Sazuna/UAT_keywords huggingface dataset:
External Photoevaporation of Protoplanetary Disks: Does Location Matter?. Many theoretical studies have shown that external photoevaporation from massive stars can severely truncate, or destroy altogether, the gaseous protoplanetary disks around young stars. In tandem, several observational studies report a correlation between the mass of a protoplanetary disk and its distance to massive ionizing stars in star-forming regions, and cite external photoevaporation by the massive stars as the origin of this correlation. We present N-body simulations of the dynamical evolution of star-forming regions and determine the mass loss in protoplanetary disks from external photoevaporation due to far-ultraviolet and extreme-ultraviolet radiation from massive stars. We find that projection effects can be significant, in that low-mass disk-hosting stars that appear close to the ionizing sources may be fore- or background stars in the star-forming region. We find very little evidence in our simulations for a trend in increasing disk mass with increasing distance from the massive star(s), even when projection effects are ignored. Furthermore, the dynamical evolution of these young star-forming regions moves stars whose disks have been photoevaporated to far-flung locations, away from the ionizing stars, and we suggest that any correlation between disk mass and distance from the ionizing star is either coincidental, or due to some process other than external photoevaporation.

Keywords: Star forming regions, Protoplanetary disks, Photodissociation regions
Thermophysical Model for Realistic Surface Layers on Airless Small Bodies: Applied to Study the Spin Orientation and Surface Dust Properties of (24) Themis from WISE/NEOWISE Multiepoch Thermal Light Curves. This work proposes a thermophysical model for realistic surface layers on airless small bodies (RSTPM) for the use of interpreting their multiepoch thermal light curves (e.g., WISE/NEOWISE). RSTPM considers the real orbital cycle, rotation cycle, rough surface, temperature-dependent thermal parameters, as well as contributions of sunlight reflection to observations. It is thus able to produce a precise temperature distribution and thermal emission of airless small bodies regarding the variations on orbital timescales. Details of the physics, mathematics, and numerical algorithms of RSTPM are presented. When used to interpret multiepoch thermal light curves by WISE/NEOWISE, RSTPM can give constraints on the spin orientation and surface physical properties, such as the mean thermal inertia or the mean size of dust grains, the roughness fraction, and the albedo via a radiometric procedure. As an application example, we apply this model to the main-belt object (24) Themis, the largest object of the Themis family, which is believed to be the source region of many main-belt comets. We find multiepoch (2010, 2014-2018) observations of Themis by WISE/NEOWISE, yielding 18 thermal light curves. By fitting these data with RSTPM, the best-fit spin orientation of Themis is derived to be (λ = 137°, β = 59°) in ecliptic coordinates, and the mean radius of dust grains on the surface is estimated to be $\tilde{b}=\,{140}_{-114}^{+500}(6\sim 640)$ μm, indicating that the surface thermal inertia varies from ∼3 Jm-2 s-0.5 K-1 to ∼60 Jm-2s-0.5 K-1 due to seasonal temperature variation. A more detailed analysis found that the thermal light curves of Themis show a weak feature that depends on the rotation phase, which is indicative of heterogeneous thermal properties or imperfections of the light-curve inversion shape model.

Keywords: Computational methods, Small Solar System bodies, Infrared photometry, Asteroid surfaces
Energy Budget of Plasma Motions, Heating, and Electron Acceleration in a Three-loop Solar Flare. Nonpotential magnetic energy promptly released in solar flares is converted to other forms of energy. This may include nonthermal energy of flare-accelerated particles, thermal energy of heated flaring plasma, and kinetic energy of eruptions, jets, upflows/downflows, and stochastic (turbulent) plasma motions. The processes or parameters governing partitioning of the released energy between these components are an open question. How these components are distributed between distinct flaring loops and what controls these spatial distributions are also unclear. Here, based on multiwavelength data and 3D modeling, we quantify the energy partitioning and spatial distribution in the well-observed SOL2014-02-16T064620 solar flare of class C1.5. Nonthermal emission of this flare displayed a simple impulsive single-spike light curve lasting about 20 s. In contrast, the thermal emission demonstrated at least three distinct heating episodes, only one of which was associated with the nonthermal component. The flare was accompanied by upflows and downflows and substantial turbulent velocities. The results of our analysis suggest that (i) the flare occurs in a multiloop system that included at least three distinct flux tubes; (ii) the released magnetic energy is divided unevenly between the thermal and nonthermal components in these loops; (iii) only one of these three flaring loops contains an energetically important amount of nonthermal electrons, while two other loops remain thermal; (iv) the amounts of direct plasma heating and that due to nonthermal electron loss are comparable; and (v) the kinetic energy in the flare footpoints constitutes only a minor fraction compared with the thermal and nonthermal energies.

