Sazuna/UAT_keywords huggingface dataset:
Binding Energies of N-bearing Species on Interstellar Water Ice Mantles by Quantum Chemical Calculations. Of the about 300 gas-phase molecular species so far detected in the interstellar medium (ISM), mostly via observations of their rotational lines, around 40% contain nitrogen (N) atoms. Likewise, of the less than a dozen interstellar molecules, firmly or likely detected in the solid-state water-dominated icy matrix by means of infrared observations, two bear N. A crucial parameter that regulates whether a species is in the gas or adsorbed on the icy phase is their binding energy (BE) toward the icy grain. Therefore, an accurate quantification of the BE is of paramount importance to properly model the ISM chemistry through numerical models. However, very few BEs are available in the literature, either determined experimentally or theoretically. In the present study, we calculate the BEs of 21 among the most abundant interstellar N-bearing species. We adopted two structural water ice models, representing a crystalline and an amorphous surface, using a reliable cost-effective procedure based on the density functional theory. While on the crystalline surface model only one BE per species is obtained due to the high symmetry of the unit cell, on the amorphous model from 5 to 10 BEs are obtained, due to its richer surface morphological variety. Most of our computed BEs agree with available experimental and other computational values. Finally, we discuss how the newly computed BEs can help estimate which N-bearing species can be frozen at the water snow line and, therefore, incorporated in water-rich ice planetesimals.

Keywords: Interstellar dust, Interstellar molecules, Solid matter physics, Dense interstellar clouds, Computational methods, Surface ices, Interstellar medium, Interstellar dust processes
Persistent Behavior in Solar Energetic Particle Time Series. We investigate the long-term persistence of solar energetic particle (SEP) time series by means of four different methods: Hurst rescaled range R/S analysis, detrended fluctuation analysis, centered moving average analysis, and the fluctuation of natural time under the time reversal method. For these analyses, we use data sets from the Integrated Science Investigation of the Sun instrument suite on board NASA's Parker Solar Probe. Background systematic noise is modeled using cross-correlation analysis between different SEP energy channels and subtracted from the original data. The use of these four methods for deriving the time-series persistence allows us to (i) differentiate between quiet- and active-Sun periods based on the values of the corresponding self-similarity exponents alone; (ii) identify the onset of an ongoing activity well before it reaches its maximum SEP flux; (iii) reveal an interesting fine structure when activity is observed; and (iv) provide, for the first time, an estimate of the maximum SEP flux of a future storm based on the entropy change of natural time under time reversal.

Keywords: Solar energetic particles, Solar wind, Astrostatistics, Interdisciplinary astronomy, Time series analysis
Exploring the Evolution of a Dwarf Spheroidal Galaxy with Smoothed-particle Hydrodynamics Simulations. I. Stellar Feedback. A fundamental question regarding the evolution of dwarf spheroidal galaxies is the identification of the key physical mechanisms responsible for gas depletion. Here, we focus on the study of stellar feedback in isolated dwarf spheroidal galaxies by performing numerical simulations using a modified version of the smoothed-particle hydrodynamics code GADGET-3. The Milky Way satellite Leo II (PGC 34176) in the Local Group was considered as our default model dwarf galaxy. The parameter space for the stellar feedback models was explored to match observational constraints of Leo II, such as residual gas mass, total mass within the tidal radius, star formation history, final stellar mass, stellar ages, and metallicity. Additionally, we examined the impact of the binary fraction of stars, initial mass function, dark matter halo mass, and initial gas reservoir. Many simulations revealed recent star formation quenching due to stellar feedback. In general, the gas depletion, expected star formation history, total mass of stars, and total mass within the tidal radius were adequately reproduced in the simulations when compared to observational estimates. However, there were discrepancies in the distribution of stellar ages and metallicities, which suggested that the cosmic gas infall would play a more complex role in our dwarf spheroidal galaxy than captured by a monolithic infall scenario. Our results suggest that currently quenched dwarf galaxies may not necessarily need to evolve within clusters or groups and that stellar feedback alone could be a sufficient factor in shaping at least some of these galaxies as we observe them today.

