adsabs/SciX_UAT_keywords huggingface dataset:
Electron-Ion Heating Partition in Imbalanced Solar-wind Turbulence

A likely candidate mechanism to heat the solar corona and solar wind is low-frequency "Alfvénic" turbulence sourced by magnetic fluctuations near the solar surface. Depending on its properties, such turbulence can heat different species via different mechanisms, and the comparison of theoretical predictions to observed temperatures, wind speeds, anisotropies, and their variation with heliocentric radius provides a sensitive test of this physics. Here we explore the importance of normalized cross helicity, or imbalance, for controlling solar-wind heating, since it is a key parameter of magnetized turbulence and varies systematically with wind speed and radius. Based on a hybrid-kinetic simulation in which the forcing's imbalance decreases with time-a crude model for a plasma parcel entrained in the outflowing wind-we demonstrate how significant changes to the turbulence and heating result from the "helicity barrier" effect. Its dissolution at low imbalance causes its characteristic features-strong perpendicular ion heating with a steep "transition-range" drop in electromagnetic fluctuation spectra-to disappear, driving a larger fraction of the energy into electrons and parallel ion heat, and halting the emission of ion-scale waves. These predictions seem to agree with a diverse array of solar-wind observations, offering to explain a variety of complex correlations and features within a single theoretical framework.

Keywords: solar wind; plasma astrophysics; interplanetary turbulence
Detection of Cosmic Fullerenes in the Almahata Sitta Meteorite: Are They an Interstellar Heritage?

Buckminsterfullerene, C60, is the largest molecule observed to date in interstellar and circumstellar environments. The mechanism of formation of this molecule is actively debated. Despite targeted searches in primitive carbonaceous chondrites, no unambiguous detection of C60 in a meteorite has been reported to date. Here we report the first firm detection of fullerenes, from C30 to at least C100, in the Almahata Sitta (AhS) polymict ureilite meteorite. This detection was achieved using highly sensitive laser desorption laser ionization mass spectrometry. Fullerenes have been unambiguously detected in seven clasts of AhS ureilites. Molecular family analysis shows that fullerenes are from a different reservoir compared to the polycyclic aromatic hydrocarbons detected in the same samples. The fullerene family correlates best with carbon clusters, some of which may have been formed by the destruction of solid carbon phases by the impacting laser. We show that the detected fullerenes are not formed in this way. We suggest that fullerenes are an intrinsic component of a specific carbon phase that has yet to be identified. The nondetection of fullerenes in the Murchison and Allende bulk samples, while using the same experimental conditions, suggests that this phase is absent or less abundant in these primitive chondrites. The former case would support the formation of fullerenes by shock-wave processing of carbonaceous phases in the ureilite parent body. However, there are no experimental data to support this scenario. This leaves open the possibility that fullerenes are an interstellar heritage and a messenger of interstellar processes.

Keywords: astrochemistry; laboratory astrophysics; meteorites
RELICS: A Strong-lens Model of SMACS J0723.3-7327

We present the details of a strong-lens model of SMACS J0723.3-7327, which was made public as part of the data and high-level science products (HLSP) release of the RELICS Hubble Space Telescope (HST) treasury program (Reionization Lensing Cluster Survey; GO-14096, PI: Coe). The model products were made available on the Mikulski Archive for Space Telescopes via 10.17909/T9SP45 in 2017. Here, we provide the list of constraints that were used in the HST-based RELICS lens model, as well as other information related to our modeling choices, which were not published with the data and HLSP release. This model was computed with Lenstool, used a total of 25 multiple images of eight sources, with no spectroscopic redshifts. The image-plane rms was 0.″58. *Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO-12166, GO-12884, GO-14096.

