Sazuna/UAT_keywords huggingface dataset:
Evidences of Two Merging Elongated Filaments Associated with AGAL323.444+0.096 and Star Formation. We study the structure, kinematics, and star-forming activity of filamentary cloud F-NE associated with AGAL323.444+0.096 using 13CO (J = 2─1) molecular line and continuum data from the far-infrared to near-infrared. The cloud comprises two elongated subfilaments, F-NE-north and F-NE-south, each spanning 25 pc, with systemic velocities of −65.25 and −67.38 km s−1, respectively. F-NE-north and F-NE-south seem to be merging by collision. They exhibit signatures of cloud─cloud collisions, including U-shaped and arc-like morphologies, complementary components, and bridge features, suggesting ongoing collisions. The interacting zones show enhanced column densities and elevated velocity dispersion, further supporting the collision scenario. All these features are consistent with the "fray and gather" model. Dense clumps and young stellar objects are predominantly concentrated in these collision regions, implying that filament merging and localized collisions drive the formation of massive dusty clumps capable of nurturing massive stars. These results demonstrate that filament merging by collision is crucial for both filament structural evolution and the formation of massive stars and clusters.

Keywords: Interstellar dynamics, Interstellar filaments, Molecular clouds, Young stellar objects, Star formation
CO in MASsive Spirals (CO-MASS): An IRAM 30 m CO Emission Line Survey of the CGM-MASS Sample. There exist extremely massive spiral galaxies in isolated environments, with stellar masses several times that of the Milky Way, yet their star formation rates (SFRs) are comparable to or even lower than that of the Milky Way. In this paper, we investigate the molecular gas properties of such galaxies to better understand the origin of their low SFRs. We present IRAM 30 m CO observations of five extremely massive spirals from the CGM-MASS sample. We compare their star formation efficiencies with the Kennicutt─Schmidt relation and find that these massive spirals generally exhibit low efficiency in converting molecular gas into stars. We further compare their molecular gas masses with their atomic gas and stellar masses, and also include the CHANG-ES sample galaxies observed with the IRAM 30 m telescope in a similar manner for comparison. Our sample galaxies show low efficiency in converting atomic to molecular gas and have lower molecular gas fractions, suggesting that their suppressed star formation stems from both limited gas supply and inefficient star formation. Considering potential cold gas sources in massive spirals, we argue that their current reservoirs likely originate from past starburst or merger events rather than ongoing accretion in present isolated environments. Finally, we examine the location of these galaxies on the baryonic Tully─Fisher relation, finding them baryon-deficient and deviating from the trend of lower-mass galaxies. This suggests either a significant undetected baryonic component or a flattening/turnover of the relation at the high-mass end, consistent with the stellar mass─halo mass relation.

Keywords: Interstellar molecules, Spiral galaxies, Interstellar medium, Star formation
Magnetic Activities of GJ 1151: Flares in TESS Data and Radio Observation in uGMRT. GJ 1151 is a nearby (8 pc), quiescent mid-M dwarf (M 4.5V) of older age, made especially interesting by the hypothesized presence of a close-in planet invoked to explain its low-frequency radio emission. We analyzed the flaring activity of GJ 1151 to investigate its stellar atmosphere and magnetic properties using 2 minute short-cadence photometry from the Transiting Exoplanet Survey Satellite (TESS) and radio observations from the upgraded Giant Metrewave Radio Telescope (uGMRT). Analysis of TESS Sector 48 revealed three flare events, with bolometric flare energies estimated in the range of 1030─1031 erg, showing that GJ 1151, previously regarded as optically inactive, does in fact exhibit flare activity, placing it in the lower-to-intermediate activity regime. Interestingly, we reported the first estimation of the most energetic flare energy to be (4.86 ± 0.19) × 1031 erg that lasted for approximately 30 minutes, implying a minimum surface magnetic field strength of 45 G to power the event. We estimated the mean spot temperature to be approximately 2886 ± 837 K and the spot area to be 1.2% of the area of the star. The nondetection of radio emission at 1.36 GHz with the uGMRT suggests either time variability in the emission or the presence of a frequency cutoff in the 3σ upper limit on its flux density of 105 μJy beam−1 in the emission mechanism, potentially governed by the changing magnetic environment of the star and the orbital configuration of its hypothesized planet.