Keywords: Hydrodynamical simulations, Stellar feedback, Dwarf spheroidal galaxies
Does the Correlation between 2MRS Galaxies and the CMB Indicate an Unmodeled CMB Foreground?. We revisit the claimed detection of a new cosmic microwave background (CMB) foreground based on the correlation between low-redshift Two Micron All Sky Survey Redshift Survey (2MRS) galaxies and CMB temperature maps from the Planck and Wilkinson Microwave Anisotropy Probe missions. We reproduce the reported measurements but argue that the original analysis significantly underestimated the uncertainties. We cross-correlate the 2MRS galaxy positions with simulated CMB maps and show that the correlation measured with the real data for late-type spiral galaxies at angular scales θ ≥ 0.°1 and redshift cz &lt; 4500 km s‑1 is consistent with zero at the 1.7σ level or less, depending on the exact CMB map and simulation construction. This was the sample that formed the basis for the original detection claim. For smaller angular separations the results are not robust to galaxy type or CMB cleaning method, and we are unable to draw firm conclusions. The original analysis did not propose a specific, falsifiable physical correlation mechanism, and it is impossible to rule out any contribution from an underlying physical effect. However, given our calculations, the lack of signal from expanding the redshift range, and the lack of corroboration from other galaxy surveys, we do not find the evidence for a new CMB foreground signal compelling.

Keywords: Observational cosmology, Cosmic microwave background radiation
Azimuthal Size Scales of Solar Wind Periodic Density Structures. Periodic density structures (PDSs) are quasiperiodic variations of solar wind density ranging from a few minutes to a few hours. PDSs advect with the solar wind and have radial length scales (L  x ) of tens to several thousand megameters, thus belonging to the class of "mesoscale structures." Current interplanetary multispacecraft observations are not at spatial separations capable of directly measuring the 3D size scale of PDSs or other mesoscale structures. Instead, previous investigations estimated characteristic spatial scales in solar wind parameters using cross-correlation and/or coherence analysis applied to multispacecraft observations. For the solar wind density and interplanetary magnetic field (IMF) intensity, the reported size scales perpendicular to the Sun–Earth line (L  y ) ranged between ≈30 and ≈200 Earth Radii (R E). Here, we implemented a similar approach for the same parameters, but focused on high-density, slow-solar-wind intervals with PDSs observed by the Wind and ARTEMIS-P1 spacecraft. Additionally, this is the first statistical study of the IMF intensity periodicities in relation to PDSs. We identified intervals in which the two spacecraft observed the same periodicity, obtaining two PDS groups based on their radial length scale: L  x1 ≈ 86R E and L  x2 ≈ 35R E. Then, we classified the events based on the periodic variations' coherence level. Reproducing the results with simulations of the PDSs' transit, we inferred the L  y  order of magnitudes for the two PDS groups: L  y1 ≈ 340R E and L  y2 ≈ 187R E. Knowing the PDSs' size scales is fundamental for constraining models aimed at reproducing these structures and is critical for better understanding the PDS–magnetosphere coupling.

Keywords: Slow solar wind, Solar coronal transients, Interplanetary turbulence, Planetary magnetospheres, Interplanetary physics
A Test of Spectroscopic Age Estimates of White Dwarfs Using Wide WD+WD Binaries. White dwarf stars have been used for decades as precise and accurate age indicators. This work presents a test of the reliability of white dwarf total ages when spectroscopic observations are available. We conduct follow-up spectroscopy of 148 individual white dwarfs in widely separated double-white-dwarf (WD+WD) binaries. We supplement the sample with 264 previously published white dwarf spectra, as well as 1292 high-confidence white dwarf spectral types inferred from their Gaia XP spectra. We find that spectroscopic fits to optical spectra do not provide noticeable improvement to the age agreement among white dwarfs in wide WD+WD binaries. The median age agreement is ≈1.5σ for both photometrically and spectroscopically determined total ages, for pairs of white dwarfs with each having a total age uncertainty &lt; 20%. For DA white dwarfs, we further find that photometrically determined atmospheric parameters from spectral energy distribution fitting give better total age agreement (1.0σ, 0.2 Gyr, or 14% of the binary's average total age) compared to spectroscopically determined parameters from Balmer-line fits (agreement of 1.5σ, 0.3 Gyr, or 28% of binary's average total age). We find further evidence of a significant merger fraction among wide WD+WD binaries: across multiple spectroscopically identified samples, roughly 20% are inconsistent with a monotonically increasing initial–final mass relation. We recommend the acquisition of an identification spectrum to ensure the correct atmospheric models are used in photometric fits in order to determine the most accurate total age of a white dwarf star.

