Sazuna/UAT_keywords huggingface dataset:
Deep Very Long Baseline Interferometry Observations Challenge Previous Evidence of a Binary Supermassive Black Hole Residing in Seyfert Galaxy NGC 7674. Previous Ku-band (15 GHz) imaging with data obtained from the Very Long Baseline Array (VLBA) had shown two compact, subparsec components at the location of a presumed kiloparsec-scale radio core in Seyfert galaxy NGC 7674. It was then presumed that these two unresolved and compact components were dual radio cores corresponding to two supermassive black holes (SMBHs) accreting surrounding gas and launching radio-bright relativistic jets. However, utilizing the original VLBA data set used to claim the detection of a binary SMBH, in addition to later multiepoch/multifrequency data sets obtained from both the VLBA and the European very long baseline interferometry (VLBI) network, we find no evidence to support the presence of a binary SMBH. We place stringent upper limits to the flux densities of any subparsec-scale radio cores that are at least an order of magnitude lower than the original VLBI radio-core detections, directly challenging the original binary SMBH detection claim. With this in mind, we discuss the possible reasons for the nondetection of any VLBI radio cores in our imaging, the possibility of a binary SMBH still residing in NGC 7674, and the prospect of future observations shedding further light on the true nature of this active galactic nucleus.

Keywords: Supermassive black holes, Radio cores, Active galactic nuclei, Gravitational waves
Impacts of Viscous Dissipation on Collisional Growth and Fragmentation of Dust Aggregates. Understanding the collisional behavior of dust aggregates consisting of submicron-sized grains is essential to unveiling how planetesimals formed in protoplanetary disks. It is known that the collisional behavior of individual dust particles strongly depends on the strength of viscous dissipation force; however, impacts of viscous dissipation on the collisional behavior of dust aggregates have not been studied in detail, especially for the cases of oblique collisions. Here we investigated the impacts of viscous dissipation on the collisional behavior of dust aggregates. We performed numerical simulations of collisions between two equal-mass dust aggregates with various collision velocities and impact parameters. We also changed the strength of viscous dissipation force systematically. We found that the threshold collision velocity for the fragmentation of dust aggregates barely depends on the strength of viscous dissipation force when we consider oblique collisions. In contrast, the size distribution of fragments changes significantly when the viscous dissipation force is considered. We obtained the empirical fitting formulae for the size distribution of fragments for the case of strong dissipation, which would be useful to study the evolution of size and spatial distributions of dust aggregates in protoplanetary disks.

Keywords: Planetesimals, Protoplanetary disks, Planet formation, Circumstellar disks
TIC: A Stokes Inversion Code for Scattering Polarization with Partial Frequency Redistribution and Arbitrary Magnetic Fields. We present the Tenerife Inversion Code (TIC), which has been developed to infer the magnetic and plasma properties of the solar chromosphere and transition region via full Stokes inversion of polarized spectral lines. The code is based on the HanleRT forward engine, which takes into account many of the physical mechanisms that are critical for a proper modeling of the Stokes profiles of spectral lines originating in the tenuous and highly dynamic plasmas of the chromosphere and transition region: the scattering polarization produced by quantum level imbalance and interference (atomic polarization), the effects of frequency coherence in polarized resonance scattering (partial redistribution), and the impact of arbitrary magnetic fields on the atomic polarization and the radiation field. We present first results of atmospheric and magnetic inversions, and discuss future developments for the project.

Keywords: Solar atmosphere, Solar magnetic fields, Radiative transfer
Extragalactic Magnetic Fields and the Arrival Direction of Ultra-high-energy Cosmic Rays. We studied the propagation of ultra-high-energy cosmic rays in extragalactic magnetic fields (EGMFs). We report on the effect of the EGMF on the large-scale anisotropy signal measured at Earth. We show how a spurious dipolar and quadrupolar signal can be generated by the EGMF even if the source distribution is isotropic.

