Sazuna/UAT_keywords huggingface dataset:
Radio-loudness Statistics of Quasars from Quaia-VLASS. Quasars are objects of high interest in extragalactic astrophysics, cosmology, and astrometry. One of their useful qualities is their potential radio-loudness. However, the fraction of radio-loud versus radio-quiet quasars is subject to ongoing investigations, where the statistical power is limited by the low number of known quasars with radio counterparts. In this analysis, we revisited the radio-loudness statistics of quasars by significantly expanding the pool of known sources. Our main goal was to create a new, value-added quasar catalog with information about their extinction-corrected magnitudes, radio flux density, possible contamination levels, and other flags, besides their sky coordinates and photometric redshifts. We cross-matched the optical Quaia catalog of about 1.3 million quasars (from the Gaia data) with 1.9 million sources from the Very Large Array Sky Survey (VLASS) radio catalog. We explored different thresholds for the matching radius, balancing completeness and purity of the resulting Quaia-VLASS catalog, and found 1 .″ 5 a sufficient choice. Our main finding is that the quasar radio-loud fraction is in good agreement with previous works (&lt;10%), and there is no significant large-scale sky pattern in radio-loudness. The exact estimate depends on the G-band magnitude limit, and we observed weak trends with redshift and absolute optical magnitude, possibly indicating remnant systematic effects in our data. The crossmatched Quaia-VLASS catalog with 43,650 sources and accompanying codes is available at doi:10.5281/zenodo.16035690. This latest census of QSOs with radio counterparts will facilitate further investigations of the dichotomy of radio-loud and radio-quiet quasars, and it may also support other lines of research.

Keywords: Quasars, Surveys, Large-scale structure of the universe, Active galaxies, Radio loud quasars, Catalogs
A Catalog of Hα Emission-line Stars and 785 Newly Identified Young Stellar Object Candidates from LAMOST Based on a Deep Learning Method. The Hα emission line commonly appears in the spectra of many stars and serves as a key indicator for tracing ionized interstellar gas, investigating stellar activity, and studying gas dynamics. Young stellar objects (YSOs), representing the early evolutionary stages of stars, typically exhibit the Hα emission line in their spectra. In this paper, we use bidirectional long short-term memory networks and convolutional neural networks to identify Hα emission-line stars in medium-resolution spectra from the Large Area Multi-Target Fiber Optic Spectroscopic Telescope (LAMOST) survey, and further search for YSO candidates via the Li absorption line. We constructed a data set by crossmatching previously published data sets with LAMOST data and performing manual verification. Using this data set, we built an identification model that achieved an accuracy of 97.58% on the testing set. Application of this model to the full survey yielded 46,867 Hα emission-line star candidates, with 41,996 visually confirmed detections (15,329 of which are recorded in SIMBAD). To further identify YSOs, we developed a dedicated Li absorption line detector, identifying 4618 preliminary candidates from the Hα emission-line stars. Rigorous vetting confirmed 4255 YSO candidates, comprising 3470 previously cataloged objects and 785 new discoveries. All catalogs (Hα emission-line stars and YSOs) and the code of the proposed model are publicly released to facilitate community research.

Keywords: Emission line stars, Convolutional neural networks, Astronomy data analysis, Stellar classification, Young stellar objects, Stellar spectral types
An S-shaped Filament Formed Due to Cloud–Cloud Collision in Molecular Cloud G178.28-00.61. We present compelling observational evidence supporting G178.28-00.61 as an early-stage candidate for cloud–cloud collision (CCC), with indications of the formation of an S-shaped filament, evenly separated dense cores, and young star clusters. The observations of CO molecular line emission demonstrate the existence of two interacting molecular clouds with systemic velocities of 0.8 km s‑1 and ‑1.2 km s‑1, respectively. The convergence zone of these two clouds reveals an S-shaped filament in the James Clerk Maxwell Telescope 850 μm continuum image, suggesting cloud interaction. In line with expectations from CCC simulations, broad bridging features are discernible in the position–velocity diagrams. An elevated concentration of identified Class I and II young stellar objects along the filament at the intersection area further supports the hypothesis of a collision-induced origin. This observation could be explained by a recent MHD model of CCC, which predicts a similar morphology, scale, density, and unbound status, as well as the orientation of the polarization.