Keywords: M dwarf stars, Starspots, Radio sources, Stellar flares, Magnetic fields, Habitable planets
The Serpent Eating Its Own Tail: Dust Destruction in the Apep Colliding Wind Nebula. Much of the carbonaceous dust observed in the early Universe may originate from colliding wind binaries (CWBs) hosting hot, luminous Wolf─Rayet (W-R) stars. Downstream of the shock between the stellar winds there exists a suitable environment for dust grain formation, and the orbital motions of the stars wrap this dust into richly structured spiral geometries. The Apep system is the most extreme W-R CWB in our Milky Way: two W-R stars produce a complex spiral dust nebula, whose slow expansion has been linked to a gamma-ray burst progenitor. It has been unclear whether the O-type supergiant 0 .″ 7 distant from the W-R + W-R binary is physically associated with the system, and whether it affects the dusty nebula. Multiepoch Very Large Telescope/VISIR and JWST/MIRI observations show that this northern companion star routinely carves a cavity in the dust nebula—the first time such an effect has been observed in a CWB—which unambiguously associates the O star as a bound component to the Apep system. These observations are used together with a new geometric model to infer the cavity geometry and the orbit of the W-R + W-R binary, yielding the first strong constraints on wind and orbital parameters. We confirm an orbital period of over 190 yr for the inner binary—nearly an order of magnitude longer than the next longest-period dust-producing W-R CWB. This, together with the confirmed classification as a hierarchical triple, cements Apep as a singular astrophysical laboratory for studying colliding winds and the terminal life stages of the most massive star systems.

Keywords: Dust nebulae, Massive stars, Stellar winds, Wolf-Rayet stars, Circumstellar dust
The Formation and Evolution of Dust in the Colliding-wind Binary Apep Revealed by JWST. Carbon-rich Wolf─Rayet (W-R) stars are significant contributors of carbonaceous dust to the galactic environment; however, the mechanisms and conditions for formation and subsequent evolution of dust around these stars remain open questions. Here we present JWST observations of the W-R+W-R colliding-wind binary Apep, which reveal an intricate series of nested concentric dust shells that are abundant in detailed substructure. The striking regularity in these substructures between successive shells suggests an exactly repeating formation mechanism combined with a highly stable outflow that maintains a consistent morphology even after reaching 0.6 pc (assuming a distance of 2.4 kpc) into the interstellar medium. The concentric dust shells show subtle deviations from spherical outflow, which could reflect orbital modulation along the eccentric binary orbit or nonsphericity in the stellar wind. Tracking the evolution of dust across the multitiered structure, we measure the dust temperature evolution that can broadly be described assuming an amorphous carbon composition in radiative thermal equilibrium with the central stars. The temperature profile and orbital period place new distance constraints that support Apep being at a greater distance than previously estimated, reducing the line-of-sight and sky-plane wind speed discrepancy previously thought to characterize the system.

Keywords: WC stars, Dust nebulae, Massive stars, WN stars, Stellar mass loss, Stellar winds, Wolf-Rayet stars, Dust shells, Circumstellar dust
Creating Pileups of Eccentric Planet Pairs Wide of Mean Motion Resonances through Divergent Migration. Observed pileups of planets with period ratios ≍1% wide of strong mean motion resonances (MMRs) pose an important puzzle. Early models showed that they can be created through sustained eccentricity damping, driving a slow separation of the orbits, but this picture is inconsistent with elevated eccentricities measured through transit-timing variations (TTVs). We argue that any source of divergent migration (tides, planet─disk interactions, etc.) will cause planets that encounter an MMR to both jump over it (piling up wide of resonance) and get a kick to their eccentricities. We find that normalizing observed deviations from resonance by the value at which the pair would encounter and jump over the resonance leads to a significantly clearer trough narrow of the resonance. We additionally find that the jumps in eccentricity expected from slow MMR crossings are sufficiently large to explain the scale of eccentricities measured through TTVs, though some residual eccentricity damping would be required to quantitatively match observations.