Keywords: Extragalactic magnetic fields, Cosmic ray astronomy, Cosmic ray sources, Ultra-high-energy cosmic radiation, Cosmic rays
Spectra of Cosmic-Ray Sodium and Aluminum and Unexpected Aluminum Excess. Since its launch, the Alpha Magnetic Spectrometer-02 (AMS-02) has delivered outstanding quality measurements of the spectra of cosmic-ray (CR) species, $\bar{p}$ , e ±, and nuclei (H-Si, Fe), which resulted in a number of breakthroughs. The most recent AMS-02 result is the measurement of the spectra of CR sodium and aluminum up to ~2 TV. Given their low solar system abundances, a significant fraction of each element is produced in fragmentations of heavier species, predominantly Ne, Mg, and Si. In this paper, we use precise measurements of the sodium and aluminum spectra by AMS-02 together with ACE-CRIS and Voyager 1 data to test their origin. We show that the sodium spectrum agrees well with the predictions made with the GALPROP-HELMOD framework, while the aluminum spectrum shows a significant excess in the rigidity range from 2-7 GV. In this context, we discuss the origin of other low-energy excesses in Li, F, and Fe found earlier. The observed excesses in Li, F, and Al appear to be consistent with the local Wolf-Rayet stars hypothesis, invoked to reproduce anomalous 22Ne/20Ne, 12C/16O, and 58Fe/56Fe ratios in CRs, while excess in Fe is likely connected with a past supernova activity in the solar neighborhood. We also provide updated local interstellar spectra (LIS) of sodium and aluminum in the rigidity range from a few megavolts to ~2 TV. Our calculations employ the self-consistent GALPROP-HELMOD framework, which has proved to be a reliable tool in deriving the LIS of CR $\bar{p}$ , e -, and nuclei Z ≤ 28.

Keywords: Interplanetary medium, Heliosphere, Secondary cosmic rays, Galactic cosmic rays, Galaxy abundances, Interstellar medium
Numerical Investigations of Catastrophe in Coronal Magnetic Configuration Triggered by Newly Emerging Flux. We performed 2D magnetohydrodynamical numerical experiments to study the response of the coronal magnetic configuration to the newly emerging magnetic flux. The configuration includes an electric-current-carrying flux rope modeling the prominence floating in the corona and the background magnetic field produced by two separated magnetic dipoles embedded in the photosphere. Parameters for one dipole are fixed in space and time to model the quiet background, and those for another one are time dependent to model the new flux. These numerical experiments duplicate important results of the analytic solution but also reveal new results. Unlike previous works, the configuration here possesses no symmetry, and the flux rope could move in any direction. The non-force-free environment causes the deviation of the flux rope equilibrium in the experiments from that determined in the analytic solution. As the flux rope radius decreases, the equilibrium could be found, and it evolves quasi-statically until the flux rope reaches the critical location at which the catastrophe occurs. As the radius increases, no equilibrium exists at all. During the catastrophe, two current sheets form in different ways. One forms as the surrounding closed magnetic field is stretched by the catastrophe, and another one forms as the flux rope squeezes the magnetic field nearby. Although reconnection happens in both the current sheets, it erases the first one quickly and enhances the second simultaneously. These results indicate the occurrence of the catastrophe in asymmetric and non-force-free environment, and the non-radial motion of the flux rope following the catastrophe.

Keywords: Solar filament eruptions, Solar magnetic flux emergence, Solar coronal mass ejections, Magnetohydrodynamical simulations
Particle Acceleration in Relativistic Shearing Flows: Energy Spectrum. We consider the acceleration of charged particles in relativistic shearing flows, with Lorentz factor up to Γ0 ~ 20. We present numerical solutions to the particle transport equation and compare these with results from analytical calculations. We show that in the highly relativistic limit the particle energy spectrum that results from acceleration approaches a power law, $N(E)\propto {E}^{-\tilde{q}}$ , with a universal value $\tilde{q}=(1+\alpha )$ for the slope of this power law, where α parameterizes the power-law momentum dependence of the particle mean free path. At mildly relativistic flow speeds, the energy spectrum becomes softer and sensitive to the underlying flow profile. We explore different flow examples, including Gaussian and power-law-type velocity profiles, showing that the latter yield comparatively harder spectra, producing $\tilde{q}\simeq 2$ for Γ0 ≃ 3 and Kolmogorov turbulence. We provide a comparison with a simplified leaky-box approach and derive an approximate relation for estimating the spectral index as a function of the maximum shear flow speed. These results are of relevance for jetted, high-energy astrophysical sources such as active galactic nuclei, since shear acceleration is a promising mechanism for the acceleration of charged particles to relativistic energies and is likely to contribute to the high-energy radiation observed.

