Sazuna/UAT_keywords huggingface dataset:
CHIMERA: A Massively Parallel Code for Core-collapse Supernova Simulations. We provide a detailed description of the CHIMERA code, a code developed to model core collapse supernovae (CCSNe) in multiple spatial dimensions. The CCSN explosion mechanism remains the subject of intense research. Progress to date demonstrates that it involves a complex interplay of neutrino production, transport, and interaction in the stellar core, three-dimensional stellar core fluid dynamics and its associated instabilities, nuclear burning, and the fundamental physics of the neutrino-stellar core weak interactions and the equations of state of all stellar core constituents—particularly, the nuclear equation of state associated with core nucleons, both free and bound in nuclei. CHIMERA, by incorporating detailed neutrino transport, realistic neutrino-matter interactions, three-dimensional hydrodynamics, realistic nuclear, leptonic, and photonic equations of state, and a nuclear reaction network, along with other refinements, can be used to study the role of neutrino radiation, hydrodynamic instabilities, and a variety of input physics in the explosion mechanism itself. It can also be used to compute observables such as neutrino signatures, gravitational radiation, and the products of nucleosynthesis associated with CCSNe. The code contains modules for neutrino transport, multidimensional compressible hydrodynamics, nuclear reactions, a variety of neutrino interactions, equations of state, and modules to provide data for post-processing observables such as the products of nucleosynthesis, and gravitational radiation. CHIMERA is an evolving code, being updated periodically with improved input physics and numerical refinements. We detail here the current version of the code, from which future improvements will stem, which can in turn be described as needed in future publications.

Keywords: Hydrodynamical simulations, Supernova neutrinos, Core-collapse supernovae, Nucleosynthesis, Reaction rates, Computational methods, Radiative transfer simulations
A Multistate Low-dissipation Advection Upstream Splitting Method for Ideal Magnetohydrodynamics. We develop a new numerical scheme for ideal magnetohydrodynamic (MHD) simulations, which is robust against one- and multidimensional shocks, and is accurate for low Mach number flows and discontinuities. The scheme belongs to a family of the advection upstream splitting method employed in computational aerodynamics, and it splits the inviscid flux in MHD equations into advection, pressure, and magnetic tension parts, and then individually evaluates mass, pressure, and magnetic tension fluxes at the interface of a computational cell. The mass flux is designed to avoid numerical shock instability in multidimensions, while preserving contact discontinuity. The pressure flux possesses a proper scaling for low Mach number flows, allowing reliable simulations of nearly incompressible flows. The magnetic tension flux is built to be consistent with the HLLD approximate Riemann solver to preserve rotational discontinuity. We demonstrate various benchmark tests to verify the novel performance of the scheme. Our results indicate that the scheme must be a promising tool to tackle astrophysical systems that include both low and high Mach number flows, as well as magnetic field inhomogeneities.

Keywords: Shocks, Magnetic fields, Magnetohydrodynamical simulations
Energy Level Structure and Transition Data of Er<SUP>2+</SUP>. A majority of Er in the universe is synthesized by the r-process, which can occur in the mergers of neutron stars (NSs). The contribution of this element to the opacity of NS ejecta should be tested, but even the energy levels of first excited configuration have not been fully presented. The main aim of this paper is to present accurate energy levels of the ground [Xe]4f12 and first excited [Xe]4f115d configurations of Er2+. The energy level structure of the Er2+ ion was computed using the multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction (RCI) methods, as implemented in the GRASP2018 program package. The Breit interaction, self-energy, and vacuum polarization corrections were included in the RCI computations. The zero-first-order approach was used in the computations. Energy levels with the identification in LS coupling for all (399) states belonging to the [Xe]4f12 and [Xe]4f115d configurations are presented. Electric dipole (E1) transition data between the levels of these two configurations are computed. The accuracy of these data is evaluated by studying the behavior of the transition rates as functions of the gauge parameter, as well as by evaluating the cancellation factors. The core electron correlations were studied using different strategies. The rms deviations obtained in this study for states of the ground and excited configurations from the available experimental data are 649 and 754 cm-1, respectively.

