Sazuna/UAT_keywords huggingface dataset:
Simulating the Arrival of the Southern Substructure in the Galaxy Cluster Abell 1758. Abell 1758 (z ∼ 0.278) is a galaxy cluster composed of two structures, A1758N and A1758S, separated by ∼2.2 Mpc. The northern cluster is itself a dissociative merging cluster that has already been modeled by dedicated simulations. Recent radio observations revealed the existence of a previously undetected bridge connecting A1758N and A1758S. New simulations are now needed to take into account the presence of A1758S. We wish to evaluate which orbital configuration would be compatible with a bridge between the clusters. Using N-body hydrodynamical simulations that build upon the previous model, we explore different scenarios that could have led to the current observed configuration. Five types of orbital approaches were tested: radial, tangential, vertical, postapocentric, and outgoing. We found that the incoming simulated scenarios are generally consistent with mild enhancements of gas density between the approaching clusters. The mock X-ray images exhibit a detectable bridge in all cases. Compared to measurements of Chandra data, the amplitude of the X-ray excess is overestimated by a factor of ∼2–3 in the best simulations. The scenario of tangential approach proved to be the one that best matches the properties of the profiles of X-ray surface brightness. The scenarios of radial approach of vertical approach are also marginally compatible.

Keywords: Galaxy clusters, Hydrodynamical simulations, Intracluster medium
Spectral Indices and Evidence of Wave–Wave Modulation in Observations of the Interplanetary Magnetic Field. We present wave and turbulence observations from the DSCOVR spacecraft during the 2017 September solar flare and coronal mass ejection (CME) events. On September 4–12, the spectral index within the magnetic field power spectral density inertial range was consistent with Kolmogorov ‑5/3. This is despite the 9 days being composed of a complex mix of different features, including solar flares, solar energetic particle events, and CMEs. When analyzing shorter time periods, the spectral index varies. For two days where there were consecutive CMEs, the index follows Kraichnan–Iroshinikov ‑3/2, while on two quiet days, it was a mixture of ‑1, ‑3/2, and ‑2. The inertial range spectral index taken over the entire 9 days hides or averages out spectral features that occur over shorter time periods. We use a more realistic estimate of the amount of Doppler shifting into the spacecraft frame a show that the break frequencies on most days were located close to the H+ cyclotron frequency. We present evidence of wave–wave modulation and suggest that lower-frequency waves in the solar wind can modulate the growth rates/propagation of ion cyclotron waves, providing a method to transfer energy in the solar wind to smaller scales. Furthermore, we suggest that the indices in the inertial range can be explained by combining containment due to wave generation/propagation and stochastic Brownian motion in the solar wind. When these two phenomena are equal, they combine to create a ‑3/2 index.

Keywords: Interplanetary turbulence, Solar wind, Heliosphere
The Temporal Evolution of Nonneutralized Electric Currents and the Complexity of Solar Active Regions. We study the evolution of electric currents during the emergence of magnetic flux in the solar photosphere and the differences exhibited between solar active regions of different Hale complexity classes. A sample of 59 active regions was analyzed using a method based on image segmentation and error analysis to determine the total amount of nonneutralized electric current along their magnetic polarity inversion lines. The time series of the total unsigned nonneutralized electric current, I NN,tot, exhibit intricate structure in the form of distinct peaks and valleys. This information is largely missing in the respective time series of the total unsigned vertical electric current I  z . Active regions with δ-spots stand out, exhibiting a 1.9 times higher flux emergence rate and 2.6 times higher I NN,tot increase. The median value of their peak I NN,tot is equal to 3.6 × 1012 A, which is more than three times higher than that of the other regions of the sample. An automated detection algorithm was also developed to pinpoint the injection events of nonneutralized electric current. The injection rates and duration of these events were higher with increasing complexity of active regions, with regions containing δ-spots exhibiting the strongest and longest events. These events do not necessarily coincide with increasing magnetic flux, although they exhibit moderate correlation. We conclude that net electric currents are injected during flux emergence but are also shaped drastically by the incurred photospheric evolution as active regions grow and evolve.

