arXiv subjects

Kengo Tachihara

Publications and source records attributed to Kengo Tachihara.

At least 19 recordsLinked to original sources

arXiv2026

ALMA Observations of DEM L241/LMC P3 in the Large Magellanic Cloud: Evidence for the Formation of Cool Molecular Jets Driven by a Microquasar

We present ALMA observations of DEML 241/LMC P3, the most luminous $\gamma$-ray binary consisting of a compact object and an O star, in CO emission. We have found an one-sided jet-like CO feature of 8 pc length and 1 pc width, which accompanies another weaker CO jet candidate with slightly different orientation. The one-sided CO jet exhibits striking alignment with LMC P3, suggesting that the jet was driven by LMC P3. We have determined kinetic temperature of the CO jet to be significantly high at 33$-$60 K as compared with $\sim$15 K in the nearby non-jet CO cloud whereas no radiative heat source is found. We interpret that the high temperatures are due to shock heating of a microquasar jet driven by the $\gamma$-ray binary, where the compact object has an accretion disk fed by the O star winds. The CO jet matches existing predictions from magneto-hydrodynamical simulations, which show that CO jet can form from the interaction of the microquasar jet and an ambient ISM cloud. These results provide strong evidence that CO jets are a signature sculptured by microquasar jets, lending support for mass accretion in LMC P3 as the $\gamma$-ray origin. The results suggest a second case of CO jets potentially driven by a microquasar along with the CO jets in the microquasar candidate HESS J1023-575 recently identified in the Milky Way. Further, our results suggest the use of sub-mm observations for identifying microquasars, opening a new possible window for their discovery and study.

astro-ph.HE↗

arXiv2026

Search for Seeds of The Cradle of Stars: Study of The Evolution From Atomic to Molecular Hydrogen Clouds with 1000 AU Scale Resolution

The aim of this science case for SKA1-Mid is to elucidate the spatial and velocity structure of the Cold Neutral Medium (CNM) on scales below the Field length, thereby elucidating the physical processes that govern CNM structure formation and its role in the earliest stages of molecular cloud formation. This goal will be achieved through a unique observational combination of several-arcsecond angular resolution, high velocity resolution, and unprecedented surface-brightness sensitivity. These observations will reveal the characteristic size, morphology, velocity structure, and internal dynamics of CNM clumps, and will directly connect such structures to the earliest phases of the atomic to molecular transition. Full-polarization observations with SKA1-Mid will also enable emission-based Zeeman measurements of the CNM, allowing the magnetic field strength to be mapped and opening a new window on the role of magnetic fields in CNM formation and evolution. In particular, this will make it possible to determine whether magnetic fields primarily inhibit fragmentation by supporting the gas against compression, or instead guide anisotropic condensation and promote the development of small-scale CNM structure through thermal instability. In combination with interferometric spatial filtering and high spectral resolution, SKA1-Mid will selectively trace the CNM and robustly identify individual clumps in both position and velocity space. These capabilities will provide decisive tests of thermal instability and the two-phase turbulence model, and will establish a new observational foundation for understanding how molecular clouds emerge from the multi-phase atomic interstellar medium.

astro-ph.GA↗

arXiv2026

Discovery of CO Clouds Associated with the X-ray Jets of SS 433: Evidence for Shock-Cloud Interaction Enhancing Nonthermal X-ray Emission

We report the first identification of molecular clumps directly associated with the re-brightening regions of the large-scale X-ray jets of SS 433, based on $^{12}$CO ($J$ = 1--0) observations with the Nobeyama 45-m Radio Telescope. Multiple clumps are detected toward the eastern and western jet heads, showing clear spatial correlation with the X-ray emission. The X-ray emission peaks immediately downstream of the molecular clumps, while the hardness ratio is enhanced at their surfaces, indicating that the observed structures cannot be explained by absorption effects. These results provide direct evidence for shock--cloud interactions between the jets and the surrounding interstellar medium. We suggest that turbulence generated at the jet--cloud interface amplifies magnetic fields, producing the observed non-thermal X-ray emission. Our findings highlight the importance of jet--ISM interactions in shaping the X-ray properties of microquasar jets.

