adsabs/SciX_UAT_keywords huggingface dataset:
The Fundamental Signature of Star Formation Quenching from AGN Feedback: A Critical Dependence of Quiescence on Supermassive Black Hole Mass, Not Accretion Rate

We identify the intrinsic dependence of star formation quenching on a variety of galactic and environmental parameters, utilizing a machine-learning approach with Random Forest classification. We have previously demonstrated the power of this technique to isolate causality, not mere correlation, in complex astronomical data. First, we analyze three cosmological hydrodynamical simulations (Eagle, Illustris, and IllustrisTNG), selecting snapshots spanning the bulk of cosmic history from comic noon (z ~ 2) to the present epoch, with stellar masses in the range $9\lt \mathrm{log}({M}_{* }/{M}_{\odot })\lt 12$ . In the simulations, black hole mass is unanimously found to be the most predictive parameter of central galaxy quenching at all epochs. Perhaps surprisingly, black hole accretion rate (and hence the bolometric luminosity of active galactic nuclei, AGN) is found to be of little predictive power over quenching. This theoretical result is important for observational studies of galaxy quenching, as it cautions against using the current AGN state of a galaxy as a useful proxy for the cumulative impact of AGN feedback on a galactic system. The latter is traced by black hole mass, not AGN luminosity. Additionally, we explore a subset of "observable" parameters, which can be readily measured in extant wide-field galaxy surveys targeting z = 0-2, at $9\lt \mathrm{log}({M}_{* }/{M}_{\odot })\lt 12$ . All three simulations predict that, in lieu of black hole mass, the stellar gravitational potential will outperform the other parameters in predicting quenching. We confirm this theoretical prediction observationally in the SDSS (at low redshifts) and in CANDELS (at intermediate and high redshifts).

Keywords: galaxy evolution
Four-dimensional Frequency-Wavenumber Power Spectrum of a Strong Turbulence Obtained from Hybrid Kinetic Simulations

We carry out three-dimensional hybrid kinetic simulations of a strong decaying turbulence. The turbulence is initiated with a seed spectrum that includes Alfvén wave modes at low wavenumbers. From the temporal and spatial distribution of the simulation output in the quasi-steady phase, we calculate a four-dimensional frequency-wavenumber spectrum of the turbulence. Our analysis shows that kinetic Alfvén waves can be identified in the wavenumber-frequency space in the vicinity of the seed turbulence spectrum. They produce a power peak consistent with a linear dispersion relation. However, further away from the seed spectrum, where most of the wave-particle interaction takes place, the signature of the Alfvén modes disappears among other fluctuations that are not described by any dispersion relations. Furthermore, at higher wavenumbers at which the signature is still identifiable, its frequency broadening becomes comparable to the frequency itself. Therefore, the use of linear waves based on the conventional dispersion relation is not necessarily justified to describe the turbulence if their signature is still present and even more so when it disappears. We find that at larger rms amplitudes of the turbulence, the signature of the dispersion relation is confined to lower parallel wavenumbers. In the range where it is visible, the frequency broadening becomes greater at larger amplitudes. This suggests that stronger nonlinearity makes the fluctuations behave less like wave modes until the conventional wave-mode approach is no longer valid.

Keywords: solar wind; interplanetary turbulence; space plasmas
Mapping Solar X-Ray Images from SDO/AIA EUV Images by Deep Learning

The full-Sun corona is now imaged every 12 s in extreme ultraviolet (EUV) passbands by Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA), whereas it is only observed several times a day at X-ray wavelengths by Hinode/X-Ray Telescope (XRT). In this paper, we apply a deep-learning method, i.e., the convolution neural network (CNN), to establish data-driven models to generate full-Sun X-ray images in XRT filters from AIA EUV images. The CNN models are trained using a number of data pairs of AIA six-passband (171, 193, 211, 335, 131, and 94 Å) images and the corresponding XRT images in three filters: "Al_mesh," "Ti_poly," and "Be_thin." It is found that the CNN models predict X-ray images in good consistency with the corresponding well-observed XRT data. In addition, the purely data-driven CNN models are better than the conventional analysis method of the coronal differential emission measure (DEM) in predicting XRT-like observations from AIA data. Therefore, under conditions where AIA provides coronal EUV data well, the CNN models can be applied to fill the gap in limited full-Sun coronal X-ray observations and improve pool-observed XRT data. It is also found that DEM inversions using AIA data and our deep-learning-predicted X-ray data jointly are better than those using AIA data alone. This work indicates that deep-learning methods provide the opportunity to study the Sun based on virtual solar observation in future.