Keywords: Solar flares, Solar extreme ultraviolet emission, Solar coronal heating, Solar x-ray emission, Solar radio emission, Solar magnetic fields
Deconvolving Pulsar Signals with Cyclic Spectroscopy: A Systematic Evaluation. Radio pulsar signals are significantly perturbed by their propagation through the ionized interstellar medium. In addition to the frequency-dependent pulse times of arrival due to dispersion, pulse shapes are also distorted and shifted, having been scattered by the inhomogeneous interstellar plasma, affecting pulse arrival times. Understanding the degree to which scattering affects pulsar timing is important for gravitational-wave detection with pulsar timing arrays (PTAs), which depend on the reliability of pulsars as stable clocks with an uncertainty of ∼100 ns or less over ∼10 yr or more. Scattering can be described as a convolution of the intrinsic pulse shape with an impulse response function representing the effects of multipath propagation. In previous studies, the technique of cyclic spectroscopy has been applied to pulsar signals to deconvolve the effects of scattering from the original emitted signals, increasing the overall timing precision. We present an analysis of simulated data to test the quality of deconvolution using cyclic spectroscopy over a range of parameters characterizing interstellar scattering and pulsar signal-to-noise ratio (S/N). We show that cyclic spectroscopy is most effective for high S/N and/or highly scattered pulsars. We conclude that cyclic spectroscopy could play an important role in scattering correction to distant populations of highly scattered pulsars not currently included in PTAs. For future telescopes and for current instruments such as the Green Bank Telescope upgraded with the ultrawide bandwidth receiver, cyclic spectroscopy could potentially double the number of PTA-quality pulsars.

Keywords: Millisecond pulsars, Interstellar plasma, Pulsars, Gravitational waves, Interstellar medium, Radio astronomy, Radio pulsars
Coronal Conditions for the Occurrence of Type II Radio Bursts. Type II radio bursts are generally observed in association with flare-generated or coronal-mass-ejection-driven shock waves. The exact shock and coronal conditions necessary for the production of type II radio emission are still under debate. Shock waves are important for the acceleration of electrons necessary for the generation of the radio emission. Additionally, the shock geometry and closed field line topology, e.g., quasi-perpendicular shock regions or shocks interacting with streamers, play an important role for the production of the emission. In this study we perform a 3D reconstruction and modeling of a shock wave observed during the 2014 November 5 solar event. We determine the spatial and temporal evolution of the shock properties and examine the conditions responsible for the generation and evolution of type II radio emission. Our results suggest that the formation and evolution of a strong, supercritical, quasi-perpendicular shock wave interacting with a coronal streamer were responsible for producing type II radio emission. We find that the shock wave is subcritical before and supercritical after the start of the type II emission. The shock geometry is mostly quasi-perpendicular throughout the event. Our analysis shows that the radio emission is produced in regions where the supercritical shock develops with an oblique to quasi-perpendicular geometry.

Keywords: Solar coronal mass ejection shocks, Solar radio emission, Solar coronal mass ejections
A Low-mass Binary Neutron Star: Long-term Ejecta Evolution and Kilonovae with Weak Blue Emission. We study the long-term evolution of ejecta formed in a binary neutron star (NS) merger that results in a long-lived remnant NS by performing a hydrodynamics simulation with the outflow data of a numerical relativity simulation as the initial condition. At the homologously expanding phase, the total ejecta mass reaches ≈ 0.1 M⊙ with an average velocity of ≈ 0.1 c and lanthanide fraction of ≈ 0.005. We further perform the radiative transfer simulation employing the obtained ejecta profile. We find that, contrary to a naive expectation from the large ejecta mass and low lanthanide fraction, the optical emission is not as bright as that in GW170817/AT2017gfo, while the infrared emission can be brighter. This light-curve property is attributed to preferential diffusion of photons toward the equatorial direction due to the prolate ejecta morphology; large opacity contribution of Zr, Y, and lanthanides; and low specific heating rate of the ejecta. Our results suggest that these light-curve features could be used as an indicator for the presence of a long-lived remnant NS. We also found that the bright optical emission broadly consistent with GW170817/AT2017gfo is realized for the case in which the high-velocity ejecta components in the polar region are suppressed. These results suggest that the remnant in GW170817/AT2017gfo is unlikely to be a long-lived NS but might have collapsed to a black hole within ${ \mathcal O }(0.1)$ s.

