Ke Wang

Context. Type Ibn supernovae (SNe) are characterized by narrow helium emission lines that arise from ejecta-circumstellar medium interaction, yet their progenitors remain debated, with both massive Wolf-Rayet stars and low-mass helium stars in binaries proposed. Aims. We aim to directly identify the progenitor of the Type Ibn SN 2023fyq and to characterize its environment in order to constrain the progenitor’s nature and evolutionary channel. Methods. We search for the SN progenitor based on pre-explosion and late-time HST and JWST images and derive its properties by fitting the spectral energy distribution. We investigate the SN environment by probing the stars, dust, ionized gas and molecular gas with a multiwavelength dataset including HST and JWST imaging, VLT/MUSE integral-field-unit spectroscopy, and ALMA CO(2−1) radio interferometry. Results. We discover a pre-explosion source at the SN position, which is consistent with a hot ( T > 15 000 K) and luminous (log( L / L _⊙ ) ≳ 5.5) SN progenitor and a possible host star cluster. The progenitor is confirmed to have disappeared after the explosion. Analysis of the SN environment implies that the progenitor likely has an age of log( t /yr) = 7.1−7.2. These phenomena disfavor a very massive single-star progenitor and instead support a binary scenario involving a low-mass helium star and a compact object; the observed progenitor emission likely arises from binary interaction that began at least ∼12 yr before the explosion. Conclusions. SN 2023fyq is the first Type Ibn SN with a directly detected progenitor and a possible host star cluster. It adds to the diversity of Type Ibn SNe in terms of their progenitor channels and mass-loss mechanisms.

Context . Infrared-dark clouds (IRDCs) are ideal sites for investigating the initial conditions of massive star and cluster formation. The A Lei Of the Habitat and Assembly of Infrared Dark Clouds (ALOHA IRDCs), a James Clerk Maxwell Telescope Large Program, has mapped nearby IRDCs utilising the SCUBA-2 continuum camera at the highest achievable sensitivity. Complementary molecular line observations are needed to characterise the physical, kinematic, and chemical properties of the dense gas. Aims . We aim to determine the thermal, kinematic, and chemical properties of clumps identified in the ALOHA IRDCs, and to assess their evolutionary status and level of star-forming activity. Methods . We performed single-pointing K -band and W -band observations towards 56 clumps pf ALOHA IRDCs using the Effelsberg 100 m and Yebes 40 m telescopes, respectively. We derived NH ₃ kinetic temperatures using the hyperfine group ratio method and identified infall and shock signatures from HCO ⁺ , H ¹³ CO ⁺ , SiO, and HNCO profiles. Water masers and NH ₂ D emission were used as complementary tracers of chemical evolution and star formation. Results . The clumps exhibit kinetic temperatures of 15–29 K. We detect NH ₂ D emission towards 18 sources; the NH ₂ D centroid velocities are consistent with those of NH ₃ , indicating the two species trace the same dense gas component. More than half of the clumps display blue-asymmetric HCO ⁺ profiles, identifying them as infall candidates. Water masers with prominent velocity ranges and variability are detected in 22 sources. Broad SiO emission (≳20 km s ⁻¹ ) indicates strong shocks, while narrower emission (≲6 km s ⁻¹ ) likely traces large-scale interactions or low-velocity shocks. Conclusions . The widespread infall signatures, shock tracers, masers, and NH ₂ D emission suggest that relatively quiescent, chemically young material can coexist with dynamically active gas affected by early protostellar feedback, providing insight into the coupled physical and chemical evolution of massive IRDC clumps.

