REVIEWS Vol. 216 ( 4 ) page： 50 2020.4

Language：English Publishing type：Research paper (international conference proceedings) Publisher：Space Science Reviews

Giant molecular clouds (GMCs) and their stellar offspring are the building blocks of galaxies. The physical characteristics of GMCs and their evolution are tightly connected to galaxy evolution. The macroscopic properties of the interstellar medium propagate into the properties of GMCs condensing out of it, with correlations between e.g. the galactic and GMC scale gas pressures, surface densities and volume densities. That way, the galactic environment sets the initial conditions for star formation within GMCs. After the onset of massive star formation, stellar feedback from e.g. photoionisation, stellar winds, and supernovae eventually contributes to dispersing the parent cloud, depositing energy, momentum and metals into the surrounding medium, thereby changing the properties of galaxies. This cycling of matter between gas and stars, governed by star formation and feedback, is therefore a major driver of galaxy evolution. Much of the recent debate has focused on the durations of the various evolutionary phases that constitute this cycle in galaxies, and what these can teach us about the physical mechanisms driving the cycle. We review results from observational, theoretical, and numerical work to build a dynamical picture of the evolutionary lifecycle of GMC evolution, star formation, and feedback in galaxies.

DOI： 10.1007/s11214-020-00674-x

Preface Invited Reviewed Open Access

Inutsuka S.

Planetary People - The Japanese Society for Planetary Sciences Vol. 29 ( 1 ) page： 3 - 3 2020.3

Dispersal of protoplanetary discs by the combination of magnetically driven and photoevaporative winds Reviewed Open Access

Kunitomo, M; Suzuki, TK; Inutsuka, S

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY Vol. 492 ( 3 ) page： 3849 - 3858 2020.3

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Monthly Notices of the Royal Astronomical Society

We investigate the roles of magnetically driven disc wind (MDW) and thermally driven photoevaporative wind (PEW) in the long-time evolution of protoplanetary discs. We start simulations from the early phase in which the disc mass is 0.118M⊙ around a 1M⊙ star and track the evolution until the disc is completely dispersed. We incorporate the mass-loss by PEW and the mass-loss and magnetic braking (wind torque) by MDW, in addition to the viscous accretion, viscous heating, and stellar irradiation. We find that MDW and PEW, respectively, have different roles: Magnetically driven wind ejects materials from an inner disc in the early phase, whereas photoevaporation has a dominant role in the late phase in the outer (≳1 au) disc. The disc lifetime, which depends on the combination of MDW, PEW, and viscous accretion, shows a large variation of ∼1-20 Myr; the gas is dispersed mainly by the MDW and the PEW in the cases with a low viscosity and the lifetime is sensitive to the mass-loss rate and torque of the MDW, whereas the lifetime is insensitive to these parameters when the viscosity is high. Even in discs with very weak turbulence, the cooperation of MDW and PEW enables the disc dispersal within a few Myr.

DOI： 10.1093/mnras/staa087

High-resolution simulations of catastrophic disruptions: Resultant shape distributions Reviewed Open Access

Sugiura, K; Kobayashi, H; Inutsuka, S

PLANETARY AND SPACE SCIENCE Vol. 181 2020.2

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Planetary and Space Science

The members of asteroid families have various shapes. We investigate the origin of their shapes by high-resolution impact simulations for catastrophic disruptions using a Smoothed Particle Hydrodynamics code. Collisional remnants produced through our simulations of the catastrophic disruptions mainly have spherical or bilobed shapes. However, no flat remnants with the ratio of minor to major axis lengths c/a≲0.5 are formed. The results of the simulations provide various shapes of asteroids and explain most of the shapes in asteroid families that are supposed to be produced through catastrophic disruptions. However, the present simulations do not explain significantly flat asteroids. We suggest that these flat asteroids may be interlopers or formed through low-velocity collisions between member asteroids.

DOI： 10.1016/j.pss.2019.104807

Possibility of the formation of the extremely elongated shape of 1I/`Oumuamua through a planetesimal collision Open Access

Sugiura K., Kobayashi H., Inutsuka S.-i.

