Sazuna/UAT_keywords huggingface dataset:
Structure and Fragmentation Scale of a Massive Star-forming Filament in NGC 6334: High-resolution Mid-infrared Absorption Imaging with JWST. Dense filaments are believed to be representative of the initial conditions of star formation in molecular clouds. We have used the MIRI instrument on JWST to image the massive filament NGC 6334M at d ∼ 1.3 kpc with unprecedented resolution and dynamic range at 7.7 and 25.5 μm. Our observations reveal the fine structure of the filament in absorption against mid-infrared background emission. From the absorption data, we derive high-resolution column density maps and perform a detailed analysis of the structure of NGC 6334M. We find a median filament width of 0.12 ± 0.02 pc at both wavelengths, resolved by almost two orders of magnitude with MIRI, and consistent with the typical half-power width of Herschel filaments in nearby (d &lt; 500 pc) clouds. The JWST data also reveal the presence of a quasi-periodic series of side filaments with a similar projected spacing of 0.125 ± 0.015 pc. Combining our JWST results with Spitzer and APEX/Herschel data, we perform a study of cloud structure over four orders of magnitude in linear scale. A convergence test shows that our width estimates for NGC 6334M are robust and reflect the presence of a true characteristic scale. While there is evidence of a Kolmogorov-like spectrum of small-scale fluctuations down to the 1.6 × 10−3 pc resolution of the JWST observations, we identify a break in the power spectrum of column density fluctuations at a scale ∼0.1─0.4 pc comparable to the width of NGC 6334M and its side filaments. This characteristic scale ∼0.1 pc has important implications for the origin of the star formation efficiency in dense gas and the initial mass function.

Keywords: Star formation, Dark interstellar clouds, Interstellar filaments, Infrared dark clouds
Spatial Age Distribution of Classical Cepheids in Spiral Galaxies: The Cases of M31 and M33. Classical Cepheids can be used as age indicators due to well-established period–age and period–age–color relations. G. De Somma et al. refined these relations by including a metallicity term and different mass–luminosity assumptions. In this study, we apply the period–age–metallicity relation for the first time to samples of classical Cepheids in M31 and M33. For both galaxies, we consider Cepheid coordinates and spatial distributions, along with the metallicity gradient by D. Zaritsky et al. and L. Magrini et al. to provide a metallicity estimate for each pulsator. Therefore, by applying the period–age–metallicity relation, we derive the individual ages of each Cepheid. By combining the individual ages and spatial distributions of classical Cepheids in M31 and M33, we built detailed age maps for both galaxies. Our analysis confirms a radial age gradient, with younger Cepheids preferentially found toward the galactic center. In M31, we confirm an outer ring at ∼11 kpc, consistent with previous studies, and identify for the first time an inner ring at ∼7 kpc, possibly associated with star formation episodes. Comparing age gradients at different angles, we find a consistent general trend of ages increasing monotonically with radius. At the same time, we observe smaller-scale differences, particularly in the 90°–180° quadrant, suggesting asymmetric star formation and possible dynamical influences. In contrast, M33 displays a steeper global age gradient, indicating a higher concentration of young stars toward its center. This study highlights the utility of Cepheids as stellar population tracers, providing insights into the star formation and dynamical evolution of spiral galaxies. Future works will extend this methodology to additional galaxies.

Keywords: Spiral galaxies, Stellar pulsations, Galaxy interactions, Cepheid variable stars, Triangulum Galaxy, Andromeda Galaxy, Stellar evolution
On the Impact of Neutrinos on the Launching of Relativistic Jets from "Magnetars" Produced in Neutron Star Mergers. A significant interest has emerged recently in assessing whether collimated and ultrarelativistic outflows can be produced by a long-lived remnant from a binary neutron star (BNS) merger, with different approaches leading to different outcomes. To clarify some of the aspect of this process, we report the results of long-term (i.e., ∼110 ms) state-of-the-art general relativistic magnetohydrodynamics simulations of the inspiral and merger of a BNS system of magnetized stars. We find that after ∼50 ms from the merger an α–Ω dynamo driven by the magnetorotational instability sets in in the densest regions of the disk and leads to the breakout of the magnetic field lines from the accretion disk around the remnant. The breakout is responsible for generating a collimated, magnetically driven outflow with only mildly relativistic velocities and for a violent eruption of electromagnetic energy. We provide evidence that this outflow is partly collimated via a Blandford–Payne mechanism. Finally, by including or not the radiative transport via neutrinos, we determine the role they play in the launching of the collimated wind. In this way, we conclude that the mechanism of magnetic field breakout we observe is robust and takes place even without neutrinos. Contrary to previous expectations, the inclusion of neutrino absorption and emission leads to a smaller baryon pollution in polar regions and hence accelerates the occurrence of the breakout, yielding a larger electromagnetic luminosity. Given the mildly relativistic nature of these disk-driven breakout outflows, it is difficult to consider them responsible for the jet phenomenology observed in short gamma-ray bursts.

