Sazuna/UAT_keywords huggingface dataset:
Chromium Nucleosynthesis and Silicon-Carbon Shell Mergers in Massive Stars. We analyze the production of the element Cr in galactic chemical evolution (GCE) models using the NuGrid nucleosynthesis yields set. We show that the unusually large [Cr/Fe] abundance at [Fe/H] ≈ 0 reported by previous studies using those yields and predicted by our Milky Way model originates from the merging of convective Si-burning and C-burning shells in a 20 M⊙ model at metallicity Z = 0.01, about an hour before the star explodes. This merger mixes the incomplete burning material in the Si shell, including 51V and 52Cr, out to the edge of the carbon/oxygen (CO) core. The adopted supernova model ejects the outer 2 M⊙ of the CO core, which includes a significant fraction of the Cr-rich material. When including this 20 M⊙ model at Z = 0.01 in the yields interpolation scheme of our GCE model for stars between 15 and 25 M⊙, we overestimate [Cr/Fe] by an order of magnitude at [Fe/H] ≈ 0 relative to observations in the Galactic disk. This raises a number of questions regarding the occurrence of Si-C shell mergers in nature, the accuracy of different simulation approaches, and the impact of such mergers on the presupernova structure and explosion dynamics. According to the conditions in this 1D stellar model, the substantial penetration of C-shell material into the Si shell could launch a convective-reactive global oscillation if a merger does take place. In any case, GCE provides stringent constraints on the outcome of this stellar evolution phase.

Keywords: Galaxy chemical evolution, Stellar abundances, Massive stars, Stellar evolutionary models, Chemical abundances, Chemical enrichment, Galaxy abundances, Stellar nucleosynthesis
M-dwarf Eclipsing Binaries with Flare Activity. The physical properties of 12 eclipsing binaries of M-type dwarfs with superflare activity are characterized by combining the ground-based spectroscopic measurements and the photometric light curves obtained by the Kepler Space Telescope. All of these binary systems have Algol-type orbital configurations. The primary components are mostly of the early M-type dwarfs (M0-M3). Even though the occurrence rate of large flares with energy &gt;1034 erg of the EBs is less than the hyperflaring M dwarfs, the corresponding cumulative flare frequency is in general about a factor of 10 higher than the single M dwarfs with flare activity. This might be the consequence of magnetic interaction between the primary and secondary component of individual binaries. The slow rotators are not as active as the fast rotators, some of which display a possible eclipsing effect in their flare activity.

Keywords: Stellar flares
The Launching of Cold Clouds by Galaxy Outflows. III. The Influence of Magnetic Fields. Motivated by observations of outflowing galaxies, we investigate the combined impact of magnetic fields and radiative cooling on the evolution of cold clouds embedded in a hot wind. We perform a collection of three-dimensional adaptive mesh refinement, magnetohydrodynamical simulations that span two resolutions, and include fields that are aligned and transverse to the oncoming, super-Alfvénic material. Aligned fields have little impact on the overall lifetime of the clouds over the non-magnetized case, although they do increase the mixing between the wind and cloud material by a factor of ≈3. Transverse fields lead to magnetic draping, which isolates the clouds, but they also squeeze material in the direction perpendicular to the field lines, which leads to rapid mass loss. A resolution study suggests that the magnetized simulations have somewhat better convergence properties than non-magnetized simulations, and that a resolution of 64 zones per cloud radius is sufficient to accurately describe these interactions. We conclude that the combined effects of radiative cooling and magnetic fields are dependent on field orientation, but are unlikely to enhance cloud lifetimes beyond the effect of radiative cooling alone.

Keywords: Galactic winds, Magnetohydrodynamics, Radiative magnetohydrodynamics, Circumgalactic medium
Angular Expansion of Nova Shells. Nova shells can provide important information on their distance, their interactions with circumstellar and interstellar media, and the evolution in morphology of the ejecta. We have obtained narrowband images of a sample of five nova shells, namely DQ Her, FH Ser, T Aur, V476 Cyg, and V533 Her, with ages ranging from 50 to 130 yr. These images have been compared with suitable available archival images to derive their angular expansion rates. We find that all the nova shells in our sample are still in the free expansion phase, which can be expected, as the mass of the ejecta is 7-45 times larger than the mass of the swept-up circumstellar medium. The nova shells will keep expanding freely for time periods up to a few hundred years, reducing their time dispersal into the interstellar medium.