Keywords: solar corona; solar atmosphere; active solar corona; quiet solar corona
Radial Diffusion of Planetary Radiation Belts' Particles by Fluctuations with Finite Correlation Time

Radial diffusion in planetary radiation belts is a dominant transport mechanism resulting in the energization and losses of charged particles by large-scale electromagnetic fluctuations. In this study, we revisit the radial diffusion formalism by relaxing the assumption of zero correlation time in the spectrum of fluctuations responsible for the transport of charged particles. We derive a diffusion coefficient by assuming fluctuations that (1) are time homogeneous, (2) too small to trap the particles, and (3) can decorrelate on timescales comparable to the transit time of the particles. We demonstrate through self-similar solutions of the Fokker-Planck equation that autocorrelation time τc much larger than the linear transit time/particle drift period ${\tau }_{L}={{\rm{\Omega }}}_{D}^{-1}$ results in characteristic time for transport independent of the drift frequency and faster than for short correlation time. In both instances, that is for short (τL ≫ τc) and long (τL ≪ τc) autocorrelation time, the diffusion of particles is subdiffusive since the variance of increments along the magnetic drift shells L*, scales as <ΔL*2> ∼ ts, with s < 1. However, in the absence of sources and sinks, particle transport for both short and long autocorrelation times result in equilibrium distribution along L* with differences of less than 10% across lower magnetic drift shells. The main consequence of incorporating finite correlation time appears in intermediate times much longer than the drift period but before the distribution function reaches equilibrium and indicates the importance of quantifying observationally the spectral properties of fluctuations for the modeling of planetary radiation belts.

Keywords: plasma astrophysics; space plasmas; plasma physics; alfven waves
PoPE: A Population-based Approach to Model the Spatial Structure of Astronomical Systems

We present a novel population-based Bayesian inference approach to model the average and population variance of the spatial distribution of a set of observables from ensemble analysis of low signal-to-noise-ratio measurements. The method consists of (1) inferring the average profile using Gaussian processes and (2) computing the covariance of the profile observables given a set of independent variables. Our model is computationally efficient and capable of inferring average profiles of a large population size from noisy measurements, without stacking data or parameterizing the shape of the mean profile. We demonstrate the performance of our method using dark matter, gas, and stellar profiles extracted from hydrodynamical cosmological simulations of galaxy formation. POPULATION PROFILE ESTIMATOR is publicly available in a GitHub repository. Our new method should be useful for measuring the spatial distribution and internal structure of a variety of astrophysical systems using large astronomical surveys.

Keywords: astronomy data modeling; astronomy data analysis; spatial point processes; astrostatistics; open source software
Hydroaluminum Isocyanide Isomers: Prediction of Spectroscopic Properties

Metal cyanides and isocyanides play a relevant role in the metal chemistry of the carbon-rich circumstellar envelope IRC+10216. It is thought that hydrometal cyanides/isocyanides could also be present in these environments; in fact, HMgNC has been detected in the same source that MgCN, MgNC, and AlNC. The aim of this work is to provide information about hydroaluminum cyanide/isocyanide. For this goal, a comprehensive analysis of the doublet and quartet potential energy surfaces of the [Al, C, H, N] system has been carried out. Different quantum chemistry methodologies from density functional theory to ab initio have been employed. For the [Al, C, H, N] isomers, the stability against dissociation and their interconversion processes have been analyzed. Our results show that the most relevant isomers from an experimental point of view are HAlCN and HAlNC. HAlNC has been found to be the most stable isomer followed by HAlCN, which is located at 1.59 kcal mol-1 (0.0689 eV) at the composite level. The interconversion process between HAlCN and HAlNC presents an energy barrier of 10.0 kcal mol-1 (5032 K) that makes this process not viable in the interstellar medium. We provide a complete set of relevant spectroscopic parameters for rotational spectroscopy for both HAlCN and HAlNC isomers using state-of-the-art quantum chemical computations, mandatory to guide an eventual laboratory or interstellar detection. Moreover, both isomers present sizable μ a dipole moment components (3.7 and 3.3 D, respectively), which are large enough to enable a characterization by means of rotational spectroscopy, further increasing their interest as interstellar candidates.

