Sazuna/UAT_keywords huggingface dataset:
ALMA-QUARKS: Few-thousand-year "Hatching out of the Egg:" The Supersonic Breakout of a Hypercompact H II Region from Its Parental Hot Core. The kinematic evolution of hypercompact (HC) H II regions around young high-mass stars remains poorly understood due to complex interactions with parental environs. We present Querying Underlying Mechanisms of Massive Star Formation with Atacama Large Millimeter/submillimeter Array─Resolved Gas Kinematics and Structures (ALMA-QUARKS) 1.3 mm and ATOMS 3 mm observations (the highest resolution is ∼0.01 pc) of a deeply embedded HC H II region (diameter ∼ 0.015 pc, electron density ∼ 2 × 105 cm−3) exhibiting a striking ≳20 km s−1 global redshift seen in optically thin H30α and H40α recombination lines relative to its parental hot molecular core within a hub─filament system. The 1.3 mm continuum data reveal a distinct 0.1 pc arc and a perpendicular 0.04 pc tail. We propose that this morphology arises from a dynamic champagne flow: the slow expansion of an HC H II region into a preexisting filament forms an arc and associated low-velocity (few kilometers per second) SiO shocks. Meanwhile, in the opposite direction ionized gas escapes along a steep density gradient traced by a tail and high-velocity (20 km s−1) SiO emission. We reject the bow shock scenario in which ionized gas comoves with a runaway high-mass star because shocked gas in the arc aligns with the hub velocity, contradicting the bow shock prediction. Non-LTE radiative transfer modeling further rules out infall of ionized gas as the velocity shift origin. We conclude that this exceptional HC H II region is undergoing a few-thousand-year transition phase of "hatching out of the egg:" the ionized gas of the HC H II region has just broken out of its parental hot core and now is flowing outward supersonically. This work highlights how anisotropic density distributions induce supersonically anisotropic ionized flows that govern HC H II region evolution.

Keywords: Star formation, H II regions, Supersonic expansion, Molecular clouds
Observing Compact Population III Star Clusters and the Presence of Cosmic Streaming. The formation of the Universe's first luminous stellar structures depends on the unique conditions at "Cosmic Dawn," which are set by the underlying cosmological model and early baryonic physics. Observations suggest that high-z star clusters reached stellar surface densities above 105 M⊙ pc−2, suggesting scenarios where models predict that the ability of stellar feedback to counter gravitational collapse is severely limited. We investigate the first star clusters in a suite of AREPO simulations, which explore the capacity for ΛCDM halos to maximally form high-density systems without feedback. We include the effects of the supersonic baryon─dark matter streaming velocity, an effect that impacts gas density and distribution in early minihalos. We show that early star clusters can reach high densities even in regions of strong supersonic streaming, provided feedback is weak. We analyze the interplay of the stream velocity and the dynamical processes of structure formation, finding that JWST has the opportunity to detect the brightest, most massive objects in our computational box. The detection of individual z ≥ 12 Population III star clusters below 107 M⊙ is challenging, although lensing could reveal these objects in rare configurations, especially if a top-heavy initial mass function is present. We find that accounting for baryonic clusters separately from dark matter halos complicates predictions for the faint end of the high-z UV luminosity function, with competing effects from the stream velocity and low-mass clusters outside of halos. Finally, we explore clustering of star clusters as a promising probe of the stream velocity in these systems.

Keywords: Hydrodynamical simulations, Population III stars, James Webb Space Telescope, High-redshift galaxies, Star clusters
TIRAMISU: Non-LTE Radiative Transfer for Molecules in Exoplanet Atmospheres. The TIRAMISU code, a new program for computing on-the-fly non-LTE molecular spectra and opacities for solving self-consistent radiative transfer problems in exoplanet atmospheres, is presented. The ultra-hot Jupiter KELT-20 b is used as a case study to identify the wavelength regions at which non-LTE effects may be detectable. It is shown that upper atmospheric OH in vibrational non-LTE should be observable primarily via hot bands in the mid-infrared and enhanced photodissociation in the visible. Varying the abundance of OH in non-LTE demonstrates a nonlinear relationship between the abundance and the strength of non-LTE effects. Using recent calculations of the photodissociation probabilities of OH, it is shown that non-LTE effects can increase the total photodissociation rate by 2 orders of magnitude in the upper atmosphere, which is likely to have a significant impact on atmospheric and chemical modelling. Increases and reductions in the molecular opacities under non-LTE conditions may lead to the mischaracterization of molecular abundances in retrievals that only consider opacities computed under LTE. Collisional data requirements to support future non-LTE modeling for a variety of exoplanet atmospheres and across a wide range of wavelengths are discussed.

