Sazuna/UAT_keywords huggingface dataset:
The Structure of the Molecular Envelope of the Ring Nebula (NGC 6720). We present the first interferometric imaging of molecular line emission from the Ring Nebula, NGC 6720, in the form of Submillimeter Array (SMA) observations of CO J = 2 → 1 emission. The SMA 12CO(2–1) mapping data, with ∼3″ spatial resolution and 2 km s‑1 velocity resolution, provide an unprecedentedly detailed, 3D view of the Ring's clumpy molecular envelope. The emission morphology displayed in the velocity-integrated SMA 12CO(2–1) image closely resembles the morphologies of near-IR H2 and polycyclic aromatic hydrocarbon emission as revealed in recent JWST/NIRCam imaging of NGC 6720. The SMA 12CO(2–1) data demonstrate that the molecular gas is found within a geometrically thin layer that immediately surrounds the ionized gas imaged by Hubble Space Telescope and JWST. A simple, geometric model of the 12CO(2–1) emission data shows that the intrinsic structure of NGC 6720's molecular envelope closely resembles a truncated, triaxial ellipsoid that is viewed close to pole-on, and that the dynamical age of the molecular envelope is ∼6000 yr. The SMA 12CO(2–1) mapping data furthermore reveal that some of the faint, filamentary features seen projected in the Ring's interior in JWST imaging are in fact fast-moving polar knots or bullets with radial velocities of ±45–50 km s‑1 relative to the systemic velocity, and that the hot progenitor star remnant is positioned at the precise geometric center of the clumpy, ellipsoidal molecular shell. We assert that the Ring's molecular envelope represents the "fossil" remnant of a relatively sudden mass ejection ∼6000 yr ago that terminated the progenitor star's asymptotic giant branch (AGB) evolution, and that this ellipsoidal envelope of AGB ejecta was then punctured by fast, collimated polar outflows or jets resulting from interactions between the progenitor and one or more companion stars. Such an evolutionary scenario may describe most if not all molecule-rich, "Ring-like" planetary nebulae.

Keywords: Radio interferometry, Molecular gas, Stellar winds, Planetary nebulae
Spatial Variations of Stellar Elemental Abundances in FIRE Simulations of Milky Way-mass Galaxies: Patterns Today Mostly Reflect Those at Formation. Spatial patterns of stellar elemental abundances encode rich information about a galaxy's formation history. We analyze the radial, vertical, and azimuthal variations of metals in stars, both today and at formation, in the FIRE-2 cosmological simulations of Milky Way (MW)-mass galaxies, and we compare them with the MW. The radial gradient today is steeper (more negative) for younger stars, which agrees with the MW, although radial gradients are shallower in FIRE-2. Importantly, this age dependence was present already at birth: radial gradients today are only modestly (≲0.01 dex kpc‑1) shallower than at birth. Disk vertical settling gives rise to negative vertical gradients across all stars, but vertical gradients of mono-age stellar populations are weak. Similar to the MW, vertical gradients in FIRE-2 are shallower at larger radii, but they are overall shallower in FIRE-2. This vertical dependence was present already at birth: vertical gradients today are only modestly (≲0.1 dex kpc‑1) shallower than at birth. Azimuthal scatter is nearly constant with radius, and it is nearly constant with age ≲8 Gyr ago but increases for older stars. Azimuthal scatter is slightly larger (≲0.04 dex) today than at formation. Galaxies with larger azimuthal scatter have a stronger radial gradient, implying that azimuthal scatter today arises primarily from the radial redistribution of gas and stars. Overall, spatial variations of stellar metallicities show only modest differences between formation and today; spatial variations today primarily reflect the conditions of stars at birth, with spatial redistribution of stars after birth contributing secondarily.

