Sazuna/UAT_keywords huggingface dataset:
A Grid-constrained Fourier Neural Operator for Magnetic Field Extrapolation of the Solar Corona. In this study, we propose a hybrid architecture for coronal magnetic field extrapolation modeling. This architecture integrates Fourier neural operators (FNOs) with grid-based finite-difference methods used to impose physical constraints and is named grid-constrained FNO (GC-FNO). The GC-FNO trains an FNO with nonlinear force-free field (NLFFF) data from any existing code, learning the mapping of the magnetic fields between two neighboring grid layers along the vertical direction. It then iteratively applies this FNO to reconstruct the three-dimensional (3D) magnetic field, optimizing the model via divergence loss and force-freeness loss computed from the 3D field using second-order finite difference. The GC-FNO excels in processing data with nonperiodic boundary condition, leveraging inherent characteristics of NLFFF data to minimize error accumulation during the iterative process. The qualitative and quantitative analyses indicate that the GC-FNO achieves reasonably accurate 3D magnetic field reconstruction and performs well in universality tests across 30 active regions as well as in generalization tests.

Keywords: Solar active region magnetic fields, Solar physics, Neural networks
GRB 240619A: Evidence for a Compact Star Merger Origin. GRB 240619A, detected by Fermi-Gamma-ray Burst Monitor with a duration of ∼36.1 s at redshift z = 0.3965, a short, hard main emission (ME), a quiescent interval, and a soft extended emission (EE). We perform a detailed analysis of the temporal and spectral properties of both phases using Bayesian inference and machine learning techniques. Our main results show: (1) the spectral lags are 0.27 ± 0.03 s (ME) and 0.13 ± 0.19 s (EE), with the ME phase following the lag─luminosity relation; (2) The minimum variability timescales are ∼0.04 s (ME) and ∼0.48 s (EE), consistent with short gamma-ray bursts (SGRB) and long gamma-ray bursts (LGRB) characteristics, respectively, suggesting that the radiation in the two phases may originate from different physical mechanisms. (3) the effective amplitude feff ≍ 3.18 suggests an intrinsic origin consistent with SGRBs; (4) the spectral hardness, peak energy, Amati/Yonetoku relations, and energy─hardness─duration classification indicate that the ME phase is more similar to SGRBs, while the EE phase resembles LGRBs; (5) the local event rate density ( 4.66−3.86+11.25×10−3  Gpc−3 yr−1) further highlights its peculiarity. Spectral analysis indicates that its nonthermal emission can be well explained by the fast-cooling synchrotron radiation model. Curvature effect analysis suggests jet acceleration in the EE phase, with the jet becoming Poynting-flux dominated. The combined evidence suggests that GRB 240619A is an SGRB with EE, likely originating from a compact binary merger, and exhibiting physical properties similar to those of GRB 211211A.

Keywords: Gamma-ray bursts
Lunar Highland Preserves Meteoritic-iron-rich Materials in the Earth─Moon System. Meteoritic impacts over 4.5 billion yr have modified the composition and properties of the Earth and Moon's surfaces. The low-iron lunar highlands (FeO ∼ 5 wt%) may provide insights into the contribution of meteoritic iron to the Earth─Moon system. However, it remains unclear whether the lunar highlands preserve the composition, distribution, and impact of the meteoritic iron. In this study, we identified 30 meteoritic iron-rich impact melts in the lunar highlands. These melts are characterized by young ages (mostly Copernican), low TiO2 content (&lt;1 wt%), and relatively high FeO (&gt;5─10 wt%). Importantly, the distributions of these impact melts are spatially correlated with the distribution of iron anomalies. This work provides geological evidence for the preservation of meteoritic iron in the lunar highlands. We also proposed that such meteoritic iron could represent potential sources of impact-related Fe─Ni anomalies on the Earth, such as Sudbury and Morokweng deposits.

