arXiv subjects

Hidetoshi Sano

Publications and source records attributed to Hidetoshi Sano.

At least 73 records · Page 4Linked to original sources

arXiv2021

Optical reconstruction of dust in the region of SNR RX J1713.7-3946 from astrometric data

The origin of the radiation observed in the region of the supernova remnant RX J1713.7-3946, one of the brightest TeV emitters, has been debated since its discovery. The existence of atomic and molecular clouds in this object supports the idea that part of the GeV gamma rays in this region originate from proton-proton collisions. However, the observed column density of protons derived from gas observations cannot explain the whole emission. Yet there could be a fraction of protons contained in fainter structures that have note been detected so far. Here we search for faint objects in the line of sight of RX J1713.7-3946 using the principle of light extinction and the ESA/Gaia DR2 astrometric and photometric data. We reveal and locate with precision a number of dust clouds and note that only one appears to be in the vicinity of RX J1713.7-3946. We estimate the embedded mass to $M_{dust} = (7.0 \pm 0.6) \times 10^3 \, M_{\odot}$ which might be big enough to contain the missing protons. Finally, using the fact that the supernova remnant is expected to be located in a dusty environment and that there appears to be only one such structure in the vicinity of RX J1713.7-3946, we set a very precise constrain to the supernova remnant distance, at ($1.12 \pm 0.01$) kpc.

astro-ph.HE↗

arXiv2021

ALMA reveals a cloud-cloud collision that triggers star formation in N66N of the Small Magellanic Cloud

We present the results of Atacama Large Millimeter/submillimeter Array (ALMA) observation in $^{12}$CO(1-0) emission at 0.58 $\times$ 0.52 pc$^2$ resolution toward the brightest HII region N66 of the Small Magellanic Cloud (SMC). The $^{12}$CO(1-0) emission toward the north of N66 reveals the clumpy filaments with multiple velocity components. Our analysis shows that a blueshifted filament at a velocity range 154.4-158.6 km s$^{-1}$ interacts with a redshifted filament at a velocity 158.0-161.8 km s$^{-1}$. A third velocity component in a velocity range 161-165.0 km s$^{-1}$ constitutes hub-filaments. An intermediate-mass young stellar object (YSO) and a young pre-main sequence star cluster have hitherto been reported in the intersection of these filaments. We find a V-shape distribution in the position-velocity diagram at the intersection of two filaments. This indicates the physical association of those filaments due to a cloud-cloud collision. We determine the collision timescale $\sim$ 0.2 Myr using the relative velocity ($\sim$ 5.1 km s$^{-1}$) and displacement ($\sim$ 1.1 pc) of those interacting filaments. These results suggest that the event occurred at about 0.2 Myr ago and triggered the star formation, possibly an intermediate-mass YSO. We report the first observational evidence for a cloud-cloud collision that triggers star formation in N66N of the low metallicity $\sim$0.2 Z$_{\odot}$ galaxy, the SMC, with similar kinematics as in N159W-South and N159E of the Large Magellanic Cloud.

astro-ph.GA↗

arXiv2021

The formation of the young massive cluster B1 in the Antennae galaxies (NGC 4038/NGC 4039) triggered by cloud-cloud collision

The Antennae Galaxies is one of the starbursts in major mergers. Tsuge et al. (2020) showed that the five giant molecular complexes in the Antennae Galaxies have signatures of cloud-cloud collisions based on the ALMA archival data at 60 pc resolution. In the present work we analyzed the new CO data toward the super star cluster (SSC) B1 at 14 pc resolution obtained with ALMA, and confirmed that two clouds show complementary distribution with a displacement of $\sim$70 pc as well as the connecting bridge features between them. The complementary distribution shows a good correspondence with the theoretical collision model (Takahira et al. 2014), and indicates that SSC B1 having $\sim$10$^{6}$ $M$$_{\odot}$ was formed by the trigger of a cloud-cloud collision with a time scale of $\sim$1Myr, which is consistent with the cluster age. It is likely that SSC B1 was formed from molecular gas of $\sim$10$^{7}$ $M$$_{\odot}$ with a star formation efficiency of $\sim$10 % in 1 Myr. We identified a few places where additional clusters are forming. Detailed gas motion indicates stellar feedback in accelerating gas is not effective, while ionization plays a role in evacuating the gas around the clusters at a $\sim$30-pc radius. The results have revealed the details of the parent gas where a cluster having mass similar to a globular is being formed.

