Massive stars strongly influence their surroundings through radiative and mechanical feedback, but its effects on dense gas structures at sub-pc scales remain poorly constrained. We investigate how feedback from a newly formed massive star affects dense cores in the filamentary molecular cloud IRAS 18530+0215. We analyze ALMA Band 6 observations of 1.3 mm dust continuum and DCN, N_2D^+, and ^13CS line emission, together with VLA K-band continuum and NH_3 observations. Dense cores are identified with astrodendro, and their temperatures, masses, velocity dispersions, and virial parameters are derived. The dynamical state of the ultra-compact H II region is examined through energy and pressure estimates. The H II region has a radius of ∼0.1 pc and an expansion velocity of ∼2.5 km s^-1, corresponding to a shell dynamical age of ∼0.06 Myr. DCN and ^13CS cores are concentrated near the H II region, whereas N_2D^+ cores preferentially lie farther away. Core temperatures and velocity dispersions decrease with projected distance from the H II region. Virial parameters increase within the inner ∼0.3 pc but decline sharply beyond this scale, while core masses show no significant trend with distance. Strong star formation signatures are found at ∼0.2 pc, whereas more distant regions still host quiescent, cold dense cores. The compact H II region appears trapped or choked within ∼0.1 pc, while its feedback extends to at least ∼0.3 pc. Within this region, feedback enhances core velocity dispersions, gas temperatures, and virial parameters, with no evidence that it promotes the formation of more massive dense cores.

The nearly edge-on starburst galaxy NGC 253 has been observed to exhibit extended halo emission in multiple bands, making it an ideal laboratory for studying the transfer of matter from the disk to the halo. We aim to determine how the cosmic-ray electrons (CREs) flow from the disk to the halo and understand what drives their propagation. By combining data from multiple observations, we generated improved total intensity images at 943 MHz with a resolution of 13 from the Australian SKA Pathfinder (ASKAP), and at 216 MHz with a resolution of 45 from the Murchison Widefield Array (MWA). The 1D advection and diffusion equations were solved, and the solutions were fitted to the observed synchrotron emission intensity and spectral-index profiles to constrain the propagation model and parameters. The ASKAP total intensity map has an rms noise of 16 μJy beam -1 $, reaching the classical confusion limit, and the MWA map has an rms noise of 1 mJy beam^-1. The sensitivities are significantly improved in comparison to previous observations at similar frequencies. In the ASKAP image, we identify a clear loop-like structure in the northwestern radio spur, extending vertically up to sim9,kpc above the disk, while the southeastern spur reaches heights of sim8,kpc. The synchrotron emission intensity profiles perpendicular to the disk can be fitted with exponential components in the central regions and with Gaussian components in the outer regions. This result implies that CREs in these two regions propagate differently. By jointly fitting the vertical synchrotron emission intensity profiles at 943 MHz and 216 MHz, together with the corresponding synchrotron spectral-index profiles, our results provide the clearest evidence to date that CREs are transported from the disk by advection in the central region and by diffusion elsewhere in NGC 253. The advection speed in the central region increases exponentially with height and reaches the escape speed to form a superwind of CREs at about 5.5 kpc. This superwind is associated with regions in the disk with active star formation and X-ray emission, indicating a bulk motion of baryons caused by the advection. The combined thermal, magnetic, cosmic-ray, and ram pressures exceed the gravitational pressure below $|z|łesssim5.5 kpc, and this overpressure condition accelerates the superwind. High-sensitivity low-frequency radio observations provide an important probe of the transport of CREs. With these observations, we have revealed a newly detailed view into the kinematic origin of the superwind from the center of NGC 253.

