adsabs/SciX_UAT_keywords huggingface dataset:
A Possible Dust Origin for an Unusual Feature in Io's Sodium Neutral Clouds

We report the results of model simulations performed to explain the nature of a sodium emission feature in Io Neutral Clouds. The feature was detected via high-resolution spectroscopic observations from the 3.6 m Italian telescope TNG. The emission feature is blueshifted compared to the main emission (the banana-shaped Neutral Cloud of Io) by a few tens of km s-1, and it is most prominent when Io is a few tens of degrees before eclipse behind Jupiters shadow. The feature's morphology changes with time, indicative of a geometrical effect. We constrained its direction, velocity, and column density with a model of sodium atom trajectories under the influence of Io's and Jupiter's gravity, and solar radiation pressure. The model that best explains this emission feature has the atoms injected into the exosphere from the leading/sub-Jovian hemisphere of Io (45°-68° west longitude), with velocities from 50 to 90 km s-1 relative to Io. These trajectories are consistent with those of negatively charged dust grains (radius ~10 nm) accelerated by the corotational electric field of Jupiters magnetosphere. We propose that sputtering of sodium atoms from Na-bearing molecules (NaCl and Na2SO4) in these nanodust grains is the process responsible for our emission feature. Both modeling and observational constraints provide an order-of-magnitude estimate of the sodium production rate of ~1026 s-1. Our work provides another method to monitor the amount of material that Io is supplying to its Neutral Clouds and plasma torus.

Keywords: io; galilean satellites; planetary magnetospheres; jovian satellites
Does the {\nu }_{\max } Scaling Relation Depend on Metallicity? Insights from 3D Convection Simulations

Solar-like oscillations have been detected in thousands of stars thanks to modern space missions. These oscillations have been used to measure stellar masses and ages, which have been widely applied in Galactic archeology. One of the pillars of such applications is the ${\nu }_{\max }$ scaling relation: the frequency of maximum power ${\nu }_{\max }$ , assumed to be proportional to the acoustic cutoff frequency, ν ac, scales with effective temperature and surface gravity. However, the theoretical basis of the ${\nu }_{\max }$ scaling relation is uncertain, and there is an ongoing debate about whether it can be applied to metal-poor stars. We investigate the metallicity dependence of the ${\nu }_{\max }$ scaling relation by carrying out 3D near-surface convection simulations for solar-type stars with [Fe/H] between ‑3 and 0.5 dex. First, we found a negative correlation between ν ac and metallicity from the 3D models. This is in tension with the positive correlation identified by studies using 1D models. Second, we estimated theoretical ${\nu }_{\max }$ values using velocity amplitudes determined from first principles, by quantifying the mode excitation and damping rates with methods validated in our previous works. We found that ${\nu }_{\max }$ does not show correlation with metallicity at solar effective temperature and surface gravity. This study opens an exciting prospect of testing the asteroseismic scaling relations against realistic 3D hydrodynamical stellar models.

Keywords: stellar oscillations; pulsation modes; radiative magnetohydrodynamics; stellar convection envelopes; stellar atmospheres
Tidal Dissipation Due to Inertial Waves Can Explain the Circularization Periods of Solar-type Binaries

Tidal dissipation is responsible for circularizing the orbits and synchronizing the spins of solar-type close binary stars, but the mechanisms responsible are not fully understood. Previous work has indicated that significant enhancements to the theoretically predicted tidal dissipation rates are required to explain the observed circularization periods (P circ) in various stellar populations and their evolution with age. This was based partly on the common belief that the dominant mechanism of tidal dissipation in solar-type stars is turbulent viscosity acting on equilibrium tides in convective envelopes. In this paper, we study tidal dissipation in both convection and radiation zones of rotating solar-type stars following their evolution. We study equilibrium tide dissipation, incorporating a frequency-dependent effective viscosity motivated by the latest hydrodynamical simulations, and inertial wave (dynamical tide) dissipation, adopting a frequency-averaged formalism that accounts for the realistic structure of the star. We demonstrate that the observed binary circularization periods can be explained by inertial wave (dynamical tide) dissipation in convective envelopes. This mechanism is particularly efficient during pre-main-sequence phases, but it also operates on the main sequence if the spin is close to synchronism. The predicted P circ due to this mechanism increases with the main-sequence age in accordance with observations. We also demonstrate that both equilibrium tide and internal gravity-wave dissipation are unlikely to explain the observed P circ, even during the pre-main sequence, based on our best current understanding of these mechanisms. Finally, we advocate more realistic dynamical studies of stellar populations that employ tidal dissipation due to inertial waves.

