Sazuna/UAT_keywords huggingface dataset:
Neutral Atmospheric Density Measurement Using Insight-HXMT Data by the Earth Occultation Technique. The Earth occultation technique has broad applications in both astronomy and atmospheric density measurements. We construct the background model during the occultation of the Crab Nebula observed by the Insight-Hard X-ray Modulation Telescope (Insight-HXMT) at energies between 6 and 100 keV. We propose a Bayesian atmospheric density retrieval method based on the Earth occultation technique, combining Poisson and Gaussian statistics. By modeling the atmospheric attenuation of X-ray photons during the occultation, we simultaneously retrieved the neutral densities of the atmosphere at different altitude ranges. Our method considers the correlation of densities between neighboring atmospheric layers and reduces the potential systematic bias to which previous work may be subject. Previous analyses based on light-curve fitting or spectral fitting also lost some spectral or temporal information of the data. In contrast to previous work, the occultation data observed by the three telescopes on board Insight-HXMT is fully used in our analysis, further reducing the statistical error in density retrieval. We apply our method to cross-check the (semi)empirical atmospheric models, using 115 sets of occultation data of the Crab Nebula observed by Insight-HXMT. We find that the retrieved neutral density is ~10%, ~20%, and ~25% less than the values of the widely used atmospheric model NRLMSISE-00, in the altitude range of 55-80 km, 80-90 km, and 90-100 km, respectively. We also show that the newly released atmospheric model NRLMSIS 2.0 is generally consistent with our density measurements.

Keywords: Atmospheric composition, Pulsar wind nebulae, Occultation, Earth atmosphere
Powerful Yet Lonely: Is 3C 297 a High-redshift Fossil Group?. The environment of the high-redshift (z = 1.408), powerful radio-loud galaxy 3C 297 has several distinctive features of a galaxy cluster. Among them, a characteristic halo of hot gas revealed by Chandra X-ray observations. In addition, a radio map obtained with the Very Large Array shows a bright hotspot in the northwestern direction, created by the interaction of the active galactic nucleus (AGN) jet arising from 3C 297 with its environment. In the X-ray images, emission cospatial with the northwestern radio lobe is detected, and peaks at the position of the radio hotspot. The extended, complex X-ray emission observed with our new Chandra data is largely unrelated to its radio structure. Despite having attributes of a galaxy cluster, no companion galaxies have been identified from 39 new spectra of neighboring targets of 3C 297 obtained with the Gemini Multi-Object Spectrograph. None of the 19 galaxies for which a redshift was determined lies at the same distance as 3C 297. The optical spectral analysis of the new Gemini spectrum of 3C 297 reveals an isolated Type II radio-loud AGN. We also detected line broadening in [O II] λ3728 with a FWHM about 1700 km s-1 and possible line shifts of up to 500-600 km s-1. We postulate that the host galaxy of 3C 297 is a fossil group, in which most of the stellar mass has merged into a single object, leaving behind an X-ray halo.

Keywords: Galaxy clusters, Brightest cluster galaxies, Intracluster medium, Active galactic nuclei
CCAT-prime Collaboration: Science Goals and Forecasts with Prime-Cam on the Fred Young Submillimeter Telescope. We present a detailed overview of the science goals and predictions for the Prime-Cam direct-detection camera-spectrometer being constructed by the CCAT-prime collaboration for dedicated use on the Fred Young Submillimeter Telescope (FYST). The FYST is a wide-field, 6 m aperture submillimeter telescope being built (first light in late 2023) by an international consortium of institutions led by Cornell University and sited at more than 5600 m on Cerro Chajnantor in northern Chile. Prime-Cam is one of two instruments planned for FYST and will provide unprecedented spectroscopic and broadband measurement capabilities to address important astrophysical questions ranging from Big Bang cosmology through reionization and the formation of the first galaxies to star formation within our own Milky Way. Prime-Cam on the FYST will have a mapping speed that is over 10 times greater than existing and near-term facilities for high-redshift science and broadband polarimetric imaging at frequencies above 300 GHz. We describe details of the science program enabled by this system and our preliminary survey strategies.

