Sazuna/UAT_keywords huggingface dataset:
Simulations of Galactic Outflows Driven by Active Galactic Nuclei and Starbursts. Using the hydro code Athena++, we run a series of large-scale hydrodynamic simulations of galactic outflows on a scale of ∼5 kpc scale over a time period of 5 Myr. We compare the kinematics, composition, and simulated X-ray emission of starburst (SB) versus active galactic nuclei (AGN) dominated galactic outflows. Our set of simulations includes galactic outflows driven solely by a nuclear SB, an AGN wind, and a mixture of SBs and AGN winds. We find significant differences in the kinematics, composition, and simulated X-ray emission between SB- versus AGN-dominated outflows. Starburst-driven outflows are characterized by turbulent, multiphase, complex flows, with each phase having a distinct kinematic profile (as traced by various oxygen ions), while AGN-driven outflows are more symmetric, more single phase, with primarily very hot (&gt;107 K) gas, and are smooth in appearance. In mixed SB-AGN simulations, the dominant component (SB or AGN) determines the outflow characteristics. In cases where the energy input of the SB is similar to the energy of the AGN, the resulting outflow appears similar to the SB-only outflow, but when the energy input from the AGN wind is much greater than the SB then the outflow appears similar to the AGN-only outflow. When we generate synthetic X-ray observations, the AGN-dominated outflows are essentially invisible in soft to medium-energy X-rays (0.1─10.0 keV), but the SB-driven outflows show complex filamentary structures that are visible in the X-ray. Finally, we show the observational possibilities for various proposed and future X-ray telescopes.

Keywords: AGN host galaxies, Starburst galaxies, Hydrodynamical simulations, X-ray astronomy, Hydrodynamics, Active galaxies, X-ray telescopes, Astronomical simulations
Lyman Continuum Leakage from Massive Leaky Starbursts: A Different Class of Emitters?. The origin of Lyman continuum (LyC) photons responsible for reionizing the Universe remains largely unknown, with the fraction of escaping LyC photons from galaxies at z ∼ 6 to 12 still uncertain. Direct detection of LyC photons from this epoch is challenging due to intergalactic medium absorption, making lower-redshift analogs valuable for studying LyC leakage. In this study, we present Hubble Space Telescope Cosmic Origins Spectrograph observations of five low-redshift (z ∼ 0.3) massive starburst galaxies, selected for high stellar mass and weak [S II] nebular emission, an indirect tracer of LyC escape. LyC leakage is detected in three of the five galaxies, highlighting weak [S II] as a reliable tracer—a finding supported by recent JWST discoveries of z &gt; 5 galaxies with similarly weak [S II] emission. The dust-corrected LyC escape fractions (fesc,H I), representing LyC photons that would escape without dust, range from 33% to 84%. However, the absolute escape fractions (fesc,tot), accounting for both neutral hydrogen absorption and dust attenuation, are substantially lower, between 1% and 3%. This indicates that, although these galaxies are nearly optically thin to H I, their significant dust content restricts LyC escape. These [S II]-weak, massive leakers differ from typical low-redshift LyC emitters, exhibiting higher metallicity, lower ionization states, greater dust extinction, and higher star formation surface densities. We suggest that feedback-driven winds in these compact starbursts generate ionized channels, allowing LyC escape in line with a "picket-fence" model, indicating a distinct mechanism for LyC leakage.

Keywords: Reionization, Emission line galaxies, Galaxies, Intergalactic medium
How Dust Models Shape High-z Galaxy Morphology: Insights from the NewCluster Simulation. Dust plays a pivotal role in shaping the observed morphology of galaxies. While traditional cosmological simulations often assume a fixed dust-to-gas or dust-to-metal (DTM) mass ratio to model dust effects, recent advancements have enabled on-the-fly (OTF) dust modeling that captures the spatial and temporal evolution of dust. In this work, we investigate the impact of dust modeling on galaxy morphology using the NEWCLUSTER simulation, which implements a detailed OTF dust model. We generate mock images of NEWCLUSTER galaxies under both OTF and fixed DTM models using the radiative transfer code SKIRT, and compare their morphology to JWST observations. We measure morphology indices and use the G─M20 test to classify galaxies. We find that the OTF galaxy models exhibit brighter centers and more pronounced bulges than those of the fixed DTM models, resulting in a lower late-type galaxy fraction, particularly at high redshifts. This central brightening is linked to a phenomenon we refer to as the DTM cavity, a localized depression in the DTM ratio driven by intense bulge starbursts. Our results highlight the importance of modeling dust evolution in a physically motivated manner, as fixed DTM models fail to capture key morphological features.

