Sazuna/UAT_keywords huggingface dataset:
Suprathermal Electron Scattering by Narrowband Whistler Waves and Broadband Electrostatic Waves: Parker Solar Probe Observations. We utilize Parker Solar Probe measurements from the first nine perihelia to investigate suprathermal electron scattering near the Sun. We employ a normalized isotropy parameter to identify pitch-angle scattering (PAS) regions in the inner heliosphere, and compare the plasma conditions during these periods to the background (BG) solar wind. Suprathermal electron scattering also commonly occurs during full/partial current sheet (PCS) heliospheric current sheet (HCS) crossings, as identified in previous work. We find slightly higher electron collisional ages in the PAS and PCS/HCS regions than in BG regions, but conclude that Coulomb collisions alone likely cannot explain the observed suprathermal scattering. We investigate plasma wave-modes that could play a role in suprathermal electron scattering, and identify trends in the wave occurrence in BG, PAS, and PCS/HCS regions. We find higher occurrence rates of narrowband whistler-mode waves with frequencies of 0.04─0.19 f/fce, and a higher occurrence of larger magnetic field wave power in this frequency band, in the PAS and PCS/HCS regions. These observations support the hypothesis that whistler-mode waves play a role in suprathermal electron scattering at moderate distances. However, closer to the Sun, narrowband whistlers are more rarely observed. Instead, we find higher occurrence rates of broadband electrostatic waves with frequencies of 0.1─4.4 f/flh, and a higher occurrence of larger electric wave power in this band, in the near-Sun PAS and PCS/HCS regions. These observations suggest a role for broadband electrostatic waves in suprathermal electron scattering closer to the Sun.

Keywords: Space plasmas, Solar wind, Plasma astrophysics
FEASTS Combined with Interferometry. IV. Mapping H I Emission to a Limit of N<SUB>H I</SUB> = 10<SUP>17.7</SUP> cm<SUP>‑2</SUP> in Seven Edge-on Galaxies. We present a statistical study of the neutral atomic hydrogen (H I) gas extending into the circumgalactic medium perpendicular to the disk for seven edge-on galaxies with inclinations above 85° from the FEASTS program with a 3σ (20 km s‑1 ) column density (NH I ) depth of 5 × 1017 cm‑2. We develop two photometric methods to separate the extraplanar H I from the disk component based on existing interferometric data and parametric modeling of the disk flux distribution, respectively. With both methods, the FEASTS data exhibit clear extended wings beyond the disk along the minor axis. The extraplanar H I accounts for 5%–20% of the total H I mass and extends to 20–50 kpc at NH I = 1018cm‑2 . We find a tight positive correlation between vertical extensions of the extraplanar H I and total H I mass MH I. The isodensity shape of H I at NH I = 1018 cm‑2 has an average axis ratio of 0.56 ± 0.11. The off-disk NH I profiles of these edge-on galaxies well represent the lower envelope of previous Lyα absorption measurements at low redshift. Our results suggest that at NH I = 5 × 1017 cm‑2, the H I extends considerably further than the known thin and thick disks in the vertical direction but still remains much flatter than a spherical distribution, consistent with theoretical expectations that outflow, circulation, and accretion should have different impacts in these two directions. We show the tension of our results with Illustris and TNG predictions, highlighting the constraining power of our results for future simulations.

Keywords: Galaxy evolution, Interstellar medium, Circumgalactic medium
R-JET: A Postprocessing Code for Radiative Transport in Relativistic Jets. We describe a postprocessing radiative transport code for computing the spectra, the core shift, and the surface-brightness distribution of special relativistic jets with arbitrary optical thickness. The jet consists of an electron–positron pair plasma and an electron–proton normal plasma. Electrons and positrons are relativistic and composed of thermal and nonthermal components, while protons are nonrelativistic and nonradiating. The fraction of a pair plasma, as well as the fraction of a nonthermal component, can be arbitrarily chosen. Only the synchrotron process is considered for emission and absorption when the radiative-transfer equation is integrated along our lines of sight. We describe a suite of test problems and confirm the frequency dependence of the core shift in the Konigl jet model when the plasma is composed of nonthermal components alone. Finally, we illustrate the capabilities of the code with model calculations, demonstrating that the jet will exhibit a limb-brightened structure in general when it is energized by the rotational energy of the black hole. It is also demonstrated that such limb-brightened jets show a ring-like structure in the brightness map when we observe the jet launching region nearly face-on.

