adsabs/SciX_UAT_keywords huggingface dataset:
GASP. XLV. Stellar Bars in Jellyfish Galaxies: Analysis of Ionized Gas and Stellar Populations

Stellar bars have been found to substantially influence the properties of stellar populations in galaxies, affecting their ability to form stars. While this can be easily seen when studying galaxies in relatively isolated environments, such type of analysis requires a higher degree of complexity when cluster galaxies are considered, due to the variety of interactions that can potentially occur in these denser environments. We use IFU MUSE data from the GASP survey to study the combined effect of the presence of a stellar bar and ram pressure, on spatially resolved properties of stellar populations. We have analyzed spatially resolved indicators of both recent star formation rates (SFRs) and average stellar population ages to check for signatures of anomalous central star formation activity, also taking into account the possible presence of nuclear activity. We found an increase in central SFR in ram-pressure-affected galaxies when compared with unperturbed ones. The most extreme cases of increased SFR and central rejuvenation occur in barred galaxies that are at advanced stages of ram pressure stripping. For low-mass barred galaxies affected by ram pressure, the combined effect is the systematic enhancement of the star formation activity as opposed to the case of high-mass galaxies, which present both enhancement and suppression. Barred galaxies that present suppression of their star formation activity also present signatures of nuclear activity. Our results indicate that the combined effect of the presence of a bar and strong perturbation by ram pressure is able to trigger the central star formation activity and probably ignite nuclear activity.

Keywords: barred spiral galaxies; ram pressure stripped tails; galaxy clusters; star formation; galaxy evolution; spiral galaxies
Mass and Age Determination of the LAMOST Data with Different Machine-learning Methods

We present a catalog of 948,216 stars with mass labels and a catalog of 163,105 red clump (RC) stars with mass and age labels simultaneously. The training data set is crossmatched from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR5, and high-resolution asteroseismology data, mass, and age are predicted by the random forest (RF) method or a convex-hull algorithm. The stellar parameters with a high correlation with mass and age are extracted and the test data set shows that the median relative error of the prediction model for the mass of the large sample is 3%, and for the mass and age of RC stars is 4% and 7%. We also compare the predicted age of RC stars with recent works and find that the final uncertainty of the RC sample could reach 18% for age and 9% for mass; meanwhile, the final precision of the mass for the large sample with different types of stars could reach 13% without considering systematics. All of this implies that this method could be widely used in the future. Moreover, we explore the performance of different machine-learning methods for our sample, including Bayesian linear regression and the gradient-boosting decision tree (GBDT), multilayer perceptron, multiple linear regression, RF, and support vector regression methods. Finally, we find that the performance of a nonlinear model is generally better than that of a linear model, and the GBDT and RF methods are relatively better.

Keywords: stellar ages; stellar masses; support vector machine; random forests
Exploring the Effects of Active Magnetic Drag in a General Circulation Model of the Ultrahot Jupiter WASP-76b

Ultrahot Jupiters represent an exciting avenue for testing extreme physics and observing atmospheric circulation regimes not found in our solar system. Their high temperatures result in thermally ionized particles embedded in atmospheric winds interacting with the planet's interior magnetic field by generating current and experiencing bulk Lorentz force drag. Previous treatments of magnetic drag in 3D general circulation models (GCMs) of ultrahot Jupiters have mostly been uniform drag timescales applied evenly throughout the planet, which neglects the strong spatial dependence of these magnetic effects. In this work, we apply our locally calculated active magnetic drag treatment in a GCM of the planet WASP-76b. We find the effects of this treatment to be most pronounced in the planet's upper atmosphere, where strong differences between the day and night side circulation are present. These circulation effects alter the resulting phase curves by reducing the hot spot offset and increasing the day-night flux contrast. We compare our models to Spitzer phase curves, which imply a magnetic field of at least 3 G for the planet. We additionally contrast our results to uniform drag timescale models. This work highlights the need for more careful treatment of magnetic effects in atmospheric models of hot gas giants.