Keywords: Gas-to-dust ratio, Dust physics, Galaxy bulges, Galaxy classification systems, Interstellar dust extinction, Galaxy evolution
Classifying Cool Dwarfs: Comprehensive Spectral Typing of Field and Peculiar Dwarfs Using Machine Learning. Low-mass stars and brown dwarfs—spectral types (SpTs) M0 and later—play a significant role in studying stellar and substellar processes and demographics, reaching down to planetary-mass objects. Currently, the classification of these sources remains heavily reliant on visual inspection of spectral features, equivalent width measurements, or narrow/wideband spectral indices. Recent advances in machine learning (ML) methods offer automated approaches for spectral typing, which are becoming increasingly important as large spectroscopic surveys such as Gaia, SDSS, and SPHEREx generate data sets containing millions of spectra. We investigate the application of ML in spectral type classification on low-resolution (R ∼ 120) near-infrared spectra of M0─T9 dwarfs obtained with the SpeX instrument on the NASA Infrared Telescope Facility. We specifically aim to classify the gravity- and metallicity-dependent subclasses for late-type dwarfs. We used binned fluxes as input features and compared the efficacy of spectral type estimators built using Random Forest (RF), Support Vector Machine, and K-Nearest Neighbor (KNN) models. We tested the influence of different normalizations and analyzed the relative importance of different spectral regions for surface gravity and metallicity subclass classification. Our best-performing model (using KNN) classifies 95.5% ± 0.6% of sources to within ±1 SpT, and assigns surface gravity and metallicity subclasses with 89.5% ± 0.9% accuracy. We test the dependence of signal-to-noise ratio on classification accuracy and find sources with SNR ≳60 have ≳95% accuracy. We also find that zy band plays the most prominent role in the RF model, with FeH and TiO having the highest feature importance.

Keywords: M dwarf stars, Brown dwarfs, M subdwarf stars, L dwarfs, Support vector machine, Stellar classification, Random Forests, T dwarfs
Long-period Variable Stars in NGC 147 and NGC 185. II. Their Dust Production. This study presents a comparative analysis of mass-loss and dust production rates in the dwarf galaxies NGC 147 and NGC 185, focusing on long-period variables (LPVs) and pulsating asymptotic giant branch stars as primary indicators of dust feedback into the interstellar medium. For NGC 147, the total mass-loss rate is calculated as (9.44 ± 3.78) × 10−4 M⊙ yr−1, with LPV luminosities ranging from (6.20 ± 0.25) × 102 L⊙ to (7.87 ± 0.32) × 103 L⊙. In NGC 185, the total mass-loss rate is higher, at (1.58 ± 0.63) × 10−3 M⊙ yr−1, with LPV luminosities spanning (5.68 ± 0.23) × 102 L⊙ to (1.54 ± 0.66) × 104 L⊙. A positive correlation is observed between stellar luminosity, intrinsic reddening due to circumstellar dust self-extinction, and elevated mass-loss rates. Additionally, comparisons of calculated dust injection rates, two-dimensional dust distribution maps, and observed dust masses provide evidence for a gravitational interaction between NGC 147 and the Andromeda galaxy, which influences the dust distribution within the system.

Keywords: Dust formation, Stellar mass loss, Asymptotic giant branch stars, Long period variable stars, Interstellar medium
Persistent Behavior of Low-energy Solar Energetic Particles Observed by Parker Solar Probe During Orbit 15. The paper develops a new statistical method for forecasting the arrival time and maximum flux of solar energetic particle (SEP) events. We recently showed the persistent behavior of the SEP time series during SEP events. In that study, we also used persistence to determine the onset time (OT) of an SEP event and suggested using the entropy change in a time domain called natural time under time reversal ΔS as a way to estimate the maximum SEP flux of the ongoing SEP event. Here, we use EPI-Lo data for H+ below 2 MeV over the whole Orbit 15 from the Integrated Science Investigation of the Sun (IS⊙IS) instrument suite on board NASA's Parker Solar Probe to investigate the broader applicability of these methods. We clearly demonstrate that during SEP events the corresponding time series is persistent and are able to employ the persistence-based OT method to predict SEP events. We find a prediction rate greater than 87.5% (14 out of the 16 SEP events) and a false alarm rate below 2.2%. These values when inserted in the receiver operating characteristics plane indicate that this method is highly statistically significant. Finally, we develop a relationship between the maximum SEP flux and the minimum of ΔS, allowing us to provide a prediction of the future maximum SEP flux during an ongoing event.

