Sazuna/UAT_keywords huggingface dataset:
Betatron Acceleration of Suprathermal Electrons within a Small-scale Flux Rope in the Solar Wind. A growing body of evidence from observations, theories, and simulations indicates that particles can be effectively accelerated in solar wind regions filled with dynamic small-scale flux ropes (FRs). The main acceleration mechanisms identified in simulations include parallel electric field acceleration, first-order Fermi acceleration, and generalized betatron acceleration in contracting or merging small-scale FRs. However, direct identification of these acceleration mechanisms from in situ measurements remains a challenge. Here we present a distinct event of local betatron acceleration within a contracting small-scale FR in the solar wind, due to a local compression. In this event, the lower-energy halo electrons were effectively accelerated through the betatron mechanism, whereas the higher-energy suprathermal electrons predominated by the superhalo component were almost not energized. The halo electron energization processes via the betatron mechanism are reproduced using an analytical model. Further examination of small-scale FRs in the vicinity of the heliospheric current sheet over the period 1995-2020 indicates that in situ signatures of the betatron acceleration process are essentially elusive.

Keywords: Interplanetary particle acceleration, Solar wind, Interplanetary physics
Spatial Extent of Molecular Gas, Dust, and Stars in Massive Galaxies at z ∼ 2.2-2.5 Determined with ALMA and JWST. We present the results of 0.″6-resolution observations of CO J = 3 - 2 line emission in 10 massive star-forming galaxies at z ~ 2.2-2.5 with the Atacama Large Millimeter/submillimeter Array (ALMA). We compare the spatial extent of molecular gas with those of dust and stars, traced by the 870 and 4.4 μm continuum emissions, respectively. The average effective radius of the CO emission is 1.75 ± 0.34 kpc, which is about 60% larger than that of the 870 μm emission and is comparable with that of the 4.4 μm emission. Utilizing the best-fit parametric models, we derive the radial gradients of the specific star formation rate (sSFR), gas depletion timescale, and gas-mass fraction within the observed galaxies. We find a more intense star formation activity with a higher sSFR and a shorter depletion timescale in the inner region than in the outer region. The central starburst may be the primary process for massive galaxies to build up a core. Furthermore, the gas-mass fraction is high, independent of the galactocentric radius in the observed galaxies, suggesting that the galaxies have not begun to quench star formation. Given the shorter gas depletion timescale in the center compared to the outer region, quenching is expected to occur in the center first and then propagate outward. We may be witnessing the observed galaxies in the formation phase of a core prior to the forthcoming phase of star formation propagating outward.

Keywords: Starburst galaxies, High-redshift galaxies
A Formation Mechanism for "Wrong Way" Radio Relics. Radio relics are typically found to be arc-like regions of synchrotron emission in the outskirts of merging galaxy clusters, bowing out from the cluster center. In most cases they show synchrotron spectra that steepen toward the cluster center, indicating that they are caused by relativistic electrons being accelerated at outward traveling merger shocks. A number of radio relics break with this ideal picture and show morphologies that are bent the opposite way and show spectral index distributions that do not follow expectations from the ideal picture. We propose that these "wrong way" relics can form when an outward traveling shock wave is bent inward by an infalling galaxy cluster or group. We test this in an ultra-high-resolution zoom-in simulation of a massive galaxy cluster with an on-the-fly spectral cosmic-ray model. This allows us to study not only the synchrotron emission at colliding shocks, but also their synchrotron spectra to address the open question of relics with strongly varying spectral indices over the relic surface.

Keywords: Galaxy clusters, Extragalactic radio sources, Cosmic rays
Is the M81 Fast Radio Burst Host Globular Cluster Special?. We use multiband archival Hubble Space Telescope (HST) observations to measure the photometric and structural parameters of the M81 globular cluster (GC) that hosts the fast radio burst FRB 20200120E. Our best-fitting King model has an effective radius r  h  = 3.06 pc with a moderate King model concentration of c = 53, and an inferred core radius of 0.81 pc. We revisit the exact astrometric location of the FRB within the cluster, and find that FRB 20200120E is located 1.92 pc from the center, but within the projected half-light radius. We estimate the relative encounter rate of the FRB host, along with the corresponding rates of 210 other GCs in M81, and compare these values with the encounter rates of Galactic GCs. The FRB resides in a GC with an encounter rate that is moderately higher than the median stellar encounter rate in our two comparison samples. While the estimated encounter rate of the FRB host cluster (e.g., ~50% of a cluster like 47 Tuc) is sufficient to allow the possibility that the FRB formed dynamically, our results do not place strong constraints on this scenario due to the limitations of the available HST data and the possible systematic uncertainties and selection effects in the comparison data.

