Sazuna/UAT_keywords huggingface dataset:
A Novel Energy-conserving Scheme for Eight-dimensional Hamiltonian Problems. We design a novel, exact energy-conserving implicit nonsymplectic integration method for an eight-dimensional Hamiltonian system with four degrees of freedom. In our algorithm, each partial derivative of the Hamiltonian with respect to one of the phase-space variables is discretized by the average of eight Hamiltonian difference terms. Such a discretization form is a second-order approximation to the Hamiltonian gradient. It is shown numerically via simulations of a Fermi-Pasta-Ulam-β system and a post-Newtonian conservative system of compact binaries with one body spinning that the newly proposed method has extremely good energy-conserving performance, compared to the Runge-Kutta an implicit midpoint symplectic method, and extended phase-space explicit symplectic-like integrators. The new method is advantageous over very long times and for large time steps compared to the state-of-the-art Runge-Kutta method in the accuracy of numerical solutions. Although such an energy-conserving integrator exhibits a higher computational cost than any one of the other three algorithms, the superior results justify its use for satisfying some specific purposes on the preservation of energies in numerical simulations with much longer times, e.g., obtaining a high enough accuracy of the semimajor axis in a Keplerian problem in the solar system or accurately grasping the frequency of a gravitational wave from a circular orbit in a post-Newtonian system of compact binaries. The new integrator will be potentially applied to model time-varying external electromagnetic fields or time-dependent spacetimes.

Keywords: Black hole physics, Computational methods, Computational astronomy, Compact binary stars
Kinetic Helicity and Lifetime of Activity Complexes During Solar Cycle 24. We study magnetic features on the solar surface that exist for several rotations during solar cycle 24. To identify them, we average synoptic maps over a range in latitude and stack the resulting longitudinal strips in time. We use synoptic maps of magnetograms obtained with the NSO/Synoptic Optical Long-term Investigations of the Sun instrument and create synoptic maps of the kinetic helicity of subsurface flows integrated over 2.0-7.1 Mm based on Solar Dynamics Observatory/Helioseismic and Magnetic Imager Dopplergrams. To distinguish between active and quiet regions, we sort the grid points of the synoptic maps by their activity level and divide the data into four subsets with 25% of activity each and into two subsets with the highest or lowest 12.5% of activity values. The kinetic helicity of these six subsets follows the hemispheric helicity rule with, on average, positive values in the southern and negative values in the northern hemisphere. However, the helicity of the subset with the highest activity is about four times higher than that of the other subsets, and the mid-quartile subsets show the weakest hemispheric helicity rule. We define the lifetime of complexes in each subset and find that for the high-activity subset, the amplitude of magnetic activity and kinetic helicity increases almost linearly with the lifetime of complexes. The distribution of flares closely resembles that of the high-activity subset. The flare-productive locations in long-lived complexes produce, on average, the same number of flares as those of short-lived complexes. However, long-lived complexes have a higher fractional number of these locations than the short-lived complexes and thus produce more flares not just because they live longer.

Keywords: Solar interior, Helioseismology, Solar magnetic fields, Solar x-ray flares, Solar activity
Elemental Abundance Distributions in the (R, V <SUB> ϕ </SUB>) Plane with LAMOST DR5 and Gaia DR2. Since Gaia DR2 was released, many velocity structures in the disk have been revealed, such as large-scale ridge-like patterns in phase space. Both kinematic information and stellar elemental abundances are needed to reveal their evolution history. We have used labels from the APOGEE survey to predict elemental abundances for a huge amount of low-resolution spectra from the Large Sky Area Multi-Object Fibre Spectroscopic Telescope survey. Deep learning with artificial neural networks can automatically draw on physically sensible features in the spectrum for their predictions. Abundances of 12 individual elements, [C/Fe], [N/Fe], [O/Fe], [Mg/Fe], [Al/Fe], [Si/Fe], [S/Fe], [Cl/Fe], [Ca/Fe], [Ti/Fe], [Mn/Fe], and [Ni/Fe], along with basic stellar labels T eff, log g, metallicity ([M/H] and [Fe/H]), and [α/M] for 1,063,386 stars have been estimated. Then, those stars were cross-matched with Gaia DR2 data to obtain kinematic parameters. We present distributions of chemical abundances in the V  ϕ  versus R coordinate. Our results extend the chemical characterization of the ridges in the (R, V  ϕ ) plane to about R = 13 kpc toward the anticenter direction. In addition, radial elemental abundance gradients for disk stars with abs(z) &lt; 0.5 kpc are investigated, and we fitted a line for median abundance values of bins of stars with galactocentric distance between R &gt; 7.84 kpc and R &lt; 15.84 kpc. The radial metallicity gradients for disk stars are, respectively, -0.0475 ± 0.0015 for R ≥ 13.09 kpc and -0.0173 ± 0.0028 for R &lt; 13.09 kpc. Gradients for other elemental abundances are also obtained for disk stars: the [α/M] gradient is 0.0030 ± 0.0002 the [Al/Fe] gradient is 0.0030 ± 0.0002; and the [Mn/Fe] gradient is -0.0078 ± 0.0005.

