Sazuna/UAT_keywords huggingface dataset:
The Astrobiological Copernican Weak and Strong Limits for Intelligent Life. We present a cosmic perspective on the search for life and examine the likely number of Communicating Extra-Terrestrial Intelligent (CETI) civilizations in our Galaxy by utilizing the latest astrophysical information. Our calculation involves Galactic star formation histories, metallicity distributions, and the likelihood of stars hosting Earth-like planets in their habitable zones, under specific assumptions which we describe as the Astrobiological Copernican Weak and Strong conditions. These assumptions are based on the one situation in which intelligent, communicative life is known to exist—on our own planet. This type of life has developed in a metal-rich environment and has taken roughly 5 Gyr to do so. We investigate the possible number of CETI civilizations based on different scenarios. At one extreme is the Weak Astrobiological Copernican scenario—such that a planet forms intelligent life sometime after 5 Gyr, but not earlier. The other is the Strong Astrobiological Copernican scenario in which life must form between 4.5 and 5.5 Gyr, as on Earth. In the Strong scenario (under the strictest set of assumptions), we find there should be at least ${36}_{-32}^{+175}$ civilizations within our Galaxy: this is a lower limit, based on the assumption that the average lifetime, L, of a communicating civilization is 100 yr (since we know that our own civilization has had radio communications for this time). If spread uniformly throughout the Galaxy this would imply that the nearest CETI is at most ${17,000}_{-10,000}^{+33,600}$ lt-yr away and most likely hosted by a low-mass M-dwarf star, likely far surpassing our ability to detect it for the foreseeable future, and making interstellar communication impossible. Furthermore, the likelihood that the host stars for this life are solar-type stars is extremely small and most would have to be M dwarfs, which may not be stable enough to host life over long timescales. We furthermore explore other scenarios and explain the likely number of CETI there are within the Galaxy based on variations of our assumptions.

Keywords: Habitable planets, Exoplanets, Stellar abundances, Astrostatistics, Exoplanet astronomy, Astrobiology, Star formation, Metallicity, Milky Way Galaxy
Neon Abundances of B Stars in the Solar Neighborhood. We constructed a comprehensive model atom for Ne I-Ne II using the most-up-to-date atomic data available and evaluated the nonlocal thermodynamic equilibrium (NLTE) line formation for Ne I and Ne II in classical 1D models representing the atmospheres of B-type stars. We find that the large NLTE strengthening of the Ne I lines corresponding to the 2p53p-2p53s transition array occurs due to extremely small photoionization cross sections of the 2p53s levels that lead to strong overpopulation of these levels relative to their LTE populations. The deviations from LTE for most Ne II lines are small and do not exceed 0.11 dex in absolute value. We analyzed 20 lines of Ne I and 13 lines of Ne II for 24 B-type stars in the temperature range of 10,400 ≤ ${T}_{\mathrm{eff}}$ ≤ 33,400 K. For five stars, the NLTE leads to consistent abundances of Ne I and Ne II, while the difference in LTE abundance can reach up to 0.50 dex. Using the experimental oscillator strengths recently measured by Piracha et al. leads to smaller line-by-line scatter for most of the investigated stars. The average neon abundance in 24 B-type stars in the solar neighborhood is 8.02 ± 0.05. This value may provide indirect constraints on the solar photospheric neon abundance.

Keywords: Early-type stars, B stars, Stellar abundances, Solar neighborhood, Chemical abundances, Solar abundances
Star-Gas Surface Density Correlations in 12 Nearby Molecular Clouds. I. Data Collection and Star-sampled Analysis. We explore the relation between the stellar mass surface density and the mass surface density of molecular hydrogen gas in 12 nearby molecular clouds that are located at &lt;1.5 kpc distance. The sample clouds span an order-of-magnitude range in mass, size, and star formation rates. We use thermal dust emission from Herschel maps to probe the gas surface density and the young stellar objects from the most recent Spitzer Extended Solar Neighborhood Archive catalog to probe the stellar surface density. Using a star-sampled nearest neighbor technique to probe the star-gas surface density correlations at the scale of a few parsecs, we find that the stellar mass surface density varies as a power law of the gas mass surface density, with a power-law index of ∼2 in all the clouds. The consistent power-law index implies that star formation efficiency is directly correlated with gas column density, and no gas column density threshold for star formation is observed. We compare the observed correlations with the predictions from an analytical model of thermal fragmentation and with the synthetic observations of a recent hydrodynamic simulation of a turbulent star-forming molecular cloud. We find that the observed correlations are consistent for some clouds with the thermal fragmentation model and can be reproduced using the hydrodynamic simulations.

