arXiv subjects

K. Tachihara

Publications and source records attributed to K. Tachihara.

At least 19 recordsLinked to original sources

arXiv2026

Molecular and Atomic Gas Associated with the Gamma Ray Supernova Remnant RCW 103

We present a study of the interstellar molecular and atomic gas associated with the gamma-ray supernova remnant (SNR) RCW 103 using the Mopra $^{12}$CO($J$ = 1-0), Atacama Large Millimeter/submillimeter Array $^{13}$CO($J$ = 1-0), and the Australia Telescope Compact Array & Parkes HI data. We find that CO clouds in the velocity range from $-58.7$ to $-43.5$ km s$^{-1}$ show a clear spatial correspondence with the X-ray shell of RCW 103, particularly extending from the northwestern to the southeastern regions. The position-velocity diagram of the CO emission reveals an expanding gas motion with an expansion velocity of $\Delta V \sim$$7.5$ km s$^{-1}$, which may have been produced by shock waves and/or stellar winds from the progenitor system. We estimate the total cosmic-ray proton energy to be $\sim$$3.0^{+1.1}_{-0.6} \times 10^{47}$ erg, adopting a total interstellar proton density of $\sim$$810$ cm$^{-3}$. This value is more than an order of magnitude lower than those inferred for other gamma-ray emitting SNRs of comparable age. Given that a substantial amount of dense gas remains within the interior of RCW 103, where thermal X-ray emission is dominant, our results possibly suggest that a significant fraction of the shock energy may have been converted into thermal energy via gas heating, thereby reducing the efficiency of cosmic-ray acceleration.

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arXiv2026

Accelerated gas flow along Ophiuchus B44 filament: Breaking Position-Position-Velocity degeneracy

(Abridged) Stellar feedback from massive stars in the Upper-Sco has been proposed to have reshaped the gas in the nearby Ophiuchus complex. In this framework, feedback organizes the gas into two filament types based on their orientation relative to the source of feedback: radial (R-type) filaments, aligned radially to the massive stars, and tangential (T-type) filaments, which are orthogonal to the feedback direction. A key prediction of this scenario is that gas within R-type filaments should flow longitudinally away from the massive stars. In this paper, we test this scenario by measuring the three-dimensional gas flow inside the potential R-type filament B44, combining the 3D orientation of the filament from Gaia-based 3D dust maps with radial velocities from CO observations. We find that gas flows longitudinally along the B44 filament away from the massive stars in Upper-Sco with both tracers yielding consistent velocity fields. This result confirms B44 is a R-type filament formed by stellar feedback from Sco-Cen with an implied filament assembly timescale of $\sim$3~Myr, well within the age of the Upper-Sco massive stars. Moreover, we find that the gas motion along B44 and away from the massive stars is accelerated with $a\sim$1.8~km/s/Myr ($\sim 6 \times 10^{-11}$~m/s$^2$). This acceleration is compatible with the accelerations recorded along the Sco-Cen cluster chains over the past $\sim$15~Myr, indicating that B44 is likely a present-day, gas-phase counterpart of the same feedback-driven process that produced those stellar sequences. We further find evidence for a shock at the wind-facing head of the filament, with a deprojected flow Mach number of $\sim$2 and a matching density jump. Our findings demonstrate that Gaia 3D dust maps can lift the line-of-sight ambiguity intrinsic to PPV spectral data, enabling direct deprojection of the gas velocity field in coherent filaments.

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arXiv2026

Deep HI observations of cold gas inflow and outflow

A major question in galaxy evolution is how galaxies acquire sufficient gas to sustain their star formation rates. HI observations with high angular resolution and sensitivity to very low column densities are some of the important observational ingredients that are currently still missing. Answers to these questions are necessary for a correct interpretation of observations of galaxy evolution in the high-redshift universe and will provide crucial input for the sub-grid physics in hydrodynamical simulations of galaxy evolutions. In this chapter we discuss the progress that has been made over the past years, describe the various processes that lead to inflow and outflow of gas, and discuss how SKA-Mid AA4 observations can contribute to further understanding these important aspects of galaxy evolution using deep observations of nearby individual disk and dwarf galaxies.

