Sazuna/UAT_keywords huggingface dataset:
Reactive Molecular Dynamics Simulations of Micrometeoroid Bombardment for Space Weathering of Asteroid (162173) Ryugu. Remote sensing observations by Hayabusa2 and laboratory measurements have revealed that the phyllosilicates on asteroid (162173) Ryugu are dehydrated/dehydroxylated due to space weathering. Reactive molecular dynamics simulations were performed to evaluate the magnitude of the dehydroxylation of Mg-rich serpentine by micrometeoroid impacts. When micrometeoroids were not coupled with interplanetary magnetic fields, serpentine could be dehydroxylated by micrometeoroids as small as 2 nm in size. In particular, ∼200 O–H bonds dissociated when the meteoroids were derived from cometary activity (the impact velocity was ∼20 km s‑1). When nano-sized dust particles were accelerated to ∼300 km s‑1 by the magnetic fields of solar wind plasma, the number of dissociated O–H bonds increased by 1 order of magnitude. Consequently, even 1 nm-sized dust particles can contribute to the space weathering of Ryugu. In all cases, Si–OH, H2O, and free OH were generated from the hydroxyls initially connected to Mg, which could partially offset dehydration. Despite the limitations of our computational resources, which restricted the simulation timescale to 1 ps, reactive molecular dynamic simulations demonstrated that micrometeoroid bombardment could influence the space weathering of asteroids.

Keywords: Molecular reactions, Asteroids, Asteroid surfaces
Characterization of Supernovae Interacting with Dense Circumstellar Matter with a Flat Density Profile. Interaction between supernova (SN) ejecta and dense circumstellar medium (CSM) with a flat density structure (ρ ∝ r ‑s , s &lt; 1.5) was recently proposed as a possible mechanism behind interacting SNe that exhibit exceptionally long rise times exceeding 100 days. In such a configuration, the interaction luminosity keeps rising until the reverse shock propagates into the inner layers of the SN ejecta. We investigate the light curves of SNe interacting with a flatly distributed CSM in detail, incorporating the effects of photon diffusion inside the CSM into the model. We show that three physical processes—the shock breakout, the propagation of the reverse shock into the inner ejecta, and the departure of the shock from the dense CSM—predominantly determine the qualitative behavior of the light curves. Based on the presence and precedence of these processes, the light curves of SNe interacting with flatly distributed CSM can be classified into five distinct morphological classes. We also show that our model can qualitatively reproduce doubly peaked SNe whose peaks are a few tens of days apart, such as SN 2005bf and SN 2022xxf. Our results show that the density distribution of the CSM is an important property of CSM that contributes to the diversity in light curves of interacting SNe.

Keywords: Circumstellar matter, Supernovae, Stellar mass loss
FEASTS Combined with Interferometry. II. Significantly Changed H I Surface Densities and Even More Inefficient Star Formation in Galaxy Outer Disks. We update the H I surface density measurements for a subset of 17 THINGS galaxies by dealing with the short-spacing problem of the original Very Large Array (VLA) H I images. It is the same sample that Bigiel et al. used to study the relation between H I surface densities and star formation (SF) rate surface densities in galaxy outer disks, which are beyond the optical radius r 25. For 10 galaxies, the update is based on combining original THINGS VLA H I images with H I images taken by the single-dish FAST in the FEASTS program. The median increment of H I surface densities in outer disks is 0.15–0.4 dex at a given new H I surface density. Several galaxies change significantly in the shape of radial profiles H I surface densities, and seven galaxies are now more than 1σ below the H I size–mass relation. We update the H I star formation laws in outer disks. The median relation between the H I surface densities and SF rate surface densities based on pixel-wise measurements shifts downward by around 0.15 dex because the H I surface density values shift rightward, and the scatter increases significantly. The scatter of the relation, indicating the star-forming efficiency, exhibits a much stronger positive correlation with the stellar mass surface density than before. Thus, detecting the previously missed, diffuse H I due to the short-spacing problem of the Very Large Array observations is important in revealing the true condition and variation in SF possibly regulated by stellar feedbacks in the localized environment of outer disks.

