Sazuna/UAT_keywords huggingface dataset:
Failures of Minimum Variance Analysis in Diagnosing Planar Structures in Space. Minimum variance analysis of the magnetic field (MVAB), among various techniques of planar structure analysis, is most widely used for its numerical simplicity and loose requirements for data. Through a large number of studies based on MVAB, a global picture of the solar wind intermittency has been established. However, the huge discrepancy between the results from MVAB and other techniques like timing/triangulation implies that the uncertainty of MVAB is a crucial issue that is not fully understood. Utilizing Cluster data, we establish a data set comprised of 6752 discontinuities, whose orientations are precisely determined by timing, as a benchmark for testing MVAB. We find that the scatter of the MVAB normals around the timing normal can be reduced by elevating the threshold for the eigenvalue ratio λ 2/λ 3 and narrowing the data window to which MVAB is applied. The misidentification of discontinuities with $\left|{B}_{N}\right|/| {\boldsymbol{B}}| $ &lt; 0.4, Δ∣ B ∣/∣ B ∣ &lt; 0.2 as rotational discontinuities (RDs, identified by $\left|{B}_{N}\right|/| {\boldsymbol{B}}| $ &gt; 0.4, Δ∣ B ∣/∣ B ∣ &lt; 0.2) is proved to be a major and inherent defect of MVAB, which can occur even when λ 2/λ 3 is large. Such a misidentification process is revealed to be related to a special discontinuity geometry. It also explains the false RD predominance reported by previous studies based on MVAB. Finally, we provide advice for the application of MVAB and discuss the possibility of obtaining the real statistical properties of interplanetary discontinuities by using MVAB.

Keywords: Interplanetary discontinuities, Solar wind, Interplanetary magnetic fields, Astronomy data analysis
A Two-element Interferometer for Millimeter-wave Solar Flare Observations. In this paper, we present the design and implementation of a two-element interferometer operating in the millimeter-wave band (39.5-40 GHz) for observing solar radio emissions through nulling interference. The system is composed of two 50 cm aperture Cassegrain antennas installed on a common equatorial mount, with a separation of 230 wavelengths. The cross-correlation of the received signals effectively cancels out the quiet solar component of the high flux density (~3000 sfu) that reduces the detection limit due to atmospheric fluctuations. The system performance is as follows: the noise factor of the analog front end in the observation band is less than 2.1 dB, system sensitivity is approximately 12.4 K (~34 sfu) with an integration time constant of 0.1 ms (default), the frequency resolution is 153 kHz, and the dynamic range is ≥30 dB. Through actual testing, the nulling interferometer observes a quiet Sun with a low level of output fluctuations (up to 50 sfu) and has a significantly lower radiation flux variability (up to 190 sfu) than an equivalent single-antenna system, even under thick cloud cover. As a result, this new design can effectively improve observation sensitivity by reducing the impact of atmospheric and system fluctuations during observation.

Keywords: Astronomical instrumentation, Radio interferometers
LSST Survey Strategy in the Galactic Plane and Magellanic Clouds. Galactic science encompasses a wide range of subjects in the study of the Milky Way and Magellanic Clouds, from young stellar objects to X-ray binaries. Mapping these populations, and exploring transient phenomena within them, are among the primary science goals of the Vera C. Rubin Observatory's Legacy Survey of Space and Time. While early versions of the survey strategy dedicated relatively few visits to the Galactic Plane region, more recent strategies under consideration envision a higher cadence within selected regions of high scientific interest. The range of galactic science presents a challenge in evaluating which strategies deliver the highest scientific returns. Here we present metrics designed to evaluate Rubin survey strategy simulations, based on the cadence of observations they deliver within regions of interest to different topics in galactic science, using variability categories defined by timescale. We also compare the fractions of exposures obtained in each filter with those recommended for the different science goals. We find that the baseline_v2.x simulations deliver observations of the high-priority regions at sufficiently high cadence to reliably detect variability on timescales &gt;10 days or more. Follow-up observations may be necessary to properly characterize variability, especially transients, on shorter timescales. Combining the regions of interest for all the science cases considered, we identify those areas of the Galactic Plane and Magellanic Clouds of highest priority. We recommend that these refined survey footprints be used in future simulations to explore rolling cadence scenarios, and to optimize the sequence of observations in different bandpasses.