astro-ph.GA↗

arXiv2020

Development of the new multi-beam receiver and telescope control system for NASCO

We report the current status of the NASCO (NAnten2 Super CO survey as legacy) project which aims to provide all-sky CO data cube of southern hemisphere using the NANTEN2 4-m submillimeter telescope installed at the Atacama Desert through developing a new multi-beam receiver and a new telescope control system. The receiver consists of 5 beams. The four beams, located at the four corners of a square with the beam separation of 720$''$, are installed with a 100 GHz band SIS receiver having 2-polarization sideband-separation filter. The other beam, located at the optical axis, is installed with a 200 GHz band SIS receiver having 2-polarization sideband-separation filter. The cooled component is modularized for each beam, and cooled mirrors are used. The IF bandwidths are 8 and 4 GHz for 100 and 200 GHz bands, respectively. Using XFFTS spectrometers with a bandwidth of 2 GHz, the lines of $^{12}$CO, $^{13}$CO, and C$^{18}$O of $J$=1$-$0 or $J$=2$-$1 can be observed simultaneously for each beam. The control system is reconstructed on the ROS architecture, which is an open source framework for robot control, to enable a flexible observation mode and to handle a large amount of data. The framework is commonly used and maintained in a robotic field, and thereby reliability, flexibility, expandability, and efficiency in development are improved as compared with the system previously used. The receiver and control system are installed on the NANTEN2 telescope in December 2019, and its commissioning and science verification are on-going. We are planning to start science operation in early 2021.

astro-ph.IM↗

arXiv2020

Cometary records revise Eastern Mediterranean chronology around 1240 CE

Eirene Laskarina, empress of John III Batatzes of the exiled Byzantine Empire of Nicaea (1204--1261 CE), was an important Eastern Mediterranean figure in the first half of the thirteenth century. We reassess the date of Eirene's death, which has been variously dated between late 1239 and 1241, with the understanding that narrowing the range in which this event occurred contributes much to understanding the political situation in the area around 1240. George Akropolites, a famous official of the Empire, gives an account that connects Eirene's death to a comet that appeared "six months earlier", thus pointing to two comet candidates that were visible from the Eastern Mediterranean between 1239 and 1241, one recorded on "3 June 1239" and the other on "31 January 1240". Recent historians prefer the former, based on historical circumstances and without a critical assessment of the comet records. We revisit the historical records and reveal that the "3 June 1239" candidate was not a comet. On the other hand, the other candidate, sighted on "31 January 1240", was a comet, as supported by multiple historical records in multiple regions, and is also a good fit with Akropolites's narrative. Therefore, we conclude that Eirene died six months after the comet that was seen on 31 January 1240, which places her death in the summer of 1240. Given that the date of her death is crucial for determining some other contemporary events across the Eastern Mediterranean, our results offer a solid basis for further research on the thirteenth-century Eastern Mediterranean.

physics.hist-ph↗

arXiv2020

Low X-ray Efficiency of a Young High-B Pulsar PSR J1208-6238 Observed with Chandra

High magnetic field (high-B) pulsars are key sources to bridge magnetars and conventional rotation powered pulsars, and thus to understand the origin of magnetar activities. We have estimated a tight upper-limit on the X-ray flux of one of the youngest high-B pulsars PSR J1208-6238 for the first time; a Chandra 10 ks observation shows no significant source. Depending on the emission models, the 3sigma upper-limit on the intrinsic 0.5-7 keV flux to (2.2-10.0)e-14 erg/s/cm2.

astro-ph.HE↗

arXiv2020

New Optically Identified Supernova Remnants in the Large Magellanic Cloud

We present a new optical sample of three Supernova Remnants and 16 Supernova Remnant (SNR) candidates in the Large Magellanic Cloud(LMC). These objects were originally selected using deep H$α$, [SII] and [OIII] narrow-band imaging. Most of the newly found objects are located in less dense regions, near or around the edges of the LMC's main body. Together with previously suggested MCSNR J0541-6659, we confirm the SNR nature for two additional new objects: MCSNR J0522-6740 and MCSNRJ0542-7104. Spectroscopic follow-up observations for 12 of the LMC objects confirm high [SII]/H$α$ a emission-line ratios ranging from 0.5 to 1.1. We consider the candidate J0509-6402 to be a special example of the remnant of a possible Type Ia Supernova which is situated some 2$^\circ$ ($\sim 1.75$kpc) north from the main body of the LMC. We also find that the SNR candidates in our sample are significantly larger in size than the currently known LMC SNRs by a factor of $\sim 2$. This could potentially imply that we are discovering a previously unknown but predicted, older class of large LMC SNRs that are only visible optically. Finally, we suggest that most of these LMC SNRs are residing in a very rarefied environment towards the end of their evolutionary span where they become less visible to radio and X-ray telescopes.