astro-ph.HE↗

arXiv2026

A multi-scale molecular and atomic gas view on the HII region N113 in the Large Magellanic Cloud:Evidence for high-mass star formation triggered by supersonically-colliding HI flows

The Large Magellanic Cloud (LMC) exhibits vigorous high-mass star formation, including the HII regions 30~Dor that is the most active site of star formation in the local group. The present paper focuses on the Giant Molecular Cloud (GMC) in the HII region N113 in the central part of the LMC. Based on the $^{12}$CO($J$ =1-0) and $^{13}$CO($J$ = 1-0) data at a resolution of approximately 0.2 pc taken with ALMA+APEX, we reveal that the GMC consists of two filamentary structures each of approximately 10 pc in length, forming a V-shape pattern with a vertex angle of 90 degrees. The filamentary structures host high-mass young stellar objects in gravitationally bound dense gas. Large-scale HI gas data covering 100 pc reveal two distinct velocity components separated by more than 40 km s$^{-1}$, that correspond to the low velocity (L-) and disk (D-) HI components of the LMC. The L-component appears to be located in a cavity-like distribution of the D-component, and the CO filaments are positioned at the cavity's edge. We find evidence for the L-component to fit the cavity by a 53 pc displacement, and suggest that collisional compression of the HI gas during the last 1.3 Myr triggered the GMC formation and the high-mass star formation. This lends support for the large scale collision driven by the tidal interaction is playing a role in evolution of interstellar medium in N113.

astro-ph.GA↗

arXiv2026

Mapping of the Cold Neutral Medium via HI Phase Separation in an Atomic Cloud Undergoing Molecular Cloud Formation

We investigate the atomic-to-molecular gas transition in the molecular cloud formation region HLCG 92-35 using GALFA-H I and NANTEN 12CO(J=1-0) observations. The HI spectra were decomposed into Cold Neutral Medium (CNM), Lukewarm Neutral Medium (LNM), and Warm Neutral Medium (WNM) components with the ROHSA algorithm, and CNM structures were identified using Astrodendro. The derived HI mass ratio is CNM:LNM:WNM = 43:47:10, indicating that a substantial fraction of the gas resides in the intermediate-temperature phase. We identify 1792 CNM clumps with characteristic sizes of ~1-2 pc and average densities of ~ 80 cm^{-3}, broadly consistent with theoretical predictions for CNM structures formed through thermal instability. The CNM mass spectrum exhibits a power-law slope similar to that of CO clumps, suggesting that molecular clouds inherit the hierarchical structure established in the atomic phase. Significant non-thermal linewidths and localized CNM-CO velocity offsets imply that the CNM consists of small-scale cloudlets with distinct kinematic properties. These results provide observational support for a scenario in which small-scale CNM structures produced by thermal instability and turbulent flows represent an early stage of molecular cloud formation.

astro-ph.GA↗

arXiv2026

ALMA Band 9 CO(6--5) Reveals a Warm Ring Structure Associated with the Embedded Protostar in the Cold Dense Core MC 27/L1521F

Infall and outflows, coupled with magnetic fields, rapidly structure the gas around newborn protostars. Shocks from interacting components encode the temperature and density distribution, offering a direct probe of the earliest evolution history. However, interferometric observations characterizing warm envelopes using high-excitation lines remain scarce. We present ALMA Band 9 observations of the Taurus dense core MC 27/L1521F, which hosts a Class 0 protostar, targeting the CO($J$=6-5) line at an angular resolution of $\sim$2\arcsec\ ($\approx$300 au). We detect an off-centered ring-like structure with a diameter of $\sim$1000 au that was not identifiable in previous low-$J$ CO data, where emission close to the systemic velocity is strongly affected by optical depth. The ring shows a typical peak brightness temperature of $\sim$3 K at our resolution. Excitation considerations indicate that the detected CO($J$=6-5) emission likely arises from relatively warm ($T \gtrsim 20$ K) and dense ($n({\rm H_2}) \gtrsim 10^{5}$ cm$^{-3}$) gas embedded within the surrounding cold, dense core. The morphology and kinematics suggest an energetic and localized shock-heating event, potentially linked to dynamical gas--magnetic-field interactions in the earliest protostellar phase. Our results demonstrate that high-$J$ CO observations provide a powerful new window on warm and dense gas components, enabling a more direct view of the physical processes operating at the onset of star formation.

