Sazuna/UAT_keywords huggingface dataset:
Impeding Turbulence Decay in Self-gravitating Cloud Cores. Turbulence governs the fragmentation of molecular clouds and plays a pivotal role in star formation. The persistence of observed cloud turbulence suggests it does not decay significantly within the turnover timescale, implying a recurrent driving mechanism. Although ubiquitous self-gravity is a plausible driver, magnetohydrodynamic simulations by E. C. Ostriker et al. in 2001 demonstrated that self-gravity alone does not modify the global turbulence decay rate. In this study, we demonstrate that the dominant diffuse volume of a cloud dictates its overall decay rate, while individual dense cores can maintain near-zero decay rates. Crucially, this phenomenon is absent in control simulations excluding self-gravity. This discrepancy cannot be attributed to contamination of turbulent velocities by core contraction because most cores in our simulations remain in a quasi-equilibrium state. Our analysis reveals that the gravitational potential energy released during core formation—not necessarily driven by self-gravity but also by turbulent compression—is sufficient to sustain the observed turbulence levels within cores.

Keywords: Magnetohydrodynamics, Molecular clouds, Interstellar medium, Magnetohydrodynamical simulations
Bright Dots and Coronal Plume Formation in Sunspot Penumbra. Coronal plumes are narrow, collimated structures that are primarily viewed above the solar poles and in coronal holes in the extreme ultraviolet, but also in sunspots. Open questions remain about plume formation, including the role of small-scale transients and whether plumes embedded in different magnetic field configurations have similar formation mechanisms. We report on coordinated Solar Orbiter/Extreme Ultraviolet Imager (EUI), Interface Region Imaging Spectrograph, and Solar Dynamics Observatory observations of the formation of a plume in sunspot penumbra in 2022 March. During this observation, Solar Orbiter was positioned near the Earth─Sun line and EUI observed at a 5 s cadence with a spatial scale of 185 km pixel−1 in the solar corona. We observe fine-scale dots at various locations in the sunspot, but the brightest and highest density of dots is at the plume base. Space-time maps along the plume axis show parabolic and V-shaped patterns, and we conclude that some of these dots are possible signatures of magneto-acoustic shocks. Compared to other radial cuts around the sunspot, along the plume shows the longest periods (∼7 minutes) and the most distinct tracks. Bright dots at the plume base are mostly circular and do not show elongations from a fixed origin, in contrast to jetlets and previously reported penumbral dots. We do not find high-speed, repeated downflows along the plume, and the plume appears to brighten coherently along its length. Our analysis suggests that jetlets and downflows are not a necessary component of this plume's formation, and that mechanisms for plume formation could be dependent on magnetic topology and the chromospheric wave field.

Keywords: Sunspots, Solar physics, Solar coronal plumes, Solar corona
Physical Constraint Preserving Higher-order Finite Volume Schemes for Divergence-free Astrophysical MHD and RMHD. Higher-order finite volume schemes for magnetohydrodynamics (MHD) and relativistic magnetohydrodynamics (RMHD) are very valuable because they allow us to carry out astrophysical simulations with very high accuracy. However, astrophysical problems sometimes have unusually large Mach numbers, exceptionally high Lorentz factors, and very strong magnetic fields. All these effects cause higher-order codes to become brittle and prone to code crashes. In this paper, we document physical constraint preserving (PCP) methods for treating numerical MHD and RMHD. While unnecessary for standard problems, for stringent astrophysical problems, these methods show their value. We describe higher-order methods that allow divergence-free evolution of the magnetic field. We present a novel two-dimensional Riemann solver. This two-dimensional Riemann solver plays a key role in the design of PCP schemes for MHD and RMHD. We present a very simple PCP formulation and show how it is amalgamated with the evolution of face-centered magnetic fields. The methods presented here are time-explicit and do not add much to the computational cost. We show that the methods meet their design accuracies and work well on problems that would otherwise be considered too extreme for typical higher-order Godunov methods of the type used in computational astrophysics.