Keywords: Milky Way disk, Galaxy structure, Chemical abundances
Impact of Clouds and Hazes on the Simulated JWST Transmission Spectra of Habitable Zone Planets in the TRAPPIST-1 System. The TRAPPIST-1 system, consisting of an ultracool host star having seven known Earth-sized planets, will be a prime target for atmospheric characterization with the James Webb Space Telescope (JWST). However, the detectability of atmospheric molecular species may be severely impacted by the presence of clouds and/or hazes. In this work, we perform 3D general circulation model (GCM) simulations with the LMD-G model supplemented by 1D photochemistry simulations at the terminator with the Atmos model to simulate several possible atmospheres for TRAPPIST-1e, 1f, and 1g: (1) modern Earth, (2) Archean Earth, and (3) CO2-rich atmospheres. The JWST synthetic transit spectra were computed using the GSFC Planetary Spectrum Generator. We find that the TRAPPIST-1e, 1f, and 1g atmospheres, with clouds and/or hazes, could be detected using JWST’s NIRSpec Prism from the CO2 absorption line at 4.3 μm in less than 15 transits at 3σ or less than 35 transits at 5σ. However, our analysis suggests that other gases would require hundreds (or thousands) of transits to be detectable. We also find that H2O, mostly confined in the lower atmosphere, is very challenging to detect for these planets or similar systems if the planets’ atmospheres are not in a moist greenhouse state. This result demonstrates that the use of GCMs, self-consistently taking into account the effect of clouds and subsaturation, is crucial to evaluate the detectability of atmospheric molecules of interest, as well as for interpreting future detections in a more global (and thus robust and relevant) approach.

Keywords: Radiative transfer
A 40 Billion Solar-mass Black Hole in the Extreme Core of Holm 15A, the Central Galaxy of Abell 85. Holm 15A, the brightest cluster galaxy of the galaxy cluster Abell 85, has an ultradiffuse central region, ∼ 2 {mag} fainter than the faintest depleted core of any early-type galaxy (ETG) that has been dynamically modeled in detail. We use orbit-based, axisymmetric Schwarzschild models to analyze the stellar kinematics of Holm 15A from new high-resolution, wide-field spectral observations obtained with the Multi-Unit Spectroscopic Explorer at the Very Large Telescope. We find a supermassive black hole with a mass of (4.0+/- 0.80)× {10}10 {M}☉  at the center of Holm 15A. This is the most massive black hole with a direct dynamical detection in the local universe. We find that the distribution of stellar orbits is increasingly biased toward tangential motions inside the core. However, the tangential bias is less than that in other cored elliptical galaxies. We compare Holm 15A with N-body simulations of mergers between galaxies with black holes and find that the observed amount of tangential anisotropy and the shape of the light profile are consistent with a formation scenario where Holm 15A is the remnant of a merger between two ETGs with pre-existing depleted cores. We find that black hole masses in cored galaxies, including Holm 15A, scale inversely with the central stellar surface brightness and mass density. These correlations are independent of a specific parameterization of the light profile.