Keywords: Molecular data, Exoplanets, Hot Jupiters, Molecular spectroscopy, Computational methods, Radiative transfer, Radiative transfer simulations, Exoplanet atmospheres
Solar Orbiter's Passage through Comet Leonard's Tail while in the He<SUP>+</SUP> Focusing Cone. The Solar Orbiter spacecraft crossed Comet Leonard's ion tail on 2021 December 17 near 1 au. In and near the ion tail, significant amounts of singly charged oxygen (O+) ions were detected by the Heavy Ion Sensor on board the spacecraft. These ions are likely the result of outgassed water molecules from the comet that became ionized and disassociated into protons and O+ ions and that were then picked up by the interplanetary magnetic field and advected outward with the solar wind. At this time, the spacecraft was also located amidst the denser parts of the interstellar helium (He) neutrals that are focused here by their gravitational interaction with the Sun. Pickup He+ ions in greater numbers are also found in this region and form when neutrals interact with solar photons. Newly ionized ions can generate waves that propagate mainly along the background magnetic field before the waves scatter the ions toward isotropy. Spectral magnetic field analyses are employed to find mainly elliptically polarized waves associated with O+ and He+ from ring-beam instabilities. Waves associated with He+ are identified, but O+ waves are not seen. Visibility is concluded to be affected by the relative amplitude of the waves to turbulence, and the visibility increases when the sampling direction is more aligned with the background magnetic field.

Keywords: Interplanetary turbulence, Pickup ions, Comets, Solar wind
Numerical Determination of the Gravitational Cross Sections of an Accreting Binary. A significant amount of work has been devoted to the study of small binary solar system objects. The majority of these binaries, especially among the near-Earth or main belt asteroids, have small radius ratios, implying a large difference in size between the primary and its companion. Farther from the Sun, the binary fraction increases, with the Kuiper Belt having many known binaries with radius ratios of order unity. In this paper, we consider the runaway growth of a binary system in an accretionary stream of small particles. We perform brute-force integrations, each with 10 million test particles, and numerically compute the gravitational cross sections for each member of the binary as a function of the system's separation and mass ratio. We show that the behavior of the cross section is complex, and it can be either diminished or enhanced depending on the orbital configuration. In regimes where gravitational focusing dominates the accretion process, we show that binaries grow toward smaller mass ratios than would be expected given single-body cross sections. Finally, we provide a grid of these cross sections for use in future studies of such systems.

Keywords: Asteroid satellites, N-body problem, N-body simulations
Stellar Evolution with Radiative Feedback in AGN Disks. Stars embedded in the inner parsec region of an active galactic nucleus (AGN) experience extreme accretion conditions that significantly alter their evolution. We present one-dimensional MESA simulations of stars growing and decaying within AGN disks, implementing radiative-feedback-regulated accretion, limiting stellar growth near the Eddington luminosity, as well as wind-driven mass loss. Unlike stand-alone stars in the field, these embedded stars follow unique evolutionary tracks with well-determined mass evolution and chemical yields. We distinguish two regimes: "immortal" stars that indefinitely remain on the main sequence due to efficient hydrogen mixing; and "metamorphic" stars whose growth is limited by feedback, ultimately enriching the disk with heavy elements upon hydrogen and helium exhaustion in their cores. Results indicate that embedded stars in AGN disks can attain large masses, but radiative feedback, gas retention, and limited mixing likely ensure the "immortal" track is unsustainable. Embedded metamorphic stars significantly enrich AGN disks with helium and α-elements, potentially explaining the observed high metallicity in broad-line regions (BLR) without excessive helium enrichment. This study underscores the critical interplay between stellar feedback and accretion physics in shaping the stellar populations and chemical evolution within AGN disks.

