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

DOI： 10.3847/1538-4357/835/2/142

Web of Science

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

DOI： 10.3847/1538-4357/835/1/108

Web of Science

Publishing type：Research paper (international conference proceedings)  

DOI： 10.1017/S1743921316000016

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/0004-637X/754/2/95

Web of Science

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/ae394a

Web of Science

Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

Abstract

We report the discovery of two CO clouds that are likely falling down to the Galactic plane at more than 35 km s$^{-1}$. The clouds show head–tail distributions elongated perpendicular to the Galactic plane at $l={331{^{\circ}_{. } }6}$ and $b={0^{\circ}_{. } }$ as revealed by an analysis of the Mopra CO $J=$1–0 survey data. We derived the distance of the clouds to be $2.46 \pm 0.18$ kpc based on the Gaia Data Release 3. The CO clouds have molecular masses of $4.8\times 10^3$ and $3.5\times 10^3\ M_{\odot }$, respectively, and show kinetic temperatures of 30–50 K as derived from the line intensities of the $^{13}$CO $J$ = 2–1, $^{12}$CO $J$ = 1–0, and $^{13}$CO $J$ = 1–0 emission. The temperature in the heads of the clouds is significantly higher than 10 K for typical molecular clouds, although no radiative heat source is found inside or close to the clouds. Based on the results, we interpret that the present clouds are falling on to the Milky Way disk and are significantly heated up by the strong shock interaction with the disk H i gas. We suggest that the clouds represent part of the H i intermediate-velocity clouds falling to the Galactic plane that were converted into molecular clouds by shock compression. This is the first unambiguous case of falling CO clouds having directly observed signatures of falling motion including clear directivity and shock heating. Possible implications of the CO clouds in the evolution of the Galactic interstellar medium are discussed.

DOI： 10.1093/pasj/psaf125

Web of Science

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/ae0460

Web of Science

Publishing type：Research paper (scientific journal)  

DOI： 10.1093/pasj/psaf081

Web of Science

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/2041-8213/adce0b

Web of Science

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4365/adb8de

Web of Science

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-3881/adae87

Web of Science

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/ad8c42

Web of Science

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/ad7098

Web of Science

Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

Abstract

We investigated the giant molecular clouds (GMCs) in M 74 (NGC 628), using data obtained from the PHANGS (Physics at High Angular resolution in Nearby GalaxieS) project. We applied GMC types according to the activity of star formation: Type I without star formation, Type II with H$\alpha$ luminosity ($L_{\mathrm{H\alpha } }$) less than $10^{37.5}\ \rm{erg\ s ^{-1 } }$, and Type III with $L_{\mathrm{H\alpha } }$ greater than $10^{37.5}\ \rm{erg\ s^{-1 } }$. A total of 432 GMCs were identified, with 59, 201, and 172 GMCs, for Types I, II, and III, respectively. The size and mass of the GMCs range from 23 to 238 pc and $10^{4.9}$ to $10^{7.1}\, M_{\odot }$, indicating that the mass and radius increase from Types I to III. Clusters younger than 4 Myr and H ii regions are concentrated within 150 pc of a GMC, indicating a tight association between these young objects and GMCs. The virial ratio decreases from Type I to Type III, indicating that Type III GMCs are the most gravitationally relaxed among the three. We interpret that the GMCs evolve from Type I to Type III, as previously observed in the Large Magellanic Cloud. Based on a steady-state assumption, the estimated evolutionary timescales of Types I, II, and III are 1, 5, and 4 Myr, respectively. We assume that the timescale of Type III is equal to the age of the associated clusters, indicating a GMC lifetime of 10 Myr or longer. Although Chevance et al. (2020, MNRAS, 493, 2872) investigated GMCs using the same PHANGS dataset of M 74, they did not define a GMC, reaching an evolutionary picture with a 20 Myr duration of the non-star-forming phase, which is five times longer than 4 Myr. We compare the present results with those of Chevance et al. (2020, MNRAS, 493, 2872) and argue that defining individual GMCs is essential for understanding GMC evolution.

DOI： 10.1093/pasj/psae071

Web of Science

Publishing type：Research paper (scientific journal)  

The evolution of giant molecular clouds (GMCs), the main sites of high-mass star formation, is an essential process to unravel the galaxy evolution. Using a GMC catalogue of M 33 from the ALMA-ACA (Atacama Large Millimeter/submillimeter Array-Atacama Compact Array) survey, we classified 848 GMCs into three types based on the association with H II regions and their H$\alpha$ luminosities $L\, (\rm{H}\alpha )$: Type I is associated with no H II regions; Type II with H II regions of $L\, (\rm{H}\alpha )$ $\lt 10^{37.5}$ erg s$^{-1}$; and Type III with H II regions of $L\, (\rm{H}\alpha )$ $\geqq$ $10^{37.5}$ erg s$^{-1}$. These criteria yield 224 Type I GMCs, 473 Type II GMCs, and 151 Type III GMCs. GMCs show changes in their physical properties according to the types; mass, radius, velocity dispersion, and $^{13}$CO detection rate of GMCs systematically increase from Type I to Type III, and additionally, Type III GMCs are closest to virial equilibrium. Type III GMCs show the highest spatial correlation with clusters younger than $10\:$Myr, Type II GMCs moderate correlation, and Type I GMCs are almost uncorrelated. We interpret that these types indicate an evolutionary sequence from Type I to Type II, and then to Type III with timescales of 4 Myr, 13 Myr, and 5 Myr, respectively, indicating a GMC lifetime of 22 Myr by assuming that a Type II GMC has the same timescale as the Large Magellanic Cloud. The evolved GMCs are concentrated on the spiral arms, while the younger GMCs are apart from the arm, both to the leading and trailing sides. This indicates that GMCs collide with each other via the spiral potential, leading to the compression of GMCs and the triggering of high-mass star formation, which may support the dynamic spiral model. Overall, we suggest that the GMC evolution concept helps illuminate the galaxy evolution, including the spiral arm formation....