Keywords: gravitational lensing; galaxy clusters
Analyses of 0.05-2 MeV Ions Associated with the 2022 February 16 Energetic Storm Particle Event Observed by Parker Solar Probe

We present analyses of 0.05-2 MeV ions from the 2022 February 16 energetic storm particle event observed by Parker Solar Probe's (PSP) IS⊙IS/EPI-Lo instrument at 0.35 au from the Sun. This event was characterized by an enhancement in ion fluxes from a quiet background, increasing gradually with time with a nearly flat spectrum, rising sharply near the arrival of the coronal mass ejection (CME)-driven shock, becoming nearly a power-law spectrum, then decaying exponentially afterward, with a rate that was independent of energy. From the observed fluxes, we determine diffusion coefficients, finding that far upstream of the shock the diffusion coefficients are nearly independent of energy, with a value of 1020 cm2 s-1. Near the shock, the diffusion coefficients are more than 1 order of magnitude smaller and increase nearly linearly with energy. We also determine the source of energetic particles, by comparing ratios of the intensities at the shock to estimates of the quiet-time intensity to predictions from diffusive shock acceleration theory. We conclude that the source of energetic ions is mostly the solar wind for this event. We also present potential interpretations of the near-exponential decay of the intensity behind the shock. One possibility we suggest is that the shock was overexpanding when it crossed PSP and the energetic particle intensity decreased behind the shock to fill the expanding volume. Overexpanding CMEs could well be more common closer to the Sun, and this is an example of such a case.

Keywords: solar energetic particles; solar coronal mass ejections; interplanetary shocks; interplanetary particle acceleration
Filament Formation due to Diffusive Instabilities in Dusty Protoplanetary Disks

We report the finding of a new, local diffusion instability in a protoplanetary disk which can operate in a dust fluid, subject to mass diffusion, shear viscosity, and dust–gas drag, provided the diffusivity, viscosity, or both, decrease sufficiently rapidly with increasing dust surface mass density. We devise a vertically averaged, axisymmetric hydrodynamic model to describe a dense, midplane dust layer in a protoplanetary disk. The gas is modeled as a passive component, imposing an effective, diffusion-dependent pressure, mass diffusivity, and viscosity onto the otherwise collisionless dust fluid, via turbulence excited by the gas alone, or dust and gas in combination. In particular, we argue that such conditions are met when the dust–gas mixture generates small-scale turbulence through the streaming instability, as supported by recent measurements of dust mass diffusion slopes in simulations. We hypothesize that the newly discovered instability may be the origin of filamentary features, almost ubiquitously found in simulations of the streaming instability. In addition, our model allows for growing oscillatory modes, which operate in a similar fashion as the axisymmetric viscous overstability in dense planetary rings. However, it remains speculative if the required conditions for such modes can be met in protoplanetary disks.

Keywords: protoplanetary disks; planet formation; circumstellar dust; hydrodynamics; astrophysical dust processes; astrophysical fluid dynamics
Atmospheric Escape From Three Terrestrial Planets in the L 98-59 System

A critically important process affecting the climate evolution and potential habitability of an exoplanet is atmospheric escape, in which high-energy radiation from a star drives the escape of hydrogen atoms and other light elements from a planet's atmosphere. L 98-59 is a benchmark system for studying such atmospheric processes, with three transiting terrestrial-sized planets receiving Venus-like instellations (4-25 S ⊕) from their M3 host star. We use the VPLanet model to simulate the evolution of the L 98-59 system and the atmospheric escape of its inner three small planets, given different assumed initial water quantities. We find that, regardless of their initial water content, all three planets accumulate significant quantities of oxygen due to efficient water photolysis and hydrogen loss. All three planets also receive enough strong X-ray and extreme-ultraviolet flux to drive rapid water loss, which considerably affects their developing climates and atmospheres. Even in scenarios of low initial water content, our results suggest that the JWST will be sensitive to observations of retained oxygen on the L 98-59 planets in its future scheduled observations, with planets b and c being the most likely targets to possess an extended atmosphere. Our results constrain the atmospheric evolution of these small rocky planets, and they provide context for current and future observations of the L 98-59 system to generalize our understanding of multiterrestrial planet systems.

Keywords: exoplanet evolution; exoplanet atmospheres; star-planet interactions
Triton: Fascinating Moon, Likely Ocean World, Compelling Destination!

