Sazuna/UAT_keywords huggingface dataset:
Ultra-relativistic Electron Acceleration during High-intensity Long-duration Continuous Auroral Electrojet Activity Events. Magnetospheric relativistic electrons are accelerated during substorms and strong convection events that occur during high-intensity long-duration continuous auroral electrojet activity (HILDCAA) events, associated with solar wind high-speed streams (coming from coronal holes). From an analysis of ∼2–20 MeV electrons at L ∼ 2–7 measured by the Van Allen Probe satellite, it is shown that ∼3.4–4.1 days long HILDCAA events are characterized by ∼7.2 MeV electron acceleration in the L ∼ 4.0–6.0 region, which occurs ∼2.9–3.4 days after the onset of HILDCAA. The dominant acceleration process is due to wave–particle interactions between magnetospheric electromagnetic chorus waves and substorm-injected ∼100 keV electrons. The longer the HILDCAA and chorus last, the higher the maximum energy of the accelerated relativistic electrons. The acceleration to higher and higher energies is due to a bootstrap mechanism.

Keywords: Interplanetary medium, Van Allen radiation belts, Interplanetary magnetic fields, Solar coronal mass ejections, Solar activity, Solar storm
The Carbon Isotopic Ratio and Planet Formation. We present the first detection of 13CCH in a protoplanetary disk (TW Hya). Using observations of C2H, we measure CCH/13CCH = 65 ± 20 gas with a CO isotopic ratio of 12CO/13CO = 21 ± 5. The TW Hya disk exhibits a gas phase C/O that exceeds unity, and C2H is the tracer of this excess carbon. We confirm that the TW Hya gaseous disk exhibits two separate carbon isotopic reservoirs, as noted previously. We explore two theoretical solutions for the development of this dichotomy. One model represents TW Hya today with a protoplanetary disk exposed to a cosmic-ray ionization rate that is below interstellar as consistent with current estimates. We find that this model does not have sufficient ionization in cold (T &lt; 40 K) layers to activate carbon isotopic fractionation. The second model investigates a younger TW Hya protostellar disk exposed to an interstellar cosmic-ray ionization rate. We find that the younger model has sources of ionization deeper in a colder disk that generates two independent isotopic reservoirs. One reservoir is 12C-enriched carried by methane/hydrocarbon ices, and the other is 13C-enriched carried by gaseous CO. The former potentially provides a source of methane/hydrocarbon ices to power the chemistry that generates the anomalously strong C2H emission in this (and other) disk systems in later stages. The latter provides a source of gaseous 13C-rich material to generate isotopic enrichments in forming giant planets, as recently detected in the super-Jupiter TYC 8998-760-1 b by Zhang et al.

Keywords: Protoplanetary disks
Detecting Gravitational Wave Bursts from Stellar-mass Binaries in the mHz Band. The dynamical formation channels of gravitational wave (GW) sources typically involve a stage when the compact object binary source interacts with the environment, which may excite its eccentricity, yielding efficient GW emission. For the wide eccentric compact object binaries, the GW emission happens mostly near the pericenter passage, creating a unique, burst-like signature in the waveform. This work examines the possibility of stellar-mass bursting sources in the mHz band for future LISA detections. Because of their long lifetime (∼107 yr) and promising detectability, the number of mHz bursting sources can be large in the local Universe. For example, based on our estimates, there will be ∼3–45 bursting binary black holes in the Milky Way, with ∼102–104 bursts detected during the LISA mission. Moreover, we find that the number of bursting sources strongly depends on their formation history. If certain regions undergo active formation of compact object binaries in the recent few million years, there will be a significantly higher bursting source fraction. Thus, the detection of mHz GW bursts not only serves as a clue for distinguishing different formation channels, but also helps us understand the star formation history in different regions of the Milky Way.

