Sazuna/UAT_keywords huggingface dataset:
Ion Energization and Thermalization in Magnetic Reconnection Exhaust Region in the Solar Wind. Plasma energization and thermalization in magnetic reconnection is an important topic in astrophysical studies. We select two magnetic reconnection exhausts encountered by Solar Orbiter and analyze the associated ion heating in the kinetic regime. Both cases feature asymmetric plasma merging in the exhaust and anisotropic heating. For a quantitative investigation of the associated complex velocity-space structures, we adopt a three-dimensional Hermite representation of the proton velocity distribution function to produce the distribution of Hermite moments. We also derive the enstrophy and Hermite spectra to analyze the free energy conversion and transfer in phase space. We find a depletion of Hermite power at small m (corresponding to large-scale structures in velocity space) inside the reconnection exhaust region, concurrent with enhanced proton temperature and decreased enstrophy. Furthermore, the slopes of the 1D time-averaged parallel Hermite spectra are lower inside the exhaust and consistent with the effect of phase mixing that creates small fluctuations in velocity space. These fluctuations store free energy at higher m and are smoothed by weak collisionality, leading to irreversible thermalization. We also suggest that the perpendicular heating may happen via perpendicular phase mixing resulting from finite Larmor radius effects around the exhaust boundary.

Keywords: Solar wind, Solar magnetic reconnection, Heliosphere
The Impact of Cosmic Ray Injection on Magnetic Flux Tubes in a Galactic Disk. In a seminal paper, Parker showed the vertical stratification of the interstellar medium (ISM) is unstable if magnetic fields and cosmic rays provide too large a fraction of pressure support. Cosmic ray acceleration is linked to star formation, so Parker's instability and its nonlinear outcomes are a type of star formation feedback. Numerical simulations have shown the instability can significantly restructure the ISM, thinning the thermal gas layer and thickening the magnetic field and cosmic ray layer. However, the timescale on which this occurs is rather long (~0.4 Gyr). Furthermore, the conditions for instability depend on the model adopted for cosmic ray transport. In this work, we connect the instability and feedback problems by examining the effect of a single, spatially and temporally localized cosmic ray injection on the ISM over ~1 kpc3 scales. We perform cosmic ray magnetohydrodynamic simulations using the Athena++ code, varying the background properties, dominant cosmic ray transport mechanism, and injection characteristics between our simulation runs. We find robust effects of buoyancy for all transport models, with disruption of the ISM on timescales as short as 100 Myr when the background equilibrium is dominated by cosmic ray pressure.

Keywords: Cosmic rays, Galaxy structure, Magnetohydrodynamical simulations
A Framework for Modeling Polycyclic Aromatic Hydrocarbon Emission in Galaxy Evolution Simulations. We present a new methodology for simulating mid-infrared emission from polycyclic aromatic hydrocarbons (PAHs) in galaxy evolution simulations. To do this, we combine theoretical models of PAH emission features as they respond to varying interstellar radiation fields, grain-size distributions, and ionization states with a new model for dust evolution in galaxy simulations. We apply these models to three idealized AREPO galaxy evolution simulations within the SMUGGLE physics framework. We use these simulations to develop numerical experiments investigating the buildup of PAH masses and luminosities in galaxies in idealized analogs of the Milky Way, a dwarf galaxy, and a starburst disk. Our main results are as follows. Galaxies with high specific star formation rates have increased feedback energy per unit mass, and are able to shatter grains efficiently, driving up the fraction of ultrasmall grains. At the same time, in our model large radiation fields per unit gas density convert aliphatic grains into aromatics. The fraction of dust grains in the form of PAHs (q PAH) can be understood as a consequence of these processes, and in our model PAHs form primarily from interstellar processing (shattering) of larger grains rather than from the growth of smaller grains. We find that the hardness of the radiation field plays a larger role than variations in the grain-size distribution in setting the total integrated PAH luminosities, though cosmological simulations are necessary to investigate fully the complex interplay of processes that drive PAH band luminosities in galaxies.

