Sazuna/UAT_keywords huggingface dataset:
Carbon Dioxide Ices—A Sexagennial Update of Infrared Intensities, Band Shapes, and the Formation and Destruction of Crystalline CO<SUB>2</SUB>. The infrared (IR) band strengths most often used to quantify laboratory and astronomical spectra of CO2 ices are now 60 yr old, from a time of slide rules and vacuum-tube technology. Not surprisingly, shortcomings are seen in the original work when viewed from a 21st-century perspective. Continuing our group's program of providing new IR intensity results, we have reexamined the original study of frozen CO2 IR band strengths and have added to it with new measurements of solid CO2 at several spectral resolutions and temperatures. Reanalysis of the earlier work has uncovered an uncertainty in the strength of the most intense IR band of CO2 (2342 cm−1, 4.27 μm) of more than 90%, which our new work reduces to about 2%. Although the literature's integrated intensities are similar to those reported here, line widths, absorption coefficients, and band shapes are significantly different. We have also made direct measurements of an IR band strength for 13CO2, apparently for the first time. Factors that influence the degree of crystallinity of a CO2 ice have been explored, spectral changes on warming and cooling CO2 ices are described, and a radiolytic destruction is quantified.

Keywords: Interstellar molecules, Infrared spectroscopy, Ice spectroscopy, Laboratory astrophysics, Chemical abundances, Astrochemistry
Disclosing Submillimeter Galaxy Formation: Mergers or Secular Evolution?. We analyze the morphology of 125 submillimeter galaxies (SMGs) in the PRIMER-COSMOS field using double Sérsic modeling on JWST NIRCam images across six bands (F150W, F200W, F277W, F356W, F410M, and F444W), with SMGs being classified by the bulge Sérsic index (n_bulge) and bulge-to-total luminosity ratio (B/T). The Kolmogorov─Smirnov test between the bright (SFR &gt; 175M⊙ yr−1) and the faint groups (SFR &lt; 175M⊙ yr−1) reveals no significant statistical differences in morphology across bands. However, we notice that SMGs skew towards higher B/T ratios and lower n_bulge from shorter to longer wavelengths. In F444W, bright SMGs exhibit higher B/T and lower n_bulge, indicating flatter, disturbed bulges, while faint SMGs show lower B/T and higher n_bulge. Notably, SMGs with higher B/T tend to have low Sérsic, challenging the local Universe dichotomy of classical bulges (B/T &gt; 0.5, n &gt; 4) versus pseudo-bulges (B/T &lt; 0.35, n &lt; 2). In the F277W, nonparametric morphological measurements indicate predominantly disk-dominated patterns, with only 24% of SMGs demonstrating merger signatures. After the removal of SMGs with disturbed morphology, the bulge classification scheme in F277W shows pseudo-bulges (21%) and clump migration bulges (16%) from secular evolution, compared to 4% merger-built bulges. Surprisingly, 48% of SMGs defy the classification scheme, showing high B/T (∼0.7) but low Sérsic index (n_bulge ≤ 1). Bars are confirmed in 7% of SMGs. This work suggests that secular evolution takes precedence over major mergers, supporting the idea that isolated evolution fueled by filamentary gas inflow plays a nonnegligible role in the formation of SMGs.

Keywords: Galaxy formation, Galaxy structure, Galaxy interactions, Galaxy bulges, Infrared astronomy, Galaxy mergers, Submillimeter astronomy, Ultraluminous infrared galaxies
The Shape of the Solar Tachocline. Early helioseismic results have shown that the tachocline has a prolate shape. However, the models used in those studies constrained the tachocline to be either prolate or oblate. We use helioseismic data obtained from long time series (2304 and 4608 days) to determine the shape of the solar tachocline. Like previous work, we use forward modeling methods; however, we allow more flexibility for the shape of the tachocline. We find that the tachocline does indeed deviate from a simple prolate structure and bulges out at midlatitudes. The center of the tachocline lies in the radiative zone at low latitudes, in the convection zone at intermediate latitudes, and back in the radiative zone at high latitudes. The high-latitude (&gt;60°) behavior is, however, uncertain and model dependent. Models that allow more variation of the shape indicate that the tachocline at high latitudes is almost coincident with the base of the convection zone.

