Sazuna/UAT_keywords huggingface dataset:
Reverse Shock Revisited in Cassiopeia A with Chandra. Using data from the Chandra X-ray Observatory, we revisit the reverse shock in the supernova remnant (SNR) Cassiopeia A. Based on spectroscopy of a series of annuli in the northwest (NW) and southeast (SE), we get the radial profiles of the S/Si Kα line flux ratio and Fe Kα line centroid energy. They both show monotonic increase, confirming that the Si- and Fe-rich ejecta are heated by the reverse shock. The abrupt change of the S and Si line flux ratio is clearly observed in Cassiopeia A, leading to the determination of the reverse-shock location (∼1.‧71 ± 0.‧16 and ∼1.‧35 ± 0.‧18 in the NW and SE, with respect to the central source). By comparing the radial profiles of the S and Si line flux, we find that the reverse shock is moving outward in the frame of the observer, and the velocities are ∼3950 ± 210 km s‑1 and ∼2900 ± 260 km s‑1 in the NW and SE, respectively. In contrast, the velocities become ∼1150 km s‑1 (NW) and ∼1300 km s‑1 (SE) in the ejecta frame. Our measured reverse-shock velocities are quite consistent with those obtained from the X-ray and/or optical images. They therefore supply a cross-check of the accuracy for the two available methods for measuring the reverse-shock velocity in SNRs. Both the location and the velocity of the reverse shock show apparent asymmetry, suggesting that the asymmetric explosion of the progenitor plays a key role in the interaction between the reverse shock and the ejecta, ultimately shaping the complex features observed in SNRs.

Keywords: Supernova remnants, Shocks, X-ray astronomy, Interstellar medium
Discovery of a 100 kpc Narrow Curved Twin Jet in the S-shaped Giant Radio Galaxy J0644+1043. We report the discovery of an S-shaped morphology of the radio galaxy J0644+1043 imaged with a 30 μJy beam‑1 sensitive 525 MHz broadband (bands 3 + 4) uGMRT map. Dedicated spectroscopic observations of the host galaxy carried out with the 2 m Rozhen telescope yielded a redshift of 0.0488, giving a projected linear size of the peculiar radio structure of over 0.7 Mpc. This giant radio galaxy is powered by a black hole of mass  4.1‑2.87+9.39×108  M ⊙, from the vicinity of which emanate well-collimated and knotty jets, each ∼100 kpc long. The entire radio structure, presumably due to the effective jet precession, is less than 50 Myr old, has a power of ∼6 × 1024 W Hz‑1 at 1.4 GHz, and has observed morphological characteristics that do not strictly conform to the traditional Fanaroff–Riley (FR) FR I or FR II categories.

Keywords: Non-thermal radiation sources, Active galaxies, Giant radio galaxies
Formation of Giant Planets by Gas Disk Gravitational Instability on Wide Orbits around Protostars with Varied Masses. II. Quadrupled Spatial Resolution and Beta Cooling. Exoplanet demographics are sufficiently advanced to provide important constraints on theories of planet formation. While core and pebble accretion are preferred for rocky and icy planets, there appears to be a need for gas disk gravitational instability (GDGI) to play a role in the formation of M-dwarf gas giants and those orbiting at large distances. Here we present GDGI models that go beyond those presented by Boss (2011) dealing with the formation of wide-orbit gas giants. The new models use quadrupled spatial resolution, in both the radial and azimuthal directions, to reduce the effects of finite spatial resolution. The new models also employ the β cooling approximation, instead of the diffusion approximation used by Boss (2011), in order to push the models further in time. As in Boss (2011), the central protostars have masses of 0.1, 0.5, 1.0, 1.5, or 2.0 M ⊙, surrounded by disks with masses ranging from 0.019 M ⊙ to 0.21 M ⊙. For each case, two models are computed, one with an initial minimum Toomre Q stability value ranging from 1.1 to 1.7, and one with a higher initial disk temperature, resulting in the initial minimum Q ranging from 2.2 to 3.4. These new models continue to show that GDGI can explain the formation of gas giants at distances of ∼30 to ∼50 au on eccentric orbits (e less than ∼0.2), though the number formed drops to 0 as the protostar mass decreases to 0.1 M ⊙.

