Sazuna/UAT_keywords huggingface dataset:
ALMA-IMF. XIV. Free─Free Templates Derived from H41α and Ionized Gas Content in 15 Massive Protoclusters. We use the H41α recombination line to create templates of the millimeter free─free emission in the ALMA-IMF continuum maps, which allows us to separate it from dust emission. This method complements spectral-index information and extrapolation from centimeter-wavelength maps. We use the derived maps to estimate the properties of up to 34 H II regions across the ALMA-IMF protoclusters. The hydrogen ionizing photon rate Q 0 and spectral types follow the evolutionary trend proposed by Motte et al. The youngest protoclusters lack detectable ionized gas, followed by protoclusters with increasing numbers of OB stars. The total Q 0 increases from ∼1045 s−1 to &gt;1049 s−1. We used the adjacent He41α line to measure the relative number abundances of helium, finding values consistent with the Galactic interstellar medium, although a few outliers are discussed. A search for sites of maser amplification of the H41α line returned negative results. We looked for possible correlations between the electron densities, emission measures, and Q 0 with H II region size D. The latter is the best correlated, with Q 0 ∝ D 2.49 ± 0.18. This favors interpretations in which smaller ultracompact H II regions are not necessarily the less dynamically evolved versions of larger ones but rather are ionized by less massive stars. Moderate correlations were found between the dynamical width ∆V dyn with D and Q 0. ∆V dyn increases from about 1 to 2 times the ionized-gas sound speed. Finally, an outlier H II region south of W43-MM2 is discussed. We suggest that this source could harbor an embedded stellar or disk wind.

Keywords: Millimeter astronomy, Star forming regions, H II regions
New Strong Gravitational Lenses from the DESI Legacy Imaging Surveys Data Release 9. We have conducted a search for strong gravitational lensing systems in the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys Data Release 9. This is the third paper in a series. These surveys together cover ∼19,000 deg2 visible from the Northern Hemisphere, reaching a z-band AB magnitude of ∼22.5. We use a deep residual neural network, trained on a compilation of known lensing systems and high-grade candidates as well as nonlenses in the same footprint. After applying our trained neural network to the survey data, we visually inspect and rank images with probabilities above a threshold which has been chosen to balance precision and recall. We have found 1895 lens candidates, of which 1512 are identified for the first time. Combining the discoveries from this work with those from Papers I (335) and II (1210), we have discovered a total of 3057 new candidates in the Legacy Surveys.

Keywords: Cosmology, Sky surveys, Surveys, Strong gravitational lensing, Convolutional neural networks, Galaxy masses, Elliptical galaxies
A Swift X-Ray View of the SMS4 Sample. II. X-Ray Properties of 17 Bright Radio Sources. Based on a proposal to observe 18 bright radio sources from the SMS4 catalog with the Neil Gehrels Swift Observatory (hereafter Swift), we obtained X-ray observations of 17 targets (one target was not observed). Following up our first paper that discussed 31 sources (see Maselli et al.; 20 sources detected as point sources and one very extended source), we present results for this final sample of 17 radio sources that previously lacked dedicated, pointed narrow-field-of-view (FOV) X-ray observations. One of these 17 sources, undetected by Swift due to a very short exposure, was instead detected by eROSITA, and given in the Data Release 1 (DR1) Catalog. No 1eRASS source was found in the DR1 for the remaining source, unobserved by Swift. The new Swift observations led to 11 X-ray source detections in the 0.3–10 keV band and six upper limits. We investigated the extent of the X-ray emission and the hardness ratio, and when statistics allowed, we carried out a spectral analysis. The X-ray emission of eight sources is consistent with pointlike emission, while three sources show clear evidence of extent, each with peculiar properties. We used the X-ray determined positions and uncertainties of the 12 detected sources to establish associations with infrared and optical sources from the AllWISE and the GSC 2.4.2 catalogs. Requiring a detection in both the infrared and the optical bands to establish a candidate counterpart for our X-ray detections, we identify counterparts for all 12 sources. Following this X-ray-based approach to derive the position of the active nucleus, we are able to confirm the same IR counterparts previously proposed by White et al. for eight sources, and provide four new IR candidates. In the optical, we identify counterparts that match the candidates previously given by Burgess &amp; Hunstead for all sources. We discuss the interesting structure of MRC B0344‑345 and PKS B2148‑555, two of the six extended X-ray sources that we detected in both our Swift campaigns, and suggest they are very promising for further X-ray and radio investigations. For the 38 SMS4 sources that lack pointed, narrow-FOV X-ray telescope observations, after our Swift campaigns, we list 18 likely counterparts from the eROSITA DR1 catalog.