Keywords: Neutron stars, Gamma-ray bursts, Stellar winds, Radiative transfer simulations, Magnetohydrodynamical simulations
MINDS: The Very Low-mass Star and Brown Dwarf Sample Hidden Water in Carbon-dominated Protoplanetary Disks. Infrared observations of the inner disks around very low-mass stars (VLMS; &lt;0.3 M⊙) have revealed a carbon-rich gas composition in the terrestrial planet-forming regions. Contrary to the typically water-rich T Tauri disk spectra, only two disks around VLMS have been observed to be water-rich among more than 10 VLMS disks observed so far with JWST/MIRI. In this Letter, we systematically search for the presence of water and other oxygen-bearing molecules in the JWST/MIRI spectra of 10 VLMS disks from the MIRI mid-INfrared Disk Survey (MINDS). In addition to the two previously reported detections of water emission in this VLMS sample, we detect water emission in the spectra of three other sources and tentatively in one source, and we provide strong evidence for water emission in the remaining disks in the MINDS sample, most of which have bright emission from carbon-bearing molecules. We show that the C2H2 emission is much stronger than that of water for sources with low luminosities, and the hydrocarbons outshine the water emission in such conditions. We propose that the appearance of water-rich versus hydrocarbon-rich spectra is related to the location of the water reservoir in the disk relative to the main hydrocarbon reservoir. Our findings indicate that the terrestrial planet-forming regions in VLMS disks have high carbon-to-oxygen ratios (C/O &gt; 1) but can still harbor ample water, similar to those in the T Tauri disks.

Keywords: Low mass stars, James Webb Space Telescope, Brown dwarfs, Protoplanetary disks
Constraints on Nonthermal Pressure at Galaxy Cluster Outskirts from a Joint SPT and XMM-Newton Analysis. We present joint South Pole Telescope and XMM-Newton observations of eight massive galaxy clusters (0.8–2 × 1015 M⊙) spanning a redshift range of 0.16–0.35. Employing a novel Sunyaev–Zel'dovich + X-ray fitting technique, we effectively constrain the thermodynamic properties of these clusters out to the virial radius. The resulting best-fit electron density, deprojected temperature, and deprojected pressure profiles are in good agreement with previous observations of massive clusters. For the majority of the cluster sample (five out of eight clusters), the entropy profiles exhibit a self-similar behavior near the virial radius. We further derive hydrostatic mass, gas mass, and gas fraction profiles for all clusters up to the virial radius. Comparing the enclosed gas fraction profiles with the universal gas fraction profile, we obtain nonthermal pressure fraction profiles for our cluster sample at &gt;0.5R500, demonstrating a steeper increase between R500 and R200 that is consistent with the hydrodynamical simulations. Our analysis yields nonthermal pressure fraction ranges of 8%–28% (median: 15% ± 11%) at R500 and 21%–35% (median: 27% ± 12%) at R200. Notably, weak-lensing mass measurements are available for only four clusters in our sample, and our recovered total cluster masses, after accounting for nonthermal pressure, are consistent with these measurements.

