Sazuna/UAT_keywords huggingface dataset:
Free-floating Planets Produced by Planet─Planet Scatterings: Ejection Velocity and Survival Rate of Their Moons. The discovery of numerous free-floating planets (FFPs) has intensified interest in their origins and dynamical histories. A leading formation mechanism is planet─planet scatterings in unstable multiplanetary systems, which can naturally lead to planetary ejections. If these planets originally host moons, it remains an open question whether such satellites can remain gravitationally bound to FFPs after ejection. In this work, we investigate both the ejection velocity of FFPs produced by planet─planet scatterings and the survival rate of their potential moons; we estimate the latter by determining the statistics of the minimum planet─planet distance prior to planet ejection, and comparing it to the initial orbital radius of the moon relative to its host planet. Using the circular restricted three-body framework, we derive an analytical boundary for the ejection velocity based on Jacobi energy conservation, which agrees with the results of integrations. We also identify a minimum planetary mass required for successful ejection. For two-planet systems with finite planetary masses, we use simulations and analytical arguments to determine how the ejection velocity scales with the planetary mass and initial semimajor axis. We contrast our results with the ejection of planets around binaries in unstable orbits. Extending our analysis to three-planet systems yields similar results, reinforcing the robustness of our conclusions. These findings offer insights into the property of FFPs and inform future efforts to search for exomoons around them.

Keywords: Free floating planets, Natural satellites (Extrasolar), Planetary dynamics
How Plasma Properties of the Fanaroff─Riley Jet Can Shape Its Morphology. Extragalactic jets are broadly classified into two categories based on radio observations: core-brightened jets, known as Fanaroff─Riley Type I (FR I), and edge-brightened jets, classified as Type II (FR II). This FR dichotomy may arise due to variation in the ambient medium and/or the properties of the jet itself, such as injection speed, temperature, composition, magnetization, etc. To investigate this, we perform large-scale three-dimensional magnetohydrodynamic simulations of low-power, supersonic jets extending to kiloparsec scales. We inject a jet beam carrying an initially toroidal magnetic field into a denser, unmagnetized, and stratified ambient medium through a cylindrical nozzle. Our simulations explore jets with varying injection parameters to investigate their impact on morphology and emission properties. Furthermore, we examine jets with significantly different plasma compositions, such as hadronic and mixed electron─positron─proton configurations, to study the conditions that may drive transitions between FR I and FR II morphologies. We find that, under the same injection parameters, mixed plasma composition jets tend to evolve into FR I structures. In contrast, electron─proton jets exhibit a transition between FR I and FR II morphologies at different stages of their evolution.

Keywords: Shocks, Active galactic nuclei, Radio jets, Magnetohydrodynamical simulations
Supernovae Exploding within Dense Extended Material: Early Emission Regimes and Degeneracies in Parameter Inference from Observations. Early light curves of many core-collapse supernovae (SNe) are thought to be powered by the interaction of the shock wave with optically thick extended material, either a bound envelope or preexplosion ejected circumstellar matter. We analytically analyze the early emission produced by a shock with velocity v traversing a material of mass Me and opacity κ extending to radius Re, and show the emission varies qualitatively with varying  τe=κMe/(4πRe2) : For τe ≫ c/v a shock breakout occurs near Re producing an "edge breakout"—a UV-dominated breakout burst followed by "cooling emission" of the shock-heated material; for τe ≲ c/v a "wind breakout" occurs—the breakout pulse is prolonged and followed by extended emission shifting from UV to X-ray as the shock becomes collisionless. We derive the dependence on {v, κ, Me, Re} of the duration and luminosity characterizing the different emission phases, and show that current observations typically do not allow inference of all parameters. In particular, since the optical bands lie in the Rayleigh─Jeans tail of radiation emitted during the cooling phase, the observed cooling luminosity depends weakly on Re,  ∝Re1/4 , leading to 1─2 orders of magnitude uncertainty in its inferred value. This suggests, e.g., that the common day-scale light curve features in stripped-envelope SNe do not necessarily imply material extending to Re ∼ 103R⊙ and are often consistent with low-mass Re ∼ 102R⊙ bound envelopes. Early multiband coverage (especially in UV/X-ray) can break these degeneracies; the forthcoming ULTRASAT UV mission will allow inferring the properties of extended material around the population of SN progenitors.