Keywords: astrochemistry; interstellar molecules; molecular spectroscopy
Search for Nearby Earth Analogs .III. Detection of 10 New Planets, 3 Planet Candidates, and Confirmation of 3 Planets around 11 Nearby M Dwarfs

Earth-sized planets in the habitable zones of M dwarfs are good candidates for the study of habitability and detection of biosignatures. To search for these planets, we analyze all available radial velocity data and apply four signal detection criteria to select the optimal candidates. We find 10 strong candidates satisfying these criteria and three weak candidates showing inconsistency over time due to data samplings. We also confirm three previous planet candidates and improve their orbital solutions through combined analyses of updated data sets. Among the strong planet candidates, HIP 38594 b is a temperate super-Earth with a mass of 8.2 ± 1.7 M⊕ and an orbital period of 60.7 ± 0.1 days, orbiting around an early-type M dwarf. Early-type M dwarfs are less active and thus are better hosts for habitable planets than mid-type and late-type M dwarfs. Moreover, we report the detection of five two-planet systems, including two systems made up of a warm or cold Neptune and a cold Jupiter, consistent with a positive correlation between these two types of planets. We also detect three temperate Neptunes, four cold Neptunes, and four cold Jupiters, contributing to a rarely explored planet population. Due to their proximity to the Sun, these planets on wide orbits are appropriate targets for direct imaging by future facilities such as the Habitable Exoplanet Observatory and the Extremely Large Telescope.

Keywords: exoplanet astronomy; radial velocity; exoplanet detection methods; m dwarf stars; astrostatistics
HST/COS Observations of Quasar Outflows in the 500-1050 Å Rest Frame. II. The Most Energetic Quasar Outflow Measured to Date

We present a study of the BAL outflows seen in quasar SDSS J1042+1646 (z = 0.978) in the rest-frame 500-1050 Å (EUV500) region. The results are based on the analysis of recent Hubble Space Telescope/Cosmic Origins Spectrograph observations. Five outflow systems are identified, where, in total, they include ∼70 outflow troughs from ionic transitions. These include the first non-solar detections from transitions of O V*, Ne V*, Ar VI, Ca VI, Ca VII, and Ca VIII. The appearance of very high-ionization species (e.g., Ne VIII, Na IX, and Mg X) in all outflows necessitates at least two ionization phases for the observed outflows. We develop an interactive Synthetic Spectral Simulation method to fit the multitude of observed troughs. Detections of density sensitive troughs (e.g., S IV* λ661.40 Å and the O V* multiplet) allow us to determine the distance of the outflows (R) as well as their energetics. Two of the outflows are at R ≃ 800 pc and one is at R ≃ 15 pc. One of the outflows has the highest kinetic luminosity on record (\dot{E}_{k} = 5 × 1046 erg s-1), which is 20% of its Eddington luminosity. Such a large ratio suggests that this outflow can provide the energy needed for active galactic nucleus feedback mechanisms.

Keywords: quasar absorption line spectroscopy; quasars; active galactic nuclei; broad-absorption line quasar; active galaxies
Modeling the Chronologies and Size Distributions of Ceres and Vesta Craters