Keywords: Astronomical techniques, Cataclysmic variable stars, Interstellar medium
Using a Higher-order Numerical Scheme to Study the Hall Magnetic Reconnection. We use our recently developed higher-order conservation element and solution element scheme to investigate the evolutionary process of Hall magnetic reconnection. The purpose of this paper is twofold: (1) to take advantage of higher-order numerical schemes to capture some fine structures very well with fewer grid points and reduced computational cost; (2) to develop a better understanding of the magnetic reconnection described by Hall MHD; as Birn et al. pointed out, the Hall effect is a critical ingredient in determining collisionless reconnection rates in the magnetosphere. The contributions of this paper mainly include the following: (1) we capture a two-step magnetic reconnection process and describe the formation mechanism; (2) the simulations show complex formation and interaction of magnetic islands and we provide the ways by which the magnetic islands form and disappear; (3) we find an oscillatory nature of the reconnection and the transfer of energy from magnetic field to kinetic energy and thermal energy; (4) we identify the merging process of the central magnetic island and the outflow region magnetic island.

Keywords: Solar magnetic reconnection
An Accurate Analytic Mass Model for Lensing Galaxies. We develop an analytic mass model for lensing galaxies, based on a broken power-law density profile, which is a power-law profile with a mass deficit or surplus in the central region. Under the assumption of an elliptically symmetric surface mass distribution, the deflection angle and magnification can be evaluated analytically for this new model. We compute the theoretical prediction for various quantities, including the volume and surface mass density profiles of the galaxies, and the aperture and luminosity-weighted line-of-sight velocity dispersions, and compare them to those measured from the Illustris simulation. We find an excellent agreement between our model prediction and the simulation, which validates our modeling. The high efficiency and accuracy of our model manifests itself as a promising tool for studying properties of galaxies with strong lensing.

Keywords: Cosmology, Galaxy dark matter halos, Strong gravitational lensing, Galaxy dynamics, Galaxy mass distribution, Gravitational lensing, Dark matter
EUCLIA. II. On the Puzzling Large UV to X-Ray Lags in Seyfert Galaxies. Recent intense X-ray and UV monitoring campaigns with Swift have detected clear UV lags behind X-ray in several local active galactic nuclei (AGNs). The UV to X-ray lags are often larger (by a factor of up to ∼20) than expected if the UV variation is simply due to the X-ray reprocessing. We previously developed a model in which the UV/optical variations are attributed to disk turbulences, and the effect of large-scale turbulence is considered. Our model, which overcomes many severe challenges to the reprocessing scheme, can explain the observed variations in NGC 5548, particularly the correlations and lags among the UV/optical bands. In this work, assuming the corona heating is associated with turbulences in the inner accretion disk, we extend our study to model the correlations and lags between the X-ray and UV/optical bands. We find that our model, without the need of light echoing, can well reproduce the observed UV to X-ray lags and the optical to UV lags simultaneously in four local Seyfert galaxies, including NGC 4151, NGC 4395, NGC 4593, and NGC 5548. In our scenario, relatively larger UV to X-ray lag is expected for AGN with smaller innermost disk radius and thus more compact corona. Interestingly, for these Seyfert galaxies studied in this work, sources with relatively larger UV to X-ray lags do have broader Fe Kα lines, indicative of relativistic broadening due to more compact corona and smaller innermost disk radius. If confirmed with more X-ray and UV monitoring campaigns, this interesting discovery would provide a new probe to the inner disk/corona.

