Most stars form in multiple systems, with profound implications in numerous astronomical phenomena intrinsically linked to multiplicity. However, our knowledge about the process of how multiple stellar systems form is incomplete and biased toward nearby molecular clouds forming only low-mass stars, which are unrepresentative of the stellar population in the Galaxy. Most stars form within dense cores in clusters alongside high-mass stars (>8 M circle dot), as the Sun likely did. Here we report deep Atacama Large Millimeter/submillimeter Array (ALMA) 1.33 mm dust continuum observations at similar to 160 au spatial resolution, revealing 72 low-mass multiple systems embedded in 23 high-mass cluster-forming regions, as part of the Digging into the Interior of Hot Cores with ALMA survey. We find that the companion separation distribution presents a distinct peak at similar to 1200 au, in contrast to the one at similar to 4000 au observed in nearby low-mass regions. The shorter fragmentation scale can be explained by considering the higher pressure exerted by the surrounding medium, which is higher than the one in low-mass regions, due to the larger turbulence and densities involved. Because the peak of the companion separation distribution occurs at much larger scales than the expected disk sizes, we argue that the observed fragmentation is produced by turbulent core fragmentation. Contrary to predictions, the multiplicity fraction remains constant as the stellar density increases. We propose that in the extremely dense environments where high-mass stars form, dynamical interactions play an important role in disrupting weakly bound systems.

Context. At the end of the long H-burning phase (main sequence), low-mass to intermediate-mass stars evolve into asymptotic giant branch (AGB) stars that can have carbon-rich envelopes depending on the initial C/O ratio. In their circumstellar envelopes (CSEs), dust particles and molecules are formed and shed back to the interstellar space. Therefore, these stars significantly contribute to the galactic astro-chemical evolution. Aims. To shed light on the chemical properties of carbon-rich CSEs, especially carbon- and silicon-bearing molecules, we performed parallel spectral-line surveys of IRC+10216 and CIT 6, the brightest and second-brightest carbon-rich star envelopes on the sky. Methods. We conducted 30−50 GHz observations towards both sources using a high-sensitivity-wide-band extended Q-band receiver (eQ) of the Nobeyama 45−m telescope. We then analysed data of CIT 6 and used data of IRC+10216 for comparison purposes. We applied the rotational-diagram method to derive their rotational temperatures and column densities for HC5N and HC7N. For other molecules, we assumed an excitation temperature to derive their column densities. Results. Molecular column densities in CIT 6 are systematically lower than those of IRC+10216, typically by one order of magnitude. Silicon- and sulfur-bearing species such as SiS and CS show the strongest depletion, whereas carbon-chain molecules (HCnN, C6H) remain relatively prominent, indicating that carbon-chain formation is still efficient in CIT 6. Rotational temperatures are higher in CIT 6, which is consistent with the fact that emission arises from warmer and more compact regions of its envelope. Both sources show low 12C/13C ratios and mildly sub-solar 28Si/29Si values, which are non-solar isotopic ratios. Conclusions. Both envelopes display canonical, carbon-rich AGB chemistry and comparable isotopic compositions. CIT 6, however, shows slightly higher excitation temperatures, stronger carbon-chain growth, and deeper depletion of Si- and S-bearing species. These signatures point to a more evolved circumstellar environment, where dust condensation and shock processing further modulated the molecular composition.

The recent discovery of an excess of luminous galaxies in the early Universe necessitates sensitive and wideband millimeter spectroscopy to understand their rapid growth. To address this, we present the development of the Far-Infrared Nebular Emission Receiver (FINER) for the Large Millimeter Telescope (LMT). The FINER frontend comprises two receivers covering 120-350 GHz (corresponding to ALMA Bands 4+5 and 6+7). The warm optics are designed to enable simultaneous two-band observations. Combined with the 10.24-GHz-wide digital spectrometer array, the system aims to deliver an instantaneous bandwidth approximately five times wider than current ALMA capabilities. We report that the 210-350 GHz receiver has already achieved commissioning-level performance, with sideband rejection further enhanced by the digital sideband separation technique. With installation expected in 2026, we discuss parallel preparations, including integrated testing and commissioning plans for first-look targets.