astro-ph.HE↗

arXiv2020

Active star formation across the whole Large Magellanic Cloud triggered by tidally-driven colliding HI flows

The galactic tidal interaction is a possible mechanism to trigger the active star formation in galaxies. Recent analyses using the Hi data in the Large Magellanic Cloud (LMC) proposed that the tidally driven colliding HI flows, induced by the galactic interaction with the Small Magellanic Cloud (SMC), triggered high-mass star formation in the southeastern HI Ridge, including R136 and $\sim$400 O/WR stars, and the galactic center region hosting the N44 region. This study performed a comprehensive HI data analysis across the LMC and found that two Hi velocity components defined in the early studies (L- and D- components) are quasi-ubiquitous with signatures of interaction dynamically toward the other prominent HII regions, such as N11 and N79. We characterize the intimidate velocity range (I-component) between the two components as the decelerated gas by momentum conservation in the collisional interaction. The spatial distributions of the I-component and those of the O/WR stars have good agreements with each other whose fraction is more than $\sim$70% at a scale of $\sim$15 pc, which is significantly smaller than the typical GMC size. Based on the results of our new simulations of the LMC-SMC interaction, we propose that the interaction about 0.2 Gyr ago induced efficient infall of gas from the SMC to the LMC and consequently ended up with recent formation of high-mass stars due to collisions of HI gas in the LMC. The new numerical simulations of the gas dynamics successfully reproduce the current distribution of the L-component. This lends theoretical support for the present picture.

astro-ph.GA↗

arXiv2020

Massive star formation in the Carina nebula complex and Gum 31 -- I. The Carina nebula complex

Herein, we present results from observations of the 12CO (J=1-0), 13CO (J=1-0), and 12CO (J=2-1) emission lines toward the Carina nebula complex (CNC) obtained with the Mopra and NANTEN2 telescopes. We focused on massive-star-forming regions associated with the CNC including the three star clusters Tr14, Tr15, and Tr16, and the isolated WR-star HD92740. We found that the molecular clouds in the CNC are separated into mainly four clouds at velocities -27, -20, -14, and -8 km/s. Their masses are 0.7x10^4Msun, 5.0x10^4 Msun, 1.6x10^4 Msun, and 0.7x10^4 Msun, respectively. Most are likely associated with the star clusters, because of their high 12CO (J=2-1)/12CO (J=1-0) intensity ratios and their correspondence to the Spitzer 8 micron distributions. In addition, these clouds show the observational signatures of cloud--cloud collisions. In particular, there is a V-shaped structure in the position--velocity diagram and a complementary spatial distribution between the -20 km/s cloud and the -14 km/s cloud. Based on these observational signatures, we propose a scenario wherein the formation of massive stars in the clusters was triggered by a collision between the two clouds. By using the path length of the collision and the assumed velocity separation, we estimate the timescale of the collision to be ~1 Myr. This is comparable to the ages of the clusters estimated in previous studies.

astro-ph.GA↗

arXiv2020

ALMA Observations of Giant Molecular Clouds in M33. II. Triggered High-mass Star Formation by Multiple Gas Colliding Events at the NGC 604 Complex