Triton is an important signpost in understanding the diverse populations of both ocean worlds and Kuiper Belt objects (KBOs). As a likely ocean world, it is unique by virtue of its kidnapped history from the Kuiper Belt: its large orbital inclination makes it the only ocean world thought to be primarily heated by obliquity tides. It is volatile-rich due to its formation in the outer solar system and its unusual surface geology may be the product of cryovolcanism. Observations from New Horizons and Cassini motivate re-examination of Triton data sets and models, with value for comparative planetology of ocean worlds and KBOs, most notably with Europa, Enceladus, Titan, and Pluto. We re-explore old data sets with the new perspective of the importance of ocean worlds in our solar system and the search for life.

Keywords: triton
Morphologies of Galaxies at z ≳ 9 Uncovered by JWST/NIRCam Imaging: Cosmic Size Evolution and an Identification of an Extremely Compact Bright Galaxy at z 12

We present morphologies of galaxies at z ≳ 9 resolved by JWST/NIRCam 2-5 μm imaging. Our sample consists of 22 galaxy candidates identified by stringent dropout and photo-z criteria in GLASS, CEERS, SMACS J0723, and Stephan's Quintet flanking fields, one of which has been spectroscopically identified at z = 11.44. We perform surface brightness (SB) profile fitting with GALFIT for six bright galaxies with a signal-to-noise ratio = 10-40 on an individual basis and for stacked faint galaxies with secure point-spread functions (PSFs) of the NIRCam real data, carefully evaluating systematics by Monte Carlo simulations. We compare our results with those of previous JWST studies, and confirm that the effective radii r e of our measurements are consistent with those of previous measurements at z ~ 9. We obtain r e ≃ 200-300 pc with the exponential-like profiles, Sérsic indexes of n ≃ 1-1.5, for galaxies at z ~ 12-16, indicating that the relation of r e ∝ (1 + z) s for $s=-{1.22}_{-0.16}^{+0.17}$ explains cosmic evolution over z ~ 0-16 for $\sim {L}_{z=3}^{* }$ galaxies. One bright (M UV = -21 mag) galaxy at z ~ 12, GL-z12-1, has an extremely compact profile with r e = 39 ± 11 pc that is surely extended over the PSF. Even in the case that the GL-z12-1 SB is fit by active galactic nuclei + galaxy composite profiles, the best-fit galaxy component is again compact, ${r}_{{\rm{e}}}={48}_{-15}^{+38}$ pc, which is significantly (>5σ) smaller than the typical r e value at z ~ 12. Compared with numerical simulations, we find that such a compact galaxy naturally forms at z ≳ 10, and that frequent mergers at the early epoch produce more extended galaxies following the r e ∝ (1 + z) s relation.

Keywords: galactic and extragalactic astronomy; galaxies; galaxy radii; galaxy structure; galaxy formation; galaxy evolution; lyman-break galaxies; high-redshift galaxies
JWST Directly Images Giant Planet Candidates Around Two Metal-polluted White Dwarf Stars

We report the discovery of two directly imaged, giant planet candidates orbiting the metal-rich, hydrogen atmosphere white dwarfs WD 1202‑232 and WD 2105‑82. JWST's Mid-Infrared Instrument (MIRI) data on these two stars show a nearby resolved source at a projected separation of 11.47 and 34.62 au, respectively. Assuming the planets formed at the same time as their host stars, with total ages of 5.3 and 1.6 Gyr, the MIRI photometry is consistent with giant planets with masses ≈1–7 M Jup. The probability of both candidates being false positives due to red background sources is approximately 1 in 3000. If confirmed, these would be the first directly imaged planets that are similar in both age and separation to the giant planets in our own solar system, and they would demonstrate that widely separated giant planets like Jupiter survive stellar evolution. Giant planet perturbers are widely used to explain the tidal disruption of asteroids around metal-polluted white dwarfs. Confirmation of these two planet candidates with future MIRI imaging would provide evidence that directly links giant planets to metal pollution in white dwarf stars.

