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We mapped two molecular cloud cores in the Orion A cloud with the 7 m Array of the Atacama Compact Array (ACA) of the Atacama Large Millimeter/submillimeterArray (ALMA) and with the Nobeyama 45 m radio telescope. These cores have bright N2D+ emission in single-pointing observations with the Nobeyama 45 m radio telescope, have a relatively high deuterium fraction, and are thought to be close to the onset of star formation. One is a star-forming core, and the other is starless. These cores are located along filaments observed in N2H+ and show narrow line widths of 0.41 km s−1 and 0.45 km s−1 in N2D+, respectively, with the Nobeyama 45 m telescope. Both cores were detected with the ALMA ACA 7 m Array in the continuum and molecular lines at Band 6. The starless core G211 shows a clumpy structure with several sub-cores, which in turn show chemical differences. Also, the sub-cores in G211 have internal motions that are almost purely thermal. The starless sub-core G211D, in particular, shows a hint of the inverse P Cygni profile, suggesting infall motion. The star-forming core G210 shows an interesting spatial feature of two N2D+ peaks of similar intensity and radial velocity located symmetrically with respect to the single dust continuum peak. One interpretation is that the two N2D+ peaks represent an edge-on pseudo-disk. The CO outflow lobes, however, are not directed perpendicular to the line connecting both N2D+ peaks. [ABSTRACT FROM AUTHOR]

We have mapped six molecular cloud cores in the Orion A giant molecular cloud (GMC), whose kinetic temperatures range from 10 to 30 K, in CCS and N2H+ with the Nobeyama 45 m radio telescope to study their chemical characteristics. We identified 31 intensity peaks in the CCS and N2H+ emission in these molecular cloud cores. We found, for cores with temperatures lower than ∼ 25 K, that the column density ratio of N(N2H+)/N(CCS) is low toward starless core regions while it is high toward star-forming core regions, in cases where we detected both the CCS and N2H+ emission. This is very similar to the tendency found in dark clouds (kinetic temperature ∼ 10 K). The criterion found in the Orion A GMC is N(N2H+)/N(CCS) ∼ 2–3. In some cases, both CCS and N2H+ emission is detected toward protostars. A secondary late-stage CCS peak in the chemical evolution caused by CO depletion may be a possible explanation for this. We found that the chemical variation of CCS and N2H+ can also be used as a tracer of evolution in warm (10–25 K) GMC cores. On the other hand, some protostars do not accompany N2H+ intensity peaks but are associated with dust continuum emitting regions, suggesting that the N2H+ abundance might be decreased due to CO evaporation in warmer star-forming sites. [ABSTRACT FROM AUTHOR]

The Atacama Large Millimeter/submillimeter Array Survey of Orion Planck Galactic Cold Clumps (ALMASOP) reveals complex nested morphological and kinematic features of molecular outflows through the CO (J = 2−1) and SiO (J = 5−4) emission. We characterize the jet and outflow kinematics of the ALMASOP sample in four representative sources (HOPS 10, 315, 358, and G203.21-11.20W2) through channel maps and position–velocity diagrams (PVDs) parallel and transverse to the outflow axes. The combined CO and SiO emission exhibits the coexistence of the conventional extremely high-velocity jets and shell-like low-velocity cavity walls and new features. More complex, nested bubble-like and filamentary structures in the images and channel maps, triangle-shaped regions near the base of the parallel PVDs, and regions composed of rhombus/oval shapes in the transverse PVDs are also evident. Such features find natural explanations within the bubble structure of the unified model of jet, wind, and ambient medium. The reverse shock cavity is revealed on the PVD base regions, and other features naturally arise within the dynamic postshock region of magnetic interaction. The finer nested shells observed within the compressed wind region reveal previously unnoticed shocked emission between the jet and the conventional large cavity walls. These pseudopulse-produced filamentary features connect to the jetlike knotty blobs, creating an impression of episodicity in mass ejection. SiO emission is enhanced downstream of the reverse shock boundary, with jetlike excitation conditions. Combined, these observed features reveal the extended structures induced by the magnetic interplay between a jet-bearing magnetized wide-angle wind and its ambient magnetized surrounding medium. [ABSTRACT FROM AUTHOR]

