Sazuna/UAT_keywords huggingface dataset:
Electron–Ion Equilibration in the Merging Galaxy Cluster A665. Galaxy cluster mergers drive powerful shock fronts that heat the intracluster medium (ICM) and accelerate particles, redistributing the energy in a merger. A665 is one of only a few clusters with such a powerful shock ( M∼  3), and it provides a unique opportunity to study the thermalization timescale of the ICM, particularly the electron–ion equilibration timescale. Understanding this timescale is crucial for determining how the energy from the merger is distributed between thermal and nonthermal particle populations. Using ∼200 ks of NuSTAR observations, we measure the temperature distribution across the shock to distinguish between two heating models: (1) an instant collisionless model, where ions and electrons are immediately heated at the shock front; and (2) a collisional model, where electrons are initially adiabatically compressed at the shock and subsequently equilibrate with the ions over ∼100 Myr. Our measurements favor the delayed-equilibration model, suggesting that electrons do not immediately reach thermal equilibrium with the ions at the shock front and instead equilibrate over teq = (4.0 ± 3.4) × 108 yr. Additionally, our temperature measurements indicate that the Mach number may be lower than previously estimated ( M=2.8±0.7 ), suggesting that the shock strength has been overestimated in past studies. These results add to our understanding of the microphysics governing how thermal energy is distributed in diffuse plasmas like the ICM, with implications for galaxy cluster evolution, large-scale structure formation, and cosmology.

Keywords: Galaxy clusters, Cosmology, Plasma astrophysics, Shocks, Intracluster medium
The z ≳ 9 Galaxy UV Luminosity Function from the JWST Advanced Deep Extragalactic Survey: Insights into Early Galaxy Evolution and Reionization. The high-redshift UV luminosity function provides important insights into the evolution of early galaxies. JWST has revealed an unexpectedly large population of bright (MUV ≲ −20) galaxies at z ≳ 10, implying fundamental changes in the star-forming properties of galaxies at increasingly early times. However, constraining the fainter population (MUV ≳ −18) has been more challenging. In this work, we present the z ≳ 9 UV luminosity function from the JWST Advanced Deep Extragalactic Survey. We calculate the UV luminosity function from several hundred z ≳ 9 galaxy candidates that reach UV luminosities of MUV ∼ −17 in redshift bins of z ∼ 8.5─12 (309 candidates) and z ∼ 12─16 (63 candidates). We search for candidates at z ∼ 16─22.5 and find none. We also estimate the z ∼ 14─16 luminosity function from the z ≥ 14 subset of the z ∼ 12─16 sample. Consistent with other measurements, we find an excess of bright galaxies that is in tension with many theoretical models, especially at z ≳ 12. However, we also find high number densities at −18 ≲ MUV ≲ −17, suggesting that there is a larger population of faint galaxies than expected, as well as bright ones. From our parametric fits for the luminosity function, we find steep faint-end slopes of −2.5 ≲ α ≲ −2.3, suggesting a large population of faint (MUV ≳ −17) galaxies. Combined, the high normalization and steep faint-end slope of the luminosity function could imply that the reionization process is appreciably underway as early as z = 10.

Keywords: Luminosity function, Galaxy formation, James Webb Space Telescope, Galaxy evolution, Reionization, Lyman-break galaxies, High-redshift galaxies
The Study of the Circumnuclear Environment of Accreting Supermassive Black Holes with Realistic X-Ray Spectral Models. X-ray spectral modeling is a powerful tool for studying the immediate environment of accreting objects, including supermassive black holes. Several models, either phenomenological or physically driven, have been developed over the past decade to study X-ray spectra, delivering important insights into the properties of circumnuclear material of active galactic nuclei. Despite the fact that these models are able to reproduce the data well, they often lack realistic geometries and most of them consist of simplified configurations such as a slab or a torus. We use the ray-tracing code REFLEX to generate new spectral models that cover a wide energy range in the X-ray band, adopting a realistic configuration for the surrounding material. We introduce two new table models that are publicly available: (1) the RXToPo model, which features an X-ray source along with a dusty torus and a polar hollow cone; and (2) the RXagn1 model, which also includes, besides the torus and polar cone, the accretion disk and the broad line region. Both models were applied to the X-ray spectrum of NGC 424, demonstrating their potential to study sources whose X-ray emission is dominated by reprocessed radiation.