astro-ph.GA↗

arXiv2026

Ring-Gap Structures in the Class I Circumstellar Disk of CrA IRS 2 Associated with Magnetic Flux-Driven Bubble

Recent ALMA observations with 0''.1 resolution reveal characteristic substructures in circumstellar disks around young Class I sources, providing clues to the early stages of morphological disk evolution. In this paper, we applied PRIISM imaging to ALMA archival Band 6 continuum data of the circumstellar disk around the Class I protostar CrA IRS 2, located in the Corona Australis molecular cloud, which is associated with an extended gas ring attributed to magnetic flux advection driven by interchange instability. The dust continuum image with 1.5 times higher spatial resolution than conventional imaging revealed, for the first time, the early-phase circumstellar disk with both inner central hole and outer ring-gap structures, making CrA IRS 2 the youngest system exhibiting such features based on the bolometric temperature of $T_{\rm bol}$=235 K. To examine planet-disk interaction as one possible origin of the outer ring-gap structure, we found the measured depth and width to be consistent with planet-disk interaction models, suggesting the existence of a giant planet with a mass of 0.1-1.8 $M_{\rm Jup}$. The additional mechanism required for rapid planet formation could be the magnetic flux dissipation driven by the interchange instability, which suppresses MRI-driven turbulence and extends the dead zone, allowing efficient dust growth and the early formation of planets. This system thus provides new insight into how substructures and planet formation can emerge during the early, accreting phase of disk evolution.

astro-ph.EP↗

arXiv2025

Head-tail molecular clouds falling onto the Milky Way disk

We report discovery of two CO clouds which 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 $l=331.6^{\circ}$ 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 $4.8\times 10^3\ M_{\odot}$ and $3.5\times 10^3\ M_{\odot}$, respectively, and show kinetic temperature 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 of the 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 onto the Milky Way disk and are significantly heated up by the strong shock interaction with the disk HI gas. We suggest that the clouds represent part of the HI intermediate velocity clouds falling to the Galactic plane which were converted into molecular clouds by shock compression. This is the first case of falling CO clouds having direct observed signatures of the falling motion including clear directivity and shock heating. Possible implications of the CO clouds in the evolution of the Galactic interstellar medium are discussed.

astro-ph.GA↗

arXiv2025

Extended and Compact Ortho-H$_2$D$^+$ Structures Close to the Moment of Star-Formation: Evidence from ALMA-ACA Observations in Taurus

Observing and characterizing pre- and protostellar cores in the earliest and densest stages of star formation is challenging due to their short timescales and high densities, limiting the suitable tracers and targets. We conducted ALMA-Atacama Compact Array (ACA) stand-alone observations of ortho-H$_2$D$^+$ (1$_{\rm 1,0}$-1$_{\rm 1,1}$) emission, which is believed to trace cold high-density regions, toward three dense cores in the Taurus molecular cloud: (1) L1544, likely in the densest prestellar phase; (2) MC 35-mm, a candidate for the first hydrostatic core; and (3) MC 27/L1521F, which hosts a Class 0 very-low luminosity object. These observations provide high angular resolution data for the line across a set of cores selected to represent consecutive stages around the onset of star formation, offering a unique opportunity to trace the time evolution of $\sim$10$^4$ years. With the single-dish total-power array, we detected ortho-H$_2$D$^+$ emission in all three cores, revealing its presence over scales of $\sim$10,000 au. In the interferometric 7 m array data with a beam size of 3.$''$5 ($\sim$500\,au), emission was detected only toward the central continuum source of MC 35-mm, with a significance of $\sim$3$\sigma$. No significant detections were found in the other targets, placing an upper limit on the H$_2$D$^{+}$ abundance of $\sim$10$^{-11}$ in the dense components traced by the interferometric continuum emission. These results suggest that ortho-H$_2$D$^+$ predominantly exhibits an extended distribution over several thousand au in the early stages of star formation. Detection in compact, dense central structures may only be achieved within a few $\times$ 10$^{4}$ years immediately before or after protostar formation.