DOI： 10.1093/pasj/psae073

Web of Science

arXiv

Publishing type：Research paper (scientific journal)  

DOI： 10.1093/pasj/psae056

Web of Science

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/ad40a6

Web of Science

Scopus

Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

Abstract

The galactic tidal interaction is a possible mechanism to trigger active star formation in galaxies. Recent analyses using H i data in the Large Magellanic Cloud (LMC) proposed that the tidally driven H i flow, the L-component, is colliding with the LMC disk, the D-component, and is triggering high-mass star formation toward the active star-forming regions R136 and N44. In order to explore the role of the collision over the entire LMC disk, we investigated the I-component, the collision-compressed gas between the L- and D-components, over the LMC disk, and found that $74\%$ of the O/WR stars are located toward the I-component, suggesting their formation in the colliding gas. We compared four star-forming regions (R136, N44, N11, and the N77–N79–N83 complex). We found a positive correlation between the number of high-mass stars and the compressed gas pressure generated by collisions, suggesting that pressure may be a key parameter in star formation.

DOI： 10.1093/pasj/psae035

Web of Science

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/ad2f9a

Web of Science

Scopus

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/ad0da3

Web of Science

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/ad12b5

Web of Science

Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

Abstract

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 ¹²CO 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 × 10⁻³M_⊙ for Source A and 3.3 × 10⁻⁴M_⊙ for Source B. C¹⁸O 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.

DOI： 10.3847/1538-4357/ad0132

Open Access

Web of Science

Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/ad0132/pdf

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/acffbe

Open Access

Web of Science

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/2041-8213/acfca9

Open Access

Web of Science

Publishing type：Research paper (scientific journal)  

We present the results of ALMA-ACA 7 m array observations in <SUP>12</SUP>CO(J = 2-1), <SUP>13</SUP>CO(J = 2-1), and C<SUP>18</SUP>O(J = 2-1) line emission toward the molecular-gas disk in the Local Group spiral galaxy M33 at an angular resolution of 7.″31 × 6.″50 (30 × 26 pc). We combined the ACA 7 m array <SUP>12</SUP>CO(J = 2-1) data with the IRAM 30 m data to compensate for emission from diffuse molecular-gas components. The ACA+IRAM combined <SUP>12</SUP>CO(J = 2-1) map clearly depicts the cloud-scale molecular-gas structure over the M33 disk. Based on the ACA+IRAM <SUP>12</SUP>CO(J = 2-1) cube data, we cataloged 848 molecular clouds with a mass range from 10<SUP>3</SUP>-10<SUP>6</SUP> M <SUB>⊙</SUB>. We found that high-mass clouds (≥10<SUP>5</SUP> M <SUB>⊙</SUB>) tend to associate with the 8 μm bright sources in the spiral arm region, while low-mass clouds (&lt;10<SUP>5</SUP> M <SUB>⊙</SUB>) tend to be apart from such 8 μm bright sources and to exist in the inter-arm region. We compared the cataloged clouds with GMCs observed by the IRAM 30 m telescope at 49 pc resolution (IRAM GMC), and found that a small IRAM GMC is likely to be identified as a single molecular cloud even in ACA+IRAM CO data, while a large IRAM GMC can be resolved into multiple ACA+IRAM clouds. The velocity dispersion of a large IRAM GMC is mainly dominated by the line-of-sight velocity difference between small clouds inside the GMC rather than the internal cloud velocity broadening....

DOI： 10.3847/1538-4357/ace4bd

Open Access

Web of Science

arXiv

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/ace10e

Open Access

Web of Science

Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

Abstract

The nature of molecular clouds and their statistical behavior in subsolar metallicity environments are not fully explored yet. We analyzed data from an unbiased CO (J = 2–1) survey at the spatial resolution of ∼2 pc in the northern region of the Small Magellanic Cloud with the Atacama Compact Array to characterize the CO cloud properties. A cloud-decomposition analysis identified 426 spatially/velocity-independent CO clouds and their substructures. Based on the cross-matching with known infrared catalogs by Spitzer and Herschel, more than 90% CO clouds show spatial correlations with point sources. We investigated the basic properties of the CO clouds and found that the radius–velocity linewidth (R–σ_v) relation follows the Milky Way-like power-law exponent, but the intercept is ∼1.5 times lower than that in the Milky Way. The mass functions (dN/dM) of the CO luminosity and virial mass are characterized by an exponent of ∼1.7, which is consistent with previously reported values in the Large Magellanic Cloud and in the Milky Way.

DOI： 10.3847/1538-4357/accadb

Open Access

Web of Science

Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/accadb/pdf

Publishing type：Research paper (scientific journal)  

DOI： 10.1093/pasj/psad001

Web of Science

Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

Abstract

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 ¹²CO(J = 2–1) images have an angular resolution of ∼1″ (∼250 au) and show high-velocity blueshifted (≳70 km s⁻¹) and redshifted (≳50 km s⁻¹) 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 ¹³CO 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.

DOI： 10.3847/1538-4357/acb930

Open Access

Web of Science

Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/acb930/pdf

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/ac90c6

Open Access

Web of Science

Scopus

Publishing type：Research paper (scientific journal)  

DOI： 10.1093/mnras/stac1087

Open Access

Web of Science

Scopus

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/ac7872

Open Access

Web of Science

Scopus

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/ac6b3c

Open Access

Web of Science

Scopus

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/ac7465

Open Access

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

Abstract

We have performed new large-scale 12CO, 13CO, and C18O J = 1–0 observations toward the Vulpecula OB association (l ∼ 60°) as part of the Nobeyama 45 m Local Spur CO survey project. Molecular clouds are distributed over ∼100 pc, with local peaks at the Sh 2-86, Sh 2-87, and Sh 2-88 high-mass star-forming regions in the Vulpecula complex. The molecular gas is associated with the Local Spur, which corresponds to the nearest inter-arm region located between the Local Arm and the Sagittarius Arm. We discovered new giant molecular filaments (GMFs) in Sh 2-86, with a length of ∼30 pc, width of ∼5 pc, and molecular mass of $\sim\!\! 4 \times 10^4\, M_{\odot }$. We also found that Sh 2-86 contains the three velocity components at 22, 27, and 33 km s−1. These clouds and GMFs are likely to be physically associated with Sh 2-86 because they have high 12CO J = 2–1 to J = 1–0 intensity ratios and coincide with the infrared dust emission. The open cluster NGC 6823 exists at the common intersection of these clouds. We argue that the multiple cloud interaction scenario, including GMFs, can explain cluster formation in the Vulpecula OB association.