Keywords: Accretion, Seyfert galaxies, Active galactic nuclei, Galaxy nuclei
The Origin of Binary Black Hole Mergers. Recently Venumadhav et al. proposed a new pipeline to analyze LIGO-Virgo Collaboration's O1-O2 data, and discovered eight new binary black hole (BBH) mergers, including one with a high effective spin, χeff. This discovery helps to clarify the origin of the observed BBHs and the dynamical capture versus field binaries debate. Using a tide-wind model that characterizes the late phases of binary evolution and captures the essence of field binary spin evolution, we show that the observed χeff distribution favors this model over capture. However, given the current limited sample size, capture scenarios (isotropic models) cannot be ruled out. Observations of roughly 100 merges will enable us to distinguish between the different formation scenarios. However, if as expected, both formation channels operate, it may be difficult to resolve their exact fraction.

Keywords: Gravitational waves, Gravitational wave sources
Planet-Disk Interaction in Disks with Cooling: Basic Theory. Gravitational coupling between young planets and their parent disks is often explored using numerical simulations, which typically treat the disk thermodynamics in a highly simplified manner. In particular, many studies adopt the locally isothermal approximation, in which the disk temperature is a fixed function of the stellocentric distance. We explore the dynamics of planet-driven density waves in disks with more general thermodynamics, in which the temperature is relaxed toward an equilibrium profile on a finite cooling timescale tc. We use both linear perturbation theory and direct numerical simulations to examine the global structure of density waves launched by planets in such disks. A key diagnostic used in this study is the behavior of the wave angular momentum flux (AMF), which directly determines the evolution of the underlying disk. The AMF of free waves is constant for slowly cooling (adiabatic) disks but scales with the disk temperature for rapidly cooling (and locally isothermal) disks. However, cooling must be extremely fast, with β = Ωtc ≲ 10-3 for the locally isothermal approximation to provide a good description of density wave dynamics in the linear regime (relaxing to β ≲ 10-2 when nonlinear effects are important). For intermediate cooling timescales, density waves are subject to a strong linear damping. This modifies the appearance of planet-driven spiral arms and the characteristics of axisymmetric structures produced by massive planets: in disks with β ≈ 0.1-1, a near-thermal mass planet opens only a single wide gap around its orbit, in contrast to the several narrow gaps produced when cooling is either faster or slower.

Keywords: Hydrodynamics, Protoplanetary disks, Planet formation
The ALMA Spectroscopic Survey in the HUDF: The Cosmic Dust and Gas Mass Densities in Galaxies up to z ∼ 3. Using the deepest 1.2 mm continuum map to date in the Hubble Ultra Deep Field, which was obtained as part of the ALMA Spectroscopic Survey (ASPECS) large program, we measure the cosmic density of dust and implied gas (H2+H I) mass in galaxies as a function of look-back time. We do so by stacking the contribution from all H-band selected galaxies above a given stellar mass in distinct redshift bins, ρdust(M* &gt; M,z) and ρgas (M* &gt; M,z). At all redshifts, ρdust(M* &gt; M,z) and ρgas(M* &gt; M,z) grow rapidly as M decreases down to 1010 M☉, but this growth slows down toward lower stellar masses. This flattening implies that at our stellar mass-completeness limits (108 M☉ and 108.9 M☉ at z ∼ 0.4 and z ∼ 3), both quantities converge toward the total cosmic dust and gas mass densities in galaxies. The cosmic dust and gas mass densities increase at early cosmic time, peak around z ∼ 2, and decrease by a factor ∼4 and 7, when compared to the density of dust and molecular gas in the local universe, respectively. The contribution of quiescent galaxies (I.e., with little on-going star formation) to the cosmic dust and gas mass densities is minor (≲10%). The redshift evolution of the cosmic gas mass density resembles that of the SFR density, as previously found by CO-based measurements. This confirms that galaxies have relatively constant star formation efficiencies (within a factor ∼2) across cosmic time. Our results also imply that by z ∼ 0, a large fraction (∼90%) of dust formed in galaxies across cosmic time has either been destroyed or ejected to the intergalactic medium.

