Sazuna/UAT_keywords huggingface dataset:
Toward Higher-order Accuracy in Self-gravitating Hydrodynamics. High-order algorithms have emerged in numerical astrophysics as a promising avenue to reduce truncation error (proportional to a power of the linear resolution Δx) with only a moderate increase to computational expense. Significant effort has been placed in the development of finite-volume algorithms for (magneto)hydrodynamics; however, state-of-the-art astrophysical simulations tightly couple a plenitude of physics, additionally including gravity, photon transport, cosmic-ray transport, chemistry, and/or diffusion, to name a few. Algorithms frequently operator-split this additional physics (often a first-order error in time) and/or adopt a model wherein their evaluation is limited to second-order accuracy in space. In this work, we present a fourth-order-accurate finite-volume scheme for self-gravitating hydrodynamics on a uniform Cartesian grid. The method supplies source terms for the gravitational acceleration (ρg) and gravitational energy release (ρv · g) associated with fourth-order-accurate solutions to the Poisson equation. Our scheme (1) guarantees the conservation of total linear momentum while (2) decreasing (in proportion to Δx4) the effects of spurious heating and/or cooling associated with truncation error in the gravity. We demonstrate expected convergence rates for the algorithm by measuring errors in test problems evolving self-gravity modified linear waves and 3D polytropic equilibria. We test robustness of the algorithm by integrating an induced "inside-out" adiabatic collapse. We also discuss a method to smoothly downgrade the solution to second-order spatial accuracy to avoid spurious overshoots near steep density and/or pressure gradients.

Keywords: Gravitation, Computational methods, Hydrodynamics
Real-time Extrapolation of Nonlinear Force-free Fields from Photospheric Vector Magnetic Fields Using a Physics-informed Neural Operator. In this study, we develop a physics-informed neural operator (PINO) model that learns the solution operator from 2D photospheric vector magnetic fields to 3D nonlinear force-free fields (NLFFFs). We train our PINO model using physics loss from NLFFF partial differential equations, as well as data loss from target NLFFFs. We validate our method using an analytical NLFFF model. We then train and evaluate our PINO model with 2327 numerical NLFFFs of 211 active regions from the Institute for Space-Earth Environmental Research database. The results show that our trained PINO model can generate an NLFFF within 1 s for any active region on a single consumer GPU, making real-time extrapolation of NLFFFs possible. Our artificial intelligence (AI)-generated NLFFFs are qualitatively and quantitatively quite similar to the target NLFFFs for 30 active regions. The magnetic energy of the AI-generated NLFFFs of active region 11158 follows a similar trend to the target NLFFFs as well as other conventional methods.

Keywords: The Sun, Solar active regions, Solar magnetic fields, Neural networks
Simulating Image Coaddition with the Nancy Grace Roman Space Telescope. III. Software Improvements and New Linear Algebra Strategies. The Nancy Grace Roman Space Telescope will implement a devoted weak gravitational lensing program with its High Latitude Wide Area Survey. For cosmological purposes, a critical step in Roman image processing is to combine dithered undersampled images into unified oversampled images and thus enable high-precision shape measurements. IMCOM is an image coaddition algorithm that offers control over point-spread functions in output images. This paper presents the refactored IMCOM software, featuring full object-oriented programming, improved data structures, and alternative linear algebra strategies for determining coaddition weights. Combining these improvements and other acceleration measures, to produce almost equivalent coadded images, the consumption of core-hours has been reduced by about an order of magnitude. We then re-coadd a 16 × 16 arcmin2 region of our previous image simulations with three linear algebra kernels in four bands, and compare the results in terms of IMCOM optimization goals, properties of coadded noise frames, and measurements of simulated stars. The Cholesky kernel is efficient and relatively accurate, yet its irregular windows for input pixels slightly bias coaddition results. The iterative kernel avoids this issue by tailoring input pixel selection for each output pixel; it yields better noise control, but can be limited by random errors due to finite tolerance. The empirical kernel coadds images using an empirical relation based on geometry; it is inaccurate, but being much faster, it provides a valid option for "quick look" purposes. We fine-tune IMCOM hyperparameters in a companion paper.