Keywords: Supermassive black holes, Radiative transfer simulations, X-ray active galactic nuclei
Cosmic Infrared Background Tomography and a Census of Cosmic Dust and Star Formation. The cosmic far-infrared background (CIB) encodes dust emission from all galaxies and carries valuable information on structure formation, star formation, and chemical enrichment across cosmic time. However, its redshift-dependent spectrum remains poorly constrained due to line-of-sight projection effects. We address this by cross-correlating 11 far-infrared intensity maps spanning a 50-fold frequency range from Planck, Herschel, and Infrared Astronomical Satellite, with spectroscopic galaxies and quasars from Sloan Digital Sky Survey I–IV tomographically. We mitigate foregrounds using a CIB-free Milky Way dust map. These cross-correlation amplitudes on two-halo scales trace bias-weighted CIB redshift distributions and collectively yield a 60σ detection of the evolving CIB spectrum, sampled across hundreds of rest-frame frequencies over 0 &lt; z &lt; 4. We break the bias–intensity degeneracy by adding monopole information from FIRAS+Planck. The recovered spectrum reveals a dust temperature distribution that is broad, spanning the full range of host environments, and moderately evolving. Using low-frequency CIB amplitudes, we constrain cosmic dust density, Ωdust, which peaks at z = 1–1.5 and declines threefold to the present. Our broad spectral coverage enables a determination of the total infrared luminosity density to 0.04 dex statistical precision, tracing star formation history with negligible cosmic variance across 90% of cosmic time. We find that cosmic star formation is 80% dust-obscured at z = 0 and 60% at z = 4. Our results, based on intensity mapping, are complete, requiring no extrapolation to faint galaxies or low-surface-brightness components. We release our tomographic CIB spectrum and redshift distributions as a public resource for future studies of the CIB, both as a cosmological matter tracer and cosmic microwave background foreground.

Keywords: Interstellar dust, Star formation, Cosmic background radiation, Large-scale structure of the universe
X-Ray and Radio Polarimetry of the Neutron Star Low-mass X-Ray Binary GX 13+1. We report the X-ray and radio polarization study of the neutron star low-mass X-ray binary (LMXB) GX 13+1 using the Imaging X-ray Polarimetry Explorer (IXPE) and Very Large Array. Simultaneous Neutron Star Interior Composition Explorer observations show that the source was in parts of the Z state during our IXPE observations, exhibiting moderate changes in the hardness─intensity diagram. The source exhibits X-ray dips in the light curve along with hints of polarization swings between the dip and nondip states. The X-ray spectropolarimetry results suggest a source geometry comprising an accretion disk component representing the softer disk emission, along with a blackbody representing the harder emission from the boundary layer or a spreading layer. We investigate the geometry of GX 13+1 by considering our X-ray and radio polarization findings.

Keywords: Neutron stars, Accretion, X-ray binary stars, Low-mass x-ray binary stars, Polarimetry
Impact of Cosmic Ray-driven Outflows on Lyα Emission in Cosmological Simulations. Cosmic ray (CR) feedback has been proposed as a powerful mechanism for driving warm gas outflows in galaxies. We use cosmological magnetohydrodynamic simulations to investigate the impact of CR feedback on neutral hydrogen (H I) in a 1011 M⊙ dark matter halo at 2 &lt; z &lt; 4. To this end, we postprocess the simulations with ionizing radiative transfer and perform Monte Carlo Lyman-α (Lyα) transfer calculations. CR feedback reduces H I column densities around young stars, thereby allowing more Lyα photons to escape and consequently offering a better match to the Lyα luminosities of observed Lyα emitters. Although galaxies with CR-driven outflows have more extended H I in the circumgalactic medium, two Lyα line properties sensitive to optical depth and gas kinematic—the location of the red peak relative to the Lyα line center in velocity space (vred) and relative strength of the blue-to-red peaks (B/R)—cannot distinguish between the CR-driven and non-CR simulations. This is because Lyα photons propagate preferentially along low H I density channels created by the ionizing radiation, thereby limiting the scattering with volume-filling H I. In contrast, the observed low flux ratios between the valley and peak and the surface brightness profiles are better reproduced in the model with CR-driven outflows because the Lyα photons interact more before escaping, rather than being destroyed by dust as is the case in the non-CR simulation. We discuss the potential cause of the paucity of sightlines in simulations that exhibit prominent red peaks and large vred, which may require the presence of more volume-filling H I.

