Sazuna/UAT_keywords huggingface dataset:
Simulating ULXs and Blazars as GRMHD Accretion Flows Around a Black Hole. General relativistic magnetohydrodynamic (GRMHD) simulations have been instrumental in our understanding of high-energy astrophysical phenomena over the past two decades. Their robustness and modularity make them a great tool for understanding the dynamics of various astrophysical objects. In this paper, we have used GRMHD simulations to understand the accretion flows of ultraluminous X-ray sources (ULXs) and blazars. ULXs are enigmatic sources that exhibit very high luminosities (super-Eddington for stellar mass black holes) even in their low-hard state. Numerical steady-state calculations have shown that this behavior can be explained by considering ULXs to be highly magnetized advective accretion sources around stellar-mass black holes. Our simulation confirms that such an accretion flow can indeed produce the high luminosities observed in ULXs. Further to continue toward the supermassive black holes, we have also modeled blazars and have used our simulation results to explain the apparent dichotomy in the two blazar classes: flat spectrum radio quasars (FSRQs) and BL Lacertae (BL Lacs). Our results show that FSRQ and BL Lacs show different spectral characteristics due to a difference in their magnetic field characteristics. The different categories of FSRQs and BL Lacs have also been explained by the interplay between the spin, magnetic field, and accretion rate of the central supermassive black hole.

Keywords: High energy astrophysics, Gravitation, Blazars, Relativistic jets, Ultraluminous x-ray sources, Stellar accretion disks, Magnetohydrodynamical simulations
Simulation of the Tianwen-4 Mission Contribution to Jupiter Gravity Field Improvement. This study comprehensively evaluates the impact of the expected Chinese Tianwen-4 mission, in conjunction with the existing data from the Juno mission, on enhancing the understanding of Jupiter's gravity field. Integrating simulated data from both missions. The methodology incorporates detailed simulations of Tianwen-4's orbit, assessing its influence on Jupiter's gravity field estimations across various orbital inclinations. It also explores the integration of multimission tracking data, combining simulated Juno and Tianwen-4 data. In addition to the static gravity coefficient, the analysis extends to include the tidal effect knm, which quantifies the tidal response of Jupiter's gravity field to forcing it by the Galilean satellites. The results indicate clear potential improvements in the precision of the gravity field models compared to those derived from the Juno mission alone, particularly in the lower degree harmonics, where accuracy improves by an average factor of 20.08 in the first 12°, gradually decreasing to 2.46, with an overall enhancement of 7.43. These enhancements underscore the value of integrating data from multiple missions, which provides a more nuanced understanding of Jupiter's gravitational properties. Improving the gravity field model is essential for gaining deeper insights into Jupiter's internal structure and dynamics, which ultimately enhances our understanding of giant planets and their formation. Accurate gravity models are crucial for interpreting a planet's physical and chemical properties, leading to better comprehension of planetary systems.

Keywords: Solid body tides, Gravitational fields, Natural satellites (Solar system), Jupiter, Orbit determination, Jovian satellites
Can the Dynamo of Spiral-arm Galaxies Be Explained by Anisotropic Conductivity?. The possibility of generating a magnetic field by a dynamo effect with anisotropic electrical conductivity rather than turbulent flow has been demonstrated theoretically and experimentally. If the electrical conductivity is anisotropic, the electrical currents will flow preferentially in certain directions rather than others, and a simple differential rotation will suffice to generate a magnetic field. In a galaxy with spiral arms, it is reasonable to assume that the electrical conductivity will be twice as large along the arms than in the perpendicular direction, suggesting the possibility of an anisotropic dynamo. However, a further geometrical criterion must be satisfied to obtain a dynamo. It is given by  , where p is the pitch angle of the spiral arms, with  , and   is the radial shear of the angular velocity. We find that the usual spiral-arm galaxies, which satisfy  , do not satisfy this dynamo condition because they have trailing arms instead of leading arms. Even galaxy NGC 4622, which has both trailing and leading arms, does not satisfy this dynamo condition either. This is confirmed by numerical simulations of the induction equation. Thus, for all spiral-arm galaxies known to date, the anisotropy of the spiral arms cannot explain the existence of galactic magnetic fields until further notice.