Keywords: Solar oscillations, The Sun, Solar rotation, Helioseismology
Multidirectional Investigations on Quiet Time Suprathermal Ions Measured by ASPEX-STEPS on Board Aditya L1. The origin, acceleration, and anisotropy of suprathermal ions in the interplanetary medium during quiet time have remained poorly understood issues in solar wind physics. Using measurements (in the energy range of 0.12−1.33 MeV n−1) by the four detectors that are part of the Supra-Thermal and Energetic Particle Spectrometer (STEPS) of Aditya Solar Wind Particle Experiment (ASPEX) on board the Aditya L1 spacecraft, we address the variations in spectral indices with directions in shorter durations during 2024 January─November, which coincides with the maximum phase of Solar Cycle 25. Three out of four detectors on STEPS—Parker Spiral, Intermediate, Earth Pointing—are in one plane, while the fourth detector—North Pointing—is in a mutually orthogonal plane. The derived spectral indices are found to be −1.99 ± 0.06 regardless of directions, suggesting directionally near isotropic behavior during quiet times. It is also shown that the influence of the Compton─Getting effect is negligible in this assessment of directional isotropy. This result has important ramifications as directional isotropy is assumed while solving the Parker transport equation to explain the acceleration of energetic particles. Further analysis of elemental abundance ratios (3He/4He, Fe/O, and C/O) during the same quiet times obtained from the Ultra Low Energy Isotope Spectrometer on board the Advanced Composition Explorer spacecraft suggests possible contributions from the leftover ions from the previous solar energetic particle events in the quiet time suprathermal ion pool.

Keywords: Solar flares, Solar energetic particles, Solar wind, Solar coronal mass ejections, Interstellar medium
Dissecting Reionization with the Cosmic Star Formation and Active Galactic Nuclei Luminosity History. The combination of the z = 0─13.5 cosmic star formation history and active galactic nuclei (AGN) luminosity history, as inferred by the James Webb Space Telescope, is connected to the cosmic spectral energy distribution (SED) to explore the sources of reionization. We compute the redshift evolution of the corresponding cosmic ionizing photon emissivity, the neutral fraction, and the cosmic microwave background optical depth. We use the generative SED modelling code PROSPECT to bracket the ionizing emissivity between escape fractions of fesc = 1%─100% for both the stars and AGN. Stars alone could have achieved reionization by z ≍ 6 with fesc ≳ 30% for solar metallicity (Z = 0.02) stars or fesc ≳ 10% for metal-poor (Z = 10−4) stars. On the other hand, AGN by themselves would have struggled to produce sufficiently many ionizing photons even with fesc = 100%. A hybrid model containing both stars and AGN is explored, where we find the best fit (median±1σ) fesc = 12% ( 14−7+9% ) for the stars and fesc = 63% ( 60−32+28% ) for the AGN, maintained at all redshifts. In essence, the joint growth of stellar mass and supermassive black holes produces neither more nor fewer ionizing photons than needed to reionize ≳99% of the intergalactic medium by z ≍ 6.

Keywords: Reionization, Active galaxies, Galaxy evolution, James Webb Space Telescope
Witnessing Magnetic Reconnection in Tangled Superpenumbral Fibrils around a Sunspot. 3D magnetic reconnection is a fundamental plasma process crucial for heating the solar corona and generating the solar wind, but resolving and characterizing it for the Sun remain challenging. Using high-quality data from the Chinese New Vacuum Solar Telescope, the Solar Dynamics Observatory, and the Interface Region Imaging Spectrograph, this work presents highly suggestive direct imaging evidence of magnetic reconnection during the untangling of braided magnetic structures above a sunspot. These magnetic structures, visible as bright superpenumbral threads in extreme-ultraviolet passbands, initially bridge opposite-polarity magnetic fluxes and then gradually tangle in their middle section. Magnetic extrapolation reveals the fibrils to form a small flux rope that is twisted and braided, possibly created by persistent and complex photospheric motions. During untangling, repetitive reconnection events occur inside the flux rope, accompanied by transient plasma heating, bidirectional outflowing blobs, and signatures of nanojets. An emission analysis reveals that the outflowing blobs are multithermal structures with temperatures well below 1 MK, undergoing rapid cooling and leaving emission imprints in Hα images. The measured reconnection angles indicate that 16%─22% of the magnetic field along each thread is antiparallel, with the remaining field acting as a guide field. The estimated energy released during these reconnection events is comparable to nanoflares, which can be powered by up to 6% of the magnetic energy stored in the antiparallel field. This work presents a textbook example of magnetic flux rope reconnection in the solar atmosphere, providing new insights into fine-scale energy release processes within sunspot superpenumbral fibrils.