We have investigated the physical properties of Planck Galactic Cold Clumps (PGCCs) located in the Galactic Plane, using the JCMT Plane Survey (JPS) and the SCUBA-2 Continuum Observations of Pre-protostellar Evolution (SCOPE) survey. By utilizing a suite of molecular-line surveys, velocities, and distances were assigned to the compact sources within the PGCCs, placing them in a Galactic context. The properties of these compact sources show no large-scale variations with Galactic environment. Investigating the star-forming content of the sample, we find that the luminosity-to-mass ratio (L / M) is an order of magnitude lower than in other Galactic studies, indicating that these objects are hosting lower levels of star formation. Finally, by comparing ATLASGAL sources that are associated or are not associated with PGCCs, we find that those associated with PGCCs are typically colder, denser, and have a lower L / M ratio, hinting that PGCCs are a distinct population of Galactic Plane sources. [ABSTRACT FROM AUTHOR]

Fragmentation during the early stages of high-mass star formation is crucial for understanding the formation of high-mass clusters. We investigated fragmentation within 39 high-mass star-forming clumps as part of the Atacama Large Millimeter/submillimeter Array Survey of 70 μ m Dark High-mass Clumps in Early Stages (ASHES) survey. Considering projection effects, we have estimated core separations for 839 cores identified from the continuum emission and found mean values between 0.08 and 0.32 pc within each clump. We find compatibility of the observed core separations and masses with the thermal Jeans length and mass, respectively. We also present subclump structures revealed by the 7 m array continuum emission. Comparison of the Jeans parameters using clump and subclump densities with the separation and masses of gravitationally bound cores suggests that they can be explained by clump fragmentation, implying the simultaneous formation of subclumps and cores within rather than a step-by-step hierarchical fragmentation. The number of cores in each clump positively correlates with the clump surface density and the number expected from the thermal Jeans fragmentation. We also find that the higher the fraction of protostellar cores, the larger the dynamic range of the core mass, implying that the cores are growing in mass as the clump evolves. The ASHES sample exhibits various fragmentation patterns: aligned, scattered, clustered, and subclustered. Using the Q -parameter, which can help distinguish between centrally condensed and subclustered spatial core distributions, we finally find that in the early evolutionary stages of high-mass star formation, cores tend to follow a subclustered distribution. [ABSTRACT FROM AUTHOR]

Investigating the temperature and density structures of gas in massive protoclusters is crucial for understanding the chemical properties therein. In this study, we present observations of the continuum and thioformaldehyde (H2CS) lines at 345 GHz of 11 massive protoclusters using the Atacama Large Millimeter/submillimeter Array telescope. High spatial resolution and sensitivity observations have detected 145 continuum cores from the 11 sources. H2CS line transitions are observed in 72 out of 145 cores, including line-rich cores, warm cores, and cold cores. The H2 column densities of the 72 cores are estimated from the continuum emission, which are larger than the density threshold value for star formation, suggesting that H2CS can be widely distributed in star-forming cores with different physical environments. The rotation temperature and column density of H2CS are derived using the XCLASS software. The results show that the H2CS abundances increase as temperature rises and higher gas temperatures are usually associated with higher H2CS column densities. The abundances of H2CS are positively correlated with its column density, suggesting that the H2CS abundances are enhanced from cold cores, warm cores, and line-rich cores in star-forming regions. [ABSTRACT FROM AUTHOR]

A correction to the article "THERMAL STARLESS AMMONIA CORE SURROUNDED BY CCS IN THE ORION A CLOUD" that was published in the previous issue is presented.

We imaged two starless molecular cloud cores, TUKH083 and TUKH122, in the Orion A giant molecular cloud in the CCS and NH3 emission with the Very Large Array. TUKH122 contains one NH3 core “TUKH122-n,” which is elongated and has a smooth oval boundary. Where observed, the CCS emission surrounds the NH3 core. This configuration resembles that of the N2H+ and CCS distribution in the Taurus starless core L1544, a well-studied example of a dense prestellar core exhibiting infall motions. The linewidth of TUKH122-n is narrow (0.20 km s–1) in the NH3 emission line and therefore dominated by thermal motions. The smooth oval shape of the core boundary and narrow linewidth in N2H+ seem to imply that TUKH122-n is dynamically relaxed and quiescent. TUKH122-n is similar to L1544 in the kinetic temperature (10 K), linear size (0.03 pc), and virial mass (∼2 M☼). Our results strongly suggest that TUKH122-n is on the verge of star formation. TUKH122-n is embedded in the 0.2 pc massive (virial mass ∼30 M☼) turbulent parent core, while the L1544 NH3 core is embedded in the 0.2 pc less-massive (virial mass ∼10 M☼) thermal parent core. TUKH083 shows complicated distribution in NH3, but was not detected in CCS. The CCS emission toward TUKH083 appears to be extended, and is resolved out in our interferometric observations. [ABSTRACT FROM AUTHOR]

