Sazuna/UAT_keywords huggingface dataset:
An Extended Closure Relation by LightGBM for Neutrino Radiation Transport in Core-collapse Supernovae. We developed a machine learning model using LightGBM, one of the most popular gradient-boosting decision tree methods these days, to predict the Eddington tensor, or the second-order angular moment, for neutrino radiation transport in core-collapse supernova simulations. We use not only the zeroth and first moments of the neutrino distribution function in momentum space as in ordinary closure relations, but also information on the background matter configuration extensively. For training the model, we utilize some post-bounce snapshots from one of our previous Boltzmann radiation–hydrodynamics simulations; the Eddington tensor, as well as the zeroth and first angular moments, are calculated from the neutrino distribution function obtained in the simulation. LightGBM is light indeed, and its high efficiency in training enables us to feed a large number of features and figure out which features are more important than others. In this paper, we report the results of this feature engineering in addition to those of the training, validation, and generalization of our model. We find that the flux factor and nonlocal features are among the most relevant features; our LightGBM model can reproduce the Eddington factor better in general than the M1 closure relation, one of the most commonly employed algebraic closure relations at present; the generalization performance is also much improved from our previous model based on the deep neural network.

Keywords: Radiative transfer, Core-collapse supernovae
SN 2023ehl: A Normal Type Ia Supernova with High-velocity Features. SN 2023ehl, a normal Type Ia supernova with a typical decline rate, was discovered in the galaxy UGC 11555 and offers valuable insights into the explosion mechanisms of white dwarfs. We present a detailed analysis of SN 2023ehl, including spectroscopic and photometric observations. The supernova exhibits high-velocity features in its ejecta, which are crucial for understanding the physical processes during the explosion. We compared the light curves of SN 2023ehl with other well-observed Type Ia supernovae, finding similarities in their evolution. The line strength ratio R(Si II) was calculated to be 0.17 ± 0.04, indicating a higher photospheric temperature compared to other supernovae. The maximum quasi-bolometric luminosity was determined to be 1.52 × 1043 erg s‑1, and the synthesized 56Ni mass was estimated at 0.77 ± 0.05 M⊙. The photospheric velocity at B-band maximum light was measured as 10,150 ± 240 km s‑1, classifying SN 2023ehl as a normal velocity Type Ia supernova. Our analysis suggests that SN 2023ehl aligns more with both the gravitationally confined detonation, providing a comprehensive view of the diversity and complexity of Type Ia supernovae.

Keywords: Ejecta, Type Ia supernovae, Supernovae
Searching for Correlations between Satellite Galaxy Populations and the Cold Circumgalactic Medium around TNG50 Galaxies. We investigate the impact of satellites, a potentially important contributor toward the cold gas assembly of a halo, on the cold gas budgets of 197 TNG50 simulated halos with masses of 1010.85 ≤ M200c/M⊙ ≤ 1012.24 at z = 0. To highlight the effect of satellites, we split the sample into three mass bins. We find that the total number of satellites, total mass of satellites, number of massive satellites, and stellar mass of the most massive satellite all correlate with the cold gas mass in halos. The total number of satellites (stellar mass of the most massive satellite) correlates the most with the halo cold gas mass for low (middle) mass halos. The number of massive or observable satellites correlates with cold gas mass in a similar manner as the total number of satellites. Our findings can, therefore, be used to guide future observers to focus on the link between the number of observable satellites and the amount of cold gas in a halo. Despite this correlation, we find that much of the cold gas lies far from the satellites. This leads us to conclude that satellites are unlikely to be the main supplier for cold gas in halos. However, we discuss how they may act in tandem with other sources, such that the satellite population correlates with the total cold gas in their host halo.

