Sazuna/UAT_keywords huggingface dataset:
Accurate OH Maser Positions from the SPLASH Survey. III. The Final 96 deg<SUP>2</SUP>. We present high spatial resolution observations of ground-state OH masers achieved with the Australia Telescope Compact Array (ATCA). These observations targeted 253 pointing centers containing OH maser candidates at all four ground-state OH transitions identified in the Southern Parkes Large-Area Survey in Hydroxyl (SPLASH) across 96 deg2 of the southern Galactic plane (332° &lt; l &lt; 334° and -2° &lt; b &lt; +2°, 344° &lt; l &lt; 355° and -2° &lt; b &lt; +2°, 358° &lt; l &lt; 4° and +2° &lt; b &lt; +6°, 5° &lt; l &lt; 10° and -2° &lt; b &lt; +2°). We detect maser emission toward 236 fields and suggest that 7 out of 17 nondetections are due to the slightly lower sensitivity of the ATCA observations, combined with some temporal variability. The superior resolution provided by the ATCA data has allowed us to identify 362 OH maser sites in the 236 target fields. Almost half (160 of 362) of these masers have been detected for the first time. Comparison between these 362 maser sites and information presented in the literature allowed us to categorize 238 sites as evolved star sites (66%), 63 as star formation (17%), 8 as supernova remnants, and 53 as unknown maser sites (15%). We present an analysis of the OH masers across the full SPLASH survey range (176 deg2) and find that the detection rate of 1.7 GHz radio continuum sources (18%) is lower than that previously found at 8.2 and 9.2 GHz (38%). We also find that the velocity separations of evolved star sites with symmetric 1612 MHz maser profiles are generally smaller than those with asymmetric profiles.

Keywords: Interstellar molecules, Post-asymptotic giant branch, Circumstellar masers, Asymptotic giant branch stars, Star formation, Interstellar masers, Catalogs
A Magnetohydrodynamic Relaxation Method for Non-force-free Magnetic Field in Magnetohydrostatic Equilibrium. A nonlinear force-free field (NLFFF) extrapolation is widely used to reconstruct the three-dimensional magnetic field in the solar corona from the observed photospheric magnetic field. However, the pressure gradient and gravitational forces are ignored in the NLFFF model, even though the photospheric and chromospheric magnetic fields are not in general force-free. Here we develop a magnetohydrodynamic (MHD) relaxation method that reconstructs the solar atmospheric (chromospheric and coronal) magnetic field as a non-force-free magnetic field (NFFF) in magnetohydrostatic equilibrium where the Lorentz, pressure gradient, and gravitational forces are balanced. The system of basic equations for the MHD relaxation method is derived, and mathematical properties of the system are investigated. A robust numerical solver for the system is constructed based on the modern high-order shock capturing scheme. Two-dimensional numerical experiments that include the pressure gradient and gravitational forces are also demonstrated.

Keywords: Solar atmosphere, Solar photosphere, Solar coronal loops, Solar corona, Solar magnetic fields, Solar chromosphere
Narrowband Ca Photometry for Dwarf Spheroidal Galaxies. I. Chemostructural Study on Draco, Sextans, and Canes Venatici I. A few dozen dwarf satellite galaxies of the Milky Way have been discovered, which are often viewed as the remaining building blocks of our Galaxy. The follow-up spectroscopy showed that dwarf galaxies have a sizeable spread in their metallicities. Several scenarios were suggested to explain the metallicity spread, which can be tested by the structural patterns of stellar subpopulations with distinct metallicities. However, such chemical plus structural examination, which we refer to as "chemostructural study," is hindered by the lack of stars with spectroscopic metallicity. Here we propose the Ca-by photometry as an alternative way to secure metallicities for a 2-3 orders of magnitude larger stellar sample than the spectroscopic sample and thus enable us to perform a chemostructural study on dwarf galaxies. In particular, we use the hk index [≅(Ca - b) - (b - y)], whose validity as a photometric metallicity indicator (and crass insensitivity to age) for red-giant-branch stars was upheld via Galactic globular clusters, and observe three dwarf spheroidal galaxies - Draco, Sextans, and Canes Venatici I (CVnI) - with Subaru/Suprime-Cam. We find that in all the galaxies the metal-rich stellar populations are more centrally concentrated than the metal-poor counterparts, suggesting that the central regions of the galaxies underwent extended star formation. Such a negative radial metallicity gradient for Sextans and CVnI opposes the traditional spectroscopic results. We also find that their metallicity distribution functions (MDFs) can be characterized by a unimodal, skewed Gaussian shape with a metal-rich peak and a metal-poor tail. We discuss their features in the chemo-structure and MDF in terms of dwarf galaxy formation theories.

