Sazuna/UAT_keywords huggingface dataset:
Iron Snails: Nonequilibrium Dynamics and Spiral Abundance Patterns. Galaxies are not in a dynamical steady state: they continually undergo perturbations, e.g., from infalling dwarf galaxies and dark matter substructure. After a dynamical perturbation, stars phase mix toward a new steady state; in so doing, they generally form spiral structures, such as spiral density waves in galaxy disks and the Gaia Snail observed in the vertical phase-space density in the solar neighborhood. Structures in phase-space density can be hard to measure accurately, because spatially varying selection effects imprint their own patterns on the density. However, stellar labels such as metallicity, or other element abundances, or stellar masses and ages, can be measured even in the face of complex or unknown spatial selection functions. We show that if the equilibrium galaxy has phase-space gradients in these labels, any perturbation that could raise a spiral wave in the phase-space density will raise a spiral wave in the distribution of labels as well. We work out the relationship between the spiral patterns in the density and in the labels. As an example, we analyze the Gaia Snail, and show that its amplitude and dynamical age as derived from elemental abundances (mainly [Mg/Fe]) follow similar patterns to those derived from the phase-space density. Our best model dates the Snail's perturbation to about 400 Myr ago, although we find significant variations with angular momentum in the best-fit age. Conceptually, the ideas presented here are related to orbital torus imaging, chemical tagging, and other methods that use stellar labels to trace dynamics.

Keywords: Galaxy stellar disks, Galaxy abundances, Stellar dynamics
The Pitfalls of Using Lyα Damping Wings in High-z Galaxy Spectra to Measure the Intergalactic Neutral Hydrogen Fraction. The Lyα damping wing is seen in absorption against the spectra of high-redshift galaxies. Modeling of this wing is a way to measure the volume neutral hydrogen fraction of the Universe, as well as to measure the strength of H I absorption in the form of a damped Lyα absorber (DLA). We use very-high-quality ultraviolet spectra of low-z galaxies to create mock high-redshift, low-resolution spectra complete with a damping wing resulting from the intergalactic medium (IGM) and H I absorption from local, dense gas to mimic current James Webb Space Telescope observations of the early Universe. The simulated spectra are used to test the ability to recover the "true" values of the column density of the DLA (NDLA) and the volume neutral hydrogen fraction (xH I) of the IGM through modified stellar continuum fitting. We find that the ability to recover the true values of NDLA and xH I simultaneously is compromised by degeneracies between these two parameters, and the spectral shape itself at low resolution (R ∼ 100). The root mean squared error between the recovered and true column density of the DLA is on the order of 1 dex. This error somewhat decreases with improved resolution (R ∼ 1000), but systematically underestimates NDLA when Lyα emission is present in the mock spectra. The recovered values of xH I are poorly constrained and do not improve substantially with the higher resolution. We recommend accounting for these sources of uncertainty and biases when using galaxies' Lyα damping wings to measure the intergalactic neutral hydrogen fraction.

Keywords: Reionization, Lyman-break galaxies, High-redshift galaxies
Physics-based Forecasting of Tomorrow's Solar Wind at 1 au. Inspired by the concept of relativity of simultaneity used in the theory of special relativity, a new approach is proposed to simulate future solar wind conditions at any point in the inner solar system. An important distinctive feature of the proposed approach is that the simulation in the solar corona is driven by hourly updated solar magnetograms and is continuously simulated in nearly real time. The model for the inner heliosphere is based on time transformation to a boosted spacetime coordinate system, in which the current state of the solar wind at the solar corona–inner heliosphere boundary and future states of the solar wind are simultaneous. The predictive capability for tomorrow's parameters of the ambient solar wind at 1 au is achieved by simulating them simultaneously with the current observations of the solar magnetic field, the time offset being enabled by the use of a boosted frame. We derive the modified governing equations for both hydrodynamics and magnetohydrodynamics and present a new numerical algorithm that solves the modified governing equations. The proposed method enables an efficient numerical implementation and thus a significantly longer forecast time than traditional solution methods. In the numerical test for transient propagation, the boosted solution for the coronal mass ejection–driven shock arrival at 1 au is 16 hr ahead of the solution at the solar corona–inner heliosphere boundary.