Keywords: Galaxy dark matter halos, Galaxy formation, Supermassive black holes, Orbits, Galaxy dynamics, Galaxy bulges, Scaling relations, Galaxy mass distribution, Galaxy photometry, Galaxy kinematics, Galaxy evolution, Galaxy mergers
The REQUIEM Survey. I. A Search for Extended Lyα Nebular Emission Around 31 z &gt; 5.7 Quasars. The discovery of quasars a few hundred megayears after the Big Bang represents a major challenge to our understanding of black holes as well as galaxy formation and evolution. Quasars' luminosity is produced by extreme gas accretion onto black holes, which have already reached masses of M BH &gt; 109 M ☉ by z ∼ 6. Simultaneously, their host galaxies form hundreds of stars per year, using up gas in the process. To understand which environments are able to sustain the rapid formation of these extreme sources, we started a Very Large Telescope/Multi-Unit Spectroscopic Explorer (MUSE) effort aimed at characterizing the surroundings of a sample of 5.7 &lt; z &lt; 6.6 quasars, which we have dubbed the Reionization Epoch QUasar InvEstigation with MUSE (REQUIEM) survey. We here present results of our searches for extended Lyα halos around the first 31 targets observed as part of this program. Reaching 5σ surface brightness limits of 0.1-1.1 × 10-17 erg s-1 cm-2 arcsec-2 over a 1 arcsec2 aperture, we were able to unveil the presence of 12 Lyα nebulae, eight of which are newly discovered. The detected nebulae show a variety of emission properties and morphologies with luminosities ranging from 8 × 1042 to 2 × 1044 erg s-1, FWHMs between 300 and 1700 km s-1, sizes &lt;30 pkpc, and redshifts consistent with those of the quasar host galaxies. As the first statistical and homogeneous investigation of the circumgalactic medium of massive galaxies at the end of the reionization epoch, the REQUIEM survey enables the study of the evolution of the cool gas surrounding quasars in the first 3 Gyr of the universe. A comparison with the extended Lyα emission observed around bright ({M}1450 ≲ -25 mag) quasars at intermediate redshift indicates little variations on the properties of the cool gas from z ∼ 6 to z ∼ 3, followed by a decline in the average surface brightness down to z ∼ 2.

Keywords: Cosmology, Early universe, Circumgalactic medium, Quasars
Climates of Warm Earth-like Planets. III. Fractional Habitability from a Water Cycle Perspective. The habitable fraction of a planet’s surface is important for the detectability of surface biosignatures. The extent and distribution of habitable areas are influenced by external parameters that control the planet’s climate, atmospheric circulation, and hydrological cycle. We explore these issues using the ROCKE-3D general circulation model, focusing on terrestrial water fluxes and thus the potential for the existence of complex life on land. Habitability is examined as a function of insolation and planet rotation for an Earth-like world with zero obliquity and eccentricity orbiting the Sun. We assess fractional habitability using an aridity index that measures the net supply of water to the land. Earth-like planets become “superhabitable” (a larger habitable surface area than Earth) as insolation and day-length increase because their climates become more equable, reminiscent of past warm periods on Earth when complex life was abundant and widespread. The most slowly rotating, most highly irradiated planets, though, occupy a hydrological regime unlike any on Earth, with extremely warm, humid conditions at high latitudes but little rain and subsurface water storage. Clouds increasingly obscure the surface as insolation increases, but visibility improves for modest increases in rotation period. Thus, moderately slowly rotating rocky planets with insolation near or somewhat greater than modern Earth’s appear to be promising targets for surface characterization by a future direct imaging mission.

Keywords: Exoplanet atmospheric variability, Habitable planets, Exoplanets
Supernovae within Pre-existing Wind-blown Bubbles: Dust Injection versus Ambient Dust Destruction. By means of 3D hydrodynamical simulations, we evaluate here the impact that supernova (SN) explosions occurring within wind-driven bubbles have on the survival or destruction of dust grains. We consider both the dust generated within the ejecta and the dust initially present in the ambient gas and later locked up in the surrounding wind-driven shell (WDS). The collision of the SN blast wave with the WDS leads to a transmitted shock that moves into the shell and a reflected shock that moves into the ejecta. The transmitted shock is capable of destroying large amounts of the dust locked in the shell, but only if the mass of the WDS is small, less than a few tens the ejected mass. Conversely, massive WDSs, with several times the ejected mass, lead upon the interaction to strong radiative cooling, which inhibits the Sedov-Taylor phase and weakens the transmitted shock, making it unable to traverse the WDS. In such a case, the destruction/disruption of the ambient dust is largely inhibited. On the other hand, the SN remnants grow rapidly in the very tenuous region excavated by the stellar winds, and thus a large fraction of the dust generated within the ejecta is not efficiently destroyed by the SN reverse shock, nor by the reflected shock. Our calculations favor a scenario in which core-collapse SNe within sufficiently massive WDSs supply more dust to the interstellar medium than they are able to destroy.