Keywords: Interstellar dust, Polycyclic aromatic hydrocarbons, James Webb Space Telescope, Interstellar dust processes, Astronomical simulations
Mapping the Skies of Ultracool Worlds: Detecting Storms and Spots with Extremely Large Telescopes. Extremely large telescopes (ELTs) present an unparalleled opportunity to study the magnetism, atmospheric dynamics, and chemistry of very-low-mass (VLM) stars, brown dwarfs, and exoplanets. Instruments such as the Giant Magellan Telescope-Consortium Large Earth Finder (GMT/GCLEF), the Thirty Meter Telescope's Multi-Objective Diffraction-limited High-Resolution Infrared Spectrograph (TMT/MODHIS), and the European Southern Observatory's Mid-Infrared ELT Imager and Spectrograph (ELT/METIS) provide the spectral resolution and signal-to-noise ratio necessary to Doppler image ultracool targets' surfaces based on temporal spectral variations due to surface inhomogeneities. Using our publicly available code, Imber, developed and validated in Plummer &amp; Wang, we evaluate these instruments' abilities to discern magnetic starspots and cloud systems on a VLM star (TRAPPIST-1), two L/T transition ultracool dwarfs (VHS J1256-1257 b and SIMP J0136+0933), and three exoplanets (Beta Pic b and HR 8799 d and e). We find that TMT/MODHIS and ELT/METIS are suitable for Doppler imaging the ultracool dwarfs and Beta Pic b over a single rotation. Uncertainties for longitude and radius are typically ≲10°, and latitude uncertainties range from ~10° to 30°. TRAPPIST-1's edge-on inclination and low $\upsilon \sin i$ provide a challenge for all three instruments, while GMT/GCLEF and the HR 8799 planets may require observations over multiple rotations. We compare the spectroscopic technique, photometry-only inference, and the combination of the two. We find combining spectroscopic and photometric observations can lead to improved Bayesian inference of surface inhomogeneities and offers insight into whether ultracool atmospheres are dominated by spotted or banded features.

Keywords: Brown dwarfs, Doppler imaging, Direct imaging, Late-type dwarf stars, Exoplanet atmospheres
EMPRESS. IX. Extremely Metal-poor Galaxies are Very Gas-rich Dispersion-dominated Systems: Will the James Webb Space Telescope Witness Gaseous Turbulent High-z Primordial Galaxies?. We present kinematics of six local extremely metal-poor galaxies (EMPGs) with low metallicities (0.016-0.098 Z ⊙) and low stellar masses (104.7-107.6 M ⊙). Taking deep medium/high-resolution (R ~ 7500) integral-field spectra with 8.2 m Subaru, we resolve the small inner velocity gradients and dispersions of the EMPGs with Hα emission. Carefully masking out substructures originating by inflow and/or outflow, we fit three-dimensional disk models to the observed Hα flux, velocity, and velocity dispersion maps. All the EMPGs show rotational velocities (v rot) of 5-23 km s-1 smaller than the velocity dispersions (σ 0) of 17-31 km s-1, indicating dispersion-dominated (v rot/σ 0 = 0.29-0.80 &lt; 1) systems affected by inflow and/or outflow. Except for two EMPGs with large uncertainties, we find that the EMPGs have very large gas-mass fractions of f gas ≃ 0.9-1.0. Comparing our results with other Hα kinematics studies, we find that v rot/σ 0 decreases and f gas increases with decreasing metallicity, decreasing stellar mass, and increasing specific star formation rate. We also find that simulated high-z (z ~ 7) forming galaxies have gas fractions and dynamics similar to the observed EMPGs. Our EMPG observations and the simulations suggest that primordial galaxies are gas-rich dispersion-dominated systems, which would be identified by the forthcoming James Webb Space Telescope observations at z ~ 7.

Keywords: Galaxy formation, Galaxy structure, Dwarf galaxies, Star formation, Galaxy kinematics
Evidence for Thermal X-Ray Emission from the Synchrotron-dominated Shocks in Tycho's Supernova Remnant. Young supernova remnant (SNR) shocks are believed to be the main sites of galactic cosmic-ray production, showing X-ray synchrotron-dominated spectra in the vicinity of their shock. While a faint thermal signature left by the shocked interstellar medium (ISM) should also be found in the spectra, proofs for such an emission in Tycho's SNR have been lacking. We perform an extended statistical analysis of the X-ray spectra of five regions behind the blast wave of Tycho's SNR using Chandra archival data. We use Bayesian inference to perform extended parameter space exploration and sample the posterior distributions of a variety of models of interest. According to Bayes factors, spectra of all five regions of analysis are best described by composite three-component models taking nonthermal emission, ejecta emission, and shocked ISM emission into account. The shocked ISM stands out the most in the northern limb of the SNR. We find for the shocked ISM a mean electron temperature ${{kT}}_{{\rm{e}}}={0.96}_{-0.51}^{+1.33}$ keV for all regions and a mean ionization timescale ${n}_{{\rm{e}}}t={2.55}_{-1.22}^{+0.5}\times {10}^{9}$ cm-3 s resulting in a mean ambient density ${n}_{{\rm{e}}}={0.32}_{-0.15}^{+0.23}$ cm-3 around the remnant. We performed an extended analysis of the northern limb and show that the measured synchrotron cutoff energy is not well constrained in the presence of a shocked ISM component. Such results cannot currently be further investigated by analyzing emission lines in the 0.5-1 keV range, because of the low Chandra spectral resolution in this band. We show with simulated spectra that Athena X-ray Integral Field Unit future performances will be crucial to address this point.