We study the kinematics of condensations in 30 fields forming high-mass stars with the Atacama Large Millimeter/submillimeter Array at a high resolution of similar to 0.'' 08 on average (similar to 230 au). The presence of disks is important for feeding high-mass stars without feedback halting growth as their masses increase. In the search for velocity gradients resembling rotation that can reveal the presence of disks, we analyze the emission of gas tracers in 49 objects using CH3OH, CH3CN, and tentative detections of HNCO and cis-HCOOH. Most of the velocity distributions show velocity gradients indicative of rotation. We reveal a total of 32 disk candidates, the largest sample to date that has been uniformly analyzed at a few hundred astronomical unit scales in the high-mass regime. Their position-velocity maps are generally asymmetric with one side brighter than the opposite. We successfully fit a power law to the position-velocity maps of the disk candidates and find indices between -0.5 (Keplerian rotation) and -1 (rotation under specific angular momentum conservation) with a median of -0.7. Under Keplerian rotation assumption, we estimate central masses, uncorrected for inclination, ranging between 7 and 45 M-circle dot. Excluding outliers, the disk candidates are relatively more compact (<200 au) and less massive (<5 M-circle dot) than previous results at coarser angular resolution. We calculate an average Toomre-Q parameter and find that most are gravitationally unstable (median of 0.5). We conclude that these observations offer the first opportunity to separate the disk and envelope components of hot cores on a statistically significant sample, and confirm that anisotropic collapse plays a role in feeding high-mass (proto)stars.

We present ∼8–40 μ m SOFIA-FORCAST images of seven regions of “clustered” star formation as part of the SOFIA Massive Star Formation Survey. We identify a total of 34 protostar candidates and build their spectral energy distributions (SEDs). We fit these SEDs with a grid of radiative transfer models based on the turbulent core accretion (TCA) theory to derive key protostellar properties, including initial core mass, M c , clump environment mass surface density, Σ cl , and current protostellar mass, m * . We also carry out empirical graybody (GB) estimation of Σ cl , which allows a case of restricted SED fitting within the TCA model grid. We also release version 2.0 of the open-source Python package sedcreator , which is designed to automate the aperture photometry and SED building and fitting process for sources in clustered environments, where flux contamination from close neighbors typically complicates the process. Using these updated methods, SED fitting yields values of M c ∼ 30–200 M ⊙ , Σ cl,SED ∼ 0.1–3 g cm −2 , and m * ∼ 4–50 M ⊙ . The GB fitting yields smaller values of Σ cl,GB ≲ 1 g cm −2 . From these results, we do not find evidence for a critical Σ cl needed to form massive (≳8 M ⊙ ) stars. However, we do find tentative evidence for a dearth of the most massive ( m * ≳ 30 M ⊙ ) protostars in the clustered regions, suggesting a potential impact of environment on the stellar initial mass function.

We have observed the 13 CH 3 OH 5 1 −4 1 A + , 13 CH 3 OH 14 1 −13 2 A − , and CH 2 DOH 8 2,6 −8 1,7 e 0 lines toward 24 high-mass star-forming regions by using Atacama Large Millimeter/submillimeter Array with an angular resolution of about 0 . ″ 3. This resolution corresponds to a linear scale of 400–1600 au, allowing us to resolve individual cores properly. We detected the 13 CH 3 OH and CH 2 DOH emission near the continuum peaks in many of these regions. From the two 13 CH 3 OH lines, we calculated the temperature toward the 13 CH 3 OH peaks, and confirm that the emission traces hot (>100 K) regions. The N(CH 2 DOH)/N( 12 CH 3 OH) ratio in the observed high-mass star-forming regions is found to be lower than that in low-mass star-forming regions. We have found no correlation between the N(CH 2 DOH)/N( 13 CH 3 OH) or N(CH 2 DOH)/N( 12 CH 3 OH) ratios and either temperatures or distance to the sources, and have also found a source-to-source variation in these ratios. Our model calculations predict that the N(CH 2 DOH)/N( 12 CH 3 OH) ratio in hot cores depends on the duration of the cold phase; the shorter the cold phase, the lower the deuterium fractionation in the hot cores. We have suggested that the lower N(CH 2 DOH)/N( 12 CH 3 OH) ratio in high-mass star-forming regions compared to that in low-mass star-forming regions is due to the shorter duration of the cold phase and that the diversity in the N(CH 2 DOH)/N( 12 CH 3 OH) ratio in high-mass star-forming regions is due to the diversity in the length of the cold prestellar phase, and not the time that the objects have been in the hot core phase.

