記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/1538-4357/ac090c

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/1538-4357/abeb65

記述言語：英語   掲載種別：研究論文（学術雑誌）  

<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 &#36;sim! 10&#37;&#36; 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

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/2041-8213/abdebb

記述言語：英語   掲載種別：研究論文（学術雑誌）  

<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 &#36;{0{^{prime prime }_{. } }17} imes {0{^{prime prime }_{. } }15}&#36; (≃ 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

記述言語：その他   掲載種別：研究論文（その他学術会議資料等）  

DOI： 10.1117/12.2560955

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/1538-4357/abb822

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/2041-8213/abc884

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/1538-4357/abb466

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/1538-4357/abb469

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/1538-4357/ab9ca7

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/2041-8213/ab9ca8

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/1538-4357/ab994d

記述言語：英語   掲載種別：研究論文（学術雑誌）  

<jats:title>Abstract</jats:title>
<jats:p>The formation mechanism of super star clusters (SSCs), present-day analogs of the ancient globulars, still remains elusive. The major merger that is the Antennae galaxies is forming SSCs and is one of the primary targets to test the cluster formation mechanism. We reanalyzed the archival ALMA CO data of the Antennae and found three typical observational signatures of a cloud–cloud collision toward SSC B1 and other SSCs in the overlap region: (i) two velocity components with ∼100 km s−1 velocity separation, (ii) bridge features connecting the two components, and (iii) a complementary spatial distribution between them, lending support to collisions of the two components as a cluster formation mechanism. We present a scenario that two clouds with 100 km s−1 velocity separation collided, and SSCs having ∼106–107 M⊙ were formed rapidly during that time scale. We compared the present results with the recent studies of star-forming regions in the Milky Way and the Large Magellanic Cloud, where the SSCs having ∼104–105 M⊙ are located. As a result, we found that there is a positive correlation between the compressed gas pressure generated by collisions and the total stellar mass of an SSC, suggesting that the pressure may be a key parameter in SSC formation.</jats:p>

DOI： 10.1093/pasj/psaa033

記述言語：英語   掲載種別：研究論文（学術雑誌）  

<jats:title>Abstract</jats:title>
<jats:p>We report the first evidence for high-mass star formation triggered by collisions of molecular clouds in M 33. Using the Atacama Large Millimeter/submillimeter Array, we spatially resolved filamentary structures of giant molecular cloud 37 in M 33 using 12CO(J = 2–1), 13CO(J = 2–1), and C18O(J = 2–1) line emission at a spatial resolution of ∼2 pc. There are two individual molecular clouds with a systematic velocity difference of ∼6 km s−1. Three continuum sources representing up to ∼10 high-mass stars with spectral types of B0V–O7.5V are embedded within the densest parts of molecular clouds bright in the C18O(J = 2–1) line emission. The two molecular clouds show a complementary spatial distribution with a spatial displacement of ∼6.2 pc, and show a V-shaped structure in the position–velocity diagram. These observational features traced by CO and its isotopes are consistent with those in high-mass star-forming regions created by cloud–cloud collisions in the Galactic and Magellanic Cloud H ii regions. Our new finding in M 33 indicates that cloud–cloud collision is a promising process for triggering high-mass star formation in the Local Group.</jats:p>

DOI： 10.1093/pasj/psaa045

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/1538-4357/ab8ad3

記述言語：英語   掲載種別：研究論文（学術雑誌）  

<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 (&#36;sim!! 4&#37;&#36;) 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

記述言語：英語   掲載種別：研究論文（学術雑誌）  

<jats:title>Abstract</jats:title>
<jats:p>We have developed a system of simultaneous observations in the 22 and 43 GHz bands using the Nobeyama 45 m telescope, and are also working to add the 86 GHz band. Multi-frequency observations are realized by mounting perforated plates in the optics as dichroic frequency-selective devices. This paper presents the development of the perforated plate for the 22 and 43 GHz bands and the results of the commissioning observations with this plate on the Nobeyama 45 m telescope. The perforated plate is designed to be installed in the large telescope optics with a physical beam diameter as large as &#36;50:&#36;cm for transmitting the higher frequency (43 GHz) band and for reflecting the lower frequency (22 GHz) band. The developed plate achieves an insertion loss of &#36;0.22:&#36;dB (5&#37;) at &#36;43:&#36;GHz. The effects of the mounted plate on the systematic offsets and on the accuracy degradation of pointing were confirmed to be negligible. The differences in the main-beam/aperture efficiencies from those without the plate were confirmed to be within a few percent points. In addition, we successfully detected interferometry fringes in a very long baseline interferometry (VLBI) observation using the 45 m telescope and the VLBI Exploration of Radio Astrometry (VERA) 20 m telescopes, which confirmed that the dual-band observation system is operationally effective in both single-dish and VLBI observations.</jats:p>