Keywords: Optical observation, Optical astronomy, Galactic bulge, Galactic and extragalactic astronomy, Astronomical methods, Time domain astronomy, Magellanic Clouds, Milky Way Galaxy
Ionized-gas Metallicity of the Strong [O III]λ5007 Emission-line Compact Galaxies in the LAMOST Survey. This article reports a sample of 1830 strong [O III]λ5007 emission-line compact galaxies discovered with the LAMOST spectroscopic survey and the photometric catalog of the Sloan Digital Sky Survey. We newly identify 402 spectra of 346 strong [O III]λ5007 emission-line compact galaxies by finding compact isolated point sources. Combined with the samples in our previous work, this returns a sample of 1830 unique strong [O III]λ5007 emission-line compact galaxies with 2033 spectra of z ≤ 0.53. For the sources with 2σ[O III]λ4363 detections, we calculate the gas-phase metallicity with the direct-T  e  method, and verify that the strong-line metallicity diagnostics calibrated with the direct-T  e  method also applies to this sample. The strong [O III]λ5007 emission-line compact galaxies fall below several T  e -calibrated mass-metallicity relations. The N/O measurements of the strong [O III]λ5007 emission-line compact galaxies mainly locate at a plateau at low metallicity, indicating the product of primary nucleosynthesis. The Ne3O2 and O32 relation follows a tight linear relation with no redshift evolution. The Ne3O2 anticorrelates with the stellar mass, and at fixed stellar mass the Ne3O2 increases with the redshift. Eight sources with asymmetric [O III]λ5007 emission-line profiles have been identified, however with no [O III]λ4363 detection, which proves the rich metal content and complex ionized-gas kinematics within the galaxies. Higher-resolution spectroscopy will be necessary to identify the ionized-gas components in detail.

Keywords: Compact galaxies
Panchromatic Photometry of Low-redshift, Massive Galaxies Selected from SDSS Stripe 82. The broadband spectral energy distribution of a galaxy encodes valuable information on its stellar mass, star formation rate (SFR), dust content, and possible fractional energy contribution from nonstellar sources. We present a comprehensive catalog of panchromatic photometry, covering 17 bands from the far-ultraviolet to 500 μm, for 2685 low-redshift (z = 0.01-0.11), massive (M * &gt; 1010 M ⊙) galaxies selected from the Stripe 82 region of the Sloan Digital Sky Survey, one of the largest areas with relatively deep, uniform observations over a wide range of wavelengths. Taking advantage of the deep optical coadded images, we develop a hybrid approach for matched-aperture photometry of the multiband data. We derive robust uncertainties and upper limits for undetected galaxies, deblend interacting/merging galaxies and sources in crowded regions, and treat contamination by foreground stars. We perform spectral energy distribution fitting to derive the stellar mass, SFR, and dust mass, critically assessing the influence of flux upper limits for undetected photometric bands and applying corrections for systematic uncertainties based on extensive mock tests. Comparison of our measurements with those of commonly used published catalogs reveals good agreement for the stellar masses. While the SFRs of galaxies on the star-forming main sequence show reasonable consistency, galaxies in and below the green valley show considerable disagreement between different sets of measurements. Our analysis suggests that one should incorporate the most accurate and inclusive photometry into the spectral energy distribution analysis, and that care should be exercised in interpreting the SFRs of galaxies with moderate to weak star formation activity.