Keywords: Exoplanet formation, Gravitational instability, Extrasolar gaseous giant planets, Protoplanetary disks
Volatile Mass Partitioned among the Atmosphere, Mantle, and Core in Proto-Mars. We analyze the distribution of volatiles such as water, hydrogen, and carbon within the atmosphere, mantle, and core of Mars during its accretion stages. The partitioning of these volatiles is crucial as it influences the generation of intrinsic magnetic fields, mantle convection, and magmatic activity. The study suggests that the accretion process is responsible for the presence of water and light elements within the Martian mantle and core. We employ a hybrid-type proto-atmosphere model, which considers an upper layer composed of nebula components and a lower layer made up of degassed components from the impact degassing of the simplified building blocks based on the two-component model. Our numerical analysis implies that the formation of a magma ocean at this high temperature and pressure after around the half-size of the present Mars triggers the migration of water vapor, carbon, and hydrogen from the primordial atmosphere into the planetary interior. Ultimately, several 1021 kg of water could have been distributed to the mantle and, if degassed again by the formation of flood basalts on the Tharsis Plateau, could have supplied Mars' ancient oceans. Meanwhile, several 1020 kg of carbon and 1019 kg of hydrogen (equivalent to 1020 kg H2O) were found to be distributed in the core. Although the distribution of sulfur was simplified so that all of the sulfur is in the core, a result of sulfur accounting for 14 wt% to 19 wt.% of the core mass would be consistent with the core density suggested by InSight.

Keywords: Atmospheric evolution, Mars, Solar system terrestrial planets, Mantle, Planetary cores, Planetary structure
MIDIS: The Relation between Strong (Hβ + [O III]) Emission, Star Formation, and Burstiness around the Epoch of Reionization. We investigate the properties of strong (Hβ + [O III]) emitters before and after the end of the "Epoch of Reionization" from z = 8 to z = 5.5. We make use of ultradeep JWST/NIRCam imaging in the parallel field (P2) of the MIRI Deep Imaging Survey (MIDIS) in the Hubble eXtreme Deep Field (H-XDF), in order to select prominent (Hβ + [O III]) emitters (with rest-frame equivalent width (EW0) ≳ 100 Å) at z = 5.5–7, based on their flux density enhancement in the F356W band with respect to the spectral energy distribution continuum. We complement our selection with other (Hβ + [O III]) emitters from the literature at similar and higher (z = 7‑8) redshifts. We find (nonindependent) anticorrelations between EW0(Hβ + [O III]) and both galaxy stellar mass and age, in agreement with previous studies, and a positive correlation with specific star formation rate (sSFR). On the SFR–M ⋆ plane, the (Hβ + [O III]) emitters populate both the star formation main sequence and the starburst region, which become indistinguishable at low stellar masses ( log10(M⋆)&lt;7.5 ). We find tentative evidence for a nonmonotonic relation between EW0(Hβ + [O III]) and SFR, such that both parameters correlate with each other at SFR ≳ 1 M ⊙ yr‑1, while the correlation flattens out at lower SFRs. This suggests that low metallicities producing high EW0(Hβ + [O III]) could be important at low SFR values. Interestingly, the properties of the strong emitters and other galaxies (33% and 67% of our z = 5.5–7 sample, respectively) are similar, including, in many cases, high sSFR. Therefore, it is crucial to consider both emitters and nonemitters to obtain a complete picture of the cosmic star formation activity around the Epoch of Reionization.

Keywords: Starburst galaxies, Reionization, Galaxy evolution
The Population Synthesis of Wolf–Rayet Stars Involving Binary Merger Channels. Wolf–Rayet (W-R) stars are very important massive stars. However, their origin and the observed binary fraction within the entire W-R population are still debated. We investigate some possible merger channels for the formation of W-R stars, including main sequence (MS)/Hertzsprung gap (HG) + MS, He + HG/giant branch (GB). We find that many products produced via binary merger can evolve into W-R stars, the MS/HG + MS merger channel can explain W-R stars with luminosities higher than ∼105.4 L ⊙, while the He + HG/GB merger channel can explain low-luminosity W-R stars in the range of 104.7 L ⊙ ∼ 105.5 L ⊙. In the population synthesis analysis of W-R stars, we assume an initial binary fraction (f ini,bin) of 50% and 100% for massive stars. We also assume that MS/HG + MS merger products are nonrotating or rapidly rotating (ω/ω crit = 0.8). In different cases, the calculated single fractions of W-R stars range from 22.2%–60.6% in the Milky Way (MW) and from 8.3%–70.9% in the Large Magellanic Cloud (LMC). The current observations fall within the range of our calculations. When the merger product of MS/HG + MS rotates rapidly, we estimate that there are approximately 1015–1396 W-R stars in the MW and 128–204 W-R stars in the LMC. Our model also roughly reproduces the observed single-peak luminosity distribution of W-R stars in the MW. However, the weak bimodal luminosity distribution observed in the LMC is not reproduced in our model. We assess that this may be due to the model underestimating the mass-loss rate in the LMC. In conclusion, we consider that the binary merger is a significant formation channel for W-R formation, and can explain the observed high fraction of the single W-R stars in the total population.