Keywords: Magnetohydrodynamics, Black holes, Very long baseline interferometry, Relativistic jets, Plasma astrophysics, Radiative transfer equation, Radio active galactic nuclei, Magnetic fields
A Large Systematic Search for Close Supermassive Binary and Rapidly Recoiling Black Holes. IV. Ultraviolet Spectroscopy. We present Hubble Space Telescope ultraviolet (UV) spectroscopy of 13 quasars at z &lt; 0.7, along with contemporaneous optical spectra from ground-based telescopes. The targets were selected to have broad Hβ emission lines with substantial velocity offsets relative to the rest frame of their host galaxy. By analogy to single-line spectroscopic binary stars, these objects have been regarded as supermassive black hole binary (SBHB) candidates where the offset emission lines may be caused by bulk orbital motion. The best alternative explanation is that the Hβ line profile is the result of nonaxisymmetric emission from a disk-like broad-line region associated with a single supermassive black hole. We use the broad UV line profiles to discriminate between these two scenarios. We describe our methodology for isolating the broad optical and UV line profiles and the criteria we apply for comparing them. Of the 13 SBHB candidates, three have strong evidence in support of the SBHB hypothesis, five have tentative support, one is disfavored, and four have such severely absorbed UV line profiles that the results are inconclusive. *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 NAS5-26555. These observations are associated with program GO-12299. †Based on observations obtained with the Hobby-Eberly Telescope (HET), which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximillians-Universitaet Muenchen, and Georg-August Universitaet Goettingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly.

Keywords: Supermassive black holes, Active galactic nuclei, Ultraviolet spectroscopy, Spectroscopy
The Initial Mass Function of the Galactic Early-type Field Stars Based on the LAMOST Survey. Research on the high-mass end of the initial mass function (IMF) has been limited due to a scarcity of samples. Recently, Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), as the most efficient spectroscopic telescope, has provided new opportunities for related research. In this study, based on approximately 70,000 main-sequence early-type stars from the LAMOST survey, we investigated the IMF of Galactic field stars at the high-mass end (1.5 ≤ M/M⊙ ≤ 7.1). First, we derived the slope of the present-day mass function (PDMF), finding   after correcting for selection effect in the observed sample. We then accounted for the effects of stellar evolution and unresolved binaries to correct the PDMF back to the IMF, resulting in αini = 2.70 ∼ 2.82. Notably, we corrected both stellar evolution and unresolved binary effects simultaneously by using binary-Star evolution code, which enhances the robustness of our results. Additionally, we investigated how different mass-ratio (q) distributions of binaries and different star formation histories of the Milky Way impact the IMF. Finally, we tested samples across different spatial scales and found that αini may exhibit a decreasing trend as the spatial scale increases, which could be attributed to variations in metallicity.

Keywords: Early-type stars, Initial mass function, Stellar evolution
Continuum Reverberation in Active Galactic Nuclei Disks Only with Sufficient X-Ray Luminosity and Low Albedo. Disk continuum reverberation mapping is one of the primary ways we learn about active galactic nuclei (AGN) accretion disks. Reverberation mapping assumes that time-varying X-rays incident on the accretion disk drive variability in UV–optical light curves emitted by AGN disks and uses lags between X-ray and UV–optical variability on the light-crossing timescale to measure the radial temperature profile and extent of AGN disks. However, recent reverberation mapping campaigns have revealed oddities in some sources, such as weakly correlated X-ray and UV light curves, longer than anticipated lags, and evidence of intrinsic variability from disk fluctuations. To understand how X-ray reverberation works with realistic accretion disk structures, we perform 3D multifrequency radiation magnetohydrodynamic simulations of X-ray reprocessing by the UV-emitting region of an AGN disk using sophisticated opacity models that include line opacities for both the X-ray and UV radiation. We find there are two important factors that determine whether X-ray irradiation and UV emission will be well-correlated: the ratio of X-ray to UV luminosity and significant absorption. When these factors are met, the reprocessing of X-rays into UV is nearly instantaneous, as is often assumed, although linear reprocessing models are insufficient to fully capture X-ray reprocessing in our simulations. Nevertheless, we can still easily recover mock lags in our light curves using software that assumes linear reprocessing. Finally, the X-rays in our simulation heat the disk, increasing temperatures by a factor of 2–5 in the optically thin region, which could help explain the discrepancy between measured and anticipated lags.