Keywords: da stars; exoplanet astronomy; exoplanet detection methods; james webb space telescope
Discovery of a New Population of Galactic H II Regions with Ionized Gas Velocity Gradients

We investigate the kinematic properties of Galactic H II regions using radio recombination line (RRL) emission detected by the Australia Telescope Compact Array at 4-10 GHz and the Jansky Very Large Array at 8-10 GHz. Our H II region sample consists of 425 independent observations of 374 nebulae that are relatively well isolated from other, potentially confusing sources and have a single RRL component with a high signal-to-noise ratio. We perform Gaussian fits to the RRL emission in position-position-velocity data cubes and discover velocity gradients in 178 (42%) of the nebulae with magnitudes between 5 and 200 ${\rm{m}}\,{{\rm{s}}}^{-1}\,{\mathrm{arcsec}}^{-1}$ . About 15% of the sources also have an RRL width spatial distribution that peaks toward the center of the nebula. The velocity gradient position angles appear to be random on the sky with no favored orientation with respect to the Galactic plane. We craft H II region simulations that include bipolar outflows or solid body rotational motions to explain the observed velocity gradients. The simulations favor solid body rotation since, unlike the bipolar outflow kinematic models, they are able to produce both the large, >40 ${\rm{m}}\,{{\rm{s}}}^{-1}\,{\mathrm{arcsec}}^{-1}$ , velocity gradients and also the RRL width structure that we observe in some sources. The bipolar outflow model, however, cannot be ruled out as a possible explanation for the observed velocity gradients for many sources in our sample. We nevertheless suggest that most H II region complexes are rotating and may have inherited angular momentum from their parent molecular clouds.

Keywords: interstellar medium; h ii regions; radio astronomy; radio spectroscopy
Rotating Motion of the Outflow of IRAS 16293-2422 A1 at Its Origin Point Near the Protostar

The Class 0 protostar IRAS 16293-2422 Source A is known to be a binary system (A1 and A2) or even a multiple system that processes a complex outflow structure. We have observed this source in the C34S, SO, and OCS lines at 3.1 mm with the Atacama Large Millimeter/submillimeter Array. A substructure of this source is traced by our high angular-resolution observation (0"12; 20 au) of the continuum emission. The northwest-southeast (NW-SE) outflow on a 2″ scale is detected in the SO (JN = 22-11) line. Based on the morphology of the SO distribution, this bipolar outflow structure seems to originate from the protostar A1 and its circumstellar disk, or the circummultiple structure of Source A. The rotation motion of the NW-SE outflow is detected in the SO and OCS emissions. We evaluate the specific angular momentum of the outflowing gas to be (8.6-14.3) × 10-4 km s-1 pc. If the driving source of this outflow is the protostar A1 and its circumstellar disk, it can be a potential mechanism to extract the specific angular momentum of the disk structure. These results can be a hint for the outflow launching mechanism in this source. Furthermore, they provide us with an important clue to resolve the complicated structure of IRAS 16293-2422 Source A.

Keywords: interstellar medium; protostars; low mass stars; stellar jets
Binding Energies of Interstellar Relevant S-bearing Species on Water Ice Mantles: A Quantum Mechanical Investigation

Binding energies (BEs) are one of the most important parameters for astrochemical modeling determining, because they govern whether a species stays in the gas phase or is frozen on the grain surfaces. It is currently known that, in the denser and colder regions of the interstellar medium, sulfur is severely depleted in the gas phase. It has been suggested that it may be locked into the grain icy mantles. However, which are the main sulfur carriers is still a matter of debate. This work aims to establish accurate BEs of 17 sulfur-containing species on two validated water ice structural models, the proton-ordered crystalline (010) surface and an amorphous water ice surface. We adopted density functional theory-based methods (the hybrid B3LYP-D3(BJ) and the hybrid meta-GGA M06-2X functionals) to predict structures and energetics of the adsorption complexes. London's dispersion interactions are shown to be crucial for an accurate estimate of the BEs due to the presence of the high polarizable sulfur element. On the crystalline model, the adsorption is restricted to a very limited number of binding sites with single valued BEs, while on the amorphous model, several adsorption structures are predicted, giving a BE distribution for each species. With the exception of a few cases, both experimental and other computational data are in agreement with our calculated BE values. A final discussion on how useful the computed BEs are with respect to the snow lines of the same species in protoplanetary disks is provided.

