Sazuna/UAT_keywords huggingface dataset:
Interaction of Magnetic Fields with a Vortex Tube at Solar Subgranular Scale. Using high-resolution spectropolarimetric data recorded with the Swedish 1 m Solar Telescope, we have identified several instances of granular lanes traveling into granules. These are believed to be the observational signature of underlying tubes of vortical flow with their axis oriented parallel to the solar surface. Associated with these horizontal vortex tubes, we detect in some cases a significant signal in linear polarization, located at the trailing dark edge of the granular lane. The linear polarization appears at a later stage of the granular lane development, and is flanked by patches of circular polarization. Stokes inversions show that the elongated patch of linear polarization signal arises from the horizontal magnetic field aligned with the granular lane. We analyze snapshots of a magnetohydrodynamic numerical simulation and find cases in which the horizontal vortex tube of the granular lane redistributes and transports the magnetic field to the solar surface causing a polarimetric signature similar to what is observed. We thus witness a mechanism capable of transporting magnetic flux to the solar surface within granules. This mechanism is probably an important component of the small-scale dynamo supposedly acting at the solar surface and generating the quiet-Sun magnetic field.

Keywords: Magnetohydrodynamics, Solar photosphere, Solar granulation, Solar magnetic fields, Magnetohydrodynamical simulations
A Terrestrial-mass Rogue Planet Candidate Detected in the Shortest-timescale Microlensing Event. Some low-mass planets are expected to be ejected from their parent planetary systems during early stages of planetary system formation. According to planet formation theories, such as the core accretion theory, typical masses of ejected planets should be between 0.3 and 1.0 M⊕. Although in practice such objects do not emit any light, they may be detected using gravitational microlensing via their light-bending gravity. Microlensing events due to terrestrial-mass rogue planets are expected to have extremely small angular Einstein radii (≲1 μas) and extremely short timescales (≲0.1 day). Here, we present the discovery of the shortest-timescale microlensing event, OGLE-2016-BLG-1928, identified to date ( ${t}_{{\rm{E}}}\approx 0.0288\,\mathrm{day}=41.5\,\mathrm{minutes}$ ). Thanks to the detection of finite-source effects in the light curve of the event, we were able to measure the angular Einstein radius of the lens ${\theta }_{{\rm{E}}}=0.842\pm 0.064$ μas, making the event the most extreme short-timescale microlens discovered to date. Depending on its unknown distance, the lens may be a Mars- to Earth-mass object, with the former possibility favored by the Gaia proper motion measurement of the source. The planet may be orbiting a star but we rule out the presence of stellar companions up to the projected distance of ∼8.0 au from the planet. Our discovery demonstrates that terrestrial-mass free-floating planets can be detected and characterized using microlensing.

Keywords: Gravitational microlensing, Free floating planets, Gravitational microlensing exoplanet detection, Finite-source photometric effect
Mirror Mode Waves Immersed in Magnetic Reconnection. Mirror mode waves with anticorrelated density and magnetic field are widely observed in the heliosphere. This paper presents the first evidence of mirror mode waves occurring in the vicinity of a magnetic reconnection site (X-line) at the interface between the solar wind and Earth&amp;'s magnetosphere based on the analyses of two Magnetospheric Multiscale (MMS) crossing events along with the Grad-Shafranov (GS) reconstruction model with temperature anisotropy. The GS scheme solves the steady two-dimensional MHD equations in the frame of references moving with the plasma by using the spacecraft measurements. Both events have mirror type of pressure anisotropy and correspond, respectively, to the symmetric and asymmetric Harris type current sheets with the total thermal and magnetic field pressures being approximately constant. The GS reconstruction results show the magnetic reconnection with X line geometry associated with the mirror mode structures on the spatial lengths of 170 ∼ 370 km or 1.3 ∼ 3 ion gyroradius. The coexistence of mirror waves and magnetic reconnection provides the first observational evidence for the prior theoretical prediction of mixed tearing and mirror instabilities in plasma current sheets with temperature anisotropy.