Keywords: Neutron stars, Stellar atmospheric opacity, Atomic spectroscopy, Radiative transfer, Transition probabilities, Chemically peculiar stars
Prediction of the Dst Index with Bagging Ensemble-learning Algorithm. The Dst index is a commonly geomagnetic index used to measure the strength of geomagnetic activity. The accurate prediction of the Dst index is one of the main subjects of space weather studies. In this study, we use the Bagging ensemble-learning algorithm, which combines three algorithms—the artificial neural network, support vector regression, and long short-term memory network—to predict the Dst index 1-6 hr in advance. Taking solar wind parameters (including the interplanetary total magnetic field, magnetic field Bz component, total electric field, solar wind speed, plasma temperature, and proton pressure) as inputs, we establish the Dst index models and complete not only the point prediction but also the interval prediction in forecasting the Dst index. The results show that the root mean square error (rmse) of the point prediction is always lower than 8.0936 nT, the correlation coefficient (R) is always higher than 0.8572 and the accuracy of interval prediction is always higher than 90%, implying that our model can improve the accuracy of point prediction and significantly promote the accuracy of interval prediction. In addition, an new proposed metric shows that the Bagging algorithm brings better stability to the model. Our model was also used to predicate a magnetic storm event from 2016 October 12-17. The most accurate prediction of this storm event is the 1 hr ahead prediction, which holds a result with the rmse of 3.7327 nT, the correlation coefficient of 0.9928, and the interval prediction accuracy of 96.69%. Moreover, we also discuss the balance in the Bagging ensemble model in this paper.

Keywords: Planetary magnetospheres, Space weather, Solar wind, Geomagnetic fields
Searching for Molecular Outflows with Support Vector Machines: The Dark Cloud Complex in Cygnus. We present a survey of molecular outflows across the dark cloud complex in the Cygnus region, based on a 46.75 deg2 field of CO isotopologue data from the Milky Way Imaging Scroll Painting survey. A supervised machine-learning algorithm, the support vector machine, is introduced to accelerate our visual assessment of outflow features in the data cube of 12CO and 13CO J = 1-0 emission. A total of 130 outflow candidates are identified, 77 of which show bipolar structures and 118 are new detections. Spatially, these outflows are located inside dense molecular clouds, and some of them are found in clusters or in elongated linear structures tracing the underlying gas filament morphology. Along the line of sight, 97, 31, and 2 candidates reside in the Local, Perseus, and Outer Arms, respectively. Young stellar objects as outflow drivers are found near most outflows, while 36 candidates show no associated source. The clusters of outflows that we detect are inhomogeneous in their properties; nevertheless, we show that the outflows cannot inject turbulent energy on cloud scales. Instead, at best, they are restricted to affecting the so-called "clump" and "core" scales, and only on short (∼0.3 Myr) estimated timescales. Combined with outflow samples in the literature, our work shows a tight outflow mass-size correlation.

Keywords: Stellar jets, Astronomical object identification, Molecular clouds
Evolutionary Models for 43 Galactic Supernova Remnants with Distances and X-Ray Spectra. The X-ray emission from a supernova remnant (SNR) is a powerful diagnostic of the state of the shocked plasma. The temperature (kT) and the emission measure (EM) of the shocked gas are related to the energy of the explosion, the age of the SNR, and the density of the surrounding medium. Progress in X-ray observations of SNRs has resulted in a significant sample of Galactic SNRs with measured kT and EM values. We apply spherically symmetric SNR evolution models to a new set of 43 SNRs to estimate ages, explosion energies, and circumstellar medium densities. The distribution of ages yields an SNR birth rate. The energies and densities are well fit with lognormal distributions, with wide dispersions. SNRs with two emission components are used to distinguish between SNR models with uniform interstellar medium and with stellar wind environment. We find Type Ia SNRs to be consistent with a stellar wind environment. Inclusion of stellar wind SNR models has a significant effect on estimated lifetimes and explosion energies of SNRs. This reduces the discrepancy between the estimated SNR birth rate and the SN rate of the Galaxy.