Keywords: Interstellar dust, Galaxy clusters, Protogalaxies, Wide-field telescopes, Observational cosmology, Sunyaev-Zeldovich effect, Recombination (cosmology), Astronomical instrumentation, Galaxy evolution, Time domain astronomy, Star formation, Reionization
Unveiling Hidden Stellar Aggregates in the Milky Way: 1656 New Star Clusters Found in Gaia EDR3. We report 1656 new star clusters found in the Galactic disk (∣b∣ &lt; 20°) beyond 1.2 kpc, using Gaia EDR3 data. Based on an unsupervised machine-learning algorithm, DBSCAN, and following our previous studies, we utilized a unique method to do the data preparation and obtain the clustering coefficients, which proved to be an effective way to search blindly for star clusters. We tabulate the physical parameters and member stars of the new clusters, and present some interesting examples, including a globular cluster candidate. The cluster parameters and member stars are available in machine-readable format in the online journal. We examine the new discoveries and discuss their statistical properties. The proper-motion dispersions and radii of the star clusters are the same as those previously reported. The new clusters beyond 1.2 kpc are older than those in the solar neighborhood, and the new objects found in the third Galactic quadrant present the lowest line-of-sight extinctions. Combined with our previous results, the total population of new clusters and candidates detected through our method is 2541, corresponding to 55% of all newly published clusters in the Gaia era. The number of cataloged Gaia star clusters was also increased to nearly 6000. In the near future, it will be necessary to make a unified confirmation and member star determination for all reported clusters.

Keywords: Open star clusters, Star clusters
A Southern Photometric Quasar Catalog from the Dark Energy Survey Data Release 2. We present a catalog of 1.4 million photometrically selected quasar candidates in the southern hemisphere over the ~5000 deg2 Dark Energy Survey (DES) wide survey area. We combine optical photometry from the DES second data release (DR2) with available near-infrared (NIR) and the all-sky unWISE mid-infrared photometry in the selection. We build models of quasars, galaxies, and stars with multivariate skew-t distributions in the multidimensional space of relative fluxes as functions of redshift (or color for stars) and magnitude. Our selection algorithm assigns probabilities for quasars, galaxies, and stars and simultaneously calculates photometric redshifts (photo-z) for quasar and galaxy candidates. Benchmarking on spectroscopically confirmed objects, we successfully classify (with photometry) 94.7% of quasars, 99.3% of galaxies, and 96.3% of stars when all IR bands (NIR YJHK and WISE W1W2) are available. The classification and photo-z regression success rates decrease when fewer bands are available. Our quasar (galaxy) photo-z quality, defined as the fraction of objects with the difference between the photo-z z  p  and the spectroscopic redshift z  s , ∣∆z∣ ≡ ∣z  s  - z  p ∣/(1 + z  s ) ≤ 0.1, is 92.2% (98.1%) when all IR bands are available, decreasing to 72.2% (90.0%) using optical DES data only. Our photometric quasar catalog achieves an estimated completeness of 89% and purity of 79% at r &lt; 21.5 (0.68 million quasar candidates), with reduced completeness and purity at 21.5 &lt; r ≲ 24. Among the 1.4 million quasar candidates, 87,857 have existing spectra, and 84,978 (96.7%) of them are spectroscopically confirmed quasars. Finally, we provide quasar, galaxy, and star probabilities for all (0.69 billion) photometric sources in the DES DR2 coadded photometric catalog.