Keywords: Solar active region magnetic fields, Magnetohydrodynamics, Solar flares, Solar active regions, Solar magnetic fields, Solar activity, Delta sunspots
A Robust Light-curve Diagnostic for Electron-capture Supernovae and Low-mass Fe-core-collapse Supernovae. Core-collapse supernovae (CCSNe) are the terminal explosions of massive stars. While most massive stars explode as iron-core-collapse supernovae (FeCCSNe), slightly less massive stars explode as electron-capture supernovae (ECSNe), shaping the low-mass end of CCSNe. ECSNe were proposed ∼40 yr ago and first-principles simulations also predict their successful explosions. Observational identification and investigation of ECSNe are important for the completion of stellar evolution theory. To date, only one promising candidate has been proposed, SN 2018zd, other than the historical progenitor of the Crab Nebula, SN 1054. We present representative synthetic light curves of low-mass FeCCSNe and ECSNe, i.e., with theoretically or observationally plausible explosion energies and distributions of circumstellar media (CSM). The ECSNe have shorter, brighter, and bluer plateaus than the FeCCSNe. To investigate the robustness of their intrinsic differences, we also calculated light curves of ECSNe and low-mass FeCCSNe adopting various explosion energies and CSM. Although they may have similar bolometric light-curve plateaus, ECSNe are bluer than FeCCSNe in the absence of strong CSM interaction, illustrating that multicolor observations are essential to identify ECSNe. This provides a robust indicator of ECSNe because the bluer plateaus stem from the low-density envelopes of their super-asymptotic-giant-branch progenitors. We propose a distance-independent method to identify ECSNe:  g‑rtPT/2&lt;0.008×tPT‑0.4 , i.e., blue g – r at the middle of the plateau  (g‑r)tPT/2 , where t PT is the transition epoch from plateau to tail. Using this method, we identified SN 2018zd as an ECSN, which we believe to be the first ECSN identified with modern observing techniques.

Keywords: Late stellar evolution, Core-collapse supernovae, Type II supernovae, Massive stars, Supernovae, Supernova dynamics
Spectroscopic Survey of Faint Planetary-nebula Nuclei. V. The EGB 6-type Central Star of Abell 57. During our spectroscopic survey of central stars of faint planetary nebulae (PNe), we found that the nucleus of Abell 57 exhibits strong nebular emission lines. Using synthetic narrowband images, we show that the emission arises from an unresolved compact emission knot (CEK) coinciding with the hot (90,000 K) central star. Thus Abell 57 belongs to the rare class of "EGB 6-type" PNe, characterized by dense emission cores. Photometric data show that the nucleus exhibits a near-infrared excess, due to a dusty companion body with the luminosity of an M0 dwarf but a temperature of ∼1800 K. Emission-line analysis reveals that the CEK is remarkably dense (electron density ∼ 1.6 × 107 cm‑3), and has a radius of only ∼4.5 au. The CEK suffers considerably more reddening than the central star, which itself is more reddened than the surrounding PN. These puzzles may suggest an interaction between the knot and central star; however, Hubble Space Telescope imaging of EGB 6 itself shows that its CEK lies more than ∼125 au from the PN nucleus. We discuss a scenario in which a portion of the asymptotic giant branch wind that created the PN was captured into a dust cloud around a distant stellar companion; this cloud has survived to the present epoch, and has an atmosphere photoionized by radiation from the hot central star. However, in this picture EGB 6-type nuclei should be relatively common, yet they are actually extremely rare; thus they may arise from a different transitory phenomenon. We suggest future observations of Abell 57 that may help unravel its mysteries. *Based on observations obtained with the Hobby–Eberly Telescope (HET), which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig–Maximillians–Universität München, and Georg–August Universität Göttingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly.

Keywords: Post-asymptotic giant branch stars, White dwarf stars, Planetary nebulae nuclei, Planetary nebulae, Infrared sources, Circumstellar dust
New Observational Recipes for Measuring Dynamical States of Galaxy Clusters. During cluster assembly, a cluster's virialization process leaves behind signatures that can provide information on its dynamical state. However, no clear consensus yet exists on the best way to achieve this. Therefore, we attempt to derive improved recipes for classifying the dynamical states of clusters in observations using cosmological simulations. The cluster halo mass and their subhalos' mass are used to 1014 M ⊙ h ‑1 and 1010 M ⊙ h ‑1 to calculate five independent dynamical state indicators. We experiment with recipes by combining two to four indicators for detecting specific merger stages, like recent and ancient mergers. These recipes are made by plotting merging clusters and a control sample of relaxed clusters in multiple-indicator parameter space, then applying a rotation matrix method to derive the best way to separate mergers from the control sample. The success of the recipe is quantified using the success rate and overlap percentage of the merger and control histograms along the newly rotated x-axis. This provides us with recipes using different numbers of combined indicators and for different merger stages. Among the recipes, the stellar mass gap and center offset are the first and second most dominant of the indicators, and using more indicators improves the effectiveness of the recipe. When applied to observations, our results show good agreement with literature values of cluster dynamical states.