Keywords: Local Group, Stellar abundances, Galaxy structure, Galaxy stellar content, Dwarf spheroidal galaxies
Iterative Phase Correlation Algorithm for High-precision Subpixel Image Registration. Many astrophysical observations and measurement techniques that rely on data from images include an image registration step. The results of such techniques thus heavily rely on the precision of the registration. We present an Iterative Phase Correlation (IPC) algorithm, which is an extension of the well-known phase correlation method of image registration and is ideally suited for problems, where the subpixel registration accuracy plays a crucial role. Furthermore, a sophisticated and reliable method of optimal IPC parameter estimation is described. The paper includes examples of such optimized parameters for Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager, SDO/Atmospheric Imaging Assembly, and Solar Terrestrial Relations Observatory A/B Sun Earth Connection Coronal and Heliospheric Investigation images. The new method (both with or without the parameter optimization step) significantly outperforms standard image registration methods, such as (non-iterative) phase correlation or (normalized) cross correlation in the sense of subpixel accuracy. A step-by-step pseudocode implementation is also included.

Keywords: Publicly available software, CCD observation, Astronomy software, Fast Fourier transform, Astronomy data analysis, Analytical mathematics, Astronomical techniques, Computational methods, Direct imaging, Astrometry, Astronomical methods, Algorithms
Magnetic Activity of F-, G-, and K-type Stars in the LAMOST-Kepler Field. Monitoring chromospheric and photospheric indexes of magnetic activity can provide valuable information, especially the interaction between different parts of the atmosphere and their response to magnetic fields. We extract chromospheric indexes, S and R_{HK}^{+}, for 59,816 stars from LAMOST spectra in the LAMOST-Kepler program, and photospheric index, Reff, for 5575 stars from Kepler light curves. The log Reff shows positive correlation with log R_{HK}^{+}. We estimate the power-law indexes between Reff and R_{HK}^{+} for F-, G-, and K-type stars, respectively. We also confirm the dependence of both chromospheric and photospheric activity on stellar rotation. Ca II H and K emissions and photospheric variations generally decrease with increasing rotation periods for stars with rotation periods exceeding a few days. The power-law indexes in exponential decay regimes show different characteristics in the two activity-rotation relations. The updated largest sample including the activity proxies and reported rotation periods provides more information to understand the magnetic activity for cool stars.

Keywords: Stellar chromospheres, Stellar magnetic fields, Stellar atmospheres, Stellar activity
Spectral Lines for Transition to Highly Excited States of Lithium in Magnetic Fields of White Dwarf Stars. We develop a two-dimensional B-spline approach in the cylindrical coordinate system to simulate spectra of lithium in magnetic fields of white dwarf stars. The advantage of the current approach is that it can be applied to calculate both low- and high-lying states, while the theoretical methods for describing magnetized lithium in the literature are limited to the treatment of the ground state and low-lying excited states. The magnetized atomic states are calculated with symmetries 20+, 20-, 2-1+}, 2(-1)-, 2(-2)+, and the lowest 10 atomic states of each symmetry are involved. The magnetic field strengths stride a scope of field strengths of white dwarf stars. Atomic data of absorption spectra corresponding to transitions from the ground state or low-lying excited states to high-lying excited states are reported for magnetized lithium. These atomic data include energy levels, wavelengths, and oscillator strengths. Comparison is made between our results, and theoretical and experimental data reported in the literature. The current two-dimensional B-spline approach can systematically produce atomic data to model discrete atomic spectra of both low- and high-lying states of lithium in magnetic white dwarf stars.