DOI： 10.1093/pasj/psab107

Web of Science

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

DOI： 10.3847/1538-4357/ac39a4

Open Access

Web of Science

Scopus

Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

DOI： 10.1117/12.2629126

Web of Science

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/1538-4357/ac1ff4

Web of Science

Scopus

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

DOI： 10.3847/1538-4357/ac0dba

Web of Science

Scopus

Language：Japanese  

DOI： 10.1093/pasj/psab071

Web of Science

Scopus

arXiv

Other Link： http://arxiv.org/pdf/2107.06671v2

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/1538-4357/ac0adb

Web of Science

Scopus

Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/ac0adb/pdf

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press ({OUP})  

<title>Abstract</title>
We performed fully sampled J = 1–0 line observations of 12CO and 13CO toward the reflection nebula NGC 2023 using the Nobeyama 45 m telescope. It covered the entire NGC 2023 region with angular and velocity resolutions of 19″ corresponding to 0.04 pc and 0.33 km s−1, respectively. We analyzed the data focusing on gas dynamics and revealed two velocity components, each with a mass of $\sim\! 3000 \mbox{$\, {M}_\odot $}$, at radial velocities of 10 and 12 km s−1. These components show spatially complementary distributions and are connected in velocity, both of which are the typical signatures of cloud–cloud collision (CCC). Although previous studies favored a scheme of triggering by the H ii region of IC 434, our results show that the effect of the H ii region is limited only to the surface of the molecular cloud, and does not contribute to the entire gas compression and the overall star formation. Comparing the present results with those for neighboring NGC 2024, we find that their active star formation can be explained by a single CCC event. We suggest that the 10 and 12 km s−1 clouds collided ∼0.4 Myr ago, which is common to the regions, but triggered the B1.5V-type star HD 37903 as well as ∼20 low-mass stars in NGC 2023, and ∼20 OB stars in NGC 2024. The column density in NGC 2023 is two to three times lower than that of NGC 2024, which may result in the different star formation activity suggested by the trend of ∼50 other CCC-triggered star-forming regions in the literature.

DOI： 10.1093/pasj/psab050

Web of Science

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/1538-4357/abff4a

Web of Science

Scopus

Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/abff4a/pdf

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/1538-4357/abeb65

Web of Science

Scopus

Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/abeb65/pdf

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

<title>Abstract</title>
The Antennae Galaxies, one of major mergers, are a starburst. Tsuge et al. (2020, PASJ, 73, S35) showed that the five giant molecular complexes in the Antennae Galaxies have signatures of cloud–cloud collisions based on the Atacama Large Millimeter Array (ALMA) archival data with 60 pc resolution. In the present work we analyzed the new CO data toward the super star cluster (SSC) B1 with 14 pc resolution obtained with ALMA, and confirm that two clouds show a complementary distribution with a displacement of ∼70 pc as well as connecting bridge features between them. The complementary distribution shows a good correspondence with the theoretical collision model (Takahira et al. 2014, ApJ, 792, 63), and the distribution indicates that the formation of SSC B1 with ∼106 M⊙ was consistent with the trigger of cloud–cloud collision on a time scale of ∼1 Myr, which is consistent with the cluster age. It is likely that SSC B1 was formed from molecular gas of ∼107 M⊙ with a star formation efficiency of $\sim\! 10\%$ in 1 Myr. We identify a few places where additional clusters are forming. Detailed gas motion indicates that the stellar feedback in the accelerating gas is not effective, while the ionization plays a role in evacuating the gas around the clusters at a ∼20 pc radius. The results have revealed the details of the parent gas where a cluster having a mass similar to a globular is being formed.

DOI： 10.1093/pasj/psab008

Web of Science

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

<title>ABSTRACT</title>
We report millimeter/submillimeter continuum and molecular line observations of the Galactic super star cluster RCW 38, obtained from the Atacama Large Millimeter/Submillimeter Array with a minimum angular resolution of ${0{^{\prime \prime }_{. } }17}\times {0{^{\prime \prime }_{. } }15}$ (≃ 289 au × 255 au). The C18O image reveals many massive condensations embedded within filamentary structures extending along the northwest–southeast direction in the center of cluster. The condensations have sizes of 0.01–0.02 pc, H2 column densities of 1023–1024 cm−2, and H2 masses of 10–130 M⊙. In addition, the 233 GHz continuum image reveals two dense, small millimeter-sources with radii of 460 and 200 au (Source A and Source B). Source A is embedded within the most massive C18O condensation, whereas no counterpart is seen for Source B. The masses of Source A and Source B are estimated as 13 and 3 M⊙ at the optically thin limit, respectively. The C18O emission shows a velocity gradient of 2 km s−1 at the central 2000 au of Source A, which could be interpreted as a Keplerian rotation with a central mass of a few M⊙ or infall motion of gas. Further, the ALMA 12CO data reveal that Source A and Source B are associated with molecular outflows exhibiting maximum velocities of ∼30–70 km s−1. The outflows have short dynamical timescales of &amp;lt;1000 yr and high-mass outflow rates of ∼10−4–10−3 M⊙ yr−1. These observational signatures suggest an early evolutionary phase of the massive star formation in Source A and Source B.

DOI： 10.1093/pasj/psaa115

Web of Science

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

DOI： 10.1093/pasj/psaa113

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press ({OUP})  

DOI： 10.1093/pasj/psy098

Web of Science

Scopus

arXiv

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

DOI： 10.1093/pasj/psy109

Web of Science

Scopus

arXiv

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press ({OUP})  

DOI： 10.1093/pasj/psaa054

Web of Science

Scopus

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

DOI： 10.1093/pasj/psaa083

Web of Science

Scopus

arXiv

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

DOI： 10.1093/pasj/psaa005

Web of Science

Scopus

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

DOI： 10.1093/pasj/psaa049

Web of Science

Scopus

arXiv

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press ({OUP})  

DOI： 10.1093/pasj/psaa078

Web of Science

Scopus

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

DOI： 10.1093/pasj/psz028

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

<title>Abstract</title>
We performed new large-scale 12CO, 13CO, and C18O J = 1–0 observations of the W 43 giant molecular cloud complex in the tangential direction of the Scutum arm (l ∼30°) as a part of the FUGIN project. The low-density gas traced by 12CO is distributed over 150 pc × 100 pc (l × b), and has a large velocity dispersion (20–30 km s−1). However, the dense gas traced by C18O is localized in the W 43 Main, G30.5, and W 43 South (G29.96−0.02) high-mass star-forming regions in the W 43 giant molecular cloud (GMC) complex, which have clumpy structures. We found at least two clouds with a velocity difference of ∼10–20 km s−1, both of which are likely to be physically associated with these high-mass star-forming regions based on the results of high 13CO J = 3–2 to J = 1–0 intensity ratio and morphological correspondence with the infrared dust emission. The velocity separation of these clouds in W 43 Main, G30.5, and W 43 South is too large for each cloud to be gravitationally bound. We also revealed that the dense gas in the W 43 GMC has a high local column density, while “the current SFE” (star formation efficiency) of the entire GMC is low ($\sim\!\! 4\%$) compared with the W 51 and M 17 GMC. We argue that the supersonic cloud–cloud collision hypothesis can explain the origin of the local mini-starbursts and dense gas formation in the W 43 GMC complex.