Keywords: Lunar highlands, Earth-moon system
The Impact of External Gas Accretion on the Distribution of H I Gas in Galaxies. Using the data from Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) and H I-MaNGA surveys, we build a sample of 37 gas─star misaligned galaxies with robust H I detections, which are believed to have undergone external gas accretion processes. Both star-forming (SF) and quiescent (QS) misaligned galaxies exhibit narrower H I line widths compared to their gas─star aligned controls. The H I profiles of SF misaligned galaxies tend to be single-peaked, displaying a slightly higher fraction of single-peaked shape compared to their aligned controls. The QS misaligned galaxies exhibit prominently single-peaked H I profiles, while their aligned controls show distinct double-horned profiles. The shape of H I profiles is expected to change with the H I surface density radial gradients through external gas accretion—the interaction between the accreted gas and the pre-existing gas leads to the redistribution of angular momentum and induces gas inflow. This suggests that the progenitors of SF misaligned galaxies are central H I enriched; in this case, the shapes of the H I profiles are insensitive to further increases in central H I surface density. The progenitors of QS misaligned galaxies are central H I deficient, hence the transition from central H I deficient to H I enriched surface density leads to significantly more single-peaked H I profiles.

Keywords: Galaxy dynamics, Galaxy kinematics, Interstellar atomic gas
The Dipole Instability in Gravitational N-body Systems: A Natural Explanation for Lopsidedness and Off-centered Nuclei in Galaxies. We explore the stability of isotropic, spherical, self-gravitating systems with a double power-law density profile. Systems with rapid transitions between the inner and outer slopes are shown to have an inflection in their isotropic distribution function (DF), where df/dE &gt; 0, thereby violating Antonov's stability criterion. Using high-resolution N-body simulations, we show that the resulting instability causes the growth of a rotating dipole (or l = 1) mode. The inflection feature in the DF responds to the mode by promoting its growth, driving the instability. The growth of the dipole results in a torque that dislodges the original cusp from its central location and sets it in motion throughout the central region. Once the mode goes nonlinear, it saturates, together with the cusp, into a long-lived soliton (the l = 1 equivalent of a bar in a disk galaxy), which maintains its sloshing motion through the center of the halo along a slowly precessing, elliptical orbit. Concurrently, the soliton traps increasingly more particles into libration, and the exchange of energy and angular momentum with these trapped particles works toward eroding the bump in the distribution function. We point out similarities between the dipole mode and the bump-on-tail instability in electrostatic plasmas, and highlight a potential connection with core stalling and dynamical buoyancy in systems with a cored density profile. Finally, we discuss the astrophysical implications in terms of lopsidedness and off-center nuclei in galaxies.

Keywords: Galaxy dynamics, Galaxy evolution, N-body simulations, Orbital resonances
Spatially Offset Active Galactic Nuclei in the Very Large Array Sky Survey: Tracers of Galaxy Mergers and Wandering Massive Black Holes. The remnants of galaxy mergers may host multiple off-nuclear massive black holes (MBHs), some of which may wander indefinitely within the host galaxy halos. Tracing the population of offset MBHs is essential for understanding how the distribution of MBHs in the Universe evolves through galaxy mergers, the efficiency of binary MBH formation, and the rates at which MBHs are seeded in low-mass satellite galaxies. Offset MBHs can be observationally traced if they are accreting and detectable as spatially offset active galactic nuclei (AGN). In this work, we build the largest uniform sample of spatially offset AGN candidates (328) by matching sources from the Very Large Array Sky Survey to galaxies in the Sloan Digital Sky Survey. Based on the radio source surface density, 29% ± 3% are unrelated chance projections. The offset AGN occupation fraction is positively correlated with host galaxy stellar mass, consistent with predictions that most offset MBHs will reside in massive halos. However, this trend vanishes, and may reverse, at the lowest stellar masses, potentially reflecting the weaker host galaxy gravitational potentials. The offset AGN occupation fraction shows no significant evolution with orbital radius, and the agreement with predictions suggests a binary MBH formation rate of &lt;0.5 per merger. Finally, for offset MBHs down to masses of 105 M⊙, the occupation fraction is ∼30−70 times lower than the expected value assuming all accreted satellites host a MBH. This result may suggest a relatively low MBH seeding efficiency.

