Sazuna/UAT_keywords huggingface dataset:
Probing the High-frequency Variability of NGC 5044: The Key to Active Galactic Nucleus Feedback. The active galactic nucleus (AGN) feeding and feedback process in the centers of galaxy clusters and groups is still not well understood. NGC 5044 is the ideal system in which to study AGN feedback. It hosts the largest known reservoir of cold gas in any cool-core galaxy group, and features several past epochs of AGN feedback imprinted as cavities in the X-ray-bright intragroup medium, as well as parsec-scale jets. We present Submillimeter Array, Karl G. Jansky Very Large Array, James Clerk Maxwell Telescope, and Atacama Large Millimeter/submillimeter Array high-frequency observations of NGC 5044 to assess the time variability of the millimeter-wave band emission from the accretion disk, and quantify the spectral energy distribution (SED) from the radio to submillimeter band. The SED is well described by an advection-dominated accretion flow (ADAF) model and self-absorbed jet emission from an aging plasma with τ ∼ 1 kyr. We find a characteristic variability timescale of 150 days, which constrains the ADAF emission region to about 0.1 pc, and the magnetic field to ∼4.7 mG in the jets and 870 G in the accretion disk. Longer monitoring/sampling will allow to understand if the underlying process is truly periodic in nature.

Keywords: Radio active galactic nuclei, Low-luminosity active galactic nuclei, Accretion, Galaxy groups
Dark Photon Dark Matter and Low-frequency Gravitational-wave Detection with Gaia-like Astrometry. Astrometric surveys offer us a method for searching for elusive cosmic signatures, such as ultralight dark photon dark matter and gravitational waves (GWs), by observing the temporal change of stars' apparent locations. The detection capabilities of such surveys rapidly decrease at low frequencies, because the signals become hardly distinguishable from the background motion of stars. In this work, we find that the background motion can be well described by a linear model over time, based on which we propose a linear background subtraction scheme. Compared to the conventional quadratic subtraction, the advantage of linear subtraction emerges within the frequency range below 6 × 10‑9 Hz. Taking dark photons with purely gravitational interactions, dark photons with additional U(1) B  or U(1) B‑L  gauge interactions, and low-frequency GWs as examples, we illustrate that the linear subtraction scheme can result in an enhancement of more than 1 order of magnitude in the exclusion limits of Gaia-like experiments in the low-frequency range.

Keywords: Gravitational wave astronomy, Astrometry, Space astrometry, Gravitational waves, Gaia, Dark matter
Compact Binary Merger Rate with Modified Gravity in Dark Matter Spikes. In this study, we investigate the impact of modified gravity (MG) on the merger rate of compact binaries within dark matter spikes surrounding supermassive black holes (SMBHs). Specifically, we calculate the binary merger rates involving primordial black holes (PBHs) and/or neutron stars (NSs) in Hu–Sawicki f(R) gravity and the normal branch of Dvali–Gabadadze–Porrati (nDGP) gravity, with three SMBH mass functions: Benson, Vika, and Shankar. The results show consistently higher merger rates predicted for PBH–PBH and PBH–NS binaries in these gravity models compared to general relativity (GR), in particular at lower SMBH masses and for steeper dark matter spike density profiles. The predicted merger rates are compared to the LIGO–Virgo–KAGRA observations in constraining the parameters of the theory. In particular, we find steeper dark matter spike density profiles in the MG scenarios compared to GR. When compared to current observational constraints on PBH abundance, the mass ranges allowed by Hu–Sawicki f(R) models are found to be wider than those allowed by nDGP models, for given merger rates. The results are highly dependent on the choice of SMBH mass function, with the Vika and Shankar mass functions predicting lower abundances. The considerable sensitivity of the results to the assumed gravity scenario and SMBH mass function demonstrates the necessity of incorporating the corresponding theoretical uncertainties when making relatively robust predictions on compact binary merger rates and, as a result, on PBH properties.