Keywords: Accretion, Chemical enrichment, Stellar winds, Active galactic nuclei, Stellar evolution
The Luminosity Function and Clustering of Hα Emitting Galaxies at z ≍ 4−6 from a Complete NIRCam Grism Redshift Survey. We study the luminosity function (LF) and clustering properties of 888 Hα emitters (HAEs) at 3.75 &lt; z &lt; 6 in the GOODS-N field. The sample, built from JWST CONGRESS and FRESCO NIRCam grism surveys using a novel redshift assignment algorithm, spans ∼62 arcmin2 and reaches LHα ∼ 1041.2 erg s−1. We identify two prominent filamentary protoclusters at z ≍ 4.41 and z ≍ 5.19, hosting 98 and 144 HAEs, respectively. The observed Hα LFs show similar shallow faint-end slopes for both protocluster and field galaxies at 3.75 &lt; z &lt; 5, and for the protocluster at 5 &lt; z &lt; 6 (α ≍ −1.2 to −1.3). In contrast, the field LF at 5 &lt; z &lt; 6 has a much steeper slope ( α=−1.87−0.23+0.30 ), suggesting that protocluster galaxies at z &gt; 5 are more evolved, resembling the populations at 3.75 &lt; z &lt; 5. The observed star formation rate density from Hα integrated down to 0.45 M⊙ yr−1, is  0.050−0.003+0.002M⊙yr−1Mpc−3  at 3.75 &lt; z &lt; 5 and  0.046−0.004+0.006M⊙yr−1Mpc−3  at 5 &lt; z &lt; 6, with protoclusters contributing about 25% and 55%, respectively. This implies a large fraction of star formation at z &gt; 4 occurs in protoclusters. For the first time, we conduct the star formation-rate-limited three-dimensional clustering analysis at z &gt; 4. We find that the filamentary geometry of protoclusters flattens the power-law shape of the HAE autocorrelation functions, with slopes much shallower than the typically assumed value. The autocorrelation function of field HAEs has a correlation length of  r0=4.61−0.68+1.00h−1Mpc  at z ≍ 4−5 and  r0=6.23−1.13+1.68h−1Mpc  at z ≍ 5−6. Comparing the observed correlation functions with the UNIVERSEMACHINE simulation, we infer the dark matter (sub-)halo masses of HAEs to be  log(Mh/M⊙)=11.0−11.2  at z ≍ 4−6, with a scatter of 0.4 dex.

Keywords: Luminosity function, High-redshift galaxy clusters, Protoclusters, Emission line galaxies, Star formation, Clustering
An Analysis of Active Galactic Nucleus Feedback in the Compact Galaxy Group Stephan's Quintet. Compact galaxy groups are ideal laboratories for studying the effects of interactions between active galactic nuclei (AGN) and multiple nearby galaxies. Recent JWST observations of the nearby compact group Stephan's Quintet highlight tidal flows between the interacting galaxies as well as outflows from the active galaxy NGC 7319. To study the kinematics on a large scale throughout the group, we obtained spatially resolved long-slit spectra of Stephan's Quintet at multiple slit positions with Apache Point Observatory's Kitt Peak Ohio State Multi-Object Spectrograph. We fit multiple Gaussians to the Hα λ6563 and [N II] λλ6548, 6583 emission lines to isolate the different kinematic components. We used the kinematics to develop the first biconical outflow model of the narrow-line region of NGC 7319. Using a combination of galactic rotation models, biconical outflow models, and kinematic maps of the ionized gas, we disentangled the outflows, rotation, and tidal flows in the group. We found outflow radial velocities up to 550 km s−1 peaking at 2.6 kpc from the central supermassive black hole, and a transition from AGN-powered outflows to gravitationally powered tidal flows at a projected distance between 2.4 and 6.3 kpc. We performed a line ratio analysis and determined the gas shows Seyfert-like ionization out to 6.3 kpc (projected), which supports our finding that gas outside this radius is predominantly powered by tidal flows. Our separation of kinematic components in Stephan's Quintet will enable future studies of the physical conditions and dynamical forces in the ionized gas to better quantify the feeding and feedback processes of AGN in compact groups.