Keywords: Supernova remnants
Extended Calculations of Energy Levels and Transition Rates for Singly Ionized Lanthanide Elements. I. Pr-Gd. Lanthanide elements play important roles as an opacity source in the ejected material from neutron star mergers. Accurate and complete atomic data are necessary to evaluate the opacities and to analyze the observed data. In this paper, we perform extended, ab initio atomic calculations from Pr II (Z = 59) to Gd II (Z = 64). By using multiconfiguration Dirac-Hartree-Fock and relativistic configuration-interaction methods, implemented in the general-purpose relativistic atomic structure package (GRASP2K), we calculate the energy levels and transition data of electric dipole transitions. These computations are based on strategies (with small variations) of Nd II published by Gaigalas et al. Accuracy of data is evaluated by comparing computed energy levels with the National Institute of Standards and Technology (NIST) database or other works. For the energy levels, we obtain the average relative accuracy of 8%, 12%, 6%, 8%, and 7% for Pr II, Pm II, Sm II, Eu II, and Gd II ions, respectively, as compared with the NIST data. Accuracy of energy transfer to the wavelength is 3%, 14%, and 11% for Pr II, Eu II, and Gd II. Our computed E1 type transition probabilities are in good agreement with experimental values presented by other authors especially for strong transitions.

Keywords: Neutron stars, R-process, Gravitational wave sources, Atomic spectroscopy, Transition probabilities
44 GHz Methanol Masers: Observations toward 95 GHz Methanol Masers. We report a simultaneous 44 and 95 GHz class I methanol maser survey toward 144 sources from the 95 GHz class I methanol maser catalog. The observations were made with the three telescopes of the Korean very long baseline interferometry network operating in single-dish mode. The detection rates are 89% at 44 GHz and 77% at 95 GHz. There are 106 new discoveries at 44 GHz. Comparing the previous 95 GHz detections with new observations of the same transitions made using the Purple Mountain Observatory 13.7 m radio telescope shows no clear evidence of variability on a timescale of six years. Emission from the 44 and 95 GHz transitions shows strong correlations in peak velocity, peak flux density, and integrated flux density, indicating that they are likely cospatial. We found that the peak flux density ratio ${S}_{\mathrm{pk},95}$ / ${S}_{\mathrm{pk},44}$ decreases as the 44 GHz peak flux density increases. We found that some class I methanol masers in our sample might be associated with infrared dark clouds, while others are associated with H II regions, indicating that some sources occur at an early stage of high-mass star formation, while others are located toward more evolved sources.

Keywords: Interstellar molecules, Star formation, Radio sources, Interstellar masers
Chemical Composition of Bright Stars in the Continuous Viewing Zone of the TESS Space Mission. Accurate atmospheric parameters and chemical composition of stars play a vital role in characterizing physical parameters of exoplanetary systems and understanding of their formation. A full asteroseismic characterization of a star is also possible if its main atmospheric parameters are known. The NASA Transiting Exoplanet Survey Satellite (TESS) space telescope will play a very important role in searching of exoplanets around bright stars and stellar asteroseismic variability research. We have observed all 302 bright (V &lt; 8 mag) and cooler than F5 spectral class stars in the northern TESS continuous viewing zone with a 1.65 m telescope at the Molėtai Astronomical Observatory of Vilnius University and the high-resolution Vilnius University Echelle Spectrograph. We uniformly determined the main atmospheric parameters, ages, orbital parameters, velocity components, and precise abundances of 24 chemical species (C(C2), N(CN), [O I], Na I, Mg I, Al I, Si I, Si II, Ca I, Ca II, Sc I, Sc II, Ti I, Ti II, V I, Cr I, Cr II, Mn I, Fe I, Fe II, Co I, Ni I, Cu I, and Zn I) for 277 slowly rotating single stars in the field. About 83% of the sample stars exhibit the Mg/Si ratios greater than 1.0 and may potentially harbor rocky planets in their systems.

Keywords: High resolution spectroscopy, Chemical abundances, Catalogs
Morpheus: A Deep Learning Framework for the Pixel-level Analysis of Astronomical Image Data. We present Morpheus, a new model for generating pixel-level morphological classifications of astronomical sources. Morpheus leverages advances in deep learning to perform source detection, source segmentation, and morphological classification pixel-by-pixel via a semantic segmentation algorithm adopted from the field of computer vision. By utilizing morphological information about the flux of real astronomical sources during object detection, Morpheus shows resiliency to false-positive identifications of sources. We evaluate Morpheus by performing source detection, source segmentation, morphological classification on the Hubble Space Telescope data in the five CANDELS fields with a focus on the GOODS South field, and demonstrate a high completeness in recovering known GOODS South 3D-HST sources with H &lt; 26 AB. We release the code publicly, provide online demonstrations, and present an interactive visualization of the Morpheus results in GOODS South.