We infer the crater chronologies of Ceres and Vesta from a self-consistent dynamical model of asteroid impactors. The model accounts for planetary migration/instability early in the history of our solar system and tracks asteroid orbits over 4.56 Gyr. It is calibrated on the current population of the asteroid belt. The model provides the number of asteroid impacts on different worlds at any time throughout the solar system's history. We combine the results with an impactor-crater scaling relationship to determine the crater distribution of Ceres and Vesta and compare these theoretical predictions with observations. We find that: (i) The Ceres and Vesta chronologies are similar, whereas they significantly differ from the lunar chronology. Therefore, using the lunar chronology for main belt asteroids, as often done in previous publications, is incorrect. (ii) The model results match the number and size distribution of large (diameter >90 km) craters observed on Vesta, but overestimate the number of large craters on Ceres. This implies that large crater erasure is required for Ceres. (iii) In a model where planetary migration/instability happens early, the probability to form the Rheasilvia basin on Vesta during the last 1 Gyr is 10%, a factor of ∼1.5 higher than for the late instability case and ∼2.5 times higher than found in previous studies. Thus, while the formation of the Rheasilvia at ∼1 Gyr ago (Ga) would be somewhat unusual, it cannot be ruled out at more than ≃1.5σ. In broader context, our work provides a self-consistent framework for modeling asteroid crater records.

Keywords: main belt asteroids; ceres; solar system formation
Isolating Dust and Free-Free Emission in ONC Proplyds with ALMA Band 3 Observations

The Orion Nebula Cluster (ONC) hosts protoplanetary disks experiencing external photoevaporation by the cluster's intense UV field. These "proplyds" are comprised of a disk surrounded by an ionization front. We present ALMA Band 3 (3.1 mm) continuum observations of 12 proplyds. Thermal emission from the dust disks and free-free emission from the ionization fronts are both detected, and the high-resolution (0.″057) of the observations allows us to spatially isolate these two components. The morphology is unique compared to images at shorter (sub)millimeter wavelengths, which only detect the disks, and images at longer centimeter wavelengths, which only detect the ionization fronts. The disks are small (r d = 6.4-38 au), likely due to truncation by ongoing photoevaporation. They have low spectral indices (α ≲ 2.1) measured between Bands 7 and 3, suggesting the dust emission is optically thick. They harbor tens of Earth masses of dust as computed from the millimeter flux using the standard method although their true masses may be larger due to the high optical depth. We derive their photoevaporative mass-loss rates in two ways: first, by invoking ionization equilibrium and second, by using the brightness of the free-free emission to compute the density of the outflow. We find decent agreement between these measurements and $\dot{M}$ = 0.6-18.4 × 10-7 M ⊙ yr-1. The photoevaporation timescales are generally shorter than the ~1 Myr age of the ONC, underscoring the known "proplyd lifetime problem." Disk masses that are underestimated due to being optically thick remains one explanation to ease this discrepancy.

Keywords: proplyds; protoplanetary disks; planet formation; photoionization; exoplanet formation; dust continuum emission; circumstellar dust
Search for Gravitational-wave Transients Associated with Magnetar Bursts in Advanced LIGO and Advanced Virgo Data from the Third Observing Run

Gravitational waves are expected to be produced from neutron star oscillations associated with magnetar giant flares and short bursts. We present the results of a search for short-duration (milliseconds to seconds) and long-duration (∼100 s) transient gravitational waves from 13 magnetar short bursts observed during Advanced LIGO, Advanced Virgo, and KAGRA's third observation run. These 13 bursts come from two magnetars, SGR 1935+2154 and Swift J1818.0‑1607. We also include three other electromagnetic burst events detected by Fermi-GBM which were identified as likely coming from one or more magnetars, but they have no association with a known magnetar. No magnetar giant flares were detected during the analysis period. We find no evidence of gravitational waves associated with any of these 16 bursts. We place upper limits on the rss of the integrated incident gravitational-wave strain that reach 3.6 × 10‑23 $/\sqrt{\mathrm{Hz}}$ at 100 Hz for the short-duration search and 1.1 × 10‑22 $/\sqrt{\mathrm{Hz}}$ at 450 Hz for the long-duration search. For a ringdown signal at 1590 Hz targeted by the short-duration search the limit is set to 2.3 × 10‑22 $/\sqrt{\mathrm{Hz}}$ . Using the estimated distance to each magnetar, we derive upper limits on the emitted gravitational-wave energy of 1.5 × 1044 erg (1.0 × 1044 erg) for SGR 1935+2154 and 9.4 × 1043 erg (1.3 × 1044 erg) for Swift J1818.0‑1607, for the short-duration (long-duration) search. Assuming isotropic emission of electromagnetic radiation of the burst fluences, we constrain the ratio of gravitational-wave energy to electromagnetic energy for bursts from SGR 1935+2154 with the available fluence information. The lowest of these ratios is 4.5 × 103.