Planetary People - The Japanese Society for Planetary Sciences Vol. 28 ( 4 ) page： 323 - 331 2019.12

FOREST Unbiased Galactic Plane Imaging Survey with the Nobeyama 45 m telescope (FUGIN). V. Dense gas mass fraction of molecular gas in the Galactic plane Open Access

Torii, K; Fujita, S; Nishimura, A; Tokuda, K; Kohno, M; Tachihara, K; Inutsuka, S; Matsuo, M; Kuriki, M; Tsuda, Y; Minamidani, T; Umemoto, T; Kuno, N; Miyamoto, Y

PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN Vol. 71 2019.12

Language：Japanese Publisher：Publications of the Astronomical Society of Japan

Recent observations of the nearby Galactic molecular clouds indicate that the dense gas in molecular clouds has quasi-universal properties on star formation, and observational studies of extra-galaxies have shown a galactic-scale correlation between the star formation rate (SFR) and the surface density of molecular gas. To reach a comprehensive understanding of both properties, it is important to quantify the fractional mass of dense gas in molecular clouds, f<inf>DG</inf>. In particular, for the Milky Way (MW) there are no previous studies resolving f<inf>DG</inf> disk over a scale of several kpc. In this study, f<inf>DG</inf> was measured over 5 kpc in the first quadrant of the MW, based on the CO J = 1-0 data in l = 10°-50° obtained as part of the FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN) project. The total molecular mass was measured using <sup>12</sup>CO, and the dense gas mass was estimated using C<sup>18</sup>O. The fractional masses, including f<inf>DG</inf>, in the region within ±30% of the distances to the tangential points of the Galactic rotation (e.g., the Galactic Bar, Far-3 kpc Arm, Norma Arm, Scutum Arm, Sagittarius Arm, and inter-arm regions) were measured. As a result, an averaged f<inf>DG</inf> of $2.9^{+2.6}_{-2.6}$% was obtained for the entirety of the target region. This low value suggests that dense gas formation is the primary factor in inefficient star formation in galaxies. It was also found that f<inf>DG</inf> shows large variations depending on the structures in the MW disk. In the Galactic arms, f<inf>DG</inf> was estimated to be ∼4%-5%, while in the bar and inter-arm regions it was as small as ∼0.1%-0.4%. These results indicate that the formation/destruction processes of the dense gas and their timescales are different for different regions in the MW, leading to differences in Star formation efficiencies.

DOI： 10.1093/pasj/psz033

Macroscopic Dynamics of Dust Grains and Formation of Multiple Rings in Protoplanetary Disks Reviewed Open Access

Tominaga R. T., Takahashi S. Z., Inutsuka S.-i.

Planetary People - The Japanese Society for Planetary Sciences Vol. 28 ( 3 ) page： 172 - 181 2019.9

Constraints on the formation of brown dwarfs by turbulent compression Open Access

Stamer, T; Inutsuka, S

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY Vol. 488 ( 2 ) page： 2644 - 2649 2019.9

Language：Japanese Publisher：Monthly Notices of the Royal Astronomical Society

We perform radiation hydrodynamical simulations in spherical symmetry in order to investigate the formation of very low mass objects, i.e. brown dwarfs, by external compression. According to the Jeans stability criterion, a very low mass molecular cloud core must reach a very high density in order to become gravitationally unstable. One possibility to create such a high density is the compression by turbulent flows within the larger molecular cloud. Using our self-developed radiation hydrodynamics code, we aim to test the validity of this scenario, and to constrain the strength of the turbulence that is needed. We find that the probability for sufficiently strong and long-lived turbulence is very low under typical conditions even when using very optimistic assumptions, and therefore conclude that turbulent compression is unlikely to be the dominant mechanism for creating brown dwarfs. We also investigate the properties of objects formed by this turbulent compression process. Specifically, we compare the lifetime of the first core stage for the cases with and without external compression. We confirm our previous findings that the first core lifetime increases by about an order of magnitude at the extremely low-mass end, but this increase is somewhat less dramatic and occurs at even lower masses than in our previous work, in which no external compression was present.

DOI： 10.1093/mnras/stz1892

An Origin for the Angular Momentum of Molecular Cloud Cores: A Prediction from Filament Fragmentation Open Access

