Sazuna/UAT_keywords huggingface dataset:
47 Tuc in Rubin Data Preview 1. Exploring Early LSST Data and Science Potential. We present analyses of the early data from Rubin Observatory's Data Preview 1 (DP1) for the field of the globular cluster 47 Tuc. The DP1 data set for 47 Tuc includes four nights of observations from the Rubin Commissioning Camera (LSSTComCam), covering multiple bands (ugriy). We address challenges of crowding in the inner region of the cluster and toward the SMC in DP1, and demonstrate improved star–galaxy separation by fitting fifth-degree polynomials to the stellar loci in color–color diagrams and applying multidimensional sigma clipping. We compile a catalog of 3576 probable 47 Tuc member stars selected via a combination of isochrone, Gaia proper-motion, and color–color space matched filtering. We explore the sources of photometric scatter in the 47 Tuc color–color sequence, evaluating contributions from various potential sources, including differential extinction within the cluster. Finally, of the 72 well-characterized variables in the field, we recover three known variable stars, including two RR Lyrae and one eclipsing binary, in the coadd-based object catalog, and identify 62 in the difference image-based object catalog. Although the DP1 lightcurves have sparse temporal sampling, they appear to follow the patterns of densely sampled literature lightcurves well. Despite some data limitations for crowded-field stellar analysis, DP1 demonstrates the promising scientific potential for future LSST data releases.

Keywords: Globular star clusters, Hertzsprung Russell diagram, Multi-color photometry, Variable stars
The Interstellar Medium in I Zw 18 Seen with JWST/MIRI. I. Highly Ionized Gas. We present JWST/MIRI spectra from the Medium-Resolution Spectrometer of I Zw 18, a nearby dwarf galaxy with a metallicity of ∼3% solar. Its proximity enables a detailed study of highly ionized gas that can be interpreted in the context of newly discovered high-redshift dwarf galaxies. We derive aperture spectra centered on 11 regions of interest; the spectra show very low extinction, AV ≲ 0.1, consistent with optical determinations. The gas is highly ionized; we have detected 10 fine-structure lines, including [O IV] 25.9 μm with an ionization potential (IP) of ∼55 eV, and [Ne V] 14.3 μm with an IP of ∼97 eV. The ionization state of I Zw 18 falls at the extreme upper end of all of the line ratios we analyzed, but not coincident with galaxies containing an accreting massive black hole (active galactic nucleus). Comparison of the line ratios with state-of-the-art photoionization and shock models suggests that the high-ionization state in I Zw 18 is not due to shocks. Rather, it can be attributed to metal-poor stellar populations with a self-consistent contribution of X-ray binaries or ultra-luminous X-ray sources. It could also be partially due to a small number of hot low-metallicity Wolf−Rayet stars ionizing the gas; a small fraction (a few percent) of the ionization could come from an intermediate-mass black hole. Our spectroscopy also revealed four 14 μm continuum sources, ≳30─100 pc in diameter, three of which were not previously identified. Their properties are consistent with H II regions ionized by young star clusters.

Keywords: Dwarf irregular galaxies, Young star clusters, Compact dwarf galaxies, Interstellar medium
A Tale of Two Stars: X-Ray and Ground-based Observations of Two Diverging Stars in Taurus─Auriga. We present XMM-Newton observations and near-simultaneous optical observations of the classical T Tauri star SU Auriga and the nearby Herbig Ae star AB Auriga, two members of the 4 Myr old Taurus─Auriga star-forming region. Combining these observations with archival ones, we examine data covering more than two decades, aiming to determine the X-ray stability of these two stars over that period. We model the X-ray spectra for each star using XSPEC models and present the results of this modeling. For SU Aur, we find evidence for absorption by both the stellar corona and an accretion column, supported by both the best-fit model to the X-ray spectra and the variable, self-absorbed Hα profile observed in the optical. We observe a single flare at the end of the observing period for SU Aur.