Keywords: X-ray astronomy, Extragalactic radio sources, Active galaxies
FAST Ultra-Deep Survey: Data Release for FUDS0. We have used the Five-hundred-meter Aperture Spherical radio Telescope (FAST) to conduct a blind ultradeep survey for neutral hydrogen (H I). We present the complete results from the first of six fields (FUDS0). These observations of 95 hr allowed us to achieve a high-sensitivity (∼50 μJy beam‑1) and a high-frequency resolution (22.9 kHz) over an area of 0.72 deg2. We detected 128 galaxies in H I distributed over the redshift range of 0 &lt; z &lt; 0.4, with H I masses in the range of  , and three faint high-velocity clouds, with a peak column density of N H I  ≤ 3.1 × 1017 cm‑2. Of the galaxies, 95 are new detections and six have z &gt; 0.38, where no unlensed H I emission has previously been directly detected. Estimates of completeness and reliability are presented for the catalog. The consistency of continuum and H I flux estimates with the NRAO VLA Sky Survey and the Arecibo Ultra-Deep Survey, respectively, confirms the accuracy of the calibration method and data reduction pipeline developed for the full FAST Ultra-Deep Survey.

Keywords: High-velocity clouds, High-redshift galaxies, Galaxy evolution, H I line emission
A Comprehensive Timing Analysis of Individual Pulses in X-Ray Bursts from SGR J0501+4516. The pulses in X-ray-burst (XRB) light curves from soft gamma-ray repeaters (SGRs) are generally thought to arise from magnetic crustal fractures or magnetic reconnection, reflecting the evolution of the energy release process in magnetars. In this study, we conduct a comprehensive timing analysis of 27 XRBs from SGR J0501+4156 detected by the Gamma-ray Burst Monitor on board Fermi. Utilizing a improved pulse-finding algorithm, we identify a total of 95 pulses and fit them using multiple FRED functions to obtain pulse-shape parameters based on the Markov Chain Monte Carlo method. We calculate the minimum variability timescales (MVTs) of the XRBs based on the shortest pulse; the distribution of MVTs follows a log-Gaussian function with a mean of   ms (1σ). The distributions of rise time, decay time, waiting time, width, skewness, and peakedness all follow the log-Gaussian function, and multiple power-law dependencies are observed between them; for example, a power-law positive correlation between decay time and rise time with 4.7σ, and a power-law negative correlation between pulse width and peakedness with 6.8σ. Besides, there is a positive correlation with 3.7σ between the number of pulses and burst duration. Our findings favor a magnetospheric origin, and some similarities with gamma-ray bursts imply that they have similar radiation mechanisms, e.g., magnetic reconnection processes.

Keywords: Magnetars
Statistics and Habitability of F-type Star–Planet Systems. F-type star–planet systems represent an intriguing case for habitability studies. Although F-type stars spend considerably less time on the main sequence (MS) than G-, K-, and M-type stars, they still offer a unique set of features, allowing for the principal possibility of exolife. Examples of these features include the increased widths of stellar habitable zones as well as the presence of enhanced UV flux, which in moderation may have added to the origin of life in the Universe. In this study, we pursue a detailed statistical analysis of the currently known planet-hosting F-type stars by making use of the NASA Exoplanet Archive. After disregarding systems with little or no information on the planet(s), we identify 206 systems of interest. We also evaluate whether the stars are on the MS based on various criteria. In one approach, we use the stellar evolution code MESA. Depending on the adopted criterion, about 60–80 stars have been identified as MS stars. In 18 systems, the planet spends at least part of its orbit within the stellar habitable zone. In one case, i.e., HD 111998, known as 38 Vir, the planet is situated in the habitable zone at all times. Our work may serve as a basis for future studies, including studies on the existence of Earth-mass planets in F-type systems, as well as investigations of possibly habitable exomoons hosted by exo-Jupiters, as the lowest-mass habitable zone planet currently identified has a mass estimate of 143 Earth masses.