Keywords: Solar energetic particles, Astrostatistics techniques, Solar wind, Interdisciplinary astronomy, Time series analysis
The Near Infrared Spectral Energy Distribution of Young Star Clusters in the FEAST Galaxies: Missing Ingredients at 1─5 μm. We present a combined Hubble Space Telescope (HST) and JWST 0.2─to─5 μm analysis of the spectral energy distributions (SED) of emerging young star clusters (eYSCs) in four nearby galaxies from the Feedback in Emerging Extrgalactic Star Clusters survey: M51, M83, NGC 628, and NGC 4449. These clusters, selected for their bright Paα and 3.3 μm polycyclic aromatic hydrocarbon emission, are still associated with their natal gas cloud and have been largely missed in previous HST optical campaigns. We modeled their SEDs using the CIGALE fitting code and identified (i) a systematic flux excess at 1.5─2.5 μm that is not accounted for by current stellar population models and (ii) the preference for a set of dust model parameters that is not aligned with expectations from self-consistent analyses of star-forming regions, suggesting model shortcomings also in the 3─5 μm. The near-infrared excess is most prominent in low-mass (≤3000 M⊙) and young (≤6 Myr) clusters. Additionally, we see that the SED fitting analysis wrongly assigns ages ≥6 Myr to a fraction of strong Paα emitters with equivalent widths suggestive of significantly younger ages. A parallel analysis with the slug code suggests that stochastic initial mass function (IMF) sampling of pre-main-sequence stars combined with extinction might partially reduce the gap. We conclude that the inclusion of young stellar object SEDs, along with more realistic sampling of the cluster IMF, might be needed to fully account for the stellar population and dust properties of eYSCs.

Keywords: Polycyclic aromatic hydrocarbons, Star formation, Spectral energy distribution, Galaxies, Star clusters
The Frequency-independent Radio Luminosity–Orbital/Rotational Period Relation of RS CVn Stars. Radio emissions from RS CVn objects exhibit distinct characteristics at low and high frequencies, widely attributed to differing radiation mechanisms. The disparate processes of high-frequency gyrosynchrotron and low-frequency electron cyclotron maser emissions have traditionally suggested an absence of correlation in their radio luminosities. Our study presents a frequency-independent linear correlation between radio luminosity (LR) and orbital/rotational periods (P) in RS CVn binaries. Analyzing the Sydney Radio Star Catalogue data, we derived orbital periods for 42 of 60 RS CVn sources using Transiting Exoplanet Survey Satellite light curves, revealing a strong positive correlation (Pearson correlation coefficient (PCC) = 0.698 and P = 3.95e-7) between  log10LR  and  log10P . This correlation remains across frequencies from 144 to 3000 MHz, showing uniform luminosity behavior. By combining light curve analysis with stellar mass–radius–luminosity relationships, we calculated parameters like binary mass, primary/secondary mass, Rossby number, and binary separation for eight RS CVn systems. The results show a notable correlation between radio luminosity and binary mass, primary mass, and separation (PCC = 0.663, 0.663, and 0.719), with separation showing the strongest correlation. This suggests the radio emission may largely originate from the binary components' interaction, challenging existing models of RS CVn radio emission mechanisms and offering insights into the individual versus collective origins of these emissions.