We present a statistical study of a sample of 17 hub-filament-system (HFS) clouds of high-mass star formation using high-angular resolution (∼1–2 arcsec) ALMA 1.3 and 3 mm continuum data. The sample includes eight infrared (IR)-dark and nine IR-bright types, which correspond to an evolutionary sequence from the IR-dark to IR-bright stage. The central massive clumps and their associated most massive cores are observed to follow a trend of increasing mass (M) and mass surface density (Σ) with evolution from the IR-dark to IR-bright stage. In addition, a mass-segregated cluster of young stellar objects (YSOs) are revealed in both IR-dark and IR-bright HFSs with massive YSOs located in the hub and the population of low-mass YSOs distributed over larger areas. Moreover, outflow feedback in all HFSs are found to escape preferentially through the inter-filamentary diffuse cavities, suggesting that outflows would render a limited effect on the disruption of the HFSs and ongoing high-mass star formation therein. From the above observations, we suggest that high-mass star formation in the HFSs can be described by a multiscale mass accretion/transfer scenario, from hub-composing filaments through clumps down to cores, which can naturally lead to a mass-segregated cluster of stars. [ABSTRACT FROM AUTHOR]

We developed a new seven-beam heterodyne receiver "7BEE" in the 72–116 GHz band for the Nobeyama 45 m telescope to investigate the early stage of star formation by deriving the deuterium fraction of dense cores. The optics for the receiver employs wideband corrugated horns covering the 72–116 GHz band and dielectric lenses to couple the incoming radiation from the antenna on to the feeds. One of the important aspects in the lens design is the anti-reflection (AR) structure to mitigate the reflections on the lens surfaces. Triangular grooves, which gradually change the effective refractive index from air to dielectric, were adopted as a basic AR design since the return loss can be in the order of 20 dB or better. The main goal of this study is to compare the radio frequency (RF) characteristics of the lenses with different patterns and sizes of AR grooving structures. We confirmed that concentric grooves degraded beam symmetry, cross-polarization characteristics, and aperture efficiency due to the birefringence of the grooves, which gave rise to wavefront distortions. Straight grooves of two different gap widths, 1.2 mm and 1.7 mm, were compared and showed similar good performance in terms of beam patterns and noise contribution. However, the latter showed a few percent higher aperture efficiency. Therefore, the straight grooves with 1.7 mm gap width were adopted as the AR structure of our lens. [ABSTRACT FROM AUTHOR]

We present ALMA Band-3/7 observations towards 'the Heart' of a massive hub-filament system (HFS) SDC335, to investigate its fragmentation and accretion. At a resolution of ∼0.03 pc, 3 mm continuum emission resolves two massive dense cores MM1 and MM2, with |$383(^{\scriptscriptstyle +234}_{\scriptscriptstyle -120})$|   M ⊙ (10–24 % mass of 'the Heart') and |$74(^{\scriptscriptstyle +47}_{\scriptscriptstyle -24})$|   M ⊙, respectively. With a resolution down to 0.01 pc, 0.87 mm continuum emission shows MM1 further fragments into six condensations and multi-transition lines of H2CS provide temperature estimation. The relation between separation and mass of condensations at a scale of 0.01 pc favors turbulent Jeans fragmentation where the turbulence seems to be scale-free rather than scale-dependent. We use the H13CO+  J  = 1 − 0 emission line to resolve the complex gas motion inside 'the Heart' in position-position-velocity space. We identify four major gas streams connected to large-scale filaments, inheriting the anti-clockwise spiral pattern. Along these streams, gas feeds the central massive core MM1. Assuming an inclination angle of 45(± 15)° and a H13CO+ abundance of 5(± 3) × 10−11, the total mass infall rate is estimated to be 2.40(± 0.78) × 10−3  M ⊙ yr−1, numerically consistent with the accretion rates derived from the clump-scale spherical infall model and the core-scale outflows. The consistency suggests a continuous, near steady-state, and efficient accretion from global collapse, therefore ensuring core feeding. Our comprehensive study of SDC335 showcases the detailed gas kinematics in a prototypical massive infalling clump, and calls for further systematic and statistical studies in a large sample. [ABSTRACT FROM AUTHOR]

We report the first detection of radio recombination lines (RRLs) of ions heavier than helium. In a highly sensitive multi-band (12–50 GHz) line survey toward Orion KL with the TianMa 65-m Radio Telescope (TMRT), we successfully detected more than fifteen unblended α lines of RRLs of singly ionized species (XII) recombined from XIII. The Ka-band (26–35 GHz) spectrum also shows tentative signals of β lines of ions. The detected lines can be successfully crossmatched with the rest frequencies of RRLs of C II and/or O II. This finding greatly expands the scope of our understanding of ion RRLs, since prior to this work, only two blended lines (105α and 121α) of He II had been reported. Our detected lines can be fitted simultaneously under assumption of local thermodynamic equilibrium (LTE). An abundance of C III and O III of 8.8×10−4 was obtained, avoiding the complexities of optical and infrared observations and the blending of RRLs of atoms. It is consistent with but approaches the upper bound of the value (10−4–10−3) estimated from optical and infrared observations. The effects of dielectronic recombination may contribute to enhancing the level populations even at large n. We expect future observations using radio interferometers could break the degeneracy between C and O, while also helping to reveal the ionization structure and dynamical evolution of various ionized regions. [ABSTRACT FROM AUTHOR]