Keywords: Hydrodynamical simulations, Early stellar evolution, Star forming regions, Molecular clouds, Far infrared astronomy, Infrared astronomy, Scaling relations, Young stellar objects, Star formation, Dust continuum emission, Protostars
AGILESim: Monte Carlo Simulation of the AGILE Gamma-Ray Telescope. The accuracy of Monte Carlo simulations in reproducing the scientific performance of space telescopes (e.g., angular resolution) is mandatory for a correct design of the mission. A brand-new Monte Carlo simulator of the Astrorivelatore Gamma ad Immagini LEggero (AGILE)/Gamma-Ray Imaging Detector (GRID) space telescope, AGILESim, is built using the customizable Bologna Geant4 Multi-Mission Simulator (BoGEMMS) architecture and the latest Geant4 library to reproduce the instrument performance of the AGILE/GRID instrument. The Monte Carlo simulation output is digitized in the BoGEMMS postprocessing pipeline, according to the instrument electronic readout logic, then converted into the onboard data handling format, and finally analyzed by the standard mission on-ground reconstruction pipeline, including the Kalman filter, as a real observation in space. In this paper we focus on the scientific validation of AGILESim, performed by reproducing (I) the conversion efficiency of the tracker planes, (II) the tracker charge readout distribution measured by the on-ground assembly, integration, and verification activity, and (III) the point-spread function of in-flight observations of the Vela pulsar in the 100 MeV-1 GeV energy range. We measure an in-flight angular resolution (full width at half-maximum) for Vela-like point sources of $2\buildrel{\circ}\over{.} {0}_{-0\buildrel{\circ}\over{.} 3}^{+0\buildrel{\circ}\over{.} 2}$ and $0\buildrel{\circ}\over{.} {8}_{-0\buildrel{\circ}\over{.} 1}^{+0\buildrel{\circ}\over{.} 1}$ in the 100-300 and 300-1000 MeV energy bands, respectively. The successful cross-comparison of the simulation results with the AGILE on-ground and in-space performance validates the BoGEMMS framework for its application to future gamma-ray trackers (e.g., e-ASTROGAM and AMEGO).

Keywords: Astronomical instrumentation, Astronomical simulations, Gamma-ray telescopes
On the Magnetic Nature of an Exploding Granule as Revealed by Sunrise/IMaX. We study the photospheric evolution of an exploding granule observed in the quiet Sun at high spatial (∼0"3) and temporal (31.5 s) resolution by the imaging magnetograph Sunrise/IMaX in 2009 June. These observations show that the exploding granule is cospatial to a magnetic flux emergence event occurring at mesogranular scale (up to ∼12 Mm2 area). Using a modified version of the SIR code for inverting the IMaX spectropolarimetric measurements, we obtain information about the magnetic configuration of this photospheric feature. In particular, we find evidence of highly inclined emerging fields in the structure, carrying a magnetic flux content up to ∼4 × 1018 Mx. The balance between gas and magnetic pressure in the region of flux emergence, compared with a very quiet region of the Sun, indicates that the additional pressure carried by the emerging flux increases the total pressure by about 5% and appears to allow the granulation to be modified, as predicted by numerical simulations. The overall characteristics suggest that a multipolar structure emerges into the photosphere, resembling an almost horizontal flux sheet. This seems to be associated with exploding granules. Finally, we discuss the origin of such flux emergence events.

Keywords: Solar magnetic flux emergence, Solar photosphere, Spectropolarimetry, Solar granulation, Solar magnetic fields, Mesogranulation, Solar granules
The Parsec-scale Jet of the Neutrino-emitting Blazar TXS 0506+056. Recently the IceCube Collaboration detected very high energy (VHE) neutrinos and associated them with the blazar TXS 0506+056, raising a possible association of VHE neutrinos with this and other individual blazars. Very long baseline interferometry (VLBI) is so far the only technique enabling the imaging of the innermost jet at milliarcsec resolution (parsec scale), where the high-energy emission possibly originates from. Here, we report on the radio properties of the parsec-scale jet in TXS 0506+056 derived from the analysis of multiepoch, multifrequency archive VLBI data. The half opening angle of the jet beam is about 3°8, and the jet inclination angle is about 20°. The overall jet structure shows a helical trajectory with a precessing period of 5-6 yr, likely originating from instabilities operating at parsec scales. The calculated beaming parameters (Doppler boosting factor, bulk Lorentz factor) suggest a moderately relativistic jet. The parsec-scale magnetic field strength is estimated in the contexts of core shift and variability, and is in general agreement in the range of 0.2-0.7 G. And it is found to decrease from a relatively larger value during the quiescent period before the ongoing flare. This suggests a conversion of magnetic field energy density to particle energy density that helps accelerate injected particles at the jet base and results in variable shocked emission. The neutrino event could be associated with the onset of energetic particle injection into the jet. This scenario then supports the lepto-hadronic origin of the VHE neutrinos and γ-ray emission owing to a cospatial origin.