Keywords: Convolutional neural networks, Galaxy classification systems, Computational methods, Extragalactic astronomy, GPU computing, Galaxies
Revisiting the Relationship between the Long GRB Rate and Cosmic Star Formation History Based on a Large Swift Sample. The exact relationship between the long gamma-ray burst (LGRB) rate and the cosmic star formation rate (CSFR) is essential for using LGRBs as cosmological probes. In this work, we collect a large sample composed of 371 Swift LGRBs with known redshifts and prompt emission properties. We first compare the rest-frame prompt properties of these bursts in different redshift bins, finding negligible redshift evolution of the luminosity of LGRBs with ${L}_{\mathrm{iso}}\gtrsim {10}^{51}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ between z ∼ 1 and z ∼ 4. Then, by utilizing the CSFR obtained from the large-scale cosmological hydrodynamical simulation, the Illustris simulation, we calculate the cumulative redshift distribution of LGRBs under different metallicity thresholds. After comparing with our sample, we find that the predictions with a moderate threshold between $0.3\,{Z}_{\odot }\leqslant {Z}_{\mathrm{th}}\leqslant 1.0\,{Z}_{\odot }$ are consistent with the sample between redshift 0 &lt; z &lt; 3, while at higher redshifts, between 3 &lt; z &lt; 5, all metallicity thresholds fit the data well. When changing to an empirical model based on observations, the predictions show similar results as well. After comparing with the metallicity distribution of the observed LGRB host galaxies between 0 &lt; z &lt; 1, we confirm that the production of LGRBs in galaxies with super-solar metallicity is suppressed. Nevertheless, considering that a significant fraction of stars are born in sub-solar metallicity environments at z ≳ 3, we suggest that, as a first approximation, LGRBs can be used as direct tracers of the CSFR in this redshift range.

Keywords: Gamma-ray bursts, Star formation, Galaxy chemical evolution
On the Physical Association of Fermi-LAT Blazars with Their Low-energy Counterparts. Associating γ-ray sources to their low-energy counterparts is one of the major challenges of modern γ-ray astronomy. In the context of the Fourth Fermi Large Area Telescope Source Catalog (4FGL), the associations rely mainly on parameters such as apparent magnitude, integrated flux, and angular separation between the γ-ray source and its low-energy candidate counterpart. In this work, we propose a new use of the likelihood ratio (LR) and a complementary supervised learning technique to associate γ-ray blazars in 4FGL, based only on spectral parameters such as the γ-ray photon index, mid-infrared colors, and radio-loudness. In the LR approach, we crossmatch the Wide-field Infrared Survey Explorer Blazar-Like Radio-Loud Sources catalog with 4FGL and compare the resulting candidate counterparts with the sources listed in the γ-ray blazar locus to compute an association probability (AP) for 1138 counterparts. In the supervised learning approach, we train a random forest algorithm with 869 high-confidence blazar associations and 711 fake associations and then compute an AP for 1311 candidate counterparts. A list with all 4FGL blazar candidates of uncertain type associated by our method is provided to guide future optical spectroscopic follow-up observations.

Keywords: Gamma-ray astronomy, Active galactic nuclei, Astronomical methods
The MUSTANG Galactic Plane Survey (MGPS90) Pilot. We report the results of a pilot program for a Green Bank Telescope MUSTANG-2 Galactic Plane survey at 3 mm (90 GHz), MGPS90. The survey achieves a typical 1σ depth of 1-2 mJy beam-1 with a 9″ beam. We describe the survey parameters, quality assessment process, cataloging, and comparison with other data sets. We have identified 709 sources over seven observed fields selecting some of the most prominent millimeter-bright regions between 0 deg &lt; ℓ &lt; 50 deg (total area ≍7.5 deg 2). The majority of these sources have counterparts at other wavelengths. By applying flux selection criteria to these sources, we successfully recovered several known hypercompact H II (HCH II) regions but did not confirm any new ones. We identify 126 sources that have mm-wavelength counterparts but do not have cm-wavelength counterparts and are therefore candidate HCH II regions; of these, 10 are morphologically compact and are strong candidates for new HCH II regions. Given the limited number of candidates in the extended area in this survey compared to the relatively large numbers seen in protoclusters W51 and W49, it appears that most HCH II regions exist within dense protoclusters. Comparing the counts of HCH II to ultracompact H II (UCH II) regions, we infer the HCH II region lifetime is 16%-46% that of the UCH II region lifetime. We additionally separated the 3 mm emission into dust and free-free emission by comparing with archival 870 $\mu {\rm{m}}$ and 20 cm data. In the selected pilot fields, most (≳80%) of the 3 mm emission comes from plasma, either through free-free or synchrotron emission.