Keywords: magnetars; gravitational waves; x-ray bursts; stellar oscillations
Asteroseismic Analyses of Slowly Pulsating B Star KIC 8324482: Ultraweak Element Mixing beyond the Central Convective Core

Asteroseismology is a powerful tool for probing the inner structure and determining the evolutionary status and the fundamental parameters of stars. The oscillation spectra of slowly pulsating B (SPB) stars show almost uniform period spans, whose pattern is sensitive to the structure of the μ-gradient shell beyond the central convective core and hence can be used to efficiently describe their shapes and constrain the convective core. The SPB star KIC 8324482 was observed by Kepler for over 1470 days with a long-cadence pattern. Nearly equidistant period spacing patterns are found for the 14 connective dipolar modes that are extracted from the oscillation spectrum by Zhang et al. In the present work, we analyze them in depth with the χ2-matching method and determine their χ2-minimization models (CMMs). Based on those calculated CMMs, we find that KIC 8324482 is a young ( ${t}_{\mathrm{age}}={20.96}_{-1.28}^{+3.85}$ Myr), metal-poor ( $[\mathrm{Fe}/{\rm{H}}]=-0.6.{9}_{-0.115}^{+0.176}$ dex), and intermediate-mass ( $M={6.075}_{-0.2500}^{+0.1375}\,{M}_{\odot }$ ) star with a convective core of ${M}_{\mathrm{CC}}={1.338}_{-0.091}^{+0.057}\,{M}_{\odot }$ in mass and ${R}_{\mathrm{CC}}={0.5175}_{-0.0103}^{+0.0048}\,{R}_{\odot }$ in radius and with a surface rotation velocity ${V}_{\mathrm{eq}}={2.61}_{-0.11}^{+0.13}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ . The central hydrogen abundance is of ${X}_{{\rm{C}}}={0.5046}_{-0.0074}^{+0.0018}$ . Asteroseismic analyses indicate that the "propagation time" of g-mode in KIC 8324482 is of ${{\rm{\Lambda }}}_{0}\,={276.85}_{-0.47}^{+1.26}$ μHz. To well match with the observed period spacing pattern, an extra diffusion mixing ( $\mathrm{log}{D}_{\mathrm{mix}}={3.125}_{-0.250}^{+0.125}$ ) should be considered, but the normal core overshooting fov must be fixed as zero in the best-fitting model. Such ultraweak mixing beyond the convective core corresponds to a fast rotation that is about 20-30 times the asteroseismic suggested rotation Ωrot ≃ 0.2 μHz, if it is thought of as shear mixing induced completely by differential rotation.

Keywords: asteroseismology; stellar interiors; stellar oscillations; stellar structures; fundamental parameters of stars; stellar rotation; stellar properties; b stars
Rapidly Spinning Compact Stars with Deconfinement Phase Transition

We study rapidly spinning compact stars with equations of state featuring a first-order phase transition between strongly coupled nuclear matter and deconfined quark matter by employing the gauge/gravity duality. We consider a family of models that allow purely hadronic uniformly rotating stars with masses up to approximately 2.9 M⊙, and are therefore compatible with the interpretation that the secondary component ( ${2.59}_{-0.09}^{+0.08}\,{M}_{\odot }$ ) in GW190814 is a neutron star. These stars have central densities that are several times the nuclear saturation density, so that strong coupling and non-perturbative effects become crucial. We construct models where the maximal mass of static (rotating) stars MTOV (Mmax) is either determined by the secular instability or a phase-transition induced collapse. We find the largest values for Mmax/MTOV in cases where the phase transition determines Mmax, which shifts our fit result to ${M}_{\max }/{M}_{\mathrm{TOV}}={1.227}_{-0.016}^{+0.031}$ , a value slightly above the Breu-Rezzolla bound ${1.203}_{-0.022}^{+0.022}$ inferred from models without phase transition.

Keywords: neutron stars; neutron star cores; nuclear astrophysics