Sazuna/UAT_keywords huggingface dataset:
Global Mapping of the Surface Composition on an Exo-Earth Using Color Variability. Photometric variation of a directly imaged planet contains information on both the geography and spectra of the planetary surface. We propose a novel technique that disentangles the spatial and spectral information from the multiband reflected light curve. This will enable us to compose a two-dimensional map of the surface composition of a planet with no prior assumption on the individual spectra, except for the number of independent surface components. We solve the unified inverse problem of the spin-orbit tomography and spectral unmixing by generalizing the nonnegative matrix factorization using a simplex volume minimization method. We evaluated our method on a toy cloudless Earth and observed that the new method could accurately retrieve the geography and unmix spectral components. Furthermore, our method is also applied to the real-color variability of the Earth as observed by Deep Space Climate Observatory. The retrieved map explicitly depicts the actual geography of the Earth, and unmixed spectra capture features of the ocean, continents, and clouds. It should be noted that the two unmixed spectra consisting of the reproduced continents resemble those of soil and vegetation.

Keywords: Habitable planets, Exoplanet surface composition, Exoplanet surface variability, Exoplanet surfaces, Direct imaging, Exoplanet surface characteristics, Astronomical methods
Radial Migration of Gap-opening Planets in Protoplanetary Disks. II. The Case of a Planet Pair. When two planets are born in a protoplanetary disk, they may enter into mean-motion resonance as a consequence of convergent planetary migration. The formation of mean-motion resonances is important for understanding how planetary systems are shaped in disk environments. Motivated by recent progress in the comprehension of the migration of partial gap-opening planets, we have investigated the orbital evolution of planet pairs in a wide range of masses and disk properties with the aim to find out when resonance capture is likely to happen. Using the formula for the migration timescale of a gap-opening planet developed in our previous work, we have derived a simple criterion that allows us to predict when the migration will be convergent (divergent). Further, we have verified the criterion using two-dimensional hydrodynamic simulations. We have found that the resonant pair of planets formed at the early phase of evolution can depart from resonance at later times because the migration speed of the outer planet slows down due to gap formation. Moreover, adopting our formula for the migration timescale, we have also carried out three-body simulations, which confirm the results of hydrodynamic simulations. Finally, we have compared our predictions with observations, selecting a sample of known two-planet systems.

Keywords: Planetary system formation, Protoplanetary disks, Planet formation
Reconstruction of Radio Relics and X-Ray Tails in an Off-axis Cluster Merger: Hydrodynamical Simulations of A115. Although a merging galaxy cluster is a useful laboratory to study many important astrophysical processes and fundamental physics, only limited interpretations are possible without careful analysis of the merger scenario. However, the study is demanding because a thorough comparison of multiwavelength observations with detailed numerical simulations is required. In this paper, we present such a study for the off-axis binary merger A115. The system possesses a number of remarkable observational features, but no convincing merger scenario explaining the shape and location of the radio relic in harmony with the orientation of the cometary X-ray tails has been presented. Our hydrodynamical simulation with adaptive mesh refinement suggests that the cometary X-ray tail of A115 might be a slingshot tail that can arise ∼0.3 Gyr after the impact, before the two subclusters reach their apocenters. This scenario can predict the location and orientation of the giant radio relic, which is parallel to the northern X-ray tail. In addition, our study indicates that diffusive shock acceleration alone cannot generate the observed radio power unless aided by stronger magnetic fields and/or more significant presence of fossil electrons.

Keywords: Galaxy clusters, Hydrodynamics, Radio continuum emission, Abell clusters, Intracluster medium
Resolving the Nuclear Radio Emission from M32 with the Very Large Array. The Local Group dwarf elliptical galaxy M32 hosts one of the nearest and most under-luminous supermassive black holes (SMBHs) ever known, offering a rare opportunity to study the physics of accreting SMBHs at the most quiescent state. Recent Very Large Array (VLA) observations detected a radio source at the nucleus of M32, which was suggested to be the radio counterpart of the SMBH. To further investigate the radio properties of this nuclear source, we have conducted follow-up, high-resolution VLA observations in four epochs between 2015 and 2017, each with dual frequencies. At 6 GHz, the nuclear source is resolved under an angular resolution of ∼0"4, exhibiting a coreless, slightly lopsided morphology with a detectable extent of ∼2"5 (∼10 pc). No significant variability can be found among the four epochs. At 15 GHz, no significant emission can be detected within the same region, pointing to a steep intrinsic radio spectrum (with a 3σ upper limit of -1.46 for the spectral index). We discuss possible scenarios for the nature of this nuclear radio source and conclude that a stellar origin, in particular, planetary nebulae, X-ray binaries, supernova remnants, or diffuse ionized gas powered by massive stars, can be ruled out. Instead, the observed radio properties can be explained by synchrotron radiation from a hypothetical wind driven by the weakly accreting SMBH.