Whether ionization feedback triggers the formation of massive stars is highly debated. Using ALMA 3-mm observations with a spatial resolution of ∼0.05 pc and a mass sensitivity of 1.1  |$\rm M_\odot$|  per beam at 20 K, we investigate the star formation and gas flow structures within the ionizing feedback-driven structure, a clump-scale massive (≳ 1500  |$\rm M_\odot$|⁠) bright-rimmed cloud (BRC) associated with IRAS 18290–0924. This BRC is bound only if external compression from ionized gas is considered. A small-scale (≲ 1 pc) age sequence along the direction of ionizing radiation is revealed for the embedded cores and protostars, which suggests triggered star formation via radiation-driven implosion (RDI). Furthermore, filamentary gas structures converge towards the cores located in the BRC's centre, indicating that these filaments are fueling mass towards cores. The local core-scale mass infall rate derived from H13CO+  J  = 1 − 0 blue profile is of the same order of magnitude as the filamentary mass inflow rate, approximately 1  |$\rm M_\odot$|  kyr−1. A photodissociation region (PDR) covering the irradiated clump surface is detected in several molecules, such as CCH, HCO+, and CS whereas the spatial distribution stratification of these molecules is indistinct. CCH spectra of the PDR possibly indicate a photoevaporation flow leaving the clump surface with a projected velocity of ∼2 km s−1. Our new observations show that RDI accompanied by a clump-fed process is operating in this massive BRC. Whether this combined process works in other massive BRCs is worth exploring with dedicated surveys. [ABSTRACT FROM AUTHOR]

Investigating the physical and chemical structure of massive star-forming regions is critical for understanding the formation and early evolution of massive stars. We performed a detailed line survey toward six dense cores, named MM1, MM4, MM6, MM7, MM8, and MM11, in the G9.62+0.19 star-forming region resolved in Atacama Large Millimeter/submillimeter Array (ALMA) band 3 observations. Toward these cores, about 172 transitions have been identified and attributed to 16 species, including organic oxygen-, nitrogen-, and sulphur-bearing molecules and their isotopologues. Four dense cores, MM7, MM8, MM4, and MM11, are line-rich sources. Modelling of these spectral lines reveals that the rotational temperature lies in the range 72–115, 100–163, 102–204, and 84–123 K for MM7, MM8, MM4, and MM11, respectively. The molecular column densities are 1.6 × 1015–9.2 × 1017 cm−2 toward the four cores. The cores MM8 and MM4 show a chemical difference between oxygen- and nitrogen-bearing species, i.e. MM4 is rich in oxygen-bearing molecules, while nitrogen-bearing molecules, especially vibrationally excited HC3N lines, are mainly observed in MM8. The distinct initial temperatures at the accretion phase may lead to this N/O differentiation. Through analysing column densities and spatial distributions of O-bearing complex organic molecules (COMs), we found that C2H5OH and CH3OCH3 might have a common precursor, CH3OH. CH3OCHO and CH3OCH3 are likely chemically linked. In addition, the observed variation in HC3N and HC5N emission may indicate their different formation mechanisms in hot and cold regions. [ABSTRACT FROM AUTHOR]

We present a comprehensive study of the gas kinematics associated with density structures at different spatial scales in the filamentary infrared dark cloud, G034.43+00.24 (G34). This study makes use of the H13CO+ (1–0) molecular line data from the ALMA Three-millimeter Observations of Massive Star-forming regions (ATOMS) survey, which has spatial and velocity resolution of ∼0.04 pc and 0.2 km s−1, respectively. Several tens of dendrogram structures have been extracted in the position-position-velocity space of H13CO+, which include 21 small-scale leaves and 20 larger-scale branches. Overall, their gas motions are supersonic but they exhibit the interesting behaviour where leaves tend to be less dynamically supersonic than the branches. For the larger scale, branch structures, the observed velocity–size relation (i.e. velocity variation/dispersion versus size) are seen to follow the Larson scaling exponent while the smaller-scale, leaf structures show a systematic deviation and display a steeper slope. We argue that the origin of the observed kinematics of the branch structures is likely to be a combination of turbulence and gravity-driven ordered gas flows. In comparison, gravity-driven chaotic gas motion is likely at the level of small-scale leaf structures. The results presented in our previous paper and this current follow-up study suggest that the main driving mechanism for mass accretion/inflow observed in G34 varies at different spatial scales. We therefore conclude that a scale-dependent combined effect of turbulence and gravity is essential to explain the star-formation processes in G34. [ABSTRACT FROM AUTHOR]