Keywords: Hydrodynamical simulations, Computational astronomy, Magnetohydrodynamics, Algorithms, Astronomical simulations, Magnetohydrodynamical simulations
The Physical Properties and Morphologies of Faint Dusty Star-forming Galaxies Identified with JWST. We identify a sample of 234 dusty star-forming galaxies (DSFGs) in the A2744 and GOODS-S fields using JWST/NIRCam-selected galaxies as priors for SCUBA-2 measurements. This method provides a large number of galaxies both above an 850 μm flux of 2 mJy (47 bright DSFGs) and below (187 faint DSFGs), representing the largest sample of individually identified (i.e., not stacked) faint DSFGs to date. We observe that fF444W and fF150W are tightly correlated with redshift, with fainter sources lying at higher redshifts, suggesting that the observed near-IR flux may be an effective way of selecting high-redshift DSFGs. We study the physical properties and morphologies of the DSFGs through spectral energy distribution fitting and parametric surface brightness profile modeling. Other than the lower star formation rates (SFRs) and total infrared luminosities in the faint DSFGs (SFR  =80−45+81 ;  LIR=11.82−0.36+0.30 ) compared to the bright DSFGs (SFR  =254−131+135 ;  LIR=12.32−0.30+0.20 ), the populations have similar properties. The stellar masses do not appear to be strongly dependent on either the SFRs or the submillimeter flux. These results suggest that the faint DSFGs are drawn from the same population of galaxies as the bright DSFGs. Based on visual inspections, we find a lower merger fraction (∼21%) relative to previous Hubble Space Telescope─based studies, suggesting that dust attenuation may have impacted previous estimates of DSFG merger rates.

Keywords: Submillimeter astronomy, Starburst galaxies, High-redshift galaxies, Galaxy evolution
Born to be Starless: Revisiting the Missing Satellite Problem. The two massive galaxies in the Local Group both host substantially fewer satellites than the subhalos expected from the cold dark matter paradigm, and recent investigations have highlighted the interplay between baryons and dark matter. We investigate the processes that make subhalos starless, using high-resolution cosmological simulations. We find that the number of satellites around Milky Way analogs closely aligns with observations, which accords with recent studies. In our simulations, the majority of subhalos are devoid of stars, i.e., "starless." We first examined supernova feedback and the environmental effects associated with subhalos' orbital motion as candidates for their origin. However, neither seems to be the main driver. Supernova feedback causes a reduction in cold gas in "starred" subhalos, but its impact is not significant. In the case of starless subhalos, supernova feedback is irrelevant because most of them do not have in situ star formation in the first place. The orbital motion in dense environments causes the removal of gas in all subhalos, but it is not enough to remove preexisting stars. The key is found to be the effect of reionization instead. Starless subhalos are initially born in regions that are less efficient in accreting matter. This makes them lack sufficiently dense gas to self-shield from UV background heating, preventing their gas from cooling below the star formation threshold. This indicates that starless subhalos are not made but born.

Keywords: Galaxy dark matter halos, Hydrodynamical simulations, Milky Way Galaxy, Disk galaxies
A Resonant Beginning for the Solar System's Terrestrial Planets. In the past two decades, transit surveys have revealed a class of planets with thick atmospheres—sub-Neptunes—that must have completed their accretion in protoplanet disks. When planets form in the gaseous disk, the gravitational interaction with the disk gas drives their migration and results in the trapping of neighboring planets in mean motion resonances, though these resonances can later be broken when the damping effects of disk gas or planetesimals wane. It is widely accepted that the outer solar system gas-giant planets originally formed in a resonant chain, which was later disrupted by dynamical instabilities. Here, we explore whether the early formation of the terrestrial planets in a resonance chain (including Theia) can evolve to the present configuration. Using N-body simulations, we demonstrate that the giant planet instability would also have destabilized the terrestrial resonance chain, triggering Moon-forming giant impacts in 20%–50% of our simulated systems, dependent on the initial resonance architecture. After the instability, the eccentricity and inclination of the simulated planets match their present-day values. Under the proposed scenario, the current period ratio of 3.05 between Mars and Venus—devoid of any special significance in traditional late-formation models—naturally arises as a relic of the former resonance chain.