Keywords: Exoplanet catalogs, Exoplanets, Exoplanet astronomy, Stellar astronomy, Astrobiology, Stellar types, Habitable zone, F stars, Catalogs, Stellar evolution
The Chandra Source Catalog Release 2 Series. The Chandra Source Catalog (CSC) is a virtual X-ray astrophysics facility that enables both detailed individual source studies and statistical studies of large samples of X-ray sources detected in Advanced CCD Imaging Spectrometer and High Resolution Camera-I imaging observations obtained by the Chandra X-ray Observatory. The catalog provides carefully curated, high-quality, and uniformly calibrated and analyzed tabulated positional, spatial, photometric, spectral, and temporal source properties, as well as science-ready X-ray data products. The latter includes multiple types of source- and field-based FITS format products that can be used as a basis for further research, significantly simplifying follow-up analysis of scientifically meaningful source samples. We discuss in detail the algorithms used for the CSC Release 2 Series, including CSC 2.0, which includes 317,167 unique X-ray sources on the sky identified in observations released publicly through the end of 2014, and CSC 2.1, which adds Chandra data released through the end of 2021 and expands the catalog to 407,806 sources. Besides adding more recent observations, the CSC Release 2 Series includes multiple algorithmic enhancements that provide significant improvements over earlier releases. The compact source sensitivity limit for most observations is ∼5 photons over most of the field of view, which is ∼2× fainter than Release 1, achieved by coadding observations and using an optimized source detection approach. A Bayesian X-ray aperture photometry code produces robust fluxes even in crowded fields and for low-count sources. The current release, CSC 2.1, is tied to the Gaia-CRF3 astrometric reference frame for the best sky positions for catalog sources.

Keywords: X-ray sources, Catalogs
Identifying Mergers in the Legacy Surveys with Few-shot Learning. Galaxy mergers exert a pivotal influence on the evolutionary trajectory of galaxies and the expansive development of cosmic structures. The primary challenge encountered in machine learning–based identification of merging galaxies arises from the scarcity of meticulously labeled data sets specifically dedicated to merging galaxies. In this paper, we propose a novel framework utilizing few-shot learning techniques to identify galaxy mergers in the Legacy Surveys. Few-shot learning enables effective classification of merging galaxies even when confronted with limited labeled training samples. We employ a deep convolutional neural network architecture trained on data sets sampled from Galaxy Zoo Decals to learn essential features and generalize to new instances. Our experimental results demonstrate the efficacy of our approach, achieving high accuracy and precision in identifying galaxy mergers with few labeled training samples. Furthermore, we investigate the impact of various factors, such as the number of training samples and network architectures, on the performance of the few-shot learning model. The proposed methodology offers a promising avenue for automating the identification of galaxy mergers in large-scale surveys, facilitating the comprehensive study of galaxy evolution and structure formation. In pursuit of identifying galaxy mergers, our methodology is applied to analyze the Data Release 9 of the Dark Energy Spectroscopic Instrument Legacy Imaging Surveys. As a result, we have unveiled an extensive catalog encompassing 648,183 galaxy merger candidates. We publicly release the catalog alongside this paper.