Keywords: Galaxy clusters
Characterizing the Impact of Alfvén Wave Forcing in Interplanetary Space on the Distribution of Near-Earth Solar Wind Speeds. Broadly, solar wind source regions can be classified by their magnetic topology as intermittently and continuously open to the heliosphere. Early models of solar wind acceleration do not account for the fastest, nontransient solar wind speeds observed near-Earth, and energy must be deposited into the solar wind after it leaves the Sun. Alfvén wave energy deposition and thermal pressure gradients are likely candidates, and the relative contribution of each acceleration mechanism likely depends on the source region. Although solar wind speed is a rough proxy for solar wind source region, it cannot unambiguously identify source region topology. Using near-Sun observations of the solar wind's kinetic energy flux, we predict the expected kinetic energy flux near Earth. This predicted kinetic energy flux corresponds to the range of solar wind speeds observed in the fast solar wind and we infer that the solar wind's near-Sun kinetic energy flux is sufficient to predict the distribution of the fastest, nontransient speeds observed near Earth. Applying a recently developed model of solar wind evolution in the inner heliosphere, we suggest that the acceleration required to generate this distribution of the fastest, nontransient speeds is likely due to the continuous deposition of energy by Alfvén wave forcing during the solar wind's propagation through interplanetary space. We infer that the solar wind's Alfvénicity can statistically map near-Earth observations to their source regions because the Alfvén wave forcing that the solar wind experiences in transit is a consequence of the source region topology.

Keywords: Interplanetary particle acceleration, Alfven waves, Fast solar wind
Gamma-Ray Burst Timing: Decoding the Hidden Slow Jets in GRB 060729. Gamma-ray bursts (GRBs) are luminous stellar explosions characterized by the ejection of relativistic jets. This work proposes a novel paradigm to study these GRB jets. By analyzing the timing information of prompt pulses and X-ray flares, in conjunction with the multiwavelength afterglow observations, we identify three distinct jets in the extraordinary GRB 060729, with initial bulk Lorentz factors ranging from approximately 20 to 80, smaller than typical values of &gt;100. These three jets undergo two successive collisions, producing the observed pair of X-ray flares. Following these interactions, the system evolves into a fast, narrow jet and a slower, hollow jet that continues to propagate in the circumburst medium, evidenced by the notable twin bumps observed in the X-ray and optical afterglow of GRB 060729. Our findings demonstrate that the timing of the early emission enables us to measure the velocities of the GRB jets. The proposed paradigm enhances our understanding of jet dynamics and shock interactions and serves as a powerful tool for probing the physics of the central engine with the expanded sample in the current golden era of GRB research.

Keywords: Relativistic jets, Non-thermal radiation sources, Time domain astronomy, Gamma-ray bursts
On the Evidence of a Dark Matter Density Spike around the Primary Black Hole in OJ 287. The central engine of blazar OJ 287 is arguably the most notable supermassive black hole (SMBH) binary candidate that emits nanohertz (nHz) gravitational waves. This inference is mainly due to our ability to predict and successfully monitor certain quasiperiodic doubly peaked high brightness flares with a period of ∼12 yr from this blazer. The use of post-Newtonian accurate SMBH binary orbital description that includes the effects of higher-order gravitational-wave emission turned out to be a crucial ingredient for accurately predicting the epochs of such Bremsstrahlung flares in our SMBH binary central engine description for OJ 287. It was very recently argued that one should include the effects of dynamical friction, induced by certain dark matter density spikes around the primary SMBH, to explain the observed decay of SMBH binary orbit in OJ 287. Invoking binary pulsar timing-based arguments, measurements, and OJ 287's orbital description, we show that observationally relevant SMBH binary orbital dynamics in OJ 287 are insensitive to dark-matter-induced dynamical friction effects. This implies that we could only provide an upper bound on the spike index parameter rather than obtaining an observationally derived value, as argued by M. H. Chan and C. M. Lee.