Keywords: T Tauri stars, Young stellar objects, Herbig Ae/Be stars, Stellar flares
On the Meaning of the Dynamo Radius in Giant Planets with Stable Layers. Current structure models of Jupiter and Saturn suggest that helium becomes immiscible in hydrogen in the outer part of the planets' electrically conducting regions. This likely leads to a layer in which overturning convection is inhibited due to a stabilizing compositional gradient. The presence of such a stably stratified layer impacts the location and mechanism of convectively driven dynamo action. Juno's measurements of Jupiter's magnetic field enabled an estimate of its dynamo radius based on the magnetic Lowes spectrum. A depth of ∼0.8RJ is obtained, where 1RJ is Jupiter's radius. This is rather deep, considering that the electrical conductivity inside Jupiter is expected to reach significant values at ∼0.9RJ. Here, we use three-dimensional numerical dynamo simulations to explore the effects of the existence and location of a stably stratified helium rain layer on both the inferred Lowes radius and the location of the radial extent of dynamo action. We focus on a Jupiter-like internal structure and electrical conductivity profile. We find that for shallower stable layers, there is no magnetic field generation occurring above the stable layer, and the effective dynamo radius and the inferred Lowes radius are at the base of the layer. For deeper stable layers, Lowes radii of ∼0.87RJ are inferred as a shallow secondary dynamo operates above the stable layer. Our results strongly suggest the existence of a stable layer extending from ∼0.8RJ up to at least ∼0.9RJ inside Jupiter. The physical origin of this extended stable layer and its connection to helium rain remain to be elucidated.

Keywords: Planetary interior, Solar system gas giant planets, Jupiter, Magnetohydrodynamical simulations
High-resolution Simulation of Coronal Mass Ejection–Corotating Interaction Region Interactions: Mesoscale Solar Wind Structure Formation Observable by the SWIFT Constellation. We present an unprecedented simulation of how two large-scale heliospheric transients—a coronal mass ejection (CME) and a corotating stream interaction region—collide, producing a dramatic increase in the complexity of the CME due to formation of mesoscale flux ropes. These structures are captured for the first time by a numerical simulation using high-resolution numerical grids. The circumstances that lead to the formation of these complex structures occur during solar maximum. At the time of the solar maximum taken for this study, 2014 September, the heliospheric current sheet is vertically inclined running over the poles, allowing the CME to impact a preceding slow-fast stream interaction region. The simulation is performed with the Alfvén Wave Solar Atmosphere Model (or AWSoM), with which we initiate a fast CME from active region (AR) 12158 by applying a Gibson–Low magnetic flux rope. Magnetic reconnection within the leading extremity of the CME results in the formation of mesoscale flux ropes, which contain sufficiently strong magnetic fields (∼30 nT) to affect planetary magnetospheres. Finally, we use a tetrahedral configuration of four virtual probes, corresponding to the Space Weather Investigation Frontier mission concept, to show that the mission can uniquely resolve the spatial characteristics and temporal evolution of reconnecting current sheets within the CME, as well as the resulting mesoscale structures.

Keywords: Solar magnetic reconnection, Interplanetary turbulence, Space weather, Solar coronal mass ejection shocks, Solar coronal mass ejections
Selecting Clusters and Protoclusters via Stellar Mass Density. I. Method and Tests on Mock HSC-SSP Catalogs. We present an algorithm designed to identify galaxy (proto)clusters in wide-area photometric surveys by first selecting their dominant galaxy—i.e., the brightest cluster galaxy (BCG) or protoBCG—through the local stellar mass density traced by massive galaxies. We focus on its application to the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) Wide Survey to detect candidates up to z ∼ 2. In this work, we apply the method to mock galaxy catalogs that replicate the observational constraints of the HSC-SSP Wide Survey. We derive functions that describe the probability of a massive galaxy being the dominant galaxy in a structure as a function of its stellar mass density contrast within a given redshift interval. We show that galaxies with probabilities greater than 50% yield a sample of BCGs/protoBCGs with ≳65% purity, where most of the contamination arises from galaxies in massive groups below our cluster threshold. Using the same threshold, the resulting (proto)cluster sample achieves 80% purity and 50% completeness for halos with Mhalo ≥ 1014M⊙, reaching nearly 100% completeness for Mhalo ≥ 1014.5M⊙. We also assign probabilistic membership to surrounding galaxies based on stellar mass and distance to the dominant galaxy, from which we define the cluster richness as the number of galaxies more likely to be true members than contaminants. This allows us to derive a halo mass─richness relation. In a companion paper, we apply the algorithm to the HSC-SSP data and compare our catalog with others based on different cluster-finding techniques and X-ray detections.