Our understanding of magnetic fields (B-fields) in massive star formation remains incomplete. Linear polarized emission from magnetically aligned dust grains provides a good way to map the morphology of the B-field on the plane of the sky. Here, we present the 1.2 mm full polarization observation of W33 A, a massive star-forming region at 2.4 kpc, obtained with the Atacama Large Mil-limeter/Submillimeter Array (ALMA) to achieve an angular resolution of ∼0″.3 (∼730 au). W33 A is resolved into 20 dense cores and nine filaments. It reveals various B-field structures, including two perpendicular large-scale components oriented northwest–southeast (NW–SE) and northeast–southwest (NE–SW), as well as two local distinct features toward the millimeter peaks MM1 and MM2. The NW–SE component could be shaped by a molecular outflow. The NE–SW one is remarkably coherent along the main filamentary structures (F1, F-Main, Tail), all with trans-Alfvénic turbulence. In F-Main, the line mass exceeds the turbulent critical limits, so magnetic support is required to prevent radial collapse and suppress local fragmentation. In F1 and Tail, turbulence is sufficient to support gravity, although B-fields can potentially provide additional support. Toward MM1, the fields follow a spiral-like, infalling streamer traced by CH ₃ CN; the inferred trans-Alfvénic turbulence in the accreting material indicates magnetic damping of turbulence and a magnetically regulated, laminar accretion flow that continues to feed the core. Toward MM2, the field exhibits an hourglass geometry described by parabolic curves. Two independent methods yield a consistently strong field strength of ∼8.1 ± 1.9 mG. The virial analysis shows that the B-field can add 25% (75% from turbulence) support against gravity but is not by itself sufficient to halt collapse. Our study shows that within one protocluster, B-fields can both help stabilize gas filament against local fragmentation to facilitate mass accretion and delay gravitational collapse. The distinct evolutionary stages of MM1 and MM2 highlight the dynamic importance of B-fields in massive star formation.

The kinetic temperature structure of the photodissociation region M17SW was mapped using the IRAM 30m telescope. This mapping employed the para-H ₂ CO triplet ( J K _a K _c = 3 ₀₃ -2 ₀₂ , 3 ₂₂ -2 ₂₁ , and 3 ₂₁ -2 ₂₀ ) near 218 GHz on a scale of ∼0.2pc. The kinetic temperatures were derived by modeling the average H ₂ CO line ratios (3 ₂₂ –2 ₂₁ /3 ₀₃ –2 ₀₂ + 3 ₂₁ –2 ₂₀ /3 ₀₃ –2 ₀₂ ) with the RADEX non-local thermodynamic equilibrium approach. These temperatures range from 28 to 181 K with an average of 54.2 ± 0.3 K at a spatial density of 5.5×10 ⁵ cm ⁻³ . Comparing with the temperature measurements obtained from multiple transitions of NH ₃ (1,1)–(6,6) and the far-infrared (FIR) dust continuum, the H ₂ CO lines show temperatures similar to those measured by NH ₃ but slightly higher than values derived from FIR observations. The high kinetic temperatures observed from H ₂ CO are associated with the ultracompact H II region UC1, dense clumps, and H ₂ O and CH ₃ OH masers, showing a similar distribution as NH ₃ . This indicates that dense gas in the M17SW region is heated by star formation activity. The presence of a significant gas temperature gradient across the M17SW region, as measured by H ₂ CO and NH ₃ , provides direct evidence for gas heated predominantly by radiation emitted from the OB star cluster NGC 6618. On a smaller scale, the dense gas surrounding the dense clumps experiences significant heating from internal protostars and/or young stellar objects. Higher temperatures traced by H ₂ CO are linked to turbulence on a scale of ∼0.2pc. The complex temperature structure of the M17SW region is revealed by H ₂ CO and NH ₃ , which may be attributed to both large-scale external radiative heating and small-scale internal radiative and turbulent heating.

Linear filamentary structures are fundamental constituents of the interstellar medium and play a central role in star formation. Their relative orientation with respect to the ambient magnetic field (B-field) provides key constraints on filament formation mechanisms. We investigate the relative orientation between Milky Way linear filaments (MWLFs) and the plane-of-sky B-field using polarization observations from the Atacama Cosmology Telescope DR6, complemented by Planck data. Filament orientations are compared with the local B-field and the Galactic plane, while projection effects and statistical significance are quantified using Monte Carlo simulations of vector pairs in three dimensions. We find no strong preferential alignment between MWLFs and the ambient B-field. Although the B-field is preferentially aligned with the Galactic plane with relative angles θ _BG ∼ 0°–25°, filament orientations exhibit a bimodal distribution, being either parallel or perpendicular to the plane ( θ _FG ∼ 0°–15° and ∼75°–90°). Filaments located far from the Galactic midplane (∣ z ∣ > 90 pc) preferentially show perpendicular alignment with both the plane and the B-field, whereas those near the midplane exhibit a bimodal orientation. These results indicate that large-scale B-fields do not dominate the formation of MWLFs and instead favor a super-Alfvénic regime in which magnetic forces are dynamically subdominant, as expected for filaments associated with supernova-driven shells. Overall, our findings suggest that a face-on view of the Milky Way would resemble nearby disk galaxies such as M74, as observed in JWST images, with its disk structured by a network of supernova-driven bubbles (i.e., a bubbly disk).

