Sazuna/UAT_keywords huggingface dataset:
NIRC2 Interferometric Imaging of the HD 34282 Transition Disk's Small Grain Structure. The HD 34282 transition disk is a favorable location for protoplanet searches given its complex substructures that may be driven by planet formation. Early millimeter continuum studies revealed a cavity with a stellar-centric radius of 0 .″ 24 and a ring that extends to 1 .″ 15, which implied the presence of a 50 MJ companion with a separation of ∼0 .″ 1. We observed HD 34282 with Keck/NIRC2 in  L'  using nonredundant masking interferometry in order to simultaneously search for protoplanets at small separations (down to ∼0.5λ/D) and characterize the inner substructures of the transition disk. We fit geometric models to the data and find that a morphology with two disk components separated by a gap best describes the data. The inner component is comprised of scattering dust with a near-circular brightness distribution on the sky. The outer component can be modeled as a ring with a cavity that extends to ∼0 .″ 26 in radius, which is about 11° more inclined than measurements from past J-band observations of material near this region. We do not detect the 50 MJ companion but place an upper limit of ∼40 MJ on companions at ≳λ/D (0 .″ 08). We find that we are sensitive to a planet mass-times-accretion rate of ∼1 × 10−6  MJ2  yr−1, or an accretion rate that could form a Jupiter analog in ≳1 Myr.

Keywords: Interferometry, Protoplanetary disks, Near infrared astronomy
A Theoretical Investigation of OH<SUP>∙</SUP> + H<SUB>2</SUB>CCNH Reactivity: Interstellar Insights into Glycolonitrile Formation. Glycolonitrile (HOCH2CN) has been a molecule of long-standing interest in astrochemistry. While its production on interstellar icy grains has been explored theoretically and experimentally, little is known about its gas-phase formation. In this work, we investigate the reaction mechanism of OH∙ + H2CCNH (ketenimine). We examine different orientations of OH∙ relative to H2CCNH, and report three chemically distinct reaction channels for the radical addition of OH∙ along the heavy atom chain of ketenimine (either at the C(1) carbon, C(2) carbon, or N). Contrary to reported literature, our calculations reveal that several different routes to gauche- and trans-glycolonitrile are possible, and that formation proceeds in a step-wise fashion through H-atom beta-scission. With energetics evaluated using the HEAT-like protocol, a sub-kilocalorie-per-mole accuracy is expected. Therefore, rate constants (incorporating anharmonic effects) yield important insights into the molecular evolution of the title reaction and the overall fate of glycolonitrile under interstellar conditions.

Keywords: Molecular reactions, Interstellar medium, Astrochemistry
KRIOS: A New Basis-expansion N-body Code for Collisional Stellar Dynamics. The gravitational N-body problem is a nearly universal problem in astrophysics, which, despite its deceptive simplicity, still presents a significant computational challenge. For collisional systems such as dense star clusters, the need to resolve individual encounters between N stars makes the direct summation of forces—with quadratic complexity—almost infeasible for systems with N ≳ 106 particles over many relaxation times. At the same time, the most common Monte Carlo N-body algorithm—that of Hénon—assumes the cluster to be spherically symmetric. This greatly limits the study of many important features of star clusters, including triaxiality, rotation, and the production of tidal debris. In this paper, we present a new hybrid code, KRIOS, that combines 3D collisionless relaxation using an adaptive self-consistent field method with collisional dynamics handled via Hénon's method. We demonstrate that KRIOS can accurately model the long-term evolution of clusters and provide its complete phase-space information over many relaxation times. As a test of our new code, we present detailed comparisons to well-known results from stellar dynamics: (i) the collisional evolution of a family of Plummer spheres with varying anisotropy and rotation to core collapse, and (ii) the emergence of the radial-orbit instability in radially anisotropic star clusters, including its nonspherical effects.