Keywords: close binary stars; stellar convective zones; exoplanet tides; tidal interaction; planet hosting stars; stellar rotation; hydrodynamics; astrophysical fluid dynamics
Transition Probabilities and Collision Strengths for Fine-structure Levels Excitation of Ti II

Several spectral features from the stellar and nebular objects arise due to the iron-peak Ti II fine-structure excitations. Transition probabilities and electron excitation collision strengths of iron-peak elements are important for a meaningful interpretation and analysis of the observed astrophysical spectra. Accurate description of atomic structure with open 3d-shell elements is the key to the reliable and accurate computation of radiative and collision rates. The term-dependent one-electron orbitals in the multiconfiguration Hartree-Fock approach with adjustable configuration expansions and semi-empirical fine-tuning for energy corrections have been used in achieving highly accurate target description. A total of 314 Ti II fine-structure levels of the ground 3d24s and excited 3d3, 3d4s2, 3d24p, 3d25s, 3d4s4p, 3d24d, 3d25p, and 3d24f configurations have been included in the calculations of these atomic parameters. The present calculation of collision strengths has been performed in a close-coupling approximation based on the B-spline Breit-Pauli R-matrix method with inclusion of spin-orbit interaction term in the Hamiltonian matrices. Effective collision strengths over a Maxwellian distribution of electron velocities at temperatures in the range from 103 to 105 K have been reported for transitions between the 314 fine-structure levels. These wide array of transitions give rise to many main Ti II infrared, optical, and ultraviolet lines from a variety of astrophysical objects. Our calculated parameters are compared with the available other theoretical and experimental results, and through this comparison likely uncertainties in our results have been estimated, especially for transitions among the low-lying fine-structure levels of astrophysical importance.

Keywords: laboratory astrophysics; excitation rates
The Role of Stochastic Fermi-type Particle Acceleration in the Inner Jets of Active Galactic Nuclei

High-resolution radio observations of nearby active galactic nuclei have revealed extended, limb-brightened structures in their inner jets. This ties in with other multiwavelength observations from radio to X-ray and gamma ray, indicating that a structured jet model is required. While electrons need to be kept energized to account for the observed features, the underlying particle acceleration mechanism is still unclear. We explore the role of stochastic Fermi-type particle acceleration, i.e., classical second-order Fermi and shear acceleration, for understanding the multiwavelength observations of the inner jets of M87. An analytical Fokker–Planck description is adopted to infer characteristic spectral indices and cutoff energies for these two mechanisms. We focus on electron synchrotron radiation as the dominant emission process. We find that the multiwavelength observations of M87 can be satisfactorily accounted for in a framework, where the X-rays are produced at a larger distance from the core than the radio emission region. This provides further support to multizone, broadband emission modeling. We use our findings to also comment on the acceleration of cosmic rays entrained in the sheath.

Keywords: active galactic nuclei; high energy astrophysics; relativistic jets; non-thermal radiation sources; galaxy jets; radio jets; plasma astrophysics
A Comparison of Multiphase Magnetic Field Tracers in a High Galactic Latitude Region of the Filamentary Interstellar Medium