Keywords: Surveys, Convolutional neural networks, Astronomical object identification, Galaxy mergers
Dependence of Virial Factors on Optical Spectral Properties of Active Galactic Nuclei. Reverberation mapping (RM) has long been a powerful tool for measuring the masses of supermassive black holes (SMBHs) at the centers of active galactic nuclei (AGNs), but the precision of these mass measurements depends on the so-called virial factors. It has been demonstrated that the virial factors exhibit significant diversity, spanning approximately 1–2 orders of magnitude across different AGNs. However, the underlying physical drivers for the diversity have not yet been finalized. Here, adopting the SMBH mass–spheroid luminosity relations of inactive galaxies with different bulge classifications, we calibrate the virial factors corresponding to the AGNs with pseudobulges (PBs) and classical bulges (or elliptical hosts, CBs) using the latest nearby RM sample. We investigate the correlations between virial factors and the AGN spectral properties, and find that for both PB and CB samples, the FWHM-based virial factors exhibit significant anticorrelations with the emission-line widths and profiles, while the σ line-based virial factors only show moderate anticorrelations with line widths for PBs. We attribute these correlations mainly to the inclination angle or opening angle of the broad-line regions. Moreover, we establish new relations to give more precise virial factors and, in combination with the latest iron-corrected radius–luminosity relation, tentatively develop new single-epoch estimators of SMBH masses, which enable more accurate measurements of SMBH masses in large AGN samples.

Keywords: Supermassive black holes, Reverberation mapping, Active galactic nuclei, Quasars
Catalog of Proper Orbits for 1.25 Million Main-belt Asteroids and Discovery of 136 New Collisional Families. The proper elements of asteroids are obtained from the instantaneous orbital elements by removing periodic oscillations produced by gravitational interactions with planets. They are unchanged in time, at least if chaotic dynamics and nongravitational forces could be ignored, and can therefore be used to identify fragments of major collisions (asteroid families) that happened eons ago. Here we present a new catalog of proper elements for 1.25 × 106 main-belt asteroids. We explain the methodology, evaluate uncertainties, and discuss how the new catalog can be used to identify asteroid families. A systematic search for families yielded 153 cases not reported in Nesvorný et al.—17 of these cases were identified in various other publications, and 136 cases are new discoveries. There are now 274 families in the asteroid belt in total (plus a handful of families in the resonant Hilda population). We analyzed several compact families in detail. The new family around the middle-belt asteroid (9332) 1990SB1 (nine members) is the youngest family found so far (estimated formation only 16–17 kyr ago). The new families (1217) Maximiliana, (6084) Bascom, (10164) Akusekijima, and (70208) 1999RX33 all formed 0.5–2.5 Myr ago. The (2110) Moore–Sitterly family is a close pair of relatively large bodies, 2110 and 44612, and 15 small members all located sunward from 2110 and 44612, presumably a consequence of the Yarkovsky drift over the estimated family age (1.2–1.5 Myr). A systematic characterization of the new asteroid families is left for future work.

Keywords: Hirayama families, Collision physics, Asteroid dynamics
Forecast of Foreground Cleaning Strategies for AliCPT-1. We report the test results of several independent foreground cleaning pipelines used in the Ali CMB Polarization Telescope experiment (AliCPT-1), a high-altitude cosmic microwave background (CMB) imager in the Northern Hemisphere with thousands of detectors dedicated to the search for a primordial CMB polarization B-mode signature. Based on simulated data from four detector modules and a single season of observation, which we refer to as Data Challenge 1 (DC1), we employ different and independent pipelines to examine the robustness and effectiveness of estimates on foreground parameters and primordial B-mode detection. The foreground cleaning strategies used in the pipelines include the parametric method of template fitting (TF) and the nonparametric methods of constrained internal linear combination (cILC), analytical blind separation (ABS), and generalized least squares (GLS). We examine the impact of possible foreground residuals on the estimate of the CMB tensor-to-scalar ratio (r) for each pipeline by changing the contamination components in the simulated maps and varying the foreground models and sky patches for various tests. According to the DC1 data with the simulation input value r true = 0.023, the foreground residual contamination levels in the TF/ABS/cILC/GLS pipelines are well within the corresponding statistical errors at the 2σ level. Furthermore, by utilizing the tension estimator, which helps identify significant residual foreground contamination in the detection of the primordial B-mode signal by quantifying the discrepancy between various r measurements, we conclude that the presence of small foreground residuals does not lead to any significant inconsistency in the estimation of r.