Keywords: Star formation, Galaxy evolution, Interstellar medium
Suppressed Cosmic-Ray Energy Densities in Molecular Clouds from Streaming Instability-regulated Transport. Cosmic rays (CRs) are the primary driver of ionization in star-forming molecular clouds (MCs). Despite their potential impacts on gas dynamics and chemistry, no simulations of star cluster formation following the creation of individual stars have included explicit cosmic-ray transport (CRT) to date. We conduct the first numerical simulations following the collapse of a 2000M ⊙ MC and the subsequent star formation including CRT using the STAR FORmation in Gaseous Environments framework implemented in the GIZMO code. We show that when CRT is streaming-dominated, the CR energy in the cloud is strongly attenuated due to energy losses from the streaming instability. Consequently, in a Milky Way–like environment the median CR ionization rate in the cloud is low (ζ ≲ 2 × 10‑19 s‑1) during the main star-forming epoch of the calculation and the impact of CRs on the star formation in the cloud is limited. However, in high-CR environments, the CR distribution in the cloud is elevated (ζ ≲ 6 × 10‑18), and the relatively higher CR pressure outside the cloud causes slightly earlier cloud collapse and increases the star formation efficiency by 50% to ∼13%. The initial mass function is similar in all cases except with possible variations in a high-CR environment. Further studies are needed to explain the range of ionization rates observed in MCs and explore star formation in extreme CR environments.

Keywords: Initial mass function, High energy astrophysics, Star formation, Ionization, Cosmic rays
Revisiting a Chemical Route to the Formation of CN<SUP>‑</SUP> in the Interstellar Medium. We discuss the HCN + H‑ reaction as a path to the formation of CN‑, the smallest cyanopolyyne anion observed in several interstellar environments. We first obtain the new ab initio reactive potential energy surface using a full 5D representation, where only the C–N bond is kept fixed, and discuss the neural network procedure employed to yield an accurate fit for the dynamics. The reaction is then investigated by using a quasi-classical trajectory approach to scan the low-temperature range of the dark molecular clouds where the anion has been sighted. Calculations are extended to room temperature to make a successful comparison with existing experimental data. We further present reduced dimensionality modeling of the reaction as a 2D process within a variational-transition state treatment with the inclusion of long-range forces. The dominant role of such forces in producing large reaction rate coefficients is discussed for both treatments, which yield very similar sizes and behavior of such coefficients from 50 to 300 K. The implications of our results for the interstellar medium formation of the CN‑ species via this chemical route are discussed, suggesting its greater significance over the radiative electron attachment paths, whose rate coefficients were found by recent calculations to be orders of magnitude smaller.

Keywords: Cosmochemistry, Molecular clouds, Chemical kinetics
Analytical and Numerical Analysis of Circumbinary Disk Dynamics. I. Coplanar Systems. We present an analytical and numerical study of a system composed of a stellar binary pair and a massless, locally isothermal viscous accretion disk that is coplanar to the binary orbital plane. Analytically, we study the effect of the binary's gravitational potential over short timescales through the stability of epicyclic orbits, and over long timescales by revisiting the concept of resonant torques. Numerically, we perform two-dimensional Newtonian simulations of the disk-binary system over a range of binary mass ratios. We find that the results of our simulations are consistent with those of previous numerical studies. We additionally show, by comparison of the analytical and numerical results, that the circumbinary gap is maintained on the orbital timescale through the driving of epicyclic instabilities, and does not depend on resonant torquing, contrary to the standard lore. While our results are applicable to any disk-binary system, we highlight the importance of this result in the search for electromagnetic and gravitational-wave signatures from supermassive black hole binaries.