DOI： 10.1093/pasj/psz126

記述言語：その他   掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/1538-4357/ab46ba

記述言語：英語   掲載種別：研究論文（学術雑誌）  

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 1.2mm continuum has identified a centrally concentrated starless condensation with a central H-2 volume density of similar to 10(6)cm(-3), MC5-N, connected to a narrow (width similar to 0.03pc) filamentary cloud in the Taurus L1495 region. The mass of the core is , 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 (similar to 20&#37;-40&#37;) 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 N2H+ and N2D+ observations using the Nobeyama 45-m telescope have confirmed the high-deuterium fractionation (similar to 30&#37;). 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

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The N159 star-forming region is one of the most massive giant molecular clouds (GMCs) in the Large Magellanic Cloud (LMC). We show the 12CO, 13CO, CS molecular gas lines observed with ALMA in N159 west (N159W) and N159 east (N159E). We relate the structure of the gas clumps to the properties of 24 massive young stellar objects (YSOs) that include 10 newly identified YSOs based on our search. We use dendrogram analysis to identify properties of the molecular clumps, such as flux, mass, linewidth, size, and virial parameter. We relate the YSO properties to the molecular gas properties. We find that the CS gas clumps have a steeper size-linewidth relation than the 12CO or 13CO gas clumps. This larger slope could potentially occur if the CS gas is tracing shocks. The virial parameters of the 13CO gas clumps in N159W and N159E are low (&lt
1). The threshold for massive star formation in N159W is 501 M o pc-2, and the threshold for massive star formation in N159E is 794 M o pc-2. We find that 13CO is more photodissociated in N159E than N159W. The most massive YSO in N159E has cleared out a molecular gas hole in its vicinity. All the massive YSO candidates in N159E have a more evolved spectral energy distribution type in comparison to the YSO candidates in N159W. These differences lead us to conclude that the giant molecular cloud complex in N159E is more evolved than the giant molecular cloud complex in N159W.

DOI： 10.3847/1538-4357/aaab5f

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We present the molecular cloud properties of N55 in the Large Magellanic Cloud using 12CO(1-0) and 13CO(1-0) observations obtained with Atacama Large Millimeter Array. We have done a detailed study of molecular gas properties, to understand how the cloud properties of N55 differ from Galactic clouds. Most CO emission appears clumpy in N55, and molecular cores that have young stellar objects (YSOs) show larger linewidths and masses. The massive clumps are associated with high and intermediate mass YSOs. The clump masses are determined by local thermodynamic equilibrium and virial analysis of the 12CO and 13CO emissions. These mass estimates lead to the conclusion that (a) the clumps are in self-gravitational virial equilibrium, and (b) the 12CO(1-0)-to-H2 conversion factor, , is 6.5 × 1020 cm-2 (K km s-1)-1. This CO-to-H2 conversion factor for N55 clumps is measured at a spatial scale of ∼0.67 pc, which is about two times higher than the value of the Orion cloud at a similar spatial scale. The core mass function of N55 clearly show a turnover below 200 , separating the low-mass end from the high-mass end. The low-mass end of the 12CO mass spectrum is fitted with a power law of index 0.5 ± 0.1, while for 13CO it is fitted with a power law index 0.6 ± 0.2. In the high-mass end, the core mass spectrum is fitted with a power index of 2.0 ± 0.3 for 12CO, and with 2.5 ± 0.4 for 13CO. This power law behavior of the core mass function in N55 is consistent with many Galactic clouds.