Keywords: RS Canum Venaticorum variable stars, Radio astronomy, Variable stars, Radio transient sources
ALMA Observations of CO in Five Planetary Nebulae: Insights into Nebular Shaping. The J = 2→1 transition of CO near 230 GHz has been imaged in five bipolar/multipolar planetary nebulae (K3-45, K3-58, M1-7, M2-48, and M3-28) using ALMA with 1″ angular resolution. Single-dish data from the Arizona Radio Observatory Submillimeter Telescope (ARO SMT) were added to provide sensitivity on spatial scales up to 30″—essential for these data. The images show that the molecular gas resides primarily in the central regions of the nebulae and not in the bipolar flows of the optical images. CO appears to trace the remnant asymptotic giant branch (AGB) wind (Vexp ∼ 12─14 km s−1) but has a higher velocity component (V &gt; 16─23 km s−1) that represents gas swept up in the outflows. The orientations, with respect to the plane of the sky, of the bipolar outflows are 45° ± 5, 65° ± 10, and 65° ± 5 for K3─45, K3-58, and M1-7, respectively, with the blueshifted lobes oriented to the NE, W, and NW. For M2-48 and M3-28, the flows lie in the plane of the sky, with the blueshifted lobes roughly lying E and N. Based on CO, velocities in the bipolar flows are estimated to be Voutflow &gt; 18─31 km s−1. Revised CO column densities are consistent with past measurements, except for M2-48, where the value increased to Ntot ∼  9.3×1016  cm−2; a value was also obtained for the first time for K3-58 (Ntot ∼ 5 × 1016 cm−2). Given the unusual 12C/13C ratios observed in two sources, the bipolar ejection may have an origin in runaway He-burning in the late AGB phase.

Keywords: Interstellar molecules, Molecular spectroscopy, Astrochemistry, Planetary nebulae, Radio astronomy
Predicting Solar Magnetic Activity from S<SUB>ph</SUB> and Seismic Parameters Using Random Forest Regression. We investigate the potential of using the photometric magnetic proxy Sph and seismic parameters, such as the frequency of maximum power ( νmax ) and the large frequency separation (Δν), derived from Solar and Heliospheric Observatory/Variability of Solar Irradiance and Gravity Oscillations observations to predict the 10.7 cm solar radio flux, a widely used index of solar magnetic activity. A random forest regression model is trained and tested on time series divided into multiple temporal subsets and input parameter combinations. The model achieves strong predictive performance (R2 &gt; 0.92) across configurations and significantly outperforms a classical linear regression model. Our results show that Sph effectively captures long-term variations, while the seismic amplitude parameter  Hmax  is more responsive to short-term fluctuations. Combining Sph with the full set of seismic parameters yields the highest accuracy and offers a promising approach for diagnosing activity in other solar-like stars where direct magnetic field measurements are infeasible.

Keywords: Solar activity, Random Forests, Asteroseismology, Helioseismology
Final Moments. III. Explosion Properties and Progenitor Constraints of CSM-interacting Type II Supernovae. We present analysis of the plateau and late-time phase properties of a sample of 39 Type II supernovae (SNe II) that show narrow, transient, high-ionization emission lines (i.e., "IIn-like") in their early-time spectra from interaction with confined, dense circumstellar material (CSM). Originally presented by W. V. Jacobson-Galán et al., this sample also includes multicolor light curves and spectra extending to late-time phases of 35 SNe with no evidence for IIn-like features at &lt;2 days after first light. We measure photospheric phase light-curve properties for the distance-corrected sample and find that SNe II with IIn-like features have significantly higher luminosities and decline rates at +50 days than the comparison sample, which could be connected to inflated progenitor radii, lower ejecta mass, and/or persistent CSM interaction. However, we find no statistical evidence that the measured plateau durations and 56Ni masses of SNe II with and without IIn-like features arise from different distributions. We estimate progenitor zero-age main-sequence (ZAMS) masses for all SNe with nebular spectroscopy through spectral model comparisons and find that most objects, both with and without IIn-like features, are consistent with progenitor masses ≤12.5 M⊙. Combining progenitor ZAMS masses with CSM densities inferred from early-time spectra suggests multiple channels for enhanced mass loss in the final years before core collapse, such as a convection-driven chromosphere or binary interaction. Finally, we find spectroscopic evidence for ongoing ejecta-CSM interaction at radii &gt;1016 cm, consistent with substantial progenitor mass-loss rates of ∼10−4─10−5 M⊙ yr−1 (vw &lt; 50 km s−1) in the final centuries to millennia before explosion.

