Sazuna/UAT_keywords huggingface dataset:
An Implicit Finite Volume Scheme to Solve the Time-dependent Radiation Transport Equation Based on Discrete Ordinates. We describe a new algorithm to implicitly solve the time-dependent, frequency-integrated radiation transport (RT) equation, which is coupled to an explicit solver for equations of magnetohydrodynamics (MHD) using Athena++. The radiation field is represented by specific intensities along discrete rays, which are evolved using a conservative finite volume approach for both Cartesian and curvilinear coordinate systems. All terms for spatial transport of photons and interactions between gas and radiation are calculated implicitly together. An efficient Jacobi-like iteration scheme is used to solve the implicit equations. This removes any time-step constraint due to the speed of light in RT. We evolve the specific intensities in the lab frame to simplify the transport step. The lab frame specific intensities are transformed to the comoving frame via Lorentz transformation when the source term is calculated. Therefore, the scheme does not need any expansion in terms of v/c. The radiation energy and momentum source terms for the gas are calculated via direct quadrature in the angular space. The time step for the whole scheme is determined by the normal Courant-Friedrichs-Lewy condition in the MHD module. We provide a variety of test problems for this algorithm, including both optically thick and thin regimes, and for both gas and radiation pressure-dominated flows to demonstrate its accuracy and efficiency.

Keywords: Computational methods, Radiative transfer
Ultra-fast Model Emulation with PRISM: Analyzing the Meraxes Galaxy Formation Model. We demonstrate the potential of an emulator-based approach to analyzing galaxy formation models in the domain where constraining data is limited. We have applied the open-source PYTHON package PRISM to the galaxy formation model MERAXES. MERAXES is a semianalytic model, purposely built to study the growth of galaxies during the Epoch of Reionization. Constraining such models is however complicated by the scarcity of observational data in the EoR. PRISM's ability to rapidly construct accurate approximations of complex scientific models using minimal data is therefore key to performing this analysis well. This paper provides an overview of our analysis of MERAXES using measurements of galaxy stellar mass densities, luminosity functions, and color-magnitude relations. We demonstrate the power of using PRISM instead of a full Bayesian analysis when dealing with highly correlated model parameters and a scarce set of observational data. Our results show that the various observational data sets constrain MERAXES differently and do not necessarily agree with each other, signifying the importance of using multiple observational data types when constraining such models. Furthermore, we show that PRISM can detect when model parameters are too correlated or cannot be constrained effectively. We conclude that a mixture of different observational data types, even when they are scarce or inaccurate, is a priority for understanding galaxy formation and that emulation frameworks such as PRISM can guide the selection of such data.

Keywords: Galaxy formation, Computational astronomy, Astronomy data modeling, Astronomy data analysis
Chromospheric Activity of Periodic Variable Stars Based on the LAMOST Low- and Medium-resolution Spectral Survey. We present a catalog of 75,867 periodic variable stars from data release 7 of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope. We calculated the chromospheric activity index, equivalent widths for 201,349 spectra, and excess fractional luminosity ( ${R}_{{\rm{H}}\alpha }^{{\prime} }$ ) for 130,796 spectra. Based on the intensity of the Hα line, we detected 30,719 F-, G-, and K-type variable stars with Hα fill-in or emission and 2521 M-type variable stars exhibiting Hα emission. Furthermore, 14,938 out of 30,573 periodic variable stars showed Hα variability. Analysis of samples with different spectral types confirmed that the activity fraction of stars with later spectral type clearly decreases as the absolute Galactic height increases away from the Galactic plane. The results also show that at the same absolute Galactic height, the activity fractions in eclipsing binaries are higher than those in single stars. In this study, we present the activity-rotation relations for F-, G-, K-, and M-type variable stars. The results of analysis show that rapid rotators keep a saturated value, and the absolute value of the power-law index exhibits an increasing trend from F- to K-type stars in the unsaturated regime. Moreover, we confirm that the angular momentum and magnetic momentum are positively correlated, which indicates that the α-ω dynamo may be working. In addition, we confirmed the correlations among the Hα, Hβ, Hγ, Hδ, Ca II H&amp;K, and Ca II infrared triplet lines.