Keywords: Ultraviolet transient sources, Late stellar evolution, High energy astrophysics, Stellar mass loss, Circumstellar matter, Time domain astronomy, Shocks, Supernovae
CHILES. XI. Resolved H I Morphologies and the Evolution of the H<SUB>2</SUB>/H I Ratio over the Last Five Billion Years. We present the neutral gas morphology of four galaxies from z = 0.22 to 0.47 obtained with the COSMOS H I Large Extragalactic Survey (CHILES). The H I is resolved at the highest redshift with the 7 .″ 5 beam of CHILES and 43 kpc linear scale, with all four galaxies having extended H I. Three are massive galaxies (M* &gt; 3 × 1010 M⊙), with H I masses of (1.6─6.7) × 1010 M⊙ and active star formation (3─30 M⊙ yr−1). The morphology and kinematics of the galaxies vary from regular to disturbed, including an asymmetric H I disk surrounding the fourth smaller galaxy (M* ∼ 109 M⊙). CO (1─0) observations of the sample, obtained with the Large Millimeter Telescope, confirm the redshifts of three of the four galaxies, and we derive H2 masses of (0.4─5.2) × 1010 M⊙. JWST imaging with four combined NIRCam filters reveals disturbed stellar components with compact knots in two of the galaxies. We combine our new higher-redshift galaxies with previously published observations to conduct a more complete study of H I and H2 evolution in the redshift range 0─0.5. With our H I flux-limited observations compared to similar lower-redshift galaxies with high stellar mass (M* &gt; 1010 M⊙), the results show that the mean H2/H I ratio at the highest redshift is 10.3 ± 3.4, larger than the mean H2/H I ratio in the local Universe.

Keywords: Galaxy evolution
Methanol Formation via the Radical─Radical Reaction of OH and CH<SUB>3</SUB> Radicals Undergoing Transient Diffusion on Ice at 10 to 60 K. Methanol (CH3OH) is thought to form on interstellar ice dust via successive hydrogenation reactions. The reaction between CH3 and OH radicals could also conceivably generate methanol at temperatures above approximately 20 K, at which temperature hydrogen atoms will not adhere to the ice surface. However, this process has not been verified by well-controlled experiments. Using a newly developed Cs+ ion pickup technique, the authors investigated the reaction between CH3 and OH radicals on the surface of amorphous solid water, an ice dust analog, at temperatures from 10 to 60 K. In the present experiments, OH radicals were generated by ultraviolet photolysis of water molecules, following which methane (CH4) gas was deposited on the ice substrate. The results show that CH3OH was formed on the ice surface through the sequential reactions CH4 + OH → CH3 + H2O and CH3 + OH → CH3OH, even at 10 K. Considering the very low surface coverage of reactants in the experimental condition, the second reaction was found to occur as a result of transient diffusion of CH3 due to the heat of the first reaction.

Keywords: Interstellar dust processes, Astrochemistry, Dense interstellar clouds
Height and Energy Evolution of X-Ray Double Sources in a Solar Flare. In the standard model, magnetic reconnection at a vertical current sheet above the flare arcade is key to explaining many aspects of solar eruptions. The supra-arcade region is where the vertical current sheet is supposedly located, and X-ray/extreme-ultraviolet emission therein reflects underlying energy release and transport processes, therefore providing valuable insight into the structure and evolution of the current sheet. Previous studies have focused primarily on the impulsive phase of flares, but phenomena in the decay phase are also crucial for understanding the complete flaring scenario. In this paper, we investigated an M6.7-class limb flare that occurred on 2022 August 28, combining observations from the Solar Orbiter (SolO) and Solar Dynamics Observatory. Coronal X-ray sources are continually observed by the Spectrometer/Telescope for Imaging X-rays onboard SolO for over 2 hr, revealing a multiphase evolution with varying velocities and multiple substructures, with higher-energy components consistently appearing at higher altitudes. Such a height-energy relation is notably observed in a double coronal source during the decay phase, which is dominated by thermal emission. The energy distribution of the double source distinguishes itself from previous studies that showed a symmetric distribution, with the higher-energy components being closer to the center of the double source during the impulsive phase. Obtained from two opposite side-on perspectives on the supra-arcade region, these findings reveal the spatiotemporal complexity of the energy release process in the postflare current sheet during the decay phase.