Keywords: Accretion, Circumstellar disks, Orbital resonances, Computational methods, Orbital theory, Astrophysical fluid dynamics, Astrophysical black holes
Unveiling Frequency-dependent Eclipsing in Spider Millisecond Pulsars Using Broadband Polarization Observations with the Parkes. This study presents an orbital-phase-dependent analysis of three black widow spider millisecond pulsars (BW MSPs), aiming to investigate the magnetic field within the eclipse environment. The ultrawide-bandwidth low-frequency receiver of the Parkes Murriyang radio telescope is utilized for full polarization observations covering frequencies from 704‑4032 MHz. Depolarization of pulsed emission is observed during the eclipse phase of three BW MSPs, namely PSR J0024‑7204J, PSR J1431‑4715, and PSR J1959+2048, consistent with previous studies of other BW MSPs. We estimated orbital-phase-dependent rotation measure values for these MSPs. The wide bandwidth observations also provided constraints on the eclipse cutoff frequency for these BW MSPs. For PSR J0024‑7204J, we report temporal variation of the eclipse cutoff frequency coupled with changes in the electron column density within the eclipse medium across six observed eclipses. Moreover, the eclipse cutoff frequency for PSR J1431‑4715 is determined to be 1251 ± 80 MHz, leading to the conclusion that synchrotron absorption is the primary mechanism responsible for the eclipsing. Additionally, for PSR J1959+2048, the estimated cutoff frequency exceeded 1400 MHz, consistent with previous studies. With this investigation, we have doubled the sample size of BW MSPs with orbital-phase-resolved studies, allowing a better probe of the eclipse environment.

Keywords: Millisecond pulsars, Binary pulsars, High energy astrophysics, Radio pulsars
Estimated Heating Rates Due to Cyclotron Damping of Ion-scale Waves Observed by the Parker Solar Probe. Circularly polarized waves consistent with parallel-propagating ion cyclotron waves (ICWs) and fast magnetosonic waves (FMWs) are often observed by the Parker Solar Probe (PSP) at ion kinetic scales. Such waves damp energy via cyclotron resonance, and cyclotron damping is expected to play a significant role in the enhanced, anisotropic heating of the solar wind observed in the inner heliosphere. We employ a linear plasma dispersion solver, PLUME, to evaluate the frequencies of ICWs and FMWs in the plasma rest frame and Doppler-shift them to the spacecraft frame, calculating their damping rates at frequencies where persistently high values of circular polarization are observed. We find that such ion-scale waves are observed during 20.37% of PSP Encounters 1 and 2 observations and their plasma frame frequencies are consistent with them being transient ICWs. We estimate significant ICW dissipation onto protons, consistent with previous empirical estimates for the total turbulent damping rates, indicating that ICW dissipation could account for the observed enhancements in the proton temperature and its anisotropy with respect to the mean magnetic field.

Keywords: Space plasmas, Interplanetary turbulence, Solar coronal heating, Solar wind, Plasma astrophysics
The Onset of Magnetic Reconnection in Dynamically Evolving Coronal Current Sheets. We present the first results of three-dimensional (3D) numerical magnetohydrodynamic (MHD) simulations of the onset of magnetic reconnection via the tearing instability in dynamically thinning current sheets in the solar corona. In all our simulations, the onset of the nonlinear tearing instability, which leads to the breakup of the thinning current sheet, does not occur until after the instability growth time becomes faster than the dynamic thinning time. Furthermore, as in previous 3D MHD simulations of static current sheets in the corona, for some parameters the amount of magnetic shear is a fundamental switch-on parameter, which has consequences for coronal heating models. These results open up the possibility of using observable quantities of coronal current sheets to predict when they will break up and release magnetic energy to power various energetic phenomena and/or heat the atmosphere.

Keywords: Solar corona, Magnetohydrodynamics, Solar coronal heating, Solar magnetic reconnection
Intrapulse Spectral Evolution in Photospheric Gamma-Ray Bursts. Photons that decouple from a relativistic jet do so over a range of radii, leading to a spreading in arrival times at the observer. Therefore, changes to the comoving photon distribution across the decoupling zone are encoded in the emitted signal. In this paper, we study such spectral evolution occurring across a pulse. We track the radiation from the deep subphotospheric regions all the way to the observed time-resolved signal, accounting for emission at various angles and radii. We assume a simple power-law photon spectrum injection over a range of optical depths and let the photons interact with the local plasma. At high optical depths, we find that the radiation exists in one of three characteristic regimes, two of which exhibit a high-energy power law. Depending on the nature of the injection, this power law can persist to low optical depths and manifest itself during the rise time of the pulse with a spectral index β ≈ α ‑ 1, where α is the low-energy spectral index. The results are given in the context of a gamma-ray burst jet, but are general to optically thick, relativistic outflows.