Keywords: Atomic spectroscopy
Radial Velocity Photon Limits for the Dwarf Stars of Spectral Classes F-M. The determination of extrasolar planet masses with the radial velocity (RV) technique requires spectroscopic Doppler information from the planet's host star, which varies with stellar brightness and temperature. We analyze the Doppler information in spectra from dwarfs of spectral types F-M utilizing empirical information from HARPS and CARMENES data and model spectra. We revisit the question of whether optical or near-infrared instruments are more efficient for RV observations in low-mass stars, and we come to the conclusion that an optical setup (BVR bands) is more efficient than a near-infrared one (YJHK) in dwarf stars hotter than 3200 K. We publish a catalog of 46,480 well-studied F-M dwarfs in the solar neighborhood, and we compare its distribution to more than 1 million stars from Gaia DR2. For all stars, we estimate the RV photon noise achievable in typical observations under the assumption of no activity jitter and slow rotation. We find that with an ESPRESSO-like instrument at an 8 m telescope, a photon noise limit of 10 cm s-1 or lower can be reached in more than 280 stars in a 5 minute observation. At 4 m telescopes, a photon noise limit of 1 m s-1 can be reached in a 10 minute exposure in approximately 10,000 predominantly Sun-like stars with a HARPS-like (optical) instrument. The same applies to ∼3000 stars for a red optical setup that covers the R and I bands and ∼700 stars for a near-infrared instrument. For the latter two, many of the targets are nearby M dwarfs. Finally, we identify targets in which Earth-mass planets within the liquid water habitable zone can cause RV amplitudes comparable to the RV photon noise. Assuming the same exposure times as above, we find that an ESPRESSO-like instrument can reach this limit for 1 M⊕ planets in more than 1000 stars. The optical, red optical, and near-infrared configurations reach the limit for 2 M⊕ planets in approximately 500, 700, and 200 stars, respectively. An online tool is provided to estimate the RV photon noise as a function of stellar temperature and brightness and wavelength coverage.

Keywords: High resolution spectroscopy, M dwarf stars, G dwarf stars, Exoplanets, K dwarf stars, Radial velocity, Catalogs
Strong Lens Models for 37 Clusters of Galaxies from the SDSS Giant Arcs Survey. We present strong gravitational lensing models for 37 galaxy clusters from the Sloan Digital Sky Survey Giant Arcs Survey. We combine data from multi-band Hubble Space Telescope Wide Field Camera 3 (WFC3) imaging, with ground-based imaging and spectroscopy from Magellan, Gemini, Apache Point Observatory, and the Multiple Mirror Telescope, in order to detect and spectroscopically confirm new multiply imaged lensed background sources behind the clusters. We report spectroscopic or photometric redshifts of sources in these fields, including cluster galaxies and background sources. Based on all available lensing evidence, we construct and present strong-lensing mass models for these galaxy clusters. The clusters span a redshift range of 0.176 &lt; z &lt; 0.66 with a median redshift of z = 0.45, and sample a wide range of dynamical masses, 1.5 &lt; M200 &lt; 35 × 1014 M_{☉}, as estimated from their velocity dispersions. As these clusters were selected as lenses primarily owing to a fortuitous alignment with background galaxies that results in giant arcs, they exhibit a wide range in Einstein radii, 1"3 &lt; θE &lt; 23"1 for a source at z = 2, with a median θE = 10"8. The reduced HST images and lens model outputs are made available to the scientific community as high-level data products with this publication.

Keywords: Galaxy clusters, Observational astronomy, Strong gravitational lensing, Star forming regions, Gravitational lensing, Spectroscopy, High-redshift galaxies, Dark matter
Investigating Taxonomic Diversity within Asteroid Families through ATLAS Dual-band Photometry. We present here the c-o colors for identified Flora, Vesta, Nysa-Polana, Themis, and Koronis family members within the historic data set (2015-2018) of the Asteroid Terrestrial-impact Last Alert System (ATLAS). The Themis and Koronis families are known to be relatively pure C- and S-type Bus-DeMeo taxonomic families, respectively, and the extracted color data from the ATLAS broadband c- and o-filters of these two families are used to demonstrate that the ATLAS c-o color is a sufficient parameter to distinguish between the C- and S-type taxonomies. The Vesta and Nysa-Polana families are known to display a mixture of taxonomies possibly due to Vesta's differentiated parent body origin and Nysa-Polana actually consisting of two nested families with differing taxonomies. Our data show that the Flora family also displays a large degree of taxonomic mixing and the data reveal a substantial H-magnitude dependence on color. We propose and exclude several interpretations for the observed taxonomic mix. Additionally, we extract rotation periods of all of the targets reported here and find good agreement with targets that have previously reported periods.