Keywords: Solar flares, Solar coronal mass ejections, X-ray sources, Solar x-ray flares
The Impact of Cosmic Filaments on the Abundance of Satellite Galaxies. The impact of cosmic web environments on galaxy properties plays a critical role in understanding galaxy formation. Using the state-of-the-art cosmological simulation IllustrisTNG, we investigate how satellite galaxy abundance differs between filaments and the field, with filaments identified using the DISPERSE algorithm. When filaments are identified using galaxies as tracers, we find that, across all magnitude bins, central galaxies in filaments tend to host more satellite galaxies than their counterparts in the field, in qualitative agreement with observational results from the Sloan Digital Sky Survey. The average ratios between satellite luminosity functions in filaments and the field are 3.49, 2.61, and 1.90 in the central galaxy r-band magnitude bins of Mr,cen ∼ −22, −21, and −20, respectively. We show that much of this excess can be attributed to the higher host halo masses of galaxies in filaments. After resampling central galaxies in both environments to match the halo mass distributions within each magnitude bin, the satellite abundance enhancement in filaments is reduced by up to 79%. Additionally, the choice of tracers used to identify filaments introduces a significant bias: when filaments are identified using the dark matter density field, the environmental difference in satellite abundance is reduced by more than 70%; after further resampling in both magnitude and halo mass, the difference is further suppressed by another ∼60%─95%. Our results highlight the importance of halo mass differences and tracer choice biases when interpreting and understanding the impact of environment on satellite galaxy properties.

Keywords: Galaxy dark matter halos, Cosmic web, Hydrodynamical simulations, Large-scale structure of the universe
Exploring Selection Biases in Fast Radio Burst Dispersion─Galaxy Cross-correlations with Magnetohydrodynamical Simulations. The dispersion measures (DMs) of fast radio bursts (FRBs) can be used as powerful probes of the distribution of extragalactic plasma. With a large enough sample, the free-electron─galaxy power spectrum Peg can be measured by cross-correlating FRB DMs with galaxy positions. However, a precise measurement of Peg requires a careful investigation of selection effects: the probability of both observing the FRB DM and obtaining a host galaxy redshift depends on their properties. We ray trace through the magnetohydrodynamic simulation IllustrisTNG to investigate the impact of expected observational selection effects on FRB dispersion─galaxy angular cross-correlations with a sample of 3000 FRBs at 0.3 ≤ z ≤ 0.4. Our results show that cross-correlations with such an FRB sample are robust to properties of the FRB host galaxy: this includes DM contributions from the FRB host and optical follow-up selection effects. We also find that such cross-correlations are robust to DM-dependent and scattering selection effects specific to the CHIME/FRB survey. However, a DM-dependent selection effect that cuts off the 10% most dispersed FRBs at a fixed redshift shell can bias the amplitude of the cross-correlation signal by over 50% at angular scales of ∼0 .° 1, corresponding to ∼Mpc physical scales. Our findings highlight the importance of both measuring and accounting for selection effects present in existing FRB surveys, as well as mitigating DM-dependent selection effects in the design of upcoming FRB surveys aiming to probe large-scale structure with FRBs.