Keywords: Neutron stars, Gravitation, Cold dark matter, Gravitational waves, Primordial black holes
The Magnetic Field in Quiescent Star-forming Filament G16.96+0.27. We present 850 μm thermal dust polarization observations with a resolution of 14.″4 (∼0.13 pc) toward an infrared dark cloud G16.96+0.27 using James Clerk Maxwell Telescope/POL-2. The average magnetic field orientation, which roughly agrees with the larger-scale magnetic field orientation traced by the Planck 353 GHz data, is approximately perpendicular to the filament structure. The estimated plane-of-sky magnetic field strength is ∼96 μG and ∼60 μG using two variants of the Davis–Chandrasekhar–Fermi methods. We calculate the virial and magnetic critical parameters to evaluate the relative importance of gravity, the magnetic field, and turbulence. The magnetic field and turbulence are both weaker than gravity, but magnetic fields and turbulence together are equal to gravity, suggesting that G16.96+0.27 is in a quasi-equilibrium state. The alignment between the magnetic field and cloud is found to have a trend moving away from perpendicularity in the dense regions, which may serve as a tracer of potential fragmentation in such quiescent filaments.

Keywords: Interstellar filaments, Infrared dark clouds, Molecular clouds, Star formation, Magnetic fields
Chemical Pathways of SO<SUB>2</SUB> with Hydrogen Atoms on Interstellar Ice Analogues. Sulfur dioxide (SO2) is a sulfur-containing molecule expected to exist as a solid in the interstellar medium. In this study, we have performed laboratory experiments and computational studies on the surface reactions of solid SO2 with hydrogen atoms on amorphous solid water (ASW) at low temperatures. After 40 minutes of exposure of SO2 deposited on ASW to H atoms, approximately 80% of the solid SO2 was lost from the substrate at 10–40 K, and approximately 50% even at 60 K, without any definite detection of reaction products. Quantum chemical calculations suggest that H atoms preferentially add to the S atom of solid SO2, forming the HSO2 radical. Further reactions of the HSO2 radical with H atoms result in the formation of several S-bearing species, including HS(O)OH, the S(O)OH radical, HO–S–OH, HS–OH, and H2S. In codeposition experiments involving H and SO2, we have confirmed the formation of H2S, HS(O)OH, and/or HO–S–OH. However, the yields of these S-bearing species are insufficient to account for the complete loss of the initial SO2 reactant. These findings suggest that some products are desorbed into the gas phase upon formation. This study indicates that a portion of the SO2 in ice mantles may remain unreacted, avoiding hydrogenation, while the remainder is converted into other species, some of which may be subject to chemical desorption.

Keywords: Pre-biotic astrochemistry, Astrochemistry
Using the Ca II Lines in T Tauri Stars to Infer the Abundance of Refractory Elements in the Innermost Disk Region. We present a study of the abundance of calcium in the innermost disk of 70 T Tauri stars in the star-forming regions of Chamaeleon I, Lupus, and Orion OB1b. We use calcium as a proxy for the refractory material that reaches the inner disk. We used magnetospheric accretion models to analyze the Ca II emission lines and estimate abundances in the accretion flows of the stars, which feed from the inner disks. We find Ca depletion in disks of all three star-forming regions, with 57% of the sample having [Ca/H] &lt; ─0.30 relative to the solar abundance. All disks with cavities and/or substructures show depletion, consistent with trapping of refractories in pressure bumps. Significant Ca depletion ([Ca/H] &lt; ─0.30) is also measured in 60% of full disks, although some of those disks may have hidden substructures or cavities. We find no correlation between Ca abundance and stellar or disk parameters except for the mass accretion rate onto the star. This could suggest that the inner and outer disks are decoupled, and that the mass accretion rate is related to a mass reservoir in the inner disk, while refractory depletion reflects phenomena in the outer disk related to the presence of structure and forming planets. Our results of refractory depletion and timescales for depletion are qualitatively consistent with expectations of dust growth and radial drift, including partitioning of elements, and constitute direct evidence that radial drift of solids locked in pebbles takes place in disks.