Keywords: Sky surveys, Redshift surveys, Catalogs, Quasars
Photochemistry and Heating/Cooling of the Multiphase Interstellar Medium with UV Radiative Transfer for Magnetohydrodynamic Simulations. We present an efficient heating/cooling method coupled with chemistry and UV radiative transfer that can be applied to numerical simulations of the interstellar medium (ISM). We follow the time-dependent evolution of hydrogen species (H2, H, H+), assume carbon/oxygen species (C, C+, CO, O, and O+) are in formation-destruction balance given the nonsteady hydrogen abundances, and include essential heating/cooling processes needed to capture the thermodynamics of all ISM phases. UV radiation from discrete point sources and the diffuse background is followed through adaptive ray tracing and a six-ray approximation, respectively, allowing for H2 self-shielding; cosmic-ray heating and ionization are also included. To validate our methods and demonstrate their application for a range of density, metallicity, and radiation fields, we conduct a series of tests, including the equilibrium curves of thermal pressure versus density, the chemical and thermal structure in photodissociation regions, H I-to-H2 transitions, and the expansion of H II regions and radiative supernova remnants. Careful treatment of photochemistry and cosmic-ray ionization is essential for many aspects of ISM physics, including identifying the thermal pressure at which cold and warm neutral phases coexist. We caution that many current heating and cooling treatments used in galaxy formation simulations do not reproduce the correct thermal pressure and ionization fraction in the neutral ISM. Our new model is implemented in the MHD code Athena and incorporated in the TIGRESS simulation framework, for use in studying the star-forming ISM in a wide range of environments.

Keywords: Hydrodynamical simulations, Interstellar phases, Radiative magnetohydrodynamics, Interstellar radiation field, Photodissociation regions, Astrochemistry, Supernova remnants, H II regions
On the General Correlation between 3D Solar Wind Speed and Density Model and Solar Proxies. The solar wind (SW) is a supersonic outflow of plasma from the solar corona, with the latitudinal speed and density profiles varying with the solar activity. The SW protons charge exchange with the inflowing interstellar neutral atoms and create energetic neutral atoms (ENAs), which bring information on the physical state of the plasma within the boundary region of the heliosphere. The speed of the ENAs depends on their energies, and consequently observations at different energies provide information on different epochs backward in time. Therefore, understanding the history of the evolution of the SW is important to understand this information. In this paper, we extend the work by Porowski et al., who provided the WawHelioIon 3DSW model of the time evolution of latitudinal profiles of the SW speed and density based on results of analysis of interplanetary scintillations (IPSs). Based on results of principal component analysis, we search for correlation between selected solar proxies and the structure of the SW obtained from IPSs and show that it is possible to reproduce the evolution of the SW structure during the past three solar cycles based on the proxies. With this, we extend the history of the evolution of the SW structure back to 1976, i.e., to the epoch when observations of the key proxies-the inclination of the SW current sheet and the solar polar magnetic fields-became available. We point out the potential of the use of the proxies for forecasting the structure of the SW into the future.

Keywords: Slow solar wind, Heliosphere, Fast solar wind, Astrosphere interstellar medium interactions, Solar wind, Stellar activity, Solar physics, Solar activity
Stellar Chromospheric Activities Revealed from the LAMOST-K2 Time-domain Survey. By using the LAMOST time-domain survey data, we study stellar activities based on the H α  lines for about 2000 stars in four K2 plates. Two indices, ${R}_{{\rm{H}}\alpha }^{{\prime} }$ and ${R}_{{\rm{H}}\alpha }^{+}$ , are computed from LAMOST spectra, the former of which is derived by excluding the photospheric contributions to the H α  lines, while the latter is derived by further subtracting the non-dynamo-driven chromospheric emission. Meanwhile, the periodicity and variation amplitudes are computed from K2 light curves. Both the ${R}_{{\rm{H}}\alpha }^{{\prime} }$ -Ro relation and ${R}_{{\rm{H}}\alpha }^{+}$ -Ro relation show complicated profiles in the nonsaturated decay region. Hot stars show flatter slopes and a higher activity level than cool stars, and the behavior is more notable in the ${R}_{{\rm{H}}\alpha }^{+}$ -R  o  relation. This is consistent with recent studies using other activity proxies, including L x/L bol, ${R}_{\mathrm{HK}}^{{\prime} }$ , and amplitudes of optical light curves. This may suggest different kinds of stars follow different power laws in the decay region. Most of our targets have multiple observations, and some of them exhibit significant variability of Hα emissions, which may cause the large scatters shown in the decay region. We find three targets exhibiting positive correlation in a rotational phase, possibly indicating that their optical light curves are dominated by hot faculae rather than cool starspots.