Keywords: exoplanets; exoplanet atmospheres; theoretical models; hot jupiters
Inverse MultiView. II. Microarcsecond Trigonometric Parallaxes for Southern Hemisphere 6.7 GHz Methanol Masers G232.62+00.99 and G323.74-00.26

We present the first results from the Southern Hemisphere Parallax Interferometric Radio Astrometry Legacy Survey: 10 μas accurate parallaxes and proper motions for two Southern Hemisphere 6.7 GHz methanol masers obtained using the inverse MultiView calibration method. Using an array of radio telescopes in Australia and New Zealand, we measured trigonometric parallaxes and proper motions for the masers associated with the star formation region G232.62+00.99 of π = 0.610 ± 0.011 mas, μ x = -2.266 ± 0.021 mas yr-1, and μ y = 2.249 ± 0.049 mas yr-1, which implies its distance to be d = 1.637 ± 0.029 kpc. These measurements represent an improvement in accuracy by more than a factor of 3 over the previous measurements obtained through Very Long Baseline Array observations of the 12 GHz methanol masers associated with this region. We also measure the trigonometric parallax and proper motion for G323.74-00.26 as π = 0.364 ± 0.009 mas, μ x = -3.239 ± 0.025 mas yr-1, and μ y = - 3.976 ± 0.039 mas yr-1, which implies a distance of d = 2.747 ± 0.068 kpc. These are the most accurate measurements of trigonometric parallax obtained for 6.7 GHz class II methanol masers to date. We confirm that G232.62+00.99 is in the Local Arm and find that G323.74-00.26 is in the Scutum-Centaurus arm. We also investigate the structure and internal dynamics of both masers.

Keywords: astrophysical masers; radio astrometry; very long baseline interferometry
ESCARGOT: Mapping Vertical Phase Spiral Characteristics Throughout the Real and Simulated Milky Way

The recent discovery of a spiral pattern in the vertical kinematic structure in the solar neighborhood provides a prime opportunity to study nonequilibrium dynamics in the Milky Way from local stellar kinematics. Furthermore, results from simulations indicate that even in a limited volume, differences in stellar orbital histories allow us to trace variations in the initial perturbation across large regions of the disk. We present ESCARGOT, a novel algorithm for studying these variations in both simulated and observed data sets. ESCARGOT automatically extracts key quantities from the structure of a given phase spiral, including the time since perturbation and the perturbation mode. We test ESCARGOT on simulated data and show that it is capable of accurately recovering information about the time since the perturbation occurred as well as subtle differences in phase spiral morphology due to stellar locations in the disk at the time of perturbation. We apply ESCARGOT to kinematic data from data release 3 of the Gaia mission in bins of guiding radius. We show that similar structural differences in morphology occur in the Gaia phase spirals as a function of stellar orbital history. These results indicate that the phase spirals are the product of a complex dynamical response in the disk with large-scale coupling between different regions of phase space.

Keywords: galaxy disks; solar neighborhood; milky way disk; galaxy kinematics; galaxy evolution
Constraining the Systematics of (Acoustic) Wave Heating Estimates in the Solar Chromosphere

Acoustic wave heating is believed to contribute significantly to the missing energy input required to maintain the solar chromosphere in its observed state. We studied the propagation of waves above the acoustic cutoff in the upper photosphere into the chromosphere with ultraviolet and optical spectral observations interpreted through comparison with 3D radiative magnetohydrodynamic Bifrost models to constrain the heating contribution from acoustic waves in the solar atmosphere. Sit-and-stare observations taken with the Interface Region Imaging Spectrograph and data from the Interferometric BIdimensional Spectrograph were used to provide the observational basis of this work. We compared the observations with synthetic observables derived from the Bifrost solar atmospheric model. Our analysis of the Bifrost simulations show that internetwork and enhanced-network regions exhibit significantly different wave-propagation properties, which are important for accurate wave flux estimates. The inferred wave energy fluxes based on our observations are not sufficient to maintain the solar chromosphere. We point out that the systematics of the modeling approaches in the literature lead to differences which could determine the conclusions of this type of study, based on the same observations.