astro-ph.GA↗

arXiv2025

A catalog of molecular clouds possibly associated with Galactic infrared bubbles I. The Southern Galactic plane

We have carried out a morphological search for molecular clouds possibly associated with 48 Galactic infrared bubbles with angular radii of $>1'$ in the southern Galactic plane of $295^\circ \le l\le 350^\circ$ and $|b|\le 1^\circ$ presented by Hanaoka et al. (2019). 116 molecular clouds in the $(l,b,V_{\rm LSR})$ space are identified from the archival $^{12}$CO~$J$~=~1--0 line data obtained by the Mopra Southern Galactic plane survey, where $V_{\rm LSR}$ is the CO-line radial velocity. The kinematic distances are derived from $V_{\rm LSR}$ using the most accurate rotation curve of the Milky Way. We also present measurements of velocity dispersion, size parameter, molecular mass, and virial mass of 116 molecular clouds. This catalog is presented to investigate star formation and the origin of molecular shells and cavities, possibly associated with infrared bubbles. CO line intensity maps and position-velocity diagrams of the molecular clouds are available online as supplementary data.

astro-ph.GA↗

arXiv2025

Dual Directional Expansion of Classical Cepheids in the Small Magellanic Cloud Revealed by Gaia DR3

We present the three-dimensional kinematics of classical Cepheids (CCs) in the Small Magellanic Cloud (SMC) using Gaia DR3 data. By cross-matching the CCs obtained from the fourth phase of the Optical Gravitational Lensing Experiment with Gaia DR3, we obtain distances and proper motions (PMs) for 4,236 CCs. Among them, 91 stars with available radial velocities (RVs) enable the construction of accurate relationship between distance and RV. Furthermore, we calculate the internal PMs of the CCs, providing the internal dynamics of the SMC while removing the distance projection effects. The CCs exhibit a northeast-southwest distance gradient, with internal PMs pointing northeast for nearer stars and southwest for more distant stars, indicating a northeast-southwest elongation. The RVs of the CCs show a northwest-southeast gradient, consistent with RVs of other stellar populations and suggesting that the SMC's northwest-southeast elongation results from interactions with the Large Magellanic Cloud. The distances and RVs of the CCs are nearly uncorrelated, implying that the two elongations arise from distinct causes.

astro-ph.GA↗

arXiv2025

Evidence of Galactic Interaction in the Small Magellanic Cloud Probed by Gaia Selected Massive Star Candidates

We present identifications and kinematic analysis of 7,426 massive ($\mathrm{\geq}8M_{\odot}$) stars in the Small Magellanic Cloud (SMC), using Gaia DR3 data. We used Gaia ($G_\mathrm{BP}-G_\mathrm{RP}$, $G$) color-magnitude diagram to select the population of massive stars, and parallax to omit foreground objects. The spatial distribution of the 7,426 massive star candidates is generally consistent with the spatial distribution of the interstellar medium, such as H$\alpha$ and H i emission. The identified massive stars show inhomogeneous distributions over the galaxy, showing several superstructures formed by massive stars with several hundred parsecs scale. The stellar superstructures defined by the surface density have opposite mean proper motions in the east and west, moving away from each other. Similarly, the mean line-of-sight velocities of the superstructures are larger to the southeast and smaller to the northwest. The different east-west properties of the superstructures' proper motion, line-of-sight velocity indicate that the SMC is being stretched by tidal forces and/or ram pressure from the Large Magellanic Cloud to the southeast, thereby rejecting the presence of galaxy rotation in the SMC.

astro-ph.GA↗

arXiv2025

Giant Molecular Clouds in RCW 106 (G333): Galactic Mini-starbursts and Massive Star Formation Induced by Supersonic Cloud-Cloud Collisions