Keywords: Galaxy magnetic fields
Survival of the Fittest: Testing Superradiance Termination with Simulated Binary Black Hole Statistics. The superradiance instability of rotating black holes (BHs) leads to the formation of an ultralight boson cloud with distinctive observational signatures, making BHs an effective probe of ultralight bosons. However, around BHs in a binary system, the superradiance effect of such clouds can be terminated by tidal perturbations from the companion, leading to cloud depletion. In this study, we focus on the superradiance of a scalar boson, and perform the first analysis of the impact of this termination effect on superradiant BH binaries, which are realistically modeled after their statistics in our Galaxy. Working with a data set of approximately 107 BH binaries simulated using the Stellar Evolution for N-body population synthesis code, we identify the superradiant candidates and those that manage to survive the termination effect. We then calculate the cloud survival rate for various boson masses and BH spin models. Our findings reveal that the l = m = 1 cloud modes are generally stable against termination, whereas the l = m = 2 modes can be significantly affected, with survival rates dropping below 10% for boson masses below approximately 0.5 × 10‑12 eV. In addition, our analysis indicates that clouds that overcome termination typically exhibit a higher superradiant growth rate and therefore a higher detectability.

Keywords: Black hole physics, Black holes, Rotating black holes, Compact objects, Dark matter, Astrophysical black holes, Stellar evolution
A Scalable Gaussian Process Approach to Shear Mapping with MuyGPs. Analysis of cosmic shear is an integral part of understanding structure growth across cosmic time, which in turn provides us with information about the nature of dark energy. Conventional methods generate shear maps from which we can infer the matter distribution in the universe. Current methods (e.g., Kaiser–Squires inversion) for generating these maps, however, are tricky to implement and can introduce bias. Recent alternatives construct a spatial process prior for the lensing potential, which allows for inference of the convergence and shear parameters given lensing shear measurements. Realizing these spatial processes, however, scales cubically in the number of observations—an unacceptable expense as near-term surveys expect billions of correlated measurements. Therefore, we present a linearly scaling shear map construction alternative using a scalable Gaussian process prior called MuyGPs. MuyGPs avoids cubic scaling by conditioning interpolation on only nearest neighbors and fits hyperparameters using batched leave-one-out cross-validation. This work is the first step toward a full, scalable mass mapping method. We work in a simplified regime where we validate our method by interpolating and analyzing maps given noisy point-estimate data from all three shear fields, taken from a suite of N-body ray-tracing simulations. We also show that we can perform these operations at the scale of billions of galaxies on high-performance computing platforms.

Keywords: Cosmology, Weak gravitational lensing, Computational astronomy, Gaussian Processes regression, Gravitational lensing shear
The AURORA Survey: An Extraordinarily Mature, Star-forming Galaxy at z ∼ 7. We present the properties of a massive, large, dusty, metal-rich, star-forming galaxy at zspec = 6.73. GOODSN-100182 was observed with JWST/NIRSpec as part of the Assembly of Ultradeep Rest-optical Observations Revealing Astrophysics (AURORA) survey, and is also covered by public multiwavelength Hubble Space Telescope and JWST imaging. While the large stellar mass of GOODSN-100182 (∼1010 M⊙) was indicated prior to JWST, NIRCam rest-frame optical imaging now reveals the presence of an extended disk (reff ∼ 1.5 kpc). In addition, the NIRSpec R ∼ 1000 spectrum of GOODSN-100182 includes the detection of a large suite of rest-frame optical nebular emission lines ranging in wavelength from [O II] λ3727 up to [N II] λ6583. The ratios of Balmer lines suggest significant dust attenuation ( ), consistent with the red rest-frame UV slope inferred for GOODSN-100182 (β = ‑0.50 ± 0.09). The star formation rate based on dust-corrected Hα emission is  , well above the z ∼ 7 star-forming main sequence in terms of specific star formation rate. Strikingly, the ratio of [N II] λ6583/Hα emission suggests almost solar metallicity, as does the ratio ([O III] λ5007/Hβ)/([N II] λ6583/Hα) and the detection of the faint [Fe II] λ4360 emission feature. Overall, the excitation and ionization properties of GOODSN-100182 more closely resemble those of typical star-forming galaxies at z ∼ 2–3 rather than z ∼ 7. Based on public spectroscopy of the GOODS-N field, we find that GOODSN-100182 resides within a significant galaxy overdensity, and is accompanied by a spectroscopically confirmed neighbor galaxy. GOODSN-100182 demonstrates the existence of mature, chemically enriched galaxies within the first billion years of cosmic time, whose properties must be explained by galaxy formation models.