Keywords: Magnetohydrodynamics, Space weather, Solar wind, Solar-terrestrial interactions, Magnetohydrodynamical simulations
Small-scale Inhomogeneity Effects on Coherent Solar Radio Emission. The coherent radio emission mechanism of solar radio bursts (SRBs) is one of the most complicated and controversial topics in solar physics. To clarify the mechanism(s) of different types of SRBs, (radio-) wave excitation by energetic electrons in homogeneous plasmas has been widely studied via particle-in-cell (PIC) code numerical simulations. The solar corona is, however, inhomogeneous over almost all spatial scales. Due to the kinetic nature of SRBs, small-scale inhomogeneities in the plasma could influence the excitation and emission properties of SRBs. In this paper, we thus investigate the effects of small-scale inhomogeneity (in the magnetic field as well as plasma density or temperature) of plasmas in the solar corona on radio-wave emission by ring-beam distributed energetic electrons utilizing 2.5-dimensional PIC simulations. The typical length scale of the small-scale inhomogeneity we consider in this study is on the order of the proton gyroradius. Both beam and electron-cyclotron maser instabilities can be triggered with the presence of energetic ring-beam electrons. The resultant spectrum of the excited electromagnetic waves presents a zebra-stripe pattern in the frequency space. The inhomogeneous density or temperature in plasmas influences the frequency bandwidth and location of these excited waves. Our results can hence help to diagnose the plasma properties at the emission sites of SRBs. Applications of our results to SRBs with a zebra-stripe pattern are discussed.

Keywords: Solar coronal radio emission, Radio bursts, Solar corona
Characterizing Exoplanets for Assessing Their Potential Habitability. The Statistical-likelihood Exoplanetary Habitability Index (SEPHI) serves as a valuable tool for prioritizing targets for further study and identifying potentially habitable environments. In this paper, we present SEPHI 2.0, which incorporates several key improvements: (1) updated methods for estimating exoplanet internal structures and magnetic fields; (2) the inclusion of orbital eccentricity in assessing the potential for liquid water on an exoplanet's surface; and (3) a new exoplanet mass–radius relationship. SEPHI 2.0 retains its probabilistic framework and combines the different subindexes by selecting the most restrictive one. In SEPHI 2.0, atmospheric retention is consolidated into a single index that incorporates both thermal (Jeans escape) and nonthermal (stellar wind and magnetic effect) processes. Recent advancements in estimating exoplanet internal structures and magnetic fields have been integrated. Additionally, a new empirical exoplanet mass–radius relationship is introduced. All this is incorporated into the SADE code, which uses key data on exoplanets and their host stars to assess habitability and prioritize targets for further study, providing a comprehensive output of an exoplanetary system's physical characteristics. SADE is available as a free online tool. Notably, this is the first approach to including estimated exoplanet magnetic fields in a habitability index. The SADE software facilitates the identification of potentially habitable exoplanets. Among the 5500+ confirmed exoplanets, only a few—such as Kepler-62f and GJ 514b—achieve SEPHI 2.0 scores close to 1. It is also noticeable that, according to our studies, TRAPPIST-1 f and g are ranked higher than TRAPPIST-1 e in terms of habitability potential.

Keywords: Exoplanet structure, Astrobiology, Exoplanet catalogs, Exoplanet atmospheres
ASURA-FDPS-ML: Star-by-star Galaxy Simulations Accelerated by Surrogate Modeling for Supernova Feedback. We introduce new high-resolution galaxy simulations accelerated by a surrogate model that reduces the computation cost by approximately 75%. Massive stars with a zero-age main-sequence mass of more than about 10 M⊙ explode as core-collapse supernovae (CCSNe), which play a critical role in galaxy formation. The energy released by CCSNe is essential for regulating star formation and driving feedback processes in the interstellar medium (ISM). However, the short integration time steps required for SN feedback have presented significant bottlenecks in astrophysical simulations across various scales. Overcoming this challenge is crucial for enabling star-by-star galaxy simulations, which aim to capture the dynamics of individual stars and the inhomogeneous shell's expansion within the turbulent ISM. To address this, our new framework combines direct numerical simulations and surrogate modeling, including machine learning and Gibbs sampling. The star formation history and the time evolution of outflow rates in the galaxy match those obtained from resolved direct numerical simulations. Our new approach achieves high-resolution fidelity while reducing computational costs, effectively bridging the physical scale gap and enabling multiscale simulations.