Filaments play an important role in star formation, but the formation process of filaments themselves is still unclear. The high-mass star-forming clump G286.21+0.17 (G286 for short) that contains an 'L' type filament was thought to undergo global collapse. Our high-resolution ALMA band 3 observations resolve the gas kinematics of G286 and reveal two sub-clumps with very different velocities inside it. We find that the 'blue profile' (an indicator of gas infall) of HCO+ lines in single dish observations of G286 is actually caused by gas emission from the two sub-clumps rather than gas infall. We advise great caution in interpreting gas kinematics (e.g. infall) from line profiles towards distant massive clumps in single dish observations. Energetic outflows are identified in G286 but the outflows are not strong enough to drive expansion of the two sub-clumps. The two parts of the 'L' type filament ('NW–SE' and 'NE–SW' filaments) show prominent velocity gradients perpendicular to their major axes, indicating that they are likely formed due to large-scale compression flows. We argue that the large-scale compression flows could be induced by the expansion of nearby giant H  ii regions. The 'NW–SE' and 'NE–SW' filaments seem to be in collision, and a large amount of gas has been accumulated in the junction region where the most massive core G286c1 forms. [ABSTRACT FROM AUTHOR]

With the aim of understanding the role of outflows in star formation, we performed a statistical study of the physical parameters of outflows in 11 massive protoclusters associated with ultracompact H  ii regions. A total of 106 outflow lobes are identified in these protoclusters using the ALMA CO (3–2), HCN (4–3), and HCO+ (4–3) line observations. Although the position angles of outflow lobes do not differ in these three tracers, HCN and HCO+ tend to detect lower terminal velocity of the identified outflows compared to CO. The majority of the outflows in our targets are young with typical dynamical time-scales of 102–104 yr, and are mostly composed of low-mass outflows along with at least one high-mass outflow in each target. An anticorrelation of outflow rate with dynamical time-scale indicates that the outflow rate possibly decreases with time. Also, a rising trend of dynamical time-scale with the mass of the associated core hints that the massive cores might have longer accretion histories than the low-mass cores. Estimation of different energies in these protoclusters shows that outflows studied here cannot account for the generation of the observed turbulence, but can sustain the turbulence at the current epoch as the energy injection rate from the outflows is similar to the estimated dissipation rate. [ABSTRACT FROM AUTHOR]

We present a spatio-kinematical analysis of the CO (J = 2 → 1) line emission, observed with the Atacama Large Millimeter/submillimeter Array (ALMA), of the outflow associated with the most massive core, ALMA1, in the 70 μm dark clump G010.991–00.082. The position–velocity (PV) diagram of the molecular outflow exhibits a peculiar S-shaped morphology that has not been seen in any other star-forming region. We propose a spatio-kinematical model for the bipolar molecular outflow that consists of a decelerating high-velocity component surrounded by a slower component whose velocity increases with distance from the central source. The physical interpretation of the model is in terms of a jet that decelerates as it entrains material from the ambient medium, which has been predicted by calculations and numerical simulations of molecular outflows in the past. One side of the outflow is shorter and shows a stronger deceleration, suggesting that the medium through which the jet moves is significantly inhomogeneous. The age of the outflow is estimated to be τ ≈ 1300 yr, after correction for a mean inclination of the system of ≈57°. [ABSTRACT FROM AUTHOR]

We present a study of outflows at extremely early stages of high-mass star formation obtained from the ALMA Survey of 70 μm dark High-mass clumps in Early Stages (ASHES). Twelve massive 3.6−70 μm dark prestellar clump candidates were observed with the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 6. Forty-three outflows are identified toward 41 out of 301 dense cores using the CO and SiO emission lines, yielding a detection rate of 14%. We discover six episodic molecular outflows associated with low- to high-mass cores, indicating that episodic outflows (and therefore episodic accretion) begin at extremely early stages of protostellar evolution for a range of core masses. The time span between consecutive ejection events is much smaller than those found in more evolved stages, which indicates that the ejection episodicity timescale is likely not constant over time. The estimated outflow dynamical timescale appears to increase with core masses, which likely indicates that more massive cores have longer accretion timescales than less massive cores. The lower accretion rates in these 70 μm dark objects compared to the more evolved protostars indicate that the accretion rates increase with time. The total outflow energy rate is smaller than the turbulent energy dissipation rate, which suggests that outflow-induced turbulence cannot sustain the internal clump turbulence at the current epoch. We often detect thermal SiO emission within these 70 μm dark clumps that is unrelated to CO outflows. This SiO emission could be produced by collisions, intersection flows, undetected protostars, or other motions. [ABSTRACT FROM AUTHOR]