The interplay of magnetic fields, turbulence, and gravity governs the structural evolution of the interstellar medium (ISM) and the initial conditions of star formation, yet observational gaps have long enforced a broken power-law description of the magnetic field–density relation. Here we assemble a unified dataset spanning ten orders of magnitude in density (10^-26–10^-16 g cm^-3) by combining pulsar and Zeeman observations. The unified data are consistent with a continuous magnetic-field evolution organised by the Alfvén Mach number ℳ_ A=√(E_K/E_B). Within this interpretation, the low-density gas is magnetically dominated (ℳ_ A<1), whereas the high-density gas becomes kinetically dominated (ℳ_ A>1) as gravity increasingly contributes to the kinetic-energy budget, with magnetic tension continuing to influence the collapse geometry. Within the Gradual Transition interpretation, the empirical break density traces the vicinity of the trans-Alfvénic equipartition point, ℳ_ A=1. This Gradual Transition model makes three predictions tested here. Its exponent and background field are fixed in advance by turbulent physics and recovered by the fits (β≈0.15–0.21 against a predicted 0.147; B_c≈2.0 μG). A dense-gas fit, extrapolated blindly across four decades, passes through the diffuse pulsar data. And, under the adopted scale mappings, the implied magnetic-energy spectrum approaches a k^-5/3-like scaling on large scales and departs from this extrapolation on small scales, where gravitational compression amplifies the field. The broken power law can therefore be viewed as a piecewise approximation to the continuous magnetic equation of state, with its fitted transition density potentially retaining a physical connection to the onset of gravity-driven motions.

The interstellar medium is ubiquitous throughout the universe across multiple scales. In this study, we introduce the multiscale decomposition reconstruction method, an equation-based model designed to derive width maps of interstellar medium structures and predict their volume density distribution on the plane of the sky from input column density data. This approach applies the constrained diffusion algorithm , based on a simple yet common physical picture: as molecular clouds evolve to form stars, the density of the interstellar medium increases while the scale decreases. Validation on simulations confirms that this method accurately predicts volume density with minimal error. Notably, the equation-based model performs comparably to or even more accurately than the AI-based denoising diffusion probabilistic models that rely on vast parameters and substantial computational resources. Unlike the “black-box” nature of AI, our equation-based model offers full transparency, making it easier to interpret, debug, and validate. The simplicity, interpretability, and computational efficiency make it powerful not only for understanding complex astrophysical phenomena but also for complementing and enhancing AI-based methods.

Complex physical systems, from supersonic turbulence to the macroscopic structure of the universe, are governed by continuous multiscale dynamics. While modern machine learning architectures excel at mapping the high-dimensional observables of these systems, it remains unclear whether they internalize the governing physical laws or merely interpolate discrete statistical correlations. Standard Explainable AI (XAI) architectures, particularly perturbation-based and gradient-saliency methods, rely on pixel-wise perturbations, which generate unphysical artifacts and push inputs off the valid empirical distribution. To resolve this, we introduce a diagnostic framework driven by Constrained Diffusion Decomposition (CDD), a diffusion-based multiscale data decomposition algorithm that enables physically constrained data generation and model evaluation via scale-aware modifications. Applying this framework to a Denoising Diffusion Probabilistic Model (DDPM), we execute deterministic interventions directly within the continuous, CDD-based scale space. We demonstrate that under moderate physical perturbations, the unconstrained generative model exhibits localized structural freezing and non-linear instability rather than continuous PDE-like responses. The network fails to maintain cross-scale continuity, causing the generative trajectory to diverge when pushed into unseen physical states. By synthesizing a continuum of physically coherent states, this scale-informed methodology establishes a controlled test ground to evaluate algorithmic vulnerabilities, providing the rigorous physical constraints necessary for future architectures to respect the multiscale causality of the natural universe.