Keywords: Surveys, Active galaxies, Infrared galaxies, Galaxy evolution
Validating Stellar Abundance Measurements from Multiresolution Spectroscopy. Large-scale surveys will provide spectroscopy for ~50 million resolved stars in the Milky Way and Local Group. However, these data will have a high degree of heterogeneity and most will be low-resolution (R &lt; 10,000), posing challenges to measuring consistent and reliable stellar labels. Here, we introduce a framework for identifying and remedying these issues. By simultaneously fitting the full spectrum and Gaia photometry with the Payne, we measure ~30 abundances for eight metal-poor red giants in M15. From degraded quality Keck/HIRES spectra, we evaluate trends with resolution and signal-to-noise ratio (S/N) and find that (i) ~20 abundances are recovered consistently within ≲0.1 dex agreement and with ≲0.05-0.15 dex systematic uncertainties from 10,000 ≲ R ≲ 80,000; (ii) for nine elements (C, Mg, Ca, Sc, Ti, Fe, Ni, Y, and Nd), this systematic precision and accuracy extends down to R ~ 2500; and (iii) while most elements do not exhibit strong S/N-dependent systematics, there are nonnegligible biases for four elements (C, Mg, Ca, and Dy) below S/N ~ 10 pixel-1. We compare statistical uncertainties from Markov Chain Monte Carlo sampling to the easier-to-compute Cramér-Rao bounds and find that they agree for ~85% of elements, indicating the latter to be a reliable and faster way to estimate uncertainties. Our analysis illustrates the great promise of low-resolution spectroscopy for stellar chemical abundance work in the low-metallicity regime, and ongoing improvements to stellar models (e.g., 3D-NLTE physics) will only further extend its viability to more stars, more elements, and higher precision and accuracy.

Keywords: Globular star clusters, Fundamental parameters of stars, Stellar abundances, Astronomy data analysis, Spectroscopy
Fantastic Fits with fantasy of Active Galactic Nuclei Spectra: Exploring the Fe II Emission near the Hα Line. In this study, a refined approach for multicomponent fitting of active galactic nuclei (AGNs) spectra is presented utilizing the newly developed Python code Fully Automated pythoN Tool for AGN Spectra analYsis (fantasy). AGN spectra are modeled by simultaneously considering the underlying broken power-law continuum, predefined emission line lists, and an Fe II model, which is here extended to cover the wavelength range 3700-11000 Å. The Fe II model, founded solely on atomic data, effectively describes the extensive emission of the complex iron ion in the vicinity of the Hγ and Hβ lines, as well as near the Hα line, which was previously rarely studied. The proposed spectral fitting approach is tested on a sample of high-quality AGN spectra from the Sloan Digital Sky Survey Data Release 17. The results indicate that when Fe II emission is present near Hβ, it is also detected redward from Hα, potentially contaminating the broad Hα line wings and thus affecting the measurements of its flux and width. The production of Fe II emission is found to be strongly correlated with Eddington luminosity and appears to be controlled by a similar mechanism as the hydrogen Balmer lines. The study highlights the benefits of fitting type 1 AGN spectra with the fantasy code, pointing that it may be used as a robust tool for analyzing a large number of AGN spectra in the coming spectral surveys.

Keywords: Spectral line lists, Active galactic nuclei, Atomic data, Quasars
An Unbiased Method of Measuring the Ratio of Two Data Sets. In certain cases of astronomical data analysis, the meaningful physical quantity to extract is the ratio R between two data sets. Examples include the lensing ratio, the interloper rate in spectroscopic redshift samples, and the decay rate of gravitational potential and E  G  to test gravity. However, simply taking the ratio of the two data sets is biased, since it renders (even statistical) errors in the denominator into systematic errors in R. Furthermore, it is not optimal in minimizing statistical errors of R. Based on Bayesian analysis and the usual assumption of Gaussian error in the data, we derive an analytical expression of the posterior probability density function P(R). This result enables fast and unbiased R measurement, with minimal statistical errors. Furthermore, it relies on no underlying model other than the proportionality relation between the two data sets. Even more generally, it applies to cases where the proportionality relation holds for the underlying physics/statistics instead of the two data sets directly. It also applies to the case of multiple ratios (R → R = (R 1, R 2, ⋯ )). We take the lensing ratio as an example to demonstrate our method. We take lenses as DESI imaging survey galaxies, and sources as DECaLS cosmic shear and Planck cosmic microwave background (CMB) lensing. We restrict the analysis to the ratio between CMB lensing and cosmic shear. The resulting P(R) values, for multiple lens-shear pairs, are all nearly Gaussian. The signal-to-noise ratio of measured R ranges from 4.9 to 8.4. We perform several tests to verify the robustness of the above result.