Keywords: Exoplanet migration, Orbital resonances, Exoplanet astronomy, Transit timing variation method, Exoplanet formation, N-body simulations
Dependency of the Bar Formation Timescale on the Halo Spin. Bars are among the most prominent structures in disk galaxies. While the widely accepted swing-amplification theory provides a qualitative framework for their formation, the detailed physical processes remain incompletely understood. Previous studies have shown that the bar formation timescale in isolated galaxies depends exponentially on the disk mass fraction (the so-called "Fujii relation") and linearly on disk hotness and thickness. However, the influence of dark matter (DM) halo spin on bar formation has not been systematically investigated. In this work, we construct a suite of N-body disk─halo models with varying disk mass fractions and amounts of random motions. By introducing prograde and retrograde spins in the DM halo, we explore how halo spin modifies the established empirical relations governing bar formation timescales. We find that these relations remain valid in both prograde and retrograde halo spin models. For rapid bar formation (short timescale), the effect of halo spin is nearly negligible. In contrast, for moderately slow bar formation, prograde (retrograde) halo spin tends to accelerate (suppress) bar onset. In cases of extremely slow bar formation, halo spin introduces a stronger but more stochastic influence. These trends might arise from the exchange of angular momentum between the stellar disk and the DM halo.

Keywords: N-body simulations, Galaxy bars, Disk galaxies
Emission-line Diagnostics at z &gt; 4: [O III]λ4364/Hγ versus [Ne III]λ3870/[O II]λ3730. We use JWST Near-Infrared Spectrograph observations from the Cosmic Evolution Early Release survey, GLASS-JWST ERS (GLASS), and JWST Advanced Deep Extragalactic Survey to measure rest-frame optical emission-line ratios of 89 galaxies at z &gt; 4. The stacked spectra of galaxies with and without a broad-line feature reveal a difference in the [O III]λ 4364 and Hγ ratios. This motivated our investigation of the [O III]λ4364/Hγ versus [Ne III]/[O II] diagram. We define two active galactic nucleus (AGN)/star formation (SF) classification lines based on 21,048 Sloan Digital Sky Survey galaxies at z ∼ 0. After applying a redshift correction to the AGN/SF lines, we find 69.2% of broad-line active galactic nuclei (BLAGN) continue to land in the AGN region of the diagnostic, largely due to the [Ne III]/[O II] ratio. However, 33.0% of non-BLAGN land is in the AGN region as well. The [O III]λ4364/Hγ versus [Ne III]/[O II] diagram does not robustly separate BLAGN from non-broad-line galaxies at z &gt; 4. This could be due to star-forming galaxies having harder ionization, or these galaxies contain a narrow line AGN, which are not accounted for. We further inspected galaxies without broad emission lines in each region of [O III]λ4364/Hγ versus [Ne III]/[O II] diagram and found that they have slightly stronger C III]λ1908 fluxes and equivalent width when landing in the BLAGN region. However, the cause of this higher ionization is unclear and may be revealed by observing UV lines.

Keywords: Active galaxies, Emission line galaxies, Galaxy evolution, Interstellar medium, Galaxies
Early Coformation of the Milky Way's Thin and Thick Disks at Redshift z &gt; 2. The Milky Way serves as a template for understanding the formation and evolution of late-type massive disk galaxies since we can obtain detailed chemical and kinematic information for large samples of individual stars. However, the early formation of the disk and the dichotomy between the chemically thick and thin disks remain under intense debate. Some mechanisms have been proposed to explain the formation of this dichotomy, such as the injection of metal-poor gas by a gas-rich merger such as Gaia-Sausage Enceladus (GSE), or by cosmic gas filaments, radial migration, and the presence of star-forming clumps at high redshift (z &gt; 2). In this work, we combine astrometric data from the Gaia mission, chemical abundances from APOGEE and LAMOST spectroscopic surveys, and StarHorse ages to study the early stage of chemical dichotomy in the Milky Way disk. The Bayesian isochrone-fitting code StarHorse can estimate ages for thousands of stars in the solar neighborhood, being most reliable for main-sequence turnoff and subgiants, computing distances and extinction simultaneously. From these samples, we show that (i) there is an old thin disk population (&gt;11 Gyr) that indicates a period of coformation between the thick and thin disks of the Milky Way before the GSE merger, i.e., the Galaxy itself could initiate the formation of a low-α disk without the need for a gas-rich merger, and (ii) this merger would have been important to stop the formation of stars in the thick disk.