Keywords: Interstellar dynamics, Star formation, Molecular clouds
Physical Parameters and Chromospheric Activity of Eclipsing Binaries Observed by the LAMOST DR10 Survey. In this study, we present a comprehensive study of more than 50,000 spectra of 32,257 eclipsing binaries from the LAMOST DR10 survey, including 5200 systems with spectroscopy. We quantified their chromospheric activity through Hα spectral subtraction with iSpec, among 20,000 binaries showing significant excess emission. The chromospheric activity increases toward shorter orbital periods and lower metallicity. By combining tidally locked rotation periods with convective turnover times, we have computed their Rossby numbers and uncovered a geometry-driven shift in the saturation threshold: the detached EA systems saturate at  logRo≃‑1.3  (Ro ≈ 0.05), whereas equivalent width (EW) contact binaries, owing to their common convective envelope (CCE), do not reach saturation until  logRo≃‑1.6  (Ro ≈ 0.025). The CCE enlarges the magnetic-flux reservoir via L1-spanning field lines and strong shear effects, demanding faster rotation to attain the chromospheric limit. For Ro ≲ 0.02, we observe a mild downturn consistent with supersaturation. The high-precision Transiting Exoplanet Survey Satellite light curves for 4326 eclipsing binaries reveal starspot amplitudes that correlate tightly with the Hα activity, confirming enhanced magnetism in close binaries. We have detected 1752 flare events (1179 from 208 EA, 429 from 44 EB, 144 from EW) on eclipsing binaries. We also determined their parameters and the flare frequency distributions in the different types of eclipsing binaries. In the end, we also give the plan of eclipsing binaries in the LAMOST low and medium-resolution spectra future survey.

Keywords: Stellar chromospheres, Stellar activity
The Lyα and Continuum Origins Survey. I. Survey Description and Lyα Imaging. Understanding the mechanisms driving the escape of ionizing or Lyman continuum (LyC) emission from the interstellar medium of galaxies is necessary to constrain the evolution of reionization and the sources responsible for it. While progress has been made in identifying the global galaxy properties linked to the ionizing escape fraction  fescLyC , little is currently known about how spatially resolved galaxy properties impact it. We present Hubble Space Telescope (HST) imaging data obtained in the Lyα and Continuum Origins Survey (LaCOS). LaCOS consists of HST imaging covering rest-frame optical and UV bands for a subsample of 42 galaxies in the Low redshift Lyman Continuum Survey, including 22 LyC emitters ( fescLyC=0.01-0.49 ). Here, we describe the sample, observations, and data reduction, and investigate connections between global and sub-kiloparsec Lyα emission and  fescLyC . We confirm the correlation between  fescLyC  and EWLyα, and the anticorrelation with r50, when using values obtained via global photometry. We also find correlations previously found with spectroscopy with global photometric LLyα,  fescLyα , ΣSFR, and  fescLyC , but with a smaller degree of correlations ( ∣∆τ∣̄∼0.1 ). We find correlations are strongest between Lyα observables (LLyα, EWLyα) and  fescLyC  when measured in a small aperture around the brightest UV source in each galaxy. We interpret these results as evidence that LyC photons escaping on the line of sight are contributed by a small number of UV-bright compact regions in most galaxies in LaCOS.