To reveal the origin of the mini-starbursts in the Milky Way, we carried out large-scale CO observations toward the RCW 106 giant molecular cloud (GMC) complex using the NANTEN2 4-m radio telescope operated by Nagoya University. We also analyzed the Mopra Southern Galactic plane CO survey and Herschel infrared continuum archival data. The RCW 106 GMC complex contains the radial velocity components of $-68$ km s$^{-1}$ and $-50$ km s$^{-1}$ reported by Nguyen et al. (2015). Focusing on the RCW 106 East and West region with the massive star formation having the bright infrared dust emission, we found that these regions have three different velocity components with $\sim 10$ km s$^{-1}$ differences. The two out of three velocity components show morphological correspondence with the infrared cold dust emission and connect with the bridge feature on a position-velocity diagram. Therefore, two molecular clouds (MCs) with $\sim 10$ km s$^{-1}$ differences are likely to be physically associated with massive star-forming regions in the GMC complex. Based on these observational results, we argue that mini-starbursts and massive star/cluster formation in the RCW 106 GMC complex are induced by supersonic cloud-cloud collisions in an agglomerate of molecular gas on the Scutum-Centaurus arm.

astro-ph.GA↗

arXiv2024

ACA CO(J=2-1) Mapping of the Nearest Spiral Galaxy M33. II. Exploring the Evolution of Giant Molecular Clouds

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 M33 from ALMA-ACA survey, we classified 848 GMCs into three types based on the association with HII regions and their H$\alpha$ luminosities $\textit{L}$(H$\alpha$): Type I is associated with no HII regions; Type II with HII regions of $\textit{L}$(H$\alpha$) $<$ 10$^{37.5}$ erg s$^{-1}$; and Type III with HII regions of $\textit{L}$(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 the GMC lifetime of 22 Myr by assuming that Type II GMC has the same timescale as the Large Magellanic Cloud. The evolved GMCs concentrate on the spiral arms, while the younger GMCs are apart from the arm both to the leading and trailing sides. This indicated that GMCs collide with each other by 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.

astro-ph.GA↗

arXiv2024

Internal 1000 AU-scale Structures of the R CrA Cluster-forming Cloud -- I: Filamentary Structures

We report on ALMA ACA observations of a high-density region of the Corona Australis cloud forming a young star cluster, and the results of resolving internal structures. In addition to embedded Class 0/I protostars in continuum, a number of complex dense filamentary structures are detected in the C18O and SO lines by the 7m array. These are sub-structures of the molecular clump that are detected by the TP array as the extended emission. We identify 101 and 37 filamentary structures with a few thousand AU widths in C18O and SO, respectively, called as feathers. The typical column density of the feathers in C18O is about 10^{22} cm^{-2}, and the volume density and line mass are ~ 10^5 cm^{-3}, and a few times M_{sun} pc^{-1}, respectively. This line mass is significantly smaller than the critical line mass expected for cold and dense gas. These structures have complex velocity fields, indicating a turbulent internal property. The number of feathers associated with Class 0/I protostars is only ~ 10, indicating that most of them do not form stars but rather being transient structures. The formation of feathers can be interpreted as a result of colliding gas flow as the morphology well reproduced by MHD simulations, supported by the the presence of HI shells in the vicinity. The colliding gas flows may accumulate gas and form filaments and feathers, and trigger the active star formation of the R CrA cluster.

astro-ph.GA↗

arXiv2024

Discovery of Asymmetric Spike-like Structures of the 10 au Disk around the Very Low-luminosity Protostar Embedded in the Taurus Dense Core MC 27/L1521F with ALMA