Keywords: Period determination, Sky surveys, Asteroids, Small Solar System bodies, Light curves, Lomb-Scargle periodogram, Main belt asteroids, Broad band photometry
Laboratory Study of Rate Coefficients for H<SUB>2</SUB>:H<SUB>2</SUB> Inelastic Collisions between 295 and 20 K. A laboratory study of state-to-state rate coefficients (STS rates) for H2:H2 inelastic collisions in the V = 0 state is reported. The study, which spans the 295-20 K thermal range, is based on the use of a kinetic master equation. It describes the time-space evolution of populations of H2 rotational levels as induced by inelastic collisions. It is applied here to a supersonic jet of natural H2. This medium bears a large amount of relevant data that allows for the establishment of best values and confidence margins for the dominant STS rates of H2:H2 inelastic collisions on an experimental basis. The primary experimental data derived from the supersonic jet are the local number density, the populations of the H2 rotational levels, and their gradients along the jet by means of high-sensitivity Raman spectroscopy with superb space resolution. First, two sets of theoretical STS rates from the literature have been tested against the experiment. The set that shows a better agreement with the experiment has then been scaled to derive an improved set of experiment-scaled STS rates (ES rates). They allow the reproduction of more than 50 experimental population gradient data within a standard deviation &lt;1.4% along the 295-20 K thermal range. The estimated uncertainty for the ES rates ranges from ≈3% near 300 K to ≈6% near 20 K. ES rates and uncertainties for H2:H2 ground-state inelastic collisions between 300 and 20 K are presented in machine-readable format. Other (incomplete) sets of theoretical rates from the literature are discussed.

Keywords: Collision physics, Laboratory astrophysics, Molecular spectroscopy, Astronomy databases
An ALMA CO(2-1) Survey of Nearby Palomar-Green Quasars. The properties of the molecular gas can shed light on the physical conditions of quasar host galaxies and the effect of feedback from accreting supermassive black holes. We present a new CO(2-1) survey of 23 z&lt;0.1 Palomar-Green quasars conducted with the Atacama Large Millimeter/submillimeter Array. CO emission was successfully detected in 91% (21/23) of the objects, from which we derive CO luminosities, molecular gas masses, and velocity line widths. Together with CO(1-0) measurements in the literature for 32 quasars (detection rate 53%), there are 15 quasars with both CO(1-0) and CO(2-1) measurements and, in total, 40 sources with CO measurements. We find that the line ratio of R_{21}≡ L_{CO}(2-1)^{'}/L_{CO(1-0)}^{'} is subthermal and broadly consistent with nearby galaxies and other quasars previously studied. No clear correlation is found between R21 and the intensity of the interstellar radiation field or the luminosity of the active nucleus. As with the general galaxy population, quasar host galaxies exhibit a strong, tight, and linear LIR-L_{CO}(1-0)^{'} relation, with a normalization consistent with that of starburst systems. We investigate the molecular-to-total-gas mass fraction with the aid of total gas masses inferred from dust masses previously derived from infrared observations. Although the scatter is considerable, the current data do not suggest that the CO-to-H2 conversion factor of quasar host galaxies significantly differs from that of normal star-forming galaxies.

Keywords: AGN host galaxies, Interstellar medium, Quasars
New Hard-TeV Extreme Blazars Detected with the MAGIC Telescopes. Extreme high-frequency-peaked BL Lac objects (EHBLs) are blazars that exhibit extremely energetic synchrotron emission. They also feature nonthermal gamma-ray emission whose peak lies in the very high-energy (VHE, E &gt; 100 GeV) range, and in some sources exceeds 1 TeV: this is the case for hard-TeV EHBLs such as 1ES 0229+200. With the aim of increasing the EHBL population, 10 targets were observed with the MAGIC telescopes from 2010 to 2017, for a total of 265 hr of good-quality data. The data were complemented by coordinated Swift observations. The X-ray data analysis confirms that all but two sources are EHBLs. The sources show only a modest variability and a harder-when-brighter behavior, typical for this class of objects. At VHE gamma-rays, three new sources were detected and a hint of a signal was found for another new source. In each case, the intrinsic spectrum is compatible with the hypothesis of a hard-TeV nature of these EHBLs. The broadband spectral energy distributions (SEDs) of all sources are built and modeled in the framework of a single-zone, purely leptonic model. The VHE gamma-ray-detected sources were also interpreted with a spine-layer model and a proton synchrotron model. The three models provide a good description of the SEDs. However, the resulting parameters differ substantially in the three scenarios, in particular the magnetization parameter. This work presents the first mini catalog of VHE gamma-ray and multiwavelength observations of EHBLs.

