Sazuna/UAT_keywords huggingface dataset:
VLT/X-Shooter Spectroscopy of Lyman Break Analogs: Direct-method O/H Abundances and Nitrogen Enhancements. We used Very Large Telescope/X-Shooter to target a sample of nearby analogs of Lyman break galaxies (LBGs). These Lyman break analogs are similar to the LBGs in many of their physical properties. We determine electron temperatures using the weak [O III] λ4363 emission line and determine the oxygen abundance (O/H) using the direct and strong-line methods. We show that the direct and strong-line abundances are consistent with established relations within ∼0.2 dex. The analogs have nitrogen-to-oxygen ratios (N/O) and ionization parameters (q) that are, on average, offset with respect to typical local galaxies but similar to galaxies at z ∼ 2 and other analogs. The N/O and q excesses correlate with the offsets observed in the strong-line ratios, again similar to z ∼ 2. The star formation rate surface densities are consistent with the high electron density and ionization, indicating that the interstellar medium (ISM) pressure is set by feedback from the starbursts. For a given O/H, the apparent N/O excess arises owing to the offset in O/H with respect to the local mass-metallicity relation. This can be explained by recent inflow of relatively metal-poor gas that lowers O/H while leaving N/O unchanged. The difficulties in determining even basic ISM parameters in these nearby analogs illustrate some of the challenges we face at much higher redshifts, where similar rest-frame optical diagnostics for large samples of galaxies can be accessed with the James Webb Space Telescope.

Keywords: Starburst galaxies, Galaxy abundances, Lyman-break galaxies, H II regions, Galaxies
Forming Diverse Super-Earth Systems In Situ. Super-Earths and mini-Neptunes exhibit great diversity in their compositional and orbital properties. Their bulk densities span a large range, from those dense enough to be purely rocky to those needing a substantial contribution from volatiles to their volumes. Their orbital configurations range from compact, circular multitransiting systems like Kepler-11 to systems like our solar system's terrestrial planets with wider spacings and modest but significant eccentricities and mutual inclinations. Here we investigate whether a continuum of formation conditions resulting from variation in the amount of solids available in the inner disk can account for the diversity of orbital and compositional properties observed for super-Earths, including the apparent dichotomy between single and multitransiting systems. We simulate in situ formation of super-Earths via giant impacts and compare to the observed Kepler sample. We find that intrinsic variations among disks in the amount of solids available for in situ formation can account for the orbital and compositional diversity observed among Kepler's transiting planets. Our simulations can account for the planets' distributions of orbital period ratios, transit duration ratios, and transit multiplicity; higher eccentricities for planets in single transiting systems than for those in multitransiting systems; smaller eccentricities for larger planets; scatter in the mass-radius relation, including lower densities for planets with masses measured with transit timing variations instead of with radial velocity; and similarities in planets' sizes and spacings within each system. Our findings support the theory that variation among super-Earth and mini-Neptune properties is primarily locked in by different in situ formation conditions, rather than arising stochastically through subsequent evolution.

Keywords: Exoplanet dynamics, Exoplanet astronomy, Exoplanet formation, Exoplanets
Ejection of Glycine Molecules Adsorbed on a Water Ice Surface by Swift-heavy Ion Irradiation. Organic molecules may be adsorbed on the ice surfaces of comets or moons. We study the desorption process induced by swift-heavy ion irradiation using a molecular dynamics simulation. Focusing on the amino acid glycine adsorbed on water ice as a prototypical example, we model a 2 MeV sulfur ion impact as it might be typical of magnetospheric ion impact on the surface of Europa. We find that molecules are ejected intact within a radius of up to 25 Å around the ion impact point. Within a core region of around 10 Å, glycine molecules are destroyed and mainly fragments are emitted. Prominent fragments produced are cyanide CN-, carbon monoxide CO, cyanate OCN-, and carbon dioxide CO2, in agreement with experimental studies. In addition, radiolysis of water ice generates the radicals H+, H3O+, and HO- as well as the gases H2, O2, and some H2O2. While the smaller fragments easily obtain velocities above 2 km s-1 - the escape velocity from Europa - most ejected glycine molecules obtain smaller velocities and will thus not leave the moon permanently. Our results thus provide a detailed example that shows to what extent intact emission of organic molecules from Europa's surface by ion irradiation is possible and may be used for modeling the height distribution of ejecta in Europa's exosphere.