Keywords: AGN host galaxies, Intermediate-mass black holes, Supermassive black holes, Galaxy mergers, Radio active galactic nuclei
Parallel Application of Slitless Spectroscopy to Analyze Galaxy Evolution (PASSAGE): Survey Overview. During the second half of Cycle 1 of the James Webb Space Telescope (JWST), we conducted the Parallel Application of Slitless Spectroscopy to Analyze Galaxy Evolution (PASSAGE) program. PASSAGE received the largest allocation of JWST observing time in Cycle 1, 591 hr of NIRISS observations to obtain direct near-IR imaging and slitless spectroscopy. About two-thirds of this was ultimately executed, to observe 63 high-latitude fields in pure-parallel mode. These have provided more than 10,000 near-infrared grism spectrograms of faint galaxies. PASSAGE brings unique advantages in studying galaxy evolution: (a) Unbiased spectroscopic search, without prior photometric preselection. By including the typical galaxies which have low masses and strong emission lines, slitless spectroscopy is the indispensable complement to any pretargeted spectroscopy. (b) The combination of several dozen independent fields to overcome cosmic variance. (c) Near-infrared spectral coverage, spanning a wide wavelength range of up to 1.0 to 2.3 μm, with minimal wavelength gaps, to measure multiple diagnostic rest-frame optical lines, minimizing sensitivity to dust reddening. (d) JWST's unprecedented spatial resolution, in some cases using two orthogonal grism orientations, to overcome contamination due to blending of overlapping spectra. (e) Discovery of rare bright objects especially for detailed JWST follow-up. PASSAGE data are public immediately, and our team plans to deliver fully processed high-level data products. In this PASSAGE overview, we describe the survey and data quality, and present examples of these accomplishments in several areas of current interest in the evolution of emission-line galaxy properties, particularly at low masses.

Keywords: Early universe, Emission line galaxies, James Webb Space Telescope, Galaxy evolution, Galaxies
JWST NIRCam Imaging of NGC 4258. I. Observation Overview. We present James Webb Space Telescope (JWST) Near-Infrared Camera imaging of the nearby Seyfert 1.9 galaxy NGC 4258, which hosts strong star formation regions as well as an anomalous jet-like radio structure that extends through a significant portion of its disk. This galaxy provides a unique environment to study active galactic nucleus (AGN)─driven shocks and their impacts on the interstellar medium (ISM), as its proximity allows for narrow-band observations of various near-infrared tracers sensitive to multiple levels of shock and radiative excitation: [Fe II] (1.64 μm), Paα (1.87 μm), H2 (2.21 μm), 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission, Brα (4.05 μm), and Pfβ (4.66 μm), allowing us to trace shocks with parsec-scale resolution. Comparing these near-infrared observations with available ultraviolet, optical, radio, and X-ray imaging, we find that shocks present in the brightest regions of the anomalous radio structure are likely of low velocity (50─100 km s−1), suggesting that these features originate from AGN-driven winds that interact with the host medium and mechanically impart energy into the disk. Further, while the cospatial [Fe II] and H2 emissions indicate multiphase shocks, PAH emission is relatively weaker in or absent from the most shock-excited regions, consistent with the destruction of small dust grains. Finally, we propose that surveys identifying enhanced [Fe II] in AGN host galaxies may systematically reveal a key population, where AGN feedback is significantly coupled with the surrounding ISM and actively shaping galaxy evolution.

Keywords: AGN host galaxies, Active galaxies, James Webb Space Telescope, Low-luminosity active galactic nuclei, X-ray active galactic nuclei, Active galactic nuclei, Radio active galactic nuclei
Emission-line Diagnostics for IMBHs in Dwarf Galaxies: Accounting for Black Hole Seeding and Ultraluminous X-Ray Source Excitation. Dwarf active galactic nuclei (AGN) serve as the ideal systems for identifying intermediate-mass black holes (IMBHs) down to the most elusive regimes (∼103─104M⊙). However, the ubiquitously metal-poor nature of dwarf galaxies gives rise to ultraluminous X-ray sources (ULXs) that can mimic the spectral signatures of IMBH excitation. We present a novel photoionization model suite that simultaneously incorporates IMBHs and ULXs in a metal-poor, highly star-forming environment. We account for changes in MBH according to formation seeding channels and metallicity, and changes in ULX populations with poststarburst age and metallicity. We find that broadband X-rays and UV emission lines are insensitive to MBH and largely unable to distinguish between ULXs and IMBHs. Many optical diagnostic diagrams cannot correctly identify dwarf AGN. The notable exceptions include He II λ4686 and [O I] λ6300, for which we redefine typical demarcations to account for ULX contributions. Emission lines in the mid-IR show the most promise in separating stellar, ULX, IMBH, and shock excitation while presenting sensitivity to MBH and fAGN. Overall, our results expose the potential biases in identifying and characterizing dwarf AGN purely on strong-line ratios and diagnostic diagrams rather than holistically evaluating the entire spectrum. As a proof of concept, we argue that recently discovered overmassive black holes (BHs) in high-z JWST AGN might not represent the overall BH population, with many galaxies in these samples potentially being falsely classified as purely star forming.