Keywords: Globular star clusters, Stellar diffusion, Gravitation
The ODYSSEUS Survey. Using Accretion and Stellar Rotation to Reveal the Star─Disk Connection in T Tauri Stars. Classical T Tauri stars (CTTSs) exhibit strong variability over timescales of minutes to decades. However, much theoretical work assumes that CTTSs are in stable spin states. Here we test expectations for CTTS angular momentum regulation by comparing star and disk rotation. We measure stellar rotation periods and disk corotation radii (Rco) for 47 CTTSs from the Hubble Space Telescope ULLYSES sample. We compare Rco to the magnetospheric truncation radii (Ri) and show that most CTTSs are in sub-equilibrium spin states based on model predictions. This may indicate efficient angular momentum loss processes that maintain slow rotation rates throughout the CTTS phase. We find evidence of such processes in the form of magnetospheric outflows and episodic accretion, and our observations are consistent with the presence of accretion-powered stellar winds. We confirm predictions that Ri is variable over timescales of days, causing some CTTSs to cross accretion stability regime boundaries. We characterize light-curve morphologies and confirm that our inclined CTTSs with Ri ∼ Rco show dipper light curves, consistent with expectations from disk warp models. However, dippers occur at all values of Ri/Rco, suggesting that they do not need to be near the propeller regime. Finally, we show that our measured Ri locations are consistent with observed ultra─short-period planet (USP) semimajor axes. If USPs are stable against tidal dissipation, as has been suggested in the literature, then our work provides a plausible USP formation channel. These results show that the star─disk connection produces a large variety of accretion and stellar spin configurations, most of which are likely not in equilibrium.

Keywords: Period determination, Light curve classification , Exoplanet formation, T Tauri stars, Protoplanetary disks, Stellar accretion, Star-planet interactions, Stellar rotation
Accurate Shear Recovery with Multiband Images of Hyper Suprime-cam. The existing large-scale weak lensing surveys typically reserve the best seeing conditions for a certain optical band to minimize shape measurement errors and maximize the number of usable background galaxies. This is because most popular shear measurement methods contain explicit or implicit thresholds on the galaxy-to-point-spread-function size ratio, below which their shape measurement errors increase abruptly. Using the Dark Energy Camera Legacy Survey data, we have previously demonstrated that the Fourier_Quad method performs very well on poorly resolved galaxy images in general. It is therefore a ready tool for shear measurement with multiband images regardless of their seeing conditions. In this paper, we apply the Fourier_Quad pipeline on the multiband images from the third public data release of the Hyper Suprime-Cam Subaru Strategic Program. We estimate the shear measurement bias using the field distortion test. The results show that the multiplicative biases of g1 in all five bands (g/r/i/z/y) and g2 in the g/i/y bands are consistent with zero within ∼2σ. Only the g2 results in r, z bands show somewhat significant biases ( 102m2r,z  = 2.18 ± 0.69, 3.46 ± 0.62 respectively). As for the additive biases, most of them are different from zero by more than 3σ ( 104c1g,r,i,z,y  = 1.0 ± 1.0, −3.3 ± 0.9, −5.8 ± 0.7, −4.6 ± 0.6, −27.0 ± 0.8;  104c2g,r,i,z,y  =−3.5 ± 0.8, −2.2 ± 0.6, −2.3 ± 0.4, −0.0 ± 0.5, 1.0 ± 0.9). Using the LOWZ and CMASS galaxies as foreground lenses, we show that the error bar in the galaxy─galaxy lensing measurement can be decreased by factors of around 15% by combining shear catalogs from different bands. This indicates that it is worth taking multiband shear measurements for better shear statistics.

Keywords: Weak gravitational lensing, Astronomy data analysis, Large-scale structure of the universe
A Million Three-body Binaries Caught by Gaia. Gaia observations have revealed over a million stellar binary candidates within ∼1 kpc of the Sun, predominantly characterized by orbital separations &gt;103 au and eccentricities &gt;0.7. The prevalence of such wide, eccentric binaries has proven challenging to explain through canonical binary formation channels. However, recent advances in our understanding of three-body binary formation (3BBF)—new binary assembly by the gravitational scattering of three unbound bodies (3UB)—have shown that 3BBF in star clusters can efficiently generate wide, highly eccentric binaries. We further explore this possibility by constructing a semi-analytic model of the Galactic binary population in the solar neighborhood, originating from 3BBF in star clusters and subsequently migrating to the solar neighborhood within a Hubble time. The model relies on 3BBF scattering experiments to determine how the 3BBF rate and resulting binary properties scale with local stellar density, velocity dispersion, and physically motivated limits to 3UB encounters within a clusters' tidal field. The Galactic star cluster population is modeled by incorporating up-to-date prescriptions for the Galaxy's star formation history as well as the birth properties and internal evolution of its star clusters. Finally, we account for binary disruption induced by perturbations from stellar interactions before cluster dissolution and the subsequent changes and disruption of binary orbital elements induced by dynamical interactions in the Galactic field. Without any explicit fine-tuning, our model closely reproduces the total number of Gaia's wide binaries and the separation and eccentricity distributions, suggesting that 3BBF may be an important formation channel for these enigmatic systems.