Keywords: Computational methods, Galilean satellites, Astrochemistry
Testing Densities and Refractive Indices of Extraterrestrial Ice Components Using Molecular Structures—Organic Compounds and Molar Refractions. The use of infrared spectra to determine molecular abundances of icy astronomical objects and to study their chemistry requires laboratory measurements of reference spectra and related quantities, such as the index of refraction (n) and density (ρ) of candidate ices. Here we present new n and ρ measurements on ices involving over 30 C-, H-, and O-containing compounds, both acyclic and cyclic, representing seven chemical families. We examine the results in a way that is rare in the astrochemical literature, namely one in which data from an ice formed from molecules of a particular chemical family are compared to measurements on another member of the same family, such as of a homologous series or a pair of isomers. Apart from the intrinsic usefulness of the n and ρ data, a structure-based comparison can help establish trends and identify possibly spurious results. As liquid-phase data sometimes are used in low-temperature astrochemical work in the absence of solid-phase measurements, we compare our new ice results to those for the corresponding room-temperature liquids. We emphasize the use of our n and ρ data to compute the molar refraction (RM) for each of our ices, and how the resulting RM values compare to those expected from molecular structures. The use of calculated RM values and measured n values to calculate ice densities, in the absence of direct measurements, is also addressed.

Keywords: Laboratory astrophysics, Molecular spectroscopy, Astrochemistry
SPCANet: Stellar Parameters and Chemical Abundances Network for LAMOST-II Medium Resolution Survey. The fundamental stellar atmospheric parameters (Teff and log g) and 13 chemical abundances are derived for medium-resolution spectroscopy from Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Medium Resolution Survey (MRS) data sets with a deep-learning method. The neural networks we designed, named SPCANet, precisely map LAMOST MRS spectra to stellar parameters and chemical abundances. The stellar labels derived by SPCANet have precisions of 119 K for Teff and 0.17 dex for log g. The abundance precision of 11 elements including [C/H], [N/H], [O/H], [Mg/H], [Al/H], [Si/H], [S/H], [Ca/H], [Ti/H], [Cr/H], [Fe/H], and [Ni/H] are 0.06 ∼ 0.12 dex, while that of [Cu/H] is 0.19 dex. These precisions can be reached even for spectra with signal-to-noise ratios as low as 10. The results of SPCANet are consistent with those from other surveys such as APOGEE, GALAH, and RAVE, and are also validated with the previous literature values including clusters and field stars. The catalog of the estimated parameters is available at doi:10.12149/101012.

Keywords: Spectroscopy, Stellar atmospheres
Effect of Vegetation on the Temperatures of TRAPPIST-1 Planets. TRAPPIST-1 is an ultracool dwarf hosting a system consisting of seven planets. While orbital properties, radii, and masses of the planets are nowadays well constrained, one of the fascinating open issues is the possibility that an environment hospitable to life could develop on some of these planets. Here, we use a simple formulation of an energy balance model that includes vegetation coverage to investigate the possibility of life affecting the climate of the planets in the TRAPPIST-1 system. Results confirm that planet TRAPPIST-1e has the best chance to be a habitable world and indicate that vegetation coverage significantly affects the resulting temperatures and habitability properties. The influence of vegetation has been evaluated in different scenarios characterized by different vegetation types, land-sea distributions and levels of greenhouse effect. While changes in vegetation type produce small changes, about 0.1%, in the habitable surface fraction, different land-sea distributions, by also affecting the vegetation growth, produce different temperature distributions. Finally, at latitudes where vegetation grows, the lowering of local albedo still represents a relevant contribution in settling the planetary temperature profiles even when levels of greenhouse effect higher than the Earth-like case are considered.

