Sazuna/UAT_keywords huggingface dataset:
GD-1 and the Milky Way Starless Dark Matter Subhalos. Measurements of the GD-1 star stream velocity distribution within ±3° of the centerline find a total line-of-sight velocity spread of 5─6 km s−1 in the-well measured ϕ1 = [−30, 0] region. The velocity spread is far above the ∼2─3 km s−1 of a dissolved globular cluster in a smooth galactic potential. Dynamical heating of the GD-1 star stream is simulated in an evolving model Milky Way potential that includes the subhalos extracted from cosmological cold dark matter (CDM) and warm dark matter (WDM) Milky Way─like halos. The model bridges fully cosmological Milky Way─like halos and late-time static Milky Way potentials, allowing individual streams to be accurately integrated. An evolving CDM subhalo population acting for ∼11 Gyr heats GD-1 to 6.2 ± 1.7 km s−1. The WDM (7 keV and lighter) models develop a velocity dispersion of 3.9 ± 0.2 km s−1, only slightly greater than the 3.5 km s−1 in an evolving smooth halo without subhalos for 11 Gyr. The dynamical age of the best model stream is close to the isochrone age of the stars in the stream. Subhalos with masses in the decade around 107.5M⊙, below the mass range of dwarf galaxies, dominate the dynamical stream heating.

Keywords: Stellar streams, Galaxy dark matter halos, Milky Way Galaxy
The Relation between Solar Spicules and Magnetohydrodynamic Shocks. Spicules are thin, elongated, jet-like features seen in observations of the solar atmosphere, at the interface between the solar photosphere and the corona. These features exhibit highly complex dynamics and are a necessary connecting link between the cooler, denser solar chromosphere and the extremely hot, tenuous corona. In this work, we explore the spatial and temporal relation between solar spicules and magnetohydrodynamic (MHD) shocks using data from a 2D radiative MHD simulation of the solar atmosphere driven by solar convection. Here, we demonstrate, through direct identification, that slow MHD shocks, which propagate along magnetic field lines, are regions of strong positive vertical acceleration of the plasma that forms the tip of the spicule material during its rise phase. We quantify the effect of pressure and Lorentz forces on the acceleration of the plasma inside the shocks during the rise of spicules. The causality between spicule and shock propagation in the atmosphere of the model is also investigated. It is further shown that the strength of these shocks may play a vital role in determining the height of the spicules, supporting the idea that shocks act as drivers of some spicules. In addition, we also find the presence of structures similar to propagating coronal disturbances (PCDs) in the simulation, linked with the spicules. Here, PCDs appear to be associated with the shock waves driving the spicules that subsequently propagate into the corona and have similar speeds to those reported in observations.

Keywords: Solar atmosphere, Radiative magnetohydrodynamics, Solar spicules, Solar physics, Solar corona, Solar magnetic fields, Solar transition region, Shocks, Solar chromosphere, Magnetohydrodynamical simulations
Magnetic Field in the Lobes of the Seyfert Galaxy NGC 3516: Suggestions of a Helical Field. We present polarization images from the Karl G. Jansky Very Large Array and the Giant Metrewave Radio Telescope at 5.5 GHz, 10 GHz, and 663 MHz of the changing-look active galactic nuclei, NGC 3516. A transverse gradient in the rotation measure (RM) is detected in the northern and southern kiloparsec-scale lobes. Such gradients have typically been suggested to be signatures of a helical magnetic (B-) field. We detect circular polarization in the core and inner jet-knot of this source, which is known to host a precessing radio jet interacting with emission-line gas. Soft X-ray emission from the Chandra X-ray Observatory suggests the presence of a hot wind emerging from the nucleus of NGC 3516. Taken together with the RM gradient, this presents a picture of jet+wind outflow in this Seyfert galaxy with the B-field confining both the jet and lobe emission. A magnetically driven outflow may, in turn, cause accretion disk warping and jet precession, which is observed in the case of NGC 3516.