Keywords: Radio transient sources, Interstellar plasma, Magnetohydrodynamical simulations, Large-scale structure of the universe
Impact of Light-mass Nuclear Reactions on the r-process Nucleosynthesis, Revisited. Light-mass nuclear reactions can play a significant role in r-process nucleosynthesis in core-collapse supernovae (SNe) and collapsars. We investigate the sensitivity of both weak and main r-process nucleosyntheses, which are responsible for the production of the first and second plus third r-process peak nuclei, respectively, to the light-mass nuclear reactions up to oxygen isotopes. We extend the reaction network to include more neutron-rich isotopes and update reaction rates using recent experimental results. For the explosion mechanisms, the sensitivity studies have previously been done in ν-driven wind SNe assuming relatively high initial neutron-to-proton ratio with high entropy. We here consider magnetohydrodynamic jet SNe and collapsars in addition to the ν-driven winds. We use a simple exponential decay model for slowly expanding disk outflows, which manifest themselves in various disk winds from collapsars, magnetohydrodynamic jets, binary neutron star mergers, as well as ν-driven winds. We study the competition between the dynamical expansion timescale of the system and the collision timescales for various nuclear reactions and β-decays in order to identify the main reaction flow paths. We find the sensitivities of the main r-process to 14C(n, γ)15C, 18O(n, γ)19O, and 8Li(α, n)11B, which are as large as 16%, 24%, and 0.6%, respectively, for the magenetohydrodynamic jet SN environment, and for the weak r-process to (n, γ) and (α, n) reactions, which depend on different astrophysical sites.

Keywords: R-process, Nuclear astrophysics, Core-collapse supernovae, Nuclear physics
Connection between Dwarf Galaxies and Globular Clusters: Insights from the Perseus Cluster Using Subaru Imaging and Keck Spectroscopy. We present a systematic study of 189 dwarf galaxies and their globular cluster (GC) systems in the Perseus Cluster, based on deep Subaru Hyper Suprime-Cam imaging and Keck spectroscopy, supplemented by literature data. This constitutes the largest sample of dwarfs in a single galaxy cluster to date with simultaneous deep imaging, spectroscopic coverage, and GC measurements, while uniquely spanning a broad and continuous range of galaxy properties. We find an anticorrelation between GC specific mass and galaxy stellar mass for dwarfs in Perseus similar to observations in other clusters. At fixed stellar mass, dwarfs with lower surface brightness or larger effective radius tend to be more GC-rich—suggesting either high GC formation efficiency in an earlier compact-galaxy phase or less efficient GC disruption. The correlation between GC richness and axis ratio in Perseus is weaker than in other environments. We find some connection between GC richness and infall time, but not with the clear correlations found in Virgo, Coma, and cosmological simulations. More complete observations are needed to test for cluster-to-cluster variations in galaxy and GC evolutionary histories. This work demonstrates the potential of new wide-field imaging and spectroscopy surveys for understanding GCs and dwarf galaxies, and highlights the need for further work in theoretical modeling.

Keywords: Globular star clusters, Dwarf galaxies, Perseus Cluster
Protoplanetary Disk Cavities with JWST-MIRI: A Dichotomy in Molecular Emission. The evolution of planet-forming regions in protoplanetary disks is of fundamental importance to understanding planet formation. Disks with a central deficit in dust emission, a "cavity," have long attracted interest as potential evidence for advanced disk clearing by protoplanets and/or winds. Before JWST, infrared spectra showed that these disks typically lack the strong molecular emission observed in full disks. In this work, we combine a sample of 12 disks with millimeter cavities of a range of sizes (∼2─70 au) and different levels of millimeter and infrared continuum deficits. We analyze their molecular spectra as observed with MIRI on JWST, homogeneously reduced with the new JDISCS pipeline. This analysis demonstrates a stark dichotomy in molecular emission where "molecule-rich" (MR) cavities follow global trends between water, CO, and OH luminosity and accretion luminosity as in full disks, while "molecule-poor" (MP) cavities are significantly subluminous in all molecules except sometimes OH. Disk cavities generally show subluminous organic emission, higher OH/H2O ratios, and suggest a lower water column density. The subthermal excitation of CO and water vibrational lines suggests a decreased gas density in the emitting layer in all cavities, supporting model expectations for C2H2 photodissociation. We discover a bifurcation in the infrared index (lower in MR cavities) suggesting that the molecular dichotomy is linked to residual μm-size dust within millimeter disk cavities. Put together, these results suggest a feedback process between dust depletion, gas density decrease, and molecule dissociation. Disk cavities may have a common evolutionary sequence where MR switch into MP over time.

