Sazuna/UAT_keywords huggingface dataset:
Laboratory Data on the EUV/Soft-X-Ray Flux Problem of Fe XVIII and Fe XIX. Observations by the spacecraft Extreme Ultraviolet Explorer (EUVE), Far Ultraviolet Spectroscopic Explorer (FUSE), Chandra, and XMM-Newton of Capella (α Aurigae) have encountered problems with the relative intensities of the Fe XVIII and Fe XIX line emission in the soft-X-ray (XUV) and extreme-ultraviolet spectral ranges versus various model predictions based on theoretical atomic data. The reason may either lie in astrophysical phenomena, e.g., at emission or because of absorption by the interstellar medium, in the theoretical atomic data, in one or more spectrometer calibrations, or in the spectral modeling. By measurements using an electron beam ion trap we provide laboratory data obtained under conditions that are reasonably close to stellar emission regions. The laboratory data on Fe XVIII and Fe XIX show line ratios that are rather similar to the observations of Capella. The measurements, therefore, rule out astrophysical phenomena and calibration errors and point to issues with the modeling of the observed Capella emission.

Keywords: Line intensities, Atomic spectroscopy, Atomic data benchmarking
The Formation of C<SUB>3</SUB>O<SUB>3</SUB>H<SUB>6</SUB> Structural Isomers in the Gas Phase through Barrierless Pathways: Formation and Spectroscopic Characterization of Methoxy Acetic Acid. Gas phase formation processes feasible at low temperatures are determined theoretically for 38 isomers obeying the C3O3H6 empirical formula, one of them, the simplest ketose dihydroxyacetone, has been observed in gas phase sources. A preliminary search for isomeric forms first targets ethoxy formic acid (C2H5-O-COOH) as the most stable isomer followed by lactic acid. Profiles corresponding to the minimum energy pathways reveal that the favored conformers of 14 of these isomers can be formed in the gas phase through 29 barrierless processes involving the OH*, CH3O*, HCO*, CH3*, CH2OH, HCOO*, and OHCO* radicals, all of them observed in the interstellar medium. Kinetic rates are provided at 200, 298, and 500 K, confirming the suitability of 16 processes at low temperatures. Faster processes involve the OH hydroxyl radical whereas, to a lesser degree, the processes involving the HOCO radical and the methoxy methyl radical CH3O*, are quite significant. Spectroscopic parameters (rovibrational and torsional) are obtained for methoxy acetic acid (CH3-O-CH2COOH) for which two low-lying isoenergetic conformers can be produced from the CH3OCH2* radical predicted to be a precursor of abundant observed molecules. Profiles and spectroscopic properties make methoxy acetic acid a good candidate to be detected in the gas phase of extraterrestrial sources.