Keywords: Radio interferometry, Seyfert galaxies, Polarimetry, Magnetic fields
Discovery of Jet─Bubble─Disk Interaction: Jet Feedback on a Protoplanetary Disk Via an Expanding Bubble in WSB 52. While stellar jets and outflows are fueled by accretion from disks, their direct influence on disks remain unexplored. Here, we revisit Atacama Large Millimeter/submillimeter Array observations of 12CO (J = 2─1) line emission for the young stellar object WSB 52. We identify an expanding bubble that interacts with its protoplanetary disk. Given that the disk axis points toward the bubble's center and the kinetic energy of the bubble is roughly 1041 erg, we postulate that stellar jets, aligned with the disk axis, have triggered the bubble. The bubble morphology is consistent with uniform expansion with partial concavity, implying the bubble-disk interaction. Correspondingly, the shape and the velocity field of protoplanetary disk appear to be deformed and exhibit high-velocity components, suggesting strong interactions and mass loss from the disk. The discovery of jet feedback onto the disk via the bubble—which we term the jet-bubble-diskjet─bubble─disk interaction—sheds new light on the dynamical processes governing star and planet formation.

Keywords: Stellar jets, Radio interferometry, Protoplanetary disks
The Coevolution of Stellar Wind-blown Bubbles and Photoionized Gas. I. Physical Principles and a Semianalytic Model. We propose a new framework for the simultaneous feedback of stellar winds and photoionizing radiation from massive stars, distinguishing the locations where forces are applied, and consequences for internal spatiotemporal evolution of the whole feedback bubble (FB). We quantify the relative dynamical importance of wind-blown bubbles (WBBs) versus the photoionized region (PIR) by the ratio of the radius at which the WBB is in pressure equilibrium with the PIR, Req, to the Strömgren radius, RSt. ζ ≡ Req/RSt quantifies the dynamical dominance of WBBs (ζ &gt; 1) or the PIR (ζ &lt; 1). We calculate ζ and find that, for momentum-driven winds, 0.1 ≲ ζ ≲ 1 for the star-forming regions in (i) typical Milky Way─like giant molecular clouds, (ii) the most massive of individual OB stars, and (iii) dense, low-metallicity environments, relevant in the early Universe. In this regime, both WBBs and the PIR are dynamically important to the expansion of the FB. We develop a semianalytic coevolution model (CEM) that takes into account the spatial distribution of forces and the back reactions of both the WBB and PIR. In the ζ &lt; 1 regime where the CEM is most relevant, the model differs in the total FB momentum by up to 25% compared to naive predictions. In the weak-wind limit of ζ ≪ 1, applicable to individual OB stars or low-mass clusters, the CEM has factors ≳2 differences in WBB properties. In a companion paper, we compare these models to 3D, turbulent hydrodynamical simulations.

Keywords: H II regions, Stellar feedback, Stellar wind bubbles
The Coevolution of Stellar Wind-blown Bubbles and Photoionized Gas. II. 3D RMHD Simulations and Tests of Semianalytic Models. In a companion paper (Paper I), we presented a coevolution model (CEM) in which to consider the evolution of feedback bubbles driven by massive stars through both stellar winds and ionizing radiation, outlining when either of these effects is dominant and providing a model for how they evolve together. Here we present results from 3D radiation magnetohydrodynamical simulations of this scenario for parameters typical of massive star-forming clouds in the Milky Way: precisely the regime where we expect both feedback mechanisms to matter. While we find that the CEM agrees with the simulations to within 25% for key parameters and modestly outperforms previous idealized models, disagreements remain. We show that these deviations originate mainly from the CEM's lack of (i) background inhomogeneity caused by turbulence and (ii) time-variable momentum enhancements in the wind-blown bubble (WBB). Additionally, we find that photoionized gas acts similarly to magnetic fields by decreasing the WBB's surface area. This causes a decrease in the amount of cooling at the WBB's interface, resulting in an enhanced WBB dynamical impact.