Understanding how the Galactic magnetic field threads the multiphase interstellar medium (ISM) remains a considerable challenge, as different magnetic field tracers probe dissimilar phases and field components. We search for evidence of a common magnetic field shared between the ionized and neutral ISM by comparing 1.4 GHz radio continuum polarization and H I line emission from the Galactic Arecibo L-Band Feed Array Continuum Transit Survey (GALFACTS) and Galactic Arecibo L-Band Feed Array H I (GALFA-H I) survey, respectively. We compute the polarization gradient of the continuum emission and search for associations with diffuse/translucent H I structures. The polarization gradient is sensitive to changes in the integrated product of the thermal electron density and line-of-sight field strength (B ∥) in warm ionized gas, while narrow H I structures highlight the plane-of-sky field orientation in cold neutral gas. We identified one region in the high Galactic latitude Arecibo sky, G216+26 centered on (ℓ, b) ~ (216°, +26°), containing filaments in the polarization gradient that are aligned with narrow H I structures roughly parallel to the Galactic plane. We present a comparison of multiphase observations and magnetic field tracers of this region, demonstrating that the warm ionized and cold neutral media are connected likely via a common magnetic field. We quantify the physical properties of a polarization gradient filament associated with Hα emission, measuring a line-of-sight field strength B ∥ = 6 ± 4 μG and a plasma beta $\beta ={2.1}_{-2.1}^{+3.1}$ . We discuss the lack of widespread multiphase magnetic field alignments and consider whether this region is associated with a short-timescale or physically rare phenomenon. This work highlights the utility of multitracer analyses for understanding the magnetized ISM.

Keywords: astrophysical magnetism; milky way magnetic fields; interstellar medium; interstellar magnetic fields; interstellar filaments; interstellar phases
On the Scarcity of Dense Cores (n > 105 cm‑3) in High-latitude Planck Galactic Cold Clumps

High-latitude (∣b∣ > 30°) molecular clouds have virial parameters that exceed 1, but whether these clouds can form stars has not been studied systematically. Using JCMT SCUBA-2 archival data, we surveyed 70 fields that target high-latitude Planck Galactic cold clumps (HLPCs) to find dense cores with density of 105–106 cm‑3 and size of <0.1 pc. The sample benefits from both the representativeness of the parent sample and its coverage of the densest clumps at the high column density end (>1 × 1021 cm‑2). At an average rms of 15 mJy beam‑1, we detected Galactic dense cores in only one field, G6.04+36.77 (L183) while also identifying 12 extragalactic objects and two young stellar objects. Compared to the low-latitude clumps, dense cores are scarce in HLPCs. With synthetic observations, the densities of cores are constrained to be n c ≲ 105 cm‑3 should they exist in HLPCs. Low-latitude clumps, Taurus clumps, and HLPCs form a sequence where a higher virial parameter corresponds to a lower dense-core detection rate. If HLPCs were affected by the Local Bubble, the scarcity should favor turbulence-inhibited rather than supernova-driven star formation. Studies of the formation mechanism of the L183 molecular cloud are warranted.

Keywords: star formation; molecular clouds; high latitude field
The Metal-poor Metallicity Distribution of the Ancient Milky Way

We present a low-metallicity map of the Milky Way consisting of ∼110,000 metal-poor giants with -3.5 < [Fe/H] < -0.75, based on public photometry from the second data release of the SkyMapper survey. These stars extend out to ∼7 kpc from the solar neighborhood and cover the main Galactic stellar populations, including the thick disk and the inner halo. Notably, this map can reliably differentiate metallicities down to [Fe/H] ∼ -3.0, and thus provides an unprecedented view into the ancient, metal-poor Milky Way. Among the more metal-rich stars in our sample ([Fe/H] > -2.0), we recover a clear spatial dependence of decreasing mean metallicity as a function of scale height that maps onto the thick disk component of the Milky Way. When only considering the very metal-poor stars in our sample ([Fe/H] < -2), we recover no such spatial dependence in their mean metallicity out to a scale height of ∣Z∣ ∼ 7 kpc. We find that the metallicity distribution function (MDF) of the most metal-poor stars in our sample (-3.0 < [Fe/H] < -2.3) is well fit with an exponential profile with a slope of and ${\rm{\Delta }}\mathrm{log}(N)/{\rm{\Delta }}$ [Fe/H] = 1.52 ± 0.05, and slightly shifts to ${\rm{\Delta }}\mathrm{log}(N)/{\rm{\Delta }}[\mathrm{Fe}/{\rm{H}}]=1.53\pm 0.10$ after accounting for target selection effects. For [Fe/H] < -2.3, the MDF is largely insensitive to scale height ∣Z∣ out to ∼5 kpc, showing that very and extremely metal-poor stars are in every galactic component.

