Lile Wang

Feedback from massive stars regulates the formation of next-generation stars and planets and thus shapes the evolution of galaxies, yet observational evidence capable of determining which mechanism dominates the feedback process has long been lacking. Here, we present a large-scale H _I survey toward Orion A. With an unprecedented sensitivity and superior resolution, FAST (Five-hundred-meter Aperture Spherical radio Telescope) reveals a well-defined heart-shaped expanding H _I bubble, enshrouding the well-known “Veil” bubble of ionized gas. The photoionization-driven and wind-driven gas expands at 10.9 and 13.8 kilometers per second, respectively, with a kinetic energy ratio of 1:2 assuming a spherical symmetry and a uniform H _I -to-H ₂ ratio. This first direct comparison within a single bubble shows that radiation does not dominate the feedback process as predicted by classical theories; instead, stellar winds contribute a comparable share of the injected kinetic energy.

Molecular hydrogen (H ₂ ) is one of the key chemical species that controls and shapes a wide spectrum of astrophysical processes from galaxy evolution to planet formation. Although catalyzation on dust grain surfaces is the dominant formation channel of H ₂ in the interstellar medium, its efficiency across 20–200 K has remained not fully understood. Here, using multiscale simulations combining ab initio level machine learning force fields, constrained path-integral Monte Carlo, and kinetic Monte Carlo, we perform a systematic, quantum-mechanical study of the full H ₂ formation sequence, including hydrogen adsorption, diffusion, association, and desorption. We explicitly consider the decoupling of gas and dust temperatures, making our results applicable to photodissociation regions and dense cold clouds. Our results show that on the bare, crystalline surfaces studied here (graphitic and silicate grains), physisorbed hydrogen is negligible, and nuclear quantum effects (NQEs) in chemisorbed hydrogen atoms are essential for efficient formation at low temperatures, overcoming the classical Boltzmann suppression. This work presents a quantitative NQEs-inclusive study on silicate surfaces (exemplified by enstatite) and graphitic grains, revealing surface-specific adsorption behavior. These findings provide a first-principles quantum foundation for interstellar H ₂ formation, complementing empirical multipliers, and enable new observational constraints on dust composition and molecular cloud evolution. The framework also extends to other astrochemical reactions on dust grains under full NQEs.

We present high-angular-resolution (∼0 . ″ 05, ∼60−250 au) Atacama Large Millimeter/submillimeter Array Band 6 observations from the HOTDISK project (Hot-Origin Tracer survey of DISKs of massive protostars) aimed at investigating the “hot-disk” chemical pattern traced by vibrationally excited water, NaCl, SiS, and SiO in the innermost regions around massive protostars. 10 targets were selected based on strong CH ₃ CN emission exhibiting clear rotational signatures and centrally concentrated SiO emission from lower-resolution observations. We detect vibrationally excited water emission toward 7 of the 10 sources. In all detections, the blueshifted and redshifted components are compact and located on opposite sides of the 1.3 mm continuum peak, with velocity gradients approximately perpendicular to the outflow axes, consistent with rotation on disk scales. Emission from NaCl and SiS is detected toward five of these seven sources and exhibits similar kinematics, further supporting the presence of compact rotating structures. In contrast, commonly used hot-core tracers (e.g., CH ₃ CN and SO ₂ ) primarily probe larger-scale envelope gas. These results demonstrate that vibrationally excited water, NaCl, and SiS are powerful tracers of disk structures on ∼100 au scales, when observed at sufficient angular resolution and sensitivity. The high detection rate suggests that hot-disk chemical patterns—and thus compact rotating disks—are common in massive star-forming regions, at least among sources with well-developed rotating envelopes.