Keywords: Extrasolar rocky planets, Ocean planets, Exoplanets, Exoplanet systems, Computational methods, Astrobiology, Exoplanet surfaces, Habitable planets
Stellar Feedback and Resolved Stellar IFU Spectroscopy in the Nearby Spiral Galaxy NGC 300. We present MUSE integral field unit (IFU) observations of five individual H II regions in two giant star-forming complexes in the low-metallicity, nearby dwarf spiral galaxy NGC 300. In combination with high spatial resolution Hubble Space Telescope photometry, we demonstrate the extraction of stellar spectra and classification of individual stars from ground-based IFU data at the distance of 2 Mpc. For the two star-forming complexes, in which no O-type stars had previously been identified, we find a total of 13 newly identified O-type stars and 4 Wolf-Rayet stars (two already-known sources and two Wolf-Rayet star candidates that this work has now confirmed). We use the derived massive stellar content to analyze the impact of stellar feedback on the H II regions. As already found for H II regions in the Magellanic Clouds, the dynamics of the analyzed NGC 300 H II regions are dominated by a combination of the pressure of the ionized gas and stellar winds. Moreover, we analyze the relation between the star formation rate and the pressure of the ionized gas as derived from small (&lt;100 pc) scales, both quantities being systematically overestimated when derived on galactic scales. With the wealth of upcoming IFU instruments and programs, this study serves as a pathfinder for the systematic investigation of resolved stellar feedback in nearby galaxies, delivering the necessary analysis tools to enable massive stellar content and feedback studies sampling an unprecedented range of H II region properties across entire galaxies in the nearby universe.

Keywords: Stellar feedback, Massive stars, Young massive clusters, Galactic and extragalactic astronomy, Intergalactic medium, H II regions
Modeling the Infrared Reverberation Response of the Circumnuclear Dusty Torus in AGNs: An Investigation of Torus Response Functions. The size and structure of the dusty circumnuclear torus in active galactic nuclei (AGNs) can be investigated by analyzing the temporal response of the torus's infrared (IR) dust emission to variations in the AGN ultraviolet/optical luminosity. This method, reverberation mapping, is applicable over a wide redshift range, but the IR response is sensitive to several poorly constrained variables relating to the dust distribution and its illumination, complicating the interpretation of measured reverberation lags. We have used an enhanced version of our torus reverberation mapping code (TORMAC) to conduct a comprehensive exploration of the torus response functions at selected wavelengths, for the standard interstellar medium grain composition. The shapes of the response functions vary widely over the parameter range covered by our models, with the largest variations occurring at shorter wavelengths (≤4.5 μm). The reverberation lag, quantified as the response-weighted delay (RWD), is most affected by the radial depth of the torus, the steepness of the radial cloud distribution, the degree of anisotropy of the AGN radiation field, and the volume filling factor. Nevertheless, we find that the RWD provides a reasonably robust estimate, to within a factor of ∼3, of the luminosity-weighted torus radius, confirming the basic assumption underlying reverberation mapping. However, overall, the models predict radii at 2.2 μm that are typically a factor of ∼2 larger than those derived from K-band reverberation mapping. This is likely an indication that the innermost region of the torus is populated by clouds dominated by large graphite grains.

Keywords: Accretion, Reverberation mapping, Active galaxies, Astrophysical dust processes, Active galactic nuclei, Infrared galaxies, Radiative transfer
On the Chemical and Kinematic Consistency between N-rich Metal-poor Field Stars and Enriched Populations in Globular Clusters. Interesting chemically peculiar field stars may reflect their stellar evolution history and their possible origin in a different environment from where they are found now; this is one of the most important research fields in Galactic archeology. To explore this further, we have used the CN-CH bands around 4000 Å to identify N-rich metal-poor field stars in LAMOST DR3. Here we expand our N-rich, metal-poor field star sample to ∼100 stars in LAMOST DR5, where 53 of them are newly found in this work. We investigate light elements of common stars between our sample and APOGEE DR14. While Mg, Al, and Si abundances generally agree with the hypothesis that N-rich metal-poor field stars come from enriched populations in globular clusters, it is still inconclusive for C, N, and O. After integrating the orbits of our N-rich field stars and a control sample of normal metal-poor field stars, we find that N-rich field stars have different orbital parameter distributions compared to the control sample - specifically, apocentric distances, maximum vertical amplitude (Zmax), orbital energy, and z-direction angular momentum (Lz). The orbital parameters of N-rich field stars indicate that most of them are inner-halo stars. The kinematics of N-rich field stars support their possible GC origin. The spatial and velocity distributions of our bona fide N-rich field star sample are important observational evidence to constrain simulations of the origin of these interesting objects.