Keywords: Wolf-Rayet stars
Chronicling the Reionization History at 6 ≲ z ≲ 7 with Emergent Quasar Damping Wings. The spectra of high-redshift (z ≳ 6) quasars contain valuable information on the progression of the Epoch of Reionization. At redshifts z &lt; 6, the observed Lyman-series forest shows that the intergalactic medium is nearly ionized, while at z &gt; 7 the observed quasar damping wings indicate high neutral gas fractions. However, there remains a gap in neutral gas fraction constraints at 6 ≲ z ≲ 7 where the Lyman-series forest becomes saturated but damping wings have yet to fully emerge. In this work, we use a sample of 18 quasar spectra at redshifts 6.0 &lt; z &lt; 7.1 to close this gap. We apply neural networks to reconstruct the quasars' continuum emission around the partially absorbed Lyα line to normalize their spectra, and stack these continuum-normalized spectra in three redshift bins. To increase the robustness of our results, we compare the stacks to a grid of models from two hydrodynamical simulations, ATON and CROC, and we measure the volume-averaged neutral gas fraction,  x̄HI , while jointly fitting for the mean quasar lifetime, t Q, for each stacked spectrum. We chronicle the evolution of neutral gas fraction using the ATON (CROC) models as follows:  x̄HI=0.21−0.07+0.17  ( x̄HI=0.10&lt;10−4+0.73 ) at 〈z〉 = 6.10,  x̄HI=0.21−0.07+0.33  ( x̄HI=0.57−0.47+0.26 ) at 〈z〉 = 6.46, and  x̄HI=0.37−0.17+0.17  ( x̄HI=0.57−0.21+0.26 ) at 〈z〉 = 6.87. At the same time, we constrain the average quasar lifetime to be t Q ≲ 7 Myr across all redshift bins, in good agreement with previous studies.

Keywords: Supermassive black holes, Quasars, Intergalactic gas, Intergalactic medium, Reionization
The Jittering Jets Explosion Mechanism in Electron Capture Supernovae. We conduct one-dimensional stellar-evolution simulations of stars with zero-age main-sequence (ZAMS) masses of M ZAMS = 8.8 ‑ 9.45 M ⊙ toward core collapse by electron capture and find that the convective zone of the precollapse core can supply the required stochastic angular momentum fluctuations to set a jet-driven electron capture supernova explosion in the frame of the jittering jets explosion mechanism. By our assumed criteria of a minimum convective specific angular momentum and an accreted mass during jet launching of M acc ≃ 0.001‑0.01 M ⊙, the layer in the convective zone that when accreted launches the exploding jittering jets resides in the helium-rich zone. Depending on the model, this exploding layer is accreted at about a minute to a few hours after core collapse occurs, much shorter than the time the exploding shock crosses the star. The final (gravitational) mass of the neutron star (NS) remnant is in the range of M NS = 1.25‑1.43 M ⊙.