Keywords: Galactic archaeology, Stellar dynamics, Three-body problem, Wide binary stars, Gaia
Binding Energies of Interstellar Complex Organic Molecules on Water Ice Surfaces: A Quantum Chemical Investigation. Interstellar dust grains are enveloped by ices of frozen molecules in cold, dense regions of the interstellar medium (ISM), which are also observed in the gas phase. Whether a species is in the solid or gaseous state is governed by its binding energy (BE) on the grains. Hence, BEs are crucial in the solid-to-gas transition and are key input parameters for astrochemical models that simulate the physicochemical processes leading to the evolution of chemistry in the ISM. About 40% of the currently detected interstellar molecules belong to the category of interstellar complex organic molecules (iCOMs). This work aims to accurately evaluate the BEs of 19 iCOMs by means of quantum chemical calculations. Atomistic surface models simulating the structures of both crystalline and amorphous water ice were employed adopting a periodic approach, thereby accounting for the hydrogen bond (H-bond) cooperativity imparted by the extensive network present in the surfaces. A cost-effective but reliable procedure based on density functional theory was used to predict the structures of the adsorption complexes and calculate their BEs, which are mainly driven by H-bond and dispersion interactions, the latter presenting a fair contribution. A final discussion on the astrophysical implications of the computed BEs and the importance of obtaining reliable BEs on realistic interstellar ice surfaces in relation to the snow lines of iCOMs in hot cores/corinos and protoplanetary disks is provided.

Keywords: Interstellar dust, Interstellar molecules, Solid matter physics, Dense interstellar clouds, Astrochemistry, Computational methods, Surface ices, Interstellar medium, Interstellar dust processes
Demystifying Strange O VI Line Widths with Hydrodynamic Simulations. We present a survey of O VI line widths obtained from hydrodynamic simulations that model the mixing between high-velocity clouds and the circumgalactic medium and track the nonequilibrium ionization populations of the ions. We run 10 simulations with various physical conditions of the clouds and ambient environments, so that our results can be compared to observations of various cloud environments. Synthetic spectra are created for the simulated sight lines that contain O VI. The range of our Doppler broadening parameter, b, is from ∼6 to ∼107 km s−1. We calculate the thermal and nonthermal contributions to the b values. Both b and the thermal contribution to b can be substantially less than the collisional ionizational equilibrium (CIE) value. These narrow line widths are due to the time delay in recombination from O VI to O V in mixing regions, which results in substantial amounts of O VI at temperatures below the 2.9 × 105 K CIE temperature. Our results show that nonequilibrium collisional ionization and mixing can produce the narrow line widths that are seen in multiple observations.

Keywords: Intergalactic medium, Interstellar line absorption, High-velocity clouds, Circumgalactic medium
Multiband Emission from Star─Disk Collisions and Implications for Quasiperiodic Eruptions. We perform two-dimensional, multigroup radiation hydrodynamic simulations to explore the observational properties of a solar-like star colliding with an accretion disk around a supermassive black hole at a separation of ∼100 gravitational radii. We find that the star-disk collision produces ejecta on both sides of the disk. As the ejecta expand and cool, transient flares arise, reaching peak bolometric luminosity of up to L ≳ 1043 erg s−1. We estimate that the typical light curve rises and decays on an hour timescale. The spectral energy distribution (SED) peaks in 20─50 eV. The optical depth in soft X-rays is lower than the frequency-integrated optical depth, yielding 100 eV─1 keV luminosity νLν ≳ 1042 erg s−1. The ejecta aligned with the star's incident direction shows breakout emission, leading to asymmetric SED evolution of the two ejecta. The SED evolution is roughly consistent with those seen in short-period quasiperiodic eruptions, which have eruption durations ranging from subhour to hours, but the ejecta cooling emission alone may not be sufficient to explain the longer duration flares. Increasing incident velocity generally produces a brighter and harder flare. A larger disk scale height prolongs the breakout emission but leads to a somewhat softer SED. A higher disk surface density can lead to higher ejecta temperature, reducing bound─free opacity and increasing luminosity. When lowering the disk surface density, we find that the ejecta becomes optically thin when the scattering optical depth across the disk is at the order of τdisk ∼ 200, and the ejecta disappear when τdisk ∼ 10.