Keywords: Galaxy clusters, Galactic and extragalactic astronomy
A New Asteroseismic Kepler Benchmark Constrains the Onset of Weakened Magnetic Braking in Mature Sun-like Stars. Stellar spin down is a critical yet poorly understood component of stellar evolution. In particular, results from the Kepler Mission imply that mature age, solar-type stars have inefficient magnetic braking, resulting in a stalled spin-down rate. However, a large number of precise asteroseismic ages are needed for mature (≥3 Gyr) stars in order to probe the regime where traditional and stalled spin-down models differ. In this paper, we present a new asteroseismic benchmark star for gyrochronology discovered using reprocessed Kepler short cadence data. KIC 11029516 (Papayu) is a bright (Kp = 9.6 mag) solar-type star with a well-measured rotation period (21.1 ± 0.8 days) from spot modulation using 4 yr of Kepler long-cadence data. We combine asteroseismology and spectroscopy to obtain T eff = 5888 ± 100 K, [Fe/H] = 0.30 ± 0.06 dex, M = 1.24 ± 0.05 M ⊙, R = 1.34 ± 0.02 R ⊙, and age of 4.0 ± 0.4 Gyr, making Papayu one of the most similar stars to the Sun in terms of temperature and radius with an asteroseismic age and a rotation period measured from spot modulation. We find that Papayu sits at the transition of where traditional and weakened spin-down models diverge. A comparison with stars of similar zero-age main-sequence temperatures supports previous findings that weakened spin-down models are required to explain the ages and rotation periods of old solar-type stars.

Keywords: Stellar ages, Stellar rotation, Asteroseismology, Stellar evolutionary tracks, Stellar evolution
A NuSTAR Census of the X-Ray Binary Population of the M31 Disk. Using hard (E &gt; 10 keV) X-ray observations with NuSTAR, we are able to differentiate between the accretion states, and thus compact object types, of neutron stars (NSs) and black holes (BHs) in X-ray binaries (XRBs) in M31, our nearest Milky Way─type neighbor. Using 10 moderate-depth (20─50 ks) observations of the disk of M31 covering a total of ∼0.45 deg2, we detect 20 sources at 2σ in the 4─25 keV bandpass, 14 of which we consider to be XRB candidates. This complements an existing, deeper (100─400 ks) survey covering ∼0.2 deg2 of the bulge and the northeastern disk. We make tentative classifications of nine of these sources with the use of diagnostic color─intensity and color─color diagrams, which separate sources into various NS and BH regimes, identifying three BHs and six NSs. In addition, we create X-ray luminosity functions (XLFs) for both the full (4─25 keV) and hard (12─25 keV) bands, as well as subpopulations of the full band based on compact object type and association with globular clusters. Our best-fit globular cluster XLF is shallower than the field XLF, and preliminary BH and NS XLFs suggest a difference in shape based on compact object type. We find that the cumulative disk XLFs in the full and hard band are best fit by power laws with indices of 1.32 and 1.28, respectively. This is consistent with models of the Milky Way XLF from Grimm et al., Voss &amp; Ajello, and Doroshenko et al.