We present the results of ALMA observations in $^{12}$CO($J=2-1$), $^{13}$CO($J=2-1$), and C$^{18}$O($J=2-1$) lines and 1.3 mm continuum emission toward a massive ($\sim 10^6 M_{\odot}$) giant molecular cloud associated with the giant H II region NGC 604 in one of the nearest spiral galaxy M33 at an angular resolution of 0''.44 $\times$ 0''.27 (1.8 pc $\times$ 1.1 pc). The $^{12}$CO and $^{13}$CO images show highly complicated molecular structures composed of a lot of filaments and shells whose lengths are 5 -- 20 pc. We found three 1.3 mm continuum sources as dense clumps at edges of two shells and also at an intersection of several filaments. We examined the velocity structures of $^{12}$CO($J=2-1$) emission in the shells and filaments containing dense clumps, and concluded that expansion of the H II regions cannot explain the formation of such dense cores. Alternatively, we suggest that cloud--cloud collisions induced by an external H I gas flow and the galactic rotation compressed the molecular material into dense filaments/shells as ongoing high-mass star formation sites. We propose that multiple gas converging/colliding events with a velocity of a few tens km s$^{-1}$ are necessary to build up NGC 604, the most significant cluster-forming complex in the Local Group of galaxies.

astro-ph.GA↗

arXiv2020

Shock-Cloud Interaction in the Southwestern Rim of RX J1713.7$-$3946 Evidenced by Chandra X-ray Observations

We report on results of Chandra X-ray observations of the southwestern part of the supernova remnant (SNR) RX J1713.7$-$3946. We measure proper motions of two X-ray bright blobs, named Blobs A and B, in regions presumably corresponding to the forward shock of the SNR. The measured velocities are $3800 \pm 100~\mathrm{km}~\mathrm{s}^{-1}$ and $2300 \pm 200~\mathrm{km}~\mathrm{s}^{-1}$ for Blobs A and B, respectively. Since a dense molecular clump is located close to Blob B, its slower velocity is attributed to shock deceleration as a result of a shock-cloud interaction. This result provides solid evidence that the forward shock of RX J1713.7$-$3946 is indeed colliding with dense gas discovered through radio observations reported in the literature. The locations and velocity differences of the two blobs lead to an estimate that the shock encountered with the dense gas $\sim 100~\mathrm{yr}$ ago. The shock velocities, together with cutoff energies of the synchrotron X-ray spectra of the blobs, indicate that particle acceleration in these regions is close to the Bohm limit. Blob B, in particular, is almost at the limit, accelerating particles at the fastest possible rate. We discuss possible influence of the shock-cloud interaction on the efficiency of particle acceleration.

astro-ph.HE↗

arXiv2020

FOREST unbiased Galactic plane imaging survey with the Nobeyama 45 m telescope (FUGIN): Possible evidence of cloud-cloud collisions triggering high-mass star formation in the giant molecular cloud M16 (Eagle Nebula)

M16, the Eagle Nebula, is an outstanding \HII \ region which exhibits extensive high-mass star formation and hosts remarkable "pillars". We herein obtained new $^{12}$CO $J=$1-0 data for the region observed with NANTEN2, which were combined with the $^{12}$CO $J=$1-0 data obtained using FUGIN survey. These observations revealed that a giant molecular cloud (GMC) of $\sim 1.3 \times 10^5$ \Msun \ is associated with M16, which is elongated by over 30 pc and is perpendicular to the galactic plane, at a distance of 1.8 kpc. This GMC can be divided into the northern (N) cloud, the eastern (E) filament, the southeast (SE) cloud, the southeast (SE) filament, and the southern (S) cloud. We also found two velocity components (blue and red shifted component) in the N cloud. The blue-shifted component shows a ring-like structure, as well as the red-shifted component coincides with the intensity depression of the ring-like structure. The position-velocity diagram of the components showed a V-shaped velocity feature. The spatial and velocity structures of the cloud indicated that two different velocity components collided with each other at a relative velocity of 11.6 \kms. The timescale of the collision was estimated to be $\sim 4 \times 10^5$ yr. The collision event reasonably explains the formation of the O9V star ALS15348, as well as the shape of the Spitzer bubble N19. A similar velocity structure was found in the SE cloud, which is associated with the O7.5V star HD168504. In addition, the complementary distributions of the two velocity components found in the entire GMC suggested that the collision event occurred globally. On the basis of the above results, we herein propose a hypothesis that the collision between the two components occurred sequentially over the last several $10^{6}$ yr and triggered the formation of O-type stars in the NGC6611 cluster.