The adsorption of volatile molecules onto dust grain surfaces fundamentally influences dust-related processes, including condensation of gas-phase molecules, dust coagulation, and planet formation in protoplanetary disks. Using advanced ab initio density functional theory with r ² SCAN+rVV10 van der Waals functionals, we calculate adsorption energies of H ₂ , H ₂ O, and CO on carbonaceous (graphene, amorphous carbon) and silicate (MgSiO ₃ ) surfaces. Results reveal fundamentally different adsorption mechanisms: weak physisorption on carbonaceous surfaces (∣Δ ϵ _ad ∣ ∼ 0.1−0.2 eV) versus strong chemisorption on silicates (∣Δ ϵ _ad ∣ ∼ 0.5−1.5 eV) via coordination bonds. Kinetic Monte Carlo simulations incorporating these energies demonstrate divergent surface evolution: carbonaceous grains exhibit distinct condensation radius compared to silicates, while the cocrystal of H ₂ O and CO significantly increases the desorption temperature of CO. The actual radii of gas-phase molecular depletion could thus be a comprehensive result of temperatures, chemical compositions, and even evolution tracks. Meanwhile, silicates maintain chemisorbed molecular coatings throughout most disk regions. Such dichotomy in surface coverage could also provide a natural mechanism for carbon depletion in inner planetary systems.

Supernovae (SNe) are among the leading candidates for powering galactic-scale turbulence. SNe drive expanding shells of neutral atomic hydrogen (HI) known as superbubbles. Due to the lack of a sensitive, dynamically complete, galaxy-wide census, superbubbles have not been used to quantify the galactic-scale turbulent energy budget. Here we present a combined Five-hundred-meter Aperture Spherical radio Telescope (FAST) and Jansky Very Large Array HI survey of the Andromeda galaxy (M31), the nearest giant spiral, with superior sensitivity and dynamical coverage. We identify 118 superbubbles across the entire disk of M31 with dynamical ages up to 40 Myr, consistent with the expected duration of SN activity in a star cluster and extending the age coverage well beyond previous surveys. Inferred from these superbubbles, the kinetic energy injection rates (10^49–10^51.5 erg kpc^-3 Myr^-1) from SNe closely match the turbulence dissipation rates derived independently from the same data, in both magnitude and spatial distribution. These results demonstrate that clustered SN feedback is sufficient to sustain galactic-scale turbulence, which shapes disk structure and influences galaxy evolution.

The inner regions of protoplanetary disks are host to the sublimation of dust grains, a process traditionally modeled using equilibrium thermodynamics. We demonstrate through ab initio density functional theory and kinetic Monte Carlo simulations that silicate dust sublimation is inherently a nonequilibrium kinetic process. The binding energies and vibrational frequencies governing desorption, calculated for MgSiO ₃ and other compositions, reveal that sublimation timescales far exceed local dynamical times, allowing grains to persist in a superheated state. This kinetic inhibition results in a broad, dynamic sublimation front whose location and morphology are strongly regulated by radial advection and dust coagulation. Our coupled simulations, integrating sublimation with advection and grain evolution, show that the front varies radially by a factor of four with accretion rate and exhibits a vertically stratified, bowl-shaped structure. These findings imply that the inner disk’s dust distribution, thermal structure, and subsequent planet formation are profoundly influenced by the kinematics and kinetics of dust grains, necessitating a departure from equilibrium prescriptions in disk models and interpretations of inner rim observations.

We present direct numerical simulations demonstrating deflagration-to-detonation transition (DDT) driven by oxygen flames in Type Ia supernova progenitors. Using the Castro hydrodynamics code coupled with the “aprox13” 13-isotope nuclear network, we simulate combustion in isolated fuel regions where oxygen flames trail carbon flames. In a fiducial 1D run at ρ ₀ = 3.5 × 10 ⁷ g cm ⁻³ we observe spontaneous DDT of the oxygen flame via the Zel’dovich gradient mechanism when the carbon–oxygen separation reaches ∼10 km. The oxygen detonation then captures the carbon flame and triggers a stable carbon detonation. Systematic 1D parameter scans show that successful carbon DDT requires upstream densities in the range (3.1–3.6) × 10 ⁷ g cm ⁻³ and a minimum carbon-flame thickness of ≳20 m. 2D simulations confirm DDT and demonstrate that the multidimensional cellular structure of the oxygen detonation can promote carbon detonation at somewhat lower densities than in one dimension. These results provide direct numerical evidence that oxygen-flame-driven DDT is physically plausible in turbulent white-dwarf environments and underscore the importance of multidimensional effects for Type Ia supernova explosion modeling.