Keywords: Radio continuum emission, Low-luminosity active galactic nuclei, Local Group
Contribution of Magnetism to the Origin of Saturn's Rings. In this paper, we derive the magnetization relationships for magnetically uniform spherical particles of Saturn's rings, and solve the problem of a solitary magnetized sphere and a spherical particle among identical particles scattered in a disk-like structure. We also derive differential equations of collisionless motion of particles in the gravitational and magnetic fields. A special approximation of these equations is solved exactly, and its solution suggests that the superposition of the gravitational and magnetic fields acting on diamagnetic ice particles can account for the stability of Saturn's rings in its equatorial plane.

Keywords: Saturn, Astrophysical magnetism, Solar system, Planetary rings, Planetary ring divisions
Trapping of Cosmic Rays in MHD Turbulence. Astrophysical plasmas are turbulent and magnetized. The interaction between cosmic rays (CRs) and magnetohydrodynamic (MHD) turbulence is a fundamental astrophysical process. Based on the current understanding of MHD turbulence, we revisit the trapping of CRs by magnetic mirrors in the context of MHD turbulence. In compressible MHD turbulence, isotropic fast modes dominate both trapping and gyroresonant scattering of CRs. The presence of trapping significantly suppresses the pitch-angle scattering and the spatial diffusion of CRs along the magnetic field. The resulting parallel diffusion coefficient has a weaker dependence on CR energy at higher energies. In incompressible MHD turbulence, the trapping by pseudo-Alfvén modes dominates over the gyroresonant scattering by anisotropic Alfvén and pseudo-Alfvén modes at all pitch angles and prevents CRs from diffusion.

Keywords: Galactic cosmic rays, Magnetohydrodynamics, Magnetic fields
Does a Solar Filament Barb Always Correspond to a Prominence Foot?. Solar filaments are dark structures on the solar disk, with an elongated spine and several barbs extending out from the spine. When appearing above the solar limb, a filament is called a prominence, with several feet extending down to the solar surface. It was generally thought that filament barbs are simply the prominence feet veering away from the spine and down to the solar surface. However, it was recently noticed that there might be another dynamic type of barb, which was proposed to be due to filament thread longitudinal oscillation. If this is the case, the dynamic barbs would not extend down to the solar surface. With the quadrature observations of a filament barb on 2011 June 5 from the Solar Dynamics Observatory and the Solar Terrestrial Relations Observatory satellites, we confirm that the filament barb is due to filament thread longitudinal oscillations. Viewed from the side, the filament barb looks like an appendix along the spine of the prominence and does not extend down to the solar surface as a foot.

Keywords: Solar magnetic fields, Solar filaments, Solar prominences
Constraining the Neutrino Mass with the Drifting Coefficient of the Field Cluster Mass Function. A new diagnostics to break the degeneracy between the total neutrino mass (Mν) and the primordial power spectrum amplitude (σ8) using the drifting coefficient of the field cluster mass function is presented. Analyzing the data from the Cosmological Massive Neutrino Simulations, we first determine the numerical mass functions of the field clusters at various redshifts. Then, we compare the numerical results with the analytical model characterized by a single parameter called the drifting coefficient, which measures the drifts of the collapse density threshold, δc, from the Einstein-de Sitter spherical value, δsc, at a given mass scale. It is found that the analytic model for the field cluster mass function is found to work excellently even in the presence of massive neutrinos, and that its drifting coefficient evolves differently in the cosmologies with different values of Mν. At low redshifts (z ≲ 0.3) the more massive neutrinos drift δc further from δsc, while the opposite trend is found at higher redshifts (z ≳ 0.3). Speculating that this distinct redshift-dependent effect of massive neutrinos on the drifting coefficient of the field cluster mass function might help break the σ8-Mν degeneracy, we also show that the sensitivity of this new diagnostics to Mν is high enough to discriminate the case of Mν = 0.1 eV from that of massless neutrinos.