Keywords: Weak gravitational lensing, Astronomy image processing
VLBI Imaging of Parsec-scale Radio Structures in Nearby Low-luminosity Active Galactic Nuclei. We report the results of high-resolution 5 GHz Very Long Baseline Array and European VLBI Network observations of 36 nearby galaxies, an extension of the Legacy e-MERLIN Multi-band Imaging of Nearby Galaxies survey. Our sample includes 21 low ionization nuclear emission regions, four Seyferts, three absorption line galaxies, and eight H II galaxies. We achieved an unprecedented detection rate, successfully imaging 23 out of 36 sources with a detection threshold of ∼20 μJy beam‑1. The radio sizes are typically of ≤5 pc. Core identification was achieved in 16 sources, while seven others were identified as core candidates. Radio luminosities of the sample range from 1034 to 1038 erg s‑1. Our analysis reveals a predominance of compact core structures, with 10 sources exhibiting a one-sided core jet morphology and NGC 2146 exhibiting a rare two-sided jet structure. The study advances our understanding of the compactness of radio sources at various scales, indicating a core-dominated nature in all but one galaxy, NGC 2655. We find moderate to strong correlations between radio luminosity, black hole (BH) mass, optical [O III] line luminosity, and hard X-ray luminosity, suggesting a common active galactic nucleus (AGN) core origin. These results provide new insights into the fundamental plane of BH activity and support the role of the synchrotron process in low-luminosity AGN radio emission.

Keywords: Supermassive black holes, Radio jets, Very long baseline interferometry, Active galaxies, Radio continuum emission
Galactic-scale Emission-line Outflow from the Radio-loud Quasar 3C 191. Quasar feedback is routinely invoked as an indispensable ingredient in galaxy formation models. Galactic outflows are a crucial agent of quasar feedback that frequently manifest themselves in absorption and emission lines. Measuring the size and energetics of outflows based on absorption lines remains a challenge, and integral field spectroscopy (IFS) mapping in emission lines is complementary. We present Very Large Telescope (VLT)/SINFONI IFS mapping of quasar 3C 191 at z ∼ 2, in which the outflow has been analyzed in absorption line spectroscopy. Three components are found based on the morphology and kinetics of [O III]-emitting gas: an unshifted component, which is consistent with the systemic redshift and the location of the nucleus, a blueshifted in the north, and a redshifted in the south. The latter two components have velocities ∼600 km s−1 and projected extents of 5 and 11 kpc, respectively, suggesting a biconical outflow structure. The blueshifted component's velocity is consistent with that derived from absorption lines. Using the electron density measured by the absorption lines and the luminosity and velocity of [O III] outflow, we derive the mass outflow rate to be   ∼ 9.5─13.4 M⊙ yr−1 and kinetic luminosity   ∼ 2.6─3.7 × 1042 erg s−1, consistent with absorption line analyses with the VLT/X-shooter spectrum. The kinetic luminosity is only 0.01% of the bolometric luminosity, rendering a relatively weak outflow compared to typical expectation for effective feedback.

Keywords: Active galactic nuclei, Quasars
A Two-moment Neutrino Transport Scheme for the CHIMERA Supernova Code. We introduce our two-moment scheme, referred to as A-M1 (analytic closure-M1), to solve the neutrino Boltzmann transport equation with the aim of using it to replace the flux-limited diffusion (FLD) scheme currently utilized in CHIMERA. We first present the A-M1 equations and the numerical method used for solving them. We then present the results of several numerical experiments that were conducted to test the ability of the scheme to perform some basic tasks that are encountered in simulating core-collapse supernovae. The first two were simply to test the ability of the code to ensure conservation of and to respect the fermionic character of neutrinos. More challenging tests were the ability of the code to match analytic solutions in the realms of both diffusion and free streaming. Finally, the ability of the code to match the analytic solution of the homogeneous sphere problem was tested. By separating a diffusive and a free-streaming regime by a density discontinuity, this test mimics the configuration of a supernova core consisting of a dense proto–neutron star below and a rarefied heating region above separated by a steepening density cliff. While the Eddington factor was prescribed in the two preceding tests, a number of analytic Eddington factors were tested in the latter test. A future paper will describe the performance of the A-M1 code on nonstatic backgrounds and will present detailed comparisons of core-collapse simulations performed with the A-M1 scheme versus the current FLD scheme.