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arXiv2026

Discovery of Molecular and Atomic Gas associated with HESS J1646-458 (Westerlund 1): Spatial TeV Gamma-Ray and Interstellar Proton Correspondence

We report CO and HI studies of molecular and atomic gas toward the TeV gamma-ray source HESS J1646$-$458, widely considered to be associated with the young massive cluster Westerlund 1 (Wd1). We found that molecular clouds at $V_\mathrm{LSR} \sim$$-32$ km s$^{-1}$ coincide with arc-like structures seen at 8 $\mu$m, likely illuminated by strong FUV radiation from Wd1. $^{12}$CO($J$ = 3-2) emission at the same velocity reveals a cavity-like structure with an expansion velocity of $\sim$$5$ km s$^{-1}$ toward the central region of Wd1, suggesting a recently formed wind-blown bubble driven by the cluster. We also identify a complementary spatial distribution between the $V_\mathrm{LSR} \sim$$-55$ and $\sim$$-32$ km s$^{-1}$ clouds, connected by an intermediate-velocity component at $V_\mathrm{LSR} \sim$$-44$ km s$^{-1}$. These characteristics are consistent with signatures of triggered star formation through a cloud-cloud collision and imply that both clouds are physically associated with Wd1. On larger scales, the total interstellar proton column density at $V_\mathrm{LSR}$ $\sim$$-36$-$-23$ km s$^{-1}$ shows a moderate spatial correspondence with the TeV gamma-ray shell. Together with this correlation, a substantial gas mass of $\sim$$1.6 \times 10^6$ $M_\odot$, and the absence of bright synchrotron X-rays, the TeV gamma-ray emission surrounding Wd1 is consistent with the hadronic origin. The present finding allows us to calculate the total energy of accelerated cosmic-ray protons to be $\sim$$6 \times 10^{49}$ erg.

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arXiv2024

Cloud-Cloud Collision: Formation of Hub-Filament Systems and Associated Gas Kinematics; Mass-collecting cone: A new signature of Cloud-Cloud Collision

Massive star-forming regions (MSFRs) are commonly associated with hub-filament systems (HFSs) and sites of cloud-cloud collision (CCC). Recent observational studies of some MSFRs suggest a possible connection between CCC and the formation of HFSs. To understand this connection, we analyzed the magneto-hydrodynamic simulation data from Inoue et al. (2018). This simulation involves the collision of a spherical turbulent molecular cloud with a plane-parallel sea of dense molecular gas at a relative velocity of about 10 km/s. Following the collision, the turbulent and non-uniform cloud undergoes shock compression, rapidly developing filamentary structures within the compressed layer. We found that CCC can lead to the formation of HFSs, which is a combined effect of turbulence, shock compression, magnetic field, and gravity. The collision between the cloud components shapes the filaments into a cone and drives inward flows among them. These inward flows merge at the vertex of the cone, rapidly accumulating high-density gas, which can lead to the formation of massive star(s). The cone acts as a mass-collecting machine, involving a non-gravitational early process of filament formation, followed by gravitational gas attraction to finalize the HFS. The gas distribution in the position-velocity (PV) and position-position spaces highlights the challenges in detecting two cloud components and confirming their complementary distribution if the colliding clouds have a large size difference. However, such CCC events can be confirmed by the PV diagrams presenting gas flow toward the vertex of the cone, which hosts gravitationally collapsing high-density objects, and by the magnetic field morphology curved toward the direction of the collision.

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arXiv2024

High-mass star formation in the Large Magellanic Cloud triggered by colliding HI flows

The galactic tidal interaction is a possible mechanism to trigger the active star formation in galaxies. The recent analyses using the HI data in the Large Magellanic Cloud (LMC) proposed that the tidally driven HI 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, 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 the pressure may be a key parameter in star formation.

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arXiv2023

ALMA Observations of Supernova Remnant N49 in the Large Magellanic Cloud. II. Non-LTE Analysis of Shock-heated Molecular Clouds