Context. Hydrogen recombination lines (HRLs) are valuable diagnostics of the physical conditions in ionized regions surrounding high-mass stars. Understanding these lines, including broadening mechanisms and intensity trends, can provide insights into HII region densities, temperatures, and kinematics. Aims. This study aims to investigate the physical properties of ionized gas around massive protostars by analysing the HRLs (Hα and Hβ) in the Q band. Methods. We carried out observations using the Yebes 40m radio telescope in the Q band (30.5–50 GHz) towards six high-mass protostars selected from the SOMA Survey (G45.12+0.13, G45.47+0.05, G28.20−0.05, G35.20−0.74, G19.08−0.29, and G31.28+0.06). The observed line profiles were analysed to assess broadening mechanisms, and electron densities and temperatures were derived. The results were compared with available Q-band data from the TianMa 65-m Radio Telescope (TMRT) that have been reported in the literature, and ALMA Band 1 (35–50 GHz) Science Verification observations towards Orion KL, analysed in this study. Results. A total of eight Hα (n = 51 to 58) and ten Hβ (n = 64 to 73) lines were detected towards G45.12+0.13, G45.47+0.05, and G28.20−0.05; there were no detections in other sources. We derived electron densities of ~1−5 × 106 cm−3 and temperatures of 8000–10 000 K for the sources. However, for Orion KL, we obtained an electron density one order of magnitude lower, while its temperature was found to be more similar. Interestingly, G45.12 and G28.20 show an increasing intensity trend with frequency for both Hα and Hβ transitions, contrary to the decreasing trend observed in Orion KL. Conclusions. The line widths of the detected HRLs indicate contributions from both thermal and dynamical broadening, suggesting the presence of high-temperature ionized gas that is likely kinematically broadened (e.g. due to turbulence, outflows, rapid rotation, or stellar winds). Pressure broadening caused by electron density may also have a minor effect. We discuss different scenarios to explain the measured line widths of the HRLs. The contrasting intensity trends between the sources may reflect variations in local physical conditions or radiative transfer effects, highlighting the need for further investigation through higher-resolution observations and detailed modelling.

We present the results of mapping and single-point spectral scans toward Orion-KL/OMC-1 performed as science demonstrations of a 2 mm superconductor–insulator–superconductor receiver, named the Band 4 Receiver (B4R), installed on the Large Millimeter Telescope (LMT), with a diameter of 50 m. To prove the capabilities of mapping and spectral scans with the B4R on the LMT, commissioning observations were conducted employing the on-the-fly mapping technique toward Orion-KL/OMC-1, which covers a map size of $5{^{\prime}} \times 5{^{\prime}}$. These mapping observations were performed with two frequency settings providing 10 GHz in total (131.4–133.9 and 145.1–147.6 GHz; 136.2–138.7 and 149.9–152.4 GHz) with a frequency resolution of 76.293 kHz. In this study, we conducted spectral line identification analysis for the hot core and compact ridge regions in the Orion-KL with a beam size of $11{^{\prime \prime }}$–$12{^{\prime \prime }}$. We detected nearly 400 emission lines and identified two recombination lines and 29 molecular species, including isotopologues, deuterated molecules, and vibrational excited states, despite the short integration time. These results of line detection are consistent with those of previous studies. The 29 molecular species include nitrogen (N)-bearing complex organic molecules (COMs) and oxygen (O)-bearing COMs. To demonstrate the capability of the B4R in astrochemistry, we conducted detailed analyses of column densities, rotational temperatures, and relative abundances with respect to H$_2$ on two representative COMs, N-bearing C$_2$H$_5$CN and O-bearing CH$_3$OCHO in the central $40{^{\prime \prime }} \times 40{^{\prime \prime }}$ area of the map. The wide bandwidth of 10 GHz enabled the use of 8 and 34 emission lines, respectively. The spatial differences in the physical and chemical properties between the above two molecules were derived at a spatial resolution of ${\sim}12{^{\prime \prime }}$. The B4R on the LMT was successfully demonstrated to be powerful for mapping and spectral scans and to have high potential for the study of interstellar chemistry.