Keywords: Space plasmas, Magnetohydrodynamics, Plasma physics, Plasma astrophysics, Alfven waves
The Atacama Cosmology Telescope: Weighing Distant Clusters with the Most Ancient Light. We use gravitational lensing of the cosmic microwave background (CMB) to measure the mass of the most distant blindly selected sample of galaxy clusters on which a lensing measurement has been performed to date. In CMB data from the the Atacama Cosmology Telescope and the Planck satellite, we detect the stacked lensing effect from 677 near-infrared-selected galaxy clusters from the Massive and Distant Clusters of WISE Survey (MaDCoWS), which have a mean redshift of $\langle z\rangle =1.08$ . There are currently no representative optical weak lensing measurements of clusters that match the distance and average mass of this sample. We detect the lensing signal with a significance of $4.2\sigma $ . We model the signal with a halo model framework to find the mean mass of the population from which these clusters are drawn. Assuming that the clusters follow Navarro-Frenk-White (NFW) density profiles, we infer a mean mass of $\langle {M}_{500c}\rangle =\left(1.7\pm 0.4\right)\times {10}^{14}\,{M}_{\odot }$ . We consider systematic uncertainties from cluster redshift errors, centering errors, and the shape of the NFW profile. These are all smaller than 30% of our reported uncertainty. This work highlights the potential of CMB lensing to enable cosmological constraints from the abundance of distant clusters populating ever larger volumes of the observable universe, beyond the capabilities of optical weak lensing measurements.

Keywords: Cosmology, Cosmic microwave background radiation, Gravitational lensing, High-redshift galaxy clusters
HAWC and Fermi-LAT Detection of Extended Emission from the Unidentified Source 2HWC J2006+341. The discovery of the TeV point source 2HWC J2006+341 was reported in the second HAWC gamma-ray catalog. We present a follow-up study of this source here. The TeV emission is best described by an extended source with a soft spectrum. At GeV energies, an extended source is significantly detected in Fermi-LAT data. The matching locations, sizes, and spectra suggest that both gamma-ray detections correspond to the same source. Different scenarios for the origin of the emission are considered and we rule out an association to the pulsar PSR J2004+3429 due to extreme energetics required, if located at a distance of 10.8 kpc.

Keywords: Gamma-rays, Interstellar medium
A Magnetized, Moon-forming Giant Impact. The Moon is believed to have formed in the aftermath of a giant impact between a planetary-mass body and the proto-Earth. In a typical giant impact scenario, a disk of vapor, liquid, and solid debris forms around the proto-Earth and—after possibly decades of evolution—condenses to form the Moon. Using state-of-the-art numerical simulations, we investigate the dynamical effects of magnetic fields on the Moon-forming giant impact. We show that turbulence generated by the collision itself, shear in the boundary layer between the post-impact debris field and the proto-Earth, and turbulence in the vapor component of the disk amplify the field to dynamically significant strengths. Magnetically driven turbulence promotes angular momentum transport in the protolunar disk. Debris material is accreted onto the proto-Earth, making Moon formation less efficient, while the disk is forced to spread to larger radii, cooling at its outer edge. Magnetic fields speed the evolution of the vapor component of the protolunar disk and hasten the formation of the Moon.

Keywords: Natural satellite formation, Magnetic fields, Magnetohydrodynamical simulations
The First Robust Constraints on the Relationship between Dust-to-gas Ratio and Metallicity in Luminous Star-forming Galaxies at High Redshift. We present rest-optical spectroscopic properties of a sample of four galaxies in the Atacama Large Millimeter/submillimeter Array Hubble Ultra Deep Field (ALMA HUDF). These galaxies span the redshift range $1.41\leqslant z\leqslant 2.54$ and the stellar mass range $10.36\leqslant \mathrm{log}({M}_{* }/{M}_{\odot })\leqslant 10.91$ . They have existing far-infrared and radio measurements of dust-continuum and molecular gas emission from which bolometric star formation rates (SFRs), dust masses, and molecular gas masses have been estimated. We use new H- and K-band near-infrared spectra from the Keck/Multi-object Spectrometer for Infrared Exploration (MOSFIRE) to estimate SFRs from dust-corrected Hα emission (SFR(Hα)) and gas-phase oxygen abundances from the ratio [N II] $\lambda 6584$ /Hα. We find that the dust-corrected SFR(Hα) is systematically lower than the bolometric SFR by a factor of several, and measure gas-phase oxygen abundances in a narrow range, $12+\mathrm{log}({\rm{O/H}})=8.59-8.69$ ( $0.8\mbox{--}1.0\ {({\rm{O/H}})}_{\odot }$ ). Relative to a large z ∼ 2 comparison sample from the MOSFIRE Deep Evolution Field (MOSDEF) survey, the ALMA HUDF galaxies scatter roughly symmetrically around the best-fit linear mass-metallicity relation, providing tentative evidence for a flattening in the SFR dependence of metallicity at high stellar mass. Combining oxygen abundances with estimates of dust and molecular gas masses, we show that there is no significant evolution in the normalization of the dust-to-gas ratio (DGR) versus metallicity relation from z ∼ 0 to z ∼ 2. This result is consistent with some semi-analytic models and cosmological simulations describing the evolution of dust in galaxies. Tracing the actual form of the DGR versus metallicity relation at high redshift now requires combined measurements of dust, gas, and metallicity over a significantly wider range in metallicity. * Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration, and was made possible by the generous financial support of the W.M. Keck Foundation.