Keywords: Type II supernovae, Red supergiant stars, Supernovae, Core-collapse supernovae
On the Stability Analysis of Astrophysical Cooling Functions. To model the temperature evolution of optically thin astrophysical environments at MHD scales, radiative and collisional cooling rates are typically either pretabulated or fit into a functional form and then input into MHD codes as a radiative loss function. Thermal balance requires estimates of the analogous heating rates, which are harder to calculate, and due to uncertainties in the underlying dissipative heating processes these rates are often simply parameterized. The resulting net cooling function defines an equilibrium curve that varies with density and temperature. Such cooling functions can make the gas prone to thermal instability (TI), which will cause departures from equilibrium. There has been no systematic study of thermally unstable parameter space for nonequilibrium states. Motivated by our recent finding that there is a related linear instability, catastrophic cooling instability, that can dominate over TI, here we carry out such a study. We show that Balbus instability criteria for TI can be used to define a critical cooling rate, Λc, that permits a nonequilibrium analysis of cooling functions through the mapping of TI zones. We furthermore illustrate how thermal conduction modifies the shape of TI zones. Upon applying a Λc-based stability analysis to coronal loop simulations, we find that loops undergoing periodic episodes of coronal rain formation are linearly unstable to catastrophic cooling instability, while TI is stabilized by thermal conduction.

Keywords: Solar coronal loops, Radiative magnetohydrodynamics, Interstellar medium
Probing the Nature of Gravity in the Low-acceleration Limit: Wide Binaries of Extreme Separations with Perspective Effects. Recent statistical analyses of wide binaries have revealed a boost in gravitational acceleration with respect to the prediction by Newtonian gravity at low internal accelerations ≲10−9 m s−2. This phenomenon is important because it does not permit the dark matter interpretation, unlike galaxy rotation curves. We extend previous analyses by increasing the maximum sky-projected separation from 30 to 50 kilo astronomical units (kau). We show that the so-called "perspective effects" are not negligible at this extended separation and, thus, incorporate it in our analysis. With wide binaries selected with very stringent criteria, we find that the gravitational acceleration boost factor, γg ≡ gobs/gN, is  1.61−0.29+0.37  (from  δobs−newt≡(log10γg)/2=0.147±0.062 ) at Newtonian accelerations gN = 10−11.0 m s−2, corresponding to separations of tens of kau for solar mass binaries. At Newtonian accelerations gN = 10−10.3 m s−2, we find  γg=1.26−0.10+0.12  (δobs−newt = 0.072 ± 0.027). For all binaries with gN ≲ 10−10 m s−2 from our sample, we find  γg=1.32−0.11+0.12  (δobs−newt = 0.085 ± 0.027). These results are consistent with the generic prediction of modified Newtonian dynamics-type modified gravity, although the current data are not sufficient to pin down the low-acceleration limiting behavior. Finally, we emphasize that the observed deviation from Newtonian gravity cannot be explained by the perspective effects or any separation-dependent eccentricity variation that we have taken into account.

Keywords: Binary stars, Gravitation, Non-standard theories of gravity, Wide binary stars, Modified Newtonian dynamics
Impact of Gravity on Changing Magnetic Field Orientations in a Sample of Massive Protostellar Clusters Observed with ALMA. The magnetic field is integral to our understanding of the formation and dynamical evolution of molecular clouds and star formation within. We present a polarimetric survey of 17 massive protostellar cluster forming clumps, covered in 34 pointings in the 230 GHz window using the Atacama Large Millimeter/submillimeter Array. The two array configurations, C43-1 and C43-4, probe linearly polarized dust emission, hence the plane-of-the-sky orientation of magnetic fields, at resolutions of 1″ and 0 .″ 4 that correspond to approximately 0.01 pc core and 103 au envelope scales, respectively. The relative orientations (ROs) of the magnetic field probed at two spatial scales are analyzed for the entire protostellar cluster sample and for a subset of objects in NGC 6334. We found a bimodal distribution of ROs with peaks at 0° (parallel) and 90° (orthogonal) for the entire sample combined, as well as for NGC 6334. We investigate the physical origin of this bimodal distribution through a projected Rayleigh statistical analysis in relation to column densities and local gravity in NGC 6334. We found an excess of parallel magnetic fields at column densities &gt;1023 cm−2. The underlying cause of the RO distribution of the magnetic field is gravitational collapse at higher gas densities, which drags and reorients the magnetic field as shown in the alignment between the magnetic field and the direction of gravitational forces. The distribution of ROs observed here is consistent with the evolution of ROs of an initially sub-Alvénic cloud that becomes magnetically supercritical and super-Alvénic as the cloud collapses to form stars.

Keywords: Dust continuum emission, Star formation, Magnetic fields, Polarimetry