We present a wide-field ( 60 ′ × 30 ′ ) study of a dense region within the Polaris Flare using 12 CO, 13 CO, and C 18 O ( J = 1–0) observations at 15″ resolution, obtained with the Nobeyama 45 m Radio Telescope. The analysis reveals molecular gas formation occurring at column densities up to ∼10 21 cm −2 , evidenced by an anticorrelation between H i and CO distributions, indicating active atomic-to-molecular gas conversion. We found a threshold column density for molecular formation at ∼5 × 10 20 cm −2 , which is common among more evolved molecular clouds. The CO-to-H 2 conversion factor, X CO , was found to be 0.7 × 10 20 H 2 cm −2 (K km s −1 ) −1 , lower than the solar neighborhood average. Our chemical models estimate the cloud’s age to be ∼​​​​​​10 5 –10 6 yr, suggesting an early stage of molecular cloud evolution. This interpretation is consistent with the observed low X CO factor. While virial analysis suggests that the entire cloud is gravitationally unbound, we identified several filamentary structures extending from the main cloud body. These filaments show systematic velocity gradients of 0.5–1.5 km s −1 pc −1 , and analysis of the velocities shows that the molecular gas within them is falling toward the main cloud body, following a freefall model. This suggests ongoing mass accumulation processes through the filaments, demonstrating that gravitational processes can be important even at column densities of ∼10 21 cm −2 .

Carbon-chain species have been widely found in star-forming regions and are considered to form via a bottom-up mechanism in which ionic and atomic carbon (C+ and C) play essential roles. Recent deep line survey observations toward the Cyanpolyyne Peak in Taurus Molecular Cloud-1 (hereafter TMC-1 CP) have achieved the discovery of new carbon-bearing species; e.g., large hydrocarbon rings and species including benzene rings such as cyanobenzene, cyanonaphthalene, and cyanopyrene. The bottom-up mechanism cannot explain their presence and now we need to revisit the carbon chemistry in the interstellar medium (ISM). One possible approach is to explore the carbon chemistry from evolved stars where carbon is ejected into the ISM through the diffuse ISM to the next-generation star-forming regions, or molecular clouds. Combining ALMA and JWST, we will be able to explore carbon chemistry including top-down mechanisms.

We have analyzed the aromatic infrared bands (AIBs) in the 6–11.2 μ m range around the Wolf–Rayet (WR) binary WR 140 ( d = 1.64 kpc) obtained with the James Webb Space Telescope Mid-Infrared Instrument Medium-Resolution Spectrometer (MRS). In WR 140’s circumstellar environment, we have detected AIBs at 6 and 7.7 μ m, which are attributed to C–C stretching modes. These features have been detected in the innermost dust shell (Shell 1; ∼2100 au from WR 140), the subsequent dust shell (Shell 2; ∼5200 au), and “off-shell” regions in the MRS coverage. The 11.2 μ m AIB, which is associated with the C–H out-of-plane bending mode, has been tentatively detected in Shell 2 and the surrounding off-shell positions around Shell 2. We compared the AIB features from WR 140 to spectra of established AIB feature classes A, B, C, and D. The detected features around WR 140 do not agree with these established classes. The peak wavelengths and full width half maxima of the 6 and 7.7 μ m features are, however, consistent with those of R Coronae Borealis stars with hydrogen-poor conditions. We discuss a possible structure of carbonaceous compounds and environments where they form around WR 140. It is proposed that hydrogen-poor carbonaceous compounds initially originate from the carbon-rich WR wind, and the hydrogen-rich stellar wind from the companion O star may provide hydrogen to these carbonaceous compounds.