Keywords: quiet solar chromosphere; solar chromospheric heating; radiative transfer
Numerical Modeling of Energetic Electron Acceleration, Transport, and Emission in Solar Flares: Connecting Loop-top and Footpoint Hard X-Ray Sources

The acceleration and transport of energetic electrons during solar flares is one of the outstanding topics in solar physics. Recent X-ray and radio imaging and spectroscopy observations have provided diagnostics of the distribution of nonthermal electrons and suggested that, in certain flare events, electrons are primarily accelerated in the loop top and likely experience trapping and/or scattering effects. By combining the focused particle transport equation with magnetohydrodynamic (MHD) simulations of solar flares, we present a macroscopic particle model that naturally incorporates electron acceleration and transport. Our simulation results indicate that physical processes such as turbulent pitch-angle scattering can have important impacts on both electron acceleration in the loop top and transport in the flare loop, and their influences are highly energy-dependent. A spatial-dependent turbulent scattering with enhancement in the loop top can enable both efficient electron acceleration to high energies and transport of abundant electrons to the footpoints. We further generate spatially resolved synthetic hard X-ray (HXR) emission images and spectra, revealing both the loop-top and footpoint HXR sources. Similar to the observations, we show that the footpoint HXR sources are brighter and harder than the loop-top HXR source. We suggest that the macroscopic particle model provides new insights into understanding the connection between the observed loop-top and footpoint nonthermal emission sources by combining the particle model with dynamically evolving MHD simulations of solar flares.

Keywords: solar flares; non-thermal radiation sources; solar magnetic reconnection; solar particle emission; solar energetic particles; shocks
Application of a Steady-state Accretion Disk Model to Spectrophotometry and High-resolution Spectra of Two Recent FU Ori Outbursts

We apply a conventional accretion disk model to the FU Ori-type objects HBC 722 and Gaia 17bpi. Our base model is a steady-state, thin Keplerian disk featuring a modified Shakura-Sunyaev temperature profile, with each annulus radiating as an area-weighted spectrum given by a NextGen atmosphere at the appropriate temperature. We explore departures from the standard model by altering the temperature distribution in the innermost region of the disk to account for "boundary region"-like effects. We consider the overall spectral energy distribution as well as medium- and high-resolution spectra in evaluating best-fit models to the data. Parameter degeneracies are studied via a Markov Chain Monte Carlo parameter estimation technique. Allowing all parameters to vary, we find accretion rates for HBC 722 of $\dot{M}={10}^{-4.90}{M}_{\odot }{\mathrm{yr}}^{-1}\,{}_{-0.40}^{+0.99}\mathrm{dex}$ and for Gaia 17bpi of $\dot{M}={10}^{-6.70}{M}_{\odot }{\mathrm{yr}}^{-1}\,{}_{-0.36}^{+0.46}\mathrm{dex};$ the corresponding maximum disk temperatures are ${7100}_{-500}^{+300}$ K and ${7900}_{-400}^{+900}$ K, respectively. While the accretion rate of HBC 722 is on the same order as other FU Ori-type objects, Gaia 17bpi has a lower rate than previously reported as typical, commensurate with its lower luminosity. Alternate models that fix some disk or stellar parameters are also presented, with tighter confidence intervals on the remaining fitted parameters. In order to improve upon the somewhat large credible intervals for the $\dot{M}$ values, and to make progress on boundary layer characterization, flux-calibrated ultraviolet spectroscopy is needed.