Keywords: Solar system terrestrial planets, Planet formation, Planetary dynamics
No Evidence of a Dichotomy in the Elliptical Galaxy Population. The advent of large integral field spectroscopic surveys has found that elliptical galaxies (EGs) can be divided into two classes: the fast rotators (whose kinematics are dominated by rotation) and the slow rotators (which exhibit slow or no rotation pattern). It is often suggested that while the slow rotators typically have boxy isophotal shapes, have a high α-to-iron abundance ratio, and are quite massive, the fast rotators often exhibit the opposite properties (that is, having disky isophotes, lower α-to-iron ratio, and of typical masses). Whether the EGs consist of two distinct populations (i.e., a dichotomy exists) remains an unsolved issue. To examine the existence of the dichotomy, we used a sample of 1895 EGs from the SDSS-IV MaNGA survey and measured robustly the stellar kinematics, isophotal shapes, and [Mg/Fe] ratio. We confirmed the previous finding that the bulk of the EGs are disky (65%) and fast rotators (67%), but we found no evidence supporting a dichotomy, based on a principal component analysis. The different classes (boxy/disky and slow/fast rotators) of EGs occupy slightly different loci in the principal component space. This may explain the observed trends that led to the premature support of a dichotomy based on small samples of galaxies.

Keywords: Stellar kinematics, Galaxy formation, Galaxy structure, Elliptical galaxies
SpecPT (Spectroscopy Pre-trained Transformer) Model for Extragalactic Spectroscopy. I. Architecture and Automated Redshift Measurement. We introduce the Spectroscopy Pre-trained Transformer (SpecPT), a transformer-based model designed to analyze spectroscopic data, with applications in spectrum reconstruction and redshift measurement. Using the Early Data Release (EDR) of the Dark Energy Spectroscopic Instrument (DESI) survey, we evaluate SpecPT's performance on two distinct data sets: the Bright Galaxy Survey (BGS) and Emission Line Galaxy (ELG) samples. SpecPT successfully reconstructs spectra, accurately capturing emission lines, absorption features, and continuum shapes while effectively reducing noise. For redshift prediction, SpecPT achieves competitive accuracy, with normalized median absolute deviation values of 0.0006 and 0.0008, and catastrophic outlier fractions of 0.20% and 0.80% for BGS and ELG, respectively. Notably, SpecPT performs consistently well across the full redshift range (0 &lt; z &lt; 1.6), demonstrating its versatility and robustness. By leveraging its learned latent representations, SpecPT lays the groundwork for a foundational spectroscopic model, with potential applications in outlier detection, interstellar medium property estimation, and transfer learning to other data sets. This work represents a first step in building a generalized framework for spectroscopic analysis, capable of scaling to the full DESI data set and beyond.

Keywords: Neural networks, Convolutional neural networks, Extragalactic astronomy, Galaxy spectroscopy, Redshift surveys
Tools for Characterizing the Numerical Error of Stellar Oscillation Codes. Stellar oscillation codes are software instruments that evaluate the normal-mode frequencies of an input stellar model. While inter-code comparisons are often used to confirm the correctness of calculations, they are not suitable for characterizing the numerical error of an individual code. To address this issue, we introduce a set of tools—"error measures"—that facilitate this characterization. We explore the behavior of these error measures as calculation parameters, such as the number of radial grid points used to discretize the oscillation equations, are varied, and we summarize this behavior via an idealized error model. While our analysis focuses on the GYRE code, it remains broadly applicable to other oscillation codes.

Keywords: Stellar structures, Astronomy software, Computational methods, Stellar oscillations, Asteroseismology
IceCube Search for Neutrino Emission from X-Ray Bright Seyfert Galaxies. The recent IceCube detection of TeV neutrino emission from the nearby active galaxy NGC 1068 suggests that active galactic nuclei (AGNs) could make a sizable contribution to the diffuse flux of astrophysical neutrinos. The absence of TeV γ-rays from NGC 1068 indicates neutrino production in the vicinity of the supermassive black hole, where the high radiation density leads to γ-ray attenuation. Therefore, any potential neutrino emission from similar sources is not expected to correlate with high-energy γ-rays. Disk-corona models predict neutrino emission from Seyfert galaxies to correlate with keV X-rays because they are tracers of coronal activity. Using through-going track events from the Northern Sky recorded by IceCube between 2011 and 2021, we report results from a search for individual and aggregated neutrino signals from 27 additional Seyfert galaxies that are contained in the Swift's Burst Alert Telescope AGN Spectroscopic Survey. Besides the generic single power law, we evaluate the spectra predicted by the disk-corona model assuming stochastic acceleration parameters that match the measured flux from NGC 1068. Assuming all sources to be intrinsically similar to NGC 1068, our findings constrain the collective neutrino emission from X-ray bright Seyfert galaxies in the northern sky, but, at the same time, show excesses of neutrinos that could be associated with the objects NGC 4151 and CGCG 420-015. These excesses result in a 2.7σ significance with respect to background expectations.