Keywords: Globular star clusters, Low-mass x-ray binary stars, Radio transient sources
The Puzzling Properties of the MACS1149-JD1 Galaxy at z = 9.11. We analyze new JWST NIRCam and NIRSpec data on the redshift 9.11 galaxy MACS1149-JD1 (hereafter JD1). Our NIRCam imaging data reveal that JD1 comprises three spatially distinct components. Our spectroscopic data indicate that JD1 appears dust free but is already enriched, $12+\mathrm{log}({\rm{O}}/{\rm{H}})={7.90}_{-0.05}^{+0.04}$ . We also find that the carbon and neon abundances in JD1 are below the solar abundance ratio. Particularly the carbon under-abundance is suggestive of recent star formation where Type II supernovae have already enriched the interstellar medium (ISM) in oxygen but intermediate mass stars have not yet enriched the ISM in carbon. A recent burst of star formation is also revealed by the star formation history derived from NIRCam photometry. Our data do not reveal the presence of a significant amount of old populations, resulting in a factor of ~7× smaller stellar mass than previous estimates. Thus, our data support the view that JD1 is a young galaxy.

Keywords: High-redshift galaxies
VERTICO and IllustrisTNG: The Spatially Resolved Effects of Environment on Galactic Gas. It has been shown in previous publications that the TNG100 simulation quantitatively reproduces the observed reduction in each of the total atomic and total molecular hydrogen gas for galaxies within massive halos, i.e., dense environments. In this Letter, we study how well TNG50 reproduces the resolved effects of a Virgo-like cluster environment on the gas surface densities of satellite galaxies with m * &gt; 109 M ☉ and star formation rate &gt; 0.05 M ☉ yr-1. We select galaxies in the simulation that are analogous to those in the HERACLES and VERTICO surveys and mock-observe them to the common specifications of the data. Although TNG50 does not quantitatively match the observed gas surface densities in the centers of galaxies, the simulation does qualitatively reproduce the trends of gas truncation and central density suppression seen in VERTICO in both H I and H2. This result promises that modern cosmological hydrodynamic simulations can be used to reliably model the post-infall histories of cluster satellite galaxies.

Keywords: Interstellar molecules, Galaxy evolution, Interstellar atomic gas, Galaxy environments
First M87 Event Horizon Telescope Results. IX. Detection of Near-horizon Circular Polarization. Event Horizon Telescope (EHT) observations have revealed a bright ring of emission around the supermassive black hole at the center of the M87 galaxy. EHT images in linear polarization have further identified a coherent spiral pattern around the black hole, produced from ordered magnetic fields threading the emitting plasma. Here we present the first analysis of circular polarization using EHT data, acquired in 2017, which can potentially provide additional insights into the magnetic fields and plasma composition near the black hole. Interferometric closure quantities provide convincing evidence for the presence of circularly polarized emission on event-horizon scales. We produce images of the circular polarization using both traditional and newly developed methods. All methods find a moderate level of resolved circular polarization across the image (&lt;∣v∣&gt; &lt; 3.7%), consistent with the low image-integrated circular polarization fraction measured by the Atacama Large Millimeter/submillimeter Array (∣v int∣ &lt; 1%). Despite this broad agreement, the methods show substantial variation in the morphology of the circularly polarized emission, indicating that our conclusions are strongly dependent on the imaging assumptions because of the limited baseline coverage, uncertain telescope gain calibration, and weakly polarized signal. We include this upper limit in an updated comparison to general relativistic magnetohydrodynamic simulation models. This analysis reinforces the previously reported preference for magnetically arrested accretion flow models. We find that most simulations naturally produce a low level of circular polarization consistent with our upper limit and that Faraday conversion is likely the dominant production mechanism for circular polarization at 230 GHz in M87*.

