Sazuna/UAT_keywords huggingface dataset:
Effects of Pressure Anisotropy on the Geometry of Magnetic Flux Rope. This paper aims to examine the effects of pressure anisotropy on the geometry of magnetic flux rope using the newly developed two-dimensional magnetohydrostatic reconstruction associated with pressure anisotropy. A small-scale magnetic flux rope observed by the Magnetospheric Multiscale mission, in the magnetosheath reconnection outflow during an outbound magnetopause crossing, is demonstrated. At the center of the flux rope, the magnetic field strength was enhanced with decreasing plasma pressure. The entire flux rope was mostly occupied by the pressure anisotropy of p ⊥ &gt; p ∥, where the subscripts ∥ and ⊥ denote the components parallel and perpendicular to the local magnetic field, respectively. The estimated aspect ratio of the width to the length of the flux rope from reconstruction was ~0.326 for p ⊥ &gt; p ∥ and ~0.389 for isotropic pressure. By comparing the magnetic field map from the isotropic Grad-Shafranov reconstruction, the results show for p ⊥ &gt; p ∥ that (1) the width of the flux rope is reduced, leading to a small aspect ratio of the flux rope, and (2) the circular field line of the flux rope is contracted. Moreover, an experiment is conducted for p ∥ &gt; p ⊥ by exchanging p ⊥ and p ∥ of the flux rope, for which the isotropic pressure is less affected. The experimental results indicate that the effects of p ∥ &gt; p ⊥ on the geometry of the flux rope are opposite to that of p ⊥ &gt; p ∥. The overall finding may provide new insight into charged particle acceleration within magnetic flux ropes/islands in anisotropic plasmas.

Keywords: Interplanetary physics
Searching Extra-tidal Features around the Globular Cluster Whiting 1. Whiting 1 is a faint and young globular cluster in the halo of the Milky Way, and was suggested to have originated in the Sagittarius spherical dwarf galaxy (Sgr dSph). In this paper, we use the deep DESI Legacy Imaging Surveys to explore tentative spatial connection between Whiting 1 and the Sgr dSph. We redetermine the fundamental parameters of Whiting 1 and use the best-fitting isochrone (age τ = 6.5 Gyr, metallicity Z = 0.005 and d ⊙ = 26.9 kpc) to construct a theoretical matched filter for the extra-tidal features searching. Without any smooth technique to the matched filter density map, we detect a round-shape feature with possible leading and trailing tails on either side of the cluster. This raw image is not totally new compared to old discoveries, but confirms that no more large-scale features can be detected under a depth of r &lt; =22.5 mag. In our results, the whole feature stretches 0°.1-0°.2 along the orbit of Whiting 1, which gives a much larger area than the cluster core. The tails on both sides of the cluster align along the orbital direction of the Sgr dSph as well as the cluster itself, which implies that these debris are probably stripped remnants of Whiting 1 by the Milky Way.

Keywords: Globular star clusters, Stellar structures, Milky Way Galaxy
The HST Large Program on ω Centauri. V. Exploring the Ultracool Dwarf Population with Stellar Atmosphere and Evolutionary Modeling. Brown dwarfs can serve as both clocks and chemical tracers of the evolutionary history of the Milky Way due to their continuous cooling and high sensitivity of spectra to composition. We focus on brown dwarfs in globular clusters that host some of the oldest coeval populations in the galaxy. Currently, no brown dwarfs in globular clusters have been confirmed, but they are expected to be uncovered with advanced observational facilities such as the James Webb Space Telescope (JWST). In this paper we present a new set of stellar models specifically designed to investigate low-mass stars and brown dwarfs in ω Centauri-the largest known globular cluster. The parameters of our models were derived from iterative fits to Hubble Space Telescope photometry of the main-sequence members of the cluster. Despite the complex distribution of abundances and the presence of multiple main sequences in ω Centauri, we find that the modal color-magnitude distribution can be represented by a single stellar population with parameters determined in this study. The observed luminosity function is well represented by two distinct stellar populations having solar and enhanced helium mass fractions and a common initial mass function, in agreement with previous studies. Our analysis confirms that the abundances of individual chemical elements play a key role in determining the physical properties of low-mass cluster members. We use our models to draw predictions of brown dwarf colors and magnitudes in anticipated JWST NIRCam data, confirming that the beginning of the substellar sequence should be detected in ω Centauri in forthcoming observations.