Keywords: Massive stars, Stellar jets, Core-collapse supernovae
Solar Eruptive Phenomena Associated with Solar Energetic Electron Spectral Types. The energy spectral shape of solar energetic electron events carries important information on the energetic electron source/acceleration at the Sun. We investigate the association of six newly identified solar energetic electron spectral types with solar eruptive phenomena, including the downward double-power-law (DDPL) spectrum with break energy E  B  above 20 keV (DDPL EB≥20keV ), DDPL with E  B  below 20 keV (DDPL EB&lt;20keV ), upward double-power law (UDPL), single-power-law (SPL), Ellision–Ramaty–like (ER), and logarithmic-parabola (LP). We find that the SPL type shows (the other five types show) an association with hard X-ray flares of ∼38% (∼55%–82%) and an association with west-limb coronal mass ejections (CMEs) of ∼76% (∼85%–93%). Among the other five types, the DDPL EB&lt;20keV  and ER (LP and DDPL EB≥20keV ) types only have an association with type II radio bursts of ∼7%–8% (∼16%–20%) and an association with halo CMEs of ∼5%–9% (∼11%–21%); however, the UDPL type exhibits a significant (∼47% and ∼50%) association with type II bursts and halo CMEs, with a significantly faster median CME speed of  1000‑120+550  km s‑1. For DDPL EB≥20keV  (DDPL EB&lt;20keV ) with a positive (no) correlation between spectral indexes and no (a positive) correlation between the spectral index and break energy, the spectrum appears to be flatter as the associated CME (flare) becomes faster (stronger). These results suggest that the SPL type can result from the initial acceleration process that likely occurs high in the corona, and then provide seed populations for further acceleration processes to form the other five types: the DDPL EB&lt;20keV  and ER types via flare-related processes, the LP and DDPL EB≥20keV  types via CME-related processes, and the UDPL type via CME-driven shocks.

Keywords: Solar energetic particles, Solar activity, Solar particle emission
Chemistry in Externally FUV-irradiated Disks in the Outskirts of the Orion Nebula Cluster. Most stars are born in stellar clusters, and their protoplanetary disks, which are the birthplaces of planets, can, therefore, be affected by the radiation of nearby massive stars. However, little is known about the chemistry of externally irradiated disks, including whether or not their properties are similar to the so-far better-studied isolated disks. Motivated by this question, we present ALMA Band 6 observations of two irradiated Class II protoplanetary disks in the outskirts of the Orion Nebula Cluster to explore the chemical composition of disks exposed to (external) far-ultraviolet (FUV) radiation fields: the 216-0939 disk and the binary system 253-1536A/B, which are exposed to radiation fields of 102–103 times the average interstellar radiation field. We detect lines from CO isotopologues, HCN, H2CO, and C2H toward both protoplanetary disks. Based on the observed disk-integrated line fluxes and flux ratios, we do not find significant differences between isolated and irradiated disks. The observed differences seem to be more closely related to the different stellar masses than to the external radiation field. This suggests that these disks are far enough away from the massive Trapezium stars, that their chemistry is no longer affected by external FUV radiation. Additional observations toward lower-mass disks and disks closer to the massive Trapezium stars are required to elucidate the level of external radiation required to make an impact on the chemistry of planet formation in different kinds of disks.

Keywords: Interstellar molecules, Astrochemistry, Circumstellar matter, Protoplanetary disks, Submillimeter astronomy
Statistical Validation of Multiple Related Data Sets—Case Study Using Interstellar Boundary Explorer Satellite Data. Space scientists often face the question of whether data collected by different instruments are measurements of the same source population. This paper proposes a statistical validation method for evaluating the agreement between such related data sets. It offers a detailed case study focused on validating a new data set from the Interstellar Boundary Explorer (IBEX) mission, which serves as a practical how-to guide for similar analyses. Since 2008, the IBEX satellite has been gathering data on heliospheric energetic neutral atoms (ENAs) while being exposed to various sources of background noise, such as cosmic rays and solar energetic particles. The IBEX mission initially released only a qualified triple-coincidence (qABC) data product, which was designed to provide observations of ENAs free of background contamination. Further measurements revealed that the qABC data were in fact susceptible to contamination, having relatively low ENA counts and high background rates. To mitigate this issue, the mission team recently considered releasing a certain qualified double-coincidence (qBC) data product, which has roughly twice the detection rate of the qABC data product. This paper presents a simulation-based validation of the new qBC data product against the already-released qABC data product. The results show that the qBCs can plausibly be said to be measuring the same source population as the qABCs up to an average absolute deviation of 3.6%. Visual diagnostics provide additional confirmation of source rate coherence across data products. The framework introduced here is general and can be applied to other validation problems both within and outside the field of space physics.