Keywords: Lyman-alpha galaxies, Stellar feedback, Radiative transfer
Spectral Evolution of Rotating Population III Stars. Population III (Pop III) stars, the first generation of stars formed from primordial gas, played a fundamental role in shaping the early Universe through their influence on cosmic reionization, early chemical enrichment, and the formation of the first galaxies. However, to date, they have eluded direct detection due to their short lifetimes and high redshifts. The launch of the James Webb Space Telescope (JWST) has revolutionized observational capabilities, providing the opportunity to detect Pop III stars via caustic lensing, where strong gravitational lensing magnifies individual stars to observable levels. This prospect makes it compelling to develop accurate models for their spectral characteristics to distinguish them from other stellar populations. Previous studies have focused on computing the spectral properties of nonrotating, zero-age main-sequence (ZAMS) Pop III stars. In this work, we expand upon these efforts by incorporating the effects of stellar rotation and post-ZAMS evolution into spectral calculations. We use the JWST bands and magnitude limits to identify the optimal observing conditions, both for isolated stars, as well as for small star clusters. We find that, while rotation does not appreciably change the observability at ZAMS, the subsequent evolution can significantly brighten the stars, making the most massive ones potentially visible with only moderate lensing.

Keywords: Early universe, Population III stars, James Webb Space Telescope, Gravitational lensing, Spectral energy distribution, Star clusters
Theoretical Perspective on the Occurrence of Electrostatic Solitary Waves and Double Layers in Ganymede's Wake Region. The first close flyby of Ganymede by Juno on 2021 June 7 provided a unique opportunity to visit the previously unexplored wake and magnetopause regions. During the flyby, the Juno Waves instrument recorded traces of the existence of electrostatic solitary waves (ESWs) in the wake and magnetopause boundary. The flyby detected the presence of H2+ and H3+ ions in Ganymede's wake for the first time, indicating that the wake is dominated by water products from the surface of Ganymede. The conditions for the occurrence of ESWs and double layers in the wake region and the associated existence domains (in parameter space) are explored in this paper. A magnetized fluid plasma is introduced to model Ganymede's wake conditions, comprising of warm H+, O+, and H3+ ions and an electron beam, in addition to a non-Maxwellian background of suprathermal electrons. We have explored in particular the role of the third ion component H3+ on the properties of ESWs. Different acoustic modes are predicted and used as basis for our analysis, namely identified as one slow and two fast ion-acoustic modes and a higher-frequency electron-acoustic mode. Nonlinear analysis shows that the model may support the existence of positive and negative potential ion-acoustic solitons and double layers depending on the number density and on the temperature of H3+ ions. The theoretical prediction is correlated with observed ESWs in Ganymede's wake.

Keywords: Space plasmas
The BlueDOG at Cosmic Noon: A Possible Analog to Little Red Dots?. We discovered a hyperluminous dust-obscured galaxy with mysterious blue-excess emission (BlueDOG) in the rest-frame UV of its spectral energy distribution (SED) from a multiwavelength survey in the AKARI Deep Field - South (ADF-S). We present the results of SED analysis with multiwavelength photometric data and spectroscopic analysis, observed with Gemini-S/GMOS, FLAMINGOS-2, to explore the origin of blue-excess emission of a hyperluminous BlueDOG, ADFS-KMTDOG-102, at z = 2.6. The SED analysis shows that this BlueDOG is a highly massive system (log M*/M⊙ = 12.3) with substantial extinction. Additionally, the proportion of the old stellar population exceeds that of the young stellar population, which suggests stellar evolution cumulated from the early Universe. The mass of the supermassive black hole estimated using the extinction-corrected broad Hα emission line yields log MBH/M⊙ = 10.2. We discuss the similarity between the BlueDOG and "Little Red Dots" (LRDs), recently discovered with the James Webb Space Telescope, showing SED shapes remarkably similar to those of LRDs. The UV emission line ratios indicate that the emission lines are primarily powered by the central active galactic nuclei (AGN). In contrast, the origin of the blue-excess UV continuum remains ambiguous, since both recent star formation and AGN-induced scattered light are viable explanations, based on the results from the SED fitting and scattered light modeling.