Keywords: Stellar wind bubbles, Interstellar medium, Radiative transfer simulations, H II regions, Magnetohydrodynamical simulations
The Radio Spectral Energy Distribution and Star Formation Calibration in MIGHTEE-COSMOS Highly Star-forming Galaxies at 1.5 &lt; z &lt; 3.5. Studying the radio spectral energy distribution (SED) of distant galaxies is essential for understanding their assembly and evolution over cosmic time. We present rest-frame radio SEDs of a sample of 160 star-forming galaxies at 1.5 &lt; z &lt; 3.5 in the Cosmic Evolution Survey field as part of the MeerKAT International GHz Tiered Extragalactic Exploration project. MeerKAT observations combined with archival Very Large Array and Giant Metrewave Radio Telescope data allow us to determine the integrated mid-radio (ν = 1–10 GHz) continuum (MRC) luminosity and magnetic field strength. A Bayesian method is used to model the SEDs and to separate the free–free and synchrotron emission. We also calibrate the star formation rate (SFR) in radio both directly through SED analysis and indirectly through the infrared–radio correlation (IRRC). With a mean value of αnt ≃ 0.7, the synchrotron spectral index flattens with both redshift and specific SFR, indicating that cosmic rays are more energetic in the early Universe due to higher star formation activity. The magnetic field strength increases with redshift, B ∝ (1 + z)(0.7±0.1), and SFR as B ∝ SFR0.3, suggesting a small-scale dynamo acting as its main amplification mechanism. Taking into account the evolution of the SEDs, the IRRC is redshift invariant, and it does not change with stellar mass at 1.5 &lt; z &lt; 3.5, although the correlation deviates from linearity. Similarly, we show that the SFR traced using the integrated MRC luminosity is redshift invariant.

Keywords: Bayesian statistics, Star formation, Galaxy evolution, Radio continuum emission, Extragalactic magnetic fields
Analysis of Ion Cyclotron Waves during Cassini's Flybys of Enceladus. Ion cyclotron waves (ICWs) are ubiquitous phenomena within Saturn's magnetosphere, particularly in the vicinity of Enceladus. This study focuses on the Cassini spacecraft's flyby data of Enceladus to investigate the spatial distribution and properties of ICWs. We categorize ICWs into two distinct types based on their frequency characteristics: Type I, with frequencies deviating from the local ion cyclotron trend, detected during high-inclination flybys; and Type II, with frequencies closely following the local trend, observed during horizontal flybys. Moreover, we identify the simultaneous detection of ICWs and magnetosonic waves within Saturn's magnetosphere, providing new insights into their generation and propagation mechanisms. Our results show that ICWs serve as crucial diagnostic tools for evaluating local plasma conditions and the dynamics of Saturn's magnetosphere. Furthermore, this study highlights the broader implications of ICWs for comparative planetary magnetospheric research, providing guidance for investigating similar processes at other planetary systems, such as Jupiter's moons Io and Europa.

Keywords: Enceladus, Saturn
GLIMPSE: An Ultrafaint ≃10<SUP>5</SUP> M<SUB>⊙</SUB> Pop III Galaxy Candidate and First Constraints on the Pop III UV Luminosity Function at z ≃ 6–7. Detecting the first generation of stars, Population III (Pop III), has been a long-standing goal in astrophysics, yet they remain elusive even in the JWST era. Here we present a novel NIRCam-based selection method for Pop III galaxies, and carefully validate it through completeness and contamination simulations. We systematically search ≃ 500 arcmin2 across JWST legacy fields for Pop III candidates, including GLIMPSE, which, assisted by gravitational lensing, has produced JWST's deepest NIRCam imaging thus far. We discover one promising Pop III galaxy candidate (GLIMPSE-16043) at  z=6.50‑0.24+0.03 , a moderately lensed galaxy ( μ=2.9‑0.2+0.1 ) with an intrinsic UV magnitude of  MUV=‑15.89‑0.14+0.12 . It exhibits key Pop III features: strong Hα emission (rest-frame EW 2810 ± 550 Å); a Balmer jump; no dust (UV slope β = ‑2.34 ± 0.36); and undetectable metal lines (e.g., [O III]; [O III]/Hβ &lt; 0.44), implying a gas-phase metallicity of Zgas/Z⊙ &lt; 0.5%. These properties indicate the presence of a nascent, metal-deficient young stellar population (&lt;5 Myr) with a stellar mass of ≃105 M⊙. Intriguingly, this source deviates significantly from the extrapolated UV–metallicity relation derived from recent JWST observations at z = 4–10, consistent with UV enhancement by a top-heavy Pop III initial mass function or the presence of an extremely metal-poor active galactic nucleus. We also derive the first observational constraints on the Pop III UV luminosity function at z ≃ 6–7. The volume density of GLIMPSE-16043 (≈10‑4 cMpc‑3) is in excellent agreement with theoretical predictions, independently reinforcing its plausibility. This study demonstrates the power of our novel NIRCam method to finally reveal distant galaxies even more pristine than the Milky Way's most metal-poor satellites, thereby promising to bring us closer to the first generation of stars than we have ever been before.