Context. Hydrogen recombination lines (HRLs) are valuable diagnostics of the physical conditions in ionized regions surrounding high-mass stars. Understanding these lines, including broadening mechanisms and intensity trends, can provide insights into HII region densities, temperatures, and kinematics. Aims. This study aims to investigate the physical properties of ionized gas around massive protostars by analysing the HRLs (H alpha and H beta) in the Q band. Methods. We carried out observations using the Yebes 40m radio telescope in the Q band (30.5-50 GHz) towards six high-mass protostars selected from the SOMA Survey (G45.12+0.13, G45.47+0.05, G28.20-0.05, G35.20-0.74, G19.08-0.29, and G31.28+0.06). The observed line profiles were analysed to assess broadening mechanisms, and electron densities and temperatures were derived. The results were compared with available Q-band data from the TianMa 65-m Radio Telescope (TMRT) that have been reported in the literature, and ALMA Band 1 (35-50 GHz) Science Verification observations towards Orion KL, analysed in this study. Results. A total of eight H alpha (n = 51 to 58) and ten H beta (n = 64 to 73) lines were detected towards G45.12+0.13, G45.47+0.05, and G28.20-0.05; there were no detections in other sources. We derived electron densities of similar to 1-5 x 10(6) cm(-3) and temperatures of 8000-10 000 K for the sources. However, for Orion KL, we obtained an electron density one order of magnitude lower, while its temperature was found to be more similar. Interestingly, G45.12 and G28.20 show an increasing intensity trend with frequency for both H alpha and H beta transitions, contrary to the decreasing trend observed in Orion KL. Conclusions. The line widths of the detected HRLs indicate contributions from both thermal and dynamical broadening, suggesting the presence of high-temperature ionized gas that is likely kinematically broadened (e.g. due to turbulence, outflows, rapid rotation, or stellar winds). Pressure broadening caused by electron density may also have a minor effect. We discuss different scenarios to explain the measured line widths of the HRLs. The contrasting intensity trends between the sources may reflect variations in local physical conditions or radiative transfer effects, highlighting the need for further investigation through higher-resolution observations and detailed modelling.

The Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures (QUARKS) survey observed 139 infrared-bright (IR-bright) massive protoclusters at 1.3 mm wavelength with the Atacama Large Millimeter/submillimeter Array (ALMA). This study investigates clump-to-core fragmentation and searches for candidate high-mass starless cores within IR-bright clumps using combined ALMA 12 m (C-2) and Atacama Compact Array 7 m data, providing ∼1″ (∼0.02 pc at 3.7 kpc) resolution and ∼0.6 mJy beam ^−1 continuum sensitivity (∼0.3 M _⊙ at 30 K). We identified 1562 compact cores from 1.3 mm continuum emission using getsf . Observed linear core separations ( λ _obs ) are significantly less than the thermal Jeans length ( λ _J ), with the λ _obs / λ _J ratios peaking at ∼0.2. This indicates that thermal Jeans fragmentation has taken place within the IR-bright protocluster clumps studied here. The observed low ratio of λ _obs / λ _J ≪ 1 could be the result of evolving core separation or hierarchical fragmentation. Based on associated signatures of star formation (e.g., outflows and ionized gas), we classified cores into three categories: 127 starless, 971 warm, and 464 evolved cores. Two starless cores have masses exceeding 16 M _⊙ , and represent high-mass candidates. The scarcity of such candidates suggests that competitive accretion-type models could be more applicable than turbulent core accretion-type models in high-mass star formation within these IR-bright protocluster clumps.