Keywords: Galaxy clusters, High-redshift galaxy clusters, Surveys, Protoclusters, Brightest cluster galaxies, High-redshift galaxies, Algorithms
Selecting Clusters and Protoclusters via Stellar Mass Density. II. Application to HSC-SSP Observations. We present a selection of candidates of clusters and protoclusters of galaxies identified in the photometric data of the HSC-SSP Wide Public Data Release 3 (PDR3), spanning the redshift range 0.1 ≤ z ≤ 2. The selection method, detailed in Vicentin et al., involves detecting massive galaxies located in high-density regions of matter, identified as potential central dominant galaxies, i.e., (proto)brightest cluster galaxies (protoBCGs or BCGs). Probabilistic criteria based on proximity to the candidate central galaxy and the expected stellar mass of member galaxies are applied to identify likely members of each structure. We produced updated photometric redshift estimates using deep learning methods trained on a data set combining spectroscopic redshifts from the HSC-SSP Wide PDR3, high-accuracy photometric redshifts from the COSMOS2020 catalog, and midinfrared data from the unWISE catalog for matched sources. Our method achieves a predicted purity of ∼90% in detecting (proto)clusters, with ≳65% correctly identifying the (proto)BCG. A total of 16,007 candidate (proto)clusters were identified over an effective area of ∼850 deg2 within the HSC-SSP Wide footprint. Comparisons with other existing catalogs reveal a good level of consistency, while also highlighting that different methods yield complementary discoveries. We further compare richness and halo masses from our optical catalog with those from recent X-ray cluster catalogs (eROSITA and MCXC-II), finding a moderate positive correlation and a scatter of ∼0.4 dex. This catalog provides a valuable new set of targets for the Prime Focus Spectrograph instrument.

Keywords: Galaxy clusters, High-redshift galaxy clusters, Surveys, Brightest cluster galaxies, Algorithms, Catalogs
HST Proper Motions of Andromeda V and Andromeda VI. We measure the absolute proper motions of Andromeda V (And V) and Andromeda VI/Pegasus (And VI) dwarf galaxies, satellites of M31 located near its galactic plane. And VI is located the farthest from M31 among the six satellites with currently measured proper motions. A combination of Advanced Camera for Surveys/wide filed channel (WFC) and WFPC2 exposures is utilized, spanning a 20 yr time baseline. The WFPC2 exposures are processed using a recently developed deep-learning centering procedure as well as the most up-to-date astrometric calibration of the camera. We use on the order of 100 background galaxies per satellite to determine the correction to absolute proper motion. For And V, we obtain an absolute proper motion of  (μα,μδ)AndV=(26.1±21.5,−74.2±19.1)μas  yr−1. For And VI, we obtain an absolute proper motion of  (μα,μδ)AndVI=(−1.6±12.3,−52.6±11.2)μas  yr−1. Orbit integrations and analyses are made for these two Andromeda satellites using two estimates of both the mass and proper motion of M31. It is found that And V has an orbit consistent within errors with alignment with M31's disk and counter orbiting it, although this alignment is not well constrained. And VI's orbit is better determined and is very much consistent with coorbiting with M31's disk. While currently at a distance of ∼280 kpc from M31, And VI will remain beyond a distance of ∼90 kpc from M31, thus experiencing low tidal influence compared to the other M31 satellites with known orbits. Both satellites are determined to be well-bound to M31.

Keywords: Local Group
Extended and Compact Ortho-H<SUB>2</SUB>D<SUP>+</SUP> Structures Close to the Moment of Star Formation: Evidence from ALMA-ACA Observations in Taurus. Observing and characterizing pre- and protostellar cores in the earliest and densest stages of star formation is challenging due to their short timescales and high densities, limiting the suitable tracers and targets. We conducted Atacama Large Millimeter/submillimeter Array-Atacama Compact Array standalone observations of ortho-H2D+ (11,0─11,1) emission, which is believed to trace cold high-density regions, toward three dense cores in the Taurus molecular cloud: (1) L1544, likely in the densest prestellar phase; (2) MC 35 mm, a candidate for the first hydrostatic core; and (3) MC 27/L1521F, which hosts a Class 0 very-low-luminosity object. These observations provide high angular resolution data for the line across a set of cores selected to represent consecutive stages around the onset of star formation, offering a unique opportunity to trace the time evolution of ∼104 yr. With the single-dish total-power array, we detected ortho-H2D+ emission in all three cores, revealing its presence over scales of ∼10,000 au. In the interferometric 7 m array data with a beam size of 3 .″ 5 (∼500 au), emission was detected only toward the central continuum source of MC 35 mm, with a significance of ∼3σ. No significant detections were found in the other targets, placing an upper limit on the H2D+ abundance of ∼10−11 in the dense components traced by the interferometric continuum emission. These results suggest that ortho-H2D+ predominantly exhibits an extended distribution over several thousand au in the early stages of star formation. Detection in compact, dense central structures may only be achieved within a few ×104 yr immediately before or after protostar formation.