Interstellar dust is a fundamental component of the Milky Way, influencing star formation, galactic evolution, and observations across the electromagnetic spectrum. Using red clump stars selected from near- and mid-infrared photometry, together with stellar catalogs from previous studies, we construct dust density maps of the Galactic plane (|Z|<25 pc) covering the full 360^∘ in longitude and reaching distances up to 7 kpc. By applying a U-Net convolutional neural network to invert the line-of-sight extinction distribution, we obtain dust density maps at resolutions of 10, 50, and 100 pc, which reveal detailed structures including spiral arms, inter-arm spurs, and giant cavities. The dust distribution in the Galactic plane exhibits a morphology closely resembling that of the so-called Phantom galaxy M74. The derived exponential scale length of the Galactic dust disk is 2.90 kpc, slightly larger than that of the stellar thin disk. Our publicly available dust maps provide a new benchmark for extinction correction, studies of Galactic structure, and the investigation of the interplay between star formation and the interstellar medium.

The nearly edge-on starburst galaxy NGC 253 exhibits extended multiwavelength halo emission, making it an ideal laboratory for studying disk-halo transport. We present improved ASKAP 943 MHz and MWA 216 MHz total-intensity images with resolutions of 13 and 45 arcsec and rms noise levels of 16 μJy beam^-1 and 1 mJy beam^-1, respectively. After subtracting the thermal emission, we fitted the vertical synchrotron emission intensity and spectral-index profiles with one-dimensional advection and diffusion models. The ASKAP image reveals a loop-like structure in the northwestern radio spur extending to ∼9 kpc above the disk, while the southeastern spur reaches ∼8 kpc. The vertical profiles are best fitted by exponential components in the central region and Gaussian components in the outer regions, indicating advection-dominated CRE transport in the center and diffusion elsewhere. In the central region, the advection speed increases exponentially with height and reaches the estimated escape speed at about 5.5 kpc. The spatial correspondence with star-forming and X-ray-emitting regions indicates that CRE advection traces the bulk motion of the magnetized outflow. Below ∼5.5 kpc, the combined thermal, magnetic, cosmic-ray, and ram pressures exceed the estimated gravitational pressure, consistent with acceleration of the galactic wind. These results demonstrate the power of sensitive low-frequency radio observations for probing CRE transport and galactic outflows.

Protostellar core formation and growth in high-mass star-forming regions remain key to understanding massive star birth. We analyze the masses of 839 cores (resolved at scales of a few thousand au) from the ASHES project targeting 39 massive infrared dark cloud clumps. The masses of the three most massive cores scale linearly with the total core mass. They maintain a constant mass fraction of 25

The Rayleigh-Taylor instability (RTI) arises at the interface between two fluids of different densities, notably when a heavier fluid lies above a lighter one in an effective gravitational field. In astrophysical systems with high velocities, relativistic corrections are necessary. We investigate the linear theory of the relativistic Rayleigh-Taylor instability (R-RTI) in a magnetized medium, where fluids can move with relativistic velocities. We chose an "intermediate frame" in which the fluids on each side of the interface move in opposite directions with identical Lorentz factors gamma(*) and derive the new dispersion relation of the R-RTI. This symmetry facilitates analytical derivations and the study of relativistic effects on the dynamics of instabilities. We find that the instability is activated when the Atwood number A=(rho(1)h(1)-rho(2)h(2))/(rho(1)h(1)+rho(2)h(2)) > 0 = , where rho(1) and rho(2) are densities measured in the rest of the fluids. The relativistic effect is mostly contained in the Lorentz transformation of the effective acceleration g' g gamma(-2)(*), which, combined with time dilation, leads to a much slower growth of instability (omega' = gamma(-1)omega(0) (*)), and a slightly elongated length of the unstable patch, due to weaker g in the intermediate frame. Taking time dilation into account, when viewed in the rest frame of the medium, we expect the instability to grow at a much reduced rate. The analytical results should guide further explorations of instability in systems such as microquasars (mu QSOs), Active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and radio pulsars (PSRs), where the apparent stability of the jet can be attributed to either the intrinsic stability (e.g. the Atwood number) or the much prolonged duration through which R-RTI can grow.