The detailed magnetic field structure of the dense core SL 42 (CrA-E) in the Corona Australis molecular cloud complex was investigated based on near-infrared polarimetric observations of background stars to measure dichroically polarized light produced by magnetically aligned dust grains. The magnetic fields in and around SL 42 were mapped using 206 stars, and curved magnetic fields were identified. On the basis of simple hourglass (parabolic) magnetic field modeling, the magnetic axis of the core on the plane of the sky was estimated to be 40° ± 3°. The plane-of-sky magnetic field strength of SL 42 was found to be 22.4 ± 13.9 μG. Taking into account the effects of thermal/turbulent pressure and the plane-of-sky magnetic field component, the critical mass of SL 42 was obtained to be Mcr = 21.2 ± 6.6 M⊙, which is close to the observed core mass of Mcore ≈ 20 M⊙. We thus conclude that SL 42 is in a condition close to the critical state if the magnetic fields lie near the plane of the sky. Because there is a very low-luminosity object toward the center of SL 42, it is unlikely that this core is in a highly subcritical condition (i.e., the magnetic inclination angle is significantly deviated from the plane of the sky). The core probably started to collapse from a nearly kinematically critical state. In addition to the hourglass magnetic field modeling, the Inoue & Fukui mechanism may explain the origin of the curved magnetic fields in the SL 42 region. [ABSTRACT FROM AUTHOR]

We report the detection of four new hot corino sources, G211.47–19.27S, G208.68–19.20N1, G210.49–19.79W, and G192.12–11.10, from a survey study of Planck Galactic Cold Clumps in the Orion Molecular Cloud Complex with the Atacama Compact Array. Three sources had been identified as low-mass Class 0 protostars in the Herschel Orion Protostar Survey. One source in the λ Orionis region is first reported as a protostellar core. We have observed abundant complex organic molecules (COMs), primarily methanol but also other oxygen-bearing COMs (in G211.47–19.27S and G208.68–19.20N1) and the molecule of prebiotic interest NH2CHO (in G211.47–19.27S), signifying the presence of hot corinos. While our spatial resolution is not sufficient to resolve most of the molecular emission structure, the large line width and high rotational temperature of COMs suggest that they likely reside in the hotter and innermost region immediately surrounding the protostar. In G211.47–19.27S, the D/H ratio of methanol ([CH2DOH]/[CH3OH]) and the 12C/13C ratio of methanol ([CH3OH]/[13CH3OH]) are comparable to those of other hot corinos. Hydrocarbons and long-carbon-chain molecules such as c-C3H2 and HCCCN are also detected in the four sources, likely tracing the outer and cooler molecular envelopes. [ABSTRACT FROM AUTHOR]

The ATOMS, standing for ALMA Three-millimeter Observations of Massive Star-forming regions, survey has observed 146 active star-forming regions with ALMA band 3, aiming to systematically investigate the spatial distribution of various dense gas tracers in a large sample of Galactic massive clumps, to study the roles of stellar feedback in star formation, and to characterize filamentary structures inside massive clumps. In this work, the observations, data analysis, and example science of the ATOMS survey are presented, using a case study for the G9.62+0.19 complex. Toward this source, some transitions, commonly assumed to trace dense gas, including CS J  = 2−1, HCO+ J  = 1−0, and HCN J  = 1−0, are found to show extended gas emission in low-density regions within the clump; less than 25 per cent of their emission is from dense cores. SO, CH3OH, H13CN, and HC3N show similar morphologies in their spatial distributions and reveal well the dense cores. Widespread narrow SiO emission is present (over ∼1 pc), which may be caused by slow shocks from large–scale colliding flows or H  ii regions. Stellar feedback from an expanding H  ii region has greatly reshaped the natal clump, significantly changed the spatial distribution of gas, and may also account for the sequential high-mass star formation in the G9.62+0.19 complex. The ATOMS survey data can be jointly analysed with other survey data, e.g. MALT90, Orion B, EMPIRE, ALMA_IMF, and ALMAGAL, to deepen our understandings of 'dense gas' star formation scaling relations and massive protocluster formation. [ABSTRACT FROM AUTHOR]

