adsabs/SciX_UAT_keywords huggingface dataset:
Three-dimensional Supernova Models Provide New Insights into the Origins of Stardust

We present the isotope yields of two post-explosion, three-dimensional 15 ${M}_{\odot }$ core-collapse supernova models, 15S and 15A, and compare them to the carbon, nitrogen, silicon, aluminum, sulfur, calcium, titanium, iron, and nickel isotopic compositions of SiC stardust. We find that these core-collapse supernova models predict similar carbon and nitrogen compositions to SiC X grains and grains with 12C/13C < 20 and 14N/15N < 60, which we will hereafter refer to as SiC 'D' grains. Material from the interior of a 15 ${M}_{\odot }$ explosion reaches high enough temperatures shortly after core collapse to produce the large enrichments of 13C and 15N necessary to replicate the compositions of SiC D grains. The innermost ejecta in a core-collapse supernova is operating in the neutrino-driven regime and undergoes fast proton capture after being heated by the supernova shockwave. Both 3D models predict 0.3 $\lt {}^{26}$ Al/27Al < 1.5, comparable to the ratios seen in SiC X, C, and D grains. Models 15S and 15A, in general, predict very large anomalies in calcium isotopes but do compare qualitatively with the SiC X grain measurements that show 44Ca and 43Ca excesses. The titanium isotopic compositions of SiC X grains are well reproduced. The models predict 57Fe excesses and depletions that are observed in SiC X grains, and in addition predict accurately the 60Ni/58Ni, 61Ni/58Ni, and 62Ni/58Ni ratios in SiC X grains, as a result of fast neutron captures initiated by the propagation of the supernova shockwave. Finally, symmetry has a noticeable effect on the production of silicon, sulfur, and iron isotopes in the SN ejecta.

Keywords: type ii supernovae; core-collapse supernovae; meteorites; chondrites; meteorite composition; asteroids; small solar system bodies; stellar winds; stellar evolutionary models; stellar evolution; theoretical models; laboratory astrophysics
Ambipolar Electric Field and Potential in the Solar Wind Estimated from Electron Velocity Distribution Functions

The solar wind escapes from the solar corona and is accelerated, over a short distance, to its terminal velocity. The energy balance associated with this acceleration remains poorly understood. To quantify the global electrostatic contribution to the solar wind dynamics, we empirically estimate the ambipolar electric field (E∥) and potential (Φr,∞). We analyze electron velocity distribution functions (VDFs) measured in the near-Sun solar wind between 20.3 RS and 85.3 RS by the Parker Solar Probe. We test the predictions of two different solar wind models. Close to the Sun, the VDFs exhibit a suprathermal electron deficit in the sunward, magnetic-field-aligned part of phase space. We argue that the sunward deficit is a remnant of the electron cutoff predicted by collisionless exospheric models. This cutoff energy is directly linked to Φr,∞. Competing effects of E∥ and Coulomb collisions in the solar wind are addressed by the Steady Electron Runaway Model (SERM). In this model, electron phase space is separated into collisionally overdamped and underdamped regions. We assume that this boundary velocity at small pitch angles coincides with the strahl break-point energy, which allows us to calculate E∥. The obtained Φr,∞ and E∥ agree well with theoretical expectations. They decrease with radial distance as power-law functions with indices αΦ = -0.66 and αE = -1.69. We finally estimate the velocity gained by protons from electrostatic acceleration, which equals 77% calculated from the exospheric models, and 44% from the SERM model.

Keywords: solar wind; space plasmas; interplanetary particle acceleration; space vehicle instruments
Surface Roughness at the Moon's South Pole: The Influence of Condensed Volatiles on Surface Roughness at the Moon's South Pole