Keywords: Hydrodynamical simulations, Dwarf galaxies, Galaxy evolution, Circumgalactic medium, Galaxies
Testing OH Megamaser Identification Methods in H I Surveys: Updated Source-flagging Algorithms and New Detections in ALFALFA. OH megamasers (OHMs) are extragalactic masers found primarily in gas-rich galaxy major mergers. To date, only ∼120 OHMs have been cataloged since their discovery in 1982, and efforts to identify distinct characteristics of OHM host galaxies have remained inconclusive. As radio astronomy advances with next-generation telescopes and extensive 21 cm H I surveys, precursors to the Square Kilometre Array are expected to detect the 18 cm OH masing line with significantly increased frequency, potentially expanding the known OHM population tenfold. These detections, however, risk confusion with lower-redshift H I emitters unless accompanied by independent spectroscopic redshifts. Building on methods proposed by Roberts et al. for distinguishing these interloping OHMs via near- to mid-IR photometry and emission line frequencies, we apply these techniques to data from the Arecibo Legacy Fast ALFA [Arecibo L-band Feed Array] (ALFALFA) survey and a preliminary Aperture Tile In Focus (Apertif) H I emission line catalog from the Westerbork Synthesis Radio Telescope. Our study, utilizing the Apache Point Observatory 3.5 m telescope to obtain optical spectroscopic redshifts of 142 candidates (107 from ALFALFA and 35 from Apertif), confirms five new OHM host galaxies and reidentifies two previously catalogued OHMs misclassified as H I emitters in ALFALFA. These findings support the predictions from Roberts et al. and underscore the evolving landscape of radio astronomy in the context of next-generation telescopes.

Keywords: Starburst galaxies, Sky surveys, Hydroxyl masers, H I line emission, Megamasers, Astrophysical masers
Gravitationally Induced Explosive Outflows. Over the past decade, there has been a significant increase in the reporting of extensive and luminous star-forming regions associated with explosive outflows. Nevertheless, there is still a lack of understanding of the possible physical mechanisms that produce such energetic and isotropic events. We propose a gravitational interaction as a likely mechanism that could trigger explosive outflows in dense star-forming regions. This could constrain the physical conditions that generate an explosive outflow produced by the close dynamical encounter of a runaway star with a clump cluster in dynamical equilibrium. We have produced a set of N-body simulations that account for the collision of a 10 M⊙ stellar object with a cluster of particles with a mass that ranges from 0 to 50 M⊙. We propose a parameter to describe the interaction, the evaporation parameter, which describes the fraction of stars that become unbound. The main result is that, when the cluster mass is less than or up to a few times the stellar mass, the collision will produce an explosive outflow, ejecting a significant fraction of the cluster members with velocities larger than the impact velocity. All of our models produce an explosive outflow, with different characteristics, which increases the probability that a close encounter could be responsible for producing the observed flows.

Keywords: Star forming regions, Interstellar dynamics, Interstellar medium
Preliminary Evidence for Lensing-induced Alignments of High-redshift Galaxies in JWST-CEERS. The majority of low-mass ( log10M*/M⊙=9─10 ) galaxies at high redshift (z &gt; 1) appear elongated in projection. We use JWST-CEERS observations to explore the role of gravitational lensing in this puzzle. The typical galaxy─galaxy lensing shear γ ∼ 1% is too low to explain the predominance of elongated early galaxies with an ellipticity e ≍ 0.6. However, nonparametric quantile regression with Bayesian Additive Regression Trees (or BART) reveals hints of an excess of tangentially aligned source─lens pairs with γ &gt; 10%. On larger scales, we also find evidence for weak-lensing shear. We rule out the null hypothesis of randomly oriented galaxies at ≳99% significance in multiple NIRCam chips, modules, and pointings. The number of such regions is small and attributable to chance, but coherent alignment patterns suggest otherwise. On the chip scale, the average complex ellipticity &lt;e&gt; ∼ 10% is nonnegligible and beyond the level of our point-spread function (PSF) uncertainties. The shear variance  &lt;γ̄2&gt;∼10−3  is an order of magnitude above the conventional weak-lensing regime but is more sensitive to PSF systematics, intrinsic alignments, cosmic variance, and other biases. Taking it as an upper limit, the maximum implied "cosmic shear" is only a few percent and cannot explain the elongated shapes of early galaxies. The alignments themselves may arise from lensing by a protocluster or filament at z ∼ 0.75 where we find an overabundance of massive lens galaxies. We recommend a weak-lensing search for overdensities in "blank" deep fields with the James Webb Space Telescope and the Roman Space Telescope.