Keywords: High energy astrophysics, Relativistic jets, Active galactic nuclei, Non-thermal radiation sources, Ultra-high-energy cosmic radiation
The Nature of Low-surface-brightness Galaxies in the Hyper Suprime-Cam Survey. We present the statistical redshift distribution of a large sample of low-surface-brightness (LSB) galaxies identified in the first 200 deg2 of the Hyper Suprime-Cam Strategic Survey Program. Through cross-correlation with the NASA-SDSS Atlas, we find that the majority of objects lie within z &lt; 0.15 or ~500 Mpc, yielding a mass range of M * ≈ 107-109 M ⊙ and a size range of r eff,g  ≈ 1-8 kpc. We find a peak in the distance distribution within 100 Mpc, corresponding mostly to ~107 M ⊙ galaxies that fall on the known mass-size relation. There is also a tail in the redshift distribution out to z ≈ 0.15, comprising more massive (M * = 108 - 109 M ⊙) galaxies at the larger end of our size range. We see tentative evidence that at the higher-mass end (M * &gt; 108 M ⊙), the LSB galaxies do not form a smooth extension of the mass-size relation of higher-surface-brightness galaxies, perhaps suggesting that the LSB galaxy population is distinct in its formation path.

Keywords: Low surface brightness galaxies
The Substructures in the Anticenter Region of the Milky Way. We investigated the observational properties of Triangulum-Andromeda (TriAnd), Monoceros Ring (MRi), and Anti-Center Stream (ACS) in the anticenter region using K giants, M giants, and RGB stars from LAMOST and SDSS survey. The Friends of Friends algorithm was applied to select member stars of these structures. We found a new spur of TriAnd at l ~ 133° based on member stars selected in this work and compiled from the literature. The distributions of radial velocity and proper motion of its member stars indicate that TriAnd is gradually moving away from the Sun. The comparisons of [Fe/H] and [α/Fe] between TriAnd and thick-disk/halo stars reveal that TriAnd is likely to originate from the thick disk. MRi and ACS are adjacent in space with a boundary around latitude 30°, and there is no significant difference between the two structures in velocity, proper motions, and orbits. We suggested that MRi and ACS probably have a common origin. We made projections of the four structures in three-dimensional space for the exploration of the movements between the Sagittarius (Sgr) stellar stream and MRi, and found that a new spur was formed by the Sgr stream members in the velocity distribution as it passed through the MRi region.

Keywords: Galaxy structure, Stellar streams
Thermocline Depth on Water-rich Exoplanets. Water-rich exoplanets are a type of terrestrial planet that is water-rich and whose ocean depth can reach tens to hundreds of kilometers with no exposed continents. Due to the lack of exposed continents, neither western boundary current nor coastal upwelling exists, and ocean overturning circulation becomes the most important way to return the nutrients deposited in the deep ocean back to the thermocline and to the surface ocean. Here we investigate the depth of the thermocline in both wind-dominated and mixing-dominated systems on water-rich exoplanets using the global ocean model MITgcm. We find that the wind-driven circulation is dominated by overturning cells through Ekman pumping and subduction and by zonal (west-east) circum-longitudinal currents, similar to the Antarctic Circumpolar Current on Earth. The wind-influenced thermocline depth shows little dependence on the ocean depth, and under a large range of parameters, the thermocline is restricted within the upper layers of the ocean. The mixing-influenced thermocline is limited within the upper 10 km of the ocean and cannot reach the bottom of the ocean even under extremely strong vertical mixing. The scaling theories for the thermocline depth on Earth are applicable for the thermocline depth on water-rich exoplanets. However, due to the lack of exposed continents, the zonal and meridional flow speeds are not in the same magnitude as that in the oceans of Earth, which results in scaling relationships for water-rich exoplanets being a little different from that used on Earth.