Keywords: BL Lacertae objects, Gamma-ray sources, Blazars, Relativistic jets, Active galactic nuclei, X-ray active galactic nuclei, Non-thermal radiation sources, Catalogs
Massive Stars in the SDSS-IV/APOGEE2 Survey. III. New OB Stars in the Direction of the Sagittarius Spiral Arm. We have applied the semi-empirical spectral analysis, developed by the Sloan Digital Sky Survey (SDSS)-IV/Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE2) Massive Star Team, to a large sample of new O- and B-type stars identified along the Sagittarius spiral arm, in the direction of the southern star clusters NGC3603 and NGC3576. We obtained H-band spectra for 265 point sources, using the APOGEE2-S spectrograph at the du Pont Telescope at the Las Campanas Observatory. We analyzed the associated spectral features deriving spectral types, as well as the massive star distribution along the line of sight. From a total of 265 science targets, 95 are classified as mid- to late-O-type stars (for which only 10 O-type stars are previously known in the literature), 38 are found to be early- to mid-B-type stars, and 32 are classified as either yellow or blue supergiants, completing a total of 165 massive stars.

Keywords: Massive stars, Stellar types, Near infrared astronomy
hammurabi X: Simulating Galactic Synchrotron Emission with Random Magnetic Fields. We present version X of the hammurabi package, the HEALPix-based numeric simulator for Galactic polarized emission. Improving on its earlier design, we have fully renewed the framework with modern C++ standards and features. Multithreading support has been built in to meet the growing computational workload in future research. For the first time, we present precision profiles of the hammurabi line-of-sight integral kernel with multilayer HEALPix shells. In addition to fundamental improvements, this report focuses on simulating polarized synchrotron emission with Gaussian random magnetic fields. Two fast methods are proposed for realizing divergence-free random magnetic fields either on the Galactic scale where field alignment and strength modulation are imposed, or on a local scale where more physically motivated models like a parameterized magnetohydrodynamic (MHD) turbulence can be applied. As an example application, we discuss the phenomenological implications of Gaussian random magnetic fields for high Galactic latitude synchrotron foregrounds. In this, we numerically find B/E polarization-mode ratios lower than unity based on Gaussian realizations of either MHD turbulent spectra or in spatially aligned magnetic fields.

Keywords: Interstellar magnetic fields, Interstellar synchrotron emission
Experimental Phase Function and Degree of Linear Polarization Curves of Millimeter-sized Cosmic Dust Analogs. We present laboratory measurements of the phase functions and degree of linear polarization (DLP) curves of a selection of millimeter-sized cosmic dust analog particles. The set includes particles with similar sizes but diverse internal structure (compact and porous) and absorbing properties. The measured phase functions are found to be in all cases very different from those of micron-sized particles. They show a monotonic decrease with increasing phase angle from the back- to the side-scattering region, reaching a minimum at large phase angles before a steep increase of the forward peak. This is in stark contrast to the phase functions of micron-sized particles, which are rather flat at low and intermediate phase angles. The maximum of the DLP for millimeter-sized compact particles is shifted toward larger phase angles (∼130°) compared to that of micron-sized particles (∼90°). Porosity plays an important role in the measured DLP curves: the maximum significantly decreases for increasing porosity as a result of multiple scattering within the particle. Large porous particles with highly absorbing inclusions can reproduce both the OSIRIS/Rosetta phase functions and ground-based DLP observations of comet 67P/Churyumov-Gerasimenko.

Keywords: Circumstellar disks, Experimental techniques, Polarimetry, Protoplanetary disks, Comets, Circumstellar dust, Debris disks