DOI： 10.1093/pasj/psaa015

Web of Science

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

DOI： 10.1093/pasj/psy120

Web of Science

Scopus

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

DOI： 10.1093/pasj/psaa045

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

DOI： 10.1093/pasj/psaa045

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

DOI： 10.1093/pasj/psaa103

Web of Science

Scopus

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

DOI： 10.1093/pasj/psaa033

Web of Science

Scopus

arXiv

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/2041-8213/abc884

Web of Science

Scopus

Other Link： https://iopscience.iop.org/article/10.3847/2041-8213/abc884

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

DOI： 10.1051/0004-6361/202038281

Open Access

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/1538-4357/abb822

Web of Science

Scopus

Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/abb822

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/1538-4357/abb469

Web of Science

Scopus

Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/abb469

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/2041-8213/ab9ca8

Web of Science

Scopus

Other Link： https://iopscience.iop.org/article/10.3847/2041-8213/ab9ca8

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

DOI： 10.3847/1538-4357/ab9ca7

Web of Science

Scopus

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

DOI： 10.3847/1538-4357/ab8ad3

Web of Science

Scopus

arXiv

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

DOI： 10.1093/pasj/psaa027

Web of Science

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

DOI： 10.1117/12.2562247

Web of Science

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press ({OUP})  

DOI： 10.1093/pasj/psy094

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

DOI： 10.1093/pasj/psz033

Web of Science

Scopus

arXiv

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

DOI： 10.3847/1538-4357/ab4900

Web of Science

Scopus

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

DOI： 10.3847/1538-4357/ab48ff

Web of Science

Scopus

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

DOI： 10.3847/1538-4357/ab2ade

Web of Science

Scopus

arXiv

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

DOI： 10.1093/pasj/psz051

Web of Science

Scopus

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

DOI： 10.3847/1538-4357/ab2051

Open Access

Web of Science

Scopus

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

Most recent numerical simulations suggest that bipolar HII regions, powered<br />
by O-type stars, can be formed at the interface of two colliding clouds. To<br />
observationally understand the birth of O-type stars, we present a detailed<br />
multi-wavelength analysis of an area of 1 deg x 1 deg hosting G8.14+0.23 HII<br />
region associated with an infrared bipolar nebula (BPN). Based on the radio<br />
continuum map, the HII region is excited by at least an O-type star, which is<br />
located toward the waist of the BPN. The NANTEN2 13CO line data reveal the<br />
existence of two extended clouds at [9, 14.3] and [15.3, 23.3] km/s toward the<br />
site G8.14+0.23, which are connected in the position-velocity space through a<br />
broad-bridge feature at the intermediate velocity range. A<br />
&quot;cavity/intensity-depression&quot; feature is evident in the blueshifted cloud, and<br />
is spatially matched by the &quot;elongated redshifted cloud&quot;. The spatial and<br />
velocity connections of the clouds suggest their interaction in the site<br />
G8.14+0.23. The analysis of deep near-infrared photometric data reveals the<br />
presence of clusters of infrared-excess sources, illustrating ongoing star<br />
formation activities in both the clouds. The O-type star is part of the<br />
embedded cluster seen in the waist of the BPN, which is observed toward the<br />
spatial matching zone of the cavity and the redshifted cloud. The observational<br />
results appear to be in reasonable agreement with the numerical simulations of<br />
cloud-cloud collision (CCC), suggesting that the CCC process seems to be<br />
responsible for the birth of the O-type star in G8.14+0.23.

DOI： 10.3847/1538-4357/ab1cba

Web of Science

arXiv

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/1538-4357/ab108f

Open Access

Web of Science

Scopus

arXiv

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

DOI： 10.1093/pasj/psz011

Web of Science

Scopus

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

We carried out new $^{12}$CO($J$ = 1-0, 3-2) observations of a N63A supernova<br />
remnant (SNR) from the LMC using ALMA and ASTE. We find three giant molecular<br />
clouds toward the northeast, east, and near the center of the SNR. Using the<br />
ALMA data, we spatially resolved clumpy molecular clouds embedded within the<br />
optical nebulae in both the shock-ionized and photoionized lobes discovered by<br />
previous H$\alpha$ and [S II] observations. The total mass of the molecular<br />
clouds is $\sim$$800$ $M_{\odot}$ for the shock-ionized region and $\sim$$1700$<br />
$M_{\odot}$ for the photoionized region. Spatially resolved X-ray spectroscopy<br />
reveals that the absorbing column densities toward the molecular clouds are<br />
$\sim$$1.5$-$6.0\times10^{21}$ cm$^{-2}$, which are $\sim$$1.5$-$15$ times less<br />
than the averaged interstellar proton column densities for each region. This<br />
means that the X-rays are produced not only behind the molecular clouds, but<br />
also in front of them. We conclude that the dense molecular clouds have been<br />
completely engulfed by the shock waves, but have still survived erosion owing<br />
to their high-density and short interacting time. The X-ray spectrum toward the<br />
gas clumps is well explained by an absorbed power-law or high-temperature<br />
plasma models in addition to the thermal plasma components, implying that the<br />
shock-cloud interaction is efficiently working for both the cases through the<br />
shock ionization and magnetic field amplification. If the hadronic gamma-ray is<br />
dominant in the GeV band, the total energy of cosmic-ray protons is calculated<br />
to be $\sim$$0.3$-$1.4\times10^{49}$ erg with the estimated ISM proton density<br />
of $\sim$$190\pm90$ cm$^{-3}$, containing both the shock-ionized gas and<br />
neutral atomic hydrogen.