Keywords: Cosmological parameters from large-scale structure, Large-scale structure of the universe
Solar Flare Modified Complex Network. A constructive approach is developed to build the solar flare complex network by utilizing a visibility graph condition alongside the Abe-Suzuki method. Solar flare information such as position, start time, and peak flux is used for this purpose. The obtained characteristics of the topological features (such as the characteristic path length, power-law behavior of the probability distribution function of degrees, and the clustering coefficient) demonstrate the scale-free and small-world properties of the solar flare modified network. To explain the complexity of the constructed network, Omori's law as well as the universal scaling features are investigated. Furthermore, a nonextensive modification of the Gutenberg-Richter law is examined for the solar flare modified network using a q-stretched exponential model. Establishing a two-dimensional map for the configuration of 118 energetic main flares observed between 2006 and 2016, it is found that the main flares are located within the regions consisting of hubs (high-connectivity regions) of the network. A fractal dimension of the solar flare network of about 0.79 is also obtained.

Keywords: Computational astronomy, Astronomy data modeling, Solar flares, Astronomy databases, Neural networks, Astronomical simulations, The Sun, Astronomy data analysis, Solar physics, Solar active regions, Computational methods, Time series analysis
Spectroscopic and Asteroseismic Analysis of the Secondary Clump Red Giant HD 226808. In order to clarify the properties of the secondary clump star HD 226808 (KIC 5307747), we combined four years of data from Kepler space photometry with high-resolution spectroscopy of the High Efficiency and Resolution Mercator Échelle Spectrograph mounted on the Mercator telescope. The fundamental atmospheric parameters, radial velocities, rotation velocities, and elemental abundance for Fe and Li were determined by analyzing line strengths and fitting-line profiles, based on a 1D local thermodynamic equilibrium model atmosphere. Second, we analyzed a photometric light curve obtained by Kepler and we extracted asteroseismic data of this target using Lets Analysis, Use and Report of Asteroseismology, a new seismic tool developed for the study of evolved FGK solar-like stars. We determined the evolutionary status and effective temperature, surface gravity, metallicity, microturbulence, and chemical abundances for Li, Ti, Fe, and Ni for HD 226808, by employing spectroscopy, asteroseismic scaling relations, and evolutionary structure models built in order to match observed data. Our results also show that an accurate synergy between good spectroscopic analysis and asteroseismology can provide a jump toward understanding evolved stars.

Keywords: High resolution spectroscopy, Stellar abundances, Asteroseismology, Red giant clump
Is the Expansion of the Universe Accelerating? All Signs Still Point to Yes: A Local Dipole Anisotropy Cannot Explain Dark Energy. Type Ia supernovae (SNe Ia) provided the first strong evidence that the expansion of the universe is accelerating. With SN samples now more than ten times larger than those used for the original discovery, and joined by other cosmological probes, this discovery is on even firmer ground. Two recent, related, studies (N16 and C19) have claimed to undermine the statistical significance of the SN Ia constraints. Rubin &amp; Hayden (RH16) showed N16 made an incorrect assumption about the distributions of SN Ia light-curve parameters, while C19 also fails to remove the impact of the motion of the solar system from the SN redshifts, interpreting the resulting errors as evidence of a dipole in the deceleration parameter. Building on RH16, we outline the errors C19 make in their treatment of the data and inference on cosmological parameters. Reproducing the C19 analysis with our proposed fixes, we find that the dipole parameters have little effect on the inferred cosmological parameters. We thus affirm the conclusion of RH16: the evidence for acceleration is secure.

