The Atacama Large Millimeter/submillimeter Array (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 (M _clump ≳ 10³ M _⊙), luminous (L _bol ≳ 10⁴ L _⊙), and blue-profile (infall signature) clumps by ALMA with resolution of ∼2200–5500 au (median value of 3500 au) at 350 GHz (870 μm). We identified 248 dense cores, 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 a 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 that 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.

The Purple Mountain Observatory 13.7 m radio telescope has been used to search for 95 GHz (8₀–7₁A⁺) class I methanol masers toward 1020 Bolocam Galactic Plane Survey (BGPS) sources, leading to 213 detections. We have compared the line width of the methanol and HCO⁺ thermal emission in all of the methanol detections, and on that basis, we find that 205 of the 213 detections are very likely to be masers. This corresponds to an overall detection rate of 95 GHz methanol masers toward our BGPS sample of 20%. Of the 205 detected masers, 144 (70%) are new discoveries. Combining our results with those of previous 95 GHz methanol maser searches, a total of 481 95 GHz methanol masers are now known. We have compiled a catalog listing the locations and properties of all known 95 GHz methanol masers.

We report Shanghai Tian Ma Radio Telescope (TMRT) detections of several long carbon-chain molecules in the C and Ku bands, including HC₃N, HC₅N, HC₇N, HC₉N, C₃S, C₆H, and C₈H toward the starless cloud Serpens South 1a. We detected some transitions (HC₉N J = 13–12, F = 12–11, and F = 14–13; H¹³CCCN J = 2–1, F = 1–0, and F = 1–1; HC¹³CCN J = 2–1, F = 2–2, F = 1–0, and F = 1–1; HCC¹³CN J = 2–1, F = 1–0, and F = 1–1) and resolved some hyperfine components (HC₅N J = 6–5, F = 5–4; H¹³CCCN J = 2–1, F = 2–1) for the first time in the interstellar medium. The column densities of these carbon-chain molecules in the range 10¹²–10¹³ cm⁻² are comparable to two carbon-chain molecule rich sources, TMC-1 and Lupus-1A. The abundance ratios are 1.00:(1.11 ± 0.15):(1.47 ± 0.18) for [H¹³CCCN]:[HC¹³CCN]:[HCC¹³CN]. This result implies that the ¹³C isotope is also concentrated in the carbon atom adjacent to the nitrogen atom in HC₃N in Serpens South 1a, which is similar to TMC-1. The [HC₃N]/[H¹³CCCN] ratio of 78 ± 9, the [HC₃N]/[HC¹³CCN] ratio of 70 ± 8, and the [HC₃N]/[HCC¹³CN] ratio of 53 ± 4 are also comparable to those in TMC-1. Serpens South 1a proves to be a suitable testing ground for understanding carbon-chain chemistry.

We report the detection of widespread CH₂OHCHO and HOCH₂CH₂OH emission in Galactic center giant molecular cloud Sagittarius B2 using the Shanghai Tianma 65 m Radio Telescope. Our observations show for the first time that the spatial distribution of these two important prebiotic molecules extends over 15 arcmin, corresponding to a linear size of approximately 36 pc. These two molecules are not just distributed in or near the hot cores. The abundance of these two molecules seems to decrease from the cold outer region to the central region associated with star formation activity. Results presented here suggest that these two molecules are likely to form through a low temperature process. Recent theoretical and experimental studies demonstrated that prebiotic molecules can be efficiently formed in icy grain mantles through several pathways. However, these complex ice features cannot be directly observed, and most constraints on the ice compositions come from millimeter observations of desorbed ice chemistry products. These results, combined with laboratory studies, strongly support the existence of abundant prebiotic molecules in ices.

We report the first detection of isotopic methanol (¹³CH₃OH) maser emission in interstellar space. The emission was detected toward the high-mass young stellar object G358.93-0.03 during monitoring of a flare in the 6.7 GHz methanol (CH₃OH) maser emission in this source. We find that the spectral and spatial distribution of the ¹³CH₃OH masers differs from the CH₃OH masers imaged at the same epoch, contrary to expectations from similarity of their pumping. This conclusively demonstrates that isotopic methanol masers are bright under different physical conditions and suggests that they can provide additional, complementary information to the CH₃OH masers from the same source. We detect a rapid decay of the ¹³CH₃OH maser lines suggesting that they are transient phenomena (masing for only a few months), likely associated with rapid changes in radiation field due to an accretion burst induced by massive disk fragmentation. Changes in the line flux density are faster than required to achieve equilibrium in the energy level populations, indicating that the pumping of these masers is likely variable.