Keywords: Weak gravitational lensing, Large-scale structure of the universe, Cosmic microwave background radiation, Observational cosmology, Astrostatistics
The LSST Cadence Impact on Non-time-critical Eclipsing Binary Science. The Legacy Survey of Space and Time (LSST) is slated to commence in 2025 at the Vera Rubin Observatory. One of the crucial parts of preparing the survey is the choice of observing cadence in an effort to optimize auxiliary science goals while maintaining the core project requirements. Here we look at the impact of proposed cadences, encoded in different operation simulations (opsims), on non-time-critical eclipsing binary science. This is particularly pertinent because LSST is the first large-scale survey that will provide us with color information in addition to high-precision coverage of faint targets. We study the differences between the baseline opsim v2.1 and the latest opsim v3.0 runs. We find that all runs provide sufficient data coverage to enable in-depth studies in the field of eclipsing binaries, and that there are no adverse impacts from any proposed opsim modification studied here.

Keywords: Optical astronomy, Optical observatories, Eclipsing binary stars
Vibrationally Resolved Absorption and Fluorescence Cross Sections of Adamantane in the Far-ultraviolet Spectral Range on an Absolute Scale. High-resolution absorption, dispersed fluorescence emission, and photoionization cross sections are presented for gas-phase adamantane excited by synchrotron radiation in the exciting-photon energy range of 6-30 eV. Relative and absolute absorption cross sections of so-far unmatched resolution of down to 0.27 cm-1 line width in the region from 6.4-28 eV are shown along with newly discovered vibronic substructures around the HOMO-LUMO transition. Absorption line positions are provided with very high accuracy and listed in tabular form to be used as spectral fingerprints for the detection of adamantane in interstellar media, where its column density may be determined via the absolute cross sections. The fluorescence emission lies in the ultraviolet range from 190-250 nm and is excited starting at the HOMO-LUMO transition at 6.49 eV, which corresponds to the highest fluorescence emission energy. Hitherto unreported fluorescence in the same spectral range and relative photoionization cross sections in the exciting-photon energy range up to 30 eV are also presented along with lifetime measurements for differentiation of the involved electronic states.

Keywords: High resolution spectroscopy, Interstellar molecules, Photoionization, Molecular spectroscopy, Ultraviolet spectroscopy, Ultraviolet surveys
ALMA High-frequency Long-baseline Campaign in 2019: Band 9 and 10 In-band and Band-to-band Observations Using ALMA's Longest Baselines. The Atacama Large Millimeter/submillimeter Array high-frequency long-baseline campaign in 2019 (HF-LBC-2019) was arranged to undertake band 9 (690 GHz) and 10 (850 GHz) observations using the longest 16 km baselines in order to explore calibration feasibility and imaging capabilities. Observations were arranged using close calibrators between 0° and 4° from the target point-source quasars (QSOs) to also explore subtle effects of calibrator separation angle. A total of 13 observations were made, five using standard in-band observations and eight using the band-to-band (B2B) observing mode, where phase solutions are transferred from a lower frequency band. At bands 9 and 10, image angular resolutions as high as 7 and 5 mas were achieved, respectively. Both in-band and B2B experiments were successful in imaging the target QSOs but with varying degrees of quality. Target image coherence varied between 0.14 and 0.79, driven by the calibrator separation angle and effectiveness of phase referencing despite observing in correct stability conditions. We conclude that the phase rms conditions and calibrator selection, specifically separation angle from the target, must carefully be considered prior to observing in order to minimize imaging defects. For bands 9 and 10, in order to achieve a coherence &gt;0.7 such that the image structure and source flux can be regarded as suitably accurate, a 1° separated calibrator should be used while the phase rms over the phase switching cycle time should ideally be &lt;30°.

Keywords: Submillimeter astronomy, Long baseline interferometry, Phase error
Results of the Photometric LSST Astronomical Time-series Classification Challenge (PLAsTiCC). Next-generation surveys like the Legacy Survey of Space and Time (LSST) on the Vera C. Rubin Observatory (Rubin) will generate orders of magnitude more discoveries of transients and variable stars than previous surveys. To prepare for this data deluge, we developed the Photometric LSST Astronomical Time-series Classification Challenge (PLAsTiCC), a competition that aimed to catalyze the development of robust classifiers under LSST-like conditions of a nonrepresentative training set for a large photometric test set of imbalanced classes. Over 1000 teams participated in PLAsTiCC, which was hosted in the Kaggle data science competition platform between 2018 September 28 and 2018 December 17, ultimately identifying three winners in 2019 February. Participants produced classifiers employing a diverse set of machine-learning techniques including hybrid combinations and ensemble averages of a range of approaches, among them boosted decision trees, neural networks, and multilayer perceptrons. The strong performance of the top three classifiers on Type Ia supernovae and kilonovae represent a major improvement over the current state of the art within astronomy. This paper summarizes the most promising methods and evaluates their results in detail, highlighting future directions both for classifier development and simulation needs for a next-generation PLAsTiCC data set.