Keywords: Interstellar dust, Hydrodynamical simulations, Hydrodynamics, Supernova remnants, Chemical enrichment, Stellar winds, Circumstellar shells, Interstellar medium, Dust shells
Combined Effects of Rotation and Age Spreads on Extended Main-Sequence Turn Offs. The extended main-sequence turn offs (eMSTOs) of several young to intermediate age clusters are examined in the Magellanic Clouds and the Milky Way. We explore the effects of extended star formation (eSF) and a range of stellar rotation rates on the behavior of the color-magnitude diagram, paying particular attention to the MSTO. We create synthetic stellar populations based on MESA stellar models to simulate observed Hubble Space Telescope and Gaia star cluster data. We model the effect of rotation as a nonparametric distribution, allowing for maximum flexibility. In our models the slow rotators comprise the blueward, and fast rotators the redward portion of the eMSTO. We simulate data under three scenarios: nonrotating eSF, a range of rotation rates with a single age, and a combination of age and rotation effects. We find that two of the five clusters (the youngest and oldest) favor an age spread, but these also achieve the overall worst fits of all clusters. The other three clusters show comparable statistical evidence between rotation and an age spread. In all five cases, a rotation-rate distribution alone is capable of qualitatively matching the observed eMSTO structure. In future work, we aim to compare our predicted V\sin i with observations in order to better constrain the physics related to stellar rotation.

Keywords: Young star clusters, Star formation, Stellar rotation, Magellanic Clouds, Milky Way Galaxy, Stellar evolution
A Dissection of Spatially Resolved AGN Feedback across the Electromagnetic Spectrum. We present optical SuperNova Integral Field Spectrograph integral field spectroscopy, Hubble Space Telescope optical imaging, Chandra X-ray imaging, and Very Large Array radio interferometry of the merging galaxy 2MASX J04234080+0408017, which hosts a Seyfert 2 active galactic nucleus (AGN) at z = 0.046. Our observations reveal that radiatively driven, ionized gas outflows are successful to distances &gt;10 kpc due to the low mass of the host system, encompassing the entirety of the observed optical emission. We also find that at large radii, where observed velocities cannot be reproduced by radiative driving models, high-velocity kinematics are likely due to mechanical driving from AGN winds impacting high-density host material. This impacting deposits sufficient energy to shock the host material, producing thermal X-ray emission and cosmic rays, which in turn promote the formation of in situ radio structure in a pseudo-jet morphology along the high-density lanes.

Keywords: AGN host galaxies, Extragalactic radio sources, X-ray active galactic nuclei, Active galactic nuclei, Spectroscopy, Galaxy kinematics, Radial velocity
On the Rapid Orbital Expansion in the Compact Low-mass X-Ray Binary 2A 1822-371. The neutron star (NS) low-mass X-ray binary 2A 1822-371 has an orbital period of 5.57 hr. Mass transfer in such short-period binaries is thought to be driven by magnetic braking with orbital shrinking. However, 2A 1822-371 shows a very rapid orbital expansion, implying that mass transfer occurs rapidly in this system. The accretion rate of the NS is observationally estimated to be higher than the Eddington limit, which is also hard to explain by the standard magnetic braking mechanism. In this work, we construct a model to account for the peculiar properties of 2A 1822-371. We assume that the donor star possesses a relatively strong magnetic field, which is coupled with the stellar winds excited by the X-ray radiation from the NS. This would generate efficient angular momentum loss, leading to a high mass transfer rate and hence orbital expansion. We provide possible evolutionary tracks of 2A 1822-371 and study how the input parameters affect the results. The observational implications of the irradiation-driven mass loss are also briefly discussed in the context of evolution of low-mass X-ray binaries and millisecond pulsars.