Keywords: Stellar rotation, Late-type stars, Stellar activity
Numerical Simulation of Solar Magnetic Flux Emergence Using the AMR-CESE-MHD Code. Magnetic flux emergence from the solar interior to the atmosphere is believed to be a key process in the formation of solar active regions and driving solar eruptions. Due to the limited capabilities of observations, the flux emergence process is commonly studied using numerical simulations. In this paper, we develop a numerical model to simulate the emergence of a twisted magnetic flux tube from the convection zone to the corona, using the AMR-CESE-MHD code, which is based on the conservation-element solution-element method, with adaptive mesh refinement. The results of our simulation agree with those of many previous studies with similar initial conditions, but by using different numerical codes. In the early stage, the flux tube rises from the convection zone, being driven by magnetic buoyancy, until it reaches close to the photosphere. The emergence is decelerated there, and with the piling up of the magnetic flux, the magnetic buoyancy instability is triggered, which allows the magnetic field to partially enter into the atmosphere. Meanwhile, two gradually separated polarity concentration zones appear in the photospheric layer, transporting the magnetic field and energy into the atmosphere through their vortical and shearing motions. Correspondingly, the coronal magnetic field is also reshaped into a sigmoid configuration, containing a thin current layer, which resembles the typical pre-eruptive magnetic configuration of an active region. Such a numerical framework of magnetic flux emergence as established will be applied to future investigations of how solar eruptions are initiated in flux emergence active regions.

Keywords: Magnetohydrodynamics, Solar active regions, Solar magnetic fields, Solar corona, Magnetohydrodynamical simulations
Empirical Temperature- and Extinction-dependent Extinction Coefficients for the GALEX, Pan-STARRS 1, Gaia, SDSS, 2MASS, and WISE Passbands. We have obtained accurate dust reddening from the far-ultraviolet to the mid-infrared for up to 5 million stars by the star-pair algorithm based on LAMOST stellar parameters along with Galaxy Evolution Explorer, Pan-STARRS 1, Gaia, Sloan Digital Sky Survey, Two Micron All Sky Survey, and Wide-field Infrared Survey Explorer photometric data. The typical errors are between 0.01 and 0.03 mag for most colors. We derived the empirical reddening coefficients for 21 colors both in the traditional (single-valued) way and as a function of T eff and E(B - V) by using the largest samples of accurate reddening measurements, together with the extinction values from Schlegel et al. The corresponding extinction coefficients have also been obtained. The results are compared with model predictions and generally in good agreement. Comparisons with measurements in the literature show that the T eff- and E(B - V)-dependent coefficients explain the discrepancies between different measurements naturally, i.e., using sample stars of different temperatures and reddening. Our coefficients are mostly valid in the extinction range of 0-0.5 mag and the temperature range of 4000-10,000 K. We recommend that the new T eff- and E(B - V)-dependent reddening and extinction coefficients should be used in the future. A Python package is also provided for the usage of the coefficients (https://github.com/vnohhf/extinction_coeffcient/).

Keywords: Interstellar dust, Interstellar dust extinction
RELICS: A Strong-lens Model of SMACS J0723.3-7327. We present the details of a strong-lens model of SMACS J0723.3-7327, which was made public as part of the data and high-level science products (HLSP) release of the RELICS Hubble Space Telescope (HST) treasury program (Reionization Lensing Cluster Survey; GO-14096, PI: Coe). The model products were made available on the Mikulski Archive for Space Telescopes via 10.17909/T9SP45 in 2017. Here, we provide the list of constraints that were used in the HST-based RELICS lens model, as well as other information related to our modeling choices, which were not published with the data and HLSP release. This model was computed with Lenstool, used a total of 25 multiple images of eight sources, with no spectroscopic redshifts. The image-plane rms was 0.″58. *Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO-12166, GO-12884, GO-14096.