Keywords: Galaxy formation, Galaxy chemical evolution, Galaxy abundances, Galaxy evolution, Milky Way evolution, Astronomical simulations
The Radio Counterpart to the Fast X-Ray Transient EP240414a. Despite being operational for only a short time, the Einstein Probe mission, with its large field of view and rapid localization capabilities, has already significantly advanced the study of rapid variability in the soft X-ray sky. We report the discovery of luminous and variable radio emission from the Einstein Probe fast X-ray transient EP240414a, the second such source with a radio counterpart. The radio emission at 3 GHz peaks at ∼30 days postexplosion and with a spectral luminosity ∼2 × 1030 erg s‑1 Hz‑1, similar to what is seen from long gamma-ray bursts, and distinct from other extragalactic transients including supernovae and tidal disruption events, although we cannot completely rule out emission from engine driven stellar explosions, e.g., the fast blue optical transients. An equipartition analysis of our radio data reveals that an outflow with at least a moderate bulk Lorentz factor (Γ ≳ 1.6) with a minimum energy of ∼1048 erg is required to explain our observations. The apparent lack of a reported gamma-ray counterpart to EP240414a could suggest that an off-axis or choked jet could be responsible for the radio emission, although a low-luminosity gamma-ray burst may have gone undetected. Our observations are consistent with the hypothesis that a significant fraction of extragalactic fast X-ray transients are associated with the deaths of massive stars.

Keywords: Gamma-ray bursts, High energy astrophysics, Extragalactic radio sources, Relativistic jets, Transient sources, X-ray transient sources, Radio transient sources
ALMA Observations of Peculiar Embedded Icy Objects. We report the results of molecular line observations with the Atacama Large Millimeter/submillimeter Array (ALMA) toward two peculiar icy objects, which were discovered serendipitously by infrared spectroscopic survey of the Galactic plane with the AKARI satellite. Previous infrared observations have reported that both objects show deep ice and dust absorption features that are often seen in embedded young stellar objects (YSOs) or background stars sitting behind dense clouds; however, they are located neither in known star-forming regions nor in known dense clouds. Their infrared spectral energy distributions (SEDs) show peaks around 5 μm, which are incompatible with existing SED models of typical embedded YSOs. The present ALMA observations have detected compact emission of CO(3–2) and SiO(8–7) at the positions of the icy objects. The observed large column ratios of gas-phase SiO/CO (∼10‑3) in both objects, as well as their broad line widths (8–14 km s‑1), imply that they are associated with shocked gas. Although a large dust extinction (AV ∼ 100 mag) is expected from their deep dust/ice absorption, no dust continuum emission is detected, which would suggest a large beam dilution effect due to their compact source sizes. Their systemic velocities are clearly separated from the surrounding CO clouds, suggesting that they are isolated. The characteristics of their SEDs, the presence of deep ice/dust absorption features, compact source size, and SiO-dominated broad molecular line emission cannot easily be accounted for by any of known interstellar ice-absorption sources. They may represent a previously unknown type of isolated icy objects.

Keywords: Interstellar molecules, OH/IR stars, Ice composition, Astrochemistry, Asymptotic giant branch stars, Star formation, Infrared sources, CO line emission, Shocks, Radio astronomy
Fifteen Years of M31* X-Ray Variability and Flares. We append an additional 15 yr (2009─2024) to the Chandra X-ray light curve of M31*, the supermassive black hole (SMBH) at the center of M31, the Andromeda galaxy. Extending and expanding on the work in Z. Li et al., we show that M31* has remained in an elevated X-ray state from 2006 through at least 2016 (when regular Chandra monitoring ceased) and likely through 2024, with the most recent observations still showing an elevated X-ray flux. We identify one moderate flare in 2013 where the other nuclear X-ray sources are in low-flux states, making that flare a valuable target for follow-up with multiwavelength and multimessenger archival data. We extract a mostly uncontaminated spectrum for M31* from this observation, showing that its X-ray properties are similar to those observed at Sgr A* in its quiescent state by Baganoff et al. Furthermore, we find no substantial change in the source's hardness ratio in the 2006 and 2013 flares compared to the post-2006 elevated state, suggesting the these flares are increases in the regular X-ray emission mechanisms instead of entirely new emission modes. Our extended light curve for M31* provides valuable context for multimessenger or multiwavelength observations of nearby SMBHs.