Keywords: Supermassive black holes, Very long baseline interferometry, Low-luminosity active galactic nuclei, Polarimetry, Galaxies
Polarimetric Geometric Modeling for mm-VLBI Observations of Black Holes. The Event Horizon Telescope (EHT) is a millimeter very long baseline interferometry (VLBI) array that has imaged the apparent shadows of the supermassive black holes M87* and Sagittarius A*. Polarimetric data from these observations contain a wealth of information on the black hole and accretion flow properties. In this work, we develop polarimetric geometric modeling methods for mm-VLBI data, focusing on approaches that fit data products with differing degrees of invariance to broad classes of calibration errors. We establish a fitting procedure using a polarimetric "m-ring" model to approximate the image structure near a black hole. By fitting this model to synthetic EHT data from general relativistic magnetohydrodynamic models, we show that the linear and circular polarization structure can be successfully approximated with relatively few model parameters. We then fit this model to EHT observations of M87* taken in 2017. In total intensity and linear polarization, the m-ring fits are consistent with previous results from imaging methods. In circular polarization, the m-ring fits indicate the presence of event-horizon-scale circular polarization structure, with a persistent dipolar asymmetry and orientation across several days. The same structure was recovered independently of observing band, used data products, and model assumptions. Despite this broad agreement, imaging methods do not produce similarly consistent results. Our circular polarization results, which imposed additional assumptions on the source structure, should thus be interpreted with some caution. Polarimetric geometric modeling provides a useful and powerful method to constrain the properties of horizon-scale polarized emission, particularly for sparse arrays like the EHT.

Keywords: Black hole physics, Supermassive black holes, Very long baseline interferometry, Active galactic nuclei, Polarimetry, High angular resolution
JWST Reveals Excess Cool Water near the Snow Line in Compact Disks, Consistent with Pebble Drift. Previous analyses of mid-infrared water spectra from young protoplanetary disks observed with the Spitzer-IRS found an anticorrelation between water luminosity and the millimeter dust disk radius observed with ALMA. This trend was suggested to be evidence for a fundamental process of inner disk water enrichment proposed decades ago to explain some properties of the solar system, in which icy pebbles drift inward from the outer disk and sublimate after crossing the snow line. Previous analyses of IRS water spectra, however, were uncertain due to the low spectral resolution that blended lines together. We present new JWST-MIRI spectra of four disks, two compact and two large with multiple radial gaps, selected to test the scenario that water vapor inside the snow line is regulated by pebble drift. The higher spectral resolving power of MIRI-MRS now yields water spectra that separate individual lines, tracing upper level energies from 900 to 10,000 K. These spectra clearly reveal excess emission in the low-energy lines in compact disks compared to large disks, demonstrating an enhanced cool component with T ≈ 170-400 K and equivalent emitting radius R eq ≈ 1-10 au. We interpret the cool water emission as ice sublimation and vapor diffusion near the snow line, suggesting that there is indeed a higher inward mass flux of icy pebbles in compact disks. Observation of this process opens up multiple exciting prospects to study planet formation chemistry in inner disks with JWST.

Keywords: Infrared spectroscopy, Molecular spectroscopy, Classical T Tauri stars, Young stellar objects, Pre-main sequence stars, Star formation, Protoplanetary disks, Circumstellar disks, Exoplanet formation, Planet formation
Dwindling Surface Cooling of a Rotating Jovian Planet Leads to a Convection Zone That Grows to a Finite Depth. Recent measurements of Jupiter's gravitational field (by Juno) and seismology of Saturn's rings (by Cassini) strongly suggest that both planets have a stably stratified core that still possesses a primordial gradient in the concentration of heavy elements. The existence of such a "diffusely" stratified core has been a surprise as it was long expected that the Jovian planets should be fully convective and hence fully mixed. A vigorous zone of convection, driven by surface cooling, forms at the surface and deepens through entrainment of fluid from underneath. In fact, it was believed that this convection zone should grow so rapidly that the entire planet would be consumed in less than a million years. Here we suggest that two processes, acting in concert, present a solution to this puzzle. All of the giant planets are rapidly rotating and have a cooling rate that declines with time. Both of these effects reduce the rate of fluid entrainment into the convection zone. Through the use of an analytic prescription of entrainment in giant planets, we demonstrate that these two effects, rotation and dwindling surface cooling, result in a convection zone that initially grows but eventually stalls. The depth to which the convective interface asymptotes depends on the rotation rate and on the stratification of the stable interior. Conversely, in a nonrotating planet, or in a planet that maintains a higher level of cooling than current models suggest, the convection zone deepens forever, eventually spanning the entire planet.

