Qizhou Zhang

Core growth is a key process in high-mass star formation. As part of the Global and Local Infall in the ASHES Sample (GLASHES) survey, we present infall velocities and mass infall rates derived from blue-asymmetric line profiles toward cores embedded in massive 70 μ m dark clumps. Robust Hill5 model fits were obtained for 70 of the 135 cores exhibiting blue-asymmetric profiles, yielding infall velocities of 0.11–1.60 km s ⁻¹ and mass infall rates ranging from ∼10 ⁻⁵ to 5 × 10 ⁻³ M _⊙ yr ⁻¹ . Both quantities increase systematically from prestellar candidates to warm cores and outflow-associated cores. The inferred infall velocities are close to the cores’ freefall velocities (mean v _in / v _ff ∼ 0.75), and t _in = R / v _in is comparable to the freefall time, indicating dynamical fast contraction. Hill5 infall velocity correlates moderately with the nonthermal velocity dispersion and Mach number measured from optically thin tracers, indicating that organized infall contributes to the observed line widths. The mass infall rate follows a power-law relation with core mass, M ̇ = 1.3 × 1 0 − 4 ( M / M ⊙ ) 0.83 ± 0.06 M ⊙ yr − 1 , across 0.1 ≲ M ≲ 30 M _⊙ . The power-law index increases from ∼0.65 for prestellar cores to ∼1.10 for outflow-associated cores, likely tracing an evolution in the dominant physical process. The Hill5 infall velocities and mass infall rates for the GLASHES cores are larger than those of cores in nearby low-mass star-forming regions but smaller than those of larger-scale high-mass clumps. These results provide the first statistical constraints on core-scale mass accumulation during the earliest stages of high-mass star formation.

Intense radiation from high-mass stars is expected to significantly affect dust grain alignment and evolution through radiative torques (RATs). We investigate this effect in a massive star-forming region, NGC 6334I, using 1.2 mm dust continuum polarization observations from the Atacama Large Millimeter/submillimeter Array. The polarization fraction spans from ≲1% to ∼10% and decreases with increasing column density, remaining below 2% in dense cores despite high temperatures (∼100 K), where efficient grain alignment by RATs is expected. We investigate how grain alignment, grain growth, grain disruption, B -field tangling, and local physical conditions affect the polarization properties of MM1, MM2, MM3, and their surroundings. Polarization-angle dispersion shows that B -field tangling contributes to depolarization at moderate densities but cannot fully explain the lowest-polarization fractions. Using RAT-based grain alignment and polarization modeling, we find that reduced alignment efficiency and high optical depth reproduce the low polarization in the densest regions. MM2 shows evidence of grain growth, with maximum grain sizes a max ∼ 0.35 – 1.0 μ m, while MM1 exhibits smaller values of ∼0.35–0.50 μ m. Accounting for optical depth increases the inferred grain sizes in MM1 to ∼1.0–2.0 μ m. Analytical estimates of RAT disruption from the intense outburst suggest that micron-sized grains in high-temperature, moderate-density regions can fragment into submicron grains. Alternatively, high optical depth may also explain the low polarization in the densest regions even in the presence of micron-sized grains. Incorporating the B -field inclination effect indicates a transition from predominantly plane-of-sky fields at low densities to more line-of-sight-aligned configurations at high densities.

Context . Massive stars form in the densest part of molecular clouds and strongly influence their surroundings through radiative and mechanical feedback. The effects of such feedback on dense gas structures at sub-parsec scales, however, remain to be better constrained by observations. Aims . We aim to investigate how feedback from a newly formed massive star affects the physical properties of dense cores embedded in a neighboring filamentary molecular cloud. Methods . We analyzed the ALMA Band 6 observations of the filamentary source IRAS 18530+0215 (I18530), including 1.3 mm dust continuum, molecular line emission from DCN, N ₂ D ⁺ , and ¹³ CS, as well as complementary VLA K-band continuum and NH ₃ metastable line observations. The dynamical state of the ultracompact (UC) H II region was investigated through energy and pressure estimates. Dense cores traced by the line emission were identified using the astrodendro algorithm, and their temperatures, masses, velocity dispersions, and virial parameters were derived from molecular line fitting and continuum emission. We further examined how the physical and kinematic properties of the dense cores vary under the influence of feedback from the H II region. Results . The H II region has a radius of ∼0.1 pc and exhibits an expansion velocity of ∼2.5 km s ⁻¹ , corresponding to a shell dynamical age of ∼0.06 Myr. The DCN and ¹³ CS cores are primarily distributed in the vicinity of the H II region, whereas N ₂ D ⁺ cores are preferentially found at larger distances. Overall, the temperatures and velocity dispersions of the dense cores show clear decreasing trends with increasing projected distance from the H II region. The virial parameters increase with projected distance within the inner ∼0.3 pc but decline sharply beyond this scale, while the core masses show no significant variation with distance. Strong star formation signatures are found at projected distances of ∼0.2 pc from the H II region, whereas more distant regions still host quiescent, cold dense cores at earlier evolutionary stages. Conclusions . Our results suggest that the compact H II region is currently trapped or choked within a scale of ∼0.1 pc. Its feedback extends to at least ∼0.3 pc and is unlikely to significantly disrupt the entire filamentary structure on short timescales. Within the affected region, the feedback enhances the velocity dispersions, gas temperatures, and virial parameters of the dense cores, with no evidence that it promotes the formation of more massive dense cores.