Keywords: Bayesian statistics, Posterior distribution, Supernova remnants, Interstellar medium, Spectroscopy
Multiphase Gas Interactions on Subarcsec Scales in the Shocked Intergalactic Medium of Stephan's Quintet with JWST and ALMA. We combine James Webb Space Telescope (JWST) and Hubble Space Telescope imaging with Atacama Large Millimeter Array CO(2-1) spectroscopy to study the highly turbulent multiphase intergalactic medium (IGM) in Stephan's Quintet on 25-150 pc scales. Previous Spitzer observations revealed luminous H2 line cooling across a 45 kpc-long filament, created by a giant shock wave, following the collision with an intruder galaxy, NGC 7318b. We demonstrate that the Mid-Infrared Instrument/F1000W/F770W filters are dominated by 0-0 S(3) H2 and a combination of polycyclic aromatic hydrocarbon and 0-0 S(5) H2 emission. These observations reveal the dissipation of kinetic energy as massive clouds experience collisions, interactions, and likely destruction/recycling within different phases of the IGM. In 1 kpc-scaled structure, warm H2 was seen to form a triangular-shaped head and tail of compressed and stripped gas behind a narrow shell of cold H2. In another region, two cold molecular clumps with very different velocities are connected by an arrow-shaped stream of warm, probably shocked, H2 suggesting a cloud-cloud collision is occurring. In both regions, a high warm-to-cold molecular gas fraction indicates that the cold clouds are being disrupted and converted into warm gas. We also map gas associated with an apparently forming dwarf galaxy. We suggest that the primary mechanism for exciting strong mid-IR H2 lines throughout Stephan's Quintet is through a fog of warm gas created by the shattering of denser cold molecular clouds and mixing/recycling in the post-shocked gas. A full picture of the diverse kinematics and excitation of the warm H2 will require future JWST mid-IR spectroscopy. The current observations reveal the rich variety of ways that different gas phases can interact with one another.

Keywords: Hickson compact group, Intergalactic clouds, Intergalactic medium phases, Galaxy groups, Intergalactic medium
Extending the Dynamic Range of Galaxy Outflow Scaling Relations: Massive Compact Galaxies with Extreme Outflows. We investigate galactic winds in the HizEA galaxies, a collection of 46 late-stage galaxy mergers at z = 0.4-0.8, with stellar masses of $\mathrm{log}({M}_{* }/{M}_{\odot })=10.4\mbox{--}11.5$ , star formation rates (SFRs) of 20-500 M ⊙ yr-1, and ultra-compact (a few 100 pc) central star-forming regions. We measure their gas kinematics using the Mg II λ λ 2796,2803 absorption lines in optical spectra from MMT, Magellan, and Keck. We find evidence of outflows in 90% of targets, with maximum outflow velocities of 550-3200 km s-1. We combine these data with ten samples from the literature to construct scaling relations for outflow velocity versus SFR, star formation surface density (ΣSFR), M *, and SFR/M *. The HizEA galaxies extend the dynamic range of the scaling relations by a factor of ~2-4 in outflow velocity and an order of magnitude in SFR and ΣSFR. The ensemble scaling relations exhibit strong correlations between outflow velocity, SFR, SFR/R, and ΣSFR, and weaker correlations with M * and SFR/M *. The HizEA galaxies are mild outliers on the SFR and M * scaling relations, but they connect smoothly with more typical star-forming galaxies on plots of outflow velocity versus SFR/R and ΣSFR. These results provide further evidence that the HizEA galaxies' exceptional outflow velocities are a consequence of their extreme star formation conditions rather than hidden black hole activity, and they strengthen previous claims that ΣSFR is one of the most important properties governing the velocities of galactic winds.