Keywords: Supernova dynamics
A New Framework for Active Galactic Nucleus Accretion and Jet Feedback in Numerical Simulations. Accurate modeling of active galactic nucleus (AGN) feedback, especially due to relativistic jets, is crucial for understanding the cool-core problem in galaxy clusters. We present a new subgrid method to model accretion onto and feedback from AGN in hydrodynamical simulations of galaxy clusters. Instead of applying the traditional Bondi formalism, we use a sink particle algorithm in which the accretion flux is measured directly through a control surface. A weighting kernel is used to reset the gas properties within the accretion radius at the end of each time step. We implement feedback in the form of bipolar jets whose properties are tied to the accretion rate. The method is tested with a spherically symmetric Bondi gas flow problem and a Bondi–Hoyle–Lyttleton wind problem, with and without jet feedback. We discuss the reliability of this model by comparing our jet simulations with those in the literature, and we examine the dependence of test results on parameters such as the resolution and size of the jet injection region. We find that the sink particle model can account for the α factor in accretion measurement, and the accretion radius must be resolved with at least two zones to produce realistic black hole accretion. We also show how underresolving the AGN feedback region in simulations can impact the feedback energy deposited and the jet dynamics. The code described here is the framework for a feedback model, described in a companion paper, that will use accretion disk modeling to more self-consistently determine the feedback efficiency.

Keywords: Galaxy clusters, Active galactic nuclei, Hydrodynamics, Astronomical simulations
Outlier Detection and Removal in Multivariate Time Series for a More Robust Machine Learning─based Solar Flare Prediction. Timely and accurate prediction of solar flares is a crucial task due to the danger they pose to human life and infrastructure beyond Earth's atmosphere. Although various machine learning algorithms have been employed to improve solar flare prediction, there has been limited focus on improving performance using outlier detection. In this study, we propose the use of a tree-based outlier detection algorithm, Isolation Forest (iForest), to identify multivariate time-series instances within the flare-forecasting benchmark data set, Space Weather Analytics for Solar Flares (SWAN-SF). By removing anomalous samples from the nonflaring class (N-class) data, we observe a significant improvement in both the true skill score and the updated Heidke skill score in two separate experiments. We focus on analyzing outliers detected by iForest at a 2.4% contamination rate, considered the most effective overall. Our analysis reveals a co-occurrence between the outliers we discovered and strong flares. Additionally, we investigated the similarity between the outliers and the strong-flare data and quantified it using Kullback─Leibler divergence. This analysis demonstrates a higher similarity between our outliers and strong-flare data when compared to the similarity between the outliers and the rest of the N-class data, supporting our rationale for using outlier detection to enhance SWAN-SF data for flare prediction. Furthermore, we explore a novel approach by treating our outliers as if they belong to flaring-class data in the training phase of our machine learning, resulting in further enhancements to our models' performance.

Keywords: Solar flares, Classification, Space weather, Outlier detection, Solar activity, Support vector machine, Time series analysis
Measuring Resolved Star Formation Histories from High-precision Color–Magnitude Diagrams with StarFormationHistories.jl. Understanding how and when galaxies formed stars over the history of the Universe is fundamental to the study of galaxy evolution. The star formation histories (SFHs) of galaxies in the local Universe can be measured with high precision using deep imaging with space telescopes. Such resolved SFHs are based on modeling the observed color–magnitude diagram (CMD) with stellar evolution models and rely on age-sensitive features like the main-sequence turnoff to measure a galaxy's star formation rate as a function of time. There are many other population-level parameters that factor into these measurements, such as the stellar initial mass function (IMF), binary fraction, and metallicity, to name a few. We present and release StarFormationHistories.jl, a modular, open-source Julia package for measuring resolved SFHs with a focus on model flexibility for these types of population parameters. The code can model unresolved photometric binaries and supports arbitrary IMFs. Random uncertainties in the SFH measurements can be quantified with Monte Carlo posterior sampling methods. We illustrate the performance of the package on JWST/NIRCAM data of the Local Group dwarf irregular galaxy Wolf–Lundmark–Melotte  , which exhibits a complex, well-sampled CMD, and Hubble Space Telescope/Advanced Camera for Surveys data of the ultrafaint Milky Way satellite dwarf galaxy Horologium I  , which has a much simpler but sparser CMD.