Keywords: Radio jets, Gamma-ray sources, Blazars, Neutrino astronomy, Non-thermal radiation sources, Radio active galactic nuclei
Keck/HIRES Spectroscopic Analysis of Barium Abundances. Based on the high-resolution, high signal-to-noise-ratio spectra from the Keck/HIRES, we have analyzed the barium abundances of 602 stars. The parameter space of our sample are in the range of 4700 &lt; ${T}_{\mathrm{eff}}$ &lt; 6100 K, -0.1 &lt; [Fe/H] &lt; 0.6 dex, and 2 &lt; log g &lt; 5 dex. It is found that the nonlocal thermodynamic equilibrium (NLTE) effects are large for barium, and the barium abundances can be underestimated by up to 0.2 dex compared to the the local thermodynamic equilibrium analysis for lines at 5853 and 6141 Å. In addition, the average barium abundances of the high- and low-α stars are -0.10 and 0.00 dex, respectively, and higher [Ba/Fe] corresponds to a lower [Mg/Fe] ratio. We note that there are 18 Ba-rich stars (with [Ba/Fe] &gt; 0.3 in NLTE), which contains six dwarfs and 12 giants. The Ba-rich objects make up around 3% in our sample.

Keywords: Stellar abundances, Galaxy structure
TESS Asteroseismic Analysis of the Known Exoplanet Host Star HD 222076. The Transiting Exoplanet Survey Satellite (TESS) is an all-sky survey mission aiming to search for exoplanets that transit bright stars. The high-quality photometric data of TESS are excellent for the asteroseismic study of solar-like stars. In this work, we present an asteroseismic analysis of the red-giant star HD 222076 hosting a long-period (2.4 yr) giant planet discovered through radial velocities. Solar-like oscillations of HD 222076 are detected around 203 μHz by TESS for the first time. Asteroseismic modeling, using global asteroseismic parameters as inputs, yields a determination of the stellar mass ( ${M}_{\star }=1.12\pm 0.12\,{M}_{\odot }$ ), radius ( ${R}_{\star }=4.34\pm 0.21\,{R}_{\odot }$ ), and age (7.4 ± 2.7 Gyr), with precisions greatly improved from previous studies. The period spacing of the dipolar mixed modes extracted from the observed power spectrum reveals that the star is on the red-giant branch burning hydrogen in a shell surrounding the core. We find that the planet will not escape the tidal pull of the star and will be engulfed into it within about 800 Myr, before the tip of the red-giant branch is reached.

Keywords: Asteroseismology, Exoplanet systems
The Effects of Metallicity and Abundance Pattern of the ISM on Supernova Feedback. Supernova (SN) feedback plays a vital role in the evolution of galaxies. While modern cosmological simulations capture the leading structures within galaxies, they struggle to provide sufficient resolution to study small-scale stellar feedback, such as the detailed evolution of SN remnants. It is thus common practice to assume subgrid models that are rarely extended to low metallicities and that routinely use the standard solar abundance pattern. With the aid of 1D hydrodynamical simulations, we extend these models to consider low metallicities and nonsolar abundance patterns as derived from spectra of Milky Way stars. For that purpose, a simple, yet effective framework has been developed to generate nonsolar abundance pattern cooling functions. We find that previous treatments markedly over-predict SN feedback at low metallicities and show that non-negligible changes in the evolution of SN remnants of up to ≈50% in cooling mass and ≈27% in momentum injection from SN remnants arise from nonsolar abundance patterns. We use our simulations to quantify these results as a function of metallicity and abundance pattern variations and present analytic formulas to accurately describe the trends. These formulas have been designed to serve as subgrid models for SN feedback in cosmological hydrodynamical simulations.