Keywords: Galaxy formation, High-redshift galaxies, Galaxy evolution
The MBHBM<SUB>⋆</SUB> Project. I. Measurement of the Central Black Hole Mass in Spiral Galaxy NGC 3504 Using Molecular Gas Kinematics. We present a dynamical mass measurement of the supermassive black hole (SMBH) in the nearby double-barred spiral galaxy NGC 3504 as part of the Measuring Black Holes in below Milky Way (M⋆) Mass Galaxies Project. Our analysis is based on Atacama Large Millimeter/submillimeter Array cycle 5 observations of the 12CO(2-1) emission line. These observations probe NGC 3504's circumnuclear gas disk (CND). Our dynamical model of the CND simultaneously constrains a black hole (BH) mass of 1.6-0.4+0.6 × 107} M⊙, which is consistent with the empirical BH-galaxy scaling relations and a mass-to-light ratio in the H band of 0.44 ± 0.12 (M⊙/L⊙). This measurement also relies on our new estimation of the distance to the galaxy of 32.4 ± 2.1 Mpc using the surface brightness fluctuation method, which is much further than the existing distance estimates. Additionally, our observations detect a central deficit in the 12CO(2-1) integrated intensity map with a diameter of 6.3 pc at the putative position of the SMBH. However, we find that a dense gas tracer CS(5 - 4) peaks at the galaxy center, filling in the 12CO(2 - 1)-attenuated hole. Holes like this one are observed in other galaxies, and our observations suggest these may be caused by changing excitation conditions rather than a true absence of molecular gas around the nucleus.

Keywords: Supermassive black holes, Spiral galaxies, Galaxy dynamics, Extragalactic astronomy, Barred spiral galaxies, Astrophysical black holes
A Two Carrier Families Spectral Profile Model for Anomalous Microwave Emission. We model anomalous microwave emission (AME) spectral profiles from 14 diverse galactic and extragalactic sources. The spectral profile model is an analytic representation of a quantum mechanical model for symmetric top rotational emission. The observed spectral shapes are well fit by superposing two model profiles originating from two distinct carrier families. Each family is composed of numerous, comparably abundant isomers of a parent carrier. The isomers have similar rotational constants, thereby producing continuous, versus resolved line, spectra that are slightly broader than the parent profiles. Ten observations are fit with comparable peak height and peak frequency ratios for the two carrier families, suggesting that AME arises from common carriers. One observation is fit using a single family, attributed to photodissociation of the less stable, smaller molecules for the missing family. Three observations are fit by combining two frequency-shifted model spectra, indicating multiple sources along their sight lines. The derived rotational constants for the two parent carriers are well determined because their rotational temperature is well characterized for the LDN 1622 dark cloud AME source. The rotational constants are consistent with the C36 and C60 fullerenes as the parent carriers. We use a Monte Carlo simulation of fullerene hydrogenation to understand the origins of source variability in the AME model fits. Other potential carriers, polycyclic aromatic hydrocarbons and very small grains, cannot be excluded; however, we find that fulleranes are also viable carriers because their aromatic cages are extremely stable to photodissociation, and their data-derived sizes suggest C36 and C60 parent fullerenes.

Keywords: Radio spectroscopy, Astronomy data modeling, Theoretical models, Molecular spectroscopy, Radio sources
Measurements of Effective Optical Depth in the Lyα Forest from the BOSS DR12 Quasar Sample. We measure the effective optical depth in the Lyα forest using 40,035 quasar spectra from the Twelfth Data Release (DR12) of the Baryon Oscillation Spectroscopic Survey of Sloan Digital Sky Survey IV. A rigorous selection based on spectral index and the equivalent width of the C IV emission line is applied to choose seven uniform samples with minimal intrinsic variations across redshifts. Modeling the redshift evolution of the effective optical depth with a power law, τeff = τ0(1+z)γ, produces τ0=(5.54 ± 0.64)× 10-3 and γ =3.182± 0.074. The 2.2% precision estimate on γ is dominated by systematic errors, likely arising from the bias and uncertainties in spectral index estimates. Even after incorporating the systematic errors, this work provides the most precise estimates of optical depth parameters to date. Finally, using the reconstructed Lyα forest continuum to directly measure the transmitted flux ratio as a function of redshift, we find deviations of less than 2.5% from the predictions from the global model and no convincing evidence for signal associated with He II reionization.