Keywords: Exoplanet dynamics, Ocean planets, Habitable planets
Parallel Plasma Loops and the Energization of the Solar Corona. The outer atmosphere of the Sun is composed of plasma heated to temperatures well in excess of the visible surface. We investigate short cool and warm (&lt;1 MK) loops seen in the core of an active region to address the role of field-line braiding in energizing these structures. We report observations from the High-resolution Coronal imager (Hi-C) that have been acquired in a coordinated campaign with the Interface Region Imaging Spectrograph (IRIS). In the core of the active region, the 172 Å band of Hi-C and the 1400 Å channel of IRIS show plasma loops at different temperatures that run in parallel. There is a small but detectable spatial offset of less than 1″ between the loops seen in the two bands. Most importantly, we do not see observational signatures that these loops might be twisted around each other. Considering the scenario of magnetic braiding, our observations of parallel loops imply that the stresses put into the magnetic field have to relax while the braiding is applied: the magnetic field never reaches a highly braided state on these length scales comparable to the separation of the loops. This supports recent numerical 3D models of loop braiding in which the effective dissipation is sufficiently large that it keeps the magnetic field from getting highly twisted within a loop.

Keywords: Magnetohydrodynamics, Solar extreme ultraviolet emission, Solar coronal loops, Solar coronal heating, Active sun
A Parameter Space Exploration of High-resolution Numerically Evolved Early Type Galaxies Including AGN Feedback and Accurate Dynamical Treatment of Stellar Orbits. An extensive exploration of the model parameter space of axisymmetric early type galaxies (ETGs) hosting a central supermassive black hole (SMBH) is conducted by means of high-resolution hydrodynamical simulations performed with our code MACER. Global properties such as (1) total SMBH accreted mass, (2) final X-ray luminosity and temperature of the X-ray emitting halos, (3) total amount of new stars formed from the cooling gas, and (4) total ejected mass in the form of supernovae and active galactic nuclei (AGN) feedback induced galactic winds, are obtained as a function of galaxy structure and internal dynamics. In addition to the galactic dark matter halo, the model galaxies are also embedded in a group/cluster dark matter halo; finally, cosmological accretion is also included, with the amount and time dependence derived from cosmological simulations. Angular momentum conservation leads to the formation of cold H I disks; these disks further evolve under the action of star formation induced by disk instabilities, of the associated mass discharge onto the central SMBH, and of the consequent AGN feedback. At the end of the simulations, the hot (metal-enriched) gas mass is roughly 10% the mass in the old stars, with twice as much having been ejected into the intergalactic medium. The cold gas disks are approximately kiloparsec in size, and the metal-rich new stars are in 0.1 kpc disks. The masses of cold gas and new stars are roughly 0.1% of the mass of the old stars. Overall, the final systems appear to reproduce quite successfully the main global properties of real ETGs.

Keywords: X-ray astronomy, Cooling flows, Stellar dynamics, Active galactic nuclei, Interstellar medium, Early-type galaxies
Photometry on Structured Backgrounds: Local Pixel-wise Infilling by Regression. Photometric pipelines struggle to estimate both the flux and flux uncertainty for stars in the presence of structured backgrounds such as filaments or clouds. However, it is exactly stars in these complex regions that are critical to understanding star formation and the structure of the interstellar medium. We develop a method, similar to Gaussian process regression, which we term local pixel-wise infilling (LPI). Using a local covariance estimate, we predict the background behind each star and the uncertainty of that prediction in order to improve estimates of flux and flux uncertainty. We show the validity of our model on synthetic data and real dust fields. We further demonstrate that the method is stable even in the crowded field limit. While we focus on optical-IR photometry, this method is not restricted to those wavelengths. We apply this technique to the 34 billion detections in the second data release of the Dark Energy Camera Plane Survey. In addition to removing many &gt;3σ outliers and improving uncertainty estimates by a factor of ~2-3 on nebulous fields, we also show that our method is well behaved on uncrowded fields. The entirely post-processing nature of our implementation of LPI photometry allows it to easily improve the flux and flux uncertainty estimates of past as well as future surveys.