Keywords: AGN host galaxies, Supermassive black holes, Hickson compact group, Seyfert galaxies, Active galactic nuclei, Galaxy winds, Galaxy kinematics, Galaxy groups
Modeling of IRIS Spectral Line Profiles via Markov Chain Monte Carlo in Bayesian Approach. Spectral line analysis is essential for investigating the solar atmospheric dynamic processes. Modeling the line profiles provides key insights into plasma motions and variations in temperature and density. This study aims to enhance the parameter estimation of spectral line profiles observed by the Interface Region Imaging Spectrograph through the application of an ensemble approach within the Bayesian Markov Chain Monte Carlo (MCMC) framework. We analyze silicon ion lines (Si IV 1394 and 1403 Å) for samples in the plage, flaring/nonflaring active regions, coronal hole, and boundary of coronal hole and quiet Sun, fitting them with single-Gaussian, double-Gaussian, and Voigt models using the Bayesian MCMC approach. The performance of the model is assessed using statistical metrics, including the reduced chi-square (χ2), Akaike information criterion, and Bayesian information criterion. The Bayesian MCMC method not only provides precise parameter estimates with associated uncertainties but also converges efficiently when initialized with Levenberg─Marquardt least-squares results. Overall, this approach enhances the accuracy of spectral line modeling and model selection, contributing to a more detailed understanding of solar atmospheric dynamics.

Keywords: Solar ultraviolet emission, The Sun, Spectroscopy, Solar transition region, Solar activity
Pulsar Gleaners: Discovery of 19 Pulsars in FAST Archival Data at ∣b∣ &lt; 5° and Decl. &lt; −5°. We report the discovery of 19 new pulsars identified from archival observations of the Five-hundred-meter Aperture Spherical radio Telescope (FAST) within Galactic latitudes ∣b∣ &lt; 5° and declinations decl. &lt; −5°. The dataset was recorded using FAST's L-band 19 beam receiver and covered ∼3.6 deg2 with a cumulative integration time of ∼500 hr and a total raw data volume of ∼700 TB. Our search employed fast Fourier transform (FFT)─based and fast folding algorithm (FFA)─based periodic searches and the single-pulse search. These new pulsars have spin periods ranging from 0.03 to 5.54 s. Two have periods under 0.1 s, suggesting they are likely young pulsars or mildly recycled pulsars. Four pulsars exhibit dispersion measures (DMs) exceeding 1000 pc cm−3, with PSR J1839─0558t having the highest value in our sample at ∼1271 pc cm−3, providing valuable samples for pulsar studies in the high-DM regime. Two rotating radio transients, PSRs J1836─0552t and J1847─0624t, were detected by FFA and single-pulse searches but failed with the FFT-based searches. In addition, three faint pulsars that were also missed by FFT-based searches were successfully detected using FFA. These discoveries demonstrate the critical role of FFA in uncovering faint, long-period, and sporadic pulsars and highlight the significant potential of FAST archival data, especially when combined with longer integration times and complementary search techniques, to reveal rare and weak pulsar populations. *The term "gleaners" in the title "Pulsar Gleaners" originates from the 1857 oil painting The Gleaners by Jean-François Millet, which depicts three peasant women collecting stray stalks of wheat left in a field after the harvest.

Keywords: Radio pulsars
Revisiting the Supernova Engines in the 3C 397 and W49B Supernova Remnants. The nature of the supernova remnants (SNRs) 3C 397 and W49B has long been a subject of debate, with prior studies offering conflicting interpretations between thermonuclear and core-collapse scenarios. To help settle this debate, we present a systematic, spatially resolved, spectroscopic analysis of both remnants using XMM-Newton. By applying multicomponent thermal models, we derive key physical properties including elemental abundances, ejecta temperatures, ambient densities, and explosion energetics. We compare the inferred metal abundance ratios to a wide range of core-collapse and thermonuclear nucleosynthesis models, including new models whose explosion energies differ from the canonical value of 1051 erg. We find that the observed Fe/Si and Ca/Si ratios in both SNRs are best matched by certain thermonuclear models. However, no model fully reproduces the complete set of observed abundance patterns. In 3C 397, high Fe enrichment and spatial abundance variations suggest interaction with a dense progenitor environment, and W49B's composition is overall consistent with a thermonuclear origin; however, both require a low-energy (∼1050 erg) supernova explosion. We additionally map the Fe Kα line centroid energies and find a spread, with W49B falling within the core-collapse region—highlighting both environmental complexity and the limitations of this diagnostic for supernova classification. Our results highlight the need for caution in relying on any single diagnostic or nucleosynthesis model for supernova typing, underscore the need for improved nucleosynthesis models, and motivate future high-resolution, high-throughput observations.