DOI： 10.3847/1538-4357/aaa5b0

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We present high-resolution (subparsec) observations of a giant molecular cloud in the nearest star-forming galaxy, the Large Magellanic Cloud. ALMA Band 6 observations trace the bulk of the molecular gas in 12CO(2-1) and the high column density regions in 13CO(2-1). Our target is a quiescent cloud (PGCC G282.98-32.40, which we refer to as the "Planck cold cloud" or PCC) in the southern outskirts of the galaxy where star formation activity is very low and largely confined to one location. We decompose the cloud into structures using a dendrogram and apply an identical analysis to matched-resolution cubes of the 30 Doradus molecular cloud (located near intense star formation) for comparison. Structures in the PCC exhibit roughly 10 times lower surface density and five times lower velocity dispersion than comparably sized structures in 30 Dor, underscoring the non-universality of molecular cloud properties. In both clouds, structures with relatively higher surface density lie closer to simple virial equilibrium, whereas lower surface-density structures tend to exhibit supervirial line widths. In the PCC, relatively high line widths are found in the vicinity of an infrared source whose properties are consistent with a luminous young stellar object. More generally, we find that the smallest resolved structures ("leaves") of the dendrogram span close to the full range of line widths observed across all scales. As a result, while the bulk of the kinetic energy is found on the largest scales, the small-scale energetics tend to be dominated by only a few structures, leading to substantial scatter in observed size-line-width relationships.

DOI： 10.3847/1538-4357/aa9333

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We have performed Atacama Large Millimeter/submillimeter Array (ALMA) observations in the (CO)-C-12(J = 2 - 1), (CO)-C-13(J = 2 - 1), (CO)-O-18(J = 2 - 1), (CO)-C-12(J = 3 - 2), (CO)-C-13(J = 3 - 2), and CS(J = 7- 6) lines toward the active star-forming region N83C in the Small Magellanic Cloud (SMC), whose metallicity is about one-fifth of the Milky Way (MW). The ALMA observations first reveal subparsec-scale molecular structures in (CO)-C-12(J = 2 - 1) and (CO)-C-13(J = 2 - 1) emissions. We found strong CO peaks associated with young stellar objects (YSOs) identified by the Spitzer Space Telescope, and we also found that overall molecular gas is distributed along the edge of the neighboring H II region. We derived a gas density of similar to 10(4) cm(-3) in molecular clouds associated with YSOs based on the virial mass estimated from the (CO)-C-12(J = 2 - 1) emission. This high gas density is presumably due to the effect of the H II region under the low-metallicity(and accordingly small- dust content) environment in the SMC; far-UV radiation from the H II region can easily penetrate and photodissociate the outer layer of (CO)-C-12 molecules in the molecular clouds, and thus only the innermost parts of the molecular clouds are observed even in (CO)-C-12 emission. We obtained the CO-to-H-2 conversion factor X-CO of 7.5 x 10(20) cm(-2) (Kkm s(-1))(-1) in N83C based on virial masses and CO luminosities, and it is four times larger than that in the MW, 2 x 10(20) cm(-2) (Kkm s(-1))(-1). We also discuss the difference in the nature between two high-mass YSOs, each of which is associated with a molecular clump with a mass of about a few x 10(3) M-circle dot.

DOI： 10.3847/1538-4357/aa7a0b

記述言語：英語   掲載種別：研究論文（学術雑誌）  

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 ∼50 M⊙. The maximum velocities of the outflow lobes are as high as 36-40km 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 ∼5 × 104 L⊙. 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

記述言語：英語   掲載種別：研究論文（学術雑誌）  

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

記述言語：英語   掲載種別：研究論文（学術雑誌）  

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 >= 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

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We present the ALMA Band 3 and Band 6 results of 12CO(2-1), 13CO(2-1), H30α 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 ∼1 pc and several parsecs. The total molecular mass is 0.92 � 105 M o from the 13CO(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 35 M o 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 35 M o. 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 H30α emission. The temperature of the molecular gas around the hole reaches ∼80 K. It indicates that this YSO has just started the distruction of parental molecular cloud.

DOI： 10.3847/1538-4357/835/1/108

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We present the results of ALMA observations of dust continuum emission and molecular rotational lines toward a dense core MC27 (aka L1521F) in Taurus, which is considered to be at a very early stage of star formation. The detailed column density distributions on size scales from a few tens to similar to 10,000 AU are revealed by combining the ALMA (12m array + 7 m array) data with the published/unpublished single-dish data. The high angular resolution observations at 0.87 mm with a synthesized beam size of similar to 0 ''.74 x 0 ''.32 reveal that a protostellar source, MMS-1, is not spatially resolved and lacks associated gas emission, while a starless high-density core, MMS-2, has substructures in both dust and molecular emission. The averaged radial column density distribution of the inner part of MC27/L1521F (r less than or similar to 3000 AU) is N-H2 similar to r(-0.4), clearly flatter than that of the outer part, similar to r(-1.0). The complex velocity/spatial structure obtained with previous ALMA observations is located inside the inner flatter region, which may reflect the dynamical status of the dense core.