Keywords: Galaxy formation, High-redshift galaxies, Galaxy evolution, Emission line galaxies
Using Convolutional Neural Networks to Search for Strongly Lensed Quasars in KiDS DR5. Gravitationally strongly lensed quasars (SL-QSO) offer invaluable insights into cosmological and astrophysical phenomena. With the data from ongoing and next-generation surveys, thousands of SL-QSO systems can be discovered expectedly, leading to unprecedented opportunities. However, the challenge lies in identifying SL-QSO from enormous data sets with high recall and purity in an automated and efficient manner. Hence, we developed a program based on a convolutional neural network (CNN) for finding SL-QSO from large-scale surveys and applied it to the Kilo-degree Survey Data Release 5. Our approach involves three key stages: first, we preselected 10 million bright objects (with r-band MAG_AUTO &lt; 22), excluding stars from the data set; second, we established realistic training and test sets to train and fine-tune the CNN, resulting in the identification of 4195 machine candidates, and the false-positive rate of ∼1/2000 and recall of 0.8125 evaluated by using the real test set containing 16 confirmed lensed quasars; third, human inspections were performed for further selections, and then, 272 SL-QSO candidates were eventually found in total, including 16 high-score, 118 median-score, and 138 lower-score candidates, separately. Removing the systems already confirmed or identified in other papers, we end up with 229 SL-QSO candidates, including 7 high-score, 95 median-score, and 127 lower-score candidates, and the corresponding catalog is publicly available online (https://github.com/EigenHermit/H24). We have also included an excellent quad candidate in the Appendix, discovered serendipitously during the fine-tuning process of the CNN.

Keywords: Gravitational lensing
Starspot Distribution and Flare Events in Two Young Low-mass Stars Using TESS Data. Wide-field high-precision photometric observations such as the Transiting Exoplanet Survey Satellite (TESS) allowed the investigation of the stellar magnetic activity of cool stars. M dwarf starspots and stellar flares are the main indicators of magnetic activity. The present study focuses on modeling light curves (LCs) to analyze the distribution and characteristics of starspots, e.g., location, temperature, and spot size. The TESS LCs of two selected young M dwarfs, i.e., GJ 182 and 2MASS J05160212+2214528, were reconstructed using the Best rAndom StarSpots Model calculAtioN software, obtaining a three-spot model for GJ 182 and two-spot model for 2MASS J05160212+2214528, describing their LCs. For GJ 182, the mean spot temperature was estimated to be approximately 3279 K, covering 5%–8.5% of the stellar surface, while for 2MASS J05160212+2214528, the average spot temperature was approximately 2631 K, with a mean spottedness of about 5.4%. Using the 2 minute cadence LC data, we identified and analyzed 48 flare events from GJ 182, while no flares were detected in 2MASS J05160212+2214528. The estimated bolometric flare energy ranges from 1032 to 1035 erg, while in the TESS bandpass, it ranges from 1031 to 1033 erg. We derived the power-law index of ‑1.53 ± 0.12 and ‑1.86 ± 0.22 for flare frequency distribution in sectors 5 and 32, respectively, in the flare energy range 1033–1035 erg, consistent with previous studies for M dwarfs. A positive linear correlation between flare energy and duration was found with a slope of 0.67 ± 0.02, suggesting a similar mechanism followed by stellar superflares and solar flares. By assuming the similarities with solar flares, we also estimated a lower limit of the magnetic field strength of around 12–232 G to produce such superflare events.