Keywords: Supernova remnants, Galaxy evolution, Interstellar medium, Astronomical simulations
Electron Jets in the Terrestrial Magnetotail: A Statistical Overview. Electron jets, common transient phenomena for which the electron velocity is much larger than the ion velocity, play an important role in the energy dissipation and transport in the terrestrial and other planetary magnetospheres. Using the unprecedented high-resolution data provided by the Magnetospheric Multiscale mission from May to August in 2017, we perform one systematically statistical study on the electron jets in the terrestrial magnetotail for the first time. In total, 466 electron jet events are selected, which mainly concentrate in the region -25 &lt; X &lt; -17 RE, -14 &lt; Y &lt; 12 RE, and 0 &lt; Z &lt; 6 RE (RE is the Earth's radius). The electron velocity within the electron jets is much larger than the local Alfvén speed, implying that these jets belong to super-Alfvénic flows. The average occurrence rate of electron jets is 0.217 events hr-1 in the X-Y plane and 0.189 events/hour in the Z-Y plane. The durations of the electron jets are mostly within 6 seconds with the average value of 2.89 seconds, which are much shorter than the duration of bursty bulk flows (BBFs) having the typical duration of several to tens of minutes. Through further analysis of the magnetic field, we find that electron jets can occur at five different structures, including 224 events detected during the crossing of current sheet, 57 events observed during the crossing of PSBL, 83 events around DFs, 79 events around magnetic holes, and 23 events around flux ropes. In addition, the relative positions of the electron jets in different structures are also identified in the present study. Our statistical results reveal the comprehensive features of electron jets in the terrestrial magnetotail, which can also be applied in the other planetary magnetosphere.

Keywords: Space plasmas, Heliosphere, Plasma jets, Plasma astrophysics, Planetary magnetospheres
Three-dimensional Analysis of the Minispiral at the Galactic Center: Orbital Parameters, Periods, and the Mass of the Black Hole. In this paper we simultaneously fit the orbits and line-of-sight velocities of the ionized gas around the supermassive black hole, Sagittarius A* (Sgr A*), at the center of the Milky Way. The data we use are taken with the K-band Multi Object Spectrograph (KMOS), presented in Feldmeier-Krause et al., and cover the central ∼2 pc of the Milky Way. From the brightest gas emission line in the K-band, the Brγ line, we derive the spatial distribution and line-of-sight velocities of the gas in the minispiral. Using the flux distribution and the line-of-sight velocity information, we perform a fit to the three main gas streamers in the minispiral, the Northern Arm, Eastern Arm, and Western Arc, using a Bayesian modeling method, and are able to reconstruct the three-dimensional orbits of these gas streamers. With the best-fit orbital parameters and the measured line-of-sight velocities, we constrain the mass of Sgr A*. The orbit of the Eastern Arm is the one that is best constrained using our data. It gives a best-fit orbital period of ${17.4}_{-11.6}^{+31.0}\times {10}^{3}$ yr and results in an enclosed mass of ${14.9}_{-10.4}^{+69.4}\times {10}^{6}{M}_{\odot }.$

Keywords: Galactic center, H II regions
Timescales for Detection of Super-Chandrasekhar White Dwarfs by Gravitational-wave Astronomy. Over the past two decades, the inference of the violation of the Chandrasekhar mass limit of white dwarfs (WDs) from indirect observation has been a revolutionary discovery in astronomy. Various researchers have already proposed different theories to explain this interesting phenomenon. However, such massive WDs usually possess very little luminosity, hence they so far cannot be detected directly by any observations. We have already proposed that the continuous gravitational wave may be one of the probes to detect them directly, and in the future various space-based detectors, such as LISA, DECIGO, and BBO, should be able to detect many of those WDs (provided they behave like pulsars). In this paper, we address various timescales related to the emission of gravitational as well as dipole radiations. This exploration sets a timescale for the detectors to observe the massive WDs.

