Sazuna/UAT_keywords huggingface dataset:
Physics-based Simulation of the 2013 April 11 Solar Energetic Particle Event. Solar energetic particles (SEPs) can pose hazardous radiation risks to both humans and spacecraft electronics in space. Numerical modeling based on first principles offers valuable insights into the underlying physics of SEPs and provides synthetic observables for SEPs at any time and location in the inner heliosphere. In this work, we present a numerical scheme, which conserves the number of particles based on integral relations for Poisson brackets, to solve the kinetic equation for particle acceleration and transport processes. We implement this scheme within the Space Weather Modeling Framework, developed at the University of Michigan. In addition, we develop a new shock-capturing tool to study the coronal mass ejection-driven shock originating from the low solar corona. These methodological advancements are applied to conduct a comprehensive study of a historical SEP event on 2013 April 11. Observations from multiple spacecraft, including the Solar and Heliospheric Observatory, Solar Dynamics Observatory, Geostationary Operational Environmental Satellite, Advanced Composition Explorer near Earth, and STEREO-A/B, are used for model─data comparison and validation. We show synthetic observables, including extreme ultraviolet and white-light images, proton time─intensity profiles, and energy spectra, and discuss their differences and probable explanations compared to observations. Our simulation results demonstrate the application of the Poisson bracket scheme with a particle solver to simulating a historical SEP event. We also show the capability of extracting the complex shock surface using our shock-capturing tool and understand how the complex shock surface affects the particle acceleration process.

Keywords: Heliosphere, Solar energetic particles, Space weather, Solar coronal mass ejection shocks, Computational methods
Metallicity Scatter Originating from Subkiloparsec Starbursting Clumps in the Core of a Protocluster at z = 7.88. We present new JWST NIRSpec integral field unit (IFU) G395H/F290LP observations of a merging galaxy system at z = 7.88, part of A2744-z7p9OD, the most distant protocluster to date. The IFU cube reveals [O III]λ5007 emissions in two previously known galaxies, ZD3 and ZD6, and a newly identified galaxy, ZD12, at zspec = 7.8762. One of the detected [O III]-emitting regions has a detection of the auroral [O III]λ4363 line, allowing us to derive a direct metallicity of   + 12 = 7.4 ± 0.2, while metallicities in other regions are measured using strong-line calibration methods. We find large deviations within the measured metallicity ( ), which suggests a fast chemical enrichment from intense star formation and merger-driven growth, as expected in early galaxies. Our analysis shows that metal-poor regions could easily be outshone by more enriched regions, posing a challenge for spectroscopic analysis based on integrated light (i.e., NIRSpec/MSA) against identifying metal-free star formation in the early Universe. NIRCam imaging reveals seven UV-bright clumps in ZD12, in a stellar mass range of  –8.9. Four of them are unresolved (≲100 pc) and intensely star-forming (&gt;30 M⊙ yr‑1 kpc‑2), likely contributing to the scatter in metallicity by producing an ideal environment for rapid chemical cycles. Lastly, we revisit the nature of the host protocluster by including new member galaxies identified here and in the literature, and obtain a local overdensity factor  , a total halo mass  , and a formal velocity dispersion 1100 ± 500 km s‑1.

Keywords: Star formation, Active galaxies, Metallicity, High-redshift galaxy clusters
A Multiline Analysis of the Distribution and Excitation of CS and H<SUB>2</SUB>CS in the HD 163296 Disk. The abundance and distribution of sulfur-bearing molecules in protoplanetary disks directly influence the composition and potential habitability of nascent planets in addition to providing powerful probes of the physical gas conditions in the disks themselves. Here, we present new and archival Atacama Large Millimeter/submillimeter Array and Submillimeter Array observations of CS and H2CS, and their C34S and H2C34S isotopologues, at high angular resolution (≍0 2─0 4; 20─40 au) in the HD 163296 disk, which reveal a central cavity and multiringed emission structure. These observations comprise the most comprehensive, multiline CS data in a planet-forming disk to date, spanning a wide range of excitation conditions from Eu = 7.1 to 129.3 K, and include new detections of C34S, H2CS, and H2C34S in this system. Using these data, we derive spatially resolved rotational temperature and column density profiles for all species. We find a column density ratio N(H2CS)/N(CS) ≍ 0.5, which is comparable to that of the similar MWC 480 disk and suggests that organic sulfur compounds may constitute a large fraction of the volatile sulfur reservoir in disks around Herbig stars generally. We derive 32S/34S ratios of ≍5 (CS/C34S) and ≍2 (H2CS/H2C34S) based on disk-averaged and spatially resolved analyses. Both values are consistent across these two pairs of optically thin molecules and are well below the expected ratio in the interstellar medium of ≍22, suggesting significant sulfur fractionation. We also constrain the CS emitting layer (z/r ≲ 0.1) using the vertical separations of the disk surfaces in the channel maps and based on the known 2D gas structure of the HD 163296 disk combined with our excitation analysis.

Keywords: High angular resolution, Protoplanetary disks, Planet formation, Astrochemistry
Large-scale Field-aligned Flows in the Heliosheath. We use a state-of-the-art 3D MHD simulation to show that large-scale thermal pressure gradients in the heliosheath drive suprathermal particles (pickup ions with 1–5 keV) to stream along magnetic field lines faster than the cold bulk solar wind. Large-scale pressure gradients between the nose and flank of the heliopause stem from neutrals flowing in from the nose direction. Hybrid simulations suggest that these gradients will also drive field-aligned flows at higher energies (5–30 keV). The field-aligned flows are stronger within 10 au of the termination shock, where the magnetic field lines in the upwind hemisphere have shorter path lengths in the heliosheath before connecting back to the termination shock. This mechanism explains the large field-aligned flows seen in the data in the first 2.5 yr of heliosheath data when Voyager 2 was above the heliospheric current sheet. This work has implications for how the bulk flows are derived in Voyager 1 from the Compton–Getting effect, where particles at all energies are assumed to move with the same speed.

Keywords: Heliosphere
The Environmental Quenching Mechanisms of Field Dwarf Galaxies. Field dwarf galaxies not actively forming stars are relatively rare in the local Universe, but are present in cosmological hydrodynamical simulations. We use the TNG50 simulation to investigate their origin and find that they all result from environmental effects that have removed or reduced their gas content. Quenched field dwarfs consist of either backsplash objects ejected from a massive host or of systems that have lost their gas after crossing overdense regions such as filaments or sheets ("cosmic web stripping"). Quenched fractions rise steeply with decreasing stellar mass, with quenched systems making up roughly ∼15% of all field dwarfs (i.e., excluding satellites) with stellar masses 107 &lt; M⋆/M⊙ &lt; 109. This fraction drops to only ∼1% when a strict isolation criterion that requires no neighbors with M⋆ &gt; 109 M⊙ within 1.5 Mpc is applied. Of these isolated dwarfs, ∼6% are backsplash, while the other ∼94% have been affected by the cosmic web. Backsplash systems are more deficient in dark matter, have retained less or no gas, and have stopped forming stars earlier than cosmic web-stripped systems. The discovery of deeply isolated dwarf galaxies that were quenched relatively recently would lend observational support to the prediction that the cosmic web is capable of inducing the cessation of star formation in dwarfs.

Keywords: Dwarf galaxies, Field galaxies, Galaxy evolution, Galaxies
From Tides to Currents: Unraveling the Mechanism that Powers WASP-107b's Internal Heat Flux. The sub-Jovian exoplanet WASP-107b ranks among the best-characterized low-density worlds, featuring a Jupiter-like radius and a mass that lies firmly in the sub-Saturn range. Recently obtained JWST spectra reveal significant methane depletion in the atmosphere, indicating that WASP-107b's envelope has both a high metallicity and an elevated internal heat flux. Together with a detected nonzero orbital eccentricity, these data have been interpreted as evidence of tidal heating. However, explaining the observed luminosity with tidal dissipation requires an unusually low tidal quality factor of Q ∼ 100. Moreover, we find that secular excitation by the radial-velocity-detected outer companion WASP-107c generally cannot sustain WASP-107b's eccentricity in steady state against tidal circularization. As an alternative explanation, we propose that ohmic dissipation—generated by interactions between zonal flows and the planetary magnetic field in a partially ionized atmosphere—maintains the observed thermal state. Under nominal assumptions for the field strength, atmospheric circulation, and ionization chemistry, we show that ohmic heating readily accounts for WASP-107b's inflated radius and anomalously large internal entropy.

Keywords: Planetary structure, Planetary dynamics, Exoplanets
Comparing Observed Properties of Winds in Low-luminosity Active Galactic Nuclei with Theoretical Predictions. Theoretical and numerical simulations of black hole hot accretion flows have shown the ubiquitous existence of winds and predicted their properties, such as velocity and mass flux. In this paper, we have summarized from the literature the physical properties of winds launched from low-luminosity active galactic nuclei (LLAGN), which are believed to be powered by hot accretion flows, and compared them with theoretical predictions. We infer that for both ultrafast outflows and hot winds, the observed wind velocity as a function of their launching radius and the ratio between wind mass flux and black hole accretion rate show good consistency with theoretical predictions. For the prototype LLAGN M81* with abundant observational data, we have examined various observed properties of wind in detail, including velocity, mass flux of the wind, the power-law index of the radial profile of inflow rate, and the jet-to-wind power ratio. Good agreements are found with theoretical predictions, providing strong support to the theory of wind launched from hot accretion flows.

Keywords: Accretion, Supermassive black holes, Low-luminosity active galactic nuclei
Evidence of Extreme-ultraviolet Resonant Excitation in the Middle Corona during a Solar Flare. We present observations of an eruptive solar flare on 2016 January 6 that occurred behind the solar limb from the perspective of the Earth, but was well observed by the Solar-Terrestrial Relations Observatory (or STEREO) and the Solar Extreme Ultraviolet Monitor on NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. Light curves showing the evolution of the flare's irradiance as a function of time taken by MAVEN are well correlated with the brightness evolution of fan structures observed in the Project for On-Board Autonomy 2's Sun Watcher with Active Pixels and Image Processing (SWAP) 174 Å passband, suggesting that the radiance of structures near the flare site was influenced by emission from the flare. Because SWAP did not directly observe the flare itself, this event represents a rare opportunity to study the evolution of emission near a flare without the risk of instrumental scattered light contaminating the observations. We analyze this evolution and implement a simple model to explore the possibility that resonant excitation (RE, also known as resonant scattering) plays an important role in driving coronal extreme-ultraviolet (EUV) emission during flaring events. Our modeling shows that for a large flare, RE could increase emission from nearby structures by about 45%, consistent with our findings that the involved structures observed by SWAP increased in brightness by about 60% during the flare. We conclude that RE may play an important role in driving coronal EUV emission under certain circumstances and should be accounted for in models and emission-based analysis tools.

Keywords: Solar E corona, Solar flares, Solar corona, Solar extreme ultraviolet emission
Multiwavelength Observation of a Candidate Pulsar Halo LHAASO J0621+3755 and the First X-Ray Detection of PSR J0622+3749. Pulsar halos are regions around middle-aged pulsars extending out to tens of parsecs. The large extent of the halos and well-defined central cosmic-ray accelerators make this new class of Galactic sources an ideal laboratory for studying cosmic-ray transport. LHAASO J0621+3755 is a candidate pulsar halo associated with the middle-aged gamma-ray pulsar PSR J0622+3749. We observed LHAASO J0621+3755 with VERITAS and XMM-Newton in the TeV and X-ray bands, respectively. For this work, we developed a novel background estimation technique for imaging atmospheric Cherenkov telescope observations of such extended sources. No halo emission was detected with VERITAS (0.3–10 TeV) or XMM-Newton (2–7 keV) within 1∘ and  10'  around PSR J0622+3749, respectively. Combined with the LHAASO Kilometer Square Array (KM2A) and Fermi-LAT data, VERITAS flux upper limits establish a spectral break at ∼1–10 TeV, a unique feature compared with Geminga, the most studied pulsar halo. We model the gamma-ray spectrum and LHAASO-KM2A surface brightness as inverse Compton emission and find suppressed diffusion around the pulsar, similar to Geminga. A smaller diffusion suppression zone and harder electron injection spectrum than Geminga are necessary to reproduce the spectral cutoff. A magnetic field ≤1 μG is required by our XMM-Newton observation and synchrotron spectral modeling, consistent with Geminga. Our findings support slower diffusion and lower magnetic field around pulsar halos than the Galactic averages, hinting at magnetohydrodynamic turbulence around pulsars. Additionally, we report the detection of an X-ray point source spatially coincident with PSR J0622+3749, whose periodicity is consistent with the gamma-ray spin period of 333.2 ms. The soft spectrum of this source suggests a thermal origin.

Keywords: X-ray astronomy, Gamma-ray astronomy, Galactic cosmic rays, Pulsars
Kiloparsec-scale Neutral Iron Kα Emission in the Starburst-AGN NGC 4945: A Relic AGN Outflow?. NGC 4945 contains a well-known heavily obscured active galactic nucleus (AGN) at its core, with prior reports of strong nuclear and off-nuclear neutral Fe Kα emission due to the AGN activity. We report the discovery of very extended Fe Kα emission with the XMM-Newton EPIC pn in a ∼5 kpc by ∼10 kpc region that is misaligned with the plane of the inclined optical galactic disk by ∼60° in projection. After a careful consideration of the crowded center of the galaxy and numerous unresolved hard X-ray sources present, we estimate that ∼15% of the Fe Kα is extended on kiloparsec-sized scales. The overall size and misalignment of the region follows an unusual pattern of radio polarization that is not typical of starbursts or normal disk galaxies but has been interpreted as possibly due to AGN activity. We suggest that the extended Fe Kα emission arose from a period of AGN eruption several million years ago—a relic of a past AGN ejection episode.

Keywords: Active galaxies
Multi-tracer Correlated Stacking: A Novel Way to Discover Anisotropy in nHz Stochastic Gravitational-wave Background. The isotropic stochastic gravitational-wave background (SGWB) generated by a population of supermassive black hole binaries (SMBHBs) provides a unique window into their cosmic evolution. In addition to the isotropic power spectrum, the anisotropic component of the signal carries additional information about the supermassive black holes (BHs) and host galaxy connection. The measurement of this signal is usually carried out by angular power spectra, which is only a sufficient measure for a Gaussian and statistically isotropic distribution of SMBHBs, where the statistical properties of a field remain unchanged across the sky. In contrast, the contribution from SMBHBs in nHz SGWB will be hosted by fewer massive galaxies, making the nHz background anisotropic and non-Gaussian. As a result, the performance of angular power spectra in extracting the underlying physics is limited. In this work, we propose a novel technique called multi-tracer correlated stacking, which enables the detection of anisotropies in the SGWB by stacking the signal from regions of the sky with tracers of BHs such as active galactic nuclei (AGN), quasars, bright galaxies, etc., that can be mapped up to high redshift. We demonstrate this technique on a simulated population of SMBHBs using an AGN catalog, which maps the underlying matter distribution approximately up to redshift z = 5. This stacking technique uniquely distinguishes between isotropic and anisotropic distributions of SGWB sources, surpassing the capabilities of angular power spectrum-based methods in detecting anisotropic signals. This highlights the effectiveness of this technique in detecting anisotropic SGWB signals, and in the future, this technique can play a crucial role in its discovery.

Keywords: Cosmology, Supermassive black holes, Gravitational waves
Simultaneous Existence of the Line-locking and Velocity Shift Signatures in Quasar SDSS J004613.54+010425.7. This study presents a detailed investigation of the broad absorption line (BAL) systems in the quasar SDSS J004613.54+010425.7 (hereafter J0046+0104), which makes characters of the simultaneous existence of line-locking and velocity shift signatures. Based on the seven-epoch observed spectra of this source, we explore the variability in equivalent widths, ionization states, locations, velocities, and profile shapes of these BAL systems. Our equivalent width (EW) analysis implies that the outflow clouds in J0046+0104 are in a relatively high ionization state and provides evidence that fluctuations in the ionizing continuum could be a reason for the EW variations of the absorption troughs. Additionally, we observe that the higher-velocity, smoother profile BAL of system A exhibits velocity shifts, whereas the lower-velocity, rougher profile BAL of system B displays line-locking signatures. These findings collectively indicate that velocity shifts typically occur in the inner, more ionized regions of the outflow, whereas line-locking phenomena are manifested in the outer, less ionized regions. Finally, we discuss the possible causes of the observed line-locking and velocity shift signatures.

Keywords: Quasars, Quasar absorption line spectroscopy, Broad-absorption line quasar
MeerKAT 1.3 GHz Observations toward the Milky Way Bulge. We present a MeerKAT survey of portions of the Milky Way bulge. The survey covers 172.8 square degrees in two contiguous mosaics above and below the Galactic center as well as 32 single pointing fields at higher longitudes. The resolution of the images is ∼8″ at a frequency of 1333 MHz with a typical Stokes I rms of 20 μJy beam‑1. Most of the emission seen is from background extragalactic sources, but many compact Galactic objects are identifiable by their polarization properties. Apparent polarized emission resulting from fine-scale Faraday rotation in the interstellar medium is widespread in this region of the Galaxy. The survey is used to search for background giant radio galaxies, &gt;700 kpc in size, identifying 17 such objects. Data products include FITS images of Stokes I, Q, U, and V as well as a Faraday analysis and lists of compact total intensity and polarized sources.

Keywords: Galactic bulge, Giant radio galaxies, Milky Way Galaxy
The Energy Content of Alfvén Waves in the Stratified Solar Atmosphere. Alfvén waves propagating in a vertically stratified plasma, such as those traveling from the solar photosphere to the corona, are partially reflected due to the gradient in the Alfvén speed. Wave reflection naturally results in the superposition of upward- and downward-propagating waves. A simple analytic model demonstrates that this superposition leads to the nonequipartition of kinetic and magnetic energies in the Alfvén wave perturbations and slows down the net energy transport. A numerical model of Alfvén wave propagation in the lower solar atmosphere reveals significant wave reflection below the transition region, leading to highly variable kinetic and magnetic energy content in the lower chromosphere. At higher altitudes, the kinetic energy eventually dominates, depending on the wave frequency. The velocity at which net energy propagates upward is significantly smaller than the local Alfvén speed throughout the chromosphere. Consequently, the commonly used expression for unidirectional Alfvén waves in a uniform plasma, which relates the energy flux to the kinetic energy density, is not generally applicable in the stratified lower solar atmosphere and cannot be reliably used to estimate the energy content of observed waves. A generalized expression is given, incorporating correction factors that account for wave reflection and energy nonequipartition. The applicability of the expression is discussed.

Keywords: Solar atmosphere, Magnetohydrodynamics, Alfven waves, Solar corona, Solar chromosphere
Reduced Thermal Conduction in Solar Coronal Loops. Thermal conduction plays an important role in the energy balance of the solar coronal plasma. In this paper, we present a new method for deriving observational constraints on the density–temperature relationship for coronal loops from the differential emission measure distributions of active regions and apply the method to measurements obtained with the Extreme-Ultraviolet Imaging Spectrometer on Hinode. Our focus is on coronal loops in the cores of active regions. We show that standard loop models do not reproduce the observed loop-top densities when the variations of cross-sectional area along the loop are taken into account. Nonstandard loop models with reduced thermal conductivity (compared to Spitzer's law) are presented. The modeling results are compared with published measurements of loop parameters obtained with the Soft X-ray Telescope on Yohkoh. We conclude that models with reduced thermal conductivity are better able to reproduce the observed loop-top densities.

Keywords: Solar magnetic fields, Solar coronal loops, Solar coronal heating, Solar corona
Stability of Hierarchical Triples Comprising a Central Massive Body and a Tight Binary: The Effect of Inner and Outer Eccentricities on the Binary Breakup Condition. We explore the stability of gravitational triple systems comprising a central massive body and a tight binary of less massive pairs. In the present paper, we focus on improving the Hill-type stability criterion for the binary in those systems, with particular attention on the effects of the eccentricities of the inner and outer orbits. We perform direct Newtonian N-body simulations over much longer integration times than previous studies, which is essential to determine the stability and breakup timescale distributions of those systems in a reliable fashion. As a result, we obtain an empirical fitting formula of the binary breakup condition that incorporates effects of the inner and outer eccentricities, the mutual inclination of the inner and outer orbits, the mass ratios of the three bodies, and the breakup timescale.

Keywords: Celestial mechanics, Multiple stars, Three-body problem, Black holes