Keywords: Early universe, Galaxy formation, Photoionization, Population III stars, Intermediate-mass black holes, Young star clusters, Emission nebulae, Galaxy evolution, Interstellar medium, Reionization, High-redshift galaxies
Cosmology with Topological Deep Learning. The standard cosmological model with cold dark matter posits a hierarchical formation of structures. We introduce topological neural networks (TNNs), implemented as message-passing neural networks on higher-order structures, to effectively capture the topological information inherent in these hierarchies that traditional graph neural networks (GNNs) fail to account for. Our approach not only considers the vertices and edges that comprise a graph but also extends to higher-order cells such as tetrahedra, clusters, and hyperedges. This enables message-passing between these heterogeneous structures within a combinatorial complex. Furthermore, our TNNs are designed to conserve the E(3) invariance, which refers to the symmetry arising from invariance against translations, reflections, and rotations. When applied to the Quijote suite, our TNNs achieve a significant reduction in the mean squared error. Compared to our GNNs, which lack higher-order message-passing, ClusterTNNs show improvements of up to 22% in Ωm and 34% in σ8 jointly, while the best FullTNN achieves an improvement of up to 60% in σ8. In the context of the CAMELS suite, our models yield results comparable to the current GNN benchmark, albeit with a slight decrease in performance. We emphasize that our topology and symmetry-aware neural networks provide enhanced expressive power in modeling the large-scale structures of our Universe.

Keywords: Neural networks, Cosmological parameters from large-scale structure
Estimating Fe and Mg Abundances in the Milky Way Dwarf Galaxies Using Subaru/HSC and DEIMOS. We investigate the chemical abundance distributions of the Fornax, Sculptor, Ursa Minor, and Draco dwarf galaxies using Subaru/Hyper Suprime-Cam (HSC) photometric data. The HSC data set, which includes broadband g and i filters and the narrowband NB515 filter, offers sensitivity to iron and magnesium abundances, as well as surface gravity, enabling the identification of giant stars and foreground dwarfs. For analysis, we selected a total of 6713 giant candidates using a random forest regressor trained on medium-resolution (R ∼ 6000) Keck/Deep Imaging Multi-Object Spectrograph spectroscopic data. Our analysis reveals the extent of radial metallicity gradients in the galaxies. Such trends, not detectable in earlier studies, are now captured owing to the substantially enlarged sample size and areal coverage provided by the HSC data. These results are also consistent with chemical abundance patterns previously observed in the central regions through spectroscopic studies. Furthermore, we infer that Fornax underwent extended star formation, whereas Sculptor formed both metal-poor and metal-rich stars over a shorter time. Ursa Minor and Draco appear to have experienced brief, intense star formation episodes leading to nearly extinguished star formation. This study underscores the critical role of the expanded HSC data set in revealing chemical gradients that were previously inaccessible. Future work incorporating additional spectra of metal-poor stars and age-sensitive isochrone modeling will enable more accurate maps of chemical abundance distributions.

Keywords: Local Group, Stellar abundances, Dwarf spheroidal galaxies, Narrow band photometry, Random Forests
Extended Emission-line Region in a Poststarburst Galaxy Hosting Tidal Disruption Event AT2019qiz and Quasiperiodic Eruptions. We present a comprehensive analysis of the extended emission-line region (EELR) in the host galaxy of the tidal disruption event (TDE) AT2019qiz, utilizing Very Large Telescope (VLT)/MUSE integral-field spectroscopy. The high spatial-resolution data reveal a biconical emission structure approximately 3.7 kpc in scale within the galactic center, characterized by a prominent [O III] line in the nucleus and significant [N II] line emission extending into the EELR. Spectral analysis of the EELR indicates line ratios consistent with Seyfert ionization in the center and LINER-type ionization in the outer diffuse region, suggesting ionization from galactic nuclear activity. The required ionizing luminosity, estimated from the Hα and Hβ luminosities based on the photoionization and recombination balance assumption, is 1041.8 erg s−1 for all spaxels classified as active galactic nucleus (AGN), and 1040.7 erg s−1 for spaxels in the central 0.9 kpc Seyfert region. However, the current bolometric luminosity of the nucleus Lbol ≤ 1040.8 erg s−1, estimated from quiescent-state soft X-ray observations, is insufficient to ionize the entire EELR, implying a recently faded AGN or a delayed response to historical activity. Stellar population analysis reveals a poststarburst characteristic in the EELR, and the gas kinematics show disturbances and noncircular components compared to the stellar kinematics. Notably, the recent detection of quasiperiodic eruptions (QPEs) in the X-ray light curve of AT2019qiz confirms the TDE─QPE association. Our findings provide direct evidence for an AGN-like EELR in the host galaxy of the nearest TDE with QPE detection, offering new insights into the complex interplay between TDEs, QPEs, AGN activity, and host-galaxy evolution.