Keywords: Cosmic microwave background radiation, Cosmological parameters
Optical Variability of Gaia CRF3 Sources with Robust Statistics and the 5000 Most Variable Quasars. Using the light-curve time-series data for more than 11.7 million variable sources published in the Gaia Data Release 3, the average magnitudes, colors, and variability parameters have been computed for 0.836 million Gaia CRF objects, which are mostly quasars and active galactic nuclei (AGNs). To mitigate the effects of occasional flukes in the data, robust statistical measures have been employed: namely, the median, median absolute deviation, and Spearman correlation. We find that the majority of the CRF sources have moderate amplitudes of variability in the Gaia G band just below 0.1 mag. The heavy-tailed distribution of variability amplitudes (quantified as robust standard deviations) does not find a single analytical form, but is closer to Maxwell distribution with a scale of 0.078 mag. The majority of CRF sources have positive correlations between G magnitude and G BP‑G RP colors, meaning that these quasars and AGNs become bluer when they are brighter. The variations in the G BP and G RP bands are also mostly positively correlated. Dependencies of all variability parameters with cosmological redshift are fairly flat for the more accurate estimates above redshift 0.7, while the median color shows strong systematic variations with redshift. Using a robust normalized score of magnitude deviations, a sample of the 5000 most variable quasars is selected and published. The intersection of this sample with the ICRF3 catalog shows a much higher rate of strongly variable quasars (mostly blazars) in ICRF3.

Keywords: Quasars, Blazars, Light curves, Astrometry, Gaia
Metrics of Astrometric Variability in the International Celestial Reference Frame. I. Statistical Analysis and Selection of the Most Variable Sources. Using very long baseline interferometry data for the sources that comprise the third International Celestial Reference Frame (ICRF3), we examine the quality of the formal source-position uncertainties of ICRF3 by determining the excess astrometric variability (unexplained variance) for each source as a function of time. We also quantify multiple qualitatively distinct aspects of astrometric variability seen in the data, using a variety of metrics. Average position offsets, statistical dispersion measures, and coherent trends over time as explored by smoothing the data are combined to characterize the most and least positionally stable ICRF3 sources. We find a notable dependence of the excess variance and statistical variability measures on decl., as is expected for unmodeled ionospheric delay errors and the Northern Hemisphere–dominated network geometries of most astrometric and geodetic observing campaigns.

Keywords: Very long baseline interferometry, Radio sources, Astrometry, Quasars
Identifying Light-curve Signals with a Deep-learning-based Object Detection Algorithm. II. A General Light-curve Classification Framework. Vast amounts of astronomical photometric data are generated from various projects, requiring significant effort to identify variable stars and other object classes. In light of this, a general, widely applicable classification framework would simplify the process of designing specific classifiers for various astronomical objects. We present a novel deep-learning framework for classifying light curves using a weakly supervised object detection model. Our framework identifies the optimal windows for both light curves and power spectra automatically, and zooms in on their corresponding data. This allows for automatic feature extraction from both time and frequency domains, enabling our model to handle data across different scales and sampling intervals. We train our model on data sets obtained from Kepler, TESS, and Zwicky Transient Facility multiband observations of variable stars and transients. We achieve an accuracy of 87% for combined variable and transient events, which is comparable to the performance of previous feature-based models. Our trained model can be utilized directly for other missions, such as the All-sky Automated Survey for Supernovae, without requiring any retraining or fine-tuning. To address known issues with miscalibrated predictive probabilities, we apply conformal prediction to generate robust predictive sets that guarantee true-label coverage with a given probability. Additionally, we incorporate various anomaly detection algorithms to empower our model with the ability to identify out-of-distribution objects. Our framework is implemented in the Deep-LC toolkit, which is an open-source Python package hosted on Github (https://github.com/ckm3/Deep-LC) and PyPI.

Keywords: Light curve classification , Convolutional neural networks, Astronomy data analysis, Transient detection, Variable stars