Misugi, Y; Inutsuka, S; Arzoumanian, D

ASTROPHYSICAL JOURNAL Vol. 881 ( 1 ) 2019.8

Language：Japanese Publisher：Astrophysical Journal

The angular momentum of a molecular cloud core plays a key role in star formation, as it is directly related to the outflow and the jet emanating from the newborn star, and it eventually results in the formation of the protoplanetary disk. However, the origin of the core rotation and its time evolution are not well understood. Recent observations reveal that molecular clouds exhibit a ubiquity of filamentary structures and that star-forming cores are associated with the densest filaments. As these results suggest that dense cores form primarily in filaments, the mechanism of core formation from filament fragmentation should explain the distribution of the angular momentum of these cores. In this paper we analyze the relation between velocity fluctuations along the filament close to equilibrium, and the angular momentum of the cores formed along its crest. We first find that an isotropic velocity fluctuation that follows the three-dimensional Kolmogorov spectrum does not reproduce the observed angular momentum of molecular cloud cores. We then identify the need for a large power at small scales and study the effect of three power spectrum models. We show that the one-dimensional Kolmogorov power spectrum with a slope of -5/3 and an anisotropic model with reasonable parameters are compatible with the observations. Our results stress the importance of more detailed and systematic observations of both the velocity structure along filaments, and the angular momentum distribution of molecular cloud cores, to determine the validity of the mechanism of core formation from filamentary molecular clouds.

DOI： 10.3847/1538-4357/ab2382

Discovery of Shocked Molecular Clouds Associated with the Shell-type Supernova Remnant RX J0046.5-7308 in the Small Magellanic Cloud Open Access

Sano, H; Matsumura, H; Yamane, Y; Maggi, P; Fujii, K; Tsuge, K; Tokuda, K; Alsaberi, RZE; Filipovic, MD; Maxted, N; Rowell, G; Uchida, H; Tanaka, T; Muraoka, K; Takekoshi, T; Onishi, T; Kawamura, A; Minamidani, T; Mizuno, N; Yamamoto, H; Tachihara, K; Inoue, T; Inutsuka, S; Voisin, F; Tothill, NFH; Sasaki, M; McClure-Griffiths, NM; Fukui, Y

ASTROPHYSICAL JOURNAL Vol. 881 ( 1 ) 2019.8

Language：Japanese Publisher：Astrophysical Journal

RX J0046.5-7308 is a shell-type supernova remnant (SNR) in the Small Magellanic Cloud (SMC). We carried out new <sup>12</sup>CO(J = 1-0, 3-2) observations toward the SNR using Mopra and the Atacama Submillimeter Telescope Experiment. We found eight molecular clouds (A-H) along the X-ray shell of the SNR. The typical cloud size and mass are ∼10-15 pc and ∼1000-3000 M , respectively. The X-ray shell is slightly deformed and has the brightest peak in the southwestern shell where two molecular clouds A and B are located. The four molecular clouds A, B, F, and G have high intensity ratios of <sup>12</sup>CO(J = 3-2)/<sup>12</sup>CO(J = 1-0) > 1.2, which are not attributable to any identified internal infrared sources or high-mass stars. The H i cavity and its expanding motion are found toward the SNR, which are likely created by strong stellar winds from a massive progenitor. We suggest that the molecular clouds A-D, F, and G and H i clouds within the wind-blown cavity at V <inf>LSR</inf> = 117.1-122.5 km s<sup>-1</sup> are associated with the SNR. The X-ray spectroscopy reveals the dynamical age of yr and the progenitor mass of ≳30 M , which is also consistent with the proposed scenario. We determine physical conditions of the giant molecular cloud LIRS 36A using the large velocity gradient analysis with archival data sets of the Atacama Large Millimeter/submillimeter Array; the kinematic temperature is K and the number density of molecular hydrogen is cm<sup>-3</sup>. The next generation of γ-ray observations will allow us to study the pion-decay γ-rays from the molecular clouds in the SMC SNR.

DOI： 10.3847/1538-4357/ab2ade

Revised Description of Dust Diffusion and a New Instability Creating Multiple Rings in Protoplanetary Disks Open Access