Keywords: Sky surveys, Astronomy data analysis, Photometry, Gaussian Processes regression, Catalogs
Dust Emission as a Function of Stellar Population Age in the Nearby Galaxy M33. Dust emission at 8 μm has been extensively calibrated as an indicator of current star formation rate for galaxies and ~kpc-size regions within galaxies. Yet, the exact link between the 8 μm emission and the young stellar populations in galaxies is still under question, as dust grains can be stochastically heated also by older field stars. In order to investigate this link, we have combined midinfrared images from the Spitzer Space Telescope with a published star cluster candidates catalog for the Local Group galaxy M33. M33 is sufficiently close that the Spitzer's 8 μm images resolve individual regions of star formation. Star clusters represent almost-single-age stellar populations, which are significantly easier to model than more complex mixtures of stars. We find a decrease in the 8 μm luminosity per unit stellar mass as a function of age of the star clusters, with a large scatter that is consistent with varying fractions of stellar light absorbed by dust. The decrease and scatter both confirm findings based on more distant galaxies and are well described by simple models for the dust emission of a young stellar population. We conclude that the dust emission at 8 μm depends sensitively on the age of the stellar population, out to at least the oldest age analyzed here: ~400 Myr. This dependence complicates the use of the 8 μm emission as a star formation rate indicator, at least for small galactic regions and individual star-forming regions. By leveraging the Spitzer legacy, this investigation paves the way for future explorations with the James Webb Space Telescope.

Keywords: Dust continuum emission, Young star clusters
An Expanding Shell of Neutral Hydrogen Associated with SN 1006: Hints for the Single-degenerate Origin and Faint Hadronic Gamma-Rays. We report new H I observations of the Type Ia supernova remnant (SNR) SN 1006 using the Australia Telescope Compact Array with an angular resolution of $4\buildrel{\,\prime}\over{.} 5\times 1\buildrel{\,\prime}\over{.} 4$ 4.'5×1.'4 (~2 pc at the assumed SNR distance of 2.2 kpc). We find an expanding gas motion in position-velocity diagrams of H I with an expansion velocity of ~4 km s-1 and a mass of ~1000 M ⊙. The spatial extent of the expanding shell is roughly the same as that of SN 1006. We here propose a hypothesis that SN 1006 exploded inside the wind-blown bubble formed by accretion winds from the progenitor system consisting of a white dwarf and a companion star, and then the forward shock has already reached the wind wall. This scenario is consistent with the single-degenerate model. We also derived the total energy of cosmic-ray protons W p to be only ~1.2-2.0 × 1047 erg by adopting the averaged interstellar proton density of ~25 cm-3. The small value is compatible with the relation between the age and W p of other gamma-ray SNRs with ages below ~6 kyr. The W p value in SN 1006 will possibly increase up to several 1049 erg in the next ~5 kyr via the cosmic-ray diffusion into the H I wind shell.

Keywords: Gamma-ray sources, Supernova remnants, Cosmic ray sources, X-ray sources, Interstellar medium
Serendipitous Discovery of Three Millisecond Pulsars with the GMRT in Fermi-directed Survey and Follow-up Radio Timing. We report the discovery of three millisecond pulsars (MSPs): PSRs J1120-3618, J1646-2142, and J1828+0625 with the Giant Metrewave Radio Telescope (GMRT) at a frequency of 322 MHz using a 32 MHz observing bandwidth. These sources were discovered serendipitously while conducting the deep observations to search for millisecond radio pulsations in the directions of unidentified Fermi Large Area Telescope (LAT) γ-ray sources. We also present phase coherent timing models for these MSPs using ~5 yr of observations with the GMRT. PSR J1120-3618 has a 5.5 ms spin period and is in a binary system with an orbital period of 5.6 days and minimum companion mass of 0.18 M ⊙, PSR J1646-2142 is an isolated object with a spin period of 5.8 ms, and PSR J1828+0625 has a spin period of 3.6 ms and is in a binary system with an orbital period of 77.9 days and minimum companion mass of 0.27 M ⊙. The two binaries have very low orbital eccentricities, in agreement with expectations for MSP-helium white dwarf systems. Using the GMRT 607 MHz receivers having a 32 MHz bandwidth, we have also detected PSR J1646-2142 and PSR J1828+0625, but not PSR J1120-3618. PSR J1646-2142 has a wide profile, with significant evolution between 322 and 607 MHz, whereas PSR J1120-3618 exhibits a single peaked profile at 322 MHz and PSR J1828+0625 exhibits a single peaked profile at both the observing frequencies. These MSPs do not have γ-ray counterparts, indicating that these are not associated with the target Fermi LAT pointing emphasizing the significance of deep blind searches for MSPs.

Keywords: Radio astronomy, Millisecond pulsars