Keywords: Molecular physics, Molecular spectroscopy
EMPRESS. II. Highly Fe-enriched Metal-poor Galaxies with ∼1.0 (Fe/O)<SUB>⊙</SUB> and 0.02 (O/H)<SUB>⊙</SUB>: Possible Traces of Supermassive (&gt;300 M<SUB>⊙</SUB>) Stars in Early Galaxies. We present element abundance ratios and ionizing radiation of local young low-mass (∼106 M⊙) extremely metal-poor galaxies (EMPGs) with a 2% solar oxygen abundance (O/H)⊙ and a high specific star formation rate (sSFR ∼ 300 Gyr-1) and other (extremely) metal-poor galaxies, which are compiled from Extremely Metal-Poor Representatives Explored by the Subaru Survey (EMPRESS) and the literature. Weak emission lines such as [Fe III] λ4658 and He II λ4686 are detected in very deep optical spectra of the EMPGs taken with 8 m class telescopes, including Keck and Subaru, enabling us to derive element abundance ratios with photoionization models. We find that neon-to-oxygen and argon-to-oxygen ratios are comparable to those of known local dwarf galaxies and that the nitrogen-to-oxygen abundance ratios (N/O) are lower than 20% (N/O)⊙, consistent with the low oxygen abundance. However, the iron-to-oxygen abundance ratios (Fe/O) of the EMPGs are generally high; the EMPGs with the 2%-solar oxygen abundance show high Fe/O ratios of ∼90%-140% (Fe/O)⊙, which are unlikely to be explained by suggested scenarios of Type Ia supernova iron productions, iron's dust depletion, and metal-poor gas inflow onto previously metal-riched galaxies with solar abundances. Moreover, the EMPGs with the 2%-solar oxygen abundance have very high He II λ4686/Hβ ratios of ∼1/40, which are not reproduced by existing models of high-mass X-ray binaries with progenitor stellar masses &lt;120 M⊙. Comparing stellar-nucleosynthesis and photoionization models with a comprehensive sample of EMPGs identified by this and previous EMPG studies, we propose that both the high Fe/O ratios and the high He II λ4686/Hβ ratios are explained by the past existence of supermassive (&gt;300 M⊙) stars, which may evolve into intermediate-mass black holes (≳100 M⊙). * Partly based on data obtained with the Subaru Telescope. The Subaru Telescope is operated by the National Astronomical Observatory of Japan. † The data presented herein were partly obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. ‡ This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: Black holes, Galaxy chemical evolution, Massive stars, Emission line galaxies, Galaxy evolution, Interstellar medium, Metallicity
Chemical Tagging N-rich Field Stars with High-resolution Spectroscopy. We measure chemical abundances for over 20 elements of 15 N-rich field stars with high-resolution (R ∼ 30,000) optical spectra. We find that Na, Mg, Al, Si, and Ca abundances of our N-rich field stars are mostly consistent with those of stars from globular clusters (GCs). Seven stars are estimated to have [Al/Fe ] &gt; 0.5, which is not found in most GC "first generation" stars. On the other hand, α element abundances (especially Ti) could show distinguishable differences between in situ stars and accreted stars. We discover that one interesting star, with consistently low [Mg/Fe], [Si/Fe], [Ca/Fe], [Ti/Fe], [Sc/Fe], [V/Fe], and [Co/Fe], show similar kinematics and [Ba/Eu] as other stars from the dissolved dwarf galaxy "Gaia-Sausage-Enceladus." The α-element abundances and the iron-peak element abundances of the N-rich field stars with metallicities - 1.25 ≤ [Fe/H] ≤ - 0.95 show consistent values with Milky Way field stars (we refer to Milky Way field stars as Milky Way halo field stars unless otherwise specified in this paper) rather than stars from dwarf galaxies, indicating that they were formed in situ. In addition, the neutron-capture elements of N-rich field stars show that most of them could be enriched by asymptotic giant branch stars with masses around 3-5 M⊙.

Keywords: Stellar abundances, Chemically peculiar stars, Stellar evolution
The Reconstruction of Dark Energy with the Ridge Regression Approach. Whether or not dark energy evolves with time may be determined by the nonparametric method. In order to avoid instability of the derivative for the functional data, we linearize the luminosity-distance integral formula in near-flat space by adopting Lagrange interpolation for the numerical integral, and proposing a method of combining principal component analysis (PCA) and biased estimation on the basis of ridge regression analysis to reconstruct the regression parameters. We also present a principal component selection criterion to better distinguish between ΛCDM and w(z) ≠ -1 models by reconstruction. We define the type I error as the situation where wtrue = -1 but wrecon ≠ -1, and the type II error as the situation where wtrue ≠ -1 but wrecon = -1; we use the various w(z) functions to test the method. The preliminary test results demonstrate that the PCA-biased method can be used to determine the most probable behavior of w(z). Finally, we apply this method to recent supernova measurements, reconstructing the continuous history of w(z) out to redshift z = 1.5.

Keywords: Cosmology, Dark energy
Model-independent Constraints on Ultralight Dark Matter from the SPARC Data. Ultralight dark matter (ULDM) is currently one of the most popular classes of cosmological dark matter. The most important advantage is that ULDM with mass m ∼ 10-22 eV can account for the small-scale problems encountered in the standard cold dark matter model like the core-cusp problem, missing satellite problem, and the too-big-to-fail problem in galaxies. In this paper, we formulate a new simple model-independent analysis using the Spitzer Photometry and Accurate Rotation Curves data to constrain the range of ULDM mass. In particular, the most stringent constraint comes from the data of a galaxy ESO563-G021, which can conservatively exclude a ULDM mass range m = (0.14-3.11) × 10-22 eV. This model-independent excluded range is consistent with many bounds obtained by recent studies and it suggests that the ULDM proposal may not be able to alleviate the small-scale problems.