Keywords: Dark matter density, Black hole physics, Dark matter distribution, BL Lacertae objects
The Exoplanet Edge: Planets Do Not Induce Observable Transit Timing Variations with a Dominant Transit Timing Variation Period Faster than Half Their Orbital Period. Transit timing variations (TTVs) are observed for exoplanets at a range of amplitudes and periods, yielding an ostensibly degenerate forest of possible explanations. We offer some clarity in this forest, showing that systems with a distant perturbing planet preferentially show TTVs with a dominant period equal to either the perturbing planet's period or half the perturbing planet's period. We demonstrate that planet-induced TTVs are not expected with dominant TTV periods below this exoplanet edge (lower period limit) and that systems with TTVs that fall below this limit likely contain additional mass in the system. We present an explanation for both of these periods, showing that both aliasing of the conjunction-induced synodic period and the near 1:2 resonance superperiod and tidal effects induce TTVs at periods equal to either the perturber's orbit or half-orbit. We provide three examples of known systems for which the recovered TTV period induced by a distant perturbing planet is equal to the perturber's orbital period or half its orbital period. We then investigate Kepler two-planet systems with TTVs and identify 13 two-planet systems with TTVs below this TTV period lower limit, thus potentially uncovering the gravitational influence of new planets and/or moons. We conclude by discussing how the exoplanet edge effects can be used to predict the presence of distant companion planets in situations where TTVs are detected and where nearby companions can be ruled out by additional observations, such as radial velocity data.

Keywords: Exoplanet dynamics, Astrostatistics, Exoplanet astronomy, Transit timing variation method, Exoplanet detection methods, Planetary dynamics
Comparison of Equations of State for Neutron Stars with First-order Phase Transitions: A Qualitative Study. The equation of state is fundamental in describing matter under the extreme conditions characteristic of neutron stars and is central to advancing our understanding of dense matter physics. A critical challenge, however, lies in accurately modeling first-order phase transitions while ensuring thermodynamic consistency and aligning with astrophysical observations. This study explores two frameworks for constructing equations of states with first-order phase transitions: the polytropic interpolation method and the randomized speed-of-sound interpolation approach. It is found that the mass–radius relation and pressure versus energy density relation are blind toward the thermodynamic consistency check. The polytropic interpolation method can exhibit discontinuities in the chemical potential for first-order phase transition, raising concerns regarding potential causality violations and thermodynamic inconsistencies. In contrast, the speed of sound interpolation approach ensures continuity in the chemical potential, offering a more thermodynamically consistent and reliable framework. Moreover, the sound speed method effectively captures the softer segment of the mass–radius spectrum, having an early phase transition, a capability not achieved by the consistent piecewise-polytropic approach due to its monotonic stiffness constraints. The speed of sound definition involving number density and chemical potential reveals the thermodynamic inconsistency, making it a more consistent and robust definition. The sound speed interpolation method also generated a sufficient number of twins, which the piecewise method failed. These findings underscore the importance of thermodynamic consistency in the equation of state construction and highlight the advantages of the randomized speed-of-sound method for modeling phase transitions in dense matter.

Keywords: Neutron stars, Neutron star cores
Denoising Diffusion Probabilistic Model for Realistic and Fast Generated Euclid-like Data for Weak Lensing Analysis. Understanding and mitigating measurement systematics in weak lensing (WL) analysis requires large data sets of realistic galaxies with diverse morphologies and colors. Missions like Euclid, the Nancy Roman Space Telescope, and Vera C. Rubin Observatory's Legacy Survey of Space and Time will provide unprecedented statistical power and control over systematic uncertainties. Achieving the stringent shear measurement requirement of ∣m∣ &lt; 10‑3 demands analyzing 109 galaxies. Accurately modeling galaxy morphology is crucial, as it is shaped by complex astrophysical processes that are not yet fully understood. Subtle deviations in shape and structural parameters can introduce biases in shear calibration. The interplay between bulges, disks, star formation, and mergers contributes to morphological diversity, requiring simulations that faithfully reproduce these features to avoid systematics in shear measurements. Generating such a large and realistic data set efficiently is feasible using advanced generative models like denoising diffusion probabilistic models. In this work, we extend Hubble Space Telescope (HST) data across Euclid's broad optical band using the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey and develop a generative AI tool to produce realistic Euclid-like galaxies while preserving morphological details. We validate our tool through visual inspection and quantitative analysis of galaxy parameters, demonstrating its capability to simulate realistic Euclid galaxy images, which will address WL challenges and enhance calibration for current and future cosmological missions.