Keywords: Globular star clusters, Galactic archaeology, Brown dwarfs, Stellar atmospheres
An Assessment of the In Situ Growth of the Intracluster Light in the High-redshift Galaxy Cluster SpARCS1049+56. The formation of the stellar mass within galaxy cluster cores is a poorly understood process. It features the complicated physics of cooling flows, active galactic nucleus feedback, star formation, and more. Here we study the growth of the stellar mass in the vicinity of the brightest cluster galaxy (BCG) in a z = 1.7 cluster, SpARCS1049+56. We synthesize a reanalysis of existing Hubble Space Telescope imaging, a previously published measurement of the star formation rate, and the results of new radio molecular gas spectroscopy. These analyses represent the past, present, and future star formation, respectively, within this system. We show that a large amount of stellar mass-between (2.2 ± 0.5) × 1010 M ⊙ and (6.6 ± 1.2) × 1010 M ⊙ depending on the data processing-exists in a long and clumpy tail-like structure that lies roughly 12 kpc off the BCG. Spatially coincident with this stellar mass is a similarly massive reservoir ((1.0 ± 0.7) × 1011 M ⊙) of molecular gas that we suggest is the fuel for the immense star formation rate of 860 ± 130 M ⊙ yr-1, as measured by infrared observations. Hlavacek-Larrondo et al. surmised that massive, runaway cooling of the hot intracluster X-ray gas was feeding this star formation, a process that had not been observed before at high redshift. We conclude, based on the amount of fuel and current stars, that this event may be rare in the lifetime of a cluster, producing roughly 15%-21% of the intracluster light mass in one go, though perhaps a common event for all galaxy clusters.

Keywords: Galaxy clusters, Intracluster medium, High-redshift galaxy clusters
Stable Mass Transfer Can Explain Massive Binary Black Hole Mergers with a High-spin Component. Recent gravitational-wave observations showed that binary black hole (BBH) mergers with massive components are more likely to have high effective spins. In the model of isolated binary evolution, BH spins mainly originate from the angular momenta of the collapsing cores before BH formation. Both observations and theories indicate that BHs tend to possess relatively low spins; the origin of fast-spinning BHs remains a puzzle. We investigate an alternative process that stable Case A mass transfer may significantly increase BH spins during the evolution of massive BH binaries. We present detailed binary evolution calculations and find that this process can explain the observed high spins of some massive BBH mergers under the assumption of mildly super-Eddington accretion.

Keywords: Stellar evolution, Compact binary stars, Gravitational waves, Black holes
Spatially Resolved Molecular Interstellar Medium in a z = 6.6 Quasar Host Galaxy. We present high spatial resolution (~0.″4, 2.2 kpc) observations of the CO(6-5), CO(7-6), and [C I]369 μm lines and dust continuum emission from the interstellar medium (ISM) in the host galaxy of the quasar J0305-3150 at z = 6.6. These, together with archival [C II]158 μm data at a comparable spatial resolution, enable studies of the spatial distribution and kinematics between the ISM in different phases. When comparing the radial profiles of CO, [C II]158 μm, and the dust continuum, we find that the CO and dust continuum exhibit similar spatial distributions, both of which are less extended than the [C II]158 μm, indicating that the CO and dust continuum are tracing the same gas component, while the [C II]158 μm is tracing a more extended one. In addition, we derive the radial profiles of the [C II]158 μm/CO, [C II]158 μm/far-infrared (FIR), CO/FIR, and dust continuum S 98.7 GHz/S 258.1 GHz ratios. We find a decreasing S 98.7 GHz/S 258.1 GHz ratio with radius, possibly indicating a decrease of dust optical depth with increasing radius. We also detect some of the ISM lines and continuum emission in the companion galaxies previously discovered in the field around J0305-3150. Through comparing the line-to-line and line-to-FIR ratios, we find no significant differences between the quasar and its companion galaxies.