Keywords: Spiral galaxies, Dark matter, Particle astrophysics
Signatures of r-process Elements in Kilonova Spectra. Binary neutron star (NS) mergers have been expected to synthesize r-process elements and emit radioactively powered radiation, called kilonovae. Although r-process nucleosynthesis was confirmed by the observations of GW170817/AT2017gfo, no trace of individual elements has been identified except for strontium. In this paper, we perform systematic calculations of line strength for bound-bound transitions and radiative transfer simulations in NS merger ejecta toward element identification in kilonova spectra. We find that Sr II triplet lines appear in the spectrum of a lanthanide-poor model, which is consistent with the absorption feature observed in GW170817/AT2017gfo. The synthetic spectrum also shows the strong Ca II triplet lines. This is natural because Ca and Sr are coproduced in the material with relatively high electron fraction and their ions have similar atomic structures with only one s-electron in the outermost shell. The line strength, however, highly depends on the abundance distribution and temperature in the ejecta. For our lanthanide-rich model, the spectra show the features of doubly ionized heavy elements, such as Ce, Tb, and Th. Our results suggest that the line-forming region of GW170817/AT2017gfo was lanthanide-poor. We show that the Sr II and Ca II lines can be used as a probe of physical conditions in NS merger ejecta. Absence of the Ca II line features in GW170817/AT2017gfo implies that the Ca/Sr ratio is &lt;0.002 in mass fraction, which is consistent with nucleosynthesis for electron fraction ≥0.40 and entropy per nucleon (in units of Boltzmann constant) ≥25.

Keywords: Neutron stars, Radiative transfer simulations, R-process, Transient sources
Constraints on the Maximum Mass of Neutron Stars with a Quark Core from GW170817 and NICER PSR J0030+0451 Data. We perform a Bayesian analysis of the maximum mass MTOV of neutron stars with a quark core, incorporating the observational data from tidal deformability of the GW170817 binary neutron star merger as detected by LIGO/Virgo and the mass and radius of PSR J0030+0451 as detected by the Neutron Star Interior Composition Explorer. The analysis is performed under the assumption that the hadron-quark phase transition is of first order, where the low-density hadronic matter described in a unified manner by the soft QMF or the stiff DD2 equation of state (EOS) transforms into a high-density phase of quark matter modeled by the generic "constant-sound-speed" parameterization. The mass distribution measured for the 2.14 M⊙ pulsar MSP J0740+6620 is used as the lower limit on MTOV. We find the most probable values of the hybrid star maximum mass are ${M}_{\mathrm{TOV}}={2.36}_{-0.26}^{+0.49}\,{\text{}}{M}_{\odot }$ ( ${2.39}_{-0.28}^{+0.47}\,{\text{}}{M}_{\odot }$ ) for QMF (DD2), with an absolute upper bound around 2.85 M⊙, to the 90% posterior credible level. Such results appear robust with respect to the uncertainties in the hadronic EOS. We also discuss astrophysical implications of this result, especially on the postmerger product of GW170817, short gamma-ray bursts, and other likely binary neutron star mergers.

Keywords: Neutron stars, Gamma-ray bursts, Neutron star cores, Gravitational waves
The Observational Uncertainty of Coronal Hole Boundaries in Automated Detection Schemes. Coronal holes are the observational manifestation of the solar magnetic field open to the heliosphere and are of pivotal importance for our understanding of the origin and acceleration of the solar wind. Observations from space missions such as the Solar Dynamics Observatory now allow us to study coronal holes in unprecedented detail. Instrumental effects and other factors, however, pose a challenge to automatically detect coronal holes in solar imagery. The science community addresses these challenges with different detection schemes. Until now, little attention has been paid to assessing the disagreement between these schemes. In this COSPAR ISWAT initiative, we present a comparison of nine automated detection schemes widely applied in solar and space science. We study, specifically, a prevailing coronal hole observed by the Atmospheric Imaging Assembly instrument on 2018 May 30. Our results indicate that the choice of detection scheme has a significant effect on the location of the coronal hole boundary. Physical properties in coronal holes such as the area, mean intensity, and mean magnetic field strength vary by a factor of up to 4.5 between the maximum and minimum values. We conclude that our findings are relevant for coronal hole research from the past decade, and are therefore of interest to the solar and space research community.