Keywords: Astronomy software, Observational cosmology, Transient detection, Astrostatistics
Multiwavelength Bulge-Disk Decomposition for the Galaxy M81 (NGC 3031). I. Morphology. A panchromatic investigation of morphology for the early-type spiral galaxy M81 is presented in this paper. We perform bulge-disk decomposition in M81 images at a total of 20 wave bands from far-UV to near-IR (NIR) obtained with GALEX, Swift, Sloan Digital Sky Survey, WIYN, Two Micron All Sky Survey, Wide-field Infrared Survey Explorer, and Spitzer. Morphological parameters such as Sérsic index, effective radius, position angle, and axis ratio for the bulge and the disk are thus derived at all of the wave bands, which enables quantifying the morphological K-correction for M81 and makes it possible to reproduce images for the bulge and the disk in the galaxy at any wave band. The morphology as a function of wavelength appears as a variable-slope trend of the Sérsic index and the effective radius, in which the variations are steep at UV-optical and shallow at optical-NIR bands; the position angle and the axis ratio keep invariable at least at optical-NIR bands. It is worth noting that the Sérsic index for the bulge reaches ~4-5 at optical and NIR bands, but drops to ~1 at UV bands. This difference brings forward a caveat that a classical bulge is likely misidentified for a pseudobulge or no bulge at high redshifts where galaxies are observed through rest-frame UV channels with optical telescopes. The next work of this series is planned to study spatially resolved spectral energy distributions for the bulge and the disk, respectively, and thereby explore stellar population properties and star formation/quenching history for the galaxy composed of the subsystems.

Keywords: Extragalactic astronomy, Galaxy photometry, Galaxies, Galaxy structure
Systematically Measuring Ultra-diffuse Galaxies (SMUDGes). V. The Complete SMUDGes Catalog and the Nature of Ultradiffuse Galaxies. We present the completed catalog of ultradiffuse galaxy (UDG) candidates (7070 objects) from our search of the DR9 Legacy Survey images, including distance and total mass estimates for 1529 and 1436 galaxies, respectively, that we provide and describe in detail. From the sample with estimated distances, we obtain a sample of 585 UDGs (μ 0,g  ≥ 24 mag arcsec-2 and r  e  ≥ 1.5 kpc) over 20,000 square degrees of sky in various environments. We conclude that UDGs in our sample are limited to 1010 ≲ M  h /M ⊙ ≲ 1011.5 and are on average a factor of 1.5-7 deficient in stars relative to the general population of galaxies of the same total mass. That factor increases with increasing galaxy size and mass up to a factor of ~10 when the total mass of the UDG increases beyond M  h  = 1011 M ⊙. We do not find evidence that this factor has a dependence on the UDGs large-scale environment.

Keywords: Galaxy formation, Galaxy evolution, Galaxy properties, Low surface brightness galaxies
RMTable2023 and PolSpectra2023: Standards for Reporting Polarization and Faraday Rotation Measurements of Radio Sources. Faraday rotation measures (RMs) have been used for many studies of cosmic magnetism, and in most cases having more RMs is beneficial for those studies. This has lead to the development of RM surveys that have produced large catalogs, as well as meta-catalogs collecting RMs from many different publications. However, it has been difficult to take full advantage of all of these RMs, as the individual catalogs have been published in many different places, and in many different formats. In addition, the polarization spectra used to determine these RMs are rarely published, limiting the ability to reanalyze data as new methods or additional observations become available. We propose a standard convention for RM catalogs, RMTable2023, and a standard for source-integrated polarized spectra of radio sources, PolSpectra2023. These standards are intended to maximize the value and utility of these data for researchers and to make them easier to access. To demonstrate the use of the RMTable2023 standard, we have produced a consolidated catalog of 55,819 RMs collected from 42 published catalogs.

Keywords: Spectropolarimetry, Radio astronomy