Keywords: Gravitational wave astronomy, Compact binary stars
Interstellar Detection of O-protonated Carbonyl Sulfide, HOCS<SUP>+</SUP>. We present the first detection in space of O-protonated carbonyl sulfide (HOCS+), in the midst of an ultradeep molecular line survey toward the G+0.693-0.027 molecular cloud. From the observation of all K  a  = 0 transitions ranging from J  lo  = 2 to J  lo  = 13 of HOCS+ covered by our survey, we derive a column density of N = (9 ± 2) × 1012 cm‑2, translating into a fractional abundance relative to H2 of ∼7 × 10‑11. Conversely, the S-protonated HSCO+ isomer remains undetected, and we derive an upper limit to its abundance with respect to H2 of ≤3 × 10‑11, a factor of ≥2.3 less abundant than HOCS+. We obtain an HOCS+/OCS ratio of ∼2.5 × 10‑3, in good agreement with the prediction of astrochemical models. These models show that one of the main chemical routes to the interstellar formation of HOCS+ is likely the protonation of OCS, which appears to be more efficient at the oxygen end. Also, we find that high values of cosmic-ray ionization rates (10‑15–10‑14 s‑1) are needed to reproduce the observed abundance of HOCS+. In addition, we compare the O/S ratio across different interstellar environments. G+0.693-0.027 appears as the source with the lowest O/S ratio. We find an HOCO+/HOCS+ ratio of ∼31, in accordance with other O/S molecular pairs detected toward this region and also close to the O/S solar value (∼37). This fact indicates that S is not significantly depleted within this cloud due to the action of large-scale shocks, unlike in other sources where S-bearing species remain trapped on icy dust grains.

Keywords: Interstellar molecules, Galactic center, Spectral line identification, Astrochemistry, Interstellar clouds
Developing an Automated Detection, Tracking, and Analysis Method for Solar Filaments Observed by CHASE via Machine Learning. Studies on the dynamics of solar filaments have significant implications for understanding their formation, evolution, and eruption, which are of great importance for space weather warning and forecasting. The Hα Imaging Spectrograph (HIS) on board the recently launched Chinese Hα Solar Explorer (CHASE) can provide full-disk solar Hα spectroscopic observations, which bring us an opportunity to systematically explore and analyze the plasma dynamics of filaments. The dramatically increased observation data require automated processing and analysis, which are impossible if dealt with manually. In this paper, we utilize the U-Net model to identify filaments and implement the Channel and Spatial Reliability Tracking algorithm for automated filament tracking. In addition, we use the cloud model to invert the line-of-sight velocity of filaments and employ the graph theory algorithm to extract the filament spine, which can advance our understanding of the dynamics of filaments. The favorable test performance confirms the validity of our method, which will be implemented in the following statistical analyses of filament features and dynamics of CHASE/HIS observations.

Keywords: Convolutional neural networks, Solar filaments, Astronomy image processing
On the Origin of the Sudden Heliospheric Open Magnetic Flux Enhancement During the 2014 Pole Reversal. Coronal holes are recognized as the primary sources of heliospheric open magnetic flux (OMF). However, a noticeable gap exists between in situ measured OMF and that derived from remote-sensing observations of the Sun. In this study, we investigate the OMF evolution and its connection to solar structures throughout 2014, with special emphasis on the period from September to October, where a sudden and significant OMF increase was reported. By deriving the OMF evolution at 1 au, modeling it at the source surface, and analyzing solar photospheric data, we provide a comprehensive analysis of the observed phenomenon. First, we establish a strong correlation between the OMF increase and the solar magnetic field derived from a potential-field source-surface model (cc Pearson = 0.94). Moreover, we find a good correlation between the OMF and the open flux derived from solar coronal holes (cc Pearson = 0.88), although the coronal holes only contain 14%─32% of the Sun's total open flux. However, we note that while the OMF evolution correlates with coronal hole open flux, there is no correlation with the coronal hole area evolution (cc Pearson = 0.0). The temporal increase in OMF correlates with the vanishing remnant magnetic field at the southern pole, caused by poleward flux circulations from the decay of numerous active regions months earlier. Additionally, our analysis suggests a potential link between the OMF enhancement and the concurrent emergence of the largest active region in solar cycle 24. In conclusion, our study provides insights into the strong increase in OMF observed during 2014 September─October.

