The parallax and 3D kinematics of water masers in the massive star-forming region G034.43+0.24

We report a trigonometric parallax measurement of 22 GHz water masers in the massive star-forming region G034.43+0.24 as part of the Bar and Spiral Structure Legacy (BeSSeL) Survey using the Very Long Baseline Array. The parallax is 0.330$\pm$50.018 mas, corresponding to a distance of $3.03^{+0.17}_{-0.16}$ kpc. This locates G034.43+0.24 near the inner edge of the Sagittarius spiral arm and at one end of a linear distribution of massive young stars which cross nearly the full width of the arm. The measured 3-dimensional motion of G034.43+0.24 indicates a near-circular Galactic orbit. The water masers display arc-like distributions, possibly bow shocks, associated with winds from one or more massive young stars

Episodic Accretion in Protostars -- An ALMA Survey of Molecular Jets in the Orion Molecular Cloud

Protostellar outflows and jets are almost ubiquitous characteristics during the mass accretion phase, and encode the history of stellar accretion, complex-organic molecule (COM) formation, and planet formation. Episodic jets are likely connected to episodic accretion through the disk. Despite the importance, there is a lack of studies of a statistically significant sample of protostars via high-sensitivity and high-resolution observations. To explore episodic accretion mechanisms and the chronologies of episodic events, we investigated 42 fields containing protostars with ALMA observations of CO, SiO, and 1.3\,mm continuum emission. We detected SiO emission in 21 fields, where 19 sources are driving confirmed molecular jets with high abundances of SiO. Jet velocities, mass-loss rates, mass-accretion rates, and periods of accretion events are found to be dependent on the driving forces of the jet (e.g., bolometric luminosity, envelope mass). Next, velocities and mass-loss rates are positively correlated with the surrounding envelope mass, suggesting that the presence of high mass around protostars increases the ejection-accretion activity. We determine mean periods of ejection events of 20$-$175 years for our sample, which could be associated with perturbation zones of $\sim$ 2$-$25\,au extent around the protostars. Also, mean ejection periods are anti-correlated with the envelope mass, where high-accretion rates may trigger more frequent ejection events. The observed periods of outburst/ejection are much shorter than the freeze-out time scale of the simplest COMs like CH$_3$OH, suggesting that episodic events largely maintain the ice-gas balance inside and around the snowline.Comment: Submitted to Journal; 27 pages, 15 Figures and additional Appendix materia

The ALMA-QUARKS survey: -- I. Survey description and data reduction

This paper presents an overview of the QUARKS survey, which stands for `Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures'. The QUARKS survey is observing 139 massive clumps covered by 156 pointings at ALMA Band 6 ($\lambda\sim$ 1.3 mm). In conjunction with data obtained from the ALMA-ATOMS survey at Band 3 ($\lambda\sim$ 3 mm), QUARKS aims to carry out an unbiased statistical investigation of massive star formation process within protoclusters down to a scale of 1000 au. This overview paper describes the observations and data reduction of the QUARKS survey, and gives a first look at an exemplar source, the mini-starburst Sgr B2(M). The wide-bandwidth (7.5 GHz) and high-angular-resolution (~0.3 arcsec) observations of the QUARKS survey allow to resolve much more compact cores than could be done by the ATOMS survey, and to detect previously unrevealed fainter filamentary structures. The spectral windows cover transitions of species including CO, SO, N$_2$D$^+$, SiO, H$_{30}\alpha$, H$_2$CO, CH$_3$CN and many other complex organic molecules, tracing gas components with different temperatures and spatial extents. QUARKS aims to deepen our understanding of several scientific topics of massive star formation, such as the mass transport within protoclusters by (hub-)filamentary structures, the existence of massive starless cores, the physical and chemical properties of dense cores within protoclusters, and the feedback from already formed high-mass young protostars.Comment: 9 figures, 4 tables, accepted by RA

ATOMS : ALMA three-millimeter observations of massive star-forming regions - VII. A catalogue of SiO clumps from ACA observations

To understand the nature of SiO emission, we conducted ACA observations of the SiO (2-1) lines toward 146 massive star-forming regions, as part of the ALMA Three-millimeter Observations of Massive Star-forming regions (ATOMS) survey. We detected SiO emission in 128 (87.7 per cent) sources and identified 171 SiO clumps, 105 of which are spatially separated from 3 mm continuum emission. A large amount of the SiO line profiles (60 per cent) are non-Gaussian. The velocity dispersion of the SiO lines ranges from 0.3 to 5.43 km s(-1). In 63 sources the SiO clumps are associated with H II regions characterized by H40 alpha emission. We find that 68 per cent (116) of the SiO clumps are associated with strong outflows. The median velocity dispersion of the SiO line for outflow sources and non-outflow sources is 1.91 km s(-1) and 0.99 km s(-1), respectively. These results indicate that outflow activities could be connected to strongly shocked gas. The velocity dispersion and [SiO]/[(HCO+)-C-13] intensity ratio do not show any correlation with the dust temperature and particle number density of clumps. We find a positive correlation between the SiO line luminosity and the bolometric luminosity, implying stronger shock activities are associated with more luminous protoclusters. The SiO clumps in associations with HII regions were found to show a steeper feature in Lsio/Lbol. The SiO line luminosity and the fraction of shocked gas have no apparent evidence of correlation with the evolutionary stages traced by luminosity to mass ratio (L-bol/M).Peer reviewe

ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP) : Evidence for a Molecular Jet Launched at an Unprecedented Early Phase of Protostellar Evolution

Protostellar outflows and jets play a vital role in star formation as they carry away excess angular momentum from the inner disk surface, allowing the material to be transferred toward the central protostar. Theoretically, low-velocity and poorly collimated outflows appear from the beginning of the collapse at the first hydrostatic core (FHSC) stage. With growing protostellar core mass, high-density jets are launched, entraininf an outflow from the infalling envelope. Until now, molecular jets have been observed at high velocity (greater than or similar to 100 km s(-1)) in early Class 0 protostars. We, for the first time, detect a dense molecular jet in SiO emission with low velocity (similar to 4.2 km s(-1), deprojected similar to 24 km s(-1)) from source G208.89-20.04Walma (hereafter G208Walma) using ALMA Band 6 observations. This object has some characteristics of FHSCs, such as a small outflow/jet velocity, extended 1.3 mm continuum emission, and N2D+ line emission. Additional characteristics, however, are typical of early protostars: collimated outflow and SiO jet. The full extent of the outflow corresponds to a dynamical timescale of similar to 930(-100)(+200) yr. The spectral energy distribution also suggests a very young source having an upper limit of T-bol similar to 31 K and L-bol similar to 0.8 L-circle dot. We conclude that G208Walma is likely in the transition phase from FHSC to protostar, and the molecular jet has been launched within a few hundred years of initial collapse. Therefore, G208Walma may be the earliest object discovered in the protostellar phase with a molecular jet.Peer reviewe

ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): How Do Dense Core Properties Affect the Multiplicity of Protostars?

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.T.L. acknowledges support from the National Natural Science Foundation of China (NSFC) through grants No. 12073061 and No. 12122307, the International Partnership Program of the Chinese Academy of Sciences (CAS) through grant No. 114231KYSB20200009, the Shanghai Pujiang Program (20PJ1415500), and science research grants from the China Manned Space Project with no. CMS-CSST-2021-B06. K.T. was supported by Japan Society for the Promotion of Science (JSPS) KAKENHI (grant No. 20H05645). D.J. and J.d.F. are supported by NRC Canada and by NSERC Discovery Grants. C.-F.L. acknowledge grants from the Ministry of Science and Technology of Taiwan (MoST 107-2119-M-001-040-MY3 and 110-2112-M-001-021-MY3) and Academia Sinica (Investigator Award AS-IA-108-M01). This research was carried out in part at the Jet Propulsion Laboratory, which is operated by the California Institute of Technology under a contract with the National Aeronautics and Space Administration (80NM0018D0004). J.-E.L. was supported by a National Research Foundation of Korea grant funded by the Korean government (MSIT) (grant No. 2021R1A2C1011718). J.H. acknowledges the support of NSFC projects 11873086 and U1631237. This work is sponsored (in part) by the CAS, through a grant to the CAS South America Center for Astronomy in Santiago, Chile. S.-L.Q. is supported by the NSFC with grant No. 12033005. S.Z. acknowledges the support of the China Postdoctoral Science Foundation through grant No. 2021M700248. L.B. gratefully acknowledges support by the ANID BASAL projects ACE210002 and FB210003. P.S. was supported by a Grant-in-Aid for Scientific Research (KAKENHI No. 18H01259) of JSPS. V.-M.P. acknowledges support by the grant PID2020-115892GB-I00 funded by MCIN/AEI/10.13039/501100011033

The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with Blue Profiles (ASSEMBLE): Core Growth, Cluster Contraction, and Primordial Mass Segregation