Keywords: Solar magnetic flux emergence, Solar extreme ultraviolet emission, Space weather, Solar wind, Solar physics, Solar magnetic fields, Solar coronal holes
Magnetic Fields in Massive Star-forming Regions (MagMaR). I. Linear Polarized Imaging of the Ultracompact H II Region G5.89-0.39. We report 1.2 mm polarized continuum emission observations carried out with the Atacama Large Millimeter/submillimeter Array toward the high-mass star formation region G5.89-0.39. The observations show a prominent 0.2 pc north-south filamentary structure. The ultracompact H II region in G5.89-0.39 breaks the filament into two pieces. Its millimeter emission shows a dusty belt with a mass of 55-115 M⊙ and 4500 au in radius, surrounding an inner part comprising mostly ionized gas, with dust emission only accounting for about 30% of the total millimeter emission. We also found a lattice of convex arches that may be produced by dragged dust and gas from the explosive dispersal event involving the O5 Feldt's star. The north-south filament has a mass between 300 and 600 M⊙ and harbors a cluster of about 20 mm envelopes with a median size and mass of 1700 au and 1.5 M⊙, respectively, some of which are already forming protostars. We interpret the polarized emission in the filament as mainly coming from magnetically aligned dust grains. The polarization fraction is ∼4.4% in the filaments and 2.1% at the shell. The magnetic fields are along the North Filament and perpendicular to the South Filament. In the Central Shell, the magnetic fields are roughly radial in a ring surrounding the dusty belt between 4500 and 7500 au, similar to the pattern recently found in the surroundings of Orion BN/KL. This may be an independent observational signpost of explosive dispersal outflows and should be further investigated in other regions.

Keywords: Interstellar magnetic fields, Star formation, Dust continuum emission, Protostars, Polarimetry
The Mass and Age Distribution of Halo White Dwarfs in the Canada-France Imaging Survey. We present optical spectroscopy for 18 halo white dwarfs identified using photometry from the Canada-France Imaging Survey and Pan-STARRS1 DR1 3π survey combined with astrometry from Gaia DR2. The sample contains 13 DA, 1 DZ, 2 DC, and 2 potentially exotic types of white dwarf. We fit both the spectrum and the spectral energy distribution in order to obtain the temperature and surface gravity, which we then convert into mass and then age using stellar isochrones and the initial-to-final mass relation. We find a large spread in ages that is not consistent with expected formation scenarios for the Galactic halo. We find a mean age of ${9.03}_{-2.03}^{+2.13}$ Gyr and a dispersion of ${4.21}_{-1.58}^{+2.33}$ Gyr for the inner halo using a maximum-likelihood method. This result suggests an extended star formation history within the local halo population.

Keywords: White dwarf stars, DZ stars, DA stars
The Onset of Chaos in Permanently Deformed Binaries from Spin-Orbit and Spin-Spin Coupling. Permanently deformed objects in binary systems can experience complex rotation evolution, arising from the extensively studied effect of spin-orbit coupling as well as more nuanced dynamics arising from spin-spin interactions. The ability of an object to sustain an aspheroidal shape largely determines whether or not it will exhibit nontrivial rotational behavior. In this work, we adopt a simplified model of a gravitationally interacting primary and satellite pair, where each body's quadrupole moment is approximated by two diametrically opposed point masses. After calculating the net gravitational torque on the satellite from the primary, as well as the associated equations of motion, we employ a Hamiltonian formalism that allows for a perturbative treatment of the spin-orbit and retrograde and prograde spin-spin coupling states. By analyzing the resonances individually and collectively, we determine the criteria for resonance overlap and the onset of chaos, as a function of orbital and geometric properties of the binary. We extend the 2D planar geometry to calculate the obliquity evolution. This calculation indicates that satellites in spin-spin resonances undergo precession when inclined out of the plane, but they do not tumble. We apply our resonance overlap criteria to the contact binary system (216) Kleopatra, and find that its satellites, Cleoselene and Alexhelios, may plausibly be exhibiting chaotic rotational dynamics from the overlap of the spin-orbit and retrograde spin-spin resonances. While this model is, by construction, generalizable to any binary system, it will be particularly useful for studies of small bodies in the Solar System, whose irregular shapes make them ideal candidates for exotic rotational states.