Keywords: Dark energy, Type Ia supernovae, Deceleration parameter, Cosmological parameters
How Much Do Underestimated Field Strengths from Zeeman-Doppler Imaging Affect Spin-down Torque Estimates?. Numerous attempts to estimate the rate at which low-mass stars lose angular momentum over their lifetimes fill the literature. One approach is to use magnetic maps derived from Zeeman-Doppler imaging (ZDI) in conjunction with so-called "braking laws." The use of ZDI maps has advantages over other methods because it allows information about the magnetic field geometry to be incorporated into the estimate. However, ZDI is known to underestimate photospheric field strengths due to flux cancellation effects. Recently, Lehmann et al. conducted synthetic ZDI reconstructions on a set of flux transport simulations to help quantify the amount by which ZDI underestimates the field strengths of relatively slowly rotating and weak activity solar-like stars. In this paper, we evaluate how underestimated angular momentum loss rate estimates based on ZDI maps may be. We find that they are relatively accurate for stars with strong magnetic fields but may be underestimated by a factor of up to ∼10 for stars with weak magnetic fields. Additionally, we re-evaluate our previous work that used ZDI maps to study the relative contributions of different magnetic field modes to angular momentum loss. We previously found that the dipole component dominates spin-down for most low-mass stars. This conclusion still holds true even in light of the work of Lehmann et al.

Keywords: Stellar rotation, Stellar magnetic fields, Low mass stars, Stellar winds
Inferring Vector Magnetic Fields from Stokes Profiles of GST/NIRIS Using a Convolutional Neural Network. We propose a new machine-learning approach to Stokes inversion based on a convolutional neural network (CNN) and the Milne-Eddington (ME) method. The Stokes measurements used in this study were taken by the Near InfraRed Imaging Spectropolarimeter (NIRIS) on the 1.6 m Goode Solar Telescope (GST) at the Big Bear Solar Observatory. By learning the latent patterns in the training data prepared by the physics-based ME tool, the proposed CNN method is able to infer vector magnetic fields from the Stokes profiles of GST/NIRIS. Experimental results show that our CNN method produces smoother and cleaner magnetic maps than the widely used ME method. Furthermore, the CNN method is four to six times faster than the ME method and able to produce vector magnetic fields in nearly real time, which is essential to space weather forecasting. Specifically, it takes ∼50 s for the CNN method to process an image of 720 × 720 pixels comprising Stokes profiles of GST/NIRIS. Finally, the CNN-inferred results are highly correlated to the ME-calculated results and closer to the ME's results with the Pearson product-moment correlation coefficient (PPMCC) being closer to 1, on average, than those from other machine-learning algorithms, such as multiple support vector regression and multilayer perceptrons (MLP). In particular, the CNN method outperforms the current best machine-learning method (MLP) by 2.6%, on average, in PPMCC according to our experimental study. Thus, the proposed physics-assisted deep learning-based CNN tool can be considered as an alternative, efficient method for Stokes inversion for high-resolution polarimetric observations obtained by GST/NIRIS.

Keywords: Computational methods, Convolutional neural networks, Solar magnetic fields
Atacama Compact Array Measurements of the Molecular Mass in the NGC 5044 Cooling-flow Group. The fate of cooling gas in the centers of galaxy clusters and groups is still not well understood, as is also the case for the complex processes of triggering star formation in central dominant galaxies, reheating of cooled gas by active galactic nuclei (AGN), and the triggering or "feeding" of supermassive black hole outbursts. We present CO observations of the early-type galaxy NGC 5044, which resides at the center of an X-ray bright group with a moderate cooling flow. For our analysis we combine CO(2-1) data from the 7 m antennae of the Atacama Compact Array (ACA) and the ACA total power array (TP). We demonstrate, using the 7 m array data, that we can recover the total flux inferred from IRAM 30 m single-dish observations, which corresponds to a total molecular mass of about 4 × 107M⊙. Most of the recovered flux is blueshifted with respect to the galaxy rest frame and is extended on kiloparsec-scales, suggesting low filling factor dispersed clouds. We find eight concentrations of molecular gas out to a radius of 10″ (1.5 kpc), which we identify with giant molecular clouds. The total molecular gas mass is more centrally concentrated than the X-ray emitting gas, but is extended in the northeast-southwest direction beyond the IRAM 30 m beam. We also compare the spatial extent of the molecular gas to the Hα emission: The CO emission coincides with the very bright Hα region in the center. We do not detect CO emission in the fainter Hα regions. Furthermore, we find two CO absorption features spatially located at the center of the galaxy, within 5 pc projected distance of the AGN, infalling at 255 and 265 km s-1 relative to the AGN. This indicates that the two giant molecular clouds seen in absorption are most likely within the sphere of influence of the supermassive black hole.