Keywords: Galactic winds, Hydrodynamical simulations, Stellar feedback, Galaxy evolution, Interstellar medium
The TRGB−SBF Project. III. Refining the HST Surface Brightness Fluctuation Distance Scale Calibration with JWST. The TRGB−SBF Project team is developing an independent distance ladder using a geometrical calibration of the tip of the red giant branch (TRGB) method in elliptical galaxies that can, in turn, be used to set the surface brightness fluctuation (SBF) distance scale independent of Cepheid variables and Type Ia supernovae. The purpose of this project is to measure the local expansion rate of the Universe independently of the methods that are most at odds with the theoretically predicted value of the Hubble─Lemaître constant H0, and therefore isolate the influence of potential systematic observational errors. In this paper, we use JWST TRGB distances calibrated using the megamaser galaxy NGC 4258 to determine a new Cepheid-independent SBF zero-point with the Hubble Space Telescope. This new calibration, along with improved optical color measurements from Pan-STARRS and DECam, gives an updated value of H0 = 73.8 ± 0.7 (statistical) ±2.3 (systematic) km s−1 Mpc−1 that is virtually identical to the SBF Hubble─Lemaître constant measured by J. P. Blakeslee et al.

Keywords: Hubble constant, Galaxy distances, Distance indicators
Low-metallicity Nova Explosions: A Site for Weak rp-process Nucleosynthesis. Classical novae are common cataclysmic events involving a binary system of a white dwarf and a main-sequence or red giant companion star. In metal-poor environments, these explosions produce ejecta differently from their solar counterparts due to the accretion of subsolar-metallicity material onto the white dwarf. In particular, it has been suggested that the nucleosynthesis flow in such low-metallicity nova explosions extends up to the Cu–Zn region, much beyond the expected endpoint, around Ca, predicted for solar-metallicity classical novae. This behavior resembles a weak rp-process, and such nuclear activity has never been observed in accreting white dwarf binaries with typical accretion flows. In this work, we study the characteristics of the weak rp-process for four nova models with metallicities Z = 2 × 10‑9, 10‑7, 2 × 10‑6, and 2 × 10‑5, and explore the impact of the nuclear physics uncertainties via a Monte Carlo sensitivity study. We identify nuclear reactions whose uncertainties affect the production of intermediate-mass nuclei under these conditions. These reactions and relevant nuclear quantities are targets for measurements at stable or radioactive beam facilities to reduce their rate uncertainties.

Keywords: Nuclear reaction cross sections, Nuclear astrophysics, Explosive nucleosynthesis, Classical novae
Photometric and Spectroscopic Studies of Two Early-type Eclipsing Binaries. Using high-precision photometric data from the Transiting Exoplanet Survey Satellite, medium-resolution spectroscopic data from the Large Sky Area Multi-Object Fiber Spectroscopy Telescope, and long-term eclipse timings, we provide orbital parameters for two early-type detached eclipsing binary systems: TYC 3740-2072-1 and TYC 2888-780-1, and analyze the orbital period variations and evolutionary status of these two targets. TYC 3740-2072-1, with a spectral type of B1V, consists of a 6.914 M⊙ subgiant and a 6.233 M⊙ main-sequence component. It is expected to evolve into a semidetached binary, potentially serving as a progenitor of a Type Ia supernova. TYC 2888-780-1 has a spectral type of A3 and consists of two main-sequence components with masses of 1.682 and 1.673 M⊙, respectively. It is undergoing stable evolution. Through eclipse timing analysis, we find that both targets exhibit apsidal motion effects, with observed apsidal motion rates of  ω̇obs=0.0412degcycle‑1  and  ω̇obs=0.0205degcycle‑1 , respectively. Additionally, TYC 2888-780-1 exhibits orbital period variations, which we attribute to the light travel time effect caused by a third body; the minimum mass of this third body is estimated to be 0.598 M⊙.