Keywords: AGN host galaxies, Intermediate-mass black holes, Dwarf galaxies, Galaxy evolution
The Altered Chaplygin Model as a Model for Dark Energy. We present a scalar-field formulation of the generalized Chaplygin gas (GCG) and modified Chaplygin gas (MCG) models, in which the cosmic fluid dynamics are reproduced by canonical Lagrangians with analytically derived energy density ρ(ϕ), pressure p(ϕ), and scalar potential V(ϕ). This framework provides a unified description of dark matter and dark energy, transitioning naturally from a matter-dominated phase at early times to a negative-pressure dark-energy phase at late times. In this scalar-field formulation, the GCG and MCG models are naturally applicable to both theoretical analyses and numerical simulations. Extending this approach, we develop a systematic method to obtain a class of integrable scalar-field cosmological models. In this study, we use this method to construct a new scalar-field altered Chaplygin gas (ACG) model. To investigate the viability of Chaplygin-type models, we perform a likelihood analysis using the Pantheon+ Type Ia supernova compilation together with Cepheid-calibrated distances. We examine four models, ΛCDM, GCG, MCG, and ACG, obtaining posterior constraints on the Hubble constant H0, the present-day effective equation of state ω0, the transition redshift z⋆, and the cosmic age t0. With the Cepheid calibration fixing the absolute distance scale, the inferred H0 remains nearly model-independent. The Chaplygin-type models predict an earlier onset of cosmic acceleration than ΛCDM and give a broader range for the inferred age of the Universe, reflecting their greater flexibility in late-time expansion histories. Among them, the ACG model provides tighter parameter constraints, while the GCG and MCG models produce broader posteriors due to parameter degeneracies.

Keywords: Cosmology, Type Ia supernovae, Hubble constant, Dark energy
Calcium Excess in Novae: Beyond Nuclear Physics Uncertainties. We examine Ca abundances in classical novae from spectroscopic observations spanning 65 yr and investigate whether they are systematically high compared to those predicted by nova models. For the first time, we perform Monte Carlo simulations assessing the impact of nuclear reaction rate uncertainties on abundances predicted by multizone nova models. While the Ca abundances in the models are sensitive to variations of rates of the reactions 37Ar(p, γ)38K and 38K(p, γ)39Ca, the nuclear physics uncertainties of these reactions cannot account for the discrepancy between the observed and predicted Ca abundances in novae. Furthermore, the overabundance of Ca has important implications for measuring 7Be in nova ejecta, as Ca lines are used to estimate 7Be abundances. If the Ca abundance is incorrectly determined, it could lead to inaccurate 7Be abundance estimates. Possible alternative explanations for the observed Ca overabundance are discussed.

Keywords: Explosive nucleosynthesis, Abundance ratios, Nucleosynthesis, Chemical abundances, Reaction rates, Nuclear astrophysics, Stellar nucleosynthesis, Cataclysmic variable stars, Classical novae
Cold Gas in a Post-starburst Pair in the z ∼ 1.4 HeavyMetal Survey: Major Mergers as a Pathway to Retain Gas in Quenched Galaxies. Recent observations at low redshift have revealed that some post-starburst galaxies retain significant molecular gas reservoirs despite low ongoing star formation rates, challenging most theoretical predictions that rely on heating or expelling gas reservoirs to shut down star formation. To test whether this finding holds during the peak epoch of quenching, here we present Atacama Large Millimeter/submillimeter Array CO(2─1) observations of five spectroscopically confirmed massive post-starburst galaxies at z ∼ 1.4 from the HeavyMetal survey. While four galaxies are undetected in CO emission, we detect  MH2∼109.7M⊙  of molecular gas in one system. The detected system is a close pair of two massive (M* = 1011.1−11.2M⊙) post-starburst galaxies with no clear tidal features, likely caught in the early stages of a major merger. These results suggest that mergers may be a key factor in retaining molecular gas while simultaneously suppressing star formation in quenched galaxies at high redshift, possibly by driving increased turbulence that decreases star formation efficiency. Our nondetected galaxies have postburst ages &gt;200 Myr, consistent with results at z &lt; 1; however, our gas-rich post-starburst pair is significantly older than typical gas-rich quenched systems at low redshift. Our results highlight the importance of major mergers in shaping the cold gas content of quiescent galaxies during the peak epoch of quenching.