Keywords: Galaxy clusters, Molecular gas, Cooling flows, Giant molecular clouds, Active galactic nuclei, Early-type galaxies
Three-dimensional Kinematic Reconstruction of the Optically Emitting, High-velocity, Oxygen-rich Ejecta of Supernova Remnant N132D. We present a three-dimensional kinematic reconstruction of the optically emitting, oxygen-rich ejecta of supernova remnant N132D in the Large Magellanic Cloud (LMC). Data were obtained with the 6.5 m Magellan telescope in combination with the IMACS+GISMO instrument and survey [O III] λλ4959, 5007 line emission in a ∼3' × 3' region centered on N132D. The spatial and spectral resolutions of our data enable detailed examination of the optical ejecta structure. The majority of N132D's optically bright oxygen ejecta are arranged in a torus-like geometry tilted approximately 28° with respect to the plane of the sky. The torus has a radius of 4.4 pc (DLMC/50 kpc), exhibits a blueshifted radial velocity asymmetry of -3000 to +2300 km s-1, and has a conspicuous break in its circumference. Assuming homologous expansion from the geometric center of O-rich filaments, the average expansion velocity of 1745 km s-1 translates to an age since explosion of 2450 ± 195 yr. A faint, spatially separated "runaway knot" (RK) with total space velocity of 3650 km s-1 is nearly perpendicular to the torus plane and coincident with X-ray emission that is substantially enhanced in Si relative to the LMC and N132D's bulk ejecta. These kinematic and chemical signatures suggest that the RK may have had its origin deep within the progenitor star. Overall, the main-shell morphology and high-velocity, Si-enriched components of N132D have remarkable similarity with those of Cassiopeia A, which was the result of a Type IIb supernova explosion. Our results underscore the need for further observations and simulations that can robustly reconcile whether the observed morphology is dominated by explosion dynamics or shaped by interaction with the environment.

Keywords: Ejecta, Interstellar line emission, Core-collapse supernovae, Large Magellanic Cloud, Supernova remnants, Stellar remnants, Supernovae
Protoplanetary Disks in the Orion Nebula Cluster: Gas-disk Morphologies and Kinematics as Seen with ALMA. We present Atacama Large Millimeter Array CO(3 - 2) and HCO+(4 - 3) observations covering the central 1'5 × 1'5 region of the Orion Nebula Cluster (ONC). The unprecedented level of sensitivity (∼0.1 mJy beam-1) and angular resolution (∼0"09 ≈ 40 au) of these line observations enable us to search for gas-disk detections toward the known positions of submillimeter-detected dust disks in this region. We detect 23 disks in gas: 17 in CO(3 - 2), 17 in HCO+(4 - 3), and 11 in both lines. Depending on where the sources are located in the ONC, we see the line detections in emission, in absorption against the warm background, or in both emission and absorption. We spectrally resolve the gas with 0.5 km s-1 channels and find that the kinematics of most sources are consistent with Keplerian rotation. We measure the distribution of gas-disk sizes and find typical radii of ∼50-200 au. As such, gas disks in the ONC are compact in comparison with the gas disks seen in low-density star-forming regions. Gas sizes are universally larger than the dust sizes. However, the gas and dust sizes are not strongly correlated. We find a positive correlation between gas size and distance from the massive star θ1 Ori C, indicating that disks in the ONC are influenced by photoionization. Finally, we use the observed kinematics of the detected gas lines to model Keplerian rotation and infer the masses of the central pre-main-sequence stars. Our dynamically derived stellar masses are not consistent with the spectroscopically derived masses, and we discuss possible reasons for this discrepancy.

Keywords: Proplyds, Millimeter astronomy, Young star clusters, Young stellar objects, Pre-main sequence stars, Protoplanetary disks, Circumstellar disks, Radio astronomy, Planet formation, Circumstellar gas