Keywords: Accretion, Radiative magnetohydrodynamics, High energy astrophysics, Quasars, Reverberation mapping, Active galactic nuclei
Warm Ionized Gas Outflows in Active Galactic Nuclei: What Causes Them?. The driving force behind outflows, often invoked to understand the correlation between the supermassive black holes powering active galactic nuclei (AGN) and their host galaxy properties, remains uncertain. We provide new insights into the mechanisms that trigger warm ionized outflows in AGN, based on findings from the MaNGA survey. Our sample comprises 538 AGN with strong [O III] λ5007 emission lines, of which 197 are detected in radio and 341 are radio-undetected. We analyzed the [O III] λ5007 line in summed spectra, extracted over their central 500 × 500 pc2 region. The calculated Balmer 4000 Å break, Dn4000, is larger than 1.45 for ∼95% of the sources, indicating that the specific star formation rate in their central regions is less than 10‑11.5 yr‑1, which points to evidence of negative AGN feedback suppressing star formation. Considering the whole sample, radio-detected sources show a greater outflow detection rate (56% ± 7%) than radio-undetected sources (25% ± 3%). They also show higher velocity, mass outflow rate, outflow power, and outflow momentum rate. We noticed a strong correlation between outflow characteristics and bolometric luminosity in both samples, except that the correlation is steeper for the radio-detected sample. Our findings suggest that (a) warm ionized outflows are prevalent in all types of AGN, (b) radiation from AGN is the primary driver of these outflows, (c) radio jets are likely to play a secondary role in enhancing the gas kinematics over and above that caused by radiation, and (d) there is very little star formation in the central regions of the galaxies, possibly due to negative feedback from AGN activity.

Keywords: AGN host galaxies, Radio jets, Active galaxies, LINER galaxies, Seyfert galaxies
Spatially-resolved TRGB JWST Color─Magnitude Diagram as a Tool to Measure Fossil Stellar Metallicity Gradients in Disk Galaxies: NGC 628. We use archival JWST/NIRCam images in the F115W, F150W, and F200W filters to measure the tip of the red giant branch (TRGB) magnitudes across the disk of the late-type spiral galaxy NGC 628. In this exploratory study, we demonstrate how the metallicity-dependence of TRGB magnitudes in the near-infrared (NIR) filters can be exploited by making use of the theoretical isochrones to determine metallicities of the fossil 10 Gyr old population over kiloparsec scales without being affected by the age─metallicity reddening degeneracy. We obtain a smooth metallicity gradient that decreases from Z = 0.003 in the central regions to Z = 0.002 in the external parts, with a typical error on Z of 0.0002. The extinction variation across the disk caused by the diffuse interstellar dust is spiky with a median value of AV = 0.12 mag. We propose that the large bubbles in the disks of galaxies offer dust-free lines of sight for measuring the TRGB magnitudes, and hence the distance to galaxies, to an accuracy that is as good as that of the halo populations. Using the Phantom Void, we obtain a TRGB distance modulus of 29.81 ± 0.05(stat) ± 0.06(sys) mag for NGC 628, which agrees well with the most recent PNLF measurement of 29.89  for this galaxy.