Keywords: Hydrodynamics, Astrophysical fluid dynamics, Solar system gas giant planets, Jupiter, Planetary thermal histories, Planetary cores, Planetary interior
Tilted Dark Halos Are Common and Long-lived, and Can Warp Galactic Disks. In the Lambda cold dark matter paradigm, the dark halo governs the gravitational potential within which a galaxy can form and evolve. In this Letter we show that the present-day inner (r &lt; 50 kpc) dark halo can be significantly misaligned with the stellar disk. To this end, we use the TNG50 run from the cosmological magnetohydrodynamic IllustrisTNG simulation suite. Such "tilted" dark halos can arise from a variety of processes including major mergers, massive flybys, or interactions with satellite companions. Furthermore, we show that tilted dark halos (1) are well traced by tilted stellar halos, (2) can maintain their tilt for &gt;5 Gyr in isolated evolution, and (3) can generate warps in the outer disks that are stable over many Gyr. A tilted dark halo holds clues to important events in the formation history of a galaxy, and could help explain the abundance of warped disks in galaxy observations, including the Milky Way.

Keywords: Galaxy dark matter halos
Production of <SUP>44</SUP>Ti and Iron-group Nuclei in the Ejecta of 3D Neutrino-driven Supernovae. The radioactive isotopes 44Ti and 56Ni are important products of explosive nucleosynthesis, which play a key role in supernova (SN) diagnostics and have been detected in several nearby young SN remnants. However, most SN models based on nonrotating single stars predict yields of 44Ti that are much lower than the values inferred from observations. We present, for the first time, the nucleosynthesis yields from a self-consistent three-dimensional SN simulation of a ~19 M ⊙ progenitor star that reaches an explosion energy comparable to that of SN 1987A and that covers the evolution of the neutrino-driven explosion until more than 7 s after core bounce. We find a significant enhancement of the Ti/Fe yield compared to recent spherically symmetric (1D) models and demonstrate that the long-time evolution is crucial to understanding the efficient production of 44Ti due to the nonmonotonic temperature and density history of the ejected material. Additionally, we identify characteristic signatures of the nucleosynthesis in proton-rich ejecta, in particular high yields of 45Sc and 64Zn.

Keywords: Explosive nucleosynthesis, Nucleosynthesis, Core-collapse supernovae, Gamma-ray sources, Supernova remnants
GOALS-JWST: Small Neutral Grains and Enhanced 3.3 μm PAH Emission in the Seyfert Galaxy NGC 7469. We present James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec) integral field spectroscopy of the nearby luminous infrared galaxy NGC 7469. We take advantage of the high spatial/spectral resolution and wavelength coverage of JWST/NIRSpec to study the 3.3 μm neutral polycyclic aromatic hydrocarbon (PAH) grain emission on ~200 pc scales. A clear change in the average grain properties between the star-forming ring and the central AGN is found. Regions in the vicinity of the AGN, with [Ne III]/[Ne II] &gt; 0.25, tend to have larger grain sizes and lower aliphatic-to-aromatic (3.4/3.3) ratios, indicating that smaller grains are preferentially removed by photodestruction in the vicinity of the AGN. PAH emission at the nucleus is weak and shows a low 11.3/3.3 PAH ratio. We find an overall suppression of the total PAH emission relative to the ionized gas in the central 1 kpc region of the AGN in NGC 7469 compared to what has been observed with Spitzer on 3 kpc scales. However, the fractional 3.3 μm-to-total PAH power is enhanced in the starburst ring, possibly due to a variety of physical effects on subkiloparsec scales, including recurrent fluorescence of small grains or multiple photon absorption by large grains. Finally, the IFU data show that while the 3.3 μm PAH-derived star formation rate (SFR) in the ring is 27% higher than that inferred from the [Ne II] and [Ne III] emission lines, the integrated SFR derived from the 3.3 μm feature would be underestimated by a factor of 2 due to the deficit of PAHs around the AGN, as might occur if a composite system like NGC 7469 were to be observed at high redshift.