Keywords: interstellar dust; surface ices; interstellar molecules; dense interstellar clouds; interstellar medium; solid matter physics; interstellar dust processes; computational methods
Methods for Averaging Spectral Line Data

The ideal spectral averaging method depends on one's science goals and the available information about one's data. Including low-quality data in the average can decrease the signal-to-noise ratio (S/N), which may necessitate an optimization method or a consideration of different weighting schemes. Here, we explore a variety of spectral averaging methods. We investigate the use of three weighting schemes during averaging: weighting by the signal divided by the variance ("intensity-noise weighting"), weighting by the inverse of the variance ("noise weighting"), and uniform weighting. Whereas for intensity-noise weighting the S/N is maximized when all spectra are averaged, for noise and uniform weighting we find that averaging the 35%-45% of spectra with the highest S/N results in the highest S/N average spectrum. With this intensity cutoff, the average spectrum with noise or uniform weighting has ~95% of the intensity of the spectrum created from intensity-noise weighting. We apply our spectral averaging methods to GBT Diffuse Ionized Gas hydrogen radio recombination line data to determine the ionic abundance ratio, y +, and discuss future applications of the methodology.

Keywords: computational methods; warm ionized medium
iPTF14hls in the Circumstellar Medium Interaction Model: A Promising Candidate for a Pulsational Pair-instability Supernova

iPTF14hls is a luminous Type II supernova (SN) with a bumpy light curve whose origin remains under debate. It maintains a roughly constant effective temperature and luminosity for about 600 days after discovery, followed by a slow decay. About ~1000 days after discovery, the light curve transitions to a very steep decline. A spectrum taken during this steep-decline phase shows clear signatures of a shock interaction with a dense circumstellar medium (CSM). Here, we explore the possibility of iPTF14hls as an interaction-powered SN. The light curve of iPTF14hls can be fitted with wind-like CSMs. Analytic modeling indicates that iPTF14hls may have undertaken six episodes of mass loss during the last ~200 yr. Assuming that the 1954 eruption triggered the last mass-loss episode, the stellar wind velocity is determined to be 40-70 km s-1, depending on different models. Mass-loss rates are in the range 0.4-3.3M ⊙ yr-1. The inferred total mass of the ejecta and CSMs (M ej + M CSMs ≃ 245M ⊙) supports the idea that iPTF14hls may be a candidate for a (pulsational) pair-instability SN. Discoveries and observations of similar stellar explosions will help us to understand these peculiar SNe.

Keywords: type ii supernovae
Integral Field Spectroscopy with the Solar Gravitational Lens

The prospect of combining integral field spectroscopy with the solar gravitational lens (SGL) to spectrally and spatially resolve the surfaces and atmospheres of extrasolar planets is investigated. The properties of hyperbolic orbits visiting the focal region of the SGL are calculated analytically, demonstrating trade-offs between departure velocity and time of arrival, as well as gravity assist maneuvers and heliocentric angular velocity. Numerical integration of the solar barycentric motion demonstrates that navigational acceleration of ${dv}\lesssim 80\tfrac{{\rm{m}}}{{\rm{s}}}+6.7\tfrac{{\rm{m}}}{{\rm{s}}}\tfrac{t}{\mathrm{year}}$ is needed to obtain and maintain alignment. Obtaining target ephemerides of sufficient precision is an open problem. The optical properties of an oblate gravitational lens are reviewed, including calculations of the magnification and the point-spread function that forms inside a telescope. Image formation for extended, incoherent sources is discussed when the projected image is smaller than, approximately equal to, and larger than the critical caustic. Sources of contamination that limit observational signal-to-noise ratio (S/N) are considered in detail, including the Sun, the solar corona, the host star, and potential background objects. A noise mitigation strategy of spectrally and spatially separating the light using integral field spectroscopy is emphasized. A pseudo-inverse-based image reconstruction scheme demonstrates that direct reconstruction of an Earth-like source from single measurements of the Einstein ring is possible when the critical caustic and observed S/N are sufficiently large. In this arrangement, a mission would not require multiple telescopes or navigational symmetry breaking, enabling continuous monitoring of the atmospheric composition and dynamics on other planets.

Keywords: astronomical instrumentation; gravitational lensing; exoplanets; spectroscopy