Keywords: Interstellar molecules, Molecular clouds, Star formation, Interstellar medium, Protostars, Collapsing clouds
Study of Neutron Capture Nucleosynthesis Based on Post─Asymptotic Giant Branch Stars. The intermediate neutron-capture process (i-process) may occur during proton ingestion events, with post─asymptotic giant branch (AGB) stars considered among its potential astrophysical sites. This study selected the post-AGB star IRAS 14325-6428, which is enriched in both Ba ([Ba/Fe] = 2.08) and Eu ([Eu/Fe] = 1.25), to investigate its elemental abundance pattern and the odd-isotope ratio of Ba. The atmospheric parameters of the star, Teff = 7900 ± 80 K, log g = 1.2 ± 0.10, [Fe/H]= −0.75 ± 0.05, and ξt = 5.8 ± 0.20 km s−1, were derived, taking into account non─local thermodynamic equilibrium effects. We match the observed elemental abundances with the pattern of abundance distributions of various astrophysical processes and find that the s- and r-processes alone or together cannot explain the heavy element enrichment mechanism in this star. The observed odd-isotope ratio of barium is fodd,Ba = 0.25 ± 0.08, suggesting that the heavy elements in post-AGB star IRAS 14325-6428 may be contaminated by the i-process.

Keywords: Stellar abundances, Post-asymptotic giant branch, Nucleosynthesis
Metallicity of the Double Red Clump in the Milky Way Bulge. We present a reanalysis of the metallicity of the double red clump (RC) stars from the Milky Way bulge. Two leading explanations for the existence of the double RC concern possible differences in chemical composition (multiple populations of stars) or distance (X-shaped bulge). We aim to verify the chemical composition hypothesis by determining the mean metallicity of each RC. We use infrared photometric data and metallicities from a previous study (that are based on the Michigan/Magellan Fiber System spectra). In contrast with previous studies, we assign stars to RCs or the red giant branch using a Bayesian approach. Our resulting difference between mean metallicity of the two RCs equals:  0.23−0.24+0.19  or  0.28−0.18+0.17dex , if the red giant branch bump is included or not, respectively. Because of the high statistical error, the result does not confirm the multiple populations hypothesis.

Keywords: Red giant clump, Stellar populations, Galactic bulge
The Impact of Enhanced Extreme-ultraviolet Flux on the Upper Atmosphere of Earth-like Exoplanets. Identifying Earth-like planets outside our solar system is a leading research goal in astronomy, but determining if candidate planets have atmospheres, and more importantly if they can retain atmospheres, is still out of reach. In this paper, we present our study on the impact of enhanced extreme-ultraviolet (EUV) flux on the stability and escape of the upper atmosphere of an Earth-like exoplanet using the Global Ionosphere and Thermosphere Model. We also investigate the differences between 1D and 3D solutions. We use a baseline case of EUV flux experienced at the Earth, and multiply this flux by a constant factor going up to 50. Our results show a clear evidence of an inflated and elevated ionosphere due to enhanced EUV flux, and they provide a detailed picture of how different heating and cooling rates, as well as the conductivity, are changing at each EUV flux level. Our results also demonstrate that 1D solutions are limited in their ability to capture a global atmosphere that is not uniform. We find that a threshold EUV flux level for a stable atmosphere occurs around a factor of 10 times the baseline level, where EUV fluxes above this level indicate a rapidly escaping atmosphere. This threshold EUV flux translates to about 0.3 au for a planet orbiting the Sun. Thus, our findings indicate that an Earth-like exoplanet orbiting its host star in a close-in orbit is likely to lose its atmosphere quickly.