Keywords: Stellar rotation, Stellar chromospheres, Stellar activity
A DG-IMEX Method for Two-moment Neutrino Transport: Nonlinear Solvers for Neutrino-Matter Coupling. Neutrino-matter interactions play an important role in core-collapse supernova (CCSN) explosions, as they contribute to both lepton number and/or four-momentum exchange between neutrinos and matter and thus act as the agent for neutrino-driven explosions. Due to the multiscale nature of neutrino transport in CCSN simulations, an implicit treatment of neutrino-matter interactions is desired, which requires solutions of coupled nonlinear systems in each step of the time integration scheme. In this paper, we design and compare nonlinear iterative solvers for implicit systems with energy-coupling neutrino-matter interactions commonly used in CCSN simulations. Specifically, we consider electron neutrinos and antineutrinos, which interact with static matter configurations through the Bruenn 85 opacity set. The implicit systems arise from the discretization of a nonrelativistic two-moment model for neutrino transport, which employs the discontinuous Galerkin (DG) method for phase-space discretization and an implicit-explicit (IMEX) time integration scheme. In the context of this DG-IMEX scheme, we propose two approaches to formulate the nonlinear systems: a coupled approach and a nested approach. For each approach, the resulting systems are solved with Anderson-accelerated fixed-point iteration and Newton's method. The performance of these four iterative solvers has been compared on relaxation problems with various degrees of collisionality, as well as proto-neutron star deleptonization problems with several matter profiles adopted from spherically symmetric CCSN simulations. Numerical results suggest that the nested Anderson-accelerated fixed-point solver is more efficient than other tested solvers for solving implicit nonlinear systems with energy-coupling neutrino-matter interactions. * This manuscript has been authored in part by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. The DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

Keywords: Radiative transfer simulations, Computational methods, Supernova neutrinos, Core-collapse supernovae
The Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region (PHATTER). I. Ultraviolet to Infrared Photometry of 22 Million Stars in M33. We present panchromatic resolved stellar photometry for 22 million stars in the Local Group dwarf spiral Triangulum (M33), derived from Hubble Space Telescope observations with the Advanced Camera for Surveys in the optical (F475W, F814W), and the Wide Field Camera 3 in the near-ultraviolet (F275W, F336W) and near-infrared (F110W, F160W) bands. The large, contiguous survey area covers ∼14 square kpc and extends to 3.5 kpc (14', or 1.5-2 scale lengths) from the center of M33. The PHATTER observing strategy and photometry technique closely mimics that of Panchromatic Hubble Andromeda Treasury, but with updated photometry techniques that take full advantage of all overlapping pointings (aligned to within &lt;5-10 milliarcseconds) and improved treatment of spatially varying point-spread functions. The photometry reaches a completeness-limited depth of F475W∼28.5 in the lowest surface density regions observed in M33 and F475W∼26.5 in the most crowded regions found near the center of M33. We find the young populations trace several relatively tight arms, while the old populations show a clear, looser two-armed structure. We present extensive analysis of the data quality, including artificial star tests to quantify completeness, photometric uncertainties, and flux biases. This stellar catalog is the largest ever produced for M33, and is publicly available for download by the community.

Keywords: Local Group, Multi-color photometry, Stellar populations, Celestial objects catalogs, Triangulum Galaxy
Galactic O-type Stars in LAMOST Data. This paper reports 209 O-type stars found with LAMOST. All 135 new O-type stars discovered so far with LAMOST are given. Among them, 94 stars are first presented in this sample. There are 1 Iafpe star, 5 Onfp stars, 12 Oe stars, 1 Ofc stars, 3 ON stars, 16 double-lined spectroscopic binaries, and 33 single-lined spectroscopic binaries. All O-type stars are determined based on LAMOST low-resolution spectra (R ∼ 1800), with their LAMOST median-resolution spectra (R ∼ 7500) as supplements.