Keywords: X-ray astronomy, Supermassive black holes, Black holes, High energy astrophysics, X-ray sources, Andromeda Galaxy
Large Molecular and Dust Reservoir of a Gravitationally Lensed Submillimeter Galaxy behind the Lupus I Molecular Cloud. We report the Australian Telescope Compact Array and Nobeyama 45 m telescope detection of a remarkably bright (S1.1mm = 44 mJy) submillimeter galaxy MM J154506.4−344318 in emission lines at 48.5 and 97.0 GHz, respectively. We also identify part of an emission line at ≍218.3 GHz using the Atacama Large Millimeter/submillimeter Array (ALMA). Together with photometric redshift estimates and the ratio between the line and infrared luminosities, we conclude that the emission lines are most likely to be the J = 2─1, 4─3, and 9─8 transitions of 12CO at redshift z = 3.753 ± 0.001. ALMA 1.3 mm continuum imaging reveals an arc and a spot separated by an angular distance of  , indicative of a strongly lensed dusty star-forming galaxy with respective molecular and dust masses of   and   after being corrected for ≍6.6× gravitational magnification. The inferred dust-to-gas mass ratio is found to be high (≍0.0083) among coeval dusty star-forming galaxies, implying the presence of a massive, chemically enriched reservoir of cool interstellar medium at z ≍ 4, or 1.6 Gyr after the Big Bang.

Keywords: Starburst galaxies, Galaxy formation, Strong gravitational lensing, Interstellar medium, Submillimeter astronomy, High-redshift galaxies
Weak-lensing Mass Reconstruction of Galaxy Clusters with a Convolutional Neural Network. II. Application to Next-generation Wide-field Surveys. Traditional weak-lensing mass reconstruction techniques suffer from various artifacts, including noise amplification and the mass-sheet degeneracy. In S. E. Hong et al., we demonstrated that many of these pitfalls of traditional mass reconstruction can be mitigated using a deep learning approach based on a convolutional neural network (CNN). In this paper, we present our improvements and report on the detailed performance of our CNN algorithm applied to next-generation wide-field (WF) observations. Assuming the field of view ( ) and depth (27 mag at 5σ) of the Vera C. Rubin Observatory, we generated training data sets of mock shear catalogs with a source density of 33 arcmin‑2 from cosmological simulation ray-tracing data. We find that the current CNN method provides high-fidelity reconstructions consistent with the true convergence field, restoring both small- and large-scale structures. In addition, the cluster detection utilizing our CNN reconstruction achieves ∼75% completeness down to ∼1014 M⊙. We anticipate that this CNN-based mass reconstruction will be a powerful tool in the Rubin era, enabling fast and robust WF mass reconstructions on a routine basis.

Keywords: Weak gravitational lensing, Convolutional neural networks, Dark matter distribution, Galaxy clusters
Magnetohydrodynamic Simulation of a Coronal Mass Ejection Observed during the Near-radial Alignment of Solar Orbiter and Earth. Interplanetary coronal mass ejections (ICMEs) are the primary sources of geomagnetic storms at Earth. The negative out-of-ecliptic component (Bz) of magnetic field in the ICME or its associated sheath region is necessary for it to be geoeffective. For this reason, magnetohydrodynamic simulations of CMEs containing data-constrained flux ropes are more suitable for forecasting their geoeffectiveness as compared to hydrodynamic models of the CME. ICMEs observed in situ by radially aligned spacecraft can provide an important setup to validate the physics-based heliospheric modeling of CMEs. In this work, we use the constant-turn flux rope (CTFR) model to study an ICME that was observed in situ by Solar Orbiter (SolO) and at Earth, when they were in a near-radial alignment. This was a stealth CME that erupted on 2020 April 14 and reached Earth on 2020 April 20 with a weak shock and a smoothly rotating magnetic field signature. We found that the CTFR model was able to reproduce the rotating magnetic field signature at both SolO and Earth with very good accuracy. The simulated ICME arrived 5 hr late at SolO and 5 hr ahead at Earth, when compared to the observed ICME. We compare the propagation of the CME front through the inner heliosphere using synthetic J-maps and those observed in the heliospheric imager data and discuss the role of incorrect ambient solar wind background on kinematics of the simulated CME. This study supports the choice of the CTFR model for reproducing the magnetic field of ICMEs.