Keywords: M dwarf stars, Starspots, Stellar activity, Stellar flares, Variable stars, Stellar rotation
Cosmological and Astrophysical Parameter Inference from Stacked Galaxy Cluster Profiles Using CAMELS-zoomGZ. We present a study on the inference of cosmological and astrophysical parameters using stacked galaxy cluster profiles. Utilizing the CAMELS-zoomGZ simulations, we explore how various cluster properties—such as X-ray surface brightness, gas density, temperature, metallicity, and Compton-y profiles—can be used to predict parameters within the 28-dimensional parameter space of the IllustrisTNG model. Through neural networks, we achieve a high correlation coefficient of 0.97 or above for all cosmological parameters, including Ωm, H0, and σ8, and over 0.90 for the remaining astrophysical parameters, showcasing the effectiveness of these profiles for parameter inference. We investigate the impact of different radial cuts, with bins ranging from 0.1R200c to 0.7R200c, to simulate current observational constraints. Additionally, we perform a noise sensitivity analysis, adding up to 40% Gaussian noise (corresponding to signal-to-noise ratios as low as 2.5), revealing that key parameters such as Ωm, H0, and the initial mass function slope remain robust even under extreme noise conditions. We also compare the performance of full radial profiles against integrated quantities, finding that profiles generally lead to more accurate parameter inferences. Our results demonstrate that stacked galaxy cluster profiles contain crucial information on both astrophysical processes within groups and clusters and the underlying cosmology of the Universe. This underscores their significance for interpreting the complex data expected from next-generation surveys and reveals, for the first time, their potential as a powerful tool for parameter inference.

Keywords: Cosmology, Galaxy clusters, Large-scale structure of the universe, Cosmological parameters, Cosmological parameters from large-scale structure
Physical Origins of Outflowing Cold Clouds in Local Star-forming Dwarf Galaxies. We study the physical origins of outflowing cold clouds in a sample of 14 low-redshift dwarf (M* ≲ 1010M⊙) galaxies from the Cosmic Origins Spectrograph Legacy Archive Spectroscopic SurveY (CLASSY) using Keck/ESI data. Outflows are traced by broad (FWHM ∼260 km s‑1) and very-broad (VB; FWHM ∼1200 km s‑1) velocity components in strong emission lines like [O III] λ5007 and Hα. The maximum velocities ( ) of broad components correlate positively with star formation rate, unlike the anticorrelation observed for VB components, and are consistent with superbubble models. In contrast, supernova-driven galactic wind models better reproduce the   of VB components. Direct radiative cooling from a hot wind significantly underestimates the luminosities of both broad and VB components. A multiphase wind model with turbulent radiative mixing reduces this discrepancy to at least 1 dex for most VB components. Stellar photoionization likely provides additional energy since broad components lie in the starburst locus of excitation diagnostic diagrams. We propose a novel interpretation of outflow origins in star-forming dwarf galaxies—broad components trace expanding superbubble shells, while VB components originate from galactic winds. One-zone photoionization models fail to explain the low-ionization lines ([S II] and [O I]) of broad components near the maximal starburst regime, which two-zone photoionization models with density-bounded channels instead reproduce. These two-zone models indicate anisotropic leakage of Lyman continuum photons through low-density channels formed by expanding superbubbles. Our study highlights extreme outflows ( ) in nine out of 14 star-forming dwarf galaxies, comparable to active galactic nucleus–driven winds.

Keywords: Dwarf galaxies, Galaxy winds, Emission line galaxies
Experimental and Numerical Studies of the Collapse of Dense Clouds Induced by Herbig–Haro Stellar Jets. This study investigates the influence of Herbig–Haro jets on initiating star formation in dense environments. When molecular clouds are nearing gravitational instability, the impact of a protostellar jet could provide the impetus needed to catalyze star formation. A high-energy-density experiment was carried out at the LULI2000 laser facility, where a supersonic jet generated by a nanosecond laser was used to compress a foam or plastic ball, mimicking the interaction of a Herbig–Haro jet with a molecular cloud. Simulations using the 3D radiation hydrodynamics code TROLL provided comprehensive data for analyzing ball compression and calculating jet characteristics. After applying scaling laws, similarities between stellar and experimental jets were explored. Diagnostic simulations—including density gradient, emission, and X-ray radiographies—showed strong agreement with experimental data. The results of the experiment, supported by simulations, demonstrate that the impact of a protostellar jet on a molecular cloud could reduce the Bonnor–Ebert mass by approximately 9%, thereby initiating collapse.