Keywords: Infrared spectroscopy, Molecular spectroscopy, T Tauri stars, Young stellar objects, Star formation, Protoplanetary disks, Pre-main sequence, Circumstellar disks, Exoplanet formation, Planet formation
Irradiated Atmosphere. V. Effects of Vertical-mixing Induced Energy Transport on the Inhomogeneity. Atmospheric variations over time and space boost planetary cooling, as outgoing internal flux responds to stellar radiation and opacity. Vertical mixing regulates this cooling. Our study examines how gravity waves or large-scale induced mixing interact with radiation transfer, affecting temperature inhomogeneity and internal flux. Through the radiative-convective-mixing equilibrium, mixing increases temperature inhomogeneity in the middle and lower atmospheres, redistributing internal flux. Stronger stellar radiation and mixing significantly reduce outgoing flux, slowing cooling. With constant infrared (IR) opacity, lower visible opacity, and stronger mixing, it significantly reduces outgoing flux. Jensen's inequality implies that greater spatial disparities in stellar flux and opacity elevate the ratio of the average internal flux in inhomogeneous columns relative to that in homogeneous columns. This effect, particularly pronounced under high opacity contrasts, amplifies deep-layer temperature inhomogeneity and may enhance cooling. However, with mixing, overall cooling is weaker than without, as both the averaged internal flux of the inhomogeneous columns and that of the homogeneous column decline more sharply for the latter. Thus, while vertical mixing-induced inhomogeneity can enhance cooling, the overall cooling effect remains weaker than in the no-mixing case. Therefore, vertical mixing, by regulating atmospheric structure and flux, is key to understanding planetary cooling.

Keywords: Radiative transfer simulations, Radiative transfer equation, Exoplanet atmospheres, Atmospheric science
Taking a Break at Cosmic Noon: Continuum-selected Low-mass Galaxies Require Long Burst Cycles. While bursty star formation in low-mass galaxies has been observed in local populations and reproduced in simulations, the dormant phase of the burst cycle has not been well studied beyond the local Universe due to observational limitations. We present a unique sample of 43 JWST PRISM spectra of low-mass galaxies (M⋆ &lt; 109.5 M⊙) at cosmic noon (1 &lt; z &lt; 3), uniformly selected on F200W magnitude and precise photometric redshifts enabled by 20-band JWST photometry from the UNCOVER and MegaScience surveys. The spectra reveal numerous strong Balmer breaks, which are negatively correlated with the galaxies' Hα equivalent width. By comparing these observations to synthetic samples of spectra generated using a simple parameterization of bursty star formation histories, we show that star formation in low-mass galaxies at cosmic noon is likely dominated by burst cycles with long timescales (≳100 Myr) and large deviations below the star-forming main sequence (≳0.8 dex). Our results suggest that galaxies in this population—at least those within our detection limits—should not be classified solely by their current star formation rates, but instead viewed as a unified population undergoing dynamic movement above and below the star-forming main sequence. The derived constraints demonstrate that long-timescale fluctuations are important for this class of galaxies, indicating that galaxy-scale gas cycles—rather than molecular-cloud-scale stochasticity—are the primary regulators of star formation variability in low-mass galaxies at cosmic noon.

Keywords: Dwarf galaxies, Star formation, Galaxy evolution
Leveraging Redshift Probabilities and Machine Learning Classification to Identify Catastrophic Outlier Photometric Redshift Estimates. We present results of using a basic binary classification neural network model to identify likely catastrophic outlier (CO) photometric redshift estimates of individual galaxies. The classification is based on individual galaxy redshift probability distributions generated by a multiclass classifier neural network and a support vector machine. Importantly, the redshift probability distributions used as input to the binary classifier can be used for photometric redshift estimates generated by a different method. We find that a simple implementation of this classification can identify a very large fraction of galaxies with CO photometric redshift estimates while erroneously categorizing only a much smaller, in some cases negligible, fraction of nonoutliers. These methods can reduce the errors introduced into science analyses by CO photometric redshift estimates.

Keywords: Outlier detection, Redshift surveys, Neural networks