Keywords: Gravitational wave astronomy, Neutron stars, Radiative transfer simulations
3D Convection-resolving Model of Temperate, Tidally Locked Exoplanets. A large fraction of known terrestrial-size exoplanets located in the habitable zone of M-dwarfs are expected to be tidally locked. Numerous efforts have been conducted to study the climate of such planets, using in particular 3D global climate models (GCMs). One of the biggest challenges in simulating such an extreme environment is to properly represent the effects of sub-grid convection. Most GCMs use either a simplistic convective-adjustment parameterization or sophisticated (e.g., mass flux scheme) Earth-tuned parameterizations. One way to improve the representation of convection is to study convection using numerical convection-resolving models (CRMs), with a fine spatial resolution. In this study, we developed a CRM coupling the non-hydrostatic dynamical core Advanced Research Weather-Weather Research and Forecast model with the radiative transfer and cloud/precipitation models of the Laboratoire de Météorologie Dynamique generic climate model to study convection and clouds on tidally locked planets, with a focus on Proxima b. Simulations were performed for a set of three surface temperatures (corresponding to three different incident fluxes) and two rotation rates, assuming an Earth-like atmosphere. The main result of our study is that while we recover the prediction of GCMs that (low-altitude) cloud albedo increases with increasing stellar flux, the cloud feedback is much weaker due to transient aggregation of convection leading to low partial cloud cover.

Keywords: Atmospheric clouds, Exoplanet atmospheres
AGNs on the Move: A Search for Off-nuclear AGNs from Recoiling Supermassive Black Holes and Ongoing Galaxy Mergers with the Zwicky Transient Facility. A supermassive black hole (SMBH) ejected from the potential well of its host galaxy via gravitational wave recoil carries important information about the mass ratio and spin alignment of the pre-merger SMBH binary. Such a recoiling SMBH may be detectable as an active galactic nucleus (AGN) broad-line region offset by up to 10 kpc from a disturbed host galaxy. We describe a novel methodology using forward modeling with The Tractor to search for such offset AGNs in a sample of 5493 optically variable AGNs detected with the Zwicky Transient Facility (ZTF). We present the discovery of nine AGNs that may be spatially offset from their host galaxies and are candidates for recoiling SMBHs. Five of these offset AGNs exhibit double-peaked broad Balmer lines, which may have arisen from unobscured accretion disk emission, and four show radio emission indicative of a relativistic jet. The fraction of double-peaked emitters in our spatially offset AGN sample is significantly larger than the 16% double-peaked emitter fraction observed for ZTF AGNs overall. In our sample of variable AGNs we also identified 52 merging galaxies, including a new spectroscopically confirmed dual AGN. Finally, we detected the dramatic rebrightening of SDSS 1133, a previously discovered variable object and recoiling SMBH candidate, in ZTF. The flare was accompanied by the reemergence of strong P Cygni line features, indicating that SDSS 1133 may be an outbursting luminous blue variable star.

Keywords: Supermassive black holes, Active galactic nuclei, Galaxy mergers
The Fundamental Plane in the LEGA-C Survey: Unraveling the M/L Ratio Variations of Massive Star-forming and Quiescent Galaxies at z ∼ 0.8. We explore the connection between the kinematics, structures and stellar populations of massive galaxies at 0.6 &lt; z &lt; 1.0 using the fundamental plane (FP). Combining stellar kinematic data from the Large Early Galaxy Astrophysics Census (LEGA-C) survey with structural parameters measured from deep Hubble Space Telescope imaging, we obtain a sample of 1419 massive ( $\mathrm{log}({M}_{* }/{M}_{\odot })\gt 10.5$ ) galaxies that span a wide range in morphology, star formation activity, and environment, and therefore is representative of the massive galaxy population at z ∼ 0.8. We find that quiescent and star-forming galaxies occupy the parameter space of the g-band FP differently and thus have different distributions in the dynamical mass-to-light ratio (Mdyn/Lg), largely owing to differences in the stellar age and recent star formation history, and to a lesser extent, the effects of dust attenuation. In contrast, we show that both star-forming and quiescent galaxies lie on the same mass FP at z ∼ 0.8, with a comparable level of intrinsic scatter about the plane. We examine the variation in Mdyn/M* through the thickness of the mass FP, finding no significant residual correlations with stellar population properties, Sérsic index, or galaxy overdensity. Our results suggest that, at fixed size and velocity dispersion, the variations in Mdyn/Lg of massive galaxies reflect an approximately equal contribution of variations in M*/Lg, and variations in the dark matter fraction or initial mass function.