Keywords: Weak gravitational lensing, Galaxy formation, Strong gravitational lensing, Large-scale structure of the universe
Probing Progression of Heating Through the Lower Flare Atmosphere via High-cadence IRIS Spectroscopy. Recent high-cadence flare campaigns by the Interface Region Imaging Spectrograph (IRIS) have offered new opportunities to study rapid processes characteristic of flare energy release, transport, and deposition. Here, we examine high-cadence chromospheric and transition region spectra acquired by IRIS during a C-class flare from 2022 September 25. Within the flare ribbon, the intensities of the Si IV 1402.77 Å, C II 1334.53 Å and Mg II k 2796.35 Å lines peaked at different times, with the transition region Si IV typically peaking before the chromospheric Mg II line by 1─6 s. To understand the nature of these delays, we probed a grid of radiative hydrodynamic flare simulations heated by electron beams, thermal conduction-only, or Alfvén waves. Electron beam parameters were constrained by hard X-ray observations from the Gamma-ray Burst Monitor (GBM) onboard the Fermi spacecraft. Reproducing light curves where Si IV peaks precede those in Mg II proved to be a challenge because only a subset of Fermi/GBM-constrained electron beam models were consistent with the observations. Light curves with relative timings consistent with the observations were found in simulations heated by either high-flux electron beams or by Alfvén waves, while the thermal conduction heating does not replicate the observed delays. Our analysis shows how delays between chromospheric and transition region emission pose tight constraints on flare models and properties of energy transport, highlighting the importance of obtaining very high-cadence data sets with IRIS and other observatories.

Keywords: Solar flares, Solar ultraviolet emission, Solar chromospheric heating, Solar flare spectra, Solar transition region, Solar chromosphere
Generalized T<SUB>e</SUB>([O III])–T<SUB>e</SUB>(He I) Discrepancies in Ionized Nebulae: Possible Evidence of Case B Deviations and Temperature Inhomogeneities. The physics of recombination lines in the He I singlet system is expected to be relatively simple, supported by accurate atomic models. We examine the intensities of He I singlets λ3614, λ3965, λ5016, λ6678, and λ7281 and the triplet He I λ5876 in various types of ionized nebulae and compare them with theoretical predictions to test the validity of the "Case B" recombination scenario and the assumption of thermal homogeneity. Our analysis includes 85 spectra from Galactic and extragalactic H II regions, 90 from star-forming galaxies, and 218 from planetary nebulae, all compiled by the Deep Spectra of Ionized Regions Database Extended (DESIRED-E) project. By evaluating the ratios He I λ7281/λ6678 and He I λ7281/λ5876, we determine Te(He I) and compare it with direct measurements of Te([O III] λ4363/λ5007). We find that Te(He I) is systematically lower than Te([O III]) across most objects and nebula types. Additionally, we identify a correlation between the abundance discrepancy factor (ADF(O2+)) and the difference Te([O III]) – Te(He I) for planetary nebulae. We explore two potential explanations: photon loss from n1P → 11S transitions and temperature inhomogeneities. Deviations from "Case B" may indicate photon absorption by H I rather than He I and/or generalized ionizing photon escape, highlighting the need for detailed consideration of radiative transfer effects. If temperature inhomogeneities are widespread, identifying a common physical phenomenon affecting all ionized nebulae is crucial. Our results suggest that both scenarios can contribute to the observed discrepancies.

Keywords: Galaxy abundances, Metallicity, Chemical abundances, Interstellar abundances
Investigating the Emission Mechanism in the Spatially Resolved Jets of Two z ≍ 3 Radio-loud Quasars. This study focuses on high-redshift, z &gt; 3, quasars where resolved X-ray jets remain underexplored in comparison to nearby sources. Building upon previous work, we identify and confirm extended kiloparsec-scale jets emission in two quasars (J1405+0415, z = 3.215; J1610+1811, z = 3.122) through meticulous analysis of Chandra X-ray data. To deepen our understanding, high-resolution radio follow-up observations were conducted to constrain relativistic parameters, providing valuable insights into the enthalpy flux of these high-redshift active galactic nucleus jets. The investigation specifically aims to test the X-ray emission mechanism in these quasars by exploring the inverse Compton scattering of cosmic microwave background photons by synchrotron-emitting electrons. Our novel method uses a prior to make a Bayesian estimate of the unknown angle of the jet to our line of sight, thus breaking the usual degeneracy of the bulk Lorentz factor and the Doppler beaming factor.