Keywords: Starburst galaxies, Galaxy evolution, Scaling relations, Compact galaxies
Precession-induced Variability in AGN Jets and OJ 287. The combined study of the flaring of active galactic nuclei (AGNs) at radio wavelengths and parsec-scale jet kinematics with Very Long Baseline Interferometry has led to the view that (i) the observed flares are associated with ejections of synchrotron blobs from the core, and (ii) most of the flaring follows a one-to-one correlation with the ejection of the component. Recent results have added to the mounting evidence showing that the quasi-regular component injections into the relativistic jet may not be the only cause of the flux variability. We propose that AGN flux variability and changes in jet morphology can both be of deterministic nature, i.e., having a geometric/kinetic origin linked to the time-variable Doppler beaming of the jet emission as its direction changes due to precession (and nutation). The physics of the underlying jet leads to shocks, instabilities, or ejections of plasmoids. The appearance (morphology, flux, etc.) of the jet can, however, be strongly affected and modulated by precession. We demonstrate this modulating power of precession for OJ 287. For the first time, we show that the spectral state of the spectral energy distribution (SED) can be directly related to the jet's precession phase. We model the SED evolution and reproduce the precession parameters. Further, we apply our precession model to 11 prominent AGNs. We show that for OJ 287 precession seems to dominate the long-term variability (≳1 yr) of the AGN flux, SED spectral state, and jet morphology, while stochastic processes affect the variability on short timescales (≲0.2 yr).

Keywords: Blazars, Relativistic jets, Active galactic nuclei, Galaxy mergers, Gravitational waves, Radio interferometry
Seeking Self-regulating Simulations of Idealized Milky Way-like Galaxies. Precipitation is potentially a mechanism through which the circumgalactic medium (CGM) can regulate a galaxy's star formation. Here, we present idealized simulations of isolated Milky Way-like galaxies intended to examine the ability of galaxies to self-regulate their star formation, in particular via precipitation. We also examine the impact of rotation in the CGM. Using six simulations, we explore variations in the initial CGM t cool/t ff ratio and rotation profile. Those variations affect the amount of gas accretion and star formation within the galactic disk. To encourage this accretion and better study its dependence on CGM structure, we gradually increase the efficiency of stellar feedback during the first half of our simulations. Yet despite this gradual increase, the resulting outflows quickly evacuate large, hot cavities within the CGM and even beyond r 200. Some of the CGM gas avoids interacting with the cavities and is able to feed the disk along its midplane, but the cooling of feedback-heated gas far from the midplane is too slow to supply the disk with additional gas. Our simulations illustrate the importance of physical mechanisms in the outer CGM and IGM for star formation regulation in Milky Way-scale halos.

Keywords: Hydrodynamical simulations, Stellar feedback, Galaxy evolution, Circumgalactic medium, Galaxy processes
A High-resolution Spectroscopic Analysis of Aminoacrylonitrile and an Interstellar Search toward G+0.693. Cyanides, ranging from three carbon atoms to polycyclic aromatic hydrocarbons, and alkenyl compounds are abundant in the interstellar medium. Aminoacrylonitrile (3-Amino-2-propenenitrile, H2N-CH=CH-C≡N), an alkenyl cyanide, thus represents a promising candidate for new interstellar detection. A comprehensive spectroscopic laboratory investigation of aminoacrylonitrile in its rotational ground vibrational state has been herein performed. The measurements carried out up to the THz regime made it possible to generate a precise set of reliable rest frequencies for its search in space up to submillimeter wavelengths. The Z-aminoacrylonitrile (Z-apn) isomer spectrum has been recorded employing a source-modulated submillimeter spectrometer, from 80 GHz to 1 THz. A combination of Doppler and sub-Doppler measurement regimes allowed one to record 600 new lines. The collected data have enabled the characterization of a set of spectroscopic parameters up to decic centrifugal distortion constants. The catalog generated from the improved spectral data has been used for the search of Z-apn in the spectral survey of the G+0.693-0.027 molecular cloud located in the central molecular zone, in the proximity of the Galactic center.