Keywords: Neutrino astronomy, High energy astrophysics
Magnetic Waves Excited by Newborn Inner-source Pickup H<SUP>+</SUP> Measured by the Voyager Spacecraft Inside 3 au. In S. J. Hollick et al., we surveyed the Voyager magnetic field data from launch through 1990 where the Voyagers 1 and 2 spacecraft reach 43.5 au and 33.6 au, respectively. We identified 637 intervals of wave activity that could be attributed to either interstellar pickup He+, H+, or both. In our quest to identify and study low-frequency magnetic waves arising from interstellar pickup H+, we found 19 intervals, 16 with thermal ion data, within ∼3 au. We compared the growth rate of the waves with the rate of background turbulence they must overcome to reach observable levels. Ionization of interstellar neutral H is highly efficient, resulting in a factor of 10 reduction in density by 1 au relative to values at R &gt; 10 au. At the same time, solar wind turbulence increases with decreasing distance to the Sun. This makes it unlikely that interstellar neutral hydrogen can penetrate within ∼3 au in sufficient number to explain the wave observations seen by the Voyager magnetometers. We consider the possibility that the so-called "inner source" for pickup H+ arising from the interaction of solar wind protons with dust grains may account for the density of newborn pickup ions required for the growth of the observed waves. Although the Voyagers lack the instrumentation required to measure pickup ions, we do conclude that the inner-source theories provide a compelling explanation for the majority of the observations while it is possible that a few could be due to either interstellar ions or shocks.

Keywords: Pickup ions, Alfven waves, Interplanetary magnetic fields, Heliosphere
A Poisson Process AutoDecoder for X-Ray Sources. X-ray observing facilities, such as the Chandra X-ray Observatory and the eROSITA, have detected over a million astronomical sources associated with high-energy phenomena. The arrival of photons as a function of time follows a Poisson process and can vary by orders-of-magnitude, presenting obstacles for common tasks such as source classification, physical property derivation, and anomaly detection. Previous work has either failed to directly capture the Poisson nature of the data or only focuses on Poisson rate function reconstruction. In this work, we present the Poisson Process AutoDecoder (PPAD), which is a neural field decoder that maps fixed-length latent features to continuous Poisson rate functions across energy band and time via unsupervised learning. PPAD reconstructs the rate function and yields a representation at the same time. We demonstrate the efficacy of PPAD via reconstruction, regression, classification, and anomaly detection experiments using the Chandra Source Catalog.

Keywords: X-ray astronomy, Multivariate analysis, Astrostatistics techniques, Time series analysis
Shock Acceleration via Idealized Short Large-amplitude Magnetic Structures. To accelerate cosmic rays (CRs) to ∼PeV energies, diffusive shock acceleration (DSA) in Galactic supernova remnants requires amplified magnetic turbulence in the shock to facilitate broadband Bohm diffusion of CRs. Recent particle-in-cell (PIC) shock simulations suggest that diffusion may be driven by short large-amplitude magnetic structures (SLAMS). Persistent SLAMS develop in the upstream of shocks with an Alfvénic Mach number MA ≳ 20 via the Bell instability and nonlinear amplification/steepening. We employ test-particle simulations to examine particle transport and acceleration in model shocks populated by analytically prescribed, idealized SLAMS that approximate the magnetic structures of PIC shock simulations. We demonstrate that SLAMS drive broadband Bohm diffusion of magnetized electrons (i.e., electron Larmor radius rL ≪ magnetic-structure length λAM) and unmagnetized electrons (i.e., rL ≫ λAM). We show that SLAMS accelerate unmagnetized electrons via DSA, and magnetized electrons via shock drift acceleration (SDA) and quasi-periodic shock acceleration (QSA). QSA, a novel Fermi-type mechanism, proceeds via rapid scattering in the converging flow between the first upstream magnetic structure and the near-downstream, shock-amplified field. QSA becomes vital for maintaining electron acceleration in shocks with superluminal SLAMS, which strongly advect magnetized electrons due to high inclination between field lines and the flow. We find that test-electron spectra are consistent with spectra from PIC simulations, indicating that the test-particle method can be used to extrapolate PIC results to longer spatial and temporal scales. Overall, our results suggest that SLAMS in MA ≳ 20 shocks may play an important role in facilitating shock acceleration.

Keywords: Galactic cosmic rays, Supernova remnants, Cosmic ray sources, Shocks, Magnetic fields, Cosmic rays
New Field OB and OBe Binaries of the SMC Wing: Observational Properties and Population Modeling. We present a radial velocity (RV) survey of the field OB and OBe stars of the SMC Wing. We use multiepoch observations of 55 targets obtained with the Magellan Inamori-Magellan Aerial Camera and Spectrograph and M2FS multi-object spectrographs to identify single- and double-lined spectroscopic binaries. We also use TESS light curves to identify new eclipsing binary candidates. We find that 10 each of our 34 OB (29%) and 21 OBe (48%) stars are confirmed binaries, and at least ∼6 more are candidates. Using our RV measurements, we set constraints on the companion masses, and in some cases, on periods, eccentricities, and inclinations. The RV data suggest that OB binaries favor more circular orbits (mean eccentricity &lt;e&gt; = 0.08 ± 0.02), while OBe binaries are eccentric (&lt;e&gt; = 0.45 ± 0.04). We identify two candidate black hole binaries, [M2002] 77616, and 81941. We use Binary Population and Spectral Synthesis to predict the frequencies of ejected OB and OBe stars and binaries, assuming OBe stars are binary mass gainers ejected by the companion supernova. We also predict the frequencies of black-hole, neutron-star, and stripped-star companions, and we model the distributions of primary and secondary masses, periods, eccentricities, and velocity distributions. The models are broadly consistent with the binary origin scenario for OBe stars, and predict an even larger number of post-supernova OB binaries. Comparison with the kinematics supports a significant contribution from dynamical ejections for both OB and OBe stars, although less so for binaries.

Keywords: Binary stars, Massive stars, Small Magellanic Cloud, Field stars, OB stars, Be stars, Runaway stars
Electron-scale Kelvin–Helmholtz Instabilities in Magnetized Shear Flows. Electron-scale Kelvin–Helmholtz instabilities (ESKHIs) are found in several astrophysical scenarios. Naturally, ESKHIs are subject to a background magnetic field, but an analytical dispersion relation and an accurate growth rate of ESKHI under this circumstance have remained open because former magnetohydrodynamics derivations are not applicable in the relativistic regime. We present a generalized dispersion relation of ESKHI in relativistic magnetized shear flows, with two-fluid equations in the cold limit. ESKHI linear growth rates in certain cases are numerically calculated. The results show that when the shear velocity is relatively small, the presence of an external magnetic field results in a decreased maximum instability growth rate, a larger cutoff wavenumber of the unstable band, and an increased wavenumber of the most unstable mode. However, when the shear velocity is sufficiently high, the external magnetic field can increase the maximum instability growth rate instead. Particle-in-cell simulations are also carried out to verify our conclusions. In simulations, we observe the generation of a kinetic direct-current (DC) magnetic field, which is shown to have a strong impact on ESKHIs. In the presence of an external magnetic field, the DC magnetic field generation is suppressed because of electron gyration across the shear interface. Beyond the stabilizing threshold external magnetic field predicted by our fluid theory, we further observe possible evidence of Weibel instabilities.

Keywords: Relativistic jets, Magnetic fields, Plasma physics, Plasma jets
Detected Abundances of Nuclei Relative to <SUB>26</SUB>Fe for Elements <SUB>14</SUB>Si through <SUB>44</SUB>Ru with CALET on the International Space Station. The Calorimetric Electron Telescope (CALET), launched to the International Space Station (ISS) in 2015 August and continuously operating since, measures cosmic-ray (CR) electrons, nuclei, and gamma rays. CALET, with its 27 radiation length deep Total Absorption Calorimeter, measures particle energy and allows for the measurement of spectra, secondary to primary ratios of the more abundant CR nuclei through 28Ni, while the main charge detector can measure ultra-heavy CR nuclei through 44Ru. The results for the abundances of elements from Z = 14 to Z = 44 relative to 26Fe over 7.5 yr of observation are presented here and compared to previous measurements from ACE-CRIS, SuperTIGER, and HEAO-3.

Keywords: Galactic cosmic rays, Interstellar medium, Particle astrophysics