Tominaga, RT; Takahashi, SZ; Inutsuka, S

ASTROPHYSICAL JOURNAL Vol. 881 ( 1 ) 2019.8

Language：Japanese Publisher：Astrophysical Journal

Various instabilities have been proposed as a promising mechanism for accumulating dust. Moreover, some of them are expected to lead to multiple-ring structure formation and planetesimal formation in protoplanetary disks. In a turbulent gaseous disk, the growth of the instabilities and the dust accumulation are quenched by the turbulent diffusion of dust grains. The diffusion process has often been modeled by a diffusion term in the continuity equation for the dust density. The dust diffusion model, however, does not guarantee conservation of angular momentum in a disk. In this study, we first formulate equations that describe dust diffusion and also conserve the total angular momentum of a disk. Second, we perform a linear perturbation analysis on the secular gravitational instability (GI) using the equations. The results show that the secular GI is a monotonically growing mode, contrary to the result of previous analyses that found it overstable. We find that the overstability is caused by the nonconservation of the angular momentum. Third, we find a new axisymmetric instability due to the combination of dust-gas friction and turbulent gas viscosity, which we refer to as two-component viscous gravitational instability (TVGI). The most unstable wavelength of TVGI is comparable to or smaller than the gas scale height. TVGI accumulates dust grains efficiently, which indicates that TVGI is a promising mechanism for the formation of multiple-ring-like structures and planetesimals. Finally, we examine the validity of the ring formation via the secular GI and TVGI in the HL Tau disk and find both instabilities can create multiple rings whose width is about 10 au at orbital radii larger than 50 au.

DOI： 10.3847/1538-4357/ab25ea

A centrally concentrated sub-solar-mass starless core in the Taurus L1495 filamentary complex Open Access

Tokuda, K; Tachihara, K; Saigo, K; André, P; Miyamoto, Y; Zahorecz, S; Inutsuka, S; Matsumoto, T; Takashima, T; Machida, MN; Tomida, K; Taniguchi, K; Fukui, Y; Kawamura, A; Tatematsu, K; Kandori, R; Onishi, T

PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN Vol. 71 ( 4 ) 2019.8

Language：Japanese Publisher：Publications of the Astronomical Society of Japan

The formation scenario of brown dwarfs is still unclear because observational studies to investigate its initial condition are quite limited. Our systematic survey of nearby low-mass star-forming regions using the Atacama Compact Array (aka the Morita array) and the IRAM 30-m telescope in 1.2 mm continuum has identified a centrally concentrated starless condensation with a central H<inf>2</inf> volume density of ∼10<sup>6</sup> cm<sup>-3</sup>, MC5-N, connected to a narrow (width ∼0.03 pc) filamentary cloud in the Taurus L1495 region. The mass of the core is ∼ 0.2-0.4, Mo , which is an order of magnitude smaller than typical low-mass pre-stellar cores. Taking into account a typical core to star formation efficiency for pre-stellar cores (∼20%-40%) in nearby molecular clouds, brown dwarf(s) or very low-mass star(s) may be going to be formed in this core. We have found possible substructures at the high-density portion of the core, although much higher angular resolution observation is needed to clearly confirm them. The subsequent N<inf>2</inf>H<sup>+</sup> and N<inf>2</inf>D<sup>+</sup> observations using the Nobeyama 45-m telescope have confirmed the high-deuterium fractionation (∼30%). These dynamically and chemically evolved features indicate that this core is on the verge of proto-brown dwarf or very low-mass star formation and is an ideal source to investigate the initial conditions of such low-mass objects via gravitational collapse and/or fragmentation of the filamentary cloud complex.

DOI： 10.1093/pasj/psz051

Collisional elongation: Possible origin of extremely elongated shape of 1I/'Oumuamua Open Access

Sugiura, K; Kobayashi, H; Inutsuka, S

ICARUS Vol. 328 page： 14 - 22 2019.8

Language：Japanese Publisher：Icarus

Light curve observations of a recently discovered interstellar object 1I/‘Oumuamua suggest that this object has an extremely elongated shape with the axis ratio 0.3 or smaller. Planetesimal collisions can produce irregular shapes including elongated shapes. In this paper, we suggest that the extremely elongated shape of 1I/‘Oumuamua may be the result of such an impact. To find detailed impact conditions to form the extremely elongated objects, we conduct numerical simulations of planetesimal collisions using Smoothed Particle Hydrodynamics method for elastic dynamics with self-gravity and interparticle friction. Impacts into strengthless target planetesimals with radius 50 m are conducted with various ratios of impactor mass to target mass q, friction angles ϕ <inf>d</inf> , impact velocities v <inf>imp</inf> , and impact angles θ <inf>imp</inf> . We find that impacts with q ≥ 0.5, ϕ <inf>d</inf> ≥ 40 <sup>°</sup> , v <inf>imp</inf> ≤ 40 cm/s, and θ <inf>imp</inf> ≤ 30 <sup>°</sup> produce remnants with the ratio of intermediate to major axis length <0.3. This impact condition suggests that the parent protoplanetary disk in the planetesimal collision stage was weakly turbulent (α < 10 <sup>−4</sup> for the inner disk) and composed of planetesimals smaller than ∼7 km to ensure small impact velocity.