Star-forming regions are key to understanding the formation and early evolution of stars. Young stellar objects (YSOs) form groups with distinct kinematic and spatial properties, inherited from the turbulent dynamics of their parent molecular clouds. The high-precision astrometry and photometry from Gaia Data Release 3 (DR3) enable detailed studies of these groups' three-dimensional motions and their evolutionary stability. This study aims to investigate the kinematic properties and evolutionary consistency of YSO associations in the solar neighbourhood. Here, we show that HDBSCAN clustering of Gaia DR3 data yields 145 YSO groups comprising 5713 stars within 1 kpc, with a derived Larson's relation of σ_v = (1.10 ± 0.13) × r^0.38 ± 0.03, consistent across age bins up to 20 Myr. This slope aligns with the canonical value of 0.38 and typical ranges of 0.4–0.5. The stable Larson's relation across ages indicates that the inherited turbulent structure from parent clouds persists without significant disruption. These findings establish a benchmark for studying the kinematic legacy of star-forming regions.

Infrared Dark Clouds 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 (JCMT) Large Program, has mapped nearby IRDCs with SCUBA-2. Complementary molecular line observations are needed to characterise the physical, kinematic, and chemical properties of the dense gas. 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. We performed single-pointing K-band and W-band observations towards 56 ALOHA IRDCs clumps using the Effelsberg 100-m and Yebes 40-m telescopes, respectively. We derived NH3 kinetic temperatures using the hyperfine group ratio (HFGR) method and identified infall and shock signatures from HCO+, H13CO+, SiO, and HNCO profiles. Water masers and NH2D emission were used as complementary tracers of chemical evolution and star formation. The clumps exhibit kinetic temperatures of 15-29 K. We detect NH2D emission towards 18 sources, with NH2D centroid velocities consistent with NH3, indicating both 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 are detected in 22 sources, with prominent velocity ranges and variability. Broad SiO emission (> 20 km/s) indicates strong shocks, while narrower extents (< 6km/s) likely trace large-scale interactions or low-velocity shocks. The widespread infall signatures, shock tracers, masers, and NH2D 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.

Disk-mediated accretion is central to theories of massive star formation, setting the initial conditions for their evolution. Yet observations of Keplerian disks around early O-type protostars remain scarce, as they are often blended into complex surrounding structures. We report Atacama Large Millimeter/submillimeter Array Band 6 observations (300 au resolution) of an accretion disk surrounding a high-mass protostar in the Sagittarius C cloud in the Central Molecular Zone (CMZ) around the Galactic center. We identify spectral lines and analyze the spatial distribution of the emission of the complex organic molecules. We use a dynamical model with an inner Keplerian disk and an outer free-fall envelope to fit the three-dimensional position-position-velocity data of the stacked CH3OCHO molecular lines and constrain the mass of the central protostar to be similar to 40-3+2M circle dot . The fitting results additionally show that the disk has a centrifugal radius at about 1300 au. Considering the infall velocity, radius, and mass of the envelope, we estimate the accretion rate from the envelope onto the disk to be similar to 7 & times; 10-3 M circle dot yr-1. We also identify spiral-like structures in the disk that can be described by free-falling streamers. Our results highlight the critical role of accretion disks and streamers in the mass accumulation of early O-type stars in the CMZ.

Due to the inhomogeneity of electron number density, radio waves emitted by pulsars undergo scattering as they pass through the interstellar medium (ISM). However, a connection between large-scale pulsar scattering data and the structure of the Galactic ISM has yet to be established. In this paper, we explore the capability of pulsar scattering time data in discovering structures in the ISM. Using a large data set of scattering time measurements for 473 pulsars, we fit the pulsar reduced scattering intensity as a function of Galactic latitude and distance, constructing a smooth model of the Galactic pulsar scattering distribution. By comparing this smooth distribution with observational data, we identify two ISM structures responsible for pulsar scattering, one is associated with the Vela supernova remnant region within the Gum Nebula, while the other is a newly discovered structure—a distant superbubble, G38, located at a distance of 2.3 kpc with a size of ~50 pc. Analysis of the correlation coefficient of the pulsar scattering distribution shows that the correlation is dominated by structures smaller than 0.15 kpc—the closest separation approachable by the current data set. As measurements of the pulsar scattering time continue to increase in the future, they can potentially become an independent tool for exploring structures in the ISM.