DOI： 10.3847/1538-4357/ab02fd

Open Access

Web of Science

arXiv

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

DOI： 10.3847/1538-4357/aafac5

Open Access

Web of Science

Scopus

arXiv

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

DOI： 10.3847/1538-4357/aaf4fb

Web of Science

Scopus

arXiv

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

DOI： 10.3847/1538-4357/aae07c

Web of Science

Scopus

arXiv

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

DOI： 10.1093/pasj/psy095

Web of Science

Scopus

arXiv

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

DOI： 10.3847/1538-4357/aad7be

Web of Science

Scopus

arXiv

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

DOI： 10.3847/1538-4357/aacfff

Web of Science

Scopus

arXiv

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

DOI： 10.3847/1538-4357/aac898

Web of Science

Scopus

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

DOI： 10.3847/1538-4357/aac16c

Web of Science

Scopus

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

DOI： 10.3847/1538-4357/aac217

Web of Science

Scopus

arXiv

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

DOI： 10.1093/pasj/psy015

Web of Science

Scopus

arXiv

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

DOI： 10.1093/pasj/psx149

Web of Science

Scopus

arXiv

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

DOI： 10.1093/pasj/psy020

Web of Science

Scopus

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

DOI： 10.1093/pasj/psy025

Web of Science

Scopus

arXiv

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

DOI： 10.1093/pasj/psy006

Open Access

Web of Science

Scopus

arXiv

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

DOI： 10.1093/pasj/psy012

Web of Science

Scopus

arXiv

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press ({OUP})  

DOI： 10.1093/pasj/psy005

Web of Science

Scopus

arXiv

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

DOI： 10.1093/pasj/psy051

Web of Science

Scopus

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

DOI： 10.1093/pasj/psy017

Web of Science

Scopus

arXiv

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

DOI： 10.1093/pasj/psy019

Web of Science

Scopus

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

DOI： 10.1093/pasj/psx141

Web of Science

Scopus

arXiv

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

DOI： 10.1093/pasj/psx144

Web of Science

Scopus

arXiv

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

DOI： 10.1093/pasj/psx137

Web of Science

Scopus

arXiv

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

DOI： 10.3847/1538-4357/aaab5f

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Physics Publishing  

We present a multiwavelength analysis of a ∼30′ ×30′ area around the Sh 2-53 region (hereafter S53 complex), which is associated with at least three H ii regions, two mid-infrared bubbles (N21 and N22), and infrared dark clouds. The 13CO line data trace the molecular content of the S53 complex in a velocity range of 36-60 km s-1 and show the presence of at least three molecular components within the selected area along this direction. Using the observed radio continuum flux of the H ii regions, the derived spectral types of the ionizing sources agree well with the previously reported results. The S53 complex harbors clusters of young stellar objects (YSOs) that are identified using the photometric 2-24 μm magnitudes. It also hosts several massive condensations (3000-30,000 M⊙) that are traced in the Herschel column density map. The complex is found at the junction of at least five molecular filaments, and the flow of gas toward the junction is evident in the velocity space of the 13CO data. Together, the S53 complex is embedded in a very similar "hub-filament" system to those reported in Myers, and the active star formation is evident toward the central "hub" inferred by the presence of the clustering of YSOs.

DOI： 10.3847/1538-4357/aaa429

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We present a new analysis of the interstellar protons toward the TeV gamma-ray SNR RX J0852.0-4622 (G266.2-1.2, Vela Jr.). We used the NANTEN2 (CO)-C-12(J = 1-0) and Australia Telescope Compact Array and Parkes H I data sets in order to derive the molecular and atomic gas associated with the TeV gamma-ray shell of the SNR. We find that atomic gas over a velocity range from V-LSR =-4 to 50 km s(-1) or 60 km s(-1) is associated with the entire SNR, while molecular gas is associated with a limited portion of the SNR. The large velocity dispersion of the H I is ascribed to the expanding motion of a few H I shells overlapping toward the SNR but is not due to the Galactic rotation. The total masses of the associated H I and molecular gases are estimated to be similar to 2.5 x 10(4) M-circle dot and similar to 10(3) M-circle dot), respectively. A comparison with the High Energy Stereoscopic System TeV gamma-rays indicates that the interstellar protons have an average density around 100 cm(-3) and shows a good spatial correspondence with the TeV gamma-rays. The total cosmic-ray proton energy is estimated to be 1048 erg for the hadronic gamma-ray production, which may still be an underestimate by a factor of a few due to a small filling factor of the SNR volume by the interstellar protons. This result presents a third case, after RX J1713.7-3946 and HESS J1731-347, of the good spatial correspondence between the TeV gamma-rays and the interstellar protons, lending further support for a hadronic component in the gamma-rays from young TeV gamma-ray SNRs.

DOI： 10.3847/1538-4357/aa9219

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

The FUGIN project is one of legacy projects using a new multi-beam FOREST (four-beam receiver system on the 45m telescope). This project aims to simultaneously investigate the distribution, kinematics, and physical properties of both diffuse and dense molecular gases in the Galaxy by observing (CO)-C-12, (CO)-C-13, and (CO)-O-18 J = 1-0 lines simultaneously. Mapping regions are parts of the first quadrant (10 degrees &lt;= l &lt;= 50 degrees, | b| &lt;= 1 degrees) and the third quadrant (198 degrees &lt;= l = 236 degrees, | b| &lt;= 1.) of the Galaxy, where spiral arms, bar structure, and the molecular gas ring are included. This survey achieves the highest angular resolution to date (similar to 20") for theGalactic plane survey in the COJ= 1-0 lines, whichmakes it possible to find dense clumps located farther away than the previous surveys. FUGIN will provide us an invaluable dataset for investigating the physics of the Galactic interstellar medium (ISM), particularly the evolution of interstellar gas covering galactic-scale structures to the internal structures of giant molecular clouds, such as small filaments/clumps/cores. We present an overview of the FUGIN project, the observation plan and initial results. These results reveal wide-field and detailed structures of molecular clouds, such as entangled filaments that have not been obvious in previous surveys, and large-scale kinematics of molecular gas, such as spiral arms.