Keywords: Gas-to-dust ratio, Metallicity, Galaxy evolution, Interstellar medium, High-redshift galaxies
Discovery of a Large Population of Nitrogen-enhanced Stars in the Magellanic Clouds. We report the APOGEE-2S+ discovery of a unique collection of nitrogen-enhanced mildly metal-poor giant stars, peaking at [Fe/H] ∼ -0.89 with no carbon enrichment, toward the Small and Large Magellanic Clouds (SMC and LMC), with abundances of light- (C, N), odd-Z (Al, K), and α-elements (O, Mg, Si) that are typically found in Galactic globular clusters (GCs). Here we present 44 stars in the SMC and LMC that exhibit significantly enhanced [N/Fe] abundance ratios, well above ([N/Fe] ≳ +0.6) typical Galactic levels at similar metallicity, and a star that is very nitrogen-enhanced ([N/Fe] &gt; +2.45). Our sample consists of luminous evolved stars on the asymptotic giant branch (AGB), eight of which are classified as bona fide semi-regular (SR) variables, as well as low-luminosity stars similar to those of stars on the tip of the red giant branch of stellar clusters in the SMC and LMC. It seems likely that whatever nucleosynthetic process is responsible for these anomalous SMC and LMC stars it is similar to that which caused the common stellar populations in GCs. We interpret these distinctive C-N patterns as observational evidence of the result of tidally shredded GCs in the SMC and LMC. These findings might explain some previous conflicting results over bulge N-rich stars, and broadly help to understand GC formation and evolution. Furthermore, the discovery of such a large population of N-rich AGB stars in the SMC and LMC suggests that multiple stellar populations might not only be exotic events from the past, but can also form at lower redshift.

Keywords: Globular star clusters, Red giant branch, Stellar abundances, Small Magellanic Cloud, Large Magellanic Cloud, Asymptotic giant branch stars, Semi-regular variable stars, Chemically peculiar stars
Effects of Spin on Constraining the Seeds and Growth of ≳10<SUP>9</SUP>M<SUB>⊙</SUB> Supermassive Black Holes in z &gt; 6.5 Quasars. The existence of ≳109M⊙ supermassive black holes (SMBHs) at redshift z &gt; 6 raises the problem of how such SMBHs can grow up within the cosmic time (&lt;1 Gyr) from small seed BHs. In this Letter, we use the observations of 14 quasars at z &gt; 6.5 with mass estimates to constrain their seeds and early growth, by self-consistently considering the spin evolution and the possibility of super-Eddington accretion. We find that spin plays an important role in the growth of early SMBHs, and the constraints on seed mass and super-Eddington accretion fraction strongly depend on the assumed accretion history. If the accretion is coherent with single (or a small number of) episode(s), leading to high spins for the majority of accretion time, then the SMBH growth is relatively slow; and if the accretion is chaotic with many episodes and in each episode the total accreted mass is much less than the SMBH mass, leading to moderate/low spins, then the growth is relatively fast. The constraints on the seed mass and super-Eddington accretion fraction are degenerate. A significant fraction (≳0.1%-1% in linear scale but ∼3-4 dex in logarithmic scale for 103-104M⊙ seeds) of super-Eddington accretion is required if the seed mass is not ≫105M⊙, and the requirements of high seed mass and/or super-Eddington accretion fraction are moderately relaxed if the accretion is chaotic.