Keywords: White dwarf stars, Binary stars, Stellar ages
Reconstruction of Cosmic Black Hole Growth and Mass Distribution from Quasar Luminosity Functions at z &gt; 4: Implications for Faint and Low-mass Populations in JWST. The evolution of the quasar luminosity function (QLF) is fundamental to understanding the cosmic evolution of black holes (BHs) through their accretion phases. In the era of the James Webb Space Telescope (JWST), Euclid, and Nancy Grace Roman Space Telescope, their unprecedented detection sensitivity and wide survey area can unveil the low-luminosity quasar and low-mass BH population, and provide new insights into quasar host galaxies. We present a theoretical model describing BH growth from initial seeding at z ≳ 20 to ∼ 4, incorporating the duration of accretion episodes, the distribution of Eddington ratios, and the mass dependency of BH accretion rates. By constraining the model parameters with the observed QLFs at 4 ≤ z ≤ 6 across a wide UV luminosity range, we find that the high-redshift BH population grows rapidly at z ≳ 6, and decelerates the pace in subsequent epochs. Toward lower redshifts (z &lt; 6), mass-dependent accretion inhibits the growth of high-mass BHs with M • &gt; 108 M ⊙, leading to mass saturation at M • ≳ 1010 M ⊙. We predict the BH mass function down to M • ∼ 106 M ⊙ for both unobscured and obscured quasar populations at 4 ≤ z ≤ 11, offering a benchmark for future observational tests. Our model accounts for the presence of both bright and faint quasars at z &gt; 4, including those discovered by JWST. Furthermore, our findings suggest two distinct pathways for the early assembly of the BH–galaxy mass correlation: the population with a BH-to-stellar-mass ratio near the local value of M •/M ⋆ ≃ 5 × 10‑3 maintains proximity to the relation via moderate growth, while the population that begins to grow above the local relation becomes as overmassive as M •/M ⋆ ∼ 0.01–0.1 by z ∼ 6 via rapid mass accretion.

Keywords: Supermassive black holes, High-redshift galaxies, Quasars
The Stability of Dense Cores near the Serpens South Protocluster. Most stars form in clusters and groups rather than in isolation. We present ≲5″ angular resolution (∼2000 au, or 0.01 pc) Very Large Array NH3 (1,1), (2,2), and (3,3) and 1.3 cm continuum emission observations of the dense gas within the Serpens South protocluster and extended filaments to the north and south. We identify 94 dense cores using a dendrogram analysis of the NH3 (1,1) integrated intensity. Gas temperatures T  K  and nonthermal line widths σ NT both increase toward the center of the young stellar cluster, in the dense gas generally and in the cores specifically. We find that most cores (54%) are supervirial, with gravitationally bound cores located primarily in the filaments. Cores in the protocluster have higher virial parameters by a factor of ∼1.7, driven primarily by the increased core σ NT values. These cores cannot collapse to form stars unless they accrete additional mass or their core internal motions are reduced. The southern filament shows a significant velocity gradient previously interpreted as mass flow toward the cluster. We find more complex kinematics in the northern filament. We find a strong correlation between σ NT and T  K , and argue that the enhanced temperatures and nonthermal motions are due to mechanical heating and interaction between the protocluster-driven outflows and the dense gas. Filament-led accretion may also contribute to the increased σ NT values. Assuming a constant fraction of core mass ends up in the young stars, future star formation in the Serpens South protocluster will shift to higher masses by a factor of ∼2.