Keywords: T Tauri stars, Protoplanetary disks, Chemical abundances
Could the Recent Rebrightening of the GW170817A Afterglow Be Caused by a Counterjet?. GRB 170817A (also GW170817) became the first binary neutron star merger event detected via gravitational waves and electromagnetic signals. Over the next 4 yr, various multiband observations have led to reimaging of the various short gamma-ray burst and interstellar medium interaction models. While these models successfully explain the observed afterglow until ∼900 days, a rebrightening or excess flux was observed in the 1 keV X-ray band after ∼1000 days. In this study, we reevaluate the jet parameters using new observations (until ∼1234 days) with a boosted fireball jet model. We study the observable effects of the counterjet for GRB 170817A, using our new afterglow code, FIREFLY. Our results show that it is indeed possible for the observed excess to coincide with the emissions from a counterjet (∼800 days). We also computed an empirical scaling law between the jet and counterjet peak emission timescales and the observer angle. The FIREFLY code can also track the simulated object through the observer's sky and numerically model the apparent motion. The calculated apparent motion (≈2.6c) does not match the observed apparent motion (5.2c‑7.5c). Hence we conclude that the excess flux of GRB 170817A may not be associated with a counterjet; however, it is not enough to reject this hypothesis from the traditional counterjet visibility timescale, which predicts ≥5000 days. The apparent motion, combined with the multiband lightcurves, is needed to break the degeneracy between the geometrical parameters and the microphysical parameters of the afterglow.

Keywords: Gamma-ray bursts, Hydrodynamics, High energy astrophysics, Relativistic jets, Gravitational waves
A New Rarity Assessment of the "Disk of Satellites": The Milky Way System Is the Exception Rather Than the Rule in the ΛCDM Cosmology. The majority of satellite galaxies around the Milky Way (MW) show disk-like distributions (the disk of satellites; DoS), which is a small-scale problem of the lambda cold dark matter cosmology. The conventional definition of the MW-like DoS is a satellite system with a minor-to-major axis ratio (c/a) lower than the MW's c/a value of 0.181. Here, we question the validity of the c/a-based DoS rarity assessment and propose an alternative approach. How satellites are placed around a galaxy is dictated mainly by two factors: the distributions of the satellites' orbital poles and their distances from the host. Based on this premise, we construct the "satellite distribution generator" code and generate 105 spatially and kinematically analogous systems (SKASs) sharing these two factors. The SKAS can disclose the intrinsic, underlying c/a probability distribution function (PDF), from which a present-day c/a value is fortuitously determined. We find that the c/a PDF of the MW DoS defined by 11 classical satellites is quite broad (σ  c/a  ∼ 0.105), implying that a simple present-day c/a value, combined with its highly time-variable nature, cannot fully represent the degree of flatness. Moreover, based on the intrinsic c/a PDF, we reevaluate the rarity of the MW DoS by comparing it with Illustris TNG50-1 host–satellite systems and find that even with the new measure, the MW DoS remains rare (0.00%–3.40%). We show that the reason behind the rareness is that both orbital poles and distances of the 11 MW satellites are far more plane-friendly than those of simulated host–satellite systems, challenging the current structure and galaxy formation model.

Keywords: Dwarf galaxies, Galaxy kinematics, Milky Way dynamics
Applying the Velocity Gradient Technique in NGC 1333: Comparison with Dust Polarization Observations. Magnetic fields (B-fields) are ubiquitous in the interstellar medium (ISM), and they play an essential role in the formation of molecular clouds and subsequent star formation. However, B-fields in interstellar environments remain challenging to measure, and their properties typically need to be inferred from dust polarization observations over multiple physical scales. In this work, we seek to use a recently proposed approach called the velocity gradient technique (VGT) to study B-fields in star-forming regions and compare the results with dust polarization observations in different wavelengths. The VGT is based on the anisotropic properties of eddies in magnetized turbulence to derive B-field properties in the ISM. We investigate that this technique is synergistic with dust polarimetry when applied to a turbulent diffused medium for the purpose of measuring its magnetization. Specifically, we use the VGT on molecular line data toward the NGC 1333 star-forming region (12CO, 13CO, C18O, and N2H+), and we compare the derived B-field properties with those inferred from 214 and 850 μm dust polarization observations of the region using Stratospheric Observatory for Infrared Astronomy/High-Resolution Airborne Wide-band Camera Plus and James Clerk Maxwell Telescope/POL-2, respectively. We estimate both the inclination angle and the 3D Alfvénic Mach number M A from the molecular line gradients. Crucially, testing this technique on gravitationally bound, dynamic, and turbulent regions, and comparing the results with those obtained from polarization observations at different wavelengths, such as the plane-of-sky field orientation, is an important test on the applicability of the VGT in various density regimes of the ISM. We in general do not find a close correlation between the velocity gradient inferred orientations and the dust inferred magnetic field orientations.