Gravity plays important roles at multiple scales in the universe. An important, yet often neglected, role of gravity is its ability in driving anisotropic fragmentation through tides. When tides dominate, fragmentation becomes anisotropic, and the Jeans length along the short axis, l_ tidal, Jeans, is approximately σ_ v/√(G ρ_ mean), determined by the external tides through the mean density ρ_ mean. We compare predictions of l_ tidal, Jeans against observational results in massive star-forming clumps, the Circumnuclear Disk (CND) around the supermassive black hole Sgr A* at the center of the Galaxy, the Central Molecular Zone in the Galactic Center, a hub-filament system, and a streamer around a young star. We find that the observed widths of these filamentary structures match theoretical predictions from tidally-controlled Jeans fragmentation. The formation of filaments can potentially shield cold gas against radiation pressure and photoevaporation, as well as hydrodynamical interaction with the ambient medium, potentially enabling the cold gas to survive. Thus, tidal forces are major players regulating gas transport around massive objects.

Kinematic information is crucial for understanding the evolution of complex systems, such as interstellar gas. Obtaining full 3D kinematic information is a crucial final step for modeling and interpretation. Molecular clouds are nurseries where stars are born. Stars at a very early stage, like young stellar objects (YSOs), inherit the spatial and kinematic structure of the gas patches they originate from. In this paper, we combine measurements of radial velocities towards the gas and the kinematic information of YSOs from Gaia DR3 to derive 3D velocities of a sample of YSO (Young Stellar Object)-MC (Molecular Cloud) complexes at d≲3.5kpc from the Sun. We find that the molecular interstellar medium traced by the YSO-MC complexes generally follows Galactic rotation, with an additional peculiar velocity of 8.6 km s^-1. The random motion of these complexes in the Galactic XY plane is more energetic than motion along the Z direction. A catalogue containing the 3D velocities of the YSO-MC complexes at different reference frames is available, and the distances and 3D velocities of well-known molecular clouds are presented. Our results set the foundation for exploring the interplay between the Galaxy, the molecular ISM, and star formation. Data available at https://doi.org/10.5281/zenodo.16364877.

Interstellar medium widely exists in the universe at multi-scales. In this study, we introduce the {\it Multi-scale Decomposition Reconstruction} method, an equation-based model designed to derive width maps of interstellar medium structures and predict their volume density distribution in the plane of the sky from input column density data. This approach applies the {\it Constrained Diffusion Algorithm}, based on a simple yet common physical picture: as molecular clouds evolve to form stars, the density of interstellar medium increases while their scale decreases. Extensive testing on simulations confirms that this method accurately predicts volume density with minimal error. Notably, the equation-based model performs comparably or even more accurately than the AI-based DDPM model(Denoising Diffusion Probabilistic Models), which relies on numerous parameters and high computational resources. Unlike the "black-box" nature of AI, our equation-based model offers full transparency, making it easier to interpret, debug, and validate. Their simplicity, interpretability, and computational efficiency make them indispensable not only for understanding complex astrophysical phenomena but also for complementing and enhancing AI-based methods.