Keywords: Interstellar molecules, Young star clusters, Molecular clouds, Star formation, Interstellar medium
Supernova Explosions of the Lowest-mass Massive Star Progenitors. We here focus on the behavior of supernovae that technically explode in 1D (spherical symmetry). When simulated in 3D, however, the outcomes of representative progenitors of this class are quite different in almost all relevant quantities. In 3D, the explosion energies can be 2 to 10 times higher, and there are correspondingly large differences in the 56Ni yields. These differences between the 3D and 1D simulations reflect in part the relative delay to explosion of the latter and in the former the presence of protoneutron star convection that boosts the driving neutrino luminosities by as much as ∼50% at later times. In addition, we find that the ejecta in 3D models are more neutron-rich, resulting in significant weak r-process and 48Ca yields. Furthermore, we find that in 3D the core is an interesting, though subdominant, source of acoustic power. In summary, we find that though a model might be found theoretically to explode in 1D, one must perform supernova simulations in 3D to capture most of the associated observables. The differences between 1D and 3D models are just too large to ignore.

Keywords: Nucleosynthesis, Supernova dynamics, Core-collapse supernovae
Discriminating between Babcock–Leighton-type Solar Dynamo Models by Torsional Oscillations. The details of the dynamo process in the Sun are an important aspect of research in solar-terrestrial physics and astrophysics. The surface part of the dynamo can be constrained by direct observations, but the subsurface part lacks direct observational constraints. The torsional oscillations, a small periodic variation of the Sun's rotation with the solar cycle, are thought to result from the Lorentz force of the cyclic magnetic field generated by the dynamo. In this study, we aim to discriminate between three Babcock–Leighton dynamo models by comparing the zonal acceleration of the three models with the observed one. The property that the poleward and equatorward branches of the torsional oscillations originate from about ±55° latitudes with their own migration time periods serves as an effective discriminator that could constrain the configuration of the magnetic field in the convection zone. The toroidal field, comprising poleward and equatorward branches separated at about ±55° latitudes, can generate the two branches of the torsional oscillations. The alternating acceleration and deceleration bands in time are the other property of the torsional oscillations that discriminates between the dynamo models. To reproduce this property, the phase difference between the radial (B  r ) and toroidal (B  ϕ ) components of the magnetic field near the surface should be about π/2.

Keywords: Solar cycle, Solar differential rotation, Helioseismology, Solar dynamo, Solar magnetic fields
Peculiar Velocity Reconstruction from Simulations and Observations Using Deep Learning Algorithms. In this paper, we introduce a U-Net model of deep learning algorithms for reconstructions of the 3D peculiar velocity field, which simplifies the reconstruction process with enhanced precision. We test the adaptability of the U-Net model with simulation data under more realistic conditions, including the redshift space distortion effect and halo mass threshold. Our results show that the U-Net model outperforms the analytical method that runs under ideal conditions, with a 16% improvement in precision, 13% in residuals, 18% in correlation coefficient, and 27% in average coherence. The deep learning algorithm exhibits exceptional capacities to capture velocity features in nonlinear regions and substantially improve reconstruction precision in boundary regions. We then apply the U-Net model trained under Sloan Digital Sky Survey (SDSS) observational conditions to the SDSS Data Release 7 data for observational 3D peculiar velocity reconstructions.