Condensed volatiles within lunar permanently shadowed regions are of high scientific and resource utilization importance. Volatiles remain elusive and difficult to observe directly, due to low direct solar illumination. In this work, we investigate correlations between, as well as possible effects of, condensed volatiles and surface roughness. We analyze topographic roughness at 50 m and 30–120 m baselines of the lunar south pole (poleward of 85° S). We focus on six south polar craters of interest and their directly surrounding non-cold-trap areas: Faustini, Shoemaker, Haworth, Cabeus, Nobile, and an unnamed region. We further analyze six analogous equatorial craters to investigate the non-ice smoothing contributions: Morozov F, Rosenberger C, Van Maanen, Fraunhofer E, Brisbane, and Asclepi. Lastly, we compare a sunlit and a permanently shaded portion of the Amundsen crater floor. Utilizing data from the Lunar Reconnaissance Orbiter's Lunar Orbiter Laser Altimeter (LOLA), Lyman Alpha Mapping Project (LAMP), Lunar Reconnaissance Orbiter Camera, and Diviner Lunar Radiometer Experiment, we find subdued roughness within cold traps but determine that roughness is not a unique identifier of condensed volatiles. However, a correlation between LOLA roughness, LAMP normalized Off-band/On-band albedo, temperature, and water-ice stability suggests possible terrain softening due to condensed volatiles, although we cannot rule out dust ponding and/or fairy castle structure contributions. We conclude that LAMP volatile signatures at the topmost ∼100 nm may be indicative of volatile deposits at depths beyond the LAMP sensing capabilities.

Keywords: the moon; lunar craters; lunar surface
A Detailed Kinematic Study of 3C 84 and Its Connection to γ-Rays

3C 84 (NGC 1275) is the bright radio core of the Perseus cluster. Even in the absence of strong relativistic effects, the source has been detected at γ-rays up to TeV energies. Despite its intensive study, the physical processes responsible for the high-energy emission in the source remain unanswered. We present a detailed kinematics study of the source and its connection to γ-ray emission. The subparsec-scale radio structure is dominated by slow-moving features in both the eastern and western lanes of the jet. The jet appears to have accelerated to its maximum speed within less than 125,000 gravitational radii. The fastest reliably detected speed in the jet was ~0.9c. This leads to a minimum viewing angle to the source of ≳42° and a maximum Doppler factor of ≲1.5. Our analysis suggests the presence of multiple high-energy sites in the source. If γ-rays are associated with kinematic changes in the jet, they are being produced in both eastern and western lanes in the jet. Three γ-ray flares are contemporaneous with epochs where the slowly moving emission region splits into two subregions. We estimate the significance of these events being associated to be ~2σ-3σ. We tested our results against theoretical predictions for magnetic-reconnection-induced mini-jets and turbulence and find them compatible.

Keywords: gamma-ray astronomy; very long baseline interferometry; wavelet analysis; high energy astrophysics
Neutral Hydrogen (H I) 21 cm as a Probe: Investigating Spatial Variations in Interstellar Turbulent Properties

Interstellar turbulence shapes the H I distribution in the Milky Way (MW). How this affects large-scale statistical properties of H I column density across the MW remains largely unconstrained. We use the ~13,000 deg2 GALFA-H I survey to map statistical fluctuations of H I over the ±40 km s-1 velocity range. We calculate the spatial power spectrum (SPS) of the H I column density image by running a 3° kernel and measuring the SPS slope over a range of angular scales from 16' to 20°. Due to GALFA's complex observing and calibration strategy, we construct detailed estimates of the noise contribution and account for GALFA beam effects on the SPS. This allows us to systematically analyze H I images that trace a wide range of interstellar environments. We find that the SPS slope varies between ~ -2.6 at high Galactic latitudes and ~ -3.2 close to the Galactic plane. The range of SPS slope values becomes tighter when we consider H I optical depth and line-of-sight length caused by the plane-parallel geometry of the H I disk. This relatively uniform, large-scale distribution of the SPS slope is suggestive of large-scale turbulent driving being a dominant mechanism for shaping H I structures in the MW and/or the stellar feedback turbulence being efficiently dissipated within dense molecular clouds. Only at latitudes above 60° do we find evidence for the H I SPS slope being consistently more shallow. Those directions are largely within the Local Bubble, suggesting that the recent history of this cavity, shaped by multiple supernova explosions, has modified the turbulent state of H I and/or fractions of H I phases.