Keywords: Milky Way disk, Stellar ages, Milky Way dynamics, Chemical abundances
Beyond MESA Defaults: The Impact of Structural Resolution Uncertainty in p-mode Asteroseismology. Observations of pressure modes (p-modes) in stars have enabled profound insights into stellar properties, and theoretical stellar evolution and oscillation models are integral to these inferences. However, modeling uncertainties are often overlooked, even as they can rival or exceed observational uncertainties. In this study, we quantify, for the first time, the impact of structural resolution choices in 1D stellar evolution calculations on predicted p-mode frequencies across the H-R diagram, using MESA and GYRE. We present demonstrative measurements of resolution-based modeling uncertainty for a range of solar-like, upper main-sequence, and Mira oscillators and compare these directly to TESS observational uncertainties. We demonstrate that resolution-driven uncertainties can significantly influence theoretical predictions and in some cases overwhelm observational uncertainties by orders of magnitude. For the illustrative case considered—an order-of-magnitude variation in mesh resolution—solar-like oscillators typically have fractional, resolution-based uncertainties at or below 1% of the test frequency. Fractional uncertainties in Miras, however, are as large as 20%. We also find that the location and morphology of the red giant branch bump and red clump are impacted substantially by resolution uncertainty. Stellar ages are impacted at the 10% level for young main-sequence stars, and the model-based correction factor for the ∆ν─ ρ  scaling relation is impacted at the 2% level. Our results underscore the need to incorporate modeling uncertainties into asteroseismic analyses and provide a reference framework for observers evaluating the reliability of theoretical models.

Keywords: Asteroseismology, Stellar evolutionary models, Variable stars
Decoding the Galactic Twirl: The Downfall of Milky Way─Mass Galaxy Rotation Curves in the FIRE Simulations. Recent measurements of the Milky Way rotation curve found a sharp decline at around 15─20 kpc from the center of the Galaxy, suggesting that the Galactic dark matter halo is much less massive than predicted by other dynamical tracers. To address this tension, we study the validity of the assumptions made in calculating the Milky Way's rotation curve. To do so, we apply the Jeans equation, the current standard approach of measuring rotation curves, to three cosmological zoom-in simulations of Milky Way─like galaxies from the FIRE-2 Latte suite. Using synthetic Gaia surveys, we replicate the sample selection process and calculation employed in measuring the Milky Way rotation curve. We examine four failure modes of this calculation and find that the measured curves deviate from the true curve by 5%─20% rather than below 5%, as estimated by previous works. Interestingly, there is a large galaxy-to-galaxy variance, and different systematics dominate different galaxies. We rederive the Milky Way's dark matter density profile with the rotation curve while incorporating systematics from the simulations. The posterior distribution of the density profiles is consistent with a fiducial Navarro─Frenk─White (NFW) profile when assuming a generalized NFW profile for dark matter. We find that the virial mass is  7.32−1.53+1.98×1011  M⊙, consistent with other probes of the Milky Way's mass. However, we recommend that the field move away from relying solely on the rotation curve when studying the dark matter profile and adopt methods that incorporate additional probes and/or do not heavily depend on assumptions described in this study.