Keywords: Radio loud quasars, Relativistic jets, X-ray quasars
The Interplay between Dust Dynamics and Turbulence Induced by the Vertical Shear Instability. The interaction between gas and dust in protoplanetary disks (PPDs) plays a crucial role in setting the stage for planet formation. In particular, the streaming instability (SI) is well recognized as the mechanism for planetesimal formation out of this interaction. The outer region of PPDs is likely subject to the vertical shear instability (VSI), representing a major source of disk turbulence characterized by vertical corrugation that leads to strong dust stirring. In the meantime, the VSI turbulence in 3D generates vortices through the Rossby wave instability (RWI), which can trap dust and thereby promote dust concentration. In this study, we use the multifluid dust module in Athena++ to conduct 2D axisymmetric global simulations of PPDs with mesh refinement and 3D global simulations with modest resolution. In 2D, the VSI corrugation mode is weakened by dust back-reaction, while the SI can still survive regardless of initial conditions. Dust clumping occurs and is seeded by VSI-induced zonal flows. In 3D, dust can settle even more with increased dusty buoyancy, suppressing the VSI corrugation mode. Meanwhile, dust back-reaction enhances dust concentration in RWI vortices, though higher resolution is needed to assess dust clumping.

Keywords: Hydrodynamical simulations, Astrophysical fluid dynamics, Protoplanetary disks, Planet formation
Assessing the Role of Large Fullerenes as Potential Carriers of Infrared Emission Plateaus. We investigate large fullerenes containing between 90 and 1750 carbon atoms and with radii ranging from 4.4 to 12.9 Å, and compare their computed emission spectra to Spitzer data for the fullerene-rich planetary nebulae SMP SMC 24 and SMP LMC 48 to assess their contribution to the broad infrared emission plateaus. The structures are computed without any bias using molecular dynamics simulations and contain mostly five- and six-membered rings, several seven-membered rings, and very few four- and eight-membered rings. Our largest structures consist of multishell fullerenes. The infrared spectra are calculated using the density-functional-based tight-binding theory. Their emission spectra exhibit broad plateaus from 6 to 10 μm and from 14 to 20 μm, whose 6–10/14–20 relative intensity ratios reach a maximum value for ∼200 carbons. The computed 6–10 μm plateaus exhibit distinct subfeatures in agreement with the observations. The subfeatures with the largest intensities peak at 6.6 and 7.7–7.9 μm. We assign these subfeatures to C–C stretching vibrations from the different types of rings arranged in many different ways. A comparison of the computed 6–10/14–20 μm intensity ratios as a function of fullerene size and photon energy with the observed 6–10/14–20 μm intensity ratio for SMP LMC 48 allows us to derive an upper bound of ∼150–200 carbons for the fullerene size.

Keywords: Theoretical techniques, Fullerenes, Molecular spectroscopy, Interstellar dust extinction, Infrared astronomy
Submillimeter Observations of the White Dwarf Pulsar AR Sco. AR Scorpii, the so-called white dwarf (WD) pulsar, contains a rapidly rotating magnetic WD (Pspin = 117.0564 s) interacting with a cool, red dwarf (RD) companion in a 3.56 hr orbit. It is a strong radio source with an inverted spectral index between 1 and 200 GHz that is indicative of synchrotron emission. This paper presents the first submillimeter observations of AR Scorpii using the Submillimeter Array, helping to fill a critical gap in the spectral energy distribution (SED) between 10 and 600 GHz. The average flux densities at 220 and 345 GHz are 124 and 86 mJy, respectively. The lower than expected flux density at 345 GHz suggests a break in the synchrotron emission at about 200 GHz. A periodogram analysis of the 220 GHz observations shows a modulation with an amplitude of ≈6% at a period of 58.26 s or at twice the spin frequency of the WD. This modulation is the first direct detection of the WD spin period at radio frequencies and implies that the synchrotron emission arises near the WD and and not from an interaction with the photosphere of the RD. A fit to the SED shows that the synchrotron emission arises from a small, low-density region with a magnetic field of 43 MG at a distance of 0.6 orbital radii from the WD. This result implies that AR Scorpii contains a weakly magnetic WD (∼15 MG) and not a strongly magnetic WD (∼500 MG) as previously asserted.