astro-ph.GA↗

arXiv2020

Element Stratification in the Middle-Aged Type Ia Supernova Remnant G344.7-0.1

Despite their importance, a detailed understanding of Type Ia supernovae (SNe Ia) remains elusive. X-ray measurements of the element distributions in supernova remnants (SNRs) offer important clues for understanding the explosion and nucleosynthesis mechanisms for SNe Ia. However, it is challenging to observe the entire ejecta mass in X-rays for young SNRs, because the central ejecta may not have been heated by the reverse shock yet. Here we present over 200 kilosecond Chandra observations of the Type Ia SNR G344.7-0.1, whose age is old enough for the reverse shock to have reached the SNR center, providing an opportunity to investigate the distribution of the entire ejecta mass. We reveal a clear stratification of heavy elements with a centrally peaked distribution of the Fe ejecta surrounded by intermediate-mass elements (IMEs: Si, S, Ar Ca) with an arc-like structure. The centroid energy of the Fe K emission is marginally lower in the central Fe-rich region than in the outer IME-rich regions, suggesting that the Fe ejecta were shock-heated more recently. These results are consistent with the prediction for standard SN Ia models, where the heavier elements are synthesized in the interior of an exploding white dwarf. We find, however, that the peak location of the Fe K emission is slightly offset to the west with respect to the geometric center of the SNR. This apparent asymmetry is likely due to the inhomogeneous density distribution of the ambient medium, consistent with our radio observations of the ambient molecular and neutral gas.

astro-ph.HE↗

arXiv2020

Near-infrared [FeII] and H2 line mapping of the supernova remnant IC443 with the IRSF/SIRIUS

We investigate properties of the interstellar medium (ISM) interacting with shocks around the Galactic supernova remnant IC443, using the results of near-infrared [FeII] and H2 line mapping with the IRSF/SIRIUS. In the present study, we newly performed H2 1-0 S(1) and 2-1 S(1) line mapping with the narrow-band filters tuned for these lines, covering the entire remnant (30'x35'). Combined with an [FeII] line map, our result shows that the H2 line emission is significantly detected in the southern region, while the [FeII] line emission is detected all over the remnant, suggesting that slow and fast shocks propagate through the southern region and the entire remnant, respectively. In particular, the H2 line emission is relatively strong compared to the [FeII] line emission in the southwestern region, where TeV gamma-ray emission is detected. As the strong H2 line emission indicates the dominance of the dense ISM, this result supports the scenario that the gamma-ray emission is likely to be produced through a heavy interaction between cosmic-ray protons and the dense ISM in the southwestern shell. We also find that the H2 and [FeII] line emissions show an anti-correlated spatial distribution in the same region, suggesting the presence of the clumpy ISM. Such a clumpy morphology of the ISM around IC443 may assist cosmic-ray protons to efficiently interact with large amounts of the ISM protons.

astro-ph.GA↗

arXiv2020

ALMA CO Observations of a Giant Molecular Cloud in M33: Evidence for High-Mass Star Formation Triggered by Cloud-Cloud Collisions

We report the first evidence for high-mass star formation triggered by collisions of molecular clouds in M33. Using the Atacama Large Millimeter/submillimeter Array, we spatially resolved filamentary structures of giant molecular cloud 37 in M33 using $^{12}$CO($J$ = 2-1), $^{13}$CO($J$ = 2-1), and C$^{18}$O($J$ = 2-1) line emission at a spatial resolution of $\sim$2 pc. There are two individual molecular clouds with a systematic velocity difference of $\sim$6 km s$^{-1}$. Three continuum sources representing up to $\sim$10 high-mass stars with the spectral types of B0V-O7.5V are embedded within the densest parts of molecular clouds bright in the C$^{18}$O($J$ = 2-1) line emission. The two molecular clouds show a complementary spatial distribution with a spatial displacement of $\sim$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 HII regions. Our new finding in M33 indicates that the cloud-cloud collision is a promising process to trigger high-mass star formation in the Local Group.

astro-ph.GA↗

arXiv2020

ALMA Observations of Giant Molecular Clouds in M33 I: Resolving Star Formation Activities in the Giant Molecular Filaments Possibly Formed by a Spiral Shock