Keywords: AGN host galaxies, Supermassive black holes, Photoionization, Tidal disruption, Active galactic nuclei
A Next-generation Exoplanet Atmospheric Retrieval Framework for Transmission Spectroscopy (NEXOTRANS): Comparative Characterization for WASP-39 b Using JWST NIRISS, NIRSpec PRISM, and MIRI Observations. The advent of JWST has marked a new era in exoplanetary atmospheric studies, offering higher-resolution data and greater precision across a broader spectral range than previous space-based telescopes. Accurate analysis of these data sets requires advanced retrieval frameworks capable of navigating complex parameter spaces. We present NEXOTRANS, an atmospheric retrieval framework that integrates Bayesian inference using UltraNest/PyMultiNest with four machine learning algorithms: Random Forest, Gradient Boosting, K-Nearest Neighbor, and Stacking Regressor. This hybrid approach enables a comparison between traditional Bayesian methods and computationally efficient machine learning techniques. Additionally, NEXOTRANS incorporates NEXOCHEM, a module for solving equilibrium chemistry. We applied NEXOTRANS to JWST observations of the Saturn-mass exoplanet WASP-39 b, spanning wavelengths from 0.6 to 12.0 μm using NIRISS, NIRSpec PRISM, and MIRI. Four chemistry models—free, equilibrium, modified hybrid equilibrium, and modified equilibrium-offset chemistry—were explored to retrieve precise volume mixing ratios (VMRs) for H2O, CO2, CO, H2S, and SO2. Absorption features in both NIRSpec PRISM and MIRI data constrained SO2 log VMRs to values between ‑6.25 and ‑5.73 for all models except equilibrium chemistry. High-altitude aerosols, including ZnS and MgSiO3, were inferred, with constraints on their VMRs, particle sizes, and terminator coverage fractions, providing insights into cloud composition. For the best-fit modified hybrid equilibrium model, we derived supersolar elemental abundances of  O/H=14.12‑1.82+2.86× solar,  C/H=21.37‑3.18+4.93× solar, and  S/H=5.37‑0.65+0.79× solar, along with a C/O ratio of  1.35‑0.02+0.05×  solar. These results demonstrate NEXOTRANS's potential to enhance JWST data interpretation, advancing comparative exoplanetology efficiently.

Keywords: Exoplanet atmospheric composition , Exoplanets, Transmission spectroscopy, Exoplanet atmospheres, Exoplanet atmospheric structure
The Hydrodynamic Thermal Continuum, with Applications to Stratified Atmospheres and 1D Coronal Loop Models. Using both analytical and numerical means, we demonstrate that linear stability analysis of a hydrodynamic stratified atmosphere or a 1D coronal loop model in nonadiabatic settings features a thermal continuum corresponding to highly localized eigenfunctions. This thermal continuum can be precomputed, involving the net heat-loss function and its partial derivatives, and is the generalization of the thermal instability introduced by E. N. Parker. We account for a thermal imbalance, directly affecting thermal instability growth rates. We present completely general equations that govern all eigenmodes, including nonadiabatically affected p- and g-modes of the stratified settings. We intend to clarify how linear thermal instability is relevant for solar loops that show spontaneous in situ condensations, and eliminate recent confusion on specific isochoric routes to linear instability alongside other thermal instability channels. The thermal continuum, previously identified as a crucial ingredient in magnetohydrodynamic eigenmode spectra for coronal loops and atmospheres, drives multithermal aspects across our Universe, such as forming solar coronal rain and prominences, or cold cloud creation in intracluster to interstellar medium environments.

Keywords: Solar atmosphere, Solar prominences, Hydrodynamics, Solar coronal loops, Solar physics, Astrophysical fluid dynamics