Keywords: young stellar objects; fu orionis stars; star formation; stellar accretion disks
A Comprehensive Radiative Magnetohydrodynamics Simulation of Active Region Scale Flux Emergence from the Convection Zone to the Corona

We present a comprehensive radiative magnetohydrodynamic simulation of the quiet Sun and large solar active regions. The 197 Mm wide simulation domain spans from 18(10) Mm beneath the photosphere to 113 Mm in the solar corona. Radiative transfer assuming local thermal equilibrium, optically thin radiative losses, and anisotropic conduction transport provide the necessary realism for synthesizing observables to compare with remote-sensing observations of the photosphere and corona. This model self-consistently reproduces observed features of the quiet Sun, emerging and developed active regions, and solar flares up to M class. Here, we report an overview of the first results. The surface magneto-convection yields an upward Poynting flux that is dissipated in the corona and heats the plasma to over 1 MK. The quiescent corona also presents ubiquitous propagating waves, jets, and bright points with sizes down to 2 Mm. Magnetic flux bundles emerge into the photosphere and give rise to strong and complex active regions with over 1023 Mx magnetic flux. The coronal free magnetic energy, which is approximately 18% of the total magnetic energy, accumulates to approximately 1033 erg. The coronal magnetic field is clearly non-force-free, as the Lorentz force needs to balance the pressure force and viscous stress as well as drive magnetic field evolution. The emission measure from ${\mathrm{log}}_{10}T=4.5$ to ${\mathrm{log}}_{10}T\gt 7$ provides a comprehensive view of the active region corona, such as coronal loops of various lengths and temperatures, mass circulation by evaporation and condensation, and eruptions from jets to large-scale mass ejections.

Keywords: radiative magnetohydrodynamics; solar magnetic fields; solar magnetic flux emergence; solar extreme ultraviolet emission; solar corona; solar active regions
The Impact of Outflows Driven by Active Galactic Nuclei on Metals in and around Galaxies

Metals in the hot gaseous halos of galaxies encode the history of star formation as well as the feedback processes that eject metals from the galaxies. X-ray observations suggest that massive galaxies have extended distributions of metals in their gas halos. We present predictions for the metal properties of massive galaxies and their gaseous halos from recent high-resolution zoom-in simulations that include mechanical and radiation-driven feedback from active galactic nuclei (AGN). In these simulations, AGN launch high-velocity outflows, mimicking observed broad absorption line winds. By comparing two sets of simulations with and without AGN feedback, we show that our prescription for AGN feedback is capable of driving winds and enriching halo gas "inside-out" by spreading centrally enriched metals to the outskirts of galaxies, into the halo and beyond. The metal (iron) profiles of halos simulated with AGN feedback have a flatter slope than those without AGN feedback, consistent with recent X-ray observations. The predicted gas iron abundance of group scale galaxies simulated with AGN feedback is ZFe = 0.23 ZFe,⊙ at 0.5r500, which is 2.5 times higher than that in simulations without AGN feedback. In these simulations, AGN winds are also important for the metal enrichment of the intergalactic medium, as the vast majority of metals ejected from the galaxy by AGN-driven winds end up beyond the halo virial radius.

Keywords: active galactic nuclei; galactic winds; chemical enrichment; galaxy chemical evolution; galaxy evolution
Polarization Criterion in Targeted SETI Observation

In this paper, we propose a novel method for distinguishing extraterrestrial intelligence (ETI) signals from radio frequency interference (RFI) by leveraging polarization features. We exploit the sinusoidal variation of the linearly polarized components of Stokes parameters with the parallactic angle as a characteristic signature of ETI signals, while such linearly polarized components remain relatively stable for terrestrial RFI. Typically, a minimum of 4-8 hr of observation time is required to detect these sinusoidal variations. The polarization approach in the search for extraterrestrial intelligence also enables us to study the radio stellar bursts emitted by M-type stars as ancillary science, which is relevant to assessing the habitability of exoplanets. Compared to the frequency drift method, the polarization method effectively reduces the required observation time for signal identification while improving the signal identification process.