Keywords: Stellar luminosities, Rotation powered pulsars, White dwarf stars, Stellar magnetic fields, Gravitational wave sources, Pulsars, Gravitational wave astronomy, Chandrasekhar limit, Gravitational waves, Astronomical radiation sources
The Radial Acceleration Relation in CLASH Galaxy Clusters. The radial acceleration relation (RAR) in galaxies describes a tight empirical scaling law between the total acceleration ${g}_{\mathrm{tot}}(r)={{GM}}_{\mathrm{tot}}(\lt r)/{r}^{2}$ observed in galaxies and that expected from their baryonic mass ${g}_{\mathrm{bar}}(r)={{GM}}_{\mathrm{bar}}(\lt r)/{r}^{2}$, with a characteristic acceleration scale of ${g}_{\dagger }\simeq 1.2\times {10}^{-10}$ m s-2. Here, we examine if such a correlation exists in galaxy clusters using weak-lensing, strong-lensing, and X-ray data sets available for 20 high-mass clusters targeted by the Cluster Lensing And Supernova survey with Hubble (CLASH). By combining our CLASH data with stellar mass estimates for the brightest cluster galaxies (BCGs) and accounting for the stellar baryonic component in clusters, we determine, for the first time, an RAR on BCG-cluster scales. The resulting RAR is well described by a tight power-law relation, ${g}_{\mathrm{tot}}\propto {g}_{\mathrm{bar}}^{{0.51}_{-0.05}^{+0.04}}$, with lognormal intrinsic scatter of ${14.7}_{-2.8}^{+2.9} \% $ . The slope is consistent with the low acceleration limit of the RAR in galaxies, ${g}_{\mathrm{tot}}=\sqrt{{g}_{\dagger }\,{g}_{\mathrm{bar}}}$, whereas the intercept implies a much higher acceleration scale of ${g}_{\unicode{x02021}}=(2.02\pm 0.11)\times {10}^{-9}$ m s-2, indicating that there is no universal RAR that holds on all scales from galaxies to clusters. We find that the observed RAR in CLASH clusters is consistent with predictions from a semianalytical model developed in the standard ΛCDM framework. Our results also predict the presence of a baryonic Faber-Jackson relation ( ${\sigma }_{V}^{4}\propto {M}_{\mathrm{bar}}$ ) on cluster scales.

Keywords: Galaxy clusters, Cosmology, X-ray astronomy, Gravitational lensing, Intracluster medium, Dark matter
Persistent Radio Emission from Synchrotron Heating by a Repeating Fast Radio Burst Source in a Nebula. The first repeating fast radio burst (FRB), FRB 121102, was found to be associated with a spatially coincident, persistent nonthermal radio source, but the origin of the persistent emission remains unknown. In this paper, we propose that the persistent emission is produced via a synchrotron-heating process by multiple bursts of FRB 121102 in a self-absorbed synchrotron nebula. With a population of bursts of the repeating FRB absorbed by the synchrotron nebula, the energy distribution of electrons in the nebula will change significantly. As a result, the spectrum of the nebula will show a hump steadily. For the persistent emission of FRB 121102, the total energy of bursts injecting into the nebula is required to be about 3.3 × 1049 erg, the burst injection age is over 6.7 × 104 yr, the nebula size is ∼0.02 pc, and the electron number is about 3.2 × 1055. We predict that as more bursts inject, the brightness of the nebula would be brighter than the current observation, and meanwhile, the peak frequency would become higher. Due to the synchrotron absorption of the nebula, some low-frequency bursts would be absorbed, which may explain why most bursts were detected above ∼1 GHz.

Keywords: Radio continuum emission, Extragalactic radio sources, Radio bursts
The Role of Gravitational Recoil in the Assembly of Massive Black Hole Seeds. When two black holes merge, the asymmetric emission of gravitational waves provides an impulse to the merged system; this gravitational-wave recoil velocity can be up to 4000 km s-1, easily fast enough for the black hole to escape its host galaxy. We combine semianalytic modeling with cosmological zoom-in simulations of a Milky Way-type galaxy to investigate the role of black hole spin and gravitational recoil in the epoch of massive black hole (MBH) seeding. We sample four different spin distributions (random, aligned, antialigned, and zero spin), and compare the resulting merger rates, occupation fractions, and MBH-host relations with what is expected by excluding the effect of recoil. The inclusion of gravitational recoil and MBH spin in the assembly of MBH seeds can reduce the final z = 5 MBH mass by up to an order of magnitude. The MBH occupation fraction, however, remains effectively unaltered due to episodes of black hole formation following a recoil event. While electromagnetic detections of these events are unlikely, the Laser Interferometer Space Antenna is ideally suited to detect gravitational-wave signals from such events.

Keywords: Black hole physics, Galaxy formation, High-redshift galaxies, N-body simulations