DOI： 10.1016/j.icarus.2019.03.014

The Generalized Nonlinear Ohm's Law: How a Strong Electric Field Influences Nonideal MHD Effects in Dusty Protoplanetary Disks Open Access

Okuzumi, S; Mori, S; Inutsuka, S

ASTROPHYSICAL JOURNAL Vol. 878 ( 2 ) 2019.6

Language：Japanese Publisher：Astrophysical Journal

The magnetohydrodynamics (MHD) of protoplanetary disks are strongly subject to the nonideal MHD effects arising from the low ionization fraction of the disk gas. A strong electric field induced by gas motions can heat ionized gas particles and can thereby affect the ionization balance in the disks. Our previous studies revealed that in dusty protoplanetary disks, the ohmic conductivity decreases with increasing electric field strength until the electrical breakdown of the disk gas occurs. In this study, we extend our previous work to more general cases where both electric and magnetic fields affect the motion of plasma particles, allowing us to study the impacts of plasma heating on all nonideal MHD effects: ohmic, Hall, and ambipolar diffusion. We find that the upper limit on the electric current we previously derived applies even in the presence of magnetic fields. Although the Hall and ambipolar resistivities can either increase or decrease with electric field strength depending on the abundance of charged dust grains, the ohmic resistivity always increases with electric field strength. An order-of-magnitude estimate suggests that a large-scale electric current generated by gas motions in the inner part of protoplanetary disks could exceed the upper limit. This implies that MHD motions of the inner disk, such as the motion driven by the Hall-shear instability, could either get suppressed or trigger electrical breakdown (lightning discharge). This may have important implications for gas accretion and chondrule formation in the inner part of protoplanetary disks.

DOI： 10.3847/1538-4357/ab2046

The JCMT BISTRO Survey: The Magnetic Field of the Barnard 1 Star-forming Region Open Access

Coudé, S; Bastien, P; Houde, M; Sadavoy, S; Friesen, R; Di Francesco, J; Johnstone, D; Mairs, S; Hasegawa, T; Kwon, W; Lai, SP; Qiu, KP; Ward-Thompson, D; Berry, D; Chen, MCY; Fiege, J; Franzmann, E; Hatchell, J; Lacaille, K; Matthews, BC; Moriarty-Schieven, GH; Pon, A; André, P; Arzoumanian, D; Aso, Y; Byun, DY; Eswaraiah, C; Chen, HR; Chen, WP; Ching, TC; Cho, J; Choi, M; Chrysostomou, A; Chung, EJ; Doi, Y; Drabek-Maunder, E; Dowell, CD; Eyres, SPS; Falle, S; Friberg, P; Fuller, G; Furuya, RS; Gledhill, T; Graves, SF; Greaves, JS; Griffin, MJ; Gu, QL; Hayashi, SS; Hoang, T; Holland, W; Inoue, T; Inutsuka, S; Iwasaki, K; Jeong, IG; Kanamori, Y; Kataoka, A; Kang, JH; Kang, MJ; Kang, SJ; Kawabata, KS; Kemper, F; Kim, G; Kim, J; Kim, KT; Kim, KH; Kim, MR; Kim, S; Kirk, JM; Kobayashi, MIN; Koch, PM; Kwon, J; Lee, JE; Lee, CW; Lee, SS; Li, DL; Li, D; Li, HB; Liu, HL; Liu, JH; Liu, SY; Liu, T; van Loo, S; Lyo, AR; Matsumura, M; Nagata, T; Nakamura, F; Nakanishi, H; Ohashi, N; Onaka, T; Parsons, H; Pattle, K; Peretto, N; Pyo, TS; Qian, L; Rao, R; Rawlings, MG; Retter, B; Richer, J; Rigby, A; Robitaille, JF; Saito, H; Savini, G; Scaife, AMM; Seta, M; Shinnaga, H; Soam, A; Tamura, M; Tang, YW; Tomisaka, K; Tsukamoto, Y; Wang, HC; Wang, JW; Whitworth, AP; Yen, HW; Yoo, H; Yuan, JH; Zenko, T; Zhang, CP; Zhang, GY; Zhou, JJ; Zhu, L