DOI： 10.3847/0004-637X/826/1/26

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We developed a dual-linear-polarization HEMT (High Electron Mobility Transistor) amplifier receiver system of the 45-GHz band (hereafter Z45), and installed it in the Nobeyama 45-m radio telescope. The receiver system is designed to conduct polarization observations by taking the cross-correlation of two linearly polarized components, from which we process full Stokes spectroscopy. We aim to measure themagnetic field strength through the Zeeman effect of the emission line of CCS (JN = 43-32) toward pre-protostellar cores. A linear-polarization receiver system has a smaller contribution of instrumental polarization components to the Stokes V spectra than that of the circular polarization system, so that it is easier to obtain the Stokes V spectra. The receiver has an RF frequency of 42-46 GHz and an intermediate frequency (IF) band of 4-8 GHz. The typical noise temperature is about 50 K, and the system noise temperature ranges from 100 to 150 K over the frequency of 42-46 GHz. The receiver system is connected to two spectrometers, SAM45 and PolariS. SAM45 is a highly flexible FX-type digital spectrometer with a finest frequency resolution of 3.81 kHz. PolariS is a newly developed digital spectrometer with a finest frequency resolution of 60 Hz, and which has a capability to process the full-Stokes spectroscopy. The half-power beam width (HPBW) was measured to be 37 '' at 43 GHz. The main beam efficiency of the Gaussian main beam was derived to be 0.72 at 43 GHz. The SiO maser observations show that the beam pattern is reasonably round at about 10&#37; of the peak intensity and the side-lobe level was less than 3&#37; of the peak intensity. Finally, we present some examples of astronomical observations using Z45.

DOI： 10.1093/pasj/psv088

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We have carried out 13CO(J = 2-1) observations of the active star-forming region N159 west in the Large Magellanic Cloud with ALMA. We have found that the CO distribution at a sub-parsec scale is highly elongated with a small width. These elongated clouds called "filaments" show straight or curved distributions with a typical width of 0.5-1.0 pc and a length of 5-10 pc. All the known infrared young stellar objects are located toward the filaments. We have found broad CO wings of two molecular outflows toward young high-mass stars in N159W-N and N159W-S, whose dynamical timescale is ∼104 years. This is the first discovery of protostellar outflow in external galaxies. For N159W-S, which is located toward an intersection of two filaments, we set up a hypothesis that the two filaments collided with each other ∼105 years ago and triggered the formation of the high-mass star having ∼37 M⊙. The colliding clouds show significant enhancement in linewidth in the intersection, suggesting excitation of turbulence in the shocked interface layer between them, as is consistent with the magnetohydrodynamical numerical simulations. This turbulence increases the mass accretion rate to ∼6 × 10-4 M⊙ yr-1, which is required to overcome the stellar feedback to form the high-mass star.

DOI： 10.1088/2041-8205/807/1/L4

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We investigated the formation of arc-like structures in the infalling envelope around protostars, motivated by the recent Atacama Large Millimeter/Submillimeter Array (ALMA) observations of the high-density molecular cloud core, MC27/L1521F. We performed self-gravitational hydrodynamical numerical simulations with an adaptive mesh refinement code. A filamentary cloud with a 0.1 pc width fragments into cloud cores because of perturbations due to weak turbulence. The cloud core undergoes gravitational collapse to form multiple protostars, and gravitational torque from the orbiting protostars produces arc structures extending up to a 1000 au scale. As well as on a spatial extent, the velocity ranges of the arc structures, similar to 0.5 km s(-1), are in agreement with the ALMA observations. We also found that circumstellar discs are often misaligned in triple system. The misalignment is caused by the tidal interaction between the protostars when they undergo close encounters because of a highly eccentric orbit of the tight binary pair.