Keywords: O dwarf stars, O subgiant stars, Of stars, O stars, Oe stars, Spectroscopic binary stars, Spectroscopy, Oef stars, O giant stars, O supergiant stars
An Energy-conserving Integrator for Conservative Hamiltonian Systems with Ten-dimensional Phase Space. In this paper, an implicit nonsymplectic exact energy-preserving integrator is specifically designed for a ten-dimensional phase-space conservative Hamiltonian system with five degrees of freedom. It is based on a suitable discretization-averaging of the Hamiltonian gradient, with a second-order accuracy to numerical solutions. A one-dimensional disordered discrete nonlinear Schrödinger equation and a post-Newtonian Hamiltonian system of spinning compact binaries are taken as our two examples. We demonstrate numerically that the proposed algorithm exhibits good long-term performance in the preservation of energy, if roundoff errors are neglected. This result is independent of time steps, initial orbital eccentricities, and regular and chaotic orbital dynamical behavior. In particular, the application of appropriately large time steps to the new algorithm is helpful in reducing time-consuming and roundoff errors. This new method, combined with fast Lyapunov indicators, is well suited to studying the influence of some parameters or initial conditions related to chaos in the two example problems. It is found that chaos in the former system is mainly responsible for one of the parameters. In the latter problem, a combination of small initial separations and high initial eccentricities can easily induce chaos.

Keywords: Celestial mechanics, Black hole physics, Computational methods, Computational astronomy
Galaxy Clusters from the DESI Legacy Imaging Surveys. I. Cluster Detection. Based on the photometric redshift catalog of Zou et al., we apply a fast clustering algorithm to identify 540,432 galaxy clusters at z ≲ 1 in the DESI legacy imaging surveys, which cover a sky area of about 20,000 deg2. Monte Carlo simulations indicate that the false-detection rate of our detecting method is about 3.1%. The total masses of galaxy clusters are derived using a calibrated richness-mass relation that is based on the observations of X-ray emission and the Sunyaev and Zel'dovich effect. The median redshift and mass of our detected clusters are about 0.53 and 1.23 × 1014 M☉, respectively. Comparing with previous clusters identified using the data of the Sloan Digital Sky Survey; we can recognize most of them, especially those with high richness. Our catalog will be used for further statistical studies on galaxy clusters and environmental effects on galaxy evolution, etc.

Keywords: Galaxy clusters, Sky surveys, Photometry
Geometric Distances of Quasars Measured by Spectroastrometry and Reverberation Mapping: Monte Carlo Simulations. Recently, GRAVITY on board the Very Large Telescope Interferometer (VLTI) first spatially resolved the structure of the quasar 3C 273 with an unprecedented resolution of ∼10 μas. A new method of measuring parallax distances has been successfully applied to the quasar through joint analysis of spectroastrometry (SA) and reverberation mapping (RM) observation of its broad-line region (BLR). The uncertainty of this SA and RM (SARM) measurement is about 16% from real data, showing its great potential as a powerful tool for precision cosmology. In this paper, we carry out detailed analyses of mock data to study impacts of data qualities of SA observations on distance measurements and establish a quantitative relationship between statistical uncertainties of distances and relative errors of differential phases. We employ a circular disk model of the BLR for the SARM analysis. We show that SARM analyses of observations generally generate reliable quasar distances, even for relatively poor SA measurements with error bars of 40% at peaks of phases. Inclinations and opening angles of BLRs are the major parameters governing distance uncertainties. It is found that BLRs with inclinations ≳10° and opening angles ≲40° are the most reliable regimes from SARM analysis for distance measurements. Through analysis of a mock sample of AGNs generated by quasar luminosity functions, we find that if the GRAVITY/GRAVITY+ can achieve a phase error of 0°1 per baseline for targets with magnitudes K ≲ 11.5, the SARM campaign can constrain H0 to an uncertainty of 2% by observing 60 targets.