Keywords: Stellar photometry, Red giant tip, Spiral galaxies, Hertzsprung Russell diagram, Metallicity
Velocity Structure Correlations between the Nebular, Molecular, and Atmospheric Gases in the Cores of Four Cool Core Clusters. We investigate the velocity structure of nebular gas in the central galaxies of four clusters: A1835, PKS 0745‑191, A262, and RXJ0820.9+0752, using data from the Keck Cosmic Web Imager. Velocity structure functions (VSFs) of the [O II] emission line are compared to VSFs of molecular clouds observed with the Atacama Large Millimeter/submillimeter Array. Apart from A262, where the gas is located in a circumnuclear disk, the nebular gas in the remaining galaxies lies in off-nuclear filamentary structures with VSFs steeper than the Kolmogorov slope. This steepening may be plausibly attributed to gravity, although other factors, such as magnetic stresses and bulk motion, may be significant. The VSFs of CO and [O II] emission are similar in RXJ0820 and A262, indicating close coupling of the nebular and molecular gases. In contrast, the nebular and molecular gases are differentiated on most scales in PKS 0745 and A1835. This discrepancy is likely due to the radioactive galactic nucleus churning the gas. We compare the scale-dependent velocity amplitudes of the hot atmospheres constrained by X-ray surface brightness fluctuation analysis using Chandra observations to the nebular VSFs. The large-scale consistency in A1835 and RXJ0820 is consistent with condensation from the hot atmospheres. We explore substantial systematic biases, including projection effects, windowing, and smoothing effects, when comparing VSFs using different telescopes and instruments.

Keywords: Galaxy clusters, Active galactic nuclei
Near-infrared Spectral Properties of Type Ib/Ic Supernova Progenitors and Implications for JWST and NGRST Observations. While about 20 type II supernova (SN II) progenitors have been identified using optical data from the Hubble Space Telescope (HST), direct detection of type Ib/Ic supernova (SN Ib/Ic) progenitors remains challenging, due to their faint optical brightness and highly obscured environments. This study aims to investigate the detection limits and advantages of near-infrared (near-IR) observations with the James Webb Space Telescope (JWST) and the Nancy Grace Roman Space Telescope (NGRST) for the detection of SN Ib/Ic progenitors. The spectral energy distributions of SN Ib/Ic progenitor models with various masses, chemical compositions, and mass-loss rates are calculated with the non-LTE radiative transfer code CMFGEN. We then assess the detectability of SN Ib/Ic progenitors using near-IR filters from JWST and NGRST, comparing the results to the capabilities of HST. Our analysis indicates that near-IR observations significantly outperform HST in detecting SN Ib/Ic progenitors when considering the effect of extinction. Near-IR magnitudes also provide better constraints on the mass-loss rates of progenitors, because of the free–free emission from the wind matter. Additionally, near-IR magnitudes and color–color diagrams are effective in distinguishing SN Ib/Ic progenitors from possible companion and/or background objects. This study suggests that JWST and NGRST can play a crucial role in advancing our understanding of SN Ib/Ic progenitors, by improving detectability and offering better constraints on progenitor properties. We emphasize that observations with exposure times exceeding 1 hr would be needed to detect typical SNe Ib/Ic progenitors at distances greater than 10 Mpc.

Keywords: Type Ic supernovae, Core-collapse supernovae, Type Ib supernovae, Massive stars, Hubble Space Telescope, Stellar astronomy, Stellar winds, James Webb Space Telescope, Radiative transfer simulations, Supernovae
PSZ2 G181.06+48.47. I. X-Ray Exploration of a Low-mass Cluster with Exceptionally Distant Radio Relics. Relics are diffuse, highly polarized radio sources that trace merger-driven shocks at the periphery of merging galaxy clusters. The Low Frequency Array survey recently discovered a rare example of double relics in the low-mass cluster PSZ2 G181.06+48.47. Through a detailed exploration of new Chandra and XMM-Newton observations, we reveal that PSZ2 G181.06+48.47 has a lower mass ( ) than previously thought. Despite its cool global temperature of   keV, PSZ2 G181.06+48.47 is one of the most disturbed clusters in the Planck sample, with a complex morphological and thermodynamic structure. We discover a set of three discontinuities within &lt;500 kpc of the cluster center, and, from a surface brightness analysis, place 5σ upper limits of   and   for any shock associated with the relic locations. We also revise established scaling relations for double radio relics by adding 12 new systems not included in previous work. The PSZ2 G181.06+48.47 relics have the widest separation (scaled for r500) of all known double relic systems. The exceptional distance from the cluster center (&gt;r200) indicates the relics may be associated with shocks in the "runaway" phase. We propose that this late-stage, post-apocenter merger is captured as the two subclusters with a mass ratio of 1.2–1.4 fall back into each other. The outer relic shocks were likely produced at the first core passage, while the inner discontinuities are associated with the second infall.