Keywords: Hydrodynamics, Herbig-Haro objects, Stellar jets, Laboratory astrophysics, Star formation
Anticorrelation Between Flux and Photon Index of Hard-X-Ray Emission from the Crab. Using Swift Burst Alert Telescope event-mode data during gamma-ray burst occurrences, we conduct spectral analysis for the Crab system. From 38 good observations, which span a period of 18 yr from 2006 to 2023, we find that the Crab's X-ray flux not only flickers but also significantly anticorrelates to its spectral power-law photon index. Since the emission contribution of the Crab pulsar in this energy range is small, this anticorrelation is mainly about the emission of the Crab nebula. We suggest that this anticorrelation provides observational supporting evidence for the long-standing notion that the nebula emission is due to synchrotron radiation of shocked pulsar winds in the nebula.

Keywords: Pulsar wind nebulae, Pulsars, Millisecond pulsars
The Source of the 2017 Cosmic-ray Half-year Modulation Event. In 2017, as the solar cycle approached solar minimum, an unusually long and large depression was observed in galactic cosmic-ray (GCR) protons, detected with the Alpha Magnetic Spectrometer, lasting for the second half of that year. The depression, as seen in the Bartel-rotation-averaged proton flux, has the form of a Forbush decrease (FD). Despite this resemblance, however, the cause of the observed depression does not have such a simple explanation as an FD, due to coronal mass ejections (CMEs), which typically last for a few days at 1 au rather than half a year. In this work, we seek the cause of the observed depression and investigate two main possibilities. First, we consider a minicycle—a temporary change in the solar dynamo that changes the behavior of the global solar magnetic field and, by this, the modulation of GCRs. Second, we investigate the behavior of solar activity, both CMEs and corotating/stream interaction regions (CIRs/SIRs), during this period. Our findings show that although there is some evidence for minicycle behavior prior to the depression, the depression is ultimately due to a combination of recurrent CMEs, SIRs, and CIRs. A particular characteristic of the depression is that the largest impacts that help to create and maintain it are due to four CMEs from the same, highly active, magnetic source that persists for several solar rotations. This active magnetic source is unusual, given the closeness of the solar cycle to solar minimum, which also helps to make the depression more evident.

Keywords: Space weather, Solar wind, Solar active regions, Solar coronal mass ejections, Solar coronal holes, Cosmic rays
New Potential Ultracompact X-Ray Binaries for Space-based Gravitational-wave Detectors from a Low-mass Main-sequence Companion Channel. We investigate the formation and evolution of ultracompact X-ray binaries (UCXBs) using the COMPAS binary evolution code, starting from the zero-age main sequence (MS). Focusing on the low-mass MS companion channel, we simulate gravitational-wave (GW) signals from UCXBs with LEGWORK and evaluate their detectability by space-based observatories such as Taiji and TianQin. By incorporating signal-to-noise ratio (SNR) calculations with a threshold of SNR &gt; 5, we provide a realistic framework to assess the detectability of the GW source. Our analysis suggests that the Milky Way currently hosts 7–32 observable UCXBs from the MS companion channel. Taiji or LISA alone could detect one to six sources over an 8 yr observation period, while TianQin, due to its high-frequency sensitivity, contributes to detecting systems with extremely short orbital periods and can also detect one to four sources. Comparison with sensitivity curves validates UCXBs as detectable GW sources, particularly at greater Galactic distances. This study improves our understanding of the evolution of UCXBs and their role as GW sources. By integrating population synthesis, SNR-based analyses, and observational data, we establish UCXBs as significant targets for GW astronomy, paving the way for future missions and theoretical studies of compact binary systems.

Keywords: Space telescopes, X-ray binary stars, Compact binary stars, Gravitational waves