DOI： 10.1093/pasj/psx061

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We have analyzed the atomic and molecular gas using the 21 cm Hi and 2.6/1.3mm CO emissions toward the young supernova remnant (SNR) RCW 86 in order to identify the interstellar medium with which the shock waves of the SNR interact. We have found an HI intensity depression in the velocity range between -46 and -28 km s(-1) toward the SNR, suggesting a cavity in the interstellar medium. The HI cavity coincides with the thermal and non-thermal emitting X-ray shell. The thermal X-rays are coincident with the edge of the HI distribution, which indicates a strong density gradient, while the non-thermal X-rays are found toward the less dense, inner part of the HI cavity. The most significant non-thermal X-rays are seen toward the southwestern part of the shell where the HI gas traces the dense and cold component. We also identified CO clouds which are likely interacting with the SNR shock waves in the same velocity range as the Hi, although the CO clouds are distributed only in a limited part of the SNR shell. The most massive cloud is located in the southeastern part of the shell, showing detailed correspondence with the thermal X-rays. These CO clouds show an enhanced CO J = 2-1/1-0 intensity ratio, suggesting heating/compression by the shock front. We interpret that the shock-cloud interaction enhances non-thermal X-rays in the southwest and the thermal X-rays are emitted by the shock-heated gas of density 10-100 cm(-3). Moreover, we can clearly see an HI envelope around the CO cloud, suggesting that the progenitor had a weaker wind than the massive progenitor of the core-collapse SNR RX J1713.7-3949. It seems likely that the progenitor of RCW 86 was a system consisting of a white dwarf and a low-mass star with low-velocity accretion winds. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jheap.2017.04.002

Web of Science

Scopus

Publishing type：Research paper (scientific journal)  

NGC 2359 is an HII region located in the outer Galaxy that contains the<br />
isolated Wolf-Rayet (WR) star HD 56925. We present new CO observations of NGC<br />
2359 with the Nobeyama 45 m radio telescope and the Atacama Submillimeter<br />
Telescope Experiment using the $^{12}$CO($J$ = 1-0, 3-2) emission lines and<br />
compare them with archived HI and radio-continuum data from the Very Large<br />
Array. Our purpose is to investigate whether the formation of the WR star in<br />
NGC 2359 was triggered by a cloud-cloud collision. We find two molecular clouds<br />
at $\sim$37 and $\sim$54 km s$^{-1}$, and two HI clouds at $\sim$54 and<br />
$\sim$63 km s$^{-1}$. All are likely to be associated with NGC 2359 as<br />
suggested by good morphological correspondence not only with an optical dark<br />
lane through the nebula but also with the radio-shell boundary. We also find<br />
that the molecular cloud at $\sim$54 km s$^{-1}$ has a high kinematic<br />
temperature of at least $\sim$40 K, thus indicating that the gas temperature<br />
has been increased because of heating by the WR star. We propose that both NGC<br />
2359 and the isolated WR star were created by a collision between the two<br />
molecular clouds. The supersonic velocity separation of the two clouds cannot<br />
be explained by stellar feedback from the WR star. The complementary spatial<br />
distributions and bridging features of CO and HI also are in good agreement<br />
with the expected observational signatures of high-mass star formations<br />
triggered by cloud-cloud collisions. We argue that NGC 2359 may be in the final<br />
phase of a cloud-cloud collision and that the collision timescale is $\sim$1.5<br />
Myr or longer. We also note that there is no significant difference between the<br />
physical properties of colliding clouds that trigger the formation of isolated<br />
O-type and WR stars.

arXiv

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We analyzed the 2.6 mm CO and 21 cm H I lines toward the Magellanic superbubble 30. Doradus. C, in order to reveal the associated molecular and atomic gas. We uncovered five molecular clouds in a velocity range from 251 to 276 km s(-1) toward the western shell. The non-thermal X-rays are clearly enhanced around the molecular clouds on a parsec scale, suggesting possible evidence for magnetic field amplification via shock-cloud interaction. The thermal X-rays are brighter in the eastern shell, where there are no dense molecular or atomic clouds, opposite to. the western shell. The TeV gamma- ray distribution may spatially match the total interstellar proton column density as well as the non-thermal X-rays. If the hadronic gamma-ray is dominant, the total energy of the cosmic-ray protons is at least similar to 1.2 x 10(50) erg with the estimated mean interstellar proton density similar to 60 cm(-3). In addition, the gamma-ray flux associated with the molecular cloud (e.g., MC3) could be detected and resolved by the Cherenkov Telescope Array (CTA). This should permit CTA to probe the diffusion of cosmic-rays into the associated dense ISM.

DOI： 10.3847/1538-4357/aa73e0

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

Understanding massive cluster formation is one of the important issues of astronomy. By analyzing the HI data, we have identified that the two HI velocity components (L- and D-components) are colliding toward the HI Ridge, in the southeastern end of the Large Magellanic Cloud (LMC), which hosts the young massive cluster R136 and similar to 400 O/Wolf-Rayet stars (Doran et al. 2013, A&A, 558, A134) including the progenitor of SN 1987A. The collision is possibly evidenced by bridge features connecting the two HI components and by complementary distributions between them. We frame a hypothesis that the collision triggered the formation of R136 and the surrounding high-mass stars as well as the HI Ridge and the Molecular Ridge. Fujimoto and Noguchi (1990, PASJ, 42, 505) advocated that the last tidal interaction between the LMC and the Small Magellanic Cloud (SMC) induced collision of the L- and D-components about 0.2 Gyr ago. Thismodel is consistent with numerical simulations (Bekki & Chiba 2007a, MNRAS, 381, L16). We suggest that a dense HI, cloud of 10(6) M-circle dot partly including CO, a precursor of R136, was formed at the shock-compressed interface between the colliding L- and D-components. We suggest that part of the low-metallicity gas from the SMC wasmixed in the tidal interaction based on the Planck/IRAS data of dust optical depth (Planck Collaboration 2014, A&A, 571, A11).

DOI： 10.1093/pasj/psx032

Web of Science

Scopus

Publishing type：Research paper (scientific journal)  

We analyzed the NANTEN2 13CO (J=2-1 and 1-0) datasets in NGC 2024. We found<br />
that the cloud consists of two velocity components, whereas the cloud shows<br />
mostly single-peaked CO profiles. The two components are physically connected<br />
to the HII region as evidenced by their close correlation with the dark lanes<br />
and the emission nebulosity. The two components show complementary distribution<br />
with a displacement of 0.4 pc. Such complementary distribution is typical to<br />
colliding clouds discovered in regions of high-mass star formation. We<br />
hypothesize that cloud-cloud collision between the two components triggered the<br />
formation of the late O stars and early B stars localized within 0.3 pc of the<br />
cloud peak. The collision timescale is estimated to be ~ 10^5 yrs from a ratio<br />
of the displacement and the relative velocity 3-4 km s-1 corrected for probable<br />
projection. The high column density of the colliding cloud 1023 cm-2 is similar<br />
to those in the other massive star clusters in RCW 38, Westerlund 2, NGC 3603,<br />
and M42, which are likely formed under trigger by cloud-cloud collision. The<br />
present results provide an additional piece of evidence favorable to high-mass<br />
star formation by a major cloud-cloud collision in Orion.