Keywords: Solar physics, Solar magnetic fields, Heliosphere
Fast Outflows and Luminous He II Emission in Dwarf Galaxies with Active Galactic Nuclei (AGN). While stellar processes are believed to be the main source of feedback in dwarf galaxies, the accumulating discoveries of active galactic nuclei (AGN) in dwarf galaxies over recent years arouse the interest to also consider AGN feedback in them. Fast, AGN-driven outflows, a major mechanism of AGN feedback, have indeed been discovered in dwarf galaxies and may be powerful enough to provide feedback to their dwarf hosts. In this paper, we search for outflows traced by the blueshifted ultraviolet absorption features in three dwarf galaxies with AGN from the sample examined in our previous ground-based study. We confirm outflows traced by blueshifted absorption features in two objects and tentatively detect an outflow in the third object. In one object where the outflow is clearly detected in multiple species, photoionization modeling suggests that this outflow is located ∼0.5 kpc from the AGN, implying a galactic-scale impact. This outflow is much faster and possesses a higher kinetic energy outflow rate than starburst-driven outflows in sources with similar star formation rates, and is likely energetic enough to provide negative feedback to its host galaxy as predicted by simulations. Much broader (∼4000 km s‑1) absorption features are also discovered in this object, which may have the same origin as that of broad absorption lines in quasars. Additionally, strong He II λ1640 emission is detected in both objects where the transition falls in the wavelength coverage and is consistent with an AGN origin. In one of these two objects, a blueshifted He II λ1640 emission line is clearly detected, likely tracing a highly ionized AGN wind.

Keywords: AGN host galaxies, Galactic winds, Dwarf galaxies, Ultraviolet spectroscopy
[O IV]- and [Ne V]-weak Active Galactic Nuclei Hidden by Compton-thick Material in Late Mergers. We study "buried" active galactic nuclei (AGNs) almost fully covered by circumnuclear material in ultra/luminous infrared galaxies (U/LIRGs), which show weak ionized lines from narrow-line regions. Employing an indicator of a [O IV] 25.89 or [Ne V] 14.32 μm line to 12 μm AGN luminosity ratio, we find 17 buried AGN candidates that are [O IV]-weak (L [O IV]/L 12,AGN ≤ ‑3.0) or [Ne V]-weak (L [Ne V]/L 12,AGN ≤ ‑3.4) among 30 AGNs in local U/LIRGs. For the [O IV]-weak AGNs, we estimate their covering fractions of Compton-thick (CT; N H ≥ 1024 cm‑2) material with an X-ray clumpy torus model to be ${f}_{\mathrm{CT}}^{(\mathrm{spec})}=0.55\pm 0.19$ on average. This value is consistent with the fraction of CT AGNs ( ${f}_{\mathrm{CT}}^{(\mathrm{stat})}=53 \% \pm 12 \% $ ) among the [O IV]-weak AGNs in U/LIRGs and much larger than that in Swift/Burst Alert Telescope (BAT) AGNs (23% ± 6%). The fraction of [O IV]-weak AGNs increases from ${27}_{-10}^{+13} \% $ (early) to ${66}_{-12}^{+10} \% $ (late mergers). Similar results are obtained with the [Ne V] line. The [O IV]- or [Ne V]-weak AGNs in late mergers show larger N H and Eddington ratios (λ Edd) than those of the Swift/BAT AGNs, and the largest N H is ≳1025 cm‑2 at $\mathrm{log}{\lambda }_{\mathrm{Edd}}\sim -1$ , close to the effective Eddington limit for CT material. These suggest that (1) the circumnuclear material in buried AGNs is regulated by the radiation force from high-λ Edd AGNs on the CT obscurers, and (2) their dense material with large ${f}_{\mathrm{CT}}^{(\mathrm{spec})}$ (∼0.5 ± 0.1) in U/LIRGs is a likely cause of a unique structure of buried AGNs, whose amount of material may be maintained through merger-induced supply from their host galaxies.