DOI： 10.1093/mnrasl/slv031

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We investigated the formation of arc-like structures in the infalling envelope around protostars, motivated by the recent Atacama Large Millimeter/Submillimeter Array (ALMA)observations of the high-density molecular cloud core, MC27/L1521F. We performed self-gravitational hydrodynamical numerical simulations with an adaptive mesh refinement code. A filamentary cloud with a 0.1 pc width fragments into cloud cores because of perturbations due to weak turbulence. The cloud core undergoes gravitational collapse to form multiple protostars, and gravitational torque from the orbiting protostars produces arc structures extending up to a 1000 au scale. As well as on a spatial extent, the velocity ranges of the arc structures, ~0.5 kms-1, are in agreement with the ALMA observations. We also found that circumstellar discs are often misaligned in triple system. The misalignment is caused by the tidal interaction between the protostars when they undergo close encounters because of a highly eccentric orbit of the tight binary pair.

DOI： 10.1093/mnrasl/slv031

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We present fully sampled similar to 3' resolution images of (CO)-C-12(J = 2-1), (CO)-C-13(J = 2-1), and (CO)-O-18(J = 2-1) emission taken with the newly developed 1.85m millimeter-submillimeter telescope over the entire area of the Orion A and B giant molecular clouds. The data were compared with J = 1-0 of the (CO)-C-12, (CO)-C-13, and (CO)-O-18 data taken with the Nagoya 4m telescope and the NANTEN telescope at the same angular resolution to derive the spatial distributions of the physical properties of the molecular gas. We explore the large velocity gradient formalism to determine the gas density and temperature using line combinations of (CO)-C-12(J = 2-1), (CO)-C-13(J = 2-1), and (CO)-C-13(J = 1-0) assuming a uniform velocity gradient and abundance ratio of CO. The derived gas density is in the range of 500 to 5000 cm(-3), and the derived gas temperature is mostly in the range of 20 to 50K along the cloud ridge with a temperature gradient depending on the distance from the star forming region. We found that the high-temperature region at the cloud edge faces the H II region, indicating that the molecular gas is interacting with the stellar wind and radiation from the massive stars. In addition, we compared the derived gas properties with the young stellar objects distribution obtained with the Spitzer telescope to investigate the relationship between the gas properties and the star formation activity therein. We found that the gas density and star formation efficiency are positively well correlated, indicating that stars form effectively in the dense gas region.

DOI： 10.1088/0067-0049/216/1/18

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The Serpens South infrared dark cloud consists of several filamentary ridges, some of which fragment into dense clumps. On the basis of CCS (J(N) = 4(3)-3(2)), HC3N (J = 5-4), N2H+ (J = 1-0), and SiO (J = 2-1, v = 0) observations, we investigated the kinematics and chemical evolution of these filamentary ridges. We find that CCS is extremely abundant along the main filament in the protocluster clump. We emphasize that Serpens South is the first cluster-forming region where extremely strong CCS emission is detected. The CCS-to-N2H+ abundance ratio is estimated to be about 0.5 toward the protocluster clump, whereas it is about 3 in the other parts of the main filament. We identify six dense ridges with different V-LSR. These ridges appear to converge toward the protocluster clump, suggesting that the collisions of these ridges may have triggered cluster formation. The collisions presumably happened within a few x 10(5) yr because CCS is abundant only for a short time. The short lifetime agrees with the fact that the number fraction of Class I objects, whose typical lifetime is 0.4 x 10(5) yr, is extremely high, about 70&#37; in the protocluster clump. In the northern part, two ridges appear to have partially collided, forming a V-shape clump. In addition, we detected strong bipolar SiO emission that is due to the molecular outflow blowing out of the protostellar clump, as well as extended weak SiO emission that may originate from the filament collisions.

DOI： 10.1088/2041-8205/791/2/L23

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Starless dense cores eventually collapse dynamically, forming protostars inside them, and the physical properties of the cores determine the nature of the forming protostars. We report ALMA observations of dust continuum emission and molecular rotational lines toward MC27 or L1521F, which is considered to be very close to the first protostellar core phase. We found a few starless high-density cores, one of which has a very high density of similar to 10(7) cm(-3), within a region of several hundred AU around a very low-luminosity protostar detected by Spitzer. A very compact bipolar outflow with a dynamical timescale of a few hundred years was found toward the protostar. The molecular line observation shows several cores with an arc-like structure, possibly due to the dynamical gas interaction. These complex structures revealed in the present observations suggest that the initial condition of star formation is highly dynamical in nature, which is considered to be a key factor in understanding fundamental issues of star formation such as the formation of multiple stars and the origin of the initial mass function of stars.

DOI： 10.1088/2041-8205/789/1/L4