Keywords: interstellar atomic gas; interstellar phases; interstellar medium; milky way galaxy; neutral hydrogen clouds
Where's the Dust?: The Deepening Anomaly of Microwave Emission in NGC 4725 B

We present new Atacama Large Millimeter Array (ALMA) observations toward NGC 4725 B, a discrete, compact, optically faint region within the star-forming disk of the nearby galaxy NGC 4725 that exhibits strong anomalous microwave emission (AME). These new ALMA data include continuum observations centered at 92, 133, 203, and 221 GHz accompanied by spectral observations of the 12CO ( $J=2\to 1$ ) line. NGC 4725 B is detected in the continuum at all frequencies, although the detection at 203 GHz is marginal. While molecular gas is not detected at the exact location of NGC 4725 B, there is molecular gas in the immediate vicinity (i.e., ≲100 pc) along with associated diffuse 8 μm emission. When combined with existing Very Large Array continuum data at 1.5, 3, 5.5, 9, 14, 22, 33, and 44 GHz, the spectrum is best fit by a combination of AME, synchrotron, and free-free emission that is free-free absorbed below ∼6 GHz. Given the strength of the AME, there is surprisingly no indication of millimeter dust emission associated with NGC 4725 B on ≲6″ spatial scales at the sensitivity of the ALMA interferometric data. Based on the properties of the nearest molecular gas complex and the inferred star formation rate, NGC 4725 B is consistent with being an extremely young (∼3-5 Myr) massive (≲105 M⊙) cluster that is undergoing active cluster feedback. However, the lack of millimeter thermal dust emission is difficult to reconcile with a spinning dust origin of the 30 GHz emission. On the other hand, modeling NGC 4725 B as a new class of background radio galaxy is also unsatisfactory.

Keywords: radio continuum emission; interstellar emissions; dust continuum emission; h ii regions; star formation; galaxies; disk galaxies
Investigating the Effect of Galaxy Interactions on the Enhancement of Active Galactic Nuclei at 0.5 < z < 3.0

Galaxy interactions and mergers are thought to play an important role in the evolution of galaxies. Studies in the nearby universe show a higher fraction of active galactic nuclei (AGNs) in interacting and merging galaxies than in their isolated counterparts, indicating that such interactions are important contributors to black hole growth. To investigate the evolution of this role at higher redshifts, we have compiled the largest known sample of major spectroscopic galaxy pairs (2381 with ΔV < 5000 km s-1) at 0.5 < z < 3.0 from observations in the COSMOS and CANDELS surveys. We identify X-ray and IR AGNs among this kinematic pair sample, a visually identified sample of mergers and interactions, and a mass-, redshift-, and environment-matched control sample for each in order to calculate AGN fractions and the level of AGN enhancement as a function of relative velocity, redshift, and X-ray luminosity. While we see a slight increase in AGN fraction with decreasing projected separation, overall, we find no significant enhancement relative to the control sample at any separation. In the closest projected separation bin (< 25 kpc, ΔV < 1000 km s-1), we find enhancements of a factor of ${0.94}_{-0.16}^{+0.21}$ and ${1.00}_{-0.31}^{+0.58}$ for X-ray and IR-selected AGNs, respectively. While we conclude that galaxy interactions do not significantly enhance AGN activity on average over 0.5 < z < 3.0 at these separations, given the errors and the small sample size at the closest projected separations, our results would be consistent with the presence of low-level AGN enhancement.

Keywords: active galactic nuclei; galaxy interactions; galaxy mergers; extragalactic astronomy; galaxy pairs; interacting galaxies; high-redshift galaxies
LOFAR Detection of Post-starburst Galaxies

We report detection of 104 radio counterparts in a sample of 1204 Sloan Digital Sky Survey-detected post-starburst (PSB) galaxies using the 144 MHz LOw-Frequency ARray (LOFAR) Two-meter Sky Survey Data Release 2 (LoTSS2). The detection rate of optically selected PSB galaxies in the 144 MHz images is ~8.6% while that in the 1.4 GHz was estimated to be ~1.8% using the Very Large Array-Faint Images of the Radio Sky at Twenty centimeter images. Although the 144 MHz radio luminosity shows no significant correlation with luminosity at other wave bands from optical to far-infrared, the fraction of radio-detected PSB galaxies shows a clear trend with absolute magnitude and colors in optical and Wide-field Infrared Survey Explorer infrared bands. A preliminary analysis suggests that the radio emission is dominated by Active Galactic Nuclei.