ASTROPHYSICAL JOURNAL Vol. 877 ( 2 ) 2019.6

Language：Japanese Publisher：Astrophysical Journal

We present the POL-2 850 μm linear polarization map of the Barnard 1 clump in the Perseus molecular cloud complex from the B-fields In STar-forming Region Observations survey at the James Clerk Maxwell Telescope. We find a trend of decreasing polarization fraction as a function of total intensity, which we link to depolarization effects toward higher-density regions of the cloud. We then use the polarization data at 850 μm to infer the plane-of-sky orientation of the large-scale magnetic field in Barnard 1. This magnetic field runs north-south across most of the cloud, with the exception of B1-c, where it turns more east-west. From the dispersion of polarization angles, we calculate a turbulence correlation length of 5.0 ±2.″5 (1500 au) and a turbulent-to-total magnetic energy ratio of 0.5 ±0.3 inside the cloud. We combine this turbulent-to-total magnetic energy ratio with observations of NH<inf>3</inf> molecular lines from the Green Bank Ammonia Survey to estimate the strength of the plane-of-sky component of the magnetic field through the Davis-Chandrasekhar-Fermi method. With a plane-of-sky amplitude of 120 ±60 μG and a criticality criterion λ <inf>c</inf> = 3.0 ±1.5, we find that Barnard 1 is a supercritical molecular cloud with a magnetic field nearly dominated by its turbulent component.

DOI： 10.3847/1538-4357/ab1b23

The JCMT BISTRO Survey: The Magnetic Field in the Starless Core ρ Ophiuchus C Open Access

Liu, JH; Qiu, KP; Berry, D; Di Francesco, J; Bastien, P; Koch, PM; Furuya, RS; Kim, KT; Coudé, S; Lee, CW; Soam, A; Eswaraiah, C; Li, D; Hwang, J; Lyo, AR; Pattle, K; Hasegawa, T; Kwon, W; Lai, SP; Ward-Thompson, D; Ching, TC; Chen, ZW; Gu, QL; Li, DL; Li, HB; Liu, HL; Qian, L; Wang, HC; Yuan, JH; Zhang, CP; Zhang, GY; Zhang, YP; Zhou, JJ; Zhu, L; André, P; Arzoumanian, D; Aso, Y; Byun, DY; Chen, MCY; Chen, HRV; Chen, WP; Cho, J; Choi, M; Chrysostomou, A; Chung, EJ; Doi, Y; Drabek-Maunder, E; Dowell, CD; Eyres, SPS; Falle, S; Fanciullo, L; Fiege, J; Franzmann, E; Friberg, P; Friesen, RK; Fuller, G; Gledhill, T; Graves, SF; Greaves, JS; Griffin, MJ; Han, I; Hatchell, J; Hayashi, SS; Hoang, T; Holland, W; Houde, M; Inoue, T; Inutsuka, S; Iwasaki, K; Jeong, IG; Johnstone, D; Kanamori, Y; Kang, JH; Kang, MJ; Kang, SJ; Kataoka, A; Kawabata, KS; Kemper, F; Kim, G; Kim, J; Kim, KH; Kim, MR; Kim, S; Kirk, JM; Kobayashi, MIN; Kusune, T; Kwon, J; Lacaille, KM; Lee, CF; Lee, JE; Lee, H; Lee, SS; Liu, SY; Liu, T; van Loo, S; Mairs, S; Matsumura, M; Matthews, BC; Moriarty-Schieven, GH; Nagata, T; Nakamura, F; Nakanishi, H; Ohashi, N; Onaka, T; Parker, J; Parsons, H; Pascale, E; Peretto, N; Pon, A; Pyo, TS; Rao, R; Rawlings, MG; Retter, B; Richer, J; Rigby, A; Robitaille, JF; Sadavoy, S; Saito, H; Savini, G; Scaife, AMM; Seta, M; Shinnaga, H; Tamura, M; Tang, YW; Tomisaka, K; Tsukamoto, Y; Wang, JW; Whitworth, AP; Yen, HW; Yoo, H; Zenko, T