Keywords: Galaxy dynamics, Galaxy structure, Galaxy kinematics, Galaxy evolution
On the Correlation between Hot Jupiters and Stellar Clustering: High-eccentricity Migration Induced by Stellar Flybys. A recent observational study suggests that the occurrence of hot Jupiters (HJs) around solar-type stars is correlated with stellar clustering. We study a new scenario for HJ formation, called "Flyby Induced High-e Migration," that may help explain this correlation. In this scenario, stellar flybys excite the eccentricity and inclination of an outer companion (giant planet, brown dwarf, or low-mass star) at large distance (10-300 au), which then triggers high-e migration of an inner cold Jupiter (at a few astronomical units) through the combined effects of von Zeipel-Lidov-Kozai (ZLK) eccentricity oscillation and tidal dissipation. Using semianalytical calculations of the effective ZLK inclination window, together with numerical simulations of stellar flybys, we obtain the analytic estimate for the HJ occurrence rate in this formation scenario. We find that this "flyby induced high-e migration" could account for a significant fraction of the observed HJ population, although the result depends on several uncertain parameters, including the density and lifetime of birth stellar clusters, and the occurrence rate of the "cold Jupiter + outer companion" systems.

Keywords: Exoplanet dynamics, Hot Jupiters
The Cluster-central Compact Steep-spectrum Radio Galaxy 1321+045. The radio galaxy 1321+045 is a rare example of a young, compact steep-spectrum source located in the center of a z = 0.263 galaxy cluster. Using a combination of Chandra, VLBA, VLA, MERLIN, and IRAM 30 m observations, we investigate the conditions that have triggered this outburst. We find that the previously identified 5 kpc scale radio lobes are probably no longer powered by the active galactic nucleus, which seems to have launched a new ∼20 pc jet on a different axis, likely within the last few hundred years. We estimate the enthalpy of the lobes to be ${8.48}_{-3.56}^{+6.04}\times {10}^{57}\,\mathrm{erg}$ , only sufficient to balance cooling in the surrounding 16 kpc for ∼9 Myr. The properties of the cluster's intracluster medium (ICM) are similar to those of rapidly cooling nearby clusters, with a low central entropy (8.6 ${}_{-1.4}^{+2.2}$ keV cm2 within 8 kpc), short central cooling time (390 ${}_{-150}^{+170}$ Myr), and tcool/tff and tcool/teddy ratios indicative of thermal instability out to ∼45 kpc. Despite previous detection of Hα emission from the brightest cluster galaxy, our IRAM 30 m observations do not detect CO emission in either the (1-0) or (3-2) transitions. We place 3σ limits on the molecular gas mass of Mmol ≤ 7.7 × 109 M⊙ and ≤5.6 × 109 M⊙ from the two lines respectively. We find indications of a recent minor cluster merger that has left a ∼200 kpc tail of stripped gas in the ICM, and probably induced sloshing motions.