Keywords: Gamma-ray bursts, Radiative processes
Unveiling the Distant Universe: Characterizing z ≥ 9 Galaxies in the First Epoch of COSMOS-Web. We report the identification of 15 galaxy candidates at z ≥ 9 using the initial COSMOS-Web JWST observations over 77 arcmin2 through four Near Infrared Camera filters (F115W, F150W, F277W, and F444W) with an overlap with the Mid-Infrared Imager (F770W) of 8.7 arcmin2. We fit the sample using several publicly available spectral energy distribution (SED) fitting and photometric redshift codes and determine their redshifts between z = 9.3 and z = 10.9 (&lt;z&gt; = 10.0), UV magnitudes between M UV = −21.2 and −19.5 (with &lt;M UV&gt; = −20.2), and rest-frame UV slopes (&lt;β&gt; = −2.4). These galaxies are, on average, more luminous than most z ≥ 9 candidates discovered by JWST so far in the literature, while exhibiting similar blue colors in their rest-frame UV. The rest-frame UV slopes derived from SED fitting are blue (β ∼ [−2.0, −2.7]) without reaching extremely blue values as reported in other recent studies at these redshifts. The blue color is consistent with models that suggest the underlying stellar population is not yet fully enriched in metals like similarly luminous galaxies in the lower-redshift Universe. The derived stellar masses with  &lt;log10(  M ⋆/M ⊙)&gt; ≍ 8─9 are not in tension with the standard Lambda cold dark matter (ΛCDM) model, and our measurement of the volume density of such UV-luminous galaxies aligns well with previously measured values presented in the literature at z ∼ 9─10. Our sample of galaxies, although compact, is significantly resolved.

Keywords: Early universe, Galaxy formation, High-redshift galaxies, Galaxy evolution
A Targeted Search for Variable Gravitationally Lensed Quasars. We present a pipeline to identify photometric variability within strong gravitationally lensing candidates, in the Dark Energy Spectroscopic Instrument Legacy Imaging Surveys. In our first paper, we laid out our pipeline and presented seven new gravitationally lensed supernovae candidates in a retrospective search. In this companion paper, we apply a modified version of that pipeline to search for gravitationally lensed quasars. From a sample of 5807 strong lenses, we have identified 13 new gravitationally lensed quasar candidates (three of them quadruply lensed). We note that our methodology differs from most lensed quasar search algorithms that solely rely on the morphology, location, and color of the candidate systems. By also accounting for the temporal photometric variability of the posited lensed images in our search via difference imaging, we have discovered new lensed quasar candidates. While variability searches using difference imaging algorithms have been done in the past, they are typically performed over vast swathes of the sky, whereas we specifically target strong gravitationally lensed candidates. We also have applied our pipeline to 655 known gravitationally lensed quasar candidates from past lensed quasar searches, of which we identified 13 that display significant variability (one of them quadruply lensed). This pipeline demonstrates a promising search strategy to discover gravitationally lensed quasars in other existing and upcoming surveys.

Keywords: Cosmology, Quasars, Strong gravitational lensing, Observational cosmology, Gravitational lensing
Birds of a Feather: Resolving Stellar Mass Assembly with JWST/NIRCam in a Pair of Kindred z ∼ 2 Dusty Star-forming Galaxies Lensed by the PLCK G165.7+67.0 Cluster. We present a new parametric lens model for the G165.7+67.0 galaxy cluster, which was discovered with Planck through its bright submillimeter flux, originating from a pair of extraordinary dusty star-forming galaxies (DSFGs) at z ≍ 2.2. Using JWST and interferometric mm/radio observations, we characterize the intrinsic physical properties of the DSFGs, which are separated by only ∼1″ (8 kpc) and a velocity difference ∆V ≲ 600 km s−1 in the source plane, and thus are likely undergoing a major merger. Boasting intrinsic star formation rates SFRIR = 320 ± 70 and 400 ± 80 M ⊙ yr−1, stellar masses of  log[M⋆/M⊙]=10.2±0.1  and 10.3 ± 0.1, and dust attenuations of A  V  = 1.5 ± 0.3 and 1.2 ± 0.3, they are remarkably similar objects. We perform spatially resolved pixel-by-pixel spectral energy distribution (SED) fitting using rest-frame near-UV to near-IR imaging from JWST/NIRCam for both galaxies, resolving some stellar structures down to 100 pc scales. Based on their resolved specific star formation rates (SFRs) and UVJ colors, both DSFGs are experiencing significant galaxy-scale star formation events. If they are indeed interacting gravitationally, this strong starburst could be the hallmark of gas that has been disrupted by an initial close passage. In contrast, the host galaxy of SN H0pe has a much lower SFR than the DSFGs, and we present evidence for the onset of inside-out quenching and large column densities of dust even in regions of low specific SFR. Based on the intrinsic SFRs of the DSFGs inferred from UV through far-infrared SED modeling, this pair of objects alone is predicted to yield an observable 1.1 ± 0.2 core-collapse supernovae per year, making this cluster field ripe for continued monitoring.