Keywords: Solar magnetic reconnection, Solar coronal loops, Solar coronal heating, Sunspots, Solar active regions, Solar corona, Solar activity
Magma Ocean Interactions Can Explain JWST Observations of the Sub-Neptune TOI-270 d. Sub-Neptunes with substantial atmospheres may possess magma oceans in contact with the overlying gas, with chemical interactions between the atmosphere and magma playing an important role in shaping atmospheric composition. Early JWST observations have found high abundances of carbon- and oxygen-bearing molecules in a number of sub-Neptune atmospheres, which may result from processes including accretion of icy material at formation or magma─atmosphere interactions. Previous work examining the effects of magma─atmosphere interactions on sub-Neptunes has mostly been limited to studying conditions at the atmosphere─mantle boundary, without considering implications for the upper atmosphere, which is probed by spectroscopic observations. In this work, we present a modeling architecture to determine observable signatures of magma─atmosphere interactions. We combine an equilibrium chemistry code which models reactions between the core, mantle, and atmosphere with a radiative─convective model that determines the composition and structure of the observable upper atmosphere. We examine how different conditions at the atmosphere─mantle boundary and different core and mantle compositions impact the upper atmospheric composition. We compare our models to JWST NIRISS + NIRSpec observations of the sub-Neptune TOI-270 d, finding that our models can provide a good fit to the observed transmission spectrum with little fine-tuning. This suggests that magma─atmosphere interactions may be sufficient to explain the high abundances of molecules such as H2O, CH4, and CO2 in sub-Neptune atmospheres, without additional accretion of icy material from the protoplanetary disk. Although other processes could lead to similar compositions, our work highlights the need to consider magma─atmosphere interactions when interpreting the observed atmospheric composition of a sub-Neptune.

Keywords: Exoplanet atmospheric composition , Exoplanets, Exoplanet evolution, Exoplanet structure, Exoplanet formation, Exoplanet atmospheres
Radiation Hydrodynamics of Self-gravitating Protoplanetary Disks. I. Direct Formation of Gas Giants via Disk Fragmentation. Gravitational instability (GI) has long been considered a viable pathway for giant planet formation in protoplanetary disks (PPDs), especially at wide orbital separations or around low-mass stars where core accretion faces significant challenges. However, a primary drawback is that disk fragmentation from GI is generally found to produce overmassive clumps, typically in the mass range of brown dwarfs, although most numerical studies adopt simplified cooling prescriptions or those with limited numerical resolution. We conduct a suite of global three-dimensional radiation hydrodynamics simulations of self-gravitating PPDs using the meshless finite-mass method. By implementing radiation transport via the M1 closure and systematically varying disk mass and opacity, we show that increasing disk mass and lowering opacity promote fragmentation by enhancing radiative cooling. Nonfragmenting disks settle into a gravitoturbulent state with low-order spiral structures and effective angular momentum transport characterized by  α∼βcool−1 . In fragmenting disks, a subset of gravitationally bound clumps survives as long-lived fragments. Their initial masses form a consistent distribution around Σ · λT · 2(cs/ΩK) (with λT denoting the Toomre wavelength), corresponding to ∼0.3─10 MJ in our simulations, consistent with the masses of gas giants. These results demonstrate that GI can produce planet-mass fragments under more realistic conditions, reinforcing it as a viable gas giant formation pathway and motivating further studies of fragment evolution and observational signatures.