Keywords: Eclipsing binary stars, Early-type stars, Fundamental parameters of stars, Stellar evolution
Low-redshift Analogs of Cosmic Noon Galaxies as Laboratories for Clumpy Star Formation. It has been established that a significant fraction of star formation at high redshift occurs in clumpy galaxies. The properties of clumps and their formation mechanisms, however, remain highly debated. In this work we analyze a sample of 18 supercompact ultraviolet luminous galaxies observed with the OSIRIS spectrograph at the Keck Telescope, targeting their Paα emission. These galaxies, although at z ∼ 0.1–0.2, share many similar properties with star-forming galaxies at cosmic noon. We find a total of 84 star-forming clumps with typical sizes of a few hundred parsecs. The star-forming clumps exhibit low values of velocity shear (∼12 km s‑1) and high velocity dispersion (∼70 km s‑1). The dynamical masses of the clumps are typically higher than the gas masses inferred from the measured star formation rate of each clump. We also artificially redshift our data to emulate observations at z = 2.2 and allow for a direct comparison with other galaxies at higher redshift. Our results indicate that, due to the effects of clump clustering and low-resolution observations, high-z clumps appear larger at greater cosmological distances. This underscores the importance of using low-redshift observations to anchor studies at earlier epochs. Finally, our results support the idea of growing clump sizes in star-forming galaxies as a function of redshift, although not to the scales of kiloparsecs as found by other works without the benefits of adaptive optics or gravitational lensing.

Keywords: Starburst galaxies, Star forming regions, Lyman-break galaxies, High-redshift galaxies, Galaxies
Relationships between Polycyclic Aromatic Hydrocarbons, Small Dust Grains, H<SUB>2</SUB>, and H I in Local Group Dwarf Galaxies NGC 6822 and WLM Using JWST, ALMA, and the VLA. We present 0.6–3.2 pc resolution mid-infrared (MIR) JWST images at 7.7 μm (F770W) and 21 μm (F2100W) covering the main star-forming regions of two of the closest star-forming low-metallicity dwarf galaxies, NGC 6822 and Wolf–Lundmark–Melotte (WLM). The images of NGC 6822 reveal filaments, edge-brightened bubbles, diffuse emission, and a plethora of point sources. By contrast, most of the MIR emission in WLM is pointlike, with a small amount of extended emission. Compared to solar-metallicity galaxies, the ratio of 7.7 μm intensity ( IνF770W ), tracing polycyclic aromatic hydrocarbons (PAHs), to 21 μm intensity ( IνF2100W ), tracing small, warm dust grain emission, is suppressed in these low-metallicity dwarfs. Using Atacama Large Millimeter/submillimeter Array CO(2–1) observations, we find that detected CO intensity versus  IνF770W  at ≈2 pc resolution in dwarfs follows a similar relationship to that at solar metallicity and lower resolution, while the CO versus  IνF2100W  relationship in dwarfs lies significantly below that derived from solar-metallicity galaxies at lower resolution, suggesting more pronounced destruction of CO molecules at low metallicity. Finally, adding in Local Group L-Band Survey 21 cm H I observations from the Very Large Array, we find that  IνF2100W  and  IνF770W  versus total gas ratios are suppressed in NGC 6822 and WLM compared to solar-metallicity galaxies. In agreement with dust models, the level of suppression appears to be at least partly accounted for by the reduced galaxy-averaged dust-to-gas and PAH-to-dust mass ratios in the dwarfs. Remaining differences are likely due to spatial variations in dust model parameters, which should be an exciting direction for future work in local dwarf galaxies.

Keywords: Interstellar dust, Dwarf irregular galaxies, Molecular gas, Dust nebulae, Polycyclic aromatic hydrocarbons, Interstellar atomic gas
Physical Conditions of the Ionized Superwind in NGC 253 with VLT/MUSE. We present an analysis of the Hα-emitting ionized gas in the warm phase of the NGC 253 outflow using integral field spectroscopy from the Multi Unit Spectroscopic Explorer. In each spaxel, we decompose Hα, [N II], and [S II] emission lines into a system of up to three Gaussian components, accounting for the velocity contributions due to the disk and both intercepted walls of an outflow cone. In the approaching southern lobe of the outflow, we find maximum deprojected outflow velocities down to ∼−500 km s−1. Velocity gradients of this outflowing gas range from ∼−350 to −550 km s−1 kpc−1 with increasing distance from the nucleus. Additionally, [N II]/Hα and [S II]/Hα integrated line ratios are suggestive of shocks as the dominant ionization source throughout the wind. Electron densities, inferred from the [S II] doublet, peak at 2100 cm−3 near the nucleus and reach ≲50 cm−3 in the wind. Finally, at an uncertainty of 0.3 dex on the inferred mass of 4 × 105 M⊙, the mass-outflow rate of the Hα-emitting gas in the southern outflow lobe is ∼0.4 M⊙ yr−1. This yields a mass-loading factor of η ∼ 0.1 and a ∼2% starburst energy efficiency.