We present the first compelling evidence of shock-heated molecular clouds associated with the supernova remnant (SNR) N49 in the Large Magellanic Cloud (LMC). Using $^{12}$CO($J$ = 2-1, 3-2) and $^{13}$CO($J$ = 2-1) line emission data taken with the Atacama Large Millimeter/Submillimeter Array, we derived the H$_2$ number density and kinetic temperature of eight $^{13}$CO-detected clouds using the large velocity gradient approximation at a resolution of 3.5$''$ (~0.8 pc at the LMC distance). The physical properties of the clouds are divided into two categories: three of them near the shock front show the highest temperatures of ~50 K with densities of ~500-700 cm$^{-3}$, while other clouds slightly distant from the SNR have moderate temperatures of ~20 K with densities of ~800-1300 cm$^{-3}$. The former clouds were heated by supernova shocks, but the latter were dominantly affected by the cosmic-ray heating. These findings are consistent with the efficient production of X-ray recombining plasma in N49 due to thermal conduction between the cold clouds and hot plasma. We also find that the gas pressure is roughly constant except for the three shock-engulfed clouds inside or on the SNR shell, suggesting that almost no clouds have evaporated within the short SNR age of ~4800 yr. This result is compatible with the shock-interaction model with dense and clumpy clouds inside a low-density wind bubble.

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arXiv2023

Giant molecular clouds and their Type classification in M74: Toward understanding star formation and cloud evolution

We investigated the giant molecular clouds (GMCs) in M74 (NGC 628), using data obtained from the PHANGS project. We applied the 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 $10^{37.5}~\mathrm{erg~s^{-1}}$, and Type III with $L_\mathrm{H\alpha}$ greater than $10^{37.5}~\mathrm{erg~s^{-1}}$. A total of 432 GMCs were identified, with 59, 201, and 172 GMCs, for Type 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 Type I to III. Clusters younger than 4 Myr and HII 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 LMC. Based on a steady-state assumption, the estimated evolutionary timescales of Type 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 M74, they did not define a GMC, reaching an evolutionary picture with a 20 Myr duration of the non-star-forming phase, which was five times longer than 4 Myr. We compare the present results with those of Chevance et al. (2020) and argue that defining individual GMCs is essential for understanding GMC evolution.

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arXiv2022

Molecular and Atomic Clouds Associated with the Gamma-Ray Supernova Remnant Puppis A

We have carried out a study of the interstellar medium (ISM) toward a shell-like supernova remnant SNR Puppis A by using the NANTEN CO and ATCA HI data. We synthesized a comprehensive picture of the SNR radiation by combining the ISM data with the gamma-ray and X-ray distributions. The ISM, both atomic and molecular gas, is dense and highly clumpy, and is distributed all around the SNR, but mainly in the north-east. The CO distribution revealed an enhanced line intensity ratio of CO($J$ = 2-1)/($J$ = 1-0) transitions as well as CO line broadening, which indicate shock heating/acceleration. The results support that Puppis A is located at 1.4 kpc, in the local arm. The ISM interacting with the SNR has a large mass of $\sim$10$^{4}$ $M_{\odot}$ which is dominated by HI, showing good spatial correspondence with the Fermi-LAT gamma-ray image. This favors the hadronic origin of the gamma-rays, while additional contribution of the leptonic component is not excluded. The distribution of the X-ray ionization timescales within the shell suggests that the shock front ionized various parts of the ISM at epochs ranging over a few to ten 1000 yr. We therefore suggest that the age of the SNR is around 10$^{4}$ yr as given by the largest ionization timescale. We estimate the total cosmic ray energy $W_{\rm p}$ to be 10$^{47}$ erg, which is well placed in the cosmic-ray escaping phase of an age-$W_{\rm p}$ plot including more than ten SNRs.

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arXiv2022

Unraveling the observational signatures of cloud-cloud collision and hub-filament systems in W31

To understand the formation process of massive stars, we present a multi-scale and multi-wavelength study of the W31 complex hosting two extended HII regions (i.e., G10.30-0.15 (hereafter, W31-N) and G10.15-0.34 (hereafter, W31-S)) powered by a cluster of O-type stars. Several Class I protostars and a total of 49 ATLASGAL 870 $μ$m dust clumps (at d = 3.55 kpc) are found toward the HII regions where some of the clumps are associated with the molecular outflow activity. These results confirm the existence of a single physical system hosting the early phases of star formation. The Herschel 250 $μ$m continuum map shows the presence of hub-filament system (HFS) toward both W31-N and W31-S. The central hubs harbour HII regions and they are depicted with extended structures (with T$_{\text{d}}$ $\sim$ 25-32 K) in the Herschel temperature map. In the direction of W31-S, an analysis of the NANTEN2 $^{12}$CO(J = 1-0) and SEDIGISM $^{13}$CO(J = 2-1) line data supports the presence of two cloud components around 8 and 16 km s$^{-1}$, and their connection in velocity space. A spatial complementary distribution between the two cloud components is also investigated toward W31-S, where the signposts of star formation, including massive O-type stars, are concentrated. These findings favor the applicability of cloud-cloud collision (CCC) around $\sim$2 Myr ago in W31-S. Overall, our observational findings support the theoretical scenario of CCC in W31, which explains the formation of massive stars and the existence of HFSs.