Keywords: Solar coronal mass ejections, Magnetohydrodynamical simulations
The White Dwarf Pareto: Tracing Mass Loss in Binary Systems. The white dwarf mass distribution has been studied primarily at two extremes: objects that presumably evolved as single stars, and members of close binaries that likely underwent substantial interaction. This work considers the intermediate separation regime of ∼1 au and demonstrates how binary interaction affects white dwarf masses. The binary mass ratio distribution is utilized for this purpose. Modeled as a truncated Pareto profile, this distribution provides insights into the populations' properties and evolutionary history. When applied to homogeneous samples of binaries with giant primaries of similar age, the distribution's shape constrains the fraction of white dwarf companions, the white dwarf mass distribution, and the properties of their progenitors. As a test case, this method is applied to a small spectroscopic sample of binaries in open clusters with red giant primaries and orbital periods between 0.5 and 20 yr. The analysis reveals that white dwarfs in these systems are ∼20% less massive than their isolated counterparts, with a typical mass of ∼0.55 M⊙. Their progenitors likely lost 80%‑85% of their mass, with binary interactions enhancing mass loss by an additional ∼0.2 M⊙. These findings highlight the utility of this approach for studying binary evolution and improving population models, particularly with future data sets from Gaia and other large-scale surveys.

Keywords: Binary stars, White dwarf stars, Astrostatistics, Spectroscopic binary stars, Mass ratio, Red giant stars
Origin of α-poor Very Metal-poor Stars. Among very metal-poor (VMP) stars, α-poor VMP (α-PVMP) stars that have subsolar values of [X/Fe] for Mg and other α elements are rare and are thought to have been formed from gas polluted by Type 1a supernova (SN 1a). However, recent analyses indicate that pure core-collapse supernova (CCSN) ejecta can also be a likely source. We perform a detailed analysis of 17 α-PVMP stars by considering six different scenarios relevant to the early Galaxy. We consider a single pair-instability supernova (PISN) and a single CCSN. Additionally, we consider the combination of ejecta from a CCSN with ejecta from another CCSN, a PISN, a near-Chandrasekhar mass (near-MCh) SN 1a, and a sub-Chandrasekhar mass (sub-MCh) SN 1a. A clear signature can only be established for sub-MCh SN 1a with a near-smoking-gun signature in SDSS J0018-0939 and a reasonably clear signature in ET0381. The majority (82%) of α-PVMP stars can be explained by pure CCSN ejecta and do not require any SN 1a contribution. However, the combination of CCSN and sub-MCh SN 1a ejecta can also explain most (76%) of α-PVMP stars. In contrast, the combination of ejecta from CCSN with near-MCh SN 1a and PISN can fit 41% and 29% of the stars, respectively. The single PISN scenario is strongly ruled out for all stars. Our results indicate that α-PVMP stars are equally compatible with pure CCSN ejecta and a combination of CCSN and SN 1a ejecta, with sub-MCh SN 1a being roughly twice as frequent as near-MCh SN 1a.

Keywords: Population III stars, Core-collapse supernovae, Type Ia supernovae, Population II stars, Stellar nucleosynthesis, Chemically peculiar stars
Green Peas in the Southern Sky: Broadband Color Selection and Spectroscopic Follow-up. We present a systematic search for 1696 green pea (GP) galaxy candidates in the southern hemisphere selected from the Dark Energy Survey Data Release 2 and provide preliminary results from spectroscopic follow-up observations of 26 targets chosen among them. Our selection criteria include the colors in the gri bands and compact morphology in the color-composite images. The multiwavelength spectral energy distribution fitting shows that the selected GP candidates exhibit star formation rates up to several tens of M⊙ yr−1. With the mean stellar mass of  , GP candidates are located at roughly 1 dex above the main sequence of star-forming galaxies at z ∼ 0.3. Spectroscopic follow-up observations of the GP candidates with Gemini/Gemini Multi-Object Spectrograph are underway. All 26 targets are spectroscopically confirmed to be at z = 0.3─0.41 and have an [O III] equivalent width larger than 85 Å, classified to be starbursts with low-to-moderate dust attenuation. These confirmed GPs show a lower metallicity offset from the mass─metallicity relation of local star-forming galaxies, indicating that GPs are less chemically evolved systems at their early stage of evolution.