Keywords: Globular star clusters, Quasar absorption line spectroscopy, Stellar kinematics, Chemical abundances, Stellar dynamics, Milky Way stellar halo, CN stars, Milky Way evolution, Chemically peculiar stars
The SPOTS Models: A Grid of Theoretical Stellar Evolution Tracks and Isochrones for Testing the Effects of Starspots on Structure and Colors. One-dimensional stellar evolution models have been successful at representing the structure and evolution of stars in diverse astrophysical contexts, but complications have been noted in the context of young, magnetically active stars, as well as close binary stars with significant tidal interactions. Numerous puzzles are associated with pre-main-sequence (pre-MS) and active main sequence (MS) stars, relating to their radii, their colors, certain elemental abundances, and the coevality of young clusters, among others. A promising explanation for these puzzles is the distorting effects of magnetic activity and starspots on the structure of active stars. To assist the community in evaluating this hypothesis, we present the Stellar Parameters of Tracks with Starspots (SPOTS) models, a grid of solar-metallicity stellar evolutionary tracks and isochrones that include a treatment of the structural effects of starspots. The models range from 0.1 to 1.3 M⊙ and from spotless to a surface covering fraction of 85%, and are evolved from the pre-MS to the red giant branch (or 15 Gyr). We also produce two-temperature synthetic colors for our models using empirically calibrated color tables. We describe the physical ingredients included in the SPOTS models and compare their predictions to other modern evolution codes. Finally, we apply these models to several open questions in the field of active stars, including the radii of young eclipsing binaries, the color scale of pre-MS stars, and the existence of sub-subgiants, demonstrating that our models can explain many peculiar features of active stars.

Keywords: Starspots, Magnetic stars, Early stellar evolution, Stellar ages, Stellar properties, Young star clusters, Stellar evolution
Global Simulations of the Vertical Shear Instability with Nonideal Magnetohydrodynamic Effects. The mechanisms of angular momentum transport and the level of turbulence in protoplanetary disks (PPDs) are crucial for understanding many aspects of planet formation. In recent years, it has been realized that the magneto-rotational instability tends to be suppressed in PPDs due to nonideal magnetohydrodynamic (MHD) effects, and the disk is primarily laminar with accretion driven by magnetized disk winds. In parallel, several hydrodynamic mechanisms have been identified that likely also generate vigorous turbulence and drive disk accretion. In this work, we study the interplay between MHD winds in PPDs with the vertical shear instability (VSI), one of the most promising hydrodynamic mechanisms, through 2D global nonideal MHD simulations with ambipolar diffusion (AD) and ohmic resistivity. For typical disk parameters, MHD winds can coexist with the VSI with accretion primarily wind-driven accompanied by vigorous VSI turbulence. The properties of the VSI remain similar to the unmagnetized case. The wind and overall field configuration are not strongly affected by the VSI turbulence, showing a modest level of variability and corrugation of the midplane current sheet. Weak AD strength or the enhanced coupling between gas and magnetic fields weakens the VSI. The VSI is also weakened with increasing magnetization, and characteristic VSI corrugation modes transition to low-amplitude breathing mode oscillations with strong magnetic fields.