Keywords: Galaxy clusters, Gravitational lensing
<SUP>12</SUP>CO (3-2) High-Resolution Survey (COHRS) of the Galactic Plane: Complete Data Release. We present the full data release of the 12CO (3-2) High-Resolution Survey (COHRS), which has mapped the inner Galactic plane over the range of 9.°5 ≤ l ≤ 62.°3 and ∣b∣ ≤ 0.°5. COHRS has been carried out using the Heterodyne Array Receiver Program on the 15 m James Clerk Maxwell Telescope in Hawaii. The released data are smoothed to have a spatial resolution of 16.″6 and a velocity resolution of 0.635 km s-1, achieving a mean rms of ~0.6 K on ${T}_{{\rm{A}}}^{* }$ . The COHRS data are useful for investigating detailed three-dimensional structures of individual molecular clouds and large-scale structures such as spiral arms in the Galactic plane. Furthermore, data from other available public surveys of different CO isotopologues and transitions with similar angular resolutions to this survey, such as FUGIN, SEDIGISM, and CHIMPS/CHIMPS2, allow studies of the physical properties of molecular clouds and comparison of their states. In this paper, we report further observations on the second release and improved data reduction since the original COHRS release. We discuss the characteristics of the COHRS data and present integrated-emission images and a position-velocity (PV) map of the region covered. The PV map shows a good match with spiral-arm traces from existing CO and H I surveys. We also obtain and compare integrated one-dimensional distributions of 12CO (1-0) and (3-2) and those of star-forming populations.

Keywords: Molecular clouds
Stellar Parameters and Spectroscopic Properties of TESS Objects Observed in the LAMOST Low- and Medium-resolution Spectral Survey. Stellar parameters and magnetic activity are important for the understanding of stellar physics and dynamo theory. We have used LAMOST spectroscopic surveys to study stellar parameters and magnetic activity properties of TESS objects. There are 46,684 spectra of 31,385 TESS objects in the LAMOST low-resolution spectral survey. We have calculated equivalent widths of Ca II H and K, and Hα lines, and discussed the relationship of chromospheric activity with stellar temperature. There are 25,710 spectra of 10,404 stars with repeated low-resolution observations. We found that there are 694 objects with variations of the Hα line and 1406 objects with varying radial velocities. Moreover, there are 14,099 spectra of 5834 TESS objects in the LAMOST medium-resolution survey, of which there are 2666 objects with Hα variations and 1480 objects with variation in radial velocities. By using the light curves of the TESS objects in the LAMOST field, we detected 4269 flare events and determined their flare parameters. We have confirmed that the fraction of the flare stars increases as stellar temperature decreases. There is also an observed relationship between the flare energy and chromospheric activity. We have calculated the power-law index between the flare energy and decay time using TESS data to be 0.27(0.01), which can be explained by the magnetic reconnection theory. We confirmed that ${R}_{{\rm{H}}\alpha }^{{\prime} }$ is stable for Rossby number R &lt; 0.1 and decreases with the increase of Rossby number R &gt; 0.1. There is a positive correlation between the brightness variation amplitude due to star spots from TESS and the Hα intensity from LAMOST.

Keywords: Stellar chromospheres, Stellar flares, Stellar activity
Light Curves of Trans-Neptunian Objects from the K2 Mission of the Kepler Space Telescope. The K2 mission of the Kepler Space Telescope allowed the observations of light curves of small solar system bodies throughout the whole solar system. In this paper, we present the results of a collection of K2 trans-Neptunian object observations between campaigns C03 (2014 November-2015 February) and C19 (2018 August-September), which includes 66 targets. Due to the faintness of our targets, the detectability rate of a light-curve period is ~56%, notably lower than in the case of other small-body populations, like Hildas or Jovian Trojans. We managed to obtain light-curve periods with an acceptable confidence for 37 targets; the majority of these cases are new identifications. We were able to give light-curve amplitude upper limits for the other 29 targets. Several of the newly detected light-curve periods are longer than ~24 hr, in many cases close to ~80 hr; i.e., these targets are slow rotators. This relative abundance of slowly rotating objects is similar to that observed among Hildas, Jovian Trojans, and Centaurs in the K2 mission, as well as among main belt asteroids measured with the TESS space telescope. Trans-Neptunian objects show notably higher light-curve amplitudes at large (D ≳ 300 km) sizes than found among large main belt asteroids, in contrast to the general expectation that due to their lower compressive strength, they reach hydrostatic equilibrium at smaller sizes than their inner solar system counterparts.

Keywords: Light curves, Kuiper belt, Trans-Neptunian objects