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arXiv2022

An Expanding Shell of Neutral Hydrogen Associated with SN 1006: Hints for the Single-Degenerate Origin and Faint Hadronic Gamma-Rays

We report new HI observations of the Type Ia supernova remnant SN 1006 using the Australia Telescope Compact Array with an angular resolution of $4.5' \times 1.4'$ ($\sim$2 pc at the assumed SNR distance of 2.2 kpc). We find an expanding gas motion in position-velocity diagrams of HI with an expansion velocity of $\sim$4 km s$^{-1}$ and a mass of $\sim$1000 $M_\odot$. The spatial extent of the expanding shell is roughly the same as that of SN 1006. We here propose a hypothesis that SN 1006 exploded inside the wind-blown bubble formed by accretion winds from the progenitor system consisting of a white dwarf and a companion star, and then the forward shock has already reached the wind wall. This scenario is consistent with the single-degenerate model. We also derived the total energy of cosmic-ray protons $W_\mathrm{p}$ to be only $\sim$1.2-$2.0 \times 10^{47}$ erg by adopting the averaged interstellar proton density of $\sim$25 cm$^{-3}$. The small value is compatible with the relation between the age and $W_\mathrm{p}$ of other gamma-ray supernova remnants with ages below $\sim$6 kyr. The $W_\mathrm{p}$ value in SN 1006 will possibly increase up to several 10$^{49}$ erg in the next $\sim$5 kyr via the cosmic-ray diffusion into the HI wind-shell.

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arXiv2022

The Long Tails of the Pegasus-Pisces Arch Intermediate Velocity Cloud

We present hydrodynamic simulations of the Pegasus-Pisces (PP Arch), an intermediate velocity cloud in our Galaxy. The PP Arch, also known as IVC 86-36, is unique among intermediate and high velocity clouds, because its twin tails are unusually long and narrow. Its -50 km/s line-of-sight velocity qualifies it as an intermediate velocity cloud, but the tails' orientations indicate that the cloud's total three-dimensional speed is at least ~100 km/s. This speed is supersonic in the Reynold's Layer and thick disk. We simulated the cloud as it travels supersonically through the Galactic thick and thin disks at an oblique angle relative to the midplane. Our simulated clouds grow long double tails and reasonably reproduce the H I 21~cm intensity and velocity of the head of the PP Arch. A bow shock protects each simulated cloud from excessive shear and lowers its Reynolds number. These factors may similarly protect the PP Arch and enable the survival of its unusually long tails. The simulations predict the future hydrodynamic behavior of the cloud when it collides with denser gas nearer to the Galactic midplane. It appears that the PP Arch's fate is to deform, dissipate, and merge with the Galactic disk.

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arXiv2021

ALMA CO Observations of the Mixed-Morphology Supernova Remnant W49B: Efficient Production of Recombining Plasma and Hadronic Gamma-rays via Shock-Cloud Interactions

We carried out new CO($J$ = 2-1) observations toward the mixed-morphology supernova remnant (SNR) W49B with the Atacama Large Millimeter/submillimeter Array (ALMA). We found that CO clouds at $\sim$10 km s$^{-1}$ show a good spatial correspondence with synchrotron radio continuum as well as an X-ray deformed shell. The bulk mass of molecular clouds accounts for the western part of the shell, not for the eastern shell where near-infrared H$_2$ emission is detected. The molecular clouds at $\sim$10 km s$^{-1}$ show higher kinetic temperature of $\sim$20-60 K, suggesting that modest shock-heating occurred. The expanding motion of the clouds with $ΔV \sim$6 km s$^{-1}$ was formed by strong winds from the progenitor system. We argue that the barrel-like structure of Fe rich ejecta was possibly formed not only by an asymmetric explosion, but also by interactions with dense molecular clouds. We also found a negative correlation between the CO intensity and the electron temperature of recombining plasma, implying that the origin of the high-temperature recombining plasma in W49B can be understood as the thermal conduction model. The total energy of accelerated cosmic-ray protons $W_\mathrm{p}$ is estimated to be $\sim$$2\times 10^{49}$ erg by adopting an averaged gas density of $\sim$$650\pm200$ cm$^{-3}$. The SNR age-$W_\mathrm{p}$ diagram indicates that W49B shows one of the highest in-situ values of $W_\mathrm{p}$ in the gamma-ray bright SNRs.