Keywords: extragalactic radio sources; post-starburst galaxies; e+a galaxies
Giant Outer Transiting Exoplanet Mass (GOT 'EM) Survey. IV. Long-term Doppler Spectroscopy for 11 Stars Thought to Host Cool Giant Exoplanets

Discovering and characterizing exoplanets at the outer edge of the transit method's sensitivity has proven challenging owing to geometric biases and the practical difficulties associated with acquiring long observational baselines. Nonetheless, a sample of giant exoplanets on orbits longer than 100 days has been identified by transit hunting missions. We present long-term Doppler spectroscopy for 11 such systems with observation baselines spanning a few years to a decade. We model these radial velocity observations jointly with transit photometry to provide initial characterizations of these objects and the systems in which they exist. Specifically, we make new precise mass measurements for four long-period giant exoplanets (Kepler-111 c, Kepler-553 c, Kepler-849 b, and PH-2 b), we place new upper limits on mass for four others (Kepler-421 b, KOI-1431.01, Kepler-1513 b, and Kepler-952 b), and we show that several confirmed planets are in fact not planetary at all. We present these findings to complement similar efforts focused on closer-in short-period giant planets, and with the hope of inspiring future dedicated studies of cool giant exoplanets.

Keywords: extrasolar gaseous giant planets; transits; radial velocity; transit timing variation method; exoplanet astronomy
Radio, EUV, and X-Ray Observations during a Filament Rise in the 2011 June 7 Solar Flare

The most energetic flares start with a filament rise followed by magnetic reconnection below this filament. The start of the reconnection corresponds to the beginning of the flare impulsive phase. In this paper we study processes before this phase. During the filament rise we recognize an unusual radio continuum with a starting boundary drifting toward lower frequencies. The estimated velocity of the agent generating this continuum boundary is about 400 km s-1, similar to that of the rising filament. In association with this filament rise, transient X-ray sources and extreme ultraviolet (EUV) brightenings are found near the filament footpoint and outside the locations where later two parallel flare ribbons appear. Moreover, oscillations with a ∼30 s period are found simultaneously in radio, EUV, and X-ray observations. Around the end of these oscillations the flare impulsive phase starts as seen in observations of the drifting pulsation structure and X-ray source located at the upper part of the rising filament. We interpret the unusual radio continuum and transient X-ray sources, which are located outside the two parallel flare ribbons, as those generated during an interaction of the rising filament with the above-lying magnetic loops. The EUV brightening at the filament footpoint could be a signature of the magnetic reconnection inside the magnetic rope carrying the filament. Possible scenarios of the ∼30 s period oscillations in radio, X-ray, and EUV are discussed.

Keywords: solar flares; solar oscillations; solar radio flares; solar ultraviolet emission; solar x-ray flares
The Factory and the Beehive. V. Chromospheric and Coronal Activity and Its Dependence on Rotation in Praesepe and the Hyades

Low-mass (≲1.2 M ⊙) main-sequence stars lose angular momentum over time, leading to a decrease in their magnetic activity. The details of this rotation–activity relation remain poorly understood, however. Using observations of members of the ≈700 Myr old Praesepe and Hyades open clusters, we aim to characterize the rotation–activity relation for different tracers of activity at this age. To complement published data, we obtained new optical spectra for 250 Praesepe stars, new X-ray detections for 10, and new rotation periods for 28. These numbers for Hyads are 131, 23, and 137, respectively. The latter increases the number of Hyads with periods by 50%. We used these data to measure the fractional Hα and X-ray luminosities, L Hα /L bol and L X/L bol, and to calculate Rossby numbers R o. We found that at ≈700 Myr almost all M dwarfs exhibit Hα emission, with binaries having the same overall color–Hα equivalent width distribution as single stars. In the R o–L Hα /L bol plane, unsaturated single stars follow a power law with index β = ‑5.9 ± 0.8 for R o > 0.3. In the R o–L X/L bol plane, we see evidence for supersaturation for single stars with R o ≲ 0.01, following a power law with index ${\beta }_{\sup }={0.5}_{-0.1}^{+0.2}$ , supporting the hypothesis that the coronae of these stars are being centrifugally stripped. We found that the critical R o value at which activity saturates is smaller for L X/L bol than for L Hα /L bol. Finally, we observed an almost 1:1 relation between L Hα /L bol and L X/L bol, suggesting that both the corona and the chromosphere experience similar magnetic heating.