Recent Atacama Large Millimeter/submillimeter Array (ALMA) observations have revealed an increasing number of compact protostellar disks with radii of less than a few tens of astronomical units and that young Class 0/I objects have an intrinsic size diversity. To deepen our understanding of the origin of such tiny disks, we performed the highest-resolution configuration observations with ALMA at a beam size of $\sim$0$''$03 (4 au) on the very low-luminosity Class 0 protostar embedded in the Taurus dense core MC 27/L1521F. The 1.3 mm continuum measurement successfully resolved a tiny, faint ($\sim$1 mJy) disk with a major axis length of $\sim$10 au, one of the smallest examples in the ALMA protostellar studies. In addition, we detected spike-like components in the northeastern direction at the disk edge. Gravitational instability or other fragmentation mechanisms cannot explain the structures, given the central stellar mass of $\sim$0.2 $M_{\odot}$ and the disk mass of $\gtrsim$10$^{-4}$ $M_{\odot}$. Instead, we propose that these small spike structures were formed by a recent dynamic magnetic flux transport event due to interchange instability that would be favorable to occur if the parental core has a strong magnetic field. The presence of complex arc-like structures on a larger ($\sim$2000 au) scale in the same direction as the spike structures suggests that the event was not single. Such episodic, dynamical events may play an important role in maintaining the compact nature of the protostellar disk in the complex gas envelope during the main accretion phase.

astro-ph.SR↗

arXiv2023

Ring Gap Structure around Class I Protostar WL 17

WL 17 is a Class I object and was considered to have a ring-hole structure. We analyzed the structure around WL 17 to investigate the detailed properties of WL 17. We used ALMA archival data, which have a higher angular resolution than previous observations. We investigated the WL 17 system with the 1.3 mm dust continuum and 12CO and C18O (J = 2-1) line emissions. The dust continuum emission showed a clear ring structure with inner and outer edges of ~11 and ~21 au, respectively. In addition, we detected an inner disk of < 5 au radius enclosing the central star within the ring, the first observation of this structure. Thus, WL 17 has a ring-gap structure, not a ring-hole structure. We did not detect any marked emission in either the gap or inner disk, indicating that there is no sign of a planet, circumplanetary disk, or binary companion. We identified the base of both blue-shifted and red-shifted outflows based on the 12CO emission, which is clearly associated with the disk around WL 17. The outflow mass ejection rate is ~3.6x10^-7 Msun yr-1 and the dynamical timescale is as short as ~ 10^4 yr. The C18O emission showed that an inhomogeneous infalling envelope, which can induce episodic mass accretion, is distributed in the region within ~1000 au from the central protostar. With these new findings, we can constrain the planet formation and dust growth scenarios in the accretion phase of star formation.

astro-ph.SR↗

arXiv2023

The Gamma Ray Origin in RXJ0852.0-4622 Quantifying the Hadronic and Leptonic Components: Further Evidence for the Cosmic Ray Acceleration in Young Shell-type SNRs

Fukui et al. (2021) quantified the hadronic and leptonic gamma rays in the young TeV gamma ray shell-type supernova remnant (SNR) RXJ1713.7-3946 (RXJ1713), and demonstrated that the gamma rays are a combination of the hadronic and leptonic gamma ray components with a ratio of $\sim 6:4$ in gamma ray counts $N_\mathrm{g}$. This discovery, which adopted a new methodology of multiple-linear gamma-ray decomposition, was the first quantification of the two gamma ray components. In the present work, we applied the same methodology to another TeV gamma ray shell-type SNR RX~J0852.0$-$4622 (RXJ0852) in the 3D space characterized by [the interstellar proton column density $N_{\mathrm{p}}$]-[the nonthermal X-ray count $N_{\mathrm{x}}$]-[$N_{\mathrm{g}}$], and quantified the hadronic and leptonic gamma ray components to have a ratio of $\sim 5:5$ in $N_{\mathrm{g}}$. The present work adopted fitting of two/three flat planes in the 3D space instead of a single flat plane, which allowed to suppress fitting errors. The quantification indicates that the hadronic and leptonic gamma rays are in the same order of magnitude in these two core-collapse SNRs, verifying the significant hadronic gamma ray components. We argue that the target interstellar protons, in particular their spatial distribution, are essential in any attempts to identify type of particles responsible for the gamma-ray emission. The present results confirm that the CR energy $\lesssim 100$\,TeV is compatible with a scheme that SNRs are the dominant source of these Galactic CRs.

astro-ph.HE↗