Keywords: Stellar populations, Hertzsprung Russell diagram, Stellar photometry
Evidence of Galactic Interaction in the Small Magellanic Cloud Probed by Gaia-selected Massive Star Candidates. We present identifications and kinematic analysis of 7426 massive (≥8M⊙) stars in the Small Magellanic Cloud (SMC), using Gaia DR3 data. We used the Gaia (GBP − GRP, G) color─magnitude diagram to select the population of massive stars, and parallax to omit foreground objects. The spatial distribution of the 7426 massive star candidates is generally consistent with the spatial distribution of the interstellar medium, such as Hα and H I emission. The identified massive stars show inhomogeneous distributions over the galaxy, showing several superstructures formed by massive stars with a several hundred parsec scale. The stellar superstructures defined by the surface density have opposite mean proper motions in the east and west, moving away from each other. Similarly, the mean line-of-sight velocities of the superstructures are larger to the southeast and smaller to the northwest. The different east─west properties of the superstructures' proper-motion, line-of-sight velocity indicate that the SMC is being stretched by tidal forces and/or ram pressure from the Large Magellanic Cloud to the southeast, thereby rejecting the presence of galactic rotation in the SMC.

Keywords: Optical astronomy, Massive stars, Galaxy interactions, Small Magellanic Cloud, Clustering, Proper motions
The Kratos Framework for Heterogeneous Astrophysical Simulations: Fundamental Infrastructures and Hydrodynamics. The field of astrophysics has long sought computational tools capable of harnessing the power of modern GPUs to simulate the complex dynamics of astrophysical phenomena. The Kratos Framework, a novel GPU-based simulation system designed to leverage heterogeneous computing architectures, is introduced to address these challenges. Kratos offers a flexible and efficient platform for a wide range of astrophysical simulations, by including its device abstraction layer, multiprocessing communication model, and mesh-management system that serves as the foundation for the physical module container. Focusing on the hydrodynamics module as an example and foundation for more complex simulations, optimizations and adaptations have been implemented for heterogeneous devices that allow for accurate and fast computations, especially the mixed-precision method that maximizes its efficiency on consumer-level GPUs while holding the conservation laws to machine accuracy. The performance and accuracy of Kratos are verified through a series of standard hydrodynamic benchmarks, demonstrating its potential as a powerful tool for astrophysical research.

Keywords: Hydrodynamical simulations, Hydrodynamics, Astronomy software, Computational methods, GPU computing
FRB Line-of-sight Ionization Measurement from Lightcone AAOmega Mapping Survey: The First Data Release. This paper presents the first public data release (DR1) of the FRB Line-of-sight Ionization Measurement From Lightcone AAOmega Mapping (FLIMFLAM) survey, a wide field spectroscopic survey targeted on the fields of 10 precisely localized fast radio bursts (FRBs). DR1 encompasses spectroscopic data for 10,468 galaxy redshifts across 10 FRB fields with z &lt; 0.4, covering approximately 26 deg2 of the sky in total. FLIMFLAM is composed of several layers, encompassing the "wide" (covering ∼degree or &gt;10 Mpc scales), "narrow" (several arcminutes or ∼Mpc), and integral field unit ("IFU"; ∼arcminute or ∼100 kpc) components. The bulk of the data comprises spectroscopy from the Two Degree Field-AAOmega instrument on the 3.9 m Anglo-Australian Telescope, while most of the narrow and IFU data was achieved using an ensemble of 8─10 m class telescopes. We summarize the information on our selected FRB fields, the criteria for target selection, methodologies employed for data reduction, spectral analysis processes, and an overview of our data products. An evaluation of our data reveals an average spectroscopic completeness of 48.43%, with over 80% of the observed targets having secure redshifts. Additionally, we describe our approach to generating angular masks and calculating the target selection functions, setting the stage for the impending reconstruction of the matter density field.