We report molecular line and continuum observations toward one of the most massive giant molecular clouds (GMCs), GMC-16, in M33 using ALMA with an angular resolution of 0$''$44 $\times$ 0$''$27 ($\sim$2 pc $\times$ 1 pc). We have found that the GMC is composed of several filamentary structures in $^{12}$CO and $^{13}$CO ($J$ = 2-1). The typical length, width, and total mass are $\sim$50-70 pc, $\sim$5-6 pc, and $\sim$10$^{5}$ $M_{\odot}$, respectively, which are consistent with those of giant molecular filaments (GMFs) as seen in the Galactic GMCs. The elongations of the GMFs are roughly perpendicular to the direction of the galaxy's rotation, and several H$\;${\sc ii} regions are located at the downstream side relative to the filaments with an offset of $\sim$10-20 pc. These observational results indicate that the GMFs are considered to be produced by a galactic spiral shock. The 1.3 mm continuum and C$^{18}$O ($J$ = 2-1) observations detected a dense clump with the size of $\sim$2 pc at the intersection of several filamentary clouds, which is referred to as the $"$hub filament,$"$ possibly formed by a cloud-cloud collision. A strong candidate for protostellar outflow in M33 has also been identified at the center of the clump. We have successfully resolved the parsec-scale local star formation activity in which the galactic scale kinematics may induce the formation of the parental filamentary clouds.

astro-ph.GA↗

arXiv2020

Triggered high-mass star formation in the HII region W28A2: A cloud-cloud collision scenario

We report on a study of the high-mass star formation in the the HII region W28A2 by investigating the molecular clouds extended over ~5-10 pc from the exciting stars using the 12CO and 13CO (J=1-0) and 12CO (J=2-1) data taken by the NANTEN2 and Mopra observations. These molecular clouds consist of three velocity components with the CO intensity peaks at V_LSR ~ -4 km s$^{-1}$, 9 km s$^{-1}$ and 16 km s$^{-1}$. The highest CO intensity is detected at V_LSR ~ 9 km s$^{-1}$, where the high-mass stars with the spectral types of O6.5-B0.5 are embedded. We found bridging features connecting these clouds toward the directions of the exciting sources. Comparisons of the gas distributions with the radio continuum emission and 8 um infrared emission show spatial coincidence/anti-coincidence, suggesting physical associations between the gas and the exciting sources. The 12CO J=2-1 to 1-0 intensity ratio shows a high value (> 0.8) toward the exciting sources for the -4 km s$^{-1}$ and +9 km s$^{-1}$ clouds, possibly due to heating by the high-mass stars, whereas the intensity ratio at the CO intensity peak (V_LSR ~ 9 km s$^{-1}$) lowers down to ~0.6, suggesting self absorption by the dense gas in the near side of the +9 km s$^{-1}$ cloud. We found partly complementary gas distributions between the -4 km s$^{-1}$ and +9 km s$^{-1}$ clouds, and the -4 km s$^{-1}$ and +16 km s$^{-1}$ clouds. The exciting sources are located toward the overlapping region in the -4 km s$^{-1}$ and +9 km s$^{-1}$ clouds. Similar gas properties are found in the Galactic massive star clusters, RCW 38 and NGC 6334, where an early stage of cloud collision to trigger the star formation is suggested. Based on these results, we discuss a possibility of the formation of high-mass stars in the W28A2 region triggered by the cloud-cloud collision.

astro-ph.GA↗

arXiv2020

FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN). VI. Dense gas and mini-starbursts in the W43 giant molecular cloud complex

We performed new large-scale $^{12}$CO, $^{13}$CO, and C$^{18}$O $J=$1--0 observations of the W43 giant molecular cloud complex in the tangential direction of the Scutum arm ($l\sim {30^\circ}$) as a part of the FUGIN project. The low-density gas traced by $^{12}$CO is distributed over 150 pc $\times$ 100 pc ($l \times b$), and has a large velocity dispersion (20-30 km s$^{-1}$). However, the dense gas traced by C$^{18}$O is localized in the W43 Main, G30.5, and W43 South (G29.96-0.02) high-mass star-forming regions in the W43 GMC complex, which have clumpy structures. We found at least two clouds with a velocity difference of $\sim$ 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 $^{13}$CO $J=$ 3-2 to $J =$ 1-0 intensity ratio and morphological correspondence with the infrared dust emission. The velocity separation of these clouds in W43 Main, G30.5, and W43 South is too large for each cloud to be gravitationally bound. We also revealed that the dense gas in the W43 GMC has a high local column density, while "the current SFE" of entire the GMC is low ($\sim 4\%$) compared with the W51 and M17 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 W43 GMC complex.

astro-ph.GA↗