Keywords: AGN host galaxies, Interstellar dust, Early universe, Molecular gas, Interstellar atomic gas, Quasars, Interstellar medium, Submillimeter astronomy, High-redshift galaxies
Microphysics of Diffusive Shock Acceleration: Impact on the Spectrum of Accelerated Particles. Diffusive shock acceleration at collisionless shocks remains the most likely process for accelerating particles in a variety of astrophysical sources. While the standard prediction for strong shocks is that the spectrum of accelerated particles is universal, f(p) ∝ p -4, numerous phenomena affect this simple conclusion. In general, the nonlinear dynamical reaction of accelerated particles leads to a concave spectrum, steeper than p -4 at momenta below a few tens of GeV c -1 and harder than the standard prediction at high energies. However, the nonlinear effects become important in the presence of magnetic field amplification, which in turn leads to higher values of the maximum momentum p max. It was recently discovered that the self-generated perturbations that enhance particle scattering, when advected downstream, move in the same direction as the background plasma, so that the effective compression factor at the shock decreases and the spectrum becomes steeper. We investigate the implications of the excitation of the non-resonant streaming instability on these spectral deformations, the dependence of the spectral steepening on the shock velocity, and the role played by the injection momentum.

Keywords: Supernova remnants, Galactic cosmic rays
AlOSO: Spectroscopy and Structure of a New Group of Astrochemical Molecules. With the ever-increasing detection of sulfur-bearing molecules and the high abundance and refractory nature of aluminum, the [Al, S, O2] isomers may play an important role in the gas-phase chemistry of circumstellar envelopes and the chemistry on the surface of dust grains. High-level theoretical exploration of the [Al, S, O2] molecular system yielded five isomers, and predictions of their rotational, vibrational, and electronic spectroscopic properties are provided to inform experimental and observational searches. Cis-AlOSO and diamond isomers are isoenergetic and connected via a very small (~1 kcal mol-1) transition-state barrier. These isomers may act as intermediates along the chemical pathway between Al + SO2 and AlO + SO. Other isomers OAlOS and SAlO2 are stable relative to their corresponding dissociation asymptotes. Large permanent dipole moments of 2.521 D (cis-AlOSO), 1.239 D (diamond), and 5.401 D (OAlOS) predict strong rotational transitions and indicate these molecules as prime candidates for experimental study. Due to the low transition-state barrier, mixing of the vibrational levels is anticipated, complicating the vibrational spectrum. Electronic spectroscopy may be used as a means to differentiate between the two isomers. Strong electronic transitions are predicted to occur in the 200-300 nm range for cis-AlOSO and diamond. Simulated electronic absorption spectra provide a starting point for experimental characterization and spectral deconvolution of these isomers.

Keywords: Circumstellar envelopes, Molecular spectroscopy, Astrochemistry, Computational methods, Interstellar medium
A Babcock-Leighton-type Solar Dynamo Operating in the Bulk of the Convection Zone. The toroidal magnetic field is assumed to be generated in the tachocline in most Babcock-Leighton (BL)-type solar dynamo models, in which the poloidal field is produced by the emergence and subsequent dispersal of sunspot groups. However, magnetic activity of fully convective stars and MHD simulations of global stellar convection have recently raised serious doubts regarding the importance of the tachocline in the generation of the toroidal field. In this study, we aim to develop a new BL-type dynamo model, in which the dynamo operates mainly within the bulk of the convection zone. Our 2D model includes the effect of solar-like differential rotation, one-cell meridional flow, near-surface radial pumping, strong turbulent diffusion, BL-type poloidal source, and nonlinear back-reaction of the magnetic field on its source with a vertical outer boundary condition. The model leads to a simple dipolar configuration of the poloidal field that has the dominant latitudinal component, which is wound up by the latitudinal shear within the bulk of the convection zone to generate the toroidal flux. As a result, the tachocline plays a negligible role in the model. The model reproduces the basic properties of the solar cycle, including (a) approximately 11 yr cycle period and 18 yr extended cycle period; (b) equatorward propagation of the antisymmetric toroidal field starting from high latitudes; and (c) polar field evolution that is consistent with observations. Our model opens the possibility for a paradigm shift in understanding the solar cycle to transition from the classical flux transport dynamo.