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arXiv2021

Associated molecular and atomic clouds with X-ray shell of superbubble 30 Doradus C in the LMC

30 Doradus C is a superbubble which emits the brightest nonthermal X- and TeV gamma-rays in the Local Group. In order to explore detailed connection between the high energy radiation and the interstellar medium, we have carried out new CO and HI observations using the Atacama Large Millimeter$/$Submillimeter Array (ALMA), Atacama Submillimeter Telescope Experiment, and the Australia Telescope Compact Array with resolutions of up to 3 pc. The ALMA data of $^{12}$CO($J$ = 1-0) emission revealed 23 molecular clouds with the typical diameters of $\sim$6-12 pc and masses of $\sim$600-10000 $M_{\odot}$. The comparison with the X-rays of $XMM$-$Newton$ at $\sim$3 pc resolution shows that X-rays are enhanced toward these clouds. The CO data were combined with the HI to estimate the total interstellar protons. Comparison of the interstellar proton column density and the X-rays revealed that the X-rays are enhanced with the total proton. These are most likely due to the shock-cloud interaction modeled by the magnetohydrodynamical simulations (Inoue et al. 2012, ApJ, 744, 71). Further, we note a trend that the X-ray photon index varies with distance from the center of the high-mass star cluster, suggesting that the cosmic-ray electrons are accelerated by one or multiple supernovae in the cluster. Based on these results we discuss the role of the interstellar medium in cosmic-ray particle acceleration.

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arXiv2021

A Kinematic Analysis of the Giant Molecular Complex W3; Possible Evidence for Cloud-Cloud Collisions that Triggered OB Star Clusters in W3 Main and W3(OH)

W3 is one of the most outstanding regions of high-mass star formation in the outer solar circle, including two active star-forming clouds, W3 Main and W3(OH). Based on a new analysis of the $^{12}$CO data obtained at 38$^{\prime\prime}$ resolution, we have found three clouds having molecular mass from 2000 to 8000~$M_\odot$ at velocities, $-50$~km s$^{-1}$, $-43$~km s$^{-1}$, and $-39$~km s$^{-1}$. The $-43$~km s$^{-1}$ cloud is the most massive one, overlapping with the $-39$~km s$^{-1}$ cloud and the $-50$~km s$^{-1}$ cloud toward W3 Main and W3(OH), respectively. In W3 Main and W3(OH), we have found typical signatures of a cloud-cloud collision, i.e., the complementary distribution with/without a displacement between the two clouds and/or a V-shape in the position-velocity diagram. We frame a hypothesis that a cloud-cloud collision triggered the high-mass star formation in each region. The collision in W3 Main involves the $-39$~km s$^{-1}$ cloud and the $-43$~km s$^{-1}$ cloud. The collision likely produced a cavity in the $-43$~km s$^{-1}$ cloud having a size similar to the $-39$~km s$^{-1}$ cloud and triggered the formation of young high-mass stars in IC~1795 2 Myr ago. We suggest that the $-39$~km s$^{-1}$ cloud is still triggering the high-mass objects younger than 1 Myr embedded in W3 Main currently. On the other hand, another collision between the $-50$~km s$^{-1}$ cloud and the $-43$~km s$^{-1}$ cloud likely formed the heavily embedded objects in W3(OH) within $\sim$0.5 Myr ago. The present results favour an idea that cloud-cloud collisions are common phenomena not only in the inner solar circle but also in the outer solar circle, where the number of reported cloud-cloud collisions is yet limited (Fukui et al. 2021, PASJ, 73, S1).