arXiv

Publishing type：Research paper (scientific journal)  

Using the NANTEN2 Observatory, we carried out a molecular line study of<br />
high-mass star forming regions with reflection nebulae, NGC 2068 and NGC 2071,<br />
in Orion in the 13CO(J=2-1) transition. The 13CO distribution shows that there<br />
are two velocity components at 9.0 and 10.5 km/s . The blue-shifted component<br />
is in the northeast associated with NGC 2071, whereas the red-shifted component<br />
is in the southwest associated with NGC 2068. The total intensity distribution<br />
of the two clouds shows a gap of ~1 pc, suggesting that they are detached at<br />
present. A detailed spatial comparison indicates that the two show<br />
complementary distributions. The blue-shifted component lies toward an<br />
intensity depression to the northwest of the red-shifted component, where we<br />
find that a displacement of 0.8 pc makes the two clouds fit well with each<br />
other. Furthermore, a new simulation of non-frontal collisions shows that<br />
observations from 60 degrees off the collisional axis agreed well with the<br />
velocity structure in this region. On the basis of these results, we<br />
hypothesize that the two components collided with each other at a projected<br />
relative velocity 3.0 km/s estimated to be 0.3 Myr for an assumed axis of the<br />
relative motion 60 degrees off the line of sight. We assume that the two most<br />
massive early B-type stars in the cloud, illuminating stars of the two<br />
reflection nebulae, were formed by collisional triggering at the interfaces<br />
between the two clouds. Given the other young high-mass star forming regions,<br />
namely, M42, M43, and NGC 2024 (Fukui et al. 2018b; Ohama et al. 2017a), it<br />
seems possible that collisional triggering has been independently working to<br />
form O-type and early B-type stars in Orion in the last Myr over a projected<br />
distance of ~80 pc.

arXiv

Publishing type：Research paper (scientific journal)  

M16, the Eagle Nebula, is an outstanding HII region where extensive high-mass<br />
star formation is taking place in the Sagittarius Arm, and hosts the remarkable<br />
&quot;pillars&quot; observed with HST. We made new CO observations of the region in the<br />
12CO J=1--0 and J=2--1 transitions with NANTEN2. These observations revealed<br />
for the first time that a giant molecular cloud of $\sim 1.3 \times 10^5$ \Msun<br />
\ is associated with M16, which is elongated vertically to the Galactic plane<br />
over 35 pc at a distance of 1.8 kpc. We found a cavity of the molecular gas of<br />
$\sim 10$ pc diameter toward the heart of M16 at \lbeq (16.95\degree,<br />
0.85\degree), where more than 10 O-type stars and $\sim 400$ stars are<br />
associated, in addition to a close-by molecular cavity toward a Spitzer bubble<br />
N19 at \lbeq (17.06\degree, 1.0\degree). We found three velocity components<br />
which show spatially complementary distribution in the entire M16 giant<br />
molecular cloud (GMC) including NGC6611 and N19, suggesting collisional<br />
interaction between them. Based on the above results we frame a hypothesis that<br />
collision between the red-shifted and blue-shifted components at a relative of<br />
$\sim 10$ \kms \ triggered formation of the O-type stars in the M16 GMC in the<br />
last 1-2 Myr. The collision is two fold in the sense that one of the<br />
collisional interactions is major toward the M16 cluster and the other toward<br />
N19 with a RCW120 type, the former triggered most of the O star formation with<br />
almost full ionization of the parent gas, and the latter an O star formation in<br />
N19.

arXiv

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Massive molecular outflows erupting from high-mass young stellar objects (YSOs) provide important clues to understanding the mechanism of high-mass star formation. Based on new CO J = 3-2 and J = 1-0 observations using the Atacama Submillimeter Telescope Experiment (ASTE) and Mopra telescope facilities, we discovered a massive bipolar outflow associated with the dense dust core AGAL G337.916-00.477 (AGAL337.9-S), located 3.48 kpc from the Sun. The outflow lobes have extensions of less than 1 pc-and thus were not fully resolved in the angular resolutions of ASTE and Mopra-and masses of similar to 50M(circle dot) The maximum velocities of the outflow lobes are as high as 36-40 km s(-1). Our analysis of the infrared and submillimeter data indicates that AGAL337.9-S is in an early evolutionary stage of high-mass star formation, having the total far-infrared luminosity of similar to 5 x 10(4) L-circle dot. We also found that another dust core, AGAL G337.922-00.456 (AGAL337.9-N), located 2' north of AGAL337.9-S, is a high-mass YSO in an earlier evolutionary stage than AGAL337.9-S, as it is less bright in the mid-infrared than AGAL337.9-S.

DOI： 10.3847/1538-4357/aa6fa8

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Comparison analyses between the gas emission data (H I 21 cm line and CO 2.6mm line) and the Planck/ IRAS dust emission data (optical depth at 353 GHz t353 and dust temperature T-d) allow us to estimate the amount and distribution of the hydrogen gas more accurately, and our previous studies revealed the existence of a large amount of optically thick H I gas in the solar neighborhood. Referring to this, we discuss the neutral hydrogen gas around the Perseus cloud in the present paper. By using the J-band extinction data, we found that t353 increases as a function of the 1.3th power of column number density of the total hydrogen (N-H), and this implies dust evolution in high density regions. This calibrated tau 353-N-H relationship shows that the amount of the H I gas can be underestimated to be similar to 60% if the optically thin H I method is used. Based on this relationship, we calculated the optical depth of the 21 cm line (tau(H) I) and found that &lt;tau(H) I &gt; similar to 0.92 around the molecular cloud. The effect of tH I is still significant, even if we take into account the dust evolution. We also estimated a spatial distribution of the CO-to-H-2 conversion factor (X-CO), and we found its average value is &lt; X-CO &gt; similar to 1.0 X 10(20) cm(-2) K(-1)Km(-1)s 20 2 1 1. Although these results are inconsistent with some previous studies, these discrepancies can be well explained by the difference of the data and analyses methods.