Keywords: Optical interferometry, Distance measure, Hubble constant, Reverberation mapping
Precise Ages of Field Stars from White Dwarf Companions in Gaia DR2. We analyze 4050 wide binary star systems involving a white dwarf (WD) and usually a main-sequence (MS) star, drawn from the large sample assembled by Tian et al. Using the modeling code BASE-9, we determine the system's ages, the WD progenitors' zero-age MS masses, the extinction values (AV), and the distance moduli. Discarding the cases with poor age convergences, we obtain ages for 3551 WDs, with a median age precision of στ/τ = 20%, and system ages typically in the range of 1-6 Gyr. We validated these ages against the very few known clusters and through cross validation of 236 WD-WD binaries. Under the assumption that the components are coeval in a binary system, this provides precise age constraints on the usually low-mass MS companions, mostly inaccessible by any other means.

Keywords: Bayesian statistics, Stellar ages, Initial mass function, Markov chain Monte Carlo, White dwarf stars, Zero-age main sequence stars, Field stars, Main sequence stars, Photometry, Wide binary stars, Stellar evolutionary tracks
Coupling a Global Heliospheric Magnetohydrodynamic Model to a Magnetofrictional Model of the Low Corona. Recent efforts coupling our Sun-to-Earth magnetohydrodynamics (MHD) model and lower-corona magnetofrictional (MF) model are described. Our Global Heliospheric MHD (GHM) model uses time-dependent three-component magnetic field data from the lower-corona MF model as time-dependent boundary values. The MF model uses data-assimilation techniques to introduce the vector magnetic field data from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager, hence as a whole this simulation coupling structure is driven with actual observations. The GHM model employs a newly developed interface boundary treatment that is based on the concept of characteristics, and it properly treats the interface boundary sphere set at a height of the sub-Alfvénic lower corona (1.15 R⊙ in this work). The coupled model framework numerically produces twisted nonpotential magnetic features and consequent eruption events in the solar corona in response to the time-dependent boundary values. The combination of our two originally independently developed models presented here is a model framework toward achieving further capabilities of modeling the nonlinear time-dependent nature of magnetic field and plasma, from small-scale solar active regions to large-scale solar wind structures. This work is a part of the Coronal Global Evolutionary Model project for enhancing our understanding of Sun-Earth physics to help improve space weather capabilities.

Keywords: Magnetohydrodynamics, Solar wind, Solar corona, Magnetohydrodynamical simulations
Exploring the Origin of Thick Disks Using the NewHorizon and Galactica Simulations. Ever since a thick disk was proposed to explain the vertical distribution of the Milky Way disk stars, its origin has been a recurrent question. We aim to answer this question by inspecting 19 disk galaxies with stellar mass greater than 1010 M⊙ in recent cosmological high-resolution zoom-in simulations: GALACTICA and NEWHORIZON. The thin and thick disks are reasonably reproduced by the simulations with scale heights and luminosity ratios as observed. We then spatially classify the thin and thick disks and find that the thick disk stars are older, metal-poorer, kinematically hotter, and higher in accreted star fraction, while both disks are dominated by the stars formed in situ. Half of the in situ stars in the thick disks are formed before the galaxies develop their disks, and the rest are formed in spatially and kinematically thinner disks and then thickened with time by heating. However, the 19 galaxies have various properties and evolutionary routes, highlighting the need for statistically large samples to draw general conclusions. We conclude from our simulations that the thin and thick disk components are not entirely distinct in terms of formation processes but rather markers of the evolution of galactic disks. Moreover, as the combined result of the thickening of the existing disk stars and the continued formation of young thin disk stars, the vertical distribution of stars does not change much after the disks settle, pointing to the modulation of both orbital diffusion and star formation by the same confounding factor: the proximity of galaxies to marginal stability.