Keywords: Gravitational instability, Radiative transfer, Protoplanetary disks, Planet formation
Kinematic Analysis of an Ultrastrong Mg II Absorber at z ≍ 1.13 Linked to Circumgalactic Gas Structures. We present a spectroscopic and imaging analysis of the zgal ≍ 1.1334 ultrastrong Mg II absorption system identified in the Very Large Telescope/UVES spectrum of a background quasar located at ρ ≍ 18 kpc from a star-forming galaxy. Low-ionization metal lines like Mg I, Fe II, and Ca II are also detected for this absorber. The H I lines are outside of the wavelength coverage. The Mg II has a rest-frame equivalent width of Wr(2796) = 3.185 ± 0.032 Å, with the absorption spread across ∆v ≍ 460 km s−1 in several components. A component-by-component ionization modeling shows several of these components having solar and higher metallicities. The models also predict a total h I column density of  log[N(HI)/cm−2]≍22.5 , consistent with ultrastrong Mg II absorbers being sub─damped Lyα and damped Lyα systems. The absorber is well within the virial radius of the nearest galaxy, which has a stellar mass M* = 4.7 × 1010 M⊙, and a star formation rate of ≍8.3 M⊙ yr−1. The absorption is along the projected major axis of the galaxy with a velocity spread that is wider than the galaxy's disk rotation. From the kinematic analysis of the absorber and the galaxy, the origin of the absorption can be attributed to a combination of circumgalactic gas structures, some corotating with the disk and the rest moving at line-of-sight velocities outside of the disk rotation.

Keywords: Quasar absorption line spectroscopy, Galaxy infall, Galaxy kinematics, Galaxy evolution, Galaxy accretion, Circumgalactic medium
DiskMINT: Self-consistent Thermochemical Disk Models with Radially Varying Gas and Dust—Application to the Massive, CO-Rich Disk of IM Lup. Disks around young stars are the birthplaces of planets, and the spatial distribution of their gas and dust masses is critical for understanding where and what types of planets can form. We present self-consistent thermochemical disk models built with DiskMINT, which extends its initial framework to allow for spatially decoupled gas and dust distributions. DiskMINT calculates the gas temperature based on thermal equilibrium with dust grains, solves vertical gas hydrostatic equilibrium, and includes key processes for the CO chemistry, specifically selective photodissociation and freeze-out with conversion CO/CO2 ice. We apply DiskMINT to study the IM Lup disk, a large massive disk, yet with an inferred CO depletion of up to 100 based on earlier thermochemical models. By fitting the multiwavelength spectral energy distribution along with the millimeter continuum, C18O radial emission profiles, we find 0.02─0.08 M⊙ for the gas disk mass, which is consistent with the dynamical-based mass within the uncertainties. We further compare the derived surface densities for dust and gas and find that the outer disk is drift dominated, with a dust-to-gas mass ratio of approximately 0.01─0.02, which is likely insufficient to meet the conditions for the streaming instability to occur. Our results suggest that when interpreted with self-consistent thermochemical models, C18O alone can serve as a reliable tracer of both the total gas mass and its radial distribution. This approach enables gas mass estimates in lower-mass disks, where dynamical constraints are not available, and in fainter systems, where rare species like N2H+ are too weak to detect.

Keywords: Chemical abundances, Astrochemistry, Protoplanetary disks, CO line emission, Planet formation
Formation of Binary Millisecond Pulsars with Helium White Dwarfs in a New Magnetic Braking Prescription. The magnetic braking (MB) mechanism plays a vital role throughout the evolution of low-mass X-ray binaries (LMXBs). Considering the standard MB prescription, the initial orbital periods of LMXBs that can evolve into binary millisecond pulsars (MSPs) with He white dwarfs (WDs) and short orbital periods (2─9 hr) are within an extremely narrow interval that was named the fine-tuning problem. Employing the detailed binary evolution model, we investigate the evolution of LMXBs in both the standard and convection and rotation-boosted (CARB) MB laws. In the standard MB case, it is difficult for donor stars to form a He core and exhaust the H envelope through mass transfer at short orbital periods, making them semidetached systems. The CARB MB mechanism can drive LMXBs to evolve toward compact detached MSP─WD systems in wide initial orbital periods over which binary MSPs with long orbital periods will be produced. We obtain the initial parameter space of binary MSPs with He WDs in the initial orbital period and donor-star mass plane, which can be applied to future statistics study by population synthesis simulations. We also discuss a new relation between orbital period and WD mass, the formation of persistent ultracompact X-ray binaries with relatively long orbital periods, and the detectability of compact MSP─WD systems as low-frequency gravitational-wave sources.