Keywords: Hydrodynamical simulations, Uncertainty bounds, Milky Way dynamics, Milky Way rotation
Interpreting Cosmological Information from Neural Networks in the Hydrodynamic Universe. What happens when a black box (neural network) meets a black box (simulation of the Universe)? Recent work has shown that convolutional neural networks (CNNs) can infer cosmological parameters from the matter density field in the presence of complex baryonic processes. A key question that arises is, which parts of the cosmic web is the neural network obtaining information from? We shed light on the matter by identifying the Fourier scales, density scales, and morphological features of the cosmic web that CNNs pay most attention to. We find that CNNs extract cosmological information from both high- and low-density regions: overdense regions provide the most information per pixel, while underdense regions—particularly deep voids and their surroundings—contribute significantly owing to their large spatial extent and coherent spatial features. Remarkably, we demonstrate that there is negligible degradation in cosmological constraining power after aggressive cutting in both maximum Fourier scale and density. Furthermore, we find similar results when considering both hydrodynamic and gravity-only simulations, implying that neural networks can marginalize over baryonic effects with minimal loss in cosmological constraining power. Our findings point to practical strategies for optimal and robust field-level cosmological inference in the presence of uncertainly modeled astrophysics.

Keywords: Hydrodynamical simulations, Convolutional neural networks, Neural networks, Cosmological parameters
From the Light Curves of Long Period Variables to Their Evolution along the Asymptotic Giant Branch. A sample of 116 long period variables is studied with the aim to reveal relations between the properties of their light curves and of their evolution along the asymptotic giant branch (AGB). Each light curve is carefully scrutinized, and its properties are summarized in a set of five parameters. One of these, which measures the relative width of the light maxima and minima, is found to be particularly efficient at revealing significant correlations with the current state of the star on the AGB. The picture that had been sketched in an earlier work is clarified, and new features are revealed. In particular, the evolution on the AGB of stars having not yet experienced a third-dredge-up event is shown to go together with a closely related path followed by the light curve in the parameter space. Moreover, evidence is found for the existence of two different types of light curves for stars having experienced dredge-up events strong enough for their impact to be detectable. For some, probably associated with higher initial mass stars, the light maximum becomes broader as the star evolves along the AGB, while for others it becomes narrower. Interpretations are proposed, however, often too speculative to be firmly ascertained: the results presented raise several unanswered questions and point to the need for new observations and analyses, suggesting that light curves still carry more messages and information than have been currently possible to decrypt.

Keywords: Late stellar evolution, Light curves, Asymptotic giant branch stars, Mira variable stars, Long period variable stars
Magnetosphere Evolution and Precursor-driven Electromagnetic Signals in Merging Binary Neutron Stars. We detail new force-free simulations to investigate magnetosphere evolution and precursor electromagnetic (EM) signals from binary neutron stars. Our simulations fully follow a representative inspiral motion, capturing the intricate magnetospheric dynamics and their impact on EM outflows. We explore a range of stellar magnetic moment orientations and relative strengths, finding that the magnetospheres and Poynting flux evolution are strongly configuration dependent. The Poynting flux exhibits pulsations at twice the orbital frequency, 2Ω, and is highly anisotropic, following a power-law dependence on orbital frequency. The index ranges from 1 to 6, shaped by the intricate dynamics of the magnetospheres. Furthermore, we present the first computation of (1) the EM forces acting on the star surfaces, revealing the presence of torques that, for highly magnetized stars, could influence the orbital dynamics or break the crust; (2) the high-energy emission signals from these systems by adopting the established isolated pulsar theory. Assuming curvature radiation in the radiation-reaction limit, we find that photons could reach TeV─PeV energies in the last ∼ms for magnetic field strengths 1010─1015 G. However, our analysis of single photon magnetic pair production suggests that these photons are unlikely to escape, with the MeV band emerging as a promising observational window for precursor high-energy emission. In this framework, we construct high-energy emission skymaps and light curves, exploring observational implications. Finally, we propose potential precursor radio emission and delayed afterglow echoes from magnetized outflows, which may contribute to late-time rebrightening in short gamma-ray bursts or to orphan afterglows.

Keywords: Neutron stars, Magnetohydrodynamics, Gamma-ray bursts, High energy astrophysics, Gravitational wave sources, Computational methods, Binary pulsars, Magnetars, Gamma-rays, Magnetohydrodynamical simulations