Keywords: open star clusters; stellar chromospheres; stellar coronae; late-type stars; stellar evolution; stellar atmospheres
3D Magnetothermal Simulations of Tangled Crustal Magnetic Field in Central Compact Objects

Central compact objects (CCOs) are young neutron stars emitting thermal X-rays with bolometric luminosities LX in the range of 1032-1034 erg s-1. Gourgouliatos, Hollerbach, and Igoshev recently suggested that peculiar emission properties of CCOs can be explained by tangled magnetic field configurations formed in a stochastic dynamo during the proto-neutron star stage. In this case the magnetic field consists of multiple small-scale components with negligible contribution of global dipolar field. We study numerically three-dimensional magnetothermal evolution of tangled crustal magnetic fields in neutron stars. We find that all configurations produce complicated surface thermal patterns that consist of multiple small hot regions located at significant separations from each other. The configurations with initial magnetic energy of (2.5-10) × 1047 erg have temperatures of hot regions that reach ≈ 0.2 keV, to be compared with the bulk temperature of ≈ 0.1 keV in our simulations with no cooling. A factor of two in temperature is also seen in observations of CCOs. The hot spots produce periodic modulations in light curve with typical amplitudes of ≤9%-11%. Therefore, the tangled magnetic field configuration can explain thermal emission properties of some CCOs.

Keywords: neutron stars; magnetic fields; astrophysical magnetism; magnetohydrodynamics; astrophysical fluid dynamics; magnetohydrodynamical simulations
Spectroscopic Confirmation of a Population of Isolated, Intermediate-mass Young Stellar Objects

Wide-field searches for young stellar objects (YSOs) can place useful constraints on the prevalence of clustered versus distributed star formation. The Spitzer/IRAC Candidate YSO (SPICY) catalog is one of the largest compilations of such objects (~120,000 candidates in the Galactic midplane). Many SPICY candidates are spatially clustered, but, perhaps surprisingly, approximately half the candidates appear spatially distributed. To better characterize this unexpected population and confirm its nature, we obtained Palomar/DBSP spectroscopy for 26 of the optically bright (G < 15 mag) "isolated" YSO candidates. We confirm the YSO classifications of all 26 sources based on their positions on the Hertzsprung-Russell diagram, H and Ca II line emission from over half the sample, and robust detection of infrared excesses. This implies a contamination rate of <10% for SPICY stars that meet our optical selection criteria. Spectral types range from B4 to K3, with A-type stars being the most common. Spectral energy distributions, diffuse interstellar bands, and Galactic extinction maps indicate moderate-to-high extinction. Stellar masses range from ~1 to 7 M ⊙, and the estimated accretion rates, ranging from 3 × 10-8 to 3 × 10-7 M ⊙ yr-1, are typical for YSOs in this mass range. The 3D spatial distribution of these stars, based on Gaia astrometry, reveals that the "isolated" YSOs are not evenly distributed in the Solar neighborhood but are concentrated in kiloparsec-scale dusty Galactic structures that also contain the majority of the SPICY YSO clusters. Thus, the processes that produce large Galactic star-forming structures may yield nearly as many distributed as clustered YSOs.

Keywords: herbig ae/be stars; t tauri stars; spectroscopy; star formation; young stellar objects
E+A Galaxies in and Around Nearby Rich Clusters of Galaxies

We have spectroscopically identified 600 new E+A galaxies and candidates across 16 fields totaling roughly 480 square degrees in the Sloan Digital Sky Survey. E+A galaxies are post-starburst systems that have undergone a significant burst of star formation within the past 1-2 Gyr and are now fully quenched. They comprise a small population that is key to understanding the transition from star-forming to quiescent galaxies. Our survey focused on four nearby rich clusters of galaxies and their surroundings: Virgo, Coma, Leo, and Hercules. 356 candidates were identified in the clusters, and an additional 244 were identified in control fields or otherwise outside cluster bounds. Understanding the distribution and dynamics of the E+As has the potential to shed light on the evolutionary mechanisms present within nearby cluster environments. In this note, we give a brief overview of our selection processes and locations, and report on ongoing analyses of the sample.

Keywords: e+a galaxies; post-starburst galaxies; galaxy evolution; galaxy quenching; quenched galaxies; galaxy clusters