Keywords: Galaxy formation, Quenched galaxies, Galaxy evolution, Galaxy quenching, Post-starburst galaxies
Hubble Space Telescope Deep Upper Limits Rule out a Surviving Massive Binary Companion to the Type Ic Supernova 2012fh. Current explanations of the mass-loss mechanism for stripped-envelope supernovae (SNe) remain divided between single and binary progenitor systems. Here we obtain deep ultraviolet (UV) imaging with the Hubble Space Telescope (HST) of the Type Ic SN 2012fh to search for the presence of a surviving companion star to the progenitor. We synthesize these observations with archival HST imaging, ground-based spectroscopy, and previous analyses from the literature to provide three independent constraints on the progenitor system. We fit the color─magnitude diagram of the surrounding population to constrain the most likely age of the system to be &lt;20 Myr. Analysis of spectra of SN 2012fh provides an estimate of the He core mass of the progenitor star, &gt;5.6 M⊙. We analyze deep HST images at the precise location after the SN faded to constrain the luminosity of any remaining main-sequence binary companion to be  log(L/L⊙)≲3.35 . Combining observational constraints with current binary population synthesis models excludes the presence of a faint stellar companion to SN 2012fh at the ≲10% level. The progenitor was therefore either effectively isolated at the time of explosion or orbited by a black-hole companion. The latter scenario dominates if we only consider models that produce successful SNe.

Keywords: Type Ic supernovae, Core-collapse supernovae
Stellar Mass Segregation in Dark Matter Halos. We study the effect of stellar mass segregation driven by collisional relaxation within the potential well of a smooth dark matter halo. This effect is of particular relevance for old stellar systems with short crossing times, where small collisional perturbations accumulate over many dynamical timescales. We run collisional N-body simulations tailored to the ambiguous stellar systems Ursa Major 3/Unions 1, Delve 1, and Eridanus 3, modeling their stellar populations as two-component systems of high- and low-mass stars, respectively. For Ursa Major 3/Unions 1 (Delve 1), assuming a dynamical-to-stellar mass ratio of 10, we find that after 10 Gyr of evolution, the radial extent of its low-mass stars will be twice as large as (40% larger than) that of its high-mass stars. We show that weak tides do not alter this relative separation of half-light radii, whereas for the case of strong tidal fields, mass segregation facilitates the tidal stripping of low-mass stars. We further find that as the population of high-mass stars contracts and cools, the number of dynamically formed binaries within that population increases. Our results call for caution when using stellar mass segregation as a criterion to separate star clusters from dwarf galaxies, and suggest that mass segregation increases the abundance of massive binaries in the central regions of dark matter-dominated dwarf galaxies.

Keywords: Galaxy dynamics, Cold dark matter, Star clusters, Dwarf spheroidal galaxies, N-body simulations, Dynamical evolution
Suppression of Composition g-modes in Chemically Equilibrating Warm Neutron Stars. We investigate the impact of chemical equilibration and the resulting bulk viscosity on nonradial oscillation modes of warm neutron stars at temperatures up to T ≍ 5 MeV, relevant for protoneutron stars and neutron star postmerger remnants. In this regime, the relaxation rate of weak interactions becomes comparable to the characteristic frequencies of composition g-modes in the core, resulting in resonant damping. To capture this effect, we introduce the dynamical sound speed, a complex, frequency-dependent generalization of the adiabatic sound speed that encodes both the restoring force and the dissipative effects of bulk compression. Using realistic weak reaction rates and three representative equations of state, we compute the complex frequencies of composition g-modes with finite-temperature profiles. We find that bulk viscous damping becomes increasingly significant with temperature and can completely suppress composition g-modes. In contrast, the f-mode remains largely unaffected by bulk viscosity due to its nearly divergence-free character. Our results highlight the sensitivity of g-mode behavior to thermal structure, weak reaction rates, and the equation of state, and establish the dynamical sound speed as a valuable descriptor characterizing oscillation properties in dissipative neutron star matter.

Keywords: Neutron stars, Nuclear astrophysics