We report studies of the relationships between the total bolometric luminosity (L bol or L TIR) and the molecular line luminosities of J  = 1 − 0 transitions of H13CN, H13CO+, HCN, and HCO+ with data obtained from ACA observations in the 'ATOMS' survey of 146 active Galactic star-forming regions. The correlations between L bol and molecular line luminosities |$L^{\prime }_{\rm mol}$| of the four transitions all appear to be approximately linear. Line emission of isotopologues shows as large scatters in L bol– |$L^{\prime }_{\rm mol}$| relations as their main line emission. The log(L bol/ |$L^{\prime }_{\rm mol}$|⁠) for different molecular line tracers have similar distributions. The L bol-to- |$L^{\prime }_{\rm mol}$| ratios do not change with galactocentric distances (R GC) and clump masses (M clump). The molecular line luminosity ratios (HCN-to-HCO+, H13CN-to-H13CO+, HCN-to-H13CN, and HCO+-to-H13CO+) all appear constant against L bol, dust temperature (T d), M clump, and R GC. Our studies suggest that both the main lines and isotopologue lines are good tracers of the total masses of dense gas in Galactic molecular clumps. The large optical depths of main lines do not affect the interpretation of the slopes in star formation relations. We find that the mean star formation efficiency (SFE) of massive Galactic clumps in the 'ATOMS' survey is reasonably consistent with other measures of the SFE for dense gas, even those using very different tracers or examining very different spatial scales. [ABSTRACT FROM AUTHOR]

We analyze the HCO+ 3-2 and H13CO+ 3-2 line profiles of 27 high-mass star-forming regions to identify asymmetries that are suggestive of mass inflow. Three quantitative measures of line asymmetry are used to indicate whether a line profile is blue, red, or neither--the ratio of the temperature of the blue and red peaks, the line skew, and the dimensionless parameter δv. We find nine HCO+ 3-2 line profiles with a significant blue asymmetry and four with significant red asymmetric profiles. Comparing our HCO+ 3-2 results to HCN 3-2 observations from Wu et al., we find that eight of the blue and three of the red have profiles with the same asymmetry in HCN. The eight sources with blue asymmetries in both tracers are considered strong candidates for inflow. Quantitative measures of the asymmetry (e.g., δv) tend to be larger for HCN. This, combined with possible HCO+ abundance enhancements in outflows, suggests that HCN may be a better tracer of inflow. Understanding the behavior of common molecular tracers like HCO+ in clumps of different masses is important for properly analyzing the line profiles seen in a sample of sources representing a broad range of clump masses. Such studies will soon be possible with the large number of sources with possible self-absorption seen in spectroscopic follow-up observations of clumps identified in the Bolocam Galactic Plane Survey. [ABSTRACT FROM AUTHOR]

The magnetic field structure, kinematical stability, and evolutionary status of the starless dense core Barnard 68 (B68) are revealed based on the near-infrared polarimetric observations of background stars, measuring the dichroically polarized light produced by aligned dust grains in the core. After subtracting unrelated ambient polarization components, the magnetic fields pervading B68 are mapped using 38 stars and axisymmetrically distorted hourglass-like magnetic fields are obtained, although the evidence for the hourglass field is not very strong. On the basis of simple 2D and 3D magnetic field modeling, the magnetic inclination angles on the plane-of-sky and in the line-of-sight direction are determined to be 47° ± 5° and 20° ± 10°, respectively. The total magnetic field strength of B68 is obtained to be |$26.1 \pm 8.7\, \mu \mbox{G}$|⁠. The critical mass of B68, evaluated using both magnetic and thermal/turbulent support, is |$M_{\rm cr} = 2.30 \pm 0.20\, {M}_{\odot }$|⁠ , which is consistent with the observed core mass of |$M_{\rm core}=2.1\, M_{\odot }$|⁠ , suggesting a nearly critical state. We found a relatively linear relationship between polarization and extinction up to AV ∼ 30 mag toward the stars with deepest obscuration. Further theoretical and observational studies are required to explain the dust alignment in cold and dense regions in the core. [ABSTRACT FROM AUTHOR]