Keywords: Supermassive black holes, Infrared astronomy, X-ray active galactic nuclei, Active galactic nuclei, Infrared galaxies
The Origin of Kinematically Persistent Planes of Satellites as Driven by the Early Evolution of the Cosmic Web in ΛCDM. Kinematically persistent planes (KPPs) of satellites are fixed sets of satellites co-orbiting around their host galaxy, whose orbital poles are conserved and clustered across long cosmic time intervals. They play the role of "skeletons," ensuring the long-term durability of positional planes. We explore the physical processes behind their formation in terms of the dynamics of the local cosmic web (CW), characterized via the so-called Lagrangian volumes (LVs) built up around two zoom-in, cosmological hydro-simulations of Milky Way–mass disk galaxy + satellites systems, where three KPPs have been identified. By analyzing the LV deformations in terms of the reduced tensor of inertia (TOI), we find an outstanding alignment between the LV principal directions and the KPP satellites' orbital poles. The most compressive local mass flows (along the ${\hat{e}}_{3}$ eigenvector) are strong at early times, feeding the so-called ${\hat{e}}_{3}$ -structure, while the smallest TOI axis rapidly decreases. The ${\hat{e}}_{3}$ -structure collapse marks the end of this regime and is the timescale for the establishment of satellite orbital pole clustering when the Universe is ≲4 Gyr old. KPP protosatellites aligned with ${\hat{e}}_{3}$ are those whose orbital poles are either aligned from early times or have been successfully bent at ${\hat{e}}_{3}$ -structure collapse. KPP satellites associated with ${\hat{e}}_{1}$ tend to have early trajectories already parallel to ${\hat{e}}_{3}$ . We show that KPPs can arise as a result of the ΛCDM-predicted large-scale dynamics acting on particular sets of protosatellites, the same dynamics that shape the local CW environment.

Keywords: Galaxy planes, Large-scale structure of the universe, Dwarf galaxies, Galaxy kinematics, Cosmic web
Secondary Whistler and Ion-cyclotron Instabilities Driven by Mirror Modes in Galaxy Clusters. Electron cyclotron waves (whistlers) are commonly observed in plasmas near Earth and the solar wind. In the presence of nonlinear mirror modes, bursts of whistlers, usually called lion roars, have been observed within low magnetic field regions associated with these modes. In the intracluster medium (ICM) of galaxy clusters, the excitation of the mirror instability is expected, but it is not yet clear whether electron and ion cyclotron (IC) waves can also be present under conditions where gas pressure dominates over magnetic pressure (high β). In this work, we perform fully kinetic particle-in-cell simulations of a plasma subject to a continuous amplification of the mean magnetic field B (t) to study the nonlinear stages of the mirror instability and the ensuing excitation of whistler and IC waves under ICM conditions. Once mirror modes reach nonlinear amplitudes, both whistler and IC waves start to emerge simultaneously, with subdominant amplitudes, propagating in low- B regions, quasi-parallel to B (t). We show that the underlying source of excitation is the pressure anisotropy of electrons and ions trapped in mirror modes with loss-cone-type distributions. We also observe that IC waves play an essential role in regulating the ion pressure anisotropy at nonlinear stages. We argue that whistler and IC waves are a concomitant feature at late stages of the mirror instability even at high β, and therefore, expected to be present in astrophysical environments like the ICM. We discuss the implications of our results for collisionless heating and dissipation of turbulence in the ICM.

Keywords: Galaxy clusters, High energy astrophysics, Plasma astrophysics, Intracluster medium, Extragalactic magnetic fields
Merger-tree-based Galaxy Matching: A Comparative Study across Different Resolutions. We introduce a novel halo/galaxy matching technique between two cosmological simulations with different resolutions, which utilizes the positions and masses of halos along their subhalo merger tree. With this tool, we conduct a study of resolution biases through the galaxy-by-galaxy inspection of a pair of simulations that have the same simulation configuration but different mass resolutions, utilizing a suite of ILLUSTRISTNG simulations to assess the impact on galaxy properties. We find that, with the subgrid physics model calibrated for TNG100-1, subhalos in TNG100-1 (high resolution) have ≲0.5 dex higher stellar masses than their counterparts in the TNG100-2 (low resolution). It is also discovered that the subhalos with M gas ∼ 108.5 M ⊙ in TNG100-1 have ∼0.5 dex higher gas mass than those in TNG100-2. The mass profiles of the subhalos reveal that the dark matter masses of subhalos in TNG100-2 converge well with those from TNG100-1, except within 4 kpc of the resolution limit. The differences in stellar mass and hot gas mass are most pronounced in the central region. We exploit machine learning to build a correction mapping for the physical quantities of subhalos from low- to high-resolution simulations (TNG300-1 and TNG100-1), which enables us to find an efficient way to compile a high-resolution galaxy catalog even from a low-resolution simulation. Our tools can easily be applied to other large cosmological simulations, testing and mitigating the resolution biases of their numerical codes and subgrid physics models.