ASTROPHYSICAL JOURNAL Vol. 877 ( 1 ) 2019.5

Language：Japanese Publisher：Astrophysical Journal

We report 850 μm dust polarization observations of a low-mass (∼12 M <inf>o</inf>) starless core in the ρ Ophiuchus cloud, Ophiuchus C, made with the POL-2 instrument on the James Clerk Maxwell Telescope (JCMT) as part of the JCMT B-fields In STar-forming Region Observations survey. We detect an ordered magnetic field projected on the plane of the sky in the starless core. The magnetic field across the ∼0.1 pc core shows a predominant northeast-southwest orientation centering between ∼40° and ∼100°, indicating that the field in the core is well aligned with the magnetic field in lower-density regions of the cloud probed by near-infrared observations and also the cloud-scale magnetic field traced by Planck observations. The polarization percentage (P) decreases with increasing total intensity (I), with a power-law index of -1.03 ± 0.05. We estimate the plane-of-sky field strength (B <inf>pos</inf>) using modified Davis-Chandrasekhar-Fermi methods based on structure function (SF), autocorrelation function (ACF), and unsharp masking (UM) analyses. We find that the estimates from the SF, ACF, and UM methods yield strengths of 103 ± 46 μG, 136 ± 69 μG, and 213 ± 115 μG, respectively. Our calculations suggest that the Ophiuchus C core is near magnetically critical or slightly magnetically supercritical (i.e., unstable to collapse). The total magnetic energy calculated from the SF method is comparable to the turbulent energy in Ophiuchus C, while the ACF method and the UM method only set upper limits for the total magnetic energy because of large uncertainties.

DOI： 10.3847/1538-4357/ab0958

JCMT BISTRO Survey: Magnetic Fields within the Hub-filament Structure in IC 5146 Open Access

Wang, JW; Lai, SP; Eswaraiah, C; Pattle, K; Di Francesco, J; Johnstone, D; Koch, PM; Liu, T; Tamura, M; Furuya, RS; Onaka, T; Ward-Thompson, D; Soam, A; Kim, KT; Lee, CW; Lee, CF; Mairs, S; Arzoumanian, D; Kim, G; Hoang, T; Hwang, J; Liu, SY; Berry, D; Bastien, P; Hasegawa, T; Kwon, W; Qiu, KP; Andre, P; Aso, Y; Byun, DY; Chen, HR; Chen, MC; Chen, WP; Ching, TC; Cho, J; Choi, M; Chrysostomou, A; Chung, EJ; Coude, S; Doi, YS; Dowell, CD; Drabek-Maunder, E; Duan, HY; Eyres, SPS; Falle, S; Fanciullo, L; Fiege, J; Franzmann, E; Friberg, P; Friesen, RK; Fuller, G; Gledhill, T; Graves, SF; Greaves, JS; Griffin, MJ; Gu, Q; Han, I; Hatchell, J; Hayashi, SS; Holland, W; Houde, M; Inoue, T; Inutsuka, S; Iwasaki, K; Jeong, IG; Kanamori, Y; Kang, J; Kang, MJ; Kang, S; Kataoka, A; Kawabata, KS; Kemper, F; Kim, J; Kim, KH; Kim, MR; Kim, S; Kirk, JM; Kobayashi, MIN; Konyves, V; Kwon, J; Lacaille, KM; Lee, H; Lee, JE; Lee, SS; Lee, YH; Li, DL; Li, D; Li, HB; Liu, HL; Liu, JH; Lyo, AR; Matsumura, M; Matthews, BC; Moriarty-Schieven, GH; Nagata, T; Nakamura, F; Nakanishi, H; Ohashi, N; Park, G; Parsons, H; Pascale, E; Peretto, N; Pon, A; Pyo, TS; Qian, L; Rao, R; Rawlings, MG; Retter, B; Richer, J; Rigby, A; Robitaille, JF; Sadavoy, S; Saito, H; Savini, G; Scaife, AMM; Seta, M; Shinnaga, H; Tang, YW; Tomisaka, K; Tsukamoto, Y; van Loo, S; Wang, HC; Whitworth, AP; Yen, HW; Yoo, H; Yuan, J; Yun, HS; Zenko, T; Zhang, CP; Zhang, GY; Zhang, YP; Zhou, JJ; Zhu, L

ASTROPHYSICAL JOURNAL Vol. 876 ( 1 ) 2019.5

Language：Japanese Publisher：Astrophysical Journal

We present the 850 μm polarization observations toward the IC 5146 filamentary cloud taken using the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) and its associated polarimeter (POL-2), mounted on the James Clerk Maxwell Telescope, as part of the B-fields In STar forming Regions Observations. This work is aimed at revealing the magnetic field morphology within a core-scale (≲1.0 pc) hub-filament structure (HFS) located at the end of a parsec-scale filament. To investigate whether the observed polarization traces the magnetic field in the HFS, we analyze the dependence between the observed polarization fraction and total intensity using a Bayesian approach with the polarization fraction described by the Rice likelihood function, which can correctly describe the probability density function of the observed polarization fraction for low signal-to-noise ratio data. We find a power-law dependence between the polarization fraction and total intensity with an index of 0.56 in A <inf>V</inf> ∼ 20-300 mag regions, suggesting that the dust grains in these dense regions can still be aligned with magnetic fields in the IC 5146 regions. Our polarization maps reveal a curved magnetic field, possibly dragged by the contraction along the parsec-scale filament. We further obtain a magnetic field strength of 0.5 ±; 0.2 mG toward the central hub using the Davis-Chandrasekhar-Fermi method, corresponding to a mass-to-flux criticality of ∼1.3 ±; 0.4 and an Alfvénic Mach number of <0.6. These results suggest that gravity and magnetic field are currently of comparable importance in the HFS and that turbulence is less important.