Keywords: Ultraviolet sources, Emission line galaxies, Ultraviolet astronomy, Lyman-alpha galaxies, Reionization, Galaxies
Identification of OB Associations Using the LAMOST–Gaia OB Star Sample. OB associations, as an intermediate stage between Galactic clusters and field stars, play an important role in understanding the star formation process, early stellar evolution, and Galactic evolution. In this work, we construct a large sample of OB stars with six-dimensional (6D) phase space parameters (l, b, d, Vlos, pmra, pmdec) by combining the distances from C. A. L. Bailer-Jones et al., radial velocities derived from low-resolution spectra of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, and proper motions from Gaia Data Release 3 (DR3). This sample includes 19,933 OB stars, most of which are located within 6 kpc of the Sun. Using 6D phase-space parameters and a friends-of-friends clustering algorithm, we identify 67 OB associations and 112 OB association candidates; among these, 49 OB associations and 107 OB association candidates are newly identified. The Galactic rotation curve derived using 67 OB association members is relatively flat in the range of Galactocentric distances 7 &lt; R &lt; 13 kpc. The angular rotation velocity at a solar Galactocentric distance of R⊙ = 8.34 kpc is Ω0 = 29.05 ± 0.55 km s‑1 kpc‑1. The spatial distribution of the 67 OB associations indicates that they are mainly located at low Galactic latitudes and near spiral arms of the Milky Way. Additionally, we estimate the velocity dispersions and sizes of these 67 OB associations. Our results show that the velocity dispersions decrease as Galactocentric distances increase, while their sizes increase as Galactocentric distances increase.

Keywords: Early-type stars, Stellar kinematics, OB associations, Open star clusters, Dynamical evolution
Optimizing Convolution Direction and Template Selection for Difference Image Analysis. Difference image analysis (DIA) is a powerful tool for studying time-variable phenomena, and has been used by many time-domain surveys. Most DIA algorithms involve matching the spatially varying point-spread function shape between science and template images, and then convolving that shape in one image to match the other. The wrong choice of which image to convolve can introduce one of the largest sources of artifacts in the final difference image. We introduce a quantitative metric to determine the optimal convolution direction that depends not only on the sharpness of the images measured by their FWHM, but also on their exposure depths. With this metric, the optimal convolution direction can be determined a priori, depending only on the FWHM and depth of the images. This not only simplifies the process, but also makes it more robust and less prone to creating suboptimal difference images due to the wrong choice of the convolution direction. As an additional benefit, for a large set of images, we define a Figure-of-Merit based on this metric, which allows us to rank a list of images and determine the ones best suited to be used as templates, thus streamlining and automating the data reduction process.

Keywords: Time domain astronomy, Astronomy data analysis, Astronomy image processing
The TESS Grand Unified Hot Jupiter Survey. III. Thirty More Giant Planets. We present the discovery of 30 transiting giant planets that were initially detected using data from NASA's Transiting Exoplanet Survey Satellite mission. These new planets orbit relatively bright (G ≤ 12.5) FGK host stars with orbital periods between 1.6 and 8.2 days, and have radii between 0.9 and 1.7 Jupiter radii. We performed follow-up ground-based photometry, high angular resolution imaging, high-resolution spectroscopy, and radial velocity monitoring for each of these objects to confirm that they are planets and determine their masses and other system parameters. The planets' masses span more than an order of magnitude (0.17 MJ &lt; Mp &lt; 3.3 MJ). For two planets, TOI-3593 b and TOI-4961 b, we measured significant nonzero eccentricities of  0.11−0.03+0.05  and  0.18−0.05+0.04  , respectively, while for the other planets, the data typically provide a 1σ upper bound of 0.15 on the eccentricity. These discoveries represent a major step toward assembling a complete, magnitude-limited sample of transiting hot Jupiters around FGK stars. *This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: Hot Jupiters, Transit photometry, Radial velocity, Exoplanets
The Three-mm Ultimate Mopra Milky Way Survey. III. Data Release 6, An Atlas of Physical Conditions, Global Mass Conversion Laws, and 3D Physical Architecture of the Molecular Interstellar Medium in the Fourth Quadrant. We present Data Release 6 of ThrUMMS, consisting of complete data cubes and various moments of line emission (12CO, 13CO, C18O) from molecular clouds, across 60° × 2° of the Fourth Quadrant (4Q) of the Milky Way at a resolution of 72″ in (l, b) and 0.09 km s‑1 in VLSR. From LTE radiative transfer analysis of the data cubes, we compute cubes and moments of the lines' opacity, excitation temperature, and column density  N12CO . Combining  I12CO  and  N12CO  data, we derive a global mass conversion law N = N0Ip, where N0 ≈ 1018 mol m‑2 and p = 2 at this resolution. We argue that the standard linear N = XI is only approximately valid: p ∼ 1.5–1.0 at coarser resolutions or in atypical locations, such as Galactic center clouds. The velocity dispersion distributions are very different between  I12CO  and  N12CO , the former preferentially tracing more diffuse molecular gas. We reevaluated Galactic rotation parameters for the 4Q, defining a new "BGT" model, and deprojected the (l, V) data onto (l, d) and (x, y) grids using standard kinematic procedures. To automate distance disambiguation inside the solar circle, we developed a simple ζ+ discriminator function and applied it to our deprojections. We discovered two previously unrecognised features of the molecular cloud population: widespread ripples in the midplane of wavelength 4 kpc and amplitude 50 pc, potentially generated by the last perigalactic passage of the Sgr dwarf; and three distant, massive molecular structures, the Far Ara Clouds, two of which exhibit an exceptional velocity gradient, possibly lying near the bar's far end or in a gas-rich dwarf galaxy ∼20–300 kpc beyond the disk.