Keywords: Starburst galaxies, Polycyclic aromatic hydrocarbons, Seyfert galaxies, Active galactic nuclei, Luminous infrared galaxies
Little Red Dots or Brown Dwarfs? NIRSpec Discovery of Three Distant Brown Dwarfs Masquerading as NIRCam-selected Highly Reddened Active Galactic Nuclei. Cold, substellar objects such as brown dwarfs have long been recognized as contaminants in color-selected samples of active galactic nuclei (AGNs). In particular, their near- to mid-infrared colors (1-5 μm) can closely resemble the V-shaped (f  λ ) spectra of highly reddened accreting supermassive black holes ("little red dots"), especially at 6 &lt; z &lt; 7. Recently, a NIRCam-selected sample of little red dots over 45 arcmin2 has been followed up with deep NIRSpec multiobject prism spectroscopy through the UNCOVER program. By investigating the acquired spectra, we identify 3 of the 14 followed-up objects as T/Y dwarfs with temperatures between 650 and 1300 K and distances between 0.8 and 4.8 kpc. At ${4.8}_{-0.1}^{+0.6}$ kpc, A2744-BD1 is the most distant brown dwarf discovered to date. We identify the remaining 11 objects as extragalactic sources at z spec ≳ 5. Given that three of these sources are strongly lensed images of the same AGN (A2744-QSO1), we derive a brown dwarf contamination fraction of 25% in this NIRCam selection of little red dots. We find that in the near-infrared filters, brown dwarfs appear much bluer than the highly reddened AGN, providing an avenue for distinguishing the two and compiling cleaner samples of photometrically selected highly reddened AGN.

Keywords: Active galactic nuclei, Brown dwarfs, Y dwarfs, T dwarfs
AC Her: Evidence of the First Polar Circumbinary Planet. We examine the geometry of the post-asymptotic giant branch (AGB) star binary AC Her and its circumbinary disk. We show that the observations describe a binary orbit that is perpendicular to the disk with an angular momentum vector that is within 9° of the binary eccentricity vector, meaning that the disk is close to a stable polar alignment. The most likely explanation for the very large inner radius of the dust is a planet within the circumbinary disk. This is therefore both the first reported detection of a polar circumbinary disk around a post-AGB binary and the first evidence of a polar circumbinary planet. We consider the dynamical constraints on the circumbinary disk size and mass. The polar circumbinary disk feeds circumstellar disks with gas on orbits that are highly inclined with respect to the binary orbit plane. The resulting circumstellar disk inclination could be anywhere from coplanar to polar depending upon the competition between the mass accretion and binary torques.

Keywords: Accretion, Post-asymptotic giant branch stars, Binary stars, Hydrodynamics, Exoplanet formation
Open Magnetic Fields in the Martian Magnetosphere Revealing Dipole-like Intrinsic Magnetic Fields at Mars. Mars's magnetosphere is hybrid, having contributions from both an induced magnetosphere like Venus and the localized crustal magnetic fields. However, the planetary fields also include large-scale, more global components. In this study, we investigate their role in Mars's magnetospheric topological responses to the interplanetary magnetic field (IMF) clock angle using observations from the Mars Atmospheric Volatile and EvolutioN mission. We show that the large-scale planetary field has a "dipole-like" influence on the Mars global magnetosphere by examining the open field topology. We find that the "dipole-like" planetary field, as at Earth, results in a more open magnetosphere during southward IMF. The clock angle effects on the twisted magnetotail current sheet are similarly consistent with this analogy. It reinforces the idea that Mars's magnetosphere and solar wind interaction are more Earth-like than previously thought.

Keywords: Magnetic anomalies, Mars, Solar-planetary interactions, Interplanetary magnetic fields, Magnetic fields