Keywords: Galaxy clusters, Radio galaxies, Active galactic nuclei, Brightest cluster galaxies, Intracluster medium
Cosmic-Ray Transport, Energy Loss, and Influence in the Multiphase Interstellar Medium. The bulk propagation speed of GeV-energy cosmic rays is limited by frequent scattering off hydromagnetic waves. Most galaxy evolution simulations that account for this confinement assume the gas is fully ionized and cosmic rays are well coupled to Alfvén waves; however, multiphase density inhomogeneities, frequently underresolved in galaxy evolution simulations, induce cosmic-ray collisions and ionization-dependent transport driven by cosmic-ray decoupling and elevated streaming speeds in partially neutral gas. How do cosmic rays navigate and influence such a medium, and can we constrain this transport with observations? In this paper, we simulate cosmic-ray fronts impinging upon idealized, partially neutral clouds and lognormally distributed clumps, with and without ionization-dependent transport. With these high-resolution simulations, we identify cloud interfaces as crucial regions where cosmic-ray fronts can develop a stairstep pressure gradient sufficient to collisionlessly generate waves, overcome ion-neutral damping, and exert a force on the cloud. We find that the acceleration of cold clouds is hindered by only a factor of a few when ionization-dependent transport is included, with additional dependencies on magnetic field strength and cloud dimensionality. We also probe how cosmic rays sample the background gas and quantify collisional losses. Hadronic gamma-ray emission maps are qualitatively different when ionization-dependent transport is included, but the overall luminosity varies by only a small factor, as the short cosmic-ray residence times in cold clouds are offset by the higher densities that cosmic rays sample.

Keywords: Galaxy evolution, Interstellar medium, Magnetic fields, Gamma-rays, Cosmic rays
Waterworlds Probably Do Not Experience Magmatic Outgassing. Terrestrial planets with large water inventories are likely ubiquitous and will be among the first Earth-sized planets to be characterized with upcoming telescopes. It has previously been argued that waterworlds—particularly those possessing more than 1% H2O—experience limited melt production and outgassing due to the immense pressure overburden of their overlying oceans, unless subject to high internal heating. But an additional, underappreciated obstacle to outgassing on waterworlds is the high solubility of volatiles in high-pressure melts. Here, we investigate this phenomenon and show that volatile solubilities in melts probably prevent almost all magmatic outgassing from waterworlds. Specifically, for Earth-like gravity and oceanic crust composition, oceans or water ice exceeding 10-100 km in depth (0.1-1 GPa) preclude the exsolution of volatiles from partial melt of silicates. This solubility limit compounds the pressure overburden effect as large surface oceans limit both melt production and degassing from any partial melt that is produced. We apply these calculations to Trappist-1 planets to show that, given current mass and radius constraints and implied surface water inventories, Trappist-1f and -1g are unlikely to experience volcanic degassing. While other mechanisms for interior-surface volatile exchange are not completely excluded, the suppression of magmatic outgassing simplifies the range of possible atmospheric evolution trajectories and has implications for interpretation of ostensible biosignature gases, which we illustrate with a coupled model of planetary interior-climate-atmosphere evolution.

Keywords: Planetary atmospheres, Exoplanet evolution, Planetary science, Planetary interior, Exoplanet atmospheres
Absorption of High-frequency Oscillations and Its Relation to Emissivity Reduction. Sunspots are known to be strong absorbers of solar oscillation modal power. The most convincing way to demonstrate this is done via Fourier-Hankel decomposition (FHD), where the local oscillation field is separated into in- and outgoing waves, showing the reduction in power. Due to the Helioseismic and Magnetic Imager's high-cadence Doppler measurements, power absorption can be investigated at frequencies beyond the acoustic cutoff frequency. We perform an FHD on five sunspot regions and two quiet-Sun control regions and study the resulting absorption spectra αℓ(ν), specifically at frequencies ν &gt; 5.3 mHz. We observe an unreported high-frequency absorption feature, which only appears in the presence of a sunspot. This feature is confined to phase speeds of one-skip waves whose origins coincide with the sunspot's center, with vph = 85.7 km s-1 in this case. By employing a fit to the absorption spectra at a constant phase speed, we find that the peak absorption strength ${\alpha }_{\max }$ lies between 0.166 and 0.222 at a noise level of about 0.009 (5%). The well-known absorption along ridges at lower frequencies can reach up to ${\alpha }_{\max }\approx 0.5$ . Thus our finding in the absorption spectrum is weaker, but nevertheless significant. From first considerations regarding the energy budget of high-frequency waves, this observation can likely be explained by the reduction of emissivity within the sunspot. We derive a simple relation between emissivity and absorption. We conclude that sunspots yield a wave power absorption signature (for certain phase speeds only), which may help in understanding the effect of strong magnetic fields on convection and source excitation and potentially in understanding the general sunspot subsurface structure.

Keywords: Helioseismology, Solar physics, Sunspots