Keywords: Hydrodynamical simulations, Galaxy formation, Astronomical simulations
Constraining Protoplanetary Disk Winds from Forbidden Line Profiles with Simulation-based Inference. Protoplanetary disks (PPDs) are sites of vigorous hydrodynamic processes, such as accretion and outflows, and ultimately establish the conditions for the formation of planets. The properties of disk outflows are often inferred through the analysis of forbidden emission lines. These lines contain multiple overlapping components, tracing different emission regions with different processes that excite them: a high-velocity component (tracing a jet), a broad low-velocity component (LVC; tracing inner disk wind), and a narrow LVC (tracing the outer disk wind). They are also heavily contaminated by background spectral features. All of these challenges call into question the traditional approach of fitting Gaussian components to the line profiles and cloud the physical interpretation of those components. We introduce a novel statistical technique to analyze emission lines in PPDs. Simulation-based inference is a computationally efficient machine-learning technique that produces posterior distributions of the parameters (e.g., magnetic field, radiation sources, and geometry) of a representative wind model when given a spectrum without any prior assumption about line shapes (e.g., symmetry). In this pathfinder study, we demonstrate that this technique indeed accurately recovers the parameters from simulated spectra without noise and background. Future work will provide an analysis of the observed spectra.

Keywords: Convolutional neural networks, Protoplanetary disks, Spectroscopy
Shell-type Tidal Features Are More Frequently Detected in Slowly Rotating Early-type Galaxies than Stream- and Tail-type Features. To enhance our understanding of the impact of galaxy mergers on the kinematics of early-type galaxies (ETGs), we examine differences in specific stellar angular momentum within the half-light radius ( ${\lambda }_{{R}_{e}}$ ) among ETGs with different types of tidal features and those without such features. This is accomplished by categorizing tidal features, which serve as direct evidence of recent mergers, into shells, streams, and tails, through deep images from the DESI Legacy Survey, and by using MaNGA data for the analysis of the kinematics of 1244 ETGs at z &lt; 0.055. We find that ETGs with tidal features typically have reduced ${\lambda }_{{R}_{e}}$ values that are lower by 0.12 dex than ETGs without tidal features. ETGs with shells contribute most to the reduction in ${\lambda }_{{R}_{e}}$ . Consequently, nearly half of ETGs with shells are classified as slow rotators, a fraction that is more than twice as high as that of ETGs with tails or streams, and over three times higher than that of ETGs without tidal features. These trends generally remain valid even when ETGs are divided into several mass bins. Our findings support the idea that radial mergers, which are more effective at reducing ${\lambda }_{{R}_{e}}$ than circular mergers, are more closely associated with the formation of shells rather than streams or tails. The detection of shells in slightly more massive ETGs compared to streams and tails may be attributed to the fact that massive satellite galaxies are more likely to be accreted through radial orbits, due to the nature of dynamical friction.

Keywords: Galaxy properties, Galaxy rotation, Tidal tails, Galaxy kinematics, Galaxy mergers, Early-type galaxies
White Dwarf Merger Remnants: The DAQ Subclass. Four years after the discovery of a unique DAQ white dwarf with a hydrogen-dominated and carbon-rich atmosphere, we report the discovery of four new DAQ white dwarfs, including two that were not recognized properly in the literature. We find all five DAQs in a relatively narrow mass and temperature range of M = 1.14–1.19 M ⊙ and T eff = 13,000–17,000 K. In addition, at least two show photometric variations due to rapid rotation with ≈10 minute periods. All five are also kinematically old, but appear photometrically young, with estimated cooling ages of about 1 Gyr based on standard cooling tracks, and their masses are roughly twice the mass of the most common white dwarfs in the solar neighborhood. These characteristics are smoking gun signatures of white dwarf merger remnants. Comparing the DAQ sample with warm DQ white dwarfs, we demonstrate that there is a range of hydrogen abundances among the warm DQ population and that the distinction between DAQ and warm DQ white dwarfs is superficial. We discuss the potential evolutionary channels for the emergence of the DAQ subclass, suggesting that DAQ white dwarfs are trapped on the crystallization sequence and may remain there for a significant fraction of the Hubble time.

Keywords: Stellar mergers, Stellar evolutionary types, White dwarf stars, Atmospheric composition, DQ stars