Keywords: Supermassive black holes, Active galaxies, High-redshift galaxies, Infrared galaxies
Not Just a Dot: The Complex UV Morphology and Underlying Properties of Little Red Dots. We analyze 99 photometrically selected Little Red Dots (LRDs) at z ≍ 4─8 in the GOODS fields, leveraging ultradeep JADES NIRCam short-wavelength (SW) data. Among the 99 selected LRDs, we examine the morphology of 30. The remaining 69 appear predominantly compact, with sizes ≲400 pc and no extended components even in stacked SW images. However, their unresolved nature may partly reflect current depth limitations, which could prevent the detection of faint diffuse components. Among the 30 morphologically analyzed LRDs, 50% show multiple associated components, while the rest exhibit highly asymmetric structures, despite appearing as single sources. This diversity in rest-frame UV morphologies may point to interactions or strong internal feedback. We find median stellar masses of  log10(M⋆/M⊙)=9.07−0.08+0.11  for pure stellar models with  AV≍1.16−0.21+0.11  mag, and  log10(M⋆/M⊙)=9.67−0.27+0.17  for models including active galactic nuclei (AGNs) with  AV≍2.74−0.71+0.55  mag, in line with recent studies suggesting higher masses and dust content for AGN-fitted LRDs. NIRSpec spectra are available for 15 sources, six of which are also in the morphological sample. Broad Hα is detected in 40% (FWHM = 1200─2900 km s−1), and one source shows broad Hβ emission. Emission line ratios indicate a composite nature, consistent with both AGN and stellar processes. Altogether, these results suggest that LRDs are a mixed population, and their rest-frame UV morphology reflects this complexity. Morphological studies of larger samples could provide a new way to understand what drives their properties and evolution.

Keywords: Galaxy formation, James Webb Space Telescope, Active galactic nuclei, Galaxy evolution, Near infrared astronomy
The M- and X-class White-light Flares in Super Active Region NOAA 13664/13697 Observed by ASO-S/LST/WST. Solar white-light flares (WLFs) have been observed since 1859, but their occurrence rate is not yet fully understood. The physical properties of WLFs in super active regions (SARs) are also well worth investigating. With full-disk images at 3600 Å (in the Balmer continuum) from the White-light Solar Telescope on board the Advanced Space-based Solar Observatory, we here study the M- and X-class WLFs occurring in SAR NOAA 13664/13697 (a same region in two solar Carrington rotations) during 2024 May/June. In all, 48 WLFs at 3600 Å are identified from 89 available samples with an occurrence rate of 53.9%, which is much higher than that (23.9%) of a long-term-continuous data set from 2022 October to 2023 May in our previous work. In particular, with an additional sample of over 730 M- and X-class flares from 2022 October to 2024 June, we find that the occurrence rate of WLFs shows a good correlation with the solar cycle represented by sunspot counts. As regards the properties of the emission at 3600 Å, the WLFs in SAR NOAA 13664/13697 have some different characteristics, say, a longer duration but a weaker relative enhancement and a smaller brightening area compared with the previous long-term-continuous sample. We also find that for WLFs in NOAA 13664/13697 the relation between the duration and energy at 3600 Å is described by a power law with index of 0.35, which is similar to the results found for superflares in Sun-like stars. All these help us understand the solar WLFs in SARs and also provide important insights into the superflares on Sun-like stars.

Keywords: Solar activity, Solar flares, Solar white-light flares, Solar x-ray emission
Stringent Constraints on the Nuclear Matter Equation of State from Heavy Nuclei and Neutron Star Properties with a Multi-iteration Bayesian Statistical Analysis. The equation of state (EoS) of dense nuclear matter, particularly the symmetry energy that characterizes its isospin dependence, is of fundamental importance in neutron star (NS) physics and nuclear physics. Apart from the extensively used multimessenger astrophysics information, we introduce three new constraints to tighten the EoS at intermediate densities: (i) the absent direct Urca process in the 1.5 M⊙ NS; (ii) the symmetry energy (coefficient) asym of 208Pb; (iii) the strong linear correlation between the slope parameter L of symmetry energy Esym(ρ) at saturation density ρ0 and Esym(ρ0) ‑ asym. These constraints turn out to be highly effective for symmetry energy. As an alternative strategy, we employ the Bayesian statistical method with a multi-iteration procedure to ensure that the resulting posterior probability distribution is free of the initial prior distribution as far as possible. The most probable result of symmetry energy exhibits a soft behavior up to ∼2.5ρ0, and then it rises rapidly as the density increases. On the one hand, our results allow one to explore a series of topics in NS physics. For instance, the radius and tidal deformability for a 1.4 M⊙ NS are  R1.4=12.46‑0.80+0.22km  and  Λ1.4=478‑183+90 . The vast majority of NSs are unlikely to contain deconfined quark matter in their cores. On the other hand, almost all the widely used nuclear many-body approaches fail to reproduce such a trend of symmetry energy, and hence our results serve as an important calibration for nuclear force and nuclear many-body approaches.