In the complex Titan atmospheric chemistry, photochemical reactions involving cyanodiacetylene (HC _5 N) may be important as reaction pathways that could lead to the production of amines and aromatic molecules. We carried out a new comprehensive search of HC _5 N in Titan’s atmosphere using Band 6 (215–275 GHz or 1.1–1.4 mm in wavelength) spectroscopic archival data from the Atacama Large Millimeter/submillimeter Array. To search for a faint spectral line feature of HC _5 N, we used a spectral stacking method that integrates different transition data. Integrating six independent observation data sets with a total integration time of ∼15,000 s, we found no statistically significant detection of an HC _5 N spectral feature. Using the Planetary Spectrum Generator for radiative transfer modeling and employing the previously predicted vertical distribution proposed by V. Vuitton et al., E. Lellouch et al., J. C. Loison et al., and V. A. Krasnopolsky, we derived the upper limit column density of HC _5 N, corresponding to 3 σ noise level, to be 0.3–10 × 10 ^13 molecules cm ^–2 above ∼60 km altitude (depending on the assumed vertical profile). The corresponding upper limit of [HC _5 N]/[HC _3 N] ratio value derived from three of four models seem to be lower than that measured in high-mass protostellar objects, possibly due to the lower abundance of C _4 H _2 .

A complete understanding of the initial conditions of high-mass star formation and what processes determine multiplicity requires the study of the magnetic field in young massive cores. Using Atacama Large Millimeter/submillimeter Array (ALMA) 250 GHz polarization observations (0 .'' 3 = 1000 au) and ALMA 220 GHz high-angular-resolution observations (0 .'' 05 = 160 au), we have performed a full energy analysis including the magnetic field at core scales and have assessed what influences the multiplicity inside a massive core previously believed to be in the prestellar phase. With a mass of 31 M circle dot, the G11.92 MM2 core has a young CS molecular outflow with a dynamical timescale of a few thousand years. At high resolution, the MM2 core fragments into a binary system, with a projected separation of 505 au and a binary mass ratio of 1.14. Using the Davis-Chandrasekhar-Fermi method with an angle dispersion function analysis, we estimate in this core a magnetic field strength of 6.2 mG and a mass-to-magnetic-flux ratio of 18. The MM2 core is strongly subvirialized, with a virial parameter of 0.064, including the magnetic field. The high mass-to-magnetic-flux ratio and low virial parameter indicate that this massive core is very likely undergoing runaway collapse, which is in direct contradiction with the core accretion model. The MM2 core is embedded in a filament that has a velocity gradient consistent with infall. In line with clump-fed scenarios, the core can grow in mass at a rate of 1.9-5.6 x 10-4 M circle dot yr-1. In spite of the magnetic field having only a minor contribution to the total energy budget at core scales (a few thousands of astronomical units), it likely plays a more important role at smaller scales (a few hundreds of astronomical units) by setting the binary properties. Considering energy ratios and a fragmentation criterion at the core scale, the binary system could have been formed by core fragmentation. The binary system properties (projected separation and mass ratio), however, are also consistent with radiation-magnetohydrodynamic simulations with super-Alfvenic or supersonic (or sonic) turbulence that form binaries by disk fragmentation.

We report on the results of the on-sky test and science demonstration conducted with the 2 mm receiver system, B4R, on the 50 m Large Millimeter Telescope (LMT), located at an altitude of 4600 m in Mexico. The B4R receiver was developed based on the dual-polarization sideband-separating mixer technology of the Atacama Large Millimeter/submillimeter Array and is equipped with a fast Fourier transform digital spectrometer, XFFTS. The primary science objective is the spectroscopic redshift identification of high-redshift dusty star-forming galaxies, complementing the existing 3 mm Redshift Search Receiver by enabling the detection of multiple carbon monoxide lines. Additionally, the B4R receiver broadens the range of science cases possible with the LMT, including astrochemistry, as the 2 mm band encompasses unique molecular lines such as deuterated molecules and shock tracers. During on-site commissioning in 2018 and 2019, we successfully demonstrated on-the-fly mapping and position-switching observations toward the Orion Molecular Cloud 1 and bright high-redshift dusty star-forming galaxies, respectively. We confirmed that the installed B4R system largely met its basic performance specifications. Furthermore, we measured the LMT’s aperture efficiencies across the entire B4R frequency range (130–160 GHz), finding them to be roughly consistent with expectations based on a surface accuracy of 100 μ m and the receiver optics design. These results with the B4R will enable the most sensitive single-dish spectroscopic observations at 2 mm using the LMT.