Keywords: Star forming regions, Galaxy structure, Molecular clouds, Galaxy kinematics, Radiative transfer, Interstellar medium
From Equipartition to Curvature: The Spectral Evolution of 4FGL Blazars. We investigate the evolution of spectral energy distribution (SED) and underlying electron energy distribution (EED) by modeling the nearly simultaneous broadband spectra of selected bright 4FGL blazars, in the context of a combined cooling and stochastic acceleration scenario. We find that a one-zone leptonic model with log-parabolic EED can successfully fit the GeV–TeV emission of blazars. The synchrotron frequency νs of blazars mainly evolves due to the variation of electron peak energy γ3p. BL Lac (BL Lacs) objects show a negative trend in the νs–νsLs SED plane, known as the blazar sequence, that does not seem to be an artifact of Doppler boosting, but is driven by the equipartition constraints. A positive correlation is found between the derived magnetic field B and electron density ne, whereas ne and γ3p negatively relate, as expected in an equipartition scenario. The flat-spectrum radio quasars (FSRQs) deviate significantly from such a scenario, indicating their jet parameters should vary independently. The synchrotron peak frequency νs and its spectral curvature bs negatively correlate for all blazars, confirming the stochastic particle acceleration in blazar jets. However, blazars do not show the signature of hard-sphere acceleration, indicating that magnetic turbulence in the jets might be soft and physical conditions might be near steady state, consistent with equipartition. Furthermore, for BL Lacs, the SED curvature bs and the EED curvature r nearly meet the theoretical relationship of r = 5bs, whereas the FSRQs show a large deviation due to a poor constraint on bs due to the presence of a thermal component.

Keywords: Blazars, Active galactic nuclei, BL Lacertae objects
The ALMA-QUARKS Survey. III. Clump-to-core Fragmentation and Searches for High-mass Starless Cores. The Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures (QUARKS) survey observed 139 infrared-bright (IR-bright) massive protoclusters at 1.3 mm wavelength with the Atacama Large Millimeter/submillimeter Array (ALMA). This study investigates clump-to-core fragmentation and searches for candidate high-mass starless cores within IR-bright clumps using combined ALMA 12 m (C-2) and Atacama Compact Array 7 m data, providing ∼1″ (∼0.02 pc at 3.7 kpc) resolution and ∼0.6 mJy beam−1 continuum sensitivity (∼0.3 M⊙ at 30 K). We identified 1562 compact cores from 1.3 mm continuum emission using getsf. Observed linear core separations (λobs) are significantly less than the thermal Jeans length (λJ), with the λobs/λJ ratios peaking at ∼0.2. This indicates that thermal Jeans fragmentation has taken place within the IR-bright protocluster clumps studied here. The observed low ratio of λobs/λJ ≪ 1 could be the result of evolving core separation or hierarchical fragmentation. Based on associated signatures of star formation (e.g., outflows and ionized gas), we classified cores into three categories: 127 starless, 971 warm, and 464 evolved cores. Two starless cores have masses exceeding 16 M⊙, and represent high-mass candidates. The scarcity of such candidates suggests that competitive accretion-type models could be more applicable than turbulent core accretion-type models in high-mass star formation within these IR-bright protocluster clumps.