Keywords: Interstellar dust, Surveys, Star forming regions, Star formation, Dust continuum emission, H II regions
The Star Formation in Radio Survey: 3-33 GHz Imaging of Nearby Galaxy Nuclei and Extranuclear Star-forming Regions. We present 3, 15, and 33 GHz imaging toward galaxy nuclei and extranuclear star-forming regions using the Karl G. Jansky Very Large Array as part of the Star Formation in Radio Survey. With 3-33 GHz radio spectra, we measured the spectral indices and corresponding thermal (free-free) emission fractions for a sample of 335 discrete regions having significant detections in at least two radio bands. After removing 14 likely background galaxies, we find that the median thermal fraction at 33 GHz is 92% ± 0.8% with a median absolute deviation of 11%, when a two-component power-law model is adopted to fit the radio spectrum. Limiting the sample to 238 sources that are confidently identified as star-forming regions and not affected by potential AGN contamination (i.e., having galactocentric radii rG ≥ 250 pc) results in a median thermal fraction of 93% ± 0.8% with a median absolute deviation of 10%. We further measure the thermal fraction at 33 GHz for 163 regions identified at 7″ resolution to be 94% ± 0.8% with a median absolute deviation of 8%. Together, these results confirm that free-free emission dominates the radio spectra of star-forming regions on scales up to ∼500 pc in normal star-forming galaxies. We additionally find a factor of ∼1.6 increase in the scatter of the measured spectral index and thermal fraction distributions as a function of decreasing galactocentric radius. This trend is likely reflective of the continuous star formation activity occurring in the galaxy centers, resulting in a larger contribution of diffuse nonthermal emission relative to star-forming regions in the disk.

Keywords: Radio astronomy, Spiral galaxies, Extragalactic radio sources, Star forming regions, Star formation, Galaxy evolution, Radio continuum emission, Radio interferometry, H II regions, Galaxies
Solar Cycle of Imaging the Global Heliosphere: Interstellar Boundary Explorer (IBEX) Observations from 2009-2019. NASA's Interstellar Boundary Explorer (IBEX) mission has operated in space for a full solar activity cycle (Solar Cycle 24), and IBEX observations have exposed the global three-dimensional structure of the heliosphere and its interaction with the very local interstellar medium for the first time. Here, we extend the prior IBEX observations of energetic neutral atoms (ENAs) by adding a comprehensive analysis of four additional years (2016 through 2019). We document several improvements and rerelease the entire 11 yr, IBEX-Hi data set. The new observations track the continuing expansion of the outer heliosphere's response to the large solar wind pressure increase in late 2014. We find that the intensification of ENAs from the heliosheath continued to expand progressively over time to directions farther from the initial, closest direction to the heliospheric boundaries, ∼20° south of the upwind direction. This expansion extended beyond the south pole in 2018 and the north pole in 2019, demonstrating that the termination shock and heliopause are closer in the south. The heliotail has not yet responded, indicating that the boundaries are significantly farther away in the downwind direction. Finally, the slow solar wind (∼1 keV) ENAs just started to intensify from the closest regions of the IBEX Ribbon. This is about two and a half years after the initial response from heliosheath ENAs and about four and a half years after the increase in solar wind output, both clearly implicating a "secondary ENA" source in the draped interstellar magnetic field, just beyond the heliopause.

Keywords: Solar cycle, Heliosphere, Solar wind, Interstellar magnetic fields, Pickup ions, Interstellar medium, Solar activity, Heliosheath