Keywords: Time domain astronomy, Supermassive black holes, Transient sources
Diverse Pathways for Supermassive Black Hole─Galaxy Coevolution. Supermassive black holes (SMBHs) are observed in diverse galaxy populations across cosmic time, yet a clear understanding of how they coevolve with their hosts has not been reached. Physical models of SMBH accretion and feedback vary widely between galaxy formation simulations due to the difficulty of modeling the range of scales important for galactic and SMBH processes. Here we use observational data to build an empirical model for SMBH growth. We apply observed specific accretion rate probability distributions as a function of star formation rate between z = 0 and 2 to the UniverseMachine galaxy formation model to determine SMBH accretion rates based on galaxy properties. We use observed z = 0 SMBH─stellar mass relations for the quiescent and star-forming populations to provide the local boundary conditions for SMBH growth histories. We then track the coevolutionary histories of SMBH and galaxy stellar mass backward in time to z = 2. We find that the most massive SMBHs at z = 0 have grown very little of their mass between z = 0 and 2, indicating early SMBH mass assembly for these systems. Conversely, lower-mass SMBHs at z = 0 assembled gradually across z = 0─2. This results in substantial evolution of the SMBH─stellar mass relation, shifting to higher normalization and shallower slope with increasing redshift. We find that the substantial scatter observed in the z = 0 SMBH─stellar mass relation results in the diversity of growth pathways found in our model, with some galaxies assembling their stellar mass before their SMBHs and others doing the opposite.

Keywords: AGN host galaxies, Supermassive black holes, Theoretical models, Galaxies
Nitrogen-bearing Species on Trans-Neptunian Objects Revealed by JWST/DiSCo-TNOs. C≡N-bearing species are valuable tracers of nitrogen chemistry in the solar system. Ranging from volatile compounds like HCN and CH3CN in cometary comae to refractory CN-bearing organics in some micrometeorites and interplanetary dust particles, these species originate in, or are derived from, molecular precursors in the interstellar medium (ISM). The icy surfaces of medium-sized trans-Neptunian objects (TNOs) represent an intermediate stage in the chemical evolution and incorporation of N-bearing molecules from the ISM into the solar system. Herein, we investigate the nature, distribution, and origin of CN-bearing species on several TNOs and one centaur observed within the James Webb Space Telescope DiSCo-TNOs program. We find a spectral feature at 4.62 μm consistent in band position and width as OCN− observed in the ISM and the laboratory. This feature is most pronounced on TNOs in the Cliff2 group (Cliff2-TNOs, a compositional subgroup characterized by low ice content that include the cold classical TNOs, suggesting they formed farthest from the Sun) and might be tracing an original chemical inventory in the protoplanetary disk. Cliff2-TNOs are also the best candidates for studying the contribution of refractory C≡N-containing organics to a broad 4.5 µm spectral feature. Finally, a close spectral resemblance between Cliff2-TNOs and the centaur in our analysis, which exhibits both the 4.62 and 4.5 μm bands, provides a plausible dynamical channel that can enrich the inner solar system with N-bearing species. Our work advances the understanding of N-bearing species in the solar system and their evolutionary history beginning in the ISM.