We present data from the ALMA Central Molecular Zone Exploration Survey (ACES) Large Program, which provides broad spectral-line and 3 mm continuum coverage of the Central Molecular Zone (CMZ) at a spatial resolution of 0.1 pc. The survey delivers homogeneous, wide-field mosaics that enable direct comparisons of the physical and chemical conditions across diverse environments in the Galactic centre. In this data release paper, we present the CS($2-1$), SO(2$_{3}-1_{2}$), CH$_3$CHO($5_{1,4}-4_{1,3}$), HC$_3$N($11-10$), and H40$\alpha$ lines observed simultaneously within two broad spectral windows. These lines reveal pronounced spatial and chemical variations across the CMZ, tracing distinct components of molecular gas, shock-affected regions, and ionized structures. The high angular resolution and multi-line capability of the ACES data set make it a powerful resource for future studies of gas dynamics, star formation activity, and the physical connection between the CMZ and Sgr A*.

The central molecular zone (CMZ) resides in the inner few hundred parsecs of our Galaxy, and despite being the largest reservoir of dense molecular gas in the Milky Way, it has a relatively low present-day star formation rate (SFR) of ∼0.08 M _⊙ yr ⁻¹ . Continuum and spectral line observations from the Atacama Large Millimeter/submillimeter Array (ALMA) CMZ Exploration Survey (ACES) provide the first full-coverage, high-resolution map of the inner 200 pc of the CMZ at 3 mm. In this paper we present the ACES catalog of compact continuum sources, the most complete catalog of potential sites of star formation in the CMZ to date. Using an automated dendrogram-based source extraction procedure in combination with a by-eye morphological classification scheme, we produce a “full” catalog of 1735 detections in total. Additionally, we use spectral index measurements to generate a “filtered” catalog of 567 sources with minimal contamination from nonthermal filaments and extended free–free emission. We find that 359 (∼63%) of the filtered catalog sources are located at column densities 23 cm ⁻² , outside of the densest molecular cloud regions, 195 of which have not been identified in previous surveys. After cross-referencing with various catalogs generated from data at different wavelengths, we consider it likely that many of these newly discovered detections are produced by pre-/protostellar sources or compact H ii regions.

Context . Accretion streamers connected to protostellar disks and/or envelopes are thought to transport material across several thousand of au. Whether the motions of the gas comprising these streamers are dominated by gravity, large scale external turbulence or the action of magnetic fields is still under scrutiny. Aims . The aim of this work is to understand the role of the magnetic fields in the star-formation processes, in particular the role that magnetic forces have in potentially leading flows of gas and accretion onto the envelopes and disks orbiting protostars. Methods . First, we try to identify large-scale accretion streamers toward the high-mass Young Stellar Object GGD 27–MM1 and fit their trajectories using the so-called Mendoza model, a modification of the classical model of pure gravitational infalling motion of fluid particles in a potential well. Second, we estimate the strength of the magnetic field associated with the streamers. Then, we determine whether the streamers are dominated by magnetic or centrifugal forces. Results . Inspecting the Atacama Large Millimeter/submillimeter Array (ALMA) H ₂ CO cube we were able to identify four accretion streamers spreading up to ∼7000 au and fit their trajectories in the position-position-velocity space. The polarized continuum emission reveals a good alignment of the magnetic field and the trajectory of the streamers. Using the Davis-Chandrasekhar-Fermi (DCF) method, we derive estimates for the magnetic field strength, find that the streamers are sub-Alfvénic, and discuss (after estimating energy terms for turbulence, ordered motions, magnetic forces, and gravity) a possible qualitative scenario in which, the gravitational well of the GGD 27–MM1 protostar dominates streamer gas motions over turbulence and magnetic forces at distances of ∼3000 au.