Keywords: Interstellar magnetic fields, Diffuse nebulae, Interstellar medium
Multiwavelength Campaign Observations of a Young Solar-type Star, EK Draconis. II. Understanding Prominence Eruption through Data-driven Modeling and Observed Magnetic Environment. EK Draconis, a nearby young solar-type star (G1.5V, 50–120 Myr), is known as one of the best proxies for inferring the environmental conditions of the young Sun. The star frequently produces superflares, and Paper I presented the first evidence of an associated gigantic prominence eruption observed as a blueshifted Hα Balmer line emission. In this paper, we present the results of the dynamical modeling of the stellar eruption and examine its relationship to the surface starspots and large-scale magnetic fields observed concurrently with the event. By performing a 1D freefall dynamical model and a 1D hydrodynamic simulation of the flow along the expanding magnetic loop, we found that the prominence eruption likely occurred near the stellar limb (12 -16  degrees from the limb) and was ejected at an angle of  -24  degrees relative to the line of sight, and the magnetic structures can expand into a coronal mass ejection. The observed prominence displayed a terminal velocity of ∼0 km s‑1 prior to disappearance, complicating the interpretation of its dynamics in Paper I. The models in this paper suggest that prominence's Hα intensity diminishes at around or before its expected maximum height, explaining the puzzling time evolution in observations. The Transiting Exoplanet Survey Satellite light curve modeling and (Zeeman) Doppler Imaging revealed large midlatitude spots with polarity inversion lines and one polar spot with dominant single polarity, all near the stellar limb during the eruption. This suggests that midlatitude spots could be the source of the gigantic prominence we reported in Paper I. These results provide valuable insights into the dynamic processes that likely influenced the environments of early Earth, Mars, Venus, and young exoplanets.

Keywords: Starspots, Solar analogs, Stellar x-ray flares, G dwarf stars, Zeeman-Doppler imaging, Doppler imaging, Flare stars, Stellar flares, Optical flares, Stellar coronal mass ejections
Eridanus III and DELVE 1: Carbon-rich Primordial Star Clusters or the Smallest Dwarf Galaxies?. We present spectroscopy of the ultra-faint Milky Way satellites Eridanus III (Eri III) and DELVE 1. We identify eight member stars in each satellite and place nonconstraining upper limits on their velocity and metallicity dispersions. The brightest star in each object is very metal poor, at [Fe/H] = ‑3.1 for Eri III and [Fe/H] = ‑2.8 for DELVE 1. Both of these stars exhibit large overabundances of carbon and very low abundances of the neutron-capture elements Ba and Sr, and we classify them as CEMP-no stars. Because their metallicities are well below those of the Milky Way globular cluster population, and because no CEMP-no stars have been identified in globular clusters, these chemical abundances could suggest that Eri III and DELVE 1 are dwarf galaxies. On the other hand, the two systems have half-light radii of 8 pc and 6 pc, respectively, which are more compact than any known ultra-faint dwarfs. We conclude that Eri III and DELVE 1 are either the smallest dwarf galaxies yet discovered, or they are representatives of a new class of star clusters that underwent chemical evolution distinct from that of ordinary globular clusters. In the latter scenario, such objects are likely the most primordial star clusters surviving today. These possibilities can be distinguished by future measurements of carbon and/or iron abundances for larger samples of stars or improved stellar kinematics for the two systems. *This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: Globular star clusters, Nucleosynthesis, Galaxy chemical evolution, Stellar abundances, R-process, Dwarf galaxies, CEMP stars
BASS. XLI. The Correlation between Mid-infrared Emission Lines and Active Galactic Nuclei Emission. We analyze Spitzer spectra of 140 active galactic nuclei (AGN) detected in the hard X-rays (14─195 keV) by the Burst Alert Telescope on board Swift. This sample allows us to probe several orders of magnitude in black hole masses (106─109 M ⊙), Eddington ratios (10−3─1), X-ray luminosities (1042─1045 erg s−1), and X-ray column densities (1020─1024 cm−2). The AGN emission is expected to be the dominant source of ionizing photons with energies ≳50 eV, and therefore, high-ionization mid-infrared (MIR) emission lines such as [Ne V] 14.32, 24.32 μm and [O IV] 25.89 μm are predicted to be good proxies of AGN activity, and robust against obscuration effects. We find high detection rates (≳85%─90%) for the MIR coronal emission lines in our AGN sample. The luminosities of these lines are correlated with the 14─150 keV luminosity (with a typical scatter of σ ∼0.4─0.5 dex), strongly indicating that the MIR coronal line (CL) emission is driven by AGN activity. CLs are also tightly correlated to the bolometric luminosity (σ ∼0.2─0.3 dex), calculated from careful analysis of the spectral energy distribution. We find that the relationship between the CL strengths and L 14─150 keV is independent of black hole mass, AGN luminosity, and Eddington ratio, and mostly not affected by high X-ray column densities. This confirms that the MIR CLs can be used as unbiased tracers of the AGN power for X-ray luminosities in the 1042─1045 erg s−1 range.