Keywords: Interstellar molecules, Spectral line identification, Molecular spectroscopy, Laboratory astrophysics, Interstellar abundances, Molecular clouds, Pre-biotic astrochemistry, Interstellar medium, Complex organic molecules
High-sensitivity Observations of the H<SUB>2</SUB>O Megamasers of NGC 1068: Precise Astrometry and Detailed Kinematics. We present High Sensitivity Array observations of the H2O megamasers of NGC 1068. We obtain absolute astrometry with 0.3 mas precision that confirms the association of the disk masers with the nuclear radio continuum source S1. The new observations reveal two new blueshifted groups of disk masers. We also detect the 22 GHz continuum on short interferometric baselines. The position-velocity diagram of the disk masers shows a curve consistent with a nonaxisymmetric distribution of maser spots. This curve is probably the result of spiral arms with a constant pitch angle ~5°. The disk kinematics are consistent with Keplerian rotation and low turbulent speeds. The inferred central mass is 17 × 106 M ☉. On the basis of disk stability arguments, the mass of the molecular disk is ≈110 × 103 M ☉. The disk masers further resolve into filamentary structures suggesting an ordered magnetic field threading the maser disk. The magnetic field strengths must be ≳2 mG to withstand turbulent motions in the partially ionized molecular gas. We note apparent asymmetries in the molecular disk that might be explained by anisotropic heating by a misaligned inner accretion disk. The new observations also detect the fainter jet masers north of the disk masers. The distribution and kinematics of the jet masers are consistent with an expanding ring of molecular gas.

Keywords: Black holes, Active galaxies, Megamasers, Astrophysical masers, Galaxies
Aluminium-26 from Massive Binary Stars. III. Binary Stars up to Core Collapse and Their Impact on the Early Solar System. Many of the short-lived radioactive nuclei that were present in the early solar system can be produced in massive stars. In the first paper in this series, we focused on the production of 26Al in massive binaries. In our second paper, we considered rotating single stars; two more short-lived radioactive nuclei, 36Cl and 41Ca; and the comparison to the early solar system data. In this work, we update our previous conclusions by further considering the impact of binary interactions. We used the MESA stellar evolution code with an extended nuclear network to compute massive (10-80 M ⊙), binary stars at various initial periods and solar metallicity (Z = 0.014), up to the onset of core collapse. The early solar system abundances of 26Al and 41Ca can be matched self-consistently by models with initial masses ≥25 M ⊙, while models with initial primary masses ≥35 M ⊙ can also match 36Cl. Almost none of the models provide positive net yields for 19F, while for 22Ne the net yields are positive from 30 M ⊙ and higher. This leads to an increase by a factor of approximately 4 in the amount of 22Ne produced by a stellar population of binary stars, relative to single stars. In addition, besides the impact on the stellar yields, our 10 M ⊙ primary star undergoing Case A mass transfer ends its life as a white dwarf instead of as a core-collapse supernova. This demonstrates that binary interactions can also strongly impact the evolution of stars close to the supernova boundary.

Keywords: Binary stars, Stellar evolutionary models, Stellar winds, Stellar nucleosynthesis, Stellar evolution
Primordial or Secondary? Testing Models of Debris Disk Gas with ALMA. The origin and evolution of gas in debris disks are still not well understood. Secondary gas production from cometary material or a primordial origin have been proposed. So far, observations have mostly concentrated on CO, with only a few C observations available. We overview the C and CO content of debris disk gas and test state-of-the-art models. We use new and archival Atacama Large Millimeter/submillimeter Array (ALMA) observations of CO and C I emission, complemented by C II data from Herschel, for a sample of 14 debris disks. This expands the number of disks with ALMA measurements of both CO and C I by 10 disks. We present new detections of C I emission toward three disks: HD 21997, HD 121191, and HD 121617. We use a simple disk model to derive gas masses and column densities. We find that current state-of-the-art models of secondary gas production overpredict the C0 content of debris disk gas. This does not rule out a secondary origin, but might indicate that the models require an additional C removal process. Alternatively, the gas might be produced in transient events rather than a steady-state collisional cascade. We also test a primordial gas origin by comparing our results to a simplified thermochemical model. This yields promising results, but more detailed work is required before a conclusion can be reached. Our work demonstrates that the combination of C and CO data is a powerful tool to advance our understanding of debris disk gas. * Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Keywords: Aperture synthesis, Chemical abundances, Radiative transfer, Submillimeter astronomy, Debris disks, Circumstellar gas