Keywords: Starburst galaxies, Galaxies, Emission line galaxies
New Perspective on the Multiple-population Phenomenon in Galactic Globular Clusters from a Wide-field Photometric Survey. Wide-field photometry of Galactic globular clusters (GCs) has been investigated to overcome limitations from the small field of view of the Hubble Space Telescope in the study of multiple populations. In particular, "chromosome maps" (ChMs) built with ground-based photometry were constructed to identify the first- and second-generation (1G and 2G) stars over the wide field of view. The ChMs allow us to derive the fraction of distinct populations in an analyzed field of view. We present here the radial distribution of the 2G fraction in 29 GCs. The distributions show that all the GCs have either a flat distribution or more centrally concentrated 2G stars. Notably, we find that the fraction of 1G stars outside the half-light radius is clearly bifurcated across all mass range. It implies that a group of GCs with lower 1G fractions (hereafter Group II) have efficiently lost their 1G stars in the outermost cluster regions. In fact, in connection with the trends of the radial distribution, most GCs of Group II have spatially mixed populations, while only less massive GCs in Group I (a group with higher 1G fraction) show that feature. Lastly, we investigate links between these two groups and host cluster parameters. We find that most GCs of Group II are distributed along a broader range of galactocentric distances with smaller perigalactic distances &lt; 3.5 kpc. Besides, by using the Gaia data, it is observed that Group II GCs have higher energy on the integrals of motion diagrams than Group I GCs.

Keywords: Globular star clusters, Population II stars, Photometry
Probing Three-dimensional Magnetic Fields. IV. Synchrotron Polarization Derivative and Vision Transformer. Measuring the 3D spatial distribution of magnetic fields in the interstellar medium and the intracluster medium is crucial yet challenging. The probing of the 3D magnetic field's 3D distribution, including the field plane-of-sky orientation (ψ), the magnetic field's inclination angle (γ) relative to the line of sight, and the magnetization (∼the inverse Alfvén Mach number  ), at different distances from the observer makes the task even more formidable. However, the anisotropy and Faraday decorrelation effect in polarized synchrotron emission offer a unique solution. We show that due to the Faraday decorrelation, only regions up to a certain effective path length along the line of sight contribute to the statistical correlation of the measured polarization. The 3D spatial information can be consequently derived from synchrotron polarization derivatives (SPDs), which are calculated from the difference in synchrotron polarization across two wavelengths. We find that the 3D magnetic field can be estimated from the anisotropy observed in SPDs: the elongation direction of the SPD structures probes ψ, and the degree of SPD anisotropy, along with its morphological curvature, provides insights into   and γ. To extract these anisotropic features and their correlation with the 3D magnetic field, we propose utilizing a machine learning approach, specifically the Vision Transformer (ViT) architecture, which was exemplified by the success of ChatGPT. We train the ViT using synthetic synchrotron observations generated from magnetohydrodynamic turbulence simulations in sub-Alfvénic and super-Alfvénic conditions. We show that ViT's application to multiwavelength SPDs can successfully reconstruct the 3D magnetic fields' 3D spatial distribution.

Keywords: Convolutional neural networks, Astrophysical magnetism, Interstellar synchrotron emission, Magnetohydrodynamics
The Polarization Signatures of the Inverse Cascade in Magnetic Turbulence. The inverse cascade of magnetic energy from smaller to larger scales is a key physical process for the formation of coherent magnetic fields in many astronomical turbulent systems. Synchrotron radiation polarization, an observable measurement closely related to the magnetic field topology and particle distribution function, is an important and promising tool for diagnosing this highly dynamic process. Here, for the first time, we use the first-principle particle-in-cell simulations to systematically investigate the polarization signatures during the inverse cascade of the magnetic field. We find that the polarization degree (PD) increases rapidly with the increase in the coherent scale of the magnetic field during the inverse transfer and its growth rate is positively correlated with the rate of inverse transfer and could be described by a logarithmic growth formula, and we also identify that the scale with the largest PD variation is coincident with this coherent scale by applying the spatial filter method. In addition, we show that the polarization signature is significantly dependent on the radiated photon energy and the line of sight, with high-energy radiation more sensitive to the increase in the coherent scale of the turbulent magnetic field than low-energy radiation, and the polarization characteristics present significant pitch-angle anisotropy due to the acceleration of particles in the presence of a strong background magnetic field. Our results provide a promising method to explore the astrophysical inverse cascade process and infer the coherent scale of turbulence, which could be validated by astronomical observations in the future.

Keywords: Interplanetary turbulence, Polarimetry, Interplanetary particle acceleration, Interstellar synchrotron emission, Magnetic fields