Keywords: Neutron stars, Luminosity function, X-ray binary stars, Black holes, Andromeda Galaxy, Galaxies
SuperSynthIA: Physics-ready Full-disk Vector Magnetograms from HMI, Hinode, and Machine Learning. Vector magnetograms of the Sun's photosphere are cornerstones for much of solar physics research. These data are often produced by data-analysis pipelines combining per-pixel Stokes polarization vector inversion with a disambiguation that resolves an intrinsic 180° ambiguity. We introduce a learning-based method, SuperSynthIA, that produces full-disk vector magnetograms from Stokes vector observations. As input, SuperSynthIA uses Stokes polarization images from Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager (HMI). As output, SuperSynthIA simultaneously emulates the inversion and disambiguation outputs from the Hinode/Solar Optical Telescope-Spectro-Polarimeter (SOT-SP) pipeline. Our method extends our previous approach SynthIA with heliographic outputs as well as using an improved data set and inference method. SuperSynthIA provides a new tool for improved magnetic fields from full-disk SDO/HMI observations using information derived from the enhanced capabilities of Hinode/SOT-SP. Compared to our previous SynthIA, SuperSynthIA provides physics-ready vector magnetograms and mitigates unphysical angle preferences and banding artifacts in SynthIA. SuperSynthIA data are substantially more temporally consistent than those from the SDO/HMI pipeline, most notably seen in, e.g., evolving active regions. SuperSynthIA substantially reduces noise in low-signal areas, resulting in less center-to-limb bias outside of strong-signal areas. We show that outputs from SuperSynthIA track the SDO/HMI-recorded evolution of the magnetic field. We discuss the limitations of SuperSynthIA that the user must understand, and we demonstrate a broad set of evaluations to test SuperSynthIA and discuss remaining known artifacts. Our tests provide both methodology and evidence that SuperSynthIA outputs are ready for use by the community, and that learning-based approaches are suitable for physics-ready magnetograms.

Keywords: Computational methods, Convolutional neural networks, Solar magnetic fields
Primordial Black Hole Dark Matter Simulations Using PopSyCLE. Primordial black holes (PBHs), theorized to have originated in the early Universe, are speculated to be a viable form of dark matter. If they exist, they should be detectable through photometric and astrometric signals resulting from gravitational microlensing of stars in the Milky Way. Population Synthesis for Compact-object Lensing Events, or PopSyCLE, is a simulation code that enables users to simulate microlensing surveys, and is the first of its kind to include both photometric and astrometric microlensing effects, which are important for potential PBH detection and characterization. To estimate the number of observable PBH microlensing events, we modify PopSyCLE to include a dark matter halo consisting of PBHs. We detail our PBH population model, and demonstrate our PopSyCLE + PBH results through simulations of the Optical Gravitational Lensing Experiment-IV (OGLE-IV) and Nancy Grace Roman Space Telescope (Roman) microlensing surveys. We provide a proof-of-concept analysis for adding PBHs into PopSyCLE, and thus include many simplifying assumptions, such as f DM, the fraction of dark matter composed of PBHs, and  m¯PBH , mean PBH mass. Assuming  m¯PBH=30  M ⊙, we find ∼3.6f DM times as many PBH microlensing events than stellar evolved black hole events, a PBH average peak Einstein crossing time of ∼91.5 days, estimate on order of 102 f DM PBH events within the 8 yr OGLE-IV results, and estimate Roman to detect ∼1000f DM PBH microlensing events throughout its planned microlensing survey.

Keywords: Microlensing parallax, Astronomy software, Astronomical simulations, Microlensing event rate, Astrometric microlensing effect, Gravitational microlensing, Dark matter, Primordial black holes
Can We Constrain Warm Dark Matter Masses with Individual Galaxies?. We study the impact of warm dark matter (WDM) mass on the internal properties of individual galaxies using a large suite of 1024 state-of-the-art cosmological hydrodynamic simulations from the DREAMS project. We take individual galaxies' properties from the simulations, which have different cosmologies, astrophysics, and WDM masses, and train normalizing flows to learn the posterior of the parameters. We find that our models cannot infer the value of the WDM mass, even when the values of the cosmological and astrophysical parameters are given explicitly. This result holds for galaxies with stellar mass larger than 2 × 108 M ⊙ h ‑1 at both low and high redshifts. We calculate the mutual information and find no significant dependence between the WDM mass and galaxy properties. On the other hand, our models can infer the value of Ωm with a ∼10% accuracy from the properties of individual galaxies while marginalizing astrophysics and WDM masses.