Keywords: Solar differential rotation, Sunspot cycle, Solar dynamo
Characterization of Supernovae Based on the Spectral-Temporal Energy Distribution: Two Possible SN Ib Subtypes. A quantitative data-driven comparison among supernovae (SNe) based on their spectral time series combined with multiband photometry is presented. We use an unsupervised random forest algorithm as a metric on a set of 82 well-documented SNe representing all the main spectroscopic types, in order to embed these in an abstract metric space reflecting shared correlations between the objects. We visualize the resulting metric space in 3D, revealing strong agreement with the current spectroscopic classification scheme. The embedding splits Type Ib supernovae into two groups, with one subgroup exhibiting broader, less prominent, higher-velocity lines than the other, possibly suggesting a new SN Ib subclass is required. The method could be to classify newly discovered SNe according to their distance from known event groups, or ultimately to devise a new, spectral-temporal classification scheme. Such an embedding could also depend on hidden parameters that may perhaps be physically interpretable.

Keywords: Type Ib supernovae, Random Forests, Supernovae, Classification
Searching Far and Long. I. Pilot ALMA 2 mm Follow-up of Bright Dusty Galaxies as a Redshift Filter. A complete census of dusty star-forming galaxies (DSFGs) at early epochs is necessary to constrain the obscured contribution to the cosmic star formation rate density (CSFRD); however, DSFGs beyond z ~ 4 are both rare and hard to identify from photometric data alone due to degeneracies in submillimeter photometry with redshift. Here, we present a pilot study obtaining follow-up Atacama Large Millimeter Array (ALMA) 2 mm observations of a complete sample of 39 850 μm-bright dusty galaxies in the SSA22 field. Empirical modeling suggests 2 mm imaging of existing samples of DSFGs selected at 850 μm-1 mm can quickly and easily isolate the "needle in a haystack" DSFGs that sit at z &gt; 4 or beyond. Combining archival submillimeter imaging with our measured ALMA 2 mm photometry (1σ ~ 0.08 mJy beam-1 rms), we characterize the galaxies' IR spectral energy distributions (SEDs) and use them to constrain redshifts. With available redshift constraints fit via the combination of six submillimeter bands, we identify 6/39 high-z candidates each with &gt;50% likelihood to sit at z &gt; 4, and find a positive correlation between redshift and 2 mm flux density. Specifically, our models suggest the addition of 2 mm to a moderately constrained IR SED will improve the accuracy of a millimeter-derived redshift from Δz/(1 + z) = 0.3 to Δz/(1 + z) = 0.2. Our IR SED characterizations provide evidence for relatively high-emissivity spectral indices (&lt;β&gt; = 2.4 ± 0.3) in the sample. We measure that especially bright (S 850μ m  &gt; 5.55 mJy) DSFGs contribute ~10% to the cosmic-averaged CSFRD from 2 &lt; z &lt; 5, confirming findings from previous work with similar samples.

Keywords: Submillimeter astronomy, Ultraluminous infrared galaxies, Starburst galaxies
Analytical Modeling of Exoplanet Transit Spectroscopy with Dimensional Analysis and Symbolic Regression. The physical characteristics and atmospheric chemical composition of newly discovered exoplanets are often inferred from their transit spectra, which are obtained from complex numerical models of radiative transfer. Alternatively, simple analytical expressions provide insightful physical intuition into the relevant atmospheric processes. The deep-learning revolution has opened the door for deriving such analytical results directly with a computer algorithm fitting to the data. As a proof of concept, we successfully demonstrate the use of symbolic regression on synthetic data for the transit radii of generic hot-Jupiter exoplanets to derive a corresponding analytical formula. As a preprocessing step, we use dimensional analysis to identify the relevant dimensionless combinations of variables and reduce the number of independent inputs, which improves the performance of the symbolic regression. The dimensional analysis also allowed us to mathematically derive and properly parameterize the most general family of degeneracies among the input atmospheric parameters that affect the characterization of an exoplanet atmosphere through transit spectroscopy.