Keywords: Starburst galaxies, Galactic winds
Statistics of the Interplanetary Magnetic Field from 0.1 to 30 au. II. Dynamical Variability. The interplanetary magnetic field (IMF) governs the coupling between the solar wind and planetary magnetospheres through a series of complex interactions. However, it is challenging to simultaneously measure both the upstream IMF conditions and magnetospheric activity in situ. A common alternative approach is to utilize recent upstream measurements obtained before the spacecraft crosses the bow shock. To assess the validity of this method, we examine the temporal variability of the IMF using spacecraft magnetic field data from multiple space missions. Our analysis reveals that the autocorrelation function employed to measure IMF temporal variability is significantly influenced by the heliocentric distance and the solar cycle. Notably, the temporal variability of each magnetic field component varies, with the component aligned with the Parker spiral direction exhibiting weaker temporal variability than those perpendicular to it. Furthermore, the autocorrelation coefficients decay slower in the outer heliosphere, possibly due to the expansion, deformation, or merging of solar wind flux tubes. Nevertheless, considering planetary bow shocks and spacecraft travel time from the solar wind to the inner planetary magnetosphere (e.g., ∼2 hrs for Mars and ∼30 days for Jupiter), it is more feasible to estimate the upstream IMF conditions for the inner planetary magnetosphere than for the outer ones. Our study unravels the long-term evolution of the solar wind magnetic field and the consequence of the flux tube interaction. These results can also benefit the investigation of the solar wind–planetary magnetosphere coupling process by providing a more robust analysis of the upstream condition.

Keywords: Planetary magnetospheres, Solar wind, Interplanetary magnetic fields
The Magnified Waltz: Simulating Light Curves of Binary Stars Passing Through Microcaustics in Strong Lensing Galaxy Clusters. Individual stars located near the caustics of galaxy clusters can undergo extreme magnification when crossing microcaustics, rendering them observable even at cosmological distances. Though most massive stars are likely to reside in binary systems rather than as single star, the influence of a binary star system on magnification events is severely underexplored. In this work, we simulate the light curves produced by detached binary stars crossing microcaustics, aiming to characterize their unique observational signatures. Using high-resolution magnification maps generated by the GPU-PMO-CAUSTIC algorithm and PARSEC stellar models with red-shifted magnitude, we examined the impact of binary star parameters and crossing geometries on microlensing magnification patterns. Our simulations reveal that binary stars produce diverse light-curve features, including overlapping peaks, plateau-like structures, and time-variable color─magnitude differences. These features, particularly the distinct temporal variations in spectral energy distributions, offer diagnostic tools for distinguishing binary systems from single stars. We further demonstrate the potential of multiband photometry using the Chinese Space Station Telescope's Multi-Channel Imager to capture these variations. Our findings provide theoretical support to identify binary systems in future caustic-crossing events, enabling more accurate characterization of high-redshift stellar populations.

Keywords: Gravitational microlensing, Gravitational lensing, Binary stars
Ultraviolet Properties of Multiphase Gas toward the Inner Galaxy. We present a systematic study of the multiphase interstellar gas in the inner Galaxy using Hubble Space Telescope/STIS absorption spectroscopy of 16 massive stars located at spectroscopic distances between 1.3 and 10 kpc in the region ‑30° ≲ l ≲ +30° and ‑15° ≲ b ≲ +15°. These sight lines probe gas above and below the Sagittarius Carina, Scutum Crux-Centaurus, Norma, and Near 3-kpc spiral arms in a range of z-height from 0 to 1.5 kpc. Along the 16 sight lines, we measure velocity centroids for 800 UV absorption-line components across multiple gas phases (molecular CO, neutral, low ion, and high ion). We find that 619/800 components have velocities that are consistent with a simple model of corotation with the disk, indicating that multiphase gas with disk-like kinematics extends at least 1 kpc into the halo. We present a database of absorption-line parameters that can be used for kinematic modeling of gas flows into and out of the Galactic disk.

Keywords: Galactic winds, Galaxy structure, Ultraviolet astronomy, Interstellar medium, Milky Way Galaxy