Keywords: population ii stars; milky way galaxy
Yarkovsky Drift Detections for 247 Near-Earth Asteroids

The Yarkovsky effect is a thermal process acting upon the orbits of small celestial bodies, which can cause these orbits to slowly expand or contract with time. The effect is subtle ( $\left\langle {da}/{dt}\right\rangle \sim {10}^{-4}$ au My-1 for a 1 km diameter object) and is thus generally difficult to measure. We analyzed both optical and radar astrometry for 600 Near-Earth Asteroids (NEAs) for the purpose of detecting and quantifying the Yarkovsky effect. We present 247 NEAs with measured drift rates, which is the largest published set of Yarkovsky detections. This large sample size provides an opportunity to examine the Yarkovsky effect in a statistical manner. In particular, we describe two independent population-based tests that verify the measurement of Yarkovsky orbital drift. First, we provide observational confirmation for the Yarkovsky effect's theoretical size dependence of 1/D, where D is diameter. Second, we find that the observed ratio of negative to positive drift rates in our sample is 2.34, which, accounting for bias and sampling uncertainty, implies an actual ratio of ${2.7}_{-0.7}^{+0.3}$ . This ratio has a vanishingly small probability of occurring due to chance or statistical noise. The observed ratio of retrograde to prograde rotators is two times lower than the ratio expected from numerical predictions from NEA population studies and traditional assumptions about the sense of rotation of NEAs originating from various main belt escape routes. We also examine the efficiency with which solar energy is converted into orbital energy and find a median efficiency in our sample of 12%. We interpret this efficiency in terms of NEA spin and thermal properties.

Keywords: asteroids; the sun; orbit determination; astrometry
Interpreting the Statistical Properties of High-z Extragalactic Sources Detected by the South Pole Telescope Survey

The results of the recently published spectroscopically complete survey of dusty star-forming galaxies detected by the South Pole Telescope over 2500 deg2 proved to be challenging for galaxy formation models that generally underpredict the observed abundance of high-z galaxies. In this paper we interpret these results in the light of a physically grounded model for the evolution of spheroidal galaxies. The model accurately reproduces the measured redshift distribution of galaxies without any adjustment of the parameters. The data do not support the indications of an excess of z > 4 dusty galaxies reported by some analyses of Herschel surveys.

Keywords: high-redshift galaxies
Powerful Radio-loud Quasars Are Triggered by Galaxy Mergers in the Cosmic Bright Ages

While supermassive black holes are ubiquitous features of galactic nuclei, only a small minority are observed during episodes of luminous accretion. The physical mechanism(s) driving the onset of fueling and ignition in these active galactic nuclei (AGN) are still largely unknown for many galaxies and AGN-selection criteria. Attention has focused on AGN triggering by means of major galaxy mergers gravitationally funneling gas toward the galactic center, with evidence both for and against this scenario. However, several recent studies have found that radio-loud AGN overwhelmingly reside in ongoing or recent major galaxy mergers. In this study, we test the hypothesis that major galaxy mergers are important triggers for radio-loud AGN activity in powerful quasars during cosmic noon (1 ≲ z ≲ 2). To this end, we compare Hubble Space Telescope WFC3/IR observations of the z > 1 3CR radio-loud broad-lined quasars to three matched radio-quiet quasar control samples. We find strong evidence for major-merger activity in nearly all radio-loud AGN, in contrast to the much lower merger fraction in the radio-quiet AGN. These results suggest major galaxy mergers are key ingredients in launching powerful radio jets. Given many of our radio-loud quasars are blue, our results present a possible challenge to the "blowout" paradigm of galaxy evolution models in which blue quasars are the quiescent end result following a period of red quasar feedback initiated by a galaxy merger. Finally, we find a tight correlation between black hole mass and host galaxy luminosity for these different high-redshift AGN samples that is inconsistent with those observed for local elliptical galaxies.