We present a detailed stellar population analysis of the strongly lensed dusty star-forming galaxy (DSFG) PLCK G165.7+67.0 DSFG-1 at z = 2.236, combining JWST NIRCam imaging with new Submillimeter Array (SMA) observations. This source is multiply imaged into two lensed components: image 1a, with a moderate magnification factor of μ ∼ 5, and image 1bc, with an extreme magnification factor of μ ∼ 40. The new SMA observations detect significant dust continuum emission at 225 and 273 GHz, with combined flux densities of S _cont = 1.19 ± 0.38 mJy in image 1a and S _cont = 10.02 ± 0.85 mJy in image 1bc, indicating active star formation at subkiloparsec scales. Based on the integrated spectral energy distribution modeling, DSFG-1 exhibits a lensing-amplification-corrected stellar mass of M _⋆ = (1.2 ± 0.4) × 10 ¹⁰ M _⊙ and a star formation rate of 103 ± 14 M _⊙ yr ⁻¹ , similar to previous H α -based results, placing it four times above the star-forming main sequence at this redshift. Its location on the size–mass plane and its morphological properties suggest that the system occupies a transitional phase between star-forming late-type galaxies and compact early-type systems. Together with its elevated star formation activity, this is consistent with a rapidly evolving galaxy observed during cosmic noon. We further investigated the spatially resolved stellar population properties and found significant spatial variations in stellar age and dust attenuation. These results point to a nonuniform star formation history and highlight the complex interplay between dust geometry, stellar growth, and gravitational lensing, consistent with a merger scenario.

Molecular bubbles are widely used as tracers of stellar feedback; yet, their identification in spectral-line surveys remains challenging because both cavity morphology and kinematic structure must be assessed consistently in position–position–velocity (PPV) space. We present the Bubble-Weight Fields (BWFields) framework, a PPV-based method that for the first time enables the automated and objective identification and analysis of enclosed molecular bubbles directly from spectral-line data cubes. BWFields constructs a bubble-weight field, W _{l , b , v} , which encodes cumulative evidence for cavity interiors by aggregating topological signatures across multiple signal-to-noise tiers and velocity-integration scales. Contiguous cavity interiors are segmented as weight-clumps and associated with surrounding molecular gas, linking candidate bubbles to the structure of their host clouds. Shell morphology is characterized using radial intensity profiles and emission-defined intensity skeletons, which capture the shell geometry as traced by the observed emission. Bubble kinematics are quantified using azimuthally sampled position–velocity (PV) diagnostics, along with a turbulence-normalized expansion significance, which serves as a direct measure of the expansion-like velocity organisation. Applied to MWISP ¹³ CO observations of the G17 region, BWFields identifies a population of bubble candidates with a broad range of morphologies and velocity structures in complex environments. BWFields establishes a scalable and physically interpretable framework for molecular-bubble studies in large surveys, enabling systematic investigations of stellar feedback in the Galactic interstellar medium.