The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with Blue Profiles (ASSEMBLE) aims to investigate the process of mass assembly and its connection to high-mass star formation theories in protoclusters in a dynamic view. We observed 11 massive (Mclump>1000 Msun), luminous (Lbol>10,000 Lsun), and blue-profile (infall signature) clumps by ALMA with resolution of 2200-5500 au at 350 GHz (870 um) in continuum and line emission. 248 dense cores were identified, including 106 cores showing protostellar signatures and 142 prestellar core candidates. Compared to early-stage infrared dark clouds (IRDCs) by ASHES, the core mass and surface density within the ASSEMBLE clumps exhibited significant increment, suggesting concurrent core accretion during the evolution of the clumps. The maximum mass of prestellar cores was found to be 2 times larger than that in IRDCs, indicating evolved protoclusters have the potential to harbor massive prestellar cores. The mass relation between clumps and their most massive core (MMCs) is observed in ASSEMBLE but not in IRDCs, which is suggested to be regulated by multiscale mass accretion. The mass correlation between the core clusters and their MMCs has a steeper slope compared to that observed in stellar clusters, which can be due to fragmentation of the MMC and stellar multiplicity. We observe a decrease in core separation and an increase in central concentration as protoclusters evolve. We confirm primordial mass segregation in the ASSEMBLE protoclusters, possibly resulting from gravitational concentration and/or gas accretion.Comment: 37 pages, 13 figures, 5 tables; accepted for publication in ApJ

Complete chloroplast genome of the medicinal herb Veronicastrum axillare (Sieb. et Zucc.) Yamazaki and the phylogenetic relationship analysis within the tribe Veroniceae

Veronicastrum axillare (Sieb. et Zucc.) Yamazaki is a traditional medical plant with versatile biological activities. Here, we reported the complete chloroplast genome sequence of V. axillare with a total length of 152,691 bp, containing two IR regions of 25,765 bp each, an LSC region of 83,559 bp, and an SSC region of 17,602 bp. The genome encodes 131 genes, including 85 protein-coding genes, 37 tRNAs, eight rRNAs, and one pseudogene (ycf1). The overall GC content is 38.3%, with the highest content of 43.31% in IR region. Comparative analysis revealed 4 potential hotspots among V. axillare and other Veroniceae plants, providing potential markers for population investigations in the tribe Veroniceae. A total of 56 simple sequence repeats were identified in V. axillare. Phylogenetic analysis indicated a sister relationship between V. axillare and V. sibiricum, suggesting a close genetic relationship between the two Veronicastrum species. Our results provide basic genetic resources for investigating the evolutionary status of V. axillare within the tribe Veroniceae

Fabrication and Piezoresistive/Piezoelectric Sensing Characteristics of Carbon Nanotube/PVA/Nano-ZnO Flexible Composite

Flexible sensors with a high sensitivity and wide-frequency response are essential for structural health monitoring (SHM) while they are attached. Here, carbon nanotube (CNT) films doped with various PVA fractions (CNT/PVA) and ZnO nanowires (nano-ZnO) on zinc sheets were first fabricated by functionalized self-assembly and hydrothermal synthesis processes. A CNT/PVA/nano-ZnO flexible composite (CNT/PVA/ZnO) sandwiched with a zinc wafer was then prepared by the spin-coating method. The piezoresistive and/or piezoelectric capabilities of the CNT/PVA/ZnO composite were comprehensively investigated under cyclic bending and impact loading after it was firmly adhered to a substrate (polypropylene sheet or mortar plate). The results show that the piezoresistive sensitivity and linear stability of the CNT/PVA films doped with 20%, 50%, and 100% PVA during bending are 5.47%/mm, 11.082%/mm, and 11.95%/mm and 2.3%, 3.42%, and 4.78%, respectively. The piezoelectric sensitivity, linear stability, and response accuracy of the CNT/PVA/ZnO composite under impulse loading are 4.87 mV/lbf, 3.42%, and 1.496 ms, respectively. These merits support the use of CNT/PVA/ZnO as a piezoresistive and/or piezoelectric compound sensor to monitor the static/dynamic loads on concrete structures while it is attached

Experimental Study on the Preparation of Recycled Admixtures by Using Construction and Demolition Waste

The use of construction and demolition waste (CDW) to prepare recycled admixtures is of great significance for the complete resource reutilization of CDW. In this paper, different kinds of CDW were prepared into recycled powder (RP) with a specific particle size (0−45 µm or 0−75 µm). The fineness, water requirement ratio (WRR), fluidity, loss on ignition (LOI), strength activity index (SAI) and compatibility of cement and superplasticizer (CCS) were examined. The above test results were analyzed by advanced analysis tools, such as laser particle size analysis, XRD, XRF, DSC-TGA, SEM, and BET. The properties of different types of RPs varied greatly, which was closely related to the microstructure, particle morphology and chemical composition of the RP. The experimental results showed that all kinds of RPs after grinding had a high fineness and good particle size distribution, and the mineral composition was dominated by SiO2 with the content exceeding 50%. The WRR of various RPs was between 105% and 112%, and the SAI was between 68% and 78%, but the LOI varied greatly. Different types of RPs had a negative impact on the CCS, but the compatibility of cement and naphthalene-based superplasticizer was less affected. The content of recycled brick powder (RBP) in a hybrid recycled powder (HRP) was an important factor. When the content of RBP in HRP exceeded 50%, the HRP could meet the basic performance requirements of fly ash