Keywords: galaxy mergers; radio loud quasars; active galactic nuclei; radio jets
Spitzer's Last Look at Extragalactic Explosions: Long-term Evolution of Interacting Supernovae

Here we present new, yet final, mid-infrared (mid-IR) data for supernovae (SNe) based on measurements with the Spitzer Space Telescope. Comparing our recent 3.6 and 4.5 μm photometry with previously published mid-IR and further multiwavelength data sets, we were able to draw some conclusions about the origin and heating mechanism of the dust in these SNe or in their environments, as well as about possible connection with circumstellar matter (CSM) originating from pre-explosion mass-loss events in the progenitor stars. We also present new results regarding both certain SN classes and single objects. We highlight the mid-IR homogeneity of SNe Ia-CSM, which may be a hint of their common progenitor type and of their basically uniform circumstellar environments. Regarding single objects, it is worth highlighting the late-time interacting Type Ib SNe 2003gk and 2004dk, for which we present the first-ever mid-IR data, which seem to be consistent with clues of ongoing CSM interaction detected in other wavelength ranges. Our current study suggests that long-term mid-IR follow-up observations play a key role in a better understanding of both pre- and post-explosion processes in SNe and their environments. While Spitzer is not available anymore, the expected unique data from the James Webb Space Telescope, as well as long-term near-IR follow-up observations of dusty SNe, can bring us closer to the hidden details of this topic.

Keywords: supernovae; infrared astronomy; infrared telescopes; circumstellar matter; circumstellar dust
Hydrodynamics and Nucleosynthesis of Jet-driven Supernovae. I. Parameter Study of the Dependence on Jet Energetics

Rotating massive stars with initial progenitor masses M prog ~ 25-140 M ⊙ can leave rapidly rotating black holes to become collapsars. The black holes and the surrounding accretion disks may develop powerful jets by magnetohydrodynamics instabilities. The propagation of the jet in the stellar envelope provides the necessary shock heating for triggering nucleosynthesis unseen in canonical core-collapse supernovae. However, the energy budget of the jet and its effects on the final chemical abundance pattern are unclear. In this exploratory work, we present a survey on the parameter dependence of collapsar nucleosynthesis on jet energetics. We use the zero-metallicity star with M prog ~ 40 M ⊙ as the progenitor. The parameters include the jet duration, its energy deposition rate, deposited energy, and the opening angle. We examine the correlations of the following observables: (1) the ejecta and remnant masses; (2) the energy deposition efficiency; (3) the 56Ni production and its correlation with the ejecta velocity, deposited energy, and the ejected mass; (4) the Sc-Ti-V correlation as observed in metal-poor stars; and (5) the [Zn/Fe] ratio as observed in some metal-poor stars. We also provide the chemical abundance table of these explosion models for the use of the galactic chemical evolution and stellar archeology.

Keywords: explosive nucleosynthesis; supernovae; hypernovae; hydrodynamical simulations; chemical abundances; relativistic jets
A MeerKAT 1.28 GHz Atlas of Southern Sources in the IRAS Revised Bright Galaxy Sample

The IRAS Revised Bright Galaxy Sample (RBGS) comprises galaxies and unresolved mergers stronger than S = 5.24 Jy at λ = 60 μm with Galactic latitudes ∣b∣ > 5°. Nearly all are dusty star-forming galaxies whose radio continuum and far-infrared luminosities are proportional to their current rates of star formation. We used the MeerKAT array of 64 dishes to make 5 × 3 minutes snapshot observations at ν = 1.28 GHz covering all 298 southern (J2000 δ < 0°) RBGS sources identified with external galaxies. The resulting images have θ ≈ 7"5 FWHM resolution and rms fluctuations σ ≈ 20 μJy beam-1 ≈ 0.26 K low enough to reveal even faint disk emission. The rms position uncertainties are σα ≈ σδ ≈ 1″ relative to accurate near-infrared positions, and the image dynamic ranges are DR ≳ 104: 1. Cropped MeerKAT images of all 298 southern RBGS sources are available in FITS format from 10.48479/dnt7-6q05.

Keywords: infrared galaxies; radio continuum emission; luminous infrared galaxies