We report on the development and commissioning of a new Q-band receiver for the Nobeyama 45 m telescope, covering 30-50 GHz with a receiver noise temperature of about 15 K. We name it eQ (extended Q-band) receiver. The system noise temperatures for observations are measured to be similar to 30 K at 33 GHz and similar to 75 K at 45 GHz. The half-power beam-width (HPBW) is around 38 '' at 43 GHz. To enhance the observation capability, we tested the smoothed bandpass calibration technique and demonstrated that the observation time can be significantly reduced compared to the standard position switch technique. The wide-bandwidth capability of this receiver provides precise determination of rest frequencies for molecular transitions with an accuracy of a few kHz through simultaneous observations of multiple transitions. Particularly, we determined the rest frequency of SO (J(N) = 1(0)-0(1)) to be 30.001542 GHz, along with the rest frequency of CCS (J(N) = 4(3)-3(2)) being 45.379033 GHz, adopting CCS (J(N) = 3(2)-2(1)) at 33.751370 GHz as a reference line. The SO profile shows a double peak shape at the Cyanopolyyne Peak (CP) position of the Taurus Molecular Cloud-1 (TMC-1). The SO peaks coincide well with the CCS sub-components located near the outer parts of the TMC-1 filament. We interpret that the gravitational infall of TMC-1 generates shocks which enhance the SO abundance. The TMC-1 map shows that carbon-chain molecules are more abundant in the southern part of the filament, whereas SO is more abundant in the northern part. The eQ's excellent sensitivity allowed us to detect faint CO (J = 1-0) spectra from the high-redshift object at a redshift of 2.442. Our receiver is expected to open new avenues for high-sensitivity molecular line observations in the Q-band.

Fragmentation contributes to the formation and evolution of stars. Observationally, high-mass stars are known to form multiple-star systems, preferentially in cluster environments. Theoretically, Jeans instability has been suggested to determine characteristic fragmentation scales, and thermal or turbulent motion in the parental gas clump mainly contributes to the instability. To search for such a characteristic fragmentation scale, we have analyzed Atacama Large Millimeter/submillimeter Array (ALMA) 1.33 mm continuum observations toward 30 high-mass star-forming clumps taken by the Digging into the Interior of Hot Cores with ALMA survey. We have identified 573 cores using the dendrogram algorithm and measured the separation of cores by using the Minimum Spanning Tree technique. The core separation corrected by projection effects has a distribution peaked around 5800 au. In order to remove biases produced by different distances and sensitivities, we further smooth the images to a common physical scale and perform completeness tests. Our careful analysis finds a characteristic fragmentation scale of similar to 7000 au, comparable to the thermal Jeans length of the clumps. We conclude that thermal Jeans fragmentation plays a dominant role in determining the clump fragmentation in high-mass star-forming regions, without the need to invoke turbulent Jeans fragmentation.

We present ∼0.″2 (∼80 au) resolution observations of the CO(2–1) and SiO(5–4) lines made with the Atacama large millimeter/submillimeter array toward an extremely young intermediate-mass protostellar source ( t dyn < 1000 yr), MMS 1 located in the Orion Molecular Cloud-3 region. We have successfully imaged a very compact CO molecular outflow associated with MMS 1, having deprojected lobe sizes of ∼1800 au (redshifted lobe) and ∼2800 au (blueshifted lobe). We have also detected an extremely compact (≲1000 au) and collimated SiO protostellar jet within the CO outflow. The maximum deprojected jet speed is measured to be as high as 93 km s −1 . The SiO jet wiggles and displays a chain of knots. Our detection of the molecular outflow and jet is the first direct evidence that MMS 1 already hosts a protostar. The position–velocity diagram obtained from the SiO emission shows two distinct structures: (i) bow shocks associated with the tips of the outflow, and (ii) a collimated jet, showing the jet velocities linearly increasing with the distance from the driving source. Comparisons between the observations and numerical simulations quantitatively share similarities such as multiple-mass ejection events within the jet and Hubble-like flow associated with each mass ejection event. Finally, while there is a weak flux decline seen in the 850 μ m light curve obtained with the James Clerk Maxwell Telescope/SCUBA 2 toward MMS 1, no dramatic flux change events are detected. This suggests that there has not been a clear burst event within the last 8 yr.