Keywords: Neutron stars, Low-mass x-ray binary stars, Pulsars
Consequences of Energetic Magnetar-like Outbursts of Nearby Neutron Stars: <SUP>14</SUP>C Events and the Cosmic Electron Spectrum. Four significant events of rapid 14C increase have taken place within the past several thousand years. The physical origin of these rapid increases is still a mystery but must be associated with extremely energetic cosmic processes. Pulsars are highly magnetized neutron stars that emit a beam of electromagnetic radiations. Any sudden release of the energy stored in the magnetic multipole field will trigger outbursts similar to the giant flares of magnetars. Here we show that the relativistic outflow from the outbursts of a nearby pulsar interacting with the interstellar medium generates a shock, which accelerates electrons to trillions of electron volts. The high-energy photons from synchrotron emission of the shock interact with Earth’s atmosphere, producing the cosmogenic nuclide 14C, which can cause the rapid 14C increases discovered in tree rings. These same relativistic electrons can account for a significant fraction of the cosmic electron spectrum in the trillion electron volts energy range, as observed by space-borne satellites. Since these outburst events can significantly affect our environment, monitoring nearby pulsars for such outbursts may be important in the future.

Keywords: Magnetars, High-energy cosmic radiation
Core-Envelope Coupling in Intermediate-mass Core-helium Burning Stars. Stars between two and three solar masses rotate rapidly on the main sequence, and the detection of slow core and surface rotation in the core-helium burning phase for these stars places strong constraints on their angular momentum transport and loss. From a detailed asteroseismic study of the mixed-dipole mode pattern in a carefully selected, representative sample of stars, we find that slow core rotation rates in the range reported by prior studies are a general phenomenon and not a selection effect. We show that the core rotation rates of these stars decline strongly with decreasing surface gravity during the core He-burning phase. We argue that this is a model-independent indication of significant rapid angular momentum transport between the cores and envelopes of these stars. We see a significant range in core rotation rates at all surface gravities, with little evidence for a convergence toward a uniform value. We demonstrate using evolutionary models that measured surface rotation periods are a biased tracer of the true surface rotation distribution, and we argue for using stellar models for interpreting the contrast between core and surface rotation rates. The core rotation rates we measure do not have a strong mass or metallicity dependence. We argue that the emerging data strongly favor a model where angular momentum transport is much more efficient during the core He-burning phase than in the shell-burning phases that precede and follow it.

Keywords: Stellar rotation, Stellar evolutionary models, Late stellar evolution, Stellar evolution
Spatially Resolved Properties of Galaxies from CANDELS+MUSE: Radial Extinction Profile and Insights on Quenching. Studying the internal processes of individual galaxies at kilo-parsec scales is crucial in enhancing our understanding of galaxy formation and evolution processes. In this work, we investigate the distribution of star formation rate (SFR), specific SFR (sSFR), and dust attenuation across individual galaxies for a sample of 32 galaxies selected from the MUSE-Wide Survey at 0.1 &lt; z &lt; 0.42 with a dynamic range in stellar masses between 107.7 and 1010.3 M ☉. We take advantage of the high spatial resolution of the MUSE integral field spectrograph and measure reliable spatially resolved Hα and Hβ emission-line maps for individual galaxies. We also derive resolved stellar mass, SFR and dust maps using pixel-by-pixel spectral energy distribution (SED) fitting on high-resolution multiband Hubble Space Telescope (HST)/Advanced Camera for Surveys and HST/Wide Field Camera 3 data from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey survey. By combining these, we analyze the radial profile of various physical parameters across these galaxies. We observe a radial dependence in both stellar and nebular color excess profiles peaking at the inner regions of galaxies. We also find the color excess profiles to most strongly correlate with the integrated sSFRs of galaxies. The median sSFRHα  radial profiles of galaxies in our sample show a 0.8 dex increase from the central regions outward. This increase compared with the almost flat median radial profile of sSFRSED, which traces longer timescales of star formation, is in favor of the inside-out quenching of star formation. We bring further evidence for this quenching scenario from the locus of different subregions of galaxies on the SFR-M * and sSFR-M * relations.

Keywords: Multi-color photometry, Interstellar reddening, Star formation, Spectroscopy, Interstellar extinction, Galaxy quenching