Keywords: Galaxy clusters, X-ray astronomy, Large-scale structure of the universe, Non-thermal radiation sources, Intracluster medium
PSZ2 G181.06+48.47. II. Radio Analysis of a Low-mass Cluster with Exceptionally Distant Radio Relics. We report upgraded Giant Metrewave Radio Telescope and Karl J. Jansky Very Large Array radio observations of a low-mass merging galaxy cluster PSZ2 G181.06+48.47. This exceptional galaxy cluster hosts two megaparsec-scale diffuse sources, symmetrically located with respect to the cluster center and separated by about 2.6 Mpc in projection. We detect these low surface brightness sources in our new high-frequency observations (0.3–2 GHz) and classify them as radio relics associated with merger-driven shock fronts. The southwest relic exhibits an inverted morphology and shows evidence of spectral steepening in the post-shock region, potentially tracing a high Mach number shock (∼4) under the framework of diffusive shock acceleration. The northeast relic is found to be highly polarized with a 22% average polarization fraction at 1.5 GHz and aligned magnetic field vectors. Its spectral and polarization properties, along with the presence of a nearby tailed galaxy, support reacceleration scenarios. The merger axis defined by the two relics is tilted by ∼45° with respect to the plane of the sky, which implies an unprecedented physical separation of ∼3.5 Mpc. We also detect a possible faint radio halo, suggesting weak turbulence in the central cluster region. We conclude that the faint double relics can be best explained by two outward-moving shock waves in which particles are (re)accelerated and that the cluster is in an evolved merger state. PSZ2 G181.06+48.47 presents a unique opportunity to investigate particle acceleration in low-mass systems characterized by large relic separations.

Keywords: Galaxy clusters, Large-scale structure of the universe, Extragalactic radio sources, Non-thermal radiation sources, Radio continuum emission
PSZ2 G181.06+48.47. III. Weak-lensing Analysis and Merging Scenario Reconstruction of a Low-mass Cluster with Exceptionally Distant Radio Relics. The galaxy cluster PSZ2 G181.06+48.47 (z = 0.234) is a post-merging system that exhibits symmetric double radio relics separated by ∼2.7 Mpc. We present the first weak-lensing analysis of PSZ2 G181.06+48.47 and propose possible merging scenarios using numerical simulations. Our analysis with Subaru Hyper Suprime-Cam imaging identifies a binary dark matter (DM) structure consisting of northern and southern components, separated by ∼500 kpc. Assuming Navarro–Frenk–White (NFW) halos, the masses for the northern and southern subclusters are   and  , respectively. By superposing the two NFW halos, we determine the total mass of the cluster to be  ( ). Our mass estimate suggests that the two relics are located around the cluster R200c, where the density of the intracluster medium is very low. Our idealized simulations find that an off-axis collision of a 3:1 major merger can simultaneously reproduce the observed relic and DM halo separations. From these findings, we suggest that the system is observed ∼0.9 Gyr after the first pericenter passage and is returning from the first apocenter.

Keywords: Galaxy clusters, Radio continuum emission, Weak gravitational lensing
Inferring Jet Physics from Neutron Star–Black Hole Mergers with Gravitational Waves. Neutron star–black hole (NSBH) mergers that undergo tidal disruption may launch jets that could power a gamma-ray burst (GRB). We use a population of simulated NSBH systems to measure jet parameters from the gravitational waves emitted by these systems. The conditions during the tidal disruption and merger phase required to power a GRB are uncertain. It is likely that the system must achieve some minimum remnant baryonic mass after the merger before a jet can be launched to power a GRB. Assuming a fiducial neutron star equation of state, we show how Bayesian hierarchical inference can be used to infer the minimum remnant mass required to launch a GRB jet as well as features of the opening angle distribution of the GRB jets. We find that with 200 NSBH observations, we can measure the minimum disk mass to within 0.01 M⊙ at 90% credibility. We simultaneously infer the GRB opening angle to within 13° at 90% credibility. We conclude that upcoming upgrades to the LIGO observatories may provide important new insights into the physics of NSBH jets.

Keywords: Neutron stars, Gamma-ray bursts, Gravitational waves, Compact objects