Keywords: Star forming regions, Protoclusters, Massive stars, Molecular clouds, Protostars, Dust continuum emission, Interstellar medium, Submillimeter astronomy
Accelerating the Fast Radio Burst Search: Data Set and Methods. Fast radio bursts (FRBs) are an extremely energetic cosmic phenomenon of short duration. Discovered only recently and with its origin still unknown, FRBs have already started to play a significant role in studying the distribution and evolution of matter in the Universe. FRBs can only be observed through radio telescopes, which produce petabytes of data, rendering the search for FRBs a challenging task. Traditional techniques are computationally expensive, time-consuming, and generally biased against weak signals. Various machine learning algorithms have been developed and employed, all of which require substantial data sets. Here, we introduce the FAST data set for FRBs EXploration, built upon the observations obtained by the Five-hundred-meter Aperture Spherical radio Telescope. Our data set comprises 600 positive samples of observed FRB signals from three sources and 1000 negative samples of noise and radio frequency interference. Furthermore, we provide a machine learning algorithm, Radio Single-Pulse Detection Algorithm Based on Visual Morphological Features (RaSPDAM), with significant improvements in efficiency and accuracy for FRB searches. We also employed the benchmark comparison between conventional single-pulse search software, namely, PRESTO and Heimdall, and RaSPDAM. RaSPDAMv2 achieves an average precision of 97% and an average recall of 83%, with notable enhancements in computational performance. Future machine learning algorithms can use this as a reference point to measure their performance and identify potential improvements. By enabling more accurate and efficient detection of transient radio events, our work facilitates the FRB and pulsars search pipeline, enhances the potential for discovering new astrophysical phenomena.

Keywords: Astronomy databases, Astronomy software, Radio transient sources
A Fast, Second-order Accurate Poisson Solver in Spherical Polar Coordinates. We present an efficient and accurate algorithm for solving the Poisson equation in spherical polar coordinates with a logarithmic radial grid and open boundary conditions. The method employs a divide-and-conquer strategy, decomposing the computational domain into hierarchical units with varying cell sizes. James's algorithm is used to compute the zero-boundary potentials of lower-level units, which are systematically integrated to reconstruct the zero-boundary potential over the entire domain. These calculations are performed efficiently via matrix-vector operations using various precomputed kernel matrices. The open-boundary potential is then obtained by applying a discrete Green's function to the effective screening density induced at the domain boundaries. The overall algorithm achieves a computational complexity of  O(N3logN) , where N denotes the number of cells in one dimension. We implement the solver in the FARGO3D magnetohydrodynamics code and demonstrate its performance and second-order accuracy through a series of test problems.

Keywords: Magnetohydrodynamics, Hydrodynamics, Gravitation, Computational methods, Astronomical simulations
PrestoZL: A GPU-accelerated High-throughput Jerk Search Toolkit for Binary Pulsars. The Fourier domain jerk search algorithm, an integral component of the PRESTO software suite, has emerged as a key tool for detecting binary pulsars. However, it is a CPU-based jerk search and is a very computationally expensive process, particularly when exploring a broad range of search parameters. In order to address this challenge, we have developed PrestoZL, a GPU-accelerated, high-throughput jerk search toolkit. PrestoZL introduces an innovative GPU parallel design for the jerk search algorithm to mitigate performance degradation caused by memory-intensive operations. We have also developed a pipelined version of PrestoZL, which adds fine-grained orchestration to the CPU–GPU execution pipeline to alleviate the GPU stall problem during the search. The experiment conducted on a 30 minute observation using a machine equipped with an A100-40G GPU and 20 i7-12700K CPUs, shows that PrestoZL achieves an end-to-end speedup of 56.38× over a CPU-based jerk search in PRESTO with OpenMP. PrestoZL achieves search results that are fully identical to the CPU-based jerk search in PRESTO, including the number of detected pulsars, as well as the output search parameters and signal-to-noise ratio values.

Keywords: GPU computing, Pulsars