Keywords: Active galactic nuclei, High energy astrophysics, Galaxy nuclei
Chemistry in the GG Tau A Disk: Constraints from H<SUB>2</SUB>D<SUP>+</SUP>, N<SUB>2</SUB>H<SUP>+</SUP>, and DCO<SUP>+</SUP> High Angular Resolution ALMA Observations. Resolved molecular line observations are essential for gaining insight into the physical and chemical structure of protoplanetary disks, particularly in cold, dense regions where planets form and acquire their chemical compositions. However, tracing these regions is challenging because most molecules freeze onto grain surfaces and are not observable in the gas phase. We investigated cold molecular chemistry in the triple stellar T Tauri disk GG Tau A, which harbours a massive gas and dust ring and an outer disk, using Atacama Large Millimeter/submillimeter Array (ALMA) Band 7 observations. We present high angular resolution maps of N2H+ and DCO+ emission, with upper limits reported for H2D+, 13CS, and SO2. The radial intensity profile of N2H+ shows most emission near the ring's outer edge, while DCO+ exhibits a double peak, one near the ring's inner edge and the other in the outer disk. With complementary observations of lower-lying transitions, we constrained the molecular surface densities and rotation temperatures. We compared the derived quantities with model predictions across different cosmic-ray ionization (CRI) rates, carbon-to-oxygen (C/O) ratios, and stellar UV fluxes. Cold molecular chemistry, affecting the N2H+, DCO+, and H2D+ abundances, is most sensitive to the CRI rate, while the stellar UV fluxes and C/O ratios have minimal impact on these three ions. Our best model requires a low CRI rate of 10‑18 s‑1. However, it fails to match the low temperatures derived from N2H+ and DCO+, 12–16 K, which are much lower than the CO freezing temperature.

Keywords: Isotopic abundances, Protoplanetary disks, Planet formation, Astrochemistry
Small-scale Current Sheets and Associated Switchback Activity in the Inner Heliosphere. Several long-standing theories postulate that turbulent dissipation can heat solar wind protons in situ. Turbulent dissipation can occur via current sheets, which are small-scale structures embedded in the solar wind magnetic field. This study examines the role that switchbacks—intermediate-scale reversals in the interplanetary magnetic field—may play in heating the solar wind by generating current sheets. We explore this possible relationship by analyzing the characteristics of current sheets within and around switchback regions. Previous studies investigated current sheet properties during Parker Solar Probe's first solar encounter, analyzed current sheets using a wide range of statistics, and explored trends that switchbacks follow with radial distance from the Sun. The present study builds on these works by analyzing the distribution and maximum values of solar wind current sheets using the Partial Variance of Increments method and focusing on how these properties correlate with the presence of switchbacks to better understand how switchbacks contribute to current sheet activity. We conclude that there are no increased current sheet populations observed within and around switchbacks, with most current sheets being observed outside switchbacks. We find a consistent distribution of current sheets regardless of whether there is concurrent switchback activity. We also observe that current sheets follow a uniform occurrence rate with increased distance from the Sun, while switchback regions significantly evolve with larger radial distances. Our findings suggest that local turbulence may be responsible for generating solar wind current sheets and does so with the same efficiency inside and outside of switchback regions.

Keywords: Space plasmas, Solar wind, Solar coronal heating, Solar physics