Keywords: Accretion, Black hole physics, Early universe, Supermassive black holes, Quasars, Galaxy nuclei
Tearing Modes in Partially Ionized Astrophysical Plasma. In many astrophysical environments the plasma is only partially ionized, and therefore the interaction of charged and neutral particles may alter both the triggering of reconnection and its subsequent dynamical evolution. We derive the tearing mode maximum growth rate for partially ionized plasmas in the cases of weak and strong coupling between the plasma and the neutrals. In addition, critical scalings for current sheet aspect ratios are presented in terms of Lundquist number and ion-neutral collision frequencies for which the tearing mode becomes fast, or ideal. In the decoupled regime the standard tearing mode is recovered with a small correction that depends on the ion-neutral collision frequency; in the intermediate regime collisions with neutrals are shown to stabilize current sheets, resulting in larger critical aspect ratios for ideal tearing to occur. In the coupled regime, the growth rate depends on the density ratio between ions and neutrals through the collision frequency between these two species.

Keywords: Collision physics, Space plasmas, Plasma astrophysics, Solar magnetic reconnection
Observable Signatures of the Ejection Speed of Interstellar Objects from Their Birth Systems. 'Oumuamua and Borisov were the first two interstellar objects confirmed in the solar system. The upcoming commencement of the Vera C. Rubin Observatory&amp;'s Legacy Survey of Space of Time (LSST) will enhance greatly the discovery rate of interstellar objects. This raises the question, what can be learned from large-number statistics of interstellar objects? Here, we show that discovery statistics provided by LSST will allow low- and high-ejection-speed populations to be distinguished using the velocity dispersion and angular anisotropy of interstellar objects. These findings can be combined with physical characterizations to yield a better understanding of planetary system origin and nature.

Keywords: Planetary system formation, Comets, Asteroids
Formation of GW190521 via Gas Accretion onto Population III Stellar Black Hole Remnants Born in High-redshift Minihalos. The recent gravitational-wave merger event, GW190521, has challenged our understanding of stellar-mass black hole (BH) formation. The primary and secondary BHs are both inferred to fall inside the pair-instability (PI) mass gap. Here we propose that the formation of such binaries is possible through gas accretion onto the BH remnants of Population III stars born in high-redshift (z &gt; 10) minihalos. Once the parent halo has grown to the atomic-cooling limit, even brief episodes of gas accretion in the dense central regions of the halo can increase the masses of Population III remnant BHs above the PI limit. Starting with a binary black hole (BBH) with an initial mass of O(100) M⊙ we find that it would only need to spend about 100 Myr in the inner few parsecs of an atomic-cooling halo to accrete about 50 M⊙ of material and resemble a system similar to GW190521. The dynamical friction timescale for the binary to sink to the dense inner region of its parent halo is comparable or shorter than the accretion timescale required to increase their mass above the PI limit. Once in the core of the halo, the binary can enter a phase of hyper-Eddington accretion, where it would only take a few thousand years to exceed the PI limit through accretion. Even more massive BBHs could form through this channel, and be detectable by detectors with improved low-frequency sensitivity. Single Population III BH remnants would also grow through accretion and could later form binaries dynamically. As little as a few percent of Population III BH remnants may be sufficient to match the rate of massive BBH mergers inferred from GW190521 of ${0.13}_{-0.11}^{+0.3}\,{\mathrm{Gpc}}^{-3}\,{\mathrm{yr}}^{-1}$ .