The formation scenario of brown dwarfs is still unclear because observational studies to investigate its initial condition are quite limited. Our systematic survey of nearby low-mass star-forming regions using the Atacama Compact Array (aka the Morita array) and the IRAM 30-m telescope in 1.2 mm continuum has identified a centrally concentrated starless condensation with a central H2 volume density of ∼106 cm−3, MC5-N, connected to a narrow (width ∼0.03 pc) filamentary cloud in the Taurus L1495 region. The mass of the core is |$\sim {0.2\!-\!0.4}\, M_{\odot }$|⁠ , which is an order of magnitude smaller than typical low-mass pre-stellar cores. Taking into account a typical core to star formation efficiency for pre-stellar cores (∼20%–40%) in nearby molecular clouds, brown dwarf(s) or very low-mass star(s) may be going to be formed in this core. We have found possible substructures at the high-density portion of the core, although much higher angular resolution observation is needed to clearly confirm them. The subsequent N2H+ and N2D+ observations using the Nobeyama 45-m telescope have confirmed the high-deuterium fractionation (∼30%). These dynamically and chemically evolved features indicate that this core is on the verge of proto-brown dwarf or very low-mass star formation and is an ideal source to investigate the initial conditions of such low-mass objects via gravitational collapse and/or fragmentation of the filamentary cloud complex. [ABSTRACT FROM AUTHOR]

We investigate the effects of supergiant shells (SGSs) and their interaction on dense molecular clumps by observing the Large Magellanic Cloud (LMC) star-forming regions N48 and N49, which are located between two SGSs, LMC 4 and LMC 5. 12CO (J = 3-2, 1-0) and 13CO(J = 1-0) observations with the ASTE and Mopra telescopes have been carried out toward these regions. A clumpy distribution of dense molecular clumps is revealed with 7 pc spatial resolution. Large velocity gradient analysis shows that the molecular hydrogen densities (n(H2)) of the clumps are distributed from low to high density (103-105 cm–3) and their kinetic temperatures (Tkin) are typically high (greater than 50 K). These clumps seem to be in the early stages of star formation, as also indicated from the distribution of Hα, young stellar object candidates, and IR emission. We found that the N48 region is located in the high column density H I envelope at the interface of the two SGSs and the star formation is relatively evolved, whereas the N49 region is associated with LMC 5 alone and the star formation is quiet. The clumps in the N48 region typically show high n(H2) and Tkin, which are as dense and warm as the clumps in LMC massive cluster-forming areas (30 Dor, N159). These results suggest that the large-scale structure of the SGSs, especially the interaction of two SGSs, works efficiently on the formation of dense molecular clumps and stars. [ABSTRACT FROM AUTHOR]

We report on spatially resolved X-ray spectroscopy of the north-eastern part of the mixed morphology supernova remnant (SNR) W 28 with XMM-Newton. The observed field of view includes a prominent and twisted shell emission forming the edge of this SNR as well as part of the center-filled X-ray emission brightening toward the south-west edge of the field of view. The shell region spectra are in general represented by an optically thin thermal plasma emission in collisional ionization equilibrium with a temperature of ∼ 0.3 keV and a density of ∼ 10 cm−3, which is much higher than the density obtained for inner parts. In contrast, we detected no significant X-ray flux from one of the TeV γ-ray peaks with an upper-limit flux of 2.1 × 10−14 erg cm−2 s−1 in the 2–10 keV band. The large flux ratio of TeV to X-ray, larger than 16, and the spatial coincidence of the molecular cloud and the TeV γ-ray emission site indicate that the TeV γ-ray of W 28 is π0-decay emission originating from collisions between accelerated protons and molecular cloud protons. Comparing the spectrum in the TeV band and the X-ray upper limit, we obtained a weak upper limit on the magnetic field strength B ≲ 1500 μG. [ABSTRACT FROM AUTHOR]

We have developed a 1.2 m submillimeter-wave telescope at the summit of Mt. Fuji to survey emission lines of the neutral carbon atom (C[sub I]) toward the Milky Way. A superconductor-insulator-superconductor mixer receiver on the Nasmyth focus is used to observe the 492 GHz band in SSB and the 345 GHz band in DSB simultaneously. The receiver noise temperature is 300 K in SSB and 200 K in DSB for 492 and 345 GHz, respectively. The intermediate frequency frequency is 1.8-2.5 GHz. An acousto-optical spectrometer which has the total bandwidth of 0.9 GHz and 1024 channel outputs has also been developed. The telescope was installed at the summit of Mt. Fuji (alt. 3725 m) in July 1998. It has been remotely operated via a satellite communication system from Tokyo or Nobeyama. Atmospheric opacity at Mt. Fuji was 0.4-1.0 at 492 GHz during 30% of the time and 0.07-0.5 at 345 GHz during 60% of the time from November 1998 to February 1999. The system noise temperature was 1000-3000 K in SSB at 492 GHz and 500-2000 K in DSB at 345 GHz. We observed the CI ([sup 3]P[sub 1]-[sup 3]P[sub 0]: 492 GHz) and CO (J=3-2: 345 GHz) emission lines from nearby molecular clouds with the beam size of 2&arcmin;2 and 3&arcmin;1, respectively. We describe the telescope system and report the performance obtained in the 1998 winter. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]