Keywords: Centaur group, Infrared spectroscopy, James Webb Space Telescope, Protoplanetary disks, Trans-Neptunian objects, Complex organic molecules
Exploring One-point Statistics in HERA Phase I Data: Effects of Foregrounds and Systematics on Measuring One-point Statistics. Measuring one-point statistics in redshifted 21 cm intensity maps offers an opportunity to explore non-Gaussian features of the early Universe. We assess the impact of instrumental effects on measurements made with the Hydrogen Epoch of Reionization Array (HERA) by forward modeling observational and simulation data. Using HERA Phase I observations over 94 nights, we examine the second (m2, variance) and third (m3) moments of images. We employ the DAYENU-filtering method for foreground removal and reduce simulated foreground residuals to 10% of the 21 cm signal residuals. In noiseless cosmological simulations, the amplitudes of one-point statistics measurements are significantly reduced by the instrument response and further reduced by wedge-filtering. Analyses with wedge-filtered observational data, along with expected noise simulations, show that systematics alter the probability distribution of the map pixels. A likelihood analysis based on the observational data shows m2 measurements disfavor the cold reionization model characterized by inefficient X-ray heating, in line with other power spectra measurements. Small signals in m3 due to the instrument response of the Phase I observation and wedge-filtering make it challenging to use these non-Gaussian statistics to explore model parameters. Forecasts with the full HERA array predict high signal-to-noise ratios for m2, m3, and S3 assuming no foregrounds, but wedge-filtering drastically reduces these ratios. This work demonstrates conclusively that a comprehensive understanding of instrumental effects on m2 and m3 is essential for their use as a cosmological probe, given their dependence on the underlying model.

Keywords: Cosmology, Early universe, Astronomy data analysis, H I line emission, Radio interferometers, Reionization, Radio astronomy
The Gamma-Ray Emission from Radio Galaxies and Their Contribution to the Isotropic Gamma-Ray Background. We evaluate the contribution to the isotropic gamma-ray background (IGRB) coming from radio galaxies (RGs), the subclass of radio-loud active galactic nuclei with the highest misalignment from the line of sight. Since only a small number of RGs are detected in γ-rays compared to the largest known radio population, the correlation between radio and γ-ray emission serves a crucial tool to characterize the γ-ray properties of these sources. We analyze the population of RGs using two samples. The first sample contains 26 sources individually detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope at γ-rays. The second sample contains 210 RGs for which the γ-ray emission is not significantly detected by the LAT. We use a stacking analysis to characterize the average properties of the γ-ray emission of the two samples, separately at first and then combined. We then evaluate the correlation between their γ-ray emission and the emission from their radio core at 5 GHz, and we use it to determine their contribution to the IGRB. Due to the limited number of RGs detected at the γ-rays, information on the γ-ray luminosity function is limited. The Lγ─LC,5GHz correlation allows us to characterize it starting from the luminosity function of the radio cores, which is modeled with greater accuracy due to the larger number of sources detected at these frequencies. We find that the diffuse emission as extrapolated from the properties of the subthreshold RGs is lower than the one inferred from detected RGs, showing that the contribution of the population of RGs to the IGRB is lower than the previous estimates and is around the ∼30% level of the IGRB intensity.

Keywords: Diffuse radiation, Gamma-ray astronomy, Radio galaxies
JWST Observations of SN 2023ixf. II. The Panchromatic Evolution between 250 and 720 Days after the Explosion. We present the nebular phase spectroscopic and photometric observations of the nearby hydrogen-rich core-collapse supernova (CCSN) SN 2023ixf, obtained through our JWST programs. These observations, combined with ground-based optical and near-infrared spectra, cover +252.67─719.96 days, creating a comprehensive, panchromatic time-series data set spanning 0.32─30 μm. In this second paper of the series, we focus on identifying key spectral emission features and tracking their evolution through the nebular phase. The JWST data reveal hydrogen emission from the Balmer to Humphreys series, as well as prominent forbidden lines from Ne, Ar, Fe, Co, and Ni. NIRSpec observations display strong emission from the first-overtone and fundamental bands of carbon monoxide, which weaken with time as the ejecta cools and dust emission dominates. The spectral energy distribution shows a clear infrared excess emerging by +252.67 days peaking around 10.0 μm, with a secondary bump at 18.0 μm developing by +719.96 days. We suggest that this evolution could arise from multiple warm dust components. In upcoming papers in this series, we will present detailed modeling of the molecular and dust properties. Overall, this work provides the community with a unique data set that can be used to advance our understanding of the mid-infrared properties of CCSNe, offering an unprecedented resource for studying their late-time line, molecular, and dust emission.

Keywords: Core-collapse supernovae, Type II supernovae, Dust formation, Infrared astronomy, James Webb Space Telescope