Keywords: Cosmology, Surveys
A Model for the Onset of Self-gravitation and Star Formation in Molecular Gas Governed by Galactic Forces. II. The Bottleneck to Collapse Set by Cloud-Environment Decoupling. In Meidt et al., we showed that gas kinematics on the scale of individual molecular clouds are not entirely dominated by self-gravity but also track a component that originates with orbital motion in the potential of the host galaxy. This agrees with observed cloud line widths, which show systematic variations from virial motions with environment, pointing at the influence of the galaxy potential. In this paper, we hypothesize that these motions act to slow down the collapse of gas and so help regulate star formation. Extending the results of Meidt et al., we derive a dynamical collapse timescale that approaches the free-fall time only once the gas has fully decoupled from the galactic potential. Using this timescale, we make predictions for how the fraction of free-falling, strongly self-gravitating gas varies throughout the disks of star-forming galaxies. We also use this collapse timescale to predict variations in the molecular gas star formation efficiency, which is lowered from a maximum, feedback-regulated level in the presence of strong coupling to the galactic potential. Our model implies that gas can only decouple from the galaxy to collapse and efficiently form stars deep within clouds. We show that this naturally explains the observed drop in star formation rate per unit gas mass in the Milky Way's Central Molecular Zone and other galaxy centers. The model for a galactic bottleneck to star formation also agrees well with resolved observations of dense gas and star formation in galaxy disks and the properties of local clouds.

Keywords: Interstellar medium, Star formation, Galaxies
Using Data Imputation for Signal Separation in High-contrast Imaging. To characterize circumstellar systems in high-contrast imaging, the fundamental step is to construct a best point-spread function (PSF) template for the noncircumstellar signals (I.e., starlight and speckles) and separate it from the observation. With existing PSF construction methods, the circumstellar signals (e.g., planets, circumstellar disks) are unavoidably altered by overfitting and/or self-subtraction, making forward modeling a necessity to recover these signals. We present a forward modeling-free solution to these problems with data imputation using sequential nonnegative matrix factorization (DI-sNMF), which first converts this signal separation problem to a "missing data" problem in statistics by flagging the regions that host circumstellar signals as missing data, then attributes PSF signals to these regions. We mathematically prove it to have negligible alteration to circumstellar signals when the imputation region is relatively small, which thus enables precise measurement of these circumstellar objects. We apply it to simulated point-source and circumstellar disk observations to demonstrate its proper recovery of them. We apply it to Gemini Planet Imager K1-band observations of the debris disk surrounding HR 4796A, finding a tentative trend that the dust is more forward scattering as the wavelength increases. We expect DI-sNMF to be applicable to other general scenarios where the separation of signals is needed.

Keywords: Astronomy data analysis, Coronagraphic imaging, Multivariate analysis, Protoplanetary disks, Debris disks, Dimensionality reduction
Magnetic Structure of an Erupting Filament. The full 3D vector magnetic field of a solar filament prior to eruption is presented. The filament was observed with the Facility Infrared Spectropolarimeter at the Dunn Solar Telescope in the chromospheric He I line at 10830 Å on 2017 May 29 and 30. We inverted the spectropolarimetric observations with the Hanle and Zeeman Light code to obtain the chromospheric magnetic field. A bimodal distribution of field strength was found in or near the filament. The average field strength was 24 Gauss, but prior to the eruption we find the 90th percentile of field strength was 435 Gauss for the observations on May 29. The field inclination was about 67° from the solar vertical. The field azimuth made an angle of about 47°-65° to the spine axis. The results suggest an inverse configuration indicative of a flux rope topology. He I intensity threads were found to be coaligned with the magnetic field direction. The filament had a sinistral configuration as expected for the southern hemisphere. The filament was stable on 2017 May 29 and started to rise during two observations on May 30, before erupting and causing a minor coronal mass ejection. There was no obvious change of the magnetic topology during the eruption process. Such information on the magnetic topology of erupting filaments could improve the prediction of the geoeffectiveness of solar storms.

Keywords: Solar magnetic fields, Solar filaments, Solar filament eruptions, Quiet solar chromosphere