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arXiv2021

Evidence for a Cloud-Cloud Collision in Sh2-233 Triggering the Formation of the High-mass Protostar Object IRAS 05358+3543

We have carried out a new kinematical analysis of the molecular gas in the Sh2-233 region by using the CO $J$ = 2-1 data taken at $\sim$0.5 pc resolution. The molecular gas consists of a filamentary cloud of 5-pc length with 1.5-pc width where two dense cloud cores are embedded. The filament lies between two clouds, which have a velocity difference of 2.6 km s$^{-1}$ and are extended over $\sim$5 pc. We frame a scenario that the two clouds are colliding with each other and compressed the gas between them to form the filament in $\sim$0.5 Myr which is perpendicular to the collision. It is likely that the collision formed not only the filamentary cloud but also the two dense cores. One of the dense cores is associated with the high-mass protostellar candidate IRAS 05358+3543, a representative high-mass protostar. In the monolithic collapse scheme of high mass star formation, a compact dense core of 100 $M_\odot$ within a volume of 0.1 pc radius is assumed as the initial condition, whereas the formation of such a core remained unexplained in the previous works. We argue that the proposed collision is a step which efficiently collects the gas of 100 $M_\odot$ into 0.1 pc radius. This lends support for that the cloud-cloud collision is an essential process in forming the compact high-mass dense core, IRAS 05358+3543.

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arXiv2020

ALMA CO Observations of the Gamma-Ray Supernova Remnant RX J1713.7-3946: Discovery of Shocked Molecular Cloudlets and Filaments at 0.01 pc scales

RX J1713.7-3946 is a unique core-collapse SNR that emits bright TeV gamma-rays and synchrotron X-rays caused by cosmic rays, in addition to interactions with interstellar gas clouds. We report here on results of ALMA $^{12}$CO($J$ = 1-0) observations toward the northwestern shell of the SNR. We newly found three molecular complexes consisting of dozens of shocked molecular cloudlets and filaments with typical radii of $\sim$0.03-0.05 pc and densities of $\sim$$10^4$ cm$^{-3}$. These cloudlets and filaments are located not only along synchrotron X-ray filaments, but also in the vicinity of X-ray hotspots with month or year-scale time variations. We argue that X-ray hotspots were generated by shock-cloudlet interactions through magnetic-field amplification up to mG. The ISM density contrast of $\sim$$10^5$, coexistence of molecular cloudlets and low-density diffuse medium of $\sim$0.1 cm$^{-3}$, is consistent with such a magnetic field amplification as well as a wind-bubble scenario. The small-scale cloud structures also affect hadronic gamma-ray spectra considering the magnetic field amplification on surface and inside clouds.

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arXiv2020

ALMA CO Observations of Gamma-Ray Supernova Remnant N132D in the Large Magellanic Cloud: Possible Evidence for Shocked Molecular Clouds Illuminated by Cosmic-Ray Protons

N132D is the brightest gamma-ray supernova remnant (SNR) in the Large Magellanic Cloud (LMC). We carried out $^{12}$CO($J$ = 1-0, 3-2) observations toward the SNR using the Atacama Large Millimeter/submillimeter Array (ALMA) and Atacama Submillimeter Telescope Experiment. We find diffuse CO emission not only at the southern edge of the SNR as previously known, but also inside the X-ray shell. We spatially resolved nine molecular clouds using ALMA with an angular resolution of $5''$, corresponding to a spatial resolution of $\sim$1 pc at the distance of the LMC. Typical cloud sizes and masses are $\sim$2.0 pc and $\sim$100 $M_\odot$, respectively. High-intensity ratios of CO $J$ = 3-2 / 1-0 $> 1.5$ are seen toward the molecular clouds, indicating that shock-heating has occurred. Spatially resolved X-ray spectroscopy reveals that thermal X-rays in the center of N132D are produced not only behind a molecular cloud, but also in front of it. Considering the absence of a thermal component associated with the forward shock towards one molecular cloud located along the line of sight to the center of the remnant, this suggests that this particular cloud is engulfed by shock waves and is positioned on the near side of remnant. If the hadronic process is the dominant contributor to the gamma-ray emission, the shock-engulfed clouds play a role as targets for cosmic-rays. We estimate the total energy of cosmic-ray protons accelerated in N132D to be $\sim$0.5-$3.8 \times 10^{49}$ erg as a conservative lower limit, which is similar to that observed in Galactic gamma-ray SNRs.

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