Keywords: search for extraterrestrial intelligence; astronomical instrumentation
Fast Optical Transients from Stellar-mass Black Hole Tidal Disruption Events in Young Star Clusters

Observational evidence suggests that the majority of stars may have been born in stellar clusters or associations. Within these dense environments, dynamical interactions lead to high rates of close stellar encounters. A variety of recent observational and theoretical indications suggest stellar-mass black holes may be present and play an active dynamical role in stellar clusters of all masses. In this study, we explore the tidal disruption of main-sequence stars by stellar-mass black holes in young star clusters. We compute a suite of over 3000 independent N-body simulations that cover a range of cluster mass, metallicity, and half-mass radii. We find stellar-mass black hole tidal disruption events (TDEs) occur at an overall rate of up to roughly 200 Gpc-3 yr-1 in young stellar clusters in the local universe. These TDEs are expected to have several characteristic features, namely, fast rise times of order a day, peak X-ray luminosities of at least 1044 erg s-1, and bright optical luminosities (roughly 1041-1044 erg s-1) associated with reprocessing by a disk wind. In particular, we show these events share many features in common with the emerging class of Fast Blue Optical Transients.

Keywords: astrophysical black holes; young star clusters; tidal disruption; transient sources; n-body simulations; x-ray transient sources
Observing the Effects of Galaxy Interactions on the Circumgalactic Medium

We continue our empirical study of the emission line flux originating in the cool (T ∼ 104 K) gas that populates the halos of galaxies and their environments. Specifically, we present results obtained for a sample of galaxy pairs with a range of projected separations, $10\lt {S}_{p}/\mathrm{kpc}\lt 200$ , and mass ratios <1:5, intersected by 5443 Sloan Digital Sky Survey lines of sight at projected radii of 10-50 kpc from either or both of the two galaxies. We find significant enhancement in Hα emission and a moderate enhancement in [N II]6583 emission for low-mass pairs (mean stellar mass per galaxy, ${\overline{M}}_{* },\lt {10}^{10.4}{M}_{\odot }$ ) relative to the results from a control sample. This enhanced Hα emission comes almost entirely from sight lines located between the galaxies, consistent with a short-term, interaction-driven origin for the enhancement. We find no enhancement in Hα emission, but significant enhancement in [N II]6583 emission for high-mass ( ${\overline{M}}_{* }\gt {10}^{10.4}{M}_{\odot }$ ) pairs. Furthermore, we find a dependence of the emission line properties on the galaxy pair mass ratio such that those with a mass ratio below 1:2.5 have enhanced [N II]6583 and those with a mass ratio between 1:2.5 and 1:5 do not. In all cases, departures from the control sample are only detected for close pairs (Sp < 100 kpc). Attributing an elevated [N II]6583/Hα ratio to shocks, we infer that shocks play a role in determining the circumgalactic medium properties for close pairs that are among the more massive and have mass ratios closer to 1:1.

Keywords: circumgalactic medium; galaxy pairs; interacting galaxies
Life on Exoplanets in the Habitable Zone of M Dwarfs?

Exoplanets orbiting in the habitable zone around M dwarf stars have been prime targets in the search for life due to the long lifetimes of the host star, the prominence of such stars in the galaxy, and the apparent excess of terrestrial planets found around M dwarfs. However, the heightened stellar activity of M dwarfs and the often tidally locked planets in these systems have raised questions about the habitability of these planets. In this Letter we examine another significant challenge that may exist: these systems seem to lack the architecture necessary to deliver asteroids to the habitable terrestrial planets, and asteroid impacts may play a crucial role in the origin of life. The most widely accepted mechanism for producing a stable asteroid belt and the late-stage delivery of asteroids after gas disk dissipation requires a giant planet exterior to the snow-line radius. We show that none of the observed systems with planets in the habitable zone of their star also contain a giant planet and therefore are unlikely to have stable asteroid belts. We consider the locations of observed giant planets relative to the snow-line radius as a function of stellar mass and find that there is a population of giant planets outside of the snow-line radius around M dwarfs. Therefore, asteroid belt formation around M dwarfs is generally possible. However, we find that multiplanetary system architectures around M dwarfs can be quite different from those around more massive stars.

Keywords: exoplanets; astrobiology; planet formation; extrasolar gaseous giant planets; extrasolar rocky planets; habitable planets