Keywords: Galaxy formation
Molecular Clouds in the Second Quadrant of the Milky Way Midplane from l = 104°75 to l = 119°75 and b = -5°25 to b = 5°25. In this work, we study the properties of molecular clouds in the second quadrant of the Milky Way Midplane, from l = 104°75 to l = 119°75, and b = -5°25 to b = 5°25, using the 12CO, 13CO, and C18O J = 1 - 0 emission line data from the Milky Way Imaging Scroll Painting project. We identify 857 and 300 clouds in the 12CO and 13CO spectral cubes, respectively, using the DENDROGRAM + SCIMES algorithms. The distances of the molecular clouds are estimated, and physical properties such as the mass, size, and surface densities of the clouds are tabulated. The molecular clouds in the Perseus Arm are about 30-50 times more massive, and 4-6 times larger than the clouds in the Local Arm. This result, however, is likely to be biased by distance selection effects. The surface densities of the clouds are enhanced in the Perseus Arm, with an average value of ∼100 M⊙ pc-2. Here. we select the 40 most extended (&gt;0.35 arcdeg2) molecular clouds from the 12CO catalog to build the H2 column density probability distribution function (N-PDF). Some 78% of the N-PDFs of the selected molecular clouds are well fitted with log-normal functions with only small deviations at high densities, corresponding to star-forming regions with scales of ∼1-5 pc in the Local Arm, and ∼5-10 pc in the Perseus Arm. About 18% of the selected molecular clouds have power-law N-PDFs at high densities. In these molecular clouds, the majority of the regions fitted with the power law correspond to molecular clumps at sizes of ∼1 pc, or filaments at widths of ∼1 pc.

Keywords: Surveys, Molecular clouds, Star formation, Interstellar clouds, Interstellar medium
Biased Tracer Reconstruction with Halo Mass Information. Plenty of crucial information about our universe is encoded in the cosmic large-scale structure (LSS). However, extractions of this information are usually hindered by the nonlinearities of the LSS, which can be largely alleviated by various techniques known as reconstruction. In realistic applications, the efficiencies of these methods are always degraded by many limiting factors, a quite important one being the shot noise induced by the finite number density of biased matter tracers (i.e., luminous galaxies or dark matter halos) in observations. In this work, we explore the gains of biased tracer reconstruction achieved from halo mass information, which can suppress the shot-noise component and dramatically improves the cross-correlation between tracer field and dark matter. To this end, we first closely study the clustering biases and the stochasticity properties of halo fields with various number densities under different weighting schemes, i.e., the uniform, mass, and optimal weightings. Then, we apply the biased tracer reconstruction method to these different weighted halo fields and investigate how linear bias and observational mass scatter affect the reconstruction performance. Our results demonstrate that halo masses are critical information for significantly improving the performance of biased tracer reconstruction, indicating great application potential for substantially promoting the precision of cosmological measurements (especially for baryon acoustic oscillations) in ambitious ongoing and future galaxy surveys.

Keywords: Cosmology, Baryon acoustic oscillations, Large-scale structure of the universe
Improved Atomic Transition Probabilities for UV and Optical Lines of Hf II and Determination of the Hf Abundance in Two Metal-poor Stars. We report new branching fraction measurements for 199 UV and optical transitions of Hf II. These transitions range in wavelength (wavenumber) from 2068 to 6584 Å (48,322-15,183 cm-1) and originate in 17 odd-parity upper levels ranging in energy from 38,578 to 53,227 cm-1. The branching fractions are combined with radiative lifetimes reported in an earlier study to produce a set of transition probabilities and log(gf) values with accuracy ranging from 5% to 25%. Comparison is made to transition probabilities from the literature where such data exist. We use these new transition probabilities to derive improved Hf abundances in two metal-poor stars. HD 196944 is enhanced in s-process elements, and we derive log ɛ (Hf) = -0.72 ± 0.03 (σ = 0.09) from 12 Hf II lines. HD 222925 is enhanced in r-process elements, and we derive log ɛ (Hf) = 0.32 ± 0.03 (σ = 0.11) from 20 Hf II lines. These measurements greatly expand the number of potentially useful Hf II lines for analysis in UV and optical spectra. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under NASA contract NAS 5-26555. These observations are associated with programs GO-12554, GO-14765, and GO-15657. This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: Transition probabilities, Atomic spectroscopy, Laboratory astrophysics, Stellar abundances