Keywords: Galaxy dark matter halos, Intergalactic medium, Galaxy spectroscopy, Redshift surveys, Radio transient sources
Not-quite-transcendental Functions for Logarithmic Interpolation of Tabulated Data. From tabulated nuclear and degenerate equations of state to photon and neutrino opacities and nuclear reaction rates, tabulated data is ubiquitous in computational astrophysics. The dynamic range that must be covered by these tables typically spans many orders of magnitude. Here we present a novel strategy for accurately and performantly interpolating tabulated data that spans these large dynamic ranges. We demonstrate the efficacy of this strategy in tabulated lookups for nuclear and terrestrial equations of state. We show that this strategy is a faster drop-in replacement for linear interpolation of logarithmic grids.

Keywords: Computational astronomy, High energy astrophysics, Astronomy software, Relativistic binary stars, Plasma astrophysics, Computational methods, GPU computing
15 yr of Interstellar Neutral Hydrogen Observed with the Interstellar Boundary Explorer. The interactions of our heliosphere with the surrounding local interstellar medium (LISM) lead to a range of observable phenomena such as energetic neutral atoms (ENAs) from the boundary regions of the heliosphere and the influx of interstellar neutrals (ISNs) into the inner solar system. Hydrogen is the dominant neutral species in the LISM, but due to ionization and radiation pressure, only a fraction of the ISN H atoms reach the inner solar system close to Earth. Monitoring this signal therefore provides observational constraints on our assumptions of the LISM and the solar-activity-dependent loss processes inside the heliosphere. The IBEX-Lo instrument on board the Interstellar Boundary Explorer has been the only instrument so far to measure ISN H atoms directly, together with ISN D, He, Ne, O, and ENAs in the energy range from tens of eV to 2 keV. This study covers 15 yr of IBEX-Lo ISN H observations, i.e., more than one solar cycle and includes two solar minima when the ISN H signal in IBEX-Lo is strongest. Despite the very intense ISN He signal, the ISN H signal can be retrieved with appropriate knowledge of the instrument, choice of optimum observation season, and supporting modeling. The retrieved ISN H signal shows a clear anticorrelation with solar activity. The resulting ISN H maps are available in orbit format and in ecliptic coordinates and will be the basis for future more detailed comparison with heliosphere models.

Keywords: Solar cycle, Heliosphere, Interstellar atomic gas, Interstellar medium, Heliosheath
Photometric Metallicity and Distance Estimates for ∼70,000 RR Lyrae Stars from the Zwicky Transient Facility. Utilizing Zwicky Transient Facility (ZTF) data and existing RR Lyrae stars (RRLs) catalogs, this study achieves the first calibration of the P ‑ ϕ31 ‑ R21 ‑ [Fe/H] and P ‑ ϕ31 ‑ A2 ‑ A1 ‑ [Fe/H] relations in the ZTF photometric system for RRab and RRc stars. We also recalibrate the period–absolute magnitude–metallicity (PMZ) and period–Wesenheit–metallicity (PWZ) relations in the ZTF gri bands for RRab and RRc stars. Based on nearly 4100 stars with precise measurements of P, ϕ31, A2, and A1, and available spectroscopic metallicity estimates, the photometric metallicity relations exhibit strong internal consistency across different bands, supporting the use of a weighted averaging method for the final estimates. The photometric metallicity estimates of globular clusters based on RR Lyrae members also show excellent agreement with high-resolution spectroscopic measurements, with a typical scatter of 0.15 dex for RRab stars and 0.14 dex for RRc stars, respectively. Using hundreds of local RRLs with newly derived photometric metallicities and precise Gaia Data Release 3 parallaxes, we establish the PMZ and PWZ relations in multiple bands. Validation with globular cluster RR Lyrae members reveals typical distance errors of 3.1% and 3.0% for the PMZ relations, and 3.1% and 2.6% for the PWZ relations for RRab and RRc stars, respectively. Compared to PMZ relations, the PWZ relations are tighter and almost unbiased, making them the recommended choice for distance calculations. We present a catalog of 73,795 RRLs with precise photometric metallicities; over 95% of them have accurate distance measurements. Compared to Gaia DR3, approximately 25,000 RRLs have precise photometric metallicities and distances derived for the first time.

Keywords: RR Lyrae variable stars, Metallicity, Distance measure