Keywords: X-ray astronomy, Core-collapse supernovae, Supernova remnants, Type Ia supernovae, X-ray sources, Spectroscopy
Electrostatic Waves in Astrophysical Druyvesteyn Plasmas. I. Langmuir Waves. Plasmas in various astrophysical systems are in nonequilibrium states, as evidenced by direct in situ measurements in the solar wind, solar corona, and planetary environments, as well as by indirect observations of nonthermal sources of waves and emissions. Specific to observed nonequilibrium plasmas are non-Maxwellian velocity distributions with suprathermal tails, most often described by kappa (power-law) distributions. In this paper, we introduce an alternative modeling for linear waves in plasmas described by the generalized Druyvesteyn distribution model. This model can reproduce not only high-energy tails, but also low-energy flat tops in velocity distributions, like those of electrons in interplanetary shocks and the solar transition region. The wave dispersion relation of longitudinal waves is derived in terms of the newly introduced Druyvesteyn dispersion function. The dispersion curves as well as damping rates of high-frequency Langmuir waves are numerically computed for the isotropic case, and their analytical approximations are provided in the limit of weak damping. We thus offer a new tool for modeling longitudinal waves, and in particular Langmuir waves under the specific conditions of Druyvesteyn distributions.

Keywords: Space plasmas, Solar wind, Plasma astrophysics, Plasma physics
The PWN─TeV Halo Transition in HESS J1809─193 Revealed by a Multizone Transport Model. HESS J1809─193 is an unassociated very-high-energy γ-ray source located in the Galactic plane. The source with a distinctive morphology and spectrum has an extension of 0 .° 62 with a compact component (r ≤ 0 .° 1). To explain its multiwavelength emission, we develop a self-consistent, spatially dependent, multizone leptonic model. The system is assumed to be spherically symmetric, with electrons injected near the pulsar termination shock and their subsequent evolution described by a Fokker─Planck-type transport equation. The evolution of the electrons includes convection, diffusion, adiabatic losses, and radiative losses. With suitable parameters, the model reproduces the observed multiwavelength fluxes of HESS J1809─193 reasonably well. The fit indicates that the compact component shows well-developed synchrotron and inverse Compton emission characteristics of a pulsar wind nebula (PWN), whereas the extension exhibits a halo-like morphology without a corresponding synchrotron counterpart, suggesting that the source is transitioning from a PWN to a TeV halo.

Keywords: Gamma-ray astronomy, Non-thermal radiation sources, Pulsar wind nebulae
Revealing the Magnetization of the Intracluster Medium of A3581 Using Background Faraday Rotation Measures from the POSSUM Survey. The line-of-sight magnetic field of galaxy clusters can be probed using Faraday rotation measure (RM) data. However, our understanding of cluster magnetism is limited due to the scarcity of polarized background radio sources, with most previous studies being constrained to ∼10 sources per cluster. Leveraging the increased source density of the POlarisation Sky Survey of the Universe's Magnetism, we probe the magnetic field properties of the galaxy cluster A3581 with 111 RMs. We find that the standard deviation in the RM declines monotonically with increasing radius up to 0.75 Mpc, agreeing with a radially declining magnetic field and electron density profile modeled as Gaussian and lognormal random fields, respectively. We compare our observations of the inner 0.75 Mpc of A3581 to various semianalytic models of the magnetic field and electron density and obtain several best-fit models. For the first time, we compare the observed RMs in a cluster to full magnetohydrodynamic simulated clusters from TNG-Cluster and find that the nonmonotonic trend in RM standard deviation past 0.75 Mpc in A3581 is likely caused by past or present merger activity. We identify a possible candidate for a merger to be the galaxy group [DZ2015b] 276, which would be the first group detected in RMs that is not strongly emitting in X-rays. We find a possible merger axis of A3581 with this group at a position angle of θ = 52 ± 4 deg.

Keywords: Galaxy clusters, Radio astronomy, Magnetic fields