Keywords: Starburst galaxies, Strong gravitational lensing, James Webb Space Telescope
Turbulence, Waves, and Taylor's Hypothesis for Heliosheath Observations. Magnetic field fluctuations measured in the heliosheath by the Voyager spacecraft are often characterized as compressible, as indicated by a strong fluctuating component parallel to the mean magnetic field. However, the interpretation of the turbulence data faces the caveat that the standard Taylor's hypothesis is invalid because the solar wind flow velocity in the heliosheath becomes subsonic and slower than the fast magnetosonic speed, given the contributions from hot pickup ions (PUIs) in the heliosheath. We attempt to overcome this caveat by introducing a 4D frequency-wavenumber spectral modeling of turbulence, which is essentially a decomposition of different wave modes following their respective dispersion relations. Isotropic Alfvén and fast mode turbulence are considered to represent the heliosheath fluctuations. We also include two dispersive fast wave modes derived from a three-fluid theory. We find that (1) magnetic fluctuations in the inner heliosheath are less compressible than previously thought, an isotropic turbulence spectral model with about 25% in compressible fluctuation power is consistent with the observed magnetic compressibility in the heliosheath; (2) the hot PUI component and the relatively cold solar wind ions induce two dispersive fast magnetosonic wave branches in the perpendicular propagation limit, PUI fast wave may account for the spectral bump near the proton gyrofrequency in the observable spectrum; (3) it is possible that the turbulence wavenumber spectrum is not Kolmogorov-like although the observed frequency spectrum has a ‑5/3 power-law index, depending on the partitioning of power among the various wave modes, and this partitioning may change with wavenumber.

Keywords: Interplanetary turbulence, Heliosheath, Solar wind termination
Flat Spectra of Energetic Particles in Interplanetary Shock Precursors. The observed energy spectra of accelerated particles at interplanetary shocks often do not match the diffusive shock acceleration (DSA) theory predictions. In some cases, the particle flux forms a plateau over a wide range of energies, extending upstream of the shock for up to seven flux e-folds before submerging into the background spectrum. Remarkably, at and downstream of the shock we have studied in detail, the flux falls off in energy as ϵ ‑1, consistent with the DSA prediction for a strong shock. The upstream plateau suggests a particle transport mechanism different from those traditionally employed in DSA models. We show that a standard (linear) DSA solution based on a widely accepted diffusive particle transport with an underlying resonant wave–particle interaction is inconsistent with the plateau in the particle flux. To resolve this contradiction, we modify the DSA theory in two ways. First, we include a dependence of the particle diffusivity κ on the particle flux F (nonlinear particle transport). Second, we invoke short-scale magnetic perturbations that are self-consistently generated by, but not resonant with, accelerated particles. They lead to the particle diffusivity increasing with the particle energy as ∝ϵ 3/2 that simultaneously decreases with the particle flux as 1/F. The combination of these two trends results in the flat spectrum upstream. We speculate that nonmonotonic spatial variations of the upstream spectrum, apart from being time-dependent, may also result from non-DSA acceleration mechanisms at work upstream, such as stochastic Fermi or magnetic pumping acceleration.

Keywords: Interplanetary particle acceleration, Interplanetary shocks