Keywords: Algorithms, Heliosphere, Astrostatistics
Particle Acceleration and Magnetic Field Amplification by Relativistic Shocks in Inhomogeneous Media. Particle acceleration and magnetic field amplification in relativistic shocks propagating in inhomogeneous media are investigated by three-dimensional magnetohydrodynamical (MHD) simulations and test-particle simulations. The MHD simulations show that the interaction between the relativistic shock and dense clumps amplifies the downstream magnetic field to the value expected from observations of the gamma-ray burst. The test-particle simulations in the electromagnetic field given by the MHD simulation show that particles are accelerated by the downstream turbulence and the relativistic shock. We provide the injection energy to the shock acceleration in this system. If the amplitude of upstream density fluctuations is sufficiently large, low-energy particles are initially accelerated to the injection energy by the downstream turbulence and then rapidly accelerated to higher energies by the relativistic shock. Therefore, the density fluctuation significantly affects particle acceleration in the relativistic shock.

Keywords: Magnetohydrodynamics, Gamma-ray bursts, High energy astrophysics, Plasma astrophysics, Shocks, Cosmic rays
The Complete CEERS Early Universe Galaxy Sample: A Surprisingly Slow Evolution of the Space Density of Bright Galaxies at z ∼ 8.5–14.5. We present a sample of 88 candidate z ∼ 8.5–14.5 galaxies selected from the completed NIRCam imaging from the Cosmic Evolution Early Release Science survey. These data cover ∼90 arcmin2 (10 NIRCam pointings) in six broadband imaging filters and one medium-band imaging filter. With this sample we confirm at higher confidence early JWST conclusions that bright galaxies in this epoch are more abundant than predicted by most theoretical models. We construct the rest-frame ultraviolet luminosity functions at z ∼ 9, 11, and 14 and show that the space density of bright (M UV = ‑20) galaxies changes only modestly from z ∼ 14 to z ∼ 9, compared to a steeper increase from z ∼ 8 to z ∼ 4. While our candidates are photometrically selected, spectroscopic follow-up has now confirmed 13 of them, with only one significant interloper, implying that the fidelity of this sample is high. Successfully explaining the evidence for a flatter evolution in the number densities of UV-bright z &gt; 10 galaxies may thus require changes to the dominant physical processes regulating star formation. While our results indicate that significant variations of dust attenuation with redshift are unlikely to be the dominant factor at these high redshifts, they are consistent with predictions from models that naturally have enhanced star formation efficiency and/or stochasticity. An evolving stellar initial mass function could also bring model predictions into better agreement with our results. Deep spectroscopic follow-up of a large sample of early galaxies can distinguish between these competing scenarios.

Keywords: Luminosity function, Early universe, Galaxy formation, Galaxy evolution
Indefinitely Flat Circular Velocities and the Baryonic Tully─Fisher Relation from Weak Lensing. We use a new deprojection formula to infer the gravitational potential around isolated galaxies from weak gravitational lensing. The results imply circular velocity curves that remain flat for hundreds of kiloparsecs, greatly extending the classic result from 21 cm observations. Indeed, there is no clear hint of a decline out to 1 Mpc, well beyond the expected virial radii of dark matter halos. Binning the data by mass reveals a correlation with the flat circular speed that closely agrees with the baryonic Tully─Fisher relation known from kinematic data. These results apply to both early- and late-type galaxies, indicating a common universal behavior.

Keywords: Weak gravitational lensing, Galaxy rotation curves, Scaling relations
Formation of a Magnetic Cloud from the Merging of Two Successive Coronal Mass Ejections. On 2022 March 28 two successive coronal mass ejections (CMEs) were observed by multiple spacecraft and resulted in a magnetic cloud (MC) at 1 au. We investigate the propagation and interaction properties of the two CMEs correlated with the MC using coordinated multipoint remote sensing and in situ observations from Solar Orbiter, STEREO-A, Solar and Heliospheric Observatory, and Wind. The first CME was triggered by a filament eruption with a high inclination angle. Roughly 9 hr later, the second CME originating from the same active region erupted with a smaller tilt angle and faster speed compared to the first one. The second CME overtook the preceding CME and formed a merged front at approximately 75 R ☉, which developed into a complex ejecta at 1 au. The descending speed and low proton temperature inside the complex ejecta suggest that the two CMEs have fully merged before reaching 1 au, leading them to begin expanding rather than compressing against each other. The complex ejecta appears to have the magnetic field and plasma signatures of an MC, although there is a discontinuity in the magnetic field implying previous interactions. The cross section of the complex ejecta, reconstructed from in situ data using a Grad–Shafranov technique, exhibits a right-handed flux rope structure. These results highlight that an MC-like complex ejecta lacking interaction features could arise from the complete merging of two CMEs.

Keywords: Solar-terrestrial interactions, Solar wind, Solar coronal mass ejections