Keywords: Magnetohydrodynamics, Astrophysical fluid dynamics, Protoplanetary disks
Radio/X-Ray Correlation in the Mini-outbursts of Black Hole X-Ray Transient GRS 1739-278. We present quasi-simultaneous radio and X-ray observations of the black hole X-ray binary GRS 1739-278 during the 2015-2016 mini-outbursts, I.e., between 2015 June 10 and 2016 October 31, with the X-ray-to-radio time interval being less than one day. The monitor campaign was run by Swift in the X-rays and by VLA in the radio (at both 5 and 8 GHz). We find that the brightest radio emission is actually achieved during the soft sate, and the spectrum is marginally optically thick with the spectral index α ≈ -0.28 ± 0.17 (flux Fν ∝ να). For the radio emission in the hard state, we find a large diversity in the spectral index, I.e., a majority of radio spectra are optically thick with -0.5 ≲ α ≲ 0.5, while a few are optically thin, with α being lower than -1 in certain cases. We then investigate the correlation between the luminosities in radio (monochromatic at 5 GHz, L_{R}) and 1-10 keV X-rays (L_{X}) during the hard state. We find that for more than two orders of magnitude variation in the X-ray luminosity, this source exhibits a flat correlation with p ≈ 0.16 (in the form of L_{R} ∝ L_{X}^{p}), I.e., it belongs to the "outlier" (to the standard correlation with p ≈ 0.6) category that may follow a hybrid correlation. Both the slope and the corresponding luminosity range agree well with those in H1743-322, the prototype of the hybrid correlation. Theoretical implications of our results are discussed.

Keywords: Stellar accretion disks, Black hole physics, Low-mass x-ray binary stars, X-ray binary stars
Mass-to-light Ratios of Spatially Resolved Stellar Populations in M31. A galaxy's stellar mass-to-light ratio (M_{\star }/L) is a useful tool for converting luminosity to stellar mass (M_{\star }). However, the practical utility of M_{\star}/L inferred from stellar population synthesis (SPS) models is limited by mismatches between the real and assumed models for star-formation history (SFH) and dust geometry, both of which vary within galaxies. Here, we measure spatial variations in M_{\star}/L and their dependence on color, SFH, and dust across the disk of M31, using a map of M_{\star}CMD derived from color-magnitude diagrams of resolved stars in the Panchromatic Hubble Andromeda Treasury survey. First, we find comparable scatter in M_{\star}/L for the optical and mid-IR, contrary to the common idea that M_{\star }/L is less variable in the IR. Second, we confirm that M_{\star}/L is correlated with color for both the optical and mid-IR and report color versus M_{\star}/L relations (CMLRs) in M31 for filters used in the Sloan Digital Sky Survey and Widefield Infrared Survey Explorer. Third, we show that the CMLR residuals correlate with recent SFH, such that quiescent regions are offset to higher M_{\star}/L than star-forming regions at a fixed color. The mid-IR CMLR, however, is not linear due to the high scatter of M_{\star}/L in star-forming regions. Finally, we find a flatter optical CMLR than any SPS-based CMLRs in the literature. We show that this is an effect of dust geometry, which is typically neglected but should be accounted for when using optical data to map M_{\star}.

Keywords: Interstellar dust, Galaxy physics, Star formation, Galaxy masses, Andromeda Galaxy
A Companion Star Launching Jets in the Wind Acceleration Zone of a Giant Star. By conducting three-dimensional hydrodynamical simulations we find that jets that a main-sequence companion launches as it orbits inside the wind acceleration zone of an asymptotic giant branch star can efficiently remove mass from that zone. We assume that during the intensive wind phase a large fraction of the gas in the acceleration zone does not reach the escape velocity. Therefore, in the numerical simulations we blow the wind with a velocity just below the escape velocity. We assume that a main-sequence companion accretes mass from the slow wind via an accretion disk, and launches two opposite jets perpendicular to the equatorial plane. This novel flow interaction shows that, by launching jets, a companion outside a giant star, but close enough to be in the acceleration zone of a slow intensive wind, can enhance the mass-loss rate from the giant star by ejecting some gas that would otherwise fall back onto the giant star. The jets are bent inside the wind acceleration zone and eject mass in a belt on the two sides of the equatorial plane. The jet-wind interaction contains instabilities that mix the shocked jets' gas with the wind, leading to energy transfer from the jets to the wind. Our new simulations add to the rich variety of jet-induced outflow morphologies from evolved stars.

Keywords: Close binary stars, Stellar jets, Planetary nebulae, Asymptotic giant branch