Keywords: Population III stars, Black holes, Bondi accretion, Gravitational waves, LIGO
Detection of CH<SUB>3</SUB>C<SUB>3</SUB>N in Titan&amp;'s Atmosphere. Titan harbors a dense, organic-rich atmosphere primarily composed of N2 and CH4, with lesser amounts of hydrocarbons and nitrogen-bearing species. As a result of high-sensitivity observations by the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 6 (∼230-272 GHz), we obtained the first spectroscopic detection of CH3C3N (methylcyanoacetylene or cyanopropyne) in Titan&amp;'s atmosphere through the observation of seven transitions in the $J=64\to 63$ and $J=62\to 61$ rotational bands. The presence of CH3C3N on Titan was suggested by the Cassini Ion and Neutral Mass Spectrometer detection of its protonated form: C4H3NH+, but the atmospheric abundance of the associated (deprotonated) neutral product is not well constrained due to the lack of appropriate laboratory reaction data. Here, we derive the column density of CH3C3N to be (3.8-5.7) × 1012 cm-2 based on radiative transfer models sensitive to altitudes above 400 km Titan&amp;'s middle atmosphere. When compared with laboratory and photochemical model results, the detection of methylcyanoacetylene provides important constraints for the determination of the associated production pathways (such as those involving CN, CCN, and hydrocarbons), and reaction rate coefficients. These results also further demonstrate the importance of ALMA and (sub)millimeter spectroscopy for future investigations of Titan&amp;'s organic inventory and atmospheric chemistry, as CH3C3N marks the heaviest polar molecule detected spectroscopically in Titan&amp;'s atmosphere to date.

Keywords: Radio spectroscopy, Saturnian satellites, Millimeter astronomy, Natural satellites (Solar system), Planetary atmospheres, Chemical abundances, Astrochemistry, Radiative transfer, Atmospheric composition, Submillimeter astronomy, Radio astronomy, Astronomical methods
Particle-in-cell Simulation of Whistler Heat-flux Instabilities in the Solar Wind: Heat-flux Regulation and Electron Halo Formation. We present results of a two-dimensional fully kinetic particle-in-cell simulation in order to shed light on the role of whistler waves in the scattering of strahl electrons and in the heat-flux regulation in the solar wind. We model the electron velocity distribution function as initially composed of core and strahl populations as typically encountered in the near-Sun solar wind as observed by Parker Solar Probe. We demonstrate that, as a consequence of the evolution of the electron velocity distribution function (VDF), two branches of the whistler heat-flux instability can be excited, which can drive whistler waves propagating in the direction oblique or parallel to the background magnetic field. First, oblique whistler waves induce pitch-angle scattering of strahl electrons, toward higher perpendicular velocities. This leads to the broadening of the strahl pitch-angle distribution and hence to the formation of a halo-like population at the expense of the strahl. Later on, the electron VDF experiences the effect of parallel whistler waves, which contributes to the redistribution of the particles scattered in the perpendicular direction into a more symmetric halo, in agreement with observations. Simulation results show a remarkable agreement with the linear theory of the oblique whistler heat-flux instability. The process is accompanied by a significant decrease of the heat flux carried by the strahl population.

Keywords: Space plasmas, Solar wind, Plasma astrophysics
A Unified Accreting Magnetar Model for Long-duration Gamma-Ray Bursts and Some Stripped-envelope Supernovae. Both the long-duration gamma-ray bursts (LGRBs) and the Type I superluminous supernovae (SLSNe I) have been proposed to be primarily powered by central magnetars. A correlation, proposed between the initial spin period (P0) and the surface magnetic field (B) of the magnetars powering the X-ray plateaus in LGRB afterglows, indicates a possibility that the magnetars have reached an equilibrium spin period due to the fallback accretion. The corresponding accretion rates are inferred as $\dot{M}\approx {10}^{-4}\mbox{--}{10}^{-1}$ M⊙ s-1, and this result holds for the cases of both isotropic and collimated magnetar wind. For the SLSNe I and a fraction of engine-powered normal Type Ic supernovae (SNe Ic) and the broad-lined subclass (SNe Ic-BL), the magnetars could also reach an accretion-induced spin equilibrium, but the corresponding $B\mbox{--}{P}_{0}$ distribution suggests a different accretion rate range, i.e., $\dot{M}\approx {10}^{-7}\mbox{--}{10}^{-3}$ M⊙ s-1. Considering the effect of fallback accretion, magnetars with relatively weak fields are responsible for the SLSNe I, while those with stronger magnetic fields could power SNe Ic/Ic-BL. Some SLSNe I in our sample could arise from compact progenitor stars, while others that require longer-term accretion may originate from the progenitor stars with more extended envelopes or circumstellar medium.

Keywords: Magnetars, Gamma-ray bursts, Supernovae