Keywords: Cosmology, Extragalactic astronomy, Astronomy data analysis, Weak gravitational lensing
Potential Flow Theory Formulation of Parker's Unsteady Solar Wind Model and Nonlinear Stability of Parker's Steady Solar Wind Solution. The purpose of this paper is to present a novel optimal theoretical framework based on potential flow theory in ideal gas dynamics, which provides a smooth extrapolation of Parker's steady solar wind model to the unsteady case. The viability of this framework is illustrated by providing the first ever systematic theoretical formulation to successfully address the long-standing open issue of regularization of the singularity associated with the Parker sonic critical point (where the solar wind flow velocity equals the speed of sound in the gas) in the linear stability problem of Parker's steady solar wind solution. This development involves going outside the framework of the linear perturbation problem and incorporating the dominant nonlinearities in this dynamical system, and hence provides an appropriate nonlinear recipe to regularize this singularity. The stability of Parker's steady wind solution is found to also extend to the neighborhood of the Parker sonic critical point upon analyzing the concomitant nonlinear problem. The new theoretical framework given here seems, therefore, to have the potential to provide a viable basis for future formulations addressing various theoretical aspects of the unsteady version of Parker's steady solar wind model.

Keywords: Solar wind, Supersonic expansion
Chemical Components in the Virgo Overdensity and Hercules–Aquila Cloud: Hints of More than One Merger Event in GSE-like Debris. Using elemental abundances for 1.26 million K giants in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR8 value-added catalog, we analyze the chemical abundances of the Virgo Overdensity and Hercules–Aquila Cloud. We find two distinct chemical populations in both overdensities, which is in disagreement with the mainstream hypothesis that both overdensities are composed of materials from a single merger event, namely, Gaia–Sausage–Enceladus (GSE). The two populations show different chemical trends: one exhibits low metallicities and high α abundances, and the other shows high metallicities and low α abundances, which are associated with the recently discovered Nereus and Virgo Radial Merger (VRM) components in the local stellar halo, respectively. The Nereus component in these overdensities uniquely exhibits a decreasing trend in the [Fe/H]–[Mn/Fe] plane. Out of all observed Milky Way dwarf galaxies, this trend is only found in the Sculptor dwarf galaxy, which provides clues for the properties of Nereus progenitor. We also find that the velocity ellipses with high anisotropy parameters that is usually considered to be part of GSE are actually a mix of the two components. Both overdensities are well mixed in kinematic spaces, confirming recent claims that the debris of merger pairs are kinematically indistinguishable in a recent simulation. We find that the velocity ellipses of the VRM stars in these overdensities have large inclination angles, which may be an indication of the merger time in simulated merger events.

Keywords: Galaxy stellar halos, Galaxy dynamics, Galaxy kinematics, Chemical abundances
Scattering Blanketing Effect of Earth's Proto-atmosphere: Enhanced Suppression of Planetary Radiation and Magma Ocean Cooling. The thermal evolution of magma oceans formed by giant impacts is strongly influenced by a proto-atmosphere through its blanketing effect, which suppresses outgoing planetary radiation. While both radiative absorption and Rayleigh scattering by atmospheric species can contribute to this effect, the role of the scattering in suppressing thermal radiation from magma oceans remains unclear. In this study, we develop a 1D radiative transfer model for planetary and solar radiation in a proto-atmosphere composed of H2O and H2, and a coupled thermal evolution model of a planetary interior and proto-atmosphere, to investigate the scattering blanketing effect on planetary radiation and magma ocean cooling. Our results show that Rayleigh scattering significantly reduces the outgoing planetary radiation at wavelengths below ∼1 μm, particularly in hot, thick atmospheres where scattering is highly effective. Consequently, the planetary outgoing radiation flux decreases by up to about 1 to 2 orders of magnitude and the magma ocean lifetime is prolonged by up to about three times due to the scattering blanketing effect when the total amounts of H2O and H2 are equivalent to or greater than the present-day terrestrial seawater. These findings suggest that the prolonged magma ocean phase facilitated efficient differentiation between compatible and incompatible elements, even in the lower mantle. Furthermore, they imply that sustained magma oceans likely persisted throughout much of the giant impact phase, supporting a magma ocean origin of the Moon, consistent with its observed chemical characteristics.

Keywords: Planetary atmospheres