ABSTRACT
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
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
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
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
We report studies of the relationships between the total bolometric luminosity (Lbol or LTIR) 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 Lbol 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 Lbol–$L^{\prime }_{\rm mol}$ relations as their main line emission. The log(Lbol/$L^{\prime }_{\rm mol}$) for different molecular line tracers have similar distributions. The Lbol-to-$L^{\prime }_{\rm mol}$ ratios do not change with galactocentric distances (RGC) and clump masses (Mclump). The molecular line luminosity ratios (HCN-to-HCO+, H13CN-to-H13CO+, HCN-to-H13CN, and HCO+-to-H13CO+) all appear constant against Lbol, dust temperature (Td), Mclump, and RGC. 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
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
We present new 3-mm continuum and molecular lines observations from the ATOMS survey towards the massive protostellar clump, MM1, located in the filamentary infrared dark cloud (IRDC), ...G034.43+00.24 (G34). The lines observed are the tracers of either dense gas (e.g. HCO+/H13CO+ J= 1–0) or outflows (e.g. CS J= 2–1). The most complete picture to date of seven cores in MM1 is revealed by dust continuum emission. These cores are found to be gravitationally bound, with virial parameter, αvir < 2. At least four outflows are identified in MM1 with a total outflowing mass of ∼45 M⊙, and a total energy of 1 × 1047 erg, typical of outflows from a B0-type star. Evidence of hierarchical fragmentation, where turbulence dominates over thermal pressure, is observed at both the cloud and the clump scales. This could be linked to the scale-dependent, dynamical mass inflow/accretion on clump and core scales. We therefore suggest that the G34 cloud could be undergoing a dynamical mass inflow/accretion process linked to the multiscale fragmentation, which leads to the sequential formation of fragments of the initial cloud, clumps, and ultimately dense cores, the sites of star formation.
Abstract
During the transition phase from a prestellar to a protostellar cloud core, one or several protostars can form within a single gas core. The detailed physical processes of this transition, ...however, remain unclear. We present 1.3 mm dust continuum and molecular line observations with the Atacama Large Millimeter/submillimeter Array toward 43 protostellar cores in the Orion molecular cloud complex (
λ
Orionis, Orion B, and Orion A) with an angular resolution of ∼0.″35 (∼140 au). In total, we detect 13 binary/multiple systems. We derive an overall multiplicity frequency (MF) of 28% ± 4% and a companion star fraction (CSF) of 51% ± 6%, over a separation range of 300–8900 au. The median separation of companions is about 2100 au. The occurrence of stellar multiplicity may depend on the physical characteristics of the dense cores. Notably, those containing binary/multiple systems tend to show a higher gas density and Mach number than cores forming single stars. The integral-shaped filament of the Orion A giant molecular cloud (GMC), which has the highest gas density and hosts high-mass star formation in its central region (the Orion Nebula cluster), shows the highest MF and CSF among the Orion GMCs. In contrast, the
λ
Orionis GMC has a lower MF and CSF than the Orion B and Orion A GMCs, indicating that feedback from H
ii
regions may suppress the formation of multiple systems. We also find that the protostars comprising a binary/multiple system are usually at different evolutionary stages.
Abstract
We have selected six sources (G209.55–19.68S2, G205.46–14.56S1
-
A, G203.21–11.20W2, G191.90–11.21S, G205.46–14.56S3, and G206.93–16.61W2) from the Atacama Large Millimeter/submillimeter ...Array Survey of Orion Planck Galactic Cold Clumps (ALMASOP), in which these sources have been mapped in the CO (
J
= 2−1), SiO (
J
= 5−4), and C
18
O (
J
= 2−1) lines. These sources have high-velocity SiO jets surrounded by low-velocity CO outflows. The SiO jets consist of a chain of knots. These knots have been thought to be produced by semiperiodic variations in jet velocity. Therefore, we adopt a shock-forming model, which uses such variations to estimate the inclination angle and velocity of the jets. We also derive the inclination angle of the CO outflows using the wide-angle wind-driven shell model and find it to be broadly consistent with that of the associated SiO jets. In addition, we apply this shock-forming model to another three protostellar sources with SiO jets in the literature—HH 211, HH 212, and L1448C(N)—and find that their inclination angle and jet velocity are consistent with those previously estimated from proper-motion and radial-velocity studies.
Microvascular complications are much earlier and common in diabetes. Advanced glycation end products (AGEs), together with high glucose, play a key role in the endothelial dysfunction of diabetic ...vascular complications. So it is of more significance to expedite the therapies to block the formation and/or the effects of AGEs. Berberine has been showed to have anti-diabetic effects, however the effects on diabetic complications were less explored, especially the effects on the microvascular complications and the formation and pathways of AGEs which have not been reported. Therefore, the present study established an in vitro model of diabetic microendothelial (microEC) injury by the combination of high glucose and AGEs to mimic the clinical situations and examine the effects and mechanisms of berberine on high glucose-AGEs-induced microEC injuries and on the formation of AGEs. We prepared AGEs, established the high glucose-AGEs injured microEC models by MTT assay, which was further supported by significantly decreased nitric oxide (NO) release, NO synthase (NOS) and thrombomodulin production with ELISA, western blot and RT-PCR analysis. Berberine treatments showed significant improvements as indicated by significantly increased NO release, NOS and thrombomodulin production. Moreover, we also observed significant inhibition effects of berberine on AGEs formation. We concluded that the in vitro model of diabetic microEC injury could be established by the combination treatments of high glucose and AGEs, while berberine could improve the diabetic microvascular injury in vitro and inhibit the formation of AGEs, suggesting the potential clinical therapies with berberine for diabetes and its vascular complications.
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