DOI： 10.3847/1538-4357/aa6747

Web of Science

Scopus

Publishing type：Research paper (scientific journal)  

We present a comparative study of CO and polycyclic aromatic hydrocarbon<br />
(PAH) emission toward a region including the massive star-forming regions of<br />
NGC 6334 and NGC 6357. We use the NANTEN $^{12}$CO($J$ = 1--0) data and the<br />
$AKARI$ 9 $\mu$m All-Sky diffuse map in order to evaluate the calibration<br />
accuracy of the $AKARI$ data. We confirm that the overall CO distribution shows<br />
a good spatial correspondence with the PAH emission, and their intensities<br />
exhibit a good power-law correlation with a spatial resolution down to 4$&#039;$<br />
over the region of 10$^\circ$$\times$10$^\circ$. We also reveal poorer<br />
correlation for small scale structures between the two quantities toward NGC<br />
6357, due to strong UV radiation from local sources. Larger scatter in the<br />
correlation toward NGC 6357 indicates higher ionization degree and/or PAH<br />
excitation than that of NGC 6334.

DOI： 10.5303/PKAS.2017.32.1.021

arXiv

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

DOI： 10.3847/0004-6256/152/6/198

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

DOI： 10.3847/0004-637X/826/1/26

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

DOI： 10.3847/0004-637X/820/1/26

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

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

DOI： 10.1088/2041-8205/807/1/L4

Web of Science

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

DOI： 10.1088/0004-637X/806/1/7

Web of Science

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

DOI： 10.1088/0004-637X/799/2/175

Web of Science

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

DOI： 10.1088/0004-637X/798/1/6

Web of Science

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

DOI： 10.1088/0004-637X/796/1/59

Web of Science

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

DOI： 10.1088/0004-637X/791/1/43

Web of Science

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

DOI： 10.1088/2041-8205/789/1/L4

Web of Science

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

DOI： 10.1088/0004-637X/784/2/116

Web of Science

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

DOI： 10.1093/pasj/pst006

Web of Science

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

DOI： 10.1088/0004-637X/778/1/59

Web of Science

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

DOI： 10.1051/0004-6361/201321603

Web of Science

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

DOI： 10.1051/0004-6361/201220739

Web of Science

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

DOI： 10.1088/2041-8205/760/2/L25

Web of Science

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

DOI： 10.1051/0004-6361/201219589

Web of Science

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

DOI： 10.1088/0004-637X/750/2/174

Web of Science

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

DOI： 10.1002/asna.201111573

Web of Science

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

DOI： 10.1111/j.1365-2966.2010.17753.x

Web of Science

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

DOI： 10.1088/0004-637X/726/1/46

Web of Science

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

DOI： 10.1051/0004-6361/200811065

Web of Science

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

DOI： 10.1051/0004-6361:200810905

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1086/512093

Web of Science

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

DOI： 10.1051/0004-6361:20066158

Web of Science

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

DOI： 10.1086/500797

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1051/0004-6361:20042197

Web of Science

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

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/asna.200310168

Web of Science

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

DOI： 10.1086/341347

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1051/0004-6361:20020180

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

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

DOI： 10.1016/j.cpc.2012.04.028

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

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

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

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

DOI： 10.1093/pasj/51.6.859

Web of Science

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

Web of Science

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

Web of Science

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

DOI： 10.1093/pasj/51.6.751

Web of Science

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

Web of Science

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

Web of Science

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

DOI： 10.1093/pasj/51.6.819

Web of Science

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

Web of Science

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

Web of Science

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

DOI： 10.1093/pasj/51.6.745

Web of Science

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

Web of Science

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

DOI： 10.1086/305493

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：IOP PUBLISHING LTD  

We present the ALMA Band 3 and Band 6 results of 12CO(2-1), (CO)-C-13(2-1), H30 alpha recombination line, free-free emission around 98 GHz, and the dust thermal emission around 230 GHz toward the N159 East Giant Molecular Cloud (N159E) in the Large Magellanic Cloud (LMC). LMC is the nearest active high-mass star-forming face-on galaxy at a distance of. 50 kpc and is the best target for studing high-mass star formation. ALMA observations show that N159E is the complex of filamentary clouds with the width and length of similar to 1 pc and several parsecs. The total molecular mass is 0.92 x 10(5)M(circle dot) from the (CO)-C-13(2-1) intensity. N159E harbors the well-known Papillon Nebula, a compact high-excitation H II region. We found that a YSO associated with the Papillon Nebula has the mass of 35M(circle dot) and is located at the intersection of three filamentary clouds. It indicates that the formation of the high-mass YSO was induced by the collision of filamentary clouds. Fukui et al. reported a similar kinematic structure toward two YSOs in the N159 West region, which are the other YSOs that have the mass of &gt;= 35M(circle dot). This suggests that the collision of filamentary clouds is a primary mechanism of high-mass star formation. We found a small molecular hole around the YSO in Papillon Nebula with a sub-parsec scale. It is filled by free-free and H30 alpha emission. The temperature of the molecular gas around the hole reaches similar to 80 K. It indicates that this YSO has just started the distruction of parental molecular cloud.

DOI： 10.3847/1538-4357/835/1/108

Web of Science

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：IOP PUBLISHING LTD  

We present the ALMA Band 3 and Band 6 results of 12CO(2-1), (CO)-C-13(2-1), H30 alpha recombination line, free-free emission around 98 GHz, and the dust thermal emission around 230 GHz toward the N159 East Giant Molecular Cloud (N159E) in the Large Magellanic Cloud (LMC). LMC is the nearest active high-mass star-forming face-on galaxy at a distance of. 50 kpc and is the best target for studing high-mass star formation. ALMA observations show that N159E is the complex of filamentary clouds with the width and length of similar to 1 pc and several parsecs. The total molecular mass is 0.92 x 10(5)M(circle dot) from the (CO)-C-13(2-1) intensity. N159E harbors the well-known Papillon Nebula, a compact high-excitation H II region. We found that a YSO associated with the Papillon Nebula has the mass of 35M(circle dot) and is located at the intersection of three filamentary clouds. It indicates that the formation of the high-mass YSO was induced by the collision of filamentary clouds. Fukui et al. reported a similar kinematic structure toward two YSOs in the N159 West region, which are the other YSOs that have the mass of &gt;= 35M(circle dot). This suggests that the collision of filamentary clouds is a primary mechanism of high-mass star formation. We found a small molecular hole around the YSO in Papillon Nebula with a sub-parsec scale. It is filled by free-free and H30 alpha emission. The temperature of the molecular gas around the hole reaches similar to 80 K. It indicates that this YSO has just started the distruction of parental molecular cloud.

DOI： 10.3847/1538-4357/835/1/108

Web of Science

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2021.7

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：オンライン   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan