Sazuna/UAT_keywords huggingface dataset:
Expulsion of Counter Evershed Flows from Sunspot Penumbrae. In addition to the Evershed flow directed from the umbra toward the outer boundary of a sunspot, under special circumstances a counter Evershed flow (CEF) in the opposite direction also occurs. We aim to characterize the proper motions and evolution of three CEFs observed by the Solar Optical Telescope on board the Japanese Hinode spacecraft and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. We use state-of-the-art inversions of the radiative-transfer equation of polarized light applied to spectropolarimetric observations of the Fe I line pair around 630 nm. The three CEFs appeared within the penumbra. Two of the CEF structures, as part of their decay process, were found to move radially outwards through the penumbra parallel to the penumbral filaments with speeds, deduced from their proper motions, ranging between 65 and 117 m s-1. In these two cases, a new spot appeared in the moat of the main sunspot after the CEFs reached the outer part of the penumbra. Meanwhile, the CEFs moved away from the umbra, and their magnetic field strengths decreased. The expulsion of these two CEFs seems to be related to the normal Evershed flow. The third CEF appeared to be dragged by the rotation of a satellite spot. Chromospheric brightenings were found to be associated with the CEFs, and those CEFs that reached the umbra-penumbra boundary showed enhanced chromospheric activity. The two CEFs, for which line-of-sight velocity maps were available during their formation phase, appear as intrusions into the penumbra. They may be associated with magnetic flux emergence.

Keywords: Solar active region velocity fields, Solar active region magnetic fields, Sunspot groups, Solar photosphere, Solar flares, Solar physics, Active solar chromosphere
The Tilt of the Velocity Ellipsoid of Different Galactic Disk Populations. The tilt of the velocity ellipsoid is a helpful tracer of the gravitational potential of the Milky Way. In this paper, we use nearly 140,000 red clump (RC) stars selected from LAMOST and Gaia to make a detailed analysis of the tilt of the velocity ellipsoid for various populations, as defined by stellar ages and chemical information, within 4.5 ≤ R ≤ 15.0 kpc and ∣Z∣ ≤ 3.0 kpc, respectively. The tilt angle of the velocity ellipsoid of the RC sample stars is accurately described as α = α 0 $\arctan $ (Z/R) with α 0 = (0.68 ± 0.05). This indicates the alignment of the velocity ellipsoid is between cylindrical and spherical, implying that any deviation from the spherical alignment of the velocity ellipsoid may be caused by the gravitational potential of the baryonic disk. The results of various populations suggest that α 0 displays an age and population dependence, with values α 0 = (0.72 ± 0.08) and α 0 = (0.64 ± 0.07) for the thin and thick disks, respectively, and α 0 displays a decreasing trend as age (and [α/Fe]) increases, meaning that the velocity ellipsoids of the kinematically relaxed stars are mainly dominated by the gravitational potential of the baryonic disk. We determine the α 0 -R relation for various populations, finding that α 0 displays oscillations with R for the different populations. The oscillations in α 0 appear in both kinematically hot and cold populations, indicating that resonances with the Galactic bar are the most likely origin for these oscillations.

Keywords: Milky Way formation, Stellar kinematics, Stellar abundances, Milky Way disk, Milky Way evolution
Interpreting the Si II and C II Line Spectra from the COS Legacy Archive Spectroscopic SurveY Using a Virtual Galaxy from a High-resolution Radiation-hydrodynamic Simulation. Observations of low-ionization state metal lines provide crucial insights into the interstellar medium (ISM) of galaxies, yet, disentangling the physical processes responsible for the emerging line profiles is difficult. This work investigates how mock spectra generated using a single galaxy in a radiation-hydrodynamical simulation can help us interpret observations of a real galaxy. We create 22,500 C II and Si II spectra from the virtual galaxy at different times and through multiple lines of sight and compare them with the 45 observations of low-redshift star-forming galaxies from the COS Legacy Spectroscopic SurveY (CLASSY). We find that the mock profiles provide accurate replicates of the observations of 38 galaxies with a broad range of stellar masses (106-109 M ⊙) and metallicities (0.02-0.55 Z ⊙). Additionally, we highlight that aperture losses explain the weakness of the fluorescent emission in several CLASSY spectra and must be accounted for when comparing simulations to observations. Overall, we show that the evolution of a single simulated galaxy can produce a large diversity of spectra whose properties are representative of galaxies of comparable or smaller masses. Building upon these results, we explore the origin of the continuum, residual flux, and fluorescent emission in the simulation. We find that these different spectral features all emerge from distinct regions in the galaxy's ISM, and their characteristics can vary as a function of the viewing angle. While these outcomes challenge simplified interpretations of down-the-barrel spectra, our results indicate that high-resolution simulations provide an optimal framework to interpret these observations.

Keywords: Ultraviolet astronomy, Starburst galaxies, Interstellar medium
Particle-in-cell Simulations of Mildly Relativistic Outflows in Kilonova Emissions. The electromagnetic emission from neutron star mergers is comprised of multiple components. Synchrotron emission from the disk-powered jet and thermal emission from the merger ejecta (powered by a variety of sources) are among the most studied sources. The low masses and high velocities of the merger ejecta quickly develop conditions where emission from collisionless shocks becomes critical and synchrotron emission from the merger ejecta constitutes a third component to the observed signal. The aim of this project is to examine shock development, magnetic field generation, and particle acceleration in the case of mildly relativistic shocks, which are expected when the tidal ejecta of neutron star mergers drive a shock into the external medium. Using LANL's vector particle-in-cell (VPIC) code, we have run simulations of such mildly relativistic, collisionless, weakly magnetized plasmas and computed the resultant magnetic fields and particle energy spectra. We show the effects of varying plasma conditions, as well as explore the validity of using different proton-to-electron mass ratios in VPIC. Our results have implications for observing late-time electromagnetic counterparts to gravitational wave detections of neutron star mergers.

Keywords: Shocks, Stellar winds, Plasma astrophysics
FAST Search for Circumstellar Atomic Hydrogen. II. Is BD+30°3639 an Interacting Planetary Nebula?. The young, compact, very high surface brightness but low excitation planetary nebula (PN) BD+30°3639 is one of the very few PNe that have been reported to exhibit the 21 cm H I emission line. As part of a long-term program to search for circumstellar atomic hydrogen, we observed the 21 cm feature toward BD+30°3639 with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Assuming a direct association between the PN and the detected H I emission, these new observations show that this surrounding emission is significantly more spatially extended than indicated by previous interferometric observations and can be resolved into two velocity components. The estimated H I mass is larger than 100 M ⊙, invalidating an origin from the host star itself or its ejecta for the emitting material. We discuss the possibility that the extended H I emission stems from the interstellar medium (ISM) swept out over time by the stellar wind. Moreover, we report tentative detections of H I absorption features lying near and blueward of the systemic velocity of this PN, which are probably from a stalled asterosphere at the outer boundary of the expanding ionized region. The mass of the gas producing the H I absorption is insufficient to solve the so-called "PN missing mass problem." We demonstrate the capability of FAST to investigate the interaction process between a PN and the surrounding ISM.

Keywords: Circumstellar envelopes, Interstellar atomic gas, Stellar mass loss, Planetary nebulae, Single-dish antennas
A JWST/NIRSpec Exploration of the Connection between Ionization Parameter, Electron Density, and Star-formation-rate Surface Density in z = 2.7-6.3 Galaxies. We examine the factors responsible for the variation in the ionization parameter (U) of high-redshift star-forming galaxies based on medium-resolution JWST/NIRSpec observations obtained by the Cosmic Evolution Early Release Science survey. The sample consists of 48 galaxies with redshifts z spec = 2.7-6.3, which are largely representative of typical galaxies at these redshifts. The [S II] λ λ6718, 6733 doublet is used to estimate electron densities (n  e ), and dust-corrected Hα luminosities are used to compute ionizing photon rates (Q). Using composite spectra of galaxies in bins of [O III] λ λ4960, 5008/[O II] λ λ3727, 3730 (O32) as a proxy for U, we determine that galaxies with higher O32 have &lt;n  e &gt; ≃ 500 cm-3 that are ≳5 × larger than that of lower-O32 galaxies. We do not find a significant difference in &lt;Q&gt; between low- and high-O32 galaxies. Photoionization modeling indicates a large spread in $\mathrm{log}U$ of ≈1.5 dex at a fixed Z neb. On the other hand, the data indicate a highly significant correlation between U and star-formation-rate surface density (ΣSFR), which appears to be redshift invariant at z ~ 1.6-6.3, and possibly up to z ~ 9.5. We consider several avenues through which metallicity and ΣSFR (or gas density) may influence U, including variations in n  e  and Q, internal dust extinction of ionizing photons, and the effects of gas density on the volume filling fraction. Based on these considerations, we conclude that gas density may play a more central role than metallicity in modulating U at these redshifts.

Keywords: Starburst galaxies, Stellar abundances, Interstellar abundances, H II regions, Interstellar medium, High-redshift galaxies
Particle Acceleration by Magnetic Reconnection in Relativistic Jets: The Transition from Small to Large Scales. Several MHD works, and, in particular, the recent one by Medina-Torrejón et al. based on three-dimensional MHD simulations of relativistic jets, have evidenced that particle acceleration by magnetic reconnection driven by the turbulence in the flow occurs from the resistive up to the large injection scale of the turbulence. Particles experience Fermi-type acceleration up to ultrahigh energies, predominantly of the parallel velocity component to the local magnetic field, in the reconnection layers in all scales due to the ideal electric fields of the background fluctuations (V × B, where V and B are the velocity and magnetic field of the fluctuations, respectively). In this work, we show MHD-particle-in-cell (MHD-PIC) simulations following the early stages of the particle acceleration in the relativistic jet, which confirm these previous results, demonstrating the strong potential of magnetic reconnection driven by turbulence to accelerate relativistic particles to extreme energies in magnetically dominated flows. Our results also show that the dynamical time variations of the background magnetic fields do not influence the acceleration of the particles in this process.

Keywords: Active galactic nuclei, Jets, Plasma astrophysics, High energy astrophysics
Exact Calculation of Nonideal Fields Demonstrates Their Dominance of Injection in Relativistic Reconnection. Magnetic reconnection is an important source of energetic particles in systems ranging from astrophysics to the laboratory. The large separation of spatiotemporal scales involved makes it critical to determine the minimum physical model containing the necessary physics for modeling particle acceleration. By resolving the energy gain from ideal and nonideal magnetohydrodynamic electric fields self-consistently in kinetic particle-in-cell simulations of reconnection, we conclusively show the dominant role of the nonideal field for the early stage of energization known as injection. The importance of the nonideal field increases with magnetization, guide field, and in three dimensions, indicating its general importance for reconnection in natural astrophysical systems. We obtain the statistical properties of the injection process from the simulations, paving the way for the development of extended MHD models capable of accurately modeling particle acceleration in large-scale systems. The novel analysis method developed in this study can be applied broadly to give new insight into a wide range of processes in plasma physics.

Keywords: Plasma astrophysics
ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): A Forming Quadruple System with Continuum "Ribbons" and Intricate Outflows. One of the most poorly understood aspects of low-mass star formation is how multiple-star systems are formed. Here we present the results of Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 observations toward a forming quadruple protostellar system, G206.93-16.61E2, in the Orion B molecular cloud. ALMA 1.3 mm continuum emission reveals four compact objects, of which two are Class I young stellar objects and the other two are likely in prestellar phase. The 1.3 mm continuum emission also shows three asymmetric ribbon-like structures that are connected to the four objects, with lengths ranging from ~500 to ~2200 au. By comparing our data with magnetohydrodynamic simulations, we suggest that these ribbons trace accretion flows and also function as gas bridges connecting the member protostars. Additionally, ALMA CO J = 2-1 line emission reveals a complicated molecular outflow associated with G206.93-16.61E2, with arc-like structures suggestive of an outflow cavity viewed pole-on.

Keywords: Multiple stars, Star forming regions, Star formation, Interstellar medium, Protostars
Early Hard X-Rays from the Nearby Core-collapse Supernova SN 2023ixf. We present NuSTAR observations of the nearby SN 2023ixf in M101 (d = 6.9 Mpc) that provide the earliest hard X-ray detection of a nonrelativistic stellar explosion to date at δ t ≈ 4 days and δ t ≈ 11 days. The spectra are well described by a hot thermal bremsstrahlung continuum with T &gt; 25 keV shining through a thick neutral medium with a neutral hydrogen column that decreases with time (initial N Hint = 2.6 × 1023 cm-2). A prominent neutral Fe Kα emission line is clearly detected, similar to other strongly interacting supernovae (SNe) such as SN 2010jl. The rapidly decreasing intrinsic absorption with time suggests the presence of a dense but confined circumstellar medium (CSM). The absorbed broadband X-ray luminosity (0.3-79 keV) is L  X  ≈ 2.5 × 1040 erg s-1 during both epochs, with the increase in overall X-ray flux related to the decrease in the absorbing column. Interpreting these observations in the context of thermal bremsstrahlung radiation originating from the interaction of the SN shock with a dense medium we infer large particle densities in excess of n CSM ≈ 4 × 108 cm-3 at r &lt; 1015 cm, corresponding to an enhanced progenitor mass-loss rate of $\dot{M}\approx 3\times {10}^{-4}$ M ⊙ yr-1 for an assumed wind velocity of v  w  = 50 km s-1.

Keywords: Core-collapse supernovae
Constraining the Thickness of TRAPPIST-1 b's Atmosphere from Its JWST Secondary Eclipse Observation at 15 μm. Recently, the first JWST measurement of thermal emission from a rocky exoplanet was reported. The inferred dayside brightness temperature of TRAPPIST-1 b at 15 μm is consistent with the planet having no atmosphere and therefore no mechanism by which to circulate heat to its nightside. In this Letter, we compare TRAPPIST-1 b's measured secondary eclipse depth to predictions from a suite of self-consistent radiative-convective equilibrium models in order to quantify the maximum atmospheric thickness consistent with the observation. We find that plausible atmospheres (i.e., those that contain at least 100 ppm CO2) with surface pressures greater than 0.3 bar are ruled out at 3σ, regardless of the choice of background atmosphere, and a Mars-like thin atmosphere with surface pressure 6.5 mbar composed entirely of CO2 is also ruled out at 3σ. Thicker atmospheres of up to 10 bar (100 bar) are consistent with the data at 1σ (3σ) only if the atmosphere lacks any strong absorbers across the mid-IR wavelength range-a scenario that we deem unlikely. We additionally model the emission spectra for bare-rock planets of various compositions. We find that a basaltic, metal-rich, and Fe-oxidized surface best matches the measured eclipse depth to within 1σ, and the best-fit gray albedo is 0.02 ± 0.11. We conclude that planned secondary eclipse observations at 12.8 μm will serve to validate TRAPPIST-1 b's high observed brightness temperature, but are unlikely to further distinguish among the consistent atmospheric and bare-rock scenarios.

Keywords: Exoplanet atmospheric composition , Exoplanet surfaces, Exoplanet atmospheres
Spectral Observations and Modeling of a Solar White-light Flare Observed by CHASE. The heating mechanisms of solar white-light flares remain unclear. We present an X1.0 white-light flare on 2022 October 2 (SOL2022-10-02T20:25) observed by the Chinese Hα Solar Explorer that provides two-dimensional spectra in the visible light for the full solar disk with a seeing-free condition. The flare shows a prominent enhancement of ∼40% in the photospheric Fe I line at 6569.2 Å, and the nearby continuum also exhibits a maximum enhancement of ∼40%. For the continuum near the Fe I line at 6173 Å from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, it is enhanced up to ∼20%. At the white-light kernels, the Fe I line at 6569.2 Å has a symmetric Gaussian profile that is still in absorption and the Hα line at 6562.8 Å displays a very broad emission profile with a central reversal plus a red or blue asymmetry. The white-light kernels are cospatial with the microwave footpoint sources observed by the Expanded Owens Valley Solar Array and the time profile of the white-light emission matches that of the hard X-ray emission above 30 keV from the Gamma-ray Burst Monitor (GBM) on Fermi. These facts indicate that the white-light emission is qualitatively related to a nonthermal electron beam. We also perform a radiative hydrodynamic simulation with the electron-beam parameters constrained by the hard X-ray observations from Fermi/GBM. The result reveals that the white-light enhancement cannot be well explained by a pure electron-beam heating together with its induced radiative backwarming but may need additional heating sources such as Alfvén waves.

Keywords: Solar flares, Solar photosphere, Solar flare spectra, Solar x-ray emission, Solar activity, Solar chromosphere
A Large Population of Faint 8 &lt; z &lt; 16 Galaxies Found in the First JWST NIRCam Observations of the NGDEEP Survey. We present an early analysis on the search for high-redshift galaxies using the deepest public JWST imaging to date, the NGDEEP field. These data consist of six-band NIRCam imaging on the Hubble Ultra Deep Field Parallel 2 (HUDF-Par2), covering a total area of 6.3 arcmin2. Based on our initial reduction of the first half of this survey, we reach 5σ depths up to mag = 29.5-29.9 between 1 and 5 μm. Such depths present an unprecedented opportunity to begin exploring the very early universe with JWST. As such, we find high-redshift galaxies by examining the spectral energy distribution of all F444W detections and present 16 new z &gt; 8.5 galaxies identified using two different photometric redshift codes: LePhare and EAZY combined with other significance criteria. The highest-redshift object in our sample is at $z={15.6}_{-0.3}^{+0.4}$ , which has a blue $\beta =-{3.02}_{-0.46}^{+0.42}$ and a very low inferred stellar mass of M * = 107.4 M ⊙. We also discover a series of faint, low-mass dwarf galaxies with M * &lt; 108.5 M ⊙ at z ~ 9 that have blue colors, flat surface brightness profiles, and small sizes &lt;1 kpc. Comparing to previous work in the HUDF-Par2, we find 21 6 &lt; z &lt; 9 candidates including two z = 8 major mergers. One of these merger candidates has an additional two z = 8 sources within 30″, indicating that it may form part of an overdensity. We also compare our results to theory, finding no significant disagreement with a few cold-dark-matter-based models. The discovery of these objects demonstrates the critical need for deeper, or similar depth but wider-area, JWST surveys to explore the early universe.

Keywords: Galaxy formation, High-redshift galaxies, James Webb Space Telescope
Binning is Sinning: Redemption for Hubble Diagram Using Photometrically Classified Type Ia Supernovae. Bayesian Estimation Applied to Multiple Species (BEAMS) is implemented in the BEAMS with Bias Corrections (BBC) framework to produce a redshift-binned Hubble diagram (HD) for Type Ia supernovae (SNe Ia). BBC corrects for selection effects and non-SN Ia contamination, and systematic uncertainties are described by a covariance matrix with dimension matching the number of BBC redshift bins. For spectroscopically confirmed SN Ia samples, a recent "Binning is Sinning" article showed that an unbinned HD and covariance matrix reduces the systematic uncertainty by a factor of ~1.5 compared to the binned approach. Here we extend their analysis to obtain an unbinned HD for a photometrically identified sample processed with BBC. To test this new method, we simulate and analyze 50 samples corresponding to the Dark Energy Survey (DES) with a low-redshift anchor; the simulation includes SNe Ia, and contaminants from core-collapse SNe and peculiar SNe Ia. The analysis includes systematic uncertainties for calibration and measures the dark energy equation of state parameter (w). Compared to a redshift-binned HD, the unbinned HD with nearly 2000 events results in a smaller systematic uncertainty, in qualitative agreement with BHS21, and averaging results among the 50 samples we find no evidence for a w-bias. To reduce computation time for fitting an unbinned HD with large samples, we propose an HD-rebinning method that defines the HD in bins of redshift, color, and stretch; the rebinned HD results in similar uncertainty as the unbinned case, and shows no evidence for a w-bias.

Keywords: Cosmology, Hubble diagram, Supernovae, Dark energy
Magnetic Braking during Direct Collapse Black Hole Formation. Magnetic fields are expected to be efficiently amplified during the formation of the first massive black holes via the small-scale dynamo and in the presence of strong accretion shocks occurring during gravitational collapse. Here, we analyze high-resolution cosmological magnetohydrodynamical simulations of gravitational collapse in atomic cooling halos, exploring the dynamical role of magnetic fields, particularly concerning the effect of magnetic braking and angular momentum transport. We find that after the initial amplification, magnetic fields contribute to the transport of angular momentum and reduce it compared to pure hydrodynamical simulations. However, the magnetic and Reynolds torques do not fully compensate for the inward advection of angular momentum, which still accumulates over timescales of ~1 Myr. A Jeans analysis further shows that magnetic pressure strongly contributes to suppressing fragmentation on scales of 0.1-10 pc. Overall, the presence of magnetic fields thus aids in the transport of angular momentum and favors the formation of massive objects.

Keywords: Early universe, Supermassive black holes, Population III stars