Keywords: Astrodynamics, Asteroids, Trans-Neptunian objects
Photometric Classifications of Evolved Massive Stars: Preparing for the Era of Webb and Roman with Machine Learning. In the coming years, next-generation space-based infrared observatories will significantly increase our samples of rare massive stars, representing a tremendous opportunity to leverage modern statistical tools and methods to test massive stellar evolution in entirely new environments. Such work is only possible if the observed objects can be reliably classified. Spectroscopic observations are infeasible with more distant targets, and so we wish to determine whether machine-learning methods can classify massive stars using broadband infrared photometry. We find that a Support Vector Machine classifier is capable of coarsely classifying massive stars with labels corresponding to hot, cool, and emission-line stars with high accuracy, while rejecting contaminating low-mass giants. Remarkably, 76% of emission-line stars can be recovered without the need for narrowband or spectroscopic observations. We classify a sample of ∼2500 objects with no existing labels and identify 14 candidate emission-line objects. Unfortunately, despite the high precision of the photometry in our sample, the heterogeneous origins of the labels for the stars in our sample severely inhibit our classifier from distinguishing classes of stars with more granularity. Ultimately, no large and homogeneously labeled sample of massive stars currently exists. Without significant efforts to robustly classify evolved massive stars—which is feasible given existing data from large all-sky spectroscopic surveys—shortcomings in the labeling of existing data sets will hinder efforts to leverage the next generation of space observatories.

Keywords: Emission line stars, Massive stars, Stellar classification, Support vector machine, Infrared photometry
Evidence of Wind Signatures in the Gas Velocity Profiles of Red Geysers. Spatially resolved spectroscopy from the Sloan Digital Sky Survey IV Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey has revealed a class of quiescent, relatively common early-type galaxies termed "red geysers" that possibly host large-scale active galactic nuclei-driven winds. Given their potential importance in maintaining a low level of star formation at late times, additional evidence confirming that winds are responsible for the red geyser phenomenon is critical. In this work, we present follow-up observations with the Echellette Spectrograph and Imager (ESI) at the Keck telescope of two red geysers (z &lt; 0.1) using multiple long slit positions to sample different regions of each galaxy. Our ESI data with a spectral resolution (R) ∼ 8000 improve upon MaNGA's resolution by a factor of 4, allowing us to resolve the ionized gas velocity profiles along the putative wind cone with an instrumental resolution of σ = 16 km s-1. The line profiles of Hα and [N II] λ6584 show asymmetric shapes that depend systematically on location: extended blue wings on the redshifted side of the galaxy and red wings on the opposite side. We construct a simple wind model and show that our results are consistent with geometric projections through an outflowing conical wind oriented at an angle toward the line of sight. An alternative hypothesis that assigns the asymmetric pattern to "beam smearing" of a rotating, ionized gas disk does a poor job matching the line asymmetry profiles. While our study features just two sources, it lends further support to the notion that red geysers are the result of galaxy-scale winds.

Keywords: AGN host galaxies, Galactic winds, Quenched galaxies, Early-type galaxies, Emission line galaxies, LINER galaxies, Elliptical galaxies, Galaxies
Stellar, Gas, and Dust Emission of Star-forming Galaxies out to z ∼ 2. While dust is a major player in galaxy evolution, its relationship with gas and stellar radiation in the early universe is still not well understood. We combine 3D-Hubble Space Telescope emission-line fluxes with far-UV through far-IR photometry in a sample of 669 emission-line galaxies (ELGs) between 1.2 &lt; z &lt; 1.9 and use the MCSED spectral energy distribution fitting code to constrain the galaxies' physical parameters, such as their star formation rates (SFRs), stellar masses, and dust masses. We find that the assumption of energy balance between dust attenuation and emission is likely unreasonable in many cases. We highlight a relationship between the mass-specific SFR, stellar mass, and dust mass, although its exact form is still unclear. Finally, a stacking of Hα and Hβ fluxes shows that nebular attenuation increases with stellar mass and SFR for IR-bright ELGs.

Keywords: Interstellar dust, Star formation, Spectral energy distribution, Galaxy evolution, High-redshift galaxies