Keywords: Habitable planets, Exoplanet atmospheres, Magnetohydrodynamical simulations
The Effect of Poloidal Magnetic Field and Helicity Injection in a Breakout Coronal Mass Ejection. Coronal mass ejections (CMEs), as crucial drivers of space weather, necessitate a comprehensive understanding of their initiation and evolution in the solar corona in order to better predict their propagation. Solar Cycle 24 exhibited lower sunspot numbers compared to Solar Cycle 23, along with a decrease in the heliospheric magnetic pressure. Consequently, a higher frequency of weak CMEs was observed during Solar Cycle 24. Forecasting CMEs is vital, and various methods, primarily involving the study of the global magnetic parameters using data sets like Space-weather Helioseismic and Magnetic Imager Active Region Patches, have been employed in earlier works. In this study, we perform numerical simulations of CMEs within a magnetohydrodynamics framework using Message Passing Interface–Adaptive Mesh Refinement Versatile Advection Code in 2.5D. By employing the breakout model for CME initiation, we introduce a multipolar magnetic field configuration within a background bipolar magnetic field, inducing shear to trigger the CME eruption. Our investigation focuses on understanding the impact of the background global magnetic field on CME eruptions. Furthermore, we analyze the evolution of various global magnetic parameters in distinct scenarios (failed eruption, single eruption, and multiple eruptions) resulting from varying amounts of helicity injection in the form of shear at the base of the magnetic arcade system. Our findings reveal that an increase in the strength of the background poloidal magnetic field constrains CME eruptions. Furthermore, we establish that the growth rate of absolute net current helicity is the crucial factor that determines the likelihood of CME eruptions.

Keywords: Solar coronal mass ejections, Solar corona, Magnetohydrodynamical simulations
Characterizing Close Binary Supermassive Black Holes in Blazars 3C 273, 3C 454.3, S0528+134, and AO 0235+164: Insights from Multifrequency Radio Monitoring and Gravitational-wave Prospects. We present new constraints on the physical properties of close binary supermassive black holes (SMBHs) in the active galactic nuclei 3C 273, 3C 454.3, S0528+134, and AO 0235+164 based on long-term, multifrequency radio monitoring. By applying a combined time-series analysis using Fourier and wavelet techniques, we identify quasiperiodic variations indicative of orbital motion in compact binary SMBH systems. The derived parameters point to highly compact configurations, with total system masses reaching up to ∼2.4 · 1010 M⊙ and near-equal mass ratios. The inferred orbital separations and periods suggest that these binaries are in a late inspiral stage, emitting gravitational waves in the nanohertz range. Estimated strain amplitudes indicate that such sources may be detectable by current and upcoming pulsar timing arrays, including IPTA, NANOGrav, and EPTA. These results support the hypothesis that a subset of bright blazars host tightly bound SMBH pairs and represent a promising population of low-frequency gravitational-wave sources.

Keywords: Blazars, Supermassive black holes, Active galactic nuclei, Gravitational wave sources
Shedding Light on the Solar Dynamo Using Data-driven Bayesian Parameter Inference. We use a zero-dimensional stochastic dynamo model describing the coupled oscillatory behavior of the toroidal and poloidal components of the solar magnetic field. The model includes a time delay, arising from the assumption that the two field components are generated in spatially segregated locations, and a quenching of the α-effect for amplitudes of the toroidal magnetic field outside a range defined by a lower and an upper threshold. We apply two distinct simulation-based Bayesian inference methods to calibrate the model parameters. The first approach employs a Simulated Annealing Approximate Bayesian Computation algorithm, based on the comparison of relevant features extracted from observed data with their counterparts from simulated data. The second one leverages a sequential neural posterior density estimation method known as Automatic Posterior Transformation. The inference was carried out using two different data sets: the observed sunspot record and a recent millennial solar activity reconstruction based on 14C cosmogenic radionuclides from tree rings. The different methods and data sets produce remarkably consistent posterior distributions for the model parameters. Bayesian inference results corroborate the hypothesis presented in a previous publication that the solar dynamo might be operating close to a critical bifurcation point characterized by the coexistence of two modes akin to normal and Grand Minima regimes. We show that the calibrated dynamo model, despite its simplicity, can be used to make predictions about solar cycles.

Keywords: Bayesian statistics, Posterior distribution, Sunspots, Solar dynamo, Solar physics