The outer Galaxy presents an optimal setting for investigating molecular clouds and star formation in environments with low-metallicity. A total of 72 Galactic edge clouds were surveyed using the CO (2-1) line with the IRAM30m telescope, leading to the identification of 112 CO clumps within molecular clouds with linear resolutions of 0.5-0.9 pc. The parameters such as size, mass, surface density, and velocity dispersion of these CO clumps, derived from CO (2-1) observations, exhibit ranges of 0.6-3.4pc, 34-8250 M _⊙ , 12-1025 M _⊙ pc ⁻² , and 0.3-1.7kms ⁻¹ , respectively. Over the galactocentric distance range of 14-23kpc, no systematic variations are found in these parameters. The velocity dispersion-size relationship of the Galactic edge clumps is modeled as σ _v = 0.69(±0.03) R _eff ^0.36(±0.10) , indicating that turbulence is present within the Galactic edge clumps, similarly to observations in the inner Galactic disk clouds. Furthermore, the luminous mass-size relation of the Galactic edge clumps is described by M _lum = 196(±17) R _eff ^2.18(±0.26) , suggesting the average column density remains almost constant for clouds of different sizes. The virial parameters range from 0.6 to 15.3, with a median value of 2.8 ± 0.6, suggesting that most clumps are gravitationally unbound. Furthermore, the virial parameters of our Galactic edge clumps show a decreasing trend with increasing galactocentric distances, described by an exponential relation α _vir = 33.0(± 10.4) e ^{− R _g /6.7(±0.9)} , consistent with previous results.

A dynamic view of mass assembly is essential for understanding the formation of massive stars and clusters. However, interpreting evolutionary diagnostics from Galactic-wide surveys requires careful consideration of distance and environmental variations. The G316.8 filament provides an excellent controlled case: a 14-parsec, nearly linear structure comprising three contiguous subregions with comparable molecular gas reservoirs (each ~10 000 M _⊙ ), yet spanning a clear evolutionary sequence from a northern infrared dark cloud (young) through a central massive young stellar object (intermediate), to a southern H II region (evolved). The Linear filament and nested cluster evolution tomography (LANCET) project mapped the entire G316.8 filament with the Atacama Compact Array (ACA) at 1.3 mm, achieving 6″ (0.08 pc) resolution over 26.7 arcmin ² (17.1 pc ² ). By combining ACA 7 m data with Herschel and APEX/ArTéMiS observations, we produced high-resolution temperature and column-density maps. We quantified subregional differences using (i) dense-fragment statistics, (ii) column-density probability distribution functions (N-PDFs), and (iii) the scale-dependent structural diagnostic, the Δ-variance. From young to intermediate to evolved, the maximum fragment mass increases from 8 to 160 to 490 M _⊙ , while the dense-gas mass fraction (>0.5 g cm ⁻² ) rises from 0.4 to 2.3 to 9.6%. Along this sequence, the N-PDF develops a slightly flatter primary power-law tail and an additional, steeper secondary tail; the Δ-variance slope becomes progressively shallower. Across G316.8, the subregional differences consistently indicate a coherent evolutionary trend of massive star formation, in which gas is continuously assembled into sub-parsec dense structures. The forthcoming 12 m array observations are about to extend this dynamic picture by resolving dense core formation and probing gas kinematics and magnetic fields.

Large-scale filaments ubiquitously exist in the Galactic interstellar medium, and their radial profiles offer insights into their formation mechanisms. We present a statistical analysis of molecular hydrogen column density (N(H ₂ )) and dust temperature ( T _d ) radial profiles for 35 Galactic large-scale filaments. We divided their spines into 315 segments, extracted the radial profiles of each segment using N(H ₂ ) and T _d maps derived from Herschel Hi-GAL data, and estimated the asymmetry degree within the radial profiles ( α _asy ), as well as the length proportion of segments with asymmetric profiles across the entire filament ( f _asy ). We found that Galactic large-scale filaments reside in surroundings distinctly asymmetric and varied in N(H ₂ ), and mildly asymmetric yet stable in T _d . Different filament morphology types do not show significant differences in α _asy or f _asy . A bent filament shape does not necessarily correspond to an asymmetric radial profile, whereas a straight filament shape may be associated with a symmetric profile. Segments with asymmetric surroundings in N(H ₂ ) may not simultaneously appear asymmetric in T _d , and vice versa. We found three filaments with 4%–44% of their spine show asymmetric N(H ₂ ) and T _d radial profiles in inverse trends, likely caused by a nearby H ii region. H ii regions of similar scale to large filaments can induce asymmetric radial profiles within them, indicating their influence on filament evolution. However, they are unlikely to independently trigger the formation of an entire Galactic large-scale filament, in contrast to their role in small-scale filament formation.