Keywords: Regression, Hot Jupiters, Exoplanet atmospheres, Transmission spectroscopy, Radiative transfer equation, Dimensionality reduction
SN 2020jfo: A Short-plateau Type II Supernova from a Low-mass Progenitor. We present spectroscopic and photometric observations of the Type IIP supernova, SN 2020jfo, in ultraviolet and optical wavelengths. SN 2020jfo occurred in the spiral galaxy M61 (NGC 4303), with eight observed supernovae in the past 100 yr. SN 2020jfo exhibited a short plateau lasting &lt; 65 days, and achieved a maximum brightness in Vband of M  V  = -17.4 ± 0.4 mag at about 8.0 ± 0.5 days since explosion. From the bolometric light curve, we have estimated the mass of 56Ni synthesized in the explosion to be 0.033 ± 0.006 M ⊙. The observed spectral features are typical for a Type IIP supernova except for shallow Hα absorption throughout the evolution and the presence of stable 58Ni feature at 7378 Å, in the nebular phase. Using hydrodynamical modeling in the MESA + STELLA framework, an ejecta mass of ~5 M ⊙ is estimated. Models also indicate SN 2020jfo could be the result of a red supergiant progenitor with M ZAMS ~ 12 M ⊙. Bolometric light-curve modeling revealed the presence of a secondary radiation source for initial ~20 days, which has been attributed to interaction with a circumstellar material of mass ~ 0.2 M ⊙, which most likely was ejected due to enhanced mass loss about 20 yr prior to the supernova explosion.

Keywords: Observational astronomy, Ejecta, Red supergiant stars, Core-collapse supernovae, Type II supernovae, Supernovae, Supernova dynamics
Kiloparsec-scale Imaging of the CO(1-0)-traced Cold Molecular Gas Reservoir in a z   3.4 Submillimeter Galaxy. We present a high-resolution study of the cold molecular gas as traced by CO(1-0) in the unlensed z ~ 3.4 submillimeter galaxy SMM J13120+4242, using multiconfiguration observations with the Karl G. Jansky Very Large Array (JVLA). The gas reservoir, imaged on 0.″39 (~3 kpc) scales, is resolved into two components separated by ~11 kpc with a total extent of 16 ± 3 kpc. Despite the large spatial extent of the reservoir, the observations show a CO(1-0) FWHM linewidth of only 267 ± 64 km s-1. We derive a revised line luminosity of ${L}_{\mathrm{CO}(1-0)}^{{\prime} }$ = (10 ± 3) × 1010 K km s-1 pc2 and a molecular gas mass of M gas = (13 ± 3)× 1010 (α CO/1) M ⊙. Despite the presence of a velocity gradient (consistent with previous resolved CO(6-5) imaging), the CO(1-0) imaging shows evidence for significant turbulent motions that are preventing the gas from fully settling into a disk. The system likely represents a merger in an advanced stage. Although the dynamical mass is highly uncertain, we use it to place an upper limit on the CO-to-H2 mass conversion factor α CO of 1.4. We revisit the SED fitting, finding that this galaxy lies on the very massive end of the main sequence at z = 3.4. Based on the low gas fraction, short gas depletion time, and evidence for a central AGN, we propose that SMM J13120 is in a rapid transitional phase between a merger-driven starburst and an unobscured quasar. The case of SMM J13120 highlights how mergers may drive important physical changes in galaxies without pushing them off the main sequence.

Keywords: Starburst galaxies, High-redshift galaxies, Galaxy evolution, Interstellar medium
A Monte Carlo Method for Evaluating Empirical Gyrochronology Models and Its Application to Wide Binary Benchmarks. Accurate stellar ages are essential for our understanding of the star formation history of the Milky Way and Galactic chemical evolution, as well as to constrain exoplanet formation models. Gyrochronology, a relationship between stellar rotation and age, appears to offer a reliable age indicator for main-sequence (MS) stars over the mass range of approximately 0.6-1.3 M ⊙. Those stars lose their angular momentum due to magnetic braking and as a result their rotation speeds decrease with age. Although current gyrochronology relations have been fairly well tested for young MS stars with masses greater than 1 M ⊙, primarily in young open clusters, insufficient tests exist for older and lower mass MS stars. Binary stars offer the potential to expand and fill in the range of ages and metallicity over which gyrochronology can be empirically tested. In this paper, we demonstrate a Monte Carlo approach to evaluate gyrochronology models using binary stars. As examples, we used five previously published wide binary pairs. We also demonstrate a Monte Carlo approach to assess the precision and accuracy of ages derived from each gyrochronology model. For the traditional Skumanich models, the age uncertainties are σ age/age = 15%-20% for stars with B - V = 0.65 and σ age/age = 5%-10% for stars with B - V = 1.5 and rotation period P ≤ 20 days.

Keywords: Binary stars, Stellar ages, Stellar colors, Wide binary stars, Main sequence stars, Stellar rotation