Keywords: Cosmology, Radial velocity, Convolutional neural networks, Large-scale structure of the universe
Boundary of the Distribution of Solar Wind Proton Beta versus Temperature Anisotropy. The frequency distribution of solar wind protons, measured in the vicinity of Earth's orbit, is customarily plotted in (β ∥, T ⊥/T ∥) phase space. Here, T ⊥/T ∥ is the ratio of perpendicular and parallel temperatures, and β ∥ = 8π nT ∥/B 2 is the ratio of parallel thermal energy to background magnetic field energy, the so-called "parallel beta," with ⊥ and ∥ denoting directions with respect to the ambient magnetic field. Such a frequency distribution, plotted as a two-dimensional histogram, forms a peculiar rhombic shape defined with an outer boundary in the said phase space. Past studies reveal that the threshold conditions for temperature anisotropy–driven plasma instability partially account for the boundary on the high-β ∥ side. The low-β ∥ side remains largely unexplained despite some efforts. Work by Vafin et al. recently showed that certain contours of collisional relaxation frequency, ν pp, when parameterized by T ⊥/T ∥ and β ∥, could match the overall shape of the left-hand boundary, thus suggesting that the collisional relaxation process might be closely related to the formation of the left-hand boundary. The present paper extends the analysis by Vafin et al. and carries out the dynamical computation of the collisional relaxation process for an ensemble of initial proton states with varying degrees of anisotropic temperatures. The final states of the relaxed protons are shown to closely match the observed boundary to the left of the (β ∥, T ⊥/T ∥) phase space. When coupled with a similar set of calculations for the ensemble in the collective instability regime, it is found that the combined collisional/collective effects provide the baseline explanation for the observation.

Keywords: Space plasmas, Heliosphere, Plasma physics, Solar wind, Interplanetary physics
A New Timescale–Mass Scaling for the Optical Variation of Active Galactic Nuclei across the Intermediate-mass to Supermassive Scales. The variability of active galactic nuclei (AGNs) has long been servicing as an essential avenue of exploring the accretion physics of a black hole (BH). There are two commonly used methods for analyzing AGN variability. First, the AGN variability, characterized by the structure function (SF) of a single band, can be well described by a damped random walk (DRW) process on timescales longer than ∼weeks, shorter than which departures have been reported. Second, the color variation (CV) between two bands behaves timescale dependent, raising challenges to the widely accepted reprocessing scenario. However, both the departure from the DRW process and the timescale-dependent CV are hitherto limited to AGNs, mainly quasars, at the supermassive scale. Here, utilizing the high-cadence multiwavelength monitoring on NGC 4395 harboring an intermediate-mass BH, we unveil at the intermediate-mass scale for the first time, prominent departures from the DRW process at timescales shorter than ∼hours in all three nights and bands, and plausible timescale-dependent CVs in the two longest nights of observation. Furthermore, comparing SFs of NGC 4395 to four AGNs at the supermassive scale, we suggest a new scaling relation between the timescale (τ; across nearly 3 orders of magnitude) and the BH mass (M BH):  τ∝MBHγ  where the exponent γ is likely ≃0.6–0.8. This exponent differs from most previous measurements, but confirms a few, and is consistent with a recent theoretical prediction, suggesting a similar accretion process in AGNs across different mass scales.

Keywords: Accretion, Intermediate-mass black holes, Supermassive black holes, Active galactic nuclei
MACE: A Machine-learning Approach to Chemistry Emulation. The chemistry of an astrophysical environment is closely coupled to its dynamics, the latter often found to be complex. Hence, to properly model these environments a 3D context is necessary. However, solving chemical kinetics within a 3D hydro simulation is computationally infeasible for even a modest parameter study. In order to develop a feasible 3D hydro-chemical simulation, the classical chemical approach needs to be replaced by a faster alternative. We present MACE, a Machine-learning Approach to Chemistry Emulation, as a proof-of-concept work on emulating chemistry in a dynamical environment. Using the context of AGB outflows, we have developed an architecture that combines the use of an autoencoder (to reduce the dimensionality of the chemical network) and a set of latent ordinary differential equations (that are solved to perform the temporal evolution of the reduced features). Training this architecture with an integrated scheme makes it possible to successfully reproduce a full chemical pathway in a dynamical environment. MACE outperforms its classical analog on average by a factor of 26. Furthermore, its efficient implementation in PyTorch results in a sublinear scaling with respect to the number of hydrodynamical simulation particles.

Keywords: Astronomy software, Astrochemistry, Asymptotic giant branch stars, Computational methods, Stellar winds, Chemical reaction network models