Keywords: Neutron stars, Accretion, X-ray binary stars, White dwarf stars, Orbital evolution
Updating the Electrostatic Model for Dust Impact Detection with Antenna Instruments. Antenna instruments deployed in space are known to be sensitive to dust impacts, and the detected signals can be used to characterize the dust populations within the solar system. Recently, an electrostatic model describing how transient impact plasmas generate characteristic signals measured by antennas was presented. This first-principles model considers the capacitive coupling between the elements of the spacecraft (SC)─antenna system and calculates the collected and induced charging from the expanding impact plasma. Here, the model is updated to include the angular and velocity distributions of the ions in the impact plasma. The relevant parameters of the impact plasma are obtained from laboratory measurements using a dust accelerator. These parameters are further refined by matching the updated electrostatic model to antenna signals collected in the laboratory using a simple model SC. The angular distribution of ion expansion is best described by a cosine distribution,  cosβθ , with β = 1. The velocity distribution considers heavy-, medium-, and low-mass ions present in the impact plasma with corresponding velocities of 3.8, 14, and 36.7 km s−1 for high speed dust impacts. The updated electrostatic model provides excellent agreement with antenna measurements collected in the laboratory and can be used as a basis for analysis and precise interpretation of dust impact data collected by antenna instruments on various space missions.

Keywords: Dust physics, Interplanetary dust
Multiperiodic Pulsations of the Unique DAQ White Dwarf J0551+4135: Insights into a Merger Remnant. 2MASS J05513444+4135297 (hereafter J0551+4135) is the only pulsating DAQ white dwarf (WD) known with a carbon and hydrogen atmosphere. Its unusual atmospheric composition and kinematics indicate a WD merger origin. We present time-series photometry of J0551+4135 obtained using the Apache Point Observatory 3.5 m, Gemini North 8 m, and Gran Telescopio Canarias 10 m telescopes. J0551+4135 exhibits variations in pulsation amplitude and frequency over time. We detect 10 significant recurring peaks across different subsets of observations, with frequencies ranging from 987 to 1180 μHz, consistent with nonradial gravity (g)-mode oscillations. We present new evolutionary models suitable for spectroscopic characterization of DAQ WDs, and derive a mass of 1.13 ± 0.01 M⊙and a cooling age of 1.7 ± 0.1 Gyr for a CO core, and 1.12 ± 0.01 M⊙and 1.6 ± 0.1 Gyr for an ONe-core WD, respectively. However, detailed asteroseismology of this unique pulsator has to wait until fully consistent DAQ evolutionary models are available. Further observations, including multisite campaigns to reduce daily aliasing and to improve the signal-to-noise ratio, would be helpful for the identification of additional modes and constraining the internal structure of this unique pulsator.

Keywords: Stellar oscillations, White dwarf stars
Distinguishing Orbiting and Infalling Dark Matter Particles with Machine Learning. Dark matter halos are typically defined as spheres that enclose some overdensity, but these sharp, somewhat arbitrary boundaries introduce nonphysical artifacts such as backsplash halos, pseudo-volution, and an incomplete accounting of halo mass. A more physically motivated alternative is to define halos as the collection of particles that are physically orbiting within their potential well. However, existing methods to classify particles as orbiting or infalling suffer from trade-offs between accuracy, computational cost, and generalizability across cosmologies. We present an efficient, yet accurate, supervised machine learning approach using decision trees. The classification is based on only the particle radii and velocities at two epochs. Compared to detailed analysis of particle trajectories, we find that our model matches the classification of 97% of particles. Consequently, we are able to quickly and accurately reproduce the density profiles of the orbiting and infalling components out to many virial radii. We demonstrate that our model generalizes to a significantly different cosmology that lies outside the training data set. We make publicly available both our final model and the code to train similar models.

Keywords: Cosmology, Random Forests, Dark matter