Keywords: Galactic radio sources, White dwarf stars, Radio astrometry, Submillimeter astronomy, Cataclysmic variable stars
The Outflow Impact on the Size of the Narrow-line Region among Type 2 Active Galactic Nuclei. We present a study of the gas kinematics in narrow-line regions (NLRs) of 2009 Type 2 active galactic nuclei (AGNs) at z &lt; 0.34. We construct [O III] λ5007 emission-line images using publicly available broadband images from the Sloan Digital Sky Survey (SDSS). The [O III] emission areas of the samples, measured down to a rest-frame isophote of 1.4 × 10‑15 erg s‑1 cm‑2 arcsec‑2, range from 3.7 up to 224 kpc2. With our broadband technique, we found a correlation between [O III] area and AGN luminosity inferred from the [O III] luminosity and the mid-infrared luminosity at rest-frame 15 μm. The isophotal threshold used to determine the [O III] area affects the correlation strength in that a brighter isophote yields a stronger correlation between the [O III] area and AGN luminosity. The presence of gas outflows is examined by the ratio of the [O III] velocity dispersion to the stellar velocity dispersion (σ[O III]/σ⋆ &gt; 1.4) using SDSS spectra. At a given luminosity, objects with and without outflows exhibit the same extent of [O III] emission. Their correlation between [O III] area and luminosity is almost identical. It is suggested that the size of NLRs is not affected by outflow mechanisms but rather by photoionization from the central AGNs.

Keywords: AGN host galaxies, Active galactic nuclei, Galaxy evolution, Galaxy kinematics, Galaxy quenching
The Internal Kinematics of NGC 2808 and Its Multiple Populations. We use new Hubble Space Telescope observations coupled with archival data spanning a total temporal baseline of 17 yr to study the internal kinematics of the multiple populations in the globular cluster NGC 2808 from its center out to ∼8 half-light radii (rh). We detect different kinematical behaviors between the first- and second-generation populations. This is especially evident towards the external regions of the cluster, where second-generation stars are increasingly more radially anisotropic. Our results are in agreement with theoretical simulations that predict that second-generation stars, initially more concentrated in the inner regions, gradually diffuse outward and develop a stronger radially anisotropic velocity distribution with respect to the first-generation stars. We find the central regions of the cluster to exhibit a higher degree of energy equipartition than the outskirts: Our analysis reveals similar levels of energy equipartition in the radial and tangential components of the motion within about 4 rh, while outside 4 rh the data suggest that the equipartition level of the radial component of the velocity dispersion is slightly higher than that of the tangential component. Finally, we measured the dispersion of the angular momentum Lz for the three main subpopulations along the main sequence, which provides further evidence of the differences in the velocity anisotropy of first-generation and second-generation stars and shows marginal evidence for the most extreme second-generation subpopulation being slightly more radially anisotropic than the other second-generation subpopulation.

Keywords: Globular star clusters, Hertzsprung Russell diagram, Proper motions, Stellar kinematics
Testing X-Ray Reprocessing and Mapping the Soft Excess of NGC 7469 with NICER. We present an X-ray/UV reverberation analysis of NGC 7469 across 210 days, using daily NICER observations with contemporaneous monitoring by Swift UVOT+XRT. We model the X-ray spectrum with a power-law continuum and a soft excess during each NICER epoch. These emission sources demonstrate correlated flux variability with a lag consistent with zero days. We find that the power-law emission is consistent with a compact X-ray corona, and that the soft excess can be explained by reflected coronal emission from the inner accretion disk. We test the relationship between changes in the flux of the X-ray corona and the UVW2 continuum, finding strong correlation and a negative X-ray lag of less than 1 day. This is consistent with a scenario in which the X-ray corona drives the UVW2 light curve through thermal reprocessing.

Keywords: Accretion, High energy astrophysics, Reverberation mapping, X-ray telescopes, X-ray active galactic nuclei, Active galactic nuclei