Keywords: Warm dark matter, Cosmology, Neural networks
Evolution of the Secondary Electron Spectrum during Cosmic-Ray Discharge in the Universe. We recently found that streaming cosmic rays (CRs) induce a resistive electric field that can accelerate secondary electrons produced by CR ionization. In this work, we study the evolution of the energy spectrum of secondary electrons by numerically solving the one-dimensional Boltzmann equation and Ohm's law. We show that the accelerated secondary electrons further ionize a gas, that is, an electron avalanche occurs, resulting in increased ionization and excitation of the gas. Although the resistive electric field becomes weaker than the one before the CR discharge, the weak resistive electric field weakly accelerates the secondary electrons. The quasi-steady state is almost independent of the initial resistive electric field but depends on the electron fraction in the gas. The resistive electric field in the quasi-steady state is larger for the higher electron fraction, which makes the number of secondary electrons that can ionize the gas larger, resulting in a higher ionization rate. The CR discharge could explain the high ionization rate that is observed in some molecular clouds.

Keywords: Secondary cosmic rays, Plasma astrophysics, Molecular clouds, Ionization, Cosmic rays
A Revisited Equilibrium Solution of the Fishbone and Moncrief Torus for Extended General Relativistic Magnetohydrodynamic Simulations. Accretion physics has become more important recently due to the detection of the first horizon-scale images of the supermassive black holes of M 87* and Sgr A* by the Event Horizon Telescope. General relativistic magnetohydrodynamic (GRMHD) simulations of magnetized accretion flows onto a Kerr black hole have been used to interpret them. However, further testing the theory of gravity by using horizon-scale images requires performing consistent GRMHD simulations in non-Kerr spacetime. In this paper, we revisited the hydrodynamical equilibrium solution of the Fishbone and Moncrief (FM) torus that can be used to study any stationary, axisymmetric, vacuum, or nonvacuum spacetime. Further, we check the stability of the FM torus in non-Kerr spacetime by general relativistic hydrodynamic simulations. We find that FM torus in non-Kerr spacetime is indeed stable under long-term evolution. We conclude that the generalized FM torus solution would be very useful for creating new GRMHD libraries in extended Kerr black holes.

Keywords: Accretion, Black hole physics, Magnetohydrodynamics, Hydrodynamics, Gravitation
Nuclear Uncertainties Associated with the Nucleosynthesis in Ejecta of a Black Hole Accretion Disk. The simulation of heavy element nucleosynthesis requires input from yet-to-be-measured nuclear properties. The uncertainty in the values of these off-stability nuclear properties propagates to uncertainties in the predictions of elemental and isotopic abundances. However, for any given astrophysical explosion, there are many different trajectories, i.e., temperature and density histories, experienced by outflowing material, and thus different nuclear properties can come into play. We consider combined nucleosynthesis results from 460,000 trajectories from a black hole accretion disk and find the spread in elemental predictions due solely to unknown nuclear properties to be a factor of a few. We analyze this relative spread in model predictions due to nuclear variations and conclude that the uncertainties can be attributed to a combination of properties in a given region of the abundance pattern. We calculate a cross-correlation between mass changes and abundance changes to show how variations among the properties of participating nuclei may be explored. Our results provide further impetus for measurements of multiple quantities on individual short-lived neutron-rich isotopes at modern experimental facilities.

Keywords: Nuclear fission, Nucleosynthesis, Nuclear reaction cross sections, Nuclear astrophysics, Nuclear decay, Nuclear physics
Debiasing with Diffusion: Probabilistic Reconstruction of Dark Matter Fields from Galaxies with CAMELS. Galaxies are biased tracers of the underlying cosmic web, which is dominated by dark matter (DM) components that cannot be directly observed. Galaxy formation simulations can be used to study the relationship between DM density fields and galaxy distributions. However, this relationship can be sensitive to assumptions in cosmology and astrophysical processes embedded in galaxy formation models, which remain uncertain in many aspects. In this work, we develop a diffusion generative model to reconstruct DM fields from galaxies. The diffusion model is trained on the CAMELS simulation suite that contains thousands of state-of-the-art galaxy formation simulations with varying cosmological parameters and subgrid astrophysics. We demonstrate that the diffusion model can predict the unbiased posterior distribution of the underlying DM fields from the given stellar density fields while being able to marginalize over uncertainties in cosmological and astrophysical models. Interestingly, the model generalizes to simulation volumes ≈500 times larger than those it was trained on and across different galaxy formation models. The code for reproducing these results can be found at https://github.com/victoriaono/variational-diffusion-cdm ✎.

Keywords: Cosmology, Galaxies, Large-scale structure of the universe