DOI： 10.3847/1538-4357/ab13a2

Possible Evidence for Cosmic-Ray Acceleration in the Type Ia SNR RCW 86: Spatial Correlation between TeV Gamma-Rays and Interstellar Atomic Protons Open Access

Sano, H; Rowell, G; Reynoso, EM; Jung-Richardt, I; Yamane, Y; Nagaya, T; Yoshiike, S; Hayashi, K; Torii, K; Maxted, N; Mitsuishi, I; Inoue, T; Inutsuka, S; Yamamoto, H; Tachihara, K; Fukui, Y

ASTROPHYSICAL JOURNAL Vol. 876 ( 1 ) 2019.5

Language：Japanese Publisher：Astrophysical Journal

We present a detailed morphological study of TeV gamma-rays, synchrotron radiation, and interstellar gas in the young Type Ia supernova remnant (SNR) RCW 86. We find that the interstellar atomic gas shows good spatial correlation with the gamma-rays, indicating that the TeV gamma-rays from RCW 86 are likely predominantly of hadronic origin. In contrast, the spatial correlation between the interstellar molecular cloud and the TeV gamma-rays is poor in the southeastern shell of the SNR. We argue that this poor correlation can be attributed to the low-energy cosmic rays (∼1 TeV) not penetrating into the dense molecular cloud due to an enhancement of the turbulent magnetic field around the dense cloud of ∼10-100 μG. We also find that the southwestern shell, which is bright in both synchrotron X-ray and radio continuum radiation, shows a significant gamma-ray excess compared with the interstellar proton column density, suggesting that leptonic gamma-rays via inverse Compton scattering possibly contribute alongside the hadronic gamma-rays. The total cosmic-ray energies of the young TeV gamma-ray SNRs - RX J1713.7-3946, Vela Jr, HESS J1731-347, and RCW 86 - are roughly similar, which indicates that cosmic rays can be accelerated in both the core-collapse and Type Ia supernovae. The total energy of cosmic rays derived using the gas density, ∼10<sup>48</sup>-10<sup>49</sup> erg, gives a safe lower limit due mainly to the low filling factor of interstellar gas within the shell.

DOI： 10.3847/1538-4357/ab108f

The Role of Magnetic Field in Molecular Cloud Formation and Evolution Open Access

Hennebelle, P; Inutsuka, S

FRONTIERS IN ASTRONOMY AND SPACE SCIENCES Vol. 6 2019.3

Publisher：Frontiers in Astronomy and Space Sciences

We review the role that magnetic field may have on the formation and evolution of molecular clouds. After a brief presentation and main assumptions leading to ideal MHD equations, their most important correction, namely the ion-neutral drift is described. The nature of the multi-phase interstellar medium (ISM) and the thermal processes that allows this gas to become denser are presented. Then we discuss our current knowledge of compressible magnetized turbulence, thought to play a fundamental role in the ISM. We also describe what is known regarding the correlation between the magnetic and the density fields. Then the influence that magnetic field may have on the interstellar filaments and the molecular clouds is discussed, notably the role it may have on the pre-stellar dense cores as well as regarding the formation of stellar clusters. Finally we briefly review its possible effects on the formation of molecular clouds themselves. We argue that given the magnetic intensities that have been measured, it is likely that magnetic field is (i) responsible of reducing the star formation rate in dense molecular cloud gas by a factor of a few, (ii) strongly shaping the interstellar gas by generating a lot of filaments and reducing the numbers of clumps, cores and stars, although its exact influence remains to be better understood. Moreover at small scales, magnetic braking is likely a dominant process that strongly modifies the outcome of the star formation process. Finally, we stress that by inducing the formation of more massive stars, magnetic field could possibly enhance the impact of stellar feedback.

DOI： 10.3389/fspas.2019.00005

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