Keywords: Neutron stars, Neutron star cores, Pulsars
The Influence of Central Body Tides on Catastrophic Disruptions of Close-in Planetary Satellites. We model the outcomes of catastrophic disruptions on small, gravity-dominated natural satellites, accounting for the tidal potential of the central body, which is neglected in classical disruption scaling laws. We introduce the concept of  QTD⋆ , the specific energy required to disperse half of the total mass involved in a collision, accounting for the tidal potential of a central body. We derive a simple scaling relation for  QTD⋆  and demonstrate that for close-in planetary or asteroidal satellites, the tides from the central body can significantly reduce their catastrophic disruption threshold. We show that many satellites in the solar system are in such a regime, where their disruption threshold should be much lower than that predicted by classical scaling laws that neglect tidal effects. Some notable examples include Mars's Phobos, Jupiter's Metis and Adrastea, Saturn's ring moons, Uranus's Ophelia, and Neptune's Naiad and Thalassa, among others. We argue that traditional impact scaling laws should be modified to account for tides when modeling the formation and evolution of these close-in satellites. Our derivation for  QTD⋆  can easily be used in existing N-body and collisional evolution codes.

Keywords: Tides, Collisional processes, Small Solar System bodies, Natural satellite evolution
Lithium Abundances of Main-sequence Stars in the Old Open Cluster NGC 188: Probes of Stellar Evolution beyond the Solar Age. We present lithium abundances for 119 main-sequence stars in the old open cluster NGC 188 (age = 6.3 Gyr), using high-resolution, high signal-to-noise ratio spectra from WIYN/Hydra. We observe the stars over multiple nights and measure radial velocities for each night, which we combine with Gaia proper motions to identify multiplicity and cluster membership. We identify 95 single members, 14 binary members, 9 members with uncertain multiplicity, and 1 single likely member. We determine effective temperatures using empirical color–temperature relations, surface gravities from isochrones, and microturbulence from empirical relations for main-sequence stars. Our sample includes G dwarfs with temperatures between 6000 and 5300 K, which expands significantly on earlier observations. We find that lithium abundances in NGC 188 are lower than predictions from standard stellar evolution theory. As expected, stars in NGC 188 are more lithium-depleted than those in the younger Hyades and Praesepe clusters (650 Myr). However, their abundances are higher, or at least comparable, to those in the slightly younger cluster M67 (4 Gyr), challenging the idea that older stars have lower lithium than younger ones. Lithium depletion may depend on factors beyond age and mass, such as metallicity. ∗This is paper 94 of The WIYN Open Cluster Study.

Keywords: Observational astronomy, Chemical abundances, Spectroscopy, Stellar evolution
A Search for Meteoroid Streams and Their Sources in the Near-Sun Zodiacal Dust Cloud. The structure and dynamics of the zodiacal cloud close to the Sun may be significantly influenced by the interaction between a background quasihomogeneous zodiacal cloud and discrete meteoroid streams associated with small bodies like comets and asteroids. The extent of this influence depends upon how many such streams exist and the mechanisms by which they modify the near-Sun zodiacal cloud. This study compares in situ dust detection data in near-Sun solar wind against predictions made by a simplified zodiacal dust cloud model to search for small-scale meteoroid stream structures. A strong localized departure from the model is found. A small number of asteroids and comets have been identified that have orbits appropriate to produce the observed departure from the model through either direct meteoroid stream detection or through enhanced β-meteoroid production. These observations suggest that discrete meteoroid streams may be common in the inner zodiacal cloud and therefore may be important for its structure and dynamics.

Keywords: Near-sun comets, Asteroid dynamics, Solar wind, Meteoroid dust clouds, Interplanetary dust