We acquired 450 and 850 μ m dust continuum polarization observations toward the inner region of the Central Molecular Zone (CMZ) as part of the B -Fields In Star-forming Region Observations survey using the POL-2 polarimeter on the James Clerk Maxwell Telescope. These observations encompassed three dense structures: the 20 km s ^−1 cloud (20MC), 50 km s ^−1 cloud (50MC), and circumnuclear disk (CND). Our aim is to investigate the magnetic field morphology and strength in the inner region of the CMZ using polarized dust continuum and the Davis–Chandrasekhar–Fermi method. The magnetic field morphology is highly ordered in all three dense regions. The plane-of-sky magnetic field strengths are ∼1 mG for the 20MC and the 50MC, and ∼2 mG for the CND. We compare the energy contributions of turbulence, gravity, and thermal motion with that of the magnetic field using the plasma β , mass-to-flux ratio, and Alfvén Mach number. The outcomes reveal the magnetic field stands out as the predominant factor within the inner region of the CMZ. The dominance of the magnetic field may explain the low star-forming rate in the CMZ. We further investigate the dust grain alignment efficiency by exploring the relationship between polarization fraction and total intensity. The results suggest that dust grains are well aligned with the magnetic fields.

Observations show that molecular gas in spiral galaxies is organized into a network of interconnected systems through the gravitational coupling of multi-scale hub-filament structures. Building on this picture, we model molecular gas in the galaxy NGC 628 as a gravitational network, where molecular clouds are represented as nodes. Through analyzing this network, we can characterize both the gravitational interactions and the physical properties of the clouds using geometry-based network metrics. A strong correlation is observed between the geometric and physical properties of the nodes (clouds). High-mass clouds tend to exhibit less clustering and greater average separations, suggesting that they generally have fewer neighbors. During their formation and evolution, high-mass clouds may deplete nearby gas via accretion or merging, leading to more isolated characteristics within the network. This aligns with observations showing a decrease in the virial ratio of molecular clouds as their mass increases. For clouds at different evolutionary stages, less evolved clouds with lower mass are typically found in tighter gravitational subnetworks, with closer proximity to neighboring clouds. As a result, they are more prone to accretion or merging during evolution.

Turbulence is a complex physical process prevalent in modern physics, particularly in ionized environments like interstellar gas, where magnetic fields play a dynamic role. However, the precise influence of magnetic fields in such settings remains unclear. We employ the Alfven Mach number, M-A = root E-k /E-B, to gauge the magnetic field's significance relative to turbulent motion, uncovering diverse interaction patterns. In the low-M-A magnetic regime, the field is force-free, yet gas motion does not align with it. At intermediate M-A (magnetic-kinetic transition regime), velocity and magnetic fields show peak alignment, likely due to rapid relaxation. In the high-MA kinetic regime, both fields are irregular and unaligned. These regimes find observational counterparts in interstellar gas, highlighting the multifaceted nature of MHD turbulence and aiding future astrophysical interpretations.

Star formation estimates based on the counting of YSOs is commonly applied to nearby star-forming regions in the Galaxy. With this method, the SFRs are measured using the counts of YSOs in a particular protostellar Class, a typical protostellar mass, and the lifetime associated with this Class. However, the assumptions underlying the validity of the method such as that of a constant star formation history (SFH) and whether the method is valid for all protostellar Classes has never been fully tested. In this work, we use Monte Carlo models to test the validity of the method. We build synthetic clusters in which stars form at times that are randomly drawn from a specified SFH. The latter is either constant or time-dependent with a burst like behavior. The masses of the protostars are randomly drawn from an IMF which can be either similar to that of the Milky Way field or be variable . For each star in every cluster, the lifetimes associated with the different protostellar classes are also randomly drawn from Gaussian distribution functions centered around their most likely value as suggested by the observations. We find that only the SFR derived using the Class 0 population can reproduce the true SFR at all epochs, and this is true irrespective of the shape of the SFH. For a constant SFH, the SFR derived using the more evolved populations of protostars (Classes I, F, II, and III) reproduce the real SFR only at later epochs which correspond to epochs at which their numbers have reached a steady state. For a time-dependent burst-like SFH, all SFR estimates based on the number counts of the evolved populations fail to reproduce the true SFR. We also show how the offsets between Class I and Class II based SFRs and the true SFR plotted as a function of the number ratios of Class I and Class II versus Class III YSOs can be used in order to constrain the SFH of observed molecular clouds.